bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature profiles in batch methyl methacrylate polymerization in gelled suspension
Authors: Polacco Giovanni , Semino Daniele , Palla Maurizio
Published: April 2004

A detailed analysis of a recently developed batch polymerization process is presented. The new technique, designed for the production of high purity polymers (e.g. for biomedical purposes), consists of a suspension polymerization in which the suspending phase is transformed into a gel before initiating polymerization. A detailed first principles model of the process is developed. Both experimental and theoretical results are for polymerization of methyl methacrylate in an aqueous phase, which has been gelled by the addition of agarose. The analysis is focused on the sensitivity of the system with respect to operating conditions, the kinetic parameters, and the heat transfer properties. The system thermal stability is a primary concern, because of the lack of agitation and the possible instability of the gelled phase at high temperature. Sensitivity to the maximum temperature is therefore examined. Parameters that can increase the polymerization rate, such as the initial initiator concentration, and many of the kinetic constants are found to affect mainly the time at which the maximum temperature appears, but not significantly its value. No problem of gel instability was found. An instability may appear only if the jacket temperature or the water to methyl methacrylate ratio is significantly varied. The model developed, and its use to compute system sensitivies, has proven to be valuable for reactor scale‐up and process understanding and optimization.
The relative influences of molecular structure on brittle fracture by fatigue and under constant load in polyethylenes
Authors: Zhou Y. , Lu X. , Zhou Z. , Brown N.
Published: April 2004

The resistance to failure under an oscillating load, fatigue, and to failure under constant load (CL), are presented for a large number of linear polyethylenes. The effects of fatigue and a CL on brittle fracture are compared with respect to the influence of the molecular structure such as branching and the molecular weight. Molecular weight has a relatively greater influence on fatigue, whereas branching is more important under CL.
Hydrolysis effects on the molecular weight degradation of condensation polymers as estimated from their prior drying condition
Authors: Sudduth Richard D.
Published: April 2004

A simple model has been developed to evaluate the potential random degradation of hydrolyzable polymers as a function of water remaining after drying but prior to processing. Molecular weight retention was found to be dependent on the initial molecular weight of the polymer as well as the hydrolysis efficiency, but independent of polymer crystallinity. At the same water content and hydrolysis efficiency, the model indicated that higher molecular weight polymers would be expected to yield a more significant molecular weight reduction. The potential degradation of hydrolyzable condensation polymers was also estimated from drying conditions recommended by producer companies. The results calculated from the hydrolysis model were in most instances consistent with producer company recommended drying conditions. A review of the literature also found that while the sensitivity of nylons to hydrolysis decreases with moisture content, nylon 6/6 specifically can sometimes increase in brittleness and viscosity to an unacceptable level after drying below a critical moisture content. Thus nylon 6/6 was found to have a preferred range of moisture content for optimum processing. The need for a test method to evaluate hydrolysis efficiency for hydrolyzable polymers was also discussed. Such a standard could be important in the practical evaluation of new materials developed to minimize hydrolysis susceptibility.
Numerical study of twin‐screw extruders by three‐dimensional flow analysis—development of analysis technique and evaluation of mixing performance for full flight screws
Authors: Kajiwara Toshihisa , Nagashima Yuki , Nakano Yoshio , Funatsu Kazumori
Published: April 2004

We have developed a method for predicting the three‐dimensional flow field in the melt conveying zone in counter‐rotating and co‐rotating twin‐screw extruders. We applied this technique to the full flight screws with thin flight width and open C‐shaped channels in both rotating type extruders having the same screw configurations. We compared the details of velocity and stress fields, the flow rates of transportation, and various kinds of leakage flows for both rotating type extruders. Also, we obtained the spatial distribution of tracer particles and residence time distribution using a numerical tracer experiment. The flow rate in the transport direction in the co‐rotating twin‐screw was larger than that in the counter‐rotating twin‐screw, and this suggested that the latter has higher transport performance when the screws have thin flight width and open C‐shaped channels as used in this study. As for the distributive mixing, it was found that the co‐rotating twin‐screw excels in the area of fluid rearrangement between the two screws and distribution in the rotational direction, while the counter‐rotating twin‐screw has the desirable characteristic of wide distribution in the axial direction. With regard to dispersive mixing, there was no considerable difference between calculated stress fields in both rotating type extruders.
Chemorheology of a highly filled epoxy compound
Authors: Spoelstra A. B. , Peters G. W. M. , Meijer H. E. H.
Published: April 2004

Based on measurements of the dynamic viscosity, a strategy is proposed to find an expression that relates the viscosity of an epoxy compound during curing, to the temperature, shear rate, and degree of reaction. It appeared that the dynamic viscosity is a unique function of the effective shear rate (i.e. the product of frequency and strain) over a wide range of frequencies and strains after being corrected for the temperature. The effective shear rate dependence of the viscosity is described with a power law with an exponent that depends on the conversion. The effect of temperature is described with an Arrhenius‐type equation with conversion dependent parameters. Differential scanning calorimetry is applied to determine the kinetic equation that is used, in combination with the thermal history, to obtain the conversion during the rheological measurements. The description of the viscosity gives a good prediction of the measured viscosity in the region between melting and gelation of the compound. The theories proposed in the literature to detect the gel point from dynamic experiments are examined. It is found that neither the G′‐G″ crossover, investigated by e.g. Tung and Dynes (1), nor the frequency‐independence of tan(δ), described by Winter (2, 3), can be used to determine the gel point of the given material. In contrast, the curves of G′ against conversion for measurements performed at equal strain but with different thermal histories appear to converge at a conversion of ∼18%, which agrees with the gel point determined through extraction experiments.
Foam formation in gas‐assisted injection molded parts: Theoretical and experimental considerations
Authors: Potente H. , Moritzer E. , Obermann C. H.
Published: April 2004

This article is concerned with a physico‐mathematical model to describe the foaming phenomenon in gas‐assisted injection molded parts. The investigations have been conducted on polycarbonate grades to begin with. When parts are produced by gas injection molding, foam has the effect of weakening the residual wall thickness and also of impairing optical quality. It would thus be an advantage if a parameter constellation could be defined in advance, which would ensure the suppression of foam formation.
Polymer blends with spatially graded structures prepared by phase separation under a temperature gradient
Authors: Tran‐Cong Qui , Okinaka Jin
Published: April 2004

Phase separation of poly(2‐chlorostyrene)/poly(vinyl methyl ether) (P2CS/PVME) blends driven by a temperature gradient was investigated by phase‐contrast optical microscopy combined with digital image analysis. The samples were set in a temperature gradient in such a way that the two ends of the gradient cover both sides of the critical point. When the high‐temperature side of the gradient is increased with a constant rate, the interface that divides the miscible and the phase separated regions of the blend moves toward the low temperature side, leaving the phase separating region behind. It was found that in the vicinity of this interface, the phase separation takes place slowly via the spinodal decomposition process, giving interconnecting structures. In the region far from the newly growing interface, the droplet morphology appears as a result of the late stage of the spinodal decomposition. These droplets grow with time according to the power law ξ ∝ tβ, with β increasing from 0.30 to 0.44 along the temperature gradient. The phase separated blends with these graded morphologies show the broadened mechanical tanδ due to the graded structures distributed along the temperature gradient.
Properties of aminosilane grafted moisture curable poly(vinyl chloride) formulations
Authors: Fernández O. S. Rodríguez , Gilbert M.
Published: April 2004

The reaction of plasticized PVC with [N‐(2‐amino ethyl)‐3aminopropyl trimethoxy silane] yielded silane‐grafted PVC that was crosslinked by a hydrolytic mechanism. It was found that crosslinking resulted in improvement of mechanical properties (tensile strength and elongation at break) specially at temperatures higher than 80°C. Properties at 130°C were substantially enhanced, showing a fourfold increase in ultimate tensile strength (UTS), and a twofold increase in elongation at break. There was a unique relationship between UTS at 130°C and gel content irrespective of processing conditions, with UTS starting to increase sharply around 30% gel content, and reaching a plateau at about 60%. Also, the softening temperature was improved. The crosslinked material had a higher softening temperature (up to 165°C, compared with 95°C for the compound without crosslinking agent), indicating that the hydrolytic crosslinking of PVC yielded a material with improved properties.
Carbon black–filled immiscible blends of poly(vinylidene fluoride) and high density polyethylene: The relationship between morphology and positive and negative temperature coefficient effects
Authors: Feng Jiyun , Chan Chi‐Ming
Published: April 2004

Conductive polymer composites were prepared by melt‐mixing of an immiscible blend of poly(vinylidene fluoride) (PVDF), high density polyethylene (HDPE), and carbon black (CB). Three major factors—the carbon black content, the carbon black type, and the composite morphology—were shown to have remarkable effects on the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effect of the composites. The relationship between the morphology and the PTC and NTC effects of the composites was investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The OM micrographs indicated that CB was selectively located in the HDPE phase and the SEM micrographs showed that there were some gaps between the two phases. The PTC effect of the composites is caused by the thermal expansion as a result of the melting of the HDPE crystallites. The morphology of the composites greatly affects the PTC and NTC behaviors of the composites. When the CB‐filled HDPE formed a continuous phase and the PVDF formed a dispersed phase, the PTC and NTC behaviors of the composites were similar to those of CB‐filled neat HDPE composite without crosslinking. When the composite exhibited an interlocking structure, a normal PTC effect could also be observed, but the NTC effect was delayed to higher temperatures. A mechanism was proposed to explain this new physical phenomenon, and the mechanism was verified by another CB‐filled polymer blend comprising an alternating copolymer of tetrafluoroethylene‐ethylene and HDPE.
The properties of recycled PVC bottle compounds. 1: Mechanical performance
Authors: Arnold J. C. , Maund B.
Published: April 2004

The properties of recycled PVC bottle material separated from the post‐consumer waste stream were investigated. In the first part of this study, attention was focused on the mechanical properties. In order to examine the effects of recycling, the properties of the recycled material were compared with those of virgin PVC and pure material that had been processed into bottles and then granulated. The effects of pulverization of the recycled material were also studied. The mechanical properties investigated included tensile, fatigue, and environmental stress cracking tests, in conjection with fracture surface examination, molecular weight determination, and impurity analysis. It was found that the recycled material did show significant reduction in strength and ductility, though pulverization improved the situation considerably. The main reason for this was the presence of impurities, especially PET, which although present at levels below 0.5% had a large effect on the properties.
The properties of recycled PVC bottle compounds. 2: Reprocessing stability
Authors: Arnold J. C. , Maund B.
Published: April 2004

Following a study of the mechanical properties of recycled PVC recovered from post‐consumer bottles, this study focuses on the effects of recycled material on processing. In particular, the effects of multiple recycling were studied to investigate any problems that may arise due to the repeated incorporation of recycled material into the processing stream. Batches of recycled flake and powder as well as pure but processed bottle flake material were subjected to simulated multiple recycling using a Torque Rheometer. Ten minutes at 170°C followed by granulation represented one recycle. Molecular weight and Infrared analyses were performed to assess the degree of degradation occurring during reprocessing. The results indicated a rapid degradation of the two recycled grades when compared with the purer bottle flake PVC. Further multiple recycling was then performed on bottle flake mixed with 0.2% polyethylene, which showed that the PE impurities accelerate the degradation process. Finally, the effects of restabilizing by adding new bottle flake material at each step were investigated. It was shown that surprisingly small levels of new material (30%) prevented degradation, even after 15 recycle steps.
Plasticization of poly(styrene‐b‐isobutylene‐b‐styrene) ionomers by acid salts of 2‐ethylhexyl‐p‐dimethylaminobenzoate
Authors: Storey Robson F. , Baugh Daniel W.
Published: April 2004

Poly(styrene‐b‐isobutylene‐b‐styrene) block copolymer ionomer (overall molecular weight = 71,200 g/mole; 25.5 wt% polystyrene, 4.7% sulfonation of phenyl units, 100% neutralized with KOH) was compounded with various organic and inorganic acid salts of 2‐ethylhexyl‐p‐dimethylaminobenzoate (ODAB) to explore the efficacy of these compounds as ionic plasticizers. Results were compared to the same polymer plasticized by zinc stearate. Plasticizers were added to the polymer at levels of ≈5 wt%. Films were prepared by solution casting from tetrachloroethylene. Thermogravimetric analysis (TGA) showed all ODAB derivatives to have lower decomposition temperatures than zinc stearate. Dynamic mechanical analysis (DMA) of the films showed varying degrees of ionic plasticization as evidenced by a lowering of the temperature at which the onset of flow occurred. With the exception of the stearic acid salt of ODAB, all ODAB derivatives were more efficient ionic plasticizers than zinc stearate. Among the ODAB derivatives, the degree of ionic plasticization varied, with the methane sulfonic and p‐toluene sulfonic acid salts being most effective, leading to the conclusion that processing temperatures could be tailored to specific applications by choice of plasticizer and level of incorporation.
Monitoring the evolution of PET branching through chemorheology
Authors: Dhavalikar R. , Xanthos M.
Published: April 2004

There is a high interest in modifying the rheological properties of polyethylene terephthalate (PET) through structural modifications while maintaining its thermoplastic nature. This article reports real‐time spectroscopic and rheological monitoring of the effects of reactive melt modification of PET with a multi‐functional epoxide—triglycidyl isocyanurate (TGIC)—that lead to chain extension/branching and subsequently formation of gel‐like structures. An infrared spectroscopic technique to monitor the simultaneously occurring degradation and chain extension/branching reactions was evaluated. The effects of reaction temperature, shear rate, and residence time were also investigated. Frequency scans at various time intervals on the reacting samples provided information on changes in the degree of branching and melt elasticity. The effect of method of sample preparation for chemorheological testing was also evaluated in this study. A 50% excess of the stoichiometric amount of TGIC for complete reaction with terminal carboxyl groups resulted in a self‐similar polymeric structure of PET near the sol‐gel transition point or a critical gel formation whose linear viscoelastic properties obey scaling law. An estimated fractal dimension from the experimental results was used to quantify the evolution of the branched network structure during the reactive melt modification. Polym. Eng. Sci. 44:474–486, 2004. © 2004 Society of Plastics Engineers.
Electrical conductivity of polymer blends containing liquid crystalline polymer and carbon black
Authors: Tchoudakov R. , Narkis M. , Siegmann A.
Published: April 2004

This paper presents results of a study of melt‐processed immiscible polymer blends of high impact polystyrene (HIPS), liquid crystalline polymer (LCP) and carbon black (CB). Relationships between composition, electrical resistivity and morphology of the blends produced by Brabender mixing followed by compression molding, extrusion through a capillary rheometer, extrusion through a single‐screw extruder and injection molding were investigated. The LCP phase morphology in the blends was found sensitive to the processing conditions. A blend composition of at least 20 wt% LCP and 2 phr CB is necessary to preserve the conductivity of filaments produced over a wide range of shear rates. Enhancement of conductivity of blends containing CB and 30 wt% or more LCP was observed, under processing at 270°C and increasing levels of shear rate. An important role of the skin region in determining the resisitivy of injection molded samples was found. A good agreement between resistivity values of extruded or injection molded blends with resistivity values of filaments produced at similar conditions by a capillary rheometer was shown. Hence, the study of shear rate effect on resistivity of capillary rheometer filaments may serve as a predictor of resistivity behavior in real processing procedures. Polym. Eng. Sci. 44:528–540, 2004. © 2004 Society of Plastics Engineers.
Constitutive equations for the viscoplastic response of isotactic polypropylene in cyclic tests: The effect of strain rate
Authors: Drozdov A. D. , deC. Christiansen J.
Published: April 2004

A series of uniaxial tensile loading‐unloading tests are performed on injection‐molded isotactic polypropylene at room temperature. In each test, a specimen is stretched up to the maximal strain ϵmax = 0.12 with a constant strain rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}, and retracted down to the zero stress with the same strain rate. The cross‐head speeds vary from 5 to 200 mm/min, which covers practically the entire range of strain rates used in conventional quasi‐static tests. A constitutive model is developed for the viscoplastic response of a semicrystalline polymer at small strains. The stress‐strain relations are determined by five adjustable parameters that are found by matching the observations. Fair agreement is demonstrated between the experimental data and the results of numerical simulation. Polym. Eng. Sci. 44:548–556, 2004. © 2004 Society of Plastics Engineers.
Experimental characterization of fill length behavior in extruders
Authors: Mudalamane Rajath , Bigio David I.
Published: April 2004

Channel Fill Length, defined as the length of fully filled regions in an extrusion screw, is gaining importance as a design parameter because of its implications for residence time distribution, distributive and dispersive mixing, and also process stability. Although models exist for theoretical estimation of fill length, it is difficult to apply these models for complex geometries and fluid rheology. Owing to the non‐linear relationship between fill length, geometry and operating conditions, it is time‐consuming to use empirical methods to characterize fill length behavior in any given extrusion process. In this work, it was found that fill length exhibits a linear relationship with the ratio of percent fill to percent empty fraction. Two different sets of fill length data taken from literature, one set from a co‐rotating, intermeshing geometry and the other from a counter‐rotating, non‐intermeshing geometry, were used to verify this relationship. This property of the extrusion process can be used by the researcher to quickly characterize fill length behavior over the entire operating range. Polym. Eng. Sci. 44:557–563, 2004. © 2004 Society of Plastics Engineers.
Production and analysis of injection molded micro‐optic components
Authors: McFarland Andrew W. , Colton Jonathan S.
Published: April 2004

Plastic micro‐optic components (smaller than 1 mm in overall dimension, with lenses on the order of 50 microns in radius) will be very useful in future digital imaging and MEMS technologies. Computational fluid dynamics (CFD) and finite element analysis (FEA) predicted the influence of different processing parameters upon the final shape of micro‐optic parts made from polystyrene, polycarbonate, and polymethylmethacrylate. Small‐scale phenomena such as surface tension and mold‐melt slip velocity were included in the models. The simulations were compared to physical parts, through birefringence and interferometry techniques, which permitted assessment of the computer modeling. The predicted radius of curvature trends match the measured trends, and the maximum difference between the predicted and corresponding measured radius of curvature was roughly 3.4%. The average difference between simulation and experiment for astigmatism and comatic aberration was less than 25%. Symmetry assumptions were tested and validated in more than 85% of the measured cases. Polym. Eng. Sci. 44:564–579, 2004. © 2004 Society of Plastics Engineers.
Polymeric composites for use in electronic and microwave devices
Authors: Moulart Alexandre , Marrett Courtney , Colton Jonathan
Published: April 2004

The dielectric and conductive properties of thermoplastic (ABS) composites filled with ceramic powder (barium titanate), conductive powders (carbon black, copper) and conductive fibers (carbon, steel) were investigated for use in electromagnetic crystals and microwave devices. Barium titanate/ABS composites were produced that had dielectric constants over 8 and loss tangents of 0.01, which are the requirements for electromagnetic crystals. Carbon black/ABS and steel fiber/ABS composites were obtained with conductivities suitable for electromagnetic shielding (over 10−3 S/cm). Fused decomposition modeling was tested as a method for building electromagnetic crystals and showed promising results. Polym. Eng. Sci. 44:588–597, 2004. © 2004 Society of Plastics Engineers.
Micromechanical properties on the surface of PVC/SBR blends spatially resolved by a nanoindentation technique
Authors: Zhu Shui‐Han , Chan Chi‐Ming , Mai Yiu‐Wing
Published: April 2004

The microhardness and micromodulus on the surface of poly(vinyl chloride) (PVC)/styrene‐butadiene rubber (SBR) blends were determined using a nanoindenter. A flat surface was obtained by microtoming the sample at −100°C in liquid nitrogen. Dozens of indents along a line with a spatial interval of 0.5 μm were performed. From the loading and unloading curves of each indentation, the stiffnesses of the unloading curve and the contact area between the sample and the indenter were evaluated, and the local modulus and hardness were calculated. Profiles of the local hardness and modulus were obtained from the lines of indents. Pure PVC and a miscible PVC/acrylonitrile‐butadiene rubber (NBR) (40/10) blend showed constant modulus and hardness values. In the case of an immiscible PVC/SBR (50/50) blend, which has a morphology of elongated PVC droplets in the SBR matrix, the hardness and modulus profiles showed regions of the different phases. At the interface between the SBR and PVC phases, a step change in the modulus and hardness profiles was observed. The force required to deform the material at the same displacement increased systematically across the interface from the SBR to the PVC phase because of the increasing contribution of the PVC phase. Polym. Eng. Sci. 44:609–614, 2004. © 2004 Society of Plastics Engineers.
Measuring professionalism
Authors: Bloland Harland G. , Tempel Eugene R.
Published: April 2004

Fundraising is now considered a profession and it has achieved a legitimacy, but during challenging times when its status is questioned, professionals must be able to monitor, defend, and continually improve its position.
The growth of fundraising: Framing the impact of research and literature on education and training
Authors: Levy Jamie D.
Published: April 2004

The proliferation of research and literature has had an impact on available training opportunities for fundraising professionals.
Synthesis and photoconductive characteristics of biphenylporphyrin‐containing poly(amic acid)s and polyimides
Authors: Zhu Bao Ku , Xu You Yi , Wei Xiu Zhen , Xu Zhi Kang
Published: April 2004

Three series of biphenylporphyrin (BPP)‐containing poly(amic acid)s (PAAs) were synthesized and converted into heat‐treated polyimides (HPIs) and chemically treated polyimides (CPIs). Viscosity measurements, UV–vis and IR spectroscopies, as well as thermogravimetric analysis (TGA), were used to characterize the structures of the polymers. UV–vis spectra revealed that the BPP units formed aggregates in PAA and CPI films, rather than in HPI films. Photoinduced discharge was used to characterize the photoconductive properties of these polymer films. It was found that the photosensitivity was greatly enhanced by introducing BPP units into the polymer chains. For these three series of polymers, the photosensitivity increased in the order PAA < HPI < CPI according to the content of BPP in the polymers. The photoconductive characteristics were interpreted by the intrinsic π—π* process of BPP aggregation and the extrinsic process of charge‐transfer complex formation. The best photoconductive performances of the CPIs were attributed to the existence of two charge‐carrier‐generation processes. Copyright © 2004 Society of Chemical Industry
Synthesis and characterization of novel polyimides starting from 1,2‐bis(p‐dimethylaminobenzylideneimino)alkane homologues and various dianhydrides
Authors: Koytepe Süleyman , Gök Yetkin , Alici Bulent , Seçkin Turgay , Çetinkaya Engin
Published: April 2004

The objective of this research was the preparation of polyimides from 1,2‐bis(p‐dimethylaminophenylimino)alkane homologues and various dianhydrides in N‐methylpyrrolidone by one‐stage polycondensation. The monomers were prepared via condensation of p‐dimethylaminobenzaldehyde and the corresponding diamines, 1,4‐diaminobutane, 1,3‐diaminopropane and 1,2‐diaminoethane. The influence of the incorporation of this moiety into the polymer backbone on the properties of the polyimides has been evaluated. The thermogram of the polyimides indicated that PI‐10 to PI‐32 had Tg values ranging from 181 to 290 °C. The inherent viscosities of the polymers ranged from 0.99 to 2.05 dl g−1, and the highest solubility was obtained without significant loss of the thermal properties. Copyright © 2004 Society of Chemical Industry
Effect of hydrotalcite on the thermal stability, mechanical properties, rheology and flame retardance of poly(vinyl chloride)
Authors: Wang Xiaodong , Zhang Qiang
Published: April 2004

Compounds of poly(vinyl chloride) (PVC) and hydrotalcite were prepared via melt blending, and the thermal stability, mechanical properties, rheology and flame retardance were studied. Transmission electron microscopy showed that the hydrotalcite achieved an optimal dispersion in PVC compounds when surface‐treated with titanate coupling agent. The Congo Red test and thermogravimetric analysis demonstrated that the thermal stability of PVC was improved significantly only in the presence of a complex of the hydrotalcite and the organotin stabilizer. Such a significantly positive thermal stabilizing effect was attributable to the stabilizing mechanisms that the electrostatic interaction generated between the electron cloud of chlorine atoms in PVC chain and the positive lay charge of hydrotalcite, which resulted in a decrease in electronic cloud density of chlorine atoms. This weakened the activity of chloride atoms, and restricted the initiation of the dehydrochlorination. A surface treatment for the hydrotalcite with the titanate coupling agent could reduce deterioration of the mechanical and rheological properties of the PVC at low concentration of hydrotalcite. The hydrotalcite also enabled useful application of PVC as a flame retardant as well as a smoke retarder in the light of a LOI value of more than 28.7 and UL 94 V‐0 grade at a PVC/hydrotalcite weight ratio of 70/30. Copyright © 2004 Society of Chemical Industry
A comprehensive characterization of the peptide and protein constituents of human seminal fluid
Authors: Fung Kim Y.C. , Glode L. Michael , Green Spencer , Duncan Mark W.
Published: April 2004

BACKGROUND

Knowledge of the peptide and protein components of seminal fluid and their role in prostate diseases including benign prostatic hyperplasia and prostate carcinoma is scant. We have undertaken a proteomic analysis of semen as a forerunner to identifying sensitive and specific diagnostic markers of prostatic diseases; to aid in improved therapeutic intervention; and, to enhance our understanding of prostate health and disease.

METHODS

Peptide and protein components of pooled human seminal fluid (n = 5) were separated by gel electrophoresis (1D and 2D) and identified by either matrix‐assisted laser desorption ionization‐time‐of‐flight‐mass spectrometry (MALDI‐TOF‐MS) or capillary liquid chromatography tandem mass spectrometry (LC–MS/MS).

RESULTS

Analysis by two‐dimensional electrophoresis (2DE) established that there were multiple post‐translational variants of the majority of the proteins. Hormones, growth factors and bioactive peptides were detected and identified.

CONCLUSIONS

We have identified over 100 protein and peptide components of normal human seminal fluid. © 2004 Wiley‐Liss, Inc.
CVS‐3983, a selective matriptase inhibitor, suppresses the growth of androgen independent prostate tumor xenografts
Authors: Galkin Anna V. , Mullen Lynne , Fox William D. , Brown Jason , Duncan David , Moreno Ofir , Madison Edwin L. , Agus David B.
Published: April 2004

BACKGROUND

Matriptase, a type‐II transmembrane serine protease, is expressed by cancers of epithelial origin including breast, colon, and prostate carcinomas and has been implicated in tumor growth and progression. We studied the effects of CVS‐3983, a selective small molecule matriptase inhibitor, on the growth of the androgen independent (AI) CWR22R and CWRSA6 human prostate cancer xenograft models.

METHODS

CVS‐3983 was administered i.p. twice‐daily 7‐days per week for 2–3 weeks to mice with established tumors. Measurements of tumor volume were made twice weekly. The effect of CVS‐3983 on CWR22RV1 cell invasion through a reconstituted basement membrane matrix of proteins was also evaluated. Matriptase expression across the tumor lines was assessed by RT‐PCR and Western blotting.

RESULTS

CVS‐3983 inhibited final mean tumor volume by 65.5% (n = 10, P = 0.0002) in the CWR22R model and by 56.2% (n = 8, P = 0.0017) in the CWRSA6 tumor model compared with vehicle‐treated tumors. CVS‐3983 did not inhibit the proliferation of CWR22RV1 cells in vitro; however, the small molecule did significantly reduce by 30.2% the invasion of these cells in vitro through a reconstituted basement membrane matrix. Molecular analysis of the xenograft tumors demonstrated high expression levels of matriptase at the RNA and protein levels, which were not affected by CVS‐3983 treatment.

CONCLUSIONS

These results identify CVS‐3983 as a potent inhibitor of AI prostate cancer cell invasion in vitro and established xenograft tumor growth in vivo. © 2004 Wiley‐Liss, Inc.
Periodic approach to the electronic structure and magnetic coupling in KCuF3, K2CuF4, and Sr2CuO2Cl2 low‐dimensional magnetic systems
Authors: Moreira Ibério de Pinho Ribeiro , Dovesi Roberto
Published: April 2004

The ab initio periodic unrestricted Hartree–Fock method and several generalized gradient algorithm (GGA) and hybrid density functional theory (DFT) approaches have been used to investigate the ground‐state electronic and magnetic properties of three low‐dimensional magnetic copper insulators, namely, KCuF3, K2CuF4, and Sr2CuO2Cl2. A Gaussian atomic basis set optimized for the crystal environment has been used to construct the crystalline orbitals in the LCAO approximation as implemented in the CRYSTAL code. The interaction between magnetic moments on Cu2+ ions (d9 local configuration) strongly depends on the crystal structure and hence on the resulting electronic structure: Sr2CuO2Cl2 is representative of 2‐D antiferromagnetic systems, closely related to the high‐Tc parent cuprate superconductors; K2CuF4 is a 2‐D ferromagnetic system and KCuF3 behaves as a quasi‐1‐D antiferromagnetic system. The most stable electronic state, the relevant magnetic coupling constants, and the magnetic form factors are calculated by means of the various Hamiltonians. The systems turn out to be large band‐gap insulators in the UHF and hybrid DFT approximations, whereas they become metallic or narrow band‐gap semiconductors in the local density approximation or GGA approximations. UHF gives a qualitatively correct description of this kind of magnetic insulators and, more important, good relative values for the relevant magnetic coupling constants. Hybrid functionals (like B3LYP) largely improve, with respect to the other Hamiltonians, the magnitude and nature of the band‐gap, the spin densities on the Cu2+ ions, and the most important magnetic coupling constants, providing a reasonable, semiquantitative description of this kind of strongly correlated materials. In addition, those functionals correctly account for the distortions due to the Jahn–Teller effect in KCuF3, in contrast to LDA and PW‐GGA, where no stabilization appears when the distortion is included. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Second quantization and Floquet quasienergies of the parabolic barrier
Authors: Palma A. , Sandoval L. , Martin M. , Lefebvre R.
Published: April 2004

In this work we show how to find the Floquet quasienergies of a parabolic barrier Hamiltonian interacting with a periodic field mode using a convenient definition of ladder operators. Although these operators are not adjoint to each other in the configuration space, they, however, keep all the other properties of the usual ladder operators for the harmonic oscillator. We also use the Bargmann–Segal representation to find the eigenvalues and eigenfunctions of the parabolic barrier in a straightforward way. The use of second‐order perturbation theory and the Bogoliubov–Tyablikov transformation enables us to obtain the Floquet shift by utilizing only the algebraic properties of these ladder operators. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Potential energy surfaces of fluorinated benzene radical cations
Authors: Vysotsky Victor P. , Salnikov George E. , Shchegoleva Lyudmila N.
Published: April 2004

Ab initio ROHF, CASSCF, UMP2, and DFT/B3LYP calculations using the standard 6‐31G* basis set have been done to study potential energy surfaces (PESs) of selected fluorobenzene radical cations. The stationary PES points have been located, their types and interrelations have been established, and the PES sections have been constructed. The points of conical intersection of π terms have been determined at the ROHF and CASSCF levels of calculations. An opposite behavior of the intersection point at the increase of calculation level has been revealed for C6H5F+ and 1,3‐F2C6H cations, and for the 1,2,3‐F3C6H cation. In the first case, the intersection point has a tendency to shift to the structure of maximum energy and may disappear at a higher level of calculation. However, the intersection is retained in the case of 1,2,3‐F3C6H, which results in the pseudorotational structure of the PES. A low barrier for pseudorotation found for the 1,2,3‐trifluorobenzene radical cation points out the possibility of revealing the pseudo‐rotation in experimental ESR spectra. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
A kinetic stability study of MN (MBe, Mg, Ca, Sr, and Ba)
Authors: Zhao Jun Fang , Li Qian Shu
Published: April 2004

This work describes a structure and kinetic stability study of some complexes with the general formula MN, where M are the alkaline earth metal atoms, Be, Mg, Ca, Sr, and Ba. A complex (A) with two points of attachment to the N5 ring is the most energetically favored for all metals considered here. Except for Be, structure (B) containing a mono‐coordinated metal atom is a transition state corresponding to the metal atom transfer around the N5 ring. Pyramidal structure (C) is kinetically unstable with the low isomerization barrier height, ranging from 0.9 to 6.7 kcal/mol. The dissociation barrier heights for the lowest energy isomers (A) are predicted to be 1.2–18.7 kcal/mol (Be to Ba), indicating that kinetic stability increases from lighter to heavier metal atoms. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Quantum dynamical manifolds: Pair states in high‐temperature superconductivity
Authors: Scofield D. F. , Collins T. C.
Published: April 2004

The formation of Dirac pair states is shown to be crucial to the formation of the superconductive state. The properties of these Dirac bipolaron states is studied using a quantum dynamical extension of Cartan's moving frame approach to differential geometry. The overall geometric method, called quantum dynamical manifold theory (QDMT), is used to obtain the Dirac quasiparticle pair states (cooperons and potential cooperons or Dirac polaron pairs) in a polarizable medium appropriate for high‐temperature superconductors (HTSCs). The matrix solutions of the equations describing the quantum dynamical manifold have a (flavor) symmetry also occurring in other closed‐shell systems. By independently coupling each Dirac electron to a polarizable background in a semiclassic approximation, and solving the resulting quantum dynamical manifold equations (QDMEs), there are found new, nonperturbative, analytic solutions to the polaron pair (bipolaron) problem. This enables us to show that these cooperon states are closed shells with su(2) Lie algebraic symmetry. These are used to describe the cooperon system above and below the superconduction critical temperature. It is shown how these Dirac polaron pairs can be correlated for electron–electron interactions via virtual exciton exchange and screened Coulomb repulsion and then used in a homogeneous Bethe–Salpeter equation approach to study the onset of superconductivity of polaronic superconductors involving pairs of Dirac polarons. The relation of these states to the formation of a Bose–Einstein condensation (BEC) is discussed. To numerically investigate the question of the existence of high‐temperature superconductivity mediated by the screened Coulomb and boson exchange of virtual excitons, a wave vector‐ and frequency‐dependent effective interaction, Veff(k, ω), between electron or hole polaron pairs in the electronic polaron model is used in lieu of a full pairing interaction, thereby simplifying the analysis of interacting pair states. We include the temperature dependence of the dielectric function, ε−1(k, ω, T), for many‐body systems of these quasiparticles. An effective mass method is employed to further simplify the computations. Analysis of the results shows that the attractive part of Veff for the electronic polaron model persists to high temperature. Further, polarons not participating in the superconductive state produce a measurable Fermi surface even in the presence of the bipolaron BEC. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Intermolecular interaction in C60‐based electron donor–acceptor complexes
Authors: Sheka Elena F.
Published: April 2004

Quantum chemical (QCh) testing of the donor–acceptor (D–A) properties of binary molecular complexes, related to the singlet state, is suggested as QCh calculations of both studied systems and their constituents, using the spin‐nondependent (RHF) and spin‐dependent (UHF) version of the exploited computational tool in common. The avoided crossing of intermolecular interaction terms of neutral molecules Eint(A0B0) and molecular ions Eint(A+B−) lays the foundation for the analysis. The dependence of D–A complex properties on the type of the ground state interaction term, space positions of its minimum, as well as interrelation of the corresponding energies, is discussed. The suggested approach has been applied to binary complexes C60 + X (XTAE, TDAE, DMMA, COANP, 2Li, Mg). © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Prediction of reactive sites for the electropolymerization of p‐benzenesulfonic acid derivatives: Ab initio and experimental study
Authors: Nabais Catarina , Fartaria Rui P. S. , Silva Fernandes Fernando M. S. , Abrantes Luísa M.
Published: April 2004

A theoretical study of the electronic structure of some p‐benzenesulfonic acid derivatives is carried out to explain the electrooxidation of these compounds, in particular the allyl ether p‐benzenesulfonic acid, sodium salt electrooxidation, and electrode surface modification observed during electrochemical studies. The effects of the alkyl side chain and of the aromatic ring during electrooxidation are considered using the UHF and B3LYP levels of theory. The changes in monomer structure after removal of an electron are explained by the nodal structure of the highest occupied molecular orbital (HOMO), α and β single occupied molecular orbitals (SOMO) and by their energies. Apart from frontier molecular orbital theory, charge reaction control, which is expected to occur at higher oxidation potentials, is also discussed. The calculations indicate that the unpaired electron spin distribution and atomic charge variation in the radical cation is very sensitive to the nature of the alkyl side chain. In fact, this distribution reflects the electronic structure of these monomers related to their oxidability. It is shown that the removal of an electron is carried out by two competing mechanisms. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Bulk mineral flows and the sustainable development of the North West of England
Authors: McEvoy Darryn , Ravetz Joe , Handley John
Published: April 2004

Although industrial economies depend on natural resources to fulfil fundamental societal needs and to improve quality of life, increasing exploitation of these resources is exerting increasing pressure on our planet's ecological integrity. This paper, focusing on construction minerals, establishes a mass balance framework for the chosen case study – the North West of England – and uses the results to examine the implications for the sustainability of the region. The authors contend that a better understanding of the regional flow of materials, and the impact of human activity on surrounding ecosystems, will help to underpin informed decision‐making. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.
A prospective health impact assessment to progress the sustainable futures of a city: the case of Salford, UK
Authors: Douglas Calbert H.
Published: April 2004

This paper sets the discussion of sustainable development into the context of a city's sustainable futures by relating to the notions and contexts of community health and well‐being. The paper discusses aspects of research carried out to identify the potential and consequential health impacts that may arise from the Salford Health Investment for Tomorrow project and the Local Improvement Finance project. The project involved the redevelopment and provision of the new specialist acute hospital facilities at Salford Royal Hospitals Trust, in the City of Salford, UK and four primary care and social centres, representing substantial capital investments across the city. The research demonstrates sustainable development in application through the insights gained from the extensive range of positive and negative health outcomes that were predicted as likely to arise from the project. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.
Bridging the unsustainability gap: a framework for sustainable development
Authors: Boron Stefan , Murray Keith
Published: April 2004

Company experience is that environmental constraints are throttling business progress. Pressures from legislation, insurance, finance and stakeholders, who all demand evidence of environmental excellence, are ever increasing. At the same time, the economic system is driving business in a predominantly unsustainable direction. In view of this dilemma, the need for a practical methodology enabling the full implementation of sustainable development into business cannot be overstated.

Central to all this is a clear definition of what sustainable development means for industry in practice; how sustainable processing can be applied from first principles and the adoption of total sustainability as the ultimate goal.

This paper aims to clarify the important issues involved in practical sustainable development and to assemble the elements of a practical methodology or toolkit, for the attainment of total sustainability in business. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.
Sustainable development: a problem of environmental disruption now instead of intertemporal ethics
Authors: Ng Yew‐Kwang
Published: April 2004

Most people regard sustainable development as essentially a matter of intertemporal ethics. This paper argues that the crux is excessive environmental disruption due to an inadequate account for the external costs on other people now, rather than due to inadequate concern for our grandchildren. Even with full concern, the excessive disruption will be virtually unchanged. This paper also argues that intertemporal impartial welfare maximization is the appropriate objective to pursue. This involves treating the welfare of future generations on a par with that of our own but with all welfare values appropriately weighted by the probability of their realization. Since the probability of non‐survival is cumulative, this acts like a discount rate, though justified on completely different grounds. This solves the paradoxes of non‐existence of a solution or incomplete rankings associated with choices involving an infinite time horizon without discounting.

Sustainable development has been a hot topic for decades now. Most people regard it as essentially a matter of intertemporal ethics. This paper argues that the crux of the matter is excessive environmental disruption. With the proper control of environmental disruption, sustainable development will not be a problem in practice. Moreover, with or without proper control, impartial welfare maximization is sufficient to answer problems of sustainable development and intertemporal ethics at least at the conceptual level. Copyright © 2004 John Wiley & Sons, Ltd and ERP Environment.