A note on cosmological Levi-Civita spacetimes in higher dimensions

We find a class of solutions to cosmological Einstein equations that generalizes the four dimensional cylindrically symmetric spacetimes to higher dimensions. The AdS soliton is a special member of this class with a unique singularity structure.Comment: 3 pages; version to appear in Phys. Rev.

Nonprofit Sector and Part-Time Work: An Analysis of Employer-Employee Matched Data of Child Care Workers

This paper uses a rich employer-employee matched data set to investigate the existence and the extent of nonprofit and part-time wage and compensation differentials in child care. The empirical strategy adjusts for workers' self-selection into the for-profit or nonprofit sectors, into full-time or part-time work, as well as unobserved worker heterogeneity using a discrete factor model. We find differences between the regimes (full-time for-profit, full-time nonprofit, part-time for-profit, part-time nonprofit) in the way in which human capital of the workers are rewarded. There is substantial variation in wages as a function of employee characteristics, and there is variation in wages within sectors. The results indicate that part-time jobs are good' jobs in center-based child care. Furthermore, despite the evidence supporting the labor donation hypothesis, our results indicate the existence of nonprofit wage and compensation premiums, which support the property rights hypothesis.

Guns, Drugs and Juvenile Crime: Evidence from a Panel of Siblings and Twins

Using a nationally-representative panel data set of U.S. high school students (AddHealth data) that contains a relatively large sample of siblings and twins, the paper investigates the impacts of gun availability at home and individual drug use on robbery, burglary, theft and damaging property for juveniles. Using a variety of fixed-effects models that exploit variations over time, the results show that gun availability at home increases the propensity to committing robbery, burglary and theft by about two percentage points for juveniles but has no impact on damaging property. It is unlikely that gun availability is merely a measure of the unobserved home environment because gun availability does not influence other risky or bad behaviors of juveniles. The results show that having access to guns increases the probability of being cut or stabbed by someone and of someone pulling a knife or gun on the juvenile. Estimates obtained from models that exploit variations over time and between siblings and twins indicate that the median impact of cocaine use on the propensity to commit various types of crimes is 23 percentage points. The impact of using inhalants or other drugs is an increase in the propensity to commit crime by 14 and 18 percentage points, respectively.

Catholic Schools and Bad Behavior: A Propensity Score Matching Analysis

Although there is a sizeable literature on the effect of private school attendance on academic student outcomes, the number of studies that investigate the impact of school sector on non-academic outcomes is limited. Using a rich data set, we analyze the impact of Catholic school attendance on the likelihood that teenagers use or sell drugs, commit property crime, have sex, join gangs, attempt suicide, and run away from home. We employ propensity score matching methods to control for the endogeneity of school choice. Catholic school attendance reduces the propensity to use cocaine and to have sex for female students. However, it increases the propensity to use and sell drugs for male students.

A Versatile Active Block: DXCCCII and Tunable Applications

The study describes dual-X controlled current conveyor (DXCCCII) as a versatile active block and its application to inductance simulators for testing. Moreover, the high pass filter application using with DXCCCII based inductance simulator and oscillator with flexible tunable oscillation frequency have been presented and simulated to confirm the theoretical validity. The proposed circuit which has a simple circuit design requires the low-voltage and the DXCCCII can also be tuned in the wide range by the biasing current. The proposed DXCCCII provides a good linearity, high output impedance at Z terminals, and a reasonable current and voltage transfer gain accuracy. The proposed DXCCCII and its applications have been simulated using the CMOS 0.18 µm technology

Gravitational charges of transverse asymptotically AdS spacetimes

Using Killing-Yano symmetries, we construct conserved charges of spacetimes that asymptotically approach to the flat or Anti-de Sitter spaces only in certain directions. In D dimensions, this allows one to define gravitational charges (such as mass and angular momenta densities) of p-dimensional branes/solitons or any other extended objects that curve the transverse space into an asymptotically flat or AdS one. Our construction answers the question of what kind of charges the antisymmetric Killing-Yano tensors lead to.Comment: 11 pages, no figures, REVTeX 4; version 2: important corrections made; version 3: one new paragraph and 2 references added, accepted for publication in PR

The Demand for Medical Care in Urban China

This is the first paper to investigate the determinants of the demand for medical care in the People's Republic of China. It uses a data set that consists of detailed characteristics of 6407 urban households, a continuous measure of health care spending, and price. A two-part model and a discrete factor model are used in the estimation. Household characteristics and work conditions impact the demand for medical care. Income elasticity is around 0.3, indicating medical care is a necessity. Medical care demand is price inelastic, and price elasticity is larger in absolute value for poorer households.

Spherically symmetric solutions of Einstein + non-polynomial gravities

We obtain the static spherically symmetric solutions of a class of gravitational models whose additions to the General Relativity (GR) action forbid Ricci-flat, in particular, Schwarzschild geometries. These theories are selected to maintain the (first) derivative order of the Einstein equations in Schwarzschild gauge. Generically, the solutions exhibit both horizons and a singularity at the origin, except for one model that forbids spherical symmetry altogether. Extensions to arbitrary dimension with a cosmological constant, Maxwell source and Gauss-Bonnet terms are also considered.Comment: 6 pages, no figures, REVTeX

Green's Matrix for a Second Order Self-Adjoint Matrix Differential Operator

A systematic construction of the Green's matrix for a second order, self-adjoint matrix differential operator from the linearly independent solutions of the corresponding homogeneous differential equation set is carried out. We follow the general approach of extracting the Green's matrix from the Green's matrix of the corresponding first order system. This construction is required in the cases where the differential equation set cannot be turned to an algebraic equation set via transform techniques.Comment: 19 page