bluuebunny/crossref_metadata_2025 huggingface dataset:
Hepatic gluconeogenesis and Krebs cycle fluxes in a CCl4 model of acute liver failure
Authors: Carvalho Rui A. , Jones John G. , McGuirk Chris , Sherry A. Dean , Malloy Craig R.
Published: August 2002

Acute liver failure was induced in rats by CCl4 administration and its effects on the hepatic Krebs cycle and gluconeogenic fluxes were evaluated in situ by 13C NMR isotopomer analysis of hepatic glucose following infusion of [U‐13C]propionate. In fed animals, CCl4 injury caused a significant increase in relative gluconeogenic flux from 0.80 ± 0.10 to 1.34 ± 0.24 times the flux through citrate synthase (p < 0.01). In 24‐h fasted animals, CCl4‐injury also significantly increased relative gluconeogenic flux from 1.36 ± 0.16 to 1.80 ± 0.22 times the flux through citrate synthase (p < 0.01). Recycling of PEP via pyruvate and oxaloacetate was extensive under all conditions and was not significantly altered by CCl4 injury. CCl4 injury significantly reduced hepatic glucose output by 26% (42.8 ± 7.3 vs 58.1 ± 2.4 µmol/kg/min, p = 0.005), which was attributed to a 26% decrease in absolute gluconeogenic flux from PEP (85.6 ± 14.6 vs 116 ± 4.8 µmol/kg/min, p < 0.01). These changes were accompanied by a 47% reduction in absolute citrate synthase flux (90.6 ± 8.0 to 47.6 ± 8.0 µmol/kg/min, p < 0.005), indicating that oxidative Krebs cycle flux was more susceptible to CCl4 injury. The reduction in absolute fluxes indicate a significant loss of hepatic metabolic capacity, while the significant increases in relative gluconeogenic fluxes suggest a reorganization of metabolic activity towards preserving hepatic glucose output. Copyright © 2002 John Wiley & Sons, Ltd.
The simplex algorithm for multicommodity networks
Authors: Detlefsen Nina K. , Wallace Stein W.
Published: August 2002

We consider multicommodity network flow problems, where external flow is allowed to vary and where flows of individual commodities may be constrained. For this problem, we describe the simplex algorithm. The simplex algorithm is based upon the inverse of the basis matrix. We discuss an approach where we only have to invert a working matrix with dimension at most equal to the number of arcs in the network. The dimension is independent of the number of commodities. The reduced cost of a nonbasic variable is found only using the working matrix that is explicitly inverted and some simple network operations. We also discuss how to pivot in the working matrix. The focus is on the detailed interpretation of the network structures arising in terms of cycles for the individual commodities. © 2002 John Wiley & Sons, Inc.
Early activation of Ca2+‐permeable AMPA receptors reduces neurite outgrowth in embryonic chick retinal neurons
Authors: Catsicas Marina , Allcorn Suzette , Mobbs Peter
Published: August 2002

Calcium entry through Ca2+‐permeable AMPA/kainate receptors may activate signaling cascades controlling neuronal development. Using the fluorescent Ca2+‐indicator Calcium Green 1‐AM we showed that the application of kainate or AMPA produced an increase of intracellular [Ca2+] in embryonic chick retina from day 6 (E6) onwards. This Ca2+ increase is due to entry through AMPA‐preferring receptors, because it was blocked by the AMPA receptor antagonist GYKI 52466 but not by the N‐methyl‐D‐aspartic acid (NMDA) receptor antagonist AP5, the voltage‐gated Ca2+ channel blockers diltiazem or nifedipine, or by the substitution of Na+ for choline in the extracellular solution to prevent the depolarizing action of kainate and AMPA. In dissociated E8 retinal cultures, application of glutamate, kainate, or AMPA reduced the number of neurites arising from these cells. The effect of kainate was prevented by the AMPA/kainate receptor antagonist CNQX and by GYKI 52466 but not by AP5, indicating that the reduction in neurite outgrowth resulted from the activation of AMPA receptors. Blocking Ca2+ influx through L‐type voltage‐gated Ca2+ channels with diltiazem and nifedipine prevented the effect of 10–100 μM kainate but not that of 500 μM kainate. In addition, joro spider toxin‐3, a blocker of Ca2+‐conducting AMPA receptors, prevented the effect of all doses of kainate. Neither GABA, which is depolarizing at this age in the retina, nor the activation of metabotropic glutamate receptors with tACPD mimicked the effects of AMPA receptor activation. Calcium entry via AMPA receptor channels themselves may therefore be important in the regulation of neurite outgrowth in developing chick retinal cells. © 2001 John Wiley & Sons, Inc. J Neurobiol 49: 200–211, 2001
Model updating by adding known masses
Authors: Cha P. D. , de Pillis L. G.
Published: August 2002

New approaches are developed that use measured data to adjust the analytical mass and stiffness matrices of a system so that the agreement between the analytical modes of vibration and the modal survey is improved. By adding known masses to the structure of interest, measuring the modes of vibration of this mass‐modified system, and finally using this set of new data in conjunction with the initial modal survey, the analytical mass matrix of the structure can be corrected, after which the analytical stiffness matrix can be readily updated. By manipulating the correction matrices into vector forms, the connectivity information can be enforced, thereby preserving the physical configuration of the system and reducing the sizes of the least‐squares problems that need to be solved. Solution techniques for updating the system matrices are introduced, and the numerical issues associated with solving overdetermined and underdetermined least squares problems are investigated. The effects of round‐off errors are also studied, and heuristic criteria are given for determining the minimum number of modes that need to be measured in order to ensure sufficiently accurate updated mass and stiffness matrices. Numerical experiments are presented to validate the proposed model‐updating techniques, to illustrate the effects of the number of measured modes on the quality of the updated model, to show how the magnitudes and locations of the added masses influence the updated matrices, and to highlight the numerical issues discussed in this paper. Copyright © 2001 John Wiley & Sons, Ltd.
Pacific ‘Babes’: issues in the origins and dispersal of Pacific pigs and the potential of mitochondrial DNA analysis1
Authors: Allen Melinda S. , Matisoo‐Smith Elizabeth , Horsburgh Ann
Published: August 2002

We explore potential sources of genetic variation in Pacific pigs over the duration of their commensal relationships with Pacific people. Three time periods are identified as critical to understanding the history of pigs in the Pacific region: (1) the late Pleistocene–early Holocene following from human movement into Near Oceania; (2) with Lapita colonization of Remote Oceania beginning ca. 3000 bp, and (3) in Polynesia, shortly after sustained Euro‐American contact (ca. late 1700s) when several new breeds were introduced into the region. This paper highlights the important role mitochondrial DNA (mtDNA) work can play in detailing the origins, directions, and frequency of pig transfers, and by extension, the movements of their human carriers. Our preliminary molecular studies identify a hypervariable region of mtDNA in the genus Sus, rendering it an ideal taxon for detailed study of the issues we raise herein. Copyright © 2001 John Wiley & Sons, Ltd.
Ancient injury recidivism: an example from the Kerma period of ancient Nubia
Authors: Judd Margaret
Published: August 2002

A topical trend in clinical research has been the study of repeat trauma, referred to by clinicians as “injury recidivism,” which lends itself to the assessment of accumulated injuries among ancient people. The present investigation examined the healed injuries among two archaeological skeletal samples from the Kerma period (ca. 2500–1500 BC) of Sudanese Nubia. Both groups were known to have a high prevalence of multiple trauma—80% of 54 adults from the rural sites (O16 and P37) located near Dongola and 42% of 212 adults from the urban site of Kerma sustained nonfatal injuries. It was observed that a higher frequency of multi‐injured adults displayed one or more violence‐associated injury (cranial trauma, parry fracture). When all injuries were considered 38% of individuals with violence‐related injuries had other traumatic lesions in contrast to 22% of individuals who experienced injuries associated with accidental falls (e.g., Colles', Smiths', Galeazzi, and paired forearm fractures), although this difference was not significant. When only the skulls and long bones were evaluated 81% of adults with multiple injuries to these major bones bore one or more violence‐related injuries, while 60% of adults with single injuries sustained violence‐related injuries. Most individuals with multiple injuries were male and less than 35 years of age; there was no significant difference in the frequency of violence‐ or accident‐related multiple injury between the rural and urban communities. Although it cannot be established whether or not some of an individual's injuries were experienced during simultaneous or independent incidents, the pattern of multiple injury among these two ancient Nubian skeletal samples reflected the profile of injury recidivism observed by modern clinicians cross‐culturally. Copyright © 2002 John Wiley & Sons, Ltd.
The long‐term effects of public housing on self‐sufficiency
Authors: Newman Sandra J. , Harkness Joseph M.
Published: August 2002

Recent years have witnessed an intensification of the debate about the fundamental purpose of public assistance to the poor and the effects of these programs on children. This study uses enriched data from the Panel Study of Income Dynamics to examine the effects of living in public housing as a child at some point between 1968 and 1982 on four young adult outcomes: welfare receipt; individual earnings; household earnings relative to the federal poverty line; and employment. Living in public housing during childhood increased employment, raised earnings, and reduced welfare use, but had no effect on household earnings relative to the poverty line. The beneficial effects could have arisen because public housing improved physical living conditions, reduced residential mobility, or enabled families to spend more of their income on items that benefit children's development. Whether these effects apply to contemporary public housing is unknown. © 2002 by the Association for Public Policy Analysis and Management.
High resolution solid‐state 13C‐NMR study of as‐cured and irradiated epoxy resins
Authors: Ngono‐Ravache Yvette , Foray Marie‐Francoise , Bardet Michel
Published: August 2002

This article presents the effects of strong ionizing radiations on the physico‐chemical modifications of aliphatic or aromatic amine‐cured epoxy resins based on diglycidyl ether of bisphenol A (DGEBA). Such epoxy resins have a considerable number of applications in the nuclear industrial field and are known to be very stable under moderate irradiation conditions.

Using extensively high resolution solid‐state 13C‐NMR spectroscopy we show that the aliphatic amine‐cured resin (DGEBA‐TETA) appears much more sensitive to gamma rays than the aromatic amine‐cured one (DGEBA‐DDM). On the one hand, qualitative analyses of the high resolution solid‐state 13C‐NMR spectra of both epoxy resins, irradiated under similar conditions (8.5 MGy), reveal almost no change in the aromatic amine‐cured resin whereas new resonances are observed for the aliphatic amine‐cured resin. These new peaks were interpreted as the formation of new functional groups such as amides, acids and/or esters and to alkene groups probably formed in the aliphatic amine skeleton. On the other hand, molecular dynamics of these polymers are investigated by measuring the relaxation times, TCH, T1ρH and T1C , before and after irradiation. The study of relaxation data shows the formation, under irradiation, of a more rigid network, especially for the aliphatic amine‐cured system and confirms that aromatic amine‐cured resin [DGEBA‐4,4′‐diaminodiphenylmethane(DDM)] is much less affected by ionizing radiations than the aliphatic amine‐cured resin [DGEBA‐triethylenetetramine(TETA)]. Moreover, it has been shown that the molecular modifications generated by irradiation on the powder of the aliphatic‐amine‐cured resin appear to be homogeneously distributed inside the polymers as no phase separations can be deduced from the above analyses. Copyright © 2001 John Wiley & Sons, Ltd.
Microtubules of polyaniline as new microwave absorbent materials
Authors: Wan Meixiang , Li Junchao , Li Shuzhen
Published: August 2002

The microtubules of polyaniline (PANI) with room temperature conductivity of 3.5–2.6 S/cm were synthesized by a template‐free method. The structural characterizations by UV‐vis and FT‐IR spectra as well as ­X‐ray diffraction showed that the polymer chain of the resulting microtubules was identical to the PANI doped with HCl, but its crystallinity was higher than that of PANI‐HCl. Moreover, the resulting microtubules exhibited an unusual magnetic loss at the microwave frequency (f = 1–18 GHz) arose from order arrangement of polaron as charge carrier caused by a tubular morphology. Copyright © 2001 John Wiley & Sons, Ltd.
Evaluation of detection methods for the reversed‐phase HPLC determination of 3′,4′,5′‐trimethoxyflavone in different phytopharmaceutical products and in human serum
Authors: Huck Christian W. , Bonn Günther K.
Published: August 2002

Quantitative determination of the major compound, 3′,4′,5′‐trimethoxyflavone (1), in plant extracts, in tablets of Flos and of Radix Primulae veris and in human serum has been accomplished using reversed‐phase HPLC with UV, fluorescence and mass spectrometric (MS) detection. Compared to UV detection, fluorescence detection showed greater selectivity, was 10‐fold more sensitive and allowed the determination of 1 in human serum after sample pre‐treatment by solid‐phase extraction. MS detection of 1 using electrospray ionisation (ESI) interface could be improved by substituting trifluoroacetic acid with the more polar and less conductive additive acetic acid, giving rise to a 230‐fold improvement in analyte detectability at the cost of an increase of only 45% in the peak width of the eluting peak at its half height. Further optimisation of the acetic acid concentration showed the highest signal intensity at 1.25% for HPLC‐atmospheric pressure chemical ionisation (APCI)‐MS and at 0.75% for HPLC‐ESI‐MS. The optimised MS method proved to be extremely selective, 50 times more sensitive than UV detection and 5 times more sensitive than fluorescence detection. Furthermore, fragment‐ion spectra produced by collision induced dissociation‐MS have been used as “fingerprints” for identifying compounds in the highly complex mixtures examine. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of precocenes in the essential oil of Ageratum spp. by reverse‐phase high‐performance liquid chromatography
Authors: Sharma Kiran , Sharma Om P.
Published: August 2002

The chromenes precocene I (7‐methoxy‐2,2‐dimethylchromene) and precocene II (6,7‐methoxy‐2,2‐dimethylchromene) extracted from Ageratum houstonianum and A. conyzoides have been analysed by reverse‐phase high‐performance liquid chromatography. Separation was achieved using a C18 column eluted with a linear gradient of acetonitrile and water. Precocenes I and II in the essential oils were determined to be 270 ± 23 and 482 ± 34 mg/mL in A. houstonianum, and 687 ± 21 and 20 ± 2 mg/mL in A. conyzoides. Copyright © 2001 John Wiley & Sons, Ltd.
Identification of benzophenanthridine alkaloids from Bocconia arborea by gas chromatography–Mass spectrometry
Authors: Gutierrez R. M. Perez , Vargas Solis R. , Gutierrez G. Diaz , Martinez‐Martinez F. J.
Published: August 2002

A methanol extract of the bark of Bocconia arborea was fractionated on silica gel and the fractions analysed using gas chromatography coupled with mass spectrometry (GC‐MS). Several benzophenanthridine alka‐loids were identified including dihydrosanguinarine, oxysanguinarine, 11‐acetonyldihydrochelerythrine, dihydrochelerythrine, chelerythrine, chelerythridimerine and angoline as the principal constituents. The results show that the direct GC‐MS analysis of these alkaloids is possible with a clear distinction between the compounds. The technique is shown to be a valuable tool and an alternative technique to classical phytochemical procedures permitting the fast analysis of alkaloids mixtures. Copyright © 2002 John Wiley & Sons, Ltd.
Maternal smoking: age distribution, levels of alpha‐fetoprotein and human chorionic gonadotrophin, and effect on detection of Down syndrome pregnancies in second‐trimester screening
Authors: Crossley J. A. , Aitken D. A. , Waugh S. M. L. , Kelly T. , Connor J. M.
Published: August 2002

Objectives

To study the levels of maternal serum alpha‐fetoprotein (AFP) and human chorionic gonadotrophin (hCG) in the second trimester in smokers and non‐smokers with unaffected and Down syndrome pregnancies; to examine the rate of smoking in different maternal age groups in a population having routine prenatal screening; and to assess the effect of smoking on the detection rates for Down syndrome and corresponding false‐positive rates, both overall and in different maternal age groups.

Methods

Information on maternal smoking status, maternal age and serum marker levels was collected from case note searches and the screening programme database on 2272 unaffected singleton pregnancies, 36 unaffected twin pregnancies and 103 singleton Down syndrome pregnancies.

Results

In unaffected pregnancies the smokers had a median age 3.3 years less than the non‐smokers, while in the Down syndrome cases the corresponding age difference was 2.0 years. Median analyte levels in multiples of the median (MoM) in the unaffected singleton pregnancies were, for non‐smokers: AFP=0.97, hCG=1.04; and for smokers, AFP=1.04, hCG=0.80. In the Down syndrome pregnancies the medians were, for non‐smokers: AFP=0.69, hCG=2.49; and for smokers, AFP=0.70, hCG=1.53. Correction for smoking status gave median MoMs of 1.0 for both AFP and hCG in the unaffected pregnancies in both smokers and non‐smokers. In the Down syndrome cases the corrected medians were, for non‐smokers: AFP=0.67, hCG=2.29; and for smokers, AFP=0.73, hCG=1.99. Before correction for maternal smoking the overall detection rate for Down syndrome was 66.7% with a false‐positive rate of 6.2%. After correction the detection rate was 67.7% with a false‐positive rate of 4.9%. Between the smoking and non‐smoking groups there was a significant difference in the detection rate (37.5% versus 76.0%) and the false‐positive rate (1.8% versus 8.1%), which disappeared after correction for smoking status (detection rate 62.5% versus 69.3%, false‐positive rate 3.9% versus 5.4%). No evidence of a lower incidence of Down syndrome in smokers was found.

Conclusions

While correcting AFP and hCG results for maternal smoking status will have little impact on the overall detection rate for Down syndrome, it may reduce the false‐positive rate and will improve the accuracy of the risks given to individual women. Copyright © 2002 John Wiley & Sons, Ltd.
The incidence of pressure sores following lower limb amputations
Authors: Spittle M. , Collins R.J. , Conner H.
Published: August 2002

In a retrospective survey of lower limb amputations (diabetic major amputations n=34, minor n=33; non‐diabetic major 28, minor 27), pressure sores developed following 55% of major and 20% of minor amputations (p<0.001). Sores developed after major amputations in 68% of diabetic but in only 39% of non‐diabetic patients (p=0.018). The incidence of sores after minor operations did not differ between the two groups. After major amputations sacral sores were more common in diabetic than in non‐diabetic patients (59 versus 36%, p=0.041), but the incidence of heel ulcers was similar. The mean age of patients developing sores was greater than in those who did not, in both diabetic (p<0.025) and non‐diabetic patients (p<0.01). Peripheral vascular disease appeared to be a more important risk factor than neuropathy for pressure sore development. Sores were no more common after epidural or spinal than after general anaesthesia. The Waterlow score was a poor predictor of the risk of developing a sore. The incidence of sores was not related to pre‐operative creatinine or albumin concentrations, but was greater in those whose haemoglobin concentration on the first or second post‐operative day was <10 g/dL (p=0.015). In conclusion, pressure sores are very common following amputation and especially so after major amputations in diabetic patients. All potential amputees should be managed as being at high risk of developing sores. Copyright © 2001 John Wiley & Sons, Ltd.
Impact of a diabetes midwifery educator on the diabetes in pregnancy service at Middlemore Hospital
Authors: Simmons D. , Conroy C. , Scott D.J.
Published: August 2002

We have assessed the effectiveness of a diabetes midwifery educator within a diabetes‐in‐pregnancy service serving a predominantly Polynesian population. A retrospective audit was undertaken of the charts of all women seen by the diabetes‐in‐pregnancy service at Middlemore Hospital, South Auckland for 8 months prior to introduction (n=76) and the same 8 months the following year (n=93). The women were well matched for age, ethnicity and past obstetric history. Previously known diabetes was present in 10%. After introduction of the role, insulin therapy (65% versus 50%. p<0.05), and maternal mean laboratory 2 hour post prandial glucose concentration (6.3±1.3 versus 5.7±1.0 mmol/l, p<0.01) were reduced and the proportion starting insulin as outpatients was increased (14% versus 89%, p<0.001). Birthweight and proportion receiving Caesarean delivery were non‐significantly lower. Total antenatal length of stay (7.5±6.6 vs 3.0±3.3 per patient, p<0.001) was reduced. The proportion receiving a post natal oral glucose tolerance test remained low but increased after the introduction of the follow up role (10% versus 29%, p<0.01). The introduction of the diabetes midwifery educator was associated with substantial reductions in resource utilisation with an improvement in glycaemic control and postnatal follow up. Copyright © 2001 John Wiley & Sons, Ltd.
Insulin injection practices
Authors: Partanen T‐M , Rissanen A
Published: August 2002

The purpose of this study was to investigate the practices of insulin injection and the grounds on which diabetic patients make decisions in relation to insulin therapy. The data for this study were collected by a structured questionnaire with a few open‐ended questions. The study group of 100 patients with type 1 diabetes was collected from two sources. The first half of them (50) came from the Central Hospital of North Karelia and the second half from the Diabetes Education Centre of the Finnish Diabetes Association. The study group consisted of 56 women and 44 men. The range of age was 17–64 (mean 32 years) and the duration of diabetes 1–40 years (mean 11 years). Injection site problems were reported by 65% of the patients. Patients utilising a small skin area for injections (the size of a stamp), or patients who had poor metabolic control (HbA1c>8.6%), reported more problems than other patients. 30% of the patients occasionally injected through clothing during unusual situations (e.g. parties, busy work etc). Occasional skipping of injections was reported by 31% of the patients for reasons such as oblivion or on purpose (e.g. low blood glucose). The most general basis for their injection routines was reported to be a habit and the other basis was patient education. The study suggests problems in insulin injection practices. Systematic checking of the injection sites and technique and the improvement of patient education are recommended. Copyright © 2000 John Wiley & Sons, Ltd.
Polyamides incorporating furan moieties: 4. Synthesis, characterisation and properties of a homologous series
Authors: Gharbi Souhir , Afli Aljia , Gharbi Rachid El , Gandini Alessandro
Published: August 2002

Interfacial polycondensation of 2,2′‐bis[2‐(5‐chloroformylfuryl)]propane with various diamines gave high yields of a novel series of furanic polyamides with high inherent viscosities. The properties of these polymers (Tg, surface energy, crystallinity, thermal stability) were assessed and examined in terms of the role of the specific structure of the bridging group borne by the diamines. Only three polyamides were partially crystalline, whereas all the others were amorphous. Thermogravimetric analysis revealed that thermal decomposition began above 300 °C in all instances.

© 2001 Society of Chemical Industry
Comparative studies on the flocculation characteristics of polyacrylamide grafted guar gum and hydroxypropyl guar gum
Authors: Nayak B R , Singh R P
Published: August 2002

The synthesis of two polysaccharide‐based graft copolymers with acrylamide, guar gum grafted polyacrylamide (GG‐g‐PAM) and hydroxypropyl guar gum grafted polyacrylamide (HPG‐g‐PAM) is described. The graft copolymers have been characterized by viscometry, infrared spectroscopy and thermal analysis. The flocculation characteristics of the graft copolymers have been studied in kaolin, iron ore, and silica suspensions. For the base polysaccharides guar gum (GG) and hydroxypropyl guar gum (HPG), it is observed that GG exhibits better performance than HPG in all three suspensions. For the graft copolymers, HPG‐g‐PAM shows better performance than GG‐g‐PAM. The flocculation characteristics of the best performing graft copolymer (HPG‐g‐PAM) are compared with various commercially available flocculants in the three suspensions mentioned above.

© 2001 Society of Chemical Industry
Influence of the polarity of ethylene–vinyl acetate copolymers on the morphology and mechanical properties of their uncompatibilised blends with polystyrene
Authors: Tang L W , Tam K C , Yue C Y , Hu X , Lam Y C , Li L
Published: August 2002

Rubber‐toughened polystyrene has been extensively studied and is a well‐established technology. However, the use of thermoplastic elastomers to toughen polystyrene (PS) is new and has the potential for further investigations. In the present study, three EVAs (ethylene–vinyl acetate copolymers) with identical melt flow indices (MFIs), of ∼2.5 dgmin−1, but different vinyl acetate (VA) contents, of 9.3 wt% (EVA760), 18.0 wt% (EVA460) and 28.0 wt% (EVA265), were melt blended with PS at 180 °C, and various ASTM test pieces were injection moulded at 200 °C. The polarity of the dispersed phase (ie EVA), has a significant effect on the mechanical properties of the blends. Both mechanical and rheological studies reveal that the uncompatibilised PS/EVA265 blends exhibit some degree of compatibility when the amount of EVA265 is lower than 30 wt%. These results indicate that EVA265 with the highest VA content is the most effective impact modifier for PS. The results clearly show that increasing the VA content in EVA increases the polarity of the dispersed phase, approaching that of the matrix (ie PS) and subsequently improving the compatibility between the two phases in terms of interfacial adhesion.

© 2002 Society of Chemical Industry
GaAs solar cells grown on Si substrates for space use
Authors: Yamaguchi Masafumi , Ohmachi Yoshiro , Oh'hara Takahiko , Kadota Yoshiaki , Imaizumi Mitsuru , Matsuda Sumio
Published: August 2002

GaAs single‐junction and InGaP/GaAs multi‐junction thin‐film solar cells fabricated on Si substrates have great potential for high‐efficiency, low‐cost, lightweight and large‐area space solar cells. Heteroepitaxy of GaAs thin films on Si substrates has been examined and high‐efficiency GaAs thin‐film solar cells with total‐area efficiencies of 18·3% at AM0 and 20·0% at AM 1·5 on Si substrates (GaAs‐on‐Si solar cells) have been fabricated. In addition, 1‐MeV electron irradiation damage to GaAs‐on‐Si cells has been studied. The GaAs‐on‐Si cells are found to show higher end‐of‐life efficiency than the conventional GaAs cells fabricated on GaAs substrates (GaAs‐ on‐GaAs cells) under high‐fluence 1‐MeV electron irradiation of more than 1 × 1015 cm−2. The first space flight to make use of them has been carried out. Forty‐eight 2 × 2 cm GaAs‐on‐Si cells with an average AM0 total‐area efficiency of 16·9% have been evaluated in the Engineering Test Satellite No.6 (ETS‐VI). The GaAs‐on‐Si cells have been demonstrated to be more radiation‐resistant in space than GaAs‐on‐GaAs cells and 50, 100 and 200‐μm‐thick Si cells. These results show that the GaAs‐on‐Si single‐junction and InGaP/GaAs‐on‐Si multi‐junction cells have great potential for space applications. Copyright © 2001 John Wiley & Sons, Ltd.
Purification of metallurgical‐grade silicon up to solar grade
Authors: Yuge N. , Abe M. , Hanazawa K. , Baba H. , Nakamura N. , Kato Y. , Sakaguchi Y. , Hiwasa S. , Aratani F.
Published: August 2002

An estimate has been made of the feasibility of a metallurgical purification process, the NEDO (New Energy and Industrial Technology Development Organization) melt‐purification process, for manufacturing solar‐grade silicon from metallurgical‐grade silicon. Equipment has been developed to pilot manufacturing plant scale. The system comprises an electron‐beam furnace for phosphorus removal and a plasma furnace for boron removal. Each furnace has a mold for directional solidification to remove metallic impurities. The concentration of each impurity in the silicon ingot purified through the whole process satisfied the solar‐grade level. The Solar‐grade silicon produced showed p‐type polarity and resistivity within the range 0·5–1·5 Ω cm. Copyright © 2001 John Wiley & Sons, Ltd.
Crystalline silicon manufacturing progress
Authors: Jester Theresa L.
Published: August 2002

The increasing demand for renewable forms of energy is making photovoltaic products an important part of the energy supply future. The costs of producing photovoltaic modules have been significantly reduced during the last 10 years as manufacturing costs per watt have dropped from over $6 per peak watt to less than half of that value now. This paper summarizes progress in several aspects of photovoltaic manufacturing which have contributed to this reduction. Crystal growth improvements, both in yield and machine design, have reduced the energy consumption by a factor of 3 and improved silicon utilization by 40%. Wafer slicing process changes have resulted in 66% more wafers being produced for a given amount of silicon. Cell production improvements in both automation and improved efficiency have reduced the labor cost contribution by 40% per watt. Larger modules and better materials have added another 10% reduction in the cost to produce photovoltaics. These improvements have contributed to a better energy payback time, reducing it from over 5 years to approximately 3. Reductions in cost and improvements in energy efficiency have made photovoltaic products a commercially viable alternate energy source. Copyright © 2002 John Wiley & Sons, Ltd.
Crystalline silicon feedstock for solar cells
Authors: Aulich Hubert A. , Schulze Friedrich‐Wilhelm
Published: August 2002

The generation of electricity with solar cells is considered to be one of the key technologies of the new century. Over the past ten years the photovoltaic (PV) industry has grown by more than a factor of five to approximately 200 MWp in the year 2000. This impressive growth is mainly based on solar cells made from crystalline silicon. One of the key factors for this growth has been the supply of economically priced silicon from the semiconductor industry. This paper gives an overview on the current silicon feedstock supply and outlines a supply and demand scenario for the next five years. The importance of better silicon utilization per Wp module power through thinner Si wafers and higher solar cell efficiency is stressed. The impact of a growing thin‐film technology on the silicon feedstock demand is considered as well. Copyright © 2002 John Wiley & Sons, Ltd.
Organosoluble and transparent polyimides derived from alicyclic dianhydride and aromatic diamines
Authors: Liu J. G. , He M. H. , Zhou H. W. , Qian Z. G. , Wang F. S. , Yang S. Y.
Published: August 2002

Organosoluble polyimides were synthesized with the alicyclic dianhydride 1,8‐dimethylbicyclo[2,2,2]oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride and aromatic diamines. The polyimides possessed good solubility both in strong dipolar solvents and in common solvents; the thermal decomposition temperature of the polyimides exceeded 420 °C. Strong and flexible films of the polyimides, with the cutoff of ultraviolet–visible absorption lower than 310–320 nm, exhibited good features as the alignment layers for nematic liquid crystals with pretilt angles of 1.5–2.9°. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 110–119, 2002
Organosoluble and light‐colored fluorinated polyimides from 4,4′‐bis(4‐amino‐2‐trifluoromethylphenoxy)biphenyl and aromatic dianhydrides
Authors: Yang Chin‐Ping , Hsiao Sheng‐Huei , Hsu Mao‐Feng
Published: August 2002

A novel fluorinated diamine monomer based on 4,4′‐biphenol was synthesized via a straightforward, high‐yielding two‐step procedure. 4,4′‐Biphenol was reacted with 2‐chloro‐5‐nitrobenzotrifluoride in the presence of potassium carbonate to yield the intermediate dinitro compound, which was subsequently reduced to afford the fluorinated diamine, 4,4′‐bis(4‐amino‐3‐trifluoromethylphenoxy)biphenyl. A series of organosoluble fluorinated polyimides were prepared from the diamine with various aromatic dianhydrides via a conventional two‐step thermal imidization method. All polyimides were soluble in strong dipolar solvents such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylacetamide. The polyimides showed excellent thermal and thermooxidative stability and good mechanical properties. No significant weight loss was observed below a temperature of 520 °C in nitrogen or in air, and the glass‐transition temperatures ranged from 247 to 313 °C. Low dielectric constants (2.57–3.65 at 10 kHz), low moisture absorption (0.1–0.7 wt %), and low color intensity were also observed. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 524–534, 2002; DOI 10.1002/pola.10113
Effect of the organophosphate structure on the physical and flame‐retardant properties of an epoxy resin
Authors: Shieh Jeng‐Yueh , Wang Chun‐Shan
Published: August 2002

2‐(6‐Oxido‐6H‐dibenzo〈c,e〉〈1,2〉oxa‐phosphorin‐6‐yl)1,4‐benzenediol (ODOPB) and bis(3‐dihydroxyphenyl) phenyl phosphate (BHPP) were successfully synthesized and used as reactive flame retardants in o‐cresol formaldehyde novolac epoxy resin. Because of the rigid, cyclic, side‐chain structure of ODOPB, the resultant phosphorus‐containing epoxy resin exhibited a higher glass‐transition temperature, better flame retardancy, higher modulus, and greater thermal stability than the regular bromine‐containing tetrabromobisphenol A epoxy resin and the linear, main‐chain, phosphorus‐containing BHPP epoxy resin. A UL‐94VO rating was achieved with a phosphorus content as low as 1.1% with ODOPB (comparable to a bromine content of 12% and a phosphorus content of 2.2% with BHPP) in the cured resins, and no fumes or toxic gas emissions were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 369–378, 2002
Synthesis and characterization of conducting poly(aniline‐co‐o‐aminophenethyl alcohol)s
Authors: Baek Sungsik , Ree Jason J. , Ree Moonhor
Published: August 2002

Poly(o‐aminophenethyl alcohol) and its copolymers containing the aniline unit were synthesized in aqueous hydrochloric acid medium by chemical oxidative polymerization. The chemical composition of these novel polymers was determined spectroscopically, and their viscosities were measured. These polymers exhibit good solubility in organic solvents that is attributed mainly to the polar hydroxyethyl side groups. Their structures (chain conformation and morphological structure) and properties (conductivity, electrochemical characteristics, glass transition, and degradation behavior) were characterized and then interpreted on the basis of the chemical composition along with the electronic and steric hindrance effects associated with the hydroxyethyl side group. Overall, the side group has a significant effect on the polymerization and influences the structure, chain conformation, and properties of the resultant polymer. The poly(aniline‐co‐o‐aminophenethyl alcohol)s containing 20–40 mol % o‐aminophenethyl alcohol units are potential conducting materials for microelectronic and electromagnetic shielding applications because they are easier to process than polyaniline but retain its beneficial properties. These polymers can also be used as a functional conducting polymer intermediate owing to the reactivity of the side group. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 983–994, 2002
Preparation of poly(N‐ethyl methacrylamide) particles via an emulsion/precipitation process: The role of the crosslinker
Authors: Hazot P. , Chapel J. P. , Pichot C. , Elaissari A. , Delair T.
Published: August 2002

Monodisperse, thermosensitive poly(N‐ethyl methacrylamide) microgel particles were prepared by the batch precipitation/emulsion polymerization of water‐soluble N‐ethyl methacrylamide and the hydrophobic crosslinker ethylene glycol dimethacrylate initiated by potassium persulfate. Particular attention was paid to the effect of the crosslinker agent on the polymerization process (kinetics, conversion, and water‐soluble oligomer content). Particles were characterized in terms of their size distribution and swelling capacity. A polymerization mechanism for the water‐soluble monomer and non‐water‐soluble crosslinker is proposed and discussed on the basis of a combination of both emulsion and precipitation polymerization processes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1808–1817, 2002
Atom transfer radical homo‐ and block copolymerization of methyl 1‐bicyclobutanecarboxylate
Authors: Chen Xiao‐Ping , Padias Anne Buyle , Hall H. K.
Published: August 2002

A non‐olefinic monomer, methyl 1‐bicyclobutanecarboxylate (MBC), was successfully polymerized by the controlled/“living” atom transfer radical polymerization (ATRP) technique, resulting in a well‐defined homopolymer, PMBC, with only cyclobutane ring units in the polymer chain. An AB block copolymer poly(methyl 1‐bicyclobutanecarboxylate)‐b‐polystyrene (PMBC‐b‐PS), having an all‐ring unit segment, was also synthesized with narrow polydispersity and designed number‐average molecular weight in addition to precise end groups. The 1H NMR spectra, glass‐transition temperature, and thermal stability of PMBC, PMBC‐b‐PS, and PS‐b‐PMBC were investigated. The experimental results showed that the cyclobutane rings in the two block polymers improved their thermal stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1929–1936, 2002
Polar, functionalized diene‐based materials. V. Free‐radical polymerization of 2‐[(N‐benzyl‐n‐methylamino)methyl]‐1,3‐butadiene and copolymerization with styrene
Authors: Wu Lifen , Sheares Valerie V.
Published: August 2002

2‐[(N‐Benzyl‐N‐methylamino)methyl]‐1,3‐butadiene (BMAMBD), the first asymmetric tertiary amino‐containing diene‐based monomer, was synthesized by sulfone chemistry and a nickel‐catalyzed Grignard coupling reaction in high purity and good yield. The bulk and solution free‐radical polymerizations of this monomer were studied. Traditional bulk free‐radical polymerization kinetics were observed, giving polymers with 〈Mn〉 values of 21 × 103 to 48 × 103 g/mol (where Mn is the number‐average molecular weight) and polydispersity indices near 1.5. In solution polymerization, polymers with higher molecular weights were obtained in cyclohexane than in tetrahydrofuran (THF) because of the higher chain transfer to the solvent. The chain‐transfer constants calculated for cyclohexane and THF were 1.97 × 10−3 and 5.77 × 10−3, respectively. To further tailor polymer properties, we also completed copolymerization studies with styrene. Kinetic studies showed that BMAMBD incorporated into the polymer chain at a faster rate than styrene. With the Mayo–Lewis equation, the monomer reactivity ratios of BMAMBD and styrene at 75 °C were determined to be 2.6 ± 0.3 and 0.28 ± 0.02, respectively. Altering the composition of BMAMBD in the copolymer from 17 to 93% caused the glass‐transition temperature of the resulting copolymer to decrease from 64 to −7 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3227–3238, 2001
Role of the in‐plane orientation of polyimide films in graphitization
Authors: Takeichi Tsutomu , Zuo Min , Hasegawa Masatoshi
Published: August 2002

Poly(amide acid) labeled with perylenetetracarboxydiimide (PEDI) was prepared from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), p‐phenylenediamine (PDA), and diamino‐PEDI. Poly(amide acid) was then reacted with sodium hydride and various kinds of alkyl iodides for transformation into various poly(amide ester)s. The cast films were imidized while fixed on glass substrates to give BPDA/PDA polyimide films. The degree of in‐plane molecular orientation (f) of the polyimides and their precursors, poly(amide acid) and poly(amide ester)s, were determined via measurements of the visible dichroic absorption at an incidence angle for a rodlike dye (PEDI) bound to the main chain. All precursor films showed relatively low degrees of in‐plane orientation. After imidization of the precursors fixed on glasses, however, striking spontaneous in‐plane orientation behavior was observed. The f value for polyimide film from a poly(amide acid) precursor was as high as 0.7–0.8. The f value for polyimide film from a methyl ester precursor, however, was lowered to 0.4–0.5, but it increased with the increasing size of the alkyl groups. Good correlations of the in‐plane orientation of the polyimide films with the tensile modulus of the films and the in‐plane orientation of the graphitized films were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3011–3019, 2001
Fatigue crack propagation mechanisms in poly(methyl methacrylate) by in situ observation with a scanning laser microscope
Authors: Ishiyama C. , Asai T. , Kobayashi M. , Shimojo M. , Higo Y.
Published: August 2002

Crack propagation tests were performed on an amorphous polymer, poly(methyl methacrylate), to investigate fatigue crack propagation mechanisms. A scanning laser microscope with a newly developed tensile testing machine was used to observe in situ crack propagation in compact‐type specimens. A crack usually propagated within the craze located at the crack tip under both static and cyclic loading conditions. When a crack stably propagated into the craze under static loading conditions, bright bands composed of the broken craze were observed at the edges along the crack wakes. However, there were successive ridges and valleys in place of bright bands along the crack wakes under cyclic loading conditions. When stable fatigue cracks were propagated at the loading half‐cycle in each cycle, new craze fragments appeared that were similar to the bright bands under static loading. However, the thickness of these fragments decreased in the following loading cycle, and a new valley was formed. This suggested that the valleys were formed by the contact between the fracture surfaces near the crack tip during unloading. Fatigue crack propagation is thought to be due to fibrils weakened by crack closure between fracture surfaces. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3103–3113, 2001
Structural characteristics and moisture sorption behavior of nylon‐6/clay hybrid films
Authors: Murase Shigemitsu , Inoue Atsushi , Miyashita Yoshiharu , Kimura Noritaka , Nishio Yoshiyuki
Published: August 2002

The structure of nylon‐6 hybrids with synthetic or natural clays was investigated for melt‐pressed films with Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, and differential scanning calorimetry in comparison with the nylon‐6 homopolymer. In contrast to the development of familiar α‐form crystals in plain nylon‐6 film, the hybrid films produced γ‐form crystals when nylon‐6 was conjugated with synthetic mica, whereas the hybridization with natural montmorillonite gave rise to both α‐ and γ‐crystalline modifications. The degree of crystallinity of the nylon‐6 hybrid with synthetic mica was the highest of the three series. Moisture sorption isotherms obtained for these nylon‐6‐based films were all typically sigmoid‐shaped, although the prevalence of a higher crystallinity in the hybrid samples lowered the degree of moisture regain. The sorption behavior was analyzed well in terms of the parameters of a Brunauer–Emmett–Teller multiplayer adsorption model and a Flory–Huggins treatment. It was also observed that the cluster formation of the water adsorbed into the nylon‐6 matrix tended to be restricted by the hybridization with clay. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 479–487, 2002; DOI 10.1002/polb.10106
Structures induced by irradiation of femto‐second laser pulse in polymeric materials
Authors: Katayama Shigeru , Horiike Mika , Hirao Kazuyuki , Tsutsumi Naoto
Published: August 2002

We investigated the structures induced by irradiation of near‐infrared femto‐second laser pulse in various polymer materials; olefin gel, acrylic adhesive, poly(ether sulphone) (PES), poly(methyl methacrylate) (PMMA), polycarbonate (PC), and block copolymers of methyl‐methacrylate and ethyl acrylate‐butyl acrylate. Line irradiation that was performed by scanning laser spots in polymer bulk formed volcano‐like upheaval structures on the surfaces of PES, PMMA, and PC, which have relatively high glass‐transition temperatures (Tg's); on the other hand, cave or channel structures on the surfaces of olefin gel and acrylic adhesive have low Tg's. For the block copolymers containing both low and high Tg's, aggregation of the submicron scale deposit was induced in the polymer bulk. The submicron scale deposit may be reproduced structures after photodecomposition or photocrosslinking of polymer‐chain components induced by multiphoton excitation with femto‐second laser irradiation. This deposit aggregation with a stripelike structure had different optical properties from the un‐irradiated region. These structures induced by irradiation of femto‐second laser pulse might be applicable for optical devices such as diffraction grating and optical guide. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 537–544, 2002; DOI 10.1002/polb.10111
Oxygen‐barrier properties of cold‐drawn polyesters
Authors: Liu R. Y. F. , Schiraldi D. A. , Hiltner A. , Baer E.
Published: August 2002

The improvement of oxygen‐barrier properties of glassy polyesters by orientation was examined. Poly(ethylene terephthalate) (PET), poly(ethylene naphthalate), and a copolymer based on PET in which 55 mol % of the terephthalate was replaced with bibenzoate (PET‐BB55) were oriented by constrained uniaxial stretching. In a fairly narrow window of stretching conditions near the glass‐transition temperature, it was possible to achieve uniform extension of the polyesters without crystallization or stress whitening. The processes of orientation and densification correlated with the conformational transformation of glycol linkages from gauche to trans. Oxygen permeability, diffusivity, and solubility decreased with the amount of orientation. A linear relationship between the oxygen solubility and polymer specific volume suggested that the cold‐drawn polyester could be regarded as a one‐phase densified glass. This allowed an analysis of oxygen solubility in accordance with free‐volume concepts of gas permeability in glassy polymers. Orientation was seen as the process of decreasing the amount of excess‐hole free volume and bringing the nonequilibrium polymer glass closer to the equilibrium (zero‐solubility) condition. Cold drawing most effectively reduced the free volume of PET‐BB55. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 862–877, 2002