177,278 research outputs found
Joining by forming technology for thermal applications: A case study of finned tube heat exchanger
No full textHeat exchangers are essential for various thermal applications, and their performance could be improved by optimization of layout/operating conditions or materials. The layout/operating conditions optimization has been widely subjected to research and development, while the implementation of different materials has been limited to the available joining solutions. Joining by forming allows to circumvent the existent limitations, since it utilizes plastic deformation to produce multi-material mechanical joints between thin sheets and thin-walled tubes. Here, joining by forming is adopted for the first time, to manufacture multi-material transversal finned tube heat exchangers. The numerical-experimental analysis explores the production of tube compression beads obtained by plastic instability to fix and support fins, and therefore manufacture a novel design of finned heat exchanger with improved performance. A case study is carried out with the help of computational fluid dynamics simulations to find an optimal layout. Then, finite element simulations are employed to analyse the joining by forming process. A prototype model of transversal finned tube heat exchangers was finally manufactured and experimentally tested. Results show considerable gains in comparison with conventional finned tube heat exchangers made from steel tubes and fins, being the multi-material heat exchanger effectiveness doubled with respect to traditional designs
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Is early gastric cancer, diffuse type, a forerunner of advanced gastric cancer
No full textAIMS AND BACKGROUND: Gastric cancer (GC) represents one of the most important causes of death by malignancy world wide. Our retrospective study was carried out on surgical stomach specimens obtained from a series of 552 consecutive cases of GC observed in the Departments of Surgical Pathology of the Public Hospitals of L'Aquila and Atri which cover the 17% of the entire population of the Italian Region Abruzzo. The aim of the study was to compare the anatomo-clinical characteristics of early GC (EGC) and advanced GC (AGC).
METHODS: The diagnosis was achieved by the criteria of the Lauren's histopathological classification (intestinal and diffuse types). Our study also stratified the cases by sex, age, lymph node metastases and associated lesions such as chronic atrophic gastritis, intestinal metaplasia and dysplasia.
RESULTS: On an average, patients affected by EGC were 8.1 years younger than those with AGC. This age gap could support the hypothesis that early lesions represent the first stage of AGC. However, when patients were subdivided according to Lauren's classification, the mean age of patients with EGC, diffuse type, was 12.2 years less than that of AGC patients of the corresponding histological type. Furthermore, the subset of patients with EGC, diffuse type, and lymph node metastases was 17.8 years younger than patients affected by AGC diffuse type, with lymph node metastases.
CONCLUSIONS: The present study offers an original survey on GC in a defined Italian population. As far as the intestinal histotype is concerned, the slight age difference between EGC and AGC suggests that these tumors are different steps of the same process. On the contrary, the age distribution suggests that EGC, diffuse type, has a different biological behaviour
Effects of different carbohydrate sources on the growth of Tuber borchii Vittad. mycelium strains in pure culture.
No full textHexokinase inactivation induced by ascorbic acid/Fe(II) in rabbit erythrocytes is independent of glutathione-reductive processes and appears to be mediated by dehydroascorbic acid.
No full textRecent studies performed in our laboratory demonstrated that rabbit red blood cell hexokinase was remarkably inhibited by the cocktail ascorbic acid/Fe(II) (Stocchi et al., 1994, Arch. Biochem. Biophys. 311, 160-167) and that the formation of dehydroascorbic acid was a key event in this process (Fiorani et al., 1996, Arch. Biochem. Biophys, 334, 357-361). The present study was undertaken to determine the final hexokinase-inactivating species using cell-free extract as a model. Our results demonstrate superimposable kinetics of hexokinase decay promoted by either ascorbic acid/Fe(II) or dehydroascorbic acid in erythrocyte lysates in which the reduced glutathione (GSH) levels were variously manipulated. In particular, neither removal nor addition of this tripeptide was able to significantly alter the rate or extent of hexokinase inhibition. Thus, GSH-reductive processes are dispensable events in the process of hexokinase inhibition promoted by ascorbic acid/Fe(II) in red blood cells. As a consequence, dehydroascorbic acid appears to be the species which directly inhibits hexokinase. This inference is further supported by the observation that addition of dehydroascorbic acid to the purified enzyme leads to a remarkable inhibition in its activity
Sodium valproate in the treatment of epilepsies: literature review [IL VALPROATO DI SODIO NEL TRATTAMENTO DELLE EPILESSIE: REVIEW DELLA LETTERATURA]
No full text"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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