bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of human rotavirus serotype G9 isolated in Japan and Thailand from 1995 to 1997
Authors: Zhou Yumei , Supawadee Jirapon , Khamwan Chantana , Tonusin Supin , Peerakome Supatra , Kim Bosu , Kaneshi Kunio , Ueda Yuichi , Nakaya Shigekazu , Akatani Kaoru , Maneekarn Niwat , Ushijima Hiroshi
Published: October 2004

Serotyping of human rotavirus was conducted in 396 Japanese and 100 Thai rotavirus‐positive fecal specimens collected from 1995 to 1997. Serotype G9 was found to be the third most common serotype with frequency of 16.2% in Thailand from 1996 to 1997. It was also detected in Japan with a low frequency (0.7%) in this year. The genetic analyses of VP4 and NSP4 genes of these G9 strains showed that 1 strain from Japan possessed P[8] genotype and NSP4 Wa‐group with long electropherotpe (e‐type). In contrast, 5 strains from Thailand belonged to P[6] and 1 strain belonged to P[4]. All of the Thai strains were in the NSP4 KUN‐group with a short e‐type. Sequence analysis of their VP7 gene revealed that there was the highest homology among fecal G9 strains (> 96.3%, amino acid identity) and a relatively high degree of homology to standard viruses, F45 from Japan (95.4–96.3%, amino acid identity) and 116E from India (92–92.3%, amino acid identity). However, immunological analysis using G9 specific monoclonal antibodies (Mabs) against VP7 protein showed that the G9 strains isolated from the two countries had different antigenic specificity. It was confirmed further by intraserotypical phylogenetic analysis of VP7 amino acid. These results indicated that the prevalence of G9 rotavirus in 1996–1997 in Thailand was relative to the continuing recent emergence of it on a worldwide basis, while the Japanese G9 strain isolated in this survey was identified to have progenitors common to the F45 strain that was prevalent in 1985 in Japan. Phylogenetic analysis of VP7 amino acid of G1‐14 prototype rotavirus showed that the G9 strains were most closely related to the equine G14 rotavirus FI23 strain but G3 strains, interserotypically. These findings suggest that G9 rotaviruses might be divided into two or more subtypes. J. Med. Virol. 65:619–628, 2001. © 2001 Wiley‐Liss, Inc.
Reconstruction of the pancreatic duct after pancreaticoduodenectomy: A modification of the Whipple procedure
Authors: Katsaragakis Stylianos , Antonakis Pantelis , Konstadoulakis Manousos M. , Androulakis George
Published: October 2004

Background and Objectives:

Pancreaticoduodenectomy is still associated with high morbidity and mortality even though there has been significant progress in the field of pancreatic surgery and postoperative follow‐up. The pancreatoenteric anastomosis, regardless of the technique used, is a major cause for both morbidity and mortality after Whipple procedure. To overcome all problems resulting from anastomotic leakage, we used external drainage of the pancreatic duct.

Methods:

In 24 patients who underwent pancreaticoduodenectomy in our Department from 1986 to 1995, a modification to the standard Whipple procedure was performed. Instead of pancreaticoenteric anastomosis, external drainage of the pancreatic duct remnant was performed. The pancreatic duct was intubated with a silastic tube, the external end of which was sutured to the skin. All patients received substitution therapy with pancreatic enzymes.

Results:

Mortality in our group of patients was 4%. No complications due to the external drainage of the pancreatic duct were reported, while no patient developed diabetes mellitus after surgery.

Conclusions:

External drainage of the pancreatic duct remnant can be used alternatively to pancreatoenteric anastomosis after pancreatoduodenectomy. The technique is safe and simple to perform and appears to reduce overall operative time. It may be an option for patients with significant comorbidity and/or intraoperative hemodynamic instability which mandates expeditious completion of the operation. J. Surg. Oncol. 2001; 77:26–29. © 2001 Wiley‐Liss, Inc.
Cell proliferative activity and expression of cell‐cell adhesion factors (E‐cadherin, α‐, β‐, and γ‐catenin, and p120) in sarcomatoid renal cell carcinoma
Authors: Kuroiwa Kentaro , Konomoto Tatsuo , Kumazawa Joichi , Naito Seiji , Tsuneyoshi Masazumi
Published: October 2004

Background and Objectives

Sarcomatoid RCC (renal cell carcinoma) is an uncommon, but not rare, neoplasm which has been shown to have a much worse prognosis than common RCC. The current study was designed to investigate the association of proliferative activity and cell‐cell adhesion molecules with sarcomatoid RCC.

Methods

Proliferative activity (Ki‐67 labeling index) and expression of cell‐cell adhesion associated molecules (E‐cadherin, α‐, β‐, and γ‐catenin, and p120) were examined using immunohistochemical techniques in 11 cases of sarcomatoid RCC.

Results

In six patients with sarcomatous component more than 50%, five were died within 24 month after diagnosis. The expression of these molecules within the carcinomatous and sarcomatous components of sarcomatoid RCC was compared. The mean Ki‐67 labeling index in the sarcomatous components (12.6%) is statistically higher than in the carcinomatous components (3.7%) (P < 0.05). The expressions of E‐cadherin, and α‐, β‐, and γ‐catenin were statistically decreased in the sarcomatous components compared to the carcinomatous components. However, no differences were observed regarding p120 immunostaining.

Conclusions

The findings of the current study suggest that the range of the sarcomatous component may be a prognostic factor in RCC, and the malignant behavior of sarcomatoid RCC is due to high cell proliferative activity and decreased expressions of E‐cadherin and α‐, β‐, and γ‐catenin in the sarcomatous component. J. Surg. Oncol. 2001; 77:123–131. © 2001 Wiley‐Liss, Inc.
Study of the reaction Fe(CN)4(bpy)2− + S2O82− in Sulfobetaine Aqueous Micellar Solutions
Authors: Del Mar Graciani María , Rodríguez Amalia , Múñoz María , Moyá María Luisa
Published: October 2004

The reaction Fe(CN)4(bpy)2− + S2O82− has been studied in aqueous micellar solutions of N‐tetradecyl‐N,N‐dimethyl‐3‐ammonio‐1‐propanesulfonate, SB3‐14. The influence of changes in the surfactant concentration as well as in the peroxodisulfate ions concentration on kobs was investigated. Spectroscopic and conductivity measurements have given information about the distribution of both anionic reagents between the aqueous and micellar pseudophases of the SB3‐14 micellar solutions. A discussion about the adequacy of various equations based on the pseudophase model to rationalize kinetic micellar effects for anion‐anion reactions in sulfobetaine micellar solutions has been done. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 225–231, 2001
Discrimination between strain and temperature with a single fiber Bragg grating
Authors: Guan Bai‐Ou , Tam Hwa‐Yaw , Chan Helen L. W. , Choy Chung‐Loong , Demokan Muhtesem Süleyman
Published: October 2004

A new scheme is proposed for simultaneous strain and temperature measurement with a single‐fiber Bragg grating. The grating sensor was written on the splice joint between two fibers and has two resonance peaks because of the different refractive index between the two fibers. By bonding one section of the grating onto the substrate of large thermal expansion coefficient, the two resonance peaks exhibit different strain and temperature response and can thus be used for strain/temperature discrimination. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 200–202, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10275
Picosecond chirped‐pulse amplification in traveling‐wave semiconductor optical amplifiers
Authors: Lin Gong‐Ru , Lee Shih‐Kai , Lin Gong‐Chen , Lin Kuei‐Huei
Published: October 2004

The characteristics of traveling‐wave semiconductor optical amplifiers (TWSOAs) used for the picosecond pulse amplification process are discussed. The distortion of a multigigabit chirped optical pulse train generated from gain‐switched optical transmitters due to a saturation of output power and a gain of TWSOAs is analyzed. The optimized injection current and operating temperature of TWSOAs in amplification of picosecond negatively chirped optical pulses are determined. The shortest optical pulse is found to broaden from 21 ps to 30 ps after amplification by TWSOA. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 202–207, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10276
Comparison of the Peano–Gosper fractile array and the regular hexagonal array
Authors: Bogard J. N. , Werner D. H. , Werner P. L.
Published: October 2004

A new class of modular broadband low‐sidelobe arrays, based on the theory of fractile (fractal tile) geometry, has been recently introduced. In this paper, the radiation properties of the Peano–Gosper fractile array are compared to those of the conventional square and hexagonal arrays. It is demonstrated that the Peano–Gosper array has the same desirable grating‐lobe conditions as the hexagonal array, while achieving a much lower overall sidelobe level. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 524–526, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20523
Mouse Xist expression begins at zygotic genome activation and is timed by a zygotic clock
Authors: Zuccotti Maurizio , Boiani Michele , Ponce Ruben , Guizzardi Stefano , Scandroglio Renato , Garagna Silvia , Redi Carlo Alberto
Published: October 2004

The imprinted mouse Xist (X‐inactive specific transcript) gene is involved in the initiation of X‐chromosome inactivation. Only the paternal Xist is expressed in preimplantation development beginning from the 4‐cell stage, preceding and in correlation with paternal X‐inactivation in the extraembryonic lineage of the blastocyst. To better understand the mechanisms regulating Xist expression in early development, we investigated the precise timing of its onset. We set up a single‐cell RT‐PCR for the simultaneous analysis on single embryos of Xist and Hprt (internal control) cDNAs and a Y‐chromosome specific DNA sequence, Zfy (for embryo sexing). Applying this procedure, we demonstrate that Xist expression begins at the G2‐phase of 2‐cell female embryos, earlier than previously reported and at the same time of the major wave of zygotic genome activation (ZGA). We then examined, if Xist expression at the 2‐cell stage is dependent on the lapse of time spent since fertilization, as previously reported for zygotic genes. One‐cell embryos at the G2‐phase of the first cell‐cycle were cultured with cytochalasin D (inhibitor of cytokinesis but not of DNA synthesis or nuclear progression) for a time equivalent to the 4‐cell stage in control, untreated embryos. We show that Xist activation occurs at a scheduled time following fertilization despite the embryos being blocked at the 1‐cell stage, suggesting the existence of a zygotic clock involved in the regulation of the transcription of this imprinted gene. Mol. Reprod. Dev. 61: 14–20, 2002. © 2002 Wiley‐Liss, Inc.
Nerve conduction changes in patients with mitochondrial diseases treated with dichloroacetate
Authors: Spruijt Liesbeth , Naviaux Robert K. , McGowan Karen A. , Nyhan William L. , Sheean Geoffrey , Haas Richard H. , Barshop Bruce A.
Published: October 2004

Serial measurements of nerve conduction velocities and amplitudes were performed in 27 patients with congenital lactic acidemia over 1 year of sodium dichloroacetate (DCA) administration. Patients were treated with oral thiamine (100 mg) and DCA (initial dose of 50 mg/kg) daily. Nerve conduction velocity and response amplitude were measured in the median, radial, tibial, and sural nerves at 0, 3, 6, and 12 months, and plasma DCA pharmacokinetics were measured at 3 and 12 months. Baseline electrophysiologic parameters in this population were generally below normal but as a group were within 2 standard deviations of normal means. Although symptoms of neuropathy were reported by only three patients or their families, nerve conduction declined in 12 patients with normal baseline studies, and worsening of nerve conduction occurred in the two who had abnormalities at baseline. Peripheral neuropathy appears to be a common side effect during chronic DCA treatment, even with coadministration of oral thiamine. Nerve conduction should be monitored during DCA treatment. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 916–924, 2001
A new importance sampling Monte Carlo method for a flow network reliability problem
Authors: Bulteau Stéphane , El Khadiri Mohamed
Published: October 2004

The exact evaluation of the probability that the maximum st‐flow is greater than or equal to a fixed demand in a stochastic flow network is an NP‐hard problem. This limitation leads one to consider Monte Carlo alternatives. In this paper, we propose a new importance sampling Monte Carlo method. It is based on a recursive use of the state space decomposition methodology of Doulliez and Jamoulle during the simulation process. We show theoretically that the resulting estimator belongs to the variance‐reduction family and we give an upper bound on its variance. As shown by experimental tests, the new sampling principle offers, in many cases, substantial speedups with respect to a previous importance sampling based on the same decomposition procedure and its best performances are obtained when highly reliable networks are analyzed. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 204–228, 2002; DOI 10.1002/nav.10004
A network based model of a promotion‐sensitive grocery logistics system
Authors: Iyer Ananth V. , Ye Jianming
Published: October 2004

We use a network model to choose retail prices in a grocery logistics system consisting of a warehouse (managed by a manufacturer) that supplies stores (managed by a retailer). We model retail prices as endogenous decisions that respond to store‐level cost and demand parameters. The retail prices are chosen to maximize the retailer's expected profits. The retail environment is captured by a three‐segment retail customer model where segments differ in their reservation price, size, and propensity to stockpile. The resulting network model chooses retail prices each period to optimize profits across the horizon. Retail price variation across time is profit‐maximizing because of the promotion sensitivity of the retail environment. We also model the impact of retail price variation on the manufacturer costs, warehouse inventory levels, and associated manufacturer expected profit. The suggested model is fit to a dataset consisting of retail prices and associated sales of canned soup. The model parameters as well as the residual variance are included in the decision model that generates the optimal retail prices that maximize the expected retail profit. We use model runs from the empirical dataset to show that (i) retail price variation can be profit‐maximizing for the retailer, (ii) retail market‐share constraints can decrease both manufacturer and retailer profits, and (iii) manufacturer price variation can be beneficial for the manufacturer and the retailer. The results show that manufacturer and retailer price variation can play a valuable role in improving logistics system performance in promotional retail environments. © 2001 John Wiley & Sons, Inc.
Neuroprotective signal transduction in model motor neurons exposed to thrombin: G‐protein modulation effects on neurite outgrowth, Ca2+ mobilization, and apoptosis
Authors: Smirnova Irina V. , Citron Bruce A. , Arnold Paul M. , Festoff Barry W.
Published: October 2004

Thrombin, the ultimate protease in the blood coagulation cascade, mediates its known cellular effects by unique proteolytic activation of G‐protein‐coupled protease‐activated receptors (PARs), such as PAR1, PAR3, and PAR4, and a “tethered ligand” mechanism. PAR1 is variably expressed in subpopulations of neurons and largely determines thrombin's effects on morphology, calcium mobilization, and caspase‐mediated apoptosis. In spinal cord motoneurons, PAR1 expression correlates with transient thrombin‐mediated [Ca2+]i flux, receptor cleavage, and elevation of rest [Ca2+]i activating intracellular proteases. At nanomolar concentrations, thrombin retracts neurites via PAR1 activation of the monomeric, 21 kDa Ras G‐protein RhoA, which is also involved in neuroprotection at lower thrombin concentrations. Such results suggest potential downstream targets for thrombin's injurious effects. Consequently, we employed several G‐protein‐specific modulators prior to thrombin exposure in an attempt to uncouple both heterotrimeric and monomeric G‐proteins from motoneuronal PAR1. Cholera toxin, stimulating Gs, and lovastatin, which blocks isoprenylation of Rho, reduced thrombin‐induced calcium mobilization. In contrast, pertussis toxin and mastoparan, inhibiting or stimulating Go/Gi, were found to exacerbate thrombin action. Effects on neuronal rounding and apoptosis were also detected, suggesting therapeutic utility may result from interference with downstream components of thrombin signaling pathways in human motor neuron disorders, and possibly other neurodegenerative diseases. Published 2001 John Wiley & Sons, Inc. J Neurobiol 48: 87–100, 2001
An interval finite element approach for the calculation of envelope frequency response functions
Authors: Moens David , Vandepitte Dirk
Published: October 2004

This paper focusses on the application of the interval finite element method in dynamic analyses. It describes a methodology for calculating frequency response function envelopes from a finite element model containing imprecise parameters defined as interval uncertainties. The resulting envelope functions give a conservative approximation of the possible range of the frequency response function, taking into account that the uncertain parameters in the model can adopt any value in their presumed uncertainty intervals. The methodology is based on the modal superposition principle. It consists of an interval aritmethic algorithm which processes the results of a preliminary global optimization performed on the modal parameters. The algorithm is constructed such that it optimally combines the advantages of both the anti‐optimization and the interval arithmetic strategy for general numerical interval calculations.

In the first stage of the development, the modal parameter ranges of each individual mode are independently combined in the modal response contributions. This yields the modal rectangle (MR) method. In order to remedy the high conservatism inherent to the MR method, the exact eigenfrequency ranges are added to the analysis. This results in the modal rectangle method with eigenfrequency interval correction (MRE). A second improvement consists of adding extra delimiters to the MRE modal parameter range approximation. This is achieved by performing an extra optimization on the modal response contributions at discrete frequencies. The method is referred to as the locally optimized modal rectangle method with eigenfrequency interval correction (OMRE). Finally, a numerical example illustrates the different algorithms. Copyright © 2004 John Wiley & Sons, Ltd.
First‐trimester combined ultrasound and biochemical screening for Down syndrome in routine clinical practice
Authors: Stenhouse E. J. , Crossley J. A. , Aitken D. A. , Brogan K. , Cameron A. D. , Connor J. M.
Published: October 2004

Objectives

To assess the effectiveness of combined ultrasound and biochemical (CUB) screening for chromosome abnormalities in singleton pregnancies in a routine antenatal clinic and laboratory setting.

Methods

Women whose pregnancies fell within the gestational age range of 11 to 14 weeks by ultrasound assessment were offered CUB screening on the basis of measurement of nuchal translucency (NT), maternal serum free beta‐human chorionic gonadotrophin (FβhCG) and pregnancy‐associated plasma protein A (PAPP‐A). NT measurements were obtained using a standardised method defined by the Fetal Medicine Foundation and FβhCG, and PAPP‐A were measured using the DELFIA immunoassay system. Each screening marker measurement was converted to a multiple of the appropriate gestational median and a risk was derived using previously published parameters for each marker in chromosomally abnormal and unaffected pregnancies. A combined risk of Down syndrome and of trisomy 18/13, incorporating the maternal age risk, was calculated for all women. Invasive diagnostic testing was offered to women whose combined risk exceeded the cut‐off risk of 1 in 250 (term).

Results

Five thousand and eighty‐four women accepted a first‐trimester screening test for Down syndrome, representing 75% of the eligible booking population. Out of the population eligible for CUB screening at the time of booking, NT measurements were obtained from 93% at the first clinic visit and 7% had to return for a second attempt. After excluding women who defaulted on a return visit, satisfactory NT measurements were obtained in 99.5% of pregnancies. Fifteen cases of Down syndrome and eleven pregnancies with other chromosome abnormalities were ascertained. The detection rate for Down syndrome was 93% (14/15) at a false‐positive rate of 5.9% and for all chromosome abnormalities it was 96% (25/26) at an overall false‐positive rate of 6.3%.

Conclusions

CUB screening offers a significant improvement in sensitivity over second‐trimester biochemical screening and is deliverable within a routine prenatal clinical setting. Copyright © 2004 John Wiley & Sons, Ltd.
Changing indications for fetal echocardiography in a University Center population
Authors: Friedberg Mark K. , Silverman Norman H.
Published: October 2004

Objectives

We hypothesized that increased facility with fetal echocardiographic diagnosis by obstetricians is associated with changes in its indications and yields.

Methods

We reviewed 300 fetal echocardiograms (December 2002–August 2003) and compared our findings with previous studies.

Results

Mean maternal age was 31 ± 6 (range 16–44) years. Gestational age was 24 ± 5 weeks (mean ± SD; median 22, range 15–38). Indications for fetal echocardiography included family history of congenital heart disease (CHD) (23%), maternal diabetes (18%), obstetrical scan suspicious for CHD (13%), arrhythmia (12%) maternal rheumatologic disease (7%), extracardiac congenital anomalies (6%), chromosomal anomaly (6%) and exposure to a potential fetal teratogen (5%). High yield indications included chromosomal anomaly (47%) and a suspicious obstetrical scan (42%). Low yield indications included family history of CHD (4%) and teratogen exposure (0%). 1/7 of the patients with increased nuchal translucency had pulmonary atresia/intact ventricular septum. No anomalies were associated with the single umbilical artery.

Conclusion

Indications and yields of fetal echocardiography have changed over the last decade. The frequency of an obstetrical scan suspicious for CHD has increased 2.5 to 3 times over a decade and continues to have high yield. Thus, increasing prenatal detection of CHD depends, to a large extent, on increasing the skills of obstetricians. Copyright © 2004 John Wiley & Sons, Ltd.
Body dissatisfaction, drive for thinness, and self‐esteem in African American college females
Authors: James Kimberly A. , Phelps LeAdelle , Bross Andrea L.
Published: October 2004

Ninety‐five African American undergraduate females who were attending three predominately Caucasian universities were evaluated for body dissatisfaction and drive for thinness as well as on four dimensions of self‐concept (physical, social, academic, and personal competence). The participants were largely middle class, with 78% reporting parental education levels between high school to college graduation. Results indicated body dissatisfaction and drive for thinness at levels commensurate with Caucasian samples. A hierarchial multiple regression found a combination of physical self‐concept, drive for thinness, and personal competence to be highly predictive of body dissatisfaction in this sample. Using this model, an effective psychosocial prevention program that focused on reduction of risk factors (e.g., drive for thinness) and enhancement of protective factors (e.g., satisfaction with physical appearance and abilities, personal efficacy) would be advantageous. It is suggested that prevention programming with African American women occur within a cultural context that may provide further support. That is, it may be beneficial to facilitate a critical evaluation of current social mores, encourage personal value clarification, and enhance individual resilience within a context of cultural pride. © 2001 John Wiley & Sons, Inc.
Middle childhood, poverty, and adjustment: Does social support have an impact?
Authors: Guest Kristi Carter , Biasini Fred J.
Published: October 2004

The present study evaluated 64 children and their primary caregivers who were living in poverty. The children were administered a stress measure, a social support measure, and a measure of self‐esteem. Caregivers completed a stress measure, a measure of child adjustment, and a demographic questionnaire. Social support was not found to moderate the relationship between stress and child outcome. However, social support was found to be one possible mediator of the child's reported stress on their self‐esteem. According to the mediating model, enhancing children's social support may positively influence their self‐esteem. Greater levels of self‐esteem can affect many aspects of children's lives, such as improving school performance and efforts toward achieving goals. Because of the important role that social support can play on children's self‐esteem, social support should be actively promoted through school and community groups and organizations, especially with children from disadvantaged economic situations. © 2001 John Wiley & Sons, Inc.
Search for highly resolved electron spin resonance spectra of the transient radical in radical polymerization
Authors: Kamachi Mikiharu
Published: October 2004

The detection of highly resolved spectra in electron spin resonance (ESR) measurements of radical polymerization is presented. Well‐resolved ESR spectra of the propagating radical were detected in the radical polymerization of several vinyl monomers with a specially designed cavity and cell. More highly resolved ESR spectra of the propagating radicals of vinyl and diene compounds were observed with aconventional spectrometer without the specially designed cavity and cell. On the basis of the ESR spectra, propagation rate constants and dynamic behavior of propagating radicals are discussed. Moreover, the application of time‐resolved ESR spectroscopy to research on the initiation process in radical polymerization is shown. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 269–285, 2002
Laser‐induced decomposition of 2,2‐dimethoxy‐2‐phenylacetophenone and benzoin in methyl methacrylate homopolymerization studied via matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Barner‐Kowollik Christopher , Vana Philipp , Davis Thomas P.
Published: October 2004

Pulsed laser polymerization (PLP) experiments were performed on the bulk polymerization of methyl methacrylate (MMA) at −34 °C. The aim of this study was to investigate the polymer end groups formed during the photoinitiation process of MMA monomer using 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA) and benzoin as initiators via matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. Analysis of the MALDI‐TOF spectra indicated that the two radical fragments generated upon pulsed laser irradiation show markedly different reactivity toward MMA: whereas the benzoyl fragment—common to both DMPA and benzoin—clearly participates in the initiation process, the acetal and benzyl alcohol fragments cannot be identified as end groups in the polymer. The complexity of the MALDI‐TOF spectrum strongly increased with increasing laser intensity, this effect being more pronounced in the case of benzoin. This indicates that a cleaner initiation process is at work when DMPA is used as the photoinitiator. In addition, the MALDI‐TOF spectra were analyzed to extract the propagation‐rate coefficient, kp, of MMA at −34 °C. The obtained value of kp = 43.8 L mol−1 s−1 agrees well with corresponding numbers obtained via size exclusion chromatography (kp = 40.5 L mol−1 s−1). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 675–681, 2002; DOI 10.1002/pola.10150
Surface modification of polystyrene latex particles via atom transfer radical polymerization
Authors: Min Ke , Hu Jianhua , Wang Changchun , Elaissari Abdelhamid
Published: October 2004

The atom transfer radical polymerization (ATRP) technique using the copper halide/ N,N′,N′,N″,N″‐pentamethyldiethylenetriamine complex was applied to the graft polymerization of methyl methacrylate and methyl acrylate on the uniform polystyrene (PS) seed particles and formed novel core‐shell particles. The core was submicron crosslinked PS particles that were prepared via emulsifier‐free emulsion polymerization. The crosslinked PS particles obtained were transferred into the organic phase (tetrahydrofuran), and surface modification using the chloromethylation method was performed. Then, the modified seed PS particles were used to initiate ATRP to prepare a controlled poly(methyl methacrylate) (PMMA) and poly(methyl acrylate) (PMA) shell. The final core‐shell particles were characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, thermogravimetric analysis, and elementary analysis. The grafting polymerization was conducted successfully on the surface of modified crosslinked PS particles, and the shell thickness and weight ratio (PMMA and PMA) of the particles were calculated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 892–900, 2002; DOI 10.1002/pola.10160
Synthesis and thermal properties of hybrid copolymers of syndiotactic polystyrene and polyhedral oligomeric silsesquioxane
Authors: Zheng Lei , Kasi Rajeswari M. , Farris Richard J. , Coughlin E. Bryan
Published: October 2004

Copolymerizations of styrene and the polyhedral oligomeric silsesquioxane (POSS)–styryl macromonomer 1‐(4‐vinylphenyl)‐3,5,7,9,11,13,15‐heptacyclopentylpentacyclo [9.5.1.13,9.15,15.17,13] octasiloxane have been performed with CpTiCl3 in conjunction with methylaluminoxane. Random copolymers of syndiotactic polystyrene (sPS) and POSS have been formed and fully characterized with 1H and 13C NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. NMR data reveal a moderately high syndiotacticity of the polystyrene backbone consistent with this use of CpTiCl3 as a catalyst and POSS loadings as high as 24 wt % and 3.2 mol %. Thermogravimetric analysis of the sPS–POSS copolymers under both nitrogen and air shows improved thermal stability with higher degradation temperatures and char yields, demonstrating that the inclusion of the inorganic POSS nanoparticles makes the organic polymer matrix more thermally robust. The polymerization activity and thermal stability are also compared with those of reported atactic polystyrene–POSS copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 885–891, 2002; DOI 10.1002/pola.10175
Synthesis of dendronized, chiral conjugated polymers with appendant Fréchet‐type dendrons
Authors: Jiang Jing , Liu Hong‐Wei , Zhao You‐Liang , Chen Chuan‐Fu , Xi Fu
Published: October 2004

New chiral binaphthyl‐based polyarylenes [(S)‐3a and (S)‐3b] with appendant Fréchet‐type poly(aryl ether) dendrons (first generation and second generation) were synthesized with Suzuki polycondensation from chiral (S)‐6,6′‐dibromo‐2,2′‐didendron‐substituted 1,1′‐binaphthyl derivatives and p‐phenylene diboronic acid. The polymers were studied with circular dichroism, fluorescence, and ultraviolet–visible spectra. Laser light scattering measurements of (S)‐3a and (S)‐3b showed that their weight‐average molecular weights were 2.39 × 105 and 1.09 × 104, respectively. The specific optical rotation [α]D was −59.6 for (S)‐3a and −62.7 for (S)‐3b. These dendronized conjugated polymers exhibited good thermal stability. The glass‐transition temperatures and the initial decomposition temperatures were 187.5 and 265.3 °C for (S)‐3a and 173.8 and 308.9 °C for (S)‐3b, respectively. (S)‐3a and (S)‐3b had high fluorescence quantum efficiencies, 87 and 91%, respectively, in tetrahydrofuran. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1167–1172, 2002
Structural features of crystallized poly(ethylene terephthalate) polymers
Authors: Lu Weijie , Debelak Kenneth A. , Witt Andrew R. , Yang Congkun , Collins W. Eugene , Lott Charles
Published: October 2004

Polyethylene terephthalate (PET) is a widely used polymeric material. In this work, the microstructural features before and after the solid‐state polymerization (SSP) of several DuPont PET products were investigated by low‐voltage scanning electron microscopy (LV‐SEM) and atomic force microscopy (AFM). The microstructural features on the cross section of various PET samples included crystallites, voids, boundaries, defects, and amorphous phases. The SEM images revealed layered and stepped structural features at the micron and 10‐micron scales that are highly crystallized at the near‐edge region of the cross section for both linear and branched PET samples after the SSP process. The AFM images demonstrate that the degree of crystallization for the linear and branched PET samples increases gradually from the central area to the edge on the cross section. The linear crystallized PET has a higher degree of orientation than the branched crystallized PET in the 10‐micron to micron scales, but their crystalline structures have no significant differences in the submicron to nanometer scales. The PET crystallization process occurs when the molecular chains in the amorphous phase are aligned and folded to form straight molecular chains at the nanometer scale, and small crystallites are formed. The crystallites aggregate and align together into a polygon rod‐like‐shaped crystallites at the submicron scale. Finally, large crystallites at the micron size are formed that appear on the edge area of the cross section. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 245–254, 2002
Microphase separation and ion‐conduction mechanisms in polypropylene oxide/lithium perchlorate (LiClO4) complexes
Authors: Furukawa Takeo , Mukasa Yasuhiko , Suzuki Toshikazu , Kano Kenji
Published: October 2004

Broadband dielectric spectroscopy was used to examine ion‐conduction mechanisms in polypropylene oxide (PPO) with a molecular weight of 4000 complexed with LiClO4. Two distinct conduction mechanisms were proposed with respect to high and low salt concentration regions. In a concentrated regime (Li/O >10%), the segmental motion of PPO molecules is significantly slowed down by enhanced cation coordination that results in a marked decrease in molar conductivity. We found a linear relationship between the ionic diffusion coefficient and the relaxation frequency of slowed segmental motion over broad temperature and salt‐concentration ranges. The use of a random walk scheme revealed that ions hop around at the same rate as slowed segmental motion for a monomer length. In a dilute regime (Li/O <0.1%), ions are temporarily localized in a limited domain. The direct current conductivity is achieved by structural renewal that releases ions from such localization and provides a diffusional character. At intermediate salt concentrations, microphase separation into ion‐depleted and ion‐rich regions was evidenced by the coexistence of fast and slow segmental processes. The molar conductivity revealed a maximum at Li/O = 3%. Its decrease at higher salt concentrations was attributed to the slowing down of segmental motion, and that at lower salt concentrations was attributed to localization of ionic motion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 613–622, 2002; DOI 10.1002/polb.10123
Nanocomposites of polyurethane with various organoclays: Thermomechanical properties, morphology, and gas permeability*
Authors: Chang Jin‐Hae , An Yeong Uk
Published: October 2004

The properties of polyurethane (PU) nanocomposites with three different organoclays were compared in terms of their thermal stabilities, mechanical properties, morphologies, and gas permeabilities. Hexadecylamine–montmorillonite, dodecyltrimethyl ammonium–montmorillonite, and Cloisite 25A were used as organoclays for making PU hybrid films. The properties were examined as a function of the organoclay content in a matrix polymer. Transmission electron microscopy photographs showed that most clay layers were dispersed homogeneously into the matrix polymer on the nanoscale, although some particles of clay were agglomerated. Moreover, the addition of only a small amount of organoclay was enough to improve the thermal stabilities and mechanical properties of PU hybrid films, whereas gas permeability was reduced. Even polymers with low organoclay contents (3–4 wt %) showed much higher strength and modulus values than pure PU. Gas permeability was reduced linearly with an increasing amount of organoclay in the PU matrix. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 670–677, 2002; DOI 10.1002/polb.10124
TiO2 distribution in aged and injected isotactic polypropylene parts by synchrotron radiation X‐ray microfluorescence
Authors: Maia Dênison R. J. , Perez Carlos A. , De Paoli Marco‐A.
Published: October 2004

We studied the TiO2 pigment distribution along cross sections of injected isotactic polypropylene samples after they were aged by light exposure for 515 and 3000 h in accelerated test equipment. The TiO2 pigment distribution was studied so that we could understand the whitening process occurring in this type of plastic. For these studies, we used a 20‐μm X‐ray microbeam from a synchrotron light source. We observed that the aged and nonaged samples had almost homogeneous distributions of Ti in the cross sections; therefore, pigment migration could not have been responsible for the surface whitening process. There were maxima of Ti intensities that were not in the same region for all samples. This behavior could be explained by the heterogeneity of the extrusion and injection‐molding processes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 657–662, 2002; DOI 10.1002/polb.10127
Proton transport in polybenzimidazole blended with H3PO4 or H2SO4
Authors: Pu Hongting , Meyer Wolfgang H. , Wegner Gerhard
Published: October 2004

Proton transport in H3PO4‐ and H2SO4‐blended polybenzimidazoles (PBIs) has been studied with both temperature‐ and pressure‐dependent dielectric spectroscopy. The influences of the acid concentration and temperature on the relative conductance and activation volume are discussed. An Arrhenius relation is used to model the temperature‐dependent conductivity at a constant acid content. The logarithm of the relative conductance for PBI blended with H3PO4 decreases linearly with increasing pressure. As the temperature increases, the activation volume becomes smaller for PBI blended with H3PO4. It is proposed that proton transport in acid‐blended PBI is mainly controlled by proton hopping and diffusion rather than a mechanism mediated by the segmental motions in the polymer. The conductivities of PBIs blended with H3PO4 and H2SO4 are compared. At a 1.45 molar acid doping concentration, the former has the higher conductivity. With water, the conductivity of H3PO4‐blended PBI increases significantly. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 663–669, 2002; DOI 10.1002/polb.10132
Congruent qualitative behavior of complete and reconstructed phase space trajectories from biomolecular dynamics simulation
Authors: Caves Leo S.D. , Verma Chandra S.
Published: October 2004

Central to the study of a complex dynamical system is knowledge of its phase space behavior. Experimentally, it is rarely possible to record a system's (multidimensional) phase space variables. Rather, the system is observed via one (or few) scalar‐valued signal(s) of emission or response. In dynamical systems analysis, the multidimensional phase space of a system can be reconstructed by manipulation of a one‐dimensional signal. The trick is in the construction of a (higher‐dimensional) space through the use of a time lag (or delay) on the signal time series. The trajectory in this embedding space can then be examined using phase portraits generated in selected subspaces. By contrast, in computer simulation, one has an embarrassment of riches: direct access to the complete multidimensional phase space variables, at arbitrary time resolution and precision. Here, the problem is one of reducing the dimensionality to make analysis tractable. This can be achieved through linear or nonlinear projection of the trajectory into subspaces containing high information content. This study considers trajectories of the small protein crambin from molecular dynamics simulations. The phase space behavior is examined using principal component analysis on the Cartesian coordinate covariance matrix of 138 dimensions. In addition, the phase space is reconstructed from a one dimensional signal, representing the radius of gyration of the structure along the trajectory. Comparison of low‐dimensional phase portraits obtained from the two methods shows that the complete phase space distribution is well represented by the reconstruction. The study suggests that it may be possible to develop a deeper connection between the experimental and simulated dynamics of biomolecules via phase space reconstruction using data emerging from recent advances in single‐molecule time‐resolved biophysical techniques. Proteins 2002;47:25–30. © 2002 Wiley‐Liss, Inc.
Solution structures of a 30‐residue amino‐terminal domain of the carp granulin‐1 protein and its amino‐terminally truncated 3‐30 subfragment: Implications for the conformational stability of the stack of two β‐hairpins
Authors: Vranken Wim F. , James Susan , Bennett Hugh P.J. , Ni Feng
Published: October 2004

Carp granulins are members of an emerging class of proteins with a sequence motif encoding a parallel stack of two to four β‐hairpins. The carp granulin‐1 protein forms a stack of four β‐hairpins, whereas its amino‐terminal fragment appears to adopt a very stable stack of two β‐hairpins in solution. Here we determined a refined three‐dimensional structure of this peptide fragment to examine potential conformational changes compared with the full‐length protein. The structures were calculated with both a traditional method and a fast semiautomated method using ambiguous NMR distance restraints. The resulting sets of structures are very similar and show that a well‐defined stack of two β‐hairpins is retained in the peptide. Conformational rearrangements compensating the loss of the carboxy‐terminal subdomain of the native protein are restricted to the carboxy‐terminal end of the peptide, the turn connecting the two β‐hairpins, and the Tyr21 and Tyr25 aromatic side chains. Further removal of the Val1 and Ile2 residues, which are part of the first β‐hairpin and components of two major hydrophobic clusters in the two β‐hairpin structure, results in the loss of the first β‐hairpin. The second β‐hairpin, which is closely associated with the first, retains a similar but somewhat less stable conformation. The invariable presence of the second β‐hairpin and the dependence of its stability on the first β‐hairpin suggest that the stack of two β‐hairpins may be an evolutionary conserved and autonomous folding unit. In addition, the high conformational stability makes the stack of two β‐hairpins an attractive scaffold for the development of peptide‐based drug candidates. Proteins 2002;47:14–24. © 2002 Wiley‐Liss, Inc.
Probabilistic sampling of protein conformations: New hope for brute force?
Authors: Feldman Howard J. , Hogue Christopher W.V.
Published: October 2004

Protein structure prediction from sequence alone by “brute force” random methods is a computationally expensive problem. Estimates have suggested that it could take all the computers in the world longer than the age of the universe to compute the structure of a single 200‐residue protein. Here we investigate the use of a faster version of our FOLDTRAJ probabilistic all‐atom protein‐structure‐sampling algorithm. We have improved the method so that it is now over twenty times faster than originally reported, and capable of rapidly sampling conformational space without lattices. It uses geometrical constraints and a Leonard‐Jones type potential for self‐avoidance. We have also implemented a novel method to add secondary structure‐prediction information to make protein‐like amounts of secondary structure in sampled structures. In a set of 100,000 probabilistic conformers of 1VII, 1ENH, and 1PMC generated, the structures with smallest Cα RMSD from native are 3.95, 5.12, and 5.95Å, respectively. Expanding this test to a set of 17 distinct protein folds, we find that all‐helical structures are “hit” by brute force more frequently than β or mixed structures. For small helical proteins or very small non‐helical ones, this approach should have a “hit” close enough to detect with a good scoring function in a pool of several million conformers. By fitting the distribution of RMSDs from the native state of each of the 17 sets of conformers to the extreme value distribution, we are able to estimate the size of conformational space for each. With a 0.5Å RMSD cutoff, the number of conformers is roughly 2Nwhere N is the number of residues in the protein. This is smaller than previous estimates, indicating an average of only two possible conformations per residue when sterics are accounted for. Our method reduces the effective number of conformations available at each residue by probabilistic bias, without requiring any particular discretization of residue conformational space, and is the fastest method of its kind. With computer speeds doubling every 18 months and parallel and distributed computing becoming more practical, the brute force approach to protein structure prediction may yet have some hope in the near future. Proteins 2002;46:8–23. © 2001 Wiley‐Liss, Inc.
Toward minimalist models of larger proteins: A ubiquitin‐like protein
Authors: Sorenson Jon M. , Head‐Gordon Teresa
Published: October 2004

Our recently developed off‐lattice bead model capable of simulating protein structures with mixed α/β content has been extended to model the folding of a ubiquitin‐like protein and provides a means for examining the more complex kinetics involved in the folding of larger proteins. Using trajectories generated from constant‐temperature Langevin dynamics simulations and sampling with the multiple multi‐histogram method over five‐order parameters, we are able to characterize the free energy landscape for folding and find evidence for folding through compact intermediates. Our model reproduces the observation that the C‐terminus loop structure in ubiquitin is the last to fold in the folding process and most likely plays a spectator role in the folding kinetics. The possibility of a productive metastable intermediate along the folding pathway consisting of collapsed states with no secondary structure, and of intermediates or transition structures involving secondary structural elements occurring early in the sequence, is also supported by our model. The kinetics of folding remain multi‐exponential below the folding temperature, with glass‐like kinetics appearing at T/Tf ∼ 0.86. This new physicochemical model, designed to be predictive, helps validate the value of modeling protein folding at this level of detail for genomic‐scale studies, and motivates further studies of other protein topologies and the impact of more complex energy functions, such as the addition of solvation forces. Proteins 2002;46:368–379. © 2002 Wiley‐Liss, Inc.