5,945 research outputs found
Understanding Self-Reported Sexual Violence Perpetration: Correlates and Prevention Participation
Bystander prevention programs seek to educate individuals on the nature of sexual violence and increase bystander efficacy. This study seeks to evaluate the effectiveness of the Bringing in the Bystander (BITB) prevention program through self-reports of perpetration behaviors as well as risk factors associated with perpetration. The bystander prevention program was implemented on a rural mid-sized public university and first-year students were surveyed three times at separate time points (2 weeks, 5 months, and 12 months) after the program conclusion. Results from a correlational and logistic regression analysis show that endorsement of violent peer norms, rape myth acceptance, and rape proclivity of self were all significant correlates of perpetration. The results also indicated that endorsement of coercive peer norms was a predictor of recent perpetration. There were no significant differences in self-reported recent perpetration between the control and treatment group. However, recent perpetration rates did decrease for the treatment group, which means BITB is on the right track to ending sexual violence on college campuses
Characterization of Maximally Random Jammed Sphere Packings: II. Correlation Functions and Density Fluctuations
In the first paper of this series, we introduced Voronoi correlation
functions to characterize the structure of maximally random jammed (MRJ) sphere
packings across length scales. In the present paper, we determine a variety of
correlation functions that can be rigorously related to effective physical
properties of MRJ sphere packings and compare them to the corresponding
statistical descriptors for overlapping spheres and equilibrium hard-sphere
systems. Such structural descriptors arise in rigorous bounds and formulas for
effective transport properties, diffusion and reactions constants, elastic
moduli, and electromagnetic characteristics. First, we calculate the two-point,
surface-void, and surface-surface correlation functions, for which we derive
explicit analytical formulas for finite hard-sphere packings. We show
analytically how the contacts between spheres in the MRJ packings translate
into distinct functional behaviors of these two-point correlation functions
that do not arise in the other two models examined here. Then, we show how the
spectral density distinguishes the MRJ packings from the other disordered
systems in that the spectral density vanishes in the limit of infinite
wavelengths. These packings are hyperuniform, which means that density
fluctuations on large length scales are anomalously suppressed. Moreover, we
study and compute exclusion probabilities and pore size distributions as well
as local density fluctuations. We conjecture that for general disordered
hard-sphere packings, a central limit theorem holds for the number of points
within an spherical observation window. Our analysis links problems of interest
in material science, chemistry, physics, and mathematics. In the third paper,
we will evaluate bounds and estimates of a host of different physical
properties of the MRJ sphere packings based on the structural characteristics
analyzed in this paper.Comment: 25 pages, 13 Figures; corrected typos, updated reference
Characterization of maximally random jammed sphere packings: Voronoi correlation functions
We characterize the structure of maximally random jammed (MRJ) sphere
packings by computing the Minkowski functionals (volume, surface area, and
integrated mean curvature) of their associated Voronoi cells. The probability
distribution functions of these functionals of Voronoi cells in MRJ sphere
packings are qualitatively similar to those of an equilibrium hard-sphere
liquid and partly even to the uncorrelated Poisson point process, implying that
such local statistics are relatively structurally insensitive. This is not
surprising because the Minkowski functionals of a single Voronoi cell
incorporate only local information and are insensitive to global structural
information. To improve upon this, we introduce descriptors that incorporate
nonlocal information via the correlation functions of the Minkowski functionals
of two cells at a given distance as well as certain cell-cell probability
density functions. We evaluate these higher-order functions for our MRJ
packings as well as equilibrium hard spheres and the Poisson point process. We
find strong anticorrelations in the Voronoi volumes for the hyperuniform MRJ
packings, consistent with previous findings for other pair correlations [A.
Donev et al., Phys. Rev. Lett. 95, 090604 (2005)], indicating that large-scale
volume fluctuations are suppressed by accompanying large Voronoi cells with
small cells, and vice versa. In contrast to the aforementioned local Voronoi
statistics, the correlation functions of the Voronoi cells qualitatively
distinguish the structure of MRJ sphere packings (prototypical glasses) from
that of the correlated equilibrium hard-sphere liquids. Moreover, while we did
not find any perfect icosahedra (the locally densest possible structure in
which a central sphere contacts 12 neighbors) in the MRJ packings, a
preliminary Voronoi topology analysis indicates the presence of strongly
distorted icosahedra.Comment: 13 pages, 10 figure
Characterization of Maximally Random Jammed Sphere Packings. III. Transport and Electromagnetic Properties via Correlation Functions
In the first two papers of this series, we characterized the structure of
maximally random jammed (MRJ) sphere packings across length scales by computing
a variety of different correlation functions, spectral functions, hole
probabilities, and local density fluctuations. From the remarkable structural
features of the MRJ packings, especially its disordered hyperuniformity,
exceptional physical properties can be expected. Here, we employ these
structural descriptors to estimate effective transport and electromagnetic
properties via rigorous bounds, exact expansions, and accurate analytical
approximation formulas. These property formulas include interfacial bounds as
well as universal scaling laws for the mean survival time and the fluid
permeability. We also estimate the principal relaxation time associated with
Brownian motion among perfectly absorbing traps. For the propagation of
electromagnetic waves in the long-wavelength limit, we show that a dispersion
of dielectric MRJ spheres within a matrix of another dielectric material forms,
to a very good approximation, a dissipationless disordered and isotropic
two-phase medium for any phase dielectric contrast ratio. We compare the
effective properties of the MRJ sphere packings to those of overlapping
spheres, equilibrium hard-sphere packings, and lattices of hard spheres.
Moreover, we generalize results to micro- and macroscopically anisotropic
packings of spheroids with tensorial effective properties. The analytic bounds
predict the qualitative trend in the physical properties associated with these
structures, which provides guidance to more time-consuming simulations and
experiments. They especially provide impetus for experiments to design
materials with unique bulk properties resulting from hyperuniformity, including
structural-color and color-sensing applications.Comment: 19 pages, 16 Figure
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