The effects of social networks on the assessment of virtual learning environments: A study for social sciences degrees

This paper deepens in the study of the appropriateness of virtual learning environments through the use and value of social networks by college students, considering the reliability, confidence and experience of the Internet. The study develop a comprehensive structural equation model conducted among 381college students of different Social Sciences degrees of the University of A Coruna (Spain). The results show that both topical social network and the Internet have a significant influence on college students’ virtual learning environment assessment, regardless the area of study. The analysis also discloses the potential utility of the above interactions on virtual learning environments in terms of downloading of material, improvement in learning efficiency and usefulness of contents, functions and supplement of other learning ICT tools. Findings reveal that the implementation of educational policies that allow adapting virtual learning environments to college students’ preferences are required.     

Digital Image Analysis and Visual Evaluation of Orange Juice: Influence of Different Measurements' Conditions

This study assesses the effect of background, surrounding, thickness and dilutions on the colour specifications of orange juice (OJ) analyzed by digital image and visual evaluation. A commercial OJ was diluted with distilled water to give ten levels of concentration (100, 90, 80, 70, 60, 50, 40, 30, 20 and 10 % of juice). These samples were evaluated instrumentally by digital image analysis using nine combinations of surroundings and backgrounds (black, grey and white) and three different thicknesses. Visual evaluation was also carried out on black, grey and white backgrounds. A grey surrounding, a white background and a fixed thickness are suggested to be used in future measurements of OJ colour by digital image analysis. Results of visual evaluation indicated that panellists were able to order correctly the OJ samples according to the dilution level, independently of the background chosen. The correlations between the instrumental and the visual analysis were significant (p?<?0.05) in all the backgrounds explored.     

Phenolic compounds in apples: varietal differences

Summary The phenolic compounds in the flesh, skin and juice of five varieties of apples have been analysed by high performance liquid chromatography. The following major compounds were quantified: catechins, procyanidins, hydroxycinnamic acid esters and flavonoid glycosides. The phenolic content showed different patterns depending on the part of the fruit studied and the variety of the apple.

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Phenolische Verbindungen in Äpfeln Unterschiede zwischen verschiedenen Apfelsorten

Zusammenfassung Nach HPLC-Trennung werden die phenolischen Verbindungen von Apfelfruchtfleisch,-Schale oder-Saft von fünf verschiedenen Apfelsorten analysiert. Die Hauptkomponenten (Catechine, Procyanidine, Hydroxyzimtsäureester mit Glucose oder Chinasäure und Flavonoidglykoside) werden quantitativ erfaßt. Die Verteilung der einzelnen Verbindungen hängt von der untersuchten Probe und der Apfelsorte ab.

     

Effect of Bonding Pressure on Silicon Nitride Joining Using a Nickel-Chromium-Boron Metal Filler

Mechanical pressure exerts a noticeable effect on the reaction that takes place at the interfacial region of Si₃N₄/Ni-Cr-B/Si₃N₄ joints. In fact, the mechanical pressure affects the thickness of the reaction layer: for lower pressures, a large interfacial reaction layer and a profusion of cracks are observed, whereas, for higher pressures, the extent of the reaction layer is limited, and no cracks are detected. The results show that joint strength increases monotonically with applied pressure.     

Secure group key establishment revisited

We examine the popular proof models for group key establishment of Bresson et al. (LNCS 2248: 290–309, 2001; Proceedings of the 8th ACM conference on computer and communications security (CCS-8), 2001) and point out missing security properties addressing malicious protocol participants. We show that established group key establishment schemes from CRYPTO 2003 and ASIACRYPT 2004 do not fully meet these new requirements. Next to giving a formal definition of these extended security properties, we prove a variant of the explored proposal from ASIACRYPT 2004 secure in this stricter sense. Our proof builds on the Computational Diffie Hellman (CDH) assumption and the random oracle model.     

Mass transfer in tube bundles with liquid fluidized particles

Experimental studies were conducted of overall and local tube-to-liquid mass transfer for bundles of horizontal tubes in staggered and in-line arrays in a liquid fluidized bed. The mass transfer coefficients are compared with those obtained using a fixed packing and those obtained without particles at the shell-side of the bundle.     

Immune reconstitution after autologous progenitor hemopoietic cell transplantation. A study comparing autologous bone marrow and autologous peripheral blood transplantation

BACKGROUND: In order to find out the effect of peripheral blood (PB) hematopoietic progenitor cells on immune reconstitution the present study compares, through a randomized trial, some lymphoid subsets after peripheral blood (PBT) or bone marrow (BMT) autologous transplantation. MATERIAL AND METHODS: Twelve patients suffering from malignant hematological disorders were included (6 BMT and 6 PBT). From these patients 14 lymphoid and natural killer (NK) subsets were sequentially analyzed using appropriate dual staining. NK activity was analyzed by measuring Cr51 release from the K562 cell line. Studies were done in days and -6, +10, +17, +24, +31, +38, +52, +66, +90, +120, +180 and +360 after transplantation. RESULTS: The CD8+ cell regeneration was produced mainly by activated cells (CD38+), and no differences were observed between BMT and PBT, but CD8+ HLADR+ cells were higher in the PBT group. During the first year after transplantation CD4+ lymphoid cells were never within normal range, and its recovery was due to the memory subset (CD4+/CD45RO+). The CD19+ lymphocytes began their regeneration after the first month and it was produced mainly by by the CD19+/CD5+ subset. NK cells recovered faster in patients who underwent PBT, but NK activity was similar in both subgroups of patients and it was within normal range from day +17 until the end of the study. CONCLUSION: T, B and NK lymphoid reconstitution do not differ significantly between patients that receive BM or PB as hemathopoietic rescue, but PB seems influence a faster reconstitution of cytotoxic subsets (CD8+/HLADR+ and NK lymphoid cells).     

Effects of Virgin Olive Oil on Blood Pressure and Renal Aminopeptidase Activities in Male Wistar Rats

High saturated fat diets have been associated with the development of obesity and hypertension, along with other pathologies related to the metabolic syndrome. In contrast, the Mediterranean diet, characterized by its high content of monounsaturated fatty acids, has been proposed as a dietary factor capable of positively regulating cardiovascular function. These effects have been linked to changes in the local renal renin angiotensin system (RAS) and the activity of the sympathetic nervous system. The main goal of this study was to analyze the role of two dietary fat sources on aminopeptidases activities involved in local kidney RAS. Male Wistar rats (six months old) were fed during 24 weeks with three different diets: the standard diet (S), the standard diet supplemented with virgin olive oil (20%) (VOO), or the standard diet enriched with butter (20%) plus cholesterol (0.1%) (Bch). Kidney samples were separated in medulla and cortex for aminopeptidase activities (AP) assay. Urine samples were collected for routine analysis by chemical tests. Aminopeptidase activities were determined by fluorometric methods in soluble (sol) and membrane-bound (mb) fractions of renal tissue, using arylamide derivatives as substrates. After the experimental period, the systolic blood pressure (SBP) values were similar in standard and VOO animals, and significantly lower than in the Bch group. At the same time, a significant increase in GluAP and IRAP activities were found in renal medulla of Bch animals. However, in VOO group the increase of GluAP activity in renal medulla was lower, while AspAP activity decreased in the renal cortex. Furthermore, the VOO diet also affected other aminopeptidase activities, such as TyrAP and pGluAP, related to the regulation of the sympathetic nervous system and the metabolic rate. These results support the beneficial effect of VOO in the regulation of SBP through changes in local AP activities of the kidney.