European Springtails Orchesella cincta (L.) and O. villosa (L.) (Collembola: Entomobryidae): Vagabond Species of the Nearctic Region

North American specimens of the European invasive springtail Orchesella cincta (L.) were compared to several published European haplotypes in a phylogenetic framework using likelihood methods based on a portion of cytochrome oxidase II (cox2). Our analyses provide direct evidence of at least two distinct introductions of this invasive to North America from different regions of Europe. Additional introduction events cannot be ruled out because detection is limited by extremely low sequence divergence among populations inhabiting different regions of the continent. Orchesella villosa (L.), another invasive from Europe, is another candidate for multiple introductions. Herein we include the cox2 sequence from single specimens of O. villosa from Maine and Oregon. Although these two specimens are identical in sequence, they differ from a published sequence from a European specimen by 15%, indicating significant undocumented genetic variation in the natal range of O. villosa. Additional sampling of Nearctic populations of O. villosa might reveal the same situation reported herein for O. cincta

Predicted changes in herd immunity levels against Rift Valley fever virus in livestock following a natural exposure

Introduction Rift Valley fever virus (RVFV) transmission gets elevated following periods of excessive and persistent rainfall. The average inter-epizootic period in Kenya has been estimated to be 3.6 years (range 1–7 years). It is presumed that herd immunity plays an important role in modifying the length of these intervals given that the risk of an epidemic intensifies when herd immunity is low. The objective of this study was to evaluate the relationship between herd immunity and RVFV transmission dynamics. Materials and methods We developed a model to simulate RVFV transmission dynamics. The model comprises 2 vectors (Aedes and Culex spp.) and 2-hosts (cattle and sheep). Vector population dynamics are driven by probability functions that use precipitation obtained from Tropical Rainfall Measuring Mission (TRMM). Host related parameters are based on socio-economic data obtained from empirical studies conducted in Ijara, Kenya. Following the predicted outbreak, we prevented further transmissions and run simulations for five years to assess the evolution of herd immunity patterns. Results and discussion The model reproduces the 2006/7 RVF outbreak and predicts a high herd immunity level at the end of that outbreak (93% in cattle and 81% in sheep). Five years after the end of the outbreak, the herd immunity levels decline to an average of 5.9% [range 2.5, 7.9%] in cattle and 0.1% [range 0, 0.43%] in sheep. The period predicted by the model closely mirrors the average inter-epizootic period in Kenya. The rate of decline is higher in sheep relative to cattle probably due to the greater population turnover associated with higher fecundity rate, off take, replacement rate and shorter lifespan. Other analyses show that seasonal/inter-annual transmissions boost herd immunity. These inter-annual transmissions might be responsible for sustaining herd immunity over time especially when there are no external shocks associated with droughts, migration and tribal animosities. Conclusions This is the first study to utilize a simulation model to demonstrate the impacts of RVF immunity on RVF transmission and it has huge potentials for use in evaluation of cost-effectiveness of vaccination campaigns

The Space Station Photovoltaic Panels Plasma Interaction Test Program: Test plan and results

The Plasma Interaction Test performed on two space station solar array panels is addressed. This includes a discussion of the test requirements, test plan, experimental set-up, and test results. It was found that parasitic current collection was insignificant (0.3 percent of the solar array delivered power). The measured arcing threshold ranged from -210 to -457 V with respect to the plasma potential. Furthermore, the dynamic response of the panels showed the panel time constant to range between 1 and 5 microsec, and the panel capacitance to be between .01 and .02 microF

Factors influencing the prevalence of trypanosomosis in Orma Boran (trypanotolerant) and Teso zebu (trypanosusceptible) cattle crosses in Teso District, western Kenya

The objective of this study was to determine factors associated with occurrence of trypanosomosis in the first generation (F1) crossbreds between trypanotolerant Orma Boran and trypanosusceptible Teso zebu cattle in a trypanosomosis endemic area in Teso District, western Kenya. The offspring were screened for trypanosomosis and other haemoparasites using parasitological methods. Packed cell volume (PCV), body weights and tsetse density (FTD) were also determined. Factors considered in the analysis included sex, age, body weight and season of the year. Generalized linear mixed models (GLMM) were used for multivariable analysis to account for clustering of observations at the animal level and estimate outcome variance parameters. The overall trypanosomosis prevalence was 2.3% (n=477) probably corresponding to low FTD in the area (<1fly/trap/day). The risk of trypanosomosis infection was higher in dry than wet season (OR = 5.4) and in older than younger offspring (OR = 1.1). The variance parameters obtained indicated that variation of trypanosomosis prevalence lay only at the animal level. Intercurrent haemoparasites detected included Anaplasma marginale, Theileria and Babesia species. Overall, the results suggested that when the tsetse density is very low, control of trypanosomosis in the Orma-Teso zebu offspring in western Kenya require targeting of individual affected animals in the dry seasons

Acral peeling skin syndrome in two East-African siblings: case report

<p>Abstract</p> <p>Background</p> <p>Acral peeling skin syndrome is a rare autosomal recessive genodermatosis due to a missense mutation in transglutaminase 5. The skin peeling occurs at the separation of the stratum corneum from the stratum granulosum.</p> <p>Case presentation</p> <p>We present a case of two siblings who developed continuous peeling of the palms and soles from the first year of life. This peeling was more severe on the soles than palms and on younger sibling than elder sibling. Peeling is worsened by occlusion and sweating.</p> <p>Conclusions</p> <p>Sporadic cases of Acral Peeling Skin Syndrome occur in African population. There is variability in time of presentation and clinical severity even within families.</p

Near-Surface Material Phases and Microstructure of Scandate Cathodes

Scandate cathodes that were fabricated using the liquid-solid process and that exhibited excellent emission performance were characterized using complementary state-of-the-art electron microscopy techniques. Sub-micron BaAl2O4 particles were observed on the surfaces and edges of tungsten particles, as seen in cross-section samples extracted from the scandate cathode surface regions. Although several BaAl2O4 particles were observed to surround smaller Sc2O3 nanoparticles, no chemical mixing of the two oxides was detected, and in fact the distinct oxide phases were separately verified by chemical analysis and also by 3D elemental tomography. Nanobeam electron diffraction confirmed that the crystal structure throughout W grains is body-centered cubic, indicating that they are metallic W and did not experience noticeable changes, even near the grain surfaces, as a result of the numerous complex chemical reactions that occur during cathode impregnation and activation. 3D reconstruction further revealed that internal Sc/Sc2O3 particles tend to exhibit a degree of correlated arrangement within a given W particle, rather than being distributed uniformly throughout. Moreover, the formation of Sc/Sc2O3 particles within W grains may arise from W surface roughening that occurs during the liquid-solid synthesis process

Three-dimensional imaging and detection efficiency performance of orthogonal coplanar CZT strip detectors

We report on recent three-dimensional imaging performance and detection efficiency measurements obtained with 5 mm thick prototype CdZnTe detectors fabricated with orthogonal coplanar anode strips. In previous work, we have shown that detectors fabricated using this design achieve both very good energy resolution and sub-millimeter spatial resolution with fewer electronic channels than are required for pixel detectors. As electron-only devices, like pixel detectors, coplanar anode strip detectors can be fabricated in the thickness required to be effective imagers for photons with energies in excess of 500 keV. Unlike conventional double-sided strip detectors, the coplanar anode strip detectors require segmented contacts and signal processing electronics on only one surface. The signals can be processed to measure the total energy deposit and the photon interaction location in three dimensions. The measurements reported here provide a quantitative assessment of the detection capabilities of orthogonal coplanar anode strip detectors

Recoiling from a kick in the head-on collision of spinning black holes

Recoil ``kicks'' induced by gravitational radiation are expected in the inspiral and merger of black holes. Recently the numerical relativity community has begun to measure the significant kicks found when both unequal masses and spins are considered. Because understanding the cause and magnitude of each component of this kick may be complicated in inspiral simulations, we consider these effects in the context of a simple test problem. We study recoils from collisions of binaries with initially head-on trajectories, starting with the simplest case of equal masses with no spin and then adding spin and varying the mass ratio, both separately and jointly. We find spin-induced recoils to be significant relative to unequal-mass recoils even in head-on configurations. Additionally, it appears that the scaling of transverse kicks with spins is consistent with post-Newtonian theory, even though the kick is generated in the nonlinear merger interaction, where post-Newtonian theory should not apply. This suggests that a simple heuristic description might be effective in the estimation of spin-kicks.Comment: 12 pages, 10 figures. Replaced with published version, including more discussion of convergence and properties of final hol

Rift Valley fever: Influence of herd immunity patterns on transmission dynamics

Introduction Rift Valley fever virus (RVFV) transmission gets elevated following periods of excessive and persistent rainfall. The average inter-epizootic period in Kenya has been estimated to be 3.6 years (range 1–7 years). It is presumed that herd immunity plays an important role in modifying the length of these intervals given that the risk of an epidemic intensifies when herd immunity is low. The objective of this study was to evaluate the relationship between herd immunity and RVFV transmission dynamics. Materials and Methods We developed a model to simulate RVFV transmission dynamics. The model comprises 2 vectors (Aedes and Culex spp.) and 2-hosts (cattle and sheep). Vector population dynamics are driven by precipitation obtained from Tropical Rainfall Measuring Mission (TRMM) while those of hosts are parameterized based on socio-economic data obtained from empirical studies conducted in Ijara, Kenya. Simulations are implemented for the period: 1st January 2005 and 23rd June 2010 in an attempt to predict the recent 2006/7 outbreak and other seasonal transmissions that occur during wet seasons. Results The model reproduces the 2006/7 RVF outbreak and predicts a high herd immunity level at the end of that outbreak, with 90% of sheep and 72% of cattle being immune. This immunity wanes overtime, declining to 18% in sheep and 42% in cattle by the end of the simulation period (~4 years). The rate of decline is higher in sheep relative to cattle probably due to the greater population turnover associated with higher fecundity rate, off take, replacement rate and shorter lifespan. These analyses also show that seasonal/inter-annual transmissions boost herd immunity. Preventing these transmissions leads to a reduction in herd immunity levels (10.9% in sheep and 30.6% in cattle) by the end of the simulation period. These inter-annual transmissions might be responsible for sustaining herd immunity over time especially when there are no external shocks associated with droughts, migration and tribal animosities. Conclusions and Recommendations This is the first study to utilize a simulation model to demonstrate the impacts of RVF immunity on RVF transmission and it has huge potentials for use in evaluation of cost-effectiveness of vaccination campaigns