The MMI cash-futures spread on October 19, 1987

Includes bibliographical references (p. 29)

S-band omnidirectional antenna for the SERT-C satellite

The program to design an S-band omnidirectional antenna system for the SERT-C spacecraft is discussed. The program involved the tasks of antenna analyses by computer techniques, scale model radiation pattern measurements of a number of antenna systems, full-scale RF measurements, and the recommended design, including detailed drawings. A number of antenna elements were considered: the cavity-backed spiral, quadrifilar helix, and crossed-dipoles were chosen for in-depth studies. The final design consisted of a two-element array of cavity-backed spirals mounted on opposite sides of spacecraft and fed in-phase through a hybrid junction. This antenna system meets the coverage requirement of having a gain of at least minus 10 dBi over 50 percent of a 4 pi steradian sphere with the solar panels in operation. This coverage level is increased if the ground station has the capability to change polarization

Massless Metric Preheating

Can super-Hubble metric perturbations be amplified exponentially during preheating ? Yes. An analytical existence proof is provided by exploiting the conformal properties of massless inflationary models. The traditional conserved quantity \zeta is non-conserved in many regions of parameter space. We include backreaction through the homogeneous parts of the inflaton and preheating fields and discuss the role of initial conditions on the post-preheating power-spectrum. Maximum field variances are strongly underestimated if metric perturbations are ignored. We illustrate this in the case of strong self-interaction of the decay products. Without metric perturbations, preheating in this case is very inefficient. However, metric perturbations increase the maximum field variances and give alternative channels for the resonance to proceed. This implies that metric perturbations can have a large impact on calculations of relic abundances of particles produced during preheating.Comment: 8 pages, 4 colour figures. Version to appear in Phys. Rev. D. Contains substantial new analysis of the ranges of parameter space for which large changes to the inflation-produced power spectrum are expecte

Letters from Raymond Weeks, W. G. Manly, C. H. Grandgent, and R. E. Bassett

Letters of recommendation for Olin Moore

Testing for double inflation with WMAP

With the WMAP data we can now begin to test realistic models of inflation involving multiple scalar fields. These naturally lead to correlated adiabatic and isocurvature (entropy) perturbations with a running spectral index. We present the first full (9 parameter) likelihood analysis of double inflation with WMAP data and find that despite the extra freedom, supersymmetric hybrid potentials are strongly constrained with less than 7% correlated isocurvature component allowed when standard priors are imposed on the cosomological parameters. As a result we also find that Akaike & Bayesian model selection criteria rather strongly prefer single-field inflation, just as equivalent analysis prefers a cosmological constant over dynamical dark energy in the late universe. It appears that simplicity is the best guide to our universe.Comment: 7 pages, 6 figure

Condom use and the risk of HIV infection: who is being protected?

A study/survey done on condom use among Zimbabwean men in Zimbabwe.Descriptive baseline data at enrolment into a cohort of male factory workers who were tested for HIV serology and monitored for sero-con version over time, were analysed for condom use. At recruitment, the 1 146 men were asked about their sexual behaviour, history of sexually transmitted diseases (STDs), condom use and circumstances under which condoms were used. HIV seroprevalence in the cohort was 18,2 pc. Self reported use of condoms was low, with only 5 pc of the men reporting using them all the time. Forty four pc reported that they had never used a condom, 11,5 pc tried a condom only once, and 30,5 pc used condoms less than half the time. HIV positive men were more likely (Odds Ratio [OR]= 2,2 95 pc Cl: 1,3 — 3,3) to use condoms than those who tested negative. Men using a condom more than once were younger and had more education (p values < 0,0005). Univariate analysis showed that men with self reported risk factors for HIV infection were more likely to use condoms. Significantly more condom users reported paying for sex, multiple sex partners or (for married men) a girlfriend (p < 0,005). Condom users also more often had a history of genital ulcers, urethral discharge or other STDs. Few married men (24 pc) reported using a condom with their wives. Condom use was more commonly reported with commercial sex workers (44 pc) or other extramarital partners (36 pc). Some risk factors for HIV infection were also present amongst men who reported that they did not use condoms. Independent determinants of condom use identified by stepwise logistic regression analysis included young age, having a girlfriend (OR = 2,2; 95 pc Cl: 1,47 — 3,3), number of sex partners in the last year (OR = 1,27; 95 pc Cl: 1,06 —1,51 per partner), and paying for sex in the preceding year (OR = 1,74; 95 pc Cl: 1,06 — 2,83). The results show that men use condoms with partners considered risky, such as prostitutes or girlfriends but use condoms less often with their wives. The results underscore theneedfor health education for behavioural change that promotes universal, consistent use of condoms or monogamous partnership

HIV seroconversion among factory workers in Harare: who is getting newly infected?

A clinical report on the impact of HIV/AIDS among factory workers in Zimbabwe's industrial areas of Harare.It was estimated that by the of 1996 more than 8.4 million AIDS cases had occurred worldwide.1 Because of the long and variable duration between infection with the human immunodeficiency virus (HIV) and the ultimate development of AIDS, a more useful indication of current trends in the epidemic is the number of new infections with HIV. Twenty eight million people from 190 countries across the world were HIV positive by mid 1996.Composed of distinct epidemics, each with its own features, degree and extent, the pandemic has had a disproportionately severe impact on the developing world. Despite wide information on HIV prevention, 3.1 million new infections occurred during 1996. Up to 93% of the HIV infections recorded in 1996 were from developing countries with 68% from sub-Saharan Africa.2 Developing countries, who have weaker economic structures, continue to bear the greatest burden of HIV infections. HIV infection appears be spreading much faster in Southern Africa than anywhere else

Preheating of the nonminimally coupled inflaton field

We investigate preheating of an inflaton field $\phi$ coupled nonminimally to a spacetime curvature. In the case of a self-coupling inflaton potential $V(\phi)=\lambda \phi^4/4$, the dynamics of preheating changes by the effect of the negative $\xi$. We find that the nonminimal coupling works in two ways. First, since the initial value of inflaton field for reheating becomes smaller with the increase of $|\xi|$, the evolution of the inflaton quanta is delayed for fixed $\lambda$. Second, the oscillation of the inflaton field is modified and the nonadiabatic change around $\phi=0$ occurs significantly. That makes the resonant band of the fluctuation field wider. Especially for strong coupling regimes $|\xi| \gg 1$, the growth of the inflaton flutuation is dominated by the resonance due to the nonminimal coupling, which leads to the significant enhancement of low momentum modes. Although the final variance of the inflaton fluctuation does notchange significantly compared with the minimally coupled case, we have found that the energy transfer from the homogeneous inflaton to created particles efficiently occurs for $\xi<-60$.Comment: 13pages, 11figure

Shrinking II -- The Distortion of the Area Distance-Redshift Relation in Inhomogeneous Isotropic Universes

This paper and the others in the series challenge the standard model of the effects of gravitational lensing on observations at large distances. We show that due to the cumulative effect of lensing, areas corresponding to an observed solid angle can be quite different than would be estimated from the corresponding Friedmann-Lema\^{\i}tre model, even when averaged over large angular scales. This paper concentrates on the specific example of spherically symmetric but spatially inhomogeneous dust universes, the Lema\^{\i}tre-Tolman-Bondi models, and shows that radial lensing significantly distorts the area distance-redshift and density-redshift relations in these exact solutions compared with the standard ones for Friedmann-Lema\^{\i}tre models. Thus inhomogeneity may introduce significant errors into distance estimates based on the standard FL relations, even after all-sky averaging. In addition a useful new gauge choice is presented for these models, solving the problem of locating the past null cone exactly.Comment: Minor technical refinement, 16 pages, RevTex, 8 eps figure

Nonlinear Effects in the Cosmic Microwave Background

Major advances in the observation and theory of cosmic microwave background anisotropies have opened up a new era in cosmology. This has encouraged the hope that the fundamental parameters of cosmology will be determined to high accuracy in the near future. However, this optimism should not obscure the ongoing need for theoretical developments that go beyond the highly successful but simplified standard model. Such developments include improvements in observational modelling (e.g. foregrounds, non-Gaussian features), extensions and alternatives to the simplest inflationary paradigm (e.g. non-adiabatic effects, defects), and investigation of nonlinear effects. In addition to well known nonlinear effects such as the Rees-Sciama and Ostriker-Vishniac effects, further nonlinear effects have recently been identified. These include a Rees-Sciama-type tensor effect, time-delay effects of scalar and tensor lensing, nonlinear Thomson scattering effects and a nonlinear shear effect. Some of the nonlinear effects and their potential implications are discussed.Comment: Invited contribution to Relativistic Cosmology Symposium (celebrating the 60th year of GFR Ellis); to appear Gen. Rel. Gra