Dielectric function of InGaAs in the visible

Measurements are reported of the dielectric function of thermodynamically stable In(x)Ga(1-x)As in the composition range 0.3 equal to or less than X = to or less than 0.7. The optically thick samples of InGaAs were made by molecular beam epitaxy (MBE) in the range 0.4 = to or less than X = to or less than 0.7 and by metal-organic chemical vapor deposition (MOCVD) for X = 0.3. The MBE made samples, usually 1 micron thick, were grown on semi-insulating InP and included a strain release structure. The MOCVD sample was grown on GaAs and was 2 microns thick. The dielectric functions were measured by variable angle spectroscopic ellipsometry in the range 1.55 to 4.4 eV. The data was analyzed assuming an optically thick InGaAs material with an oxide layer on top. The thickness of this layer was estimated by comparing the results for the InP lattice matched material, i.e., X = 0.53, with results published in the literature. The top oxide layer mathematically for X = 0.3 and X = 0.53 was removed to get the dielectric function of the bare InGaAs. In addition, the dielectric function of GaAs in vacuum, after a protective arsenic layer was removed. The dielectric functions for X = 0, 0.3, and 0.53 together with the X = 1 result from the literature to evaluate an algorithm for calculating the dielectric function of InGaAs for an arbitrary value of X(0 = to or less than X = to or less than 1) were used. Results of the dielectric function calculated using the algorithm were compared with experimental data

Study of InGaAs based MODFET structures using variable angle spectroscopic ellipsometry

Variable angle spectroscopic ellipsometry was used to estimate the thicknesses of all layers within the optical penetration depth of InGaAs based MODFET structures. Strained and unstrained InGaAs channels were made by MBE on InP substrates and by MOCVD on GaAs substrates. In most cases, ellipsometrically determined thicknesses were within 10 percent of the growth calibration results. The MBE made InGaAs strained layers showed large strain effects, indicating a probable shift in the critical points of their dielectric function toward the InP lattice matched concentration

Coupled model simulations of current Australian surface climate and its changes under greenhouse warming: an analysis of 18 CMIP2 models

Coupled climate models have been extensively used to further our understanding of the dynamics and physics of the Earth's climate system and the potential changes of regional and global climates in the future, especially due to human activities such as fossil fuel burning and land-use activities. Nevertheless, there are still large uncertainties in our knowledge of the global climate system and in our representations of such a complex system. The confidence of our projected future climate change, therefore, inevitably depends on how well the current climate is simulated by coupled climate models and how large the scatter is among the model simulations of current and future climates. As one of the diagnostic subprojects within the Coupled Model Intercomparison Project phase II (CMIP2), we present an evaluation of 18 CMIP2 coupled model simulations over the Australian region.Monthly rainfall and surface air temperature climatologies over the Australian region have been derived from the 18 CMIP2 control simulations and compared with observations from the Australian Bureau of Meteorology. The gross spatial patterns of austral summer rainfall (DJF) are reasonably simulated by the majority of the models. However, there are significant model errors in simulating the intensity and location of the heavy Australian monsoon rainfall in the north and eastern parts of the continent, with about half of the models showing more than 100 mm/month biases and a number of models simulating wrong locations of the monsoon rainfall. The seasonal cycle of the surface temperature is reasonably reproduced in the models although there are biases of around 2-4 degrees C present in the model simulated surface air temperature climatology.Based on the 80-year model simulations of perturbed climate, with 1% per year increase of atmospheric CO2 concentration, the changes of surface air temperature and precipitation have also been analysed. The average annual surface temperature change in the last 20-year period of the model simulations against the model control simulations over the Australian region varies from 1.00 degrees C to 2.18 degrees C, with an ensemble average of 1.59 degrees C and 0.33 degrees C scatter measured by one standard deviation. The models give a mixed signal in predicting averaged Australian rainfall changes, with some models simulating more than 3 mm/month increase while others show more than 4 mm/month decrease with on average no change. The spatial distributions of the model-simulated surface temperature and precipitation changes have also been analysed. Surface temperature is increased over the whole continent in all models, while the changes in precipitation show large spatial variations. The ensemble mean model shows decreases in winter rainfall across southern Australia and over northwestern Australia during summer. Increased rainfall is simulated over parts of eastern Australia during winter, extending further north during summer. Besides the analysis of changes in mean climate, the potential impacts of global warming on Australian climate variability is explored in a preliminary way by analysing the changes in tropical Australian precipitation correlations with surface temperature variations over four key oceanic regions. Results suggest that the influence of tropical and subtropical sea-surface temperature (SST) forcing on the Australian climate may change under greenhouse warmin

The azygos system as a rare alternative for chronic indwelling catheters placement

Chronic indwelling catheters are plagued with a high rate of complications, including infection, central venous occlusion, or thrombosis. When direct access to the superior or inferior vena cava is not possible, venography may identify alternatives that might be viable with current endovascular techniques. This case report describes the successful placement of a tunneled catheter for total parenteral nutrition in the azygos arch through a small collateral vein from the left jugular vein in a patient with no other alternatives because of superior vena cava occlusion and inferior vena cava thrombophlebitis

An Exploratory Study of Communication Freelancers and Online Communities. A Mixed Methods Approach

The present study explores the nature and dynamics of online communities populated by communication freelancers. Drawing from limited scholarship focusing on freelance work practices in communication industries and a reduced number of studies in communication literature regarding online communities, this research applies a complex analytical framework, with mixed methodology: content analysis, social network analysis and thematic analysis. Our main findings reveal the key features of the discursive environment of two Facebook groups, the communication functions employed by group administrators, the engagement practices of group members particularly regarding knowledge production and consumption and the impact of the COVID-19 pandemic on group practices and dynamic. We conclude by highlighting the supportive and participative culture developed within the two groups

Communication Freelancers, Facebook Groups and COVID-19. A Qualitative Analysis. Research Report

The study looked at the relationship between communication freelancers and online communities, in particular Facebook groups populated by communication professionals. We were interested in the dynamic of the group, in knowledge production and knowledge sharing, as well as in the challenges faced by communication freelancers during the COVID-19 pandemic and the role of Facebook groups during this particularly difficult time

A matrix solution to pentagon equation with anticommuting variables

We construct a solution to pentagon equation with anticommuting variables living on two-dimensional faces of tetrahedra. In this solution, matrix coordinates are ascribed to tetrahedron vertices. As matrix multiplication is noncommutative, this provides a "more quantum" topological field theory than in our previous works