90 research outputs found
Thermal control characteristics of a diffuse bladed specular base louver system Final report
Diffuse bladed specular base louver system for spacecraft temperature contro
Surface Hydrogen Modeling of Super Soft X-ray Sources: Are They Supernova Ia Progenitors?
Nova explosions occur on the white dwarf (WD) component of a Cataclysmic
Variable stellar system which is accreting matter lost by a companion. A Type
Ia supernova explosion is thought to result when a WD, in a similar binary
configuration, grows in mass to the Chandrasekhar Limit. Here, we present
calculations of accretion of Solar matter, at a variety of mass accretion
rates, onto hot (K), luminous (30L), massive
(1.25M, 1.35M) Carbon-Oxygen WDs. In contrast to our nova
simulations where the WD has a low initial luminosity and a thermonuclear
runaway (TNR) occurs and ejects material, these simulations do not eject
material (or only a small fraction of the accreted material) and the WD grows
in mass. A hydrogen TNR does not occur because hydrogen fuses to helium in the
surface layers, and we call this process Surface Hydrogen Burning (SHB). As the
helium layer grows in mass, it gradually fuses either to carbon and oxygen or
to more massive nuclei depending on the WD mass and mass accretion rate. If
such a WD were to explode in a SN Ia event, therefore, it would show neither
hydrogen nor helium in its spectrum as is observed. Moreover, the luminosities
and effective temperatures of our simulations agree with the observations of
some of the Super Soft X-ray Binary Sources and, therefore, our results
strengthen previous speculation that some of them (CAL 83 and CAL 87 for
example) are probably progenitors of SN Ia explosions. Finally, we have
achieved SHB for values of the mass accretion rate that almost span the
observed values of the Cataclysmic Variables.Comment: Accepted by APJL, 4 pages, 1 figure, LaTex (uses emulateapj.sty
Assessing the Effect of Four Types of Direct Mail Messages to Promote the Uptake of Residential Lead Remediation Funds
Objective To examine the efficacy of direct mailing using four types of messaging on promoting the uptake of residential lead remediation (RLR) funds in Lancaster, PA, USA. Study design We designed a quasi-experiment to assess the effect of 4 RLR messages sent to households in Lancaster, PA by direct mail between September and December 2020: a brief flyer (F); a detailed brochure + the flyer (BF); a health infographic + the flyer (IF); and an application form + the flyer (AFF). Methods Mailers were sent to addresses in four census tracts; each census tract received a different message. Both English and Spanish versions were sent. The outcomes were the event rate defined as the number of phone call inquiries received, and the number of applications received. The association between type of messaging and household type (owner-vs renter-occupied) was assessed using a chi square test. Results The event rates for the renter-occupied households were lower than for owner-occupied households, regardless of treatment. The event rates for renter-occupied households in the F, BF, IF and AFF groups were 0.00%, 0.35%, 0.12% and 0.18% respectively compared to 0.93%, 0.45%, 0.86% and 1.32% for homeowners. More applications were received from homeowners, and the event rate of the owner-occupied households was significantly different from that of renter-occupied homes (p-value = 0.001). Conclusions Event rates and applications received were higher for owner-occupied households than they were for renter-occupied households. Direct mailing of RLR information is feasible especially if households at high risk for lead poisoning are targeted
P3HT-Based Solar Cells: Structural Properties and Photovoltaic Performance
Each year we are bombarded with B.Sc. and Ph.D. applications from students that want to improve the world. They have learned that their future depends on changing the type of fuel we use and that solar energy is our future. The hope and energy of these young people will transform future energy technologies, but it will not happen quickly. Organic photovoltaic devices are easy to sketch, but the materials, processing steps, and ways of measuring the properties of the materials are very complicated. It is not trivial to make a systematic measurement that will change the way other research groups think or practice. In approaching this chapter, we thought about what a new researcher would need to know about organic photovoltaic devices and materials in order to have a good start in the subject. Then, we simplified that to focus on what a new researcher would need to know about poly-3-hexylthiophene:phenyl-C61-butyric acid methyl ester blends (P3HT: PCBM) to make research progress with these materials. This chapter is by no means authoritative or a compendium of all things on P3HT:PCBM. We have selected to explain how the sample fabrication techniques lead to control of morphology and structural features and how these morphological features have specific optical and electronic consequences for organic photovoltaic device applications
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