bluuebunny/crossref_metadata_2025 huggingface dataset:
A new policy‐aware terminal for QoS, AAA and mobility management
Authors: Chaouchi Hakima
Published: March 2004

Policy‐based management has been widely studied in recent years. The Internet Engineering Task Force (IETF) has recently introduced the policy‐based networking as a means of managing IP networks according to the new constraints defined in the network, such as the guarantee of the quality of service (QoS). Network management based on policies, is modelled as a state machine, which moves from one state to another according to the enforced policy. The IETF policy‐based networking is defined for application to network nodes. However, some recent work suggests extending the policy‐based networking to the end‐user terminals. In this paper, we present an analysis of such an extension and we propose some possible solutions to support new policy‐aware terminals. In addition, we present AAA, QoS and mobility management that user such a policy‐aware terminals. Copyright © 2004 John Wiley & Sons, Ltd.
Call admission control in cellular networks: A reinforcement learning solution
Authors: Senouci Sidi‐Mohammed , Beylot André‐Luc , Pujolle Guy
Published: March 2004

In this paper, we address the call admission control (CAC) problem in a cellular network that handles several classes of traffic with different resource requirements. The problem is formulated as a semi‐Markov decision process (SMDP) problem. We use a real‐time reinforcement learning (RL) [neuro‐dynamic programming (NDP)] algorithm to construct a dynamic call admission control policy. We show that the policies obtained using our TQ‐CAC and NQ‐CAC algorithms, which are two different implementations of the RL algorithm, provide a good solution and are able to earn significantly higher revenues than classical solutions such as guard channel. A large number of experiments illustrates the robustness of our policies and shows how they improve quality of service (QoS) and reduce call‐blocking probabilities of handoff calls even with variable traffic conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Efficient visualization of large routing topologies
Authors: Au Siew Cheong , Leckie Christopher , Parhar Ajeet , Wong Gerard
Published: March 2004

As the Internet grows in size and complexity, network managers face a significant challenge in trying to understand the behaviour of routing protocols in large networks. In this paper, we present a tool called VLNT (visualizing large network topologies), which helps network managers to analyse complex routing topologies. A key contribution of our system is a novel hybrid layout algorithm, which significantly reduces the computation time required to layout large network topologies in comparison to conventional layout approaches. In addition our algorithm includes a novel termination criterion that avoids unnecessary iterations when optimizing the network layout. We demonstrate how the visualization features of VLNT can be used to analyse and improve BGP routing topologies, and provide examples using real‐life routing data. Copyright © 2004 John Wiley & Sons, Ltd.
Self‐similar and fractal nature of Internet traffic
Authors: Chakraborty D. , Ashir A. , Suganuma T. , Mansfield Keeni G. , Roy T. K. , Shiratori N.
Published: March 2004

The self‐similar bursty Internet traffic is usually characterized by the Hurst parameter (H). Such a process is also seen to possess fractal characteristics in time described by a parameter (β), with multifractals in most cases. We observe that these highly stochastic traffics have fractals in flow density too, described by a fractal dimension (D), also with the possibiliy of multifractals as in the former. This requires another parameter for the description of Internet traffic, besides the usual self‐similarity parameter β or H and the different simulations or models worked out to understand the Internet traffic to reproduce the characteristics as found in the present work. We also find a notable self‐similarity feature of the autocorrelations in the data and its aggregates, in all the cases studied. Copyright © 2004 John Wiley & Sons, Ltd.
Scalability and performance of an agent‐based network management middleware
Authors: Bivens Alan , Gupta Rashim , McLean Ingo , Szymanski Boleslaw , White Jerome
Published: March 2004

Rapid growth of computer network sizes and uses necessitate analysis of network application middleware in terms of its scalability as well as performance. In this paper we analyze a distributed network management middleware based on agents that can be dispatched to locations where they can execute close to the managed nodes. The described middleware operates between the network protocol layer and the application layer and uses standard TCP protocol and SNMP probes to interface the network. By aggregating requests from many users into a single agent, our system allows multiple managers to probe problem areas with minimal management traffic overhead. We discuss and quantify the benefits of the described middleware by implementing real‐time network managers using our system.

The main result of this paper is a comparison of scalability and efficiency of our agent‐based management middleware and traditional SNMP‐based data collection. To this end, we measured traffic in both real and simulated networks. In the latter case, we designed, used and described here a method of separating simulated application flow into separate subflows to simplify design of simulations. Copyright © 2004 John Wiley & Sons, Ltd.
Treatment effects and satisfaction in diabetic patients changing from multiple daily insulin injections to CSII
Authors: Garmo A , Pettersson‐Frank B , Ehrenberg A
Published: March 2004

The aims of this study were to describe how patients with diabetes mellitus type 1 experience a new treatment and daily living conditions when changing from multiple daily insulin injections to continuous subcutaneous insulin infusion (CSII) and to study the effects on metabolic control when changing therapy.

In all, 23 patients responded to Bradley's Diabetes Treatment Satisfaction Questionnaire (DTSQ) before and six months after change of treatment. HbA1c was collected from records and semi‐structured interviews were conducted with four of the patients after the change of therapy.

The findings show significant improvement concerning metabolic control, treatment satisfaction and perceived frequency of unacceptable hypo‐ and hyperglycaemic events six months after changing to CSII. The interview data indicated a pronounced concern for high values of HbA1c, but at the same time patients expressed the view that health care personnel focused too narrowly on this measure. The patients reported a greater sense of freedom and that planning daily living was made easier with CSII. However, they were anxious regarding incidents of pump breakdown. All patients conveyed their satisfaction with CSII in that it had positively changed their daily life. The patients also reported disadvantages with CSII, but they felt that the advantages far outweighed the disadvantages. Copyright © 2004 John Wiley & Sons, Ltd.
Diabetes service provision in primary care: a baseline survey in a city primary care trust (PCT)
Authors: Farooqi A , Dodd L , Stribling B , Jarvis J , Davies MJ , Khunti K
Published: March 2004

Primary care trusts (PCTs) are a key plank of the modernisation of the NHS in the UK. They have a unique role in the commissioning and provision of services to local communities. A baseline assessment of diabetes service provision in primary care is vital in establishing current levels of service and in developing service models relevant to local populations. We have developed and evaluated an audit tool to baseline diabetes services in primary care. We used this tool in the Eastern Leicester PCT which serves a population of 180 000 with a high South Asian population, estimated to be around 50%. This PCT has a high number of single‐handed general practices serving a deprived population. The survey was undertaken using direct interviewing of key members of the primary health care team, using a semi‐structured interview lasting for around an hour. All practices in the PCT were involved. The results of this survey highlighted major deficiencies in current services, e.g. only 10% of the practices had a structured plan for providing education for people with diabetes. It also demonstrated how regional estimates of the prevalence of diabetes in the UK may seriously underestimate the ‘true’ prevalence in some localities. This study highlights the uphill task many PCTs will face in terms of meeting the national service framework standards and providing basic elements of diabetes care. Copyright © 2004 John Wiley & Sons, Ltd.
The Kerraboot®: A novel wound dressing device for the management of leg and foot ulcers
Authors: Leigh R , Barker S , Murray N , Hurel SJ
Published: March 2004

Foot and lower leg ulcers are particularly common in patients with diabetes. Current management strategies are often complex and time consuming for health care professionals and uncomfortable for the patient. A novel wound dressing device, the Kerraboot®, was assessed for its ease of use and patient acceptability in 14 patients with foot and lower leg ulcers. The dressing device was used for a period of up to 28 days, after which patients and health care professionals were asked to complete questionnaires. The results confirmed the comfort, utility, convenience and ease of application and removal of the Kerraboot® in the management of such ulcers. Copyright © 2004 John Wiley & Sons, Ltd.
Toward a compact description of molecular electron densities
Authors: Chodkiewicz Michał L. , Howard Siân T. , Woźniak Krzysztof
Published: March 2004

A formalism is presented for the description of the electron density in a molecule or its fragment, using only a small number of parameters. The method is based on statistical analysis of a set of fragment electron densities obtained for a given quantum mechanical subsystem embedded in different environments (e.g., substituent groups, external fields). The electron density is expressed as the sum of its average value in such a subsystem and a linear combination of orthonormal functions expressed on a molecular orbital basis and chosen in such a way that each successive function maximally reduces the residual density. The technique used is functional principal component analysis (FPCA), which seems well suited to the statistical properties of the electron density. In addition to providing an efficient means of parameterizing an electron density, the FPCA also appears to provide the basis of a scheme for systematic analysis of the perturbations in electron density caused by changes of the molecular environment. An example of the application of this method, to the aldehyde fragment of HCOX compounds, is presented. Most of the variation of electron density in this fragment (97%) is described by only four functions. The coefficients of the first function correlate (−0.93) with the resonance substituent constants, and the second one with the induction parameterF(−0.9). This approach appears to have many potential applications: in developing rapid density functional methods for large molecules, in more efficient parameterizations of reconstructed experimental densities (from scattering experiments), and in analyzing substituent effects. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Rotavirus typing methods and algorithms
Authors: Fischer Thea K. , Gentsch Jon R.
Published: March 2004

Vaccination is the current strategy for control and prevention of severe rotavirus infections, a major cause of acute, dehydrating diarrhoea in young children worldwide. Public health interventions aimed at improving water, food and sanitation are unlikely adequately to control the disease. The development of vaccines against severe rotavirus diarrhoea is based upon homotypic or heterotypic protection provided against either a single common G serotype (monovalent vaccines) or against multiple serotypes (multivalent vaccines). Rotavirus strain surveillance has a high priority in disease control programmes worldwide. The continued identification of the most common G and P serotypes for inclusion in vaccines is an important priority. And subsequent to the introduction of a vaccine candidate, not only monitoring of circulating strains is recommended, but also surveillance of potential reassortment of animal rotavirus genes from the vaccine into human rotavirus strains is critical. Conventional methods used in the characterisation of rotavirus strains, such as enzyme immunoassay serotyping and reverse‐transcription PCR‐based genotyping often fail to identify uncommon and newly appearing strains. The application of newer molecular approaches, including sequencing and oligonucleotide microarray hybridisation, may be required to characterise such strains. The present paper presents a brief overview of the variety of standard methods available, followed by suggestions for a systematic approach for routine rotavirus strain surveillance as well as for characterisation of incompletely typed rotavirus strains. Improved detection and characterisation of incompletely typed strains will help to develop a comprehensive strain surveillance that may be required for tailoring effective rotavirus vaccines. Published in 2004 by John Wiley & Sons, Ltd.
Epidemiological and clinical aspects of human papillomavirus detection in the prevention of cervical cancer
Authors: Bekkers Ruud L. M. , Massuger Leon F. A. G. , Bulten Johan , Melchers Willem J. G.
Published: March 2004

Cervical cancer is a major cause of death, and the second most frequent cancer in women worldwide. Many studies have indicated a causal relation between genital human papillomavirus (HPV) infections and cervical cancer. High‐risk HPV genotypes have been detected in almost 100% of all cervical cancers, and the process of HPV mediated carcinogenesis has been partly clarified. The concept that HPV is a obligatory cause in cervical cancer development has lead to extensive research regarding the incorporation of HPV detection in (1) cervical cancer prevention programs, (2) triage of women with abnormal cervical scrapes in the screening program, and (3) follow‐up of patients treated for cervical intraepithelial neoplasia (CIN).

Epidemiological studies indicate that 50% of women becoming sexually active contract a genital HPV infection within 2 years. The lifetime risk of a genital HPV infection is estimated to be 80%, but very few of these women will develop cervical cancer. Several studies have shown that the persistence of genital HPV infections is especially related to the development of cervical cancer. As a result, HPV detection at a single moment was shown to be of limited clinical value in the triage of patients with abnormal cervical scrapes, or during follow‐up after treatment for CIN. Furthermore, major variations in the sensitivity of different HPV detection methods, as well as differences in HPV detection related to the menstrual cycle, have shown that many facts regarding HPV transmission, replication, and detection need to be clarified, before HPV detection can be of clinical value. Copyright © 2004 John Wiley & Sons, Ltd.
The molecular basis of HIV capsid assembly—five years of progress
Authors: Adamson Catherine S. , Jones Ian M.
Published: March 2004

The assembly of HIV is relatively poorly investigated when compared with the process of virus entry. Yet a detailed understanding of the mechanism of assembly is fundamental to our knowledge of the complete life cycle of this virus and also has the potential to inform the development of new antiviral strategies. The repeated multiple interaction of the basic structural unit, Gag, might first appear to be little more than concentration dependent self‐assembly but the precise mechanisms emerging for HIV are far from simple. Gag interacts not only with itself but also with host cell lipids and proteins in an ordered and stepwise manner. It binds both the genomic RNA and the virus envelope protein and must do this at an appropriate time and place within the infected cell. The assembled virus particle must successfully release from the cell surface and, whilst being robust enough for transmission between hosts, must nonetheless be primed for rapid disassembly when infection occurs. Our current understanding of these processes and the domains of Gag involved at each stage is the subject of this review. Copyright © 2004 John Wiley & Sons, Ltd.
Valency of antibody binding to virions and its determination by surface plasmon resonance
Authors: Dimmock Nigel J. , Hardy Sam A.
Published: March 2004

All IgGs are homobivalent, but their ability to bind bivalently to the surface of a virus particle depends mainly on a favourable spacing of cognate epitopes and the angle that the FAb arm makes with the virus surface. If the angle of binding forces the second FAb arm to point into solution, monovalent binding is inevitable. This IgG will have the same affinity as its FAb, will be less stably bound than if it were bound bivalently, cannot cross‐link epitopes on the surface of a virion, and cannot neutralise by cross‐linking surface proteins. However, at moderate IgG concentrations, monovalently bound IgG can reduce infectivity by aggregating virions, a phenomenon that cannot occur with IgG bound bivalently. This review describes how surface plasmon resonance can be used to determine the valency of IgG binding to enveloped and non‐enveloped virus particles, and discusses the implications of this new methodology. Copyright © 2004 John Wiley & Sons, Ltd.
Specific recognition of virus‐infected cells by paired NK receptors
Authors: Arase Hisashi , Lanier Lewis L.
Published: March 2004

NK cells show cytotoxicity and cytokine production upon recognition of virus‐infected cells and play an important role in conferring protective immunity against virus infection. Patients who lack functional NK cells are susceptible to severe infectious diseases such as herpesvirus infection. In addition, when NK cells are removed from cytomegalovirus‐resistant mice, the virus titre after infection is markedly increased and the mice are likely to die due to infection. However, the exact mechanism of how NK cells recognise virus‐infected cells has remained unclear for a long time. Recent findings of the presence of virus‐specific NK cell receptors and their ligands on virus‐infected cells have provided a new vision of a protective role of NK cells in virus infection. Furthermore, the recognition of virus‐infected cells by paired receptors consisting of activating and inhibitory receptors was found to correlate with the degree of host susceptibility to virus infection. Current topics on the role of NK cells in anti‐virus immunity are reviewed. Copyright © 2004 John Wiley & Sons, Ltd.
Estimating equations for association structures
Authors: Yan Jun , Fine Jason
Published: March 2004

This paper investigates generalized estimating equations for association parameters, which are frequently of interest in family studies, with emphasis on covariance estimation. Separate link functions are used to connect the mean, the scale, and the correlation to linear predictors involving possibly different sets of covariates, and separate estimating equations are proposed for the three sets of parameters. Simulations show that the robust ‘sandwich’ variance estimator and the jackknife variance estimator for the correlation parameters are generally close to the empirical variance for the sample size of 50 clusters. The results contradict Ziegleret al. and Kastner and Ziegler, where the ‘sandwich’ estimator obtained from the software MAREG was shown to be unsuitable for practical usage. The problem appears to arise because the MAREG variance estimator does not account for variability in estimation of the scale parameters, but may be valid with fixed scale. We also find that the formula for the approximate jackknife variance estimator in Ziegleret al. is deficient, resulting in systematic deviations from the fully iterated jackknife variance estimator. A general jackknife formula is provided and performs well in numerical studies. Data from a study on the genetics of alcoholism is used to illustrate the importance of reliable variance estimation in biomedical applications. Copyright © 2004 John Wiley & Sons, Ltd.
On the estimation of the binomial probability in multistage clinical trials
Authors: Jung Sin‐Ho , Kim Kyung Mann
Published: March 2004

Due to the optional sampling effect in a sequential design, the maximum likelihood estimator (MLE) following sequential tests is generally biased. In a typical two‐stage design employed in a phase II clinical trial in cancer drug screening, a fixed number of patients are enrolled initially. The trial may be terminated for lack of clinical efficacy of treatment if the observed number of treatment responses after the first stage is too small. Otherwise, an additional fixed number of patients are enrolled to accumulate additional information on efficacy as well as on safety. There have been numerous suggestions for design of such two‐stage studies. Here we establish that under the two‐stage design the sufficient statistic, i.e. stopping stage and the number of treatment responses, for the parameter of the binomial distribution is also complete. Then, based on the Rao–Blackwell theorem, we derive the uniformly minimum variance unbiased estimator (UMVUE) as the conditional expectation of an unbiased estimator, which in this case is simply the maximum likelihood estimator based only on the first stage data, given the complete sufficient statistic. Our results generalize to a multistage design. We will illustrate features of the UMVUE based on two‐stage phase II clinical trial design examples and present results of numerical studies on the properties of the UMVUE in comparison to the usual MLE. Copyright © 2004 John Wiley & Sons, Ltd.
Goodness‐of‐fit tests for ordinal response regression models
Authors: Pulkstenis Erik , Robinson Timothy J.
Published: March 2004

It is well documented that the commonly used Pearson chi‐square and deviance statistics are not adequate for assessing goodness‐of‐fit in logistic regression models when continuous covariates are modelled. In recent years, several methods have been proposed which address this shortcoming in the binary logistic regression setting or assess model fit differently. However, these techniques have typically not been extended to the ordinal response setting and few techniques exist to assess model fit in that case. We present the modified Pearson chi‐square and deviance tests that are appropriate for assessing goodness‐of‐fit in ordinal response models when both categorical and continuous covariates are present. The methods have good power to detect omitted interaction terms and reasonable power to detect failure of the proportional odds assumption or modelling the wrong functional form of a continuous covariate. These tests also provide immediate information as to where a model may not fit well. In addition, the methods are simple to understand and implement, and are non‐specific. That is, they do not require prespecification of a type of lack‐of‐fit to detect. Copyright © 2004 John Wiley & Sons, Ltd.
Estimation of magnitude in gene–environment interactions in the presence of measurement error
Authors: Wong M. Y. , Day N. E. , Luan J. A. , Wareham N. J.
Published: March 2004

The design of studies aimed at identifying the interaction between genetic and environmental determinants in disease risk is attracting increased attention. In this paper, we study the effect of errors on measuring exposures and the effect of assessing genotype at one locus on the association of a continuous outcome measure with continuous exposures and genotype. The estimation of misclassification errors in assessing genotypes from a separate study is proposed.

If the exposure measurement error is substantial, then even relatively small errors in genotyping within limits that are often quoted can have an appreciable effect on interaction estimates. We, thus, consider a method for correcting the measurement errors when the interaction between the exposures and the genetic factor is significant. Finally, we present an epidemiological example to demonstrate the importance of correcting measurement errors. Copyright © 2004 John Wiley & Sons, Ltd.
Pseudo‐likelihood estimation for a marginal multivariate survival model
Authors: Tibaldi Fabián , Molenberghs Geert , Burzykowski Tomasz , Geys Helena
Published: March 2004

In this paper, we propose a multivariate Plackett–Dale model for survival outcomes. A pseudo‐likelihood method for the estimation of the parameters is proposed and these ideas are applied to two case studies. The modelling approach is similar in spirit but different from Parner's approach. The first study is in AIDS, where the overall survival time and different opportunistic infections in HIV‐infected patients are studied. The second study is on adoption data where the association of the survival times within families is modelled, illustrating the use of the proposed methodology for the context of population genetics. Copyright © 2004 John Wiley & Sons, Ltd.
Comparing completely and stratified randomized designs in cluster randomized trials when the stratifying factor is cluster size: a simulation study
Authors: Lewsey J. D.
Published: March 2004

Stratified randomized designs are popular in cluster randomized trials (CRTs) because they increase the chance of the intervention groups being well balanced in terms of identified prognostic factors at baseline and may increase statistical power. The objective of this paper is to assess the gains in power obtained by stratifying randomization by cluster size, when cluster size is associated with an important cluster level factor which is otherwise unaccounted for in data analysis. A simulation study was carried out using a CRT where UK general practices were the randomized units as a template. The results show that when cluster size is strongly associated with a cluster level factor which is predictive of outcome, the stratified randomized design has superior power results to the completely randomized design and that the superiority is related to the number of clusters. Copyright © 2004 John Wiley & Sons, Ltd.
Predicting meningococcal disease outbreaks in structured populations
Authors: Ranta J. , Mäkelä P. H. , Arjas E.
Published: March 2004

Rational decision making on whether some form of intervention would be necessary to control the spread of a meningococcal epidemic is based on predictions concerning its potential natural progression. Unfortunately, reliable predictions are difficult to make during the early stages of an outbreak. A stochastic discrete time epidemic model was applied to adaptively predict the development of outbreaks of meningococcal disease in ‘closed’ populations such as military garrisons or boarding schools, which are further divided into subgroups called ‘units’. The performance of the adaptive method was assessed by using 3 simulated epidemics representing substantially different realizations in a ‘garrison’ of 20 units, with 68 men in each. Predictions of the weekly number of disease cases, of the number of carriers, and of the number of new infections were computed. Simulations suggest that predictions based only on the observed numbers of disease cases are generally inaccurate. These predictions can be improved if temporal observations on asymptomatic carriers in different units are utilized together with observed time series of the disease. A sample of 15 per cent from all units can be sufficient for a major improvement if the alternative is to obtain a full sample of only some units. Exploiting fully such information requires computer intensive Markov chain Monte Carlo methods. Copyright © 2004 John Wiley & Sons, Ltd.
Construction and validation of a prognostic model across several studies, with an application in superficial bladder cancer
Authors: Royston Patrick , Parmar Mahesh K. B. , Sylvester Richard
Published: March 2004

Many models for clinical prediction (prognosis or diagnosis) are published in the medical literature every year but few such models find their way into clinical practice. The reason may be that since in most cases models have not been validated in independent data, they lack generality and/or credibility. In this paper we consider the situation in which several compatible, independent data sets relating to a given disease with a time‐to‐event endpoint are available for analysis. The aim is to construct and evaluate a single prognostic model. Building a multivariable model from the available prognostic factors is accomplished within the Cox proportional hazards framework, stratifying by study. Non‐linear relationships with continuous predictors are modelled by using fractional polynomials. To assess the discrimination or separation of a survival model, we use theDstatistic of Royston and Sauerbrei.Dmay be interpreted as the separation (log hazard ratio) between the survival distributions for two independent prognostic groups. To evaluate the generality of a prognostic model across the data sets, we propose ‘internal–external cross‐validation’ onD: each study is omitted in turn, the model parameters are estimated from the remaining studies andDis evaluated in the omitted study. Because the linear predictor of a survival model tells only part of the story, we also suggest a method for investigating heterogeneity in the baseline distribution function across studies which involves fitting completely specified, flexible parametric survival models (Royston and Parmar). Our final models combine the prognostic index (obtained with stratification by study) with the pooled baseline survival distribution (estimated parametrically). By applying this methodology, we construct two prognostic scores in superficial bladder cancer. The simpler of the two scores is more suited to clinical application. We show that a three‐group prognostic classification scheme based on either score produces well‐separated survival curves for each of the data sets, despite identifiable heterogeneity among the baseline distribution functions and to a lesser extent among the prognostic indexes for the individual studies. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling of cardiac imaging data with spatial correlation
Authors: Bowman F. DuBois , Waller Lance A.
Published: March 2004

Cardiac imaging with single photon emission computed tomography (SPECT) is a common approach for quantifying myocardial perfusion. Fusing serial SPECT studies allows detection and quantification of changes in myocardial perfusion such as those resulting from disease progression or successful treatment therapy for patients with coronary artery disease. The abundance of data for each subject along with the inherent intra‐subject correlation due to spatial proximity of multiple perfusion measurements present special analytical challenges. We utilize a standard physiological model of the left ventricle (LV) to construct a general statistical model for cardiac perfusion that incorporates spatial correlation. We illustrate the use of mixed effects models and linear models with correlated errors to estimate myocardial perfusion counts and to compare these counts across serial studies. We address different types of spatial correlation among perfusion measurements in the LV, and we consider various parametric structures for these correlations. We apply the model to data from serial SPECT studies conducted while subjects were in both restful and stressful states approximately two days and one year following a myocardial infarction. Copyright © 2004 John Wiley & Sons, Ltd.
A testbed for performance evaluation of load‐balancing strategies for Web server systems
Authors: Sanghi Dheeraj , Jalote Pankaj , Agarwal Puneet , Jain Nitin , Bose Supriyo
Published: March 2004

To improve response time of a Web site, one replicates the site on multiple servers. The effectiveness of a replicated server system will depend on how the incoming requests are distributed among replicas. A large number of load‐balancing strategies for Web server systems have been proposed.

In this paper we describe a testbed that can be used to evaluate the performance of different load‐balancing strategies. The testbed uses a general architecture which allows different load‐balancing approaches to be supported easily. It emulates a typical World Wide Web scenario and allows variable load generation and performance measurement. We have performed some preliminary experiments to measure the performance of a few policies for load balancing using this testbed. Copyright © 2003 John Wiley & Sons, Ltd.
High‐intensity focused ultrasound in the treatment of postpartum hemorrhage: an animal model
Authors: Nizard J. , Pessel M. , De Keersmaecker B. , Barbet J. P. , Ville Y.
Published: March 2004

Objective

To investigate the use of high‐intensity focused ultrasound (HIFUS) to reduce uterine artery blood flow in ewes in the postpartum period.

Methods

HIFUS was applied to the uterine arteries of seven ewes in the postpartum period. Arterial flow velocities were measured before and after the procedure at the site of HIFUS application (target), as well as 3 cm upstream and 3 cm downstream from the target. The uterine arteries were then removed for macroscopic and histological examination.

Results

Maximum flow velocities in the target area increased after the procedure by 350% and those upstream from the target decreased by 65%. Macroscopically, the vessel diameter was shown to have reduced at the site of HIFUS application. Microscopically, both the endothelium and media showed thermal lesions. Tissues surrounding the arteries were macroscopically and microscopically normal.

Conclusion

Exposure of uterine arteries to HIFUS reduces the vessel diameter and thus induces a dramatic increase in the maximum flow velocities within the target area. HIFUS may have a role in the treatment of postpartum hemorrhage. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Assessment of the fetal nasal bone at 11–14 weeks of gestation by three‐dimensional ultrasound
Authors: Rembouskos G. , Cicero S. , Longo D. , Vandecruys H. , Nicolaides K. H.
Published: March 2004

Objective

To evaluate the benefit of three‐dimensional (3D) ultrasound in the examination of the fetal nasal bone at 11–14 weeks of gestation.

Method

We examined the fetal nasal bone in 120 stored volumes acquired transabdominally with a 3D scanner from singleton pregnancies at 11–14 weeks of gestation. The volume acquisition had been performed following conventional ultrasound examination that had demonstrated presence of the fetal nasal bone. The volumes were obtained with two‐dimensional (2D) start images in transverse, coronal mid‐sagittal, parasagittal and oblique longitudinal sections of the fetal head.

Results

In the transverse and coronal sections, a satisfactory image demonstrating presence of the nasal bone was achieved in only three and one, respectively, of the 20 volumes that we obtained. In mid‐sagittal sections, the nasal bone was always visible when the angle was within a range of 30–60°, without the need for sectional image analysis. None of the images with an angle >60° or <30° was satisfactory. In the parasagittal sections with the fetal profile at 45°, a good‐quality image of the nasal bone was possible in all cases that were examined, irrespective of the distance from the mid‐sagittal plane. In the oblique longitudinal sections with the fetal profile at 45°, there were 10 volumes where the 2D start section was at 0–25° from the midline and in all these cases the nasal bone was successfully visualized. In contrast, only 5/20 cases where the 2D start section was at 25–90° from the midline provided a satisfactory image demonstrating the nasal bone. In 5/10 volumes obtained with the fetus facing downwards the nasal bone was visible in both the 2D and 3D images.

Conclusion

In a 3D volume the extent to which the nasal bone can be demonstrated to be present in a given reconstructed section is entirely dependent on obtaining a good initial 2D view. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Do maternal cerebral vascular changes assessed by transcranial Doppler antedate pre‐eclampsia?
Authors: Williams K. P. , Moutquin J. M.
Published: March 2004

Objective

To determine whether maternal transcranial Doppler (TCD) evaluation of the middle cerebral artery identifies changes in the cerebral circulation prior to the development of pre‐eclampsia.

Methods

In a nested, case‐controlled study developed from a previous prospective cohort study, 20 pre‐eclamptic and 40 normotensive pregnancies, matched for maternal age, were assessed with the traditional middle cerebrovascular Doppler parameters (pulsatility index, mean cerebral blood flow velocity), together with non‐traditional Doppler parameters including time taken to achieve end systole (EST) and percentage time to achieve end systole (% EST). Assessments done at 20–24 and 28–32 weeks' gestational age were compared using Student's t‐tests. Significance was set at the P < 0.05 level.

Results

In the second trimester (20–24 weeks) there were no significant differences in any of the Doppler waveform characteristics in either group. In the third trimester (28–32 weeks) there was a significant increase in the % EST in the group who subsequently developed pre‐eclampsia (45.2 ± 4.2 vs. 42.3 ± 4.1; P < 0.01).

Conclusions

Patients who subsequently develop pre‐eclampsia show a significant lengthening in the EST in the third trimester as a late finding, which indicates an increase in the cerebrovascular resistance. Earlier prediction of pre‐eclampsia using TCD waveform analysis will require more provocative testing (i.e. hand grip and CO2 reactivity). Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Umbilical cord diameter at 11–14 weeks of gestation: relation to chromosomal defects
Authors: Rembouskos G. , Cicero S. , Papadopoulos V. , Tripsanas C. , Nicolaides K. H.
Published: March 2004

Objective

To determine the potential value of measuring umbilical cord diameter (UCD) at 11–14 weeks of gestation in screening for chromosomal defects.

Methods

The UCD was measured in 1323 fetuses immediately before chorionic villus sampling for karyotyping at 11–14 weeks of gestation. In the group of chromosomally normal fetuses, regression analysis was used to determine the association between UCD and crown–rump length (CRL). UCD was compared in normal fetuses and those with chromosomal abnormalities.

Results

The median gestation was 12 (range, 11–14) weeks. The UCD was successfully measured in all cases. The fetal karyotype was normal in 1150 pregnancies and abnormal in 173, including 97 cases of trisomy 21. In the chromosomally normal group the UCD increased significantly with CRL from a mean of 2.9 mm at a CRL of 45 mm to 4.4 mm at a CRL of 84 mm. The UCD in the group of fetuses with trisomy 21 was significantly smaller than normal. Conversely, there were no significant differences from normal in the UCD of fetuses with other chromosomal abnormalities.

Conclusion

At 11–14 weeks of gestation the UCD of fetuses with trisomy 21 is significantly smaller than normal but the magnitude of the difference is too small for useful inclusion of this measurement in screening. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Cesarean scar pregnancy: issues in management
Authors: Seow K.‐M. , Huang L.‐W. , Lin Y.‐H. , Yan‐Sheng Lin M. , Tsai Y.‐L. , Hwang J.‐L.
Published: March 2004

Objective

To evaluate our experience with the diagnosis and treatment of Cesarean scar pregnancy.

Methods

During a 6‐year period, 12 cases of Cesarean scar pregnancy were diagnosed using transvaginal color Doppler sonography and treated conservatively to preserve fertility. Incidence, gestational age, sonographic findings, β‐human chorionic gonadotropin ( β‐hCG) levels, flow profiles of transvaginal color Doppler ultrasound, and methods of treatment were recorded.

Results

The incidence of Cesarean scar pregnancy was 1:2216 and its rate was 6.1% in women with an ectopic pregnancy and at least one previous Cesarean section. Gestational age at diagnosis ranged from 5 + 0 to 12 + 4 weeks. The time interval from the last Cesarean section to the diagnosis of Cesarean scar pregnancy ranged from 6 months to 12 years. High‐velocity and low‐impedance subtrophoblastic flow (resistance index, 0.38) persisted until β‐hCG declined to normal. Patients were treated as follows: transvaginal ultrasound‐guided injection of methotrexate into the embryo or gestational sac (n = 3), transabdominal ultrasound‐guided injection of methotrexate (n = 2), transabdominal ultrasound‐guided injection of methotrexate followed by systemic methotrexate administration (n = 2), systemic methotrexate administration alone (n = 2), dilatation and curettage (n = 2), or local resection of the gestation mass (n = 1). Eleven of the 12 patients preserved their reproductive capacity; the remaining patient, treated by dilatation and curettage, underwent a hysterectomy because of profuse vaginal bleeding. The Cesarean scar mass regressed from 2 months to as long as 1 year after treatment. Uterine rupture occurred in one patient during the following pregnancy at 38 + 3 weeks' gestational age.

Conclusion

Ultrasound‐guided methotrexate injection emerges as the treatment of choice to terminate Cesarean scar pregnancy. Surgical or invasive techniques, including dilatation and curettage are not recommended for Cesarean scar pregnancy due to high morbidity and poor prognosis. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Affective state of women following a prenatal diagnosis: predictors of a negative psychological outcome
Authors: Leithner K. , Maar A. , Fischer‐Kern M. , Hilger E. , Löffler‐Stastka H. , Ponocny‐Seliger E.
Published: March 2004

Objective

The benefits of prenatal diagnostic procedures are well documented. However, the investigation of psychological consequences related to these procedures has remained a surprisingly neglected area of research. The main aim of the present study was to investigate the potential relationship between psychological outcome and associated (socio‐demographic, psychological and obstetric) variables in women attending a tertiary referral center for prenatal diagnosis and therapy for ultrasound scanning (due to the suspicion of a fetal malformation raised by the gynecologist in private practice), amniocentesis or chorionic villus sampling.

Methods

Affective state was assessed by means of standardized measures of anxiety and depression (State‐Trait Anxiety Inventory; Mood Scale) in 77 consecutive, unselected women. A follow‐up investigation, including an additional assessment of coping mechanisms, took place 6 months after the first contact. Given the considerable number of intervening and correlating factors, a path analysis was undertaken.

Results

We found that all women in our sample experienced acute distress, not only those with proven fetal malformations, genetic disorders or intrauterine fetal death, but also those with the diagnosis of a sonographic sign. At baseline (i.e. immediately after the diagnostic procedure), mood and anxiety scores in our sample were found to be comparable to those of patients with a major depressive episode. A high trait anxiety level, implementation of negative coping strategies and loss of the child during pregnancy were found to be predictive of a negative psychological outcome at follow‐up. Socio‐demographic variables did not have a significant predictive function for the psychological outcome.

Conclusions

We assume that a considerable number of women undergoing prenatal diagnostic procedures experience psychological distress, which may be underestimated by workers in prenatal care. Establishment of interdisciplinary treatment settings, in which access to psychological support is facilitated, may be extremely beneficial for women following a prenatal diagnosis. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Introital ultrasound of the lower genital tract before and after colposuspension: a 4‐year objective follow‐up
Authors: Viereck V. , Pauer H.‐U. , Bader W. , Oppermann M. , Hilgers R. , Gauruder‐Burmester A. , Lange R. , Emons G. , Hackenberg R. , Krauß T.
Published: March 2004

Objective

To assess the topography of the bladder neck by introital ultrasound before and after open colposuspension.

Methods

Three hundred and ten women with urodynamically proven stress urinary incontinence were included in this long‐term study to investigate the position and function of the bladder neck at rest and during straining. Height (H), distance (D), and urethrovesical angle of the bladder neck (β) were measured by means of preoperative and postoperative introital ultrasound. Women were followed up; 152 of them (49%) completed 48 months of follow‐up.

Results

At the 6‐month follow‐up examination, 90.0% of the women were continent (279/310), 3.5% (11/310) showed voiding difficulties, 3.5% (11/310) had urgency, and 1.6% (5/310) had developed de novo urge incontinence. At the 48‐month follow‐up, 76.8% of the patients were still continent. All postoperative measurements yielded significantly lower values for angle β at rest and during straining compared with the preoperative results (P < 0.0001). The median linear movement of the bladder neck during straining decreased from 18.0 mm before surgery to 6.4 mm at the 48‐month follow‐up (P < 0.0001). The median level of ventrocranial elevation of the vesicourethral junction was 14.3 mm immediately after surgery, 9.9 mm after 6 months and 6.6 mm after 48 months. The degree of surgical bladder‐neck elevation was associated with postoperative urgency/de novo urge incontinence (P < 0.0001) and voiding difficulty (P < 0.0001).

Conclusions

The colposuspension procedure reduces angle β at rest and during straining, restricts linear movement with straining, and elevates the bladder neck. Perioperative introital ultrasound improves understanding of this surgical procedure and might help to prevent postoperative complications. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Two‐ and three‐dimensional sonographic assessment of the fetal face. 1. A systematic analysis of the normal face
Authors: Rotten D. , Levaillant J. M.
Published: March 2004

Objectives

To detail fetal facial examination in utero using ultrasound, to distinguish between requirements for routine screening and those for precise analysis of fetal facial features, and to assess the use of three‐dimensional (3D) ultrasound imaging in fetal facial examination.

Methods

This was a retrospective study, based on the examination of approximately 10 500 fetuses. The usual age at screening ultrasound examination was 22 ± 1 gestational weeks.

Results

The sonographic anatomy of the normal fetal face was depicted, and the relevance of the three reference scanning planes, sagittal, coronal and axial, was specified.

Conclusions

At routine screening using two‐dimensional sonography, at least two selected views must be imaged: the mid‐sagittal plane (search for facial dysmorphology) and the anterior ‘nose–mouth’ coronal plane (search for disruption in lip continuity or deformation of the narinal bend). Precise analysis of fetal facial anomalies requires visualization and thorough step‐by‐step analysis in the three planes. The difference between routine screening and precise facial features' analysis has been greatly decreased since 3D and 4D sonography have become readily available. Using this modality, after surface analysis of the fetal face, the three reference planes are simultaneously imaged, using the multiplanar modality, and detailed. 3D/4D ultrasound imaging allows easier, more rapid screening and more precise evaluation of the different facial features. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.