bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ethyl methacrylate grafted on two starches as polymeric matrices for drug delivery
Authors: Echeverria I. , Silva I. , Goñi I. , Gurruchaga M. 
Published: February 2005

AbstractThe use of copolymers grafted on starch for controlled‐release technology is an interesting proposal, since a modification of a natural polymer is more suitable than synthetic polymers because of its biocompatibility and biodegradability. The aim of this paper is to synthesize acrylic polymers grafted on carbohydrates to investigate the release kinetic of different solubility drugs from polymeric matrix systems and to observe the effect of grafted copolymers and drug solubility on the release mechanism. Copolymer variables such as carbohydrate content, stereoregularity of grafted chains, particle size, morphology, sensitivity to hydration, and rheological properties are discussed. Tablets were prepared by direct compression of the graft copolymer and drug. The drugs' release in vitro kinetics was studied by dissolution testing. Drug release from tablets depends on polymer matrix, polymer content, drug, and pH. An increase in drug solubility results in an increase in the rate of dissolution, as in the case of a poor hydrophilic matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 523–536, 2005
Reactive blends of epoxy resin (DGEBA) crosslinked by anionically polymerized polycaprolactam. II. Mechanical and electrical properties
Authors: Gupta Alka , Singhal Reena , Nagpal A. K. 
Published: February 2005

AbstractVarious reactive blends of diglycidyl ether of bisphenol A (DGEBA)/polycaprolactam were synthesized by anionic polymerization at 140°C, conducted by sodium hydride catalyst, a strong base, along with N‐acetyl caprolactam as a cocatalyst. The experiments were performed to study the effect of composition on the mechanical and electrical properties of the reactive blends, such as tensile properties, flexural properties, Izod impact strength, Rockwell hardness, and volume resistivity. It was observed that the DGEBA was crosslinked by the polycaprolactam through the rapid reaction of the oxirane group with amide nitrogen. The heat of reaction and heat‐deflection temperature of the reactive blends increased with increasing DGEBA content from 50 to 80 wt %, and increased dramatically above 70 wt % DGEBA content. The mechanical and electrical properties of the reactive blends increased with increasing DGEBA content from 50 to 80 wt %. Substantial increases in these properties were observed above 70 wt % DGEBA content in the reactive blends. SEM studies revealed that the reactive blends show a multiphase system with an increase in the DGEBA content from 50 to 80 wt % as the mixing of the two phases increased. The reactive blend Ep80Ca20, with 80 wt % DGEBA content, resembles a single‐phase system because of better mixing of the two phases; as a result, this reactive blend showed the highest mechanical and electrical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 537–549, 2005
Electrospinning of nanofibers
Authors: Subbiah Thandavamoorthy , Bhat G. S. , Tock R. W. , Parameswaran S. , Ramkumar S. S. 
Published: February 2005

AbstractNanotechnology is the study and development of materials at nano levels. It is one of the rapidly growing scientific disciplines due to its enormous potential in creating novel materials that have advanced applications. This technology has tremendously impacted many different science and engineering disciplines, such as electronics, materials science, and polymer engineering. Nanofibers, due to their high surface area and porosity, find applications as filter medium, adsorption layers in protective clothing, etc. Electrospinning has been found to be a viable technique to produce nanofibers. An in‐depth review of research activities on the development of nanofibers, fundamental understanding of the electrospinning process, and properties of nanostructured fibrous materials and their applications is provided in this article. A detailed account on the type of fibers that have been electrospun and their characteristics is also elaborated. It is hoped that the overview article will serve as a good reference tool for nanoscience researchers in fibers, textiles, and polymer fields. Furthermore, this article will help with the planning of future research activities and better understanding of nanofiber characteristics and their applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 557–569, 2005
Novel thermally stable poly(ether imide ester)s from 2,6‐bis (4‐aminophenoxy) pyridine
Authors: Mehdipour‐Ataei Shahram , Amirshaghaghi Ahmad 
Published: February 2005

Abstract2,6‐Bis (4‐aminophenoxy) pyridine was prepared via reaction of 4‐aminophenol with 2,6‐dichloropyridine in the presence of potassium carbonate in N‐methyl‐2‐pyrrolidone (NMP). This pyridine‐based ether diamine was reacted with two moles of trimellitic anhydride to synthesize related diimide‐diacid (DIDA). A high temperature solution polycondensation reaction of DIDA with different diols in the presence of triethylamine hydrochloride in dichlorobenzene resulted in different poly(ether imide ester)s. The monomer and polymers were fully characterized, and the physical and thermal properties of the polymers were studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 570–576, 2005
Investigation of the self‐association behavior of a thermosensitive copolymer with lower critical solubility temperature near human heat by dynamic laser light scattering
Authors: Yin Weisi , Yang Hu , Zhang Xueqin , Wang Zhiliu , Ding Yanwei , Zhang Guangzhao , Cheng Rongshi 
Published: February 2005

AbstractThe special thermosensitive copolymer with lower critical solubility temperature near human heat of 37°C in aqueous solution has been prepared successfully by copolymerizing N‐isopropylacrylamide (NIPAM) and N‐isopropylmethacrylamide (NIPMAM) randomly at an appropriate monomer ratio. The self‐association behavior of the poly[NIPAM‐ran‐NIPMAM] copolymer has been studied by dynamic laser light scattering (DLLS) at a concentration higher than the critical concentration of the self‐association calculated from viscosity data according to cluster theory. The effect of the concentration and temperature on the self‐association behavior in water has been discussed respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 583–588, 2005
Formation of conjugated carbon bonds on poly(vinyl chloride) films by microwave‐discharge oxygen‐plasma treatments
Authors: Kumagai Hidetoshi , Tashiro Tomokatu , Kobayashi Takaomi 
Published: February 2005

AbstractConjugated polyene bonds on poly(vinyl chloride) (PVC) films were rapidly formed by the treatment of oxygen plasma produced by microwave discharge. Changes affecting the formation of conjugated carbon bonds on PVC were studied with respect to plasma emission diagnostic and surface properties of the film with fluorescence, refractant absorption spectroscopy, X‐ray photoelectron spectroscopy analysis, and Raman spectroscopy. The formation of polyene bonds on the film surface was responsible for both the dechlorination and dehydrogenation of PVC in the plasma atmosphere. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 589–594, 2005
Superior Safety in Noninferiority Trials
Authors: Bristol David R. 
Published: February 2005

AbstractNoninferiority of a new treatment to a reference treatment with respect to efficacy is usually associated with the superiority of the new treatment to the reference treatment with respect to other aspects not associated with efficacy. When the superiority of the new treatment to the reference treatment is with respect to a specified safety variable, it may be necessary to perform the between‐treatment comparisons. The efficacy and safety comparisons may be considered separately or simultaneous comparisons may be performed. Here techniques are discussed for the simultaneous consideration of both aspects. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Biostatistical Assessment of Mutagenicity Studies by Including the Positive Control
Authors: Hauschke Dieter , Slacik‐Erben Renate , Hensen Sabrina , Kaufmann Ronny 
Published: February 2005

AbstractStatistical analysis plays a fundamental part in the evaluation of mutagenicity experiments. However, a statistically significant or non‐significant test result without incorporating the biological relevance cannot be a valid scientific criterion for concluding a positive or negative effect of the underlying compound (Hauschke et al., 1997). The classification of an experiment as being negative or positive should be based also on the magnitude of the responses in the positive control. We address the problem of determining the maximum safe dose by incorporating a biologically meaningful threshold value, which is expressed as a fraction of the difference between positive and vehicle control. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Methods for Assessing Noninferiority with Censored Data
Authors: Freitag Gudrun 
Published: February 2005

AbstractIn this paper we present the existing approaches to the problem of showing noninferiority with randomly right censored data. The main focus is on the choice of the discrepancy measure which is used to define the deviation from the classical null hypothesis, i.e. the noninferiority margin. Most methods are based on certain parametric or semiparametric assumptions. In contrast, a new, completely nonparametric approach is suggested and discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Regulatory Perspective on Choice of Margin and Statistical Inference Issue in Non‐inferiority Trials
Authors: Hung H. M. James , Wang Sue‐Jane , O'Neill Robert 
Published: February 2005

AbstractWithout a placebo arm, any non‐inferiority inference involving assessment of the placebo effect under the active control trial setting is difficult. The statistical risk for falsely concluding non‐inferiority cannot be evaluated unless the constancy assumption approximately holds that the effect of the active control under the historical trial setting where the control effect can be assessed carries to the non‐inferiority trial setting. The constancy assumption cannot be checked because of missing the placebo arm in the non‐inferiority trial. Depending on how serious the violation of the assumption is thought to be, one may need to seek an alternative design strategy that includes a cushion for a very conservative non‐inferiority analysis or shows superiority of the experimental treatment over the control. Determination of the non‐inferiority margin depends on what objective the non‐inferiority analysis is intended to achieve. The margin can be a fixed margin or a margin functionally defined. Between‐trial differences always exist and need to be properly considered. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Special Invited Papers Section: Therapeutic Equivalence – Clinical Issues and Statistical Methodology in Noninferiority Trials
Authors: Lange S. , Freitag G. 
Published: February 2005

AbstractAn essential problem in planning clinical non‐inferiority or equivalence studies is the specification of the ‘irrelevant difference’ (irrelevance margin; delta). This quantifies the amount of non‐inferiority or difference, respectively, between a new test therapy and an established standard treatment which is to be considered as tolerable. In the past, most recommendations and guidelines for clinical non‐inferiority and equivalence studies contained only general statements and formulations concerning the specification of delta. The current unsatisfactory situation was the reason for performing a systematic review of published clinical non‐inferiority and equivalence studies. It was the aim to gain an overview on the irrelevance margins used in such studies, and on reasons for choosing the particular margins. For the sake of comparability, the irrelevance margins were converted into standardized differences and odds ratios. Overall, there were 332 non‐inferiority or equivalence trials obtained by means of an extensive literature search. The results of the systematic review show that current requirements on the choice of delta and the reality of recent clinical non‐inferiority and equivalence trials differ substantially. In about one half of the trials a difference of 0.5 standard deviations or more was regarded as ‘irrelevant’ – explicitly or implicitly. Estimates of standard‐placebo differences formed the basis of the irrelevance margin in less than every tenth trial. Reasons for this very low proportion might be (1) the possibly resulting very small irrelevance margins, and (2) unsolved problems of the requirements themselves. Overall, it seems that a more global definition of ‘irrelevance’ might be warranted. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Testing Superiority and Non‐Inferiority Hypotheses in Active Controlled Clinical Trials
Authors: Tsong Yi , Zhang Juan (Joanne) 
Published: February 2005

AbstractSwitching between testing for superiority and non‐inferiority has been an important statistical issue in the design and analysis of active controlled clinical trial. In practice, it is often conducted with a two‐stage testing procedure. It has been assumed that there is no type I error rate adjustment required when either switching to test for non‐inferiority once the data fail to support the superiority claim or switching to test for superiority once the null hypothesis of non‐inferiority is rejected with a pre‐specified non‐inferiority margin in a generalized historical control approach. However, when using a cross‐trial comparison approach for non‐inferiority testing, controlling the type I error rate sometimes becomes an issue with the conventional two‐stage procedure. We propose to adopt a single‐stage simultaneous testing concept as proposed by Ng (2003) to test both non‐inferiority and superiority hypotheses simultaneously. The proposed procedure is based on Fieller's confidence interval procedure as proposed by Hauschke et al. (1999). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistical Methods for the Analysis of Two‐Arm Non‐inferiority Trials with Binary Outcomes
Authors: Wellek Stefan 
Published: February 2005

AbstractThe aim of this contribution is to give an overview of approaches to testing for non‐inferiority of one out of two binomial distributions as compared to the other in settings involving independent samples (the paired samples case is not considered here but the major conclusions and recommendations can be shown to hold for both sampling schemes). In principle, there is an infinite number of different ways of defining (one‐sided) equivalence in any multiparameter setting. In the binomial two‐sample problem, the following three choices of a measure of dissimilarity between the underlying distributions are of major importance for real applications: the odds ratio (OR), the relative risk (RR), and the difference (DEL) of both binomial parameters. It is shown that for all three possibilities of formulating the hypotheses of a non‐inferiority problem concerning two binomial proportions, reasonable testing procedures providing exact control over the type‐I error risk are available. As a particularly useful and versatile way of handling mathematically nonnatural parametrizations like RR and DELTA, the approach through Bayesian posterior probabilities of hypotheses with respect to some non‐informative reference prior has much to recommend it. In order to ensure that the corresponding testing procedure be valid in the classical, i.e. frequentist sense, it suffices to use straightforward computational techniques yielding suitably corrected nominal significance levels.In view of the availability of testing procedures with satisfactory properties for all parametrizations of main practical interest, the discussion of the pros and cons of these methods has to focus on the question of which of the underlying measures of dissimilarity should be preferred on grounds of logic and intuition. It is argued that the OR clearly merits to be given preference also with regard to this latter kind of criteria since the non‐inferiority hypotheses defined in terms of the other parametric functions are bounded by lines which cross the boundaries of the parameter space. From this fact, we conclude that the exact Fisher type test for one‐sided equivalence provides the most reasonable approach to the confirmatory analysis of non‐inferiority trials involving two independent samples of binary data. The marked conservatism of the nonrandomized version of this test can largely be removed by using a suitably increased nominal significance level (depending, in addition to the target level, on the sample sizes and the equivalence margin), or by replacing it with a Bayesian test for non‐inferiority with respect to the odds ratio. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Therapeutic Equivalence – Clinical Issues and Statistical Methodology in Noninferiority Trials
Authors: Munk Axel , Trampisch Hans J. 
Published: February 2005

AbstractThis special issue on therapeutic equivalence contains a selection of 8 papers presented at the conference ‘Therapeutic Equivalence – Clinical Issues and Statistical Methodology in Noninferiority Trials’ held in Düsseldorf, December 12–13, 2003. The aim of this conference was to gather experts from academics, industry and regulatory agencies in the field of therapeutic equivalence, in particular of noninferiority trials. Originally initiated as a small workshop, it soon turned out that there is obviously strong need to discuss these challenging issues at a broader auditorium. Indeed, the feedback to this conference was overwhelming, finally more than 300 researchers participated. Hence the idea emerged to collect the results and discussions in a single journal issue. It took more than a year to finish it, and various activities in this rapidly developing area have been going on and were incorporated.We are very grateful to the Editors E. Brunner and M. Schumacher of the Biometrical Journal for their encouragement and support to publish this special issue on the occasion of this conference. Further, the technical assistance and expertise of G. Skipka and K. Thangavelu is gratefully acknowledged. We are also indebted to Peter Bauer and Stephen Senn for their discussions of the subsequent articles by Bristol, Freitag, Hauschke, Slacik‐Erben, Hensen and Kaufmann, Hung, Wang and O'Neill, Lange and Freitag, Tsong and Zhang, Wellek, and last but not least we would like to thank Joachim Röhmel for his contribution to this special issue. Joachim Röhmel contributed significantly during the last three decades to various branches of biostatistical research, and in particular to the design and analysis of equivalence trials. The aim of this special issue is therefore twofold, it is also devoted to the occasion of Joachim Röhmel's retirement from BfArM in 2004. In the following we would briefly like to express our deep appreciation of his scientific work. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistical optimization of culture conditions for bacterial cellulose production using Box‐Behnken design
Authors: Bae Sangok , Shoda Makoto 
Published: February 2005

AbstractCulture conditions in a jar fermentor for bacterial cellulose (BC) production from A. xylinum BPR2001 were optimized by statistical analysis using Box‐Behnken design. Response surface methodology was used to predict the levels of the factors, fructose (X1), corn steep liquor (CSL) (X2), dissolved oxygen (DO) (X3), and agar concentration (X4). Total 27 experimental runs by combination of each factor were carried out in a 10‐L jar fermentor, and a three‐dimensional response surface was generated to determine the effect of the factors and to find out the optimum concentration of each factor for maximum BC production and BC yield. The fructose and agar concentration highly influenced the BC production and BC yield. However, the optimum conditions according to changes in CSL and DO concentrations were predicted at almost central values of tested ranges. The predicted results showed that BC production was 14.3 g/L under the condition of 4.99% fructose, 2.85% CSL, 28.33% DO, and 0.38% agar concentration. On the other hand, BC yield was predicted in 0.34 g/g under the condition of 3.63% fructose, 2.90% CSL, 31.14% DO, and 0.42% agar concentration. Under optimized culture conditions, improvement of BC production and BC yield were experimentally confirmed, which increased 76% and 57%, respectively, compared to BC production and BC yield before optimizing the culture conditions. © 2005 Wiley Periodicals, Inc.
Engineered Saccharomyces cerevisiae strain BioS‐1, for the detection of water‐borne toxic metal contaminants
Authors: Radhika V. , Milkevitch Matthew , Audigé Valéry , Proikas‐Cezanne Tassula , Dhanasekaran N. 
Published: February 2005

AbstractSaccharomyces cerevisiae responds to extracellular toxic stimuli by increasing intracellular cyclic AMP levels, leading to activation of a cAMP‐dependent protein kinase, protein kinase A (PKA). Activated PKA phosphorylates downstream substrates, including specific DNA‐binding proteins, to turn off the expression of most or all of the yeast genes. Such cAMP‐PKA‐mediated inhibition of gene expression in response to toxic stimuli appears to be unique to S. cerevisiae. For instance, in mammalian cells, the cAMP‐PKA signaling pathway is rather responsive to growth factors and hormones in addition to being primarily involved in the activation of gene expression. Activation of gene expression by the cAMP‐PKA pathway in mammalian cells is due mainly to the presence of cAMP‐response elements (CREs) located in the promoters of many mammalian genes, and the expression of PKA‐responsive stimulatory transcription factor CRE‐binding protein, commonly referred as CREBP, which binds to the CREs. Thus, activation of the cAMP‐PKA signaling pathway results in the phosphorylation of CREBP by PKA, and phosphorylated CREBP transactivates specific gene expression by interacting with the cognate CRE. Based on these findings, we sought to engineer a yeast‐based biosensor, in which the stress‐sensing cAMP‐PKA pathway of yeast is coupled to the mammalian CREBP‐CRE‐stimulated gene expression pathway, which drives the expression of a reporter protein, such as green fluorescent protein (GFP). As a primary step toward the development of this biosensor, we engineered a yeast strain, BioS‐1, by genetically altering YPH 501, a wild‐type strain of S. cerevisiae, to express human CREBP and human CRE promoter‐driven GFP. Exposure of BioS‐1 to varying concentrations of As3+, Fe2+, Pb2+, and Cd2+ elicits concentration‐dependent expression of the GFP reporter that can be easily monitored by the fluorescence emitted by GFP. The results also indicate that the engineered BioS‐1 yeast cells can detect 2.5 ppm of these toxic metals and report it through the expression of GFP within 3 h. The results presented herein demonstrate that this engineered yeast strain can detect metal toxicants and can validate the use of this prototypic yeast strain to develop a biosensor that can be used to detect and monitor cytotoxic water‐borne toxic heavy metals. © 2005 Wiley Periodicals, Inc.