96 research outputs found
A prototype system for detecting the radio-frequency pulse associated with cosmic ray air showers
The development of a system to detect the radio-frequency (RF) pulse
associated with extensive air showers of cosmic rays is described. This work
was performed at the CASA/MIA array in Utah, with the intention of designing
equipment that can be used in conjunction with the Auger Giant Array. A small
subset of data (less than 40 out of a total of 600 hours of running time),
taken under low-noise conditions, permitted upper limits to be placed on the
rate for pulses accompanying showers of energies around eV.Comment: 53 pages, LaTeX, 19 figures, published in Nuclear Instruments and
Methods. Revised version; some references update
Strengthening differential and linear attacks using virtual isomorphisms
The ciphers y = C (x, k) and y = C(x, k) are isomorphic if there is a computable in both directions map y ↔ y, x ↔ x, k ↔ k. The cipher is vulnerable to an attack if the isomorphic cipher is vulnerable to it. If φ is a substitution and T is an encryption operator, then T = φT φ 1 is a cipher isomorphism. For cryptanalysis it is reasonable to choose substitution φ in such a way that it has a lot of fixed points. It is shown that byte substitution φ can have no more than 130 fixed points. Isomorphic AES (IAES) is proposed where the only non-linear operation is an isomorphic image of the XOR operation. On average, maximum probabilities of IAES differentials are 8.5 times higher in comparison with the original whereas dominance of the linear sum is increased by 3 times. IAES has differentials with zero output difference and probability 1, which slows down replication of active non-linearities and decreases complexity of an attack. Presumably, resistance of AES to linear and differential attacks can be twice reduced by magnitude in comparison with the generally accepted estimates
Bipolaron Binding in Quantum Wires
A theory of bipolaron states in quantum wires with a parabolic potential well
is developed applying the Feynman variational principle. The basic parameters
of the bipolaron ground state (the binding energy, the number of phonons in the
bipolaron cloud, the effective mass, and the bipolaron radius) are studied as a
function of sizes of the potential well. Two cases are considered in detail: a
cylindrical quantum wire and a planar quantum wire. Analytical expressions for
the bipolaron parameters are obtained at large and small sizes of the quantum
well. It is shown that at [where means the radius (halfwidth) of a
cylindrical (planar) quantum wire, expressed in Feynman units], the influence
of confinement on the bipolaron binding energy is described by the function
for both cases, while at small sizes this influence is different
in each case. In quantum wires, the bipolaron binding energy increases
logarithmically with decreasing radius. The shapes and the sizes of a
nanostructure, which are favorable for observation of stable bipolaron states,
are determined.Comment: 17 pages, 6 figures, E-mail addresses: [email protected];
[email protected]
Charmless decays using flavor SU(3) symmetry
The decays of mesons to a pair of charmless pseudoscalar () mesons are
analyzed within a framework of flavor SU(3). Symmetry breaking is taken into
account in tree () amplitudes through ratios of decay constants; exact SU(3)
is assumed elsewhere. Acceptable fits to and
branching ratios and CP asymmetries are obtained with tree, color-suppressed
(), penguin (), and electroweak penguin () amplitudes. Crucial
additional terms for describing processes involving and include
a large flavor-singlet penguin amplitude () as proposed earlier and a
penguin amplitude associated with intermediate and quarks. For
the mode a term associated with intermediate
and quarks also may be needed. Values of the weak phase are
obtained consistent with an earlier analysis of decays, where
denotes a vector meson, and with other analyses of CKM parameters.Comment: 26 pages, 1 figure. To be submitted to Phys. Rev. D. Reference
update
Exploring Flavor Structure of Supersymmetry Breaking at B factories
We investigate quark flavor signals in three different supersymmetric models,
the minimal supergravity, the SU(5) SUSY GUT with right handed neutrinos, and
the minimal supersymmetric standard model with U(2) flavor symmetry, in order
to study physics potential of the present and future factories. We evaluate
CP asymmetries in various B decay modes, , ,
and . The allowed regions of the CP asymmetry in
and are different for the three models so that
precise determinations of these observables in near future experiments are
useful to distinguish the three models. We also investigate possible deviations
from the standard model predictions of CP asymmetries in other B decay modes.
In particular, a large deviation is possible for the U(2) model. The
consistency check of the unitarity triangle including , and so on, at future high
luminosity factories and hadronic experiments is therefore
important to distinguish flavor structures of different supersymmetric models.Comment: revtex4, 31 pages, 7 figure
P and CP violation in B physics
While the Kobayashi--Maskawa single phase origin of CP violation passed its
first crucial precision test in , the chirality of weak
-quark couplings has not yet been carefully tested. We discuss recent
proposals for studying the chiral and CP-violating structure of these couplings
in radiative and in hadronic B decays.Comment: 15 pages, talk at PASCOS'03, Tata Inst., Mumbai, Jan. 200
Time-Dependent CP Violation Effects in Partially Reconstructed Decays
We report measurements of time-dependent decay rates for decays and extraction of CP violation parameters related to .
We use a partial reconstruction technique, whereby signal events are identified
using information only from the primary pion and the charged pion from the
decay of the . The analysis uses of data
accumulated at the resonance with the Belle detector at the KEKB
asymmetric-energy collider. We measure the CP violation parameters
and .Comment: 15 pages, 5 figures. To appear in Physics Letters
Froehlich Polaron and Bipolaron: Recent Developments
It is remarkable how the Froehlich polaron, one of the simplest examples of a
Quantum Field Theoretical problem, as it basically consists of a single fermion
interacting with a scalar Bose field of ion displacements, has resisted full
analytical or numerical solution at all coupling since 1950, when its
Hamiltonian was first written. The field has been a testing ground for
analytical, semi-analytical, and numerical techniques, such as path integrals,
strong-coupling perturbation expansion, advanced variational, exact
diagonalisation (ED), and quantum Monte Carlo (QMC) techniques. This article
reviews recent developments in the field of continuum and discrete (lattice)
Froehlich (bi)polarons starting with the basics and covering a number of active
directions of research.Comment: 131 pages, 17 figures, 409 references, appear in Reports on Progress
in Physic
The Antarctic Impulsive Transient Antenna Ultra-high Energy Neutrino Detector Design, Performance, and Sensitivity for 2006-2007 Balloon Flight
We present a detailed report on the experimental details of the Antarctic
Impulsive Transient Antenna (ANITA) long duration balloon payload, including
the design philosophy and realization, physics simulations, performance of the
instrument during its first Antarctic flight completed in January of 2007, and
expectations for the limiting neutrino detection sensitivity. Neutrino physics
results will be reported separately.Comment: 50 pages, 49 figures, in preparation for PR
Effects of Once-Weekly Exenatide on Cardiovascular Outcomes in Type 2 Diabetes.
Abstract
BACKGROUND:
The cardiovascular effects of adding once-weekly treatment with exenatide to usual care in patients with type 2 diabetes are unknown.
METHODS:
We randomly assigned patients with type 2 diabetes, with or without previous cardiovascular disease, to receive subcutaneous injections of extended-release exenatide at a dose of 2 mg or matching placebo once weekly. The primary composite outcome was the first occurrence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke. The coprimary hypotheses were that exenatide, administered once weekly, would be noninferior to placebo with respect to safety and superior to placebo with respect to efficacy.
RESULTS:
In all, 14,752 patients (of whom 10,782 [73.1%] had previous cardiovascular disease) were followed for a median of 3.2 years (interquartile range, 2.2 to 4.4). A primary composite outcome event occurred in 839 of 7356 patients (11.4%; 3.7 events per 100 person-years) in the exenatide group and in 905 of 7396 patients (12.2%; 4.0 events per 100 person-years) in the placebo group (hazard ratio, 0.91; 95% confidence interval [CI], 0.83 to 1.00), with the intention-to-treat analysis indicating that exenatide, administered once weekly, was noninferior to placebo with respect to safety (P<0.001 for noninferiority) but was not superior to placebo with respect to efficacy (P=0.06 for superiority). The rates of death from cardiovascular causes, fatal or nonfatal myocardial infarction, fatal or nonfatal stroke, hospitalization for heart failure, and hospitalization for acute coronary syndrome, and the incidence of acute pancreatitis, pancreatic cancer, medullary thyroid carcinoma, and serious adverse events did not differ significantly between the two groups.
CONCLUSIONS:
Among patients with type 2 diabetes with or without previous cardiovascular disease, the incidence of major adverse cardiovascular events did not differ significantly between patients who received exenatide and those who received placebo. (Funded by Amylin Pharmaceuticals; EXSCEL ClinicalTrials.gov number, NCT01144338 .)
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