A study of the break-up characteristics of Chena River Basin using ERTS imagery

The author has identified the following significant results. The Chena River Basin was selected because of the availability of ground truth data for comparison. Very good agreement for snow distribution and rates of ablation was found between the ERTS-1 imagery, the snowmelt model, and field measurements. Monitoring snowmelt rates for relatively small basins appears to be practical. The main limitation of the ERTS-1 imagery is the interval of coverage. More frequent overflights providing coverage are needed for the study of transient hydrologic events. ERTS-1 data is most useful when used in conjunction with snowmelt prediction models and existing snow course data. These results should prove very useful in preliminary assessment of hydrologic conditions in ungaged watersheds and will provide a tool for month-to-month volume forecasting

Break-up characteristics of the Chena River watershed, central Alaska

The author has identified the following significant results. The snow melt for a small watershed (5130 sq km) in Central Alaska was successfully monitored with ERTS-1 imagery. Aerial photography was used as supporting data for periods without satellite coverage. Comparison both with actual measurements and with a computer model showed good agreement

Some Observations of Alaskan Glacier Winds in Midsummer

Discusses 21 June-12 July observations at Castner Glacier in the Alaska Range and 16 July-11 Aug 1967 at Worthington Glacier in the Chugach Range. The purpose was to study the frequency and diurnal variation of glacier winds and differences due to location and exposure. In both cases max windspeed occurs slightly before sunrise and in the mid-afternoon. In the absence of a daytime glacier wind at Castner, a regular night downslope circulation is often observed.Quelques observations sur les vents de glacier de l'Alaska au milieu de l'été. Les auteurs dévrivent les caractères des vents de glacier observés au milieu de l'été pour les glaciers Worthington et Castner. Chacun présente un double maximum quotidien de vélocité, soit juste avant l'aurore et vers le milieu de l'après-midi. Lorsqu'il n'y a pas de vent de glacier diurne à Castner, on observe souvent une circulation nocturne très régulière et descendante

Cómputo métrico, análisis de costos y presupuestación – POCSE S.A.

Práctica Supervisada (IC)--FCEFN-UNC, 2013.Presenta la misión de colaborar con las tareas de presupuestación de servicios, y obras (Dr House / Pacse) conseguir los mejores precios y la responsabilidad de desarrollar la asistencia en la presupuestación, control y actualización de precios y costos, desarrollo y actualización de proveedore

Localized magnetoplasmon modes arising from broken translational symmetry in semiconductor superlattices

The electromagnetic propagator associated with the localized collective magnetoplasmon excitations in a semiconductor superlattice with broken translational symmetry, is calculated analytically within linear response theory. We discuss the properties of these collective excitations in both radiative and non-radiative regimes of the electromagnetic spectra. We find that low frequency retarded modes arise when the surface density of carriers at the symmetry breaking layer is lower than the density at the remaining layers. Otherwise a doublet of localized, high-frequency magnetoplasmon-like modes occurs.Comment: Revtex file + separate pdf figure

Solar radiation climatology of Alaska

Summary There are only six locations in Alaska for which global radiation data of more than a year in duration are available. This is an extremely sparse coverage for a state which covers 1.5Â10 6 km 2 and stretches over at least three climatic zones. Cloud observations are, however, available from 18 stations. We used fractional cloud cover and cloud type data to model the global radiation and thus obtain a more complete radiation coverage for Alaska. This extended data set allowed an analysis of geographic and seasonal trends. A simple 1-layer model based on Haurwitz's semiempirical approach, allowing for changes in cloud type and fractional coverage, was developed. The model predicts the annual global radiation¯uxes to within 2±11% of the observed values. Estimated monthly mean values gave an average accuracy within about 6% of the measurements. The estimates agree well with the observations during the ®rst four months of the year but less so for the last four. Changing surface albedo might explain this deviation. Previously, the 1993 National Solar Radiation Data Base (NSRDB) from the National Renewable Energy Laboratory (NREL) modeled global radiation data for 16 Alaskan stations. Although more complete and complex, the NREL model requires a larger number of input parameters, which are not available for Alaska. Hence, we believe that our model, which is based on cloud-radiation relationship and is speci®cally tuned to Alaskan conditions, produces better results for this region. Annual global solar radiation¯ux measurements are compared with results from global coverage models based on the International Satellite Cloud Climatology Project (ISCCP) data. Contour plots of seasonal and mean annual spatial distribution of global radiation for Alaska are presented and discussed in the context of their climatic and geographic settings

Extracellular vesicles swarm the cancer microenvironment: from tumor–stroma communication to drug intervention

Intercellular communication sets the pace for transformed cells to survive and to thrive. Extracellular vesicles (EVs), such as exosomes, microvesicles and large oncosomes, are involved in this process shuttling reciprocal signals and other molecules between transformed and stromal cells, including fibroblasts, endothelial and immune cells. As a result, these cells are adapted or recruited to a constantly evolving cancer microenvironment. Moreover, EVs take part in the response to anticancer therapeutics not least by promoting drug resistance throughout the targeted tumor. Finally, circulating EVs can also transport important molecules to remote destinations in order to prime metastatic niches in an otherwise healthy tissue. Although the understanding of EV biology remains a major challenge in the field, their characteristics create new opportunities for advances in cancer diagnostics and therapeutics

Mean parameter model for the Pekar-Fr\"{o}hlich polaron in a multilayered heterostructure

The polaron energy and the effective mass are calculated for an electron confined in a finite quantum well constructed of $GaAs/Al_x Ga_{1-x} As$ layers. To simplify the study we suggest a model in which parameters of a medium are averaged over the ground-state wave function. The rectangular and the Rosen-Morse potential are used as examples. To describe the confined electron properties explicitly to the second order of perturbations in powers of the electron-phonon coupling constant we use the exact energy-dependent Green function for the Rosen-Morse confining potential. In the case of the rectangular potential, the sum over all intermediate virtual states is calculated. The comparison is made with the often used leading term approximation when only the ground-state is taken into account as a virtual state. It is shown that the results are quite different, so the incorporation of all virtual states and especially those of the continuous spectrum is essential. Our model reproduces the correct three-dimensional asymptotics at both small and large widths. We obtained a rather monotonous behavior of the polaron energy as a function of the confining potential width and found a peak of the effective mass. The comparison is made with theoretical results by other authors. We found that our model gives practically the same (or very close) results as the explicit calculations for potential widths $L \geq 10 \AA$.Comment: 12 pages, LaTeX, including 5 PS-figures, subm. to Phys. Rev. B, new data are discusse