2,870 research outputs found
Advanced techniques for determining long term compatibility of materials with propellants
A method for the prediction of propellant-material compatibility for periods of time up to ten years is presented. Advanced sensitive measurement techniques used in the prediction method are described. These include: neutron activation analysis, radioactive tracer technique, and atomic absorption spectroscopy with a graphite tube furnace sampler. The results of laboratory tests performed to verify the prediction method are presented
Isolating Geometry in Weak Lensing Measurements
Given a foreground galaxy-density field or shear field, its cross-correlation
with the shear field from a background population of source galaxies scales
with the source redshift in a way that is specific to lensing. Such a
source-scaling can be exploited to effectively measure geometrical distances as
a function of redshift and thereby constrain dark energy properties, free of
any assumptions about the galaxy-mass/mass power spectrum (its shape, amplitude
or growth). Such a geometrical method can yield a ~ 0.03 - 0.07 f_{sky}^{-1/2}
measurement on the dark energy abundance and equation of state, for a
photometric redshift accuracy of dz ~ 0.01 - 0.05 and a survey with median
redshift of ~ 1. While these constraints are weaker than conventional weak
lensing methods, they provide an important consistency check because the
geometrical method carries less theoretical baggage: there is no need to assume
any structure formation model (e.g. CDM). The geometrical method is at the most
conservative end of a whole spectrum of methods which obtain smaller errorbars
by making more restrictive assumptions -- we discuss some examples. Our
geometrical approach differs from previous investigations along similar lines
in three respects. First, the source-scaling we propose to use is less
demanding on the photometric redshift accuracy. Second, the scaling works for
both galaxy-shear and shear-shear correlations. Third, we find that previous
studies underestimate the statistical errors associated with similar
geometrical methods, the origin of which is discussed.Comment: 13 pages, 4 figures, submitted to Ap
The construction of identities in narratives about serious leisure occupations
Engagement in occupation contributes to the shaping of identity throughout the human life. The act of telling about such engagement involves interaction based on symbolic meaning; the speaker constructing an identity by conveying how the occupation is personally meaningful. This study explored meaning in narratives told by people who engage in serious leisure occupations. A total of 78 narratives were extracted from interviews with 17 people who invest considerable time and other resources into their leisure. Analysis focused on the content, structure and performance of each narrative in order to explore meaning. The meanings were organised into a framework based around three dimensions: the located self, the active self and the changing self. Each dimension has facets that the individual might emphasise, constructing a unique identity. The framework offers a structured basis for conceptualising how occupation contributes to the shaping of the internalised self and the socially situated identity
Therapy of pancreatic cancer via an EphA2 receptor-targeted delivery of gemcitabine.
First line treatment for pancreatic cancer consists of surgical resection, if possible, and a subsequent course of chemotherapy using the nucleoside analogue gemcitabine. In some patients, an active transport mechanism allows gemcitabine to enter efficiently into the tumor cells, resulting in a significant clinical benefit. However, in most patients, low expression of gemcitabine transporters limits the efficacy of the drug to marginal levels, and patients need frequent administration of the drug at high doses, significantly increasing systemic drug toxicity. In this article we focus on a novel targeted delivery approach for gemcitabine consisting of conjugating the drug with an EphA2 targeting agent. We show that the EphA2 receptor is highly expressed in pancreatic cancers, and accordingly, the drug-conjugate is more effective than gemcitabine alone in targeting pancreatic tumors. Our preliminary observations suggest that this approach may provide a general benefit to pancreatic cancer patients and offers a comprehensive strategy for enhancing delivery of diverse therapeutic agents to a wide range of cancers overexpressing EphA2, thereby potentially reducing toxicity while enhancing therapeutic efficacy
- âŠ