7,994 research outputs found
Submarine groundwater discharge: an unseen yet potentially important coastal phenomenon
In collaboration with researchers from Florida
State University, Florida Sea Grant introduces an important but poorly known topic:
submarine groundwater discharge. Although nearly invisible, submarine
groundwater discharge influences coastal systems. This brochure helps explain this important phenomenon. (8pp.
Probing States in the Mott Insulator Regime
We propose a method to probe states in the Mott insulator regime produced
from a condensate in an optical lattice. We consider a system in which we
create time-dependent number fluctuations in a given site by turning off the
atomic interactions and lowering the potential barriers on a nearly pure Mott
state to allow the atoms to tunnel between sites. We calculate the expected
interference pattern and number fluctuations from such a system and show that
one can potentially observe a deviation from a pure Mott state. We also discuss
a method in which to detect these number fluctuations using time-of-flight
imaging.Comment: 4 pages, 3 figures. Send correspondence to
[email protected]
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Solar and solar-wind oxygen isotopes and the Genesis mission
The solar oxygen isotope composition is thought to hold important clues to pre-planetary processing of materials in the solar nebula, yet it is essentially unmeasured. Here we describe plans for O isotope analyses of Genesis solar-wind samples
Effects of industrial development on rural welfare
Writers and exponents of the decentralization-of-industry theory seem to think that it is the hope of rural people. It is not the purpose or intention of this study to prove that industrial development is desirable or objectionable, but to find out its effects on rural welfare as revealed by data collected in four survey areas. Precaution was taken to be fair in all statements and not to be biased or let preconceived ideas about the problem influence the conclusions drawn
Collective excitations of atomic Bose-Einstein condensates
We apply linear-response analysis of the Gross-Pitaevskii equation to obtain
the excitation frequencies of a Bose-Einstein condensate confined in a
time-averaged orbiting potential trap. Our calculated values are in excellent
agreement with those observed in a recent experiment.Comment: 11 pages, 2 Postscript figures, uses psbox.tex for automatic figure
inclusion. More info at http://amo.phy.gasou.edu/bec.htm
Mass fractionation of the lunar surface by solar wind sputtering
The sputtering of the lunar surface by the solar wind is examined as a possible mechanism of mass fractionation. Simple arguments based on current theories of sputtering and the ballistics of the sputtered atoms suggest that most ejected atoms will have sufficiently high energy to escape lunar gravity. However, the fraction of atoms which falls back to the surface is enriched in the heavier atomic components relative to the lighter ones. This material is incorporated into the heavily radiation-damaged outer surfaces of grains where it is subject to resputtering. Over the course of several hundred years an equilibrium surface layer, enriched in heavier atoms, is found to form. The dependence of the calculated results upon the sputtering rate and on the details of the energy spectrum of sputtered particles is investigated. It is concluded that mass fractionation by solar wind sputtering is likely to be an important phenomenon on the lunar surface
Stochastic Gene Expression in a Lentiviral Positive Feedback Loop: HIV-1 Tat Fluctuations Drive Phenotypic Diversity
Stochastic gene expression has been implicated in a variety of cellular
processes, including cell differentiation and disease. In this issue of Cell,
Weinberger et al. (2005) take an integrated computational-experimental approach
to study the Tat transactivation feedback loop in HIV-1 and show that
fluctuations in a key regulator, Tat, can result in a phenotypic bifurcation.
This phenomenon is observed in an isogenic population where individual cells
display two distinct expression states corresponding to latent and productive
infection by HIV-1. These findings demonstrate the importance of stochastic
gene expression in molecular "decision-making."Comment: Supplemental data available as q-bio.MN/060800
Grandparents as Family Caregivers: Lessons for Intergenerational Education
The number of grandparents who have responsibility for raising grandchildren has increased dramatically over the past several decades. From an educational perspective, content on custodial grandparents can promote an increased interest in, and understanding of, the complexities of aging by stressing the intergenerational aspects of this family form. This paper describes the growing population of custodial grandparents, and the larger socio environmental contexts of these families. In addition, it highlights instructional approaches for including content on grandparent-headed families within didactic and experiential courses
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