5,872 research outputs found
Telemedicine in Primary Health: The Virtual Doctor Project Zambia
This paper is a commentary on a project application of telemedicine to alleviate primary health care problems in Lundazi district in the Eastern province of Zambia. The project dubbed 'The Virtual Doctor Project' will use hard body vehicles fitted with satellite communication devices and modern medical equipment to deliver primary health care services to some of the neediest areas of the country. The relevance and importance of the project lies in the fact that these areas are hard-to-reach due to rugged natural terrain and have very limited telecommunications infrastructure. The lack of these and other basic services makes it difficult for medical personnel to settle in these areas, which leads to an acute shortage of medical personnel. We comment on this problem and how it is addressed by 'The Virtual Doctor Project', emphasizing that while the telemedicine concept is not new in sub-Saharan Africa, the combination of mobility and connectivity to service a number of villages 'on the go' is an important variation in the shift back to the 1978 Alma Ata principles of the United Nations World Health Organization [WHO]
The Signature of Primordial Grain Growth in the Polarized Light of the AU Mic Debris Disk
We have used the Hubble Space Telescope/ACS coronagraph to make polarization
maps of the AU Mic debris disk. The fractional linear polarization rises
monotonically from about 0.05 to 0.4 between 20 and 80 AU. The polarization is
perpendicular to the disk, indicating that the scattered light originates from
micron sized grains in an optically thin disk. Disk models, which
simultaneously fit the surface brightness and polarization, show that the inner
disk (< 40-50 AU) is depleted of micron-sized dust by a factor of more than
300, which means that the disk is collision dominated. The grains have high
maximum linear polarization and strong forward scattering. Spherical grains
composed of conventional materials cannot reproduce these optical properties. A
Mie/Maxwell-Garnett analysis implicates highly porous (91-94%) particles. In
the inner Solar System, porous particles form in cometary dust, where the
sublimation of ices leaves a "bird's nest" of refractory organic and silicate
material. In AU Mic, the grain porosity may be primordial, because the dust
"birth ring" lies beyond the ice sublimation point. The observed porosities
span the range of values implied by laboratory studies of particle coagulation
by ballistic cluster-cluster aggregation. To avoid compactification, the upper
size limit for the parent bodies is in the decimeter range, in agreement with
theoretical predictions based on collisional lifetime arguments. Consequently,
AU Mic may exhibit the signature of the primordial agglomeration process
whereby interstellar grains first assembled to form macroscopic objects.Comment: 12 pages, 8 figures, ApJ, in pres
The Microchannel X-ray Telescope for the Gamma-Ray Burst mission SVOM
We present the Microchannel X-ray Telescope, a new light and compact
focussing telescope that will be flying on the Sino-French SVOM mission
dedicated to Gamma-Ray Burst science. The MXT design is based on the coupling
of square pore micro-channel plates with a low noise pnCCD. MXT will provide an
effective area of about 50 cmsq, and its point spread function is expected to
be better than 3.7 arc min (FWHM) on axis. The estimated sensitivity is
adequate to detect all the afterglows of the SVOM GRBs, and to localize them to
better then 60 arc sec after five minutes of observation.Comment: 12 pages, 8 figures, to be published in SPIE Astronomical Telescopes
+ Instrumentation, Montreal, June 201
Possible Evidence for MeV Dark Matter In Dwarf Spheroidals
It has been recently proposed that the observed 511 keV emission from the
Galactic bulge could be the product of very light (1-100 MeV) annihilating dark
matter particles. Other possible explanations for this signal are associated
with stellar objects, such as hypernovae. In order to distinguish between
annihilating light dark matter scenario and more conventional astrophysical
sources for the bulge emission, we here propose the study of dwarf spheroidals
such as Sagittarius. These galaxies have typical luminosities of
but mass-to-light ratios of . As there are comparatively few stars,
the prospects for 511 keV emission from standard astrophysical scenarios are
minimal. The dwarf spheroidals do, however, contain copious amounts of dark
matter. INTEGRAL/SPI has observed the Sagittarius region. Analysis of this data
for 511 keV emission will provide a test of MeV dark matter which can
distinguish between annihilating dark matter and more standard astrophysics.
The observation of such a signal from Sagittarius should be a ``smoking gun''
for MeV dark matter.Comment: 4 pages, no figures. Version accepted by Physical Review Letter
The targeted delivery of multicomponent cargos to cancer cells by nanoporous particle-supported lipid bilayers.
Encapsulation of drugs within nanocarriers that selectively target malignant cells promises to mitigate side effects of conventional chemotherapy and to enable delivery of the unique drug combinations needed for personalized medicine. To realize this potential, however, targeted nanocarriers must simultaneously overcome multiple challenges, including specificity, stability and a high capacity for disparate cargos. Here we report porous nanoparticle-supported lipid bilayers (protocells) that synergistically combine properties of liposomes and nanoporous particles. Protocells modified with a targeting peptide that binds to human hepatocellular carcinoma exhibit a 10,000-fold greater affinity for human hepatocellular carcinoma than for hepatocytes, endothelial cells or immune cells. Furthermore, protocells can be loaded with combinations of therapeutic (drugs, small interfering RNA and toxins) and diagnostic (quantum dots) agents and modified to promote endosomal escape and nuclear accumulation of selected cargos. The enormous capacity of the high-surface-area nanoporous core combined with the enhanced targeting efficacy enabled by the fluid supported lipid bilayer enable a single protocell loaded with a drug cocktail to kill a drug-resistant human hepatocellular carcinoma cell, representing a 10(6)-fold improvement over comparable liposomes
Channel formation in single-monolayer pentacene thin film transistors
Abstract The geometrical arrangement of single-molecule-high islands and the contact between them have large roles in determining the electrical properties of field effect transistors (FETs) based on monolayer-scale pentacene thin films. As the pentacene coverage increases through the submonolayer regime there is a percolation transition where islands come into contact and a simultaneous rapid onset of current. At coverages just above the percolation threshold, the electrical properties vary with geometrical changes in the contacts between the pentacene islands. At higher coverages, the FET mobility is much lower than the mobility measured by the van der Pauw method because of high contact resistances in monolayer-scale pentacene film devices. An increase in the van der Pauw mobility of holes as a function of pentacene coverage shows that second layer islands take part in charge transport
Temperature-dependent phenology of Plutella xylostella (Lepidoptera: Plutellidae): Simulation and visualization of current and future distributions along the Eastern Afromontane
There is a scarcity of laboratory and field-based results showing the movement of the diamondback moth (DBM) Plutella xylostella (L.) across a spatial scale. We studied the population growth of the diamondback moth (DBM) Plutella xylostella (L.) under six constant temperatures, to understand and predict population changes along altitudinal gradients and under climate change scenarios. Non-linear functions were fitted to continuously model DBM development, mortality, longevity and oviposition. We compiled the best-fitted functions for each life stage to yield a phenology model, which we stochastically simulated to estimate the life table parameters. Three temperature-dependent indices (establishment, generation and activity) were derived from a logistic population growth model and then coupled to collected current (2013) and downscaled temperature data from AFRICLIM (2055) for geospatial mapping. To measure and predict the impacts of temperature change on the pest's biology, we mapped the indices along the altitudinal gradients of Mt. Kilimanjaro (Tanzania) and Taita Hills (Kenya) and assessed the differences between 2013 and 2055 climate scenarios. The optimal temperatures for development of DBM were 32.5, 33.5 and 33ÊC for eggs, larvae and pupae, respectively. Mortality rates increased due to extreme temperatures to 53.3, 70.0 and 52.4% for egg, larvae and pupae, respectively. The net reproduction rate reached a peak of 87.4 female offspring/female/generation at 20ÊC. Spatial simulations indicated that survival and establishment of DBM increased with a decrease in temperature, from low to high altitude. However, we observed a higher number of DBM generations at low altitude. The model predicted DBM population growth reduction in the low and medium altitudes by 2055. At higher altitude, it predicted an increase in the level of suitability for establishment with a decrease in the number of generations per year. If climate change occurs as per the selected scenario, DBM infestation may reduce in the selected region. The study highlights the need to validate these predictions with other interacting factors such as cropping practices, host plants and natural enemies.Peer reviewe
Collision statistics in sheared inelastic hard spheres
The dynamics of sheared inelastic-hard-sphere systems are studied using
non-equilibrium molecular dynamics simulations and direct simulation Monte
Carlo. In the molecular dynamics simulations Lees-Edwards boundary conditions
are used to impose the shear. The dimensions of the simulation box are chosen
to ensure that the systems are homogeneous and that the shear is applied
uniformly. Various system properties are monitored, including the one-particle
velocity distribution, granular temperature, stress tensor, collision rates,
and time between collisions. The one-particle velocity distribution is found to
agree reasonably well with an anisotropic Gaussian distribution, with only a
slight overpopulation of the high velocity tails. The velocity distribution is
strongly anisotropic, especially at lower densities and lower values of the
coefficient of restitution, with the largest variance in the direction of
shear. The density dependence of the compressibility factor of the sheared
inelastic hard sphere system is quite similar to that of elastic hard sphere
fluids. As the systems become more inelastic, the glancing collisions begin to
dominate more direct, head-on collisions. Examination of the distribution of
the time between collisions indicates that the collisions experienced by the
particles are strongly correlated in the highly inelastic systems. A comparison
of the simulation data is made with DSMC simulation of the Enskog equation.
Results of the kinetic model of Montanero et al. {[}Montanero et al., J. Fluid
Mech. 389, 391 (1999){]} based on the Enskog equation are also included. In
general, good agreement is found for high density, weakly inelastic systems.Comment: 10 figures, 1 table, 27 page
Shell Neurons of the Master Circadian Clock Coordinate the Phase of Tissue Clocks Throughout the Brain and Body
Background: Daily rhythms in mammals are programmed by a master clock in the suprachiasmatic nucleus (SCN). The SCN contains two main compartments (shell and core), but the role of each region in system-level coordination remains ill defined. Herein, we use a functional assay to investigate how downstream tissues interpret region-specific outputs by using in vivo exposure to long day photoperiods to temporally dissociate the SCN. We then analyze resulting changes in the rhythms of clocks located throughout the brain and body to examine whether they maintain phase synchrony with the SCN shell or core. Results: Nearly all of the 17 tissues examined in the brain and body maintain phase synchrony with the SCN shell, but not the SCN core, which indicates that downstream oscillators are set by cues controlled specifically by the SCN shell. Interestingly, we also found that SCN dissociation diminished the amplitude of rhythms in core clock gene and protein expression in brain tissues by 50–75 %, which suggests that light-driven changes in the functional organization of the SCN markedly influence the strength of rhythms in downstream tissues. Conclusions: Overall, our results reveal that body clocks receive time-of-day cues specifically from the SCN shell, which may be an adaptive design principle that serves to maintain system-level phase relationships in a changing environment. Further, we demonstrate that lighting conditions alter the amplitude of the molecular clock in downstream tissues, which uncovers a new form of plasticity that may contribute to seasonal changes in physiology and behavior
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