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Dilution Factor (dilution + factor)
Selected AbstractsDirect in situ detection of cells in deep-sea sediment cores from the Peru Margin (ODP Leg 201, Site 1229)GEOBIOLOGY, Issue 4 2004L. MAUCLAIRE ABSTRACT Microbiological investigations of deep-sea sediments recovered from the Peru Margin during the ODP Leg 201 (Hole 1229A, 1,110 mbsf) demonstrated that microoganisms were a consistent component throughout the profile. Optimization of the dilution factor and DAPI-staining procedures for direct cell counts allowed the determination of the abundance of the entire microbial community, which was about 108 cells per g dry sediment. Microbial diversity in discrete samples taken from the 110-m profile was analysed using horseradish-peroxydase-rRNA-probes. In general, the majority of the detected cells belonged to the Eubacteria kingdom with a dominance of sulphate-reducing bacteria. The composition of the suflate-reducing community varied with depth. Desulfobacteriaceae were dominant in the uppermost sulphate-reducing zone and Desulfovibrionaceae at deeper depths in the upward diffusing sulphate-rich brines. Both sulphate-reducing groups were also detected in the methanogenic zone. Similarly, Archaea were detected throughout the profile, not only in the methanogenic zone but also in the upper and lower sulphate-reducing zones. [source] Determination of Lithium Contents in Silicates by Isotope Dilution ICP-MS and its Evaluation by Isotope Dilution Thermal Ionisation Mass SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 3 2004Takuya Moriguti Lithium; ICP-MS avec dilution isotopique; TIMS; matériaux silicatés de référence; météorites A precise and simple method for the determination of lithium concentrations in small amounts of silicate sample was developed by applying isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS). Samples plus a Li spike were digested with HF-HClO4, dried and diluted with HNO3, and measured by ICP-MS. No matrix effects were observed for 7Li/6Li in rock solutions with a dilution factor (DF) of 97 at an ICP power of 1.7 kW. By this method, the determination of 0.5 ,g g -1 Li in a silicate sample of 1 mg can be made with a blank correction of < 1%. Lithium contents of ultrabasic to acidic silicate reference materials (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR-1 and JR-2 from the Geological Survey of Japan, and PCC-1 from the US Geological Survey) and chondrites (three different Allende and one Murchison sample) of 8 to 81 mg were determined. The relative standard deviation (RSD) was typically < 1.7%. Lithium contents of these samples were further determined by isotope dilution-thermal ionisation mass spectrometry (ID-TIMS). The relative differences between ID-ICP-MS and ID-TIMS were typically < 2%, indicating the high accuracy of ID-ICP-MS developed in this study. Nous avons développé une méthode simple et précise de détermination des concentrations en lithium dans de très petits échantillons silicatés. Elle est basée sur la méthode de dilution isotopique couplée à l'analyse par spectrométrie de masse avec couplage induit (ID-ICP-MS). Les échantillons auxquels est ajouté le spike de Li, sont mis en solution avec un mélange HF-HclO4, évaporés à sec, puis repris avec HNO3 et analysés à l'ICP-MS. Aucun effet de matrice n'est observé sur les rapports 7Li/6Li dans les solutions quand les facteurs de dilution sont 97 et qu'elles sont analysées avec une puissance du plasma de 1.7 kW. Par cette méthode, la détermination de 0.5 ,g g -1 de Li dans un échantillon silicaté de 1 mg peut être effectuée avec une correction de blanc < 1 %. Les teneurs en lithium des matériaux de référence de composition ultrabasique à acide (JP-1, JB-2, JB-3, JA-1, JA-2, JA-3, JR- 1 et JR-2 du Service Géologique du Japon, et PCC-1 du Service Géologique des USA) et de chondrites (trois échantillons différents d'Allende et un de Murchison), de poids variant entre 8 et 81 mg ont été déterminées. La déviation standard relative typique était < 1.7%. Les teneurs en lithium de ces échantillons ont été ensuite mesurées par dilution isotopique et spectrométrie de masse à thermo-ionisation (ID-TIMS). Les différences entre les résultats obtenus par ID-ICP-MS et ID-TIMS étaient < 2%, démontrant ainsi la grande justesse de la technique ID-ICP-MS développée dans cette étude. [source] Effect of cream treatment on phospholipids and protein recovery in butter-making processINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2008Michel Britten Summary A simple approach is proposed to recover native protein and phospholipid fractions from butter-making process using equipments available in dairy-processing plant. A washing treatment was used to remove protein from the cream and increase the phospholipids purity in buttermilk. Cream from a first separation was diluted with milk ultrafitration permeate and separated a second time. A 10X dilution factor reduced protein concentration in the cream from 1.6 ± 0.2 to 0.52 ± 0.03%. As a result, the phospholipids to protein ratio in buttermilk increased from 53 ± 10 to 172 ± 7 mg g,1. In butter-making process, an important portion of total phospholipids (,26%) is retained in butter. Butter serum made from washed cream could then be used to produce phospholipid concentrates with phospholipids to protein ratio of 473 ± 3 mg g,1. Interestingly, the extracts from butter serum are characterised by a higher proportion of sphingomyelin compared with those from buttermilk. [source] The effect of dilution on the in vitro erosive potential of a range of dilutable fruit drinksINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 4 2008MARGARET L. HUNTER Background., Only one previous study has investigated the effect which dilution has on the erosive potential of dilutable fruit drinks. Based solely on measurement of neutralizable acidity, the authors concluded that the erosive potential of diluting juices may be reduced substantially by the addition of water. This has not been verified in an in vitro enamel erosion model. Objective., The aim of this study was to examine the effect of dilution on the erosive potential of five dilutable fruit drinks. Methods., For each product, the erosive potential of three dilutions (1 : 3, 1 : 6 and 1 : 15) was assessed by measuring the initial pH and neutralizable acidity; in vitro enamel erosion was measured by profilometry following immersion for 1 h. Results., For the majority of products, increasing dilution from 1 : 3 to 1 : 15 produced a statistically significant rise in initial pH, though they remained markedly acidic. Increasing the dilution factor consistently produced a statistically significant decrease in neutralizable acidity. Increasing the dilution factor from 1 : 3 to 1 : 15 produced a statistically significant reduction in in vitro enamel erosion in only three of the five products tested. Conclusions., Increasing the dilution factor of dilutable fruit drinks within a range likely to be acceptable to the consumer may not effectively reduce their erosive potential. [source] Effects of NaCl Concentration on Salting-in and Dilution During Salting-out on Soy Protein FractionationJOURNAL OF FOOD SCIENCE, Issue 4 2006N. A. Deak ABSTRACT:, Glycinin and ,-conglycinin are the main storage proteins in soybeans that can be fractionated by using alkali extraction, SO2, salting-in with NaCl, salting-out by dilution and pH adjustment to produce a glycinin-rich fraction, a ,-conglycinin,rich fraction, and an intermediate fraction, which is a mixture of the two proteins. Two different strategies were employed to optimize the procedure to achieve high efficiency in recovering the ,-conglycinin,rich fraction. The first strategy was to optimize salting-in effects of NaCl, and the effects of NaCl concentration on the yields and purities of the protein fractions were investigated. The maximum protein yield of the ,-conglycinin,rich fraction was obtained at 500 mM NaCl, but at the expense of purity. The optimum NaCl concentration was 250 mM, at which good protein yield (18.5%) and purity (84.5%) were achieved. At higher NaCl concentrations, the protein yields of the intermediate fractions were significantly lower, and the protein loss in the whey fraction increased. The second strategy was to improve the salting-out step for the ,-conglycinin,rich fraction. At 0- and 0.5-fold dilution, the purities and yields of the ,-conglycinin,rich fractions were significantly lower than at 1.0- and 2.0-fold dilution. There were no differences in protein yields or purities when using 1.0- or 2.0-fold dilution. According to these results, the recommended NaCl concentration for the salting-in step is 250 mM and the dilution factor for salting-out is 1.0. [source] Estimating numbers of infectious units from serial dilution assaysJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 1 2006Nigel Stallard Summary., The paper concerns the design and analysis of serial dilution assays to estimate the infectivity of a sample of tissue when it is assumed that the sample contains a finite number of indivisible infectious units such that a subsample will be infectious if it contains one or more of these units. The aim of the study is to estimate the number of infectious units in the original sample. The standard approach to the analysis of data from such a study is based on the assumption of independence of aliquots both at the same dilution level and at different dilution levels, so that the numbers of infectious units in the aliquots follow independent Poisson distributions. An alternative approach is based on calculation of the expected value of the total number of samples tested that are not infectious. We derive the likelihood for the data on the basis of the discrete number of infectious units, enabling calculation of the maximum likelihood estimate and likelihood-based confidence intervals. We use the exact probabilities that are obtained to compare the maximum likelihood estimate with those given by the other methods in terms of bias and standard error and to compare the coverage of the confidence intervals. We show that the methods have very similar properties and conclude that for practical use the method that is based on the Poisson assumption is to be recommended, since it can be implemented by using standard statistical software. Finally we consider the design of serial dilution assays, concluding that it is important that neither the dilution factor nor the number of samples that remain untested should be too large. [source] Software algorithm for automatic interpretation of mass spectra of glycerolipidsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2002J.-P. Kurvinen A new software algorithm for automatic interpretation of mass spectra of glycerolipids has been developed. The algorithm utilizes a user-specified list of parameters needed to process the spectra. The compounds in mass spectra are identified according to range of measured m/z values, after which the spectra are automatically corrected by the content of naturally occurring isotopes and ion intensities of identified compounds by response correction factors. Automatic processing of the spectra was shown to be accurate and reliable by testing with numerous spectra of glycerophospholipids obtained by liquid chromatography/electrospray ionization mass spectrometry and by comparing the results with manual interpretation of the spectra. If quantitative analysis using internal standards is performed, all the identified compounds in the sample are quantified automatically. A dilution factor may be defined for each sample and is applied to correct the alterations in sample concentration during sample preparation. Processing of several replicate spectra simultaneously produces mean results with standard deviations. The software may also be used to subtract the results of two analyses and to calculate the mean result of replicate subtractions. The algorithm was shown to save time and labor in repetitive processing of mass spectra of similar type. It may be applied to processing of spectra obtained by various mass spectrometric methods. Copyright © 2002 John Wiley & Sons, Ltd. [source] Carbon dioxide generation calorimetry,Errors induced by the simplifying assumptions in the standard test methodsFIRE AND MATERIALS, Issue 2 2009S. Brohez Abstract Carbon dioxide generation (CDG) calorimetry is commonly used for measuring heat release rates of materials. Calorimetric equation provided in the ASTM E 2058 and the NFPA code 287 is a simplified equation since the water content in the ambient air and the fumes as well as the expansion factor of the combustion gases are neglected. This paper provides general equation for CDG calorimetry based on the Tewarson formulation. A comparison is proposed between the Standard test methods (simplified equation) and the general one. It is shown that the errors induced by the simplifying assumptions are negligible for oxygen depletion factor values commonly encountered in the Fire Propagation Apparatus (where large dilution factors of the combustion gases are used before the measurements of species concentrations). Copyright © 2009 John Wiley & Sons, Ltd. [source] EVALUATION OF THE CHARACTER IMPACT ODORANTS IN SKIM MILK POWDER BY SENSORY STUDIES ON MODEL MIXTURESJOURNAL OF SENSORY STUDIES, Issue 1 2004Y. KARAGÜL-YÜCEER ABSTRACT The objective of this study was to verify key aroma-active compounds responsible for reconstituted fresh skim milk powder (SMP) aroma using threshold analysis, odor activity values, and model systems. Twelve odor-active compounds of SMP and one odor-active compound from fluid milk were selected based on flavor dilution factors from gas chromatography-olfactometry. Thresholds for the 13 odor-active compounds were identified using five-set ascending forced choice threshold analysis in odor-free water and fluid skim milk. Model systems were prepared using rehydrated milk retentate (RMR). The aroma of each model was evaluated by descriptive sensory analysis and by difference-from-control testing using a trained panel. The aroma of reconstituted fresh SMP and liquid skim milk were used as controls. Models containing a mixture of twelve of the thirteen chemicals had the most similar odor characteristics to rehydrated SMP aroma (9.0/10) indicating that these compounds constitute the character impact odorants of rehydrated fresh SMP. [source] Comparison of inductively coupled plasma mass spectrometry techniques in the determination of platinum in urine: quadrupole vs. sector fieldRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2005Sandro Spezia In recent years the increasing use of platinum (Pt) both in medical and in industrial applications has caused its growing anthropogenic emission and spread in the environment. Pt is released into the atmosphere by exhaust catalytic converters, and Pt compounds are often used in antitumour therapies. As a consequence, significant amounts of Pt can be detected in hospital wastewaters. This can lead to an increase in the exposure levels to Pt, especially in urban areas. It is therefore necessary to determine Pt reference values in the general population, by using suitable procedures able to achieve adequate analytical performances. Several measurements of Pt in biological fluids have been reported, but the analytical methods used for the determination of Pt often lack information about the uncertainty of the results, especially for low concentrations of urinary Pt in non-occupationally exposed subjects. The present paper considers the measurement of urinary Pt levels in a general population group from central Italy, by both quadrupole (Q) and sector field (SF) inductively coupled plasma mass spectrometry (ICP-MS). The two procedures were validated and their expanded uncertainties were evaluated. The limits of detection (LODs), calculated taking into account dilution factors, were 0.18 and 0.05,ng L,1 of Pt for the Q and SF procedures, respectively. The median value observed was 4.13,ng L,1 of Pt in urine, while the relative combined uncertainty at 5,ng L,1 was below 20% with both ICP-MS techniques. These data are in good agreement with those reported in the literature for similar studies. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||