19,258 research outputs found
Concepts for on-board satellite image registration. Volume 3: Impact of VLSI/VHSIC on satellite on-board signal processing
Anticipated major advances in integrated circuit technology in the near future are described as well as their impact on satellite onboard signal processing systems. Dramatic improvements in chip density, speed, power consumption, and system reliability are expected from very large scale integration. Improvements are expected from very large scale integration enable more intelligence to be placed on remote sensing platforms in space, meeting the goals of NASA's information adaptive system concept, a major component of the NASA End-to-End Data System program. A forecast of VLSI technological advances is presented, including a description of the Defense Department's very high speed integrated circuit program, a seven-year research and development effort
Effect of disorder on the thermal transport and elastic properties in thermoelectric Zn4Sb3
Zn4Sb3 undergoes a phase transition from alpha to beta phase at T1[approximate]250 K. The high temperature beta-Zn4Sb3 phase has been widely investigated as a potential state-of-the-art thermoelectric (TE) material, due to its remarkably low thermal conductivity. We have performed electronic and thermal transport measurements exploring the structural phase transition at 250 K. The alpha to beta phase transition manifests itself by anomalies in the resistivity, thermopower, and specific heat at 250 K as well as by a reduction in the thermal conductivity as Zn4Sb3 changes phase from the ordered alpha to the disordered beta-phase. Moreover, measurements of the elastic constants using resonant ultrasound spectroscopy (RUS) reveal a dramatic softening at the order-disorder transition upon warming. These measurements provide further evidence that the remarkable thermoelectric properties of beta-Zn4Sb3 are tied to the disorder in the crystal structure
Orbital-free Bond Breaking via Machine Learning
Machine learning is used to approximate the kinetic energy of one dimensional
diatomics as a functional of the electron density. The functional can
accurately dissociate a diatomic, and can be systematically improved with
training. Highly accurate self-consistent densities and molecular forces are
found, indicating the possibility for ab-initio molecular dynamics simulations
Some Legal and Economic Implications of Sea Water Intrusion - A Case Study of Ground Water Management
Hartree-Fock-Bogoliubov Model and Simulation of Attractive and Repulsive Bose-Einstein Condensates
We describe a model of dynamic Bose-Einstein condensates near a Feshbach
resonance that is computationally feasible under assumptions of spherical or
cylindrical symmetry. Simulations in spherical symmetry approximate the
experimentally measured time to collapse of an unstably attractive condensate
only when the molecular binding energy in the model is correct, demonstrating
that the quantum fluctuations and atom-molecule pairing included in the model
are the dominant mechanisms during collapse. Simulations of condensates with
repulsive interactions find some quantitative disagreement, suggesting that
pairing and quantum fluctuations are not the only significant factors for
condensate loss or burst formation. Inclusion of three-body recombination was
found to be inconsequential in all of our simulations, though we do not
consider recent experiments [1] conducted at higher densities
Understanding the Health and Safety Risks for British Columbia’s Outbound Medical Tourists
When patients choose to go abroad to privately purchase medical care they are engaging in ‘medical tourism’, which isthe most commonly used name for this practice. Several studies and reports suggest that there are a number of healthand safety risks to patients who choose to purchase private medical care abroad. Much of our existing knowledgeabout the health and safety risks of medical tourism for patients is, however, limited due to a lack of comprehensiveresearch and reporting. Acknowledging this and the reportedtrends of Canadians’ increasing involvement in medicaltourism, a consultative meeting was held in September, 2011with individuals whose professional roles relate to patientsafety, health, and risk management. This meeting, held in Vancouver, British Columbia, aimed to learn more aboutthe types of concerns that these professionals have observed or believe exist in principle as a result of British Columbians’ involvement in medical touris
Medical Tourism in the Caribbean: A Call for Cooperation
Numerous Caribbean countries have discussed plans for developing medical tourism activities as a means of tourism diversification and economic development. These plans have been encouraged and shaped by outside agencies whose influence might cause a race-to-the-bottom environment between countries competing for the same niche of tourists. This paper provides a call for cooperation between local health officials in the Caribbean region to coordinate plans for the development of a medical tourism industry that enhances regional access to specialized healthcare and facilitates the movement of patients and healthcare resources throughout the region to enhance health equity and health outcomes in the Caribbean
Early Acquisition of Neural Crest Competence During hESCs Neuralization
Background:
Neural crest stem cells (NCSCs) are a transient multipotent embryonic cell population that represents a defining characteristic of vertebrates. The neural crest (NC) gives rise to many derivatives including the neurons and glia of the sensory and autonomic ganglia of the peripheral nervous system, enteric neurons and glia, melanocytes, and the cartilaginous, bony and connective tissue of the craniofacial skeleton, cephalic neuroendocrine organs, and some heart vessels.
Methodology/Principal Findings:
We present evidence that neural crest (NC) competence can be acquired very early when human embryonic stem cells (hESCs) are selectively neuralized towards dorsal neuroepithelium in the absence of feeder cells in fully defined conditions. When hESC-derived neurospheres are plated on fibronectin, some cells emigrate onto the substrate. These early migratory Neural Crest Stem Cells (emNCSCs) uniformly upregulate Sox10 and vimentin, downregulate N-cadherin, and remodel F-actin, consistent with a transition from neuroepithelium to a mesenchymal NC cell. Over 13% of emNCSCs upregulate CD73, a marker of mesenchymal lineage characteristic of cephalic NC and connexin 43, found on early migratory NC cells. We demonstrated that emNCSCs give rise in vitro to all NC lineages, are multipotent on clonal level, and appropriately respond to developmental factors. We suggest that human emNCSC resemble cephalic NC described in model organisms. Ex vivo emNCSCs can differentiate into neurons in Ret.k- mouse embryonic gut tissue cultures and transplanted emNCSCs incorporate into NC-derived structures but not CNS tissues in chick embryos.
Conclusions/Significance:
These findings will provide a framework for further studying early human NC development including the epithelial to mesenchymal transition during NC delamination
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