bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Chemical Evolution of a Nitrogenase Model, XXIY. Correlational Analysis of Effects of Organic Acids on in vitro MoFe-Protein Substrate Reduction Activities
Authors: Schrauzer Gerhard N. , Palmer John G. 
Published: February 2015

Abstract
Among 29 organic acids whose effects on the in vitro enzymatic substrate reducing activity on the MoFe-protein of nitrogenase have been investigated, 12 acids stimulate the in vitro C2H2-reducing activities in proportion to the H+-reducing activities. A second group com­ prised of eight acids significantly stimulates the H+-reducing activity but has only modest stimulatory effects on C2H2-and N2-reducing activities. A third group of nine acids causes only slight increases of MoFe-protein substrate reducing activities. The stimulatory effects of acids on MoFe-protein substrate reducing activity depend on their mode of interaction with molybdenum. Hydroxycarboxylic acids acting as bidentate ligands such as homocitric acid and its derivatives leave a sufficient number of molybdenum coordination sites available for interactions with the substrates, they have the highest stimulatory effects both on the C2H2-and N2-reducing activities, and their H+-reducing activities are not inhibited by CO. Acids acting as tridentate ligands, which include citric acid, have weaker stimulatory effects on the C2H2-and especially on the N2-reducing activities, and CO inhibits their H+-reducing activity. Whereas with the first group of acids the C2H2-reducing activities are linearly correlated with H+-reducing activities, the N2-reducing activities are directly correlated with H+-reducing activities in the presence of CO, and the association is exponential rather than linear. This exponential dependence is consistent with a stepwise mechanism of nitrogen reduction via diazene and hydrazine as the intermediates, the latter blocking one molybdenum coordina­tion site prior to its reduction to NH3. In the reduction of C2H2 to C2H4, no such blockage occurs as product C2H4 does not accumulate at the active site and is not reduced further.
Elektrostatische Aktivierung der SNAr-Reaktivität durch Sulfonyloniosubstituenten/Electrostatic Activation of SNAr-Reactivity by Sulfonylonio Substituents
Authors: Weiss Robert , Pühlhofer Frank 
Published: February 2015

Abstract
4-Fluorobenzenesulfonyl chloride (1) and pentafluorobenzenesulfonyl chloride (2) are transformed into the corresponding N-sulfonylpyridinium triflates 4a-d by treatment with one equivalent of the reagent pair L/TMSOTf (L = 4-dimethylaminopyridine (DMAP), 4-ferf-butylpyridine (TBUPY), 1-methylimidazole (NMI); TMSOTf = trimethylsilyl triflate). Due to the electrostatic effect of the sulfonylonio function, SNAr reactions on these systems can be performed under mild conditions. So the reaction of 2 with excess DMAP/TMSOTf leads by way of peronio substitution to hexakis[(4-dimethylamino)-l-pyridinio]benzene hexa-kis(trifluoromethansulfonate) (7) [22] at room temperature. Additionally, a new reaction path to 4-(1-pyridinio)-substituted benzenesulfonamides, a class of pharmaceutically interesting substances, is shown.
N-Ferrocenyl Amines Bearing Boryl and Silyl Substituents at the Nitrogen Atom, Studied by 57Fe NMR Spectroscopy
Authors: Wrackmeyer Bernd , Maisel Heidi E. , Herberhold Max 
Published: February 2015

Abstract
A series of ferrocene sandwich compounds such as N-ferrocenyl amine, Fc-NH2 (1), the Nsilylated derivatives Fc-NH -SiMe3 (2), Fc- NH -SiMe2H (3), (Fc-NH )2SiMe2 (4), the N-silyl- N-boryl derivatives Fc-N(SiMe3)(9-BBN) (5) (9-BBN = 9-borabicyclo[3.3.1]nonyl) and Fc- N(SiMe3)BEt2 (6), and the N-borylated derivatives Fc-NH -(9-BBN) (7) and Fc-NH -BEt2 (8) were studied by 57Fe NMR spectroscopy. The δ57Fe data reveal that CFcN(pp)π interactions lead to 57Fe nuclear magnetic deshielding (with respect to ferrocene) which is attenuated if competing BN(pp)π bonding becomes efficient (7, 8).
Redox behavior of Dicerium trioxide and the Possible Formation of Sesquioxide- C for Fuel cells
Authors: Yue Yang , Santhanam K.S.V. , Reed K. , Allston T. 
Published: February 2015

ABSTRACTCerium oxide is an important electrode material in fuel cells. It has been interconverted in the gaseous phase at high temperatures or in the presence of oxygen and more recently in the solid state by applying an electric field. In the dynamic change that occurs, the migration of oxygen vacancies have been initiated at a critical potential of 2.8 V. We wish to report here an electrochemical method where the conversion of cerium oxides is brought out in aqueous medium where hydrogen ion is assisting the process of conversion. Keeping dissolved oxygen level negligible, the conversion of Ce2O3 to CeO2 occurs at 0.72 V vs saturated calomel electrode (SCE) with hydrogen ion assisting the process and the reversible conversion at 0.15 V (SCE). The hydrogen ion assisted conversion is compared with the solid state conversion that operates on oxygen vacancy creation.
Influence of Ga Substitution on the Nature of Glasses in Zr69.5Al7.5-xGaxCu12Ni11 and Ce75Al25-xGax Metallic Glass Compositions
Authors: Mandal R.K. , Tiwari R.S. , Singh Devinder , Singh Dharmendra 
Published: February 2015

ABSTRACTIn this presentation, results of our recent investigations on the role of Ga on Al site in Zr69.5Al7.5-xGaxCu12Ni11 and Ce75Al25-xGax metallic glass compositions will be discussed. Ga like Al is normally expected to be in trivalent state. However, it may go in monovalent state depending on other alloying elements. The rapidly solidified melt spun ribbons of above two alloys gave rise to two important conclusions. The Zr69.5Al7.5-xGaxCu12Ni11 system displayed metallic glass formation in the range of x=0 to 7.5. In this process, we have come out with a new composition of glass without Al corresponding to x=7.5. In contrast to the above, for Ce-Al(Ga) system, we have observed phase separation in glass after dilute substitution of Ga. It seems that such a phase separation in this system cannot be understood in terms of summation of enthalpy of mixing of the various possible binaries in this system. The substitution of Ga in different valence states might have created chemical pressure leading to creation of two types of distinct major clusters. The phase separation may be due to this. This has also given rise to excursion of Ce 4f-states of the alloy. This and aforesaid ‘chemical pressure’ will be corroborated based on results of binary Ce-Al system under pressure by other investigators.
Thermoelectric properties control of Half-Heusler compounds by lattice defects and interfaces introduced based on the close relationship with Heusler compounds
Authors: Kimura Yoshisato , Chai Yaw-Wang , Oniki Toshinori , Itagaki Takahiko , Otani Shinya 
Published: February 2015

ABSTRACTHalf-Heusler MNiSn (M=Ti, Zr, Hf) compounds are well-known, excellent n-type thermoelectric materials. The n-type Seebeck coefficients of ZrNiSn are reduced because of the precipitation of the metallic Heusler ZrNi2Sn phase. An excellent n-type Seebeck coefficient can be converted to p-type based on the vacancy site occupation by the solute Co atoms in the half-Heusler TiNiSn phase as well as ZrNiSn. The Heusler phase precipitates, including their precursor nano-structure in the half-Heusler matrix and the vacancy site occupation of the half-Heusler phase, are regarded as lattice defects based on the crystallographically and thermodynamically close relationship between half-Heusler and Heusler phases.
Electrically Tunable Ultra-specific Zinc Oxide Biosensor
Authors: Munje Rujuta D. , Wangzhou Andi , Selvam Anjan Panneer , Muthukumar Sriram , Prasad Shalini 
Published: February 2015

ABSTRACTZinc oxide surface states can be utilized for ultra-specific detection of biomolecules. The major challenges in using ZnO for bio-sensing are attaining enhanced sensitivity and specificity. In this study, we explore the functionalization of zinc in ZnO through utilizing the thiol bond. The purpose of this study is to demonstrate that the ZnO based sensor is capable of achieving high specificity in presence of competitive surface binding through the thiol bond. The final goal is to design an ultra-specific biosensor to detect low occurring biomolecules. In this study, we have selected cortisol as a stress marker to demonstrate quantification and detection from synthetic sweat. In order to demonstrate ultra-specificity, we have used two competitive thiol based molecules binding to zinc, a linker Dithiobis succinimidyl propionate (DSP) and reducing agent of DSP, Dithiothreitol (DTT). Electrochemical impedance spectroscopy (EIS) is used to quantify the signal obtained through various ratiometric concentrations of DSP and DTT. To validate the EIS study results, inherent fluorescence studies are done by mapping changes in green emission spectrum of ZnO before and after linker functionalization. The optimal combination in terms of highest signal is identified to be of 25mM DTT and 50mM DSP. This is implemented in the experiments performed to calibrate the cortisol concentration in synthetic sweat. This study demonstrates the detection of cortisol antigen in synthetic sweat present within the physiological levels of 8 ng/mL to 140 ng/mL.
Using Cell-Free Expression to Create Light-Activated Proteins In Situ in Droplet Interface Bilayer Networks
Authors: Taylor Graham J. , Sarles Stephen A. 
Published: February 2015

ABSTRACTDroplet interface bilayers (DIBs) are physical lipid bilayers that mimic real membranes in living cells, and they are formed quickly using droplets of water and lipids in oil (Fig. 1A). DIBs allow biomolecular sensing and direct detection of transmembrane proteins or peptides and small molecules such as drugs, anesthetics, or even ions. Cell-free expression systems allow in vitro protein synthesis using actual natural machinery extracted from organisms (Fig. 1B). Previous attempts to combine DIBs with cell-free extracts (CFE) encountered bilayer destabilization due to components in the expression system. This study evaluates incorporation of Promega’s T7 S30 High Yield (HY) Expression system with DIBs to pave the way for future in situ expression of light-activated bacteriorhodopsin (BR) and other complex transmembrane proteins in DIBs. A secondary output includes establishing a method for real-time monitoring and modeling of CF expression reactions using minimal volume. The ability to quantify CF output in such small volumes reduces cost per reaction from $20 to around $0.40, and synthesized protein levels reach tens to hundreds of micrograms per milliliter in less than 1 hour at 37°C.
Development of Novel Magnetostrictive Fe-Co-B Thin Films as a High Frequency Sensor Platform
Authors: Sheng Zhizhi , Cheng Z.-Y. 
Published: February 2015

ABSTRACTFe-Co-B was identified as a potential candidate for the development of high-frequency sensors and high-frequency actuators. To fabricate high-frequency magnetostrictive resonators, Fe-Co-B magetostrictive thin films were prepared by combining electrochemical deposition and microfabrication processes. It is crucial to obtain thin films with proper microstructure and composition. Results showed that Fe-rich Fe-Co-B thin films exhibited better resonance behavior than those with Co-rich and equiatomic Fe and Co compositions. It is also found that the deposition condition plays an important role on the performance of the films. Fe55Co28B17 thin films were fabricated under the same current density for different times. The films exhibited nanocrystalline structure, circular nodules as surface morphology and good resonance behavior. Fe/Co ratio on surface and cross section slightly decreased with increasing the deposition time. The resonance frequency slightly increased and the Q value was found to decrease with increasing deposition time.
Determination of Diffusion Length of Carriers in Graphene Using Contactless Photoelectromagnetic Method of Investigations
Authors: Nowak Marian , Solecka Barbara , Jesionek Marcin 
Published: February 2015

ABSTRACTThe photoelectromagnetic (PEM) investigations are proposed for determination of diffusion length of carriers in graphene. The presented measurements are performed in Corbino configuration using noncontact technique. The circular PEM currents are detected in an outer coil by induction if illumination intensity is periodically varied. The theoretical dependence of PEM response on magnetic field induction, intensity and spatial distribution of illumination as well as on frequency of illumination chopping is presented. Experimental PEM data are presented for graphene films grown by CVD processing on a cooper foil and transferred onto a glass substrate. The presented method of investigations should be essential for development of graphene electronic and optoelectronic devices.
First-principles study of electronic transport properties of graphene nanoribbons with pentagon-heptagon (5-7) line defects
Authors: Nishida Yasutaka , Yoshida Takashi , Aiga Fumihiko , Yamazaki Yuichi , Miyazaki Hisao , Kajita Akihiro , Sakai Tadashi 
Published: February 2015

ABSTRACTIn this study, we investigated the influence of line defects consisting of pentagon-heptagon (5-7) pairs on the electronic transport properties of zigzag-edged and armchair-edged graphene nanoribbons (GNRs). Using the first-principles density functional theory, we study their electronic properties. To investigate their current-voltage (I-V) characteristics at low bias voltage (∼ 1 meV), we use the nonequilibrium Green’s function method. As a result, we found that the conductance of the GNRs having a connected line defect between source and drain shows better performance than that of the ideal zigzag-edged GNRs (ZGNRs). A detailed investigation of the transmission spectra and the wave function around the Fermi level reveals that the line defects arranged along the transport direction work similar to an edge state of the ZGNRs and can be an additional conduction channel. Our results suggest that such a line defect can be effective for low-resistance GNR interconnects.
A Facile Synthesis of Graphene Quantum Dots via Size-Selective Precipitation and Their Application in GQD-layer Modified DSSC
Authors: Ryu Jaehoon , Jang Jyongsik 
Published: February 2015

ABSTRACTA novel approach to synthesize highly luminescent graphene quantum dots (GQDs) with well-defined sizes was explored based on simple oxidation of herringbone-type carbon nanofibers (HCNFs) and size-selective precipitation. In addition, the upconversion properties of GQD were investigated by applying GQD in working electrode of dye-sensitized solar cells (DSSCs).
The Fabrication of High-Performance Flexible Mercury Aptasensor Based on Graphene
Authors: An Ji Hyun , Jang Jyongsik 
Published: February 2015

ABSTRACTLiquid-ion gated FET-type flexible graphene-based aptasensor was fabricated for Hg detection in real world samples. Single-layer graphene was grown and transferred onto a flexible substrate and integrated into the liquid-ion gated FET system via surface engineerging process. Field-induced responses to Hg2+ ions in real world samples were highly rapid, sensitive and selective, leading to the high-perfromance graphene aptasensor. The aptasensor also displayed excellent flexibility and mechanical durability.
nanoHUB.org: A Gateway to Undergraduate Simulation-Based Research in Materials Science and Related Fields
Authors: Faltens Tanya A. , Bermel Peter , Buckles Amanda , Douglas K. Anna , Strachan Alejandro , Zentner Lynn K. , Klimeck Gerhard 
Published: February 2015

ABSTRACTOur future engineers and scientists will likely be required to use advanced simulations to solve many of tomorrow's challenges in nanotechnology. To prepare students to meet this need, the Network for Computational Nanotechnology (NCN) provides simulation-focused research experiences for undergraduates at an early point in their educational path, to increase the likelihood that they will ultimately complete a doctoral program. The NCN summer research program currently serves over 20 undergraduate students per year who are recruited nationwide, and selected by NCN and the faculty for aptitude in their chosen field within STEM, as well as complementary skills such as coding and written communication. Under the guidance of graduate student and faculty mentors, undergraduates modify or build nanoHUB simulation tools for exploring interdisciplinary problems in materials science and engineering, and related fields. While the summer projects exist within an overarching research context, the specific tasks that NCN undergraduate students engage in range from modifying existing tools to building new tools for nanoHUB and using them to conduct original research. Simulation tool development takes place within nanoHUB, using nanoHUB’s workspace, computational clusters, and additional training and educational resources. One objective of the program is for the students to publish their simulation tools on nanoHUB. These tools can be accessed and executed freely from around the world using a standard web-browser, and students can remain engaged with their work beyond the summer and into their careers. In this work, we will describe the NCN model for undergraduate summer research. We believe that our model is one that can be adopted by other universities, and will discuss the potential for others to engage undergraduate students in simulation-based research using free nanoHUB resources.
Experimental and Theoretical Investigation of Minimization of Forming-Induced Variability in Resistive Memory Devices
Authors: Geist Brian L. , Strukov Dmitri , Kochergin Vladimir 
Published: February 2015

ABSTRACTResistive memory materials and devices (often called memristors) are an area of intense research, with metal/metal oxide/metal resistive elements a prominent example of such devices. Electroforming (the formation of a conductive filament in the metal oxide layer) represents one of the often necessary steps of resistive memory device fabrication that results in large and poorly controlled variability in device performance. In this contribution we present a numerical investigation of the electroforming process. In our model, drift and Ficks and Soret diffusion processes are responsible for movement of vacancies in the oxide material. Simulations predict filament formation and qualitatively agreed with a reduction of the forming voltage in structures with a top electrode. The forming and switching results of the study are compared with numerical simulations and show a possible pathway toward more repeatable and controllable resistive memory devices.
Effects of morphology of buffer layers on ZnO/sapphire heteroepitaxial growth by RF magnetron sputtering
Authors: Ide Tomoaki , Matsushima Koichi , Shimizu Ryota , Yamashita Daisuke , Seo Hynwoong , Koga Kazunori , Shiratani Masaharu , Itagaki Naho 
Published: February 2015

ABSTRACTEffects of surface morphology of buffer layers on ZnO/sapphire heteroepitaxial growth have been investigated by means of “nitrogen mediated crystallization (NMC) method”, where the crystal nucleation and growth are controlled by absorbed nitrogen atoms. We found a strong correlation between the height distribution profile of NMC-ZnO buffer layers and the crystal quality of ZnO films. On the buffer layer with a sharp peak in height distribution, a single-crystalline ZnO film with atomically-flat surface was grown. Our results indicate that homogeneous and high-density nucleation at the initial growth stages is critical in heteroepitaxy of ZnO on lattice mismatched substrates.
High Pressure Induced Binding Between Linear Carbon Chains and Nanotubes
Authors: Brunetto Gustavo , Andrade Nádia F. , Galvão Douglas S. , Souza Filho Antônio G. 
Published: February 2015

ABSTRACTRecent studies of single-walled carbon nanotubes (CNTs) in aqueous media have showed that water can significantly affect the tube mechanical properties. CNTs under hydrostatic compression can preserve their elastic properties up to large pressure values, while exhibiting exceptional resistance to mechanical loadings. It was experimentally observed that CNTs with encapsulated linear carbon chains (LCCs), when subjected to high hydrostatic pressure values, present irreversible red shifts in some of their vibrational frequencies. In order to address the cause of this phenomenon, we have carried out fully atomistic reactive (ReaxFF) molecular dynamics (MD) simulations for model structures mimicking the experimental conditions. We have considered the cases of finite and infinite (cyclic boundary conditions) CNTs filled with LCCs (LCC@CNTs) of different lengths (from 9 up to 40 atoms). Our results show that increasing the hydrostatic pressure causes the CNT to be deformed in an inhomogeneous way due to the LCC presence. The LCC/CNT interface regions exhibit convex curvatures, which results in more reactive sites, thus favoring the formation of covalent chemical bonds between the chain and the nanotube. This process is irreversible with the newly formed bonds continuing to exist even after releasing the external pressure and causing an irreversibly red shift in the chain vibrational modes from 1850 to 1500 cm−1.
Variación en grados de latencia en semillas entre colectas de chile piquín ( Capsicum annuum var. glabriusculum )
Authors: Cano-Vázquez Anaid , López-Peralta Ma. Cristina , Zavaleta-Mancera Hilda A. , Cruz-Huerta Nicacio , Ramírez-Ramírez Iván , Gardea-Béjar Alfonso , González-Hernández Víctor A. 
Published: February 2015

El chile piquín ( Capsicum annuum var. glabriusculum ) que se consume en México es, en su mayoría, recolectado de plantas silvestres. Esta actividad podría amenazar la diversidad genética de la especie. Idealmente, el chile piquín debería producirse intensivamente para proteger la población silvestre y satisfacer la demanda; sin embargo, la baja germinación de semillas de esta especie de chile ha sido tradicionalmente un problema para su establecimiento a nivel comercial. Las causas de lo anterior son desconocidas. Identificar las causas de la baja germinación y la diversidad entre colectas es, por tanto, de importancia. Se evaluaron 16 diferentes colectas de chile piquín provenientes de siete estados del país y del sur de Estados Unidos. Un estudio morfológico determinó que en las colectas evaluadas no existen diferencias ni barreras morfológicas que impidan la germinación apropiada de las semillas. Una cinética de imbibición determinó que no existen impedimentos físicos para el paso apropiado de agua al interior de las semillas; sin embargo, la germinación de las 16 colectas fue muy variable (0 a 66%), con un promedio de 15%. El pretratamiento de las semillas con la hormona AG3 (5,000 ppm), elevó la tasa promedio de germinación a 59% en 14 de las 16 colectas, mientras que los tratamientos de acondicionamiento con peróxido de hidrógeno y nitrato de potasio solamente mejoraron la germinación de semillas en dos y cuatro colectas, respectivamente. El presente trabajo corrobora que la limitante de germinación en semillas de chile piquín se debe a un fenómeno de latencia fisiológica, la cual puede romperse con aplicación exógena de AG3 a 5,000 ppm, cuyos efectos varían entre colectas.