Realizability of Polytopes as a Low Rank Matrix Completion Problem

This article gives necessary and sufficient conditions for a relation to be the containment relation between the facets and vertices of a polytope. Also given here, are a set of matrices parameterizing the linear moduli space and another set parameterizing the projective moduli space of a combinatorial polytope

Structural basis for Fullerene geometry in a human endogenous retrovirus capsid

The HML2 (HERV-K) group constitutes the most recently acquired family of human endogenous retroviruses, with many proviruses less than one million years old. Many maintain intact open reading frames and provirus expression together with HML2 particle formation are observed in early stage human embryo development and are associated with pluripotency as well as inflammatory disease, cancers and HIV-1 infection. Here, we reconstruct the core structural protein (CA) of an HML2 retrovirus, assemble particles in vitro and employ single particle cryogenic electron microscopy (cryo-EM) to determine structures of four classes of CA Fullerene shell assemblies. These icosahedral and capsular assemblies reveal at high-resolution the molecular interactions that allow CA to form both pentamers and hexamers and show how invariant pentamers and structurally plastic hexamers associate to form the unique polyhedral structures found in retroviral cores

Who sleeps under bednets in Ghana? A doer/non-doer analysis of malaria prevention behaviours

BACKGROUND: Malaria prevention programmes should be based in part on knowledge of why some individuals use bednets while others do not. This paper identifies factors and characteristics of women that affect bednet use among their children less than five years of age in Ghana. METHODS: Data come from the baseline component of an evaluation of Freedom from Hunger's malaria curriculum. A quasi-experimental design was used to select clients (n = 516) of Credit with Education (an integrated package of microfinance and health education) and non-clients (n = 535). Chi-squares, Fisher's Exact tests and logistic regression were used to compare the characteristics of mothers whose children use bednets (doers) with those whose children do not (non-doers) and to identify factors associated with bednet use among children less than five years of age. RESULTS: The following factors were most closely associated with bednet use: region of residence; greater food security; and caregivers' beliefs about symptoms, causation and groups most vulnerable to malaria. Most respondents knew mosquitoes caused malaria; however, 20.6% of doers and 12.3% of non-doers (p = .0228) thought overworking oneself caused malaria. Ninety percent of doers and 77.0% of non-doers felt that sleeping under a net was protective against malaria (p = .0040). In addition, 16.5% of doers and 7.5% of non-doers (p = .0025) identified adult males as most vulnerable to malaria. CONCLUSION: Greater knowledge about malaria does not always translate into improved bednet use. Though culturally-based ideas about malaria may vary between communities, integrating them into traditional health education messages may enhance the effectiveness of public health efforts

Meteorological Controls on Local and Regional Volcanic Ash Dispersal

Volcanic ash has the capacity to impact human health, livestock, crops and infrastructure, including international air traffic. For recent major eruptions, information on the volcanic ash plume has been combined with relatively coarse-resolution meteorological model output to provide simulations of regional ash dispersal, with reasonable success on the scale of hundreds of kilometres. However, to predict and mitigate these impacts locally, significant improvements in modelling capability are required. Here, we present results from a dynamic meteorological-ash-dispersion model configured with sufficient resolution to represent local topographic and convectively-forced flows. We focus on an archetypal volcanic setting, Soufrière, St Vincent, and use the exceptional historical records of the 1902 and 1979 eruptions to challenge our simulations. We find that the evolution and characteristics of ash deposition on St Vincent and nearby islands can be accurately simulated when the wind shear associated with the trade wind inversion and topographically-forced flows are represented. The wind shear plays a primary role and topographic flows a secondary role on ash distribution on local to regional scales. We propose a new explanation for the downwind ash deposition maxima, commonly observed in volcanic eruptions, as resulting from the detailed forcing of mesoscale meteorology on the ash plume

Insulin-Like Peptides and the Target of Rapamycin Pathway Coordinately Regulate Blood Digestion and Egg Maturation in the Mosquito Aedes aegypti

Mosquitoes are insects that vector many serious pathogens to humans and other vertebrates. Most mosquitoes must feed on the blood of a vertebrate host to produce eggs. In turn, multiple cycles of blood feeding promote frequent contacts with hosts and make mosquitoes ideal disease vectors. Both hormonal and nutritional factors are involved in regulating egg development in the mosquito, Aedes aegypti. However, the processes that regulate digestion of the blood meal remain unclear.Here we report that insulin peptide 3 (ILP3) directly stimulated late phase trypsin-like gene expression in blood fed females. In vivo knockdown of the mosquito insulin receptor (MIR) by RNA interference (RNAi) delayed but did not fully inhibit trypsin-like gene expression in the midgut, ecdysteroid (ECD) production by ovaries, and vitellogenin (Vg) expression by the fat body. In contrast, in vivo treatment with double-stranded MIR RNA and rapamycin completely blocked egg production. In vitro experiments showed that amino acids did not simulate late phase trypsin-like gene expression in the midgut or ECD production by the ovaries. However, amino acids did enhance ILP3-mediated stimulation of trypsin-like gene expression and ECD production.Overall, our results indicate that ILPs from the brain synchronize blood meal digestion and amino acid availability with ovarian ECD production to maximize Vg expression by the fat body. The activation of digestion by ILPs may also underlie the growth promoting effects of insulin and TOR signaling in other species

The Role of Column Density in the Formation of Stars and Black Holes

The stellar mass in disk galaxies scales approximately with the fourth power of the rotation velocity, and the masses of the central black holes in galactic nuclei scale approximately with the fourth power of the bulge velocity dispersion. It is shown here that these relations can be accounted for if, in a forming galaxy with an isothermal mass distribution, gas with a column density above about 8 Msun/pc^2 goes into stars while gas with a column density above about 2 g/cm^2 (10^4 Msun/pc^2) goes into a central black hole. The lower critical value is close to the column density of about 10 Msun/pc^2 at which atomic gas becomes molecular, and the upper value agrees approximately with the column density of about 1 g/cm^2 at which the gas becomes optically thick to its cooling radiation. These results are plausible because molecule formation is evidently necessary for star formation, and because the onset of a high optical depth in a galactic nucleus may suppress continuing star formation and favour the growth of a central black hole.Comment: Accepted by Nature Physic

DNMT (DNA methyltransferase) inhibitors radiosensitize human cancer cells by suppressing DNA repair activity

<p>Abstract</p> <p>Background</p> <p>Histone modifications and DNA methylation are two major factors in epigenetic phenomenon. Unlike the histone deacetylase inhibitors, which are known to exert radiosensitizing effects, there have only been a few studies thus far concerning the role of DNA methyltransferase (DNMT) inhibitors as radiosensitizers. The principal objective of this study was to evaluate the effects of DNMT inhibitors on the radiosensitivity of human cancer cell lines, and to elucidate the mechanisms relevant to that process.</p> <p>Methods</p> <p>A549 (lung cancer) and U373MG (glioblastoma) cells were exposed to radiation with or without six DNMT inhibitors (5-azacytidine, 5-aza-2'-deoxycytidine, zebularine, hydralazine, epigallocatechin gallate, and psammaplin A) for 18 hours prior to radiation, after which cell survival was evaluated via clonogenic assays. Cell cycle and apoptosis were analyzed via flow cytometry. Expressions of DNMT1, 3A/3B, and cleaved caspase-3 were detected via Western blotting. Expression of γH2AX, a marker of radiation-induced DNA double-strand break, was examined by immunocytochemistry.</p> <p>Results</p> <p>Pretreatment with psammaplin A, 5-aza-2'-deoxycytidine, and zebularine radiosensitized both A549 and U373MG cells. Pretreatment with psammaplin A increased the sub-G1 fraction of A549 cells, as compared to cells exposed to radiation alone. Prolongation of γH2AX expression was observed in the cells treated with DNMT inhibitors prior to radiation as compared with those treated by radiation alone.</p> <p>Conclusions</p> <p>Psammaplin A, 5-aza-2'-deoxycytidine, and zebularine induce radiosensitivity in both A549 and U373MG cell lines, and suggest that this effect might be associated with the inhibition of DNA repair.</p

Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo

We use data from the second science run of the LIGO gravitational-wave detectors to search for the gravitational waves from primordial black hole (PBH) binary coalescence with component masses in the range 0.2--$1.0 M_\odot$. The analysis requires a signal to be found in the data from both LIGO observatories, according to a set of coincidence criteria. No inspiral signals were found. Assuming a spherical halo with core radius 5 kpc extending to 50 kpc containing non-spinning black holes with masses in the range 0.2--$1.0 M_\odot$, we place an observational upper limit on the rate of PBH coalescence of 63 per year per Milky Way halo (MWH) with 90% confidence.Comment: 7 pages, 4 figures, to be submitted to Phys. Rev.

Low Frequency Scattering by a Planar Crack

The detection of cracks with the aid of ultrasonics is an important nondestructive evaluation technique. The corresponding theoretical problem of the scattering of elastic waves by cracks has attracted considerable attention. Scattering of time harmonic plane wave by an isolated two dimensional Griffith, or an penny-shaped crack in an unbounded elastic medium has been studied extensively. However, studies of the scattering problem by a three dimensional crack other than circular shape have been rather limited. Few studies of scattering from an elliptical crack in an elastic body of infinite extent can be found in the literature. Datta[1] studied the problem using the method of matched asymptotic expansion. Gubernatis et al. [2] and Budiansky and O’Connell [3] have used the elastostatic approximation to determine the scattered field. The backscattered field from an elliptical crack has been obtained by Kino [4] in the low frequency limit by a formula derived from elastodynamic reciprocity theorem. An integro-differential equation technique was employed by Roy [5]–[6] to study the same problem.</p