1,000 research outputs found
Wide range and tunable linear TMR sensor using two exchange pinned electrodes
A magnetic tunnel junction sensor is proposed, with both the detection and
the reference layers pinned by IrMn. Using the differences in the blocking
temperatures of the IrMn films with different thicknesses, crossed anisotropies
can be induced between the detection and the reference electrodes. The pinning
of the sensing electrode ensures a linear and reversible output. It also allows
tuning both the sensitivity and the linear range of the sensor. The authors
show that the sensitivity varies linearly with the ferromagnetic thickness of
the detection electrode. It is demonstrated that an increased thickness leads
to a rise of sensitivity and a reduction of the operating range
Coupling techniques for nonlinear hyperbolic equations. III. The well-balanced approximation of thick interfaces
We continue our analysis of the coupling between nonlinear hyperbolic
problems across possibly resonant interfaces. In the first two parts of this
series, we introduced a new framework for coupling problems which is based on
the so-called thin interface model and uses an augmented formulation and an
additional unknown for the interface location; this framework has the advantage
of avoiding any explicit modeling of the interface structure. In the present
paper, we pursue our investigation of the augmented formulation and we
introduce a new coupling framework which is now based on the so-called thick
interface model. For scalar nonlinear hyperbolic equations in one space
variable, we observe that the Cauchy problem is well-posed. Then, our main
achievement in the present paper is the design of a new well-balanced finite
volume scheme which is adapted to the thick interface model, together with a
proof of its convergence toward the unique entropy solution (for a broad class
of nonlinear hyperbolic equations). Due to the presence of a possibly resonant
interface, the standard technique based on a total variation estimate does not
apply, and DiPerna's uniqueness theorem must be used. Following a method
proposed by Coquel and LeFloch, our proof relies on discrete entropy
inequalities for the coupling problem and an estimate of the discrete entropy
dissipation in the proposed scheme.Comment: 21 page
New DRIE-Patterned Electrets for Vibration Energy Harvesting
This paper is about a new manufacturing process aimed at developing stable
SiO2/Si3N4 patterned electrets using a Deep Reactive Ion Etching (DRIE) step
for an application in electret-based Vibration Energy Harvesters (e-VEH). This
process consists in forming continuous layers of SiO2/Si3N4 electrets in order
to limit surface conduction phenomena and is a new way to see the problem of
electret patterning. Experimental results prove that patterned electrets
charged by a positive corona discharge show excellent stability with high
surface charge densities that may reach 5mC/m^2 on 1.1\mu m-thick layers, even
with fine patterning and harsh temperature conditions (up to 250{\deg}C). This
paves the way to new e-VEH designs and manufacturing processes.Comment: Proc. European Energy Conference, 201
Conversion of Lignocellulosic Biomass in Biobutanol by a Novel Thermal Process
This work aims at demonstrating the possibility of producing 2-butanol from lignocellulosic biomass through a new thermochemical approach. The production of biobutanol was carried out using different lignocellulosic feedstock through a 3-step process: first the whole lignocellulosic biomass is hydrolyzed under acid catalyst to produce levulinates, then the levulinates go through decarboxylation to produce 2-butanone which is, in a final step, reduced to produce of 2-butanol. The experimental conditions for the first two steps of the process were optimized using the response surface methodology (RSM). The latter could represent an opportunity for the production of economical second-generation butanol without having to go through the classical pathway requiring the production of sugar prior to microbial conversion.The authors are grateful for the financial support to MITACS (Grant number ITO3931) and for the grant to the Natural Sciences and Engineering Research Council of Canada (NSERC, Grant number EGP 487206-15)
From LTL and Limit-Deterministic B\"uchi Automata to Deterministic Parity Automata
Controller synthesis for general linear temporal logic (LTL) objectives is a
challenging task. The standard approach involves translating the LTL objective
into a deterministic parity automaton (DPA) by means of the Safra-Piterman
construction. One of the challenges is the size of the DPA, which often grows
very fast in practice, and can reach double exponential size in the length of
the LTL formula. In this paper we describe a single exponential translation
from limit-deterministic B\"uchi automata (LDBA) to DPA, and show that it can
be concatenated with a recent efficient translation from LTL to LDBA to yield a
double exponential, \enquote{Safraless} LTL-to-DPA construction. We also report
on an implementation, a comparison with the SPOT library, and performance on
several sets of formulas, including instances from the 2016 SyntComp
competition
The Role of GC-Biased Gene Conversion in Shaping the Fastest Evolving Regions of the Human Genome
GC-biased gene conversion (gBGC) is a recombination-associated evolutionary process that accelerates the fixation of guanine or cytosine alleles, regardless of their effects on fitness. gBGC can increase the overall rate of substitutions, a hallmark of positive selection. Many fast-evolving genes and noncoding sequences in the human genome have GC-biased substitution patterns, suggesting that gBGC—in contrast to adaptive processes—may have driven the human changes in these sequences. To investigate this hypothesis, we developed a substitution model for DNA sequence evolution that quantifies the nonlinear interacting effects of selection and gBGC on substitution rates and patterns. Based on this model, we used a series of lineage-specific likelihood ratio tests to evaluate sequence alignments for evidence of changes in mode of selection, action of gBGC, or both. With a false positive rate of less than 5% for individual tests, we found that the majority (76%) of previously identified human accelerated regions are best explained without gBGC, whereas a substantial minority (19%) are best explained by the action of gBGC alone. Further, more than half (55%) have substitution rates that significantly exceed local estimates of the neutral rate, suggesting that these regions may have been shaped by positive selection rather than by relaxation of constraint. By distinguishing the effects of gBGC, relaxation of constraint, and positive selection we provide an integrated analysis of the evolutionary forces that shaped the fastest evolving regions of the human genome, which facilitates the design of targeted functional studies of adaptation in humans
A Model-Based Analysis of GC-Biased Gene Conversion in the Human and Chimpanzee Genomes
GC-biased gene conversion (gBGC) is a recombination-associated process that favors the fixation of G/C alleles over A/T alleles. In mammals, gBGC is hypothesized to contribute to variation in GC content, rapidly evolving sequences, and the fixation of deleterious mutations, but its prevalence and general functional consequences remain poorly understood. gBGC is difficult to incorporate into models of molecular evolution and so far has primarily been studied using summary statistics from genomic comparisons. Here, we introduce a new probabilistic model that captures the joint effects of natural selection and gBGC on nucleotide substitution patterns, while allowing for correlations along the genome in these effects. We implemented our model in a computer program, called phastBias, that can accurately detect gBGC tracts about 1 kilobase or longer in simulated sequence alignments. When applied to real primate genome sequences, phastBias predicts gBGC tracts that cover roughly 0.3% of the human and chimpanzee genomes and account for 1.2% of human-chimpanzee nucleotide differences. These tracts fall in clusters, particularly in subtelomeric regions; they are enriched for recombination hotspots and fast-evolving sequences; and they display an ongoing fixation preference for G and C alleles. They are also significantly enriched for disease-associated polymorphisms, suggesting that they contribute to the fixation of deleterious alleles. The gBGC tracts provide a unique window into historical recombination processes along the human and chimpanzee lineages. They supply additional evidence of long-term conservation of megabase-scale recombination rates accompanied by rapid turnover of hotspots. Together, these findings shed new light on the evolutionary, functional, and disease implications of gBGC. The phastBias program and our predicted tracts are freely available. © 2013 Capra et al
Tests of achromatic phase shifters performed on the SYNAPSE test bench: a progress report
The achromatic phase shifter (APS) is a component of the Bracewell nulling
interferometer studied in preparation for future space missions (viz.
Darwin/TPF-I) focusing on spectroscopic study of Earth-like exo-planets.
Several possible designs of such an optical subsystem exist. Four approaches
were selected for further study. Thales Alenia Space developed a dielectric
prism APS. A focus crossing APS prototype was developed by the OCA, Nice,
France. A field reversal APS prototype was prepared by the MPIA in Heidelberg,
Germany. Centre Spatial de Li\`ege develops a concept based on Fresnel's
rhombs. This paper presents a progress report on the current work aiming at
evaluating these prototypes on the SYNAPSE test bench at the Institut
d'Astrophysique Spatiale in Orsay, France
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