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1.
Intestinal calcium absorption has been shown to include two processes, a saturable transcellular movement and a non-saturable paracellular pathway. The potential utility of cell monolayers for studying transepithelial intestinal calcium transport has already been demonstrated; however, simultaneous evaluation of the contribution of the saturable transcellular and of the non-saturable paracellular processes to the total transepithelial transport has not yet been attempted. The aim of this study was to investigate the contribution both of transcellular and paracellular transport processes to the total transepithelial calcium transport in two cell culture monolayers. Caco-2 cells and a clone derived from HT-29 cells (HT29-Cl.19A), two cell lines derived from colon adenocarcinomas which are known to be able to exhibit typical enterocytic differentiation, were used. Cell monolayers were grown on a permeable support and used after 15 days of culture when these cells express enterocytic differentiation and high transepithelial resistance. Isotopic transport rate measurements were performed in the absence of a chemical gradient. The paracellular route was evaluated using [3H]mannitol. Calcium and [3H]mannitol transport rates across cell monolayers were not significantly different. Augmentation of calcium uptake by 200 mM sorbitol did not significantly increase calcium or mannitol transepithelial transport; however, calcium accumulation in the cells was increased by about 200%. Modulation of the monolayer permeability by addition of 10 nM vasoactive intestinal polypeptide (VIP) or 0.5 mM carbachol treatment, which respectively increased and decreased the transepithelial resistance, consequently modified calcium and mannitol transport in a parallel manner. Our results show that Caco-2 and HT29-Cl.19A cell monolayers are good models for studying the calcium paracellular transport pathway. 相似文献
2.
This study examines the links between antecedents and consequences of Gabonese teachers' (N= 152) work motivation. The theoretical underpinnings are based on the Motivational Model of Job Burnout (MMJB) which is grounded in Self-Determination Theory (SDT) and states that the more supervisors satisfy an employee's need for self-determination, competence, and relatedness, the more self-determined is the latter's work motivation. The level of self-determined motivation has an impact on job satisfaction, which in turn determines life satisfaction. Higher levels of self-determined motivation also buffer emotional exhaustion and psychological distress. The model was confirmed via structural equation modeling and provides support for the validity and generalizability of the MMJB and SDT. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
In recent work, Kalai, Klivans, Mansour, and Servedio (2005) studied a variant of the “Low-Degree (Fourier) Algorithm” for learning under the uniform probability distribution on {0,1} n . They showed that the L 1 polynomial regression algorithm yields agnostic (tolerant to arbitrary noise) learning algorithms with respect to the class of threshold functions—under certain restricted instance distributions, including uniform on {0,1} n and Gaussian on ? n . In this work we show how all learning results based on the Low-Degree Algorithm can be generalized to give almost identical agnostic guarantees under arbitrary product distributions on instance spaces X 1×???×X n . We also extend these results to learning under mixtures of product distributions. The main technical innovation is the use of (Hoeffding) orthogonal decomposition and the extension of the “noise sensitivity method” to arbitrary product spaces. In particular, we give a very simple proof that threshold functions over arbitrary product spaces have δ-noise sensitivity $O(\sqrt{\delta})$ , resolving an open problem suggested by Peres (2004). 相似文献
4.
Detection of hazelnut proteins in foods by enzyme immunoassay using egg yolk antibodies 总被引:1,自引:0,他引:1
An enzyme immunoassay (EIA) was developed for the detection of hazelnut proteins in foods. This assay used inexpensive chicken egg yolk antibodies in a sandwich EIA format for the immunospecific capture and detection of hazelnut proteins present in a variety of different food matrices. The assay was able to detect less than 1 ppm of hazelnut protein in most of the foods tested and did not exhibit any appreciable cross-reactivity with other nuts or food matrices. This assay will be a useful tool for the food industry and regulatory agencies that wish to test foods for the presence of undeclared hazelnut allergens. 相似文献
5.
It is well known that a large proportion of ferrous PM components require secondary machining operations for dimensional conformance or for producing geometrical features that cannot be generated during die compaction. Nevertheless, the machining behavior of PM parts is generally characterized as being “difficult” due to the presence of residual porosity that lowers thermal conductivity and induces interrupted cutting. Several admixed additives such as MnS and BN-h can be used to improve the machining behavior of PM steels. Nevertheless, their negative effect on mechanical properties, especially fatigue resistance, makes their utilization uninteresting for the fabrication of high-performance PM steel components. This article summarizes the work carried out to develop a novel PM steel that was especially engineered to form machinability enhancing precipitates. This new material is pre-alloyed with tin (Sn) in order to form Cu-Sn (Cu(α)) precipitates during transient liquid phase sintering. The newly developed material presents machinability improvement of 165% compared to reference material used in the PM industry as well as increases in toughness and fatigue resistance of 100% and 13%, respectively. 相似文献
6.
Nielsen Guillaume Janin Amelie Coudert Lucie Blais Jean Francois Mercier Guy 《Mine Water and the Environment》2018,37(1):42-55
Mine Water and the Environment - Passive treatment is a promising, green technology that is increasingly being used for mine drainage treatment. However, several challenges remain concerning its... 相似文献
7.
Nathalie Meunier Myriam Chartier Guy Mercier Jean-Fran?ois Blais 《Canadian Metallurgical Quarterly》2009,135(9):869-875
Many problems are associated with pig manure production like high biochemical oxygen demand, chemical oxygen demand, nitrogen, and phosphorus contents. Manure produces may be used in land spreading for agricultural purposes. Over application of liquid manure or runoff caused by precipitation contribute notably to surface or overland flow of phosphorus. In this study, the LISOX process is proposed for use in medium size farms, namely a 2,000-head swine farm. The LISOX process uses biological passive flotation, without any gas addition, to enable the flocs to rise to the surface. Results show that this technology is able to considerably reduce the solids content in the final effluent to 1.1±0.3% and reached solids content of 17.9±2.6% in the combined solid manure obtained at the end of the LISOX process. Total phosphorus (Pt) concentrations have been reduced from 1,234±428?mg/L to 146±46?mg/L in the final effluent, while a value of Pt of 20.6±7.9?g/kg has been obtained in the final solid fraction of the treated manure. The initial ammonium ion/total phosphorus ratio of 2.3±1.0 has been increased to respectively 16.4±4.6 and 17.6±5.4 after the primary and the secondary flotation, which is clearly much higher than the target value (NH4/Pt>7). 相似文献
8.
Quantitative soil ingestion studies employing a mass balance tracer approach have been used to provide a defensible means to estimate soil ingestion for human health risk assessments. Past studies have focused on soil ingestion in populations living in urban/suburban environments. There is a paucity of reliable quantitative soil ingestion data to support human health risk assessments of other lifestyles that may be predisposed to ingesting soil, such as agricultural workers or indigenous populations following traditional lifestyles. The results of a preliminary analysis of sampling and analytical variability that would result from assessing activities typical of populations in rural or wilderness areas and conducted over wide areas show that approximately 225 subject days would be required to detect a difference of 20 mg/d in soil ingestion. Given the typically small populations in these areas, future soil ingestion studies should be focused on specific activities with a high potential for soil ingestion. 相似文献
9.
Monfette Marie-Eve; Grimard Fran?ois; Ivers Hans; Blais Marie-Claude; Lavoie Vicky; Boisvert Jean-Marie 《Canadian Metallurgical Quarterly》2006,38(3):261
The popularity of the Fear of Negative Evaluation scale (FNE; Watson & Friend, 1969) stems from the centrality of this construct in personality, social and clinical psychology. In order to meet the needs of the Francophone researchers community, Kéroack, Boisvert, and Prévost (1987) traduced the short version of this instrument. Since social anxiety is most salient in adolescence, there is a need for normative and psychometric data for this population. This research aims at documenting the psychometric properties and norms for Francophone adolescents. Five hundred and seventy-eight participants aged from 14 to 19 years completed the French versions of the short FNE and the Social Avoidance and Distress scale. The factorial structure, the internal consistency and the convergent validity analyses confirm the traduction's quality and the questionnaire's validity. Norms are presented separately for females and males. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.