bluuebunny/crossref_metadata_2025 huggingface dataset:
Ways of selective polycondensation of L‐lysine towards linear α‐ and ε‐poly‐L‐lysine
Authors: Ho Chau Hon , Odermatt Erich , Berndt Ingo , Tiller Joerg C.
Published: June 2008

Polylysines (PL) are highly interesting polymers due to their biocompatibility and their high number of reactive amino groups. So far it was not possible to synthesize them directly from L‐lysine. Here, we describe two different synthesis routes to selectively polymerize lysine in one batch without the use of protection groups. Applying 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide as activating agent for the polycondensation of L‐lysine in water gave selectively linear ε‐PLL. In contrast to this, the polymerization of L‐lysine in chloroform in the presence of dicyclohexyl carbodiimide and 18‐crown‐6 ether selectively afforded pure α‐PLL. We also assessed the capability of polylysine derivatization by polymer analog reactions with acetic anhydride, methyl iodide and 2,4,6‐trinitrobenzenesulfonic acid. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5053–5063, 2008
Dendronized tricyanopyrroline‐based chromophores in nonlinear optical active host polymer
Authors: Hoang Mai Ha , Kim Myung Hee , Cho Min Ju , Kim Kyung Hwan , Kim Kyu Nam , Jin Jung‐Il , Choi Dong Hoon
Published: June 2008

We synthesized new nonlinear optical (NLO) chromophores containing a 3,5‐bis(3,5‐bisbenzyloxy‐benzyloxy)‐benzoate dendron. Tricyanopyrroline (TCP)‐based chromophores were designed and prepared by virtue of its strong electron withdrawing property. A soluble polyimide containing 6‐({4‐[2‐(1‐allyl‐4‐cyano‐5‐dicyanomethylene‐2‐oxo‐2,5‐dihydro‐1H‐pyrrol‐3‐yl)‐vinyl]‐phenyl}‐butyl‐amino)‐hexanoyl group in the side chain was also prepared as an NLO active host polymer. A benzoate dendron was tethered at two different binding positions of the chromophore to yield two different guest molecules. Thin‐film composites of these dendronized chromophores dissolved in the NLO active polyimide host were employed to fabricate the electro‐optic (EO) samples. The EO properties of new NLO polyimides containing dendronized chromophores were compared with those of the sample with nondendronized plain chromophores. The effect of a bulky dendron on the EO properties was investigated using an in situ reflection technique. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5064–5076, 2008
One‐pot synthesis and characterization of hyperbranched poly(ester‐amide)s from commercially available dicarboxylic acids and multihydroxyl secondary amines
Authors: Lin Ying , Dong Zhongmin , Li Yuesheng
Published: June 2008

A convenient and cost‐effective strategy for synthesis of hyperbranched poly(ester‐amide)s from commercially available dicarboxylic acids (A2) and multihydroxyl secondary amine (CB2) has been developed. By optimizing the conditions of model reactions, the AB2‐type intermediates were formed dominantly during the initial reaction stage. Without any purification, the AB2 intermediate was subjected to thermal polycondensation in the absence of any catalyst to prepare the aliphatic and semiaromatic hyperbranched poly(ester‐amide)s bearing multi‐hydroxyl end‐groups. The FTIR and 1H NMR spectra indicated that the polymerization proceeded in the proposed way. The DBs of the resulting polymers were confirmed by a combination of inverse‐gated decoupling 13C NMR, and DEPT‐135 NMR techniques. The DBs of the hyperbranched poly(ester‐amide)s were in the range of 0.44–0.73, depending on the structure of the monomers used. The hyperbranched polymers exhibited moderate molecular weights with relatively broad distributions determined by SEC. All the polymers displayed low inherent viscosity (0.11–0.25 dL/g) due to the branched nature. Structural and end‐group effects on the thermal properties of the hyperbranched polymers were investigated using DSC. The thermogravimetric analysis revealed that the resulting polymers exhibit reasonable thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5077–5092, 2008
End group transformations of RAFT‐generated polymers with bismaleimides: Functional telechelics and modular block copolymers
Authors: Li Ming , De Priyadarsi , Gondi Sudershan R. , Sumerlin Brent S.
Published: June 2008

End group activation of polymers prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization was accomplished by conversion of thiocarbonylthio end groups to thiols and subsequent reaction with excess of a bismaleimide. Poly(N‐isopropylacrylamide) (PNIPAM) was prepared by RAFT, and subsequent aminolysis led to sulfhydryl‐terminated polymers that reacted with an excess of 1,8‐bismaleimidodiethyleneglycol to yield maleimido‐terminated macromolecules. The maleimido end groups allowed near‐quantitative coupling with model low molecular weight thiols or dienes by Michael addition or Diels‐Alder reactions, respectively. Reaction of maleimide‐activated PNIPAM with another thiol‐terminated polymer proved an efficient means of preparing block copolymers by a modular coupling approach. Successful end group functionalization of the well‐defined polymers was confirmed by combination of UV–vis, FTIR, and NMR spectroscopy and gel permeation chromatography. The general strategy proved to be versatile for the preparation of functional telechelics and modular block copolymers from RAFT‐generated (co)polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5093–5100, 2008
Side chain liquid crystal poly(fumarate)s bearing tolane‐based mesogens
Authors: Noguchi Hiroshi , Michinobu Tsuyoshi , Fujii Nozomu , Funahashi Masahiro , Tokita Masatoshi , Watanabe Junji , Shigehara Kiyotaka
Published: June 2008

Cyanotolane or fluorotolane mesogens were for the first time introduced into the fumarate monomer under basic conditions. All fumarate monomers undergo radical polymerization in benzene in the presence of dimethyl 2,2′‐azobis(isobutyrate) as an initiator at 60 °C, affording the corresponding poly(fumarate)s with a molecular weight (Mn) of ∼ 104 and an exceptionally narrow polydispersity. The phase behaviors of the fumarate monomers and the correspoding poly(fumarate)s were comprehensively investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction (XRD) analysis. For the fumarate monomers, fluorotolane derivatives were prone to form higher‐order liquid crystal phases such as a smectic phase, while cyanotolane derivatives tended to show a wide mesophase temperature range, depending on the alkyl chain spacer length. Very surprisingly, these features dramatically weakened when they were polymerized. The mesophase temperature ranges became narrow and completely disappeared for the poly(fumarate)s with a shorter alkyl chain spacer. A nematic phase representing lower‐order arrangements became a predominant liquid crystal phase for the poly(fumarate) carrying cyanotolane mesogens. Only the poly(fumarate) carrying fluorotolane mesogens with a longer alkyl chain spacer displayed the characteristic XRD patterns of the smectic B phase. The transient photocurrent measurements of the fumarate monomer with cyanotolane mesogens displayed a hole mobility of the order of 10−4–10−5 cm2 V−1 s−1 at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5101–5114, 2008
Synthesis and characterization of a novel polymer based on anthracene moiety for organic thin film transistor
Authors: Li Yinam , Kim Tae‐Hoon , Zhao Qinghua , Kim Euh‐Kyung , Han Seung‐Hon , Kim Yun‐Hi , Jang Jin , Kwon Soon‐Ki
Published: June 2008

We have designed and synthesized a new polymer, which could be used in the organic thin film transistor (OTFT). Poly[2,6‐bis(3′‐dodecythiophene‐2′‐yl)anthracene] (PDTAn), which is composed with anthracene moiety and dodecyl alkyl thiophene, was synthesized by oxidative polymerization using iron (III) chloride. The mole ratio of FeCl3 and monomer (4.2:1), keeping low temperature during the initiation reaction, amount of solvent, and dropping order were very important for oxidative polymerization without crosslinking. The molecular weight of the polymer (Mw) was measured to be 40,000 with 2.85 of polydispersity index by GPC. The physical and optical properties of the polymer were characterized by differential scanning calorimetry (DSC), cyclic voltammetry (CV), and optical absorption and photoluminescence (PL) spectroscopy. A field‐effect mobility of 1.1 × 10−4 cm2 V−1 S−1, a current on/off ratio of 105, and the Vth at −15.2 V had been obtained for OTFTs using this polymer semiconductor by solution coating. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5115–5122, 2008
Electromagnetic nanocomposites prepared by cryomilling of polyaniline and Fe nanoparticles
Authors: Zhu Yanguo , Li Zhiqiang , Zhang Di
Published: June 2008

The polyaniline (PANI)/iron nanocomposites have been prepared by high‐energy ball milling under cryogenic temperatures, namely cryomilling, of PANI with Fe nanoparticles. It takes 5 h to refine the Fe into an average grain size of 20 nm and to get homogeneously dispersed in PANI matrix. The obtained PANI/Fe nanocomposites have a maximum conductivity of 0.78 S cm−1 after 2‐h cryomilling, whereas its coercivity increases monotonously with time in the range of experiment up to 10 h. It is found that the sizes of Fe particles have obvious effects on both electrical and magnetic properties. When compared with micrometer Fe particles as raw materials, Fe nanoparticles result in somewhat lower conductivity but a much higher coercivity exceeding 400 Oe. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1571–1576, 2008
Crystallization behavior of some unimodal and bimodal linear low‐density polyethylenes at moderate and high supercooling
Authors: Krumme Andres , Lehtinen Arja , Adamovsky Sergey , Schick Christoph , Roots Jaan , Viikna Anti
Published: June 2008

Effect of molar mass distribution (MMD) and composition distribution (CD) on crystallization behavior of linear low‐density polyethylene materials at moderate and high supercooling was studied using differential scanning calorimetry, hot‐stage polarized light microscopy, small‐angle light scattering, and chip nanocalorimetry methods. A set of uni‐ and bimodal materials having small variation in average molar mass, density, and melt flow rate, but large differences in MMD and CD, was investigated. The results indicate a clear effect of structural heterogeneity on morphology and crystallization behavior of the materials. Broader MMD and CD increased in average radius of superstructures, melting, crystallization temperatures, and isothermal crystallization rate at different supercoolings. Origin of such behavior is discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1577–1588, 2008
Modeling on swelling behavior of a confined polymer network
Authors: Li Xue‐Mei , Shen Zhou , He Tao , Wessling Matthias
Published: June 2008

Polymeric membranes suffer from plasticization in gas separation, extensive swollen in pervaporation, nanofiltration, and fuel cells by losing performance. Growing research has experimentally realized that the membrane performance could be stabilized by blending with inert second polymer or imbedding in a porous inert confinement. In this article, we introduce a generic model based on Flory–Rehner's swelling theory to describe various membrane processes using a measurable parameter. We assume the membrane polymer to be a network and the constraint as an expandable structure with an energy density equal to its E‐Modulus. The model reveals that the isotropic constraint is far more efficient in swelling control. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1589–1593, 2008
Graft copolymerization kinetics of acrylic acid onto the poly(ethylene terephthalate) surface by atmospheric pressure plasma inducement
Authors: Wang Jiku , Liu Xuyan , Choi Ho‐Suk
Published: June 2008

After one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft‐copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma‐induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 °C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1594–1601, 2008
Near infrared analysis of blends of sulfonated polystyrene ionomers and poly(ε‐caprolactam)
Authors: Ghebremeskel Yacob , Weiss R. A.
Published: June 2008

Near infrared spectroscopy (NIR) was used to characterize the nature of specific interactions in blends of lightly sulfonated polystyrene ionomers (M‐SPS where M = Zn+2, Mn+2, or Li+) and polycaprolactam (PA6). The assignments of the NIR overtone bands that arise due to the interactions between the cation of the ionomer, and the amide groups were made using spectra of model compounds. The relative populations of the different environments of the NH groups were qualitatively determined by deconvoluting the NIR spectra into five absorbances representing hydrogen‐bonded NH in crystalline and amorphous phases and an ion‐amide complex. The ion‐amide complex was specific for the blends. The interpolymer interactions were sensitive to composition and temperature, but qualitatively the behavior was the same for all three ionomer salts investigated. © 2008 Wiley Periodicals, Inc. JPolym Sci Part B: Polym Phys 46: 1602–1610, 2008
HIF‐1α: A key survival factor for serum‐deprived prostate cancer cells
Authors: Thomas Rusha , Kim Myoung H.
Published: June 2008

BACKGROUND

Hypoxia‐inducible factor‐1α (HIF‐1α) is commonly overexpressed in prostate cancer (PCa) cells. As PCa cells are known to survive serum deprivation, we investigated the effect of prolonged serum deprivation on HIF‐1α expression, and the function of HIF‐1α in regulating the survival of normoxic serum‐deprived PCa cells.

METHODS

HIF‐1α protein was assessed by immunoblots. Cell viability and proliferation were assessed by trypan blue assay and flow cytometric analysis. Transcriptional activity was assessed by luciferase reporter assay and RT‐PCR. HIF‐1α expression was suppressed with siRNA. Activities of HIF‐1α‐target genes were inhibited with neutralizing antibody.

RESULTS

Prolonged serum deprivation is a potent inducer of HIF‐1α in PC‐3 and LNCaP PCa cells, despite normal oxygen conditions. In contrast, cells grown in the presence of serum did not show HIF‐1α protein accumulation. Moreover, HIF‐1α protein increase during serum deprivation correlated with increased cell survival, while suppression of HIF‐1α expression significantly decreased PCa cell viability. Our results further demonstrate that HIF‐1α protein increase is due to increased HIF‐1α protein synthesis. First, there was no significant increase in HIF‐1α mRNA. Secondly, cycloheximide, a protein synthesis inhibitor, prevented HIF‐1α protein increase in serum‐deprived PCa cells. Moreover, the expression of HIF‐1α‐target genes, VEGF and IGF‐2, was concomitantly increased in serum‐deprived PCa cells, while suppression of HIF‐1α expression significantly inhibited their induction. Furthermore, inhibition of IGF‐2 activity resulted in a significant decline in PCa cell survival.

CONCLUSION

PCa cells counteract the stress of prolonged serum deprivation by upregulating HIF‐1α protein which increases IGF‐2 expression to promote cell survival. Prostate 68: 1405–1415, 2008. © 2008 Wiley‐Liss, Inc.
Knockdown resistance to DDT and pyrethroids: from target‐site mutations to molecular modelling
Authors: Davies TG Emyr , O'Reilly Andrias O , Field Linda M , Wallace BA , Williamson Martin S
Published: June 2008

Naturally derived insecticides such as pyrethrum and man‐made insecticides such as DDT and the synthetic pyrethroids act on the voltage‐gated sodium channel proteins found in insect nerve‐cell membranes. The correct functioning of these channels is essential for the normal transmission of nerve impulses, and this process is disrupted by binding of the insecticides, leading to paralysis and eventual death. Some insect pest populations have evolved modifications of the sodium channel protein that inhibit the binding of the insecticide and result in the insect developing resistance. This perspective outlines the current understanding of the molecular processes underlying target‐site resistance to these insecticides (termed kdr and super‐kdr), and how this knowledge may in future contribute to the design of novel insecticidal compounds. Copyright © 2008 Society of Chemical Industry
Intensity and temperature dependent characterization of eta solar cell
Authors: Musembi Robinson J. , Rusu Marin , Mwabora Julius M. , Aduda Bernard O. , Fostiropoulos Konstantinos , Lux‐Steiner Martha Ch.
Published: June 2008

Temperature‐dependent electrical characterization of a highly structured TiO2/In(OH)x Sy /Pb(OH)x Sy /PEDOT:PSS eta solar cell has been carried out. The transport mechanism in this type of solar cell has been investigated. A schematic energy band diagram which explains the photoelectrical properties of the device has been proposed. The solar cell has been characterized in the temperature range 200–320 K at illumination intensities between 0.05 mW/cm2 and 100 mW/cm2. The diode ideality factor A under illumination has been found to vary between 1.2 and 1.6, whereas in the dark 6.9 ≤ A ≤ 10.1. The device has been found to undergo a thermally activated recombination under illumination, while tunnelling enhanced recombination has been established to dominate the current in the dark. The solar cell efficiency shows a logarithmic dependence on illumination in the whole temperature range investigated, achieving its maximum at an illumination of ∼45 mW/cm2. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication and characterization of GaN‐based LEDs grown on nanopatterned sapphire substrates
Authors: Gao Haiyong , Yan Fawang , Zhang Yang , Li Jinmin , Zeng Yiping , Wang Guohong
Published: June 2008

Sapphire substrates were nanopatterned by dry (inductively coupled plasma, ICP) etching to improve the performance of GaN‐based light‐emitting diodes (LEDs). GaN‐based LEDs on nanopatterned sapphire substrates (NPSS) were fabricated by metal organic chemical vapor deposition (MOCVD). The characteristics of LEDs fabricated on NPSS prepared by dry etching were studied. The light output power and wall‐plug efficiency of the LEDs fabricated on NPSS were greater than those of the conventional LEDs fabricated on common planar sapphire substrates when the injection currents were the same. The LEDs on NPSS and common planar sapphire substrates have similar I –V characteristics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromagnetic structures of nanocrystalline ferromagnetic materials – comparison of simulation and experiment
Authors: Saranu S. , Grob A. , Weissmüller J. , Herr U.
Published: June 2008

The micromagnetic structure of nanocrystalline ferromagnetic materials is characterized by local fluctuations induced by the randomly varying magnetocrystalline anisotropy of the individual grains. Micromagnetic simulations may improve the understanding of the relevant features and the interpretation of the experimental observations of the magnetic structure. In this study we investigate the magnetic structure of nanocrystalline FeSi and Co model systems with average grain sizes of 20 nm to 60 nm. Small angle neutron scattering (SANS) is a suitable technique to study the micromagnetic structures of nanocrystalline materials at the nanometer scale. The simulated SANS curves for the FeSi model systems are compared with the experimental SANS curves of Vitroperm samples. It is found that the scattering at high fields is dominated by the local anisotropy fluctuations which can be well reproduced by the simulations. The simulations of the nanocrystalline hcp Co show that the stray fields resulting from the local magnetic fluctuations should lead to an observable contrast in magnetic force microscopy (MFM) images. We show that the contrast observed in the real MFM images of thin nanocrystalline hcp Co films compares well with the simulated image contrast with respect to magnitude and length scale of the observed fluctuations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the magnetism of the σ‐phase Fe–Cr alloys
Authors: Cies’︁lak J. , Reissner M. , Steiner W. , Dubiel S. M.
Published: June 2008

Magnetic properties of microcrystalline σ‐Fe100–x Crx (45 ≤ x ≤ 50) alloys were investigated with Mössbauer‐effect and magnetization measurements performed as a function of temperature and external magnetic field up to 15 T. The Curie temperature, TC, and the average magnetic moment per Fe atom, 〈μ 〉, which were determined, decrease linearly with x; the former at the rate of ∼7 K/at% and the latter at the rate of 0.033 μB/at%. The 〈μ 〉‐values determined are significantly larger than those in the literature. The characteristic features of the magnetization curves are that they (a) do not saturate even at 15 T, and (b) show bending approximately up to 3 times the derived TC values. The relationship between the average hyperfine field and 〈μ 〉 was revealed to be non‐linear. The latter, non‐saturating character of isothermal magnetization curves and Rhodes‐Wohlfarth plot are in favour of the itinerant model of magnetism in the investigated samples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of oxygen partial pressure on optical and electrical properties of co‐sputtered amorphous zinc indium tin oxide thin films
Authors: Saji K. J. , Jayaraj M. K.
Published: June 2008

Transparent thin films of amorphous zinc indium tin oxide were prepared at room temperature by co‐sputtering of zinc oxide and indium tin oxide. Effect of oxygen partial pressure on the optical and electrical properties of amorphous zinc indium tin oxide thin films were investigated. Conductivity, carrier concentration and Hall mobility showed strong dependence on the oxygen partial pressure and these parameters decreased with the increase of oxygen pressure. The effect of subgap states caused a sharp difference in measured optical band gap values between the films deposited with and without oxygen partial pressure. Carrier transport studies were carried out by temperature dependent conductivity measurements. At low electron density, the conductivity showed thermally activated behaviour and at higher carrier concentrations it changed to almost degenerate band conduction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Compensation effect of Sn in PbI2 polycrystalline layers
Authors: Ponpon J. P. , Mousa A. M. , Amann M.
Published: June 2008

Tin has been introduced into polycrystalline lead iodide during solution growth of thin films. Electrical characterization (current vs. voltage measurements as a function of the temperature and thermally stimulated current experiments) demonstrates that tin introduces a deep donor level in the PbI2 bandgap and compensates the native acceptor defects of lead iodide. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of excess Sb on crystallization of δ‐phase SbTe binary thin films
Authors: Youm Min Soo , Kim Yong Tae , Kim Young Hwan , Sung Man Young
Published: June 2008

The phase‐change temperature and crystal structures of the δ‐phase SbTe alloy for Sb contents of 64 at%, 72 at%, and 76 at% have been investigated. The δ‐phase SbTe alloy has a rhombohedral crystal structure, and crystallization occurs in an extremely narrow temperature range of 140–145 °C compared with Sb40Te60. We have determined the relationship between the Sb content and the crystalline structure using X‐ray diffraction and selected area electron diffraction. When the Sb content increases, the number of Sb layers stacked with Sb2Te3 in the unit cell increases, which results in the lowering of the activation energy for crystallization and a lower ovonic threshold voltage. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of the milling conditions on the formation of nanostructured Fe–Co powders
Authors: Alleg Safia , Bentayeb Fatima Zohra , Bensalem Rachid , Djebbari Chafia , Bessais Lotfi , Greneche Jean Marc
Published: June 2008

Nanostructured Fe–12Co (wt%) powders were prepared by mechanical alloying in a planetary ball mill. The milling process was carried out at different milling conditions. The obtained powders were characterized by X‐ray diffraction, 57Fe Mössbauer spectrometry and magnetic measurements. The low and high speed ball‐milling conditions lead to the formation of a single and two‐bcc Fe(Co) structure, respectively, having different crystallite sizes, microstrains hyperfine parameters and magnetic properties. The average hyperfine magnetic field values: 〈B〉1 = 34.8 T and 〈B〉2 = 28.2 T of the two‐bcc Fe(Co) structure could be attributed to the nanocrystalline grains and to the grain boundaries, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of carrier effective mass, impurity energy levels, and compensation ratio in Ga4Se3S layered crystals by Hall effect measurements
Authors: Qasrawi A. F. , Gasanly N. M.
Published: June 2008

In this work, the dark electrical resistivity, charge carriers density and Hall mobility of Ga4Se3S single crystals have been measured and analyzed in the temperature region of 200–350 K. The data analyses have shown that this crystal exhibits an extrinsic n‐type of conduction. The temperature‐dependent dark electrical resistivity analysis reflected the existence of energy level as 0.31 eV. The temperature dependence of carrier density was analyzed by using the single donor‐single acceptor model. The latter analysis allowed the determination of electron effective mass as 0.38m0, hole effective mass as 0.42m0, donor impurity energy level as 0.45 eV, acceptor–donor concentration ratio (Na/Nd) as 0.97 and a donor–acceptor concentration difference as Nd – Na = 1.5 × 1011 cm–3. The Hall mobility of Ga4Se3S is found to increase with decreasing temperature following a power law of slope of ∼(–6.3). The abnormal behavior of mobility was attributed to the domination of phonon scattering and/or crystals anisotropy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A simplified water temperature model for the Colorado River below Glen Canyon Dam
Authors: Wright Scott A. , Anderson Craig R. , Voichick Nicholas
Published: June 2008

Glen Canyon Dam, located on the Colorado River in northern Arizona, has affected the physical, biological and cultural resources of the river downstream in Grand Canyon. One of the impacts to the downstream physical environment that has important implications for the aquatic ecosystem is the transformation of the thermal regime from highly variable seasonally to relatively constant year‐round, owing to hypolimnetic releases from the upstream reservoir, Lake Powell. Because of the perceived impacts on the downstream aquatic ecosystem and native fish communities, the Glen Canyon Dam Adaptive Management Program has considered modifications to flow releases and release temperatures designed to increase downstream temperatures. Here, we present a new model of monthly average water temperatures below Glen Canyon Dam designed for first‐order, relatively simple evaluation of various alternative dam operations. The model is based on a simplified heat‐exchange equation, and model parameters are estimated empirically. The model predicts monthly average temperatures at locations up to 421 km downstream from the dam with average absolute errors less than 0.5°C for the dataset considered. The modelling approach used here may also prove useful for other systems, particularly below large dams where release temperatures are substantially out of equilibrium with meteorological conditions. We also present some examples of how the model can be used to evaluate scenarios for the operation of Glen Canyon Dam. Published in 2008 by John Wiley & Sons, Ltd.
Optimum treatment allocation rules under a variance heterogeneity model
Authors: Wong Weng Kee , Zhu Wei
Published: June 2008

We provide optimal treatment allocation schemes when the outcome variance varies across the treatment groups and our objectives are to estimate treatment effects with equal or unequal interest. Unlike other optimal designs, such asA‐optimal designs, the proposed designs can be found without an iterative scheme. We evaluate robustness properties of the optimal designs to mis‐specification in the expected variance from each group and identify situations when popular allocation schemes have poor efficiencies. An application to design a randomized rheumatoid arthritis trial is discussed, along with a potential application to design a cancer screening trial when the main outcome is a continuous variable. Copyright © 2008 John Wiley & Sons, Ltd.
Dose–schedule finding in phase I/II clinical trials using a Bayesian isotonic transformation
Authors: Li Yisheng , Bekele B. Nebiyou , Ji Yuan , Cook John D.
Published: June 2008

A dose–schedule‐finding trial is a new type of oncology trial in which investigators aim to find a combination of dose and treatment schedule that has a large probability of efficacy yet a relatively small probability of toxicity. We demonstrate that a major difference between traditional dose‐finding and dose–schedule‐finding trials is that while the toxicity probabilities follow a simple nondecreasing order in dose‐finding trials, those of dose–schedule‐finding trials may adhere to a matrix order. We show that the success of a dose–schedule‐finding method requires careful statistical modeling and a sensible dose–schedule allocation scheme. We propose a Bayesian hierarchical model that jointly models the unordered probabilities of toxicity and efficacy and apply a Bayesian isotonic transformation to the posterior samples of the toxicity probabilities, so that the transformed posterior samples adhere to the matrix‐order constraints. On the basis of the joint posterior distribution of the order‐constrained toxicity probabilities and the unordered efficacy probabilities, we develop a dose–schedule‐finding algorithm that sequentially allocates patients to the best dose–schedule combination under certain criteria. We illustrate our methodology through its application to a clinical trial in leukemia and compare it with two alternative approaches. Copyright © 2008 John Wiley & Sons, Ltd.
Atomic Force Microscopy‐Derived Nanoscale Chip for the Detection of Human Pathogenic Viruses
Authors: Artelsmair Helga , Kienberger Ferry , Tinazli Ali , Schlapak Robert , Zhu Rong , Preiner Johannes , Wruss Juergen , Kastner Markus , Saucedo‐Zeni Nadia , Hoelzl Martin , Rankl Christian , Baumgartner Werner , Howorka Stefan , Blaas Dieter , Gruber Hermann J. , Tampé Robert , Hinterdorfer Peter
Published: June 2008

Native‐protein nanolithography (NPNL) was used to fabricate stable bioactive arrays of viral receptor spots. The arrays were specific for the cognate virus and devoid of nonspecific protein and virus adsorption under physiologic conditions. The spot size ranged from 200 nm × 200 nm to 2 µm × 2 µm and up to 3 × 3 spots were arranged per array. With proper force adjustment in the patterning experiments, His6‐tagged bovine serum albumin (BSA) molecules were selectively removed from the underlying self‐assembled monolayer (SAM) while leaving the latter intact. Injection of His6‐tagged very low density lipoprotein receptor (VLDLR‐His6) constructs resulted in specific, oriented binding to the Ni2+‐loaded bis‐(nitrolotriacetic acid) (bis‐NTA) groups to the re‐exposed SAM areas. The arrays of viral receptors were used for the detection of human rhinovirus particles (serotype 2; HRV2) under native conditions by topographical imaging at high signal‐to‐noise ratio. The kinetic on‐rate of the HRV2‐VLDLR interaction was derived from the time‐dependent binding of the virions to the VLDL receptor spots. No significant binding was observed for the major group virus HRV14 that uses the unrelated receptor ICAM‐1.
Bioavailability of chemical pollutants in contaminated soils and pitfalls of chemical analyses in hazard assessment
Authors: Vasseur P. , Bonnard M. , Palais F. , Eom I. C. , Morel J. L.
Published: June 2008

Decision‐making for remediation of industrial wastelands are still based on the concentrations of pollutants of concern measured in soils. In this work, two soils polluted by polycyclic aromatic hydrocarbons (PAHs) and metals were investigated for their toxicity on earthworms (Eisenia fetida), collembolae (Folsomia candida), and higher plants (Brassica chinensis, Lactucca sativa and Avena sativa) in order to study the relationships between chemical contamination and biological effects. Although the level of contamination by PAHs was elevated and commensurate in the two soils, their toxicity profile was quite different. Soil A affected survival and reproduction of invertebrates and growth of higher plants. Surprisingly, soil B, heavily contaminated by metals in addition to PAHs, was devoid of toxicity. Our results indicate that toxicity cannot simply be extrapolated from pollutant concentrations in a complex matrix in which bioavailability of pollutants may be reduced by ageing. Moreover, the use of toxicity data obtained from spiked soils characterized by readily bioavailable pollutants can also be called into question for such extrapolations. Predicting biological effects therefore requires biological tools to avoid any erroneous conclusions that can be drawn from sole extrapolation of analytical results. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.
Distribution of oil‐degrading bacteria in coastal seawater, Toyama Bay, Japan
Authors: Tanaka Daisuke , Tanaka Shunsuke , Yamashiro Yoko , Nakamura Shogo
Published: June 2008

Oil‐degrading bacteria are considered to play an important role in the biodegradation of spilled or released oil in the sea. The distribution of indigenous oil‐degrading bacteria in the coastal seawater of Toyama Bay, Japan, was examined. Surface seawater samples with or without oil film in fishing port were analyzed by denaturing gradient gel electrophoresis (DGGE) of the PCR‐amplified V3 region of bacterial 16S rDNA. Sequence analysis revealed that several DGGE bands clearly detected only in samples with oil film corresponded to Cyanobacteria. Moreover, we cultured surface seawater samples with oil film in two different liquid culture media, a marine broth and an NSW medium; each culture contained 0.5% (w/v) C‐heavy oil. Emulsification of the oil was observed at day 6 in the marine broth and day 9 in the NSW medium. Time‐dependent changes of bacterial communities in those culture media were analyzed by DGGE. Interestingly, we found that Alcanivorax sp. became one of the dominant bacteria in each culture medium when emulsification of the oil began. Alcanivorax sp. is one of the well‐known oil‐degrading bacteria in seawater and is associated with the production of biosurfactants. These results suggest that Cyanobacteria and Alcanivorax play important roles in the bioremediation of oil‐contaminated areas in Toyama Bay. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.
Assessment of mixture toxicity of copper, cadmium, and phenanthrenequinone to the marine bacterium Vibrio fischeri
Authors: Wang Wenxi , Lampi Mark A. , Huang Xiao‐Dong , Gerhardt Karen , Dixon D. George , Greenberg Bruce M.
Published: June 2008

Transition metals and polycyclic aromatic hydrocarbons (PAHs) are cocontaminants at many sites. Contaminants in mixtures are known to interact with biological systems in ways that can greatly alter the toxicity of individual compounds. The toxicities (individually and as mixtures) of copper (Cu), a redox‐active metal; cadmium (Cd), a nonredox active metal; and phenanthrenequinone (PHQ), a redox‐active oxygenated PAH, were examined using the bioluminescent bacterium Vibrio
fischeri. We found that the cotoxicity of Cu/PHQ was dependent on the ratio of concentrations of each chemical in the mixture. Different interaction types (synergism, antagonism, and additivity) were observed with different combinations of these toxicants. The interaction types changed from antagonism at a low Cu to PHQ ratio (1:4), to additive at an intermediate Cu to PHQ ratio (2:3), to synergistic at higher Cu to PHQ ratios (3:2 and 4:1). In contrast to Cu/PHQ mixtures, the cotoxicity of Cd/PHQ did not change at different mixture ratios and was found for the most part to be additive. For the individual chemicals and their mixtures, reactive oxygen species (ROS) production was observed in V. fischeri, suggesting that individual and mixture toxicity of Cu, Cd, and PHQ to V. fischeri involves ROS‐related mechanisms. This study shows that mixture ratios can alter individual chemical toxicity, and should be taken into account in risk assessment. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.
Effects of methyl parathion exposure on development and reproduction in the viviparous fish Girardinichthys multiradiatus
Authors: Arellano‐Aguilar Omar , Macías Garcia Constantino
Published: June 2008

Methyl parathion (MeP), an insecticide commonly used in Mexico, has been detected in water bodies adjacent to agricultural crops and is accumulated in the tissue of the amarillo (Girardinichthys multiradiatus), a viviparous fish unique to Central Mexico. Evidence of MeP accumulation in a G. multiradiatus population prompted assessment of the consequences of exposure to MeP during the gestation period and adult life. We exposed adult fish to MeP in the diet at concentrations ranging from 0.001 to 0.165 μg/g dry weight of food. Fish accumulated MeP at concentrations from 0.21 to 5.87 μg/g of fish and exhibited a significant reduction in weight and growth rate. We also evaluated the effects on broods of pregnant females exposed to 0.005, 0.01, and 0.1 μg/g dry weight of food. Although these pregnant females were not affected, their offspring showed an increase in spinal cord malformation and a reduction in survival to adulthood. Finally, we sampled seven localities inhabited by G. multiradiatus; this revealed the presence of MeP in two water bodies at concentrations of 0.0036 and 0.037 μg/mL respectively. Our results suggest that low MeP concentrations affect immature fish with possible consequences later in life. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.
In situ evaluation of sediment toxicity in Guadalete Estuary (SW Spain) after exposure of caged Arenicola marina
Authors: Ramos‐Gómez Julia , Martín‐Díaz M. Laura , Rodríguez Araceli , Riba Inmaculada , DelValls T. Ángel
Published: June 2008

A 7 day in situ assay to assess sediment toxicity was carried out per replicate in two sites from Guadalete Estuary (Guad1 and Guad2) (South‐West, Spain) using the polychaete Arenicola marina (n = 20) in benthic cages. After the exposure period, a battery of biomarkers were determined to asses the sediment toxicity. Five of them were exposure biomarkers [ethoxyresorufin O‐deethylase (EROD), dibenzylfluorescein (DBF) dependant CytP450, gluthation reductase (GR), and gluthation‐S‐transferase (GST) activities] and one of them was an effect biomarker [lipid peroxidation (LPO)]. Toxicity due to metals bound to the sediment was found in Guad2. Metals provoke the inhibition of EROD, DBF, and GR and the induction of GST, which is showed to carry out antioxidative stress defense. Toxicity caused by metals and also PAH was detected in Guad1. The presence of these chemicals leads to GST induction in and presumably in consequence, to LPO inhibition. GST activity resulted to be the main protection mechanism against oxidative stress in Arenicola marina. We suggest further research in Guadalete Estuary focusing on the detection and toxicity assessment of pharmaceutical and personal care products. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.
In vivo genotoxic potential of microcystin‐LR: A cyanobacterial toxin, investigated both by the unscheduled DNA synthesis (UDS) and the comet assays after intravenous administration
Authors: Gaudin Julien , Le Hegarat Ludovic , Nesslany Fabrice , Marzin Daniel , Fessard Valérie
Published: June 2008

Microcystin‐LR (MC‐LR) is a toxin produced by freshwater cyanobacteria and is a potential threat to human health. MC‐LR has been shown to be both a specific inhibitor of serine/threonine protein phosphatases PP1 and PP2A and a potent tumor promoter in rat liver. However, the genotoxic potential of MCs remains unclear. In this article, we investigated the ability of MC‐LR to induce DNA damage on rat hepatocytes following intravenous (iv) administration by using two in vivo genotoxicity assays: the unscheduled DNA synthesis (UDS) and the comet assays. The UDS assay measures DNA synthesis induced from the excision repair of DNA damaged regions and the comet assay is a very sensitive technique for detecting various forms of DNA damage. After an exposure time of 2–4 h or 12–16 h and a dose ranging from 12.5 to 50 μg/kg bw, no DNA damage could be observed in both assays on rat hepatocytes following iv administration. These findings have been discussed and compared with recently published genotoxic results obtained in other organs from mice after oral and intraperitoneal treatments to better understand the mechanism of action of this toxin in relation with its cancerogenicity potential. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.
Breast‐Conserving Surgery in Hong Kong Chinese Women
Authors: Suen Dacita , Chow Lorraine , Kwong Ava
Published: June 2008

Background

Since the introduction of breast‐conserving surgery (BCS), it has been increasingly accepted as the standard surgical option for suitable breast cancer patients in Western countries. However, there have been reports suggesting striking ethnic variations in those undergoing BCS. This study aimed to review the rate of BCS in Hong Kong Chinese breast cancer patients and the possible clinicopathologic and psychosocial factors that may have affected the choice of surgery.

Methods

Patients in a university academic surgical center with early‐stage breast cancer (stage I/II invasive carcinoma and carcinoma in situ) who underwent definitive surgery from January 2001 to December 2005 were studied. BCS was considered feasible for those with (1) the optimal tumor size for which an acceptable cosmetic outcome can be achieved after surgery, (2) unifocal disease, and (3) no contraindication for postoperative radiotherapy. The proportion of women undergoing BCS or mastectomy were compared. Factors affecting the choice of surgery were correlated.

Results

Six hundred eighty female patients with early‐stage breast cancer underwent surgery during the study period; 495 (72.8%) mastectomies, 149 (21.9%) BCS, and 36 (5.3%) mastectomies with immediate reconstruction were performed. For those patients who had mastectomies, 54.8% (271/495) had considered BCS as the initial surgical option. Among these, 19.6% (53/271) failed to have BCS performed due to margin involvement or extensive disease, and 80.4% (218/271) declined BCS and opted for mastectomy only. Age, marital status, and educational level were found to be independent significant factors affecting the choice of BCS.

Conclusion

The rate of BCS in Hong Kong is relatively low compared to that of Western countries. Patients who opted for mastectomies tended to be older, married, and have a lower educational level. Prospective studies on how sociocultural, clinicopathologic, and other factors important in treatment decision‐making processes and psychosocial impact of choice of surgery are important so that an ethnic‐specific assessment can be made. Suitability and acceptance of BCS by Chinese women should increase with better understanding and education.
Surgical Education in China
Authors: Shen Bai‐Yong , Zhan Qian
Published: June 2008

A highly skilled surgical team relies on a standardized training system and the most important subject in the development of general surgery in China is to set up standardized education and training systems for surgeons. This article reviews the history of the training of residents, delineates the current situation and problems of residency training in general surgery, and discusses reform and future development of surgical training systems and assessment of competence in surgical practice, in order to put forward the solutions and countermeasures. China needs a large number of highly trained surgeons to improve its medical care system, and some fundamental changes of its residency training system, especially in the field of surgical education, have been made. All of the experts working in this area sum up the historical experience and apply the advanced experience of foreign countries as a reference to build up a surgical education system with Chinese characteristics to achieve a continuous, sound, and rapid development of surgical education in China.
The Number of Metastatic Lymph Nodes is a Significant Risk Factor for Bone Metastasis and Poor Outcome After Surgery for Linitis Plastica‐type Gastric Carcinoma
Authors: Kodera Yasuhiro , Ito Seiji , Mochizuki Yoshinari , Yamamura Yoshitaka , Misawa Kazunari , Ohashi Norifumi , Nakayama Goro , Koike Masahiko , Fujiwara Michitaka , Nakao Akimasa
Published: June 2008

Background

Linitis plastica‐type gastric carcinoma remains a disease with poor prognosis despite an aggressive surgical approach. Although a prominent pattern of disease failure is peritoneal carcinomatosis, some patients experience rapid disease progression without signs of the peritoneal disease.

Methods

Clinicopathologic data from 178 patients with linitis plastica‐type gastric cancer operated on between 1991 and 2000 were analyzed. Survival stratified by curability of surgery, pN stage, and patterns of failure were evaluated by using the Kaplan‐Meier method, and χ2 test was used to evaluate correlation between the number of metastatic lymph nodes in terms of pN categories and the incidence of various patterns of metastasis and recurrence. Cox regression hazard model was used to identify independent prognostic factors.

Results

R0 resection was performed only among 82 patients (46% of those who underwent laparotomy). Node metastasis was frequent with only 22 patients classified as pN0. Peritoneal carcinomatosis was observed in 131 patients and was the commonest pattern of recurrence. Bone metastasis, found in 13 patients, was associated with poor outcome, and its incidence was significantly correlated with the number of metastatic nodes. pT4 status and pN3 status were identified as significant independent prognostic determinants.

Conclusion

Treatment strategy for the linitis plastica should in general combine surgery with aggressive treatment directed toward peritoneal disease. However, patients with >16 metastatic nodes more often are associated with bone metastasis than those with modest nodal involvement and suffer from poor prognosis.