bluuebunny/crossref_metadata_2025 huggingface dataset:
Mainstreaming Equality: The Implications for Disabled People
Authors: Witcher Sally
Published: January 2005

Mainstreaming equality involves integrating equality considerations from the outset into how an organization operates, its policies and practices. Whether this works to the advantage of disabled people depends critically on the quality of understanding of equality issues for different groups. This paper begins by clarifying goals for social justice, social inclusion and equality and then considers the salience of disabled people as a social category. It briefly reviews different equality strategies, before focusing on mainstreaming and its potential to promote cultural change and socially just distribution. An analytical framework to support mainstreaming is outlined. The paper concludes by stressing the importance of disabled people's involvement with mainstreaming equality if outcomes are to promote social justice.
Disabled People, Employment and Social Justice
Authors: Thornton Patricia
Published: January 2005

Since it came to power in 1997 the Labour Government has conceived of low levels labour market participation by disabled people as not just an economic concern but also an indicator of social exclusion or social injustice. This article presents some evidence about inequalities between disabled and non-disabled people in the labour market; reviews the evidence on discrimination in employment and discusses the potential of anti-discrimination legislation as a tool to reduce social injustice; discusses sources of social justice in the benefits system; and considers whether people in receipt of Incapacity Benefits should be expected to seek work. It concludes that rights and responsibilities are unjustly distributed between government and disabled people.
Role of the Hoggar massif in the West African monsoon onset
Authors: Drobinski Philippe , Sultan Benjamin , Janicot Serge
Published: January 2005

It has been observed that the West African monsoon onset is concomitant with the enhancement of the Saharan heat low. We show through a combined diagnostic and linear modeling study a possible interaction between northern Africa orography and the deepening of the Saharan heat low at the time of the monsoon onset. The amplification of an anticyclonic circulation above and north of the Hoggar massif leads to an increase and a southeasterly‐northeasterly rotation of the wind ahead of the Hoggar which contribute to an increased leeward‐trough effect enhancing the Saharan heat low. The Atlas does not play any role during the monsoon onset but contributes to the mean climatological location of the Saharan heat low.
Unified explanation of envelope broadening and maximum‐amplitude decay of high‐frequency seismograms based on the envelope simulation using the Markov approximation: Forearc side of the volcanic front in northeastern Honshu, Japan
Authors: Saito Tatsuhiko , Sato Haruo , Ohtake Masakazu , Obara Kazushige
Published: January 2005

During propagation through heterogeneous lithosphere, S waves impulsively radiated from a source increase in duration and decrease in maximum amplitude with increasing travel distance. We term these phenomena “envelope broadening” and “maximum‐amplitude decay,” respectively. The present study is the first attempt to make a unified explanation of the envelope broadening and the maximum‐amplitude decay based on wave scattering in random media. S wave envelopes observed at the forearc side of the volcanic front in northeastern Honshu, Japan, have the following characteristics in the frequency range from 2 to 16 Hz in the distance range from 75 to 410 km: Envelope duration increases with increasing travel distance in proportion to the distance to the power 1.7 to 1.8, and maximum amplitude decreases with increasing travel distance in proportion to the distance to the power −3 to −2. These observations are modeled by considering small‐angle wave scattering around the forward direction in the media having randomly fluctuating wave velocity with frequency‐dependent attenuation. The joint analysis of envelope duration and maximum amplitude is superior in estimating medium inhomogeneity and attenuation over the analysis of envelope duration or maximum amplitude alone. Assuming the von Kármán–type random media, we estimate the power spectral density function of S wave velocity fluctuation as P(m) ≈ 0.004m−5.0–0.01m−4.0 km3 in the range between 0.5 < m < 50 km−1, where m is the wave number of the inhomogeneity. The theoretical envelope calculated from the estimated random inhomogeneity and attenuation successfully gives a unified explanation of the envelope broadening and the maximum‐amplitude decay in northeastern Honshu, Japan.
Infrasound from earthquakes
Authors: Mutschlecner J. Paul , Whitaker Rodney W.
Published: January 2005

Infrasonic signals have been observed from 31 earthquakes by arrays of microphones operated by the Los Alamos National Laboratory between 1983 and 2003. The properties of the signals are presented. Signal amplitudes corrected for propagation and distance show a relation with seismic magnitude. The variance in the relation is understood primarily in terms of the uncertainties or errors in the ground motion, deduced from an independent data set, and the stratospheric winds, which strongly influence signal propagation. Signal durations can extend over many minutes. A relation is found between signal duration and magnitude. To understand this, we propose a model in which regions distant from the epicenter are excited by seismic surface waves. The surface motion of these regions, in turn, produces signals which precede or follow the signals from the epicenter. Analysis failed to detect signals from 56 earthquakes during the observation period. Predicted signal‐to‐noise ratios for these earthquakes indicated that the signals would have been too weak for detection.
A stochastic analysis of steady state two‐phase flow in heterogeneous media
Authors: Chen Mingjie , Zhang Dongxiao , Keller Arturo A. , Lu Zhiming
Published: January 2005

We present a novel approach to modeling stochastic multiphase flow problems, for example, nonaqueous phase liquid flow, in a heterogeneous subsurface medium with random soil properties, in particular, with randomly heterogeneous intrinsic permeability and soil pore size distribution. A stochastic numerical model for steady state water‐oil flow in a random soil property field is developed using the Karhunen‐Loeve moment equation (KLME) approach and is numerically implemented. An exponential model is adopted to define the constitutive relationship between phase relative permeability and capillary pressure. The log‐transformed intrinsic permeability Y(x) and soil pore size distribution β(x) are assumed to be Gaussian random functions with a separable exponential covariance function. The perturbation part of these two log‐transformed soil properties is then decomposed into an infinite series based on a set of orthogonal normal random variables {ξn}. The phase pressure, capillary pressure, and phase mobility are decomposed by polynomial expansions and the perturbation method. Combining these expansions of Y(x), β(x) and dependent pressures, the steady state water‐oil flow equations and corresponding boundary conditions are reformulated as a series of differential equations up to second order. These differential equations are solved numerically, and the solutions are directly used to construct moments of phase pressure and capillary pressure. We demonstrate the validity of the proposed KLME model by favorably comparing first‐ and second‐order approximations to Monte Carlo simulations. The significant computational efficiency of the KLME approach over Monte Carlo simulation is also illustrated.
Development of an Ischemic Tolerance Model in a PC12 Cell Line
Authors: Hillion Joëlle A , Takahashi Kenzo , Maric Dragan , Ruetzler Christl , Barker Jeffery L , Hallenbeck John M
Published: January 2005

Although ischemic tolerance has been described in a variety of primary cell culture systems, no similar in vitro models have been reported with any cell line. A model of ischemic preconditioning in the rat pheochromocytoma PC12 cell line is described here. When compared to nonpreconditioned cells, preexposure of PC12 cells to 6 hours of oxygen and glucose deprivation (OGD) significantly increased cell viability after 15 hours of OGD 24 hours later. Flow cytometry analysis of cells labeled with specific markers for apoptosis, Annexin V, and Hoechst 33342, and of DNA content, revealed that apoptosis is involved in OGD-induced PC12 cell death and that preconditioning of the cells mainly counteracts the effect of apoptosis. Immunocytochemistry of caspase-3, a central executioner in the apoptotic process, further confirmed the activation of apoptotic pathways in OGD-induced PC12 cell death. This model may be useful to investigate the cellular mechanisms involved in neuronal transient tolerance following ischemia.
Development of Posttraumatic Hyperthermia after Traumatic Brain Injury in Rats is Associated with Increased Periventricular Inflammation
Authors: Thompson Hilaire J , Hoover Rachel C , Tkacs Nancy C , Saatman Kathryn E , McIntosh Tracy K
Published: January 2005

Posttraumatic hyperthermia (PTH) is a noninfectious elevation in body temperature that negatively influences outcome after traumatic brain injury (TBI). We sought to (1) characterize a clinically relevant model and (2) investigate potential cellular mechanisms of PTH. In study I, body temperature patterns were analyzed for 1 week in male rats after severe lateral fluid percussion (FP) brain injury ( n=75) or sham injury ( n=17). After injury, 27% of surviving animals experienced PTH, while 69% experienced acute hypothermia with a slow return to baseline. A profound blunting or loss of circadian rhythmicity (CR) that persisted up to 5 days after injury was experienced by 75% of brain-injured animals. At 2 and 7 days after injury, patterns of cell loss and inflammation were assessed in selected brain thermoregulatory and circadian centers. Significant cell loss was not observed, but PTH was associated with inflammatory changes in the hypothalamic paraventricular nucleus (PVN) by one week after injury. In brain-injured animals with altered CR, reactive astrocytes were bilaterally localized in the suprachiasmatic nucleus (SCN) and the PVN. Occasional IL-1 β+/ED-1+ macrophages/microglia were observed in the PVN and SCN exclusively in brain-injured animals developing PTH. In animals with PTH there was a significant positive correlation ( r=0.788, P<0.01) between the degree of postinjury hyperthermia and the total number of cells positive for inflammatory markers within selected thermoregulatory and circadian nuclei. In study II, a separate group of animals underwent the same injury and temperature monitoring paradigm as in study I, but had additional physiologic data obtained, including vital signs, arterial blood gases, white blood cell counts, and C-reactive protein levels. All parameters remained within normal ranges after injury. These data suggest that PTH and the alteration in CR of temperature may be due, in part, to acute reactive astrocytosis and inflammation in hypothalamic centers responsible for both thermoregulation and CR.
TNFR1 Upregulation Mediates Tolerance after Brain Ischemic Preconditioning
Authors: Pradillo Jesús M , Romera Cristina , Hurtado Olivia , Cárdenas Antonio , Moro María A , Leza Juan C , Dávalos Antoni , Castillo José , Lorenzo Pedro , Lizasoain Ignacio
Published: January 2005

A short ischemic event (ischemic preconditioning (IPC)) can result in subsequent resistance to severe ischemic injury (ischemic tolerance (IT)). The expression and neuroprotective role of tumor necrosis factor (TNF- α) have been described in models of IPC and we have showed the participation of its processing enzyme, the TNF- α convertase enzyme (TACE) in this process. We have now decided to explore the expression and localization of TNF receptors (TNFR) as well as other signalling mechanisms involved in IT. A period of 10 mins of temporary middle cerebral artery occlusion (tMCAO) was used for focal IPC. To evaluate the ability of IPC to produce IT, permanent MCAO was performed 48 hours after IPC. Ischemic preconditioning produced a reduction in infarct volume, as we showed previously. Ischemic preconditioning caused upregulation of neuronal TNFR1 that was reduced by the selective TACE inhibitor BB1101. Intracerebral administration of TNFR1 antisense oligodeoxynucleotide, which caused a reduction in TNFR1 expression, inhibited the IPC-induced protective effect, showing that TNFR1 upregulation is implicated in IT. Moreover, treatment with BB1101, TNFR1 antisense and lactacystin—a specific proteasome inhibitor—blocked IPC-induced NF- κB. Immunohistochemical studies showed the expression of TACE and TNFR1 in neurons. In summary, these data show that IPC produces neuronal upregulation of TACE and TNFR1, and that the pathway TACE/TNF- α/TNFR1/NF- κB is involved in IT.
Few electrons injection in silicon nanocrystals probed by ultrahigh vacuum atomic force microscopy
Authors: Decossas S. , Vitiello J. , Baron T. , Mazen F. , Gidon S.
Published: January 2005

Ultrahigh vacuum atomic force microscopy has been used to inject and detect charges in individual silicon nanocrystals. The sensitivity of our measurements is shown to be better than 2e. Injected charge saturates as a function of injection time for a given electric field. The potential of the charged nanocrystal as a function of the number of charges in the dot is in good agreement with a simple electrostatic model.
Capture and inception of bubbles near line vortices
Authors: Oweis G. F. , van der Hout I. E. , Iyer C. , Tryggvason G. , Ceccio S. L.
Published: January 2005

Motivated by the need to predict vortex cavitation inception, a study has been conducted to investigate bubble capture by a concentrated line vortex of core size rc and circulation Γ0 under noncavitating and cavitating conditions. Direct numerical simulations that solve simultaneously for the two phase flow field, as well as a simpler one-way coupled point-particle-tracking model (PTM) were used to investigate the capture process. The capture times were compared to experimental observations. It was found that the point-particle-tracking model can successfully predict the capture of noncavitating small nuclei by a line vortex released far from the vortex axis. The nucleus grows very slowly during capture until the late stages of the process, where bubble/vortex interaction and bubble deformation become important. Consequently, PTM can be used to study the capture of cavitating nuclei by dividing the process into the noncavitating capture of the nucleus, and then the growth of the nucleus in the low-pressure core region. Bubble growth and deformation act to speed up the capture process.
Gaussian split Ewald: A fast Ewald mesh method for molecular simulation
Authors: Shan Yibing , Klepeis John L. , Eastwood Michael P. , Dror Ron O. , Shaw David E.
Published: January 2005

Gaussian split Ewald (GSE) is a versatile Ewald mesh method that is fast and accurate when used with both real-space and k-space Poisson solvers. While real-space methods are known to be asymptotically superior to k-space methods in terms of both computational cost and parallelization efficiency, k-space methods such as smooth particle-mesh Ewald (SPME) have thus far remained dominant because they have been more efficient than existing real-space methods for simulations of typical systems in the size range of current practical interest. Real-space GSE, however, is approximately a factor of 2 faster than previously described real-space Ewald methods for the level of force accuracy typically required in biomolecular simulations, and is competitive with leading k-space methods even for systems of moderate size. Alternatively, GSE may be combined with a k-space Poisson solver, providing a conveniently tunable k-space method that performs comparably to SPME. The GSE method follows naturally from a uniform framework that we introduce to concisely describe the differences between existing Ewald mesh methods.
Breakdown of the mirror image symmetry in the optical absorption/emission spectra of oligo(para-phenylene)s
Authors: Heimel Georg , Daghofer Maria , Gierschner Johannes , List Emil J. W. , Grimsdale Andrew C. , Müllen Klaus , Beljonne David , Brédas Jean-Luc , Zojer Egbert
Published: January 2005

The absorption and emission spectra of most luminescent, π-conjugated, organic molecules are the mirror image of each other. In some cases, however, this symmetry is severely broken. In the present work, the asymmetry between the absorption and fluorescence spectra in molecular systems consisting of para-linked phenyl rings is studied. The vibronic structure of the emission and absorption bands is calculated from ab initio quantum chemical methods and a subsequent, rigorous Franck-Condon treatment. Good agreement with experiment is achieved. A clear relation can be established between the strongly anharmonic double-well potential for the phenylene ring librations around the long molecular axis and the observed deviation from the mirror image symmetry. Consequences for related compounds and temperature dependent optical measurements are also discussed.
Drop dynamics in an oscillating extensional flow at finite Reynolds numbers
Authors: Li Xiaoyi , Sarkar Kausik
Published: January 2005

A viscous drop deforming in a planar oscillating extensional flow is numerically simulated using a front-tracking finite-difference method. The effects of periodic forcing and interfacial tension are studied at low but finite inertia. The oscillation leads to decreased deformation and bounded drop shapes for conditions for which steady extension results in drop breakup. The drop displays a resonance phenomenon where the deformation reaches a maximum when the forcing frequency matches the natural frequency of the drop. The large deformation at resonance indicates a possible mechanism for size selective breakup by flows with appropriate fluctuation frequency. The detail structure of the flow at different time instants within a period for various values of interfacial tension and frequency is investigated. The drop dynamics shows a complex phase relation with the forcing flow. Competition between the inertia-induced dynamic pressure and the viscous stresses leads to both positive and negative values of the phase and a complex variation with interfacial tension and forcing frequency. A second-order ordinary differential equation model with appropriate representation of the pressure and viscous forces is developed that qualitatively explains the phase behaviors. For the highest inertia case considered in this paper (Re=10.0), the drop dynamics becomes aperiodic at resonance marked by a strong subharmonic component in the frequency spectrum.
Dispersive destabilization of nonlinear light propagation in fiber Bragg gratings
Authors: Martel Carlos
Published: January 2005

The effect of retaining the material dispersion terms in the nonlinear coupled mode equations (NLCME) that describe light propagation in fiber Bragg gratings is analyzed. It is found that dispersion is responsible for new instabilities of the uniform states and gives rise to new complex spatio-temporal dynamics that is not captured by the standard NLCME formulation. A detailed analysis of the effect of dispersion on the linear stability characteristics of the uniform solutions is presented and some numerical integrations of the NLCME with dispersion are also performed in order to corroborate the theoretical results.
Tunneling effects and intersubband absorption in AlN/GaN superlattices
Authors: Baumann E. , Giorgetta F. R. , Hofstetter D. , Wu H. , Schaff W. J. , Eastman L. F. , Kirste L.
Published: January 2005

We report on intersubband absorption and photovoltage measurements on regular GaN/AlN-based superlattice structures. For barrier thicknesses larger than about 25 Å, the optical intersubband absorption peaks at a considerably smaller energy than the photovoltage spectrum. A simple model taking into account the oscillator strength of the involved transitions and the corresponding tunneling probabilities agrees with the experimental findings. According to this model, the observed photovoltage is the macroscopic manifestation that the two-dimensional electron gas at the top of the superlattice changes its carrier density by a vertical transport of electrons.
Homeotropically aligned nematic liquid crystal device locked by a polymer wall with wide viewing angle
Authors: Lee S. H. , Park S. H. , Lee M.-H. , Oh S. T. , Lee G.-D.
Published: January 2005

We fabricated a homeotropically aligned nematic liquid crystal display (LCD), where the chiral-doped LC with negative dielectric anisotropy is locked by a polymer wall under crossed polarizers and whose on and off states are controlled by a vertical electric field. In the absence of an electric field, the rubbing-free device appears to be dark. In the presence of the field, the homeotropically aligned LCs tilt down, giving rise to brightness but four brush schlieren textures appear with point singularity S=+1. This indicates that the mid-directors have radial alignment inside the polymer wall in the voltage-on state. Consequently, the device shows excellent viewing angle characteristics. The electro-optic characteristics of one prototype with excellent viewing angles are reported herein.
Low-loss and directional output ZnO thin-film ridge waveguide random lasers with MgO capped layer
Authors: Yuen Clement , Yu S. F. , Leong Eunice S. P. , Yang H. Y. , Lau S. P. , Chen N. S. , Hng H. H.
Published: January 2005

Room-temperature ultraviolet lasing characteristics of ZnO thin-film ridge-waveguide random lasers with MgO capped layer fabricated on n-type (100) Si substrate are reported. It is demonstrated that highly directional emission from the facets of the random lasers can be achieved. Reduction of scattering loss inside the random cavities can also be obtained. In addition, the improvement in the efficiency of the lasing characteristics of the random lasers by optical feedback is studied.
Growth mechanisms of highly mismatched AlSb on a Si substrate
Authors: Balakrishnan G. , Huang S. , Dawson L. R. , Xin Y.-C. , Conlin P. , Huffaker D. L.
Published: January 2005

We describe the growth mechanisms of highly mismatched (Δao∕ao=13%) defect-free AlSb on Si(001) substrates. Nucleation occurs during the first few monolayers of AlSb deposition by crystalline quantum dot formation. With continued growth, the islands coalesce into a bulk material with no vertically propagating defects. Strain energy from the AlSb∕Si interface is dissipated by crystallographic undulations in the zinc-blende lattice, as confirmed by high-resolution transmission electron microscopy (TEM) images. Reciprocal space analysis of the TEM images corroborates a crystallographic rotation associated with the undulations. The resulting AlSb material is >98% relaxed according to x-ray diffraction analysis.
Electrical properties of ZnO nanowire field effect transistors characterized with scanning probes
Authors: Fan Zhiyong , Lu Jia G.
Published: January 2005

Single ZnO nanowires are configured as field effect transistors and their electrical properties are characterized using scanning probe microscopy (SPM). Scanning surface potential microscopy is used to map the electric potential distribution on the nanowire. Potential drop along the nanowire and at the contacts are resolved, and contact resistances are estimated. Furthermore, conductive SPM tip is used as a local gate to manipulate the electrical property. The local change of electron density induced by a negatively biased tip significantly affects the current transport through the nanowire.
Vacuum laser-driven acceleration by a slits-truncated Bessel beam
Authors: Li D. , Imasaki K.
Published: January 2005

An approach of vacuum acceleration by the longitudinal electric field of laser Bessel beam is proposed in this letter. Laser Bessel beam, truncated by a set of annular slits, exhibits several special zones over its propagation path, where an electron could avoid deceleration as it slides into the decelerating phase. Because of the “diffraction-free” properties of Bessel beam, a long interaction distance could be sustained and multistage configuration becomes possible. With the help of single particle model, the potential of a multistage acceleration scheme driven by a Laser Bessel beam is shown.
Natural hydrogen treatment effect during formation of double amorphous silicon-carbide p layer structures producing high-efficiency pin-type amorphous silicon solar cells
Authors: Myong Seung Yeop , Lim Koeng Su
Published: January 2005

We proposed a double p-type amorphous silicon-carbide (p-a-SiC:H) layer structure to improve the p∕i interface of pin-type amorphous silicon based solar cells. We found a natural hydrogen treatment involving an etch of the defective undiluted p-a-SiC:H window layer before the hydrogen-diluted p-a-SiC:H buffer layer deposition and an improvement of the order in the window layer. It is beneficial to increase overall solar cell parameters by successfully reducing recombination at the p∕i interface.
Effect of growth polarity on vacancy defect and impurity incorporation in dislocation-free GaN
Authors: Tuomisto F. , Saarinen K. , Lucznik B. , Grzegory I. , Teisseyre H. , Suski T. , Porowski S. , Hageman P. R. , Likonen J.
Published: January 2005

We have used positron annihilation, secondary ion mass spectrometry, and photoluminescence to study the point defects in GaN grown by hydride vapor phase epitaxy (HVPE) on GaN bulk crystals. The results show that N polar growth incorporates many more donor and acceptor type impurities and also Ga vacancies. Vacancy clusters with a positron lifetime τD=470±50ps were found near the N polar surfaces of both the HVPE GaN layers and bulk crystals.
Stereokinetic Shapes and Their Shadows
Authors: Albertazzi Liliana
Published: January 2005

The visual space of phenomenal appearances has a complex geometry which cannot be reduced strictly to Euclidean or projective geometry. The distinctive nature of this space and its objects is evidenced paradigmatically by stereokinetic phenomena, which are perceptual objects in actual three-dimensional coming into being. Stereokinetic phenomena produce the appearance not only of corporeality but also, in certain circumstances, of shadows. By altering certain components of his experiments on the three-dimensional appearance of a truncated cone, in fact, Musatti discovered that on its white base floats some sort of shadow obscuring stretches of the white lines. These shadows are connected to phenomena of amodal presentations successively analysed by Kanizsa. The continuity of the unfolding in visual space of stereokinetic transformations produces a diversified series of percepts coming into being, shadows included, and highlights the role of configurational movement as a factor of formal unification, thereby proposing once again the hypothesis of assimilative factors as responsible for the field organisation of past experience.
Shape-from-Shading Depends on Visual, Gravitational, and Body-Orientation Cues
Authors: Jenkin Heather L , Jenkin Michael R , Dyde Richard T , Harris Laurence R
Published: January 2005

The perception of shading-defined form results from an interaction between shading cues and the frames of reference within which those cues are interpreted. In the absence of a clear source of illumination, the definition of ‘up’ becomes critical to deducing the perceived shape from a particular pattern of shading. In our experiments, twelve subjects adjusted the orientation of a planar disc painted with a linear luminance gradient from one side to the other, until the disc appeared maximally convex—that is, until the luminance gradient induced the maximum perception of a three-dimensional shape. The vision, gravity, and body-orientation cues were altered relative to each other. Visual cues were manipulated by the York Tilted Room facility, and body cues were altered by simply lying on one side. The orientation of the disc that appeared maximally convex varied in a systematic fashion with these manipulations. We present a model in which the direction of perceptual ‘up’ is determined from the sum of three weighted vectors corresponding to the vision, gravity, and body-orientation cues. The model predicts the perceived direction of ‘up’, contributes to our understanding of how shape-from-shading is deduced, and also predicts the confidence with which the ‘up’ direction is perceived.
Perceived Contrast Explains Asymmetries in Visual-Search Tasks with Shaded Stimuli
Authors: Chacón José
Published: January 2005

Shaded stimuli have traditionally been used in the context of three-dimensional (3-D) shape perception. Many studies have shown a persistent asymmetry in that a circle filled with a shaded gradient that is dark at the top and bright at the bottom (top-dark circle) is much easier to locate among top-bright circles than in the opposite arrangement (a top-bright circle among top-dark circles). The immediate 3-D interpretation of top-dark and top-bright circles as hollows and protuberances, respectively, and the asymmetry just described have been explained in terms of 3-D percepts. The work described here challenges this view: the results of the first experiment show that top-dark circles are perceived as having 10% higher contrast than top-bright circles of the same physical contrast. Experiment 2 replicates classical visual-search experiments but adding a new condition where target and distractors were subjectively equated in contrast. For five of six subjects, the ubiquitous asymmetry disappears in this condition.
Light Direction from Shad(ow)ed Random Gaussian Surfaces
Authors: Koenderink Jan J , van Doorn Andrea J , Pont Sylvia C
Published: January 2005

Three human observers estimated the illumination direction for samples of random Gaussian surfaces illuminated by a collimated beam from random directions. These stimuli appear as ‘texture’ due to shading and shadowing (the surface on the microscale was Lambertian of uniform albedo; thus texture appears only through shading and shadowing). We found that observers were able to estimate the azimuth of the source with remarkable accuracy. In the shading regime (no shadows) the observers committed 180° azimuth errors with 50% probability, whereas in the shadow-dominated regime they were able to avoid this convex/concave confusion to a large extent. They evidently relied on second-order statistics in the shading regime and used an unidentified first-order cue in the shadow regime. The elevations of the source were also estimated with remarkable precision. We attribute this to the statistical homogeneity of the sample which can apparently be exploited by the observers. Likely cues are the fraction of shadowed surface, average intensity and rms contrast. The ability of human observers to estimate the illumination direction from surface texture no doubt contributes to the ability to estimate the light field in scenes, which is a prerequisite to the photometric parsing of scenes (shape from shading, and so forth).
Are Size Illusions in Simple Line Drawings Affected by Shading?
Authors: Zanker Johannes M , Abdullah Abd-Al-Jalil Kane
Published: January 2005

In a number of simple line drawings, such as the Müller-Lyer or Judd figures, we can experience strong distortions of perceived space—geometric illusions. One way of explaining these effects is based on the perspective information that can be read from the line drawings. For instance, the ‘inappropriate constancy scaling’ theory advocates that the inferred three-dimensional structure of the pictured object is used by the perceptual system to adjust the size of line-drawing components. Such a theory would predict that additional depth cues, for instance shading added to line drawings, should affect these illusions because they influence the three-dimensional appearance. We present here systematic measurements of the magnitude of length misjudgments in horizontal Müller-Lyer and Judd figures for three configurations: (i) pure line drawings, and with shading attached to (ii) the top, and (iii) the bottom of the figures. The latter two configurations are unambiguously interpreted as ‘folded’ structures with a horizontal edge behind the image plane or protruding from it, respectively. While we could not find any effect of shading in our experimental data, we did observe a length misjudgment in Judd figures that corresponds precisely to the asymmetry that can be observed in the Müller-Lyer illusion for inward and outward fins. This pattern of results is not consistent with notions of inappropriate constancy scaling but is fully coherent with the view that neural filtering mechanisms, which are affecting the perceived position of line intersections, are responsible for this type of geometrical illusions.
A Biologically Inspired Algorithm for the Recovery of Shading and Reflectance Images
Authors: Olmos Adriana , Kingdom Frederick A A
Published: January 2005

We present an algorithm for separating the shading and reflectance images of photographed natural scenes. The algorithm exploits the constraint that in natural scenes chromatic and luminance variations that are co-aligned mainly arise from changes in surface reflectance, whereas near-pure luminance variations mainly arise from shading and shadows. The novel aspect of the algorithm is the initial separation of the image into luminance and chromatic image planes that correspond to the luminance, red–green, and blue–yellow channels of the primate visual system. The red–green and blue–yellow image planes are analysed to provide a map of the changes in surface reflectance, which is then used to separate the reflectance from shading changes in both the luminance and chromatic image planes. The final reflectance image is obtained by reconstructing the chromatic and luminance-reflectance-change maps, while the shading image is obtained by subtracting the reconstructed luminance-reflectance image from the original luminance image. A number of image examples are included to illustrate the successes and limitations of the algorithm.
Visual Discrimination of Spectral Distributions
Authors: Pas Susan F te , Koenderink Jan J
Published: January 2005

Human observers seem to be able to use different features that classify materials with a large degree of accuracy. In this paper, we look at human perception of statistical properties of the spectral distribution in a scene.

We investigated whether human observers can discriminate just as accurately between coloured textures that have a spectral distribution due either to shading only or to both shading and specular reflectance as between uniform colours. Thresholds for the discrimination of coloured textures are about 15 times as high as thresholds for the discrimination of uniform colours, provided there is a sharp transition between the two colours. However, the coloured texture thresholds are only 1.5 times higher when we introduce a gradual transition between the two colours. There are also distinct qualitative differences in discrimination thresholds for different base colours. These differences cannot be predicted from discrimination thresholds for uniform colours.

Human observers are surprisingly good at discriminating between a material edge and a shadow edge in complex scenes. Statistical differences in the orientation of the colour distributions in colour space might be used to accomplish this. In a second experiment we investigated how well observers can discriminate between two linear distributions in colour space that have the same base colour but different orientations. When we vary the line-length in R, G, B space, thresholds cannot be predicted completely by the conservation of the average distance between the two distributions. This means that observers use not only the maximum colour difference in the stimulus to do the task, but other cues are also involved.
Essential role of Flk-1 (VEGF receptor 2) tyrosine residue 1173 in vasculogenesis in mice
Authors: Sakurai Yoshiko , Ohgimoto Kaori , Kataoka Yuki , Yoshida Nobuaki , Shibuya Masabumi
Published: January 2005

Flk-1 (human counterpart, KDR) tyrosine kinase, which is one of the two VEGF receptors, is crucial for vascular development. Recently, we showed that, among tyrosine residues of KDR, tyrosine residues 1175 (Y1175, corresponding to Y1173 in murine Flk-1) and Y1214 (Y1212 in Flk-1) are autophosphorylated in response to VEGF, and that Y1175 is important for VEGF-dependent phospholipase Cγ/PKC/mitogen-activated protein kinase activation leading to DNA synthesis in cultured endothelial cells. However, the importance of these tyrosine residues in Flk-1/KDR
in vivo
is not yet known. To examine the role of these Flk-1 tyrosine residues
in vivo
, we generated knock-in mice substituting Y1173 and Y1212 of the
Flk-1
gene with phenylalanine, respectively. As a result,

Flk-1
1173F

homozygous mice died between embryonic days 8.5 and 9.5 without any organized blood vessels or yolk sac blood islands, and hematopoietic progenitors were severely reduced, similar to the case of
Flk-1
null mice. In contrast,

Flk-1
1212F

homozygous mice were viable and fertile. These results suggest that the signaling via Y1173 of Flk-1 is essential for endothelial and hematopoietic development during embryogenesis.
Calcineurin/NFAT-induced up-regulation of the Fas ligand/Fas death pathway is involved in methamphetamine-induced neuronal apoptosis
Authors: Jayanthi Subramaniam , Deng Xiaolin , Ladenheim Bruce , McCoy Michael T. , Cluster Andrew , Cai Ning-sheng , Cadet Jean Lud
Published: January 2005

Methamphetamine [METH (“speed”)] is an abused psychostimulant that can cause psychotic, cognitive, and psychomotor impairment in humans. These signs and symptoms are thought to be related to dysfunctions in basal ganglionic structures of the brain. To identify possible molecular bases for these clinical manifestations, we first used cDNA microarray technology to measure METH-induced transcriptional responses in the striatum of rats treated with an apoptosis-inducing dose of the drug. METH injection resulted in increased expression of members of the Jun, Egr, and Nur77 subfamilies of transcription factors (TFs), changes that were confirmed by quantitative PCR. Because pathways linked to these factors are involved in the up-regulation of Fas ligand (FasL), FasL mRNA was quantified and found to be increased. Immunohistochemical studies also revealed METH-induced increased FasL protein expression in striatal GABAergic neurons that express enkephalin. Moreover, there were METH-mediated increases in calcineurin, as well as shuttling of nuclear factor of activated T cells (NFAT)c3 and NFATc4 from the cytosol to the nucleus of METH-treated rats, mechanisms also known to be involved in FasL regulation. Furthermore, METH induced cleavage of caspase-3 in FasL- and Fas-containing neurons. Finally, the METH-induced changes in the FasL-Fas death pathway were attenuated by pretreatment with the dopamine D1 receptor antagonist, SCH23390, which also caused attenuation of METH-induced apoptosis. These observations indicate that METH causes some of its neurodegenerative effects, in part, via stimulation of the Fas-mediated cell death pathway consequent to FasL up-regulation mediated by activation of multiple TFs.
Thermodynamic prediction of protein neutrality
Authors: Bloom Jesse D. , Silberg Jonathan J. , Wilke Claus O. , Drummond D. Allan , Adami Christoph , Arnold Frances H.
Published: January 2005

We present a simple theory that uses thermodynamic parameters to predict the probability that a protein retains the wild-type structure after one or more random amino acid substitutions. Our theory predicts that for large numbers of substitutions the probability that a protein retains its structure will decline exponentially with the number of substitutions, with the severity of this decline determined by properties of the structure. Our theory also predicts that a protein can gain extra robustness to the first few substitutions by increasing its thermodynamic stability. We validate our theory with simulations on lattice protein models and by showing that it quantitatively predicts previously published experimental measurements on subtilisin and our own measurements on variants of TEM1 β-lactamase. Our work unifies observations about the clustering of functional proteins in sequence space, and provides a basis for interpreting the response of proteins to substitutions in protein engineering applications.
Φ-Value analysis by molecular dynamics simulations of reversible folding
Authors: Settanni Giovanni , Rao Francesco , Caflisch Amedeo
Published: January 2005

In Φ-value analysis, the effects of mutations on the folding kinetics are compared with the corresponding effects on thermodynamic stability to investigate the structure of the protein-folding transition state (TS). Here, molecular dynamics (MD) simulations (totaling 0.65 ms) have been performed for a large set of single-point mutants of a 20-residue three-stranded antiparallel β-sheet peptide. Between 57 and 120 folding events were sampled at near equilibrium for each mutant, allowing for accurate estimates of folding/unfolding rates and stability changes. The Φ values calculated from folding and unfolding rates extracted from the MD trajectories are reliable if the stability loss upon mutation is larger than ≈0.6 kcal/mol, which is observed for 8 of the 32 single-point mutants. The same heterogeneity of the TS of the wild type was found in the mutated peptides, showing two possible pathways for folding. Single-point mutations can induce significant TS shifts not always detected by Φ-value analysis. Specific nonnative interactions at the TS were observed in most of the peptides studied here. The interpretation of Φ values based on the ratio of atomic contacts at the TS over the native state, which has been used in the past in MD and Monte Carlo simulations, is in agreement with the TS structures of wild-type peptide. However, Φ values tend to overestimate the nativeness of the TS ensemble, when interpreted neglecting the nonnative interactions.
Melatonin synthesis: 14-3-3-dependent activation and inhibition of arylalkylamine
N
-acetyltransferase mediated by phosphoserine-205
Authors: Ganguly Surajit , Weller Joan L. , Ho Anthony , Chemineau Philippe , Malpaux Benoit , Klein David C.
Published: January 2005

The nocturnal increase in circulating melatonin in vertebrates is regulated by the activity of arylalkylamine
N
-acetyltransferase (AANAT), the penultimate enzyme in the melatonin pathway (serotonin →
N
-acetylserotonin → melatonin). Large changes in activity are linked to cyclic AMP-dependent protein kinase-mediated phosphorylation of AANAT T31. Phosphorylation of T31 promotes binding of AANAT to the dimeric 14-3-3 protein, which activates AANAT by increasing arylalkylamine affinity. In the current study, a putative second AANAT cyclic AMP-dependent protein kinase phosphorylation site, S205, was found to be ≈55% phosphorylated at night, when T31 is ≈40% phosphorylated. These findings indicate that ovine AANAT is dual-phosphorylated. Moreover, light exposure at night decreases T31 and S205 phosphorylation, consistent with a regulatory role of both sites. AANAT peptides containing either T31 or S205 associate with 14-3-3ζ in a phosphorylation-dependent manner; binding through phosphorylated (p)T31 is stronger than that through pS205, consistent with the location of only pT31 in a mode I binding motif, one of two recognized high-affinity 14-3-3-binding motifs AANAT protein binds to 14-3-3ζ through pT31 or pS205. Two-site binding lowers the
K
m
for arylalkylamine substrate to ≈30 μM. In contrast, single-site pS205 binding increases the
K
m
to ≈1,200 μM. Accordingly, the switch from dual to single pS205 binding of AANAT to 14-3-3 changes the
K
m
for substrates by ≈40-fold. pS205 seems to be part of a previously unrecognized 14-3-3-binding motif-pS/pT (X
1–2
)-COOH, referred to here as mode III.
Mini-thin filaments regulated by troponin–tropomyosin
Authors: Gong Huiyu , Hatch Victoria , Ali Laith , Lehman William , Craig Roger , Tobacman Larry S.
Published: January 2005

Striated muscle thin filaments contain hundreds of actin monomers and scores of troponins and tropomyosins. To study the cooperative mechanism of thin filaments, “mini-thin filaments” were generated by isolating particles nearly matching the minimal structural repeat of thin filaments: a double helix of actin subunits with each strand approximately seven actins long and spanned by a troponin–tropomyosin complex. One end of the particles was capped by a gelsolin (segment 1–3)–TnT fusion protein (substituting for normal TnT), and the other end was capped by tropomodulin. EM showed that the particles were 46 ± 9 nm long, with a knob-like mass attributable to gelsolin at one end. Average actin, tropomyosin, and gelsolin–troponin composition indicated one troponin–tropomyosin attached to each strand of the two-stranded actin filament. The minifilaments thus nearly represent single regulatory units of thin filaments. The myosin S1 MgATPase rate stimulated by the minifilaments was Ca
2+
-sensitive, indicating that single regulatory length particles are sufficient for regulation. Ca
2+
bound cooperatively to cardiac TnC in conventional thin filaments but noncooperatively to cardiac TnC in minifilaments in the absence of myosin. This suggests that thin filament Ca
2+
-binding cooperativity reflects indirect troponin–troponin interactions along the long axis of conventional filaments, which do not occur in minifilaments. Despite noncooperative Ca
2+
binding to minifilaments in the absence of myosin, Ca
2+
cooperatively activated the myosin S1-particle ATPase rate. Two-stranded single regulatory units therefore may be sufficient for myosin-mediated Ca
2+
-binding cooperativity. Functional mini-thin filaments are well suited for biochemical and structural analysis of thin-filament regulation.
Insulin-like growth factor-binding protein-1 (IGFBP-1) mediates hypoxia-induced embryonic growth and developmental retardation
Authors: Kajimura Shingo , Aida Katsumi , Duan Cunming
Published: January 2005

Although reduced fetal growth in response to hypoxia has been appreciated for decades, we have a poor understanding of the effects of hypoxia on embryonic development and the underlying cellular and molecular mechanisms. Here we show that hypoxia treatment not only resulted in embryonic growth retardation but also caused significant delay in developmental speed and the timing of morphogenesis in vital organs of zebrafish. Hypoxia strongly induced the expression of insulin-like growth factor (IGF)-binding protein (IGFBP)-1, a secreted protein that binds IGFs in extracellular environments. Hypoxia did not change the expression levels of IGFs, IGF receptors, or other IGFBPs. The hypothesis that elevated IGFBP-1 mediates hypoxia-induced embryonic growth retardation and developmental delay by binding to and inhibiting the activities of IGFs was tested by loss- and gain-of-function approaches. Knockdown of IGFBP-1 significantly alleviated the hypoxia-induced growth retardation and developmental delay. Overexpression of IGFBP-1 caused growth and developmental retardation under normoxia. Furthermore, reintroduction of IGFBP-1 to the IGFBP-1 knocked-down embryos restored the hypoxic effects on embryonic growth and development. When tested
in vitro
with cultured zebrafish embryonic cells, IGFBP-1 itself had no mitogenic activity, but it inhibited IGF-1- and IGF-2-stimulated cell proliferation. This inhibitory effect was abolished when IGF-1 or IGF-2 was added in molar excess, suggesting that IGFBP-1 inhibits embryonic growth and development by binding to and inhibiting the activities of IGFs. The induction of IGFBP-1 expression may be a conserved physiological mechanism to restrict the IGF-stimulated growth and developmental process under hypoxic stress.