Chemical potentials of oxygen for three-phase assemblages of CaSiO3(s) + Ca3Si2O7(s) + {CaO + SiO2 + FexO} melt and Ca3Si2O7(s) + Ca2SiO4(s) + {CaO + SiO2 + FexO} melt

By employing an electrochemical technique involving stabilized zirconia as solid electrolyte and Mo + MoO₂ mixture as reference electrode, the equilibrium oxygen partial pressures for three-phase assemblages of CaSiO₃(s) + Ca₃Si₂O₇(s) + {CaO + SiO₂ + Fe_xO} melt and Ca₃Si₂O₇(s) + Ca₂SiO₄(s) + {CaO + SiO₂ + Fe_xO} melt were determined as: - log {P_O2 (CS + C₃S₂ + L)/bar} = - 3.22 13000/(T/K) ± 0.05 - log {P_O2 (C₃S₂ + C₂S + L)/bar} = - 0.92 16400/ (T/K) ± 0.04. respectively, where CS, C₃S₂ and C₂S indicate CaSiO₃(s), Ca₃Si₂O₇(s). and Ca₂SiO₄(s), respectively.     

A 10 bit 20 MS/s 3 V supply CMOS A/D converter

A 10 bit CMOS A/D converter with 3 V power supply has been developed for being integrated into system VLSI's. In this A/D converter, redundant binary encoders named “twin encoders” enhance tolerance to substrate noise, together with employing differential amplifiers in comparators. The bias circuit using a replica of the amplifier is developed for biasing differential comparators with 3 V power supply. Subranging architecture along with a multilevel tree decoding structure improves dynamic performance of the ADC at 3 V power supply. The A/D converter is fabricated in double-polysilicon, double-metal, 0.8 μm CMOS technology. The experimental results show that the ADC operates at 20 MS/s and the twin encoders suppress the influence of substrate noise effectively. This ADC has a single power supply of 3 V, and dissipates 135 mW at 20 MS/s operation     

A mutation in NPS1/STH1, an essential gene encoding a component of a novel chromatin-remodeling complex RSC, alters the chromatin structure of Saccharomyces cerevisiae centromeres

The NPS1/STH1 gene encodes a nuclear protein essential for the progression of G2/M phase in Saccharomyces cerevisiae . Nps1p shares homology to Snf2/Swi2p, a subunit of a protein complex known as the SNF/SWI complex. Recently, Nps1p was found to be a component of a protein complex termed RSC (3) essential for mitotic growth, whereas its function is unknown. We isolated a temperature-sensitive mutant allele of NPS1 , nps1-105, and found that the mutation increases the sensitivity to thiabendazole (TBZ). At the restrictive temperature, nps1-105 arrested at the G2/M phase in MAD1-dependent manner and missegregated the mini-chromosome with higher frequency than the wild type cells. The nuclease digestion of the chromatin of the mutant cells revealed that the mutation causes the alteration of the chromatin structure around centromeres at the restrictive temperature. The results suggested that, in the nps1-105 mutant, impaired chromatin structure surrounding centromeres may lead to an impairment of kinetochore function and the cells arrest at G2/M phase through the spindle-assembly checkpoint system.     

Response of human insulinoma cells to extracellular calcium is different from normal B cells

The preoperative determination of the localization of a small insulinoma is sometimes difficult using routine imaging techniques. We have used the selective arterial calcium injection (SACI) test to determine the location of the tumor preoperatively. The pathophysiologic basis of the SACI test is based on the responsiveness of insulinomas to calcium injected into the feeding artery. In this study, we demonstrated the in vitro response of the insulinoma cells to the extracellular calcium challenge by using primary-cultured insulinoma cells. Human insulinoma cells were obtained from three patients. MIN6 cells (normal pancreatic B cells) were used as a control; their insulin response to various stimuli resembles that of normal B cells. The insulin secretory dynamics in response to extracellular calcium were observed using a perfusion system. Second, the change of the concentration of cytosolic free calcium ([Ca2+]i) was monitored by fluorometry using fura-2/AM. When the concentration of extracellular calcium ([Ca2+]o) was changed from 2.54 mM to 10 mM, insulin secretion from the insulinoma cells was markedly increased within 6 min (10- to 18-fold at maximum), and rapidly returned to the basal level; at the same time, [Ca2+]i was immediately elevated and reached a peak within 1 min. In contrast, in the MIN6 cells, the insulin secretion and [Ca2+]i were not significantly changed when [Ca2+]o was switched to 10 mM. The results of these in vitro experiments agreed with the clinical results of the SACI test. The positive response of the insulinoma to the SACI test is probably due to the different response of insulinoma cells to the extracellular calcium challenge compared with normal B cells. The role of [Ca2+]i may be important in the mechanism underlying the SACI test.     

A novel zero-voltage-switching current-resonant converter using rectifier deadtime technique in the 10-MHz range

A novel zero-voltage-switching current resonant converter is presented. The rectifier deadtime technique proposed in this paper enables this converter to achieve zero-voltage switching on all semiconductor devices, including rectifier diodes, in any load range, and to operate form full load to no load within a high and narrow frequency range. The circuit operation is analyzed and is verified experimentally by two converters designed for 1 MHz and 10-MHz switching frequency operation. In the experiments, zero-voltage switching is achieved even at light load or no load, and a maximum efficiency of 93.5% in the 1-MHz-class converter and of 85.2% in the 10-MHz-class converter is realized. © 1998 Scripta Technica. Electr Eng Jpn, 121(4): 1–10, 1997     

Quantitative analysis of carcinoembryonic antigen messenger RNA in peripheral venous blood and portal blood of patients with pancreatic ductal adenocarcinoma

OBJECTIVES: We sought to investigate the long-term efficacy of slow-pathway catheter ablation in patients with spontaneous, documented paroxysmal supraventricular tachycardia (PSVT) and dual atrioventricular (AV) node pathways but without inducible tachycardia. BACKGROUND: The lack of reproduction of clinical PSVT by programmed electrical stimulation, which is not uncommon in AV node reentrant tachycardia (AVNRT), is a dilemma in making the decision of the therapeutic end point of radiofrequency catheter ablation. METHODS: Twenty-seven patients (group A) with documented but noninducible PSVT and with dual AV node pathways were prospectively studied. Programmed electrical stimulation could induce a single AV node echo beat in 12 patients, double echo beats in 4 patients and none in 11 patients at baseline or during isoproterenol infusion. Of the patients in group A, 16 underwent slow-pathway catheter ablation and 11 did not. The clinical and electrophysiologic characteristics of the 27 patients were compared with those of patients with dual AV node pathways and inducible AVNRT (group B, n = 55) and patients with dual AV node pathways alone without clinical PSVT (group C, n = 47). RESULTS: During 23+/-13 months of follow-up, none of the 16 patients with slow-pathway catheter ablation had recurrence of PSVT. However, 7 of the 11 patients without ablation had PSVT recurrence at 13+/-14 months of follow-up (p < 0.03 by Kaplan-Meier analysis). Compared with groups B and C, group A consisted predominantly of men who had better retrograde AV node conduction and a narrower zone for anterograde slow-pathway conduction. CONCLUSIONS: Slow-pathway catheter ablation is highly effective in eliminating spontaneous PSVT in which the tachycardia is not inducible despite the presence of dual AV node pathways.