3,265 research outputs found
Compensation for Primary Reflector Wavefront Error
The object of the invention is to compensate for errors in a large telescope primary reflector by making certain compensating deviations in a smaller, auxiliary reflector of the telescope. At least one intermediate element forms an image of the primary surface onto the secondary surface, so each point on the secondary surface corresponds to a point on the primary surface. The secondary surface is formed with a deviation from an ideal secondary surface, with the piston distance of each point on the actual secondary surface equal to the piston distance of a corresponding piston on the actual primary surface from the ideal primary surface. It is found that this results in electromagnetic (e.g., light) rays which strike a deviating area of the actual primary surface being brought to the same focus as if the actual primary surface did not have a diviation from an ideal primary surface
Polarization and Extent of Maser Emission from Late-Type Stars: Support for a Plasma Turbulence Model of Maser Production
The integrated spectrum of OH emission from late-type stars is often
circularly polarized, by as much as 50% in some cases. While the spectra are
partially polarized, the individual maser components revealed by VLBI are much
more so. Using VLBI observations of late-type stars from the literature, we
show that the difference in circular polarization between main lines correlates
with a difference in angular extent for a given object. This is a natural
result if turbulent magnetic fields are causing the masers to be polarized via
the Cook mechanism, and might serve as a good diagnostic for determining which
objects should be investigated in the search for magnetic fields around evolved
stars.Comment: 5 pages, 2 figs ApJL, accepte
Dual-functional materials via CCTP and selective orthogonal thiol-Michael addition/epoxide ring opening reactions
Poly(glycidyl methacrylate) (PGMA) has been synthesised by cobalt catalysed chain transfer polymerisation (CCTP) yielding, in one step, polymers with two points for post polymerisation functionalisation; the activated terminal vinyl bond and in chain epoxide groups. Epoxide ring-opening and a combination of thiol-Michael addition and epoxide ring-opening has been used for the post-functionalisation with amines and thiols to prepare a range of functional materials
Primary goals, information-giving and men\u27s understanding: A qualitative study of Australian and UK doctors\u27 varied communication about PSA screening
Objectives: (1) To characterise variation in general practitionersâ (GPsâ) accounts of communicating with men about prostate cancer screening using the prostate-specific antigen (PSA) test, (2) to characterise GPsâ reasons for communicating as they do and (3) to explain why and under what conditions GP communication approaches vary.
Study design and setting: A grounded theory study. We interviewed 69 GPs consulting in primary care practices in Australia (n=40) and the UK (n=29).
Results: GPs explained their communication practices in relation to their primary goals. In Australia, three different communication goals were reported: to encourage asymptomatic men to either have a PSA test, or not test, or alternatively, to support men to make their own decision. As well as having different primary goals, GPs aimed to provide different information (from comprehensive to strongly filtered) and to support men to develop different kinds of understanding, from population-level to âgistâ understanding. Taking into account these three dimensions (goals, information, understanding) and building on Entwistle et alâs Consider an Offer framework, we derived four overarching approaches to communication: Be screened, Do not be screened, Analyse and choose, and As you wish. We also describe ways in which situational and relational factors influenced GPsâ preferred communication approach.
Conclusion: GPsâ reported approach to communicating about prostate cancer screening varies according to three dimensionsâtheir primary goal, information provision preference and understanding soughtâand in response to specific practice situations. If GP communication about PSA screening is to become more standardized in Australia, it is likely that each of these dimensions will require attention in policy and practice support interventions
Four-way regulation of mosquito yolk protein precursor genes by juvenile hormone-, ecdysone-, nutrient-, and insulin-like peptide signaling pathways.
Anautogenous mosquito females require a meal of vertebrate blood in order to initiate the production of yolk protein precursors by the fat body. Yolk protein precursor gene expression is tightly repressed in a state-of-arrest before blood meal-related signals activate it and expression levels rise rapidly. The best understood example of yolk protein precursor gene regulation is the vitellogenin-A gene (vg) of the yellow fever mosquito Aedes aegypti. Vg-A is regulated by (1) juvenile hormone signaling, (2) the ecdysone-signaling cascade, (3) the nutrient sensitive target-of-rapamycin signaling pathway, and (4) the insulin-like peptide (ILP) signaling pathway. A plethora of new studies have refined our understanding of the regulation of yolk protein precursor genes since the last review on this topic in 2005 (Attardo et al., 2005). This review summarizes the role of these four signaling pathways in the regulation of vg-A and focuses upon new findings regarding the interplay between them on an organismal level
Leave as an Accommodation: When is Enough, Enough?
The right to reasonable accommodations under the Americans with Disabilities Act includes leave that will enable an employee with a disability to return to work rather than being discharged. This right may seem unreasonable for an employer needing employees to be at work to be productive, raising the question of when leave as an accommodation becomes unreasonable or imposes an undue hardship on an employer. In the absence of specific guidance from the Supreme Court, the circuit courts apply a variety of approaches, ranging from individualized analysis to determinations that any leave exceeding some number of weeks is unreasonable. In this paper, three hundred and fifty-three decisions addressing this question have been analyzed to determine which factors are determinative of reasonableness, including factors identified in the various approaches of the circuit courts as well as those which economists would use to determine the value of an employee and the cost of replacing that employee
Chapter 22 FEMINIST BIOETHICS AND EMPIRICAL RESEARCH
The Routledge Handbook of Feminist Bioethics is an outstanding resource for anyone with an interest in feminist
bioethics, with chapters covering topics from justice and power to the climate crisis. Comprising forty-two
chapters by emerging and established scholars, the volume is divided into six parts:
I Foundations of feminist bioethics
II Identity and identifications
III Science, technology and research
IV Health and social care
V Reproduction and making families
VI Widening the scope of feminist bioethics
The volume is essential reading for anyone with an interest in bioethics or feminist philosophy, and will prove
an invaluable resource for scholars, teachers and advanced students
A Chandra X-Ray Survey of Ultraluminous Infrared Galaxies
We present results from Chandra observations of 14 ultraluminous infrared
galaxies (ULIRGs; log(L_IR/L_Sun) >= 12) with redshifts between 0.04 and 0.16.
The goals of the observations were to investigate any correlation between
infrared color or luminosity and the properties of the X-ray emission and to
attempt to determine whether these objects are powered by starbursts or active
galactic nuclei (AGNs). The sample contains approximately the same number of
high and low luminosity objects and ``warm'' and ``cool'' ULIRGs. All 14
galaxies were detected by Chandra. Our analysis shows that the X-ray emission
of the two Seyfert 1 galaxies in our sample are dominated by AGN. The remaining
12 sources are too faint for conventional spectral fitting to be applicable.
Hardness ratios were used to estimate the spectral properties of these faint
sources. The photon indices for our sample plus the Chandra-observed sample
from Ptak et al.(2003) peak in the range of 1.0-1.5, consistent with
expectations for X-ray binaries in a starburst, an absorbed AGN, or hot
bremsstrahlung from a starburst or AGN. The values of photon index for the
objects in our sample classified as Seyferts (type 1 or 2) are larger than 2,
while those classified as HII regions or LINERs tend to be less than 2. The
hard X-ray to far-infrared ratios for the 12 weak sources are similar to those
of starbursts, but we cannot rule out the possibility of absorbed, possibly
Compton-thick, AGNs in some of these objects. Two of these faint sources were
found to have X-ray counterparts to their double optical and infrared nuclei.Comment: 40 pages, 5 tables, 14 figures, accepted by Ap
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