Severe Flooding and Malaria Transmission in the Western Ugandan Highlands: Implications for Disease Control in an Era of Global Climate Change

Background. There are several mechanisms by which global climate change may impact malaria transmission. We sought to assess how the increased frequency of extreme precipitation events associated with global climate change will influence malaria transmission in highland areas of East Africa

Beans with bugs: Covert carnivory and infested seed selection by the red-nosed cuxiú monkey

Members of the Neotropical primate genus Chiropotes eat large volumes of immature seeds. However, such items are often low in available proteins, and digestion of seeds is further inhibited by tannins. This suggests that overall plant-derived protein intake is relatively low. We examined the presence of insect larvae in partially eaten fruits, compared with intact fruit on trees, and examined fecal pellets for the presence of larvae. We found that red-nosed cuxiú (Chiropotes albinasus) individuals may supplement their limited seed-derived protein intake by ingesting seed-inhabiting insects. Comparison of fruits partially eaten for their seeds with those sampled directly from trees showed that fruits with insect-containing seeds were positively selected in 20 of the 41 C. albinasus diet items tested, suggesting that fruits with infested seeds are actively selected by foraging animals. We found no differences in accessibility to seeds, that is, no differences in husk penetrability between fruits with infested and uninfested seeds excluding the likelihood that insect-infestation results in easier access to the seeds in such fruits. Additionally, none of the C. albinasus fecal samples showed any evidence of living pupae or larvae, indicating that infesting larvae are digested. Our findings raise the possibility that these seed-predating primates might provide net benefits to the plant species they feed on, since they feed from many species of plants and their actions may reduce the populations of seed-infesting insects

X‐ray spectroscopy of hot solid density plasmas produced by subpicosecond high contrast laser pulses at 1018–1019 W/cm2

Analysis is presented of K‐shell spectra obtained from solid density plasmas produced by a high contrast (1010:1) subpicosecond laser pulse (0.5 μm) at 1018–1019 W/cm2. Stark broadening measurements of He‐like and Li‐like lines are used to infer the mean electron density at which emission takes place. The measurements indicate that there is an optimum condition to produce x‐ray emission at solid density for a given isoelectronic sequence, and that the window of optimum conditions to obtain simultaneously the shortest and the brightest x‐ray pulse at a given wavelength is relatively narrow. Lower intensity produces a short x‐ray pulse but low brightness. The x‐ray yield (and also the energy fraction in hot electrons) increases with the laser intensity, but above some laser intensity (1018 W/cm2 for Al) the plasma is overdriven: during the expansion, the plasma is still hot enough to emit, so that emission occurs at lower density and lasts much longer. Energy transport measurements indicate that approximately 6% of the laser energy is coupled to the target at 1018 W/cm2 (1% in thermal electrons with Te≊0.6 keV and 5% in suprathermal electrons with Th≊25 keV). At Iλ2=1018 W μm2/cm2 (no prepulse) around 1010 photons are emitted per laser shot, in 2π srd in cold Kα radiation (2–9 Å, depending on the target material) and up to 2×1011 photons are obtained in 2π srd with the unresolved transition array (UTA) emission from the Ta target. © 1995 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69900/2/PHPAEN-2-5-1702-1.pd

Theorems on shear-free perfect fluids with their Newtonian analogues

In this paper we provide fully covariant proofs of some theorems on shear-free perfect fluids. In particular, we explicitly show that any shear-free perfect fluid with the acceleration proportional to the vorticity vector (including the simpler case of vanishing acceleration) must be either non-expanding or non-rotating. We also show that these results are not necessarily true in the Newtonian case, and present an explicit comparison of shear-free dust in Newtonian and relativistic theories in order to see where and why the differences appear.Comment: 23 pages, LaTeX. Submitted to GR

Gravito-electromagnetism

We develop and apply a fully covariant 1+3 electromagnetic analogy for gravity. The free gravitational field is covariantly characterized by the Weyl gravito-electric and gravito-magnetic spatial tensor fields, whose dynamical equations are the Bianchi identities. Using a covariant generalization of spatial vector algebra and calculus to spatial tensor fields, we exhibit the covariant analogy between the tensor Bianchi equations and the vector Maxwell equations. We identify gravitational source terms, couplings and potentials with and without electromagnetic analogues. The nonlinear vacuum Bianchi equations are shown to be invariant under covariant spatial duality rotation of the gravito-electric and gravito-magnetic tensor fields. We construct the super-energy density and super-Poynting vector of the gravitational field as natural U(1) group invariants, and derive their super-energy conservation equation. A covariant approach to gravito-electric/magnetic monopoles is also presented.Comment: 14 pages. Version to appear in Class. Quant. Gra

Ultrafast x‐ray sources@f|

Time‐resolved spectroscopy (with a 2 psec temporal resolution) of plasmas produced by the interaction between solid targets and a high contrast subpicosecond table top terawatt (T3) laser at 1016 W/cm2, is used to study the basic processes which control the x‐ray pulse duration. Short x‐ray pulses have been obtained by spectral selection or by plasma gradient scalelength control. Time‐dependent calculations of the atomic physics [Phys. Fluids B 4, 2007, 1992] coupled to a Fokker–Planck code [Phys. Rev. Lett. 53, 1461, 1984] indicate that it is essential to take into account the non‐Maxwellian character of the electron distribution for a quantitative analysis of the experimental results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70417/2/PFBPEI-5-7-2676-1.pd

How do Black Holes Spin in Chern-Simons Modified Gravity?

No Kerr-like exact solution has yet been found in Chern-Simons modified gravity. Intrigued by this absence, we study stationary and axisymmetric metrics that could represent the exterior field of spinning black holes. For the standard choice of the background scalar, the modified field equations decouple into the Einstein equations and additional constraints. These constraints eliminate essentially all solutions except for Schwarzschild. For non-canonical choices of the background scalar, we find several exact solutions of the modified field equations, including mathematical black holes and pp-waves. We show that the ultrarelativistically boosted Kerr metric can satisfy the modified field equations, and we argue that physical spinning black holes may exist in Chern-Simons modified gravity only if the metric breaks stationarity, axisymmetry or energy-momentum conservation.Comment: 20 pages, 1 figure. Submitted to PR

Line Defects in Molybdenum Disulfide Layers

Layered molecular materials and especially MoS2 are already accepted as promising candidates for nanoelectronics. In contrast to the bulk material, the observed electron mobility in single-layer MoS2 is unexpectedly low. Here we reveal the occurrence of intrinsic defects in MoS2 layers, known as inversion domains, where the layer changes its direction through a line defect. The line defects are observed experimentally by atomic resolution TEM. The structures were modeled and the stability and electronic properties of the defects were calculated using quantum-mechanical calculations based on the Density-Functional Tight-Binding method. The results of these calculations indicate the occurrence of new states within the band gap of the semiconducting MoS2. The most stable non-stoichiometric defect structures are observed experimentally, one of which contains metallic Mo-Mo bonds and another one bridging S atoms