A novel high-performance utility-interactive photovoltaic inverter system

This paper presents a novel photovoltaic inverter that cannot only synchronize a sinusoidal AC output current with a utility line voltage, but also control the power generation of each photovoltaic module in an array. The proposed inverter system is composed of a half-bridge inverter at the utility interface and a novel generation control circuit which compensates for reductions in the output power of the system that are attributable to variations in the generation conditions of respective photovoltaic modules. The generation control circuit allows each photovoltaic module to operate independently at peak capacity, simply by detecting the output power of the system. Furthermore, the generation control circuit attenuates low-frequency ripple voltage, which is caused by the half-bridge inverter, across the photovoltaic modules. Consequently, the output power of the system is increased due to the increase in average power generated by the photovoltaic modules. The effectiveness of the proposed inverter system is confirmed experimentally and by means of simulation.     

Histologic and biologic patterns of microscopic pancreatic ductal adenocarcinomas detected incidentally at autopsy

BACKGROUND: The major clinical problems with pancreatic carcinoma are its silent course and late, fatal clinical manifestation. The results of treatments of small pancreatic carcinomas (<2 cm in greatest dimension) have led to the assumption that the detection of these cancers at earlier stages would lead to better survival and possible cure. Currently, there is no information about the histologic and biologic patterns of early stage pancreatic carcinoma, and the available data on incidentally detected tumors are fragmentary. The authors observed two incidental microscopic pancreatic ductal adenocarcinomas in female patients who died of advanced gastric carcinoma (Case 1) and renal carcinoma (Case 2). METHODS: The pancreatic lesions were examined histologically in serial sections and immunocytochemically for islet cells. Microdissection was performed so that the lesions could be examined for c-Ki-ras mutation. RESULTS: In Case 1, the pancreatic lesion was composed of cystic and solid components. The cystic component consisted of four small cysts compatible with a mucinous cystic tumor and showed no invasion. The solid component was a well-differentiated adenocarcinoma that occupied a 4 x 2 mm area. In Case 2, the pancreatic lesion contained two small, separate cysts, one of which was surrounded by two apparently separate, invasive adenocarcinomas 2.6 x 0.7 mm and 1.2 x 0.5 mm in greatest dimension. There was invasion of pancreatic islets and perineural spaces in both cases; and in Case 2, there was invasion of peripancreatic fatty tissue. In both cases, the epithelia of the cystic components and tumors showed mutation of the c-Ki-ras oncogene at codon 12, with GGT-to-GAT transition. CONCLUSIONS. Pancreatic carcinoma seems to occur under occult circumstances and maintain a silent course. Even in its early developmental stage, the cancer is invasive, primarily affects islets and nerves, and exhibits mutation of the c-Ki-ras oncogene. These findings call for urgency in the development of preventive modalities.     

Hypnotic activities of N3-benzyl and xylyl substituted arabinofuranosyluracil

N3-Substituted derivatives of arabinofuranosyluracil (1), methyl (2), ethyl (3), propyl (4), butyl (5), allyl (6), benzyl (7), o-, m-, p-xylyls (8, 9, 10) and alpha-phenethyl (11) derivatives, were synthesized and their CNS depressant effects were evaluated by intracerebroventricular (i.c.v.) injection in mice by using hypnotic activity and pentobarbital-induced sleep prolongation as indices. At a dose of 2.0 mumol/mouse, the values of mean sleeping time induced by 7, 8, 9, and 10 were 144, 154, 117, and 33 min, respectively. Although the alkyl (2-6) derivatives did not cause any hypnotic activity, some derivatives tested (5, 7-10) significantly prolonged the pentobarbital-induced sleeping time.     

Ultrastable harmonically and regeneratively modelockedpolarisation-maintaining erbium fibre ring laser

The authors report the operation of a harmonically and regeneratively modelocked erbium fibre ring laser at 1.55 μm for the first time. Harmonic regenerative modelocking was achieved by feeding back the harmonic longitudinal beat signal which was detected with a high speed photodetector and a high Q dielectric filter. The repetition rate was 10 GHz and the soliton effect shortened-the pulse width from 7.0 to 2.7 ps     

New concept for multiple-valued optical memory

The authors propose and demonstrate a new concept for multiple-valued optical memory, instead of the usual binary optical memory, based on the recognition of an angle of the slender diffracted-light pattern from one of the slits or slender pits formed, in order, along a track of the optical disk. A photodiode array arranged in a clock face configuration is used for the light pattern recognition     

A novel transmitter/receiver switching circuit configuration forhigh-performance LD transceiver in subscriber loop

LD (laser diode) transceivers are very effective in reducing optical subscriber systems cost because they act as transmitters and receivers. This paper proposes a new transceiver switching circuit configuration, and two techniques for suppressing and canceling the discharge current effect of laser diodes. The new techniques, including mounting substrate optimization such as high-isolation and low parasitic capacitance, yield a high-performance LD transceiver module with the minimum average receiving optical power level of -37.0 dBm and a wide dynamic range of up to 25 dB for burst mode optical input at 29.0 Mb/s     

High compression ratio backward Raman conversion for highbrightness excimer laser systems

A scheme of backward Raman pulse compression is proposed in which the backward first Stokes pulse is amplified under stationary conditions and the backward second Stokes under transient conditions by choosing an appropriate Raman medium. The compression factor and efficiency are improved by insertion of selective absorbers for the second Stokes component. The feasibility of such a scheme is demonstrated by an experiment in which a 249-nm UV pulse of 20-ns duration has been compressed into a 30-ps pulse with an power gain of 150 and energy conversion efficiency of 22%. Higher compression ratio and higher efficiency is expected under improved conditions