19,699 research outputs found
Structure of super-families
At present the study of nuclear interactions induced by cosmic rays is the unique source of information on the nuclear interactions in the energy region above 10 to the 15th power eV. The phenomena in this energy region are observed by air shower arrays or emulsion chambers installed at high mountain. An emulsion chamber is the pile of lead plates and photo-sensitive layers (nuclear emulsion plates and/or X-ray films) used to detect electron showers. High spatial resolution of photographic material used in the emulsion chamber enables the observation of the phenomena in detail, and recent experiments of emulsion chamber with large area are being carried out at high mountain altitudes by several groups in the world
Effective Theory Approach to the Skyrme model and Application to Pentaquarks
The Skyrme model is reconsidered from an effective theory point of view. From
the most general chiral Lagrangian up to including terms of order ,
and (), new interactions, which have never
been considered before, appear upon collective coordinate quantization. We
obtain the parameter set best fitted to the observed low-lying baryon masses,
by performing the second order perturbative calculations with respect to
. We calculate the masses and the decay widths of the other members
of (mainly) anti-decuplet pentaquark states. The formula for the decay widths
is reconsidered and its baryon mass dependence is clarified.Comment: 65 pages, 1 figure. Revised version:the complete second order
perturbative calculations performed and two appendices adde
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Software fault characteristics: A synthesis of the literature
Faults continue to be a significant problem in software. Understanding the nature of these faults is important for practitioners and researchers. There are many published fault characteristics schemes but no one scheme dominates. Consequently it is difficult for practitioners to effectively evaluate the nature of faults in their software systems, and it is difficult for researchers to compare the types of faults found by different fault detection techniques. In this paper we synthesise previous fault characteristics schemes into one comprehensive scheme. Our scheme provides a richer view of faults than the previous schemes published and presents a comprehensive, unified approach which accommodates the many previous schemes. A characteristics-based view of faults should be considered by future researchers in the analysis of software faults and in the design and evaluation of new fault detection tools. We recommend that our fault characteristics scheme be used as a benchmark scheme
Preparation of Neutron-activated Xenon for Liquid Xenon Detector Calibration
We report the preparation of neutron-activated xenon for the calibration of
liquid xenon (LXe) detectors. Gamma rays from the decay of xenon metastable
states, produced by fast neutron activation, were detected and their activities
measured in a LXe scintillation detector. Following a five-day activation of
natural xenon gas with a Cf-252 (4 x 10^5 n/s) source, the activities of two
gamma ray lines at 164 keV and 236 keV, from Xe-131m and Xe-129m metastable
states, were measured at about 95 and 130 Bq/kg, respectively. We also observed
three additional lines at 35 keV, 100 keV and 275 keV, which decay away within
a few days. No long-lifetime activity was observed after the neutron
activation.Comment: to be published in NIM A, corrected typos in Table 1 and Fig.6 of the
previous versio
Maximal entanglement of two spinor Bose-Einstein condensates
Starting with two weakly-coupled anti-ferromagnetic spinor condensates, we
show that by changing the sign of the coefficient of the spin interaction,
, via an optically-induced Feshbach resonance one can create an
entangled state consisting of two anti-correlated ferromagnetic condensates.
This state is maximally entangled and a generalization of the Bell state from
two anti-correlated spin-1/2 particles to two anti-correlated spin atomic
samples, where is the total number of atoms.Comment: 5 pages, 3 figures, accepted for publication in PR
Molecular Hydrogen Emission Lines in Far Ultraviolet Spectroscopic Explorer Observations of Mira B
We present new Far Ultraviolet Spectroscopic Explorer (FUSE) observations of
Mira A's wind-accreting companion star, Mira B. We find that the strongest
lines in the FUSE spectrum are H2 lines fluoresced by H I Lyman-alpha. A
previously analyzed Hubble Space Telescope (HST) spectrum also shows numerous
Lyman-alpha fluoresced H2 lines. The HST lines are all Lyman band lines, while
the FUSE H2 lines are mostly Werner band lines, many of them never before
identified in an astrophysical spectrum. We combine the FUSE and HST data to
refine estimates of the physical properties of the emitting H2 gas. We find
that the emission can be reproduced by an H2 layer with a temperature and
column density of T=3900 K and log N(H2)=17.1, respectively. Another similarity
between the HST and FUSE data, besides the prevalence of H2 emission, is the
surprising weakness of the continuum and high temperature emission lines,
suggesting that accretion onto Mira B has weakened dramatically. The UV fluxes
observed by HST on 1999 August 2 were previously reported to be over an order
of magnitude lower than those observed by HST and the International Ultraviolet
Explorer (IUE) from 1979--1995. Analysis of the FUSE data reveals that Mira B
was still in a similarly low state on 2001 November 22.Comment: 23 pages, 6 figures; AASTEX v5.0 plus EPSF extensions in mkfig.sty;
accepted by Ap
Extremely high energy hadron and gamma-ray families(3). Core structure of the halo of superfamily
The study of the core structure seen in the halo of Mini-Andromeda 3(M.A.3), which was observed in the Chacaltaya emulsion chamber, is presented. On the assumption that lateral distribution of darkness of the core is exponential type, i.e., D=D0exp(-R/r0), subtraction of D from halo darkness is performed until the cores are gone. The same quantity on cores obtained by this way are summarized. The analysis is preliminary and is going to be developed
Meeting in a Polygon by Anonymous Oblivious Robots
The Meeting problem for searchers in a polygon (possibly with
holes) consists in making the searchers move within , according to a
distributed algorithm, in such a way that at least two of them eventually come
to see each other, regardless of their initial positions. The polygon is
initially unknown to the searchers, and its edges obstruct both movement and
vision. Depending on the shape of , we minimize the number of searchers
for which the Meeting problem is solvable. Specifically, if has a
rotational symmetry of order (where corresponds to no
rotational symmetry), we prove that searchers are sufficient, and
the bound is tight. Furthermore, we give an improved algorithm that optimally
solves the Meeting problem with searchers in all polygons whose
barycenter is not in a hole (which includes the polygons with no holes). Our
algorithms can be implemented in a variety of standard models of mobile robots
operating in Look-Compute-Move cycles. For instance, if the searchers have
memory but are anonymous, asynchronous, and have no agreement on a coordinate
system or a notion of clockwise direction, then our algorithms work even if the
initial memory contents of the searchers are arbitrary and possibly misleading.
Moreover, oblivious searchers can execute our algorithms as well, encoding
information by carefully positioning themselves within the polygon. This code
is computable with basic arithmetic operations, and each searcher can
geometrically construct its own destination point at each cycle using only a
compass. We stress that such memoryless searchers may be located anywhere in
the polygon when the execution begins, and hence the information they initially
encode is arbitrary. Our algorithms use a self-stabilizing map construction
subroutine which is of independent interest.Comment: 37 pages, 9 figure
Learning to Eat Appreciatively and Thoughtfully (EAT): Connecting with Food through School Gardens
Many young people today do not learn to cook, or eat nutritious, regular meals together with their families, or go shopping for produce. Because of this, they do not have the opportunity to develop any real appreciation for food. To make matters worse, many public schools fail to teach students anything at all about the complex environmental and cultural history of food ā how it is produced, preserved, prepared, and distributed. At the same time, schools serve lunches that often lack nutritional value. In this thesis, I argue the importance of giving students the opportunity to connect to food through school gardens and food education programs in schools. First, I trace the history and philosophical origins of school gardens, focusing particularly on the growth of school gardens and relevant literature at the turn of the 20th century and during the two world wars. I then examine the decline and subsequent rise of school gardens during the latter half of the 20th century and analyze two examples of current school gardening and food education programs in the United States: the Edible Schoolyard in Berkeley, California, and the Burlington School Food Project in Burlington, Vermont. Finally, I consider the feasibility of incorporating school gardens and food education into classrooms in Oberlinās schools, and suggest that educating students to be āfood literateā is one critical step towards addressing complex problems that we face today, including climate change and obesity
Effective range from tetramer dissociation data for cesium atoms
The shifts in the four-body recombination peaks, due to an effective range
correction to the zero-range model close to the unitary limit, are obtained and
used to extract the corresponding effective range of a given atomic system. The
approach is applied to an ultracold gas of cesium atoms close to broad Feshbach
resonances, where deviations of experimental values from universal model
predictions are associated to effective range corrections. The effective range
correction is extracted, with a weighted average given by 3.9,
where is the van der Waals length scale; which is consistent with the
van der Waals potential tail for the system. The method can be generally
applied to other cold atom experimental setups to determine the contribution of
the effective range to the tetramer dissociation position.Comment: A section for two-, three- and four-boson bound state formalism is
added, accepted for publication in Phys. Rev.
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