bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal continuous sequential boundaries for monitoring toxicity in clinical trials: a restricted search algorithm
Authors: Goldman Anne I. , Hannan Peter J.
Published: August 2002

Continuous monitoring of severe adverse experiences can ensure the timely termination of a clinical trial if the therapy is shown to be harmful. In this paper we present methods for choosing a stopping rule for continuous monitoring of toxicity in small trials. They are especially useful for small phase II trials of about 30 patients for monitoring a binary toxicity event that is observed relatively quickly compared to the efficacy outcome. In 1987 Goldman described an algorithm for computing the exact type I error rate (α) and power (1−β) of a specified discrete stopping boundary for sequential monitoring of a study with a fixed maximum number of patients (N) to be enrolled on the experimental therapy. Only an upper boundary was used since trials are only terminated for an excess frequency of toxicity and not for a low rate. By repeated use of this algorithm a stopping rule can be identified which has nearly the chosen level of (α) and a reasonable power depending on the design parameters of the study. The work reported here embeds this earlier algorithm as a subroutine in a larger FORTRAN program which searches all boundaries that fulfil constraints on size and power, as specified by the user. The search is restricted so that only those boundaries with size in a small neighbourhood of the chosen α are examined and displayed if the power is above a set minimum. These restrictions reduce the number of boundaries examined to only 0.4 per cent of all possible boundaries, thus reducing running time to a practical few seconds. Many such boundaries exist, the one with the largest power can then be chosen for monitoring the trial. The average sample number (ASN) and the expected relative loss (ERL) are also computed. The criterion for choosing may also be based on small ASN or low ERL in addition to power and appropriate α. Copyright © 2001 John Wiley & Sons, Ltd.
Variance estimation of a survival function for interval‐censored survival data
Authors: Sun Jianguo
Published: August 2002

Interval‐censored survival data often occur in medical studies, especially in clinical trials. In this case, many authors have considered estimation of a survival function. There is, however, relatively little discussion on estimating the variance of estimated survival functions. For right‐censored data, a special case of interval‐censored data, the most commonly used method for variance estimation is to use the Greenwood formula. In this paper we propose a generalization of the Greenwood formula for variance estimation of a survival function based on interval‐censored data. Also a simple bootstrap approach is presented. The two methods are evaluated and compared using simulation studies and a real data set. The simulation results suggest that the methods work well. Copyright © 2001 John Wiley & Sons, Ltd.
Computational tools for exact conditional logistic regression
Authors: Corcoran Chris , Mehta Cyrus , Patel Nitin , Senchaudhuri Pralay
Published: August 2002

Logistic regression analyses are often challenged by the inability of unconditional likelihood‐based approximations to yield consistent, valid estimates andp‐values for model parameters. This can be due to sparseness or separability in the data. Conditional logistic regression, though useful in such situations, can also be computationally unfeasible when the sample size or number of explanatory covariates is large. We review recent developments that allow efficient approximate conditional inference, including Monte Carlo sampling and saddlepoint approximations. We demonstrate through real examples that these methods enable the analysis of significantly larger and more complex data sets. We find in this investigation that for these moderately large data sets Monte Carlo seems a better alternative, as it provides unbiased estimates of the exact results and can be executed in less CPU time than can the single saddlepoint approximation. Moreover, the double saddlepoint approximation, while computationally the easiest to obtain, offers little practical advantage. It produces unreliable results and cannot be computed when a maximum likelihood solution does not exist. Copyright © 2001 John Wiley & Sons, Ltd.
Graphical model checking with correlated response data
Authors: Pan Wei , Connett John E. , Porzio Giovanni C. , Weisberg Sanford
Published: August 2002

Correlated response data arise often in biomedical studies. The generalized estimation equation (GEE) approach is widely used in regression analysis for such data. However, there are few methods available to check the adequacy of regression models in GEE. In this paper, a graphical method is proposed based on Cook and Weisberg's marginal model plot. A bootstrap method is applied to obtain the reference band to assess statistical uncertainties in comparing two marginal mean functions. We also propose using the generalized additive model (GAM) in a similar fashion. The proposed two methods are easy to implement by taking advantage of existing smoothing and GAM softwares for independent data. The usefulness of the methodology is demonstrated through application to a correlated binary data set drawn from a clinical trial, the Lung Health Study. Copyright © 2001 John Wiley & Sons, Ltd.
Estimating the difference between differences: measurement of additive scale interaction for proportions
Authors: Newcombe Robert G.
Published: August 2002

A simple, effective closed‐form method to calculate a confidence interval for the difference between two differences of proportions is proposed. The method is based on the Wilson score interval for the single proportion, and may be used to compare either unpaired or paired differences. It is equally applicable whether cell frequencies are large or small; and coverage properties are favourable. It is easily adapted to give a confidence interval for the treatment effect for a binary outcome in a two‐period cross‐over trial. Copyright © 2001 John Wiley & Sons, Ltd.
Monitoring a clinical trial with multiple hypotheses concerning the treatment effect on a single primary endpoint
Authors: Denne Jonathan S. , Koch Gary G.
Published: August 2002

In a number of clinical trials there is interest in testing more than one hypothesis concerning the treatment effect on a single primary endpoint. For instance, a sponsor of a trial to demonstrate that a test treatment (T) is non‐inferior to an active control (R) may also be interested in showing that T is superior to R, if this is the case. Using theclosed testingmethod for constructing tests of multiple hypotheses which control the multiple level of significance, we provide a framework for testing these hypotheses sequentially during a trial at pre‐planned interim analyses. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of childhood brain tumour data in New York City using frailty models
Authors: Xue Xiaonan
Published: August 2002

This paper uses frailty models to analyse overall survival and progression‐free survival times for children with a brain tumour. We are interested in how surgery resection affects survival times. We are also interested in how strong a child's progression‐free survival correlates with his/her overall survival and if the association differs with age. Traditionally the frailty is modelled parametrically and a maximum likelihood approach is used to estimate the parameters of interest. However, the result is sensitive to the misspecification of the frailty distribution and the currently developed algorithms for the maximum likelihood approach do not allow the association parameter to depend on covariates. Xue formulates a Poisson regression model and applies an estimating equation approach to obtain a consistent estimate of the covariate effect on survival. This paper extends that approach to obtain consistent and efficient estimates of the association parameter as well as the covariate effect and to allow the association parameter to depend on the covariates. The approach does not require the specification of the frailty distribution. The performance of the method is evaluated through simulation studies. We apply this method to a childhood brain tumour data set in New York City. Copyright © 2001 John Wiley & Sons, Ltd.
An adjustment for a post‐randomization variable in the comparison of two treatments for survival
Authors: Heller Glenn
Published: August 2002

A method is proposed to infer the randomized treatment effect on survival after an adjustment for a post‐randomization variable. The post‐randomization variable is made independent of the treatment assignment and is considered a surrogate for baseline prognostic factors. The relationship between the post‐randomization surrogate and baseline prognostic factors for survival is considered smooth, but otherwise unknown. The effect of these factors on survival is modelled using the Cox proportional hazards model with a semi‐parametric relative risk function. Likelihood based estimates and tests for the treatment effect are demonstrated. An example from a randomized clinical trial in cancer illustrates the methodology. Copyright © 2001 John Wiley & Sons, Ltd.
A comparison of generalized linear mixed model procedures with estimating equations for variance and covariance parameter estimation in longitudinal studies and group randomized trials
Authors: Evans Brent A. , Feng Ziding , Peterson Arthur V.
Published: August 2002

Response data in longitudinal studies and group randomized trials are gathered on units that belong to clusters, within which data are usually positively correlated. Therefore, estimates and confidence intervals for intraclass correlation or variance components are helpful when designing a longitudinal study or group randomized trial. Data simulated from both study designs are used to investigate the estimation of variance and covariance parameters from the following procedures: for continuous outcomes, restricted maximum likelihood (REML) and estimating equations (EE); for binary outcomes, restricted pseudo‐likelihood (REPL) and estimating equations (EE). We evaluate these procedures to see which provide valid and precise estimates as well as correct standard errors for the intraclass correlation coefficient or variance components. REML seems the better choice for estimating terms related to correlation for models with normal outcomes, especially in group randomized trial situations. Results for REML and EE are mixed when outcomes are continuous and non‐normal. With binary outcomes neither REPL nor EE provides satisfactory estimation or inference in longitudinal study situations, while REPL is preferable for group randomized trials. Copyright © 2001 John Wiley & Sons, Ltd.
Security in the Ajanta mobile agent system
Authors: Karnik Neeran M. , Tripathi Anand R.
Published: August 2002

A mobile agent is an object which can autonomously migrate in a distributed system to perform tasks on behalf of its creator. Security issues in regard to the protection of host resources, as well as the agent themselves, raise significant obstacles in practical applications of the agent paradigm. This article describes the security architecture of Ajanta, a Java‐based system for mobile agent programming. This architecture provides mechanisms to protect server resources from malicious agents, agent data from tampering by malicious servers and communication channels during its travel, and protection of name service data and the global namespace. We present here a proxy based mechanism for secure access to server resources by agents. Using Java's class loader model and thread group mechanism, isolated execution domains are created for agents at a server. An agent can contain three kinds of protected objects: read‐only objects whose tampering can be detected, encrypted objects for specific servers, and a secure append‐only log of objects. A generic authentication protocol is used for all client–server interactions when protection is required. Using this mechanism, the security model of Ajanta enforces protection of namespaces, and secure execution of control primitives such as agent recall or abort. Ajanta also supports communication between agents using RMI, which can be controlled if required by the servers' security policies. Copyright © 2001 John Wiley & Sons, Ltd.
A framework for the development of videogames
Authors: Santelices Raúl A. , Nussbaum Miguel
Published: August 2002

A framework is a high‐level solution for the reuse of software pieces, a step forward in simple library‐based reuse, that allows the sharing of not only common functions but also the generic logic of a domain application. It also ensures a better level of quality for the final product, given the fact that an important fraction of the application is already found within the framework and has therefore already been tested. This case study takes the systematic generation of hot‐spot subsystems approach as a reference point to describe the underlying concepts in the design of a framework for the development of 2D action videogames for low‐performance machines. The main goal of this paper is to show the applicability of framework‐based reuse to videogames. Both standard and framework‐based game implementations are compared and the results are analysed. Special attention is paid to the (potential) benefits that the use of frameworks brings to the fulfillment of maintenance tasks along the game's life cycle, a stage that normally consumes most resources in software projects. At the end of the paper, based on the implementation results, this study shows the predicted conditions under which building a framework is cost effective for the development of videogames similar to the ones from the studied domain. Copyright © 2001 John Wiley & Sons, Ltd.
Postoperative radiotherapy of astrocytomas
Authors: Herfarth Klaus K. , Gutwein Sybille , Debus Jürgen
Published: August 2002

Astrocytomas account for the majority of primary brain tumors. Low‐grade tumors are slowly growing tumors with relatively long overall survival. However, a high percentage of these tumors transform to more malignant, high‐grade tumors. High‐grade gliomas (anaplastic astrocytomas and glioblastoma multiforme) have a poor prognosis. Treatment options are capable of prolonging the natural history of the disease, but the long‐term survival is poor. This review discusses the different postoperative treatment options and the prognostic factors in low‐ and high‐grade astrocytomas. Semin. Surg. Oncol. 20:13–23, 2001. © 2001 Wiley‐Liss, Inc.
SCH 58261, an A2A adenosine receptor antagonist, counteracts parkinsonian‐like muscle rigidity in rats
Authors: Wardas Jadwiga , Konieczny Jolanta , Lorenc‐Koci Elżbieta
Published: August 2002

The aim of the present study was to find out whether blockade of adenosine A2A receptors by a selective antagonist, SCH 58261, influenced parkinsonian‐like muscle rigidity. Muscle tone was examined using a combined mechano‐ and electromyographic method which simultaneously measured muscle resistance (MMG) of a rat hindfoot to passive extension and flexion in the ankle joint and electromyographic activity (EMG) of the antagonistic muscles of that joint: gastrocnemius and tibialis anterior. Muscle rigidity produced by reserpine (5 mg/kg + α‐methyl‐p‐tyrosine, 250 mg/kg) was antagonized by SCH 58261 (0.1–5 mg/kg). SCH 58261 (5 mg/kg) also reduced reserpine‐enhanced tonic and reflex EMG activities in both the gastrocnemius and the tibialis muscles. Moreover, SCH 58261 in doses of 1 and 5 mg/kg abolished muscle resistance induced by haloperidol (0.5 mg/kg). However, only the highest dose of SCH 58261 (5 mg/kg) decreased tonic EMG activity enhanced by haloperidol. Administration of L‐DOPA (75 and 100 mg/kg) dose‐dependently decreased the muscle resistance as well as tonic EMG activity evoked by haloperidol. Combined administration of SCH 58261 (0.1 mg/kg) and L‐DOPA (50 mg/kg) in doses which did not affect the haloperidol‐induced muscle rigidity produced a pronounced synergistic effect. The ability of SCH 58261 to diminish the parkinsonian‐like muscle rigidity and to potentiate the effect of L‐DOPA in this model seems to indicate a therapeutic value of this compound in the treatment of Parkinson's disease. Synapse 41:160–171, 2001. © 2001 Wiley‐Liss, Inc.
Building blocks for a decision‐based integrated product development and system realization process
Authors: Prasad Biren (Brian)
Published: August 2002

A key requirement, in a distributed product development environment at General Motors, was to provide a series of quantitative and qualitative mechanisms for integrating competing information from distributed agents. Such mechanisms must also account for provisions for combining different opinions, for resolving conflicts, and for finding a feasible or optimal solution at the end. We, at Electronic Data Systems (EDS), General Motors Account, developed a Decision‐based Integrated Product Development (DIPD) methodology to capture a system‐level optimization formulation as part of a product design, development and delivery (PD3) process. The paper describes this methodology in the context of system‐level optimization. DIPD employs the inputs, requirement, constraints, and output conventions to formulate the product realization problem in a distributed manner. The purpose of this DIPD methodology is to improve the performance characteristics of the product, process, and organization (PPO) relative to automobile consumer needs and expectations. DIPD builds the theory through a systematic revision and extension of the paradigms introduced earlier by optimization experts and practitioners including this author [Prasad,1996]. The eight parts of this DIPD methodology, called building blocks, are discussed at length in this paper. The first four blocks, 1–4, provide a conceptual framework for understanding the challenges and opportunities in DIPD. The last four parts, 5–8, of this methodology provide the building blocks for an analytical and conceptual framework for decision‐making, PPO improvements, and a large‐scale system optimization. © 2002 Wiley Periodicals, Inc. Syst Eng 5: 123–144, 2002
Aneuploidy induced in lymphocytes of parents of trisomic 21 children
Authors: Caria Helena , Chaveca Teresa , Rueff José
Published: August 2002

A possible predisposition to aneuploidy in trisomic 21 individuals, their parents, and a control group was evaluated. Peripheral blood lymphocytes from those three groups were used to study the induction of micronuclei (MN) by mitomycin C, cyclophosphamide, and quercetin. Induced MN were further analysed by C‐banding and CREST antibody. Trisomic 21 individuals have spontaneous frequencies of MN significantly higher than their parents and the control group. Quercetin without metabolic activation induces MN in trisomic 21 and their parents at a significantly higher level than in control group. The group of the parents of trisomic 21 individuals exhibits higher frequencies of induced MN by mitomycin C and cyclophosphamide than controls. Mitomycin C significantly induced CREST‐positive‐MN in ten of the sixteen parents evaluated. The results obtained seem to suggest a unique behaviour for the parents of trisomic 21 patients consisting in an increased susceptibility to chromosome loss in the presence of clastogenic genotoxicants, suggesting a higher predisposition to aneuploidy. Teratogenesis Carcinog. Mutagen. 21:369–382, 2001. © 2001 Wiley‐Liss, Inc.
Polychlorinated biphenyls promote 1‐nitropyrene‐induced lung tumorigenesis without the induction of K‐ras gene mutation in A/J mice
Authors: Nakanishi Yoichi , Bai Feng , Inoue Koji , Takayama Koichi , Pei Xin‐Hai , Harada Taishi , Izumi Miiru , Kimotsuki Kanehito , Tokiwa Hiroshi , Hara Nobuyuki
Published: August 2002

Although the effects of polychlorinated biphenyls (PCBs) on human lung carcinogenesis are suggested from the massive PCBs poisoning that occurred in Japan designated “Yusho,” the detailed molecular mechanism are unknown. 1 nitropyrene (1‐NP), an ubiquitous and abundant environmental pollutant, is known to be detected in lung tissues derived from patients with lung cancer in Japan, and its relation to lung carcinogenesis is also suggested. We investigated the effects of PCBs (Kanechlor‐400) on 1‐NP‐induced lung tumorigenesis in A/J mice. PCBs were administered intraperitoneally followed by ip injection of 1‐NP. The lung lesions were examined 18 weeks after the final treatment. In the control group, no neoplastic lesions were induced in the lung. In the PCB group, preneoplastic lesions such as hyperplasia and adenoma were induced in 2/10 (20%) mice. In 1‐NP group and in PCB + 1‐NP group, lung lesions including adenocarcinoma were induced in 16/20 (80%) and 13/13 (100%) mice, respectively. Both the number and the size of tumors in PCB + 1‐NP group were significantly greater than those in 1‐NP group. K‐ras gene mutation, CAA to CGA in codon 61 or GGT to GAT in codon 12, was found in either 1‐NP group or PCB + 1‐NP group but not in the PCB group. There was no difference in the pattern of K‐ras mutation associated with the pretreatment with PCBs. These results suggest that PCBs promote 1‐NP‐induced lung tumorigenesis and may support, at least in part, the mechanism of the high incidence of lung cancer in patients with Yusho. Teratogenesis Carcinog. Mutagen. 21:395–403, 2001. © 2001 Wiley‐Liss, Inc.
Chemistry and chemical biology of taxane anticancer agents
Authors: Miller Michael L. , Ojima Iwao
Published: August 2002

Taxol® (paclitaxel) and Taxotère® (docetaxel) are currently considered to be among the most important anticancer drugs in cancer chemotherapy. The anticancer activity of these drugs is ascribed to their unique mechanism of action, i.e., causing mitotic arrest in cancer cells, leading to apoptosis through inhibition of the depolymerization of microtubules. Although both paclitaxel and docetaxel possess potent antitumor activity, treatment with these drugs often results in a number of undesirable side effects, as well as multidrug resistance (MDR). Therefore, it has become essential to develop new anticancer agents with superior pharmacological properties, improved activity against various classes of tumors, and fewer side effects. This paper describes an account of our research on the chemistry of paclitaxel and taxoid anticancer agents at the biomedical interface, including:

The structure‐activity relationship (SAR) study of taxoids leading to the development of the “second‐generation” taxoids, which possess exceptional activity against drug‐resistant cancer cells expressing the MDR phenotype.

Development of fluorinated taxoids to study the bioactive conformation of paclitaxel and photoaffinity labeling taxoids for mapping of the drug‐binding domain on both microtubules and P‐glycoprotein.

The synthesis of novel macrocyclic taxoids for the investigation into the common pharmacophore for microtubule stabilizing anticancer agents.

© 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:195–211, 2001
Learning science through technological design
Authors: Roth Wolff‐Michael
Published: August 2002

In the course of a decade of research on learning in technology‐centered classrooms, my research group has gained considerable understanding of why and how students learn science by designing technology. In this article I briefly review two dimensions in which science and technology share fundamental similarities: (a) the production and transformation of representations and (b∥ the action‐oriented language describing the two domains. Because it is fundamentally problematic to derive whatoughtto happen in science classrooms from other dimensions, I provide three episodes to illustrate what and how students know and learn science during technological design activities. Episodes and analyses embody the two dimensions previously outlined. Because these episodes are representative of the database established during an extensive research program, I suggest there is sufficient ground for using and investigating science‐through‐technology curricula. © 2001 John Wiley & Sons, Inc. J Res Sci Teach 38: 768–790, 2001
Urban school leadership for elementary science instruction: Identifying and activating resources in an undervalued school subject
Authors: Spillane James P. , Diamond John B. , Walker Lisa J. , Halverson Rich , Jita Loyiso
Published: August 2002

This article explores school leadership for elementary school science teaching in an urban setting. We examine how school leaders bring resources together to enhance science instruction when there appear to be relatively few resources available for it. From our study of 13 Chicago elementary (K–8) schools' efforts to lead instructional change in mathematics, language arts, and science education, we show how resources for leading instruction are unequally distributed across subject areas. We also explore how over time leaders in one school successfullyidentifiedandactivatedresources for leading change in science education. The result has been a steady, although not always certain, development of science as an instructional area in the school. We argue that leading change in science education involves the identification and activation of material resources, the development of teachers' and school leaders' human capital, and the development and use of social capital. © 2001 John Wiley & Sons, Inc. J Res Sci Teach 38: 918–940, 2001
Teratogen update: Lyme disease
Authors: Elliott Daniel J. , Eppes Stephen C. , Klein Joel D.
Published: August 2002

We reviewed the world literature concerning the reproductive effects of Lyme disease (LD).Borrelia burgdorferi, which is the etiology of LD, is a spirochete and, as such, may share the potential for causing fetal infection, which may occur in the setting of maternal spirochetemia. Information concerning the effects of gestational LD derives from case reports and series, epidemiologic studies, and experimental animal models. Although provocative, these studies fail to define a characteristic teratogenic effect. However, skin and cardiac involvement have predominated in some reports. Pregnancy wastage has been suggested primarily by animal studies. Gestational LD appears to be associated with a low risk of adverse pregnancy outcome, particularly with appropriated antibiotic therapy. Suggestions for management of clinical situations are presented. Teratology 64:276–281, 2001. © 2001 Wiley‐Liss, Inc.
Interpreting the Numbers: Using a Narrative to Help Others Read Student Evaluations of Your Teaching Accurately
Authors: Franklin Jennifer
Published: August 2002

People who use and interpret the numbers provided by student ratings need to know what the numbers mean and how to use them correctly.
A match moving technique for merging CG cloth and human movie sequences
Authors: Hoshino Jun'ichi , Yamamoto Masanobu , Saito Hirofumi
Published: August 2002

Merging computer‐generated objects onto a human video sequence is an important technique for many applications such as augmented reality and special effects in movies. In this paper, we propose a new method for merging virtual objects onto the human video sequence. First, we track the current 3D pose of the human body by using spatio‐temporal analysis. Then we generate CG objects and merge them with the human body in video. In this paper, we demonstrate examples of merging virtual cloth with the video‐captured images. Copyright © 2001 John Wiley & Sons, Ltd.
A 3D parametric tongue model for animated speech
Authors: King Scott A. , Parent Richard E.
Published: August 2002

We present a tongue model for use in computer‐animated speech. The model is capable of representing tongue shapes during the production of English vowels and consonants as well as general motion of the tongue. Geometrically, the model is composed of a B‐spline surface with 60 control points and an 8×13 grid of bi‐cubic patches. We also present a parameterization of the model that requires only six parameters for use during speech production. This parameterization can also be used to define the deformation of other tongue models. Copyright © 2001 John Wiley & Sons, Ltd.
A grasp‐based motion planning algorithm for character animation
Authors: Kalisiak Maciej , van de Panne Michiel
Published: August 2002

The design of autonomous characters capable of planning their own motions continues to be a challenge for computer animation. We present a novel kinematic motion‐planning algorithm for character animation which addresses some of the outstanding problems. The problem domain for our algorithm is as follows: given a constrained environment with designated handholds and footholds, plan a motion through this space towards some desired goal. Our algorithm is based on a stochastic search procedure which is guided by a combination of geometric constraints, posture heuristics, and distance‐to‐goal metrics. The method provides a single framework for the use of multiple modes of locomotion in planning motions through these constrained, unstructured environments. We illustrate our results with demonstrations of a human character using walking, swinging, climbing, and crawling in order to navigate through various obstacle courses. Copyright © 2001 John Wiley & Sons, Ltd.
Function‐based flow modeling and animation
Authors: Akleman Ergun , Melek Zeki , Haberl Jeff S.
Published: August 2002

This paper summarizes a function‐based approach to model and animate 2D and 3D flows. We use periodic functions to create cyclical animations that represent 2D and 3D flows. These periodic functions are constructed with an extremely simple algorithm from a set of oriented lines. The speed and orientation of the flow are described directly by the orientation and the lengths of these oriented lines. The resulting cyclical animations are then obtained by sampling the constructed periodic functions. Our approach is independent of dimension, i.e. for 2D and 3D flow the same types of periodic functions are used. Rendering images for 2D and 3D flows is slightly different. In 2D function values directly are mapped to color values. On the other hand, in 3D function values are first mapped to color and opacity and then the volume is rendered by our volume renderer. Modeled and animated flows are used to improve the visualization of operations of rolling piston and rotary vane compressors. Copyright © 2001 John Wiley & Sons, Ltd.
Adaptation techniques for ubiquitous Internet multimedia
Authors: Margaritidis Margaritis , Polyzos George C.
Published: August 2002

We identify the importance of adaptation for the ubiquitous access to Internet multimedia content. The variety of media types combined with the diversity of Internet connection characteristics raises momentous challenges to the achievement of this goal. With adaptation, the characteristics of various media can be adjusted to better match those of the network path and the end device. As a result, adaptive streams enjoy superior robustness and provide substantially better presentation quality than traditional, non‐adaptive ones, especially in variable, capacity‐limited environments.

We examine several important factors that influence the design and optimization of the adaptation architecture. First, the location of the adaptation mechanism on the end‐to‐end path must be chosen. Second, the adaptation policy, i.e., the agility in adapting to variations in network path performance, must be specified. Third, the adaptation mechanism needs to be aware of the value of the perceptual quality that the different representations of each medium and the necessary resources to sustain it. Finally, we emphasize the role of supporting mechanisms in enhancing the adaptation process, namely, prioritization, admission control and hand‐off notifications.

Based on the aforementioned criteria, we classify existing research approaches and present some of them as case studies. We also describe current commercial solutions and, finally, we discuss future trends in application adaptation in conjunction with recent developments towards wireless access to the Internet. Copyright © 2001 John Wiley & Sons, Ltd.
Supporting multicasting in mobile ad‐hoc wireless networks: issues, challenges, and current protocols
Authors: Papavassiliou Symeon , An Beongku
Published: August 2002

The basic philosophy of personal communication services is to provide user‐to‐user, location independent communication services. The emerging group communication wireless applications, such as multipoint data dissemination and multiparty conferencing tools have made the design and development of efficient multicast techniques in mobile ad‐hoc networking environments a necessity and not just a desire. Multicast protocols in mobile ad‐hoc networks have been an area of active research for the past couple of years. This paper summarizes the activities and recent advances in this work‐in‐progress area by identifying the main issues and challenges that multicast protocols are facing in mobile ad‐hoc networking environments, and by surveying several existing multicasting protocols. This article presents a classification of the current multicast protocols, discusses the functionality of the individual existing protocols, and provides a qualitative comparison of their characteristics according to several distinct features and performance parameters. Furthermore, since many of the additional issues and constraints associated with the mobile ad‐hoc networks are due, to a large extent, to the attribute of user mobility, we also present an overview of research and development efforts in the area of group mobility modeling in mobile ad‐hoc networks. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of the WAP protocol over SMS in GSM networks
Authors: Andreadis Alessandro , Benelli Giuliano , Giambene Giovanni , Marzucchi Bernardo
Published: August 2002

This paper, based on the PALIO Project within the fifth Research Framework of the European Commission, deals with an information tourist service accessible through mobile phones by means of theWireless Application Protocol(WAP). We have considered aGlobal System for Mobile communications(GSM) network where the WAP traffic is transported by theShort Message Service(SMS) on a logical channel that also conveys signaling messages. Suitable models have been considered for both WAP browsing traffic and signaling traffic. We have proposed a theoretical approach to evaluate the mean delay to browse a WAP page taking into account the impact of the signaling load. Analytical predictions have been validated through comparisons with simulation results. Moreover, we have also considered a specificQuality of Service(QoS) requirement in terms of the maximum deck transmission delay that is guaranteed in 95 per cent of cases. Consequently, it has been possible to evaluate the number of WAP users that can be supported per cell. The study carried out in this paper permits to prove the feasibility for the envisaged mobile service based on WAP and it also allows dimensioning WAP pages so that each user experiences reasonable browsing delays. Copyright © 2001 John Wiley & Sons, Ltd.
Energy‐efficient wireless networking for multimedia applications
Authors: Havinga Paul J. M. , Smit Gerard J. M.
Published: August 2002

In this paper we identify the most prominent problems of wireless multimedia networking and present several state‐of‐the‐art solutions with a focus on energy efficiency. Three key problems in networked wireless multimedia systems are: (1) the need to maintain a minimum quality of service over time‐varying channels; (2) to operate with limited energy resources; and (3) to operate in a heterogeneous environment. We identify two main principles to solve these problems. The first principle is that energy efficiency should involve all layers of the system. Second, Quality of Service is an essential mechanism for mobile multimedia systems not only to give users an adequate level of service, but also as a tool to achieve an energy‐efficient system. Owing to the dynamic wireless environment, adaptability of the system will be a key issue in achieving this. Copyright © 2001 John Wiley & Sons, Ltd.
Non‐invasive treatments of luteinizing hormone‐releasing hormone for inducing spermiation in American (Bufo americanus) and Gulf Coast (Bufo valliceps) toads
Authors: Rowson Angela D. , Obringer Amy R. , Roth Terri L.
Published: August 2002

As many as 20% of all assessed amphibian species are threatened with extinction, and captive breeding programs are becoming important components of conservation strategies for this taxon. For some species, exogenous hormone administration has been integrated into breeding protocols to improve propagation. However, most treatments are administered by an intraperitoneal injection that can be associated with some risks. The general goal of this study was to identify a non‐invasive method of applying luteinizing hormone‐releasing hormone (LHRH), which reliably induces sperm release in toads. Specific objectives were to 1) test the spermiation response after topical application of different LHRH doses to the abdominal seat region, 2) evaluate the effects of adding the absorption enhancers dimethyl sulfoxide (DMSO), acetone, and glyceryl monocaprylate (GMC) to the LHRH, 3) assess the spermiation response after oral delivery of LHRH in a mealworm vehicle, and 4) compare sperm characteristics and spermiation responses to treatments in two different toad species. Male American (n= 9) and Gulf Coast (n= 7) toads were rotated systematically through a series of treatments. Urine was collected and evaluated for the presence of sperm at 0, 3, 7, 12, and 24 hours post‐treatment. There were no statistical differences in spermiation induction or sperm characteristics between American and Gulf Coast toads after the treatments. Oral administration of 100 μg LHRH was occasionally successful in inducing spermiation, but results appeared largely unreliable. Ventral dermal application of 100 or 10 μg LHRH in 40% DMSO were more effective (P< 0.05) at inducing spermiation compared with the other treatments tested, eliciting sperm release in more than 70% of toads tested. In breeding programs for rare and/or fragile anurans, these non‐invasive methods of exogenous hormone administration might be preferred over intraperitoneal injections. Zoo Biol 20:63–74, 2001. © 2001 Wiley‐Liss, Inc.
Winskel is (almost) Right: Towards a Mechanized Semantics Textbook
Authors: Nipkow Tobias
Published: August 2002

We present a formalization of the first 100 pages of Winskel's textbook The Formal Semantics of Programming Languages in the theorem prover Isabelle/HOL: 2 operational, 2 denotational, 2 axiomatic semantics, a verification condition generator, and the necessary soundness, completeness and equivalence proofs, all for a simple imperative programming language.
Formal Verification of a Railway Interlocking System using Model Checking
Authors: Cimatti A. , Giunchiglia F. , Mongardi G. , Romano D. , Torielli F. , Traverso P.
Published: August 2002

In this paper we describe an industrial application of formal methods. We have used model checking techniques to model and formally verify a rather complex software, i.e. part of the “safety logic” of a railway interlocking system. The formal model is structured to retain the reusability and scalability properties of the system being modelled. Part of it is defined once for all at a low cost, and re-used. The rest of the model can be mechanically generated from the designers' current specification language. The model checker is “hidden” to the user, it runs as a powerful debugger. Its performances are impressive: exhaustive analysis of quite complex configurations with respect to rather complex properties are run in the order of minutes. The main reason for this achievement is essentially a carefully designed model, which exploits all the behaviour evolution constraints. The re-usability/scalability of the model and the fact that formal verification is automatic and efficient are the key factors which open up the possibility of a real usage by designers at design time. We have thus assessed the possibility of introducing the novel technique in the development cycle with an advantageous costs/benefits relation.
Cases with Fewer than Four Parathyroid Glands in Patients withRenal Hyperparathyroidism at Initial Parathyroidectomy
Authors: Hibi Yatsuka , Tominaga Yoshihiro , Uchida Kazuharu , Takagi Hiroshi , Imai Tsuneo , Funahashi Hiroomi , Nakao Akimasa
Published: August 2002

In the surgical treatment of secondaryhyperparathyroidism (2HPT) due to uremia, it is considered necessary toremove all parathyroid glands from the neck to prevent persistent andrecurrent parathyroid hyperfunction. However, in some cases fewer thanfour parathyroid glands can be recognized at initial operation; in thepresent study, we evaluated the long‐term prognosis and estimatedsurgical strategy in such cases. Between March 1981 and January 1999,822 patients underwent total parathyroidectomy (PTx) with forearmautograft for advanced 2HPT at the Department of Transplant Surgery of Nagoya Second Red Cross Hospital. In 21 cases (2.6%) fewer than fourparathyroid glands were macroscopically found at the initial operation.These cases were followed up and their parathyroid function wasevaluated by measurement of intact parathyroid hormone (PTH). In 20 ofthe 21 cases three glands were found, in 1 patient only two glands. In5 of these cases the fourth gland was identified first afterpostoperative histopathologic evaluation. In all these cases the intactPTH level was normalized. In 8 of the remaining 16 cases high PTHlevels persisted after the initial operation, including 3 patients who underwent neck reexploration. However, in the other 7 patients PTHlevels dropped within normal range immediately after PTx and a fourthgland has never been recognized. One patient was lost to follow‐up. Thus, using our operative strategy, 12 of 822 cases (0.85%) did notdevelop persistent or recurrent HPT even though only three glands wereidentified at the operation. To avoid postoperative hypoparathyroidism,autotransplantation should be performed when fewer than four parathyroid glands are found at the initial operation.
Experimental Evaluation of a New Layered Prosthesis Exhibiting a Low Tensile Modulus of Elasticity: Long‐term Integration Response within the Rat Abdominal Wall
Authors: Ferrando José M. , Vidal José , Armengol Manuel , Gil Javier , Manero José M. , Huguet Pedro , Segarra Alfonso , Quiles María T. , Schwartz Simón , Arbós i Via María A.
Published: August 2002

The use of a new type of prosthesis, Bard Composix (BC), constructed of two layers of polypropylene mesh (PP) and one layer of expanded polytetrafluoroethylene (ePTFE), could provide a good solution for hernia repair when both minimal adhesions and maximum collagenous infiltration are necessary. We experimentally evaluated long‐term stability of this composite. In 15 Sprague‐Dawley rats, a full thickness defect was created in the anterior abdominal wall and repaired with BC. Studies were performed over implantation intervals of
2, 4, and 6 months in strips obtained from the prosthesis‐host tissue interfaces. Light microscopy, environmental scanning electron microscopy (ESEM), immunohistochemistry, and tensiometry were used.
Overall findings provide evidence that PP and ePTFE association renders the alloy well suited for hernia repair, promoting a robust and durable alloplast‐soft tissue union. At all points studied, the patch was well tolerated and meshes did not shrink, come loose, or migrate.
Neovascularization continued 6 months after implantation. Ex vivo mechanical characterization demonstrated that the primary advantage of the new device stems from a low modulus of elasticity, a property that can be exploited to enhance mechanical load transfer from prosthetic materials to the relatively frail surrounding tissues. After implantation, adequate tensile strength and a low modulus of elasticity were detected in the restored zone, conferring great adaptability to the abdominal wall. In conclusion, the BC layered prosthesis proved suitable for implantation in abdominal wall defects, exhibiting favorable biocompatibility and integration with minimal side effects.
Complications of Thyroid Surgery: How to Avoid Them, How to Manage Them, and Observations on Their Possible Effect on the Whole Patient
Authors: Reeve Tom , Thompson Norman W.
Published: August 2002

Surgery of the thyroid takes place in an area of complicated anatomy and in which a number of vital physiologic functions and special senses are controlled. Thyroidectomy rarely is associated with mortality; but unless the surgeon performing it is well trained in operative surgery and is knowledgeable of the gland and its function, pathology, and anatomy, excellent results cannot be achieved. Failure to observe cardinal surgical principles may result in legal difficulties, which can be avoided. It is well to observe the principles and avoid problems. We address this issue herein.
Experimental Study of the Effect of Nitric Oxide Inhibition on Mesenteric Blood Flow and Interleukin‐10 Levels with a Lipopolysaccharide Challenge
Authors: Baykal Ataç , Kavuklu Burak , Iskit Alper B. , Guc M. Oguz , Hascelik Gulsen , Sayek Iskender
Published: August 2002

The septic shock‐induced decrease in mesenteric blood flow and release of proinflammatory cytokines are among the major pathophysiologic changes presumed to lead to multiple organ dysfunction syndrome (MODS). Increased nitric oxide (NO) levels are associated with both decreased mesenteric blood flow and positive modulation of proinflammatory cytokine release. In this study we aimed to determine the effect of the timing of the inhibition of nitric oxide synthase (NOS) on mesenteric blood flow and serum interleukin‐10 (IL‐10) concentrations during endotoxin shock. A nonspecific NOS inhibitor NG‐nitro‐l‐arginine methyl ester (l‐NAME), a specific NOS inhibitor aminoguanidine (AG), or placebo were injected 20 minutes before or 20 minutes after a lipopolysaccharide (LPS) or placebo challenge to Swiss‐albino mice, as pretreatment or posttreatment, respectively. At 120 minutes after LPS or placebo injection the mesenteric blood flow was measured, and blood samples from the heart were obtained for IL‐10 levels in both groups. Pretreatment and posttreatment with both NOS inhibitors prevented the LPS‐induced decrease in mesenteric blood flow. Pretreatment was more effective for this purpose. Pretreatment accentuated the LPS‐induced increase in serum IL‐10 concentrations, whereas posttreatment had no significant effect. We conclude that the timing of NOS inhibition is important for attenuating some deleterious effects of endotoxin.