Men Experiencing Homelessness: A Qualitative Investigation of Multiple Stigmas

Homelessness is a pervasive and problematic phenomenon. Unfortunately, programs designed to reduce or eliminate homelessness face a number of challenges. One such challenge involves difficulty engaging and retaining clientele who are experiencing homelessness in services. The literature suggests that one explanation for this difficulty involves the stigmatization experiences that individuals who are homeless accumulate over time. However, the relationship between stigmatization and the psychosocial functioning of individuals facing homelessness has rarely been investigated empirically, and it is unclear how well various theories of stigma apply to this unique population. The purpose of the current paper is to propose a grounded theory study of how a specific subgroup of the homeless population experiences and responds to multiple sources of social stigmatization: African American men experiencing homelessness and facing co-occurring mental illness and substance use disorders

Microcanonical Approach to the Simulation of First-Order Phase Transitions

A generalization of the microcanonical ensemble suggests a simple strategy for the simulation of first order phase transitions. At variance with flat-histogram methods, there is no iterative parameters optimization, nor long waits for tunneling between the ordered and the disordered phases. We test the method in the standard benchmark: the Q-states Potts model (Q=10 in 2 dimensions and Q=4 in 3 dimensions), where we develop a cluster algorithm. We obtain accurate results for systems with more than one million of spins, outperforming flat-histogram methods that handle up to tens of thousands of spins.Comment: 4 pages, 3 postscript figure

Nomenclatorial corrections for Dasytidae and Malachiidae (Coleoptera)

Nomenclatorial corrections are proposed for 9 cases of homonymy and 5 cases of synonymy in the Dasytidae and Malachiidae. For the homonyms, the following new names are proposed: Aplocnemus montbabor Mayor, new name, for A. baborensis Pic 1922; Dasytes loboensis Mayor, new name, for D. nevadensis Pic 1954; Dasyte sminor Mayor, new name, for D. minutus Casey 1895; Amalthocuspici Mayor, new name, for A. metallicus (Pic 1955); Attalus tribandipennis Mayor, new name, for A. tricoloripennis Pic 1927; Attalus ulkei Mayor, new name, for A. laevicollis (Horn 1872); Laiuscephalus Mayor, new name, for L. verticalis Fairmaire; Sphinginopalpus mpumalangaensis Mayor, new name, for S. nigriceps Wittmer 1994; Sphinginopalpus rufinotus Mayor, new name, for S. rufithorax Wittmer 1994. Scelopristis Mayor new genus, is proposed for the species of Pristocelis LeConte 1862, a junior synonym of Trichochrous Motschulsky 1860; the available name Hadrocnemus Kraatz 1895 is proposed for the species of Apalochrus Erichson 1840 a senior objective synonym of Paritinus Abeille de Perrin 1891. The following new subjective synonyms are proposed: Pristoscelis Le Conte 1862 is a junior synonym of Trichochrous Motschulsky 1860; Anthocomus (Paremballus) Abeille de Perrin 1891 is a junior synonym of Anthocomus (Anthocomus) Erichson 1840; Anthocomus (Neotrotus) Abeille de Perrin 1891 is a juniorsynonym of Anthocomus (Celidus) Mulsant and Rey 1867; Amanicollops Pic 1908 is a junior synonym of Hadrocnemus Kraatz 1895. Paratinus Abeille de Perrin 1891 is a junior objective synonym of Apalochrus Erichson 1840). New combinations for North American species from Attalus Erichson, Anthocomus Erichson, Microlipus LeConte and Tanaops LeConte formalized here were suggested by Mayor (2002). The Characters indicating the close relationship of Neadasytes Hatch 1962 to Dasytastes Casey 1895, and of Paradasytes Hatch 1962 to Dasytellus Casey 1895 are discussed. Afrocolotes Wittmer 1960 and Olistherarthrus Champion 1922, listed as synonyms of Temnopsophus Horn 1872 by Evers (1989: 6), are here considered distinct genera. These changes are proposed here so that they can be included in a world catalog in preparation

Noise-enhanced computation in a model of a cortical column

Varied sensory systems use noise in order to enhance detection of weak signals. It has been conjectured in the literature that this effect, known as stochastic resonance, may take place in central cognitive processes such as the memory retrieval of arithmetical multiplication. We show in a simplified model of cortical tissue, that complex arithmetical calculations can be carried out and are enhanced in the presence of a stochastic background. The performance is shown to be positively correlated to the susceptibility of the network, defined as its sensitivity to a variation of the mean of its inputs. For nontrivial arithmetic tasks such as multiplication, stochastic resonance is an emergent property of the microcircuitry of the model network

Transient Information Flow in a Network of Excitatory and Inhibitory Model Neurons: Role of Noise and Signal Autocorrelation

We investigate the performance of sparsely-connected networks of integrate-and-fire neurons for ultra-short term information processing. We exploit the fact that the population activity of networks with balanced excitation and inhibition can switch from an oscillatory firing regime to a state of asynchronous irregular firing or quiescence depending on the rate of external background spikes. We find that in terms of information buffering the network performs best for a moderate, non-zero, amount of noise. Analogous to the phenomenon of stochastic resonance the performance decreases for higher and lower noise levels. The optimal amount of noise corresponds to the transition zone between a quiescent state and a regime of stochastic dynamics. This provides a potential explanation on the role of non-oscillatory population activity in a simplified model of cortical micro-circuits.Comment: 27 pages, 7 figures, to appear in J. Physiology (Paris) Vol. 9

The Stellar Dynamics of Omega Centauri

The stellar dynamics of Omega Centauri are inferred from the radial velocities of 469 stars measured with CORAVEL (Mayor et al. 1997). Rather than fit the data to a family of models, we generate estimates of all dynamical functions nonparametrically, by direct operation on the data. The cluster is assumed to be oblate and edge-on but mass is not assumed to follow light. The mean motions are consistent with axisymmetry but the rotation is not cylindrical. The peak rotational velocity is 7.9 km/s at 11 pc from the center. The apparent rotation of Omega Centauri is attributable in part to its proper motion. We reconstruct the stellar velocity ellipsoid as a function of position, assuming isotropy in the meridional plane. We find no significant evidence for a difference between the velocity dispersions parallel and perpendicular to the meridional plane. The mass distribution inferred from the kinematics is slightly more extended than, though not strongly inconsistent with, the luminosity distribution. We also derive the two-integral distribution function f(E,Lz) implied by the velocity data.Comment: 25 Latex pages, 12 Postscript figures, uses aastex, epsf.sty. Submitted to The Astronomical Journal, December 199

Mean-value identities as an opportunity for Monte Carlo error reduction

In the Monte Carlo simulation of both Lattice field-theories and of models of Statistical Mechanics, identities verified by exact mean-values such as Schwinger-Dyson equations, Guerra relations, Callen identities, etc., provide well known and sensitive tests of thermalization bias as well as checks of pseudo random number generators. We point out that they can be further exploited as "control variates" to reduce statistical errors. The strategy is general, very simple, and almost costless in CPU time. The method is demonstrated in the two dimensional Ising model at criticality, where the CPU gain factor lies between 2 and 4.Comment: 10 pages, 2 tables. References updated and typos correcte

Testing statics-dynamics equivalence at the spin-glass transition in three dimensions

The statics-dynamics correspondence in spin glasses relate non-equilibrium results on large samples (the experimental realm) with equilibrium quantities computed on small systems (the typical arena for theoretical computations). Here we employ statics-dynamics equivalence to study the Ising spin-glass critical behavior in three dimensions. By means of Monte Carlo simulation, we follow the growth of the coherence length (the size of the glassy domains), on lattices too large to be thermalized. Thanks to the large coherence lengths we reach, we are able to obtain accurate results in excellent agreement with the best available equilibrium computations. To do so, we need to clarify the several physical meanings of the dynamic exponent close to the critical temperature.Comment: Version to appear in Physical Review

The dynamical structure factor in disordered systems

We study the spectral width as a function of the external momentum for the dynamical structure factor of a disordered harmonic solid, considered as a toy model for supercooled liquids and glasses. Both in the context of single-link coherent potential approximation and of a single-defect approximation, two different regimes are clearly identified: if the density of states at zero energy is zero, the Rayleigh $p^4$ law is recovered for small momentum. On the contrary, if the disorder induces a non vanishing density of states at zero energy, a linear behaviour is obtained. The dynamical structure factor is numerically calculated in lattices as large as $96^3$, and satisfactorily agrees with the analytical computations.Comment: 7 pages plus 4 postscript figure

Evaluating the stability of atmospheric lines with HARPS

Context: In the search for extrasolar systems by radial velocity technique, a precise wavelength calibration is necessary for high-precision measurements. The choice of the calibrator is a particularly important question in the infra-red domain, where the precision and exploits still fall behind the achievements of the optical. Aims: We investigate the long-term stability of atmospheric lines as a precise wavelength reference and analyze their sensitivity to different atmospheric and observing conditions. Methods: We use HARPS archive data on three bright stars, Tau Ceti, Mu Arae and Epsilon Eri, spanning 6 years and containing high-cadence measurements over several nights. We cross-correlate this data with an O2 mask and evaluate both radial velocity and bisector variations down to a photon noise of 1 m/s. Results: We find that the telluric lines in the three data-sets are stable down to 10 m/s (r.m.s.) over the 6 years. We also show that the radial velocity variations can be accounted for by simple atmospheric models, yielding a final precision of 1-2 m/s. Conclusions: The long-term stability of atmospheric lines was measured as being of 10 m/s over six years, in spite of atmospheric phenomena. Atmospheric lines can be used as a wavelength reference for short-time-scales programs, yielding a precision of 5 m/s "out-of-the box". A higher precision, down to 2 m/s can be reached if the atmospheric phenomena are corrected for by the simple atmospheric model described, making it a very competitive method even on long time-scales.Comment: 7 pages, accepted for publication in A&