bluuebunny/crossref_metadata_2025 huggingface dataset:
Bayesian belief networks for system fault diagnostics
Authors: Lampis M. , Andrews J. D.
Published: November 2008

Fault diagnostic methods aim to recognize when faults exist on a system and to identify the failures that have caused the fault. The symptoms of the fault are obtained from readings from sensors located on the system. When the observed readings do not match those expected then a fault can exist. Using the detailed information provided by the sensors, a list of the failures (singly or in combinations) that could cause the symptoms can be deduced. In the last two decades, fault diagnosis has received growing attention due to the complexity of modern systems and the consequent need for more sophisticated techniques to identify the failures when they occur. Detecting the causes of a fault quickly and efficiently means reducing the costs associated with the system unavailability and, in certain cases, avoiding the risks of unsafe operating conditions. Bayesian belief networks (BBNs) are probabilistic models that were developed in artificial intelligence applications but are now applied in many fields. They are ideal for modelling the causal relations between faults and symptoms used in the detection process. The probabilities of events within the BBN can be updated following observations (evidence) about the system state. In this paper we investigate how BBNs can be applied to diagnose faults on a system. Initially Fault trees (FTs) are constructed to indicate how the component failures can combine to cause unexpected deviations in the variables monitored by the sensors. Converting FTs into BNs enables the creation of a model that represents the system with a single network, which is constituted by sub‐networks. The posterior probabilities of the components' failures give a measure of those components that have caused the symptoms observed. The method gives a procedure that can be generalized for any system where the causality structure can be developed relating the system component states to the sensor readings. The technique is demonstrated with a simple example system. Copyright © 2008 John Wiley & Sons, Ltd.
The general balance metric for mixed‐level fractional factorial designs
Authors: Guo Yong , Simpson James R. , Pignatiello Joseph J.
Published: November 2008

Mixed‐level designs are employed when factors with different numbers of levels are involved. Practitioners use mixed‐level fractional factorial designs as the total number of runs of the full factorial increases rapidly as the number of factors and/or the number of factor levels increases. One important decision is to determine which fractional designs should be chosen. A new criterion, the general balance metric (GBM), is proposed to evaluate and compare mixed‐level fractional factorial designs. The GBM measures the degree of balance for both main effects and interaction effects. This criterion is tied to, and dominates orthogonality criteria as well as traditional minimum aberration criteria. Furthermore, the proposal is easy to use and has practical interpretations. As part of the GBM, the concept of resolution is generalized and the confounding structure of mixed‐level fractional factorial designs is also revealed. Moreover, the metric can also be used for the purpose of design augmentation. Examples are provided to compare this approach with existing criteria. Copyright © 2008 John Wiley & Sons, Ltd.
Theoretical study on the spectroscopic properties and electronic structures of heteroleptic phosphorescent Ir(III) complexes
Authors: Zhang Min , Li Ze‐Sheng , Li Yan , Liu Jia , Sun Jia‐Zhong
Published: November 2008

The geometries, spectroscopic and electronic structures properties of a series of heteroleptic phosphorescent Ir(III) complexes including N981, N982, N983, N984 have been characterized by density functional theory calculations. The excited‐state properties of the Ir(III) complexes have been characterized by CIS method. The ground‐ and excited‐state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. By using the time‐dependent density functional theory method, the absorption and phosphorescence spectra were calculated based on the optimized ground‐ and excited‐state geometries, respectively. The results show that the absorption and emission data agree well with the corresponding experimental results. The calculated results also revealed that the nature of the substituent at the 4‐position of the pyridyl moiety can influence the distributions of HOMO and LUMO and their energies. In addition, the charge transport quality has been estimated approximately by the calculated reorganization energy (λ). Our result also indicates that the positions of the substitute groups not only change the transition characters but also affect the charge transfer rate and balance, and complex N982 is a very good charge transfer material for green OLEDs. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Structural classification of acyl‐substituted Quillaja saponins by electrospray ionisation ion trap multiple‐stage mass spectrometry in combination with multivariate analysis
Authors: Bankefors Johan , Nord Lars I. , Kenne Lennart
Published: November 2008

Thirty‐eight saponins in two chromatographic fractions (QH‐B and QH‐C) from Quillaja saponaria Molina have been separated by a two‐step high‐performance liquid chromatography (HPLC) procedure and investigated by electrospray ionisation ion trap multiple‐stage mass spectrometry (ESI‐ITMSn) in positive ion mode. MS2 and MS3 spectra of the compounds were investigated by principal component analysis (PCA) and could be classified by partial least squares – discriminant analysis (PLS‐DA) according to the structures of the oligosaccharides at C‐3 and C‐28 of the saponins. Four minor components with novel structures were found in a previously non‐investigated fraction of QH‐C. The structures of two of these components, J1 and J1a, were predicted by PLS‐DA whereas the structures of the two others, J2 and J3, were only partly predicted. The structures of J1 and J1a were composed of structural elements found in the 34 known saponins whereas a new acyl substituent, not included in the training set used for calibration of the PLS‐DA models, was found in J2 and J3, making these two components outliers. The complete structures of the four components were confirmed by monosaccharide analysis, MSn data and 1H NMR spectroscopy. Copyright © 2008 John Wiley & Sons, Ltd.
Observer‐based stabilization of linear switching systems
Authors: Caravani Paolo , De Santis Elena
Published: November 2008

The discrete component of the hybrid state of a discrete‐time linear switching system is assumed to be uncontrolled and unobserved. Conditions of stabilizability for this class of systems are given in terms of a new definition of control invariance, based on the realization of a discrete observer that permits reconstruction of the discrete‐state in certain intervals of the time basis. This paper highlights the relationship between the minimum dwell time of the system and its stabilizability. An almost complete characterization of stabilizability is offered in terms of certain subsets of the continuous‐state space. These sets are amenable to tractable parametric procedures for controller synthesis. Copyright © 2008 John Wiley & Sons, Ltd.
Kalman filter‐based adaptive control for networked systems with unknown parameters and randomly missing outputs
Authors: Shi Y. , Fang H. , Yan M.
Published: November 2008

This paper investigates the problem of adaptive control for networked control systems with unknown model parameters and randomly missing outputs. In particular, for a system with the autoregressive model with exogenous input placed in a network environment, the randomly missing output feature is modeled as a Bernoulli process. Then, an output estimator is designed to online estimate the missing output measurements, and further a Kalman filter‐based method is proposed for parameter estimation. Based on the estimated output and the available output, and the estimated model parameters, an adaptive control is designed to make the output track the desired signal. Convergence properties of the proposed algorithms are analyzed in detail. Simulation examples illustrate the effectiveness of the proposed method. Copyright © 2008 John Wiley & Sons, Ltd.
Asymmetric Ramsey properties of random graphs involving cliques
Authors: Marciniszyn Martin , Skokan Jozef , Spöhel Reto , Steger Angelika
Published: November 2008

Consider the following problem: For given graphs G and F1,…,Fk, find a coloring of the edges of G with k colors such that G does not contain Fi in color i. Rödl and Ruciński studied this problem for the random graph Gn,p in the symmetric case when k is fixed and F1 = ··· = Fk = F. They proved that such a coloring exists asymptotically almost surely (a.a.s.) provided that p ≤ bn−β for some constants b = b(F,k) and β = β(F). This result is essentially best possible because for p ≥ Bn−β, where B = B(F,k) is a large constant, such an edge‐coloring does not exist. Kohayakawa and Kreuter conjectured a threshold function n for arbitrary F1,…,Fk.

In this article we address the case when F1,…,Fk are cliques of different sizes and propose an algorithm that a.a.s. finds a valid k‐edge‐coloring of Gn,p with p ≤ bn−β for some constant b = b(F1,…,Fk), where β = β(F1,…,Fk) as conjectured. With a few exceptions, this algorithm also works in the general symmetric case. We also show that there exists a constant B = B(F1,…,Fk) such that for p ≥ Bn−β the random graph Gn,p a.a.s. does not have a valid k‐edge‐coloring provided the so‐called KŁR‐conjecture holds. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Computing in fault tolerant broadcast networks and noisy decision trees
Authors: Newman Ilan
Published: November 2008

We consider a fault tolerant broadcast network of n processors each holding one bit of information. The goal is to compute a given Boolean function on the n bits. In each step, a processor may broadcast one bit of information. Each listening processor receives the bit that was broadcast with error probability bounded by a fixed constant ϵ. The errors in different steps, as well as for different receiving processors in the same step, are mutually independent. The protocols that are considered in this model are oblivious protocols: At each step, the processors that broadcast are fixed in advanced and independent of the input and the outcome of previous steps.

We present here the first linear complexity protocols for several classes of Boolean functions. This answer an open question of Yao (Invited talk in the 5th ISTCS Conf., 1997), considering this fault tolerant model that was introduced by El Gamal (Open problems presented at the 1984 workshop on Specific Problems in Communication and Computation sponsored by Bell Communication Research) and studied also by Gallager IEEE Tran Info Theory 34 (1988) 176–180. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Delaunay graphs of point sets in the plane with respect to axis‐parallel rectangles
Authors: Chen Xiaomin , Pach János , Szegedy Mario , Tardos Gábor
Published: November 2008

Given a point set P in the plane, the Delaunay graph with respect to axis‐parallel rectangles is a graph defined on the vertex set P, whose two points p,q ∈ P are connected by an edge if and only if there is a rectangle parallel to the coordinate axes that contains p and q, but no other elements of P. The following question of Even et al. (SIAM J Comput 33 (2003) 94–136) was motivated by a frequency assignment problem in cellular telephone networks: Does there exist a constant c > 0 such that the Delaunay graph of any set of n points in general position in the plane contains an independent set of size at least cn? We answer this question in the negative, by proving that the largest independent set in a randomly and uniformly selected point set in the unit square is O(nlog 2 log n/log n), with probability tending to 1. We also show that our bound is not far from optimal, as the Delaunay graph of a uniform random set of n points almost surely has an independent set of size at least cn log log n/(log n log log log n).

We give two further applications of our methods: (1) We construct two‐dimensional n‐element partially ordered sets such that the size of the largest independent sets of vertices in their Hasse diagrams is o(n). This answers a question of Matoušek and Přívětivý (Combinat Probab Comput 15 (2006) 473–475) and improves a result of Kříž and Nešetřil (Order 8 (1991) 41–48). (2) For any positive integers c and d, we prove the existence of a planar point set with the property that no matter how we color its elements by c colors, we find an axis‐parallel rectangle containing at least d points, all of which have the same color. This solves an old problem from the work of Brass et al. (Research Problem in Discrete Geometry Springer‐Verlag, New York, 2005). © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Induced subgraphs with distinct sizes
Authors: Alon Noga , Kostochka A.V.
Published: November 2008

We show that for every 0 < ϵ < 1/2, there is an n0 = n0(ϵ) such that if n > n0 then every n‐vertex graph G of size at least $\varepsilon \left( {\matrix{ {\matrix{ n \cr 2 \cr } } \cr } } \right)$ and at most $(1- \varepsilon) \left( {\matrix{ {\matrix{ n \cr 2 \cr } } \cr } } \right)$ contains induced k‐vertex subgraphs with at least 10−7k different sizes, for every $k \le {{\varepsilon n} \over 3}$. This is best possible, up to a constant factor. This is also a step toward a conjecture by Erdős, Faudree, and Sós on the number of distinct pairs (|V (H)|,|E(H)|) of induced subgraphs of Ramsey graphs. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009
Covariate adjustment in randomized trials with binary outcomes: Targeted maximum likelihood estimation
Authors: Moore K. L. , van der Laan M. J.
Published: November 2008

Covariate adjustment using linear models for continuous outcomes in randomized trials has been shown to increase efficiency and power over the unadjusted method in estimating the marginal effect of treatment. However, for binary outcomes, investigators generally rely on the unadjusted estimate as the literature indicates that covariate‐adjusted estimates based on the logistic regression models are less efficient. The crucial step that has been missing when adjusting for covariates is that one must integrate/average the adjusted estimate over those covariates in order to obtain the marginal effect. We apply the method of targeted maximum likelihood estimation (tMLE) to obtain estimators for the marginal effect using covariate adjustment for binary outcomes. We show that the covariate adjustment in randomized trials using the logistic regression models can be mapped, by averaging over the covariate(s), to obtain a fully robust and efficient estimator of the marginal effect, which equals a targeted maximum likelihood estimator. This tMLE is obtained by simply adding a clever covariate to a fixed initial regression. We present simulation studies that demonstrate that this tMLE increases efficiency and power over the unadjusted method, particularly for smaller sample sizes, even when the regression model is mis‐specified. Copyright © 2008 John Wiley & Sons, Ltd.
A flexible strategy for testing subgroups and overall population
Authors: Alosh Mohamed , Huque Mohammad F.
Published: November 2008

Subgroup analyses in addition to the total study population analysis are common in clinical trials. However, it is well recognized that findings from subgroup analyses do not provide confirmatory evidence for subgroup treatment effects without placing a priori criteria for ensuring that their findings are scientifically sound. In this paper we address some of the common pitfalls of subgroup analyses. Subgroups analyses inherently have low power for detecting treatment effects. We investigate the power interplay for a subgroup analysis and that for the total study population and list factors that impact the power of a subgroup analysis. Then we introduce a flexible statistical strategy for testing a pre‐specified sequence of hypotheses for both the overall and a subgroup. The proposed method strongly controls the familywise Type I error rate and enjoys higher power than other traditional methods. This testing strategy allows testing for a subgroup once a pre‐specified degree of consistency in the efficacy findings between the subgroup and the overall study population is met. In addition, it accounts for the dependency between test statistics for the subgroup and the overall study population. We discuss the power performance of this new method and provide significance levels for subgroup analysis. Finally, we illustrate its application through retrospective analysis of data from three published clinical trials. Copyright © 2008 John Wiley & Sons, Ltd.
Transformation‐invariant and nonparametric monotone smooth estimation of ROC curves
Authors: Du Pang , Tang Liansheng
Published: November 2008

When a new diagnostic test is developed, it is of interest to evaluate its accuracy in distinguishing diseased subjects from non‐diseased subjects. The accuracy of the test is often evaluated by receiver operating characteristic (ROC) curves. Smooth ROC estimates are often preferable for continuous test results when the underlying ROC curves are in fact continuous. Nonparametric and parametric methods have been proposed by various authors to obtain smooth ROC curve estimates. However, there are certain drawbacks with the existing methods. Parametric methods need specific model assumptions. Nonparametric methods do not always satisfy the inherent properties of the ROC curves, such as monotonicity and transformation invariance. In this paper we propose a monotone spline approach to obtain smooth monotone ROC curves. Our method ensures important inherent properties of the underlying ROC curves, which include monotonicity, transformation invariance, and boundary constraints. We compare the finite sample performance of the newly proposed ROC method with other ROC smoothing methods in large‐scale simulation studies. We illustrate our method through a real life example. Copyright © 2008 John Wiley & Sons, Ltd.
Intercommunity relationships and community growth in China's high technology industries 1988–2000
Authors: Zhang Yan , Li Haiyang , Schoonhoven Claudia Bird
Published: November 2008

In this study, we examine how intercommunity relationships affect the growth of organizational communities. Using a unique panel dataset on 53 technology development communities in China spanning 1988–2000, we found that regional community density, a community's geographic proximity to the nearest community and its domain overlap with the nearest community have an inverted U‐shaped relationship with the community's growth. These non‐monotonic results suggest that adjacent communities have both mutualistic and competitive effects on each other. Theoretical and managerial implications are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
An architecture‐centric software maintainability assessment using information theory
Authors: Anan Muhammad , Saiedian Hossein , Ryoo Jungwoo
Published: November 2008

Architecture‐based metrics can provide valuable information on whether or not one can localize the effects of modification (such as adjusting data flows or control flows) in software and can therefore be used to prevent the changes from adversely affecting other software components. This paper proposes an architecture‐centric metric using entropy for assessing structural dependencies among software components. The proposed metric is based on a mathematical model representing the maintainability snapshot of a system. The introduced architectural‐level metric includes measures for coupling and cohesion. From this model, the relative maintainability of a component, referred to as a maintainability profile, can be developed to identify architectural decisions that are detrimental to the maintainability of a system. Copyright © 2008 John Wiley & Sons, Ltd.
Nuchal translucency and nasal bone in first‐trimester ultrasound screening for aneuploidy in multiple pregnancies
Authors: Sepulveda W. , Wong A. E. , Casasbuenas A.
Published: November 2008

Objective

To review our experience with first‐trimester screening of chromosomal abnormalities in multiple pregnancies using nuchal translucency (NT) thickness measurement and nasal bone assessment.

Methods

Cases of multiple pregnancy presenting for first‐trimester ultrasound evaluation and with viable fetuses measuring between 45 and 84 mm were recruited for this study. Crown–rump length, NT thickness, the presence or absence of the nasal bone and chorionicity were determined and the information prospectively collected in a dedicated database.

Results

There were 206 twin pregnancies, eight sets of triplets, and one set of quadruplets, totalling 440 screened fetuses. Information on perinatal outcome was available in all cases. The NT thickness was measured in all cases and was found to be greater than the 95th percentile in six (8.6%) of the 70 monochorionic fetuses and in 10 (2.7%) of the 370 dichorionic fetuses (P < 0.05, Fisher's exact test). The nasal bone was successfully assessed in 421 of the 440 (95.7%) fetuses and found to be absent in only four cases, three of which were found to have aneuploidy. Chromosomal abnormalities were diagnosed in six fetuses from one monochorionic and four dichorionic twin pregnancies. Five of the six affected cases were associated with increased NT thickness (sensitivity 83.3%), whereas the nasal bone was absent in only three of the aneuploid fetuses (sensitivity 50%).

Conclusions

First‐trimester ultrasound screening for chromosomal abnormalities using NT thickness in multiple pregnancies is highly sensitive. However, nasal bone assessment is not only limited in sensitivity but also more challenging in multiple than in singleton pregnancies owing to difficulties in obtaining adequate views of the fetal face. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
E‐CLEMA: A cross‐layer design for improved quality of service in mobile WiMAX networks
Authors: Triantafyllopoulou Dionysia , Passas Nikos , Merakos Lazaros , Sagias Nikos C. , Mathiopoulos P. Takis
Published: November 2008

In this paper, an efficient cross‐layer design that performs joint adaptation of the physical (PHY) and application layers of a mobile WiMAX network is proposed. The design takes into account channel state and performance information from the PHY and medium access control (MAC) layers, respectively. It uses a decision algorithm to evaluate this information, specify unfavorable conditions regarding low channel quality and increased congestion, and take measures by coordinating modulation order, transmission power, and media encoding rate, toward improved overall quality of service (QoS) offered to the user. Extensive simulation results show that the proposed design achieves considerably reduced packet loss and power consumption, combined with increased throughput as compared to a typical mobile WiMAX system. Copyright © 2008 John Wiley & Sons, Ltd.
E2SRT: enhanced event‐to‐sink reliable transport for wireless sensor networks
Authors: Kumar Sunil , Feng Zhenhua , Hu Fei , Xiao Yang
Published: November 2008

An event‐to‐sink reliable transport (ESRT) control scheme was recently proposed to address the event‐to‐sink reliability issues in wireless sensor network (WSN). In this paper, we study the performance of ESRT in the presence of ‘over‐demanding’ event reliability, using both the analytical and simulation approaches. We show that the ESRT protocol does not achieve optimum reliability and begins to fluctuate between two inefficient network states. With insights from update mechanism in ESRT, we propose a new algorithm, called enhanced ESRT (E2SRT), to solve the ‘over‐demanding’ event reliability problem and to stabilize the network. Simulation results show that E2SRT outperforms ESRT in terms of both reliability and energy consumption in the presence of ‘over‐demanding’ event reliability. Besides, it ensures robust convergence in the presence of dynamic network environments. Copyright © 2008 John Wiley & Sons, Ltd.
Chemical character of BCxNy layers grown by CVD with trimethylamine borane
Authors: Baake O. , Hoffmann P. S. , Klein A. , Pollakowski B. , Beckhoff B. , Ensinger W. , Kosinova M. , Fainer N. , Sulyaeva V. S. , Trunova V.
Published: November 2008

Layers of BCxNy were produced in a chemical vapour deposition (CVD) process using trimethylamine borane with He, N2, and NH3, respectively, as precursor. These layers deposited on Si (100) wafers were characterized chemically by X‐ray photoelectron spectroscopy (XPS) and synchrotron radiation‐based total reflection X‐ray fluorescence analysis combined with near‐edge X‐ray absorption fine structure spectroscopy (TXRF‐NEXAFS). As a result, the composition of the material produced without NH3 is a B‐C bonds containing compound with an atomic relation 1:1. Adding NH3 with a partial pressure of up to about 1.3 Pa the product could be identified as B2C2N. Increasing the partial pressure of NH3 to 1.7 and 2.1 Pa the product was enriched in nitrogen yielding a compound characterized as h‐BCN. In all cases an impurity of oxygen was observed. Copyright © 2008 John Wiley & Sons, Ltd.
Qualitative urinary organic acid analysis: Methodological approaches and performance
Authors: Peters V. , Garbade S. F. , Langhans C. D. , Hoffmann G. F. , Pollitt R. J. , Downing M. , Bonham J. R.
Published: November 2008

A programme for proficiency testing of biochemical genetics laboratories undertaking urinary qualitative organic acid analysis and its results for 50 samples examined for factors contributing to poor performance are described. Urine samples from patients in whom inherited metabolic disorders have been confirmed as well as control urines were circulated to participants and the results from 94 laboratories were evaluated. Laboratories showed variability both in terms of their individual performance and on a disease‐specific basis. In general, conditions including methylmalonic aciduria, propionic aciduria, isovaleric aciduria, mevalonic aciduria, Canavan disease and 3‐methylcrotonyl‐CoA carboxylase were readily identified. Detection was poorer for other diseases such as glutaric aciduria type II, glyceric aciduria and, in one sample, 3‐methylcrotonyl‐CoA carboxylase deficiency. To identify the factors that allow some laboratories to perform well on a consistent basis while others perform badly, we devised a questionnaire and compared the responses with the results for performance in the scheme. A trend towards better performance could be demonstrated for those laboratories that regularly use internal quality control (QC) samples in their sample preparation (p = 0.079) and those that participate in further external quality assurance (EQA) schemes (p = 0,040). Clinicians who depend upon these diagnostic services to identify patients with these defects and the laboratories that provide them should be aware of the potential for missed diagnoses and the factors that may lead to improved performance.
Xanthogranulomatous Pyelonephritis: No Longer A Contraindication for Laparoscopic Surgery?
Authors: Qadan Motaz , Wines Michael , Tolley David A.
Published: November 2008

Background:

Xanthogranulomatous pyelonephritis is a chronic renal inflammatory condition associated with significant renal and peri-renal inflammation. Consequently, operative treatment of this condition has traditionally been by open nephrectomy rather than the laparoscopic approach. We report our experience with the diagnosis and management of XGP in our department, which has subsequently been histologically confirmed.

Patients and methods:

We reviewed records of all patients with a histological diagnosis of XGP between 1984 and 2007. 20 patients with a diagnosis were included. Patient demographics, preoperative presentation, diagnostic imaging, operative details, post-operative recovery and complications were included in our data.

Results:

13 patients underwent open nephrectomy and 7 patients underwent a laparoscopic procedure, of which 1 was subsequently converted to an open procedure. Blood loss, analgesic requirement, time to first meal and length of stay (LOS) in hospital were all lower in the laparoscopic group compared with the open group (362.5 ml vs. 723.6 ml, p = 0.049; 65.3 mg vs. 146.9 mg, p = 0.153; 2.8 days vs. 4.2 days, p= 0.184; 4.4 days vs. 9.8 days, p = 0.084). Operative times were similar in both groups (157.5 min vs. 154.2 min, p= 0.888). There were 5 complications in the laparoscopic group and 13 in the open group.

Conclusion:

The laparoscopic approach, although technically challenging, provides superior intra-operative and post-operative recovery results compared to the open approach with comparable operative times and incidences of complications. In specialised centres and in experienced hands, laparoscopic nephrectomy should be considered as the first choice procedure in those patients with a suspected diagnosis of XGP.
Transcardiac increase in norepinephrine and prognosis in patients with chronic heart failure
Authors: Tsutamoto Takayoshi , Nishiyama Keizo , Sakai Hiroshi , Tanaka Toshinari , Fujii Masanori , Yamamoto Takashi , Yamaji Masayuki , Horie Minoru
Published: November 2008

Background:

No previous study has compared the transcardiac gradient of norepinephrine (NE) and the prognosis of patients with chronic heart failure (CHF).

Aim:

To evaluate the prognostic role of the transcardiac gradient of NE in patients with CHF.

Methods:

We measured haemodynamic parameters and plasma levels of NE, brain natriuretic peptide (BNP) and N‐terminal proBNP (NT‐proBNP) in the aortic root (AO) and coronary sinus (CS) in 356 consecutive patients with CHF.

Results:

During a median follow‐up of 3.5 years, 40 patients died. Transcardiac gradients of BNP (273±276 vs. 472±433 pg/mL, p<0.0001), NT‐proBNP (417±700 vs. 928±1093 pg/mL, p<0.0001) and NE (114±160 vs. 473±992 pg/mL, p<0.0001) were significantly higher in non‐survivors than survivors. After adjustment for clinical variables associated with CHF including haemodynamics and neurohumoral factors, the transcardiac gradient of NE (p<0.0001) and plasma log NT‐proBNP (p<0.0001) were independent prognostic predictors. Among 67 patients in whom 123I‐metaiodobenzylguanidine (MIBG) could be performed, transcardiac increase in NE was correlated with the washout rate (r=0.398, p=0.0009) and was a superior predictor of mortality than MIBG parameters on stepwise multivariable Cox proportional hazards regression analyses.

Conclusion:

The transcardiac increase in NE is an independent and useful prognostic predictor for evaluating the prognosis of CHF patients.
Unfriendly takeover: Successor parties in Ukraine
Authors: Zimmer Kerstin , Haran Olexiy
Published: November 2008

Research on successor parties in the former Soviet Union has mostly focused on leftist parties and paid little attention to their interplay with centrist forces which equally have their roots in the Soviet system. This article examines the development of both leftist and centrist successor parties in post-Soviet Ukraine. After consideration of the role of legacies of the old regime as well as the current legal and societal framework, the evolution of leftist parties and the so-called parties of power is explored. The analysis shows that the leftists were weakened by internal splits and a partial inability to modernize. But equally important was the logic of power preservation in the Leonid Kuchma regime, which promoted the formalization of the party of power and crowded out the leftist competitors.
A party for all seasons: Electoral adaptation of Romanian Communist successor parties
Authors: Pop-Eleches Grigore
Published: November 2008

This article analyzes the reasons for the remarkable adaptability and electoral success of Communist successor parties in post-1990 Romania. The first part develops a three-dimensional classification scheme to identify Communist successor parties on the basis of their institutional, personnel and ideological continuity with the defunct Communist Party. The second section traces the political evolution of Communist successor parties, and argues that their remarkably strong and consistent electoral performance is primarily due to their ability to appeal to voters beyond the traditional base of East European ex-Communist parties on the left of the ideological spectrum. The final section uses survey data to suggest that the continued electoral appeal of Communist successor parties in Romania is due neither to Communist nostalgia or lack of democracy but to the complicated legacy of the Ceauşescu regime and the 1989 revolution.
A NEW CHARACTERIZATION OF REFLEXIVITY
Authors: WANG RUIDONG
Published: November 2008

In this paper, we give a new characterization of reflexive Banach spaces in terms of the sum of two closed bounded convex sets.
VARIETIES OF ABELIAN TOPOLOGICAL GROUPS AND SCATTERED SPACES
Authors: MCPHAIL CAROLYN E. , MORRIS SIDNEY A.
Published: November 2008

The variety of topological groups generated by the class of all abelian kω-groups has been shown to equal the variety of topological groups generated by the free abelian topological group on [0, 1]. In this paper it is proved that the free abelian topological group on a compact Hausdorff space X generates the same variety if and only if X is not scattered.
THE CHANGING JUDICIAL ROLE: HUMAN RIGHTS, COMMUNITY LAW AND THE INTENTION OF PARLIAMENT
Authors: Mary Arden Dame
Published: November 2008

A member of the Bar who appeared before us recently said he was an engineer by training and that what he did when he was looking at a problem was to turn it by 90° and examine it on a different plane.
CIVIL LITIGATION: WHAT'S IT FOR?
Authors: Jolowicz J A
Published: November 2008

The object of this article is to consider, or to speculate about, the roles and purposes of the institution of civil litigation in the 21st Century.
ISSUER CHOICE IN EUROPE
Authors: Enriques Luca , Tröger Tobias H
Published: November 2008

Regulatory competition is a salient feature of US federalism. The fifty States potentially serve as the rivalling jurisdictions' laboratories breeding constant legislative innovation.
TAXONOMIC PROPERTY
Authors: Sherman Brad
Published: November 2008

Intellectual property law has been dealing with botanical innovations in a sustained way for over a century.
THE DRAFTING OF CRIMINAL LEGISLATION: NEED IT BE SO IMPENETRABLE?
Authors: Spencer J R
Published: November 2008

[1] Section 174(1)(b)(i) of the Criminal Justice Act 2003 requires a court passing sentence to explain to an offender in ordinary language the effect of the sentence.
DAMAGES IN TORT AND UNDER THE HUMAN RIGHTS ACT: REMEDIAL OR FUNCTIONAL SEPARATION?
Authors: Steele Jenny
Published: November 2008

Since the creation of a new domestic action for violation of “Convention rights” under the Human Rights Act 1998 (“HRA”),
The lift force on a bubble in a sheared suspension in a slightly inclined channel
Authors: YIN XIAOLONG , KOCH DONALD L.
Published: November 2008

The lattice Boltzmann method was applied to simulate the free rise of monodisperse non-coalescing spherical bubbles in slightly inclined channels bound by solid walls. The Reynolds number based on the relative velocity between the bubbles and the fluid ranged from 4 to 16, the volume fraction from 5% to 10% and the inclination angle from 2° to 6°. The simulations revealed that the weak buoyancy component normal to the walls led to a layer of bubbles near the upper wall and a depleted layer near the bottom wall. These thin layers drove a nearly viscometric shear flow within the bulk of the channel that allowed an unambiguous determination of the lift force in a sheared homogeneous and freely evolving bubble suspension. The lift force coefficients calculated from our simulations were always higher than those for isolated spherical bubbles, suggesting that the lift force is enhanced by hydrodynamic interactions among the bubbles. Experimental measurements of the velocity gradient in 10% volume fraction bubble suspensions in glycerine–water–electrolyte mixtures in slightly inclined channels yielded lift coefficients in excess of those predicted for isolated bubbles and confirmed the qualitative predictions of the simulations.
Azimuthal structure of turbulence in high Reynolds number pipe flow
Authors: BAILEY SEAN C. C. , HULTMARK MARCUS , SMITS ALEXANDER J. , SCHULTZ MICHAEL P.
Published: November 2008

Two-point hot-wire measurements of streamwise velocity were performed in the logarithmic and wake regions of turbulent pipe flow for Reynolds numbers, based on pipe diameter, ranging from 7.6 × 104to 8.3 × 106at four wall-normal positions with azimuthal probe separation. The azimuthal correlations were found to be consistent with the presence of very large-scale coherent regions of low-wavenumber, low-momentum fluid observed in previous studies of wall-bounded flows and were found to be independent of changing Reynolds number and surface roughness effects. At the edge of the logarithmic layer the azimuthal scale determined from the correlations was found to be similar to that observed for channel flows but larger than that observed for boundary layers, inconsistent with the concept of a universal logarithmic region. As the wall-normal position increased outside the logarithmic layer, there was a decrease in azimuthal scale relative to that of channel flow. Using cross-spectral analysis, high-wavenumber motion was found to grow azimuthally with wall-normal distance at a faster rate than the low-wavenumber motions.
Effects of three-dimensionality on thrust production by a pitching panel
Authors: GREEN MELISSA A. , SMITS ALEXANDER J.
Published: November 2008

To understand the fluid dynamics of a biologically inspired unsteady low-aspect-ratio propulsor, unsteady pressure distributions were measured and compared with time-averaged thrust performance and wake visualizations. The experiments were performed on rigid rectangular panels with different aspect ratios, pitching in a uniform flow. Panel aspect ratio and pitching amplitude were shown to affect the magnitude and time dependence of the pressure distribution on the panel surface, the vorticity generation on the panel, and thrust production. A new scaling is proposed that includes these parameters and collapses the oscillating pressure magnitude and the thrust coefficient.
A unified framework for nonlinear combustion instability analysis based on the flame describing function
Authors: NOIRAY N. , DUROX D. , SCHULLER T. , CANDEL S.
Published: November 2008

Analysis of combustion instabilities relies in most cases on linear analysis but most observations of these processes are carried out in the nonlinear regime where the system oscillates at a limit cycle. The objective of this paper is to deal with these two manifestations of combustion instabilities in a unified framework. The flame is recognized as the main nonlinear element in the system and its response to perturbations is characterized in terms of generalized transfer functions which assume that the gain and phase depend on the amplitude level of the input. This ‘describing function’ framework implies that the fundamental frequency is predominant and that the higher harmonics generated in the nonlinear element are weak because the higher frequencies are filtered out by the other components of the system. Based on this idea, a methodology is proposed to investigate the nonlinear stability of burners by associating the flame describing function with a frequency-domain analysis of the burner acoustics. These elements yield a nonlinear dispersion relation which can be solved, yielding growth rates and eigenfrequencies, which depend on the amplitude level of perturbations impinging on the flame. This method is used to investigate the regimes of oscillation of a well-controlled experiment. The system includes a resonant upstream manifold formed by a duct having a continuously adjustable length and a combustion region comprising a large number of flames stabilized on a multipoint injection system. The growth rates and eigenfrequencies are determined for a wide range of duct lengths. For certain values of this parameter we find a positive growth rate for vanishingly small amplitude levels, indicating that the system is linearly unstable. The growth rate then changes as the amplitude is increased and eventually vanishes for a finite amplitude, indicating the existence of a limit cycle. For other values of the length, the growth rate is initially negative, becomes positive for a finite amplitude and drops to zero for a higher value. This indicates that the system is linearly stable but nonlinearly unstable. Using calculated growth rates it is possible to predict amplitudes of oscillation when the system operates on a limit cycle. Mode switching and instability triggering may also be anticipated by comparing the growth rate curves. Theoretical results are found to be in excellent agreement with measurements, indicating that the flame describing function (FDF) methodology constitutes a suitable framework for nonlinear instability analysis.
Sensitivity analysis and passive control of cylinder flow
Authors: MARQUET OLIVIER , SIPP DENIS , JACQUIN LAURENT
Published: November 2008

A general theoretical formalism is developed to assess how base-flow modifications may alter the stability properties of flows studied in a global approach of linear stability theory. It also comprises a systematic approach to the passive control of globally unstable flows by the use of small control devices. This formalism is based on a sensitivity analysis of any global eigenvalue to base-flow modifications. The base-flow modifications investigated are either arbitrary or specific ones induced by a steady force. This leads to a definition of the so-called sensitivity to base-flow modifications and sensitivity to a steady force. These sensitivity analyses are applied to the unstable global modes responsible for the onset of vortex shedding in the wake of a cylinder for Reynolds numbers in the range 47≤Re≤80. First, it is demonstrated how the sensitivity to arbitrary base-flow modifications may be used to identify regions and properties of the base flow that contribute to the onset of vortex shedding. Secondly, the sensitivity to a steady force determines the regions of the flow where a steady force acting on the base flow stabilizes the unstable global modes. Upon modelling the presence of a control device by a steady force acting on the base flow, these predictions are then extensively compared with the experimental results of Strykowski & Sreenivasan (J. Fluid Mech., vol. 218, 1990, p. 71). A physical interpretation of the suppression of vortex shedding by use of a control cylinder is proposed in the light of the sensitivity analysis.
The sources of jet noise: experimental evidence
Authors: TAM CHRISTOPHER K. W. , VISWANATHAN K. , AHUJA K. K. , PANDA J.
Published: November 2008

The primary objective of this investigation is to determine experimentally the sources of jet mixing noise. In the present study, four different approaches are used. It is reasonable to assume that the characteristics of the noise sources are imprinted on their radiation fields. Under this assumption, it becomes possible to analyse the characteristics of the far-field sound and then infer back to the characteristics of the sources. The first approach is to make use of the spectral and directional information measured by a single microphone in the far field. A detailed analysis of a large collection of far-field noise data has been carried out. The purpose is to identify special characteristics that can be linked directly to those of the sources. The second approach is to measure the coherence of the sound field using two microphones. The autocorrelations and cross-correlations of these measurements offer not only valuable information on the spatial structure of the noise field in the radial and polar angle directions, but also on the sources inside the jet. The third approach involves measuring the correlation between turbulence fluctuations inside a jet and the radiated noise in the far field. This is the most direct and unambiguous way of identifying the sources of jet noise. In the fourth approach, a mirror microphone is used to measure the noise source distribution along the lengths of high-speed jets. Features and trends observed in noise source strength distributions are expected to shed light on the source mechanisms. It will be shown that all four types of data indicate clearly the existence of two distinct noise sources in jets. One source of noise is the fine-scale turbulence and the other source is the large turbulence structures of the jet flow. Some of the salient features of the sound field associated with the two noise sources are reported in this paper.
Turbulent flow between counter-rotating concentric cylinders: a direct numerical simulation study
Authors: DONG S.
Published: November 2008

We report three-dimensional direct numerical simulations of the turbulent flow between counter-rotating concentric cylinders with a radius ratio 0.5. The inner- and outer-cylinder Reynolds numbers have the same magnitude, which ranges from 500 to 4000 in the simulations. We show that with the increase of Reynolds number, the prevailing structures in the flow are azimuthal vortices with scales much smaller than the cylinder gap. At high Reynolds numbers, while the instantaneous small-scale vortices permeate the entire domain, the large-scale Taylor vortex motions manifested by the time-averaged field do not penetrate a layer of fluid near the outer cylinder. Comparisons between the standard Taylor–Couette system (rotating inner cylinder, fixed outer cylinder) and the counter-rotating system demonstrate the profound effects of the Coriolis force on the mean flow and other statistical quantities. The dynamical and statistical features of the flow have been investigated in detail.
An interactive bypass transition mechanism in wall-bounded flows
Authors: TARDU F. SEDAT , NACEREDDINE RABIA , DOCHE OLIVIER
Published: November 2008

The interaction between two localized disturbances is analysed in a subcritical channel flow through direct numerical simulations. The initial perturbations are in the form of two pairs of counter-rotating vortices. One of them interacts with the wall-normal vorticity layers set up near the wall, by locally compressing or stretching part of them through the straining motion it induces. The breakdown of spanwise symmetry leads to the rapid development of a new wall-normal vorticity patch that is tilted by the shear and rolls up into a new small-scale streamwise vortex. The process results in a localized turbulent spot at later stages of development. A detailed analysis is carried out to determine the role of different parameters entering the physics of the mechanism. Several critical thresholds that trigger the interactive bypass transition process are found and analysed. The similarity parameters resulting from the parametric investigation coincide well with those governing the self-sustaining Reynolds-shear-stress-producing eddies in the buffer layer of a fully developed turbulent wall flow. It is suggested that the mechanism we propose may play a role in the regeneration cycle of the near-wall turbulence-generating structures by bypassing the three-dimensional streak instability mechanism.