Transmission of Schistosoma haematobium in seasonal pools in the Gambia, with particular reference to the role of human contact

The transmission of S. haematobium in seasonal pools in The Gambia was investigated during the 1982 and 1983 transmission seasons. Studies were carried out on (a) infections in the snail intermediate host, Bulinus senegalensis, (b) cercarial densities in the pools, (c) water contact behaviour at the pools, and (d) the pattern of human infection. It was found that seasonal changes in the pools influenced both the snail populatons and the water contact patterns. Snail infection rates were low overall but were high in particular months and pools. Most infections occurred in one pool (maximum monthly mean infection rate 5.9%). Field and laboratory studies indicated that high mortality of B. senegalensis was counteracted by a high intrinsic rate of natural increase, and transmission of S. haematobium was maintained by a short prepatent period of the parasite. The cercariometric technique used had a 74% recovery accuracy in the laboratory. Cercarial densities in the pools were generally below 1 cercaria/litre, and the maximum density was 5.8 c/1. Cercarial densities were highest around midday, close to the vegetation in the middle of the pool as the pools were drying out. Transmission potential, as measured by cercarial density, varied between contact sites, months, times of day and position within a site. Human water contact was monitored by direct observation using a new "time-point" method and by recording frequency and duration of water contact of individuals. The observed activities were mainly for domestic and recreational purposes. Water contact was focal and seasonal, and the exposure potential (product of cercarial density and duration of contact at each pool) was highest at two pools and in the latter half of the season. The amount of water contact varied markedly between sexes and age groups. Contact increased progressively between ages 2-9 years, remaining at very high levels in females over the age of 10 years but declining to low levels in adult males. Substantial variation occurred in the contact of individuals in a narrow age group. An index of individual exposure to infection was calculated for two cohorts, aged 8-13 years and 2-70 years, by modifying the duration of contact by each individual by factors for the cercarial density at the pool used and for the activity performed. The resultant pattern of exposure to infection was markedly different from the pattern of duration of water contact: in particular, the mean exposure of adult women was reduced to less than that of children, although individual adult women had higher exposure levels than some children. The intensity of S. haematobium infection was highest in children aged 5-14 years and declined to low levels in adults. In 2-14 year olds increased exposure to infection was associated with an increase in reinfection after treatment. Adults had low levels of both infection and reinfection, although some had high levels of exposure to infection. It is concluded that both exposure and age influenced the pattern of infection in the community. The combined results of these studies indicates the complexity of transmission of schistosomiasis from snail to man, and shows that contact to very low cercarial densities can result in high levels of human infection

Single-parameter non-adiabatic quantized charge pumping

Controlled charge pumping in an AlGaAs/GaAs gated nanowire by single-parameter modulation is studied experimentally and theoretically. Transfer of integral multiples of the elementary charge per modulation cycle is clearly demonstrated. A simple theoretical model shows that such a quantized current can be generated via loading and unloading of a dynamic quasi-bound state. It demonstrates that non-adiabatic blockade of unwanted tunnel events can obliterate the requirement of having at least two phase-shifted periodic signals to realize quantized pumping. The simple configuration without multiple pumping signals might find wide application in metrological experiments and quantum electronics.Comment: 4 pages, 4 figure

Inverse Compton Scattering as the Source of Diffuse EUV Emission in the Coma Cluster of Galaxies

We have examined the hypothesis that the majority of the diffuse EUV flux in the Coma cluster is due to inverse Compton scattering of low energy cosmic ray electrons (0.16 < epsilon < 0.31 GeV) against the 3K black-body background. We present data on the two-dimensional spatial distribution of the EUV flux and show that these data provide strong support for a non-thermal origin for the EUV flux. However, we show that this emission cannot be produced by an extrapolation to lower energies of the observed synchrotron radio emitting electrons and an additional component of low energy cosmic ray electrons is required.Comment: 11 pages, 5 figure

Partitioning of on-demand electron pairs

We demonstrate the high fidelity splitting of electron pairs emitted on demand from a dynamic quantum dot by an electronic beam splitter. The fidelity of pair splitting is inferred from the coincidence of arrival in two detector paths probed by a measurement of the partitioning noise. The emission characteristic of the on-demand electron source is tunable from electrons being partitioned equally and independently to electron pairs being split with a fidelity of 90%. For low beam splitter transmittance we further find evidence of pair bunching violating statistical expectations for independent fermions

Simultaneous X-ray spectroscopy of YY Gem with Chandra and XMM-Newton

We report on a detailed study of the X-ray spectrum of the nearby eclipsing spectroscopic binary YY Gem. Observations were obtained simultaneously with both large X-ray observatories, XMM-Newton and Chandra. We compare the high-resolution spectra acquired with the Reflection Grating Spectrometer onboard XMM-Newton and with the Low Energy Transmission Grating Spectrometer onboard Chandra, and evidence in direct comparison the good performance of both instruments in terms of wavelength and flux calibration. The strongest lines in the X-ray spectrum of YY Gem are from oxygen. Oxygen line ratios indicate the presence of a low-temperature component (1-4 MK) with density n_e < 2 10^{10} cm^-3. The X-ray lightcurve reveals two flares and a dip corresponding to the secondary eclipse. An increase of the density during phases of high activity is suggested from time-resolved spectroscopy. Time-resolved global fitting of the European Photon Imaging Camera CCD spectrum traces the evolution of temperature and emission measure during the flares. These medium-resolution spectra show that temperatures > 10^7 K are relevant in the corona of YY Gem although not as dominant as the lower temperatures represented by the strongest lines in the high-resolution spectrum. Magnetic loops with length on the order of 10^9 cm, i.e., about 5 % of the radius of each star, are inferred from a comparison with a one-dimensional hydrodynamic model. This suggests that the flares did not erupt in the (presumably more extended) inter-binary magnetosphere but are related to one of the components of the binary.Comment: 15 pages, accepted for publication in A&

Cosmology at the Millennium

One hundred years ago we did not know how stars generate energy, the age of the Universe was thought to be only millions of years, and our Milky Way galaxy was the only galaxy known. Today, we know that we live in an evolving and expanding Universe comprising billions of galaxies, all held together by dark matter. With the hot big-bang model, we can trace the evolution of the Universe from the hot soup of quarks and leptons that existed a fraction of a second after the beginning to the formation of galaxies a few billion years later, and finally to the Universe we see today 13 billion years after the big bang, with its clusters of galaxies, superclusters, voids, and great walls. The attractive force of gravity acting on tiny primeval inhomogeneities in the distribution of matter gave rise to all the structure seen today. A paradigm based upon deep connections between cosmology and elementary particle physics -- inflation + cold dark matter -- holds the promise of extending our understanding to an even more fundamental level and much earlier times, as well as shedding light on the unification of the forces and particles of nature. As we enter the 21st century, a flood of observations is testing this paradigm.Comment: 44 pages LaTeX with 14 eps figures. To be published in the Centennial Volume of Reviews of Modern Physic

Two refreshing views of Fluctuation Theorems through Kinematics Elements and Exponential Martingale

In the context of Markov evolution, we present two original approaches to obtain Generalized Fluctuation-Dissipation Theorems (GFDT), by using the language of stochastic derivatives and by using a family of exponential martingales functionals. We show that GFDT are perturbative versions of relations verified by these exponential martingales. Along the way, we prove GFDT and Fluctuation Relations (FR) for general Markov processes, beyond the usual proof for diffusion and pure jump processes. Finally, we relate the FR to a family of backward and forward exponential martingales.Comment: 41 pages, 7 figures; version2: 45 pages, 7 figures, minor revisions, new results in Section

Understanding Galaxy Formation and Evolution

The old dream of integrating into one the study of micro and macrocosmos is now a reality. Cosmology, astrophysics, and particle physics intersect in a scenario (but still not a theory) of cosmic structure formation and evolution called Lambda Cold Dark Matter (LCDM) model. This scenario emerged mainly to explain the origin of galaxies. In these lecture notes, I first present a review of the main galaxy properties, highlighting the questions that any theory of galaxy formation should explain. Then, the cosmological framework and the main aspects of primordial perturbation generation and evolution are pedagogically detached. Next, I focus on the ``dark side'' of galaxy formation, presenting a review on LCDM halo assembling and properties, and on the main candidates for non-baryonic dark matter. It is shown how the nature of elemental particles can influence on the features of galaxies and their systems. Finally, the complex processes of baryon dissipation inside the non-linearly evolving CDM halos, formation of disks and spheroids, and transformation of gas into stars are briefly described, remarking on the possibility of a few driving factors and parameters able to explain the main body of galaxy properties. A summary and a discussion of some of the issues and open problems of the LCDM paradigm are given in the final part of these notes.Comment: 50 pages, 10 low-resolution figures (for normal-resolution, DOWNLOAD THE PAPER (PDF, 1.9 Mb) FROM http://www.astroscu.unam.mx/~avila/avila.pdf). Lectures given at the IV Mexican School of Astrophysics, July 18-25, 2005 (submitted to the Editors on March 15, 2006

International Research Institute for Climate and Society

Contemporary ecological research supports focus on the preservation of habitats and the preservation of keystone species that are critical to the ecological character of the habitats. Conservation of endangered species works best with attention not only to the species but also to the needs of the people who may be adjacent to or bordering habitats. Southern Sri Lanka fall into the category of globally important biodiversity hotspots. The biggest land animal, the elephant is the keystone species in Sri Lanka outside the highlands. The population of elephants in Sri Lanka is estimated to be between 3000 and 4,000; yet there has been an alarming loss of 1000 elephants during from 1990-2003. Given its island setting and rich hydro-climatic data, Sri Lanka provides a unique opportunity to study the dynamics leading to species loss. Our work in this project was initially motivated by the practical concerns of our project partners in the Mahaweli River Basin in Sri Lanka where the human-elephant conflict was a major problem. The question that arose was: “Are the climate, water availability and river basin management practices contributing to conflict between elephants and people?” If this was indeed the case, then, could one adaptively manage the river basin, organize agricultural practices, and prioritize conflict mitigation options such as separate habitat enrichment programs? Moreover, could we propose various adaptive measures in changes if one could monitor the climate and environmental conditions and take advantage of seasonal climate predictions

An All-Sky Search for Three Flavors of Neutrinos from Gamma-Ray Bursts with the IceCube Neutrino Observatory

We present the results and methodology of a search for neutrinos produced in the decay of charged pions created in interactions between protons and gamma-rays during the prompt emission of 807 gamma-ray bursts (GRBs) over the entire sky. This three-year search is the first in IceCube for shower-like Cherenkov light patterns from electron, muon, and tau neutrinos correlated with GRBs. We detect five low-significance events correlated with five GRBs. These events are consistent with the background expectation from atmospheric muons and neutrinos. The results of this search in combination with those of IceCube's four years of searches for track-like Cherenkov light patterns from muon neutrinos correlated with Northern-Hemisphere GRBs produce limits that tightly constrain current models of neutrino and ultra high energy cosmic ray production in GRB fireballs.Comment: 33 pages, 14 figures; minor changes made to match published version in the Astrophysical Journal, 2016 June 2