Beyond the Small-Angle Approximation For MBR Anisotropy from Seeds

In this paper we give a general expression for the energy shift of massless particles travelling through the gravitational field of an arbitrary matter distribution as calculated in the weak field limit in an asymptotically flat space-time. It is {\it not} assumed that matter is non-relativistic. We demonstrate the surprising result that if the matter is illuminated by a uniform brightness background that the brightness pattern observed at a given point in space-time (modulo a term dependent on the oberver's velocity) depends only on the matter distribution on the observer's past light-cone. These results apply directly to the cosmological MBR anisotropy pattern generated in the immediate vicinity of of an object like a cosmic string or global texture. We apply these results to cosmic strings, finding a correction to previously published results for in the small-angle approximation. We also derive the full-sky anisotropy pattern of a collapsing texture knot.Comment: 23 pages, FERMILAB-Pub-94/047-

A Causal Source which Mimics Inflation

How unique are the inflationary predictions for the cosmic microwave anisotropy pattern? In this paper, it is asked whether an arbitrary causal source for perturbations in the standard hot big bang could effectively mimic the predictions of the simplest inflationary models. A surprisingly simple example of a `scaling' causal source is found to closely reproduce the inflationary predictions. This letter extends the work of a previous paper (ref. 6) to a full computation of the anisotropy pattern, including the Sachs Wolfe integral. I speculate on the possible physics behind such a source.Comment: 4 pages, RevTex, 3 figure

The Doppler Peaks from Cosmic Texture

We compute the angular power spectrum of temperature anisotropies on the microwave sky in the cosmic texture theory, with standard recombination assumed. The spectrum shows `Doppler' peaks analogous to those in scenarios based on primordial adiabatic fluctuations such as `standard CDM', but at quite different angular scales. There appear to be excellent prospects for using this as a discriminant between inflationary and cosmic defect theories.Comment: 14 pages, latex, 3 figures, compressed and uuencoded, replaced version has minor typographical correction

Cosmic Strings in an Open Universe with Baryonic and Non-Baryonic Dark Matter

We study the effects of cosmic strings on structure formation in open universes. We calculate the power spectrum of density perturbations for two class of models: one in which all the dark matter is non baryonic (CDM) and one in which it is all baryonic (BDM). Our results are compared to the 1 in 6 IRAS QDOT power spectrum. The best candidates are then used to estimate $\mu$, the energy per unit length of the string network. Some comments are made on mechanisms by which structures are formed in the two theories.Comment: uu-encoded compressed tar of postscript files, Imperial/TP/94-95/0

Doppler peaks from active perturbations

We examine how the qualitative structure of the Doppler peaks in the angular power spectrum of the cosmic microwave anisotropy depends on the fundamental nature of the perturbations which produced them. The formalism of Hu and Sugiyama is extended to treat models with cosmic defects. We discuss how perturbations can be ``active'' or ``passive'' and ``incoherent'' or ``coherent'', and show how causality and scale invariance play rather different roles in these various cases. We find that the existence of secondary Doppler peaks and the rough placing of the primary peak unambiguously reflect these basic properties.Comment: uufile, 8pages, 3 figures. Now available at http://euclid.tp.ph/Papers/index.html; Changes: URL added, Eqn. (8) expanded, grant numbers include

The growth of linear perturbations in generic defect models for structure formation

We study the growth of linear perturbations induced by a generic causal scaling source as a function of the cosmological parameters $h$, $\Omega^m_0$ and $\Omega^\Lambda_0$. We show that for wavenumbers k \gsim 0.01 h/Mpc the spectrum of density and velocity perturbations scale in a similar way to that found in inflationary models with primordial perturbations. We show that this result is independent of the more or less incoherent nature of the source, the small scale power spectrum of the source and of deviations from scaling which naturally occur at late times if $\Omega^m_0 \neq 1$.Comment: 4 pages, 2 figure

Studies on the host range of Piricularia oryzae Cav. causing blast disease of rice

This article does not have an abstract

Synthesis of α-glucan in mycobacteria involves a hetero-octameric complex of trehalose synthase TreS and Maltokinase Pep2

Recent evidence established that the cell envelope of Mycobacterium tuberculosis, the bacillus causing tuberculosis (TB), is coated by an α-glucan-containing capsule that has been implicated in persistence in a mouse infection model. As one of three known metabolic routes to α-glucan in mycobacteria, the cytoplasmic GlgE-pathway converts trehalose to α(1 → 4),α(1 → 6)-linked glucan in 4 steps. Whether individual reaction steps, catalyzed by trehalose synthase TreS, maltokinase Pep2, and glycosyltransferases GlgE and GlgB, occur independently or in a coordinated fashion is not known. Here, we report the crystal structure of M. tuberculosis TreS, and show by small-angle X-ray scattering and analytical ultracentrifugation that TreS forms tetramers in solution. Together with Pep2, TreS forms a hetero-octameric complex, and we demonstrate that complex formation markedly accelerates maltokinase activity of Pep2. Thus, complex formation may act as part of a regulatory mechanism of the GlgE pathway, which overall must avoid accumulation of toxic pathway intermediates, such as maltose-1-phosphate, and optimize the use of scarce nutrients

Correlations in Cosmic String Networks

We investigate scaling and correlations of the energy and momentum in an evolving network of cosmic strings in Minkowski space. These quantities are of great interest, as they must be understood before accurate predictions for the power spectra of the perturbations in the matter and radiation in the early Universe can be made. We argue that Minkowski space provides a reasonable approximation to a Friedmann background for string dynamics and we use our results to construct a simple model of the network, in which it is considered to consist of randomly placed segments moving with random velocities. This model works well in accounting for features of the two-time correlation functions, and even better for the power spectra.Comment: 20pp Plain LaTeX, 11 EPS figures, uses epsf.st

Predicting the Impact of Vaccination on the Transmission Dynamics of Typhoid in South Asia: A Mathematical Modeling Study

Background: Modeling of the transmission dynamics of typhoid allows for an evaluation of the potential direct and indirect effects of vaccination; however, relevant typhoid models rooted in data have rarely been deployed. Methodology/Principal Findings We developed a parsimonious age-structured model describing the natural history and immunity to typhoid infection. The model was fit to data on culture-confirmed cases of typhoid fever presenting to Christian Medical College hospital in Vellore, India from 2000–2012. The model was then used to evaluate the potential impact of school-based vaccination strategies using live oral, Vi-polysaccharide, and Vi-conjugate vaccines. The model was able to reproduce the incidence and age distribution of typhoid cases in Vellore. The basic reproductive number (R0) of typhoid was estimated to be 2.8 in this setting. Vaccination was predicted to confer substantial indirect protection leading to a decrease in the incidence of typhoid in the short term, but (intuitively) typhoid incidence was predicted to rebound 5–15 years following a one-time campaign. Conclusions/Significance: We found that model predictions for the overall and indirect effects of vaccination depend strongly on the role of chronic carriers in transmission. Carrier transmissibility was tentatively estimated to be low, consistent with recent studies, but was identified as a pivotal area for future research. It is unlikely that typhoid can be eliminated from endemic settings through vaccination alone