7,504 research outputs found
Self-Repairing Disk Arrays
As the prices of magnetic storage continue to decrease, the cost of replacing
failed disks becomes increasingly dominated by the cost of the service call
itself. We propose to eliminate these calls by building disk arrays that
contain enough spare disks to operate without any human intervention during
their whole lifetime. To evaluate the feasibility of this approach, we have
simulated the behavior of two-dimensional disk arrays with n parity disks and
n(n-1)/2 data disks under realistic failure and repair assumptions. Our
conclusion is that having n(n+1)/2 spare disks is more than enough to achieve a
99.999 percent probability of not losing data over four years. We observe that
the same objectives cannot be reached with RAID level 6 organizations and would
require RAID stripes that could tolerate triple disk failures.Comment: Part of ADAPT Workshop proceedings, 2015 (arXiv:1412.2347
Self-Assembled Triply Periodic Minimal Surfaces as moulds for Photonic Band Gap Materials
We propose systems with structures defined by self-assembled triply periodic
minimal surfaces (STPMS) as candidates for photonic bandgap materials. To
support our proposal we have calculated the photonic bands for different STPMS
and we have found that, at least, the double diamond and gyroid structures
present full photonic bandgaps. Given the great variety of systems which
crystalize in these structures, the diversity of possible materials that form
them and the range of lattice constants they present, the construction of
photonic bandgap materials with gaps in the visible range may be presently
within reach.Comment: 3 pages, 2 figures, RevTe
Search for low-mass WIMPs in a 0.6 kg day exposure of the DAMIC experiment at SNOLAB
We present results of a dark matter search performed with a 0.6 kg day
exposure of the DAMIC experiment at the SNOLAB underground laboratory. We
measure the energy spectrum of ionization events in the bulk silicon of
charge-coupled devices down to a signal of 60 eV electron equivalent. The data
are consistent with radiogenic backgrounds, and constraints on the
spin-independent WIMP-nucleon elastic-scattering cross section are accordingly
placed. A region of parameter space relevant to the potential signal from the
CDMS-II Si experiment is excluded using the same target for the first time.
This result obtained with a limited exposure demonstrates the potential to
explore the low-mass WIMP region (<10 GeV/) of the upcoming DAMIC100, a
100 g detector currently being installed in SNOLAB.Comment: 11 pages, 11 figure
Comprehensive characterization of molecular interactions based on nanomechanics
Molecular interaction is a key concept in our understanding of the biological mechanisms of life. Two physical properties change when one molecular partner binds to another. Firstly, the masses combine and secondly, the structure of at least one binding partner is altered, mechanically transducing the binding into subsequent biological reactions. Here we present a nanomechanical micro-array technique for bio-medical research, which not only monitors the binding of effector molecules to their target but also the subsequent effect on a biological system in vitro. This label-free and real-time method directly and simultaneously tracks mass and nanomechanical changes at the sensor interface using micro-cantilever technology. To prove the concept we measured lipid vesicle (approximately 748*10(6) Da) adsorption on the sensor interface followed by subsequent binding of the bee venom peptide melittin (2840 Da) to the vesicles. The results show the high dynamic range of the instrument and that measuring the mass and structural changes simultaneously allow a comprehensive discussion of molecular interactions
The SEURAT-1 Approach towards Animal Free Human Safety Assessment
SEURAT-1 is a European public-private research consortium that is working towards animal-free testing of chemical compounds and the highest level of consumer protection. A research strategy was formulated based on the guiding principle to adopt a toxicological mode-of-action framework to describe how any substance may adversely affect human health. The proof of the initiative will be in demonstrating the applicability of the concepts on which SEURAT-1 is built on three levels: (i) Theoretical prototypes for adverse outcome pathways are formulated based on knowledge already available in the scientific literature on investigating the toxicological modes-of-action leading to adverse outcomes (addressing mainly liver toxicity); (ii) adverse outcome pathway descriptions are used as a guide for the formulation of case studies to further elucidate the theoretical model and to develop integrated testing strategies for the prediction of certain toxicological effects (i.e., those related to the adverse outcome pathway descriptions); (iii) further case studies target the application of knowledge gained within SEURAT-1 in the context of safety assessment. The ultimate goal would be to perform ab initio predictions based on a complete understanding of toxicological mechanisms. In the near-term, it is more realistic that data from innovative testing methods will support read-across arguments. Both scenarios are addressed with case studies for improved safety assessment. A conceptual framework for a rational integrated assessment strategy emerged from designing the case studies and is discussed in the context of international developments focusing on alternative approaches for evaluating chemicals using the new 21st century tools for toxicity testing
Correspondence between kinematical backreaction and scalar field cosmologies - the `morphon field'
Spatially averaged inhomogeneous cosmologies in classical general relativity
can be written in the form of effective Friedmann equations with sources that
include backreaction terms. In this paper we propose to describe these
backreaction terms with the help of a homogeneous scalar field evolving in a
potential; we call it the `morphon field'. This new field links classical
inhomogeneous cosmologies to scalar field cosmologies, allowing to reinterpret,
e.g., quintessence scenarios by routing the physical origin of the scalar field
source to inhomogeneities in the Universe. We investigate a one-parameter
family of scaling solutions to the backreaction problem. Subcases of these
solutions (all without an assumed cosmological constant) include
scale-dependent models with Friedmannian kinematics that can mimic the presence
of a cosmological constant or a time-dependent cosmological term. We explicitly
reconstruct the scalar field potential for the scaling solutions, and discuss
those cases that provide a solution to the Dark Energy and coincidence
problems. In this approach, Dark Energy emerges from morphon fields, a
mechanism that can be understood through the proposed correspondence: the
averaged cosmology is characterized by a weak decay (quintessence) or growth
(phantom quintessence) of kinematical fluctuations, fed by `curvature energy'
that is stored in the averaged 3-Ricci curvature. We find that the late-time
trajectories of those models approach attractors that lie in the future of a
state that is predicted by observational constraints.Comment: 36 pages and 6 Figures, matches published version in Class.Quant.Gra
A Precision Measurement of pp Elastic Scattering Cross Sections at Intermediate Energies
We have measured differential cross sections for \pp elastic scattering with
internal fiber targets in the recirculating beam of the proton synchrotron
COSY. Measurements were made continuously during acceleration for projectile
kinetic energies between 0.23 and 2.59 GeV in the angular range deg. Details of the apparatus and the data analysis are
given and the resulting excitation functions and angular distributions
presented. The precision of each data point is typically better than 4%, and a
relative normalization uncertainty of only 2.5% within an excitation function
has been reached. The impact on phase shift analysis as well as upper bounds on
possible resonant contributions in lower partial waves are discussed.Comment: 23 pages 29 figure
AdS_4/CFT_3 -- Squashed, Stretched and Warped
We use group theoretic methods to calculate the spectrum of short multiplets
around the extremum of N=8 gauged supergravity potential which possesses N=2
supersymmetry and SU(3) global symmetry. Upon uplifting to M-theory, it
describes a warped product of AdS_4 and a certain squashed and stretched
7-sphere. We find quantum numbers in agreement with those of the gauge
invariant operators in the N=2 superconformal Chern-Simons theory recently
proposed to be the dual of this M-theory background. This theory is obtained
from the U(N)xU(N) theory through deforming the superpotential by a term
quadratic in one of the superfields. To construct this model explicitly, one
needs to employ monopole operators whose complete understanding is still
lacking. However, for the U(2)xU(2) gauge theory we make a proposal for the
form of the monopole operators which has a number of desired properties. In
particular, this proposal implies enhanced symmetry of the U(2)xU(2) ABJM
theory for k=1,2; it makes its similarity to and subtle difference from the BLG
theory quite explicit.Comment: 32 pages, v2: references added, minor changes, v3: some
clarifications, published versio
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