bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steering a course for risk assessment: The impact of new draft guidance, 21 CFR part 11, scope and application, on the electronic records; electronic signatures rule
Authors: Kuniholm George G. 
Published: July 2003

AbstractAs a result of some re‐organization in the US Food and Drug Administration (FDA) and the introduction of the CGMP risk‐based approach, 21 CFR Part 11 is being revisited. The FDA has decided to re‐evaluate Part 11 and during the re‐evaluation, the FDA issued guidance on how Part 11 will be interpreted. The proposed guidance defines the FDA's approach to the scope and application of Part 11. The draft guidance has substantial regulatory impact by withdrawing previous Part 11 draft guidance as well as the Compliance Policy Guide 71523.17.The scope of Part 11 is defined to be records required by predicate rules kept electronically in lieu of paper records or relied upon for regulated activities, as well as records submitted to the agency, and electronic signatures. Emphasis is given to following predicate rule requirements.In applying Part 11, the FDA will exercise enforcement discretion in the areas of audit trail requirements, validation, copying electronic records, electronic record maintenance, and legacy systems. Emphasis is given to creating and following documented Risk Assessment practice.This article examines the change in FDA focus and highlights key points in the draft guidance. Further, this article provides practical advice for industry, provides an overview on comments (industry feedback) submitted to the Agency on the guidance, and provides an interpretation of the likely direction for future Part 11 regulation. Copyright © 2003 John Wiley & Sons, Ltd.
What's New?
Authors: Bohaychuk Wendy , Broughton Steve 
Published: July 2003

AbstractThe What's New? section in the Quality Assurance Journal aims to draw attention to items of importance to QA professionals. There is usually a three‐month interval between final submission of manuscripts and distribution of the journal. For this issue, the entries in the What's New? Section arise from the period of 01 March 2003 to 31 May 2003. If you feel that there is any other new information that should be brought to the attention of readers, please let us know by e‐mailing wbohaychuk@aol.com Copyright © 2003 John Wiley & Sons, Ltd.
Dynamics of TCP over BoD satellite networks
Authors: Sooriyabandara Mahesh , Fairhurst Gorry 
Published: July 2003

AbstractBandwidth‐on‐Demand (BoD) mechanisms are used by most next generation satellite systems to efficiently share a limited radio spectrum among a large number of users. BoD design needs to consider a range of engineering issues: the anticipated number of users, interactions with other subsystems, and the contradictory design goals of optimising system utilization and delay/capacity offered to the network traffic. A BoD system may provide a range of quality of service classes to support different user classes and allow optimisation of allocation efficiency. Each class may have different delay and delay variation characteristics. The performance achieved by a TCP flow using such a BoD satellite network is highly dependent on the delay and the variation of the delay experienced by TCP. This paper describes the BoD mechanisms, and their expected impact on TCP behaviour. This discussion is supplemented by simulation results using an implementation of TCP combined with a model of some simple satellite BoD access schemes to characterize the performance and efficiency of BoD algorithms. Copyright © 2003 John Wiley & Sons, Ltd.
QoS‐oriented traffic management in multimedia satellite systems
Authors: Courville Nicolas 
Published: July 2003

AbstractThe next generation of satellite systems will likely use some on‐board switching techniques enabling the direct transmission of data from any up‐link spot‐beam to any down‐link spot‐beam. If the switch used in the payload of the system is an ATM‐based shared buffer switch, some losses and delays can occur. Fortunately, these drawbacks can be fought thanks to some buffer management policies (HSPO, SMXQ, EPD) that either ensure low delay or low loss ratio.Real‐time (voice or MPEG video streams) and non‐real‐time applications (file transfer, email, web browsing using TCP/IP protocols) should be carried over these satellite systems with different quality of service (QoS) requirements. Different combinations of buffer management policies are presented to guaranty the QoS required by the user. Especially, special emphasis is put on the way to transmit efficiently layer 3 messages (IP datagrams) within a mix of traffic in order to avoid some high layer retransmission techniques (provided in TCP for instance) wasting both time and bandwidth. Copyright © 2003 John Wiley & Sons, Ltd.
A gateway architecture for IP satellite networks with dynamic resource management and DiffServ QoS provision
Authors: Ronga L. S. , Pecorella T. , Del Re E. , Fantacci R. 
Published: July 2003

AbstractIP satellite networks are gaining a considerable interest mainly due to their ability to deliver high bandwidth services to nation‐wide areas. However some difficulties still exist to implement IP‐based transport mechanisms on geostationary satellite networks (i.e. TCP‐based protocols are affected by the large delay‐bandwidth product). The satellite network architecture presented in this paper is designed to provide a complete QoS support for IP traffic based on the DS paradigm, while minimizing the waste of the valuable satellite resource. The proposed technique operates on two time scales: a short‐term reaction compensates fast traffic variations by an appropriate scheduling while a medium term resource allocation mechanism reduces the wasted bandwidth. Copyright © 2003 John Wiley & Sons, Ltd.
An IP‐based satellite communication system architecture for interactive multimedia services
Authors: Iuoras Nicolae , Le‐Ngoc Tho , Ashour Mohamed , Elshabrawy Tallal 
Published: July 2003

AbstractThe paper presents an IP‐based broadband satellite access (BSA) network architecture for interactive multimedia services with an emphasis on the return link (upstream direction). Dynamic capacity allocation (DCA) strategies based on the Combined Free and Demand Assignment Multiple Access (CFDAMA) scheme to support the Digital Video Broadcasting‐Return Channel via Satellite (DVB‐RCS) standard and Differentiated Services (DiffServ) architecture in order to achieve short delay and different QoS requirements are proposed. DCA scheduling algorithms and multiple‐queue user terminal structures are presented. Simulation results on the traffic performance for various traffic loads, types and conditions confirm the effectiveness of the proposed structures. Copyright © 2003 John Wiley & Sons, Ltd.
A predictive demand assignment multiple access protocol for Internet access over broadband satellite networks
Authors: Jiang Zhifeng , C. M. Leung Victor 
Published: July 2003

AbstractMedium access control (MAC) protocol is responsible for wireless resource management, which is crucial to satellite communication. To enhance the performance of broadband satellite networks, the application characteristics should be considered in the design of the MAC protocol. With the rapid expansion of Internet applications and the attractiveness of high speed Internet access via broadband satellite networks, it becomes an attractive objective to take into account the self‐similar nature of Internet traffic in MAC protocol designs. This paper presents a novel predictive demand assignment multiple access (PRDAMA) protocol for packet communications over broadband satellite networks. PRDAMA allocates free bandwidth resources by estimating the positive varying trend of the Internet traffic to facilitate prediction of the bandwidth requirements of the earth stations. Simulation results demonstrate that PRDAMA achieves a lower average delay and delay jitter compared with other DAMA protocols under highly bursty traffic due to its accurate traffic trend prediction. With less bursty traffic, PRDAMA still performs better than the other DAMA protocols under a heavy traffic load. Copyright © 2003 John Wiley & Sons, Ltd.
Static and dynamic resource allocation in a multiservice satellite network with fading
Authors: Celandroni Nedo , Davoli Franco , Ferro Erina 
Published: July 2003

AbstractA control architecture for resource allocation in satellite networks is proposed, along with the specification of performance indexes and control strategies. The latter, besides being based on information on traffic statistics and network status, rely upon some knowledge of the fading conditions over the satellite network channels. The resource allocation problem consists of the assignment, by a master station, of a total available bandwidth among traffic earth stations in the presence of different traffic types. Traffic stations are assumed to measure continuously their signal fade level, but this information may either be used only locally or also communicated to the master station. According to the information made available on‐line to the master station on the level of the fading attenuation of the traffic stations, the assignment can be made static, based on the a priori knowledge of long‐term fading statistics, or dynamic, based on the updated measurements. In any case, the decisions can be adapted to slowly time‐varying traffic characteristics. At each earth station, two basic traffic types are assumed to be present, namely guaranteed bandwidth, real time, synchronous data (stream traffic) and best‐effort traffic (datagram traffic). Numerical results are provided for a specific architecture in the dynamic case, in a real environment, based on the Italsat satellite national coverage payload characteristics. Copyright © 2003 John Wiley & Sons, Ltd.
Networking issues in IP multicast over satellite
Authors: Sun Z. , Howarth M.P. , Cruickshank H. , Iyengar S. , Claverotte L. 
Published: July 2003

AbstractThis paper describes the issues that arise when using satellites for IP multicast, with the emphasis on multicast protocols and how their implementation depends on the satellite communications platform. Various link layer standards such as DVB‐S, DVB‐RCS and ATM can be used in satellites with on‐board processing, and applied to meet user and network requirements for IP multicast. The paper provides an overview of the networking issues and their interactions. Specifically, we show how multicast networking protocols have to be modified to take into account the satellite link characteristics: these protocols include IGMP, multicast routing protocols and reliable multicast protocols. We also discuss how security systems support IP multicast. Copyright © 2003 John Wiley & Sons, Ltd.
Quality of service for satellite IP networks: a survey
Authors: Kota Sastri , Marchese Mario 
Published: July 2003

AbstractThe future media rich applications such as media streaming, content delivery distribution and broadband access require a network infrastructure that offers greater bandwidth and service level guarantees. As the demand for new applications increases, ‘best effort’ service is inadequate and results in lack of user satisfaction. End‐to‐end quality of service (QoS) requires the functional co‐operation of all network layers. To meet future application requirements, satellite is an excellent candidate due to features such as global coverage, bandwidth flexibility, broadcast, multicast and reliability. At each layer, the user performance requirements should be achieved by implementation of efficient bandwidth allocation algorithms and satellite link impairment mitigation techniques.In this paper, a QoS framework for satellite IP networks including requirements, objectives and mechanisms are described. To fully understand end‐to‐end QoS at each layer, QoS parameters and the current research are surveyed. For example at physical layer (modulation, adaptive coding), link layer (bandwidth allocation), network layer (IntServ/DiffServ, MPLS traffic engineering), transport layer (TCP enhancements, and alternative transport protocols) and security issues are discussed. Some planned system examples, QoS simulations and experimental results are provided. The paper also includes the current status of the standardization of satellite IP by ETSI, ITU and IETF organizations. Copyright © 2003 John Wiley & Sons, Ltd.
Present possibilities of thin‐layer analysis by GDOES
Authors: Hoffmann Volker , Dorka Roland , Wilken Ludger , Hodoroaba Vasile‐Dan , Wetzig Klaus 
Published: August 2003

AbstractThe analysis of thin layers of thickness ∼100 nm has become a new field of application for glow discharge optical emission spectroscopy (GDOES). In this paper an overview is given of the experiences and possibilities gained by the authors in later years at their research, development and application of GDOES.During GDOES analysis of a multilayer system the depth resolution was determined using the inverse maximal slope method. Under optimized discharge conditions a depth resolution of ∼25 nm at 100 nm depth was achieved. The gas flow in a Grimm‐type source for glow discharge mass spectrometry (GDMS) was simulated and a correlation between calculated pressure and crater shape was found. Cleanness of the sample and source turned out to be essential for a fast stabilization time and reduction of the influence of light elements and molecules. Thereby, a 10 nm layer at the top surface of a sample could be quantified. Apart from the influence of density, the reflectivity of the sample surface is discussed. It is shown that a high sample reflectivity can cause up to 100% more light to be measured by the spectrometer. Copyright © 2003 John Wiley & Sons, Ltd.
Secondary electron emission coefficients of standard samples for GDOES
Authors: Guillot Ph. , Belenguer Ph. , Therese L. , Lavoine V. , Chollet H. 
Published: August 2003

AbstractThe purpose of this work is to determine Paschen curves for standard samples used for calibration in glow discharge optical emission spectroscopy. The experimental set‐up is described for measuring the breakdown voltage of a material–gas couple. This voltage corresponds to the Townsend regime of the discharge. Several materials (copper, nickel, iron and titanium) have been studied in the presence of argon and the results are presented here. From this preliminary work, effective secondary emission coefficients have been calculated versus the reduced electric field for each standard sample. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of anodic films on Nb and NbNx by glow discharge optical emission spectroscopy
Authors: Habazaki H. , Matsuo T. , Konno H. , Shimizu K. , Matsumoto K. , Takayama K. , Oda Y. , Skeldon P. , Thompson G. E. 
Published: August 2003

AbstractSputter‐deposited niobium layers containing nitrogen form anodic films with resultant capacitance and leakage current density little influenced by annealing up to 523 K. The nitrogen species incorporated into the anodic oxide films at the alloy/film interface are distributed in the inner 70–75% of the film thickness, with fine bubbles containing high‐pressure N2O gas being evident. Glow discharge optical emission spectroscopy (GDOES) analysis reveals their continued presence after annealing at 523 K. The insignificant changes in GDOES depth profiles also suggest that the formation of low‐valent oxide at the metal/film interface as a result of annealing is not responsible for the behaviour. For thermal treatments above 400 K, capacitances and leakage currents increase significantly for niobium, with nitrogen additions diminishing the effects. Such behaviour is suggested to arise from suppression of mechanical damage to films through the presence of highly pressurized gas in the inner part of the films. Copyright © 2003 John Wiley & Sons, Ltd.
Adjusting power for a baseline covariate in linear models
Authors: Glueck Deborah H. , Muller Keith E. 
Published: July 2003

AbstractThe analysis of covariance provides a common approach to adjusting for a baseline covariate in medical research. With Gaussian errors, adding random covariates does not change either the theory or the computations of general linear model data analysis. However, adding random covariates does change the theory and computation of power analysis. Many data analysts fail to fully account for this complication in planning a study. We present our results in five parts. (i) A review of published results helps document the importance of the problem and the limitations of available methods. (ii) A taxonomy for general linear multivariate models and hypotheses allows identifying a particular problem. (iii) We describe how random covariates introduce the need to consider quantiles and conditional values of power. (iv) We provide new exact and approximate methods for power analysis of a range of multivariate models with a Gaussian baseline covariate, for both small and large samples. The new results apply to the Hotelling–Lawley test and the four tests in the “univariate” approach to repeated measures (unadjusted, Huynh‐Feldt, Geisser‐Greenhouse, Box). The techniques allow rapid calculation and an interactive, graphical approach to sample size choice. (v) Calculating power for a clinical trial of a treatment for increasing bone density illustrates the new methods. We particularly recommend using quantile power with a new Satterthwaite‐style approximation. Copyright © 2003 John Wiley & Sons, Ltd.
Error in timing in regression with observed longitudinal measurements
Authors: Wang C. Y. , Huang Yijian 
Published: July 2003

AbstractWe consider regression analysis of a disease outcome in relation to longitudinal data which are observations from a random effects model. The covariate variables of interest are the values of the underlying trajectory at some time points, which may be fixed or subject‐specific. Because the underlying random coefficients are unknown, the covariates to the primary model are generally unobserved. In addition, measurements are often not observed at the time points of interest. A motivating example to our model is the effects of age at adiposity rebound and the associated body mass index on the risk of adult obesity. The adiposity rebound is a time point at which the trajectory of a child's body fatness declines to a minimum. This general error in timing problem may be applied to an analysis when time‐dependent marker variables follow a polynomial model in which the effect of a local maximum or minimum point may be of interest. It can be seen that directly applying estimated covariates, possibly obtained from estimated time points, may lead to bias. Estimation procedures based on expected estimating equations, regression calibration and simulation extrapolation are applied to this problem. Copyright © 2003 John Wiley & Sons, Ltd.
Estimation of k for the poly‐k test with application to animal carcinogenicity studies
Authors: Moon Hojin , Ahn Hongshik , Kodell Ralph L. , Lee J. Jack 
Published: July 2003

AbstractThis paper extends the survival‐adjusted Cochran–Armitage test in order to achieve improved robustness to a variety of tumour onset distributions. The Cochran–Armitage test is routinely applied for detecting a linear trend in the incidence of a tumour of interest across dose groups. To improve the robustness to the effects of differential mortality across groups, Bailer and Portier introduced the poly‐3 test by a survival adjustment using a fractional weighting scheme for subjects not at full risk of tumour development. The performance of the poly‐3 test depends on how closely it represents the correct specification of the time‐at‐risk weight in the data. Bailer and Portier further suggested that this test can be improved by using a general k reflecting the shape of the tumour onset distribution. In this paper, we propose a method to estimate k by equating the empirical lifetime tumour incidence rate obtained from the data based on the fractional weighting scheme to a separately estimated cumulative lifetime tumour incidence rate. This poly‐k test with the statistically estimated k appears to perform better than the poly‐3 test which is conducted without prior knowledge of the tumour onset distribution. Our simulation shows that the proposed method improves the robustness to various tumour onset distributions in addition to the robustness to the effects of mortality achieved by the poly‐3 test. Large sample properties are shown via simulations to illustrate the consistency of the proposed method. The proposed methods are applied to analyse two real data sets. One is to find a dose‐related linear trend on animal carcinogenicity, and the other is to test an effect of calorie restriction on experimental animals. Copyright © 2003 John Wiley & Sons, Ltd.
Characterizing classes of antiretroviral drugs by genotype
Authors: Foulkes A. S. , DeGruttola V. 
Published: July 2003

AbstractThis paper develops methods for using HIV‐1 genotypic information to group patients who are expected to have similar patterns of sensitivity or resistance to two or more drugs. The methods presented are an extension of prediction based classification to handle multiple drug responses. Here, the goal is to determine the probability that one antiretroviral therapy will be more favourable than another for an individual given the specific genotypic or other characteristics of the infecting viral population. This approach requires a model relating genotype to a vector of drug specific phenotypic responses. A comparison of Nelfinavir and Indinavir is provided using 2746 protease sequences and corresponding in vitro sensitivity assays provided to us by the Virco Group. Copyright © 2003 John Wiley & Sons, Ltd.
Use of max and min scores for trend tests for association when the genetic model is unknown
Authors: Zheng Gang 
Published: July 2003

AbstractIn case‐control studies, the Cochran–Armitage (CA) trend test is powerful for detection of an association between a risk allele and a marker. To apply this test, a score should be assigned to the genotypes based on the genetic model. When the underlying genetic model is unknown, the trend test statistic is a function of the score. In this paper, simple procedures are given to obtain two scores (max and min), which respectively maximize and minimize the CA trend test statistics for genetic associations. These two scores can be used to examine the effect of the choice of scores on the test of no association. When the CA trend test statistic with the max (or min) score is less (or greater) than a prespecified value, the conclusion is clear: we will accept (or reject) the null hypothesis of no association for any scores used. When this value is less than the CA trend test statistic with the max score but greater than the one with the min score, the decision of whether or not to reject the null hypothesis depends on the choice of scores. In this situation, the CA trend test with a prespecified score cannot be used without careful scientific justification of the choice of scores. The use of max and min scoring schemes is applied to a real data set. Published in 2003 by John Wiley & Sons, Ltd.