Neural substrates of orthographic processing: Are they specific to written language?

The primary systems hypothesis of written language processing postulates that orthographic information is processed by the same brain regions recruited for visual object recognition. We conducted two experiments in order to examine whether common visual processing regions are engaged in reading, spelling, and non-orthographic language task. The left mid fusiform gyrus was activated not only in orthographic processing during both written language tasks, but also in recognition of pictures of objects. Our results suggest that orthographic processing is supported by the general visual processing region rather than a specialized brain region dedicated to reading or spelling

A surface forces platform for dielectric measurements

Methods are described to implement dielectric spectroscopy (frequency range 10(-1)-10(6) Hz) within a surface forces apparatus by using as electrodes silver sheets on the backside of mica. These methods are applied to study the competitive effects of surface alignment, confinement, and shear field on 5CB (5-cyanobiphenyl), a nematic liquid crystal at the experimental temperature of 25degreesC. In the planar orientation, films could be squeezed to a minimum thickness of approximate to5 Angstrom, the molecule's thickness. In the perpendicular (homeotropic) orientation, films could be squeezed to approximate to25 Angstrom, the expected thickness of the head-to-tail 5CB dimer. It was difficult to discuss responses at f >10(5) Hz quantitatively because the peak was not visible in the experimental frequency window. Nonetheless, the onset of the relaxation mode for the planar oriented molecules appears at higher frequency than for the homeotropic orientation. A slower relaxation mode, peaked at f approximate to 10 Hz, was assigned to electrode polarization due to the mobility of trace ions within the 5CB samples although these samples were >99.7% pure. The peak frequency was a factor of 3 slower with homeotropic than planar alignment and, in both cases, independent of film thickness except when the film thickness exceeded 10 mum. This was explained using a simple model based on the assumption that trace ions move to oppositely charged electrodes to form electric double layers. A small influence of shear on the dielectric response was observed but only when the dielectric response was measured at the same frequency as the large-amplitude shear deformation. Also described is the use of capacitance to measure force-distance profiles.open8

Dielectric response of polymer films confined between mica surfaces

The thin-film dielectric response of organic films confined within a surface forces apparatus (SFA) and also between parallel sheets of atomically smooth mica is reported for the first time. Analysis is presented to infer dielectric properties of the organic film from the measured capacitance of the total system: sample, and mica sheets intervening between sample and electrodes. Measurements concerned the frequency dependence of normal-mode dielectric relaxation of cis-polyisoprene having dipoles aligned in the same direction along the chain backbone. We find that in thin-film geometries the peak frequency, f(peak), of normal mode dielectric loss (epsilon") is moderately lower than for bulk samples and that, more important, the expected terminal tail, observed in the bulk sample (epsilon"proportional to f for f < f(peak)), is not observed even at the lowest frequency examined. Thus the slow normal mode distribution is much broader and the terminal relaxation time is much longer for chains in the thin layers. These dielectric features are attributed to spatial constraints on global chain motion in the thin layers and also to adsorption of chains on mica surfaces when the layer thickness is comparable to the unperturbed chain dimension. Independent measurements of shear relaxation, performed using a SFA modified for measurement of dynamical mechanical shear rheology, found a tremendously retarded viscoelastic response relative to bulk samples. There is the possibility that the broad distribution of the dielectric response of individual polymer chains may correspond to the observed retarded viscoelastic relaxation. However, we cannot rule out the other possibility that the dielectrically detected relaxation of individual chains is still faster than the terminal viscoelastic relaxation and that the latter thus corresponds to the collective motion of many confined chains.open333

Memristor MOS Content Addressable Memory (MCAM): Hybrid Architecture for Future High Performance Search Engines

Large-capacity Content Addressable Memory (CAM) is a key element in a wide variety of applications. The inevitable complexities of scaling MOS transistors introduce a major challenge in the realization of such systems. Convergence of disparate technologies, which are compatible with CMOS processing, may allow extension of Moore's Law for a few more years. This paper provides a new approach towards the design and modeling of Memristor (Memory resistor) based Content Addressable Memory (MCAM) using a combination of memristor MOS devices to form the core of a memory/compare logic cell that forms the building block of the CAM architecture. The non-volatile characteristic and the nanoscale geometry together with compatibility of the memristor with CMOS processing technology increases the packing density, provides for new approaches towards power management through disabling CAM blocks without loss of stored data, reduces power dissipation, and has scope for speed improvement as the technology matures.Comment: 10 pages, 11 figure

EXCHANGE RATE MISALIGNMENT AND AGRICULTURAL TRADE

Using a sample consisting of bilateral trade flows across 10 developed countries between 1974 and 1995, this paper explores the effect of exchange rate misalignment on the growth of agricultural trade as compared to other sectors. Controlling for other factors likely to determine the growth in bilateral agricultural trade, the results show that long-run real exchange rate variability has had a significant negative effect on the growth of agricultural trade over this period. Keywords: Exchange rates, misalignment, agricultural tradeExchange rates, misalignment, agricultural trade, International Relations/Trade,

Catalytic enzymes are active matter

Using a microscopic theory to analyze experiments, we demonstrate that enzymes are active matter. Superresolution fluorescence measurements—performed across four orders of magnitude of substrate concentration, with emphasis on the biologically relevant regime around or below the Michaelis–Menten constant—show that catalysis boosts the motion of enzymes to be superdiffusive for a few microseconds, enhancing their effective diffusivity over longer timescales. Occurring at the catalytic turnover rate, these fast ballistic leaps maintain direction over a duration limited by rotational diffusion, driving enzymes to execute wormlike trajectories by piconewton forces performing work of a few kBT against viscosity. The boosts are more frequent at high substrate concentrations, biasing the trajectories toward substrate-poor regions, thus exhibiting antichemotaxis, demonstrated here experimentally over a wide range of aqueous concentrations. Alternative noncatalytic, passive mechanisms that predict chemotaxis, cross-diffusion, and phoresis, are critically analyzed. We examine the physical interpretation of our findings, speculate on the underlying mechanism, and discuss the avenues they open with biological and technological implications. These findings violate the classical paradigm that chemical reaction and motility are distinct processes, and suggest reaction–motion coupling as a general principle of catalysis.11sciescopu

Enzyme leaps fuel antichemotaxis

There is mounting evidence that enzyme diffusivity is enhanced when the enzyme is catalytically active. Here, using superresolution microscopy [stimulated emission-depletion fluorescence correlation spectroscopy (STED-FCS)], we show that active enzymes migrate spontaneously in the direction of lower substrate concentration (???antichemotaxis???) by a process analogous to the run-and-tumble foraging strategy of swimming microorganisms and our theory quantifies the mechanism. The two enzymes studied, urease and acetylcholinesterase, display two families of transit times through subdiffraction-sized focus spots, a diffusive mode and a ballistic mode, and the latter transit time is close to the inverse rate of catalytic turnover. This biochemical information-processing algorithm may be useful to design synthetic self-propelled swimmers and nanoparticles relevant to active materials. Executed by molecules lacking the decision-making circuitry of microorganisms, antichemotaxis by this run-and-tumble process offers the biological function to homogenize product concentration, which could be significant in situations when the reactant concentration varies from spot to spot

Fast Decision Support for Air Traffic Management at Urban Air Mobility Vertiports using Graph Learning

Urban Air Mobility (UAM) promises a new dimension to decongested, safe, and fast travel in urban and suburban hubs. These UAM aircraft are conceived to operate from small airports called vertiports each comprising multiple take-off/landing and battery-recharging spots. Since they might be situated in dense urban areas and need to handle many aircraft landings and take-offs each hour, managing this schedule in real-time becomes challenging for a traditional air-traffic controller but instead calls for an automated solution. This paper provides a novel approach to this problem of Urban Air Mobility - Vertiport Schedule Management (UAM-VSM), which leverages graph reinforcement learning to generate decision-support policies. Here the designated physical spots within the vertiport's airspace and the vehicles being managed are represented as two separate graphs, with feature extraction performed through a graph convolutional network (GCN). Extracted features are passed onto perceptron layers to decide actions such as continue to hover or cruise, continue idling or take-off, or land on an allocated vertiport spot. Performance is measured based on delays, safety (no. of collisions) and battery consumption. Through realistic simulations in AirSim applied to scaled down multi-rotor vehicles, our results demonstrate the suitability of using graph reinforcement learning to solve the UAM-VSM problem and its superiority to basic reinforcement learning (with graph embeddings) or random choice baselines.Comment: Accepted for presentation in proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems 202

Enzyme leaps fuel antichemotaxis

There is mounting evidence that enzyme diffusivity is enhanced when the enzyme is catalytically active. Here, using superresolution microscopy [stimulated emission-depletion fluorescence correlation spectroscopy (STED-FCS)], we show that active enzymes migrate spontaneously in the direction of lower substrate concentration (???antichemotaxis???) by a process analogous to the run-and-tumble foraging strategy of swimming microorganisms and our theory quantifies the mechanism. The two enzymes studied, urease and acetylcholinesterase, display two families of transit times through subdiffraction-sized focus spots, a diffusive mode and a ballistic mode, and the latter transit time is close to the inverse rate of catalytic turnover. This biochemical information-processing algorithm may be useful to design synthetic self-propelled swimmers and nanoparticles relevant to active materials. Executed by molecules lacking the decision-making circuitry of microorganisms, antichemotaxis by this run-and-tumble process offers the biological function to homogenize product concentration, which could be significant in situations when the reactant concentration varies from spot to spot