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Kale, Uma, i Edward Voigtman. "Gated Integration of Transient Signals in 1/f Noise". Applied Spectroscopy 46, nr 11 (listopad 1992): 1636–43. http://dx.doi.org/10.1366/0003702924926916.
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The Mueller optical calculus is used to model common spectrometric experimental schemes. The effects of source and preamplifier noise on the precision of the measurement are investigated, and the effect of gate width variation for gated integration of Gaussian signal peaks in the presence of white or 1/ f type noise is evaluated. The results indicate that, for integration of a transient absorbance signal, the choice of gate width depends upon the type of noise, but not its source. For a transmittance (or emission) type of experiment, both the type and the source of the noise determine the gate width to be used for integration of the signal.
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Kawahara, Toshio, Satarou Yamaguchi, Yasuhide Ohno, Kenzo Maehashi, Kazuhiko Matsumoto, Shin Mizutani i Kenji Itaka. "Diameter dependence of 1/f noise in carbon nanotube field effect transistors using noise spectroscopy". Applied Surface Science 267 (luty 2013): 101–5. http://dx.doi.org/10.1016/j.apsusc.2012.08.003.
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Achtenberg, Krzysztof, Janusz Mikołajczyk, Zbigniew Bielecki i Jacek Wojtas. "Cross-correlation method for noise measurements of photodetectors used for laser absorption spectroscopy". Bulletin of the Military University of Technology 69, nr 4 (31.12.2020): 73–83. http://dx.doi.org/10.5604/01.3001.0015.3826.
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The paper presents noise measurements of low-resistance photon detectors with a specially developed system. These measurements are significant for many applications. This issue is particularly critical for laser absorption spectroscopy systems to detect trace amounts of gases. In these systems, the detection limit is determined by noise origins, e.g., light source, background, and detector noise and its readout electronics. The use of some specially designed components of the system (low-noise - 3.6 × 10<sub>-19</sub> V<sub>2</sub>/Hz for f >1 kHz) cross-correlation signal processing provides to obtain a measuring floor noise below 10<sub>-18</sub> V<sub>2</sub>/Hz for f > 10 Hz and below 10<sub>-19</sub> V<sub>2</sub>/Hz for f > 1 kHz after ten minutes’ analysis. Measurements of some reference resistors have verified the system’s performance. Finally, the system was also applied to determine the spectral noise density of the II -Type SuperLattice photodetector made of InAs / InAsSb.
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Kaku, K., A. T. Williams, B. G. Mendis i C. Groves. "Examining charge transport networks in organic bulk heterojunction photovoltaic diodes using 1/f noise spectroscopy". Journal of Materials Chemistry C 3, nr 23 (2015): 6077–85. http://dx.doi.org/10.1039/c5tc00348b.
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In this article we present 1/f noise spectroscopy measurements relating to charge transport networks in poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) space-charge limited diode (SCLD) and organic photovoltaic (OPV) devices.
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Monnig, Curtis A., i Gary M. Hieftje. "An Investigation of Noise Amplitude Spectra Produced by a Direct-Current Plasma". Applied Spectroscopy 43, nr 5 (lipiec 1989): 742–46. http://dx.doi.org/10.1366/0003702894202283.
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Noise amplitude spectra for direct-current plasma atomic emission spectrometry (DCP-AES) were acquired. Flicker (1/ f) noise dominates the signal at low frequencies, and white noise prevails at higher frequencies. Broad-band audio-frequency (af) noise was observed in the plasma continuum emission when the nebulizer gas was directed into the discharge. By increasing the electrode-gas flows, it was possible to narrow the frequency range and increase the amplitude of this af noise. The introduction of an easily ionized element into the plasma had little effect on the noise characteristics of the source.
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Stadler, Adam, i Andrzej Dziedzic. "Virtual instruments in low-frequency noise spectroscopy experiments". Facta universitatis - series: Electronics and Energetics 28, nr 1 (2015): 17–28. http://dx.doi.org/10.2298/fuee1501017s.
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Low-frequency noise spectroscopy (LFNS) is an experimental technique to study noise spectra, typically below 10 kHz, as a function of temperature. Results of LFNS may be presented as the ?so-called? noise maps, giving a detailed insight into fluctuating phenomena in electronic devices and materials. The authors show the usefulness of virtual instrument concept in developing and controlling the measurement setup for LFNS experiments. An example of a noise map obtained for polymer thick-film resistors (PTFRs), made of commercial compositions, for temperature range 77 K - 300 K has been shown. The experiments proved that 1/f noise caused by resistance fluctuations is the dominant noise component in the studied samples. However, the obtained noise map revealed also thermally activated noise sources. Furthermore, parameters describing noise properties of resistive materials and components have been introduced and calculated using data from LFNS. The results of the work may be useful for comparison of noise properties of different resistive materials, giving also directions for improvement of thick-film technology in order to manufacture reliable, low-noise and stable PTFRs.
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Lebedev, Alexander A., Vitalii V. Kozlovski, Leonid Fursin, Anatoly M. Strel'chuk, Mikhail E. Levinshtein, Pavel A. Ivanov i Alexander V. Zubov. "Impact of Proton Irradiation on Power 4H-SiC MOSFETs". Materials Science Forum 1004 (lipiec 2020): 1074–80. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.1074.
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Impact of 15 MeV proton irradiation on electrical characteristics and low frequency noise has been studied in high-power vertical 4H-SiC MOSFETs of 1.2 kV-class at doses 1012 £ F £ 1014 cm-2. The maximum value of the field-effect mobility µFЕ depends weakly on F up to F = 2×1013 cm-2. At F = 4×1013 cm-2, the character of the µFЕ(Vg) dependence changes radically. The maximum µFЕ decreases approximately threefold. The dose Fcr corresponding to the complete degradation of the device is about 1014 cm-2. It can be estimated as Fcr» he/n0, where he is the electron removal rate and n0 is the initial electron concentration in the drift layer. In the entire frequency range of analysis f, gate voltages, and drain-source biases, the frequency dependence of the current spectral noise density SI(f) follows the law SI ~ 1/f. From the data of noise spectroscopy, the density of traps in the gate oxide Ntv has been estimated. In non-irradiated structures, Ntv » 5.4×1018 cm-3eV-1. At Ф = 6×1013 cm-2, the Ntv value increases to Ntv » 7.2×1019cm-3eV-1. The non-monotonic behavior of the output current Id and the level of low frequency noise on dose F has been demonstrated.
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Stadler, Adam Witold, Zbigniew Zawiślak, Andrzej Dziedzic i Damian Nowak. "NOISE SPECTROSCOPY OF RESISTIVE COMPONENTS AT ELEVATED TEMPERATURE". Metrology and Measurement Systems 21, nr 1 (1.03.2014): 15–26. http://dx.doi.org/10.2478/mms-2014-0002.
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Abstract Studies of electrical properties, including noise properties, of thick-film resistors prepared from various resistive and conductive materials on LTCC substrates have been described. Experiments have been carried out in the temperature range from 300 K up to 650 K using two methods, i.e. measuring (i) spectra of voltage fluctuations observed on the studied samples and (ii) the current noise index by a standard meter, both at constant temperature and during a temperature sweep with a slow rate. The 1/f noise component caused by resistance fluctuations occurred to be dominant in the entire range of temperature. The dependence of the noise intensity on temperature revealed that a temperature change from 300 K to 650 K causes a rise in magnitude of the noise intensity approximately one order of magnitude. Using the experimental data, the parameters describing noise properties of the used materials have been calculated and compared to the properties of other previously studied thick-film materials.
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Holmberg, Måns, i Nikku Madhusudhan. "Exoplanet spectroscopy with JWST NIRISS: diagnostics and case studies". Monthly Notices of the Royal Astronomical Society 524, nr 1 (4.07.2023): 377–402. http://dx.doi.org/10.1093/mnras/stad1580.
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ABSTRACT The JWST is ushering in a new era in remote sensing of exoplanetary atmospheres. Atmospheric retrievals of exoplanets can be highly sensitive to high-precision JWST data. It is, therefore, imperative to characterize the instruments and noise sources using early observations to enable robust characterization of exoplanetary atmospheres using JWST-quality spectra. This work is a step in that direction, focusing on the Near Infrared Imager and Slitless Spectrograph (NIRISS) Single Object Slitless Spectroscopy (SOSS) instrument mode, with a wavelength coverage of 0.6–2.8 $\mu$m and R ∼ 700. Using a custom-built pipeline, JExoRES, we investigate key diagnostics of NIRISS SOSS with observations of two giant exoplanets, WASP-39 b and WASP-96 b, as case studies. We conduct a detailed evaluation of the different aspects of the data reduction and analysis, including sources of contamination, 1/f noise, and system properties such as limb darkening. The slitless nature of NIRISS SOSS makes it susceptible to contamination due to background sources. We present a method to model and correct for dispersed field stars that can significantly improve the accuracy of the observed spectra. In doing so, we also report an empirically determined throughput function for the instrument. We find significant correlated noise in the derived spectra, which may be attributed to 1/f noise, and discuss its implications for spectral binning. We quantify the covariance matrix that would enable the consideration of correlated noise in atmospheric retrievals. Finally, we conduct a comparative assessment of NIRISS SOSS spectra of WASP-39 b reported using different pipelines and highlight important lessons for exoplanet spectroscopy with JWST NIRISS.
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Busch, Kenneth W., Marianna A. Busch, Renaud Mercier Ythier i Arvie J. Kuehn. "Design Parameters for an Optimized Flame/Furnace Infrared Emission (FIRE) Radiometer". Applied Spectroscopy 47, nr 12 (grudzień 1993): 2072–80. http://dx.doi.org/10.1366/0003702934066433.
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Several design aspects of an optimized flame/furnace infrared emission (FIRE) radiometer are discussed. For a source in thermal equilibrium, the optimum excitation temperature for CO2 is predicted to be 2500 K, based on the stability of the molecule and the population of excited states as functions of temperature. The influence of spectral bandpass on the magnitude of flame background was studied for several wavelengths within the profile of the 4.4-µm emission band of CO2. For the dispersive FIRE radiometer used in this study, the system was found to be detectornoise limited over the range of spectral bandwidths accessible by the instrument (0.01–0.08 µm). When a hydrogen/air flame was used as the excitation source, the maximum signal-to-background ratio was obtained at 4.40 µm with a spectral bandpass of 0.08 µm. For this same experimental arrangement, a mathematical model was used to predict that the maximum signal-to-noise ratio would occur at 4.40 µm with a spectral bandpass of about 0.25 µm. The influence of chopping frequency on detector noise was determined for two different types of wavelength isolation. When a room-temperature bandpass filter was employed, a modulation frequency of 600–1000 Hz was satisfactory for avoiding 1/ f noise from the PbSe detector. However, when a monochromator was employed, chopping frequencies beyond 1000 Hz produced some additional reduction in 1/ f noise. The specific detectivity for the PbSe detector (6.2 × 108 cm Hz0.5 W−1), calculated from the measured noise at a modulation frequency of 600 Hz, is in good agreement with values reported in the literature for 4.40 µm under the same experimental conditions.
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Mu, Ye, Tianli Hu, He Gong, Ruiwen Ni i Shijun Li. "A Trace C2H2 Sensor Based on an Absorption Spectrum Technique Using a Mid-Infrared Interband Cascade Laser". Micromachines 9, nr 10 (19.10.2018): 530. http://dx.doi.org/10.3390/mi9100530.
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In this study, tunable diode laser absorption spectroscopy (TDLAS) combined with wavelength modulation spectroscopy (WMS) was used to develop a trace C2H2 sensor based on the principle of gas absorption spectroscopy. The core of this sensor is an interband cascade laser that releases wavelength locks to the best absorption line of C2H2 at 3305 cm−1 (3026 nm) using a driving current and a working temperature control. As the detected result was influenced by 1/f noise caused by the laser or external environmental factors, the TDLAS-WMS technology was used to suppress the 1/f noise effectively, to obtain a better minimum detection limit (MDL) performance. The experimental results using C2H2 gas with five different concentrations show a good linear relationship between the peak value of the second harmonic signal and the gas concentration, with a linearity of 0.9987 and detection accuracy of 0.4%. In total, 1 ppmv of C2H2 gas sample was used for a 2 h observation experiment. The data show that the MDL is low as 1 ppbv at an integration time of 63 s. In addition, the sensor can be realized by changing the wavelength of the laser to detect a variety of gases, which shows the flexibility and practicability of the proposed sensor.
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Shin, Wonjun, Kyung Kyu Min, Jong-Ho Bae, Jiyong Yim, Dongseok Kwon, Yeonwoo Kim, Junsu Yu i in. "Comprehensive and accurate analysis of the working principle in ferroelectric tunnel junctions using low-frequency noise spectroscopy". Nanoscale 14, nr 6 (2022): 2177–85. http://dx.doi.org/10.1039/d1nr06525d.
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In contrast to RRAMs, the 1/f noise of the FTJ in the LRS is approximately two orders of magnitude larger than that in the HRS, indicating that the conduction mechanism in each state differs significantly.
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Zeng, X., i D. L. Boïko. "1/f noise in external-cavity InGaN diode laser at 420 nm wavelength for atomic spectroscopy". Optics Letters 39, nr 6 (14.03.2014): 1685. http://dx.doi.org/10.1364/ol.39.001685.
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Muthukumaran, B., i B. Ramachandran. "High Gain CMOS Transimpedance Amplifier For Near Infrared Spectroscopy Applications". Journal of Physics: Conference Series 2335, nr 1 (1.09.2022): 012039. http://dx.doi.org/10.1088/1742-6596/2335/1/012039.
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Abstract In this paper, design and analysis of High Gain CMOS Transimpedance Amplifier (HGCTIA) is presented which is greatly necessitated for frequency domain functional Near Infrared Spectroscopy (FD-f NIRS). Generally, feedback resistor and drain resistor play a major role in deciding TIA gain and bandwidth. Most of the research work have utilized only feedback resistor and drain resistor. Here, the gain improvement is greatly achieved by replacing the drain resistor by an active inductor which is designed using CMOS transistor. The active inductor loaded based TIA exhibits only 0.01mW power dissipation which is comparatively lesser than previous research works. Also the proposed design achieves maximum value of transimpedance gain 140dB, bandwidth of 10 MHz, where average noise over the bandwidth is 4.6pA/√Hz with 0.68nArms. Input referred noise is 3.38pA/√Hz. These results are obtained by simulating the proposed approach using cadence 45nm technology. The simulated results shows that the proposed HGCTIA is superior in terms of power, gain and bandwidth.
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Лебедев, А. А., М. Е. Левинштейн, П. А. Иванов, В. В. Козловский, А. М. Стрельчук, Е. И. Шабунина i L. Fursin. "Влияние протонного облучения (15 МэВ) на низкочастотный шум мощных SiC MOSFETs". Физика и техника полупроводников 53, nr 12 (2019): 1604. http://dx.doi.org/10.21883/ftp.2019.12.48610.9219.
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Low frequency noise has been studied in power4H-SiC MOSFETs after proton(15 MeV) irradiation. The noise was studied at room temperature in the frequency range 1 Hz−50 kHz after irradiation with doses of 1012 ≤Ф≤ 6•1013 cm−2. Frequency dependence of the spectral noise density SI follows with good accuracy to the law SI∝1/f. The correlation between the saturation current of the output characteristics of Id(Vd) and the level of low-frequency noise is established. In the dose range Ф studied the value of the saturation current varies within about 20%, while the noise level changes by 2orders of magnitude. From the data of noise spectroscopy, the density of traps in the gate oxide, Ntv was estimated. In non-irradiated structures Ntv ≈5.4•1018cm−3•eV−1, at = 6•1013 cm−2, Ntv increases to a value of Ntv ≈7.2•1019cm−3•eV−1.
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Tong, William G., i Dennis A. Chen. "Doppler-Free Spectroscopy Based on Phase Conjugation by Degenerate Four-Wave Mixing in Hollow Cathode Discharge". Applied Spectroscopy 41, nr 4 (maj 1987): 586–90. http://dx.doi.org/10.1366/0003702874448599.
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Optical phase conjugation in the hollow cathode lamp by degnerate four-wave mixing is a novel analytical laser spectroscopic method in which a laser beam is generated as the signal beam. With the use of a demountable hollow cathode discharge cell and a continuous-wave dye laser, the signal beam is clearly visible to the naked eye when 1 µg of sodium is placed inside the cathode cavity. Since the signal beam is a time-reversed replica of the probe laser beam, highly efficient optical signal detection can be performed with minimum optical background noise. Since the signal is Doppler-free with negligible Lorentzian broadening (30 Torr discharge pressure), it provides excellent spectral resolution. Sodium D2 hyperfine lines of 3s 2S1/2 ( F' = 2) → 3p 2P3/2 ( F = 3) and 3s 2S1/2 ( F' = 1) → 3p 2P3/2 ( F = 0) were resolved. In addition to excellent spectral resolution and ease of signal detection, the technique also offers unique properties of optical phase conjugation.
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Sita, Zdenek, Vlasta Sedlakova, Jiri Majzner, Petr Sedlak, Josef Sikula i Lubomir Grmela. "Analysis of Noise and Non-Linearity of I-V Characteristics of Positive Temperature Coefficient Chip Thermistors". Metrology and Measurement Systems 20, nr 4 (1.12.2013): 635–44. http://dx.doi.org/10.2478/mms-2013-0054.
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Abstract Noise spectroscopy and I-V characteristic non-linearity measurement were applied as diagnostic tools in order to characterize the volume and contact quality of positive temperature coefficient (PTC) chip sensors and to predict possible contact failure. Correctly made and stable contacts are crucial for proper sensing. I-V characteristics and time dependences of resistance were measured for studied sensors and, besides the samples with stable resistance value, spike type resistance fluctuation was observed for some samples. These spikes often disappear after about 24 hours of voltage application. Linear I-V characteristics were measured for the samples with stable resistance. The resistance fluctuation of burst noise type was observed for some samples showing the I-V characteristic dependent on the electric field orientation. We have found that the thermistors with high quality contacts had a linear I-V characteristic, the noise spectral density is of 1/f type and the third harmonic index is lower than 60 dB. The samples with poor quality contacts show non-linear I-V characteristics and excess noise is given by superposition of g-r and 1/fn type noises, and the third harmonic index is higher than 60 dB.
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Hoornweg, Gerard Ph, Tjipke De Beer, Nel H. Velthorst i Cees Gooijer. "Forward Degenerate Four-Wave Mixing as a Detection Method in Liquid Separation Systems: Improving Detection Limits by Means of a Fabry—Perot Interferometer". Applied Spectroscopy 51, nr 7 (lipiec 1997): 1008–11. http://dx.doi.org/10.1366/0003702971941395.
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A simple, small, and low-resolution confocal Fabry–Perot interferometer (CFP) has been developed to improve the signal-to-noise ratio (S/N) in forward degenerate four-wave mixing (F-D4WM) detection, coupled to high-performance liquid chromatography (HPLC). Its appropriateness is based on the difference in coherence between the F-D4WM signal and the background stray light. A detailed description of the specially designed CFP and its performance is presented. The improvement in S/N was calculated from the chromatographic peaks recorded after an HPLC separation of 1- and 2-aminoanthraquinone. The concentration limit of detection (LOD) was improved by a factor of 30; for 1-aminoanthraquinone it was 2 × 10−8 M injected (corresponding to about 3 × 10−9 M in the detector cell), which is quite favorable in view of its low molar extinction coefficient being 2000 M−1 cm−1 at the utilized laser wavelength (514.5 nm).
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Zubrzycka, W., i P. Grybos. "Optimization of low-noise read-out electronics for high energy resolution X-ray strip detectors". Journal of Instrumentation 18, nr 01 (1.01.2023): C01033. http://dx.doi.org/10.1088/1748-0221/18/01/c01033.
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Abstract Semiconductor strip sensors applied as solid-state radiation or particle detectors can be used in radiation detection and measurement for various applications in particle physics experiments, X-ray imaging (e.g. medical), or material science. The X-ray imaging devices with spectroscopic and position resolution features are a very important research topic at many institutes and companies worldwide. Short strip silicon detectors are good candidates for X-ray spectroscopy, because of their relatively small capacitance and leakage current. If additionally, strip pitch is below 100 μm, then the high spatial resolution is also possible. In this paper, the analysis and noise optimization of the read-out electronics for short silicon strip detectors with Charge Sensitive Amplifier (CSA) and shaping amplifier (shaper) is presented. The CSA is optimized for the detector capacitance of around 1.5 pF, and the shaper nominal peaking time is about 1 μs (controlled by the sets of switches). We take into account the sources of noise in a radiation imaging system (current parallel noise, voltage series noise, and 1/f or flicker series noise) both internal (related to the front-end electronics itself) but also external, stemming from a sensor, interconnect, or printed circuit board parasitic components. We target the noise level below 40 el. rms, considering low power consumption (a few mW) and limited channel area.
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Ibrahim, Kiagus Aufa, Marlin Ramadhan Baidillah, Ridwan Wicaksono i Masahiro Takei. "Skin layer classification by feedforward neural network in bioelectrical impedance spectroscopy". Journal of Electrical Bioimpedance 14, nr 1 (1.01.2023): 19–31. http://dx.doi.org/10.2478/joeb-2023-0004.
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Abstract Conductivity change in skin layers has been classified by source indicator ok (k=1: Stratum corneum, k=2: Epidermis, k=3: Dermis, k=4: Fat, and k=5: Stratum corneum + Epidermis) trained from feedforward neural network (FNN) in bioelectrical impedance spectroscopy (BIS). In BIS studies, treating the skin as a bulk, limits the differentiation of conductivity changes in individual skin layers, however skin layer classification using FNN shows promise in accurately categorizing skin layers, which is essential for predicting source indicators ok and initiating skin dielectric characteristics diagnosis. The ok is trained by three main conceptual points which are (i) implementing FNN for predicting k in conductivity change, (ii) profiling four impedance inputs αξ consisting of magnitude input α| z |, phase angle input αθ , resistance input αR , and reactance input αx for filtering nonessential input, and (iii) selecting low and high frequency pair ( f r l h ) $$(f_{r}^{lh})$$ by distribution of relaxation time (DRT) for eliminating parasitic noise effect. The training data set of FNN is generated to obtain the αξ ∈ R 10×17×10 by 10,200 cases by simulation under configuration and measurement parameters. The trained skin layer classification is validated through experiments with porcine skin under various sodium chloride (NaCl) solutions CNaCl = {15, 20, 25, 30, 35}[mM] in the dermis layer. FNN successfully classified conductivity change in the dermis layer from experiment with accuracy of 90.6% for the bipolar set-up at f 6 l h = 10 & 100 [ kHz] $$f_{6}^{lh}=10\,\And 100\,{\rm{[kHz]}}$$ and with the same accuracy for the tetrapolar at f 8 l h = 35 & 100 [ kHz] $$f_{8}^{lh}=35\,\And 100\,{\rm{[kHz]}}$$ . The measurement noise and systematic error in the experimental results are minimized by the proposed method using the feature extraction based on αξ at f r l h $$f_{r}^{lh}$$ .
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Ho, W. Y., W. K. Fong, Charles Surya, K. Y. Tong, L. W. Lu i W. K. Ge. "Characterization of Hot-Electron Effects on Flicker Noise in III-V Nitride Based Heterojunctions". MRS Internet Journal of Nitride Semiconductor Research 4, S1 (1999): 560–64. http://dx.doi.org/10.1557/s1092578300003045.
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We report experiments on hot-electron stressing in commercial III-V nitride based heterojunction light-emitting diodes. Stressing currents ranging from 100 mA to 200 mA were used. Degradations in the device properties were investigated through detailed studies of the I-V characteristics, electroluminescence, Deep-Level Transient Fourier Spectroscopy and flicker noise. Our experimental data demonstrated significant distortions in the I-V characteristics. The room temperature electroluminescence of the devices exhibited 25% decrement in the peak emission intensity. Concentration of the deep-levels was examined by measuring the Deep-Level Transient Fourier Spectroscopy, which indicated an increase in the density of deep-traps from 2.7 × 1013 cm−3 to 4.21 × 1013 cm−3 at E1 = EC − 1.1eV. The result is consistent with our study of 1/f noise, which exhibited up to three orders of magnitude increase in the voltage noise power spectra. Our experiments show large increase in both the interface traps and deep-levels resulted from hot-carrier stressing.
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Sun, Jiaxin, Avinash Kumar Thakur i Liviu Movileanu. "Protein Ligand-Induced Amplification in the 1/f Noise of a Protein-Selective Nanopore". Langmuir 36, nr 50 (13.12.2020): 15247–57. http://dx.doi.org/10.1021/acs.langmuir.0c02498.
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Shin, Wonjun, Jong-Ho Bae, Jaehyeon Kim, Ryun-Han Koo, Jae-Joon Kim, Daewoong Kwon i Jong-Ho Lee. "Variability analysis of ferroelectric FETs in program operation using low-frequency noise spectroscopy". Applied Physics Letters 121, nr 16 (17.10.2022): 163501. http://dx.doi.org/10.1063/5.0111309.
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We investigate the variability of a ferroelectric FET (FEFET) in program operation using low-frequency noise (LFN) spectroscopy. Contrary to the previous report, LFN characteristics of FEFETs differ significantly depending on the program [low threshold voltage ( Vth)] or erase state [high Vth)] [Shin et al., IEEE Electron Device Lett. 43, 13 (2022)]. Furthermore, the 1/ f noise variation of the FEFETs is much larger in the program state than that in the erase state. It is revealed that the change in the number of electrons trapped at the FE/dielectric interface and oxygen vacancy in each program operation is the main reason for the variability of the FEFET in program operation. The variation stemming from the change in the number of trapped charges is significantly worsened when the channel area is scaled down.
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Barone, C., P. Orgiani, G. Carapella, V. Granata, S. K. Chaluvadi i S. Pagano. "Investigation of topological regime in Bi2Se3 thin films through low-frequency electric noise". Applied Physics Letters 122, nr 14 (3.04.2023): 143103. http://dx.doi.org/10.1063/5.0144893.
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Topological insulators are considered new states of quantum matter that cannot be systematically related to conventional insulators and semiconductors. Among them, Bi2Se3 has attracted an increasing interest due to a simple surface band structure and due to a strong contribution of the surface to transport. While the dc electric transport properties have been extensively studied, intrinsic fluctuations and their effect on the surface conduction have received less attention. In order to better investigate these aspects, a detailed characterization of the low-frequency noise, also known as noise spectroscopy, has been made in Bi2Se3 thin films. The experimental results have been obtained for different samples thickness and geometry, in a temperature range from 300 down to 8 K, and as a function of dc bias current and gate voltage. While the observed spectral noise shows a typical thermal and shot noise part, an unusual reduction of the 1/ f noise component is found, especially in the low-temperature region. A correlation of this behavior with structural and dc electric transport investigations suggests that it could be an indication of the occurrence of the topological regime. Flicker noise measurements, therefore, could be considered as a valid alternative technique to standard topological surface state spectroscopy.
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Andreev, Alexey, Ondrej Sik, Lubomir Grmela i Josef Sikula. "Ageing of Cadmium Telluride Radiation Detectors and its Diagnostics with Low Frequency Noise". Metrology and Measurement Systems 20, nr 3 (1.09.2013): 385–94. http://dx.doi.org/10.2478/mms-2013-0033.
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Abstract Samples of CdTe single crystals which are used as radiation detectors were periodically measured during a long time interval with different values of an applied voltage. The samples were also periodically exposed during long time periods to high temperatures of 390 K and to rapid changes of temperature from 300 K to 390 K. After 1.5 years of measurements we observed ageing of the samples which resulted in deterioration of their transport characteristics. The resistance of the samples increased significantly and current-voltage characteristics were unstable in time. Noise spectroscopy showed that low frequency noise can be used for detection of CdTe sample ageing as its spectral density increases significantly comparing to the 1/f noise of a high quality sample
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Eliseyev, I. A., A. S. Usikov, S. P. Lebedev, A. D. Roenkov, M. V. Puzyk, Yu M. Makarov, E. V. Gushchina i in. "Investigation of electrolysis-related modification of graphene films in biosensors". Journal of Physics: Conference Series 2103, nr 1 (1.11.2021): 012103. http://dx.doi.org/10.1088/1742-6596/2103/1/012103.
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Abstract In this work, the modification of the surface parameters of graphene chips after electrolysis treatment in a NaClO4 aqueous solution has been studied. Two electrolysis modes have been analysed. In the first one, a negative potential (-0.2 V) is applied to the graphene chips, while in the second one the potential is positive (0.8 V). Investigation using a number of techniques including atomic force microscopy, Kelvin probe force microscopy, Raman spectroscopy, measurements of current-voltage characteristics and low-frequency noise has shown that the electrolysis mode with application of a positive potential on graphene chips decreases the 1/f noise and allows one to obtain a uniform surface potential distribution while leaving the graphene structure undamaged. The results of this study help to understand the efficiency and reproducibility of the procedure for electrolysis treatment of graphene chips.
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Kaminaka, Shoji, i Richard A. Mathies. "High-Throughput Large-Aperture Prism Prefilter for Ultraviolet Resonance Raman Spectroscopy". Applied Spectroscopy 52, nr 3 (marzec 1998): 469–73. http://dx.doi.org/10.1366/0003702981943707.
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For the acquisition of high-quality ultraviolet resonance Raman spectra of strongly scattering samples such as membrane protein suspensions, an f/3.5 Littrow prism prefilter has been designed, built, and characterized. This prefilter has a Czerny–Turner configuration, and its focal length is 25 cm. The apex angle of the dispersive prism (20°) was chosen to provide maximum performance in the 220 to 240 nm range. The prism prefilter significantly reduced stray background due to Rayleigh scattering and visible fluorescence, while maintaining a low dispersion of 1300 cm−1/mm at 253 nm as well as a large f/3.5 aperture. The sharpness of the transmission edge (at 242 nm, the T = 0% to 95% transition occurs in 1.3 nm) quantitates its effectiveness as a sharp-cut Rayleigh scattering filter. The total throughput of the prefilter is ∼60% at 235 nm and ∼50% at 632.8 nm. The utility of this prefilter is demonstrated by obtaining high signal-to-noise resonance Raman spectra of bacteriorhodopsin in a purple membrane suspension with 239.5 nm excitation.
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Rustamkulov, Zafar, David K. Sing, Rongrong Liu i Ashley Wang. "Analysis of a JWST NIRSpec Lab Time Series: Characterizing Systematics, Recovering Exoplanet Transit Spectroscopy, and Constraining a Noise Floor". Astrophysical Journal Letters 928, nr 1 (1.03.2022): L7. http://dx.doi.org/10.3847/2041-8213/ac5b6f.
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Abstract The James Webb Space Telescope’s (JWST) NIRSpec instrument will unveil the nature of exoplanet atmospheres across the wealth of planet types, from temperate terrestrial worlds to ultrahot Jupiters. In particular, the 0.6–5.3 μm PRISM mode is especially well suited for efficient spectroscopic exoplanet observations spanning a number of important spectral features. We analyze a lab-measured NIRSpec PRISM mode Bright Object Time Series observation from the perspective of a JWST user to understand the instrument performance and detector properties. We create two realistic transiting exoplanet time-series observations by performing injection-recovery tests on the lab-measured data to quantify the effects of real instrument jitter, drift, intrapixel sensitivity variations, and 1/f noise on measured transmission spectra. By fitting the time-series systematics simultaneously with the injected transit, we can obtain more realistic transit-depth uncertainties that take into account noise sources that are currently not modeled by traditional exposure time calculators. We find that sources of systematic noise related to intrapixel sensitivity variations and point-spread function motions are apparent in the data at the level of a few hundred ppm but can be effectively detrended using a low-order polynomial with detector position. We recover the injected spectral features of GJ 436 b and TRAPPIST-1 d and place a 3σ upper limit on the detector noise floor of 14 ppm. We find that the noise floor is consistent with <10 ppm at the 1.7σ level, which bodes well for future observations of challenging targets with faint atmospheric signatures.
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Albert, Loïc, David Lafrenière, Doyon, René, Étienne Artigau, Kevin Volk, Paul Goudfrooij, André R. Martel i in. "The Near Infrared Imager and Slitless Spectrograph for the James Webb Space Telescope. III. Single Object Slitless Spectroscopy". Publications of the Astronomical Society of the Pacific 135, nr 1049 (1.07.2023): 075001. http://dx.doi.org/10.1088/1538-3873/acd7a3.
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Abstract The Near Infrared Imager and Slitless Spectrograph instrument (NIRISS) is the Canadian Space Agency contribution to the suite of four science instruments of the James Webb Space Telescope. As one of the three NIRISS observing modes, the Single Object Slitless Spectroscopy (SOSS) mode is tailor-made to undertake time-series observations of exoplanets to perform transit spectroscopy. The SOSS permits observing point sources between 0.6 and 2.8 μm at a resolving power of 650 at 1.25 μm using a slitless cross-dispersing grism while its defocussing cylindrical lens enables observing targets as bright as J = 6.7 by spreading light across 23 pixels along the cross-dispersion axis. This paper officially presents the design of the SOSS mode, its operation, characterization, and its performance, from ground-based testing and flight-based commissioning. On-sky measurements demonstrate a peak photon conversion efficiency of 55% at 1.2 μm. The first time series on the A-type star BD+60°1753 achieves a flux stability close to the photon-noise limit, so far tested to a level of 20 parts per million on a 40 minute timescale after simply subtracting a long-term trend. Uncorrected 1/f noise residuals underneath the spectral traces add an extra source of noise equivalent to doubling the readout noise. Preliminary analysis of an HAT-P-14b transit time series indicates that it is difficult to remove all of the noise in pixels with partially saturated ramps. Overall, the SOSS delivers performance at the level required to tackle key exoplanetary science programs such as detecting secondary atmospheres on terrestrial planets and measuring abundances of several chemical species in gas giants.
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Waldron, Abigail, Ashley Allen, Arelis Colón, J. Chance Carter i S. Michael Angel. "A Monolithic Spatial Heterodyne Raman Spectrometer: Initial Tests". Applied Spectroscopy 75, nr 1 (27.08.2020): 57–69. http://dx.doi.org/10.1177/0003702820936643.
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A monolithic spatial heterodyne Raman spectrometer (mSHRS) is described, where the optical components of the spectrometer are bonded to make a small, stable, one-piece structure. This builds on previous work, where we described bench top spatial heterodyne Raman spectrometers (SHRS), developed for planetary spacecraft and rovers. The SHRS is based on a fixed grating spatial heterodyne spectrometer (SHS) that offers high spectral resolution and high light throughput in a small footprint. The resolution of the SHS is not dependent on a slit, and high resolution can be realized without using long focal length dispersing optics since it is not a dispersive device. Thus, the SHS can be used as a component in a compact Raman spectrometer with high spectral resolution and a large spectral range using a standard 1024 element charge-coupled device. Since the resolution of the SHRS is not dependent on a long optical path, it is amenable to the use of monolithic construction techniques to make a compact and robust device. In this paper, we describe the use of two different monolithic SHSs (mSHSs), with Littrow wavelengths of 531.6 nm and 541.05 nm, each about 3.5 × 3.5 × 2.5 cm in size and weighing about 80 g, in a Raman spectrometer that provides ∼3500 cm−1 spectral range with 4–5 cm−1 and 8–9 cm−1 resolution, for 600 grooves/mm and 150 grooves/mm grating-based mSHS devices, respectively. In this proof of concept paper, the stability, spectral resolution, spectral range, and signal-to-noise ratio of the mSHRS spectrometers are compared to our bench top SHRS that uses free-standing optics, and signal to noise comparisons are also made to a Kaiser Holospec f/1.8 Raman spectrometer.
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Chang, Kuan-Chang, Tianjiao Dai, Zhengda Wang, Zhangwei Huang, Xinnan Lin i Lei Li. "The observation of Gaussian distribution and origination identification of deep defects in AlGaN/GaN MIS-HEMT". Applied Physics Letters 120, nr 17 (25.04.2022): 172107. http://dx.doi.org/10.1063/5.0088928.
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This paper proposes a math-physical correlative method that monitors deep defect response by electrical measurement and calculates the state density by designed mathematical processing. The extracted Gaussian distribution of deep defects was discussed according to the theoretical model for the density of states. The accuracy of this method was also verified through 1/f low frequency noise analysis. The origination of deep defects was investigated by transmission electron microscope, x-ray photoelectron spectroscopy, and photoluminescence analysis, and a molecular model was constructed. Therefore, multiple perspectives of deep defects have been studied by combining electrical measurements, mathematical data processing, and materials analysis, providing inspiration for future comprehensive study on deep defects of the GaN-based device.
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Chang, Kuan-Chang, Tianjiao Dai, Zhengda Wang, Zhangwei Huang, Xinnan Lin i Lei Li. "The observation of Gaussian distribution and origination identification of deep defects in AlGaN/GaN MIS-HEMT". Applied Physics Letters 120, nr 17 (25.04.2022): 172107. http://dx.doi.org/10.1063/5.0088928.
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This paper proposes a math-physical correlative method that monitors deep defect response by electrical measurement and calculates the state density by designed mathematical processing. The extracted Gaussian distribution of deep defects was discussed according to the theoretical model for the density of states. The accuracy of this method was also verified through 1/f low frequency noise analysis. The origination of deep defects was investigated by transmission electron microscope, x-ray photoelectron spectroscopy, and photoluminescence analysis, and a molecular model was constructed. Therefore, multiple perspectives of deep defects have been studied by combining electrical measurements, mathematical data processing, and materials analysis, providing inspiration for future comprehensive study on deep defects of the GaN-based device.
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Rao, Bing-Jie, Pan Zhang, Ming-Kun Ling, Xi-Guang Yang, Lu-Lu Yan, Xin Chen, Shou-Gang Zhang, Yan-Yan Zhang i Hai-Feng Jiang. "Multi-branch erbium fiber-based femtosecond optical frequency comb for measurement of cavity ring-down spectroscopy". Acta Physica Sinica 71, nr 8 (2022): 084203. http://dx.doi.org/10.7498/aps.71.20212162.
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<sec>In this paper, we demonstrate an optical frequency comb (OFC) based on an erbium-doped-fiber femtosecond laser, for the measurement of cavity ring-down spectroscopy (CRDS) with wavelengths of 1064, 1083, 1240, 1380, 1500, 1600, 1750 and 2100 nm. We adopt a multi-branch structure to produce high power at the specific wavelengths to meet the requirement for application in the spectral measurement. The OFC is developed by using a mode-locked fiber ring laser based on the nonlinear amplifying loop mirror mechanism. The laser is self-starting by introducing a nonreciprocal phase bias in the cavity and insensitive to the environmental perturbation. Using the chirped pulse amplification and highly nonlinear fibers, the broad spectra at the specific wavelengths are obtained. By optimizing the parameters of the pulses, the power of per mode at each target wavelength is greater than 300 nW.</sec><sec>The<i> f</i><sub>rep</sub> is obtained by detecting the output of the femtosecond laser directly, while the<i> f</i><sub>ceo</sub> is detected by <i>f</i>–2<i>f</i> interference. The signal-to-noise ratio of the<i> f</i><sub>ceo</sub> is about 35 dB with a 300-kHz resolution bandwidth. By controlling the intra-cavity electro-optic modulator and piezoactuator , the <i>f</i><sub>rep</sub> is stabilized with high bandwidth and large range (about megahertz bandwidth and 3 kHz range). The <i>f</i><sub>ceo</sub> is stabilized by using feedback to the pump current of the femtosecond laser dynamically. The in-loop frequency instability degree of the <i>f</i><sub>ceo</sub>, evaluated by the Allan deviation, is approximately 4.95 × 10<sup>–18</sup>/<i>τ</i><sup>1/2</sup> at 1 s and integrates down to 10<sup>–20</sup> level after 2000 s, while that of the <i>f</i><sub>rep</sub> is well below 5.85 × 10<sup>–13</sup>/<i>τ</i>. The all polarization-maintaining erbium fiber-based femtosecond optical frequency comb with multi-application branches we demonstrate in this paper is efficient and reliable for many other applications including optical frequency metrology and optical atomic clocks.</sec>
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Zhang, Zi-Yin, Yun-Sheng Deng, Hai-Bing Tian, Han Yan, Hong-Liang Cui i De-Qiang Wang. "Noise Analysis of Monolayer Graphene Nanopores". International Journal of Molecular Sciences 19, nr 9 (6.09.2018): 2639. http://dx.doi.org/10.3390/ijms19092639.
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Graphene-based nanopore devices have shown tantalizing potential in single molecule detection for their monoatomic membrane thickness which is roughly equal to the gap between nucleobases. However, high noise level hampers applications of graphene nanopore sensors, especially at low frequencies. In this article, we report on a study of the contribution of suspended graphene area to noise level in full frequency band. Monolayer graphene films are transferred onto SiNx substrates preset with holes in varied diameters and formed self-supported films. After that, the films are perforated with smaller, nanoscale holes. Experimental studies indicate a dependency of low-frequency 1/f noise on the underlying SiNx geometry. The contribution of the suspended graphene area to capacitance which affects the noise level in the high frequency range reveals that the graphene free-standing film area influences noise level over a wide frequency region. In addition, the low-frequency noise demonstrates a weak dependency on salt concentration, in deviation from Hooge’s relation. These findings and attendant analysis provide a systematic understanding of the noise characteristics and can serve as a guide to designing free-standing monolayer graphene nanopore devices.
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Akhgari, Farhad, Naser Samadi, Khalil Farhadi i Mehrdad Akhgari. "A green one-pot synthesis of nitrogen and sulfur co-doped carbon quantum dots for sensitive and selective detection of cephalexin". Canadian Journal of Chemistry 95, nr 6 (czerwiec 2017): 641–48. http://dx.doi.org/10.1139/cjc-2016-0531.
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The article reports a simple, economic, and green method for preparing water-soluble, nitrogen and sulfur co-doped carbon quantum dots via a one-step hydrothermal method. Pomegranate juice served as the carbon source, and the L-cysteine provided nitrogen and sulfur. Co-doped carbon dots were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy techniques. The co-doped carbon dots served as fluorescent probes for sensitive and selective detection of cephalexin. Briefly, the co-doped carbon dot systems showed quenching of photoluminescence intensity in the presence of cephalexin. The decrease of fluorescence intensity made it possible to analyze cephalexin with satisfactory detection limits and linear ranges. The Sterne–Volmer plot showed a linear relationship (R2 = 0.998) between F0/F and the concentration of cephalexin over the range from 0.3 to 10 μmol L−1. The limit of detection (LOD) was estimated to be 1 × 10−7 mol L−1 (at a signal to noise ratio of 3). To validate the applicability, the described method was successfully applied for the detection of cephalexin in human urine and raw milk samples.
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Li, Chuanliang, Ligang Shao, Lijun Jiang, Xuanbing Qiu, Jilin Wei i Weiguang Ma. "Simultaneous Measurements of CO and CO2 Employing Wavelength Modulation Spectroscopy Using a Signal Averaging Technique at 1.578 μm". Applied Spectroscopy 72, nr 9 (25.04.2018): 1380–87. http://dx.doi.org/10.1177/0003702818766904.
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A resolved line pair was selected for simultaneous measurement of carbon monoxide (CO) and carbon dioxide (CO2) in the near-infrared (NIR) region. The spectral lines of CO and CO2 at 1.578 µm were measured by wavelength modulation spectroscopy (WMS)-2 f and the absorption was enhanced with a multipass absorption cell. The white noise was further reduced by averaging technology. The detection sensitivity (1σ) for the system is estimated at 2.63 × 10−7 cm−1 for direct absorption spectroscopy. The ultimate detection limits of CO2 and CO mixed with pure N2 at 75 Torr are 29 parts per million (ppm) and 47 ppm, respectively. It is demonstrated that the signal is highly linear with the concentration in the range of 100–800 ppm. Based on an Allan variation analysis, the minimum detectable limit of CO2 and CO is 7.5 and 14 ppm, respectively. The response time of the system is about 30 s and a relationship of temperature dependence was obtained. As an example, an in situ measurement of exhaust of alkane combustion emission is presented.
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Su, Y. K., i C. T. Lin. "The Performance of Hg0.8Cd0.2Te Photodetectors by Using Photo Surface Treatment". International Journal of High Speed Electronics and Systems 08, nr 04 (grudzień 1997): 703–17. http://dx.doi.org/10.1142/s0129156497000287.
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The principal aim of this paper is to propose an easy, vapor phase, and reproducible photo surface treatment method to improve the device performance of the Hg0.8Cd0.2Te photoconductive detector. Experimental results, including Auger electron spectroscopy (AES), MIS leakage current, 1/f noise voltage spectrum, 1/fknee frequency, responsivity Rλ, and specific detectivity D* for stacked photo surface treatment and ZnS or CdTe passivation layers are presented. By using this method, we found that there is no accumulation of Hg in the oxide/HgCdTe interface regions. Since the photo chemical vapor native oxidation is a dry oxidation method deposited at a low temperature, it can effectively suppress the Hg enhancement and the Cd depletion effects and thus obtain a high quality interface. We also found that the photo surface treatment in combination with thermally eveporated ZnS or CdTe layer would shift the 1/fknee under 100Hz in an electrical field under 50 V/cm, reduce the noise power spectrum, and achieve a lower surface recombination velocity S of 300 cm/sec as well as a high D* of 3 × 1010 cm [Formula: see text] for blackbody radiation. It was also found that HgCdTe photoconductor passivated with stacked layers shows improved interface properties when compared to the photoconductor passivated with a single passivation layer.
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Robert, H., D. Pusiol, E. Rommel i R. Kimmich. "On the Reconstruction of NQR Nutation Spectra in Solids with Powder Geometry". Zeitschrift für Naturforschung A 49, nr 1-2 (1.02.1994): 35–41. http://dx.doi.org/10.1515/zna-1994-1-209.
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Abstract In single crystals the NQR nutation frequency depends on the relative orientation of the coil and the quadrupole axes. In powders the nutation lineshape is a superposition of spectra from the randomly oriented single crystals, so that powder patterns appear in such experiments if the reconstruction is performed by the Fourier transform method. In this paper an alternative reconstruction method of nutation spectra is suggested making use of the Hankel Transform. In this way the nutation spectra are simplified. Singularities arising with experiments for the determination of the asymmetry parameter η can easily be resolved. In the particular case of an axially symmetric quadrupolar tensor and a homogeneous radiofrequency field one can reduce the powder pattern to a single line without heterogeneous broadening with respect to orientation. Further improvement o f the nutation spectra can be achieved by taking advantage of the maximum entropy method, which strongly reduces apodisation and noise problems. Applications of the new data manipulation techniques to N Q R imaging methods published elsewhere and 2D zero-field N Q R spectroscopy are reported.
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Reid, A. H. N., C. T. Bolton, R. A. Crowe, M. S. Fieldus, A. W. Fullerton, D. R. Gies, I. D. Howarth, D. McDavid, R. K. Prinja i K. C. Smith. "Time-Series Spectroscopy of ζ Ophiuchi". International Astronomical Union Colloquium 139 (1993): 190. http://dx.doi.org/10.1017/s0252921100117294.
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AbstractWe have undertaken a multi-site, multi-wavelength observing campaign on the archetypal O stars ζ Puppis (O4 I(n)f) and ζ Ophiuchi (O9.5 V). Both stars are well known for the strength of their line profile variations (lpv's), and represent extremes of O spectral type and luminosity class. UV time-series spectroscopy of ζ Pup and ζ Oph is described by Prinja et al. (Ap.J. 1992, 390, 266), and Howarth et al. (Ap.J. 1992, submitted) respectively. The optical spectroscopic results of ζ Oph are reported by Reid et al. (1992, ApJ submitted), of which some of the principal results are given here.During late April, and early May, 1989, we obtained high-resolution, high signal-to-noise optical spectra of the late O-type, rapid rotator ζ Oph. Time-series analysis, using the CLEAN algorithm, has shown that the characteristic lpv seen in HeI λ447lÅ, Si III λλ4552, 4567, 4575Å, and MgII λ448lÅ can be satisfactorily represented as a set of 4 sinusoids. No substantial variation is observed in HeII λ4541, or NIII λ4517Å. We attribute this behaviour to a combination of equatorial gravity-darkening and a latitudinally-confined origin for the lpv.The phase changes over the line profiles indicate repetitive patterns of axial symmetry, rotating prograde in the co-rotating frame of the star. The periods are 3.339 hours (-m = 4), 2.435 hours (-m = 5 or -m = 6), 1.859 hours (-m = 9 ± 1), and either 1.366 hours or 1.292 hours (-m = 11 ± 1); -m represents the spatial frequency around the stellar equator. The first three periods confirm those found at earlier epochs, and we conclude that some lpv characteristics are reproduced over at least a 2-year interval.Since no commensurate superperiod (|m|P) exists, and since the super-periods are less than our estimated minimum rotation period for ζ Oph (> 18 hours), we reject a rotational modulation origin for the lpv and conclude that the star is undergoing multi-mode, sectorial, non-radial pulsations.
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Stadler, Adam Witold, Andrzej Kolek, Krzysztof Mleczko, Zbigniew Zawiślak, Andrzej Dziedzic i Wojciech Stęplewski. "Noise sources in polymer thick-film resistors". Soldering & Surface Mount Technology 27, nr 3 (1.06.2015): 115–19. http://dx.doi.org/10.1108/ssmt-04-2015-0014.
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Purpose – The paper aims to get the knowledge about electrical properties, including noise, of modern polymer thick-film resistors (TFRs) in a wide range of temperature values, i.e. from 77 K up to room temperature. The sample resistors have been made of different combinations of resistive compositions, either ED7100 or MINICO (M2013, M2010), and conducting pastes (for contacts) Cu- or Au-based, deposited on FR-4 laminate. Design/methodology/approach – The paper opted for an experimental study using either current noise index measurement in room temperature for large batch of samples or noise spectra measurement in temperature range 77-300 K for selected samples. Obtained noise maps, i.e. plots of power spectral density of voltage fluctuations vs frequency and temperature, have been used for evaluation of noise describing parameters like material noise intensity C and figure of merit K, for TFRs made of different combinations of resistive/conductive materials. Comparison of the parameters gives the information about the quality of the technology and matching the conductive/resistive materials. Findings – Experiments confirmed that the main noise component is 1/f resistance noise. However, low-frequency noise spectroscopy revealed that also noise components of Lorentzian shape, associated with thermally activated noise sources exist. Their activation energies have been found to be of a few tenths of eV. Research limitations/implications – The noise intensity of polymer TFRs depends on technology process and/or contacts materials. The use of Au contacts leads to better noise properties of the resistors. The results of the studies might be helpful for further improvement of thick-film technology, especially for manufacturing low-noise, stable and reliable TFRs. Practical implications – The paper includes indications for the materials selection for thick-film technology to manufacture low-noise, reliable and stable TFRs. Originality/value – Experimental studies of electrical properties of polymer TFRs by means of noise spectra measurements in wide range of temperature is rare. They give fundamental knowledge about noise sources in the modern passive electronic components as well as practical indications of selection material for thick-film technology, to obtain high performance components and get technological advantage.
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Steele, A. W., i G. M. Hieftje. "A Modulated Sample Introduction System for Atomic Emission Spectrometry". Applied Spectroscopy 40, nr 3 (marzec 1986): 357–63. http://dx.doi.org/10.1366/0003702864509240.
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A modulated sample-introduction device for use in flame emission spectrometry has been constructed and evaluated. With this device, the flow of aerosol to the excitation source is modulated by the application, at a specific frequency, of a pressure pulse to the nebulizer chamber; the use of frequency-selective detection then permits efficient signal recovery. If source background remains at a constant level, it is not detected and the signal-to-background ratio (S/B) is consequently improved. Because the technique provides a decrease in the instrument 1/f and flame-background flicker noise, detection limits are improved. These features are especially prominent when the analyte line of interest is in a spectral region of high source background. Modulation frequencies of 8 to 20 Hz have been explored and have resulted in good depth of modulation (>99%) and signal-pulse separation. The construction and operation of the device will be described and its performance for several elements evaluated in terms of detection limits, S/B enhancement, and working curve linearity. Also, the extension of the technique to selective spectralline modulation schemes and to inductively coupled plasma emission spectrometry will be considered.
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Barnes, Charles C., Kathleen T. Yee i Douglas E. Vetter. "Conditional Ablation of Glucocorticoid and Mineralocorticoid Receptors from Cochlear Supporting Cells Reveals Their Differential Roles for Hearing Sensitivity and Dynamics of Recovery from Noise-Induced Hearing Loss". International Journal of Molecular Sciences 24, nr 4 (7.02.2023): 3320. http://dx.doi.org/10.3390/ijms24043320.
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Endogenous glucocorticoids (GC) are known to modulate basic elements of cochlear physiology. These include both noise-induced injury and circadian rhythms. While GC signaling in the cochlea can directly influence auditory transduction via actions on hair cells and spiral ganglion neurons, evidence also indicates that GC signaling exerts effects via tissue homeostatic processes that can include effects on cochlear immunomodulation. GCs act at both the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR). Most cell types in the cochlea express both receptors sensitive to GCs. The GR is associated with acquired sensorineural hearing loss (SNHL) through its effects on both gene expression and immunomodulatory programs. The MR has been associated with age-related hearing loss through dysfunction of ionic homeostatic balance. Cochlear supporting cells maintain local homeostatic requirements, are sensitive to perturbation, and participate in inflammatory signaling. Here, we have used conditional gene manipulation techniques to target Nr3c1 (GR) or Nr3c2 (MR) for tamoxifen-induced gene ablation in Sox9-expressing cochlear supporting cells of adult mice to investigate whether either of the receptors sensitive to GCs plays a role in protecting against (or exacerbating) noise-induced cochlear damage. We have selected mild intensity noise exposure to examine the role of these receptors related to more commonly experienced noise levels. Our results reveal distinct roles of these GC receptors for both basal auditory thresholds prior to noise exposure and during recovery from mild noise exposure. Prior to noise exposure, auditory brainstem responses (ABRs) were measured in mice carrying the floxed allele of interest and the Cre recombinase transgene, but not receiving tamoxifen injections (defined as control (no tamoxifen treatment), versus conditional knockout (cKO) mice, defined as mice having received tamoxifen injections. Results revealed hypersensitive thresholds to mid- to low-frequencies after tamoxifen-induced GR ablation from Sox9-expressing cochlear supporting cells compared to control (no tamoxifen) mice. GR ablation from Sox9-expressing cochlear supporting cells resulted in a permanent threshold shift in mid-basal cochlear frequency regions after mild noise exposure that produced only a temporary threshold shift in both control (no tamoxifen) f/fGR:Sox9iCre+ and heterozygous f/+GR:Sox9iCre+ tamoxifen-treated mice. A similar comparison of basal ABRs measured in control (no tamoxifen) and tamoxifen-treated, floxed MR mice prior to noise exposure indicated no difference in baseline thresholds. After mild noise exposure, MR ablation was initially associated with a complete threshold recovery at 22.6 kHz by 3 days post-noise. Threshold continued to shift to higher sensitivity over time such that by 30 days post-noise exposure the 22.6 kHz ABR threshold was 10 dB more sensitive than baseline. Further, MR ablation produced a temporary reduction in peak 1 neural amplitude one day post-noise. While supporting cell GR ablation trended towards reducing numbers of ribbon synapses, MR ablation reduced ribbon synapse counts but did not exacerbate noise-induced damage including synapse loss at the experimental endpoint. GR ablation from the targeted supporting cells increased the basal resting number of Iba1-positive (innate) immune cells (no noise exposure) and decreased the number of Iba1-positive cells seven days following noise exposure. MR ablation did not alter innate immune cell numbers at seven days post-noise exposure. Taken together, these findings support differential roles of cochlear supporting cell MR and GR expression at basal, resting conditions and especially during recovery from noise exposure.
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Kellmann, S., T. von Clarmann, G. P. Stiller, E. Eckert, N. Glatthor, M. Höpfner, M. Kiefer i in. "Global CFC-11 (CCl<sub>3</sub>F) and CFC-12 (CCl<sub>2</sub>F<sub>2</sub>) measurements with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS): retrieval, climatologies and trends". Atmospheric Chemistry and Physics 12, nr 24 (17.12.2012): 11857–75. http://dx.doi.org/10.5194/acp-12-11857-2012.
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Abstract. Vertical profiles of CFC-11 (CCl3F) and CFC-12 (CCl2F2) have been measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with global coverage under daytime and nighttime conditions. The profile retrieval is based on constrained nonlinear least squares fitting of measured limb spectral radiance to modeled spectra. CFC-11 is measured in its ν4-band at 850 cm−1, and CFC-12 is analyzed in its ν6-band at 922 cm−1. To stabilize the retrievals, a Tikhonov-type smoothing constraint is applied. Main retrieval error sources are measurement noise and elevation pointing uncertainties. The estimated CFC-11 retrieval errors including noise and parameter errors but excluding spectroscopic data uncertainties are below 10 pptv in the middle stratosphere, depending on altitude, the MIPAS measurement mode and the actual atmospheric situation. For CFC-12 the total retrieval errors are below 28 pptv at an altitude resolution varying from 3 to 5 km. Time series of altitude/latitude bins were fitted by a simple parametric approach including constant and linear terms, a quasi-biennial oscillation (QBO) proxy and sine and cosine terms of several periods. In the time series from 2002 to 2011, quasi-biennial and annual oscillations are clearly visible. A decrease of stratospheric CFC mixing ratios in response to the Montreal Protocol is observed for most altitudes and latitudes. However, the trends differ from the trends measured in the troposphere, they are even positive at some latitudes and altitudes, and can in some cases only be explained by decadal changes in atmospheric age of air spectra or vertical mixing patterns.
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Shmidt, Natalia M., Evgeniya I. Shabunina, Ekaterina V. Gushchina, Vasiliy N. Petrov, Ilya A. Eliseyev, Sergey P. Lebedev, Sergei Iu Priobrazhenskii i in. "Quality Assessment of Processed Graphene Chips for Biosensor Application". Materials 16, nr 16 (15.08.2023): 5628. http://dx.doi.org/10.3390/ma16165628.
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The quality of graphene intended for use in biosensors was assessed on manufactured chips using a set of methods including atomic force microscopy (AFM), Raman spectroscopy, and low-frequency noise investigation. It is shown that local areas of residues on the graphene surface, formed as a result of the interaction of graphene with a photoresist at the initial stage of chip development, led to a spread of chip resistance (R) in the range of 1–10 kOhm and to an increase in the root mean square (RMS) roughness up to 10 times, which can significantly worsen the reproducibility of the parameters of graphene chips for biosensor applications. It was observed that the control of the photoresist residues after photolithography (PLG) using AFM and subsequent additional cleaning reduced the spread of R values in chips to 1–1.6 kOhm and obtained an RMS roughness similar to the roughness in the graphene film before PLG. Monitoring of the spectral density of low-frequency voltage fluctuation (SU), which provides integral information about the system of defects and quality of the material, makes it possible to identify chips with low graphene quality and with inhomogeneously distributed areas of compressive stresses by the type of frequency dependence SU(f).
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Albosta, R., B. Geiger, G. McKee, D. Den Hartog, J. Schellpfeffer, T. Gallenberger, S. Stewart i R. Dux. "Design study of an edge current density diagnostic using new high-performance single-channel beam emission spectrometers at DIII-D". Review of Scientific Instruments 93, nr 11 (1.11.2022): 113546. http://dx.doi.org/10.1063/5.0101781.
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A novel Motional Stark Effect spectroscopy system has been designed for application at the DIII-D tokamak. The system is optimized for studies of the poloidal and toroidal magnetic field in the plasma pedestal region with frame rates of up to 10 kHz. Light from an existing high-photon-throughput collection lens is analyzed using four single-channel f/2.8 Czerny–Turner spectrometers that use custom-made lens systems instead of mirrors. Each spectrometer has two separate outgoing legs and is operated in a positive grating order, which allows for simultaneous observations of D-alpha and D-beta spectra. Forward modeling using the code FIDASIM shows a radial resolution of the system close to 0.6 cm and sufficiently good spectral resolution when masking the high throughput light collection lens in the horizontal direction to avoid overly strong Doppler broadening of beam emission lines. Moreover, a detailed sensitivity study considering realistic levels of readout and photon noise shows that the poloidal and toroidal magnetic field strengths can be inferred with an uncertainty of less than 1%, which will allow the inference of changes of the plasma current during transient events.
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Espinoza, Néstor, Leonardo Úbeda, Stephan M. Birkmann, Pierre Ferruit, Jeff A. Valenti, David K. Sing, Zafar Rustamkulov i in. "Spectroscopic Time-series Performance of JWST/NIRSpec from Commissioning Observations". Publications of the Astronomical Society of the Pacific 135, nr 1043 (1.01.2023): 018002. http://dx.doi.org/10.1088/1538-3873/aca3d3.
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Abstract We report on James Webb Space Telescope (JWST) commissioning observations of the transiting exoplanet HAT-P-14 b, obtained using the Bright Object Time Series (BOTS) mode of the NIRSpec instrument with the G395H/F290LP grating/filter combination (3–5 μm). While the data were used primarily to verify that the NIRSpec BOTS mode is working as expected, and to enable it for general scientific use, they yield a precise transmission spectrum which we find is featureless down to the precision level of the instrument, consistent with expectations given HAT-P-14 b’s small scale-height and hence expected atmospheric features. The exquisite quality and stability of the JWST/NIRSpec transit spectrum—almost devoid of any systematic effects—allowed us to obtain median uncertainties of 50–60 ppm in this wavelength range at a resolution of R = 100 in a single exposure, which is in excellent agreement with pre-flight expectations and close to the (or at the) photon-noise limit for a J = 9.094, F-type star like HAT-P-14. These observations showcase the ability of NIRSpec/BOTS to perform cutting-edge transiting exoplanet atmospheric science, setting the stage for observations and discoveries to be made in Cycle 1 and beyond.
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Singh, Paramjit, Harish Pungotra i Nirmal S. Kalsi. "Parametric optimization of deep cryogenic treatment for the wear response of implant material UNS R56700: Taguchi’s approach". Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 234, nr 1 (5.11.2019): 61–73. http://dx.doi.org/10.1177/0954411919884775.
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Using the Taguchi’s robust design of experiments methodology, this article presents the systematic identification and optimization of most influential parameters of deep cryogenic treatment process to minimize the specific wear rate of UNS R56700 (Ti6Al7Nb). In addition to the different soaking durations (0–96 h) at 77 K and different tempering temperatures (room temperature, 403–523 K), three commonly used variables of pin-on-disk test, namely, sliding speed (1.047–2.723 ms−1), contact pressure (0.641–1.282 MPa), and sliding time (600–2280 s) were chosen to conduct the tests. During dry sliding conditions, pin-on-disk tribo-tests were performed to slide Ti6Al7Nb on the surface of UNS 52986 (En31) material as per standardized ASTM G99 guidelines. Experimentally measured wear rate values were converted to signal–noise ratio to statistically analyze the influence of five control variables using pooled analysis of variance and F-test. Statistically found influential control variables are confirmed experimentally. The results show that sliding speed, contact pressure and soaking duration are the most significant factors influencing the wear rate. In contrast, the parameters, that is, tempering temperature and sliding time, exhibit a lower level of influence. Microstructural characterizations done using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques suggested that deep cryogenic treatment favors the refinement of grain size of present phases with reduction in β-stabilization (β-phase) in Ti6Al7Nb. The possible reasons for the improvement in wear rate of Ti6Al7Nb underlying the morphological alterations have been explained.
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Yang, Mingxi, John Prytherch, Elena Kozlova, Margaret J. Yelland, Deepulal Parenkat Mony i Thomas G. Bell. "Comparison of two closed-path cavity-based spectrometers for measuring air–water CO<sub>2</sub> and CH<sub>4</sub> fluxes by eddy covariance". Atmospheric Measurement Techniques 9, nr 11 (18.11.2016): 5509–22. http://dx.doi.org/10.5194/amt-9-5509-2016.
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Abstract. In recent years several commercialised closed-path cavity-based spectroscopic instruments designed for eddy covariance flux measurements of carbon dioxide (CO2), methane (CH4), and water vapour (H2O) have become available. Here we compare the performance of two leading models – the Picarro G2311-f and the Los Gatos Research (LGR) Fast Greenhouse Gas Analyzer (FGGA) at a coastal site. Both instruments can compute dry mixing ratios of CO2 and CH4 based on concurrently measured H2O, temperature, and pressure. Additionally, we used a high throughput Nafion dryer to physically remove H2O from the Picarro airstream. Observed air–sea CO2 and CH4 fluxes from these two analysers, averaging about 12 and 0.12 mmol m−2 day−1 respectively, agree within the measurement uncertainties. For the purpose of quantifying dry CO2 and CH4 fluxes downstream of a long inlet, the numerical H2O corrections appear to be reasonably effective and lead to results that are comparable to physical removal of H2O with a Nafion dryer in the mean. We estimate the high-frequency attenuation of fluxes in our closed-path set-up, which was relatively small ( ≤ 10 %) for CO2 and CH4 but very large for the more polar H2O. The Picarro showed significantly lower noise and flux detection limits than the LGR. The hourly flux detection limit for the Picarro was about 2 mmol m−2 day−1 for CO2 and 0.02 mmol m−2 day−1 for CH4. For the LGR these detection limits were about 8 and 0.05 mmol m−2 day−1. Using global maps of monthly mean air–sea CO2 flux as reference, we estimate that the Picarro and LGR can resolve hourly CO2 fluxes from roughly 40 and 4 % of the world's oceans respectively. Averaging over longer timescales would be required in regions with smaller fluxes. Hourly flux detection limits of CH4 from both instruments are generally higher than the expected emissions from the open ocean, though the signal to noise of this measurement may improve closer to the coast.
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Holdsworth, Daniel L., Hideyuki Saio i Donald W. Kurtz. "HD 42659: the only known roAp star in a spectroscopic binary observed with B photometry, TESS, and SALT". Monthly Notices of the Royal Astronomical Society 489, nr 3 (2.09.2019): 4063–71. http://dx.doi.org/10.1093/mnras/stz2419.
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ABSTRACT We present a multi-instrument analysis of the rapidly oscillating Ap (roAp) star HD 42659. We have obtained B photometric data for this star and use these data, in conjunction with the Transiting Exoplanet Survey Satellite (TESS) observations, to analyse the high-frequency pulsation in detail. We find a triplet that is split by the rotation frequency of the star (νrot = 0.3756 d−1; Prot = 2.66 d) and present both distorted dipole and distorted quadrupole mode models. We show that the pulsation frequency, 150.9898 d−1 (Ppuls = 9.54 min), is greater than the acoustic cut-off frequency. We utilize 27 high-resolution ($R\simeq 65\, 000$), high signal-to-noise ratio (∼120) spectra to provide new orbital parameters for this, the only known roAp star to be in a short-period binary (Porb = 93.266 d). We find the system to be more eccentric than previously thought, with e = 0.317, and suggest the companion is a mid-F to early-K star. We find no significant trend in the average pulsation mode amplitude with time, as measured by TESS, implying that the companion does not have an effect on the pulsation in this roAp star. We suggest further photometric observations of this star, and further studies to find more roAp stars in close binaries to characterize how binarity may affect the detection of roAp pulsations.
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Ward, Lawrence, i Priscilla Greenwood. "1/f noise". Scholarpedia 2, nr 12 (2007): 1537. http://dx.doi.org/10.4249/scholarpedia.1537.
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