bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of laser‐modified polystyrene substrate on CHO cell growth and alignment
Authors: Zhu Bangshang , Lu Qinhua , Yin Jie , Hu Jun , Wang Zongguang
Published: June 2004

Biomaterial surface chemistry and nanoscale topography of biomaterials can significantly influence cell behavior in vitro. Polystyrene (PS) Petri dishes were subjected to Nd:YAG laser irradiation at 266 nm, which resulted in well‐defined three‐dimensional (3D) periodic nanoscale surface topographies and surface oxidation. The surface changes were analyzed by X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and a contact‐angle goniometer. The samples were then used to investigate the cell behavior of Chinese hamster ovary (CHO) cells. The surface laser modification affected the CHO cell adhesion and alignment, and caused morphological changes in comparison with unmodified PS. The results obtained from the cell‐behavior studies revealed that nanoscale hydrophilic surface topography cues affected the adhesion, extension, alignment, and morphology of cells. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 43–48, 2004
Donor age and gender effects on osteoinductivity of demineralized bone matrix
Authors: Traianedes Kathy , Russell James L. , Edwards Jean T. , Stubbs Harrison A. , Shanahan Ileene R. , Knaack David
Published: June 2004

Allogeneic demineralized bone matrix (DBM) has been used extensively as a clinical graft material because of its inherent osteoinductive and osteoconductive properties. There is continued debate over the acceptable age range of donors for bone and whether the effectiveness of the tissue as a graft is influenced by gender. Contradictory evidence has been obtained with DBM prepared from both animals and humans. The goal of the present investigation was to evaluate the effect of donor age and gender on the osteoinductivity of DBM prepared from human donors [male (133) and female (115) donors grouped in 10‐year age brackets up to 85 years] with a statistically relevant sample size using the athymic rat ectopic bone formation model. Among males, there was a statistically significant linear association between age and osteoinductivity value (p <.001), but not among females (p =.20). The rate of change among males was 0.009 units per year. The biological relevance of such a small change in osteoinductivity is likely to be negligible, as the total variation explained by the regressions was only 8.2%. A two‐way ANOVA as related to donor age (only donors < 76 years of age) and gender yielded no significant statistical association of osteoinductivity with age group, gender, and their interaction. The results confirm that properly processed demineralized bone from donors through at least 85 years of age is a viable grafting material. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 21–29, 2004
Color changes of dental resin composites by a salivary enzyme
Authors: Lee Yong‐Keun , Lim Bum‐Soon , Powers John M.
Published: June 2004

The objective of this study was to evaluate the color change (ΔE) of dental resin composites immersed in a salivary enzyme of esterase (ETE, porcine liver esterase, 400 mU/ml) compared to those immersed in phosphate‐buffered saline (PBS). The colors of three brands of resin composites of 13 shades were measured after polymerization and polishing with 1500‐grit SiC paper and after immersion in PBS or ETE up to 9 weeks. Color was measured according to the CIELAB color scale. ΔEafter immersion was calculated by the equation ΔE = [(ΔL*)2 + (Δa*)2 + (Δb*)2]1/2. Surface roughness (Ra) and Vickers hardness number (VHN) were measured. ΔEvalues after immersion in ETE was not higher than those in PBS. Immersion in solutions more than 3 weeks resulted in perceivable color changes (ΔE > 3.3) in one material, and immersion in solutions up to 9 weeks resulted in not‐perceivable color changes in the other materials. Discoloration generally increased as the immersion period increased. For one composite, the value increased abruptly in the period of 3 days to 3 weeks of immersion. The change in Ra value after immersion was varied by the composite and shade. VHN decreased significantly after immersion in ETE for nine weeks. Immersion in PBS resulted in decreased VHN in two composites. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 66–72, 2004
Fully quantum mechanical energy optimization for protein–ligand structure
Authors: Xiang Yun , Zhang Da W. , Zhang John Z. H.
Published: June 2004

We present a quantum mechanical approach to study protein–ligand binding structure with application to a Adipocyte lipid‐binding protein complexed with Propanoic Acid. The present approach employs a recently develop molecular fractionation with a conjugate caps (MFCC) method to compute protein–ligand interaction energy and performs energy optimization using the quasi‐Newton method. The MFCC method enables us to compute fully quantum mechanical ab initio protein–ligand interaction energy and its gradients that are used in energy minimization. This quantum optimization approach is applied to study the Adipocyte lipid‐binding protein complexed with Propanoic Acid system, a complex system consisting of a 2057‐atom protein and a 10‐atom ligand. The MFCC calculation is carried out at the Hartree–Fock level with a 3‐21G basis set. The quantum optimized structure of this complex is in good agreement with the experimental crystal structure. The quantum energy calculation is implemented in a parallel program that dramatically speeds up the MFCC calculation for the protein–ligand system. Similarly good agreement between MFCC optimized structure and the experimental structure is also obtained for the streptavidin–biotin complex. Due to heavy computational cost, the quantum energy minimization is carried out in a six‐dimensional space that corresponds to the rigid‐body protein–ligand interaction. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1431–1437, 2004
BF3 etherate catalysed formation of [11C]methyl esters: a novel radiolabelling technique
Authors: Ackermann U. , Tochon‐Danguy H. J. , Scott A. M.
Published: June 2004

A novel way of preparing 11C labelled methyl esters using [11C]methanol and either BF3 etherate or trimethylsilyl chloride as catalyst was investigated. Radiochemical yields with BF3 etherate were between 30 and 33% for [11C]methyl benzoate and less than 1% for [11C]methyl thio salicylate. No [11C]methyl ester formation could be observed with trimethylsilyl chloride for all compounds investigated.

This method is an alternative to using [11C]methyl iodide in the presence of a base. It is particularly suited for carboxylic acids bearing functional groups which would compete for [11C]methyl iodide, thus eliminating the need to introduce protecting groups. However, o‐anisic acid formed [11C]methyl salicylate in 33–30% decay corrected radiochemical yield due to hydrolytic cleavage of the methyl ether, and none of the desired [11C]methyl 2‐methoxy benzoate could be obtained. When salicylic acid was used as starting material, [11C]methyl salicylate could only be obtained in 5–8% decay corrected radiochemical yield. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis of multi‐unit protein hetero‐complexes in the gas phase via ion–ion chemistry
Authors: Gunawardena Harsha P. , McLuckey Scott A.
Published: June 2004

The synthesis of protein hetero‐complex ions via ion–ion reactions in the gas phase is demonstrated in a quadrupole ion trap. Bovine cytochrome c cations and bovine ubiquitin anions are used as reactant species in the stepwise construction of complexes containing as many as six protein sub‐units. For any set of reactants, a series of competitive and consecutive reactions is possible. The yield of complex ions for any given sequence of reactions is primarily limited by the presence of competitive reactions. Proton transfer represents the most important competitive reaction that adversely affects protein complex synthesis. In the present data, proton transfer takes place most extensively in the first step of complex synthesis, when single protein sub‐units are subjected to reaction with one another. Proton transfer is found to be less extensive when one of the reactants is a protein complex. The generation of hexameric hetero‐complexes containing two cytochrome c molecules and four ubiquitin molecules is demonstrated with two different synthesis approaches. The first involved the initial reaction of several charge states of cytochrome c and several charges states of ubiquitin. The sequence of reactions in this example illustrates the array of possible competitive and consecutive reactions associated with even a relatively simple set of multiply charged reactants. The second approach involved the initial reaction of the 9+ charge state of cytochrome c and the 5− charge state of ubiquitin. The latter approach highlights the utility of the multi‐stage mass spectrometric (MSn) capabilities of the ion trap in defining reactant ion identities (i.e. charge states and polarities) so that synthesis reactions can be directed along a particular set of pathways. Copyright © 2004 John Wiley & Sons, Ltd.
Performance in long‐term memory tasks is augmented by a phosphorylated growth factor receptor fragment
Authors: Dash P.K. , Mach S.A. , Moody M.R. , Moore A.N.
Published: June 2004

To elucidate the role of enhanced phosphoinositide‐3‐kinase (PI3‐kinase) activity in memory, a synthetic phosphopeptide (TAT‐YPMDM) containing the p85 regulatory subunit receptor‐binding motif (YXXM) coupled to the cell transduction domain of HIV‐TAT protein was employed. This phosphopeptide bound the p85 subunit of PI3‐kinase, and was internalized by both granule and pyramidal neurons when injected into the hippocampus. Increased lipid kinase activity and enhanced phosphorylation of the PI3‐kinase substrates Akt (protein kinase B) and ribosomal S6 kinase were associated with TAT‐YPMDM administration. Bilateral infusion of the phosphopeptide into the dorsal hippocampus after training improved performance in three hippocampus‐dependent memory tasks: contextual fear conditioning, trace fear conditioning, and the Morris water maze. Both the biochemical and behavioral effects of the TAT‐YPMDM phosphopeptide could be blocked by wortmannin. No effect was observed when a nonphosphorylated peptide (TAT‐YMDM), or a second, unrelated phosphopeptide (TAT‐YPLDL) was utilized. In addition, infusion of the TAT‐YPMDM phosphopeptide did not interfere with memory acquisition or 4 hr memory. In addition, pretesting administration did not affect the ability to recall a previously established long‐term memory. These findings suggest that stimulation of PI3‐kinase activity by phosphorylated receptor fragments containing the YMDM motif augments long‐term memory. © 2004 Wiley‐Liss, Inc.
Effects of sodium caseinate‐ and milk protein concentrate‐based edible coatings on the postharvest quality of Bing cherries
Authors: Certel Muharrem , Uslu Mustafa K , Ozdemir Feramuz
Published: June 2004

Bing cherries were coated with sodium caseinate‐ or milk protein concentrate‐based edible coatings. Besides the proteins (100 g kg−1), the coating formulations also included glycerol (about 300 g kg−1 protein) and either beeswax or a stearic–palmitic acid blend at a concentration of 0, 100 or 300 g lipid phase kg−1 of protein. All coatings, especially those containing 300 g kg−1 stearic–palmitic acid blend, successfully reduced water loss of the fruits. The edible coatings had a beneficial effect on the sensory quality of the cherries, and there were significant (p < 0.05) effects of the coating treatments on soluble solids, titratable acidity and pH. Copyright © 2004 Society of Chemical Industry
Elevated threshold for intracortical inhibition in focal hand dystonia
Authors: Stinear Cathy M. , Byblow Winston D.
Published: June 2004

Differences between control and focal hand dystonia (FHD) subject groups in short interval intracortical inhibition (SICI) as determined by paired transcranial magnetic stimulation (TMS) can be difficult to demonstrate, due to interindividual differences. The purpose of this study was to compare two TMS methods for assessing SICI in 8 control and 7 FHD subjects. Electromyographic (EMG) data were recorded from the first dorsal interosseous (FDI) muscle of the dominant hands of the control subjects and affected hands of the FHD subjects. The first method used a conventional approach of setting conditioning stimulus intensity to 80% of rest threshold (RTh) and test stimulus intensity to 120% RTh. Three interstimulus intervals (ISIs) were used: 2 msec, 3 msec, and the ISI between 2 and 3 msec that produced optimal SICI. The second method was novel in that test stimulus intensity was set to 150% active threshold (ATh), and conditioning stimulus intensity was varied between 50% and 100% ATh. The latter was determined at the threshold for SICI and expressed as a ratio of ATh. There was no difference between the subject groups in the degree of SICI produced using the first method, at the three ISIs studied. However, using the second method, the SICI threshold:ATh ratio was found to be significantly higher for FHD subjects. This finding suggests that determining the SICI threshold:ATh ratio may be a more sensitive measure of intracortical inhibitory function than more conventional methods. © 2004 Movement Disorder Society
Colonic transit time, sphincter EMG, and rectoanal videomanometry in multiple system atrophy
Authors: Sakakibara Ryuji , Odaka Takeo , Uchiyama Tomoyuki , Liu Rhi , Asahina Masato , Yamaguchi Kazuya , Yamaguchi Taketo , Yamanishi Tomoyuki , Hattori Takamichi
Published: June 2004

Both constipation and fecal incontinence are prominent lower gastrointestinal tract (LGIT) dysfunctions that occur frequently in multiple system atrophy (MSA). We investigated the mechanism of constipation and fecal incontinence in MSA. Colonic transit time (CTT), sphincter electromyography (EMG), and rectoanal videomanometry were performed in 15 patients with MSA (10 men, 5 women; mean age, 63.5 years; mean duration of disease, 3 years; decreased bowel frequency [< 3 times a week] in 9; difficulty in expulsion in 11; fecal incontinence in 3) and 10 age‐matched healthy control subjects (7 men and 3 women; mean age, 62 years; decreased bowel frequency in 2; mild difficulty in expulsion in 2; fecal incontinence in none). Compared to the control subjects, MSA patients had significantly prolonged CTT in the rectosigmoid segment and total colon. Sphincter EMG showed neurogenic motor unit potentials in none of control subjects but in 93% of MSA patients. At the resting state, MSA patients showed a lower anal squeeze pressure (external sphincter weakness) and a smaller increase in abdominal pressure on coughing. During rectal filling, MSA patients showed smaller amplitude in phasic rectal contraction, which was accompanied by an increase in anal pressure that normally decreased, together with leaking in 3 patients. During defecation, most MSA patients could not defecate completely and had larger postdefecation residuals. MSA patients had weak abdominal strain, smaller rectal contraction on defecation, and larger anal contraction on defecation (paradoxical sphincter contraction on defecation), although these differences were not statistically significant. These findings in MSA patients were similar to those in Parkinson's disease patients in our previous study, except for the sphincter denervation and weakness in MSA. Constipation in MSA most probably results from slow colonic transit, decreased phasic rectal contraction, and weak abdominal strain, and fecal incontinence results from weak anal sphincter due to denervation. The responsible sites for these dysfunctions seem to be both central and peripheral nervous systems that regulate the LGIT. © 2004 Movement Disorder Society
Signal‐to‐interference‐plus‐noise ratio estimation for wireless communication systems: Methods and analysis
Authors: Jeske Daniel R. , Sampath Ashwin
Published: June 2004

The Signal‐to‐Interference‐plus‐Noise Ratio (SINR) is an important metric of wireless communication link quality. SINR estimates have several important applications. These include optimizing the transmit power level for a target quality of service, assisting with handoff decisions and dynamically adapting the data rate for wireless Internet applications. Accurate SINR estimation provides for both a more efficient system and a higher user‐perceived quality of service. In this paper, we develop new SINR estimators and compare their mean squared error (MSE) performance. We show that our new estimators dominate estimators that have previously appeared in the literature with respect to MSE. The sequence of transmitted bits in wireless communication systems consists of both pilot bits (which are known both to the transmitter and receiver) and user bits (which are known only by the transmitter). The SINR estimators we consider alternatively depend exclusively on pilot bits, exclusively on user bits, or simultaneously use both pilot and user bits. In addition, we consider estimators that utilize smoothing and feedback mechanisms. Smoothed estimators are motivated by the fact that the interference component of the SINR changes relatively slowly with time, typically with the addition or departure of a user to the system. Feedback estimators are motivated by the fact that receivers typically decode bits correctly with a very high probability, and therefore user bits can be thought of as quasipilot bits. For each estimator discussed, we derive an exact or approximate formula for its MSE. Satterthwaite approximations, noncentral F distributions (singly and doubly) and distribution theory of quadratic forms are the key statistical tools used in developing the MSE formulas. In the case of approximate MSE formulas, we validate their accuracy using simulation techniques. The approximate MSE formulas, of interest in their own right for comparing the quality of the estimators, are also used for optimally combining estimators. In particular, we derive optimal weights for linearly combining an estimator based on pilot bits with an estimator based on user bits. The optimal weights depend on the MSE of the two estimators being combined, and thus the accurate approximate MSE formulas can conveniently be used. The optimal weights also depend on the unknown SINR, and therefore need to be estimated in order to construct a useable combined estimator. The impact on the MSE of the combined estimator due to estimating the weights is examined. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
Revenue management: A real options approach
Authors: Anderson C.K. , Davison M. , Rasmussen H.
Published: June 2004

Revenue management is the process of actively managing inventory or capacity to maximize revenues. The active management typically occurs through managerial levers such as price, promotion, or availability. We present a novel real options approach to revenue management that is specifically suited to the car rental business. We illustrate the concept with actual car rental data. The model produces minimally acceptable prices and inventory release quantities (number of cars available for rent at a given price) as a function of remaining time and available inventory. The pricing and inventory release recommendations of the developed model confirm earlier empirical analysis that suggested current practises discount too deeply early in the booking cycle. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004
Treatment of CML in pediatric patients: Should imatinib mesylate (STI‐571, Gleevec) or allogeneic hematopoietic cell transplant be front‐line therapy?
Authors: Pulsipher Michael A.
Published: June 2004

Background

Long‐term survival of pediatric patients with chronic myelogenous leukemia (CML) receiving myeloablative hematopoietic stem cell transplantation from fully‐matched related and unrelated donors has been reported between 60 and 75%, but is associated with significant morbidity. Imatinib mesylate (STI‐571, Gleevec) and reduced intensity conditioning stem cell transplantation (RIC) are two promising new tools that offer potential for decreasing therapy associated morbidity for patients with CML.

Results

Large trials have shown significant responses in chronic phase patients treated with imatinib and reasonable but short‐lived responses in advanced phase CML. Data from adult studies is beginning to define populations likely to progress or have prolonged responses to imatinib, and some adult treatment paradigms are moving toward reserving transplantation until patients are at risk of failure with imatinib. Early trials of RIC transplantation in CML show decreased transplant related morbidity with efficacy similar to conventional transplantation, but the approach has yet to be verified in phase III studies. Data in pediatric patients with imatinib and RIC transplantation is limited.

Conclusions

Studies with imatinib are underway in pediatrics, but whether pediatric dosing schemes will lead to outcomes similar to adults is unknown. Because HLA‐matched myeloablative transplantation offers a high rate of cure in the pediatric population, clinical studies assessing the role of imatinib mesylate and RIC transplantation should be planned carefully in order to avoid sub‐optimal outcomes. © 2004 Wiley‐Liss, Inc.
How do women of diverse backgrounds value prenatal testing outcomes?
Authors: Kuppermann Miriam , Nease Jr Robert F. , Gates Elena , Learman Lee A. , Blumberg Bruce , Gildengorin Virginia , Washington A. Eugene
Published: June 2004

Objectives

To describe women's preferences for prenatal testing outcomes and to explore their association with sociodemographic characteristics and attitudes.

Methods

We conducted a cross‐sectional study of 584 racially/ethnically and socioeconomically diverse pregnant women aged 16 to 47 years recruited from 23 San Francisco Bay Area practices. We assessed preferences for 12 potential prenatal testing outcomes using the time trade‐off metric for all outcomes and the standard gamble metric for two outcomes. Preferences were calculated on a scale of 0 (death) to 1 (perfect health). Participants also completed a sociodemographic and attitude survey.

Results

Highest preference scores were assigned to outcomes resulting in the birth of a chromosomally normal infant (mean = 0.91–0.93; median = 0.99–1.00). Lower scores were obtained for outcomes involving pregnancy loss (mean = 0.69–0.87; median = 0.76–0.92), which were correlated with attitudes regarding miscarriage, pregnancy termination, and Down syndrome. The lowest scores were assigned to Down syndrome–affected births (mean = 0.67–0.69; median = 0.73–0.75), which also were correlated with attitudes toward Down syndrome. We did not find a statistically significant relationship between participants' preference scores and age.

Conclusion

Preferences for prenatal testing outcomes vary according to the pregnant women's underlying attitudes about pregnancy loss and Down syndrome, and not according to her age. Current age/risk‐based guidelines should account for individual variation in patient preferences. Copyright © 2004 John Wiley & Sons, Ltd.
First‐trimester nuchal translucency and maternal serum free β‐hCG and PAPP‐A can detect triploidy and determine the parental origin
Authors: Yaron Yuval , Ochshorn Yifat , Tsabari Sigal , Shira Anat Bar
Published: June 2004

Objective

To evaluate the levels of first‐trimester screening markers in triploid pregnancies and to determine the parental origin of triploidy.

Study Design

During the five‐year study period, 12 322 patients with singleton pregnancies underwent combined first‐trimester screening using nuchal translucency (NT) and maternal serum free β‐human chorionic gonadotrophin (free β‐hCG) and pregnancy associated plasma protein‐A (PAPP‐A) at 10 to 14 weeks' gestation. Maternal serum markers and NT were evaluated in cases of triploidy. Molecular analysis was performed using polymorphic markers to establish the parental source of triploidy.

Results

Eight cases of triploidy were detected at a rate of at least 1 in 1540. All cases were electively terminated early in gestation or resulted in spontaneous miscarriage. Two patterns of first‐trimester markers emerged: type I, characterized by extremely high levels of free β‐hCG and elevated NT; and type II, characterized by very low levels of PAPP‐A and free β‐hCG with normal NT. Molecular analysis demonstrated that type I triploidy is of paternal origin (diandric) and type II is of maternal origin (digynic).

Conclusions

On the basis of these results, it may be possible to detect triploid pregnancies in the first trimester and determine their origin using combined first‐trimester screening. Copyright © 2004 John Wiley & Sons, Ltd.
Second‐trimester diagnosis of complete trisomy 9 associated with abnormal maternal serum screen results, open sacral spina bifida and congenital diaphragmatic hernia, and review of the literature
Authors: Chen Chih‐Ping , Chern Schu‐Rern , Cheng Sho‐Jen , Chang Tung‐Yao , Yeh Li‐Fan , Lee Chen‐Chi , Pan Chen‐Wen , Wang Wayseen , Tzen Chin‐Yuan
Published: June 2004

Objectives

To present the prenatal diagnosis of complete trisomy 9 and to review the literature

Case

A 25‐year‐old primigravida woman was referred for amniocentesis at 19 weeks' gestation because of abnormal maternal screen results showing an elevated maternal serum alpha‐fetoprotein (MSAFP) level and a low maternal serum free β‐human chorionic gonadotrophin (MSfreeβ‐hCG) level.

Results

Genetic amniocentesis revealed a karyotype of 47,XX,+9 in the amniocytes and an elevated amniotic fluid AFP level. Ultrasonography demonstrated intrauterine growth restriction, left congenital diaphragmatic hernia, fetal ascites, a sacral spina bifida, a horseshoe kidney, and absence of amniotic fluid. Ultrafast magnetic resonance imaging scans further depicted detailed anatomical configurations of the major congenital malformations. The pregnancy was terminated subsequently. The proband postnatally manifested characteristic facial dysmorphism, limb deformities, and an open sacral spina bifida with myelomeningocele. Cytogenetic analysis of the skin fibroblasts revealed a karyotype of 47,XX,+9. Molecular studies of various uncultured fetal tissues using microsatellite markers confirmed a diagnosis of complete trisomy 9 resulting from a meiotic I nondisjunction error of maternal origin.

Conclusion

Complete trisomy 9 can be identified prenatally with advanced maternal age, sonographically detected fetal structural abnormalities, and abnormal maternal serum screen results. Fetuses with complete trisomy 9 may be associated with congenital diaphragmatic hernia, an open sacral spina bifida, elevated MSAFP, and low MSfreeβ‐hCG. We suggest detailed prenatal imaging investigations and genetic analyses of multiple fetal tissues when a prenatal diagnosis of trisomy 9 is made. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and characterization of novel optically active poly(amide–imide)s containing N,N′‐(pyromellitoyl)‐bis‐L‐valine diacid chloride and 5,5‐disubstituted hydantoin derivatives under microwave irradiation
Authors: Faghihi Khalil , Zamani Khosrow , Mirsamie Azzizullah , Mallakpour Shadpour
Published: June 2004

Pyromellitic dianhydride (1,2,4,5‐benzenetetracarboxylic acid 1,2,4,5‐dianhydide) was reacted with L‐valine in a mixture of acetic acid and pyridine (3:2) at room temperature, and then was refluxed at 90–100 °C, N,N′‐(pyromellitoyl)‐bis‐L‐valine diacid was obtained in quantitative yield. The imide–acid was converted to N,N′‐(pyromellitoyl)‐bis‐L‐valine diacid chloride by reaction with thionyl chloride. Rapid and highly efficient synthesis of a number of poly(amide–imide)s was achieved under microwave irradiation using a domestic microwave oven by polycondensation of N,N′‐(pyromellitoyl)‐bis‐L‐valine diacid chloride with six different derivatives of 5,5‐disubstituted hydantoin compounds in the presence of a small amount of a polar organic medium that acts as a primary microwave absorber. A suitable organic medium was o‐cresol. The polycondensation proceeded rapidly, compared with conventional melt polycondensation and solution polycondensation and was almost completed within 8 min, giving a series of poly(amide–imide)s with inherent viscosities in the range 0.15–0.36 dl g−1. The resulting poly(amide–imide)s were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, elemental analysis, inherent viscosity (ηinh) measurements, solubility testing and specific rotation measurements. The thermal properties of the poly(amide–imide)s were investigated by using thermogravimetric analysis. Copyright © 2004 Society of Chemical Industry
Synthesis and characterization of polyimide/oligomeric methylsilsesquioxane hybrid films
Authors: Lin Wei‐Jung , Chen Wen‐Chang
Published: June 2004

In this study, polyimide/silsesquioxane hybrid materials were synthesized from aminoalkoxysilane‐capped poly(pyromellitic dianhydride‐co‐4,4′‐oxydianiline) (PMDA‐ODA) and oligomeric methylsilsesquioxane (O‐MSSQ) precursors. The O‐MSSQ moiety was used to obtain well characterized nano‐inorganic cage and network structures in the hybrid materials. The effects of molecular structures and composition on the morphologies and properties of the prepared hybrid materials were studied. The phase separation of the prepared hybrid materials could be controlled by varying the molecular weight of the polyimide moiety, the SiOH end group content of the O‐MSSQ or the coupling agent. Homogeneous and transparent hybrid thin films were obtained from the low molecular weight polyimide moiety with a coupling agent, 3‐aminopropyltrimethoxysilane (APrTMS). However, microphase separation occurred if the molecular weight of the polyimide moiety was enhanced or was prepared without a coupling agent, as evidenced by atomic force microscopy (AFM), field emission scanning electron microscopy (FE‐SEM), and electron spectroscopy for chemical analysis (ESCA). The high SiOH content of the O‐MSSQ could enhance the bonding density between the organic and inorganic moiety and thus retard phase separation. The thermal and mechanical properties of the prepared hybrid materials were largely improved compared with the parent polyimide, PMDA‐ODA, and were demonstrated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and thermal‐stress analysis. The hybrid materials showed adjustable refractive index and dielectric constant by varying the O‐MSSQ content. The birefringence of the PMDA‐ODA was reduced by incorporating the O‐MSSQ moiety. This work revealed that the polyimide/O‐MSSQ hybrid materials could have potential applications as optical films or low dielectric constant materials. Copyright © 2004 Society of Chemical Industry
Synthesis, characterization and conformational transitions in copolymers of 2‐(o‐chlorophenyl)‐4‐methylene‐1,3‐dioxolane with vinyl monomers
Authors: Morariu Simona , Bercea Maria
Published: June 2004

Copolymers of 2‐(o‐chlorophenyl)‐4‐methylene‐1,3‐dioxolane with methyl methacrylate and styrene were synthesized in benzene at 85 °C in the presence of 2,2′‐azobisisobutyronitrile as initiator. The structure of the resulting copolymers was investigated and a polymerization mechanism was proposed. The intrinsic viscosity of the copolymers in dilute solutions of carbon tetrachloride was determined as a function of temperature and conformational transitions were investigated. Copyright © 2004 Society of Chemical Industry
Study of crystallization and melting behavior of polypropylene‐block‐polyethylenes copolymers fractionated from polypropylene and polyethylene mixtures
Authors: Xu Jun‐Ting , Ding Ping‐Jing , Fu Zhi‐Sheng , Fan Zhi‐Qiang
Published: June 2004

A series of ethylene–propylene block copolymer fractions of differing compositions, while still retaining broad molecular weight distributions, were obtained by fractionation of polypropylene (PP) and polyethylene (PE) copolymers prepared by sequential polymerization of ethylene and propylene. The crystallization and melting behavior of the polypropylene‐block‐polyethylene fractions were studied. It was observed that the major component could suppress crystallization of the minor component, leading to a decrease in crystallinity and melting temperature. Non‐isothermal crystallization showed that crystallization of the ethylene block was less influenced by composition and cooling rate than the propylene block. At fast cooling rates, the ethylene block could crystallize prior to the propylene block. Isothermal crystallization kinetics experiments were also conducted. We found that the block copolymers with minor ethylene components had smaller Avrami exponents (n ≈ 1.0), hence indicating a reduced growth dimension of the PE crystals by the pre‐existing PP crystals. On the other hand, the ethylene block exhibited much larger Avrami exponents in those block copolymers with major ethylene contents. Copyright © 2004 Society of Chemical Industry
A relaxational and conductive study on two poly(ether imide)s
Authors: Sanchis MJ , Díaz–Calleja R , Jaïmes C , Belana J , Cañadas JC , Diego JA , Mudarra M , Sellarès J
Published: June 2004

A study of the relaxations and the conductivity of poly(ether imide) (PEI) ULTEM 5000 was carried out. The results were compared with the ones obtained in a previous study of PEI ULTEM 1000. The glass transition temperature was determined by differential scanning calorimetry (DSC). Then, the relaxations of PEI ULTEM 5000 using the thermally stimulated depolarization current technique (TSDC) on conventionally polarized electrets were studied. Owing to the interesting structure indicated by this technique a more detailed analysis of the β relaxation was done using window polarization (WP). It was possible to isolate 7 subrelaxations that we related to their counterparts in PEI ULTEM 1000. WP was also used to compare, one by one, the other relaxations that both materials present. The analysis of the ρ relaxation showed that the space trapping capability is stronger in PEI ULTEM 5000. The role of conductivity was analyzed using open circuit polarized samples and, more quantitatively, using dielectric analysis (DEA) and the dielectric modulus formalism. DEA and dynamic mechanical thermal analysis (DMTA) were also used to obtain information about the polar relaxations, complementary to that obtained by TSDC. Copyright © 2004 Society of Chemical Industry
Synthesis of narrow‐polydispersity degradable dendronized aliphatic polyesters
Authors: Lee Cameron C. , Grayson Scott M. , Fréchet Jean M. J.
Published: June 2004

The divergent dendronization of an ϵ‐caprolactone‐based polymer has been performed to provide access to dendronized polymers with sufficient biocompatibility and degradability for use as drug‐delivery scaffolds. The synthesis was performed through the tin(II) 2‐ethylhexanoate‐catalyzed polymerization of a γ‐functionalized ϵ‐caprolactone monomer, followed by the divergent growth of pendant polyester dendrons at each repeat unit. The resulting dendronized polymers were obtained up to the fourth generation with molecular weights as high as 80,000 Da and with polydispersities between 1.11 and 1.22. The fourth‐generation hydroxyl‐terminated dendronized polymer was degradable under a variety of aqueous conditions. A comparison of the dendronization approach with a procedure involving the ring‐opening polymerization of a second‐generation dendritic macromonomer reveals that the former procedure is best suited for the preparation of this family of dendronized polyesters because it requires shorter reaction times and affords materials with higher degrees of polymerization. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3563–3578, 2004
Heterochain model for simultaneous long‐chain branching and crosslinking. II. Application to free‐radical polymerization
Authors: Tobita Hidetaka
Published: June 2004

The matrix formula developed in the context of hetrochain theory, M̄w = M̄wp + WF(I − M)−1S, was applied to describe the molecular weight development during free‐radical homopolymerization. All of the required probabilistic parameters are expressed in terms of the kinetic‐rate constants and various concentrations. In free‐radical polymerization, the primary chains are formed consecutively, and the number of heterochain types, N, is extrapolated to infinity. Practically, such extrapolation can be conducted on the basis of the calculated values for only three different N values with sufficient accuracy. This matrix formula is valid regardless of the chemical and reactor systems used, as long as the primary chain‐connection statistics is considered Markovian. The gel point can be determined simply by solving an equation det(I − M) = 0. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2791–2800, 2004
Heterochain model for simultaneous long‐chain branching and crosslinking. III. Multicomponent polymerization
Authors: Tobita Hidetaka
Published: June 2004

The matrix formula developed in the context of heterochain theory, M̄w = M̄wp + WF(I − M)−1S, was applied to describe the molecular weight development during free‐radical multicomponent polymerization. All of the required probabilistic parameters are expressed in terms of the kinetic‐rate constants and the various concentrations associated with them. In free‐radical polymerization, the number of heterochain types, N, needs to be extrapolated to infinity, and such extrapolation is conducted with only three different N values. This matrix formula can be used as a benchmark test if other approximate approaches can give reasonable estimates of the weight‐average molecular weights. The moment equations with the average pseudo‐kinetic‐rate constants for branching and crosslinking reactions may provide poor estimates when the copolymer composition drift during polymerization is very significant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2801–2812, 2004
Toxicity of the entomopathogenic fungus, Metarhizium anisopliae (Deuteromycotina: Hyphomycetes) to adult females of the blowfly Lucilia sericata (Diptera: Calliphoridae)
Authors: Wright C , Brooks A , Wall R
Published: June 2004

The fungus Metarhizium anisopliae (Metchnikoff) (Deuteromycotina: Hyphomycetes) is a natural component of soil flora world‐wide and is a causal agent of the green muscardine diseases of insects. The use of this pathogen as a potential biocontrol agent against adult females of the blowfly, Lucilia sericata (Meigen) (Diptera: Calliphoridae) was considered. The blowfly L sericata is an economically important agent of cutaneous myiasis of sheep, particularly in northern Europe. Exposure of flies to suspensions of fungal spores by immersion, topical application or tarsal contact with treated surfaces all resulted in high levels of fatal infection. Spores suspended in silicone oil resulted in higher levels of infection (50–70%) than those formulated in a 0.3 g litre−1 solution of the detergent Tween 80 (10–20%). Spore concentration had a significant effect on levels of infection of flies, with the highest levels of mortality (64%) resulting from a suspension of 1 × 107 conidia ml−1. The duration of tarsal contact had a significant effect on levels of infection. Mean infection levels of 30% were observed following exposure of free‐flying adults to a single spore‐treated, 5 × 15 cm2 cloth surface suspended from the roof of a cage (30 cm cube). The implications of the results for the potential use of M anisopliae in the biocontrol of blowflies are discussed. Copyright © 2004 Society of Chemical Industry
Determination of aldicarb, carbofuran and some of their main metabolites in groundwater by application of micellar electrokinetic capillary chromatography with diode‐array detection and solid‐phase extraction
Authors: Arráez‐Román David , Segura‐Carretero Antonio , Cruces‐Blanco Carmen , Fernández‐Gutiérrez Alberto
Published: June 2004

This paper describes a UV detection method for the pesticides aldicarb and carbofuran, and some of their main metabolites, aldicarb‐sulfoxide, aldicarb‐sulfone and 3‐hydroxy‐carbofuran, in ground waters. Micellar electrokinetic chromatography (MEKC) with diode‐array detection was developed for their determination at 210 nm. The experimental study was performed using sodium dodecyl sulfate (SDS) at a concentration level of 140 mM, and a buffer of borax/HCl 20 mM at pH 8 which gives the best resolution with an analysis time of less than 20 min. Different instrumental parameters such as voltage (23 kV), injection time (12 s) and temperature (25 °C) were optimized. The detection limits were in the range 2–7.4 µg litre−1 by solid‐phase extraction (SPE) with a subsequent evaporation step. Groundwater spiked samples were pre‐concentrated off‐line with graphite carbon and subsequently analyzed by MEKC with diode‐array detection yielding average recoveries between 77 and 97% (n = 4) with RSD between 2–7%. Copyright © 2004 Society of Chemical Industry
Novel features of amphiphilic peptide Mas7 in signalling via heterotrimeric G‐proteins
Authors: Bavec Aljoša
Published: June 2004

Amphiphilic peptide Mas7, a structural analogue of mastoparan is a known activator of heterotrimeric Gi‐proteins and its downstream effectors. This study investigated the functional interaction of Mas7 with a plasma membrane protein from CHO cells, the endogenous mono‐ADP‐ribosyltransferase. The substrate of endogenous mono‐ADP‐ribosyltransferase was the ADP‐ribosylated protein with a molecular mass of 36 kDa, which corresponded to the β subunit of heterotrimeric G‐proteins. The effect of Mas7 on endogenous mono‐ADP‐ribosyltransferase activity was in the micromolar range with a maximal activation of 205% over the basal. In pertussis treated plasma membranes, it was found that the effect of Mas7 on endogenous mono‐ADP‐ribosyltransferase was partially blocked, which suggests the involvement of G‐proteins, such as Gi or G0. In addition, an immunoassay was developed for the visualization of interaction between the α subunit and the βγ dimer of G‐protein on a Ni‐NTA support. The physical interaction was tested of Mas7 with the heterotrimeric G‐protein αi2 subunit, which was overexpressed together with β1γ2–His6 subunits in sf9 cells. An interaction between Gi2 heterotrimer and Mas7 was not observed, which was not in accordance with previously reported results of mastoparan obtained for Gi‐proteins from bovine brain. In conclusion, the signal is mediated from Mas7 to endogenous mono‐ADP‐ribosyltransferase via pertussis sensitive G‐proteins. Furthermore, it is hypothesized that Gi2 G‐proteins are not involved in the process. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
A Note on Weighted Least‐squares Estimation of the Shape Parameter of the Weibull Distribution
Authors: Lu Hai‐Lin , Chen Chong‐Hong , Wu Jong‐Wuu
Published: June 2004

This study proposes an alternative to the weighted least‐squares (WLS) procedure for estimating the shape parameter of the Weibull distribution. Bergman (Journal of Materials Science Letters 1986; 5:611–614), Faucher and Tyson (F&T) (Journal of Materials Science Letters 1988; 7:1199–1203) suggested using different WLS approaches for Weibull parameters. However, the simulation results show that the novel approach is better than that of Bergman, and is not significantly different from that of F&T. Furthermore, the novel approach is also simpler and easier to comprehend. Copyright © 2004 John Wiley & Sons, Ltd.
Refined Rank Regression Method with Censors
Authors: Wang Wendai
Published: June 2004

Reliability engineers often face failure data with suspensions. The rank regression method with an approach introduced by Johnson has been commonly used to handle data with suspensions in engineering practice and commercial software. However, the Johnson method makes partial use of suspension information only—the positions of suspensions, not the exact times to suspensions. A new approach for rank regression with censored data is proposed in this paper, which makes full use of suspension information. Taking advantage of the parametric approach, the refined rank regression obtains the ‘exact’ mean order number for each failure point in the sample. With the ‘exact’ mean order number, the proposed method gives the ‘best’ fit to sample data for an assumed times‐to‐failure distribution. This refined rank regression is simple to implement and appears to have good statistical and convergence properties. An example is provided to illustrate the proposed method. Copyright © 2004 John Wiley & Sons, Ltd.
Derivation of a general formula for the Shibuya–Wulfman matrix
Authors: Red Eddie , Weatherford Charles A.
Published: June 2004

An explicit and general formula for the Shibuya–Wulfman matrix, which may easily be programmed, is derived. The derivation closely follows the Fourier transform methods of Weniger. A graph of a number of typical matrix elements is given to show the dependence of the Shibuya–Wulfman matrix on the translation distance multiplied by the screening parameter. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
On the computation of (2‐2) three‐center Slater‐type orbital integrals of 1/r12 using Fourier‐transform‐based analytical formulas
Authors: Antolovic Danko , Silverstone Harris J.
Published: June 2004

We describe a computational scheme devised for using Fourier‐transform‐based analytic formulas for three‐center integrals of r, wherein each electron is described by a two‐center product of Slater‐type orbitals. The asymptotic behavior of the auxiliary functions, which are related to modified spherical Bessel functions and to exponential integrals, is investigated, and recursive computational schemes are derived that are shown to be numerically stable for high summation indices and large internuclear distances. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Fast and stable algorithm for analytical evaluation of two‐center overlap integrals over Slater‐type orbitals with integer and noninteger principal quantum numbers
Authors: Özdoğan Telhat
Published: June 2004

A unified algorithm is presented for analytical evaluation of two‐center overlap integrals over Slater‐type orbitals with integer and noninteger principal quantum numbers. Two‐center overlap integrals are expressed as finite sum of Gaunt coefficients and auxiliary functions S(p, t). Special attention is paid to the efficient calculation of this auxiliary function by introducing analytic and recurrence relations. In order to test the accuracy of the formula for two‐center overlap integrals, we performed an extensive study in which quantum numbers, orbital exponents, and internuclear distances were varied over wide ranges. We found that the method presented here for two‐center overlap integrals is fully reliable for very high quantum numbers and the computation times are very low. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004