Form factor in K+ --> pi+ pi0 gamma: interference versus direct emission

We analyze the effect of a form factor in the magnetic contribution to K+ --> pi+ pi0 gamma. We emphasize how this can show up experimentally: in particular we try to explore the difference between a possible interference contribution and a form factor in the magnetic part. The form factor used for K+ --> pi+ pi0 gamma is analogous to the one for KL --> pi+ pi- gamma, experimentally well established.Comment: 9 pages revtex, 10 eps figures; improved presentation of theoretical and experimental status; refs. adde

Adnexal Torsion in Pediatric Age: Does Bolli's Score Work? Report of Two Cases

Adnexal torsion is a surgical emergency requiring early diagnosis in order to avoid demolitive surgery. Adnexal torsion's diagnosis could be very difficult in pediatric patients because children cannot explain symptoms accurately. Furthermore reproductive organs lie high in abdomen, causing unclear examinations findings. For reducing diagnostic mistakes or delay clinical and hematological criteria could be useful. No radiological criteria (CT or MRI) should be taken in count because of the costs and the required time. By combining clinical presentation in patients with OT three useful diagnostic variables have been identified: age, duration of pain, vomiting. Presence of vomiting, short duration of abdominal pain and high CRP levels have great predictive value for the diagnosis of adnexal torsion. In those patients an exploratory laparoscopy should be performed without any doubt and/or delay. These data may aid physicians in the evaluation of abdominal pain in premenarchal girls

Simulation of the effect of grain-boundaries in backside-passivated CIGS solar cells

We carry out numerical 3D simulations of CIGS cells with back-side Al2O3 passivation and point contact openings in the presence of grain boundaries in the absorber. We consider CIGS cells with different absorber thickness, from 0.35 to 3 mu mathrm{m}. For thinner absorbers (1 mu mathrm{m} or less) we observe that GBs terminating on the Al2O3 are completely or almost completely passivated, while the effectiveness of the passivation decreases for thicker absorbers. GBs terminating on the point contact, instead, significantly lower the efficiency, regardless of absorber thickness. The presence of grain boundaries and the dimension of grains should therefore be taken into consideration when optimizing the back-side point contact array geometry

OCVD Measurement of Ambipolar and Minority Carrier Lifetime in 4H-SiC Devices: Relevance of the Measurement Setup

The open-circuit voltage decay (OCVD) method is a well-known technique for conducting electrical measurements of carrier lifetime: the main advantages lie in the simple setup and the possibility of carrying out measurements in commercial devices without the need of removing the package, as for optical methods. Despite several researchers having reported carrier lifetimes measured by the OCVD method in different devices, there has been little discussion about the potential effect of the experimental setup on the obtained results. By comparing the outputs of the experimental measurements with those of numerical simulations, this study investigates the overlooked effect of the OCVD measurement setup on the former. Due to the growing importance of SiC-based devices, the analysis is applied to a 4H-SiC p-i-n diode. Two main points are addressed: 1) the effect of circuit setup on the ambipolar lifetime is discussed and a method, originally developed for improving the estimate of low-level carrier lifetime in OCVD measurements, is used to correct the measured lifetime for this influence; 2) the origin of the local minimum eventually appearing in the lifetime versus time curves is also investigated. It is found that the minimum can also be related to the time constant of the experimental setup, giving rise to doubts about the usual interpretation of this minimum as the minority carrier lifetime. A method is thus proposed to help discriminate between the two interpretations

A simulation study on the effect of sodium on grain boundary passivation in CIGS thin-film solar cells

3D numerical simulations of CIGS thin-film solar cells with different grain-boundary (GB) characteristics have been carried out in order to investigate the effect of defect properties and band edge shifts at GBs on the cell performance. Simulation results are compared with experimental data taken on cells with and without NaF post deposition treatment. GBs with different energy gaps and defect properties have been analyzed. Simulations support the idea that the detrimental effect of defective GBs on the cell performance might be reduced by a treatment with Na. The results of this study can help with the interpretation of experimental findings

Correlation between OCVD carrier lifetime vs temperature measurements and reverse recovery behavior of the body diode of SiC power MOSFETs

The reverse recovery (RR) behavior of SiC MOSFET body diode is of great importance in power application, where these devices are used in a wide range of operating temperatures. The carrier lifetime in the drift region varies with temperature, and it heavily affects the tailoring of the RR current, opening reliability issues related to the RR voltage amplitude and to possible anomalous voltage oscillations during the recovery. From the users' point of view, it would be useful to have a simple technique able to give predictive information about the body diode RR behavior of commercial devices over the whole range of working temperatures. An experimental-simulation approach is presented in this paper to correlate the carrier lifetime measured by simple OCVD measurements versus temperature with the RR behavior of the body diode, that can be useful at the design stage of power converters. Simulations of the body diode reverse-recovery are performed for a wide range of carrier lifetimes. This allows to estimate the effect of changes of carrier lifetime with temperature on the body diode switching transients. Preliminary results obtained with a 1700 V/5A commercial MOSFET are shown

An evaluation of |Vus| and precise tests of the Standard Model from world data on leptonic and semileptonic kaon decays

We present a global analysis of leptonic and semileptonic kaon decay data, including all recent results published by the BNL-E865, KLOE, KTeV, ISTRA+ and NA48 experiments. This analysis, in conjunction with precise lattice calculations of the hadronic matrix elements now available, leads to a very precise determination of |Vus| and allows us to perform several stringent tests of the Standard Model.Comment: LaTeX, 25 pages, 12 figures, 16 tables. Submitted to EPJC. v2: Minor changes for accepted version. No numerical results change

Boundary layer convective-like activity at Dome Concordia, Antarctica

The paper presents the micro-meteorological field experiment carried out at the plateau station of Dome Concordia (3300 m a.s.l.) during the Antarctic summer of 1997. The experiment dealt with the study of the trends of boundary layer features and the characteristics of the surface energy and momentum exchanges. A monostatic Doppler sodar, fast-response sensors and radiometers were used for this study. The experiment was part of a program that aims to assess the role of the continental polar regions in shaping the surface circulation over Antarctica. In spite of the markedly stable conditions found throughout the investigated period, some convective-like activity was detected during the warmer hours of the day

Integrated Trigger and Data Acquisition system for the NA62 experiment at CERN

The main goal of the NA62 experiment is to measure the branching ratio of the K+decay, collecting O(100) events in two years of data taking. Efficient online selection of interesting events and loss-less readout at high rate will be key issues for such experiment. An integrated trigger and data acquisition system has been designed. Only the very first trigger stage will be implemented in hardware, in order to reduce the total rate for the software levels on PC farms. Readout uniformity among different subdetectors and scalability were taken into account in the architecture design