bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bisphosphonate units in the main polymer chain: The first synthesis
Authors: Penczek Stanislaw , Kaluzynski Krzysztof , Pretula Julia 
Published: May 2012

AbstractRadical copolymerization of tetraethyl vinylidene phosphonate (B) with vinyl monomers has been described for the first time. In copolymerization with vinyl acetate (V) strictly alternating copolymer was formed even when [V]0/[B]0 was equal to 80. In copolymerization with acrylic acid (A) copolymers of the general structure ‐[(B)1Ax)]n‐ were formed. The number of A units (x) was shown to depend on the [A]0/[B]0 ratio in the monomers feed. The reactivity ratio rA was determined as equal to 2.1 and on this basis, the distribution of x as a function of [A]0/[B]0 was found. Bisphosphonic units were deblocked and the corresponding polyacids were analyzed by NMR spectra. Mn > 0.5 × 106 were measured by SEC for copolymers of B with A. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Kinetic studies on the imine base/isocyanate‐induced radical polymerization of vinyl monomers
Authors: Polenz Ingmar , Schmidt Friedrich Georg , Spange Stefan 
Published: May 2012

AbstractSpecific imine bases (IB) in conjunction with various isocyanates (IC) mediate the radical polymerization of radically polymerizable monomers such as methyl methacrylate (MMA). Advantageously, the 2‐(methylmercapto)‐2‐thiazoline MMT/IC combination as initiator works even at room temperature for polymerization of MMA. The coefficients a, b, and c of the basic rate law of monomer consumption d[M]/dt = kp·[IC]a·[IB]b·[M]c were determined. The order a has been determined to 0.5 showing the root law of radical polymerization with respect to the IC component as initiator. Moreover, b and c amount 1. The initiator combination MMT/ IC was applied to determine the influence of the molecular structure of the IC on the rate of monomer conversion. For aromatic isocyantes, the gross rate constant of monomer consumption correlates with the Hammet constant of aromatic substituents. The activation energies of the gross polymerization rate constant of several initiator mixtures were determined whereby the value of EA,Br was found to be between typical values of radical polymerization initiated by photochemical reactions (∼20 kJ/mol) and commonly used thermal decomposing initiators (∼80 kJ/mol). Presumptions on the initiating and terminating step of the IB/IC mediated polymerization were done by means of electrospray ionization mass spectrometry, NMR spectroscopy, and the elemental composition of the head and end group of the resulting polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Poly(isobornyl methacrylate‐co‐methyl acrylate): Synthesis and stereosequence distribution analysis by NMR spectroscopy
Authors: Khandelwal Deepika , Hooda Sunita , Brar A. S. , Shankar Ravi 
Published: May 2012

AbstractCopolymerization of isobornyl methacrylate and methyl acrylate (I/M) is performed by atom transfer radical polymerization using methyl‐2‐bromopropionate as an initiator and PMDETA/CuBr as catalyst under nitrogen atmosphere at 70 °C. The copolymer compositions determined from 1H NMR spectra are used to determine reactivity ratios of the monomers. The reactivity ratio determined from linear Kelen–Tudos method and non‐linear error‐in‐variable method, are rI = 1.25 ± 0.10, rM = 0.84 ± 0.08 and rI = 1.20, rM = 0.82, respectively. 1D, distortion less enhancement by polarization transfer and 2D, heteronuclear single quantum coherence, and total correlation spectroscopy NMR experiments are employed to resolve highly overlapped and complex 1H and 13C{1H} NMR spectra of the copolymers. The carbonyl carbon of I and M units and methyl carbon of I unit are assigned up to triad compositional and configurational sequences, whereas β‐methylene carbons are assigned up to tetrad compositional and configurational sequences. Similarly, methine carbon of I unit is assigned up to triad level. The couplings of carbonyl carbon and quaternary carbon resonances are studied in detail using 2D hetero nuclear multiple bond correlation spectra. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Synthesis, swelling properties, and network structure of new stimuli‐responsive poly(N‐acryloyl‐N′‐ethyl piperazine‐co‐N‐isopropylacrylamide) hydrogels
Authors: Deen G. Roshan , Chua Vivien , Ilyas Usman 
Published: May 2012

AbstractPoly(N‐acryloyl‐N′‐ethyl piperazine‐co‐N‐isopropylacrylamide) hydrogels were prepared by thermal free‐radical copolymerization of N‐acryloyl‐N′‐ethyl piperazine (AcrNEP) and N‐isopropylacrylamide (NIPAM) in solution using N, N′‐methylene bisacrylamide as the crosslinking agent. The gels were responsive to changes in external stimuli such as pH and temperature. The pH and temperature responsive character of the gels was greatly dependent on the monomer content, namely AcrNEP and NIPAM, respectively. The gels swelled in acidic (pH 2) and de‐swelled in basic (pH 10) solutions with a response time of 60 min. With increase in temperature from 23 to 80 °C the swelling of the gels decreased continuously and this effect was different in acidic and basic solutions. The temperature dependence of equilibrium water content of the gels was evaluated by the Gibbs–Helmholtz equation. Detailed analysis of the swelling properties of these new gels in relation to molecular heterogeneity in acidic (pH 2) and basic (pH 10) solutions were performed. Water transport property of the gels was studied gravimetrically. In acidic solution, the diffusion process was non‐Fickian (anomalous) while in basic solution, the diffusion was quasi‐Fickian. The effect was more evident in solution of pH 2 than in pH 10. Various structural parameters of the gels such as number‐average molar mass between crosslink (Mc), the crosslink density (ρc), and the mesh size (ξ) were evaluated. The mesh sizes of the hydrogels were between 64 and 783 Å in the swollen state in acidic solution and 20 and 195 Å in the collapsed state in basic solution. The mesh size increased between three to four times during the pH‐dependent swelling process. The amount of unbound water (free water) and bound water of the gels was also evaluated using differential scanning calorimetry. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Stereoregular control of poly(4‐vinyl pyridine) on free radical polymerization by using the inclusion complex with randomly methylated β‐cyclodextrin
Authors: Saito Reiko , Saito Yoichi , Kamoshita Hideyasu , Tokubuchi Yoichi 
Published: May 2012

AbstractHighly heterotactic poly(4‐vinyl pyridine)s (P4VPs) with the fraction of mr content (fmr) > 0.81 were synthesized by free radical polymerization of 4‐vinyl pyridine (4VP) with randomly methylated β‐cyclodextrin (β‐RMCD) in acidic aqueous media of HNO3 and CF3COOH at 40 °C. The heterotacticity of P4VP strongly depended on the neutralization of 4VP. The complete neutralization of 4VP with HNO3 or CF3COOH increased the heterotacticity of P4VP, whereas atactic P4VP was obtained in water. The partial decomposition of β‐RMCD by HCl reduced the heterotacticity of P4VP (fmr ≈ 0.74). The structures of inclusion complexed monomers were determined by Job's plot, 2D NMR with nuclear Overhauser enhancement spectroscopy analyses, and simulation by MM2. The 1:2 complex with [β‐RMCD]:[4VP] with meso placement of 4VPs in β‐RMCD was formed when 4VP was completely neutralized with acid, whereas the 1:1 complex was formed in water. The mechanism of heterospecific control by using β‐RMCD was proposed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Large‐scale aligned fiber mats prepared by salt‐induced pulse electrospinning
Authors: Zhang Quanchao , Wang Lihua , Wei Zhimei , Wang Xiaojun , Long Shengru , Yang Jie 
Published: May 2012

AbstractIn this article, a new large‐scale aligned fiber mats formation method called salt‐induced pulse electrospinning was developed. By electrospinning salted solution in a humid environment, traditional continuous electrospinning changed into pulse electrospinning and aligned fibers were thus formed. The possible mechanisms for the occurrence of salt‐induced pulse electrospinning and the formation of fiber alignment were studied. The continuous electrospinning changing into the pulse electrospinning was due to the change of viscosity and conductivity of salted polymer solution in a wet electrospinning condition. Fishing net‐shaped whipping region of the electrospinning jet during pulse electrospinning process was considered as the key factor for the formation of fiber alignment. The mechanical properties of the aligned fiber mat increased significantly compared with that of the random fiber mat. This aligned fiber preparation method only requires a very low rotating drum speed as the receiver and can produce large‐scale aligned fiber mats for many applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Characterization of Particle Size Standard NIST 1019b with Synchrotron X‐ray Microtomography and Digital Data Extraction
Authors: Friedrich Jon M. , Rivers Mark L. , Perrin Michael A. , Meinhart Zachary , Ramirez Vanessa V. 
Published: May 2012

AbstractWe show that synchrotron x‐ray microtomography (μCT) followed by digital data extraction can be used to examine the size distribution and particle morphologies of the polydisperse (750 to 2450 μm diameter) particle size standard NIST 1019b. Our size distribution results are within errors of certified values with data collected at 19.5 μm/voxel. One of the advantages of using μCT to investigate the particles examined here is that the morphology of the glass beads can be directly examined. We use the shape metrics aspect ratio and sphericity to examine of individual standard beads morphologies as a function of spherical equivalent diameters. We find that the majority of standard beads possess near‐spherical aspect ratios and sphericities, but deviations are present at the lower end of the size range. The majority (> 98 %) of particles also possess an equant form when examined using a common measure of equidimensionality. Although the NIST 1019b standard consists of loose particles, we point out that an advantage of μCT is that coherent materials comprised of particles can be examined without disaggregation.
The dynamical response of hen egg white lysozyme to the binding of a carbohydrate ligand
Authors: Moorman Veronica R. , Valentine Kathleen G. , Wand A. Joshua 
Published: May 2012

AbstractIt has become clear that the binding of small and large ligands to proteins can invoke significant changes in side chain and main chain motion in the fast picosecond to nanosecond timescale. Recently, the use of a “dynamical proxy” has indicated that changes in these motions often reflect significant changes in conformational entropy. These entropic contributions are sometimes of the same order as the total entropy of binding. Thus, it is important to understand the connections amongst motion between the manifold of states accessible to the native state of proteins, the corresponding entropy, and how this impacts the overall energetics of protein function. The interaction of proteins with carbohydrate ligands is central to a range of biological functions. Here, we examine a classic carbohydrate interaction with an enzyme: the binding of wild‐type hen egg white lysozyme (HEWL) to the natural, competitive inhibitor chitotriose. Using NMR relaxation experiments, backbone amide and side chain methyl axial order parameters were obtained across apo and chitotriose‐bound HEWL. Upon binding, changes in the apparent amplitude of picosecond to nanosecond main chain and side chain motions are seen across the protein. Indeed, binding of chitotriose renders a large contiguous fraction of HEWL effectively completely rigid. Changes in methyl flexibility are most pronounced closest to the binding site, but average to only a small overall change in the dynamics across the protein. The corresponding change in conformational entropy is unfavorable and estimated to be a significant fraction of the total binding entropy.
Is there any association between the severity of lower urinary tract symptoms and the risk of biopsy‐detectable prostate cancer in patients with PSA level below 20 ng/ml in multi‐core prostate biopsy?
Authors: Oh Jong Jin , Jeong Seong Jin , Jeong Chang Wook , Byun Seok‐Soo , Hong Sung Kyu , Choe Gheeyoung , Lee Sang Eun 
Published: May 2012

AbstractBACKGROUNDTo assess whether the severity of lower urinary tract symptoms (LUTS) is associated with the risk of prostate cancer (PCa) detection via a multi (≥12)‐core prostate biopsy.METHODSFrom January 2004 to May 2011, 3,107 patients underwent transrectal ultrasound (TRUS) prostate biopsies due to elevated PSA levels ranging between 3 and 20 ng/ml or abnormal digital rectal exams (DREs). Multivariate logistic analysis was used to assess the potential association of LUTS and PCa detection via biopsy. The predictive accuracy of the multivariate model was assessed based on the receiver operating characteristics‐derived area under the curve.RESULTSThe median International Prostate Symptom Score (IPSS) was 11, and the mean PSA was 6.81 ng/ml. Of the total subjects, PCa was detected from biopsy in 931 (30.0%) patients. In a comparison of 1,465 patients with IPSS ≥11 and 1,642 patients with IPSS <11, those with a higher IPSS were older, had higher PSA and had a larger prostate, but there were no significant differences in the PCa detection rates. However, in multivariate analysis incorporating other associated variables, a higher IPSS was significantly associated with lower odds of PCa detection (P = 0.016). Nevertheless, addition of the IPSS did not significantly increase the accuracy of the multivariate model devised for the detection of PCa (P = 0.098).CONCLUSIONSAlthough PCa was detected less commonly among men with higher LUTS, LUTS may not provide additional prognostic information beyond that which can be obtained via previously established prognostic factors. Prostate 73: 42–47, 2013. © 2012 Wiley Periodicals, Inc.
Effect of vacuum annealing on the structural, optical, and electrical properties of spray‐deposited Ga‐doped ZnO thin films
Authors: Gokulakrishnan V. , Purushothaman V. , Arthi E. , Jeganathan K. , Ramamurthi K. 
Published: May 2012

AbstractGallium‐doped zinc oxide (GZO) transparent conducting thin films were prepared by a cost‐effective spray‐pyrolysis method on glass substrates at 400 °C for various concentration of gallium (0–5 at.%) in the spray solution. Electrical, optical, and structural properties of as‐deposited and annealed GZO films were investigated using Hall measurement, optical transmission, X‐ray diffraction, and atomic force microscopy. As‐prepared and vacuum annealed GZO films at 400 °C are preferentially orientated along the (002) crystallographic direction and annealing has enhanced the crystallinity of the films. A vacuum‐annealed GZO film (3 at.%) acquired the lowest resistivity of 6.5 × 10−3 Ω cm with Hall mobility and carrier concentration of 18 cm2/V s and 5.4 × 1019 cm−3, respectively. The transmittance of GZO film for 1 at.% is ∼84% in the visible region (400–800 nm) and it is markedly increased to ∼92% with the transmission edge shift towards the shorter‐wavelength side on annealing. However, neither doping nor vacuum annealing of ZnO films modify the near band edge (3.26 eV) of the film appreciably. Ga doping is found to compensate the radiative oxygen vacancy levels and thus quench the green luminescence at 2.8 eV.
Scanning near‐field optical spectroscopy of AlGaN epitaxial layers
Authors: Pinos Andrea , Marcinkevičius Saulius , Liuolia Vytautas , Yang Jinwei , Gaska Remis , Shur Michael S. 
Published: May 2012

AbstractBand gap fluctuations and carrier localization in AlxGa1‐xN films with x values varying from 0.30 to 0.50 has been studied by scanning near‐field optical microscopy (SNOM) by measuring photoluminescence. The measurements have revealed a dual localization potential. Microscopic scale potential variations, detected by the SNOM, were most pronounced in the lower Al content samples. The nanoscopic carrier localization potentials, evaluated from the width of the photoluminescence spectra, were largest in layers with the largest AlN molar fraction. The large scale potential fluctuations were attributed to Ga rich regions close to grain boundaries or atomic layer steps. The density, size and band gap energy of these domains were found to be composition dependent. The nanoscopic potential variations have been assigned to small‐scale compositional fluctuations, possibly, occurring due to formation of Al rich grains during growth. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Near‐ and far‐field optical characterization of InGaN photonic crystal light emitting diodes
Authors: Liuolia Vytautas , Marcinkevičius Saulius , Wang Qin , Andersson Jan , Kim Sang‐Mook , Baek Jong Hyeob 
Published: May 2012

AbstractLight extraction from InGaN photonic crystal (PhC) light emitting diodes (LEDs) has been studied by scanning near‐field optical microscopy and time‐resolved photoluminescence. The observed patterns of the near‐field intensity are complex and do not correspond to the physical structure of the photonic crystal. Comparison with conventional LEDs without the PhC showed that PhC not only improves the light extraction, but also makes the LED emission more homogeneous (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and characterization of GaP layers on silicon substrates by metal‐organic vapour phase epitaxy
Authors: Jussila Henri , Nagarajan Subramaniyam , Mattila Päivi , Riikonen Juha , Huhtio Teppo , Sopanen Markku , Lipsanen Harri 
Published: May 2012

AbstractThis paper presents X‐ray diffraction and atomic force microscopy investigation of GaP thin films grown on silicon (100) substrate by metalorganic vapour phase epitaxy. Crystalline GaP has been grown by two‐step growth method, in which first a low temperature nucleation layer is grown at 475 °C, and then, a 100‐nm‐thick layer is grown at 700 °C. The GaP layer is comprised of trenches and smooth terraces which are attributed to anti‐phase domains. Without the two‐step growth method, GaP forms a cross‐hatch pattern of wires. Formation of GaP wires is attributed to anisotropic diffusion, and thus, the GaP wires grow along [011] crystal directions (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin injection in a heterovalent structure with coupled quantum wells GaAs/(Al,Ga)As/(Zn,Mn)Se/ZnSe
Authors: Liaci F. , Kaibyshev V. Kh. , Toropov A. A. , Terent'ev Ya. V. , Mukhin M. S. , Klimko G. V. , Gronin S. V. , Sedova I. V. , Sorokin S. V. , Ivanov S. V. 
Published: May 2012

AbstractIn this report we present the study, by means of low‐temperature magneto‐optical measurements, of the spin transport dynamics in a heterovalent MBE‐grown III‐V/II‐VI structure under optical pumping. The structure consists of two coupled GaAs quantum wells (QWs) of 100 Å and 50 Å surrounded by (Al,Ga)As barriers, a heterovalent (Al,Ga)As/ZnSe interface, a 10 nm (Zn,Mn)Se spin aligner, and a 70 nm thick ZnSe cap layer. We obtain values of about 30% at 4.5 T for the degree of circular polarization. These results give some hints on the design improvements needed for higher spin‐filtering efficiency. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stark effects of ZnO thin film and ZnO/ZnMgO quantum wells
Authors: Sato K. , Abe T. , Fujinuma R. , Yasuda K. , Yamaguchi T. , Kasada H. , Ando K. 
Published: May 2012

AbstractWe have investigated external electric field dependent Stark effects of ZnO thin film and ZnO/ZnMgO QWs by electroreflectance (ER) spectroscopy to develop electroabsorption modulators. The ZnO single film and ZnO/ZnMgO QWs were grown by plasma‐assisted molecular beam epitaxy (PA‐MBE). ZnO single film exhibited red‐shift of 8 meV by applying external bias at 18 K. This red‐shift is due to Stark effect in a low electric field, but it was changed to Franz‐Keldysh effect in a high electric field region. We confirmed a large blue‐shift of 39 meV for ZnO/ZnMgO QWs by external bias at room temperature. This energy shift, originated from quantum confined Stark effect (QCSE) in ZnO/ZnMgO QWs, proved a large exciton binding energy of this system. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of dopant transport rate upon photoluminescence and electrical properties of phosphorus‐doped ZnMgTe layers grown by MOVPE
Authors: Saito K. , Saeki T. , Tanaka T. , Guo Q. X. , Nishio M. 
Published: May 2012

Abstractp‐type doping of Zn1‐xMgx Te has been investigated by metalorganic vapour phase epitaxy using tris‐dimethylaminophosphorus as a dopant source. The photoluminescence (PL) and electrical properties of the as‐grown and post‐annealed layers have been clarified as a function of the dopant transport rate. In PL spectra at 4.2 K, the strong donor acceptor pair emission vanished and instead enhancement of P acceptor‐related excitonic emission and/or appearance of free‐to‐bound emission were observed for all the layers by the post‐annealing treatment. In accordance with the PL behavior, the hole concentration at room temperature of the annealed layers was significantly enhanced from 2×1015∼2×1016 cm‐3 to 5×1016∼2×1018 cm‐3 by a maximum factor of ∼600. The enhanced hole concentration shows saturation tendency with increasing dopant transport rate. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Density functional theory study of ordered defect Cu‐(In,Ga)‐Se compounds
Authors: Zhao Hanyue , Kumar Mukesh , Persson Clas 
Published: May 2012

AbstractCuIn1–xGaxSe2 is used as absorber material in thin‐film photovoltaics. Presence of defect arrays of 2VCu– + XCu2+ complexes (X = In or Ga) in the material results in the formation of ordered defect phases, like for instance Cu(In1–xGax)3Se5 and Cu(In1–xGax)5Se8. An understanding of these defects phases is of considerably importance since they can strongly affect the performance of the solar cell. Density functional theory calculation with a hybrid functional is carried out to study the electronic structures and optical properties of these ordered defect phases. Fundamental properties, such as the band bowing, the band alignment and the absorption coefficients, are presented, and their dependence on material composition is discussed (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of atomic‐layer‐deposited AlN on near‐surface InGaAs/GaAs structures
Authors: Mattila Päivi , Bosund Markus , Jussila Henri , Tuomi Turkka , Riikonen Juha , Huhtio Teppo , Lipsanen Harri , Sopanen Markku 
Published: May 2012

AbstractNear‐surface InGaAs/GaAs quantum well and strain‐induced InGaAs/GaAs quantum dot structures are coated with AlN by plasma‐enhanced atomic layer deposition. Due to its relatively low fabrication temperature (<300 °C), AlN is an interesting candidate for the coating of strain‐induced quantum dots whose covering has been challenging in the past. As these quantum dots are sensitive to changes in the strain field they are utilized to show that a 10‐nm‐thick layer of AlN does not affect the strain field inside the near‐surface InGaAs/GaAs structures. Both the integrated photoluminescence intensity and the spacing between quantum dot energy levels remain approximately unchanged when the structures are coated by AlN. All in all, the coating of InGaAs/GaAs strain‐induced quantum dot structures with AlN could pave the way for the first strain‐induced quantum dot based optical components (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)