Frequency shifts and depth dependence of premotor beta band activity during perceptual decision-making

Neural activity in the premotor and motor cortices shows prominent structure in the beta frequency range (13–30 Hz). Currently, the behavioral relevance of this beta band activity (BBA) is debated. The underlying source of motor BBA and how it changes as a function of cortical depth are also not completely understood. Here, we addressed these unresolved questions by investigating BBA recorded using laminar electrodes in the dorsal premotor cortex of 2 male rhesus macaques performing a visual reaction time (RT) reach discrimination task. We observed robust BBA before and after the onset of the visual stimulus but not during the arm movement. While poststimulus BBA was positively correlated with RT throughout the beta frequency range, prestimulus correlation varied by frequency. Low beta frequencies (∼12–20 Hz) were positively correlated with RT, and high beta frequencies (∼22–30 Hz) were negatively correlated with RT. Analysis and simulations suggested that these frequency-dependent correlations could emerge due to a shift in the component frequencies of the prestimulus BBA as a function of RT, such that faster RTs are accompanied by greater power in high beta frequencies. We also observed a laminar dependence of BBA, with deeper electrodes demonstrating stronger power in low beta frequencies both prestimulus and poststimulus. The heterogeneous nature of BBA and the changing relationship between BBA and RT in different task epochs may be a sign of the differential network dynamics involved in cue expectation, decision-making, motor preparation, and movement execution.Published versio

Self-timed design in GaAs - case study of a high-speed parallel multiplier

Journal ArticleAbstract-The problems with synchronous designs at high clock frequencies have been well documented. This makes an asynchronous approach attractive for high speed technologies like GaAs. We investigate the issues involved by describing the design of a parallel multiplier that can be part of a floating point multiplier. We first present a new architecture called the partial army of array (PAA) that is more regular than a partial tree approach while having the same latency. We then show how this architecture can be used in a self-timed implementation in the style of micropipelines. We next describe how we can design the final carry propagate adder using a new precharged logic family in GaAs that we developed as part of this project. We conclude with some genera1 observations on doing asynchronous design in GaAs

Eddy Current Testing of Zircaloy Wires

Fuel bundles for Rajasthan Atomic Power Reactor, consist of a cluster of 19 elements held together by zir-caloy and plates and spaced by wire helices on the six elements of the inner ring and alternative elements of the outer ring. As in the case of all other reactor mater-ials, the zircaloy wire also need be inspected 100% to avoid any defective part entering the reactor system. The zircaloy wire must be free from defects such as seams, internal voids, welded spots etc apart from the dimensio-nal and metallurgical requirements

Eddy Current Testing of Zirconium Wires

FUEL bundles for Rajasthan Atomic Power Reactor, as per the design, consist of a cluster of 19 elements held together by zircaloy end plates and spaced by wire helices on the six elements of the inner ring and alte-rnate elements of the outer ring. Each element is a zircaloy-2 tube 495 min long,1524 mm in diameter and of 0.4 nom wall thickness containing the nuclear fuel in the form of sintered uranium dioxide pellets and sealed at both ends. In order to provide the required spacing between the elements, zircaloy wire of 1.25 mm dia. is spot-welded around the elements in the helix form. The wire helices serve to separate the elements to maintain the dimensions of the coolant sub-channels between them and to increase the mixing of coolant between inner and outer sub-channels. Zircaloy wire of 1.63 mm dia. is spot-welded on the outer elements so as to provide bearing surfaces for the bundle when it moves through the fuel channels in the coolant assemblies

Assessment of Multi-Scale Approaches for Computing UV-Vis Spectra in Condensed Phases: Toward an Effective yet Reliable Integration of Variational and Perturbative QM/MM Approaches

Computational simulation of UV/vis spectra in condensed phases can be performed starting from converged molecular dynamics (MD) simulations and then performing quantum mechanical/molecular mechanical (QM/MM) computations for a statistically significant number of snapshots. However, the need of variational solutions (e.g., ONIOM/EE) for a huge number of snapshots makes unpractical the use of state-of-the-art QM Hamiltonians. On the other hand, the effectivity of perturbative approaches (e.g., perturbed matrix method, PMM) comes at the price of poor convergence for configurations strongly different from the reference one. In this paper we introduce an integrated strategy based on a cluster analysis of the MD snapshots. Next, a representative configuration for each cluster is treated at the ONIOM/EE level, whereas local fluctuations within each cluster are described at the PMM level. Some representative systems (uracil in dimethylformamide and in water and tyrosine zwitterion in water) are analyzed to show the effectivity and flexibility of the proposed strategy

Logarithmic Correction to BPS Black Hole Entropy from Supersymmetric Index at Finite Temperature

It has been argued by Iliesiu, Kologlu and Turiaci in arXiv:2107.09062 that one can compute the supersymmetric index of black holes using black hole geometry carrying finite temperature but a specific complex angular velocity. We follow their prescription to compute the logarithmic correction to the entropy of BPS states in four dimensions, defined as the log of the index of supersymmetric black holes, and find perfect agreement with the previous results for the same quantity computed using the near horizon $AdS_2 \times S^2$ geometry of zero temperature black holes. Besides giving an independent computation of supersymmetric black hole entropy, this analysis also provides a test of the procedure used previously for computing logarithmic corrections to Schwarzschild and other non-extremal black hole entropy.Comment: 23 page

Computational Spectroscopy in Solution by Integration of Variational and Perturbative Approaches on Top of Clusterized Molecular Dynamics

Multiscale QM/MM approaches have become the most suitable and effective methods for the investigation of spectroscopic properties of medium-or large-size chromophores in condensed phases. On these grounds, we are developing a novel workflow aimed at improving the generality, reliability, and ease of use of the available tools. In the present paper, we report the latest developments of such an approach with specific reference to a general workplan starting with the addition of acetonitrile to the panel of solvents already available in the General Liquid Optimized Boundary (GLOB) model enforcing nonperiodic boundary conditions (NPBC). Next, the solvatochromic shifts induced by acetonitrile on both rigid (uracil and thymine) and flexible (thyrosine) chromophores have been studied introducing in our software a number of new features ranging from rigid-geometry NPBC molecular dynamics based on the quaternion formalism to a full integration of variational (ONIOM) and perturbative (perturbed matrix method (PMM)) approaches for describing different solute-solvent topologies and local fluctuations, respectively. Finally, thymine and uracil have been studied also in methanol to point out the generality of the computational strategy. While further developments are surely needed, the strengths of our integrated approach even in its present version are demonstrated by the accuracy of the results obtained by an unsupervised approach and coupled to a computational cost strongly reduced with respect to that of conventional QM/MM models without any appreciable accuracy deterioration

Selection of Voltage Thresholds for Delay Measurement

Since all physical devices have a finite non-zero responsetime, the notion of delay between the input and output logicsignals arises naturally once digital abstraction is done. Thisdelay should be positive and non-zero, since a physical devicetakes a finite amount of time to respond to the input. Defininga strictly positive delay is not a problem in the abstract domainof logic signals, since input and output ’’events‘‘ are preciselydefined. However, when the signal non-idealities are accountedfor, the notion of events is blurred and it is not obvious howto define delay such that it reflects the causal relationshipbetween the input and the output. By necessity, we define thestart and end points of these events by determining the timeinstants when the signals cross some appropriate voltage thresholds.The selection of these voltage thresholds for logic gates aswell as simple interconnect wires, is the subject of this paper.We begin by a discussion of what we mean by signal delay andhow it arises in a logic gate. With this background, startingfrom ideal inputs to ideal inverters and concluding with physicalinputs to physical inverters, we examine the problem of thresholdselection for inverters through a logical sequence of model refinement,using a combination of analytical and experimental techniques.Based on the insight gained through this analysis, we examinethe problem for multi-input (both static and dynamic) gates aswell as point-to-point interconnect wires. We show that thresholdsderived from the gate‘s DC voltage transfer characteristic removesthe anomalies, such as negative delay and large sensitivity toinput waveshape effects, that can arise with the widely used50% and 10%–90% thresholds. Despite its fundamentalnature, however, we note that the problem of threshold selectionhas received scant attention in the literature. To the best ofour knowledge, this is the first detailed study of this problem.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44035/1/10470_2004_Article_137059.pd