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Reproducible Measurements (reproducible + measurement)
Selected AbstractsMeasurement of bone blood flow using the hydrogen washout technique,part II: Validation by comparison to microsphere entrapmentJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2008Mikko Larsen Abstract Accurate and reproducible measurement of bone blood flow has important clinical and experimental applications. Hydrogen washout is simple, safe, and widely used, but its use in bone tissue has not been validated. To this end, we have compared cortical bone blood flow measurements obtained by radioactive-labeled microsphere entrapment with those from hydrogen washout. Blood flow was measured in tibial cortical bone of 12 New Zealand White rabbits by radioactive microsphere entrapment and by hydrogen washout. Besides a control group (n,=,6), four animals were treated with systemic epinephrine (0.8 µg/kg/min) (group 2) and two with nitroprusside (100 µg/kg/min) (group 3). Furthermore, nine femora from seven rats were isolated on their vascular pedicles and repeated bone blood flow measurements were made at each location with the hydrogen washout method to confirm reproducibility of blood flow determinations by hydrogen washout. An average flow of 2.3,±,2.0 mL/min/100 g was obtained with the microsphere method and 2.0,±,0.5 mL/min/100 g with the hydrogen washout method. There was a significant correlation and agreement: R2,=,0.97 (p,<,0.01). No consistent flow variations were found with systemic vasoactive drug administration. Hydrogen washout provided reproducible results and showed high sensitivity to flow changes. Hydrogen washout is both sensitive and reproducible in measuring bone blood flow. Results agree well with flow values obtained by labeled microsphere entrapment. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:746,752, 2008 [source] Normal ranges of angiogenesis regulatory proteins in human platelets,AMERICAN JOURNAL OF HEMATOLOGY, Issue 7 2010Jon E. Peterson Platelets sequester angiogenesis regulatory proteins early in tumor growth, which suggests a new avenue for monitoring disease. To date, there are no clinically relevant reference ranges for markers of early angiogenesis. We introduce a new ELISA-based method for accurate and reproducible measurement of vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), platelet factor 4 (PF4), thrombospondin-1 (TSP-1), fibroblast growth factor, basic (bFGF), and endostatin in platelets. To facilitate clinical applicability, the platelet levels in isolated samples were determined utilizing a new actin ELISA method. Platelets from healthy donors at single and repetitive time points were used for the assessment of normal ranges of these proteins. The physiological levels in platelets were: VEGF (0.74 ± 0.37 pg/106 platelets); PDGF (23 ± 6 pg/106); PF4 (12 ± 5 ng/106); TSP-1 (31 ± 12 ng/106); bFGF (0.44 ± 0.15 pg/106); and endostatin (5.6 ± 3.0 pg/106). There was an excellent correlation (R2 = 0.7) between the platelet levels calculated with the actin ELISA and complete blood count. The levels of the platelets were higher than those in platelet-poor plasma by factors of: VEGF (215-fold); PDGF (914-fold); PF-4 (516-fold); TSP-1 (813-fold); and bFGF (17-fold). The endostatin levels were nearly equivalent. The biovariability of the platelet proteins in eight healthy subjects over a 5-week period was found to be minimal. We describe accurate and direct measurements of the concentrations of VEGF, bFGF, PDGF, TSP-1, endostatin, and PF4 in platelets of healthy human subjects. In contrast to the highly variable levels in plasma and serum, the platelet-derived measurements were accurate and reproducible with minimal biovariability. Am. J. Hematol., 2010. © 2010 Wiley-Liss, Inc. [source] The fundamental aspects of carbon nanotube metrologyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2007Ado Jorio Abstract The accurate and reproducible measurement of the properties and performance characteristics of nanoscale materials, devices and systems are essential for quality and process control, commercial transactions and effective regulations. Scientists, manufacturers, governments, regulators and health and environmental protection agencies, will need measurement systems and evaluation protocols supported by well founded and robust standards, both physical and documentary. In this paper we discuss some fundamental aspects of the use of the resonance Raman spectroscopy of the radial breathing mode (RBM) of single wall carbon nanotubes (SWNTs) for metrological purposes. The achievements and problems are pointed, hoping for the development of procedures capable of making the promised nanotechnology revolution to become a reality. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reliable and reproducible anterior active rhinomanometry for the assessment of unilateral nasal resistanceCLINICAL OTOLARYNGOLOGY, Issue 6 2000A.S. Carney Unilateral nasal resistance is now thought to be more important than total resistance in promoting obstructive symptoms. We assessed the reproducibility of anterior active rhinomanometry in measuring unilateral nasal resistance. Ten baseline readings of unilateral nasal resistance were made over a 30-min period in seven healthy subjects (14 nostrils) using anterior active rhinomanometry performed according to the International Committee for the Standardization of Rhinomanometry (ICSR) guidelines. Baseline readings revealed that measurements using anterior active rhinomanometry had an unacceptably high coefficient of variation (19%,60%). With a more time-consuming revised protocol involving multiple recordings and the identification and exclusion of erroneous data, coefficients of variation of 7%,15% were obtained. We conclude that single anterior active rhinomanometry readings are potentially prone to large errors and each researcher using such equipment must satisfy his/herself that their methodology has an acceptable coefficient of variation in their hands. The ICSR guidelines are not always sufficient to allow reproducible measurement and specially designed protocols may be necessary to produce reliable results. [source] A Comparison of Echocardiographic Techniques in Determination of Arterial Elasticity in the Pediatric PopulationECHOCARDIOGRAPHY, Issue 5 2009Michael Fahey M.D. Background: Many methods are used to measure arterial elasticity in children using echocardiography. There is no data to support the equivalence of the different techniques. The goal of this study was to evaluate the reproducibility of several techniques used to measure arterial elasticity using echocardiography. Methods: Aortic distension in two different sites (arterial distension) through the cardiac cycle was measured by (four) two-dimensional (2D) and M-mode echocardiographic techniques in 20 children without significant structural heart disease. These measurements combined with noninvasive blood pressure measurements were used to calculate arterial elastic indices. Arterial elasticity was expressed in terms of distensibility and stiffness. Data were collected by two sonographers and interpreted by two reviewers. Paired Student's t-test and Pitman's test for equality of variance for correlated observations were used to detect differences between different sonographers, different reviewers, and different techniques. Results: No significant difference in the measured elasticity between sonographers or reviewers was observed. There was a somewhat increased variance in two of the four techniques evaluated. There was no significant difference in elasticity measured using different techniques to evaluate the same arterial site, although a significantly decreased elasticity was noted from measurements taken in the proximal ascending aorta as compared with the distal ascending aorta. Conclusions: Many echocardiographic techniques produce reproducible measurements of arterial elasticity. There may be intrinsic differences in arterial elasticity between different segments of the ascending aorta, which have not been previously described in children with normal cardiac anatomy. Comparisons of data from separate studies must take these differences into account. [source] Carbon Powder Based Films on Traditional Solid Electrodes as an Alternative to Disposable ElectrodesELECTROANALYSIS, Issue 11 2006Bogdan Yosypchuk Abstract The covering of conventional solid electrode with a film using an ink containing a conductive powder and a polymer enables to broaden the potential window of the original solid electrode. A solid silver amalgam electrode covered with such a film exhibits a potential window from ,600,mV to +1400,mV vs. SCE reference electrode. The renewal of the film is fast and simple: the electrode can be simply wiped with a filter paper to remove the old film and immersed into an ink solution or 1,2,,L of this ink solution can be applied to the surface of the electrode with a micro dispenser to form a new film. Therefore, just the inexpensive film at the electrode surface is disposable and there is no need to dispose the whole, more expensive electrode. Moreover, when a suitable electrochemical pretreatment of the film electrode is applied, the same film can be used for reproducible measurements for several days. [source] Liver fat is reproducibly measured using computed tomography in the Framingham Heart StudyJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 6 2008Elizabeth K Speliotes Abstract Background and Aims:, Fatty liver is the hepatic manifestation of obesity, but community-based assessment of fatty liver among unselected patients is limited. We sought to determine the feasibility of and optimal protocol for quantifying fat content in the liver in the Framingham Heart Study using multidetector computed tomography (MDCT) scanning. Methods:, Participants (n = 100, 49% women, mean age 59.4 years, mean body mass index 27.8 kg/m2) were drawn from the Framingham Heart Study cohort. Two readers measured the attenuation of the liver, spleen, paraspinal muscles, and an external standard from MDCT scans using multiple slices in chest and abdominal scans. Results:, The mean measurement variation was larger within a single axial computed tomography (CT) slice than between multiple axial CT slices for the liver and spleen, whereas it was similar for the paraspinal muscles. Measurement variation in the liver, spleen, and paraspinal muscles was smaller in the abdomen than in the chest. Three versus six measures of attenuation in the liver and two versus three measures in the spleen gave reproducible measurements of tissue attenuation (intraclass correlation coefficient [ICCC] of 1 in the abdomen). Intrareader and interreader reproducibility (ICCC) of the liver-to-spleen ratio was 0.98 and 0.99, the liver-to-phantom ratio was 0.99 and 0.99, and the liver-to-muscle ratio was 0.93 and 0.86, respectively. Conclusion:, One cross-sectional slice is adequate to capture the majority of variance of fat content in the liver per individual. Abdominal scan measures as compared to chest scan measures of fat content in the liver are more precise. The measurement of fat content in the liver on MDCT scans is feasible and reproducible. [source] Assessing arterial blood flow and vessel area variations using real-time zonal phase-contrast MRIJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2006Markus Oelhafen PhD Abstract Purpose To measure peripheral artery function using a real-time phase-contrast (PC)-MRI sequence with tailored image-processing algorithms for flow computation. Materials and Methods An approach to real-time flow measurements was developed based on two-dimensional spatially selective excitation pulses and consecutive tailored processing of the data to derive blood flow and vessel area variations. The data acquisition strategy allows for flow measurements at high spatial and temporal resolutions of 1 mm2 and 50 msec, respectively. In postprocessing the vessel area is automatically extracted using correlation measures in conjunction with morphological image operators. By means of in vitro and in vivo validations, it is shown that the current methods provide accurate and reproducible measurements of flow and vessel area variations. Results In vitro the comparison between the lumen area measured with the presented method and the values obtained by calliper gauge measurement showed a difference of 3.4% ± 3.4% (mean ± 2 SD). Similarly, the comparison between the stroke volumes determined with the presented method and by stopwatch and bucket measurements yielded a difference of 6.1% ± 2.1%. In vivo the results from the real-time measurements for lumen area and stroke volume were compared with those from a gated PC-MRI technique with differences of 4.8% ± 14% and 3.0% ± 24.7%, respectively. Conclusion The presented method constitutes a reliable tool set for quantifying the variations of blood flow and lumen area in the superficial femoral artery during reactive hyperemia and for studying their correlation with cardiovascular risk factors. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Assessing the skeleton in children and adolescents with disabilities: Avoiding pitfalls, maximising outcomes.JOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 6 2009A guide for the general paediatrician Abstract: Assessment of bone health of a young person with a severe disability is complex. Age of onset of disability, degree of physical limitation, nutritional status, calcium and vitamin D intake and pubertal progress all contribute to adult outcomes. Concomitant medical conditions may further adversely affect bone accrual. Bone quality, until growth is complete, must be interpreted in light of growth, height and puberty. For those children and adolescents who have disabilities where weight bearing is limited, satisfactory and reproducible measurements of bone density may be impossible to obtain. Fracture risk is dependent on the degree of immobilisation and on bone quality at any age. Meeting the goal of reducing extent and complications of adult osteoporosis is dependent upon an understanding of the nature and contribution of individual components of bone accrual, so that interventions can be appropriately targeted to optimise outcomes. [source] Wide area illumination Raman scheme for simple and nondestructive discrimination of seawater cultured pearlsJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2009Seok Chan Park Abstract Raman spectroscopy, along with discriminant partial least squares (PLS), was successfully used to discriminate among three different groups of cultured pearls (fresh water, Akoya and South seawater). The discrimination between Akoya and South seawater pearls using XRF (X-ray fluorescence), one of the most frequently adopted analytical methods in pearl analysis, has been especially difficult owing to their similar mineral compositions. The selective Raman features helped in effectively discriminating between these two pearl groups. The difference in the intensities of the CaCO3 bands of Akoya and South seawater pearls provided a valuable clue. Along with the selective Raman feature, a reproducible Raman spectral collection achieved using a wide area illumination (WAI) scheme played an important role in the determination of the pearl groups, although the pearls were hard-surfaced, round, solid samples of different sizes and surface shapes. Unwanted spectral variation originating from sensitivity to sample placement relative to the focal plane and from unsuccessful sample representation due to the probing of a localized area, factors that could possibly deteriorate Raman reproducibility, were substantially lessened using the WAI scheme. ATR (attenuated total reflection) IR spectroscopy requiring direct contact with the pearl could be inadequate for discrimination or classification where large numbers of repeating and reproducible measurements are required. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determining Contact Angles of Powders by Liquid PenetrationPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2004Ulrich Teipel Abstract The wettability of a powder is important, especially in chemical and pharmaceutical technologies when considering the manufacturing process and the properties of the final product. However, contact angle methods for powders are problematic. The common measurement techniques are the sessile drop method and the liquid penetration method. In this work the determination of contact angles of powders by liquid penetration is considered. In particular, we investigated the influence of the sample preparation and sampling device on the wetting process. A bulk with constant properties during the measurement must be guaranteed. We postulate a packing procedure to obtain reproducible measurements by ensuring constant powder properties. [source] Measurement of exhaled nitric oxide in young children during tidal breathing through a facemaskPEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 3 2005Peter Fleng Daniel Measurement of exhaled nitric oxide (eNO) offers a non-invasive means for assessment of airway inflammation. The currently available methods are difficult to apply in preschool children. We evaluated four methods potentially applicable for eNO measurement during tidal breathing in young children. eNO was assessed during tidal breathing in 24 children, 2,7 yr old, using a facemask which separated nasal and oral airflow. Facemasks with and without a one-way valve allowing exhalation through the nose were used. Expiratory flow control was not attempted. Measurements of eNO were performed both on-line and off-line. In 11 children, 8,12 yr old, measurements were compared with the standard single breath on-line method. eNO was significantly lower applying the one-way valve in on-line and off-line measurements in comparison with measurements without the valve [4.6 and 3.9 parts per billion (ppb) vs. 6.9 ppb and 6.5 ppb]. The mean within subject coefficient of variation (CV) was significantly lower in on-line measurements with the one-way valve (9.6%) compared with the other three methods (18.8, 27.7 and 29.3% respectively). Measurements with a facemask fitted with a one-way valve yielded similar eNO levels as the standard single breath method (7.0 ppb vs. 6.9 ppb) and reproducibility (9.8% vs. 7.1%). In conclusion, reproducible measurements of eNO can be obtained without control of expiration flow using a facemask fitted with a one-way valve on the nasal compartment. The likely explanation to this is that the one-way valve reduces the admixture of nasal NO, thereby improving the reliability of eNO measurements. [source] Integrated Sampling Procedure for Metabolome AnalysisBIOTECHNOLOGY PROGRESS, Issue 5 2006Jochen Schaub Metabolome analysis, the analysis of large sets of intracellular metabolites, has become an important systems analysis method in biotechnological and pharmaceutical research. In metabolic engineering, the integration of metabolome data with fluxome and proteome data into large-scale mathematical models promises to foster rational strategies for strain and cell line improvement. However, the development of reproducible sampling procedures for quantitative analysis of intracellular metabolite concentrations represents a major challenge, accomplishing (i) fast transfer of sample, (ii) efficient quenching of metabolism, (iii) quantitative metabolite extraction, and (iv) optimum sample conditioning for subsequent quantitative analysis. In addressing these requirements, we propose an integrated sampling procedure. Simultaneous quenching and quantitative extraction of intracellular metabolites were realized by short-time exposure of cells to temperatures ,95 °C, where intracellular metabolites are released quantitatively. Based on these findings, we combined principles of heat transfer with knowledge on physiology, for example, turnover rates of energy metabolites, to develop an optimized sampling procedure based on a coiled single tube heat exchanger. As a result, this sampling procedure enables reliable and reproducible measurements through (i) the integration of three unit operations into a one unit operation, (ii) the avoidance of any alteration of the sample due to chemical reagents in quenching and extraction, and (iii) automation. A sampling frequency of 5 s,1 and an overall individual sample processing time faster than 30 s allow observing responses of intracellular metabolite concentrations to extracellular stimuli on a subsecond time scale. Recovery and reliability of the unit operations were analyzed. Impact of sample conditioning on subsequent IC-MS analysis of metabolites was examined as well. The integrated sampling procedure was validated through consistent results from steady-state metabolite analysis of Escherichia coli cultivated in a chemostat at D = 0.1 h,1. [source] Development of a Transient Segregated Mathematical Model of the Semicontinuous Microbial Production Process of DihydroxyacetoneBIOTECHNOLOGY PROGRESS, Issue 1 2006Rüdiger Bauer For the mathematical description of the semicontinuous two-stage repeated-fed-batch fermentation of dihydroxyacetone (DHA), a novel segregated model incorporating transient growth rates was developed. The fermentation process was carried out in two stages. A viable, not irreversibly product-inhibited culture was maintained in the first reactor stage until a predetermined DHA threshold value was reached. In the second reactor stage, high final product concentrations of up to 220 g L,1 were reached while the culture was irreversibly product-inhibited. The experimentally observed changes of the physiological state of the culture due to product inhibition were taken into account by introducing a segregation into the mathematical model. It was shown that the state of the cells was dependent on the current environment and on the previous history. This phenomenon was considered in the model by utilizing delay time equations for the specific rates of growth on the primary and the secondary substrate. A comparison with reproducible measurements gave a good correlation between computation and experiment. The mathematical model was validated using independent own experimental data. A comparison with a stationary and nonsegregated model demonstrated the essential improvements of the novel model. It was deduced from the model calculations that high product formation rates of 3.3,3.5 g L,1 h,1 as well as high final DHA concentrations of 196,215 g L,1 can be obtained with a residual broth volume in the first reactor stage of 2% and a DHA threshold value in the range of 100,110g L,1. [source] The use of sputum cell counts to evaluate asthma medicationsBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 2 2001Krishnan Parameswaran Total and differential cell counts from hypertonic-induced, dithiothreitol-dispersed sputum provide reproducible measurements of airway inflammatory cell counts, which are responsive to treatment with anti-inflammatory drugs. They have helped to understand the kinetics of inflammatory cell changes in asthma after the reduction of corticosteroids and the subsequent re-introduction of treatment. They have identified that the presence of sputum eosinophilia in asthma, chronic cough and chronic airflow limitation is a predictor of steroid-responsiveness and of lack of ,asthma control'. They can be used to study the dose,response effect of inhaled corticosteroids and may be useful to establish the relative potency of different corticosteroid formulations and delivery devices. Sputum cell counts are also useful to study the potential anti-inflammatory effects of drugs like theophylline, long-acting ,-adrenoceptor agonists, leukotriene antagonists and newer drugs in development. They may be helpful to select add-on therapy to corticosteroids in ,difficult-to-control' asthma. [source] | ||||||||||||||||