1,041 research outputs found
Structural Properties of the Caenorhabditis elegans Neuronal Network
Despite recent interest in reconstructing neuronal networks, complete wiring
diagrams on the level of individual synapses remain scarce and the insights
into function they can provide remain unclear. Even for Caenorhabditis elegans,
whose neuronal network is relatively small and stereotypical from animal to
animal, published wiring diagrams are neither accurate nor complete and
self-consistent. Using materials from White et al. and new electron micrographs
we assemble whole, self-consistent gap junction and chemical synapse networks
of hermaphrodite C. elegans. We propose a method to visualize the wiring
diagram, which reflects network signal flow. We calculate statistical and
topological properties of the network, such as degree distributions, synaptic
multiplicities, and small-world properties, that help in understanding network
signal propagation. We identify neurons that may play central roles in
information processing and network motifs that could serve as functional
modules of the network. We explore propagation of neuronal activity in response
to sensory or artificial stimulation using linear systems theory and find
several activity patterns that could serve as substrates of previously
described behaviors. Finally, we analyze the interaction between the gap
junction and the chemical synapse networks. Since several statistical
properties of the C. elegans network, such as multiplicity and motif
distributions are similar to those found in mammalian neocortex, they likely
point to general principles of neuronal networks. The wiring diagram reported
here can help in understanding the mechanistic basis of behavior by generating
predictions about future experiments involving genetic perturbations, laser
ablations, or monitoring propagation of neuronal activity in response to
stimulation
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The impact of HIV stigma in accessing sexual health services among black sub-Sahara African woman and gay men: a systematic literature review
For many years HIV related stigma and denial has characterized the pandemic and presented a major challenge to the uptake of HIV testing, prevention and normalization among black sub-Sahara African (BSSA) women and gay men. The challenges have had a ripple effect on the access to sexual health services and resources within the communities in question. This article reviews literature on the types of HIV stigma and its impact in accessing sexual health services and resources by the aforesaid communities. Furthermore the article will review literature on attempts made to de-mystify HIV stigma in order to increase its uptake among the groups in question. The findings from the literature suggest that HIV stigma remains a big challenge to the uptake of HIV testing and access to sexual health services including resources among different social groups under consideration in this article. Despite the efforts to normalize HIV testing, including access to sexual health services and resources, HIV stigma has tended to take a new complex dimension and has proved hard to disappear. In addition to the current efforts to end HIV stigma there is need to understand more about the forms, contexts and social construction of HIV stigma and sexual health seeking behavior in different communities, if we are to succeed in our endeavor to control the epidemic
Distribution of Savage’s Anole, Dactyloa savagei (Poe and Ryan 2017) (Squamata: Dactyloidae), in Costa Rica
Broadband telecom transparency of semiconductor-coated metal nanowires: more transparent than glass
Metallic nanowires (NW) coated with a high permittivity dielectric are
proposed as means to strongly reduce the light scattering of the conducting NW,
rendering them transparent at infrared wavelengths of interest in
telecommunications. Based on a simple, universal law derived from
electrostatics arguments, we find appropriate parameters to reduce the
scattering efficiency of hybrid metal-dielectric NW by up to three orders of
magnitude as compared with the scattering efficiency of the homogeneous
metallic NW. We show that metal@dielectric structures are much more robust
against fabrication imperfections than analogous dielectric@metal ones. The
bandwidth of the transparent region entirely covers the near IR
telecommunications range. Although this effect is optimum at normal incidence
and for a given polarization, rigorous theoretical and numerical calculations
reveal that transparency is robust against changes in polarization and angle of
incidence, and also holds for relatively dense periodic or random arrangements.
A wealth of applications based on metal-NWs may benefit from such invisibility
Federating heterogeneous datasets to enhance data sharing and experiment reproducibility
Recent studies have demonstrated the difficulties to replicate scientific findings and/or experiments published in past.1 The effects seen in the replicated experiments were smaller than previously reported. Some of the explanations for these findings include the complexity of the experimental design and the pressure on researches to report positive findings. The International Committee of Medical Journal Editors (ICMJE) suggests that every study considered for publication must submit a plan to share the de-identified patient data no later than 6 months after publication. There is a growing demand to enhance the management of clinical data, facilitate data sharing across institutions and also to keep track of the data from previous experiments. The ultimate goal is to assure the reproducibility of experiments in the future. This paper describes Shiny-tooth, a web based application created to improve clinical data acquisition during the clinical trial; data federation of such data as well as morphological data derived from medical images; Currently, this application is being used to store clinical data from an osteoarthritis (OA) study. This work is submitted to the SPIE Biomedical Applications in Molecular, Structural, and Functional Imaging conference
A GIS-based multivariate clustering for characterization and ecoregion mapping from a viticultural perspective
In wine-growing regions, zoning studies define areas according to their potential to produce specific wines and also identify the key drivers behind their variability and optimize vineyard management for sustainable viticulture. However, delineation of homogeneous zones is difficult because of the complex combination of factors which could affect zone classifications. One possibility to capture potential variability is the use of natural environmental properties as they are related to success in grape growing. With the aim of characterizing the spatial variability of the main vine-related environmental variables and determining different zones, climate and topographical data were obtained for Extremadura (southwestern Spain), an important wine region. Firstly, accurate maps of all climate indices were generated by using regression-kriging as the most suitable algorithm in which exhaustive secondary information on elevation was incorporated, and maps of topography-derived variables were obtained using GIS (Geographical Information System) tools. Secondly, principal component analysis and multivariate geographic classification were used to define homogeneous classes, resulting in three zones. Each zone was further characterized by overlaying the zonation map with a geology map and all enviromental layers. It was obtained that although a wide part of the Extremaduran territory has warm climate characteristics, the zones have different viticultural potential and a high proportion of the region lays on suitable substrate. This zonation in Extremadura is the basis for further zoning studies at more detailed field scale and the modeling of vineyard response to climate change
Localized magnetic plasmons in all-dielectric mu<0 metastructures
Metamaterials are known to exhibit a variety of electromagnetic properties
non-existing in nature. We show that an all-dielectric (non-magnetic) system
consisting of deep subwavelength, high permittivity resonant spheres possess
effective negative magnetic permeability (dielectric permittivity being
positive and small). Due to the symmetry of the electromagnetic wave equations
in classical electrodynamics, localized "magnetic" plasmon resonances can be
excited in a metasphere made of such metamaterial. This is theoretically
demonstrated by the coupled-dipole approximation and numerically for real
spheres, in full agreement with the exact analytical solution for the
scattering process by the same metasphere with effective material properties
predicted by effective medium theory. The emergence of this phenomenon as a
function of structural order within the metastructures is also studied.
Universal conditions enabling effective negative magnetic permeability relate
subwavelength sphere permittivity and size with critical filling fraction. Our
proposal paves the way towards (all-dielectric) magnetic plasmonics, with a
wealth of fascinating applications.Comment: 7 pages, 4 figures; figure 3 modified and new figure (4) added, with
corresponding discussio
\u3cem\u3eHelicobacter pylori\u3c/em\u3e infection in Havana, Cuba. Prevalence and \u3cem\u3ecagA\u3c/em\u3e status of the strains
There is a great paucity of information about Helicobacter pylori infection in the countries of the Caribbean basin. Almost no studies have been performed to determine the prevalence, antibiotic resistance or virulence factors of the bacterium. To measure the prevalence of H. pylori infection among patients attending endoscopy in three clinics in Havana, Cuba, to evaluate clarithromycin resistance, and to determine the cagA status of the strains obtained. Endoscopy was performed and biopsies were obtained from 117 successive patients attending the Institute of Oncology, the Institute of Gastroenterology, and the Calixto Garcia Hospital in Havana, Cuba. Biopsies were maintained at –70 ºC before being cultured on three different media (two selective and one non-selective) and incubated for 7 days at 37 °C under a microaerobic atmosphere. The presence of H. pylori was identified by oxidase, catalase and urease activities. DNA was extracted, and PCR was performed with primers H2761676 which amplify a 397 bp fragment of the cagA gene. Clarithromycin susceptibility was measured by the gel diffusion method. The diagnoses of patients were: 1 gastric carcinoma; 19 duodenal ulcers; 8 gastric ulcers; and 89 non-ulcer dyspepsia, including (62) gastritis, (9) hiatal hernia,(2) biliary reflux, (1) gastric polyps, and (15) no abnormality. Among the 117 biopsies tested, 83 were H. pylori positive (70.9%). The cagA status determined for 35 cases gave a positive result in 31 cases (88.5%). Only 3% of the strains were resistant to clarithromycin. The prevalence of Helicobacter pylori infection in the symptomatic population of La Habana is the same as reported for other developing countries. Most strains were cagA positive and are likely harbour the cag pathogenicity island. The low resistance to clarithromycin in the strains studied probably reflects the low degree of use of the antibiotic in this population
Co-occurrence and character convergence in two Neotropical bats
When functionally similar species co-occur, they are expected to differ in at least 1 niche axis to avoid competition. In bats, small differences in body size can influence ecology, potentially reducing niche overlap. We used yellow-shouldered bats (genus Sturnira) in Mexico as a model to investigate whether interspecific differences in body size increase when 2 related and ecologically similar species occur in sympatry. We hypothesized that size divergence would take place in sympatry, following known patterns whereby larger bats eat larger fruits and smaller bats forage and roost in more cluttered habitats. We collected data on body mass, forearm length, and skull size from museum specimens to characterize the overall dimensions of these bats. Using linear mixed effect models and permutation tests, we tested for differences between areas where these species occur in sympatry or allopatry, while controlling for the confounding effect of environmental variables and sexual dimorphism. Contrary to our original hypothesis, we detected size convergence in sympatric areas, an uncommon pattern in bats. We found no evidence of character displacement for forearm length and body mass, but an effect of co-occurrence on overall skull size and head length. Convergence in overall skull dimensions may reflect shared environmental pressures and similar food resources, which may not represent a limiting factor. Interspecific differences in forearm length remain constant in sympatry or allopatry. These differences likely preceded the 2 species coming into contact and could have allowed initial and ongoing coexistence by influencing wing properties and flight. We highlight the need for multivariate approaches in the study of character displacement, as selective pressures can act differently on different traits allowing both local adaptation and coexistence
Interfase patológica por fricción metal-metal y metal-polietileno: diferencias microscópicas
—Las partículas de polietileno han sido reconocidas como responsables de los aflojamientos
asépticos y la osteólisis en las artroplastias totales de cadera. Algunos autores han vuelto
a proponer la fricción metal-metal inentando mejorar los resultados. Aportamos 2 casos de revisión
quirúrgica por aflojamiento aséptico, 1 prótesis de McKee y 1 doble cúpula de Freeman,
ambas cementadas y aflojadas, que cursaron con osteólisis. Hemos estudiado la reacción tisular de
la interfase del cotilo protésico y presentamos las diferencias histológicas entre el primer caso de
fricción metal-metal y el segundo de fricción metal-polietileno, encontrando mayor presencia de
histiocitos y células gigantes multinucleadas en el caso de fricción metal-polietileno.Polyethylene wear debris have been implicated as a major cause of aseptic loosening
and osteolysis in total hip arthroplasty. Some authors propose metal-metal friction intending
to improve the results. We report two cases of revision surgery, due to aseptic loosening: one
McKee prothesis and a Freeman double cupule, both cemented and loose, failing with osteolysis.
We have studied the tissue reaction of the interface socket and the histological differences between
the first case of metal-metal friction and the second case of metal-polyethylene friction. We
found more histiocytes and multinucleated giant cells in metal-polyethylene friction case
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