bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wood‐fiber/high‐density‐polyethylene composites: Compounding process
Authors: Lu J. Z. , Wu Q. , Negulescu I. I. 
Published: July 2004

AbstractThe compounding process directly influenced the compounding quality of wood–polymer blends and finally affected the interfacial bonding strength and flexural modulus of the resultant composites. With 50 wt % wood fiber, the optimum compounding parameters for the wood‐fiber/high‐density‐polyethylene blends at 60 rpm were a temperature of 180°C and a mixing time of 10 min for the one‐step process with a rotor mixer. The optimum compounding conditions at 90 rpm were a temperature of 165°C and a mixing time of 10 min. Therefore, a short compounding time, appropriate mixing temperatures, and a moderate rotation speed improved the compounding quality of the modified blends and the dynamic mechanical properties of the resultant composites. The melt torque and blend temperature followed a polynomial relationship with the loading ratio of the wood fiber. The highest melt torque and blend temperature were obtained with 50% wood fiber. The coupling treatment was effective for improving the compatibility and adhesion at the interface. The two‐step process was better than the one‐step process because the coupling agents were more evenly distributed at the interface with the two‐step process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2570–2578, 2004
Properties of acrylonitrile–butadiene–styrene/polycarbonate blends with styrene–butadiene–styrene block copolymer
Authors: Taşdemir Münir 
Published: July 2004

AbstractThe importance of alloys and blends has increased gradually in the polymer industry so that the plastics industry has moved toward complex systems. The main reasons for making polymer blends are the strengthening and the economic aspects of the resultant product. In this study, I attempted to improve compatibility in a polymer blend composed of two normally incompatible constituents, namely, acrylonitrile–butadiene–styrene (ABS) and polycarbonate (PC), through the addition of a compatibilizer. The compatibilizing agent, styrene–butadiene–styrene block copolymer (SBS), was added to the polymer blend in ratios of 1, 5, and 10% with a twin‐screw extruder. The morphology and the compatibility of the mixtures were examined by scanning electron microscopy and differential scanning calorimetry. Further, all three blends of ABS/PC/SBS were subjected to examination to obtain their yield and tensile strengths, elasticity modulus, percentage elongation, Izod impact strength, hardness, heat deflection temperature, Vicat softening point, and melt flow index. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2521–2527, 2004
Preparation and characterization of conductive latex based on polyaniline–perlite composite
Authors: Arsalani Nasser , Hayatifar Mohammad 
Published: July 2004

AbstractThe development of polymers with high electrical conductivity has attracted significant research interest because of the possibility of new applications. Electrically conductive latexes have drawn the attention of scientists over the last few years. The present work reports the preparation of composites in which polyaniline was deposited onto perlite particles by oxidative polymerization. Electrically conductive latex was prepared by homogeneously mixing submicron conductive composites with poly(vinylacetate‐co‐butylacrylate‐co‐butylversitate) resin in a desirable ratio. The conductivity of composites and latex was measured by a standard four‐point probe. Morphology of composites was studied by scanning electron microscopy. Adhesion and electroactivity of the latex were also investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2528–2531, 2004
Preparation and properties of a salt‐resistant superabsorbent polymer
Authors: Ma Songmei , Liu Mingzhu , Chen Zhenbin 
Published: July 2004

AbstractCrosslinked sodium polyacrylate was prepared by solution polymerization with N,N‐methylene‐bisacrylamide (bisAM) as crosslinking agent; it was subsequently surface‐crosslinked by ethylene glycol diglycidyl ether (EGDE) and then was modified with inorganic salt to obtain a superabsorbent with water absorbency in 0.9 wt % NaCl aqueous solution at atmosphere and applied pressure (P ≈ 2 × 103 Pa) of 55 and 20 g.g−1, respectively. Moreover, it also had excellent hydrogel strength. The effects of reaction temperature, reaction time, neutralization degree (ND) of acrylic acid, amount of initiator, crosslinking agent, and surface‐crosslinking agent, mass ratio of inorganic salt to initial superabsorbent, molar ratio of sodium aluminate (NaAlO2) to potassium dihydrogen hyphosphate (KH2PO4) on water absorbency (WA) in 0.9 wt % NaCl aqueous, and the hydrogel modulus were investigated and optimized. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2532–2541, 2004
Syntheses and properties of low‐level melamine‐modified urea–melamine–formaldehyde resins
Authors: No B. Young , Kim Moon G. 
Published: July 2004

AbstractSyntheses of urea–melamine–formaldehyde (UMF) resins were studied using 2–12% melamine levels and UF base resins that were preadvanced to various different extents. The melamine reaction was carried out at pH 6.3 with F/(U + M) mole ratio of 2.1 until a target viscosity of V was reached (Gardener–Holdt) and then the second urea added at pH 8.0 to give a final F/(U + M) mole ratio of 1.15. Analyses with 13C‐NMR and viscosity measurements showed that MF components react fast and the UF components very slowly in the melamine reaction. Therefore, as the extent of preadvancement of UF base resin was decreased, the reaction time to reach the target viscosity became longer and the MF resin components showed high degrees of polymerization. The overpolymerization of MF components resulted in increasingly more opaque resins, with viscosity remaining stable for more than a month. As the preadvancement of UF base resin was increased, the extent of advancement of MF components decreased, to give clearer resins, with viscosity slowly increasing at room temperature. Overall, preadvancing the UF base resin components to an appropriate extent was found to be a key to synthesizing various low‐level melamine‐modified UMF resins. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2559–2569, 2004
Characterization of crosslinked starch materials with spectroscopic techniques
Authors: Delval Franck , Crini Grégorio , Bertini Sabrina , Morin‐Crini Nadia , Badot Pierre‐Marie , Vebrel Joël , Torri Giangiacomo 
Published: July 2004

AbstractThe structure, mobility, and properties of crosslinked starch materials of various compositions were investigated with FTIR and NMR spectroscopy, and relaxation time measurements were taken with cross‐polarization/magic‐angle‐spinning (CP–MAS) and magic‐angle‐spinning (MAS) spectroscopy. Characterization by Fourier transform infrared spectroscopy confirmed the crosslinking reaction. The CP–MAS and MAS spectra allowed the assignment of the principal 13C signals. The molecular mobility of these polysaccharides was analyzed in terms of the cross‐relaxation time between the protons and carbons, the 1H spin–lattice relaxation time in the rotating frame, and the 1H longitudinal spin–lattice relaxation time. Relaxation studies showed that increasing the crosslinking degree increased the amorphous content, and the material became rigid as an increasing number of covalent bonds in the polymer network reduced mobility. The values of the spin–lattice relaxation in the rotating frame reflected the homogeneous nature of the materials. The correlation between the crosslinking degree, structure, and mobility and the sorption properties of these sorbents was examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2650–2663, 2004
The plasma pharmacokinetics and cerebral spinal fluid penetration of intravenous topiramate in newborn pigs
Authors: Galinkin Jeffrey L. , Kurth C. Dean , Shi Heng , Priestley Margaret A. , Loepke Andreas W. , Adamson Peter C. 
Published: July 2004

AbstractIntroduction—Pre‐clinical studies suggest that the anticonvulsant topiramate confers neurologic protection against ischemia. An intravenous formulation of topiramate has been developed for administration during conditions such as hypoxia‐ischemia when enteral absorption may be unpredictable. The plasma pharmacokinetics, cerebrospinal fluid (CSF) penetration and pharmacodynamics of intravenous topiramate were studied in an established piglet model of hypoxia‐ischemia.Methods—The plasma pharmacokinetics of topiramate were studied in a group of chronically instrumented conscious piglets (n = 8), and in a group of piglets following an episode of hypoxia‐ischemia (n = 8). These groups were divided into equal dose cohorts in which two doses of intravenously administered topiramate, 5 and 40 mg/kg, were studied. The animals' heart rate, arterial pressure and EEG were monitored. Plasma for topiramate concentration was sampled for up to 26 h. A single CSF topiramate concentration was determined 1 h following drug administration. Topiramate was quantified using a specific LC/MS assay.Results—The animals tolerated intravenous topiramate well, with no significant changes in physiologic and neurologic parameters. Plasma topiramate concentrations following an intravenous dose were best described by a bi‐exponential equation, with a mean clearance of 39±18 ml/h/kg, and a terminal half‐life of 14.3 (range 7.5–48.1) h. A dose of 5 mg/kg was sufficient to maintain plasma drug concentrations greater than 10 µM for 24 h. CSF topiramate concentration at 1 h was 12±1 µM and 109±26 µM at the 5 and 40 mg/kg doses, respectively.Conclusion—Topiramate administered intravenously was well tolerated. Slow clearance of the drug allowed for maintenance of potential neuroprotective concentrations following a single dose of drug for 24 h. High drug penetration into the CSF is an ideal pharmacologic characteristic of any potential neuroprotective agent. The pharmacokinetic profile of intravenously administered topiramate, including its penetration into the CSF, appears to achieve this goal. Copyright © 2004 John Wiley & Sons, Ltd.
Prognostic value of age and sex in early gastric cancer
Authors: Bando E , Kojima N , Kawamura T , Takahashi S , Fukushima N , Yonemura Y 
Published: July 2004

AbstractBackgroundThe need for lymph node dissection in early gastric cancer (EGC) is controversial. The present study investigated the possibility of planning treatment for EGC according to age and sex rather than node status.MethodsOverall survival rate and cause of death were analysed according to age (5-year increments) and sex in 4231 patients with EGC. Cox proportional hazard regression analyses were used to identify the most valuable predictor.ResultsIn patients with EGC 5- and 10-year cancer-specific survival rates were 98·4 and 96·3 per cent respectively, whereas corresponding overall survival rates were 90·2 and 80·9 per cent. The critical age for determining prognosis was 70 years for men (χ2 = 131·34, P &lt; 0·001) and 75 years for women (χ2 = 64·35, P &lt; 0·001). For both sexes, the 10-year overall survival rate was less than 30 per cent in patients over 80 years old. Multivariate Cox stepwise regression analysis identified age as the most powerful prognostic indicator in EGC. The rate of death from causes unrelated to the tumour increased significantly with age, whereas that from recurrence was not affected by age.ConclusionAge is a better prognostic indicator than node status in both men and women with EGC. Age and sex should be taken into account as well as conventional clinicopathological variables related to lymph node metastases when determining appropriate therapy for EGC.
Prognostic significance of serum vascular endothelial growth factor and endostatin in patients with hepatocellular carcinoma
Authors: Poon R T P , Ho J W Y , Tong C S W , Lau C , Ng I O L , Fan S-T 
Published: July 2004

Abstract

Background
Vascular endothelial growth factor (VEGF) and endostatin stimulate and inhibit tumour angiogenesis respectively. Recent studies have demonstrated the prognostic value of serum levels of both VEGF and endostatin in patients with various types of cancer. Their significance in patients with hepatocellular carcinoma (HCC) remains unclear.

Methods
Serum VEGF and endostatin levels were measured by enzyme immunoassay in 108 patients with HCC before surgical resection and in 20 healthy controls. Preoperative serum VEGF and endostatin levels were correlated with clinicopathological features and long-term survival.

Results
Serum VEGF levels in patients with HCC were significantly higher than those in controls, but serum levels of endostatin were similar in the two groups. High serum levels of VEGF, but not endostatin, were significantly associated with venous invasion and advanced tumour stage. Patients with a serum VEGF level higher than median (over 245·0 pg/ml) had significantly worse overall and disease-free survival than those with a lower level (P = 0·012 and P = 0·022 respectively). On multivariate analysis, serum VEGF level was an independent prognostic factor (hazard ratio 1·86 (95 per cent confidence interval 1·10 to 3·92); P = 0·032). Serum endostatin levels did not have significant prognostic influence on overall or disease-free survival.

Conclusion
A high serum level of VEGF is a predictor of poor outcome after resection of HCC. Serum VEGF, but not endostatin, may be a useful prognostic marker in patients with HCC.
A fully automated amino acid analyzer using NBD‐F as a ﬂuorescent derivatization reagent
Authors: Aoyama Chiaki , Santa Tomofumi , Tsunoda Makoto , Fukushima Takeshi , Kitada Chieko , Imai Kazuhiro 
Published: July 2004

AbstractA fully automated amino acid analyzer using NBD‐F (4‐ﬂuoro‐7‐nitro‐2,1,3‐benzoxadiazole) as a ﬂuorescent derivatization reagent was developed. The whole analytical process was fully automated from derivatization, injection to HPLC separation and quantitation. The derivatization reaction conditions were re‐evaluated and optimized. Amino acids were derivatized by NBD‐F for 40 min at room temperature in the borate buffer (pH 9.5). The derivatives were separated within 100 min and ﬂuorometrically detected at 540 nm with excitation at 470 nm. The detection limits for amino acids were in the range of 2.8–20 fmol. The calibration curves were linear over the range of 20 fmol to 20 pmol on column with the correlation coefﬁcients of 0.999. The coefﬁcients of variation were less than 5% at 3 pmol injection for all amino acids. Amino acids in rat plasma were determined by the proposed HPLC method. Copyright © 2004 John Wiley & Sons, Ltd.
Evaluation of 3‐hydroxy‐3‐methylglutaryl‐COA‐reductase, cholesterol‐7α‐hydroxylase and acyl‐COA:cholesterol acyltransferase activities: alternative chromatographic methods to separate metabolites
Authors: Montoudis Alain , Boileau Serge , Simoneau Lucie , Mounier Catherine , Lafond Julie 
Published: July 2004

AbstractAlternative HPLC and solid‐phase extraction column methods were developed to separate metabolites of enzymes involved in cholesterol metabolism in rabbit liver microsomes: hydroxyl‐methylglutaryl‐CoA reductase, cholesterol‐7α‐hydroxylase and acyl‐CoA:cholesterol acyltransferase. A comparison method of thin‐layer chromatography and solid‐phase extraction column were assayed to separate substrate and metabolite of hydroxy‐methylglutaryl‐CoA reductase, whereas for cholesterol‐7α‐hydroxylase and acyl‐CoA:cholesterol acyltransferase, this comparison was done between thin layer chromatography and HPLC. The results obtained by the new analytical chromatographic methods are not signiﬁcantly different than those observed in literature. Moreover a larger percentage recovery was obtained for analysed metabolites. Our results demonstrate the reliability of these alternative chromatographic techniques and showed that they are valuable tools to precisely and rapidly measure the activity of those enzymes. Copyright © 2004 John Wiley & Sons, Ltd.
Inﬂuence of the sample preparation method on the serotonin determination in plasma and platelets
Authors: Morgadinho Maria T. , Fontes Ribeiro C. A. , Macedo Tice R. A. 
Published: July 2004

AbstractPlasma or platelet serotonin concentration is commonly used to provide information about the serotonergic activity in various psychiatric or neurological diseases. Some difﬁculties have been described in the measurement of serotonin (5‐HT) levels in plasma or platelets. We describe an isocratic liquid‐chromatographic assay with amperometric detection for determination of 5‐HT in the platelet pellet and in platelet‐rich and platelet‐poor plasma (PRP and PPP) in sample sizes of 100 µL of plasma. The method uses an RP18 column and an amperometric detector with a thin‐layer type electrochemical ﬂow cell, with glassy carbon electrode maintained at a potential of +0.600 V vs an Ag/AgCl reference electrode. Determinations were performed in the presence or in the absence of plasma, since the biological matrix may affect the results. Different validation parameters were analysed: selectivity, accuracy, precision, linearity and stability. Reference values for 5‐HT concentration in healthy adults (n = 12) were 6.6 nmol/109 platelets, for the platelet pellet, and 5.5 nmol/109 platelets, for PRP. The 100 µL sample volume used for the preparation of PPP did not make possible the determination of 5‐HT levels with accuracy and precision. Copyright © 2004 John Wiley & Sons, Ltd.
Simultaneous determination of D‐ and L‐serine in rat brain microdialysis sample using a column‐switching HPLC with ﬂuorimetric detection
Authors: Fukushima Takeshi , Kawai Junko , Imai Kazuhiro , Toyo'oka Toshimasa 
Published: July 2004

AbstractBoth d‐ and l‐serine in rat brain microdialysis sample were simultaneously determined by pre‐column ﬂuorescence derivatization with 4‐ﬂuoro‐7‐nitro‐2,1,3‐benzoxadiazole (NBD‐F), separation of the derivatives on ODS column, TSKgel ODS‐80TsQA, followed by Pirkle type chiral columns, Sumichiral OA‐2500 (S), which gave a sufﬁcient enantiomeric separation of NBD–d‐serine and NBD‐l‐serine, and ﬂuorimetric detection at a wavelength of 540 nm with an excitation wavelength of 470 nm. The peaks of NBD–d‐serine and NBD–l‐serine in the rat brain microdialysis sample were clearly found, and the validation study showed satisfactory results; the precision and accuracy were within 5.14 and 109%, respectively. Using the proposed HPLC method, the time‐course proﬁle of d‐serine concentration in rat prefrontal cortex following intraperitoneal administration of d‐serine was investigated. As a consequence, d‐serine appeared to be rapidly distributed in the brain, and then decreased gradually with time in the extracellular ﬂuid of the rat prefrontal cortex. The proposed HPLC method will be useful for in vivo studies on d‐serine, which acts as a coagonist for N‐methyl‐d‐aspartate receptor, to the extracellular ﬂuid of rat brain. Copyright © 2004 John Wiley & Sons, Ltd.
Separation and determination of two sesquiterpene lactones in Radix inulae and Liuwei Anxian San by microemulsion electrokinetic chromatography
Authors: Gao Wenhua , yaowen Chen , Yin Yegao , Chen Xingguo , Hu Zhide 
Published: July 2004

AbstractA novel microemulsion electrokinetic chromatography (MEEKC) method for separating and determining two sesquoterpene lactones, alantolactone (AL) and isoalantolactone (IAL), in Radix inulae and Liuwei Anxian San has been developed. The effects of several important factors such as internal organic phases, concentration of microemusion, concentration of acetonitrile, injection time and running voltage were systematically investigated to determine the optimum conditions. The optimum microemulsion system was composed of n‐hexane (0.32% w/w), SDS (1.24% w/w), 1‐butanol (2.64% w/w), acetonitrile (10% w/w) and 10 mm sodium tetraborate buffer (85.80% w/w, pH 9.2). The applied voltage was 20 kV. The analytes were detected at 214 nm. Regression equations revealed linear relationships (correlation coefﬁcients 0.9950 for AL and 0.9946 for IAL) between the peak area of each analyte and the concentration. The limits of detection (deﬁned as a signal‐to‐noise ratio of about 3) were approximately 0.45 µg/mL for AL and 0.56 µg/mL for IAL. The levels of the analytes were successfully determined with recoveries ranging from 98.2 to 104.3%. Furthermore, a simple and effective extraction method, with methanol in an ultrasonic water bath for 60 min, was used for sample preparing. Also, MEEKC was compared with micellar electrokinetic chromatography (MEKC) and shown better separation results. Copyright © 2004 John Wiley & Sons, Ltd.
Direct determination of S‐(−)‐ and R‐(+)‐propranolol glucuronide in rat hepatic microsomes by RP‐HPLC
Authors: Yu Lushan , Luan Lianjun , Shao Qing , Zeng Su 
Published: July 2004

AbstractPropranolol, available commercially as a racemic mixture, is a non‐selective β‐adrenergic blocking agent used in the treatment of hypertension, angina pectoris and cardic arrhythmias. We have developed and validated an RP‐HPLC assay method for direct determination of R‐(+)‐ and S‐(−)‐propranolol glucuronide in rat hepatic microsomes to investigate the enantioselectivity of propranolol glucuronidation metabolism. A baseline separation of propranolol glucuronide enantiomers was achieved on a 5 µm reversed‐phase ODS column, with a mixture of phosphate buffer (pH 3.5, 0.067 mol/L) and methanol (55:45, v/v) as mobile phase. Ultraviolet detection was set at 220 nm, and p‐nitrobenzoic acid was used as internal standard. The standard curve of assay for R‐(+)‐ and S‐(−)‐propranolol glucuronide in spiked microsomal incubate showed good linearity throughout the concentration range from 0.50 to 20.0 µmol/L. The analytical method affords average recovery of 99.8 and 100.1% for R‐(+)‐ and S‐(−)‐propranolol glucuronide, respectively. The method provides a high sensitivity and good precision for R‐(+)‐ and S‐(−)‐propranolol glucuronide (RSD < 10%). The LOD was 0.15 µmol/L and the LOQ was 0.5 µmol/L (RSD < 8%, n = 5) for both R‐(+)‐ and S‐(−)‐propranolol glucuronide. The method is simple, precise and accurate, and is suitable for quantifying the propranolol glucuronides enantiomers in rat hepatic microsomes. Copyright © 2004 John Wiley & Sons, Ltd.
Diastereoselective Remote CH Activation by Hydroboration
Authors: Varela Jesús A. , Peña Diego , Goldfuss Bernd , Denisenko Dmitri , Kulhanek Jiri , Polborn Kurt , Knochel Paul 
Published: July 2004

AbstractHydroboration of tetrasubstituted or trisubstituted alkenes with BH3 and subsequent thermolysis allows remote diastereoselective CH activation of neighboring aryl rings. Tetrasubstituted and trisubstituted 1,1‐diphenylethylene derivatives undergo a highly stereoselective 1,2‐rearrangement followed by remote CH activation to lead, after oxidative workup, to a diol in which the relative stereochemistry of two stereocenters has been controlled. The mechanism of this remote activation has been studied and extended to related molecules that undergo this stereoselective CH activation, namely alkenylbiphenyl systems or alkenes with only one phenyl ring, such as alkenylbenzenes, or bicyclic systems. We have shown that this reaction allows diastereoselective synthesis of molecules with up to three contiguous chiral centers.