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Rate Measurements (rate + measurement)
Kinds of Rate Measurements Selected AbstractsVoxel-based T2 Relaxation Rate Measurements in Temporal Lobe Epilepsy (TLE) with and without Mesial Temporal SclerosisEPILEPSIA, Issue 2 2007Susanne G. Mueller Summary:,Introduction: Quantitative measurements of T2 relaxation in the hippocampus for focus lateralization in mesial temporal lobe epilepsy (mTLE) are well established. Less is known to what degree such relaxation abnormalities also affect regions beyond the ipsilateral hippocampus. Therefore, the aim of this study was to characterize extent and distribution pattern of extrahippocampal relaxation abnormalities in TLE with (TLE-MTS) and without MRI evidence of mesial-temporal sclerosis (TLE-no). Methods: Double spin echo images (TE1/2: 20/80 ms) acquired in 24 TLE-MTS and 18 TLE-no were used to calculate relaxation rate maps. These maps were analyzed by SPM2 and by selecting regions of interest (ROI) in the hippocampus and several extrahippocampal brain regions. Results: In TLE-MTS, the results of the SPM and ROI analysis were in good agreement and showed the most severe relaxation rate decreases in the ipsilateral hippocampus but also in other ipsilateral temporal regions, orbitofrontal, and parietal regions and to a lesser degree in contralateral frontal regions. The relaxation rate decreases in TLE-no were confined to small regions in the ipsilateral anterior inferior and medial temporal lobe in the SPM analysis while ROI analysis showed additional regions in the ipsilateral hippocampus, amygdala, and anterior cingulate. Conclusion: TLE-MTS showed extensive, widespread but predominantly ipsilateral temporal and also extratemporal T2 relaxation rate decreases. In contrast, the findings of the SPM and ROI analyses in TLE-no suggested that if relaxation rate decreases are present, they are less uniform and generally milder than in TLE-MTS. This further supports the hypothesis that TLE-no is a distinct clinicopathological entity from TLE-MTS and probably heterogeneous in itself. [source] Temperature effects on the mass flow rate in the SBI and similar heat-release rate test equipmentFIRE AND MATERIALS, Issue 1 2007Bart J. G. Sette Abstract In various medium-to-large-scale fire test equipments like the ISO room corner test (RC), and more recently, the single burning item test (SBI) the mass flow rate measurement of the combustion gases plays a key role in the determination of the heat-release rate and smoke-production rate. With the knowledge of the velocity profile and the temperature of the flow, the mass flow rate is obtained by measuring the velocity on the axis of the duct. This is done by means of a bi-directional probe based on the pitot principle. However, due to the variation of the mean temperature and the temperature gradient in any cross section of the duct, introduced by ever changing combustion gas temperatures, the velocity nor the density profile are constant in time. This paper examines the resulting uncertainty on the mass flow rate. Copyright © 2006 John Wiley & Sons, Ltd. [source] Uncertainty analysis of heat release rate measurement from oxygen consumption calorimetryFIRE AND MATERIALS, Issue 6 2005Sylvain BrohezArticle first published online: 1 JUL 200 Abstract Oxygen consumption calorimetry remains the most widespread method for the measurement of the heat release rate from experimental fire tests. In a first step, this paper examines by theoretical analysis the uncertainty associated with this measurement, especially when CO and soot corrections are applied. Application of theoretical equations is presented for chlorobenzene which leads to high values of CO and soot yields. It appears that the uncertainty of CO and soot corrections are high when the fuel composition is unknown. In a second step, a theoretical analysis is provided when the simplest measurement procedure is used for oxygen consumption calorimetry. The overall uncertainty can be dominated either by the uncertainty associated with the oxygen concentration, the assumed heat of combustion, the fumes mass flow rate or the assumed combustion expansion factor depending on the oxygen depletion. Copyright © 2005 John Wiley & Sons, Ltd. [source] Prediction method of critical power by film flow rate measurement and subchannel analysisHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2005Miyuki Akiba Abstract This paper presents a method that can estimate the critical power of boiling water reactors, BWRs, with regard to spacer geometry. The current experimental method for estimating the critical power for BWR design requires many trained experts and expensive facilities to conduct the experiments. In the present method, the liquid film flow rate of adiabatic gas-liquid two-phase flow and a subchannel analysis of the actual BWR flow condition are measured experimentally and analyzed. In the experiment, deposition enhancement coefficients of three spacer geometries,a ferrule, an egg-crate, and a ferrule spacer with twisted tape (CYCLONE spacer),were estimated by measuring the liquid film flow rate of air-water two-phase flow flowing up in a vertical square (4 × 4) rod bundle that simulated the rod bundle of a BWR. Using these coefficients, the critical powers for bundles using each type of spacer geometry were calculated in the subchannel analysis. This method was validated using previous critical power data in the actual BWR flow condition. The critical powers predicted by this method agreed well with those of the experimental data. The result confirmed the effectiveness of this experiment-simulation combined method, as well as the advantage over current experimental methods in terms of human and facility costs. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(5): 309,323, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20069 [source] Gastric emptying rate in subjects with experimentally shortened dental arches: a pilot studyJOURNAL OF ORAL REHABILITATION, Issue 6 2008Y. HATTORI Summary, Although a shortened dental arch has been reported to provide sufficient subjective chewing ability, the loss of molar occlusion significantly reduces trituration ability, and may result in an impaired digestive function including delayed gastric emptying. This study investigated the effect of the experimental loss of molar occlusion on gastric emptying rate. Thirteen healthy dentate males underwent two sessions of gastric emptying rate measurement after ingestion of the same test meal that contained ham, bread and an egg mixed with carbon-labelled octanoic acid. A test food was divided into nine equal portions, and each was consumed in 60 cycles of chewing. In one of the two sessions, the subjects wore an intraoral appliance devised to simulate the occlusal conditions of the shortened dental arches. Two parameters of gastric emptying; namely, the lag phase (Tlag) and gastric half-emptying time (T1/2), were evaluated by means of a 13C-octanoic acid breath test. Following the measurement of gastric emptying in each session, masticatory performance was evaluated by a conventional sieve test. Masticatory performance decreased significantly in case of loss of molar occlusion (78·1 ± 11·1% versus 33·4 ± 18·2%, P <0·001); however, no significant changes were observed in terms of the gastric emptying parameters (Tlag: 99 ± 19 versus 105 ± 34 min; T1/2: 168 ± 32 versus 178 ± 48 min). Within the limitations of this study, it was concluded that reduction in food trituration caused by shortening of the dental arch does not significantly affect gastrointestinal digestive function. [source] Color inhibition of phenolic antioxidants in Ziegler-Natta polyethylene.JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 1 2009Although the level of transition-metal catalyst residues in polyethylene (PE) has been drastically reduced over the years, they can still give rise to discoloration, particularly when associated with other additives such as antioxidants. This first of this series of papers screens a variety of candidate color suppressants featuring a range of functional groups, including alcohols, amine/sulfur compounds, and acid-containing species. These candidate color suppressants were melt-blended into a Ziegler-Natta linear low-density PE in combination with 2,2,-isobutylidenebis(4,6-dimethylphenol) (a highly discoloring hindered bisphenol antioxidant) and zinc stearate antacid. Yellowness index measurements made after multiple extruder passes indicated that dipentaerythritol (DPE) and triisopropylamine (TIPA) gave good color inhibition and, in some cases, outperformed established phosphites. The DPE and TIPA were found (via melt flow rate measurement) not to affect melt stability, and hydroperoxide determination revealed that DPE had no peroxide decomposition activity. The latter results indicate that the color-suppression mechanism of DPE and TIPA is different from that associated with phosphites. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers [source] Preparation and properties of diatomite composite superabsorbentPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2007Xiaohua Qi Abstract A novel diatomite composite superabsorbent was synthesized by solution polymerization of partially neutralized acrylic acid and diatomite, using N,N,-methylenebisacrylamide as a crosslinking agent and hydrogen peroxide and L -ascorbic acid as a redox initial system. The influences of some reaction conditions, such as diatomite content, neutralization degree of acrylic acid, amount of initiator, amount of crosslinking agent, monomer concentration, and the reaction temperature on swelling characteristic were investigated. The water absorbency of the sample prepared at optimum conditions was 99,g/g in 0.9,wt% NaCl solution. The results of swelling rate measurement showed that diatomite composite superabsorbent had better swelling rate than that of poly(sodium acrylate) prepared in the same conditions. Other properties, i.e. water retention, reswelling ability and resistance to salt, were also examined. Copyright © 2007 John Wiley & Sons, Ltd. [source] Preoperative urodynamic and symptom evaluation of patients undergoing transurethral prostatectomy: analysis of variables relevant for outcomeBJU INTERNATIONAL, Issue 4 2003O.W. Hakenberg OBJECTIVE To assess the value of preoperative symptom score assessment and pressure-flow measurement in men undergoing transurethral prostatectomy (TURP). PATIENTS AND METHODS In a prospective study, 95 men (mean age 74.3 years) scheduled for TURP because of their lower urinary tract symptoms, flow rates and urinary residual volumes were assessed using the self-administered International Prostate Symptom Score (IPSS) and urodynamic pressure-flow studies. At 3 months after TURP the patients were reassessed with a flow rate measurement and the IPSS. The baseline IPSS and urodynamic values were analysed with respect to the endpoints of the study, flow rate and IPSS after TURP, and the improvements thereof, respectively. RESULTS There were significant improvements in mean IPSS (, 10.87 points) and peak flow rate (+ 7.06 mL/s) 3 months after TURP. Classifying the patients into subgroups with distinctly different initial values for IPSS, flow rate, residual urine volume and degree of obstruction (as expressed by Abrams-Griffiths number) showed that the flow rate and degree of obstruction influenced the improvement in flow rate but not in symptoms after TURP. Symptom improvement was only related to the initial level of symptoms. In a multivariate analysis, only age was an independent predictor of the outcome variables of flow rate and symptoms. CONCLUSIONS Clinical decision-making remains a valid instrument for selecting patients for TURP. Both the IPSS and pressure-flow assessment are useful to exclude patients who are unlikely to benefit from TURP. Age is an important predictor of the improvement in symptoms and flow rates after TURP for the lower urinary tract symptom complex associated with benign prostatic enlargement. [source] A prospective study of conservatively managed acute urinary retention: prostate size mattersBJU INTERNATIONAL, Issue 7 2000V. Kumar Objective To evaluate in a prospective study the medium- to long-term outcome of a policy of conservatively managing acute urinary retention (AUR), arising solely by bladder outlet obstruction caused by benign prostatic enlargement (BPE), and to identify the factors favouring a positive outcome of a trial without catheter (TWOC). Patients and methods All men admitted as an emergency with primary AUR caused by BPE (from August 1997 to March 2000) underwent a TWOC. The following variables were recorded; the nature and duration of any preceding lower urinary tract symptoms, previous episodes of retention, concomitant anticholinergic medication, coexisting constipation, alcohol as a precipitating cause of AUR, previous prostatectomy, confirmed urinary tract infection, residual urine drained on catheterization and prostate size, as determined by a digital rectal examination (DRE) carried out by one consultant urologist in all patients. Those voiding successfully were followed up prospectively using the International Prostate Symptom Score (IPSS), quality-of-life score, urinary flow rate measurement and ultrasonographic measurement of the postvoid residual (PVR). Results Of the 40 men with AUR, 22 (55%) voided spontaneously after removing the catheter and continued to do so with mean peak flow rates of 12.2 mL/s and mean PVRs of 69.6 mL over a follow-up of 8,24 months. These patients remained asymptomatic, with a mean IPSS of 5.2 and quality-of-life score of 0.9. These men had a mean prostatic size of 15.9 g and a mean catheterized residual volume of 814 mL, while in those who had an unsuccessful TWOC the mean prostate size was 27.5 g (P = 0.006) and a mean catheterized residual volume of 1062 mL (P = 0.09). Prostate size as assessed by the DRE was the most significant factor in predicting the outcome of a TWOC. Conclusion A TWOC is justified in the long-term for men presenting with AUR caused by BPE. Prostate size is the most important factor for predicting the outcome of such a trial. [source] Radiation doses to staff involved in sentinel node operations for breast cancerCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 4 2005T. L. Klausen Summary Background:, The use of radioactive compounds for sentinel node biopsy is now a generally accepted part of the surgical treatment of breast cancer and melanoma, with the risk of radiation exposure to the operating team. The aim of this investigation was to study the levels of this exposure in relation to the permissible radiation dose limits. Methods:, The radiation exposure to the hands and bodies of the operating surgeons (the ,risk persons') was measured by thermoluminescent dosemeters in 79 operations and to the pathologists handling the specimens in 17 cases. Radioactivity and dose rate measurement from tumours and breast specimens were also performed. Results:, During an operation the mean skin dose (±SD) to the thermoluminescent dosemeters placed at the hand and the abdominal wall were 0·04 ± 0·04 mSv (79 operations) and 0·01 ± 0·02 mSv (67 operations) respectively. For the pathologist, the mean hand dose per operation was below the detection limit (17 operations). Correlation between the measured dose rate and the radioactive content of the tumours was 0·998. Conclusions:, The radiation exposure to the staff involved in sentinel node (SN) biopsy for breast cancer using radioactive labelled tracers will be considerably below the permissible limits, even with high numbers of SN biopsy procedures. Pregnant staff members should participate in <100 SN operations. [source] Cardiovascular responses to pacifier experience and feeding in newborn infantsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 1 2001Morris Cohen Abstract This study examined the effects of sucking on a pacifier immediately before feeding on cardiovascular responses to feeding. Twenty-eight bottle-feeding infants were studied at 12 to 40 hr of age. Blood pressure and heart rate measurements were made during three periods: Period 1,while infants rested in their cribs before a regularly scheduled feeding, Period 2,while being held by the feeder immediately before feeding, and Period 3,during the first 3 to 5 min of feeding. Half of the infants were given a pacifier during Period 2. Blood pressures and heart rates increased across the periods; however, increases in systolic blood pressure during feeding were reduced for the group of infants given a pacifier prior to feeding. We suggest that cardiovascular responses to feeding in infants are comprised of multiple elements. Most of the systolic blood pressure responses to feeding are elicited by sucking whereas the heart rate response is dependent on both sucking and nutrient intake. © 2001 John Wiley & Sons, Inc. Dev Psychobiol 39: 34,39, 2001 [source] Regional Diastolic and Systolic Function by Strain Rate Imaging for the Detection of Intramural Viability during Dobutamine Stress Echocardiography in a Porcine Model of Myocardial InfarctionECHOCARDIOGRAPHY, Issue 5 2010Carsten Schneider M.D. The aim of this study was to evaluate diastolic and systolic strain rate measurements for differentiation of transmural/nontransmural infarction during dobutamine stress echocardiography (DSE). An ameroid constrictor was placed around the circumflex artery in 23 pigs inducing chronic vessel occlusion. Five pigs without constrictor served as controls. During high-dose DSE systolic strain rates (SRsys), systolic and postsystolic strain values (,sys, ,ps) and early and late diastolic strain rates (SRE and SRA) were determined. At week 6, animals were evaluated regarding myocardial fibrosis. Histology revealed nontransmural in 14 and transmural infarction in 9 animals. In controls, dobutamine induced a linear increase of SRsys to 12.3 ± 0.4 s,1 at 40 ,g/kg per minute (P = 0.001) and a linear decrease of SRE to ,6.6 ± 0.3 s,1 (P = 0.001). In the nontransmural group, SRsys, ,sys, ,ps at rest, and during DSE were higher and SRE was lower than in the transmural infarction group (P = 0.01). Best predictors for viability were SRsys (ROC 0.96, P = 0.0003), SRE at 10 ,g/kg per minute dobutamine stimulation (ROC 0.94, P = 0.001) and positive SR values during isovolumetric relaxation at 40 ,g/kg per minute dobutamine (ROC 0.86, P = 0.004). The extension of fibrosis correlated with SRsys at rest, ,sys at rest, and SRE at rest (P < 0.001). For the detection of viability similar diagnostic accuracies of SRE and SRsys were seen (sensitivity 93%/93%, specificity 96%/94%, respectively). Diastolic SR analysis seems to be equipotent for the identification of viable myocardium in comparison to systolic SR parameters and allows the differentiation of nontransmural from transmural myocardial infarction with high diagnostic accuracy. (Echocardiography 2010;27:552-562) [source] Methods for crack opening load and crack tip shielding determination: a reviewFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2003S. STOYCHEV and ABSTRACT In this paper a review of the literature on crack closure/opening load and crack tip shielding effects determination methods is presented. Commonly used ,subjective' (visual) and ,non-subjective' approaches have been included. Procedures associated with the determination of an effective crack driving force for both Elber type and that of partial (or incremental) crack closure models have been covered. Comparison among different methods of analyses based on compliance and fatigue crack growth rate measurements is discussed together with their implications and difficulties in fatigue crack growth correlations. [source] Pristine New Zealand forest soil is a strong methane sinkGLOBAL CHANGE BIOLOGY, Issue 1 2004Sally J. Price Abstract Methanotrophic bacteria oxidize methane (CH4) in forest soils that cover ,30% of Earth's land surface. The first measurements for a pristine Southern Hemisphere forest are reported here. Soil CH4 oxidation rate averaged 10.5±0.6 kg CH4 ha,1 yr,1, with the greatest rates in dry warm soil (up to 17 kg CH4 ha,1 yr,1). Methanotrophic activity was concentrated beneath the organic horizon at 50,100 mm depth. Water content was the principal regulator of (r2=0.88) from the most common value of field capacity to less than half of this when the soil was driest. Multiple linear regression analysis showed that soil temperature was not very influential. However, inverse co-variability confounded the separation of soil water and temperature effects in situ. Fick's law explained the role of water content in regulating gas diffusion and substrate supply to the methanotrophs and the importance of pore size distribution and tortuosity. This analysis also showed that the chambers used in the study did not affect the oxidation rate measurements. The soil was always a net sink for atmospheric CH4 and no net CH4 (or nitrous oxide, N2O) emissions were measured over the 17-month long study. For New Zealand, national-scale extrapolation of our data suggested the potential to offset 13% of CH4 emissions from ca. 90 M ruminant animals. Our average was about 6.5 times higher than rates reported for most Northern Hemisphere forest soils. This very high was attributed to the lack of anthropogenic disturbance for at least 3000,5000 years and the low rate of atmospheric nitrogen deposition. Our truly baseline data could represent a valid preagricultural, preindustrial estimate of the soil sink for temperate latitudes. [source] Shock tube study of 1,3,5-triazine dissociation and relaxation and relaxation of pyrazineINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2010Hui Xu The three-body dissociation of 1,3,5-triazine (s-triazine, s-C3H3N3 , 3HCN) has been observed in incident shock waves with the laser-schlieren technique. The experiments use 5% triazine/Kr and cover 1630,2350 K for 100,600 Torr. These experiments show dissociation rates with strong falloff and a slight but fully expected pressure dependence. The dissociation is without secondary reaction save for a possible, but rather unlikely, contribution from the isomerization HCN , HNC. Electronic structure calculations of the transition-state properties (G3B3, HL1, Eo = 84.6 kcal/mol) are used to construct a Rice,Ramsperger,Kassel,Marcus (RRKM) model whose fit to the rate measurements suggests a ,,E,down of 1200 cm,1. However, a seemingly better fit is achieved using the barrier of 81 kcal/mol proposed by Dyakov et al. (J. Phys. Chem. A 2007, 111, 9591,9599). With this barrier k, (s,1) = 5.3 × 1016 exp(,86.6(kcal/mol)/RT), and the fit now accepts the more routine ,,E,down = 126(T/298)0.9. It seems the dissociation most likely occurs by a direct, one-step, "triple" dissociation to 3HCN, although the present experiments cannot rule out a multistep process. Vibrational relaxation of the triazine was also examined in 5% and 20% mixtures with Kr over 770,1500 K for pressures between 6 and 14 Torr. Relaxation is very fast, with a slight inverse temperature dependence, P, rising from 100 to 200 ns-atm over the full temperature range. Integrated gradients are in good accord with calculated total changes in density, indicating a single exponential relaxation. A separate investigation of relaxation in the related molecule pyrazine (500,1300 K, in 1% and 5% in Kr, between 13 and 66 Torr) is included. Again relaxation is rapid, but here the temperature dependence seems more normal, the relaxation times decreasing slightly with temperature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 211,220, 2010 [source] Comparison of global and local sensitivity techniques for rate constants determined using complex reaction mechanismsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2001James J. Scire Jr. Many rate constant measurements, including some "direct" measurements, involve fitting a complex reaction mechanism to experimental data. Two techniques for estimating the error in such measurements were compared. In the first technique, local first-order elementary sensitivities were used to rapidly estimate the sensitivity of the fitted rate constants to the remaining mechanism parameters. Our group and others have used this technique for error estimation and experimental design. However, the nonlinearity and strong coupling found in reaction mechanisms make verification against globally valid results desirable. Here, the local results were compared with analogous importance-sampled Monte Carlo calculations in which the parameter values were distributed according to their uncertainties. Two of our published rate measurements were examined. The local uncertainty estimates were compared with Monte Carlo confidence intervals. The local sensitivity coefficients were compared with coefficients from first and second-degree polynomial regressions over the whole parameter space. The first-order uncertainty estimates were found to be sufficiently accurate for experimental design, but were subject to error in the presence of higher order sensitivities. In addition, global uncertainty estimates were found to narrow when the quality of the fit was used to weight the randomly distributed points. For final results, the global technique was found to provide efficient, accurate values without the assumptions inherent in the local analysis. The rigorous error estimates derived in this way were used to address literature criticism of one of the studies discussed here. Given its efficiency and the variety of problems it can detect, the global technique could also be used to check local results during the experimental design phase. The global routine, coded using SENKIN, can easily be extended to different types of data, and therefore can serve as a valuable tool for assessing error in rate constants determined using complex mechanisms. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 784,802, 2001 [source] Postprandial Hypotension in Long-Term Care Elderly Patients on Enteral FeedingJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 9 2006Emily Lubart MD OBJECTIVES: To examine the prevalence and nature of postprandial hypotension (PPH) in orally fed (OF), nasogastric tube (NGT)-fed, and percutaneous endoscopic gastrostomy (PEG)-fed older people. DESIGN: Prospective comparative study. SETTING: Nursing and skilled nursing wards of three geriatrics hospitals. PARTICIPANTS: Three groups (OF, PEG, NGT) of long-term care patients (50 in each cohort) were enrolled. MEASUREMENTS: Blood pressure (BP) and heart rate measurements were obtained just before lunch and at 15-minute intervals for 90 minutes after the completion of the meal. The meals were similar in caloric content and composition. RESULTS: PPH was evidenced in 64 (43%) patients. No significant intergroup (OF, PEG, NGT) differences were present. In 68% of PPH patients, the systolic BP (SBP) drop appeared within 30 minutes, and 70% reached their systolic nadir at 60 minutes. In 31%, the SBP drop was registered on only one measurement, whereas in 25%, the drop was detected on five to six measurements. All parameters were without notable intergroup differences. CONCLUSION: In enterally fed elderly patients (NGT or PEG), the rate and pattern of PPH are similar and not significantly different from that observed in OF patients. [source] Effect of activation type on bioregeneration of various activated carbons loaded with phenolJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2006Özgür Akta Abstract Thermally and chemically activated powdered carbons (PAC), and their granular countertypes (GAC) with similar physical characteristics were used to investigate the extent of bioregeneration in laboratory-scale activated sludge reactors. Bioregeneration of activated carbon was determined by measurement of bulk phenol concentrations and loadings remaining on activated carbon. It was also followed by oxygen uptake rate measurements. For the carbons used in this study, bioregeneration of chemically activated carbons was found to be higher than thermally activated ones. This was in accordance with their higher reversibility of adsorption and showed that bioregeneration was controlled by the reversibility of adsorption. Oxidative polymerization of phenol was a plausible explanation for low bioregeneration of thermally activated carbons. However, bioregeneration efficiencies of thermally activated carbons were much higher than their total desorbabilities. This unexpectedly high bioregeneration indicated that some exoenzymatic reactions had occurred. These results suggest that carbon activation type is of crucial importance for bioregeneration. PAC and GAC countertypes showed comparable bioregeneration efficiencies indicating that carbon size was not an effective factor. The environmental scanning electron microscopy (ESEM) studies showed that microorganisms were attached both on the external surface and interval cavities of activated carbon particles. Copyright © 2006 Society of Chemical Industry [source] Methodological considerations for measuring rates of brain atrophyJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2003Jeffrey L. Gunter PhD Abstract Purpose To systematically compare two techniques for measuring brain atrophy rates from serial magnetic resonance imaging (MRI) studies. Materials and Methods Using the separation in atrophy rate between cohorts of cognitively normal elderly subjects and patients with Alzheimer's disease (AD) as the gold standard, we evaluated 1) different methods of computing volume change; 2) different methods for steps in image preprocessing,intensity normalization, alignment mask used, and bias field correction; 3) the effect of MRI acquisition hardware changes; and 4) the sensitivity of the method to variations in initial manual volume editing. For each of the preceding evaluations, measurements of whole-brain and ventricular atrophy rates were calculated. Results In general, greater separation between the clinical groups was seen with ventricular rather than whole-brain measures. Surprisingly, neither the use of bias field correction nor a major hardware change between the scan pairs affected group separation. Conclusion Atrophy rate measurements from serial MRI are candidates for use as surrogate markers of disease progression in AD and other dementing neurodegenerative disorders. The final method has excellent precision and accurately captures the expected biology of AD,arguably the two most important features if this technique is to be used as a biomarker of disease progression. J. Magn. Reson. Imaging 2003;18:16,24. © 2003 Wiley-Liss, Inc. [source] Monolithic poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for simultaneous separation of low- and high-molecular-weight compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009Andreas Greiderer Abstract Monolithic poly(1,2-bis(p -vinylphenyl)ethane (BVPE)) capillary columns were prepared by thermally initiated free radical polymerisation of 1,2-bis(p -vinylphenyl)ethane in the presence of inert diluents (porogens) and ,,,,-azoisobutyronitrile (AIBN) as initiator. Polymerisations were accomplished in 200 ,m ID fused silica capillaries at 65°C and for 60 min. Mercury intrusion porosimetry measurements of the polymeric RP support showed a broad bimodal pore-size-distribution of mesopores and small macropores in the range of 5,400 nm and flow-channels in the ,m range. N2 -adsorption (BET) analysis resulted in a tremendous enhancement of surface area (101 m2/g) of BVPE stationary phases compared to typical organic monoliths (,20 m2/g), indicating the presence of a considerable amount of mesopores. Consequently, the adequate proportion of both meso- and (small) macropores allowed the rapid and high-resolution separation of low-molecular-weight compounds as well as biomolecules on the same monolithic support. At the same time, the high fraction of flow-channels provided enhanced column permeability. The chromatographic performance of poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for the separation of biomolecules (proteins, oligonucleotides) and small molecules (alkyl benzenes, phenols, phenons) are demonstrated in this article. Additionally, pressure drop versus flow rate measurements of novel poly(1,2-bis(p -vinylphenyl)ethane) capillary columns confirmed high mechanical robustness, low swelling in organic solvents and high permeability. Due to the simplicity of monolith fabrication, comprehensive studies of the retention and separation behaviour of monolithic BVPE columns resulted in high run-to-run and batch-to-batch reproducibilities. All these attributes prove the excellent applicability of monolithic poly(1,2-bis(p -vinylphenyl)ethane) capillary columns for ,-HPLC towards a huge range of analytes of different chemistries and molecular sizes. [source] Deposition of Plasma-Polymerized 1-Cyanoisoquinoline Thin Films and Their Dielectric PropertiesPLASMA PROCESSES AND POLYMERS, Issue 9 2007Xiong-Yan Zhao Abstract A novel plasma-polymerized 1-cyanoisoquinoline (PPCIQ) thin film of desired thickness was prepared by plasma polymerization under different glow discharge conditions. The effect of the discharge power on the chemical structure, surface composition and morphology of the PPCIQ thin films were investigated by Fourier Transform Infrared (FTIR) Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and deposition rate measurements. A high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained at a low discharge power of 15 W. The plasma-synthesized films are homogeneous and quite suitable for the measurement of dielectric properties. The dielectric measurements show that a low dielectric constant of 2.62 has been obtained for the PPCIQ thin films for the first time. [source] Study of interphase in glass fiber,reinforced poly(butylene terephthalate) compositesPOLYMER COMPOSITES, Issue 1 2004A. Bergeret It is well known that application of a coupling agent to a glass fiber surface will improve fiber/matrix adhesion in composites. However, on commercial glass fibers the coupling agent forms only a small fraction of the coating, the larger part being a mixture of processing aids whose contribution to composite properties is not well defined. The interfacial region of the composite will therefore be affected by the coating composition but also by the chemical reactions involved in the vicinity of the fiber and inside the surrounding matrix. The main feature of this study consists in dividing the interface region into two separate regions: the fiber/sizing interphase and the sizing/matrix interphase. A wide range of techniques was used, including mechanical and thermomechanical tests, infrared spectroscopy, gel permeation chromatography, carboxyl end group titrations, extraction rate measurements, and viscosity analysis. Experiments were performed on poly(butylene terephthalate) composites and results indicate that the adhesion improvement is due to the presence of a short chain coupling agent and of a polyfunctional additive, which may react both with the coupling agent and the matrix. According to the nature of this additive, it may be possible to soften the interphase and then to increase the composite impact strength. [source] Reactive compatibilization of biodegradable poly(lactic acid)/poly(,-caprolactone) blends with reactive processing agentsPOLYMER ENGINEERING & SCIENCE, Issue 7 2008Masaki Harada Poly(lactic acid) (PLA) blended with poly(,-caprolactone) (PCL) was prepared with various reactive processing agents. Four isocyanates-lysine triisocyanate (LTI); lysine diisocyanate (LDI); 1,3,5-tris(6-isocyanatohexyl)-1,3,5-triazinane-2,4,6-trione (Duranate TPA-100); 1,3,5-tris(6-isocyanatohexyl)biuret (Duranate 24A-100)-and an industrial epoxide-trimethylolpropane triglycidyl ether (Epiclon 725)-were used as reactive processing agents. PLA/PCL blended in the presence of LTI had the highest torque in a mixer test. The test specimens were prepared by injection molding. The mechanical properties, thermal properties, molecular weight, melt viscosity, phase behavior, and morphology were investigated using tensile strength, impact strength, differential scanning calorimetry, melt mass-flow rate measurements, capillary rheometery, gel permeation chromatography, laser scanning confocal microscopy (LSCM), and visco-elasticity atomic force microscopy (VE-AFM). The impact strength increased considerably at 20 wt% PCL. The nominal tensile strain of PLA/PCL blended with LTI increased by 270%. The MFR values of PLA/PCL blends decreased with increasing LTI. Similar results were observed for shear viscosity. LSCM measurements showed that the diameters of PCL were dispersed about 0.4 ,m in the presence of LTI. VE-AFM showed that spherical particles with diameters of 50 nm were PCL-rich domain. These results indicate that isocyanate groups of LTI react with both terminal hydroxyl or carboxyl groups of polymers, and the compatibility of PLA/PCL blends improves with LTI by reactive processing. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Assessment of Salivary Flow Rate: Biologic Variation and Measure Error,THE LARYNGOSCOPE, Issue 10 2004Peter H. Jongerius MD Abstract Objective: To investigate the applicability of the swab method in the measurement of salivary flow rate in multiple-handicap drooling children. To quantify the measurement error of the procedure and the biologic variation in the population. Study Design: Cohort study. Methods: In a repeated measurements design, a baseline series of salivary flow rates were obtained from 45 children. The within-subject SD (SW) was calculated to express the measurements error according to a procedure introduced by Bland and Altman. Results: Two hundred twenty-four samples (mean 0.40 mL/min, SD 0.19 mL/min) were obtained and analyzed. The results of this study indicate that consistent scores were obtained at subsequent measurements, and good parity existed between the two measurements of salivary flow rate at each session. The SW could be estimated (0.11 mL/min), which was applied to quantify the specific variation of the salivary flow rate in our population. Conclusion: According to Bland and Altman, the SW, which is a quantification of the measurement error and biologic variation, was found to be a useful tool to evaluate the obtained baseline salivary flow rate measurements. The swab method can be used to evaluate salivary flow rates in drooling children with cerebral palsy during interventional studies that aim to reduce saliva production. [source] Severe Vascular Lesions and Poor Functional Outcome in Kidney Transplant Recipients with Lupus Anticoagulant AntibodiesAMERICAN JOURNAL OF TRANSPLANTATION, Issue 9 2010G. Canaud The impact of antiphospholipid antibodies (APA) on clinical outcome and graft histology following renal transplantation remains poorly known and controversial. We retrospectively explored the functional and histological significance of APA, primarily lupus anticoagulant (LA), in kidney transplant recipients using a systematic evaluation of 3- and 12-month posttransplant screening biopsies and glomerular filtration rate measurements (mGFR). During the study period, 37 patients had APA (2.7%), primarily LA, and 12 fulfiled antiphospholipid syndrome (APS) diagnostic criteria (0.8%) at the time of transplantation. Early after transplantion, 4 of the 12 APS patients died. Early thrombosis of graft vessels and deep venous thrombosis occurred more frequently in APA+ patients than in controls (27% vs. 7%, p < 0.05 and 35% vs. 14%, p < 0.05, respectively). The survival rate was significantly lower in patients with APS. Strikingly, the hallmark lesions of APS-associated nephropathy (APSN) were found in most of screening graft biopsies in APA+ patients but not in the controls. Accordingly, APA+ patients had a dramatic increase in chronic vascular scores and a faster decline in mGFR at 1 year. In conclusion, renal transplantation may be life-threatening in APS patients, and the presence of LA at the time of transplantation is associated with a high rate of allograft APSN and poor transplantation outcomes. [source] Albedo, atmospheric solar absorption and heating rate measurements with stacked UAVsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 629 2007M. V. Ramana Abstract This paper reports unique measurements of albedo, atmospheric solar absorption, and heating rates in the visible (0.4 to 0.7 µm) and broadband (0.3 to 2.8 µm) spectral regions using vertically stacked multiple lightweight autonomous unmanned aerial vehicles (UAVs). The most significant finding of this study is that when absorbing aerosols and water vapour concentrations are measured accurately and accounted for in models, and when heating rates are measured directly with stacked aircraft, the simulated clear sky heating rates are consistent with the observed broadband heating rates within experimental errors (about 15%). We conclude that there is no need to invoke anomalous or excess absorption or unknown physics in clear skies. Aerosol,radiation,cloud measurements were made over the tropical Indian Ocean within the lowest 3 km of the atmosphere during the Maldives Autonomous UAV Campaign (MAC). The UAVs and ground-based remote sensing instruments determined most of the parameters required for calculating the albedo and vertical distribution of solar fluxes. The paper provides a refined analytical procedure to reduce errors and biases due to the offset errors arising from mounting of the radiometers on the aircraft and due to the aircraft attitude. Measured fluxes have been compared with those derived from a Monte-Carlo radiative transfer algorithm which can incorporate both gaseous and aerosol components. Under cloud-free conditions the calculated and measured incoming fluxes agree within 2,10 W m,2 (<1%) depending upon the altitudes. Similarly, the measured and calculated reflected fluxes agreed within 2,5 W m,2 (<5%). The analysis focuses on a cloud-free day when the air was polluted due to long-range transport from India, and the mean aerosol optical depth (AOD) was 0.31 and mean single scattering albedo was 0.92. The UAV-measured absorption AOD was 0.019 which agreed within 20% of the value of 0.024 reported by a ground-based instrument. The observed and simulated solar absorption agreed within 5% above 1.0 km and aerosol absorption accounted for 30% to 50% of the absorption depending upon the altitude and solar zenith angle. Thus there was no need to invoke spurious or anomalous absorption, provided we accounted for aerosol black carbon. The diurnal mean absorption values for altitudes between 0.5 and 3.0 km above mean sea level were observed to be 41 ± 3 W m,2 (1.5 K/day) in the broadband region and 8 ± 2 W m,2 (0.3 K/day) in the visible region. The contribution of absorbing aerosols to the heating rate was an order of magnitude larger than the contribution of CO2 and one-third that of the water vapour. In the lowest 3 km of the tropical atmosphere, aerosols accounted for more than 80% of the atmospheric absorption in the visible region. Copyright © 2007 Royal Meteorological Society [source] Mechanistic model for prediction of formate dehydrogenase kinetics under industrially relevant conditionsBIOTECHNOLOGY PROGRESS, Issue 1 2010T. Schmidt Abstract Formate dehydrogenase (FDH) from Candida boidinii is an important biocatalyst for the regeneration of the cofactor NADH in industrial enzyme-catalyzed reductions. The mathematical model that is currently applied to predict progress curves during (semi-)batch reactions has been derived from initial rate studies. Here, it is demonstrated that such extrapolation from initial reaction rates to performance during a complete batch leads to considerable prediction errors. This observation can be attributed to an invalid simplification during the development of the literature model. A novel mechanistic model that describes the course and performance of FDH-catalyzed NADH regeneration under industrially relevant process conditions is introduced and evaluated. Based on progress curve instead of initial reaction rate measurements, it was discriminated from a comprehensive set of mechanistic model candidates. For the prediction of reaction courses on long time horizons (>1 h), decomposition of NADH has to be considered. The model accurately describes the regeneration reaction under all conditions, even at high concentrations of the substrate formate and thus is clearly superior to the existing model. As a result, for the first time, course and performance of NADH regeneration in industrial enzyme-catalyzed reductions can be accurately predicted and used to optimize the cost efficiency of the respective processes. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Mechanistic Investigation of Chiral Phosphoric Acid Catalyzed Asymmetric Baeyer,Villiger Reaction of 3-Substituted Cyclobutanones with H2O2 as the OxidantCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2010Senmiao Xu Dr. Abstract The mechanism of the chiral phosphoric acid catalyzed Baeyer,Villiger (B,V) reaction of cyclobutanones with hydrogen peroxide was investigated by using a combination of experimental and theoretical methods. Of the two pathways that have been proposed for the present reaction, the pathway involving a peroxyphosphate intermediate is not viable. The reaction progress kinetic analysis indicates that the reaction is partially inhibited by the ,-lactone product. Initial rate measurements suggest that the reaction follows Michaelis,Menten-type kinetics consistent with a bifunctional mechanism in which the catalyst is actively involved in both carbonyl addition and the subsequent rearrangement steps through hydrogen-bonding interactions with the reactants or the intermediate. High-level quantum chemical calculations strongly support a two-step concerted mechanism in which the phosphoric acid activates the reactants or the intermediate in a synergistic manner through partial proton transfer. The catalyst simultaneously acts as a general acid, by increasing the electrophilicity of the carbonyl carbon, increases the nucleophilicity of hydrogen peroxide as a Lewis base in the addition step, and facilitates the dissociation of the OH group from the Criegee intermediate in the rearrangement step. The overall reaction is highly exothermic, and the rearrangement of the Criegee intermediate is the rate-determining step. The observed reactivity of this catalytic B,V reaction also results, in part, from the ring strain in cyclobutanones. The sense of chiral induction is rationalized by the analysis of the relative energies of the competing diastereomeric transition states, in which the steric repulsion between the 3-substituent of the cyclobutanone and the 3- and 3,-substituents of the catalyst, as well as the entropy and solvent effects, are found to be critically important. [source] Heteropolynuclear Palladium Complexes with Pyrazolate and Its 3- tert -Butyl Derivatives: The Effect of Heterometal Ions on the Rate of IsomerizationCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2006Keisuke Umakoshi Prof. Dr. Abstract The heteropolynuclear complexes [Pd2M,2(,-pz)6] (M,=Ag (1), Au (2); pzH=pyrazole), HT -[Pd2M,2(,-3- tBupz)6] (M,=Ag (3,a), Au (4,a); 3- tBupzH=3- tert -butylpyrazole), and HH -[Pd2Au2(,-3- tBupz)6] (4,b) have been prepared and some of them were structurally characterized. When 3- tert -butylpyrazolate was employed as a bridging ligand, two linkage isomers (head-to-tail (HT) and head-to-head (HH)) arise from the difference in orientation of the substituent groups on the pyrazolate bridges between the two Pd atoms. 1H NMR spectroscopy has been used to identify and to follow the reversible stereochemical rearrangement of the HH isomer of [Pd2Ag2(,-3- tBupz)6] (3,b) to form the HT isomer 3,a in CDCl3 and the HT isomer of [Pd2Au2(,-3- tBupz)6] (4,a) to form the HH isomer 4,b in C6D6. Kinetic studies of the reaction have established the rate law to be ,d(HH)/dt=d(HT)/dt=k2[HH],k1[HT] for 3,b and ,d(HT)/dt=d(HH)/dt=k1[HT],k2[HH] for 4,a, where k1 and k2 denote the rate of isomerization from the HT to the HH isomer and that from the HH to the HT isomer, respectively. For typical runs at 50,°C in C6D6, k1=13.8×10,5 s,1, k2=18.6×10,5 s,1, and Keq=k2/k1=1.24 for 3,b, and k1=1.26×10,5 s,1, k2=3.52×10,5 s,1, and Keq=k1/k2=0.36 for 4,a. Temperature-dependent rate measurements reveal ,H, and ,S, to be 100(1) kJ,mol,1 and 0(3) J,mol,1,K,1 for 3,b and 112(5) kJ,mol,1 and 20(17) J,mol,1,K,1 for 4,a, respectively. The rate of isomerization is essentially unaffected by the concentration of the complex or by the presence of neutral bridging ligands. These data and observations imply that the isomerization involves an intramolecular exchange process. [source] Blood flow rate measurements with indicator techniques revisitedCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2009Per Sejrsen Summary In view of the emerging role, disturbances in regional blood flow rate seem to play in the pathogenesis of the metabolic syndrome; we review the concepts of the classical indicator dilution and washout techniques used for determinations of regional blood flow rate. Prerequisites, assumptions, necessary precautions for the application of these experimental techniques are emphasized. Special attention has been carried out to elucidate the consequence of a choice of indicators having a large distribution volume in the tissues. [source] | |||||||||||||||||||||||||