187 research outputs found
Absorptive part of meson--baryon scattering amplitude and baryon polarization in chiral perturbation theory
We compute the spin asymmetry and polarization of the final-state baryon in
its rest frame in two-body meson--baryon low-energy scattering with unpolarized
initial state, to lowest non-trivial order in BChPT. The required absorptive
amplitudes are obtained analytically at one-loop level. We discuss the
polarization results numerically for several meson--baryon processes. Even at
low energies above threshold, where BChPT can reasonably be expected to be
applicable, sizable values of polarization are found for some processes
Theoretical Aspects of Standard-Model Higgs-Boson Physics at a Future e^+ e^- Linear Collider
The Higgs boson is the missing link of the Standard Model of elementary
particle physics. We review its decay properties and production mechanisms at a
future e^+ e^- linear collider and its e^- e^-, e^+- gamma, and gamma gamma
modes, with special emphasis on the influence of quantum corrections. We also
discuss how its quantum numbers and couplings can be extracted from the study
of appropriate final states.Comment: 23 pages (Latex), 15 figures (Postscript), to appear in Int. J. Mod.
Phys.
Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions
The star-forming regions in Chamaeleon are one of the nearest (distance ~165
pc) and youngest (age ~2 Myrs) conglomerates of recently formed stars and the
ideal target for population studies of star formation. We investigate a total
of 16 Cha targets, which have been suggested, but not confirmed as binaries or
multiple systems in previous literature. We used the adaptive optics instrument
Naos-Conica (NACO) at the Very Large Telescope Unit Telescope 4 of the Paranal
Observatory, at 2-5 different epochs, in order to obtain relative and absolute
astrometric measurements, as well as differential photometry in the J, H, and K
band. On the basis of known proper motions and these observations, we analyse
the astrometric results in our "Proper Motion Diagram" (PMD: angular separation
/ position angle versus time), to eliminate possible (non-moving) background
stars, establish co-moving binaries and multiples, and search for curvature as
indications for orbital motion. All previously suggested close components are
co-moving and no background stars are found. The angular separations range
between 0.07 and 9 arcseconds, corresponding to projected distances between the
components of 6-845 AU. Thirteen stars are at least binaries and the remaining
three (RX J0919.4-7738, RX J0952.7-7933, VW Cha) are confirmed high-order
multiple systems with up to four components. In 13 cases, we found significant
slopes in the PMDs, which are compatible with orbital motion whose periods
range from 60 to 550 years. However, in only four cases there are indications
of a curved orbit, the ultimate proof of a gravitational bond. Massive primary
components appear to avoid the simultaneous formation of equal-mass secondary
components. (abridged)Comment: 33 pages, 22 figures, accepted for publication in A&A, 2nd version:
typos and measurement unit added in Table
Computational Methods for Stability and Control (COMSAC): The Time Has Come
Powerful computational fluid dynamics (CFD) tools have emerged that appear to offer significant benefits as an adjunct to the experimental methods used by the stability and control community to predict aerodynamic parameters. The decreasing costs for and increasing availability of computing hours are making these applications increasingly viable as time goes on and the cost of computing continues to drop. This paper summarizes the efforts of four organizations to utilize high-end computational fluid dynamics (CFD) tools to address the challenges of the stability and control arena. General motivation and the backdrop for these efforts will be summarized as well as examples of current applications
Domain and Antidomain Semigroups
Abstract. We axiomatise and study operations for relational domain and antidomain on semigroups and monoids. We relate this approach with previous axiomatisations for semirings, partial transformation semi-groups and dynamic predicate logic.
A new concept for the combination of optical interferometers and high-resolution spectrographs
The combination of high spatial and spectral resolution in optical astronomy
enables new observational approaches to many open problems in stellar and
circumstellar astrophysics. However, constructing a high-resolution
spectrograph for an interferometer is a costly and time-intensive undertaking.
Our aim is to show that, by coupling existing high-resolution spectrographs to
existing interferometers, one could observe in the domain of high spectral and
spatial resolution, and avoid the construction of a new complex and expensive
instrument. We investigate in this article the different challenges which arise
from combining an interferometer with a high-resolution spectrograph. The
requirements for the different sub-systems are determined, with special
attention given to the problems of fringe tracking and dispersion. A concept
study for the combination of the VLTI (Very Large Telescope Interferometer)
with UVES (UV-Visual Echelle Spectrograph) is carried out, and several other
specific instrument pairings are discussed. We show that the proposed
combination of an interferometer with a high-resolution spectrograph is indeed
feasible with current technology, for a fraction of the cost of building a
whole new spectrograph. The impact on the existing instruments and their
ongoing programs would be minimal.Comment: 27 pages, 9 figures, Experimental Astronomy; v2: accepted versio
Evaluation of Thawing Curves of Beef Strip Loin Steaks Using Various Thawing Methods
Objective:The objective of this study was to evaluate and determine thaw rate and time of strip steaks thawed using methods that are recommended by the U.S. Department of Agriculture and those commonly used by consumers.
Study Description:Strip steaks collected from a beef packing facility were randomly assigned a thaw method. Initially, steaks were vacuum packaged and then frozen at -40°F until thawed. Two thawing methods were USDA-approved: thawing in a refrigerator (REF) and in cold water (CW); while the other two methods evaluated are commonly used by consumers: thawing on the countertop (CT) and in hot water (HW). The thawing temperatures were: REF at 35.6–37.4°F in the refrigerator; CW maintained at 35.6–37.4°F in water; CT at 68°F; and HW at 104°F. Temperatures of the steaks were recorded every 30 minutes for CW and REF, every 10 minutes for CT, and every thirty seconds for HW to determine the thaw time and rate.
Results:Thawing time differed (P\u3c0.05) among treatments in this study (HWP\u3c0.05) among treatments with a similar trend (HWP\u3c0.05) from REF until 5 hours prior to thaw point, at which point the temperatures were similar (P\u3e0.05) for the remaining thawing period. Moreover, REF steaks were warmer (P\u3c0.05) than CW steaks from 13 to 5 hours prior to thaw point. In the final 5 hours, CW and REF steaks were similar (P\u3e0.05) in temperature. Furthermore, among all treatments, CT steaks were the coldest(P\u3c0.05) from 5 to 2 hours prior to thaw point. However, in the final 2 hours, CT steaks were at similar (P\u3e0.05) temperatures as CW and REF. Due to the short period of thawing time and the observed rapid thawing rate, HW samples were the coldest (P\u3c0.05) in the final 10 minutes prior to thaw point.
The Bottom Line:Of the four thaw methods utilized in this study, the safest methods are those approved by the USDA (CW and REF). Thawing meat on the countertop or in hot water may be efficient and convenient methods for consumers, but it is important to take the extra time to thaw meat properly for safety
Baryon polarization in low-energy unpolarized meson-baryon scattering
We compute the polarization of the final-state baryon, in its rest frame, in
low-energy meson--baryon scattering with unpolarized initial state, in
Unitarized BChPT. Free parameters are determined by fitting total and
differential cross-section data (and spin-asymmetry or polarization data if
available) for , and scattering. We also compare our
results with those of leading-order BChPT
The Higgs resonance in vector boson scattering
A heavy Higgs resonance is described in a representation-independent way
which is valid for the whole energy range of 2 -> 2 scattering processes,
including the asymptotic behavior at low and high energies. The low-energy
theorems which follow from to the custodial SU_2 symmetry of the Higgs sector
restrict the possible parameterizations of the lineshape that are consistent in
perturbation theory. Matching conditions are specified which are necessary and
sufficient to relate the parameters arising in different expansions. The
construction is performed explicitly up to next-to-leading order.Comment: 25 pages, revtex, uses epsf, amssym
A survey of free software for the design, analysis, modelling, and simulation of an unmanned aerial vehicle
The objective of this paper is to analyze free software for the design, analysis, modelling, and simulation of an unmanned aerial vehicle (UAV). Free software is the best choice when the reduction of production costs is necessary; nevertheless, the quality of free software may vary. This paper probably does not include all of the free software, but tries to describe or mention at least the most interesting programs. The first part of this paper summarizes the essential knowledge about UAVs, including the fundamentals of flight mechanics and aerodynamics, and the structure of a UAV system. The second section generally explains the modelling and simulation of a UAV. In the main section, more than 50 free programs for the design, analysis, modelling, and simulation of a UAV are described. Although the selection of the free software has been focused on small subsonic UAVs, the software can also be used for other categories of aircraft in some cases; e.g. for MAVs and large gliders. The applications with an historical importance are also included. Finally, the results of the analysis are evaluated and discussed—a block diagram of the free software is presented, possible connections between the programs are outlined, and future improvements of the free software are suggested. © 2015, CIMNE, Barcelona, Spain.Internal Grant Agency of Tomas Bata University in Zlin [IGA/FAI/2015/001, IGA/FAI/2014/006
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