bluuebunny/crossref_metadata_2025 huggingface dataset:
Source and development of large manganese enrichments above eastern Mediterranean sapropel S1
Authors: Reitz Anja , Thomson John , de Lange Gert J. , Hensen Christian
Published: August 2006

The residual dark unit of the most recent eastern Mediterranean sapropel (S1) is usually overlain by sediments with enhanced concentrations of MnOx in two separated layers. The variability and magnitude of the Mn enrichment at different locations and water depths indicate that Mn must have been added preferentially to sediments at intermediate (1–2 km) water depths. We propose a two‐stage mechanism for the Mn enrichment that involves decreasing oxygenation with increasing water depth. This mechanism involves the loss of reduced Mn2+ from the deepest sediments (>2 km water depth) into overlying anoxic waters and a variable gain of MnOx in sediments in contact with oxygenated waters at shallower depth. In the S1 unit that receives the extra MnOx input, an upper higher Mn‐enriched zone (>3 wt %) is maintained continuously at the top of the accumulating S1 unit because the pore waters are anoxic at shallow sediment depth while bottom waters are oxic to some degree. In a reactive‐transport model, the Mn enrichment in the upper zone could not be supported by normal sediment diagenesis. Thus the MnOx in the upper Mn horizon must have formed mainly in the water column. The MnOx in the upper Mn‐enriched zone adsorbed Mo and Li from seawater in a similar manner as other Mn‐enriched oxic sediments, nodules, and crusts, with a Mn:Mo ratio of ∼600:1, a Mn:Li ratio of ∼750:1, and a δ98/95MoMOMO of −2.5 ‰.
The reconstructed Indonesian warm pool sea surface temperatures from tree rings and corals: Linkages to Asian monsoon drought and El Niño–Southern Oscillation
Authors: D'Arrigo Rosanne , Wilson Rob , Palmer Jonathan , Krusic Paul , Curtis Ashley , Sakulich John , Bijaksana Satria , Zulaikah Siti , Ngkoimani La Ode , Tudhope Alexander
Published: August 2006

The west Pacific warm pool is the heat engine for the globe's climate system. Its vast moisture and heat exchange profoundly impact conditions in the tropics and higher latitudes. Here, September–November sea surface temperature (SST) variability is reconstructed for the warm pool region (15°S–5°N, 110–160°E) surrounding Indonesia using annually resolved teak ring width and coral δ18O records. The reconstruction dates from A.D. 1782–1992 and accounts for 52% of the SST variance over the most replicated period. Significant correlations are found with El Niño–Southern Oscillation (ENSO) and monsoon indices at interannual to decadal frequency bands. Negative reconstructed SST anomalies coincide with major volcanic eruptions, while other noteworthy extremes are at times synchronous with Indian and Indonesian monsoon drought, particularly during major warm ENSO episodes. While the reconstruction adds to the sparse network of proxy reconstructions available for the tropical Indo‐Pacific, additional proxies are needed to clarify how warm pool dynamics have interacted with global climate in past centuries to millennia.
Role of dispersive effects in determining probe and electromagnetic parameters by time domain reflectometry
Authors: Mattei Elisabetta , Di Matteo Andrea , De Santis Alberto , Pettinelli Elena , Vannaroni Giuliano
Published: August 2006

Time domain reflectometry (TDR) measurements, performed in a cylindrical tube filled with air, glass beads, and water, are analyzed in the time and frequency domains. In the time domain, air and water provide contrasting results of the probe length if the standard tangent line fitting procedure is used. An alternative method, based on the time derivative of the TDR response, is introduced. Its application suggests that the anomalous result provided by the tangent method in water is explained by dispersion effects. To account for the frequency dependence of the permittivity, an analysis in the frequency domain is performed. The problems of the input function choice and of the noise control are investigated. This allows us to correct the experimental scatter function S(ν) and to perform the best fit of its parameterized expression, which is theoretically evaluated from the Debye model of the permittivity. Consistent values of the probe length are derived. It is concluded that the tangent method cannot be applied for determining the geometrical and electromagnetic parameters of a probe filled by dispersive media. As an application, the calibrated probe is used for measuring the TDR trace of glass beads, which simulate sandy soils, and for deriving the frequency‐dependent permittivity within the Debye model.
Light scattering by single ice crystals of cirrus clouds
Authors: Shcherbakov Valery , Gayet Jean‐François , Jourdan Olivier , Ström Johan , Minikin Andreas
Published: August 2006

In situ measurements of angular scattering intensities (ASIs) related to single ice crystals of cirrus clouds were obtained for the first time with the airborne Polar Nephelometer instrument. These observations were performed in the southern mid‐latitudes during the INCA project. The analysis of the data shows that the well marked peaks of the ASIs are undoubtedly attributed to quasi‐specular reflections from crystal facets and the refracted rays passed through the ice crystals. Emphasizing that it is not enough to know the shape of the crystal, but also the internal structure is of great importance. Ray tracing simulations reproduce most of the observed ASIs features. The model of surface roughness, which assumes the Weibull statistics, enables to reproduce the quasi‐specular external reflection from crystal facets. It follows from the retrievals that the surface of the crystals was deeply rough and the amount of the internal inclusions (air bubbles) was quite high.
Configuration of the Indian Moho beneath the NW Himalaya and Ladakh
Authors: Rai S. S. , Priestley K. , Gaur V. K. , Mitra S. , Singh M. P. , Searle M.
Published: August 2006

Teleseismic receiver function analysis of seismograms recorded on a ∼700 km long profile of 17 broadband seismographs traversing the NW Himalaya shows a progressive northward deepening of the Indian Moho from ∼40 km beneath Delhi south of the Himalayan foredeep to ∼75 km beneath Taksha at the Karakoram Fault. Similar studies by Wittlinger et al. (2004) to the north of the Karakoram Fault show that the Moho continues to deepen to ∼90 km beneath western Tibet before shallowing substantially to 50–60 km at the Altyn Tagh Fault. The continuity of the Indian Moho imaged in the receiver functions reported here, along with those of Wittlinger et al. (2004), suggest that in this part of the Himalayan orogen the Indian plate may penetrate as far as the Bangong Suture, and possibly as far north as the Altyn Tagh.
On the flux of oxygenated volatile organic compounds from organic aerosol oxidation
Authors: Kwan Alan J. , Crounse John D. , Clarke Antony D. , Shinozuka Yohei , Anderson Bruce E. , Crawford James H. , Avery Melody A. , McNaughton Cameron S. , Brune William H. , Singh Hanwant B. , Wennberg Paul O.
Published: August 2006

Previous laboratory and field studies suggest that oxidation of organic aerosols can be a source of oxygenated volatile organic compounds (OVOC). Using measurements of atmospheric oxidants and aerosol size distributions performed on the NASA DC‐8 during the INTEX‐NA campaign, we estimate the potential magnitude of the continental summertime OVOC flux from organic aerosol oxidation by OH to be as large as ∼70 pptv C/day in the free troposphere. Contributions from O3, H2O2, photolysis, and other oxidants may increase this estimate. These processes may provide a large, diffuse source of OVOC that has not been included in current atmospheric models, and thus have a significant impact on our understanding of organic aerosol, OVOC, PAN, and HOx chemistry. The potential importance and highly uncertain nature of our estimate highlights the need for more field and laboratory studies on organic aerosol composition and aging.
Observations of an interplanetary slow shock associated with magnetic cloud boundary layer
Authors: Zuo P. B. , Wei F. S. , Feng X. S.
Published: August 2006

The observations of the slow shocks associated with the interplanetary coronal mass ejections near 1 AU have seldom been reported in the past several decades. In this paper we report the identification of an interplanetary slow shock observed by Wind on September 18, 1997. This slow shock is found to be just the front boundary of a magnetic cloud boundary layer. A self‐consistent method based on the entire R‐H relations is introduced to determine the shock normal. It is found that the observations of the jump conditions across the shock are in good agreement with the R‐H solutions. The intermediate Mach numberMI=Un/(VAcosθBn) is less than 1 on both sides of the shock. In the upstream region, the slow Mach numberMs1=Un1/Vs1is 1.44 (above unity), and in the downstream region, the slow Mach numberMs2=Un2/Vs2is 0.8 (below unity). HereVsandVArepresent the slow magnetoacoustic speed and Alfvén speed respectively. In addition, the typical interior magnetic structure inside the shock layer is also analyzed using the 3s time resolution magnetic field data since the time for the spacecraft traversing the shock layer is much longer (about 17s). As a potential explanation to the formation of this kind of slow shock associated with magnetic clouds, this slow shock could be a signature of reconnection that probably occurs inside the magnetic cloud boundary layer.
Two‐decadal aerosol trends as a likely explanation of the global dimming/brightening transition
Authors: Streets David G. , Wu Ye , Chin Mian
Published: August 2006

Global average trends in solar radiation reaching the Earth's surface show a transition from dimming to brightening that occurred in about 1990. We show that the inter‐annual trend in solar radiation between 1980 and 2000 mirrors the trend in primary emissions of SO2 and black carbon, which together contribute about one‐third of global average aerosol optical depth. Combined global emissions of these two species peaked in 1988–1989. The two‐decadal rate of decline in aerosol loading resulting from these emission changes, 0.13% yr−1, can be compared with the reported increase in solar radiation of 0.10% yr−1 in 1983–2001. Regional patterns of aerosol and radiation changes are also qualitatively consistent. We conclude that changes in the aerosol burden due to changing patterns of anthropogenic emissions are likely contributing to the trends in surface solar radiation.
A new approach to modeling non‐force free coronal magnetic field
Authors: Hu Qiang , Dasgupta Brahmananda
Published: August 2006

We propose a new approach to deriving the local three‐dimensional (3D) non‐force free coronal magnetic field structure from photospheric vector magnetograph measurements. Based on the Principle of Minimum Dissipation Rate, a general non‐force free magnetic field can be expressed as the superposition of two linear (constant‐α) force free field. The parameter, α, for each of the two linear force free field, can be determined by optimizing the requirement that the recovered transverse magnetic field components as the superposition of the corresponding components of the two linear force free field agree with the observed ones at the photospheric level. A preliminary test case study of an analytic non‐force free field model is presented to illustrate the method. We discuss the difficulties associated with the linear force free field extrapolation and the feasibility of our method.
Anomalous resistivity of current-driven isothermal plasmas due to phase space structuring
Authors: Büchner Jörg , Elkina Nina
Published: August 2006

The anomalous electric resistivity of collisionless plasmas is an important issue in the physics of hot plasmas, e.g., in the context of auroral particle acceleration and of reconnection in the solar corona. The linear stability theory of isothermal current driven space plasmas predicts an ion-acoustic instability if the relative drift velocity of the current carrying particles exceeds a certain threshold, which, generally, depends on the plasma parameters. The spectrum of waves, excited by a marginal instability, is very narrow. Hence, the wave power at saturation and the corresponding electric resistivity due to wave-particle interaction cannot be obtained by means of a quasilinear, weak turbulence approach and the nonlinear single mode theory provides too small saturation amplitudes. To solve the nonlinear problem a newly developed unsplit conservative Eulerian Vlasov code is applied to simulate a strongly magnetized current driven plasma, which can be considered in 1D1V (one spatial, one velocity space direction). Instead of periodic boundary conditions, usually used as they are simpler to treat, open boundaries are implemented which allow to maintain a constant current flow. Simulated is a typical almost isothermal (Te=2Ti) hot (κTi=1keV) space plasma for the real mass ratio mi∕me=1836. The initial spontaneous instability is followed by a three-stage nonlinear evolution: First electron trapping leads to the formation of electron phase space holes. Due to a steepening of the leading edges of the potential wells the electron phase space holes gradually become asymmetric, they grow in size and deepen. The phase space holes accelerate until they move much faster than the initial ion-acoustic waves. The interaction of the current carriers with the asymmetric potential wells and causes a nonvanishing net momentum transfer between the particles and the self-generated electric field. After a few ion plasma periods ion trapping starts until, finally, an electrostatic double layer arises. It is found that the nonlinear saturated state of the system is dominated by the particle interaction with coherent phase space structures. The corresponding anomalous resistivity is slightly modulated with an oscillation period τ≈ωpi−1). For a macroscopic description its major part can be parameterized by means of an effective collision rate νeff of the order of 10−2ωpe≈0.5ωpi, where ωpe is the electron and ωpi the ion plasma frequency.
Segmental dynamics in poly(methyl acrylate) on silica: Molecular-mass effects
Authors: Metin Burak , Blum Frank D.
Published: August 2006

The effect of molecular mass on the segmental dynamics of poly(methyl acrylate) (PMA) adsorbed on silica was studied using deuterium quadrupole-echo nuclear magnetic resonance (NMR) and modulated differential scanning calorimetry. Samples adsorbed on silica (all about 1.5mgPMA∕m2 silica) were shown to have more restricted segmental mobility, and higher Tg’s, than the corresponding bulk PMA samples. Around the glass-transition region, adsorbed samples exhibited segmental mobility, which could be classified as heterogeneous due to a superposition of more-mobile and less-mobile components present in the deuterium NMR spectra. This heterogeneity was consistent with a motional gradient with more-mobile segments near the polymer-air interface and the less-mobile species near the polymer-silica interface. The mobility of the adsorbed 77kDa PMA sample was the lowest among the four different molecular-mass samples studied. Samples studied with masses both larger and smaller than 77kDa had larger mobile-component fractions in the adsorbed polymer. The additional mobility was attributed to the presence of either longer tail and loop conformations in the higher molecular-mass samples or the inherent mobility of the tails in the lower molecular-mass samples on the surface.
On the possible manifestation of harmonic-anharmonic dynamical transition in glassy media in electron paramagnetic resonance of nitroxide spin probes
Authors: Dzuba S. A. , Kirilina E. P. , Salnikov E. S.
Published: August 2006

Continuous wave (cw) electron paramagnetic resonance (EPR) and echo-detected (ED) EPR were applied to study molecular motions of nitroxide spin probes in glassy glycerol and o-terphenyl. A linear decrease with increasing temperature of the total splitting in the cw EPR line shape was observed at low temperatures in both solvents. Above some temperature points the temperature dependencies become sharper. Within the model of molecular librations, this behavior is in qualitative and quantitative agreement with the numerical data on neutron scattering and Mössbauer absorption for molecular glasses and biomolecules, where temperature dependence of the mean-squared amplitude of the vibrational motion was obtained. In analogy with these data the departure from linear temperature dependence in cw EPR may be ascribed to the transition from harmonic to anharmonic motion (this transition is called dynamical transition). ED EPR spectra were found to change drastically above 195K in glycerol and above 245K in o-terphenyl, indicating the appearance of anisotropic transverse spin relaxation. This appearance may also be attributed to the dynamical transition as an estimation shows the anisotropic relaxation rates for harmonic and anharmonic librational motions and because these temperature points correspond well to those known from neutron scattering for these solvents. The low sensitivity of ED EPR to harmonic motion and its high sensitivity to the anharmonic one suggests that ED EPR may serve as a sensitive tool to detect dynamical transition in glasses and biomolecules.
Chemical diffusion of CO in mixed CO+O adlayers and reaction-front propagation in CO oxidation on Pd(100)
Authors: Liu Da-Jiang , Evans J. W.
Published: August 2006

Within the framework of a realistic atomistic lattice-gas model, we present the theoretical formulation and simulation procedures for precise analysis of the chemical diffusion flux of highly mobile CO within a nonuniform interacting mixed CO+O adlayer on a Pd(100) surface. The approach applies in both regimes of relatively immobile unequilibrated and fairly mobile near-equilibrated O adlayer distributions. Spatiotemporal behavior in surface reactions is controlled by chemical diffusion in mixed adlayers. Thus, we naturally integrate the above analysis with a previously developed multiscale modeling strategy to describe mesoscale reaction front propagation in CO oxidation on Pd(100). This treatment avoids using a simplified prescription of chemical diffusion and reaction kinetics as in traditional mean-field reaction-diffusion equation approaches.
Minimally disturbing Heisenberg–Weyl symmetric measurements using hard-core collisions of Schrödinger particles
Authors: Janzing Dominik , Decker Thomas
Published: August 2006

In a previous paper we have presented a general scheme for the implementation of symmetric generalized measurements (POVMs) on a quantum computer. This scheme is based on representation theory of groups and methods to decompose matrices that intertwine two representations. We extend this scheme in such a way that the measurement is minimally disturbing, i.e., it changes the state vector ∣Ψ⟩ of the system to Π∣Ψ⟩ where Π is the positive operator corresponding to the measured result. Using this method, we construct quantum circuits for measurements with Heisenberg–Weyl symmetry. A continuous generalization leads to a scheme for optimal simultaneous measurements of position and momentum of a Schrödinger particle moving in one dimension such that the outcomes satisfy ΔxΔp⩾ℏ. The particle to be measured collides with two probe particles, one for the position and the other for the momentum measurement. The position and momentum resolution can be tuned by the entangled joint state of the probe particles which is also generated by a collision with hard-core potential. The parameters of the POVM can then be controlled by the initial widths of the wave functions of the probe particles. We point out some formal similarities and differences to simultaneous measurements of quadrature amplitudes in quantum optics.
Formation of germanium nanocrystals embedded in silicon-oxygen-nitride layer
Authors: Tu Chun-Hao , Chang Ting-Chang , Liu Po-Tsun , Liu Hsin-Chou , Tsai Chia-Chou , Chang Li-Ting , Tseng Tseung-Yuan , Sze Simon M. , Chang Chun-Yen
Published: August 2006

The formation of germanium nanocrystals embedded in silicon-oxygen nitride with distributed charge storage elements is proposed in this work. A large memory window is observed due to isolated Ge nanocrystals in the SiON gate stack layer. The Ge nanocrystals were nucleated after high temperature oxidized SiGeN layer. The nonvolatile memory with the Ge nanocrystals embedded in SiON stack layer exhibits 4V threshold voltage shift under 10V write operation. Also, the manufacture technology using the sequent high-temperature oxidation of the a-Si layer acting as the blocking oxide is proposed to enhance the performance of nonvolatile memory devices.
Existence of bulk acoustic modes in pair plasmas
Authors: Verheest Frank
Published: August 2006

In view of applications to electron-positron and fullerene pair plasmas, a thorough discussion is given of the dispersion of linear electrostatic waves, before finding the parameter ranges in which stationary nonlinear electrostatic modes can exist, when there is a thermodynamic asymmetry between both constituents. Arguments for such an asymmetry can be found in the observed dispersion in fullerene pair plasma experiments, but point to small asymmetries. The existence of solitary modes is first discussed in general terms for various polytropic pressure-density relations, showing that the solitons are always compressive in both pair components. For large thermal asymmetries, there is at most a doubling of the densities, but small asymmetries lead to weakly nonlinear amplitudes, described by familiar Korteweg-de Vries solitons. Observations of an intermediate wave in the theoretical gap between the acoustic and Langmuir branches of the linear dispersion diagram might be accounted for, at least partially, by a train of weak solitons, as the difference between weak solitary modes and linear harmonic waves is rather difficult to ascertain experimentally.
Observations of x-ray radiation pressure force on individual gold nanocrystals
Authors: Sasaki Yuji C. , Okumura Yasuaki , Miyazaki Takuya , Higurashi Takashi , Oishi Noboru
Published: August 2006

We report observations of x-ray radiation pressure force on individual single nanocrystals using an x-ray single molecular methodology. The observed gold nanocrystals are linked to the adsorbed protein molecules. We observed the directed Brownian motion of individual linked nanocrystals. The observed force is estimated at about 0.13–0.63aN. We will be able to control and measure dynamics of micro- or nanocrystalline materials using x-ray radiation pressure force.
Improved n-type organic transistors by introducing organic heterojunction buffer layer under source/drain electrodes
Authors: Yan Xuanjun , Wang Jun , Wang Haibo , Wang He , Yan Donghang
Published: August 2006

N -type organic thin-film transistors (OTFTs) employing hexadecafluorophthalocyaninatocopper (F16CuPc) as active layer and p-type copper phthalocyanine (CuPc) as buffer layer are demonstrated. The highest field-effect mobility is 7.6×10−2cm2∕Vs. The improved performance was attributed to the decrease of contact resistance due to the introduction of highly conductive F16CuPc∕CuPc organic heterojunction. Therefore, current method provides an effective path to improve the performance of OTFTs.
Theoretical analysis of polydispersity in the nematic phase of self-assembled semiflexible chains
Authors: Lü Xinjiang , Kindt James T.
Published: August 2006

In recent simulations of semiflexible equilibrium polymers [X. Lü and J. T. Kindt, J. Chem. Phys. 120, 10328 (2004)] a roughly biexponential distribution of chain lengths was observed in the nematic phase. In this study, we show that a theory representing the nematic phase as an equilibrium mixture of randomly oriented chains below a critical length Lc and chains above Lc obeying a Gaussian orientational distribution reproduces this distribution qualitatively. The agreement between predicted and simulated phase boundaries is improved, with a narrower isotropic-nematic coexistence region, compared with a monoexponential chain distribution. We find, furthermore, that the critical length Lc scales as the inverse of monomer concentration, irrespective of the bond strength of the chains, but that at the phase boundary, the fraction of monomers found in disordered chains peaks at a certain bond strength.
Field-effect transistors with SrHfO3 as gate oxide
Authors: Rossel C. , Mereu B. , Marchiori C. , Caimi D. , Sousa M. , Guiller A. , Siegwart H. , Germann R. , Locquet J.-P. , Fompeyrine J. , Webb D. J. , Dieker Ch. , Seo Jin Won
Published: August 2006

The authors demonstrate that the compound SrHfO3 grown epitaxially on Si(100) by molecular-beam epitaxy is a potential gate dielectric to fabricate n- and p-metal-oxide semiconductor field-effect transistors with equivalent oxide thickness (EOT) below 1nm. The electrical properties on capacitors and transistors show low gate leakage and good capacitance and I-V output characteristics. The lower electron and hole mobilities, which are strongly limited by charge trapping, nevertheless fit well with the general trend of channel mobility reduction with decreasing EOT.
High-quality bulk a-plane GaN sliced from boules in comparison to heteroepitaxially grown thick films on r-plane sapphire
Authors: Paskova T. , Kroeger R. , Figge S. , Hommel D. , Darakchieva V. , Monemar B. , Preble E. , Hanser A. , Williams N. M. , Tutor M.
Published: August 2006

Thick GaN bars with [112̱0] orientation have been sliced from GaN boules grown on freestanding films by hydride vapor phase epitaxy (HVPE) in the [0001] direction. High-resolution x-ray diffraction and transmission electron microscopy have been used to study the structural quality and defect distribution in the material in comparison to heteroepitaxially grown thick HVPE-GaN films grown in the [112̱0] direction on (11̱02)-plane sapphire. It is demonstrated that while the heteroepitaxial material possesses a high density of stacking faults and partial dislocations, leading to anisotropic structural characteristics, the (112̱0)-plane bulk GaN, sliced from boules, exhibits low dislocation density and narrow rocking curves with isotropic in-plane character.
Development of backgammon-type multiwire proportional counters for the detection of x rays
Authors: Kimpton J. A. , Kinnane M. N. , Chantler C. T.
Published: August 2006

A multiwire proportional counter (MWPC) based on a backgammon-type design has been developed for the detection of x-ray photons in two dimensions over the energy range of 4–6keV. The MWPC was designed for operation in an experimental spectroscopy application requiring single photon counting over a wide range of count rates, high photon detection efficiency and resolution, and a highly linear response function across the detector face. A model based on attenuation of the incident x-ray beam by the various components of the detector is presented and highlights key areas for efficiency optimization. The design, construction, testing procedure, and performance of the backgammon MWPC are presented and all objectives are met including a particularly impressive differential nonlinearity.
Quantum effects in liquid water and ice: Model dependence
Authors: Hernández de la Peña Lisandro , Kusalik Peter G.
Published: August 2006

This paper explores the influence of choice of potential model on the quantum effects observed in liquid water and ice. This study utilizes standard rigid models and a more formal context for the rigid-body centroid molecular dynamics methodology used to perform the quantum simulations is provided. Quantum and classical molecular dynamics simulations are carried out for liquid water and ice Ih at 298 and 220K, respectively, with the simple point charge/extended and TIP4P-Ew water models. The results obtained for equilibrium and dynamical properties are compared with those recently reported on TIP4P [L. Hernández de la Peña and P. G. Kusalik, J. Chem. Phys. 121, 5992 (2004); L. Hernández de la Peña et al., J. Chem. Phys 123, 144506 (2005)]. For the liquid, an energy shift of about 8% and an average molecular uncertainty of about 11° were found independently of the water model. The self-diffusion coefficient consistently increases by more than 50% when going from the classical to the quantum system and quantum dynamics are found to reproduce the experimental isotopic shifts with the models examined. The ice results compare remarkably well with those previously reported for the TIP4P water model; they confirm that quantum effects are considerable and that the quantum mechanical uncertainty and the energy shifts due to quantization are smaller in ice than in liquid water. The relevance of these findings in the context of the construction of water models is briefly discussed.
A nonlinear global model of a dual frequency capacitive discharge
Authors: Mussenbrock Thomas , Ziegler Dennis , Peter Brinkmann Ralf
Published: August 2006

The behavior of dual frequency capacitively coupled plasmas is investigated. Assuming a realistic reactor configuration represented by effective geometry factors and taking into account two separate sinusoidal voltage sources operating at different frequencies, an ordinary differential equation is derived which describes the nonlinear dynamics of such discharges. An exact analytical solution of the equation is presented and employed for a parameter study of the discharge current characteristics. Simulation results for various gas pressures (=various electron-neutral collision rates), various amplitude ratios of the two independent rf sources, and various integer frequency ratios are shown. When the two frequencies are comparable, surprising nonlinear effects are observed. Particular under study is the heating at the plasma series resonance, either by direct excitation or via the nonlinear electron resonance heating mechanism.
Enhancing luminescence efficiency of InAs quantum dots at 1.5μm using a carrier blocking layer
Authors: Hsieh Tung-Po , Chiu Pei-Chin , Chyi Jen-Inn , Chang Hsiang-Szu , Chen Wen-Yen , Hsu Tzu Min , Chang Wen-Hao
Published: August 2006

The authors report an effective way to enhance the optical efficiency of InAs quantum dots (QDs) on GaAs emitting at the wavelength of 1.5μm. It is found that the loss of holes from QDs to their proximity via the high indium composition InGaAs overgrown layer, which is necessary for achieving long wavelength emission, is the origin of photoluminescence intensity degradation at high temperature. Inserting a 4nm thick Al0.45Ga0.55As layer, acting as a carrier blocking layer, into the GaAs capping matrix can improve the room temperature photoluminescence peak intensity by five and two times for the ground and first excited states, respectively.
Temperature dependence of very deep emission from an exciton bound to an isoelectronic defect in polycrystalline CuInS2
Authors: Krustok J. , Raudoja J. , Jaaniso R.
Published: August 2006

Zero-phonon lines (ZPLs) of deep exciton bound to isoelectronic deep-donor–deep-acceptor pair in CuInS2 are studied by photoluminescence. These ZPLs have peak positions at 0.6241eV (A line) and 0.6220eV (B line), followed by two series of phonon replicas with phonon energies of 8 and 40.5meV. Temperature dependence of the intensity of these ZPLs is explained by electron-phonon coupling to a single phonon mode with energy of 8meV and shows that the lines are originated from two excited state levels of the same exciton. The (anomalously strong) temperature broadening of ZPLs follows ∼T2.6 law and can be explained by assuming a strong vibronic coupling between two excited states.
FeNi-based bulk glassy alloys with superhigh mechanical strength and excellent soft-magnetic properties
Authors: Chang Chuntao , Shen Baolong , Inoue Akihisa
Published: August 2006

FeNi-based bulk glassy alloys (BGAs) with diameters up to 4mm were formed in [(Fe1−xNix)0.75B0.2Si0.05]96Nb4 system. The increase of Ni to Fe concentration ratio is effective in improving the glass-forming ability. The BGAs exhibit a superhigh fracture strength of 4150–4300MPa, Young’s modulus of 203–215GPa, elastic strain of 0.02, plastic strain of 0.0015, and a well developed vein pattern in the fracture surface. The glassy alloys also exhibit excellent soft-magnetic properties, i.e., rather high saturation magnetization of 0.8–1.1T, low coercive force of 1.2–2.3A∕m, and high permeability of 16 000–24 000 at 1kHz under a field of 1A∕m.
La
Mn
O
3
∕
Sr
Mn
O
3
interfaces with coupled charge-spin-orbital modulation
Authors: Yamada Hiroyuki , Kawasaki M. , Lottermoser T. , Arima T. , Tokura Y.
Published: August 2006

The artificial perovskite superlattices composed of LaMnO3 and SrMnO3 have been investigated to elucidate the interface electronic phases created by adjoining the two Mott insulators. Charge transfer at the interface due to chemical potential difference, as observed in p-n junctions of semiconductors, can realize metallic ferromagnet instead of resulting in insulating depletion layer. The interface electronic phases strongly depend on the orbital states at the interface which can be tuned by epitaxial strain.
Bandwidth enhancement phenomenon of a high-speed GaAs–AlGaAs based unitraveling carrier photodiode with an optimally designed absorption layer at an 830nm wavelength
Authors: Shi Jin-Wei , Li Yu-Tai , Pan Ci-Ling , Lin M. L. , Wu Y. S. , Liu W. S. , Chyi J.-I.
Published: August 2006

In this letter, the authors introduce a GaAs∕AlGaAs based unitraveling carrier photodiode (UTC-PD) for a wavelength of around 830nm. There is significant bias- and output-current-dependent bandwidth enhancement phenomena observed with this device. According to their microwave and optical-to-electrical measurement results, such distinct phenomena can occur under a much lower current density (0.3mA∕μm2 vs 0.05mA∕μm2) than previously reported for InP–InGaAs UTC-PDs. This can be attributed to the self-induced field in the absorption region, made possible due to the optimized p-type doping profile.
Multiferroic Pb(Zr0.52Ti0.48)O3–Co0.9Zn0.1Fe2O4 bilayer thin films via a solution processing
Authors: He Hong-Cai , Zhou Jian-Ping , Wang Jing , Nan Ce-Wen
Published: August 2006

Bilayer multiferroic nanocomposite films of Pb(Zr0.52Ti0.48)O3 (PZT) and Co0.9Zn0.1Fe2O4 (CZFO) were prepared on general Pt∕Ti∕SiO2∕Si substrate via a simple solution processing. Different growth sequences of PZT and CZFO on the substrate yielded two kinds of bilayered structures, i.e., PZT/CZFO/substrate. and CZFO/PZT/substrate. Structural characterization by x-ray diffraction and electron microscopies showed good surface morphology and interfaces of these bilayered thin films. Strong ferroelectric and ferromagnetic responses were simultaneously observed in the bilayered thin films, depending on their structures.
Controllable left-handed metamaterial and its application to a steerable antenna
Authors: Chen Hongsheng , Wu Bae-Ian , Ran Lixin , Grzegorczyk Tomasz M. , Kong Jin Au
Published: August 2006

A controllable left-handed metamaterial based on a varactor-loaded S-shaped resonator structure is presented to realize an active radome. By controlling the phase properties of the radome, the antenna exhibits continuous scanning capability in a range of ±40°, which is confirmed by theoretical analysis.
Dynamic behaviors of dual frequency liquid crystals in bistable chiral tilted-homeotropic nematic liquid crystal cell
Authors: Hsu Jy-Shan , Liang Bau-Jy , Chen Shu-Hsia
Published: August 2006

The switching behaviors of dual frequency liquid crystals (DFLC) in a bistable chiral tilted-homeotropic nematic (BHN) LC cell are simulated and compared with the observed results. This cell can be switched between tilted-homeotropic state and twisted state under the applied voltage as low as 5V. The reason for the low switching voltage is attributed to the dielectric anisotropy character of DFLC. The analysis also shows that the switching wave form accelerates the switching behaviors of the directors which results in faster response in BHN LC cell.
Thermochemical behavior of hydrogen in hafnium silicate films on Si
Authors: Driemeier C. , Chambers J. J. , Colombo L. , Baumvol I. J. R.
Published: August 2006

HfSiO films on Si were sequentially annealed in vacuum, oxygen, hydrogen, or deuterium atmospheres followed by quantification of H and D by nuclear reaction analysis. The observed H(D) incorporation and desorption behaviors are discussed in terms of two H bonding states in the films. Si–H bonds are easier to break thermally and formation of these bonds can be suppressed by annealing in O2 to fully oxidize Si atoms. O–H bonds are harder to break thermally. However, hydrogen atmospheres ease desorption of H in O–H species. The results indicate possible paths to achieve low H content in HfSiO gate dielectrics.
Vesicles surfing on a lipid bilayer: Self-induced haptotactic motion
Authors: Solon Jérôme , Streicher Pia , Richter Ralf , Brochard-Wyart Françoise , Bassereau Patricia
Published: August 2006

Haptotaxis is a mechanism proposed at the end of the 1960s to explain cell motility. It describes cell movement induced by an adhesion gradient. In this work, we present evidence for self-induced haptotaxis using negatively charged giant vesicles interacting with positively charged supported lipid bilayers, which has not been previously described. Depending on the charge of the vesicle, we observed different behaviors. At low charge, no adhesion occurs. At high charge, the vesicle adheres but does not move. In a restricted range of intermediate charge densities, we found that the vesicle moves spontaneously with velocities of the order of a few micrometers per second over distances of >100 μm. We show that a local lipid transfer between the giant vesicle and the supported lipid bilayer takes place during the adhesion, breaking the symmetry and inducing a lateral charge gradient. This charge gradient polarizes the giant vesicle and induces its motion. To explain our observations, we propose a scaling model that relates the adhesion energy to the velocity of vesicle motion and to the characteristic lipid transfer time. Our measurements indicate that the effective adhesion energy is strongly reduced by counterions, which are dynamically trapped between the vesicle and the supported bilayer.
Molecular and functional analysis of nicotinate catabolism in
Eubacterium barkeri
Authors: Alhapel Ashraf , Darley Daniel J. , Wagener Nadine , Eckel Elke , Elsner Nora , Pierik Antonio J.
Published: August 2006

The anaerobic soil bacterium
Eubacterium barkeri
catabolizes nicotinate to pyruvate and propionate via a unique fermentation. A full molecular characterization of nicotinate fermentation in this organism was accomplished by the following results: (
i
) A 23.2-kb DNA segment with a gene cluster encoding all nine enzymes was cloned and sequenced, (
ii
) two chiral intermediates were discovered, and (
iii
) three enzymes were found, completing the hitherto unknown part of the pathway. Nicotinate dehydrogenase, a (nonselenocysteine) selenium-containing four-subunit enzyme, is encoded by
ndhF
(FAD subunit),
ndhS
(2 x [2Fe-2S] subunit), and by the
ndhL
/
ndhM
genes. In contrast to all enzymes of the xanthine dehydrogenase family, the latter two encode a two-subunit molybdopterin protein. The 6-hydroxynicotinate reductase, catalyzing reduction of 6-hydroxynicotinate to 1,4,5,6-tetrahydro-6-oxonicotinate, was purified and shown to contain a covalently bound flavin cofactor, one [2Fe-2S]
2+/1+
and two [4Fe-4S]
2+/1+
clusters. Enamidase, a bifunctional Fe-Zn enzyme belonging to the amidohydrolase family, mediates hydrolysis of 1,4,5,6-tetrahydro-6-oxonicotinate to ammonia and (
S
)-2-formylglutarate. NADH-dependent reduction of the latter to (
S
)-2-(hydroxymethyl)glutarate is catalyzed by a member of the 3-hydroxyisobutyrate/phosphogluconate dehydrogenase family. A [4Fe-4S]-containing serine dehydratase-like enzyme is predicted to form 2-methyleneglutarate. After the action of the coenzyme B
12
-dependent 2-methyleneglutarate mutase and 3-methylitaconate isomerase, an aconitase and isocitrate lyase family pair of enzymes, (2
R
,3
S
)-dimethylmalate dehydratase and lyase, completes the pathway. Genes corresponding to the first three enzymes of the
E. barkeri
nicotinate catabolism were identified in nine Proteobacteria.
Transient receptor potential family members PKD1L3 and PKD2L1 form a candidate sour taste receptor
Authors: Ishimaru Yoshiro , Inada Hitoshi , Kubota Momoka , Zhuang Hanyi , Tominaga Makoto , Matsunami Hiroaki
Published: August 2006

Animals use their gustatory systems to evaluate the nutritious value, toxicity, sodium content, and acidity of food. Although characterization of molecular identities that receive taste chemicals is essential, molecular receptors underlying sour taste sensation remain unclear. Here, we show that two transient receptor potential (TRP) channel members, PKD1L3 and PKD2L1, are coexpressed in a subset of taste receptor cells in specific taste areas. Cells expressing these molecules are distinct from taste cells having receptors for bitter, sweet, or umami tastants. The PKD2L1 proteins are accumulated at the taste pore region, where taste chemicals are detected. PKD1L3 and PKD2L1 proteins can interact with each other, and coexpression of the PKD1L3 and PKD2L1 is necessary for their functional cell surface expression. Finally, PKD1L3 and PKD2L1 are activated by various acids when coexpressed in heterologous cells but not by other classes of tastants. These results suggest that PKD1L3 and PKD2L1 heteromers may function as sour taste receptors.
Ouabain affinity determining residues lie close to the Na/K pump ion pathway
Authors: Artigas Pablo , Gadsby David C.
Published: August 2006

The Na/K pump establishes essential ion concentration gradients across animal cell membranes. Cardiotonic steroids, such as ouabain, are specific inhibitors of the Na/K pump. We exploited the marine toxin, palytoxin, to probe both the ion translocation pathway through the Na/K pump and the site of its interaction with ouabain. Palytoxin uncouples the pump’s gates, which normally open strictly alternately, thus allowing both gates to sometimes be open, so transforming the pump into an ion channel. Palytoxin therefore permits electrophysiological analysis of even a single Na/K pump. We used outside-out patch recording of
Xenopus
α1β3 Na/K pumps, which were made ouabain-resistant by point mutation, after expressing them in
Xenopus
oocytes. Endogenous, ouabain-sensitive,
Xenopus
α1β3 Na/K pumps were silenced by continuous exposure to ouabain. We found that side-chain charge of two residues at either end of the α subunit’s first extracellular loop, known to make a major contribution to ouabain affinity, strongly influenced conductance of single palytoxin-bound pump-channels by an electrostatic mechanism. The effects were mimicked by modification of cysteines introduced at those two positions with variously charged methanethiosulfonate reagents. The consequences of these modifications demonstrate that both residues lie in a wide vestibule near the mouth of the pump’s ion pathway. Bound ouabain protects the site with the strongest influence on conductance from methanethiosulfonate modification, while leaving the site with the weaker influence unprotected. The results suggest a method for mapping the footprint of bound cardiotonic steroid on the extracellular surface of the Na/K pump.
Galactoglucomannans Increase Cell Population Density and Alter the Protoxylem/Metaxylem Tracheary Element Ratio in Xylogenic Cultures of Zinnia
Authors: Beňová-Kákošová Anna , Digonnet Catherine , Goubet Florence , Ranocha Philippe , Jauneau Alain , Pesquet Edouard , Barbier Odile , Zhang Zhinong , Capek Peter , Dupree Paul , Lišková Desana , Goffner Deborah
Published: August 2006

Xylogenic cultures of zinnia (Zinnia elegans) provide a unique opportunity to study signaling pathways of tracheary element (TE) differentiation. In vitro TEs differentiate into either protoxylem (PX)-like TEs characterized by annular/helical secondary wall thickening or metaxylem (MX)-like TEs with reticulate/scalariform/pitted thickening. The factors that determine these different cell fates are largely unknown. We show here that supplementing zinnia cultures with exogenous galactoglucomannan oligosaccharides (GGMOs) derived from spruce (Picea abies) xylem had two major effects: an increase in cell population density and a decrease in the ratio of PX to MX TEs. In an attempt to link these two effects, the consequence of the plane of cell division on PX-MX differentiation was assessed. Although GGMOs did not affect the plane of cell division per se, they significantly increased the proportion of longitudinally divided cells differentiating into MX. To test the biological significance of these findings, we have determined the presence of mannan-containing oligosaccharides in zinnia cultures in vitro. Immunoblot assays indicated that β-1,4-mannosyl epitopes accumulate specifically in TE-inductive media. These epitopes were homogeneously distributed within the thickened secondary walls of TEs when the primary cell wall was weakly labeled. Using polysaccharide analysis carbohydrate gel electrophoresis, glucomannans were specifically detected in cell walls of differentiating zinnia cultures. Finally, zinnia macroarrays probed with cDNAs from cells cultured in the presence or absence of GGMOs indicated that significantly more genes were down-regulated rather than up-regulated by GGMOs. This study constitutes a major step in the elucidation of signaling mechanisms of PX- and MX-specific genetic programs in zinnia.
Transgenic Tobacco Plants Overexpressing Chitinases of Fungal Origin Show Enhanced Resistance to Biotic and Abiotic Stress Agents
Authors: Dana María de las Mercedes , Pintor-Toro José A. , Cubero Beatriz
Published: August 2006

Genes encoding defense-related proteins have been used to alter the resistance of plants to pathogens and other environmental challenges, but no single fungal gene overexpression has produced broad-spectrum stress resistance in transgenic lines. We have generated transgenic tobacco (Nicotiana tabacum) lines that overexpress the endochitinases CHIT33 and CHIT42 from the mycoparasitic fungus Trichoderma harzianum and have evaluated their tolerance to biotic and abiotic stress. Both CHIT33 and CHIT42, individually, conferred broad resistance to fungal and bacterial pathogens, salinity, and heavy metals. Such broad-range protective effects came off with no obvious detrimental effect on the growth of tobacco plants.
Whole-Genome Analysis of Oryza sativa Reveals Similar Architecture of Two-Component Signaling Machinery with Arabidopsis
Authors: Pareek Ashwani , Singh Anupama , Kumar Manoj , Kushwaha Hemant R. , Lynn Andrew M. , Singla-Pareek Sneh L.
Published: August 2006

The two-component system (TCS), which works on the principle of histidine-aspartate phosphorelay signaling, is known to play an important role in diverse physiological processes in lower organisms and has recently emerged as an important signaling system in plants. Employing the tools of bioinformatics, we have characterized TCS signaling candidate genes in the genome of Oryza sativa L. subsp. japonica. We present a complete overview of TCS gene families in O. sativa, including gene structures, conserved motifs, chromosome locations, and phylogeny. Our analysis indicates a total of 51 genes encoding 73 putative TCS proteins. Fourteen genes encode 22 putative histidine kinases with a conserved histidine and other typical histidine kinase signature sequences, five phosphotransfer genes encoding seven phosphotransfer proteins, and 32 response regulator genes encoding 44 proteins. The variations seen between gene and protein numbers are assumed to result from alternative splicing. These putative proteins have high homology with TCS members that have been shown experimentally to participate in several important physiological phenomena in plants, such as ethylene and cytokinin signaling and phytochrome-mediated responses to light. We conclude that the overall architecture of the TCS machinery in O. sativa and Arabidopsis thaliana is similar, and our analysis provides insights into the conservation and divergence of this important signaling machinery in higher plants.