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Accurate Tool (accurate + tool)
Selected AbstractsDynamic Wavelet Neural Network for Nonlinear Identification of Highrise BuildingsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2005Xiaomo Jiang Compared with conventional neural networks, training of a dynamic neural network for system identification of large-scale structures is substantially more complicated and time consuming because both input and output of the network are not single valued but involve thousands of time steps. In this article, an adaptive Levenberg,Marquardt least-squares algorithm with a backtracking inexact linear search scheme is presented for training of the dynamic fuzzy WNN model. The approach avoids the second-order differentiation required in the Gauss,Newton algorithm and overcomes the numerical instabilities encountered in the steepest descent algorithm with improved learning convergence rate and high computational efficiency. The model is applied to two highrise moment-resisting building structures, taking into account their geometric nonlinearities. Validation results demonstrate that the new methodology provides an efficient and accurate tool for nonlinear system identification of high-rising buildings. [source] Development and validation of a smoothing-splines-based correction method for improving the analysis of CEST-MR imagesCONTRAST MEDIA & MOLECULAR IMAGING, Issue 4 2008J. Stancanello Abstract Chemical exchange saturation transfer (CEST) imaging is an emerging MRI technique relying on the use of endogenous or exogenous molecules containing exchangeable proton pools. The heterogeneity of the water resonance frequency offset plays a key role in the occurrence of artifacts in CEST-MR images. To limit this drawback, a new smoothing-splines-based method for fitting and correcting Z -spectra in order to compensate for low signal-to-noise ratio (SNR) without any a priori model was developed. Global and local voxel-by-voxel Z -spectra were interpolated by smoothing splines with smoothing terms aimed at suppressing noise. Thus, a map of the water frequency offset (,zero' map) was used to correctly calculate the saturation transfer (ST) for each voxel. Simulations were performed to compare the method to polynomials and zero-only-corrected splines on the basis of SNR improvement. In vitro acquisitions of capillaries containing solutions of LIPOCEST agents at different concentrations were performed to experimentally validate the results from simulations. Additionally, ex vivo investigations of bovine muscle mass injected with LIPOCEST agents were performed as a function of increasing pulse power. The results from simulations and experiments highlighted the importance of a proper ,zero' correction (15% decrease of fictitious CEST signal in phantoms and ex vivo preparations) and proved the method to be more accurate compared with the previously published ones, often providing a SNR higher than 5 in different simulated and experimentally noisy conditions. In conclusion, the proposed method offers an accurate tool in CEST investigation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fundamentals of Metal-induced Crystallization of Amorphous SemiconductorsADVANCED ENGINEERING MATERIALS, Issue 3 2009Zumin Wang Abstract A general, quantitative model has been developed that provides fundamental understanding of the metal-induced crystallization (MIC) of amorphous semiconductors. Interface thermodynamics has been shown to play a decisive role for the whether or not occurrence of MIC. The model has been employed to predict the MIC temperature for various metal/amorphous-semiconductor systems. A consequence of the model is the prediction that the thickness of an ultrathin, pure Al film put on the top of an amorphous Si layer can be used as a very accurate tool to tune the crystallization temperature of amorphous Si. These theoretical predictions have been confirmed experimentally. The fundamental understanding reached may lead to pronounced technological progress in the low-temperature manufacturing of crystalline-Si-based devices deposited on cheap and flexible substrates such as glasses, plastics, and possibly even papers. [source] Shared near neighbours neural network model: a debris flow warning systemHYDROLOGICAL PROCESSES, Issue 14 2007Fi-John Chang Abstract The main purpose of this study is to develop a new type of artificial neural network based model for constructing a debris flow warning system. The Chen-Eu-Lan river basin, which is located in Central Taiwan, is assigned as the study area. The creek is one of the most well-known debris flow areas where several damaging debris flows have been reported in the last two decades. The hydrological and geological data, which might have great influence on the occurrence of debris flows, are first collected and analysed, then, the shared near neighbours neural network (SNN + NN) is presented to construct the debris flow warning system for the watershed. SNN is an unsupervised learning method that has the advantage of dealing with non-globular clusters, besides presenting computational efficiency. By using SNN, the compiled hydro-geological data set can easily and meaningfully be clustered into several categories. These categories can then be identified as ,occurrence' or ,no-occurrence' of debris flows. To improve the effectiveness of the debris flow warning system, a neural network framework is designed to connect all the clusters produced by the SNN method, whereas the connected weights of the network are adjusted through a supervised learning method. This framework is used and its applicability and practicability for debris flow warning are investigated. The results demonstrate that the proposed SNN + NN model is an efficient and accurate tool for the development of a debris flow warning system. Copyright © 2007 John Wiley & Sons, Ltd. [source] A ,-coordinate three-dimensional numerical model for surface wave propagationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2002Pengzhi Lin Abstract A three-dimensional numerical model based on the full Navier,Stokes equations (NSE) in , -coordinate is developed in this study. The , -coordinate transformation is first introduced to map the irregular physical domain with the wavy free surface and uneven bottom to the regular computational domain with the shape of a rectangular prism. Using the chain rule of partial differentiation, a new set of governing equations is derived in the , -coordinate from the original NSE defined in the Cartesian coordinate. The operator splitting method (Li and Yu, Int. J. Num. Meth. Fluids 1996; 23: 485,501), which splits the solution procedure into the advection, diffusion, and propagation steps, is used to solve the modified NSE. The model is first tested for mass and energy conservation as well as mesh convergence by using an example of water sloshing in a confined tank. Excellent agreements between numerical results and analytical solutions are obtained. The model is then used to simulate two- and three-dimensional solitary waves propagating in constant depth. Very good agreements between numerical results and analytical solutions are obtained for both free surface displacements and velocities. Finally, a more realistic case of periodic wave train passing through a submerged breakwater is simulated. Comparisons between numerical results and experimental data are promising. The model is proven to be an accurate tool for consequent studies of wave-structure interaction. Copyright © 2002 John Wiley & Sons, Ltd. [source] Using the Barnes Language Assessment with older ethnic minority groupsINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 4 2009Victoria Ramsey Abstract Objective There are many issues concerning the assessment of older people from ethnic minority groups, the most significant being the language barrier experienced by those whose English is an additional language (EAL). This study aimed to test the hypothesis that EAL participants would score less well than those with English as a first language (EFL) on the sub-tests of the Barnes Language Assessment (BLA), elucidate the reasons for any such differences and discuss the implications. Methods The Barnes Language Assessment (BLA) is an accurate tool providing information about expected patterns of language in different dementia syndromes. This study compares the performance of EAL participants with EFL participants. The BLA was administered to 144 participants, divided into sub-groups with respect to age, gender and educational background, none of whom had a working diagnosis of dementia. Results Results suggest that EAL speakers performed less well compared to EFL speakers when other variables were matched. Significantly better BLA scores, at the one percent level, were found in both EAL and EFL groups with higher educational achievement for eight of the 15 sub-tests. Conclusion Differences were found in performance on the BLA between EAL and EFL participants. The degree of difference between EAL and EFL speakers decreased as educational achievement rose. The consequences of these findings for service delivery and the problems of recruitment of older EAL participants are discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Rietveld quantitative amorphous content analysisJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2001A. G. De La Torre A procedure for Rietveld quantitative amorphous content analysis (RQACA) is outlined, in which the effects of systematic errors in the powder patterns are studied. The method derives the amorphous content from the small overestimation of an internal crystalline standard in a Rietveld refinement of an appropriate mixture. Of several standards studied, Al2O3 gave the best results. The statistical analysis of standard mixtures with a known amount of amorphous content indicated that this is a precise and accurate tool. It enables the measurement of the amorphous content with an accuracy close to 1%. Sample preparation and Rietveld analysis need to be optimized in order to minimize the systematic errors. The analysis of samples with phases displaying strong preferred orientation effects gives very high errors in the amorphous content. Samples with different absorption coefficients have also been studied in order to evaluate the importance of microabsorption. This plays an important role but it can be adequately corrected if the absorption coefficients of the standard and the sample are not very different. RQACA has been applied to tricalcium silicate, C3S, which is the main component of Portland cement. The average amorphous content of C3S, after microabsorption correction using two standards of higher and lower absorption coefficients, was found to be 19%. [source] Should TPMT genotype and activity be used to monitor 6-mercaptopurine treatment in children with acute lymphoblastic leukaemia?JOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 6 2007M. Fakhoury PharmD PhD Summary Background and objective: The activity of thiopurine S -methyltransferase (TPMT), a key enzyme in the metabolism of purine analogues, displays wide inter-subject variability partly due to a genetic polymorphism. Previous studies have suggested adjusting purine analogues dosing according to TPMT activity but measurements are costly and time-consuming. It is still unclear, especially under treatment, whether the simpler TPMT genotyping reliably predicts enzyme activity. Our aim was to study the possible correlation of TPMT genotype with phenotype. Methods: We determined the genotypic status and TMPT activity, at diagnosis and after 6 months of maintenance therapy, of 118 children with acute lymphoblastic leukaemia (ALL). Results and Discussion: Eighty-nine per cent of the children had a homozygous wild-type genotype (group 1), 11% had one or two mutant allele(s) (group 2). At both time points, TPMT activity (U/mL peripheral red blood cell) was significantly higher in group 1 than in group 2 (P < 0·001) but inter-group levels overlapped considerably. There was considerable heterogeneity in the percentage increase in TPMT activity after therapy, and little correlation between metabolites ratio [6-methylmercaptopurine derivative/6-thioguanine nucleotides (6-TGN)] and TPMT activity at the end of 6 months' maintenance treatment. These results show that TPMT activity cannot be used as an accurate tool for 6-mercaptopurine monitoring. Conclusion: Genotyping at diagnosis identifies patients with a homozygous mutant TPMT and may prevent severe and life-threatening toxicity. ALL treatment monitoring should preferentially be based on repeated determinations of intracellular active metabolites (6-TGN) and methylated metabolites. [source] Duplex sonographic criteria for measuring carotid stenosesJOURNAL OF CLINICAL ULTRASOUND, Issue 5 2002Ivan N. Staikov MD Abstract Purpose The aim of this retrospective study was to determine optimal duplex sonographic criteria for use in our institution for diagnosing severe carotid stenoses and to correlate those findings with angiographic measurements obtained by the European Carotid Surgery Trial (ECST), North American Symptomatic Carotid Endarterectomy Trial (NASCET), and Common Carotid (CC) methods of grading carotid stenoses. Methods We analyzed the angiographic data using the ECST, NASCET, and CC methods and compared the results with the duplex sonographic findings. We then calculated the sensitivity, specificity, positive and negative predictive values, and accuracy of the duplex sonographic method. Taking these parameters into account, the optimal intrastenotic peak systolic velocity (PSV) and end diastolic velocity (EDV) were derived for diagnosing severe stenoses according to the 3 angiographic methods. Results Optimal PSV and EDV values for diagnosing a 70% or greater stenosis in our laboratory were as follows: with the NASCET method of angiographic grading of stenoses, PSV 220 cm/second or greater and EDV 80 cm/second or greater, and with the ECST and CC methods, PSV 190 cm/second or greater, and EDV 65 cm/second or greater. The optimal PSV and EDV for diagnosing a stenosis of 80% or greater with the ECST grading method were 215 cm/second or greater and 90 cm/second or greater, respectively. Conclusions Duplex sonography is a sensitive and accurate tool for evaluating severe carotid stenoses. Optimal PSVs and EDVs vary according to the angiographic method used to grade the stenosis. They are similar for stenoses 70% or greater with the NASCET method and for stenoses 80% or greater with the ECST method. © 2002 Wiley Periodicals, Inc. J Clin Ultrasound 30:275,281, 2002; Published online in Wiley InterScience (www. interscience.wiley.com). DOI: 10.1002/jcu.10078 [source] Computer,Mediated Negotiated Interaction: An Expanded ModelMODERN LANGUAGE JOURNAL, Issue 1 2003Bryan Smith This study examines task,based, synchronous computer,mediated communication (CMC) among intermediate,level learners of English. The research specifically explores (a) whether learners engage in negotiated interaction when they encounter new lexical items, (b) whether task type has an effect on the amount of negotiation that transpires, and (c) how this computer,mediated negotiation compares to that noted in the face,to,face literature. Fourteen nonnative,nonnative dyads collaboratively completed 4 communicative tasks using ChatNet, a browser,based chat program. Each dyad completed 2 jigsaw and 2 decision,making tasks, which were each "seeded" with 8 target lexical items. The chatscripts reveal that learners do in fact negotiate for meaning in the CMC environment when nonunderstanding occurs. Furthermore, task type was found to have a definite influence on the extent to which learners engaged in negotiation, but not necessarily in the same way that has been observed in the face,to,face literature. Though the negotiation that occurs in the CMC environment proceeds in ways that are roughly similar to face,to,face negotiation, the observed differences call for a new model of computer,mediated negotiation. This new model is presented as a more accurate tool for describing computer,mediated negotiated interaction than those offered to chart face,to,face negotiation episodes. [source] Impact of off-pump coronary artery bypass surgery on postoperative renal dysfunction: Current best available evidence (Review Article)NEPHROLOGY, Issue 4 2006SHAHZAD G RAJA SUMMARY: Renal dysfunction is a serious complication after coronary artery bypass surgery with cardiopulmonary bypass. Cardiopulmonary bypass-related non-pulsatile flow, hypothermia, haemolysis, systemic inflammatory reactions and emboli are mentioned as possible causes for this postoperative renal dysfunction. In an attempt to avoid these deleterious effects of cardiopulmonary bypass, off-pump coronary artery bypass surgery has been rediscovered. Resurgence of interest in off-pump coronary artery bypass surgery is associated with the expectation that avoiding deleterious effects of the cardiopulmonary bypass leads to better outcomes and possibly decreased costs and resource use. We are currently practising in an era of evidence-based medicine that mandates the prospective randomized controlled trial as the most accurate tool for determining a treatment benefit compared with a control population. The present review article attempts to evaluate the current best available evidence from randomized controlled trials on the impact of off-pump coronary artery bypass surgery on postoperative renal dysfunction. [source] Investigation of binary polymer/surfactant or ternary polymer/surfactant/Cu2+ complexes in aqueous solution through Nile red probingPOLYMER INTERNATIONAL, Issue 8 2010Zacharoula Iatridi Abstract The optical properties (absorption and emission) of Nile red have been widely used for staining or probing purposes in diverse aqueous systems. However, the applications of Nile red for the determination of the critical aggregation concentration of polymer/surfactant complexes or for the investigation of ternary polymer/surfactant/Cu2+ systems are very limited. The interactions between anionic polyelectrolytes and the oppositely charged surfactant N,N,N,N -dodecyltrimethylammonium chloride were investigated in dilute aqueous solution, exploiting the optical properties of Nile red. It is shown that the emission properties of Nile red present better sensitivity than its absorption properties, concerning the detection of the hydrophobic polymer/surfactant complexes formed in aqueous solution. Moreover, it is found that the formation of ternary polymer/surfactant/Cu2+ complexes leads to a pronounced quenching of the luminescence of Nile red. The corresponding Stern,Volmer plots indicate that quenching is more favourable when coordination of Cu2+ ions with poly(sodium acrylate) takes place, as compared to simple electrostatic binding of these ions with poly(sodium styrene sulfonate). Nile red is a sensitive and accurate tool, as an alternative to pyrene, for the characterization of binary polymer/surfactant complexes or for obtaining information on the local arrangement of ternary polymer/surfactant/Cu2+ systems in aqueous solution. Copyright © 2010 Society of Chemical Industry [source] Performance of commercial latex agglutination tests for the differentiation of Candida dubliniensis and Candida albicans in routine diagnostics,APMIS, Issue 11 2007E. CHRYSSANTHOU Candida dubliniensis is phenotypically similar to Candida albicans and may therefore be underdiagnosed in the clinical microbiology laboratory. The performance of Bichro-Dubli latex agglutination test for rapid species identification of C. dubliniensis was prospectively evaluated on 111 vaginal and 118 respiratory isolates. These had presumptively been identified as C. albicans/C. dubliniensis by their green colonies on CHROMagar Candida plates. Bichro-Dubli test identifed 2 (1.8%) vaginal and 6 (5.1%) respiratory isolates as C. dubliniensis. The test was also positive for 37 C. dubliniensis control strains characterised by 18S-28S DNA-sequencing. Bichro-Dubli test is thus a sensitive and accurate tool for rapid diagnostics in routine laboratories. [source] "Nanoions": Fundamental Properties and Analytical Applications of Charged NanoparticlesCHEMPHYSCHEM, Issue 15 2007Kyle J. M. Bishop Abstract Mixtures of oppositely charged nanoparticles (NPs) precipitate sharply only at the point of NP electroneutrality. This behavior,reminiscent of the threshold precipitation of inorganic ions,is specific to the nanoscale and can be attributed to the formation of like-charged NP clusters stabilized in solution by mutual electrostatic repulsions. NP titrations based on this phenomenon provide a uniquely accurate tool for measuring charges tethered onto nanoscopic objects and for studying the thermodynamics of surface reactions at the nanoscale. [source] Diagnostic value of self-reported symptoms in Danish outpatients referred with symptoms consistent with colorectal cancerCOLORECTAL DISEASE, Issue 5 2007N. C. Bjerregaard Abstract Objective, To assess the association between self-reported symptoms and a diagnosis of colorectal cancer (CRC) in symptomatic outpatients without CRC risk factors, defined by a Danish expert group. Method, A cross-sectional study of patients aged 40 years and older referred by general practitioners to two Danish surgical outpatient clinics for symptoms consistent with CRC during a 16-month period. CRC was diagnosed at endoscopy and through follow up. Before their first appointment, participants completed a questionnaire about symptoms. Results, The study included 2172 patients. Of these, 122 were diagnosed with CRC (5.6%). Median age was 61 years (range: 40,97) and 44.0% were men. All symptoms had high (93.4,96.8%) negative predictive values for CRC. The highest positive predictive values (PPV) were found for dark rectal bleeding (PPV: 20.6%) and CRC was diagnosed in a first-degree relative over the age of 50 years (PPV: 11.2%). At multiple logistic regression analysis dark rectal blood was the most important predictor of CRC (OR: 7.4). Other predictors were age 60 years or older (OR: 3.0), change in frequency of bowel movements (OR: 2.5), CRC diagnosed in a first-degree relative over the age of 50 years (OR: 2.6), male gender (OR: 2.2) and mono-symptomatic fresh rectal blood (OR: 1.7). Conclusion, No self-reported symptoms presented by outpatients without CRC risk factors can be used accurately to identify patients with CRC with certainty. For clinical purposes self-reported symptoms seems thus not to be a useful accurate tool to distinguish between symptomatic outpatients with and without CRC. [source] Targeting Alzheimer's disease: Is there a light at the end of the tunnel?DRUG DEVELOPMENT RESEARCH, Issue 2 2002David Gurwitz Abstract The prevalence of Alzheimer's disease (AD) is on the rise in developed nations as a consequence of longer human lifespan. Current costs to society are alarming, and are projected to become even more demanding on future health budgets. Considering the relative success of Parkinson's disease pharmacotherapy, the success of AD therapy has been disappointing. Quite a few novel and promising AD drug targets are presented in this special issue of Drug Development Research. These are built on countless research studies, by many bright minds, carried out over the last several decades. However, the answer to the growing AD threat must include reliable and accurate tools, presently lacking, for its early diagnosis in at-risk individuals. Drug Dev. Res. 56:45,48, 2002. © 2002 Wiley-Liss, Inc. [source] Performance of sequence analysis, INNO-LiPA line probe assays and AFFIGENE assays in the detection of hepatitis B virus polymerase and precore/core promoter mutationsJOURNAL OF VIRAL HEPATITIS, Issue 6 2006A. Olivero Summary., In this study, we compare results obtained by sequences analysis and commercial kits in the detection of hepatitis B virus (HBV) polymerase and precore (PC) and core promoter mutations. A total of 23 serum samples from lamivudine treated patients were tested for polymerase mutations by direct sequencing, INNO-LiPA HBV DR and AFFIGENE HBV DE/3TC. Full concordance among the three assays was observed in 63% of the total analysed codons. Concordant results were obtained between sequencing and LiPA in 80%, between sequencing and AFFIGENE in 73% and between LiPA and AFFIGENE in 74% of all tested codons. All discrepancies were observed in mixed population samples in which AFFIGENE and LiPA detected additional viral variants not revealed by sequence. In two patients, with serial samples, LiPA detected earlier than sequence and AFFIGENE an emerging mutate strain. PC and core promoter viral variants were detected in 28 serum samples collected from 14 HBV inactive carriers and from 14 hepatitis B patients with chronic liver disease. Direct sequencing, INNO-LiPA HBV PreCore and AFFIGENE HBV MUTANT VL 19 showed fully coincident results in 88% of tested positions. These findings showed that all assays evaluated were sensitive and accurate tools to analyse HBV genomic variability. Sequence analysis is essential to study new emerging mutations as LiPA and AFFIGENE assays are more easily useful in clinical laboratories to detect the appearance of well-characterized HBV variants. [source] The combination of a blood test and Fibroscan improves the non-invasive diagnosis of liver fibrosisLIVER INTERNATIONAL, Issue 10 2009Jérôme Boursier Abstract Background and aims: Blood tests and liver stiffness evaluation (LSE) by ultrasonographic elastometry are accurate tools for diagnosing liver fibrosis. We evaluated whether their synchronous combination in new scores could improve the diagnostic accuracy and reduce liver biopsy requirement in algorithm. Methods: Three hundred and ninety patients with chronic liver disease of miscellaneous causes were included. Five blood fibrosis tests were evaluated: APRI, FIB-4, Hepascore, Fibrotest and FibroMeter. The reference was fibrosis Metavir staging. Results: Diagnosis of significant fibrosis (Metavir F,2). The most accurate synchronous combination was FibroMeter+LSE, which provided a significantly higher area under the receiver operating characteristic curve (0.892) than LSE alone (0.867, P=0.011) or Fibrometer (0.834, P<10,3). An algorithm using the FibroMeter+LSE combination and then a liver biopsy in indeterminate cases had 91.9% diagnostic accuracy and required significantly fewer biopsies (20.2%) than previously published Bordeaux algorithm (28.6%, P=0.02) or sequential algorithm for fibrosis evaluation (SAFE) (55.7%, P<10,3). The Angers algorithm performance was not significantly different between viral hepatitis and other causes. Diagnosis of cirrhosis. The most accurate synchronous combination was LSE+FibroMeter, which provided ,90% predictive values for cirrhosis in 90.6% of patients vs 87.4% for LSE (P=0.02) and 57.9% for FibroMeter (P<10,3). An algorithm including the LSE+FibroMeter combination, and then a liver biopsy in indeterminate cases, had a significantly higher diagnostic accuracy than the SAFE algorithm (91.0 vs 79.8%, P<10,3), and required significantly fewer biopsies than the Bordeaux algorithm (9.3 vs 25.3%, P<10,3). Conclusion: The synchronous combination of a blood test plus LSE improves the accuracy of the non-invasive diagnosis of liver fibrosis and, consequently, markedly decreases the biopsy requirement in the diagnostic algorithm, notably to <10% in cirrhosis diagnosis. [source] | |||||||||||||||||||