bluuebunny/crossref_metadata_2025 huggingface dataset:
Wake instability of a fixed spheroidal bubble
Authors: MAGNAUDET JACQUES , MOUGIN GUILLAUME
Published: January 2007

Direct numerical simulations of the flow past a fixed oblate spheroidal bubble are carried out to determine the range of parameters within which the flow may be unstable, and to gain some insight into the instability mechanism. The bubble aspect ratio χ (i.e. the ratio of the major axis length over the minor axis length) is varied from 2.0 to 2.5 while the Reynolds number (based on the upstream velocity and equivalent bubble diameter) is varied in the range 102 ≤ Re ≤ 3 × 103. As vorticity generation at the bubble surface is at the root of the instability, theoretical estimates for the maximum of the surface vorticity and the surface vorticity flux are first derived. It is shown that, for large aspect ratios and high Reynolds numbers, the former evolves as χ8/3 while the latter is proportional to χ7/2Re−1/2. Then it is found numerically that the flow first becomes unstable for χ = χc ≈ 2.21. As the surface vorticity becomes independent of Re for large enough Reynolds number, the flow is unstable only within a finite range of Re, this range being an increasing function of χ − χc. An empirical criterion based on the maximum of the vorticity generated at the body surface is built to determine whether the flow is stable or not. It is shown that this criterion also predicts the correct threshold for the wake instability past a rigid sphere, suggesting that the nature of the body surface does not really matter in the instability mechanism. Also the first two bifurcations of the flow are similar in nature to those found in flows past rigid axisymmetric bluff bodies, such as a sphere or a disk. Wake dynamics become more complex at higher Reynolds number, until the Re−1/2-dependency of the surface vorticity flux makes the flow recover its steadiness and eventually its axisymmetry. A qualitative analysis of the azimuthal vorticity field in the base flow at the rear of the bubble is finally carried out to make some progress in the understanding of the primary instability. It is suggested that the instability originates in a thin region of the flow where the vorticity gradients have to turn almost at right angle to satisfy two different constraints, one at the bubble surface, the other within the standing eddy.
Instability of a chemically dense layer heated from below and overlain by a deep less viscous fluid
Authors: JAUPART CLAUDE , MOLNAR PETER , COTTRELL ELIZABETH
Published: January 2007

Near the threshold of stability, an intrinsically denser fluid heated from below and underlying an isothermal fluid can undergo oscillatory instability, whereby perturbations to the interface between the fluids rise and fall periodically, or it can be mechanically stable and in thermal equilibrium with heat flux extracted by small-scale convection at the interface. Both the analysis of marginal stability and laboratory experiments in large-Prandtl-number fluids show that the critical Rayleigh number, scaled to parameters of the lower fluid, depends strongly on the buoyancy number, B, the ratio of the intrinsic density difference between the fluids and the maximum density difference due to thermal expansion. For small buoyancy number, B < ∼ 0.1, the critical Rayleigh number, RaC, for oscillatory instability is small RaC < ∼50, and increases steeply for B ∼ 0.25. For B > ∼ 0.5 and RaC > ∼1100, a second form of instability develops, in which convection is confined to the lower layer. The analysis of marginal stability for layers with very different viscosities shows further that two modes of oscillatory instability exist, depending on the value of B. For B < 0.275, the entire lower layer is unstable, and wavelengths of perturbations that grow fastest are much larger than its thickness. For B > 0.275, only the bottom of the lower layer is buoyant, and instability occurs by its penetrating the upper part of the lower layer; the wavelengths of the perturbations that grow fastest are much smaller than those for B < 0.275, and the maximum frequency of oscillatory instability is much larger than that for B < 0.275. Oscillations in the laboratory experiments show that the heights to which plumes of the lower fluid rise into the upper one increase with the Rayleigh number. Moreover, in the finite-amplitude regime, the oscillation is not symmetrical. Plumes that reach maximum heights fall quickly, folding on themselves and entraining some of the upper fluid. Hence oscillatory convection provides a mechanism for mixing the fluids. Applied to the Earth, these results bear on the development of continental lithosphere, whose mantle part is chemically different from the underlying asthenosphere. As shown by the laboratory experiments and stability analysis, the lithosphere can be mechanically stable and in thermal equilibrium such that heat supplied by small-scale convection at the top of the asthenosphere is conducted through it. The lithosphere seems to have developed in a state near that of instability with different thicknesses depending on its intrinsic buoyancy. It may have grown not only by chemical differentiation during melting, but also by oscillatory convection entraining chemically denser material from the asthenosphere.
Optical altimetry: a new method for observing rotating fluids with applications to Rossby and inertial waves on a polar beta-plane
Authors: RHINES P. B. , LINDAHL E. G. , MENDEZ A. J.
Published: January 2007

The entire free-surface elevation field of a rotating fluid in the laboratory can be imaged and analysed, by using it as a parabolic Newtonian telescope mirror. This ‘optical altimetry’ readily achieves a precision of better than 1 μm of surface elevation. The surface topography corresponds to the pressure field just beneath the surface. It is the streamfunction for the geostrophic hydrostatic circulation, which can be resolved to better than 0.1 mm s−1. Still and animated images thus produced, of the entire surface elevation field, are of value in themselves, and using a projected image (a speckle pattern), have the promise of providing quantitative slope and height field data recovered by PIV (particle imaging velocimetry) techniques. With homogeneous fluid, geostrophic flow is the same at all depths. Yet of equal interest are sheared stratified rotating flows where the surface pressure is associated with inertial waves, convection, and other motions, geostrophic or ageostrophic.

Although the technique is designed for experiments in which Coriolis effects are strong, it is possible to use reflective imaging for flows at such high Rossby number that Coriolis effects are negligible, and hence this becomes a tool of more general interest in non-rotating fluid dynamics (for example, illuminating surface gravity waves).

Examples are given, involving (i) the Taylor–Proudman effect with very slow flows over topography; (ii) quasi-geostrophic and inertial-wave flows over a mountain (f-plane); (iii) inertial waves generated by oscillatory forcing; (iv) Kelvin waves (v) free oscillatory Rossby waves on a polar β-plane; and (vi) stationary waves, blocking, jets and wakes with β-plane zonal flow past a mountain. Movies are available with the online version of the paper.
The granular jump
Authors: BOUDET J. F. , AMAROUCHENE Y. , BONNIER B. , KELLAY H.
Published: January 2007

When a fluid jet hits a solid surface, a hydraulic jumps occurs. This jump sharply delimits a thin film of liquid from a thicker film. We show here that a granular jet impinging on a solid surface also gives rise to several features reminiscent of the hydraulic jump and we refer to this situation as the granular jump. We describe, in detail, this phenomenon and show that if many of its features can be understood in analogy with the hydraulic jump, others are directly related to the granular nature of the medium and, in particular, the small-scale dynamics of the jump.
Vitamin D Status in Patients with Osteopenia or Osteoporosis – an Audit of an Endocrine Clinic
Authors: Kocjan  , Tan  , Conway  , Prelevic
Published: January 2007

Vitamin D deficiency and insufficiency may further increase fracture risk in patients with decreased bone mineral density. We audited serum 25-hydroxyvitamin D (25OHD) concentrations in patients with osteopenia or osteoporosis attending endocrine osteoporosis clinics in North London between January 1998 and September 2001. The total number of patients analyzed was 448 (age range 17–89 years), with 191 patients being < 50 years old (42.6%). The following cut-off points for serum 25OHD were used: levels ≤ 30 nmol/L for deficiency, > 30–50 nmol/L for insufficiency, and > 50 nmol/L for sufficiency. The overall prevalence of vitamin D deficiency was 30.5% and of vitamin D insufficiency was 35.9%. Vitamin D deficiency was as prevalent in young patients as in older ones: the prevalence of serum 25OHD ≤ 30 nmol/L in those < 50 years of age was 33.0% (n = 63 of 191), compared with 31.1% (n = 80 of 257) in patients aged ≥ 50 years. Our results indicate that vitamin D deficiency and insufficiency is a common problem in patients with osteopenia or osteoporosis. This situation persists despite dietary advice and prescription of vitamin D3 supplementation. Vitamin D deficiency affects all age groups, not merely the elderly.
Solar cycle signature and secular long‐term trend in OH airglow temperature observations at South Pole, Antarctica
Authors: Azeem S. M. I. , Sivjee G. G. , Won Y.‐I. , Mutiso Charles
Published: January 2007

We have examined Michelson Interferometer OH airglow temperature data to investigate solar cycle and long‐term variations of mesospheric temperatures at South Pole Station (SPS), Antarctica (90°S). The data set used here is continuous (24 hours a day) and taken during 1994–2004 austral winters. We have used a Multiple Linear Regression (MLR) technique to elucidate solar cycle and the trend term in the MI temperature time series data. The 11‐year time series of OH rotational temperature shows a strong correlation with F10.7 radio flux (R = 0.60). The amplitude of solar cycle response seen in the mesopause temperature records at South Pole is about 0.04 ± 0.01 K/sfu (Solar Flux Units), however, the trend term is statistically insignificant and is about 0.1 ± 0.2 K/year. Superposed epoch studies have been carried out in order to determine climatological variations in OH temperatures above South Pole derived from 11 years of austral winter observations. The mean amplitude of this variation is about 12.6 K and its maximum occurs near 30 May which is in agreement with the Fabry‐Perot Spectrometer (FPS) observations of OH temperatures at SPS (Hernandez, 2003). However, whereas Hernandez (2003) reported 35 K cooling in 2002, MI OH temperatures at SPS do not show any significant deviation from previous years.
Taking The Time To Study Competitive Antagonism
Authors: Wyllie D J A , Chen P E
Published: January 2007

Selective receptor antagonists are one of the most powerful resources in a pharmacologist's toolkit and are essential for the identification and classification of receptor subtypes and dissecting their roles in normal and abnormal body function. However, when the actions of antagonists are measured inappropriately and misleading results are reported, confusion and wrong interpretations ensue. This article gives a general overview of Schild analysis and the method of determining antagonist equilibrium constants. We demonstrate why this technique is preferable in the study of competitive receptor antagonism than the calculation of antagonist concentration that inhibit agonist‐evoked responses by 50%. In addition we show how the use of Schild analysis can provide information on the outcome of single amino acid mutations in structure‐function studies of receptors. Finally, we illustrate the need for caution when studying the effects of potent antagonists on synaptic transmission where the timescale of events under investigation is such that ligands and receptors never reach steady‐state occupancy.

British Journal of Pharmacology (2007) 150, 541–551. doi:10.1038/sj.bjp.0706997
The calcium ionophore A23187 induces endothelium‐dependent contractions in femoral arteries from rats with streptozotocin‐induced diabetes
Authors: Shi Y , Feletou M , Ku D D , Man R Y K , Vanhoutte P M
Published: January 2007

Background and purpose:

To study the importance of endothelium‐derived contracting factors (EDCFs) in arteries of rats with type I diabetes.

Experimental approach:

Rat femoral arteries were collected four or twelve weeks after induction of diabetes with streptozotocin. Rings, with or without endothelium, were suspended in organ chambers for isometric tension measurement. COX protein levels were determined by Western blotting.

Key results:

Four weeks after the injection of streptozotocin, the endothelium‐dependent relaxations (during contractions to phenylephrine) to A23817 were attenuated, but the endothelium‐dependent contractions (quiescent preparations) to the ionophore were augmented. Indomethacin and S18886 prevented the endothelium‐dependent contractions, while dazoxiben reduced them in rings from streptozotocin‐treated rats, suggesting that thromboxane A2, activating TP‐ receptors, is involved. Twelve weeks after the injection of streptozotocin, the changes in endothelium‐dependent relaxations and contractions to A23187 were even more noticeable. The protein expression of COX‐1 was increased in femoral arteries of the diabetic rats. Valeryl salicylate and SC560 inhibited the contractions, suggesting that the EDCFs are produced by COX‐1. At that time, a combination of S18886 with EP1‐blockers was required to abolish the contractions, suggesting that the EDCFs involved act at both TP‐ and EP‐receptors. Rings without endothelium from streptozotocin‐treated rats exhibited a reduced maximal contraction to potassium chloride and U46619, combined with hyper‐responsiveness to the latter, suggesting that more prolonged diabetes also alters the responsiveness of vascular smooth muscle.

Conclusion and Implications:

The production of EDCFs is progressively increased in the course of type I diabetes. Eventually, the disease also damages vascular smooth muscle.

British Journal of Pharmacology (2007) 150, 624–632. doi:10.1038/sj.bjp.0706999
Cardiovascular protection with sildenafil following chronic inhibition of nitric oxide synthase
Authors: Kukreja R C
Published: January 2007

During the past 18 years, sildenafil has evolved from a potential anti‐angina drug to an on‐demand treatment for erectile dysfunction and more recently to a new orally active treatment for pulmonary hypertension. Recent studies suggest that the drug has powerful cardioprotective effect against ischemia/reperfusion injury, doxorubicin‐induced cardiomyopathy and anti‐hypertensive effect induced by chronic inhibition of nitric oxide synthase in animals. Based on several recent basic and clinical studies, it is clear that sildenafil and other clinically approved type‐5 phosphodiesterase‐5 inhibitors including vardenafil and tadalafil will eventually be developed for several cardiovascular indications including essential hypertension, endothelial dysfunction, ischemia/reperfusion injury, myocardial infarction, ventricular remodeling and heart failure.

British Journal of Pharmacology (2007) 150, 538–540. doi:10.1038/sj.bjp.0707132
Effect of the cannabinoid CB1receptor antagonist rimonabant on nociceptive responses and adjuvant‐induced arthritis in obese and lean rats
Authors: Croci T , Zarini E
Published: January 2007

Background and purpose:

Obesity is a risk factor for several inflammation‐based diseases including arthritis. We investigated the anti‐nociceptive and anti‐inflammatory effects of the cannabinoid CB1receptor antagonist rimonabant in lean and diet‐induced obese female rats with arthritis induced by complete Freund's adjuvant (CFA) injected in the right hind‐paw.

Experimental approach:

The effect of oral rimonabant was assessed in rat paws on thermal hyperalgesia, mechanical allodynia, oedema, global arthritis score, nitrite/nitrate levels and ankle widths.

Key results:

After 7 but not after 14 days, the inflammatory response to CFA was significantly higher in obese than lean rats; however, the nociceptive response (thermal hyperalgesia and mechanical allodynia) was similar. Oral rimonabant (3 or 10 mg kg−1, once a day for 1 week from day 7 after CFA) only reduced the global arthritic score and joint width in obese rats, with no effect on the paw oedema. It also markedly reduced thermal hyperalgesia and mechanical allodynia in both lean and obese rats, with a greater effect in the latter.

Conclusion and implications:

Rimonabant appears to be a potent inhibitor of sensorial hypersensitivity associated with CFA‐induced arthritis in obese rats, in which the inflammatory reaction is more severe than in lean rats. It may thus have therapeutic potential in obesity‐associated inflammatory diseases, particularly in the treatment of the pain associated with arthritis.

British Journal of Pharmacology(2007)150, 559–566. doi:10.1038/sj.bjp.0707138
Induction of neutralizing antibody responses to hepatitis C virus with synthetic peptide constructs incorporating both antibody and T‐helper epitopes
Authors: Torresi Joseph , Fischer Alex , Grollo Lara , Zeng Weiguang , Drummer Heidi , Jackson David C
Published: January 2007

We describe a peptide‐based strategy for hepatitis C virus (HCV) vaccine design that exploits synthetic peptides representing antibody epitopes of the hypervariable region 1 (HVR1) of the E2 glycoprotein and also less variable regions immediately downstream of HVR1. These epitopes were linked to a T‐helper (Th) epitope (KLIPNASLIENCTKAEL) derived from the Morbillivirus canine distemper virus. Antibody titres induced by the two vaccine candidates Th‐A (E2 amino acid 384–414) and Th‐B (E2 amino acid 390–414) were significantly higher than those produced against vaccines lacking the Th epitope (P<0.05). Mice inoculated with the vaccine candidates Th‐C (E2 amino acids 412–423) and Th‐F (E2 amino acids 436–447) emulsified in complete Freund's adjuvant each elicited antibody titres that were significantly higher than those elicited by Th‐E (E2 amino acids 396–407) and Th‐D (E2 amino acids 432–443) (P<0.01). Antisera obtained from mice inoculated with the epitope vaccines Th‐A, Th‐B, Th‐D and Th‐E bound to E2 expressed at the surface of 293T cells that had been transfected with E1E2. Furthermore, IgG from the sera of mice inoculated with four of the vaccine candidates, Th‐A, Th‐C, Th‐D and Th‐E, inhibited the entry of HCV/human immunodeficieny virus pseudoparticles (HCVpps) into Huh‐7 cells. These results demonstrate the potential of synthetic peptide‐based constructs in the delivery of potential neutralizing epitopes that are present within the viral envelope of HCV.
Structure of the dense cores and ablation plasmas in the initiation phase of tungsten wire-array Z pinches
Authors: Douglass J. D. , Pikuz S. A. , Shelkovenko T. A. , Hammer D. A. , Bland S. N. , Bott S. C. , McBride R. D.
Published: January 2007

The early stages of tungsten (W) wire-array Z-pinch implosions have been studied using two-frame point projection x-ray backlighting on the 1MA COBRA pulsed power generator [J. D. Douglass, J. B. Greenly, D. A. Hammer, and B. R. Kusse, in Proceedings of the 15th IEEE International Pulsed Power Conference, Monterey, 2005 (to be published)]. X-pinch backlighter images with subnanosecond time resolution and 4–10μm spatial resolution have been obtained of individual W exploding wires in 8-wire arrays that show evolution of wire-core and coronal plasma structures. The timing of the X-pinch x-ray bursts relative to the Z-pinch initiation time was adjusted over a 50ns time interval by varying the X-pinch mass per unit length. Wire-cores seen in two images separated in view by 120° show that the expansion is remarkably azimuthally symmetric. A strong correlation is observed between the structure on the dense exploding wire-cores and the structure of the ⩾1018∕cm3 ablation plasma being drawn from radial prominences. Plasma ablation velocity was estimated to have a lower bound of 24km∕s. The wire-core expansion rate was found to be approximately constant with time over the interval 50–100ns after the start of the current pulse. Finally, micron-scale axial gaps, seen as early as 70ns into the current pulse and persisting from that time, were observed along the wire-core.
Fluorescent polymer-porous silicon microcavity devices for explosive detection
Authors: Levitsky I. A. , Euler W. B. , Tokranova N. , Rose A.
Published: January 2007

Conjugated polymers entrapped in porous silicon microcavity have been studied as optical sensors for low volatility explosives such as trinitrotoluene. The fluorescence spectra of entrapped polymers were modulated by the microcavity via a spectral “hole” that matches the resonance peak of the microcavity reflectance. Exposure of the porous silicon microcavity containing entrapped polymer to explosives vapor results in a red shift of the resonance peak and the spectral hole, accompanied by the quenching of the fluorescence. This multiplexed response provides multiple monitoring parameters, enabling the development of an optical sensor array for the detection of target explosive vapor.
Direct full compensation of the aberrations in quantitative phase microscopy of thin objects by a single digital hologram
Authors: Miccio L. , Alfieri D. , Grilli S. , Ferraro P. , Finizio A. , De Petrocellis L. , Nicola S. D.
Published: January 2007

Aberrations and the distortions due to the imaging optics can be compensated in quantitative phase microscopy of thin phase objects by digital holography using a single hologram. The reconstructed quantitative phase microscopy phase distribution map can be directly corrected in the reconstructed image plane by a numerical method. To remove this unwanted aberration, in the special case of thin objects, the authors perform a two-dimensional fit with the Zernike polynomials of the reconstructed unwrapped phase. Subtraction of the fitted polynomial from the original phase map gives quantitative phase microscopy phase map free of aberrations.
Modeling of imprint in hysteresis loop of ferroelectric thin films with top and bottom interface layers
Authors: Ye Z. , Tang M. H. , Zhou Y. C. , Zheng X. J. , Cheng C. P. , Hu Z. S. , Hu H. P.
Published: January 2007

The imprint of a ferroelectric thin film capacitor is studied using an improved model consisting of two nonswitching thin interface layers near the top and bottom electrodes. The difference in electrical conductivity between the two interface layers induces voltage offset and deformation behaviors in hysteresis loops. Size dependence of shift effect of Bi4−xNdxTi3O12 thin film is explained qualitatively by taking into account the thickness ratio of the interface layer and the bulk film. Various shifts and anamorphic shapes with different electrodes and processes have been effectively reproduced through changing the layer conductivities. The simulated shifted hysteresis loops agree well with the experiment. Theoretical prediction based on this approach may provide a method to reduce imprint failure.
Integrated cantilever sensors with a torsional resonance mode for ultraresoluble on-the-spot bio/chemical detection
Authors: Jin Dazhong , Li Xinxin , Bao Hanhan , Zhang Zhixiang , Wang Yuelin , Yu Haitao , Zuo Guomin
Published: January 2007

Torsion-mode resonance is built in an integrated cantilever sensor for ultraresoluble detection of specifically bio/chemical mass adsorption. The superior mass resolution of the torsion-mode cantilever to a conventional bending-mode one is verified by energy-dissipation analysis and Q-factor simulation. With integrated transverse piezoresistance for frequency-shift signal readout and Lorentz force for resonance excitation, the torsion-mode sensor is optimally designed for high sensitivity. The microfabricated torsion-mode sensor is measured with a high close-loop Q factor in air. By Allan-variance analysis for the measured frequency stability, 23fg resolution is obtained for the torsion-mode sensor, which is much improved compared to the 313fg for the conventional flexure-mode sensor. The torsional sensor is used to recognize biotin-avidin specific combination, resulting in 443Hz frequency shift for 50μM streptavidin solution.
Wavelength dependence of light-induced domain nucleation in MgO-doped congruent LiNbO3 crystal
Authors: Zhi Ya’nan , Liu De’an , Qu Weijuan , Luan Zhu , Liu Liren
Published: January 2007

Within the wavelength range from 351to799nm, the different reductions of nucleation field induced by the focused continuous laser irradiation are achieved in the 5mol% MgO-doped congruent LiNbO3 crystals. The reduction proportion increases exponentially with decreasing irradiation wavelength and decreases exponentially with increasing irradiation wavelength. At one given wavelength, the reduction proportion increases exponentially with increasing irradiation intensity. An assumption is proposed that the reduction of nucleation field is directly related to the defect structure of crystal lattice generated by the complex coaction of incident irradiation field and external electric field.
Visually Preadapted Constituents of Manipulatory Action
Authors: Bruner J S , Koslowski Barbara
Published: January 2007

Every two weeks infants 8 to 22 weeks old were shown two balls, one at a time. Although both balls were within reach, one was of a graspable size while the other was too large to grasp. Before the infants were capable of reaching, grasping at the midline was more likely to occur in the presence of the graspable rather than the non-graspable ball. This suggests that grasping activity is coordinated with visual information about the graspability of an object even before the infant has had experience reaching.
Object Perception in Infants
Authors: Bower T G R
Published: January 2007

Natural responses, reaching and grasping, are used in an attempt to show that young infants perceive the distal properties of objects rather than their proximal correlates. The attempt seems to be successful for the properties, solidity, size, and distance. The developmental bases of these capacities are discussed.
Process and Product in Children's Drawing
Authors: Freeman N H
Published: January 2007

Aesthetic and expressive theorists have tried to understand what children's drawings represent. It is, however, a prior necessity to investigate the perceptual–cognitive mechanisms which permit the development of representational drawing, and to specify the role played by developing graphic and cognitive skills. In the first place it is argued that the concept of interpretation, as carried out by the child himself as well as by adults, rests on a dual basis consisting of perceptual processes and the recognition of conventions. Secondly some empirical examples of the problems of organisation with which the child has to deal are given. Through a critique of the model and the developmental taxonomy worked out by Luquet, the elements of a general model, embodying the concepts of interpretation and organisation, are put forward.
An Information Processing Model for Visual and Tactile Reading
Authors: Taenzer J C
Published: January 2007

A mathematical model consistent with both visual and tactile reading data and accurately predicting at least one set of visual reading data is presented. This model is based upon the results of a free-rate tactile reading experiment in which word scanning times were measured. A thorough analysis of the results of the experiment showed that, although the average scanning time per letterspace is quite consistent over a wide range of word length and word familiarity (assumed to be inversely related to word rank), the distribution of the word scanning times contains a lot of information about the mental decision processes. From a study of the word scanning time histograms a four-degree-of-freedom model was derived and used to calculate a predicted visual constant-rate reading performance curve. In order to make the calculation, an equation describing the relationship between free-rate and constant-rate reading was also derived. The predicted performance curve is in excellent agreement with the measured data.
The Interstimulus Interval for Taste: 1. The Efficiency of Expectoration and Mouthrinsing in Clearing the Mouth of Salt Residuals
Authors: O'Mahony M
Published: January 2007

Various interstimulus procedures ranging from rapid expectoration to up to 50 tapwater mouthrinses were examined in relation to how efficiently they cleared the mouth of residuals from a mouthrinse with equimolar 1 M NaCl and LiCl. Samples of expectorated saliva were analysed for Na and Li by flame photometry, the Li being used as a tracer for exogenous Na. It was found that exogenous salt residuals were not cleared from the mouth after 30 min rapid expectoration nor by fewer than 20 mouthrinses. On the other hand, ‘suprathreshold’ concentrations were cleared by ∼10 min rapid expectoration or 5 mouthrinses. Such rigorous interstimulus procedures are not generally used in taste experiments with stimuli of comparable concentration. Tapwater rinses were also seen to leave their own residuals in the mouth while the ad-lib rinsing procedure was found to be not only uncontrolled but also ineffective.
Two Empirical Tests of Informal Predictions from Helson's Adaptation-Level Theory
Authors: Ellis H D
Published: January 2007

Two experiments on adaptation-level theory are reported which arise from informal predictions made by Helson (1964). They both involved interpolated anchors in comparative judgments, in order to avoid the sorts of response factors inherent in the category scaling technique normally employed in adaptation level studies. The first experiment indicated the operation of time error as interstimulus intervals are increased. The second showed that if the anchor stimulus is not judged it is less effective in producing contrast compared with when it is judged. In addition, response times and confidence ratings of judgments were shown to be potentially useful indices of differences in effectiveness among the various anchor stimulus levels used. The strong relationship between these two measures is discussed.
Single Units and Sensation: A Neuron Doctrine for Perceptual Psychology?
Authors: Barlow H B
Published: January 2007

The problem discussed is the relationship between the firing of single neurons in sensory pathways and subjectively experienced sensations. The conclusions are formulated as the following five dogmas:

To understand nervous function one needs to look at interactions at a cellular level, rather than either a more macroscopic or microscopic level, because behaviour depends upon the organized pattern of these intercellular interactions. The sensory system is organized to achieve as complete a representation of the sensory stimulus as possible with the minimum number of active neurons. Trigger features of sensory neurons are matched to redundant patterns of stimulation by experience as well as by developmental processes. Perception corresponds to the activity of a small selection from the very numerous high-level neurons, each of which corresponds to a pattern of external events of the order of complexity of the events symbolized by a word. High impulse frequency in such neurons corresponds to high certainty that the trigger feature is present.

The development of the concepts leading up to these speculative dogmas, their experimental basis, and some of their limitations are discussed.
Selectivity of Attention and the Perception of Duration
Authors: Underwood G , Swain R A
Published: January 2007

The attention necessary to detect target digits in prose passages of equal length was varied by partially masking the passages with varying intensities of white noise. The subjects assessed the duration of the passages by use of a magnitude estimation scale, without reference to clock time. It was found that those passages requiring more attention for analysis were judged to be of greater duration than those requiring less attention. Ornstein's cognitive theory of the perception of duration is criticized on the grounds that it explains inadequately the effects of attention upon the experience of the passage of time.
The Autonomy of Visual Kinaesthesis
Authors: Lishman J R , Lee D N
Published: January 2007

Kinaesthesis, the sensing of body movement, which is essential for controlling activity, depends on registering the changes which accompany body movement. While there are two basic types of change—mechanical (articular, cutaneous, and vestibular) and visual—and so two potential sources of kinaesthetic information, the mechanical changes have traditionally been considered the basis of kinaesthesis, vision being considered a purely exteroceptive sense. J.J. Gibson, on the other hand, has argued that vision is a powerful kinaesthetic sense. To test this idea visual–mechanical kinaesthetic conflicts were created by moving the visible surroundings linearly forward and backward around a passively or actively moving subject. In most cases vision dominated. Therefore vision is not a purely exteroceptive sense, nor is visual kinaesthesis simply an adjunct to mechanical kinaesthesis. Vision is an autonomous kinaesthetic sense.
Inability of Humans to Discriminate between Visual Textures That Agree in Second-Order Statistics—Revisited
Authors: Julesz B , Gilbert E N , Shepp L A , Frisch H L
Published: January 2007

In an earlier study by Julesz (1962) pairs of random textures were generated side-by-side using a Markov process with different third-order joint-probability distributions but identical first- and second-order distributions. Such texture pairs could not be discriminated from each other by the human visual system without scrutiny. Unfortunately, Markov processes are inherently one-dimensional while the general processes underlying visual texture discrimination are two-dimensional. Here three new methods are introduced that generate two-dimensional non-Markovian textures with different third-order but identical first- and second-order statistics. All three methods generate texture pairs that cannot be discriminated from each other.

The lack of texture discrimination is the more astonishing since the individual elements that form the texture pair are clearly perceived as being very different. However, a counterexample was found that yields discrimination although the texture pair has approximately identical second-order statistics. This case can be explained by assuming that early feature extractors do some preprocessing. These new demonstrations give support to a model of texture discrimination in which the stimulus is first analyzed by local feature extractors that can detect only simple features such as dots and edges of given sizes and orientations. Then the outputs of these simple extractors are evaluated by a global processor that can compute only second- or first-order statistics (that is can compare at most two such outputs).
A Computational View of Perception
Authors: Rosenberg B , Langridge D J
Published: January 2007

A computational approach to visual perception is outlined. The investigation centres on two problems. One concerns the shape, and the other the edges, of dot figures. In determining edges it is not possible to delimit arbitrarily the region on which each point computes. So in this context a global computation is defined. This leads to a novel way of investigating clustering. When the edges of a figure have been sequenced to yield the boundary it is then possible to determine its shape. The study of shape has been confined to convex figures. In these an attempt is made to extract global units which correspond to corner-like regions. Finally, it is suggested that a theory which evolves in the manner described has a more unitary aspect than other approaches.
The Effect of Early Anomalous Visual Inputs on Orientation Selectivity
Authors: Abadi R V
Published: January 2007

It is now well established that the cortical neurones of cats and monkeys respond best to either lines or edges of a specific orientation. The respective tuning curves of these cells can be broadened by rearing the animals in abnormal visual environments during their critical period of development.

Since neurones in the human visual system probably also possess this orientational selectivity, then it is not inconceivable that humans also could demonstrate similar orientational selectivity loss if they too have an anomalous visual input during their early years of life. To test this hypothesis, a simultaneous subthreshold masking technique is proposed as a means for assessing psychophysically the selectivity properties within the human striate cortex. Both visually normal and abnormal systems were considered.

No selectivity loss is demonstrated for either the orientationally deprived (i.e. high astigmats) or monocular form deprived (high anisometrope) subjects. The effect of large eye movements (nystagmus) does, however, bring about a coarser selectivity. These results are discussed in relation to recent neurophysiological studies of the critical period in lower vertebrates.
Some Perceptual Effects Generated by Rotating Gratings
Authors: Wade N J
Published: January 2007

Rotation of a grating at around 2π rad s−1 in continuous illumination results in the appearance of a band lying almost perpendicular to the lines. Two possible bases for the occurrence of this effect were examined. Firstly, the band might represent a moiré fringe due to the overlap of the present grating with one persisting in the visual system from a previous position. Secondly, those parts of the lines farthest from the bisecting diameter will have the greatest linear displacement during rotation; thus, the extremities of each line might fail to be resolved, while those parts nearer the centre are adequately resolved, resulting in the appearance of a band. Three experiments were conducted to test predictions from the two hypotheses. The first experiment involved manipulation of the spatial frequency of the square-wave gratings and the size of the discs bearing them. In the second the line spacing was varied while the line width was kept constant. In the third experiment the angular velocities required to produce bands of different widths were determined. The results did not support either hypothesis unequivocally, and the possibility that both are involved in the effect cannot be discounted.

Observation of the rotating gratings under stroboscopic illumination produced either moiré fringes or complex doily-like patterns, depending upon the angular velocity and strobe frequency. These ‘overlap’ effects were used to determine the duration of visual persistence in a fourth experiment. At certain combinations of high angular velocities and strobe frequencies, apparent rotation effects are visible simultaneously in opposite directions.
Inter-Hemispheric Differences in Problem Solving
Authors: Golding Evelyn , Reich Shuli S , Wason P C
Published: January 2007

Previous studies of a difficult reasoning problem have elicited inconsistent utterances. This study tested the hypothesis that the inconsistency is due to an asymmetrical encoding of the problem between the two hemispheres in the brain. The hypothesis was confirmed.
Vision in a Monkey without Striate Cortex: A Case Study
Authors: Humphrey N K
Published: January 2007

A rhesus monkey, Helen, from whom the striate cortex was almost totally removed, was studied intensively over a period of 8 years. During this time she regained an effective, though limited, degree of visually guided behaviour. The evidence suggests that while Helen suffered a permanent loss of ‘focal vision’ she retained (initially unexpressed) the capacity for ‘ambient vision’.
Rotating Patterns: Factors in the Veridical Perception of the Phenomenon
Authors: Farnè M , Campione F , Andreoli Anna R
Published: January 2007

The hypotheses tested were that, with rotating patterns, the veridical perception of (a) the direction of movement, and (b) its three-dimensionality, depends on the number of linear components in the pattern itself. Experiment 1 analyzed the answers obtained with discs, triangles, and squares. Contrary to expectation the discs, although lacking in linear components, evoked a maximum of three-dimensional percepts; the hypothesis concerning the direction of movement was, on the contrary, confirmed. Experiment 2 substantiated this result by rotating discs marked with two or four lines, and with different intervals between them. Experiment 3 was on the shape constancy exhibited by a stationary disc, triangle, and square. The disc, which in experiment 1 showed the highest ‘constancy’ was now, in this new condition, the lowest of the three in the results.
Stereomovement Suppression for Transient Disparity Changes
Authors: Tyler C W , Foley J M
Published: January 2007

In a comparison between stereo and vernier thresholds in displacement and misalignment paradigms, the stereo displacement threshold was found to be about three times higher than the other thresholds. This result is consistent with the disparity inhibition hypothesis. In a second experiment thresholds in a movement/no movement discrimination task were about half those in the direction discrimination task, with the stereo threshold remaining about three times higher than the vernier threshold. This suggests that motion discrimination has a different basis from direction discrimination.
Learning to See Complex Random-Dot Stereograms
Authors: Frisby John P , Clatworthy Jeremy L
Published: January 2007

Many observers of complex random-dot stereograms find that the depth effect takes several seconds, or even minutes, to develop. Julesz (1971) has noted that giving a priori information to such observers about the nature of the ‘hidden’ cyclopean object appears to facilitate their stereopsis. An experiment is reported which investigated this possible facilitation. Naive subjects were shown a complex stereogram following various kinds of preliminary assistance, ranging from simply telling them about the amount of depth they could expect to see to showing them a full-scale model of the cyclopean object. Surprisingly, no benefit from such assistance could be demonstrated. All observers improved their stereopsis perception times with repeated presentations of the stereogram, showing that they could, in principle, benefit from assistance. A follow-up study three weeks later revealed that a substantial part of this improvement was maintained, indicating that the perceptual learning involved can last for a considerable period of time.
The Effect of Orientation Difference on Stereopsis as a Function of Line Length
Authors: Frisby John P , Julesz Bela
Published: January 2007

The amount of depth seen in a multi-line stereogram composed of horizontal lines steadily decreases as the lines in one field of view are rotated about their midpoints. This effect of orientation difference on stereopsis is more acute the longer the lines in the stereogram. It is suggested that the critical factor underlying the depth reduction is not orientation difference per se, but rather the vertical disparity which an orientation difference introduces into the display between the tips of corresponding lines. This interpretation is supported by the fact that similar vertical disparities caused similar depth reductions regardless of the length of the lines in the stereogram.
Orientation of the Diamond and the Square
Authors: Naeli Hossein , Harris Paul L
Published: January 2007

Two experiments show that the young child copies or places diamond and square shapes in alignment with the surrounding frame. The results are related to the difficulty exhibited by young children in drawing diamonds versus squares.
Coordination of Auditory and Visual Space in Newborn Human Infants
Authors: Butterworth George , Castillo Marcela
Published: January 2007

Two experiments are reported which demonstrate that the newborn human infant can make eye movements which are spatially coordinated with the locus of a sound. The results suggest that there may be an innate coordination of auditory and visual—motor space.
Implicit-Shape Constancy: A Cross-Cultural Comparison
Authors: Deregowski Jan B
Published: January 2007

A group of Scottish schoolchildren were tested on a task intended to measure the effect of implicit-shape constancy, and the scores were compared with those obtained from African samples. It was found that both groups were influenced by the implicit-shape constancy although the influence was less in the African sample. The relationship of these findings to other published reports of cross-cultural research into pictorial perception and susceptibility to illusions is discussed.
Early Stages of Tactual Matching
Authors: Millar Susanna
Published: January 2007

Naive sighted subjects tested under blind conditions were able to match raised dot (Braille letters) patterns relatively accurately by touch, but showed no advantage in judging identical pairs over different pairs of patterns. This was the case also for letters subjects had been taught to name. Instructions to match on name or feel had significant effects, but these did not relate differentially to ‘same’/‘different’ judgments. Under visual conditions subjects matched ‘same’ letters faster than ‘different’ letters. Errors in drawing the letters after tactual exposure and naming training showed that subjects had no accurate idea of the spatial relations or configuration of the dot patterns. The findings suggested that early stages of tactual matching involve exhaustive comparisons and rechecking of features, and that correct notions of tactual dot configurations may be built up rather slowly, and depend on identifying features along orthogonal axes.
Studies on Visual Perception of Locomotion
Authors: Johansson Gunnar
Published: January 2007

The problem about visual discrimination between seeing objects in motion and perception of motion of the perceiver (locomotion) was taken up. A flow of vertical motion was presented to limited areas of the far periphery (45°–90°) of the retina simultaneously with optical information about a stationary room over the rest of the retina. The result was that most subjects perceived themselves as sitting in an elevator continuously moving upward or downward. Thus, peripheral motion stimulation over a few percent of the retinal area determines locomotion perception in apparent competition with information about a static state over the rest of the retina. The same type of stimulus presented to the central part of the retina always brought about perception of object motion and a static perceiver.

Effects of size and localization of the area stimulated with the motion flow was studied. Theoretical consequences and problems for further experimental analyses are discussed.