High-Temperature Degradation of GaN LEDs Related to Passivation

This paper describes the thermally activated failure mechanisms of GaN light-emitting diode (LED)-test structures related with the presence of a hydrogen-rich SiN passivation layer. It is shown that the properties of the passivation layer can remarkably affect devices' stability during high-temperature stress: Degradation mechanisms identified consist of radiative efficiency loss, emission crowding, and forward-current decrease. The radiative efficiency degradation was found to be thermally activated, with activation energy equal to 1.3 eV. This failure mechanism of LEDs is attributed to the thermally activated indiffusion of hydrogen from the passivation layer to p-type region of the diodes, with subsequent p-doping compensation and/or worsening of the transport properties of the p-side ohmic contact and p-type semiconductor     

Traffic and Interference Adaptive Scheduling for Internet Traffic in UMTS

In this paper we propose a scheduling strategy for the radio resources management when transmitting Internet traffic over third-generation systems. More precisely, we consider the UMTS Terrestrial Radio Access Network (UTRAN) Time Division Duplex (TDD) mode standardized by ETSI. UTRAN TDD uses a hybrid solution of code and time division multiple access, called TD-CDMA. In UMTS systems a key issue in developing access methodologies for the available spectrum is an optimal management of the rare radio resources. In this paper we present a fair and efficient scheduling algorithm that adapts its behavior to traffic and interference conditions. Specifically, our scheduling algorithm is able to manage the radio resources taking into account both the traffic fluctuations in the uplink and downlink direction and the variations of the system interference. The goal of our scheduler is the data-throughput maximization for an efficient utilization of available radio resources. The effectiveness of our scheduling algorithm is shown by exploiting analytical tools.     

Technical-economic aspects of the utilization of geothermal waters

This paper reports on the world energy consumption between 1960 and 1984 from primary energy sources (coal, natural gas, oil, hydropower, nuclear energy) and the same in percentages from 1925. This highlights the diminishing role of coal and the increased consumption of gas and oil. The latter has stabilized around 42% of the total after the drop in demand resulting from the oil crisis of 1973.The world energy consumption has then been divided into industrialized and developing countries. It appears that the latter, with a population equal to 68% of the total world population, consumed 23% of the world energy in 1982. Furthermore, the consumption figures show that the demand for domestic energy is much smaller in developing countries, and it is well-known that domestic energy consumed is one of the parameters used to assess standard of living.The total installed electric capacity throughout the world is then reported, divided between developed and developing countries, showing that the latter consumed 11% of all the electricity generated in the world in 1981. The world installed electric power of geothermal origin at the end of 1985 is shown, along with estimates for 1990. Geothermal energy represents 0.2% of the world electric power. This is obviously a small figure and indicates that geothermal energy plays a minor role on the world energy scene. However, if we distinguish between industrialized and developing countries, we can observe that, with their currently limited electrical consumption but good geothermal prospects, the developing countries could achieve quite a significant contribution to their total electric energy from that of geothermal origin, increasing at the moment from 3 to 19%.Finally, a comparison is made between electricity generating costs of different sources, showing that geothermal energy is competitive. A table illustrates the world evolution in installed geothermal capacity from 1950 to 1985.The non-electric uses of geothermal energy, on the other hand, have a rather insignificant role in both the developing and industrialized countries. It is unlikely that geothermal energy will ever achieve a greater significance in this sector, with a few rare exceptions.     

A data-driven approach for predicting failure scenarios in nuclear systems

A data-driven approach is presented for the on-line identification of the system Failure Mode (FM) and the prediction of the available Recovery Time (RT) during a failure scenario, i.e., the time remaining until the system can no longer perform its function in an irreversible manner. The FM identification and RT prediction modules are linked in a general framework that recognizes the patterns of dynamic evolution of the process variables in the different system failure modes. When a new failure scenario develops, its evolution pattern is compared by fuzzy similarity analysis to a library of reference multidimensional trajectory patterns of process variables evolution; the failure mode of the developing scenario is identified by combining the modes of failure of the reference patterns, weighed by their similarity to the developing pattern; the similarity weights are then fed to the RT prediction module that estimates the time remaining before the developing trajectory pattern hits a failure threshold.     

Some gender effects in a brief psychotherapy.

Two studies investigated the influence of therapist gender as well as patient age and pretreatment distress level on process and outcome in a brief 12-session psychodynamic psychotherapy. Pre- and posttherapy assessments disclosed that patients treated by female therapists experienced more symptomatic improvement and reported more satisfaction with treatment than those treated by male therapists. However, patient age accounted for twice, and patient pretreatment level of disturbance more than three times, the outcome variance contributed by gender. In Study 2 female therapists were judged to arouse less negative affect in women patients and to arouse fewer interpersonal difficulties. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of allergenic potency by REAST inhibition. A new tool for the standardization of allergenic extracts

The potency of allergenic extracts can be determined in vitro by RAST inhibition, and this has become the preferred method for the standardization of allergens. A disadvantage of this technique is the impossibility of obtaining data about allergens bound to the solid phase, i.e., the counterpart of the inhibiting extract. The REAST (reverse enzyme allergosorbent test) is based on the capture of IgE by a specific antibody bound to microtiter wells, the reaction of captured IgE with biotinylated allergen and the development of a colour reaction by subsequent addition of streptavidin-peroxidase and chromogenic substrate. The addition of an allergen extract in a dose-response fashion competes with the biotinylated allergen and inhibits the test. In the present study REAST inhibition has been evaluated with Dermatophagoides pteronyssinus, Parietaria judaica and mixed grass pollen extracts. The correlation of REAST inhibition with RAST inhibition and both intra-assay and inter-assay reproducibility have been evaluated. REAST inhibition is a potentially valuable new tool for the standardization of allergenic extracts.     

Quantitative developments in the cognitive reliability and error analysis method (CREAM) for the assessment of human performance

The current ‘second generation’ approaches in human reliability analysis focus their attention on the contextual conditions under which a given action is performed rather than on the notion of inherent human error probabilities, as was done in the earlier ‘first generation’ techniques. Among the ‘second generation’ methods, this paper considers the Cognitive Reliability and Error Analysis Method (CREAM) and proposes some developments with respect to a systematic procedure for computing probabilities of action failure. The starting point for the quantification is a previously introduced fuzzy version of the CREAM paradigm which is here further extended to include uncertainty on the qualification of the conditions under which the action is performed and to account for the fact that the effects of the common performance conditions (CPCs) on performance reliability may not all be equal. By the proposed approach, the probability of action failure is estimated by rating the performance conditions in terms of their effect on the action.     

Impact of selected agricultural management options on the reduction of nitrogen loads in three representative meso scale catchments in Central Germany

Nitrogen inputs into surface waters from diffuse sources are still unduly high and the assessment of mitigation measures is associated with large uncertainties. The objective of this paper is to investigate selected agricultural management scenarios on nitrogen loads and to assess the impact of differing catchment characteristics in central Germany. A new modelling approach, which simulates spatially distributed N-transport and transformation processes in soil and groundwater, was applied to three meso scale catchments with strongly deviating climate, soil and topography conditions. The approach uses the integrated modelling framework JAMS to link an agro-ecosystem, a rainfall-runoff and a groundwater nitrogen transport model. Different agricultural management measures with deviating levels of acceptance were analysed in the three study catchments.N-leaching rates in all three catchments varied with soil type, the lowest leaching rates being obtained for loess soil catchment (18.5 kg nitrate N ha^− 1 yr^− 1) and the highest for the sandy soils catchment (41.2 kg nitrate N ha^− 1 yr^− 1). The simulated baseflow nitrogen concentrations varied between the catchments from 1 to 6 mg N l^− 1, reflecting the nitrogen reduction capacity of the subsurfaces. The management scenarios showed that the highest N leaching reduction could be achieved by good site-adapted agricultural management options. Nitrogen retention in the subsurface did not alter the ranking of the management scenarios calculated as losses from the soil zone. The reduction effect depended strongly on site specific conditions, especially climate, soil variety and the regional formation of the crop rotations.     

Developmental toxicity, uptake and distribution of sodium chromate assayed by frog embryo teratogenesis assay-Xenopus(FETAX)

The embryotoxicity and teratogenicity of Cr(VI) on the survival and morphology of the anuran Xenopus laevis have been assessed by frog embryo teratogenesis assay-Xenopus (FETAX). The lethal median (LC₅₀) and teratogenic median (TC₅₀) concentration values of Cr(VI) were 890 µM and 260 µM, respectively. The calculated teratogenic index (TI) value was 3.42, suggesting that hexavalent chromium has a teratogenic potential. Malformations of embryos included lifting of the body, coiling of the tail and body oedema. Furthermore, the chromium salt caused significant growth retardation at 25 µM exposure concentrations. The use of radiolabelled ⁵¹Cr(VI) allowed the determination of the time course uptake of Cr in Xenopus exposed to concentrations ranging from 0.025 to 500 µM. The evaluation of its distribution into the body (head-abdomen-tail) was evaluated at different exposure times. Chromium is taken up at 24 h by Xenopus embryos for all concentrations tested. At 48 h post fertilization (stage of larva) the amount of Cr accumulated by the two-day-old larva ranged from 0.42 to 580 pg mg^− 1 wet weight at 0.025 and 500 µM respectively. These amounts were lower than those at 24 h (2.77 to 11016 pg mg^− 1 wet weight embryo) reaching values of the same order of magnitude at 120 h (five-days-old larva). Since at 48 h Xenopus development leads to a swimming embryo, the observed uptake at 24 h could be the result of the binding of Cr to jelly coat compounds surrounding the embryo body as confirmed by gel filtration experiments on ⁵¹Cr-jelly coat. The interaction of Cr with jelly coat is in agreement with the role of jelly coat in protecting the embryo against pathogen and chemical toxins to ensure fertilization. This work further supports the hypothesis that Cr contamination of surface waters could contribute to explain the reported worldwide depletion of frog population.