Observation of differences in the quenching of the Photocurrent in GaAs containing EL2 and EL0

The quenching of the photocurrent and photo-Hall effect of several undoped semi-insulating gallium arsenide samples has been measured and compared with the deep-level photoluminescence spectra from neighboring samples. Samples that show either EL2 (0.68 eV) or ELO (0.63 eV) photoluminescence have distinctly different photocurrent quenching behaviors. EL2 samples show a photocurrent decrease of several orders of magnitude, and a change fromn-type to p-type conduction during quenching at 80 K with 1.1 eV light. ELO samples show a reduction in photocurrent of less than an order of magnitude with no change in the carrier type at this temperature. Photo-Hall effect experiments at 80 K indicate that the conduction isn-type for the ELO samples, but changes fromn- to p-type during the quench for the EL2 samples. The temperature dependence of the quenching has also been studied. EL2 samples show little variation in the range 10-80 K, while ELO samples show significant quenching similar to EL2 after the temperature is reduced below 70 K. These results indicate that defects other than EL2 can significantly affect photocurrent quenching experiments.     

A layered architecture for flexible Web service invocation

Web service composition is emerging as an interesting approach to integrate business applications and create intra‐organizational business processes. Single Web services are combined to create a complex Web service that will realize the process business logic. Once the process is created, it is executed by an orchestration engine that invokes individual Web services in the correct order. However, Web services composing the workflow sometimes become unavailable during the run‐time phase, blocking process execution. This paper describes an architecture that allows the flexible orchestration of business processes. With this approach, Web services composing the process can be automatically substituted with other compatible Web services during process execution. A methodology is defined to evaluate Web service compatibility based on interface matching, in order to select substitutable Web services. Copyright © 2005 John Wiley & Sons, Ltd.     

The ponding problem on flat steel roof grids

Due to several reasons, a flat steel roof grid of industrial or commercial single-story buildings may be very flexible in the vertical direction. Due to its flexibility, a ponding effect can take place. The rainwater fills the space created by vertical deflection of the roof grid and this space increases under the gradually accumulated rainwater until equilibrium is reached.Ponding may be full or partial, and it is a self exciting phenomenon that can lead to grid instability. The problem is strongly non-linear, since the rainwater distribution on the roof grid in not known a priori.A closed form response to particular ponding cases and a simple grid geometry is achieved. Moreover, a non-linear finite element technique is presented in order to study the small/large deflection solution to the ponding problem of a complex flat steel roof grid.Finally, several steel roof grids are examined in order to illustrate the effect of precambering, grid dimensions and vertical flexibility on the ponding effect. The practical significance of a large deflection analysis for practical situations is also elucidated.     

Linear MMSE estimation of time-frequency variant channels for MIMO-OFDM systems

This paper proposes two low-complexity two-dimensional channel estimators for MIMO-OFDM systems derived from a joint time-frequency channel estimator. The estimators exploit both time and frequency correlations of the wireless channel via use of Slepian-basis expansions. The computational saving comes from replacing a two-dimensional Slepian-basis expansion with two serially concatenated one-dimensional Slepian-basis expansions. Performance in terms of normalized mean square error (NMSE) vs. signal-to-noise ratio (SNR) is analyzed via numerical simulations and compared with the original estimator. The analysis of the performance takes into account the impact of both system and channel parameters. The estimators are finally tested when used within the loop of an iterative receiver for MIMO-OFDM systems.     

Fatigue behaviour of tensile steel/CFRP joints

In this paper the fatigue performance of tensile steel/CFRP (Carbon Fibre Reinforced Polymer) double shear lap joints is discussed. Joints were realized with two steel plates and two CFRP strips bonded using epoxy adhesive. Fatigue tests were performed on 16 specimens under constant stress range loading cycles. Two stress ratios (R = 0.1 and R = 0.4) were considered to investigate their influence on the fatigue lifetime. Debonding was observed to occur at stress concentration zones and propagate along the CFRP/adhesive interfaces. The stiffness degradation of the steel joint due to progressive debonding of the adhesive represents an index for the subsequent and progressive global failure. S–N curves are defined and compared to the fatigue resistance of welded detail categories of the Eurocode 3. The tests showed that the stress ratio, R, has a marginal influence on the fatigue lifetime of the steel/CFRP double shear lap joints. Finally, a fatigue limit corresponding to a stress range in the steel plate equal to 75 MPa was conservatively estimated during the tests. The fatigue limit seems to be insensitive to the stress ratio R.     

No Time to Die: How Kidney Cancer Evades Cell Death

The understanding of the pathogenesis of renal cell carcinoma led to the development of targeted therapies, which dramatically changed the overall survival rate. Nonetheless, despite innovative lines of therapy accessible to patients, the prognosis remains severe in most cases. Kidney cancer rarely shows mutations in the genes coding for proteins involved in programmed cell death, including p53. In this paper, we show that the molecular machinery responsible for different forms of cell death, such as apoptosis, ferroptosis, pyroptosis, and necroptosis, which are somehow impaired in kidney cancer to allow cancer cell growth and development, was reactivated by targeted pharmacological intervention. The aim of the present review was to summarize the modality of programmed cell death in the pathogenesis of renal cell carcinoma, showing in vitro and in vivo evidence of their potential role in controlling kidney cancer growth, and highlighting their possible therapeutic value.     

Understanding the Behaviour of Human Cell Types under Simulated Microgravity Conditions: The Case of Erythrocytes

Erythrocytes are highly specialized cells in human body, and their main function is to ensure the gas exchanges, O₂ and CO₂, within the body. The exposure to microgravity environment leads to several health risks such as those affecting red blood cells. In this work, we investigated the changes that occur in the structure and function of red blood cells under simulated microgravity, compared to terrestrial conditions, at different time points using biochemical and biophysical techniques. Erythrocytes exposed to simulated microgravity showed morphological changes, a constant increase in reactive oxygen species (ROS), a significant reduction in total antioxidant capacity (TAC), a remarkable and constant decrease in total glutathione (GSH) concentration, and an augmentation in malondialdehyde (MDA) at increasing times. Moreover, experiments were performed to evaluate the lipid profile of erythrocyte membranes which showed an upregulation in the following membrane phosphocholines (PC): PC16:0_16:0, PC 33:5, PC18:2_18:2, PC 15:1_20:4 and SM d42:1. Thus, remarkable changes in erythrocyte cytoskeletal architecture and membrane stiffness due to oxidative damage have been found under microgravity conditions, in addition to factors that contribute to the plasticity of the red blood cells (RBCs) including shape, size, cell viscosity and membrane rigidity. This study represents our first investigation into the effects of microgravity on erythrocytes and will be followed by other experiments towards understanding the behaviour of different human cell types in microgravity.     

Molecular Features and Diagnostic Challenges in Alpha/Beta T-Cell Large Granular Lymphocyte Leukemia

Large granular lymphocyte leukemia is a rare chronic lymphoproliferative disease of cytotoxic lymphocytes. The diagnosis, according to the WHO, is based on a persistent (>6 months) increase in the number of LGL cells in the peripheral blood without an identifiable cause. A further distinction is made between T-LGL and NK-LGL leukemia. The molecular sign of LGL leukemia is the mutation of STAT3 and other genes associated with the JAK/STAT pathway. The most common clinical features are neutropenia, anemia, and thrombocytopenia, and it is often associated with various autoimmune conditions. It usually has an indolent course. Due to the rarity of the disease, no specific treatment has yet been identified. Immunosuppressive therapy is used and may allow for disease control and long-term survival, but not eradication of the leukemic clone. Here, we discuss the clinical presentation, diagnostic challenges, pathophysiology, and different treatment options available for alpha/beta T-LGL leukemia, which is the most common disease (85%), in order to better understand and manage this often misunderstood disease.