bluuebunny/crossref_metadata_2025 huggingface dataset:
Terahertz Spectroscopy
Authors: Wilke Ingrid
Published: October 2008

Terahertz spectroscopy has attracted great interest in recent years due to the development of improved terahertz radiation sources and terahertz radiation detectors as well as novel terahertz spectroscopy systems. This article discusses Fourier transform far‐infrared spectroscopy, backward‐wave oscillator terahertz spectroscopy, and time‐domain terahertz spectroscopy. Terahertz spectroscopy is spectroscopy with electromagnetic radiation in the terahertz (THz) frequency range. THz radiation is invisible. The THz frequency range is located between microwaves and the infrared. THz spectroscopy measures the dielectric properties of liquid and solid as well as inorganic and organic materials in the THz frequency range. Furthermore, THz spectroscopy is a method for vibrational and rotational spectroscopy of gases.

Specifications and merits of Far‐infrared Fourier transform spectroscopy, backward‐wave oscillator terahertz spectroscopy, and time‐domain terahertz spectroscopy for applications in analytical chemistry are compared. The frequency range, frequency resolution, and dynamic range of each method are discussed. Various measurement modalities such as transmission and reflection spectroscopy, phase‐sensitive spectroscopy, and time‐resolved THz spectroscopy are explained. The physical measurement principle of each method is discussed. The relationship between the measurement observed and the dielectric function of a material are presented for each method. Technical descriptions of the methods are provided. An overview on specific applications of THz spectroscopy is presented.
UV curing kinetics and mechanism of a highly branched polycarbosilane
Authors: Li Houbu , Zhang Litong , Cheng Laifei , Kang Haitao , Wang Yiguang
Published: October 2008

The UV curing process in both air and nitrogen atmosphere for the highly branched polycarbosilane system was investigated by differential scanning photo calorimeter. The UV cured products were characterized by Fourier‐transform infrared spectrometry (FTIR). By comparison with the FTIR results of the uncured liquid mixture and the cured samples, the possible cross‐linking reactions were determined. The kinetics of the curing systems was studied. The rate constant k was calculated based on the experimental results. The activation energies in different curing conditions were obtained. According to these results, it was learned that the mechanism for the UV curing in nitrogen was controlled by the photolysis of photoinitiator. Comparably, the UV curing process in air was complicated. It was affected by not only the photolysis of photoinitiator, but also oxygen and tripropane glycol diacrylate. Copyright © 2008 John Wiley & Sons, Ltd.
Tensile and elastic properties of triblock copolymer based on aramide end‐segments and polyether mid‐segments
Authors: Arun Araichimani , Gaymans Reinoud J.
Published: October 2008

The tensile and elastic behavior of triblock copolymers containing uniform aramide (TΦB) hard end‐segments (HS) and poly(tetramethylene oxide) (PTMO, Mn = 2900 g/mol) soft segments (SSs) was studied. The molecular weight of the copolymer was varied by changing the length of the soft mid‐segment; by extending the PTMO2900 with terephthalate units, the SS length was increased from 2900 g/mol to 21,000 g/mol and concurrently the aramide concentration decreased from 18 to 3 wt %. The mechanical properties were investigated by means of tensile testing, stress relaxation (SR) experiments, and cyclic tensile set (TS) tests. The E‐modulus was found to increase with increasing aramide content. The low molecular weight copolymers were brittle whereas the high molecular weight copolymers displayed large fracture strain values. The transition from brittle to ductile seemed to occur at a triblock copolymer molecular weight of 6600 g/mol. A strain‐induced crystallization was observed at strains above 250%, and both the fracture strain and stress were found to be highly dependant on the molecular weight of the copolymer. Cyclic tensile experiments showed that the materials had low TS values up to the strain hardening point. On the other hand, the SR data at 10% strain seemed to be little dependant on the molecular weight. The higher molecular weight copolymers did not display lower SR values than their low molecular weight counterparts. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Poly(acrylamide/laponite) nanocomposite hydrogels: Swelling and cationic dye adsorption properties
Authors: Li Peng , Siddaramaiah  , Kim Nam Hoon , Yoo Gye‐Hyoung , Lee Joong‐Hee
Published: October 2008

Super adsorbent polyacrylamide (PAAm)/nanoclay (laponite, Lap) hydrogels were prepared by in situ free radical polymerization of AAm in an aqueous solution with clay as a crosslinker. The swelling properties and water‐soluble cationic dye adsorption behaviors of the PAAm/laponite (PAAm/Lap) nanocomposite (NC) hydrogels were investigated. The parameters of swelling and diffusion of water in dye solutions were evaluated for the PAAm/Lap NC hydrogels. The adsorption behavior of the monovalent cationic dyes such as Basic Blue 12 (BB 12), Basic Blue 9 (BB 9), and Basic Violet 1 (BV 1), were studied on the NC hydrogels. The effects of the clay content of the hydrogel on its cationic dye uptake behavior were studied. The adsorption studies indicated that the rates of dye uptake by the NC hydrogels increased in the following order: BB 9 > BB 12 > BV 1. This order is similar to the swelling results of the PAAm/Lap NC hydrogel in the dye solutions. The equilibrium uptakes of the different dyes by the PAAm/Lap NC hydrogel were nearly the same. In the dye absorption studies, S‐type adsorption in the Giles classification system was found for the BB 12 and BV 1 dyes, whereas L‐type was observed for the BB 9 dye. After the heat treatment of PAAm/Lap, the rate of dye uptake and equilibrium dye uptake were increased. The NC hydrogels may be considered as a good candidate for environmental applications to retain more water and to remove dyes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and characterization of new polyamides derived from 1,3‐(4‐carboxy phenoxy) propane and aromatic diamines
Authors: Nasr‐Isfahani Hossein , Faghihi Khalil , Valikhani Nasim
Published: October 2008

Six new polyamides 5a‐f containing flexible trimethylene segments in the main chain were synthesized through the direct polycondensation reaction of 1,3‐(4‐carboxy phenoxy) propane 3 with six derivatives of aromatic diamines 4a‐f in a medium consisting of N‐methyl‐2‐pyrrolidone, triphenyl phosphite, calcium chloride, and pyridine. The polycondensation reaction produced a series of novel polyamides containing flexible trimethylene segments in the main chain in high yield with inherent viscosities between 0.32 and 0.68 dL/g. The resulted polymers were fully characterized by means of FTIR spectroscopy, elemental analyses, inherent viscosity, and solubility tests. Thermal properties of these polymers were investigated by using thermal gravimetric analysis (TGA) and differential thermal gravimetric (DTG). The glass‐transition temperatures of these polyamides were recorded between 165 and 190°C by differential scanning calorimetry, and the 10% weight loss temperatures were ranging from 360 to 430°C under nitrogen. 1,3‐(4‐Carboxy phenoxy) propane 3 was prepared from the reaction of 4‐hydroxy benzoic acid 1 with 1,3‐dibromo propane 2 in the presence of NaOH solution. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
New Mechanistic Insight in the Thermal Helix Inversion of Second‐Generation Molecular Motors
Authors: Klok Martin , Walko Martin , Geertsema Edzard M. , Ruangsupapichat Nopporn , Kistemaker Jos C. M. , Meetsma Auke , Feringa Ben L.
Published: October 2008

The introduction of dibenzocyclohepten‐5‐ylidene as part of a unidirectional light‐driven molecular motor allows a more complete picture of the pathway of thermal helix inversion to be developed. The most stable conformation is similar to that found in related motors in that it has, overall, an anti‐folded structure with the substituent at the stereogenic centre adopting an axial orientation. Photochemical cis/trans isomerisation at −40 °C results in the formation of an isomer in a syn‐folded conformation with the methyl group in an axial orientation. This contrasts with previous studies on related molecular rotary motors. The conformation of the higher energy intermediate typically observed for this class of compound is the anti‐folded conformation, in which the methyl group is in an equatorial orientation. This conformation is available through an energetically uphill upper half ring inversion of the observed photochemical product. However, this pathway competes with a second process that leads to the more stable anti‐folded conformation in which the methyl group is oriented axially. It has been shown that the conformations and pathways available for second‐generation molecular motors can be described by using similar overall geometries. Differences in the metastable high‐energy species are attributable to the relative energy and position on the reaction coordinate of the transition states. Kinetic studies on these new molecular motors thus provide important insights into the conformational dynamics of the rotation cycle.
Synthesis and Cannabinoid Receptor Activity of Ketoalkenes from Echinacea pallida and Nonnatural Analogues
Authors: Egger Michael , Pellett Patrina , Nickl Kathrin , Geiger Sarah , Graetz Stephanie , Seifert Roland , Heilmann Jörg , König Burkhard
Published: October 2008

Despite its popularity and widespread use, the efficacy of Echinacea products remains unclear and controversial. Among the various compounds isolated from Echinacea, ketoalkenes and ketoalkenynes exclusively found in the pale purple coneflower (E. pallida) are major components of the extracts. In contrast to E. purpurea alkamides, these compounds have not been synthesized and studied for immunostimulatory effects. We present a practical and useful synthetic approach to the ketoalkenes using palladium‐catalyzed cross‐coupling reactions and the pharmaceutical results at the human cannabinoid receptors. The synthetic route developed provides overall good yields for the ketoalkenes and is applicable to other natural products with similar 1,4‐diene motifs. No significant activity was observed at either receptor, indicating that the ketoalkenes from E. pallida are not responsible for immunomodulatory effects mediated via the cannabinergic system. However, newly synthesized non‐natural analogues showed micro‐molar potency at both cannabinoid receptors.
Asymmetric 1,4‐Addition of Oxazolones to Nitroalkenes by Bifunctional Cinchona Alkaloid Thiourea Organocatalysts: Synthesis of α,α‐Disubstituted α‐Amino Acids
Authors: Alemán José , Milelli Andrea , Cabrera Silvia , Reyes Efraim , Jørgensen Karl Anker
Published: October 2008

An easy and simple synthetic approach to optically active α,α‐quaternary α‐amino acids using asymmetric organocatalysis is presented. The addition of oxazolones to nitroalkenes catalyzed by thiourea cinchona derivatives provides the corresponding α,α‐quaternary α‐amino acid derivatives with good yields, excellent diastereoselectivities (up to 98 % dr), and from moderate to good enantioselectivities (up to 92 % ee). The reaction can be performed on a large scale. The optically active oxazolone–nitroalkene addition products can be opened in a one‐pot reaction to the corresponding ester–amide derivatives. Additional transformations are also presented, such as the synthesis of amino esters, amino acids, and transformation into 3,4‐disubstituted pyrrolidin‐2‐ones.
High‐performance liquid chromatographic chiral separation of β2‐homoamino acids
Authors: Pataj Zoltán , Berkecz Robert , Ilisz István , Misicka Aleksandra , Tymecka Dagmara , Fülöp Ferenc , Armstrong Daniel W. , Péter Antal
Published: October 2008

Reversed‐phase high‐performance liquid chromatographic methods were developed for the separation of enantiomers of eleven unnatural β2‐homoamino acids on chiral stationary phases containing macrocyclic glycopeptides (teicoplanin‐containing Chirobiotic T and T2) or the macrocyclic peptide teicoplanin aglycone (Chirobiotic TAG) as chiral selectors. The effects of the organic modifier, the mobile phase composition, temperature, and the structures of the analytes on the separations were investigated. Separations were carried out at constant mobile phase compositions in temperature range 7–45°C and the changes in enthalpy, Δ(ΔH°), entropy, Δ(ΔS°), and free energy, Δ(ΔG°), were calculated. The −Δ(ΔG°) values obtained on the three columns indicated that Chirobiotic TAG, without sugar units, may promote the interactions of the enantiomers of β2‐homoamino acids with branched alkyl or aryl side‐chains, whereas for β2‐homoamino acids with alkyl side‐chains Chirobiotic T and T2 seem to be more favorable. The elution sequence was determined in some cases and was observed to be R < S. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Modeling of the Intestinal Peptide Transporter hPepT1 and Analysis of Its Transport Capacities by Docking and Pharmacophore Mapping
Authors: Pedretti Alessandro , De Luca Laura , Marconi Cristina , Negrisoli Gianpaolo , Aldini Giancarlo , Vistoli Giulio
Published: October 2008

An early pharmacokinetic screen for peptidomimetic drugs should have the ability to predict molecules with high affinity for intestinal transporters, as peptide‐like derivatives are seldom absorbed passively. Hence, the first objective of this study was to generate a reliable model for the structure of the hPepT1 protein, which is the main intestinal transporter involved in the absorption of both dietary peptides and peptidomimetics. The modeling was based on the resolved structure of the homologous bacterial lactose permease LacY using a fragmental strategy. The interaction capacities of the hPepT1 model were explored by docking a set of 50 known ligands. Despite the known predilection of hPepT1 for hydrophobic ligands, docking results unveiled the key role of the polar interactions stabilized by charged termini, especially concerning the ammonium head group. The docking results were further verified by developing a pharmacophore model that confirmed the key features required for optimal hPepT1 affinity. The consistency of the docking results and the agreement with the pharmacophore model afford an encouraging validation for the proposed model and suggest that it can be exploited to design peptide‐like molecules with an improved affinity for such a transporter.
IRMPD Spectroscopy of a Protonated, Phosphorylated Dipeptide
Authors: Correia Catarina F. , Clavaguera Carine , Erlekam Undine , Scuderi Debora , Ohanessian Gilles
Published: October 2008

The protonated, phosphorylated dipeptide [GpY+H]+ is characterized by mid‐infrared multiple‐photon dissociation (IRMPD) spectroscopy and quantum‐chemical calculations. The ions are generated in an external electrospray source and analyzed in a Fourier transform ion cyclotron resonance mass spectrometer, and their fragmentation is induced by resonant absorption of multiple photons emitted by a tunable free‐electron laser. The IRMPD spectra are recorded in the 900–1730 cm−1 range and compared to the absorption spectra computed for the lowest energy structures. A detailed calibration of computational levels, including B3LYP‐D and coupled cluster, is carried out to obtain reliable relative energies of the low‐energy conformers. It turns out that a single structure can be invoked to assign the IRMPD spectrum. Protonation at the N terminus leads to the formation of a strong ionic hydrogen bond with the phosphate PO group in all low‐energy structures. This leads to a PO stretching frequency for [GpY+H]+ that is closer to that of [pS+H]+ than to that of [pY+H]+ and thus demonstrates the sensitivity of this mode to the phosphate environment. The COP phosphate ester stretching mode is confirmed to be an intrinsic diagnostic for identification of which type of amino acid is phosphorylated.
Tolerance and reactivity of NK cells: Two sides of the same coin?
Authors: Held Werner
Published: October 2008

NK cells can kill transformed, infected and stressed cells while most normal cells are spared. NK cells are activated by various endogenous self‐ligands, some of which are actually expressed by normal cells. Thus, NK cells are inherently self‐reactive and consequently, potentially auto‐aggressive. How these cells are prevented from attacking normal cells while ensuring reactivity to diseased cells is a major unresolved question for NK‐cell biologists.
Beyond licensing and disarming: A quantitative view on NK‐cell education
Authors: Brodin Petter , Höglund Petter
Published: October 2008

In this article, we will move beyond the current controversy of different models for NK‐cell education and instead discuss the properties characterizing MHC class I‐guided functional development of NK cells. We will argue that this development, which represents the endpoint of NK‐cell education, is a quantitative and dynamic, and perhaps even reversible, process.
Aluminium Complexes of a Phenoxyimine Ligand with a Pendant Imidazolium Moiety: Synthesis, Characterisation and Evidence for Hydrogen Bonding in Solution
Authors: Milione Stefano , Grisi Fabia , Centore Roberto , Tuzi Angela
Published: October 2008

Novel alkylaluminium complexes (phim)AlMe2 (1) and(phimid)AlR2+Br– [R = Me (2), R = iBu (3)] bearing the Schiff base ligands 3,5‐tBu2‐2‐(OH)C6H2CH=NiPr (phim‐H) and3,5‐tBu2‐2‐(OH)C6H2CH=NCH2CH2[CH(NCHCHNiPr)]Br(phimid‐H·Br) have been prepared and fully characterised. Complexes 1–3 each have a tetrahedral structure, with the aluminium atom surrounded by the oxygen and nitrogen atoms of the chelating ligand and two alkyl groups. The structures of phimid‐H·Br and of complex 1 have been determined by X‐ray diffraction studies. Investigation of the solution structures of 1–3 by 1H NMR spectroscopy revealed that the coordinated phimid ligand is involved in hydrogen bonding with bromide anion. Treatment of 1 with B(C6F5)3 led smoothly to (phim)Al(C6F5)Me (4) by transfer of a C6F5 group from MeB(C6F5)3– to the initially formed coordinatively unsaturated cationic intermediate. In contrast, treatment of 2 with one equiv. of B(C6F5)3 afforded the cationic monomethyl species (phimid)AlMeBr+ MeB(C6F5)3– (5), stabilised by the coordination of the bromide anion acting as a Lewis base.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
On the Effect of Coordination and Protonation Preferences in the Amphiphilic Behavior of Metallosurfactants with Asymmetric Headgroups
Authors: Lesh Frank D. , Hindo Sarmad Sahiel , Heeg Mary Jane , Allard Marco M. , Jain Prateek , Peng Bo , Hryhorczuk Lew , Verani Cláudio N.
Published: October 2008

The metallosurfactants [NiII(LtBuODA)(OAc)] (1), [NiII(LtBuODA)2](2), [CuII(HLtBuODA)(LtBuODA)]ClO4·CH3OH (3), and [ZnII(HLtBuODA)2](ClO4)2 (4) {where HLtBuODA = 2,4‐di‐tert‐butyl‐6‐[(octadecyl(pyridin‐2‐ylmethyl)amino)methyl]phenol}were synthesized and characterized in an attempt to establish how coordination modes and protonation preferences relate to amphiphilic behavior. The archetypical compounds [NiII(LtBuI)(OAc)]·CH3OH (5), [NiII(LA)2]·CH3OH·H2O (6), [NiII(LtBuA)2]·2CH3OH (7), [CuII(HLtBuA)(LtBuA)]ClO4 (8), and [ZnII(HLtBuA)(LtBuA)]ClO4 (9) were synthesized to model the stoichiometric, coordination, and protonation chemistry in the waxy metallosurfactants 1–4. Detailed data analysis and comparison between 1–4 and 5–9 involved mass spectrometric and spectroscopic methods along with crystallographic determination of 5 (P21/c), 6 (P$\bar {1}$), 7 (P21/c), 8′ (the analogue of 8 with tetraphenylborate counterions, P21/c), and 9 (P$\bar {1}$). DFT calculations were used to identify the frontier orbitals, polarizability, and dipole moments. Species 1–4 had their compression isotherms measured and monitored by means of Brewster angle miscroscopy. The nickel‐containing 1 is square planar, while 2 has a neutral octahedral core with two deprotonated ligands. The five‐coordinate copper‐containing 3 has a monocationic core associated with one protonated ligand, whereas the dicationic zinc‐containing 4 has a four‐coordinate core with protonated ligands. It was observed that Langmuir films of 1 display approximately half of the average molecular area observed for 2–4 and that the flexibility and coordination number of the cores foster distinctive collapse mechanisms. Therefore, careful choice of the metal ion leads to control of surfactant‐to‐metal ratio, selection of coordination modes and structural properties, and the understanding of the protonation preferences of the ligands. This information will play an important role in the development of metal‐containing responsive films. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
A Combined NMR, Computational, and HPLC Study of the Inclusion of Aromatic and Fluoroaromatic Compounds in Cyclodextrins as a Model for Studying Carbohydrate–Aromatic Interactions
Authors: Ribeiro Joao P. , Bacchi Sergio , Dell'Anna Gianmaria , Morando Maria , Cañada F. Javier , Cozzi Franco , Jiménez‐Barbero Jesús
Published: October 2008

A combined NMR, computational, and HPLC study of the inclusion of aromatic and fluoroaromatic compounds in cyclodextrins has been carried out with the aim of studying this process as a model for carbohydrate···aromatic interactions. NMR experiments showed that although β‐CD formed an inclusion complex with benzene, no stable inclusion adduct was formed with hexafluorobenzene. MM3* calculations confirmed these data and, when extended to naphthalene, anthracene, phenanthrene, and their partially and fully fluorinated analogues, showed that β‐CD formed inclusion adducts only with the hydrocarbons, whereas the partially fluorinated derivatives were shown to enter the cavity only with their non‐fluorinated part, and the perfluoro compounds were not included. HPLC experiments, carried out by eluting these compounds through CD‐modified HPLC columns, also confirmed these results, at least with the mono‐ and bicyclic arenes. Indeed, the elution of these derivatives showed that the efficiency of the inclusion, as determined by comparing HPLC retention times, decreased on passing from hydrocarbons to partially fluorinated compounds, and reached a minimum with perfluorinated derivatives. In contrast with this general trend, 1,2,3,4‐tetrafluoroanthracene had longer retentions times on β‐ and γ‐CD‐modified HPLC columns than anthracene, possibly for solubility reasons. As a whole, these results were interpreted in terms of carbohydrate···aromatic interactions between the C5–H5 bonds on the hydrophobic faces of the sugars and the π electrons of the aromatic partner. The interactions seem to have an important dispersive component.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Convenient Microwave‐Assisted Synthesis of 5‐Functionalized 1,2,4‐Triazolium Ylides Starting from N′,N′‐Disubstituted Carbohydrazonamides
Authors: Khankischpur Mehdi , Kurz Thomas
Published: October 2008

5‐Functionalized 1,2,4‐triazolium ylides have been prepared in good yields and in very short reaction times by reacting N′,N′‐disubstituted carbohydrazonamides with 1,1′‐carbonylbis(1,2,4‐triazole), 1,1′‐thiocarbonyldiimidazole or diphenyl N‐cyanimidocarbonate under microwave irradiation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Optimization of hydrophobic interaction chromatography using a mathematical model of elution curves of a protein mixture
Authors: Lienqueo María Elena , Shene Carolina , Asenjo Juan
Published: October 2008

This paper describes a methodology for optimizing performance of hydrophobic interaction chromatography (HIC) for protein mixtures in which Rate Model simulations and evaluation of cost function are used. The system under study was HIC of a two‐protein mixture (α‐chymotrypsin and α‐amylase), carried out with different conditions (gradient steepness, salt, concentration, volume of sample, pH, type of matrix, and flow rates). Parameters in the rate model were obtained from different sources. Mass transfer parameters (Reynolds, Peclet, and Biot numbers) were calculated using empirical correlations. Under the experimental conditions Re number was small (0.23) and axial dispersion negligible (PeL > 300). Mass transfer was controlled by intraparticle diffusion (Bi > 50). The model assumes that equilibrium constant (b) in the Langmuir isotherm was salt concentration (I) dependent [b(I)]. Parameters in the relationship for b(I) were estimated from experimental single protein elution curves and used to simulate protein mixtures. Rate model simulations showed that if protein sample load to the column was below 1 mg, displacement effects were negligible; in other cases protein interactions would limit the proposed mathematical description of HIC. The calibrated Rate Model successfully predicted elution curves of the protein mixture with deviations lower than 6 × 10−4 absorbance units. The model was also able to predict that the Butyl Sepharose—NaCl 4 M system allowed to obtain the highest resolution (>1) for the two‐protein mixture evaluated. The cost function built for optimizing the performance of HIC considers yield, purity, concentration, and the time needed to accomplish the separation. This function contains two types of parameters that have to be determined. The ones dependent on the HIC system and process conditions were obtained from simulations of elution curves of the two‐protein mixture, by the calibrated Rate Model. The other parameters are dependent on characteristic and quality of the protein product; these were assumed for illustration purpose. Minimization of the cost function allows determination of flow rate, gradient steepness, and the fraction of eluted peak that has to be collected. Novelty of the present work is in showing how parameters in the fundamentally based Rate Model for HIC can be calibrated and how simulations can be used for the optimization of process conditions for the separation of a protein mixture. Copyright © 2008 John Wiley & Sons, Ltd.
Assessment of grassland degradation in Guinan county, Qinghai Province, China, in the past 30 years
Authors: FENG Y. , LU Q. , TOKOLA T. , LIU H. , WANG X.
Published: October 2008

In this study, the quantity, quality and spatial changes of grassland in Guinan County, Qinghai Province, China, were assessed by means of interpreting remote sensing satellite imagery during four key periods (1976, 1996, 2001 and 2006) as well as by applying various methods of analysis such as a transition matrix, fractal dimension, dynamic degree modelling and a spatial model of land use change. The assessment results were summarized from three positions. First, grassland area decreased and grassland quality degraded in the past 30 years. The decreased rate of area and the degraded degree of quality were significantly different during different time periods. Both the decline in grassland area and the degradation in grassland quality were determined to be most severe from 1976 to 1996 (especially for high density grassland) and moderate from 1996 to 2001 and from 2001 to 2006. Second, the grassland centre of gravity trended to move along a general southeastern direction; however, the direction of movement of grassland centre of gravity displayed multidirectional and irregular tendencies during different time periods. The primary reason that caused this situation was that the cultivation and protection of grasslands occurred during successive turns. Third, the change observed in grassland behaviour was shaped by a range of factors including natural forces as well as human‐induced disturbances. The dominant factor was primarily human activity. The transition matrix method, the fractal dimension method and the spatial model of land use change method showed similar results. Copyright © 2008 John Wiley & Sons, Ltd.
Controlled Grafting‐From of Polystyrene on Polybutadiene: Mechanism and Spectroscopic Evidence of the Functionalization of Polybutadiene with 4‐Oxo‐TEMPO
Authors: Bonilla‐Cruz José , Saldívar‐Guerra Enrique , Torres‐Lubián José Román , Guerrero‐Santos Ramiro , López‐Carpy Bruno , Luna‐Bárcenas Gabriel
Published: October 2008

Polybutadienes functionalized with nitroxide (multifunctional macroalkoxyamines) were synthesized by heating PB in the presence of a nitroxide radical (N) and a radical initiator (I). Another functional PB was prepared by using only nitroxide. These functionalized polymers were characterized by FT‐IR, GPC, and NMR and as a result it was possible to elucidate the resulting structure of the macroalkoxyamines, to propose likely functionalization mechanisms, and to estimate functionalization characteristics. One of these polymers was heated in the presence of styrene to obtain PB grafted with polystyrene, which was characterized in detail in order to investigate its structure and level of grafting control.

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Macromol. Chem. Phys. 21/2008
Authors: Gallyamov Marat O. , Chaschin Ivan S. , Gamzazade Arif I. , Khokhlov Alexei R.
Published: October 2008

Cover: The cover image presents scanning force microscopy (SFM) images of individual chitosan molecules deposited from supercritical (sc) CO2 (A: Ca‐chitosan, B: pretreated sample). The direct deposition method from sc CO2 is the most gentle way for macromolecular transfer to occur from a solution (3D) onto a surface (2D) from the viewpoint of the solvent removal problem. Further details can be found in the article by M. O. Gallyamov,* I. S. Chaschin, A. I. Gamzazade,* and A. R. Khokhlov on page 2204.
On the formation and persistence of superfog in woodland smoke
Authors: Achtemeier Gary L.
Published: October 2008

Dense fogs, comparable to historical fogs in England, have been implicated in numerous roadway accidents in the southern United States. Many of the fogs have occurred in association with prescribed burning. Direct measurements of superfog (fog reducing visibility to less than 3 m) were taken during burning of forest litter on 22 March 2003. Visibility was measured at 0.1 m implying an extinction coefficient of 39 120 km−1. The number of condensation nuclei required for fog to produce the observed visibility was about 1% of the number of particles released in wood smoke as reported in the literature. A recursive non‐gradient mixing model shows (1) maximum excess liquid water (LWC) released was approximately 7.0 g kg−1, 23 times the LWC in natural fog, (2) superfog can form at the site of combustion then continue to form as it drifts downwind, and (3) superfog can modify air mass stability near the ground and persist for hours until dispersed by changing wind conditions or by solar heating after sunrise. Published in 2008 by John Wiley & Sons Ltd.
Thioredoxin system inhibitors as mediators of apoptosis for cancer therapy
Authors: Tonissen Kathryn F. , Di Trapani Giovanna
Published: October 2008

The thioredoxin (Trx) system is a major antioxidant system integral to maintaining the intracellular redox state. It contains Trx, a redox active protein, which regulates the activity of various enzymes including those that function to counteract oxidative stress within the cell. Trx can also scavenge reactive oxygen species (ROS) and directly inhibits proapoptotic proteins such as apoptosis signal‐regulating kinase 1 (ASK1). The oxidized form of Trx is reduced by thioredoxin reductase (TrxR). The cytoplasm and mitochondria contain equivalent Trx systems and inhibition of either system can lead to activation of apoptotic signaling pathways. There are a number of inhibitors with chemotherapy applications that target either Trx or TrxR to induce apoptosis in cancer cells. Suberoylanilide hydroxamic acid (SAHA) is effective against many cancer cells and functions by up‐regulating an endogenous inhibitor of Trx. Other compounds target the selenocysteine‐containing active site of TrxR. These include gold compounds, platinum compounds, arsenic trioxide, motexafin gadolinium, nitrous compounds, and various flavonoids. Inhibition of TrxR leads to an accumulation of oxidized Trx resulting in cellular conditions that promote apoptosis. In addition, some compounds also convert TrxR to a ROS generating enzyme. The role of Trx system inhibitors in cancer therapy is discussed in this review.
Theoretical estimation of the electron affinity of enolate radicals
Authors: González‐Rivas Nelly , Cedillo Andrés
Published: October 2008

The electron affinity of some enolate radicals coming from methyl substituted five‐ and six‐member carbon rings is estimated by the use of the density functional theory model B3LYP/6‐311++g(3df,3pd). The computed electron affinities show an excellent agreement with recent gas phase experimental results (Walthall et al., J Phys Chem A, 2005, 109, 8785). The comparison shows differences around 1 kcal/mol for most of the compounds, except for four substituted compounds whose methyl group is neighbor to the double bond, in this case the variation increases up to 3 kcal/mol. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Diamide derivatives as photostabilizers for plasticized poly(vinyl chloride)
Authors: Rabie S.T. , Khalil A.M. , Nada A.A.
Published: October 2008

Some diamide derivatives have been prepared, characterized, and investigated as photostabilizers for plasticized poly(vinyl chloride) (PVC), containing dioctyl phthalate and dibutyl phthalate in a concentration of 30% by weight of the polymer. The stabilizing efficiency of the prepared diamides was evaluated by determining the weight loss percentage that resulted from HCl evolution during the photodegradation process. Moreover, the efficiency was evaluated by determining the amount of gel formed as well as the intrinsic viscosity of the soluble fractions of the photodegraded polymer. The extent of discoloration of the photodegraded stabilized and plasticized PVC was also investigated. The stabilization mechanism and the effect of plasticizers on the photostability of PVC are discussed. J. Vinyl Addit. Technol., 2008. © 2008 Society of Plastics Engineers
Are Patient Rights to Information and Self‐Determination in Diagnostic Genetic Testing Upheld? A Comparison Of Patients’ and Providers’ Perceptions
Authors: Nyrhinen Tarja , Hietala Marja , Puukka Pauli , Leino‐Kilpi Helena
Published: October 2008

This study assessed how the patient's right to receive information and the right to self‐determination were followed during diagnostic testing, according to the perceptions of patients and parents of tested children (group 1, n = 106) and healthcare personnel (group 2, n = 162). Data were collected in three Finnish university hospitals using a questionnaire. Results revealed one between group difference: patients/parents agreed more strongly than did personnel that self‐determination was followed before testing. Within groups included: patients/parents had stronger agreement that self‐determination was followed before testing than after testing; personnel had stronger agreement about information received after testing than before testing, and they had weaker agreement about how well self‐determination was followed before testing than after testing. Received information was experienced as similar both before and after testing and by patients/parents and by personnel. Providing adequate time to consider whether or not to be tested and giving more support to patients after testing would promote the rights of patients. Furthermore, assessment of personnel characteristics is needed to determine, for example, the kinds of value conflicts that exist between personnel's own values and patients’ values.
Life Trajectories, Genetic Testing, and Risk Reduction Decisions in 18–39 Year Old Women at Risk for Hereditary Breast and Ovarian Cancer
Authors: Hamilton Rebekah , Williams Janet K. , Bowers Barbara J. , Calzone Kathleen
Published: October 2008

This qualitative study identified four life trajectories that influenced the decision in young women to have genetic testing for mutations in BRCA1/2 and subsequent risk reduction decisions after receiving a positive mutation result. Fifty nine women between the ages of 18–39 years were interviewed in this grounded theory study, 44 of those tested were found to have a mutation in either BRCA1 or BRCA2. Of those with a mutation, 23 had no history of cancer and 21 had a breast cancer diagnosis. Analysis of the 44 participants tested found that risk reducing decisions were related to the life trajectories that preceded genetic testing. These life trajectories included: 1) Long‐standing awareness of breast cancer in the family, 2) Loss of one's mother to breast cancer at a young age, 3) Expression of concern by a health care provider, and 4) Personal diagnosis of breast cancer. Understanding possible influences behind decision making for genetic testing and risk reduction in young women may assist health care providers in offering age appropriate guidance and support.
Cutaneous afferent C‐fibers regenerating along the distal nerve stump after crush lesion show two types of cold sensitivity
Authors: Grossmann Lydia , Gorodetskaya Natalia , Teliban Alina , Baron Ralf , Jänig Wilfrid
Published: October 2008

Cutaneous C‐fiber afferents show two distinct types of cold sensitivity corresponding to non‐noxious and noxious cold sensations. Here, responses to cold stimulation of afferent fibers regenerating in the rat sural nerve were studied in vivo 7–14 days after nerve crush and compared with responses to mechanical and heat stimulation. The physiological stimuli were applied to the sural nerve at or distal to the lesion site. Ectopic activity was evoked in 43% of 98 A‐fibers (all mechanosensitive; a few additionally weakly thermosensitive). Ectopic activity was evoked in 127 (49.2%) of 258 electrically identified C‐fibers by the physiological stimuli. Eight C‐fibers were spontaneously active only. Of the 127 C‐fibers, 46% had one of two distinct response patterns to cooling: (1) type 1 cold‐sensitive C‐fibers (n=29) had a high rate of activity at 28°C on the nerve surface and showed graded responses to cooling with maximal discharge rates of 11.5±1.1imp/s. This activity was completely inhibited by heating, while 12/29 fibers were also excited at high threshold (median 48°C) by heating. Only one type 1 cold‐sensitive C‐fiber was mechanosensitive. (2) Type 2 cold‐sensitive C‐fibers (n=29) were silent or showed a low rate of activity at 28°C, had a high threshold (median 5°C) and low maximal discharge rates (2.4±0.4imp/s) to cooling. They were also heat‐sensitive (n=25) and/or mechanosensitive (n=20). These C‐fibers were, apart from their cold sensitivity, functionally indistinguishable from C‐fibers with mechano‐ and/or heat sensitivity only. Thus regenerating cutaneous C‐fibers show two types of cold sensitivity similar to those observed in intact skin: fibers of one group are predominantly sensitive to cooling, whereas the others are polymodal.
ON INFINITESIMAL TEICHMÜLLER SPACE
Authors: JINHUA FAN , JIXIU CHEN
Published: October 2008

Much research has been done on the geometry of Teichmüller space and Hamilton sequences of extremal Beltrami differentials. This paper discusses some problems concerning infinitesimal Teichmüller geodesic discs and Hamilton sequences of extremal Beltrami differentials in the tangent space of an infinite-dimensional Teichmüller space.
OPERATOR KERNELS FOR IRREDUCIBLE REPRESENTATIONS OF EXPONENTIAL LIE GROUPS
Authors: POGUNTKE DETLEV
Published: October 2008

A nine-dimensional exponential Lie group G and a linear form ℓ on the Lie algebra of G are presented such that for all Pukanszky polarizations 𝔭 at ℓ the canonically associated unitary representation ρ=ρ(ℓ,𝔭) of G has the property that ρ(ℒ1(G)) does not contain any nonzero operator given by a compactly supported kernel function. This example shows that one of Leptin’s results is wrong, and it cannot be repaired.
ON A RECENT GENERALIZATION OF SEMIPERFECT RINGS
Authors: BÜYÜKAŞIK ENGIN , LOMP CHRISTIAN
Published: October 2008

In a recent paper by Wang and Ding, it was stated that any ring which is generalized supplemented as a left module over itself is semiperfect. The purpose of this note is to show that Wang and Ding’s claim is not true and that the class of generalized supplemented rings lies properly between the classes of semilocal and semiperfect rings. Moreover, we propose a corrected version of the theorem by introducing a wider notion of ‘local’ for submodules.
ON NEAR EXACT BANACH FRAMES IN BANACH SPACES
Authors: JAIN P. K. , KAUSHIK S. K. , GUPTA NISHA
Published: October 2008

Near exact Banach frames are introduced and studied, and examples demonstrating the existence of near exact Banach frames are given. Also, a sufficient condition for a Banach frame to be near exact is obtained. Further, we consider block perturbation of retro Banach frames, and prove that a block perturbation of a retro Banach frame is also a retro Banach frame. Finally, it is proved that if E and F are both Banach spaces having Banach frames, then the product space E×F has an exact Banach frame.
Population fluctuations of light-attracted chrysomelid beetles in relation to supra-annual environmental changes in a Bornean rainforest
Authors: Kishimoto-Yamada K. , Itioka T. , Sakai S. , Momose K. , Nagamitsu T. , Kaliang H. , Meleng P. , Chong L. , Hamid Karim A.A. , Yamane S. , Kato M. , Reid C.A.M. , Nakashizuka T. , Inoue T.
Published: October 2008

In Southeast Asian tropical rainforests, two events, severe droughts associated with the El Niño-Southern Oscillation and general flowering, a type of community-wide mass flowering, occur at irregular, supra-annual intervals. The relationship between these two supra-annual events and patterns of insect population fluctuations has yet to be clearly elucidated. Leaf beetles (Chrysomelidae) are major herbivores and flower-visitors of canopy trees, affecting their growth and reproduction and, in turn, affected by tree phenology; but their population fluctuations in the Southeast Asian tropics have not been extensively investigated. We examined population fluctuation patterns of the 34 most dominant chrysomelid species in relation to the two supra-annual events by conducting monthly light-trapping over seven years in a lowland dipterocarp forest in Borneo. Our results showed large community variation in population fluctuation patterns and a supra-annual (between-year) variation in abundance for most of the dominant chrysomelids that was significantly larger than the annual (within-year) variation. Specifically, in response to a severe drought in 1998, chrysomelid species exhibited different population responses. These results show that population fluctuations of individual species, rather than the entire assemblage, must be analyzed to determine the effects of changes in environmental conditions on the structure of insect assemblages in the tropics, especially in regions where supra-annual environmental changes are relatively more important than seasonal changes.
ASSOCIATION OF SOCIOECONOMIC STATUS WITH SUCCESSFUL AGEING: DIFFERENCES IN THE COMPONENTS OF SUCCESSFUL AGEING
Authors: JANG SOONG-NANG , CHOI YONG-JUN , KIM DONG-HYUN
Published: October 2008

This study sought to determine which factors among the indicators of socioeconomic status have the most influence on physical, mental and social functions, and on subjective well-being, all of which are components of successful ageing. A representative random sample of 1825 persons aged 65 years or older was surveyed by face-to-face interview. Socioeconomic status was measured by educational level, family household income, personal income and property ownership. The factors measured were chronic diseases, activities of daily living (ADL) for physical functioning, history of mental disease, Mini-Mental Status Examination questionnaire (MMSE) scores for mental functioning, social activity participation per week for social functioning, and the Philadelphia Geriatric Center Morale Scale (PGCMS) for subjective well-being. Multiple logistic regression analyses were performed. Education level was the most important factor in physical and mental functioning, whereas personal income was the most important in social functioning. Educational level, household income and personal income were significantly associated with subjective well-being as assessed by PGCMS scores. Subjects who demonstrated successful ageing were more likely to have a higher education and higher personal income. The results point to the importance of focusing on disparities in each component of successful ageing, which may point to appropriate health-promotion strategies for eliminating inequality in successful ageing.
Temperature measurement of warm-dense-matter generated by intense heavy-ion beams
Authors: Ni P.A. , Kulish M.I. , Mintsev V. , Nikolaev D.N. , Ternovoi V.Ya. , Hoffmann D.H.H. , Udrea S. , Hug A. , Tahir N.A. , Varentsov D.
Published: October 2008

This paper describes a fast multi-channel radiation pyrometer that was developed for warm dense-matter experiments with intense heavy ion beams at the Gesellschaft für Schwerionenforschung mbH (GSI). The pyrometer is capable of measuring brightness temperatures from 2000 K to 50,000 K, at six wavelengths in the visible and near-infrared parts of the spectrum, with 5 ns temporal resolution, and several micrometers spatial resolution. The pyrometer's spectral discrimination technique is based on interference filters, which also act as mirrors to allow for simultaneous spectral discrimination of the same ray at multiple wavelengths.
The inextensible string
Authors: Walker A. G.
Published: October 2008

An object to which we were all introduced at an early stage in mechanics is the inextensible string. This appears frequently without causing much trouble, but there is one type of problem which, in my opinion, stands apart from the rest, and which certainly caused me a lot of trouble. Such a problem is when impulses are given to a system which includes an inextensible string, as, for example, a system consisting of two rigid parts joined by a string. If an impulse is applied to one of these parts, an impulsive tension (T) may be set up in the string, which, in turn, gives an impulse to the other part. One new quantity, T, has appeared, and one equation in addition to the ordinary dynamical equations is thus required before the problem of finding the change in motion of the system can be solved. It is at this stage that opinions can differ, for this extra equation depends essentially upon what concept of an inextensible string is being adopted, and there is more than one. The usual procedure is to employ a “geometrical equation” based upon the argument that the two ends must have equal component velocities in the line of the string as long as the string is taut. This seems almost obvious when described in such general terms, and is followed by such eminent writers as Routh and Loney, amongst others. I suggest, however, that this method implies a concept which leads to results contrary to common-sense and to everyday experience. This is best illustrated by a simple example.
On the Number of Distinct Terms in the Expansion of Symmetric and Skew Determinants
Authors: Aitken A. C.
Published: October 2008

The expansion of the symmetric determinant

is familiar. It is of six terms; but one term, fgh, is duplicated, and so there are five distinct terms. If we ascertain the number un of distinct terms in the expansions of symmetric determinants of increasing order, we find the following sequence of values, for n = 0, 1, 2, …,

where by convention u0 = 1.
An Expansion for xn + yn
Authors: Waterson A.
Published: October 2008

In this note an expansion is found for the expression xn + yn in terms of x + y and of xy. Two illustrative applications are appended.
Some elementary inequalities in function theory
Authors: Macintyre A. J. , Rogosinski W. W.
Published: October 2008

Let 0 < r < 1 and let f(z) be regular for |z| ≤ 1.

Then from Cauchy's integral

we have the inequality
Some properties of the curve of constant bearing
Authors: Martin D.
Published: October 2008

If Z is a fixed point on the surface of the earth (assumed spherical) and P is the North Pole, then the locus of a point X, which moves in such a way that the angle α between the great circle arcs PX, ZX is constant, is called a curve of constant bearing.