115,540 research outputs found
Compressive Sensing DNA Microarrays
Compressive sensing microarrays (CSMs) are DNA-based sensors that operate using group testing and compressive sensing (CS) principles. In contrast to conventional DNA microarrays, in which each genetic sensor is designed to respond to a single target, in a CSM, each sensor responds to a set of targets. We study the problem of designing CSMs that simultaneously account for both the constraints from CS theory and the biochemistry of probe-target DNA hybridization. An appropriate cross-hybridization model is proposed for CSMs, and several methods are developed for probe design and CS signal recovery based on the new model. Lab experiments suggest that in order to achieve accurate hybridization profiling, consensus probe sequences are required to have sequence homology of at least 80% with all targets to be detected. Furthermore, out-of-equilibrium datasets are usually as accurate as those obtained from equilibrium conditions. Consequently, one can use CSMs in applications in which only short hybridization times are allowed
Superconductivity in the -carbide-type oxides Zr4Rh2Ox
We report on the synthesis and the superconductivity of ZrRhO
( = 0.4, 0.5, 0.6, 0.7, 1.0). These compounds crystallize in the
-carbide structure, which is a filled version of the complex
intermetallic TiNi structure. We find that in the system
ZrRhO, already a small amount ( 0.4) of oxygen addition
stabilizes the -carbide structure over the more common intermetallic
CuAl structure-type, in which ZrRh crystallizes. We show that
ZrRhO and ZrRhO are bulk superconductors with critical
temperatures of 2.8 K and 4.7 K in the resistivity, respectively.
Our analysis of the superconducting properties reveal both compounds to be
strongly type-II superconductors with critical fields up to (0)
8.8 mT and (0) 6.08 T. Our results support
that the -carbides are a versatile family of compounds for the
investigation of the interplay of interstitial doping on physical properties,
especially for superconductivity
Shape-induced magnetic anisotropy in dilute magnetic alloys
We extend the theory of the surface-induced magnetic anisotropy to mesoscopic
samples with arbitrary geometry. The shape-induced anisotropy of impurity spins
in small brick-shaped grains of dilute magnetic alloys is studied in detail.
The surface-induced blocking of a magnetic-impurity spin is shown to be very
sensitive to geometric parameters of a grain. This implies that the apparent
discrepancy between the experimental data of different groups on the size
dependence of the Kondo resistivity can result from different microstructure of
the used samples. In order to interpret recent experimental data on the
anomalous Hall effect in thin polycrystalline Fe doped Au films, we analyse the
magnetisation of impurity spins as a function of the impurity position and of
the grain shape.Comment: 10 pages, 6 figures, E-mail addresses: [email protected],
[email protected], [email protected]
Instability-induced formation and non-equilibrium dynamics of phase defects in polariton condensates
We study, theoretically and numerically, the onset and development of
modulational instability in an incoherently pumped spatially homogeneous
polariton condensate. Within the framework of mean-field theory, we identify
regimes of modulational instability in two cases: 1) Strong feedback between
the condensate and reservoir, which may occur in scalar condensates, and 2)
Parametric scattering in the presence of polarization splitting in spinor
condensates. In both cases we investigate the instability induced textures in
space and time including non-equilibrium dynamics of phase dislocations and
vortices. In particular we discuss the mechanism of vortex destabilization and
formation of spiraling waves. We also identify the presence of topological
defects, which take the form of half-vortex pairs in the spinor case, giving an
"eyelet" structure in intensity and dipole type structure in the spin
polarization. In the modulationally stable parameter domains, we observe
formation of the phase defects in the process of condensate formation from an
initially spatially incoherent low-density state. In analogy to the
Kibble-Zurek type scaling for nonequilibrium phase transitions, we find that
the defect density scales with the pumping rate.Comment: 13 pages, 9 figures, revised manuscript sent to Phys. Rev.
Observation of magnetization reversal in epitaxial Gd0.67Ca0.33MnO3 thin films
High quality epitaxial thin films of Gd0.67Ca0.33MnO3 have been deposited
onto (100) SrTiO3 substrates by pulsed-laser deposition. Enhanced properties in
comparison with bulk samples were observed. The magnetic transition temperature
(Tc) of the as-grown films is much higher than the corresponding bulk values.
Most interestingly, magnetization measurements performed under small applied
fields, exhibit magnetization reversals below Tc, no matter whether the film is
field-cooled (FC) or zero-field-cooled (ZFC). A rapid magnetization reversal
occurs at 7 K when field cooled, while as for the ZFC process the magnetization
decreases gradually with increasing temperatures, taking negative values above
7 K and changing to positive values again, above 83 K. In higher magnetic
fields the magnetization does not change sign. The reversal mechanism is
discussed in terms of a negative exchange f-d interaction and magnetic
anisotropy, this later enhanced by strain effects induced by the lattice
mismatch between the film and the substrate.Comment: 16 pages, 4 figure
Altruism and Voluntary Provision of Public Goods.
We study how people's predisposition towards altruism, as measured by tools developed by psychologists, affects their behaviour in a voluntary contributions public good environment. Earlier experiments provide evidence against the strong free rider hypothesis; however, contributions to the public good decrease with repetition. We investigate whether a high level of contributions can be sustained in groups of subjects who have been pre-selected on the basis of their altruistic inclinations. In the first stage of the experiment, each subject responds to a psychology questionnaire that measures various dimensions of one's personality. The subjects are then matched in groups according to their altruism scores, and engage in a voluntary contribution game. We consider whether the levels and dynamics of group contributions differ significantly between the groups with altruists and non-altruists. We find that subjects' altruism has a weak but positive effect on group behaviour in the public good game.PUBLIC OWNERSHIP ; BEHAVIOUR ; GAMES
Using surveys of Affymetrix GeneChips to study antisense expression.
We have used large surveys of Affymetrix GeneChip data in the public domain to conduct a study of antisense expression across diverse conditions. We derive correlations between groups of probes which map uniquely to the same exon in the antisense direction. When there are no probes assigned to an exon in the sense direction we find that many of the antisense groups fail to detect a coherent block of transcription. We find that only a minority of these groups contain coherent blocks of antisense expression suggesting transcription. We also derive correlations between groups of probes which map uniquely to the same exon in both sense and antisense direction. In some of these cases the locations of sense probes overlap with the antisense probes, and the sense and antisense probe intensities are correlated with each other. This configuration suggests the existence of a Natural Antisense Transcript (NAT) pair. We find the majority of such NAT pairs detected by GeneChips are formed by a transcript of an established gene and either an EST or an mRNA. In order to determine the exact antisense regulatory mechanism indicated by the correlation of sense probes with antisense probes, a further investigation is necessary for every particular case of interest. However, the analysis of microarray data has proved to be a good method to reconfirm known NATs, discover new ones, as well as to notice possible problems in the annotation of antisense transcripts
Locking classical information
It is known that the maximum classical mutual information that can be
achieved between measurements on a pair of quantum systems can drastically
underestimate the quantum mutual information between those systems. In this
article, we quantify this distinction between classical and quantum information
by demonstrating that after removing a logarithmic-sized quantum system from
one half of a pair of perfectly correlated bitstrings, even the most sensitive
pair of measurements might only yield outcomes essentially independent of each
other. This effect is a form of information locking but the definition we use
is strictly stronger than those used previously. Moreover, we find that this
property is generic, in the sense that it occurs when removing a random
subsystem. As such, the effect might be relevant to statistical mechanics or
black hole physics. Previous work on information locking had always assumed a
uniform message. In this article, we assume only a min-entropy bound on the
message and also explore the effect of entanglement. We find that classical
information is strongly locked almost until it can be completely decoded. As a
cryptographic application of these results, we exhibit a quantum key
distribution protocol that is "secure" if the eavesdropper's information about
the secret key is measured using the accessible information but in which
leakage of even a logarithmic number of key bits compromises the secrecy of all
the others.Comment: 32 pages, 2 figure
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