bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction and characterization of HCCH⋅⋅⋅AuX (X = OH, F, Cl, Br, CH3, CCH, CN, and NC) complexes: A π Au-bond
Authors: Li Hui , Li Qingzhong , Li Ran , Li Wenzuo , Cheng Jianbo
Published: August 2011

In this article, we performed quantum chemical calculations to study the π Au-bond in the HCCH⋅⋅⋅AuX (X = OH, F, Cl, Br, CH3, CCH, CN, and NC) system. For comparison, we also investigated the HCCH⋅⋅⋅Au+ and H2CCH2⋅⋅⋅AuF complexes. The equilibrium geometries and infrared spectra at the MP2 level were reported. The interaction energies were calculated at the MP2 and coupled-cluster single double triple levels. The natural bond orbital results support the Dewar-Chatt-Duncanson model. Moreover, we focused on the influence of X atom on the geometries, interaction energies, and orbital interactions as well as the comparison between HCCH⋅⋅⋅AuF and H2CCH2⋅⋅⋅AuF complexes. Although the π Au-bond in these complexes is electrostatic in nature, the weight of covalent nature is also important.
Time scale separation leads to position-dependent diffusion along a slow coordinate
Authors: Berezhkovskii Alexander , Szabo Attila
Published: August 2011

When there is a separation of time scales, an effective description of the dynamics of the slow variables can be obtained by adiabatic elimination of fast ones. For example, for anisotropic Langevin dynamics in two dimensions, the conventional procedure leads to a Langevin equation for the slow coordinate that involves the potential of the mean force. The friction constant along this coordinate remains unchanged. Here, we show that a more accurate, but still Markovian, description of the slow dynamics can be obtained by using position-dependent friction that is related to the time integral of the autocorrelation function of the difference between the actual force and the mean force by a Kirkwood-like formula. The result is generalized to many dimensions, where the slow or reaction coordinate is an arbitrary function of the Cartesian coordinates. When the fast variables are effectively one-dimensional, the additional friction along the slow coordinate can be expressed in closed form for an arbitrary potential. For a cylindrically symmetric channel of varying cross section with winding centerline, our analytical expression immediately yields the multidimensional version of the Zwanzig-Bradley formula for the position-dependent diffusion coefficient.
The dependence of scaling law on stoichiometry for horizontally propagating vertical chemical fronts
Authors: Pópity-Tóth Éva , Horváth Dezső , Tóth Ágota
Published: August 2011

Horizontally propagating fronts in the iodate–arsenous acid reaction are investigated experimentally in a vertically oriented Hele-Shaw cell by varying the height of liquid layer for various stoichiometry. At the preset conditions, a stable pattern develops which can be characterized by its mixing length defined as the standard deviation of the front position in the direction of propagation. The mixing length scales with the height of the reaction vessel, and although the exponent significantly changes by varying the ratio of the reactants, it has a universal value when the reaction front is thin and simple convection arises.
Perfect spin-filtering and giant magnetoresistance with Fe-terminated graphene nanoribbon
Authors: Cao Chao , Wang Yan , Cheng Hai-Ping , Jiang J.-Z.
Published: August 2011

Spin-dependent electronic transport properties of Fe-terminated zig-zag graphene nanoribbons (zGNRs) have been studied using first-principles transport simulations. The spin configuration of proposed zGNRs junction can be controlled with external magnetic field, and the tunneling junction show magnetoresistance > 1000 at small bias and is a perfect spin-filter by applying uniform external magnetic filed at small bias.
Communication: Configuration interaction singles has a large systematic bias against charge-transfer states
Authors: Subotnik Joseph E.
Published: August 2011

We show that standard configuration interaction singles (CIS) has a systematic bias against charge-transfer (CT) states, wherein the computed vertical excitation energies for CT states are disproportionately too high (by >1 eV) as compared with non-CT states. We demonstrate this bias empirically for a set of chemical problems with both inter- and intra-molecular electron transfer, and then, for a small analytical model, we prove that this large difference in accuracy stems from the massive changes in electronic structure that must accompany long-range charge transfer. Thus far, the conclusion from this research is that, even in the context of wave function theory, CIS alone is insufficient for offering a balanced description of excited state surfaces (both CT and non-CT) and explicit electron-electron correlation must be included additionally (e.g., via CIS(D)) for charge-transfer applications.
Charge balance and photon collection in polymer based ternary bulk heterojunction photovoltaic devices containing cadmium selenide nanoparticles
Authors: Peterson Eric D. , Smith Gregory M. , Fu Minglai , Adams Richard D. , Coffin Robert C. , Carroll David L.
Published: August 2011

Solar cells employing a ternary bulk heterojunction active layer comprised of poly(3-hexylthiophene) (P3HT), 6,6-phenyl C61-butyric acid methyl ester (PCBM) doped with composites constructed from a combination of 2.5 nm CdSe nanoparticles (NP), and methyl viologen (MV) have been examined. It was found that the devices containing the CdSe NP/MV composite exhibit significantly more photocurrent in a region surrounding the absorption peak of the particles (560-660 nm) when compared to pristine P3HT:PCBM devices. For a low ratio of CdSe to PCBM, the photocurrent collection was accompanied by space charge build up that limited the performance of the devices. When the ratio of CdSe to PCBM was raised, the space charge dissipated and performance recovered. JV curve shape analysis suggests that charge balance was achieved; however, electrode selectivity was reduced.
Interface state and dipole assisted hole injection improvement with 1,4,5,8,-naphthalene-tetracarboxylic-dianhydride in organic light-emitting devices
Authors: Jeon Pyungeun , Lee Hyunbok , Lee Jeihyun , Jeong Kwangho , Lee JinWoo , Yi Yeonjin
Published: August 2011

1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA) is known to improve hole injection when inserted between the hole transport layer and the indium tin oxide (ITO) anode in organic light emitting devices. To clarify the origin of the improvement, the interfacial electronic structures between N,N′-diphenyl-N, N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4′ diamine (NPB, typical hole transport layer) and ITO with a NTCDA insertion layer were explored. The NTCDA layer generates an interface state when it interacts with ITO and also induces large interface dipole. The interface state assists hole transport and the interface dipole pulls entire energy levels of NPB up, reducing the hole injection barrier.
Microwave absorption properties of MWCNT-SiC composites synthesized via a low temperature induced reaction
Authors: Zhu Hui-Ling , Bai Yu-Jun , Liu Rui , Lun Ning , Qi Yong-Xin , Han Fu-Dong , Meng Xiang-Lin , Bi Jian-Qiang , Fan Run-Hua
Published: August 2011

The composites containing SiC and multiwalled carbon nanotubes (MWCNTs) were synthesized via the reaction of Si powders and MWCNTs induced by that of Na and sulfur. The MWCNT-SiC composites prepared at 600 °C exhibit excellent microwave absorbing properties, which reach a minimum reflection loss of -38.7 dB at a frequency around 12.9 GHz. The absorbing properties are bound up with the high yield of porous SiC spheres comprised of nanocrystals. The porous structure, high density of stacking faults in SiC crystallites, interfaces between MWCNTs and SiC spheres, grain boundaries between SiC nanocrystals, as well as the interfacial polarizations aroused therefrom, are responsible for the excellent microwave absorbing properties.
Redox-controlled memristive switching in the junctions employing Ti reactive electrodes
Authors: Li Haitao , Xia Yidong , Xu Hanni , Liu Lifei , Li Xuefei , Tang Zhenjie , Chen Xiangzhong , Li Aidong , Yin Jiang , Liu Zhiguo
Published: August 2011

We have proposed a kind of memristive device based on the junctions employing Ti as the reactive electrodes. The role of electrically-derived redox of Ti in such memristive switching is shown. The structural and chemical evidence of the electrically-derived oxidation is presented by TEM and XPS experiment, respectively. Due to the redox of the top electrode Ti and the consequent drift of oxygen vacancies, the device shows two distinct resistance states under a sweeping voltage loading. ON state is controlled by tunneling process, while OFF state is controlled by Schottky emission conductive mechanism. The failure behaviors of such memristive junctions are also discussed. In the light of the redox principle, we demonstrate that the devices could be recovered by loading a long electrical reduction treatment.
Nitrogen/argon diluted acetylene and ethylene blue flames under infrared CO2 laser irradiation
Authors: Pikhitsa Peter V. , Kim Daegyu , Choi Mansoo
Published: August 2011

We investigated changes in emission spectra from nitrogen/argon diluted laminar diffusion acetylene and ethylene blue flames irradiated by a powerful cw infrared CO2 laser. The changes in the radical emission bands can be interpreted as an indication of laser-induced decomposition of ethylene (for laser absorbing C2H4 fuel) and of laser-absorbing intermediates (for non-absorbing C2H2 fuel). The results indicate that released active hydrogen plays an important role in addition/abstraction reactions without any participation of oxygen.
Supercontinuum ultra wide range confocal microscope for reflectance spectroscopy of living matter and material science surfaces
Authors: Selci Stefano , Bertani Francesca R. , Ferrari Luisa
Published: August 2011

We report the design and implementation of a new reflectance laser scanning confocal system with spectroscopy imaging capabilities. Confocal spectroscopy is achieved by using a very broad spectral range supercontinuum source capable of high precision reflectance data in the VIS-IR spectral range thanks to an almost achromatic optical layout. With this apparatus we collect each single scanning point as a whole spectrum in a continuous range, associated with the optical section imaging possibilities typical of a confocal set up. While such a microscope has been developed for bio medical analysis of human skin and other similar applications, first test results on solid samples produce spectroscopic results that, compared to analytical models based on the Abelés matrix transfer methods, show a very good agreement, opening new possibilities of a complete spectroscopic fingerprinting of samples with microscopic details.
Reversible Addition–Fragmentation Chain Transfer (RAFT) Polymerization in Miniemulsion Based on In Situ Surfactant Generation
Authors: Ting S. R. Simon , Min Eun Hee , Zetterlund Per B.
Published: August 2011

Reversible addition–fragmentation chain transfer (RAFT) polymerization of styrene has been implemented in aqueous miniemulsion based on the in situ surfactant generation approach using oleic acid and potassium hydroxide in the absence of high energy mixing. The best results were obtained using the RAFT agent 3-benzylsulfanyl thiocarbonyl sufanylpropionic acid (BSPAC), most likely as a result of the presence of a carboxylic acid functionality in the RAFT agent that renders it surface active and thus imparts increased colloidal stability. Stable final miniemulsions were obtained with no coagulum with particle diameters less than 200 nm. The results demonstrate that the RAFT miniemulsion polymerization of styrene employing the low energy in situ surfactant method is challenging, but that a system that proceeds predominantly by a miniemulsion mechanism can be achieved under carefully selected conditions.
Star-shaped Poly(2-oxazoline)s by Dendrimer Endcapping
Authors: Lambermont-Thijs Hanneke M. L. , Fijten Martin W. M. , Schubert Ulrich S. , Hoogenboom Richard
Published: August 2011

The synthesis of star-shaped poly(2-ethyl-2-oxazoline) is reported by direct end-capping of the living polymer chains with dendritic multiamines. The end-capping kinetics after addition of a first generation polypropylenimine dendrimer are discussed based on monitoring by size exclusion chromatography, revealing less efficient end-capping with larger poly(2-ethyl-2-oxazoline) chains and increasing dendrimer generation. In addition, it is demonstrated that the solution viscosity and cloud point temperature of the star-shaped polymers are much less affected by chain length compared with their linear analogues.
pH-Responsive Chiral Nanostructures
Authors: Du Jianzhong , Willcock Helen , Ieong Nga Sze , O'Reilly Rachel K.
Published: August 2011

There is great current interest in the design of robust synthetic polymers for the preparation of novel functional, well-defined, biocompatible and tailorable materials for a range of possible applications. In this work we have used reversible addition fragmentation chain transfer (RAFT) polymerization to prepare chiral and responsive amphiphilic block copolymers (based on polyphenylalanine acrylamide), which can be assembled at different pHs to form well-defined nanostructures. The morphology and size of the derived block polymers were explored using TEM, DLS and SLS measurements, while stability was examined by fluorescence and NMR spectroscopy. The application of these chiral and responsive nanostructures in the resolution of hydrophilic racemic amino acids has also been explored.
'Pseudo-star' Copolymers Formed by a Combination of RAFT Polymerization and Isocyanate-Coupling
Authors: Moraes John , Maschmeyer Thomas , Perrier Sébastien
Published: August 2011

We describe the formation of pseudo-star copolymers via incorporation of an isocyanate-bearing monomer, dimethyl meta-isopropenyl benzyl isocyanate (TMI) into a homopolymer of butyl acrylate (BA) using a one-pot, two-step synthesis. The resultant product maintains the functionality of the isocyanate moiety, which is used to attach poly(ethylene glycol) methyl ether onto the copolymeric chain under benign reaction conditions. The resultant pseudo-star copolymers were isolated and their self-assembly in the presence of water studied.
Soft Core–Hard Shell Silicone Hybrid Nanoparticles Synthesized by Miniemulsion Polymerization: Effect of Silicone Content and Crosslinking on Latex Film Properties
Authors: Paiphansiri Umaporn , Reyes Yuri , Hoffmann-Richter Carola , Theisinger Sonja , Landfester Katharina
Published: August 2011

Composite nanoparticles consisting of ‘soft’ silicone oil and ‘hard’ polyacrylate with core–shell morphology were obtained by a one-step synthesis via the miniemulsion process. Various parameters, i.e. the viscosity and amount of the silicone, the surfactant content, the (co)monomers affecting the particle size and morphology were studied. With an optimum hydrophilicity of the polymer shell, composite particles possessing a well-defined core–shell morphology were obtained as determined by transmission electron microscopy. The fully encapsulated silicone oil (40 wt-%) in a slightly crosslinked polyacrylate shell showed good film formation as revealed by atomic force microscopy. The ability to highly confine silicone oil in the composite film could clearly be evaluated from contact angle measurements. By finely changing the crosslink concentration in the polymeric shell, tunable hydrophobic properties of films cast from silicone core–polyacrylate shell latexes could be achieved. In addition, the high thermal resistance and excellent water-resistant properties of the film were shown by thermal gravimetric analysis and water swelling determination. These composite latexes are presented as new alternatives for practical utility in waterborne coatings.
Progress Toward Robust Polymer Hydrogels
Authors: Naficy Sina , Brown Hugh R. , Razal Joselito M. , Spinks Geoffrey M. , Whitten Philip G.
Published: August 2011

In this review we highlight new developments in tough hydrogel materials in terms of their enhanced mechanical performance and their corresponding toughening mechanisms. These mechanically robust hydrogels have been developed over the past 10 years with many now showing mechanical properties comparable with those of natural tissues. By first reviewing the brittleness of conventional synthetic hydrogels, we introduce each new class of tough hydrogel: homogeneous gels, slip-link gels, double-network gels, nanocomposite gels and gels formed using poly-functional crosslinkers. In each case we provide a description of the fracture process that may be occurring. With the exception of double network gels where the enhanced toughness is quite well understood, these descriptions remain to be confirmed. We also introduce material property charts for conventional and tough synthetic hydrogels to illustrate the wide range of mechanical and swelling properties exhibited by these materials and to highlight links between these properties and the network topology. Finally, we provide some suggestions for further work particularly with regard to some unanswered questions and possible avenues for further enhancement of gel toughness.
NHC-Based Self-Assembled Monolayers on Solid Gold Substrates
Authors: Weidner Tobias , Baio Joe E. , Mundstock Alexander , Große Christoph , Karthäuser Silvia , Bruhn Clemens , Siemeling Ulrich
Published: August 2011

Thin films of 1,3-diethylbenzimidazol-2-ylidene (BIEt) were fabricated from THF solution on solid gold substrates and characterised by high-resolution X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. The surface-analytical data are in accord with the formation of self-assembled monolayers of BIEt molecules exhibiting an approximately vertical orientation on the substrate. The crystal structure of (BIEt)2 was also determined.
Temperature Dependent Stress Relaxation in a Model Diels–Alder Network
Authors: Sheridan Richard J. , Adzima Brian J. , Bowman Christopher N.
Published: August 2011

The effect of temperature on the complex shear modulus (G*(ω)) of a model reversible covalent network formed by the Diels–Alder reaction was studied. The gel temperature of 119°C and the functional group conversion at this temperature were determined by the Winter–Chambon criterion. The complex modulus of the cross-linked network was measured from 110°C to 121°C, near the gel temperature, to determine the frequency ranges over which stress relaxation could occur. The crossover time was found to have a strong dependence on temperature (Ea ∼ 260 kJ mol–1); greater than would be expected from a typical thermally-activated retro-Diels–Alder process. Low frequency scaling of G*(ω) over the experimental frequency and temperature range was interpreted to be a result of the existence of a distribution of transient clusters in these thermoreversible covalent gels.
1,3,4-Trisubtituted-1,2,3-Triazol-5-ylidene 'Click' Carbene Ligands: Synthesis, Catalysis and Self-Assembly
Authors: Crowley James D. , Lee Ai-Lan , Kilpin Kelly J.
Published: August 2011

This review examines the use of the Cu(I)-catalyzed 1,3-cycloaddition of organic azides with terminal alkynes (the CuAAC ‘click’ reaction) for development of a novel family of abnormal/mesoionic N-heterocyclic carbenes and their corresponding metal complexes. These 1,3,4-trisubstituted-1,2,3-triazol-5-ylidenes have donor properties that are intermediate between the traditional Arduengo-type imidazol-2-ylidenes and more highly σ-donating abnormal carbenes, such as imidazol-4-ylidenes or pyrazolin-4-ylidenes. Metal complexes of the 1,3,4-trisubstituted-1,2,3-triazol-5-ylidenes have been used as catalysts for a variety of reactions including the CuAAC cycloaddition, Pd cross-couplings, and ring closing/ring opening metathesis. Additionally, ‘click’ carbene ligands have been used to generate self-assembled metallo-macrocycles and novel photosensitizers. The mild, modular CuAAC approach to these ligands should allow the rapid generation of libraries of 1,3,4-trisubstituted-1,2,3-triazol-5-ylidenes that can be further exploited to generate novel catalysts, metallo-pharmaceuticals and materials.
A Neutral Gallium(I) N-Heterocyclic Carbene Analogue: Synthesis, Characterization and Theoretical Analysis
Authors: Choong Sam L. , Woodul William D. , Stasch Andreas , Schenk Christian , Jones Cameron
Published: August 2011

The six-membered N-heterocyclic gallium(I) compound [:Ga(ButNacnac)] (ButNacnac– = [{N(Dip)C(But)}2CH]–, Dip =2,6-diisopropylphenyl) has been synthesized, crystallographically characterized, and its electronic properties analyzed using density functional theory. For purposes of comparison, the isoelectronic cationic germanium(II) complex, [:Ge(ButNacnac)][Al{OC(CF3)3}4], has been prepared and structurally authenticated.
Synthesis and Self-assembly of Amphiphilic Hetero-arm Molecular Brushes
Authors: Hadasha Waled , Mothunya Mpho , Akeroyd Niels , Klumperman Bert
Published: August 2011

We report the synthesis of amphiphilic hetero-arm molecular brushes (AMBs), which were prepared by a combination of ‘grafting from’ and ‘grafting onto’ methodologies. First, styrene-terminated polyethylene glycol macromonomer (VB-PEG12, ∼666 g mol–1) was copolymerized with maleic anhydride (MAnh) to yield a polymer containing hydrophilic PEG chains and reactive (MAnh) groups. Subsequently, the reactive MAnh units in the obtained polymer were modified via a ring-opening reaction using primary alkyl amines, with different alkyl chain lengths, as the nucleophile. In situ ring closure yielded the styrene–maleimide-based AMB. The amphiphilic character of the AMBs was used for their self-assembly in different solvents. The effect of the ratio in hydrophilic to hydrophobic graft length on the morphology of the assemblies was studied using scanning electron microscopy.
Characterization of the Non-uniform Reaction in Chemically Amplified Calix[4]resorcinarene Molecular Resist Thin Films
Authors: Prabhu Vivek M. , Kang Shuhui , Kline R. Joseph , DeLongchamp Dean M. , Fischer Daniel A. , Wu Wen-li , Satija Sushil K. , Bonnesen Peter V. , Sha Jing , Ober Christopher K.
Published: August 2011

The ccc stereoisomer-purified tert-butoxycarbonyloxy-protected calix[4]resorcinarene molecular resists blended with photoacid generator exhibit a non-uniform photoacid-catalyzed reaction in thin films. The surface displays a reduced reaction extent, compared with the bulk, with average surface-layer thickness 7.0 ± 1.8 nm determined by neutron reflectivity with deuterium-labelled tert-butoxycarbonyloxy groups. Ambient impurities (amines and organic bases) are known to quench surface reactions and contribute, but grazing-incidence X-ray diffraction shows an additional effect that the protected molecular resists are preferentially oriented at the surface, whereas the bulk of the film displays diffuse scattering representative of amorphous packing. The surface deprotection reaction and presence of photoacid were quantified by near-edge X-ray absorption fine-structure measurements.
Novel Intramolecular CAryl–S Bond Activation by an Electron Rich, Ring-Expanded-NHC-Rh centre: A Combined Experimental and DFT Study
Authors: Binobaid Abeer , Cavell Kingsley J. , Nechaev Mikhail S. , Kariuki Benson M.
Published: August 2011

The reaction of (o-MeSPh)-N-functionalized tetrahydropyrimidinium salts with KN(SiMe3)2 and [Rh(COD)Cl]2 in THF leads to the formation of a novel dimeric RhIII bis-carbene complex. The reaction involves the unexpected cleavage/oxidative addition of the aryl-sulfur bond to give dimeric metallated RhIII with bridging MeS< moieties. This unusual reaction is probably a consequence of the sterically imposing structure and strong donor capacity of ring-expanded N-heterocyclic carbenes (RE-NHCs). An X-ray structure of the [(Ph,DIPP-NHC)Rh(Cl)(SMe)2] product complex has been obtained, and DFT studies were undertaken to gain an insight into the reaction pathway.
Carbene-Based Lewis Pairs for Hydrogen Activation
Authors: Runyon Jason W. , Steinhof Oliver , Dias H. V. Rasika , Calabrese Joseph C. , Marshall William J. , Arduengo Anthony J.
Published: August 2011

A series of Lewis acid–base pairs containing sterically demanding carbenes were investigated for hydrogen activation that could potentially be reversible for use in hydrogen storage applications. When electron-rich boranes are employed as electrophiles, the imidazolium cation is reduced to a 2H-imidazoline (aminal). The aminals were synthesized independently by reduction of imidazolium cations with strong reducing agents. Carbocations were also found to act as electrophiles for hydrogen activation. Preliminary results revealed that it is possible to reduce an alcohol to an alkane using hydrogen gas as a reducing agent in these systems. Finally, it was demonstrated that a transition metal can be used as an electrophile to activate hydrogen through heterolytic cleavage.
N-Heterocyclic Carbene-Promoted Rauhut–Currier Reactions between Vinyl Sulfones and ?,?-Unsaturated Aldehydes
Authors: Atienza Roxanne L. , Scheidt Karl A.
Published: August 2011

N-heterocyclic carbenes (NHCs) promote the addition of 1,1-bis(phenylsulfonyl)ethylene to the α-position of α,β-unsaturated aldehydes. The proposed reaction pathway for this Rauhut–Currier-type reaction includes an unusual conjugate addition of an NHC to a bis-vinyl sulfone.
Abnormal N-heterocyclic Carbenes: More than Just Exceptionally Strong Donor Ligands
Authors: Krüger Anneke , Albrecht Martin
Published: August 2011

Complexes comprising a so-called abnormal carbene ligand, which displays pronounced mesoionic character, have recently been shown to be competent catalyst precursors for bond activation processes and oxidative transformations, including base-free alcohol oxidation and water oxidation. In this highlight we propose that these abnormal carbene ligands are not just useful spectator ligands but also actively participate in the bond activation step. This mode of action is partially based on the exceptionally strong donor properties of the ligand and, specifically, on the mesoionic character of these abnormal carbenes. The mesoionic properties provide a reservoir for charges and holes and thus induce efficient ligand-metal cooperativity, which is beneficial in particular for oxidation catalysis that involves concerted proton and electron transfer processes.
Quantification of sleep behavior and of its impact on the cross-talk between the brain and peripheral metabolism
Authors: Hanlon Erin C. , Van Cauter Eve
Published: August 2011

Rates of obesity have been steadily increasing, along with disorders commonly associated with obesity, such as cardiovascular disease and type II diabetes. Simultaneously, average sleep times have progressively decreased. Recently, evidence from both laboratory and epidemiologic studies has suggested that insufficient sleep may stimulate overeating and thus play a role in the current epidemic of obesity and diabetes. In the human sleep laboratory it is now possible to carefully control sleep behavior and study the link between sleep duration and alterations in circulating hormones involved in feeding behavior, glucose metabolism, hunger, and appetite. This article focuses on the methodologies used in experimental protocols that have examined modifications produced by sleep restriction (or extension) compared with normal sleep. The findings provide evidence that sleep restriction does indeed impair glucose metabolism and alters the cross-talk between the periphery and the brain, favoring excessive food intake. A better understanding of the adverse effects of sleep restriction on the CNS control of hunger and appetite may have important implications for public health.
Identification and characterization of a functional mitochondrial angiotensin system
Authors: Abadir Peter M. , Foster D. Brian , Crow Michael , Cooke Carol A. , Rucker Jasma J. , Jain Alka , Smith Barbara J. , Burks Tyesha N. , Cohn Ronald D. , Fedarko Neal S. , Carey Robert M. , O’Rourke Brian , Walston Jeremy D.
Published: August 2011

The renin-angiotensin (Ang) system regulates multiple physiological functions through Ang II type 1 and type 2 receptors. Prior studies suggest an intracellular pool of Ang II that may be released in an autocrine manner upon stretch to activate surface membrane Ang receptors. Alternatively, an intracellular renin-Ang system has been proposed, with a primary focus on nuclear Ang receptors. A mitochondrial Ang system has not been previously described. Here we report that functional Ang II type 2 receptors are present on mitochondrial inner membranes and are colocalized with endogenous Ang. We demonstrate that activation of the mitochondrial Ang system is coupled to mitochondrial nitric oxide production and can modulate respiration. In addition, we present evidence of age-related changes in mitochondrial Ang receptor expression, i.e., increased mitochondrial Ang II type 1 receptor and decreased type 2 receptor density that is reversed by chronic treatment with the Ang II type 1 receptor blocker losartan. The presence of a functional Ang system in human mitochondria provides a foundation for understanding the interaction between mitochondria and chronic disease states and reveals potential therapeutic targets for optimizing mitochondrial function and decreasing chronic disease burden with aging.
Permafrost carbon-climate feedbacks accelerate global warming
Authors: Koven Charles D. , Ringeval Bruno , Friedlingstein Pierre , Ciais Philippe , Cadule Patricia , Khvorostyanov Dmitry , Krinner Gerhard , Tarnocai Charles
Published: August 2011

Permafrost soils contain enormous amounts of organic carbon, which could act as a positive feedback to global climate change due to enhanced respiration rates with warming. We have used a terrestrial ecosystem model that includes permafrost carbon dynamics, inhibition of respiration in frozen soil layers, vertical mixing of soil carbon from surface to permafrost layers, and CH4emissions from flooded areas, and which better matches new circumpolar inventories of soil carbon stocks, to explore the potential for carbon-climate feedbacks at high latitudes. Contrary to model results for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), when permafrost processes are included, terrestrial ecosystems north of 60°N could shift from being a sink to a source of CO2by the end of the 21st century when forced by a Special Report on Emissions Scenarios (SRES) A2 climate change scenario. Between 1860 and 2100, the model response to combined CO2fertilization and climate change changes from a sink of 68 Pg to a 27 + -7 Pg sink to 4 + -18 Pg source, depending on the processes and parameter values used. The integrated change in carbon due to climate change shifts from near zero, which is within the range of previous model estimates, to a climate-induced loss of carbon by ecosystems in the range of 25 + -3 to 85 + -16 Pg C, depending on processes included in the model, with a best estimate of a 62 + -7 Pg C loss. Methane emissions from high-latitude regions are calculated to increase from 34 Tg CH4/y to 41–70 Tg CH4/y, with increases due to CO2fertilization, permafrost thaw, and warming-induced increased CH4flux densities partially offset by a reduction in wetland extent.
Proteasome assembly defect due to a proteasome subunit beta type 8 (PSMB8) mutation causes the autoinflammatory disorder, Nakajo-Nishimura syndrome
Authors: Arima Kazuhiko , Kinoshita Akira , Mishima Hiroyuki , Kanazawa Nobuo , Kaneko Takeumi , Mizushima Tsunehiro , Ichinose Kunihiro , Nakamura Hideki , Tsujino Akira , Kawakami Atsushi , Matsunaka Masahiro , Kasagi Shimpei , Kawano Seiji , Kumagai Shunichi , Ohmura Koichiro , Mimori Tsuneyo , Hirano Makito , Ueno Satoshi , Tanaka Keiko , Tanaka Masami , Toyoshima Itaru , Sugino Hirotoshi , Yamakawa Akio , Tanaka Keiji , Niikawa Norio , Furukawa Fukumi , Murata Shigeo , Eguchi Katsumi , Ida Hiroaki , Yoshiura Koh-ichiro
Published: August 2011

Nakajo-Nishimura syndrome (NNS) is a disorder that segregates in an autosomal recessive fashion. Symptoms include periodic fever, skin rash, partial lipomuscular atrophy, and joint contracture. Here, we report a mutation in the human proteasome subunit beta type 8 gene (PSMB8) that encodes the immunoproteasome subunit β5i in patients with NNS. This G201V mutation disrupts the β-sheet structure, protrudes from the loop that interfaces with the β4 subunit, and is in close proximity to the catalytic threonine residue. The β5i mutant is not efficiently incorporated during immunoproteasome biogenesis, resulting in reduced proteasome activity and accumulation of ubiquitinated and oxidized proteins within cells expressing immunoproteasomes. As a result, the level of interleukin (IL)-6 and IFN-γ inducible protein (IP)-10 in patient sera is markedly increased. Nuclear phosphorylated p38 and the secretion of IL-6 are increased in patient cells both in vitro and in vivo, which may account for the inflammatory response and periodic fever observed in these patients. These results show that a mutation within a proteasome subunit is the direct cause of a human disease and suggest that decreased proteasome activity can cause inflammation.
Energetics of Al
13
Keggin cluster compounds
Authors: Armstrong Christopher R. , Casey William H. , Navrotsky Alexandra
Published: August 2011

The
ϵ
-Al
13
Keggin aluminum hydroxide clusters are essential models in establishing molecular pathways for geochemical reactions. Enthalpies of formation are reported for two salts of aluminum centered ϵ-Keggin clusters, Al
13
selenate, (Na(AlO
4
)Al
12
(OH)
24
(SeO
4
)
4
•12H
2
O) and Al
13
sulfate, (NaAlO
4
Al
12
(OH)
24
(SO
4
)
4
•12H
2
O). The measured enthalpies of solution, ΔH
sol
, at 28 °C in 5 N HCl for the
ε
-Al
13
selenate and sulfate are −924.57 (± 3.83) and −944.30 ( ± 5.66) kJ·mol
-1
, respectively. The enthalpies of formation from the elements, Δ
H

f
,el

, for Al
13
selenate and sulfate are −19,656.35 ( ± 67.30) kJ·mol
-1
, and −20,892.39 ( ± 70.01) kJ·mol
-1
, respectively. In addition, Δ
H

f
,el

for sodium selenate decahydrate was calculated using data from high temperature oxide melt solution calorimetry measurements: −4,006.39 ( ± 11.91) kJ·mol
-1
. The formation of both
ε
-Al
13
Keggin cluster compounds is exothermic from oxide-based components but energetically unfavorable with respect to a gibbsite-based assemblage. To understand the relative affinity of the ϵ-Keggin clusters for selenate and sulfate, the enthalpy associated with two S-Se exchange reactions was calculated. In the solid state, selenium is favored in the Al
13
compound relative to the binary chalcogenate, while in 5 N HCl, sulfur is energetically favored in the cluster compound compared to the aqueous solution. This contribution represents the first thermodynamic study of
ε
-Al
13
cluster compounds and establishes a method for other such molecules, including the substituted versions that have been created for kinetic studies. Underscoring the importance of
ε
-Al
13
clusters in natural and anthropogenic systems, these data provide conclusive thermodynamic evidence that the Al
13
Keggin cluster is a crucial intermediate species in the formation pathway from aqueous aluminum monomers to aluminum hydroxide precipitates.
Exploring African American Women's Perceptions of a Social Marketing Campaign to Promote HIV Testing
Authors: Davis Kevin C. , Uhrig Jennifer , Bann Carla , Rupert Doug , Fraze Jami
Published: August 2011

We tested the reliability of a new perceived effectiveness scale for HIV testing media messages and examined whether perceived effectiveness of the Take Charge. Take the Test campaign is predictive of downstream outcomes. We used data from an online survey of young, single, African American women ( N = 428), collected from October 2007 to March 2008. Participants were recruited from online web panels maintained by Knowledge Networks and Survey Sampling International. The survey included a baseline and two longitudinal follow-ups at 2 and 6 weeks post-baseline. African American women aged 18 to 24 years, with annual incomes of less than $20,000, children at home, 3 or more sexual partners, and who only occasionally use condoms were more receptive to the materials. Perceived ad effectiveness significantly predicted 6- and 12-month HIV testing intentions at wave 3 of the survey. Perceived ad effectiveness is an important upstream indicator of ad success beyond impact that may occur from exposure alone. Measures of perceived ad effectiveness should be used to quantitatively pretest future HIV/AIDS-focused social marketing campaign messages. This study is also informative for media planning and other similar future interventions in terms of which types of messages and ads may be effective in promoting HIV/AIDS testing intentions and eventual behaviors.
The Mental Healthiness and Aging Initiative: Lessons from a Social Marketing-Informed Research Campaign in Kentucky
Authors: Kruger Tina M. , Murray Deborah , Zanjani Faika
Published: August 2011

The Mental Healthiness and Aging Initiative (MHAI) was a multifaceted social marketing-informed communication campaign designed to promote community awareness of mental health and aging. We hypothesized that MHAI would extend communication channels, providing a network for rapidly diffusing innovative mental health messages in Kentucky. Key messages discovered during formative research were incorporated into a communication campaign, which included a train-the-trainer curriculum, “Real Life Stories,” social advertising on radio and television, and a 12-month full-color calendar. We evaluated the impact of the train-the-trainer curriculum on the level of mental health and aging knowledge of Family and Consumer Science Agents in the Kentucky Cooperative Extension Service, who later diffused the campaign in local communities. Posttest scores showed a significant improvement ( p = .005) in objective knowledge about mental health and aging. Two months after diffusion of MHAI, a random telephone survey of 744 Kentucky residents found that respondents from the full-intervention counties more frequently reported feeling able to assist older adults with a potential mental illness ( p = .047) compared to residents in either partial intervention counties (social advertising only) or control counties (no contact). Lessons learned through the MHAI project can be applied by community mental health advocates to improve mental health outcomes.
“It's a Beautiful Day for Cancer”: An Innovative Communication Strategy to Engage Youth in Skin Cancer Prevention
Authors: Potente Sofia , McIver Jackie , Anderson Caroline , Coppa Kay
Published: August 2011

Despite 3 decades of traditional media campaigns to raise awareness about skin cancer, Australian youth continue to exhibit poor sun protection behaviors. This article reports on a creative promotional strategy that used entertainment-education and social media marketing to stimulate dialogue and address barriers to sun protection. The campaign centered on an ironic music video launched across multiple media channels, with a focus on social media sites. Process evaluation included campaign reach; and online surveys and thematic analysis of online conversations appraised sun protection attitudes and behaviors. The video received 250,000 views in 4 months, and online surveys identified positive differences between those exposed and not exposed to the video in attitudes toward skin cancer risk, perceived ability to avoid skin cancer by regularly using sun protection, and several self-reported sun protection behaviors, but no differences in peer perceptions of tanning. Of those who watched the video, 25% forwarded the video to friends, 44% reported that the video changed the way they felt about sun protection, and 19% of spontaneous online comments reported an intention to change behavior. The campaign results suggest that entertaining, peer-to-peer messages can be used to engage youth with an important health message for skin cancer prevention.
Bulk anisotropic nanocomposite magnets prepared by the thermo-mechanical processing of Nd3.6Pr5.4Fe83Co3B5 with different microstructures
Authors: Xu Lei , Liu Yanguo , Guo Defeng , Zhou Lipeng , Wang Fengqing , Zhang Haitian , Zhang Xiangyi
Published: August 2011

Bulk nanocomposite magnets with enhanced magnetic properties and (0 0 l) crystallographic texture for the (Nd,Pr)2Fe14B hard magnetic phase were prepared by thermo-mechanical process of Nd3.6Pr5.4Fe83Co3B5 ribbons. Ribbons with different microstructures, i.e. an amorphous state and amorphous matrix with a few α-(Fe,Co) nanocrystals, were employed in this study. Optimum magnetic properties were obtained in the magnets made by the hot deformation of the ribbons with nanocrystals in the amorphous matrix; the maximum energy product (BH)max = 118.6 kJ m−3. The magnets made from ribbons with a fully amorphous structure showed the largest magnetic anisotropy, and the values of (BH)max measured parallel (∥) and perpendicular (⊥) to the stress direction were ∼102.7 kJ m−3 and 79.6 kJ m−3, respectively. This study is of importance for the development of bulk anisotropic nanocomposite magnets with enhanced magnetic properties.
Comprehensive thermal characterization using ruby R fluorescence lines of sapphire and GaNE2-high Raman mode from Raman spectra in high-power flip-chip InGaN/GaN LEDs
Authors: Cui M , Zhou T F , Wang M R , Huang J , Huang H J , Zhang J P , Xu K , Yang H
Published: August 2011

A comprehensive temperature characterization method based on the GaNE
2-high Raman mode and sapphire ruby R fluorescence lines from Raman spectra was developed to analyse the thermal distribution and heat transfer process of high-power flip-chip InGaN/GaN LEDs (FC LEDs). Our analysis demonstrated that in addition to the known problem that the edges of mesa were always the hottest point of FC LEDs, which was due to the current crowding effect, a noteworthy temperature difference was first observed between the sapphire substrate and n-GaN when the injection current was above 300 mA. A ‘heat reservoir’ was suggested to occur at the interface between the sapphire and n-GaN due to poor thermal conductivity of sapphire when a large amount of heat from the hottest spot cannot be effectively transferred to the Si mount via the active region under high injection currents.
Explicit exact three-dimensional analytical temperature distribution in passively and actively cooled high-power fibre lasers
Authors: Ashoori V , Malakzadeh A
Published: August 2011

Efficiency and beam quality enhancement of high-power lasers require effective thermal management. In order to determine the temperature distribution in double-cladding high-power continuous wave fibre lasers, the heat transfer equation is analytically solved. Using the exact derived temperature distributions, the ultimate pump power before thermal damage, which is one of the key subjects of consideration in high-power laser design, is achieved.
Amorphous carbon film deposition on the inner surface of tubes using atmospheric pressure pulsed filamentary plasma source
Authors: Pothiraja Ramasamy , Bibinov Nikita , Awakowicz Peter
Published: August 2011

Uniform amorphous carbon film is deposited on the inner surface of quartz tubes having an inner diameter of 6 mm and an outer diameter of 8 mm. A pulsed filamentary plasma source is used for the deposition. Long plasma filaments (∼140 mm) are generated inside the tube in argon with methane admixture. FTIR–ATR, XRD, scanning electron microscope, laser scanning microscope and XPS analyses give the conclusion that deposited film is amorphous composed of non-hydrogenated sp2 carbon and hydrogenated sp3 carbon. Plasma is characterized using optical emission spectroscopy, voltage–current measurement, microphotography and numerical simulation. On the basis of observed plasma parameters, the kinetics of the film deposition process is discussed.
Thermophysical properties of carbon–argon and carbon–helium plasmas
Authors: Wang WeiZong , Rong MingZhe , Murphy Anthony B , Wu Yi , Spencer Joseph W , Yan Joseph D , Fang Michael T C
Published: August 2011

The calculated values of thermodynamic and transport properties of mixtures of carbon and argon, and carbon and helium, at high temperatures are presented in this paper. The thermodynamic properties are determined by the method of Gibbs free energy minimization, using standard thermodynamic tables. The transport properties including electron diffusion coefficients, viscosity, thermal conductivity and electrical conductivity are evaluated using the Chapman–Enskog method expanded up to the third-order approximation (second order for viscosity). Collision integrals are obtained using the most accurate cross-section data that could be located. The calculations, which assume local thermodynamic equilibrium, are performed for atmospheric pressure plasmas in the temperature range from 300 to 30 000 K for different pressures between 0.1 and 10 atm. The results are compared with those of previously published studies. Good agreement is found for pure argon and helium. Larger discrepancies occur for carbon and mixtures of carbon and argon, and carbon and helium; these are explained in terms of the different values of the collision integrals that were used. The results presented here are expected to be more accurate because of the improved collision integrals employed.
Angle-resolved electron probe microanalysis revisited
Authors: Cazaux J
Published: August 2011

In electron probe microanalysis (EPMA), the general strategy of characterizing specimens with their depth-dependent composition consists of changing the incident beam energy, E°, in order to change the effective thickness of the electron-irradiated volume. Initiated by two pioneering works an alternative way consists of changing the take-off angle of the measured characteristic x-ray line intensities but keeping unchanged the excitation conditions and the detector's position. In continuity to these previous investigations the present contribution suggests several improvements and applications for angle-resolved electron probe microanalysis (AR-EPMA). In particular, optimized angular conditions are defined and a new sample set-up is proposed. A simple model of Φ(z) function is also used to simulate various angular profiles relative to a variety of situations including inhomogeneous in-depth concentration profiles and multi-stratified samples, etc. Comparisons with published data are also performed when available and the relative advantages of AR-EPMA to conventional EPMA are discussed. The suggested device may be implemented into dedicated electron microprobes but its implementation into a SEM (+EDS equipment) seems the most promising for rapid and automatic acquisitions of angular profiles at selected points of a sample. The same device may also be used for other beam techniques such as Auger electron spectroscopy: AR-AES.