bluuebunny/crossref_metadata_2025 huggingface dataset:
Cloudy and clear‐sky relative humidity in the upper troposphere observed by the A‐train
Authors: Kahn Brian H. , Gettelman Andrew , Fetzer Eric J. , Eldering Annmarie , Liang Calvin K.
Published: July 2009

Cloudy and clear‐sky distributions of relative humidity with respect to ice (RHI) are derived from the Atmospheric Infrared Sounder and cloud profiles from CloudSat and the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation satellites. A peak frequency in RHI of 10–20% exists for clear sky, increasing to 75–95% within clouds detected by CloudSat. The range of values depends on the season, altitude, latitude, cloud type, and ice water content. Global distributions of RHI reveal persistent supersaturation in the clear and cloudy tropical upper troposphere and lower tropospheric polar regions, large but variable RHI in the cloudy midlatitude storm tracks, and small yet variable RHI in the clear‐sky subtropics. Previous studies using satellite and in situ observations have shown a greater frequency of midlatitude supersaturation in the Southern Hemisphere (SH). Seasonal and interannual variations in RHI are also demonstrated with larger frequencies of supersaturation generally present in the winter hemisphere. An analytical method quantifies the impacts of mean temperature () and temperature variance (σT) on the distribution characteristics of RHI. The seasonal variation of RHI in the Northern Hemisphere is primarily modulated by seasonal changes in σT, whereas in the SH, both and σT modulate variations in RHI. However, variations in and σT do not explain the presence of slightly greater supersaturation frequency in the SH, suggesting a link between anthropogenic aerosol and ice cloud processes.
Processes regulating short‐lived species in the tropical tropopause layer
Authors: Gettelman A. , Lauritzen P. H. , Park M. , Kay J. E.
Published: July 2009

A one‐dimensional model of vertical transport in the tropical tropopause layer (TTL) is developed. The model uses vertical advection, a convective source, and a chemical sink to simulate the profiles of very short lived substances in the TTL. The model simulates evanescent profiles of short‐lived hydrocarbon species observed by satellite and is also used to simulate short‐lived bromine species. Tracers with chemical lifetimes of 25 days or longer have significant concentrations in the stratosphere, and vertical advection is critical. Convection is important up to its peak altitude, nearly 19 km. Convection dominates the distribution of species with lifetimes less than 25 days. The annual cycle of species with lifetimes longer than 25 days is governed primarily by the variations of vertical velocity, not convection. This is particularly true for carbon monoxide, where a seasonal cycle in the lower stratosphere of the right phase is produced without variations in tropospheric emissions. An analysis of critical short‐lived bromine species (CH2Br2 and CHBr3) indicates that substantial amounts of these tracers may get advected into the lower stratosphere as source gases at 18 km, and are estimated to contribute 2.8 pptv (1.1–4.1) to stratospheric bromine.
Vertically resolved separation of dust and smoke over Cape Verde using multiwavelength Raman and polarization lidars during Saharan Mineral Dust Experiment 2008
Authors: Tesche M. , Ansmann A. , Müller D. , Althausen D. , Engelmann R. , Freudenthaler V. , Groß S.
Published: July 2009

Multiwavelength aerosol Raman lidar in combination with polarization lidar at Praia (14.9°N, 23.5°W), Cape Verde, is used to separate the optical properties of desert dust and biomass burning particles as a function of height in the mixed dust and smoke plumes over the tropical North Atlantic west of the African continent. The advanced lidar method furthermore permits the derivation of the single‐scattering albedo and microphysical properties of the African biomass burning smoke. A case study is presented to discuss the potential of the technique. The observations were performed during the Saharan Mineral Dust Experiment (SAMUM) in January and February 2008. The height‐resolved lidar results are compared with column‐integrated products obtained with Aerosol Robotic Network Sun photometer. Good agreement is found. Furthermore, the findings are compared with lidar and aircraft observations recently performed in western Africa and with our previous lidar observations taken in tropical and subtropical regions of southern and eastern Asia. The SAMUM case study represents typical aerosol layering conditions in the tropical outflow regime of western Africa during winter season. Above a dense desert dust layer (with an optical depth of about 0.25 at 532 nm) which reached to 1500 m, a lofted layer consisting of desert dust (0.08 optical depth) and biomass burning smoke (0.24 optical depth) extended from 1500 to 5000 m height. Extinction values were 20 ± 10 Mm−1 (desert dust) and 20–80 Mm−1 (smoke) in the lofted plume. The smoke extinction‐to‐backscatter ratios were rather high, with values up to more than 100 sr, effective radii ranged from 0.15 to 0.35 μm, and the smoke single‐scattering albedo was partly below 0.7.
Steady‐state dendritic cells continuously inactivate T cells that escape thymic negative selection
Authors: Doan Tracy , McNally Alice , Thomas Ranjeny , Steptoe Raymond J
Published: July 2009

Induction of peripheral tolerance by steady‐state peripheral dendritic cells (DCs) presenting self antigen may be important in preventing autoimmune diseases mediated by self‐reactive T cells that escape thymic deletion. However, the relative contribution of thymic and peripheral tolerance to the inactivation of self‐specific repertoires is yet to be clearly defined. Here we tested the relative contribution of thymic and peripheral tolerance induction, using mice (11c.OVA) in which ovalbumin (OVA) expression is genetically targeted to DCs in conjunction with mice (Vβ5 TCR transgenic), where a polyclonal repertoire of OVA‐specific T cells of diverse affinity is present. The expression of OVA in thymic DC reduced the frequency of OVA257−264‐specific mature CD8 single‐positive thymocytes although some functional OVA‐specific CD8+ T cells escaped negative selection and were detectable in the periphery. After adult thymectomy, OVA257−264‐reactive T cells declined in the periphery indicating that the repertoire of OVA257−264‐specific T cells that escaped negative selection and egressed to the periphery, were susceptible to inactivation by steady‐state peripheral DC. Thus, in the face of inefficient negative selection, peripheral tolerance induction to cognate antigen by resting DC is a crucial requirement for the inactivation of a self‐specific repertoire.
Two dimensional Langevin recombination in regioregular poly(3-hexylthiophene)
Authors: Juška Gytis , Genevičius Kristijonas , Nekrašas Nerijus , Sliaužys Gytis , Österbacka Ronald
Published: July 2009

In this work, it is shown that recombination in regioregular poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (RRP3HT:PCBM) bulk-heterojunction solar cells is caused by the two dimensional (2D) Langevin recombination in the lamellar structures of RRP3HT, which are formed after annealing process. Due to 2D Langevin process, bimolecular recombination coefficient is reduced in comparison with three dimensional Langevin case, and bimolecular recombination coefficient depends on the density of charge carriers n1/2. Data obtained from the different experimental techniques (charge extraction with linearly increasing voltage, integral time of flight, double injection current transients and transient absorption spectroscopy) confirms 2D Langevin recombination in RR3PHT.
Magnetic linear response properties calculations with the Gaussian and augmented-plane-wave method
Authors: Weber Valéry , Iannuzzi Marcella , Giani Samuele , Hutter Jürg , Declerck Reinout , Waroquier Michel
Published: July 2009

We introduce a method for the all-electron calculation of the NMR chemical shifts and the EPR g tensor using the Gaussian and augmented-plane-wave method. The presented approach is based on the generalized density functional perturbation theory. The method is validated by comparison with other theoretical methods for a selection of small molecules. We also present two exemplary applications that involve the calculation of the chemical shifts of a hydrated adenine and the g tensor for the E1′ center in α-quartz using a quantum mechanical/molecular mechanical approach.
Charge-pumping in a synthetic leaf for harvesting energy from evaporation-driven flows
Authors: Borno Ruba T. , Steinmeyer Joseph D. , Maharbiz Michel M.
Published: July 2009

Inspired by water transport in plants, we present a synthetic, microfabricated “leaf” that can scavenge electrical power from evaporative flow. Evaporation at the surface of the device produces flows with velocities up to 1.5 cm/s within etched microchannels. Gas-liquid interfaces within the channels move across an embedded capacitor at this velocity, generating 250 ms, 10–50 pF transient changes in capacitance. If connected to a rectified charge-pump circuit, each capacitive transient can increase the voltage in a 100 μF storage capacitor by ∼2–5 μV. We provide estimates of power density, energy density, and scavenging efficiency.
Analysis of the nucleotide-dependent conformations of kinesin-1 in the hydrolysis cycle
Authors: Ciudad Aleix , Sancho J. M.
Published: July 2009

Kinesin-1 motion on a microtubule (MT) is still receiving a great attention due to its relevance in understanding molecular motion triggered by adenosine triphosphate (ATP) hydrolysis. Recent experimental data on kinesin-tubulin-nucleotide interactions have clarified some of the conformational details involved in the hydrolysis process [T. Mori et al., Nature (London) 450, 750 (2007)]. Specifically, fluorescence resonance energy transfer was used to measure the affinity of motor domains to tubulin heterodimers. Our work is directly devoted to understand and reproduce the main output of these experiments as well as to go beyond and give a global dynamical picture of the whole hydrolysis cycle. We predict that phosphate groups have the ability to confine to the tubulin domains in order to explain the delay between ATP hydrolysis and head detaching, which seems crucial for the achievement of processivity. In our approach me make use of chemical kinetics complemented with stochastic molecular simulations of the elements involved.
Fast electro-optic device controlled by dielectric response of planarly aligned cholesteric liquid crystals
Authors: Lee Ho Hyun , Yu Jeong-Seon , Kim Jong-Hyun , Yamamoto Shin-ichi , Kikuchi Hirotsugu
Published: July 2009

Planarly aligned cholesteric liquid crystals of short pitch were applied by the in-plane electric field. The reorientation of the director, increasing pitch, and flexoelectricity induce the change of transmission. The main effect in this research is due to the director reorientation along the electric field. The flexoelectricity deters the change in the birefringence induced by the dielectric response. The response was very fast for the effectively thin periodic boundary of the half-pitch of liquid crystal. The contrast ratio was more than 80 for red light and the response time was less than 0.1 ms for the experimental conditions.
Quantization of a symplectic manifold associated to a manifold with projective structure
Authors: Biswas Indranil
Published: July 2009

Let X be a complex manifold equipped with a projective structure P. There is a holomorphic principal C∗-bundle LP′ over X associated with P. We show that the holomorphic cotangent bundle of the total space of LP′ equipped with the Liouville symplectic form has a canonical deformation quantization. This generalizes the construction in the work of and Ben-Zvi and Biswas [“A quantization on Riemann surfaces with projective structure,” Lett. Math. Phys. 54, 73 (2000)] done under the assumption that dimC X=1.
The observation of a positive magnetoresistance and close correlation among lattice, spin, and charge around TC in antipervoskite SnCMn3
Authors: Wang B. S. , Tong P. , Sun Y. P. , Zhu X. B. , Song W. H. , Yang Z. R. , Dai J. M.
Published: July 2009

The temperature dependences of magnetization, electrical transport, and thermal transport properties of antiperovskite compound SnCMn3 have been investigated systematically. A positive magnetoresistance (∼11%) is observed around the ferrimagnetic-paramagnetic transition (TC∼280 K) in the field of 50 kOe, which can be attributed to the field-induced magnetic phase transition. The abnormalities of resistivity, Seebeck coefficient, normal Hall effect, and thermal conductivity near TC are suggested to be associated with an abrupt reconstruction of electronic structure. Further, our results indicate an essential interaction among lattice, spin, and charge degrees of freedom around TC. Such an interaction among various degrees of freedom associated with sudden phase transition is suggested to be characteristic of Mn-based antiperovskite compounds.
Molecular dissociation of hydrogen peroxide (HOOH) on a neural network ab initio potential surface with a new configuration sampling method involving gradient fitting
Authors: Le Hung M. , Huynh Sau , Raff Lionel M.
Published: July 2009

The O–O bond dissociation of HOOH is investigated on an analytic ab initio potential-energy surface obtained by fitting the energies of 25 608 configurations using neural network (NN) methods. The electronic structure calculations are executed using MP2 calculations with the 6-31G∗ basis set. A new data-sampling technique is introduced to collect HOOH configurations in the six-dimensional hyperspace. This method is based on a comparison of the NN-computed gradients at configuration points currently in the database with the target gradients. By requiring that the NN gradients closely fit the MP2 target gradients, both the potential and the gradients are more accurately fitted. The selection criteria also ensure a more uniform distribution of configuration points throughout the important regions of configuration space. Molecular dynamics (MD) trajectories are not involved in the sampling. The final NN fitting yields average absolute and root-mean-squared testing set errors of 0.0060 eV (0.58 kJ mol−1) and 0.0099 eV (0.96 kJ mol−1), respectively. The effectiveness of the support vector machine (SVM) method in fitting large ab initio databases for MD calculations is investigated by using this method to fit the same HOOH database. The SVM fitting quality is tested by comparison to the NN fit. It is found that the average absolute and root-mean-squared testing set errors for the SVM fit are significantly larger than those obtained using NN methods. The total number of parameters in the SVM fit is more than a factor of 11 times the number of parameters in the NN fit. The trajectory computation time using a single NN averages about 1.8 s per picosecond of trajectory time. This increases to 9.0 s per picosecond of trajectory time if a five-NN committee is employed. The corresponding SVM computational time is almost 24 s per picosecond of trajectory time. Consequently, we conclude that a SVM is not as effective in fitting large databases for MD calculations as previously proposed methods, and thus is not employed to conduct MD studies. We employ the five-member NN committee to perform MD calculations at five different internal energies from 3.4 to 4.2 eV, including zero point energy. The rate coefficients are obtained directly from the first-order decay plots. They vary from 0.117 to 0.324 ps−1. A Rice–Ramsperger–Kassel plot is found to exhibit good linearity.
Linear and nonlinear magneto-optics of ferritin
Authors: Pankowska M. , Dobek A.
Published: July 2009

Measurements of Rayleigh light scattering and Cotton–Mouton (CM) effect are carried out at room temperature for 100 mM NaCl solutions of apoferritin/ferritin loaded with 0, 90, 100, 500, 700, and 1500 Fe atoms/molecule. Because of the spherical shape, ferritin macromolecule should not manifest magnetic anisotropy; however, in solution it shows the induced magnetic birefringence (CM effect) and changes in intensity of the scattered light components. The newly obtained data support the previously reported conclusions indicating that the deformation of linear optical polarizability induced in the ferritin by a magnetic field and the orientation of the induced magnetic dipole moment by this field are the main sources of the magneto-optical phenomena observed. Nevertheless, it is also found that the orientation of the permanent magnetic dipole moment contributes to both effects. The magnetic field induced changes in the light scattering and the CM effect theoretically depend on the linear magneto-optical polarizability, χ, on the nonlinear magneto-optical polarizability, η, and square of the permanent magnetic dipole moment value of the macromolecule, μ2. On the basis of the theory describing both effects as well as the experimental data, the values of the anisotropy of linear magneto-optical polarizabilities components, the values of the linear optical polarizability and its anisotropy, nonlinear magneto-optical polarizability and its anisotropy, are estimated. Also the magnetic dipole moment of the ferritin macromolecule is found. Interestingly, not all iron atoms in the ferritin are indicated to be in the superparamagnetic state, some of them occur in the diamagnetic form.
Nonthermal effects on the symmetric resonant charge transfer in Lorentzian plasmas
Authors: Kim Hwa-Min , Jung Young-Dae
Published: July 2009

The nonthermal and plasma screening effects on the symmetric resonant charge transfer process are investigated in Lorentzian plasmas. It is shown that the nonthermal character of the Lorentzian plasma enhances the symmetric resonant charge transfer probability as well as the charge transfer cross section. The plasma screening effects on the charge transfer cross section are found to be quite significant for small values of the spectral index. In addition, the nonthermal effects on the symmetric resonant charge transfer process are found to be more significant in Lorentzian plasmas with higher densities. It is also shown that the nonthermal character of the Lorentzian plasmas enhances the rate coefficient.
Nonlinear positron acoustic solitary waves
Authors: Tribeche Mouloud , Aoutou Kamel , Younsi Smain , Amour Rabia
Published: July 2009

The problem of nonlinear positron acoustic solitary waves involving the dynamics of mobile cold positrons is addressed. A theoretical work is presented to show their existence and possible realization in a simple four-component plasma model. The results should be useful for the understanding of the localized structures that may occur in space and laboratory plasmas as new sources of cold positrons are now well developed.
One-dimensional particle simulation of the filamentation instability: Electrostatic field driven by the magnetic pressure gradient force
Authors: Dieckmann M. E. , Kourakis I. , Borghesi M. , Rowlands G.
Published: July 2009

Two counterpropagating cool and equally dense electron beams are modeled with particle-in-cell simulations. The electron beam filamentation instability is examined in one spatial dimension, which is an approximation for a quasiplanar filament boundary. It is confirmed that the force on the electrons imposed by the electrostatic field, which develops during the nonlinear stage of the instability, oscillates around a mean value that equals the magnetic pressure gradient force. The forces acting on the electrons due to the electrostatic and the magnetic field have a similar strength. The electrostatic field reduces the confining force close to the stable equilibrium of each filament and increases it farther away, limiting the peak density. The confining time-averaged total potential permits an overlap of current filaments with an opposite flow direction.
Formation and shape control of InAsSb/InP (001) nanostructures
Authors: Lei W. , Tan H. H. , Jagadish C.
Published: July 2009

This paper presents a study on the formation and shape control of InAsSb/InP nanostructures on InP (001) substrates. For the formation of InAsSb nanostructures, incorporation of Sb atoms into InAs islands results in significant morphology change in the islands due to the surfactant effect of Sb atoms and the large strain in the system. And, shape control of InAsSb/InP nanostructures is achieved by optimizing their growth parameters. Low growth temperature and high growth rate will induce the formation of InAsSb elongated quantum dots, while high growth temperature and low growth rate will promote the formation of InAsSb quantum wires or dashes.
Stability study of a gyrotron-traveling-wave amplifier based on a lossy dielectric-loaded mode-selective circuit
Authors: Du Chao-Hai , Liu Pu-Kun
Published: July 2009

The millimeter microwave source of gyrotron-traveling-wave amplifier (gyro-TWT) is capable of generating high power coherent radiation in a broad bandwidth, while its performance is severely deteriorated by the stability problems. This paper focuses on modeling and the stability analysis of the Naval Research Laboratory (NRL) Ka-band TE01 mode gyro-TWT based on an interaction circuit alternately loaded with lossy ceramic shells and metal rings. The propagation characteristics of the interaction circuit is analyzed first, based on which the boundary impedance method is employed to build an equivalent uniform lossy circuit. Then the stability of the interaction system is studied using linear and nonlinear theories. The analysis reveals that, due to the special waveguide structure and the dielectric loss, the propagation characteristics of the complex waveguide are similar to that of a uniform lossy circuit. The analysis of the absolute instabilities characterizes the roles the forward-backward-wave components played. The study indicates that the lowest threshold current of the absolute instabilities is higher than the operating current, which brings the system high stability. The reliability of the analysis is proved by the consistency between the analysis and the NRL experimental results.
Simplified dragonfly airfoil aerodynamics at Reynolds numbers below 8000
Authors: Levy David-Elie , Seifert Avraham
Published: July 2009

Effective aerodynamics at Reynolds numbers lower than 10 000 is of great technological interest and a fundamental scientific challenge. The current study covers a Reynolds number range of 2000–8000. At these Reynolds numbers, natural insect flight could provide inspiration for technology development. Insect wings are commonly characterized by corrugated airfoils. In particular, the airfoil of the dragonfly, which is able to glide, can be used for two-dimensional aerodynamic study of fixed rigid wings. In this study, a simplified dragonfly airfoil is numerically analyzed in a steady free-stream flow. The aerodynamic performance (such as mean and fluctuating lift and drag), are first compared to a “traditional” low Reynolds number airfoil: the Eppler-E61. The numerical results demonstrate superior performances of the corrugated airfoil. A series of low-speed wind and water tunnel experiments were performed on the corrugated airfoil, to validate the numerical results. The findings indicate quantitative agreement with the mean wake velocity profiles and shedding frequencies while validating the two dimensionality of the flow. A flow physics numerical study was performed in order to understand the underlying mechanism of corrugated airfoils at these Reynolds numbers. Airfoil shapes based on the flow field characteristics of the corrugated airfoil were built and analyzed. Their performances were compared to those of the corrugated airfoil, stressing the advantages of the latter. It was found that the flow which separates from the corrugations and forms spanwise vortices intermittently reattaches to the aft-upper arc region of the airfoil. This mechanism is responsible for the relatively low intensity of the vortices in the airfoil wake, reducing the drag and increasing the flight performances of this kind of corrugated airfoil as compared to traditional low Reynolds number airfoils such as the Eppler E-61.
High efficiency GaN-based light-emitting diodes fabricated on dielectric mask-embedded structures
Authors: Lee J. W. , Sone C. , Park Y. , Lee S.-N. , Ryou J.-H. , Dupuis R. D. , Hong C.-H. , Kim H.
Published: July 2009

We report on the enhanced quantum efficiency of GaN-based light-emitting diodes (LEDs) fabricated on inverted hexagonal pyramid dielectric mask (IHPDM)-embedded structure. The ray-tracing calculation showed that the extraction efficiency of LEDs fabricated on IHPDM-embedded structure could be enhanced up to 56%. Compared to the reference, the n-GaN template grown on IHPDM-embedded structure also showed a reduction in the dislocation density by 57%, leading to an increase in photoluminescence intensity by 82%. The LED fabricated on IHPDM-embedded structure exhibited a reduction in the forward leakage current by one order of magnitude (<1.5 V) and an enhancement in the output power by 41%.
Athermalization in atomic force microscope based force spectroscopy using matched microstructure coupling
Authors: Torun H. , Finkler O. , Degertekin F. L.
Published: July 2009

The authors describe a method for athermalization in atomic force microscope (AFM) based force spectroscopy applications using microstructures that thermomechanically match the AFM probes. The method uses a setup where the AFM probe is coupled with the matched structure and the displacements of both structures are read out simultaneously. The matched structure displaces with the AFM probe as temperature changes, thus the force applied to the sample can be kept constant without the need for a separate feedback loop for thermal drift compensation, and the differential signal can be used to cancel the shift in zero-force level of the AFM.
Theoretical investigation of the divacancies in boron nitride nanotubes: Properties and surface reactivity toward various adsorbates
Authors: Zhao Jing-xiang , Ding Yi-hong
Published: July 2009

The recent study has shown that the point defects formed under electron irradiation in the boron nitride nanotubes (BNNTs) are primarily BN divacancies. In the present work, we explore the properties of BNNTs with divacancies and estimate their surface reactivity toward various adsorbates through density functional theory calculations. Divacancies in BNNTs can self-heal by spontaneously reconstructing stable structures that have two pentagons side by side with an octagon (585). The formation energies, which strongly depend on the divacancy orientation with respect to the tube axis, increase with increasing tube diameters. Compared to the reactivity of the perfect BNNT, those sites near the divacancies have a higher reactivity due to the formation of frustrated B–B and N–N bonds and the local strain induced by pentagonal and octagonal rings. The present results might be useful for deeply understanding the nature of defects in BNNTs and rendering BNNTs promising for many applications, especially in nanoelectronics.
Global transient dynamics of three-dimensional hydrodynamical disturbances in a thin viscous accretion disk
Authors: Rebusco P. , Umurhan O. M. , Kluźniak W. , Regev O.
Published: July 2009

Thin viscous Keplerian accretion disks are considered asymptotically stable, even though they can show significant dynamic activity on short time scales. In this paper the dynamics of nonaxisymmetric hydrodynamical disturbances of disks are investigated analytically, building upon the steady state three-dimensional structure and evolution of axisymmetric perturbations explored in previous work. Assuming a polytropic equation of state, solutions are found by means of an asymptotic expansion in the small parameter measuring the ratio of the disk thickness to characteristic radius. In-depth analysis shows that every perturbation that disturbs the radial velocity induces significant transient growth in the (acoustic) energy of the evolving disturbance. This effect is most evident in the density and vertical velocity. The transient growth observed is tied to the nonseparable nature of the solutions where, in particular, pattern evolution is controlled by a similarity variable composed of the radial coordinate and time. This leads to growing winding perturbations that display successive radial peaks and troughs. We argue that these transient nonaxisymmetric structures may precipitate secondary instabilities which, consequently, may be a critical element for a new alternative picture of turbulence arousal in nonmagnetized astrophysical disks.
Transfer of patterned vertically aligned carbon nanotubes onto plastic substrates for flexible electronics and field emission devices
Authors: Tsai T. Y. , Lee C. Y. , Tai N. H. , Tuan W. H.
Published: July 2009

A direct transfer method for fabricating flexible electronics without the assistance of an adhesive layer and stamp is reported in this paper. This rapid and simple method provides an approach for the application of vertically aligned carbon nanotubes (VA-CNTs) on plastic substrates. After transfer, the VA-CNTs maintained their initial orientation in the designed pattern and showed sufficient adhesion to the substrate under extreme bending conditions. The flexible device performed an emission on the transparent substrate and showed a low turn-on of 1.13 V/μm. This VA-CNT-based flexible device, which exhibits electrical resistance sensitive to bending, is also described herein.
First-principles study to obtain evidence of low interface defect density at Ge/GeO2 interfaces
Authors: Saito Shoichiro , Hosoi Takuji , Watanabe Heiji , Ono Tomoya
Published: July 2009

We present evidence of low defect density at Ge/GeO2 interfaces on the basis of first-principles total energy calculations. The energy advantages of atom emission from the Ge/GeO2 interface to release stress due to lattice mismatch are compared with those from the Si/SiO2 interface. The advantages of Ge/GeO2 are found to be less than those of Si/SiO2 because of the high flexibility of the bonding networks in GeO2. Thus, the suppression of Ge-atom emission during the oxidation process leads to improved electrical properties of the Ge/GeO2 interfaces.
Ultrafast optical control of terahertz surface plasmons in subwavelength hole arrays at room temperature
Authors: Azad Abul K. , Chen Hou-Tong , Kasarla Satish R. , Taylor Antoinette J. , Tian Zhen , Lu Xinchao , Zhang Weili , Lu Hong , Gossard Arthur C. , O’Hara John F.
Published: July 2009

We demonstrate optical control of surface plasmon enhanced resonant terahertz transmission in two-dimensional subwavelength metallic hole arrays fabricated on gallium arsenide based substrates. Optically pumping the arrays creates a conductive layer in the substrate, reducing the terahertz transmission amplitude of both the resonant mode and the direct transmission. Under low optical fluence, the terahertz transmission is more greatly affected by resonance damping than by propagation loss in the substrate. An ErAs:GaAs nanoisland superlattice substrate is shown to allow ultrafast control with a switching recovery time of ∼10 ps.
Double magnetic tunnel junctions with cross-magnetization configurations for electrical detection of domain-wall structures
Authors: Uemura Tetsuya , Sawada Keisuke , Matsuda Ken-ichi , Yamamoto Masafumi
Published: July 2009

A device consisting of double magnetic tunnel junctions with cross-magnetization configurations is proposed to enable simultaneous electrical detection of both the structure and motion of a domain-wall (DW). Operation of this device has been confirmed through micromagnetic simulation. Owing to the cross-magnetization configurations, two types of DW structure formed in a ferromagnetic wire were clearly identified: a transverse wall (TW) in which the magnetization at the center of the wall is directed transversely to the wire axis and a vortex wall (VW) in which the magnetization circulates in the plane around a small perpendicular vortex core. In addition to the structural difference between TW and VW, the velocity of the DW motion was detected through the time response of the tunneling magnetoresistance.
Nonsingular two dimensional cloak of arbitrary shape
Authors: Hu Jin , Zhou Xiaoming , Hu Gengkai
Published: July 2009

We propose a general method to circumvent the singularity (infinitely large values of material parameters) of arbitrary two dimensional (2D) cloaks. The presented method is based on the deformation view of the transformation design method. It is shown that by adjusting the principle stretch out of the cloaking plane, 2D cloaks of arbitrary shapes without singularity can be constructed. It is also demonstrated that the method based on the equivalent dispersion relation and the design method for nonsingular 2D cloak from mirror-symmetric cross section of a three dimensional (3D) cloak can be derived from the proposed theory. Examples of a cylindrical electromagnetic cloak and an arbitrary shaped 2D electromagnetic cloak without singularity are provided to demonstrate the method.
Broadband high-efficiency surface-plasmon-polariton coupler with silicon-metal interface
Authors: Tian Jie , Yu Shuqing , Yan Wei , Qiu Min
Published: July 2009

A high efficiency surface plasmonic coupler composed of a tapered silicon strip waveguide and a subwavelength scale metal gap waveguide is experimentally demonstrated. By tuning the parameters of the taper and the metal gap, the theoretical coupling efficiencies can be as high as 88% for a wide wavelength range. A silicon-gold plasmonic coupler is then fabricated, demonstrating 35% coupling efficiency per facet. Our experimental demonstration is a crucial step for hybrid integration of plasmonic components with conventional dielectric components.
Current conduction of 0.72 nm equivalent-oxide-thickness LaO/HfO2 stacked gate dielectrics
Authors: Liu Chuan-Hsi , Chen Hung-Wen , Chen Shung-Yuan , Huang Heng-Sheng , Cheng Li-Wei
Published: July 2009

Metal-oxide-semiconductor capacitors (MOSCs) incorporating atomic layer deposited (ALD) LaO/HfO2 stacked gate dielectrics were fabricated, where the equivalent oxide thickness (EOT) of the high-k dielectrics is only 0.72 nm and the gate leakage (Jg) is as low as 6.8×10−2 A/cm2. Based on the analysis of the temperature dependence of the gate leakage current from 300 to 500 K, the main current conduction is found to be Schottky emission or Poole–Frankel emission. Moreover, the barrier height (ΦB) at TaC and HfLaO interface is estimated to be about 1.21 eV, and the trap energy level (Φt) is about 0.51 eV.
Existence conditions for single-vertex structure of polarization in ferroelectric nanoparticles
Authors: Su Yu , Du Jing-Na
Published: July 2009

The distribution of polarization in low-dimensional ferroelectric nanostructures appears to form vertex structures under open-circuit boundary conditions. A thermodynamics-based continuum phase field approach is employed to investigate the conditions for existence of single-vertex structure in two-dimensional (2D) square-shaped nanodots. It has been observed that, for a given material, such structure exists only in a certain range in dimension, which is associated to an exchange energy parameter in the model. It has been further noticed that, instead of a double-vertex structure, a single-vertex distribution remains in a 2D rectangular-shaped nanodot with initial conditions of polarization in favor of single-toroid shape.
Large-scale production and study of a synthetic G protein-coupled receptor: Human olfactory receptor 17-4
Authors: Cook Brian L. , Steuerwald Dirk , Kaiser Liselotte , Graveland-Bikker Johanna , Vanberghem Melanie , Berke Allison P. , Herlihy Kara , Pick Horst , Vogel Horst , Zhang Shuguang
Published: July 2009

Although understanding of the olfactory system has progressed at the level of downstream receptor signaling and the wiring of olfactory neurons, the system remains poorly understood at the molecular level of the receptors and their interaction with and recognition of odorant ligands. The structure and functional mechanisms of these receptors still remain a tantalizing enigma, because numerous previous attempts at the large-scale production of functional olfactory receptors (ORs) have not been successful to date. To investigate the elusive biochemistry and molecular mechanisms of olfaction, we have developed a mammalian expression system for the large-scale production and purification of a functional OR protein in milligram quantities. Here, we report the study of human OR17-4 (hOR17-4) purified from a HEK293S tetracycline-inducible system. Scale-up of production yield was achieved through suspension culture in a bioreactor, which enabled the preparation of >10 mg of monomeric hOR17-4 receptor after immunoaffinity and size exclusion chromatography, with expression yields reaching 3 mg/L of culture medium. Several key post-translational modifications were identified using MS, and CD spectroscopy showed the receptor to be ≈50% α-helix, similar to other recently determined G protein-coupled receptor structures. Detergent-solubilized hOR17-4 specifically bound its known activating odorants lilial and floralozone in vitro, as measured by surface plasmon resonance. The hOR17-4 also recognized specific odorants in heterologous cells as determined by calcium ion mobilization. Our system is feasible for the production of large quantities of OR necessary for structural and functional analyses and research into OR biosensor devices.
Supply and demand determine the market value of food providers in wild vervet monkeys
Authors: Fruteau Cécile , Voelkl Bernhard , van Damme Eric , Noë Ronald
Published: July 2009

Animals neither negotiate verbally nor conclude binding contracts, but nevertheless regularly exchange goods and services without overt coercion and manage to arrive at agreements over exchange rates. Biological market theory predicts that such exchange rates fluctuate according to the law of supply and demand. Previous studies showed that primates pay more when commodities become scarcer: subordinates groomed dominants longer before being tolerated at food sites in periods of shortage; females groomed mothers longer before obtaining permission to handle their infants when there were fewer newborns and males groomed fertile females longer before obtaining their compliance when fewer such females were present. We further substantiated these results by conducting a 2-step experiment in 2 groups of free-ranging vervet monkeys in the Loskop Dam Nature Reserve, South Africa. We first allowed a single low-ranking female to repeatedly provide food to her entire group by triggering the opening of a container and measured grooming bouts involving this female in the hour after she made the reward available. We then measured the shifts in grooming patterns after we added a second food container that could be opened by another low-ranking female, the second provider. All 4 providers received more grooming, relative to the amount of grooming they provided themselves. As biological market theory predicts, the initial gain of first providers was partially lost again after the introduction of a second provider in both groups. We conclude that grooming was fine-tuned to changes in the value of these females as social partners.
Model structure of APOBEC3C reveals a binding pocket modulating ribonucleic acid interaction required for encapsidation
Authors: Stauch Benjamin , Hofmann Henning , Perković Mario , Weisel Martin , Kopietz Ferdinand , Cichutek Klaus , Münk Carsten , Schneider Gisbert
Published: July 2009

Human APOBEC3 (A3) proteins form part of the intrinsic immunity to retroviruses. Carrying 1 or 2 copies of a cytidine deaminase motif, A3s act by deamination of retroviral genomes during reverse transcription. HIV-1 overcomes this inhibition by the Vif protein, which prevents incorporation of A3 into virions. In this study we modeled and probed the structure of APOBEC3C (A3C), a single-domain A3 with strong antilentiviral activity. The 3-dimensional protein model was used to predict the effect of mutations on antiviral activity, which was tested in a Δ
vif
simian immunodeficiency virus (SIV) reporter virus assay. We found that A3C activity requires protein dimerization for antiviral activity against SIV. Furthermore, by using a structure-based algorithm for automated pocket extraction, we detected a putative substrate binding pocket of A3C distal from the zinc-coordinating deaminase motif. Mutations in this region diminished antiviral activity by excluding A3C from virions. We found evidence that the small 5.8S RNA specifically binds to this locus and mediates incorporation of A3C into virus particles.
Asymmetrical cross-resistance betweenBacillus thuringiensistoxins Cry1Ac and Cry2Ab in pink bollworm
Authors: Tabashnik Bruce E. , Unnithan Gopalan C. , Masson Luke , Crowder David W. , Li Xianchun , Carrière Yves
Published: July 2009

Transgenic crops producingBacillus thuringiensis(Bt) toxins kill some key insect pests and can reduce reliance on insecticide sprays. Sustainable use of such crops requires methods for delaying evolution of resistance by pests. To thwart pest resistance, some transgenic crops produce 2 different Bt toxins targeting the same pest. This “pyramid” strategy is expected to work best when selection for resistance to 1 toxin does not cause cross-resistance to the other toxin. The most widely used pyramid is transgenic cotton producing Bt toxins Cry1Ac and Cry2Ab. Cross-resistance between these toxins was presumed unlikely because they bind to different larval midgut target sites. Previous results showed that laboratory selection with Cry1Ac caused little or no cross-resistance to Cry2A toxins in pink bollworm (Pectinophora gossypiella), a major cotton pest. We show here, however, that laboratory selection of pink bollworm with Cry2Ab caused up to 420-fold cross-resistance to Cry1Ac as well as 240-fold resistance to Cry2Ab. Inheritance of resistance to high concentrations of Cry2Ab was recessive. Larvae from a laboratory strain resistant to Cry1Ac and Cry2Ab in diet bioassays survived on cotton bolls producing only Cry1Ac, but not on cotton bolls producing both toxins. Thus, the asymmetrical cross-resistance seen here does not threaten the efficacy of pyramided Bt cotton against pink bollworm. Nonetheless, the results here and previous evidence indicate that cross-resistance occurs between Cry1Ac and Cry2Ab in some key cotton pests. Incorporating the potential effects of such cross-resistance in resistance management plans may help to sustain the efficacy of pyramided Bt crops.
High-pressure photodissociation of water as a tool for hydrogen synthesis and fundamental chemistry
Authors: Ceppatelli Matteo , Bini Roberto , Schettino Vincenzo
Published: July 2009

High-pressure methods have been demonstrated to be efficient in providing new routes for the synthesis of materials of technological interest. In several molecular compounds, the drastic pressure conditions required for spontaneous transformations have been lowered to the kilobar range by photoactivation of the reactions. At these pressures, the syntheses are accessible to large-volume applications and are of interest to bioscience, space, and environmental chemistry. Here, we show that the short-lived hydroxyl radicals, produced in the photodissociation of water molecules by near-UV radiation at room temperature and pressures of a few tenths of a gigapascal (GPa), can be successfully used to trigger chemical reactions in mixtures of water with carbon monoxide or nitrogen. The detection of molecular hydrogen among the reaction products is of particular relevance. Besides the implications in fundamental chemistry, the mild pressure and irradiation conditions, the efficiency of the process, and the nature of the reactant and product molecules suggest applications in synthesis.
Ku86 represses lethal telomere deletion events in human somatic cells
Authors: Wang Yongbao , Ghosh Goutam , Hendrickson Eric A.
Published: July 2009

Nonhomologous end joining (NHEJ), a form of DNA double-strand break (DSB) repair, is conserved from bacteria to humans. One essential NHEJ factor is Ku, which consists of a heterodimer of Ku70 and Ku86. In a plethora of model systems, null mutations for Ku70 or Ku86 present with defects in DNA DSB repair, variable(diversity)joining [V(D)J] recombination, and/or telomere maintenance. The complete loss of Ku from bacteria to mice is, however, compatible with viability. In striking contrast, human patients with mutations of either Ku subunit have never been described. Here, we have used recombinant adeno-associated virus-mediated gene targeting to produce a human somatic cell line that expresses a conditionally null allele of Ku86. The induced loss of Ku86 results in cell death accompanied by massive telomere loss in the form of t-circles. Thus, Ku86 is an essential gene in human somatic cells because of its requirement, not in NHEJ or V(D)J recombination, but in telomere maintenance.
Identification of tumor-associated, MHC class II-restricted phosphopeptides as targets for immunotherapy
Authors: Depontieu Florence R. , Qian Jie , Zarling Angela L. , McMiller Tracee L. , Salay Theresa M. , Norris Andrew , English A. Michelle , Shabanowitz Jeffrey , Engelhard Victor H. , Hunt Donald F. , Topalian Suzanne L.
Published: July 2009

The activation and recruitment of CD4+T cells are critical for the development of efficient antitumor immunity and may allow for the optimization of current cancer immunotherapy strategies. Searching for more optimal and selective targets for CD4+T cells, we have investigated phosphopeptides, a new category of tumor-derived epitopes linked to proteins with vital cellular functions. Although MHC I-restricted phosphopeptides have been identified, it was previously unknown whether human MHC II molecules present phosphopeptides for specific CD4+T cell recognition. We first demonstrated the fine specificity of human CD4+T cells to discriminate a phosphoresidue by using cells raised against the candidate melanoma antigen mutant B-Raf or its phosphorylated counterpart. Then, we assessed the presence and complexity of human MHC II-associated phosphopeptides by analyzing 2 autologous pairs of melanoma and EBV-transformed B lymphoblastoid lines. By using sequential affinity isolation, biochemical enrichment, mass spectrometric sequencing, and comparative analysis, a total of 175 HLA-DR-associated phosphopeptides were characterized. Many were derived from source proteins that may have roles in cancer development, growth, and metastasis. Most were expressed exclusively by either melanomas or transformed B cells, suggesting the potential to define cell type-specific phosphatome “fingerprints.” We then generated HLA-DRβ1*0101-restricted CD4+T cells specific for a phospho-MART-1 peptide identified in both melanoma cell lines. These T cells showed specificity for phosphopeptide-pulsed antigen-presenting cells as well as for intact melanoma cells. This previously undescribed demonstration of MHC II-restricted phosphopeptides recognizable by human CD4+T cells provides potential new targets for cancer immunotherapy.