bluuebunny/crossref_metadata_2025 huggingface dataset:
Discovery of novel 1,3,5-triazine-thiazolidine-2,4-diones as dipeptidyl peptidase-4 inhibitors with antibacterial activity targeting the S1 pocket for the treatment of type 2 diabetes
Authors: Srivastava Jitendra Kumar , Dubey Pragya , Singh Saumya , Bhat Hans Raj , Kumawat Mukesh Kumar , Singh Udaya Pratap
Published: January 2015

A novel series of 1,3,5-triazine-thiazolidine-2,4-diones was synthesized and characterized by a number of analytical and spectroscopic techniques.
2D protein arrays induce 3D in vivo-like assemblies of cells
Authors: Moreno-Flores S. , Küpcü S.
Published: January 2015

Bacterial S-layers trigger the formation of viable multicellular spheroids of adequate morphology, kinetics of growth and lifespan for biomedical research.
Atomistic simulations of the structure of highly crosslinked sulfonated poly(styrene-co-divinylbenzene) ion exchange resins
Authors: Pérez-Maciá María A. , Curcó David , Bringué Roger , Iborra Montserrat , Alemán Carlos
Published: January 2015

The microscopic structures of highly crosslinked sulfonated poly(styrene-co-divinylbenzene) resins have been modeled by generating atomistic microstructures using stochastic-like algorithms, which are subsequently relaxed using molecular dynamics.
A novel Li4Ti5O12-based high-performance lithium-ion electrode at elevated temperature
Authors: Guo Junling , Zuo Wenhua , Cai Yingjun , Chen Shimou , Zhang Suojiang , Liu Jinping
Published: January 2015

A Li4Ti5O12-based nanowire array electrode that can be cycled at elevated temperature (60 °C; 500 cycles) has been constructed.
Fully indium-free flexible Ag nanowires/ZnO:F composite transparent conductive electrodes with high haze
Authors: Han Jun , Yuan Shuai , Liu Lina , Qiu Xiaofeng , Gong Haibo , Yang Xiaopeng , Li Cuncheng , Hao Yufeng , Cao Bingqiang
Published: January 2015

Fully indium-free flexible Ag nanowires/ZnO:F composite transparent conductive electrodes with high haze can improve the perovskite solar cell efficiency.
Enhanced thermal conductivity for polyimide composites with a three-dimensional silicon carbide nanowire@graphene sheets filler
Authors: Dai Wen , Yu Jinhong , Wang Yi , Song Yingze , Alam Fakhr E. , Nishimura Kazuhito , Lin Cheng-Te , Jiang Nan
Published: January 2015

3DSG incorporated into a polyimide matrix greatly enhanced its thermal conductivity (up to 2.63 W m−1 K−1), approximately a 10-fold enhancement in comparison with that of neat polyimide.
Highly branched cobalt phosphide nanostructures for hydrogen-evolution electrocatalysis
Authors: Popczun Eric J. , Roske Christopher W. , Read Carlos G. , Crompton J. Chance , McEnaney Joshua M. , Callejas Juan F. , Lewis Nathan S. , Schaak Raymond E.
Published: January 2015

Highly branched cobalt phosphide (CoP) nanostructures that expose predominantly (111) crystal facets are active electrocatalysts for the hydrogen evolution reaction in acidic aqueous solutions.
One-step pyrolytic synthesis of small iron carbide nanoparticles/3D porous nitrogen-rich graphene for efficient electrocatalysis
Authors: Huang Hao , Feng Xun , Du Cuicui , Wu Siyuan , Song Wenbo
Published: January 2015

3D porous Fe3C/NGr is in situ pyrolytically achieved, demonstrating extra ORR catalytic activity with a 40 mV more positive peak potential than Pt/C.
A lithium–sulfur full cell with ultralong cycle life: influence of cathode structure and polysulfide additive
Authors: Thieme Sören , Brückner Jan , Meier Andreas , Bauer Ingolf , Gruber Katharina , Kaspar Jörg , Helmer Alexandra , Althues Holger , Schmuck Martin , Kaskel Stefan
Published: January 2015

A carbide-derived carbon with hierarchical pore structure, large pore volume and high surface area was applied as a rigid, conductive scaffold for sulfur conversion. Full cell tests revealed high performance and reversible cycling over 4100 cycles.
Antifouling property of monothiol-terminated bottle-brush poly(methylacrylic acid)-graft-poly(2-methyl-2-oxazoline) copolymer on gold surfaces
Authors: Zheng Xiajun , Zhang Chong , Bai Longchao , Liu Songtao , Tan Lin , Wang Yanmei
Published: January 2015

A series of well-controlled bottle-brush poly(methylacrylic acid)-graft-poly(2-methyl-2-oxazoline) copolymers were grafted to gold surfaces through an in situ aminolysis reaction to reduce protein adsorption and platelet adhesion.
Design of multi-functional linear polymers that capture and neutralize a toxic peptide: a comparison with cross-linked nanoparticles
Authors: Wada Yusuke , Lee Haejoo , Hoshino Yu , Kotani Shunsuke , Shea Kenneth J. , Miura Yoshiko
Published: January 2015

In this paper, a library of multi-functional linear poly-N-isopropylacrylamide (pNIPAm) polymers having a range of molecular weights and functional groups were synthesized and their interaction with the hemolytic peptide, melittin, was examined.
Fine-tuning thermoresponsive functional poly(ε-caprolactone)s to enhance micelle stability and drug loading
Authors: Rainbolt Elizabeth A. , Miller Jason B. , Washington Katherine E. , Senevirathne Suchithra A. , Biewer Michael C. , Siegwart Daniel J. , Stefan Mihaela C.
Published: January 2015

New caprolactone-based amphiphilic terpolymers feature thermoresponsive behavior, biodegradable backbones, and enhanced micelle stability.
Multivalent manganese complex decorated amphiphilic dextran micelles as sensitive MRI probes
Authors: Wu Changqiang , Li Danyang , Yang Li , Lin Bingbing , Zhang Houbing , Xu Ye , Cheng Zhuzhong , Xia Chunchao , Gong Qiyong , Song Bin , Ai Hua
Published: January 2015

Manganese complex decorated amphiphilic dextran micelles were prepared and have a high T1 relaxivity in MRI.
Mechanosynthesis and multiferroic properties of the BiFeO3–BiMnO3–PbTiO3 ternary system along its morphotropic phase boundary
Authors: Fernández-Posada Carmen M. , Amorín Harvey , Correas Covadonga , Peña Octavio , Algueró Miguel , Castro Alicia
Published: January 2015

Mechanosynthesis and analysis of the multiferroicity of new compositions of the BiFeO3–BiMnO3–PbTiO3 ternary system liable to show room-temperature magnetoelectricity.
Magnetostructural phase transformations in Tb1−xMn2
Authors: Zou Junding , Paudyal Durga , Liu Jing , Mudryk Yaroslav , Pecharsky Vitalij K. , Gschneidner Karl A.
Published: January 2015

Magnetism and phase transformations in non-stoichiometric Tb1−xMn2(x= 0.056, 0.039) have been studied as functions of temperature and magnetic field.
Multiple horizontal-dip-coating of small molecular emission layers for solution-processable organic light-emitting devices
Authors: Jeon Hong Goo , Park Byoungchoo
Published: January 2015

Small molecular organic light-emitting layers are successfully deposited by multiple horizontal-dip-coating to achieve highly bright and efficient solution-processable OLEDs.
Highly efficient ultra-deep blue organic light-emitting diodes with a wet- and dry-process feasible cyanofluorene acetylene based emitter
Authors: Jou Jwo-Huei , Kumar Sudhir , Fang Po-Hsun , Venkateswararao A. , Thomas K. R. Justin , Shyue Jing-Jong , Wang Ya-Chi , Li Tsung-Han , Yu Hui-Huan
Published: January 2015

This article describes the synthesis and characteristics of a cyanofluorene–acetylene conjugate based blue emitter C3FLA-2. In the host doped device, C3FLA-2 shows an EQE of 8.0% and CIExyof (0.156, 0.048).
A rare earth-free GaZnON phosphor prepared by combustion for white light-emitting diodes
Authors: Chouhan Neelu , Lin Chun Che , Hu Shu-Fen , Liu Ru-Shi
Published: January 2015

Rare earth-free phosphor GaZnON was synthesized by combustion of a unimolar mixture of metal oxides and urea, which can be used in WLEDs.
Fast fabrication of transparent and multi-luminescent TEMPO-oxidized nanofibrillated cellulose nanopaper functionalized with lanthanide complexes
Authors: Miao Miao , Zhao Jingpeng , Feng Xin , Cao Yang , Cao Shaomei , Zhao Yafei , Ge Xiaoqian , Sun Lining , Shi Liyi , Fang Jianhui
Published: January 2015

Transparent and multi-luminescent nanopaper was rapidly fabricated by TEMPO oxidized NFC grafting with lanthanide complexes via a pressured extrusion process.
Carbon-encapsulated CdSe quantum dot inorganic hybrid nanobelts for high performance photoelectronic devices based on the efficient separation and transfer of photoinduced holes
Authors: Zhao Jie , Cao Minghui , Cheng Baochang , Wu Guohong , Guo Huijun , Ai Yilong , Su Xiaohui , Xiao Yanhe , Lei Shuijin
Published: January 2015

We developed a facile method of combustion synthesis followed by a selenylation process to synthesize carbon-encapsulated CdSe hybrid nanobelts.
Perylenebisimide-based multi-modal cyanide recognition: molecular logic gate deciphering magnetic memory units
Authors: Kaloo Masood Ayoub , Mishra Ruchika , Sankar Jeyaraman
Published: January 2015

An electron-deficient perylenebisimide has been identified as the first example of a molecular Boolean logic gate having a magnetic signalling mechanism.
An isoindigo containing donor–acceptor polymer: synthesis and photovoltaic properties of all-solution-processed ITO- and vacuum-free large area roll-coated single junction and tandem solar cells
Authors: Brandt Rasmus Guldbaek , Yue Wei , Andersen Thomas Rieks , Larsen-Olsen Thue Trofod , Hinge Mogens , Bundgaard Eva , Krebs Frederik C. , Yu Donghong
Published: January 2015

A novel isoindigo containing D–A polymer was developed for large area single junction and tandem solar cells.
Controlling and self assembling of monodisperse platinum nanocubes as efficient methanol oxidation electrocatalysts
Authors: Sun Xiuhui , Zhu Xing , Zhang Nan , Guo Jun , Guo Shaojun , Huang Xiaoqing
Published: January 2015

An efficient approach that enables the direct controlling and assembling of Pt nanocubes was developed for the first time.
Sink or swim: using density as a signal for quantitative immunoassays
Authors: Huang Tony Jun
Published: January 2015

Tony Jun Huang provides a commentary to accompany the article by Whitesides et al. (DOI: 10.1039/C4LC01161A).
Enantioselective addition of oxazolones to N-protected imines catalysed by chiral thioureas
Authors: Žabka Matej , Malastová Andrea , Šebesta Radovan
Published: January 2015

Chiral thiourea-catalysed Mannich-type addition of oxazolones to imines, which provide highly functionalized amino oxazolones with quaternary stereogenic centres.
Upconverting nanoparticle to quantum dot FRET for homogeneous double-nano biosensors
Authors: Mattsson Leena , Wegner K. David , Hildebrandt Niko , Soukka Tero
Published: January 2015

The unique photophysical properties of upconverting nanoparticles (UCNPs) and semiconductor quantum dots (QDs) render them an attractive donor–acceptor combination for near-infrared (NIR) excited FRET-based optical biosensing.
An interplay between the p38 MAPK pathway and AUBPs regulates c-fos mRNA stability during mitogenic stimulation
Authors: Degese Maria Sol , Tanos Tamara , Naipauer Julian , Gingerich Tim , Chiappe Diego , Echeverria Pablo , LaMarre Jonathan , Gutkind J. Silvio , Coso Omar A.
Published: January 2015

MAPK pathways are well-studied regulatory elements linked to the regulation of nuclear gene expression by its interaction with transcription factors. An additional and equally interesting level of control of gene expression is provided by mechanisms that control mRNA stability. Our results indicate that while ERK2 promotes fos gene transcription, another MAPK (p38 MAPK) regulates fos mRNA decay by affecting the state of phosphorylation of specific mRNA binding proteins. In this fashion, concerted early (ERK) or late (p38) MAPK activation can contribute to both rapid and transient activation of the early responsive gene fos.
The VPS-20 subunit of the endosomal sorting complex ESCRT-III exhibits an open conformation in the absence of upstream activation
Authors: Schuh Amber L. , Hanna Michael , Quinney Kyle , Wang Lei , Sarkeshik Ali , Yates John R. , Audhya Anjon
Published: January 2015

SAXS analysis reveals that the endosomal sorting complex required for transport (ESCRT)-III subunit vacuolar protein sorting (VPS)-20 exhibits an extended open conformation in solution, but does not homo-polymerize. These findings challenge the concept that all ESCRT-III subunits adopt closed auto-inhibited conformations to prevent premature polymer assembly.
Alteration of structure and function of ATP synthase and cytochromecoxidase by lack of Fo-a and Cox3 subunits caused by mitochondrial DNA 9205delTA mutation
Authors: Hejzlarová Kateřina , Kaplanová Vilma , Nůsková Hana , Kovářová Nikola , Ješina Pavel , Drahota Zdeněk , Mráček Tomáš , Seneca Sara , Houštěk Josef
Published: January 2015

MtDNA 9205delTA microdeletion in the MT-ATP6/MT-CO3 gene alters the structure of ATP synthase, down-regulates the content of cytochrome c oxidase and thus impairs mitochondrial ATP production. The disease severity depends on the threshold at about 90% of the mutation load.
Venous Thromboembolism Prophylaxis in Critically Ill Patients
Authors: Boonyawat Kochawan , Crowther Mark
Published: January 2015

Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is recognized as a common complication in critically ill patients. Risk factors including critical illness, mechanical ventilation, sedative medications, and central venous catheter insertion are major contributing factors to the high risk of VTE. Because of their impaired cardiopulmonary reserve, PE arising from thrombosis in the deep veins of the calf that propagates proximally is poorly tolerated by critically ill patients. Pharmacologic prophylaxis with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) has been shown to decrease the incidence of VTE in medical, surgical, and critically ill patients. As a result, over the past decades, VTE prophylaxis had become a standard of preventive measure in the intensive care unit (ICU). In clinical practice, the rate of VTE prophylaxis varies and may be inadequate in some centers. A perception of a high bleeding risk in critically ill patients is a major concern for most physicians that may lead to inadequate prophylaxis.
Trend and Characteristics of 2,636 Maxillofacial Fracture Cases over 32 Years in Suburban City of Japan
Authors: Yamamoto Kazuhiko , Matsusue Yumiko , Horita Satoshi , Murakami Kazuhiro , Sugiura Tsutomu , Kirita Tadaaki
Published: January 2015

Trend and characteristics of maxillofacial fractures in 2,636 patients over 32 years were analyzed retrospectively. Patients comprised 1,764 males and 872 females with ages ranging from 0 to 99 years. Patients younger than 30 years consisted of 60% maxillofacial fractures in the early period but decreased to 40% in the late period. In contrast, patients older than 60 years gradually increased to 30%. In terms of cause, traffic accidents consisted of more than 50%, predominantly motorcycle accidents, but gradually decreased to 40%. In contrast, falls markedly increased from less than 10 to 30%. Fractures occurred in the midface in 938 patients, in the mandible in 1,490, and in both in 208. In the midface, zygoma fractures consisted of 50% throughout the period. In the mandible, condyle fractures were observed in 40%, followed by fractures of the symphysis and angle. The ratio of condylar fractures slightly increased. Open reduction and internal fixation (ORIF) were performed in 782 patients, followed by observation in 716, maxillomandibular fixation (MMF) in 605, intramaxillary splinting (IMS) in 294, transcutaneous reduction (TCR) in 126, and others in 113. MMF markedly decreased from more than 30 to less than 5% and observation increased from 20 to 40%.
Accuracy of maximum likelihood estimates of a two-state model in single-molecule FRET
Authors: Gopich Irina V.
Published: January 2015

Photon sequences from single-molecule Förster resonance energy transfer (FRET) experiments can be analyzed using a maximum likelihood method. Parameters of the underlying kinetic model (FRET efficiencies of the states and transition rates between conformational states) are obtained by maximizing the appropriate likelihood function. In addition, the errors (uncertainties) of the extracted parameters can be obtained from the curvature of the likelihood function at the maximum. We study the standard deviations of the parameters of a two-state model obtained from photon sequences with recorded colors and arrival times. The standard deviations can be obtained analytically in a special case when the FRET efficiencies of the states are 0 and 1 and in the limiting cases of fast and slow conformational dynamics. These results are compared with the results of numerical simulations. The accuracy and, therefore, the ability to predict model parameters depend on how fast the transition rates are compared to the photon count rate. In the limit of slow transitions, the key parameters that determine the accuracy are the number of transitions between the states and the number of independent photon sequences. In the fast transition limit, the accuracy is determined by the small fraction of photons that are correlated with their neighbors. The relative standard deviation of the relaxation rate has a “chevron” shape as a function of the transition rate in the log-log scale. The location of the minimum of this function dramatically depends on how well the FRET efficiencies of the states are separated.
Theoretical investigation of stabilities and optical properties of Si12C12 clusters
Authors: Duan Xiaofeng F. , Burggraf Larry W.
Published: January 2015

By sorting through hundreds of globally stable Si12C12 isomers using a potential surface search and using simulated annealing, we have identified low-energy structures. Unlike isomers knit together by Si–C bonds, the lowest energy isomers have segregated carbon and silicon regions that maximize stronger C–C bonding. Positing that charge separation between the carbon and silicon regions would produce interesting optical absorption in these cluster molecules, we used time-dependent density functional theory to compare the calculated optical properties of four isomers representing structural classes having different types of silicon and carbon segregation regions. Absorptions involving charge transfer between segregated carbon and silicon regions produce lower excitation energies than do structures having alternating Si–C bonding for which frontier orbital charge transfer is exclusively from separated carbon atoms to silicon atoms. The most stable Si12C12 isomer at temperatures below 1100 K is unique as regards its high symmetry and large optical oscillator strength in the visible blue. Its high-energy and low-energy visible transitions (1.15 eV and 2.56 eV) are nearly pure one-electron silicon-to-carbon transitions, while an intermediate energy transition (1.28 eV) is a nearly pure carbon-to-silicon one-electron charge transfer.
Bianchi type-I magnetized cosmological models for the Einstein-Boltzmann equation with the cosmological constant
Authors: Ayissi Raoul Domingo , Noutchegueme Norbert
Published: January 2015

Global solutions regular for the Einstein-Boltzmann equation on a magnetized Bianchi type-I cosmological model with the cosmological constant are investigated. We suppose that the metric is locally rotationally symmetric. The Einstein-Boltzmann equation has been already considered by some authors. But, in general Bancel and Choquet-Bruhat [Ann. Henri Poincaré XVIII(3), 263 (1973); Commun. Math. Phys. 33, 83 (1973)], they proved only the local existence, and in the case of the nonrelativistic Boltzmann equation. Mucha [Global existence of solutions of the Einstein-Boltzmann equation in the spatially homogeneous case. Evolution equation, existence, regularity and singularities (Banach Center Publications, Institute of Mathematics, Polish Academy of Science, 2000), Vol. 52] obtained a global existence result, for the relativistic Boltzmann equation coupled with the Einstein equations and using the Yosida operator, but confusing unfortunately with the nonrelativistic case. Noutchegueme and Dongho [Classical Quantum Gravity 23, 2979 (2006)] and Noutchegueme, Dongho, and Takou [Gen. Relativ. Gravitation 37, 2047 (2005)], have obtained a global solution in time, but still using the Yosida operator and considering only the uncharged case. Noutchegueme and Ayissi [Adv. Stud. Theor. Phys. 4, 855 (2010)] also proved a global existence of solutions to the Maxwell-Boltzmann system using the characteristic method. In this paper, we obtain using a method totally different from those used in the works of Noutchegueme and Dongho [Classical Quantum Gravity 23, 2979 (2006)], Noutchegueme, Dongho, and Takou [Gen. Relativ. Gravitation 37, 2047 (2005)], Noutchegueme and Ayissi [Adv. Stud. Theor. Phys. 4, 855 (2010)], and Mucha [Global existence of solutions of the Einstein-Boltzmann equation in the spatially homogeneous case. Evolution equation, existence, regularity and singularities (Banach Center Publications, Institute of Mathematics, Polish Academy of Science, 2000), Vol. 52] the global in time existence and uniqueness of a regular solution to the Einstein-Maxwell-Boltzmann system with the cosmological constant. We define and we use the weighted Sobolev separable spaces for the Boltzmann equation; some special spaces for the Einstein equations, then we clearly display all the proofs leading to the global existence theorems.
DNA denaturation bubbles: Free-energy landscape and nucleation/closure rates
Authors: Sicard François , Destainville Nicolas , Manghi Manoel
Published: January 2015

The issue of the nucleation and slow closure mechanisms of non-superhelical stress-induced denaturation bubbles in DNA is tackled using coarse-grained MetaDynamics and Brownian simulations. A minimal mesoscopic model is used where the double helix is made of two interacting bead-spring rotating strands with a prescribed torsional modulus in the duplex state. We demonstrate that timescales for the nucleation (respectively, closure) of an approximately 10 base-pair bubble, in agreement with experiments, are associated with the crossing of a free-energy barrier of 22 kBT (respectively, 13 kBT) at room temperature T. MetaDynamics allows us to reconstruct accurately the free-energy landscape, to show that the free-energy barriers come from the difference in torsional energy between the bubble and duplex states, and thus to highlight the limiting step, a collective twisting, that controls the nucleation/closure mechanism, and to access opening time scales on the millisecond range. Contrary to small breathing bubbles, those more than 4 base-pair bubbles are of biological relevance, for example, when a pre-existing state of denaturation is required by specific DNA-binding proteins.
Collimated electron beam accelerated at 12 kV from a Penning discharge
Authors: Toader D. , Oane M. , Ticoş C. M.
Published: January 2015

A pulsed electron beam accelerated at 12 kV with a duration of 40 μs per pulse is obtained from a Penning discharge with a hollow anode and two cathodes. The electrons are extracted through a hole in one of the cathodes and focused by a pair of coils. The electron beam has a diameter of a few mm in the cross section, while the beam current reaches peak values of 400 mA, depending on the magnetic field inside the focussing coils. This relatively inexpensive and compact device is suitable for the irradiation of small material samples placed in high vacuum.
Boron carbide coatings for neutron detection probed by x-rays, ions, and neutrons to determine thin film quality
Authors: Nowak G. , Störmer M. , Becker H.-W. , Horstmann C. , Kampmann R. , Höche D. , Haese-Seiller M. , Moulin J.-F. , Pomm M. , Randau C. , Lorenz U. , Hall-Wilton R. , Müller M. , Schreyer A.
Published: January 2015

Due to the present shortage of 3He and the associated tremendous increase of its price, the supply of large neutron detection systems with 3He becomes unaffordable. Alternative neutron detection concepts, therefore, have been invented based on solid 10B converters. These concepts require development in thin film deposition technique regarding high adhesion, thickness uniformity and chemical purity of the converter coating on large area substrates. We report on the sputter deposition of highly uniform large-area 10B4C coatings of up to 2 μm thickness with a thickness deviation below 4% using the Helmholtz-Zentrum Geesthacht large area sputtering system. The 10B4C coatings are x-ray amorphous and highly adhesive to the substrate. Material analysis by means of X-ray-Photoelectron Spectroscopy, Secondary-Ion-Mass-Spectrometry, and Rutherford-Back-Scattering (RBS) revealed low impurities concentration in the coatings. The isotope composition determined by Secondary-Ion-Mass-Spectrometry, RBS, and inelastic nuclear reaction analysis of the converter coatings evidences almost identical 10B isotope contents in the sputter target and in the deposited coating. Neutron conversion and detection test measurements with variable irradiation geometry of the converter coating demonstrate an average relative quantum efficiency ranging from 65% to 90% for cold neutrons as compared to a black 3He-monitor. Thus, these converter coatings contribute to the development of 3He-free prototype detectors based on neutron grazing incidence. Transferring the developed coating process to an industrial scale sputtering system can make alternative 3He-free converter elements available for large area neutron detection systems.
Effects of rotational symmetry breaking in polymer-coated nanopores
Authors: Osmanović D. , Kerr-Winter M. , Eccleston R. C. , Hoogenboom B. W. , Ford I. J.
Published: January 2015

The statistical theory of polymers tethered around the inner surface of a cylindrical channel has traditionally employed the assumption that the equilibrium density of the polymers is independent of the azimuthal coordinate. However, simulations have shown that this rotational symmetry can be broken when there are attractive interactions between the polymers. We investigate the phases that emerge in these circumstances, and we quantify the effect of the symmetry assumption on the phase behavior of the system. In the absence of this assumption, one can observe large differences in the equilibrium densities between the rotationally symmetric case and the non-rotationally symmetric case. A simple analytical model is developed that illustrates the driving thermodynamic forces responsible for this symmetry breaking. Our results have implications for the current understanding of the behavior of polymers in cylindrical nanopores.
On the accuracy of coherent modified Redfield theory in simulating excitation energy transfer dynamics
Authors: Chang Yu , Cheng Yuan-Chung
Published: January 2015

In this study, we investigate the accuracy of a recently developed coherent modified Redfield theory (CMRT) in simulating excitation energy transfer (EET) dynamics. The CMRT is a secular non-Markovian quantum master equation that is derived by extending the modified Redfield theory to treat coherence dynamics in molecular excitonic systems. Herein, we systematically survey the applicability of the CMRT in a large EET parameter space through the comparisons of the CMRT EET dynamics in a dimer system with the numerically exact results. The results confirm that the CMRT exhibits a broad applicable range and allow us to locate the specific parameter regimes where CMRT fails to provide adequate results. Moreover, we propose an accuracy criterion based on the magnitude of second-order perturbation to characterize the applicability of CMRT and show that the criterion summarizes all the benchmark results and the physics described by CMRT. Finally, we employ the accuracy criterion to quantitatively compare the performance of CMRT to that of a small polaron quantum master equation approach. The comparison demonstrates the complementary nature of these two methods, and as a result, the combination of the two methods provides accurate simulations of EET dynamics for the full parameter space investigated in this study. Our results not only delicately evaluate the applicability of the CMRT but also reveal new physical insights for factors controlling the dynamics of EET that should be useful for developing more accurate and efficient methods for simulations of EET dynamics in molecular aggregate systems.
Theory of melt polyelectrolyte blends and block copolymers: Phase behavior, surface tension, and microphase periodicity
Authors: Sing Charles E. , Zwanikken Jos W. , de la Cruz Monica Olvera
Published: January 2015

Polymer mixtures such as blends or block copolymers are of great interest in energy applications and functional materials, and often, one or more of these species contain charges. The traditional fashion in which such materials are studied uses Self-Consistent Field Theory (SCFT) methods that incorporate electrostatics using Poisson-Boltzmann (PB) theory. We adapt a new and rigorous approach that does not rely on the mean-field assumptions inherent in the PB theory and instead uses Liquid State (LS) integral equation theory to articulate charge correlations that are completely neglected in PB. We use this theory to calculate phase diagrams for both blends and block copolyelectrolytes using SCFT-LS and demonstrate how their phase behavior is highly dependent on chain length, charge fraction, charge size, and the strength of Coulombic interactions. Beyond providing phase behavior of blends and block copolyelectrolytes, we can use this theory to investigate the interfacial properties such as surface tension and block copolyelectrolyte lamellar spacing. Lamellar spacing provides a way to directly compare the SCFT-LS theory to the results of experiments. SCFT-LS will provide conceptual and mathematical clarification of the role of charge correlations in these systems and aid in the design of materials based on charge polymers.
Nanoliter-sized overheated reactor
Authors: Neužil P. , Sun W. , Karásek T. , Manz A.
Published: January 2015

We report on a microfluidic system formed by 200 nl water droplets, encapsulated by a 600 nl mineral oil placed on a hydrophobically coated glass microscope cover slip. The micromachined heater underneath the glass was able to heat up the sample at a heating rate of 650 °C/s, heating the water sample up to 200 °C in less than 2 s. The sample/glass and the sample/oil interface did not have nucleation centers, showing that the sample reached a superheated stage without the necessity of being pressurized to suppress boiling. This method can be utilized for various applications currently being conducted in autoclaves.
Development of high frequency and wide bandwidth Johnson noise thermometry
Authors: Crossno Jesse , Liu Xiaomeng , Ohki Thomas A. , Kim Philip , Fong Kin Chung
Published: January 2015

We develop a high frequency, wide bandwidth radiometer operating at room temperature, which augments the traditional technique of Johnson noise thermometry for nanoscale thermal transport studies. Employing low noise amplifiers and an analog multiplier operating at 2 GHz, auto- and cross-correlated Johnson noise measurements are performed in the temperature range of 3 to 300 K, achieving a sensitivity of 5.5 mK (110 ppm) in 1 s of integration time. This setup allows us to measure the thermal conductance of a boron nitride encapsulated monolayer graphene device over a wide temperature range. Our data show a high power law (T ∼ 4) deviation from the Wiedemann-Franz law above T ∼ 100 K.
Theoretical limits on the stability of single-phase kesterite-Cu2ZnSnS4
Authors: Sarker Pranab , Al-Jassim Mowafak M. , Huda Muhammad N.
Published: January 2015

The single-phase stability of Cu2ZnSnS4 (CZTS), after an intrinsic defect was incorporated in it, has been examined here for the first time based on ab initio calculations. The stability analysis of such a non-stoichiometric-defect incorporated CZTS shows that the single-phase formation is unlikely at thermodynamic equilibrium conditions. In addition, the effective growth condition of CZTS is determined and quantified for all the elements (Cu-poor, Zn-rich, Sn-poor, and S-rich) to extract maximum photovoltaic efficiency from CZTS. These conditions promote (i) spontaneous formation of Cu vacancy (VCu), which might benefit p-type conduction, and (ii) the co-existence of ZnS while suppressing other harmful defects and secondary phases. Further, the results presented here explain the unavailability of single-phase CZTS to date.
Electric radiation mapping of silver/zinc oxide nanoantennas by using electron holography
Authors: Sanchez J. E. , Mendoza-Santoyo F. , Cantu-Valle J. , Velazquez-Salazar J. , José Yacaman M. , González F. J. , Diaz de Leon R. , Ponce A.
Published: January 2015

In this work, we report the fabrication of self-assembled zinc oxide nanorods grown on pentagonal faces of silver nanowires by using microwaves irradiation. The nanostructures resemble a hierarchal nanoantenna and were used to study the far and near field electrical metal-semiconductor behavior from the electrical radiation pattern resulting from the phase map reconstruction obtained using off-axis electron holography. As a comparison, we use electric numerical approximations methods for a finite number of ZnO nanorods on the Ag nanowires and show that the electric radiation intensities maps match closely the experimental results obtained with electron holography. The time evolution of the radiation pattern as generated from the nanostructure was recorded under in-situ radio frequency signal stimulation, in which the generated electrical source amplitude and frequency were varied from 0 to 5 V and from 1 to 10 MHz, respectively. The phase maps obtained from electron holography show the change in the distribution of the electric radiation pattern for individual nanoantennas. The mapping of this electrical behavior is of the utmost importance to gain a complete understanding for the metal-semiconductor (Ag/ZnO) heterojunction that will help to show the mechanism through which these receiving/transmitting structures behave at nanoscale level.
Blockage of domain growth by nanoscale heterogeneities in a relaxor ferroelectric Sr0.61Ba0.39Nb2O6
Authors: Pertsev N. A. , Gainutdinov R. V. , Bodnarchuk Ya. V. , Volk T. R.
Published: January 2015

The growth of localized subsurface domains in a relaxor ferroelectric Sr0.61Ba0.39Nb2O6 is studied using the technique of piezoresponse force microscopy (PFM). Ferroelectric domains are created by applying moderate voltages of 10–50 V to the conductive tip of a scanning force microscope brought into contact with a nonpolar face of a Sr0.61Ba0.39Nb2O6 crystal. PFM images of written domains are acquired and analyzed quantitatively to determine the domain length along the polar axis and its width in the transverse direction. The dependences of domain sizes on the applied voltage, pulse duration, and the time passed after completion of the voltage pulse are reported and analyzed theoretically. It is shown that the observed kinetics of domain growth can be explained by the creep of domain boundaries occurring in the presence of random electric fields inherent in Sr0.61Ba0.39Nb2O6. The comparison of measured domain sizes with their equilibrium values calculated with the aid of the thermodynamic theory demonstrates that the growth of subsurface domains in Sr0.61Ba0.39Nb2O6 is blocked by nanoscale heterogeneities characteristic of this relaxor ferroelectric. These results may have important implications for the development of nonlinear optical devices based on nanoheterogeneous ferroelectrics.
Evidence of ion intercalation mediated band structure modification and opto-ionic coupling in lithium niobite
Authors: Shank Joshua C. , Tellekamp M. Brooks , Doolittle W. Alan
Published: January 2015

The theoretically suggested band structure of the novel p-type semiconductor lithium niobite (LiNbO2), the direct coupling of photons to ion motion, and optically induced band structure modifications are investigated by temperature dependent photoluminescence. LiNbO2 has previously been used as a memristor material but is shown here to be useful as a sensor owing to the electrical, optical, and chemical ease of lithium removal and insertion. Despite the high concentration of vacancies present in lithium niobite due to the intentional removal of lithium atoms, strong photoluminescence spectra are observed even at room temperature that experimentally confirm the suggested band structure implying transitions from a flat conduction band to a degenerate valence band. Removal of small amounts of lithium significantly modifies the photoluminescence spectra including additional larger than stoichiometric-band gap features. Sufficient removal of lithium results in the elimination of the photoluminescence response supporting the predicted transition from a direct to indirect band gap semiconductor. In addition, non-thermal coupling between the incident laser and lithium ions is observed and results in modulation of the electrical impedance.
Impact of isotopic disorders on thermal transport properties of nanotubes and nanowires
Authors: Sun Tao , Kang Wei , Wang Jianxiang
Published: January 2015

We present a one-dimensional lattice model to describe thermal transport in isotopically doped nanotubes and nanowires. The thermal conductivities thus predicted, as a function of isotopic concentration, agree well with recent experiments and other simulations. Our results display that for any given concentration of isotopic atoms in a lattice without sharp atomic interfaces, the maximum thermal conductivity is attained when isotopic atoms are placed regularly with an equal space, whereas the minimum is achieved when they are randomly inserted with a uniform distribution. Non-uniformity of disorder can further tune the thermal conductivity between the two values. Moreover, the dependence of the thermal conductivity on the nanoscale feature size becomes weak at low temperature when disorder exists. In addition, when self-consistent thermal reservoirs are included to describe diffusive nanomaterials, the thermal conductivities predicted by our model are in line with the results of macroscopic theories with an interfacial effect. Our results suggest that the disorder provides an additional freedom to tune the thermal properties of nanomaterials in many technological applications including nanoelectronics, solid-state lighting, energy conservation, and conversion.
Distinct photoresponse in graphene induced by laser irradiation
Authors: Wang Wen Hui , Nan Hai Yan , Liu Qi , Liang Zheng , Yu Zhi Hao , Liu Feng Yuan , Hu Wei Da , Zhang Wei , Wang Xin Ran , Ni Zhen Hua
Published: January 2015

The graphene-based photodetector with tunable p-p+-p junctions was fabricated through a simple laser irradiation process. Distinct photoresponse was observed at the graphene (G)-laser irradiated graphene (LIG) junction by scanning photocurrent measurements, and its magnitude can be modulated as a result of a positive correlation between the photocurrent and doping concentration in LIG region. Detailed investigation suggests that the photo-thermoelectric effect, instead of the photovoltaic effect, dominates the photocurrent generation at the G-LIG junctions. Such a simple and low-cost technique offers an alternative way for the fabrication of graphene-based optoelectronic devices.
Electron transport behaviors through donor-induced quantum dot array in heavily n-doped junctionless nanowire transistors
Authors: Ma Liuhong , Han Weihua , Wang Hao , Hong Wenting , Lyu Qifeng , Yang Xiang , Yang Fuhua
Published: January 2015

We investigated single electron tunneling through a phosphorus donor-induced quantum dot array in heavily n-doped junctionless nanowire transistor. Seven subpeaks splitting in current oscillations are clearly observed due to the coupling of quantum dot array under the bias voltage below 1.0 mV at the temperature of 6 K. The conduction system can be well described by a two-band Hubbard model. The activation energy of phosphorus donors is tuned by the gate voltage to be 7.0 meV for the lower Hubbard band and 4.4 meV for the upper Hubbard band due to the localization effects below threshold voltage. The evolution of electron behaviors in the quantum dots is identified by adjusting the gate voltage from quantum-dot regime to one-dimensional regime.
Critical analysis of lattice thermal conductivity of half-Heusler alloys using variations of Callaway model
Authors: Petersen Alex , Bhattacharya S. , Tritt T. M. , Poon S. J.
Published: January 2015

Half-Heusler alloys have been the focus of recent experimental research as emerging thermoelectric materials. Particular attention has been focused on the MNiSn (M = Ti, Zr, and Hf) alloys with substitutions made to reduce the lattice thermal conductivity and enhance the electrical transport properties. The effect of these substitutions on the relaxation time of phonon scattering in the material, and the impact on the lattice thermal conductivity, was investigated with a focus on modeling the experimental data. A modified Callaway model was used to describe experimental data, which were then compared to theoretical results predicted using phonon scattering by mass fluctuation and strain field models. The correlation between the coefficients obtained with experimental fits and theoretical models shows a predictable and systematic relationship between alloy composition and the thermal conductivity. In addition, the role of the normal (N) phonon-phonon scattering process is investigated following a recent theoretical study that indicated that the effect of N-process was underestimated in original Callaway's model. A comparison of the lattice thermal conductivity behavior using the phonon relaxation times in the original Callaway's model and the newly suggested theoretical model by Allen for the normal process is presented and discussed.
Determination of subcell I-V parameters by a pulsed suns-Voc method including optical coupling
Authors: Nesswetter H. , Jost N. R. , Lugli P. , Bett A. W. , Zimmermann C. G.
Published: January 2015

The open circuit voltage of a single subcell in a multijunction cell stack can be measured with the help of pulsed, millisecond illumination. This concept makes use of the fact that the charging of the non-illuminated cell capacitances takes place on a much longer timescale than of the illuminated one. Optical coupling introduces a photocurrent in the subcell underneath. Its efficiency can be quantified in parallel under short circuit conditions. A suns-Voc approach, applied to this subcell pair, yields all relevant diode parameters. Applied to all subcells of a Ga0.50In0.50P/Ga0.99In0.01As/Ge triple junction cell, a very good match to the dark I-V curve is obtained.
Deformation mechanisms of Cu nanowires with planar defects
Authors: Tian Xia , Yang Haixia , Cui Junzhi , Yu Xingang , Wan Rui
Published: January 2015

Molecular dynamics simulations are used to investigate the mechanical behavior of Cu nanowires (NWs) with planar defects such as grain boundaries (GBs), twin boundaries (TBs), stacking faults (SFs), etc. To investigate how the planar defects affect the deformation and fracture mechanisms of naowires, three types of nanowires are considered in this paper: (1) polycrystalline Cu nanowire; (2) single-crystalline Cu nanowire with twin boundaries; and (3) single-crystalline Cu nanowire with stacking faults. Because of the large fraction of atoms at grain boundaries, the energy of grain boundaries is higher than that of the grains. Thus, grain boundaries are proved to be the preferred sites for dislocations to nucleate. Moreover, necking and fracture prefer to occur at the grain boundary interface owing to the weakness of grain boundaries. For Cu nanowires in the presence of twin boundaries, it is found that twin boundaries can strength nanowires due to the restriction of the movement of dislocations. The pile up of dislocations on twin boundaries makes them rough, inducing high energy in twin boundaries. Hence, twin boundaries can emit dislocations, and necking initiates at twin boundaries. In the case of Cu nanowires with stacking faults, all pre-existing stacking faults in the nanowires are observed to disappear during deformation, giving rise to a fracture process resembling the samples without stacking fault.
Domain structures and magnetization reversal in Co/Pd and CoFeB/Pd multilayers
Authors: Sbiaa R. , Ranjbar M. , Åkerman J.
Published: January 2015

Domain structures and magnetization reversal of (Co/Pd) and (CoFeB/Pd) multilayers with 7 and 14 repeats were investigated. The Co-based multilayers show much larger coercivities, a better squareness, and a sharper magnetization switching than CoFeB-based multilayers. From magnetic force microscopy observations, both structures show strong reduction in domains size as the number of repeats increases but the magnetic domains for Co-based multilayers are more than one order of magnitude larger than for CoFeB-based multilayers. By imaging domains at different times, breaks in the (CoFeB/Pd) multilayer stripes were observed within only few hours, while no change could be seen for (Co/Pd) multilayers. Although CoFeB single layers are suitable for magnetoresistive devices due to their large spin polarization and low damping constants, their lamination with Pd suffers mainly from thermal instability.
Demonstration of a GaAs-based 1550-nm continuous wave photomixer
Authors: Zhang W.-D. , Middendorf J. R. , Brown E. R.
Published: January 2015

An Er:GaAs-based 1550-nm CW photomixer is demonstrated. The related mechanism is extrinsic photoconductivity with optical absorption between the localized deep levels created by the Er and the extended states above the conduction band edge of GaAs. With the power boost made possible by a fiber-coupled erbium-doped-fiber amplifier, the Er:GaAs photomixers, operating at 1550 nm, radiate THz power levels easily measured by a Golay cell, and display a power spectrum having a −3 dB roll-off frequency of 307 GHz. This corresponds to a photocarrier lifetime of 520 fs, in good agreement with a previous measurement of the bandwidth of the same material in a photoconductive switch.
Dislocations limited electronic transport in hydride vapour phase epitaxy grown GaN templates: A word of caution for the epitaxial growers
Authors: Chatterjee Abhishek , Khamari Shailesh K. , Kumar R. , Dixit V. K. , Oak S. M. , Sharma T. K.
Published: January 2015

GaN templates grown by hydride vapour phase epitaxy (HVPE) and metal organic vapour phase epitaxy (MOVPE) techniques are compared through electronic transport measurements. Carrier concentration measured by Hall technique is about two orders larger than the values estimated by capacitance voltage method for HVPE templates. It is learnt that there exists a critical thickness of HVPE templates below which the transport properties of epitaxial layers grown on top of them are going to be severely limited by the density of charged dislocations lying at layer-substrate interface. On the contrary MOVPE grown templates are found to be free from such limitations.
Micromagnetic simulation of exchange coupled ferri-/ferromagnetic composite in bit patterned media
Authors: Oezelt Harald , Kovacs Alexander , Wohlhüter Phillip , Kirk Eugenie , Nissen Dennis , Matthes Patrick , Heyderman Laura Jane , Albrecht Manfred , Schrefl Thomas
Published: January 2015

Ferri-/ferromagnetic exchange coupled composites are promising candidates for bit patterned media because of the ability to control the magnetic properties of the ferrimagnet by its composition. A micromagnetic model for the bilayer system is presented where we also incorporate the microstructural features of both layers. Micromagnetic finite element simulations are performed to investigate the magnetization reversal behaviour of such media. By adding the exchange coupled ferrimagnet to the ferromagnet, the switching field could be reduced by up to 40% and also the switching field distribution is narrowed. To reach these significant improvements, an interface exchange coupling strength of 2 mJ/m2 is required.