bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐Density Periodically Ordered Magnetic Cobalt Ferrite Nanodot Arrays by Template‐Assisted Pulsed Laser Deposition
Authors: Gao Xingsen , Liu Lifeng , Birajdar Balaji , Ziese Michael , Lee Woo , Alexe Marin , Hesse Dietrich
Published: August 2009

A novel nanopatterning method using pulsed laser deposition through an ultrathin anodic aluminium oxide (AAO) membrane mask is proposed to synthesize well‐ordered nanodot arrays of magnetic CoFe2O4 that feature a wide range of applications like sensors, drug delivery, and data storage. This technique allows the adjustment of the array dimension from ∼35 to ∼300 nm in diameter and ∼65 to ∼500 nm in inter‐dot distance. The dot density can be as high as 0.21 Terabit in.−2. The microstructure of the nanodots is characterized by SEM, TEM, and XRD and their magnetic properties are confirmed by well‐defined magnetic force microscopy contrasts and by hysteresis loops recorded by a superconducting quantum interference device. Moreover, the high stability of the AAO mask enables the epitaxial growth of nanodots at a temperature as high as 550 °C. The epitaxial dots demonstrate unique complex magnetic domains such as bubble and stripe domains, which are switchable by external magnetic fields. This patterning method creates opportunities for studying novel physics in oxide nanomagnets and may find applications in spintronic devices.
Stimuli‐Responsive Thin Coatings Using Elastin‐Like Polymers for Biomedical Applications
Authors: Costa Rui R. , Custódio Catarina A. , Testera Ana M. , Arias Francisco J. , Rodríguez‐Cabello José C. , Alves Natália M. , Mano João F.
Published: August 2009

Smart thin coatings using a recombinant elastin‐like polymer (ELP) containing the cell attachment sequence arginine–glycine–(aspartic acid) (RGD) are fabricated for the first time through simple deposition of the ELP dissolved in aqueous‐based solutions. The biopolymer is produced and characterized using electrophoresis and mass spectroscopy. The temperature and pH responsiveness are assessed by aggregate size measurements and differential scanning calorimetry. The deposition of the studied ELP onto chitosan is followed in situ with a quartz‐crystal microbalance with dissipation monitoring (QCM‐D). Contact angle measurements are performed at room temperature and at 50 °C, showing reversible changes from a moderate hydrophobic behavior to an extremely wettable surface. AFM analysis performed at room temperature reveals a smooth surface and no organized structure. At 50 °C, the surface presents spherical nanometer‐sized structures of collapsed biopolymer chains. Such results suggest that the ELP chains, when collapsed, aggregate into micelle‐like structures at the surface of the substrate, increasing its water affinity. Cell adhesion tests on the developed coatings are conducted using a SaOS‐2 cell line. Enhanced cell adhesion could be observed in the H‐RGD6‐coated surfaces, as compared with the original chitosan monolayer. An intermediate behavior is found in chitosan coated with the corresponding ELP without the RGD sequence. Therefore, the developed films have great potential as biomimetic coatings of biomaterials for different biomedical applications, including tissue engineering and controlled delivery of bioactive agents. Their thermo‐responsive behavior can also be exploited for tunable cell adhesion and controlled protein adsorption.
Synthesis of Hexagonal Yb3+,Er3+‐Doped NaYF4 Nanocrystals at Low Temperature
Authors: Schäfer Helmut , Ptacek Pavel , Eickmeier Henning , Haase Markus
Published: August 2009

Nanocrystals of NaYF4 doped with Yb3+ and Er3+ are synthesized in oleylamine using Y2(CO3)3, Yb2(CO3)3, Er2(CO3)3, Na2CO3, and NH4F as precursors. In contrast to other starting materials normally used for such syntheses, these precursors react even at room temperature to form hexagonal‐phase (β‐phase) NaYF4:Er,Yb nanoparticles. Cubic‐phase (α‐phase) NaYF4:Yb,Er particles are formed only at elevated temperatures (>250 °C). The formation of the cubic phase at high temperatures can be suppressed by replacing pure oleylamine with oleic acid/oleylamine mixtures. Under optimized reaction conditions, particles with an average particle size of about 7 nm are generated in 84% yield. Heat treatment (30 min, 280 °C) of the particles significantly increases the luminescence efficiency. A transparent solution of the heat‐treated, nanometer‐sized phosphor in toluene shows intense visible light emission upon excitation in the near infrared.
Effect of Alkyl Side‐Chain Length on Photovoltaic Properties of Poly(3‐alkylthiophene)/PCBM Bulk Heterojunctions
Authors: Gadisa Abay , Oosterbaan Wibren D. , Vandewal Koen , Bolsée Jean‐Christophe , Bertho Sabine , D'Haen Jan , Lutsen Laurence , Vanderzande Dirk , Manca Jean V.
Published: August 2009

The morphological, bipolar charge‐carrier transport, and photovoltaic characteristics of poly(3‐alkylthiophene) (P3AT):[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) blends are studied as a function of alkyl side‐chain length m, where m equals the number of alkyl carbon atoms. The P3ATs studied are poly(3‐butylthiophene) (P3BT, m = 4), poly(3‐pentylthiophene) (P3PT, m = 5), and poly(3‐hexylthiophene) (P3HT, m = 6). Solar cells with these blends deliver similar order of photo‐current yield (exceeding 10 mA cm−2) irrespective of side‐chain length. Power conversion efficiencies of 3.2, 4.3, and 4.6% are within reach using solar cells with active layers of P3BT:PCBM (1:0.8), P3PT:PCBM (1:1), and P3HT:PCBM (1:1), respectively. A difference in fill factor values is found to be the main source of efficiency difference. Morphological studies reveal an increase in the degree of phase separation with increasing alkyl chain length. Moreover, while P3PT:PCBM and P3HT:PCBM films have similar hole mobility, measured by hole‐only diodes, the hole mobility in P3BT:PCBM lowers by nearly a factor of four. Bipolar measurements made by field‐effect transistor showed a decrease in the hole mobility and an increase in the electron mobility with increasing alkyl chain length. Balanced charge transport is only achieved in the P3HT:PCBM blend. This, together with better processing properties, explains the superior properties of P3HT as a solar cell material. P3PT is proved to be a potentially competitive material. The optoelectronic and charge transport properties observed in the different P3AT:PCBM bulk heterojunction (BHJ) blends provide useful information for understanding the physics of BHJ films and the working principles of the corresponding solar cells.
Non‐Close‐Packed Crystals from Self‐Assembled Polystyrene Spheres by Isotropic Plasma Etching: Adding Flexibility to Colloid Lithography
Authors: Plettl Alfred , Enderle Fabian , Saitner Marc , Manzke Achim , Pfahler Christian , Wiedemann Stefan , Ziemann Paul
Published: August 2009

Hexagonally ordered arrays of non‐close‐packed nanoscaled spherical polystyrene (PS) particles are prepared exhibiting precisely controlled diameters and interparticle distances. For this purpose, a newly developed isotropic plasma etching process is applied to extended monolayers of PS colloids (starting diameters <300 nm) deposited onto hydrophilic silicon. Accurate size, shape, and smoothness control of such particles is accomplished by etching at low temperatures (−150 °C) with small rates not usually available in standard reactive ion etching equipment. The applicability of such PS arrays as masks for subsequent pattern transfer is demonstrated by fabricating arrays of cylindrical nanopores into Si.
Nonstationary fault detection and diagnosis for multimode processes
Authors: Liu Jialin , Chen Ding‐Sou
Published: August 2009

Fault isolation based on data‐driven approaches usually assume the abnormal event data will be formed into a new operating region, measuring the differences between normal and faulty states to identify the faulty variables. In practice, operators intervene in processes when they are aware of abnormalities occurring. The process behavior is nonstationary, whereas the operators are trying to bring it back to normal states. Therefore, the faulty variables have to be located in the first place when the process leaves its normal operating regions. For an industrial process, multiple normal operations are common. On the basis of the assumption that the operating data follow a Gaussian distribution within an operating region, the Gaussian mixture model is employed to extract a series of operating modes from the historical process data. The local statisticT2and its normalized contribution chart have been derived for detecting abnormalities early and isolating faulty variables in this article. © 2009 American Institute of Chemical Engineers AIChE J, 2010
Thermal and mass transients in the developing region of a homogeneous tubular chemical reactor
Authors: Alkam Mohammad K. , Darwish Feras H. , Almuhtasib Aziz A.
Published: August 2009

The current investigation presents a finite difference simulation of a homogeneous tubular reactor under laminar flow conditions. The present simulation considers the unsteady operation where transients in flow hydrodynamics, temperature field, and species concentrations have been considered. Flow development in the entrance region of the present reactor has been considered. Present results exhibit reactant concentration and mixing cup temperature profiles for a variety of operating conditions. Effects of several parameters on the performance of the current reactor have been examined, including, reaction parameter, order of reaction, and Schmidt number. © 2009 American Institute of Chemical Engineers AIChE J, 2009
Optimal design of single‐contaminant regeneration reuse water networks with process decomposition
Authors: Bai Jie , Feng Xiao , Deng Chun
Published: August 2009

Water network with regeneration schemes (e.g., regeneration reuse, regeneration recycling) can reduce freshwater consumption further than water network merely with direct reuse. Regeneration reuse, compared with regeneration recycling, can additionally avoid unexpected accumulation of contaminants. Owing to these features, process decomposition can help to reduce freshwater usage and wastewater discharge of regeneration reuse water systems and achieve the results, which graphical method delivers. In this article, the effect of decomposition on water‐using process and further on regeneration reuse water system is briefly analyzed on the concentration‐mass load diagram. Then a superstructure and three sequential mathematical models, which take process decomposition into account, are in turn developed to optimize single contaminant regeneration reuse water systems. By several examples, the reliability of the models is verified. Moreover, several decomposition strategies are summarized to realize the regeneration reuse water network, which attains the targets from graphical method. The results indicate that postregeneration concentration has a major impact on the scheme of process decomposition. © 2009 American Institute of Chemical Engineers AIChE J, 2009
An engineering‐purpose preparation strategy for ammonium‐type ionic liquid with high purity
Authors: Sun Xiaoqi , Ji Yang , Liu Yu , Chen Ji , Li Deqian
Published: August 2009

A new strategy for preparing ammonium‐type ionic liquid (IL) by acid/base neutralization reaction was proposed. The method contributed to preparing hydroxide‐based ammonium IL and resulting task specific ionic liquid (TSIL) with high purity using a low‐costly and environment‐friendly synthetic route. Halide contamination in the prepared ILs could be markedly decreased than those prepared by well‐established anion metathesis method. Moreover, some novel TSILs composed of cations and anions with big steric hindrances could be prepared by this method. Physicochemical properties of the bifunctional TSILs, i.e., density, water content, decomposition temperature, and munal solubility, were also studied in this article. © 2009 American Institute of Chemical Engineers AIChE J, 2009
Possibilities and challenges in occupational injury surveillance of day laborers
Authors: Lowry Sarah J. , Blecker Hillary , Camp Janice , De Castro Butch , Hecker Steven , Arbabi Saman , Traven Neal , Seixas Noah S.
Published: August 2009

Background

Day laborers in the US, comprised largely of undocumented immigrants from Mexico and Central America, suffer high rates of occupational injury according to recent estimates. Adequate surveillance methods for this highly transient, largely unregulated group do not currently exist. This study explores chart abstraction of hospital‐based trauma registry records as a potential injury surveillance method for contingent workers and day laborers. We sought to determine the degree of completeness of work information in the medical records, and to identify day laborers and contingent workers to the extent possible.

Methods

Work‐related injury cases from a hospital‐based trauma registry (2001–2006) were divided by ethnicity (Hispanic vs. non‐Hispanic origin) and presence of social security number (SSN: yes, no), resulting in four groups of cases. Medical records were abstracted for 40 cases from each group; each case was assigned values for the variables “day labor status” (yes, no, probably not, probable, unknown) and “employment type” (contingent, formal, unknown).

Results

Work information was missing for 60% of Hispanic cases lacking SSN, as compared with 33–47% of the other three groups. One “probable” day laborer was identified from the same group. Non‐Hispanics with SSN were less frequently identified as contingent workers (5% as compared with 15–19%).

Conclusions

This method revealed severe limitations, including incomplete and inconsistent information in the trauma registry and medical records. Approaches to improve existing resources for use in surveillance systems are identified. The potential of an active surveillance approach at day labor hiring centers is also briefly discussed. Am. J. Ind. Med. 53:126–134 2010. © 2009 Wiley‐Liss, Inc.
Are employment shifts into non‐manufacturing industries partially responsible for the decline in occupational injury rates?
Authors: Morse Tim F. , Deloreto Albert , St. Louis Thomas , Meyer John D.
Published: August 2009

Background

Bureau of Labor Statistics figures have shown declines in injury and illness rates over the past 25 years. It is unclear what factors are contributing to that decline.

Methods

Connecticut injury and illness data was industry‐adjusted to account for the shifts in employment by industry sector for the 25‐year period from 1976 to 2000. Additional adjustment was made for manufacturing sub‐sectors, since declines in manufacturing employment accounted for the largest proportion of the shift in injuries over that period.

Results

Approximately 18% of the decline in injury and illness rates was associated with a shift in employment from more hazardous to less hazardous industries. Shifts in manufacturing sub‐sectors accounted for an additional 5.7% of the decline.

Conclusion

A significant proportion of the decline in injury and illness rates appears to be due to demographic shifts in industry composition. Am. J. Ind. Med. 52:735–741, 2009. © 2009 Wiley‐Liss, Inc.
Preparation and in vitro degradation of novel bioactive polylactide/wollastonite scaffolds
Authors: Xu Liang , Xiong Zuo Chun , Yang Dejuan , Zhang Li Fang , Chang Jiang , Xiong Cheng Dong
Published: August 2009

Composite scaffolds for applications in bone engineering from poly(D,L‐lactide) (PDLLA) incorporated with different proportional bioactive wollastonite powders were prepared through a salt‐leaching method, using NH4HCO3 as porogen. The pore structures and morphology of the scaffolds were determined by scanning electron microscopy (SEM). The bioactivity of composite materials was evaluated by examining its ability to initiate the formation of hydroxyapatite (Ca10(PO4)6(OH)2)(HAp) on its surface when immersed in simulated body fluids (SBF). The in vitro degradation behaviors of these scaffolds were systematically monitored at varying time periods of 1, 2, 4, 6, 8, 11, 14, 17, 20, 24, and 28 weeks postimmersion in SBF at 37°C. FT‐IR, XPS, XRD, and SEM measurements revealed that hydroxyapatite commenced to form on the surface of the scaffolds after 7 days of immersion in SBF. The measurements of weight loss, pH, and molecular weight of the samples indicated that PDLLA/wollastonite composite scaffolds degraded slower than the pure PDLLA scaffolds do. Addition of wollastonite enhanced the mechanical property of the composite scaffolds. The in vitro osteoblast culture experiment confirmed the biocompatibility of the scaffold for the growth of osteo‐blasts. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009.
Mechanical and thermal properties of functionalized multiwalled carbon nanotubes and multiwalled carbon nanotube–polyurethane composites
Authors: Chen Xianhong , Wang Jianfeng , Zou Jiagui , Wu Xiaoli , Chen Xiaojin , Xue Feng
Published: August 2009

Multiwalled carbon nanotube (MWNT)–polyurethane (PU) composites were obtained by an in situ polycondensation approach. The effects of the number of functional groups on the dispersion and mechanical properties were investigated. The results showed that the functionalized MWNTs had more advantages for improving the dispersion and stability in water and N,N′‐dimethylformamide. The tensile strength and elongation at break of the composites exhibited obvious increases with the addition of MWNT contents below 1 wt % and then decreases with additions above 1 wt %. The maximum values of the tensile strength and elongation at break increased by 900 and 741%, respectively, at a 1 wt % loading of MWNTs. Differential scanning calorimetry measurements indicated that the addition of MWNTs resulted in an alteration of the glass‐transition temperature of the soft‐segment phase of MWNT–PU. Additionally, new peaks near 54°C were observed with differential scanning calorimetry because of the microphase‐separation structures and alteration of the segment molecular weights of the hard segment and soft segment of PU with the addition of MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthetic paper from plastic waste: Influence of a surface treatment with corona discharge
Authors: Santana R. M. Campomanes , Manrich S.
Published: August 2009

Polymers generally have a chemically inert surface, are nonporous, and have low surface energy, which is characterized by their relatively weak adhesion to other materials. Numerous methods have been developed to modify polymer surfaces chemically. This study was an investigation of how the surface energy of synthetic paper (composite film) could be altered after treatment by corona discharge and of the stability of the surface energy of a film produced from postconsumer polypropylene (PP). A PP/filler (70/30 w/w) composite film was processed in a single‐screw extruder with a flat‐film dye. In this study, the film stretching rate and electric charge potential of the film surface treatment were the process parameters analyzed. The results showed that the conditions of the surface treatment by corona discharge and the presence of a filler (calcium carbonate) influenced some surface properties: the contact angle, surface energy, and ink adhesion. The surface energy of the composite film increased from 38.7 × 10−3 N/m2 without treatment to 52.3 × 10−3 N/m2 with treatment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Incorporation of triclosan into polydioxanone monofilaments and evaluation of the corresponding release
Authors: Blanco M. G. , Franco L. , Puiggalí J. , Rodríguez‐Galán A.
Published: August 2009

Poly(p‐dioxanone) monofilaments were loaded with triclosan, a drug with a well‐known antimicrobial effect. Two different procedures were considered: loading by molecular diffusion with a swelling solvent such as dichloromethane and loading by means of a coating based on polycaprolactone or polycaprolactone/magnesium stearate mixtures. Triclosan release was studied in different media by high‐performance liquid chromatography. The kinetics of loading by diffusion and the release from both kinds of preparations were evaluated with well‐established models. In general, the first stages of the loading process fit with the Higuchi approximation, whereas the final stages fit with the first‐order model. The last model could be applied to predict the release behavior. A sustained release over a period that could reach 400 h was attained when ethanol was added to the release medium, whereas equilibrium conditions were reached when Sörensen's hydrophilic medium was used. Significant differences in the release profiles of a Sörensen's/ethanol medium were observed, which depended on the loading methodology. Thus, an 80% release was attained after 36 h for a polycaprolactone‐coated sample and after 80–100 h for a sample loaded by diffusion. Degradation studies of the triclosan‐loaded samples were also performed because the increase in the hydrophobicity of the samples could hinder the hydrolytic degradation. The weight‐average molecular weight of unloaded and loaded (29,075 μg/g) sutures dropped to 220.000 and 110.000 after 45 days of exposure to the medium at 37°C, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Microwave absorbing properties of ternary linear low‐density polyethylene/carbonyl iron powder/carbon black composites
Authors: Shen Xiang‐Zhong , Xie Shan‐Mei , Guo Jun , Liu Zhi‐Cheng
Published: August 2009

Linear low‐density polyethylene (LLDPE) was used as polymer matrix, carbonyl iron powder (CIP) and carbon black (CB) were used as fillers, and ternary composites with microwave absorbing properties were prepared by melt blending. Transmission electron microscopy was used to characterize the prepared samples. The absorbing ability (reflection loss) of the prepared composites was measured using the arch method, and the electromagnetic parameters of composites were determined by the transmission/reflection method. The filler contents of CIP and CB have effects on the absorbing peak positions and reflection loss, and there is the optimum filler content in composites to obtain the maximum microwave absorbing. The microwave absorption of LLDPE/CIP/CB composites comes from the combining contributions of the dielectric loss and the magnetic loss. The synergistic effects of CIP and CB effectively improve the microwave absorbing properties of polymer composites. CIP and CB are uniformly distributed in the polymer matrix. The theoretical calculation results of the absorbing ability are in agreement with the experimental results using the transmission line theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of novel organosoluble polyesters based on a DIOL with azaquinoxaline ring
Authors: Ghaemy M. , Mighani H. , Ziaei P.
Published: August 2009

A series of new polyesters were synthesized by polycondensation of aliphatic and aromatic dicarboxylic dichlorides with a novel quinoxaline diol, 2,3‐bis (4‐hydroxy phenyl)‐5‐azaquinoxaline (DIOL). The DIOL was synthesized by reacting 4,4′‐dihydroxy benzil with 2, 3‐diaminopyridine (yield: 85%), and characterized by FTIR and 1H‐NMR spectra. All polyesters showed good solubility in most aprotic polar solvents such as NMP (N‐methylpyrrolidone), DMF (dimethylformamide), DMSO (dimethylsulfoxide), DMAc (dimethylacetamide), HMPA (hexamethylenephosphoramide), and Py (pyridine). The inherent viscosity of polyesters was obtained in the range of 1.1–1.22 dL/mg. The glass transition temperatures of the polyesters were in the range of 200–280°C, as determined by DSC. The initial decomposition temperatures of the polyesters were above 300°C and the char yield at 750°C ranged from 30 to 60% under nitrogen atmosphere. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation of liquid‐filled micelles based on an amphiphilic triblock copolymer
Authors: Jiang G.
Published: August 2009

A series of novel amphiphilic triblock poly(ethylene glycol)‐b‐poly(2‐aminoethyl methacrylate hydrochloride)‐b‐poly(heptadeca‐fluorodecyl acrylate) (PEG‐b‐PAEMA‐b‐PHFDA) comprised of two hydrophilic PEG and PAEMA segments and one hydrophobic PHFDA segment was designed and synthesized. The structure of the triblock copolymer was characterized by 1H‐NMR and GPC analysis. The amphiphilic triblock copolymer was capable of self‐assembling into liquid‐filled micelles that consisted of PHFDA and liquid perfluorocarbons (PFCs) as the core and PEG as outer shell. PAEMA can be used as cross‐linking sites to increase the stability of the liquid‐filled micelles. The shape, size, and Acoustic properties of the obtained liquid‐filled micelles were investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Influence of the spinning conditions on the structure and properties of polyamide 12/carbon nanotube composite fibers
Authors: Perrot Carine , Piccione Patrick M. , Zakri Cécile , Gaillard Patrice , Poulin Philippe
Published: August 2009

The inclusion of nanoparticles in polymer fibers is potentially useful for improving or bringing new properties such as mechanical strength, electrical conductivity, piezoresistivity, and flame retardancy. In this study, composite fibers made of polyamide 12 and multiwall carbon nanotubes were investigated. The fibers were spun via a melt‐spinning process and stretched at different draw ratios. The influence of several spinning factors, including spinning speed, extrusion rate, and draw ratio were investigated and correlated to the structure and properties of the fibers. X‐ray diffraction analyses and mechanical tests indicated that the spinning speed barely affected the structure and mechanical properties of the fibers under tension. The spinning speed, however, is critical for future industrial applications because it determines the possible production rates. By contrast, drawing during spinning or after spinning strongly affected the polymer chain alignment and fiber mechanical properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Needleless electrospinning. I. A comparison of cylinder and disk nozzles
Authors: Niu Haitao , Lin Tong , Wang Xungai
Published: August 2009

In this study, we demonstrated the needleless electrospinning of poly(vinyl alcohol) (PVA) nanofibers with two nozzles, a rotating disk and a cylinder, and examined the effect of the nozzle shape on the electrospinning process and resultant fiber morphology. The disk nozzle needed a relatively low applied voltage to initiate fiber formation, and the fibers were mainly formed on the top disk edge. Also, the PVA concentration had little influence on the disk electrospinning process (up to 11 wt %). In comparison, the cylinder electrospinning showed a higher dependence on the applied voltage and polymer concentration. The fibers were initiated from the cylinder ends first and then from the entire cylinder surface only if the applied voltage were increased to a certain level. With the same polymer solution, the critical voltage needed to generate nanofibers from the disk nozzle was lower than that needed to generate nanofibers from the cylinder. Both electrospinning systems could produce uniform nanofibers, but the fibers produced from the disk nozzle were finer than those from the cylinder when the operating conditions were the same. A thin disk (8 cm in diameter and 2 mm thick) could produce nanofibers at a rate similar to that of a cylinder of the same diameter but 100 times wider (i.e., 20 cm long). Finite element analysis of electric field profiles of the nozzles revealed a concentrated electric field on the disk edge. For the cylinder nozzle, an uneven distribution of the electric field intensity profile along the nozzle surface was observed. The field lines were mainly concentrated on the cylinder ends, with a much lower electric field intensity formed in the middle surface area. At the same applied voltage, the electric field intensity on the disk edge was much higher than that on the cylinder end. These differences in the electric field intensity profiles could explain the differences in the fiber fineness and rate of the nanofibers produced from these two nozzles. These findings will benefit the design and further development of large‐scale electrospinning systems for the mass production of nanofibers for advanced applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation of poly(vinyl amine)‐grafted crosslinked poly(vinyl alcohol) microspheres
Authors: Gao Baojiao , Lu Jinhua , Zhuang Rubin , Zhang Guohai
Published: August 2009

Crosslinked poly(vinyl alcohol) (CPVA) microspheres were first prepared via the suspension polymerization of vinyl acetate and the alcoholysis of poly(vinyl acetate). Afterwards, a two‐step method involving graft polymerization and Hofmann degradation was used to prepare functional poly(vinyl amine)‐grafted crosslinked poly(vinyl alcohol) (PVAm–CPVA) microspheres, onto which poly(vinyl amine) (PVAm) macromolecules were grafted. The graft polymerization of acrylamide (AM) on CPVA microspheres was performed with cerium salt as the initiator in an acidic aqueous medium, resulting in polyacrylamide (PAM)‐grafted CPVA microspheres. Subsequently, the grafted PAM was transformed into PVAm via the Hofmann degradation reaction, and PVAm–CPVA microspheres were prepared. The effects of the main factors on the graft polymerization and Hofmann degradation were examined, and the reaction mechanisms were researched in depth. The experimental results showed that for the graft polymerization of AM on CPVA microspheres initiated by cerium salt, the acid concentration and the amount of cerium salt affected the grafting degree of PAM greatly. For the Hofmann degradation reaction of the grafted PAM, the amination degree of PVAm–CPVA microspheres was obviously affected by the amount of sodium hypochlorite in the presence of sodium hydroxide. The preliminary adsorption tests showed that PVAm–CPVA microspheres were multifunctional and had strong adsorption ability for Fe(III) ions by chelation action and for chromate ions (CrO) by strong electrostatic interactions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Antipolyelectrolyte superabsorbing nanocomposites: Synthesis and properties
Authors: Pourjavadi A. , Kheirabadi M. , Zohuriaan‐Mehr M. J. , Kabiri K.
Published: August 2009

Novel polyampholytic superabsorbing nanocomposites based on the zwitterionic sulfobetaine monomer [3‐(methacrylamido)propyl)]dimethyl(3‐sulfopropyl)ammonium hydroxide were synthesized through in situ polymerization in aqueous solution with different contents of an organo‐modified clay (OMMT, Cloisite 30B). Structural and thermomechanical properties of hydrogels were characterized by FT‐IR, XRD, and DMTA, respectively. Swollen gel strength of hydrogels was determined by a rheological method. Storage modulus of the hydrogels was considerably improved in comparison with its the clay‐free counterpart. The nanocomposite hydrogel containing 15% OMMT possessed the highest gel strength. The glass transition temperature was increased from 58.4 to 67.0°C for the clay‐free and nanocomposite hydrogel containing 8% OMMT, respectively. The swelling behavior of the hydrogel in various salt solutions was investigated. Antipolyelectrolyte behavior was observed with enhancement of concentration of mono‐ and multivalent salts. Swelling in the various pH media was nearly pH‐independent over a wide range of pH. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Evaluation of water sorption behavior and in vitro blood compatibility of polyvinyl alcohol based magnetic bionanocomposites
Authors: Bajpai A. K. , Gupta Rashmi
Published: August 2009

In recent past magnetic bionanocomposites have shown potential in biomedical applications mainly due to their superparamagnetic and biocompatible nature. They have also established themselves as a promising class of hybrid organic–inorganic materials derived from polymers and organic/inorganic fillers. In this study biocompatible nanocomposites were prepared by in situ synthesis of magnetic nanoparticles within the polyvinyl alcohol‐grafted‐polymethyl methacrylate hydrogels and characterized by techniques such as FT‐IR, scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, and differential scanning calorimetry. The bionanocomposites were evaluated for water sorption behavior and in vitro biocompatibility by performing thrombus formation and hemolysis tests. The influence of chemical composition of the grafted hydrogel was investigated on water sorption behavior and in vitro blood compatibility of magnetic bionanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Improved mechanical properties and structure of polypropylene pipe prepared under vibration force field
Authors: Chen Kai‐Yuan , Zhou Nan‐Qiao , Liu Bin , Jin Gang
Published: August 2009

The polypropylene (PP) pipes were prepared using a self‐made electromagnetic dynamic plasticating extruder, which introduced a vibration force field into the whole plasticating and extrusion process by the axial vibration of the screw. The effects of the vibration frequency and the vibration amplitude on the mechanical properties and microstructure of PP pipes were investigated using bursting pressure testing, tensile testing, impact testing, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WAXD). The mechanical properties testing showed that the circumferential strength of PP pipes increased significantly, and the biaxial self‐reinforcement pipes could be obtained. Also, the impact strength was improved. When compared with the conventional static extruded specimens, the maximum increase of bursting pressure, tensile yield strength, and impact strength were 27.03%, 7.3%, and 16.2%, respectively. DSC and WAXD analysis showed that the PP pipes obtained by vibration plasticating extrusion (VPE) had higher crystallinity, higher melting temperature, more perfect crystals, and smaller crystal sizes, but no new polymeric crystalline peak appeared. The improvement of mechanical properties of the PP pipes prepared by VPE was attributed to the higher crystallinity and the improvement of the molecular orientation and of the crystalline morphology under the action of the vibration force field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Hirsch index rankings require scaling and higher moment
Authors: Bletsas Aggelos , Sahalos John N.
Published: August 2009

Simple bibliometric indicators, such as average number of citations per publication per researcher, or the recently proposed Hirsch index (h‐index), are nowadays tracked by online repositories, including Web of Science (WOS), and often affect critical decision making. This work proposes appropriate scaling of the h‐index based on its probability distribution that is calculated for any underlying citation distribution. The proposed approach outperforms existing index estimation models that have focused on the expected value only (i.e., first moment). Furthermore, it is shown that average number of citations per publication per scientific field, total number of publications per researcher, as well as researcher's h‐index measured value, expected value, and standard deviation constitute the minimum information required for meaningful h‐index ranking campaigns; otherwise contradicting ranking results emerge. This work may potentially shed light to (current or future) large‐scale, h‐index‐based bibliometric evaluations.
An indicator of research front activity: Measuring intellectual organization as uncertainty reduction in document sets
Authors: Lucio‐Arias Diana , Leydesdorff Loet
Published: August 2009

When using scientific literature to model scholarly discourse, a research specialty can be operationalized as an evolving set of related documents. Each publication can be expected to contribute to the further development of the specialty at the research front. The specific combinations of title words and cited references in a paper can then be considered as a signature of the knowledge claim in the paper: New words and combinations of words can be expected to represent variation, while each paper is at the same time selectively positioned into the intellectual organization of a field using context‐relevant references. Can the mutual information among these three dimensions—title words, cited references, and sequence numbers—be used as an indicator of the extent to which intellectual organization structures the uncertainty prevailing at a research front? The effect of the discovery of nanotubes (1991) on the previously existing field of fullerenes is used as a test case. Thereafter, this method is applied to science studies with a focus on scientometrics using various sample delineations. An emerging research front about citation analysis can be indicated.
Metabolism, oral bioavailability and pharmacokinetics of chemopreventive kaempferol in rats
Authors: Barve Avantika , Chen Chi , Hebbar Vidya , Desiderio Joseph , Saw Constance Lay‐Lay , Kong Ah‐Ng
Published: August 2009

The purpose of this study was to compare the hepatic and small intestinal metabolism, and to examine bioavailability and gastro‐intestinal first‐pass effects, of kaempferol in rats. Liver and small intestinal microsomes fortified with either NADPH or UDPGA were incubated with varying concentrations of kaempferol for up to 120 min. Based on the values of the kinetic constants (Km and Vmax), the propensity for UDPGA‐dependent conjugation compared with NADPH‐dependent oxidative metabolism was higher for both hepatic and small intestinal microsomes. Male Sprague‐Dawley rats were administered kaempferol intravenously (i.v.) (10, 25 mg/kg) or orally (100, 250 mg/kg). Gastro‐intestinal first‐pass effects were observed by collecting portal blood after oral administration of 100 mg/kg kaempferol. Pharmacokinetic parameters were obtained by non‐compartmental analysis using WinNonlin. After i.v. administration, the plasma concentration–time profiles for 10 and 25 mg/kg were consistent with high clearance (∼3 L/hr/kg) and large volumes of distribution (8–12 L/hr/kg). The disposition was characterized by a terminal half‐life value of 3–4 h. After oral administration the plasma concentration–time profiles demonstrated fairly rapid absorption (tmax∼1–2 h). The area under the curve (AUC) values after i.v. and oral doses increased approximately proportional to the dose. The bioavailability (F) was poor at ∼2%. Analysis of portal plasma after oral administration revealed low to moderate absorption. Taken together, the low F of kaempferol is attributed in part to extensive first‐pass metabolism by glucuronidation and other metabolic pathways in the gut and in the liver. Copyright © 2009 John Wiley & Sons, Ltd.
When experience is better than description: Time delays and complexity
Authors: Lejarraga Tomás
Published: August 2009

The dominant sampling paradigm of experience‐based choice is extended by exploring two realistic aspects of decisions. First, frequency judgments were studied in situations involving a delay between information acquisition and judgment. This time gap undermines recall from working memory and favors the natural human capacity to encode frequencies effortlessly. Deferred judgments from experience were found to be more accurate than judgments from description, both for absolute and rank‐order judgments. Second, task complexity was varied. This showed that—as decision tasks become more complex—participants are willing to trade‐off detailed but complex descriptive information for less accurate but simpler information sampled from experience. Moreover, there were no individual differences due to numerical/rational abilities. Results from the two studies suggest that information obtained from experience can be more valuable than descriptive information in that it can both lead to better frequency judgments in deferred tasks and simplify cognitive representations of complex choice tasks. Copyright © 2009 John Wiley & Sons, Ltd.
Lack of a co‐promotion effect of 60 Hz circularly polarized magnetic fields on spontaneous development of lymphoma in AKR mice
Authors: Chung Moon‐Koo , Yu Wook‐Joon , Kim Yong‐Bum , Myung Sung‐Ho
Published: August 2009

The present study was conducted to investigate the possible effect of 60 Hz circularly polarized magnetic fields (MFs) as promoters of genetically initiated lymphoma in AKR mice. One hundred sixty female animals were divided into four different groups. They were exposed to four different intensities of circularly polarized MFs. Animals received exposure to 60 Hz circularly polarized MF at field strengths (rms‐value) of 0 µT (sham control, T1, Group I), 5 µT(T2, Group II), 83.3 µT (T3, Group III), or 500 µT(T4, Group IV), for 21 h/day from the age of 4–6 weeks to the age of 44–46 weeks. There were no exposure‐related changes in mean survival time, clinical signs, body weights, hematological values, micronucleus assay, gene expression arrays, analysis of apoptosis, and necropsy findings. At histopathological examination, lymphoma was seen in all the groups. The tumor incidence was 31/40(78%), 30/40(75%), 32/40(80%), and 31/40(78%) in sham control, 5, 83.3, and 500 µT groups, respectively. However, there were no differences in the tumor incidence between the sham control (T1) and circularly polarized MF exposure groups (T2–T4). In conclusion, there was no evidence that exposure to 60 Hz circularly polarized MF strengths up to 500 µT promoted lymphoma in AKR mice. Bioelectromagnetics 31:130–139, 2010. © 2009 Wiley‐Liss, Inc.
Making the right connections: biological networks in the light of evolution
Authors: Knight Christopher G. , Pinney John W.
Published: August 2009

Our understanding of how evolution acts on biological networks remains patchy, as is our knowledge of how that action is best identified, modelled and understood. Starting with network structure and the evolution of protein–protein interaction networks, we briefly survey the ways in which network evolution is being addressed in the fields of systems biology, development and ecology. The approaches highlighted demonstrate a movement away from a focus on network topology towards a more integrated view, placing biological properties centre‐stage. We argue that there remains great potential in a closer synergy between evolutionary biology and biological network analysis, although that may require the development of novel approaches and even different analogies for biological networks themselves.
Gene networks and liar paradoxes
Authors: Isalan Mark
Published: August 2009

Network motifs are small patterns of connections, found over‐represented in gene regulatory networks. An example is the negative feedback loop (e.g. factor A represses itself). This opposes its own state so that when ‘on’ it tends towards ‘off’ – and vice versa. Here, we argue that such self‐opposition, if considered dimensionlessly, is analogous to the liar paradox: ‘This statement is false’. When ‘true’ it implies ‘false’ – and vice versa. Such logical constructs have provided philosophical consternation for over 2000 years. Extending the analogy, other network topologies give strikingly varying outputs over different dimensions. For example, the motif ‘A activates B and A. B inhibits A’ can give switches or oscillators with time only, or can lead to Turing‐type patterns with both space and time (spots, stripes or waves). It is argued here that the dimensionless form reduces to a variant of ‘The following statement is true. The preceding statement is false’. Thus, merely having a static topological description of a gene network can lead to a liar paradox. Network diagrams are only snapshots of dynamic biological processes and apparent paradoxes can reveal important biological mechanisms that are far from paradoxical when considered explicitly in time and space.
Revisiting the neighbor exclusion model and its applications
Authors: Rocha Marcio S.
Published: August 2009

We review the neighbor exclusion model and some of its applications to analyze the binding data of DNA‐ligand complexes. We revisit the closed form of the model developed by McGhee and von Hippel in 1974, showing that this classic model can be used to help studying the behavior of DNA contour and persistence lengths when interacting with intercalating ligands. We present methods to quantitatively analyze the variation of these two quantities, allowing one to determine important parameters of the interaction such as the intrinsic binding constant and the exclusion number of the ligand. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 1–7, 2010.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Case study and application of process analytical technology (PAT) towards bioprocessing: Use of tryptophan fluorescence as at‐line tool for making pooling decisions for process chromatography
Authors: Rathore Anurag S. , Li Xiaohui , Bartkowski Wojciech , Sharma Ashutosh , Lu Yuefeng
Published: September 2009

Process analytical technology (PAT) has been gaining momentum in the biopharmaceutical community due to the potential for continuous real time quality assurance resulting in improved operational control and compliance. Two imperatives for implementing any PAT tool are that “variability is managed by the process” and “product quality attributes can be accurately and reliably predicted over the design space established for materials used, process parameters, manufacturing, environmental, and other conditions.” Recently, we have been examining the feasibility of applying different analytical tools to bioprocessing unit operations. We have previously demonstarted that commercially available online‐high performance liquid chromatography and ultra performance liquid chromatography systems can be used for analysis that can facilitate real‐time decisions for column pooling based on product quality attributes (Rathore et al., 2008a,b). In this article, we review an at‐line tool that can be used for pooling of process chromatography columns. We have demonstrated that our tryptophan fluorescence method offers a feasible approach and meets the requirements of a PAT application. It is significantly faster than the alternative of fractionation, offline analysis followed by pooling. Although the method as presented here is not an online method, this technique may offer better resolution for certain applications and may be a more optimal approach as it is very conducive to implementation in a manufacturing environment. This technique is also amenable to be used as an online tool via front face fluorescence measurements done concurrently with product concentration determination by UV. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009