Debris Disk Radiative Transfer Simulation Tool (DDS)

A WWW interface for the simulation of spectral energy distributions of optically thin dust configurations with an embedded radiative source is presented. The density distribution, radiative source, and dust parameters can be selected either from an internal database or defined by the user. This tool is optimized for studying circumstellar debris disks where large grains are expected to determine the far-infrared through millimeter dust reemission spectral energy distribution. The tool is available at http://aida28.mpia-hd.mpg.de/~swolf/ddsComment: Comp. Phys. Comm, 2005, in pres

Atrazine Degradation, Sorption and Bioconcentration in Water Systems

The herbicide atrazine is used extensively to control broadleaf and grass weeds in such crops as sorghum and corn. A small portion of the atrazine may be lost from the area of application by surface runoff and could enter a stream or lake. The objective of this study was to evaluate atrazine degradation, sorption, and bioconcentration in watersediment systems. The results indicated that sediments with lower pH values and higher organic matter levels adsorbed higher levels of atrazine than sediments with neutral pH values and lower organic matter levels. Microbial decomposition of the herbicide was slow under the conditions of this study. Accumulation of atrazine by microorganisms in an aqueous system was demonstrated4 The results indicated that the organic fraction of a water system may be the most important adsorption ccmponent. Data from this study will be useful in assessing the ramifications of herbicides in aquatic ecosystems and provide a better understanding of the reactions of herbicides in sediment-water systans

Nonparametric detection using extreme-value theory

Nonparametric extreme value statistics for constant signal detection in additive nois

Effects of Bulk Viscosity on Cosmological Evolution

The effect of bulk viscisity on the evolution of the homogeneous and isotropic cosmological models is considered. Solutions are found, with a barotropic equation of state, and a viscosity coefficient that is proportional to a power of the energy density of the universe. For flat space, power law expansions, related to extended inflation are found as well as exponential solutions, related to old inflation; also a solution with expansion that is an exponential of an exponential of the time is found.Comment: 8 pages, latex, no figure

Experimental assembly of structures in EVA: Hardware morphology and development issues

A large body of data was obtained by MIT during neutral boyancy testing at Marshall Space Flight Center from 1980 to the present. These efforts, and the most significant results are summarized. The Experimental Assembly of Structure in EVA (EASE) flight experiment was undertaken to validate these results and flown on the STS 61-B in November 1985. The EASE experiment hardware is discussed and how the experiment goals dictate its size, shape, and operational characteristics, are illustrated

A theoretical study of the propagation and attenuation of acoustic waves in the lunar surface Interim report

Acoustic wave propagation and attenuation in lunar space environmen

Exact real-time dynamics of the quantum Rabi model

We use the analytical solution of the quantum Rabi model to obtain absolutely convergent series expressions of the exact eigenstates and their scalar products with Fock states. This enables us to calculate the numerically exact time evolution of and for all regimes of the coupling strength, without truncation of the Hilbert space. We find a qualitatively different behavior of both observables which can be related to their representations in the invariant parity subspaces.Comment: 8 pages, 7 figures, published versio

Missing Work and Quitting Work: Child Care-Related Employment Problems

Qualitative research points to logistical problems in coordinating child care as a key obstacle to maternal employment for low-income mothers. But quantitative research has largely overlooked this everyday aspect of combining work and family. This article provides quantitative analyses of child-care related employment problems among urban working mothers of infants and asks how social support, the complexity of work and care arrangements and demographic characteristics relate to these problems. We use the Fragile Families and Child Well-Being Study to estimate logistic regression models of child care failure and missing or quitting work due to care-related problems. Child-care related problems are widespread regardless of race, class or family structure. Mothers with potential backup providers are less likely to experience care-related problems. Mothers who hold more than one job, use more than one care provider or change providers encounter problems more often. Logistical challenges surrounding child care represent a serious obstacle to continued employment for all urban working mothers. Care-related employment problems are more closely associated with the availability of backup care and the complexity of work and care arrangements than with class. These problems merit further study given their potential impact on the gender wage gap.