Publications by authors named "Levitan S"

Coronavirus disease 2019 (COVID-19) started in Wuhan, China, in late 2019, and after being utterly contagious in Asian countries, it rapidly spread to other countries. This disease caused governments worldwide to declare a public health crisis with severe measures taken to reduce the speed of the spread of the disease. This pandemic affected the lives of millions of people.

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Inspired by the advances in both materials and computer science, we describe efforts to design "materials that compute" where the material and the computer are the same entity. Using theory and simulation, we devise systems that integrate the behavior of self-oscillating gels and fundamental concepts from oscillator-based computing. We specifically focus on gels that undergo the Belousov-Zhabotinsky (BZ) reaction and thus exhibit self-sustained oscillations.

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Driven by advances in materials and computer science, researchers are attempting to design systems where the computer and material are one and the same entity. Using theoretical and computational modeling, we design a hybrid material system that can autonomously transduce chemical, mechanical, and electrical energy to perform a computational task in a self-organized manner, without the need for external electrical power sources. Each unit in this system integrates a self-oscillating gel, which undergoes the Belousov-Zhabotinsky (BZ) reaction, with an overlaying piezoelectric (PZ) cantilever.

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Cnidarians are widely distributed basal metazoans that play an important role in the marine ecosystem. Their genetic diversity and dispersal depends on successful oogenesis, fertilization and embryogenesis. To understand the processes that lead to successful embryogenesis in these basal organisms, we conducted comparative proteomics on the model sea anemone Nematostella vectensis.

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Polymer gels undergoing the oscillatory Belousov-Zhabotinsky (BZ) reaction are one of the few synthetic materials that exhibit biomimetic mechano-chemical transduction, converting mechanical input into chemical energy. Here, we consider self-oscillating BZ gels that are subjected to periodic mechanical forcing, and model the entrainment of the oscillatory gel dynamics to this external stimulus. The gel size is assumed to be sufficiently small that the chemo-mechanical oscillations are spatially uniform.

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Lightweight, deformable materials that can sense and respond to human touch and motion can be the basis of future wearable computers, where the material itself will be capable of performing computations. To facilitate the creation of "materials that compute", we draw from two emerging modalities for computation: chemical computing, which relies on reaction-diffusion mechanisms to perform operations, and oscillatory computing, which performs pattern recognition through synchronization of coupled oscillators. Chemical computing systems, however, suffer from the fact that the reacting species are coupled only locally; the coupling is limited by diffusion as the chemical waves propagate throughout the system.

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In this paper we present a novel methodology for classifying cells by using a combination of dielectrophoresis, image tracking and classification algorithms. We use dielectrophoresis to induce unique motion patterns in cells of interest. Motion is extracted via multi-target multiple-hypothesis tracking.

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Using computational modeling, we design colonies of biomimetic microcapsules that exploit chemical mechanisms to communicate and alter their local environment. As a result, these synthetic objects can self-organize into various autonomously moving structures and exhibit ant-like tracking behavior. In the simulations, signaling microcapsules release agonist particles, whereas target microcapsules release antagonist particles and the permeabilities of both capsule types depend on the local particle concentration in the surrounding solution.

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Through five experiments, we demonstrate and characterize the basic functionality of imaging fiber bundles for optoelectronic chip-level interconnections. We demonstrate the transmission of spot arrays with spot sizes and a spot pitch roughly equal to 2 and 4 times the core pitch, respectively. We show that optoelectronic integrated circuits, including sources and detectors, can be butt coupled directly to fiber bundles without any additional optical elements.

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Chatoyant is a tool for the simulation and the analysis of heterogeneous free-space optoelectronic architectures. It is capable of modeling digital and analog electronic and optical signal propagation with mechanical tolerancing at the system level. We present models for a variety of optoelectronic devices and results that demonstrate the system's ability to predict the effects of various component parameters, such as detector geometry, and system parameters, such as alignment tolerances, on system-performance measures, such as the bit-error rate.

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Welcome to the first special issue of Applied Optics on computer-aided design for optoelectronic systems. This special issue stemmed from our realization of the need for dialogue between optoelectronic system designers and computer-aided-design developers, as well as from the realization that various research groups are developing or, in some instances, have already developed and commercialized such tools. Our goal for this special issue is to enhance this type of dialogue by showing to the optoelectronic system design community the current state of optoelectronic computer-aided-design tools.

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We present simulation and experimental results of fiber Bragg grating responses to transverse stress in microstructure fibers. The grating wavelength shifts and peak splits are studied as a function of external load and fiber orientation. Both simulation and measurement results indicate that the sensitivity of grating sensors to the transverse stress can be enhanced by a factor of eight in a two-hole fiber over that in a standard fiber.

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There is long-standing disagreement among experimentalists about whether transcallosal interhemispheric influences are primarily excitatory or inhibitory. Past computational models exploring this issue have encountered a similar dilemma: inhibitory callosal influences best explain hemispheric functional asymmetries, but excitatory callosal influences best explain transcallosal diaschisis. We recently hypothesized that this dilemma might be resolved by assuming excitatory callosal influences and a subcortical mechanism for cross-midline inhibition.

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While recent experimental work has defined asymmetries and lateralization in left and right cortical maps, the mechanisms underlying these phenomena are currently not established. In order to explore some possible mechanisms in theory, we studied a neural model consisting of paired cerebral hemispheric regions interacting via a simulated corpus callosum. Starting with random synaptic strengths, unsupervised (Hebbian) synaptic modifications led to the emergence of a topographic map in one or both hemispheric regions.

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During recent years there has been increasing use of neural models to investigate the implications of hypotheses about brain and cognitive disorders. Here we systematically study the effects of sudden simulated lesions on cortical maps in a neural model consisting of left and right hemispheric regions connected by a corpus callosum. The model identifies conditions under which damage to one hemispheric region leads to reorganization of the contralateral, intact hemispheric region.

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Cerebral lateralization refers to the poorly understood fact that some functions are better controlled by one side of the brain than the other (e.g. handedness, language).

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We present an investigation of the architecture of an optoelectronic cache that can integrate terabit optical memories with the electronic caches associated with high-performance uniprocessors and multiprocessors. The use of optoelectronic-cache memories enables these terabit technologies to provide transparently low-latency secondary memory with frame sizes comparable with disk pages but with latencies that approach those of electronic secondary-cache memories. This enables the implementation of terabit memories with effective access times comparable with the cycle times of current microprocessors.

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We designed a questionnaire to identify the factors influencing both day of admission surgery (DAS) and ambulatory (AMB) patients in their decision whether to participate in and give informed consent for clinical anesthesia research. On the day of surgery, 276 patients were approached to complete a questionnaire and a visual analog scale (VAS) to assess anxiety. The data collected were observational and are presented as percentages for each group (DAS and AMB).

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Hybrid optoelectronic computing structures are required for providing the information processing capabilities for the next generation of computing and communications systems. Reconfigurable optoelectronic interconnection networks are networks constructed of optical waveguides in which messages are switched or routed by means of optoelectronic devices. For these networks, the dichotomy between the bandwidth of the optical channels that carry messages and the performance of the electronic controllers and decoders that determine the routing and destination of those messages is a significant bottleneck.

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We present several optical interconnection structures which support communication requirements unique to multiprocessor systems, namely, broadcasting, multicasting, simulcasting, and multiport memory access. The structures are based on guided wave time division multiplexed channels and use coincident pulse techniques to optically demultiplex individual bits at selected destinations. We describe 1-and 2-D structures which are appropriate for processor to processor interconnections and for processor to memory interconnections, respectively.

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Strong emotions are aroused in people in the presence of child abuse. For the therapist trying to help abusive families, these feelings can destroy any prospect of achieving a therapeutic process. This problem is particularly acute in the in-home situation.

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The in vivo effects of 1,25(OH)2D3 on cell proliferation, tissue organization and matrix mineralization have been studied in condylar cartilage of neonatal mice. A relatively low dose of the metabolite, 50 ng/kg body weight, significantly reduced the incorporation of [3H]thymidine as well as the number of chondroblasts. The cartilage as a whole underwent a marked derangement in its organization, as many fibroblastlike cells appeared to occupy the zone of progenitor cells.

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A liaison psychiatrist participated in the postoperative care of a group of elderly patients who underwent surgery for fractured femurs. Clinical outcomes for this group were compared with a control group of patients who were not treated by a liaison psychiatrist. Length of stay for the treatment group was 12 days shorter than for the control group, and twice as many patients in the treatment group returned home rather than being discharged to a nursing home or other health-related institution; therefore, a substantial reduction in the cost of their medical care was effected.

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Immature A/J mice were treated for up to 7 weeks intermittent doses of triamcinolone hexacetonide and were thereafter allowed to recover for 7 weeks. Qualitative and quantitative morphological measurements were performed on the epiphyseal cartilage plate and diaphyseal bone of the humerus. By the third injection significant structural changes were noted in the cartilaginous tissue followed by a complete cessation of bone growth.

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