A radiation tolerant phototube power supply for the electromagnetic calorimeter of the HERA- experiment

The design of the phototube power supply for the HERA-B  Electromagnetic Calorimeter is presented. A choice of the solution on the basis of the Cockcroft–Walton voltage multiplier is validated. Schematics developed are discussed. A special section describes the behaviour of the crucial components under irradiation since radiation tolerance becomes one of the most important items in the severe HERA-B  radiation environment. Finally, performance achieved is presented.     

The development of hyperventilation in patients with chronic heart failure and Cheyne-Strokes respiration: a possible role of chronic hypoxia

AIM: To analyze the relationship between daytime respiratory and cardiac function in patients with compensated chronic heart failure (CHF) with and without periodic breathing (PB) or Cheyne-Stokes respiration (CSR). PATIENTS: We studied 132 patients (female, 13%; mean age, 53+/-8 years; body mass index, 25.9+/-3.5 kg/m2; left ventricular ejection fraction <40%; 23% in New York Heart Association class I, 43% in class II, and 34% in class III-IV). METHODS: Measurement of pulmonary function and blood gases, hemodynamic evaluation, analysis of breathing profile, echocardiography, recording of ECG, beat-to-beat arterial oxygen saturation, and respiration during spontaneous breathing. RESULTS: Fifty-eight percent of patients showed PB or CSR. Patients with PB or CSR have greater cardiac function impairment. Mean values of lung volumes and PaO2 were similar in the three groups of patients considered. In contrast, patients with PB or CSR had an increased minute ventilation and reduced PaCO2 values. Interestingly, patients with PB or CSR had lower values of arterial content of O2 and systemic oxygen transport (SOT) than patients with a normal breathing pattern (SOT, 394+/-9.8, 347+/-9.6, 438+/-11 mL of O2/min/m2, respectively; analysis of variance p<0.001). Weak correlations were found among lung volumes, blood gases, and cardiac function parameters: ie, vital capacity was correlated inversely with pulmonary capillary wedge pressure (PCWP) (-0.25; p<0.05); PaCO2 with PCWP (r=0.26; p<0.05), lung-to-ear circulation time (LECT) (r=-0.4; p<0.05), SOT (r=-0.33; p<0.0001), and cardiac index (CI) (r=0.27; p=0.003). Multiple regression analyses showed that arterial PCO2 was significantly correlated with SOT, LECT, and CI (r=0.51; r2=0.26; p<0.000001); the correlation became stronger considering only CSR patients (r=0.64; r2=0.4; p<0.001). CONCLUSIONS: Our study shows that patients with daytime breathing disorders have chronic hypocapnia. A reduced SOT may be one of the stimuli determining increased minute ventilation in these patients.     

A high current drive CMOS output stage with a tunable quiescent current limiting circuit

A CMOS output stage based on a complementary common source with an original quiescent current limiting circuit is presented. The quiescent current can be varied over a wide range by means of a control current with no need to modify the transistor aspect ratios. The output stage has been coupled to a conventional complementary input stage to form a rail-to-rail buffer. A prototype with the inclusion of auxiliary pins for biasing and current monitoring purposes has been designed using the 1-/spl mu/m double-polysilicon BCD3S process of STMicroelectronics. On a single 5-V power supply, the maximum output current is 20 mA. The amplifier, biased for a total power dissipation of 1 mW, exhibits a total harmonic distortion of -58 dB at 1 kHz with 4-V peak-to-peak on a 330-/spl Omega/ load. Correct operation of the quiescent current limiting circuit has been demonstrated for a minimum supply voltage of 2.2 V.     

Secure Multicast in Wireless Networks of Mobile Hosts: Protocols and Issues

Multicast services and wireless interconnection networks are among the emerging technologies of the last decade. A significant amount of research has been separately performed in the areas of secure multicast and wireless interconnection networks. In this paper we investigate the issues of designing secure multicast services in wireless mobile environments for dynamic groups and propose protocols for key management for a variety of scenarios. Our solution decouples mobility management from group dynamics management, by taking into account the level of trust in the support stations. In particular, we show that protocol efficiency on the mobile host side can be traded-off with the level of trust in the support stations.     

The three RF additional heating systems for FAST

FAST (Fusion Advanced Studies Torus) is a new tokamak machine proposed by the Italian Fusion Association as a Satellite Tokamak for the ITER programme. FAST will operate with deuterium plasmas to avoid the complexity deriving from the use of tritium. Therefore burning plasma conditions, where energy density of fast ions and of charged fusion products is a significant fraction of the total plasma energy density, will be achieved by accelerating plasma ions above the half-MeV range through an Ion Cyclotron Resonance Heating (ICRH) system (P = 30 MW, f = 60–90 MHz). For long pulse Advanced Tokamak (AT) scenarios, a Lower Hybrid Current Drive (LHCD) system (P = 6 MW, f = 3.7 GHz) has been envisaged to actively control the current profile, whereas an Electron Cyclotron Resonant Heating (ECRH) system (P = 4 MW, f = 170 GHz) will provide enough RF power for MHD control.     

A Low-Power 2-D Wind Sensor Based on Integrated Flow Meters

A 2-D wind sensor, based on microelectromechanical systems (MEMS) flow sensors, is presented. The device consists of a cylinder with a channel network connecting the internal flow sensors with the lateral surface. The pressure distribution developed by the wind on the cylinder's surface is thus converted into two air flows from which, due to the special channel configuration, wind speed and direction can be unequivocally determined. Since the MEMS devices are located in the channels, their fragile sensing structures are protected from direct exposure to the wind. Performance estimation based on literature data of pressure distributions indicates that the approach is applicable to a wide wind velocity range. The feasibility of the idea is supported by measurements performed on a prototype.     

Preliminary Experimental Analysis of a CHP Hydromethane System

The aim of this paper is to present the preliminary experimental analysis results carried out on the commercial internal combustion engine set in a CHP （combined heat and power） mode, fueled by renewable hydrogen and methane mixtures. The hydrogen is produced by an alkaline electrolyser fed by a 5.8 kWp grid connected PV （photovoltaic） plant. The acceptance test conducted with hydrogen percentages ranging from 0%-10% has been carried out at partial load： 45 kW~l instead of the full power of 60 kWe~. In order to evaluate the CHP energy consumption and environmental performance （NOx and CO）, the analysis was conducted for 240 h, using a portable flue gas analyser and two mass flow meters for hydrogen and methane. Without engine parameters optimization--relative equivalence ratio （2） and spark advance--increasing hydrogen addition rate, a slight enhancement in electrical efficiency occurs. Furthermore, due to the engine control system and lower blends LHV （lower heating value）, the methane consumption decreases disproportionately to the hydrogen amount in the mixture. Finally, referring to standard operating condition, the environmental results show that using enrichment of 10%, running the engine with 18 degrees spark advance and 2 of 1.4, CO and NOx emissions are reduced by 6.3% and 27% respectively.     

Drastic influence of a single heme axial ligand replacement on the thermostability of cytochrome c3

The thermostability of wild type Desulfovibrio vulgaris Hildenborough tetraheme cytochrome c3 and its H22M, H25M, H35M and H70M mutants was studied by circular dichroism technique in the far UV and Soret regions. It was shown that wild type cytochrome is extremely thermostable and retains structural and functional properties up to 110 degrees C. Mutations do not change overall secondary structure and local structure of the hemes vicinity. All mutants are much more unstable to heat denaturation than the wild type cytochrome. Point mutation (His/Met replacement) results in extraordinary 30-45 degrees C decrease in the protein thermostability depending on the mutation. We may conclude therefore that the heme region is important not only for the functional properties of the cytochrome but also for the overall protein thermostability.     

Structural and kinetic studies of the Y73E mutant of octaheme cytochrome c3 (Mr = 26 000) from Desulfovibrio desulfuricans Norway

A combination of structural, kinetic, and interaction experiments has been used to study the role of a highly conserved aromatic residue, Tyr73, parallel to the sixth heme axial ligand of heme 4 in multiheme cytochrome c3 (Mr = 26 000), also called cytochrome cc3 or octaheme cytochrome, from Desulfovibrio desulfuricans Norway. This residue is expected to be involved in intermolecular electron transfer and protein-protein interaction, since heme 4 is described to be the interaction site between physiological partners. The kinetic experiments show that the Y73E replacement provokes no significant change in the electron-transfer reaction with the physiological partner, the [NiFeSe] hydrogenase, but that the protein-protein interaction between cytochrome c3 (Mr = 26 000) and hydrogenase is strongly affected by the mutation. The aromatic residue does not play a role in maintaining the axial heme ligand in a particular orientation, since the mutation did not affect the orientation of histidine 77, the sixth axial ligand of heme 4. The structural analysis by X-ray crystallography clearly shows that a rearrangement of the charged residues in the vicinity of the mutation site is responsible for the change in protein-protein interaction, which is of an electrostatic nature. Lys22 and Arg66, residues which are located at the interacting surface, are twisted toward the mutated position Glu73 in order to compensate for the negative charge and therefore are no longer accessible for the docking with a physiological partner. Tyr73 has instead a structural function and probably a role in maintaining the hydrophobic environment of the heme 4 cavity rather than a function in the intermolecular electron transfer with the physiological partners.