860 resultados para Cation exchange


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While the Internet has given educators access to a steady supply of Open Educational Resources, the educational rubrics commonly shared on the Web are generally in the form of static, non-semantic presentational documents or in the proprietary data structures of commercial content and learning management systems.With the advent of Semantic Web Standards, producers of online resources have a new framework to support the open exchange of software-readable datasets. Despite these advances, the state of the art of digital representation of rubrics as sharable documents has not progressed.This paper proposes an ontological model for digital rubrics. This model is built upon the Semantic Web Standards of the World Wide Web Consortium (W3C), principally the Resource Description Framework (RDF) and Web Ontology Language (OWL).

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Latin medical texts transmit medical theories and practices that originated mainly in Greece. This interaction took place through juxtaposition, assimilation and transformation of ideas. 'Greek' and 'Roman' in Latin Medical Texts studies the ways in which this cultural interaction influenced the development of the medical profession and the growth of knowledge of human and animal bodies, and especially how it provided the foundations for innovations in the areas of anatomy, pathology and pharmacology, from the earliest Latin medical texts until well into the medieval world.

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Arbuscular mycorrhizal fungi (AMF) form symbioses with the majority of plants and form extensive underground hyphal networks simultaneously connecting the roots of different plant species. No empirical evidence exists for either anastomosis between genetically different AMF or genetic exchange.Five isolates of one population of Glomus intraradices were used to study anastomosis between hyphae of germinating spores. We show that genetically distinct AMF, from the same field, anastomose, resulting in viable cytoplasmic connections through which genetic exchange could potentially occur.Pairs of genetically different isolates were then co-cultured in an in vitro system.Freshly produced spores were individually germinated to establish new cultures.Using several molecular tools, we show that genetic exchange occurred between genetically different AMF. Specific genetic markers from each parent were transmitted to the progeny. The progeny were viable, forming symbioses with plant roots. The phenotypes of some of the progeny were significantly different from either parent.Our results indicate that considerable promiscuity could occur in these fungi because nine out of 10 combinations of different isolates anastomosed. The ability to perform genetic crosses between AMF experimentally lays a foundation for understanding the genetics and evolutionary biology of these important plants symbionts.

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Mitochondria in intact cells maintain low Na(+) levels despite the large electrochemical gradient favoring cation influx into the matrix. In addition, they display individual spontaneous transient depolarizations. The authors report here that individual mitochondria in living astrocytes exhibit spontaneous increases in their Na(+) concentration (Na(mit)(+) spiking), as measured using the mitochondrial probe CoroNa Red. In a field of view with approximately 30 astrocytes, up to 1,400 transients per minute were typically detected under resting conditions. Na(mit)(+) spiking was also observed in neurons, but was scarce in two nonneural cell types tested. Astrocytic Na(mit)(+) spikes averaged 12.2 +/- 0.8 s in duration and 35.5 +/- 3.2 mM in amplitude and coincided with brief mitochondrial depolarizations; they were impaired by mitochondrial depolarization and ruthenium red pointing to the involvement of a cation uniporter. Na(mit)(+) spiking activity was significantly inhibited by mitochondrial Na(+)/H(+) exchanger inhibition and sensitive to cellular pH and Na(+) concentration. Ca(2+) played a permissive role on Na(mit)(+) spiking activity. Finally, the authors present evidence suggesting that Na(mit)(+) spiking frequency was correlated with cellular ATP levels. This study shows that, under physiological conditions, individual mitochondria in living astrocytes exhibit fast Na(+) exchange across their inner membrane, which reveals a new form of highly dynamic and localized functional regulation.

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We systematically investigated the effect of heterology on RecA-mediated strand exchange between double-stranded linear and single-stranded circular DNA. Strand exchange took place through heterologies of up to 150-200 base pairs when the insertion was at the proximal (initiating) end of the duplex DNA but was completely blocked by an insert of only 22 base pairs placed at the distal end of the duplex. In the case of medial heterology created by insertion either in the duplex or the single-stranded DNA, the ability of RecA to exchange strands decreased as the heterology was shifted toward the distal end of the duplex. These results suggest that two different strand exchange mechanisms operate in the proximal and distal portions of the duplex substrate.

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The role of ATP hydrolysis during the RecA-mediated recombination reaction is addressed in this paper. Recent studies indicated that the RecA-promoted DNA strand exchange between completely homologous double- and single-stranded DNA can be very efficient in the absence of ATP hydrolysis. In this work we demonstrate that the energy derived from the ATP hydrolysis is strictly needed to drive the DNA strand exchange through the regions where the interacting DNA molecules are not in a homologous register. Therefore, in addition to the role of the ATP hydrolysis in promoting the dissociation of RecA from the products of the recombination reaction, as described earlier, ATP hydrolysis also plays a crucial role in the actual process of strand exchange, provided that the lack of homologous register obstructs the process of branch migration.

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Background: The glycosylated hemoglobin (HbA1c) is used to help monitor the degree of a diabetic’s hyperglycemia. Security and accuracy of the methods used in its detection are affected by variants forms of Hb or elevations in levels of Fetal Hb (HbF). These interference are the result of a change in the haemoglobin total net charge of the variant due of a substitution of one amino acid in the remaining amino terminal of the beta chain. International Standardization for HbA1c values (NGSP) not include interference assessment as part of the certification program. Therefore, the effect of each variant or the lifting of the HbF on HbA1c result should be examined in each sample depending on the detected variant and the method used for the detection of the same. The objectives were: to describe the possible variants of Hb and their interference in HbA1c measurement by our method, after the implementation of a computer program for their detection. To identify some variants detected by chromatography liquid ion exchange high resolution (HPLC) with DNA molecular sequencing.

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Considerable experimental evidence suggests that non-pecuniary motives must be addressed when modeling behavior in economic contexts. Recent models of non-pecuniary motives can be classified as either altruism- based, equity-based, or reciprocity-based. We estimate and compare leading approaches in these categories, using experimental data. We then offer a flexible approach that nests the above three approaches, thereby allowing for nested hypothesis testing and for determining the relative strength of each of the competing theories. In addition, the encompassing approach provides a functional form for utility in different settings without the restrictive nature of the approaches nested within it. Using this flexible form for nested tests, we find that intentional reciprocity, distributive concerns, and altruistic considerations all play a significant role in players' decisions.

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Objectives: The aim of this study was to compare specificity and sensitivity of different biological markers that can be used in a forensic field to identify potentially dangerous drivers because of their alcohol habits. Methods: We studied 280 Swiss drivers after driving while under the alcohol influence. 33 were excluded for not having CDT N results, 247 were included (218 men (88%) and 29 women (12%). Mean age was 42,4 (SD:12, min: 20 max: 76). The evaluation of the alcohol consumption concerned the month before the CDT test and was considered as such after the interview: Heavy drinkers (>3 drinks per day): 60 (32.7%), < 3 drinks per day and moderate: 127 (51.4%) 114 (46.5%), abstinent: 60 (24.3%) 51 (21%). Alcohol intake was monitored by structured interviews, self-reported drinking habits and the C-Audit questionnaire as well as information provided by their family and general practitioner. Consumption was quantified in terms of standard drinks, which contain approximately 10 grams of pure alcohol (Ref. WHO). Results: comparison between moderate (less or equal to 3 drinks per day) and excessive drinkers (more than 3 drinks) Marker ROC area 95% CI cut-off sensitivity specificity CDT TIA 0.852 0.786-0917 2.6* 0.93 LR+1.43 0.35 LR-0.192 CDT N latex 0.875 0.821-0.930 2.5* 0.66 LR+ 6.93 0.90 LR- 0.369 Asialo+disialo-tf 0.881 0.826-0.936 1.2* 0.78 LR+4.07 0.80 LR-0.268 1.7° 0.66 LR+8.9 0.93 LR-0.360 GGT 0.659 0.580-0.737 85* 0.37 LR+2.14 0.83 LR-0.764 * cut-off point suggested by the manufacturer ° cut-off point suggested by our laboratory Conclusion: With the cut-off point established by the manufacturer, CDT TIA performed poorly in term of specificity. N latex CDT and CZE CDT were better, especially if a 1.7 cut-off is used with CZE

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This paper presents an analysis of the credibility of the EMScurrencies that covers the period before and after the increase in thebands of fluctuation. Our credibility indicator is based on the inferredprobabilities derived from the estimation of a Markov-switching model(Hamilton (1989)) applied to the expected rate of depreciation. Theresults show that, for most of the currencies, credibility has improved,at least transitorily, after the increase in the bands. However, for allcurrencies, the credibility measured by the indicator proposed in thispaper has been eroded recently even with the widened bands.

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We characterize the Walrasian allocations correspondence by means offour axioms: consistency, replica invariance, individual rationality andPareto optimality. It is shown that for any given class of exchange economiesany solution that satisfies the axioms is a selection from the Walrasianallocations with slack. Preferences are assumed to be smooth, but may besatiated and non--convex. A class of economies is defined as all economieswhose agents' preferences belong to an arbitrary family (finite or infinite)of types. The result can be modified to characterize equal budget Walrasianallocations with slack by replacing individual rationality with individualrationality from equal division. The results are valid also for classes ofeconomies in which core--Walras equivalence does not hold.