In Which Schools Does Police Presence Most Exacerbate Racial Differentials in Arrest?

This study looks at racial disproportionalities in student arrests, particularly with school police presence. This study extends Homer and Fisher’s (2020) work, which finds higher arrest rates and stronger effects of police presence for Black than White students across schools, by investigating school racial compositions and context factors that are associated with the strongest relationships between police presence and higher arrest rates of Black than White students. Results show the largest within-school arrest rate differences between Black and White students in high schools with officers and that schools with lower Black student enrollment percentages show larger Black-White student arrest gaps

Fluid leakage detector for vacuum applications

A leak detection system for use with a fluid conducting system in a vacuum environment, such as space, is described. The system preferably includes a mesh-like member substantially disposed about the fluid conducting system, and at least one sensor disposed within the mesh-like member. The sensor is capable of detecting a decrease in temperature of the mesh-like member when a leak condition causes the fluid of the fluid conducting system to freeze when exposed to the vacuum environment. Additionally, a signal processor in preferably in communication with the sensor. The sensor transmits an electrical signal to the signal processor such that the signal processor is capable of indicating the location of the fluid leak in the fluid conducting system

Mining Telecommunication Circles via the Call Record and Short Messages

Telecommunication circles are groups of similar customers in telecommunication networks. Mining such circles provides with telecommunication operators great value in developing prospective customers while retaining old ones. However, most of the existing community detecting algorithms utilize mainly the structure of the complex network and ignore the strength of relationship. This paper improves the classic CPM (Clique Percolation Method) algorithm by taking into account both the call record and short messages, and proposes a new algorithms called SR_CPM (Strengthened Relationship CPM). The new algorithm is applied to telecommunication networks and demonstrates superior effectiveness over CPM

Diffusion on Complex Networks : A way to probe their large scale topological structures

A diffusion process on complex networks is introduced in order to uncover their large scale topological structures. This is achieved by focusing on the slowest decaying diffusive modes of the network. The proposed procedure is applied to real-world networks like a friendship network of known modular structure, and an Internet routing network. For the friendship network, its known structure is well reproduced. In case of the Internet, where the structure is far less well-known, one indeed finds a modular structure, and modules can roughly be associated with individual countries. Quantitatively the modular structure of the Internet manifests itself in an approximately 10 times larger participation ratio of its slowest decaying modes as compared to the null model -- a random scale-free network. The extreme edges of the Internet are found to correspond to Russian and US military sites.Comment: Latex, 13 pages, 4 figures (To appear Physica A

Smartphone-based multispectral imaging: system development and potential for mobile skin diagnosis

We investigate the potential of mobile smartphone-based multispectral imaging for the quantitative diagnosis and management of skin lesions. Recently, various mobile devices such as a smartphone have emerged as healthcare tools. They have been applied for the early diagnosis of nonmalignant and malignant skin diseases. Particularly, when they are combined with an advanced optical imaging technique such as multispectral imaging and analysis, it would be beneficial for the early diagnosis of such skin diseases and for further quantitative prognosis monitoring after treatment at home. Thus, we demonstrate here the development of a smartphone-based multispectral imaging system with high portability and its potential for mobile skin diagnosis. The results suggest that smartphone-based multispectral imaging and analysis has great potential as a healthcare tool for quantitative mobile skin diagnosis. © 2016 Optical Society of America.1

A Brownian Model for Crystal Nucleation

In this work a phenomenological stochastic differential equation is proposed to model the time evolution of the radius of a pre-critical molecular cluster during nucleation (the classical order parameter). Such a stochastic differential equation constitutes the basis for the calculation of the (nucleation) induction time under Kramers' theory of thermally activated escape processes. Considering the nucleation stage as a Poisson rare-event, analytical expressions for the induction time statistics are deduced for both steady and unsteady conditions, the latter assuming the semiadiabatic limit. These expressions can be used to identify the underlying mechanism of molecular cluster formation (distinguishing between homogeneous or heterogeneous nucleation from the nucleation statistics is possible) as well as to predict induction times and induction time distributions. The predictions of this model are in good agreement with experimentally measured induction times at constant temperature, unlike the values obtained from the classical equation, but agreement is not so good for induction time statistics. Stochastic simulations truncated to the maximum waiting time of the experiments confirm that this fact is due to the time constraints imposed by experiments. Correcting for this effect, the experimental and predicted curves fit remarkably well. Thus, the proposed model seems to be a versatile tool to predict cluster size distributions, nucleation rates, (nucleation) induction time and induction time statistics for a wide range of conditions (e.g. time-dependent temperature, supersaturation, pH, etc.) where classical nucleation theory is of limited applicability.Comment: 20 pages, 3 figure

Rate description of Fokker-Planck processes with time-periodic parameters

The large time dynamics of a periodically driven Fokker-Planck process possessing several metastable states is investigated. At weak noise transitions between the metastable states are rare. Their dynamics then represent a discrete Markovian process characterized by time dependent rates. Apart from the occupation probabilities, so-called specific probability densities and localizing functions can be associated to each metastable state. Together, these three sets of functions uniquely characterize the large time dynamics of the conditional probability density of the original process. Exact equations of motion are formulated for these three sets of functions and strategies are discussed how to solve them. These methods are illustrated and their usefulness is demonstrated by means of the example of a bistable Brownian oscillator within a large range of driving frequencies from the slow semiadiabatic to the fast driving regime

Evolution of scale-free random graphs: Potts model formulation

We study the bond percolation problem in random graphs of $N$ weighted vertices, where each vertex $i$ has a prescribed weight $P_i$ and an edge can connect vertices $i$ and $j$ with rate $P_iP_j$. The problem is solved by the $q\to 1$ limit of the $q$-state Potts model with inhomogeneous interactions for all pairs of spins. We apply this approach to the static model having $P_i\propto i^{-\mu} (0<\mu<1)$ so that the resulting graph is scale-free with the degree exponent $\lambda=1+1/\mu$. The number of loops as well as the giant cluster size and the mean cluster size are obtained in the thermodynamic limit as a function of the edge density, and their associated critical exponents are also obtained. Finite-size scaling behaviors are derived using the largest cluster size in the critical regime, which is calculated from the cluster size distribution, and checked against numerical simulation results. We find that the process of forming the giant cluster is qualitatively different between the cases of $\lambda >3$ and $2 < \lambda <3$. While for the former, the giant cluster forms abruptly at the percolation transition, for the latter, however, the formation of the giant cluster is gradual and the mean cluster size for finite $N$ shows double peaks.Comment: 34 pages, 9 figures, elsart.cls, final version appeared in NP