bluuebunny/crossref_metadata_2025 huggingface dataset:
A two-step synthetic route to GdOF:Ln3+ nanocrystals with multicolor luminescence properties
Authors: Shao Baiqi , Feng Yang , Jiao Mengmeng , Lü Wei , You Hongpeng
Published: December 2015

GdOF:Ln3+ (Ln = Eu, Tb, Eu/Tb, Ce/Tb, Yb/Er, and Yb/Tm) nanocrystals with multicolor emissions have been synthesized by a novel topotactic transformation route.
Compositional control of pore geometry in multivariate metal–organic frameworks: an experimental and computational study
Authors: Cadman Laura K. , Bristow Jessica K. , Stubbs Naomi E. , Tiana Davide , Mahon Mary F. , Walsh Aron , Burrows Andrew D.
Published: December 2015

Changing the ratio of the dicarboxylates, L : L′, in MOFs of the general formula [Zn2(L)2–x(L′)x(dabco)] affords control of the pore geometry, through non-covalent interactions between the ligands.
Discovery of a ternary pseudobrookite phase in the earth-abundant Ti–Zn–O system
Authors: Perry Nicola H. , Stevanovic Vladan , Lim Linda Y. , Mason Thomas O.
Published: December 2015

We apply a combined theoretical and experimental approach to the search for “missing”, stable materials within the ternary Zn–Ti–O chemical system, leading to the discovery of a new pseudobrookite phase, ZnxTi3−xo5−δ.
Cobalt complexes of tetradentate, bipyridine-based macrocycles: their structures, properties and photocatalytic proton reduction
Authors: Joliat E. , Schnidrig S. , Probst B. , Bachmann C. , Spingler B. , Baldridge K. K. , von Rohr F. , Schilling A. , Alberto R.
Published: December 2015

Photocatalytic proton reduction is demonstrated using a new type of cobalt catalyst with macrocyclic bis-bipyridine ligand frameworks, achieving turnover numbers up to 20 000 H2/Co.
ZnO nanowire interfaces for high strength multifunctional composites with embedded energy harvesting
Authors: Malakooti Mohammad H. , Patterson Brendan A. , Hwang Hyun-Sik , Sodano Henry A.
Published: December 2015

We introduce the first multifunctional material that simultaneously exhibits enhanced mechanical strength and embedded energy harvesting functionality.
A homology modelling-driven study leading to the discovery of the first mouse trace amine-associated receptor 5 (TAAR5) antagonists
Authors: Cichero Elena , Espinoza Stefano , Tonelli Michele , Franchini Silvia , Gerasimov Andrey S. , Sorbi Claudia , Gainetdinov Raul R. , Brasili Livio , Fossa Paola
Published: December 2015

The computational study here proposed allowed us to discovery for the first time two TAAR5 antagonist, selective over the TAAR1 receptor.
Effect of fluorination pattern and extent on the properties of PCDTBT derivatives
Authors: Cartwright Luke , Yi Hunan , Iraqi Ahmed
Published: December 2015

Fluorination ofPCDTBTderivatives at different positions and to different extents causes major changes in their properties.
In vitro antiproliferative activity of palladium(ii) thiosemicarbazone complexes and the corresponding functionalized chitosan coated magnetite nanoparticles
Authors: Hernández Wilfredo , Vaisberg Abraham. J. , Tobar Mabel , Álvarez Melisa , Manzur Jorge , Echevarría Yuri , Spodine Evgenia
Published: December 2015

Magnetite functionalized nanoparticles with Pd(L3)2 and Pd(L4)2 show antiproliferative activity against DU-145 and HuTu80; Pd(L2)2 is found to be a promising pharmacological agent.
Structure activity related, mechanistic, and modeling studies of gallotannins containing a glucitol-core and α-glucosidase
Authors: Ma Hang , Wang Ling , Niesen Daniel B. , Cai Ang , Cho Bongsup P. , Tan Wen , Gu Qiong , Xu Jun , Seeram Navindra P.
Published: December 2015

Evaluation of the mechanisms of inhibitory activities of gallotannins containing a glucitol core (GCGs) on α-glucosidase.
Bio-inspired polydopamine functionalization of carbon fiber for improving the interfacial adhesion of polypropylene composites
Authors: Liu Yuan , Fang Yichao , Qian Jianhua , Liu Zuozhen , Yang Bin , Wang Xinling
Published: December 2015

Carbon fiber was surface-functionalized by a facile dopamine self-polymerization method to improve the interfacial interaction with maleic anhydride grafted polypropylene modified PP.
Palladium nanoparticles supported on a titanium dioxide cellulose composite (PdNPs@TiO2–Cell) for ligand-free carbon–carbon cross coupling reactions
Authors: Jadhav Sanjay , Jagdale Ashutosh , Kamble Santosh , Kumbhar Arjun , Salunkhe Rajshri
Published: December 2015

Well-dispersed non-spherical PdNPs with a diameter of 39–45 nm supported on a TiO2–cellulose composite can be synthesized by a simple route, and used for many coupling reactions under mild reaction conditions.
Effects of C1–3-doping on electronic and structural properties of Stone–Wales defective boron nitride nanotubes as well as their NO gas sensitivity
Authors: Roohi Hossein , Maleki Layla
Published: December 2015

In this work, a first principle exploration was performed to investigate the electronic and structural properties of C-doped Stone–Wales (SW) defective (6,0) single-walled boron nitride nanotubes (BNNTs) as well as their chemical sensitivity toward NO gas using DFT approach.
The pore network and the adsorption characteristics of mesoporous silica aerogel: adsorption kinetics on a timescale of seconds
Authors: Kalmár József , Kéri Mónika , Erdei Zsolt , Bányai István , Lázár István , Lente Gábor , Fábián István
Published: December 2015

Pore network and adsorption properties of mesoporous silica aerogel: a mechanistic study on the timescale of seconds.
Structural evolution, electronic and magnetic manners of small rhodium Rhn+/−(n = 2–8) clusters: a detailed density functional theory study
Authors: Dutta Abhijit , Mondal Paritosh
Published: December 2015

We have evaluated the stable electronic structure and magnetic properties of all neutral and ionic Rhn(n= 2–8) clusters using density functional theory. This study reveals that Rh4is the magic cluster based on the calculated reactivity parameters.
Impact of different nanostructures of a PEDOT decorated 3D multilayered graphene foam by chemical methods on supercapacitive performance
Authors: Sohn Ji Soo , Patil Umakant M. , Kang Seokwon , Kang Shinill , Jun Seong Chan
Published: December 2015

The present research article describes chemically grown different nanostructures of poly(3,4-ethylenedioxythiophene) (PEDOT) on porous multilayered graphene foam (PEDOT/3D GF) as a supercapacitor electrode with enhanced electrochemical performance.
One-step synthesis of solution processed time-dependent highly efficient and stable PbS counter electrodes for quantum dot-sensitized solar cells
Authors: Gopi Chandu V. V. M. , Bae Jin-Ho , Venkata-Haritha Mallineni , Kim Soo-Kyoung , Lee Young-Seok , Sarat Govindu , Kim Hee-Je
Published: December 2015

A QDSSC with time-dependent optimized PbS CE exhibits a higherηof 4.61% than that of Pt CE (1.34%).
Novel Eu-containing titania composites derived from a new Eu(iii)-doped polyoxotitanate cage
Authors: Lv Yaokang , Cai Zhiwei , Yan Dongpeng , Su Chang , Li Weijun , Chen Wei , Ren Zhuochao , Wei Yongge , Mi Ouyang , Zhang Cheng , Wright Dominic S.
Published: December 2015

The new cage [Ti2O(OEt)8(EtOH)EuCl]2 (1) can be used as a single-source precursor to nano-structured Eu(iii)-containing titania composites, nanoporous composites and flexible films, which are attractive fluorescent materials.
Immobilized polyazomethines containing triphenylamine groups on ITO: synthesis and acidochromic, electrochemical, electrochromic and photoelectronic properties
Authors: Ma Xiaochuan , Wu Yanshuang , Wen Hailin , Niu Haijun , Wang Cheng , Qin Chuanli , Bai Xuduo , Lei Lei , Wang Wen
Published: December 2015

A new series of polyazomethines (PAMs) containing triphenylamine (TPA) as easily-oxidized units were synthesized as highly soluble materials with electrochromism.
Deoxygenation of methyl palmitate over SiO2-supported nickel phosphide catalysts: effects of pressure and kinetic investigation
Authors: Han Fei , Guan Qingxin , Li Wei
Published: December 2015

Hydrodeoxygenation of methyl palmitate was performed on Ni2P/SiO2. Reaction constant rate and active energy were calculated. The result shows that conversion and selectivity of the HDO path were raised with increasing temperature and pressure.
Novel nanostructured star-shaped polyaniline derivatives and their electrospun nanofibers with gelatin
Authors: Massoumi Bakhshali , Aali Nazila , Jaymand Mehdi
Published: December 2015

The aim of this study is the synthesis, characterization and investigation of some physicochemical properties of the star-shaped polyaniline derivatives. The nanofibers of the synthesized star-shaped polymers with gelatin were also prepared.
A sensitive electrochemical immunosensor for the detection of human chorionic gonadotropin based on a hierarchical nanoporous AuAg alloy
Authors: Zhao Dianyun , Yu Yang , Xu Caixia
Published: December 2015

A sensitive immunosensor for hCG detection is designed based on assembling the antibody on graphene sheets and ionic liquid composite film. The HNP-AuAg alloy is used as hCG antibody carrier for the preparation of a highly sensitive immunosensor.
A significant by-product of the industrial processing of pistachios: shell skin – RP-HPLC analysis, and antioxidant and enzyme inhibitory activities of the methanol extracts of Pistacia vera L. shell skins cultivated in Gaziantep, Turkey
Authors: Kilic Ibrahim Halil , Sarikurkcu Cengiz , Karagoz Isik Didem , Uren Mehmet Cemil , Kocak Mehmet Sefa , Cilkiz Mustafa , Tepe Bektas
Published: December 2015

The antioxidant and enzyme inhibitory activities of the methanol extracts of immature and mature shell skins ofPistacia veraL. were evaluated.
Determination of enantiomeric excess of carboxylates by fluorescent macrocyclic sensors
Authors: Akdeniz Ali , Minami Tsuyoshi , Watanabe Sagiri , Yokoyama Maki , Ema Tadashi , Anzenbacher Pavel
Published: December 2015

Chiral fluorescent macrocycles enable detection of carboxylate enantiomers using naked eye, which allows for quantitative measurement of the enantiomeric excess with high accuracy (error < 1.6%).
Influence of polymer shape on depletion potentials and crowding in colloid–polymer mixtures
Authors: Lim Wei Kang , Denton Alan R.
Published: December 2015

Crowding by hard-sphere colloids affects shape distribution of a polymer coil, modeled as a fluctuating ellipsoid, modifying depletion-induced interactions.
Electronic and optical properties of single crystal SnS2: an earth-abundant disulfide photocatalyst
Authors: Burton Lee A. , Whittles Thomas J. , Hesp David , Linhart Wojciech M. , Skelton Jonathan M. , Hou Bo , Webster Richard F. , O'Dowd Graeme , Reece Christian , Cherns David , Fermin David J. , Veal Tim D. , Dhanak Vin R. , Walsh Aron
Published: December 2015

Crystals of earth-abundant tin disulfide exhibit high-surface-area platelet formation with ideal photocatalytic properties for water splitting in their ground state.
Magnetic field responsive drug release from magnetoliposomes in biological fluids
Authors: Nappini Silvia , Fogli Silvia , Castroflorio Benedetta , Bonini Massimo , Baldelli Bombelli Francesca , Baglioni Piero
Published: December 2015

The magnetically triggered drug release properties of magnetoliposomes are strongly affected by the presence of serum proteins.
Structural and magnetic investigations on a wet chemically synthesized nanoscale S = 1/2 spin chain compound – CuSe2O5
Authors: Shyam Priyank , Chaturvedi Smita , Karmakar Koushik , Bhattacharya Arpan , Singh Surjeet , Kulkarni Sulabha
Published: December 2015

Observation of an enhanced Curie tail in the low temperature susceptibility indicates the presence of uncompensated spins at the ends of the CuSe2O5nanorods. The enhanced curie tail also contributes towards the shift in susceptibility hump of CuSe2O5nanorods to ∼75 K (from ∼101 K for single crystal).
A two-step approach to realize size- and shape-selective separation of crude gold nanotriangles with high purification
Authors: Zhang Fan , Zhu Jian , An Hui-Qin , Li Jian-Jun , Zhao Jun-Wu
Published: December 2015

A two-step separation strategy that combined CTAB and CTAC has been proposed that enables the purification of gold nanotriangles effectively.
Intramedullary Spinal Capillary Hemangioma: Case Report
Authors: Welling Leonardo , Welling Mariana , Figueiredo Eberval
Published: December 2015

Capillary hemangiomas involving the neuraxis are very uncommon. In the spinal cord, they are located mainly intradural and extramedullary. To our knowledge, only four cases in conus medullaris have been previously described. In our case, a 46-year-old man was admitted with back pain, sphincter disturbances, as well as progressive weakness and numbness on the lower extremities. Magnetic resonance imaging revealed an undefined intramedullary lesion on the conus medullaris. The patient underwent microsurgery, which achieved complete removal. Histopathological diagnosis was compatible with capillary hemangioma. His postoperative course was uneventful and all symptoms, including bladder dysfunction clearly regressed. The treatment of intramedullary capillary hemangiomas is very critical in preventing unnecessary morbidity, providing accurate information with respect to prognosis, and establishes a regular outpatient follow-up. The natural history of this lesion involving the spinal cord is not well described, although they are common elsewhere in the body.
The effect of oscillating force field on the dynamics of free inner core in a rotating fluid-filled spherical cavity
Authors: Kozlov V. G. , Kozlov N. V. , Subbotin S. V.
Published: December 2015

This research involves experimental studies of the dynamics of a free spherical core in a fluid-filled spherical cavity rotating around the horizontal axis and subject to vibration perpendicular to the rotation axis. The core stays in the center of the cavity under the action of a centrifugal force (the core density is less than the fluid density). The vibration manifests itself in resonance regions when the vibration frequency coincides with one of the core’s natural frequencies. The amplitude of the core oscillations and generation of its intensive differential rotation rise steeply, with the differential rotation lagging or leading, depending on the frequency of the core oscillations. Excitation of leading rotation is accompanied by the core shift from the cavity center to one of the poles with the core rotation axis deviated from the cavity rotation axis. The research shows that the superposition of different force fields, oscillating vibrational field, and static gravitational force field determines the differential rotation rate of the core. The gravity field causes the lagging circular oscillations of the core with respect to the cavity, and consequently its steady lagging differential rotation, which decreases as the cavity rotation rate increases. The research shows that 2D steady flow in the form of a Taylor-Proudman column accompanies the differential rotation of the core. The resulting flow is a linear superposition of flows excited independently by gravity and vibration. The instability of the flow manifests itself, as an azimuthal two-dimensional wave is propagating on the Taylor-Proudman column boundary, and depends on the flow structure.
Electrostatic analysis of n-doped SrTiO3 metal-insulator-semiconductor systems
Authors: Kamerbeek A. M. , Banerjee T. , Hueting R. J. E.
Published: December 2015

Electron doped SrTiO3, a complex-oxide semiconductor, possesses novel electronic properties due to its strong temperature and electric-field dependent permittivity. Due to the high permittivity, metal/n-SrTiO3 systems show reasonably strong rectification even when SrTiO3 is degenerately doped. Our experiments show that the insertion of a sub nanometer layer of AlOx in between the metal and n-SrTiO3 interface leads to a dramatic reduction of the Schottky barrier height (from around 0.90 V to 0.25 V). This reduces the interface resistivity by 4 orders of magnitude. The derived electrostatic analysis of the metal-insulator-semiconductor (n-SrTiO3) system is consistent with this trend. When compared with a Si based MIS system, the change is much larger and mainly governed by the high permittivity of SrTiO3. The non-linear permittivity of n-SrTiO3 leads to unconventional properties such as a temperature dependent surface potential non-existent for semiconductors with linear permittivity such as Si. This allows tuning of the interfacial band alignment, and consequently the Schottky barrier height, in a much more drastic way than in conventional semiconductors.
Transport properties and c/a ratio of V2O3 thin films grown on C- and R-plane sapphire substrates by pulsed laser deposition
Authors: Sakai Joe , Limelette Patrice , Funakubo Hiroshi
Published: December 2015

We prepared V2O3 thin films on C- or R-plane sapphire (Al2O3) substrates by a pulsed laser deposition method. X-ray diffraction analyses confirmed that single-phase V2O3 films were epitaxially grown on both C- and R-planes under an Ar gas ambient of 2 × 10−2 mbar at a substrate temperature of 873 K. Depending on the deposition conditions, c/a ratios at room temperature of (0001)-oriented V2O3 films widely ranged from 2.79 to 2.88. Among them, the films of 2.81 ≤ c/a ≤ 2.84 showed complex metal (M)–insulator (I)–M transition during cooling from 300 to 10 K, while those of larger c/a ratios were accompanied by metallic properties throughout this temperature range. All the films on R-plane substrates underwent simple M-I transition at ∼150 K, which was more abrupt than the films on C-plane, whereas their c/a ratios were narrowly distributed. The distinct difference of M-I transition properties between C- and R-plane films is explained by the intrinsic a- and c-axes evolution through the transition from M to I phases.
Transparent bulk-size nanocomposites with high inorganic loading
Authors: Chen Shi , Gaume Romain
Published: December 2015

With relatively high nanoparticle loading in polymer matrices, hybrid nanocomposites made by colloidal dispersion routes suffer from severe inhomogeneous agglomeration, a phenomenon that deteriorates light transmission even when the refractive indices of the inorganic and organic phases are closely matched. The dispersion of particles in a matrix is of paramount importance to obtain composites of high optical quality. Here, we describe an innovative, yet straightforward method to fabricate monolithic transparent hybrid nanocomposites with very high particle loading and high refractive index mismatch tolerance between the inorganic and organic constituents. We demonstrate 77% transmission at 800 nm in a 2 mm-thick acrylate polymer nanocomposite containing 61 vol. % CaF2 nanoparticles. Modeling shows that similar performance could easily be obtained with various inorganic phases relevant to a number of photonic applications.
Photoluminescence study of oxidation-induced faults in 4H-SiC epilayers
Authors: Miyano Yutaro , Asafuji Ryosuke , Yagi Shuhei , Hijikata Yasuto , Yaguchi Hiroyuki
Published: December 2015

We investigated the effect of thermal oxidation on crystalline faults in 4H-SiC epilayers using photoluminescence imaging. We found that a comb-shaped dislocation array was deformed by thermal oxidation. We also found that line-shaped faults perpendicular to the off-cut direction were formed during oxidation and were stretched and increased with the oxidation time. Since these line-shaped faults were peculiar to the oxidation and stretched/increased with the oxide growth, they were identified as oxidation-induced stacking faults as seen in Si oxidation.
Interference, Not Enhancement, When Attending to Two Nearby Targets
Authors: Bahcall D , Kowler E
Published: December 2015

In an attempt to determine the size of the spatial window of attention we required subjects to identify 2 target letters from a display of 24 letters, expecting performance to improve the closer the targets were to each other. The results were opposite to this expectation.

The 2 target letters were chosen randomly from a circular display (radius 4 deg) containing 24 letters. The display (duration 100 to 300 ms) was preceded and followed by masks. Attention was directed to the target locations by means of either a colour cue or a numeral cue. Identification of target letters improved as the directional separation between targets was increased from 15° to 180°. Performance was better when targets were in different hemifields but also improved with increasing separation within a hemifield.

The results demonstrate interference at an attentional level analogous to lateral sensory masking. Attending to one item does not enhance recognition of nearby items, as might be expected with an expandable attentional beam or zoom lens, but rather interferes with the perception of nearby items. This outcome is consistent with the idea that nearby locations share limited processing resources and with neurophysiological findings on attentionally-mediated changes in receptive fields.
The Role of Attention in the Detection of Luminance Changes: Endogenous versus Exogenous Cueing
Authors: Brawn P T , Snowden R J
Published: December 2015

Many visual tasks have been shown to be influenced by the attentional state of the observer. However the conditions under which attention has effects is still unclear. Here we report upon a series of experiments where the observer has to react to changes in the luminance of a target amongst many distractors. We have systematically manipulated the nature of the cue (endogenous vs exogenous) and the task to be performed (detection of changes vs discrimination of direction of change).

Stimuli consisted of a number of circles upon a screen. At some point in time one of the circles changed in luminance and subjects reacted as quickly as possible. Typically half the circles were red and half green. Subjects could be cued to attend to a particular colour by instruction (endogenous) or by a brief flash of the lines that joined the same coloured elements (exogenous). In most cases the cue was appropriate on 80% of the trials and hence we could compare response times between valid and invalid trials.

Our results show that (1) for simple detection endogenous cues were ineffective whereas exogenous cues provided a small advantage for the valid trials, and (2) for discrimination of direction of change endogenous cues provided a small advantage, whereas exogenous cues provided a large advantage for the valid trials. It appears that both cueing type and task type modulate the attentional effects on this ‘preattentive’ task.
Categorical Perception or Cue Combination in Vision: A Sensory Coding Model that Predicts the Form of the Psychometric Function
Authors: Treisman M , Johnston R E
Published: December 2015

Certain psychophysical tasks produce psychometric functions that diverge from normal distribution functions. Such curves occur for speech sound discrimination, where the concept of categorical perception (CP) is applied. It has been claimed that categorical perception also occurs at the critical fusion frequency (CFF) for visual flicker. An alternative model is put forward in which the processing of complex stimuli that contain more than one source of discriminative information (cues) may lead to non-normal functions similar to the Weibull function. For the CFF the cue combination model predicts a hybrid curve that is neither normal nor Weibull. We report psychometric functions for visual flicker discrimination in which rectangular or sinusoidal visual flicker stimuli were presented at varying frequencies with time-average luminance controlled or with luminance correlated with frequency, and the responses required were either categorical or comparative. At the CFF, curves are obtained of the hybrid form predicted by the cue combination model but that is not compatible with categorical perception theory. Other evidence supporting the cue combination model is reported. We conclude that the sensory coding model may explain some of the variation in the form of the psychometric function in different visual tasks.
Texture Segmentation and Visual Search in Deaf and Hearing Subjects: Evidence for Compensation?
Authors: Sireteanu R , Rettenbach R , Diller G
Published: December 2015

Do deaf people develop capacities of their remaining senses that exceed those of hearing individuals? Are the compensatory effects due to attention-dependent strategies? We investigated these questions, using texture segmentation and visual search tasks. The advantage of these tasks is that they contain attention-dependent and attention-independent components. We investigated 8 hearing adult observers, and 99 hearing and 89 deaf subjects aged between 6 and 20 years. The subject's task was to search for a discrepant stimulus among a number of distracting items. We used four different visual search tasks (circles with and without a 90° gap; circles with and without an added vertical line; pairs of convergent and parallel lines; tilted and vertical single lines) and oriented textures containing either a single line or a group of 16 discrepant lines. Visual search and texture segmentation tasks were randomly intermingled. Each subject participated in eight experimental runs, on two consecutive days.

Both groups of subjects showed consistent learning effects for all tasks. In both groups, reaction times for all tasks decreased with age and reached an optimum at about 16 – 18 years. However, statistical comparisons do not indicate compensatory effects for deafness: reaction times and error rates of the deaf subjects were higher than those of the age-matched hearing subjects, for both the serial and the parallel tasks. These results were independent of the age and gender of the subjects and occurred for all etiologies for deafness. These results suggest deficiencies in the visual processing capacity of deaf subjects in tasks with and without attentional load.
Visual Coherence Affects Smooth Pursuit
Authors: Beutter B R , Lorenceau J , Stone L S
Published: December 2015

For four subjects (one naive), we measured pursuit of a line-figure diamond moving along an elliptical path behind an invisible X-shaped aperture under two conditions. The diamond's corners were occluded and only four moving line segments were visible over the background (38 cd m−2). At low segment luminance (44 cd m−2), the percept is largely a coherently moving diamond. At high luminance (108 cd m−2), the percept is largely four independently moving segments. Along with this perceptual effect, there were parallel changes in pursuit. In the low-contrast condition, pursuit was more related to object motion. A \chi2 analysis showed ( p>0.05) that for 98% of trials subjects were more likely tracking the object than the segments, for 29% of trials one could not reject the hypothesis that subjects were tracking the object and not the segments, and for 100% of trials one could reject the hypothesis that subjects were tracking the segments and not the object. Conversely, in the high-contrast condition, pursuit appeared more related to segment motion. For 66% of trials subjects were more likely tracking the segments than the object; for 94% of trials one could reject the hypothesis that subjects were tracking the object and not the segments; and for 13% of trials one could not reject the hypothesis that subjects were tracking the segments and not the object. These results suggest that pursuit is driven by the same object-motion signal as perception, rather than by simple retinal image motion.
Biological Motion Perception: From Inversion to Upright Display Orientation
Authors: Pavlova M A
Published: December 2015

How does biological motion perception change with display orientation? As previously shown, display inversion (180°) completely prevents veridical perception of biological motion. However, with upright orientation (0°), observers are able to recover the invariant structure through biological motion despite reverse transformation (showing the film backwards) or changing the presentation rate (Pavlova, 1995 Perception24 Supplement, 112). In the present experiments, observers saw the biological motion pattern at various display deviations, from inverted to upright orientation (180°, 150°, 120°, 90°, 60°, 30°, 0°), in the right or left hemifield, on a circular screen monitor. The display consisted of an array of 11 dots on the main joints of an invisible walker moving as if on a treadmill. While viewing (60 s), observers pressed a key each time their perception changed from one stable percept to another (eg when the direction of apparent rotation of the pattern reversed). The perceived multistability (the number of key-presses) increased as orientation was varied from inverted to 90°, and then decreased between 90° and upright. The recognition of walking figure improved abruptly with changing orientation: at deviations of 60° and 30° most observer reported seeing the walking figure spontaneously, yet the pattern was seen as multistable. The findings imply the relative power of constraints (such as orientation) in perception of biological motion that is discussed in relation to the KSD principle in event perception [Runeson, 1994, in Perceiving Events and Objects Eds Jansson, Epstein, Bergström (Hillsdale, NJ: Erlbaum) pp 383 – 405].
Motion Perception in High-Pass Filtered Random-Dot Patterns: Motion Energy, Element-Matching, or Both?
Authors: Smith A T , Ledgeway T
Published: December 2015

We have measured perception of the direction of displacement of two-frame random-dot patterns (50% light/dark pixels) that have been spatially high-pass filtered. In the ‘standard’ condition, pairs of high-pass filtered images, identical apart from the displacement, were presented in succession. The displacement could be in either of two opposite directions and the task was to identify the direction. The ‘reverse’ condition was the same except that image contrast was inverted between the two frames. Various element sizes and filter cut-offs were used. Two distinct patterns of results were obtained. For small check sizes, performance alternated cyclically between veridical direction perception and incorrect direction perception (aliasing) as displacement size was increased over a wide range. The period of the cycle was close to one period of the lowest spatial frequency remaining in the image after filtering, ie performance was as would be expected for a grating of that spatial frequency. In the ‘reverse’ condition the cyclical psychometric functions were inverted, ie reversed-phi motion occurred. For large check sizes, and particularly for high filter cut-offs, there was no cyclical alternation of direction perception and reversed phi did not occur in the ‘reverse’ condition. The results suggest that two mechanisms are at play. In most circumstances, detection appears to be based on motion energy since the cyclical alternation is predicted by a consideration of the spatiotemporal energy of the stimulus but not by element-matching theories. But for large elements, particularly when most of the low spatial frequencies have been removed, element-matching takes over. Elements are matched without regard to their contrast polarity. The results are thus inconsistent with the single front-end filter mechanism which Morgan [1992 Nature (London)355 344] has advanced to explain performance in this type of task.
Signal Pooling across ON and OFF Motion Detectors
Authors: van der Smagt M J , van de Grind W A
Published: December 2015

In motion studies with random-dot patterns or random-pixel-arrays (RPAs) and a signal-to-noise ratio (SNR) paradigm, detection thresholds have been found to depend upon size, form, and duration of the stimuli. This suggests a pooling of information from motion detectors in local space-time neighbourhood regions. Spatial pooling changed the threshold in inverse proportion to the square root of the number of pooled detectors, while temporal summation could be described as signal build-up in a leaky integrator. We investigated the size of these space-time neighbourhoods and their contrast-sign specificity (if any). Is information from equal-sign and opposite-sign motion detectors combined separately or also mutually, and if so, how?

Equal-area RPA-patches [256 square pixels, from 256 × 1 (height × width) to 4 × 64] were presented on a larger background RPA (256 × 256 pixels of equal size, C=70%, L=50 cd m−2), and displaced relative to the background (velocity 1.41 deg s−1). With the use of a staircase procedure, SNR thresholds for direction detection were determined in a 2AFC design. In a second experiment, lines containing 64 pixels (either all dark or all bright or both randomly distributed) were divided in 1 to 64 segments, oriented vertically or horizontally. Minimal thresholds were obtained when temporal and spatial summations were possible in about equal proportion. Sensitivity to fractionated arrays decreased gradually as a function of the number of fractions. Whereas subjects showed equal sensitivity to the bright and dark segments, fractionated RPAs were far less effective stimuli. A preliminary model explaining these results is presented.
Spatial and Temporal Properties of Motion Linking
Authors: Lorenceau J , Zago L , Shiffrar M
Published: December 2015

Because estimates of velocity are local and inaccurate at early stages, motion linking is necessary to recover global object velocities. Such a process could involve the V1 projections of the magnocellular system into area MT. In the present study, we determined the spatiotemporal characteristics of motion linking and its dependence upon local spatial interactions in order to better understand the dynamics and topology of integration across scales and features. For that purpose, we used structurally different textures comprising nonoverlapping patches of drifting sine-wave gratings of variable spatial and temporal frequencies. The gratings (relative orientation: 90°) were arranged to form either L or T junctions and could either drift smoothly or sinusoidally 90° out of phase. In this latter condition, combining motion signals across space results in clockwise or counterclockwise translations that observers were asked to discriminate. Contrast response functions for both a coherence and a discrimination task indicate that integration is easy at low, but not at high, contrast. In addition, coherence is less likely at low spatial frequencies and high speeds and for small as compared to large patches (for a constant stimulus area). Performance is far better for L than for T junctions, although this effect is attenuated for vertical and horizontal as compared to oblique (±45°) gratings. These results are not compatible with the view that the magnocellular system is primarily responsible for motion linking and we further suggest that complex interactions between the magno and parvo systems are involved in this process. Finally, the better performance observed for L as compared to T junctions brings evidence that spatial grouping provides a handle for motion linking.
Detection of Relative Motion
Authors: Hogervorst M A , Kappers A M L , Koenderink J J , Bongaerts J
Published: December 2015

We measured human sensitivity to the relative motion of blobs moving in the peripheral visual field. The stimuli consisted of one or two blobs (Gaussian luminance profiles) oscillating relative to an (invisible) reference frame which rotated with constant angular velocity about a fixation point. We determined thresholds for detecting the oscillation of different configurations of one or two blobs as a function of velocity, eccentricity (viewing distance), and temporal frequency. By determining thresholds as a function of frequency the temporal characteristics of the detection system could be revealed.

Thresholds are higher for oscillations in the motion direction of the reference frame than perpendicular to it. No influence has been found of the position of the blobs in the frame of reference. The thresholds are scale-invariant. For low frequencies (<2 Hz) the threshold amplitude of the velocity modulation is constant whereas for high frequencies (>2 Hz) the threshold amplitude of the position modulation is constant. This behaviour can be well described by a model which detects the oscillations whenever, within a critical time (of about 200 ms for two blobs), the relative displacement is larger than a critical distance. The critical distance shows the same dependence on velocity as the span in the bilocal detector model of Koenderink et al (1985 Journal of the Optical Society of America A2 252 – 259).
Feature Contribution to Motion Signal Predicted by Magnitude of Intersection-of-Constraints Projection
Authors: Bowns L
Published: December 2015

Yo and Wilson (1992 Vision Research32 135 – 147) reported that Type II plaids move in the vector sum (VS) direction at short durations. Bowns ( Vision Research in press) showed that the result did not generalise to all Type II plaids. Computational analysis of the stimuli revealed an alternative explanation of the result in terms of features that were shown to move in a similar direction to the VS. When features (or VS) moved in a different direction to the intersection of constraints (IOC) the plaids were often perceived to move in the direction of the feature. It is hypothesised that a feature will contribute only when there is sufficient projection of the IOC in the feature direction. The direction of the features and the IOC for the stimuli used by Bowns was computed for a set of plaids that shifted from being perceived in the feature direction to the IOC. If projection is critical, then it should decrease as the stimuli shift direction. This was confirmed. A different set of plaids comprising a feature that moved in the opposite direction to the IOC and varied in terms of the magnitude of projection was presented to subjects in a forced-choice task. The plaids moved as predicted from the hypothesis. These results show a correlation between the amount of projection of the IOC in the direction of a feature and the incidence of perceived movement in the direction of the feature. The hypothesis that perceived movement of a plaid is influenced by the degree of projection of the IOC onto another available motion signal such as a displaced feature is supported.
Transsaccadic Memory: A Postsaccadic Gap Enhances the Perception of Intrasaccadic Object Changes Differently for Dorsal and Ventral Representations
Authors: Schneider W X , Deubel H
Published: December 2015

We previously demonstrated that an intrasaccadic displacement of an object is reported with higher accuracy when the object is momentarily blanked after the saccade (Deubel, Schneider, and Bridgeman Vision Research in press). Here we tested whether the blanking manipulation (size of gap between onset of saccade and change in stimulus) also improves the perception of intrasaccadic changes with respect to size, luminance, orientation, colour, and shape. The task required subjects to saccade to a peripheral target. The saccade triggered a change in an attribute of the target (eg size of the saccade target) and subjects had to report this intrasaccadic change (eg whether the postsaccadic target was larger or smaller). The results indeed show for dorsal attributes (eg size, orientation)—generally used for spatio-motor actions like grasping—that the blanking manipulation improved performance (report of intrasaccadic changes). However, ventral attributes (eg colour)—used by the object recognition system—did not profit from the postsaccadic gap. The findings are discussed in relation to the kind of temporary object representations that are implemented across the saccade and how these are updated.
The Effects of Remote Distractors on Saccade Programming
Authors: Walker R , Deubel H , Findlay J M
Published: December 2015

The time taken to initiate a saccade (latency) is increased under conditions in which a distractor is presented in the opposite visual field to the saccade target. We have termed this latency increase the ‘remote distractor effect’ (RDE). Conditions which produce the RDE are different from those used to demonstrate the ‘global effect’ amplitude modulation. In the global effect paradigm, distractors are presented in the same hemifield as the target and there is no effect on saccade latency. We report the results from a series of studies in which distractors were presented at various 2-D locations in both visual fields. Saccade latency was increased when distractors were presented in both visual fields, with the greatest increase for distractors at central fixation. Saccade latency was not affected by distractors presented on the horizontal axis in the same hemifield as the target, in which case the global effect was observed. For locations other than the horizontal axis, the critical location for modulating amplitude appeared to be within ±15 deg of the target location. Distractors presented outside this region increased latency but had no effect on amplitude. Furthermore, the latency increase observed was found to depend in a systematic way on the relationship between target and distractor eccentricities. Our data demonstrate that inhibitory processes similar to those thought to operate in the rostral pole of the superior colliculus may operate in other regions of the visual map.
Effect of Eye Movements on the Magnitude of fMRI Responses in Extrastriate Cortex during Visual Motion Perception
Authors: Greenlee M W , Freitag P , Boos M , Lacina T , Scheffler K , Radü E W
Published: December 2015

We have studied the effects of eye movements on the functional magnetic resonance imaging (fMRI) response during global dot motion in extrastriate temporo-occipital cortex. Susceptibility-based functional magnetic resonance, applying gradient-recalled echo-planar imaging (EPI) sequences, was conducted, in 12 volunteers who viewed episodes of moving dots. Anatomical and functional images were recorded with a 1.5 T Siemens Magnetom Vision (TR 5000 ms, TE 70 ms, flip angle 90°, FOV 250 mm, matrix 112 × 128, twelve 4-mm slices parallel to ac — pc plane, ranging from z=-14 – 34 mm). Sagittal T1-weighted images were acquired to determine the ac — pc plane and important anatomical landmarks. Eye movements were monitored with the use of MR-compatible EOG electrodes. Stimuli were back-projected onto a translucent screen and viewed through prisms. The four test conditions were: fronto-parallel motion, during fixation and during target pursuit; expansion-contraction motion, also during fixation and during pursuit. Pixelwise t-tests were performed on functional series recorded during rest and stimulation periods (50 s each) to identify significantly activated voxels. Planes −8 to +8 mm around the ac — pc plane and 20 – 28 mm superior to ac — pc were activated most by visual motion. In addition to primary visual cortical areas, a ventral area in the temporo-occipital cortex (human MT) responded well to both types of visual motion and these responses were enhanced by eye movements. Human MST, located dorsal of MT, showed activation by visual motion during fixation. Its response was also enhanced by pursuit.
On the Generation of Antisaccades in Different Conditions
Authors: Fischer B , Weber H
Published: December 2015

To generate a saccade in the direction opposite to the stimulus site (antisaccade) takes a conscious voluntary effort: first, one needs an intact fixation system to prevent saccades to the stimulus (prosaccades) and second, one has to generate a saccade to a location with no target. While the maintenance of fixation relies on an intact tectum, the correct performance of the antitask relies on an intact frontal system. Valid peripheral precues for attention capture indicating the direction of the antisaccade increase the error rate and the reaction time of the antisaccades. In this study we investigated how different conditions of stimulus presentation influence the performance of the antitask. We varied systematically the duration of the gap (time between fixation point offset and stimulus onset) from zero to 600 ms, and the stimulus eccentricity from 1 to 12 deg. Eye movements were recorded under infrared light. We analysed the reaction time of the correct antisaccades (a-srt) and of the erratic prosaccades (p-srt), and the percentage of errors (%-err) separately for the right and the left stimulus.

Increasing the gap to 200 ms increased the %-err by 10% and decreased the a-srt by 30 ms. For longer gap durations these effects disappeared. With larger saccades the p-err rates decreased and the p-srt were reduced by 10 ms mostly staying in the range of express saccades and following the corresponding prosaccades in protasks. The a-srt decreased systematically with increasing eccentricity. The results have implications for voluntary versus involuntary control of saccades and are related to the significance of the antitask in clinical studies.
Visual Attention and Manual Aiming: Evidence for Obligatory and Selective Spatial Coupling
Authors: Deubel H , Schneider W X , Paprotta I
Published: December 2015

We recently demonstrated that visual attention before saccadic eye movements is focused on the saccade target, allowing for spatially selective object recognition (Deubel and Schneider Vision Research in press). Here we investigate the role of visual selective attention in the preparation of aiming hand movements.

The interaction of visual attention and manual aiming was studied in a dual-task paradigm that required manual pointing to a target in combination with a letter discrimination task. Subjects were asked to keep fixation in the centre of a screen. Upon offset of a central cue, they had to aim, with unseen hand, to locations within horizontal letter strings left or right from the central fixation; movements were registered with a Polhemus FastTrack system. The ability to discriminate between the symbol “E” and its mirror image presented tachistoscopically within the surrounding distractors was taken as the measure of visual attention.

The results reveal that discrimination performance is far superior when the discrimination stimulus is also the target for manual aiming; when discrimination stimulus and pointing target refer to different objects, performance deteriorates.

We conclude that it is not possible to maintain attention on a stimulus while directing a manual movement to a spatially separate object. Rather, our results argue for an obligatory and selective coupling of visual attention and movement programming, just as found for saccadic eye movements. This is consistent with a model of visual attention (proposed by Schneider) in which a unitary attention mechanism selects a goal object for visual processing, and simultaneously provides the information necessary for goal-directed motor action such as saccades, pointing, and grasping.