25,869 research outputs found
Fast and secure laptop backups with encrypted de-duplication
Many people now store large quantities of personal and corporate data on laptops or home computers. These often have poor or intermittent connectivity, and are vulnerable to theft or hardware failure. Conventional backup solutions are not well suited to this environment, and backup regimes are frequently inadequate. This paper describes an algorithm which takes advantage of the data which is common between users to increase the speed of backups, and reduce the storage requirements. This algorithm supports client-end per-user encryption which is necessary for confidential personal data. It also supports a unique feature which allows immediate detection of common subtrees, avoiding the need to query the backup system for every file. We describe a prototype implementation of this algorithm for Apple OS X, and present an analysis of the potential effectiveness, using real data obtained from a set of typical users. Finally, we discuss the use of this prototype in conjunction with remote cloud storage, and present an analysis of the typical cost savings.
Disruption in the Supply Chain for Beef and Pork: What Has Happened and What Was NAFTA Doing
Industrial Organization, International Relations/Trade,
Telemedicine of family-based treatment for adolescent anorexia nervosa: A protocol of a treatment development study.
BackgroundFamily-based treatment is an efficacious treatment available for adolescents with anorexia nervosa. Yet the implementation of this treatment, at least in the United States, is challenging due to a limited number of trained family-based treatment therapists and the concentration of these therapists in a limited number of urban centers. The use of telemedicine in the delivery of family-based treatment can increase access to this therapy for this patient population.Methods/designThis two-year treatment development study (December 2013-November 2015) follows a two-wave iterative case series design. The study is ongoing and addresses the treatment needs of families in remote, rural, or underrepresented parts of the United States by delivering family-based treatment via telemedicine (video chat). The first six months of the study was dedicated to selecting a cloud-based secure telemedicine portal for use with participants. Recruitment for the first of two consecutive case series (N = 5) began during month seven. After these five patients completed treatment, a systematic review of treatment via feedback from participants and therapists related to the delivery of this model and use of technology was completed. A second wave of recruitment is underway (N = 5). At the end of both waves (N = 10), and after a second review of treatment, we should be able to establish the feasibility and acceptability of family-based treatment delivered via telemedicine for this patient population.DiscussionThis study is the first attempt to deliver family-based treatment for adolescents with anorexia nervosa via telemedicine. If delivering family-based treatment in this format is feasible, it will provide access to an evidence-based treatment for families heretofore unable to participate in specialist treatment for their child's eating disorder
Quaternion Singular Value Decomposition based on Bidiagonalization to a Real Matrix using Quaternion Householder Transformations
We present a practical and efficient means to compute the singular value
decomposition (svd) of a quaternion matrix A based on bidiagonalization of A to
a real bidiagonal matrix B using quaternionic Householder transformations.
Computation of the svd of B using an existing subroutine library such as lapack
provides the singular values of A. The singular vectors of A are obtained
trivially from the product of the Householder transformations and the real
singular vectors of B. We show in the paper that left and right quaternionic
Householder transformations are different because of the noncommutative
multiplication of quaternions and we present formulae for computing the
Householder vector and matrix in each case
The probability density function tail of the Kardar-Parisi-Zhang equation in the strongly non-linear regime
An analytical derivation of the probability density function (PDF) tail
describing the strongly correlated interface growth governed by the nonlinear
Kardar-Parisi-Zhang equation is provided. The PDF tail exactly coincides with a
Tracy-Widom distribution i.e. a PDF tail proportional to , where is the the width of the interface. The PDF tail is
computed by the instanton method in the strongly non-linear regime within the
Martin-Siggia-Rose framework using a careful treatment of the non-linear
interactions. In addition, the effect of spatial dimensions on the PDF tail
scaling is discussed. This gives a novel approach to understand the rightmost
PDF tail of the interface width distribution and the analysis suggests that
there is no upper critical dimension.Comment: 17 pages, 2 figure
Dielectric constant of glasses: first observation of a two-dimensional behavior
The 1kHz real part of the dielectric constant of a structural glass
was measured at low temperature down to 14 mK. Reducing the sample
thickness to 10 nm suppresses the usual minimum of for measuring
fields MV/m. This contradicts the Two Level System (TLS) model but is
well accounted for by including TLS-TLS interactions where excitations
delocalize between TLS's through a -induced mechanism recently designed: for
small 's this interaction is reduced, which explains the two-dimensional
behavior of . Hence, interactions play a key role in standard thick
samples.Comment: latex finesse3.tex, 5 files, 4 figures, 4 pages [SPEC-S02/050],
submitted to Phys. Rev. Let
Observational calibration of the projection factor of Cepheids. II. Application to nine Cepheids with HST/FGS parallax measurements
The distance to pulsating stars is classically estimated using the
parallax-of-pulsation (PoP) method, which combines spectroscopic radial
velocity measurements and angular diameter estimates to derive the distance of
the star. An important application of this method is the determination of
Cepheid distances, in view of the calibration of their distance scale. However,
the conversion of radial to pulsational velocities in the PoP method relies on
a poorly calibrated parameter, the projection factor (p-factor). We aim to
measure empirically the value of the p-factors of a homogeneous sample of nine
Galactic Cepheids for which trigonometric parallaxes were measured with the
Hubble Space Telescope Fine Guidance Sensor. We use the SPIPS algorithm, a
robust implementation of the PoP method that combines photometry,
interferometry, and radial velocity measurements in a global modeling of the
pulsation. We obtained new interferometric angular diameters using the PIONIER
instrument at the Very Large Telescope Interferometer, completed by data from
the literature. Using the known distance as an input, we derive the value of
the p-factor and study its dependence with the pulsation period. We find the
following p-factors: 1.20 0.12 for RT Aur, 1.48 0.18 for T Vul,
1.14 0.10 for FF Aql, 1.31 0.19 for Y Sgr, 1.39 0.09 for X
Sgr, 1.35 0.13 for W Sgr, 1.36 0.08 for Dor, 1.41
0.10 for Gem, and 1.23 0.12 for Car. These values are
consistently close to p = 1.324 0.024. We observe some dispersion around
this average value, but the observed distribution is statistically consistent
with a constant value of the p-factor as a function of the pulsation period.
The error budget of our determination of the p-factor values is presently
dominated by the uncertainty on the parallax, a limitation that will soon be
waived by Gaia.Comment: 18 pages, 13 figure
A Mesoscopic Resonating Valence Bond system on a triple dot
We introduce a mesoscopic pendulum from a triple dot. The pendulum is
fastened through a singly-occupied dot (spin qubit). Two other strongly
capacitively islands form a double-dot charge qubit with one electron in excess
oscillating between the two low-energy charge states (1,0) and (0,1); this
embodies the weight of the pendulum. The triple dot is placed between two
superconducting leads as shown in Fig. 1. Under well-defined conditions, the
main proximity effect stems from the injection of resonating singlet (valence)
bonds on the triple dot. This gives rise to a Josephson current that is charge-
and spin-dependent. Consequences in a SQUID-geometry are carefully
investigated.Comment: final version to appear in PR
Observational calibration of the projection factor of Cepheids I. The Type II Cepheid kappa Pavonis
The distances of pulsating stars, in particular Cepheids, are commonly
measured using the parallax of pulsation technique. The different versions of
this technique combine measurements of the linear diameter variation (from
spectroscopy) and the angular diameter variation (from photometry or
interferometry) amplitudes, to retrieve the distance in a quasi-geometrical
way. However, the linear diameter amplitude is directly proportional to the
projection factor (hereafter p-factor), which is used to convert spectroscopic
radial velocities (i.e., disk integrated) into pulsating (i.e., photospheric)
velocities. The value of the p-factor and its possible dependence on the
pulsation period are still widely debated. Our goal is to measure an
observational value of the p-factor of the type-II Cepheid kappa Pavonis, whose
parallax was measured with an accuracy of 5% using HST/FGS. We used this
parallax as a starting point to derive the p-factor of kappa Pav, using the
SPIPS technique, which is a robust version of the parallax-of-pulsation method
that employs radial velocity, interferometric and photometric data. We applied
this technique to a combination of new VLTI/PIONIER optical interferometric
angular diameters, new CORALIE and HARPS radial velocities, as well as
multi-colour photometry and radial velocities from the literature. We obtain a
value of p = 1.26 +/- 0.07 for the p-factor of kappa Pav. This result agrees
with several of the recently derived Period-p-factor relationships from the
literature, as well as previous observational determinations for Cepheids.
Individual estimates of the p-factor are fundamental to calibrating the
parallax of pulsation distances of Cepheids. Together with previous
observational estimates, the projection factor we obtain points to a weak
dependence of the p-factor on period.Comment: 8 pages, 6 figures, accepted in A&
The ocean carbon sink – impacts, vulnerabilities and challenges
Carbon dioxide (CO2) is, next to water vapour, considered to be the most important natural greenhouse gas on Earth. Rapidly rising atmospheric CO2 concentrations caused by human actions such as fossil fuel burning, land-use change or cement production over the past 250 years have given cause for concern that changes in Earth’s climate system may progress at a much faster pace and larger extent than during the past 20 000 years. Investigating global carbon cycle pathways and finding suitable adaptation and mitigation strategies has, therefore, become of major concern in many research fields. The oceans have a key role in regulating atmospheric CO2 concentrations and currently take up about 25% of annual anthropogenic carbon emissions to the atmosphere. Questions that yet need to be answered are what the carbon uptake kinetics of the oceans will be in the future and how the increase in oceanic carbon inventory will affect its ecosystems and their services. This requires comprehensive investigations, including high-quality ocean carbon measurements on different spatial and temporal scales, the management of data in sophisticated databases, the application of Earth system models to provide future projections for given emission scenarios as well as a global synthesis and outreach to policy makers. In this paper, the current understanding of the ocean as an important carbon sink is reviewed with respect to these topics. Emphasis is placed on the complex interplay of different physical, chemical and biological processes that yield both positive and negative air–sea flux values for natural and anthropogenic CO2 as well as on increased CO2 (uptake) as the regulating force of the radiative warming of the atmosphere and the gradual acidification of the oceans. Major future ocean carbon challenges in the fields of ocean observations, modelling and process research as well as the relevance of other biogeochemical cycles and greenhouse gases are discussed
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