High frequency of inadequate test requests for antiphospholipid antibodies in daily clinical practice

Abstract Background: We have empirically noted that many physicians routinely request anti-phospholipid antibodies (aPL) without a correct clinical indication. The aim of this study was to evaluate retrospectively whether aPL testing at our Thrombosis Centre was justified. Methods: Medical records from 520 subjects for aPL screening tests for various clinical conditions were reviewed. The aPL screening tests were: lupus anticoagulant (LA), anti-cardiolipin antibodies (aCL) and anti-β(2) glycoptotein I (aβ(2) GPI). Requests for aPL screening were divided into justified, potentially justified or not adequately justified. Results: aPL testing requests were considered justified in 358 (69%) patients, potentially justified in 66 (12.6%) and not adequately justified in 96 (18.4%). LA was positive in 65 (18%) of justified requests and in only one (1%) of the 96 potentially justified requests. None of the 66 not adequately justified for aPL testing was positive for LA. aβ(2) ..

Mathematical approach to large-signal modelling of electron devices

A general purpose mathematical approach is proposed for the large-signal modelling of microwave electron devices (e.g. MESFETs, bipolar transistors, diodes, etc.). The mathematical model, which is based on mild assumptions valid both for field effect and bipolar devices in typical large-signal operating conditions, can easily be identified through conventional measurements and is particularly suitable for nonlinear microwave circuit analysis based on harmonic balance technique

Frequency stability in resonator-stabilized oscillators

A simplified stability analysis of resonator-stabilized oscillators is carried out by using the describing function approach. On this basis a criterion for the evaluation and optimization of the frequency stabilization introduction in an oscillator by a resonating element with a large quality factor is proposed. In particular, a frequency-stabilization index which can be conveniently used in the design of highly stable oscillators is defined. The validity of this performance index has been verified in the design of microwave oscillators using dielectric resonators as frequency-stabilizing element

A nonlinear integral model of electron devices for HB circuit analysis

A technology-independent large-signal model of electron devices, the nonlinear integral model (NIM), is proposed. It is rigorously derived from the Volterra series under basic assumptions valid for most types of electron devices and is suitable for harmonic-balance circuit analysis. Unlike other Volterra-based approaches, the validity of the NIM is not limited to weakly nonlinear operation. In particular, the proposed model allows the large-signal dynamic response of an electron device to be directly computed on the basis of data obtained either by conventional measurements or by physics-based numerical simulations. In this perspective, it provides a valuable tool for linking accurate device simulations based on carrier transport physics and harmonic-balance circuit analysis algorithms. Simulations and experimental results, which confirm the validity of the NIM, are also presente

Tool for efficient intermodulation analysis using conventional HB packages

A simple and efficient approach is proposed for the intermodulation analysis of nonlinear microwave circuits. The algorithm, which is based on a very mild assumption about the frequency response of the linear part of the circuit, allows for a reduction in computing time and memory requirement. Moreover. It can be easily implemented using any conventional tool for harmonic-balance circuit analysi

'Backgating' model including self-heating for low-frequency dispersive effects in III-V FETs

A new approach is proposed which takes into account both traps and thermal phenomena for the modelling of deviations between static and dynamic drain current characteristics in III-V field effect transistors. The model is based on the well-known `backgating' concept and can easily be identified on the basis of conventional static drain current characteristics and small-signal, low-frequency S parameters. Experimental results confirm the accuracy of the proposed mode

Isotopic Composition of Fragments in Nuclear Multifragmentation

The isotope yields of fragments, produced in the decay of the quasiprojectile in Au+Au peripheral collisions at 35 MeV/nucleon and those coming from the disassembly of the unique source formed in Xe+Cu central reactions at 30 MeV/nucleon, were measured. We show that the relative yields of neutron-rich isotopes increase with the excitation energy in multifragmentation reaction. In the framework of the statistical multifragmentation model which fairly well reproduces the experimental observables, this behaviour can be explained by increasing N/Z ratio of hot primary fragments, that corresponds to the statistical evolution of the decay mechanism with the excitation energy: from a compound-like decay to complete multifragmentation.Comment: 10 pages. 4 Postscript figures. Submitted to Physical Review C, Rapid Communicatio