bluuebunny/crossref_metadata_2025 huggingface dataset:
Renewable Resources for Functional Polymers and Biomaterials
Authors:   Royal Society of Chemistry
Published: August 2011

This book details polysaccharides and other important biomacromolecules covering their source, production, structures, properties, and current and potential application in the fields of biotechnology and medicine. It includes a systematic discussion on the general strategies of isolation, separation and characterization of polysaccharides and proteins. Subsequent chapters are devoted to polysaccharides obtained from various sources, including botanical, algal, animal and microbial.

In the area of botanical polysaccharides, separate chapters are devoted to the sources, structure, properties and medical applications of cellulose and its derivatives, starch and its derivatives, pectins, and exudate gums, notably gum arabic. Another chapter discusses the potential of hemicelluloses (xylans and xylan derivatives) as a new source of functional biopolymers for biomedical and industrial applications. The algal polysaccharide, alginate, has significant application in food, pharmaceuticals and the medical field, all of which are reviewed in a separate chapter. Polysaccharides of animal origin are included with separate chapters on the sources, production, biocompatibility, biodegradability and biomedical applications of chitin (chitosan) and hyaluronan. With the increasing knowledge and applications of genetic engineering there is also an introduction in the book to nucleic acid polymers, the genome research and genetic engineering.

Proteins and protein conjugates are covered, with one chapter providing a general review of structural glycoproteins, fibronectin and laminin, together with their role in the promotion of cell adhesion in vascular grafts, implants and tissue engineering. Another chapter discusses general aspects of a number of industrial proteins, including casein, caseinates, whey protein, gluten and soy proteins, with emphasis on their medical applications, and with reference to the potential of bacterial proteins. Another natural polymer resource, microbial polyesters, although small compared with polysaccharides and proteins, is also gaining increasing interest in biomedical technology and other industrial sectors. One chapter, therefore, is devoted to microbial polyesters, with comprehensive coverage of their biosynthesis, properties, enzymic degradation and applications.

By dealing with biopolymers at the molecular level, the book is aimed at the biomedical and wider materials science communities and provides an advanced overview of biopolymers at the graduate and postgraduate level. In addition it will appeal to both academic and industrial life scientists who are involved in research and development activities in the medical and biotechnology field.
Natural Polymer Resources: Isolation, Separation and Characterization
Authors: Praznik Werner , Löppert Renate , Huber Anton
Published: August 2011

This chapter describes various strategies and analytical techniques used for isolation, separation and characterization of natural polymers as the essential first step for their applications in food, feed and non-food products. It discusses different methods used for isolation and characterization of polysaccharides at the molecular and supramolecular levels. The discussion is exemplified by the detailed structural analysis of, among others, heteropolysaccharides like mucilage and fructans by permethylation, reductive cleavage and acetylation, followed by gas liquid chromatography. Data are also presented for supramolecular dimensions and molecular weights of poly-saccharides from various sources by different chromatographic methods combined with inline multiple detection systems (mass, light scattering, viscosity, fluorescence). The analysis and characterisation of plant and animal proteins are also briefly discussed.
Cellulose and Its Derivatives in Medical Use
Authors: Shibata Tohru
Published: August 2011

This chapter presents a review of cellulose and its derivatives used for medical, biotechnology and related applications. The cellulosic material covered includes micricrystalline cellulose, regenerated cellulose, and cellulose ethers and esters. The applications covered include hemodialysis, removal of pathogen in blood products, cellulosic adsorbents for purification of biopharmaceuticals, blood purification, and chiral separation, excipients for drugs, and some other medical applications. In most cases, the biological inertness, mechanical strength, and good availability are the key properties of cellulosics. However, its specific adsorption properties are important in some uses.
Hyaluronan: a Simple Molecule with Complex Character
Authors: Vercruysse Koen P.
Published: August 2011

This review aims to summarize the properties and applications of hyaluronan, a naturally-occurring, anionic polysaccharide. It provides an overview of its physic chemical properties, biosynthesis and biodegradation. It includes a discussion of the principal hyaluronan-binding proteins studied thus far. The existence of such proteins underscores the importance of this polysaccharide in cell-biological processes like cancer, inflammation or wound healing and these properties are discussed. Finally, this review summarizes some of the applications of hyaluronan in medicine, biotechnology and cosmetics.
Microbial Polyesters: Biosynthesis, Properties, Biodegradation and Applications
Authors: Ha Chang-Sik , Lee Won-Ki
Published: August 2011

This chapter presents a general review of microbial polyesters, their biosynthesis, properties and enzymic degradation. The discussion is framed around poly((R)-3-hydroxybutyrate-3-hydroxyvalerate), P(3HB-3HV), as this polymer is the focal point of research and application on microbial polyesters. Accordingly the biosynthesis, molecular weights, mechanical properties and biodegradation of a wide range of microbial polyesters and copolyesters are compared with those of P(3HB-3HV). The authors discuss how the biodegradability of microbial polyesters can be controlled by blending with different biodegradable and nonbiodegrable polymers (e.g. other polyesters or polystyrene), or surface modification by oxygen and CHF3 plasma treatment. Numerous current and potential applications of microbial polyesters in industry, agriculture, food and medicine are also highlighted, and hence the need for bringing down the relatively high production costs of these polymers.
Ionotropic glutamate receptor (iGluR)-like channels mediate MAMP-induced calcium influx in Arabidopsis thaliana
Authors: Kwaaitaal Mark , Huisman Rik , Maintz Jens , Reinstädler Anja , Panstruga Ralph
Published: August 2011

Binding of specific microbial epitopes [MAMPs (microbe-associated molecular patterns)] to PRRs (pattern recognition receptors) and subsequent receptor kinase activation are key steps in plant innate immunity. One of the earliest detectable events after MAMP perception is a rapid and transient rise in cytosolic Ca2+ levels. In plants, knowledge about the signalling events leading to Ca2+ influx and on the molecular identity of the channels involved is scarce. We used a transgenic Arabidopsis thaliana line stably expressing the luminescent aequorin Ca2+ biosensor to monitor pharmacological interference with Ca2+ signatures following treatment with the bacterial peptide MAMPs flg22 and elf18, and the fungal carbohydrate MAMP chitin. Using a comprehensive set of compounds known to impede Ca2+-transport processes in plants and animals we found strong evidence for a prominent role of amino acid-controlled Ca2+ fluxes, probably through iGluR (ionotropic glutamate receptor)-like channels. Interference with amino acid-mediated Ca2+ fluxes modulates MAMP-triggered MAPK (mitogen-activated protein kinase) activity and affects MAMP-induced accumulation of defence gene transcripts. We conclude that the initiation of innate immune responses upon flg22, elf18 and chitin recognition involves apoplastic Ca2+ influx via iGluR-like channels.
A microdevice for the creation of patent, three-dimensional endothelial cell-based microcirculatory networks
Authors: Chau Lien T. , Rolfe Barbara E. , Cooper-White Justin J.
Published: August 2011

Microvascular network formation is a significant and challenging goal in the engineering of large three-dimensional artificial tissue structures. We show here the development of a fully patent, 3D endothelial cell (microvascular) microfluidic network that has a single inlet and outlet, created in only 28 h in a microdevice involving fluid flow equivalent to natural vasculature. Our microdevice features a tailored “multi-rung ladder” network, a stylized mimic of an arterial-to-venous pedicle, designed to also allow for systematic and reproducible cell seeding. Immunofluorescence staining revealed a highly contiguous endothelial monolayer (human umbilical vein endothelial cells) throughout the whole network after 24 h of continuous perfusion. This network persisted for up to 72 h of culture, providing a useful template from which the effects of surface chemistry, fluid flow, and environmental conditions on the development of artificial vascular networks ex vivo may be rapidly and robustly evaluated.
Extended infrared photoresponse and gain in chalcogen-supersaturated silicon photodiodes
Authors: Said Aurore J. , Recht Daniel , Sullivan Joseph T. , Warrender Jeffrey M. , Buonassisi Tonio , Persans Peter D. , Aziz Michael J.
Published: August 2011

Highly supersaturated solid solutions of selenium or sulfur in silicon were formed by ion implantation followed by nanosecond pulsed laser melting. n+p photodiodes fabricated from these materials exhibit gain (external quantum efficiency >3000%) at 12 V of reverse bias and substantial optoelectronic response to light of wavelengths as long as 1250 nm. The amount of gain and the strength of the extended response both decrease with decreasing magnitude of bias voltage, but >100% external quantum efficiency is observed even at 2 V of reverse bias. The behavior is inconsistent with our expectations for avalanche gain or photoconductive gain.
Particle fluxes through the separatrix in the trapped particle diocotron mode
Authors: Tsidulko Yu. A. , Hilsabeck T. J. , O’Neil T. M.
Published: August 2011

In the trapped particle diocotron mode, the trapped particles undergo E × B drift motion in a uniform B field. Since such a flow is incompressible one is tempted to assume that the trapped particle density is constant along a fluid element. However, this is not the case since there is interchange of trapped and passing particles through the separatrix. This paper shows that a corrected fluid analysis, taking into account the particle flux through the separatrix, reproduces the same trapped particle density perturbation as obtained from the kinetic theory, thereby resolving confusion in earlier papers.
Conventional and inverse magnetocaloric effects in La0.45Sr0.55MnO3 nanoparticles
Authors: Rostamnejadi A. , Venkatesan M. , Alaria J. , Boese M. , Kameli P. , Salamati H. , Coey J. M. D.
Published: August 2011

The magnetocaloric effect of La0.45Sr0.55MnO3 nanoparticles was studied by dc magnetization measurements. A sample with mean particle size of about 140 nm exhibits both a conventional magnetocaloric effect around the Curie temperature (≈ 295 K) and a large inverse magnetocaloric effect around the antiferromagnetic-ferromagnetic transition temperature (≈ 200 K). The change of magnetic entropy increases monotonically with applied magnetic field and reaches the values of 5.51 J/kg K and − 2.35 J/kg K at 200 K and 295 K, respectively, in an applied field of 5 T. The antiferromagnetic-ferromagnetic transition is absent in a 36 nm size sample, which shows only a broad ferromagnetic transition around 340 K and a small change in magnetic entropy near room temperature. The results are discussed in terms of the entropy difference between the A-type antiferromagnetic ground state of La0.45Sr0.55MnO3 and the low moment ferromagnetic state. By comparing the results obtained on nanoparticles and bulk La0.45Sr0.55MnO3, one can conclude that the inverse magnetocaloric effect in a material showing the antiferromagnetic-ferromagnetic transition could be improved over a wide range of temperature by tuning the spin disorder in the antiferromagnetic state.
Calculations of the thermal conductivity of National Ignition Facility target materials at temperatures near 10 eV and densities near 10 g/cc using finite-temperature quantum molecular dynamics
Authors: Hanson David E. , Collins Lee A. , Kress Joel D. , Desjarlais Michael P.
Published: August 2011

Using quantum finite-temperature density functional theory molecular dynamics (QMD), we performed simulations of several important materials in the Inertial Confinement Fusion-National Ignition Facility nominal target designs, comprising various mixtures of proposed ablator materials (Be or CH) with the DT fuel. Simulations were done over a range of temperatures between 5 eV and 20 eV, at densities between 7.5 and ∼12.5 g/cc. From the QMD trajectories, we calculated the electrical and thermal conductivity. We estimated the number of free electrons per atom by fitting the frequency-dependent electrical conductivity to the Drude formula. The thermal conductivity of the fuel increases with density but that of the ablator material is insensitive to modest density variations. We find that the thermal conductivity depends strongly on the ablator/fuel mix fraction but a Faber-Ziman interpolation scheme provides a reasonable approximation. We also compare our QMD results to the Hubbard and Lee-More models.
Cascading failures and the emergence of cooperation in evolutionary-game based models of social and economical networks
Authors: Wang Wen-Xu , Lai Ying-Cheng , Armbruster Dieter
Published: August 2011

We study catastrophic behaviors in large networked systems in the paradigm of evolutionary games by incorporating a realistic “death” or “bankruptcy” mechanism. We find that a cascading bankruptcy process can arise when defection strategies exist and individuals are vulnerable to deficit. Strikingly, we observe that, after the catastrophic cascading process terminates, cooperators are the sole survivors, regardless of the game types and of the connection patterns among individuals as determined by the topology of the underlying network. It is necessary that individuals cooperate with each other to survive the catastrophic failures. Cooperation thus becomes the optimal strategy and absolutely outperforms defection in the game evolution with respect to the “death” mechanism. Our results can be useful for understanding large-scale catastrophe in real-world systems and in particular, they may yield insights into significant social and economical phenomena such as large-scale failures of financial institutions and corporations during an economic recession.
Stokesian peristaltic pumping in a three-dimensional tube with a phase-shifted asymmetry
Authors: Aranda Vivian , Cortez Ricardo , Fauci Lisa
Published: August 2011

Many physiological flows are driven by waves of muscular contractions passed along a tubular structure. This peristaltic pumping plays a role in ovum transport in the oviduct and in rapid sperm transport through the uterus. As such, flow due to peristalsis has been a central theme in classical biological fluid dynamics. Analytical approaches and numerical methods have been used to study flow in two-dimensional channels and three-dimensional tubes. In two dimensions, the effect of asymmetry due to a phase shift between the channel walls has been examined. However, in three dimensions, peristalsis in a non-axisymmetric tube has received little attention. Here, we present a computational model of peristaltic pumping of a viscous fluid in three dimensions based upon the method of regularized Stokeslets. In particular, we study the flow structure and mean flow in a three-dimensional tube whose asymmetry is governed by a single phase-shift parameter. We view this as a three-dimensional analog of the phase-shifted two-dimensional channel. We find that the maximum mean flow rate is achieved for the parameter that results in an axisymmetric tube. We also validate this approach by comparing our computational results with classical long-wavelength theory for the three-dimensional axisymmetric tube. This computational framework is easily implemented and may be adapted to more comprehensive physiological models where the kinematics of the tube walls are not specified a priori, but emerge due to the coupling of its passive elastic properties, force generating mechanisms, and the surrounding viscous fluid.
Comment on “Interaction of two solitary waves in quantum electron-positron-ion plasma” [Phys. Plasmas 18, 052301 (2011)]
Authors: Akbari-Moghanjoughi M.
Published: August 2011

Recently, Xu et al. [Phys. Plasmas 18, 052301 (2011)] have studied the effects of various plasma parameters on interaction of two ion-acoustic solitary waves in an unmagnetized three-dimensional electron-positron-ion quantum plasma. They have used the extended reductive perturbation technique, the so-called, extended Poincare-Lighthill-Kuo technique, to deduce from the model governing the quantum hydrodynamics differential equations leading to the soliton dynamical properties, namely, Korteweg-de Vries evolution equations (one for each wave) and coupled differential equations describing the phase-shift in trajectories of solitons due to the two dimensional collision. The variation of the calculated collision phase-shifts are then numerically inspected in terms of numerous plasma fractional parameters. In this comment, we give some notes specific to the validity of the results of above-mentioned article and refer to important misconceptions about the use of the Fermi-temperature in quantum plasmas, appearing in this article and many other recently published ones.
A combined high-pressure experimental and theoretical study of the electronic band-structure of scheelite-type AWO4 (A = Ca, Sr, Ba, Pb) compounds
Authors: Lacomba-Perales R. , Errandonea D. , Segura A. , Ruiz-Fuertes J. , Rodríguez-Hernández P. , Radescu S. , López-Solano J. , Mujica A. , Muñoz A.
Published: August 2011

The optical-absorption edge of single crystals of CaWO4, SrWO4, BaWO4, and PbWO4 has been measured under high pressure up to ∼20 GPa at room temperature. From these measurements, we have obtained the evolution of the band-gap energy with pressure. We found a low-pressure range (up to 7–10 GPa) where alkaline-earth tungstates present a very small Eg pressure dependence (− 2.1 < dEg/dP < 8.9 meV/GPa). In contrast, in the same pressure range, PbWO4 has a pressure coefficient of − 62 meV/GPa. The high-pressure range is characterized in the four compounds by an abrupt decrease of Eg followed by changes in dEg/dP. The band-gap collapse is larger than 1.2 eV in BaWO4. We also calculated the electronic-band structures and their pressure evolution. The calculations allow us to interpret experiments considering the different electronic configurations of divalent metals. Changes in the pressure evolution of Eg are correlated with the occurrence of pressure-induced phase transitions. The band structures for the low- and high-pressure phases are also reported. No metallization of any of the compounds is detected in experiments nor is it predicted by the calculations.
The dislocation density and twin-boundary frequency determined by X-ray peak profile analysis in cold rolled magnetron-sputter deposited nanotwinned copper
Authors: Csiszár Gábor , Balogh Levente , Misra Amit , Zhang Xinghang , Ungár Tamás
Published: August 2011

The dislocation density and the average twin boundary frequency is determined quantitatively in as-deposited and cold-rolled nanotwinned Cu thin films by high-resolution X-ray line profile analysis. After cold-rolling the dislocation density increases considerably, whereas the twin boundary frequency decreases only slightly. The physical parameters of the substructure provided by the quantitative X-ray analysis are in agreement with earlier transmission electron microscopy observations. The flow stress of the as-deposited and the cold-rolled films is directly correlated with the average thickness of twin lamellae and the dislocation density by taking into account the Hall-Petch and Taylor type strengthening mechanisms.
Structural and electronic properties of nitrogen ion implanted ultra nanocrystalline diamond surfaces
Authors: Panda Kalpataru , Sundaravel B. , Panigrahi B. K. , Magudapathy P. , Nandagopala Krishna D. , Nair K. G. M. , Chen Huang-Chin , Lin I-Nan
Published: August 2011

Enhanced electron field emission (EFE) properties have been observed for nitrogen implanted ultra-nanocrystalline diamond (UNCD) films grown by microwave plasma enhanced CVD. X-ray photoelectron spectroscopy (XPS) measurements show that sp2 fraction and C-N bonding increase upon N-implantation and annealing. Significant difference in current-voltage (I-V) curves at the grain and grain boundary has been observed from scanning tunneling spectroscopic (STS) measurement. From the variation of normalized conductance (dI/dV)/(I/V) versus V, bandgap is measured to be 4.8 eV at the grain and 3.8 eV at the grain boundary for as prepared UNCD. Upon nitrogen implantation and annealing, the bandgap decreases for both grain and grain boundary and density of states are introduced in the bandgap. Current imaging tunneling spectroscopy (CITS) imaging shows that the grain boundaries have higher conductivity than the grains and are the prominent electron emitters. The enhancement in EFE properties upon nitrogen implantation is accounted for by the decrease in bandgap, increase in density of states in the bandgap caused by increase in sp2 content and new bonds at the diamond grains, and increase in conductivity at the grain boundary.
Infrared photoluminescence of arsenic-doped HgCdTe in a wide temperature range of up to 290 K
Authors: Zhang Xiaohua , Shao Jun , Chen Lu , Lü Xiang , Guo Shaoling , He Li , Chu Junhao
Published: August 2011

Infrared modulated photoluminescence (PL) spectra are recorded in the temperature range of 11.5-290 K for both as-grown and p-type annealed arsenic-doped narrow-gap HgCdTe epilayers prepared by molecular beam epitaxy. Curve fittings indicate that conduction band-to-valence band transition is just detectable at 77 K but will dominate the PL line shape at temperatures above about 200 K. Below 100 K, transitions are mainly impurity-related. Shallow impurity levels are estimated to be about 12, 20, 17, and 26 meV, respectively, for VHg and AsTe as acceptors, and AsHg and TeHg as donors, which are very similar to those established by theory and/or infrared photoreflectance spectroscopy. The p-type annealing removes deep level-related PL features that are only observed in the as-grown HgCdTe epilayer. Comparison with previous PL study suggests that infrared modulated PL technique can serve as an easily accessible pathway for characterizing impurities in narrow-gap HgCdTe when PL spectra are recorded with good signal-to-noise ratio in a wide range of up to room temperature.
Proton evolved local field solid-state nuclear magnetic resonance using Hadamard encoding: Theory and application to membrane proteins
Authors: Gopinath T. , Mote Kaustubh R. , Veglia Gianluigi
Published: August 2011

NMR anisotropic parameters such as dipolar couplings and chemical shifts are central to structure and orientation determination of aligned membrane proteins and liquid crystals. Among the separated local field experiments, the proton evolved local field (PELF) scheme is particularly suitable to measure dynamically averaged dipolar couplings and give information on local molecular motions. However, the PELF experiment requires the acquisition of several 2D datasets at different mixing times to optimize the sensitivity for the complete range of dipolar couplings of the resonances in the spectrum. Here, we propose a new PELF experiment that takes the advantage of the Hadamard encoding (HE) to obtain higher sensitivity for a broad range of dipolar couplings using a single 2D experiment. The HE scheme is obtained by selecting the spin operators with phase switching of hard pulses. This approach enables one to detect four spin operators, simultaneously, which can be processed into two 2D spectra covering a broader range of dipolar couplings. The advantages of the new approach are illustrated for a U-15N NAL single crystal and the U-15N labeled single-pass membrane protein sarcolipin reconstituted in oriented lipid bicelles. The HE-PELF scheme can be implemented in other multidimensional experiments to speed up the characterization of the structure and dynamics of oriented membrane proteins and liquid crystalline samples.
Spintronic properties of graphene films grown on Ni(111) substrate
Authors: Gong S. J. , Li Z. Y. , Yang Z. Q. , Gong Cheng , Duan Chun-Gang , Chu J. H.
Published: August 2011

Graphene is believed to be a promising candidate for spintronic applications. In this study, we investigate the electronic, magnetic, and, especially, spintronic properties of graphene films grown on Ni(111) substrate using relativistic density-functional calculations. Enhanced Rashba spin-orbit coupling (SOC), with a magnitude of up to 20 meV—several orders of magnitude larger than the intrinsic SOC strength in freestanding graphene—is found at the graphene–Ni(111) interface. The hybridization between graphene’s pz states and Ni’s 3d states magnetizes the interfacial carbon atoms and induces a sizable exchange splitting in the π band of the graphene sheet. The calculated results agree well with the recently reported experimental data and provide a deep understanding of the spintronic behavior of graphene in contact with a 3d-ferromagnet.
Optical avalanche in Ho:Yb:Gd2O3 nanocrystals
Authors: Dwivedi Y. , Bahadur A. , Rai S. B.
Published: August 2011

Intense green upconversion emission in Ho:Yb:Gd2O3 spherical nanoparticles is reported through hetrolooping enhanced energy transfer process. Different techniques used for structural characterization divulge the formation of spherical Ho:Yb:Gd2O3 crystals of diameter ∼100 nm. Efficient energy transfer from Yb3+ → Ho3+ ions set spherical nanocrystal to emit in the range of UV-NIR via three NIR photons absorption process. Power dependence and the temporal evolution of upconversion emission intensity suggest the occurrence of a photon avalanche process. The enhancement in emission intensity in nanophosphor sample has been explained and the photophysics involved is correlated with the unique structural properties of the crystallites formed and the time resolved spectroscopy.
Using singular values to build a subgrid-scale model for large eddy simulations
Authors: Nicoud Franck , Toda Hubert Baya , Cabrit Olivier , Bose Sanjeeb , Lee Jungil
Published: August 2011

An eddy-viscosity based, subgrid-scale model for large eddy simulations is derived from the analysis of the singular values of the resolved velocity gradient tensor. The proposed σ-model has, by construction, the property to automatically vanish as soon as the resolved field is either two-dimensional or two-component, including the pure shear and solid rotation cases. In addition, the model generates no subgrid-scale viscosity when the resolved scales are in pure axisymmetric or isotropic contraction/expansion. At last, it is shown analytically that it has the appropriate cubic behavior in the vicinity of solid boundaries without requiring any ad-hoc treatment. Results for two classical test cases (decaying isotropic turbulence and periodic channel flow) obtained from three different solvers with a variety of numerics (finite elements, finite differences, or spectral methods) are presented to illustrate the potential of this model. The results obtained with the proposed model are systematically equivalent or slightly better than the results from the Dynamic Smagorinsky model. Still, the σ-model has a low computational cost, is easy to implement, and does not require any homogeneous direction in space or time. It is thus anticipated that it has a high potential for the computation of non-homogeneous, wall-bounded flows.
The immobilization and electrical response of single-stranded DNA molecules on pentacene transistors
Authors: Zhu Qingping , Xing Feifei , Liu Changhe , Hu Yulei , Liu Na , Wang Jun
Published: August 2011

The immobilization and electrical response of single-stranded deoxyribonucleic acid (ssDNA) on pentacene-based transistors have been studied. The result displays that ssDNA molecules may be well immobilized onto pentacene film surface observed by atomic force microscopy. The device parameters of transistors including drain-source current and threshold voltage exhibit an obvious change by comparing with pristine transistors that can be attributed to the additional positive charges induced by immobilized ssDNA molecules. Furthermore, the dependence of electrical response on the ssDNA solution concentration was disclosed.
A stochastic surrogate Hamiltonian approach of coherent and incoherent exciton transport in the Fenna-Matthews-Olson complex
Authors: Renaud N. , Ratner M. A. , Mujica V.
Published: August 2011

The capture and transduction of energy in biological systems is clearly necessary for life, and nature has evolved remarkable macromolecular entities to serve these purposes. The Fenna-Matthews-Olson (FMO) complex serves as an intermediate to transfer the energy from the chlorosome to the special pairs of different photo systems. Recent observations have both suggested the importance of coherent exciton transport within the FMO and motivated an elegant and appropriate theoretical construct for interpreting these observations. Here we employ a different approach to exciton transport in a relaxing environment, one based on the stochastic surrogate Hamiltonian method. With it, we calculate the quantum trajectories through the FMO complex both for the model involving seven bacteriochlorophylls that has been used before, and for one involving an eighth bacteriochlorophyll, which has been observed in some new and very important structural work. We find that in both systems, efficient energy transfer to the ultimate receptor occurs, but that because of the placement of, and energy relaxation among, the different bacteriochlorophyll subunits in the FMO complex, the importance of coherent oscillation that was discussed extensively for the seven site system is far less striking for the eight site system, effectively because of the weak mixing between the initial site and the remainder of the system. We suggest that the relevant spectral densities can be determinative for the energy transport route and may provide a new way to enhance energy transfer in artificial devices.
High-level ab initio potential energy surfaces and vibrational energies of H2CS
Authors: Yachmenev Andrey , Yurchenko Sergei N. , Ribeyre Tristan , Thiel Walter
Published: August 2011

Six-dimensional (6D) potential energy surfaces (PESs) of H2CS have been generated ab initio using the recently proposed explicitly correlated (F12) singles and doubles coupled cluster method including a perturbational estimate of connected triple excitations, CCSD(T)-F12b [T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys. 127, 221106 (2007)] in conjunction with F12-optimized correlation consistent basis sets. Core-electron correlation, high-order correlation, scalar relativistic, and diagonal Born-Oppenheimer terms were included as additive high-level (HL) corrections. The resulting 6D PESs were represented by analytical functions which were used in variational calculations of the vibrational term values below 5000 cm−1. The best PESs obtained with and without the HL corrections, VQZ-\documentclass[12pt]{minimal}\begin{document}${\rm F12}^{*\rm HL}$\end{document}F12* HL and VQZ-F12*, reproduce the fundamental vibrational wavenumbers with mean absolute deviations of 1.13 and 1.22 cm−1, respectively. A detailed analysis of the effects of the HL corrections shows how the VQZ-F12 results benefit from error cancellation. The present purely ab initio PESs will be useful as starting points for empirical refinements towards an accurate “spectroscopic” PES of H2CS.
Open-shell reduced density matrix functional theory
Authors: Rohr Daniel R. , Pernal Katarzyna
Published: August 2011

Open-shell reduced density matrix functional theory is established by investigating the domain of the exact functional. For spin states that are the ground state, a particularly simple set is found to be the domain. It cannot be generalized to other spin states. A number of conditions satisfied by the exact density matrix functional is formulated and tested for approximate functionals. The exact functional does not suffer from fractional spin error, which is the source of the static correlation error in dissociated molecules. We prove that a simple approximation (called the Buijse-Baerends functional, Müller or square root functional) has a non-positive fractional spin error. In the case of the H atom the error is zero. Numerical results for a few atoms are given for approximate density and density matrix functionals as well as a recently developed range-separated combination of both.
High-speed analog fiber-optic link for electromagnetic interference suppression in infrared power measurement
Authors: Liu Fei , Strauch Stefanie , Horton Robert , Evans Russell , Hwang David
Published: August 2011

Electromagnetic interference (EMI) is a common problem in a high-power pulsed infrared laser measurement. In order to eliminate susceptibility to radiated EMI, we developed, tested and implemented an infrared power measurement system using a high-speed analog fiber-optic link. Key components are commercially available parts designed for high-speed digital data transmission, but can be operated in analog mode. We successfully utilized the system for time-resolved measurements of high-power transversely-excited atmospheric-pressure CO2 lasers in amplifier and oscillator configurations. This paper presents experimental setup, testing results, and the details of the laser power measurements results.
An enthalpy landscape view of homogeneous melting in crystals
Authors: Nieves Alex M. , Sinno Talid
Published: August 2011

A detailed analysis of homogeneous melting in crystalline materials modeled by empirical interatomic potentials is presented using the theory of inherent structures. We show that the homogeneous melting of a perfect, infinite crystalline material can be inferred directly from the growth exponent of the inherent structure density-of-states distribution expressed as a function of formation enthalpy. Interestingly, this growth is already established by the presence of very few homogeneously nucleated point defects in the form of Frenkel pairs. This finding supports the notion that homogeneous melting is appropriately defined in terms of a one-phase theory and does not require detailed consideration of the liquid phase. We then apply this framework to the study of applied hydrostatic compression on homogeneous melting and show that the inherent structure analysis used here is able to capture the correct pressure-dependence for two crystalline materials, namely silicon and aluminum. The coupling between the melting temperature and applied pressure arises through the distribution of formation volumes for the various inherent structures.
High resolution 3D gas-jet characterization
Authors: Landgraf Björn , Schnell Michael , Sävert Alexander , Kaluza Malte C. , Spielmann Christian
Published: August 2011

We present a tomographic characterization of gas jets employed for high-intensity laser-plasma interaction experiments where the shape can be non-symmetrically. With a Mach-Zehnder interferometer we measured the phase shift for different directions through the neutral density distribution of the gas jet. From the recorded interferograms it is possible to retrieve 3-dimensional neutral density distributions by tomographic reconstruction based on the filtered back projections. We report on criteria for the smallest number of recorded interferograms as well as a comparison with the widely used phase retrieval based on an Abel inversion. As an example for the performance of our approach, we present the characterization of nozzles with rectangular openings or gas jets with shock waves. With our setup we obtained a spatial resolution of less than 60 μm for an Argon density as low as 2 × 1017 cm−3.
Wang’s shrinking cylinder problem with suction near a stagnation point
Authors: Lok Y. Y. , Pop I.
Published: August 2011

In this paper, the steady axisymmetric stagnation point flow of a viscous and incompressible fluid over a shrinking circular cylinder with mass transfer (suction) is studied. The flow is induced by a cylinder shrinking with a linear velocity distribution from the stagnation line. The fluid flow solution is an exact solution of the Navier-Stokes equation, which is reduced to a nonlinear ordinary differential equation. This equation is solved numerically for some values of the governing parameters that involves a Reynolds number R, a shrinking parameter λ, and a suction parameter γ. The effects of these governing parameters on the velocity and temperature profiles, skin friction coefficient, Nusselt number, as well as the distributions of the streamlines are investigated. The obtained results for the case of fixed cylinder are compared with those from the open literature and it is shown that they are in excellent agreement. The solutions are non-unique for some values of λ (<0). The streamlines show that the flow structures become complicated due to the shrinking and suction effects.
Laser operation of Ga(NAsP) lattice-matched to (001) silicon substrate
Authors: Liebich S. , Zimprich M. , Beyer A. , Lange C. , Franzbach D. J. , Chatterjee S. , Hossain N. , Sweeney S. J. , Volz K. , Kunert B. , Stolz W.
Published: August 2011

The lattice-matched growth of the direct band gap material Ga(NAsP) is a seminal concept for the monolithic integration of III/V laser on a silicon substrate. Here, we report on the growth, characterization, and lasing properties of Ga(NAsP)/(BGa)(AsP) multi quantum well heterostructures embedded in (BGa)P cladding layers which were deposited on an exactly oriented (001) Si substrate. Structural investigations confirm a high crystal quality without any indication for misfit or threading dislocation formation. Laser operation between 800 nm and 900 nm of these broad area device structures was achieved under optical pumping as well as electrical injection for temperatures up to 150 K. This “proof of principle” points to the enormous potential of Ga(NAsP) as an optical complement to Si microelectronics.
Organosilane deposition for microfluidic applications
Authors: Glass Nick R. , Tjeung Ricky , Chan Peggy , Yeo Leslie Y. , Friend James R.
Published: August 2011

Treatment of surfaces to change the interaction of fluids with them is a critical step in constructing useful microfluidics devices, especially those used in biological applications. Silanization, the generic term applied to the formation of organosilane monolayers on substrates, is both widely reported in the literature and troublesome in actual application for the uninitiated. These monolayers can be subsequently modified to produce a surface of a specific functionality. Here various organosilane deposition protocols and some application notes are provided as a basis for the novice reader to construct their own silanization procedures, and as a practical resource to a broader range of techniques even for the experienced user.
Modeling and reconstruction of optical tomography for endoscopic applications: Simulation demonstration
Authors: Chen Xueli , Liang Jimin , Zhao Heng , Qu Xiaochao , Chen Duofang , Zhang Qitan , Gao Xinbo , Tian Jie
Published: August 2011

Applications of optical tomography in noninvasive cancer imaging have been restricted to specific organs that can be measured or transilluminated externally. However, these external measurements are limited to superficial area or small animals, and inaccurate or immeasurable for imaging the internal organ deep inside the large body. Endoscopic optical tomography (EOT) overcomes this limitation and improves this inaccuracy or immeasurability by taking the detector closer to the region of interest with a minimally invasive approach. In this letter, we present an endoscopic algorithm for EOT, including establishing a realistic endoscopic geometry, constructing an accurate forward model and advancing an effective inverse reconstruction algorithm. Bioluminescent mode based simulations show the accuracy and effectiveness of the endoscopic algorithm in both localization and quantification.
Detection of metallic In nanoparticles in InGaN alloys
Authors: Komissarova T. A. , Jmerik V. N. , Ivanov S. V. , Paturi P.
Published: August 2011

We report on detection of metallic indium nanoparticles in the InxGa1−xN alloys grown by plasma-assisted molecular beam epitaxy at x exceeding 0.38 ± 0.03, using Hall effect measurements in a wide magnetic field range (up to 30 T). Observation of the abnormally increasing magnetic field dependences of the absolute value of Hall coefficient, approximated in the frames of the model taking into account influence of the highly conductive inclusions, was employed as a reliable criterion of presence of the In nanoparticles in the studied layers. The onset of In inclusions is governed by x rather than growth stoichiometric conditions.
A tunable electron wave filter based on graphene superlattices with periodic potential patterns
Authors: Hui-yun Zhang , Ying Gao , Yu-ping Zhang , Shi-lin Xu , Shi-fan Wang
Published: August 2011

We have theoretically calculated a tunable electron wave filter based on graphene superlattices with one-dimensional periodic potentials. It is found that such structure with defect layer possess an unusual tunneling state occurring inside the forbidden gap, and the tunneling state can be modulated by changing the width of the defect layer. We have also achieved independently tunable multichannel electron wave filters by constructing fractal structures. The modulation of the transmission gap by width, period number, and incidence angle may lead to potential applications in graphene-based electronic devices.
Strong terahertz radiation by beating of spatial-triangular lasers in a plasma
Authors: Malik Anil K. , Malik Hitendra K. , Stroth Ulrich
Published: August 2011

Resonant excitation of terahertz (THz) radiation by beating of two spatial-triangular laser beams having different frequencies and wave numbers but the same electric fields is proposed, where the ponderomotive force in the transverse direction is realized due to the beating and spatial variation of the lasers’ fields. This gives rise to a stronger transient transverse current due to a sharp gradient in the laser field, and subsequently THz radiation is excited resonantly in the presence of a periodic density structure. The present scheme yields the THz field ∼105 kV/cm and the efficiency ∼10−2 for the laser intensity ∼1014 W/cm2.
Highly efficient bi-directional organic light-emitting diodes by strong micro-cavity effects
Authors: Lee Jonghee , Hofmann Simone , Thomschke Michael , Furno Mauro , Hyun Kim Yong , Lüssem Björn , Leo Karl
Published: August 2011

We report on highly enhanced light outcoupling of bi-directional red phosphorescent organic light-emitting diodes (BiOLEDs) by strong micro-cavity effects. Inserting additional metal layers between the indium tin oxide (ITO) anode and the hole transporting layer (HTL) and controlling the thickness of the counter metal electrode result in dramatic changes in electroluminescence spectra and angular distribution. We find that the external quantum efficiency (EQE) for both bottom and top emitting side can be significantly improved: the overall EQE reaches up to 24.24%.
Ignition of a large volume plasma with a plasma jet
Authors: Laroussi M. , Akman M. A.
Published: August 2011

Here we report on a method to generate a long plasma plume and to ignite a large volume plasma by means of the jet. The plasma plume is generated by our tube reactor and then introduced into a chamber where the pressure is controlled. We discovered there are three operating phases: A phase where the plume length remains approximately constant, followed by a second phase where the jet increases in length as the pressure decreases. Then at pressures below 70 Torr a mode transition occurs where the plume length decreases and the plasma expands until the entire chamber is filled.
Contact Zones: Participation, Materiality, and the Messiness of Interaction
Authors: Askins Kye , Pain Rachel
Published: August 2011

Recent debates around urban encounter, integration cosmopolitanism, and renewed engagement with contact theory have raised questions about the spaces of interaction that may enable meaningful encounters between different social groups. Reflecting on a participatory art project with young people of African and British heritage in northeast England, we argue that discussion and practice around participatory action research, including the deployment of contact zones as theory and method, can cast some light on what fosters transformative spaces. Through analysis of two different approaches to community art used in the project, we show how elements of each enabled and disabled meaningful interaction between young people. We draw attention to the materiality of art (the tools) within participatory practices (the doing of it) in contributing to a space where interactions might take place, emphasising a complex interplay across/between actors, materials, and space that frames encounters as emergent, transitory, fragile, and yet hopeful. We examine the potential of a focus on the material in thinking beyond moments of encounter to how transformative social relations may be ‘scaled up’ before considering the implications for research and policy.
Face Viewpoint Effects about Three Axes: The Role of Configural and Featural Processing
Authors: Favelle Simone K , Palmisano Stephen , Avery Georgina
Published: August 2011

We directly compared recognition for faces following 0° – 75° viewpoint rotation about the yaw, pitch, and roll axes. The aim was to determine the extent to which configural and featural information supported face recognition following rotations about each of these axes. Experiment 1 showed that performance on a sequential-matching task was viewpoint-dependent for all three types of rotation. The best face-recognition accuracy and shortest reaction time was found for roll rotations, then for yaw rotations, and finally the worst accuracy and slowest reaction time was found for pitch rotations. Directional differences in recognition were found for pitch rotations, but not for roll or yaw. Experiment 2 provided evidence that, in all three cases, viewpoint-dependent declines in recognition were primarily driven by the loss of configural information. However, it also appeared that significant featural information was lost following yaw and pitch (but not roll) rotations. Together, these findings show that unfamiliar-face recognition is viewpoint-dependent following rotation about each axis (and in each direction), and that performance is based on the availability of configural and, to a lesser extent, featural information.