149 research outputs found
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A long-term strategic plan for development of solar thermal electric technology
Solar thermal electric (STE) technologies--parabolic troughs, power towers, and dish/engine systems--can convert sunlight into electricity efficiently and with minimum effect on the environment. These technologies currently range from developmental to early commercial stages of maturity. This paper summarizes the results of a recent strategic planning effort conducted by the US department of Energy (DOE) to develop a long-term strategy for the development of STE technologies. The planning team led by DOE included representatives from the solar thermal industry, domestic utilities, state energy offices, and Sun{center_dot}Lab (the cooperative Sandia National laboratories/National Renewable Energy Laboratory partnership that supports the STE Program) as well as project developers. The plan was aimed at identifying specific activities necessary to achieve the DOE vision of 20 gigawatts of installed STE capability by the year 2020. The planning team developed five strategies that both build on the strengths of, and opportunities for, STE technology and address weaknesses and threats. These strategies are to: support future commercial opportunities for STE technologies; demonstrate improved performance and reliability of STE components and systems; reduce STE energy costs; develop advanced STE systems and applications; and address nontechnical barriers and champion STE power. The details of each of these strategies are discussed
Dynamics of escaping Earth ejecta and their collision probability with different Solar System bodies
It has been suggested that the ejection to interplanetary space of
terrestrial crustal material, accelerated in a large impact, may result in the
interchange of biological material between Earth and other Solar System bodies.
In this paper, we analyze the fate of debris ejected from Earth by means of
numerical simulations of the dynamics of a large collection of test particles.
This allows us to determine the probability and conditions for the collision of
ejecta with other planets of the Solar System. We also estimate the amount of
particles falling-back to Earth as a function of time after being ejected. We
find that, in general, the collision rates of Earth ejecta with Venus and the
Moon, as well as the fall-back rates, are consistent with results reported in
the literature. By considering a larger number of particles than in all
previous calculations we have also determined directly the collision
probability with Mars and, for the first time, computed collision probabilities
with Jupiter. We find that the collision probability with Mars is greater than
values determined from collision cross section estimations previously reported.Comment: 9 pages, 4 figures & 1 table. Submitted to Icaru
Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum
We report a first measurement for ultra-high energy cosmic rays of the
correlation between the depth of shower maximum and the signal in the water
Cherenkov stations of air-showers registered simultaneously by the fluorescence
and the surface detectors of the Pierre Auger Observatory. Such a correlation
measurement is a unique feature of a hybrid air-shower observatory with
sensitivity to both the electromagnetic and muonic components. It allows an
accurate determination of the spread of primary masses in the cosmic-ray flux.
Up till now, constraints on the spread of primary masses have been dominated by
systematic uncertainties. The present correlation measurement is not affected
by systematics in the measurement of the depth of shower maximum or the signal
in the water Cherenkov stations. The analysis relies on general characteristics
of air showers and is thus robust also with respect to uncertainties in
hadronic event generators. The observed correlation in the energy range around
the `ankle' at differs significantly from
expectations for pure primary cosmic-ray compositions. A light composition made
up of proton and helium only is equally inconsistent with observations. The
data are explained well by a mixed composition including nuclei with mass . Scenarios such as the proton dip model, with almost pure compositions, are
thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray
flux at Earth.Comment: Published version. Added journal reference and DOI. Added Report
Numbe
A selective ATP-binding cassette subfamily G member 2 efflux inhibitor revealed via high-throughput flow cytometry
Chemotherapeutics tumor resistance is a principal reason for treatment failure, and clinical and experimental data indicate that multidrug transporters such as ATP-binding cassette (ABC) B1 and ABCG2 play a leading role by preventing cytotoxic intracellular drug concentrations. Functional efflux inhibition of existing chemotherapeutics by these pumps continues to present a promising approach for treatment. A contributing factor to the failure of existing inhibitors in clinical applications is limited understanding of specific substrate/inhibitor/pump interactions. We have identified selective efflux inhibitors by profiling multiple ABC transporters against a library of small molecules to find molecular probes to further explore such interactions. In our primary screening protocol using JC-1 as a dual-pump fluorescent reporter substrate, we identified a piperazine-substituted pyrazolo[1,5-a]pyrimidine substructure with promise for selective efflux inhibition. As a result of a focused structure-activity relationship (SAR)-driven chemistry effort, we describe compound 1 (CID44640177), an efflux inhibitor with selectivity toward ABCG2 over ABCB1. Compound 1 is also shown to potentiate the activity of mitoxantrone in vitro as well as preliminarily in vivo in an ABCG2-overexpressing tumor model. At least two analogues significantly reduce tumor size in combination with the chemotherapeutic topotecan. To our knowledge, low nanomolar chemoreversal activity coupled with direct evidence of efflux inhibition for ABCG2 is unprecedented
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