3,729 research outputs found
Importance of Baryon-Baryon Coupling in Hypernuclei
The coupling in --hypernuclei and coupling in --hypernuclei produce novel
physics not observed in the conventional, nonstrange sector. Effects of
conversion in H are reviewed.
The role of coupling suppression in the
--hypernuclei due to Pauli blocking is highlighted, and the
implications for the structure of B are explored.
Suppression of conversion in He is hypothesized as the reason that the
matrix element is small. Measurement of H is
proposed to investigate the full interaction. The
implication for analog states is discussed.Comment: 17 pages LATEX, 1 figure uuencoded postscrip
Discharge destination from an acute care for the elderly (ACE) unit
Older adults age 65 and over account for a disproportional number of hospital stays and discharges compared to other age groups. The objective of this paper is to describe placement and characteristics of older patients discharged from an acute care for the elderly (ACE) unit. The study sample consists of 1,351 men and women aged 65 years or older that were discharged from the ACE Unit during a 12-month period. The mean number of discharges per month was 109.2 ± 28.4. Most of the subjects were discharged home or home with home health 841, 62.3%. The oldest elderly and patients who had been admitted from long term care institutions or from skilled nursing facilities to the ACE unit were less likely to return to home
Idealness of k-wise intersecting families
A clutter is k-wise intersecting if every k members have a common element, yet no element belongs to all members. We conjecture that, for some integer k â„ 4, every k-wise intersecting clutter is non-ideal. As evidence for our conjecture, we prove it for k = 4 for the class of binary clutters. Two key ingredients for our proof are Jaegerâs 8-flow theorem for graphs, and Seymourâs characterization of the binary matroids with the sums of circuits property. As further evidence for our conjecture, we also note that it follows from an unpublished conjecture of Seymour from 1975. We also discuss connections to the chromatic number of a clutter, projective geometries over the two-element field, uniform cycle covers in graphs, and quarter-integral packings of value two in ideal clutters
Population coding by globally coupled phase oscillators
A system of globally coupled phase oscillators subject to an external input
is considered as a simple model of neural circuits coding external stimulus.
The information coding efficiency of the system in its asynchronous state is
quantified using Fisher information. The effect of coupling and noise on the
information coding efficiency in the stationary state is analyzed. The
relaxation process of the system after the presentation of an external input is
also studied. It is found that the information coding efficiency exhibits a
large transient increase before the system relaxes to the final stationary
state.Comment: 7 pages, 9 figures, revised version, new figures added, to appear in
JPSJ Vol 75, No.
Ideal hierarchical secret sharing schemes
Hierarchical secret sharing is among the most natural generalizations of threshold secret sharing, and it has attracted a lot of attention from the invention of secret sharing until nowadays. Several constructions of ideal hierarchical secret sharing schemes have been proposed, but it was not known what access structures admit such a scheme. We solve this problem by providing a natural definition for the family of the hierarchical access structures and, more importantly, by presenting a complete characterization of the ideal hierarchical access structures, that is, the ones admitting an ideal secret sharing scheme. Our characterization deals with the properties of the hierarchically minimal sets of the access structure, which are the minimal qualified sets whose participants are in the lowest possible levels in the hierarchy. By using our characterization, it can be efficiently checked whether any given hierarchical access structure that is defined by its hierarchically minimal sets is ideal. We use the well known connection between ideal secret sharing and matroids and, in particular, the fact that every ideal access structure is a matroid port. In addition, we use recent results on ideal multipartite access structures and the connection between multipartite matroids and integer polymatroids. We prove that every ideal hierarchical access structure is the port of a representable matroid and, more specifically, we prove that every ideal structure in this family admits ideal linear secret sharing schemes over fields of all characteristics. In addition, methods to construct such ideal schemes can be derived from the results in this paper and the aforementioned ones on ideal multipartite secret sharing. Finally, we use our results to find a new proof for the characterization of the ideal weighted threshold access structures that is simpler than the existing one.Peer ReviewedPostprint (author's final draft
Synthesis of Spherical 4R Mechanism for Path Generation using Differential Evolution
The problem of path generation for the spherical 4R mechanism is solved using
the Differential Evolution algorithm (DE). Formulas for the spherical geodesics
are employed in order to obtain the parametric equation for the generated
trajectory. Direct optimization of the objective function gives the solution to
the path generation task without prescribed timing. Therefore, there is no need
to separate this task into two stages to make the optimization. Moreover, the
order defect problem can be solved without difficulty by means of manipulations
of the individuals in the DE algorithm. Two examples of optimum synthesis
showing the simplicity and effectiveness of this approach are included.Comment: Submitted to Mechanism and Machine Theor
On Hilberg's Law and Its Links with Guiraud's Law
Hilberg (1990) supposed that finite-order excess entropy of a random human
text is proportional to the square root of the text length. Assuming that
Hilberg's hypothesis is true, we derive Guiraud's law, which states that the
number of word types in a text is greater than proportional to the square root
of the text length. Our derivation is based on some mathematical conjecture in
coding theory and on several experiments suggesting that words can be defined
approximately as the nonterminals of the shortest context-free grammar for the
text. Such operational definition of words can be applied even to texts
deprived of spaces, which do not allow for Mandelbrot's ``intermittent
silence'' explanation of Zipf's and Guiraud's laws. In contrast to
Mandelbrot's, our model assumes some probabilistic long-memory effects in human
narration and might be capable of explaining Menzerath's law.Comment: To appear in Journal of Quantitative Linguistic
Evaluating Greek equity funds using data envelopment analysis
This study assesses the relative performance of Greek equity funds employing a non-parametric method, specifically Data Envelopment Analysis (DEA). Using an original sample of cost and operational attributes we explore the e€ect of each variable on funds' operational efficiency for an oligopolistic and bank-dominated fund industry. Our results have significant implications for the investors' fund selection process since we are able to identify potential sources of inefficiencies for the funds. The most striking result is that the percentage of assets under management affects performance negatively, a conclusion which may be related to the structure of the domestic stock market. Furthermore, we provide evidence against the notion of funds' mean-variance efficiency
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