bluuebunny/crossref_metadata_2025 huggingface dataset:
Atom transfer radical polymerization synthesis and photoresponsive solution behavior of spiropyran end‐functionalized polymers as simplistic molecular probes
Authors: Ventura Claudia , Byrne Robert , Audouin Fabrice , Heise Andreas
Published: June 2011

Poly(methyl methacrylate)s (PMMAs) of two different molecular weights having a single photochromic benzospiropyran (BSP) end‐group were synthesized by atom transfer radical polymerization (ATRP). Polymer characterization by 1H NMR and matrix‐assisted laser desorption/ionitiation time of flight‐mass spectroscopy confirms that using an ATRP initiator equipped with BSP, a near quantitative functionalization of the PMMA with the BSP was achieved. Both polymers exhibit photochroism characterized by the UV‐induced transition from BSP to benzomerocyanine (BMC) in acetonitrile. However, a strong molecular weight dependence of the thermal relaxation kinetic of the BMC was found with a significantly faster temperature‐dependent transition for the higher molecular weight polymer. Thermodynamic analysis of the process revealed a higher gain in the entropy of activation ΔS± for the transition process in the higher molecular weight polymer. This suggests an energetically unfavorable nonpolar environment of the BMC group in the higher molecular weight polymers, although a higher solvation of the BMC in the lower molecular weight polymer contributes to its stabilization. The ability of the BMC polymer end‐groups to organize was shown in metal ion‐binding experiments forming bivalently linked complexes with Co ions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Versatile synthesis of asymmetrical dendron‐like/dendron‐like poly(ε‐caprolactone)‐b‐poly(γ‐benzyl‐L‐glutamate) block copolymers
Authors: Liu Wei , Dong Chang‐Ming
Published: June 2011

Dendron‐like/dendron‐like poly(ε‐caprolactone)‐b‐poly(γ‐benzyl‐L‐glutamate) block copolymers with asymmetrical topology (PCL‐b‐PBLGn, both the subscript and the superscript denote the degree of polymerization and the branch number, respectively; n = 1, 2, and 4) were synthesized by combining ring‐opening polymerization (ROP) and click chemistry. The dendron‐like propargyl focal point PCL precursor with eight branches was synthesized from the controlled ROP of ε‐caprolactone, and then click conjugated with azido focal point poly(amido amine) dendrons to generate the PCL‐dendrons with multiple primary amine groups. The PCL‐dendrons were further used as macroinitiators for the ROP of γ‐benzyl‐L‐glutamate N‐carboxyanhydride to produce the targeted asymmetrical block copolymers. Their molecular structures and physicochemical properties were thoroughly characterized by means of FT‐IR, 1H NMR, gel permeation chromatography, differential scanning calorimetry, and wide angle X‐ray diffraction. Both the maximal melting temperature and the degree of crystallinity of PCL block within copolymers decreased with increasing the PBLG branches and/or the chain length, demonstrating that the crystallinity of PCL block was progressively suppressed by PBLG block. Meanwhile, the PBLG block within copolymers progressively transformed from β‐sheet to α‐helical conformation with increasing the PBLG chain length. Consequently, this provides a versatile strategy for the synthesis of biodegradable and biomimetic block copolymers with asymmetrical dendritic topology. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Liquid crystalline dendrimers containing photoactive cinnamate units
Authors: Viñuales Ana I. , Serrano Jose Luis , Giménez Raquel , Piñol Milagros , Tomczyk Jaroslaw , Stumpe Joachim
Published: June 2011

Cinnamate‐containing dendrimers have been prepared by peripheral functionalization of the amine groups of a poly(propyleneimine) dendrimer with 4‐methoxycinnamate‐ or 4‐(N,N‐dimethylamino)cinnamate‐derived units and/or 4‐cyanobiphenyl units in different proportions. The synthesis, full characterization in solution, thermal properties and optical properties of the novel monomers, homodendrimers and codendrimers are reported. The composition of the molecular structure of the codendrimers has been elucidated by matrix assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). These liquid crystalline dendrimers display lamellar SmA mesophases. The codendrimers have been tailored in such a way that the photoactive units and the liquid crystal units absorb in different regions in order to allow better control over the processes induced by light. Linearly polarized UV light irradiation studies performed on thin films of the cinnamate codendrimers show that they are photoresponsive. A photoinduced anisotropy is generated with increasing exposure time, but in‐plane amplification of anisotropy by thermal annealing in the mesophase was not observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Synthesis of π‐conjugated copolymers composed of benzo[2,1,3]thiadiazole and thiophene units bearing various alkyl groups and their application to photovoltaic cells
Authors: Lee Kwang‐Hoi , Lee Ho‐Jin , Kuramoto Kouji , Tanaka Yohei , Morino Kazuhide , Sudo Atsushi , Okauchi Tatsuo , Tsuge Akihiko , Endo Takeshi
Published: June 2011

π‐Conjugated polymers, PTOTBT, PTEHTBT, and PTt‐BTBT, composed of benzothiadiazole as an electron accepting unit and terthiophene as an electron donating unit in the backbone were prepared. PTOTBT, PTEHTBT, and PTt‐BTBT contained side chain groups of n‐octyl, 2‐ethylhexyl, and t‐butyl groups, respectively. Solubility, optical and thermal properties of the polymers showed strong dependences on their side chain groups. PTEHTBT having 2‐ethylhexyl groups in the side chain exhibited absorption maximum (λmax) at longer wavelength (565 nm) than PTOTBT (534 nm) and PTt‐BTBT (495 nm). PTOTBT showed higher thermal stability than the others. The prepared polymers were employed to polymer solar cells (PSCs) with a configuration of ITO/PEDOT‐PSS/polymer: PC61BH/LiF/Al. Power conversion efficiency of the PSC‐based on PTEHTBT was 1.32%. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Synthesis and structure‐activity relationship of several aromatic ketone‐based two‐photon initiators
Authors: Li Zhiquan , Siklos Marton , Pucher Niklas , Cicha Klaus , Ajami Aliasghar , Husinsky Wolfgang , Rosspeintner Arnulf , Vauthey Eric , Gescheidt Georg , Stampfl Jürgen , Liska Robert
Published: June 2011

Several novel aromatic ketone‐based two‐photon initiators containing triple bonds and dialkylamino groups were synthesized and the structure‐activity relationships were evaluated. Branched alkyl chains were used at the terminal donor groups to improve the solubility in the multifunctional monomers. Because of the long conjugation length and good coplanarity, the evaluated initiators showed large two‐photon cross section values, while their fluorescence lifetimes and quantum yields strongly depend on the solvent polarity. All novel initiators exhibited high activity in terms of two‐photon‐induced microfabrication. This is especially true for fluorenone‐based derivatives, which displayed much broader processing windows than well‐known highly active initiators from the literature and commercially available initiators. While the new photoinitiators gave high reactivity in two‐photon‐induced photopolymerization at concentration as low as 0.1% wt, these compounds are surprisingly stable under one photon condition and nearly no photo initiation activity was found in classical photo DSC experiment. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Molecular dynamics simulations of the effects of carbon dioxide on the interfacial bonding of polystyrene thin films
Authors: Alleman Coleman , Srivastava Anand , Ghosh Somnath
Published: June 2011

Fabrication of nanoscale polymer‐based devices, especially in biomedical applications, is a challenging process due to requirements of precise dimensions. Methods that involve elevated temperature or chemical adhesives are not practicable due to the fragility of the device components and associated deformation. To effectively fabricate devices for lab‐on‐a‐chip or drug delivery applications, a process is required that permits bonding at low temperatures. The use of carbon dioxide (CO2) to assist the bonding process shows promise in reaching this goal. It is now well established that CO2 can be used to depress the glass transition temperature (Tg) of a polymer, allowing bonding to occur at lower temperatures. Furthermore, it has been shown that CO2 can preferentially soften a polymer surface, which should allow for effective bonding at temperatures even below the bulk Tg. However, the impact of this effect on bonding has not been quantified, and the optimal bonding temperature and CO2 pressure conditions are unknown. In this study, a molecular dynamics model is used to examine the atomic scale behavior of polystyrene in an effort to develop understanding of the physical mechanisms of bonding and to quantify how the process is impacted by CO2. The final result is the identification of a range of CO2 pressure conditions which produce the strongest bonding between PS thin films at room temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011
Identification of Ternary Phases in TiBC/a‐C Nanocomposite Thin Films: Influence on the Electrical and Optical Properties
Authors: Abad Manuel David , Sanjinés Rosendo , Endrino Jose Luis , Gago Raúl , Andersson Joakim , Sánchez‐López Juan Carlos
Published: June 2011

The local structure of TiBC and amorphous carbon (a‐C) nanocomposite films (TiBC/a‐C) was correlated with their optical and electrical properties. TiBC/a‐C films with increasing C content were deposited by magnetron co‐sputtering from TiC:TiB2 (60:40) and graphite targets. Chemical composition is determined by electron energy‐loss spectroscopy. Grazing incidence X‐ray diffraction reveals that the microstructure of the films is amorphous with small nanocrystallites emerging by increasing the C content that could be attributed to the formation of ternary (TiBxCy) or mixed binary (TiB2 and TiC) phases. Further information was then obtained by studying the chemical bonding by measuring the near‐edge fine structure (NES) by electron energy‐loss (B K‐, C K‐, and Ti L‐edges) and X‐ray absorption (B K‐ and Ti L‐edges) spectroscopies. The NES analysis indicates the formation of a nanocrystalline ternary TiBxCy compound concomitant with the segregation of an a‐C phase as the carbon content is increased. The optical properties were studied by spectroscopic ellipsometry and the electrical resistivity was measured by the Van der Pauw method between 20 and 300 K. The films continuously lose their metallic character in terms of optical constants and resistivity with increasing carbon content. Theoretical fitting of the electrical properties using the grain‐boundary scattering model supported the formation of a nanocomposite structure based on a ternary TiBxCy phase embedded in a matrix of a‐C. The electron transport properties are mainly limited by the high density of point defects, grain size, and transmission probability.

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A designed redox‐controlled caspase
Authors: Witkowski Witold A. , Hardy Jeanne A.
Published: June 2011

Caspases are a powerful class of cysteine proteases. Introduction of activated caspases in healthy or cancerous cells results in induction of apoptotic cell death. In this study, we have designed and characterized a version of caspase‐7 that can be inactivated under oxidizing extracellular conditions and then reactivated under reducing intracellular conditions. This version of caspase‐7 is allosterically inactivated when two of the substrate‐binding loops are locked together via an engineered disulfide. When this disulfide is reduced, the protein regains its full function. The inactive loop‐locked version of caspase‐7 can be readily observed by immunoblotting and mass spectrometry. The reduced and reactivated form of the enzyme observed crystallographically is the first caspase‐7 structure in which the substrate‐binding groove is properly ordered even in the absence of an active‐site ligand. In the reactivated structure, the catalytic‐dyad cysteine–histidine are positioned 3.5 Å apart in an orientation that is capable of supporting catalysis. This redox‐controlled version of caspase‐7 is particularly well suited for targeted cell death in concert with redox‐triggered delivery vehicles.
Integration of cell‐free protein coexpression with an enzyme‐linked immunosorbent assay enables rapid analysis of protein–protein interactions directly from DNA
Authors: Layton Curtis J. , Hellinga Homme W.
Published: June 2011

Assays that integrate detection of binding with cell‐free protein expression directly from DNA can dramatically increase the pace at which protein–protein interactions (PPIs) can be analyzed by mutagenesis. In this study, we present a method that combines in vitro protein production with an enzyme‐linked immunosorbent assay (ELISA) to measure PPIs. This method uses readily available commodity instrumentation and generic antibody–affinity tag interactions. It is straightforward and rapid to execute, enabling many interactions to be assessed in parallel. In traditional ELISAs, reporter complexes are assembled stepwise with one layer at a time. In the method presented here, all the members of the reporter complex are present and assembled together. The signal strength is dependent on all the intercomponent interaction affinities and concentrations. Although this assay is straightforward to execute, establishing proper conditions and analysis of the results require a thorough understanding of the processes that determine the signal strength. The formation of the fully assembled reporter sandwich can be modeled as a competition between Langmuir adsorption isotherms for the immobilized components and binding equilibria of the solution components. We have shown that modeling this process provides semiquantitative understanding of the effects of affinity and concentration and can guide strategies for the development of experimental protocols. We tested the method experimentally using the interaction between a synthetic ankyrin repeat protein (Off7) and maltose‐binding protein. Measurements obtained for a collection of alanine mutations in the interface between these two proteins demonstrate that a range of affinities can be analyzed.
Comparative functional analysis of the human macrophage chitotriosidase
Authors: Vandevenne Marylène , Campisi Vincent , Freichels Astrid , Gillard Carole , Gaspard Gilles , Frère Jean‐Marie , Galleni Moreno , Filée Patrice
Published: June 2011

This work analyses the chitin‐binding and catalytic domains of the human macrophage chitotriosidase and investigates the physiological role of this glycoside hydrolase in a complex mechanism such as the innate immune system, especially its antifungal activity. Accordingly, we first analyzed the ability of its chitin‐binding domain to interact with chitin embedded in fungal cell walls using the β‐lactamase activity reporter system described in our previous work. The data showed that the chitin‐binding activity was related to the cell wall composition of the fungi strains and that their peptide‐N‐glycosidase/zymolyase treatments increased binding to fungal by increasing protein permeability. We also investigated the antifungal activity of the enzyme against Candida albicans. The antifungal properties of the complete chitotriosidase were analyzed and compared with those of the isolated chitin‐binding and catalytic domains. The isolated catalytic domain but not the chitin‐binding domain was sufficient to provide antifungal activity. Furthermore, to explain the lack of obvious pathologic phenotypes in humans homozygous for a widespread mutation that renders chitotriosidase inactive, we postulated that the absence of an active chitotriosidase might be compensated by the expression of another human hydrolytic enzyme such as lysozyme. The comparison of the antifungal properties of chitotriosidase and lysozyme indicated that surprisingly, both enzymes have similar in vitro antifungal properties. Furthermore, despite its more efficient hydrolytic activity on chitin, the observed antifungal activity of chitotriosidase was lower than that of lysozyme. Finally, this antifungal duality between chitotriosidase and lysozyme is discussed in the context of innate immunity.
Mass spectrometric identification of an intramolecular disulfide bond in thermally inactivated triosephosphate isomerase from a thermophilic organism Methanocaldococcus jannaschii
Authors: Banerjee Mousumi , Gupta Kallol , Balaram Hemalatha , Balaram Padmanabhan
Published: June 2011

The triosephosphate isomerase from the hyperthermophilic organism Methanocaldococcus jannaschii (MjTIM) is a tetrameric enzyme, with a monomer molecular mass of 23245 Da. The kinetic parameters, the kcat and the Km values, of the enzyme, examined at 25°C and 50°C, are 4.18 × 104 min−1 and 3.26 × 105 min−1, and 0.33 and 0.86 mM−1 min−1, respectively. Although the circular dichroism and fluorescence emission spectra of the protein remain unchanged up to 95°C, suggesting that the secondary and tertiary structures are not lost even at this extreme temperature, surprisingly, incubation of this thermophilic enzyme at elevated temperature (65–85°C) results in time‐dependent inactivation, with almost complete loss of activity after 3 h at 75°C. High‐resolution electrospray ionization mass spectrometry (ESI‐MS) reveals the monomeric mass of the heated sample to be 23243 Da. The 2 Da difference between native and heated samples suggests a probable formation of a disulfide bridge between proximal cysteine thiol groups. Liquid chromatography (LC)/ESI‐MS/MS analysis of tryptic digests in the heated samples permits identification of a pentapeptide (DCGCK, residues 80‐84) in which a disulfide bond formation between Cys81 and Cys83 was established through the collision‐induced dissociation (CID) fragmentation of the intact disulfide‐bonded molecule, yielding characteristic fragmentation patterns with key neutral losses. Neither residue is directly involved in the catalytic activity. Inspection of the three‐dimensional structure suggests that subtle conformation effects transmitted through a network of hydrogen bonds to the active site residue Lys8 may be responsible for the loss of catalytic activity. Copyright © 2011 John Wiley & Sons, Ltd.
Carbon disulfide reagent allows the characterization of nonpolar analytes by atmospheric pressure chemical ionization mass spectrometry
Authors: Owen Benjamin C. , Gao Jinshan , Borton David J. , Amundson Lucas M. , Archibold Enada F. , Tan Xiaoli , Azyat Khalid , Tykwinski Rik , Gray Murray , Kenttämaa Hilkka I.
Published: June 2011

While atmospheric pressure ionization methodologies have revolutionized the mass spectrometric analysis of nonvolatile analytes, limitations native to the chemistry of these methodologies hinder or entirely inhibit the analysis of certain analytes, specifically, many nonpolar compounds. Examination of various analytes, including asphaltene and lignin model compounds as well as saturated hydrocarbons, demonstrates that atmospheric pressure chemical ionization (APCI) using CS2 as the reagent produces an abundant and stable molecular ion (M+•) for all model compounds studied, with the exception of completely saturated aliphatic hydrocarbons and the two amino acids tested, arginine and phenylalanine. This reagent substantially broadens the applicability of mass spectrometry to nonvolatile nonpolar analytes and also facilitates the examination of radical cation chemistry by mass spectrometry. Copyright © 2011 John Wiley & Sons, Ltd.
Acetonitrile covalent adduct chemical ionization tandem mass spectrometry of non‐methylene‐interrupted pentaene fatty acid methyl esters
Authors: Alves Susana P. , Tyburczy Cynthia , Lawrence Peter , Bessa Rui J. B. , Thomas Brenna J.
Published: June 2011

Acetonitrile covalent adduct chemical ionization tandem mass spectrometry (CACIMS/MS) has shown to be an efficient method for the identification of double‐bond position in homoallylic, conjugated and several polyene non‐methylene‐interrupted (NMI) fatty acid methyl esters. However, it has not been thoroughly evaluated for NMI highly unsaturated fatty acids (HUFA) with more than four double bonds. Docosahexaenoic acid (DHA)‐rich single cell oil (DHASCO®; Martek Biosciences, Corp.) was partially hydrogenated (partially hydrogenated DHASCO; PHDO) producing ten novel 22:5 and 22:6 HUFA isomers. In single‐stage MS, the ratio of [M+54]+/[M+54‐32]+ for the 22:5 and 22:6 isomers indicated the presence of homoallylic or partially conjugated double‐bond systems. The CACIMS/MS spectra revealed six 22:5 isomers with diagnostic ions corresponding to the homoallylic 22:5n‐6 and 22:5n‐3 isomers, and four distinct NMI 22:5 isomers. Diagnostic ions for four 22:6 isomers were identical to the native DHA illustrating that CACIMS/MS is sensitive to double‐bond position but not geometry. Three gas chromatography (GC) peaks for partially conjugated 22:6 isomers were also detected and clearly distinguishable from homoallylic 22:6 isomers, but their CACIMS/MS spectra did not yield prominent ions indicative of double‐bond position, possibly due to co‐elution. Overall, CACIMS/MS was effective for determining double‐bond position in NMI 22:5 isomers. Further investigations are warranted to evaluate and determine fragmentation patterns for partially conjugated and NMI 22:6 HUFA. Copyright © 2011 John Wiley & Sons, Ltd.
Stable isotope ratio measurements of royal jelly samples for controlling production procedures: impact of sugar feeding
Authors: Daniele Gaëlle , Wytrychowski Marine , Batteau Magali , Guibert Sylvie , Casabianca Hervé
Published: June 2011

The carbon and nitrogen stable ratios of royal jelly (RJ) samples from various origins are determined using an elemental analyser linked online to an isotope ratio mass spectrometer to evaluate authenticity and adulteration. The 13C/12C and 15N/14N stable isotope ratios are measured in more than 500 RJs (domestic, imported and derived from feeding experiments) in order to obtain isotopic measurements that take into account seasonal, botanical and geographical effects. Authenticity intervals are established for traditional beekeeping practices, without feeding, in the range −22.48 to −27.90‰ for δ13C. For these samples, the δ15N values range from −1.58 to 7.98‰, depending on the plant sources of pollen and nectar. The δ13C values of the commercial samples vary from −18.54 to −26.58‰. High δ13C values are typical of sugar cane or corn syrups which have distinctive isotopic 13C signatures because both plants use the C4 photosynthetic cycle, in contrast to most RJs which are derived from C3 plants. These differences in the 13C‐isotopic composition allow the detection of the addition of such sugars. RJs from traditional sources and from industrial production by sugar feeding are thus successfully distinguished. Copyright © 2011 John Wiley & Sons, Ltd.
Determination of vitamins A, D and E in a small volume of human plasma by a high‐throughput method based on liquid chromatography/tandem mass spectrometry
Authors: Midttun Øivind , Ueland Per M.
Published: June 2011

We have developed an automated high‐throughput assay for the determination of vitamin A (retinol), ergocalciferol (25‐OH D2), cholecalciferol (25‐OH D3) and vitamin E (α‐tocopherol) in a small volume of human plasma. Sample preparation involved mixing 50 μL of plasma with 100 μL of ethanol containing isotope‐labelled internal standards, followed by mixing with isooctane/chloroform (3:1, 300 μL). The organic phase was evaporated, and the sample reconstituted in 50 μL methanol. The analysis was performed using reversed‐phase liquid chromatography with a gradient mobile phase containing water, methanol and ammonium formate. Chromatographic run‐time was 5 min, and positive mode electrospray tandem mass spectrometry (MS/MS) was used for detection. The limits of detection were 0.10 μM for all‐trans retinol and 3.3 nM for 25‐OH D2 and 25‐OH D3. Recoveries were 91.9–105.0%, and within‐ and between‐day coefficients of variance (CVs) 2.4–5.3 and 3.1–8.2, respectively. The assay is presently being used in large‐scale studies. Copyright © 2011 John Wiley & Sons, Ltd.
Dissociation of deprotonated microcystin variants by collision‐induced dissociation following electrospray ionization
Authors: Dörr Felipe Augusto , Oliveira‐Silva Diogo , Lopes Norberto Peporine , Iglesias Jacobo , Volmer Dietrich A. , Pinto Ernani
Published: June 2011

Microcystins (MC) are a family of hepatotoxic cyclic heptapeptides produced by a number of different cyanobacterial species. Considering the recent advances in the characterization of deprotonated peptides by mass spectrometry, the fragmentation behavior of four structurally related microcystin compounds was investigated using collision‐induced dissociation (CID) experiments on an orbitrap mass spectrometer. It is demonstrated in this study that significant structural information can be obtained from the CID spectra of deprotonated microcystins. A predominant ring‐opening reaction at the isoMeAsp residue, as well as two major complementary fragmentation pathways, was observed, reducing the complexity of the product ion spectra in comparison with spectra observed from protonated species. This proposed fragmentation behavior was applied to characterize [Leu1]MC‐LR from a cyanobacterial cell extract. In conclusion, CID spectra of microcystins in the negative ion mode provide rich structurally informative mass spectra which greatly enhance confidence in structural assignments, in particular when combined with complementary positive ion CID spectra. Copyright © 2011 John Wiley & Sons, Ltd.
High resolution at low beam energy in the SEM: resolution measurement of a monochromated SEM
Authors: Michael Joseph R.
Published: June 2011

The resolution of secondary electron low beam energy imaging of a scanning electron microscope equipped with a monochromator is quantitatively measured using the contrast transfer function (CTF) method. High‐resolution images, with sub‐nm resolutions, were produced using low beam energies. The use of a monochromator is shown to quantitatively improve the resolution of the SEM at low beam energies by limiting the chromatic aberration contribution to the electron probe size as demonstrated with calculations and images of suitable samples. Secondary electron image resolution at low beam energies is ultimately limited by noise in the images as shown by the CTFs. SCANNING 33: 147–154, 2011. © 2011 Wiley Periodicals, Inc.
Science, engineering, and technology in the policy process for mitigating natural–societal risk
Authors: Taylor Timothy R. B. , Ford David N. , Yvon‐Lewis Shari A. , Lindquist Eric
Published: June 2011

Increased societal risks due to the anthropogenic degradation of natural systems often require public policy action to mitigate. For example, increased skin cancer risks associated with anthropogenic stratospheric ozone depletion led to public policies limiting the emission of many ozone‐depleting substances. Natural–societal system interaction is complex and often requires expert knowledge and technology to develop effective and sustainable societal risk mitigation policies. However, available knowledge and technology are not always successful in increasing policy makers' attention to or understanding of these risks. The current work uses a system dynamics model of a feedback system that describes the stratospheric ozone depletion case to identify high leverage points for domain experts to influence policy makers in addressing risks posed by changes in a natural system. Model analysis suggests that the rate at which policy makers' attention to natural system risk is increased has a significant influence on the development of knowledge and technology and the ability of policy makers to mitigate societal risks. Copyright © 2011 System Dynamics Society.
High energy resolution Auger spectroscopy on a CMA instrument
Authors: Watson D. G. , Larson P. E. , Paul D. F. , Negri R. E.
Published: June 2011

An experimental method that increases the analyzer resolution of cylindrical mirror analyzer CMA‐based Auger spectrometers is described. By means of electrically biasing the sample, the effective energy resolution obtainable from the CMA instrument is improved from the native 0.5 to 0.1% or even better for higher kinetic energy Auger transitions. In addition, the maximum kinetic energy Auger transition observable by the CMA Auger instrument is increased from 3200 to 5700 eV, in the current realization. It is also shown that the sensitivity of the energy scale calibration to sample working distance with respect to the analyzer is simultaneously reduced, making the method suitable for chemical surface analysis. The biasing is accomplished using a special sample holder with electronics and software that can be added to an existing instrument. The overall capability of the Auger instrument for chemical analysis is, therefore, increased, while preserving all the analytical functionality and features of the CMA. Copyright © 2011 John Wiley & Sons, Ltd.
Size‐dependent aggregation behavior in monodisperse silica: a nitrogen adsorption study
Authors: Cui Juqing , Han Shuguang , Zhou Zhaobing , Jia Chong , Zhang Yang
Published: June 2011

The present study focused on the aggregation behavior that resulted from surface interaction between monodisperse silicas synthesized with Stöber method using nitrogen adsorption method at cryogenic temperature (77 K). Specific surface area, pore size distribution and surface fractal dimension from adsorption isotherm were evaluated. For relatively large particle, (190 nm in diameter), it was observed that nitrogen adsorption isotherm could be classified to type I. However, others with small size (below 100 nm) have shown the characteristic of type IV with the evident character of hysteresis loop in the isotherm. The increment of specific surface area (SBET) changed with the decrease of particle size, which could be fitted with an exponential decay equation. Pore size distribution (PSD) indicated that there exist an amount of mesopore (between 2 and ∼50 nm) and shift toward the smaller with decreasing the size of silica. Surface fractal dimension (DSF) from thermodynamic method demonstrated that the DSF increased with the decreasing the size of silica. PSD and DSF clearly embodied the size‐dependent aggregation of monodisperse silica nanoparticle, which could be used to explain the inferior performance of polymer nanocomposite filled with smaller monodisperse silica. Copyright © 2011 John Wiley & Sons, Ltd.
Modification of glassy carbon electrode by the electrochemical oxidation of 3‐aminophenylcalix[4]pyrrole in nonaqueous media
Authors: Taner Bilge , Deveci Pervin , Üstündaǧ Zafer , Keskin Selda , Özcan Emine , Osman Solak Ali
Published: June 2011

3‐Aminophenylcalix[4]pyrrole (3APCP) was grafted to a glassy carbon (GC) surface during the electrochemical oxidation process in 0.1 M tetrabutylammoniumtetra‐fluoroborate (TBATFB) containing acetonitrile solution. The presence of a surface film was confirmed electrochemically by comparing voltammograms of dopamine and ferricyanide redox probes at the bare and modified electrodes. Reflection‐absorption infrared spectroscopy (RAIRS), XPS, atomic force microscopy (AFM), ellipsometry and the contact angle measurements were also employed to characterize 3APCP film on GC electrode. RAIRS analysis revealed that calix[4]pyrrole was bonded to the glassy carbon surface via the etheric linkage. The stability of the modified GC electrode was also studied. Copyright © 2011 John Wiley & Sons, Ltd.
Functional Characterization of Quiescent Keratinocyte Stem Cells and Their Progeny Reveals a Hierarchical Organization in Human Skin Epidermis
Authors: Schlüter Holger , Paquet-Fifield Sophie , Gangatirkar Pradnya , Li Jason , Kaur Pritinder
Published: June 2011

Although homeostatic renewal of human skin epidermis is achieved by the combined activity of quiescent stem cells (SCs) and their actively cycling progeny, whether these two populations are equipotent in their capacity to regenerate tissue has not been determined in biological assays that mimic lifelong renewal. Using fluorescence activated cell separation strategy validated previously by us, human epidermis was fractionated into three distinct subsets: that is, α 6briCD71dim, α 6briCD71bri, and α 6dim with characteristics of keratinocyte stem, transient amplifying, and early differentiating cells, respectively. The global gene expression profile of these fractions was determined by microarray, confirming that the α 6briCD71dim subset was quiescent, the α 6briCD71bri was actively cycling, and the α 6dim subset expressed markers of differentiation. More importantly, functional evaluation of these populations in an in vivo model for tissue reconstitution at limiting cell dilutions revealed that the quiescent α 6briCD71dim fraction was the most potent proliferative and tissue regenerative population of the epidermis, capable of long-term (LT) epidermal renewal from as little as 100 cells for up to 10 weeks. In contrast, the cycling α 6briCD71bri fraction was the first to initiate tissue reconstitution, although this was not sustained in the LT, while differentiating α 6dim cells possessed the lowest demonstrable tissue regenerative capacity. Our data suggest that in human skin, the epidermal proliferative compartment is not composed of equipotent cells, but rather is organized in a functionally hierarchical manner with the most potent quiescent SCs at its apex (i.e., α 6briCD71dim) followed by cycling progenitors (i.e., α 6briCD71bri) and finally early differentiating keratinocytes (i.e., α 6dim).
Specific α4β2 nicotinic acetylcholine receptor binding of [F‐18]nifene in the rhesus monkey
Authors: Hillmer A.T. , Wooten D.W. , Moirano J.M. , Slesarev M. , Barnhart T.E. , Engle J.W. , Nickles R.J. , Murali D. , Schneider M.L. , Mukherjee J. , Christian B.T.
Published: June 2011

Objective:

[F‐18]Nifene is a PET radioligand developed to image α4β2* nicotinic acetylcholine receptors (nAChR) in the brain. This work assesses the in vivo binding and imaging characteristics of [F‐18]nifene in rhesus monkeys for the development of PET experiments examining nAChR binding.

Methods:

Dynamic PET imaging experiments with [F‐18]nifene were acquired in four anesthetized Macaca mulatta (rhesus) monkeys using a microPET P4 scanner. Data acquisition was initiated with a bolus injection of 109 ± 17 MBq [F‐18]nifene and the time course of the radioligand in the brain was measured for up to 120 min. For two experiments, a displacement dose of (‐)nicotine (0.03 mg kg−1, i.v.) was given 45–60 min post injection and followed 30 min later with a second [F‐18]nifene injection to measure radioligand nondisplaceable uptake. Time activity curves were extracted in the regions of the antereoventral thalamus (AVT), lateral geniculate nucleus region (LGN), frontal cortex, and the cerebellum (CB).

Results:

The highest levels of [F‐18]nifene uptake were observed in the AVT and LGN. Target‐to‐CB ratios reached maximum values of 3.3 ± 0.4 in the AVT and 3.2 ± 0.3 in the LGN 30–45 min postinjection. Significant binding of [F‐18]nifene was observed in the subiculum, insula cortex, temporal cortex, cingulate gyrus, frontal cortex, striatum, and midbrain areas. The (‐)nicotine displaced bound [F‐18]nifene to near background levels within 15 min postdrug injection. No discernable displacement was observed in the CB, suggesting its potential as a reference region. Logan graphical estimates using the CB as a reference region yielded binding potentials of 1.6 ± 0.2 in the AVT and 1.3 ± 0.1 in the LGN. The postnicotine injection displayed uniform nondisplaceable uptake of [F‐18]nifene throughout gray and white brain matter.

Conclusions:

[F‐18]Nifene exhibits rapid equilibration and a moderately high target to background binding profile in the α4β2* nAChR rich regions of the brain, thus providing favorable imaging characteristics as a PET radiotracer for nAChR assay. Synapse, 2011. © 2011 Wiley‐Liss, Inc.
A review of fetal volumetry: the need for standardization and definitions in measurement methodology
Authors: Ioannou C. , Sarris I. , Salomon L. J. , Papageorghiou A. T.
Published: June 2011

Volume charts of fetal organs and structures vary considerably among studies. This review identified 42 studies reporting normal volumes, namely for fetal brain (n = 3), cerebellum (n = 4), liver (n = 6), femur (n = 2), lungs (n = 15), kidneys (n = 3) and first‐trimester embryo (n = 9). The differences among median volumes were expressed both in percentage form and as standard deviation scores. Wide discrepancies in reported normal volumes make it extremely difficult to diagnose pathological organ growth reliably. Given its magnitude, this variation is likely to be due to inconsistencies in volumetric methodology, rather than population differences. Complicating factors include the absence of clearly defined anatomical landmarks for measurement; inadequate assessment and reporting of method repeatability; the inherent difficulty in validating fetal measurements in vivo against a reference standard; and a multitude of mutually incompatible three‐dimensional (3D) imaging formats and software measuring tools. An attempt to standardize these factors would improve intra‐ and inter‐researcher agreement concerning reported volumetric measures, would allow generalization of reference data across different populations and different ultrasound systems, and would allow quality assurance in 3D fetal biometry. Failure to ensure a quality control process may hamper the wide use of 3D ultrasound. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.
Longitudinal study of aortic isthmus Doppler in appropriately grown and small‐for‐gestational‐age fetuses with normal and abnormal umbilical artery Doppler
Authors: Kennelly M. M. , Farah N. , Hogan J. , Reilly A. , Turner M. J. , Stuart B.
Published: June 2011

Objective

To establish reference ranges using longitudinal data for aortic isthmus (AoI) Doppler indices in appropriate‐for‐gestational‐age (AGA) fetuses and to document the longitudinal trends in a cohort of small‐for‐gestational‐age (SGA) fetuses with normal umbilical artery Doppler and in fetuses with intrauterine growth restriction (IUGR) and abnormal umbilical artery Doppler.

Methods

AoI Doppler reference ranges were established from longitudinal data on 72 AGA singleton fetuses. Reliability of AoI Doppler flow measurements at two different sites and reproducibility between two operators was reviewed. A prospective longitudinal study of AoI Doppler indices in 48 SGA fetuses with normal umbilical artery Doppler and 10 IUGR fetuses was performed.

Results

The AoI pulsatility index (PI) and peak systolic velocity (PSV) in AGA fetuses showed a significant increase with gestational age. Analysis of intra‐ and interoperator variability revealed no significant mean difference in measurements of AoI‐PI or AoI‐PSV. Observations of AoI‐PI and AoI‐PSV from SGA fetuses did not differ significantly from those of AGA or IUGR fetuses. Retrograde flow in the AoI did not predate changes in the ductus venosus in IUGR fetuses.

Conclusions

Reference ranges for fetal AoI Doppler parameters in AGA fetuses constructed using longitudinal data are consistent with those obtained from cross‐sectional data. The AoI Doppler parameters in SGA fetuses did not differ from those in AGA fetuses. Preterm IUGR fetuses did not manifest alterations in AoI‐PI or AoI‐PSV prior to changes in biophysical profile or ductus venosus Doppler. Further large‐scale prospective studies are needed to determine whether AoI Doppler parameters are of any value in timing delivery or reducing adverse neurodevelopmental outcome. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Does climate change knowledge really matter?
Authors: Sarewitz Daniel
Published: June 2011

Climate science and climate policy have been tightly linked for more than two decades. Science is supposed to provide the factual basis for action on climate, and a single policy approach to dealing with climate (through the UN Framework Convention process) has been dominant throughout this period. As a result, debates about climate policy and debates about climate science are impossible to disaggregate, and opposition to the prevailing international climate regime is often expressed as distrust of the science. Until new policy options are available that can enfranchise more diverse political constituencies, climate science will continue to exist as a largely political phenomenon. WIREs Clim Change 2011 2 475–481 DOI: 10.1002/wcc.126

This article is categorized under:

Social Status of Climate Change Knowledge > Climate Science and Decision Making
An Empirical Examination of Women's Empowerment and Transformative Change in the Context of International Development
Authors: Grabe Shelly
Published: June 2011

This paper responds to calls from social scientists in the area of globalization and women's empowerment to test a model that investigates both structural and individual components of women's empowerment in the context of globalization. The investigation uses a liberation psychology framework by taking into account the effects of globalization, human rights discourse, and women's activism within social movements to identify how structural inequities may be related to empowerment. Surveys conducted in rural Nicaragua revealed that land ownership and organizational participation among women were related to more progressive gender ideology, and in turn, women's power and control within the marital relationship, individual levels of agency, and subjective well‐being. The study demonstrates that psychology can bridge the theoretical arguments surrounding human rights with the practical implementation of development interventions, and provide empirical support that has yet to be demonstrated elsewhere. The findings have important implications for strategies and interventions that can improve conditions for women and contribute to the aims of social justice articulated in the Beijing Platform for Action.
Seasonal variation in plant hydraulic traits of two co‐occurring desert shrubs, Tamarix ramosissima and Haloxylon ammodendron, with different rooting patterns
Authors: Xu Gui‐Qing , Li Yan , Xu Hao
Published: June 2011

Effective hydraulic responses to varying soil moisture and evaporative demand are crucial to plant survival in arid ecosystems. This study was carried out during two growing seasons (2004–2005) on two typical desert shrub species, Tamarix ramosissima and Haloxylon ammodendron, co‐occurring in the Gurbantonggut Desert (Central Asia), to investigate their hydraulic responses to seasonal variations in water availability. The root distribution was studied by excavating the intact root systems. Leaf‐specific apparent hydraulic conductance (Kl) for the two species was calculated based on leaf water potential (ψl) and transpiration rate (Tr), which were monitored during the growing seasons. T. ramosissima had a deeper taproot (3.1 vs. 2.6 m) and a larger root surface area (3.02 vs. 1.28 m2) than H. ammodendron. Combined with a higher ψl, this meant that it maintained a better water status in general. For the deep‐rooting T. ramosissima, the seasonal pattern of its predawn leaf water potential (ψpd) was in high accordance with the seasonal changes in soil moisture at a depth of 2.6–2.8 m, which was largely influenced by the upflow of groundwater through capillary ascent, and barely responded to rain events. For the shallow‐rooting H. ammodendron, the seasonal pattern of ψpd was closely related to soil moisture in the upper layer at a depth of 0–0.2 and 0.6–0.8 m, which was recharged periodically by rain events and responded acutely to rainfall above 5 mm. The two species differed in their maximum transpiration rates (Trmax) and ψpd: in T. ramosissima, Trmax gradually dropped with decreasing ψpd; in H. ammodendron, Trmax showed no significant response to ψpd. For T. ramosissima, the major water resource was groundwater and vadose zone water, and ψl contributed significantly to transpiration regulation. For H. ammodendron, the primary water resource was precipitation input, which was not sufficient to keep the ψl for this species outside the critical range of leaf shedding in summer. Thus, for these two representative species that share the same habitat, contrasting response strategies to water limitation were observed in relation to water acquisition and root distribution characteristics.
Dyslipidemic Diabetic Serum Increases Lipid Accumulation and Expression of Stearoyl‐CoA Desaturase in Human Macrophages
Authors: Wong Bruce X. W. , Kyle Reece A. , Myhill Paul C. , Croft Kevin D. , Quinn Carmel M. , Jessup Wendy , Yeap Bu B.
Published: June 2011

Type 2 diabetes and dyslipidemia are risk factors for cardiovascular disease. However, mechanisms by which hypertriglyceridemia influences atherogenesis remain unclear. We examined effects of dyslipidemic diabetic serum on macrophage lipid accumulation as a model of foam cell formation. Normal human macrophages were cultured in media supplemented with 10% serum from non‐diabetic normolipidemic or non‐diabetic hypercholesterolemic adults versus adults with Type 2 diabetes; diabetes and hypertriglyceridemia; or diabetes and hypercholesterolemia. Exposure to diabetic sera resulted in increased macrophage fatty acids (2–3 fold higher, both saturated and unsaturated). Macrophage expression of CD36, scavenger receptor A (SR‐A) and stearoyl‐CoA desaturase (SCD) was increased, most prominently in macrophages exposed to hypertriglyceridemic diabetic serum (twofold increase in CD36 and fourfold increase in SCD, p < 0.05). In these conditions, RNA inhibition of CD36 reduced macrophage free cholesterol (163.9 ± 10.5 vs. 221.9 ± 26.2 mmol free cholesterol/g protein, p = 0.04). RNA inhibition of SCD decreased macrophage fatty acid content, increased ABCA1 level and enhanced cholesterol efflux (18.0 ± 3.9 vs. 8.0 ± 0.8% at 48 h, p = 0.03). Diabetic dyslipidemia may contribute to accelerated atherosclerosis via alterations in macrophage lipid metabolism favoring foam cell formation. Increased expression of CD36 and SR‐A would facilitate macrophage lipid uptake, while increased expression of SCD could block compensatory upregulation of ABCA1 and cholesterol efflux. Further studies are needed to clarify whether modulation of macrophage lipid metabolism might reduce progression of diabetic atherosclerosis.
ON A CURIOUS PROPERTY OF BELL NUMBERS
Authors: SUN ZHI-WEI , ZAGIER DON
Published: June 2011

In this paper we derive congruences expressing Bell numbers and derangement numbers in terms of each other modulo any prime.
The braided monoidal structures on the category of vector spaces graded by the Klein group
Authors: Bulacu D. , Caenepeel S. , Torrecillas B.
Published: June 2011

Let k be a field, let k* = k \ {0} and let C2 be a cyclic group of order 2. We compute all of the braided monoidal structures on the category of k-vector spaces graded by the Klein group C2 × C2. For the monoidal structures we compute the explicit form of the 3-cocycles on C2 × C2 with coefficients in k*, while, for the braided monoidal structures, we compute the explicit form of the abelian 3-cocycles on C2 × C2 with coefficients in k*. In particular, this will allow us to produce examples of quasi-Hopf algebras and weak braided Hopf algebras with underlying vector space k[C2 × C2].
A biharmonic equation with singular nonlinearity
Authors: Ghergu Marius
Published: June 2011

We study the biharmonic equation Δ2u=u−α, 0 < α < 1, in a smooth and bounded domain Ω ⊂ ℝn,n≥ 2, subject to Dirichlet boundary conditions. Under some suitable assumptions on Ω related to the positivity of the Green function for the biharmonic operator, we prove the existence and uniqueness of a solution.
Alternating units as free factors in the group of units of integral group rings
Authors: Gonçalves Jairo Z. , Veloso Paula M.
Published: June 2011

Let G be a group of odd order that contains a non-central element x whose order is either a prime p ≥ 5 or 3l, with l ≥ 2. Then, in $\mathcal{U}(\mathbb{Z}G)$, the group of units of ℤG, we can find an alternating unit u based on x, and another unit v, which can be either a bicyclic or an alternating unit, such that for all sufficiently large integers m we have that 〈um, vm〉 = 〈um〉 ∗ 〈vm〉 ≌ ℤ ∗ ℤ