Solid-State Synthesis and Thermoelectric Properties of Sb-Doped Mg2Si Materials

Sb-doped magnesium silicide compounds have been prepared through ball milling and solid-state reaction. Materials produced were near-stoichiometric. The structural modifications have been studied with powder x-ray diffraction. Highly dense pellets of Mg₂Si_1?x Sb _x (0 ≤ x ≤ 0.04) were fabricated via hot pressing and studied in terms of Seebeck coefficient, electrical and thermal conductivity, and free carrier concentration as a function of Sb concentration. Their thermoelectric performance in the high temperature range is presented, and the maximum value of the dimensionless figure of merit was found to be 0.46 at 810 K, for the Mg₂Si_0.915Sb_0.015 member.     

The origin of free fatty acids formed in frozen cape hake mince (Merluccius capensis,castelnau) during cold storage at −18°C

Hake mince was stored at ?18°C and samples were withdrawn at intervals during a 300-day period. The extracted lipids were examined for free fatty acid (FFA) and phosphorus (P) content. Total FFA contents were corrected for a phospholipid contribution and converted into genuine FFA contents. Using these genuine FFA contents and the knowledge that the loss of one mole of lipid-P produces two moles of FFA made it possible to calculate the separate contribution of the phospholipids and the neutral lipids to the FFA formed on storage. It was found that FFA originated from both phospholipids and neutral lipids and after an initial rapid surge of FFA formation from both sources the rates declined and became virtually constant. The results for the Cape hake are compared with literature data of the Atlantic cod and the Baltic herring.     

Cholecystokinin changes the duration but not the rate of licking in vagotomized rats.

Abdominal vagotomy markedly reduces or abolishes the inhibitory effect of cholecystokinin (CCK-8) on meal size. To investigate the rate and microstructure of licking underlying this phenomenon, licking was measured throughout a meal of milk in intact and vagotomized rats after intraperitoneal injections of isotonic saline or CCK-8. CCK-8 increased the slope of the decay of licking, decreased the efficiency of licking, and decreased the duration of licking in intact rats but had no effect on either the slope of the decay of licking or the efficiency of licking, but it increased the duration of licking in vagotomized rats. These results demonstrate that abdominal vagal nerves are necessary for CCK-8 to increase the rate of decay of licking, but nonvagal mechanisms mediate the effect of CCK-8 on duration of licking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abdominal vagotomy attenuates the inhibiting effect of mannitol on the ingestive behavior of rats.

Intact and abdominally vagotomized rats were offered for ingestion during a 30-min period a saccharin and glucose solution or another with 0.1 M mannitol added. The addition of mannitol to the test solution caused a large reduction in intake of intact rats caused by a very rapid decline in the rate of licking during the test. This did not occur with the vagotomized rats. This demonstrates that abdominal vagal nerves are necessary for the inhibitory effect of mannitol on the ingestive behavior of rats. Vagotomized rats also differed from the intact ones by ingesting less of the mannitol-free solution. This was suggested to result from accelerated gastric clearance, leading to abnormally rapid stimulation of negative feedback from the small intestine conveyed to the CNS by extravagal pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Focussed crawling of environmental Web resources based on the combination of multimedia evidence

Focussed crawlers enable the automatic discovery of Web resources about a given topic by automatically navigating the Web link structure and selecting the hyperlinks to follow by estimating their relevance to the topic based on evidence obtained from the already downloaded pages. This work proposes a classifier-guided focussed crawling approach that estimates the relevance of a hyperlink to an unvisited Web resource based on the combination of textual evidence representing its local context, namely the textual content appearing in its vicinity in the parent page, with visual evidence associated with its global context, namely the presence of images relevant to the topic within the parent page. The proposed focussed crawling approach is applied towards the discovery of environmental Web resources that provide air quality measurements and forecasts, since such measurements (and particularly the forecasts) are not only provided in textual form, but are also commonly encoded as multimedia, mainly in the form of heatmaps. Our evaluation experiments indicate the effectiveness of incorporating visual evidence in the link selection process applied by the focussed crawler over the use of textual features alone, particularly in conjunction with hyperlink exploration strategies that allow for the discovery of highly relevant pages that lie behind apparently irrelevant ones.     

Design of Ball-Milling Experiments on Bi2Te3 Thermoelectric Material

In this work, factorial ball-milling experiments have been applied to Bi₂Te₃ material, for the first time, aiming to investigate the effect of the main process parameters on the structural features and thermoelectric properties of the ball-milled materials. The selected main parameters were the duration of milling, the speed, and the ball-to-material ratio. Analysis suggests a strong effect of the speed and duration of processing, whereas the ball-to-material ratio is of minor importance. This approach is advantageous for better understanding of the milling mechanism and the importance of the role of each independent parameter as well as their interaction. All experiments led to nanocrystalline Bi₂Te₃, whose structural features were studied. The nanocrystalline size was estimated based on x-ray diffraction analysis, while transmission electron microscopy (TEM) studies were also performed to confirm the presence of nanoscale crystals. A mathematical model was developed based on statistical analysis for prediction of the crystalline size and the Seebeck coefficient of the nanopowders. The thermoelectric properties were also investigated on selected, highly dense pellets fabricated via hot-pressing of the nanopowders.     

Three different types of quasi-model networks: synthesis by group transfer polymerization and characterization

Summary Group transfer polymerization (GTP) chemistry was employed for the preparation of polymethacrylate networks of controlled structure (quasi-model networks) of three different types: (a) regular quasi-model networks, in which all polymer chains were linked at their ends, leaving, in principle, no free chain ends, (b) crosslinked star polymer quasi-model networks, in which star polymers were interlinked via half of their chains, letting the other half free (dangling), and (c) shell-crosslinked polymer quasi-model networks, in which the outer part of the network contained polymer arms (dangling chains). Combination of hydrophilic and hydrophobic monomers led to amphiphilic networks whose aqueous swelling behavior was characterized gravimetrically.     

Structure reinforcement of porous hydroxyapatite pellets using sodium carbonate as sintering aid: Microstructure,secondary phases and mechanical properties

Porous HAP pellets suitable for loading therapeutic agents were prepared using microcrystalline cellulose (MCC) as pore former and sodium carbonate as sintering aid (SAID). The effect of sintering temperature on the microstructure, mechanical properties and disintegration of pellets prepared at different SAID content was studied. Pellets were characterized by SEM, image analysis, porosimetry and surface area. Secondary phases were identified by PXRD, ATR-FTIR and Raman spectroscopy. Increasing the sintering temperature decreased the diameter, porosity, surface area and friability of the pellets but increased the pore size, tensile strength and disintegration time. The effect of SAID was dependent on sintering temperature. With 5% SAID, a secondary β-tricalcium phosphate (β-TCP) phase was formed, indicated by FTIR peak at 980 cm^?1 and characteristic PXRD reflections, whereas with 10%, a secondary B-type carbonated hydroxyapatite phase (CHA) formed, indicated by FTIR peaks at 878 and 1450 cm^?1, a broad Raman peak in the region 1020 to 1050 cm^?1 and PXRD reflections. Pellets prepared with SAID showed high strength and also porosity. The biphasic HAP/β-TCP pellets exhibited remarkably great strength (4.39 MPa) at the high sintering temperature, while still retaining 43.9% porosity. Relationships were established between the mechanical properties or disintegration time of the porous pellets and the microstructural parameters.     

Robust Sequential Data Modeling Using an Outlier Tolerant Hidden Markov Model

Hidden Markov (chain) models using finite Gaussian mixture models as their hidden state distributions have been successfully applied in sequential data modeling and classification applications. Nevertheless, Gaussian mixture models are well known to be highly intolerant to the presence of untypical data within the fitting data sets used for their estimation. Finite Student's t-mixture models have recently emerged as a heavier-tailed, robust alternative to Gaussian mixture models, overcoming these hurdles. To exploit these merits of Student's t-mixture models in the context of a sequential data modeling setting, we introduce, in this paper, a novel hidden Markov model where the hidden state distributions are considered to be finite mixtures of multivariate Student's t-densities. We derive an algorithm for the model parameters estimation under a maximum likelihood framework, assuming full, diagonal, and factor-analyzed covariance matrices. The advantages of the proposed model over conventional approaches are experimentally demonstrated through a series of sequential data modeling applications.