Malaria on the Amazonian frontier: Transmission dynamics, risk factors, spatial distribution, and prospects for control

Little follow-up data on malaria transmission in communities originating from frontier settlements in Amazonia are available. Here we describe a cohort study in a frontier settlement in Acre, Brazil, where 509 subjects contributed 489.7 person-years of follow-up. The association between malaria morbidity during the follow-up and individual, household, and spatial covariates was explored with mixed-effects logistic regression models and spatial analysis. Incidence rates for Plasmodium vivax and Plasmodium falciparum malaria were 30.0/100 and 16.3/100 person-years at risk, respectively. Malaria morbidity was strongly associated with land clearing and farming, and decreased after five years of residence in the area, suggesting that clinical immunity develops among subjects exposed to low malaria endemicity. Significant spatial clustering of malaria was observed in the areas of most recent occupation, indicating that the continuous influx of nonimmune settlers to forest-fringe areas perpetuates the cycle of environmental change and colonization that favors malaria transmission in rural Amazonia.

Phylogeny of snake trypanosomes inferred by SSU rDNA sequences, their possible transmission by phlebotomines, and taxonomic appraisal by molecular, cross-infection and morphological analysis

Blood examination by microhaematocrit and haemoculture of 459 snakes belonging to 37 species revealed 24% trypanosome prevalence in species of Viperidae (Crotalus durissus and Bothrops jararaca) and Colubridae (Pseudoboa nigra). Trypanosome cultures from C. durissus and P. nigra were behaviourally and morphologically indistinguishable. In addition, the growth and morphological features of a trypanosome from the sand fly Viannaniyia tuberculata were similar to those of snake isolates. Cross-infection experiments revealed a lack of host restriction, as snakes of 3 species were infected with the trypanosome from C. durissus. Phylogeny based on ribosomal sequences revealed that snake trypanosomes clustered together with the sand fly trypanosome, forming a new phylogenetic lineage within Trypanosoma closest to a clade of lizard trypanosomes transmitted by sand flies dagger. The clade of trypanosomes from snakes and lizards suggests an association between the evolutionary histories of these trypanosomes and their squamate hosts. Moreover, data strongly indicated that these trypanosomes are transmitted by sand flies. The flaws of the current taxonomy of snake trypanosomes are discussed, and the need for molecular parameters to be adopted is emphasized. To our knowledge, this is the first molecular phylogenetic study of snake trypanosomes.

The South American Plasmodium falciparum var gene repertoire is limited, highly shared and possibly lacks several antigenic types

The Plasmodium falciparum var gene family encodes large variant antigens, which are important virulence factors, and also targets of the humoral host response. The frequently observed mild outcomes of falciparum malaria in many places of the Amazon area prompted us to ask whether a globally restricted variant (var) gene repertoire is present in currently circulating and older isolates of this area. By exhaustive analysis of var gene tags from 89 isolates and clones taken during many years from all over the Brazilian Amazon, we estimate that there are probably no more than 350-430 distinct sequence types, less than for any similar sized area studied so far. Detailed analysis of the var tags from genetically distinct clones obtained from single isolates revealed restricted and redundant repertoires suggesting either a low incidence of infective bites or restricted variant gene diversity in inoculated parasites. Additionally, we found a structuring of var gene repertoires observed as a higher pairwise typing sharing in isolates from the same microregion compared to isolates from different regions. Fine analysis of translated var tags revealed that certain Distinct Sequence Identifiers (DSIDs) were differently represented in Brazilian/South American isolates when compared to datasets from other continents. By global alignment of worldwide var DBL alpha sequences and sorting in groups with more than 76% identity, 125 clusters were formed and more than half of all genes were found in nine clusters with 50 or more sequences. While Brazilian/South American sequences were represented only in 64 groups, African sequences were found in the majority of clusters. DSID type 1 related sequences accumulated almost completely in one single cluster, indicating that limited recombination occurs in these specific var gene types. These data demonstrate the so far highest pairwise type sharing values for the var gene family in isolates from all over an entire subcontinent. The apparent lack of specific sequences types suggests that the P. falciparum transmission dynamics in the whole Amazon are probably different from any other endemic region studied and possibly interfere with the parasite`s ability to efficiently diversify its variant gene repertoires. (C) 2010 Elsevier B.V. All rights reserved.

Electrical, optical, and structural studies of shallow-buried Au-polymethylmethacrylate composite films formed by very low energy ion implantation

The authors present here a summary of their investigations of ultrathin films formed by gold nanoclusters embedded in polymethylmethacrylate polymer. The clusters are formed from the self-organization of subplantated gold ions in the polymer. The source of the low energy ion stream used for the subplantation is a unidirectionally drifting gold plasma created by a magnetically filtered vacuum arc plasma gun. The material properties change according to subplantation dose, including nanocluster sizes and agglomeration state and, consequently also the material electrical behavior and optical activity. They have investigated the composite experimentally and by computer simulation in order to better understand the self-organization and the properties of the material. They present here the results of conductivity measurements and percolation behavior, dynamic TRIM simulations, surface plasmon resonance activity, transmission electron microscopy, small angle x-ray scattering, atomic force microscopy, and scanning tunneling microscopy. (C) 2010 American Vacuum Society [DOI: 10.1116/1.3357287]

Characterization and spectroscopic analysis of phenol-ethanol hydrogen bonded clusters

Different hydrogen bonded clusters involving phenol and ethanol are studied theoretically using MP2/aug-cc-pVDZ. Nine different 1: 1 clusters are obtained and analyzed according to their stability and spectroscopic properties. Different isomeric forms of ethanol are considered. Attention is also devoted to the spectral shift of the characteristic pi -> pi* transition of phenol. Using TDHF, CIS, CIS(D) and TDB3LYP in aug-cc-pVDZ basis set, all results agree that a red shift is obtained when phenol is the hydrogen donor and a blue shift is obtained in the opposite case. These results are used to rationalize the red shift observed for phenol in liquid ethanol. (C) 2010 Elsevier B.V. All rights reserved.

Many-body energy decomposition of hydrogen-bonded glycine clusters in gas-phase

A detailed analysis of the many-body contribution to the interaction energies of the gas-phase hydrogen-bonded glycine clusters, (Gly)(N), N = 1-4 is presented. The energetics of the hydrogen-bonded dimer, trimer and tetramer complexes have been analyzed using density-functional theory. The magnitude of the two-through four-body energy terms have been calculated and compared. The relaxation energy and the two-body energy terms are the principal contributors to the total binding energy. Four-body contribution is negligible. However, the three-body contribution is found to be sizable and the formation of the cyclic glycine trimer presents geometric strains that make it less favorable. (C) 2010 Elsevier B.V. All rights reserved.

The imprint of the interaction between dark sectors in galaxy clusters

Based on perturbation theory, we study the dynamics of how dark matter and dark energy in the collapsing system approach dynamical equilibrium when they are in interaction. We find that the interaction between dark sectors cannot ensure the dark energy to fully cluster along with dark matter. When dark energy does not trace dark matter, we present a new treatment on studying the structure formation in the spherical collapsing system. Furthermore we examine the cluster number counts dependence on the interaction between dark sectors and analyze how dark energy inhomogeneities affect cluster abundances. It is shown that cluster number counts can provide specific signature of dark sectors interaction and dark energy inhomogeneities.

Signature of the interaction between dark energy and dark matter in galaxy clusters

We investigate the influence of ail interaction between dark energy and dark matter upon the dynamics of galaxy clusters. We obtain file general Layser-Irvine equation in the presence of interactions, and find how, in that case. the virial theorem stands corrected. Using optical, X-ray and weak lensing data from 33 relaxed galaxy clusters, we put constraints on the strength of the coupling between the dark sectors. Available data Suggests that this coupling is small but positive, indicating that dark energy might be decaying into dark matter. Systematic effects between the several mass estimates, however, should be better known, before definitive conclusions oil the magnitude and significance of this coupling could be established. (C) 2009 Published by Elsevier B.V.

High-density gas aggregation nanoparticle gun applied to the production of SmCo clusters

We describe in this article the application of a high-density gas aggregation nanoparticle gun to the production and characterization of high anisotropy SmCo nanoparticles. We give a detailed description of the simple but efficient experimental apparatus with a focus on the microscopic processes of the gas aggregation technique. Using high values of gas flux (similar to 45 sccm) we are able to operate in regimes of high collimation of material. In this regime, as we explain in terms of a phenomenological model, the power applied to the sputtering target becomes the main variable to change the size of the clusters. Also presented are the morphological, structural, and magnetic characterizations of SmCo nanoparticles produced using 10 and 50 W of sputtering power. These values resulted in mean sizes of similar to 12 and similar to 20 nm. Significant differences are seen in the structural and magnetic properties of the samples with the 50 W sample showing a largely enhanced crystalline structure and magnetic anisotropy.

Hyperfine and magnetic properties of Fe-Cu clusters and Fe precipitates embedded in a Cu matrix

Using the first-principles real-space linear muffin-tin orbital method within the atomic sphere approximation (RS-LMTO-ASA) we study hyperfine and local magnetic properties of substituted pure Fe and Fe-Cu clusters in an fcc Cu matrix. Spin and orbital contributions to magnetic moments, hyperfine fields and the Mossbauer isomer shifts at the Fe sites in Fe precipitates and Fe-Cu alloy clusters of sizes up to 60 Fe atoms embedded in the Cu matrix are calculated and the influence of the local environment on these properties is discussed.

X-ray transmission through nanostructured and microstructured CuO materials

This study presents a comparison of the X-ray transmission through microsized and nanosized materials. For this purpose CuO nanoparticles, with 13.4 nm average grain size, and CuO microparticles, with a mean particle size of 56 mu m, were incorporated separately to beeswax in a concentration of 5%. Results show that the transmission through the above material plates with microsized and nanosized CuO was almost the same for X-ray beams generated at 60 and 102 kV tube voltages. However, for the radiation beams generated at 26 and 30 kV tube voltages the X-rays are more attenuated by the nanostructured CuO plates by a factor of at least 14%. Results suggest that the difference in the low energy range may be due to the higher number of particles/gram in the plates designed with CuO nanoparticles and due to the grain size effect on the X-ray transmission. (C) 2010 Elsevier Ltd. All rights reserved.

Optical and dielectric relaxor behaviour of Ba(Zr(0.25)Ti(0.75))O(3) ceramic explained by means of distorted clusters

In this work, Ba(Zr(0.25)Ti(0.75))O(3) ceramic was prepared by solid-state reaction. This material was characterized by x-ray diffraction and Fourier transform Raman spectroscopy. The temperature dependent dielectric properties were investigated in the frequency range from 1 kHz to 1 MHz. The dielectric measurements indicated a diffuse phase transition. The broadening of the dielectric permittivity in the frequency range as well as its shifting at higher temperatures indicated a relaxor-like behaviour for this material. The diffusivity and the relaxation strength were estimated using the modified Curie-Weiss law. The optical properties were analysed by ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements at room temperature. The UV-vis spectrum indicated that the Ba(Zr(0.25)Ti(0.75))O(3) ceramic has an optical band gap of 2.98 eV. A blue PL emission was observed for this compound when excited with 350 nm wavelength. The polarity as well as the PL property of this material was attributed to the presence of polar [TiO(6)] distorted clusters into a globally cubic matrix.

Effect of Different Solvent Ratios (Water/Ethylene Glycol) on the Growth Process of CaMoO(4) Crystals and Their Optical Properties

In this paper, calcium molybdate (CaMoO(4)) crystals (meso- and nanoscale) were synthesized by the coprecipitation method using different solvent volume ratios (water/ethylene glycol). Subsequently, the obtained suspensions were processed in microwave-assisted hydrothermal/solvothermal systems at 140 degrees C for 1 h. These meso- and nanocrystals processed were characterized by X-ray diffraction (X R I)), Fourier transform Raman (FT-Raman), Fourier transform infrared (FT-IR). ultraviolet visible (UV-vis) absorption spectroscopies, held-emission gun scanning electron microscopy (FEG-SEM). transmission electron microscopy (TEM). and photoluminescence (PL) measurements. X RI) patterns and FT-Raman spectra showed that these meso- and nanocrystals have a scheelite-type tetragonal structure without the presence of deleterious phases. FT-IR spectra exhibited a large absorption band situated at around 827 cm(-1), which is associated with the Mo-O anti-symmetric stretching vibrations into the [MoO(4)] clusters. FEG-SEM micrographs indicated that the ethylene glycol concentration in the aqueous solution plays an important role in the morphological evolution of CaMoO(4) crystals. High-resolution TEM micrographs demonstrated that the mesocrystals consist of several aggregated nanoparticles with electron diffraction patterns of monocrystal. In addition, the differences observed in the selected area electron diffraction patterns of CaMoO(4) crystals proved the coexistence of both nano- and mesostructures, First-principles quantum mechanical calculations based on the density functional theory at the B3LYP level were employed in order to understand the band structure find density of states For the CaMoO(4). UV-vis absorption measurements evidenced a variation in optical band gap values (from 3.42 to 3.72 cV) for the distinct morphologies. The blue and green PI. emissions observed in these crystals were ascribed to the intermediary energy levels arising from the distortions on the [MoO(4)] clusters clue to intrinsic defects in the lattice of anisotropic/isotropic crystals.

Refraction corrected transmission ultrasound computed tomography for application in breast imaging

Purpose: We present an iterative framework for CT reconstruction from transmission ultrasound data which accurately and efficiently models the strong refraction effects that occur in our target application: Imaging the female breast. Methods: Our refractive ray tracing framework has its foundation in the fast marching method (FNMM) and it allows an accurate as well as efficient modeling of curved rays. We also describe a novel regularization scheme that yields further significant reconstruction quality improvements. A final contribution is the development of a realistic anthropomorphic digital breast phantom based on the NIH Visible Female data set. Results: Our system is able to resolve very fine details even in the presence of significant noise, and it reconstructs both sound speed and attenuation data. Excellent correspondence with a traditional, but significantly more computationally expensive wave equation solver is achieved. Conclusions: Apart from the accurate modeling of curved rays, decisive factors have also been our regularization scheme and the high-quality interpolation filter we have used. An added benefit of our framework is that it accelerates well on GPUs where we have shown that clinical 3D reconstruction speeds on the order of minutes are possible.

Catalytic oxidation of hydrocarbons by trinuclear mu-oxo-bridged ruthenium-acetate clusters: Radical versus non-radical mechanisms

The [Ru(3)O(H(3)CCO(2))(6)(py)(2)(L)]PF(6) clusters, where L=methanol or dimethyl sulfoxide, can be activated by peroxide or oxygen donor species, such as tert-butyl hydroperoxide (TBHP) or iodosylbenzene (PhIO), respectively, generating reactive intermediates of the type [Ru(3)(IV,IV,III)=0](+). In this way, they catalyse the oxidation of cyclohexane or cyclohexene by TBHP and PhIO, via oxygen atom transfer, rather than by the alternative oxygen radical mechanism characteristic of this type of complexes. In addition to their ability to perform efficient olefin epoxydation catalysis, these clusters also promote the cleavage of the C-H bond in hydrocarbons, resembling the oxidation catalysis by metal porphyrins. (C) 2008 Elsevier Inc. All rights reserved.