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1
Doehne, Eric. "Charge Contrast: Some ESEM Observations of A New/Old Phenomenon." Microscopy and Microanalysis 4, S2 (July 1998): 292–93. http://dx.doi.org/10.1017/s1431927600021589.
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Over the past few years there have been occasional reports of unusual secondary electron contrasts in certain nonmetallic materials using conventional (CSEM-Johansen et al, 1997), low voltage (LV-SEM-Harker et al, 1993; Harker et al, 1994) and environmental scanning electron microscopy (ESEM-Griffin, 1997; T. Hardt, personal communication) which have documented novel contrast mechanisms whose origins are not yet well understood. Indeed, similar observations were made over 20 years ago in certain uncoated materials (such as SiC) using conventional SEM (Sawyer and Page, 1978). Aspects of these charge contrast imaging (CCI) phenomena are further documented here in a series of ESEM experiments on polished cross sections of uncoated travertine calcite. What is “old” is the fact that these contrasts have been reported on several occasions. What is “new” is the observation that these unusual contrasts are more readily studied and, in some cases, have been found in a wider range of materials using ESEM.
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Lawrence, J. K., and G. A. Chapman. "Photometric observations of facular contrasts near the solar limb." Astrophysical Journal 335 (December 1988): 996. http://dx.doi.org/10.1086/166986.
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Hordern, J. H. "Some observations on the Persae of Timotheus (PMG 791)." Classical Quarterly 49, no. 2 (December 1999): 433–38. http://dx.doi.org/10.1093/cq/49.2.433.
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At lines 7–10 the description of the sea-battle appears to involve the destruction of the oars of the enemy ship (accepting Page's ῥηγì[κωπ] ος at 9), with the result that the sailors fall over (9–10 suppl. Danielsson). We would expect lines 11–13 to provide some sort of contrast with this description, since εἰ δέ at 11 contrasts with 7 ảλλ’ εἰμέυ, but the exact sense is not quite clear.
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Tracey, John P., Peter J. S. Fleming, and Gavin J. Melville. "Accuracy of some aerial survey estimators: contrasts with known numbers." Wildlife Research 35, no. 4 (2008): 377. http://dx.doi.org/10.1071/wr07105.
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Density estimates are seldom examined against actual population size, hence the ability of estimators to correct for bias is unknown. Studies that compare techniques are difficult to interpret because of the uncertainty of adherence to their respective assumptions. Factors influencing detection probability, estimators that correct for bias, the validity of their assumptions and how these relate to true density are important considerations for selecting suitable methods. Here we contrasted five estimates of feral goat (Capra hircus) densities obtained from aerial surveys (strip counts, Petersen, stratified Petersen, Chao, Alho) against known densities derived from total counts. After correcting for recounting, the Alho and stratified Petersen estimators applied to helicopter surveys were the most accurate (bias = 0.08 and –0.09 respectively), which suggests that estimates were improved by correcting individual observations according to the characteristics of each observation. An approach using modified Horvitz–Thompson equations for unequal-sized units is described and is recommended to allow for this. Both the Chao (bias = 0.35) and Petersen (bias = 0.22) estimators were positively biased, which is likely to be a consequence of averaging detection probability across all observations. Helicopter survey using capture–recapture with multiple observers is recommended for estimating the density of wildlife populations. However, adjustment for the factors that influence detection probability is required.
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Keppel-Aleks, G., P. O. Wennberg, C. W. O'Dell, and D. Wunch. "Towards constraints on fossil fuel emissions from total column carbon dioxide." Atmospheric Chemistry and Physics Discussions 12, no. 11 (November 21, 2012): 29887–913. http://dx.doi.org/10.5194/acpd-12-29887-2012.
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Abstract. We assess the large-scale, top-down constraints on regional fossil fuel emissions provided by observations of atmospheric total column CO2, XCO2. Using an atmospheric GCM with underlying fossil emissions, we determine the influence of regional fossil fuel emissions on global XCO2 fields. We quantify the regional contrasts between source and upwind regions and probe the sensitivity of atmospheric XCO2 to changes in fossil fuel emissions. Regional fossil fuel XCO2 contrasts can exceed 0.7 ppm based on 2007 emission estimates, but have large seasonal variations due to biospheric fluxes. Contamination by clouds reduces the discernible fossil signatures. Nevertheless, our simulations show that atmospheric fossil XCO2 can be tied to its source region and that changes in the regional XCO2 contrasts scale linearly with emissions. We test the GCM results against XCO2 data from the GOSAT satellite. Regional XCO2 contrasts in GOSAT data generally scale with the predictions from the GCM, but the comparison is limited by the moderate precision of and relatively few observations from the satellite. We discuss how this approach may be useful as a policy tool to verify national fossil emissions, as it provides an independent, observational constraint.
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Keppel-Aleks, G., P. O. Wennberg, C. W. O'Dell, and D. Wunch. "Towards constraints on fossil fuel emissions from total column carbon dioxide." Atmospheric Chemistry and Physics 13, no. 8 (April 26, 2013): 4349–57. http://dx.doi.org/10.5194/acp-13-4349-2013.
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Abstract. We assess the large-scale, top-down constraints on regional fossil fuel emissions provided by observations of atmospheric total column CO2, XCO2. Using an atmospheric general circulation model (GCM) with underlying fossil emissions, we determine the influence of regional fossil fuel emissions on global XCO2 fields. We quantify the regional contrasts between source and upwind regions and probe the sensitivity of atmospheric XCO2 to changes in fossil fuel emissions. Regional fossil fuel XCO2 contrasts can exceed 0.7 ppm based on 2007 emission estimates, but have large seasonal variations due to biospheric fluxes. Contamination by clouds reduces the discernible fossil signatures. Nevertheless, our simulations show that atmospheric fossil XCO2 can be tied to its source region and that changes in the regional XCO2 contrasts scale linearly with emissions. We test the GCM results against XCO2 data from the GOSAT satellite. Regional XCO2 contrasts in GOSAT data generally scale with the predictions from the GCM, but the comparison is limited by the moderate precision of and relatively few observations from the satellite. We discuss how this approach may be useful as a policy tool to verify national fossil emissions, as it provides an independent, observational constraint.
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Einasto, Jaan, Maret Einasto, Enn Saar, Bernard J. T. Jones, and Vicent J. Martinez. "Superclustering: Theory Versus Observations." Symposium - International Astronomical Union 130 (1988): 245–54. http://dx.doi.org/10.1017/s0074180900136113.
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The spatial distribution of galaxies is compared with model distributions. It is demonstrated that giant and dwarf galaxies in the Local Supercluster occupy statistically identical regions. Various tests suggest that galaxy formation is biased since all unbiased model distributions are in conflict with observed distribution of galaxies. Multifractal analysis shows that a cold dark matter dominated universe with biased galaxy formation has a fairly constant fractal dimension over a broad range of scales. This contrasts with the observed distribution which does not show simple fractal features.
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Kuhn, Jeffrey R. "Brightness Observations of the Sun." International Astronomical Union Colloquium 143 (1994): 130–37. http://dx.doi.org/10.1017/s0252921100024635.
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There are few solar surface brightness observations with sufficient accuracy to have direct bearing on the question of the origin of the Sun’s bolometric luminosity and irradiance changes (the correlative observations have been reviewed elsewhere in these proceedings). This paper contrasts these observations with a model for the solar variability and illustrates our clear need for high precision surface photometry, in combination with helioseismic data and numerical experiments.
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Foukal, P., and T. Moran. "Properties of Faculae from Observations Near the Opacity Minimum." Symposium - International Astronomical Union 154 (1994): 23–27. http://dx.doi.org/10.1017/s0074180900124210.
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Imaging of active regions in continuum around 1.6 μm shows that many facular regions are less bright than the photosphere when observed nearer to disk center than μ = cos θ ~ 0.75. The contrast of these dark faculae increases with magnetic flux above a threshold of approximately 2 × 1018 Mx. This explains why not all faculae are dark at 1.6 μm, since the magnetic flux density in many regions of bright Ca K plage emission falls below this threshold. After correction for blurring, the typical contrast value is about 4-5%, so the brightness temperature deficit is about 130 K. Faculae are brighter than the photosphere at 1.63 μm nearer to the limb than μ ~ 0.5. The negative contrast of dark faculae may arise from cooling of the surrounding photosphere, or from increased visibility of cool layers of the facular flux tube itself. Quantitative comparison of these IR data with MHD models awaits calculation of flux tube contrasts at realistic angular resolution.
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Tsai, Feng, and J. M. Cowley. "Contrasts of planar defects in reflection electron microscopy." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 1004–5. http://dx.doi.org/10.1017/s042482010015085x.
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Reflection electron microscopy (REM) has been used to study surface defects such as surface steps, dislocations emerging on crystal surfaces, and surface reconstructions. However, only a few REM studies have been reported about the planar defects emerging on surfaces. The interaction of planar defects with surfaces may be of considerable practical importance but so far there seems to be only one relatively simple theoretical treatment of the REM contrast and very little experimental evidence to support its predications. Recently, intersections of both 90° and 180° ferroelectric domain boundaries with BaTiO3 crystal surfaces have been investigated by Tsai and Cowley with REM.The REM observations of several planar defects, such as stacking faults and domain boundaries have been continued by the present authors. All REM observations are performed on a JEM-2000FX transmission electron microscope. The sample preparations may be seen somewhere else. In REM, the incident electron beam strikes the surface of a crystal with a small glancing angle.
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Kodama, T., N. Koyama, and Y. Uchikawa. "Condition of Energy and Incident Angle of Primary Beam for Voltage Contrast Observation Over Passivated Devices." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 1 (August 12, 1990): 390–91. http://dx.doi.org/10.1017/s0424820100180707.
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Inspection of passivated micro devices using the scanning electron microscope (SEM) at a low primary electron energy has been increasingly studied. Under an appropriate condition of energy Ep and incident angle Φp of the primary beam, the voltage contrasts follow regular and reversible variations, corresponding to the device electrode voltage under the passivation; i.e., the capacitive coupling voltage contrasts (CCVC). In our previous papers, we reported an empirical formula for conditions under which SEM observations over the passivation layer can be made without serious charging disturbances. In the present work we investigate the charging free conditions of PSG, SiN and Si3N4 passivated devices and the storage time of the voltage contrast is measured for various values of Ep and Φp.There exist a clear threshold of imaging conditions of CCVC with respect to Ep and Φp. Below the threshold, while continued imaging, the observed voltage contrasts follow regular and reversible variations. Above the threshold serious charging occurs and appears as bright and unclear contrast which never disappears throughout the observation. The two kinds of contrasts can be readily distinguished, since the charging contrast does not change its polarity whereas CCVC dose, when the applied voltages to the device electrodes are turned on and off. As was done in our previous works, the threshold values are determined by observing whether or not the observed voltage contrast follows reversible variation. The specimen used are PSG (1.2μm thick), SiN (1.1μm thick) and Si3N4 (0.8μm thick) passivated devices. Table 1 shows the threshold values of Ep for eachΦ p. The value of product Ep· cos2 Φp for each material becomes practically constant (= Ec). The value of Ec does not depend on the other imaging parameters such as magnification, primary beam current and scanning time per frame.
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Lee, Joonyeol, and John H. R. Maunsell. "The Effect of Attention on Neuronal Responses to High and Low Contrast Stimuli." Journal of Neurophysiology 104, no. 2 (August 2010): 960–71. http://dx.doi.org/10.1152/jn.01019.2009.
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It remains unclear how attention affects the tuning of individual neurons in visual cerebral cortex. Some observations suggest that attention preferentially enhances responses to low contrast stimuli, whereas others suggest that attention proportionally affects responses to all stimuli. Resolving how attention affects responses to different stimuli is essential for understanding the mechanism by which it acts. To explore the effects of attention on stimuli of different contrasts, we recorded from individual neurons in the middle temporal visual area (MT) of rhesus monkeys while shifting their attention between preferred and nonpreferred stimuli within their receptive fields. This configuration results in robust attentional modulation that makes it possible to readily distinguish whether attention acts preferentially on low contrast stimuli. We found no evidence for greater enhancement of low contrast stimuli. Instead, the strong attentional modulations were well explained by a model in which attention proportionally enhances responses to stimuli of all contrasts. These data, together with observations on the effects of attention on responses to other stimulus dimensions, suggest that the primary effect of attention in visual cortex may be to simply increase the strength of responses to all stimuli by the same proportion.
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Victor, Jonathan D., Mary M. Conte, and Keith P. Purpura. "Dynamic shifts of the contrast-response function." Visual Neuroscience 14, no. 3 (May 1997): 577–87. http://dx.doi.org/10.1017/s0952523800012232.
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AbstractWe recorded visual evoked potentials in response to square-wave contrast-reversal checkerboards undergoing a transition in the mean contrast level. Checkerboards were modulated at 4.22 Hz (8.45-Hz reversal rate). After each set of 16 cycles of reversals, stimulus contrast abruptly switched between a “high” contrast level (0.06 to 1.0) to a “low” contrast level (0.03 to 0.5). Higher contrasts attenuated responses to lower contrasts by up to a factor of 2 during the period immediately following the contrast change. Contrast-response functions derived from the initial second following a conditioning contrast shifted by a factor of 2–4 along the contrast axis. For low-contrast stimuli, response phase was an advancing function of the contrast level in the immediately preceding second. For high-contrast stimuli, response phase was independent of the prior contrast history. Steady stimulation for periods as long as 1 min produced only minor effects on response amplitude, and no detectable effects on response phase. These observations delineate the dynamics of a contrast gain control in human vision.
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Close, L. M., K. Follette, J. R. Males, K. Morzinski, T. J. Rodigas, P. Hinz, Y.-L. Wu, et al. "Visible AO Observations at Halpha for Accreting Young Planets." Proceedings of the International Astronomical Union 8, S299 (June 2013): 32–33. http://dx.doi.org/10.1017/s1743921313007734.
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AbstractWe utilized the new high-order (250-378 mode) Magellan Adaptive Optics system (MagAO) to obtain very high-resolution science in the visible with MagAO's VisAO CCD camera. In the good-median seeing conditions of Magellan (0.5–0.7″) we find MagAO delivers individual short exposure images as good as 19 mas optical resolution. Due to telescope vibrations, long exposure (60s) r' (0.63μm) images are slightly coarser at FWHM = 23-29 mas (Strehl ~ 28%) with bright (R < 9 mag) guide stars. These are the highest resolution filled-aperture images published to date. Images of the young (~ 1 Myr) Orion Trapezium θ1 Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32 mas binary θ1 Ori C1C2 was easily resolved in non-interferometric images for the first time. Relative positions of the bright trapezium binary stars were measured with ~ 0.6–5 mas accuracy. In the second commissioning run we were able to correct 378 modes and achieved good contrasts (Strehl>20% on young transition disks at Hα). We discuss the contrasts achieved at Hα and the possibility of detecting low mass (~ 1–5 Mjup) planets (past 5AU) with our new SAPPHIRES survey with MagAO at Hα.
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Wensveen, Janice M., Ronald S. Harwerth, and Earl L. Smith. "Binocular Deficits Associated With Early Alternating Monocular Defocus. I. Behavioral Observations." Journal of Neurophysiology 90, no. 5 (November 2003): 3001–11. http://dx.doi.org/10.1152/jn.00976.2002.
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To study the binocular vision deficits associated with anisometropia, monkeys were reared with alternating monocular defocus, which allowed monocular mechanisms to develop normally while binocular mechanisms were selectively compromised. A defocusing contact lens of –1.5 D, –3 D, or –6 D was worn on alternate eyes on successive days ( n = 3 per lens power) from 3 wk to 9 mo of age. The control subjects were two normally reared monkeys and two human observers. Functional binocular vision was assessed through behavioral measurements of stereoscopic depth discrimination thresholds as a function of spatial frequency. To characterize the extent of the deficits in disparity processing at a given spatial frequency, the contrast required to support stereopsis was determined for a range of disparities that exceeded the subjects' measured stereoacuity. The lens-reared monkeys showed spatial-frequency-selective deficits in stereopsis that depended on the magnitude of the simulated anisometropia experienced during the rearing period. For a given spatial frequency, the treated monkeys generally required higher than normal contrasts to support stereopsis even for large disparities. Moreover, a given increase in contrast produced smaller than normal improvements in stereo discrimination in our treated subjects, which suggests that in addition to deficits in contrast sensitivity, disparity-sensitive mechanisms exhibited low contrast gains. The spatial-frequency selective nature of the binocular deficits produced by the imposed anisometropia indicate that disparity processing mechanisms are normally spatial-frequency selective and that mechanisms tuned to different spatial frequencies can be differentially affected by abnormal binocular visual experience.
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Enderlin, Ellyn M., and Timothy C. Bartholomaus. "Sharp contrasts in observed and modeled crevasse patterns at Greenland's marine terminating glaciers." Cryosphere 14, no. 11 (November 18, 2020): 4121–33. http://dx.doi.org/10.5194/tc-14-4121-2020.
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Abstract. Crevasses are affected by and affect both the stresses and the surface mass balance of glaciers. These effects are brought on through potentially important controls on meltwater routing, glacier viscosity, and iceberg calving, yet there are few direct observations of crevasse sizes and locations to inform our understanding of these interactions. Here we extract depth estimates for the visible portion of crevasses from high-resolution surface elevation observations for 52 644 crevasses from 19 Greenland glaciers. We then compare our observed depths with those calculated using two popular models that assume crevasse depths are functions of local stresses: the Nye and linear elastic fracture mechanics (LEFM) formulations. When informed by the observed crevasse depths, the LEFM formulation produces kilometer-scale variations in crevasse depth, in decent agreement with observations. However, neither formulation accurately captures smaller-scale variations in the observed crevasse depths. Critically, we find that along-flow patterns in crevasse depths are unrelated to along-flow patterns in strain rates (and therefore stresses). Cumulative strain rate is moderately more predictive of crevasse depths at the majority of glaciers. Our reliance on lidar limits the inference we can make regarding fracture depths. However, given the discordant patterns in observed and modeled crevasses, we recommend additional in situ and remote sensing analyses before Nye and LEFM models are considered predictive. Such analyses should span extensional and compressive regions to better understand the influence of advection on crevasse geometry. Ultimately, such additional study will enable more reliable projection of terminus position change and supraglacial meltwater routing that relies on accurate modeling of crevasse occurrence.
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Kotov, V. A., and S. Koutchmy. "On Sunspot and Facular Contrast Variations Near 2 μm and 4 μm." Symposium - International Astronomical Union 154 (1994): 265–70. http://dx.doi.org/10.1017/s0074180900124519.
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Observations of the Sun at 2.2 and 3.75 μm have been made at the Pic-du-Midi and Crimean observatories. High resolution (~ 1″) records of the sunspot and facular contrasts at various heliocentric distances as well as those at the extreme solar limb are presented. We find substantial variations in the sunspot-core relative intensity caused by magnetic activity of the spot. The extreme-limb contrasts of faculae at 3.75 μm are strong thus support flux-tube models which result in an enhancement of the extreme-limb facular brightness.
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Rajaguru, S. P., and S. S. Hasan. "Magnetohydrostatic equilibrium in starspots: dependences on color (Teff) and surface gravity (g)." Proceedings of the International Astronomical Union 6, S273 (August 2010): 276–80. http://dx.doi.org/10.1017/s1743921311015377.
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AbstractTemperature contrasts and magnetic field strengths of sunspot umbrae broadly follow the thermal-magnetic relationship obtained from magnetohydrostatic equilibrium. Using a compilation of recent observations, especially in molecular bands, of temperature contrasts of starspots in cool stars, and a grid of Kurucz stellar model atmospheres constructed to cover layers of sub-surface convection zone, we examine how the above relationship scales with effective temperature (Teff), surface gravity g and the associated changes in opacity of stellar photospheric gas. We calculate expected field strengths in starpots and find that a given relative reduction in temperatures (or the same darkness contrasts) yield increasing field strengths against decreasing Teff due to a combination of pressure and opacity variations against Teff.
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Stewart, Finlay J., Michiyo Kinoshita, and Kentaro Arikawa. "The butterfly Papilio xuthus detects visual motion using chromatic contrast." Biology Letters 11, no. 10 (October 2015): 20150687. http://dx.doi.org/10.1098/rsbl.2015.0687.
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Many insects’ motion vision is achromatic and thus dependent on brightness rather than on colour contrast. We investigate whether this is true of the butterfly Papilio xuthus , an animal noted for its complex retinal organization, by measuring head movements of restrained animals in response to moving two-colour patterns. Responses were never eliminated across a range of relative colour intensities, indicating that motion can be detected through chromatic contrast in the absence of luminance contrast. Furthermore, we identify an interaction between colour and contrast polarity in sensitivity to achromatic patterns, suggesting that ON and OFF contrasts are processed by two channels with different spectral sensitivities. We propose a model of the motion detection process in the retina/lamina based on these observations.
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Vasilenko, O. V., and N. N. Voropay. "Microclimatic features of landscapes in the territory with a sparse network of meteorological observations." IOP Conference Series: Earth and Environmental Science 885, no. 1 (October 1, 2021): 012037. http://dx.doi.org/10.1088/1755-1315/885/1/012037.
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Abstract Automatic monitoring of air temperature and humidity in the mountain-depression landscapes of the Tunka depression has been organized. The results of the analysis of observation data for 10 years showed significant differences in the temperature regime in different landscapes. The sites can be divided into three groups – the slopes of the depression, pine- herbaceous landscapes, and the lacustrine-bog complex of the central part. The average annual air temperature at all sites is negative and vary in range -0.7 … -2.1°C. Vegetation has the greatest influence on microclimatic characteristics. The maximum contrasts in the temperature regime of the air throughout the year are observed in open areas with cloudless skies. In winter, this is explained by radiation cooling, and in summer – by the heating of the open surface in the daytime. In this case, not only the daily amplitude of air temperature in the open areas increases, but also the largest contrasts between the open and closed areas are observed.
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Habib, Nouraly, Anhum Konan, and Tra Bi Zamble Olivier Didier. "A Case of Progressive Ossifying Fibrodysplasia of Tracheobronchial Respiratory Muscles." Case Reports in Radiology 2019 (February 11, 2019): 1–4. http://dx.doi.org/10.1155/2019/5095343.
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The authors report a case of progressive ossifying myositis (POM) in a 13-year-old boy, revealed by dry cough and dyspnea. Conventional chest x-rays and whole-body CT showed extraskeletal ossification that seems to affect the left bronchial strain and trachea. This lesional topography, if established, not yet described to our knowledge, contrasts with the observations of all the authors, including Munchmeyer, for whom smooth muscles and muscles attached to the skeleton by a single end are spared by the heterotopic ossifications characteristic of the disease. Therefore, this observation raises the question of the ubiquity of muscle ossifications during POM.
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Horgan, Huw J., Sridhar Anandakrishnan, Richard B. Alley, Peter G. Burkett, and Leo E. Peters. "Englacial seismic reflectivity: imaging crystal-orientation fabric in West Antarctica." Journal of Glaciology 57, no. 204 (2011): 639–50. http://dx.doi.org/10.3189/002214311797409686.
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AbstractAbrupt changes in crystal-orientation fabric (COF), and therefore viscosity, are observed near the base of the ice sheet throughout West Antarctica. We report on active-source seismic observations from WAIS Divide, mid-stream and downstream on Thwaites Glacier, and the onset region of Bindschadler Ice Stream. These data reveal a prevalence of englacial seismic reflectivity in the bottom quarter of the ice sheet. The observed seismic reflectivity is complex but largely bed-conformable, with long-spatial-wavelength features observed in the flow direction and short-wavelength features observed across flow. A correspondence of englacial structures with bed features is also observed. We determine the origin of the reflectivity to be abrupt changes in the COF of ice, based on the following: (1) observations of englacial reflectivity are consistent with current knowledge of COF within ice sheets, (2) englacial reflectivity caused by COF contrasts requires the simplest genesis, especially at ice divides, and (3) amplitude analysis shows that the observed englacial reflectivity can be explained by contrasts in seismic velocity due to COF changes. We note that the downstream increase in the quantity and complexity of observations indicates that direct observations of COF at ice divides likely underestimate the role that fabric plays in ice-sheet dynamics.
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Urbanik, M., U. Klein, R. Beck, and R. Wielebinski. "The magnetic-field structure and dynamics of NGC 253." Symposium - International Astronomical Union 106 (1985): 247–48. http://dx.doi.org/10.1017/s0074180900242551.
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Total-power and polarization observations of NGC 253 at 10.7 GHz have been performed with the 100-m MPIfR radio telescope. The observed arm/interarm polarization contrasts are discussed in the context of possible field configurations in spiral arms.
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Matsui, Toshi, Brenda Dolan, Takamichi Iguchi, Steven A. Rutledge, Wei-Kuo Tao, and Stephen Lang. "Polarimetric Radar Characteristics of Simulated and Observed Intense Convective Cores for a Midlatitude Continental and Tropical Maritime Environment." Journal of Hydrometeorology 21, no. 3 (March 2020): 501–17. http://dx.doi.org/10.1175/jhm-d-19-0185.1.
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AbstractThis study contrasts midlatitude continental and tropical maritime deep convective cores using polarimetric radar observables and retrievals from selected deep convection episodes during the MC3E and TWPICE field campaigns. The continental convective cores produce stronger radar reflectivities throughout the profiles, while maritime convective cores produce more positive differential reflectivity Zdr and larger specific differential phase Kdp above the melting level. Hydrometeor identification retrievals revealed the presence of large fractions of rimed ice particles (snow aggregates) in the continental (maritime) convective cores, consistent with the Zdr and Kdp observations. The regional cloud-resolving model simulations with bulk and size-resolved bin microphysics are conducted for the selected cases, and the simulation outputs are converted into polarimetric radar signals and retrievals identical to the observational composites. Both the bulk and the bin microphysics reproduce realistic land and ocean (L-O) contrasts in reflectivity, polarimetric variables of rain drops, and hydrometeor profiles, but there are still large uncertainties in describing Zdr and Kdp of ice crystals associated with the ice particle shapes/orientation assumptions. Sensitivity experiments are conducted by swapping background aerosols between the continental and maritime environments, revealing that background aerosols play a role in shaping the distinct L-O contrasts in radar reflectivity associated with raindrop sizes, in addition to the dominant role of background thermodynamics.
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Henry, Steven G., and Henry N. Pollack. "Heat flow in the presence of topography: Numerical analysis of data ensembles." GEOPHYSICS 50, no. 8 (August 1985): 1335–41. http://dx.doi.org/10.1190/1.1442004.
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We present a method of estimating subsurface temperatures and true regional heat flow in the presence of perturbing topography, variable surface temperature, and subsurface thermal conductivity contrasts. The method involves solution of the steady‐state three‐dimensional heat conduction equation by finite‐difference numerical techniques. The topography is represented by an irregular upper boundary and the variable surface temperature as a boundary condition along the irregular upper surface. Internal structural configurations and conductivity contrasts are easily accommodated. The principal variable input into the system is the deep basal (unperturbed) heat flow. The best value of heat flow is obtained by minimizing, in a least‐squares sense, the differences between observed and calculated temperatures. Temperature observations commonly are distributed irregularly in the near‐surface (perturbed) environment, in multiple vertical or inclined boreholes, tunnels, and/or mine galleries. The method is particularly suited to simultaneous analysis of an ensemble of distributed observations, in contrast to methods that focus on the perturbation to the temperature gradient in the vicinity of a single borehole. We used the method to reduce data obtained at fifteen newly established heat flow sites in the Bolivian and Peruvian Andes. We illustrate with three examples—a two‐dimensional model from the Bolivar Mine, Bolivia; (2) a three‐dimensional model using variable conductivity from the Cerro Verde Mine, Peru; and (3) a three‐dimensional model at the Colquiri Mine, Bolivia where temperature measurements were few and the distance between the individual boreholes was fairly large.
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Bohnert, Amanda, and Kelly H. Berkson. "Lip posture of high and high-mid vowels in Hnaring Lutuv." Journal of the Acoustical Society of America 153, no. 3_supplement (March 1, 2023): A372. http://dx.doi.org/10.1121/10.0019216.
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Lutuv is an under-documented South Central Tibeto-Burman language which is reported to contain six high monophthongs /i, y, ɨ, ʉ, Ɯ, u/ and four diphthongal vowels with high onsets /ie̯, yə̯, uɔ̯, Ɯə̯/ (Bohnert etal., 2022). No articulatory work on Lutuv exists to date, but impressionistic observations suggest that while the contrast between /i, y/ and /u, Ɯ/ is one of rounding (as implied by their IPA transcriptions), the contrast between /ɨ, ʉ/ is instead one of lip spreading. In addition, /ʉ/ seems to involve a degree of frication from labiodental contact. To further investigate these observations, the current paper utilizes facial landmark recognition through OpenFace 2.0 (Baltrusaitis et al., 2018) to analyze the lip posture of these vowels, measuring horizontal, vertical, and lateral lip aperture over the duration of each vowel produced by one native speaker in a curated word list. These measurements are compared both within and across pairs to determine (1) the articulatory characteristics of Lutuv rounding contrasts, and (2) whether the central high vowels display these characteristics. These data complement existing acoustic analyses and provide a more detailed understanding of the articulation of a typologically rare contrast.
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Staughton, Sir Christopher. "How do Courts Interpret Commercial Contracts." Cambridge Law Journal 58, no. 2 (July 1999): 303–13. http://dx.doi.org/10.1017/s0008197399002032.
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CHRISTOPHER Staughton, a former Lord Justice of Appeal, writes of the four principal rules for the interpretation of written contracts. First, there is the exclusion of negotiations and subjective evidence of intention. Secondly he considers what material can qualify as background evidence, or as some would say matrix. Thirdly, there is the rule that a meaning which is less obvious =N but still consistent with the words used =N may be preferred. Fourthly, he deals with the very limited extent to which evidence of market practice is admissible.The article contrasts recent observations of Lord Hoffmann in two cases in the House of Lords with other authority, both ancient and modern.
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Grunhut, Jason H., and E. Alecian. "Magnetic higher-mass stars in the early stages of their evolution." Proceedings of the International Astronomical Union 9, S302 (August 2013): 70–79. http://dx.doi.org/10.1017/s1743921314001756.
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AbstractOver the past decade, significant investigations have been made through the use of high-resolution spectropolarimetry to probe the surface magnetic field characteristics of young higher-mass (M ≳ 1.5 M⊙) stars from pre-main sequence to zero-age main sequence evolutionary phases. The results of these observational campaigns suggest that these young higher-mass stars host similar magnetic properties to their main sequence descendants - strong, stable, globally-ordered fields that are detected in approximately 10 percent of all stars. This strongly contrasts with lower-mass stars, where it is generally accepted that a solar-like dynamo is in operation that generates more complex, globally-weak fields that are ubiquitous. The consensus is magnetic fields in higher-mass stars are fossil remnants of a magnetic field present in the molecular cloud, or generated very early during stellar formation. This review discusses the spectropolarimetric observations of higher-mass stars and how these observations have guided our current understanding of the magnetic characteristics of young higher-mass stars.
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Xu, Yan, Xu Yang, Graham S. Kerr, Vanessa Polito, Viacheslav M. Sadykov, Ju Jing, Wenda Cao, and Haimin Wang. "Multi-passband Observations of a Solar Flare over the He i 10830 Å line." Astrophysical Journal Letters 924, no. 1 (January 1, 2022): L18. http://dx.doi.org/10.3847/2041-8213/ac447c.
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Abstract This study presents a C3.0 flare observed by the Big Bear Solar Observatory/Goode Solar Telescope (GST) and Interface Region Imaging Spectrograph (IRIS) on 2018 May 28 around 17:10 UT. The Near-Infrared Imaging Spectropolarimeter of GST was set to spectral imaging mode to scan five spectral positions at ±0.8, ±0.4 Å and line center of He i 10830 Å. At the flare ribbon’s leading edge, the line is observed to undergo enhanced absorption, while the rest of the ribbon is observed to be in emission. When in emission, the contrast compared to the preflare ranges from about 30% to nearly 100% at different spectral positions. Two types of spectra, “convex” shape with higher intensity at line core and “concave” shape with higher emission in the line wings, are found at the trailing and peak flaring areas, respectively. On the ribbon front, negative contrasts, or enhanced absorption, of about ∼10%–20% appear in all five wavelengths. This observation strongly suggests that the negative flares observed in He i 10830 Å with mono-filtergram previously were not caused by pure Doppler shifts of this spectral line. Instead, the enhanced absorption appears to be a consequence of flare-energy injection, namely nonthermal collisional ionization of helium caused by the precipitation of high-energy electrons, as found in our recent numerical modeling results. In addition, though not strictly simultaneous, observations of Mg ii from the IRIS spacecraft, show an obvious central reversal pattern at the locations where enhanced absorption of He i 10830 Å is seen, which is consistent with previous observations.
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Henderson, Stephen M., R. T. Guza, Steve Elgar, and T. H. C. Herbers. "Refraction of Surface Gravity Waves by Shear Waves." Journal of Physical Oceanography 36, no. 4 (April 1, 2006): 629–35. http://dx.doi.org/10.1175/jpo2890.1.
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Abstract Previous field observations indicate that the directional spread of swell-frequency (nominally 0.1 Hz) surface gravity waves increases during shoreward propagation across the surf zone. This directional broadening contrasts with the narrowing observed seaward of the surf zone and predicted by Snell’s law for bathymetric refraction. Field-observed broadening was predicted by a new model for refraction of swell by lower-frequency (nominally 0.01 Hz) current and elevation fluctuations. The observations and the model suggest that refraction by the cross-shore currents of energetic shear waves contributed substantially to the observed broadening.
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Wylie, Donald, Darren L. Jackson, W. Paul Menzel, and John J. Bates. "Trends in Global Cloud Cover in Two Decades of HIRS Observations." Journal of Climate 18, no. 15 (August 1, 2005): 3021–31. http://dx.doi.org/10.1175/jcli3461.1.
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Abstract The frequency of cloud detection and the frequency with which these clouds are found in the upper troposphere have been extracted from NOAA High Resolution Infrared Radiometer Sounder (HIRS) polar-orbiting satellite data from 1979 to 2001. The HIRS/2 sensor was flown on nine satellites from the Television Infrared Observation Satellite-Next Generation (TIROS-N) through NOAA-14, forming a 22-yr record. Carbon dioxide slicing was used to infer cloud amount and height. Trends in cloud cover and high-cloud frequency were found to be small in these data. High clouds show a small but statistically significant increase in the Tropics and the Northern Hemisphere. The HIRS analysis contrasts with the International Satellite Cloud Climatology Project (ISCCP), which shows a decrease in both total cloud cover and high clouds during most of this period.
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Ceau, A., D. Mary, A. Greenbaum, F. Martinache, A. Sivaramakrishnan, R. Laugier, and M. N’Diaye. "Kernel-phase detection limits." Astronomy & Astrophysics 630 (October 2019): A120. http://dx.doi.org/10.1051/0004-6361/201935247.
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Context. The James Webb Space Telescope (JWST) will offer high angular resolution observing capability in the near-infrared with masking interferometry on the Near-Infrared Imager and Slitless Spectrograph (NIRISS), and coronagraphic imaging on the Near-Infrared Camera (NIRCam) and the Mid-Infrared Instrument (MIRI). Full-aperture kernel-phase-based interferometry complements these observing modes by allowing us to probe for companions at small angular resolution while preserving the telescope throughput. Aims. Our goal is to derive both theoretical and operational contrast-detection limits for the kernel-phase analysis of JWST NIRISS full-pupil observations using tools from hypothesis testing theory. The study is immediately applied to observations of faint brown dwarfs with this instrument, but the tools and methods introduced here are applicable in a wide variety of contexts. Methods. We construct a statistically independent set of observable quantities from a collection of aberration-robust kernel phases. Three detection tests based on these observable quantities are designed and analysed, all having the property of guaranteeing a constant false-alarm rate for phase aberrations smaller than about one radian. One of these tests, the likelihood ratio or Neyman-Pearson test, provides a theoretical performance bound for any detection test. Results. The operational detection method considered here is shown to exhibit only marginal power loss with respect to the theoretical bound. In principle, for the test set to a false-alarm probability of 1%, companions at contrasts reaching 103 and separations of 200 mas around objects of magnitude 14.1 are detectable with a probability of 68%. For the brightest objects observable using the full pupil of JWST and NIRISS, contrasts of up to 104 at separations of 200 mas could ultimately be achieved, barring significant wavefront drift. We also provide a statistical analysis of the uncertainties affecting the contrasts and separations that are estimated for the detected companions. Conclusions. The proposed detection method is close to the ultimate bound and offers guarantees on the probability of making a false detection for binaries, as well as on the error bars for the estimated parameters of the binaries that will be detected by JWST NIRISS. This method is not only applicable to JWST NIRISS but to any imaging system with adequate sampling.
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Plavin, A., Z. Paragi, B. Marcote, A. Keimpema, J. W. T. Hessels, K. Nimmo, H. K. Vedantham, and L. G. Spitler. "FRB 121102: Drastic changes in the burst polarization contrasts with the stability of the persistent emission." Monthly Notices of the Royal Astronomical Society 511, no. 4 (February 24, 2022): 6033–41. http://dx.doi.org/10.1093/mnras/stac500.
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ABSTRACT We study milliarcsecond-scale properties of the persistent radio counterpart to FRB 121102 and investigate the spectro-polarimetric properties of a bright burst. For the former, we use European VLBI Network (EVN) observations in 2017 at 1.7 and 4.8 GHz. For the latter, we reanalyse the 1.7-GHz data from the 100-m Effelseberg telescope taken in 2016. These observations predate other polarimetric studies of FRB 121102, and yield the highest burst Faraday rotation measure (RM) to date, RM = 1.27 · 105 rad m−2, consistent with the decreasing RM trend. The fractional polarization of the burst emission is 15 per cent at 1.7 GHz. This can be reconciled with the high-fractional polarization at higher frequencies if the Faraday width of the burst environment is 150 rad m−2 – a bare 0.1 per cent of the total Faraday rotation. The width may originate from minor non-uniformities in the Faraday screen, or from effects in the emitting region itself. The upper limit on the persistent source size is 1 pc, barely consistent with a young supernova (SN) scenario. The flux variability limit of $\lt 10{{\ \rm per\ cent}}$ is not in favour of the young SN scenario, and challenges other interpretations as well. The fractional polarization of the faint persistent source is constrained at $\lt 25{{\ \rm per\ cent}}$ at 4.8 GHz ruling out a common origin with the highly polarized individual bursts.
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De Chiara-Quenzer, Deborah. "Commentary on Pappas." Proceedings of the Boston Area Colloquium of Ancient Philosophy 32, no. 1 (July 25, 2017): 59–65. http://dx.doi.org/10.1163/22134417-00321p06.
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This commentary on Nicholas Pappas’s paper, “Telling Good Love from Bad in Plato’s Phaedrus,” reflects on a number of Pappas’s thoughtful observations and interpretations of features woven into the drama of the discussion (for example, Typho and Boreas, wings, left and right). However, unlike Pappas, who refrains from claiming that divinely inspired human love (good love) can be discerned by turning to the earthly, this commentary suggests that Pappas’s contrasts of wings which conceal versus wings which elevate, of left and right, and my added contrast of traditional Greek mythology versus Platonic mythology, lay the groundwork to discern the divine in the earthly, and to distinguish concomitantly bad from good human love. Additionally, the commentary discusses how Plato’s use of collection and division is used to distinguish good and bad human love.
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Tandokoro, Kohei, Masayasu Nagoshi, Takashi Kawano, Kaoru Sato, and Katsushige Tsuno. "Low-voltage SEM contrasts of steel surface studied by observations and electron trajectory simulations for GEMINI lens system." Microscopy 67, no. 5 (July 6, 2018): 274–79. http://dx.doi.org/10.1093/jmicro/dfy030.
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Ruggiero, Frank H., George D. Modica, and Alan E. Lipton. "Assimilation of Satellite Imager Data and Surface Observations to Improve Analysis of Circulations Forced by Cloud Shading Contrasts." Monthly Weather Review 128, no. 2 (2000): 434. http://dx.doi.org/10.1175/1520-0493(2000)128<0434:aosida>2.0.co;2.
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Gibbs, William J. "Innovation, Programmable Media and the Human Computer Interface." International Journal of E-Entrepreneurship and Innovation 9, no. 1 (January 2019): 30–46. http://dx.doi.org/10.4018/ijeei.2019010104.
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In this article, the author examines fundamental principles or characteristics (e.g., programmability, modularity, variability) of digital media that make much of today's digital innovations possible. These precepts offer context for understanding the rapid and pervasive innovation currently taking place in society and, more specifically, how this innovation impacts trends in human computer interfaces. A focus of the article will be news-orientated interfaces. This article contrasts traditional informational sources such as newspapers and television news with digital interfaces. Finally, this article makes several observations regarding technology innovation that have bearing on the interaction experience of news consumers. This article categorized these observations broadly as rapid innovation, interaction, social interaction, scale, convergence, and Internet of Things and data.
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Slovic, Paul. "The Psychology of risk." Saúde e Sociedade 19, no. 4 (December 2010): 731–47. http://dx.doi.org/10.1590/s0104-12902010000400002.
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The essay contrasts the scientific approach to analyzing and making decisions about risk with the ways that ordinary people perceive and respond to risk. It highlights the importance of trust as a determiner of perceived risk. It describes relatively new research on "risk as feelings" and the "Affect Heuristic". Finally reflects on the importance of this work for risk communication and concludes with some observations about human rationality and irrationality in the face of risk.
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Toda, Takako. "Interlanguage phonology." Australian Review of Applied Linguistics 17, no. 2 (January 1, 1994): 51–76. http://dx.doi.org/10.1075/aral.17.2.03tod.
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Abstract This paper presents the results of a study pertaining to the acquisition of timing control by Australian subjects who are enrolled in first-year Japanese at tertiary level. Instrumental techniques are used to observe segment duration and pitch patterns in the speech production of learners and native speakers of Japanese. The observations concern vowels and obstruents based on minimal pairs with durational contrasts, and the results are discussed within the framework of interlanguage phonology. The results obtained from this study demonstrate problems of beginning-level learners, including the underdifferentiation of durational contrasts (Han 1992). From the viewpoint of interlanguage phonology, however, the results seem to indicate that the learners have the ability to control timing and that they try to achieve durational distinctions in their speech production, but that their phonetic realisation is different from that of native speakers.
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Ha, Kyung-Ja, Sun-Hee Shin, and Larry Mahrt. "Spatial Variation of the Regional Wind Field with Land–Sea Contrasts and Complex Topography." Journal of Applied Meteorology and Climatology 48, no. 9 (September 1, 2009): 1929–39. http://dx.doi.org/10.1175/2009jamc2105.1.
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Abstract This study examines the spatial variation of the wind field observed in the coastal zone of southeast Korea with its complex terrain, using measurements from a regional network 75 km across and centered about Busan. Results are compared with observations from an inland regional network centered around Daegu, Korea, with less dramatic, but still significant, surface heterogeneity. The coherency between stations is examined in terms of the between-station correlations of the wind components for all pairs of stations as a function of separation distance between stations. A mesovelocity scale is defined as a measure of the spatial variability of the wind field within the network. This variability is related to wind speed and cloud cover for the two contrasting regional networks. Additional comparisons are made with a homogenous rural network in Iowa. The results underscore the complexity of flow with topography, urban areas, and land–sea contrasts and demonstrate the inadequacy of existing network strategies.
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M, Susanne, Becker Brown, and Peter E. Brown. "Stoping versus ductile deformation in the emplacement of the rapakivi intrusion of Qemertoq, South Greenland." Bulletin of the Geological Society of Denmark 33 (February 28, 1985): 363–70. http://dx.doi.org/10.37570/bgsd-1984-33-29.
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Subsidence of Ketilidian metamorphic rocks adjacent to mushroomshaped intrusions of rapakivi granite in South Greenland has been described by Bridgwater et al. (1974) and compared to the theoretical predictions of Ramberg (1967). Observations on the island of Qemertoq show that where the rapakivi magma rose through massive granite rather than schistose country rocks sloping was a major factor. This difference in intrusive mechanisms can be attributed to ductility contrasts in the different types of country rock.
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Maresh, Jennifer, Robert S. White, Richard W. Hobbs, and John R. Smallwood. "Seismic attenuation of Atlantic margin basalts: Observations and modeling." GEOPHYSICS 71, no. 6 (November 2006): B211—B221. http://dx.doi.org/10.1190/1.2335875.
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Paleogene basalts are present over much of the northeastern Atlantic European margin. In regions containing significant thicknesses of layered basalt flows, conducting seismic imaging within and beneath the volcanic section has proven difficult, largely because the basalts severely attenuate and scatter seismic energy. We use data from a vertical seismic profile (VSP) from well 164/07-1 that penetrated [Formula: see text] of basalt in the northern Rockall Trough west of Britain to measure the seismic attenuation caused by the in-situ basalts. The effective quality factor [Formula: see text] of the basalt layer is found from the VSP to be 15–35, which is considerably lower (more attenuative) than the intrinsic attenuation measured on basalt samples in the laboratory. We then run synthetic seismogram models to investigate the likely cause of the attenuation. Full waveform 1D modeling of stacked sequences of lava flows based on rock properties from the same well indicates that much of the seismic attenuation observed from the VSP can be accounted for by the scattering effects of multiple thin layers with high impedance contrasts. Phase-screen seismic modeling of the rugose basalt surface at the top-of-basalt sediment interface, with the magnitude and wavelength of the relief constrained by a 3D seismic survey around the well, suggests that surface scattering from this interface plays a much smaller role than internal scattering in attenuating the seismic signal as it passes through the basalt sequence.
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Ensign, Julene, Amelia Mays Woods, and Pamela Hodges Kulinna. "Teacher Development in First-Year Physical Educators: A Comparison of Effectiveness Among Different Physical Education Teacher Education Backgrounds." Journal of Teaching in Physical Education 36, no. 4 (October 2017): 455–66. http://dx.doi.org/10.1123/jtpe.2016-0105.
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Purpose:This study evaluated the teaching effectiveness of six first-year physical educators, three Southwestern and three Midwestern graduates, employing different curricular approaches.Method:Utilizing surveys, interviews, questionnaires, and systematic observations, data were analyzed through a framework of seven essential teaching tasks (Rink, 2002).Results:Data indicated overall mean scores of 34% motor appropriate activity with Academic Learning Time-Physical Education (ALT-PE) and a rating of 70.37 on the Qualitative Measures of Teacher Performance Scale (QMTPS). Notable contrasts included higher mean scores for Southwest participants for motor-appropriate and motor-inappropriate activity. Midwest participants devoted more time to game situations, management, and social behavior. For QMTPS, Southwest means were higher in every category. Qualitative themes produced similarities in teaching philosophy, fidelity to preservice training, and perceived value of reflective practices. Contrasts existed in curricular emphases and approaches to classroom management.Discussion/Conclusion:Characteristics of effective teaching were demonstrated by all participants regardless of curricular emphasis.
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Dowdeswell, Julian A., Gordon S. Hamilton, and Jon Ove Hagen. "The duration of the active phase on surge-type glaciers: contrasts between Svalbard and other regions." Journal of Glaciology 37, no. 127 (1991): 388–400. http://dx.doi.org/10.1017/s0022143000005827.
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AbstractMany glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Data on active-phase duration in Svalbard come from aerial photographs, satellite imagery, field surveys and airborne reconnaissance. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250 km2. Worldwide, active-phase duration is recorded for less than 50 glaciers. Few observations are available on high polar ice masses. The duration of the active phase is significantly longer for Svalbard glaciers than for surge-type glaciers in other areas from which data are available. In Svalbard, the active phase may last from 3 to 10 years. By contrast, a surge duration of 1–2 years is more typical of ice masses in northwest North America, Iceland and the Pamirs. Ice velocities during the protracted active phase on Svalbard glaciers are considerably lower than those for many surge-type glaciers in these other regions. Mass is transferred down-glacier more slowly but over a considerably longer period. Svalbard surge-type glaciers do not exhibit the very abrupt termination of the active phase, over periods of a few days, observed for several Alaskan glaciers. The duration of the active phase in Svalbard is not dependent on parameters related to glacier size. The quiescent phase is also relatively long (50–500 years) for Svalbard ice masses. Detailed field monitoring of changing basal conditions through the surge cycle is required from surge-type glaciers in Svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago, which may also typify other high polar ice masses. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges.
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Dowdeswell, Julian A., Gordon S. Hamilton, and Jon Ove Hagen. "The duration of the active phase on surge-type glaciers: contrasts between Svalbard and other regions." Journal of Glaciology 37, no. 127 (1991): 388–400. http://dx.doi.org/10.3189/s0022143000005827.
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AbstractMany glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Data on active-phase duration in Svalbard come from aerial photographs, satellite imagery, field surveys and airborne reconnaissance. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250 km2. Worldwide, active-phase duration is recorded for less than 50 glaciers. Few observations are available on high polar ice masses. The duration of the active phase is significantly longer for Svalbard glaciers than for surge-type glaciers in other areas from which data are available. In Svalbard, the active phase may last from 3 to 10 years. By contrast, a surge duration of 1–2 years is more typical of ice masses in northwest North America, Iceland and the Pamirs. Ice velocities during the protracted active phase on Svalbard glaciers are considerably lower than those for many surge-type glaciers in these other regions. Mass is transferred down-glacier more slowly but over a considerably longer period. Svalbard surge-type glaciers do not exhibit the very abrupt termination of the active phase, over periods of a few days, observed for several Alaskan glaciers. The duration of the active phase in Svalbard is not dependent on parameters related to glacier size. The quiescent phase is also relatively long (50–500 years) for Svalbard ice masses. Detailed field monitoring of changing basal conditions through the surge cycle is required from surge-type glaciers in Svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago, which may also typify other high polar ice masses. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges.
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Mandal, Nripes Kumar. "On Robust Designs." Calcutta Statistical Association Bulletin 38, no. 1-2 (March 1989): 115–20. http://dx.doi.org/10.1177/0008068319890109.
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Box and Draper (1975) proposed a criterion of robustness against the presence of wild observations for the problem of estimation of Xβ in the response surface model E( Y) = Xβ, D(Y) = σ2.I. Gopalau and Dey (1976) elttended this concept to block designs setting, for the problem of estimation of σ2. In the present note an attempt has been made to examine the robustness of block designs for the problem of estimation of any full set of orthonormal varietal contrasts.
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Mahoney, James. "After KKV: The New Methodology of Qualitative Research." World Politics 62, no. 1 (December 18, 2009): 120–47. http://dx.doi.org/10.1017/s0043887109990220.
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This article discusses developments in the field of qualitative methodology since the publication of King, Keohane, and Verba's (KKV's) Designing Social Inquiry. Three areas of the new methodology are examined: (1) process tracing and causal-process observations; (2) methods using set theory and logic; and (3) strategies for combining qualitative and quantitative research. In each of these areas, the article argues, the new literature encompasses KKV's helpful insights while avoiding their most obvious missteps. Discussion focuses especially on contrasts between the kind of observations that are used in qualitative versus quantitative research, differences between regression-oriented approaches and those based on set theory and logic, and new approaches for bringing out complementarities between qualitative and quantitative research. The article concludes by discussing research frontiers in the field of qualitative methodology.
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Mattsson, P. "Energy-efficient lighting and visually impaired users in homelike environments." IOP Conference Series: Earth and Environmental Science 1099, no. 1 (November 1, 2022): 012049. http://dx.doi.org/10.1088/1755-1315/1099/1/012049.
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Abstract Despite a rapid transition to LED lamps, it is still little knowledge about the effects of these light sources on users with low vision. The study’s main objective was to acquire a better understanding about how correlated colour temperatures (CCTs) of non-directional LED affect visual accessibility and perceptions of lighting quality in homelike environments among visually impaired persons. The study took place in a full scale laboratory in which CCTs of 2,700 K and 4,000 K were tested. Participants having normal vision (N=60, 24 males, 36 females, M = 25.50) were divided into three groups of 20 to assess the two lit environments with cataract goggle, severe cataract goggle and normal vision respectively. They were asked to perform everyday activities while the observer recorded the time and conducted observations, and to rate the difficulty of each activity. Thereafter, the participants were asked to rate their perceptions of lighting quality and contrasts in the room. With the same CRI of Ra80, there were no differences in the performance of everyday activities between the two CCTs whereas the differences in the perceived lighting quality and the perceived contrasts were found. The cool white CCT was found to positively affect visual accessibility and perceived contrasts however, its comfort quality remains questionable.
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Vanhonacker, Wilfried R. "Estimating an Autoregressive Current Effects Model of Sales Response when Observations are Aggregated over Time: Least Squares versus Maximum Likelihood." Journal of Marketing Research 25, no. 3 (August 1988): 301–7. http://dx.doi.org/10.1177/002224378802500308.
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Estimating autoregressive current effects models is not straightforward when observations are aggregated over time. The author evaluates a familiar iterative generalized least squares (IGLS) approach and contrasts it to a maximum likelihood (ML) approach. Analytic and numerical results suggest that (1) IGLS and ML provide good estimates for the response parameters in instances of positive serial correlation, (2) ML provides superior (in mean squared error) estimates for the serial correlation coefficient, and (3) IGLS might have difficulty in deriving parameter estimates in instances of negative serial correlation.
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Schutgens, N. A. J., D. G. Partridge, and P. Stier. "The importance of temporal collocation for the evaluation of aerosol models with observations." Atmospheric Chemistry and Physics 16, no. 2 (January 29, 2016): 1065–79. http://dx.doi.org/10.5194/acp-16-1065-2016.
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Abstract. It is often implicitly assumed that over suitably long periods the mean of observations and models should be comparable, even if they have different temporal sampling. We assess the errors incurred due to ignoring temporal sampling and show that they are of similar magnitude as (but smaller than) actual model errors (20–60 %).Using temporal sampling from remote-sensing data sets, the satellite imager MODIS (MODerate resolution Imaging Spectroradiometer) and the ground-based sun photometer network AERONET (AErosol Robotic NETwork), and three different global aerosol models, we compare annual and monthly averages of full model data to sampled model data. Our results show that sampling errors as large as 100 % in AOT (aerosol optical thickness), 0.4 in AE (Ångström Exponent) and 0.05 in SSA (single scattering albedo) are possible. Even in daily averages, sampling errors can be significant. Moreover these sampling errors are often correlated over long distances giving rise to artificial contrasts between pristine and polluted events and regions. Additionally, we provide evidence that suggests that models will underestimate these errors. To prevent sampling errors, model data should be temporally collocated to the observations before any analysis is made.We also discuss how this work has consequences for in situ measurements (e.g. aircraft campaigns or surface measurements) in model evaluation.Although this study is framed in the context of model evaluation, it has a clear and direct relevance to climatologies derived from observational data sets.