bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of amphiphilic multiblock and triblock copolymers of polydimethylsiloxane and poly(N,N‐dimethylacrylamide)
Authors: Pavlović Dražen , Linhardt Jeffrey G. , Künzler Jay F. , Shipp Devon A. 
Published: September 2008

AbstractThe synthesis and spectroscopic characterization of a new family of amphiphilic multiblock and triblock copolymers is described. The synthetic methodology rests on the preparation of telechelic multifunctional and difunctional chain transfer agents easily available in two synthetic steps from commercially available polydimethylsiloxane‐containing starting materials. Telechelic polymers thus synthesized are used as macromolecular chain transfer agents in the reversible addition fragmentation chain transfer (RAFT) polymerization of N,N‐dimethylacrylamide (DMA) enabling the synthesis of (AB)n‐type multiblock and ABA‐type triblock copolymers of varying compositions possessing monomodal molecular weight distribution. (AB)n multiblock copolymers [(PDMA‐b‐PDMS)n] were prepared with between 52 and 95 wt % poly(dimethylacrylamide) with number average molecular weights (Mn) between 14,000 and 86,000 (polydispersities of 1.20–2.30). On the other hand, ABA block copolymers with DMA led to amphiphilic block copolymers (PDMA‐b‐PDMS‐b‐PDMA) with Mn values between 9000 and 44,000 (polydispersities of 1.24–1.62). © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7033–7048, 2008
Recent advances in controlled/living radical polymerization in emulsion and dispersion
Authors: Oh Jung Kwon 
Published: September 2008

AbstractEffective ways to conduct controlled/living radical polymerization (CRP) in emulsion systems are necessary for commercial latex production without significant modification of current industrial facilities. Conducting CRP in emulsion media is more complicated and more challenging than its application in homogeneous bulk. These challenges come from the intrinsic kinetics of emulsion polymerization. They include mass transport, slow chain growth mechanism, and exit of short radicals from polymeric particles. This review describes the recent developments of CRP in heterogeneous dispersion, including miniemulsion, microemulsion, dispersion, and especially emulsion. Various approaches for conducting emulsion CRP are detailed, including controlled seeded emulsion polymerization, nanoprecipitation, use of short oligomers as macroinitiators for in situ block copolymerization, and RAFT‐mediated self‐assembly. In addition many remaining challenges of the current methods barring wide spread industrial application of emulsion CRP are also suggested. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6983–7001, 2008
Ethylene polymerization of the new titanium complexes bearing a phosphine oxide‐bridged bisphenolato ligand
Authors: He Li‐Peng , Liu Jing‐Yu , Pan Li , Li Yue‐Sheng 
Published: September 2008

AbstractA series of novel titanium(IV) complexes combining a phosphine oxide‐bridged bisphenolato ligand TiCl2{2,2′‐OP‐R3 (4‐R2‐6‐R1‐C6H2O)2}(THF) (6a: R1 = tBu, R2 = H, R3 = Ph; 6b: R1 = Ph, R2 = H, R3 = Ph; 6c: R1 = R2 = tBu, R3 = Ph; 6d: R1 = R2 = cumyl, R3 = Ph; 6e: R1 = tBu, R2 = H, R3 = PhF5) were prepared by the reaction of corresponding bisphenolato ligands with TiCl4 in THF. X‐ray analysis reveals that complex 6a adopts distorted octahedral geometry around the titanium center. These catalysts were performed for ethylene polymerization in the presence of modified methyaluminoxane (MMAO). The effects of reaction parameters on ethylene polymerization behaviors, such as cocatalyst concentration, polymerization temperature, and reaction time were studied in detail. In general, these new complexes exhibited high catalytic activity, good temperature tolerance, and long lifetime for ethylene polymerization. The resulting polymers possess high molecular weight, unimodal distribution, and linear structure. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7062–7073, 2008
High temperature resistant tailor‐made poly(meth)acrylates bearing adamantyl group via atom transfer radical polymerization
Authors: Kavitha A. Amalin , Singha Nikhil K. 
Published: September 2008

AbstractThis investigation reports preparation of tailor‐made poly(meth)acrylates bearing adamantyl group using atom transfer radical homo and copolymerization via initiator as well as via monomer approach. The ATRP of methyl methacrylate was investigated using different initiators having adamantyl group (like AdMBr or AdBr) as well as conventional EBiB initiator and CuBr as catalyst in combination with PMDETA as ligand. It was observed that the incorporation of the bulky adamantyl group increased the rate of polymerization. The polymerization proceeded through first‐order kinetics and molecular weights increased linearly with conversion, close to the targeted molecular weights. The living nature of the end‐group was confirmed by MALDI‐TOF‐mass spectrometry and chain extension experiment. The homopolymerization of adamantyl methyl acrylate (AdMA) and its copolymerization with MA was successfully carried out using methylbromopropionate (MBrP) as initiator and CuBr/dNbpy as the catalyst. Interestingly, the resultant poly(meth)acrylates bearing the adamantyl group had excellent thermal stability and much better thermal stability than the similar polymers without adamantyl group as evidenced from thermogravimetry analysis (TGA) and isothermal TGA studies. Importantly, incorporation of adamantyl group “adamantly” increases rate of polymerization, thermal stability, and glass transition temperature of the polymers. All the polymers were characterized by NMR, MALDI‐TOF‐MS, DSC, and TGA analysis. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7101–7113, 2008
Molecular design of outermost surface functionalized thermoresponsive polymeric micelles with biodegradable cores
Authors: Akimoto Jun , Nakayama Masamichi , Sakai Kiyotaka , Okano Teruo 
Published: September 2008

AbstractWe prepared well‐defined diblock copolymers of thermoresponsive poly(N‐isopropylacrylamide‐co‐N,N‐dimethylacrylamide) blocks and biodegradable poly(D,L‐lactide) blocks by combination of reversible addition‐fragmentation chain transfer radical (RAFT) polymerization and ring‐opening polymerization. α‐Hydroxyl, ω‐dithiobenzoate thermoresponsive polymers were synthesized by RAFT polymerization using hydroxyl RAFT agents. Biodegradable blocks were prepared by ring‐opening polymerization of D,L‐lactide initiated by α‐hydroxyl groups of thermoresponsive polymers, which inhibit the thermal decomposition of ω‐dithioester groups. Terminal dithiobenzoate (DTBz) groups of thermoresponsive blocks were easily reduced to thiol groups and reacted with maleimide (Mal). In aqueous media, diblock copolymer products formed surface‐functionalized thermoresponsive micelles. These polymeric micelles had a low critical micelle concentration of 22 μg/L. In thermoresponsive studies of the micelles, hydrophobic DTBz‐surface micelles demonstrated a significant shift in lower critical solution temperature (LCST) to a lower temperature of 30.7 °C than that for Mal‐surface micelles (40.0 °C). In addition, micellar LCST was controlled by changing bulk mixture ratios of respective heterogeneous end‐functional diblock copolymers. Micellar disruption at acidic condition (pH 5.0) was completed within 5 days due to hydrolytic degradation of PLA cores, regardless of showing a slow disruption rate at physiological condition. Furthermore, we successfully improved water‐solubility of hydrophobic drug, paclitaxel by incorporating into the micellar cores. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7127–7137, 2008
Libraries of methacrylic acid and oligo(ethylene glycol) methacrylate copolymers with LCST behavior
Authors: Becer C. Remzi , Hahn Sabine , Fijten Martin W. M. , Thijs Hanneke M. L. , Hoogenboom Richard , Schubert Ulrich S. 
Published: September 2008

AbstractHomopolymers of methacrylic acid (MAA), monoethyleneglycol methyl ether methacrylate (MEOMA), diethyleneglycol methyl ether methacrylate (MEO2MA), oligo(ethyleneglycol) methyl ether methacrylate (OEGMA475 and OEGMA1100) and oligo(ethyleneglycol) ethyl ether methacrylate (OEGEMA246) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization. The homopolymers of MAA, MEOMA and OEGMA1100 did not show any cloud point (CP) in the range of 0–100 °C, whereas at a pH value of 7, the CPs were found to be 20.6, 93.7, and 20.0 °C for p(MEO2MA), p(OEGMA475) and p(OEGEMA246), respectively, with an initial monomer to initiator ratio of 50. Furthermore, statistical copolymer libraries of MAA with OEGMA475 and OEGMA1100 were prepared. The cloud points of the random copolymers of MAA and OEGMA475 were found to be in the range of 20–90 °C; surprisingly, even though the homopolymers of MAA and OEGMA1100 did not exhibit any LCST behavior, the copolymers of these monomers at certain molar ratios (up to 40% OEGMA1100) revealed a double responsive behavior for both temperature and pH. Finally, the cloud points were found to be in the range of 22–98 °C, measured at pH values of 2, 4, and 7, while no cloud point was detected at pH 10. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7138–7147, 2008
Novel biomarkers for risk of prostate cancer: Results from a case–control study
Authors: Yang Li , Gaikwad Nilesh W. , Meza Jane , Cavalieri Ercole L. , Muti Paola , Trock Bruce , Rogan Eleanor G. 
Published: September 2008

AbstractBACKGROUNDAlthough the estrogens estrone and estradiol are recognized to play very important roles in the risk of developing prostate cancer (Pca), the molecular mechanism by which estrogens initiate and/or promote Pca is still unknown. Substantial evidence supports that specific metabolites of estrogens, catechol estrogen quinones, can react with DNA to form depurinating estrogen‐DNA adducts. Apurinic sites derived from depurination of these adducts can induce mutations leading to cancer. Once released from DNA, depurinating estrogen‐DNA adducts are shed from cells into the bloodstream and excreted in urine. By analyzing profiles of estrogen metabolites, conjugates, and depurinating DNA adducts in urine from men with and without prostate cancer, potential biomarkers of Pca can be detected. The goal of this case–control study was to detect and identify potential biomarkers of Pca.METHODSUrine samples from fourteen cases, men diagnosed with Pca, and 125 controls, men who had not been diagnosed with Pca, were partially purified by solid phase extraction and analyzed by ultraperformance liquid chromatography/tandem mass spectrometry. The urinary levels of androgens, estrogens, estrogen metabolites, conjugates and depurinating DNA adducts were measured.RESULTSThe ratio of depurinating estrogen‐DNA adducts to the sum of the corresponding estrogen metabolites and conjugates was significantly higher in cases (median: 57.34) compared to controls (median: 23.39) (P < 0.001).CONCLUSIONSThis study suggests that depurinating estrogen‐DNA adducts could serve as potential biomarkers to predict risk of Pca. They also could be useful tools for early clinical diagnosis and development of suitable strategies to prevent Pca. Prostate 69: 41–48, 2009. © 2008 Wiley–Liss, Inc.
Computational studies on the backbone‐dependent side‐chain orientation induced by the (S,S)‐CXC motif
Authors: Stavrakoudis Athanassios , Tsikaris Vassilios 
Published: September 2008

AbstractDisulfide cyclization is a well‐known procedure to impose conformational restriction to peptides undergoing backbone flexibility. Rigid conformations are induced only for small rings with a specific combination of amino acids. In this work, we present a computational search of the backbone and backbone‐dependent side‐chain orientation of two series of linear and cyclic peptide analogs. The ‐C[XY]C‐ scaffold (where X,Y is arginine, aspartic acid or alanine residue) in its open and (S,S) cyclic form was used for the design of the studied analogs. Thirty‐six compounds, resulting from the extension with one residue at either the N‐ or the C‐terminus were studied with classical MD. The local backbone conformation and the relative orientation of the X and Y side chains induced by either cyclization and/or the presence of the charged residues are discussed. From the present study it is concluded that cyclization has a great impact on the synplanar orientation of the X and Y side chains in the (S,S)Ac‐XCYC‐NH2 series of compounds while charge–charge interaction has only a weak synergic effect. On the contrary, the antiplanar orientation is favored in the case of (S,S)Ac‐CXCY‐NH2. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Evaluating the coupling efficiency of phosphorylated amino acids for SPOT synthesis
Authors: Tapia Victor , Ay Bernhard , Triebus Julia , Wolter Eike , Boisguerin Prisca , Volkmer Rudolf 
Published: September 2008

AbstractA high demand of interest concerning binding assays to study the consequences of posttranscriptional phosphorylation may be addressed by peptide array‐based methods. A crucial factor forde novochemical approaches to generate such arrays is the possibility to rationally permutate phosphorylation events along a huge number of sequences. The simple principle behind this advantage is the stepwise synthesis of peptides, which allows the incorporation of either phosphorylated or nonphosphorylated derivates at serine, threonine, and tyrosine positions. In spite of several reported applications of phosphopeptide arrays, there is, to our best knowledge, no reported analysis of the efficiency of the involved techniques. Here, we analyze different coupling conditions to introduce phosphoamino acids in standard SPOT synthesis. Our results clearly indicate that EEDQ is the preferable activator and can also be used in fully automated SPOT synthesis. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Broadband electrical characterization of macroporous silicon at microwave frequencies
Authors: Contopanagos H. , Pagonis D. N. , Nassiopoulou A. G. 
Published: September 2008

AbstractMacroporous silicon layers with randomly distributed vertical cylindrical pores of average diameter 120 nm were fabricated on selected areas on a p+ (resistivity 5 mΩcm) silicon substrate by anodization in HFxethanol solution. The thickness of the layers was 50 μm and they are intended for use as RF isolation micro‐plates for on‐chip passive devices operated at microwave frequencies. In this respect, we present in this work results of their electrical characterization in the 40 MHz‐7 GHz frequency range using a macroscopic platform, where the die containing the porous silicon layer on the highly doped Si substrate is inserted directly underneath a microstrip line. The highly doped Si substrate used acts as a lossy metal ground for the microstrip. We measured and simulated the scattering parameters of the system using a finite‐element full‐wave electromagnetic solver. We have chosen a broad frequency band extending from 40 MHz up to 7 GHz, beyond the first harmonic of the transmission line. By identifying measured and simulated S‐parameters over the whole frequency band we extract both geometrical characteristics of the measurement set‐up not accessible to direct measurements and the complex permittivity of porous silicon. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of processing parameters on the fabrication of auxetic extruded polypropylene films
Authors: Chirima G. , Ravirala N. , Rawal A. , Simkins V. R. , Alderson A. , Alderson K. L. 
Published: September 2008

AbstractA processing parameter study for extruded polypropylene films has been carried out. Films were extruded at temperatures varying from 157 °C to 230 °C, screw speed from 0.525 rad s–1 to 2.10 rad s–1 and take up speed from 0.0225 m s–1 to 0.15 m s–1. Characterisation of the films was undertaken to determine Poisson's ratio, ν, using video exten‐ sometry and it was found that it was possible to vary the Poisson's ratio from positive (ν = +0.4) to negative (as low as ν = –1) by varying the processing parameters, allowing the possibility of tailoring the Poisson's ratio to specified applications driven values. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The ensemble Kalman filter in an operational regional NWP system: preliminary results with real observations
Authors: Bonavita Massimo , Torrisi Lucio , Marcucci Francesca 
Published: September 2008

AbstractThe ensemble Kalman filter (EnKF) has been widely tested as a possible candidate for the next generation of meteorological and oceanographic data assimilation algorithms. While a number of tests with models of varying realism have been successfully performed, the EnKF has been seldom evaluated in an operational regional NWP environment at realistic spatial resolution. In this work one particular EnKF implementation (Local Ensemble Transform Kalman Filter, LETKF) has been implemented and its performance evaluated in comparison with CNMCA operational 3D‐Var.One of the most important issues in EnKF implementations lies in the filter tendency to become underdispersive for practical ensemble sizes. While multiplicative (or additive) covariance inflation has been used to deal with this problem, tuning its values is an expensive and possibly never‐ending task. Following ideas from linear estimation theory, we test an adaptive estimation procedure to evaluate forecast covariance inflation factors and observation errors. Our results show that, differently from previous experiences, the online estimation technique can be successfully employed in a realistic state‐of‐the‐art NWP system. More generally the LETKF analysis is shown to be of superior quality with respect to the operational 3D‐Var and a likely candidate for its replacement in the not‐too‐distant future. Copyright © 2008 Royal Meteorological Society
Sunny Greenland
Authors: Scorer R. S. 
Published: September 2008

AbstractGreenland is about the same size as the plateau of Tibet. It is, by contrast, a cold source and a complete obstruction to the advance of air at sea level. Air flowing from the ice plateau originates at around plateau level. The general slope towards the north and west causes a katabatic land breeze on the west coast. The so‐called Iceland low in its movements from Cape Farewell more than half way to Spitzbergen causes a prevailing wind from the north or north‐east along the lee coast which drives ice as far as Cape Farewell all year round. The earth's rotation causes the ocean current to turn the cape and occasionally carry ice 100‐200 km up the west coast. But for most of the year the wind is from the north while the salty water moves from the south.When cirrus moves inland it is not accompanied by air at sea level and when air descends from the plateau the flow at cirrus level is usually upslope so that a trail of orographic cirrus leaves the coast.The Iceland low frequently carries warm air across the Faeroes and Jan Mayen to the east coast at Scoresbysund and even to the west of Iceland and at the same time draws arctic air from the Davis Strait across the Atlantic to Britain to form an inverted front on which a row of small cyclones forms.The general picture formed from looking at about nine years of satellite pictures is that the weather goes on around Greenland and is steered by it, but only occasionally penetrates over the plateau and then neither far nor for long. While Spitzbergen, Iceland, and other territories around are some of the cloudiest places on earth, Greenland is a very sunny place, and yet it remains a very significant source of cold.
Airmass transformation over the South China Sea during a winter MONEX cold surge
Authors: Martin David W. , Reiff J. , Mower R. N. 
Published: September 2008

AbstractSeveral studies have linked a wintertime cycle of deep, moist near‐equatorial convection to surges of cold air from Asia. According to an early hypothesis two successive streams of surge air reach north Borneo and offshore waters of the South China Sea. The first, which follows a long over‐water trajectory, is warm by the time it arrives off Borneo. The second, which follows a short over‐water trajectory, still is cool when it arrives off Borneo. More recent hypotheses suggest only the second stage of the surge involves an airstream from Asia and drying rather than cooling is the predominant downstream thermodynamic effect on this airstream.By means of trajectory calculations and an airmass transformation (AMT) model we test these ideas for a moderate cold surge from December 1978. In particular, we contrast the roles, in the transformation process, of surface fluxes of latent and sensible heat and of boundary layer entrainment. At no time through the course of the surge did we find boundary layer trajectories of the second (short path) type. Nevertheless, late in the course of the case study surge dry air did appear at the surface off the south‐east coast of Vietnam. Neither sea surface temperature nor initial airmass structure could account for the local nature of the drying. The explanation most consistent both with observations and AMT model results is entrainment of air that had been dried by local subsidence at and above the top of the marine boundary layer.
Numerical studies of eddy transport properties in eddy‐resolving and parametrized models
Authors: Vallis G. K. 
Published: September 2008

AbstractThis paper is a study of the transport properties of large‐scale quasi‐geostrophic flow, when it is forced by an unstable shear of much greater horizontal scale than the scale of the resultant eddies. One of the purposes is thereby to test certain phenomenological parametrization schemes which predict the transport of potential vorticity or heat, or which predict the time‐mean state of the zonally averaged atmosphere. Models used are highly nonlinear spectral quasi‐geostrophic models, with sufficient resolution to resolve the energy‐containing scales and partially resolve an enstrophy inertial range. A scale separation is enforced between the mean and eddy flow, this being a necessary condition for transfer theories to work. An expression is derived for the rate of change of the mean flow in such cases. As a quantitative predictor of the time‐mean state of the zonal flow, baroclinic adjustment is found to work only when nonlinear wave‐wave interaction between eddies is small. In such cases, the amplitude of the eddy flow is determined by the forcing on the zonal flow, which itself equilibrates close to the critical value for linear instability. In fully nonlinear models if the zonal flow is strongly forced the mean flow can be highly supercritical. The flux of potential vorticity is found to depend strongly and monotonically on the mean shear, although no obvious simple relationship is found relating it to potential vorticity gradient. In part because potential vorticity is not a passive scalar, using phenomenological transfer coefficients is by no means straightforward. Such transfer relationships are seen to be in some ways unsatisfactory.