86,574 research outputs found
“F. Cánovas Sánchez, Benito Pérez Galdós. Vida, obra y compromiso, Madrid, Alianza, 2019, pp. 499. Y. Arencibia, Galdós. Una biografía, Barcelona, Tusquets, 2020, pp. 862”
No full textAccelerated Tests on Si and SiC Power Transistors with Thermal, Fast and Ultra-Fast Neutrons
No full textNeutron test campaigns on silicon (Si) and silicon carbide (SiC) power MOSFETs and IGBTs were conducted at the TRIGA (Training, Research, Isotopes, General Atomics) Mark II (Pavia, Italy) nuclear reactor and ChipIr-ISIS Neutron and Muon Source (Didcot, U.K.) facility. About 2000 power transistors made by STMicroelectronics were tested in all the experiments. Tests with thermal and fast neutrons (up to about 10 MeV) at the TRIGA Mark II reactor showed that single-event burnout (SEB) failures only occurred at voltages close to the rated drain-source voltage. Thermal neutrons did not induce SEB, nor degradation in the electrical parameters of the devices. SEB failures during testing at ChipIr with ultra-fast neutrons (1-800 MeV) were evaluated in terms of failure in time (FIT) versus derating voltage curves according to the JEP151 procedure of the Joint Electron Device Engineering Council (JEDEC). These curves, even if scaled with die size and avalanche voltage, were strongly linked to the technological processes of the devices, although a common trend was observed that highlighted commonalities among the failures of different types of MOSFETs. In both experiments, we observed only SEB failures without single-event gate rupture (SEGR) during the tests. None of the power devices that survived the neutron tests were degraded in their electrical performances. A study of the worst-case bias condition (gate and/or drain) during irradiation was performed
“F. García Lorca, De viva voz. Conferencias y alocuciones. Edición a cargo de Víctor Fernández y Jesús Ortega, Barcelona, DeBols!llo, 2021, 416 pp.”
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Stereochemistry and Near-Infrared Circular Dichroism of a Chiral Yb Complex
No full textThe near-infrared CD spectrum of ytterbium complexed by DOTMA, [DOTMA = (1R,4R,7R, 10R)-alpha, alpha', alpha ", alpha'''-tetramethyl-1,4,7, 10-tetraazacyclododecane-1,4,7,10-tetraacetic acid)] is presented. This is the first report of a near-infrared CD spectrum in solution of the f-f transitions of ytterbium in a complex whose solution structure and dynamics are completely defined. The spectrum shows several well-resolved transitions around 980 nm with very high dissymmetry factors. In water and in methanol, there are two diastereomeric conformations of YbDOTMA in equilibrium, Lambda(delta delta delta delta) or n and Lambda(lambda lambda lambda lambda) or p, being the latter always in a large excess. The relative proportion depends on temperature and solvent composition, but the CD spectrum is rather insensitive to these parameters, which demonstrates that neglecting the minor form contribution is an acceptable approximation. On lowering the temperature, the presence of hot bands is highlighted, which leads to a tentative assignment of the transitions. The absorption counterpart compares very well with that of YbDOTA, an achiral analogue, largely studied and well understood
Redefining the role of radiology in the postoperative management of laparoscopic adjustable gastric banding (LAGB)
No full textBackground: Upper gastro-intestinal series (UGI) are routinely employed in early and late postoperative management of LAGB patients, with the aim to assess early or late complications and to perform band adjustment. We here report the prospective results of our series in order to redefine the role of radiology in the post- operative management.
Methods: From September 1993 through January 2006, 2000 patients had LAGB at our hospital. In 2000 we abandoned routine UGI series in all patients at post-op day 1. Since then, 869 UGI were performed on 373 patients (295 F, 78 M, average age 40 (16- 67) years) who were either symptomatic (early and late postoper- atively) or had inadequate weight loss. We compared these patients with a control group of 38 subjects undergone yearly UGI after LAGB with satisfactory weight loss and uneventful follow-up.
Results: No postoperative mortality or gastric perforation was reported. Major postoperative complications included 21 (5.6%) late large-volume gastric slippage (127.4 + 52.3 mL) with outlet obstruc- tion and 15 (4%) middle volume (39.46 + 23.32 mL) with patent out- let. 12% of these patients were operated via perigastric approach while 2% via pars flaccida. In the control group a little gastric pouch (9.9 + 12 mL) without clinical relevance was observed in 13.2%. Tube disconnection was reported in 16 cases (4.3%) who experi- enced acute loss of satiety, while none in the control group.
Conclusion: An extensive radiological protocol is unnecessary for the postoperative management of LAGB, since a prompt cus- tomized approach allows a safer and better treatment of patients with complications or insufficient weight loss. Only large and mid- dle slippages mandate re-do surgery
Temperature Dependence of Terrestrial Neutron Induced Failures in Commercial Silicon and Silicon Carbide Power MOSFETs
No full textAccelerated neutron tests on Si and SiC power MOSFETs at different temperatures were performed at ChipIr facility (Didcot, UK). The results show a strong correlation between the temperature dependence of the avalanche voltage and that of the neutron failure rate
Yb(fod)3 in the spectroscopic determination of the configuration of chiral diols: a survey of the lanthanide diketonate method
No full textA modification of the diketonate method for the determination of the absolute configuration of chiral vicinal diols, first proposed by Nakanishi, is taken under object and tested with a set of aliphatic and aromatic substrates; Yb(fod)(3) (fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionate) is employed as the chromophoric species. The replacement of dpm (dpm = dipivalomethanate) with fod ensures the formation of strong and stable signals in the UV region, whose signs are related to the configuration of the chelating molecule. The choice of ytterbium as the central cation introduces two major advantages: the electronic f-f transition of the rare-earth supplies a second spectral window in the near-IR, which is sensitive to the chemical environment around the atom. This allowed us to ascertain the number of different species present in solution and the observation of an induced CD also for strongly UV-absorbing substrates. The pseudocontact shifts induced in the H-1-NMR spectrum by the unpaired electron of the lanthanide ion provide valuable structural information on the adducts
Correction of cardiovascular risks factor after an acute coronary syndrome: impact of pharmacological therapies on a two-years follow-up
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Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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