bluuebunny/crossref_metadata_2025 huggingface dataset:
Polio eradication: the OPV paradox
Authors: Dowdle Walter R. , De Gourville Esther , Kew Olen M. , Pallansch Mark A. , Wood David J.
Published: August 2003

Routine and mass administration of oral polio vaccine (OPV) since 1961 has prevented many millions of cases of paralytic poliomyelitis. The public health value of this inexpensive and easily administered product has been extraordinary. Progress of the Global Polio Eradication Initiative has further defined the value of OPV as well as its risk through vaccine‐associated paralytic poliomyelitis (VAPP) and vaccine‐derived polioviruses (VDPV). Although both are rare, once wild poliovirus transmission has been interrupted by OPV, the only poliomyelitis due to poliovirus will be caused by OPV. Poliovirus will be eradicated only when OPV use is discontinued. This paradox provides a major incentive for eventually stopping polio immunization or replacing OPV, but it also introduces complexity into the process of identifying safe and scientifically sound strategies for doing so. The core post eradication immunization issues include the risk/benefits of continued OPV use, the extent of OPV replacement with IPV, possible strategies for discontinuing OPV, and the potential for development and licensure of a safe and effective replacement for OPV. Formulation of an informed post eradication immunization policy requires careful evaluation of polio epidemiology, surveillance capability, vaccine availability, laboratory containment, and the risks posed by the very tool responsible for successful interruption of wild poliovirus transmission. Copyright © 2003 John Wiley & Sons, Ltd.
Protein kinases conserved in herpesviruses potentially share a function mimicking the cellular protein kinase cdc2
Authors: Kawaguchi Yasushi , Kato Kentaro
Published: August 2003

Herpesviruses encode protein kinases. A subset of these proteins, represented by HSV‐1 UL13, are conserved throughout all members of the Herpesviridae, and here, are designated CHPKs (conserved herpesvirus protein kinases). In addition to conserved gene products like CHPKs, herpesviruses encode genes specific to respective herpesviruses. When acting upon conserved viral gene products or cellular factors, CHPKs may play conserved roles in the life cycles of herpesviruses. CHPKs may also express unique functions within the infectious process of individual herpesviruses when specific viral gene products are targeted. CHPKs demonstrate specific activity in multiple herpesvirus infections, functioning in the regulation of viral gene expression in HSV‐1, tissue tropism in VZV, and viral DNA synthesis, encapsidation and egress from the nucleus in HCMV. The HCMV CHPK, however, can partially substitute for the HSV‐1 CHPK. Representative CHPKs from all Herpesviridae subfamilies can also facilitate the hyperphosphorylation of the cellular translation factor, EF‐1δ. This indicates that CHPKs have conserved functions. Recent data have shown that both CHPKs and a cellular protein kinase, cdc2, phosphorylate the same amino acid residues of target proteins. Thus, CHPKs may mimic cdc2 function in infected cells. Copyright © 2003 John Wiley & Sons, Ltd.
Xenotransplantation and pig endogenous retroviruses
Authors: Magre Saema , Takeuchi Yasuhiro , Bartosch Birke
Published: August 2003

Xenotransplantation, in particular transplantation of pig cells, tissues and organs into human patients, may alleviate the current shortage of suitable allografts available for human transplantation. This overview addresses the physiological, immunological and virological factors considered with regard to xenotransplantation. Among the issues reviewed are the merits of using pigs as xenograft source species, the compatibility of pig and human organ physiology and the immunological hindrances with regard to the various types of rejection and attempts at abrogating rejection. Advances in the prevention of pig organ rejection by creating genetically modified pigs that are more suited to the human microenvironment are also discussed. Finally, with regard to virology, possible zoonotic infections emanating from pigs are reviewed, with special emphasis on the pig endogenous retrovirus (PERV). An in depth account of PERV studies, comprising their discovery as well as recent knowledge of the virus, is given. To date, all retrospective studies on patients with pig xenografts have shown no evidence of PERV transmission, however, many factors make us interpret these results with caution. Although the lack of PERV infection in xenograft recipients up to now is encouraging, more basic research and controlled animal studies that mimic the pig to human xenotransplantation setting more closely are required for safety assessment. Copyright © 2003 John Wiley & Sons, Ltd.
Refined discretized Lyapunov functional method for systems with multiple delays
Authors: Gu Keqin
Published: August 2003

The previously proposed discretized Lyapunov functional method for systems with multiple delay is refined using variable elimination and Jensen inequality. The resulting new stability criterion is simpler. Numerical examples indicate that the new method is much less conservative for a given discretization mesh. Copyright © 2003 John Wiley & Sons, Ltd.
Nonlinear controls for a class of discrete‐time bilinear systems
Authors: Chen Min‐Shin , Hwang Yean‐Ren , Huang Kun‐Chi
Published: August 2003

For a discrete‐time neutrally stable bilinear system, a nonlinear state feedback control based on the passivity design has been proposed to stabilize the system globally and asymptotically. This paper shows that the decay rate resulting from the passivity control is not exponential, and the system's response speed becomes very sluggish asymptotically. A ‘normalized’ nonlinear control is therefore proposed to achieve exponential stability. The new exponentially stabilizing control not only improves the system's response speed, but also enhances the system's robustness against small parametric perturbations. Copyright © 2003 John Wiley & Sons, Ltd.
Dynamic force/torque balance of 2D polygonal objects by a pair of rolling contacts and sensory‐motor coordination
Authors: Arimoto S. , Yoshida M. , Bae J.‐H. , Tahara K.
Published: August 2003

It is well known that three frictionless fingers suffice to immobilize any 2D object with triangular shape but four fingers are necessary for a parallelepiped. However, it has been recently shown that only two fingers are enough to realize secure grasp of a rigid object with parallel flat surfaces in a dynamic sense if finger ends have a hemispherical shape with appropriate radius and thereby rollings are induced between finger ends and object surfaces. This paper focuses on the two problems: (1) dynamic force/torque balance of 2D polygonal objects under the effect of gravity force by means of a pair of rolling contacts and (2) concurrent realization of dynamically secure grasp and orientation control of 2D polygonal objects by using a pair of multi‐fingered hands with hemispherical ends and sensory feedback signals without knowing object kinematics and mass center. It is shown that the force/torque balance can be attained by controlling both the contact positions and inducing adequate forces in both normal and tangential directions at each of contact points indirectly through finger joints without knowing object mass center and other kinematic parameters. © 2003 Wiley Periodicals, Inc.
Designing and optimization of parameters of delta‐4 parallel manipulator for a given workspace
Authors: Kosinska A. , Galicki M. , Kedzior K.
Published: August 2003

In the paper, the algorithm of designing some geometrical parameters of a Delta parallel manipulator has been described. The manipulator is to work in a specified workspace, which is given as a set of points. The first step of the algorithm seeks the possible solutions, and because there are an infinite number of them, the objective of the second step is to limit the number by an optimization. Owing to this, it is possible to find parameters of the manipulator, whose workspace contains the specified points. © 2003 Wiley Periodicals, Inc.
Design issues of mobile haptic interfaces
Authors: Nitzsche Norbert , Hanebeck Uwe D. , Schmidt G.
Published: August 2003

As a novel approach to force‐reflecting telepresence, the concept ofmobile haptic interfaces(MHI) is presented. An MHIactivelyfollows the locomotion of an operator, who is no longer bound to be stationary during teleoperation. Thus, operator locomotion can be used as an input for locomotion control of a real teleoperator or control of locomotion in a virtual environment while keeping the advantage of force‐reflection. The article focuses on basic design issues and presents a prototype MHI for haptic exploration of extended virtual environments. © 2003 Wiley Periodicals, Inc.
Case study: robotic person following using fuzzy control and image segmentation
Authors: Tarokh M. , Ferrari P.
Published: August 2003

The paper proposes a scheme for amobile robot to follow a person in reasonably complex dynamic environments. The scheme consists of an image processing technique for person identification, and a fuzzy controller for following the person. The identification process utilizes image color, shape characteristics, and a region growing technique. The fuzzy logic controller receives image data such as the mass, center of mass, and their rates of change to produce steering and speed commands for the robot. A behavior control strategy is also incorporated to cope with several situations, such as hazard, that are not accounted for in the fuzzy controller. Descriptions of the software/hardware as well as experimental setup and results are provided to demonstrate the feasibility of the scheme. © 2003 Wiley Periodicals, Inc.
Design and construction of continuous alternate wheels for an omnidirectional mobile robot
Authors: Byun Kyung‐Seok , Song Jae‐Bok
Published: August 2003

Many types of omnidirectional wheels with passive rollers have gaps between rollers. Since these gaps cause a wheel to make discontinuous contact with the ground, they lead to vertical and/or horizontal vibrations during wheel operation. In addition, the radii of passive rollers are related to the height of a bump an omnidirectional wheel can surmount. In this research a new design of the alternate wheel is proposed. Because this wheel makes continuous contact with the ground and has alternating large and small rollers around the wheel, it is termed a continuous alternate wheel (CAW). In this paper a design procedure is also presented to determine the optimum number of rollers, the radii of rollers and the inside inclination angle of an outer roller for given design specifications. The CAW based on this design is compared to the existing alternate wheels in terms of design. Finally, an actual continuous alternate wheel is constructed to verify validity of the design guidelines. © 2003 Wiley Periodicals, Inc.
Regularity properties for triple systems
Authors: Nagle Brendan , Rödl Vojtěch
Published: August 2003

Szemerédi's Regularity Lemma proved to be a powerful tool in the area of extremal graph theory J. Komlós and M. Simonovits, Szemerédi's Regularity Lemma and its applications in graph theory, Combinatorics 2 (1996), 295–352. Many of its applications are based on the following technical fact: If G is a k‐partite graph with V(G) = ∪Vi, |Vi| = n for all i ∈ [k], and all pairs {Vi, Vj}, 1 ≤ i < j ≤ k, are ϵ‐regular of density d, then G contains dnk(1 + f(ϵ)) cliques K, where f(ϵ) → 0 as ϵ → 0. The aim of this paper is to establish the analogous statement for 3‐uniform hypergraphs. Our result, to which we refer as The Counting Lemma, together with Theorem 3.5 of P. Frankl and V. Rödl [Extremal problems on set systems, Random Structures Algorithms 20(2) (2002), 131–164, a Regularity Lemma for Hypergraphs, can be applied in various situations as Szemerédi's Regularity Lemma is for graphs. Some of these applications are discussed in previous papers, as well as in upcoming papers, of the authors and others. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 23: 264–332, 2003
On the noise sensitivity of monotone functions
Authors: Mossel Elchanan , O'Donnell Ryan
Published: August 2003

It is known that for all monotone functions f : {0, 1}n → {0, 1}, if x ∈ {0, 1}n is chosen uniformly at random and y is obtained from x by flipping each of the bits of x independently with probability ϵ = n−α, then P[f(x) ≠ f(y)] < cn−α+1/2, for some c > 0.

Previously, the best construction of monotone functions satisfying P[fn(x) ≠ fn(y)] ≥ δ, where 0 < δ < 1/2, required ϵ ≥ c(δ)n−α, where α = 1 − ln 2/ln 3 = 0.36907 …, and c(δ) > 0. We improve this result by achieving for every 0 < δ < 1/2, P[fn(x) ≠ fn(y)] ≥ δ, with:

ϵ = c(δ)n−α for any α < 1/2, using the recursive majority function with arity k = k(α);

ϵ = c(δ)n−1/2logtn for t = log2
$$\sqrt{\pi / 2}$$
= .3257 …, using an explicit recursive majority function with increasing arities; and

ϵ = c(δ)n−1/2, nonconstructively, following a probabilistic CNF construction due to Talagrand.

We also study the problem of achieving the best dependence on δ in the case that the noise rate ϵ is at least a small constant; the results we obtain are tight to within logarithmic factors. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 23: 333–350, 2003
A fault‐tolerant combinational circuit with fault diagnosis capability—To mask and detect the loss of any one connection between gate circuits
Authors: Nishigaki Masakatsu , Nakano Makoto , Soga Masakazu
Published: August 2003

We will produce a fault‐tolerant circuit with fault diagnosis function by using neuron‐MOS transistors. As to the fault range, we hypothesize a single disconnection fault in the wiring between gates. First, the inverter, AND gate, and OR gate are fault‐tolerant implemented and the fault‐tolerant logic gates with fault diagnosis mode are designed. Then, we will show that after optimally combining these fault‐tolerant logic gates by the configuration of multiplication standard form, any fault‐tolerant combinational circuit with fault diagnosis function can be obtained by multiplexing the result using interwoven logics. An ideal fault‐tolerant combinational circuit with both fault masking function and fault detection function can be realized. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 67–80, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10081
Variational Bayes method for Mixture of Principal Component Analyzers
Authors: Oba Shigeyuki , Sato Masa‐aki , Ishii Shin
Published: August 2003

When dealing with high‐dimensional data, it is proper to construct an appropriate feature space consisting of relevant features extracted from given data. Mixture of Principal Component Analyzers (MPCA) is a feature extracting tool in which clustering in the data space and principal component analysis in each cluster are simultaneously done. A probabilistic model of MPCA and its maximum likelihood (ML) inference were presented by Tipping and Bishop (1999). Although the probabilistic formulation can be satisfactorily advantageous within Bayesian inference instead of ML inference, Bayesian inference often requires difficult integrations. Such difficulty comes to be overcome by the variational Bayes (VB) approximation that has recently been developed. In this paper, we present a VB inference algorithm for MPCA, and its application to a recognition problem of handwritten digit images. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 55–66, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10394
A concepts‐of‐sentences associative neural network
Authors: Tanaka Hitoshi , Huang Jingtao , Hagiwara Masafumi
Published: August 2003

This paper proposes a new neural network (the concepts‐of‐sentences associative neural network, CSANN) which performs memory and recall of sentences represented by a semantic network, as an approach toward natural language processing. The semantic network is represented in terms of the triples representation of concepts. The triples representation of concepts consists of concepts linked by relations in sentences represented by natural language. CSANN handles sentence data, which are difficult to handle since the data size is not unique, by decomposing the data into triples representations of concepts and integrating them into the semantic network format. It is verified by computer simulation that the proposed network can store sentences and recall sentences even if the input information is incomplete. Thus, the effectiveness of the proposed network in natural language processing is demonstrated. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 43–54, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10476
The niching method for obtaining global optima and local optima in multimodal functions
Authors: Himeno Masako , Himeno Ryutaro
Published: August 2003

Sometimes it is desirable to know the secondary candidates as well as the global optima of multimodal functions. The Deterministic Crowding (DC) method is an effective type of genetic algorithm for discovering multiple global optima, but it has difficulties discovering local optima. An improvement on this method called “Dispersing Deterministic Crowding” (DDC) is therefore proposed which encourages dispersion of individuals and creation of species within the population in order to increase the discovery of local optima, as well as of global optima. A method for preferential identification of solutions with a fitness exceeding some demanded level is also developed. The performance of DDC is compared with those of other niching methods, DC, sharing, RTS, GA with tabu search, and the immune algorithm, to show its effectiveness. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 30–42, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10480
A test sequence generation method for communication protocols using the SAT algorithm
Authors: Mori Takanori , Otsuka Hirotaka , Funabiki Nobuo , Nakata Akio , Higashino Teruo
Published: August 2003

The specification for a communication protocol is generally represented by a finite‐state machine, and the operation of the machine is represented by transitions among states. The device implementing such specification is called the implementation under test (IUT). It is important for the IUT that its operation should be verified for all state transitions on the finite‐state machine given in the specification. This test is called the conformance testing. In such testing it is important to generate efficiently a route containing all state transitions from the initial state. This problem is called the test sequence generation problem. This paper considers the test sequence generation problem for a communication protocol and proposes an application of an algorithm for satisfiability problem (SAT) that can flexibly handle various constraints, such as the order constraint and the time constraint among multiple constraints. The proposed method is applied to the dynamic host configuration protocol (DHCP) and its effectiveness is demonstrated. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 20–29, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10482
A color image compression scheme based on the adaptive orthogonalized transform—Accelerated by sorted dictionary
Authors: Miura Takashi , Itagaki Fumihiko , Yokoyama Akihiko , Yamaguchi Momoe
Published: August 2003

The paper proposes an improvement of vector search performance for a vector quantization method based on the adaptive orthogonalized transform (AOT). The principle of the improvement is reducing the number of vector comparison by limiting the range of the dictionary. To limit the range of the dictionary, the dictionary vectors are sorted by the angle to the standard vectors in advance. The optimal vector position is estimated by the angle to the standard vectors in accordance with the position tables, and comparison is made around the estimated position. The effectiveness of the proposal is confirmed by numerical experiments. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 10–19, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10491
Image reconstruction with a source space tree algorithm for Compton CT
Authors: Ogawa Koichi , Ohta Jin
Published: August 2003

This paper proposes a Compton CT technique which accurately reconstructs the image of the radiation source distribution in the object cross section from the data observed by Compton scattering. The source space tree algorithm (SSTA) is proposed as an image reconstruction method in Compton CT. The method consists of reconstructing the source distribution by summing the weights assigned to the voxels intersecting the surface of a cone determined by the Compton scattering angle. In this process, it is necessary to make a decision about the intersection between the voxels composing the back‐projection space and the cone surface. In the conventional method, the spherical region is used in making the decision. This may produce an incorrect judgment of intersection, resulting in an artifact on the image. In the proposed method, a cube is used instead of a sphere. This makes the intersection decision more accurate, resulting in reconstruction of the image without artifacts. The effectiveness of the proposed method is verified by simulations. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 1–9, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10496
A panoramic view system for extracting key sentences and discovering keywords that express the features of a document
Authors: Sunayama Wataru , Yachida Masahiko
Published: August 2003

With the widespread use of the Internet in recent years, documents are increasingly handled by electronic means. However, due to physical and time limitations it is difficult to review all of these documents. To allow selection of desired documents, it is useful to prepare a summary representing the content of each document. Consequently, this paper proposes a panoramic view system which extracts important sentences by a unique method. The system surveys the whole text and detects the keywords that express the features of the text. The feature keywords are extracted as words closely related to the main topic of the text and help to extract important relevant sentences. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 81–90, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1215
Real‐time rendering system of human figures from arbitrary viewpoints using multiple cameras
Authors: Kunita Yutaka , Inami Masahiko , Maeda Taro , Tachi Susumu
Published: August 2003

To enable face‐to‐face communication between remote users, we developed a prototype system that projects real‐time realistic images of human figures into a virtual space. Since real‐time responsiveness, in particular, is required for this kind of use, the prototype equipment has the following special features. First, it uses a simple technique that extracts images captured by multiple cameras and projects them onto a plane located in the virtual space. Since the geometric shape of the human figure need not be obtained when using this technique, the required computing power is extremely small. The generated image error becomes large if the subject is not in the vicinity of the virtual plane. We formulated this by defining a fixed range within which the subject should exist as the “equivalent depth of field.” Also, among the video signals obtained by the multiple cameras, the implemented system selects only the ones required for image generation and enters them into the computer in terms of scan line units. By selectively discarding information at an early stage in this way, a high‐precision image can be generated without degradation even if there are few video‐capture boards. These special features enabled us to show the effectiveness of the proposed technique by successfully generating real‐time images using a consumer‐oriented, low‐cost personal computer. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 91–100, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1216
Hierarchical Bayesian air conditioning load prediction—A nonlinear dynamical systems approach
Authors: Nakajima Yoshinori , Saito Motoki , Sugi Junjiro , Hamagishi Hiroaki , Matsumoto Takashi
Published: August 2003

This paper considers the energy demand prediction problem and formulates it in the framework of hierarchical Bayesian nonlinear time series prediction with a neural net. As a practical problem, the method is applied to thermal load prediction of a formal energy storage system and the results are presented. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(11): 101–110, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1217
Molecular orientation of EVA chains adsorbed on chemically controlled surfaces: influence of specific interactions
Authors: Elzein Tamara , Brogly Maurice , Schultz Jacques
Published: August 2003

Molecular orientation of ethylene–vinyl acetate (EVA) copolymer nanofilms adsorbed on chemically controlled surfaces is studied. Four EVA copolymers with different contents of vinyl acetate (VA) were spin‐coated onto gold, COOH and NH2 functionalized substrates in order to study chain behaviour when adsorbed in a quasi‐two‐dimensional system. Polarization‐modulation infrared reflection–absorption spectroscopy (PM‐IRRAS), a very suitable technique to study thin films, was the key to quantitative calculation of EVA chain orientational angles. Acid–base interactions between carbonyl groups of the chain ramification (vinyl acetate units) and the surface functionalities are evidenced on the basis of infrared spectra. Their incidence on the molecular orientation is also discussed.

Our results show a quasi‐parallel orientation of EVA main chains with respect to the surface plane for all adsorption substrates. At the same time, orientation changes of the acetate groups are observed when the EVA copolymer is adsorbed onto functionalized substrates, suggesting that acid–base interactions could influence the orientation of these groups. However, these changes are limited and cannot reorient the main chain axis. Moreover, our results show that increasing VA content in the chain does not lead to more carbonyl functions involved in acid–base interactions with the adsorption surface. This fact also will be discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Denoising and multivariate analysis of time‐of‐flight SIMS images
Authors: Wickes Bronwyn T. , Kim Yongmin , Castner David G.
Published: August 2003

Time‐of‐flight SIMS (ToF‐SIMS) imaging offers a modality for simultaneously visualizing the spatial distribution of different surface species. However, the utility of ToF‐SIMS datasets may be limited by their large size, degraded mass resolution and low ion counts per pixel. Through denoising and multivariate image analysis, regions of similar chemistries may be differentiated more readily in ToF‐SIMS image data. Three established denoising algorithms—down‐binning, boxcar and wavelet filtering—were applied to ToF‐SIMS images of different surface geometries and chemistries. The effect of these filters on the performance of principal component analysis (PCA) was evaluated in terms of the capture of important chemical image features in the principal component score images, the quality of the principal component score images and the ability of the principal components to explain the chemistries responsible for the image contrast. All filtering methods were found to improve the performance of PCA for all image datasets studied by improving capture of image features and producing principal component score images of higher quality than the unfiltered ion images. The loadings for filtered and unfiltered PCA models described the regions of chemical contrast by identifying peaks defining the regions of different surface chemistry. Down‐binning the images to increase pixel size and signal was the most effective technique to improve PCA performance. Copyright © 2003 John Wiley & Sons, Ltd.
The distribution of hydroxyl ions at the surface of anodic alumina
Authors: Alexander M. R. , Beamson G. , Bailey P. , Noakes T. C. Q. , Skeldon P. , Thompson G. E.
Published: August 2003

Barrier‐type anodic films 3–15 nm thick have been formed on electropolished 99.999% aluminium. Variable‐angle XPS has been used to identify a significant proportion of hydroxyl ions at the surface of the relatively compact alumina films. The location of an oxygen‐rich region at the outer surface of the oxide has been confirmed by medium‐energy ion scattering (MEIS). Combining the information from these two techniques leads to the conclusion that a hydroxyl‐containing surface region is responsible for this oxygen‐rich surface layer, MEIS revealing an approximately linear relationship between the total oxide thickness and the thickness of the hydroxyl‐rich surface region. From consideration of the mechanisms of amorphous alumina formation by ionic transport, with incorporation of electrolyte‐derived species into the thickening film, the generation of the hydroxyl‐rich outermost region is considered to result from the formation of gel‐like material at the film/electrolyte interface. Copyright © 2003 John Wiley & Sons, Ltd.
Fabrication of β″‐alumina films as a thermoelectric material by thermal plasma processing
Authors: Kim Jong‐Taek , Lim Kyung‐Bum , Lee Duck‐Chool
Published: August 2003

The fabrication of β″‐alumina films as thermoelectric materials was investigated by thermal plasma processing based on the forced constrictive‐type reactor. Under both atmospheric and low pressures, β″‐alumina films were synthesized successfully from a mixed powder of α‐Al2O3, Na2CO3 and MgO. The jet powder and substrate position strongly affect the properties of plasma‐processed β″‐alumina, which were found to be correlated with jet temperature. For both pressures, the films show good thermoelectric properties. Copyright © 2003 John Wiley & Sons, Ltd.
Calculation of the surface energy of bcc metals by using the modified embedded‐atom method
Authors: Zhang Jian‐Min , Ma Fei , Xu Ke‐Wei
Published: August 2003

The surface energies for 24 surfaces of bcc metals Li, Na, K, V, Nb, Ta, Cr, Mo, W and Fe have been calculated by using the modified embedded‐atom method. The results show that for most bcc metals the lowest surface energies correspond to the (110) surface, as predicted from the bcc lattice, and the highest surface energies correspond to the (433) surface. From surface energy minimization, the (110) texture should be favourable in the bcc films. This is consistent with experimental results. Copyright © 2003 John Wiley & Sons, Ltd.
Adsorption of polyamides and polyamide–silane mixtures at glass surfaces
Authors: Shallenberger Jeffrey R. , Metwalli EzzEldin , Pantano Carlo G. , Tuller F. Norman , Fry Douglas F.
Published: August 2003

The individual and combined adsorption behavior of polyamides and two different silanes to multicomponent glass surfaces was probed with a combination of x‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and static contact angle measurements. Samples were analyzed with and without solvent rinsing to separate the weakly bound (physisorbed) and more strongly bound (chemisorbed) species. High‐resolution XPS on N 1s revealed that the polyamides adsorb to the glass surfaces via protonated amine species at the acidic (OH) sites on the glass surface. Angle‐resolved XPS confirmed this by showing that the alkyl portion of the polymer is oriented away from the glass interface. In competitive coadsorption studies it was found that amino‐terminated silanes preferentially adsorb to the glass surface, relegating the polyamide to a physisorbed outer layer. When mercaptoterminated silanes were competitively coadsorbed the polyamide was preferentially adsorbed even when present at a concentration twenty times less than that of the silane. Altogether, this work reveals the strong interaction between surface silanols and amino‐functionalized organics. Copyright © 2003 John Wiley & Sons, Ltd.
Radiation‐induced migration of additives in PVC‐based biomedical disposable devices Part 2. Surface analysis by XPS
Authors: Atzei D. , Elsener B. , Manfredini M. , Marchetti A. , Malagoli M. , Galavotti F. , Rossi A.
Published: August 2003

Extruded parts of non‐sterilized and β‐irradiated (25 and 50 kGy) plasticized poly(vinyl chloride) (PVC) used for disposable medical devices have been studied to investigate the effect of sterilization on surface chemical composition. The polymer surfaces were analysed using angle‐resolved x‐ray photoelectron spectroscopy. The inner surface of the blood tubing lines showed a fairly smooth surface both before and after sterilization, so a laterally homogeneous surface can be assumed for XPS analysis. The XPS survey spectra exhibited no signals besides carbon, chlorine, oxygen and calcium. Detailed analysis of the regions showed the C 1s, Cl 2p and O 1s signals to be multi‐component, presenting signals of the PVC, the plasticizer and the other additives. Binding energies remained constant irrespective of β‐radiation dosage, but the amount of chlorine component at 198.4 ± 0.1 eV (associated with modified PVC) decreased with sterilization dosage. Angle‐resolved XPS revealed that this component is located at the outermost surface of the polymer. It can be hypothesized that the production processes themselves (extrusion and/or injection molded) already induce modifications of the polymer surface and also lead to surface segregation of the plasticizer. During the subsequent thermal sterilization of the polymer dehydrochlorination continues but, because of the very short time required by the β‐irradiation technology to sterilize devices, the atmospheric oxygen is unable to diffuse into the irradiated material, thus inhibiting further side‐degradation of the materials, such as thermo‐oxidative degradation. Copyright © 2003 John Wiley & Sons, Ltd.
Cationization of dendritic macromolecule adsorbates on metals studied by time‐of‐flight secondary ion mass spectrometry
Authors: Coullerez Géraldine , Mathieu Hans Jörg , Lundmark Stefan , Malkoch Michael , Magnusson Heléne , Hult Anders
Published: August 2003

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was utilized to study dendritic macromolecules with various architectures, such as dendrons, dendrimers and hyperbranched polyesters prepared from bis‐(hydroxymethyl)propionic acid (Bis‐MPA) and a series of hyperbranched polyethers based on 3‐ethyl‐3(hydroxymethyl)oxetane. The measurements were performed on spin‐coated thin films of the branched molecules (D) onto silicon, chemically etched copper foil and silver‐coated wafers. They showed weak signatures of molecular ions by proton capture (D + H)+ in the high mass range of the spectra (m/z > 400). On the contrary, cationization of the intact molecules with alkali or transition metal ions such as Na+, Cu+ or Ag+ was observed. High‐intensity quasi‐molecular ions (D + M)+ (with M = Na+, Cu+ or Ag+) allowed the studied polymers to be identified. The whole molecular species were observed for Bis‐MPA dendrons and dendrimers up to 3000 Da for hydroxyl or acetonide‐terminated derivatives. The success of the so‐called cationization experiments with metal substrates compared with analysis of molecular adsorbates on silicon is highlighted. The ToF‐SIMS sensitivity appeared useful to provide information about the molecular end‐groups or to highlight incomplete reaction occurring during some deprotection step of the synthesis. Only uncationized fragments of low masses were detected for the hyperbranched polyesters. This result suggested the effect of molecular asymmetry and/or flattening of the molecules on the substrates, which hampered the molecule lift‐off efficiency. Nevertheless, the hyperbranched polyethers were characterized based on the peak distribution of intensities, which allowed estimation of their molecular weight average. This work was intended to illustrate the capabilities of ToF‐SIMS to analyse dendritic polymers on surfaces. Copyright © 2003 John Wiley & Sons, Ltd.
ToF‐SIMS for the characterization of hyperbranched aliphatic polyesters: probing their molecular weight on surfaces based on principal component analysis (PCA)
Authors: Coullerez Géraldine , Lundmark Stefan , Malmström Eva , Hult Anders , Mathieu Hans Jörg
Published: August 2003

A series of 2,2‐bis(hydroxymethyl)propionic acid (Bis‐MPA) hyperbranched aliphatic polyesters with different molecular weights (generations) is analysed for the first time by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The main negative and positive low‐mass fragments are identified in the fingerprint part of the spectra (m/z < 400) and are principally assigned to fragmentation of the Bis‐MPA repeating units. In addition, it is shown that the fragmentation pattern is highly affected by the functional end‐groups. This is illustrated for a phthalic acid end‐capped hyperbranched polymer and for an acetonide‐terminated dendrimer analog. Also, typical fragments assigned to the ethoxylated pentaerythritol core molecule are detected. These ions show decreasing intensities with increasing molecular weight. This intensity dependency on the generation is used to calibrate the molecular weight of hyperbranched polyesters on the surface. To obtain quantitative information, a principal component analysis (PCA) multivariate statistical method is applied to the ToF‐SIMS data. The influence of different normalization procedures prior to PCA calculation is tested, e.g. normalization to the total intensity, to the intensities of ions assigned to the Bis‐MPA repeating unit or to intensities of fragments due to the core molecule. It is shown that only one principal component (PC1) is needed to describe most of the variance between the samples. In addition, PC1 takes into account the generation effect. However, different relationships between the PC1 scores and the hyperbranched mass average molecular weights are observed depending on the normalization procedure used. Normalization of data set ion intensities by ion intensities from the core molecule allows linearization of the SIMS intensities versus the molecular weight and allows the hyperbranched polymers to be discriminated up to the highest generations. In addition, PCA applied to ToF‐SIMS data provides an extended interpretation of the spectra leading to further identification of the correlated mass peaks, such as those of the Bis‐MPA repeating unit (terminal, dendritic and linear) and those of the core molecule. Finally, the work presented demonstrates the extreme potential of the static ToF‐SIMS and PCA techniques in the analysis of dendritic molecules on solid surfaces. Copyright © 2003 John Wiley & Sons, Ltd.
Relation between adsorption of some anionic surfactants on barite and solution/air interfaces
Authors: Omar A. M. A. , Azzam E. M. S.
Published: August 2003

The adsorption behaviour of synthesized anionic surfactants with chemical structure RO–Ph–NN–Ph–X, where R is octyl, dodecyl or cetyl and X is SO3Na, was analysed. Analysis of the behaviour of the surfactants was made using a modified version of the Frumkin adsorption isotherm. The values of thermodynamic parameters were calculated at the solution/air interface. The relation between adsorption of the surfactants at the solution/air interface and solid/liquid interface was investigated. The surface properties of these synthetic surfactants were studied. The results show that the length of the hydrocarbon chain of these surfactants plays a major role in determining the surface and thermodynamic properties. The results also indicate that there is a good relationship between effectiveness of adsorption of the surfactant and its efficiency as a collector. Copyright © 2003 John Wiley & Sons, Ltd.
A comparison of several regression models for analysing cost of CABG surgery
Authors: Austin Peter C. , Ghali William A. , Tu Jack V.
Published: August 2003

Investigators in clinical research are often interested in determining the association between patient characteristics and cost of medical or surgical treatment. However, there is no uniformly agreed upon regression model with which to analyse cost data. The objective of the current study was to compare the performance of linear regression, linear regression with log‐transformed cost, generalized linear models with Poisson, negative binomial and gamma distributions, median regression, and proportional hazards models for analysing costs in a cohort of patients undergoing CABG surgery. The study was performed on data comprising 1959 patients who underwent CABG surgery in Calgary, Alberta, between June 1994 and March 1998. Ten of 21 patient characteristics were significantly associated with cost of surgery in all seven models. Eight variables were not significantly associated with cost of surgery in all seven models. Using mean squared prediction error as a loss function, proportional hazards regression and the three generalized linear models were best able to predict cost in independent validation data. Using mean absolute error, linear regression with log‐transformed cost, proportional hazards regression, and median regression to predict median cost, were best able to predict cost in independent validation data. Since the models demonstrated good consistency in identifying factors associated with increased cost of CABG surgery, any of the seven models can be used for identifying factors associated with increased cost of surgery. However, the magnitude of, and the interpretation of, the coefficients vary across models. Researchers are encouraged to consider a variety of candidate models, including those better known in the econometrics literature, rather than begin data analysis with one regression model selected a priori. The final choice of regression model should be made after a careful assessment of how best to assess predictive ability and should be tailored to the particular data in question. Copyright © 2003 John Wiley & Sons, Ltd.
Confidence intervals for the mean of a variable taking the values 0,1 and 2
Authors: Newcombe Robert G.
Published: August 2003

The problem of setting a confidence interval for the mean of a variable on {0, 1,2} arises in three contexts: paired organ procedure rates; estimation of gene frequency, and three‐point Likert scales. An effective approach to its estimation may be based on a good interval for a paired difference of proportions. Four good methods due to Newcombe and Tango are shown to have much better performance than more naive methods over regions of the parameter space corresponding to the above applications. Copyright © 2003 John Wiley & Sons, Ltd.
Prediction of cancer incidence in the Nordic countries: empirical comparison of different approaches
Authors: Møller Bjørn , Fekjær Harald , Hakulinen Timo , Sigvaldason Helgi , Storm Hans H. , Talbäck Mats , Haldorsen Tor
Published: August 2003

Prediction of the future number of cancer cases is of great interest to society. The classical approach is to use the age‐period‐cohort model for making cancer incidence predictions. We made an empirical comparison of different versions of this model, using data from cancer registries in the Nordic countries for the period 1958–1997. We have applied 15 different methods to 20 sites for each sex in Denmark, Finland, Norway and Sweden. Median absolute value of the relative difference between observed and predicted numbers of cases for these 160 combinations of site, sex and country was calculated. The medians varied between 10.4 per cent and 15.3 per cent in predictions 10 years ahead, and between 15.1 per cent and 32.0 per cent for 20 year predictions. We have four main conclusions: (i) projecting current trends worked better than assuming that future rates are equal to present rates; (ii) the method based on the multiplicative APC model often overestimated the number of cancer cases due to its exponential growth over time, but using a power function to level off this growth improved the predictions; (iii) projecting only half of the trend after the first 10 years also gave better long‐term predictions; (iv) methods that emphasize trends in the last decade seem to perform better than those that include earlier time trends. Copyright © 2003 John Wiley & Sons, Ltd.
Improved tests for a random effects meta‐regression with a single covariate
Authors: Knapp Guido , Hartung Joachim
Published: August 2003

The explanation of heterogeneity plays an important role in meta‐analysis. The random effects meta‐regression model allows the inclusion of trial‐specific covariates which may explain a part of the heterogeneity. We examine the commonly used tests on the parameters in the random effects meta‐regression with one covariate and propose some new test statistics based on an improved estimator of the variance of the parameter estimates. The approximation of the distribution of the newly proposed tests is based on some theoretical considerations. Moreover, the newly proposed tests can easily be extended to the case of more than one covariate. In a simulation study, we compare the tests with regard to their actual significance level and we consider the log relative risk as the parameter of interest. Our simulation study reflects the meta‐analysis of the efficacy of a vaccine for the prevention of tuberculosis originally discussed in Berkey et al. The simulation study shows that the newly proposed tests are superior to the commonly used test in holding the nominal significance level. Copyright © 2003 John Wiley & Sons, Ltd.
Baseline adjustments for binary data in repeated cross‐sectional cluster randomized trials
Authors: Nixon R. M. , Thompson S. G.
Published: August 2003

Analysis of covariance models, which adjust for a baseline covariate, are often used to compare treatment groups in a controlled trial in which individuals are randomized. Such analysis adjusts for any baseline imbalance and usually increases the precision of the treatment effect estimate. We assess the value of such adjustments in the context of a cluster randomized trial with repeated cross‐sectional design and a binary outcome. In such a design, a new sample of individuals is taken from the clusters at each measurement occasion, so that baseline adjustment has to be at the cluster level. Logistic regression models are used to analyse the data, with cluster level random effects to allow for different outcome probabilities in each cluster. We compare the estimated treatment effect and its precision in models that incorporate a covariate measuring the cluster level probabilities at baseline and those that do not. In two data sets, taken from a cluster randomized trial in the treatment of menorrhagia, the value of baseline adjustment is only evident when the number of subjects per cluster is large. We assess the generalizability of these findings by undertaking a simulation study, and find that increased precision of the treatment effect requires both large cluster sizes and substantial heterogeneity between clusters at baseline, but baseline imbalance arising by chance in a randomized study can always be effectively adjusted for. Copyright © 2003 John Wiley & Sons, Ltd.