bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition or facilitation of return: Does chromatic component
count?
Authors: CANTO-PEREIRA LUIZ HENRIQUE M. DO , PARAMEI GALINA V. , MORYA EDGARD , RANVAUD RONALD D.
Published: September 2006

Inhibitory effects have been reported when a target is preceded by a
cue of the same color and location. Color-based inhibition was found using
red and blue nonisoluminant stimuli (Law et al., 1995). Here we investigate whether this phenomenon
depends on the chromatic subsystem involved by employing isoluminant
colors varying along either the violet-yellow or purple-turquoise cardinal
axis. Experiment 1 replicated Law et al.'s study: After fixating
magenta, either a red or blue cue was presented, followed by a magenta
“neutral attractor,” and, finally, by a red or blue target. In
Experiment 2, violet and yellow, cue or target, varied along a tritan
confusion line in the CIE 1976 chromaticity diagram. In Experiment 3,
purple and turquoise, cue or target, varied along a deutan confusion line
in the CIE 1976 chromaticity diagram. Normal trichromats (n = 19)
participated in all three experiments. In Experiment 1, color repetition
indeed resulted in longer reaction times (RTs) (4.7 ms, P =
0.038). In Experiment 2, however, no significant color repetition effect
was found; RTs to violet and yellow were not significantly different,
though tending toward slower responses (2 ms) for violet repetition but
faster (5 ms) for yellow. Experiment 3 also showed no color repetition
effect (P = 0.58); notably, RTs were overall faster for purple
than for turquoise (22 ms, P < 0.0001). Furthermore, responses
tended to be slower for purple repetition (4 ms, P > 0.05),
but faster for turquoise (7 ms, P > 0.05). These findings
demonstrate that color repetition is not always inhibitory but may turn
facilitatory depending on the colors employed. The results indicate that
disengagement of attention is an unlikely mechanism to be the sole
explanation of previously reported color-based inhibition of return. We
suggest a complementary, perceptual explanation: response (dis)advantage
depends on whether the stimuli are isoluminant and on the opponent
chromatic subsystem involved. The choice of the colors employed and the
cue-attractor-target constellation also may be of significance.
Color shifts induced by S-cone patterns are mediated by a neural representation driven by multiple cone types
Authors: SHEVELL STEVEN K. , MONNIER PATRICK
Published: September 2006

This study investigated chromatic induction from inhomogeneous background patterns. Previous work showed that a background pattern detected by only S cones induced strong color shifts in a nearby test area (Monnier & Shevell, 2003). In that work, the S-cone patterns were composed with constant L- and M-cone stimulation over the entire background; in terms of L and M cones, therefore, the background was uniform. S-cone stimulation was varied over space to produce S-cone-isolated background patterns. These S-cone patterns, however, established spatial structure (the pattern) at both the receptoral level (S-cone stimulation) and the postreceptoral level (S/(L+M)). Here, these two levels of pattern representation were unconfounded to determine whether color shifts induced by S-cone patterns were due to spatial structure within an S-cone-specific neural pathway versus a pathway that combines responses from S cones and other cone types (e.g. S/(L+M)). The results showed that the induced color shifts were mediated by signals within a pathway that combines responses from multiple cone types. These results are consistent with a +s/−sspatially antagonistic neural receptive field, which is found in some neurons in V1 and V2.
Dark-adapted rod suppression of cone flicker detection: Evaluation
of receptoral and postreceptoral interactions
Authors: CAO DINGCAI , ZELE ANDREW J. , POKORNY JOEL
Published: September 2006

Dark-adapted rods in the area surrounding a luminance-modulated field
can suppress flicker detection. However, the characteristics of the
interaction between rods and each of the cone types are unclear. To
address this issue, the effect that dark-adapted rods have on specific
classes of receptoral and postreceptoral signals was determined by
measuring the critical fusion frequencies (CFF) for receptoral L-, M-, and
S-cone and postreceptoral luminance ([L+M+S] and
[L+M+S+Rod]) and chromatic ([L/(L+M)]) signals in
the presence of different levels of surrounding rod activity. Stimuli were
generated with a two-channel photostimulator that has four primaries for a
central field and four primaries for the surround, allowing independent
control of rod and cone excitation. Measurements were made either with
adaptation to the stimulus field after dark adaptation or during a brief
period following light adaptation. The results show that dark-adapted rods
maximally suppressed the CFF by ∼6 Hz for L-cone, M-cone, and
luminance modulation. Dark-adapted rods, however, did not significantly
alter the S-cone CFF. The [L/(L+M)] postreceptoral CFF was
slightly suppressed at higher surround illuminances, that is, higher than
surround luminances resulting in suppression for L-cone, M-cone, or
luminance modulation. We conclude that rod-cone interactions in flicker
detection occurred strongly in the magnocellular pathway.
Transitions between color categories mapped with a reverse Stroop
task
Authors: SMITHSON HANNAH E. , KHAN SABAH S. , SHARPE LINDSAY T. , STOCKMAN ANDREW
Published: September 2006

In the reverse Stroop task, observers are instructed to ignore the ink
color in which a color word is printed (the distractor color) and to
respond to the meaning of the color word (the target). Reaction times
(RTs) are faster with congruent combinations when the ink color matches
the word than with incongruent combinations when the ink color does not
match the word. We manipulated the distracting ink color from congruent to
incongruent and measured the transition from facilitation to interference.
In Experiment 1, we confirmed that this transition could be assessed
independently from the contextual influence of particular sets of stimuli
and responses, implying that the color space in which interference and
facilitation occurs is generalizable. In Experiment 2, we obtained reverse
Stroop data for transitions between red and yellow, yellow and green,
green and blue, and blue and red, and compared them with independent
estimates of color appearance obtained by hue scaling for the same
chromaticity samples. We find that the magnitude of the reverse Stroop
effect can provide a reliable index of the similarity of color appearance
between the distracting chromaticity and the color category represented by
the target color word. Moreover, it will allow us to quantify the mapping
between the chromaticity space defined at the cone photoreceptors and a
cognitive color space defined at an advanced level of neural
processing.
Independent variation of retinal S and M cone photoreceptor topographies: A survey of four families of mammals
Authors: AHNELT PETER KURT , SCHUBERT CHRISTIAN , KÜBBER-HEISS ANNA , SCHIVIZ ALEXANDRA , ANGER ELISABETH
Published: September 2006

In mammals, cone photoreceptor subtypes are thought to establish topographies that reflect the species-relevant properties of the visual environment. Middle- to long-wavelength-sensitive (M) cones are the dominant population and in most species they form an area centralis at the visual axis. Short-wavelength-sensitive (S) cone topographies do not always match this pattern. We here correlate the interrelationship of S and M cone topographies in representatives of several mammalian orders with different visual ecology, including man, cheetah, cat, Eurasian lynx, African lion, wild hog, roe deer, and red deer. Retinas were labeled with opsin antisera and S and M cone distributions as well as S/M cone ratios were mapped. We find that species inhabiting open environments show M cone horizontal streaks (cheetah, pig, deer). Species living in structured habitats (tiger, lynx, red deer) have increased S cone densities along the retinal margin. In species with active vision (cheetah, bear, tiger, man), S cone distributions are more likely to follow the centripetal M cone gradients. Small species show a ventral bias of peak S cone density which either matches the peak of M cone density in a temporal area centralis (diurnal sciurid rodents, tree shrews) or not (cat, manul, roe deer).

Thus, in addition to habitat structure, physical size and specific lifestyle patterns (e.g. food acquisition) appear to underlie the independent variations of M and S cone topographies.
Color constancy in natural scenes explained by global image
statistics
Authors: FOSTER DAVID H. , AMANO KINJIRO , NASCIMENTO SÉRGIO M.C.
Published: September 2006

To what extent do observers' judgments of surface color with
natural scenes depend on global image statistics? To address this
question, a psychophysical experiment was performed in which images of
natural scenes under two successive daylights were presented on a
computer-controlled high-resolution color monitor. Observers reported
whether there was a change in reflectance of a test surface in the scene.
The scenes were obtained with a hyperspectral imaging system and included
variously trees, shrubs, grasses, ferns, flowers, rocks, and buildings.
Discrimination performance, quantified on a scale of 0 to 1 with a
color-constancy index, varied from 0.69 to 0.97 over 21 scenes and two
illuminant changes, from a correlated color temperature of 25,000 K to
6700 K and from 4000 K to 6700 K. The best account of these effects was
provided by receptor-based rather than colorimetric properties of the
images. Thus, in a linear regression, 43% of the variance in constancy
index was explained by the log of the mean relative deviation in spatial
cone-excitation ratios evaluated globally across the two images of a
scene. A further 20% was explained by including the mean chroma of the
first image and its difference from that of the second image and a further
7% by the mean difference in hue. Together, all four global color
properties accounted for 70% of the variance and provided a good fit to
the effects of scene and of illuminant change on color constancy, and,
additionally, of changing test-surface position. By contrast, a
spatial-frequency analysis of the images showed that the gradient of the
luminance amplitude spectrum accounted for only 5% of the variance.
The color of night: Surface color perception under dim
illuminations
Authors: POKORNY JOEL , LUTZE MARGARET , CAO DINGCAI , ZELE ANDREW J.
Published: September 2006

Several studies document rudimentary color vision under dim
illumination. Here, hue perceptions of paper color samples were determined
for a wide range of light levels, including very low light levels where
rods alone mediate vision. The appearances of 24 paper color samples from
the OSA Uniform Color Scales were gauged under successively dimmer
illuminations from 10–0.0003 Lux. Triads of samples were chosen
representing each of eight basic color categories; red, pink, orange,
yellow, green, blue, purple, and gray. Samples within each triad varied in
lightness. Observers sorted samples into groups that they could categorize
with specific color names. Above 0.32 Lux, observers sorted the samples
into the originally chosen color groups with few exceptions. For
0.1–0.01 Lux, the red and orange samples were usually correctly
identified as either red or orange. The remaining samples tended to be
grouped into two categories, associated with the scotopic sample
reflectance. The lowest reflectance samples were below threshold and were
named black. The higher reflectance group was named predominately as green
or blue-green (three observers; the fourth observer used blue or
achromatic). At the three dimmest levels (≤ 0.0032 Lux) there continued
to be conspicuous color percepts. Color categories were reliably assigned
based on relative sample scotopic lightness. Of the samples above
threshold, those with lower reflectance were classified as red or orange
(all observers) and the higher reflectance samples as green or blue-green
(three observers) or achromatic or blue (the fourth observer). Rods and
L-cones presumably mediated color percepts at the intermediate light
levels used in the study. At the three lowest light levels there were
distinct color appearances mediated exclusively by rods. We speculate that
at these light levels the visual system estimates probable colors based on
prior natural experience.
Do rods influence the hue of foveal stimuli?
Authors: BUCK STEVEN L. , THOMAS LAURA P. , HILLYER NICK , SAMUELSON ERIC M.
Published: September 2006

To understand the generality and mechanisms of previously reported rod
hue biases, we examined whether they are present for small foveal stimuli
by comparing the wavelengths of the three spectral unique hues under
dark-adapted and flash-bleached conditions. Rod green bias (shift of
unique yellow) and rod blue bias (shift of unique green) were found for
some observers with 1°-diameter foveal stimuli, the size most likely
to stimulate rods. Smaller stimuli (0.2° and 0.6° diameter), which
were least likely to stimulate rods, produced no large or consistent
differences between dark-adapted and bleached conditions. This suggests
that rod hue biases result from the local stimulation of rods by light,
not from remote suppression by dark-adapted, unstimulated rods,
and not from bleaching light artifacts.
Macular pigment and color discrimination
Authors: MORELAND J.D. , WESTLAND S.
Published: September 2006

An earlier modeling study of the effect of changes in macular pigment optical density (MPOD) on a wide range of surface colors is re-examined. That study reported changes in local chromaticity variance and in color spacing, some of which were incompatible with tritan-like confusions in normals associated with high-simulated MPOD. This disagreement might have arisen through the use of the von Kries correction for adaptation. The analysis is repeated, using 1782 reflectance spectra of natural and man-made colors. These colors are segregated into an array of 25 equally populated cells in an analogue of the MacLeod-Boynton cone excitation diagram. Removing the von Kries correction restores compatibility with other experimental data. Differences between the results for normal and anomalous trichromats, noted in the earlier study, are confirmed. An analysis of local chromaticity variance across color space indicates the presence of systematic patterns. The earlier study also reported differences in results across observer types (for example, between normals and protanomals) and this is addressed here by utilizing fundamentals defined by a variable photopigment template. Chromaticities are computed for the same 1782 reflectance spectra for normals and for a set of protanomals (for whom the anomalous L pigment is shifted between the normal L and M spectral locations). Colors are segregated into an array of 100 cells in an analogue of the MacLeod-Boynton cone excitation diagram. Changes in chromaticity variance with MPOD for these cells are mapped for normals and protanomals. Variance along the L/(L + M) axis is sensitive to the number of cells used for segmentation. It also increases with MPOD for normal observers but this trend reverses as the wavelength of maximum sensitivity of the L cone shifts towards shorter wavelengths (protanomalous locations).
The Didactic Trial: Filtering History and Memory into the Courtroom
Authors: DOUGLAS LAWRENCE
Published: September 2006

The principle that perpetrators of atrocity should be brought to justice before courts of criminal law enjoys near total acceptance. However, because of the nature of the transgressions adjudicated, the major trials of perpetrators have also served a didactic and moral function in redefining and re-imposing rule-based legality. As a consequence, these trials address history and memory in the course of trying the accused. This essay examines three particular filters that affect the way the memory and history of the events concerned enter the trial process: first, the nature of the evidence admitted; second, the substantive incriminations directed at the accused; and third, the principle of criminal accountability deployed by the prosecution. The essay also considers how the timing and place of the trial influence its didactic value. Ultimately, the didactic and moral effectiveness of such trials is beyond the control of the courts and can only be evaluated over the longer term.
Thoughtful People Thinking About People Thinking About Thinking
People
Authors: Fein Deborah
Published: September 2006

Social Neuroscience: People Thinking About Thinking People.
John T. Cacioppo, Penny S. Visser, and Cynthia L. Pickett (Eds.). 2006.
Cambridge, MA: The MIT Press, 328 pp., $45.00 (HB)

Perhaps not since the flowering of clinical neuropsychology thirty
years ago have we seen this sense of exhilaration about the emergence of a
new field through the integration of existing disciplines. Clearly, these
authors and thinkers feel the same excitement that could be felt when new
collaborations were being forged among neurologists, psychiatrists,
psychologists, and communication specialists in earlier decades. For the
emerging field of social neuroscience, the parent fields include social
psychology (see, for example, chapters on Race and Emotion, The Social
Neuroscience of Stereotyping and Prejudice, Social and Physical Pain, and
Animal Models of Human Attitudes), clinical neuropsychology (Neurological
Substrates of Emotional and Social Intelligence: Evidence from Patients
with Focal Brain Lesions), social cognition (Neural Substrates of Self
Awareness, and three chapters bearing directly on Theory of Mind) and, of
course, cognitive and basic neuroscience. Each chapter includes
theoretical perspectives from multiple fields and reviews studies that use
diverse techniques (including functional imaging, ERP, behavioral scales,
lesion studies, developmental studies, and animal studies), although the
book is very heavy on functional imaging data. As the editors acknowledge,
animal and patient data are not represented in a thorough way.
Ocean carbon cycling in the Indian Ocean: 1. Spatiotemporal variability of inorganic carbon and air‐sea CO2 gas exchange
Authors: Bates Nicholas R. , Pequignet A. Christine , Sabine Christopher L.
Published: September 2006

The spatiotemporal variability of upper ocean inorganic carbon parameters and air‐sea CO2 exchange in the Indian Ocean was examined using inorganic carbon data collected as part of the World Ocean Circulation Experiment (WOCE) cruises in 1995. Multiple linear regression methods were used to interpolate and extrapolate the temporally and geographically limited inorganic carbon data set to the entire Indian Ocean basin using other climatological hydrographic and biogeochemical data. The spatiotemporal distributions of total carbon dioxide (TCO2), alkalinity, and seawater pCO2 were evaluated for the Indian Ocean and regions of interest including the Arabian Sea, Bay of Bengal, and 10°N–35°S zones. The Indian Ocean was a net source of CO2 to the atmosphere, and a net sea‐to‐air CO2 flux of +237 ± 132 Tg C yr−1 (+0.24 Pg C yr−1) was estimated. Regionally, the Arabian Sea, Bay of Bengal, and 10°N–10°S zones were perennial sources of CO2 to the atmosphere. In the 10°S–35°S zone, the CO2 sink or source status of the surface ocean shifts seasonally, although the region is a net oceanic sink of atmospheric CO2.
Geomorphologic controls on the age of particulate organic carbon from small mountainous and upland rivers
Authors: Leithold Elana L. , Blair Neal E. , Perkey David W.
Published: September 2006

To assess the role that erosion processes play in governing the character of particulate organic carbon (POC) discharged from small mountainous and upland rivers, a suite of watersheds from Oregon, California, and New Zealand was investigated. The rivers share similar geology, tectonic setting, and climate, but have sediment yields that range over 3 orders of magnitude. The 14C age of the POC loads is highly correlated with sediment yield. Carbon isotope mass balances reveal that the rivers carry bimodal mixtures of modern‐plant‐ and ancient‐rock‐derived OC. At lower yields, modern plant OC dominates the material delivered to the river by sheetwash and shallow landsliding. With increasing yield, a progressively larger part of the POC is contributed directly from bedrock erosion via deep gully incision. Our results support the inference that active margin watersheds are important sources of aged POC to the ocean.
SABER observations of the OH Meinel airglow variability near the mesopause
Authors: Marsh Daniel R. , Smith Anne K. , Mlynczak Martin G. , Russell James M.
Published: September 2006

The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument, one of four on board the TIMED satellite, observes the OH Meinel emission at 2.0 μm that peaks near the mesopause. The emission results from reactions between members of the oxygen and hydrogen chemical families that can be significantly affected by mesopause dynamics. In this study we compare SABER measurements of OH Meinel emission rates and temperatures with predictions from a three‐dimensional chemical dynamical model. In general, the model is capable of reproducing both the observed diurnal and seasonal OH Meinel emission variability. The results indicate that the diurnal tide has a large effect on the overall magnitude and temporal variation of the emission in low latitudes. This tidal variability is so dominant that the seasonal cycle in the nighttime emission depends very strongly on the local time of the analysis. At higher latitudes the emission has an annual cycle that is due mainly to transport of oxygen by the seasonally reversing mean circulation.
Fate of rising methane bubbles in stratified waters: How much methane reaches the atmosphere?
Authors: McGinnis D. F. , Greinert J. , Artemov Y. , Beaubien S. E. , Wüest A.
Published: September 2006

There is growing concern about the transfer of methane originating from water bodies to the atmosphere. Methane from sediments can reach the atmosphere directly via bubbles or indirectly via vertical turbulent transport. This work quantifies methane gas bubble dissolution using a combination of bubble modeling and acoustic observations of rising bubbles to determine what fraction of the methane transported by bubbles will reach the atmosphere. The bubble model predicts the evolving bubble size, gas composition, and rise distance and is suitable for almost all aquatic environments. The model was validated using methane and argon bubble dissolution measurements obtained from the literature for deep, oxic, saline water with excellent results. Methane bubbles from within the hydrate stability zone (typically below ∼500 m water depth in the ocean) are believed to form an outer hydrate rim. To explain the subsequent slow dissolution, a model calibration was performed using bubble dissolution data from the literature measured within the hydrate stability zone. The calibrated model explains the impressively tall flares (>1300 m) observed in the hydrate stability zone of the Black Sea. This study suggests that only a small amount of methane reaches the surface at active seep sites in the Black Sea, and this only from very shallow water areas (<100 m). Clearly, the Black Sea and the ocean are rather effective barriers against the transfer of bubble methane to the atmosphere, although substantial amounts of methane may reach the surface in shallow lakes and reservoirs.
Dependence of an eastern boundary current on the horizontal resolution in thermally driven circulations
Authors: Park Young‐Gyu
Published: September 2006

Through an idealized modeling study with a depth level coordinate general ocean circulation model (GFDL/MOM), the sensitivity of an eastern boundary current on the horizontal resolution in thermally driven circulations is investigated. In general the circulation patterns do not show significant sensitivity to the resolution except in the northern and the eastern boundaries. When the resolution is low, a notable eastern boundary current is not observed. As the resolution becomes higher, a northward eastern boundary current emerges. A simple scaling analysis based on a linear vorticity equation reveals that such an eastern boundary current is initiated by vortex column stretching due to the downwelling of a zonal flow, which is driven by the sea surface temperature gradient, along the eastern wall. The scaling law predicts that the magnitude of the boundary current is inversely proportional to the horizontal resolution, if the downwelling occurs along the eastern most grid points. The model results follow the scaling law very well when the eastern boundary current, and subsequently the vertical stratification along the eastern wall are weak. In higher resolution cases, when the eastern boundary current becomes strong enough, the vertical stratification along the eastern wall becomes higher due to warm advection by the current, and downwelling is reduced. Therefore a larger part of the zonal flow turns to the north, and the eastern boundary current becomes stronger than predicted by the scaling law, which neglects the effects of the vertical stratification.
Attribution of recovery in lower‐stratospheric ozone
Authors: Yang Eun‐Su , Cunnold Derek M. , Salawitch Ross J. , McCormick M. Patrick , Russell James , Zawodny Joseph M. , Oltmans Samuel , Newchurch Michael J.
Published: September 2006

Multiple satellite and ground‐based observations provide consistent evidence that the thickness of Earth's protective ozone layer has stopped declining since 1997, close to the time of peak stratospheric halogen loading. Regression analyses with Effective Equivalent Stratospheric Chlorine (EESC) in conjunction with further analyses using more sophisticated photochemical model calculations constrained by satellite data demonstrate that the cessation of ozone depletion between 18 and 25 km altitude is consistent with a leveling off of stratospheric abundances of chlorine and bromine, due to the Montreal Protocol and its amendments. However, ozone increases in the lowest part of the stratosphere, from the tropopause to 18 km, account for about half of the improvement in total column ozone during the past 9 years at Northern Hemisphere midlatitudes. The increase in ozone for altitudes below 18 km is most likely driven by changes in transport, rather than driven by declining chlorine and bromine. Even with this evidence that the Montreal Protocol and its amendments are having the desired, positive effect on ozone above 18 km, total column ozone is recovering faster than expected because of the apparent transport driven changes at lower altitudes. Accurate prediction of future levels of stratospheric ozone will require comprehensive understanding of the factors that drive temporal changes at various altitudes and partitioning of the recent transport‐driven increases between natural variability and changes in atmospheric structure perhaps related to anthropogenic climate change.
An optimized particle size bin scheme for modeling mineral dust aerosol
Authors: Foret G. , Bergametti G. , Dulac F. , Menut L.
Published: September 2006

During transport, atmospheric aerosol particles experience nonlinear size‐dependent deposition processes which affect their size distribution. This implies that the aerosol particle size distribution (PSD) should be well represented in three‐dimensional transport models that simulate their transport and their radiative or biogeochemical impacts. In particular, mineral dust aerosols exhibit a broad range of particle sizes but the dust PSD is generally described in such models by a limited number of particle size bins. A common approach in the literature consists in defining such bins following a geometric progression of the particle diameter (“isolog” bins). Here we propose to define size bins following the size dependence in dry deposition velocity (Vd), by satisfying an “isogradient” in Vd. We use a box model and reference simulations with 1000 particle size bin to test the accuracy of both approaches with 4 to 30 bins, in simulating (1) the mineral dust number and mass PSD evolution due to dry and wet deposition, and (2) the derived visible aerosol optical thickness (AOT). Both schemes show a trend in increasing accuracy when increasing the number of bins. The classical isolog scheme, however, exhibits strong, embarrassing oscillations in accuracy when varying the number of bins. For a given number of particle size bins, the isogradient scheme significantly improves the accuracy of results in terms of mass PSD and greatly suppresses oscillations of errors in both mass and number distributions. We conclude that at least eight isogradient size bins are necessary to secure an 8% accuracy on the total suspended dust mass after two days of transport. In terms of particle number distribution, errors remain small for both schemes but they become somewhat larger (∼8%) in terms of AOT for 12–30 isogradient size bins. This drawback can be compensated by weighting the average aerosol extinction cross section within each size bin by the initial dust particle number distribution. We conclude that at least eight isogradient size bins are necessary.
Vertical distribution of ozone on Mars as measured by SPICAM/Mars Express using stellar occultations
Authors: Lebonnois Sébastien , Quémerais Eric , Montmessin Franck , Lefèvre Franck , Perrier Séverine , Bertaux Jean‐Loup , Forget François
Published: September 2006

The ultraviolet spectrometer of the SPICAM instrument on board the European Mars Express mission has performed stellar occultations to probe the atmosphere. Vertical profiles of ozone are retrieved from inversion of transmission spectra in the altitude range 20–30 to 70 km. They are analyzed here as functions of latitude and season of the observations. These occultations have been monitored on the night side, from northern spring equinox (Ls = 8°) to northern winter solstice (Ls = 270°). The profiles show the presence of two ozone layers: (1) one located near the surface, the top of which is visible below 30 km altitude, and (2) one layer located in the altitude range 30 to 60 km, a feature that is highly variable with latitude and season. This layer is first seen after Ls = 11°, and the ozone abundance at the peak tends to increase until Ls ∼ 40°, when it stabilizes around 6–8 × 109 cm−3. After southern winter solstice (Ls ∼ 100°), the peak abundance starts decreasing again, and this ozone layer is no longer detected after Ls ∼ 130°. A recent model (Lefèvre et al., 2004) predicted the presence of these ozone layers, the altitude one being only present at night. Though the agreement between model and observations is quite good, this nocturnal altitude layer is present in SPICAM data over a less extended period than predicted. Though a possible role of heterogeneous chemistry is not excluded, this difference is probably linked to the seasonal evolution of the vertical distribution of water vapor.
Raindrop size distribution observed with the Equatorial Atmosphere Radar (EAR) during the Coupling Processes in the Equatorial Atmosphere (CPEA‐I) observation campaign
Authors: Renggono Findy , Yamamoto Masayuki K. , Hashiguchi Hiroyuki , Fukao Shoichiro , Shimomai Toyoshi , Kawashima Masayuki , Kudsy Mahally
Published: September 2006

The diurnal variability of raindrop size distribution (DSD) in precipitating clouds over Kototabang, West Sumatra, Indonesia (0.20°S, 100.32°E), is studied using three types of Doppler radars, operated at VHF (47 MHz), UHF (1.3 GHz), and X band (9.4 GHz) frequencies. Two precipitation events from 5 to 6 May 2004 in the first observation campaign of the first Coupling Processes in the Equatorial Atmosphere (CPEA‐I) project reveal a difference between clouds precipitating in the early afternoon and clouds precipitating in the nighttime. In the early afternoon, the precipitating clouds were dominated by shallow convective types with high rainfall rate at the surface. In the nighttime, precipitating clouds were dominated by stratiform types with small rainfall rate at the surface. A diurnal variation of horizontal wind was observed over this area. The westerly in the lower troposphere and the easterly in the middle troposphere began to be enhanced in the afternoon (1400–1700 LT). DSD parameters were retrieved from VHF band Doppler radar data. A modified gamma distribution was used to model DSD parameters. The shape parameter (μ) was larger during stratiform precipitation than during shallow convective precipitation events, as shown by previous studies. During stratiform rain events on 5 May 2004, the median volume diameter (D0) was dominantly greater than 1 mm, which is larger than D0 during shallow convective rain events. Results presented in this paper indicate that DSD has a diurnal cycle over the mountainous region of Sumatra.
Particle filtering and ensemble Kalman filtering for state updating with hydrological conceptual rainfall‐runoff models
Authors: Weerts Albrecht H. , El Serafy Ghada Y. H.
Published: September 2006

Sequential importance resampling (SIR) filter, residual resampling filter (RR), and an ensemble Kalman (EnKF) filter that can handle dynamic nonlinear/non‐Gaussian models are compared to correct erroneous model inputs and to obtain a rainfall‐runoff update with a conceptual rainfall‐runoff model HBV‐96 for flood forecasting purposes. EnKF performs best with a low number of ensemble members. The RR filter performs best at intermediate and high number of particles, although differences are small. With all filters the rainfall error could be estimated during a synthetic experiment when the soil is not too dry and the measurement error on the discharge is not dominant. The temperature error could only be estimated when the temperature is close to 0°C. When applying these methods to a real case, good results are obtained. For low flows, EnKF outperforms both particle filters, because it is less sensitive to misspecification of the model and uncertainties. These methods are feasible and easy to implement in real flood forecasting systems. Further research on the assumptions on model uncertainties and measurement uncertainties is recommended.
Impact of Atlantic multidecadal oscillations on India/Sahel rainfall and Atlantic hurricanes
Authors: Zhang Rong , Delworth Thomas L.
Published: September 2006

Prominent multidecadal fluctuations of India summer rainfall, Sahel summer rainfall, and Atlantic Hurricane activity have been observed during the 20th century. Understanding their mechanism(s) will have enormous social and economic implications. We first use statistical analyses to show that these climate phenomena are coherently linked. Next, we use the GFDL CM2.1 climate model to show that the multidecadal variability in the Atlantic ocean can cause the observed multidecadal variations of India summer rainfall, Sahel summer rainfall and Atlantic Hurricane activity (as inferred from vertical wind shear changes). These results suggest that to interpret recent climate change we cannot ignore the important role of Atlantic multidecadal variability.
Single‐spacecraft detection of rolled‐up Kelvin‐Helmholtz vortices at the flank magnetopause
Authors: Hasegawa H. , Fujimoto M. , Takagi K. , Saito Y. , Mukai T. , Rème H.
Published: September 2006

Recent numerical simulations suggest that as soon as the Kelvin‐Helmholtz instability (KHI) has grown nonlinearly to form a highly rolled‐up vortex, plasma mixing is inevitably achieved within the vortex. Identification of rolled‐up vortices by in situ measurements is therefore an important task as a step to establish the mechanism by which solar wind plasmas enter the magnetosphere and to understand conditions under which the vortices form. In the present study we show that the rolled‐up vortices are detectable even from single‐spacecraft measurements. Numerical simulations of the KHI indicate that in the rolled‐up vortex the tailward speed of a fraction of low‐density, magnetospheric plasmas exceeds that of the magnetosheath flow. This feature appears only after a vortex is rolled up and thus can be used as a marker of roll‐up. This signature was indeed found in the Cluster multispacecraft measurements of the rolled‐up vortices at the flank magnetopause. By use of this marker, we have searched for events consistent with the roll‐up from Geotail observations showing quasi‐periodic plasma and field fluctuations in the flank low‐latitude boundary layer (LLBL) under northward interplanetary magnetic field (IMF), presumably associated with KH waves. The survey shows that such rolled‐up events do occur on both dawn and dusk flanks and are not rare for northward IMF conditions. In addition, in all the rolled‐up cases, magnetosheath‐like ions are detected on the magnetospheric side of the boundary. These findings indicate that the KHI plays a nonnegligible role in the formation of the flank LLBL under northward IMF.
Io: Loki Patera as a magma sea
Authors: Matson Dennis L. , Davies Ashley Gerard , Veeder Glenn J. , Rathbun Julie A. , Johnson Torrence V. , Castillo Julie C.
Published: September 2006

We develop a physical model for Loki Patera as a magma sea. We calculate the total volume of magma moving through the Loki Patera volcanic system every resurfacing cycle (∼540 days) and the resulting variation in thermal emission. The rate of magma solidification at times reaches 3 × 106 kg s−1, with a total solidified volume averaging 100 km3 yr−1. A simulation of gas physical chemistry evolution yields the crust porosity profile and the timescale when it will become dense enough to founder in a manner consistent with observations. The Loki Patera surface temperature distribution shows that different areas are at different life cycle stages. On a regional scale, however, there can be coordinated activity, indicated by the wave of thermal change which progresses from Loki Patera's SW quadrant toward the NE at a rate of ∼1 km d−1. Using the observed surface temperature distribution, we test several mechanisms for resurfacing Loki Patera, finding that resurfacing with lava flows is not realistic. Only the crustal foundering process is consistent with observations. These tests also discovered that sinking crust has a “heat deficit” which promotes the solidification of additional magma onto the sinking plate (“bulking up”). In the limiting case, the mass of sinking material can increase to a mass of ∼3 times that of the foundering plate. With all this solid matter sinking, there is a compensating upward motion in the liquid magma. This can be in excess of 2 m yr−1. In this manner, solid‐liquid convection is occurring in the sea.
Hydrothermal sediments as a potential record of seawater Nd isotope compositions: The Rainbow vent site (36°14′N, Mid‐Atlantic Ridge)
Authors: Chavagnac Valérie , Palmer Martin R. , Milton J. Andrew , Green Darryl R. H. , German Christopher R.
Published: September 2006

Geochemical compositions and Sr and Nd isotopes were measured in two cores collected ∼2 and 5 km from the Rainbow hydrothermal vent site on the Mid‐Atlantic Ridge. Overall, the cores record enrichments in Fe and other metals from hydrothermal fallout, but sequential dissolution of the sediments allows discrimination between a leach phase (easily leachable) and a residue phase (refractory). The oxy‐anion and transition metal distribution combined with rare earth element (REE) patterns suggest that (1) the leach fraction is a mixture of biogenic carbonate and hydrothermal Fe‐Mn oxy‐hydroxide with no significant contribution from detrital material and (2) >99.5% of the REE content of the leach fraction is of seawater origin. In addition, the leach fraction has an average 87Sr/86Sr ratio indistinguishable from modern seawater at 0.70916. Although we lack the ɛNd value of present‐day deep water at the Rainbow vent site, we believe that the REE budget of the leach fraction is predominantly of seawater origin. We suggest therefore that the leach fraction provides a record of local seawater ɛNd values. Nd isotope data from these cores span the period of 4–14 ka (14C ages) and yield ɛNd values for North East Atlantic Deep Water (NEADW) that are higher (−9.3 to −11.1) than those observed in the nearby Madeira Abyssal Plain from the same depth (−12.4 ± 0.9). This observation suggests that either the Iceland‐Scotland Overflow Water (ISOW) and Lower Deep Water contributions to the formation of NEADW are higher along the Mid‐Atlantic Ridge than in the surrounding basins or that the relative proportion of ISOW was higher during this period than is observed today. This study indicates that hydrothermal sediments have the potential to provide a higher‐resolution record of deep water ɛNd values, and hence deepwater circulation patterns in the oceans, than is possible from other types of sediments.
Composite origin of an early Variscan transported suture: Ophiolitic units of the Morais Nappe Complex (north Portugal)
Authors: Pin C. , Paquette J. L. , Ábalos B. , Santos F. J. , Gil Ibarguchi J. I.
Published: September 2006

The two structural units that constitute the ophiolitic complex of the Morais allochthonous complex display different geochemical features. Amphibolites from the lower unit are nearly homogeneous, chemically similar to normal mid‐ocean ridge basalts, with low Th/Nb and highly radiogenic Nd isotope signature (ɛNd = +8.7), and might derive from igneous protoliths formed in an oceanic ridge setting 447 ± 24 Myr ago (Sm‐Nd whole rock isochron). In contrast, the upper unit consists largely of metaperidotites together with gabbroic rocks and minor amphibolites and felsic veins. U‐Pb zircon ages of the upper unit range from 405 ± 1 Ma to 396 ± 1 Ma. These rocks are geochemically more variable but share in common high Th/Nb ratios and high initial ɛNd (from +7.5 to +8.9) interpreted to reflect generation above an intraoceanic subduction zone. This implies that the Morais ophiolitic complex is composite and consists of two distinct, relatively thin tectonic slivers that were detached from contrasting oceanic domains before being finally imbricated. This occurred broadly coeval, at the regional scale, with eclogite‐facies metamorphism documented in several separate tectonic units of NW Iberia. On the basis of this space and time association, we interpret the early stage of the Variscan (in the broad sense) evolution (circa ≥ 405–400 Ma) in terms of intraoceanic subduction, followed by an arc‐continent collision, circa 395 Ma. This model may account for the long‐recognized polycyclic evolution of the north Portuguese catazonal complexes without resorting to the existence of a high‐grade Precambrian basement.
Abrogation of the CLK‐2 checkpoint leads to tolerance to base‐excision repair intermediates
Authors: Dengg Marlene , Garcia‐Muse Tatiana , Gill Stephen G , Ashcroft Neville , Boulton Simon J , Nilsen Hilde
Published: September 2006

Incorporation of uracil during DNA synthesis is among the most common types of endogenously generated DNA damage. Depletion of Caenorhabditis elegans dUTPase by RNA interference allowed us to study the role of DNA damage response (DDR) pathways when responding to high levels of uracil in DNA. dUTPase depletion compromised development, caused embryonic lethality and led to activation of cell‐cycle arrest and apoptosis. These phenotypes manifested as a result of processing misincorporated uracil by the uracil‐DNA glycosylase UNG‐1. Strikingly, abrogation of the clk‐2 checkpoint gene rescued lethality and developmental defects, and eliminated cell‐cycle arrest and apoptosis after dUTPase depletion. These data show a genetic interaction between UNG‐1 and activation of the CLK‐2 DDR pathway after uracil incorporation into DNA. Our results indicate that persistent repair intermediates and/or single‐stranded DNA formed during repair of misincorporated uracil are tolerated in the absence of the CLK‐2 checkpoint in C. elegans.
Insight into the role of hydration on protein dynamics
Authors: Hamelberg Donald , Shen Tongye , McCammon J. Andrew
Published: September 2006

The potential energy surface of a protein is rough. This intrinsic energetic roughness affects diffusion, and hence the kinetics. The dynamics of a system undergoing Brownian motion on this surface in an implicit continuum solvent simulation can be tuned via the frictional drag or collision frequency to be comparable to that of experiments or explicit solvent simulations. We show that the kinetic rate constant for a local rotational isomerization in stochastic simulations with continuum solvent and a collision frequency of 2ps−1 is about 104 times faster than that in explicit water and experiments. A further increase in the collision frequency to 60ps−1 slows down the dynamics, but does not fully compensate for the lack of explicit water. We also show that the addition of explicit water does not only slow down the dynamics by increasing the frictional drag, but also increases the local energetic roughness of the energy landscape by as much as 1.0kcal∕mol.
On the mutual diffusion properties of ethanol-water mixtures
Authors: Zhang Li , Wang Qi , Liu Ying-Chun , Zhang Lian-Zhong
Published: September 2006

The structural organization, the number of hydrogen bonds (H bond), and the self- and mutual diffusion coefficients of ethanol-water mixtures were studied by molecular dynamics simulation. It was found that both the numbers of H bonds per water and per ethanol decrease as the mole fraction of ethanol increases. The composition dependences and the relationships between the self- and the mutual diffusion coefficients were further discussed. The self-diffusion coefficient of water has a large drop as the concentration of ethanol increases from 0 to 0.3 and then it nearly keeps constant, while that of ethanol has a minimum around ethanol mole fraction of 0.5. The mutual diffusion coefficient could be divided into two parts, the kinematic factor and the thermodynamic factor. Both the kinematic and thermodynamic factors for ethanol-water mixtures were calculated. It was found that the change trend of mutual diffusion coefficients with the composition is mainly dependent on the thermodynamic factors.
Superficial segregation in nanoparticles: From facets to infinite surfaces
Authors: Lequien F. , Creuze J. , Berthier F. , Legrand B.
Published: September 2006

We compare the superficial segregations of the Cu–Ag system for a nanoparticle and for surfaces that are structurally equivalent to each of its facet. Based on a lattice-gas model and within a mean-field formalism, we derive segregation isotherms at various temperatures in the canonical ensemble, i.e., for a given overall solute concentration, and in the semigrand canonical ensemble, i.e., for a given bulk solute concentration. If both processes are very similar for high temperatures, they differ substantially at lower temperatures. Due to the finite-size effect and the indirect coupling between facets and edges, the relative position of the phase transitions of the facets and the corresponding surfaces is inversed when displayed as a function of the solute bulk concentration. Moreover, we show that working in the semigrand canonical ensemble is a much more efficient way to study this phenomenon, although nanoparticles are “canonical” objects in essence.
Insight into the solvent effect: A density functional theory study of cisplatin hydrolysis
Authors: Song Tao , Hu P.
Published: September 2006

The solvent effect on reactions in solutions is crucial for many systems. In this study, the reaction barrier with respect to the number of solvent molecules included in the system is systematically studied using density function theory calculations. Our results show that the barriers rapidly converge with respect to the number of solvent molecules. The solvent effect is investigated by calculating cisplatin hydrolysis in several types of solvents. The results are analyzed and a linear relationship between the reaction barrier and the interaction strength of solvent–reactants is found. Insight into the general solvent effect is obtained.