A simple antireflection overcoat for opaque coatings in the submillimeter region

An antireflection overcoat for opaque baffle coatings in the far infrared (FIR)/submillimeter region was made from a simple Teflon spray-on lubricant. The Teflon overcoat reduced the specular reflectance of four different opaque coatings by nearly a factor of two. Analysis, based on the interference term of a reflecting-layer model, indicates that in the submillimeter region the reduced reflectance depends primarily on the refractive index of the overcoat and very little on its thickness

BRDF measurements of sunshield and baffle materials for the IRAS telescope

Measurements of the far-infrared bidirectional reflectance distribution functions (BRDF) of four samples of Martin Black coating and one sample of gold coated aluminum from the telescope to be flown on the Infrared Astronomy Satellite (IRAS) are presented. At incidence angles near 35 deg Martin Black is a diffuse reflector at wavelengths as long as 36 microns. The gold coated aluminum sample from the IRAS sunshield has a visible grain which causes a strong diffraction enhancement of the BRDF at large nonspecular angles. This enhancement from the sunshield will increase the stray light level inside the telescope

Review of the absorption spectra of solid O2 and N2 as they relate to contamination of a cooled infrared telescope

During contamination studies for the liquid helium cooled shuttle infrared telescope facility, a literature search was conducted to determine the absorption spectra of the solid state of homonuclear molecules of O2 and N2, and ascertain what laboratory measurements of the solid have been made in the infrared. With the inclusion of one unpublished spectrum, the absorption spectrum of the solid oxygen molecule has been thoroughly studied from visible to millimeter wavelengths. Only two lines appear in the solid that do not also appear in the gas or liquid. A similar result is implied for the solid nitrogen molecule because it also is homonuclear. The observed infrared absorption lines result from lattice modes of the alpha phase of the solid, and disappear at the warmer temperatures of the beta, gamma, and liquid phases. They are not observed from polycrystalline forms of O2, while strong scattering is. Scattering, rather than absorption, is considered to be the principal natural contamination problem for cooled infrared telescopes in low earth orbit

Does welfare reform affect fertility? Evidence from the UK

In 1999 the UK government made major reforms to the system of child-contingent benefits, including the introduction of Working Families’ Tax Credit and an increase in means-tested Income Support for families with children. Between 1999-2003 government spending per-child on these benefits rose by 50 per cent in real terms, a change that was unprecedented over a thirty year period. This paper examines whether there was a response in childbearing. To identify the effect of the reforms, we exploit the fact that the spending increases were targeted at low-income households and we use the (exogenously determined) education of the woman and her partner to define treatment and control groups. We argue that the reforms are most likely to have a positive fertility effect for women in couples and show that this is the case. We find that there was an increase in births (by around 15 per cent) among the group affected by the reforms

A Reflective Evaluation of Group Assessment

There is a general agreement in the literature that groupwork helps to develop important interpersonal and personal skills (Race, 2001; Visram & Joy, 2003; Elliot & Higgins, 2005; Kench et al, 2008). However, one of the problems with groupwork for both students and lecturers is how the work should be assessed (Parsons & Kassabova, 2002). The possibility of having ‘free-riders’ and the difficulty of fairly awarding marks to reflect the level of students’ contribution to a group output are some of the key problem areas in groupwork assessment (Race, 2001). Peer assessment is seen as one of the methods to deal with these problems. It can generally involve students assessing each other’s level of contribution to the group’s output (Visram & Joy, 2003). This paper provides our reflection on the use of peer assessment on a student group project

Stable oxygen and carbon isotope compositional fields for skeletal and diagenetic components in New Zealand Cenozoic nontropical carbonate sediments and limestones: a synthesis and review

The stable oxygen isotope composition (d¹⁸O) of a precipitated carbonate depends mainly on the isotope composition, salinity, and temperature of the host fluid, whereas the stable carbon isotope composition (d¹³C) reflects the source of CO2 for precipitation, such as meteoric or sea water, shell dissolution, or various biochemical origins, including microbial oxidation of organic matter and methane. Despite the potentially complex array of controls, natural waters tend to show a characteristic range of isotope values which in turn are mimicked or tracked by the carbonate minerals precipitated from them. Consequently, plots of d¹⁸O versus d¹³C for carbonate materials can help identify their depositional and/or diagenetic environment(s)

Online participation: the Woodberry Down experiment

The internet and world wide web are generating radical changes in the way we are able tocommunicate. Our ability to engage communities and individuals in designing theirenvironment is also beginning to change as new digital media provide ways in whichindividuals and groups can interact with planners and politicians in exploring their future.This paper tells the story of how the residents of one of the most disadvantagedcommunities in Britain ? the Woodberry Down Estate in the London borough ofHackney ? have begun to use an online system which delivers everything from routineservices about their housing to ideas about options for their future. Woodberry Down isone of the biggest regeneration projects in Western Europe. It will take at least 10 years,probably much longer, to complete, at a cost of over £150 million. Online participation isone of the many ways in which this community is being engaged but as we will show, itis beginning to act as a catalyst. The kinds of networks which are evolving aroundsystems like these will change the nature of participation itself, the ways we need to thinkabout it, and the ways we need to respond. Before the experiment is described, we set thecontext by describing the wide range of digital media for communicating plans andplanning which suggests a new typology for web participation consistent with this fastemerging network culture

Spectroscopic determination of electrical conductivity in an MHD duct from absolute intensity measurements

Measurements of the electrical conductivity in the NASA Lewis cesium seeded, H2-O2 MHD duct have been previously reported. In order to corroborate the above measurements and to analyze the possibility of nonuniform seed injection as a cause of the deviations, a spectroscopic investigation of the plasma conductivity has been undertaken. Transverse profiles of the absolute integrated intensity were measured from the optically thin lines of CSI-.5664 microns and .5636 microns. Radial profiles of emission coefficient were obtained from the measured transverse profiles of intensity by Abel inversion. Radial profiles of electrical conductivity were then obtained under two different assumptions. In the first, the Cs seed fraction is assumed uniform and equal to the measured flow rate at the time when the temperature and conductivity were obtained. In the second method, the local temperature and pressure are taken to be those given by a one-dimensional channel calculation including heat transfer and friction. In this case profiles of conductivity and seed fractions are obtained. The results of the two methods are compared to the previously measured conductivity