bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological properties, oil, and thermal resistance in sulfur‐cured CPE/NR blends
Authors: Sirisinha Chakrit , Saeoui Pongdhorn , Pattanawanidchai Sirichai 
Published: April 2004

AbstractThe use of natural rubber (NR) for partly substituting elastomeric chlorinated polyethylene (CPE) was carried out. Sulfur curing was used to vulcanize NR phase in the blends. Mechanical, rheological, and thermal aging properties as well as oil resistance of the blends were investigated. The amount of NR in blends significantly affects properties of the blends. With NR content in blends up to 20 wt %, tensile properties are similar to those of the pure CPE, even after either oil immersion or thermal aging. Rheological properties of CPE/NR blends determined from the rubber process analyzer (RPA 2000) and parallel‐plate rheometer are controlled strongly by the blend composition. The viscoelastic behavior of pure CPE and the blends with CPE as a major component is governed by the viscous response, which could be seen from the high damping factor, particularly at high strain, the short linear viscoelastic range, and the high degree of pseudoplasticity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1129–1135, 2004
Thermal properties of poly(vinyl alcohol)–solute blends studied by TMDSC
Authors: Stavropoulou A. , Papadokostaki K. G. , Sanopoulou M. 
Published: April 2004

AbstractA thermal analysis study of blends of semicrystalline poly(vinyl alcohol) (PVA) with a pharmaceutical substance, buflomedil pyridoxal phosphate (BPP) is presented. Temperature‐modulated DSC (TMDSC) was used to determine the Tg as well as the crystallinity of blends with various polymer to drug ratios, for different annealing procedures. Positive deviations from a simple expression for the composition dependence of the glass transition of the blend were found. This result, together with the increased thermal stability of PVA–BPP blends, evidenced by TGA analysis, indicates the existence of specific interactions between the polar groups of the two components. The incorporation of dispersed BPP in the PVA matrix results in a composition‐dependent lowering of the polymer's Tm and degree of crystallinity. In addition, we found that, while melting of pure PVA is predominantly reversing, its melting in the blends acquires an increasingly higher nonreversing component with increasing BPP content in the blend. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1151–1156, 2004
Swelling behavior of polyelectrolyte complex hydrogels composed of chitosan and hyaluronic acid
Authors: Kim Seon Jeong , Lee Ki Jung , Kim Sun I. 
Published: April 2004

AbstractPolyelectrolyte complex (PEC) hydrogels composed of various weight ratios of chitosan and hyaluronic acid were prepared. The PEC hydrogels were formed by the reaction of the oppositely charged chitosan polymers. The PEC films swelled in water rapidly, reaching equilibrium within 30 min, and exhibited relatively high swelling ratios, 243–322%, at 25°C. The swelling ratio increased with increasing temperature. The transport phenomena of all PEC samples were non‐Fickian and diffusion and relaxation controlled. The diffusion coefficients of the PEC films ranged from 2.22 × 10−6 to 10.05 × 10−6 cm2/s. The activation energy of the polyelectrolyte complexes ranged from 37.14 to 54.58 kJ/mol and proved to be hydrophilic. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1097–1101, 2004
Comparison of different foaming agents in making plywood glue
Authors: Luukko Petra , Nyström Marianne , Rainio Jouni 
Published: April 2004

AbstractFoaming of a phenol formaldehyde resin was studied. Twenty‐one foaming agents were tried out in the experiments. Foaming was evaluated by viscosity, density, and surface tension measurements. The study shows that spray dried blood and β‐lactoglobulin‐enriched whey were the best foaming agents to foam phenol formaldehyde resin. There are also some other materials, which might work as foaming agents for phenol formaldehyde resin after some formula optimization. They include sodium lauryl sulfate, sodium‐n‐alkyl (C10‐C13) benzene sulfonate, and a fatty acid amine derivate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1060–1064, 2004
Synthesis of 2′‐Aminoalkyl‐Substituted Fluorinated Nucleobases and Their Influence on the Kinetic Properties of Hammerhead Ribozymes
Authors: Klöpffer Astrid E. , Engels Joachim W. 
Published: April 2004

AbstractHammerhead ribozymes are ribonucleic acids that catalyse the hydrolytic cleavage of RNA. They interfere with gene expression in a highly specific manner and recognize the mRNA target through Watson–Crick base pairing. To overcome the problem of point mutations (Watson–Crick “mismatches”) occurring in viral genomes, we developed 2′‐aminoethyl‐substituted fluorinated nucleosides, which are universal nucleobases. The highly efficient synthetic pathway, which features a direct phthaloylamination of a primary alcohol under Mitsunobu conditions, leads to modified phosphoroamidites. The 1′‐deoxy‐1′‐(4,6‐difluoro‐1H‐benzimidazol‐1‐yl)‐2′‐(β‐aminoethyl)‐β‐D‐ribofuranose nucleoside analogue does not differentiate between the four natural nucleosides and leads to a RNA duplex that is as stable as the unmodified parent duplex. Upon incorporation into a ribozyme, the analogue's catalytic activity is equal for all four possible substrates, and the cleavage rates for the modified ribozymes are significantly higher (up to a factor of 13) than for the natural Watson–Crick “mismatch” base pairs. In agreement with the thermodynamic data obtained by measurement of the Tm values of the RNA 12‐mers, the cleavage rates for the 2′‐substituted fluorinated benzimidazole derivative 4 are slightly higher than for the corresponding fluorinated benzene derivative 3.
Synthesis of Phthalide Derivatives Using Nickel‐Catalyzed Cyclization of o‐Haloesters with Aldehydes
Authors: Rayabarapu Dinesh Kumar , Chang Hong‐Tai , Cheng Chien‐Hong 
Published: April 2004

AbstractThe reaction of o‐bromobenzoate (1 b) with benzaldehyde (2 a) in the presence of [NiBr2(dppe)] (dppe=1,2‐bis(diphenylphosphino)ethane) and zinc powder in THF (24 hours, reflux temperature), afforded 3‐phenyl‐3H‐isobenzofuran‐1‐one (3 a) in an 86 % yield. Similarly, o‐iodobenzoate reacts with 2 a to give 3 a, but in a lower yield (50 %). A series of substituted aromatic and aliphatic aldehydes (2 b, 4‐MeC6H4CHO; 2 c, 4‐MeOC6H4CHO; 2 d, 3‐MeOC6H4CHO; 2 e, 2‐MeOC6H4CHO; 2 f, 4‐CNC6H4CHO; 2 g, 4‐(Me)3CC6H4CHO; 2 h, 4‐C6H5C6H4CHO; 2 i, 4‐ClC6H4CHO; 2 j, 4‐CF3C6H4CHO; 2 k, CH3(CH2)5CHO; 2 l, CH3(CH2)2CHO) also underwent cyclization with o‐bromobenzoate (1 b) producing the corresponding phthalide derivatives in moderate to excellent yields and with high chemoselectivity. Like 1 b, methyl 2‐bromo‐4,5‐dimethoxybenzoate (1 c) reacts with tolualdehyde (2 b) to give the corresponding substituted phthalide 3 m in a 71 % yield. The methodology can be further applied to the synthesis of six‐membered lactones. The reaction of methyl 2‐(2‐bromophenyl)acetate (1 d) with benzaldehyde under similar reaction conditions afforded six‐membered lactone 3 o in a 68 % yield. A possible catalytic mechanism for this cyclization is also proposed.
Intermetallics as Zintl Phases: Yb2Ga4Ge6 and RE3Ga4Ge6 (RE=Yb, Eu): Structural Response of a [Ga4Ge6]4− Framework to Reduction by Two Electrons
Authors: Zhuravleva Marina A. , Salvador James , Bilc Daniel , Mahanti Subhendra D. , Ireland John , Kannewurf Carl R. , Kanatzidis Mercouri G. 
Published: April 2004

AbstractTwo new intermetallic compounds, Yb2Ga4Ge6 and Yb3Ga4Ge6, were obtained from reactions in molten Ga. A third compound, Eu3Ga4Ge6, was produced by direct combination of the elements. The crystal structures of these compounds were studied by single‐crystal X‐ray diffraction. Yb2Ga4Ge6 crystallizes in an orthorhombic cell with a=4.1698(7), b=23.254(4), c=10.7299(18) Å in the polar space group Cmc21. The structure of RE3Ga4Ge6 is monoclinic, space group C2/m, with cell parameters a=23.941(6), b=4.1928(11), c=10.918(3) Å, β=91.426(4)° for RE=Yb, and a=24.136(2), b=4.3118(4), c=11.017(1) Å, β=91.683(2)° for RE=Eu. The refinement [I>2 σ(I)] converged to the final residuals R1/wR2=0.0229/0.0589, 0.0411/0.1114, and 0.0342/0.0786 for Yb2Ga4Ge6, Yb3Ga4Ge6, and Eu3Ga4Ge6, respectively. The structures of these two families of compounds can be described by a Zintl concept of bonding, in which the three‐dimensional [Ga4Ge6]n− framework serves as a host and electron sink for the electropositive RE atoms. The structural relation of RE3Ga4Ge6 to of Yb2Ga4Ge6 lies in a monoclinic distortion of the orthorhombic cell of Yb2Ga4Ge6 and reduction of the [Ga4Ge6] network by two electrons per formula unit. The results of theoretical calculations of the electronic structure, electrical transport data, and thermochemical and magnetic measurements are also reported.
Optimizing the point spread function in phase‐encoded magnetic resonance microscopy
Authors: Webb A.G. 
Published: April 2004

AbstractThree‐dimensional phase‐encoded magnetic resonance microscopy is the most promising method for obtaining images with isotropic spatial resolutions on the order of a few micrometers. The attainable spatial resolution is limited by the available gradient strength (Gmax) and the molecular self‐diffusion coefficient (D) of the sample. In this study, numerical simulations in the microscopic‐size regime are presented in order to show that for given values of Gmax and D, there exists an optimum number of phase‐encoding steps that maximize the spatial resolution in terms of minimizing the full‐width at half‐maximum (FWHM) of the image point spread function (PSF). Unlike the case of “macroscopic” imaging, in which diffusion plays an insignificant role in determining spatial resolution, acquiring data beyond this optimal value actually degrades the image PSF. An alternative version of phase encoding, using a variable phase‐encoding time rather than a variable gradient strength, is analyzed in terms of improvements in the image PSF and/or reductions in the data acquisition time for a given spatial resolution. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 22A: 25–36, 2004.
Racial differences in the expression of cell cycle–regulatory proteins in breast carcinoma
Authors: Porter Peggy L. , Lund Mary Jo , Lin Ming Gang , Yuan Xiaopu , Liff Jonathan M. , Flagg Elaine W. , Coates Ralph J. , Eley J. William 
Published: April 2004

AbstractBACKGROUNDAfrican‐American (AA) women are more likely to be diagnosed with an advanced stage of breast carcinoma than are white women. After adjustment for disease stage, many studies indicate that tumors in AA women are more likely than tumors in white women are to exhibit a high level of cell proliferation and features of poor prognosis. The purpose of the current study was to compare tumor characteristics and cell cycle alterations in AA women and white women that might affect the aggressiveness of breast carcinoma.METHODSThe study included 124 AA and 397 white women, ages 20–54 years. These women were enrolled in a case–control study in Atlanta, Georgia, between 1990 and 1992. Breast tumor specimens obtained from these women were centrally reviewed for histologic characteristics and evaluated for expression of estrogen and progesterone receptors (ER/PR), c‐ErbB‐2, Ki‐67, p53, cyclin E, cyclin D1, p27, p16, pRb, and p21 by immunohistochemistry. Logistic regression models were used to assess the age‐ and stage‐adjusted associations of various tumor characteristics with race.RESULTSThe odds of a breast carcinoma diagnosis at a younger age and at a later stage were higher for AA women than for white women. After adjustment for disease stage and age at diagnosis, AA women also were found to have increased odds of having a higher‐grade tumor, a higher mitotic index, marked tumor necrosis, ductal histology, loss of ER and PR, overexpression of cyclin E, p16, and p53 and low expression of cyclin D1 at diagnosis.CONCLUSIONSThe observed differences between tumor specimens obtained from AA women and tumor specimens obtained from white women, independent of stage and age at diagnosis, indicated that race may be a determinant, or a surrogate for other determinants, of aggressive breast carcinoma and specific cell cycle defects. Cancer 2004. Published 2004 American Cancer Society.
Inhibition of macrophage development and foreign body giant cell formation by hydrophilic interpenetrating polymer network
Authors: Collier Terry O. , Anderson James M. , Brodbeck William G. , Barber Thomas , Healy Kevin E. 
Published: April 2004

AbstractThe ability of monocytes to adhere, differentiate into macrophages, and fuse to form foreign body giant cells (FBGCs) on an implanted material surface is a critical step toward biomaterial degradation. Novel homogenous surfaces were utilized to mediate adhesion. These surfaces consisted of N‐(2 aminoethyl)‐3‐aminopropyltrimethoxysilane (EDS) and an interpenetrating polymer network (IPN) of polyacrylamide and poly(ethylene glycol). These surfaces were designed to control cell adhesion and morphology and mediate cell differentiation, activation, metabolic ability, and apoptosis, resulting in a reduced or controlled inflammatory response. The EDS surface promotes cell adhesion and the IPN minimizes protein adsorption and subsequent cell adhesion. Both surfaces had similar cellular adhesion rates at each respective time point. However, the adherent macrophage morphology was similar at 2 h and day 3, and at days 7 and 10 adherent macrophages on the EDS surface formed FBGCs (46% at day 7 and 40% at day 10). Adherent cells on the IPN surface did not form FBGCs but instead formed monocyte aggregates (73% of adherent cells formed aggregates at day 7 and 63% at day 10). It is indicated that the two surface chemistries differentially controlled monocyte differentiation into macrophages and subsequent macrophage fusion to form FBGCs. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 644–650, 2004
Tooth–composite interface from specific and nonspecific adhesive restorative systems
Authors: Haßhoff Gitte , Schneider Hartmut , Merte Knut 
Published: April 2004

AbstractThe aim of this in vitro study was to do a morphological comparison of tooth/composite interface by means of three composite systems: (1) a specific formulated primer adhesive and Organically Modified Ceramics (ORMOCER) composite, (2) an universal self‐etching adhesive and the same ORMOCER composite, (3) and the same universal adhesive used for Group 2 and a fine‐particle hybrid resin composite. The rational for this study was based on the recommendations from manufacturers that nonspecific dentin bonding agents can be used with ORMOCER. Twenty‐one Class II cavities were prepared in extracted third molars. Seven randomly assigned teeth were restored with one of the three methods according to the instructions provided by the manufacturer. Following completion of the restorations, the teeth were sectioned and evaluated by means of scanning electron microscopy for evaluation of interfacial morphology and light microscopy for the determination of microleakage. The last was scored as being present or absent. The best results were observed using method 1, in which a special primer adhesive and ORMOCER composite was used. In this group there were statistically significant fewer gaps in enamel (4.7± 7.5%) and dentin (22.8 ± 7.4%) compared to the other two groups (Group 2: enamel 21.1 ± 8.3% and dentin 66.3 ± 17.3%; and Group 3: enamel 40.6 ± 35.2% and dentin 89.4 ± 13.3%). The interfaceof method 2, universal self‐etching adhesive and ORMOCER, was of a lesser quality than Group 1. Within the limitations of this study the recommendation is made to use the ORMOCER tested in this experiment with the matching specifically formulated primer adhesive system. A lack of adhesion as well as microleakage, were prominent features for Groups 2 and 3. From the data of this study the practitioner is cautioned not to indiscriminately exchange specific dentin bonding agents for nonspecific ones. Considering the shear endless number of possible combinations and the numerous different tests that would be required to test these all, selection of different combinations will remain a theoretical exercise. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 38–45, 2004
Transperineal sonographic findings in a woman with urethral mucosa prolapse
Authors: Yang Jenn‐Ming , Huang Wen‐Chen 
Published: April 2004

AbstractWe present a case of urethral mucosa prolapse in a postmenopausal woman. Transperineal gray‐scale sonograms revealed a clover‐shaped, hypoechoic mass protruding from the urethral meatus. Doppler studies revealed blood flow within the protruding mass. Detection of feeding arteries and draining veins contributed to exclude the possibility of necrosis and gangrene, thus allowing conservative medical treatment to be tried. The mucosal prolapse regressed after 1 week's treatment with topical estrogen and antibiotics and sitz baths. Follow‐up sonograms showed a normal urethral configuration and diminished vascular flow when compared with the initial study. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:261–263, 2004; Published online in Wiley InterScience (www. interscience.wiley.com). DOI: 10.1002/jcu.20026
Sonographic demonstration of duodenobiliary reflux with soda enhancement
Authors: Wu Chien‐Hsien , Chiu Han‐Mo , Liu Kao‐Lang , Lin Jaw‐Town , Wang Hsiu‐Po 
Published: April 2004

AbstractCholangitis rarely occurs after sphincteroplasty if there is no biliary obstruction. We report the case of a patient who developed recurrent cholangitis despite having a patent biliary tract after sphincteroplasty. Duodenobiliary reflux was demonstrated on sonography after enhancement of the reflux flow with a novel oral contrast agent, a carbonated soda beverage. Sonography with contrast enhancement provided by soda solution may prove satisfactory to detect duodenobiliary reflux after sphincteroplasty safely, effectively, and economically. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:249–252, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jcu.20030
The role of polyadenylation signal secondary structures on the resistance of plasmid vectors to nucleases
Authors: Ribeiro Sofia C. , Monteiro Gabriel A. , Prazeres Duarte M. F. 
Published: April 2004

AbstractBackgroundNuclease degradation of plasmid DNA (pDNA) vectors after delivery and during trafficking to the nucleus is a barrier to gene expression. This barrier may be circumvented by shielding the pDNA from the nuclease‐rich cell environment with adjuvants or by using nuclease inhibitors. A different alternative that is explored in this work is to make pDNA vectors more nuclease‐resistant a priori.Methods and resultsThe hypothesis that a significant part of nuclease attack is directed towards certain labile sequences in a pDNA model (pVAX1/lacZ) was first tested. Homopurine‐rich tracts in the bovine growth hormone polyadenylation signal (BGH poly A) were identified as labile sequences using S1 nuclease as a probe. Two pDNA variants were then created by replacing the BGH poly A region with the SV40 or a synthetic poly A signal. A study of plasmid degradation in eukaryotic cell lysates and mice plasma showed that the half‐life of the supercoiled isoforms of the new vectors was always higher when compared with the control plasmid. An in vitro assay of the reporter β‐galactosidase in transfected CHO cells further showed that gene expression with the new pDNA variants was not affected negatively by the plasmid modifications.ConclusionsThe replacement of labile sequences in plasmid DNA vectors improves resistance towards nuclease attack as shown by the increased half‐lives of supercoiled plasmid isoforms incubated with endo/lysosomal, cytoplasmatic and blood plasma enzymes. Copyright © 2004 John Wiley & Sons, Ltd.
Dependent edges in Mycielski graphs and 4‐colorings of 4‐skeletons
Authors: Collins Karen L. , Tysdal Kimberly 
Published: April 2004

AbstractA dependent edge in an acyclic orientation of a graph is one whose reversal creates a directed cycle. In answer to a question of Erdös, Fisher et al. [5] define dmin(G) to be the minimum number of dependent edges of a graph G, where the minimum is taken over all acyclic orientations of G, and also rm,k as the supremum of the ratio dmin(G)/e(G), where e(G) is the number of edges in G and the supremum is taken over all graphs G with chromatic number m and girth k. They show that $r_{m,k}\le (m-2)/m$ and r4,4 ≥ 1/20. We show that r5,4 ≥ 4/71, r6,4 ≥ 7/236, and r7,4 ≥ 11/755 and that the Mycielski construction on a triangle‐free graph with at least one dependent edge yields a graph with at least three dependent edges. In addition, we give an alternative proof of the answer to Erdös's question, based on Tysdal [6] and Youngs [7]. © 2004 Wiley Periodicals, Inc. J Graph Theory 46: 285–296, 2004
Volatile organic compound permeation through porous polymeric films for modified atmosphere packaging of foods
Authors: Del‐Valle Valeria , Almenar Eva , Hernández‐Muñoz Pilar , Lagarón José M , Catala Ramón , Gavara Rafael 
Published: April 2004

AbstractThe use of perforated packaging films is increasing with the application of modified atmosphere packaging (MAP) to fresh produce. These films provide high to very high mass exchange rates which usefully allow oxygen ingress and carbon dioxide exit. However, the use of porous films also increases the loss of other food volatile components through similar processes. In this paper we present data on the permeation through porous films of several organic compounds found in many fruits and vegetables. The results are compared with those predicted by theoretical equations describing pore permeation processes. A discussion on the significance of these very high permeation values for product quality is also presented through the analysis of ethanol concentration evolution during MAP of mandarin segments. It was found that the barrier effectiveness of the fruit cuticle and the elevated partition coefficient of the organic compounds between the fruit (flesh) and the headspace appear to be responsible for the reduced food aroma compound loss. Copyright © 2004 Society of Chemical Industry
Effect of α‐tocopherol and α‐tocotrienol on the performance of Chilean hazelnut oil (Gevuina avellana Mol) at high temperature
Authors: Romero Nalda , Robert Paz , Masson Lilia , Ortiz Jaime , Pavez Jacquelinne , Garrido Carolina , Foster Mariela , Dobarganes Carmen 
Published: April 2004

AbstractThe high temperature antioxidant efficiency of α‐tocopherol, α‐tocotrienol and a mixture of both on hazelnut oil were evaluated. Crude hazelnut oil (HZO), crude hazelnut oil treated with alumina (THZO), as well as three samples of THZO to which 150 mg kg−1 of α‐tocopherol, 140 mg kg−1 of α‐tocotrienol or a mixture containing 70 mg kg−1 of α‐tocopherol and 70 mg kg−1 of α‐tocotrienol, were added and submitted to thermal treatment at 180°C for 18 h. The addition of tocols to THZO decreased the formation of polar compounds and increased its oxidative stability in all the systems studied. However, α‐tocopherol showed a higher antioxidant capacity than α‐tocotrienol at high temperature. In addition, α‐tocotrienol showed a more rapid degradation rate than α‐tocopherol under the conditions studied. Copyright © 2004 Society of Chemical Industry