Wakes and differential charging of large bodies in low Earth orbit

Highlights of earlier results using the Inside-Out WAKE code on wake structures of LEO spacecraft are reviewed. For conducting bodies of radius large compared with the Debye length, a high Mach number wake develops a negative potential well. Quasineutrality is violated in the very near wake region, and the wake is relatively empty for a distance downstream of about one half of a Mach number of radii. There is also a suggestion of a core of high density along the axis. A comparison of rigorous numerical solutions with in situ wake data from the AE-C satellite suggests that the so called neutral approximation for ions (straight line trajectories, independent of fields) may be a reasonable approximation except near the center of the near wake. This approximation is adopted for very large bodies. Work concerned with the wake point potential of very large nonconducting bodies such as the shuttle orbiter is described. Using a cylindrical model for bodies of this size or larger in LEO (body radius up to 10 to the 5th power Debye lengths), approximate solutions are presented based on the neutral approximation (but with rigorous trajectory calculations for surface current balance). There is a negative potential well if the body is conducting, and no well if the body is nonconducting. In the latter case the wake surface itself becomes highly negative. The wake point potential is governed by the ion drift energy

Thundercloud electrification models in atmospheric electricity and meteorology

A survey is presented of presently-available theoretical models. The models are classified into three main groups: (1) convection models, (2) precipitation models, and (3) general models. The strengths and weaknesses of the models, their dimensionalities and degrees of sophistication, the nature of their inputs and outputs, and the various specific charging mechanisms treated by them, are considered. In results obtained to date, the convection models predict no significant electrification enhancement based on conductivity gradients and convection alone, with the assumed air circulation patterns. Results of the precipitation models show that the initial electrification can occur rapidly and stably through noninductive collision mechanisms involving ice, and breakdown-strength electric fields can relatively easily be achieved subsequently through the collisional-inductive mechanism. A critical difficulty of the collision mechanisms is imprecise knowledge of relaxation times versus contact times, which can easily lead to overestimates of electrification. The general model results tend to support those of the precipitation models in emphasizing the high potential effectiveness of the collisional-inductive mechanism

Elderly Health and Salaries in the Mexican Labor Market

Little work exists on elderly health, work and salaries in developing countries. This paper aims to contribute to this literature in the areas of health and income of the elderly. The main purpose of this paper is to investigate the determinants of elderly health in the context of a developing country, Mexico,and the relationship between these health indicators and earnings in the labor market. We analyze the determinants of elderly health in Mexico, considering a number of different measures of health status, and we use these indicators to evaluate the impact of health on the income of working elderly individuals. We use the National Mexican Aging Survey of 1994, which contains detailed self-reported indicators of health as well as labor market information, to tease out these potential relationships. The results find that health measures have a strong negative effect on wages for male elderly workers. Our lowest point estimations demonstrate that poor health lowers hourly earnings by 58 percent. These are sizable effects, particularly within the context of a developing country, which does not have a universal social security system and may therefore imply that many elderly individuals work, whether or not their health level permits it. Poor health may also prevent others from working, and thereby contribute to high poverty rates among the elderly.

Computer program for afterheat temperature distribution for mobile nuclear power plant

ESATA computer program was developed to analyze thermal safety aspects of post-impacted mobile nuclear power plants. Program is written in FORTRAN 4 and designed for IBM 7094/7044 direct coupled system

Labor market shocks and their impacts on work and schooling

The authors use individual observations from a panel of families during the period of the peso crisis in Mexico to investigate whether and how labor market shocks, as proxied by changes in the gender- and age-specific unemployment rates in the metropolitan area of the household, affect the intertemporal time allocation of adult members and children. Their findings suggest that significant added-worker effects are in operation, especially for adult females of poorer households and in some cases children. The same shocks also increase significantly the probability that children do not continue school in the next year. The paper also presents evidence suggesting differential treatment based on the sex of children within families.FCND ,Unemployment Mexico. ,Labor market Mexico. ,Urban economics. ,Economic situation. ,Insurance. ,Gender issues. ,

Kelvin-Helmholtz instability in an atomic superfluid

We demonstrate an experimentally feasible method for generating the classical Kelvin-Helmholtz instability in a single component atomic Bose-Einstein condensate. By progressively reducing a potential barrier between two counter-flowing channels we seed a line of quantised vortices, which precede to form progressively larger clusters, mimicking the classical roll-up behaviour of the Kelvin-Helmholtz instability. This cluster formation leads to an effective superfluid shear layer, formed through the collective motion of many quantised vortices. From this we demonstrate a straightforward method to measure the effective viscosity of a turbulent quantum fluid in a system with a moderate number of vortices, within the range of current experimental capabilities.Comment: 7 pages, 8 figure

Monitoring of solar far ultraviolet radiation from the OSO-5 satellite

A spectrophotometer for monitoring the solar EUV in three broad wavelength bands is described. The kind of data obtained, along with sources of error, are presented. The content of the tape library which contains the data is outlined. The scientific results are discussed. These include the following: solar flares in the EUV, solar eclipse observations in the EUV, SFD's and relationship to solar flares, and the application of satellite sunrise and sunset data for the study of model upper atmospheres for the earth

Conditional cash transfers and their impact on child work and schooling

In this paper we investigate whether a conditional cash transfer program such as the Programa Nacional de Educación, Salud y Alimentación (PROGRESA) can simultaneously combat the problems of low school attendance and child work. PROGRESA is a new program of the Mexican government aimed at alleviating extreme poverty in rural areas. It combats the different causes of poverty by providing cash benefits that are targeted directly to households on the condition of children attending school and visiting health clinics on a regular basis. Some of the questions addressed are as follows: Does the program reduce child labor? Does it increase participation in school activities? Does the latter occur at the expense of children's leisure time? And how do the effects of the program vary by age group and gender? Our empirical analysis relies on data from a quasi-experimental design used to evaluate the impact of the program involving a sample of communities that receive PROGRESA benefits (treatment) and comparable communities that receive benefits at a later time (control). We estimate the effect of “treatment on the treated” using both double-difference and cross sectional difference estimators. Our estimates show significant increases in the school attendance of boys and girls that are accompanied by significant reductions in the participation of boys and girls in work activities. We also find that the program has a lower impact on the incidence of work for girls relative to boys.FCND ,Transfer payments. ,Income Mexico. ,Public health. ,Children Mexico. ,Poverty. ,

Calculation of sheath and wake structure about a pillbox-shaped spacecraft in a flowing plasma

A computer program was used for studies of the disturbed zones around bodies in flowing plasmas, particularly spacecraft and their associated sheaths and wakes. The program solved a coupled Poisson-Vlasov system of nonlinear partial differential integral equations to obtain distributions of electric potential and ion and electron density about a finite length cylinder in a plasma flow at arbitrary ion Mach numbers. The approach was applicable to a larger range of parameters than other available approaches. In sample calculations, bodies up to 100 Debye lengths in radius were treated, that is, larger than any previously treated realistically. Applications were made to in-situ satellite experiments