Visual adaptation to convexity in macaque area V4

Aftereffects are perceptual illusions caused by visual adaptation to one or more stimulus attribute, such as orientation, motion, or shape. Neurophysiological studies seeking to understand the basis of visual adaptation have observed firing rate reduction and changes in tuning of stimulus-selective neurons following periods of prolonged visual stimulation. In the domain of shape, recent psychophysical work has shown that adaptation to a convex pattern induces a subsequently seen rectangle to appear slightly concave. In the present study, we investigate the possible contribution of V4 neurons of rhesus monkeys, which are thought to be involved in the coding of convexity, to shape-specific adaptation. Visually responsive neurons were monitored during the brief presentation of simple shapes varying in their convexity level. Each test presentation was preceded by either a blank period or several seconds of adaptation to a convex or concave stimulus, presented in two different sizes. Adaptation consistently shifted the tuning of neurons away from the convex or concave adapter, including shifting response to the neutral rectangle in the direction of the opposite convexity. This repulsive shift resembled the known perceptual distortion associated with adaptation to such stimuli. In addition, adaptation caused a nonspecific response decrease, as well as a specific decrease for repeated stimuli. The latter effects were observed whether or not the adapting and test stimuli matched closely in their size. Taken together, these results provide evidence for shape-specific adaptation of neurons in area V4, which may contribute to the perception of the convexity aftereffect

The persistence of small dairy farms in Austria from an economic perspective

In the international comparison the structure of milk production in Austria is small scale. The present study presents two theoretical approaches to explain the persistence of small dairy farms in Austria: the opportunity cost principle and the theory of the agricultural household. With regard to the first one it is debatable whether the flat rates really can represent the costs of own production factors in their alternative uses in small enterprises. An illustration on the basis of production cost accounts shows that small dairy farms with no possibilities for the utilization of their own production factors (especially for labour) can cover the production costs by revenues only. Secondly it is argued that agricultural production is likely to continue in small dairy farms as long as the enterprise contributes persistently to the household income of the family. Indicators from the Farm Accountancy Data Network (FADN) of voluntarily participating farms in Austria support the notion that labour is allocated efficiently between the enterprise and the household in small operations in order to achieve maximum total income. The study proposes arguments according to which it can be expected that rather small dairy farms are going to be a prominent presence in Austrian agriculture also in the future.Small dairy farms, production costs, farm household, opportunity costs, FADN, Consumer/Household Economics, Q12, R20,

Designs of multi-spacecraft swarms for the deflection of apophis by solar sublimation

This paper presents two conceptual designs of multi-spacecraft swarms used for deflecting Apophis. Each spacecraft is equipped with a solar concentrator assembly, which focuses the solar light, and a beaming system that projects a beam of light onto the surface of the asteroid. When the beams from each spacecraft are superimposed, the temperature on the surface is enough to sublimate the rock, creating a debris plume with enough force to slowly alter the orbit of Apophis. An overview of the dynamics, control and navigation strategies are presented along with preliminary system budgets

Liquidation Under the Chandler Act: Bankruptcy Practice and Procedure Is Changed by Act of Congress Effective September 22, 1938

In 1938 Congress enacted the Chandler Bill, which became effective September 22, 1938. Its purpose, among other things, as explained by the House Judiciary Committee report, was to clarify certain of the definitions and to add desirable new definitions, to straighten out certain overlapping provisions, to increase efficiency in administration, to make clearer certain ambiguous provisions, to improve the procedural sections of the act, and in general to modernize and bring up to date the bankruptcy law of our country. Congress went somewhat further than a mere modernization of the existing statute. It expanded the law by adding chapters on Arrangements , which liberalize plans of debtors for settlement, satisfaction or extension of debts; on Real Property Arrangements by Persons Other Than Corporations which permit alteration or modification of debts secured by real property or chattels real; on Wage Earners Plans which enable individuals who work for wages or salary to compose or have extended the time for the payment of their debts; and on Maritime Commission Liens which facilitate the continued operation of established steamship lines facing financial difficulties

Parameterizing Quasiperiodicity: Generalized Poisson Summation and Its Application to Modified-Fibonacci Antenna Arrays

The fairly recent discovery of "quasicrystals", whose X-ray diffraction patterns reveal certain peculiar features which do not conform with spatial periodicity, has motivated studies of the wave-dynamical implications of "aperiodic order". Within the context of the radiation properties of antenna arrays, an instructive novel (canonical) example of wave interactions with quasiperiodic order is illustrated here for one-dimensional (1-D) array configurations based on the "modified-Fibonacci" sequence, with utilization of a two-scale generalization of the standard Poisson summation formula for periodic arrays. This allows for a "quasi-Floquet" analytic parameterization of the radiated field, which provides instructive insights into some of the basic wave mechanisms associated with quasiperiodic order, highlighting similarities and differences with the periodic case. Examples are shown for quasiperiodic infinite and spatially-truncated arrays, with brief discussion of computational issues and potential applications.Comment: 29 pages, 10 figures. To be published in IEEE Trans. Antennas Propagat., vol. 53, No. 6, June 200

Headwaters are critical reservoirs of microbial diversity for fluvial networks

Streams and rivers form conspicuous networks on the Earth and are among nature's most effective integrators. Their dendritic structure reaches into the terrestrial landscape and accumulates water and sediment en route from abundant headwater streams to a single river mouth. The prevailing view over the last decades has been that biological diversity also accumulates downstream. Here, we show that this pattern does not hold for fluvial biofilms, which are the dominant mode of microbial life in streams and rivers and which fulfil critical ecosystem functions therein. Using 454 pyrosequencing on benthic biofilms from 114 streams, we found that microbial diversity decreased from headwaters downstream and especially at confluences. We suggest that the local environment and biotic interactions may modify the influence of metacommunity connectivity on local biofilm biodiversity throughout the network. In addition, there was a high degree of variability in species composition among headwater streams that could not be explained by geographical distance between catchments. This suggests that the dendritic nature of fluvial networks constrains the distributional patterns of microbial diversity similar to that of animals. Our observations highlight the contributions that headwaters make in the maintenance of microbial biodiversity in fluvial networks

Alternative Splicing: Associating Frequency with Isoforms

In the simplest model of protein production, a gene gives rise to a single protein; DNA is transcribed to form pre-mRNA, which is converted to mRNA by splicing or removing introns. The result is a chain of exons that is translated to form a protein. Alternative splicing of exons may result in the formation of multiple proteins from the same gene sequence. However, not all of these proteins may be functional. Thus, we ask whether we can predict and rank (in order of frequency of occurrence and functional importance) the set of possible proteins for a gene. Herein we describe a tool that predicts the relative frequencies of isoforms that can be produced from a given gene

Interactive Anatomy Online

The scientific community and general public can best take advantage of the benefits of 3D digital reconstructions if they are stored in a Web-accessible, easy-to-access database. We describe MorphologyNet/sup /spl copy// a Web-based digital library of realistic, 3D interactive and customizable images of anatomy currently in development at the University of Missouri-Rolla