bluuebunny/crossref_metadata_2025 huggingface dataset:
A Double-Exponential Fast Gauss Transform Algorithm for Pricing Discrete Path-Dependent Options
Authors: Broadie M. , Yamamoto Y.
Published: October 2005

This paper develops algorithms for the pricing of discretely sampled barrier, lookback, and hindsight options and discretely exercisable American options. Under the Black-Scholes framework, the pricing of these options can be reduced to evaluation of a series of convolutions of the Gaussian distribution and a known function. We compute these convolutions efficiently using the double-exponential integration formula and the fast Gauss transform. The resulting algorithms have computational complexity of O(nN), where the number of monitoring/exercise dates is n and the number of sample points at each date is N, and our results show the error decreases exponentially with N. We also extend the approach and provide results for Merton’s lognormal jump-diffusion model.
Operations Research 2004 Meritorious Service Award Recipients and Appreciation to 2004 Referees
Authors: Chen Chun-Hung , Kleijnen Jack , Wilson James R. , Ozer Ozalp
Published: October 2005

All too often, the hard work that members of the scholarly community do to support our profession goes unrecognized. For the sixth year, the Editorial Board of Operations Research has decided to reward outstanding service to the journal’s scholarly mission. Associate editors and referees who did an exceptionally professional job by submitting timely, unbiased, and thoughtful reviews were considered for this award. This award is just a small token of the appreciation for exceptional work performed on behalf of Operations Research and our profession. We regret that the following names were inadvertently omitted from the list published in the July–August issue, and we thank these individuals for their effort to make Operations Research the premier journal of the field.

The Editorial Board would like to thank the following individual who acted as a referee for papers considered or published during the 2004 calendar year. Without the assistance of our valued referees, it would be impossible for INFORMS to publish a journal of high professional standards. We regret that the following name was inadvertently omitted from the list published in the July-August issue, and we thank him for his effort to make Operations Research the premier journal of the field.
Decision making and effort in the self‐regulation of hypertension: Testing two competing theories
Authors: Taylor Stephanie D. , Bagozzi Richard P. , Gaither Caroline A.
Published: October 2005

We compare the ability of two social psychological models to explain self‐regulation decisions to control hypertension by 208 patients at a hospital clinic: the theory of planned behaviour (TPB) and the model of goal‐directed behaviour (MGB). The sample was drawn from patients at a large research hospital in North America. The findings show that the MGB not only explains significantly more variance in decision making than the TPB, but it provides an account for how reasons for acting become integrated and transformed into intentions to act, which the TPB does not address. The MGB does this in part by introducing the variable, desire, as an essential mediator between reasons for acting and intentions. The MGB also incorporates the effects of anticipated emotions on decision making, which are forms of forward‐looking counterfactual thinking with respect to goals. In addition, the present study reconceptualized instrumental behaviour to encompass how hard one tries to act in the senses of (1) devoting time to planning with respect to reducing/maintaining blood pressure, (2) expending mental/physical energy to reduce/maintain blood pressure, (3) maintaining will power to reduce/maintain blood pressure, and (4) sustaining self‐discipline (e.g. in overcoming obstacles) to reduce/maintain blood pressure. Key differences, as well as commonalities, in decision making are pointed‐out between men and women and between people whose goal is to reduce versus maintain blood pressure.
Optimism, positive affectivity, and salivary cortisol
Authors: Lai Julian C. L. , Evans Phil D. , Ng Sik Hung , Chong Alice M. L. , Siu Oswald T. , Chan Cecilia L. W. , Ho Samuel M. Y. , Ho Rainbow T. H. , Chan Plato , Chan Charles C.
Published: October 2005

Objectives.Research on stress and salivary cortisol has focused almost exclusively on the effects of negative psychological conditions or emotional states. Little attention has been drawn to the impact associated with positive psychological conditions, which have been shown recently to have significant influences on neuroendocrine regulation. The aim of this study is to examine the impact of optimism and positive affect on salivary cortisol with the effects of their negative counterparts controlled for.

Design.Optimism and pessimism, and positive and negative affectivity were studied in relation to the diurnal rhythm of salivary cortisol in a group of 80 Hong Kong Chinese, who provided six saliva samples over the course of a day on two consecutive days. The separate effects of optimism and positive affect on two dynamic components of cortisol secretion, awakening response, and diurnal decline were examined.

Methods.Optimism and pessimism were measured using the Chinese version of the revised Life Orientation Test while generalized affects and mood states were assessed by the Chinese Affect Scale. An enzyme‐linked immunoabsorbent assay kit (EIA) developed for use in saliva was adopted for the biochemical analysis of cortisol. Testing of major group differences associated with positive psychological conditions was carried out using two‐way (group by saliva collection time) ANOVAs for repeated measures with negative psychological conditions and mood states as covariates.

Results.Participants having higher optimism scores exhibited less cortisol secretion in the awakening period when the effect of pessimism and mood were controlled. This effect was more apparent in men than in women who had higher cortisol levels in the awakening period. Optimism did not have similar effect on cortisol levels during the underlying period of diurnal decline. On the other hand, higher generalized positive affect was associated with lower cortisol levels during the underlying period of diurnal decline after the effects of negative affect and mood states had been controlled. Generalized positive affect did not significantly influence cortisol secretion during the awakening period.

Conclusions.These findings suggest that positive psychological resources including optimism and generalized positive affect had higher impact on cortisol secretion than their negative counterparts, and point to the need for increased attention to the potential contribution of positive mental states to well‐being.
Understanding affective and cognitive self‐evaluations about the body for adolescent girls
Authors: Bornholt Laurel , Brake Nicki , Thomas Sian , Russell Lesley , Madden Sloane , Anderson Gail , Kohn Michael , Clarke Simon
Published: October 2005

Objective. The aim of this study was to understand relations between cognitive and affective self‐evaluations about the body for adolescent girls in the context of their diverse experiences of the body.

Method. The project involved adolescent girls (N =141), including underweight to overweight schoolgirls, and hospitalized girls with anorexia nervosa (AN). Materials were brief, reliable inventories of self‐concepts about body, movement and appearance, and feelings about the body.

Results. Measurement models confirmed the related yet discrete self‐concepts about the body, movement and appearance, and feeling OK, guilt, worry, disgust, and anger about the body. Self‐concepts and feelings were not correlated with body weight, and were sensitive and specific for girls with AN versus low‐weight schoolgirls. Relations among self‐concepts and feelings about the body vary with the context. In particular, self‐concepts and feelings about the body were incongruent for AN girls with acute experiences of making self‐evaluations of their bodies.

Discussion. It is clear that self‐evaluations by adolescent girls do not necessarily reflect actual body weight. Findings suggest that associations between thoughts and feelings about the body vary with diverse experiences of the body. Results support brief, reliable, and valid indicators of self‐concepts and feelings about the body that are vital in the design of prevention, intervention, and monitoring, and the evaluation of programmes for girls in clinical and educational settings.
Randomized controlled trial of a brief research‐based intervention promoting fruit and vegetable consumption
Authors: Kellar Ian , Abraham Charles
Published: October 2005

Objective. The present study sought to test the efficacy of a brief research‐based, leaflet‐like intervention to promote eating the recommended daily intake of fruit and vegetables (RDIFV).

Design. A controlled, pre‐ post‐test experimental study with random allocation and a 1 week self‐report behavioural follow‐up was conducted.

Method. The intervention employed persuasive communication targeting self‐efficacy and intention, and invited participants to form implementation intentions in relation to acquiring and preparing fruit and vegetables for consumption.

Results. Intervention participants had stronger post‐intervention intentions to consume the RDIFV, and higher anticipated regret in relation to failing to do so, compared with controls, controlling for pre‐intervention scores. At follow‐up, the intervention group was found to have eaten more fruit and vegetables and to have consumed the RDIFV more frequently.

Discussion. It is concluded that this study supports the previously reported power of implementation intentions to prompt enactment of intentions, and that a brief research‐based leaflet‐like intervention could result in immediate enhancement of intentions and anticipated regret, and promote greater fruit and vegetable consumption.
His brain is totally different: An analysisof care‐staff explanations of aggressive challenging behaviour and the impactof gendered discourses
Authors: Wilcox Esther , Finlay W. M. , Edmonds Jane
Published: October 2005

Using a discourse analysis on the texts of 10 interviews with care staff, this research explored the discourses used by care staff in constructing the aggressive challenging behaviours of men and women with learning disabilities. The research also explored discourses used differentially to understand the aggressive challenging behaviour of one gender. The analysis demonstrated the use of two main discourses, an individual pathology discourse which constructed the behaviour as originating in factors stable and internal to the client, and a context discourse which constructed the behaviour as a response to the client's circumstances. Participants used these accounts flexibly within their talk, and also used a mixed discourse which constructed the behaviour as due to both individual pathology and context. Despite the staff presenting their understandings as not being affected by the client's gender, the presence of two gendered individualizing discourses within the interviews was also demonstrated. Women's behaviour, unlike men's, was constructed with the use of discourses about their menstrual cycle or character flaws. The consequences of the use of these different discourses are discussed, as are the subject positions which they afford for both staff and clients. It is argued that clients are disempowered by the individual pathology discourse; that consideration of the broad contexts within which care‐staff actions are situated may allow them to manage blame whilst reflecting on their practice, and that the impact of gender stereotypes on the understandings staff have of a client's behaviour should be a legitimate area for consideration in clinical practice.
The self‐regulatory model in women with rheumatoid arthritis: Relationships between illness representations, coping strategies, and illness outcome
Authors: Carlisle Alexandra C. S. , John Alexandra M. H. , Fife‐Schaw Chris , Lloyd Mark
Published: October 2005

Objectives. The self‐regulatory model proposes that an individual's cognitive representations of illness threat (illness representations) influence the selection and performance of strategies to cope with that illness (Leventhal, Meyer, & Nerenz, 1980). Also implicit in the model is the proposal that such coping strategies influence illness outcomes. These relationships represent a mediational model (Baron & Kenny, 1986). The aim of the present study is to test the hypothesis that coping strategies partially mediate the relationship between illness representations and illness outcome in women with rheumatoid arthritis.

Design and methods. The study is an observational cross‐sectional design. Self‐report measures of illness representations, coping strategies, and illness outcome were collected from 125 women with rheumatoid arthritis attending rheumatology out‐patient clinics. Clinical measures of disease activity and severity were obtained from hospital records.

Results. Avoidant and resigned coping were found to partially mediate the relationship between symptom identity and the illness outcome measures of disability and psychiatric morbidity. As in other studies, strong relationships were found between illness representations and illness outcome.

Conclusions. The finding that avoidant and resigned coping partially mediated the relationships between the illness representation dimension of symptom identity and two of the illness outcome measures (disability and psychiatric morbidity) provided some support for the hypothesis. However, the hypothesis was not fully supported, as coping did not partially mediate the relationship between any of the other illness representations and illness outcomes.
Serum Concentrations of Cross-Linked N-Telopeptides of Type I Collagen: New Marker for Bone Resorption in Hemodialysis Patients
Authors: Maeno Yoshifumi , Inaba Masaaki , Okuno Senji , Yamakawa Tomoyuki , Ishimura Eiji , Nishizawa Yoshiki
Published: October 2005

Background: Urinary cross-linked N-telopeptide of type I collagen (NTX) is a reliable bone resorption marker in patients with metabolic bone disease. We assessed a clinically available serum NTX assay suitable for anuric patients on hemodialysis (HD).

Methods: Serum concentrations of NTX, C-terminal telopeptide of type I collagen (β-CTX), pyridinoline (PYD), and deoxypyridinoline (DPD) were determined as bone resorption markers, and those of bone alkaline phosphatase (BAP) and intact osteocalcin (OC) as bone formation markers, in 113 male HD patients (mean age, 59.3 years; mean HD duration, 67.7 months). Each patient’s bone mineral density (BMD) in the distal third of the radius was measured twice, with a 2-year interval between measurements, by dual-energy x-ray absorptiometry.

Results: Serum NTX correlated significantly with β-CTX, PYD, DPD, BAP, and intact OC. NTX, as well as β-CTX, PYD, DPD, BAP, and intact OC, correlated significantly with BMD at the time of measurement. NTX, β-CTX, and DPD correlated significantly with the annual change in BMD during the 2-year period thereafter, in contrast to PYD, BAP, and intact OC. Patients in the highest quartile of serum NTX concentrations showed the fastest rate of bone loss. The sensitivity and specificity for detecting rapid bone loss were 48% and 83%, respectively, for serum NTX.

Conclusion: Serum NTX may provide a clinically relevant serum assay to estimate bone turnover in HD patients.
Feasibility Study of the Use of Frozen Human Sera in Split-Sample Comparison of Immunoassays with Candidate Reference Measurement Procedures for Total Thyroxine and Total Triiodothyronine Measurements
Authors: Thienpont Linda M , Van Uytfanghe Katleen , Marriott John , Stokes Peter , Siekmann Lothar , Kessler Anja , Bunk David , Tai Susan
Published: October 2005

Background: Diagnostic manufacturers must ensure/document metrologically traceable assays. We report on a feasibility study of a split-sample comparison for that purpose. Processed, frozen single-donation sera, assigned target values by candidate reference measurement procedures (cRMPs), were used with immunoassays for total thyroxine (TT4) and triiodothyronine (TT3) as models.

Methods: Two serum panels were quantified for TT4 and TT3 with validated cRMPs and measured in parallel with at least 14 immunoassays. The results were interpreted in terms of traceability of calibration (trueness) and of the individual measurement result (accuracy) by linear regression analysis and graphical representation against specifications. The commutability of the sera was investigated by parallel analysis of TT4 in freshly collected but nonfiltered specimens.

Results: The TT4 (TT3) concentrations in the sera (according to the cRMPs) were 64–269 nmol/L (0.88–13.7 nmol/L). The method comparison showed that for TT4, on average, the immunoassays produced results in agreement with the cRMPs, whereas for TT3, results were typically higher. It also demonstrated a considerable between-assay divergence in traceability of calibration and accuracy. The evidence of noncommutability of the sera attributable to processing, however, indicates that the interpretation should be treated with caution.

Conclusions: Frozen sera can be used for documenting/validating traceability of total thyroid measurements. The way in which the sera are processed may jeopardize commutability, however, and therefore requires in-depth investigation.
Detection of Outliers in Reference Distributions: Performance of Horn’s Algorithm
Authors: Solberg Helge Erik , Lahti Ari
Published: October 2005

Background: Medical laboratory reference data may be contaminated with outliers that should be eliminated before estimation of the reference interval. A statistical test for outliers has been proposed by Paul S. Horn and coworkers (Clin Chem 2001;47:2137–45). The algorithm operates in 2 steps: (a) mathematically transform the original data to approximate a gaussian distribution; and (b) establish detection limits (Tukey fences) based on the central part of the transformed distribution.

Methods: We studied the specificity of Horn’s test algorithm (probability of false detection of outliers), using Monte Carlo computer simulations performed on 13 types of probability distributions covering a wide range of positive and negative skewness. Distributions with 3% of the original observations replaced by random outliers were used to also examine the sensitivity of the test (probability of detection of true outliers). Three data transformations were used: the Box and Cox function (used in the original Horn’s test), the Manly exponential function, and the John and Draper modulus function.

Results: For many of the probability distributions, the specificity of Horn’s algorithm was rather poor compared with the theoretical expectation. The cause for such poor performance was at least partially related to remaining nongaussian kurtosis (peakedness). The sensitivity showed great variation, dependent on both the type of underlying distribution and the location of the outliers (upper and/or lower tail).

Conclusion: Although Horn’s algorithm undoubtedly is an improvement compared with older methods for outlier detection, reliable statistical identification of outliers in reference data remains a challenge.
Miniature Personal Electronic UVR Dosimeter with Erythema Response and Time‐stamped Readings in a Wristwatch
Authors: Heydenreich Jakob , Wulf Hans Christian
Published: October 2005

Personal ultraviolet radiation (UVR) dosimetry is important because sunlight is the most important risk factor for skin cancer and a risk factor for some eye diseases and immunosuppression and related disorders. Integrating devices, such as polysulphone film dosimeters, are generally used. To measure the exact dose at specific times, we have developed a personal electronic UVR dosimeter that makes time‐stamped measurements. It has a sensor with an erythema action spectrum response and a linear sensitivity (dose–response) with no offset. The sensor has cosine response, and the dosimeter can cope with environmental conditions such as rain, temperature and dirt. It can be programmed to measure with different time intervals and save the average of a specified number of measurements in the memory that can store 32 000 time‐stamped measurements. It is small (36 × 28 × 13 mm), weighs 14 g and can work for 4 months without maintenance. It is worn on the wrist, is equipped with a watch showing the time and may thus be used in large‐scale studies. The sensitivity can change by 10% due to temperature changes from −5 to 40°C. The UVR dosimeter sensitivity is 0.09 standard erythema doses (SED)/h and the difference in total received dose during 7 days between a Solar Light 501 UV‐Biometer (186 SED) and our UVR dosimeter was 3% and the median difference in daily total dose was 2.2%. The dosimeter provides unique possibilities. Examples of personal UVR measurements, data calculations and how they can be interpreted are given.
Fluorescence-Activated Cell Sorting–Based Purification of Embryonic Stem Cell–Derived Neural Precursors Averts Tumor Formation after Transplantation
Authors: Fukuda Hitoshi , Takahashi Jun , Watanabe Kiichi , Hayashi Hideki , Morizane Asuka , Koyanagi Masaomi , Sasai Yoshiki , Hashimoto Nobuo
Published: October 2005

The differentiation of dopaminergic (DA) neurons from mouse embryonic stem cells (ESCs) can be efficiently induced, making these neurons a potential source for transplantation as a treatment for Parkinson's disease, a condition characterized by the gradual loss of midbrain DA neurons. One of the major persistent obstacles to the successful implementation of therapeutic ESC transplantation is the propensity of ESC-derived grafts to form tumors in vivo. To address this problem, we used fluorescence-activated cell sorting to purify mouse ESC-derived neural precursors expressing the neural precursor marker Sox1. ESC-derived, Sox1+ cells began to express neuronal cell markers and differentiated into DA neurons upon transplantation into mouse brains but did not generate tumors in this site. In contrast, Sox1− cells that expressed ESC markers frequently formed tumors in vivo. These results indicate that Sox1-based cell sorting of neural precursors prevents graft-derived tumor formation after transplantation, providing a promising strategy for cell transplantation therapy of neurodegenerative disorders.
Myocardial Homing of Nonmobilized Peripheral-Blood CD34+ Cells After Intracoronary Injection
Authors: Blocklet Didier , Toungouz Michel , Berkenboom Guy , Lambermont Micheline , Unger Philippe , Preumont Nicolas , Stoupel Eric , Egrise Dominique , Degaute Jean-Paul , Goldman Michel , Goldman Serge
Published: October 2005

Granulocyte– colony-stimulating factor administered for autologous hematopoietic stem cell isolation from blood may favor restenosis in patients implanted after acute myocardial infarction (AMI). We therefore tested the isolation of peripheral-blood CD34+ cells without mobilization in six patients with AMI. After large-volume cytapheresis and positive CD34+ cell selection, 3.6 to 27.6 million CD34+ cells were obtained. We performed intra-coronary implantation of these cells and recorded no restenosis or arrhythmia. We used positron emission tomography (PET) to assess myocardial-labeled CD34+ cell homing, which accounted for 5.5% of injected cells 1 hour after implantation. In conclusion, large amounts of CD34+ cells, in the range reported in previous studies, can be obtained from nonmobilized peripheral blood. PET with [18F]-fluorodeoxyglucose cell labeling is an efficient imaging method for homing assessment.
Intervertebral Disc Cell–Mediated Mesenchymal Stem Cell Differentiation
Authors: Richardson Stephen M. , Walker Rachael V. , Parker Siân , Rhodes Nicholas P. , Hunt John A. , Freemont Anthony J. , Hoyland Judith A.
Published: October 2005

Low back pain is one of the largest health problems in the Western world today, and intervertebral disc degeneration has been identified as a main cause. Currently, treatments are symptomatic, but cell-based tissue engineering methods are realistic alternatives for tissue regeneration. However, the major problem for these strategies is the generation of a suitable population of cells. Adult bone marrow–derived mesenchymal stem cells (MSCs) are undifferentiated, multipotent cells that have the ability to differentiate into a number of cell types, including the chondrocyte-like cells found within the nucleus pulposus (NP) of the intervertebral disc; however, no method exists to differentiate these cells in an accessible monolayer environment. We have conducted coculture experiments to determine whether cells from the human NP can initiate the differentiation of human MSCs with or without cell–cell contact. Fluorescent labeling of the stem cell population and high-speed cell sorting after coculture with cell–cell contact allowed examination of individual cell populations. Real-time quantitative polymerase chain reaction showed significant increases in NP marker genes in stem cells when cells were cocultured with contact for 7 days, and this change was regulated by cell ratio. No significant change in NP marker gene expression in either NP cells or stem cells was observed when cells were cultured without contact, regardless of cell ratio. Thus, we have shown that human NP and MSC coculture with contact is a viable method for generating a large population of differentiated cells that could be used in cell-based tissue engineering therapies for regeneration of the degenerate intervertebral disc.
Human Umbilical Cord Matrix Stem Cells: Preliminary Characterization and Effect of Transplantation in a Rodent Model of Parkinson's Disease
Authors: Weiss Mark L. , Medicetty Satish , Bledsoe Amber R. , Rachakatla Raja Shekar , Choi Michael , Merchav Shosh , Luo Yongquan , Rao Mahendra S. , Velagaleti Gopalrao , Troyer Deryl
Published: October 2005

The umbilical cord contains an inexhaustible, noncontroversial source of stem cells for therapy. In the U.S., stem cells found in the umbilical cord are routinely placed into bio-hazardous waste after birth. Here, stem cells derived from human umbilical cord Wharton's Jelly, called umbilical cord matrix stem (UCMS) cells, are characterized. UCMS cells have several properties that make them of interest as a source of cells for therapeutic use. For example, they 1) can be isolated in large numbers, 2) are negative for CD34 and CD45, 3) grow robustly and can be frozen/thawed, 4) can be clonally expanded, and 5) can easily be engineered to express exogenous proteins. UCMS cells have genetic and surface markers of mesenchymal stem cells (positive for CD10, CD13, CD29, CD44, and CD90 and negative for CD14, CD33, CD56, CD31, CD34, CD45, and HLA-DR) and appear to be stable in terms of their surface marker expression in early passage (passages 4–8). Unlike traditional mesenchymal stem cells derived from adult bone marrow stromal cells, small populations of UCMS cells express endoglin (SH2, CD105) and CD49e at passage 8. UCMS cells express growth factors and angiogenic factors, suggesting that they may be used to treat neurodegenerative disease. To test the therapeutic value of UCMS cells, undifferentiated human UCMS cells were transplanted into the brains of hemiparkinsonian rats that were not immune-suppressed. UCMS cells ameliorated apomorphine-induced rotations in the pilot test. UCMS cells transplanted into normal rats did not produce brain tumors, rotational behavior, or a frank host immune rejection response. In summary, the umbilical cord matrix appears to be a rich, noncontroversial, and inexhaustible source of primitive mesenchymal stem cells.
Transport phenomena in a catalytic monolith: Effect of the superficial reaction
Authors: Di Benedetto A. , Marra F. S. , Donsi F. , Russo G.
Published: October 2005

The effect of a fast exothermic surface reaction on the fluid flow and on heat transfer between bulk gas phase, and the catalytic wall in a monolithic reactor has been studied by means of a 2‐D mathematical model. The radial profiles of temperature, concentration, and velocity in the ignition region show that the perturbation induced by the reaction is qualitatively comparable to the entrance effects. From the standpoint of heat transfer efficiency the channel may be divided into two zones, the first dominated by the entrance effects and the second dominated by the reaction effects. In the first zone the interphase heat transfer resembles the constant wall heat flux (NuH), while after ignition resembles the constant wall temperature (NuT) only once the perturbation generated by the reaction ignition has extinguished. It is, hence, showed that the Nu number may be calculated as the interpolation between NuH, and a modified Nusselt number Nuad, which is defined as a function of the difference between the adiabatic temperature and gas bulk temperature rather than wall‐gas temperature difference. It is anchored to the ignition location, depends on the operating and kinetic parameters and asymptotically tends to NuT. © 2005 American Institute of Chemical Engineers AIChE J, 2006
Supramolekulare Ansätze zur Erzeugung von Bibliotheken zweizähniger Chelatliganden für die homogene Katalyse
Authors: Breit Bernhard
Published: October 2005

Die kombinatorische Katalysatorentwicklung und ‐optimierung leidet bislang an der schlechten Zugänglichkeit strukturell diverser Ligandenbibliotheken, vor allem für die Klasse der strukturell komplexeren Chelatliganden. Ein völlig neuer Ansatz umgeht das Problem der schwierigen Ligandensynthese durch die Selbstorganisation von strukturell einfacheren einzähnigen Liganden zu zweizähnigen Liganden durch anziehende nichtkovalente Ligand‐Ligand‐Wechselwirkungen. Bei Verwendung komplementärer Ligand‐Ligand‐Bindungsmotive führt schon einfaches Mischen von jeweils zwei unterschiedlichen einzähnigen Liganden zum Aufbau von Bibliotheken definierter Chelatligand‐Katalysatoren. Dieser Kurzaufsatz fasst die ersten Ansätze und Ergebnisse in diesem vielversprechenden Forschungsgebiet der homogenen Katalyse zusammen.
Titelbild: The Design and Evaluation of Heparin‐Binding Foldamers (Angew. Chem. 41/2005)
Authors: Choi Sungwook , Clements Dylan J. , Pophristic Vojislava , Ivanov Ivaylo , Vemparala Satyavani , Bennett Joel S. , Klein Michael L. , Winkler Jeffrey D. , DeGrado William F.
Published: October 2005

Kleine Inhibitoren für niedermolekulares Heparin sind mithilfe von Moleküldynamikrechnungen entworfene kurze Arylamidfoldamere. Das Titelbild zeigt, dass vor allem elektrostatische Wechselwirkungen zwischen einer Pentasaccharidsequenz von Heparin und dem Antagonisten für die Bindung wichtig sind. W F. DeGrado et al. schildern in ihrer Zuschrift auf S. 6843 ff., dass die Wechselwirkungen von Heparin mit einer Vielzahl an Proteinen, darunter Antithrombin II und Faktor Xa, durch diesen Antagonisten unterbunden werden.
Supramolecular Approaches to Generate Libraries of Chelating Bidentate Ligands for Homogeneous Catalysis
Authors: Breit Bernhard
Published: October 2005

The process of catalyst discovery and development relying on combinatorial methods has suffered so far from the difficult access to structurally diverse and large libraries of ligands, in particular the structurally more complex class of bidentate ligands. A completely new approach to streamline the difficult ligand synthesis process is to use structurally less complex monodentate ligands that self‐assemble in the coordination sphere of a metal center through noncovalent attractive ligand–ligand interactions to generate bidentate, chelating ligands. When complementary attractive ligand–ligand interactions are employed, it is even possible to generate libraries of defined chelate–ligand catalysts by simply mixing two different monomeric ligands. This Minireview summarizes the first approaches and results in this new field of combinatorial homogeneous catalysis.
Improvement of a gram‐scale mixer for polymer blending
Authors: Yang Bin , Sato Misaki , Kuriyama Takashi , Inoue Takashi
Published: October 2005

A small‐scale mixer designed by Bryce Maxwell is commercialized by Custom Scientific Instruments, Inc. under the name of MINI‐MAX Molder. It is very useful for the study of polymer blends, especially when the available amount of polymer specimen is limited, for example, less than a few grams. However, it gives essentially shear flow and suffers from poor distribution and dispersion capabilities in comparison with large scale extruder and internal mixers. We propose here an improvement of the mixing and dispersing capabilities of the Maxwell small‐scale mixer by the addition of Teflon disk and steel balls together with the mixed materials. When polypropylene and high impact polystyrene were mixed at 70/30 wt. ratio at 180°C without the disk and balls, the high impact polystyrene particle size (D) was 6.27 μm. A finer dispersion (D = 1.44 μm) was achieved by the introduction of one Teflon disk at the center of mixing cup and three steel balls. Furthermore, with increasing the number of steel balls from three to seven, and with using different sizes of balls, much finer dispersions were achieved (D = 0.58 μm and 0.47 μm). This may be caused by: (1) the addition of Teflon disk eliminates the low shear regions in the mixing cavity, and (2) the addition of steel balls induces asymmetric circulation of the materials, some changes in the flow lines going from the center to the border or from the top to the bottom, some reorientation of the materials, and higher shear fields. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1–5, 2006
Novel polyether polyurethane/clay nanocomposites synthesized with organicly modified montmorillonite as chain extenders
Authors: Ni Ping , Wang Quanlin , Li Jing , Suo Jishuan , Li Shuben
Published: October 2005

A kind of novel polyether polyurethane (PU)/clay nanocomposite was synthesized using poly(tetramethylene glycol), 4,4′‐diphenylmethane diisocyanate (MDI), 1,6‐hexamethylenediamine, and modified Na+‐montmorillonite (MMT). Here, organicly modified MMT (O‐MMT) was formed by applying 1,6‐hexamethylenediamine as a swelling agent to treat the Na+‐MMT. The X‐ray analysis showed that exfoliation occurred for the higher O‐MMT content (40 wt %) in the polymer matrix. The mechanical analysis indicated that, when the O‐MMT was used as a chain extender to replace a part of the 1,2‐diaminopropane to form PU/clay nanocomposites, the strength and strain at break of the polymer was enhanced when increasing the content of O‐MMT in the matrix. When the O‐MMT content reached about 5%, the tensile strength and elongation at break were over 2 times that of the pure PU. The thermal stability and the glass transition of the O‐MMT/PU nanocomposites also increased with increasing O‐MMT content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 6–13, 2006
Thermal decomposition behaviors of PVP coated on platinum nanoparticles
Authors: Du Y. K. , Yang P. , Mou Z. G. , Hua N. P. , Jiang L.
Published: October 2005

TG‐DTA, TEM, and IR were used to investigate the thermal decomposition behavior of poly(N‐vinyl‐2‐pyrrolidone) (PVP). The TG‐DTA results show that the thermal decomposition behavior of PVP on platinum (Pt) is quite different from that of pure PVP. For pure PVP, 95.25% is decomposed when the temperature is increased up to 500°C; while under the same experimental condition, PVP coated on the Pt nanoparticles is only 66.7% decomposed. This is further supported by IR measurement. TEM results exhibited that the partially decomposed PVP still plays a role in stabilizing Pt nanoparticles: after heating treatment at 500°C for half an hour, the platinum nanoparticles did not aggregate heavily. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 23–26, 2006
Stress failure of airborne optical assembly resulting from rigid, high modulus epoxy adhesive and quality improvements
Authors: Xiao Jun , Li Hong‐Su , Lu Xin , Meng Jian‐Qi
Published: October 2005

Up to 40% failure odds on an airborne optical assembly were found during finalizing the design‐production phase. It resulted in lens splitting, cracking, and shattering. The combined stress of residual stress originated from solidification shrinkage and deformation stress and from temperature changes that drastically caused the failures. The optical assembly was composed of aluminum shell, rigid epoxy adhesive layer, and glass lens. Mechanism and affecting factors of the failure were investigated on process, operation, and materials. A series of comparative trail experiments were carried out. It was recommended to prevent the failures by redesigning match clearance between duralumin wall and lens, replacing rigid epoxy adhesive with flexible polyurethane adhesive. Via these new measures, all optical assemblies made hereafter succeeded and passed all military environmental tests and inspections, with a zero percent failure odds. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 45–51, 2006
Initiator effects in reactive extrusion of starch–polyacrylamide graft copolymers
Authors: Willett J. L. , Finkenstadt V. L.
Published: October 2005

Starch–polyacrylamide (PAAm) graft copolymers were prepared by reactive extrusion using ammonium persulfate (APS), ceric ammonium nitrate (CAN), or ferrous ammonium sulfate/hydrogen peroxide (FAS/H2O2) as initiator. The initiator contents, measured as anhydroglucose units per initiator radical (AGU/I), ranged from 70 to 280 AGU/I for CAN and FAS and 70 to 1140 for APS. CAN was not an effective initiator, giving low conversions, low graft content, low grafting efficiencies, and no detectable high molecular weight PAAm. FAS/H2O2 gave conversions of approximately 80%, graft efficiencies of approximately 50%, and PAAm molecular weights from 75,000 to 357,000, depending on the initiator content and starch/AAm ratio. APS gave conversions exceeding 90% with graft efficiencies of approximately 75%. PAAm molecular weights with APS were 575,000 and higher. As the AGU/I ratio increased above 280 for APS, the conversion and graft content decreased whereas the graft efficiency was essentially constant. Initiation with APS gave fewer PAAm grafts of higher molecular weight compared to FAS/H2O2. Published 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 52–58, 2006
Nature of compounds formed in phase of strongly basic anion exchanger in contact with Fe2(SO4)3 solutions
Authors: Gutsanu V. , Gafiichuk V. , Shofransky V. , Turta C.
Published: October 2005

The thermochemical changes taking place in the phase of a Fe(III)‐containing strongly basic anion exchanger (AV‐17) are investigated by using Mössbauer, IR, and EPR spectroscopy. During the heating of Fe(III)‐containing resin in air up to 200°C, redox processes in the polymer phase take place. On boiling in water, the jarosite‐type compounds in the polymer are converted into higher dispersed β‐FeOOH particles. After sorption–boiling in water cycles in the polymer phase, relatively massive and magnetically ordered β‐FeOOH particles are formed. A portion of the β‐FeOOH particles remains in the highly dispersed superparamagnetic state distributed in the narrow pores of the exchanger. It is suggested that the Fe(III) ion sorption from Fe2(SO4)3 solutions by an exchanger takes place through the formation in the polymer phase of solid ultrafine particles of jarosite mineral‐type compounds. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 59–64, 2006
Copolymers of aniline and o‐methoxyaniline: Synthesis and characterization
Authors: Mokreva Pavlina , Tsocheva Dimitrinka , Ivanova Galya , Terlemezyan Levon
Published: October 2005

High‐conversion (HC) copolymers of aniline and o‐methoxyaniline (o‐anizidine) were synthesized for the first time by chemical oxidative copolymerization using various polymerization techniques (simultaneous or consecutive introduction of comonomers into the polymerizing system). Low‐conversion (LC) copolymers have also been synthesized for comparison. The polymers obtained were characterized using 1H‐NMR, infrared, and electronic absorption spectroscopy, differential scanning calorimetry, and electrical conductivity measurements. Solubility characteristics and composition of different fractions of the copolymers were also determined. It was shown that in contrast to the LC copolymers, HC copolymers reveal relatively poor solubility. Electrical conductivity of copolymers and also of o‐methoxyaniline homopolymer is lower compared to polyaniline, which correlates with notable hypsochromic (blue) shift of the bands in electronic absorption spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 75–81, 2006
Structural effect of photoinitiators on electro‐optical properties of polymer‐dispersed liquid crystal composite films
Authors: Seok Jae‐Wook , Han Yoon Soo , Kwon Younghwan , Park Lee Soon
Published: October 2005

Two types of photoinitiators were synthesized: (1) a α,ω‐telechelic oligomeric photoinitiator, by the reaction of poly(propylene glycol) diglycidylether (PPGDGE) and 2‐hydroxy‐2‐methyl‐1‐phenyl‐propan‐1‐one (Darocur 1173), and (2) a polymeric photoinitiator, by copolymerization of a monomer that had a liquid crystalline property, 4‐[ω‐(2‐methylpropenoyloxy)decanoxy]‐4′‐cyanobiphenyl, with a vinyl monomer that had a photosensitive group. For comparison, low‐molecular‐weight (low‐MW) photoinitiator (Darocur 1173) also was used. Attention was directed to the structural effect of the photoinitiators on the electro‐optical properties of polymer‐dispersed liquid crystal (PDLC) film in which the LC phase occupied a major volume (80 wt % of the composite film). For the preparation of PDLC films by the polymerization‐induced phase separation method, the optimum UV‐curing temperature was observed at 50°C, a temperature slightly higher than the cloud temperature (Tcloud) of the low‐MW LC/matrix‐forming material mixture. It was found that the electro‐optical performance of the PDLC cell fabricated with the oligomeric or polymeric photoinitiator was better than that of the PDLC cell made with a low‐MW photoinitiator (Darocur 1173), exhibiting lower driving voltage (V90) and higher contrast ratio under identical formulation conditions. Oligomeric photoinitiators allowed premature phase separation between the LC and matrix phases, resulting in relatively pure LC‐rich phases. For the polymeric photoinitiator, incorporation of mesogenic moieties into the photoinitiator resulted in not only a well‐defined LC/matrix morphology but also in low driving voltage (V90) because of reduced friction at the LC/matrix interfaces. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 162–169, 2006
Chemical components and properties of core–shell acrylate latex containing fluorine in the shell and their films
Authors: Chen Yanjun , Cheng Shiyuan , Wang Yifeng , Zhang Chaocan
Published: October 2005

Core–shell acrylate latices containing fluorine in the shell were prepared by semicontinuous emulsion polymerization. The chemical components of the latices were determined by Fourier transform infrared, ion‐selective electrode analysis, and differential scanning calorimetry. The average size and morphology of the latex particles were characterized by photocorrelation spectroscopy and transmission electron microscopy, respectively. The latex particles were mainly composed of a non‐fluorine core and a fluorinated shell. The dynamic water contact angles of the latex films from the Wilhelmy method indicated that the latex films containing fluorine in the shell could be wetted by water only with difficulty. The amount of the fluoromonomer played an important role in the modification on the water contact angles, water absorption, and thermal stability of the latex films. In comparison with a random structure, the core–shell structure was more effective for improving the thermal properties of the latex films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 107–114, 2006
Mechanical properties and blend compatibility of natural rubber –chlorosulfonated polyethylene blends
Authors: Tanrattanakul Varaporn , Petchkaew Anida
Published: October 2005

Natural rubber (NR) was blended with chlorosulfonated polyethylene (CSM) with various formulation and blend ratios (NR/CSM: 80/20 –20/80, wt/wt). Rubber blends were prepared by using a two‐roll mill and vulcanized in a compression mold to obtain the 2 mm‐thick sheets. Tensile properties, tear resistance, thermal aging resistance, ozone resistance, and oil resistance were determined according to ASTM. Compatible NR/CSM blends are derived from certain blends containing 20–30% CSM without adding any compatibilizing agent. Tensile and tear strength of NR‐rich blends for certain formulations show positive deviation from the rule of mixture. Thermal aging resistance depends on formulation and blend ratio, while ozone and oil resistance of the blends increase with CSM content. Homogenizing agents used were Stuktol®60NS and Epoxyprene®25. Stuktol®60NS tends to decrease the mechanical properties of the blends and shows no significant effect on blend morphology. Addition of 5–10 phr of epoxidized natural rubber (ENR, Epoxyprene® 25) increases tensile strength, thermal aging resistance, and ozone resistance of the blends. It is found that ENR acts as a compatibilizer of the NR/CSM blends by decreasing both CSM particle size diameter and α transition temperature of CSM. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 127–140, 2006
Modeling the factors affecting individuals' use of community networks: A theoretical explanation of community‐based information and communication technology use
Authors: Kwon Nahyun , Onwuegbuzie Anthony J.
Published: October 2005

Understanding users' attitudes and perceptions and their influence on behavior is crucial to predict the use of community information and communication technology. In this study, the authors attempt to uncover this process by elaborating on I. Ajzen's (1985,1991) theory of planned behavior (TPB), a widely applied social behavior model. The developed structural equation model (SEM) was tested using a sample of 417 users of a community network. The final selected model, which was called thecommunity network use model, included seven predictors of use: three behavioral beliefs (i.e., Learning, Social Interactions, and Community Connection), Normative Beliefs Individuals, Attitude, Subjective Norm, and Intention. In particular, Intention moderated the relationships between Use and the other six variables. Further, beliefs in both Community Connection and Social Interactions were directly related to community network use, as was Attitude. Belief in Community Connection was indirectly and positively related to community network use via Intention; Belief in Community Connection was directly and negatively related to Use. These latter two findings suggest that Belief in Community Connection serves as both a facilitator and inhibitor of community network use depending on whether belief is followed by intention. Implications are discussed.