4,778 research outputs found
Characterization and Improvement of EOS Land Products Using Measurements at AMERIFLUX Grassland and Wheat Sites in the ARM/CART Region: Research Annual Performance Report for Period March 1, 1999- February 29, 2000.
Diversification and hybridization in firm knowledge bases in nanotechnologies
The paper investigates the linkages between the characteristics of
technologies and the structure of a firms' knowledge base. Nanotechnologies
have been defined as converging technologies that operate at the nanoscale, and
which require integration to fulfill their economic promises. Based on a
worldwide database of nanofirms, the paper analyses the degree of convergence
and the convergence mechanisms within firms. It argues that the degree of
convergence in a firm's nano-knowledge base is relatively independent from the
size of the firm's nano-knowledge base. However, while firms with small
nano-knowledge bases tend to exploit convergence in each of their
patents/publications, firms with large nano-knowledge bases tend to separate
their nano-R&D activities in the different established fields and achieve
diversity through the juxtaposition of the output of these independent
activitie
Effect of religiosity/spirituality and sense of coherence on depression within a rural population in Greece: the Spili III project
Background: Recent research has addressed the hypothesis that religiosity/spirituality and sense of coherence buffer the negative effects of stress on numerous health issues. The aim of the current study was to further this work by exploring potential links between psycho-social factors such as religiosity/ spirituality and sense of coherence with depression.
Methods: A total of 220 subjects of the SPILI III cohort (1988-2012) attending a primary care setting in the town of Spili on rural Crete represented the target group. All participants underwent a standardized procedure. Validated questionnaires were used to evaluate sense of coherence, depression levels and religious and spiritual beliefs. A multiple linear regression analysis of the Beck Depression Inventory Scale (BDI) in relation to demographic characteristics, scores on the Royal Free Interview for Spiritual and Religious Beliefs scale (RFI-SRB) and Sense of Coherence scale (SOC) was used.
Results: A significant inverse association was found between BDI and RFI-SRB scale (B-coef=-0.6999, p<0.001), as well as among BDI and SOC scale (B-coef=-0.556, p<0.001).
Conclusions: The findings of the current observational study indicate that highly religious participants are less likely to score high in the depression scale. Furthermore, participants with high SOC scored significantly low in the BDI scale. Further research is required in order to explore the potential effect of SOC and religiosity/spirituality in mental health
Fractal-like Distributions over the Rational Numbers in High-throughput Biological and Clinical Data
Recent developments in extracting and processing biological and clinical data are allowing quantitative approaches to studying living systems. High-throughput sequencing, expression profiles, proteomics, and electronic health records are some examples of such technologies. Extracting meaningful information from those technologies requires careful analysis of the large volumes of data they produce. In this note, we present a set of distributions that commonly appear in the analysis of such data. These distributions present some interesting features: they are discontinuous in the rational numbers, but continuous in the irrational numbers, and possess a certain self-similar (fractal-like) structure. The first set of examples which we present here are drawn from a high-throughput sequencing experiment. Here, the self-similar distributions appear as part of the evaluation of the error rate of the sequencing technology and the identification of tumorogenic genomic alterations. The other examples are obtained from risk factor evaluation and analysis of relative disease prevalence and co-mordbidity as these appear in electronic clinical data. The distributions are also relevant to identification of subclonal populations in tumors and the study of the evolution of infectious diseases, and more precisely the study of quasi-species and intrahost diversity of viral populations
Neurofilaments form flexible bundles during neuritogenesis in culture and in mature axons in situ
Neurofilaments (NFs) undergo cation-dependent phospho-mediated associations with each other and other cytoskeletal elements that support axonal outgrowth. Progressive NF-NF associations generate a resident, bundled population that undergoes exchange with transporting NFs. We examined the properties of bundled NFs. Bundles did not always display a fully linear profile but curved and twisted at various points along the neurite length. Bundles retracted faster than neurites and retracted bundles did not expand following extraction with Triton, indicating that they coiled passively rather than due to pressure from the cell. Bundles consisted of helically wound NFs, which may provide flexibility necessary for turning of growing axons during pathfinding. Interactions between NFs and other cytoskeletal elements may be disrupted en masse during neurite retraction or regionally during remodeling. It is suggested that bundles within long axons that cannot be fully retracted into the soma could provide maintain proximal support yet still allow more distal flexibility for remodeling and changing direction during pathfinding
A point process framework for modeling electrical stimulation of the auditory nerve
Model-based studies of auditory nerve responses to electrical stimulation can
provide insight into the functioning of cochlear implants. Ideally, these
studies can identify limitations in sound processing strategies and lead to
improved methods for providing sound information to cochlear implant users. To
accomplish this, models must accurately describe auditory nerve spiking while
avoiding excessive complexity that would preclude large-scale simulations of
populations of auditory nerve fibers and obscure insight into the mechanisms
that influence neural encoding of sound information. In this spirit, we develop
a point process model of the auditory nerve that provides a compact and
accurate description of neural responses to electric stimulation. Inspired by
the framework of generalized linear models, the proposed model consists of a
cascade of linear and nonlinear stages. We show how each of these stages can be
associated with biophysical mechanisms and related to models of neuronal
dynamics. Moreover, we derive a semi-analytical procedure that uniquely
determines each parameter in the model on the basis of fundamental statistics
from recordings of single fiber responses to electric stimulation, including
threshold, relative spread, jitter, and chronaxie. The model also accounts for
refractory and summation effects that influence the responses of auditory nerve
fibers to high pulse rate stimulation. Throughout, we compare model predictions
to published physiological data and explain differences in auditory nerve
responses to high and low pulse rate stimulation. We close by performing an
ideal observer analysis of simulated spike trains in response to sinusoidally
amplitude modulated stimuli and find that carrier pulse rate does not affect
modulation detection thresholds.Comment: 1 title page, 27 manuscript pages, 14 figures, 1 table, 1 appendi
Electromagnetic and corpuscular emission from the solar flare of 1991 June 15: Continuous acceleraton of relativistic particles
Data on X-,γ-ray, optical and radio emission from the 1991 June 15 solar flare are considered. We have calculated the spectrum of protons that producesγ-rays during the gradual phase of the flare. The primary proton spectrum can be described as a Bessel-function-type up to 0.8 GeV and a power law with the spectral index ≈3 from 0.8 up to 10 GeV or above. We have also analyzed data on energetic particles near the Earth. Their spectrum differed from that of primary protons producingγ-ray line emission. In the gradual phase of the flare additional pulses of energy release occurred and the time profiles of cm-radio emission andγ-rays in the 0.8–10 MeV energy band and above 50 MeV coincided. A continuous and simultaneous stochastic acceleration of the protons and relativistic electrons at the gradual phase of the flare is considered as a natural explanation of the data
Discrete breathers in dc biased Josephson-junction arrays
We propose a method to excite and detect a rotor localized mode
(rotobreather) in a Josephson-junction array biased by dc currents. In our
numerical studies of the dynamics we have used experimentally realizable
parameters and included self-inductances. We have uncovered two families of
rotobreathers. Both types are stable under thermal fluctuations and exist for a
broad range of array parameters and sizes including arrays as small as a single
plaquette. We suggest a single Josephson-junction plaquette as an ideal system
to experimentally investigate these solutions.Comment: 5 pages, 5 figure, to appear June 1, 1999 in PR
Laser Light Sheet Flow Visualization of the Space Launch System Booster Separation Test
Planar flow visualizations were obtained in a wind tunnel test in the NASA Langley Research Centers Unitary Plan Wind Tunnel using the laser-light-sheet method. This method uses a laser to illuminate fine particles generated in the wind tunnel to visualize flow structures. The test article was designed to simulate the separation of the two solid rocket boosters (SRBs) from the core stage of the NASA Space Launch System (SLS) at Mach 4 using a scale model. The test was run on of the SLS Block 1B Cargo (27005) configuration and the SLS Block 1B Crew (28005) configuration. Planar flow visualization was obtained only on the crew configuration. Air at pressures up to 1500 psi was used to simulate plumes from the booster separation motors (BSMs) located at the nose, and aft skirt of the two boosters. The facility free stream was seeded with water vapor, which condensed and froze into small ice crystals in the tunnel nozzle expansion. A continuous wave green (532 nm) laser sheet was used to illuminate the ice crystals, and the resulting Mie-scattered light was collected with a camera. The resulting images clearly identify shock waves and other flow features including BSM plume shapes. Measurements were acquired for different BSM pressures and booster separation locations
Protein folding mediated by solvation: water expelling and formation of the hydrophobic core occurs after the structure collapse
The interplay between structure-search of the native structure and
desolvation in protein folding has been explored using a minimalist model.
These results support a folding mechanism where most of the structural
formation of the protein is achieved before water is expelled from the
hydrophobic core. This view integrates water expulsion effects into the funnel
energy landscape theory of protein folding. Comparisons to experimental results
are shown for the SH3 protein. After the folding transition, a near-native
intermediate with partially solvated hydrophobic core is found. This transition
is followed by a final step that cooperatively squeezes out water molecules
from the partially hydrated protein core.Comment: Proceedings of the National Academy of Science, 2002, Vol.99. 685-69
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