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High Precision (high + precision)
Selected AbstractsComputer-Based Analysis of Dynamic QT Changes: Toward High Precision and Individual Rate CorrectionANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2002Corina Dota M.D. Background: New strategies are needed to improve the results of automatic measurement of the various parts of the ECG signal and their dynamic changes. Methods: The EClysis software processes digitally-recorded ECGs from up to 12 leads at 500 Hz, using strictly defined algorithms to detect the PQRSTU points and to measure ECG intervals and amplitudes. Calculations are made on the averaged curve of each sampling period (beat group) or as means ± SD for beat groups, after being analyzed at the individual beat level in each lead. Resulting data sets can be exported for further statistical analyses. Using QT and R-R measured on beat level, an individual correction for the R-R dependence can be performed. Results: EClysis assigns PQRSTU points and intervals in a sensitive and highly reproducible manner, with coefficients of variation in ECG intervals corresponding to ca. 2 ms in the simulated ECG. In the normal ECG, the CVs are 2% for QRS, 0.8% for QT, and almost 6% for PQ intervals. EClysis highlights the increase in QT intervals and the decrease of T-wave amplitudes during almokalant infusion versus placebo. Using the observed linear or exponential relationships to adjust QT for R-R dependence in healthy subjects, one can eliminate this dependence almost completely by individualized correction. Conclusions: The EClysis system provides a precise and reproducible method to analyze ECGs. A.N.E. 2002;7(4):289,301 [source] Optimized sample preparation for isotopic analyses of CO2 in air: systematic study of precision and accuracy dependence on driving variables during CO2 purification processJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2005T. Bertolini Abstract A systematic analysis of efficiency, reproducibility and accuracy of cryogenic purification of CO2 from air samples for isotopic analyses is presented. The technical characteristics of the cryogenic line are given in detail. To study the cryogenic process, three different operating parameters are considered: flow rate of the gas entering the line, pressure of the gas in the line, and CO2 -trap shape. Experimental results demonstrate that efficiency, reproducibility and accuracy strongly depend on the CO2trap shape. Moreover, a dependence of reproducibility and accuracy on the flow rate of the gas is found, but not on its pressure. High precision (,0.02, for ,13C and ,0.05, for ,18O) and good accuracy (<0.09, for ,13C and <0.14, for ,18O) is achieved after applying the N2O correction. Copyright © 2005 John Wiley & Sons, Ltd. [source] NMR chemical shift measurements revisited: High precision measurementsCONCEPTS IN MAGNETIC RESONANCE, Issue 4 2007P. Granger Abstract Accurate chemical shifts are now accessible with high field NMR spectrometers. After the recall of the basic formulae, methods are proposed to measure chemical shifts with a high precision. Using two coaxial rotors at the magic angle, the necessary parameters used for correction are measured. The influence of different factors on the precision of the NMR measurements is discussed. Some proposals are given for MAS experiments used with solid-state samples. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 184,193, 2007. [source] How correct is the EOS of weakly nonideal hydrogen plasmas?CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2003A.N. Starostin Abstract Helioseismology opens new possibility to check EOS of weakly nonideal hydrogen plasmas with high precision, using reconstructed local sound velocities within 10-4 accuracy. A comparison of different theoretical models with experiment permits to verify the existing methods of calculation bound states and continuum contribution to the second virial coefficient within the framework of physical nature. The regular way of the deduction expression for EOS is presented and generalization of the EOS for broad atomic states and two temperature non-equilibrium case is proposed. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Pigments and proteins in green bacterial chlorosomes studied by matrix-assisted laser desorption ionization mass spectrometryFEBS JOURNAL, Issue 2 2000Søren Persson We have used matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) for mass determination of pigments and proteins in chlorosomes, the light-harvesting organelles from the photosynthetic green sulfur bacterium Chlorobium tepidum. By applying a small volume (1 µL) of a concentrated suspension of isolated chlorosomes directly to the target of the mass spectrometer we have been able to detect bacteriochlorophyll a and all the major homologs of bacteriochlorophyll c. The peak heights of the different bacteriochlorophyll c homologs in the MALDI spectra were proportional to peak areas obtained from HPLC analysis of the same sample. The same result was also obtained when whole cells of Chl. tepidum were applied to the target, indicating that MALDI-MS can provide a rapid method for obtaining a semiquantitative determination or finger-print of the bacteriochlorophyll homologs in a small amount of green bacterial cells. In addition to information on pigments, the MALDI spectra also contained peaks from chlorosome proteins. Thus we have been able with high precision to confirm the molecular masses of the chlorosome proteins CsmA and CsmE which have been previously determined by conventional biochemical and genetic methods, and demonstrate the presence of truncated versions of CsmA and CsmB. [source] Force Spectroscopic Investigations During the Local Oxidation of n -Octadecyltrichlorosilane Monolayers,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2006S. Hoeppener Abstract Scanning force spectroscopy (SFS) is a powerful tool for investigating surface properties with high precision. Unlike most common spectroscopic techniques, information about local properties can also be obtained from surface areas with nanometer dimensions. This makes SFS a useful investigative tool for small lithographic structures. We apply the continuous recording of force curves to extract valuable information about the local oxidation of a monolayer of n -octadecyltrichlorosilane molecules self-assembled on silicon. The oxidation is carried out while simultaneously recording the force curves during the application of a bias voltage to the tip. The dynamics of the induced surface modifications and changes in the surface properties are followed by analyzing specific spots in the force curves. [source] Slope stability analysis based on elasto-plastic finite element methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 14 2005H. Zheng Abstract The paper deals with two essential and related closely processes involved in the finite element slope stability analysis in two-dimensional problems, i.e. computation of the factors of safety (FOS) and location of the critical slide surfaces. A so-called ,,v inequality, sin ,,1 , 2v is proved for any elasto-plastic material satisfying Mohr,Coulomb's yield criterion. In order to obtain an FOS of high precision with less calculation and a proper distribution of plastic zones in the critical equilibrium state, it is stated that the Poisson's ratio v should be adjusted according to the principle that the ,,v inequality always holds as reducing the strength parameters c and ,. While locating the critical slide surface represented by the critical slide line (CSL) under the plane strain condition, an initial value problem of a system of ordinary differential equations defining the CSL is formulated. A robust numerical solution for the initial value problem based on the predictor,corrector method is given in conjunction with the necessary and sufficient condition ensuring the convergence of solution. A simple example, the kinematic solution of which is available, and a challenging example from a hydraulic project in construction are analysed to demonstrate the effectiveness of the proposed procedures. Copyright © 2005 John Wiley & Sons, Ltd. [source] Determination of phthalate esters in cosmetics by gas chromatography with flame ionization detection and mass spectrometric detectionINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 4 2005Huiming Chen GC-FID; GC-MS; Produits cosmétiques; Esters Phtaliques Synopsis A gas chromatography coupled with flame ionization detection (GC-FID) and mass spectrometric detection (MSD) method was developed to determine the six kinds of phthalate esters [dimethyl phthalate (DMP), diethyl phthalate (DEP), di- n -butyl phthalate (DBP), benzyl butyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP) and di- n -octyl phthalate (DOP)] in cosmetics (solid, cream and liquid cosmetics). The cosmetics were extracted with methanol by ultrasonic and then separated with high-speed centrifugation. The upper clear layer was dried and filtered through a 0.45 ,m pore diameter filter. The filtrate was injected into GC-FID/GC-MS for detection. GC-FID chromatogram was applied for qualitative analysis, external standard method was used for quantitative analysis. Confirmation of phthalate presence was undertaken by GC-EI-MS. The recovery range of all phthalates were between 92.0 and 110.0% with relative standard deviations between 1.95 and 5.92%. The low detection limits of the method were: 0.1 ng for DMP, DEP, DBP and BBP, 0.5 ng for DEHP and DOP. The method had advantages of high precision and sensitivity, simplicity of pretreatment. The method can be used to test the six kinds of phthalate esters in cosmetics. Resume Une méthode d'analyse par chromatographie gazeuse couplée à une détection par ionization de flamme (GC - FID) et une détection spectrométrique de masse (MSD) a été développée pour analyser 6 sortes d'esters phtaliques (phtalate de diméthyle (DMP), phtalate de diéthyle (DEP), phtalate de di- n -butyle (DBP), phtalate de benzylbutyle (BBP), phtalate de di-2-éthylhexyle (DEHP) et phtalate de di- n -octyle (DOP)) dans des produits cosmétiques (solides, crèmes et liquides). Les produits cosmétiques sont extraits au méthanol sous ultrason, puis séparés par ultracentrifugation. La phase supérieure limpide est déshydratée et filtrée sur un filtre de diamètre de pore moyen égal à 0,45 ,m. Le filtrat est injecté dans le système GC - FID/GC-MS pour analyse. Les chromatogrammes GC-FID sont utilisés pour l'analyse qualitative, des standards externes ont été utilisés pour l'analyse quantitative. La GC-EI-MS permet de confirmer la présence des esters phtaliques. Le taux de récupération de tous les esters est compris entre 92 et 110% avec une déviation standard allant de 1,95%à 5,92%. La limite de détection par cette méthode est de 0,1 ng pour DMP, DEP, DBP et BBP, 0,5 ng pour DEHP et DOP. Les avantages de cette méthode sont sa haute précision, sa sensibilité et la simplicité du prétraitement. Cette méthode peut être utilisée pour doser la présence des six sortes d'esters phtaliques dans des produits cosmétiques. [source] Inducing whole-assemblage change by experimental manipulation of habitat structureJOURNAL OF ANIMAL ECOLOGY, Issue 4 2007RALPH MAC NALLY Summary 1Habitat structure long has been identified as a primary factor influencing local assemblage composition. Most evidence has been in the form of correlations of species occurrence and assemblage composition over a range of habitats, with experimental verification of relationships being relatively uncommon because of the difficulties of enacting precise manipulations of habitat structure. 2Fallen timber (also known as coarse or large woody debris) is one of the few habitat-structural elements in forests and woodlands that can be manipulated with relatively high precision. We report on manipulations of wood-loads on 30 experimental 1-ha plots in floodplain forests of northern Victoria, Australia, over 4 years (one pre- and three post-manipulation). 3We show that very high wood-loads (80 Mg ha,1) and intermediate wood-loads derived from tree crowns (40 Mg ha,1) increase species richness (all species and ground-foraging species) and numbers of birds (all species and ground-foraging species) relative to the control plots. 4Three bird species consistently increased most following manipulations: white-plumed honeyeater Lichenostomus penicillatus (Gould 1837) (fam. Meliphagidae), brown treecreeper Climacteris picumnus (Temm. & Laug. 1824) (fam. Climacteridae) and yellow rosella Platycercus elegans flaveolus (Gould 1837) (fam. Psittacidae). The honeyeater is not considered as a ground or fallen timber dependent species, while the treecreeper and rosella both are regarded as being dependent on ground-layer structure. 5Fallen timber management needs to be considered in a landscape and temporal context for improving conservation of avian biodiversity. [source] A novel lattice-spacing comparator with resolution of 10,8JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2003Xiaowei Zhang A novel, fast and stable system for measuring the lattice spacing of a silicon crystal with a precision of 10,8 is described. Self selection of monochromatic X-rays by a monolithic double channel-cut crystal monochromator (MDCM), producing silicon 264 and 624 diffraction, may lead to a stable, highly collimated and narrow-bandwidth beam. When utilizing the 264 and 624 Bragg reflections of a silicon sample, the angular distance between the two associated Bragg peaks must be extremely small, so that the diffraction angle can be determined with high precision and the traveling time from one peak to the other can be considerably reduced by the order of at least three compared with the established classical Bond method. This so-called self-reference comparator method can dramatically save measurement time and can provide an absolute measurement on the basis of the known X-ray wavelength available from the MDCM. Thus a lattice-spacing measurement with resolution of 10,8, within a few tens of seconds for an area of 1,mm2 on a silicon sample, has been realised. [source] Transverse relaxation time (T2) mapping in the brain with off-resonance correction using phase-cycled steady-state free precession imagingJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2009Sean C.L. Deoni PhD Abstract Purpose To investigate a new approach for more completely accounting for off-resonance affects in the DESPOT2 (driven equilibrium single pulse observation of T2) mapping technique. Materials and Methods The DESPOT2 method derives T2 information from fully balanced steady-state free precession (bSSFP) images acquired over multiple flip angles. Off-resonance affects, which present as bands of altered signal intensity throughout the bSSFP images, results in erroneous T2 values in the corresponding calculated maps. Radiofrequency (RF) phase-cycling, in which the phase of the RF pulse is incremented along the pulse train, offers a potential method for eliminating these artifacts. In this work we present a general method, referred to as DESPOT2, with full modeling (DESPOT2-FM), for deriving T2, as well as off-resonance frequency, from dual flip angle bSSFP data acquired with two RF phase increments. Results The method is demonstrated in vivo through the acquisition of whole-brain, 1 mm3 isotropic T2 maps at 3T and shown to provide near artifact-free maps, even in areas with steep susceptibility-induced gradients. Conclusion DESPOT2-FM offers an efficient method for acquiring high spatial resolution, whole-brain T2 maps at 3T with high precision and free of artifact. J. Magn. Reson. Imaging 2009;30:411,417. © 2009 Wiley-Liss, Inc. [source] Enrichment and low-level determination of glyphosate, aminomethylphosphonic acid and glufosinate in drinking water after cleanup by cation exchange resinJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2010Markus Küsters Abstract For the determination of glyphosate, aminomethylphosphonic acid and glufosinate in drinking water, different procedures of enrichment and cleanup were examined using anion exchange or SPE. In many cases interactions of, e.g. alkaline earth metal ions especially calcium could be observed during enrichment and cleanup resulting in loss of analytes. For that reason, a novel cleanup and enrichment procedure for the determination of these phosphonic acid herbicides has been developed in drinking water using cation-exchange resin. In summary, the cleanup procedure with cation-exchange resin developed in this study avoids interactions as described above and is applicable to calcium-rich drinking water samples. After derivatization with 9-fluorenylmethylchloroformate followed by LC with fluorescence detection, LOD of 12, 14 and 12,ng/L and mean recoveries from real-world drinking water samples of 98±9, 100±16 and 101±11% were obtained for glyphosate, aminomethylphosphonic acid and glufosinate, respectively. The low LODs and the high precision permit the analysis of these phosphonic acid herbicides according to the guidelines of the European Commission. [source] Quantitative capillary electrophoresis and its application in analysis of alkaloids in tea, coffee, coca cola, and theophylline tabletsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 2 2009Mengjia Li Abstract A quantitative CE (qCE) system with high precision has been developed, in which a 4-port nano-valve was isolated from the electric field and served as sample injector. The accurate amount of sample was introduced into the CE system with high reproducibility. Based on this system, consecutive injections and separations were performed without voltage interruption. Reproducibilities in terms of RSD lower than 0.8% for retention time and 1.7% for peak area were achieved. The effectiveness of the system was demonstrated by the quantitative analysis of caffeine, theobromine, and theophylline in real samples, such as tea leaf, roasted coffee, coca cola, and theophylline tablets. [source] Characterization of biodiesel and biodiesel blends using comprehensive two-dimensional gas chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2008Warawut Tiyapongpattana Abstract In this work the development of a comprehensive 2-D GC flame ionization detection (GC×GC FID) method for biodiesel fuels is reported. This method is used for the analysis of fatty acid methyl esters (FAMEs) in both biodiesel (B100) and biodiesel blend (B5) samples. The separation of FAME was based on component boiling point in the first dimension and polarity in the second dimension by using a BPX5/BP20 column set to provide a measure of ,orthogonality' in the 2-D space. Here the columns are coupled with a cryogenic modulator operating in a novel temperature programmed mode (TM) whereby the cryotrap is progressively incremented in temperature as the oven temperature is increased. The final method employs eight cryotrap temperature settings. The developed GC×GC method is able to successfully characterize and identify both B100 and B5 FAME components, which are produced from a variety of vegetable oils, animal fats and waste cooking oils, with high precision. The method is capable of analysing FAME with carbon numbers C4,C24, and is particularly suitable to characterize various types of biodiesel, making it possible to differentiate the origin and type of FAME used in the biodiesel samples. [source] RP-HPTLC densitometric determination and validation of vanillin and related phenolic compounds in accelerated solvent extract of Vanilla planifolia,*JOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2007Upendra Kumar Sharma Abstract A simple, fast and sensitive RP-HPTLC method is developed for simultaneous quantitative determination of vanillin and related phenolic compounds in ethanolic extracts of Vanilla planifolia pods. In addition to this, the applicability of accelerated solvent extraction (ASE) as an alternative to microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and Soxhlet extraction was also explored for the rapid extraction of phenolic compounds in vanilla pods. Good separation was achieved on aluminium plates precoated with silica gel RP-18 F254S in the mobile phase of methanol/water/isopropanol/acetic acid (30:65:2:3, by volume). The method showed good linearity, high precision and good recovery of compounds of interest. ASE showed good extraction efficiency in less time as compared to other techniques for all the phenolic compounds. The present method would be useful for analytical research and for routine analysis of vanilla extracts for their quality control. [source] An automated approach for abstracting execution logs to execution eventsJOURNAL OF SOFTWARE MAINTENANCE AND EVOLUTION: RESEARCH AND PRACTICE, Issue 4 2008Zhen Ming Jiang Abstract Execution logs are generated by output statements that developers insert into the source code. Execution logs are widely available and are helpful in monitoring, remote issue resolution, and system understanding of complex enterprise applications. There are many proposals for standardized log formats such as the W3C and SNMP formats. However, most applications use ad hoc non-standardized logging formats. Automated analysis of such logs is complex due to the loosely defined structure and a large non-fixed vocabulary of words. The large volume of logs, produced by enterprise applications, limits the usefulness of manual analysis techniques. Automated techniques are needed to uncover the structure of execution logs. Using the uncovered structure, sophisticated analysis of logs can be performed. In this paper, we propose a log abstraction technique that recognizes the internal structure of each log line. Using the recovered structure, log lines can be easily summarized and categorized to help comprehend and investigate the complex behavior of large software applications. Our proposed approach handles free-form log lines with minimal requirements on the format of a log line. Through a case study using log files from four enterprise applications, we demonstrate that our approach abstracts log files of different complexities with high precision and recall. Copyright © 2008 John Wiley & Sons, Ltd. [source] Precision 1H,1H distance measurement via 13C NMR signals: utilization of 1H,1H double-quantum dipolar interactions recoupled under magic angle spinning conditionsMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2004Yoh Matsuki Abstract We applied the POST-C7 DQ-dipolar recoupling pulse sequence to the measurement of 1H,1H distances with high precision. The spectral resolution is enhanced by detecting the 1H magnetization via 13C signals. A least-squares fitting of the build-up curve of the transferred magnetization to the exact numerical simulations yielded a 1H,,1H, distance of 248 ± 4 pm for fully 13C-labeled L -valine. This distance agrees with the neutron diffraction study. The negative transferred magnetization clearly indicates that the direct DQ 1H,1H dipolar couplings have the largest effect. The signal for the magnetization transfer builds up rapidly by the direct 1H,1H dipolar coupling, and decreases to zero at longer mixing time when the relayed magnetization transfer becomes significant. This large intensity change of the signal leads to the high precision in the distance measurement. We inspected factors that limit the effective bandwidth of the POST-C7 recoupling for the 1H and 13C homonuclear spin systems. The spin interactions at times shorter than the cycle time of the C7 sequence were also evaluated to measure the distances. The carbon-detected 2D 1H DQ mixing experiment was demonstrated for the measurement of multiple 1H,1H distances. Copyright © 2004 John Wiley & Sons, Ltd. [source] Robust automated shimming technique using arbitrary mapping acquisition parameters (RASTAMAP)MAGNETIC RESONANCE IN MEDICINE, Issue 5 2004L. Martyn Klassen Abstract Quantitative MRI techniques as well as methods such as blood oxygen level-dependent (BOLD) imaging and in vivo spectroscopy require stringent optimization of magnetic field homogeneity, particularly when using high main magnetic fields. Automated shimming approaches require a method of measuring the main magnetic field, B0, followed by adjusting the currents in resistive shim coils to maximize homogeneity. A robust automated shimming technique using arbitrary mapping acquisition parameters (RASTAMAP) using a 3D multiecho gradient echo sequence that measures B0 with high precision was developed. Inherent compensation and postprocessing methods enable removal of artifacts due to hardware timing errors, gradient propagation delays, gradient amplifier asymmetry, and eddy currents. This allows field maps to be generated for any field of view, bandwidth, resolution, or acquisition orientation without custom tuning of sequence parameters. Field maps of an aqueous phantom show ± 1 Hz variation with altered acquisition orientations and bandwidths. Subsequent fitting of measured shim coil field maps allows calculation of shim currents to produce optimum field homogeneity. Magn Reson Med 51:881,887, 2004. © 2004 Wiley-Liss, Inc. [source] Accumulated thermal time, a key factor in affecting generation initiation and duration of top borer, Scirpophaga excerptalis Walker of sugarcane for its model-based chemical controlMETEOROLOGICAL APPLICATIONS, Issue 1 2010Arun K. Srivastava Abstract The seasonal variation in the initiation and duration of the I,III generations of the top borer was observed and analysed during five crop cycles from 2002,2003 to 2006,2007 at Lucknow in central Uttar Pradesh. The durations of the I,III generations were significantly correlated with the accumulated thermal time (Tbase = 10°C). Relatively higher temperature and consequently higher accumulated thermal time shortened the brood duration and early initiation of successive generations and vice versa. Based on these correlations, models were developed for predicting the initiation and duration of these generations. These models were validated for 2007,2008 crop cycle. The differences between observed and predicted duration of the I,III generation of the pest were 3, 1 and 3 days respectively reflecting high precision of the models. As the current management strategy for the chemical control of the pest is based on a calendar week, the shift of III generation initiation due to seasonal fluctuations could lead to escape from insecticide and render the chemical application pointless. The model-based control strategy is more precise and foretells the time of application of chemical against III generation of top borer which is most damaging to sugarcane crop. Copyright © 2009 Royal Meteorological Society [source] An adaptive spectroellipsometer for ecological monitoringMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2009F. A. Mkrtchyan Abstract In this article, the creation of multichannel polarization optical instrumentation and the use of spectroellipsometric technology for the real-time ecological control of aquatic environment is discussed. It was shown that spectroellipsometric devices give high precision of measurements of water quality characteristics. Spectroellipsometric multichannel measurements in an aquatic environment are conducted by the algorithms for the recognition and identification of pollutants. Some results of an adaptive spectroellipsometer applications are given. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2792,2795, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24730 [source] A Crank,Nicholson-based unconditionally stable time-domain algorithm for 2D and 3D problemsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2007Xin Xie Abstract It has been shown that both ADI-FDTD and CN-FDTD are unconditionally stable. While the ADI is a second-order approximation, CN is only in the first order. However, analytical expressions reveal that the CN-FDTD has much smaller truncation errors and is more accurate than the ADI-FDTD. Nonetheless, it is more difficult to implement the CN than the ADI, especially for 3D problems. In this paper, we present an unconditionally stable time-domain method, CNRG-TD, which is based upon the Crank,Nicholson scheme and implemented with the Ritz,Galerkin procedure. We provide a physically meaningful stability proof, without resorting to tedious symbolic derivations. Numerical examples of the new method demonstrate high precision and high efficiency. In a 2D capacitance problem, we have enlarged the time step, ,t, 400 times of the CFL limit, yet preserved good accuracy. In the 3D antenna case, we use the time step, ,t, 7.6 times larger that that of the ADI-FDTD i.e., more than 38 times of the CFL limit, with excellent agreement of the benchmark solution. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 261,265, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22101 [source] A hybrid N -body code incorporating algorithmic regularization and post-Newtonian forcesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008S. Harfst ABSTRACT We describe a novel N -body code designed for simulations of the central regions of galaxies containing massive black holes. The code incorporates Mikkola's ,algorithmic' chain regularization scheme including post-Newtonian terms up to PN2.5 order. Stars moving beyond the chain are advanced using a fourth-order integrator with forces computed on a GRAPE board. Performance tests confirm that the hybrid code achieves better energy conservation, in less elapsed time, than the standard scheme and that it reproduces the orbits of stars tightly bound to the black hole with high precision. The hybrid code is applied to two sample problems: the effect of finite- N gravitational fluctuations on the orbits of the S-stars, and inspiral of an intermediate-mass black hole into the Galactic Centre. [source] Diagnostic accuracy of verbal autopsies in ascertaining the causes of stillbirths and neonatal deaths in rural GhanaPAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 5 2008Karen M. Edmond Summary This study evaluated the diagnostic accuracy of a verbal autopsy (VA) tool in ascertaining the causes of stillbirths and neonatal deaths in rural Ghana and was nested within a community-based maternal vitamin A supplementation trial (ObaapaVitA trial). All stillbirths and neonatal deaths between 1 January 2003 and 30 June 2004 were prospectively included. Community VAs were carried out within 6 months of death and were classified with a primary cause of death by three experienced paediatricans. The reference standard diagnosis was obtained by the study paediatrician in 4 district hospitals in the study area. There were 20 317 deliveries, 661 stillbirths and 590 neonatal deaths with a VA diagnosis in the study population. A total of 311 stillbirths and 191 neonatal deaths had both a VA and a hospital reference standard diagnosis. The VA performed poorly for stillbirth diagnoses such as congenital abnormalities and maternal haemorrhage. Accuracy was higher for intrapartum obstetric complications and antepartum maternal disease. For neonatal deaths, sensitivity was >60% for all major causes; specificity was 76% for birth asphyxia but >85% for prematurity and infection. Overall, VA diagnostic accuracy was higher than expected in this rural African setting. Our classification system was based on the expected public health importance of the individual causes of death, differing implications for intervention and the ability to distinguish between the individual causes in low-resource settings. We believe this system was easier to use than traditional approaches and resulted in high precision and accuracy. However, further simplifications are needed to allow use of the World Health Organisation VA in routine child health programmes. The diagnostic accuracy of the VA tool should also be assessed in other regions and in multicentre studies. [source] Determination of lead content in medicinal plants by pre-concentration flow injection analysis,flame atomic absorption spectrometryPHYTOCHEMICAL ANALYSIS, Issue 6 2009Marina M. A. Campos Abstract Introduction , Although medicinal plants are widely used throughout the world, few studies have been carried out concerning the levels of heavy metal contaminants present. Such metals are highly toxic to living organisms even in low concentrations owing to their cumulative effect. The present paper describes the the development of a pre-concentration flow injection analysis-flame atomic absorption spectrometric system to determine the lead content in medicinal plants at the ppb level. Objective , To develop a pre-concentration flow injection analysis-flame atomic absorption spectrometric system to determine the lead content in medicinal plants at the ppb level. Methodology , A pre-concentration flow system was coupled to a flame atomic absorption spectrometer. The plant samples were analysed after nitroperchloric digestion. The proposed system was optimised by evaluating the following parameters: nature, concentration and volume of the eluent solution, elution flow rate, elution efficiency, pre-concentration flow rate and pre-concentration time. Results , The proposed system exhibited good performance with high precision and repeatability (RSD , 2.36%), excellent linearity (r = 0.9999), low sample consumption (10.5 mL per determination) and an analytical throughput of 55 samples/h. Lead concentrations ranged from 3.37 ± 0.25 to 7.03 ± 0.51 ,g/g in dry material. This concentration interval is greater than that previously published in the literature. Conclusion , The inclusion of a pre-concentration column in the flow manifold improved the sensitivity of the spectrometer. Thus, it was possible to determine the analyte at the ng/mL level in sample solutions of medicinal plants. This is a very important accomplishment, especially when the cumulative effect of heavy metals in living organisms is considered. Copyright © 2009 John Wiley & Sons, Ltd. [source] NIR, DSC, and FTIR as quantitative methods for compositional analysis of blends of polymers obtained from recycled mixed plastic wastePOLYMER ENGINEERING & SCIENCE, Issue 9 2001Walker Camacho Methods for the determination of the composition of two binary blends in mixtures of recycled polymeric materials were analyzed and compared. Recycled polypropylene/polyethylene (PP/HDPE) and recycled poly(acryl-butadiene-styrene) and polypropylene(ABS/PP) were used to develop and validate the methods. Diffuse reflectance near infrared spectroscopy (NIRS) offers high sensitivity and ease of operation and a possibility to perform multivariate data analysis. In comparison, differential scanning calorimetry (DSC) and Mid-IR, which are commonly used for this purpose require certain sample preparation and are indeed time consuming. In addition, the low sensitivity of these two methods to concentrations lower than 1% wt makes their application in quality control of recycled polymers inappropriate. NIR can be used for estimating the composition of the recyclate on-line in only a few seconds, no sample preparation is required, and high precision is achieved. We obtained a root mean square error of prediction (RMSEP) equal to 0.21% wt in the interval from 0-15% wt of PP in HDPE and a RMSEP equal to 0.91% wt in the interval 0-100%. For blends of PP/ABS a RMSEP of 0.74% wt in the range 0-100% and 0.32% wt in the range 0-15% wt PP was calculated. Most of the variation in the spectral data with respect to the polymer blend composition for all the studied blends were explained by two principal components (PC). The optimal number of factors (PC) was determined by cross-validation analysis. [source] The structure and dynamics in solution of Cu(I) pseudoazurin from Paracoccus pantotrophusPROTEIN SCIENCE, Issue 5 2000Gary S. Thompson Abstract The solution structure and backbone dynamics of Cu(I) pseudoazurin, a 123 amino acid electron transfer protein from Paracoccus pantotrophus, have been determined using NMR methods. The structure was calculated to high precision, with a backbone RMS deviation for secondary structure elements of 0.35 ± 0.06 A, using 1,498 distance and 55 torsion angle constraints. The protein has a double-wound Greek-key fold with two ,-helices toward its C-terminus, similar to that of its oxidized counterpart determined by X-ray crystallography. Comparison of the Cu(I) solution structure with the X-ray structure of the Cu(II) protein shows only small differences in the positions of some of the secondary structure elements. Order parameters S2, measured for amide nitrogens, indicate that the backbone of the protein is rigid on the picosecond to nanosecond timescale. [source] Methods to adjust for the interference of N2O on ,13C and ,18O measurements of CO2 from soil mineralization,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2005D. Beheydt In this paper we present an overview of the present knowledge relating to methods that avoid interference of N2O on ,13C and ,18O measurements of CO2. The main focus of research to date has been on atmospheric samples. However, N2O is predominantly generated by soil processes. Isotope analyses related to soil trace gas emissions are often performed with continuous flow isotope ratio mass spectrometers, which do not necessarily have the high precision needed for atmospheric research. However, it was shown by using laboratory and field samples that a correction to obtain reliable ,13C and ,18O values is also required for a commercial continuous flow isotope ratio mass spectrometer. The capillary gas chromatography column of the original equipment was changed to a packed Porapak Q column. This adaptation resulted in an improved accuracy and precision of ,13C (standard deviationGhent: from 0.2 to 0.08,; standard deviationLincoln: from 0.2 to 0.13,) of CO2 for N2O/CO2 ratios up to 0.1. For ,18O there was an improvement for the standard deviation measured at Ghent University (0.13 to 0.08,) but not for the measurements at Lincoln University (0.08 to 0.23,). The benefits of using the packed Porapak Q column compared with the theoretical correction method meant that samples were not limited to small N2O concentrations, they did not require an extra N2O concentration measurement, and measurements were independent of the variable isotopic composition of N2O from soil. Copyright © 2005 John Wiley & Sons, Ltd. [source] Natural intramolecular isotope measurements in physiology: elements of the case for an effort toward high-precision position-specific isotope analysis,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 15 2001J. T. Brenna Chemical information available in organisms can be categorized into three major domains, macromolecular, small molecules, and isotope ratios. Information about physiological state is commonly obtained by qualitative and quantitative analysis in the macromolecular and small molecule domains. Genomics and proteomics are emerging approaches to analysis of macromolecules, and both areas yield definitive information on present physiological state. There is relatively little record of past physiological states of the individual available in these domains. Natural isotopic variability, particularly on an intramolecular level, is likely to retain more physiological history. Because of ubiquitous isotopic fractionation, every stereochemically unique position in every molecule has an isotope ratio that reflects the processes of synthesis and degradation. This fact highlights a vast amount of organismal chemical information that is essentially unstudied. Isotope measurements can be classified according to the chemical complexity of the analyte into bulk, compound-specific, and position-specific or intramolecular levels. Recent advances in analysis of isotope ratios are transforming natural science, and particularly answering questions about ecosystems using bulk methods; however, they have had relatively little impact on physiology. This may be because the vast complexities of physiological questions demand very selective information available in position-specific isotope analysis (PSIA). The relatively few high-precision PSIA studies, based on isotope ratio mass spectrometry (IRMS), have revealed intramolecular isotope ratio differences in pivotal physiological compounds including amino acids, glucose, glycerol, acetate, fatty acids, and purines. The majority of these analyses have been accomplished by laborious offline methods; however, recent advances in instrumentation presage rapid PSIA that will be necessary to attack real physiological problems. Gas-phase pyrolysis has been shown to be an effective method to determine 13C/12C at high precision for molecular fragments, and technologies to extend C-based PSIA to N and other organic elements are emerging. Two related efforts are warranted, (a) development of rapid, convenient, and sensitive methods for high-precision PSIA, a necessary precursor to (b) a concerted investigation into the relationship of metabolic state to intramolecular isotope ratio. Inherent in this latter goal is the need to identify long-lived molecules in long-lived cells that retain a record of early isotopic conditions, as has been shown for post-mortem human neuronal DNA. Using known metabolic precursor-product relationships between intramolecular positions, future studies of physiological isotope fractionation should reveal the relationship of diet and environment to observed isotope ratio. This science of isotope physiology, or simply isotopics, should add an important tool for elucidation of early factors that effect later health, probably the most difficult class of biomedical issues. Copyright © 2001 John Wiley & Sons, Ltd. [source] Soft measurement of pulp suspension flow velocity based on wavelet transformTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010Qiang Zhou Abstract A soft measurement technique is presented, which the pulp suspension flow velocity (PSFV) can be obtained by analysis of pulp fibre consistency signal without using the flow sensor or flow meter. Doppler Effect in pulp fibre consistency signal, which is caused by the relative motion between pulp suspension flowing in pulp pipe and consistency sensor fixed in the pipe, is discovered on the basis of studying the structure of pulp suspension and the properties of pulp fibre consistency signal, and it is proved by wavelet transform (WT) in this paper. WT are used to analyse pulp fibre consistency signal based on Doppler Effect. PSFV can be determined by the average period of WT which is used to analyse pulp fibre consistency signal based on Doppler Effect. The corresponding tests indicate that the measurement technique is feasible with high precision and better dynamic characteristics. Une technique de mesurage douce est présentée selon laquelle la vélocité de débit de suspension de pâte (pulp suspension flow velocity - PSFV) peut être obtenue par analyse du signal de la consistance de la pâte sans faire appel à des détecteurs de débit ou à des débitmètres. L'effet Doppler dans le signal de consistance de la pâte, causé par le mouvement relatif entre la pâte en suspension s'écoulant dans la conduite de pâte et le senseur de consistance fixé dans la conduite, a été découvert en se basant sur l'étude de la structure de la pâte en suspension et les propriétés du signal de consistance de la pâte et il est prouvé par transformation d'ondelettes. La masse atomique est utilisée pour analyser le signal de consistance de la pâte basée sur l'effet Dopler. Le PSFV peut être déterminé par la période moyenne de la masse atomique utilisée pour analyser la consistance de la fibre de la pâte s'appuyant sur l'effet Dopler. Les essais correspondants indiquent que la technique de mesurage est réalisable avec grande précision et de meilleures caractéristiques dynamiques. [source] Robotics in neurosurgery: state of the art and future technological challengesTHE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 1 2004L Zamorano Abstract The use of robotic technologies to assist surgeons was conceptually described almost thirty years ago but has only recently become feasible. In Neurosurgery, medical robots have been applied to neurosurgery for over 19 years. Nevertheless this field remains unknown to most neurosurgeons. The intrinsic characteristics of robots, such as high precision, repeatability and endurance make them ideal surgeon's assistants. Unfortunately, limitations in the current available systems make its use limited to very few centers in the world. During the last decade, important efforts have been made between academic and industry partnerships to develop robots suitable for use in the operating room environment. Although some applications have been successful in areas of laparoscopic surgery and orthopaedics, Neurosurgery has presented a major challenge due to the eloquence of the surrounding anatomy. This review focuses on the application of medical robotics in neurosurgery. The paper begins with an overview of the development of the medical robotics, followed by the current clinical applications in neurosurgery and an analysis of current limitations. We discuss robotic applications based in our own experience in the field. Next, we discuss the technological challenges and research areas to overcome those limitations, including some of our current research approaches for future progress in the field Copyright © 2004 Robotic Publications Ltd. [source] | |||||||||||||||||||||||||||||||||||||