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MPI
Selected AbstractsAn MPI Parallel Implementation of Newmark's MethodCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2000Ali Namazifard The standard message-passing interface (MPI) is used to parallelize Newmark's method. The linear matrix equation encountered at each time step is solved using a preconditioned conjugate gradient algorithm. Data are distributed over the processors of a given parallel computer on a degree-of-freedom basis; this produces effective load balance between the processors and leads to a highly parallelized code. The portability of the implementation of this scheme is tested by solving some simple problems on two different machines: an SGI Origin2000 and an IBM SP2. The measured times demonstrate the efficiency of the approach and highlight the maintenance advantages that arise from using a standard parallel library such as MPI. [source] A comparative study of Java and C performance in two large-scale parallel applicationsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2009Aamir Shafi Abstract In the 1990s the Message Passing Interface Forum defined MPI bindings for Fortran, C, and C++. With the success of MPI these relatively conservative languages have continued to dominate in the parallel computing community. There are compelling arguments in favour of more modern languages like Java. These include portability, better runtime error checking, modularity, and multi-threading. But these arguments have not converted many HPC programmers, perhaps due to the scarcity of full-scale scientific Java codes, and the lack of evidence for performance competitive with C or Fortran. This paper tries to redress this situation by porting two scientific applications to Java. Both of these applications are parallelized using our thread-safe Java messaging system,MPJ Express. The first application is the Gadget-2 code, which is a massively parallel structure formation code for cosmological simulations. The second application uses the finite-domain time-difference method for simulations in the area of computational electromagnetics. We evaluate and compare the performance of the Java and C versions of these two scientific applications, and demonstrate that the Java codes can achieve performance comparable with legacy applications written in conventional HPC languages. Copyright © 2009 John Wiley & Sons, Ltd. [source] Factors affecting the performance of parallel mining of minimal unique itemsets on diverse architecturesCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 9 2009D. J. Haglin Abstract Three parallel implementations of a divide-and-conquer search algorithm (called SUDA2) for finding minimal unique itemsets (MUIs) are compared in this paper. The identification of MUIs is used by national statistics agencies for statistical disclosure assessment. The first parallel implementation adapts SUDA2 to a symmetric multi-processor cluster using the message passing interface (MPI), which we call an MPI cluster; the second optimizes the code for the Cray MTA2 (a shared-memory, multi-threaded architecture) and the third uses a heterogeneous ,group' of workstations connected by LAN. Each implementation considers the parallel structure of SUDA2, and how the subsearch computation times and sequence of subsearches affect load balancing. All three approaches scale with the number of processors, enabling SUDA2 to handle larger problems than before. For example, the MPI implementation is able to achieve nearly two orders of magnitude improvement with 132 processors. Performance results are given for a number of data sets. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structural testing criteria for message-passing parallel programsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 16 2008S. R. S. Souza Abstract Parallel programs present some features such as concurrency, communication and synchronization that make the test a challenging activity. Because of these characteristics, the direct application of traditional testing is not always possible and adequate testing criteria and tools are necessary. In this paper we investigate the challenges of validating message-passing parallel programs and present a set of specific testing criteria. We introduce a family of structural testing criteria based on a test model. The model captures control and data flow of the message-passing programs, by considering their sequential and parallel aspects. The criteria provide a coverage measure that can be used for evaluating the progress of the testing activity and also provide guidelines for the generation of test data. We also describe a tool, called ValiPar, which supports the application of the proposed testing criteria. Currently, ValiPar is configured for parallel virtual machine (PVM) and message-passing interface (MPI). Results of the application of the proposed criteria to MPI programs are also presented and analyzed. Copyright © 2008 John Wiley & Sons, Ltd. [source] An adaptive extension library for improving collective communication operationsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 10 2008O. Hartmann Abstract In this paper, we present an adaptive extension library that combines the advantage of using a portable MPI library with the ability to optimize the performance of specific collective communication operations. The extension library is built on top of MPI and can be used with any MPI library. Using the extension library, performance improvements can be achieved by an orthogonal organization of the processors in 2D or 3D meshes and by decomposing the collective communication operations into several consecutive phases of MPI communication. Additional point-to-point-based algorithms are also provided. The extension library works in two steps, an a priori configuration phase detecting possible improvements for implementing collective communication for the MPI library used and an execution phase selecting a better implementation during execution time. This allows an adaptation of the performance of MPI programs to a specific execution platform and communication situation. The experimental evaluation shows that significant performance improvements can be obtained for different MPI libraries by using the library extension for collective MPI communication operations in isolation as well as in the context of application programs. Copyright © 2007 John Wiley & Sons, Ltd. [source] APEX-Map: a parameterized scalable memory access probe for high-performance computing systems,CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 17 2007Erich Strohmaier Abstract The memory wall between the peak performance of microprocessors and their memory performance has become the prominent performance bottleneck for many scientific application codes. New benchmarks measuring data access speeds locally and globally in a variety of different ways are needed to explore the ever increasing diversity of architectures for high-performance computing. In this paper, we introduce a novel benchmark, APEX-Map, which focuses on global data movement and measures how fast global data can be fed into computational units. APEX-Map is a parameterized, synthetic performance probe and integrates concepts for temporal and spatial locality into its design. Our first parallel implementation in MPI and various results obtained with it are discussed in detail. By measuring the APEX-Map performance with parameter sweeps for a whole range of temporal and spatial localities performance surfaces can be generated. These surfaces are ideally suited to study the characteristics of the computational platforms and are useful for performance comparison. Results on a global-memory vector platform and distributed-memory superscalar platforms clearly reflect the design differences between these different architectures. Published in 2007 by John Wiley & Sons, Ltd. [source] A test suite for parallel performance analysis toolsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 11 2007Michael Gerndt Abstract Parallel performance analysis tools must be tested as to whether they perform their task correctly, which comprises at least three aspects. First, it must be ensured that the tools neither alter the semantics nor distort the run-time behavior of the application under investigation. Next, it must be verified that the tools collect the correct performance data as required by their specification. Finally, it must be checked that the tools perform their intended tasks and detect relevant performance problems. Focusing on the latter (correctness) aspect, testing can be done using synthetic test functions with controllable performance properties, possibly complemented by real-world applications with known performance behavior. A systematic test suite can be built from synthetic test functions and other components, possibly with the help of tools to assist the user in putting the pieces together into executable test programs. Clearly, such a test suite can be highly useful to builders of performance analysis tools. It is surprising that, up until now, no systematic effort has been undertaken to provide such a suite. In this paper we describe the APART Test Suite (ATS) for checking the correctness (in the above sense) of parallel performance analysis tools. In particular, we describe a collection of synthetic test functions which allows one to easily construct both simple and more complex test programs with desired performance properties. We briefly report on experience with MPI and OpenMP performance tools when applied to the test cases generated by ATS. Copyright © 2006 John Wiley & Sons, Ltd. [source] Seine: a dynamic geometry-based shared-space interaction framework for parallel scientific applicationsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2006L. Zhang Abstract While large-scale parallel/distributed simulations are rapidly becoming critical research modalities in academia and industry, their efficient and scalable implementations continue to present many challenges. A key challenge is that the dynamic and complex communication/coordination required by these applications (dependent on the state of the phenomenon being modeled) are determined by the specific numerical formulation, the domain decomposition and/or sub-domain refinement algorithms used, etc. and are known only at runtime. This paper presents Seine, a dynamic geometry-based shared-space interaction framework for scientific applications. The framework provides the flexibility of shared-space-based models and supports extremely dynamic communication/coordination patterns, while still enabling scalable implementations. The design and prototype implementation of Seine are presented. Seine complements and can be used in conjunction with existing parallel programming systems such as MPI and OpenMP. An experimental evaluation using an adaptive multi-block oil-reservoir simulation is used to demonstrate the performance and scalability of applications using Seine. Copyright © 2006 John Wiley & Sons, Ltd. [source] Parallel divide-and-conquer scheme for 2D Delaunay triangulationCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2006Min-Bin Chen Abstract This work describes a parallel divide-and-conquer Delaunay triangulation scheme. This algorithm finds the affected zone, which covers the triangulation and may be modified when two sub-block triangulations are merged. Finding the affected zone can reduce the amount of data required to be transmitted between processors. The time complexity of the divide-and-conquer scheme remains O(n log n), and the affected region can be located in O(n) time steps, where n denotes the number of points. The code was implemented with C, FORTRAN and MPI, making it portable to many computer systems. Experimental results on an IBM SP2 show that a parallel efficiency of 44,95% for general distributions can be attained on a 16-node distributed memory system. Copyright © 2006 John Wiley & Sons, Ltd. [source] Performance comparison of MPI and OpenMP on shared memory multiprocessorsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2006Géraud Krawezik Abstract When using a shared memory multiprocessor, the programmer faces the issue of selecting the portable programming model which will provide the best performance. Even if they restricts their choice to the standard programming environments (MPI and OpenMP), they have to select a programming approach among MPI and the variety of OpenMP programming styles. To help the programmer in their decision, we compare MPI with three OpenMP programming styles (loop level, loop level with large parallel sections, SPMD) using a subset of the NAS benchmark (CG, MG, FT, LU), two dataset sizes (A and B), and two shared memory multiprocessors (IBM SP3 NightHawk II, SGI Origin 3800). We have developed the first SPMD OpenMP version of the NAS benchmark and gathered other OpenMP versions from independent sources (PBN, SDSC and RWCP). Experimental results demonstrate that OpenMP provides competitive performance compared with MPI for a large set of experimental conditions. Not surprisingly, the two best OpenMP versions are those requiring the strongest programming effort. MPI still provides the best performance under some conditions. We present breakdowns of the execution times and measurements of hardware performance counters to explain the performance differences. Copyright © 2005 John Wiley & Sons, Ltd. [source] JOPI: a Java object-passing interfaceCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 7-8 2005Jameela Al-Jaroodi Abstract Recently there has been an increasing interest in developing parallel programming capabilities in Java to harness the vast resources available in clusters, grids and heterogeneous networked systems. In this paper, we introduce a Java object-passing interface (JOPI) library. JOPI provides Java programmers with the necessary functionality to write object-passing parallel programs in distributed heterogeneous systems. JOPI provides a Message Passing Interface (MPI)-like interface that can be used to exchange objects among processes. In addition to the well-known benefits of the object-oriented development model, using objects to exchange information in JOPI is advantageous because it facilitates passing complex structures and enables the programmer to isolate the problem space from the parallelization problem. The run-time environment for JOPI is portable, efficient and provides the necessary functionality to deploy and execute parallel Java programs. Experiments were conducted on a cluster system and a collection of heterogeneous platforms to measure JOPI's performance and compare it with MPI. The results show good performance gains using JOPI. Copyright © 2005 John Wiley & Sons, Ltd. [source] Parallel bandwidth characteristics calculations for thin avalanche photodiodes on a SGI Origin 2000 supercomputerCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2004Yi Pan Abstract An important factor for high-speed optical communication is the availability of ultrafast and low-noise photodetectors. Among the semiconductor photodetectors that are commonly used in today's long-haul and metro-area fiber-optic systems, avalanche photodiodes (APDs) are often preferred over p - i - n photodiodes due to their internal gain, which significantly improves the receiver sensitivity and alleviates the need for optical pre-amplification. Unfortunately, the random nature of the very process of carrier impact ionization, which generates the gain, is inherently noisy and results in fluctuations not only in the gain but also in the time response. Recently, a theory characterizing the autocorrelation function of APDs has been developed by us which incorporates the dead-space effect, an effect that is very significant in thin, high-performance APDs. The research extends the time-domain analysis of the dead-space multiplication model to compute the autocorrelation function of the APD impulse response. However, the computation requires a large amount of memory space and is very time consuming. In this research, we describe our experiences in parallelizing the code in MPI and OpenMP using CAPTools. Several array partitioning schemes and scheduling policies are implemented and tested. Our results show that the code is scalable up to 64 processors on a SGI Origin 2000 machine and has small average errors. Copyright © 2004 John Wiley & Sons, Ltd. [source] Compiling data-parallel programs for clusters of SMPsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 2-3 2004Siegfried Benkner Abstract Clusters of shared-memory multiprocessors (SMPs) have become the most promising parallel computing platforms for scientific computing. However, SMP clusters significantly increase the complexity of user application development when using the low-level application programming interfaces MPI and OpenMP, forcing users to deal with both distributed-memory and shared-memory parallelization details. In this paper we present extensions of High Performance Fortran (HPF) for SMP clusters which enable the compiler to adopt a hybrid parallelization strategy, efficiently combining distributed-memory with shared-memory parallelism. By means of a small set of new language features, the hierarchical structure of SMP clusters may be specified. This information is utilized by the compiler to derive inter-node data mappings for controlling distributed-memory parallelization across the nodes of a cluster and intra-node data mappings for extracting shared-memory parallelism within nodes. Additional mechanisms are proposed for specifying inter- and intra-node data mappings explicitly, for controlling specific shared-memory parallelization issues and for integrating OpenMP routines in HPF applications. The proposed features have been realized within the ADAPTOR and VFC compilers. The parallelization strategy for clusters of SMPs adopted by these compilers is discussed as well as a hybrid-parallel execution model based on a combination of MPI and OpenMP. Experimental results indicate the effectiveness of the proposed features. Copyright © 2004 John Wiley & Sons, Ltd. [source] Managing distributed shared arrays in a bulk-synchronous parallel programming environmentCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 2-3 2004Christoph W. KesslerArticle first published online: 7 JAN 200 Abstract NestStep is a parallel programming language for the BSP (bulk-hronous parallel) programming model. In this article we describe the concept of distributed shared arrays in NestStep and its implementation on top of MPI. In particular, we present a novel method for runtime scheduling of irregular, direct remote accesses to sections of distributed shared arrays. Our method, which is fully parallelized, uses conventional two-sided message passing and thus avoids the overhead of a standard implementation of direct remote memory access based on one-sided communication. The main prerequisite is that the given program is structured in a BSP-compliant way. Copyright © 2004 John Wiley & Sons, Ltd. [source] Performance and scalability of MPI on PC clustersCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2004Glenn R. Luecke Abstract The purpose of this paper is to compare the communication performance and scalability of MPI communication routines on a Windows Cluster, a Linux Cluster, a Cray T3E-600, and an SGI Origin 2000. All tests in this paper were run using various numbers of processors and two message sizes. In spite of the fact that the Cray T3E-600 is about 7 years old, it performed best of all machines for most of the tests. The Linux Cluster with the Myrinet interconnect and Myricom's MPI performed and scaled quite well and, in most cases, performed better than the Origin 2000, and in some cases better than the T3E. The Windows Cluster using the Giganet Full Interconnect and MPI/Pro's MPI performed and scaled poorly for small messages compared with all of the other machines. Copyright © 2004 John Wiley & Sons, Ltd. [source] SCALEA: a performance analysis tool for parallel programsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 11-12 2003Hong-Linh Truong Abstract Many existing performance analysis tools lack the flexibility to control instrumentation and performance measurement for code regions and performance metrics of interest. Performance analysis is commonly restricted to single experiments. In this paper we present SCALEA, which is a performance instrumentation, measurement, analysis, and visualization tool for parallel programs that supports post-mortem performance analysis. SCALEA currently focuses on performance analysis for OpenMP, MPI, HPF, and mixed parallel programs. It computes a variety of performance metrics based on a novel classification of overhead. SCALEA also supports multi-experiment performance analysis that allows one to compare and to evaluate the performance outcome of several experiments. A highly flexible instrumentation and measurement system is provided which can be controlled by command-line options and program directives. SCALEA can be interfaced by external tools through the provision of a full Fortran90 OpenMP/MPI/HPF frontend that allows one to instrument an abstract syntax tree at a very high-level with C-function calls and to generate source code. A graphical user interface is provided to view a large variety of performance metrics at the level of arbitrary code regions, threads, processes, and computational nodes for single- and multi-experiment performance analysis. Copyright © 2003 John Wiley & Sons, Ltd. [source] Deadlock detection in MPI programsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 11 2002Glenn R. Luecke Abstract The Message-Passing Interface (MPI) is commonly used to write parallel programs for distributed memory parallel computers. MPI-CHECK is a tool developed to aid in the debugging of MPI programs that are written in free or fixed format Fortran 90 and Fortran 77. This paper presents the methods used in MPI-CHECK 2.0 to detect many situations where actual and potential deadlocks occur when using blocking and non-blocking point-to-point routines as well as when using collective routines. Copyright © 2002 John Wiley & Sons, Ltd. [source] Acute Adaptation to Volume Unloading of the Functional Single Ventricle in Children Undergoing Bidirectional Glenn AnastomosisCONGENITAL HEART DISEASE, Issue 2 2009Catherine Ikemba MD ABSTRACT Objective., Volume unloading of the functional single ventricle after a bidirectional Glenn anastomosis (BDG) prior to 1 year of age leads to improved global ventricular function as measured by the myocardial performance index (MPI), a Doppler-derived measurement of combined systolic and diastolic ventricular function. Systolic function remains unchanged after BDG according to previous studies; however, acute changes in global and diastolic function have not been previously investigated in this cohort. Our objective was to assess the short-term effects of the BDG on global ventricular function in patients with a functional single ventricle. Design., Echocardiograms to obtain MPI, isovolumic contraction time, and isovolumic relaxation time were performed at four time periods: in the operating room, in the operating room prior to BDG, shortly after separation from cardiopulmonary bypass, less than 24 hours postoperatively, and either prior to hospital discharge or at the first clinic follow-up visit. Results., Twenty-six patients were enrolled. There was significant ventricular dysfunction noted shortly after separation from cardiopulmonary bypass, median MPI 0.63 (0.39,0.81), that persisted in the short term postoperatively median MPI 0.50 (0.40,0.63). Isovolumic contraction time did not change, however, isovolumic relaxation time was significantly prolonged following BDG. Conclusion., In the postoperative patient after BDG, systolic function is preserved; however, there is evidence of diastolic and global ventricular dysfunction, at least in the short term. [source] Identifying Left Ventricular Dysfunction in Pulmonary HypertensionCONGESTIVE HEART FAILURE, Issue 5 2009Navin Rajagopalan MD The significance of left ventricular (LV) dysfunction in patients with pulmonary hypertension (PH) is unknown. Our purpose was to quantify LV function in PH patients by measuring LV myocardial performance index (MPI) and correlating it with invasively determined hemodynamic variables. The authors prospectively measured LV MPI via transthoracic echocardiography in 50 patients with PH (53±11 years; 35 women) who also underwent right heart catheterization within 1 day of echocardiography. For comparative purposes, LV MPI was also measured in 15 healthy volunteers who served as controls. LV MPI was significantly increased in the PH group compared with controls (0.62±0.27 vs 0.36±0.08; P<.001), indicating worse LV dysfunction despite that LV ejection fraction was not significantly different between the groups (58%±4% vs 60%±3%). LV MPI demonstrated significant correlations with invasively determined mean pulmonary artery pressure (r=.50; P<.001), pulmonary vascular resistance (r=.57; P<.001), and cardiac index (r=,.64; P<.001). By receiver operating characteristic analysis, LV MPI >0.75 predicted cardiac index <2 L/min/m2 with 89% sensitivity and 78% specificity (area under the curve, 0.89). In a multivariate model, LV MPI was independently associated with cardiac index (P<.01). Patients with PH demonstrate abnormal LV function as quantified by elevated LV MPI, which correlates significantly with pulmonary vascular resistance and cardiac index. [source] Sexual dysfunction and physicians' perception in medicated patients with major depression in TaiwanDEPRESSION AND ANXIETY, Issue 9 2008Kao Ching Chen M.D. Abstract Although prevalent during antidepressant treatment, sexual dysfunction (SD) is frequently ignored by both physicians and patients in Asia. In spite of impact of SD on medicated patients with major depression, sexual issues and illness remain a forbidden topic for most Asian people. The aims of this study were to: (1) estimate the prevalence of SD among stable outpatients taking different antidepressants in Taiwan; (2) investigate the factors related to SD; (3) compare physician-perceived with patient-reported prevalence rates of antidepressant-associated SD; and (4) study the differences of SD among antidepressant subgroups. In this cross-sectional observational study, 125 medicated patients with major depression were recruited. Patients were assessed using the Changes in Sexual Functioning Questionnaire (CSFQ), Taiwanese Depression Questionnaire (TDQ), Quality of Life Index (QOL), and neuroticism scores in the Maudsley Personality Inventory (MPI). Sixty-two physicians completed the Physician Antidepressant Experience Questionnaire. The estimated prevalence rate of SD was 53.6% (95% CI = 44.9,62.3%) in medicated patients with major depression. There were no significant differences in prevalence rate of SD among different antidepressants. The SD subgroup had poorer quality of life and lower moods than the non-dysfunction subgroup. An underestimation of the prevalence of SD by physicians was noted. Because antidepressant-associated SD is highly prevalent and seriously underestimated by physicians, greater physicians' recognition and better patients' education are imperative when prescribing antidepressants. Depression and Anxiety. © 2007 Wiley-Liss, Inc. [source] Myocardial perfusion imaging and cardiac events in a cohort of asymptomatic patients with diabetes living in southern FranceDIABETIC MEDICINE, Issue 4 2006A. Sultan Abstract Aims, To assess the association between abnormal stress myocardial perfusion imaging (MPI) and cardiac events (CE) in asymptomatic patients with diabetes and with , 1 additional risk factor. Predictors of abnormal stress MPI were also evaluated. Methods, Four hundred and forty-seven consecutive patients who underwent stress MPI were prospectively followed for 2.1 [0.5,4.1] years for the subsequent occurrence of hard CE (myocardial infarction and sudden or coronary death) and soft CE (unstable angina and ischaemic heart failure requiring hospitalization). Re-vascularization procedures performed as a result of the screening protocol were not included in the analysis. Results, Follow-up was successful in 419 of 447 patients (94%), of whom 71 had abnormal MPI at baseline. Medical therapy was intensified in all subjects and especially in those with abnormal MPI. Twenty-three patients with abnormal MPI underwent a re-vascularization procedure. CEs occurred in 14 patients, including six of 71 patients (8.5%) with abnormal MPI and eight of 348 patients (2.3%) with normal MPI (P < 0.005). Only two patients developed a hard CE and 12 a soft CE. In multivariate analysis, abnormal MPI was the strongest predictor for CEs [odds ratio (OR) (95% CI) = 5.6 (1.7,18.5)]. Low-density lipoprotein cholesterol , 3.35 mmol/l [OR (95% CI) = 7.3; 1.5,34.7] and age > median [OR (95% CI) = 6.0 (1.2,28.6)] were additional independent predictors for CE. The independent predictors for abnormal MPI were male gender, plasma triglycerides , 1.70 mmol/l, creatinine clearance < 60 ml/min and HbA1c > 8%, with male gender the strongest [OR (95% CI) = 4.0 (1.8,8.8)]. Conclusions, Asymptomatic patients with diabetes in this study had a very low hard cardiac event rate over an intermediate period. This could be explained by the effects of intervention or by the low event rate in the background population. Randomized studies of cardiac heart disease screening are required in asymptomatic subjects with diabetes to determine the effectiveness of this intervention. Diabet. Med. (2006) [source] 2,2,-Nitrophenylisatogen potentiates P2X1 receptor mediated vascular contraction and blood pressure elevationDRUG DEVELOPMENT RESEARCH, Issue 1 2003Anna-Karin Wihlborg Abstract The objective of this research was to examine the effects of chemical compounds with possible P2 receptor modulating effects and to characterize the potentiating effects of 2,2,-nitrophenylisatogen (NPI) on P2X1 receptors in vitro and in vivo. Chemical compounds were tested in an in vitro pharmacological assay using vascular segments from the rat mesenteric artery stimulated by P2 receptor-specific agonists. Contractions were expressed as a percentage of 60 mM K+ -induced contractions. Blood pressure was evaluated in pithed rats. NPI (30 ,M) added 15 min before addition of the P2X1 receptor-specific agonist ,,-MeATP increased the maximum vasoconstriction from 23% to 49% (an increase of 113%). Furthermore, NPI prevented the desensitization of repeated ,,-MeATP contractions. Related compounds were examined, and 2-(3-methoxy-phenyl)-1-oxy-indol-3-one (MPI) had similar effects as NPI, but several others lacked effect. NPI had no effect on ADP,S (P2Y1) or acetylcholine-mediated vasodilatation, nor on UTP (P2Y2/4), UDP (P2Y6), or noradrenaline-mediated contractions. In pithed rats, the blood pressure response to 50 nmol/kg-infusion of ,,-MeATP was increased from 50±6 to 63±5 mmHg (P<0.05), but had no effect on basal blood pressure or on the cardiovascular response to preganglionic nerve stimulation. In conclusion, NPI and MPI potentiates P2X1 receptor vascular contractions in vitro and (NPI) blood pressure effects in vivo. It is possible that the effect is mediated by an inhibition of P2X1 receptor desensitization. Drug Dev. Res. 59:82,87, 2003. © 2003 Wiley-Liss, Inc. [source] Evaluation of Right Ventricular Function by Using Tissue Doppler Imaging in Patients after Repair of Tetralogy of FallotECHOCARDIOGRAPHY, Issue 8 2009lker Çetin M.D. Background: The aim of this study was to assess the relation between plasma B-type natriuretic peptide (BNP) levels and right ventricular function evaluated by tissue Doppler imaging (TDI) in patients after repair of tetralogy of Fallot (ToF). Methods: Twenty-five patients with a mean age of 14.1 ± 4.4 years who underwent repair of ToF at a mean age of 4.9 ± 5.1 years enrolled in this study. The control group consisted of 29 healthy children at a mean age of 13.1 ± 2.8 years. The right ventricle and pulmonary regurgitation (PR) were assessed by two-dimensional echocardiography and color Doppler. Blood samples for BNP levels were taken and TDI was performed at rest. Results: Plasma BNP levels were significantly higher in patients than in controls (28.3 ± 24.1 vs. 7.4 ± 2.3 pg/mL, P = 0.0001). The myocardial performance index (MPI) (1.08 ± 0.35 vs. 0.58 ± 0.11, P = 0.0001) was higher and isovolumic acceleration (IVA) (3.1 ± 0.7 vs. 5.4 ± 1.0 m/s2, P = 0.0001) was lower in patients. The correlations were also significant between the degree of PR and MPI (r = 0.7, P = 0.0001) and also IVA (r =,0.7, P = 0.0001). The correlations were also significant between the BNP level and MPI (r = 0.6, P = 0.0001), IVA (r =,0.4, P = 0.002) and the degree of PR (r = 0.6, P = 0.0001). Conclusion: As a result, plasma BNP level increases in patients with ToF and both MPI and IVA from the right ventricular basal segments might be used to assess the right ventricular function. [source] The Effects of Antihypertensive Treatment on the Doppler-Derived Myocardial Performance Index in Patients with Hypertensive Left Ventricular Hypertrophy: Results from the Swedish Irbesartan in Left Ventricular Hypertrophy Investigation Versus Atenolol (SILVHIA)ECHOCARDIOGRAPHY, Issue 7 2009Stefan Liljedahl M.D. Objectives: To investigate the effects of antihypertensive treatment on the Doppler-derived myocardial performance index (MPI) in patients with hypertensive left ventricular hypertrophy. Methods: The MPI was measured at baseline and after 48 weeks of antihypertensive treatment in 93 participants of the SILVHIA trial, where individuals with primary hypertension and left ventricular hypertrophy were randomized to double blind treatment with either irbesartan or atenolol. Results: Antihypertensive treatment lowered MPI (mean difference ,0.03 ± 0.01, P = 0.04). Changes in MPI by treatment were associated with changes in left ventricular ejection fraction (,-coefficient ,0.35 P = 0.005), stroke volume/pulse pressure (reflecting arterial compliance, ,-coefficient ,0.39 P < 0.001) and peripheral vascular resistance (,-coefficient 0.28 P < 0.04). Furthermore, there was a borderline significant association between changes in MPI and changes in E-wave deceleration time (reflecting diastolic function, ,-coefficient 0.23, P = 0.06). No associations were found between changes in MPI and changes in blood pressure, E/A-ratio, left ventricular mass index, relative wall thickness or heart rate. A stepwise multivariable regression model confirmed the association between changes in MPI and changes in ejection fraction and stroke volume/pulse pressure (all P < 0.05), as well as the trend for E-wave deceleration time (P = 0.08), but not in the case of peripheral vascular resistance. Conclusion: The MPI exhibited a modest decrease after 48 weeks of antihypertensive treatment in patients with hypertensive left ventricular hypertrophy. Changes in MPI were associated with changes in left ventricular function and vascular compliance, rather than with changes in left ventricular remodeling or blood pressure. [source] Evaluation of the Left Ventricular Function with Tissue Tracking and Tissue Doppler Echocardiography in Pediatric Malignancy Survivors after Anthracycline TherapyECHOCARDIOGRAPHY, Issue 8 2008it Karakurt M.D. Although the anthracyclines have gained widespread use in the treatment of childhood hematological malignancies and solid tumors, cardiotoxicity is the major limiting factor in the use of anthracyclines. The aim of this study was to assess the mitral annular displacement by tissue tracking in pediatric malignancy survivors who had been treated with anthracycline groups chemotheraphy and compare with the tissue Doppler and conventional two dimensional measurements and Doppler indices. In this study, 32 pediatric malignancy survivors and 22 healthy children were assessed with 2D, colour-coded echocardiography. Left ventricular ejection fraction, fractional shortening, stroke volume, cardiac output, cardiac index and diastolic functions were measured. All subjects were assessed with tissue Doppler echocardiography, mitral annular displacements, and also with tissue tracking method. We detected that peak velocity of the early rapid filling on tissue Doppler (E,) was lower (p < 0.05) and the ratio of early peak velocity of rapid filling on pulse Doppler to tissue Doppler (E/E,) values were statistically higher in patient group than control group (p < 0.05). Myocardial performance index values were also higher in patient group than the control group (p < 0.01). It appears that MPI is a useful echocardiograghic method than tissue tracking of mitral annular displacement in patients with pediatric cancer survivors who had subclinical diastolic dysfunction. [source] Myocardial Performance Index (Tei Index) Does Not Reflect Long-Term Changes in Left Ventricular Function after Acute Myocardial InfarctionECHOCARDIOGRAPHY, Issue 1 2003Torstein Hole M.D. Aims: To evaluate whether changes in myocardial performance index (MPI or Tei index) were related to changes in other Doppler echocardiographic parameters after acute myocardial infarction, or had any independent prognostic impact in a 2-year observational study. Methods and Results: Seventy-one patients with acute myocardial infarction without heart failure were examined at baseline, 3 months, and 2 years. MPI was significantly related to end-diastolic and end-systolic volume indexes, ejection fraction, maximal velocity, and time velocity integral of early mitral filling wave at 3 months and 2 years. MPI did not contribute significantly to the prediction of any changes in the measures of diastolic or systolic function at 3 months or 2 years. Baseline MPI was significantly higher in patients who later developed heart failure(0.55 ± 0.16)than in other patients(0.43 ± 0.13, P = 0.006), but had no independent predictive power for the development of heart failure or death relative to end-systolic volume index and deceleration time of early mitral filling wave. Conclusion: MPI did not accurately reflect changes in Doppler and two-dimensional echocardiographic measures of diastolic or systolic function during a 2-year follow-up after acute myocardial infarction, and did not have any independent prognostic impact. (ECHOCARDIOGRAPHY, Volume 20, January 2003) [source] The Myocardial Performance Index in Patients with Aortic StenosisECHOCARDIOGRAPHY, Issue 4 2002Jude A. Mugerwa M.D. Objectives: This study was designed to determine the effect of chronic afterload on a Doppler-derived myocardial performance index (MPI) combining both systolic and diastolic left ventricular dysfunction. Methods: The study included 36 patients with a diagnosis of aortic stenosis and 36 normal subjects. Doppler-derived myocardial performance index (MPI), defined as the sum of the isovolumic contraction time and isovolumic relaxation time divided by ejection time, was measured from the mitral valve inflow and left ventricular outflow velocity patterns and was then related to the aortic valve area, valve gradient, and other echocardiographic variables. Results: The values of the Doppler-derived MPI in the patients with aortic stenosis were significantly higher than those in the controls (0.54 ± 0.20 vs 0.38 ± 0.04, respectively; P < 0.001). Transmitral deceleration time and the E/A ratio (r = 0.47 and r = 0.35, respectively; P < 0.05) were significant univariate correlates, and mitral deceleration time was the only significant correlate of MPI. However the index did not correlate with aortic valve area, peak and mean valve gradients, left ventricular mass, or age. Conclusions: Doppler-derived MPI reflects severity of global left ventricular dysfunction in patients with aortic stenosis and may be of clinical value in this patient population. [source] Active Vegetations Can Be Differentiated from Chronic Vegetations by Visual Inspection of Standardized Two-Dimensional EchocardiogramsECHOCARDIOGRAPHY, Issue 2 2000PH.D., TAHIR TAK M.D. The ability to differentiate active from chronic valvular vegetations (VEGs) by digital image processing and by visual observation was evaluated in 18 patients with a clinical diagnosis of infective endocarditis (IE). Two-dimensional echocardiographic (2-DE) examinations were performed on all patients at diagnosis and after a mean period of 52 days. Two comparable images (active and chronic) from the same patient and in the same phase of the cardiac cycle were digitized, magnified, and displayed on a high resolution monitor. The mean pixel intensity (MPI) was 72 ± 14 in the active stage and 143 ± 23 in the chronic stage (P < 0.0001). The VEG size was 0.64 ± 0.15 cm2 in the active stage and decreased to 0.46 ± 0.17 cm2 in the chronic stage (P < 0.001). Two experienced echocar-diographers, who were blinded to the age of the VEGs, identified each echocardiographic image as active or chronic based on visual observation of density of the VEGs. The VEGs were correctly identified as active or chronic in 17 out of the 18 patients. In summary, although digital image processing of 2-DE may be useful, the density of VEGs assessed by visual inspection will help differentiate between active and chronic VEGs of IE. The standardization procedure at the time of the initial study and use of identical gain settings in subsequent studies are key factors in making this distinction. [source] Simulation of high velocity concrete fragmentation using SPH/MLSPHINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 10 2003T. Rabczuk Abstract The simulation of concrete fragmentation under explosive loading by a meshfree Lagrangian method, the smooth particle hydrodynamics method (SPH) is described. Two improvements regarding the completeness of the SPH-method are examined, first a normalization developed by Johnson and Beissel (NSPH) and second a moving least square (MLS) approach as modified by Scheffer (MLSPH). The SPH-Code is implemented in FORTRAN 90 and parallelized with MPI. A macroscopic constitutive law with isotropic damage for fracture and fragmentation for concrete is implemented in the SPH-Code. It is shown that the SPH-method is able to simulate the fracture and fragmentation of concrete slabs under contact detonation. The numerical results from the different SPH-methods are compared with the data from tests. The good agreement between calculation and experiment suggests that the SPH-program can predict the correct maximum pressure as well as the damage of the concrete slabs. Finally the fragment distributions of the tests and the numerical calculations are compared. Copyright © 2003 John Wiley & Sons, Ltd. [source] Parallel computation of a highly nonlinear Boussinesq equation model through domain decompositionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 1 2005Khairil Irfan Sitanggang Abstract Implementations of the Boussinesq wave model to calculate free surface wave evolution in large basins are, in general, computationally very expensive, requiring huge amounts of CPU time and memory. For large scale problems, it is either not affordable or practical to run on a single PC. To facilitate such extensive computations, a parallel Boussinesq wave model is developed using the domain decomposition technique in conjunction with the message passing interface (MPI). The published and well-tested numerical scheme used by the serial model, a high-order finite difference method, is identical to that employed in the parallel model. Parallelization of the tridiagonal matrix systems included in the serial scheme is the most challenging aspect of the work, and is accomplished using a parallel matrix solver combined with an efficient data transfer scheme. Numerical tests on a distributed-memory super-computer show that the performance of the current parallel model in simulating wave evolution is very satisfactory. A linear speedup is gained as the number of processors increases. These tests showed that the CPU time efficiency of the model is about 75,90%. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||