179 research outputs found

    Small Renal Masses: Incidental Diagnosis, Clinical Symptoms, and Prognostic Factors

    Get PDF
    Introduction. The small renal masses (SRMs) have increased over the past two decades due to more liberal use of imaging techniques. SRMs have allowed discussions regarding their prognostic, diagnosis, and therapeutic approach. Materials and methods. Clinical presentation, incidental diagnosis, and prognosis factors of SRMs are discussed in this review. Results. SRMs are defined as lesions less than 4 cm in diameter. SRM could be benign, and most malignant SMRs are low stage and low grade. Clinical symptoms like hematuria are very rare, being diagnosed by chance (incidental) in most cases. Size, stage, and grade are still the most consistent prognosis factors in (RCC). An enhanced contrast SRM that grows during active surveillance is clearly malignant, and its aggressive potential increases in those greater than 3 cm. Clear cell carcinoma is the most frequent cellular type of malign SRM. Conclusions. Only some SRMs are benign. The great majority of malign SRMs have good prognosis (low stage and grade, no metastasis) with open or laparoscopic surgical treatment (nephron sparing techniques). Active surveillance is an accepted attitude in selected cases

    GESTIÓN DEL CONOCIMIENTO COMO PROCESO CLAVE PARA EL DESARROLLO DE LA PRAXIS INVESTIGATIVA EN ORGANIZACIONES INTELIGENTES

    Get PDF
    Universities over the years have been intelligent organizations that generate and disseminate scientific and technological knowledge, the research function being the source of this knowledge and, in turn, the propitious mechanism for its constant updating. Therefore, the core purpose of this study was to analyze knowledge management as a key process for the development of investigative praxis in intelligent organizations. The research was analytical and descriptive, with a non-experimental, cross-sectional field design. The population was made up of eight hundred teachers; likewise, the structured sample of 89 teachers was calculated, subsequently a stratified sampling by institution was applied: 48 teachers from the Popular University of Cesar (Valledupar campus and 41 from the Aguachica campus, respectively. The information was collected through the survey technique by through a questionnaire validated by 10 experts, whose Cronbach's Alpha coefficient was equivalent to 0.96.The results obtained revealed that knowledge management as a key element for the development of investigative praxis in university institutions conceived as intelligent organizations, is underdeveloped, requiring apply technological tools to turn them into open and connected institutions, characterized by their autonomy and trust, where the group learns to investigate together.Las Universidades a lo largo de los años han sido organizaciones inteligentes que generan y difunden conocimientos científicos y tecnológicos, siendo la función de investigación la fuente de estos conocimientos y a su vez, el mecanismo propicio para su constante actualización. Por ello, el propósito medular del presente estudio fue analizar Gestión del conocimiento como proceso clave para el desarrollo de la praxis investigativa en organizaciones inteligentes. La investigación fue de carácter analítica y   descriptiva, con un diseño no experimental, transeccional de campo. La población estuvo conformada por ochocientos docentes; asimismo, se calculó la muestra estructurada por 89 docentes, posteriormente se aplicó un muestreo estratificado por institución: 48 docentes de la Universidad Popular del Cesar (Sede Valledupar y 41 de la sede Aguachica, respectivamente. La información fue recabada mediante la técnica de encuesta por medio de un cuestionario validado por 10 expertos, cuyo coeficiente Alfa de Cronbach fue equivalente a 0.96. Los resultados obtenidos develaron que la gestión del conocimiento como elemento clave para el desarrollo de la praxis investigativa en instituciones universitarias concebidas organizaciones inteligentes, se encuentra poco desarrollada requiriendo aplicar herramientas tecnológicas para convertirlas en instituciones abiertas y conectadas, caracterizadas por su autonomía y confianza, donde el colectivo aprende a investigar en conjunto

    Modeling elastic and photoassisted transport in organic molecular wires: length dependence and current-voltage characteristics

    Get PDF
    Using a pi-orbital tight-binding model, we study the elastic and photoassisted transport properties of metal-molecule-metal junctions based on oligophenylenes of varying lengths. The effect of monochromatic light is modeled with an ac voltage over the contact. We first show how the low-bias transmission function can be obtained analytically, using methods previously employed for simpler chain models. In particular, the decay coefficient of the off-resonant transmission is extracted by considering both a finite-length chain and infinitely extended polyphenylene. Based on these analytical results, we discuss the length-dependence of the linear-response conductance, the thermopower, and the light-induced enhancement of the conductance in the limit of weak intensity and low frequency. In general the conductance-enhancement is calculated numerically as a function of the light frequency. Finally, we compute the current-voltage characteristics at finite dc voltages, and show that in the low-voltage regime, the effect of low-frequency light is to induce current steps with a voltage separation determined by twice the frequency. These effects are more pronounced for longer molecules. We study two different profiles for the dc and ac voltages, and it is found that the results are robust with respect to such variations. Although we concentrate here on the specific model of oligophenylenes, the results should be qualitatively similar for many other organic molecules with a large enough electronic gap.Comment: 15 pages, 11 figures, minor corrections to old versio

    Computational study of [1,3] sigmatropic rearrangement of the (Z)-3-(4-(dimethylamino)benzyliden)thiocroman-4- one

    Get PDF
    This research is based on a computational study of a [1,3] sigmatropic intramolecular hydrogen rearrangement for (Z)-3-(4-(dimethylamino)benzylidene)thiochroman-4-one, applying the Density Functional Theory with the exchangecorrelation functional B3LYP and 6-31G(d,p) set basis using software package Gaussian 09W. Two possible suprafacials and anatarafacials migrations of the hydrogen atom bonded to ring thiopyran-4-one of the (Z)-3-(4-(Dimethylamino)- benzylidene)thiochroman-4-one were evaluated, results show an activation energy of 4 Kcal/mol which is more favorable for a transition state featuring characteristics related to a [1,2] suprafacial shift, in comparison with the amount of activation energy of a [1,3] antarafacial shift transition state

    Energy and Flux Measurements of Ultra-High Energy Cosmic Rays Observed During the First ANITA Flight

    Get PDF
    The first flight of the Antarctic Impulsive Transient Antenna (ANITA) experiment recorded 16 radio signals that were emitted by cosmic-ray induced air showers. For 14 of these events, this radiation was reflected from the ice. The dominant contribution to the radiation from the deflection of positrons and electrons in the geomagnetic field, which is beamed in the direction of motion of the air shower. This radiation is reflected from the ice and subsequently detected by the ANITA experiment at a flight altitude of 36km. In this paper, we estimate the energy of the 14 individual events and find that the mean energy of the cosmic-ray sample is 2.9 EeV. By simulating the ANITA flight, we calculate its exposure for ultra-high energy cosmic rays. We estimate for the first time the cosmic-ray flux derived only from radio observations. In addition, we find that the Monte Carlo simulation of the ANITA data set is in agreement with the total number of observed events and with the properties of those events.Comment: Added more explanation of the experimental setup and textual improvement

    Evidence of two lineages of the dengue vector Aedes aegypti in the Brazilian Amazon, based on mitochondrial DNA ND4 gene sequences

    Get PDF
    Genetic variation was estimated in ten samples populations of Aedes aegypti from the Brazilian Amazon, by using a 380 bp fragment of the mitochocondrial NADH dehydrogenase subunit 4 (ND4) gene. A total of 123 individuals were analyzed, whereby 13 haplotypes were found. Mean genetic diversity was slightly high (h = 0.666 ± 0.029; π = 0.0115 ± 0.0010). Two AMOVA analyses indicated that most of the variation (~70%-72%) occurred within populations. The variation found among and between populations within the groups disclosed lower, but even so, highly significant values. FST values were not significant in most of the comparisons, except for the samples from Pacaraima and Rio Branco. The isolation by distance (IBD) model was not significant (r = 0.2880; p = 0.097) when the samples from Pacaraima and Rio Branco were excluded from the analyses, this indicating that genetic distance is not related to geographic distance. This result may be explained either by passive dispersal patterns (via human migrations and commercial exchange) or be due to the recent expansion of this mosquito in the Brazilian Amazon. Phylogenetic relationship analysis showed two genetically distinct groups (lineages) within the Brazilian Amazon, each sharing haplotypes with populations from West Africa and Asia

    South American Plasmodium falciparum after the Malaria Eradication Era: Clonal Population Expansion and Survival of the Fittest Hybrids

    Get PDF
    Malaria has reemerged in many regions where once it was nearly eliminated. Yet the source of these parasites, the process of repopulation, their population structure, and dynamics are ill defined. Peru was one of malaria eradication's successes, where Plasmodium falciparum was nearly eliminated for two decades. It reemerged in the 1990s. In the new era of malaria elimination, Peruvian P. falciparum is a model of malaria reinvasion. We investigated its population structure and drug resistance profiles. We hypothesized that only populations adapted to local ecological niches could expand and repopulate and originated as vestigial populations or recent introductions. We investigated the genetic structure (using microsatellites) and drug resistant genotypes of 220 parasites collected from patients immediately after peak epidemic expansion (1999–2000) from seven sites across the country. The majority of parasites could be grouped into five clonal lineages by networks and AMOVA. The distribution of clonal lineages and their drug sensitivity profiles suggested geographic structure. In 2001, artesunate combination therapy was introduced in Peru. We tested 62 parasites collected in 2006–2007 for changes in genetic structure. Clonal lineages had recombined under selection for the fittest parasites. Our findings illustrate that local adaptations in the post-eradication era have contributed to clonal lineage expansion. Within the shifting confluence of drug policy and malaria incidence, populations continue to evolve through genetic outcrossing influenced by antimalarial selection pressure. Understanding the population substructure of P. falciparum has implications for vaccine, drug, and epidemiologic studies, including monitoring malaria during and after the elimination phase
    corecore