bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of high electrical fields on ageing and polarization properties of polyethylene
Authors: Crine Jean‐Pierre 
Published: December 2002

AbstractThe influence of high electrical fields (above 20  kV mm−1) on ageing, polarization and morphology of polyethylene (PE) is discussed. Infrared and positron annihilation spectroscopy measurements together with capacitance measurements tend to indicate that polymer morphology is modified by high fields. We show that accelerated electrical ageing characteristics of PE are directly linked to morphology changes induced by the field. Below a so‐called critical field, the activation volume of the ageing process is dependent on field‐induced strain. Above the critical field, the amorphous phase is significantly deformed and weak van der Waals bonds are broken, leading to another faster ageing regime. There is excellent agreement between the proposed model and experimental data obtained with PE‐insulated high voltage cables. The possible relation between the submicrocavity formation proposed in our ageing model and various polarization measurements is discussed. It is our contention that strong charge injection occurs only after submicrocavity formation, ie after weak bonds are broken. As is well known, polarization currents obtained under high fields are controlled by space charges. It seems that wave packets and the negative resistance observed above 100 kV mm−1in PE are associated with a steady state in field‐induced defect formation. This suggests that space charges are related to the formation of submicrocavities and, therefore, are a consequence and not a cause of high field ageing.© 2002 Society of Chemical Industry
Ageing of polymeric insulating materials and insulation system design
Authors: Montanari Gian Carlo , Mazzanti Giovanni 
Published: December 2002

AbstractThis paper presents an overview of the problem of modelling the ageing of polymeric insulating materials used for electrical applications; a relation between ageing and life models; the different approaches brought to phenomenological or chemical–physical life models; the need to search for diagnostic properties and to investigate the prevailing degradation mechanisms as a function of applied stresses and material morphology; and the way design stresses are chosen and reliability evaluations of insulation systems are carried out.© 2002 Society of Chemical Industry
Covalent immobilization of fluorescent indicators in photo‐ and electropolymers for the preparation of fibreoptic chemical sensors
Authors: Uttamlal Mahesh , Sloan William D , Millar David 
Published: December 2002

AbstractA photo‐ and an electrochemical method for the immobilization of fluorescein derivatives for the preparation of fibreoptic pH and Ca2+ sensors are presented. The methods results in the covalent attachment of the indicator in a polymer matrix. In the electrochemical approach, a fluorescein‐derivatized thiophene, thiophene‐3‐acetylfluoresceinamide (TAF), has been prepared and electrochemically polymerized onto Pt‐coated indium tin oxide glass. The fluorescence intensity responses as a function of pH, for TAF and polyTAF, are similar to that of fluorescein in solution. In the photochemical approach, two fluorescein derivatives have been prepared, fluorescein acrylamide (FA) and calcein acrylamide (CA). CA is sensitive to both pH and Ca2+. FA and CA have been immobilized covalently within polyacrylamide and polyacrylamide/[(3‐methacryoylamino)propyl]trimethylammonium chloride (MAPTAC) copolymers using photoinitiated radical polymerization directly on the end of a chemically‐modified glass surface. The spectroscopic properties of the bound FA and CA are similar to FA and CA in free solution, respectively; however, the cationic properties of the polymers result in a shift in the pKa of the indicator. The electrochemical and photochemical immobilization of fluorescent indicators within polymer matrices is an ideal arrangement, because it improves the operational lifetime of the chemical sensors.© 2002 Society of Chemical Industry
Clustering of poly(ethylene oxide) in water revisited
Authors: Ho Derek L. , Hammouda Boualem , Kline Steven R. 
Published: December 2002

AbstractThe dynamic light scattering results presented in this letter demonstrate that the clustering of poly(ethylene oxide) (PEO) can be observed even in ultrapure, freshly double‐distilled and filtered deionized water. It is confirmed that the filtration of solutions removes the clustering structure and that a steady‐state amount of PEO in clusters is reformed in filtered solutions within 24 h. Adding a drop of chloroform to unfiltered aqueous solutions of PEO temporarily alters the clustering structure, but it prevents the clustering of PEO in filtered solutions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 135–138, 2003
Phase diagrams of poly(siloxane)/liquid crystal blends
Authors: Gogibus Nicolas , Benmouna Farida , Ewen Bernd , Pakula Tadeusz , Coqueret Xavier , Benmouna Mustapha , Maschke Ulrich 
Published: December 2002

AbstractPhase diagrams of blends of poly(methylphenylsiloxane) in short PMPS and two low molecular weight liquid crystals (4‐cyano‐4′‐n‐pentyl‐biphenyl and an eutectic mixture of paraphenylenes) are reported. Two polymers with very different weight‐average molar masses are considered in an evaluation of the loss of miscibility resulting from a known increase in the weight‐average molar mass. The experimental diagrams have been constructed via polarized optical microscopy and are rationalized in terms of the Flory–Huggins theory of isotropic mixtures and the Maier–Saupe theory of nematic order. The results show a good agreement between the theory and experiments and reveal a remarkable enhancement of miscibility with respect to similar systems involving poly(dimethylsiloxane). Variations of the interaction parameter with the temperature are compared for different systems of polysiloxanes. The effects of the nature of the liquid crystal and the polymer molar mass on the χ parameter are evaluated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 39–43, 2003
Transient and athermal effects in the crystallization of polymers. II. Nonisothermal crystallization
Authors: Sajkiewicz Paweł 
Published: December 2002

AbstractNonisothermal crystallization of several polymers was investigated with differential scanning calorimetry and optical microscopy. The results indicated that as in the case of isothermal processes, crystallization starts with nucleation on noncompletely melted crystalline residues. It is assumed that if the crystalline residues are subcritical at melting temperatures, they can become stable by an athermal mechanism during cooling. There is also some contribution of nucleation on heterogeneities. The next mechanism of nucleation is a classical homogeneous process occurring by thermal fluctuations. The results showed the non‐steady‐state character of the nonisothermal crystallization of polymers. In the investigated range of cooling rates, the non‐steady‐state character of nonisothermal crystallization of polymers is dominated by the transient thermal effects. In the range of high temperatures, the transient homogeneous nucleation can be interpreted with the Ziabicki model, and the steady‐state rate determined from nonisothermal experiments coincides with the rate determined in isothermal crystallization. The athermal nucleation occurring at the beginning of crystallization from noncompletely melted aggregates seems to be independent of the applied cooling rate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 68–79, 2003
Intercalated poly(vinylidene fluoride)/clay nanocomposites: Structure and properties
Authors: Priya L. , Jog J. P. 
Published: December 2002

AbstractThe preparation and characterization of melt‐intercalated poly(vinylidene fluoride) (PVDF)/clay nanocomposites are reported. Organophilic clay (clay treated with dimethyl dihydrogenated tallow quaternary ammonium chloride) was used for the nanocomposite preparation. The composites were characterized with X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). XRD results indicated the intercalation of the polymer in the interlayer spacing. The incorporation of clay in PVDF resulted in the β form of PVDF. DSC nonisothermal curves showed an increase in the melting and crystallization temperatures along with a decrease in crystallinity. Isothermal crystallization studies show an enhanced rate of crystallization with the addition of clay. DMA indicated significant improvements in the storage modulus over a temperature range of −100 to 150 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 31–38, 2003
Antihyperglycaemic effect and acute toxicity of Securigera Securidaca L. seed extracts in mice
Authors: Hosseinzadeh H. , Ramezani M. , Danaei A. R. 
Published: December 2002

AbstractThe antihyperglycaemic activity of a Securigera securidaca aqueous infusion and an ethanol maceration extract of seeds was studied in normoglycaemic, glucose‐induced hyperglycaemic and alloxan‐induced diabetic mice. The acute toxicity of the ethanol extract was more than that of the aqueous one. The phytochemical analysis showed that the seed extracts were rich in flavonoids. The intraperitoneal and oral administration of the aqueous and ethanol extracts significantly reduced blood glucose in alloxan‐induced diabetic mice. In normoglycaemic and glucose‐induced hyperglycaemic mice, the blood glucose levels were not significantly different from the control. Glibenclamide was not able to lower blood glucose in alloxan‐induced diabetic mice, while it significantly lowered the blood sugar in normoglycaemic mice. The results indicate that S. securidaca seed extracts significantly reduce blood glucose in alloxan‐induced diabetic mice by a mechanism different from that of sulfonylurea agents. Copyright © 2002 John Wiley & Sons, Ltd.
The influence of long‐term Aloe vera ingestion on age‐related disease in male Fischer 344 rats
Authors: Ikeno Yuji , Hubbard Gene B. , Lee Shuko , Yu Byung Pal , Herlihy Jeremiah T. 
Published: December 2002

AbstractThe effects of long‐term Aloe vera ingestion on age‐related diseases were investigated using male specific pathogen‐free (SPF) Fischer 344 rats. Experimental animals were divided into four groups: Group A, the control rats fed a semi‐synthetic diet without Aloe vera; Group B, rats fed a diet containing 1% freeze‐dried Aloe vera filet; Group C, rats fed a diet containing 1% charcoal‐processed, freeze‐dried Aloe vera filet; and Group D, rats fed the control diet and given whole leaf charcoal‐processed Aloe vera (0.02%) in the drinking water. This study demonstrates that life‐long Aloe vera ingestion produced neither harmful effects nor deleterious changes. In addition, Aloe vera ingestion appeared to be associated with some beneficial effects on age‐related diseases. Groups B exhibited significantly less occurrence of multiple causes of death, and a slightly lower incidence of fatal chronic nephropathy compared with Group A rats. Groups B and C rats showed the trend, slightly lower incidences of thrombosis in the cardiac atrium than Group A rats. Therefore, these findings suggest that life‐long Aloe vera ingestion does not cause any obvious harmful and deleterious side effects, and could also be beneficial for the prevention of age‐related pathology. Copyright © 2002 John Wiley & Sons, Ltd.
Antibacterial effect of Melia azedarach flowers on rabbits
Authors: Saleem Rubeena , Ahmed Syed Iqbal , Shamim Syed Mohammad , Faizi Shaheen , Siddiqui Bina Shaheen 
Published: December 2002

AbstractA methanol extract of Melia azedarach flowers showed potent antibacterial action in rabbits suffering from a skin infection produced by Stapyhlococcus aureus. The healing effects were found comparable to neomycin. Copyright © 2002 John Wiley & Sons, Ltd.
Antibacterial and antifungal activity of essential oils of Mentha suaveolens
Authors: Oumzil H. , Ghoulami S. , Rhajaoui M. , Ilidrissi A. , Fkih‐Tetouani S. , Faid M. , Benjouad A. 
Published: December 2002

AbstractThe essential oils (EO) of Mentha suaveolens, a wild Labiatae, which grows in several regions in Morocco, were characterized and their antimicrobial activity assessed. The main aromatic constituents of this plant, as characterized by IR, NMR and MS studies, were pulegone, piperitenone oxide (PEO) and piperitone oxide (PO) occurring in different amounts depending on the subspecies. These constituents as well as a series of other aromatic products such as carvone, limonene and menthone, were tested for their antimicrobial activity against 19 bacteria including Gram‐positive and Gram‐negative and against three fungi, using solid phase and microtitration assays. Pulegone‐rich essential oil inhibited efficiently all the micro‐organisms tested with MICs ranging between 0.69 and 2.77 ppm. Among the components from Mentha suaveolens EO, pulegone was the most effective against the tested microorganisms, followed by PEO and PO. The structure–activity relationship is discussed on the basis of the activity of the other aromatic derivatives tested such as carvone, limonene, menthone and the profile of the essential oils of Mentha suaveolens was compared with other Mentha species. Copyright © 2002 John Wiley & Sons, Ltd.
Hypolipidaemic activity of methanol extract of Aleurites moluccana
Authors: Pedrosa R. C. , Meyre‐Silva C. , Cechinel‐Filho V. , Benassi J. C. , Oliveira L. F. S. , Zancanaro V. , Dal Magro J. , Yunes R. A. 
Published: December 2002

AbstractThe lipid‐lowering action of the leaves of the Aleurites moluccana methanol extract was studied in Triton W‐1339 and high‐fat‐diet fed rats. The serum lipids (total cholesterol, LDL‐ and HDL‐cholesterol and triglycerides) and body weight were found to be lowered by A. moluccana (300 mg/kg, b.w.) in rats with Triton‐induced hypercholesterolaemia and on a hyperlipaemic diet. The results suggest that the lipid lowering action of this natural product is mediated through inhibition of hepatic cholesterol biosynthesis and reduction of lipid absorption in the intestine. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluation of the central properties of several Hypericum species from the Canary Islands
Authors: Prado Begoña , Rabanal Rosa M. , Sánchez‐Mateo Candelaria C. 
Published: December 2002

AbstractThe infusions of the aerial parts in blossom of Hypericum canariense, H. glandulosum, H. reflexum and H. grandifolium (Hypericaceae) were evaluated for their pharmacological activity on the central nervous system in mice using various behavioural models including locomotor and muscle relaxant activity, effect on normal body temperature, pentobarbital‐induced sleep, oxotremorine and tetrabenazine‐induced syndrome, apomorphine‐induced hypothermia and 5‐hydroxytryptophan‐induced head twitches, as well as a forced swimming test. These infusions did not alter significantly the locomotor activity, pentobarbital induced sleeping time and body temperature, with the exception of H. canariense which produced a slight but significant hypothermia. Additionally, no muscle relaxant or anticholinergic activity were observed. These infusions antagonized the ptosis and/or motor depression induced by tetrabenazine as well as shortening the immobility time in the forced swimming test. The observations suggest that the infusions of these Hypericum species possess antidepressant activity in mice, without inducing muscle relaxation, anticholinergic and sedative properties. Copyright © 2002 John Wiley & Sons, Ltd.
Potent suppressive activity of fresh and dried peels from Satsuma mandarin Citrus unshiu (Marcorv.) on hydroperoxide generation from oxidized linoleic acid
Authors: Higashi‐Okai Kiyoka , Kamimoto Kyoko , Yoshioka Aya , Okai Yasuji 
Published: December 2002

AbstractThe effects of various extracts prepared from fresh and dried peels of Satsuma mandarin (Citrus unshiu Marcov.) on hydroperoxide generation from oxidized linoleic acid were compared under different extraction conditions. The cold‐and hot‐water extracts of fresh peels showed significant suppressive activity against hydroperoxide generation in a dose‐dependent manner. However, the methanol or acetone extract of fresh peels did not exhibit significant suppressive effects. The commercially available ascorbic acids equivalent to their concentrations in the water extracts of fresh peels showed roughly equal antioxidative activities compared with those of the water extracts of fresh peels. Although the cold‐ and hot‐ water extracts of dried peels indicated a considerable reduction of ascorbic acid concentration, they exhibited much higher antioxidative activities than those of the fresh peels. The methanol extract of dried peels also showed significant antioxidative activities, but did not contain significant ascorbic acid. These results suggest that the fresh peels of Satsuma mandarin have potential antioxidant activities, and the drying treatment of fresh peels caused an enhancement of the antioxidant activity. The pharmacological significance of this finding is discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Approaching the problem of bioequivalence of herbal medicinal products
Authors: Loew D. , Kaszkin M. 
Published: December 2002

AbstractHerbal medicinal products (HMP) contain exclusively herbal drugs or herbal drug preparations (HDP) and are a complex mixture of different compounds, which may act in an agonistic, synergistic, complementary, antagonistic or toxic way. A specific scientific challenge is for methods to prone the bioequivalence of herbal drug preparations (HDP). Depending on the type of herbal drug preparations, different approaches are possible. If the constituents responsible for therapeutic activity are known, the concept of essential similarity used with chemically defined substances can be fully applied. For extracts with unknown active markers, data on defined chemical constituents are useful for control purposes (charge conformity), but not sufficient to prove bioequivalence. In this case bioassays or pharmacological studies, which measure therapeutically relevant activity, should be used. A phytogeneric is only comparable to the innovator preparation under the following conditions: (i) pharmaceutical equivalence (standardization), (ii) biopharmaceutical equivalence (in vitro dissolution), (iii) bioequivalence with different endpoints (in vitro model, animal model) or (iv) clinical study. An uncritical substitution of herbal drug preparations without considering these scientific criteria should be avoided. Copyright © 2002 John Wiley & Sons, Ltd.
Perceived stress in adults: prevalence and association of depression, anxiety and medication in a Swedish population
Authors: Bergdahl Jan , Bergdahl Maud 
Published: December 2002

AbstractThe objectives were to measure the prevalence of perceived stress in adults and to evaluate gender and age differences in stress level. Association between perceived stress and depression, anxiety and medication was also studied. A total of 1275 subjects (581 men and 694 women) were randomly selected in equal age groups. Perceived stress was measured with the Perceived Stress Questionnaire (PSQ). Two PSQ cut‐off scores, moderate and high stress level, were yielded by using mean score and standard deviation. Depression was assessed with the Beck Depression Inventory (BDI) and anxiety with the State and Trait Anxiety Inventory (STAI). The intake of medications was registered and classified. The prevalence of moderate stress was estimated to be 10.0 per cent, lowest in the 60–69‐year and highest in the 40–44‐year age group. Women of 30–34 years had a higher frequency of moderate stress (11.1 per cent) than men in the same age group (5.9 per cent). The prevalence of high stress was 4.0 per cent, higher in women (5.5 per cent) than in men (2.2 per cent). Women in the age groups 30–34 years (12.7 per cent) and 35–39 years (8.1 per cent) reported a greater proportion of high stress than the men (0 per cent for both age groups). Low and moderate stress were associated with STAI and high stress with the BDI. The BDI attitudes self‐punitive wishes, sleep disturbances and loss of appetite were associated with high stress. High stress was associated with psychotropic drugs. Antidepressants comprised the majority of psychotropic drugs used. It was concluded that women in the 30 to 39‐year age group are exposed to high stress and are therefore a vulnerable group. Anxiety is more important in moderate stress levels and depression in high stress levels. Clinicians should be aware of the suicidal risk associated with high stress levels. It seems that psychotropic drugs alone are not sufficient to reduce stress levels. Copyright © 2002 John Wiley & Sons, Ltd.
Stress management for mental health professionals: a review of effective techniques
Authors: Edwards Deborah , Hannigan Ben , Fothergill Anne , Burnard Philip 
Published: December 2002

AbstractThis paper presents the findings of a systematic review of the current evidence for the effectiveness of stress management interventions for those working in the mental health field. Research articles from 1966 to 2000 which reported studies undertaken in the United Kingdom and which specifically identified participants as mental health workers were included in the review. Studies from other European countries and from the USA were examined as potential models of good practice. The review demonstrated that a great deal is known about the sources of stress at work, about how to measure them and about their interaction and impact on a range of outcome indicators. What was found to be lacking was a translation of these results into practice, into research that assessed the impact of interventions that attempted to moderate, minimize or eliminate some of these stressors. Three papers were retrieved which reported intervention strategies for workers classified as working within the mental health arena. Copyright © 2002 John Wiley & Sons, Ltd.
Is performance driven by industry‐or firm‐specific factors? A new look at the evidence
Authors: Hawawini Gabriel , Subramanian Venkat , Verdin Paul 
Published: December 2002

AbstractIn this study we revisit the question of whether firms' performance is driven primarily by industry or firm factors, extending past studies in two major ways. Firstly, in a departure from past research, we use value‐based measures of performance (economic profit or residual income and market‐to‐book value) instead of accounting ratios (such as return on assets). We also use a new data set and a different statistical approach for testing the significance of the independent effects. Secondly, we examine whether the findings of past research can be generalized across all firms in an industry or whether they apply to a particular class of firms within the same industry. We find that a significant proportion of the absolute estimates of the variance of firm factors is due to the presence of a few exceptional firms in any given industry. In other words, only for a few dominant value creators (leaders) and destroyers (losers) do firm‐specific assets seem to matter significantly more than industry factors. For most other firms, i.e., for those that are not notable leaders or losers in their industry, however, the industry effect turns out to be more important for performance than firm‐specific factors. Copyright © 2002 John Wiley & Sons, Ltd.