bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rehearing Machaut's Motets
Authors: Hartt Jared C. 
Published: May 2011

The extant fourteenth-century contrapunctus manuals are concerned almost exclusively with counterpoint in two parts, but one treatise, “Quicumque voluerit duos contrapuncti,” sheds light on three-voice composition and lays the groundwork for a refined classification of sonority types in Guillaume de Machaut's nineteen three-voice motets. Building initially upon Sarah Fuller's work, the proposed schema introduces a more nuanced approach to categorizing the intervallic content of consonant and dissonant sonorities. Moreover, by calling attention to the outer voices of certain sonority types, the classification highlights salient structural and aural differences. A systematic study of sonority usage in Machaut's motets also reveals his preference for particular combinations of intervals over others.An examination of passages from several motets illustrates the classification's potential. A discussion of Motet 7's opening describes the relationship between the underlying contrapunctus and various sonority types, consonant and dissonant, and advances a broader definition for the directed progression. An anomalous progression in Motet 18 suggests that the careful study of sonority may contribute to our current understanding of motet chronology. An analysis of several passages from Motet 4 illustrates how the proposed nomenclature may offer a more nuanced understanding of musical syntax, particularly at phrase endings.
High catalytic efficiency and resistance to denaturing in bacterial Rho GTPase-activating proteins
Authors: Litvak Yael , Levin-Klein Rena , Avner Moti , Selinger Zvi 
Published: May 2011

AbstractSeveral major bacterial pathogens use the type III secretion system (TTSS) to deliver virulence factors into host cells. Bacterial Rho GTPase activating proteins (RhoGAPs) comprise a remarkable family of type III secreted toxins that modulate cytoskeletal dynamics and manipulate cellular signaling pathways. We show that the RhoGAP activity ofSalmonellaSptP andPseudomonasExoS toxins is resistant to variations in the concentration of NaCl or MgCl2, unlike the known salt dependant nature of the activity of some eukaryotic GAPs such as p190, RanGAP and p120GAP. Furthermore, SptP-GAP and ExoS-GAP display full activity after treatment at 80°C or with 6 murea, which suggests that these protein domains are capable of spontaneous folding into an active state following denaturing such as what might occur upon transit through the TTSS needle. We determined the catalytic activity of bacterial GAPs for Rac1, CDC42 and RhoA GTPases and found that ExoS, in addition toYersiniaYopE andAeromonasAexT toxins, display higher catalytic efficiencies for Rac1 and CDC42 than the known eukaryotic GAPs, making them the most catalytically efficient RhoGAPs known. This study expands our knowledge of the mechanism of action of GAPs and of the ways bacteria mimic host activities and promote catalysis of eukaryotic signaling proteins.
Symmetry mode analysis of the phase transitions in Rb2ZnBr4
Authors: Zúñiga Fco. Javier , Perez-Mato Juan Manuel , Orobengoa Danel , Petricek Václav , Breczewski Tomasz 
Published: May 2011

Abstract
Crystal structures of low temperature phases III, IV and V of Rubidium Zinc Bromide have been determined by single crystal X-ray diffraction at 90 K, 85 K, and 30 K, respectively. The analysis of the structures in terms of symmetry-adapted modes of the high temperature prototype phase permits the identification of the modes responsible for each phase and to assess its thermal evolution. The primary mode responsible for the incommensurate and lock-in phases remains dominant throughout the whole transition sequence, maintaining its structure and slightly increasing its amplitude as temperature decreases. The two monoclinic phases IV and V are presumably due to the instability of a second mode associated with a single active irreducible representation. However, the presence with similar weights of several symmetry-adapted distortions of different symmetry indicates a strong hybridization in phase III of the softer normal modes. A symmetry-mode description of the structures of phase IV and V fully consistent with a simple Landau model, can then only be obtained if phase III is taken as effective parent phase. Besides the insight on the microscopic origin of the different phases, the symmetry modes were used as crystallographic coordinates in the refinement of the structure of phase V. The result shows the advantages of using these non-conventional collective structural parameters instead of individual atomic coordinates. The refinable parameters can be reduced to the amplitudes of those symmetry modes with significant weight in the distortions.
Structural ordering principles in quasi one-dimensional Wigner crystals of the series Na1+x
CuO2 (0 ≤ x ≤ 1)
Authors: Nuss Jürgen , Wedig Ulrich , Jansen Martin 
Published: May 2011

Abstract
The general building principle of the commensurate subset of mixed valent sodium cuprates Na1+x
CuO2 (0 ≤ x ≤ 1) has been revealed. Starting from parent ­NaCuO2, spin doping of the chain of edge sharing CuO4 plaquettes requires to incorporate further sodium ions for charge compensation. The accessible space needed for this purpose is generated by elongating the NaO6 octahedra present in NaCuO2. In this way, from one octahedron two square pyramidal and two tetrahedral sites result, out of which at best one each tetrahedral and square pyramidal site per original octahedron can be occupied, excluding combinations of electrostatically blocked sites. This general building principle has been employed to predict further structure candidates of this series (x = 1/4, 1/3, 2/3, 5/7, 3/4, 1). Density functional calculations (x = 0, 5/7, 3/4, 1) confirm the predicted charge ordering as well as the related structural features. The structure candidates are identified as local minima on the energy landscape.
Large Amplitude Motions in Cyclopentene and 1-Butene: Quantum Chemical Insights into the Ground- and Excited State Potential Energy Surfaces
Authors: Knippenberg Stefan , Kunitski Maksim , Dreuw Andreas 
Published: May 2011

Abstract
The ring-puckering motion in cyclopentene as well as the hindered internal rotation around the central C–C bond in 1-butene have been studied by high-level quantum chemical calculations. Relevant potential energy surfaces of these molecules along these large-amplitude motions are provided as well as rotational constants are given allowing for thorough comparison with recent results from time-resolved femtosecond degenerate four-wave mixing (fs DFWM) spectroscopy. Emphasis is put on the performance of various post-Hartree Fock methods, the required level of electron correlation as well as the basis set quality.
Nonequilibrium NMR Methods for Monitoring Protein and RNA Folding
Authors: Schlepckow Kai , Fürtig Boris , Schwalbe Harald 
Published: May 2011

AbstractThe review introduces to time-resolved NMR spectroscopic investigations of the kinetics of protein and RNA folding. The description of the experimental investigations is discussed in the context of possible kinetic folding pathways showing the extent of information that can be gained from the various kinetic experiments. The review introduces to four different methods to initiate folding reactions in connection with time-resolved NMR experiments and discusses examples of refolding of the model proteinα-lactalbumin and of bistable RNAs.
Young Maternal Age and Poor Child Development: Predictive Validity From a Birth Cohort
Authors: Chittleborough Catherine R. , Lawlor Debbie A. , Lynch John W. 
Published: May 2011

OBJECTIVE:We aimed to examine the ability of mother's age, and other factors measured during pregnancy (education, financial difficulties, partner status, smoking, and depression), to predict child development outcomes up to age 5 years.METHODS:Data were obtained from the Avon Longitudinal Study of Parents and Children (ALSPAC). Poor child development was defined as scoring in the worst 10% of a parent-reported ALSPAC developmental scale (ADS) at 18 months (n = 7546), the Strengths and Difficulties Questionnaire (SDQ) at 47 months (n = 8328), or teacher-reported School Entry Assessment (SEA) scores at 4 to 5 years (n = 7345).RESULTS:Only a small proportion of children with poor development had mothers aged younger than 20 years at their birth (3.3%, 6.4%, and 9.2%, for the ADS, SDQ, and SEA, respectively). A greater proportion with each measure of poor development would be identified (48.9%, 63.6%, and 74.4%, respectively) if all 6 predictors were used and a woman had at least 1 of these. Model discrimination was poor using maternal age only (area under the receiver operator characteristic curve ∼0.5 for all 3 outcomes). This improved when all 6 predictors were included in the model (ADS: 0.56; SDQ: 0.66; SEA: 0.67). Calibration also improved with the model including all 6 predictors.CONCLUSIONS:Even if programs targeted at teen-aged mothers are successful in improving child development, they will have little impact on population levels of poor child development if young maternal age is the sole or main means of identifying eligibility for the program.
Synthesis of Ultra-Small Si Nano Particle Colloids and Thin Films-High Temperature Single Electronics
Authors: Therrien J. M. , Belomoin G. , Nayfeh M. H. 
Published: May 2011

ABSTRACTWe describe a procedure for dispersing electrochemical etched silicon into a colloid of ultra-small (∼1 nm) silicon nano particles. The particles are then reconstituted on a Si substrate by gentle evaporation from a volatile colloid, forming thin films. When the colloid or the film is excited with UV radiation at 355 nm, strong blue emission band at 390 nm is observable with the naked eye in room light. Two-terminal I-V spectra of the deposited film, taken using a scanning tunneling microscope (STM), show a single regular conductance resonance at a spacing of 0.25-0.30 eV, consistent with single electron charging. However, under light irradiation, we observe a second regular resonance, for negative tip biasing less than -1 eV, that modulates the charging structure at ∼ 1.0 eV period, consistent with the particle's quantum energy level spacing. This paves the way for operation of high-temperature Si-based single electron devices.
Fabrication Methods for Au Nanocluster Devices
Authors: Snow A.W. , Ancona M.G. , Kruppa W. , Park D. , Boos J.B. , Jernigan G.G. 
Published: May 2011

ABSTRACTThe deposition chemistry of hexanethiol-stabilized gold nanoclusters self-assembled on Au and SiO2 surfaces by reaction with a series of α,ω-alkanedithiols is studied using X-ray photoelectron spectroscopy and electrical measurements. Testing of micron-scale devices shows that high conductivity is achieved only for a narrow range of dithiols and with a sharp efficiency threshold. Nanoscale devices exhibit similar behavior though with much evidence of “granularity” in the deposition.
Organometallic Synthesis and Spectroscopic Characterization of Manganese Doped CdSe Nanocrystals
Authors: Mikulec Frederic V. , Kuno Masaru , Bennati Marina , Hall Dennis A. , Griffin Robert G. , Bawendi Moungi G. 
Published: May 2011

ABSTRACTFor CdSe quantum dots (QDs) produced via high temperature pyrolysis in trioctylphosphine oxide (TOPO), a MnSe precursor such as Mn2(μ-SeMe)2(CO)8appears to be necessary to successfully incorporate low levels of Mn. A simple etching experiment and electron paramagnetic resonance (EPR) measurements reveal that most of the dopant atoms reside in the surface layers of the inorganic lattice. The dopant dramatically affects 113Cd solid state NMR spectra; the observed paramagnetic shift and decreased longitudinal relaxation time reproduce bulk material behavior. Paramagnetic atoms in QDs generate large effective magnetic fields, which implies that magneto-optical experiments can be performed simply by doping. Results from fluorescence line narrowing (FLN) studies on Mn doped CdSe QDs mirror previous findings on undoped QDs in an external magnetic field. Experimental fitting of photoluminescence excitation (PLE) spectra of doped QDs reveals that the effective absorption lineshape contains a new feature which is believed to be a previously unobserved – but theoretically predicted – optically dark fine structure state.
Transport Calculations in Molecular Devices from First Principles
Authors: Ventr M. Di , Langa D. , Pantelid S.T. 
Published: May 2011

ABSTRACTFor molecular electronics, Boltzmann's equation is no longer valid for simulating device characteristics. We resent the first fully ab initio simulation of a molecular device that has already been studied ex erimentally, namely a benzene-1,4-dithiolate molecule between gold electrodes. The theoretical I-V curve has the same overall sha e as the ex erimental curve —reflecting the electronic structure of the molecule in the resence of the electric field — but the absolute value of the current is very sensitive to contact chemistry and geometry. In articular the resence ol a single gold atom between the molecule and the electrode surface reduces the conductance by more than an order of magnitude. Re lacement of the single gold atom by an aluminum atom, whose p orbitals cou le more effectively to the molecule's T orbitals, increases the conductance by about an order of magnitude. We have also studied the olarization effects induced by a third terminal (gate) on the I-V characteristics of the above device. In articular, we have found that current gain due to the gate bias can be achieved at reasonable gate fields. Finally the effect of current-induced forces on the device will be discussed.
Electronic Structure of Organic/Metal Interfaces Studied by UPS and Kelvin Probe
Authors: Seki Kazuhiko , Oji Hiroshi , Ito Eisuke , Yoshimura Daisuke , Hayashi Naoki , Ouchi Yukio , Ishii Hisao 
Published: May 2011

ABSTRACTThe interfaces of organic materials with other solids play important roles in the function of various organic devices such as organic light-emitting diodes (OLEDs), spectral sensitization in photography, organic solar cells, and electrophotography. Also they should be important in future molecular devices, both in the central part of the device and at the connection with outside circuits. However, serious experimental examination of such interfaces has started only recently. In this talk we focus our attention on the organic/metal interfaces, and summarize our understanding about (1) the energy level alignment right at the interface, and (2) possible band bending within an organic layer, mainly using the techniques of UV photoemission spectroscopy (UPS) and Kelvin probe method. As for (1), the formation of electric dipole layer was observed in most organic/metal interfaces, and its origin is discussed. As for (2), recent examination of the existence/absence of band bending in ultrahigh vacuum will be reported. It is also pointed out that there can be much effects of (i) atmosphere at sample preparation and measurements, and (2) chemistry and interdiffusion at the interface.
Effects of Φ-Stacking on the Absorption and Emission of Light by Conjugated Polymers and Oligomers
Authors: Curtis M. David , Koren Amy , Kampf Jeff W. 
Published: May 2011

ABSTRACTWe have determined the crystal structures of regioregular HH-TT oligomers with a variety of side chains, including hydroxy-bearing side chains capable of H-bonding. The H-bonding orders the molecular packing into infinite 2-D sheets of Φ-stacks. In these H-bonded sheets, the Φ-stacks are insulated from each other by the aliphatic side chains and form one-dimensional “wires”. In contrast, the structures of similar oligomers that do not have H-bonded side-chains feature a structure in which neighboring Φ-stacks in are in contact (“shorted wires”). The effects of these differing molecular arrangements on the spectral properties and exciton splitting are discussed.
Effect of ITO Carrier Concentration on the Performance of Organic Light-Emitting Diodes
Authors: Zhu Furong , Zhang Keran , Huan C. H. A. , Wee A.T.S. , Guenther Ewald , Jin Chua Soo 
Published: May 2011

ABSTRACTThe indium tin oxide (ITO) anodes for organic light emitting diode (OLED) were made from an oxidised target with In2O3 and SnO2 in a weight proportion of 9:1 using the RF magnetron sputtering method. The comparable ITO anodes with different carrier concentrations were prepared by varying the hydrogen partial pressure during film deposition. The current-luminance-voltage characteristics of the devices indicated that a high carrier concentration in ITO plays a role in improving OLED performance. A maximum efficiency of 3.8 cd/A was achieved when an ITO anode with a higher carrier concentration of 9×1020 cm−3 was used in a fluorene based OLED. This efficiency is about 1.5 times higher than that of an identical device made with an ITO anode having a lower carrier concentration of 5×1020 cm−3. The increase in electroluminescent efficie ncy reflects an enhanced hole-injection in the device. We consider that enhanced hole injection is due to the reduced band bending in ITO when it has a high carrier concentration
Design and Synthesis of Highly Efficient Nonlinear Optical Chromophores
Authors: Wu Xiaoming , Jen Alex K.-Y. 
Published: May 2011

ABSTRACTTwo series of highly hyperpolarizable nonlinear optical (NLO) chromophores, containing perfluoroaryl dicyanovinyl and phenyl tetracyanobutadienyl acceptors, have been designed and synthesized. These chromophores show good thermal and chemical stability. The 3D conformational structures, confirmed by computational modeling, enhance polymer matrix compatibility and decrease optical loss of the polymer films. The guest-host polymers of the chromophores show large electro-optical activities.
Multi-Mode Emission from an ALQ Based Optical Microcavity
Authors: Feng Jimeng , Liu Xingyuan 
Published: May 2011

ABSTRACTOrganic light emitting device (OLED) with a microcavity structure has been fabricated. A kind of chirped distributed Bragg reflector (DBR) and a metal Al film was used as the two reflectors of the microcavity. A multimode light emission was achieved due to the structure of the microcavity. The emission peaks of the microcavity were located at 476nm, 520nm, 597nm and 626nm, respectively.
Excitons in Segmented Polymers for High Photo- and Electro-Luminesence Efficiency
Authors: Epstein Arthur J. , Sun Runguang , Wang Daike , Gustafson Terry L. , Kyllo Erica M. , Delucia Frank C. , Zheng Qianbing 
Published: May 2011

ABSTRACTThe photoluminesence (PL) quantum efficiency of poly(p-phenylene vinylene) (PPV) varies with preparation and processing. We report the achievement of nearly 100% PL quantum efficiency through design and synthesis of alternating rigid conjugated segments of dimethoxy -PV (three dimethoxy -phenyl and two vinyl units) and flexible nonconjugated segments along the polymer backbone. There is enhanced solubility in desired solvents and increased interchain separation through the incorporation of the methoxy sidegroups, forming poly [1,6-hexanedioxy -2,6-dimethoxy-1,4-phenylene]-1,2-ethenylene-[3,6-dimethoxy-1,4-phenylene]-1,2-ethenylene-[3,5-dimethoxy-1,4-phenylene], or GDBBC. The nearly temperature-independence of the PL decay at different emission wavelengths of the alternating block co-polymer (ABC) shows that the excitons are highly localized due to the blocking by non-conjugated segments as well as due to increased interchain separation due to the methoxy sidegroups. The contrasting temperature- and time- dependent results for the corresponding PV oligomer and PPV, supports the role of reduced exciton migration in achieving high quantum efficiency. The results are compared to the exciton confinement at the interface of light emitting electron and hole transporting polymers, forming an exciplex, for which the luminescence decay is also temperature independent. Electroluminescent devices using GDBBC as the lightemitting layer and incorporating poly[1-phenyl-2-(p-n-carbazolylphenyl) acetylene], (PDPA-Cz), as hole transporting layer, in the structure ITO/PDPACz/GDBBC/Alq/MgAg have ~1% external quantum efficiency with green emission from the GDBBC. EL devices based on exciplex emission are also discussed.
Magnetic Orientation of Polymers A Novel Technique of Controlling Birefringence
Authors: Kimura Tsunehisa , Ito Eiko 
Published: May 2011

ABSTRACTMagnetic -field induced orientation of crystalline polymers recently reported by our group is briefly summarized and a possible application of this new phenomenon is presented. We have recently reported a new finding that crystalline polymers including poly(ethylene-2,6-naphthalate), isotactic polystyrene, isotactic polypropylene, poly(ethylene terephthalate), and paraffin align under a strong magnetic field during the phase transition from melt to crystal. We have assumed that some ordered structure, most likely liquid-crystalline-like structure, appearing transiently during the transition is responsible for this phenomenon. Aligned films were transparent and exhibited retardation of several hundred nanometers, suggesting a possible application to fabrication of materials demanded for optical use.
Environmental Effects on the Electronic Spectra of Electrostatically Assembled Layers of Conjugated Polymers
Authors: Kim Myunghwan , Sandman Daniel J. 
Published: May 2011

ABSTRACTConjugated polyelectrolytes, poly[2-(3-thienyl)-ethanolhydroxycarbonylmethylurethane] (HPURET) and PDA from 5,7-dodecadiyn-1,12-bis-(hydroxycarbonylmethylurethane) (HP4BCMU), were processed by programmed electrostatic assembly, respectively, with two different polycations that have significantly different refractive indices – one is poly(diallydimethylammonium) chloride (PDADMAC), the other poly(4-vinyl pyridine) quaternized with dimethylsulfate (QPVP). The optical properties of these conjugated polymers have been studied with particular attention to local environmental effects and adaption (post-assembly-processing). The electronic absorption spectra of these assemblies were dependent on the details of the assembly process.
Langmuir-Blodgett Film of a Processable Polydiacetylene with Tricyanovinyldialkylaniline Chromophore
Authors: Lee D.-C. , Li L. , Samuelson L. A. , Sandman D. J. 
Published: May 2011

ABSTRACTA soluble and processable polydiacetylene (PDA) with functionalizable N,N-dialkylaniline and glutamate ester substituted alkylurethane side groups was synthesized. This PDA was further reacted with tetracyanoethylene to effect postpolymerization functionalization. This new strategy further functionalizes conjugated polymers and introduces a tricyanovinyl (TCV)-aniline chromophore. The resulting polymer was soluble in common organic solvents. Asymmetric multilayers of the tricyanovinylated PDA were fabricated using the Langmuir-Blodgett (LB) technique. Thickness, visible absorption, and second harmonic (SH) intensity were found to increase linearly as a function of the number of layers. Polarized UV-visible and IR studies revealed that the main chain preferentially orients vertical to the compression direction with out-of-plane orientation of the TCV-aniline group with respect to the glass substrate. The resonant enhanced second-order nonlinear optical (NLO) coefficient (d33) of the 20 LB layers was found to be 21 pm/V at 1.064 µm, while no SHG signal was observed for cast or spincoated films.