bluuebunny/crossref_metadata_2025 huggingface dataset:
Maltose neopentyl glycol-3 (MNG-3) analogues for membrane protein study
Authors: Cho Kyung Ho , Husri Mohd , Amin Anowarul , Gotfryd Kamil , Lee Ho Jin , Go Juyeon , Kim Jin Woong , Loland Claus J. , Guan Lan , Byrne Bernadette , Chae Pil Seok
Published: March 2015

The hydrophobic variants of the original MNG (MNG-3-C10) were evaluated with a few membrane proteins. The optimal MNG was variable for different membrane proteins, indicative of importance of match/mismatch between detergent hydrophobicity and membrane protein propensity to aggregate and denature.
Bifunctional alkyl chain barriers for efficient perovskite solar cells
Authors: Zhang Jing , Hu Zhelu , Huang Like , Yue Guoqiang , Liu Jinwang , Lu Xingwei , Hu Ziyang , Shang Minghui , Han Liyuan , Zhu Yuejin
Published: March 2015

An insulating alkyl chain layer is self-assembled at the perovskite/hole transport material interface, which successfully exhibits a dual function: blocking electron recombination and resisting moisture.
The synthesis of condensed C-PDA–g-C3N4 composites with superior photocatalytic performance
Authors: He Fang , Chen Gang , Yu Yaoguang , Zhou Yansong , Zheng Yi , Hao Sue
Published: March 2015

C-PDA–g-C3N4 composites have been obtained using the in situ polymerization approach followed by carbonization and condensation for the first time and display superior photocatalytic performance.
A template-confined fabrication of controllable gold nanoparticles based on the two-dimensional nanostructure of macrocycles
Authors: Geng Yanfang , Liu Miaoqing , Xue Jindong , Xu Peng , Wang Yifei , Shu Lijin , Zeng Qingdao , Wang Chen
Published: March 2015

An amine-substituted macrocycle 6Y, a rigid hexagonal ring, self-assembled into a network architecture on the surface, which could be used as a molecular template to directly fabricate gold nanoparticles (AuNPs) with narrow size distribution (2.2 ± 0.1 nm).
Acid-labile boronate-bridged dextran–bortezomib conjugate with up-regulated hypoxic tumor suppression
Authors: Xu Weiguo , Ding Jianxun , Li Lingyu , Xiao Chunsheng , Zhuang Xiuli , Chen Xuesi
Published: March 2015

An acid-labile dextran–bortezomib conjugate exhibits improved inhibition efficacy toward hypoxic tumor through both NF-κB- and ERS-mediated apoptosis signaling pathways.
An organic photovoltaic featuring graphene nanoribbons
Authors: Lee Seung Joo , Kim Jae-Yeon , Kim Hyeong Pil , Kim Dongcheon , da Silva Wilson Jose , Schneider Fabio Kurt , Mohd Yusoff Abd. Rashid bin , Jang Jin
Published: March 2015

A combination of graphene nanoribbons (GNRs) and carbon nanotubes (CNTs) was deployed as a potential candidate to replace the commonly used hole transport material poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in a high performance organic photovoltaic.
Cascade upgrading of γ-valerolactone to biofuels
Authors: Yan Kai , Lafleur Todd , Wu Xu , Chai Jiajue , Wu Guosheng , Xie Xianmei
Published: March 2015

Cascade upgrading of γ-valerolactone (GVL), produced from renewable cellulosic biomass, with selective conversion to biofuels pentyl valerate (PV) and pentane in one pot using a bifunctional Pd/HY catalyst is described.
Catalysis at the room temperature ionic liquid|water interface: H2O2 generation
Authors: Jedraszko Justyna , Nogala Wojciech , Adamiak Wojciech , Dongmo Saustin , Wittstock Gunther , Girault Hubert H. , Opallo Marcin
Published: March 2015

H2O2 is produced at the interface between a room-temperature ionic liquid with decamethylferrocene as an electron donor and an acidic aqueous solution. The electron donor can be regenerated electrochemically.
A single quantum dot-based biosensor for telomerase assay
Authors: Zhu Guichi , Yang Kun , Zhang Chun-yang
Published: March 2015

We develop a single quantum dot-based biosensor for the sensitive detection of telomerase in tumor cells and screening of anticancer drugs.
In-line and selective phase separation of medium-chain carboxylic acids using membrane electrolysis
Authors: Xu Jiajie , Guzman Juan J. L. , Andersen Stephen J. , Rabaey Korneel , Angenent Largus T.
Published: March 2015

A membrane electrolysis system that was coupled with a bioreactor and pertraction system accomplished phase separation of oil, which consisted of >90% medium-chain carboxylic acids, without addition of chemicals.
Modelling of phase diagrams of nanoalloys with complex metallic phases: application to Ni–Sn
Authors: Kroupa A. , Káňa T. , Buršík J. , Zemanová A. , Šob M.
Published: March 2015

A novel method for modelling of size-dependent phase diagrams combines the CALPHAD method and ab initio calculations of surface stresses.
Getting order in mesostructured thin films, from pore organization to crystalline walls, the case of 3-glycidoxypropyltrimethoxysilane
Authors: Carboni Davide , Pinna Alessandra , Amenitsch Heinz , Casula Maria F. , Loche Danilo , Malfatti Luca , Innocenzi Plinio
Published: March 2015

A new type of hybrid organic–inorganic film showing long-range ordered mesostructure and crystalline pore walls has been successfully prepared.
Synthesis and hydrolysis of gas-phase lanthanide and actinide oxide nitrate complexes: a correspondence to trivalent metal ion redox potentials and ionization energies
Authors: Lucena Ana F. , Lourenço Célia , Michelini Maria C. , Rutkowski Philip X. , Carretas José M. , Zorz Nicole , Berthon Laurence , Dias Ana , Conceição Oliveira M. , Gibson John K. , Marçalo Joaquim
Published: March 2015

Gas-phase hydrolysis of lanthanide/actinide MO3(NO3)3−ions relates to the stabilities of the MIVoxidation states, which correlate with IV/III solution reduction potentials and 4th ionization energies.
Toward a stabilized lattice framework and surface structure of layered lithium-rich cathode materials with Ti modification
Authors: Wang Sihui , Li Yixiao , Wu Jue , Zheng Bizhu , McDonald Matthew J. , Yang Yong
Published: March 2015

Ti modification improves the cycling performance of lithium-rich materials by stabilizing the framework structure and the electrode/electrolyte interface.
4-Hydroxy-1-naphthaldehydes: proton transfer or deprotonation
Authors: Manolova Y. , Kurteva V. , Antonov L. , Marciniak H. , Lochbrunner S. , Crochet A. , Fromm K. M. , Kamounah F. S. , Hansen P. E.
Published: March 2015

Proton captured/proton lost: in 4-hydroxy-1-naphthaldehyde concentration dependent deprotonation is observed, while when a piperidine unit is attached the proton is captured.
Development of a diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) cell for the in situ analysis of co-electrolysis in a solid oxide cell
Authors: Cumming Denis J. , Tumilson Christopher , Taylor S. F. Rebecca , Chansai Sarayute , Call Ann V. , Jacquemin Johan , Hardacre Christopher , Elder Rachael H.
Published: March 2015

Co-electrolysis of carbon dioxide and steam has been shown to be an efficient way to produce syngas, however further optimisation requires detailed understanding of the complex reactions, transport processes and degradation mechanisms occurring in the solid oxide cell (SOC) during operation. Whilst electrochemical measurements are currently conducted in situ, many analytical techniques can only be used ex situ and may even be destructive to the cell (e.g. SEM imaging of the microstructure). In order to fully understand and characterise co-electrolysis, in situ monitoring of the reactants, products and SOC is necessary. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) is ideal for in situ monitoring of co-electrolysis as both gaseous and adsorbed CO and CO2 species can be detected, however it has previously not been used for this purpose. The challenges of designing an experimental rig which allows optical access alongside electrochemical measurements at high temperature and operates in a dual atmosphere are discussed. The rig developed has thus far been used for symmetric cell testing at temperatures from 450 °C to 600 °C. Under a CO atmosphere, significant changes in spectra were observed even over a simple Au|10Sc1CeSZ|Au SOC. The changes relate to a combination of CO oxidation, the water gas shift reaction, carbonate formation and decomposition processes, with the dominant process being both potential and temperature dependent.
A novel nanotube-shaped polypyrrole–Pd composite prepared using reverse microemulsion polymerization and its evaluation as an antibacterial agent
Authors: Salabat Alireza , Mirhoseini Farid , Mahdieh Majid , Saydi Hassan
Published: March 2015

A nanotube-shaped PPy–Pd composite, as an antibacterial agent, was prepared using a unique combination of green synthesis and a microemulsion method.
Sulfate-based anionic diblock copolymer nanoparticles for efficient occlusion within zinc oxide
Authors: Ning Y. , Fielding L. A. , Andrews T. S. , Growney D. J. , Armes S. P.
Published: March 2015

Efficient occlusion of sulfate-based diblock copolymer nanoparticles within ZnO crystals produces unique organic/inorganic hybrid materials.
Unusual 1,2-aryl migration in Pd(ii)-catalyzed aza-Wacker-type cyclization of 2-alkenylanilines
Authors: Youn So Won , Lee So Ra
Published: March 2015

The discovery of an unprecedented 1,2-aryl migratory process in Pd(ii)-catalyzed aza-Wacker-type cyclization of 2-alkenylanilines that led to a novel synthesis of C3-substituted indoles is demonstrated.
Nucleophilic addition of amines, alcohols, and thiophenol with epoxide/olefin using highly efficient zirconium metal organic framework heterogeneous catalyst
Authors: Rani Poonam , Srivastava Rajendra
Published: March 2015

Zr based MOF exhibited excellent activity in the ring opening of epoxides/nucleophilic addition of activated olefins with wide range of nucleophiles.
Template-assisted synthesis of CdS nanocrystal arrays in chemically inhomogeneous pores using a vapor–solid mechanism
Authors: Grynko Dmytro O. , Fedoryak Alexander N. , Dimitriev Oleg P. , Lin Andrew , Laghumavarapu Ramesh B. , Huffaker Diana L. , Kratzer Markus , Piryatinski Yuri P.
Published: March 2015

Template of chemically inhomogeneous pores enables one to grow an ordered array of CdS multi-armed nanocrystals free of catalyst.
Resolution of enantiomers with both achiral phases in chromatography: conceptual challenge
Authors: Bhushan Ravi , Nagar Hariom , Martens Jürgen
Published: March 2015

(A): TLC enantioresolution of (±)-selenomethionine and (B): three β-blockers, using (−)-quinine andl-glutamic acid, aschiral inducing reagents, respectively, mobile and stationary phase are achiral.
Conversion of canola oil and canola oil methyl ester (CME) to green aromatics over a HZSM-5 catalyst: a comparative study
Authors: Bayat A. , Sadrameli S. M.
Published: March 2015

The catalytic conversions of canola oil and canola oil methyl ester (CME) for the production of green aromatics over a HZSM-5 catalyst were investigated.
Ginsenoside Rb1 prevents hypoxia-reoxygenation-induced apoptosis in H9c2 cardiomyocytes via an estrogen receptor-dependent crosstalk among the Akt, JNK, and ERK 1/2 pathways using a label-free quantitative proteomics analysis
Authors: Ai Qidi , Sun Guibo , Luo Yun , Dong Xi , Hu Ruifeng , Meng Xiangbao , Sun Xiaobo
Published: March 2015

Rb1 prevents H/R-induced apoptosis of H9c2 cells via an estrogen receptor-dependent crosstalk among the Akt, JNK, and ERK 1/2 pathways.
Porous amorphous Ge/C composites with excellent electrochemical properties
Authors: Li Xiu , Guo Wei , Wan Qian , Ma Jianmin
Published: March 2015

Porous amorphous germanium/carbon (Ge/C) composites exhibit a high-capacity, high-rate and long-life performance due to the synergistic effect of the porous structure and carbon.
Luminescent coordination polymer–fullerene composite as a highly sensitive and selective optical detector for 2,4,6-trinitrophenol (TNP)
Authors: Singha Debal Kanti , Mahata Partha
Published: March 2015

A blue emitting coordination polymer–fullerene composite as a highly sensitive and selective luminescence quenching based optical detector for 2,4,6-trinitrophenol.
One-step hydrothermal synthesis of nano zinc carbonate and its use as a promising substitute for antimony trioxide in flame retardant flexible poly(vinyl chloride)
Authors: Pan Ye-Tang , Wang De-Yi
Published: March 2015

Nano-scale zinc carbonate synthesized by novel one-step hydrothermal method presented a promising to substitute antimony trioxide in flame retardant flexible poly(vinyl chloride).
Rare-earth free narrow-band green-emitting KAlSi2O6:Mn2+ phosphor excited by blue light for LED-phosphor material
Authors: Ding Xin , Zhu Ge , Wang Qian , Wang Yuhua
Published: March 2015

A novel rare-earth free narrow-band green-emitting KAlSi2O6:Mn2+ phosphor excited by blue light for LED is synthesized by solid-state reaction.
Multi-bond forming and iodo-selective base-promoted homolytic aromatic substitution
Authors: Masters Kye-Simeon
Published: March 2015

Base-promoted homolytic aromatic substitution (BHAS) has been applied as a means to effect multi-bond forming reactions.
Interaction mechanism between a functionalized protective layer and dissolved polysulfide for extended cycle life of lithium sulfur batteries
Authors: Ahn Wook , Lim Sung Nam , Lee Dong Un , Kim Kwang-Bum , Chen Zhongwei , Yeon Sun-Hwa
Published: March 2015

A sulfur–MWCNT composite battery containing a protective layer based on a MMT-coated separator was examined for its electrochemical properties.
Electric field control of magnetism in Ti/ZnO/Pt and Ti/ZnO/SRO devices
Authors: Ren Shu-xia , Zhang Li-yong , Dong Jing-yu , Huang Yan-fang , Guo Jia-jun , Zhang Li , Zhao Jing , Zhao Xu , Chen Wei
Published: March 2015

Opposite magnetic switching was achieved in ZnO with different electrodes under an electric field. This can be used to alter the magnetism.
Design principles of tuning oxygen vacancy diffusion in SrZrO3 for resistance random access memory
Authors: Guo Zhonglu , Zhu Linggang , Zhou Jian , Sun Zhimei
Published: March 2015

Resistance random access memory (RRAM) is known to be a promising candidate for next generation non-volatile memory devices, in which the diffusion of oxygen vacancies plays a key role in resistance switching.
An Exploratory Study of Reading Comprehension in College Students After Acquired Brain Injury
Authors: Sohlberg McKay Moore , Griffiths Gina G. , Fickas Stephen
Published: March 2015

Purpose

This exploratory study builds on the small body of existing research investigating reading comprehension deficits in college students with acquired brain injury (ABI).

Method

Twenty-four community college students with ABI completed a battery of questionnaires and standardized tests to characterize self-perceptions of academic reading ability, performance on a standardized reading comprehension measure, and a variety of cognitive functions of this population. Half of the participants in the sample reported traumatic brain injury (
n
= 12) and half reported nontraumatic ABI (
n
= 12).

Results

College students with both traumatic and nontraumatic ABI cite problems with reading comprehension and academic performance postinjury. Mean performance on a standardized reading measure, the Nelson-Denny Reading Test (Brown, Fischo, & Hanna, 1993), was low to below average and was significantly correlated with performance on the Speed and Capacity of Language Processing Test (Baddeley, Emslie, & Nimmo-Smith, 1992). Injury status of traumatic versus nontraumatic ABI did not differentiate results. Regression analysis showed that measures of verbal attention and suppression obtained from the California Verbal Language Test–II (Delis, Kramer, Kaplan, & Ober, 2000) predicted total scores on the Nelson-Denny Reading Test.

Conclusions

College students with ABI are vulnerable to reading comprehension problems. Results align with other research suggesting that verbal attention and suppression problems may be contributing factors.
Two cooperative multicast schemes of scalable video in relay‐based cellular networks
Authors: Hwang Duckdong , Chau Phuc , Shin Jitae , Lee Tae‐Jin
Published: March 2015

This study investigates the cooperative multicast of scalable video over dedicated relay‐based cellular networks. Different layers in a scalable video tend to have different transmission quality requirements, and legacy cellular network has limitations in providing homogeneous service quality within its coverage area. The authors propose two realistic cooperative transmission schemes with a capacity performance analysis for scalable video over dedicated relay‐based cellular networks. The proposed transmission schemes with multiple antennas at an evolved node B and the dedicated relay utilise the combinations of beamforming and space‐time coding in order to enhance the multicast performance of scalable video. The proposed schemes ensure that the received base layer (BL) of scalable video guarantees the minimum video quality to all user terminals throughout the cell coverage with given outage probability, while the terminals inside the relay coverage can achieve better video quality by receiving both the BL and additional enhancement layer data according to the received channel condition. The antennas configuration and the video type determine which multicast scheme to choose.
Fundamentals of Clinical Outcomes Assessment for Spinal Disorders: Study Designs, Methodologies, and Analyses
Authors: Vavken Patrick , Ganal-Antonio Anne Kathleen B. , Shen Francis H. , Chapman Jens R. , Samartzis Dino
Published: March 2015

Study Design

A broad narrative review.

Objective

Management of spinal disorders is continuously evolving, with new technologies being constantly developed. Regardless, assessment of patient outcomes is key in understanding the safety and efficacy of various therapeutic interventions. As such, evidence-based spine care is an essential component to the armamentarium of the spine specialist in an effort to critically analyze the reported literature and execute studies in an effort to improve patient care and change clinical practice. The following article, part one of a two-part series, is meant to bring attention to the pros and cons of various study designs, their methodological issues, as well as statistical considerations.

Methods

An extensive review of the peer-reviewed literature was performed, irrespective of language of publication, addressing study designs and their methodologies as well as statistical concepts.

Results

Numerous articles and concepts addressing study designs and their methodological considerations as well as statistical analytical concepts have been reported. Their applications in the context of spine-related conditions and disorders were noted.

Conclusion

Understanding the fundamental principles of study designs and their methodological considerations as well as statistical analyses can further advance and improve future spine-related research.
Charge balancing in GaN-based 2-D electron gas devices employing an additional 2-D hole gas and its influence on dynamic behaviour of GaN-based heterostructure field effect transistors
Authors: Hahn Herwig , Reuters Benjamin , Geipel Sascha , Schauerte Meike , Benkhelifa Fouad , Ambacher Oliver , Kalisch Holger , Vescan Andrei
Published: March 2015

GaN-based heterostructure FETs (HFETs) featuring a 2-D electron gas (2DEG) can offer very attractive device performance for power-switching applications. This performance can be assessed by evaluation of the dynamic on-resistance Ron,dyn vs. the breakdown voltage Vbd. In literature, it has been shown that with a high Vbd, Ron,dyn is deteriorated. The impairment of Ron,dyn is mainly driven by electron injection into surface, barrier, and buffer traps. Electron injection itself depends on the electric field which typically peaks at the gate edge towards the drain. A concept suitable to circumvent this issue is the charge-balancing concept which employs a 2-D hole gas (2DHG) on top of the 2DEG allowing for the electric field peak to be suppressed. Furthermore, the 2DEG concentration in the active channel cannot decrease by a change of the surface potential. Hence, beside an improvement in breakdown voltage, also an improvement in dynamic behaviour can be expected. Whereas the first aspect has already been demonstrated, the second one has not been under investigation so far. Hence, in this report, the effect of charge-balancing is discussed and its impact on the dynamic characteristics of HFETs is evaluated. It will be shown that with appropriate device design, the dynamic behaviour of HFETs can be improved by inserting an additional 2DHG.
A note on the breathing mode of an elastic sphere in Newtonian and complex fluids
Authors: Galstyan Vahe , Pak On Shun , Stone Howard A.
Published: March 2015

Experiments on the acoustic vibrations of elastic nanostructures in fluid media have been used to study the mechanical properties of materials, as well as for mechanical and biological sensing. The medium surrounding the nanostructure is typically modeled as a Newtonian fluid. A recent experiment however suggested that high-frequency longitudinal vibration of bipyramidal nanoparticles could trigger a viscoelastic response in water-glycerol mixtures [Pelton et al., “Viscoelastic flows in simple liquids generated by vibrating nanostructures,” Phys. Rev. Lett. 111, 244502 (2013)]. Motivated by these experimental studies, we first revisit a classical continuum mechanics problem of the purely radial vibration of an elastic sphere, also called the breathing mode, in a compressible viscous fluid and then extend our analysis to a viscoelastic medium using the Maxwell fluid model. The effects of fluid compressibility and viscoelasticity are discussed. Although in the case of longitudinal vibration of bipyramidal nanoparticles, the effects of fluid compressibility were shown to be negligible, we demonstrate that it plays a significant role in the breathing mode of an elastic sphere. On the other hand, despite the different vibration modes, the breathing mode of a sphere triggers a viscoelastic response in water-glycerol mixtures similar to that triggered by the longitudinal vibration of bipyramidal nanoparticles. We also comment on the effect of fluid viscoelasticity on the idea of destroying virus particles by acoustic resonance.
A novel experimental approach to investigate radiolysis processes in liquid samples using collimated radiation sources
Authors: Polin Chris , Wardlow Nathan , McQuaid Harold , Orr Philip , Villagomez-Bernabe Balder , Figueira Catarina , Alexander Grace , Srigengan Shajeth , Brun Emilie , Gilles Manon , Sicard-Roselli Cécile , Currell Fred J.
Published: March 2015

Here is detailed a novel and low-cost experimental method for high-throughput automated fluid sample irradiation. The sample is delivered via syringe pump to a nozzle, where it is expressed in the form of a hanging droplet into the path of a beam of ionising radiation. The dose delivery is controlled by an upstream lead shutter, which allows the beam to reach the droplet for a user defined period of time. The droplet is then further expressed after irradiation until it falls into one well of a standard microplate. The entire system is automated and can be operated remotely using software designed in-house, allowing for use in environments deemed unsafe for the user (synchrotron beamlines, for example). Depending on the number of wells in the microplate, several droplets can be irradiated before any human interaction is necessary, and the user may choose up to 10 samples per microplate using an array of identical syringe pumps, the design of which is described here. The nozzles consistently produce droplets of 25.1 ± 0.5 μl.
Femtosecond stimulated Raman spectroscopy by six-wave mixing
Authors: Molesky Brian P. , Guo Zhenkun , Moran Andrew M.
Published: March 2015

Femtosecond Stimulated Raman Spectroscopy (FSRS) is motivated by the knowledge of the molecular geometry changes that accompany sub-picosecond chemical reactions. The detection of vibrational resonances throughout the entire fingerprint region of the spectrum with sub-100-fs delay precision is fairly straightforward to accomplish with the FSRS technique. Despite its utility, FSRS must contend with substantial technical challenges that stem from a large background of residual laser light and lower-order nonlinearities when all laser pulses are electronically resonant with the equilibrium system. In this work, a geometry based on five incident laser beams is used to eliminate much of this undesired background in experiments conducted on metmyoglobin. Compared to a three-beam FSRS geometry with all electronically resonant laser pulses, the five-beam approach described here offers major improvements in the data acquisition rate, sensitivity, and background suppression. The susceptibility of the five-beam geometry to experimental artifacts is investigated using control experiments and model calculations. Of particular concern are undesired cascades of third-order nonlinearities, which are known to challenge FSRS measurements carried out on electronically off-resonant systems. It is generally understood that “forbidden” steps in the desired nonlinear optical processes are the origin of the problems encountered under off-resonant conditions. In contrast, the present experiments are carried out under electronically resonant conditions, where such unfortunate selection rules do not apply. Nonetheless, control experiments based on spectroscopic line shapes, signal phases, and sample concentrations are conducted to rule out significant contributions from cascades of third-order processes. Theoretical calculations are further used to estimate the relative intensities of the direct and cascaded responses. Overall, the control experiments and model calculations presented in this work suggest promise for multidimensional resonance Raman investigations of heme proteins.
Machine learning of single molecule free energy surfaces and the impact of chemistry and environment upon structure and dynamics
Authors: Mansbach Rachael A. , Ferguson Andrew L.
Published: March 2015

The conformational states explored by polymers and proteins can be controlled by environmental conditions (e.g., temperature, pressure, and solvent) and molecular chemistry (e.g., molecular weight and side chain identity). We introduce an approach employing the diffusion map nonlinear machine learning technique to recover single molecule free energy landscapes from molecular simulations, quantify changes to the landscape as a function of external conditions and molecular chemistry, and relate these changes to modifications of molecular structure and dynamics. In an application to an n-eicosane chain, we quantify the thermally accessible chain configurations as a function of temperature and solvent conditions. In an application to a family of polyglutamate-derivative homopeptides, we quantify helical stability as a function of side chain length, resolve the critical side chain length for the helix-coil transition, and expose the molecular mechanisms underpinning side chain-mediated helix stability. By quantifying single molecule responses through perturbations to the underlying free energy surface, our approach provides a quantitative bridge between experimentally controllable variables and microscopic molecular behavior, guiding and informing rational engineering of desirable molecular structure and function.
Origin of the 900 cm−1 broad double-hump OH vibrational feature of strongly hydrogen-bonded carboxylic acids
Authors: Van Hoozen Brian L. , Petersen Poul B.
Published: March 2015

Medium and strong hydrogen bonds are common in biological systems. Here, they provide structural support and can act as proton transfer relays to drive electron and/or energy transfer. Infrared spectroscopy is a sensitive probe of molecular structure and hydrogen bond strength but strongly hydrogen-bonded structures often exhibit very broad and complex vibrational bands. As an example, strong hydrogen bonds between carboxylic acids and nitrogen-containing aromatic bases commonly display a 900 cm−1 broad feature with a remarkable double-hump structure. Although previous studies have assigned this feature to the OH, the exact origin of the shape and width of this unusual feature is not well understood. In this study, we present ab initio calculations of the contributions of the OH stretch and bend vibrational modes to the vibrational spectrum of strongly hydrogen-bonded heterodimers of carboxylic acids and nitrogen-containing aromatic bases, taking the 7-azaindole—acetic acid and pyridine—acetic acid dimers as examples. Our calculations take into account coupling between the OH stretch and bend modes as well as how both of these modes are affected by lower frequency dimer stretch modes, which modulate the distance between the monomers. Our calculations reproduce the broadness and the double-hump structure of the OH vibrational feature. Where the spectral broadness is primarily caused by the dimer stretch modes strongly modulating the frequency of the OH stretch mode, the double-hump structure results from a Fermi resonance between the out of the plane OH bend and the OH stretch modes.
Metal insulator semiconductor solar cell devices based on a Cu2O substrate utilizing h-BN as an insulating and passivating layer
Authors: Ergen Onur , Gibb Ashley , Vazquez-Mena Oscar , Regan William Raymond , Zettl Alex
Published: March 2015

We demonstrate cuprous oxide (Cu2O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation and insulation layer on the active Cu2O layer. The devices are the most efficient of any Cu2O based MIS-Schottky solar cells reported to date.
Self-absorption in a light-emitting electrochemical cell based on an ionic transition metal complex
Authors: Kaihovirta Nikolai , Longo Giulia , Gil-Escrig Lidón , Bolink Henk J. , Edman Ludvig
Published: March 2015

We report on the quantitative and qualitative effects of self-absorption in light-emitting electrochemical cells (LECs) based on ionic transition metal complexes (iTMCs), as measured in-situ during electric driving. A yellow-emitting iTMC-LEC comprising an active material thickness of 95 nm suffers a 4% loss of the emission intensity to self-absorption, whereas the same type of device but with a larger active-material thickness of 1 μm will lose a significant 40% of the light intensity. We also find that the LEC-specific effect of doping-induced self-absorption can result in a drift of the emission spectrum with time for iTMC-LECs, but note that the overall magnitude of doping-induced self-absorption is much smaller than for conjugated-polymer LECs.
Utilizing fast multipole expansions for efficient and accurate quantum-classical molecular dynamics simulations
Authors: Schwörer Magnus , Lorenzen Konstantin , Mathias Gerald , Tavan Paul
Published: March 2015

Recently, a novel approach to hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations has been suggested [Schwörer et al., J. Chem. Phys. 138, 244103 (2013)]. Here, the forces acting on the atoms are calculated by grid-based density functional theory (DFT) for a solute molecule and by a polarizable molecular mechanics (PMM) force field for a large solvent environment composed of several 103-105 molecules as negative gradients of a DFT/PMM hybrid Hamiltonian. The electrostatic interactions are efficiently described by a hierarchical fast multipole method (FMM). Adopting recent progress of this FMM technique [Lorenzen et al., J. Chem. Theory Comput. 10, 3244 (2014)], which particularly entails a strictly linear scaling of the computational effort with the system size, and adapting this revised FMM approach to the computation of the interactions between the DFT and PMM fragments of a simulation system, here, we show how one can further enhance the efficiency and accuracy of such DFT/PMM-MD simulations. The resulting gain of total performance, as measured for alanine dipeptide (DFT) embedded in water (PMM) by the product of the gains in efficiency and accuracy, amounts to about one order of magnitude. We also demonstrate that the jointly parallelized implementation of the DFT and PMM-MD parts of the computation enables the efficient use of high-performance computing systems. The associated software is available online.
On the steady-state solutions of a nonlinear photonic lattice model
Authors: Liu Chungen , Ren Qiang
Published: March 2015

In this paper, we consider the steady-state solutions of the following equation related with nonlinear photonic lattice model Δu=Pu1+u2+v2+λu, Δv=Qv1+u2+v2+λv, where u, v are real-value function defined on R/(τ1Z) × R/(τ2Z). The existence and non-existence of non-constant semi-trivial (with only one component zero) solutions are considered.
Effect of Eu substitution on superconductivity in Ba8−xEuxAl6Si40 clathrates
Authors: Liu Lihua , Bi Shanli , Peng Bailu , Li Yang
Published: March 2015

The silicon clathrate superconductor is uncommon as its structure is dominated by strong Si-Si covalent bonds, rather than the metallic bond, that are more typical of traditional superconductors. To understand the influence of large magnetic moment of Eu on superconductivity for type-I clathrates, a series of samples with the chemical formula Ba8−xEuxAl6Si40 (x = 0, 0.5, 1, and 2) were synthesised in which Eu occupied Ba sites in cage center. With the increase of Eu content, the cubic lattice parameter decreases monotonically signifying continuous shrinkage of the constituting (Ba/Eu)@Si20 and (Ba/Eu)@Si24 cages. The temperature dependence of magnetization at low temperature revealed that Ba8Al6Si40 is superconductive with transition temperature at TC = 5.6 K. The substitution of Eu for Ba results in a strong superconductivity suppression; Eu-doping largely decreases the superconducting volume and transition temperature TC. Eu atoms enter the clathrate lattice and their magnetic moments break paired electrons. The Curie-Weiss temperatures were observed at 3.9, 6.6, and 10.9 K, respectively, for samples with x = 0.5, 1.0, and 2.0. Such ferromagnetic interaction of Eu can destroy superconductivity.
High-performance carbon nanotube thin-film transistors on flexible paper substrates
Authors: Liu Na , Yun Ki Nam , Yu Hyun-Yong , Shim Joon Hyung , Lee Cheol Jin
Published: March 2015

Single-walled carbon nanotubes (SWCNTs) are promising materials as active channels for flexible transistors owing to their excellent electrical and mechanical properties. However, flexible SWCNT transistors have never been realized on paper substrates, which are widely used, inexpensive, and recyclable. In this study, we fabricated SWCNT thin-film transistors on photo paper substrates. The devices exhibited a high on/off current ratio of more than 106 and a field-effect mobility of approximately 3 cm2/V·s. The proof-of-concept demonstration indicates that SWCNT transistors on flexible paper substrates could be applied as low-cost and recyclable flexible electronics.
Magnetocaloric effect in La0.7Ca0.3MnO3 nanotube arrays with broad working temperature span
Authors: Kumaresavanji M. , Sousa C. T. , Pires A. , Pereira A. M. , Lopes A. M. L. , Araujo J. P.
Published: March 2015

We have studied the magnetic entropy change of highly ordered La0.7Ca0.3MnO3 nanotube arrays synthesized by template assisted sol-gel method in temperatures ranging from 179 to 293 K and in magnetic fields up to 5 T. From the measurements of isothermal magnetization, we have calculated the maximum isothermal magnetic entropy change of −△SM = 1.9 J/kg K around the Curie temperature at 236 K for a field of 5 T. The nanotubes present lower magnetic entropy change compared with their bulk counterpart (−△SM = 4.8 J/kg K) which was prepared by the same sol-gel route. Such diminished magnetic entropy change observed in nanotubes is explained by the disordered magnetic states which are created on the surface sites of nanograins due to the larger surface to volume ratio. However, the nanotubes present an expanded magnetic transition that extends over a wide temperature range and suggest that such manganite nanotubes could be used for magnetic refrigeration with broad working temperature span.
Transport properties of La2/3Sr1/3MnO3/LaAlO3/Pt tunnel junctions
Authors: Galceran R. , Balcells Ll. , Pomar A. , Konstantinović Z. , Sandiumenge F. , Martínez B.
Published: March 2015

Magnetotransport properties of La2/3Sr1/3MnO3/LaAlO3/Pt tunnel junctions have been thoroughly analyzed, as a function of temperature and magnetic field, to test the suitability of LaAlO3 for insulating barriers and spin injection processes. The insulating behavior of LaAlO3 maintained down to 1–2 nm (corresponding to 4–5 unit cells) renders this material useful as tunnel barrier. The temperature dependence of the junction resistance, R(T), down to 200 K confirms direct tunneling as the dominant conduction channel. The barrier parameters of the junctions, φ0 and s, are estimated using Simmons' model in the intermediate voltage range. The energy of the barrier was estimated to be φ0 ∼ 0.4 eV at room temperature. The dependence of R(T) and φ0 on the magnetic field shows an anisotropic tunneling magnetoresistance of ∼4% at low T when changing the direction of the magnetization with respect to the current flow.
Parameter estimation, nonlinearity, and Occam's razor
Authors: Alonso Leandro M.
Published: March 2015

Nonlinear systems are capable of displaying complex behavior even if this is the result of a small number of interacting time scales. A widely studied case is when complex dynamics emerges out of a nonlinear system being forced by a simple harmonic function. In order to identify if a recorded time series is the result of a nonlinear system responding to a simpler forcing, we develop a discrete nonlinear transformation for time series based on synchronization techniques. This allows a parameter estimation procedure which simultaneously searches for a good fit of the recorded data, and small complexity of a fluctuating driving parameter. We illustrate this procedure using data from respiratory patterns during birdsong production.
Reaction enhancement of initially distant scalars by Lagrangian coherent structures
Authors: Pratt Kenneth R. , Meiss James D. , Crimaldi John P.
Published: March 2015

Turbulent fluid flows have long been recognized as a superior means of diluting initial concentrations of scalars due to rapid stirring. Conversely, experiments have shown that the structures responsible for this rapid dilution can also aggregate initially distant reactive scalars and thereby greatly enhance reaction rates. Indeed, chaotic flows not only enhance dilution by shearing and stretching but also organize initially distant scalars along transiently attracting regions in the flow. To show the robustness of this phenomenon, a hierarchical set of three numerical flows is used: the periodic wake downstream of a stationary cylinder, a chaotic double gyre flow, and a chaotic, aperiodic flow consisting of interacting Taylor vortices. We demonstrate that Lagrangian coherent structures (LCS), as identified by ridges in finite time Lyapunov exponents, are directly responsible for this coalescence of reactive scalar filaments. When highly concentrated filaments coalesce, reaction rates can be orders of magnitude greater than would be predicted in a well-mixed system. This is further supported by an idealized, analytical model that was developed to quantify the competing effects of scalar dilution and coalescence. Chaotic flows, known for their ability to efficiently dilute scalars, therefore have the competing effect of organizing initially distant scalars along the LCS at timescales shorter than that required for dilution, resulting in reaction enhancement.
Enhancement of ambipolar characteristics in single-walled carbon nanotubes using C60 and fabrication of logic gates
Authors: Park Steve , Nam Ji Hyun , Koo Ja Hoon , Lei Ting , Bao Zhenan
Published: March 2015

We demonstrate a technique to convert p-type single-walled carbon nanotube (SWNT) network transistor into ambipolar transistor by thermally evaporating C60 on top. The addition of C60 was observed to have two effects in enhancing ambipolar characteristics. First, C60 served as an encapsulating layer that enhanced the ambipolar characteristics of SWNTs. Second, C60 itself served as an electron transporting layer that contributed to the n-type conduction. Such a dual effect enables effective conversion of p-type into ambipolar characteristics. We have fabricated inverters using our SWNT/C60 ambipolar transistors with gain as high as 24, along with adaptive NAND and NOR logic gates.
Contribution of individual interfaces in the MgO/Co/Pd trilayer to perpendicular magnetic anisotropy upon annealing
Authors: Kim Minseok , Kim Sanghoon , Ko Jungho , Hong Jongill
Published: March 2015

The contribution of each interface of the MgO/Co/Pd trilayer to the perpendicular magnetic anisotropy (PMA) was studied by changing chemical and crystalline structures through annealing. We found that volumetric anisotropy in the MgO/Co/Pd trilayer was significantly increased due to enhanced magnetoelastic anisotropy caused by stress built up most likely at the MgO/Co interface during annealing. When the trilayer was annealed at 400 °C, the alloy formation at the Co/Pd interface additionally increased the volumetric anisotropy. Our x-ray magnetic circular dichroism study supported that those structural modifications led to an increase in the orbital moment through spin-orbit coupling (SOC) along the film normal two times larger than that of the as-deposited trilayer, thereby enhancing PMA greatly. Our experimental results prove that the Co/Pd interface, rather than the MgO/Co interface, plays an essential role in inducing strong PMA in the trilayer. The precise investigation of annealing effect on both volumetric and interfacial anisotropies can provide a methodological solution to improve the SOC of the trilayer that can serve as the core unit of spintronic devices.
Unidirectional light emission from low-index polymer microlasers
Authors: Schermer M. , Bittner S. , Singh G. , Ulysse C. , Lebental M. , Wiersig J.
Published: March 2015

We report on experiments with deformed polymer microlasers that have a low refractive index and exhibit unidirectional light emission. We demonstrate that the highly directional emission is due to transport of light rays along the unstable manifold of the chaotic saddle in phase space. Experiments, ray-tracing simulations, and mode calculations show very good agreement.
Spin injection induced phase transition in YBa2Cu3O7−δ/Nd0.35Sr0.65MnO3 bilayer
Authors: Cheng S. L. , Lin J. G. , Chuang T. H.
Published: March 2015

The spin injection effects from C-type antiferromagnetic Nd0.35Sr0.65MnO3 (NSMO) to superconductor YBa2Cu3O7−δ (YBCO) are investigated via the measurement of temperature dependent resistivity with input current from 10−2 mA to 90 mA. The superconducting transition temperature (Tco) of YBCO decreases with increasing current but at a higher rate with larger thickness of NSMO. Two spin states below Tco are identified as non-equilibrium spin-state and pair-breaking state judging from the width of transition. In particular, the transition from former to later one is observed with NSMO = 30 nm at the current of 30 mA.
Damping factor estimation using spin wave attenuation in permalloy film
Authors: Manago Takashi , Yamanoi Kazuto , Kasai Shinya , Mitani Seiji
Published: March 2015

Damping factor of a Permalloy (Py) thin film is estimated by using the magnetostatic spin wave propagation. The attenuation lengths are obtained by the dependence of the transmission intensity on the antenna distance, and decrease with increasing magnetic fields. The relationship between the attenuation length, damping factor, and external magnetic field is derived theoretically, and the damping factor was determined to be 0.0063 by fitting the magnetic field dependence of the attenuation length, using the derived equation. The obtained value is in good agreement with the general value of Py. Thus, this estimation method of the damping factor using spin waves attenuation can be useful tool for ferromagnetic thin films.
Effect of injected spins with different polarized orientations on the vortex phase transition in La0.7Sr0.3MnO3/La1.85Sr0.15CuO4 heterostructure
Authors: Zhang M. J. , Teng M. L. , Hao F. X. , Yin Y. W. , Zeng Z. , Li X. G.
Published: March 2015

The current-voltage (I-V) characteristics with spin injection were investigated for the epitaxial La0.7Sr0.3MnO3/La1.85Sr0.15CuO4 heterostructure rotated from H//c to H//ab in magnetic fields up to 14 T. It is found that all the I-V curves in various magnetic fields can be scaled with a three dimensional (3D) vortex glass model, and the spin injection can induce a better 3D scaling behavior, which is closely related to the decrease of the anisotropy parameter. A vortex phase diagram for the evolution of vortex glass transition field (Hg) and upper critical field (Hc2) indicates that both Hg and Hc2 are suppressed by spin injection, and this effect becomes more obvious in the case of H//ab, which probably originates from the different suppression on the superconducting pairing strength by different injected spins' orientations.
Unipolar self-doping behavior in perovskite CH3NH3PbBr3
Authors: Shi Tingting , Yin Wan-Jian , Hong Feng , Zhu Kai , Yan Yanfa
Published: March 2015

Recent theoretical and experimental reports have shown that the perovskite CH3NH3PbI3 exhibits unique ambipolar self-doping properties. Here, we show by density-functional theory calculation that its sister perovskite, CH3NH3PbBr3, exhibits a unipolar self-doping behavior—CH3NH3PbBr3 presents only good p-type conductivity under thermal equilibrium growth conditions. We further show that despite a large bandgap of 2.2 eV, all dominant defects in CH3NH3PbBr3 create shallow levels, which partially explains the ultra-high open-circuit voltages achieved by CH3NH3PbBr3-based thin-film solar cells. Our results suggest that the perovskite CH3NH3PbBr3 can be both an excellent solar cell absorber and a promising low-cost hole-transport material for lead halide perovskite solar cells.
Collisionless absorption, hot electron generation, and energy scaling in intense laser-target interaction
Authors: Liseykina T. , Mulser P. , Murakami M.
Published: March 2015

Among the various attempts to understand collisionless absorption of intense and superintense ultrashort laser pulses, a whole variety of models and hypotheses has been invented to describe the laser beam target interaction. In terms of basic physics, collisionless absorption is understood now as the interplay of the oscillating laser field with the space charge field produced by it in the plasma. A first approach to this idea is realized in Brunel's model the essence of which consists in the formation of an oscillating charge cloud in the vacuum in front of the target, therefore frequently addressed by the vague term “vacuum heating.” The investigation of statistical ensembles of orbits shows that the absorption process is localized at the ion-vacuum interface and in the skin layer: Single electrons enter into resonance with the laser field thereby undergoing a phase shift which causes orbit crossing and braking of Brunel's laminar flow. This anharmonic resonance acts like an attractor for the electrons and leads to the formation of a Maxwellian tail in the electron energy spectrum. Most remarkable results of our investigations are the Brunel like spectral hot electron distribution at the relativistic threshold, the minimum of absorption at Iλ2≅(0.3−1.2)×1021 Wcm−2μm2 in the plasma target with the electron density of neλ2∼1023cm−3μm2, the drastic reduction of the number of hot electrons in this domain and their reappearance in the highly relativistic domain, and strong coupling, beyond expectation, of the fast electron jets with the return current through Cherenkov emission of plasmons. The hot electron energy scaling shows a strong dependence on intensity in the moderately relativistic domain Iλ2≅(1018−1020) Wcm−2μm2, a scaling in vague accordance with current published estimates in the range Iλ2≅(0.14−3.5)×1021 Wcm−2μm2, and again a distinct power increase beyond I=3.5×1021 Wcm−2μm2. The low energy electrons penetrate normally to the target surface, the energetic electrons propagate in laser beam direction.