Measurement of the complex permittivity of low-loss planarmicrowave substrates using aperture-coupled microstrip resonators

This paper describes a technique for the determination of the complex permittivity of low-loss dielectric substrates at microwave frequencies. The technique utilizes an aperture-coupled microstrip resonator fed using a microstrip line in a two layer configuration. The ends of the resonator are shorted in order to avoid radiation. The technique can also be used for the measurement of the complex permittivity of other electronic materials such as thin and thick film materials at microwave frequencies. Nonresonant modes and conductor losses are taken into account in the analysis to improve the accuracy of the results. Analysis procedure as well as experimental results are presented     

High-speed InGaP/GaAs HBTs with a strained InxGa1-xAs base

A self-aligned InGaP/GaAs heterojunction bipolar transistor with a compositionally graded In_xGa_1-xAs base has been demonstrated with f_T=83 GHz and f_max=197 GHz. To our knowledge, these results are the highest reported for both parameters in InGaP/GaAs HBT's. The graded base, which improves electron transport through the base, results in a DC current gain and a cutoff frequency which are 100% and 20% higher, respectively, than that achieved by an identical device with a nongraded base. The high f_max results from a heavily doped base, self-aligned base contacts, and a self-aligned collector etch. These results demonstrate the applicability of InGaP/GaAs HBT's in high-speed microwave applications     

Psychological stress symptoms before and after autologous bone marrow transplantation in patients with solid tumors

This study sought to examine patterns of changes of psychological stress symptoms in autologous bone marrow transplantation (ABMT) recipients. Forty-nine patients affected by solid tumors were assessed using the Symptom Questionnaire on admission to hospital (before high-dose chemotherapy and ABMT) and before discharge. Symptoms of anxiety and anger tended to decrease and relaxation of improve over time. Nevertheless, on admission to hospital 30-50% of the patients reported severe to moderate symptoms of anxiety and depression. Before discharge, the prevalence was still high (20-35%). The implications of these findings are discussed in terms of the need to monitor the evolution of emotional functioning of cancer patients undergoing ABMT.     

Renal effects of aspirin and low dose methotrexate in rheumatoid arthritis

OBJECTIVES: The aim of this investigation was to study the glomerular and tubular effects of low doses (15 mg) of methotrexate in patients with rheumatoid arthritis with and without combined treatment with aspirin (2 g single dose). METHODS: Renal function was measured by the plasma clearance of EDTA labelled with chromium-51 (51Cr-EDTA) and mercaptoacetyltriglycine labelled with technetium-99m (99mTc-MAG-3). RESULTS: Clearance of 51Cr-EDTA was reduced from 98 (6) to 87 (5) ml/min (mean (SEM)) for patients receiving methotrexate only and further reduced to 76 (5) ml/min for patients receiving methotrexate and aspirin. This effect was reversible as 51Cr-EDTA increased to 85 (6) ml/min during continued treatment with methotrexate alone. Clearance of 99mTc-MAG-3 also decreased from 366 (18) to 315 (17) ml/min in patients receiving methotrexate alone and further to 295 (17) ml/min during treatment with aspirin and methotrexate. Continued treatment with methotrexate alone resulted in a further decrease in the 99mTc-MAG-3 clearance to 253 (17) ml/min. CONCLUSIONS: The study shows that treatment with low doses of methotrexate particularly when combined with aspirin affects glomerular and tubular function. These effects may be of clinical importance and renal function should therefore be monitored with more sensitive methods than serum creatinine as this may not reflect these changes.     

Performance analysis of concurrency control using locking withdeferred blocking

The concurrency control (CC) method employed can be critical to the performance of transaction processing systems. Conventional locking suffers from the blocking phenomenon, where waiting transactions continue to hold locks and block other transactions from progressing. In a high data contention environment, as an increasing number of transactions wait, a larger number of lock requests get blocked and fewer lock requests can get through. The proposed scheme reduces the blocking probability by deferring the blocking behavior of transactions to the later stages of their execution. By properly balancing the blocking and abort effects, the proposed scheme can lead to better performance than either the conventional locking or the optimistic concurrency control (OCC) schemes at all data and resource contention levels. We consider both static and dynamic approaches to determine when to switch from the nonblocking phase to the blocking phase. An analytical model is developed to estimate the performance of this scheme and determine the optimal operating or switching point. The accuracy of the analytic model is validated through a detailed simulation