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A method is described for sensitive and reliable determination of trace concentrations of cadmium, lead and copper in real samples by stripping potentiometry with a home-made flow cell. The selection of the experimental conditions was made using experimental design methodology. The optimum conditions for the method include an acetic acid–acetate buffer mixture (pH 3.4) as supporting electrolyte, an electrolysis potential of −1.1 V and a flow rate of 3 ml min−1. The detection limits were 6.51 × 10−10 mol l−1 for cadmium, 4.60 × 10−10 mol l−1 for lead and 8.59 × 10−10 mol l−1 for copper, with an electrolysis time of 900 s. The relative standard deviations at this concentration level were 0.038, 0.086 and 0.095, respectively. In order to check the analytical accuracy, standard solutions have been used and recoveries close to 100% were obtained. The method was successfully applied to the determination of cadmium, lead and copper in powdered milk, using the method of standard additions. 相似文献
84.
Perfect Timothy J.; Watson Emma L.; Wagstaff Graham F. 《Canadian Metallurgical Quarterly》1993,78(1):144
The confidence–accuracy (C–A) relation for general knowledge (GK) and eyewitness memory (EM) was compared in both within- and between-Ss analyses. Researchers in the cognitive tradition tend to use within-Ss designs and to find moderately positive C–A relations, whereas those in the forensic tradition tend to use between-Ss designs and to find no relations. 80 Ss took part in 1 of 2 conditions, EM or GK. No difference between conditions was found on the within-Ss measure of the C–A relation, but there was differentiation with a between-Ss measure. There was a strong positive C–A correlation (r?=?.58, p?r?=?–.11, ns). One source of this difference may be the differing opportunities for calibration offered by the 2 kinds of memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
This study examined differences in self-reported psychiatric symptomatology on the Minnesota Multiphasic Personality Inventory-2 according to adult attachment status on the Adult Attachment Interview in first-time mothers from a high-risk poverty sample. Participants reported fairly high levels of symptomatology regardless of attachment status. The dismissing adult attachment group reported comparatively little psychiatric distress, emphasized independence, and scored the lowest on self-reported anxiety. The preoccupied group was highest on a range of indices of psychiatric symptoms indicative of self-perceived distress and relationship problems. The autonomous group's scores ranged between the scores of the other 2 groups on most scales. These different symptom patterns are consistent with adult attachment status as an index of self-representation and as a set of strategies for processing emotions and thoughts related to distress and to attachment relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
86.
Emma?HartEmail author Peter?Ross David?Corne 《Genetic Programming and Evolvable Machines》2005,6(2):191-220
Early and seminal work which applied evolutionary computing methods to scheduling problems from 1985 onwards laid a strong and exciting foundation for the work which has been reported over the past decade or so. A survey of the current state-of-the-art was produced in 1999 for the European Network of Excellence on Evolutionary Computing EVONET—this paper provides a more up-to-date overview of the area, reporting on current trends, achievements, and suggesting the way forward. 相似文献
87.
Wittig de Penna E Curia A Calderón S López L Fuenzalida R Hough G 《Archivos latinoamericanos de nutrición》2005,55(1):77-85
The present work was designed in order to obtain the cut off point, to be used in a shelf life study on whole stirred strawberry yogurt. The study was simultaneously carried out in Argentina, Chile and Costa Rica, assaying the same kind of product, elaborated in each one of the countries. The sensory quality parameters obtained from trained panelists and the consumers acceptability, were correlated by using the cut off point methodology through a quality evaluation by the Karlsruhe scale. According to preliminary studies, the storage at 42 degrees C produced considerable damage on parameters such as pH, acidity (volumetric assay), viscosity and sensory quality. For each sample, the cut off point was determined. This value corresponds to the threshold score for the sensory quality, where the consumer starts to perceive negative changes in the product, when comparing with the fresh product. The rejection percentage was also calculated according to the cut off point. The cut off points and the percentage of rejection obtained by the three participating countries were similar. Data obtained from Costa Rica showed changes in color, acidity and rancidity. Argentinean yogurts developed acidity that had a negative effect on texture, appearance and residual flavors. Chilean samples presented a sensory quality that remains almost without change through the studied time. The differences of the deterioration pattern amongst the three countries, demonstrates that the products are different in formulation and elaboration process, in spite of been the same kind of yogurt. This could be explained by differences specified in the regulation of each country. 相似文献
88.
Raúl F. Guerrero Belén Puertas María I. Fernández Miguel Palma Emma Cantos-Villar 《Innovative Food Science and Emerging Technologies》2010,11(1):231-238
Bioactive products enriched in stilbenes are considered of potential future interest, and the main sources of stilbenes in human diet are grapes. Postharvest ultraviolet C (UV-C) treatment was used to induce stilbene biosynthesis in grapes of three varieties of Vitis vinifera sylvestris, seven of Vitis vinifera sativa, and two Hybrid Direct Producers (HDPs). Stilbenes have been identified by UPLC-DAD-TQD and quantified by HPLC-DAD, and cluster analyses have been performed to classify subspecies by their stilbene profile. After UV-C treatment, the Syrah variety reached a maximum of 25 mg kg? 1 f.w. of total stilbenes in the 2008 vintage, and in the statistical analysis, this variety stood out from the other Vitis varieties tested. In 2008, varieties belonging to the sylvestris group and Vitis vinifera sativa Merlot also presented high stilbene production; however, the expected concentration in the HDPs was not obtained.Industrial relevanceIn this study, postharvest UV-C treatment has been applied to obtain stilbene-enriched grapes from several subspecies of Vitis. The most suitable raw material for bioactive stilbene-enriched products, such as nutraceutics and wines, has been established. This is an essential prerequisite to scaling up the process. Such stilbene-enriched products are known to have added-value as a result of the confirmed positive bioactivity of these compounds, and are gaining market acceptance. 相似文献
89.
Sabine Grüschow Dr. Emma J. Rackham Benjamin Elkins Philip L. A. Newill Lionel M. Hill Dr. Rebecca J. M. Goss Dr. 《Chembiochem : a European journal of chemical biology》2009,10(2):355-360
Pacidamycins, mureidomycins and napsamycins are structurally related uridyl peptide antibiotics that inhibit translocase I, an as yet clinically unexploited target. This potentially important bioactivity coupled to the biosynthetically intriguing structure of pacidamycin make this natural product a fascinating subject for study. A precursor‐directed biosynthesis approach was employed in order to access new pacidamycin derivatives. Strikingly, the biosynthetic machinery exhibited highly relaxed substrate specificity with the majority of the tryptophan analogues that were administered; this resulted in the production of new pacidamycin derivatives. Remarkably, 2‐methyl‐, 7‐methyl‐, 7‐chloro‐ and 7‐bromotryptophans produced their corresponding pacidamycin analogues in larger amounts than the natural pacidamycin. Low levels or no incorporation was observed for tryptophans substituted at positions 4, 5 and 6. The ability to generate bromo‐ and chloropacidamycins opens up the possibility of further functionalising these compounds through chemical cross‐coupling in order to access a much larger family of derivatives. 相似文献
90.
Stephen Patterson Dr. Deuan C. Jones Dr. Emma J. Shanks Dr. Julie A. Frearson Prof. Ian H. Gilbert Prof. Paul G. Wyatt Prof. Alan H. Fairlamb Prof. 《ChemMedChem》2009,4(8):1341-1353
Thirty two analogues of phencyclidine were synthesised and tested as inhibitors of trypanothione reductase (TryR), a potential drug target in trypanosome and leishmania parasites. The lead compound BTCP ( 1 , 1‐(1‐benzo[b]thiophen‐2‐yl‐cyclohexyl) piperidine) was found to be a competitive inhibitor of the enzyme (Ki=1 μM ) and biologically active against bloodstream T. brucei (EC50=10 μM ), but with poor selectivity against mammalian MRC5 cells (EC50=29 μM ). Analogues with improved enzymatic and biological activity were obtained. The structure–activity relationships of this novel series are discussed. 相似文献