1,484 research outputs found
Optical quenching and recovery of photoconductivity in single-crystal diamond
We study the photocurrent induced by pulsed-light illumination (pulse
duration is several nanoseconds) of single-crystal diamond containing nitrogen
impurities. Application of additional continuous-wave light of the same
wavelength quenches pulsed photocurrent. Characterization of the optically
quenched photocurrent and its recovery is important for the development of
diamond based electronics and sensing
FEATURE SELECTION APPLIED TO THE TIME-FREQUENCY REPRESENTATION OF MUSCLE NEAR-INFRARED SPECTROSCOPY (NIRS) SIGNALS: CHARACTERIZATION OF DIABETIC OXYGENATION PATTERNS
Diabetic patients might present peripheral microcirculation impairment and might benefit from physical training. Thirty-nine diabetic patients underwent the monitoring of the tibialis anterior muscle oxygenation during a series of voluntary ankle flexo-extensions by near-infrared spectroscopy (NIRS). NIRS signals were acquired before and after training protocols. Sixteen control subjects were tested with the same protocol. Time-frequency distributions of the Cohen's class were used to process the NIRS signals relative to the concentration changes of oxygenated and reduced hemoglobin. A total of 24 variables were measured for each subject and the most discriminative were selected by using four feature selection algorithms: QuickReduct, Genetic Rough-Set Attribute Reduction, Ant Rough-Set Attribute Reduction, and traditional ANOVA. Artificial neural networks were used to validate the discriminative power of the selected features. Results showed that different algorithms extracted different sets of variables, but all the combinations were discriminative. The best classification accuracy was about 70%. The oxygenation variables were selected when comparing controls to diabetic patients or diabetic patients before and after training. This preliminary study showed the importance of feature selection techniques in NIRS assessment of diabetic peripheral vascular impairmen
Dialogue based interfaces for universal access.
Conversation provides an excellent means of communication for almost all people. Consequently, a conversational interface is an excellent mechanism for allowing people to interact with systems. Conversational systems are an active research area, but a wide range of systems can be developed with current technology. More sophisticated interfaces can take considerable effort, but simple interfaces can be developed quite rapidly. This paper gives an introduction to the current state of the art of conversational systems and interfaces. It describes a methodology for developing conversational interfaces and gives an example of an interface for a state benefits web site. The paper discusses how this interface could improve access for a wide range of people, and how further development of this interface would allow a larger range of people to use the system and give them more functionality
Microscopic mechanism for mechanical polishing of diamond (110) surfaces
Mechanically induced degradation of diamond, as occurs during polishing, is
studied using total--energy pseudopotential calculations. The strong asymmetry
in the rate of polishing between different directions on the diamond (110)
surface is explained in terms of an atomistic mechanism for nano--groove
formation. The post--polishing surface morphology and the nature of the
polishing residue predicted by this mechanism are consistent with experimental
evidence.Comment: 4 pages, 5 figure
Central neuropeptide Y infusion and melanocortin 4 receptor antagonism inhibit thyrotropic function by divergent pathways
Squeezing superfluid from a stone: Coupling superfluidity and elasticity in a supersolid
In this work we start from the assumption that normal solid to supersolid
(NS-SS) phase transition is continuous, and develop a phenomenological Landau
theory of the transition in which superfluidity is coupled to the elasticity of
the crystalline He lattice. We find that the elasticity does not affect the
universal properties of the superfluid transition, so that in an unstressed
crystal the well-known -anomaly in the heat capacity of the superfluid
transition should also appear at the NS-SS transition. We also find that the
onset of supersolidity leads to anomalies in the elastic constants near the
transition; conversely, inhomogeneous strains in the lattice can induce local
variations of the superfluid transition temperature, leading to a broadened
transition.Comment: 4 page
One Health approach to controlling a Q fever outbreak on an Australian goat farm
A recent outbreak of Q fever was linked to an intensive goat and sheep dairy farm in Victoria, Australia, 2012-2014. Seventeen employees and one family member were confirmed with Q fever over a 28-month period, including two culture-positive cases. The outbreak investigation and management involved a One Health approach with representation from human, animal, environmental and public health. Seroprevalence in non-pregnant milking goats was 15% [95% confidence interval (CI) 7–27]; active infection was confirmed by positive quantitative PCR on several animal specimens. Genotyping of Coxiella burnetii DNA obtained from goat and human specimens was identical by two typing methods. A number of farming practices probably contributed to the outbreak, with similar precipitating factors to the Netherlands outbreak, 2007-2012. Compared to workers in a high-efficiency particulate arrestance (HEPA) filtered factory, administrative staff in an unfiltered adjoining office and those regularly handling goats and kids had 5·49 (95% CI 1·29–23·4) and 5·65 (95% CI 1·09–29·3) times the risk of infection, respectively; suggesting factory workers were protected from windborne spread of organisms. Reduction in the incidence of human cases was achieved through an intensive human vaccination programme plus environmental and biosecurity interventions. Subsequent non-occupational acquisition of Q fever in the spouse of an employee, indicates that infection remains endemic in the goat herd, and remains a challenge to manage without source control
Statistics of Atmospheric Correlations
For a large class of quantum systems the statistical properties of their
spectrum show remarkable agreement with random matrix predictions. Recent
advances show that the scope of random matrix theory is much wider. In this
work, we show that the random matrix approach can be beneficially applied to a
completely different classical domain, namely, to the empirical correlation
matrices obtained from the analysis of the basic atmospheric parameters that
characterise the state of atmosphere. We show that the spectrum of atmospheric
correlation matrices satisfy the random matrix prescription. In particular, the
eigenmodes of the atmospheric empirical correlation matrices that have physical
significance are marked by deviations from the eigenvector distribution.Comment: 8 pages, 9 figs, revtex; To appear in Phys. Rev.
Large Deviations of the Maximum Eigenvalue for Wishart and Gaussian Random Matrices
We present a simple Coulomb gas method to calculate analytically the
probability of rare events where the maximum eigenvalue of a random matrix is
much larger than its typical value. The large deviation function that
characterizes this probability is computed explicitly for Wishart and Gaussian
ensembles. The method is quite general and applies to other related problems,
e.g. the joint large deviation function for large fluctuations of top
eigenvalues. Our results are relevant to widely employed data compression
techniques, namely the principal components analysis. Analytical predictions
are verified by extensive numerical simulations.Comment: 4 pages, 3 .eps figures include
Electromagnetic energy penetration in the self-induced transparency regime of relativistic laser-plasma interactions
Two scenarios for the penetration of relativistically intense laser radiation
into an overdense plasma, accessible by self-induced transparency, are
presented. For supercritical densities less than 1.5 times the critical one,
penetration of laser energy occurs by soliton-like structures moving into the
plasma. At higher background densities laser light penetrates over a finite
length only, that increases with the incident intensity. In this regime
plasma-field structures represent alternating electron layers separated by
about half a wavelength by depleted regions.Comment: 9 pages, 4 figures, submitted for publication to PR
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