4,770 research outputs found
Pathways to Disability Income among Persons with Severe, Persistent Psychiatric Disorders
[Excerpt] Harsh skepticism pervades current public debate about who deserves public support and on what basis, particularly regarding the claims of individuals with disabling illness and injury. Heretofore, these claims were accepted, even reservedly, and the needs of such individuals were considered to be legitimate even when they were monitored closely. The Supplemental Security Income (SSI) and Social Security Disability Insurance (SSDI) programs and their recipients have been among the most visible and vulnerable targets of increased scrutiny and shrinking public beneficence. In 1997, congressional legislation redefined SSI eligibility for children, sparked largely by concerns that children have been deployed to engage in a type of public begging by acting crazy in order to secure benefits for their families. Maladaptive behaviors was removed from the mental disorder listings, and the Social Security Administration (SSA) estimates that 135,000 children will lose their benefits after review. In March 1996, Congress eliminated SSI, SSDI, Medicare, and Medicaid benefits for persons whose drug addiction or alcoholism is a prominent cause of disability, and as a result 141,000 recipients have been terminated. The SSA also was ordered to begin another sweeping review of all recipients of disability income. SSA officials reportedly expect this process to produce a termination rate of 14 percent, resulting in an estimated 196,000 additional individuals who would cease to receive SSI and SSDI
The parity-violating asymmetry in the 3He(n,p)3H reaction
The longitudinal asymmetry induced by parity-violating (PV) components in the
nucleon-nucleon potential is studied in the charge-exchange reaction 3He(n,p)3H
at vanishing incident neutron energies. An expression for the PV observable is
derived in terms of T-matrix elements for transitions from the {2S+1}L_J=1S_0
and 3S_1 states in the incoming n-3He channel to states with J=0 and 1 in the
outgoing p-3H channel. The T-matrix elements involving PV transitions are
obtained in first-order perturbation theory in the hadronic weak-interaction
potential, while those connecting states of the same parity are derived from
solutions of the strong-interaction Hamiltonian with the
hyperspherical-harmonics method. The coupled-channel nature of the scattering
problem is fully accounted for. Results are obtained corresponding to realistic
or chiral two- and three-nucleon strong-interaction potentials in combination
with either the DDH or pionless EFT model for the weak-interaction potential.
The asymmetries, predicted with PV pion and vector-meson coupling constants
corresponding (essentially) to the DDH "best values" set, range from -9.44 to
-2.48 in units of 10^{-8}, depending on the input strong-interaction
Hamiltonian. This large model dependence is a consequence of cancellations
between long-range (pion) and short-range (vector-meson) contributions, and is
of course sensitive to the assumed values for the PV coupling constants.Comment: 19 pages, 15 tables, revtex
Quantum critical point in the spin glass-antiferromagnetism competition in Kondo-lattice systems
A theory is proposed to describe the competition among antiferromagnetism
(AF), spin glass (SG) and Kondo effect. The model describes two Kondo
sublattices with an intrasite Kondo interaction strength and an
interlattice quantum Ising interaction in the presence of a transverse field
. The interlattice coupling is a random Gaussian distributed variable
(with average and variance ) while the field is
introduced as a quantum mechanism to produce spin flipping. The path integral
formalism is used to study this fermionic problem where the spin operators are
represented by bilinear combinations of Grassmann fields. The disorder is
treated within the framework of the replica trick. The free energy and the
order parameters of the problem are obtained by using the static ansatz and by
choosing both and to allow, as previously,
a better comparison with the experimental findings.
The results indicate the presence of a SG solution at low and for
temperature ( is the freezing temperature). When is
increased, a mixed phase AF+SG appears, then an AF solution and finally a Kondo
state is obtained for high values of . Moreover, the behaviors of the
freezing and Neel temperatures are also affected by the relationship between
and the transverse field . The first one presents a slight
decrease while the second one decreases towards a Quantum Critical Point (QCP).
The obtained phase diagram has the same sequence as the experimental one for
, if is assumed to increase with , and
in addition, it also shows a qualitative agreement concerning the behavior of
the freezing and the Neel temperatures.Comment: 11 pages, 3 figures, accepted for publication in J. Phys.
Cost benefit analysis of space communications technology. Volume 2: Final report
For abstract, see preceding accession
Cost benefit analysis of space communications technology: Volume 1: Executive summary
The questions of (1) whether or not NASA should support the further development of space communications technology, and, if so, (2) which technology's support should be given the highest priority are addressed. Insofar as the issues deal principally with resource allocation, an economics perspective is adopted. The resultant cost benefit methodology utilizes the net present value concept in three distinct analysis stages to evaluate and rank those technologies which pass a qualification test based upon probable (private sector) market failure. User-preference and technology state-of-the-art surveys were conducted (in 1975) to form a data base for the technology evaluation. The program encompassed near-future technologies in space communications earth stations and satellites, including the noncommunication subsystems of the satellite (station keeping, electrical power system, etc.). Results of the research program include confirmation of the applicability of the methodology as well as a list of space communications technologies ranked according to the estimated net present value of their support (development) by NASA
Benefit-cost methodology study with example application of the use of wind generators
An example application for cost-benefit methodology is presented for the use of wind generators. The approach adopted for the example application consisted of the following activities: (1) surveying of the available wind data and wind power system information, (2) developing models which quantitatively described wind distributions, wind power systems, and cost-benefit differences between conventional systems and wind power systems, and (3) applying the cost-benefit methodology to compare a conventional electrical energy generation system with systems which included wind power generators. Wind speed distribution data were obtained from sites throughout the contiguous United States and were used to compute plant factor contours shown on an annual and seasonal basis. Plant factor values (ratio of average output power to rated power) are found to be as high as 0.6 (on an annual average basis) in portions of the central U. S. and in sections of the New England coastal area. Two types of wind power systems were selected for the application of the cost-benefit methodology. A cost-benefit model was designed and implemented on a computer to establish a practical tool for studying the relative costs and benefits of wind power systems under a variety of conditions and to efficiently and effectively perform associated sensitivity analyses
Hypothalamic Agrp Neurons Drive Stereotypic Behaviors beyond Feeding
SummaryThe nervous system evolved to coordinate flexible goal-directed behaviors by integrating interoceptive and sensory information. Hypothalamic Agrp neurons are known to be crucial for feeding behavior. Here, however, we show that these neurons also orchestrate other complex behaviors in adult mice. Activation of Agrp neurons in the absence of food triggers foraging and repetitive behaviors, which are reverted by food consumption. These stereotypic behaviors that are triggered by Agrp neurons are coupled with decreased anxiety. NPY5 receptor signaling is necessary to mediate the repetitive behaviors after Agrp neuron activation while having minor effects on feeding. Thus, we have unmasked a functional role for Agrp neurons in controlling repetitive behaviors mediated, at least in part, by neuropeptidergic signaling. The findings reveal a new set of behaviors coupled to the energy homeostasis circuit and suggest potential therapeutic avenues for diseases with stereotypic behaviors.PaperCli
Random billiards with wall temperature and associated Markov chains
By a random billiard we mean a billiard system in which the standard specular
reflection rule is replaced with a Markov transition probabilities operator P
that, at each collision of the billiard particle with the boundary of the
billiard domain, gives the probability distribution of the post-collision
velocity for a given pre-collision velocity. A random billiard with
microstructure (RBM) is a random billiard for which P is derived from a choice
of geometric/mechanical structure on the boundary of the billiard domain. RBMs
provide simple and explicit mechanical models of particle-surface interaction
that can incorporate thermal effects and permit a detailed study of
thermostatic action from the perspective of the standard theory of Markov
chains on general state spaces.
We focus on the operator P itself and how it relates to the
mechanical/geometric features of the microstructure, such as mass ratios,
curvatures, and potentials. The main results are as follows: (1) we
characterize the stationary probabilities (equilibrium states) of P and show
how standard equilibrium distributions studied in classical statistical
mechanics, such as the Maxwell-Boltzmann distribution and the Knudsen cosine
law, arise naturally as generalized invariant billiard measures; (2) we obtain
some basic functional theoretic properties of P. Under very general conditions,
we show that P is a self-adjoint operator of norm 1 on an appropriate Hilbert
space. In a simple but illustrative example, we show that P is a compact
(Hilbert-Schmidt) operator. This leads to the issue of relating the spectrum of
eigenvalues of P to the features of the microstructure;(3) we explore the
latter issue both analytically and numerically in a few representative
examples;(4) we present a general algorithm for simulating these Markov chains
based on a geometric description of the invariant volumes of classical
statistical mechanics
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