Plain Background Research Articles

Comprehensive constraint on the tectono-sedimentary setting of Late Paleozoic turbidites of the Kamuste area, eastern Junggar, Xinjiang

Petrography and geochemistry, combined with sedimentation analyses allow for a thorough evaluation of the tectono-sedimentary setting of late Paleozoic turbidites of the Kamuste area, eastern Junggar. Sandstones of the Alabiye1) Formation are composed mostly of volcanic and sedimentary detritus with lesser amounts of plagioclase and quartz. They were derived from an undissected magmatic-arc provenance. The geochemistry of sandstone-mudrock suites indicates a fesic-intermediate igneous provenance, and constrains the Alabiye Formation to have derived from a differentiated oceanic-continental margin island-arc tectonic setting. Likewise, geochemistry and sandstone petrography of the Kamuste Formation reflect a mixed provenance signature dominated by magmatic arc, basement uplift, and subduction-complex sources of a differentiated continental-island arc. Sedimentation analysis indicates that the Alabiye and Kamuste formations are two sets of turbidite sequences deposited on a submarine slope and a submarine fan and basin plain respectively. In conclusion, submarine slope turbidite deposition of the Alabiye Formation records the main sedimentary response to the development of early Devonian back-arc basins of the northern Junggar tectonic belt. Submarine fan and basin plain turbidite and background hemipelagic deposition of the Kamuste Formation record the main sedimentary response to the late Early Carboniferous development of an inter-arc relict ocean basin of the eastern Junggar composite terrane.

Position invariant recognition in the visual system with cluttered environments

The effects of cluttered environments are investigated on the performance of a hierarchical multilayer model of invariant object recognition in the visual system (VisNet) that employs learning rules that utilise a trace of previous neural activity. This class of model relies on the spatio-temporal statistics of natural visual inputs to be able to associate together different exemplars of the same stimulus or object which will tend to occur in temporal proximity. In this paper the different exemplars of a stimulus are the same stimulus in different positions. First it is shown that if the stimuli have been learned previously against a plain background, then the stimuli can be correctly recognised even in environments with cluttered (e.g. natural) backgrounds which form complex scenes. Second it is shown that the functional architecture has difficulty in learning new objects if they are presented against cluttered backgrounds. It is suggested that processes such as the use of a high-resolution fovea, or attention, may be particularly useful in suppressing the effects of background noise and in segmenting objects from their background when new objects need to be learned. However, it is shown third that this problem may be ameliorated by the prior existence of stimulus tuned feature detecting neurons in the early layers of the VisNet, and that these feature detecting neurons may be set up through previous exposure to the relevant class of objects. Fourth we extend these results to partially occluded objects, showing that (in contrast with many artificial vision systems) correct recognition in this class of architecture can occur if the objects have been learned previously without occlusion.

Manipulation of Interference in the Passive Visual Store

Three experiments are reported that examine the circumstances under which irrelevant material causes interference with visual memory. Experiment 1 indicates that the amount of interference is related to the extent of the dynamic aspect within a visual noise field when the field is used as the irrelevant material. When the dynamic aspect comprises only a single dot changing within a field of 80 x 80 dots, interference is significant. Experiments 2 and 3 indicate that when the dot is extracted from the noise field and presented against a uniform plain background interference crucially depends on whether the dot is presented and re-presented at the same spatial location or at different locations. Only when the dot occupies successively different locations is interference caused. It is argued that the results are to be understood in terms of the two component parts of the VSSP. When the dot is presented against a uniform field and in different spatial locations, interference acts through the active spatial component. When the dot occupies a single position, interference acts through the passive visual store. The passive visual store only is sensitive to the visual noise background.

Locating head and face boundaries for head–shoulder images

This paper presents a model-based approach to locate head and face boundaries in a head-shoulder image with plain background. Three models are constructed for the images, where the head boundary is divided into left/right sub-boundaries and the face boundary is divided into left/right and top/bottom sub-boundaries. The left/right head boundaries are located from two thresholded images and the final result is the combination of them. After the head boundary is located, the four face sub-boundaries are located from the grey edge image. The algorithm is carried out iteratively by detecting low-level edges and then organizing/verifying them using high-level knowledge of the general shape of a head. The experimental results using a database of 300 images show that this approach is promising.

Contrast and Contextual Effects: Detection of Subthreshold Lines

Contextual effects of collinear lines and features on the processing of line targets, finding expression in detection facilitation, have been described recently in the literature (Dresp and Bonnet, 1995 Vision Research35 1071 – 1078; Kapadia, Ito, Gilbert, and Westheimer, 1995 Neuron15 843 – 856). We are reporting a study of the effects of contrast intensity and contrast polarity on these contextual effects. Thin subthreshold lines, not detectable on a plain background, were flashed at a position collinear with a context line of varying luminance and polarity. A temporal 2AFC procedure was used to determine detection thresholds. The mere presence of a collinear context line of weak contrast, regardless of its polarity, was found to make the subthreshold lines detectable. For target lines and context lines of the same contrast polarity, increasing context contrast first enhances, then diminishes, target detectability. For target lines and context lines of opposite contrast polarity, increasing context contrast enhances target detectability. These preliminary results indicate that contrast intensity and relative contrast polarity interact in the genesis of grouping effects or contextual effects at early stages of visual processing.

Sur un Fond Blanc: Ecrits Japonais sur la Peinture du IX au XIX1 Siecle

VERA LINHARTOVA'S Sur un fond blanc ('On a White Background') is a critical anthology of ten centuries of Japanese writings about painting, many of which have never before been translated into a Western language. The book brings together a rich fund of primary sources on aesthetics, particularly valuable to those who do not read Japanese. It will also be of great interest to specialists, not only because of the author's choice of texts but also because of her critical approach and her inspiring overview of artistic movements and aesthetic trends. While the anthology proper starts in the ninth century with Kuikai's fundamental teachings on the use of images in religion, Linhartova' nevertheless analyzes the first Japanese written sources, Kojiki, 712, and Nihon Shoki, 720. There, as so often, a continental influence is evident (references to yin and yang, for example), but typically enough the Chinese abstract Taoist cosmology is transformed into uniquely Japanese images and anthropomorphic descriptions of the landscape. In Nihon Shoki, references to craftsmen are to be found, the craftsmen-artists who would later form the schools typically organized on a strong hierarchical basis, perpetuate the master-pupil tradition, and maintain the harmony of the arts and crafts in contrast to the West. Even though covering the eight centuries from the Nara period to the Momoyama, the first part of the anthology is shorter than the second, which surveys less than three centuries, the Edo period. Up to the seventeenth century, Linhartova' explains, documents on the theory of painting were scarce, and her extracts are taken mainly from literary and historical sources. Chinese writings were known from early times, but they do not appear to have attracted many commentaries until the Edo period, when a renewal of interest in China took place and Chinese artistic theories were studied systematically by literati painters. In fact, throughout the centuries, Chinese influence penetrated Japanese culture and art to a greater or lesser degree. The title for the anthology is not, significantly enough, a Japanese original image, but rather the Japanese adaptation of Confucius's cryptic words in Analects: 'All painting is done on a white (or plain) background,' (huishi housu, J. kaishi koso), an expression similar to the Western idiom, 'Starting with a blank canvas.' The way in which the Chinese expression was adapted to Japanese may be seen as a symbolic example of the way in which continental influences were assimilated and transformed into Japanese aesthetics: the four ideograms of the original expression were abridged to koso, or 'blank background', and these two characters surprisingly became synonymous with painting by the time Kano Ikkei wrote his Kososhu ('On Painting'), 1663. This two-part anthology is organized under evocative headings. The title 'Une image du monde et les premieres chroniques du Japon' is echoed and reversed in the following chapter, Le monde des images dans l'ceuvre de Kukai. Here the great Esoteric Buddhist master expounds beautifully how art helps express what is beyond words, 'the Ultimate Reality' that is 'totally formless and colorless', but which 'can be grasped through forms and colors.... What the sutras and commentaries say in a veiled or cursory fashion, images reveal with total clarity' (p. 44). Kuikai's metaphysical view of art is in total contrast with Tachibana Narisue's comments of the Heian period

Complex contrast, a definition for structured targets and backgrounds

A contrast definition allowing for structured as well as plain targets and backgrounds is presented. It consists of two parts: area contrast and edge contrast, both of which are logarithmic functions of target/background luminance ratios. This so-called complex contrast is considered to have advantages over existing contrast definitions when the luminance of target, background, or both is nonuniform.

DIFFERENTIAL AVOIDANCE OF CORAL SNAKE BANDED PATTERNS BY FREE-RANGING AVIAN PREDATORS IN COSTA RICA.

Empirical studies of mimicry have rarely been conducted under natural conditions. Field investigations of some lepidopteran systems have provided a bridge between experiments examining artificial situations and the mimicry process in nature, but these systems do not include all types of mimicry. The presence of dangerous or deadly models is thought to alter the usual rules for mimicry complexes. In particular, a deadly model is expected to protect a wide variety of mimics. Avoidance of different types of mimics should vary according to how closely they resemble the model. Coral snake mimicry complexes in the neotropics may provide natural systems in which these ideas can be examined, but there is no direct evidence that the patterns of venomous coral snakes or potential mimics are avoided in the wild. Plasticine replicas of snakes were used to assess the frequency of avian predation attempts as a function of color pattern. Avian predators left identifiable marks on the replicas, the position of which indicated that replicas were perceived as potentially dangerous prey items by birds. The number of attacks on unmarked brown replicas was greater than that on tricolor coral snake banded replicas. This result was true whether replicas were placed on natural or plain white backgrounds, suggesting that coral snake banded patterns function aposematically. In a separate experiment, replicas representing all six patterns of proposed coral mimics at the study site were attacked less often than unmarked brown replicas. Within these six banded patterns, some were attacked significantly more often than others. This study provides direct field evidence that coral snake banded patterns are avoided by free-ranging avian predators and supports theoretical predictions about mimicry systems involving deadly models.

Preventing a Feature-Positive Effect in Pigeons

The feature-positive effect (FPE) is a widespread and robust phenomenon in the context of discrimination learning. It refers to the fact that a distinctive feature associated with a stimulus that is reinforced leads to efficient discrimination learning, whereas the same feature associated with the nonreinforced stimulus inhibits discrimination learning. Two experiments with pigeons showed that the FPE also occurs with a simultaneous discrimination paradigm involving brief discrete trials and no intertrial intervals. A pre-training treatment unexpectedly prevented the expression of the FPE in this discrimination task. The pretraining consisted of having pigeons discriminate the feature/nonfeature visual shapes from a plain background disc. Rewarding responses to the shapes, or alternatively to the blank disc, had the same FPE-preventing effect. A reversal of a feature/nonfeature stimulus discrimination led to an analogous erasure of the FPE. The results are discussed in terms of the concurrence or interference between the various associations that the subjects formed on the basis of the different stimulus-reward correlations they experienced in the different phases of the experiments.

Patients and the Habits of House Officers

To the Editor.— The data collected by Dunn et al 1 are valuable for faculty who are interested in enlightening students and residents about the importance of physician attire and etiquette. We were interested in obtaining similar information for our teaching activities. We found that unexpected and useful information concerning patient expectations of physician appearance can also be obtained using an open-ended format. Study.— During the summer of 1986, 12 photographs were made of people standing in front of a standard plain background. Their attire varied and included men with and without white coats, blue jeans, sneakers, and ties. Women wore either skirts or slacks with or without white coats. After obtaining informed consent in accord with University of Louisville policy, pairs of these photographs were shown to 90 patients waiting for routine care in the waiting rooms of private family practitioners or the university family practice center. Patients were

The Orbison Visual Illusion and Radar Scopes

In the Orbison visual illusion, the sides of a square, although straight, appear to be bowed when the square is superimposed over a set of concentric circles. In the present study, the illusion is demonstrated for moving objects. Male and female college students watched carets move either across a background of four concentric circles or across a plain background. The carets moved across the top or along the left side of the scene. A number of situations were assessed. It was found that subjects do make errors that can be attributed to the Orbison illusion.

Figure-background perception in right and left hemispheres of human commissurotomy subjects.

The right and left hemispheres of four complete commissurotomy subjects were tested for the ability to recognize and integrate figure and background elements of composite visual stimuli. In the first experiment the subjects were required to identify from a four-choice array in free vision the stimulus card that matched the briefly lateralized sample stimulus. For all subjects the left hemispheres was proficient at identifying the figure, but performed at near-chance level in recognizing the textured background. In contrast, the right hemisphere was equally adapt at identifying figures and backgrounds. Both hemispheres could easily identify the isolated figure or background from a choice array, demonstrating that the observed hemisphere effects were due to figure-background interactions rather than the result of any difficulty in processing specific elements of the composite stimulus. The second experiment involved the determination of the size and position of a dot that appeared against various plain and textured backgrounds. The right hemisphere of two subjects, but not the left, performed with greater accuracy when the background consisted of a 'natural' texture gradient rather than a plain white backing. Similar though less consistent results were obtained when an inverted gradient or an evenly spaced grid was used as the background. For each condition, right-hemisphere performance resembled that of normal control subjects. In contrast, the left hemisphere provided a pattern of results dissimilar to that of control subjects for the various figure-background tasks described. It appeared to be generally insensitive to background effects, except when the information provided by the background was highly unusual, as from an inverted texture gradient. The results suggest a preeminent role for the right hemisphere in the recognition of background components of a whole-field stimulus, sensitivity to the influence of the background on the perception of an object, and the ability to use natural perspective cues to assist in the accurate perception of an object.

Peintures murales romaines fragmentaires à Bavay

Bij de bouw van een supermarkt ten noorden van Bavay hebben archeologen een reeks overblijfselen ontdekt van een gebouw dat met de grond gelijk gemaakt en geëffend werd in de loop van de IIIe eeuw. Men vond daarin fragmenten van twee groepen beschilderde bepleistering. De eerste komt van een polychroom decor met panelen met effen achter- grond, waarop misschien een figuratief tafereel stond. Met de stukken van de tweede groep heeft men een compositie kunnen reconstitueren met een rode omlijsting en een zwart netwerk op een witte grond, boven een lager gedeelte met roze vlekken. Men kan uit de observatie van de techniek afleiden dat het hier niet om tweederangswerk gaat : de schijnbare eenvoud van het dekor gaat immers gepaard met een zeer verzorgde uitvoe- ring. Daar men in andere noordelijke sites gelijkaardige dekors heeft aangetroffen, kan men stellen dat het niet om een toevallig tot stand gekomen rudimentaire beschildering gaat, maar wel om een exemplaar van een specifieke decoratieve catégorie, waarvan men in de toekomst de geografische verspreiding en de chronologie zal moeten onderzoeken.

Multipurpose background for standardization in medical photography.

A dual photography background system consisting of a quadrilled format on one side and a plain background on the other is described. It is mobile and efficient as a space- and time-saving device for medical photography.

Documenting your patient with photography in office practice.

The basic requirements for the proper photographic documentation of the foot is a single lens reflex camera, electronic flash unit, and a closeup lens set. Preoperative photographs should be a routine part of the patient workup prior to any treatment or corrective surgery. Clinical photographs should be taken with the patient standing on a plain background and should include the front, side, and back views. The electronic flash unit gives a consistent light and is well balanced with daylight color film. Surgical photographs are best taken with a telephoto macro lens or a telephoto lens with a closeup attachment. An electronic flash unit provides a consistent light. The flash unit is utilized with the AC adapter in order to give a rapid recycling and a consistent light output. Any pathological specimen should be photographed immediately following the case. Excellent specimen photographs can be taken with the use of the electronic flash held at a 30 degree angle and a sheet of white paper on the opposite of the specimen to act as a reflector. The most important aspect of the photography is to standardize the procedures so that consistent results may be obtained.

The effects of objective and perceived size properties on visual form matching.

The present experiments examined the effect of perceived size on the time it takes to make veridical form judgments. Recent studies have demonstrated an increase in the time required to match forms, as a function of increasing size, orientation, contrast, or color differences between the forms to be matched. The increase in reaction time to match forms has been explained by suggesting that form perception and matching is dependent on the degree of difference that exists in the objective size of the forms to be matched. This conflicts with the generally accepted view that form matching is independent of irrelevant proximal stimulus properties. The key to this issue seems to be whether form perception depends on objective or perceived stimulus properties. Studies in this area all involve manipulations of the objective stimulus properties, thus making it difficult to examine the effects of perceived properties. The current series of studies decoupled objective and perceived size differences by employing an illusion. The results demonstrated that the time to match forms is a function perceived differences in the stimulus forms, not the differences that exist in the objective size of the forms to be matched. In Experiment 1 three conditions were employed: a plain background condition in which the forms to be matched were objectively and subjectively equal in size, a double-illusion condition in which the forms were objectively and subjectively equal in size, and an illusion condition in which the forms were objectively equal in size but perceived as unequal in size. The results indicated a significant increase in reaction time for the illusion condition in which the forms were perceived to be different sizes, compared to the other two conditions in which perceived and objective size were equal. Experiment 2 results converged with and replicated those of Experiment 1. In Experiment 2 perceived size was equated for each subject in the context of the size illusion, thus varying the objective size of the stimuli. This manipulation led to a significant decrease in reaction time in this added condition, as compared to the illusion condition from Experiment 1 in which objective size was equal and perceived size differed. The results of Experiment 2 were replicated in a third experiment. Experiment 3 replicated the decrease in reaction time noted in the perceptually equal illusion condition. The decrease between illusion conditions was also approximated by an increase in a plain background condition with objective size differences. Thus the effect of perceived size accounts for the additional time to match forms of unequal size. The conclusion drawn from this series of experiments is that the time required to make veridical form judgments depends on perceived differences in the forms to be judged, not on the objective properties of the proximal stimulus. Implications of these results on models of pattern recognition are examined.

Some evidence for colour-blindness in Octopus.

ABSTRACT Groups of O. vulgaris were trained successively to make brightness and hue discriminations with painted vertical rectangles. These were of approximately the same physical intensity and were equally preferred. Using one-cue discrimination training we found that (a) Seven octopuses that discriminated between dark blue and light blue did not discriminate between dark blue and dark red shapes. (b) Nine octopuses that discriminated between light red and black did not discriminate between light red and light green shapes, (c) Fifteen octopuses that discriminated between medium green and light green did not discriminate between medium green and medium blue shapes. All these octopuses later discriminated between black and white shapes. Another group of octopuses was trained with two cues, one or both of which were relevant. The cues used were brightness (dark or light) and hue (blue or green), (a) Group 1 (N =14) discriminated between dark and light shapes where hue was irrelevant. (b) Group 2 (N = 14) discriminated between dark blue and light green shapes, (c) Group 3 (N =14) failed to discriminate between blue and green shapes where brightness was irrelevant. Overall the scores of Groups 1 and 2 did not differ significantly. Thus under experimental conditions where octopuses rapidly learned to make brightness discriminations they did not learn discriminations based on hue alone; even if colour is perceived, it seems a relatively unimportant cue for this animal. Another group of octopuses (N = 10) was tested, in a special apparatus, for nystagmus and optomotor responses. Such responses were always given when stripes of different brightness moved relative to the retina, but when stripes of the same subjective brightness but different hue moved across the eyes they rarely occurred. Such occurrences were no more frequent than the responses given to a plain grey background. Similar results were obtained under conditions of illumination ranging from less than 1 lux to 7·5 × 104 lux. The absence of visual response to moving coloured stripes suggests that the failure of octopuses to learn a hue discrimination may be the result of an inherent incapacity at the retinal level. Together with other findings, which are discussed, this strongly suggests that O. vulgaris is colour-blind.

Optomotor responses and nystagmus in intact, blinded and statocystless cuttlefish (Sepia officinalis L.).

ABSTRACT Evidence is reviewed confirming that the eyes of Sepia move under the influence of gravity, angular acceleration and visual receptors. Visual nystagmus and optomotor responses are described in free-swimming Sepia; these survive bilateral destruction of the statocysts, though they are abolished by blinding. Post-rotatory nystagmus is shown by intact animals in a plain background; in bilaterally blinded animals there are post-rotatory movements of the head. These responses disappear if the statocysts are removed. The post-rotatory nystagmus of intact animals is almost completely suppressed by visual cues. Other effects of blinding and statocyst removal are described.

The vertical-horizontal illusion in a visually-rich environment

In the vertical-horizontal illusion the vertical dimension of a figure typically appears longer than the horizontal. Although there is a large body of research literature on this illusion, all of it refers to simple figures with well-drawn lines, exhibited against plain backgrounds. Our experiment has investigated the illusion using real-world objects in a visually-rich environment. Ten male and 10 female Ss were asked to judge the heights of 10 objects of various sizes and shapes. They made their estimates by having the experimenter mark off a horizontal distance that corresponded to the judged height of the object. Each S estimated the height of each object once a day for three consecutive days. The results show that, by and large, the illusion can be demonstrated for real objects in a visually-rich environment. There was, however,considerable variation among the objects. It appears that estimates of this kind may be influenced by size, size constancy, anchor effects, and angle of regard, along with other, as yet, unidentified factors.