bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trans–cis isomerisation of the carotenoid lycopene upon complexation with cholesteric polyester carriers investigated by Raman spectroscopy and density functional theory
Authors: López‐Ramírez, M. R. , Sanchez‐Cortes S. , Pérez‐Méndez M. , Blanch G. 
Published: January 2010

AbstractRaman spectroscopy and density functional theory (DFT) were used in this work for the structural characterisation of lycopene, the antioxidant carotenoid, and its complexes with two synthetic thermotropic cholesteric polyesters. Both polyesters were employed successfully to encapsulate the carotenoid lycopene (Lyc). Besides protecting it from oxidation, they induced the trans–cis isomerisation of lycopene towards the more biologically active and bioavailable isomer cis‐Lyc. The Raman spectra revealed changes mainly concerning the band ν1 and bands of methyl groups. This would explain the interaction mechanism between lycopene and cholesteric polyesters, inducing structural changes in the carotenoid by formation of a cis CC bond in central positions of the isomer chain and hydrophobic interaction that affects the side methyl groups. DFT calculations confirmed that the isomerisation occurs at central positions of lycopene molecule. The analysis of ν1 and ν2 bands and those of methyl groups in the calculated spectra of lycopene indicates that the interaction with the synthetic cholesteric polyesters could mainly lead to the 13‐cis‐Lyc isomer. The analysis of marker structural bands of the polyesters revealed structural changes in the host which mainly affect the ester groups, most probably due to a restructuring of the polyester chain to better accommodate the ligand. Copyright © 2010 John Wiley & Sons, Ltd.
Surface‐enhanced Raman scattering study of Ag@PPy nanoparticles
Authors: Ye Sunjie , Fang Li , Qing Xutang , Lu Yun 
Published: January 2010

AbstractSurface‐enhanced Raman scattering (SERS) spectra of Ag@polypyrrole (PPy) nanoparticles with both 488 and 1064 nm excitation were investigated. Experimental results as well as theoretical analysis demonstrated that electromagnetic (EM) enhancement and charge transfer (CT) both rebounded to the SERS effect of Ag@PPy nanoparticles. When near‐IR excitation (1064 nm) was used for the SERS measurements, the contribution from CT was amplified relative to that from EM because the energy of the near‐IR excitation is far from the surface plasmon resonance of the nanosized Ag particles. The increased doping level of PPy, leading to optimal energy matching between the Fermi levels of the Ag nanoparticles and the energy levels in PPy molecules, could obviouslyenhance the SERS signal. These results suggested that the SERStechnique wasan effective tool for investigating the doping effect and interface interaction in metal‐conductingpolymer composite nanoparticles. In particular, the SERS technique with near‐IR excitation could give more information regarding the contribution of the charge‐transfer mechanism to the spectral enhancement of this kind of system. Copyright © 2010 John Wiley & Sons, Ltd.
Resonance Raman intensity analysisof the excited‐state photochemical dynamicsof dimethyl 1,3‐dithiole‐2‐thione‐4,5‐dicarboxylate in the A‐band absorption
Authors: Liu Bo , Wu Bin , Xu Jun , Wu Zhangzhu , Zhao Yanying , Zheng Xuming , Wang Huigang 
Published: January 2010

AbstractDimethyl 1,3‐dithiole‐2‐thione‐4,5‐dicarboxylate (DDTD) was synthesized and characterized using NMR, Fourier transform (FT)‐Raman, Fourier transform‐infrared (FT‐IR) and UV spectroscopies. Resonance Raman spectra (RRs) were obtained with 341.5, 354.7 and 368.9 nm excitation wavelengths and density functional calculations were carried out to elucidate the π (SCS) →π* (SCS) electronic transitions and the RRs of DDTD in cyclohexane solution. The RRs indicate that the Franck–Condon region photo dynamics have a multidimensional character with motion predominantly along the CS stretch and the CS symmetric stretch modes in the five‐member heterocycle. A preliminary resonance Raman intensity analysis was carried out and the results for DDTD were compared with previously reported results for 1,3‐dithiole‐2‐thione (DTT). Differences and similarities of the spectra in terms of molecular symmetry and electron density are also discussed. Copyright © 2010 John Wiley & Sons, Ltd.
Experimental study of the Raman strain rosette based on the carbon nanotube strain sensor
Authors: Qiu Wei , Kang Yi‐Lan , Lei Zhen‐Kun , Qin Qing‐Hua , Li Qiu , Wang Quan 
Published: January 2010

AbstractThis work presents a new technique named Raman strain rosette for the micro‐strain measurement of both Raman active and Raman inactive materials. The technique is based on the theoretical model of the carbon nanotube (CNT) strain sensor that applies the resonance and polarization Raman properties of CNTs and calculates the synthetic contributions of uniformly dispersed CNTs to the entire Raman spectrum. In our work, the proposed technique is applied in different experiments on the Raman inactive materials, such as step‐by‐step uniaxial tensile and Raman mapping around a circular hole. The experimental results reached by the Raman strain rosette are consistent with the actual values as a whole. This study verifies that the Raman strain rosette is applicable to quantitative measurement of all the in‐plane components of the strain tensor (including both normal and shear strains) by three polarized Raman detections for each sampling spot on a microscale. The technique is further applicable to achieving the strain fields through Raman mapping. Copyright © 2010 John Wiley & Sons, Ltd.
Photonic nanoarchitectures in butterflies and beetles: valuable sources for bioinspiration
Authors: Biró L.P. , Vigneron J.P. 
Published: January 2010

AbstractNature began developing photonic nanoarchitectures millions of years before humankind. Often, in the living world, color is a communication channel that may influence the chance of the individual surviving as well as the chance to reproduce. Therefore, natural color‐generating structures are highly optimized by many millennia of evolution. In this review, a survey is presented of the development of natural photonic crystal‐type nanoarchitectures occurring in butterflies and beetles from the standpoint of physics and materials science, covering the past ten years. One‐, two‐, and three‐dimensional structures are reviewed, emphasizing the role that disorder, or irregularity, may play in natural nanoarchitectures to achieve certain visual effects. The characterization, modeling methods, and rapidly growing number of bioinspired or biomimetic applications are discussed.
Stabilized lasers for advanced gravitational wave detectors
Authors: Willke B. 
Published: January 2010

AbstractSecond‐generation interferometric gravitational wave detectors require high‐power lasers with approximately 200 W of output power in a linear polarized, single‐frequency, fundamental‐mode laser beam. Furthermore very high temporal and spatial stability is required. This paper discusses the design of a 200 W pre‐stabilized laser (PSL) system and the underlying concepts. The PSL requirements for advanced gravitational wave detectors as well as for the laser system are described. The laser stabilization scheme proposed for the Advanced LIGO gravitational wave detector and the so‐called diagnostic breadboard will serve as examples to explain the general laser stabilization concepts and the achieved performance and its limitations.
Poly(N,N‐dimethylacrylamide)‐block‐Poly(L‐lysine) Hybrid Block Copolymers: Synthesis and Aqueous Solution Characterization
Authors: Triftaridou Aggeliki I. , Chécot Frédéric , Iliopoulos Ilias 
Published: January 2010

AbstractFour poly(N,N‐dimethylacrylamide)‐block‐poly(L‐lysine) (PDMAM‐block‐PLL) hybrid diblock copolymers and two PLL homo‐polypeptides are prepared via ROP of ε‐trifluoroacetyl‐L‐lysine N‐carboxyanhydride initiated by primary amino‐terminated PDMAM and n‐hexylamine respectively. The PLL blocks render the copolymers a multi‐responsive behavior in aqueous solution due to their conformational transitions from random coil to α‐helix with increasing pH, and from α‐helix to β‐sheet upon heating. The random coil‐to‐α‐helix transition is found to depend on the PLL length: the longer the peptide segment, the more readily the transition occurred. The same trend was observed for the α‐helix‐to‐β‐sheet transition, which was found to be inhibited for short polypeptides unless conjugated with the PDMAM block.magnified image
Enhanced Properties of Dissimilar Rubber Blends Using Microencapsulated Sulfur Through Acetylene Plasma Polymerization
Authors: Guo Rui , Talma Auke G. , Datta Rabin N. , Dierkes Wilma K. , Noordermeer Jacques W. M. 
Published: January 2010

AbstractSurface modification of sulfur by vacuum plasma polymerization with acetylene was applied in order to modify its surface properties without losing reactivity for vulcanization. A nm‐thin layer of crosslinked polyacetylene was deposited on the surface of the sulfur powder. Its surface energy was decreased as monitored by wetting in liquids of various polarities. A delay in the onset of weight loss by sublimation in thermal gravimetric analysis was shown by the plasma‐modified sulfur. Scanning electron microscopy showed a core/shell structure of the coated sulfur. In 50:50 blends of styrene‐butadiene rubber and ethylene‐propylene‐diene rubber, the encapsulated sulfur samples resulted in pronounced improvements in the mechanical properties relative to the use of unmodified sulfur.magnified image
Collagen Cryogel Cross‐Linked by Dialdehyde Starch
Authors: Mu Changdao , Liu Fang , Cheng Qingsu , Li Hongli , Wu Bo , Zhang Guangzhao , Lin Wei 
Published: January 2010

AbstractA 3D spongy collagen cryogel was prepared using DAS as the cross‐linker. FTIR and CD studies demonstrate that crosslinking is achieved through the reaction of the DAS aldehyde groups with the free amino groups in collagen without affecting the triple helix of collagen. SEM demonstrates that the cryogel has a heteroporous structure with interconnecting pores. DSC measurements reveal that the cryogels have improved thermal stability in comparison with pure collagen. Moreover, the ESR shows that the water uptake of the cryogel decreases with DAS content. Evaporation tests indicate that the cryogel can hold moisture for a long time. Since both collagen and DAS are nontoxic and the resultant cryogel is blood‐compatible, the cryogel is expected to be useful, e.g., as wound dressing.magnified image
The Advantages of In Situ Surfactant Generation for Miniemulsions
Authors: El‐Jaby Ula , Cunningham Michael , McKenna Timothy F. L. 
Published: January 2010

AbstractThe stabilisation of miniemulsions using an in situ generated surfactant is presented. This surfactant, prepared from of a water‐soluble base and an oil‐soluble long chain acid was successfully used to create stable miniemulsions with up to 60 vol.‐% organic phase. It is shown that the creation of a surface active species at the oil–water interface allowed stable miniemulsions to be generated more rapidly than when using conventional surfactant. In addition, polymerised miniemulsions exhibited less secondary nucleation when in situ surfactants were used.magnified image
Investigation of Cationic Polymerization of β‐Pinene Using Calorimetric Measurements
Authors: Poço João Guilherme Rocha , Danese Modesto , Giudici Reinaldo 
Published: January 2010

AbstractAn experimental investigation of the kinetics of cationic polymerization of β‐pinene was performed using two different initiator systems under two different operating conditions (shot additions of initiator, and continuous feeding of monomer). The experiments were done using calorimetric measurements under isoperibolic conditions. The heat of polymerization of β‐pinene was found to be −30.6 kcal · mol−1. A simple kinetic model was tentatively proposed, and the model fit reasonably well to the different experimental runs. Different values of the fitting parameters were obtained for runs carried out under different conditions, which can probably be ascribed to the presence of adventitious impurities in the commercial‐grade monomer used.magnified image
Kinetic Study of Ethylene Homopolymerization in Slurry Using a Ziegler‐Natta Catalyst
Authors: Gemoets Frederik , Zhang Min , Karjala Thomas W. , Kolthammer Brian W. S. 
Published: January 2010

AbstractThe kinetic behavior of a Ziegler‐Natta catalyst at 86 °C under homopolymerization conditions in a continuous slurry polymerization reactor is studied. The effects of ethylene and hydrogen concentrations on the polymerization rate and polymer properties such as $\overline M _{\rm n}$ and $\overline M _{\rm w}$ were investigated. A kinetic model based on two catalytic lumped sites was developed to predict polymerization rate and $\overline M _{\rm n}$ and $\overline M _{\rm w}$ from reactor operating conditions. Each lumped site is assumed to be activated instantaneously. Such activation either is spontaneous or requires an ethylene molecule. The model has high fidelity in predicting experimental observations using kinetic parameters estimated from the experimental data and is used for industrial process development, optimization, and new product development.magnified image
Functionalization of Polymer Nanoparticles Formed by Microemulsion RAFT‐Mediated Polymerization
Authors: Pascual Sagrario , Urbani Carl N. , Monteiro Michael J. 
Published: January 2010

AbstractPolymer nanoparticles were prepared via a microemulsion RAFT polymerization using a xanthate chain transfer agent. The xanthate moiety at the polymer chain‐end preferentially resides at the polymer/water interface. This allows not only the formation of block copolymers to be synthesized in water but also further functionalization of the nanoparticle surface with other macromolecules. The synthesis of polystyrene latex nanoparticles by xanthate‐mediated microemulsion polymerization is described. The resulting nanoparticles had an average hydrodynamic diameter of 25 nm and a narrow particle size distribution, with PNIPAM being bound to the surface. Our novel method of functionalized polymer nanoparticles can be used for the coupling of important biomacromolecules.magnified image
Study of Burn Rate Suppressants in AP‐Based Composite Propellants
Authors: Ghorpade Vishwas Govindrao , Dey Abhijit , Jawale Lalita Sudhir , Kotbagi Amarnath Madiwal , Kumar Arvind , Gupta Manoj 
Published: January 2010

AbstractA number of composite propellant compositions based on various burn rate suppressants were formulated and studied with the aim to select a suitable burn rate suppressant for reducing the burn rate of the basic propellant composition. Theoretical properties of the compositions were computed by using NASA CEC‐71 program and the burn rate performance was evaluated. In addition, sensitivity, thermal, and mechanical properties of the compositions were also evaluated. The composition containing 60% AP, 10% Al, 20% binder, and 10% burn rate suppressant (melamine) was insensitive to friction and impact (28.8 kg and 0.56 m) and showed 90% weight loss. The formulation was found to be relatively superior.
A comprehensive examination of the contributions to the binding entropy of protein–ligand complexes
Authors: Singh Nidhi , Warshel Arieh 
Published: January 2010

AbstractOne of the most important requirements in computer‐aided drug design is the ability to reliably evaluate the binding free energies. However, the process of ligand binding is very complex because of the intricacy of the interrelated processes that are difficult to predict and quantify. In fact, the deeper understanding of the origin of the observed binding free energies requires the ability to decompose these free energies to their contributions from different interactions. Furthermore, it is important to evaluate the relative entropic and enthalpic contributions to the overall free energy. Such an evaluation is useful for assessing temperature effects and exploring specialized options in enzyme design. Unfortunately, calculations of binding entropies have been much more challenging than calculations of binding free energies. This work is probably the first to present microscopic evaluation of all of the relevant components to the binding entropy, namely configurational, polar solvation, and hydrophobic entropies. All of these contributions are evaluated by the restraint release approach. The calculated results shed an interesting light on major compensation effects in both the solvation and hydrophobic effect and, despite some overestimate, can provide very useful insight. This study also helps in analyzing some problems with the widely used molecular mechanics/Poisson‐Boltzmann surface area approach. Proteins 2010. © 2010 Wiley‐Liss, Inc.
Interpretation and consequences of Meyer–Neldel rule for conductivity of phase change alloys
Authors: Savransky S. D. , Yelon A. 
Published: January 2010

AbstractMeasurements of conductivity as a function of temperature were performed on a large number of memory cells of a GeSbTe phase change memory alloy, in both the set and reset states. Conductivity obeys the Meyer–Neldel rule in both states, with the same Meyer–Neldel, or isokinetic, temperature, but with conductivity prefactors about six orders of magnitude larger in the set than in the reset state. These observations are interpreted in terms of the multiexcitation entropy model, and conduction mechanisms are suggested. Their effect on the expected behavior of memories is considered.
High‐forward‐bias transport mechanism in a‐Si:H/c‐Si heterojunction solar cells
Authors: Schulze T. F. , Korte L. , Conrad E. , Schmidt M. , Rech B. 
Published: January 2010

AbstractIn order to elucidate the transport mechanism in a‐Si:H/c‐Si heterojunction solar cells under high forward bias (U > 0.5 V), we conducted temperature‐dependent measurements of current–voltage (I–V) curves in the dark and under illumination. ZnO:Al/(p)a‐Si:H/(n)c‐Si/(n+)a‐Si:H cells are compared with inversely doped structures and the impact of thin undoped a‐Si:H buffer layers on charge carrier transport is explored. The solar cell I–V curves are analyzed employing a generalized two‐diode model which allows fitting I–V data for a broad range of samples. The fitting results are complemented with numerical simulations using AFORS‐HET under consideration of microscopic a‐Si:H parameters as determined by constant‐final‐state‐yield photoelectron spectroscopy (CFSYS) to identify possible origins for a systematic increase of the high‐forward‐bias ideality factor along with the open‐circuit voltage (Voc). It is further shown that also for a‐Si:H/c‐Si heterojunctions, dark I–V curve fit parameters can unequivocally be linked to Voc under illumination, which may prove helpful for device assessment.
75As NMR relaxation in glassy Ge–As–Se
Authors: Mammadov Eldar , Taylor P. Craig , Reyes Arneil , Mehdiyeva Salima , Kuhns Phillip 
Published: January 2010

AbstractWe have used high magnetic fields to perform 75As nuclear magnetic resonance (NMR) relaxation measurements in Ge–As–Se glasses. The spin–lattice relaxation time T1 has been studied as a function of average coordination number, 〈r〉 and temperature, T. We show that the relaxation time constant, T1, in this system can be a useful tool to probe rigidity of the glassy matrix. In the two extreme cases, zero‐field nuclear quadrupole resonance (NQR) and high‐field NMR, T1 exhibits a similar dependence on the average coordination number. Namely, there is a region in this dependence at low 〈r〉 values, where the spin–lattice relaxation time does not change remarkably, followed by an increase in T1 in glasses with 〈r〉 more than 2.54. This transition can be correlated with the onset of rigidity percolation in the glassy matrix. The temperature dependence of the spin–lattice relaxation rate is found in the form T ∝ T2. This behavior is typical for As and other nuclei in glasses at temperatures below 300 K and is indicative of Raman‐like relaxation mechanism involving low‐frequency modes. Spin‐echo intensity for Ge2As2Se5 as a function of pulse separation exhibits exponential decay whose slope is the same as one of the average of the decay found from 75As NQR measurements. This result indicates to the presence of indirect dipolar coupling of arsenic atoms in this composition.
Passivation study of the amorphous–crystalline silicon interface formed using DC saddle‐field glow discharge
Authors: Bahardoust Barzin , Chutinan Alongkarn , Leong Keith , Gougam Adel B. , Yeghikyan Davit , Kosteski Tome , Kherani Nazir P. , Zukotynski Stefan 
Published: January 2010

AbstractThe DC saddle‐field (DCSF) glow discharge method was used to deposit intrinsic a‐Si:H onto c‐Si to passivate the c‐Si surface. The effective minority carrier lifetime in the heterostructures as a function of the excess minority carrier density in the c‐Si wafers was measured. The results were then analyzed in the context of recombination associated with interface defect states using three known recombination models. The defect density and the charge density at the interface are inferred. In addition subsequent annealing of the samples was studied. It is shown that for our intrinsic a‐Si:H samples improvements in surface passivation are directly correlated with the reduction of interface defects and not the reduction of minority carrier concentration at the interface due to electric field. We have achieved excellent surface passivation with effective carrier lifetime >4 ms for an intrinsic a‐Si:H sample deposited at a process temperature of 200 °C and thickness of about 30 nm. It is also demonstrated that subsequent annealing, at 240 °C, of the samples which were prepared at process temperatures <240 °C greatly increases the effective lifetime.
High efficiency amorphous and nanocrystalline silicon solar cells
Authors: Yan Baojie , Yue Guozhen , Xu Xixiang , Yang Jeffrey , Guha Subhendu 
Published: January 2010

AbstractThis paper reviews our progress of using nc‐Si:H as a low bandgap absorber material to substitute for a‐SiGe:H alloys in multi‐junction solar cells. We have focused on three topics: (1) high deposition rate, (2) large area uniformity of thickness and material properties, (3) high solar cell and module efficiencies. Initially, we investigated various deposition methods, including RF, VHF, and microwave glow discharges. After several years of systematic studies, we have been convinced that VHF glow discharge is an applicable method to attain high rate and large‐area uniform nc‐Si:H depositions. We also studied the stability of nc‐Si:H solar cells and observed various metastability phenomena in nc‐Si:H solar cells. We have reported an initial active‐area cell efficiency of 15.4% using an a‐Si:H/a‐SiGe:H/nc‐Si:H triple‐junction structure. Subsequently, we have increased the deposition rates to around 1.0–1.5 nm/s and achieved an initial active‐area efficiency of 13.4% using an a‐Si:H/nc‐Si:H/nc‐Si:H triple‐junction structure. Recently, a stable total‐area efficiency of 12.5% was measured at NREL on our a‐Si:H/nc‐Si:H/nc‐Si:H triple‐junction solar cell. We have also developed large‐area VHF deposition systems and demonstrated encouraging module efficiencies using a‐Si:H/nc‐Si:H/nc‐Si:H triple‐junction structures. Initial and stable aperture‐area (400 cm2) efficiencies of 11.0 and 10.1% have been achieved with fully encapsulated modules with a‐Si:H/nc‐Si:H/nc‐Si:H triple‐junction structures. In this paper, various aspects of nc‐Si:H solar cells are discussed, including the material structures, device design, light trapping, metastability, high efficiency solar cell optimization, and large‐area deposition.