45,604 research outputs found
Holddown arm release mechanism used on Saturn vehicles
With the development of the Saturn launch vehicle, it became mandatory to develop a system for restraining the vehicle until after all checks and engine thrust buildup were completed. The basic Saturn I holddown arm constrains the vehicle by clamping it between a fixed support and a movable jaw. The jaw is on a link pinned to rotate sufficiently to release the vehicle. There are three links in the jaw (restraining) system arranged so that with a small force provided by a pneumatic separator mechanism, the large loads of the vehicle can be restrained. Design details discussed are the link system, the separator, adjustments, and the energy absorber. The function of preloading is discussed. The secondary release system is described. Finally, the design differences between the Saturn I and the Saturn V arm are described
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Reform and Representation: A New Method Applied to Recent Electoral Changes
Can electoral reforms such as an independent redistricting commission and the top-two primary create conditions that lead to better legislative representation? We explore this question by presenting a new method for measuring a key indicator of representation - the congruence between a legislator's ideological position and the average position of her district's voters. Our novel approach combines two methods: the joint classification of voters and political candidates on the same ideological scale, along with multilevel regression and post-stratification to estimate the position of the average voter across many districts in multiple elections. After validating our approach, we use it to study the recent impact of reforms in California, showing that they did not bring their hoped-for effects
Applications of airborne remote sensing in atmospheric sciences research
This paper explores the potential for airborne remote sensing for atmospheric sciences research. Passive and active techniques from the microwave to visible bands are discussed. It is concluded that technology has progressed sufficiently in several areas that the time is right to develop and operate new remote sensing instruments for use by the community of atmospheric scientists as general purpose tools. Promising candidates include Doppler radar and lidar, infrared short range radiometry, and microwave radiometry
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Modelling the injured spinal cord using 3-dimensional cell cultures; strategies for improving tissue engineered repair
Abstract not available
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Assessing the Effect of Photodynamic Therapy on Peripheral Nerve and Cancer Cells Using a Thin Tissue Engineered Collagen Culture Model
Abstract not available
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Intracellular localisation of mTHPC and effect of photodynamic therapy in cells of the mammalian peripheral nervous system
Fewer nerve-related side effects have been noted after treating head and neck cancer with photodynamic therapy (PDT) compared to conventional cancer therapy. Our aim is to investigate the biological basis for any such nerve-sparing effect. In this study the intracellular localisation and effect on cell viability of the photosensitiser meta-tetrahydroxylphenylchlorin (mTHPC) was investigated in cell culture models using peripheral nerve cells.
Primary cells from adult rat dorsal root ganglia (containing both neurons and glia) were used in these experiments. Localisation of mTHPC was detected using fluorescence and confocal microscopy. Levels of mTHPC fluorescence were quantified using digital image analysis. Immunocytochemistry with anti-?-III-tubulin and anti-S100 was used to distinguish neuronal and glial cell populations respectively. A cell-death assay using propidium iodide was used to evaluate neural cell susceptibility to PDT following incubation with mTHPC.
The results showed that mTHPC was localised in cytoplasmic regions of neurons and glia, but was not detected in neuronal axons. Necrotic cell death was detected after PDT in these neural cell types.
These results suggest that the cells of the peripheral nervous system are susceptible to PDT-mediated necrosis, but that the sparing of nerves observed during clinical PDT may be related to the heterogeneous distribution of mTHPC within neurons
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Differences in sensitivity to mTHPC-mediated photodynamic therapy of neurons, glial cells and MCF7 cells in a 3-dimensional cell culture model
The effect of photodynamic therapy (PDT) on the cells of the nervous system is an important consideration in the treatment of tumours that are located within or adjacent to the brain, spinal cord and peripheral nerves. Previous studies have reported the sparing of nerves during PDT using meta-tetrahydroxyphenylchlorin (mTHPC, Foscan®) in patients and in animal models. The aim of this study was to investigate the effects of mTHPC on key nervous system cells using a 3-dimensional cell culture system for the accurate detection of differences in sensitivity
RESIK observations of He-like Ar X-ray line emission in solar flares
The Ar XVII X-ray line group principally due to transitions 1s2 - 1s2l (l=s,
p) near 4 Anstroms was observed in numerous flares by the RESIK bent crystal
spectrometer aboard CORONAS-F between 2001 and 2003. The three line features
include the Ar XVII w (resonance line), a blend of x and y (intercombination
lines), and z (forbidden line), all of which are blended with Ar XVI
dielectronic satellites. The ratio G, equal to [I(x+y) + I(z)]/I(w), varies
with electron temperature Te mostly because of unresolved dielectronic
satellites. With temperatures estimated from GOES X-ray emission, the observed
G ratios agree fairly well with those calculated from CHIANTI and other data.
With a two-component emission measure, better agreement is achieved. Some S XV
and S XVI lines blend with the Ar lines, the effect of which occurs at
temperatures greater than 8MK, allowing the S/Ar abundance ratio to be
determined. This is found to agree with coronal values. A nonthermal
contribution is indicated for some spectra in the repeating-pulse flare of 2003
February 6.Comment: Latex file and 3 ps files. Astrophysical Journal Letters (accepted,
June 2008
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