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51.
52.
Julieta Ventura S. K. Varma 《JOM Journal of the Minerals, Metals and Materials Society》2009,61(7):72-75
Nb-20Mo-15Si-5B-20Cr alloy has been oxidized in air in a range of temperatures from 700 to 1,300°C. A 24 hour exposure to
air shows a minimum in weight gain per unit area at 900 and 1,000°C. Below and above this temperature the alloy has an oxide
scale composed of oxide-metal interface which has been characterized by x-ray diffraction, scanning electron microscopy, energy
dispersive spectroscopy, and x-ray mapping. Formation of CrNbO4 appears to be beneficial for the oxidation resistance while another Cr oxide, Cr2O3, may form mainly at temperatures below 1,000°C. SiO2 formation has been restricted to temperatures above 1,000°C. Long term oxidation consisting of seven successive 24 hour cycles
of heating shows better oxidation resistance at 1,300°C for times longer than 96 hours but below that usual lower weight gain
per unit area at lower temperature has been observed. 相似文献
53.
M. Ventura F. Scandellari E. Bonora M. Tagliavini 《Nutrient Cycling in Agroecosystems》2010,87(1):115-125
The decomposition of plant residues has a pivotal role in carbon and nutrient cycles in agricultural ecosystems, where it
can contribute to the sustainable management of the crops. In this paper we report a study on the release of C and nutrients
during the decomposition of peach abscised leaves in northern Italy. Litter bags containing a representative amount of leaf
material were installed under tree canopies either on the soil surface under open field conditions or on the soil surface
in pots under partially controlled conditions. Potted leaf litter was pre-labelled with 15N. We observed that in 3 years, peach leaves lost 85% of their initial mass mostly attributable to cellulose decomposition,
while new lignin or lignin-like compounds were synthesised during the first stages of the decomposition process. Nutrient
dynamics differed depending on the considered element. Nitrogen and sulphur were initially immobilized into the litter to
be released only starting after 44 weeks from the beginning of the decomposition. Potassium and magnesium were rapidly released
in the winter following leaf abscission, reaching an amount that remained constant up to the end of the trial. Calcium and
phosphorus release was slow, but constant throughout the three-year study period. With the only exception of Mg, 80–90% of
initial amounts of mineral elements had released from decomposing peach leaves after 3 year from leaf abscission. Since in
mature stands leaf litters of different ages coexist on the soil surface 80–90% of the nutrients contained in the abscised
leaves are expected to return annually to the soil and potentially be available for subsequent root and/or microbial uptake. 相似文献
54.
M. Barucci C. Brofferio A. Giuliani E. Gottardi I. Peroni G. Ventura 《Journal of Low Temperature Physics》2001,123(5-6):303-314
The optimization of bolometric detectors, like those that will be developed for the rare event experiment CUORE, requires a complete knowledge of the detector's thermal parameters. Since the CUORE detecting elements will consist of TeO2 crystals, we have measured the specific heat of this material down to 60 mK with the thermal relaxation method. Previous available data were taken at temperatures higher than 0.6 K. Our results are clearly consistent with a lattice dominated specific heat. The Debye temperature, evaluated to be (232±7) K, is in excellent agreement with the elastic constant values measured by other authors. The knowledge of the Debye temperature allows a simple prediction of the pulse amplitude of presently working bolometers. 相似文献
55.
A. Zafra C. Romero S. Ventura E. Herrera-Viedma 《Expert systems with applications》2009,36(9):11470-11479
This article introduces the use of a multi-instance genetic programming algorithm for modelling user preferences in web index recommendation systems. The developed algorithm learns user interest by means of rules which add comprehensibility and clarity to the discovered models and increase the quality of the recommendations. This new model, called G3P-MI algorithm, is evaluated and compared with other available algorithms. Computational experiments show that our methodology achieves competitive results and provide high-quality user models which improve the accuracy of recommendations. 相似文献
56.
57.
CJ Kurek IL Cohen J Lambrinos K Minatoya FV Booth DB Chalfin 《Canadian Metallurgical Quarterly》1997,25(6):983-988
OBJECTIVE: To examine and describe the relation between age and disposition in patients undergoing tracheostomy. DESIGN: Retrospective analysis of a statewide database. SETTING: All acute care hospitals in New York state. PATIENTS: All patients (n = 6,353) > or = 18 yrs of age who were discharged from the hospital during 1993 with a final diagnosis-related groups code of 483. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The final disposition, according to six disposition codes (other acute care facility, residential healthcare facility, other healthcare facility, home, home healthcare services, and death) was examined for the entire population. Cost per case was assumed to equal the average statewide Medicaid rate. An inverse relation between survival rate and age was observed, which resulted in an age-related increased cost per survivor. Also, survivors in older age groups had an increased rate of discharge to residential healthcare facilities. There was a negative, albeit less marked, effect of older age on the rates of survivors discharged to home and to other healthcare facilities. CONCLUSIONS: Care of patients who undergo tracheostomy for prolonged mechanical ventilation is expensive. The older the patient, the less satisfactory the outcome from an economic, clinical, and possibly social perspective. 相似文献
58.
FA Ventura 《Canadian Metallurgical Quarterly》1996,9(7-9):241-245
The increased incidence of Imported Tropical Diseases in Portugal is correlated to a recent higher standard of living, influence of media and a consequent expansion of tourism, and above all to the close relationship existing between Portugal and Africa. The number and pathology (parasitic diarrhoeas, protozoal and helminthic infections) of in-patients with Tropical Diseases at the Unidade de Doen?as Infecciosas, Parasitárias e de Medicina Tropical (UDIP-MT) were described, with special emphasis on Malaria (155 in-patients during the period from 1989 to 1993) and on Sleeping Sickness, where Eflornitin (DFMO) was for the first time used in Portugal. Finally, the impact of HIV epidemic on incidence and different clinical presentations of parasitic and other tropical pathology was also evaluated. 相似文献
59.
OBJECTIVE: To evaluate the association between admission serum concentrations of the actin-scavenger, Gc-globulin, and the subsequent development of multiple organ failure in patients with fulminant hepatic failure. DESIGN: Retrospective study. SETTING: A hepatologic intensive care unit. PATIENTS: Seventy-nine patients with hepatic encephalopathy grade 3 or 4. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Serum admission concentrations of both total and nonactin-complexed (free) Gc-globulin were determined. The development of cardiovascular failure, renal failure, pulmonary failure, intracranial hypertension, and infections were recorded in each patient. Both total and free Gc-globulin values were significantly lower in the patients, compared with normal controls. The Gc-globulin values were significantly reduced in patients who subsequently developed cardiovascular failure (p < .01), intracranial hypertension (p < .001), and infections (p < .001), compared with those patients who did not. No differences were found between patients with and without pulmonary or renal failure. Patients with total Gc-globulin values in the lowest quintile had on average 2.6 organ failures, whereas patients with Gc-globulin concentrations in the highest quintile had 0.9 organ failures. The corresponding figures for the lowest and highest quintiles of free Gc-globulin were 3.0 and 1.1 organ failures, respectively. Both total and free Gc-globulin were inversely correlated to the number of organ failures (p < .005 in both cases). Patients with multiple organ failure (> or = 2 organ failures) had significantly reduced Gc-globulin values compared with patients without multiple organ failure (p < .0001). CONCLUSIONS: In patients with fulminant hepatic failure, the lowest admission Gc-globulin concentrations were associated with the subsequent development of cardiovascular failure, intracranial hypertension, and infections. Lack of Gc-globulin correlated significantly with the development of multiple organ failure and may be pathogenetically involved in this condition. 相似文献
60.
A Ziolkowski AS Shashkov AS Swierzko SN Senchenkova FV Toukach M Cedzynski KI Amano W Kaca YA Knirel 《Canadian Metallurgical Quarterly》1997,411(2-3):221-224
Structures of the O-specific polysaccharide chains of lipopolysaccharides from Proteus group OX strains (serogroups O1-O3) used as antigens in Weil-Felix test for diagnosis of rickettsiosis, were established. From them, the acid-labile polysaccharide of Proteus vulgaris OX19 (O1) is built up of the following branched pentasaccharide repeating units connected via a phosphate group: [structure in text] where QuiNAc stands for 2-acetamido-2,6-dideoxyglucose (N-acetylquinovosamine). The basis of serospecificity of the Proteus group OX antigens and their cross-reactivity with human anti-rickettsial antibodies is discussed. 相似文献