25,723 research outputs found
Proton-proton and deuteron-gold collisions at RHIC
We try to understand recent data on proton-proton and deuteron-gold
collisions at RHIC, employing a modified parton model approach.Comment: Invited talk, given at the XXth Winter Workshop on Nuclear Dynamics,
Trelawny Beach, Jamaica, March 200
Propagation and spectral properties of quantum walks in electric fields
We study one-dimensional quantum walks in a homogeneous electric field. The
field is given by a phase which depends linearly on position and is applied
after each step. The long time propagation properties of this system, such as
revivals, ballistic expansion and Anderson localization, depend very
sensitively on the value of the electric field , e.g., on whether
is rational or irrational. We relate these properties to the
continued fraction expansion of the field. When the field is given only with
finite accuracy, the beginning of the expansion allows analogous conclusions
about the behavior on finite time scales.Comment: 7 pages, 4 figure
Equilibrium states and invariant measures for random dynamical systems
Random dynamical systems with countably many maps which admit countable
Markov partitions on complete metric spaces such that the resulting Markov
systems are uniformly continuous and contractive are considered. A
non-degeneracy and a consistency conditions for such systems, which admit some
proper Markov partitions of connected spaces, are introduced, and further
sufficient conditions for them are provided. It is shown that every uniformly
continuous Markov system associated with a continuous random dynamical system
is consistent if it has a dominating Markov chain. A necessary and sufficient
condition for the existence of an invariant Borel probability measure for such
a non-degenerate system with a dominating Markov chain and a finite (16) is
given. The condition is also sufficient if the non-degeneracy is weakened with
the consistency condition. A further sufficient condition for the existence of
an invariant measure for such a consistent system which involves only the
properties of the dominating Markov chain is provided. In particular, it
implies that every such a consistent system with a finite Markov partition and
a finite (16) has an invariant Borel probability measure. A bijective map
between these measures and equilibrium states associated with such a system is
established in the non-degenerate case. Some properties of the map and the
measures are given.Comment: The article is published in DCDS-A, but without the 3rd paragraph on
page 4 (the complete removal of the paragraph became the condition for the
publication in the DCDS-A after the reviewer ran out of the citation
suggestions collected in the paragraph
Quantum Walks with Non-Orthogonal Position States
Quantum walks have by now been realized in a large variety of different
physical settings. In some of these, particularly with trapped ions, the walk
is implemented in phase space, where the corresponding position states are not
orthogonal. We develop a general description of such a quantum walk and show
how to map it into a standard one with orthogonal states, thereby making
available all the tools developed for the latter. This enables a variety of
experiments, which can be implemented with smaller step sizes and more steps.
Tuning the non-orthogonality allows for an easy preparation of extended states
such as momentum eigenstates, which travel at a well-defined speed with low
dispersion. We introduce a method to adjust their velocity by momentum shifts,
which allows to investigate intriguing effects such as the analog of Bloch
oscillations.Comment: 5 pages, 4 figure
A model for melting of confined DNA
When DNA molecules are heated they denature. This occurs locally so that
loops of molten single DNA strands form, connected by intact double-stranded
DNA pieces. The properties of this "melting" transition have been intensively
investigated. Recently there has been a surge of interest in this question,
caused by experiments determining the properties of partially bound DNA
confined to nanochannels. But how does such confinement affect the melting
transition? To answer this question we introduce, and solve a model predicting
how confinement affects the melting transition for a simple model system by
first disregarding the effect of self-avoidance. We find that the transition is
smoother for narrower channels. By means of Monte-Carlo simulations we then
show that a model incorporating self-avoidance shows qualitatively the same
behaviour and that the effect of confinement is stronger than in the ideal
case.Comment: 5 pages, 4 figures, supplementary materia
First detection of bromine and antimony in hot stars
Bromine (atomic number Z=35) and antimony (Z=51) are extremely difficult to
detect in stars. In very few instances, weak and mostly uncertain
identifications of Br I, Br II, and Sb II in relatively cool, chemically
peculiar stars were successful. Adopted solar abundance values rely on
meteoritic determinations. Here, we announce the first identification of these
species in far-ultraviolet spectra of hot stars (with effective temperatures of
49,500-70,000 K), namely in helium-rich (spectral type DO) white dwarfs. We
identify the Br VI resonance line at 945.96 A. A previous claim of Br detection
based on this line is incorrect because its wavelength position is inaccurate
by about 7 A in atomic databases. Taking advantage of precise laboratory
measurements, we identify this line as well as two other, subordinate Br VI
lines. Antimony is detected by the Sb V resonance doublet at 1104.23/1225.98 A,
as well as two subordinate Sb VI lines. A model-atmosphere analysis reveals
strongly oversolar Br and Sb abundances that are caused by radiative-levitation
dominated atomic diffusion.Comment: Accepted for publication in A&
A New String Model: NEXUS 3
After discussing conceptual problems with the conventional string model, we
present a new approach, based on a theoretically consistent multiple scattering
formalism.
First results for proton-proton scattering at 158 GeV are discussed.Comment: invited talk given at the 9th Winter Workshop on Nuclear Dynamics,
Breckenridge, Colorado, February 9 - 14, 200
SGLT-2 Inhibitors: A Novel Mechanism in Targeting Glycemic Control in Type 2 Diabetes Mellitus
OBJECTIVE: To review the chemistry, pharmacology, pharmacodynamics, pharmacokinetics, clinical efficacy, tolerability, dosing, drug interactions, and administration of canagliflozin, dapagliflozin, and empagliflozin, and comparing the benefit and risk aspects of using these agents in the older adult diabetes patient population.
DATA SOURCES, STUDY SELECTION, DATA EXTRACTION, AND DATA SYNTHESIS: A search of PubMed using the terms SGLT-2 inhibitors, canagliflozin, dapagliflozin, empagliflozin, efficacy, and tolerability was performed to find relevant primary literature on each of the sodium/glucose cotransporter 2 (SGLT-2) inhibitors currently approved for use in type 2 diabetes. Phase III trials for all agents were included. All English-language articles from 2010 to 2015 appearing in these searches were reviewed for relevance to this paper. In addition, related articles suggested in the PubMed search were also reviewed. The SGLT-2 inhibitors have shown a reduction in hemoglobin A1c values and fasting plasma glucose levels with a low incidence of hypoglycemia. The incidence of mycotic infections is increased in patients taking an SGLT-2 inhibitor.
CONCLUSION: SGLT-2 inhibitors may be a viable treatment option for patients not controlled on other oral agents. The risk of hypoglycemia is small. However, the clinical efficacy and tolerability of these agents has not been fully elucidated in older and frail patients
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