bluuebunny/crossref_metadata_2025 huggingface dataset:
Suspended sediments in river ecosystems: Photochemical sources of dissolved organic carbon, dissolved organic nitrogen, and adsorptive removal of dissolved iron
Authors: Riggsbee J. Adam , Orr Cailin H. , Leech Dina M. , Doyle Martin W. , Wetzel Robert G.
Published: August 2008

We generated suspended sediment solutions using river sediments and river water at concentrations similar to those observed during 1.5 year floods (Q1.5) and a dam removal (∼325 mg L−1) on the Deep River, North Carolina. Suspended sediment solutions were exposed to simulated solar radiation, equivalent to one clear, summer day at the study site (35°N). Concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), total dissolved nitrogen (TDN), dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), soluble reactive phosphorus (SRP) and total dissolved iron (Fed) were measured before and after exposure. Total dissolved carbon (TDC) budgets for each experiment were produced using DOC and DIC data. Sediment suspensions in the presence of simulated solar radiation were significant sources of dissolved C (119 ± 11 μmol C L−1 d−1; ± values indicate 1 standard error) and DON (1.7 ± 0.5 μmol N L−1 d−1) but not DIN or SRP. Extrapolations through the Deep River water column suggest that suspended sediments in the presence of light represent dissolved organic matter fluxes of 3.92 mmol C m−2 d−1 and 40 μmol N m−2 d−1. Additionally, sediment suspensions lowered river water Fed concentrations immediately (∼24%) and progressively (∼40–90%) in both light and dark treatments. Our research suggests suspended sediments in river ecosystems are potential sources of dissolved organic C and dissolved organic N while effectively removing Fed from the water column.
Pre‐monsoon to monsoon change in direction of vertical motions in the tropical lower troposphere from UHF radar observations
Authors: Ernest Raj P. , Deshpande Sachin M.
Published: August 2008

Multi‐height vertical wind data in the lower troposphere (1.05 – 3.75 km) obtained from Wind Profiler/UHF radar at Pune (18°32′N, 73°51′E), India during June 2003 – May 2006 has been used here to investigate the seasonal evolution in the vertical structure, especially the change taking place from pre‐monsoon (March – May) to south west monsoon (June – September) season. Vertical motions are predominantly upward during winter (December – February) and are strongly downward during pre‐monsoon. A transition from downward to upward motion takes place around early June coinciding with the local onset of SW monsoon. Kinetic energy computed from zonal and meridional winds is small in magnitude during pre‐monsoon but shows an abrupt and explosive increase around the time onset of monsoon. The results thus provide an observational evidence of existence of strong subsidence in the lower troposphere during pre‐monsoon which weakens and vertical winds turn upward signaling the arrival of monsoon conditions.
Ambient solar wind's effect on ICME transit times
Authors: Case A. W. , Spence H. E. , Owens M. J. , Riley P. , Odstrcil D.
Published: August 2008

Most empirical and numerical models of Interplanetary Coronal Mass Ejection (ICME) propagation use the initial CME velocity as their primary, if not only, observational input. These models generally predict a wide spread of 1 AU transit times for ICMEs with the same initial velocity. We use a 3D coupled MHD model of the corona and heliosphere to determine the ambient solar wind's effect on the propagation of ICMEs from 30 solar radii to 1 AU. We quantitatively characterize this deceleration by the velocity of the upstream ambient solar wind. The effects of varying solar wind parameters on the ICME transit time are quantified and can explain the observed spread in transit times for ICMEs of the same initial velocity. We develop an adjustment formula that can be used in conjunction with other models to reduce the spread in predicted transit times of Earth‐directed ICMEs.
Contrasting the 2007 and 2005 hurricane seasons: Evidence of possible impacts of Saharan dry air and dust on tropical cyclone activity in the Atlantic basin
Authors: Sun Donglian , Lau K. M. , Kafatos Menas
Published: August 2008

In this study, we provide preliminary evidence of possible modulation by Saharan dust of hurricane genesis and intensification, by contrasting the 2007 and 2005 hurricane seasons. It is found that dust aerosol loadings over the Atlantic Ocean are much higher in 2007 than in 2005. The temperature difference between 2007 and 2005 shows warming in the low‐middle troposphere (900–700 hPa) in the dusty region in the eastern North Atlantic, and cooling in the Main Development Region (MDR). The humidity (wind) differences between 2007 and 2005 indicate significant drying (subsidence) in the Western North Atlantic (WNA) in 2007. The drier air in the WNA in 2007 is found to be associated with the further westward transport of the Saharan air layer (SAL). To quantify wind pattern favorable for transport of SAL over the WNA, we define a zonal wind stretch index which shows significant long‐term correlation with the mid‐level humidity in the WNA. Analyses of the stretch index and related environmental controls suggest that the westward expansion of the Saharan dry air and dust layer can be an important factor in contributing to the difference between the relatively quiescent hurricane season in 2007 and the very active season of 2005.
Solar flare effect preceding Halloween storm (28 October 2003): Results of a worldwide analysis
Authors: Villante U. , Regi M.
Published: August 2008

On 28 October 2003 an extreme solar flare with significant increases in the EUV and X‐ray flux caused increased photoionization effects in the dayside ionosphere and determined a remarkable solar flare effect (SFE) manifestation that preceded Halloween storm. An analysis conducted at 53 stations revealed that the geomagnetic disturbance had greatest amplitude and longest duration at lowest latitudes in the dayside hemisphere, and its characteristics were basically controlled by the zenith angle of the observing stations. The aspects of the SFE onset and initial phase reveal a close correspondence with those of the EUV flux. At equatorial/electrojet latitudes, the SFE manifestation can be mostly interpreted in terms of a significant enhancement of the preflare current system during normal electrojet conditions, with some evidence for a highly confined counter electrojet in the dawn sector. Additional elements, at higher latitudes, might suggest in these regions a more significant role of the X‐ray flux and the onset of additional currents below the normal dynamo current region.
A Monte Carlo study for ion outflows at high altitude and high latitude: Barghouthi model
Authors: Barghouthi I. A.
Published: August 2008

A comparison has been made between the results of three different wave‐particle interactions models, RCC model, Bouhram model, and Barghouthi model. These models have been used for investigating the H+ and O+ ion outflows at high altitudes equatorward of the cusp, and their simulation results have been compared to the corresponding observations. The comparison showed that the simulation results of O+ ion temperature (202 eV), H+ ion temperature (74 eV), and H+ and O+ ions velocity distributions (toroids) at 4.8 RE, geocentric distance, in the equatorward region of the cusp, obtained by using Barghouthi model, when the characteristic perpendicular wavelength of the electromagnetic turbulence λ⊥ = 8 km, are close to the corresponding observations, T(O+) = 200 eV, T(H+) = 78 eV, and H+ and O+ toroids at 4.8 RE. This close agreement between Monte Carlo simulations and observations provides evidence that the diffusion coefficient, D⊥(r, v⊥) described in this paper and consequently, the Barghouthi model are appropriate to be used when modeling the ion's acceleration through wave‐particle interactions (i.e., ion interactions with electromagnetic turbulence) in the auroral regions of Earth's magnetosphere. The model includes the effects of velocity‐ and altitude‐dependent wave‐particle interactions, gravitational field, polarization electrostatic field, and diverging auroral geomagnetic field lines. Also, we present much evidence, i.e., comparisons between the simulations results of Barghouthi model for H+ and O+ ions outflows with the corresponding observations at different altitudes in the auroral region, that support the choice of Barghouthi model.
Simultaneous inversion of mantle properties and initial conditions using an adjoint of mantle convection
Authors: Liu Lijun , Gurnis Michael
Published: August 2008

Through the assimilation of present‐day mantle seismic structure, adjoint methods can be used to constrain the structure of the mantle at earlier times, i.e., mantle initial conditions. However, the application to geophysical problems is restricted through both the high computational expense from repeated iteration between forward and adjoint models and the need to know mantle properties (such as viscosity and the absolute magnitude of temperature or density) a priori. We propose that an optimal first guess to the initial condition can be obtained through a simple backward integration (SBI) of the governing equations, thus lessening the computational expense. Given a model with known mantle properties, we show that a solution based on an SBI‐generated first guess has smaller residuals than arbitrary guesses. Mantle viscosity and the effective Rayleigh number are crucial for mantle convection models, neither of which is exactly known. We place additional constraints on these basic mantle properties when the convection‐induced dynamic topography on Earth's surface is considered within an adjoint inverse method. Besides assimilating present‐day seismic structure as a constraint, we use dynamic topography and its rate of change in an inverse method that allows simultaneous inversion of the absolute upper and lower mantle viscosities, scaling between seismic velocity and thermal anomalies, and initial condition. The theory is derived from the governing equations of mantle convection and validated by synthetic experiments for both one‐layer viscosity and two‐layer viscosity regionally bounded spherical shells. For the one‐layer model, at any instant of time, the magnitude of dynamic topography is controlled by the temperature scaling while the rate of change of topography is controlled by the absolute value of viscosity. For the two‐layer case, the rate of change of topography constrains upper mantle viscosity while the magnitude of dynamic topography determines the temperature scaling (lower mantle viscosity) when upper‐mantle (lower‐mantle) density anomaly dominates the flow field; this two‐stage scheme minimizes the tradeoff between temperature and lower mantle viscosity. For both cases, we show that the theory can constrain mantle properties with errors arising through the adjoint recovery of the initial condition; for the two‐layer model, this error is manifest as a tradeoff between the temperature scaling and lower mantle viscosity.
Study by means of liquid side acoustic barrier of the influence of leaky Rayleigh waves on bounded beam reflection
Authors: Declercq Nico F. , Lamkanfi Ebrahim
Published: August 2008

The Schoch effect in ultrasonics, when sound is incident at the Rayleigh angle on a liquid-solid interface, consists of a forward beam displacement of the reflected beam, usually accompanied by a null strip in between the specular portion and the nonspecular reflected beam portion. It is a widely accepted idea that the effect is caused by reflected sound in combination with a sound field emitted by leaky Rayleigh waves. The current work presents an experimental technique to separate and investigate both fields separately by applying an acoustic barrier. The experiments are based on acousto-optic Schlieren photography.
Fe valence state of Sr2FeMoO6 probed by x-ray absorption spectroscopy: The sample age matters
Authors: Kuepper K. , Raekers M. , Taubitz C. , Hesse H. , Neumann M. , Young A. T. , Piamonteze C. , Bondino F. , Prince K. C.
Published: August 2008

Several studies of the magnetic properties of Sr2FeMoO6, a half metallic double perovskite showing large magneto resistance effects at room temperature, by means of site specific x-ray absorption spectroscopy (XAS) have led to very different results concerning the Fe valence state. We present a detailed study of a Sr2FeMoO6 sample, which has been probed by means of XAS and x-ray magnetic circular dichroism (XMCD) over several years. We find a mixed valent Fe2+, Fe3+ state, which shifts toward Fe3+ with time. An understanding of such a chemical change is of importance for potential applications of Sr2FeMoO6 and related transition metal oxides.
Reaction Brownian dynamics and the effect of spatial fluctuations on the gain of a push-pull network
Authors: Morelli Marco J. , ten Wolde Pieter Rein
Published: August 2008

Brownian Dynamics algorithms have been widely used for simulating systems in soft-condensed matter physics. In recent times, their application has been extended to the simulation of coarse-grained models of biochemical networks. In these models, components move by diffusion and interact with one another upon contact. However, when reactions are incorporated into a Brownian dynamics algorithm, care must be taken to avoid violations of the detailed-balance rule, which would introduce systematic errors in the simulation. We present a Brownian dynamics algorithm for simulating reaction-diffusion systems that rigorously obeys detailed balance for equilibrium reactions. By comparing the simulation results to exact analytical results for a bimolecular reaction, we show that the algorithm correctly reproduces both equilibrium and dynamical quantities. We apply our scheme to a “push-pull” network in which two antagonistic enzymes covalently modify a substrate. Our results highlight that spatial fluctuations of the network components can strongly reduce the gain of the response of a biochemical network.
Whispering-gallery mode resonators: Surface enhanced Raman scattering without plasmons
Authors: Ausman Logan K. , Schatz George C.
Published: August 2008

Calculations based on the Mie theory are performed to determine the locally enhanced electric fields due to whispering-gallery mode resonances for dielectric microspheres, with emphasis on electromagnetic “hot spots” that are located along the wavevector direction on the surface of the sphere. The local electric field enhancement associated with these hot spots is used to determine the surface enhanced Raman scattering enhancement factors for a molecule, here treated as a classical dipole, located near the surface of the sphere. Both incident and Raman emission enhancements are calculated accurately using an extension of the Mie theory that includes interaction of the Raman dipole field with the sphere. The enhancement factors are calculated for dielectric spheres in vacuum with a refractive index of 1.9 and radii of 5, 10, and 20μm and for wavelengths that span the visible spectrum. Maximum Raman scattering enhancement factors on the order of 103–104 are found at locations slightly off the propagation axis when the incident excitation but not the Stokes-shifted radiation is coincident with a whispering-gallery mode resonance. The enhancement factors are found to vary inversely with the resonance width, and this determines the influence of the mode number and order on the results. Additional calculations are performed for the case where the Stokes-shifted radiation is also on-resonance and Raman enhancement factors as large as 108 are found. These enhancement factors are typically a factor of 102 smaller than would be obtained from ∣E∣4 enhancement estimates, as enhancement of the Raman dipole emission is significantly reduced compared to the local field enhancement for micron size particles or larger. Conditions under which single-molecule or few-molecule measurements are feasible are identified.
High-performance amorphous gallium indium zinc oxide thin-film transistors through N2O plasma passivation
Authors: Park Jaechul , Kim Sangwook , Kim Changjung , Kim Sunil , Song Ihun , Yin Huaxiang , Kim Kyoung-Kok , Lee Sunghoon , Hong Kiha , Lee Jaecheol , Jung Jaekwan , Lee Eunha , Kwon Kee-Won , Park Youngsoo
Published: August 2008

Amorphous-gallium-indium-zinc-oxide (a-GIZO) thin filmtransistors (TFTs) are fabricated without annealing, using processes and equipment for conventional a-Si:H TFTs. It has been very difficult to obtain sound TFT characteristics, because the a-GIZO active layer becomes conductive after dry etching the Mo source/drain electrode and depositing the a-SiO2 passivation layer. To prevent such damages, N2O plasma is applied to the back surface of the a-GIZO channel layer before a-SiO2 deposition. N2O plasma-treated a-GIZO TFTs exhibit excellent electrical properties: a field effect mobility of 37cm2∕Vs, a threshold voltage of 0.1V, a subthreshold swing of 0.25V/decade, and an Ion∕off ratio of 7.
Studies of supersonic, radiative plasma jet interaction with gases at the Prague Asterix Laser System facility
Authors: Nicolaï Ph. , Stenz C. , Kasperczuk A. , Pisarczyk T. , Klir D. , Juha L. , Krousky E. , Masek K. , Pfeifer M. , Rohlena K. , Skala J. , Tikhonchuk V. , Ribeyre X. , Galera S. , Schurtz G. , Ullschmied J. , Kalal M. , Kravarik J. , Kubes P. , Pisarczyk P. , Schlegel T.
Published: August 2008

The interaction of laser driven jets with gas puffs at various pressures is investigated experimentally and is analyzed by means of numerical tools. In the experiment, a combination of two complementary diagnostics allowed to characterize the main structures in the interaction zone. By changing the gas composition and its density, the plasma cooling time can be controlled and one can pass from a quasiadiabatic outflow to a strongly radiation cooling jet. This tuning yields hydrodynamic structures very similar to those seen in astrophysical objects; the bow shock propagating through the gas, the shocked materials, the contact discontinuity, and the Mach disk. From a dimensional analysis, a scaling is made between both systems and shows the study relevance for the jet velocity, the Mach number, the jet-gas density ratio, and the dissipative processes. The use of a two-dimensional radiation hydrodynamic code, confirms the previous analysis and provides detailed structure of the interaction zone and energy repartition between jet and surrounding gases.
Dissociation of H-related defect complex in InP using high energy light ions
Authors: Kabiraj D. , Roy A. , Pivin J. C. , Ghosh Subhasis
Published: August 2008

High energy light ion irradiation has been used to anneal H-related defect complexes and to modify the electronic properties of semi-insulating InP (SI-InP). Raman and infrared spectroscopic measurements have been used to investigate the annihilation of native defects in SI-InP irradiated with 85 MeV C. Irradiation resulted in a decrease in sample resistivity by four orders of magnitudes and a change in the type of conductivity. The Raman spectroscopic results indicate an improvement in the InP sample due to irradiation up to an optimum fluence. The role of high electronic energy loss in defect annealing, which includes modification of the electrical properties and crystal structure of irradiated SI-InP, is discussed.
Xe-excitation efficiency and plasma saturation in plasma display microdischarges
Authors: Oversluizen G. , Itoh K. , Shiga T. , Mikoshiba S.
Published: August 2008

Plasma display panel (PDP) efficiency data are correlated with panel emission measurements. A large visible/infrared (vis/IR) ratio of the phosphor emission in the visible to the Xe emission in the infrared indicates a high Xe-excitation efficiency. Monitoring the changes in the vis/IR ratio allows a decomposition of the discharge efficiency into Xe-excitation efficiency and electron heating efficiency contributions. For several different PDP efficiency dependencies on sustain voltage and frequency, consistent trends in Xe-excitation efficiency and electron heating efficiency are found. In addition, in order to follow the discharge development, the time dependence and the spatial distribution of the Xe emission are monitored. The combined results show that plasma saturation is significant to low Xe-content panels in default operation conditions and that plasma saturation decreases with the high voltage high frequency operation of high Xe-content panels. These driving conditions, which are especially suited for high Xe-content panels, govern a fast and spatially distributed discharge development with a lower effective electron temperature, increased Xe-excitation efficiency, and decreased plasma saturation.
Design and electrical properties’ investigation of (K0.5Na0.5)NbO3–BiMeO3 lead-free piezoelectric ceramics
Authors: Du Hongliang , Zhou Wancheng , Luo Fa , Zhu Dongmei , Qu Shaobo , Li Ye , Pei Zhibin
Published: August 2008

Based on the discussion on the “origin” of the high piezoelectric properties of Pb-based piezoelectric ceramics, it was predicted that (K0.5Na0.5)NbO3–BiMeO3 solid solutions (where Me3+=Sc, Al, Ga, Y, In, etc.) should possess high piezoelectric properties because of the formation of the morphotropic phase boundary and the hybridization between the Bi 6p and O 2p orbits. (1−x)(K0.5Na0.5)NbO3–xBiScO3 [(1−x)KNN-xBS] ceramics were selected as an example to verify this prediction. (1−x)KNN-xBS ceramics were synthesized by conventional solid-state sintering. The phase structure, microstructure, and dielectric and piezoelectric properties of (1−x)KNN-xBS ceramics were investigated. At room temperature, the polymorphic phase transition (PPT) (from the orthorhombic to the tetragonal phase) in (1−x)KNN-xBS ceramics is identified at x=0.0175 by the analysis of x-ray diffraction patterns and dielectric spectroscopy. The ceramics (x=0.0175) with PPT near room temperature exhibit excellent electrical properties (d33=∼253 pC/N, kp=0.48, kt=0.49, and TC=351 °C). The related mechanisms for the high piezoelectric properties in (1−x)KNN-xBS (x=0.0175) ceramics are also systematically discussed. Compared to the other KNN-based ceramics and hard Pb(Zr,Ti)O3 ceramics, it is concluded that the (1−x)KNN-xBS (x=0.0175) ceramic is a promising lead-free piezoelectric candidate material. In addition, this article could provide an alternative approach for the development of lead-free piezoelectric ceramics.
Thermocapillary migration of nondeformable drops
Authors: Yin Z. , Gao P. , Hu W. , Chang L.
Published: August 2008

In this paper, we present a numerical study on the thermocapillary migration of drops. The Navier–Stokes equations coupled with the energy conservation equation are solved by the finite-difference front-tracking scheme. The axisymmetric model is adopted in our simulations, and the drops are assumed to be perfectly spherical and nondeformable. The benchmark simulation starts from the classical initial condition with a uniform temperature gradient. The detailed discussions and physical explanations of migration phenomena are presented for the different values of (1) the Marangoni numbers and Reynolds numbers of continuous phases and drops and (2) the ratios of drop densities and specific heats to those of continuous phases. It is found that fairly large Marangoni numbers may lead to fluctuations in drop velocities at the beginning part of simulations. Finally, we also discuss the influence of initial conditions on the thermocapillary migrations.
Intraband Auger effect in InAs∕InGaAlAs∕InP quantum dot structures
Authors: Gebhard T. , Alvarenga D. , Souza P. L. , Guimarães P. S. S. , Unterrainer K. , Pires M. P. , Vieira G. S. , Villas-Boas J. M.
Published: August 2008

InAs quantum dot structures grown on InGaAlAs have been investigated for midinfrared photodetection. Intraband photocurrent and absorption measurements, together with a full three-dimensional theoretical modeling revealed that a bound-to-bound optical transition, where the final state is about 200meV deep below the conduction band continuum, is responsible for the photogenerated current. The reported results strongly suggest that an Auger process plays a fundamental role in generating the observed intraband photocurrent. Photoluminescence and interband photocurrent spectra of the same structures further support the reached conclusions.
Comment on “Encryption and decryption of images with chaotic map lattices” [Chaos 16, 033118 (2006)]
Authors: Solak Ercan , Çokal Cahit
Published: August 2008

In this paper, we comment on the chaotic encryption algorithm proposed by A. N. Pisarchik et al. [Chaos 16, 033118 (2006)]. We demonstrate that the algorithm is not invertible. We suggest simple modifications that can remedy some of the problems we identified.
Double layer formation at the interface of complex plasmas
Authors: Yaroshenko V. V. , Thoma M. H. , Thomas H. M. , Morfill G. E.
Published: August 2008

Necessary conditions are formulated for the generation of a double layer at the interface of a complex plasma and a particle-free electron-ion plasma in a weakly collisional discharge. Examples are calculated for realistic observed complex plasmas, and it is shown that situations of both “smooth” transitions and “sharp” transitions can exist. The model can explain the abrupt boundaries observed.
Electrostatic drift waves in nonuniform quantum magnetized plasmas
Authors: Wu Zhengwei , Ren Haijun , Cao Jintao , Chu Paul K.
Published: August 2008

Electrostatic drift waves (EDWs) in nonuniform quantum magnetized plasmas are described by the quantum hydrodynamic model. Electrons are viewed as a low-temperature Fermi gas. Analytical expression of the dispersion relationship of the quantum EDW is presented. Quantum effects are shown to affect the dispersion of the EDW significantly. The effects on the dispersion relation due to the magnetic field and spatial inhomogeneity give rise to results similar to the classical case. Our results should be relevant to dense astrophysical objects, e.g., neutron stars, magnet-stars, and white dwarfs.
Low thermal conductivity in nanoscale layered materials synthesized by the method of modulated elemental reactants
Authors: Chiritescu Catalin , Cahill David G. , Heideman Colby , Lin Qiyin , Mortensen Clay , Nguyen Ngoc T. , Johnson David , Rostek Raimar , Böttner Harald
Published: August 2008

We report the room-temperature, cross-plane thermal conductivities, and longitudinal speeds of sound of multilayer films [(TiTe2)3(Bi2Te3)x(TiTe2)3(Sb2Te3)y]i (x=1−5,y=1−5) and misfit-layer dichalcogenide films [(PbSe)m(TSe2)n]i (T=W or Mo, m=1–5, and n=1–5) synthesized by the modulated elemental reactants method. The thermal conductivities of these nanoscale layered materials fall below the predicted minimum thermal conductivity of the component compounds: two times lower than the minimum thermal conductivity of Bi2Te3 for multilayer [(TiTe2)3(Bi2Te3)x(TiTe2)3(Sb2Te3)y]i films and five to six times lower than the minimum thermal conductivity of PbSe for misfit-layer dichalcogenides [(PbSe)m(TSe2)n]i. We attribute the low thermal conductivities to the anisotropic bonding of the layered crystals and orientational disorder in the stacking of layered crystals along the direction perpendicular to the surface.
Model for the combination of diffusional and inertial particle deposition on inverse surfaces at low pressure
Authors: Asbach Christof , Fissan Heinz , Kuhlbusch Thomas A. J. , Wang Jing , Pui David Y. H.
Published: August 2008

A model was developed to estimate particle contamination probabilities on inverse surfaces at low pressure for inertial and diffusional particle deposition under the influence of gravity, drag, and thermophoresis. The model shows that contamination probabilities strongly depend on particle size, initial velocity, and initial distance between particle and surface. While thermophoresis effectively protects the surface against deposition of particles with 10mm (or more) initial distance and velocities below 1m∕s, the contamination probability of particles with an initial distance of 0.1mm is very high for small particles due to their high diffusivity and for fast particles due to inertia.
Nano-optical microlens with ultrashort focal length using negative refraction
Authors: Casse B. D. F. , Lu W. T. , Huang Y. J. , Sridhar S.
Published: August 2008

We have experimentally realized an ultrashort focal length planoconcave microlens in an InP/InGaAsP semiconductor two-dimensional (2D) photonic crystal with negative index of refraction (−0.7). At λ=1.5 μm, the lens exhibits ultrashort focal lengths of 12 μm (∼8λ) and numerical aperture close to unity. The focused beam has a near diffraction-limited spot size of 1.05 μm (∼0.68λ) at full width at half maximum. The negative refractive index and focusing properties of the microlens are confirmed by 2D finite-difference time-domain simulations. Such ultrarefractive negative-index nano-optical microlenses can be integrated into existing semiconductor heterostructure platforms for next-generation optoelectronic applications.
Photoinduced microchannels inside silicon by femtosecond pulses
Authors: Chen Tao , Si Jinhai , Hou Xun , Kanehira Shingo , Miura Kiyotaka , Hirao Kazuyuki
Published: August 2008

We reported on the fabrication of microchannels in the interior of silicon wafers using a femtosecond laser of 800nm wavelength, which was in the absorption region of silicon. The scanning electron micrographs showed that microchannels were induced inside the silicon wafer when the femtosecond laser beam was focused inside the wafer. The aspect ratio of the microchannel cross section decreased with the increase in scan velocity of the laser. The formation of the photoinduced microchannels probably resulted from the microexplosions due to both the linear absorption and avalanche ionization.
Migration enhanced lateral epitaxial overgrowth of AlN and AlGaN for high reliability deep ultraviolet light emitting diodes
Authors: Jain R. , Sun W. , Yang J. , Shatalov M. , Hu X. , Sattu A. , Lunev A. , Deng J. , Shturm I. , Bilenko Y. , Gaska R. , Shur M. S.
Published: August 2008

We report on the growth of low-defect thick films of AlN and AlGaN on trenched AlGaN/sapphire templates using migration enhanced lateral epitaxial overgrowth. Incoherent coalescence-related defects were alleviated by controlling the tilt angle of growth fronts and by allowing Al adatoms sufficient residence time to incorporate at the most energetically favorable lattice sites. Deep ultraviolet light emitting diode structures (310nm) deposited over fully coalesced thick AlN films exhibited cw output power of 1.6mW at 50mA current with extrapolated lifetime in excess of 5000hours. The results demonstrate substantial improvement in the device lifetime, primarily due to the reduced density of growth defects.
Effect of surface application of benzylaminopurine before and during water deficit on herbage production and quality
Authors: Lee J. M. , Elborough K. , Whittaker D. , Donaghy D. J. , Roche J. R.
Published: August 2008

Insufficient water availability is one of the most serious environmental stresses for a plant and can be a major limitation to herbage production in many regions. Plant hormones, such as cytokinins, have been reported to reduce the detrimental effects of low water availability in many different plant species. However, there is little research available concerning the effect on pasture grasses. The aim of the present study was to quantify the effect of surface applications of 6-benzylaminopurine (BAP) before and during water deficit on herbage growth and quality of perennial ryegrass–white clover pastures. Pastures fertilised with BAP were compared with unfertilised pastures and pastures receiving nitrogen. Exogenous BAP application did not significantly affect herbage production or quality relative to unfertilised pastures. Nitrogen fertiliser increased total herbage production, but had little effect on herbage quality compared with BAP. The failure of surface applications of exogenous BAP to improve herbage production or quality suggests that it is not an appropriate method to enhance plant tolerance to water deficit at the concentration applied in this study.
Incomplete milking has no detectable effect on somatic cell count but increased cell count appears to increase strip yield
Authors: Clarke T. , Cuthbertson E. M. , Greenall R. K. , Hannah M. C. , Shoesmith D.
Published: August 2008

Milking regimes that can greatly shorten the milking duration of slow-milking cows to improve labour productivity can also result in less complete milking for some cows. There is also a common belief and limited experimental evidence that incomplete milking of subclinically infected cows can cause increased somatic cell count (SCC). To test for this possible detrimental effect of shorter milking regimes, ‘complete’ milking [to automatic cluster remover (ACR) setting of 300 mL/min] and ‘incomplete’ milking (to an ACR setting of 800 mL/min) were applied sequentially to 45 cows over 7 weeks. Incomplete milking resulted in an average of 0.3 L of extra milk being left in the udders, but there was no significant increase in quarter SCC in either infected or uninfected udder quarters. Change in SCC was not related to change in strip yield induced by incomplete milking treatment. In contrast, cow strip yield was positively related to SCC, or the number of infected quarters/cow, regardless of the applied ACR treatment. These apparently contradictory findings are reconciled by noting that infection causes both high strip yields (via uneven yielding quarters) and high SCC. It is concluded that, contrary to popular belief, high SCC, as an indicator of infection, causes high strip yield and that increasing strip yield does not increase cell count.
Short- and long-range dispersal of the Queensland fruit fly, Bactrocera tryoni and its relevance to invasive potential, sterile insect technique and surveillance trapping
Authors: Meats A. , Edgerton J. E.
Published: August 2008

Dispersal of immature and sexually mature Queensland fruit fly, Bactrocera tryoni (Froggatt) from releases made at a single point was assessed from recapture rates obtained by using arrays of traps. The recapture data (pertaining to distances up to 480 m) fitted both logarithmic and Cauchy models although the fits for the releases of immature flies were inferior because of high variability in catches at certain distances. When combined with data previously published for longer distances, a Cauchy model fitted data for releases of immature flies well and indicated that the median distance dispersed after emerging from the puparium was ~120 m and that 90% of flies would displace less than 800 m despite the fact that a consistent trend in declining catch rates can be obtained up to at least 85 km. This is consistent with the tail of the Cauchy distribution having a slope congruent with a negative power curve and thus being scale invariant for longer distances. The distribution of recaptured flies that were released as adults also fitted a Cauchy model with a tail of the same slope, suggesting that the spatial distribution of long-distance dispersers is not only scale invariant but also age invariant. This has significance to the ability of surveillance trapping arrays to detect infestations and also to methods of distributing insects for the sterile insect technique. Whereas the spread of invading propagules in the first generation is likely to be limited by a decline to non-viable density within 1 km or less of the incursion point, the influence of larger infestations on nearby uninfested regions would be limited by the longevity of the dispersers.
Behavioural effects of yearling grain-finished heifers exposed to differing environmental conditions and growth-promoting agents
Authors: Mader T. L. , Gaughan J. B. , Kreikemeier W. M. , Parkhurst A. M.
Published: August 2008

Two groups of 108 Angus cross yearling heifers were utilised to determine the effects of growth-promoting agents on behaviour, when utilised under thermoneutral, hot and cold environmental conditions. Pens of heifers were observed throughout the day for feed intake pattern via bunk score, panting (hot), degree of bunching and shivering (cold). For cattle that were exposed to cold stress, feed intake was greater earlier in the day, with the majority of the feed consumed by 1500 hours and little or no feed consumed at night, while the opposite trend occurred under heat stress. Nearly 46% of the pens containing heat-stressed heifers had greater than 50% of their feed remaining in the bunk at 1900 hours. Pens of heifers exposed to thermoneutral conditions had a tendency to show elevated panting scores at 0700 hours, while heifers exposed to hot conditions did not, indicating some acclimation to heat stress had already taken place for the heifers exposed to hot conditions. Panting score did not appear to be affected by growth-promoting treatment. Under cold stress, 100% of the cattle displayed bunching behaviour throughout the day, while under hot and thermoneutral conditions, maximum bunching (25 to 30%) occurred at 1500 hours. Within an environmental condition, trenbolone acetate cattle tended to bunch more under thermoneutral and hot conditions, particularly in the morning, when compared with other treatment groups; control and oestrogen-treated cattle tended to bunch less under the same conditions, regardless of the time of day. Although data were inconclusive as to overall effects of growth promotants on mitigating cold stress, shivering scores were increased with a more aggressive growth-promoting treatment (P < 0.05). These findings suggest that if growth promotants, which are used in feedlot cattle, impact cattle exposed to adverse environmental conditions, then they tend to be more effective at mitigating heat stress than cold stress.
Desorption electrospray ionization mass spectrometry: Imaging drugs and metabolites in tissues
Authors: Wiseman Justin M. , Ifa Demian R. , Zhu Yongxin , Kissinger Candice B. , Manicke Nicholas E. , Kissinger Peter T. , Cooks R. Graham
Published: August 2008

Ambient ionization methods for MS enable direct, high-throughput measurements of samples in the open air. Here, we report on one such method, desorption electrospray ionization (DESI), which is coupled to a linear ion trap mass spectrometer and used to record the spatial intensity distribution of a drug directly from histological sections of brain, lung, kidney, and testis without prior chemical treatment. DESI imaging provided identification and distribution of clozapine after an oral dose of 50 mg/kg by:i) measuring the abundance of the intact ion atm/z327.1, andii) monitoring the dissociation of the protonated drug compound atm/z327.1 to its dominant product ion atm/z270.1. In lung tissues, DESI imaging was performed in the full-scan mode over anm/zrange of 200-1100, providing an opportunity for relative quantitation by using an endogenous lipid to normalize the signal response of clozapine. The presence of clozapine was detected in all tissue types, whereas the presence of theN-desmethyl metabolite was detected only in the lung sections. Quantitation of clozapine from the brain, lung, kidney, and testis, by using LC-MS/MS, revealed concentrations ranging from 0.05 μg/g (brain) to a high of 10.6 μg/g (lung). Comparisons of the results recorded by DESI with those by LC-MS/MS show good agreement and are favorable for the use of DESI imaging in drug and metabolite detection directly from biological tissues.
T current potentiation increases the occurrence and temporal fidelity of synaptically evoked burst firing in sensory thalamic neurons
Authors: Bessaïh Thomas , Leresche Nathalie , Lambert Régis C.
Published: August 2008

A growing number of
in vivo
experiments shows that high frequency bursts of action potentials can be recorded in thalamocortical neurons of awake animals. The mechanism underlying these bursts, however, remains controversial, because they have been proposed to depend on T-type Ca
2+
channels that are inactivated at the depolarized membrane potentials usually associated with the awake state. Here, we show that the transient potentiation of the T current amplitude, which is induced by neuronal depolarization, drastically increases the probability of occurrence and the temporal precision of T-channel-dependent high frequency bursts. The data, therefore, provides the first biophysical mechanism that might account for the generation of these high frequency bursts of action potentials in the awake state. Remarkably, this regulation finely tunes the response of thalamocortical neurons to the corticofugal excitatory and intrathalamic inhibitory afferents but not to sensory inputs.
Diverse cytokine production by NKT cell subsets and identification of an IL-17–producing CD4
−
NK1.1
−
NKT cell population
Authors: Coquet Jonathan M. , Chakravarti Sumone , Kyparissoudis Konstantinos , McNab Finlay W. , Pitt Lauren A. , McKenzie Brent S. , Berzins Stuart P. , Smyth Mark J. , Godfrey Dale I.
Published: August 2008

NKT cell subsets can be divided based on CD4 and NK1.1 expression and tissue of origin, but the developmental and functional relationships between the different subsets still are poorly understood. A comprehensive study of 19 cytokines across different NKT cell subsets revealed that no two NKT subpopulations exhibited the same cytokine profile, and, remarkably, the amounts of each cytokine produced varied by up to 100-fold or more among subsets. This study also revealed the existence of a population of CD4
−
NK1.1
−
NKT cells that produce high levels of the proinflammatory cytokine IL-17 within 2–3 h of activation. On intrathymic transfer these cells develop into mature CD4
−
NK1.1
+
but not into CD4
+
NK1.1
+
NKT cells, indicating that CD4
−
NK1.1
−
NKT cells include an IL-17–producing subpopulation, and also mark the elusive branch point for CD4
+
and CD4
−
NKT cell sublineages.
Muscle-wide secretion of a miniaturized form of neural agrin rescues focal neuromuscular innervation in agrin mutant mice
Authors: Lin Shuo , Maj Marcin , Bezakova Gabriela , Magyar Josef P. , Brenner Hans Rudolf , Ruegg Markus A.
Published: August 2008

Agrin and its receptor MuSK are required for the formation of the postsynaptic apparatus at the neuromuscular junction (NMJ). In the current model the local deposition of agrin by the nerve and the resulting local activation of MuSK are responsible for creating and maintaining the postsynaptic apparatus including clusters of acetylcholine receptors (AChRs). Concomitantly, the release of acetylcholine (ACh) and the resulting depolarization disperses those postsynaptic structures that are not apposed by the nerve and thus not stabilized by agrin-MuSK signaling. Here we show that a miniaturized form of agrin, consisting of the laminin-binding and MuSK-activating domains, is sufficient to fully restore NMJs in agrin mutant mice when expressed by developing muscle. Although miniagrin is expressed uniformly throughout muscle fibers and induces ectopic AChR clusters, the size and the number of those AChR clusters contacted by the motor nerve increase during development. We provide experimental evidence that this is due to ACh, because the AChR agonist carbachol stabilizes AChR clusters in organotypic cultures of embryonic diaphragms. In summary, our results show that agrin function in NMJ development requires only two small domains, and that this function does not depend on the local deposition of agrin at synapses. Finally, they suggest a novel local function of ACh in stabilizing postsynaptic structures.
Large-scale, heterogeneous integration of nanowire arrays for image sensor circuitry
Authors: Fan Zhiyong , Ho Johnny C. , Jacobson Zachery A. , Razavi Haleh , Javey Ali
Published: August 2008

We report large-scale integration of nanowires for heterogeneous, multifunctional circuitry that utilizes both the sensory and electronic functionalities of single crystalline nanomaterials. Highly ordered and parallel arrays of optically active CdSe nanowires and high-mobility Ge/Si nanowires are deterministically positioned on substrates, and configured as photodiodes and transistors, respectively. The nanowire sensors and electronic devices are then interfaced to enable an all-nanowire circuitry with on-chip integration, capable of detecting and amplifying an optical signal with high sensitivity and precision. Notably, the process is highly reproducible and scalable with a yield of ≈80% functional circuits, therefore, enabling the fabrication of large arrays (i.e., 13 × 20) of nanowire photosensor circuitry with image-sensing functionality. The ability to interface nanowire sensors with integrated electronics on large scales and with high uniformity presents an important advance toward the integration of nanomaterials for sensor applications.
Rapid shifts in plant distribution with recent climate change
Authors: Kelly Anne E. , Goulden Michael L.
Published: August 2008

A change in climate would be expected to shift plant distribution as species expand in newly favorable areas and decline in increasingly hostile locations. We compared surveys of plant cover that were made in 1977 and 2006–2007 along a 2,314-m elevation gradient in Southern California's Santa Rosa Mountains. Southern California's climate warmed at the surface, the precipitation variability increased, and the amount of snow decreased during the 30-year period preceding the second survey. We found that the average elevation of the dominant plant species rose by ≈65 m between the surveys. This shift cannot be attributed to changes in air pollution or fire frequency and appears to be a consequence of changes in regional climate.
Minimization of exogenous signals in ES cell culture induces rostral hypothalamic differentiation
Authors: Wataya Takafumi , Ando Satoshi , Muguruma Keiko , Ikeda Hanako , Watanabe Kiichi , Eiraku Mototsugu , Kawada Masako , Takahashi Jun , Hashimoto Nobuo , Sasai Yoshiki
Published: August 2008

Embryonic stem (ES) cells differentiate into neuroectodermal progenitors when cultured as floating aggregates in serum-free conditions. Here, we show that strict removal of exogenous patterning factors during early differentiation steps induces efficient generation of rostral hypothalamic-like progenitors (Rax
+
/Six3
+
/Vax1
+
) in mouse ES cell-derived neuroectodermal cells. The use of growth factor-free chemically defined medium is critical and even the presence of exogenous insulin, which is commonly used in cell culture, strongly inhibits the differentiation via the Akt-dependent pathway. The ES cell-derived Rax
+
progenitors generate Otp
+
/Brn2
+
neuronal precursors (characteristic of rostral–dorsal hypothalamic neurons) and subsequently magnocellular vasopressinergic neurons that efficiently release the hormone upon stimulation. Differentiation markers of rostral–ventral hypothalamic precursors and neurons are induced from ES cell-derived Rax
+
progenitors by treatment with Shh. Thus, in the absence of exogenous growth factors in medium, the ES cell-derived neuroectodermal cells spontaneously differentiate into rostral (particularly rostral–dorsal) hypothalamic-like progenitors, which generate characteristic hypothalamic neuroendocrine neurons in a stepwise fashion, as observed
in vivo
. These findings indicate that, instead of the addition of inductive signals, minimization of exogenous patterning signaling plays a key role in rostral hypothalamic specification of neural progenitors derived from pluripotent cells.