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Many Parameters (many + parameter)
Selected AbstractsDetermination of Trace Amounts of Copper in Tap Water Samples with a Calix[4]arene Modified Carbon Paste Electrode by Differential Pulse Anodic Stripping VoltammetryELECTROANALYSIS, Issue 10 2007Çelik Canpolat Abstract A calix[4]arene modified carbon paste electrode was used for trace determination of copper. The study of the preconcentration of copper as well as the other heavy metal ions at the modified electrode, with subsequent measurement by differential pulse anodic stripping voltammetry (DPASV), indicates the efficient open-circuit accumulation of the analytes onto the electrode. Many parameters such as the composition of the paste, pH, preconcentration time and stirring rate influence the response of the measurement. The procedure was optimized for copper determination. For a 10-minute preconcentration time at pH,6.5,7.5, the detection limit (LOD) was 1.1,,g L,1. The optimized method was successfully applied to the determination of copper in tap water sample by means of standard addition procedure. The copper content of the sample was comparable with the result obtained with AAS method. [source] When does parameter drift decrease the uncertainty in extinction risk estimates?ECOLOGY LETTERS, Issue 12 2003Stephen P. Ellner Abstract Halley (2003) proposed that parameter drift decreases the uncertainty in long-range extinction risk estimates, because drift mitigates the extreme sensitivity of estimated risk to estimated mean growth rate. However, parameter drift has a second, opposing effect: it increases the uncertainty in parameter estimates from a given data set. When both effects are taken into account, parameter drift can increase, sometimes substantially, the uncertainty in risk estimates. The net effect depends sensitively on the type of drift and on which model parameters must be estimated from observational data on the population at risk. In general, unless many parameters are estimated from independent data, parameter drift increases the uncertainty in extinction risk. These findings suggest that more mechanistic PVA models, using long-term data on key environmental variables and experiments to quantify their demographic impacts, offer the best prospects for escaping the high data requirements when extinction risk is estimated from observational data. [source] The role of policy instruments for promoting combined heat and power production with low CO2 emissions in district heating systemsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2005Å. Marbe Abstract Policy instruments clearly influence the choice of production technologies and fuels in large energy systems, including district heating networks. Current Swedish policy instruments aim at promoting the use of biofuel in district heating systems, and at promoting electric power generation from renewable energy sources. However, there is increasing pressure to harmonize energy policy instruments within the EU. In addition, natural gas based combined cycle technology has emerged as the technology of choice in the power generation sector in the EU. This study aims at exploring the role of policy instruments for promoting the use of low CO2 emissions fuels in high performance combined heat and power systems in the district heating sector. The paper presents the results of a case study for a Swedish district heating network where new large size natural gas combined cycle (NGCC) combined heat and power (CHP) is being built. Given the aim of current Swedish energy policy, it is assumed that it could be of interest in the future to integrate a biofuel gasifier to the CHP plant and co-fire the gasified biofuel in the gas turbine unit, thereby reducing usage of fossil fuel. The goals of the study are to evaluate which policy instruments promote construction of the planned NGCC CHP unit, the technical performance of an integrated biofuelled pressurized gasifier with or without dryer on plant site, and which combination of policy instruments promote integration of a biofuel gasifier to the planned CHP unit. The power plant simulation program GateCycle was used for plant performance evaluation. The results show that current Swedish energy policy instruments favour investing in the NGCC CHP unit. The corresponding cost of electricity (COE) from the NGCC CHP unit is estimated at 253 SEK MWh,1, which is lower than the reference power price of 284 SEK MWh,1. Investing in the NGCC CHP unit is also shown to be attractive if a CO2 trading system is implemented. If the value of tradable emission permits (TEP) in such as system is 250 SEK tonne,1, COE is 353 SEK MWh,1 compared to the reference power price of 384 SEK MWh,1. It is possible to integrate a pressurized biofuel gasifier to the NGCC CHP plant without any major re-design of the combined cycle provided that the maximum degree of co-firing is limited to 27,38% (energy basis) product gas, depending on the design of the gasifier system. There are many parameters that affect the economic performance of an integrated biofuel gasifier for product gas co-firing of a NGCC CHP plant. The premium value of the co-generated renewable electricity and the value of TEPs are very important parameters. Assuming a future CO2 trading system with a TEP value of 250 SEK tonne,1 and a premium value of renewable electricity of 200 SEK MWh,1 COE from a CHP plant with an integrated biofuelled gasifier could be 336 SEK MWh,1, which is lower than both the reference market electric power price and COE for the plant operating on natural gas alone. Copyright © 2005 John Wiley & Sons, Ltd. [source] Satellite image segmentation using hybrid variable genetic algorithmINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 3 2009Mohamad M. Awad Abstract Image segmentation is an important task in image processing and analysis. Many segmentation methods have been used to segment satellite images. The success of each method depends on the characteristics of the acquired image such as resolution limitations and on the percentage of imperfections in the process of image acquisition due to noise. Many of these methods require a priori knowledge which is difficult to obtain. Some of them are parametric statistical methods that use many parameters which are dependent on image property. In this article, a new unsupervised nonparametric method is developed to segment satellite images into homogeneous regions without any a priori knowledge. The new method is called hybrid variable genetic algorithm (HVGA). The variability is found in the variable number of cluster centers and in the changeable mutation rate. In addition, this new method uses different heuristic processes to increase the efficiency of genetic algorithm in avoiding local optimal solutions. Experiments performed on two different satellite images (Landsat and Spot) proved the high accuracy and efficiency of HVGA compared with another two unsupervised and nonparametric segmentation methods genetic algorithm (GA) and self-organizing map (SOM). The verification of the results included stability and accuracy measurements using an evaluation method implemented from the functional model (FM) and field surveys. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 199,207, 2009 [source] The gingival biotype revisited: transparency of the periodontal probe through the gingival margin as a method to discriminate thin from thick gingivaJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 5 2009Tim De Rouck Abstract Aim: To detect groups of subjects in a sample of 100 periodontally healthy volunteers with different combinations of morphometric data related to central maxillary incisors and surrounding soft tissues. Material and Methods: Four clinical parameters were included in a cluster analysis: crown width/crown length ratio (CW/CL), gingival width (GW), papilla height (PH) and gingival thickness (GT). The latter was based on the transparency of the periodontal probe through the gingival margin while probing the buccal sulcus. Every first volunteer out of 10 was re-examined to evaluate intra-examiner repeatability for all variables. Results: High agreement between duplicate recordings was found for all parameters, in particular for GT, pointing to 85% (,=0.70; p=0.002). The partitioning method identified three clusters with specific features. Cluster A1 (nine males, 28 females) displayed a slender tooth form (CW/CL=0.79), a GW of 4.92 mm, a PH of 4.29 mm and a thin gingiva (probe visible on one or both incisors in 100% of the subjects). Cluster A2 (29 males, five females) presented similar features (CW/CL=0.77; GW=5.2 mm; PH=4.54 mm), except for GT. These subjects showed a clear thick gingiva (probe concealed on both incisors in 97% of the subjects). The third group (cluster B: 12 males, 17 females) differed substantially from the other clusters in many parameters. These subjects showed a more quadratic tooth form (CW/CL=0.88), a broad zone of keratinized tissue (GW=5.84 mm), low papillae (PH=2.84 mm) and a thick gingiva (probe concealed on both incisors in 83% of the subjects). Conclusions: The present analysis, using a simple and reproducible method for GT assessment, confirmed the existence of gingival biotypes. A clear thin gingiva was found in about one-third of the sample in mainly female subjects with slender teeth, a narrow zone of keratinized tissue and a highly scalloped gingival margin corresponding to the features of the previously introduced "thin-scalloped biotype" (cluster A1). A clear thick gingiva was found in about two-thirds of the sample in mainly male subjects. About half of them showed quadratic teeth, a broad zone of keratinized tissue and a flat gingival margin corresponding to the features of the previously introduced "thick-flat biotype" (cluster B). The other half could not be classified as such. These subjects showed a clear thick gingiva with slender teeth, a narrow zone of keratinized tissue and a high gingival scallop (cluster A2). [source] Anti- Helicobacter pylori therapy in India: Differences in eradication efficiency associated with particular alleles of vacuolating cytotoxin (vacA) geneJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 2 2003SUJIT CHAUDHURI Abstract Background and Aims:, The efficiency of Helicobacter pylori eradication varies geographically, as do many parameters that might affect therapeutic efficiency, including bacterial genotype. The aim of the present study was to determine the efficiency of H. pylori eradication using a 10-day proton pump inhibitor-based triple-therapy regimen (omeprazole, clarithromycin and amoxycillin) in an eastern Indian patient population, and to find out the relationship, if any, of the success or failure of the therapy to known features of bacterial genotype. Methods,Helicobacter pylori infections were analyzed in 66 duodenal ulcer patients by upper gastrointestinal endoscopy, rapid urease tests, histology and culture. The cytotoxin-associated gene (cagA) and vacuolating cytotoxin (vacA) gene status of cultured strains were studied by polymerase chain reaction. Treatment was given for 10 days and endoscopy was repeated at 4 and 12 weeks post therapy to monitor ulcer healing and H. pylori eradication. Results:, Ulcer healing was observed in 60 patients (96.77%). Helicobacter pylori was eradicated in 41 (62.12% intention to treat, 66.13% per protocol) of the 66 duodenal ulcer patients, but not in the other 25. The bacteria from 47 patients were genotyped. The only significant disease-associated difference in patterns observed was that the vacA m1 allele was represented more disproportionately among patients with eradication failures (68%) than in those with successful eradication (39%) (P < 0.05) No significant association of vacAs1 (signal sequence allele) or cag pathogenicity island status with persistence was detected. Conclusions:, This study highlights the public health need for cheaper, more cost-effective anti- H. pylori therapies for developing countries, and suggests that subtle features of bacterial genotype can influence therapeutic efficiency. The possibility that particular vacA mid region alleles affect persistence, perhaps through toxin action on particular gastric cell types, merits further study. [source] Apoptosis and necrosis in liver diseaseLIVER INTERNATIONAL, Issue 2 2004Hartmut Jaeschke Abstract: Liver cell injury and cell death is a prominent feature in all liver disease processes. During the last 5,10 years, most research activities focused almost exclusively on evaluating apoptotic cell death and the corresponding intracellular signaling pathways. Although this effort led to substantial progress in our understanding of the mechanisms of apoptosis, it also created substantial confusion regarding the predominant mode of cell death and the relevance of apoptosis in a variety of liver disease models, as discussed in this review for acetaminophen and troglitazone hepatotoxicity, obstructive cholestasis and viral hepatitis. Part of the problem is related to the fact that there is no specific assay or parameter, with the exception of morphological changes in vivo, which allows the unequivocal distinction between apoptosis and oncotic necrosis. In addition, some aspects of the signaling pathways are similar. Therefore, to make progress in identifying relevant pharmacological intervention strategies to prevent or attenuate human liver disease processes, it is of critical importance to apply several different experimental approaches and analyze as many parameters as possible. In addition, positive controls for the assumed process should be used whenever possible and mechanisms of cell injury should only be investigated in model systems relevant for the human pathophysiology. [source] Experimental model for creep groan analysisLUBRICATION SCIENCE, Issue 1 2009Z. Fuadi Abstract A simple experimental model for a fundamental investigation of creep groan generating mechanism is introduced. It is a calliper slider model that is developed based on the operating principle of a real brake system and has the ability to generate creep groan quantitatively comparable to those recorded on the real brake system. The advantage of the model is that it is possible to take into account many parameters, such as surface roughness of mating materials, properties of mating materials and structure's stiffness, so that their effects for creep groan phenomenon can be analysed. The usefulness and potential of the model are demonstrated by its ability to generate creep groan using a real brake lining material that is well known to the brake industry as a material that easily produces creep groan in real applications. Parametric analysis is conducted, and the effects of several sensitive parameters to stick-slip frequency characteristic of creep groan are highlighted. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fretting behaviour of low-friction coatingsLUBRICATION SCIENCE, Issue 3 2005C. Langlade Abstract The choice of an appropriate low-friction coating for an industrial application is generally a difficult task. As many parameters are involved and are often unknown, selection criteria are hard to define. In order to elucidate the case of fretting conditions, a simulator has been used to reproduce the degradation mechanisms observed for real situations. Numerous experiments performed with this machine permit one to define endurance life criteria. The evolution of the life observed has been analysed as a function of the contact pressure and the film thickness. Using a Wöhler approach, endurance curves have been plotted that give useful information for selecting appropriate coatings. As other parameters may be of some interest, performance indices have been associated with them, and the results can be presented on a multi-axis (polar) diagram. [source] Statistical hypothesis testing in intraspecific phylogeography: nested clade phylogeographical analysis vs. approximate Bayesian computationMOLECULAR ECOLOGY, Issue 2 2009ALAN R. TEMPLETON Abstract Nested clade phylogeographical analysis (NCPA) and approximate Bayesian computation (ABC) have been used to test phylogeographical hypotheses. Multilocus NCPA tests null hypotheses, whereas ABC discriminates among a finite set of alternatives. The interpretive criteria of NCPA are explicit and allow complex models to be built from simple components. The interpretive criteria of ABC are ad hoc and require the specification of a complete phylogeographical model. The conclusions from ABC are often influenced by implicit assumptions arising from the many parameters needed to specify a complex model. These complex models confound many assumptions so that biological interpretations are difficult. Sampling error is accounted for in NCPA, but ABC ignores important sources of sampling error that creates pseudo-statistical power. NCPA generates the full sampling distribution of its statistics, but ABC only yields local probabilities, which in turn make it impossible to distinguish between a good fitting model, a non-informative model, and an over-determined model. Both NCPA and ABC use approximations, but convergences of the approximations used in NCPA are well defined whereas those in ABC are not. NCPA can analyse a large number of locations, but ABC cannot. Finally, the dimensionality of tested hypothesis is known in NCPA, but not for ABC. As a consequence, the ,probabilities' generated by ABC are not true probabilities and are statistically non-interpretable. Accordingly, ABC should not be used for hypothesis testing, but simulation approaches are valuable when used in conjunction with NCPA or other methods that do not rely on highly parameterized models. [source] Comparison of the quality of some Croatian and German wheat varieties according to the German standard protocolMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 2 2003Ljiljana Unbehend Abstract Ten Croatian and five German wheat varieties were tested. They were carried out using the German standard testing protocol. The results demonstrated that the quality of the Croatian wheat varieties could be ranged in A,C quality groups according to the German testing protocol. Croatian wheat varieties were comparable in many parameters (protein content, hardness, water absorption, dough handling properties and volume yield) with chosen German wheat varieties. Some differences were found in falling number, sedimentation value, flour yield, and ash value number. [source] Mechanisms of cholinergic dysfunction in rabbits following recurrent aspiration of cow's milk,PEDIATRIC PULMONOLOGY, Issue 6 2001Gary L. Larsen MD Abstract Recurrent aspiration of cow's milk has been shown to alter neural control of airways in young rabbits (Gelfand et al., 1997). The purpose of this study was to define the mechanisms responsible for in vitro cholinergic hyperresponsiveness in this model. Beginning at 1 week of age, rabbits received either 0.5 mL/kg whole cow's milk or sterile saline intranasally while under light anesthesia. This was repeated each weekday for 2 weeks. At 8 weeks of age, rabbits were sacrificed. Portions of lungs underwent lavage with sterile saline. Tracheal smooth muscle (TSM) segments were also removed. Segments were assessed for acetylcholine (ACh) release by high-performance liquid chromatography ( HPLC) with electrochemical detection or acetylcholinesterase (AChE) kinetic activity by spectrophotometry. Substance P (SP), a neuropeptide that can increase ACh release from nerves, was also assessed using an enzyme immunoassay to define the content in lavage and TSM segments. Immunohistochemistry for SP within airways was also assessed. We found that recurrent aspiration of milk led to statistically significant alterations in many parameters. Acetylcholine release was significantly greater in segments of airways from rabbits that had aspirated cow's milk (27.5,±,1.7 vs. 20.1,±,1.6 pmol/min/g tissue) than saline. At the same time, AChE activity was less in the group that aspirated milk (8.7,±,0.4 vs. 10.2,±,0.5 nmol/min/mg protein) compared to saline. The amount of SP within both lavage as well as tissue homogenates was greater in the group that had aspirated the foreign protein (159.1,±,28.9 vs. 41.9,±,5.2 pmol/mg protein in lavage; 158.7,±,31.9 vs. 80.5,±,7.8 pmol/mg protein in tissues) than saline controls. While total cholinergic nerve density as assessed by choline acetyltransferase was not significantly different between groups, SP-positive immunoreactive nerves were easily identified in the group that aspirated cow's milk. This study suggests that cholinergic hyperresponsiveness caused by repeated aspiration of milk is due to several abnormalities, including prejunctional (increase in ACh release) as well as junctional (decrease in AChE) mechanisms within the airways. In addition, an upregulation of SP within airways is part of this process. Pediatr Pulmonol. 2001; 32:409,417. © 2001 Wiley-Liss, Inc. [source] Can density functional theory (DFT) be used as an aid to a deeper understanding of tandem mass spectrometric fragmentation pathways?RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2009Alexander Alex Prediction of tandem mass spectrometric (MS/MS) fragmentation for non-peptidic molecules based on structure is of immense interest to the mass spectrometrist. If a reliable approach to MS/MS prediction could be achieved its impact within the pharmaceutical industry could be immense. Many publications have stressed that the fragmentation of a molecular ion or protonated molecule is a complex process that depends on many parameters, making prediction difficult. Commercial prediction software relies on a collection of general heuristic rules of fragmentation, which involve cleaving every bond in the structure to produce a list of ,expected' masses which can be compared with the experimental data. These approaches do not take into account the thermodynamic or molecular orbital effects that impact on the molecule at the point of protonation which could influence the potential sites of bond cleavage based on the structural motif. A series of compounds have been studied by examining the experimentally derived high-resolution MS/MS data and comparing it with the in silico modelling of the neutral and protonated structures. The effect that protonation at specific sites can have on the bond lengths has also been determined. We have calculated the thermodynamically most stable protonated species and have observed how that information can help predict the cleavage site for that ion. The data have shown that this use of in silico techniques could be a possible way to predict MS/MS spectra. Copyright © 2009 John Wiley & Sons, Ltd. [source] Using Case-parent Triads to Estimate Relative Risks Associated with a Candidate HaplotypeANNALS OF HUMAN GENETICS, Issue 3 2009Min Shi Summary Estimating haplotype relative risks in a family-based study is complicated by phase ambiguity and the many parameters needed to quantify relative risks for all possible diplotypes. This problem becomes manageable if a particular haplotype has been implicated previously as relevant to risk. We fit log-linear models to estimate the risks associated with a candidate haplotype relative to the aggregate of other haplotypes. Our approach uses existing haplotype-reconstruction algorithms but requires assumptions about the distribution of haplotypes among triads in the source population. We consider three levels of stringency for those assumptions: Hardy-Weinberg Equilibrium (HWE), random mating, and no assumptions at all. We assessed our method's performance through simulations encompassing a range of risk haplotype frequencies, missing data patterns, and relative risks for either offspring or maternal genetic effects. The unconstrained model provides robustness to bias from population structure but requires excessively large sample sizes unless there are few haplotypes. Assuming HWE accommodates many more haplotypes but sacrifices robustness. The model assuming random mating is intermediate, both in the number of haplotypes it can handle and in robustness. To illustrate, we reanalyze data from a study of orofacial clefts to investigate a 9-SNP candidate haplotype of the IRF6 gene. [source] | |||||||||||||||||||