bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure homology and interaction redundancy for discovering virus–host protein interactions
Authors: de Chassey Benoît , Meyniel‐Schicklin Laurène , Aublin‐Gex Anne , Navratil Vincent , Chantier Thibaut , André Patrice , Lotteau Vincent
Published: September 2013

Virus–host interactomes are instrumental to understand global perturbations of cellular functions induced by infection and discover new therapies. The construction of such interactomes is, however, technically challenging and time consuming. Here we describe an original method for the prediction of high‐confidence interactions between viral and human proteins through a combination of structure and high‐quality interactome data. Validation was performed for the NS1 protein of the influenza virus, which led to the identification of new host factors that control viral replication.
Brain site-specific proteome changes in aging-related dementia
Authors: Manavalan Arulmani , Mishra Manisha , Feng Lin , Sze Siu Kwan , Akatsu Hiroyasu , Heese Klaus
Published: September 2013

This study is aimed at gaining insights into the brain site-specific proteomic senescence signature while comparing physiologically aged brains with aging-related dementia brains (for example, Alzheimer’s disease (AD)). Our study of proteomic differences within the hippocampus (Hp), parietal cortex (pCx) and cerebellum (Cb) could provide conceptual insights into the molecular mechanisms involved in aging-related neurodegeneration. Using an isobaric tag for relative and absolute quantitation (iTRAQ)-based two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D-LC-MS/MS) brain site-specific proteomic strategy, we identified 950 proteins in the Hp, pCx and Cb of AD brains. Of these proteins, 31 were significantly altered. Most of the differentially regulated proteins are involved in molecular transport, nervous system development, synaptic plasticity and apoptosis. Particularly, proteins such as Gelsolin (GSN), Tenascin-R (TNR) and AHNAK could potentially act as novel biomarkers of aging-related neurodegeneration. Importantly, our Ingenuity Pathway Analysis (IPA)-based network analysis further revealed ubiquitin C (UBC) as a pivotal protein to interact with diverse AD-associated pathophysiological molecular factors and suggests the reduced ubiquitin proteasome degradation system (UPS) as one of the causative factors of AD.
Role of Plant Biomass in Heavy Metal Treatment of Contaminated Water
Authors: Srinivasan Rajani
Published: September 2013

This chapter gives an account of recent developments in biomass derived from plants as treatment agents in removal of heavy metals from wastewater. Several conventional methods, like chemical precipitation, lime coagulation, ion exchange, reverse osmosis and solvent extraction, are being used for metal removal. These conventional methods for heavy metal removal from wastewaters are often cost prohibitive, having inadequate efficiencies at low metal concentrations. The major advantages of biosorption over conventional treatment methods include low cost and high efficiency of metal removal from dilute solutions, minimization of chemical and/or biological sludge, no additional nutrient requirement, and regeneration of the biosorbent and the possibility of metal recovery. This chapter also describes the types of mechanism involved in the biosorption process and the variables affecting the biosorption of different metals. Recent developments in plant-based biosorbents, their types and the metals removed are tabulated.
Microchip Technology in Metabolomics
Authors: Sikanen Tiina M.
Published: September 2013

Device miniaturization is generally considered to improve the efficiency and throughput of instrumental chemical analysis. In this chapter, the power of miniaturization is examined from the viewpoint of microfabrication. Currently, microfabrication techniques are being increasingly applied to prepare fluidic arrays on silicon, glass, and polymer substrates with the final goal of realizing so‐called micro total chemical analysis systems (µTAS), also referred to as lab(oratory)‐on‐a‐chip. These miniaturized arrays aim at integration of multiple analytical unit operations on a single microfabricated chip (i.e., microchip), including sample preparation, injection, separation and detection. Sometimes reaction chambers are also implemented on the chip and integrated with on‐line sample preparation and/or separation systems. Although exploitation of microchip‐based analysis in small‐molecule analysis remains somewhat limited compared with proteomics, the vast potential of this technology is reviewed in the light of potential future applications in metabolomics. Often, examples are given to technological solutions which are not applied to metabolomics per se, but rather to related fields. Throughout this chapter, the emphasis is put on microchip electrophoresis (MCE) techniques. In addition, practical aspects related to pressurized methods, such as microchip liquid chromatography, are also presented. Microchip‐based off‐line and on‐line integrated sample clean‐up and preconcentration techniques are mainly touched upon where amenable to integration with a microfluidic separation system.
Data Handling
Authors: Hyötyläinen Tuulia , Orešič Matej
Published: September 2013

Typical metabolomics experiments produce large amounts of information that need to be transformed into biologically relevant information such as metabolite identities and concentrations. The data preprocessing steps include peak detection, alignment, normalization and quantification. As for analytical quality, the quality of the data processing also needs to be monitored; which is generally a challenging task. Owing to the increasing demand for metabolomics analyses of large sample series, such as in a medical epidemiological setting, there is also a need to correct the potential ‘batch effect,’ i.e., the analytical variation that may occur due to minor changes in laboratory conditions over extended periods in time. Advances have been made in this area, although processing of large‐scale metabolomics data remains an important and emerging aspect of methodological developments.
Introduction
Authors: Schneider Hans-Jörg
Published: September 2013

Non-covalent interactions dominate central parts of living systems, and provide a major role for chemistry in healthcare and in biotechnology. Modern synthetic methods have made it possible to prepare host compounds for virtually each target molecule, including those which function in the natural medium, water. This book concentrates on the progress achieved with synthetic ligands interacting with biological systems.
Complexation of Biomedically Important Organic Compounds
Authors: Schneider Hans-Jörg
Published: September 2013

This chapter deals with applications of synthetic receptors for sensing organic molecules, from metabolites via nucleotides, aminoacids, peptides, carbohydrates and alkaloids to drugs and toxins. Many synthetic host compounds have been designed for a highly sensitive and selective detection, most often with suitable units for optical signalling. The uses of such receptors for modulation of protein interactions and for detoxification, etc. are also mentioned. Emphasis is given to host structures which are not treated specifically in other chapters, namely to cyclophanes, molecular tweezers, and crown ethers.
Cucurbiturils in Drug Delivery And For Biomedical Applications
Authors: Saleh Na’il , Ghosh Indrajit , Nau Werner M.
Published: September 2013

This chapter illustrates the potential of cucurbiturils, a synthetic class of macrocycles, as well as their derivatives and analogues for drug delivery applications, attempting a comprehensive coverage of the rapidly unfolding scholarly activity in this area up to including early 2013. Cucurbiturils are water soluble, pumpkin-shaped, symmetrical, and rigid host molecules, that encapsulate various types of drug molecules, neutral as well as positively charged, via non-covalent interactions which lead up to femtomolar affinities. Due to their peculiar chemical structure, a secluded hydrophobic inner cavity with two partially negative charged carbonyl portals, they provide an inert environment to protect several drug molecules from unwanted bimolecular chemical and photochemical reactions, and the complexation alters the chemical reactivities of encapsulated drugs. Examples of the effects of cucurbiturils on the solubilization, ionization, activation, stabilization, and chemical protection (in vitro as well as in vivo) of drug molecules are provided. In addition, applications of cucurbiturils and their derivatives in targeted drug delivery, for controlled drug release, and for sensing biologically important molecules are discussed. The spurred interest in cucurbituril-based drug delivery systems and their low, if not negligible, acute toxicity are expected to lead to drug delivery approaches, which are complementary to those for other supramolecular host molecules, particularly cyclodextrins, and to alternative formulation systems such as polymers, hydrogels, and liposomes.
Biomolecular Interactions of Platinum Complexes
Authors: Harper Benjamin W. , Li Feng , Beard Rhys , Garbutcheon-Singh K. Benjamin , Ng Neville S. , Aldrich-Wright Janice R.
Published: September 2013

Deoxyribonucleic acid is generally accepted as the primary biomolecular target of the first platinum-based chemotherapeutic agent, cisplatin, which was documented in 1845, characterised in 1893 and its potential discovered in 1965. Initial attempts to understand the structural significance of the compound by combinatorial means saw early conceptions of structure–activity relationships that were soon challenged. Almost 50 years and thousands of complexes later, DNA still remains the primary target in a variety of interactions ranging from differences in base-pair preference, irreversible covalent binding, and reversible minor/major groove binding and intercalation. Developmental efforts have seen active cytotoxic platinum complexes with structures derived beyond initial assumptions through a diversity of ligand substitution and multinuclear linkages. Nonetheless nephrotoxicity and neurotoxicity pose as dire inherent side-effects in clinical trials and application of platinum therapeutics. Subsequent development has called for means to avoid diminished efficacy due to inactivation by endogenous glutathione and other complex-binding or chelating proteins. Platinum(IV) derivatives may solve issues of unintended toxicity by means of intrinsic extracellular stability, degrading to their active platinum(II) forms once internalised within a cytosol and in acidic tumour environments. Selectivity may also be gained by the axial/apical coordination of ligands that typically bind to receptors that are overexpressed in certain tumours, such as modified-estrogen ligands. The development of platinum complexes has required an in-depth understanding of their DNA-binding interactions in order to facilitate further structural modification without loss of effective function for their eventual application as chemotherapeutics. Although platinum complexes are the focus of this chapter, some other metal complexes that interact with nucleic acids, such as ruthenium, iridium, osmium, iron, copper, titanium, vanadium gold and silver, are discussed.
Supramolecular Metal Complexes for Imaging and Radiotherapy
Authors: Schatz Jürgen , Schühle Daniel
Published: September 2013

Modern medicinal diagnosis strongly relies on imaging techniques. Supramolecular chemistry can help radiologists by enhancing images that are acquired with the help of exogenous contrast agents. Most targeting functions such as peptides, saccharides, antibodies etc. bind to their receptors via non-covalent interactions. When reporter groups are attached to these vectors via linkers, a rather complex supramolecular guest is designed that finds its host in vivo. In these cases, supramolecular chemistry is used to adjust the biodistribution of reporter groups to medical needs. When metal ions are used in imaging, they need to be complexed in most cases in order to control their biodistribution and to make them safe. Macrocycles are common ligands for metal complexation in this field and thus, almost any metal based contrast agent is a supramolecular complex per se. A very efficient tool for “a closer look into the body” is magnetic resonance imaging (MRI). The resolution and specificity of conventional MRI can be enhanced using contrast agents. MRI has very good resolution but it is a rather insensitive technique. A consequence is that targets that are expressed at low concentrations cannot be imaged using MRI. Both nuclear and optical imaging have much higher sensitivity but have the disadvantage of the need of radiation plus lower resolution and very limited deep tissue penetration respectively. In all these techniques, supramolecular chemistry offers possibilities that classical chemistry cannot fulfill. Radioactive metals can also be used to destroy diseased tissue for therapeutic applications—again utilizing supramolecular principles.
Supramolecular Gels for Pharmaceutical and Biomedical Applications
Authors: Miravet Juan F. , Escuder Beatriu
Published: September 2013

The supramolecular aggregation of low molecular weight species affords supramolecular gels. These materials consist of solid-like micro(nano)fibrillar networks and their formation is reversible and dependant on different stimuli. Their use in pharmaceutical and biomedical applications opens new possibilities when compared with conventional macromolecular gels. For example, improved therapeutic properties due to a high local concentration of functional groups at the surface of the fibres. The three-dimensional fibrillar network of these gels has been used successfully in different examples of cell culture and tissue engineering. Finally, cases of controlled release of drugs are reported which are based in the reversible nature of supramolecular gels.
Supramolecular Enzyme Assays
Authors: Hennig Andreas
Published: September 2013

The development of enzyme assays for the detection of enzymatic activity is of prime interest in academic and industrial research, for example, in enzyme engineering and drug discovery. Therein, each application has different specifications for an ideal enzyme assay. Recent developments include enzyme assays exploiting principles and achievements from the field of supramolecular chemistry. This affords label-free, continuously monitored, fluorescence-based assays, which are well suited for high-throughput screening applications. This chapter provides a comprehensive overview of supramolecular approaches towards enzyme assays, including methods based on specifically designed chemoreceptors, on membrane transport systems and on macrocyclic receptors such as cyclodextrins, calixarenes and cucurbiturils. Focus is given to the particular applications and the challenges during development of enzyme assays.
Designing Polymeric Binders for Pharmaceutical Applications
Authors: Bertrand Nicolas , Colin Patrick , Ranger Maxime , Leblond Jeanne
Published: September 2013

The properties of polyvalent polymers to form supramolecular complexes with biological substrates offer many attractive therapeutic possibilities. Polymeric binders are macromolecules designed to exert a pharmacological effect by selectively interacting with exogenous or endogenous substrates. They can be employed to prevent the harmful effects of toxins, inhibit virus colonization or even trigger apoptosis of diseased cells. This chapter presents the fundamentals of developing polymeric binders as new drug entities. The basics of finding the right target, establishing structure–activity relationships and measuring efficacy are highlighted, with numerous examples of polymeric binders at different development stages, including commercialization. Orally administered scavengers represent the most advanced examples in clinical use. Their binding in the gastrointestinal tract results in either local or systemic therapeutic effects. Although they are designed to be non-absorbable, their low systemic exposure is not always devoid of side effects. The required approaches to confirm innocuousness of the macromolecules and the challenges encountered during the clinical phases are also presented.
Analysis of Arabidopsis thioredoxin-h isotypes identifies discrete domains that confer specific structural and functional properties
Authors: Jung Young Jun , Chi Yong Hun , Chae Ho Byoung , Shin Mi Rim , Lee Eun Seon , Cha Joon-Yung , Paeng Seol Ki , Lee Yuno , Park Jin Ho , Kim Woe Yeon , Kang Chang Ho , Lee Kyun Oh , Lee Keun Woo , Yun Dae-Jin , Lee Sang Yeol
Published: September 2013

Multiple isoforms of Arabidopsis thaliana h-type thioredoxins (AtTrx-hs) have distinct structural and functional specificities. AtTrx-h3 acts as both a disulfide reductase and as a molecular chaperone. We prepared five representative AtTrx-hs and compared their protein structures and disulfide reductase and molecular chaperone activities. AtTrx-h2 with an N-terminal extension exhibited distinct functional properties with respect to other AtTrx-hs. AtTrx-h2 formed low-molecular-mass structures and exhibited only disulfide reductase activity, whereas the other AtTrx-h isoforms formed high-molecular-mass complexes and displayed both disulfide reductase and molecular chaperone activities. The domains that determine the unique structural and functional properties of each AtTrx-hs protein were determined by constructing a domain-swap between the N- and C-terminal regions of AtTrx-h2 and AtTrx-h3 (designated AtTrx-h-2N3C and AtTrx-h-3N2C respectively), an N-terminal deletion mutant of AtTrx-h2 [AtTrx-h2-N(∆19)] and site-directed mutagenesis of AtTrx-h3. AtTrx-h2-N(∆19) and AtTrx-h-3N2C exhibited similar properties to those of AtTrx-h2, but AtTrx-h-2N3C behaved more like AtTrx-h3, suggesting that the structural and functional specificities of AtTrx-hs are determined by their C-terminal regions. Hydrophobicity profiling and molecular modelling revealed that Ala100 and Ala106 in AtTrx-h3 play critical roles in its structural and functional regulation. When these two residues in AtTrx-h3 were replaced with lysine, AtTrx-h3 functioned like AtTrx-h2. The chaperone function of AtTrx-hs conferred enhanced heat-shock-resistance on a thermosensitive trx1/2-null yeast mutant.
Robust and accurate online pose estimation algorithm via efficient three‐dimensional collinearity model
Authors: Fan Baojie , Du Yingkui , Cong Yang
Published: September 2013

In this study, the authors propose a robust and high accurate pose estimation algorithm to solve the perspective‐N‐point problem in real time. This algorithm does away with the distinction between coplanar and non‐coplanar point configurations, and provides a unified formulation for the configurations. Based on the inverse projection ray, an efficient collinearity model in object–space is proposed as the cost function. The principle depth and the relative depth of reference points are introduced to remove the residual error of the cost function and to improve the robustness and the accuracy of the authors pose estimation method. The authors solve the pose information and the depth of the points iteratively by minimising the cost function, and then reconstruct their coordinates in camera coordinate system. In the following, the optimal absolute orientation solution gives the relative pose information between the estimated three‐dimensional (3D) point set and the 3D mode point set. This procedure with the above two steps is repeated until the result converges. The experimental results on simulated and real data show that the superior performance of the proposed algorithm: its accuracy is higher than the state‐of‐the‐art algorithms, and has best anti‐noise property and least deviation by the influence of outlier among the tested algorithms.
Light-induced changes in an alkali metal atomic vapor cell coating studied by X-ray photoelectron spectroscopy
Authors: Hibberd A. M. , Seltzer S. J. , Balabas M. V. , Morse M. , Budker D. , Bernasek S. L.
Published: September 2013

The light-induced desorption of Rb atoms from a paraffin coating is studied with depth-profiling X-ray photoelectron spectroscopy (XPS) using tunable synchrotron radiation. Following Rb exposure, shifts of the C1s signal to higher binding energies, as well as the appearance of lower binding energy components in the O1s region, were observed. These effects were diminished after irradiation with desorbing light. Additionally, following desorbing-light irradiation, changes in the depth-dependent concentration of carbon were observed. These observations offer an insight into the microscopic changes that occur during light-induced atomic desorption and demonstrate the utility of XPS in understanding atom-coating interactions.
A semi-analytical method for near-trapped mode and fictitious frequencies of multiple scattering by an array of elliptical cylinders in water waves
Authors: Chen Jeng-Tzong , Lee Jia-Wei
Published: September 2013

In this paper, we focus on the water wave scattering by an array of four elliptical cylinders. The null-field boundary integral equation method (BIEM) is used in conjunction with degenerate kernels and eigenfunctions expansion. The closed-form fundamental solution is expressed in terms of the degenerate kernel containing the Mathieu and the modified Mathieu functions in the elliptical coordinates. Boundary densities are represented by using the eigenfunction expansion. To avoid using the addition theorem to translate the Mathieu functions, the present approach can solve the water wave problem containing multiple elliptical cylinders in a semi-analytical manner by introducing the adaptive observer system. Regarding water wave problems, the phenomena of numerical instability of fictitious frequencies may appear when the BIEM/boundary element method (BEM) is used. Besides, the near-trapped mode for an array of four identical elliptical cylinders is observed in a special layout. Both physical (near-trapped mode) and mathematical (fictitious frequency) resonances simultaneously appear in the present paper for a water wave problem by an array of four identical elliptical cylinders. Two regularization techniques, the combined Helmholtz interior integral equation formulation (CHIEF) method and the Burton and Miller approach, are adopted to alleviate the numerical resonance due to fictitious frequency.
Antiferromagnetic magnetostatic coupling in Co/Au/Co films with perpendicular anisotropy
Authors: Matczak M. , Szymański B. , Urbaniak M. , Nowicki M. , Głowiński H. , Kuświk P. , Schmidt M. , Aleksiejew J. , Dubowik J. , Stobiecki F.
Published: September 2013

Magnetization reversal processes in Au/Co/Au-wedge/Co/Au pseudo-spin-valve structures characterized by perpendicular anisotropy of 0.6-nm-thick Co layers were investigated by magneto-optical Kerr effect. The samples were deposited on a Ti/Au buffer layer of differing Au-layer thickness (different surface roughness and crystallite size). The distinctive influence of the buffer layer thickness on the dependences of switching fields, and energy of the effective interlayer coupling, versus Au spacer thickness is presented. In particular, increasing the buffer-layer thickness results in a decrease in the oscillation amplitude of the Ruderman–Kittel–Kasuya–Yosida-type interaction and in the enhancement of the antiferromagnetic coupling related to magnetostatic (orange peel) interactions.
Type B 3-fold supersymmetry and non-polynomial invariant subspaces
Authors: Tanaka Toshiaki
Published: September 2013

We obtain the most general type B 3-fold supersymmetry by solving directly the intertwining relation. We then show that it is a necessary and sufficient condition for a second-order linear differential operator to have three linearly independent local analytic solutions. We find that there are eight linearly independent non-trivial linear differential operators of this kind. As a by-product, we find new quasi-solvable second-order operators preserving a monomial or polynomial subspace, one in type B, two in type C, and four in type X2, all of which have been missed in the existing literature. In addition, we show that type A, type B, and type C 3-fold supersymmetries are connected continuously via one parameter. A few new quasi-solvable models are also presented.
Voltage-gated pinning in a magnetic domain-wall conduit
Authors: Franken J. H. , Yin Y. , Schellekens A. J. , van den Brink A. , Swagten H. J. M. , Koopmans B.
Published: September 2013

In spintronic devices relying on magnetic domain-wall (DW) motion, robust control over the DW position is required. We use electric-field control of perpendicular magnetic anisotropy to create a voltage-gated pinning site in a microstructured Pt/Co/AlOx DW conduit. A DW pins at the edge of a gate electrode, and the strength of pinning can be tuned linearly and reversibly with an efficiency of 0.22(1) mT/V. This result is supported by a micromagnetic model, taking full account of the anisotropy step at the gate edge, which is directly caused by a change in the electron density due to the choice of material.
Measurement of the full stress tensor in a crystal using photoluminescence from point defects: The example of nitrogen vacancy centers in diamond
Authors: Grazioso Fabio , Patton Brian R. , Delaney Paul , Markham Matthew L. , Twitchen Daniel J. , Smith Jason M.
Published: September 2013

We introduce a method for measuring the full stress tensor in a crystal utilising the properties of individual point defects. By measuring the perturbation to the electronic states of three point defects with C3v symmetry in a cubic crystal, sufficient information is obtained to construct all six independent components of the symmetric stress tensor. We demonstrate the method using photoluminescence from nitrogen-vacancy colour centers in diamond. The method breaks the inverse relationship between spatial resolution and sensitivity that is inherent to existing bulk strain measurement techniques, and thus, offers a route to nanoscale strain mapping in diamond and other materials in which individual point defects can be interrogated.
Plasma reactivity in high-power impulse magnetron sputtering through oxygen kinetics
Authors: Vitelaru Catalin , Lundin Daniel , Brenning Nils , Minea Tiberiu
Published: September 2013

The atomic oxygen metastable dynamics in a Reactive High-Power Impulse Magnetron Sputtering (R-HiPIMS) discharge has been characterized using time-resolved diode laser absorption in an Ar/O2 gas mixture with a Ti target. Two plasma regions are identified: the ionization region (IR) close to the target and further out the diffusion region (DR), separated by a transition region. The μs temporal resolution allows identifying the main atomic oxygen production and destruction routes, which are found to be very different during the pulse as compared to the afterglow as deduced from their evolution in space and time.
Note: Manipulation of supersonic atomic beams with static magnetic fields
Authors: Gardner Jamie , Castillo-Garza Rodrigo , Raizen Mark G.
Published: September 2013

The inhomogeneous magnetic field of a permanent-magnet planar Halbach array is used to either deflect or to specularly reflect a supersonic beam of neutral atoms. Metastable neon and helium beams are tested to experimentally evaluate the performance of this array in a range of configurations. Results are compared with numerical simulations and the device is presented as a high precision tool for the manipulation of neutral atom beams.
Resonant acoustic radiation force optical coherence elastography
Authors: Qi Wenjuan , Li Rui , Ma Teng , Li Jiawen , Kirk Shung K. , Zhou Qifa , Chen Zhongping
Published: September 2013

We report on a resonant acoustic radiation force optical coherence elastography (ARF-OCE) technique that uses mechanical resonant frequency to characterize and identify tissues of different types. The linear dependency of the resonant frequency on the square root of Young's modulus was validated on silicone phantoms. Both the frequency response spectrum and the 3D imaging results from the agar phantoms with hard inclusions confirmed the feasibility of deploying the resonant frequency as a mechanical contrast for tissue imaging. Furthermore, the results of resonant ARF-OCE imaging of a post-mortem human coronary artery with atherosclerosis demonstrate the potential of the resonant ARF-OCE as a non-invasive method for imaging and characterizing vulnerable plaques.
Polarity driven morphology of zinc oxide nanostructures
Authors: Käbisch S. , Gluba M. A. , Klimm C. , Krause S. , Koch N. , Nickel N. H.
Published: September 2013

Catalyst-free ZnO nanostructures were grown by pulsed-laser deposition on c-oriented sapphire. The nanostructure morphology can be controlled by introducing a nucleation layer. Depending on the doping concentration in the nucleation layer two distinct types of nanostructures are observed. On intrinsic nucleation layers nanowires form, while Al-doping results in a honeycomb network of nanoscale walls. From scanning-electron microscopy and X-ray photoelectron spectroscopy a correlation between nanostructure morphology and the polarity of the nucleation layers is derived.
Structurally stabilized mesoporous TiO2 nanofibres for efficient dye-sensitized solar cells
Authors: Bijarbooneh Fargol Hasani , Zhao Yue , Sun Ziqi , Heo Yoon-Uk , Malgras Victor , Kim Jung Ho , Dou Shi Xue
Published: September 2013

One-dimensional (1D) TiO2 nanostructures are very desirable for providing fascinating properties and features, such as high electron mobility, quantum confinement effects, and high specific surface area. Herein, 1D mesoporous TiO2 nanofibres were prepared using the electrospinning method to verify their potential for use as the photoelectrode of dye-sensitized solar cells (DSSCs). The 1D mesoporous nanofibres, 300 nm in diameter and 10-20 μm in length, were aggregated from anatase nanoparticles 20-30 nm in size. The employment of these novel 1D mesoporous nanofibres significantly improved dye loading and light scattering of the DSSC photoanode, and resulted in conversion cell efficiency of 8.14%, corresponding to an ∼35% enhancement over the Degussa P25 reference photoanode.
Method for improving the electrical insulating properties of wet thermal oxide of AlAsSb on GaSb substrates
Authors: Laaroussi Y. , Doucet J. B. , Fadel P. , Cerutti L. , Suarez I. , Mlayah A. , Almuneau G.
Published: September 2013

In this report, we describe the selective wet thermal oxidation of AlAsSb layers lattice-matched on GaSb substrate for lateral oxide-confinement in mid-infrared lasers. A two-step process of wet thermal oxidation followed by thermal annealing at a higher temperature was used. Raman spectroscopy revealed the formation of antimony oxides and the volatilization of these oxidation byproducts after post-oxidation annealing. Using this method, we obtained higher electrical resistivity of the annealed oxide, which was suitable for confinement applications.
Study of radio frequency breakdown in pressurized L-band waveguide for the International Linear Collider
Authors: Wang Faya , Adolphsen Chris , Nantista Christopher
Published: September 2013

An L-band (1.3 GHz) radio frequency (rf) waveguide system was assembled at SLAC to test components of a high power distribution scheme proposed for the International Linear Collider (ILC). All parts were made of aluminum and pressurized with dry nitrogen. The rf breakdown rate measured in this resonantly powered system is presented as a function of field level at different gas pressures and rf pulse widths (typically, only breakdown thresholds are reported.). The data are compared to predictions of a simple model which relates the breakdown phenomenon to the rate at which the free electron density builds in the gas.
Transistor operation and mobility enhancement in top-gated LaAlO3/SrTiO3 heterostructures
Authors: Hosoda Masayuki , Hikita Yasuyuki , Hwang Harold Y. , Bell Christopher
Published: September 2013

We report the operation of LaAlO3/SrTiO3 depletion mode top-gated junction field-effect transistors using a range of LaAlO3 thicknesses as the top gate insulator. Gated Hall bars show near ideal transistor characteristics at room temperature with on-off ratios greater than 1000. Lower temperature measurements demonstrate a systematic increase in the Hall mobility as the sheet carrier density in the channel is depleted via the top gate, providing a route to higher mobility, lower density electron gases in this system.
Long-term stabilization of sprayed zinc oxide thin film transistors by hexafluoropropylene oxide self assembled monolayers
Authors: Ortel Marlis , Kalinovich Nataliya , Röschenthaler Gerd-Volker , Wagner Veit
Published: September 2013

Surface functionalization of solution processed zinc oxide layers was studied in transistors with bottom-gate bottom-contact configuration aiming at suppression of trapping processes to increase device stability. Saturation of electrically active surface sites and formation of a moisture barrier to decrease the impact of humid atmosphere was successfully shown by binding hexafluoropropylene oxide (HFPO) on the metal oxide semiconductor. Deep trap level related electrical parameters, i.e., stability, hysteresis, and on-set voltage, improved rapidly within 60 s of exposure which was attributed to occupation of sites characterized by low adsorption energies, e.g., at edges. In contrast, shallow trap level related parameters, i.e., mobility, showed a much slower process of improvement. Identical behavior was determined for the contact angle. A physical model is presented by applying first order reaction kinetics equation to Young's law and multiple trapping and release model which relates the dependence of the contact angle and the mobility to the hexafluoropropylene oxide deposition time. Consistent time constants of τ = ≪1 min, 2 min, and 250 min were extracted for mobility and contact angle which implies a direct dependence on the surface coverage. Mobility decreased at short deposition times, recovered at medium deposition times and improved strongly by 2.4 cm2 V−1 s−1 for long deposition times of 1400 min. A microscopic model of these phenomena is given with interpretation of the different time constants found in the experiment.
Investigation of activated oxygen molecules on the surface of Y2O3 nanocrystals by Raman scattering
Authors: Xu J. Q. , Xiong S. J. , Wu X. L. , Li T. H. , Shen J. C. , Chu Paul K.
Published: September 2013

Activation of surface oxygen molecules on cubic Y2O3 nanocrystals (NCs) is investigated. As the annealing temperature under O2 is increased, the strong Raman band at 965 cm−1 previously never assigned weakens gradually, while the intensity of the 378 cm−1 Raman band arising from Y3+-O2− vibration increases. X-ray diffraction reveals no structural change during annealing and energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and theoretical calculation suggest that the interstitial oxygen O22− connected to the F centers gives rise to the 965 cm−1 Raman band. The results provide direct evidence of the existence of activated oxygen ions on Y2O3 NCs.
Tunable electronic and magnetic properties of WS2 nanoribbons
Authors: Zhang Hui , Li Xi-Bo , Liu Li-Min
Published: September 2013

Two dimensional transition metal dichalcogenides (TMDs) have attracted great attention because of the versatile electronic structures. The electronic and magnetic properties of the nanoribbons are still not fully understood, which are crucial for their applications in nanodevices. In this work, the detailed atomic structural, electronic, and magnetic properties of the one dimensional WS2 nanoribbons have been carefully explored by first-principles calculations. The results suggest that the single layer WS2 will first transform into direct band gap semiconductor from indirect band gap of bulk one. Interestingly, the properties of WS2 nanoribbons are greatly affected by the type of the edges: Armchair nanoribbons (ANRs) remain nonmagnetic and semiconducting as that of bulk, whereas zigzag nanoribbons (ZNRs) exhibit ferromagnetic and metallic. Further, the electronic properties can be tuned by applying the external strains to WS2 nanoribbons: Band gap of ANRs experiences a direct-indirect-direct transition and the magnetic moment of ZNRs can be easily tuned by the different strains. All these findings suggest that the TMDs nanoribbons may exhibit extraordinary electronic and magnetic properties, and more importantly, such fascinating characters can be precisely modulated by controlling the edge types and applied strains.
Properties of two-dimensional silicon grown on graphene substrate
Authors: Zhou R. , Lew Yan Voon L. C. , Zhuang Y.
Published: September 2013

The structure and electrical properties of two-dimensional (2D) sheets of silicon on a graphene substrate are studied using first-principles calculations. Two forms of corrugated silicon sheets are proposed to be energetically favorable structures. A shift of the Fermi energy level is found in both corrugated structures. Calculations of electron density show a weak coupling between the silicon layer and graphene substrate in both structures. The two forms of 2D silicon sheets turn out to be metallic and exhibit anisotropic transport properties.
Initial preorder as condition for L1 ordering in ultrathin CoPt films
Authors: Reichel L. , Fähler S. , Schultz L. , Leistner K.
Published: September 2013

Materials with high magnetocrystalline anisotropy have been of interest for magnetic data storage for a long time. It is, however, still challenging to achieve sufficient L10 order when dimensions are reduced to the nanometer range needed for these applications. We report on formation of L10 order in continuous epitaxial CoPt films with a thickness below 3 nm. The ordering mechanism for pulsed laser deposited films has been elucidated by a systematic analysis of the thermal and depositional conditions. In addition to deposition temperature and post annealing, deposition rate is found to have a major influence on ordering. High order is achieved at very high and very low deposition rates. We propose that this rate dependent ordering is due to an initial short range order formed by surface diffusion during the deposition step. The realisation of such a preorder is found to be decisive for the progression of ordering during post annealing.
Influence of the piezoeffect on static and dynamic ferroelectric properties
Authors: Leschhorn Andreas , Kliem Herbert
Published: September 2013

Typical ferroelectric properties like polarization hysteresis and a phase transition from ferroelectric to paraelectric at the Curie temperature can be deduced from the Weiss field model. This model is based on a feedback loop where the polarization influences itself by the electrostatic interaction between the dipoles inside the material. An extension of this model considers that the strain due to the piezoelectric effect changes the lengths of the dipoles inside the sample. In this extended model, a positive piezocoefficient converts the second order to a first order phase transition and splits simultaneously the single polarization hysteresis loop to a double loop close to the Curie temperature. The same behaviour we find for negative piezocoefficients if the piezoelectric effect influences the dipole density of the sample or the coupling between the dipoles instead of the dipole lengths. The dependence of the electrode distance on the polarization due to the piezoeffect has only small influence on the polarization hysteresis and the coercive field below the Curie temperature; remanent polarization or order of the phase transition is not changed. Furthermore, dynamic simulations show the effect of the velocity of temperature and external voltage variation on the polarization.
Heteroepitaxial growth and multiferroic properties of Mn-doped BiFeO3 films on SrTiO3 buffered III–V semiconductor GaAs
Authors: Gao G. Y. , Yang Z. B. , Huang W. , Zeng H. Z. , Wang Y. , Chan H. L. W. , Wu W. B. , Hao J. H.
Published: September 2013

Epitaxial Mn-doped BiFeO3 (MBFO) thin films were grown on GaAs (001) substrate with SrTiO3 (STO) buffer layer by pulsed laser deposition. X-ray diffraction results demonstrate that the films show pure (00l) orientation, and MBFO (100)//STO(100), whereas STO (100)//GaAs (110). Piezoresponse force microscopy images and polarization versus electric field loops indicate that the MBFO films grown on GaAs have an effective ferroelectric switching. The MBFO films exhibit good ferroelectric behavior (2Pr ∼ 92 μC/cm2 and 2EC ∼ 372 kV/cm). Ferromagnetic property with saturated magnetization of 6.5 emu/cm3 and coercive field of about 123 Oe is also found in the heterostructure at room temperature.
Mixing enhancement by biologically inspired convection in a micro-chamber using alternating current galvanotactic control of the Tetrahymena pyriformis
Authors: Kim Jihoon , Jang Yonghee , Byun Doyoung , Hyung Kim Dal , Jun Kim Min
Published: September 2013

Recently, there has been increasing interest in the swimming behavior of microorganisms and biologically inspired micro-robots. In this study, we investigated biologically induced convection flow with living microorganism using galvanotaxis. We fabricated and evaluated our micro-mixer with motile cells. For the cell based active micro-mixers, two miscible fluids were used to measure the mixing index. Under alternating current (AC) electric fields with varying frequency, a group of motile Tetrahymena pyriformis cells generated reciprocal motion with circulating flows around their pathline, enhancing the mixing ratio.
Observation of double exchange driven electroresistance of La0.67Ca0.33MnO3 thin film
Authors: Kambhala Nagaiah , Viswanath P. , Angappane S.
Published: September 2013

We report the electroresistance measurements on La0.67Ca0.33MnO3 thin film in two different configurations. In the in-plane configuration, a shift of metal-insulator transition towards low temperatures is seen with increase in applied current, which is attributed to Joule heating effect. In contrast, the metal-insulator transition is found to shift towards high temperatures for out-of-plane configuration. This observation agrees well with the predictions of the double exchange theory towards explaining both magnetoresistance and electroresistance behaviours of manganites.
Assessment of pulse conditions effects on reliability in GaN-based high electron mobility transistors by transient temperature measurements
Authors: Zhang Yamin , Feng Shiwei , Zhu Hui , Zhang Guangchen , Deng Bing , Ma Lin
Published: September 2013

The forward Schottky characteristic method, utilizing the temperature dependence of forward gate-source Schottky junction voltage, has been used to measure the transient temperature rise under DC and cycle pulse for multi-finger AlGaN/GaN high electron mobility transistor. The effect of electrical pulse on channel temperature has been studied. The transient temperature rise of channel under pulses with different duty cycles and frequencies are determined, respectively. The measurement results show that operation under high frequency and/or low duty cycle can improve the lifetime and performance reliability of AlGaN/GaN HEMT devices effectively. Furthermore, the measurement results are found to be consistent with the electro-thermal simulation results performed for the device.
Great emission enhancement and excitonic recombination dynamics of InGaN/GaN nanorod structures
Authors: Liu Bin , Smith Rick , Bai Jie , Gong Yipin , Wang Tao
Published: September 2013

Excitonic recombination dynamics has been investigated on a series of InxGa1−xN/GaN (0.10 ≤ x ≤ 0.30) nanorod (NR) structures with a diameter of ∼220 nm by time-revolved photoluminescence (PL). The NR structures are fabricated by means of a post-growth etching technique. Compared with their corresponding as-grown samples, the time-integrated PL intensities of the NR samples show a remarkable enhancement with a factor of up to 52 at room temperature. The ratios of the radiative to non-radiative recombination lifetime of the NR structures are much less sensitive to temperature than those of their corresponding as-grown samples. This becomes more prominent with increasing indium composition. A distinct delay in transition temperature, where the dominating emission mechanism changes from radiative to non-radiative recombination, has been observed on the NR structures. The great enhancement in optical properties is attributed to both strain relaxation and extra in-plane excitonic confinement due to the nanostructures.
Metal liner-driven quasi-isentropic compression of deuterium
Authors: Weinwurm Marcus , Bland Simon N. , Chittenden Jeremy P.
Published: September 2013

Properties of degenerate hydrogen and deuterium (D) at pressures of the order of terapascals are of key interest to Planetary Science and Inertial Confinement Fusion. In order to recreate these conditions in the laboratory, we present a scheme, where a metal liner drives a cylindrically convergent quasi-isentropic compression in a D fill. We first determined an external pressure history for driving a self-similar implosion of a D shell from a fictitious flow simulation [D. S. Clark and M. Tabak, Nucl. Fusion 47, 1147 (2007)]. Then, it is shown that this D implosion can be recreated inside a beryllium liner by shaping the current pulse. For a peak current of 10.8 MA cold and nearly isochoric D is assembled at around 12 500 kg/m3. Finally, our two-dimensional Gorgon simulations show the robustness of the implosion method to the magneto-Rayleigh-Taylor instability when using a sufficiently thick liner.
A frequency-tunable 90°-polarization rotation device using composite chiral metamaterials
Authors: Song Kun , Zhao Xiaopeng , Liu Yahong , Fu Quanhong , Luo Chunrong
Published: September 2013

The electromagnetic behaviors of the metamaterial can be artificially controlled by changing the effective permittivity of the nearby background medium. Utilizing this fantastic feature, an ultrathin and frequency-tunable polarization rotation device, which can achieve 90° polarization rotation for a linearly polarized incident wave, is constructed via the combination of a composite chiral metamaterial and two auxiliary dielectric slabs. It shows that the operating frequency of the resulting 90°-polarization rotation device can be continuously and reversibly tuned in a wide frequency range by mechanical means. The experimentally measured results are in agreement with the numerical values.
Inspecting and locating foreign body in biological sample by laser confocal feedback technology
Authors: Tan Yidong , Zhang Shulian , Xu Chunxin , Zhao Shijie
Published: September 2013

A promising method is proposed to inspect and locate foreign bodies in biological samples. It combines advantages of confocal microscopy and optical feedback effect of microchip solid-state laser, and retrieves both spatial positioning and specific images by the sensitive detection of extremely weak signals retro-diffused by the interface in samples. By testing onion samples containing pins as foreign bodies, this approach has been demonstrated to examine the foreign body and locate its position within several millimeters depth below the sample surface.
Wavelength conversion via four-wave mixing in a triple-coupled multilayer cavity
Authors: Kitada Takahiro , Yasunaga Yukinori , Nakagawa Yoshinori , Morita Ken , Isu Toshiro
Published: September 2013

Four-wave mixing in a triple-coupled multilayer cavity has been investigated for planar-type wavelength conversion devices. Three half-wavelength cavity layers are connected in series using GaAs/AlAs distributed Bragg reflector multilayers to yield three cavity modes with equal frequency separation. The enhanced internal electric fields of the three cavity modes indicate that efficient ultrafast wavelength conversion via four-wave mixing can be achieved even in the normal incidence configuration. Wavelength conversion was experimentally demonstrated using spectrally shaped laser pulses. A clear converted wavelength signal was observed in the measured spectrum. The temporal response was almost limited by the photon lifetime of each cavity mode.