bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoinitiated grafting of maleic anhydride onto polypropylene
Authors: Pan Bo , Viswanathan Kalyanaraman , Hoyle Charles E. , Moore Robert B. 
Published: March 2004

AbstractThe photoinitiated grafting of maleic anhydride (MAH) onto polypropylene with the use of benzophenone (BP) as the initiator has been investigated. In comparison with the process of thermally initiated grafting with peroxide as the initiator, photoinitiated grafting affords a higher grafting efficiency. The efficient photografting sensitized by BP can be explained by two possible mechanistic processes: the sensitization of the formation of the excited triplet state of MAH by BP and electron transfer followed by proton transfer between MAH and the benzopinacol radical, which may operate together. In the former case, the generated MAH excited triplet state abstracts a hydrogen from the polymer substrate to initiate grafting. A rate constant of 3.6 × 109 M −1 s −1 has been determined by laser flash photolysis for the process of quenching the excited triplet state of BP with ground‐state MAH. In comparison, the rate constant for the quenching of the excited triplet state of BP by hydrogen abstraction has been determined to be 4.1 × 105 M −1 s −1. In a study of photografting using a model compound, 2,4‐dimethylpentane, as a small‐molecule analogue of polypropylene, the loss of BP was significantly reduced upon the addition of MAH, and this is consistent with the proposed mechanistic processes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1953–1962, 2004
Near‐infrared spectroscopy investigation of water effects on the cationic photopolymerization of vinyl ether systems
Authors: Lin Yan , Stansbury Jeffrey W. 
Published: March 2004

AbstractReal‐time Fourier transform near‐infrared spectroscopy has been used to monitor monomer and water concentrations simultaneously during cationic vinyl ether photopolymerization. The use of near‐infrared peak area methods allows the water content to be conveniently and nondestructively determined in any monomer or polymer for which the water peak has previously been calibrated by gravimetric analysis. Although the shape of the absorption band due to absorbed water in a monomer changes with the quantity of water, the integrated intensity from about 5350 to 4900 cm−1 can be correlated directly to the water concentration, and this region is well removed from the vinyl‐based absorption at approximately 6190 cm−1. This approach provides a highly informative, dynamic technique for examining the influence of moisture on polymerization reactions. Significant differences have been observed in the effects of absorbed water on the cationic photopolymerization kinetics of vinyl ether monomers with or without an OH group. Along with the rapid consumption of water coupled to vinyl ether polymerization, acid‐catalyzed hydrolysis reactions have also been spectroscopically observed, giving rise to the formation of aldehyde groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1985–1998, 2004
Synthesis of hydrophilic sorbents from N‐vinylimidazole/divinylbenzene and the evaluation of their sorption properties in the solid‐phase extraction of polar compounds
Authors: Fontanals Núria , Maria Marcé Rosa , Galià Marina , Borrull Francesc 
Published: March 2004

AbstractThis article reports the synthesis of N‐vinylimidazole/divinylbenzene resins by suspension polymerization. Several polymerization conditions were tested to achieve a quantitative incorporation of the N‐vinylimidazole monomer into the final polymer while a high specific surface area was maintained. The retention properties of several copolymers with different nitrogen contents were evaluated with the solid‐phase extraction of polar compounds from water samples, and the best results were obtained for a polymer containing 6.3% N with a surface area of 627 m2 g−1. The sorption properties of the resins were compared to those of styrene–divinylbenzene and other copolymers containing nitrogen, and the results were best for the new sorbents with N‐vinylimidazole as the polar monomer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2019–2025, 2004
Synthesis of phosphorus‐containing vinyl ether monomers and oligomers and their photoinitiated polymerization
Authors: Minegishi Shouji , Otsuka Tetsurou , Kameyama Atsushi , Nishikubo Tadatomi 
Published: March 2004

AbstractDivinyl ether monomers containing phosphorous residues were synthesized by the addition reaction of glycidyl vinyl ether (GVE) with various phosphonic dichlorides or dichlorophosphates with quaternary onium salts as catalysts. The reaction of GVE with phenylphosphonic dichloride gave bis[1‐(chloromethyl)‐2‐(vinyloxy)ethyl]phenylphosphonate (1a) in a 77% yield. The polycondensation of 1a with terephthalic acid was also carried out with 1,8‐diazabicyclo[5.4.0]undecene‐7 (DBU) as a condensing agent to afford the corresponding phosphorus‐containing polyester. A multifunctional monomer containing both vinyl ether groups and methacrylate groups was prepared by the reaction of 1a with methacrylic acid with DBU. The photoinitiated cationic polymerization of these vinyl ether compounds proceeded rapidly with bis[4‐(diphenylsulfonio)phenyl]sulfide‐bishexafluorophosphate as the cationic photoinitiator without a solvent upon ultraviolet irradiation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2031–2042, 2004
A new approach to estimating shelf‐life
Authors: Kiermeier Andreas , Jarrett Richard G. , Verbyla Arūnas P. 
Published: March 2004

AbstractThe current approach to the estimation of shelf‐life and the determination of the label shelf‐life as detailed in the International Conference on Harmonisation guidelines to industry is presented. The shortcomings of the status quo are explained and a possible solution is offered, which gives rise to a new definition of shelf‐life. Several methods for calculating a label shelf‐life are presented and investigated using a simulation study. Recommendations to adopt the new definition and to increase sample sizes are made. Copyright © 2004 John Wiley & Sons, Ltd.
A note on sample size savings with the use of a single well‐controlled clinical trial to support the efficacy of a new drug
Authors: Darken Patrick F. , Ho Shu‐Yen 
Published: March 2004

AbstractIn terms of the risk of making a Type I error in evaluating a null hypothesis of equality, requiring two independent confirmatory trials with two‐sided p‐values less than 0.05 is equivalent to requiring one confirmatory trial with two‐sided p‐value less than 0.001 25. Furthermore, the use of a single confirmatory trial is gaining acceptability, with discussion in both ICH E9 and a CPMP Points to Consider document. Given the growing acceptance of this approach, this note provides a formula for the sample size savings that are obtained with the single clinical trial approach depending on the levels of Type I and Type II errors chosen. For two replicate trials each powered at 90%, which corresponds to a single larger trial powered at 81%, an approximate 19% reduction in total sample size is achieved with the single trial approach. Alternatively, a single trial with the same sample size as the total sample size from two smaller trials will have much greater power. For example, in the case where two trials are each powered at 90% for two‐sided α=0.05 yielding an overall power of 81%, a single trial using two‐sided α=0.001 25 would have 91% power. Copyright © 2004 John Wiley & Sons, Ltd.
An application of a multi‐stage strategy involving confidence intervals to evaluate whether a response rate is favourable or not
Authors: Murray Sharon C. , Otterness Mary F. , Forster John K. , Catellier Diane J. , Koch Gary G. 
Published: March 2004

AbstractIn early clinical development of new medicines, a single‐arm study with a limited number of patients is often used to provide a preliminary assessment of a response rate. A multi‐stage design may be indicated, especially when the first stage should only include very few patients so as to enable rapid identification of an ineffective drug. We used decision rules based on several types of nominal confidence intervals to evaluate a three‐stage design for a study that includes at most 30 patients. For each decision rule, we used exact binomial calculations to determine the probability of continuing to further stages as well as to evaluate Type I and Type II error rates. Examples are provided to illustrate the methods for evaluating alternative decision rules and to provide guidance on how to extend the methods to situations with modifications to the number of stages or number of patients per stage in the study design. Copyright © 2004 John Wiley & Sons, Ltd.
The double triangular test in practice
Authors: Whitehead John , Todd Susan 
Published: March 2004

AbstractThe double triangular test was introduced twenty years ago, and the purpose of this paper is to review applications that have been made since then. In fact, take‐up of the method was rather slow until the late 1990s, but in recent years several clinical trial reports have been published describing its use in a wide range of therapeutic areas. The core of this paper is a detailed account of five trials that have been published since 2000 in which the method was applied to studies of pancreatic cancer, breast cancer, myocardial infarction, epilepsy and bedsores. Before those accounts are given, the method is described and the history behind its evolution is presented. The future potential of the method for sequential case–control and equivalence trials is also discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Applications of graphic method to C20, C60, and achiral single‐wall nanotubes
Authors: Zhang Liling , Wu Wei , Mo Yirong , Zhang Qianer 
Published: March 2004

AbstractA reduced Hückel graph (HG) algorithm within the Hückel theory is presented and applied to C20, C60, and achiral single‐wall nanotubes (SWNTs). The applications show that reduced HG algorithm is a more efficient way to the secular problem in the Hückel theory than other algorithms based on the Hückel method, although they give the same results. Furthermore, the applications of HG to achiral SWNT provide a general electronic structure not only on infinite achiral tubes, but also on finite‐sized tubes. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
New realizations of electronic configuration interaction spaces
Authors: Panin A. I. 
Published: March 2004

AbstractThe general properties of new models of the electronic spaces based on the notion of (p, q)‐sheaves are studied. The interrelation between simple sheaves and density operators is established. Explicit expressions for the transformed reduced Hamiltonians in terms of the standard creation‐annihilation operators are presented. The general scheme of parametrization of p‐electron states by κ‐electron means (κ = 2, 3, …) is described and studied in detail for the case of sheaves induced by κ‐electron wave functions. It is demonstrated that, under certain conditions, a p‐electron problem may be reformulated as the eigenvalue problem in κ‐electron space equipped with certain p‐electron metric. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Ab initio study of hydrogen bonding interaction and photoinduced electron transfer between 4‐nitroquinoline‐1‐oxide and tryptophan
Authors: Liu Ji‐Feng , Li Xiang‐Yuan , Zhu Quan 
Published: March 2004

AbstractIn the present article, the electronic structure of 4‐nitroquinoline‐1‐oxide (4NQO) has been theoretically investigated at the level of HFSCF/6‐31G**. Conformation of monomeric 4NQO has been found to be the most stable when the nitro group twists from the quinoline plane by about 24°. The absorption spectra of the twisted 4NQO have been calculated by using complete active space self‐consistent field method. The hydrogen bonded complexes of 4NQO and tryptophan have been intensively studied. The absorption spectra of the most stable complex have been calculated to investigate the photoinduced electron transfer between 4NQO and tryptophan. The first and second excited singlet states are found to be charge‐separated. Population analysis shows that the low‐lying triplet states are charge‐separated as well, except for the lowest one that presents the characters of a locally excited state. A solvent effect on transition energies has been considered based on the Ooshika–Lippert–Martaga equation. Theoretical study shows that the optical excitation can lead to charge separation in the 4NQO–tryptophan complex. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Bound state calculations for some three‐body electronic and muonic atomic systems with Fues‐Kratzer–type potential
Authors: Yalçin Zeynel 
Published: March 2004

AbstractThe coupled Schrödinger equation for three‐body atomic systems such as Ps−(e+e−e−), Mu(μ+e−e−), p+μ−μ−, d+μ−μ−, and t+μ−μ− is solved by using the hyperspherical harmonic‐generalized Laguerre polynomial expansion method (HHGLP). Ground‐state eigenenergies are calculated for the certain number of basis functions. The eigenenergies of the first excited states are obtained for both pure Coulomb, V(r, Ω) = $\hat{Z}$(Ω)/r, and Fues‐Kratzer‐type (FK‐type) potential, V(r, Ω) = $\hat{Z}$(Ω)/r + $\hat{A}$(Ω)/r2. As an example, to illustrate the effect of FK‐type interaction on the lowest excited states, the eigenenergies of the Mu− ion are given together as a function of the certain number of basis functions for both potentials. Our results were compared with the other theoretical calculations. Ground‐state eigenenergies of atoms such as X+Y−Y− as a function of the reduced mass were investigated. The potential curves of the ground and first excited states of Ps−(e+e−e−), Mu−(μ+e−e−), p+μ−μ− systems were obtained by a diagonalization process. It is pointed out that the FK‐type potential makes the HH method more useful and more extended for atomic calculations. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Discussion on the variable Wolfsberg–Helmholtz parameter, a new simplified Löwdin transformation and the characteristic structure of the transformed EHT Hamiltonian matrices
Authors: Carbó‐Dorca Ramon 
Published: March 2004

AbstractThree related problems are discussed: (1) the variable nature of the Wolfsberg–Helmholtz parameter and its relationship with the overlap eigenvalue range; (2) the possibility of deriving an efficient framework, describing a simplified Löwdin transformation to solve generalized secular equations; and (3) the structure of the transformed classical EHT Hamiltonian. This work shows how the simplified Löwdin transformation permits expression of the resulting transformed Hamiltonian elements by means of inward matrix products and total matrix sums. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Spontaneous assembly of ordered nanoclusters and nanowires
Authors: Liang Xue‐Jin , Li Jian‐Long , Liu Xi , Wang Jun‐Zhong , Liu Hong , Xue Qi‐Kun , Jia Jin‐Feng 
Published: March 2004

AbstractA novel strategy for the spontaneous formation of spatially ordered nanoclusters and nanowires by taking advantage of templates is reported. With this method, a large‐scale perfectly ordered identical‐size indium nanocluster array and ordered indium nanowire array are obtained on Si(111)‐(7 × 7) and Si(001)‐2 × n, respectively. It can be applied also to other metals such as Ga, Al, Ag and Mn. The atomic structures of the indium nanoclusters and nanowires are determined by in situ scanning tunnelling microscopy analysis, combined with first‐principles theoretical calculations. The formation mechanism is discussed based on the results. Copyright © 2004 John Wiley & Sons, Ltd.
Morphological evolution of erbium disilicide nanowires on Si(001)
Authors: Yang Jianshu , Cai Qun , Wang X.‐D. , Koch R. 
Published: March 2004

AbstractThe morphological evolution of ErSi2 nanowires on Si(001) with Er coverage was investigated by scanning tunnelling microscopy, low‐energy electron diffraction and x‐ray diffraction. At low Er coverages, elongated ErSi2 nanowires in a hexagonal crystal structure are formed. The nanowires are exclusively oriented perpendicular to the dimer rows of the Si(001) substrate, thus suggesting a method to control the nanowire arrangement via the substrate configuration. At 3 ML of Er rectangular islands with flat tops are observed, which crystallize in the tetragonal lattice of ErSi2. Our experiments suggest that the structural transformation from hexagonal to tetragonal takes place when the nanostructures reach the height of the c‐axis of the tetragonal unit cell. Copyright © 2004 John Wiley & Sons, Ltd.
Manipulation of large molecules by low temperature STM
Authors: Moresco Francesca , Joachim Christian , Rieder Karl Heinz 
Published: March 2004

AbstractThe possibilities offered by low‐temperature scanning tunnelling microscopy to perform controlled manipulation of single atoms and small molecules and to build structures at the atomic scale have been extended recently to the manipulation of specially designed organic molecules. In this article, some recent applications of the manipulation techniques to large complex molecules are reviewed. Single porphyrin‐based molecules deposited on copper substrates have been manipulated by means of their interaction with the microscope tip. Manipulation of the molecules on Cu(211) offers the possibility to modify selective their internal conformation, realizing the principle of a conformational molecular switch. In a constant height mode of manipulation, the tunnelling current recorded during the process contains detailed information on the internal mechanics of the molecule when guided by the microscope tip. Copyright © 2004 John Wiley & Sons, Ltd.
Lorentz‐force‐induced excitation of cantilevers for oscillation‐mode scanning probe microscopy
Authors: Enders O. , Korte F. , Kolb H.‐A. 
Published: March 2004

AbstractIn the field of scanning probe microscopy, imaging modes with oscillating cantilevers are used to image soft samples with high resolution. The tapping mode is most frequently realized by a vibrating chip‐holder, which is coupled to the cantilever chip to excite the cantilever acoustically. A new promising approach is a direct excitation of a V‐shaped cantilever by a Lorentz force acting on the V‐shaped cantilever. The Lorentz force is generated by an alternating current flowing through the cantilever while being placed in a static magnetic field. Here we show an appropriate method, to microstructure the reflective coating of commercial cantilever chips for a current flow through the cantilever, that is based on a laser system. The laser microstructuring method allows chips to be processed without changing the mechanical properties of the cantilever itself, leading to excellent dynamic properties of the vibrating cantilever. Because the cantilever is excited directly, no peripheral resonances except the eigen‐resonance of the cantilever were apparent in the frequency spectrum. For a current of high amplitude at a static magnetic field of low intensity it is observed that the bimetal properties of the cantilever cause an additional thermal excitation. The results show that commercial cantilevers can be microstructured to implement this new excitation method for a frequency spectrum with a high‐quality factor of oscillation. Copyright © 2004 John Wiley & Sons, Ltd.
Nanomanipulation of single DNA molecules and its applications
Authors: Hu J. , Zhang Y. , Li B. , Gao H. B. , Hartmann U. , Li M. Q. 
Published: March 2004

AbstractIn this short review paper we briefly introduce recent results from our research work on the manipulation of single biological molecules deposited on the surface of mica by using scanning force microscopes: results of a cooperation between the Shanghai joint group and the University of Saarland on the manipulation of single DNA molecules and some possible applications based on single molecule manipulation and structural characterization. These results emanate from the Shanghai research teams in studying DNA molecular combing, cutting, pushing and pick‐up. Future prospects are briefly outlined. Copyright © 2004 John Wiley & Sons, Ltd.
Carrier density and confined polaron effects in the photoluminescence of fresh and oxidized porous silicon
Authors: Zou Bingsuo , Dai Jiahua , Xie Sishen 
Published: March 2004

AbstractIn this report the temperature‐dependent photoluminescence spectra, Fourier transform infrared (FTIR) spectra and time‐resolved FTIR spectra of freshly prepared porous silicon and oxidized porous silicon are examined. The experimental results indicate that there is a gradual transformation of electronic states with ageing in air, because ageing led to the surface oxidation and size reduction of Si nanostructures. This surface variation from hydrogen to oxygen during ageing leads to a red shift of the emissions. A clear quantum‐confinement effect exists for both H‐ and O‐capped porous silicon but the emissions in O‐capped porous silicon show clear polaronic nature. The photoinduced polaron is evidenced by the time‐resolved FTIR results. A reversible H‐detrapping process in silicon wafer occurs with temperature, which influences the conduction of silicon wafer and the photoluminescence of as‐prepared porous silicon due to the carrier density changes. Copyright © 2004 John Wiley & Sons, Ltd.
Characterization of delta‐doped B/Si multilayers by low‐energy secondary ion mass spectrometry
Authors: Liu R. , Wee A. T. S. , Shen D. H. , Takenaka Hisataka 
Published: March 2004

AbstractAchieving a high depth resolution (of the order of 1 nm) is critical in the semiconductor industry today, and various methods have been developed to optimize depth resolution. Well characterized reference materials are also important in accurate quantitative analysis of doping profiles. International Standard Organization (ISO)/Technique Commission (TC201)/Surface Chemical Analysis (SC6‐SIMS) committees are engaged in the development of the international standardization of depth profiling of dopants in silicon using secondary ion mass spectrometry (SIMS). In this paper, the low‐energy primary ion O2+is employed in SIMS depth profiling of BN delta‐doped Si samples grown by magnetron sputtering to achieve high depth resolution and minimize the surface roughening. The11B+and30Si+yields were monitored in the depth profiles. Profiling using a 0.5 keV energy O2+beam is complicated by the early onset of surface roughening. The effects of oxygen flooding and sample rotation, used to suppress surface roughening, are also investigated. For analysis of the topography of the samples an atomic force microscope has been used. Copyright © 2004 John Wiley & Sons, Ltd.
Microstructures of magnetic nanoscale metallic multilayer and granular alloys with GMR effects
Authors: Lai Wuyan 
Published: March 2004

AbstractAmong the magnetic metallic multilayer and granular alloys displaying a giant magnetoresistance effect are a wide variety of inhomogeneous magnetic nanostructures. The two characteristic length scales in these systems—spin‐dependent electron mean free path and exchange coupling—vary from a few tens of nanometres to interatomic distances. Advanced methods for the characterization of surface and interface structures have been applied: x‐ray diffraction with a synchrotron radiation source; high‐resolution electron microscopy; field ion microscopy with an atom probe, etc. Some major achievements of research performed mainly at the Institute of Physics, Beijing, are reviewed with an emphasis on the roles of the interface structure and local morphology of nanoscale structures. For example, the structure of the nano‐oxide layers and its physical mechanism in an advanced specular giant magnetoresistance spin valve are characterized. The morphology of the nanoscaled granules has been determined directly in a CuCo granular alloy with giant magnetoresistance effects. The columnar crystallites in the multilayers, which is a very general phenomenon, were confirmed. Copyright © 2004 John Wiley & Sons, Ltd.