238 research outputs found
A monolithically integrated optical repeater
A monolithically integrated optical repeater has been fabricated on a single-crystal semi-insulating GaAs substrate. The repeater consists of an optical detector, an electronic amplifier, and a double heterostructure crowding effect laser. The repeater makes use of three metal semiconductor field effect transistors, one of which is used as the optical detector. With light from an external GaAlAs laser incident on the detector, an overall optical power gain of 10 dB from both laser facets was obtained
Stationary structures of irrotational binary systems -- models for close binary systems of compact stars
We propose a new numerical method to calculate irrotational binary systems
composed of compressible gaseous stars in Newtonian gravity. Assuming
irrotationality, i.e. vanishing of the vorticity vector everywhere in the star
in the inertial frame, we can introduce the velocity potential for the flow
field. Using this velocity potential we can derive a set of basic equations for
stationary states which consist of (i) the generalized Bernoulli equation, (ii)
the Poisson equation for the Newtonian gravitational potential and (iii) the
equation for the velocity potential with the Neumann type boundary condition.
We succeeded in developing a new code to compute numerically exact solutions to
these equations for the first time. Such irrotational configurations of binary
systems are appropriate models for realistic neutron star binaries composed of
inviscid gases, just prior to coalescence of two stars caused by emission of
gravitational waves. Accuracies of our numerical solutions are so high that we
can compute reliable models for fully deformed final stationary configurations
and hence determine the inner most stable circular orbit of binary neutron star
systems under the approximations of weak gravity and inviscid limit.Comment: 32 pages, 25 bitmapped ps files, to appear in ApJ supplemen
Mediation in the Law Curriculum
Cited by Lord Neuberger in ‘Educating Future Mediators’ at the 4th Civil Mediation Council National Conference, May 201
Monolithic integration of a GaAlAs buried‐heterostructure laser and a bipolar phototransistor
Haptoglobin Phenotype, Preeclampsia Risk and the Efficacy of Vitamin C and E Supplementation to Prevent Preeclampsia in a Racially Diverse Population
Haptoglobin's (Hp) antioxidant and pro-angiogenic properties differ between the 1-1, 2-1, and 2-2 phenotypes. Hp phenotype affects cardiovascular disease risk and treatment response to antioxidant vitamins in some non-pregnant populations. We previously demonstrated that preeclampsia risk was doubled in white Hp 2-1 women, compared to Hp 1-1 women. Our objectives were to determine whether we could reproduce this finding in a larger cohort, and to determine whether Hp phenotype influences lack of efficacy of antioxidant vitamins in preventing preeclampsia and serious complications of pregnancy-associated hypertension (PAH). This is a secondary analysis of a randomized controlled trial in which 10,154 low-risk women received daily vitamin C and E, or placebo, from 9-16 weeks gestation until delivery. Hp phenotype was determined in the study prediction cohort (n = 2,393) and a case-control cohort (703 cases, 1,406 controls). The primary outcome was severe PAH, or mild or severe PAH with elevated liver enzymes, elevated serum creatinine, thrombocytopenia, eclampsia, fetal growth restriction, medically indicated preterm birth or perinatal death. Preeclampsia was a secondary outcome. Odds ratios were estimated by logistic regression. Sampling weights were used to reduce bias from an overrepresentation of women with preeclampsia or the primary outcome. There was no relationship between Hp phenotype and the primary outcome or preeclampsia in Hispanic, white/other or black women. Vitamin supplementation did not reduce the risk of the primary outcome or preeclampsia in women of any phenotype. Supplementation increased preeclampsia risk (odds ratio 3.30; 95% confidence interval 1.61-6.82, p<0.01) in Hispanic Hp 2-2 women. Hp phenotype does not influence preeclampsia risk, or identify a subset of women who may benefit from vitamin C and E supplementation to prevent preeclampsia
Erasmus Language students in a British University – a case study
Students’ assessment of their academic experience is actively sought by Higher Education institutions, as evidenced in the National Student Survey introduced in 2005. Erasmus students, despite their growing numbers, tend to be excluded from these satisfaction surveys, even though they, too, are primary customers of a University. This study aims to present results from bespoke questionnaires and semi-structured interviews with a sample of Erasmus students studying languages in a British University. These methods allow us insight into the experience of these students and their assessment as a primary customer, with a focus on language learning and teaching, university facilities and student support. It investigates to what extent these factors influence their levels of satisfaction and what costs of adaptation if any, they encounter. Although excellent levels of satisfaction were found, some costs affect their experience. They relate to difficulties in adapting to a learning methodology based on a low number of hours and independent learning and to a guidance and support system seen as too stifling. The results portray this cohort’s British University as a well-equipped and well-meaning but ultimately overbearing institution, which may indicate that minimising costs can eliminate some sources of dissatisfaction
Photonic quantum ring laser
We report a quantum ring-like toroidal cavity naturally formed in a
vertical-cavity-like active microdisk plane due to Rayleigh's band of
whispering gallery modes. The -dependent redshift and a square-law
property of microampere-range threshold currents down to 2 A are
consistent with a photonic quantum wire view, due to whispering gallery
mode-induced dimensional reduction.Comment: 4 pages, 5 figures, REVTEX, Submitted to Phys. Rev. Lett. 06/08/98,
revised 10/28/98, To appear in Phys. Rev. Lett., Vol. 82(3), Jan. 199
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