bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of TAP1 and TAP2 gene polymorphism in idiopathic bronchiectasis in children
Authors: Doğru Deniz , Özbaş Gerçeker Filiz , Yalçın Ebru , Çobanoğlu Nazan , Pekcan Sevgi , Özçelik Uğur , Kiper Nural , Özgüç Meral
Published: January 2007

Bronchiectasis is characterized by permanent changes in the structure and function of the airways. Its cause cannot be identified in some cases. A genetic disease can predispose to bronchiectasis in our country, where consanguinity of parents is common. Transporter associated with antigen presentation (TAP) deficiency syndrome is characterized by recurrent bacterial lower respiratory tract infections, which cause bronchiectasis. Our aim was to document the relationship between idiopathic bronchiectasis and TAP gene polymorphisms. Forty‐four patients with idiopathic bronchiectasis and 100 healthy individuals as the control group were included. DNA was extracted and gene polymorphisms for TAP1 and TAP2 were studied. When compared to healthy controls, in the patient group, Ile/Ile genotype was decreased and Ile/Val genotype was increased in TAP1‐333 polymorphism analysis; Asp/Asp and Gly/Gly genotypes were decreased and Asp/Gly frequency was increased in TAP1‐637 polymorphism analysis; Ile/Val genotype was increased and Ile/Ile genotype was decreased in TAP2‐379 polymorphism analysis; and Thr/Thr genotype frequency was decreased and Thr/Ala and Ala/Ala genotypes were increased in TAP2‐665 polymorphism analysis. No statistically significant difference between patient and control groups was noted only in TAP2‐565 polymorphism analysis. These results indicate that TAP gene polymorphisms may have had a role in the development of bronchiectasis in our patient group. Therefore, TAP deficiency syndrome should be considered in children with idiopathic diagnosis, since early diagnosis of the disease will improve life quality and survival. Pediatr Pulmonol. 2007; 42:237–241. © 2007 Wiley‐Liss, Inc.
Topological map learning from outdoor image sequences
Authors: He Xuming , Zemel Richard S. , Mnih Volodymyr
Published: January 2007

We propose an approach to building topological maps of environments based on image sequences. The central idea is to use manifold constraints to find representative feature prototypes, so that images can be related to each other, and thereby to camera poses in the environment. Our topological map is built incrementally, performing well after only a few visits to a location. We compare our method to several other approaches to representing images. During tests on novel images from the same environment, our method attains the highest accuracy in finding images depicting similar camera poses, including generalizing across considerable seasonal variations. © 2007 Wiley Periodicals, Inc.
Field emission devices for space applications
Authors: Rüdenauer Friedrich G.
Published: January 2007

In the late 1950s, interest arose in the US to use electrostatic droplet sprayers as a new heavy charged particle source for electric space propulsion. Originally, charged droplets were produced from conductive organic liquids. Around 1960, first attempts were made to use liquid metals as the charge material. It was discovered that the device was a very high brightness source of metal ions, which could be focused to spots of nanometer dimensions. This liquid metal ion source (LMIS) has developed into a commercially exploited device for ion microbeam technology. In Europe, the potential of the LMIS as a very high specific impulse ion thruster has been recognized. Since the 1970s, development of cesium and, later, indium ion thrusters has been going on. Presently, the development is at an advanced stage. Contracts have been issued by ESA to equip microsatellites with an attitude control system based on field (ion) emission electric propulsion (FEEP). The first technological test to verify microgravity operation of the indium LMIS was performed in 1991 on the Russian MIR space station, and from 1992 the device has been exploited for active potential control of scientific satellites and for on‐site planetary mass spectrometry in seven space missions. The first gas field‐ionization source was flown as early as 1977 on a sounding rocket and in 1986 to comet Halley. Apart from these field emission devices actually flown, field ion‐ and electron devices are under development or discussion for a number of other space applications. The latest developments and future prospects are discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Investigation of new aspects in the initial stages of decomposition of Cu2at.%Co with the tomographic atom probe and the field ion microscope
Authors: Heinrich Alexander , Al‐Kassab Tala'at , Kirchheim Reiner
Published: January 2007

The initial stages of nucleation and precipitation of the Co‐rich phase in a supersaturated Cu2at.%Co alloy were studied with the field ion microscope (FIM) and the tomographic atom probe (TAP). The specimens of nominal composition Cu2at.%Co were homogenised at 1173 K and aged for different times at different temperatures from 703 to 853 K to follow the decomposition path at these reaction temperatures. In this paper, results on the time evolution of the decomposition are presented. New aspects in the decomposition of CuCo were found, which are discussed. At the initial stages of the nucleation, fluctuations were observed, which could be quantitatively characterised.

Decomposition was found to take different paths at different annealing temperatures. At 853 K individual precipitates grew, whereas during coarsening the elastic soft [100] directions were preferred.

At 763 K, cigar‐shaped precipitates formed along the [100] directions as a metastable state, which degraded into individual spherical precipitates for longer aging times. The initial stages of decomposition were also characterised for 703 K by using the cluster search algorithm. Copyright © 2007 John Wiley & Sons, Ltd.
Glycogen synthesis by the direct or indirect pathways depends on glucose availability: In vivo studies in frog oocytes
Authors: Preller Ana , Kessi Eduardo , Ureta Tito
Published: January 2007

Besides the classic direct route, frog oocytes incorporate glucosyl units into glycogen by the so‐called indirect pathway. The operation of both pathways depends on glucose availability. Below 0.5 mM glucose (calculated intracellular concentration), the indirect route accounts for 90% of polysaccharide formation, while the direct pathway supports 70% of total glucose incorporation when administered glucose is above 1.5 mM. A sigmoidal curve was obtained for the direct pathway with n
H
= 2.04, and half saturation was reached at 2.6 mM glucose. The curve for the indirect route presented an n
H of 1.15 and an S
0.5 of 0.9 mM glucose.
Chemical composition and fermentation characteristics of grain and different parts of the stover from maize land races harvested at different growing periods in two zones of central Mexico
Authors: Estrada-Flores J. G. , González-Ronquillo M. , Mould F.L. , Arriaga-Jordán C. M. , Castelán-Ortega O. A.
Published: January 2007

The objective of this work was to determine the rumen fermentation characteristics of maize land races used as forage in central Mexico. In vitro gas production (ml per 200 mg dry matter (DM)) incubations were carried out, and cumulative gas volumes were fitted to the Krishnamoorthyet al.(1991) model. The trial used a split-plot design with cultivation practices associated with maize colour (COL) as the main plot with three levels: white, yellow and black maize; growing periods (PER) were the split plots where PER1, PER2 and PER3 represented the first, second and third periods, respectively and two contrasting zones (Z1=valley and Z2=mountain) were used as blocking factors. The principal effects observed were associated with the maturity of the plants and potential gas production increased (P<0·05) in stems (PER1=51·8, PER2=56·3, PER3=58·4 ml per 200 mg DM) and in whole plant (PER1=60·9, PER2=60·8, PER3=70·9 ml per 200 mg DM). An inverse effect was observed with fermentation rates in leaves (P<0·01) with 0·061, 0·053 and 0·0509 (per h) and in whole plant (P<0·05) with 0·068, 0·057, 0·050 (per h) in PER1, PER2 and PER3 respectively. The digestibility of the neutral-detergent fibre (NDF) decreased with maturity especially in leaves (P<0·05) with values of 0·71, 0·67 and 0·66 g/kg; in rachis (P<0·01) 0·75, 0·72, and 0·65 in PER1, PER2 and PER3 respectively. The NDF content in leaves in leaves (668, 705 and 713 g/kg DM for PER1, PER2 and PER3, respectively), stems (580, 594 and 644 g/kg DM) and, husk (663, 774 and, 808 g/kg DM) increased (P<0·05) with increasing plant maturity, rachis were significantly different between periods (P<0·01). The structure with the best nutritive characteristics was the husk, because it had the lowest fibre contents, especially in acid-detergent lignin, with values of 22·6, 28·6 and 37·6 g/kg DM in PER1, PER2 and PER3, respectively.
Genetic variation in serum copper concentration in Angus cattle
Authors: Morris C. A. , Amyes N. C. , Hickey S. M.
Published: January 2007

Following the discovery of low serum copper (Cu) concentrations in 9-month-old beef calves at pasture in autumn (50% of animals had values <7·5 μmol/l), genetic variation in serum Cu concentration was studied in an experimental Angus herd in New Zealand, monitoring at intervals from about 7 to 17 months of age. The study was initiated in autumn when animals were supplemented with zinc (Zn) salts (to protect against liver injury from toxin-producing facial eczema spores on the pasture), and later in the production year after Cu supplementation but without Zn supplementation. Heritabilities of Cu concentration were estimated in 837 calves from six calf crops, the progeny of 47 sires, using restricted maximum likelihood procedures with an animal model. Correlations between Cu concentration and Zn concentration were also estimated, along with correlations between Cu concentration and 6-month, 9-month and yearling live weights. The heritability estimate for Cu concentration at all times outside the autumn Zn supplementation period was 0·28±0·08 (between-animal repeatability, 0·30±0·05), and the heritability estimates for autumn Cu concentration and Zn concentration were 0·35±0·11 and 0·26±0·13, respectively. The genetic and environmental correlations between autumn Cu concentration and Zn concentration were ?0·29±0·31 and 0·15±0·11, respectively, suggesting antagonistic effects between Zn and Cu only at the genetic level, with a net (phenotypic) correlation of 0·02±0·06. Genetic correlations between Cu concentration (outside the autumn season) and 6-month, 9-month and yearling weights ranged from 0·15±0·15 to 0·17±0·16. It was concluded that serum Cu and Zn concentrations in calves were heritable traits under the grazing conditions encountered, and that index selection to increase live weights and Cu concentrations could be applied if desired.
Interaction of a deep-water wave with a vertical cylinder: effect of self-excited vibrations on quantitative flow patterns
Authors: OZGOREN M. , ROCKWELL D.
Published: January 2007

Interaction of a deep-water wave with a cylinder gives rise to ordered patterns of the flow structure, which are quantitatively characterized using a technique of high-image-density particle image velocimetry. When the cylinder is stationary, the patterns of instantaneous flow structure take on increasingly complex forms for increasing Keulegan--Carpenter number KC. These patterns involve stacking of small-scale vorticity concentrations, as well as large-scale vortex shedding. The time-averaged consequence of these patterns involves, at sufficiently high KC, an array of vorticity concentrations about the cylinder.

When the lightly damped cylinder is allowed to undergo bidirectional oscillations, the trajectories can be classified according to ranges of KC. At low values of KC, the trajectory is elliptical, and further increases of KC allow, first of all, both elliptical and in-line trajectories as possibilities, followed by predominantly in-line and figure-of-eight oscillations at the largest value of KC.

Representations of the quantitative flow structure, in relation to the instantaneous cylinder position on its oscillation trajectory, show basic classes of patterns. When the trajectory is elliptical, layers of vorticity rotate about the cylinder surface, in accordance with rotation of the relative velocity vector of the wave motion with respect to the oscillating cylinder. Simultaneously, the patterns of streamline topology take the form of large-scale bubbles, which also rotate about the cylinder. When the cylinder trajectory is predominantly in-line with the wave motion, generic classes of vortex formation and shedding can be identified; they include sweeping of previously shed vorticity concentrations past the cylinder to the opposite side. Certain of these patterns are directly analogous to those from the stationary cylinder.
The long-term circulation driven by density currents in a two-layer stratified basin
Authors: WELLS M. G. , WETTLAUFER J. S.
Published: January 2007

Experimentation and theory are used to study the long-term dynamics of a two-dimensional density current flowing into a two-layer stratified basin. When the initial Richardson number,$\hbox{\it Ri}_{\rho}^{\hbox{\scriptsize\it in}}$, characterizing the ratio of the background stratification to the buoyancy flux of the density current, is less than the critical value of$\hbox{\it Ri}_{\rho}^{*} \,{=}\, 21-27$, it is found that the density current penetrates the stratified interface. This result is ostensibly independent of slope for angles between 30° and 90°. If the current does not initially penetrate the interface, then it slowly increases the density of the top layer until the interfacial density difference is reduced sufficiently to drive penetration. The time scale for this to occur,$t_{p} \,{=}\, (\hbox{\it Ri}^{\hbox{\scriptsize\it in}}_{\rho} - \hbox{\it Ri}_{\rho}^{*}) L/B^{1/3}$, is explicitly a function of the buoyancy fluxBand the length of the basinL. The initial Richardson number,$\hbox{\it Ri}^{\hbox{\scriptsize\it in}}_{\rho}$, is a function of depth, the initial reduced gravity of the interface and a weak function of slope angle. In the absence of initial penetration for very steep slopes of 75° and 90°, we observe that penetrative convection at the interface leads to significant local entrainment. In consequence, the top layer thickens and the interfacial entrainment rate increases as the fifth power of the interfacial Froude number. In contrast, such a process is not observed at comparable interfacial Froude numbers on lower slopes of 30°, 45° and 60°, thereby demonstrating the important role of impact angle on penetrative convection. We attribute the increased interfacial entrainment by the steep density currents as the result of the transition from an undular bore to a turbulent hydraulic jump at the point where the density current intrudes. We discuss the applicability of the observed circulation to the stability of the Arctic halocline where we find$0.56\,{\lesssim}\, t_{p} \,{\lesssim}\,1.2$years for a range of contemporary oceanographic conditions.
Measurement of interstitial velocity of homogeneous bubbly flows at low to moderate void fraction
Authors: ROIG V. , DE TOURNEMINE A. LARUE
Published: January 2007

We develop a new methodology to examine the conditional and unconditional vertical velocity induced by high-Reynolds-number bubbles rising in a uniform flow, at low to moderate void fraction α (up to 15%). These statistics provide a local description of the perturbation of the liquid velocity around a test bubble in the swarm. In particular, the attenuation of the length of the wakes with increasing void fraction is measured for a large range of void fraction. The strong attenuation of the wakes is related to wake intermingling mechanisms. The methodology also enables a definition of the interstitial liquid flow. The velocity of the fluid averaged over all the interstitial volume far away from the bubbles is introduced. It is a useful concept, in particular to define the relative velocity, or for drift models. Our experimental results allow a discussion of the predictions of irrotational drift models. For low void fraction (α≤2%), potential flow models provide practical estimates of the interstitial velocity field. At higher void fractions, the effect of vorticity is important. A simple phenomenological model is proposed to include the effect of the flow generated by the bubble wakes.
Zytogenetische Veränderungen durch Methylphenidat?
Authors: Holtmann Martin , Kaina Bernd , Poustka Fritz
Published: January 2007

Zusammenfassung: Fragestellung: Wegen des Verdachts, dass Methylphenidat (MPH) zytogenetische Veränderungen beim Menschen induzieren könnte, wird der Einsatz dieser Substanz kontrovers debattiert. Die Diskussion wurde ausgelöst durch eine Studie von El-Zein et al. (2005) , die bei zwölf Kindern nach dreimonatiger Behandlung mit MPH eine signifikante Häufung chromosomaler Aberrationen, Schwesterchromatiden-Austausche und Kleinkerne fanden. Methodik: Die vorliegende Arbeit diskutiert die Untersuchung von El-Zein et al. unter Berücksichtigung gegenwärtig geltender zytogenetischer Standards und ordnet sie ein in den Zusammenhang bisheriger Studien zur Mutagenität, Klastogenität und Kanzerogenität von MPH. Ergebnisse: Die Aussagekraft der El-Zein-Studie ist wegen methodischer Mängel begrenzt. Tierexperimentelle Befunde zur Mutagenität und Klastogenität von MPH sind uneinheitlich. MPH hatte bei Bakterien und Säugetierzellen keine mutagenen Effekte, verfügte aber über das Potential, in Säugetierzellen zu DNS-Brüchen zu führen. Während bei Ratten die Inzidenz von Neoplasien unter MPH nicht erhöht war, wurden bei Mäusen vermehrt Leber-Neoplasien beobachtet. In einer epidemiologischen Studie fanden sich nach MPH-Behandlung beim Menschen weniger Krebserkrankungen als erwartet. Schlussfolgerungen: Angesichts der widersprüchlichen Befunde tierexperimenteller Daten ist der Mangel an toxikologischen Langzeitdaten zu MPH beim Menschen beunruhigend. Zwar sollten nicht vorschnell Schlüsse hinsichtlich einer mutagenen Gefährdung durch MPH gezogen werden; der durch El-Zein et al. aufgeworfene Verdacht erfordert aber eine fundierte Klärung.
Defining the Competence of Psychologists with a View to Public Accountability *
Authors: Poortinga Ype H. , Lunt Ingrid
Published: January 2007

In national codes of ethics the practice of psychology is presented as rooted in scientific knowledge, professional skills, and experience. However, it is not self-evident that the body of scientific knowledge in psychology provides an adequate basis for current professional practice. Professional training and experience are seen as necessary for the application of psychological knowledge, but they appear insufficient to defend the soundness of one's practices when challenged in judicial proceedings of a kind that may be faced by psychologists in the European Union in the not too distant future. In seeking to define the basis for the professional competence of psychologists, this article recommends taking a position of modesty concerning the scope and effectiveness of psychological interventions. In many circumstances, psychologists can only provide partial advice, narrowing down the range of possible courses of action more by eliminating unpromising ones than by pointing out the most correct or most favorable one. By emphasizing rigorous evaluation, the profession should gain in accountability and, in the long term, in respectability.
Global impacts of aerosols from particular source regions and sectors
Authors: Koch Dorothy , Bond Tami C. , Streets David , Unger Nadine , van der Werf Guido R.
Published: January 2007

We study the impacts of present‐day aerosols emitted from particular regions and from particular sectors, as predicted by the Goddard Institute for Space Studies GCM. We track the distribution and direct radiative forcing of aerosols, including sulfate and black and organic carbon, emitted from major source regions (North America, Europe, south Asia, Southeast Asia, South America, and Africa). We also partition the emissions by sector, including industrial, power, residential, transport, biomass burning, and natural. Southeast Asia produces 15% and 10% of the world's black carbon and sulfate and exports over 2/3 of this burden over the Northern Hemisphere. About 1/2 of the SO2 emitted by Southeast Asia and Europe is not converted to sulfate because of oxidant limitation. Although Africa has the largest biomass burning emissions, South America generates a larger (about 20% of the global carbonaceous) aerosol burden; about 1/2 of this burden is exported and dominates the carbonaceous aerosol load in the Southern Hemisphere. Calculated direct anthropogenic radiative forcings are −0.29, −0.06, and 0.24 W m−2 for sulfate, organic, and black carbon, respectively. The largest BC radiative forcings are from residential (0.09 W m−2) and transport (0.06 W m−2) sectors, making these potential targets to counter global warming. However, scattering components within these sectors reduce these to 0.04 and 0.03 W m−2, respectively. Most anthropogenic sulfate comes from power and industry sectors, and these sectors are responsible for the large negative aerosol forcings over the central Northern Hemisphere.
Kinematics of the Nicaraguan forearc from GPS geodesy
Authors: Turner Henry L. , LaFemina Peter , Saballos Armando , Mattioli Glen S. , Jansma Pamela E. , Dixon Timothy
Published: January 2007

Campaign GPS data from a network in the Nicaraguan forearc show a strong component of arc‐parallel motion indicating northwest translation of a nearly rigid forearc sliver. Our measured mean velocity for forearc sites of 15.1 mm yr−1 agrees well with the arc‐parallel sliver motion predicted previously by DeMets (2001) derived from closure constraints on oblique convergence between the Cocos and Caribbean plates. The lack of a northeasterly oriented arc‐normal component of motion in forearc velocities indicates that there are complexities involved beyond a simple interpretation of sliver motion being driven by oblique convergence. The forearc is reasonably well‐fit by rigid rotation about an Euler pole with a rms misfit of residual velocities of 4.9 ± 2.6 mm yr−1. Current motion of the forearc sliver relative to the stable Caribbean plate yields predominantly boundary parallel NW motion with boundary normal extension in the northwestern region averaging ∼5 mm yr−1.
Hygroscopic growth and measured and modeled critical super‐saturations of an atmospheric HULIS sample
Authors: Wex H. , Hennig T. , Salma I. , Ocskay R. , Kiselev A. , Henning S. , Massling A. , Wiedensohler A. , Stratmann F.
Published: January 2007

An atmospheric HULIS (humic‐like substance) sample dissolved in water was used to generate particles with different dry diameters. A HHTDMA (High Humidity Tandem Differential Mobility Analyzer) and LACIS (Leipzig Aerosol Cloud Interaction Simulator) were used to measure hygroscopic growth of the HULIS particles. LACIS also was used to measure the critical super‐saturation for the activation of HULIS particles with dry diameters of 50, 75, 100, and 125 nm. Simple Köhler theory was used to simulate the measured hygroscopic growth factors. For this, a new technique was used, where the ionic density (ρion) was defined as a combination of the HULIS physical properties for which values could not be reliably determined. By adjusting ρion in the Köhler equation, modeled hygroscopic growth could be brought into agreement with the measurements, even without the explicit knowledge of the different HULIS properties. It was demonstrated that the values of ρion determined with our procedure can be reproduced from combinations of physically realistic values of the physical properties represented by ρion. Adjustments of the ionic density were done for two different surface tensions, that of water as the upper limit, and the lowest value that had been measured for this HULIS sample (published previously) as the lower limit. The two adjusted values of ρion were used in the Köhler model to derive critical super‐saturations. For more dilute droplets, measured and modeled critical super‐saturations were in agreement for both values of the surface tension, whereas for the less dilute solutions, agreement only could be achieved when a lowering of the surface tension due to HULIS was taken into account.
High-temperature multipass cell for infrared spectroscopy of heated gases and vapors
Authors: Bartlome R. , Baer M. , Sigrist M. W.
Published: January 2007

In absorption spectroscopy, infrared spectra of heated gases or condensed samples in the vapor phase are usually recorded with a single pass heated gas cell. This device exhibits two orders of magnitude lower sensitivity than the high-temperature multipass cell presented in this article. Our device is a novel type of compact long path absorption cell that can withstand aggressive chemicals in addition to temperatures up to 723K. The construction of the cell and its technical features are described in detail, paying special attention to the mechanisms that compensate for thermal expansion and that allow the user to vary the optical path length under any thermal or vacuum condition. The cell may be used with a laser source or implemented within a Fourier transform infrared spectrometer. Its design is compatible with optical arrangements using astigmatic mirrors or spherical mirrors in a Herriott configuration. Here we implement a homebuilt Herriott-type cell with a total optical path length of up to 35m. In order to demonstrate the feasibility of the cell, methane and water vapor absorption lines showing dissimilar temperature effects on line intensity were recorded with the help of a mid-infrared laser source tunable between 3 and 4μm. Emphasis is put on lines that are too weak to be recorded with a single pass cell.
Effect of 3C-SiC(100) initial surface stoichiometry on bias enhanced diamond nucleation
Authors: Arnault J. C. , Intiso L. , Saada S. , Delclos S. , Bergonzo P. , Polini R.
Published: January 2007

Two 3C-SiC(100) reconstructed surfaces have been exposed to bias enhanced nucleation (BEN) treatments performed in a microwave plasma chemical vapor deposition reactor. For both BEN steps, a significant enhancement of the diamond nucleation density has been observed on the initial C-terminated surface compared to the Si-rich surface. Samples have been characterized by in situ surface analysis, namely, x-ray photoelectron spectroscopy and x-ray Auger electron spectroscopy, and by field emission gun scanning electron microscopy.
Structures and dielectric properties of Bi1.5Zn1.0Nb1.5−xTixO7 (x=0, 0.05, and 0.10) thin films
Authors: Zhang Shan-Tao , Yi-Zhang  , Lu Ming-Hui , Chen Yan-Feng , Liu Zhi-Guo
Published: January 2007

B -site Ti-substituted Bi1.5Zn1.0Nb1.5O7 (Bi1.5Zn1.0Nb1.5−xTixO7, x=0, 0.05, and 0.10) thin films have been fabricated on Pt∕Ti∕SiO2∕Si substrates by pulsed laser deposition. The x-ray diffraction and scanning electron microscopy measurements show that the films have a single phase and are well crystallized and homogeneous. Dielectric properties are investigated as function of temperature and frequency. It is found that the Ti substitution increases the dielectric constant. At 10kHz, the room temperature dielectric constant and loss tangent (ε, tanδ) are (163, 0.006), (182, 0.014), (197, 0.010) for the films with x=0, 0.05, and 0.10, respectively. In a wide temperature and frequency range (−100°C∼50°C, 1kHz∼1MHz), the dielectric constant is almost constant. However, below −100°C, a dielectric relaxation depending on Ti content is observed. The relationship between structure and property of this thin film system is discussed.
Effet de la distance spatiale dans le masquage latéral rétroactif et proactif
Authors: Blanc-Garin Jeanine
Published: January 2007

Dans une expérience de masquage latéral, on étudie les modifications de l'intensité apparente d'un stimulus lumineux lorsqu'il est suivi ou précédé d'un stimulus masquant voisin. Les facteurs expérimentaux sont: (i) le délai Δ t entre les deux stimulus (axe des abscisses sur les graphes) et (ii) l'écart spatial entre les stimulus. Les variations de la brillance (estimée sur une échelle d'intervalle en 9 points) sont analysées par rapport à la valeur de référence (V.R.: estimation du stimulus-test présenté seul). On obtient un effet de diminution de brillance lorsque les deux stimulus (test et masquant) sont proches à la fois dans le temps et dans l'espace (délai inférieur à 50 ms et écart inférieur à 10 minutes d'angle). Si l'écart spatial est augmenté (entre 0 et 10′), cet effet de masquage est atténué; cette atténuation est importante surtout en situation rétroactive contrairement à l'atténuation obtenue par d'autres facteurs (diminution d'énergie du stimulus masquant ou bien séparation dichoptique). On obtient un effet d'augmentation de brillance lorsqu'un intervalle, temporel ou spatial, est augmenté: le maximum étant obtenu lorsque le stimulus-test suit le stimulus inducteur (situation proactive), pour les délais de 75–150 ms. Ces résultats sont discutés en fonction des données obtenues dans d'autres travaux analysant les effets d'inhibition et de facilitation dans des expériences d'interaction spatiale ou temporelle.
Multiple Representations of the Same Reversible Figure: Implications for Cognitive Decisional Interpretations
Authors: Long Gerald M , Toppino Thomas C
Published: January 2007

Observations are reported with the side-by-side presentation of rotating Necker cubes and other well-known reversible (ambiguous) figures. The fact that the two representations can be seen in the opposite direction of rotation, or perspective, at the same time is regarded as a serious difficulty for the cognitive or decisional interpretations of the spontaneous alternations in these figures. It is suggested that separate and fatiguable cortical ‘channels' are a more likely basis for the dual-presentation effect than multiple decisional or attentional processes. The relationship between this proposal and recent research consistent with the visual system as a multichannel processor is noted.
Dynamics of Adaptation to Contrast
Authors: Rose David , Lowe Ivan
Published: January 2007

An investigation has been made into the temporal parameters with which the detection threshold for a sinusoidal grating changes during and after adaptation to the same grating at high contrast. Stationary high-spatial-frequency gratings and a phase-reversing low-spatial-frequency grating have been studied separately. It was found that the threshold continues to rise during adaptation for at least 6 min without sign of levelling off, and that full recovery from 6 min of adaptation can take more than 45 min. Intermittent adaptation and continuous adaptation for the same period produce similar effects. Single-phase and dual-phase exponential fits to the data are rejected, and it is concluded that the level of adaptation of the visual system to spatial contrast changes as a power function of time. However, recovery is not always monotonic, especially after adaptation to phase-reversing gratings. This may be due to inhibitory interactions between channels (in particular, those for pattern and movement information).
Brightness Induction and the Café Wall Illusion
Authors: McCourt Mark E
Published: January 2007

The Café Wall illusion is a distortion illusion in which the parallel lines of a chessboard-like figure consisting solely of parallel and perpendicular line elements appear to converge in alternating rows, creating a wedge distortion similar to that of the well-known Zöllner illusion. Gregory and Heard have formulated an explanation for the Café Wall illusion which relies upon the operation of a ‘border-locking mechanism’ in the visual system. The results of the present experiment suggest an alternative explanation in which the operation of brightness induction within the mortar regions of the Café Wall produces a series of ‘twisted cords' or slanted line elements akin to those of the Fraser or Zöllner figures. A series of such ‘twisted cords' is shown to be capable of itself to produce an illusory convergence like that of the Café Wall. Manipulations of the luminance of discrete regions in the mortar lines of the Café Wall, designed either to augment or cancel the effects of brightness induction in the production of these slanted line elements, are successful in enhancing or reducing, respectively, the wedge distortion of this visual illusion.
Perception of Movement and Correlation in Stroboscopically Presented Noise Patterns
Authors: van Doorn Andrea J , Koenderink Jan J , van de Grind Wim A
Published: January 2007

The detection of spatiotemporal correlation in visual displays has been studied with stroboscopically presented random-noise patterns and with a signal-to-noise ratio paradigm in which the moving pattern was masked with spatiotemporal white noise. These methods reveal the ability of the visual system to detect correlation of spatiotemporal structures, rather than luminance contrast. The effects of stroboscopic rate, exposure duration, target size, and the extent of discrete spatial shifts were studied in both the central and the peripheral visual field. Evidence for orientation-selective and speed-selective mechanisms was found, as well as for extensive spatiotemporal integration. Bounds on parameters of spatial and temporal correlation and integration were obtained. The results are similar to those reported earlier, and also extend them. Their relation to results obtained through other paradigms (eg the motion aftereffect) is explored.
Odour Memory and Odour Hedonics in Children
Authors: Hvastja Loredana , Zanuttini Lucia
Published: January 2007

The characteristics of olfactory memory during development were investigated and the hypothesis that the pleasantness of smells may be affected by previous associations with pleasant or unpleasant objects or events was tested. This type of emotional memory was compared in the immediate and long-term recognition of olfactory stimuli. Children from three different age groups (mean ages: 6 years 6 months; 8 years 9 months; and 10 years 5 months) were subdivided into two groups. One group was presented with six different odours, each with a slide depicting a pleasant picture. The other group was presented with the odours accompanied by unpleasant pictures. Immediately after stimulus presentation the subjects underwent a recognition test. One month later the subjects underwent a second recognition test, at the end of which they were required to give an evaluation of the pleasantness of each odour on a nine-point scale. At no age level did the pictures matched to the odours affect the recognition score. Olfactory memory varied with age, chiefly because memory decay increased with age, perhaps because of greater proactive interference. With increasing age more rapid decay was set against better immediate recognition. The hypothesis that the hedonic characteristics of odours are partially learned and are affected by events experienced in other modalities was supported.
Boundary Conditions on Parallel Processing in Human Vision
Authors: Duncan John
Published: January 2007

A new theory of visual search is tested experimentally with simple colour patches. The essential element of this new theory is that, whatever the search materials, efficiency increases continuously with (i) decreasing similarity between targets and nontargets, and (ii) increasing similarity between one nontarget and another. Control of ‘attention’ (access to visual short-term memory) is seen as a competitive interaction between display elements, and the theory shows how stimulus similarities influence the outcome of this competition. One alternative view is that parallel visual processes are limited to local mismatch detection. Search is parallel if the target forms a break in an otherwise homogeneous field, but is serial when absolute stimulus identification is required. It is shown, however, that even colour identification can be parallel, providing targets and nontargets are sufficiently dissimilar. A second alternative view is that search for simple features is parallel whereas search for conjunctions is serial. Conjunction search, however, has a characteristic similarity structure: different kinds of nontarget each share one relevant attribute with the target, but none with one another. When this structure is mimicked in search for colour patches, correspondingly poor performance is obtained.
Odor Intensity of Mixed and Unmixed Stimuli under Environmentally Realistic Conditions
Authors: Schiet Franc T , Cain William S
Published: January 2007

Subjects judged the odor intensity of single odorants and binary mixtures of fixed or varying proportions presented in the atmosphere of an environmental chamber. The subjects were exposed to the vapors either continuously (15 min) or periodically (once a minute for 15 min). As found previously, the mixtures smelled less intense than predicted from the simple sum of their unmixed components. The degree of hypoadditivity proved about the same for the four pairs of odorants studied, but varied from periodic to continuous exposure. Periodic exposure led to a greater departure from simple additivity and confirmed the presence of the phenomenon of compromise whereby the mixture can smell less intense than its stronger component alone. Continous exposure led to a closer approximation to simple additivity and exhibited no compromise. Nevertheless, the behavior seen under continuous exposure apparently derived from a tendency for mixtures to exhibit less adaptation than their components. Whereas mixtures may seem to lack potency relative to their unmixed components, they may in fact compensate for any deficiency in momentary intensity through an increase in durability.
Illusory Displacement of Equiluminous Kinetic Edges
Authors: Ramachandran Vilayanur S , Anstis Stuart M
Published: January 2007

A stationary window was cut out of a stationary random-dot pattern. When a field of dots was moved continuously behind the window (a) the window appeared to move in the same direction even though it was stationary, (b) the position of the ‘kinetic edges’ defining the window was also displaced along the direction of dot motion, and (c) the edges of the window tended to fade on steady fixation even though the dots were still clearly visible. The illusory displacement was enhanced considerably if the kinetic edge was equiluminous and if the ‘window’ region was seen as ‘figure’ rather than ‘ground’. Since the extraction of kinetic edges probably involves the use of direction-selective cells, the illusion may provide insights into how the visual system uses the output of these cells to localize the kinetic edges.
Gaze Angle Explanations of the Induced Effect
Authors: Clement Richard A
Published: January 2007

Mayhew and Longuet-Higgins formulated a computational explanation of the induced effect which successfully predicts the conditions under which the induced effect will occur. Underlying their theories are the assumptions that disparity information is separated into horizontal and vertical components and that the vertical disparities are used to calculate the gaze angles. An implementation of the fusional explanation introduced by Petrov makes similar predictions for the induced effect, but does not depend on these two assumptions.
Direct Evidence for Competition between Local and Global Mechanisms of Two-Dimensional Orientation Illusions
Authors: Wenderoth Peter , van der Zwan Rick , Williams Martin
Published: January 2007

Orientation illusions induced by two-dimensional stimuli, such as square outline frames or plaids, have been more or less adequately accounted for in terms of repulsion of the vertical test stimulus from the axis of symmetry nearest vertical of the inducing stimulus, whether that axis is real or virtual. Recently, data have been obtained which directly suggest a more complex mechanism: one in which the observed illusion is the sum of all effects—complementary and antagonistic—induced by all axes flanking vertical which are sufficiently close to vertical to exert a significant effect. Experiments are reported in which this latter hypothesis was directly tested by using nonorthogonal plaid component gratings and varying the real-axis orientations while a virtual plaid axis remained fixed in orientation at 10° from vertical. The data indicate that the real component gratings modulate the virtual-axis effect.
Effects of Element Type and Spatial Grouping on Symmetry Detection
Authors: Locher Paul J , Wagemans Johan
Published: January 2007

The influence of local and global attributes of symmetric patterns on the perceptual salience of symmetry was investigated. After tachistoscopic viewing, subjects discriminated between symmetric and either random patterns (experiment 1) or their perturbed counterparts (experiment 2) created by replacing one third of the mirror element-pairs of symmetric stimuli with ‘random’ elements. In general, it was found that perceptibility of symmetry, measured by response time and detection accuracy, was not influenced in a consistent way by type of pattern element (dots or line segments oriented vertically, horizontally, obliquely, or in all three orientations about the symmetry axis). Nor did axis orientation (vertical, horizontal, oblique), advance knowledge of axis orientation, practice effects, or subject sophistication differentially affect detection. A highly salient global percept of symmetry emerged, on the other hand, when elements were clustered together within a pattern, or grouped in symmetric pairs along a single symmetry axis or two orthogonal axes. Results suggest that mirror symmetry is detected preattentively, presumably by some kind of integral code which emerges from the interaction between display elements and the way they are organized spatially. It is proposed that symmetry is coded and signalled by the same spatial grouping processes as those responsible for construction of the full primal sketch.
Toward a Computational Model of Constraint-Driven Exploration and Haptic Object Identification
Authors: Klatzky Roberta L , Lederman Susan J
Published: January 2007

A conceptual model of the human haptic system in relation to object identification is presented. The model encompasses major architectural elements including representations of haptically accessible object properties and exploratory procedures (EPs)—dedicated movement patterns that are specialized to extract particular properties. These architectural units are related in processing-specific ways. Properties are associated with exploratory procedures in keeping with the extent to which a given procedure delivers information about a given property. The EPs are associated with one another in keeping with their compatibility, as determined by parameters of motor execution and interactions with the object and the workspace. The resulting architecture is treated as a system of constraints which guide the exploration of an object during the course of identification. The selection of the next step in a sequence of exploration requires that constraints be optimally satisfied. A network approach to constraint satisfaction is implemented and shown to account for a number of previous empirical results concerning the time course of exploration, object classification speed, and incidental learning about object properties. This system has potential applications for robotic haptic exploration.
Shape from Shading. II. Geodesic Bisection and Alignment
Authors: Johnston Alan , Passmore Peter J
Published: January 2007

Pattern-acuity tasks have provided valuable information about the precision with which the visual system can make judgments about relative spatial position in two-dimensional images. However, outside the laboratory the visual system is habitually faced with the more difficult task of making positional judgments within a three-dimensional spatial environment. Thus our perceptual systems for representing surface shape also need to support the recovery of the location and disposition of features in a three-dimensional space. An investigation of the precision of three-dimensional position judgments in two spatial-judgment tasks, arc length bisection along geodesics and geodesic alignment, is reported. The spatial-judgment tasks were defined with reference to a sphere rendered by means of ray-casting techniques. The presence of shading and texture cues had no effect on discrimination thresholds in either task. Observers' constant errors were generally less than the just noticeable distance, demonstrating that the observers can perform these positional judgment tasks without substantial bias. It is argued that there is no explicit computation of arc length on the basis of shading and texture information and that surface-orientation information cannot be used as a reference in geodesic-alignment tasks. The results raise questions about the utility of a representation of surface orientation in the human visual system.
Human Pattern Recognition: Parallel Processing and Perceptual Learning
Authors: Fahle Manfred
Published: January 2007

A new theory of visual object recognition by Poggio et al that is based on multidimensional interpolation between stored templates requires fast, stimulus-specific learning in the visual cortex. Indeed, performance in a number of perceptual tasks improves as a result of practice. We distinguish between two phases of learning a vernier-acuity task, a fast one that takes place within less than 20 min and a slow phase that continues over 10 h of training and probably beyond. The improvement is specific for relatively ‘simple’ features, such as the orientation of the stimulus presented during training, for the position in the visual field, and for the eye through which learning occurred. Some of these results are simulated by means of a computer model that relies on object recognition by multidimensional interpolation between stored templates. Orientation specificity of learning is also found in a jump-displacement task. In a manner parallel to the improvement in performance, cortical potentials evoked by the jump displacement tend to decrease in latency and to increase in amplitude as a result of training. The distribution of potentials over the brain changes significantly as a result of repeated exposure to the same stimulus. The results both of psychophysical and of electrophysiological experiments indicate that some form of perceptual learning might occur very early during cortical information processing. The hypothesis that vernier breaks are detected ‘early’ during pattern recognition is supported by the fact that reaction times for the detection of verniers depend hardly at all on the number of stimuli presented simultaneously. Hence, vernier breaks can be detected in parallel at different locations in the visual field, indicating that deviation from straightness is an elementary feature for visual pattern recognition in humans that is detected at an early stage of pattern recognition. Several results obtained during the last few years are reviewed, some new results are presented, and all these results are discussed with regard to their implications for models of pattern recognition.
Flexible, Diagnosticity-Driven, Rather Than Fixed, Perceptually Determined Scale Selection in Scene and Face Recognition
Authors: Schyns Philippe G , Oliva Aude
Published: January 2007

Different classifications of an identical visual stimulus may require different perceptual properties from the visual input. How do processes of object and scene categorisation use the information associated with different perceptual spatial scales? One scenario suggests that recognition should use coarse blobs before fine-scale edges because scale usage is perceptually determined. However, perceptual determination neglects one important aspect of any recognition task: the information demands of the considered classification of the input. Evidence is reviewed suggesting that scale usage could be flexibly determined by the diagnosticity of scale-specific cues for different categorisations of scenes and faces.