498 research outputs found
Mars riometer system
A riometer (relative ionospheric opacity meter) measures
the intensity of cosmic radio noise at the surface of a planet.
When an electromagnetic wave passes through the
ionosphere collisions between charged particles (usually
electrons) and neutral gases remove energy from the wave.
By measuring the received signal intensity at the planet's
surface and comparing it to the expected value (the quietday
curve) a riometer can deduce the absorption
(attenuation) of the trans-ionospheric signal. Thus the
absorption measurements provide an indication of ionisation
changes occurring in the ionosphere.
To avoid the need for orbiting sounders riometers use the
cosmic noise background as a signal source. Earth-based
systems are not subject to the challenging power, volume
and mass restriction that would apply to a riometer for
Mars. Some Earth-based riometers utilise phased-array
antennas in order to provide an imaging capability.UnpublishedVienna - Austria3.9. Fisica della magnetosfera, ionosfera e meteorologia spazialeope
Longer Duration of Diabetes Strongly Impacts Fracture Risk Assessment: The Manitoba BMD Cohort
Context: Type 2 diabetes is associated with a higher risk for major osteoporotic fracture (MOF) and
hip fracture than predicted by the World Health Organization fracture risk assessment (FRAX) tool.
Objective: The objective of the study was to examine the impact of diabetes duration on fracture
risk.
Methods: Using a clinical dual-energy x-ray absorptiometry registry linked with the Manitoba
administrative databases, we identified all women age 40 years or older with 10 or more years of
prior health care coverage undergoing hip dual-energy x-ray absorptiometry measurements
(1996 â2013). Incident MOF and incident hip fractures were each studied over 7 years. Cox proportional
hazards models were adjusted for FRAX (FRAX adjusted) and then FRAX plus comorbidity,
falls, osteoporosis therapy, or insulin (fully adjusted). FRAX calibration was assessed comparing
observed vs predicted probabilities.
Results: There were 49 098 women without and 8840 women with diabetes (31.4%10 y duration;
20.1% 5â10 y; 23.7%5 y; 24.8% new onset). In FRAX-adjusted analyses, only duration longer than
10 years was associated with a higher risk for MOF (hazard ratio [HR] 1.47, 95% confidence interval
[CI] 1.30 â1.66), and this was similar in the fully adjusted models (HR 1.34, 95% CI 1.17â1.54). In
contrast, a higher risk for hip fracture was seen for all durations in a dose-dependent fashion (eg,
FRAX adjusted HR 2.10, 95% CI 1.71â2.59 for duration 10 y vs HR 1.32, 95% CI 1.03â1.69 for new
onset). FRAX significantly underestimated the MOF risk (calibration ratio 1.24, 95% CI 1.08 â1.39)
and hip fracture risk (1.93, 95% CI 1.50 â2.35) in those with a diabetes duration longer than 10 years.
Conclusion: Diabetes is a FRAX-independent risk factor for MOF only in women with a long duration
of diabetes, but diabetes increases hip fracture risk, regardless of duration. Those with
diabetes longer than 10 years are at particularly high risk of fracture, and this elevated risk is
currently underestimated by FRAX
Application of the National Osteoporosis Foundation Guidelines to postmenopausal women and men: the Framingham Osteoporosis Study.
Summary
We applied the 2008 National Osteoporosis Foundation (NOF) Guidelines to Framingham Osteoporosis Study participants and found nearly one half of Caucasian postmenopausal women and one sixth of men aged 50 years and older would be recommended for osteoporosis treatment. Given the high proportion of persons recommended for treatment, NOF Guidelines may need to be re-evaluated with respect to budget impact.
Introduction
Little is known about the public health impact of the NOF Guidelines. Therefore, we determined the proportion of US Caucasians recommended for treatment of osteoporosis according to NOF Guidelines (2003 and 2008).
Methods
One thousand nine hundred and forty-six postmenopausal women and 1,681 men aged â„50 years from the Framingham Study with information on bone mineral density (1987â2001) were included. Information on clinical predictors was used to estimate the 10-year probability of hip and major osteoporotic fracture by FRAXÂź (version 3.0).
Results
Overall proportion of women meeting treatment criterion was less when the 2008 NOF Guidelines were applied (41.1%) compared with 2003 Guidelines (47.8%). The proportion of women aged 75 years increased slightly (78.3% in 2003, 86.0% in 2008). Seventeen percent of men aged â„50 years met treatment criterion (2.5% aged 50â64 years, 49.8% aged >75 years).
Conclusions
Nearly one half of Caucasian postmenopausal women and one sixth of men aged 50 years and older would be recommended for osteoporosis treatment according to 2008 NOF Guidelines. Given the high proportion of persons recommended for treatment, NOF Guidelines may need to be re-evaluated with respect to budget impact
The Conditional Correlation Attack: A Practical Attack on Bluetooth Encryption
Abstract. Motivated by the security of the nonlinear filter generator, the concept of correlation was previously extended to the conditional correlation, that studied the linear correlation of the inputs conditioned on a given (short) output pattern of some specific nonlinear function. Based on the conditional correlations, conditional correlation attacks were shown to be successful and efficient against the nonlinear filter generator. In this paper, we further generalize the concept of conditional correlations by assigning it with a different meaning, i.e. the correlation of the output of an arbitrary function conditioned on the unknown (partial) input which is uniformly distributed. Based on this generalized conditional correlation, a general statistical model is studied for dedicated key-recovery distinguishers. It is shown that the generalized conditional correlation is no smaller than the unconditional correlation. Consequently, our distinguisher improves on the traditional one (in the worst case it degrades into the traditional one). In particular, the distinguisher may be successful even if no ordinary correlation exists. As an application, a conditional correlation attack is developed and optimized against Bluetooth two-level E0. The attack is based on a recently detected flaw in the resynchronization of E0, as well as the investigation of conditional correlations in the Finite State Machine (FSM) governing the keystream output of E0. Our best attack finds the original encryption key for two-level E0 using the first 24 bits of 2 23.8 frames and with 2 38 computations. This is clearly the fastest and only practical known-plaintext attack on Bluetooth encryption compared with all existing attacks. Current experiments confirm our analysis
Doping-dependent study of the periodic Anderson model in three dimensions
We study a simple model for -electron systems, the three-dimensional
periodic Anderson model, in which localized states hybridize with
neighboring states. The states have a strong on-site repulsion which
suppresses the double occupancy and can lead to the formation of a Mott-Hubbard
insulator. When the hybridization between the and states increases, the
effects of these strong electron correlations gradually diminish, giving rise
to interesting phenomena on the way. We use the exact quantum Monte-Carlo,
approximate diagrammatic fluctuation-exchange approximation, and mean-field
Hartree-Fock methods to calculate the local moment, entropy, antiferromagnetic
structure factor, singlet-correlator, and internal energy as a function of the
hybridization for various dopings. Finally, we discuss the relevance of
this work to the volume-collapse phenomenon experimentally observed in
f-electron systems.Comment: 12 pages, 8 figure
Theory of the first-order isostructural valence phase transitions in mixed valence compounds YbIn_{x}Ag_{1-x}Cu_{4}
For describing the first-order isostructural valence phase transition in
mixed valence compounds we develop a new approach based on the lattice Anderson
model. We take into account the Coulomb interaction between localized f and
conduction band electrons and two mechanisms of electron-lattice coupling. One
is related to the volume dependence of the hybridization. The other is related
to local deformations produced by f- shell size fluctuations accompanying
valence fluctuations. The large f -state degeneracy allows us to use the 1/N
expansion method. Within the model we develop a mean-field theory for the
first-order valence phase transition in YbInCu_{4}. It is shown that the
Coulomb interaction enhances the exchange interaction between f and conduction
band electron spins and is the driving force of the phase transition. A
comparison between the theoretical calculations and experimental measurements
of the valence change, susceptibility, specific heat, entropy, elastic
constants and volume change in YbInCu_{4} and YbAgCu_{4} are presented, and a
good quantitative agreement is found. On the basis of the model we describe the
evolution from the first-order valence phase transition to the continuous
transition into the heavy-fermion ground state in the series of compounds
YbIn_{1-x}Ag_{x}Cu_{4}. The effect of pressure on physical properties of
YbInCu_{4} is studied and the H-T phase diagram is found.Comment: 17 pages RevTeX, 9 Postscript figures, to be submitted to Phys.Rev.
The prognostic significance of low-frequency somatic mutations in metastatic cutaneous melanoma
Background: Little is known about the prognostic significance of somatically mutated genes in metastatic melanoma (MM). We have employed a combined clinical and bioinformatics approach on tumor samples from cutaneous melanoma (SKCM) as part of The Cancer Genome Atlas project (TCGA) to identify mutated genes with potential clinical relevance. Methods: After limiting our DNA sequencing analysis to MM samples (n = 356) and to the CANCER CENSUS gene list, we filtered out mutations with low functional significance (snpEFF). We performed Cox analysis on 53 genes that were mutated in â„3% of samples, and had â„50% difference in incidence of mutations in deceased subjects versus alive subjects. Results: Four genes were potentially prognostic [RAC1, FGFR1, CARD11, CIITA; false discovery rate (FDR) 75% of the samples that exhibited corresponding DNA mutations. The low frequency, UV signature type and RNA expression of the 22 genes in MM samples were confirmed in a separate multi-institution validation cohort (n = 413). An underpowered analysis within a subset of this validation cohort with available patient follow-up (n = 224) showed that somatic mutations in SPEN and RAC1 reached borderline prognostic significance [log-rank favorable (p = 0.09) and adverse (p = 0.07), respectively]. Somatic mutations in SPEN, and to a lesser extent RAC1, were not associated with definite gene copy number or RNA expression alterations. High (>2+) nuclear plus cytoplasmic expression intensity for SPEN was associated with longer melanoma-specific overall survival (OS) compared to lower (†2+) nuclear intensity (p = 0.048). We conclude that expressed somatic mutations in infrequently mutated genes beyond the well-characterized ones (e.g., BRAF, RAS, CDKN2A, PTEN, TP53), such as RAC1 and SPEN, may have prognostic significance in MM
All-particle cosmic ray energy spectrum measured with 26 IceTop stations
We report on a measurement of the cosmic ray energy spectrum with the IceTop
air shower array, the surface component of the IceCube Neutrino Observatory at
the South Pole. The data used in this analysis were taken between June and
October, 2007, with 26 surface stations operational at that time, corresponding
to about one third of the final array. The fiducial area used in this analysis
was 0.122 km^2. The analysis investigated the energy spectrum from 1 to 100 PeV
measured for three different zenith angle ranges between 0{\deg} and 46{\deg}.
Because of the isotropy of cosmic rays in this energy range the spectra from
all zenith angle intervals have to agree. The cosmic-ray energy spectrum was
determined under different assumptions on the primary mass composition. Good
agreement of spectra in the three zenith angle ranges was found for the
assumption of pure proton and a simple two-component model. For zenith angles
{\theta} < 30{\deg}, where the mass dependence is smallest, the knee in the
cosmic ray energy spectrum was observed between 3.5 and 4.32 PeV, depending on
composition assumption. Spectral indices above the knee range from -3.08 to
-3.11 depending on primary mass composition assumption. Moreover, an indication
of a flattening of the spectrum above 22 PeV were observed.Comment: 38 pages, 17 figure
Molecular cloning and transcriptional regulation of ompT , a ToxR-repressed gene in Vibrio cholerae
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72189/1/j.1365-2958.2000.01699.x.pd
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
- âŠ