bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of Cell Proliferation by 5‐Bromodeoxyuridine (BrdU) Labeling for Multicolor Flow Cytometry
Authors: Rothaeusler Kristina , Baumgarth Nicole 
Published: April 2007

AbstractCell proliferation assays are used for a large variety of applications in the life sciences. This unit describes a flow‐cytometry‐based method that uses BrdU labeling in conjunction with multiple fluorescently labeled cell surface markers, allowing extensive phenotypic characterization of dividing cells in addition to assessment of their frequency. BrdU labeling has the advantage of constituting a nonradioactive technique that, when combined with additional fluorescent‐based reagents, avoids time‐consuming and often costly cell isolation procedures. Moreover, because BrdU is stably integrated into the DNA, it can be measured in a cell for many months. The method presented in this unit is based on paraformaldehyde fixation and reversible saponin‐based cell membrane permeabilization, which maintains cell integrity as well as fluorescent labeling with a large number of different fluorochromes, allowing 10‐ to 12‐color flow cytometric analysis of proliferating cells.
Viral clearance using surfactant‐aided size‐exclusion chromatography
Authors: Horneman D. A. , Ottens M. , van der Wielen L. A. M. , Keurentjes J. T. F. 
Published: April 2007

AbstractSurfactant‐aided size‐exclusion chromatography (SASEC) is applied to the viral clearance of blood proteins, taking BSA as an example. Fixed bed systems as well as simulated moving bed (SMB) systems are examined. SASEC shows a better performance of this separation in terms of log reduction value (LRV), productivity of BSA, yield on BSA and solvent consumption compared to normal size‐exclusion chromatography (SEC) in fixed bed as well as in SMB systems. © 2007 American Institute of Chemical Engineers AIChE J, 2007
Minimalist Active‐Site Redesign: Teaching Old Enzymes New Tricks
Authors: Toscano Miguel D. , Woycechowsky Kenneth J. , Hilvert Donald 
Published: April 2007

AbstractAlthough nature evolves its catalysts over millions of years, enzyme engineers try to do it a bit faster. Enzyme active sites provide highly optimized microenvironments for the catalysis of biologically useful chemical transformations. Consequently, changes at these centers can have large effects on enzyme activity. The prediction and control of these effects provides a promising way to access new functions. The development of methods and strategies to explore the untapped catalytic potential of natural enzyme scaffolds has been pushed by the increasing demand for industrial biocatalysts. This Review describes the use of minimal modifications at enzyme active sites to expand their catalytic repertoires, including targeted mutagenesis and the addition of new reactive functionalities. Often, a novel activity can be obtained with only a single point mutation. The many successful examples of active‐site engineering through minimal mutations give useful insights into enzyme evolution and open new avenues in biocatalyst research.
Effect of in situ synthesized macroactivator on morphology of PA6/PS blends via successive polymerization
Authors: Pei Aihua , Liu Andong , Xie Tingxiu , Yang Guisheng 
Published: April 2007

AbstractIn situ polymerization and in situ compatibilization was adopted for preparation of ternary PA6/PS‐g‐PA6/PS blends by means of successive polymerization of styrene, with TMI and ε‐caprolactam, via free radical copolymerization and anionic ring‐opening polymerization, respectively. Copolymer poly(St‐g‐TMI), the chain of which bears isocyanate (NCO), acts as a macroactivator to initiate PA6 chain growth from the PS chain and graft copolymer of PS‐g‐PA6 and pure PA6 form, simultaneously. The effect of the macroactivator poly(St‐g‐TMI) on the phase morphology was investigated in detail, using scanning electron microscopy. In case of blends with higher content of PS‐g‐PA6 copolymer, copolymer nanoparticles coexisting with the PS formed the matrix, in which PA6 microspheres were dispersed evenly as minor phase. The content of the compositions (homopolystyrene, homopolyamide 6, and PS‐g‐PA6) of the blends were determined by selective solvent extraction technique. The mechanical properties of PA6/PS‐g‐PA6/PS blends were better than that of PA6/PS blends. Especially for the blends T10 with lower PS‐g‐PA6 copolymer content, both the flexural strength and flexural modulus showed significantly improving because of the improved interfacial adhesion between PS and PA6. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation and magnetic properties of Fe/Si/C/N ceramics derived from a polymeric precursor
Authors: Li Junping , Zhang Zhijie , Zheng Zhimin , Guo Li , Xu Guiyun , Xie Zemin 
Published: April 2007

AbstractIron‐containing polysilazanes (PSZI) were prepared by the amine displacement reaction along with heat‐induced vinyl crosslinking reactions between Fe[N(SiMe2Vi)2]3 (Vi = CHCH2) and polysilazane containing SiVi (PVSZ). The PSZIs were converted into magnetic ceramics by the pyrolysis in N2. The ceramics produced were investigated by X‐ray diffraction, transmission electron microscope and vibrating sample magnetometer at room temperature. It was indicated that α‐Fe is the only magnetic crystalline embedded in the amorphous Si/C/N‐based matrix from 500 to 900°C. Moreover, the sample prepared at 500°C showed few hysteresis at room temperature, consistent with the behavior of superparamagnetic particles, which was confirmed by the zero‐field‐cooled and field‐cooled magnetization measurement. Additionally, the results indicated that the magnetic properties of the ceramics could be tuned by controlling the content of iron and the pyrolysis temperature. This flexibility may be advantageous for some particular magnetic materials applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Synthesis and liquid‐crystal‐aligning properties of novel aromatic poly(amide imide)s bearing n‐alkyloxy side chains
Authors: Sarkar Anjana , More Arvind S. , Wadgaonkar Prakash P. , Jic Shin Gyo , Chul Jung Jin 
Published: April 2007

AbstractNovel aromatic poly(amide imide)s (m‐PAIs, m = 8, 12, 16) containing preformed isophthalamide unit and pendent n‐alkyloxy (‐O‐n‐CmH2m+1, m = 8, 12, 16) side chains were prepared in thin films by polymerization of pyromellitic dianhydride (PMDA) with N,N′‐bis(4‐aminophenyl)‐5‐(n‐alkyloxy)isophthalamides (m‐DAs) obtained from N,N′‐bis(4‐nitrophenyl)‐5‐(n‐alkyloxy)isophthalamides (m‐DNs). The m‐PAI films were tough, flexible and transparent with inherent viscosities in the 1.25–1.67 dL/g range in DMAc and soluble in DMAc and NMP on heating. In TGA m‐PAIs began to degrade around 440°C and in DSC no phase transitions were detected. In X‐ray diffractometry the m‐PAIs appeared amorphous with loosely developed layered crystalline structure. In liquid crystal (LC)‐aligning performance measured using 4‐n‐pentyl‐4′‐cyanobiphenyl (5CB) on thin film surfaces rubbed with standard velvet fibers, the m‐PAIs showed homogeneous LC alignment parallel to the rubbing direction with 2.5–17.5° pretilt angles, depending on the rubbing density and n‐alkyloxy side chain length. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Radiation‐induced graft copolymerization of cellulosic fabric waste and its application in the removal of cyanide and dichromate from aqueous solution
Authors: El‐Kelesh N. A. , Abd Elaal S. E. , Hashem A. , Sokker H. H. 
Published: April 2007

AbstractGraft polymerization and crosslinking in radiation processing are attractive techniques for modification of the chemical and physical properties of the conventional polymer. The graft polymerization and subsequent chemical treatment can introduce a chelate agent function into a conventional polymer such as cellulosic fabric. Cellulosic graft copolymers were prepared by the reaction of the fiber with acrylonitrile (AN) and 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) in DMF initiated by γ‐radiation 60Co. The grafted fabric was chemically treated with hydroxyl amine to obtain amidoxime from. Factors affecting the grafting such as radiation dose, monomer concentration and solvent concentration as well as monomer composition was investigated. The chemically modified graft fabric was applied for recovery of cyanide and dichromate from aqueous solution. CN− shows 89% removal, whereas dichromate has 65% removal. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Influence of organic modification on mechanical properties of melt processed intercalated poly(methyl methacrylate)–organoclay nanocomposites
Authors: Tiwari Rajkiran R. , Natarajan Upendra 
Published: April 2007

AbstractThe influence of organic modifiers on intercalation extent, structure, thermal and mechanical properties of poly(methyl methacrylate) (PMMA)–clay nanocomposites were studied. Two different organic modifiers with varying hydrophobicity (single tallow versus ditallow) were investigated. The nanocomposites were prepared from melt processing method and characterized using wide angle X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), and tensile tests. Mechanical properties such as tensile modulus (E), break stress (σbrk), and % break strain (εbrk) were determined for nanocomposites at various clay loadings. Extent of PMMA intercalation is sufficient and in the range 9–15 Å depending on organoclay and filler loading. Overall thermal stability of nanocomposites increases by 16–30°C. The enhancement in Tg of nanocomposite is merely by 2–4°C. With increase in clay loading, tensile modulus increases linearly while % break strain decreases. Break stress is found to increase till 4 wt % and further decreases at higher clay loadings. The overall improvement in thermal and mechanical properties was higher for the organoclay containing organic modifier with lower hydrophobicity and single tallow amine chemical structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Effect of a chiral dopant on the electro‐optical properties of polymer‐dispersed liquid‐crystal films
Authors: Li Wenbo , Zhang Hongxue , Wang Liping , Ouyang Canbin , Ding Xiaokang , Cao Hui , Yang Huai 
Published: April 2007

AbstractPolymer‐dispersed liquid crystal (PDLC) films were prepared by the ultraviolet‐light‐induced polymerization of photopolymerizable monomers in nematic liquid crystal/monomer/chiral dopant composites, and the effect of the chiral dopant on the electro‐optical properties of the PDLC films was studied. It was demonstrated that the addition of a small amount of the chiral dopant increased the driving voltage somewhat but decreased the turn‐off time significantly. Furthermore, the transmittance of ultraviolet, visible, and near‐infrared light of the off state of PDLC films showing light scattering increased with increasing content of the chiral dopant, and the optimum electro‐optical properties of the PDLC films were obtained when the content of the chiral dopant was not more than 2 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Noncovalent imprinted microspheres: Preparation, evaluation and selectivity of DBU template
Authors: Del Sole Roberta , De Luca Agnese , Catalano Massimo , Mele Giuseppe , Vasapollo Giuseppe 
Published: April 2007

Abstract1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) imprinted polymer was prepared as microspheres by precipitation polymerization method to obtain molecular recognition systems based on the noncovalent interactions between DBU template, methacrylic acid (MAA), and ethylene .glycol dimethacrylate (EDMA) in acetonitrile. 1H NMR analysis of DBU/MAA mixture has been performed and hydrogen bonding interactions have been established. Microspheres have been characterized by FTIR studies with evidence of DBU linkage in polymer particles and by Scanning Electron Microscopy (SEM) to study their morphological properties. How pH values affect the binding capacity of imprinted polymer during the binding stage has been also discussed and results suggest that imprinted poly‐(MAA‐EDMA) behavior is related to the influence of DBU basicity during rebinding processes and the optimum pH value for binding has been found around neutral range. Binding ability of the imprinted polymer towards different concentration of DBU buffered solutions has been evaluated and compared with binding ability of the non‐imprinted polymer. A more sensitive response to the template in the imprinted system suggests that a reasonable number of specific binding sites is formed. Finally, differential selectivity towards other less strong than DBU nitrogen bases, such as pyridine, imidazole, and 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN) has been also discussed. Our results indicate that both specific sites and basic properties are involved in the rebinding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Sesbania gum xanthate supported palladium complex as an efficient catalyst for heck reaction
Authors: Zhang Lei , Zhang Puyu , Li Xiang , Cui Yuanchen 
Published: April 2007

AbstractSesbania gum xanthate supported palladium complex (SG‐CS2‐Pd) was synthesized and characterized by XPS, TGA, DTA, etc. The complex exhibits high activity and stereoseletivity for Heck reaction under atmospheric condition and can be easily recovered and reused. Heck reaction of styrene with iodobenzene can be carried out efficiently by using SG‐CS2‐Pd as catalyst even at the low temperature (70°C) or with tiny amount of the catalyst (0.1 mol % Pd). SG‐CS2‐Pd has high catalytic activity for arylation of acrylic acid or styrene with iodobenzene under the condition of NMP as solvent and the yield of cinnamic or trans‐stilbene exceeded 90%. The Heck arylation of substituted iodobenzene with acrylic acid or styrene with iodobenzene can also be efficiently catalyzed by using SG‐CS2‐Pd as catalyst under the conditions of 90°C, NMP as solvent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Conductivity relaxation in zirconia nanoparticles dispersed in conducting polymer
Authors: Dey Ashis , De S. K. 
Published: April 2007

AbstractZirconia‐polyaniline (ZrO2‐PANI) nanocomposites have been synthesized using the colloidal stability of ZrO2 sol. Complex impedance and dielectric permittivity of ZrO2‐PANI nanocomposites have been investigated as a function of frequency and temperature for different compositions. Grain conductivity is about two orders of magnitude higher than the grain boundary conductivity. A very large dielectric permittivity of about 2500 at room temperature has been observed for the composite with highest content of ZrO2. The high dielectric permittivity is mainly dominated by interfacial polarization because of Maxwell‐Wagner relaxation effect. The electric modulus spectra reveal two types of conductivity relaxation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Alternate method for grafting thermoresponsive polymer for transferring in vitro cell sheet structures
Authors: Kumar P. R. Anil , Sreenivasan K. , Kumary T. V. 
Published: April 2007

AbstractRetrieval of cells for various applications involves enzymatic or mechanical methods that hamper the cell–cell and cell–extracellular matrix (ECM) binding. Poly(N‐isopropylacrylamide) (PIPAAm) is a known temperature‐sensitive polymer that exhibits a lower critical solution temperature (LCST) around 32°C and is hydrophobic over LCST and hydrophilic below LCST. PIPAAm‐grafted culture surface can be used for detaching adhered cells by lowering the temperature below LCST. In this study, polymerization and grafting of PIPPAm was done by gamma (γ) ray irradiation instead of the conventional method of electron beam irradiation. The efficacy of the grafted surface was confirmed by the successful growth of different cell lines such as L‐929, NRK‐49F, HOS, and SIRC. The cell sheet structures with intact cell–cell and cell–ECM contact was detached by lowering incubation temperature below 20°C. Live–dead staining of cells before and after transfer showed that cell sheet structures maintained viability. This approach of synthesizing thermoresponsive surface by γ‐ray irradiation method can be used to culture many other cell types and could be utilized to prepare in vitro tissue constructs for bioengineering. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Hierarchy structure in injection molded polypropylene/ethylene–octane copolymer blends
Authors: Li Jiang , Zhang Xiaoqing , Qu Cheng , Zhang Qin , Du RongNi , Fu Qiang 
Published: April 2007

AbstractIn this article, the phase morphology and mechanical properties of polypropylene (PP)/ethylene–octane copolymer (POE) blends with fixed ratio (60/40) obtained via different processing conditions, including barrel temperature, injection speed, and mold temperature, have been investigated. SEM was carried out for detailed characterization of phase morphology from the skin to the core, layer by layer. It was interesting that for all the processing conditions no dispersed POE elastomer was observed in the skin layer but elongated POE particles with large size were observed in the subskin layer. From the transition zone to the core layer, an increased phase separation was observed, which could lead to a formation of cocontinuous morphology, depending on the processing condition used. Higher barrel temperature, lower mold temperature, and higher injection speed could result in a smaller size of POE phase. The tensile strength and impact strength were found not sensitive to barrel temperature and mold temperature but to the low injection speed, both tensile strength and impact strength had a higher value for specimen obtained via low injection speed. The formation of the skin‐core morphology and the effect of processing conditions on the phase morphology were discussed based on crystallization kinetics of PP matrix, rheology, and shear induced phase mixing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Metal–polymer nanocomposites produced by the melt‐compounding interaction of an aliphatic polyamide with metal particles
Authors: Pesetskii S. S. , Jurkowski B. , Krivoguz Y. M. , Davydov A. A. , Bogdanovich S. P. 
Published: April 2007

AbstractComposites prepared at 200°C by the melt compounding of copolymer polyamide 6/66 and ferric chloride, ferric oxalate, cupric chloride, cupric formiate, cupric acetate, Cr‐carbonyl, Mo‐carbonyl, or W‐carbonyl have been studied. The solution stability and aggregation suppression for nanoparticles in a polyamide can be explained by the formation of stable polymer–metal complexes. The nitrogen atoms of amide and amine groups of polymers serve as ligands for the coordination compounds that form. The dynamic viscosity of the solutions suggests that Cr‐carbonyl forms mostly intermolecular complexes, whereas ferric oxalate, ferric chloride, cupric formiate, cupric acetate, cupric chloride, Cr‐carbonyl, Mo‐carbonyl, and W‐carbonyl form intramolecular complexes. The critical concentrations for metal‐containing compounds at which a dispersion rises to nanodimensions without aggregating in the polymer matrix under the experimental conditions are 0.024 wt % for ferric oxalate, 0.12 wt % for ferric chloride, 0.08 wt % for cupric formiate, 0.096 wt % for cupric acetate, and 0.19 wt % for cupric chloride. Metal carbonyls undergo dispersion (with their concentration up to 5 wt %) in polyamide 6/66 without aggregating into larger formations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Preparations and properties of thermosensitive terpolymers of N‐isopropylacrylamide, sodium 2‐acrylamido‐2‐methyl‐propanesuphonate, and N‐tert‐butylacrylamide
Authors: Shao Dan , Ni Caihua 
Published: April 2007

AbstractTerpolymers based on N‐isopropylacrylamide, sodium 2‐acrylamido‐2‐methyl‐propanesulfonate, and N‐tert‐butylacrylamide were synthesized by free‐radical copolymerization with 2,2′‐azobisisobutyronitrile as an initiator. The lower critical solution temperatures (LCSTs) of the linear polymer aqueous solutions were determined by the measurement of the transmittance on UV at different temperatures. The influence of the polymer concentration, polymer composition, and ionic strength on the LCSTs of the linear polymers was investigated. The LCST decreased with increases in the hydrophobic monomer N‐tert‐butylacrylamide, polymer concentration, and ionic strength. The phase transition became sharp when the polymer concentration and ionic strength increased. Meanwhile, the crosslinked hydrogels were prepared with the same recipe used for the linear terpolymers, but a crosslinker was added to the reaction system. The swelling ratios of the hydrogels at various temperatures and salt solutions were determined. The hydrogels possessed both high swelling ratios and thermosensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Modification of silica gel, cellulose, and polyurethane with a sterically hindered N‐halamine moiety to produce antimicrobial activity
Authors: Barnes K. , Liang J. , Worley S. D. , Lee J. , Broughton R. M. , Huang T. S. 
Published: April 2007

AbstractThe sterically hindered amine monomer 4‐[3‐triethoxysilylpropoxyl]‐2,2,6,6‐tetramethylpiperidine has been synthesized and covalently bonded to the surfaces of silica gel particles and cellulose (cotton) and copolymerized in a polyurethane coating formulation. Upon exposure to dilute sodium hypochlorite (household bleach), a very stable N‐Cl bond is formed in situ at the hindered amine nitrogen site. This source of oxidative chlorine provides an antimicrobial function to the silica gel, cotton, and polyurethane. Stability, regenerability, and biocidal efficacy data are presented. The new N‐halamine materials were remarkably effective against Staphylococcus aureus and Escherichia coli O157 : H7 in brief periods of contact. The materials should find application in water treatment and medical applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Influence of processing conditions on the morphological and mechanical properties of compatibilized PP/LCP blends
Authors: Filipe Susana , Manuel Maia João , Rosa Leal Catarina , Teresa Cidade Maria 
Published: April 2007

AbstractThe main aim of this work is to study the influence of the application of different processing conditions on the morphological and mechanical properties of thermoplastic/LCP blends, in which the viscosity ratios are inferior to unity and decrease with increasing temperature. The way the microstructure evolves along the extruder determines the final morphology and thus, the mechanical performance of the systems. In the present case, the mechanical properties are related with the degree of fibrillation in the final composites. The best degree of fibrillation was obtained for low screw speeds and temperatures and for intermediate outputs. The use of high screw speeds and processing temperatures results in a decrease of the viscosity ratio, in the former case via an increase in the viscous dissipation, at the regions of higher shear rates (kneading‐elements). The application of a lower processing temperature is advantageous for deformation, break‐up, and fibrillar formation because of the higher viscosity ratios and higher shear stresses involved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Toughened electrospun nanofibers from crosslinked elastomer‐thermoplastic blends
Authors: Fang Jian , Lin Tong , Tian Wendy , Sharma Arnav , Wang Xungai 
Published: April 2007

AbstractA crosslink‐able elastomeric polyester urethane (PEU) was blended with a thermoplastic, polyacrylonitrile (PAN), and electrospun into nanofibers. The effects of the PEU/PAN ratio and the crosslinking reaction on the morphology and the tensile properties of the as‐spun fiber mats were investigated. With the same overall polymer concentration (9 wt %), the nanofiber containing higher composition of PEU shows a slight decrease in the average fiber diameter, but the tensile strength, the elongation at break and tensile modulus of the nanofiber mats are all improved. These tensile properties are further enhanced by slight crosslinking of the PEU component within the nanofibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007