bluuebunny/crossref_metadata_2025 huggingface dataset:
The Ligand Effect: CO Desorption from Pt/Ru Catalysts
Authors: Davies J. C. , Bonde J. , Logadóttir Á. , Nørskov J. K. , Chorkendorff I.
Published: December 2005

Density Functional Theory (DFT) calculations of the adsorption energy of CO, for a platinum overlayer on Ru(0001), have been performed. For all coverages a significant reduction in the binding energy of up to 0.5 eV has been observed compared to that obtained on Pt(111). In addition, a Steady‐State Isotopic Transient Kinetic Analysis (SSITKA) study has been performed to determine the desorption rate dependence on the partial pressure of CO over commercial Pt/Ru electrocatalysts. As expected, no significant difference in the rate of exchange of CO at any given pressure is observed on going from Pt to Pt/Ru electrocatalysts when the diluted gas used was argon since the CO states will be filled to the same desorption energy for the two catalysts. However on changing the diluent gas to hydrogen, a reduction in the exchange rate for CO is observed clearly reflecting the lower CO binding energy and the increased competition for sites at the surface of the catalyst. The reduction efficiency of the Pt/Ru electrocatalyst was also studied and found to be highly dependent on whether CO or hydrogen was used. These results will be discussed with reference to the anode catalysis of the Polymer Electrolyte Membrane Fuel Cell (PEMFC).
Intensity‐modulated radiation therapy in head and neck cancers: An update
Authors: Lee Nancy , Puri Dev R. , Blanco Angel I. , Chao K. S. Clifford
Published: December 2005

Intensity‐modulated radiation therapy (IMRT), an advent of three‐dimensional conformal radiotherapy (3D CRT), has excited the profession of radiation oncology more than any other new invention since the introduction of the linear accelerator. Approximately 1000 articles have been published on this topic to date, more than 200 of which focus on head and neck cancer. IMRT is based on computer‐optimized treatment planning and a computer‐controlled treatment delivery system. The computer‐driven technology generates dose distributions that sharply conform to the tumor target while minimizing the dose delivered to the surrounding normal tissues. The high dose volume that tailors to the 3D configuration of the tumor along with the ability to spare the nearby normal tissues allows the option of tumor dose escalation.

The head and neck region is an ideal target for this new technology for several reasons. First, IMRT offers the potential for improved tumor control through delivery of high doses to the target volume. Second, because of sharp dose gradients, IMRT results in the relative sparing of normal structures, such as the parotid glands, in the head and neck region. Third, organ motion is virtually absent in the head and neck region so, with proper immobilization, treatment can be accurately delivered. Although this is a relatively new technology, single‐institution retrospective studies show better dosimetric profiles compared with conventional radiation techniques, as well as excellent clinical results. Salivary gland sparing using IMRT has also resulted in reduced incidence and severity of xerostomia, and this has been tested in a randomized trial against conventional radiotherapy for early‐stage nasopharyngeal cancer. The results do confirm that IMRT does decrease xerostomia compared with conventional radiotherapy. © 2005 Wiley Periodicals, Inc. Head Neck 27: XXX–XXX, 2005
Ventral hippocampal muscimol disrupts context‐specific fear memory retrieval after extinction in rats
Authors: Hobin Jennifer A. , Ji Jinzhao , Maren Stephen
Published: December 2005

Research aimed at understanding Pavlovian fear memory extinction has yielded considerable insight into the conditions under which fear memories may become inhibited. After extinction, Pavlovian fear memory retrieval is context‐specific. Fear memories are not expressed in the extinction context, but they are expressed in every other context. Research indicates that the dorsal hippocampus mediates the context‐specific expression of fear memory, but the role of the ventral hippocampus in mediating this process is unknown. Insofar as the ventral hippocampus is involved in the acquisition and expression of both context and tone fear, we asked whether GABA systems in the ventral hippocampus mediate context‐specific fear memory retrieval after extinction. Experiment 1 showed that ventral hippocampal inactivation with muscimol disrupted context‐specific fear memory retrieval. Experiment 2 showed that rats infused with muscimol can discriminate a context in which they were shocked from a neutral context. Nonetheless, they do appear to have a mild impairment in this task. Experiment 3 showed that ventral hippocampal muscimol did not disrupt locomotor activity, but did result in a slight increase in freezing and grooming, an effect that cannot explain the context‐specific retrieval deficit demonstrated in experiment 1. These data are consistent with a role for the ventral hippocampus in mediating context‐specific fear memory retrieval. © 2005 Wiley‐Liss, Inc.
Characterization of a faster resorbing polymer after real time aging
Authors: McManus Anastasia J. , Moser Rodney C. , Thomas Kevin A.
Published: December 2005

This study evaluated the in vitro strength retention and polymer characteristics of specimens made from commercially available 85:15 poly(D,L‐lactide‐co‐glycolide). Test samples included dogbone tensile specimens with a nominal thickness of either 0.75 and 1.0 mm, which were machined from compression‐molded sheets, and screws with a major diameter of 2.71 mm and minor diameter of 2.14 mm, which were manufactured by injection molding. All samples were sterilized by e‐beam irradiation prior to in vitro aging following a standard methodology. Mechanical testing and polymer analysis were performed at time zero and weekly up to 15 weeks of real time aging. The time zero maximum tensile strength of the 0.75 mm dogbone specimens averaged 55.86 ± 0.72 MPa. The 1.0‐mm dogbone specimens tested at time zero had an average maximum tensile strength of 34.55 ± 0.36 MPa. The 0.75‐mm and 1.0‐mm thick dogbone specimens exhibited a controlled decrease in their tensile strength. The initial shear strength of the injection‐molded screws was 32.86 ± 4.15 MPa. After 3 weeks of real time in vitro aging, the screws maintained approximately 70% of their initial (time zero) strength. The inherent viscosity and molecular weight (Mw) at time zero averaged approximately 0.9 dL/g and 98,000 g/mol respectively, and decreased at similar rates for both dogbones and screws. These results demonstrate a controlled, rapid degradation in the mechanical properties of 85:15 poly(D,L‐lactide‐co‐glycolide) material, with sufficient strength for pediatric craniofacial applications. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006
Effects of applied voltages on hydroxyapatite coating of titanium by electrophoretic deposition
Authors: Meng Xianwei , Kwon Tae‐Yub , Yang Yunzhi , Ong Joo L. , Kim Kyo‐Han
Published: December 2005

Hydroxyapatite (HA) coatings were deposited on titanium substrates by electrophoretic deposition (EPD) at constant voltage and dynamic voltage, respectively. Various surface morphologies were observed under different type of voltages. Under a constant voltage of 20 V, a dense HA coating could be prepared. Under a constant voltage of 200 V, big HA particles were deposited and the coating was porous. Under a dynamic voltage, a continuous gradient HA coating could be obtained. HA coatings were characterized with a field emission‐scanning electron microscopy (FE‐SEM) and an X‐ray diffraction (XRD). XRD indicated no significant HA decomposition when the coatings were sintered for 2 h at 800°C. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006
Using internal and collective variables in Monte Carlo simulations of nucleic acid structures: Chain breakage/closure algorithm and associated Jacobians
Authors: Sklenar Heinz , Wüstner Daniel , Rohs Remo
Published: December 2005

This article describes a method for solving the geometric closure problem for simplified models of nucleic acid structures by using the constant bond lengths approximation. The resulting chain breakage/closure equations, formulated in the space of variable torsion and bond angles, are easy to solve, and have only two solutions. The analytical simplicity is in contrast with the high complexity of the closure problem in the torsion angle space with at most 16 solutions, which has been dealt with by several authors and was solved analytically by Wu and Deem (J. Chem. Phys. 1999, 111, 6625). The discussion on the choice of variables and associated Jacobians is focussed on the question of how conformational equilibration is affected in Monte Carlo simulations of molecular systems. In addition to the closure of the phosphate backbone, it is necessary to also solve the closure problem for the five‐membered flexible furanose sugar ring. Explicit closure equations and the resulting Jacobians are given both for the complete four‐variable model of the furanose ring and simulations in the phase‐amplitude space of the five‐membered ring, which are based on the approximate two‐variable model of furanose introduced by Gabb et al. (J. Comput. Chem. 1995, 16, 667). The suggested closure algorithm can be combined with collective variables defined by translations and rotations of the monomeric nucleotide units. In comparison with simple internal coordinate moves, the resulting concerted moves describe local structural changes that have high acceptance rates and enable fast conformational equilibration. Appropriate molecular models are put forward for prospective Monte Carlo simulations of nucleic acids, but can be easily adapted to other biomolecular systems, such as proteins and lipid structures in biological membranes. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 309–315, 2006
On the acyclic choosability of graphs
Authors: Montassier Mickaël , Ochem Pascal , Raspaud André
Published: December 2005

A proper vertex coloring of a graph G =  (V,E) is acyclic if G contains no bicolored cycle. A graph G is L‐list colorable if for a given list assignment L = {L(v): v ∈ V}, there exists a proper coloring c of G such that c (v) ∈ L(v) for all v ∈ V. If G is L‐list colorable for every list assignment with |L (v)| ≥ k for all v ∈ V, then G is said k‐choosable. A graph is said to be acyclically k‐choosable if the obtained coloring is acyclic. In this paper, we study the links between acyclic k‐choosability of G and Mad(G) defined as the maximum average degree of the subgraphs of G and give some observations about the relationship between acyclic coloring, choosability, and acyclic choosability. © 2005 Wiley Periodicals, Inc. J Graph Theory 51: 281–300, 2006
Palaeoindian occupation of the Atacama Desert, northern Chile
Authors: Grosjean Martin , Núñez Lautaro , Cartajena Isabel
Published: December 2005

Palaeoindian occupation of the Atacama Desert in northern Chile has been found between 12 600 and 10 200 cal. yr BP. The new site at Salar Punta Negra (24°28′S/60°53′W/2976 m) includes about 1000 classifiable, mostly unifacial artefacts and, uniquely, three different diagnostic types of early projectile points. Two of the Lateglacial/early Holocene projectile types have wide distribution and are known from different geographical areas in South America: the Palaeoindian ‘Fell’ fish‐tail point mainly from the southern cone of South America, and the triangular ‘Tuina’ points typical of the Puna of the south‐central Andes in northern Chile and northwestern Argentina. In addition, we found a third type, a stemmed point typical for the Salar Punta Negra. Filling a large geographical gap of ‘Fell’ occupation, the site at Salar Punta Negra provides evidence for generally much higher mobility and diversity of early cultures, and supports an Andean‐Pacific route for early human exploration of South America to the south through the desert at intermediate altitudes. Contemporaneous high‐amplitude climatic changes were fundamental preconditions to provide adequate environments and habitats, and to make Palaeoindian hunting‐gathering occupation possible in the Atacama Desert. Copyright © 2005 John Wiley & Sons, Ltd.
A 17 000‐year history of Andean climate and vegetation change from Laguna de Chochos, Peru
Authors: Bush Mark B. , Hansen Barbara C. S. , Rodbell Donald T. , Seltzer Geoffrey O. , Young Kenneth R. , León Blanca , Abbott Mark B. , Silman Miles R. , Gosling William D.
Published: December 2005

The manifestation of major climatic events such as the timing of deglaciation and whether, or not, the Younger Dryas affected Andean systems has garnered considerable recent attention. Even the Holocene is rapidly emerging as a time of considerable interest in Neotropical palaeoclimatology and palaeoecology. The Holocene of the Neotropics is now revealed as a time of some temperature change with precipitation:evaporation ratios fluctuating markedly. Major changes in lake level, ice‐accumulation, and vegetation are indicative of changes both in precipitation and temperature regimes. Although global‐scale forcing mechanisms may underlie some of these changes, e.g. the precessional rhythm, other variability appears to be localised. In a record from near the upper forest limit of the eastern Peruvian Andes, pollen, charcoal, and sedimentary data suggest that the deglaciational period from ca. 17 000 to ca. 11 500 cal. yr BP was a period of rapid climatic oscillations, set against an overall trend of warming. A warm‐dry event is evident between ca. 9500 and ca. 7300 cal. yr BP, and comparisons with other regional archives suggest that it was regional in scale. A ca. 1500‐yr periodicity in the magnetic susceptibility data is evident between 12 000 and 6000 cal. yr BP, reaching a peak intensity during the dry event. A weaker oscillation with a 500–600‐yr periodicity is present throughout much of the Holocene. The uppermost sample of the pollen analysis reveals deforestation as modern human land use simplified the landscape. Copyright © 2005 John Wiley & Sons, Ltd.
Holocene hydrologic variation at Lake Titicaca, Bolivia/Peru, and its relationship to North Atlantic climate variation
Authors: Baker P. A. , Fritz S. C. , Garland J. , Ekdahl E.
Published: December 2005

A growing number of sites in the Northern Hemisphere show centennial‐ to millennial‐scale climate variation that has been correlated with change in solar variability or with change in North Atlantic circulation. However, it is unclear how (or whether) these oscillations in the climate system are manifest in the Southern Hemisphere because of a lack of sites with suitably high sampling resolution. In this paper, we reconstruct the lake‐level history of Lake Titicaca, using the carbon isotopic content of sedimentary organic matter, to evaluate centennial‐ to millennial‐scale precipitation variation and its phasing relative to sites in the Northern Hemisphere. The pattern and timing of lake‐level change in Lake Titicaca is similar to the ice‐rafted debris record of Holocene Bond events, demonstrating a possible coupling between precipitation variation on the Altiplano and North Atlantic sea‐surface temperatures (SSTs). The cold periods of the Holocene Bond events correspond with periods of increased precipitation on the Altiplano. Holocene precipitation variability on the Altiplano is anti‐phased with respect to precipitation in the Northern Hemisphere monsoon region. More generally, the tropical Andes underwent large changes in precipitation on centennial‐to‐millennial timescales during the Holocene. Copyright © 2005 John Wiley & Sons, Ltd.
Palaeohydrology of Laguna de Tagua Tagua (34° 30′ S) and moisture fluctuations in Central Chile for the last 46 000 yr
Authors: Valero‐Garcés Blas L. , Jenny Bettina , Rondanelli Mauricio , Delgado‐Huertas Antonio , Burns Stephen J. , Veit Heinz , Moreno Ana
Published: December 2005

Central Chile (32–35° S) lies at the northern border of the strong influence of the westerly circulation belt and thus exhibits a steep rainfall gradient. A new core from Laguna de Tagua Tagua (34° 30′ S) provides a sedimentologic, geochemical and palynological record of regional hydrologic balance for the last 46 000 cal. yr BP. According to our age model, relatively humid conditions occurred during glacial times before 43 500 cal. yr BP and from 40 000 to 21 500 cal. yr BP. Reduced moisture conditions and likely lower temperatures occurred from 42 400–40 100 cal. yr BP. Higher lake levels, and pollen assemblages with Valdivian rainforest taxa, imply much higher precipitation during glacial times (40 100–21 000 cal. yr BP) compared to today and, therefore, enhanced westerly activity in northern Central Chile. Afterwards, the general decrease in moisture was punctuated by two abrupt arid periods at 21 000–19 500 cal. yr BP and 17 000–15 000 cal. yr BP, and two more humid intervals: 19 500–17 000 (almost coincident with the global Last Glacial Maximum, LGM) and 13 500–11 500 cal. yr BP. The early and mid‐Holocene were the most arid periods in Central Chile for the studied time interval. Millennial‐scale palaeohydrological reconstructions from Tagua Tagua are consistent with regional climatic records. Copyright © 2005 John Wiley & Sons, Ltd.
Perception of casinos as disruptive influences in USA communities
Authors: Stitt B. Grant , Nichols Mark , Giacopassi David
Published: December 2005

Casino gambling has been adopted by many communities as a means of increasing tourism and tax revenue. Casinos, however, are a controversial tourism development strategy. The present paper uses social exchange theory to examine the effects of casinos in eight communities that have had casino gambling for at least 4 years. Residents were asked to comment on possible disruptive influences that could be tied to casino presence. These disruptive influences include not only serious crimes but also publicly visible nuisance crimes such as drinking in public, vandalism and prostitution. Also assessed are such factors as perceived increases or decreases in physical decay of the communities, presence of litter on streets and sidewalks, homelessness, traffic congestion, and prevalence of divorce, suicide and bankruptcy. The majority of respondents do not perceive significant changes in most disruptive influences. However, findings vary significantly by community, by type of disruptive influence, and by whether the respondent was a gambler or non‐gambler. The results of this analysis should be of interest to communities considering casino gambling as a new tourist attraction. Copyright © 2005 John Wiley & Sons, Ltd.
Seasonality research: the state of the art
Authors: Koenig‐Lewis Nicole , Bischoff Eberhard E.
Published: December 2005

The paper reviews progress in the area of tourism seasonality research and is intended as a guide to the literature. The emphasis is on recent advances in this field. Amongst the various aspects considered are the definitions of seasonality, its causes and impacts, policy‐related issues, studies into consumer behaviour and approaches to measuring seasonality. The paper concludes that considerable gaps still exist in published research in this area and it argues that the field lacks a sound theoretical framework. It also suggests that adopting a more exacting quantitative perspective might facilitate and accelerate progress. Copyright © 2005 John Wiley & Sons, Ltd.
An analysis of the environmental reporting structures of selected European airlines
Authors: Chan Wilco W. , Mak Barry
Published: December 2005

This article draws on a survey of eight Europe based airlines' environmental reports to illustrate the status and progress of environmental reporting in the airline industry in Europe. Four major categories of components in the report are differentiated, namely recognised core components, recognised important components, recognised add‐on components and recognised developing components. The study further finds that the units used in the fuel efficiency indicator are not the same in the airlines studied and therefore benchmarking is difficult. The results also indicate that the topics pertinent to employee and community involvement exceed the technical data of discharge and compliance‐based environmental performance in their environmental policy statements. In addition, some new features of environmental reporting are identified. Copyright © 2005 John Wiley & Sons, Ltd.
Fixed tree games with multilocated players
Authors: Miquel S. , van Velzen B. , Hamers H. , Norde H.
Published: December 2005

This article introduces fixed tree games with multilocated players (FMP games), which are a generalization of standard fixed tree games. This generalization consists of allowing players to be located in more than one vertex. As a consequence, these players can choose among several ways of connection to the root. In this article we show that FMP games are balanced. Moreover, we prove that the core of an FMP game coincides with the core of a related submodular standard fixed tree game. We show how to find the nucleolus and we characterize the orders that provide marginal vectors in the core of an FMP game. Finally, we study the Shapley value and the average of the extreme points of the core. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 47(2), 93–101 2006
The multiroute maximum flow problem revisited
Authors: Du Donglei , Chandrasekaran R.
Published: December 2005

We are given a directed network G = (V,A,u) with vertex set V, arc set A, a source vertex s ∈ V, a destination vertex t ∈ V, a finite capacity vector u = {uij}(i,j)∈A, and a positive integer m ∈ Z+. The multiroute maximum flow problem (m‐MFP) generalizes the ordinary maximum flow problem by seeking a maximum flow from s to t subject to not only the regular flow conservation constraints at the vertices (except s and t) and the flow capacity constraints at the arcs, but also the extra constraints that any flow must be routed along m arc‐disjoint s‐t paths. In this article, we devise two new combinatorial algorithms for m‐MFP. One is based on Newton's method and another is based on an augmenting‐path technique. We also show how the Newton‐based algorithm unifies two existing algorithms, and how the augmenting‐path algorithm is strongly polynomial for case m = 2. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 47(2), 81–92 2006
Incidence of catheter‐related infections within 30 days from insertion of Hickman–Broviac catheters
Authors: Castagnola Elio , Molinari Angelo Claudio , Giacchino Mareva , Chiapello Nadia , Moroni Cristina , Caviglia Ilaria , Fratino Giuseppe , Haupt Riccardo
Published: December 2005

Aim

To evaluate the incidence of surgical site infections and bacteremias occurring within 30 days from insertion of partially implanted central venous catheters.

Patients and Methods

Four hundred eighteen devices positioned in children with cancer or undergoing bone marrow transplant were followed prospectively.

Results

During a follow‐up of 12,394 catheter‐days, a total of 13 infectious episodes were documented, with an overall incidence of 3.1% and 1.05 episodes/1,000 catheter‐days. Coagulase‐negative staphylococci represented the causative pathogens of all episodes. Overall, surgical wound infections occurred in 1.4% of all catheters, with a rate of 0.48/1,000 catheter‐days, while isolated bacteremias were observed in 1.7% of all inserted devices, with a rate of 0.57/1,000 catheter‐days.

Conclusions

Infections are rare events within 30 days from insertion of partially implanted central venous catheters and coagulase‐negative staphylococci represent the most frequently isolated cause of these complications. Pediatr Blood Cancer 2007;48:35–38. © 2005 Wiley‐Liss, Inc.
Low efficacy of methotrexate in childhood acute myeloid leukemia (AML): Single‐agent therapeutic window study in relapsed AML
Authors: Kaspers G.J.L. , Reinhardt D. , Fleischhack G. , Armendariz H. , Stark B. , Zwaan C.M. , Zimmermann M. , Creutzig U.
Published: December 2005

Background

The efficacy in pediatric acute myeloid leukemia (AML) of single‐agent methotrexate (MTX) at a higher dose than previously applied, 1,000 mg/m2, given as a theoretically beneficial 36‐hr continuous infusion, is unknown, but may be beneficial based on preclinical data.

Procedure

We performed a therapeutic window study in children with first relapsed AML treated in four different countries.

Results

Based on a comparison between the percentage of leukemic blasts in the bone marrow shortly before and 7–10 days after the MTX infusion, none of the first cohort of nine patients showed a good response, defined as a reduction of blasts of at least 50%. Therefore, the study was closed, concluding that the probability of a good response in this patient‐group was most likely to be less than 30%. By that time, another four patients had been enrolled, of which one patient with a late relapsed AML FAB type M7 showed a good response. Toxicity of MTX was limited and tolerable.

Conclusions

This study shows that single‐agent MTX in the applied regimen in pediatric relapsed AML has limited efficacy. However, it also demonstrates the feasibility of an international and therapeutic window phase II study in pediatric relapsed AML. Pediatr Blood Cancer 2006; 47:539–542. © 2005 Wiley‐Liss, Inc.
Synthesis and thermoresponsive property of end‐functionalized poly(N‐isopropylacrylamide) with pyrenyl group
Authors: Duan Qian , Miura Yutaka , Narumi Atsushi , Shen Xiande , Sato Shin‐Ichiro , Satoh Toshifumi , Kakuchi Toyoji
Published: December 2005

N–Isopropylacrylamide (NIPAM) was polymerized using 1‐pyrenyl 2‐chloropropionate (PyCP) as the initiator and CuCl/tris[2‐(dimethylamino)ethyl]amine (Me6TREN) as the catalyst system. The polymerizations were performed using the feed ratio of [NIPAM]0/[PyCP]0/[CuCl]0/[Me6TREN]0 = 50/1/1/1 in DMF/water of 13/2 at 20 °C to afford an end‐functionalized poly(N‐isopropylacrylamide) with the pyrenyl group (Py–PNIPAM). The characterization of the Py–PNIPAM using matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry provided the number–average molecular weight (Mn,MS). The lower critical solution temperature (LCST) for the liquid–solid phase transition was 21.7, 24.8, 26.5, and 29.3 °C for the Py–PNIPAMs with the Mn,MS's of 3000, 3400, 4200, and 5000, respectively; hence, the LCST was dramatically lowered with the decreasing Mn,MS. The aqueous Py–PNIPAM solution below the LCST was characterized using a static laser light scattering (SLS) measurement to determine its molar mass, Mw,SLS. The aqueous solutions of the Py–PNIPAMs with the Mn,MS's of 3000, 3400, 4200, and 5000 showed the Mw,SLS of 586,000, 386,000, 223,000, and 170,000, respectively. Thus, lowering the LCST for Py–PNIPAM should be attributable to the formation of the PNIPAM aggregates. The LCST of 21.7 °C for Py–PNIPAM with the Mn,MS of 3000 was effectively raised by adding β‐cyclodextrin (β‐CD) and reached the constant value of ∼26 °C above the molar ratio of [β‐CD]/[Py–PNIPAM] = 2/1, suggesting that β‐CD formed an inclusion complex with pyrene in the chain‐end to disturb the formation of PNIPAM aggregates, thus raising the LCST. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1117–1124, 2006
Low potential electrosyntheses of free‐standing poly(dibenzofuran) films in mixed electrolytes of boron trifluoride diethyl etherate and trifluoroacetic acid
Authors: Xu Jingkun , Zhou Weiqiang , Chen Bing , Pu Shouzhi , Wang Jingwu , Wan Yiqun
Published: December 2005

Free‐standing poly(dibenzofuran) (PDBF) films were synthesized electrochemically by direct anodic oxidation of dibenzofuran in mixed electrolytes of boron trifluoride diethyl etherate (BFEE) containing certain amount of trifluoroacetic acid (TFA). The oxidation potential of dibenzofuran in pure BFEE was measured to be only 1.31 V versus saturated calomel electrode (SCE). This value was much lower than that determined in acetonitrile + 0.1 mol L−1 TBATFB (2.14 V vs. SCE). The addition of TFA to BFEE can further decrease the oxidation potential of the monomer to 1.07 V versus SCE in the mixed electrolyte of BFEE + 30% TFA. PDBF films obtained from this medium showed good electrochemical behavior, good electrochromic properties, and good thermal stability with conductivity of 100 S cm−1. FTIR and 1H NMR spectra showed that the polymer was grown mainly via the coupling of the monomer at C(3) C(10) or C(4) C(9) positions (Scheme 1). As‐formed PDBF films were partly soluble in tetrahydrofuran (THF) or chloroform. Fluorescent spectral studies indicated that either soluble or PDBF in solid state was a good blue light PDBF emitter. To the best of our knowledge, this is the first report that free‐standing PDBF films can be electrodeposited. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1125–1135, 2006
Monoaryloxo ytterbium(III) chlorides supported by β‐diketiminato ligands as novel initiators for the living ring‐opening polymerization of ε‐caprolactone
Authors: Xue Mingqiang , Sun Hongmei , Zhou Hui , Yao Yingming , Shen Qi , Zhang Yong
Published: December 2005

Ring‐opening polymerization of ε‐caprolactone (ε‐CL) was carried out using β‐diketiminato‐supported monoaryloxo ytterbium chlorides L1Yb(OAr)Cl(THF) (1) [L1 = N,N′‐bis(2,6‐dimethylphenyl)‐2,4‐pentanediiminato, OAr = 2,6‐di‐tert‐butylphenoxo‐], and L2Yb(OAr′)Cl(THF) (2) [L2 = N,N′‐bis(2,6‐diisopropylphenyl)‐2,4‐pentanediiminato, OAr′ = 2,6‐di‐tert‐butyl‐4‐methylphenoxo‐], respectively, as single‐component initiator. The influence of reaction conditions, such as polymerization temperature, polymerization time, initiator, and initiator concentration, on the monomer conversion, molecular weight, and molecular weight distribution of the resulting polymers was investigated. Complex 1 was well characterized and its crystal structure was determined. Some features and kinetic behaviors of the CL polymerization initiated by these two complexes were studied. The polymerization rate is first order with respect to monomer. The Mn of the polymer increases linearly with the increase of the polymer yield, while polydispersity remained narrow and unchanged throughout the polymerization in a broad range of temperatures from 0 to 50 °C. The results indicated that the present system has a “living character”. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1147–1152, 2006
Surface‐initiated atom transfer radical polymerization grafting of poly(2,2,2‐trifluoroethyl methacrylate) from flat silicon wafer surfaces
Authors: Chen Renxu , Feng Wei , Zhu Shiping , Botton Gianluigi , Ong Beng , Wu Yiliang
Published: December 2005

Poly(2,2,2‐trifluoroethyl methacrylate) (PTFEMA), a partially fluorinated polymer, was directly grafted from silicon wafer surfaces by a surface‐initiated atom‐transfer radical polymerization (ATRP). The polymer layer thickness increased linearly with monomer conversion and molecular weight of free polymers in solution. The thickness was mainly determined by the experimental conditions such as activator/deactivator ratio, monomer/catalyst ratio, and monomer concentration. PTFEMA layers of more than 100‐nm thick were obtained. The grafted PTFEMA chains were “living” and allowed the extension of a second block of PMMA. X‐ray photoelectron spectroscopy study showed that the chemical compositions at the surfaces agreed well with their theoretical values. A novel surface‐attachable difunctional initiator was also synthesized and applied to the grafting of PTFEMA. The grafting density was doubled using this difunctional initiator, from 0.48 to 0.86 chains/nm2. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1252–1262, 2006
Quinone transfer radical polymerization of styrene: Synthesis of the actual initiator
Authors: Debuigne Antoine , Caille Jean‐Raphaël , Jérôme Robert
Published: December 2005

ortho‐Quinones, such as phenanthrenequinone and 3,6‐dimethoxyphenanthrenequinone, added with a catalytic amount of metal complexes, impart control to styrene polymerization via the previously reported quinone transfer radical polymerization (QTRP) process. In this study, compounds that mimic the dormant species proposed in the QTRP mechanism have been synthesized and tested as initiators in the presence of cobalt(II) acetylacetonate. These compounds, and particularly 3,6‐dimethoxy‐10‐hydroxy‐10‐(1‐phenyl‐ethyl)‐phenanthren‐9‐one, are effective control agents for the radical polymerization of styrene, in agreement with the recently proposed mechanism. Moreover, the induction period, which has been systematically reported in the presence of ortho‐quinones, is no longer observed. The end capping of the polystyrene chains by the control agent has been confirmed by 1H NMR analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1233–1244, 2006
Synthesis and micellization of amphiphilic poly(sebacic anhydride)–poly(ethylene glycol)–poly(sebacic anhydride) block copolymers
Authors: Zhang Na , Guo Sheng‐Rong
Published: December 2005

Amphiphilic biodegradable block copolymers [poly(sebacic anhydride)–poly(ethylene glycol)–poly(sebacic anhydride)] were synthesized by the melt polycondensation of poly(ethylene glycol) and sebacic anhydride prepolymers. The chemical structure, crystalline nature, and phase behavior of the resulting copolymers were characterized with 1H NMR, Fourier transform infrared, gel permeation chromatography, and differential scanning calorimetry. Microphase separation of the copolymers occurred, and the crystallinity of the poly(sebacic anhydride) (PSA) blocks diminished when the sebacic anhydride unit content in the copolymer was only 21.6%. 1H NMR spectra carried out in CDCl3 and D2O were used to demonstrate the existence of hydrophobic PSA domains as the core of the micelle. In aqueous media, the copolymers formed micelles after precipitation from water‐miscible solvents. The effects on the micelle sizes due to the micelle preparation conditions, such as the organic phase, dropping rate of the polymer organic solution into the aqueous phase, and copolymer concentrations in the organic phase, were studied. There was an increase in the micelle size as the molecular weight of the PSA block was increased. The diameters of the copolymer micelles were also found to increase as the concentration of the copolymer dissolved in the organic phase was increased, and the dependence of the micelle diameters on the concentration of the copolymer varied with the copolymer composition. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1271–1278, 2006
Sulfonated poly(ether ether ketone)/poly(vinylpyrrolidone) acid–base polymer blends for direct methanol fuel cell application
Authors: Wu Han‐Lang , Ma Chen‐Chi M. , Kuan Hsu‐Chiang , Wang Chung‐Hao , Chen Chih‐Yuan , Chiang Chin‐Lung
Published: December 2005

Acid–base polymer blends for polymer electrolyte membranes have been prepared by blending sulfonated poly(ether ether ketone) (SPEEK) with poly(vinylpyrrolidone) (PVP) to reduce methanol uptake and to decrease methanol permeability while maintaining high proton conductivity. The acid‐base interaction occurring on the sulfonic acid group and on the tertiary amide group was characterized by FTIR and DMA. As the composition of PVP lowered than 20 wt % in the blends, the acid–base interaction causes great reduction on methanol uptake and the methanol permeability; however, the proton conductivity is still high. In this work, membrane–electrode assemblies (MEAs) have been prepared for direct methanol fuel cell (DMFC) from both blend membrane and Nafion 117. DMFC single cell performance was also evaluated. Results confirmed that SPEEK (with the degree of sulfonation (DS) = 69%) blended with PVP (Mn = 1,300,000) with a ratio of 80/20 (w/w) exhibits higher open‐circuit voltages (OCV) and lower polarization loss than those of Nafion 117. These acid–base blends will be suitable for DMFC application. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 565–572, 2006
PII structure in the model peptides for unfolded proteins: Studies on ubiquitin fragments and several alanine‐rich peptides containing QQQ, SSS, FFF, and VVV
Authors: Shi Zhengshuang , Chen Kang , Liu Zhigang , Sosnick Tobin R. , Kallenbach Neville R.
Published: December 2005

A great deal of attention has been paid lately to the structures in unfolded proteins due to the recent discovery of many biologically functional but natively unfolded proteins and the far‐reaching implications of order in unfolded states for protein folding. Recently, studies on oligo‐Ala, oligo‐Lys, oligo‐Asp, and oligo‐Glu, as well as oligo‐Pro, have indicated that the left‐handed polyproline II (PII) is the major local structure in these short peptides. Here, we show by NMR and CD studies that ubiquitin fragments, model unfolded peptides composed of nonrepeating amino acids, and four alanine‐rich peptides containing QQQ, SSS, FFF, and VVV sequences are all present in aqueous solution predominantly in the extended PII or β conformation. The results from this and related studies indicate that PII might be a major backbone conformation in unfolded proteins. The presence of defined local backbone structure in unfolded proteins is inconsistent with predictions from random coil models. Proteins 2006. © 2005 Wiley‐Liss, Inc.
Binding site‐based classification of coronaviral papain‐like proteases
Authors: Sulea Traian , Lindner Holger A. , Purisima Enrico O. , Ménard Robert
Published: December 2005

The coronavirus replicase gene encodes one or two papain‐like proteases (termed PL1pro and PL2pro) implicated in the N‐terminal processing of the replicase polyprotein and thus contributing to the formation of the viral replicase complex that mediates genome replication. Using consensus fold recognition with the 3D‐JURY meta‐predictor followed by model building and refinement, we developed a structural model for the single PLpro present in the severe acute respiratory syndrome coronavirus (SCoV) genome, based on significant structural relationships to the catalytic core domain of HAUSP, a ubiquitin‐specific protease (USP). By combining the SCoV PLpro model with comparative sequence analyses we show that all currently known coronaviral PLpros can be classified into two groups according to their binding site architectures. One group includes all PL2pros and some of the PL1pros, which are characterized by a restricted USP‐like binding site. This group is designated the R‐group. The remaining PL1pros from some of the coronaviruses form the other group, featuring a more open papain‐like binding site, and is referred to as the O‐group. This two‐group, binding site‐based classification is consistent with experimental data accumulated to date for the specificity of PLpro‐mediated polyprotein processing and PLpro inhibition. It also provides an independent evaluation of the similarity‐based annotation of PLpro‐mediated cleavage sites, as well as a basis for comparison with previous groupings based on phylogenetic analyses. Proteins 2006.
Insights on HIV‐1 Tat:P/CAF bromodomain molecular recognition from in vivo experiments and molecular dynamics simulations
Authors: Pantano Sergio , Marcello Alessandro , Ferrari Aldo , Gaudiosi Daniele , Sabò Arianna , Pellegrini Vittorio , Beltram Fabio , Giacca Mauro , Carloni Paolo
Published: December 2005

Structural and functional studies indicate that, through its bromodomain, the cellular acetyltransferase P/CAF binds the acetylated Tat protein of human immunodeficiency virus type 1 (HIV‐1) and promotes transcriptional activation of the integrated provirus. Based on the NMR structure of P/CAF complexed with an acetylated Tat peptide, here we use molecular dynamics simulations to construct a model describing the interaction between full length Tat and the P/CAF bromodomain. Our calculations show that the protein–protein interface involves hydrophobic interactions between the P/CAF ZA loop and the Tat core domain. In particular, tyrosines 760 and 761 of P/CAF, two residues that are highly conserved in most known bromodomains, play an essential role for the binding. Fluorescence resonance energy transfer (FRET) experiments performed in this work demonstrate that P/CAF proteins in which these tyrosines are mutated into hydrophilic residues neither bind to Tat inside the cells nor mediate Tat transactivation. The combination of theoretical and in vivo studies provides new insights into the specificity of bromodomain recognition. Proteins 2006. © 2005 Wiley‐Liss, Inc.
The role of backbone stability near Ala44 in the high reduction potential class of rubredoxins
Authors: Tan Ming‐Liang , Kang ChulHee , Ichiye Toshiko
Published: December 2005

Rubredoxins may be separated into high and low reduction potential classes, with reduction potentials differing by ∼50 mV. Our previous work showed that a local shift in the polar backbone due to an A44 versus V44 side‐chain size causes this reduction potential difference. However, this work also indicated that in the low potential Clostridium pasteurianum (Cp) rubredoxin, a V44 → A44 mutation causes larger local backbone flexibility, because the V44 side‐chain present in the wild‐type (wt) is no longer present to interlock with neighboring residues to stabilize the subsequent G45. Since Pyrococcus furiosus (Pf) and other high potential rubredoxins generally have a P45, it was presumed that a G45 → P45 mutation might stabilize a V44 → A44 mutation in Cp rubredoxin. Here crystal structure analysis, energy minimization, and molecular dynamics (MD) were performed for wt V44G45, single mutant A44G45 and double mutant A44P45 Cp, and for wt A44P45 Pf rubredoxins. The local structural, dynamical, and electrostatic properties of Cp gradually approach wt Pf in the order wt Cp to single to double mutant because of greater sequence similarity, as expected. The double mutant A44P45 Cp exhibits increased backbone stability near residue 44 and thus enhances the probability that the backbone dipoles point toward the redox site, which favors an increase in the electrostatic contribution to the reduction potential. It appears that the electrostatic potential of residue 44 and the solvent accessibility to the redox are both determinants for the reduction potentials of homologous rubredoxins. Overall, these results indicate that an A44 in a rubredoxin may require a P45 for backbone stability whereas a V44 can accommodate a G45, since the valine side‐chain can interlock with its neighbors. Proteins 2006. © 2005 Wiley‐Liss, Inc.
Strategies for Semi‐folding Fractional Factorial Designs
Authors: Wang P. C. , Lee Carl
Published: December 2005

Engineers utilize screening experiments to find significant main effects of factors for quality improvement. After the analysis of the data resulting from this type of experiment, further investigation into the significance of some two‐factor interactions might be desirable. Repeating an experiment of the same size can be costly and time consuming. A follow‐up experiment with half the number of runs from the initial experiment is a good alternative. In this article, we propose two strategies for selecting additional runs to investigate the significance of two‐way interactions that are important to the experimenter. These strategies are based on the findings from the initial experiment. Two examples are presented to illustrate the application of these strategies. Copyright © 2005 John Wiley & Sons, Ltd.
Estimating the Change Point of a Poisson Rate Parameter with a Linear Trend Disturbance
Authors: Perry Marcus B. , Pignatiello Joseph J. , Simpson James R.
Published: December 2005

Knowing when a process changed would simplify the search and identification of the special cause. In this paper, we compare the maximum likelihood estimator (MLE) of the process change point designed for linear trends to the MLE of the process change point designed for step changes when a linear trend disturbance is present. We conclude that the MLE of the process change point designed for linear trends outperforms the MLE designed for step changes when a linear trend disturbance is present. We also present an approach based on the likelihood function for estimating a confidence set for the process change point. We study the performance of this estimator when it is used with a cumulative sum (CUSUM) control chart and make direct performance comparisons with the estimated confidence sets obtained from the MLE for step changes. The results show that better confidence can be obtained using the MLE for linear trends when a linear trend disturbance is present. Copyright © 2005 John Wiley & Sons, Ltd.
A Hybrid SPC Method with the Chi‐Square Distance Monitoring Procedure for Large‐scale, Complex Process Data
Authors: Ye Nong , Parmar Darshit , Borror Connie M.
Published: December 2005

Standard multivariate statistical process control (SPC) techniques, such as Hotelling's T2, cannot easily handle large‐scale, complex process data and often fail to detect out‐of‐control anomalies for such data. We develop a computationally efficient and scalable Chi‐Square ($\chi^2$) Distance Monitoring (CSDM) procedure for monitoring large‐scale, complex process data to detect out‐of‐control anomalies, and test the performance of the CSDM procedure using various kinds of process data involving uncorrelated, correlated, auto‐correlated, normally distributed, and non‐normally distributed data variables. Based on advantages and disadvantages of the CSDM procedure in comparison with Hotelling's T2 for various kinds of process data, we design a hybrid SPC method with the CSDM procedure for monitoring large‐scale, complex process data. Copyright © 2005 John Wiley & Sons, Ltd.
Setup Error Adjustment: Sensitivity Analysis and a New MCMC Control Rule
Authors: Lian Z. , Colosimo B. M. , del Castillo E.
Published: December 2005

In this paper, we focus on the performance of adjustment rules for a machine that produces items in batches and that can experience errors at each setup operation performed before machining a batch. The adjustment rule is applied to compensate for the setup offset in order to bring back the process to target. In particular, we deal with the case in which no prior information about the distribution of the offset or about the within‐batch variability is available. Under such conditions, adjustment rules that can be applied are Grubbs' rules, the exponentially‐weighted moving average (EWMA) controller and the Markov chain Monte Carlo (MCMC) adjustment rule, based on a Bayesian sequential estimation of unknown parameters that uses MCMC simulation. The performance metric of the different adjustment rules is the sum of the quadratic off‐target costs over the set of batches machined. Given the number of batches and the batch size, different production scenarios (characterized by different values of the lot‐to‐lot and the within‐lot variability and of the mean offset over the set of batches) are considered. The MCMC adjustment rule is shown to have better performance in almost all of the cases examined. Furthermore, a closer study of the cases in which the MCMC policy is not the best adjustment rule motivates a modified version of this rule which outperforms alternative adjustment policies in all the scenarios considered. Copyright © 2005 John Wiley & Sons, Ltd.
Technology and student affairs: Redux
Authors: Moneta Larry
Published: December 2005

The author addresses two critical questions related to technology: How has students' use of technology influenced student affairs work? How do we best align our business practices with advances in information technology?
The way technology changes how we do what we do
Authors: Shier Maria Tess
Published: December 2005

Changing technologies give students new ways to stay connected, be entertained, and interact with their institution. Student affairs practitioners must find ways to use these emerging technologies to further their educational goals and purposes.