23,197 research outputs found
Determining DfT Hardware by VHDL-AMS Fault Simulation for Biological Micro-Electronic Fluidic Arrays
The interest of microelectronic fluidic arrays for biomedical applications, like DNA determination, is rapidly increasing. In order to evaluate these systems in terms of required Design-for-Test structures, fault simulations in both fluidic and electronic domains are necessary. VHDL-AMS can be used successfully in this case. This paper shows a highly testable architecture of a DNA Bio-Sensing array, its basic sensing concept, fluidic modeling and sensitivity analysis. The overall VHDL-AMS fault simulation of the system is shown
Turbulent Pair Diffusion
Kinematic Simulations of turbulent pair diffusion in planar turbulence with a
-5/3 energy spectrum reproduce the results of the laboratory measurements of
Jullien Phys. Rev. Lett. 82, 2872 (1999), in particular the stretched
exponential form of the PDF of pair separations and their correlation
functions. The root mean square separation is found to be strongly dependent on
initial conditions for very long stretches of times. This dependence is
consistent with the topological picture of turbulent pair diffusion where pairs
initially close enough travel together for long stretches of time and separate
violently when they meet straining regions around hyperbolic points. A new
argument based on the divergence of accelerations is given to support this
picture
Dispersion of tracer particles in a compressible flow
The turbulent diffusion of Lagrangian tracer particles has been studied in a
flow on the surface of a large tank of water and in computer simulations. The
effect of flow compressibility is captured in images of particle fields. The
velocity field of floating particles has a divergence, whose probability
density function shows exponential tails. Also studied is the motion of pairs
and triplets of particles. The mean square separation is fitted to
the scaling form ~ t^alpha, and in contrast with the
Richardson-Kolmogorov prediction, an extended range with a reduced scaling
exponent of alpha=1.65 pm 0.1 is found. Clustering is also manifest in strongly
deformed triangles spanned within triplets of tracers.Comment: 6 pages, 4 figure
A method for spatial deconvolution of spectra
A method for spatial deconvolution of spectra is presented. It follows the
same fundamental principles as the ``MCS image deconvolution algorithm''
(Magain, Courbin, Sohy, 1998) and uses information contained in the spectrum of
a reference Point Spread Function (PSF) to spatially deconvolve spectra of very
blended sources. An improved resolution rather than an infinite one is aimed
at, overcoming the well known problem of ``deconvolution artefacts''. As in the
MCS algorithm, the data are decomposed into a sum of analytical point sources
and a numerically deconvolved background, so that the spectrum of extended
sources in the immediate vicinity of bright point sources may be accurately
extracted and sharpened. The algorithm has been tested on simulated data
including seeing variation as a function of wavelength and atmospheric
refraction. It is shown that the spectra of severely blended point sources can
be resolved while fully preserving the spectrophotometric properties of the
data. Extended objects ``hidden'' by bright point sources (up to 4-5 magnitudes
brighter) can be accurately recovered as well, provided the data have a
sufficiently high total signal-to-noise ratio (200-300 per spectral resolution
element). Such spectra are relatively easy to obtain, even down to faint
magnitudes, within a few hours of integration time with 10m class telescopes.Comment: 18 pages, 6 postscript figures, in press in Ap
Multichannel wavelength conversion of 40 Gbit/s NRZ DPSK signals in a highly nonlinear dispersion flattened lead silicate fibre
We experimentally demonstrate the wavelength conversion of three wavelength multiplexed 40 Gbit/s Differential Phase Shift Keyed (DPSK) signals in a 2.2m length of highly nonlinear, dispersion tailored W-type lead-silicate optical fibre
X-ray emission from PSR B1800-21, its wind nebula, and similar systems
We detected X-ray emission from PSR B1800-21 and its synchrotron nebula with
the Chandra X-ray Observatory. The pulsar's observed flux is (1.4+/-0.2)
10^{-14} ergs cm^{-2} s^{-1} in the 1-6 keV band. The spectrum can be described
by a two-component PL+BB model, suggesting a mixture of thermal and
magnetospheric emission. For a plausible hydrogen column density n_{H}=1.4
10^{22} cm^{-2}, the PL component has a slope Gamma=1.4+/-0.6 and a luminosity
L_{psr}^{nonth}=4 10^{31}(d/4 kpc)^2 ergs s^{-1}. The properties of the thermal
component (kT=0.1-0.3 keV, L^{bol}=10^{31}-10^{33} ergs s^{-1}) are very poorly
constrained because of the strong interstellar absorption. The compact,
7''\times4'', inner pulsar-wind nebula (PWN), elongated perpendicular to the
pulsar's proper motion, is immersed in a fainter asymmetric emission. The
observed flux of the PWN is (5.5+/-0.6) 10^{-14} ergs cm^{-2} s^{-1} in the 1-8
keV band. The PWN spectrum fits by a PL model with Gamma=1.6+/-0.3, L=1.6
10^{32} (d/4 kpc})^2 ergs s^{-1}. The shape of the inner PWN suggests that the
pulsar moves subsonically and X-ray emission emerges from a torus associated
with the termination shock in the equatorial pulsar wind. The inferred
PWN-pulsar properties (e.g., the PWN X-ray efficiency, L_{pwn}/\dot{E}~10^{-4};
the luminosity ratio, L_{pwn}/L_{psr}^{nonth}=4; the pulsar wind pressure at
the termination shock, p_s=10^{-9} ergs cm^{-3}) are very similar to those of
other subsonically moving Vela-like objects detected with Chandra
(L_{pwn}/\dot{E}=10^{-4.5}-10^{-3.5}, L_{pwn}/L_{psr}^{nonth}~5,
p_s=10^{-10}-10^{-8} ergs cm^{-1}).Comment: 11 pages, 10 figures, 2 tables; submitted to ApJ. Version with the
high-resolution figures is available at
http://www.astro.psu.edu/users/green/B1800/B1800_ApJ.pd
Reaction Diffusion and Ballistic Annihilation Near an Impenetrable Boundary
The behavior of the single-species reaction process is examined
near an impenetrable boundary, representing the flask containing the reactants.
Two types of dynamics are considered for the reactants: diffusive and ballistic
propagation. It is shown that the effect of the boundary is quite different in
both cases: diffusion-reaction leads to a density excess, whereas ballistic
annihilation exhibits a density deficit, and in both cases the effect is not
localized at the boundary but penetrates into the system. The field-theoretic
renormalization group is used to obtain the universal properties of the density
excess in two dimensions and below for the reaction-diffusion system. In one
dimension the excess decays with the same exponent as the bulk and is found by
an exact solution. In two dimensions the excess is marginally less relevant
than the bulk decay and the density profile is again found exactly for late
times from the RG-improved field theory. The results obtained for the diffusive
case are relevant for Mg or Cd doping in the TMMC crystal's
exciton coalescence process and also imply a surprising result for the dynamic
magnetization in the critical one-dimensional Ising model with a fixed spin.
For the case of ballistic reactants, a model is introduced and solved exactly
in one dimension. The density-deficit profile is obtained, as is the density of
left and right moving reactants near the impenetrable boundary.Comment: to appear in J. Phys.
Significance of low energy impact damage on modal parameters of composite beams by design of experiments
This paper presents an experimental study on the effects of multi-site damage on the vibration response of composite beams damaged by low energy impacts around the barely visible impact damage limit (BVID). The variation of the modal parameters with different levels of impact energy and density of damage is studied. Vibration tests have been carried out with both burst random and classical sine dwell excitations in order to compare that which of the methods among Polymax and Half Bandwidth Method is more suitable for damping estimation in the presence of damage. Design of experiments (DOE) performed on the experimental data show that natural frequency is a more sensitive parameter for damage detection than the damping ratio. It also highlighted energy of impact as the factor having a more significant effect on the modal parameters. Half Bandwidth Method is found to be unsuitable for damping estimation in the presence of damage
The monetary benefit of early flood warnings in Europe
Effective disaster risk management relies on science-based solutions to close the gap between prevention and preparedness measures. The consultation on the United Nations post-2015 framework for disaster risk reduction highlights the need for cross-border early warning systems to strengthen the preparedness phases of disaster risk management, in order to save lives and property and reduce the overall impact of severe events. Continental and global scale flood forecasting systems provide vital early flood warning information to national and international civil protection authorities, who can use this information to make decisions on how to prepare for upcoming floods. Here the potential monetary benefits of early flood warnings are estimated based on the forecasts of the continental-scale European Flood Awareness System (EFAS) using existing flood damage cost information and calculations of potential avoided flood damages. The benefits are of the order of 400 Euro for every 1 Euro invested. A sensitivity analysis is performed in order to test the uncertainty in the method and develop an envelope of potential monetary benefits of EFAS warnings. The results provide clear evidence that there is likely a substantial monetary benefit in this cross-border continental-scale flood early warning system. This supports the wider drive to implement early warning systems at the continental or global scale to improve our resilience to natural hazards
Jahn-Teller stabilization of a "polar" metal oxide surface: Fe3O4(001)
Using ab initio thermodynamics we compile a phase diagram for the surface of
Fe3O4(001) as a function of temperature and oxygen pressures. A hitherto
ignored polar termination with octahedral iron and oxygen forming a wave-like
structure along the [110]-direction is identified as the lowest energy
configuration over a broad range of oxygen gas-phase conditions. This novel
geometry is confirmed in a x-ray diffraction analysis. The stabilization of the
Fe3O4(001)-surface goes together with dramatic changes in the electronic and
magnetic properties, e.g., a halfmetal-to-metal transition.Comment: 4 pages, 4 figure
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