979 resultados para variational mean-field method
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The result and experience of field implementation of the maturity method on 14 portland cement concrete (PCC) paving and patching projects during 1995 are summarized in this report. The procedure for developing reference PCC maturity-strength curve of concrete is discussed. Temperature measurement as well as effects of datum temperature, entrained air content and type of aggregate on maturity-strength relationship are examined. Some limitations of the maturity method are discussed. The available field experience and results indicate that the maturity method provides a simple approach to determine strength of concrete, and can be easily implemented in field paving and patching projects. The use of the maturity method may result in reduced project construction time.
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The role of busulfan (Bu) metabolites in the adverse events seen during hematopoietic stem cell transplantation and in drug interactions is not explored. Lack of availability of established analytical methods limits our understanding in this area. The present work describes a novel gas chromatography-tandem mass spectrometric assay for the analysis of sulfolane (Su) in plasma of patients receiving high-dose Bu. Su and Bu were extracted from a single 100 μL plasma sample by liquid-liquid extraction. Bu was separately derivatized with 2,3,5,6-tetrafluorothiophenolfluorinated agent. Mass spectrometric detection of the analytes was performed in the selected reaction monitoring mode on a triple quadrupole instrument after electronic impact ionization. Bu and Su were analyzed with separate chromatographic programs, lasting 5 min each. The assay for Su was found to be linear in the concentration range of 20-400 ng/mL. The method has satisfactory sensitivity (lower limit of quantification, 20 ng/mL) and precision (relative standard deviation less than 15 %) for all the concentrations tested with a good trueness (100 ± 5 %). This method was applied to measure Su from pediatric patients with samples collected 4 h after dose 1 (n = 46), before dose 7 (n = 56), and after dose 9 (n = 54) infusions of Bu. Su (mean ± SD) was detectable in plasma of patients 4 h after dose 1, and higher levels were observed after dose 9 (249.9 ± 123.4 ng/mL). This method may be used in clinical studies investigating the role of Su on adverse events and drug interactions associated with Bu therapy.
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Background: b-value is the parameter characterizing the intensity of the diffusion weighting during image acquisition. Data acquisition is usually performed with low b value (b~1000 s/mm2). Evidence shows that high b-values (b>2000 s/mm2) are more sensitive to the slow diffusion compartment (SDC) and maybe more sensitive in detecting white matter (WM) anomalies in schizophrenia.Methods: 12 male patients with schizophrenia (mean age 35 +/-3 years) and 16 healthy male controls matched for age were scanned with a low b-value (1000 s/mm2) and a high b-value (4000 s/mm2) protocol. Apparent diffusion coefficient (ADC) is a measure of the average diffusion distance of water molecules per time unit (mm2/s). ADC maps were generated for all individuals. 8 region of interests (frontal and parietal region bilaterally, centrum semi-ovale bilaterally and anterior and posterior corpus callosum) were manually traced blind to diagnosis.Results: ADC measures acquired with high b-value imaging were more sensitive in detecting differences between schizophrenia patients and healthy controls than low b-value imaging with a gain in significance by a factor of 20- 100 times despite the lower image Signal-to-noise ratio (SNR). Increased ADC was identified in patient's WM (p=0.00015) with major contributions from left and right centrum semi-ovale and to a lesser extent right parietal region.Conclusions: Our results may be related to the sensitivity of high b-value imaging to the SDC believed to reflect mainly the intra-axonal and myelin bound water pool. High b-value imaging might be more sensitive and specific to WM anomalies in schizophrenia than low b-value imaging
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A review of the Iowa Department of Transportation's field data collection and reporting system has been performed. Included were several systems used by the Office of Construction and Local Jurisdictions. The entire field data collection and reporting systems for asphalt cement concrete (ACC) paving, portland cement concrete (PCC) paving, and PCC structures were streamlined and computerized. The field procedures for materials acceptance were also reviewed. Best practices were identified and a method was developed to prioritize materials so transportation agencies could focus their efforts on high priority materials. Iowa State University researchers facilitated a discussion about Equal Employment Opportunity (EEO) and Affirmative Action (AA) procedures between the Office of Construction field staff and the Office of Contracts. A set of alternative procedures was developed. Later the Office of Contracts considered these alternatives as they developed new procedures that are currently being implemented. The job close-out package was reviewed and two unnecessary procedures were eliminated. Numerous other procedures were reviewed and flowcharted. Several changes have been recommended that will increase efficiency and allow staff time to be devoted to higher priority activities. It is estimated the improvements in ACC paving, PCC paving and structural concrete will by similar to three full time equivalent (FTE) positions to field construction, field materials and Office of Materials. Elimination of EEO interviews will be equivalent to one FTE position. It is estimated that other miscellaneous changes will be equivalent to at least one other FTE person. This is a total five FTEs. These are conservative estimates based on savings that are easily quantified. It is likely that total positive effect is greater when items that are difficult to quantify are considered.
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Cold in-place recycling (CIR) has become an attractive method for rehabilitating asphalt roads that have good subgrade support and are suffering distress related to non-structural aging and cracking of the pavement layer. Although CIR is widely used, its use could be expanded if its performance were more predictable. Transportation officials have observed roads that were recycled under similar circumstances perform very differently for no clear reason. Moreover, a rational mix design has not yet been developed, design assumptions regarding the structural support of the CIR layer remain empirical and conservative, and there is no clear understanding of the cause-effect relationships between the choices made during the design/construction process and the resulting performance. The objective of this project is to investigate these relationships, especially concerning the age of the recycled pavement, cumulative traffic volume, support conditions, aged engineering properties of the CIR materials, and road performance. Twenty-four CIR asphalt roads constructed in Iowa from 1986 to 2004 were studied: 18 were selected from a sample of roads studied in a previous research project (HR-392), and 6 were selected from newer CIR projects constructed after 1999. This report summarizes the results of a comprehensive program of field distress surveys, field testing, and laboratory testing for these CIR asphalt roads. The results of this research can help identify changes that should be made with regard to design, material selection, and construction in order to lengthen the time between rehabilitation cycles and improve the performance and cost-effectiveness of future recycled roads.
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The multiscale finite-volume (MSFV) method has been derived to efficiently solve large problems with spatially varying coefficients. The fine-scale problem is subdivided into local problems that can be solved separately and are coupled by a global problem. This algorithm, in consequence, shares some characteristics with two-level domain decomposition (DD) methods. However, the MSFV algorithm is different in that it incorporates a flux reconstruction step, which delivers a fine-scale mass conservative flux field without the need for iterating. This is achieved by the use of two overlapping coarse grids. The recently introduced correction function allows for a consistent handling of source terms, which makes the MSFV method a flexible algorithm that is applicable to a wide spectrum of problems. It is demonstrated that the MSFV operator, used to compute an approximate pressure solution, can be equivalently constructed by writing the Schur complement with a tangential approximation of a single-cell overlapping grid and incorporation of appropriate coarse-scale mass-balance equations.
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This handbook describes the peer review methodology that was applied at the GODIAC project fi eld studies1. The peer review evaluation method as initiated by Otto Adang in the Netherlands and further developed in a European football context (Adang & Brown, 2008) involves experienced police offi cers cooperating with researchers to perform observational fi eld studies to identify good practices and learning points for public order management. The handbook builds on the GODIAC seminars and workshops, for the fi eld study members, which took place in September 2010, January 2012 and January 2013. The handbook has been discussed in the project group and in the steering committee. It is primarily written for the GODIAC fi eld study members as background material for understanding the fi eld study process and for clarifying the different responsibilities that enable active participation in the fi eld study. The handbook has been developed during the project period and incorporates learning points and developments of the peer review method. The handbook aims at promoting the use of fi eld studies for evaluation of policing major events.
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The ability of a PCR-based restriction fragment length polymorphism (RFLP) analysis of the cytochrome b (mtDNA) to distinguish Apodemus alpicola from two other Apodemus species was investigated. The partial sequencing of the cytochrome b allowed the identification of one enzyme as being potentially diagnostic. This was supported by an analysis of 131 specimens previously identified using morphometric and/or allozymic data, indicating that the PCR-based RFLP method provides a rapid and reliable tool for distinguishing A. alpicola from its two co-occurring congenerics. The method is applicable to samples taken in the field for ecological studies, and could easily be adapted to the identification of museum samples.
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A simple method determining airborne monoethanolamine has been developed. Monoethanolamine determination has traditionally been difficult due to analytical separation problems. Even in recent sophisticated methods, this difficulty remains as the major issue often resulting in time-consuming sample preparations. Impregnated glass fiber filters were used for sampling. Desorption of monoethanolamine was followed by capillary GC analysis and nitrogen phosphorous selective detection. Separation was achieved using a specific column for monoethanolamines (35% diphenyl and 65% dimethyl polysiloxane). The internal standard was quinoline. Derivatization steps were not needed. The calibration range was 0.5-80 μg/mL with a good correlation (R(2) = 0.996). Averaged overall precisions and accuracies were 4.8% and -7.8% for intraday (n = 30), and 10.5% and -5.9% for interday (n = 72). Mean recovery from spiked filters was 92.8% for the intraday variation, and 94.1% for the interday variation. Monoethanolamine on stored spiked filters was stable for at least 4 weeks at 5°C. This newly developed method was used among professional cleaners and air concentrations (n = 4) were 0.42 and 0.17 mg/m(3) for personal and 0.23 and 0.43 mg/m(3) for stationary measurements. The monoethanolamine air concentration method described here was simple, sensitive, and convenient both in terms of sampling and analytical analysis.
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Background: Conventional magnetic resonance imaging (MRI) techniques are highly sensitive to detect multiple sclerosis (MS) plaques, enabling a quantitative assessment of inflammatory activity and lesion load. In quantitative analyses of focal lesions, manual or semi-automated segmentations have been widely used to compute the total number of lesions and the total lesion volume. These techniques, however, are both challenging and time-consuming, being also prone to intra-observer and inter-observer variability.Aim: To develop an automated approach to segment brain tissues and MS lesions from brain MRI images. The goal is to reduce the user interaction and to provide an objective tool that eliminates the inter- and intra-observer variability.Methods: Based on the recent methods developed by Souplet et al. and de Boer et al., we propose a novel pipeline which includes the following steps: bias correction, skull stripping, atlas registration, tissue classification, and lesion segmentation. After the initial pre-processing steps, a MRI scan is automatically segmented into 4 classes: white matter (WM), grey matter (GM), cerebrospinal fluid (CSF) and partial volume. An expectation maximisation method which fits a multivariate Gaussian mixture model to T1-w, T2-w and PD-w images is used for this purpose. Based on the obtained tissue masks and using the estimated GM mean and variance, we apply an intensity threshold to the FLAIR image, which provides the lesion segmentation. With the aim of improving this initial result, spatial information coming from the neighbouring tissue labels is used to refine the final lesion segmentation.Results:The experimental evaluation was performed using real data sets of 1.5T and the corresponding ground truth annotations provided by expert radiologists. The following values were obtained: 64% of true positive (TP) fraction, 80% of false positive (FP) fraction, and an average surface distance of 7.89 mm. The results of our approach were quantitatively compared to our implementations of the works of Souplet et al. and de Boer et al., obtaining higher TP and lower FP values.Conclusion: Promising MS lesion segmentation results have been obtained in terms of TP. However, the high number of FP which is still a well-known problem of all the automated MS lesion segmentation approaches has to be improved in order to use them for the standard clinical practice. Our future work will focus on tackling this issue.
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BACKGROUND: The activity of the renin-angiotensin system is usually evaluated as plasma renin activity (PRA, ngAI/ml per h) but the reproducibility of this enzymatic assay is notoriously scarce. We compared the inter and intralaboratory reproducibilities of PRA with those of a new automated chemiluminescent assay, which allows the direct quantification of immunoreactive renin [chemiluminescent immunoreactive renin (CLIR), microU/ml]. METHODS: Aliquots from six pool plasmas of patients with very low to very high PRA levels were measured in 12 centres with both the enzymatic and the direct assays. The same methods were applied to three control plasma preparations with known renin content. RESULTS: In pool plasmas, mean PRA values ranged from 0.14 +/- 0.08 to 18.9 +/- 4.1 ngAI/ml per h, whereas those of CLIR ranged from 4.2 +/- 1.7 to 436 +/- 47 microU/ml. In control plasmas, mean values of PRA and of CLIR were always within the expected range. Overall, there was a significant correlation between the two methods (r = 0.73, P < 0.01). Similar correlations were found in plasmas subdivided in those with low, intermediate and high PRA. However, the coefficients of variation among laboratories found for PRA were always higher than those of CLIR, ranging from 59.4 to 17.1% for PRA, and from 41.0 to 10.7% for CLIR (P < 0.01). Also, the mean intralaboratory variability was higher for PRA than for CLIR, being respectively, 8.5 and 4.5% (P < 0.01). CONCLUSION: The measurement of renin with the chemiluminescent method is a reliable alternative to PRA, having the advantage of a superior inter and intralaboratory reproducibility.
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Background: Our goal was to determine whether short-term intermittent hypoxia exposure, at a level well tolerated by healthy humans and previously shown by our group to increase EPO and erythropoiesis, could mobilizehematopoietic stem cells (HSC) and increase their presence in peripheral circulation. Methods: Four healthy male subjects were subjected to three different protocols: one with only a hypoxic stimulus (OH), another with a hypoxic stimulus plus muscle electrostimulation (HME) and the third with only muscle electrostimulation (OME). Intermittent hypobaric hypoxia exposureconsisted of only three sessions of three hours at barometric pressure 540 hPa (equivalent to an altitude of 5000 m) for three consecutive days, whereas muscular electrostimulation was performed in two separate periods of 25 min in each session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment and 24 h, 48 h, 4 days and 7 days after the last day of hypoxic exposure. Results: There was a clear increase in the number of circulating CD34+ cells after combined hypobaric hypoxia and muscular electrostimulation. This response was not observed after the isolated application of the same stimuli. Conclusion: Our results open a new application field for hypobaric systems as a way to increase efficiency in peripheral HSC collection.
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Background: Our goal was to determine whether short-term intermittent hypoxia exposure, at a level well tolerated by healthy humans and previously shown by our group to increase EPO and erythropoiesis, could mobilizehematopoietic stem cells (HSC) and increase their presence in peripheral circulation. Methods: Four healthy male subjects were subjected to three different protocols: one with only a hypoxic stimulus (OH), another with a hypoxic stimulus plus muscle electrostimulation (HME) and the third with only muscle electrostimulation (OME). Intermittent hypobaric hypoxia exposureconsisted of only three sessions of three hours at barometric pressure 540 hPa (equivalent to an altitude of 5000 m) for three consecutive days, whereas muscular electrostimulation was performed in two separate periods of 25 min in each session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment and 24 h, 48 h, 4 days and 7 days after the last day of hypoxic exposure. Results: There was a clear increase in the number of circulating CD34+ cells after combined hypobaric hypoxia and muscular electrostimulation. This response was not observed after the isolated application of the same stimuli. Conclusion: Our results open a new application field for hypobaric systems as a way to increase efficiency in peripheral HSC collection.
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An analytical model based on Bowen and Holman [1989] is used to prove the existence of instabilities due to the presence of a second extremum of the background vorticity at the front side of the longshore current. The growth rate of the so-called frontshear waves depends primarily upon the frontshear but also upon the backshear and the maximum and the width of the current. Depending on the values of these parameters, either the frontshear or the backshear instabilities may dominate. Both types of waves have a cross-shore extension of the order of the width of the current, but the frontshear modes are localized closer to the coast than are the backshear modes. Moreover, under certain conditions both unstable waves have similar growth rates with close wave numbers and angular frequencies, leading to the possibility of having modulated shear waves in the alongshore direction. Numerical analysis performed on realistic current profiles confirm the behavior anticipated by the analytical model. The theory has been applied to a current profile fitted to data measured during the 1980 Nearshore Sediment Transport Studies experiment at Leadbetter Beach that has an extremum of background vorticity at the front side of the current. In this case and in agreement with field observations, the model predicts instability, whereas the theory based only on backshear instability fai led to do so.
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Objective: Blood pressure is known to aggregate in families. Yet, heritability estimates are population-specific and no Swiss data have been published so far. Moreover, little is known on the heritability of the white-coat effect. We investigated the heritability of various blood pressure (BP) traits in a Swiss population-based sample. Methods: SKIPOGH (Swiss Kidney Project on Genes in Hypertension) is a family-based multi-centre (Lausanne, Bern, Geneva) cross-sectional study that examines the role of genes in determining BP levels. Office and 24-hour ambulatory BP were measured using validated devices (A&D UM-101 and Diasys Integra). We estimated the heritability of systolic BP (SBP), diastolic BP (DBP), heart rate (HR), pulse pressure (PP), proportional white-coat effect (i.e. [office BP-mean ambulatory daytime BP]/mean ambulatory daytime BP), and nocturnal BP dipping (difference between mean ambulatory daytime and night-time BP) using a maximum likelihood method implemented in the SAGE software. Analyses were adjusted for age, sex, body mass index (BMI), and study centre. Analyses involving PP were additionally adjusted for DBP. Results: The 517 men and 579 women included in this analysis had a mean (}SD) age of 46.8 (17.8) and 47.8 (17.1) years and a mean BMI of 26.0 (4.2) and 24.2 (4.6) kg/m2, respectively. Heritability estimates (}SE) for office SBP, DBP, HR, and PP were 0.20}0.07, 0.20}0.07, 0.39}0.08, and 0.16}0.07 (all P<0.01). Heritability estimates for 24-hour ambulatory SBP, DBP, HR, and PP were, respectively, 0.39}0.07, 0.30}.08, 0.19}0.09, and 0.25}0.08 (all P<0.05). The heritability of the white-coat effect was 0.29}0.07 for SBP and 0.31}0.07 for DBP (both P<0.001). The heritability of nocturnal BP dipping was 0.15}0.08 for SBP and 0.22}0.07 for DBP (both P<0.05). Conclusions: We found that the white-coat effect is significantly heritable. Our findings show that BP traits are moderately heritable in a multi-centric study in Switzerland, in line with previous population-based studies, justifying the ongoing search for genetic determinants in this field.