The oxidation resistance of Nb-20Mo-15Si-5B-20Cr up to 1,300°C

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.     

Nutrient release during decomposition of leaf litter in a peach (<Emphasis Type="Italic">Prunus persica L.</Emphasis>) orchard

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.     

Use of antimicrobial agents in patients with cardiovascular disease

Antimicrobial agents are widely utilized in the prevention and treatment of infection in patients with cardiovascular diseases. Knowledge of spectrum of activity, pharmacology, adverse effect and toxicity profile, and emergence of resistant pathogens is critical to the appropriate use of these agents. The following review will emphasize the safe, effective use of antimicrobial drugs in the cardiovascular patient.     

Measurement of Low Temperature Specific Heat of Crystalline TeO2 for the Optimization of Bolometric Detectors

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.     

Multi-instance genetic programming for web index recommendation

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.     

Profile of tropical diseases in Portugal

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.     

A pseudo-neural system for hypothesis selection

The article describes a system for hypothesis elicitation and ranking formed by a net of computational elements obtained by modifying the classical neural model of Caianiello. This neural structure was chosen on the basis both of knowledge representation and of parallel processing considerations. the two fundamental components of the system are an elaboration layer and, in case the available evidences are insufficient to trigger explanatory hypotheses, a query layer that enables the system to gather additional information. Algorithms that help setting the crucial variable parameters of the net are described in the Appendix. © 1992 John Wiley & Sons, Inc.     

Beta-1-integrin expression in adult acute lymphoblastic leukemia: possible relationship with the stem cell antigen CD34

In the hemopoietic system, interactions between stem cells and components of the bone marrow microenvironment play a pivotal role in blood cell proliferation and differentiation. Among the adhesion molecules, the integrins of the beta 1-subfamily are known to direct cell-cell and cell-matrix interactions and evidence has been provided that CD34-positive stem cells bind either to the bone marrow stroma or to the extracellular matrix proteins through the beta 1-integrins. It seems that changes in their expression pattern or signalling function are likely to reflect disturbances at the hemopoietic bone marrow microenvironmental level. Any alteration of their biological functions makes them attractive candidates for playing decisive roles in the leukemic processes. In this view, beta 1-integrins have been recognized to mediate those cellular interactions and migrations that are important in the biology of leukemia. In this paper we review some aspects of the role played by beta 1-integrins, especially VLA-4 and VLA-5, in adult acute lymphoblastic leukemia in relation with the expression rate of the stem cell antigen CD34.     

The incidence, morbidity, and mortality of surgical procedures after orthotopic heart transplantation

OBJECTIVE: The authors present their experience with patients having undergone orthotopic heart transplantation (OHT) in whom surgical conditions subsequently developed that required operative intervention. The incidence, morbidity, and mortality of these procedures are reported. SUMMARY BACKGROUND DATA: Several studies have evaluated the management options of biliary tract disease after OHT. Multiple reports of patients having undergone OHT who subsequently underwent peripheral vascular reconstructions, plastic reconstructive, and thoracic procedures also have been published. METHODS: A chart review of 349 patients who underwent OHT between 1985 and 1996 was conducted to identify surgical procedures that were required in the post-transplant period. Their outcomes are reported. RESULTS: Of 349 patients who underwent OHT, conditions requiring 94 surgical procedures developed in 54 patients (15%). Biliary tract disease developed in 17 patients (5%) who required cholecystectomy, 2 of the 5 patients with acute cholecystitis died. Eight patients (2%) underwent orthopedic procedures with no operative mortality. Flap advancements for sternal wound infections were performed in five patients and four deaths occurred. Seventeen thoracic procedures were performed in 11 patients with an overall mortality of 45%. Twenty-one vascular procedures were performed on 17 patients with 1 delayed death due to a malignancy. Seven patients underwent procedures of the colon and rectum with no mortality. Seven patients underwent repair of inguinal or incisional hernias with no mortality. Various infections occurred with one resultant death after operative intervention. Six procedures were performed for diseases of the small intestine with no resultant mortalities. CONCLUSIONS: Patients having undergone OHT and chronic immunosuppression are at increased risk of having complications develop from infection. Acute cholecystitis and sternal wound infection caused an inordinate risk of complications and death. Malignancies developed in four patients who required surgical intervention. A heightened awareness of coexisting peripheral vascular disease in patients transplanted for ischemic cardiomyopathy should exist. Close screening before surgery and surveillance after surgery to identify risk factors for infection and vascular disease and to screen for malignancies are essential.