bluuebunny/crossref_metadata_2025 huggingface dataset:
Accurate analytic potentials for Li2(X Σ1g+) and Li2(A Σ1u+) from 2 to 90 Å, and the radiative lifetime of Li(2p)
Authors: Le Roy Robert J. , Dattani Nikesh S. , Coxon John A. , Ross Amanda J. , Crozet Patrick , Linton Colan
Published: November 2009

Extensions of the recently introduced “Morse/long-range” (MLR) potential function form allow a straightforward treatment of a molecular state for which the inverse-power long-range potential changes character with internuclear separation. Use of this function in a direct-potential-fit analysis of a combination of new fluorescence data for L7,7i2, L6,6i2, and L6,7i2 with previously reported data for the A(Σ1u+) and X(Σ1g+) states yields accurate, fully analytic potentials for both states, together with the analytic “adiabatic” Born–Oppenheimer breakdown radial correction functions which are responsible for the difference between the interaction potentials and well depths for the different isotopologues. This analysis yields accurate well depths of De=8516.709(±0.004) and 8516.774(±0.004) cm−1 and scattering lengths of 18.11(±0.05) and 23.84(±0.05) Å for the ground-states of L7,7i2 and L6,6i2, respectively, as well as improved atomic radiative lifetimes of τ(2p)=27.1018(±0.0014) ns for L7i(2p) and 27.1024(±0.0014) ns for L6i(2p).
Comparative study of multireference perturbative theories for ground and excited states
Authors: Hoffmann Mark R. , Datta Dipayan , Das Sanghamitra , Mukherjee Debashis , Szabados Ágnes , Rolik Zoltán , Surján Péter R.
Published: November 2009

Three recently developed multireference perturbation theories (PTs)—generalized Van Vleck PT (GVVPT), state-specific multireference PT (SS-MRPT), and multiconfiguration PT (MCPT)–are briefly reviewed and compared numerically on representative examples, at the second order of approximations. We compute the dissociation potential curve of the LiH molecule and the BeH2 system at various geometries, both in the ground and in the first excited singlet state. Furthermore, the ethylene twisting process is studied. Both Møller–Plesset (MP) and Epstein–Nesbet partition are used for MCPT and SS-MRPT, while GVVPT uses MP partitioning. An important thrust in our comparative study is to ascertain the degree of interplay of dynamical and nondynamical correlation for both ground and excited states. The same basis set and the same set of orbitals are used in all calculations to keep artifactual differences away when comparing the results. Nonparallelity error is used as a measure of the performance of the respective theories. Significant differences among the three methods appear when an intruder state is present. Additionally, difficulties arise (a) in MCPT when the choice of a pivot determinant becomes problematic, and (b) in SS-MRPT when there are small coefficients of the model function and there is implicit division by these coefficients, which generates a potential instability of the solutions. Ways to alleviate these latter shortcomings are suggested.
Symmetries of the master equation and long-lived states of nuclear spins
Authors: Karabanov Alexander A. , Bretschneider Christian , Köckenberger Walter
Published: November 2009

In terms of the master equation of relaxation, long-lived states in systems of n interacting spin-1/2 nuclei are described as those with eigenvalues much less than the characteristic T1 rate. It is demonstrated that degeneracies of correlations between interacting dipole-dipole pairs are responsible for their presence. The case n=3 is considered in full detail.
Molecular dynamics characterization of void defects in crystalline (1,3,5-trinitro-1,3,5-triazacyclohexane)
Authors: Boyd Sylke , Murray Jane S. , Politzer Peter
Published: November 2009

In the context of a continuing investigation of factors that affect the sensitivities of energetic materials to detonation initiation, we have carried out a molecular dynamics characterization of void defects in crystalline (1,3,5-trinitro-1,3,5-triazacyclo-hexane). An empirical force field that is capable of handling flexible molecules in a pliable crystal was used. Voids ranging in size from 2 to 30 adjacent vacated sites were created in model lattices of 216 or 512 molecules. Energetic and geometric ground state properties were determined. The void formation energy per molecule removed was found to decrease from 50 kcal/mol for a single vacancy to about 23±2 kcal/mol for voids larger than one unit cell (8 molecules). Analysis of the local binding energies in the vicinity of a void reveals not only the expected decrease for molecules directly on the void surface but also a wide spread of values in the first 5–10 Å away from the surface; this includes some molecules with local binding energies significantly higher than in the defect-free lattice. Molecular conformational changes and reorientations begin to be found in the vicinities of voids larger than one unit cell. Thermal behavior investigated includes void and molecular diffusion coefficients and fluctuations in void size.
Suppression of ambipolar behavior in metallic source/drain metal-oxide-semiconductor field-effect transistors
Authors: Ghoneim H. , Knoch J. , Riel H. , Webb D. , Björk M. T. , Karg S. , Lörtscher E. , Schmid H. , Riess W.
Published: November 2009

We present a study on suppressing the ambipolar behavior of Schottky barrier metal-oxide-semiconductor field-effect transistors (MOSFET). Inserting a silicon nitride layer of appropriate thickness between the metallic source/drain electrodes and the silicon yields a low Schottky-barrier and simultaneously tunes the properties of the contact from metal-semiconductor-like to the behavior of a doped contact. Moreover, device characteristics of pseudo-MOSFETs reveal an efficient suppression of ambipolar behavior. Comparison with an alternative way of achieving low Schottky-barrier contacts, i.e., by inserting a strong dipole layer such as LiF between the metal and the silicon, reveals that the suppression is not a result of shifting the Fermi level closer to the conduction band but is caused by a reduction of metal-induced gap states. The trade-off between suppression of the ambipolar behavior, contact length and on-state current is investigated with simulations.
Semiclassical nonlinear response functions for coupled anharmonic vibrations
Authors: Gruenbaum Scott M. , Loring Roger F.
Published: November 2009

Observables in linear and nonlinear infrared spectroscopy may be computed from vibrational response functions describing nuclear dynamics on a single electronic surface. We demonstrate that the Herman–Kluk (HK) semiclassical approximation to the quantum propagator yields an accurate representation of quantum coherence effects in linear and nonlinear response functions for coupled anharmonic oscillators. A considerable numerical price is paid for this accuracy; the calculation requires a multidimensional integral over a highly oscillatory integrand that also grows without bound as a function of evolution times. The interference among classical trajectories in the HK approximation produces quantization of good action variables. By treating this interference analytically, we develop a mean-trajectory (MT) approximation that requires only the propagation of classical trajectories linked by transitions in action. The MT approximation accurately reproduces coherence effects in response functions of coupled anharmonic oscillators in a regime in which the observables are strongly influenced by these interactions among vibrations.
Thermoelectric properties and anisotropic electronic band structure on the In4Se3−x compounds
Authors: Rhyee Jong-Soo , Cho Eunseog , Lee Kyu Hyoung , Lee Sang Mock , Kim Sang Il , Kim Hyun-Sik , Kwon Yong Seung , Kim Sung Jin
Published: November 2009

We report the high thermoelectric figure-of-merit (ZT) on the Se-deficient polycrystalline compounds of In4Se3−x (0.02≤x≤0.5) and the anisotropic electronic band structure. The Se-deficiency (x) has the effect of decreasing the semiconducting band gap and increasing the power factor. The band structure calculation for In4Se3−x (x=0.25) exhibits localized hole bands at the Γ-point and Y-S symmetry line, whereas the significant electronic band dispersion is observed along the c-axis. Here, we propose that the high ZT values on those compounds are originated from the anisotropic electronic band structure as well as Peierls distortion.
Hybrid quantum/classical simulation of the vibrational relaxation of the bend fundamental in liquid water
Authors: Bastida Adolfo , Zúñiga José , Requena Alberto , Miguel Beatriz
Published: November 2009

The Ehrenfest method with quantum corrections is used to describe the vibrational relaxation of the bend fundamental in liquid water. All the vibrational degrees of freedom of the water molecules are described using quantum mechanics, while the remaining translational and rotational degrees of freedom are described classically. The relaxation time obtained compares well with experiment and with relaxation times calculated using other theoretical approximations. The presence of resonant intermolecular vibrational energy (VV) transfer is established with a maximum percentage of excited molecules, different from the initial one, of 9.2%. It is found through an effective kinetic fit that two VV transfers occur before relaxation of water to the vibrational ground state.
Magnetoelectroluminescence in tris (8-hydroxyquinolato) aluminum-based organic light-emitting diodes doped with fluorescent dyes
Authors: Chen P. , Lei Y. L. , Song Q. L. , Zhang Y. , Liu R. , Zhang Q. M. , Xiong Z. H.
Published: November 2009

The influences of fluorescent dye doping on the magnetoelectroluminescence in tris (8-hydroxyquinolato) aluminum (Alq3)-based organic light-emitting diodes have been investigated systematically by varying the dopant concentrations and its energy band gap. Our results show that the decrease in electroluminescence intensity at high magnetic field, which survives only at low temperatures for pure Alq3-based devices, persists in dye-doped devices even at room temperature. This is explained here as the result of magnetic field dependent triplet-triplet annihilation process, in which the triplet excitons trapped on the dye molecules play the most important role.
Ferromagnetic to weak-magnetic transition accompanied by bcc to fcc transformation in Fe–Mn–Al alloy
Authors: Ando K. , Omori T. , Ohnuma I. , Kainuma R. , Ishida K.
Published: November 2009

Magnetic properties and phase change in Fe-36 at. %Mn-15 at. %Al ternary alloy were investigated. Direct evidence of a ferromagnetic to weak-magnetic transition accompanied by martensitic transformation from the bcc-α (A2) phase to the fcc-γ′ (2M) phase was obtained, where the magnetic state of the parent and the martensite phases are ferromagnetic and weak-magnetic, respectively. The origin of this unique phase change is caused by the peculiar γ-loop of α∕γ equilibrium formed in Fe–Mn–X (X: ferrite stabilizing element) system due to the magnetic effect.
Highly efficient yellow organic light emitting diode based on a layer-cross faded emission layer allowing easy color tuning
Authors: Lindla Florian , Boesing Manuel , Zimmermann Christoph , Jessen Frank , van Gemmern Philipp , Bertram Dietrich , Keiper Dietmar , Meyer Nico , Heuken Michael , Kalisch Holger , Jansen Rolf H.
Published: November 2009

An easy way to adjust the color of yellow organic light emitting diodes (OLED) is realized by basing the emission layer on a cross-fading zone of two unipolar-conducting host materials doping parts of it either with a red or green phosphorescent emitter at varying thickness ratios. At color coordinates of 0.47/0.50, a current efficacy of 42.2 cd/A (16.2% external quantum efficiency) and a power efficacy of 32.9 lm/W (1000 cd/m2) are measured without light extraction enhancement. Mixed-host emission layer OLED without cross-fading are processed for comparison. Exciton distributions are studied. The concept is suggested to be useful for white OLED.
Enhancement of electrical property by oxygen doping to copper phthalocyanine in inverted top emitting organic light emitting diodes
Authors: Hong Kihyon , Kim Kisoo , Lee Jong-Lam
Published: November 2009

We reported the evidence of oxygen doping to copper-phthalocyanine (CuPc) by O2-plasma treatment to inverted top-emitting organic light-emitting diodes (ITOLEDs). In situ synchrotron-radiation photoelectron spectroscopy results showed that a new Cu–O bond appeared and the energy difference between the highest-occupied molecular orbital and EF is lowered by 0.15 eV after plasma treatment. The oxygen ions chemically interacted with Cu atoms and transferred charges to the CuPc. Thus the hole injection barrier was lowered, enhancing the electroluminescent property of ITOLEDs.
Grain size dependence of electrical and optical properties in Nb-doped anatase TiO2
Authors: Yang J. Y. , Li W. S. , Li H. , Sun Y. , Dou R. F. , Xiong C. M. , He L. , Nie J. C.
Published: November 2009

Anatase thin films of pure TiO2 and 6% niobium doped TiO2 (Nb:TiO2) were fabricated on LaAlO3(100) by pulsed laser deposition. The electrical properties of Nb:TiO2 films are grain-size dependent, i.e., the larger grain size, the higher conductivity, and mobility. For all TiO2 and for Nb:TiO2 with small mean grain size (d<15 nm), the band gap energy is found to increase systematically with the decrease in d, which is consistent with the quantum confinement model. For the films with large mean grain size (d>15 nm), particularly, a blueshift in Nb:TiO2 is governed by the Burstein–Moss effect.
UV/visible spectroscopy of matrix-isolated hexa-peri-hexabenzocoronene: Interacting electronic states and astrophysical context
Authors: Rouillé Gaël , Steglich Mathias , Huisken Friedrich , Henning Thomas , Müllen Klaus
Published: November 2009

Absorption spectra of hexa-peri-hexabenzocoronene isolated in rare-gas matrices are reported for the wavelength range between 200 and 500 nm. Measurements were carried out in neon and in argon at 5.8 and 12.0 K, respectively. Calculations based on semiempirical models and on density-functional theory were performed to assign the observed features. The electronically excited states involved in Clar’s α- and p-bands are identified as S1(B2u) and S2(B1u), respectively. Although the upper state associated with the β-band is found to be a E11u state, it remains undetermined whether it is S3 or S4. Structures in the β-band are interpreted as resulting from the interaction between the E11u state and the e2g vibrational manifold of S2(B1u). The new measurements are used to narrow down the wavelength ranges where the bands of hexa-peri-hexabenzocoronene should be found in the gas phase. A previous estimate of the interstellar abundance of this polycyclic aromatic hydrocarbon is discussed.
Quantification of biomolecule agglutination by magnetorelaxometry
Authors: Eberbeck D. , Wiekhorst F. , Steinhoff U. , Trahms L.
Published: November 2009

The agglutination of probes, i.e., biomolecules labeled by magnetic nanoparticles, due to their binding to complement analyte molecules (e.g., biomolecules) was quantified by magnetorelaxometry in terms of the mean and the width of the size distribution of the formed aggregates. We observed a clear maximum of the agglutination at a specific analyte-to-probe concentration ratio. By means of controlled variation of this ratio, the concentration of an analyte in solution can be measured in turbid media by two step preparation using magnetic measurement techniques without the need of a solid phase for immobilization of analyte or probe.
Electric field control of magnetoresistance in a lateral InAs quantum well spin valve
Authors: Kum Hyun , Basu Debashish , Bhattacharya Pallab , Guo Wei
Published: November 2009

The control of magnetoresistance of a lateral spin valve with bias applied to a gate placed outside the channel region is demonstrated. The spin valve channel consists of an InAs/In0.53Ga0.47As/In0.52Al0.48As two-dimensional electron gas lattice matched to (001) InP. The polarizer and analyzer contacts are made with 35 nm type B MnAs/In0.52Al0.48As Schottky tunnel barriers. The magnetoresistance changes from 0.14% to 4% at 10 K in a device in which the spin transport is in the direction of magnetization of the polarizer and analyzer contacts. The effect is absent in a GaAs channel spin valve and other control devices indicating that the change in magnetoresistance is due to Rashba spin-orbit coupling.
Analog memory capacitor based on field-configurable ion-doped polymers
Authors: Lai Qianxi , Zhang Lei , Li Zhiyong , Stickle William F. , Williams R. Stanley , Chen Yong
Published: November 2009

A memory capacitor based on a field-configurable ion-doped polymer is reported. The device can be dynamically and reversibly programed to analog capacitances with low-voltage (<5V) pulses. After the device is programed to a specific value, its capacitance remains nonvolatile. The field-configurable capacitance is attributed to the modification of ionic dopant concentrations in the polymer. The memory capacitors might be used for analog memory, nonlinear analog, and neuromorphic circuits.
Soft recovery technique to investigate dynamic fragmentation of laser shock-loaded metals
Authors: Lescoute E. , De Rességuier T. , Chevalier J.-M. , Boustie M. , Cuq-Lelandais J.-P. , Berthe L.
Published: November 2009

With the development of high energy laser facilities dedicated to inertial confinement fusion, the question of debris ejection from metallic shells subjected to intense laser irradiation has become a key issue. We have used two diagnostics to investigate fragmentation processes. Recovery of ejected fragments has been performed in a highly transparent gel of density 0.9 g/cm3. Fragments sizes, shapes, and penetration depths, can be easily observed with a spatial resolution of micrometer-order. Complementary data are provided by transverse shadowgraphy which allows to obtain quasi-instantaneous, successive pictures of the debris clouds and mean ejection velocities.
Electrically driven ultraviolet lasing behavior from phosphorus-doped p-ZnO nanonail array/n-Si heterojunction
Authors: Zhang Jun-Yan , Zhang Qi-Feng , Deng Tian-Song , Wu Jin-Lei
Published: November 2009

Electrically driven ultraviolet lasing behavior from p-ZnO:P nanonail array/n-Si heterojunction was demonstrated. Phosphorus-doped ZnO nanonail arrays were grown by chemical vapor deposition method. The constructed heterojunction with indium tin oxide films as the contacted electrodes demonstrated clear rectifying behavior, and the turn-on voltage was about 2.5 V. The p-n junction lowered the excitation threshold effectively and the electrically driven ultraviolet lasing behavior exhibited high monochromaticity: when the applied forward current reached 24 mA, distinct ultraviolet laser emission peaks were obtained at room temperature, and the full width at half maxims were 0.7, 0.9, and 0.5 nm, respectively. The three sharp peaks represented different lasing modes.
Microfluidics for reconfigurable electromagnetic metamaterials
Authors: Kasirga T. Serkan , Ertas Y. Nuri , Bayindir Mehmet
Published: November 2009

We propose microfluidics as a useful platform for reconfigurable electromagnetic metamaterials. Microfluidic split-ring resonators (MF-SRRs) are fabricated inside a flexible elastomeric material by employing rapid prototyping. The transmission measurements performed for mercury-injected MF-SRR exhibits sharp magnetic resonances at microwave wavelengths. We further calculate transmission properties of the MF-SRR array and the effect of electrical conductivity of the liquid inside the channel on the magnetic resonance. The measured results agree well with numerical calculations. Our proposal may open up directions toward switchable metamaterials and reconfigurable devices such as filters, switches, and resonators.
Nanocrystalline tungsten carbide: As incompressible as diamond
Authors: Lin Zhijun , Wang Lin , Zhang Jianzhong , Mao Ho-kwang , Zhao Yusheng
Published: November 2009

We investigate the compressibility of nanocrystalline tungsten carbide (nano-WC) using synchrotron x-ray diffraction. Nano-WC displays a bulk modulus (452 GPa) comparable to that of diamond; it is 10%–15% larger than previously reported values for bulk WC. This finding is consistent with a generalized model of nanocrystal with a compressed surface layer. The linear bulk moduli of nano-WC along a- and c-axes were determined to be 407 and 546 GPa, respectively. First-principles density functional theory (DFT) calculations confirm the experimental observations of an anisotropic linear compressibility and a lower bulk modulus for microsized WC.
Surface transformation and inversion domain boundaries in gallium nitride nanorods
Authors: Xiao Pan , Wang Xu , Wang Jun , Ke Fujiu , Zhou Min , Bai Yilong
Published: November 2009

Phase transformation and subdomain structure in [0001]-oriented gallium nitride (GaN) nanorods of different sizes are studied using molecular dynamics simulations. The analysis concerns the structure of GaN nanorods at 300 K without external loading. Calculations show that a transformation from wurtzite to a tetragonal structure occurs along {011¯0} lateral surfaces, leading to the formation of a six-sided columnar inversion domain boundary (IDB) in the [0001] direction of the nanorods. This structural configuration is similar to the IDB structure observed experimentally in GaN epitaxial layers. The transformation is significantly dependent on the size of the nanorods.
Thermal flying-height control sliders in hard disk drives filled with air-helium gas mixtures
Authors: Liu Nan , Zheng Jinglin , Bogy David B.
Published: November 2009

This letter employs established approaches to calculate the physical properties of the air-helium gas mixtures and investigates the thermal flying-height control slider’s flying performance in these environments. It is found that at a fixed heater power, the slider’s flying height first increases and then decreases with the fraction of helium in the gas mixture due to the combined effects of changes in the mean free path, viscosity, and thermal conductivity of the gas mixture with helium content. These findings, together with the proposed approach, are useful for future designs of sliders in air-helium mixtures.
Excitonic characteristics in direct wide-band-gap CuScO2 epitaxial thin films
Authors: Hiraga H. , Makino T. , Fukumura T. , Ohtomo A. , Kawasaki M.
Published: November 2009

Thin films of a delafossite compound CuScO2 were grown on spinel MgAl2O4 (111) substrates, yielding in highly crystalline and (0001)-oriented epitaxial structures. Absorption spectra at 20 K revealed a sharp exciton resonance at 3.97 eV, which persisted up to 300 K. Its direct transition band gap at 20 K and exciton binding energies were determined to be about 4.35 and 380 meV, both of which are considerably larger than those of ZnO. In view of its capability of naturally layered structure and p-type doping, this compound will be interesting for exciton physics as well as implementation of heterostructured devices.
Efficient semitransparent small-molecule organic solar cells
Authors: Meiss Jan , Leo Karl , Riede Moritz K. , Uhrich Christian , Gnehr Wolf-Michael , Sonntag Stefan , Pfeiffer Martin
Published: November 2009

We present semitransparent small-molecule organic solar cells (OSC) deposited by thermal evaporation onto indium tin oxide (ITO)-coated glass substrates. The devices employ ITO-free ultrathin metal layers as top electrodes, containing 1nm metal surfactant interlayer for improved morphology. Using a bulk heterojunction of zinc phthalocyanine and C60, sandwiched in between doped dedicated transport layers for efficient charge carrier extraction, power conversion efficiencies comparable to conventional OSC with an intransparent thick back electrode and similar device layout are achieved: the semitransparent OSC yield power conversion efficiencies well above 2% with external quantum efficiencies above 30%–40%. Organic light incoupling layers improve the transmission to up to 50% in the visible part of the optical spectrum.
Tailoring light emission properties of organic emitter by coupling to resonance-tuned silver nanoantenna arrays
Authors: Qiu Teng , Kong Fan , Yu Xiaoqiang , Zhang Wenjun , Lang Xianzhong , Chu Paul K.
Published: November 2009

A convenient nanotechnique is reported to tailor the light emission properties of organic emitter poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) by coupling to resonance-tuned silver nanoantenna arrays. It is revealed experimentally and theoretically that the enhanced photoluminescence from the MEH-PPV/silver nanoantenna complex may originate from the energy transfer effect in the surface plasmon resonance coupling between the MEH-PPV and silver nanocaps and from local electromagnetic field enhancement of nanogaps between the silver nanocaps in the background of the light-emitting MEH-PPV. The results are corroborated by the finite difference time domain simulation results.
Time-shifted synchronization of chaotic oscillator chains without explicit coupling delays
Authors: Blakely Jonathan N. , Stahl Mark T. , Corron Ned J.
Published: November 2009

We examine chains of unidirectionally coupled oscillators in which time-shifted synchronization occurs without explicit delays in the coupling. In numerical simulations and in an experimental system of electronic oscillators, we examine the time shift and the degree of distortion (primarily in the form of attenuation) of the waveforms of the oscillators located far from the drive oscillator. Surprisingly, under weak coupling we observe minimal attenuation in spite of a significant total time shift. In contrast, at higher coupling strengths the observed attenuation increases dramatically and approaches the value predicted by an analytically derived estimate. In this regime, we verify directly that generalized synchronization is maintained over the entire chain length despite severe attenuation. These results suggest that weak coupling generally may produce higher quality synchronization in systems for which truly identical synchronization is not possible.
Ambipolar-transporting coaxial nanotubes with a tailored molecular graphene–fullerene heterojunction
Authors: Yamamoto Yohei , Zhang Guanxin , Jin Wusong , Fukushima Takanori , Ishii Noriyuki , Saeki Akinori , Seki Shu , Tagawa Seiichi , Minari Takeo , Tsukagoshi Kazuhito , Aida Takuzo
Published: November 2009

Despite a large steric bulk of C
60
, a molecular graphene with a covalently linked C
60
pendant [hexabenzocoronene (HBC)–C
60
; 1] self-assembles into a coaxial nanotube whose wall consists of a graphite-like π-stacked HBC array, whereas the nanotube surface is fully covered by a molecular layer of clustering C
60
. Because of this explicit coaxial configuration, the nanotube exhibits an ambipolar character in the field-effect transistor output [hole mobility (μ
h
) = 9.7 × 10
−7
cm
2
V
−1
s
−1
; electron mobility (μ
e
) = 1.1 × 10
−5
cm
2
V
−1
s
−1
] and displays a photovoltaic response upon light illumination. Successful coassembly of 1 and an HBC derivative without C
60
(
2
) allows for tailoring the p/n heterojunction in the nanotube, so that its ambipolar carrier transport property can be optimized for enhancing the open-circuit voltage in the photovoltaic output. As evaluated by an electrodeless method called flash-photolysis time-resolved microwave conductivity technique, the intratubular hole mobility (2.0 cm
2
V
−1
s
−1
) of a coassembled nanotube containing 10 mol % of HBC–C
60
(
1
) is as large as the intersheet mobility in graphite. The homotropic nanotube of 2 blended with a soluble C
60
derivative [(6,6)-phenyl C
61
butyric acid methyl ester] displayed a photovoltaic response with a much different composition dependency, where the largest open-circuit voltage attained was obviously lower than that realized by the coassembly of 1 and 2.
Circumpolar synchrony in big river bacterioplankton
Authors: Crump Byron C. , Peterson Bruce J. , Raymond Peter A. , Amon Rainer M. W. , Rinehart Amanda , McClelland James W. , Holmes Robert M.
Published: November 2009

Natural bacterial communities are extremely diverse and highly dynamic, but evidence is mounting that the compositions of these communities follow predictable temporal patterns. We investigated these patterns with a 3-year, circumpolar study of bacterioplankton communities in the six largest rivers of the pan-arctic watershed (Ob', Yenisey, Lena, Kolyma, Yukon, and Mackenzie), five of which are among Earth's 25 largest rivers. Communities in the six rivers shifted synchronously over time, correlating with seasonal shifts in hydrology and biogeochemistry and clustering into three groups: winter/spring, spring freshet, and summer/fall. This synchrony indicates that hemisphere-scale variation in seasonal climate sets the pace of variation in microbial diversity. Moreover, these seasonal communities reassembled each year in all six rivers, suggesting a long-term, predictable succession in the composition of big river bacterioplankton communities.
Molecular priming of Lyn by GPVI enables an immune receptor to adopt a hemostatic role
Authors: Schmaier Alec A. , Zou Zhiying , Kazlauskas Arunas , Emert-Sedlak Lori , Fong Karen P. , Neeves Keith B. , Maloney Sean F. , Diamond Scott L. , Kunapuli Satya P. , Ware Jerry , Brass Lawrence F. , Smithgall Thomas E. , Saksela Kalle , Kahn Mark L.
Published: November 2009

The immune receptor signaling pathway is used by nonimmune cells, but the molecular adaptations that underlie its functional diversification are not known. Circulating platelets use the immune receptor homologue glycoprotein VI (GPVI) to respond to collagen exposed at sites of vessel injury. In contrast to immune cell responses, platelet activation must take place within seconds to successfully form thrombi in flowing blood. Here, we show that the GPVI receptor utilizes a unique intracellular proline-rich domain (PRD) to accelerate platelet activation, a requirement for efficient platelet adhesion to collagen under flow. The GPVI PRD specifically binds the Src-family kinase Lyn and directly activates it, presumably through SH3 displacement. In resting platelets, Lyn is constitutively bound to GPVI in an activated state and platelets lacking Lyn exhibit defective collagen adhesion like that of platelets with GPVI receptors lacking the PRD. These findings define a molecular priming mechanism that enables an immune-type receptor to adopt a hemostatic function. These studies also demonstrate that active kinases can constitutively associate with immune-type receptors without initiating signal transduction before receptor ligation, consistent with a recent molecular model of immune receptor signaling in which receptor ligation is required to bring active kinases to their receptor substrates.
Derivation of burn scar depths and estimation of carbon emissions with LIDAR in Indonesian peatlands
Authors: Ballhorn Uwe , Siegert Florian , Mason Mike , Limin Suwido
Published: November 2009

During the 1997/98 El Niño-induced drought peatland fires in Indonesia may have released 13–40% of the mean annual global carbon emissions from fossil fuels. One major unknown in current peatland emission estimations is how much peat is combusted by fire. Using a light detection and ranging data set acquired in Central Kalimantan, Borneo, in 2007, one year after the severe peatland fires of 2006, we determined an average burn scar depth of 0.33 ± 0.18 m. Based on this result and the burned area determined from satellite imagery, we estimate that within the 2.79 million hectare study area 49.15 ± 26.81 megatons of carbon were released during the 2006 El Niño episode. This represents 10–33% of all carbon emissions from transport for the European Community in the year 2006. These emissions, originating from a comparatively small area (approximately 13% of the Indonesian peatland area), underline the importance of peat fires in the context of green house gas emissions and global warming. In the past decade severe peat fires occurred during El Niño-induced droughts in 1997, 2002, 2004, 2006, and 2009. Currently, this important source of carbon emissions is not included in IPCC carbon accounting or in regional and global carbon emission models. Precise spatial measurements of peat combusted and potential avoided emissions in tropical peat swamp forests will also be required for future emission trading schemes in the framework of Reduced Emissions from Deforestation and Degradation in developing countries.
Genetic dissection of floridean starch synthesis in the cytosol of the model dinoflagellate
Crypthecodinium cohnii
Authors: Dauvillée David , Deschamps Philippe , Ral Jean-Philippe , Plancke Charlotte , Putaux Jean-Luc , Devassine Jimi , Durand-Terrasson Amandine , Devin Aline , Ball Steven G.
Published: November 2009

Starch defines an insoluble semicrystalline form of storage polysaccharides restricted to Archaeplastida (red and green algae, land plants, and glaucophytes) and some secondary endosymbiosis derivatives of the latter. While green algae and land-plants store starch in plastids by using an ADP-glucose-based pathway related to that of cyanobacteria, red algae, glaucophytes, cryptophytes, dinoflagellates, and apicomplexa parasites store a similar type of polysaccharide named floridean starch in their cytosol or periplast. These organisms are suspected to store their floridean starch from UDP-glucose in a fashion similar to heterotrophic eukaryotes. However, experimental proof of this suspicion has never been produced. Dinoflagellates define an important group of both photoautotrophic and heterotrophic protists. We now report the selection and characterization of a low starch mutant of the heterotrophic dinoflagellate
Crypthecodinium cohnii
. We show that the
sta1-1
mutation of
C. cohnii
leads to a modification of the UDP-glucose-specific soluble starch synthase activity that correlates with a decrease in starch content and an alteration of amylopectin structure. These experimental results validate the UDP-glucose-based pathway proposed for floridean starch synthesis.
Cerebellar theta oscillations are synchronized during hippocampal theta-contingent trace conditioning
Authors: Hoffmann Loren C. , Berry Stephen D.
Published: November 2009

The hippocampus and cerebellum are critically involved in trace eyeblink classical conditioning (EBCC). The mechanisms underlying the hippocampal-cerebellar interaction during this task are not well-understood, although hippocampal theta (3–7 Hz) oscillations are known to reflect a favorable state for EBCC. Two groups of rabbits received trace EBCC in which a brain-computer interface administered trials in either the explicit presence or absence of naturally occurring hippocampal theta. A high percentage of robust theta led to a striking enhancement of learning accompanied by rhythmic theta-band (6–7 Hz) oscillations in the interpositus nucleus (IPN) and cerebellar cortex that were time-locked both to hippocampal rhythms and sensory stimuli during training. Rhythmic oscillations were absent in the cerebellum of the non-theta group. These data strongly suggest a beneficial impact of theta-based coordination of hippocampus and cerebellum and, importantly, demonstrate that hippocampal theta oscillations can be used to index, and perhaps modulate, the functional properties of the cerebellum.
The structure of a DnaA/HobA complex from
Helicobacter pylori
provides insight into regulation of DNA replication in bacteria
Authors: Natrajan Ganesh , Noirot-Gros Marie Francoise , Zawilak-Pawlik Anna , Kapp Ulrike , Terradot Laurent
Published: November 2009

Bacterial DNA replication requires DnaA, an AAA+ ATPase that initiates replication at a specific chromosome region,
oriC
, and is regulated by species-specific regulators that directly bind DnaA. HobA is a DnaA binding protein, recently identified as an essential regulator of DNA replication in
Helicobacter pylori
. We report the crystal structure of HobA in complex with domains I and II of DnaA (DnaA
I–II
) from
H. pylori
, the first structure of DnaA bound to one of its regulators. Biochemical characterization of the complex formed shows that a tetramer of HobA binds four DnaA
I–II
molecules, and that DnaA
I–II
is unable to oligomerize by itself. Mutagenesis and protein–protein interaction studies demonstrate that some of the residues located at the HobA-DnaA
I–II
interface in the structure are necessary for complex formation. Introduction of selected mutations into
H. pylori
shows that the disruption of the interaction between HobA and DnaA is lethal for the bacteria. Remarkably, the DnaA binding site of HobA is conserved in DiaA from
Escherichia coli
, suggesting that the structure of the HobA/DnaA complex represents a model for DnaA regulation in other Gram-negative bacteria. Our data, together with those from other studies, indicate that HobA could play a crucial scaffolding role during the initiation of replication in
H. pylori
by organizing the first step of DnaA oligomerization and attachment to
oriC
.
Discovery of
Plasmodium
modulators by genome-wide analysis of circulating hemocytes in
Anopheles gambiae
Authors: Pinto Sofia B. , Lombardo Fabrizio , Koutsos Anastasios C. , Waterhouse Robert M. , McKay Krista , An Chunju , Ramakrishnan Chandra , Kafatos Fotis C. , Michel Kristin
Published: November 2009

Insect hemocytes mediate important cellular immune responses including phagocytosis and encapsulation and also secrete immune factors such as opsonins, melanization factors, and antimicrobial peptides. However, the molecular composition of these important immune cells has not been elucidated in depth, because of their scarcity in the circulating hemolymph, their adhesion to multiple tissues and the lack of primary culture methods to produce sufficient material for a genome-wide analysis. In this study, we report a genome-wide molecular characterization of circulating hemocytes collected from the hemolymph of adult female
Anopheles gambiae
mosquitoes—the major mosquito vector of human malaria in subSaharan Africa. Their molecular profile identified 1,485 transcripts with enriched expression in these cells, and many of these genes belong to innate immune gene families. This hemocyte-specific transcriptome is compared to those of
Drosophila melanogaster
and two other mosquitoes,
Aedes aegypti
and
Armigeres subalbatus
. We report the identification of two genes as ubiquitous hemocyte markers and several others as hemocyte subpopulation markers. We assess, via an RNAi screen, the roles in development of
Plasmodium berghei
of 63 genes expressed in hemocytes and provide a molecular comparison of the transcriptome of these cells during malaria infection.
Time of feeding and the intrinsic circadian clock drive rhythms in hepatic gene expression
Authors: Vollmers Christopher , Gill Shubhroz , DiTacchio Luciano , Pulivarthy Sandhya R. , Le Hiep D. , Panda Satchidananda
Published: November 2009

In mammals, the circadian oscillator generates approximately 24-h rhythms in feeding behavior, even under constant environmental conditions. Livers of mice held under constant darkness exhibit circadian rhythm in abundance in up to 15% of expressed transcripts. Therefore, oscillations in hepatic transcripts could be driven by rhythmic food intake or sustained by the hepatic circadian oscillator, or a combination of both. To address this question, we used distinct feeding and fasting paradigms on wild-type (WT) and circadian clock-deficient mice. We monitored temporal patterns of feeding and hepatic transcription. Both food availability and the temporal pattern of feeding determined the repertoire, phase, and amplitude of the circadian transcriptome in WT liver. In the absence of feeding, only a small subset of transcripts continued to express circadian patterns. Conversely, temporally restricted feeding restored rhythmic transcription of hundreds of genes in oscillator-deficient mouse liver. Our findings show that both temporal pattern of food intake and the circadian clock drive rhythmic transcription, thereby highlighting temporal regulation of hepatic transcription as an emergent property of the circadian system.
NADP
+
-dependent farnesol dehydrogenase, a
corpora allata
enzyme involved in juvenile hormone synthesis
Authors: Mayoral Jaime G. , Nouzova Marcela , Navare Arti , Noriega Fernando G.
Published: November 2009

The synthesis of juvenile hormone (JH) is an attractive target for control of insect pests and vectors of disease, but the minute size of the corpora allata (CA), the glands that synthesize JH, has made it difficult to identify important biosynthetic enzymes by classical biochemical approaches. Here, we report identification and characterization of an insect farnesol dehydrogenase (
Aa
SDR-1) that oxidizes farnesol into farnesal, a precursor of JH, in the CA.
Aa
SDR-1 was isolated as an EST in a library of the corpora allata-corpora cardiaca of the mosquito
Aedes aegypti
. The 245-amino acid protein presents the typical short-chain dehydrogenase (SDR) Rossmann-fold motif for nucleotide binding. This feature, together with other conserved sequence motifs, place
Aa
SDR-1 into the “classical” NADP
+
-dependent cP2 SDR subfamily. The gene is part of a group of highly conserved paralogs that cluster together in the mosquito genome; similar clusters of orthologs were found in other insect species.
Aa
SDR-1 acts as a homodimer and efficiently oxidizes C
10
to C
15
isoprenoid and aliphatic alcohols, showing the highest affinity for the conversion of farnesol into farnesal. Farnesol dehydrogenase activity was not detected in the CA of newly emerged mosquitoes but significant activity was detected 24 h later. Real time PCR experiments revealed that
Aa
SDR-1 mRNA levels were very low in the inactive CA of the newly emerged female, but increased >30-fold 24 h later during the peak of JH synthesis. These results suggest that oxidation of farnesol might be a rate-limiting step in JH III synthesis in adult mosquitoes.
A two-subunit bacterial σ-factor activates transcription in
Bacillus subtilis
Authors: MacLellan Shawn R. , Guariglia-Oropeza Veronica , Gaballa Ahmed , Helmann John D.
Published: November 2009

The σ-like factor YvrI and coregulator YvrHa activate transcription from a small set of conserved promoters in
Bacillus subtilis
. We report here that these two proteins independently contribute σ-region 2 and σ-region 4 functions to a holoenzyme-promoter DNA complex. YvrI binds RNA polymerase (RNAP) through a region 4 interaction with the β-subunit flap domain and mediates specific promoter recognition but cannot initiate DNA melting at the -10 promoter element. Conversely, YvrHa possesses sequence similarity to a conserved core-binding motif in σ-region 2 and binds to the N-terminal coiled-coil element in the RNAP β′-subunit previously implicated in interaction with region 2 of σ-factors. YvrHa plays an essential role in stabilizing the open complex and interacts specifically with the N-terminus of YvrI. Based on these results, we propose that YvrHa is situated in the transcription complex proximal to the -10 element of the promoter, whereas YvrI is responsible for -35 region recognition. This system presents an unusual example of a two-subunit bacterial σ-factor.
Astrocyte elevated gene-1 (AEG-1) functions as an oncogene and regulates angiogenesis
Authors: Emdad Luni , Lee Seok-Geun , Su Zhao Zhong , Jeon Hyun Yong , Boukerche Habib , Sarkar Devanand , Fisher Paul B.
Published: November 2009

Astrocyte-elevated gene-1 (AEG-1) expression is increased in multiple cancers and plays a central role in Ha-
ras
-mediated oncogenesis through the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Additionally, overexpression of AEG-1 protects primary and transformed human and rat cells from serum starvation-induced apoptosis through activation of PI3K/Akt signaling. These findings suggest, but do not prove, that AEG-1 may function as an oncogene. We now provide definitive evidence that AEG-1 is indeed a transforming oncogene and show that stable expression of AEG-1 in normal immortal cloned rat embryo fibroblast (CREF) cells induces morphological transformation and enhances invasion and anchorage-independent growth in soft agar, two fundamental biological events associated with cellular transformation. Additionally, AEG-1-expressing CREF clones form aggressive tumors in nude mice. Immunohistochemistry analysis of tumor sections demonstrates that AEG-1-expressing tumors have increased microvessel density throughout the entire tumor sections. Overexpression of AEG-1 increases expression of molecular markers of angiogenesis, including angiopoietin-1, matrix metalloprotease-2, and hypoxia-inducible factor 1-α. In vitro angiogenesis studies further demonstrate that AEG-1 promotes tube formation in Matrigel and increases invasion of human umbilical vein endothelial cells via the PI3K/Akt signaling pathway. Tube formation induced by AEG-1 correlates with increased expression of angiogenesis markers, including Tie2 and hypoxia-inducible factor-α, and blocking AEG-1-induced Tie2 with Tie2 siRNA significantly inhibits AEG-1-induced tube formation in Matrigel. Overall, our findings demonstrate that aberrant AEG-1 expression plays a dominant positive role in regulating oncogenic transformation and angiogenesis. These findings suggest that AEG-1 may provide a viable target for directly suppressing the cancer phenotype.
Vertically integrated, three-dimensional nanowire complementary metal-oxide-semiconductor circuits
Authors: Nam SungWoo , Jiang Xiaocheng , Xiong Qihua , Ham Donhee , Lieber Charles M.
Published: November 2009

Three-dimensional (3D), multi-transistor-layer, integrated circuits represent an important technological pursuit promising advantages in integration density, operation speed, and power consumption compared with 2D circuits. We report fully functional, 3D integrated complementary metal-oxide-semiconductor (CMOS) circuits based on separate interconnected layers of high-mobility n-type indium arsenide (n-InAs) and p-type germanium/silicon core/shell (p-Ge/Si) nanowire (NW) field-effect transistors (FETs). The DC voltage output (
V
out
) versus input (
V
in
) response of vertically interconnected CMOS inverters showed sharp switching at close to the ideal value of one-half the supply voltage and, moreover, exhibited substantial DC gain of ≈45. The gain and the rail-to-rail output switching are consistent with the large noise margin and minimal static power consumption of CMOS. Vertically interconnected, three-stage CMOS ring oscillators were also fabricated by using layer-1 InAs NW n-FETs and layer-2 Ge/Si NW p-FETs. Significantly, measurements of these circuits demonstrated stable, self-sustained oscillations with a maximum frequency of 108 MHz, which represents the highest-frequency integrated circuit based on chemically synthesized nanoscale materials. These results highlight the flexibility of bottom-up assembly of distinct nanoscale materials and suggest substantial promise for 3D integrated circuits.
Golgi protein FAPP2 tubulates membranes
Authors: Cao Xinwang , Coskun Ünal , Rössle Manfred , Buschhorn Sabine B. , Grzybek Michal , Dafforn Timothy R. , Lenoir Marc , Overduin Michael , Simons Kai
Published: November 2009

The Golgi-associated four-phosphate adaptor protein 2 (FAPP2) has been shown to possess transfer activity for glucosylceramide both in vitro and in cells. We have previously shown that FAPP2 is involved in apical transport from the Golgi complex in epithelial MDCK cells. In this paper we assign an unknown activity for the protein as well as providing structural insight into protein assembly and a low-resolution envelope structure. By applying analytical ultracentrifugation and small-angle x-ray scattering, we show that FAPP2 is a dimeric protein in solution, having a curved shape 30 nm in length. The purified FAPP2 protein has the capability to form tubules from membrane sheets in vitro. This activity is dependent on the phosphoinositide-binding activity of the PH domain of FAPP2. These data suggest that FAPP2 functions directly in the formation of apical carriers in the trans-Golgi network.