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1
Novelli, A., K. Hens, C. Tatum Ernest, D. Kubistin, E. Regelin, T. Elste, C. Plass-Dülmer, M. Martinez, J. Lelieveld und H. Harder. „Characterisation of an inlet pre-injector laser-induced fluorescence instrument for the measurement of atmospheric hydroxyl radicals“. Atmospheric Measurement Techniques 7, Nr. 10 (08.10.2014): 3413–30. http://dx.doi.org/10.5194/amt-7-3413-2014.
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Abstract. Atmospheric measurements of hydroxyl radicals (OH) are challenging due to a high reactivity and consequently low concentration. The importance of OH as an atmospheric oxidant has motivated a sustained effort leading to the development of a number of highly sensitive analytical techniques. Recent work has indicated that the laser-induced fluorescence of the OH molecules method based on the fluorescence assay by gas expansion technique (LIF-FAGE) for the measurement of atmospheric OH in some environments may be influenced by artificial OH generated within the instrument, and a chemical method to remove this interference was implemented in a LIF-FAGE system by Mao et al. (2012). While it is not clear whether other LIF-FAGE instruments suffer from the same interference, we have applied this method to our LIF-FAGE HORUS (Hydroxyl Radical Measurement Unit based on fluorescence Spectroscopy) system, and developed and deployed an inlet pre-injector (IPI) to determine the chemical zero level in the instrument via scavenging the ambient OH radical. We describe and characterise this technique in addition to its application at field sites in forested locations in Finland, Spain and Germany. Ambient measurements show that OH generated within the HORUS instrument is a non-negligible fraction of the total OH signal, which can comprise 30 to 80% during daytime and 60 to 100% during the night. The contribution of the background OH varied greatly between measurement sites and was likely related to the type and concentration of volatile organic compounds (VOCs) present at each particular location. Two inter-comparisons in contrasting environments between the HORUS instrument and two different chemical ionisation mass spectrometers (CIMS) are described to demonstrate the efficacy of IPI and the necessity of the chemical zeroing method for our LIF-FAGE instrument in such environments.
2
Chan, C. Y., T. M. Hard, A. A. Mehrabzadeh, L. A. George und R. J. O'Brien. „Third-generation FAGE instrument for tropospheric hydroxyl radical measurement“. Journal of Geophysical Research 95, Nr. D11 (1990): 18569. http://dx.doi.org/10.1029/jd095id11p18569.
3
Novelli, A., K. Hens, C. Tatum Ernest, D. Kubistin, E. Regelin, T. Elste, C. Plass-Dülmer, M. Martinez, J. Lelieveld und H. Harder. „Characterisation of an inlet pre-injector laser induced fluorescence instrument for the measurement of ambient hydroxyl radicals“. Atmospheric Measurement Techniques Discussions 7, Nr. 1 (28.01.2014): 819–58. http://dx.doi.org/10.5194/amtd-7-819-2014.
Annotation:
Abstract. Ambient measurements of hydroxyl radicals (OH) are challenging due to a high reactivity and consequently low concentration. The importance of OH as an atmospheric oxidant has resulted in a sustained effort leading to the development of a number of analytical techniques. Recent work has indicated that the laser-induced fluorescence of the OH molecules method based on the fluorescence assay by gas expansion technique (LIF-FAGE) for the measurement of atmospheric OH in some environments may be influenced by artificial OH generated within the instrument, and a chemical method to remove this interference was implemented in a LIF-FAGE system by Mao et al. (2012). We have applied this method to our LIF-FAGE HORUS (HydrOxyl Radical Measurement Unit based on fluorescence Spectroscopy) system, and developed and deployed an inlet pre-injector (IPI) to determine the chemical zero level in the instrument via scavenging the ambient OH radical. We describe and characterise this technique in addition to its application at field sites in forested locations in Finland, Spain, and Germany. Ambient measurements show that OH generated within the HORUS instrument is a non-negligible fraction of the total OH signal, which can comprise 30% to 80% during the day and 60% to 100% during the night. The contribution of the background OH varied greatly between measurement sites and was likely related to the type and concentration of volatile organic compounds (VOCs) present at each particular location. Two inter-comparisons in contrasting environments between the HORUS instrument and two different chemical ionisation mass spectrometers (CIMS) are described to demonstrate the efficacy of the inlet-pre-injector and the necessity of the chemical zeroing method in such environments.
4
Glowacki, D. R., A. Goddard, K. Hemavibool, T. L. Malkin, R. Commane, F. Anderson, W. J. Bloss et al. „Design of and initial results from a Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC)“. Atmospheric Chemistry and Physics 7, Nr. 20 (17.10.2007): 5371–90. http://dx.doi.org/10.5194/acp-7-5371-2007.
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Abstract. The design of a Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) is described and initial results obtained from HIRAC are presented. The ability of HIRAC to perform in-situ laser-induced fluorescence detection of OH and HO2 radicals with the Fluorescence Assay by Gas Expansion (FAGE) technique establishes it as internationally unique for a chamber of its size and pressure/temperature variable capabilities. In addition to the FAGE technique, HIRAC features a suite of analytical instrumentation, including: a multipass FTIR system; a conventional gas chromatography (GC) instrument and a GC instrument for formaldehyde detection; NO/NO2, CO, O3, and H2O vapour analysers. Ray tracing simulations and NO2 actinometry have been utilized to develop a detailed model of the radiation field within HIRAC. Comparisons between the analysers and the FTIR coupled to HIRAC have been performed, and HIRAC has also been used to investigate pressure dependent kinetics of the chlorine atom reaction with ethene and the reaction of O3 and t-2-butene. The results obtained are in good agreement with literature recommendations and Master Chemical Mechanism predictions. HIRAC thereby offers a highly instrumented platform with the potential for: (1) high precision kinetics investigations over a range of atmospheric conditions; (2) detailed mechanism development, significantly enhanced according to its capability for measuring radicals; and (3) field instrument intercomparison, calibration, development, and investigations of instrument response at a range of atmospheric conditions.
5
Hansen, R. F., M. Blocquet, C. Schoemaecker, T. Léonardis, N. Locoge, C. Fittschen, B. Hanoune, P. S. Stevens, V. Sinha und S. Dusanter. „Intercomparison of the comparative reactivity method (CRM) and pump–probe technique for measuring total OH reactivity in an urban environment“. Atmospheric Measurement Techniques 8, Nr. 10 (14.10.2015): 4243–64. http://dx.doi.org/10.5194/amt-8-4243-2015.
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Abstract. The investigation of hydroxyl radical (OH) chemistry during intensive field campaigns has led to the development of several techniques dedicated to ambient measurements of total OH reactivity, which is the inverse of the OH lifetime. Three techniques are currently used during field campaigns, including the total OH loss rate method, the pump–probe method, and the comparative reactivity method. However, no formal intercomparison of these techniques has been published so far, and there is a need to ensure that measurements of total OH reactivity are consistent among the different techniques. An intercomparison of two OH reactivity instruments, one based on the comparative reactivity method (CRM) and the other based on the pump–probe method, was performed in October 2012 in a NOx-rich environment, which is known to be challenging for the CRM technique. This study presents an extensive description of the two instruments, the CRM instrument from Mines Douai (MD-CRM) and the pump–probe instrument from the University of Lille (UL-FAGE), and highlights instrumental issues associated with the two techniques. It was found that the CRM instrument used in this study underestimates ambient OH reactivity by approximately 20 % due to the photolysis of volatile organic compounds (VOCs) inside the sampling reactor; this value is dependent on the position of the lamp within the reactor. However, this issue can easily be fixed, and the photolysis of VOCs was successfully reduced to a negligible level after this intercomparison campaign. The UL-FAGE instrument may also underestimate ambient OH reactivity due to the difficulty to accurately measure the instrumental zero. It was found that the measurements are likely biased by approximately 2 s-1, due to impurities in humid zero air. Two weeks of ambient sampling indicate that the measurements performed by the two OH reactivity instruments are in agreement, within the measurement uncertainties for each instrument, for NOx mixing ratios up to 100 ppbv. The CRM technique has hitherto mainly been used in low-NOx environments, i.e. environments with ambient NOx mixing ratios lower than a few ppbv, due to a measurement artifact generated by ambient NO inside the sampling reactor. However, this study shows that this technique can also be used under NOx-rich conditions if a NOx-dependent correction is carefully applied on the OH reactivity measurements. A full suite of 52 VOCs, NOx, and other inorganic species were monitored during this intercomparison. An investigation of the OH reactivity budget for this urban site suggests that this suite of trace gases can account for the measured total OH reactivity.
6
Hansen, R. F., M. Blocquet, C. Schoemaecker, T. Léonardis, N. Locoge, C. Fittschen, B. Hanoune, P. S. Stevens, V. Sinha und S. Dusanter. „Intercomparison of the comparative reactivity method (CRM) and pump-probe technique for measuring total OH reactivity in an urban environment“. Atmospheric Measurement Techniques Discussions 8, Nr. 6 (19.06.2015): 6119–78. http://dx.doi.org/10.5194/amtd-8-6119-2015.
Annotation:
Abstract. The investigation of hydroxyl radical (OH) chemistry during intensive field campaigns has led to the development of several techniques dedicated to ambient measurements of total OH reactivity, which is the inverse of the OH lifetime. Three techniques are currently used during field campaigns, including the total OH loss rate method, the pump-probe method, and the comparative reactivity method. However, no formal intercomparison of these techniques has been published so far, and there is a need to ensure that measurements of total OH reactivity are consistent among the different techniques. An intercomparison of two OH reactivity instruments, one based on the Comparative Reactivity Method (CRM) and the other based on the pump-probe method, was performed in October 2012 in a NOx-rich environment, which is known to be challenging for the CRM technique. This study presents an extensive description of the two instruments, the CRM instrument from Mines Douai (MD-CRM) and the pump-probe instrument from the University of Lille (UL-FAGE), and highlights instrumental issues associated with the two techniques. It was found that the CRM instrument used in this study underestimates ambient OH reactivity by approximately 20 % due to the photolysis of Volatile Organic Compounds (VOCs) inside the sampling reactor; this value is dependent on the position of the lamp within the reactor. However, this issue can easily be fixed, and the photolysis of VOCs was successfully reduced to a negligible level after this intercomparison campaign. The UL-FAGE instrument may also underestimate ambient OH reactivity due to the difficulty to accurately measure the instrumental zero. It was found that the measurements are likely biased by approximately 2 s−1, due to impurities in humid zero air. Two weeks of ambient sampling indicate that the measurements performed by the two OH reactivity instruments are in agreement, within the measurement uncertainties for each instrument, for NOx mixing ratios up to 100 ppbv. The CRM technique has hitherto mainly been used in low-NOx environments, i.e. environments with ambient NOx mixing ratios lower than a few ppbv, due to a measurement artifact generated by ambient NO inside the sampling reactor. However, this study shows that this technique can also be used under NOx-rich conditions if a NOx-dependent correction is carefully applied on the OH reactivity measurements. A full suite of 52 VOCs, NOx, and other inorganic species were monitored during this intercomparison. An investigation of the OH reactivity budget for this urban site suggests that this suite of trace gases can account for the measured total OH reactivity.
7
Glowacki, D. R., A. Goddard, K. Hemavibool, T. L. Malkin, R. Commane, F. Anderson, W. J. Bloss et al. „Design of and initial results from a highly instrumented reactor for atmospheric chemistry (HIRAC)“. Atmospheric Chemistry and Physics Discussions 7, Nr. 4 (24.07.2007): 10687–742. http://dx.doi.org/10.5194/acpd-7-10687-2007.
Annotation:
Abstract. The design of a Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) is described and initial results obtained from HIRAC are presented. The ability of HIRAC to perform in-situ laser-induced fluorescence detection of OH and HO2 radicals with the Fluorescence Assay by Gas Expansion (FAGE) technique establishes it as internationally unique for a chamber of its size and pressure/temperature variable capabilities. In addition to the FAGE technique, HIRAC features a suite of analytical instrumentation, including: a multipass FTIR system; a conventional gas chromatography (GC) instrument and a GC instrument for formaldehyde detection; and NO/NO2, CO, O3, and H2O vapour analysers. Ray tracing simulations and measurements of the blacklamp flux have been utilized to develop a detailed model of the radiation field within HIRAC. Comparisons between the analysers and the FTIR coupled to HIRAC have been performed, and HIRAC has also been used to investigate pressure dependent kinetics of the chlorine atom reaction with ethene and the reaction of O3 and t-2-butene. The results obtained are in good agreement with literature recommendations and Master Chemical Mechanism predictions. HIRAC thereby offers a highly instrumented platform with the potential for: (1) high precision kinetics investigations over a range of atmospheric conditions; (2) detailed mechanism development, significantly enhanced according to its capability for measuring radicals; and (3) field instrument intercomparison, calibration, development, and investigations of instrument response under a range of atmospheric conditions.
8
Winiberg, F. A. F., S. C. Smith, I. Bejan, C. A. Brumby, T. Ingham, T. L. Malkin, S. C. Orr, D. E. Heard und P. W. Seakins. „Pressure-dependent calibration of the OH and HO<sub>2</sub> channels of a FAGE HO<sub>x</sub> instrument using the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC)“. Atmospheric Measurement Techniques 8, Nr. 2 (03.02.2015): 523–40. http://dx.doi.org/10.5194/amt-8-523-2015.
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Abstract. The calibration of field instruments used to measure concentrations of OH and HO2 worldwide has traditionally relied on a single method utilising the photolysis of water vapour in air in a flow tube at atmospheric pressure. Here the calibration of two FAGE (fluorescence assay by gaseous expansion) apparatuses designed for HOx (OH and HO2) measurements have been investigated as a function of external pressure using two different laser systems. The conventional method of generating known concentrations of HOx from H2O vapour photolysis in a turbulent flow tube impinging just outside the FAGE sample inlet has been used to study instrument sensitivity as a function of internal fluorescence cell pressure (1.8–3.8 mbar). An increase in the calibration constants CHO and CHO2 with pressure was observed, and an empirical linear regression of the data was used to describe the trends, with ΔCHO = (17 ± 11) % and ΔCHO2 = (31.6 ± 4.4)% increase per millibar air (uncertainties quoted to 2σ). Presented here are the first direct measurements of the FAGE calibration constants as a function of external pressure (440–1000 mbar) in a controlled environment using the University of Leeds HIRAC chamber (Highly Instrumented Reactor for Atmospheric Chemistry). Two methods were used: the temporal decay of hydrocarbons for calibration of OH, and the kinetics of the second-order recombination of HO2 for HO2 calibrations. Over comparable conditions for the FAGE cell, the two alternative methods are in good agreement with the conventional method, with the average ratio of calibration factors (conventional : alternative) across the entire pressure range, COH(conv)/COH(alt) = 1.19 ± 0.26 and CHO2(conv)/CHO2(alt) = 0.96 ± 0.18 (2σ). These alternative calibration methods currently have comparable systematic uncertainties to the conventional method: ~ 28% and ~ 41% for the alternative OH and HO2 calibration methods respectively compared to 35% for the H2O vapour photolysis method; ways in which these can be reduced in the future are discussed. The good agreement between the very different methods of calibration leads to increased confidence in HOx field measurements and particularly in aircraft-based HOx measurements, where there are substantial variations in external pressure, and assumptions are made regarding loss rates on inlets as a function of pressure.
9
Winiberg, F. A. F., S. C. Smith, I. Bejan, C. A. Brumby, T. Ingham, T. L. Malkin, S. C. Orr, D. E. Heard und P. W. Seakins. „Pressure dependent calibration of the OH and HO<sub>x</sub> channels of a FAGE HO<sub>x</sub> instrument using the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC)“. Atmospheric Measurement Techniques Discussions 7, Nr. 7 (31.07.2014): 7963–8011. http://dx.doi.org/10.5194/amtd-7-7963-2014.
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Abstract. The calibration of field instruments used to measure concentrations of OH and HO2 worldwide have traditionally relied on a single method utilising the photolysis of water vapour in air in a flow tube at atmospheric pressure. Here the calibration of two FAGE (Fluorescence Assay by Gaseous Expansion) apparatuses designed for HOx (OH and HO2) measurements have been investigated as a function of external pressure and temperature, using two different laser systems. The conventional method of generating known concentrations of HOx from H2O vapour photolysis in a turbulent flowtube impinging just outside the FAGE sample inlet has been used to study instrument sensitivity as a function of internal fluorescence cell pressure (1.8–3.8 mbar). An increase in the calibration constants COH and CHO2 with pressure was observed and an empirical linear regression of the data was used to describe the trends, with ΔCOH = (17 ± 11)% and ΔCHO2 = (31.6 ± 4.4)% increase per mbar air (uncertainties quoted to 2σ). Presented here are the first direct measurements of the FAGE calibration constants as a function of external pressure (440–1000 mbar) in a controlled environment using the University of Leeds HIRAC chamber (Highly Instrumented Reactor for Atmospheric Chemistry). Two methods were used: the temporal decay of hydrocarbons for calibration of OH, and the kinetics of the second-order recombination of HO2 for HO2 calibrations. Over comparable conditions for the FAGE cell, the two alternative methods are in good agreement with the conventional method, with the average ratio of calibration factors (conventional : alternative) across the entire pressure range COH(conv)/COH(alt) = 1.19 ± 0.26 and CHO2(conv)/CHO2(alt) = 0.96 ± 0.18 (2σ). These alternative calibration methods currently have comparable systematic uncertainties than the conventional method: ~28% and ~41% for the alternative OH and HO2 calibration methods respectively compared to 35% for the H2O vapour photolysis method; ways in which these can be reduced in the future are discussed. The good agreement between the very different methods of calibration leads to increased confidence in HOx field measurements and particularly in aircraft based HOx measurements, where there are substantial variations in external pressure, and assumptions are made regarding loss rates on inlets as a function of pressure.
10
Bottorff, Brandon, Emily Reidy, Levi Mielke, Sebastien Dusanter und Philip S. Stevens. „Development of a laser-photofragmentation laser-induced fluorescence instrument for the detection of nitrous acid and hydroxyl radicals in the atmosphere“. Atmospheric Measurement Techniques 14, Nr. 9 (16.09.2021): 6039–56. http://dx.doi.org/10.5194/amt-14-6039-2021.
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Abstract. A new instrument for the measurement of atmospheric nitrous acid (HONO) and hydroxyl radicals (OH) has been developed using laser photofragmentation (LP) of HONO at 355 nm after expansion into a low-pressure cell, followed by resonant laser-induced fluorescence (LIF) of the resulting OH radical fragment at 308 nm similar to the fluorescence assay by gas expansion technique (FAGE). The LP/LIF instrument is calibrated by determining the photofragmentation efficiency of HONO and calibrating the instrument sensitivity for detection of the OH fragment. In this method, a known concentration of OH from the photo-dissociation of water vapor is titrated with nitric oxide to produce a known concentration of HONO. Measurement of the concentration of the OH radical fragment relative to the concentration of HONO provides a measurement of the photofragmentation efficiency. The LP/LIF instrument has demonstrated a 1σ detection limit for HONO of 9 ppt for a 10 min integration time. Ambient measurements of HONO and OH from a forested environment and an urban setting are presented along with indoor measurements to demonstrate the performance of the instrument.
11
Novelli, Anna, Korbinian Hens, Cheryl Tatum Ernest, Monica Martinez, Anke C. Nölscher, Vinayak Sinha, Pauli Paasonen et al. „Estimating the atmospheric concentration of Criegee intermediates and their possible interference in a FAGE-LIF instrument“. Atmospheric Chemistry and Physics 17, Nr. 12 (29.06.2017): 7807–26. http://dx.doi.org/10.5194/acp-17-7807-2017.
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Abstract. We analysed the extensive dataset from the HUMPPA-COPEC 2010 and the HOPE 2012 field campaigns in the boreal forest and rural environments of Finland and Germany, respectively, and estimated the abundance of stabilised Criegee intermediates (SCIs) in the lower troposphere. Based on laboratory tests, we propose that the background OH signal observed in our IPI-LIF-FAGE instrument during the aforementioned campaigns is caused at least partially by SCIs. This hypothesis is based on observed correlations with temperature and with concentrations of unsaturated volatile organic compounds and ozone. Just like SCIs, the background OH concentration can be removed through the addition of sulfur dioxide. SCIs also add to the previously underestimated production rate of sulfuric acid. An average estimate of the SCI concentration of ∼ 5.0 × 104 molecules cm−3 (with an order of magnitude uncertainty) is calculated for the two environments. This implies a very low ambient concentration of SCIs, though, over the boreal forest, significant for the conversion of SO2 into H2SO4. The large uncertainties in these calculations, owing to the many unknowns in the chemistry of Criegee intermediates, emphasise the need to better understand these processes and their potential effect on the self-cleaning capacity of the atmosphere.
12
Marno, Daniel, Cheryl Ernest, Korbinian Hens, Umar Javed, Thomas Klimach, Monica Martinez, Markus Rudolf, Jos Lelieveld und Hartwig Harder. „Calibration of an airborne HO<sub><i>x</i></sub> instrument using the All Pressure Altitude-based Calibrator for HO<sub><i>x</i></sub> Experimentation (APACHE)“. Atmospheric Measurement Techniques 13, Nr. 5 (27.05.2020): 2711–31. http://dx.doi.org/10.5194/amt-13-2711-2020.
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Abstract. Laser-induced fluorescence (LIF) is a widely used technique for both laboratory-based and ambient atmospheric chemistry measurements. However, LIF instruments require calibrations in order to translate instrument response into concentrations of chemical species. Calibration of LIF instruments measuring OH and HO2 (HOx) typically involves the photolysis of water vapor by 184.9 nm light, thereby producing quantitative amounts of OH and HO2. For ground-based HOx instruments, this method of calibration is done at one pressure (typically ambient pressure) at the instrument inlet. However, airborne HOx instruments can experience varying cell pressures, internal residence times, temperatures, and humidity during flight. Therefore, replication of such variances when calibrating in the lab is essential to acquire the appropriate sensitivities. This requirement resulted in the development of the APACHE (All Pressure Altitude-based Calibrator for HOx Experimentation) chamber to characterize the sensitivity of the airborne LIF-FAGE (fluorescence assay by gas expansion) HOx instrument, HORUS, which took part in an intensive airborne campaign, OMO-Asia 2015. It utilizes photolysis of water vapor but has the additional ability to alter the pressure at the nozzle of the HORUS instrument. With APACHE, the HORUS instrument sensitivity towards OH (26.1–7.8 cts s−1 pptv−1 mW−1, ±22.6 % 1σ; cts stands for counts by the detector) and HO2 (21.2–8.1 cts s−1 pptv−1 mW−1, ±22.1 % 1σ) was characterized to the external pressure range at the instrument nozzle of 227–900 mbar. Measurements supported by a computational fluid dynamics model, COMSOL Multiphysics, revealed that, for all pressures explored in this study, APACHE is capable of initializing a homogenous flow and maintaining near-uniform flow speeds across the internal cross section of the chamber. This reduces the uncertainty regarding average exposure times across the mercury (Hg) UV ring lamp. Two different actinometrical approaches characterized the APACHE UV ring lamp flux as 6.37×1014(±1.3×1014) photons cm−2 s−1. One approach used the HORUS instrument as a transfer standard in conjunction with a calibrated on-ground calibration system traceable to NIST standards, which characterized the UV ring lamp flux to be 6.9(±1.1)×1014 photons cm−2 s−1. The second approach involved measuring ozone production by the UV ring lamp using an ANSYCO O3 41 M ozone monitor, which characterized the UV ring lamp flux to be 6.11(±0.8)×1014 photons cm−2 s−1. Data presented in this study are the first direct calibrations of an airborne HOx instrument, performed in a controlled environment in the lab using APACHE.
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Dusanter, S., D. Vimal, P. S. Stevens, R. Volkamer und L. T. Molina. „Measurements of OH and HO<sub>2</sub> concentrations during the MCMA-2006 field campaign – Part 1: Deployment of the Indiana University laser-induced fluorescence instrument“. Atmospheric Chemistry and Physics 9, Nr. 5 (05.03.2009): 1665–85. http://dx.doi.org/10.5194/acp-9-1665-2009.
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Abstract. Measurements of tropospheric hydroxyl (OH) and hydroperoxy (HO2) radicals were made during the MCMA (Mexico City Metropolitan Area) field campaign as part of the MILAGRO (Megacity Initiative: Local and Global Research Observations) project during March 2006. These radicals were measured using a laser-induced fluorescence instrument developed at Indiana University. This new instrument takes advantage of the Fluorescence Assay by Gas Expansion technique (FAGE) together with direct excitation and detection of OH at 308 nm. HO2 is indirectly measured as OH by titration with NO inside the fluorescence cell. At this stage of development, IU-FAGE is capable of detecting 3.9×105 molecule/cm3 of both OH and HO2, with a signal to noise ratio of 1, an averaged laser power of 10-mW and an averaging time of 5-min. The calibration accuracies (1σ) are ±17% for OH and ±18% for HO2 using the water-vapor photolysis/O2 actinometry calibration technique. OH and HO2 concentrations were successfully measured at an urban site in Mexico City, with observed concentrations comparable to those measured in other polluted environments. Enhanced levels of OH and HO2 radicals were observed on several days between 09:30–11:00 a.m. and suggest an intense photochemistry during morning hours that may be due to elevated sources of HOx (OH+HO2) and a fast cycling between the radicals under the high NOx (NO+NO2) conditions of the MCMA.
14
Rickly, Pamela, und Philip S. Stevens. „Measurements of a potential interference with laser-induced fluorescence measurements of ambient OH from the ozonolysis of biogenic alkenes“. Atmospheric Measurement Techniques 11, Nr. 1 (03.01.2018): 1–16. http://dx.doi.org/10.5194/amt-11-1-2018.
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Abstract. Reactions of the hydroxyl radical (OH) play a central role in the chemistry of the atmosphere, and measurements of its concentration can provide a rigorous test of our understanding of atmospheric oxidation. Several recent studies have shown large discrepancies between measured and modeled OH concentrations in forested areas impacted by emissions of biogenic volatile organic compounds (BVOCs), where modeled concentrations were significantly lower than measurements. A potential reason for some of these discrepancies involves interferences associated with the measurement of OH using the laser-induced fluorescence–fluorescence assay by gas expansion (LIF-FAGE) technique in these environments. In this study, a turbulent flow reactor operating at atmospheric pressure was coupled to a LIF-FAGE cell and the OH signal produced from the ozonolysis of α-pinene, β-pinene, ocimene, isoprene, and 2-methyl-3-buten-2-ol (MBO) was measured. To distinguish between OH produced from the ozonolysis reactions and any OH artifact produced inside the LIF-FAGE cell, an external chemical scrubbing technique was used, allowing for the direct measurement of any interference. An interference under high ozone (between 2 × 1013 and 10 × 1013 cm−3) and BVOC concentrations (between approximately 0.1 × 1012 and 40 × 1012 cm−3) was observed that was not laser generated and was independent of the ozonolysis reaction time. For the ozonolysis of α- and β-pinene, the observed interference accounted for approximately 40 % of the total OH signal, while for the ozonolysis of ocimene the observed interference accounted for approximately 70 % of the total OH signal. Addition of acetic acid to the reactor eliminated the interference, suggesting that the source of the interference in these experiments involved the decomposition of stabilized Criegee intermediates (SCIs) inside the FAGE detection cell. Extrapolation of these measurements to ambient concentrations suggests that these interferences should be below the detection limit of the instrument.
15
Dusanter, S., D. Vimal, P. S. Stevens, R. Volkamer und L. T. Molina. „Measurements of OH and HO<sub>2</sub> concentrations during the MCMA-2006 field campaign – Part 1: Deployment of the Indiana University laser-induced fluorescence instrument“. Atmospheric Chemistry and Physics Discussions 8, Nr. 4 (17.07.2008): 13689–739. http://dx.doi.org/10.5194/acpd-8-13689-2008.
Annotation:
Abstract. Measurements of tropospheric hydroxyl (OH) and hydroperoxy (HO2) radicals were made during the MCMA (Mexico City Metropolitan Area) field campaign as part of the MILAGRO (Megacity Initiative: Local and Global Research Observations) project during March 2006. These radicals were measured using a laser-induced fluorescence instrument developed at Indiana University. This new instrument takes advantage of the Fluorescence Assay by Gas Expansion technique (FAGE) together with direct excitation and detection of OH at 308 nm. HO2 is indirectly measured as OH by titration with NO inside the fluorescence cell. At this stage of development, IU-FAGE is capable of detecting 3.9×105molec cm−3 of both OH and HO2, with a signal to noise ratio of 1, an averaged laser power of 10 mW and an averaging time of 5 min. The calibration accuracies (1σ) are ±17% for OH and ±18% for HO2 using the water-vapor photolysis/O2 actinometry calibration technique. OH and HO2 concentrations were successfully measured at an urban site in Mexico City, with observed concentrations comparable to those measured in other polluted environments. Enhanced levels of OH and HO2 radicals were observed on several days between 09:30–11 a.m. and suggest an intense photochemistry during morning hours that may be due to elevated sources of HOx (OH+HO2) and a fast cycling between the radicals under the high NOx conditions of the MCMA. A comparison with other urban and sub-urban field measurements suggests that OH concentrations are highly buffered under these conditions. In contrast, HO2 concentrations are highly variable between different urban sites.
16
Dusanter, S., D. Vimal und P. S. Stevens. „Technical Note: Measuring tropospheric OH and HO<sub>2</sub> by laser-induced fluorescence at low pressure – a comparison of calibration techniques“. Atmospheric Chemistry and Physics Discussions 7, Nr. 5 (04.09.2007): 12877–926. http://dx.doi.org/10.5194/acpd-7-12877-2007.
Annotation:
Abstract. The hydroxyl radical (OH) is one of the most important oxidants in the atmosphere, as it is involved in many reactions that affect regional air quality and global climate change. Because of its high reactivity, measurements of OH radical concentrations in the atmosphere are difficult, and often require careful calibrations that rely on the production of a known concentration of OH at atmospheric pressure. The Indiana University OH instrument, based on the Fluorescence Assay by Gas Expansion technique (FAGE), has been calibrated in the laboratory using two different approaches: the production of OH from the UV-photolysis of water-vapor, and the steady-state production of OH from the reaction of ozone with alkenes. Both techniques are shown to agree within their experimental uncertainties, although the sensitivities derived from the ozone-alkene technique were systematically lower than those derived from the water-vapor UV-photolysis technique. The agreement between the two different methods improves the confidence of the water-vapor photolysis method as an accurate calibration technique for HOx instruments. Because several aspects of the mechanism of the gas phase ozonolysis of alkenes are still uncertain, this technique should be used with caution to calibrate OH instruments.
17
Winiberg, Frank A. F., William J. Warman, Charlotte A. Brumby, Graham Boustead, Iustinian G. Bejan, Thomas H. Speak, Dwayne E. Heard, Daniel Stone und Paul W. Seakins. „Comparison of temperature-dependent calibration methods of an instrument to measure OH and HO2 radicals using laser-induced fluorescence spectroscopy“. Atmospheric Measurement Techniques 16, Nr. 19 (05.10.2023): 4375–90. http://dx.doi.org/10.5194/amt-16-4375-2023.
Annotation:
Abstract. Laser-induced fluorescence (LIF) spectroscopy has been widely applied to fieldwork measurements of OH radicals and HO2, following conversion to OH, over a wide variety of conditions, on different platforms and in simulation chambers. Conventional calibration of HOx (OH + HO2) instruments has mainly relied on a single method, generating known concentrations of HOx from H2O vapour photolysis in a flow of zero air impinging just outside the sample inlet (SHOx=CHOx. [HOx], where SHOx is the observed signal and CHOx is the calibration factor). The fluorescence assay by gaseous expansion (FAGE) apparatus designed for HOx measurements in the Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) at the University of Leeds has been used to examine the sensitivity of FAGE to external gas temperatures (266–348 K). The conventional calibration methods give the temperature dependence of COH (relative to the value at 293 K) of (0.0059±0.0015) K−1 and CHO2 of (0.014±0.013) K−1. Errors are 2σ. COH was also determined by observing the decay of hydrocarbons (typically cyclohexane) caused by OH reactions giving COH (again, relative to the value at 293 K) of (0.0038±0.0007) K−1. Additionally, CHO2 was determined based on the second-order kinetics of HO2 recombination with the temperature dependence of CHO2, relative to 293 K being (0.0064±0.0034) K−1. The temperature dependence of CHOx depends on the HOx number density, quenching, the relative population of the probed OH rotational level and HOx transmission from the inlet to the detection axis. The first three terms can be calculated and, in combination with the measured values of CHOx, show that HOx transmission increases with temperature. Comparisons with other instruments and the implications of this work are discussed.
18
Whalley, L. K., M. A. Blitz, M. Desservettaz, P. W. Seakins und D. E. Heard. „Reporting the sensitivity of laser-induced fluorescence instruments used for HO<sub>2</sub> detection to an interference from RO<sub>2</sub> radicals and introducing a novel approach that enables HO<sub>2</sub> and certain RO<sub>2</sub> types to be selectively measured“. Atmospheric Measurement Techniques 6, Nr. 12 (09.12.2013): 3425–40. http://dx.doi.org/10.5194/amt-6-3425-2013.
Annotation:
Abstract. Laboratory studies have revealed that alkene-derived RO2 and longer chain alkane-derived RO2 (> C3) radicals rapidly convert to HO2 and then to OH in the presence of NO in a fluorescence assay by gas expansion (FAGE) detection cell (Fuchs et al., 2011). Three different FAGE cells that have been used to make ambient measurements of OH and HO2 in the University of Leeds ground-based instrument have been assessed to determine the sensitivity of each cell, when operating in HO2 detection mode, to RO2 radicals. The sensitivity to this interference was found to be highly dependent on cell design and operating parameters. Under the operating conditions employed, during fieldwork undertaken in the Borneo rainforest in 2008, an OH yield of 17% was experimentally determined for both ethene- and isoprene-derived RO2 radicals. The high pumping capacity of this system, resulting in a short residence time in the cell, coupled with poor mixing of NO into the ambient air-stream for the titration of HO2 to OH effectively minimised this potential interference. An OH yield of 46% was observed for ethene-derived RO2 radicals when a smaller detection cell was used, in which the mixing of NO into the ambient air was improved and the cell residence times were much longer. For a newly developed ROxLIF cell, used for detection of HO2 and RO2 radicals an OH yield of 95% was observed for ethene-derived RO2 radicals, when running in HO2 mode. In experiments in which conditions ensured the conversion of RO2 to OH were complete, the yields of OH from a range of different RO2 species agreed well with model predictions based on the Master Chemical Mechanism version 3.2. For ethene and isoprene-derived RO2 species, the relative sensitivity of FAGE was found to be close to that for HO2, with an OH yield of 100% and 92%, respectively. For the longer chain or cyclic alkane-derived RO2 radicals (> C3), model predicted OH yields were highly dependent upon temperature. A model predicted OH yield of 74% at 298 K and 36% at 255 K were calculated for cyclohexane-derived RO2 radicals, and an experimental yield of 38% was observed indicating that the temperature within the cell was below ambient owing to the supersonic expansion of the airstream in the low pressure cell. These findings suggest that observations of HO2 by some LIF instruments worldwide may be higher than the true value if the instruments were sensitive to these RO2 species. If this is the case, it becomes necessary to compare atmospheric chemistry model simulations to HO2* observations, where HO2* = [HO2] + Σi αi [RO2i], and αi is the mean fractional contribution of the RO2 species that interfere (RO2i). This methodology, however, relies on model simulations of speciated RO2 radicals, as instrumentation to make speciated RO2 measurements does not currently exist. Here we present an approach that enables the concentration of HO2 and RO2i to be selectively determined by varying the concentration of NO injected into a FAGE cell. Measurements of [HO2] and [RO2i] taken in London are presented.
19
Whalley, L. K., M. A. Blitz, M. Desservettaz, P. W. Seakins und D. E. Heard. „Reporting the sensitivity of Laser Induced Fluorescence instruments used for HO<sub>2</sub> detection to an interference from RO<sub>2</sub> radicals and introducing a novel approach that enables HO<sub>2</sub> and certain RO<sub>2</sub> types to be selectively measured“. Atmospheric Measurement Techniques Discussions 6, Nr. 4 (09.07.2013): 6249–92. http://dx.doi.org/10.5194/amtd-6-6249-2013.
Annotation:
Abstract. Laboratory studies have revealed that alkene-derived RO2 and longer-chain alkane-derived RO2 (>C3) radicals rapidly convert to HO2 and then to OH in the presence of NO in a Fluorescence Assay by Gas Expansion (FAGE) detection cell (Fuchs et al., 2011). Three different FAGE cells that have been used to make ambient measurements of OH and HO2 in the University of Leeds ground-based instrument have been assessed to determine the sensitivity of each cell, when operating in HO2 detection mode, to RO2 radicals. The sensitivity to this interference was found to be highly dependent on cell design and operating parameters. Under the operating conditions employed during fieldwork undertaken in the Borneo rainforest in 2008, an OH yield of 17% was experimentally determined for both ethene- and isoprene-derived RO2 radicals. The high pumping capacity of this system, resulting in a short residence time, coupled with poor mixing of NO into the ambient air-stream for the titration of HO2 to OH effectively minimised this potential interference. An OH yield of 46% was observed for ethene-derived RO2 radicals when a smaller detection cell was used, in which the mixing of NO into the ambient air was improved and the cell residence times were longer. For a newly developed ROx LIF cell, used for detection of HO2 and RO2 radicals, when running in HOx mode an OH yield of 95% was observed for ethene-derived RO2 radicals. In experiments in which conditions ensured the conversion of RO2 to OH was complete, the yields of OH from a range of different RO2 species agreed well with model predictions based on the Master Chemical Mechanism version 3.2. For ethene and isoprene derived RO2 species, the relative sensitivity of FAGE was found to be close to that for HO2 with an OH yield of 100% and 92% respectively. For the longer-chain alkane-derived RO2 radicals, model predicted OH yields were highly dependent upon temperature. A model predicted OH yield of 74% at 298 K and 36% at 255 K were calculated for cyclohexane derived RO2 radicals and an experimental yield of 38% was observed indicating that the temperature within the cell was below ambient owing to the supersonic expansion of the airstream in the low pressure cell. These findings suggest that observations of HO2 by some LIF instruments worldwide may be higher than the true value if the instruments were sensitive to these RO2 species. If this is the case, it becomes necessary to compare atmospheric chemistry model simulations to HO2* observations, where HO2&ast; = [HO2] + α [RO2] and α is the mean fractional contribution of the RO2 species that interfere RO2i). This methodology, however, relies on model simulations of speciated RO2 radicals, as instrumentation to make speciated RO2 measurements does not currently exist. Here we present an approach that enables the concentration of HO2 and RO2i to be selectively determined by varying the concentration of NO injected into a FAGE cell. Measurements of [HO2] and [RO2i] taken in London are presented.
20
Onel, Lavinia, Alexander Brennan, Michele Gianella, James Hooper, Nicole Ng, Gus Hancock, Lisa Whalley, Paul W. Seakins, Grant A. D. Ritchie und Dwayne E. Heard. „An intercomparison of CH<sub>3</sub>O<sub>2</sub> measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)“. Atmospheric Measurement Techniques 13, Nr. 5 (15.05.2020): 2441–56. http://dx.doi.org/10.5194/amt-13-2441-2020.
Annotation:
Abstract. Simultaneous measurements of CH3O2 radical concentrations have been performed using two different methods in the Leeds HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) chamber at 295 K and in 80 mbar of a mixture of 3:1 He∕O2 and 100 or 1000 mbar of synthetic air. The first detection method consisted of the indirect detection of CH3O2 using the conversion of CH3O2 into CH3O by excess NO with subsequent detection of CH3O by fluorescence assay by gas expansion (FAGE). The FAGE instrument was calibrated for CH3O2 in two ways. In the first method, a known concentration of CH3O2 was generated using the 185 nm photolysis of water vapour in synthetic air at atmospheric pressure followed by the conversion of the generated OH radicals to CH3O2 by reaction with CH4∕O2. This calibration can be used for experiments performed in HIRAC at 1000 mbar in air. In the second method, calibration was achieved by generating a near steady state of CH3O2 and then switching off the photolysis lamps within HIRAC and monitoring the subsequent decay of CH3O2, which was controlled via its self-reaction, and analysing the decay using second-order kinetics. This calibration could be used for experiments performed at all pressures. In the second detection method, CH3O2 was measured directly using cavity ring-down spectroscopy (CRDS) using the absorption at 7487.98 cm−1 in the A←X (ν12) band with the optical path along the ∼1.4 m chamber diameter. Analysis of the second-order kinetic decays of CH3O2 by self-reaction monitored by CRDS has been used for the determination of the CH3O2 absorption cross section at 7487.98 cm−1, both at 100 mbar of air and at 80 mbar of a 3:1 He∕O2 mixture, from which σCH3O2=(1.49±0.19)×10-20 cm2 molecule−1 was determined for both pressures. The absorption spectrum of CH3O2 between 7486 and 7491 cm−1 did not change shape when the total pressure was increased to 1000 mbar, from which we determined that σCH3O2 is independent of pressure over the pressure range 100–1000 mbar in air. CH3O2 was generated in HIRAC using either the photolysis of Cl2 with UV black lamps in the presence of CH4 and O2 or the photolysis of acetone at 254 nm in the presence of O2. At 1000 mbar of synthetic air the correlation plot of [CH3O2]FAGE against [CH3O2]CRDS gave a gradient of 1.09±0.06. At 100 mbar of synthetic air the FAGE–CRDS correlation plot had a gradient of 0.95±0.024, and at 80 mbar of 3:1 He∕O2 mixture the correlation plot gradient was 1.03±0.05. These results provide a validation of the FAGE method to determine concentrations of CH3O2.
21
Onel, Lavinia, Alexander Brennan, Paul W. Seakins, Lisa Whalley und Dwayne E. Heard. „A new method for atmospheric detection of the CH<sub>3</sub>O<sub>2</sub> radical“. Atmospheric Measurement Techniques 10, Nr. 10 (27.10.2017): 3985–4000. http://dx.doi.org/10.5194/amt-10-3985-2017.
Annotation:
Abstract. A new method for measurement of the methyl peroxy (CH3O2) radical has been developed using the conversion of CH3O2 into CH3O by excess NO with subsequent detection of CH3O by fluorescence assay by gas expansion (FAGE) with laser excitation at ca. 298 nm. The method can also directly detect CH3O, when no nitric oxide is added. Laboratory calibrations were performed to characterise the FAGE instrument sensitivity using the conventional radical source employed in OH calibration with conversion of a known concentration of OH into CH3O2 via reaction with CH4 in the presence of O2. Detection limits of 3.8 × 108 and 3.0 × 108 molecule cm−3 were determined for CH3O2 and CH3O respectively for a signal-to-noise ratio of 2 and 5 min averaging time. Averaging over 1 h reduces the detection limit for CH3O2 to 1.1 × 108 molecule cm−3, which is comparable to atmospheric concentrations. The kinetics of the second-order decay of CH3O2 via its self-reaction were observed in HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) at 295 K and 1 bar and used as an alternative method of calibration to obtain a calibration constant with overlapping error limits at the 1σ level with the result of the conventional method of calibration. The overall uncertainties of the two methods of calibrations are similar – 15 % for the kinetic method and 17 % for the conventional method – and are discussed in detail. The capability to quantitatively measure CH3O in chamber experiments is demonstrated via observation in HIRAC of CH3O formed as a product of the CH3O2 self-reaction.
22
Dusanter, S., D. Vimal und P. S. Stevens. „Technical note: Measuring tropospheric OH and HO<sub>2</sub> by laser-induced fluorescence at low pressure. A comparison of calibration techniques“. Atmospheric Chemistry and Physics 8, Nr. 2 (25.01.2008): 321–40. http://dx.doi.org/10.5194/acp-8-321-2008.
Annotation:
Abstract. The hydroxyl radical (OH) is one of the most important oxidants in the atmosphere, as it is involved in many reactions that affect regional air quality and global climate change. Because of its high reactivity, measurements of OH radical concentrations in the atmosphere are difficult, and often require careful calibrations that rely on the production of a known concentration of OH at atmospheric pressure. The Indiana University OH instrument, based on the Fluorescence Assay by Gas Expansion technique (FAGE), has been calibrated in the laboratory using two different approaches: the production of OH from the UV-photolysis of water-vapor, and the steady-state production of OH from the reaction of ozone with alkenes. The former technique relies on two different actinometric methods to measure the product of the lamp flux at 184.9 nm and the photolysis time. This quantity derived from N2O actinometry was found to be 1.5 times higher than that derived from O2 actinometry. The water photolysis and ozone-alkene techniques are shown to agree within their experimental uncertainties (respectively 17% and 44%), although the sensitivities derived from the ozone-alkene technique were systematically lower by 40% than those derived from the water-vapor UV- photolysis technique using O2 actinometry. The agreement between the two different methods improves the confidence of the water-vapor photolysis method as an accurate calibration technique for HOx instruments. Because several aspects of the mechanism of the gas phase ozonolysis of alkenes are still uncertain, this technique should be used with caution to calibrate OH instruments.
23
Kundu, Shuvashish, Benjamin L. Deming, Michelle M. Lew, Brandon P. Bottorff, Pamela Rickly, Philip S. Stevens, Sebastien Dusanter et al. „Peroxy radical measurements by ethane – nitric oxide chemical amplification and laser-induced fluorescence during the IRRONIC field campaign in a forest in Indiana“. Atmospheric Chemistry and Physics 19, Nr. 14 (30.07.2019): 9563–79. http://dx.doi.org/10.5194/acp-19-9563-2019.
Annotation:
Abstract. Peroxy radicals were measured in a mixed deciduous forest atmosphere in Bloomington, Indiana, USA, during the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC) during the summer of 2015. Total peroxy radicals ([XO2]≡[HO2]+Σ[RO2]) were measured by a newly developed technique involving chemical amplification using nitric oxide (NO) and ethane (C2H6) followed by NO2 detection by cavity-attenuated phase-shift spectroscopy (hereinafter referred to as ECHAMP – Ethane CHemical AMPlifier). The sum of hydroperoxy radicals (HO2) and a portion of organic peroxy radicals ([HO2*]=[HO2]+Σαi[RiO2], 0<α<1) was measured by the Indiana University (IU) laser-induced fluorescence–fluorescence assay by gas expansion instrument (LIF-FAGE). Additional collocated measurements include concentrations of NO, NO2, O3, and a wide range of volatile organic compounds (VOCs) and meteorological parameters. XO2 concentrations measured by ECHAMP peaked between 13:00 and 16:00 local time (LT), with campaign average concentrations of 41±15 ppt (1σ) at 14:00 LT. Daytime concentrations of isoprene averaged 3.6±1.9 ppb (1σ), whereas average concentrations of NOx ([NO] + [NO2]) and toluene were 1.2 and 0.1 ppb, respectively, indicating a low impact from anthropogenic emissions at this site. We compared ambient measurements from both instruments and conducted a calibration source comparison. For the calibration comparison, the ECHAMP instrument, which is primarily calibrated with an acetone photolysis method, sampled the output of the LIF-FAGE calibration source which is based on the water vapor photolysis method and, for these comparisons, generated a 50 %–50 % mixture of HO2 and either butane or isoprene-derived RO2. A bivariate fit of the data yields the relation [XO2]ECHAMP=(0.88±0.02;[HO2]+[RO2])IU_cal+(6.6±4.5) ppt. This level of agreement is within the combined analytical uncertainties for the two instruments' calibration methods. A linear fit of the daytime (09:00–22:00 LT) 30 min averaged [XO2] ambient data with the 1 min averaged [HO2*] data (one point per 30 min) yields the relation [XO2]=(1.08±0.05)[HO2*]-(1.4±0.3). Day-to-day variability in the [XO2]/[HO2*] ratio was observed. The lowest [XO2]/[HO2*] ratios between 13:00 and 16:00 LT were 0.8 on 13 and 18 July, whereas the highest ratios of 1.1 to 1.3 were observed on 24 and 25 July – the same 2 d on which the highest concentrations of isoprene and ozone were observed. Although the exact composition of the peroxy radicals during IRRONIC is not known, zero-dimensional photochemical modeling of the IRRONIC dataset using two versions of the Regional Atmospheric Chemistry Mechanism (RACM2 and RACM2-LIM1) and the Master Chemical Mechanism (MCM 3.2 and MCM 3.3.1) all predict afternoon [XO2]/[HO2*] ratios of between 1.2 and 1.5. Differences between the observed ambient [XO2]/[HO2*] ratio and that predicted with the 0-D modeling can be attributed to deficiencies in the model, errors in one of the two measurement techniques, or both. Time periods in which the ambient ratio was less than 1 are definitely caused by measurement errors (including calibration differences), as such ratios are not physically meaningful. Although these comparison results are encouraging and demonstrate the viability in using the new ECHAMP technique for field measurements of peroxy radicals, further research investigating the overall accuracy of the measurements and possible interferences from both methods is warranted.
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Speak, Thomas H., Mark A. Blitz, Daniel Stone und Paul W. Seakins. „A new instrument for time-resolved measurement of HO<sub>2</sub> radicals“. Atmospheric Measurement Techniques 13, Nr. 2 (20.02.2020): 839–52. http://dx.doi.org/10.5194/amt-13-839-2020.
Annotation:
Abstract. OH and HO2 radicals are closely coupled in the atmospheric oxidation and combustion of volatile organic compounds (VOCs). Simultaneous measurement of HO2 yields and OH kinetics can provide the ability to assign site-specific rate coefficients that are important for understanding the oxidation mechanisms of VOCs. By coupling a fluorescence assay by gaseous expansion (FAGE) laser-induced fluorescence (LIF) detection system for OH and HO2 with a high-pressure laser flash photolysis system, it is possible to accurately measure OH pseudo-1st-order loss processes up to ∼100 000 s−1 and to determine HO2 yields via time-resolved measurements. This time resolution allows discrimination between primary HO2 from the target reaction and secondary production from side reactions. The apparatus was characterized by measuring yields from the reactions of OH with H2O2 (1:1 link between OH and HO2), with C2H4∕O2 (where secondary chemistry can generate HO2), with C2H6∕O2 (where there should be zero HO2 yield), and with CH3OH∕O2 (where there is a well-defined HO2 yield). As an application of the new instrument, the reaction of OH with n-butanol has been studied at 293 and 616 K. The bimolecular rate coefficient at 293 K, (9.24±0.21)×10-12 cm3 molec.−1 s−1, is in good agreement with recent literature, verifying that this instrument can measure accurate OH kinetics. At 616 K the regeneration of OH in the absence of O2, from the decomposition of the β-hydroxy radical, was observed, which allowed the determination of the fraction of OH reacting at the β site (0.23±0.04). Direct observation of the HO2 product in the presence of oxygen has allowed the assignment of the α-branching fractions (0.57±0.06) at 293 K and (0.54±0.04) at 616 K, again in good agreement with recent literature; branching ratios are key to modelling the ignition delay times of this potential “drop-in” biofuel.
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Woodward-Massey, Robert, Eloise J. Slater, Jake Alen, Trevor Ingham, Danny R. Cryer, Leanne M. Stimpson, Chunxiang Ye, Paul W. Seakins, Lisa K. Whalley und Dwayne E. Heard. „Implementation of a chemical background method for atmospheric OH measurements by laser-induced fluorescence: characterisation and observations from the UK and China“. Atmospheric Measurement Techniques 13, Nr. 6 (12.06.2020): 3119–46. http://dx.doi.org/10.5194/amt-13-3119-2020.
Annotation:
Abstract. Hydroxyl (OH) and hydroperoxy (HO2) radicals are central to the understanding of atmospheric chemistry. Owing to their short lifetimes, these species are frequently used to test the accuracy of model predictions and their underlying chemical mechanisms. In forested environments, laser-induced fluorescence–fluorescence assay by gas expansion (LIF–FAGE) measurements of OH have often shown substantial disagreement with model predictions, suggesting the presence of unknown OH sources in such environments. However, it is also possible that the measurements have been affected by instrumental artefacts, due to the presence of interfering species that cannot be discriminated using the traditional method of obtaining background signals via modulation of the laser excitation wavelength (“OHwave”). The interference hypothesis can be tested by using an alternative method to determine the OH background signal, via the addition of a chemical scavenger prior to sampling of ambient air (“OHchem”). In this work, the Leeds FAGE instrument was modified to include such a system to facilitate measurements of OHchem, in which propane was used to selectively remove OH from ambient air using an inlet pre-injector (IPI). The IPI system was characterised in detail, and it was found that the system did not reduce the instrument sensitivity towards OH (< 5 % difference to conventional sampling) and was able to efficiently scavenge external OH (> 99 %) without the removal of OH formed inside the fluorescence cell (< 5 %). Tests of the photolytic interference from ozone in the presence of water vapour revealed a small but potentially significant interference, equivalent to an OH concentration of ∼4×105 molec. cm−3 under typical atmospheric conditions of [O3] =50 ppbv and [H2O] =1 %. Laboratory experiments to investigate potential interferences from products of isoprene ozonolysis did result in interference signals, but these were negligible when extrapolated down to ambient ozone and isoprene levels. The interference from NO3 radicals was also tested but was found to be insignificant in our system. The Leeds IPI module was deployed during three separate field intensives that took place in summer at a coastal site in the UK and both in summer and winter in the megacity of Beijing, China, allowing for investigations of ambient OH interferences under a wide range of chemical and meteorological conditions. Comparisons of ambient OHchem measurements to the traditional OHwave method showed excellent agreement, with OHwave vs OHchem slopes of 1.05–1.16 and identical behaviour on a diel basis, consistent with laboratory interference tests. The difference between OHwave and OHchem (“OHint”) was found to scale non-linearly with OHchem, resulting in an upper limit interference of (5.0±1.4) ×106 molec. cm−3 at the very highest OHchem concentrations measured (23×106 molec. cm−3), accounting for ∼14 %–21 % of the total OHwave signal.
26
Lew, Michelle M., Sebastien Dusanter und Philip S. Stevens. „Measurement of interferences associated with the detection of the hydroperoxy radical in the atmosphere using laser-induced fluorescence“. Atmospheric Measurement Techniques 11, Nr. 1 (10.01.2018): 95–109. http://dx.doi.org/10.5194/amt-11-95-2018.
Annotation:
Abstract. One technique used to measure concentrations of the hydroperoxy radical (HO2) in the atmosphere involves chemically converting it to OH by addition of NO and subsequent detection of OH. However, some organic peroxy radicals (RO2) can also be rapidly converted to HO2 (and subsequently OH) in the presence of NO, interfering with measurements of ambient HO2 radical concentrations. This interference must be characterized for each instrument to determine to what extent various RO2 radicals interfere with measurements of HO2 and to assess the impact of this interference on past measurements. The efficiency of RO2-to-HO2 conversion for the Indiana University laser-induced fluorescence–fluorescence assay by gas expansion (IU-FAGE) instrument was measured for a variety of RO2 radicals. Known quantities of OH and HO2 radicals were produced from the photolysis of water vapor at 184.9 nm, and RO2 radicals were produced by the reaction of several volatile organic compounds (VOCs) with OH. The conversion efficiency of RO2 radicals to HO2 was measured when NO was added to the sampling cell for conditions employed during several previous field campaigns. For these conditions, approximately 80 % of alkene-derived RO2 radicals and 20 % of alkane-derived RO2 radicals were converted to HO2. Based on these measurements, interferences from various RO2 radicals contributed to approximately 35 % of the measured HO2 signal during the Mexico City Metropolitan Area (MCMA) 2006 campaign (MCMA-2006), where the measured VOCs consisted of a mixture of saturated and unsaturated species. However, this interference can contribute more significantly to the measured HO2 signal in forested environments dominated by unsaturated biogenic emissions such as isoprene.
27
Commane, R., C. F. A. Floquet, T. Ingham, D. Stone, M. J. Evans und D. E. Heard. „Observations of OH and HO<sub>2</sub> radicals over West Africa“. Atmospheric Chemistry and Physics Discussions 10, Nr. 3 (18.03.2010): 7265–322. http://dx.doi.org/10.5194/acpd-10-7265-2010.
Annotation:
Abstract. The hydroxyl radical (OH) plays a key role in the oxidation of trace gases in the troposphere. However, observations of OH and the closely related hydroperoxy radical (HO2) have been sparse, especially in the tropics. Based on a low-pressure laser-induced fluorescence technique (FAGE – Fluorescence Assay by Gas Expansion), an instrument has been developed to measure OH and HO2 aboard the Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft. The instrument is described and the calibration method is discussed. During the African Monsoon Multidisciplinary Analyses (AMMA) campaign, observations of OH and HO2 (HOx) were made in the boundary layer and free troposphere over West Africa on 13 flights during July and August 2006. Mixing ratios of both OH and HO2 were found to be highly variable but followed a diurnal cycle, with a median HO2/OH ratio of 95. Daytime OH observations were compared with the primary production rate of OH from ozone photolysis in the presence of water vapour. Daytime HO2 observations were generally reproduced by a simple steady-state HOx calculation, where HOx was assumed to be formed from the primary production of OH and lost through HO2 self-reaction. Deviations between the observations and this simple model were found to be grouped into a number of specific cases: (a) in the presence of high levels of isoprene in the boundary layer, (b) within a biomass burning plume and (c) within cloud. In the forested boundary layer, HO2 was underestimated at altitudes below 500 m but overestimated between 500 m and 2 km. In the biomass burning plume, OH and HO2 were both significantly reduced compared to calculations. HO2 was sampled in and around cloud, with significant short-lived reductions of HO2 observed. HO2 observations were better reproduced by a steady state calculation with heterogeneous loss of HO2 onto cloud droplets included. Up to 9 pptv of HO2 was observed at night, increasing early in the morning. Potential sources of high altitude HO2 at night are also discussed.
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Mohd. Sajari, Fenny Farhana, Hafizhah Zulkifli und Shahlan Surat. „Kesahan dan Kebolehpercayaan Instruman Kesediaan GPI Melaksanakan Model Tasmik j-QAF Secara Dalam Talian“. Journal of Quran Sunnah Education & Special Needs 7, Nr. 1 (01.06.2023): 16–29. http://dx.doi.org/10.33102/jqss.vol7no1.183.
Annotation:
The implementation of teaching in the COVID-19 pandemic season has urged teachers to be more prepared and open to face teaching and learning sessions (PdP) that require a comprehensive technology approach. Therefore, the preparation of a readiness instrument for the use of technology in PdP in this study has been adapted from several literature studies based on the theories and models used. The main purpose of this study is to evaluate the validity and reliability of the preparedness instrument that has been adapted according to the needs of the study. Testing of readiness instruments through a process of validity and reliability is done to produce more consistent results. A preliminary survey was conducted on 36 primary school Islamic Education Teachers (GPIs) in Gombak district, Selangor. A total of three experts were appointed as evaluators for the content validity of the instrument while a Malay teacher was chosen as the face validity evaluator. The instrument's content validity test is measured by using the Content Validity Index (CVI) to determine whether the items used should be dropped or retained. The reliability of the readiness instrument was measured using Cronbach Alpha. The findings of the study show that there are five items that need to be dropped and one negative item created, making the total number of items as many as 36 items out of 40 items in the initial stage. The results of the study also found that the value of the Cronbach Alpha coefficient of this research instrument is very high. Overall, the items in this instrument can be used and can answer the objectives and research questions. This instrument can also be improved according to the suitability of the study in the future.
Abstrak
Pelaksanaan pengajaran di musim pandemik COVID-19 telah mendesak para guru untuk lebih bersedia dan terbuka berhadapan dengan sesi pengajaran dan pembelajaran (PdP) yang memerlukan pendekatan teknologi secara menyeluruh. Oleh itu, penyediaan instrumen kesediaan terhadap penggunaan teknologi dalam PdP dalam kajian ini telah diadaptasi dari beberapa kajian literatur berdasarkan teori dan model yang digunakan. Tujuan utama kajian ini adalah untuk menilai kesahan dan kebolehpercayaan instrumen kesediaan yang telah disesuaikan mengikut keperluan kajian. Pengujian terhadap instrumen kesediaan melalui proses kesahan dan kebolehpercayaan dibuat bagi menghasilkan keputusan yang lebih konsisten. Tinjauan awal telah dilakukan ke atas 36 orang Guru Pendidikan Islam (GPI) sekolah rendah di daerah Gombak, Selangor. Seramai tiga orang pakar dilantik sebagai penilai bagi kesahan kandungan instrumen manakala seorang guru Bahasa Melayu dipilih sebagai penilai kesahan muka. Ujian kesahan kandungan instrumen diukur dengan menggunakan Content Validity Index (CVI) bagi menentukan sama ada item-item yang digunakan perlu digugurkan atau dikekalkan. Kebolehpercayaan instrumen kesediaan pula diukur menggunakan Cronbach Alpha. Dapatan kajian menunjukkan terdapat lima item perlu digugurkan dan satu item negatif diwujudkan menjadikan keseluruhan item adalah sebanyak 36 item daripada 40 item di peringkat awalnya. Hasil kajian juga mendapati nilai pekali Cronbach Alpha instrumen kajian ini adalah sangat tinggi. Secara keseluruhan, item-item dalam instrumen ini boleh digunakan dan dapat menjawab objektif serta persoalan kajian. Instrumen ini juga boleh diberi penambahbaikan mengikut kesesuaian kajian pada masa akan datang.
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Commane, R., C. F. A. Floquet, T. Ingham, D. Stone, M. J. Evans und D. E. Heard. „Observations of OH and HO<sub>2</sub> radicals over West Africa“. Atmospheric Chemistry and Physics 10, Nr. 18 (17.09.2010): 8783–801. http://dx.doi.org/10.5194/acp-10-8783-2010.
Annotation:
Abstract. The hydroxyl radical (OH) plays a key role in the oxidation of trace gases in the troposphere. However, observations of OH and the closely related hydroperoxy radical (HO2) have been sparse, especially in the tropics. Based on a low-pressure laser-induced fluorescence technique (FAGE – Fluorescence Assay by Gas Expansion), an instrument has been developed to measure OH and HO2 aboard the Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft. During the African Monsoon Multidisciplinary Analyses (AMMA) campaign, observations of OH and HO2 (HOx) were made in the boundary layer and free troposphere over West Africa on 13 flights during July and August 2006. Mixing ratios of both OH and HO2 were found to be highly variable, but followed a diurnal cycle: OH varied from 1.3 pptv to below the instrumental limit of detection, with a median mixing ratio of 0.17 pptv. HO2 varied from 42.7 pptv to below the limit of detection, with a median mixing ratio of 8.0 pptv. A median HO2/OH ratio of 95 was observed. Daytime OH observations were compared with the primary production rate of OH from ozone photolysis in the presence of water vapour. Daytime HO2 observations were generally reproduced by a simple steady-state HOx calculation, where HOx was assumed to be formed from the primary production of OH and lost through HO2 self-reaction. Deviations between the observations and this simple model were found to be grouped into a number of specific cases: (a) within cloud, (b) in the presence of high levels of isoprene in the boundary layer and (c) within a biomass burning plume. HO2 was sampled in and around cloud, with significant short-lived reductions of HO2 observed. Up to 9 pptv of HO2 was observed at night, with HO2 above 6 pptv observed at altitudes above 6 km. In the forested boundary layer, HO2 was underestimated by a steady state calculation at altitudes below 500 m but overestimated between 500 m and 2 km. In a biomass burning plume, observed HO2 concentrations were significantly below those calculated.
30
Al-Fatih, Sholahuddin, und Sara Sinha. „Capturing Law Reform in The Digital Age: Indonesian and Estonian Perspectives“. Indonesia Law Reform Journal 3, Nr. 3 (11.03.2024): 304–15. http://dx.doi.org/10.22219/ilrej.v3i3.31970.
Annotation:
This article examines how law reform in the digital age happens in Indonesia and Estonia. Indonesia and Estonia are located in different cultures and also areas. While law reform in the digital age happens, the two countries above will also demonstrate differences. This article uses normative legal studies to capture which legal instrument is better in both countries. This article found that Estonia is leading in providing legal instruments to face the digital age, while Indonesia needs to catch up. Some legal instruments in Indonesia such as AI law, Digital ID law, and e-government law should be drafted and implemented. Abstrak Artikel ini mengkaji bagaimana reformasi hukum di era digital terjadi di Indonesia dan Estonia. Indonesia dan Estonia terletak dalam budaya dan wilayah yang berbeda. Meskipun reformasi hukum di era digital terjadi, kedua negara di atas pasti akan menunjukkan perbedaan dalam menghadapinya. Artikel ini menggunakan metode penelitian hukum normatif untuk menemukan instrumen hukum mana yang lebih baik di kedua negara. Hasilnya, artikel ini menemukan bahwa Estonia lebih unggul dalam menyediakan instrumen hukum untuk menghadapi era digital, sementara Indonesia tertinggal dalam hal tersebut. Beberapa instrumen hukum di Indonesia harus dirancang dan diterapkan, seperti Rancangan Undang-Undang AI, Rancangan Undang-Undang Identitas Kependudukan Digital, dan Rancangan Undang-Undang Pemerintahan Digital.
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MOHD NOR, FAZRUL, ABD RAHMAN TAMURI, ABD KHAMIM ISMAIL, MOHD ERFY ISMAIL und MOHD HASRIL AMIRUDDIN. „PENGUKURAN KETULENAN EMAS MENGGUNAKAN KAEDAH UJIAN TANPA MUSNAH: SUATU ULASAN PERBANDINGAN“. International Journal of Creative Future and Heritage (TENIAT) 9, Nr. 2 (29.09.2021): 91–106. http://dx.doi.org/10.47252/teniat.v9i2.745.
Annotation:
AbstrakPenentuan ketulenan jongkong emas dengan kaedah ujian tanpa musnah adalah perkara yang paling mencabar dalam industri emas terutama jika jongkong emas dipalsukan dengan cara meletakkan tungsten di dalamnya. Instrumen yang sedia ada mempunyai keterbatasan untuk menentukan ketulenan jongkong emas dan sukar untuk mengesan tungsten di dalamnya kerana tungsten mempunyai ketumpatan yang hampir sama dengan emas. Kajian ini mengemukakan keterbatasan instrumen kaedah ujian tanpa musnah seperti densimeter, alat timbangan, sinar-x pendarfluor dan ultrasonik. Dalam kajian ini menemui kesukaran untuk mengenal pasti emas palsu menggunakan instrumen kaedah ujian tanpa musnah seperti ultrasonik dan x-ray fluorescence (XRF) kerana instrumen ini mempunyai batasan. Setakat ini tiada lagi kajian yang berkaitan pemalsuan jongkong emas kerana harganya yang mahal untuk dijadikan sebagai sampel kajian. Masalah jongkong emas palsu dapat diselesaikan jika ketepatan instrumen yang digunakan untuk mengukur ketumpatan dapat ditingkatkan lagi sehingga 0.01 g/ml. Ini kerana perbezaan antara ketumpatan emas dan tungsten adalah 0.05 g/ml. Pemalsuan emas dengan mencampurkan tungsten akan dapat dikesan jika ada instrumen yang mempunyai ketepatan sekurang-kurangnya 0.01 g/ml. Manakala instrumen lain seperti XRF digunakan untuk mengesahkan ketulenan emas di bahagian permukaan sahaja. Oleh itu, bagi pengujian yang lebih menyeluruh masalah jongkong emas palsu ini perlu diselesaikan dengan menggabungkan kedua-dua kaedah ini.
Abstract
Determination of the gold bar purity by non-destructive method remains one of the most challenging in gold industry especially when the tungsten is inside the gold bar. The existing instruments have limitations in their accuracy to determine the purity of gold when tungsten also inside the gold bar since both tungsten and gold have almost similar densities. This study presents the limitations of the non-destructive test method instruments such as densimeter, weighing balance, x-ray fluorescence (XRF) and ultrasonic in determining the purity of gold. In this study found the difficulty in identifying counterfeit gold using non-destructive test method instruments such as ultrasonic and XRF due to some limitations. So far, there are no studies related to the counterfeiting of gold bars due to its expensive price to be used as a study sample. The problem of counterfeit gold bars can be solved if the accuracy of the instrument used to measure the density can be further increased up to 0.01 g/ml. This is because the difference between the density of gold and tungsten is 0.05 g/ml. Gold counterfeiting by mixing tungsten will be detectable if there is an instrument that has an accuracy of at least 0.01 g/ml. While other instruments such as XRF will be used to verify the purity of gold on the surface only. Therefore, for more thorough testing the problem of fake gold ingots needs to be solved by combining these two methods.
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Sugiyono, Sugiyono, Djemari Mardapi und I. Gusti Putu Suryadarma. „Developing assesment instruments for the sensory acceptability of food products“. Research and Evaluation in Education 3, Nr. 1 (30.08.2017): 92. http://dx.doi.org/10.21831/reid.v3i1.13940.
Annotation:
The study investigated the constructs and characteristics of physiological, psychological, and sensory instruments. The data were collected by means of a questionnaire, physiological instrument, psychological instrument, and sensory instrument. The expert judgment conclusions were calculated by means of Aiken formula; the instrument construct validity was analyzed with confirmatory factor analysis by the goodness-of-fit test at the significance level of 0.05; the reliability estimate by generalizability with a G-study coefficient ≥ 0.7 and an ICC coefficient ≥ 0.7; and the instrument characteristics were analyzed by D-study. The results of the study are as follows: (1) the physiological instrument consisted of nine constructs: four constructs of psychological instrument and five constructs of sensory instrument; (2) three instruments had good face validity, content validity and construct validity, supported by the empirical evidence at p > 0.05; (3) the reliability estimate of the three instruments was good and the reliability estimate was supported by empirical evidence with G coefficients of > 0.7 and ICC coefficients of > 0.7, (4) the three instruments had characteristics that might be appropriate to be used by the university students of culinary program and the vocational high school students of culinary program.
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Wara, Michael. „Instrument Choice, Carbon Emissions, and Information“. Michigan Journal of Environmental & Administrative Law, Nr. 4.2 (2015): 261. http://dx.doi.org/10.36640/mjeal.4.2.instrument.
Annotation:
This Article examines the consequences of a previously unrecognized difference between pollutant cap-and-trade schemes and pollution taxes. Implementation of cap-and-trade relies on a forecast of future emissions, while implementation of a pollution tax does not. Realistic policy designs using either regulatory instrument almost always involve a phase-in over time to avoid economic disruption. Cap-and-trade accomplishes this phase-in via a limit on emissions that falls gradually below the forecast of future pollutant emissions. Emissions taxation accomplishes the same via a gradually increasing levy on pollution. Because of the administrative complexity of establishing an emissions trading market, cap-and-trade programs typically require between three and five years lead time before imposing obligations on emitters. In this Article, I present new evidence showing that forecast error over this timeframe for United States energy- related carbon dioxide emissions from the Department of Energy’s energy model—the model used for policy design by Congress and EPA—is biased and imprecise to such a degree as to make its use impractical. The forecasted emissions are insufficiently accurate to allow for creation of a reliable or predictable market signal to incentivize emission reductions. By contrast, carbon taxes, because they do not depend upon a baseline emissions forecast, create a relatively clear level of policy stringency. This difference matters because policies that end up weaker than intended face low odds for strengthening, while those that end up stronger than intended are likely to be weakened. The political asymmetry combined with actual model forecast errors leads to bias in favor of suboptimal, weak, policies for cap-and-trade. This is a serious concern if, as is usually the case, a cap is set based on political bargaining rather than on an optimal balancing of abatement costs and avoided climate damage. By contrast, the same model bias would lead to more environmentally effective than forecast carbon taxes but without the political consequences created by price volatility, were such programs to be implemented in the United States. Thus, while theory tells us that cap-and-trade and carbon taxes can be equivalent, imperfect information leads to suboptimal environmental performance of emissions trading, relative to carbon taxation policies. Policymakers should weigh these practical, information-related concerns when considering approaches to controlling emissions of greenhouse gases.
34
Smith, S. C., J. D. Lee, W. J. Bloss, G. P. Johnson und D. E. Heard. „Concentrations of OH and HO<sub>2</sub> radicals during NAMBLEX: measurements and steady state analysis“. Atmospheric Chemistry and Physics Discussions 5, Nr. 6 (28.11.2005): 12403–64. http://dx.doi.org/10.5194/acpd-5-12403-2005.
Annotation:
Abstract. OH and HO2 concentrations were measured simultaneously at the Mace Head Atmospheric Research Station in the summer of 2002 during the NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) field campaign. OH was measured by laser-induced fluorescence employing the FAGE (Fluorescence Assay by Gas Expansion) technique, with a mean daytime detection limit of 2.7×105 molecule cm−3 (5 min acquisition period; signal-to-noise ratio = 1). HO2 was detected as OH following its chemical conversion through addition of NO, with a mean detection limit of 4.4×106 molecule cm−3. The diurnal variation of OH was measured on 24 days, and that of HO2 on 17 days. The local solar noon OH concentrations ranged between (3–8)×106 molecule cm−3, with a 24 h mean concentration of 9.1×105 molecule cm−3. The local solar noon HO2 concentrations were (0.9–2.1)×108 molecule cm−3 (3.5–8.2 pptv), with a 24 h mean concentration of 4.2×107 molecule cm−3. HO2 radicals in the range (2–3)×107 molecule cm−3 were observed at night. During NAMBLEX, a comprehensive suite of supporting measurements enabled a detailed study of the behaviour of HOx radicals under primarily clean marine conditions. Case study periods highlight the typical radical levels observed under different conditions. Steady state expressions are used to calculate OH and HO2 concentrations and to evaluate the effect of different free-radical sources and sinks. The diurnally averaged calculated to measured OH ratio was 1.04±0.36, but the ratio displays a distinct diurnal variation, being less than 1 during the early morning and late afternoon/evening, and greater than 1 in the middle of the day. For HO2 there was an overprediction, with the agreement between calculated and measured concentrations improved by including reaction with measured IO and BrO radicals and uptake to aerosols. Increasing the concentration of IO radicals included in the calculations to above that measured by a DOAS instrument with an absorption path located mainly over the ocean, reflecting the domination of the inter-tidal region as an iodine source at Mace Head, led to further improvement. The results are compared with previous measurements at Mace Head, and elsewhere in the remote marine boundary layer.
35
Smith, S. C., J. D. Lee, W. J. Bloss, G. P. Johnson, T. Ingham und D. E. Heard. „Concentrations of OH and HO<sub>2</sub> radicals during NAMBLEX: measurements and steady state analysis“. Atmospheric Chemistry and Physics 6, Nr. 5 (04.05.2006): 1435–53. http://dx.doi.org/10.5194/acp-6-1435-2006.
Annotation:
Abstract. OH and HO2 concentrations were measured simultaneously at the Mace Head Atmospheric Research Station in the summer of 2002 during the NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) field campaign. OH was measured by laser-induced fluorescence employing the FAGE (Fluorescence Assay by Gas Expansion) technique, with a mean daytime detection limit of 2.7×105 molecule cm−3 (5 min acquisition period; signal-to-noise ratio = 1). HO2 was detected as OH following its chemical conversion through addition of NO, with a mean detection limit of 4.4×106 molecule cm−3. The diurnal variation of OH was measured on 24 days, and that of HO2 on 17 days. The local solar noon OH concentrations ranged between (3–8)×106 molecule cm−3, with a 24 h mean concentration of 9.1×105 molecule cm−3. The local solar noon HO2 concentrations were (0.9–2.1)×108 molecule cm−3 (3.5–8.2 pptv), with a 24 h mean concentration of 4.2×107 molecule cm−3 (1.6 pptv). HO2 radicals in the range (2–3)×107 molecule cm−3 were observed at night. During NAMBLEX, a comprehensive suite of supporting measurements enabled a detailed study of the behaviour of HOx radicals under primarily clean marine conditions. Steady state expressions are used to calculate OH and HO2 concentrations and to evaluate the effect of different free-radical sources and sinks. The diurnally averaged calculated to measured OH ratio was 1.04±0.36, but the ratio displays a distinct diurnal variation, being less than 1 during the early morning and late afternoon/evening, and greater than 1 in the middle of the day. For HO2 there was an overprediction, with the agreement between calculated and measured concentrations improved by including reaction with measured IO and BrO radicals and uptake to aerosols. Increasing the concentration of IO radicals included in the calculations to above that measured by a DOAS instrument with an absorption path located mainly over the ocean, reflecting the domination of the inter-tidal region as an iodine source at Mace Head, led to further improvement. The results are compared with previous measurements at Mace Head, and elsewhere in the remote marine boundary layer.
36
Bottorff, Brandon, Michelle M. Lew, Youngjun Woo, Pamela Rickly, Matthew D. Rollings, Benjamin Deming, Daniel C. Anderson et al. „OH, HO2, and RO2 radical chemistry in a rural forest environment: measurements, model comparisons, and evidence of a missing radical sink“. Atmospheric Chemistry and Physics 23, Nr. 18 (15.09.2023): 10287–311. http://dx.doi.org/10.5194/acp-23-10287-2023.
Annotation:
Abstract. The hydroxyl (OH), hydroperoxy (HO2), and organic peroxy (RO2) radicals play important roles in atmospheric chemistry. In the presence of nitrogen oxides (NOx), reactions between OH and volatile organic compounds (VOCs) can initiate a radical propagation cycle that leads to the production of ozone and secondary organic aerosols. Previous measurements of these radicals under low-NOx conditions in forested environments characterized by emissions of biogenic VOCs, including isoprene and monoterpenes, have shown discrepancies with modeled concentrations. During the summer of 2016, OH, HO2, and RO2 radical concentrations were measured as part of the Program for Research on Oxidants: Photochemistry, Emissions, and Transport – Atmospheric Measurements of Oxidants in Summer (PROPHET-AMOS) campaign in a midlatitude deciduous broadleaf forest. Measurements of OH and HO2 were made by laser-induced fluorescence–fluorescence assay by gas expansion (LIF-FAGE) techniques, and total peroxy radical (XO2) mixing ratios were measured by the Ethane CHemical AMPlifier (ECHAMP) instrument. Supporting measurements of photolysis frequencies, VOCs, NOx, O3, and meteorological data were used to constrain a zero-dimensional box model utilizing either the Regional Atmospheric Chemical Mechanism (RACM2) or the Master Chemical Mechanism (MCM). Model simulations tested the influence of HOx regeneration reactions within the isoprene oxidation scheme from the Leuven Isoprene Mechanism (LIM1). On average, the LIM1 models overestimated daytime maximum measurements by approximately 40 % for OH, 65 % for HO2, and more than a factor of 2 for XO2. Modeled XO2 mixing ratios were also significantly higher than measured at night. Addition of RO2 + RO2 accretion reactions for terpene-derived RO2 radicals to the model can partially explain the discrepancy between measurements and modeled peroxy radical concentrations at night but cannot explain the daytime discrepancies when OH reactivity is dominated by isoprene. The models also overestimated measured concentrations of isoprene-derived hydroxyhydroperoxides (ISOPOOH) by a factor of 10 during the daytime, consistent with the model overestimation of peroxy radical concentrations. Constraining the model to the measured concentration of peroxy radicals improves the agreement with the measured ISOPOOH concentrations, suggesting that the measured radical concentrations are more consistent with the measured ISOPOOH concentrations. These results suggest that the models may be missing an important daytime radical sink and could be overestimating the rate of ozone and secondary product formation in this forest.
37
Sugiyono, Sugiyono, Badraningsih Lastariwati, Emy Budiastuti und A. Yudianto. „Development of Authentic Assessment Instruments for Saintifical Learning in Tourism Vocational High Schools“. Jurnal Pendidikan Teknologi dan Kejuruan 24, Nr. 1 (17.04.2018): 52–61. http://dx.doi.org/10.21831/jptk.v24i1.16670.
Annotation:
Teachers of Tourism Vocational High Schools in assessing students’ performance generally use an invalid written test. It does not measure what it was designed to measure. Measurement of performance should use authentic assessments. The objectives of this study were (1) identifying aspects required to develop an instrument, (2) developing authentic assessment instruments on scientific learning of Tourism Vocational High Schools, and (3) developing authentic rubrics of scientific learning. This study was Research and Development applying the 4D model consisting of Define, Design, Developed, and Disseminate. The first year study completed stages of Defining and Designing, while the second year completed stages of Developing and Disseminating. The results of the first year study were the prototype of the instruments and the rubric script. This study generated 3 instrument prototypes, namely attitude instrument (8 items), knowledge instrument (9 items), and skills instrument (18 items), along with the rubrics for each instrument. The three instruments qualify face validity with expert judgment, content validity with Aiken formula, construct validity with goodness-of-fit test, and reliability estimate with Intraclass Correlation Coefficient.
38
Hobart, Jeremy, Stefan Cano, Rachel Baron, Alan Thompson, Steven Schwid, John Zajicek und David Andrich. „Achieving valid patient-reported outcomes measurement: a lesson from fatigue in multiple sclerosis“. Multiple Sclerosis Journal 19, Nr. 13 (10.04.2013): 1773–83. http://dx.doi.org/10.1177/1352458513483378.
Annotation:
Background:The increasing influence of patient-reported outcome (PRO) measurement instruments indicates their scrutiny has never been more crucial. Above all, PRO instruments should be valid: shown to assess what they purport to assess.Objectives:To evaluate a widely used fatigue PRO instrument, highlight key issues in understanding PRO instrument validity, demonstrate limitations of those approaches and justify notable changes in the validation process.Methods:A two-phase evaluation of the 40-item Fatigue Impact scale (FIS): a qualitative evaluation of content and face validity using expert opinion ( n=30) and a modified Delphi technique; a quantitative psychometric evaluation of internal and external construct validity of data from 333 people with multiple sclerosis using traditional and modern methods.Results:Qualitative evaluation did not support content or face validity of the FIS. Expert opinion agreed with the subscale placement of 23 items (58%), and classified all 40 items as being non-specific to fatigue impact. Nevertheless, standard quantitative psychometric evaluations implied, largely, FIS subscales were reliable and valid.Conclusions:Standard quantitative ‘psychometric’ evaluations of PRO instrument validity can be misleading. Evaluation of existing PRO instruments requires both qualitative and statistical methods. Development of new PRO instruments requires stronger conceptual underpinning, clearer definitions of the substantive variables for measurement and hypothesis-testing experimental designs.
39
MORSE, PAIGE MARIE. „INSTRUMENT MAKERS FACE 2000 PROBLEM“. Chemical & Engineering News 75, Nr. 39 (29.09.1997): 13–15. http://dx.doi.org/10.1021/cen-v075n039.p013.
40
Isnaintri, Endah, Hepsi Nindiasari und Sukirwan -. „Development of Numeracy Literacy Instrument in the Context of Local Wisdom in Pandeglang at the Madrasah Tsanawiyah“. Phenomenon : Jurnal Pendidikan MIPA 13, Nr. 1 (27.09.2023): 111–31. http://dx.doi.org/10.21580/phen.2023.13.1.16783.
Annotation:
Literasi numerasi sebagai kemampuan memahami dan menggunakan konsep matematika dalam kehidupan sehari-hari, telah diakui sebagai salah satu kompetensi penting dalam era ini. Dalam konteks pendidikan formal, banyak siswa menghadapi tantangan dalam mengembangkan kemampuan literasi numerasinya, sehingga diperlukan adanya pengembangan instrumen yang berpotensi memberikan kontribusi penting yang kontekstual dan memperkaya pengalaman belajar literasi numerasi siswa. Tujuan dari penelitian ini adalah untuk menghasilkan produk pengembangan instrumen literasi numerasi berbasis kearifan lokal di Kabupaten Pandeglang bagi siswa kelas IX MTs dengan elemen materi pola bilangan, peluang, bangun ruang sisi datar dan aljabar. Penelitian ini termasuk dalam kategori penelitian pengembangan yang mengacu pada model penelitian formatif Tessmer. Subjek hingga di prototipe akhir pada penelitian ini adalah 38 orang siswa kelas IX di MTsN 2 Pandeglang. Instrumen yang digunakan untuk pengumpulan data adalah lembar validasi, pedoman wawancara dan soal tes instrumen literasi numerasi berbasis kearifan lokal Kabupaten Pandeglang. Metode analisis data yang digunakan adalah dengan mengevaluasi kesesuaian, kualitas dan akurasi instrumen yang dikembangkan melalui ahli dan analisis statistik. Hasil penelitian menunjukkan bahwa bahwa pertanyaan-pertanyaan yang dikembangkan memiliki tingkat validitas yang baik, meskipun masih memerlukan perbaikan berdasarkan saran dan umpan balik yang diberikan oleh validator, selanjutnya untuk kualitas tes yang dikembangkan diantaranya indeks kesukaran keempat soal berada pada kategori sedang, daya pembeda soal dapat diterima dengan baik dan valid serta memiliki realibilitas yang tinggi (0,93). Berdasarkan hasil penelitian tersebut, maka dapat disimpulkan instrumen literasi numerasi berbasis kearifan lokal di Kabupaten Pandeglang yang dikembangkan sudah layak untuk digunakan.Numeracy literacy, as the ability to understand and apply mathematical concepts in everyday life, has been recognized as a crucial competence in this era. In the context of formal education, many students face challenges in developing their numeracy literacy skills, thus necessitating the development of instruments that have the potential to contribute significantly by being contextual and enriching students' numeracy literacy learning experiences. The aim of this research is to produce a development product of a numeracy literacy instrument based on local wisdom in Pandeglang Regency for grade IX students at Madrasah Tsanawiyah, focusing on number patterns, probability, two-dimensional shapes, and algebraic elements. This research falls under the category of development research, referring to Tessmer's formative research model. The subjects up to the final prototype in this research are 38 students from class IX at MTsN 2 Pandeglang. The instruments used for data collection were validation sheets, interview guidelines, and a numeracy literacy test instrument based on local wisdom in Pandeglang Regency. The data analysis method used involved evaluating the suitability, quality, and accuracy of the developed instrument through expert judgment and statistical analysis. The research results indicate that the developed questions have a good level of validity, although they still require improvement based on the suggestions and feedback provided by the validators. Furthermore, in terms of the quality of the developed test, the difficulty index of the four items falls under the moderate category, the item discrimination is acceptable and valid, and the test exhibits high reliability (0.93). Based on these research results, it can be concluded that the developed numeracy literacy instrument based on local wisdom in Pandeglang Regency is suitable for use.
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Darodjat, Darodjat, und Darmiyati Zuchdi. „MODEL EVALUASI PEMBELAJARAN AKIDAH DAN AKHLAK DI MADRASAH TSANAWIYAH (MTs)“. Jurnal Penelitian dan Evaluasi Pendidikan 20, Nr. 1 (21.06.2016): 11–26. http://dx.doi.org/10.21831/pep.v20i1.7517.
Annotation:
Penelitian ini bertujuan: (1) menghasilkan model evaluasi pembelajaran Akidah dan Akhlak di MTs, (2) menghasilkan instrumen evaluasi yang memiliki reliabilitas dan validitas, (3) mengetahui kelayakan Model Logik Evaluasi Pembelajaran Akidah dan Akhlak (MLEPAA). Penelitian ini menggunakan model Borg dan Gall. Teknik penentuan subjek penelitian untuk unit analisis siswa dengan simple random sampling sejumlah 330 siswa dari tiga MTsN di Kabupaten Banyumas, 3 orang Guru Akidah dan Akhlak, dan 3 orang Kepala MTsN. Teknik pengumpulan data yang digunakan adalah: kuesioner, tes, dan penilaian antarteman. Validitas instrumen meliputi face validity dan content validity, dianalisis dengan expert judgment, validasi konstruk dianalisis dengan konfirmatori faktor analisis (CFA), sedangkan instrumen tes dianalisis dengan bantuan program ITEMAN. Estimasi reliabilitas instrumen menggunakan formula Alpha Cronbach dan reliabilitas interrater menggunakan Cohens’ Kappa dengan program SPSS for Window 16.0. Simpulan penelitian: pertama, model evaluasi yang dihasilkan (MLEPAA) mencakup empat komponen utama, yaitu: input, activities, output, dan outcomes. Kedua, hasil analisis dengan CFA diperoleh indeks: (1) ρ-value > 0,05; (2) Root Mean Square Error of Approximation (RMSEA) < 0,8; dan (3) Goodness of Fit Index (GFI) < 0,90. Ketiga, instrumen yang dikembangkan memenuhi validitas dan reliabilitas yang baik. Keempat, berdasarkan penilaian user, MLEPAA layak digunakan.Kata kunci: model logik, evaluasi pembelajaran Akidah dan Akhlak, MTs AKIDAH AND AKHLAK LEARNING EVALUATION MODEL IN THE MADRASAH TSANAWIYAHAbstractThis study aimed to: (1) develop an evaluation model on Akidah Akhlak subject of Madrasah Tsanawiyah (MTs), (2) generate some instruments of evaluation which have validity and reliability, (3) know a worthiness model evaluation of Akidah Akhlak subject in implementation. This study was a research and development of Borg and Gall model. The subjects were determined by simple random sampling which consisted of 330 students, 3 teachers, and 3 principles in three public Madrasah Tsanawiyah in Banyumas regencies. The data gathering techniques used were questionnaires, tests, and peer assessment. The instrument validation process was carried out in terms of the face validity and content validity through expert judgment, the construct validity through the confirmatory factor analysis (CFA), and test by using ITEMAN program. The instrument reliability was analyzed using the Cronbach's Alpha technique, and inter-rater reliability was assessed using SPSS for Window 16.0. with Cohens' Kappa technique. The results of the research were as follows: firstly, the components of MLEPAA evaluation model consisted of input, activities, output, and outcomes. Secondly, the results of CFA analysis were as follows: (a) Chi-Square, p > 0.05, the acquired value is= 553.72, (b) Goodness of Fit Indices (GFI) must be 0 to 1, the acquired value is = 0.892, and (c) Root Mean Square Error of Approximation (RMSEA) < 0.05, the acquired value is = 0.000. Thirdly, instrument utilized in research had fulfilled reliability and validity. Fourth, based on assessment from user, the MLEPAA was suitable for using in MTs.Keywords: logic model, Akidah Akhlak learning evaluation, MTs
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Jumini, Jumini. „Development of Teacher Innovativeness Instruments in the Face of Educational Innovation“. Ideguru: Jurnal Karya Ilmiah Guru 8, Nr. 2 (07.02.2023): 247–56. http://dx.doi.org/10.51169/ideguru.v8i2.523.
Annotation:
Teachers had different responses in facing top-down educational innovation. Hence, policymakers must create a map to implement a more effective strategy for innovation success. This study aimed to develop a teacher innovativeness instrument through theoretical development methods. Based on the synthesis of the theoretical research, five indicators were obtained and expanded into 25 four-scale Likert statements. Content validity was proven by eight experts and then quantified by the Aiken formula, resulting in a coefficient of 0.84 or a high category. The trial was conducted on 85 teachers from various levels and regions in Indonesia to get empirical data. Construct validity was proven by Exploratory Factor Analysis (EFA) and resulted in four factors with Eigenvalue > 1 which were factors that underlie the level of teachers innovativeness, namely volition, coverage novelty, structural obedience, and environmental communication. The Principal Component Analysis (PCA) extraction and Varimax rotation proved that all items had good criteria because their factor loading was> 0.4, proving the construct validity. The instrument reliability estimated by the Cronbach Alpha formula resulted in a reliability coefficient of 0.954, or a very high category. Thus, this instrument qualifies as a good instrument and could be utilized singly or with the addition of supporting instruments.
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Mentula, Arttu, Mikko Uimonen, Andrew Lindford, Sinikka Suominen, Jussi P. Repo und Tuija Ylä-Kotola. „Translation and validation of a Finnish version of the Facial Clinimetric Evaluation (FaCE) Scale“. Journal of Plastic Surgery and Hand Surgery 58 (14.06.2023): 33–39. http://dx.doi.org/10.2340/jphs.v58.6533.
Annotation:
Background: The Facial Clinimetric Evaluation (FaCE) scale is a patient-reported health status instrument developed for assessing the health-related quality of life (HRQoL) in patients with facial nerve paralysis. The aim of this study was to translate and validate the FaCE scale for the Finnish-speaking population.Methods: The FaCE scale was translated according to international guidelines. Sixty patients in an outpatient clinic prospectively completed the translated FaCE scale and generic HRQoL instrument (15D). The objective facial paralysis grading was made using the Sunnybrook and House-Brackmann scales. Repeated FaCE and 15D instruments were mailed to patients 2 weeks later. Total scores of the FaCE instrument and subscales were calculated, and floor and ceiling effects were examined. Exploratory factor analysis was made. Internal consistency, reliability, and repeatability were assessed. Convergence with 15D instrument, Sunnybrook, and House-Brackmann scales was examined.Results: The total internal consistency of the FaCE scale was high (Cronbach’s alpha 0.83). There were no statistically significant differences found between mean scores of the subscales in test-retest analysis (p > 0.05). Intra-class correlations coefficients were high, ranging between 0.78 and 0.92, and the correlations were statistically significant (p < 0.001). There were statistically significant correlations observed between the FaCE scale and the 15D, Sunnybrook, and House-Brackmann scores. Conclusion: The FaCE scale was successfully translated and validated in Finnish with good validity and reliability. We also demonstrated statistically significant correlations between the generic HRQoL15D instrument and both the Sunnybrook and House-Brackmann physician-based grading scales. The FaCE scale is now ready for use in Finnish facial paralysis patients.
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Shah, Punit, Anne Gaule, Sophie Sowden, Geoffrey Bird und Richard Cook. „The 20-item prosopagnosia index (PI20): a self-report instrument for identifying developmental prosopagnosia“. Royal Society Open Science 2, Nr. 6 (Juni 2015): 140343. http://dx.doi.org/10.1098/rsos.140343.
Annotation:
Self-report plays a key role in the identification of developmental prosopagnosia (DP), providing complementary evidence to computer-based tests of face recognition ability, aiding interpretation of scores. However, the lack of standardized self-report instruments has contributed to heterogeneous reporting standards for self-report evidence in DP research. The lack of standardization prevents comparison across samples and limits investigation of the relationship between objective tests of face processing and self-report measures. To address these issues, this paper introduces the PI20; a 20-item self-report measure for quantifying prosopagnosic traits. The new instrument successfully distinguishes suspected prosopagnosics from typically developed adults. Strong correlations were also observed between PI20 scores and performance on objective tests of familiar and unfamiliar face recognition ability, confirming that people have the necessary insight into their own face recognition ability required by a self-report instrument. Importantly, PI20 scores did not correlate with recognition of non-face objects, indicating that the instrument measures face recognition, and not a general perceptual impairment. These results suggest that the PI20 can play a valuable role in identifying DP. A freely available self-report instrument will permit more effective description of self-report diagnostic evidence, thereby facilitating greater comparison of prosopagnosic samples, and more reliable classification.
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Purwandari, Bernadetta Ersi, S. Supriyatin und Rizhal Hendi Ristanto. „The Development of creative thinking and problem-solving skill instrument of plant growth in high school“. Biosfer 15, Nr. 2 (27.10.2022): 302–12. http://dx.doi.org/10.21009/biosferjpb.26535.
Annotation:
Creative thinking and problem-solving skills are needed to face the 21st century of 4.0 industrial revolution. Improving the quality of human resources to face the era of the industrial revolution 4.0 must be developed in education. Biology as one of the subjects in high school, especially in plant growth and development matters, allows to develop creative thinking and problem-solving skills because in it there is a student project on plant growth and development. It takes the right instrument to measure the achievement of creative thinking skills and problem solving skills in Biology learning, especially on the topic of plant growth and development. Two instrument questions have been developed, namely the instrument for creative thinking skills and problem solving skills. The development of this instrument was carried out through the stages of Research and Development Borg and Gall 1983. It produced 10 essay questions measuring creative thinking skills and 8 questions measuring problem solving skills. The question gets very decent expert validation criteria with a score of 91% - 97%. The results of the validation test based on the Pearson Product Moment formula show that the ten items of creative thinking skills are valid with a significance level of 0.05. The reliability test of the two instruments has a result of 0.82, above Cronbach's Alpha coefficient, which is reliable for creative thinking skills instruments. Meanwhile, the instrument of problem solving skills showed very reliable results with Cronbach's Alpha value of 0.95.
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Rasmawan, Rahmat. „PENGEMBANGAN INSTRUMEN MICROTEACHING BERDASARKAN PEMBELAJARAN ABAD KE-21“. Edukasi: Jurnal Pendidikan 19, Nr. 1 (30.04.2021): 31. http://dx.doi.org/10.31571/edukasi.v19i1.2348.
Annotation:
<p><strong>Abstrak </strong></p><p>Penelitian bertujuan untuk mengembangkan instrumen<em> Microteaching</em> berkesesuaian dengan keterampilan abad ke-21 yang valid dan reliabel sehingga layak digunakan. Bentuk penelitian yang digunakan adalah <em>Research and Development</em> (R&D) dengan mengikuti alur pengembangan ADDIE (<em>Analyze, Design, Develop, Implement</em><em>, and Evaluate</em>). Subjek penelitian yaitu 30 dosen dan 70 mahasiswa. Validitas instrumen menggunakan <em>Content Validity Index</em> dan <em>Face Validity</em> yang menunjukkan bahwa instrumen dinyatakan valid. Reliabilitas instrumen menggunakan koefisien interkelas korelasi pada merancang dan melaksanakan pembelajaran dan diperoleh nilai koefisien interkelas korelasi dengan kategori sangat reliabel. Berdasarkan hasil penelitian disimpulkan bahwa instrumen yang dikembangkan valid dan layak digunakan untuk mengukur keterampilan peserta <em>Microteaching</em> dalam merancang dan melaksanakan proses pembelajaran abad ke-21.</p><p> </p><p><strong><em>Abstract</em></strong></p><p><em>The aim of this research was to develop Microteaching assessment instrument that are compatible with the 21<sup>st</sup>-century skill that is valid and reliable so that appropriate to use. The design of this research was Research and Development (R&D) which refers to ADDIE </em><strong>(</strong><em>Analyze, Design, Develop, Implement, and Evaluate</em><strong>)</strong><em>. The research subjects were 30 lecturers and 70 students. The validity of the instrument using the Content Validity Index and Face Validity showed that the instrument was valid. Instrument reliability was using the intraclass correlation coefficient in designing and implementing the learning process obtained result as very reliable. It can be concluded that the developed instrument was valid to be used in assessing participant’s Microteaching skills in designing and implementing the 21<sup>st</sup>-century learning process.</em></p>
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Uddhav, Pravin. „Origin, Development, Classification and Historicity of Ancient Percussion Instruments“. Journal of Fine Arts Campus 3, Nr. 1 (31.12.2021): 23–30. http://dx.doi.org/10.3126/jfac.v3i1.42492.
Annotation:
Music has a prominent place in fine arts. This art has been considered as a means of spiritual satisfaction. Apart from material excellence and fame, music has an important place in all the different ways of devotion or worship in India. There have been two main types of worship since ancient times as Vedic and Tantric. The Avanaddha instrument maintains the rhythm in singing, dancing and instrument-playing. Different opinions, legends, stories, statements of the origin of instruments are prevalent but differences are found in them. The article describes the method and material of ancient Avanaddha instruments on the basis of various texts. Thereafter, under the classification of instruments opinion of various scholars on Tat, Ghan, Sushir, and Avanaddha instruments and the various classifications have been mentioned and discussed in detail. The origin and association of ancient Avanaddha instruments is described with reference to various deities. The article lists ancient and medieval Avanaddha instruments. The use of instruments by gods, demons, human beings in various ceremonies, events, worship lessons, war sites, on auspicious occasions is evidently shown with their importance, use and antiquity. A musical instrument with serious sound was used at warrior sites and Yagna. From different sources like; ancient texts & other facts, it can be concluded that since ancient times eastern musical instruments have been used in music right from the beginning of the era. Avanaddha vadya were invented to support the singer, accompany his song, engage his mind more, cover up his faults, and measure his singing activity in Taal.
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Oliver La Rosa, Jaime E. „Theremin in the Press: Instrument remediation and code-instrument transduction“. Organised Sound 23, Nr. 3 (Dezember 2018): 256–69. http://dx.doi.org/10.1017/s135577181800016x.
Annotation:
This article shows how the theremin as a new musical medium enacted a double logic throughout its century-old techno-cultural life. On the one hand, in an attempt to be a ‘better’ instrument, the theremin imitated or remediated traditional musical instruments and in this way affirmed the musical values these instruments materialised; simultaneously, by being a new and different medium, with unprecedented flexibility for designing sound and human–machine interaction, it eroded and challenged these same values and gradually enacted change. On the other hand, the theremin inadvertently inaugurated a practice of musical instrument circulation using electronics schematics that allowed for the instrument’s reproduction, starting with the publication of schematics and tutorials in amateur electronics magazines and which can be seen as a predecessor to today’s circulation of open source code. This circulation practice, which I call instrument-code transduction, emerged from and was amplified by the fame the theremin obtained using its touchless interface to imitate or remediate traditional musical instruments, and in turn, this circulation practice has kept the instrument alive throughout the decades. Thus remediation and code-instrument transduction are not just mutually dependent, but are in fact, two interdependent processes of the same media phenomenon. Drawing from early reactions to the theremin documented in the press, from new media theory, and from publications in amateur electronics, this article attempts to use episodes from the history of the theremin to understand the early and profound changes that electric technologies brought to the concept of musical instruments at large.
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Semedo, Deisa Salyse dos Reis Cabral, Marlene Teda Pelzer, Diva Elci dos Reis Cabral, Mara Regina Santos da Silva und Ariana Sofia Barradas da Silva. „Adaptação transcultural e validação do instrumento WHOQOL-BREF para idosos de Cabo Verde/África“. Revista Recien - Revista Científica de Enfermagem 13, Nr. 41 (26.03.2023): 378–89. http://dx.doi.org/10.24276/rrecien2023.13.41.378-389.
Annotation:
Adaptar culturalmente e validar o instrumento The World Health Organization Quality of Life (WHOQOL-BREF) para idosos cabo-verdianos. Estudo transversal, realizado com 405 idosos do arquipélago de Cabo Verde. Realizou-se a adaptação transcultural do instrumento WHOQOL-BREF, segundo recomendações internacionais e sua validação para utilização no contexto Cabo-verdiano, através de análise fatorial e do alfa de Cronbach. A validade de face e conteúdo do instrumento foi considerada satisfatória mediante avaliação de comitê de especialistas e realização do pré-teste, a partir da análise fatorial, foram identificados quatro constructos: domínio I-Físico, domínio II- Ambiente, domínio III- Relações sociais e domínio IV-Sexualidade. O instrumento apresentou consistência interna satisfatória, com valores de alfa de Cronbach entre 0,67 a 0,71. Conclui-se que o WHOQOL-BREF - versão cabo-verdiana é um instrumento válido e fidedigno para ser utilizado na avaliação da qualidade de vida dos idosos cabo-verdianos.
Descritores: Qualidade de Vida, Enfermagem, Saúde do Idoso, Estudos de Validação.
Cross-cultural adaptation and validation of the WHOQOL-BREF instrument for elderly people in Cape Verde/Africa
Abstract: To culturally adapt and validate The World Health Organization Quality of Life (WHOQOL-BREF) instrument for Cape Verdean elderly. Cross-sectional study, conducted with 405 elderly people from the archipelago of Cape Verde. The WHOQOL-BREF instrument was cross-culturally adapted according to international recommendations and validated for use in the Cape Verdean context through factor analysis and Cronbach's alpha. The face and content validity of the instrument was considered satisfactory after evaluation by an expert committee and pre-test. From the factor analysis, four constructs were identified: domain I-Physical, domain II-Environment, domain III-Social Relationships and domain IV-Sexuality. The instrument showed satisfactory internal consistency, with Cronbach's alpha values between 0.67 and 0.71. It is concluded that the WHOQOL-BREF - Cape Verdean version is a valid and reliable instrument to be used in the assessment of the quality of life of elderly Cape Verdeans.
Descriptors: Quality of Life, Nursing, Health of the Elderly, Validation Studies.
Adaptación y validación transcultural del instrumento WHOQOL-BREF para personas mayores en Cabo Verde/África
Resumen: Adaptar culturalmente y validar el instrumento The World Health Organization Quality of Life (WHOQOL-BREF) para ancianos caboverdianos. Estudio transversal, realizado con 405 ancianos del archipiélago de Cabo Verde. Se realizó la adaptación transcultural del instrumento WHOQOL-BREF, según recomendaciones internacionales y su validación para su uso en el contexto caboverdiano, mediante análisis factorial y alfa de Cronbach. La validez de apariencia y contenido del instrumento fue considerada satisfactoria después de la evaluación por un comité de especialistas y el pre-test.Con base en el análisis factorial, se identificaron cuatro constructos: dominio I-Físico, dominio II-Ambiente, dominio III- Relaciones sociales y dominio IV-Sexualidad. El instrumento mostró consistencia interna satisfactoria, con valores de alfa de Cronbach entre 0,67 y 0,71. Se concluye que el WHOQOL-BREF - versión caboverdiana es un instrumento válido y fiable para ser utilizado en la evaluación de la calidad de vida de los ancianos caboverdianos.
Descriptores: Calidad de Vida, Enfermería, Salud de los Ancianos, Estudios de Validación.
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Suwanto und Wiwik Lestari. „How to Assess Digital Literacy Skills of Elementary School Students?“ Eduscape : Journal of Education Insight 2, Nr. 1 (10.01.2024): 11–24. http://dx.doi.org/10.61978/eduscape.v2i1.108.
Annotation:
Students need digital literacy skills to face the 21st century, so teachers must monitor the development of their digital literacy skills. Therefore, instruments are needed to monitor digital literacy skills, but the instruments currently available have not taken into account the psychological, cognitive, and psychomotor development of elementary school children, even though they have limitations in accessing digital devices and limited vocabulary. These problems prompted the need for instrument development using the modified Tiagarajan 4-D development model, Difine, Design, and Development. Instrument development criteria must meet the validity and practicality of the instrument. The instrument was prepared using the Google Form platform, consisting of 13 statements in the form of a Likert questionnaire and 22 statements in the form of an essay test. Qualitative data were analyzed by data collection, data reduction, data presentation, and data verification, while descriptive statistics and item analysis analyzed quantitative data. The instrument design was validated by five validators with a validation level of 3.4, which was declared valid, although the instrument had to be revised. Then the instrument trials were carried out and the quality of the instruments was obtained with a validity level of 19 questions declared valid, 3 quite valid, and 3 very valid, while the Reliability Level was 0.885 for the questionnaire and 0.871 for the test instrument. At the same time, the level of practicality of the instrument was obtained from the teacher's response to the instrument at 76.1 or practical. Even though it meets practical, valid, and effective criteria, apart from having to present it through digital devices, attention needs to be paid to the ability to use symbols and tools and at a minimum must fulfill information skills, digital tools usage, and digital transformation.