bluuebunny/crossref_metadata_2025 huggingface dataset:
Bacterial community succession during in situ uranium bioremediation: spatial similarities along controlled flow paths
Authors: Hwang Chiachi , Wu Weimin , Gentry Terry J , Carley Jack , Corbin Gail A , Carroll Sue L , Watson David B , Jardine Phil M , Zhou Jizhong , Criddle Craig S , Fields Matthew W
Published: September 2008

Bacterial community succession was investigated in a field-scale subsurface reactor formed by a series of wells that received weekly ethanol additions to re-circulating groundwater. Ethanol additions stimulated denitrification, metal reduction, sulfate reduction and U(VI) reduction to sparingly soluble U(IV). Clone libraries of SSU rRNA gene sequences from groundwater samples enabled tracking of spatial and temporal changes over a 1.5-year period. Analyses showed that the communities changed in a manner consistent with geochemical variations that occurred along temporal and spatial scales. Canonical correspondence analysis revealed that the levels of nitrate, uranium, sulfide, sulfate and ethanol were strongly correlated with particular bacterial populations. As sulfate and U(VI) levels declined, sequences representative of sulfate reducers and metal reducers were detected at high levels. Ultimately, sequences associated with sulfate-reducing populations predominated, and sulfate levels declined as U(VI) remained at low levels. When engineering controls were compared with the population variation through canonical ordination, changes could be related to dissolved oxygen control and ethanol addition. The data also indicated that the indigenous populations responded differently to stimulation for bioreduction; however, the two biostimulated communities became more similar after different transitions in an idiosyncratic manner. The strong associations between particular environmental variables and certain populations provide insight into the establishment of practical and successful remediation strategies in radionuclide-contaminated environments with respect to engineering controls and microbial ecology.
Acoustic waves guided by a fluid layer on a piezoelectric substrate
Authors: Darinskii A. N. , Weihnacht M.
Published: September 2008

This paper theoretically studies the propagation and the generation of leaky acoustic waves in a fluid layer enclosed between the half-infinite YZ-LiNbO3 (lithium niobate) substrate coated with a thin SiO2 (silicone dioxide) layer and the half-infinite domain occupied by silicone rubber. The plane wave spectrum in the structure is computed, and the specific features of the behavior of the real and imaginary parts of the leaky wave velocity depending on the fluid layer thickness and the electric boundary conditions are analyzed. Besides, the numerical estimations are made of the coupling-of-mode (COM) parameters describing a periodic grating deposited on the LiNbO3 substrate under the SiO2 layer. The dependence of the COM parameters is investigated on characteristics and conditions specifying the structure, such as the fluid layer thickness, the SiO2 coating thickness, and the presence or the absence of projections on the SiO2 coating face in contact with the fluid. In particular, it is found that the reflection and the transduction coefficients remain high enough even when the fluid layer is several wavelengths thick provided that the frequency is close to the value f0=vl0′∕2p, where vl0′ is the real leaky wave velocity at the zeroth thickness of the fluid layer and p is the grating period. It is also found that projections on the SiO2-fluid interface significantly increase the reflection coefficient.
Development of a high-brightness and low-divergence lithium neutral beam for a Zeeman polarimetry on JT-60U
Authors: Kojima Atshushi , Kamiya Kensaku , Iguchi Harukazu , Fujita Takaaki , Kakiuchi Hideto , Kamada Yutaka
Published: September 2008

A high-brightness and low-divergence neutral beam is obtained for a Zeeman polarimetry of edge plasmas on JT-60U. The electron density and the pitch angle of the magnetic field line, thus the plasma current density distribution, can be measured by the Zeeman polarimetry using the lithium beam. A thermionic ion source heated by an electron beam is developed in order to obtain the ion beam current extraction over 10mA. The beam optics is designed after detailed numerical simulation taking the space charge effects into account because a low-divergence angle of the neutral lithium beam leads to a narrow spectrum of the beam emission. It is also necessary to keep the beam radius small for good spatial resolution due to a long beam line of 6.5m. The newly developed ion gun is operated on a test stand which simulates the diagnostic arrangement on JT-60U. The ion beam current of 10mA at a beam energy of 10keV is successfully extracted from the ion source operated at the temperature over 1300°C and focused by Einzel lens. The full width at half maximum radius of the ion beam at the neutralizer is about 9mm. A sodium vapor neutralizer neutralizes the collimated ion beam fully at the temperature of 300°C. The neutral beam profiles are measured at two locations of the beam line at Z=2.3m (beam monitor position) and Z=6.5m (plasma region). The half-width at half maximum radius of the neutral beam of 26mm and the equivalent beam current of 3mA with the beam divergence angle of 0.2deg which is the half-angle divergence are obtained. Those parameters satisfy the requirements of the Zeeman polarimetry. Furthermore, a long pulse extraction with a current of 10mA and duration of 50s is attained.
The flip-over effect in self-similar laser-induced plasma expansion
Authors: Baxter Nathan P. , Shabanov Sergei V.
Published: September 2008

We present a rigorous study of a dynamical model for a nonsymmetric expansion of laser-induced plasma plumes into the vacuum. The model is used in the laser film deposition technique and for remote chemical analysis in the so-called laser-induced breakdown spectroscopy. It defines a particular class of solutions of the hydrodynamics equations when the (plasma) mass density, pressure, and temperature as functions of position have level surfaces that are ellipsoids. The time evolution of ellipsoid semiaxes is determined by the dynamical model. In this model we investigate the flip-over effect: A pancakelike shape of the plasma plume turns into a cigarlike shape and vice versa in due course of its expansion. The effect has been observed in experiments as well as in numerical simulations. In many practical cases, axially symmetric plasma plumes with the adiabatic constant of 53 (ideal gas) are used. For this case we prove that the flip-over effect occurs exactly once in the above dynamical model. This rigorous result agrees with the earlier experimental and numerical evidence and, hence, validates a wide applicability of the model.
Thermal instability during an electrical wire explosion
Authors: Oreshkin V. I.
Published: September 2008

The development of thermal instabilities during an electrical wire explosion is analyzed in the present work based on the methods of small perturbation theory. For two cases, with and without allowance for motion, the dispersion equations are derived that describe a relationship between the instantaneous buildup increment and the axial wave vector component. It is demonstrated that the thermal instabilities are always formed during electrical explosion, irrespective of the explosion mode. There are three destabilizing factors leading to the development of the thermal instabilities: a temperature rise, an increase in the specific resistance with increasing temperature, and an increase in the specific resistance with decreasing density. The critical value of current density below which the sausage instabilities grow faster than the thermal ones and above which, on the contrary, the thermal instabilities are dominant can be found for each metal.
Finite element modeling for temperature stabilization of gated Hall sensors
Authors: Jouault B. , Bouguen L. , Contreras S. , Kerlain A. , Mosser V.
Published: September 2008

Using finite element analysis, we have calculated the Hall voltage of gated Hall sensors in the temperature range (−55 °C, 125 °C). We investigated how both the sensor shape and the external connections influence the Hall voltage and its thermal drift. The numerical results are in excellent agreement with the experimental measurements. By contrast, we checked that simplified analytical methods lead to a large numerical error, which is not acceptable in these sensors devoted to metrological applications. In particular, it is found that the thermal drift in the Hall voltage can be canceled for a current of the order of 300 μA, a much higher value than that predicted by the corresponding analytical calculations.
Adapting a triple-axis spectrometer for small angle neutron scattering measurements
Authors: Nieh Mu-Ping , Yamani Zahra , Kučerka Norbert , Katsaras John , Burgess Darcy , Breton Hugo
Published: September 2008

Small angle neutron scattering (SANS) instruments typically cover a q (scattering vector) range from 0.001 to 0.6 Å−1. This range in q is achieved through a combination of cold neutrons (λ>4 Å) and a highly collimated beam. However, as a direct result of the unavailability of a cold source at the Canadian Neutron Beam Centre (CNBC), we have resorted to adapting a triple-axis spectrometer to perform SANS measurements. This is achieved through the use of multiple converging incident beams which enhance the neutron flux on the sample by a factor of 20, compared to a single beam of the same spot size. Furthermore, smearing effects due to vertical divergence from the slit geometry are reduced through the use of horizontal Soller collimators. As a result, this modified triple-axis spectrometer enables SANS measurements to a minimum q value (qmin) of ∼0.006 Å−1. Data obtained from the modified triple-axis spectrometer are in good agreement with those data from the 30 m NG3-SANS instrument located at the National Institute of Standards and Technology (Gaithersburg, MD, USA).
Numerical study of the Guderley and Vasilev reflections in steady two-dimensional shallow water flow
Authors: Defina Andrea , Susin Francesca Maria , Viero Daniele Pietro
Published: September 2008

We present high-resolution numerical solutions of the depth-averaged two-dimensional inviscid shallow water equations which provide new information on shock reflection configuration within the von Neumann paradox conditions. The computed flow field and shock wave patterns close to the triple point for the Guderley and the Vasilev reflections confirm the four-wave theory. We suggest that the most likely Guderley reflection model is a four-wave pattern with a compression wave that originates along the downstream boundary of the supercritical patch. The compression wave, after being refracted by the slip stream, turns the flow behind the Guderley stem further toward the wall until critical condition is achieved.
Theory of ultrafast electron diffraction: The role of the electron bunch properties
Authors: Michalik A. M. , Sherman E. Ya. , Sipe J. E.
Published: September 2008

We present a general formalism for scattering of electron bunches used in ultrafast electron diffraction experiments. To perform the scattering calculation, we associate the classical distribution function that describes the electron bunch just before scattering with the asymptotic-in Wigner distribution. Using single scattering and far-field approximations, we derive an expression for the diffracted signal and discuss the effects of the different bunch parameters on the measured diffracted flux. We identify the transverse and longitudinal coherence lengths and discuss the importance of these length scales in diffraction pattern formation. We present sample numerical calculations for scattering by nanosize particles based on our model and discuss the results in terms of bunch and scattering target parameters.
Favorable pressure gradient turbulent flow over straight and inclined ribs on both channel walls
Authors: Tachie Mark F. , Shah Mohammad K.
Published: September 2008

This paper reports on experimental study of turbulent flows over straight and inclined transverse ribs of square and triangular cross sections attached to the bottom and top walls of an asymmetric converging channel. The pitch-to-height ratio of the ribs was 10. A particle image velocimetry technique was used to conduct extensive velocity measurements at channel midspan and in planes close to the leading and trailing edges of the inclined ribs. From these measurements, spatial averaged profiles of the mean velocity and higher order statistics were obtained to study the effects of rib geometry, pressure gradient, spanwise plane, and rib inclination on the flow characteristics. The results show that rib geometry has no significant effects on the mean flow and turbulent quantities. The roughness effects produced by the straight ribs outweighed pressure gradient effects in the inner region of the flow. As a result, the skin friction coefficient is nearly independent of pressure gradient. The Reynolds shear stress and turbulent transport of the shear stress are also independent of pressure gradient. On the contrary, favorable pressure gradient decreased the Reynolds normal stresses in the outer region and increased the magnitudes of the triple velocity correlations and transport of turbulent kinetic energy (TKE). The three-dimensional secondary motion produced by the inclined ribs distorted the mean flow pattern and substantially diminished the ribs’ effectiveness to augment skin friction and turbulence. For example, the skin friction over the inclined ribs is only 50%–70% of the value measured over the straight ribs. Furthermore, the size of equivalent sand grain required to produce the same amount of drag is one-tenth to one-third of the rib height for the inclined ribs compared to two- to fourfold for the straight ribs. The inclined ribs also reduced the level of the Reynolds stresses, triple velocity correlations, and transport of both the turbulent kinetic energy and Reynolds shear stress compared to the straight ribs. The skewness factors showed that important structural differences exist between flows over straight and inclined ribs.
Electronic properties of doped silicon nanocrystal films
Authors: Lechner Robert , Stegner Andre R. , Pereira Rui N. , Dietmueller Roland , Brandt Martin S. , Ebbers André , Trocha Martin , Wiggers Hartmut , Stutzmann Martin
Published: September 2008

The structural and electrical properties before and after laser annealing of spin-coated films of doped silicon nanocrystals (ncs) produced from the gas phase are presented. While the as-deposited films form a porous network of ncs and show only weak electrical conductivity independent of the doping level, a laser annealing step leads to sintering and melting of the particles and tremendously increases the lateral conductivity. By controlled doping of the initial particles, the conductivity can be further enhanced by seven orders of magnitude reaching values of up to 5 Ω−1 cm−1. The conductivity is found to increase with the doping concentration for highly doped samples while it is independent of the doping level below a critical concentration of 1019 cm−3. The results are discussed within a compensational model taking into account the defect concentration from electron paramagnetic resonance measurements and the activation energies of the electrical conductivity. Surface segregation of phosphorus during growth is identified as the origin of the apparently small phosphorus doping efficiency.
Lateral shearing interferometer for measuring photoinduced refractive index change in As2S3
Authors: Krishnaswami Kannan , Bernacki Bruce E. , Hô Nicolas , Allen Paul J. , Anheier Norman C.
Published: September 2008

We have built and demonstrated a lateral shearing interferometer as a process engineering and control tool for the fabrication and characterization of direct-laser-written waveguide structures in chalcogenide glasses. Photoinduced change in refractive index of 0.154±0.002 was measured for as-deposited amorphous As2S3 thin films at 633nm with an estimated measurement uncertainty of 1.3% for this air-gap interferometer configuration. The simple design of this interferometer can easily be adapted to other wavelengths including mid- and long-wave infrared regions to measure changes in refractive index or material inhomogeneities in transmissive materials.
Truncated photonic crystal cavities with optimized mode confinement
Authors: Bauer Carl A. , Werner Gregory R. , Cary John R.
Published: September 2008

Optimization of a truncated, dielectric photonic crystal cavity leads to configurations that are far from truncated crystal cavities, and which have significantly better radiation confinement. Starting from a two-dimensional truncated photonic crystal cavity with optimal Q-factor, moving the rods from the lattice positions can increase the Q-factor by orders of magnitude, e.g., from 130 to 11 000 for a cavity constructed from 18 rods. In the process, parity symmetry breaking occurs. Achieving the same Q-factor with a regular lattice requires 60 rods. Therefore, using optimized irregular structures for photonic cavities can greatly reduce material requirements and device size.
Sequential tunneling through a two-level semiconductor quantum dot system coupled to magnetic leads
Authors: Ma M. J. , Jalil M. B. A. , Tan S. G.
Published: September 2008

Sequential transport through a semiconductor quantum dot (QD) weakly coupled to two collinear magnetic leads is analyzed theoretically based on the master equation method. The transport model considers two discrete energy levels in the dot, i.e., the lowest unoccupied ϵe (electron) and the highest occupied ϵh (hole) energy levels, with associated Coulomb correlation energies Ue and Uh, respectively, and the spin-flip effect within the dot. The charge and spin currents and the tunneling magnetoresistance are evaluated in the sequential tunneling regime. It was found that when both energy levels, ϵe and ϵh, contribute to the tunneling transport, there is enhancement of the current as well as tunneling magnetoresistance, compared to the case of a single-level QD transport considered previously. The tunneling transport through the two levels of the QD also results in additional bias-dependence: it was observed that spin accumulation and magnetoresistance of the system are particularly suppressed by spin flip within the bias range corresponding to single QD occupancy.
GaN-based microdisk light emitting diodes on (111)-oriented nanosilicon-on-insulator templates
Authors: Tripathy S. , Sale T. E. , Dadgar A. , Lin V. K. X. , Zang K. Y. , Teo S. L. , Chua S. J. , Bläsing J. , Krost A.
Published: September 2008

InGaN/GaN microdisk light emitting diodes (LEDs) on (111)-oriented nanosilicon-on-insulator (nano-SOI) substrates are demonstrated. The (111)-oriented thin SOI substrates are prepared by separation by implantation of oxygen (SIMOX) method. The InGaN/GaN LED structures are grown on these SIMOX templates by metal-organic chemical vapor deposition. The circular mesa patterns are created by standard LED processing steps including photolithography, inductively coupled plasma etching, and contact metallization. Due to the reflectivity changes at the bottom Si/SiO2 interfaces beneath AlN buffer, an improved light extraction from these LEDs has been observed. The room-temperature electroluminescence (EL) spectrum of the microdisk LEDs on SOI shows multiple interference peaks due to the reflections at the Fabry-Pérot boundaries and such effect resulted in an increased integrated EL intensity. For a comparative analysis of light extraction with respect to similar LED structures grown on bulk Si(111), a detailed reflectivity analysis has been carried out to verify the LED structures and to model the EL lineshapes.
Anisotropic behavior of exchange coupling in textured Nd2Fe14B/α-Fe multilayer films
Authors: Cui W. B. , Zheng S. J. , Liu W. , Ma X. L. , Yang F. , Yao Q. , Zhao X. G. , Zhang Z. D.
Published: September 2008

Exchange coupling has been realized in textured Nd2Fe14B/α-Fe multilayer films. A Mo spacer layer has proved to be effective for preventing interdiffusion at the interface region between the hard-magnetic Nd16Fe71B13 and the soft-magnetic α-Fe layer in these multilayer films. Anisotropic behavior of the exchange coupling in the films is observed by means of magnetic measurements. Furthermore, the effective critical correlation length is found to exhibit anisotropic behavior, which is smaller in the parallel than in the perpendicular direction at the same temperature. This anisotropic behavior of the multilayer films can be well explained by taking into account the shape anisotropy of the textured grains.
Composite electrode of carbon nanotubes and vitreous carbon for electron field emission
Authors: Matsubara E. Y. , Rosolen J. M. , Silva S. Ravi P.
Published: September 2008

In this work, the electron field emission behaviour of electrodes formed by carbon nanotubes (CNTs) grown onto monolithic vitreous carbon (VCarbon) substrates with microcavities is presented. Scanning electron microscopy was used to characterize the microstructure of the films. Tungsten probes, stainless steel sphere, and phosphor electrodes were employed in the electron field emission study. The CNT/VCarbon composite represents a route to inexpensive excellent large area electron emission cathodes with fields as low as 2.1 V μm−1. In preliminary lifetime tests for a period of about 24 h at an emission current of about 4 mA cm−2, there is an onset degradation of the emission current of about 28%, which then stabilizes. Electron emission images of the composites show the cavity of the samples act as separate emission sites and predominantly control the emission process. The emission of CNTs/VCarbon was found to be stable for several hours.
Theory of tunneling magnetoresistance and tunneling electroresistance in Co/BiFeO3/La2/3Sr1/3MnO3 junctions
Authors: Ju Sheng , Cai Tian-Yi , Guo Guang-Yu , Li Zhen-Ya
Published: September 2008

We present a theory of tunnel magnetoresistance (TMR) and tunnel electroresistance (TER) in multiferroic Co/BiFeO3/La2/3Sr1/3MnO3 junctions. Both the half-metallic band structure of the La2/3Sr1/3MnO3 electrode and the multiferroicity in the BiFeO3 barrier are considered explicitly in our model. Using transfer matrix method, we have derived an analytic formula for TMR in these structures. The calculations indicate that TMR is larger when the electric polarization in BiFeO3 points to half-metallic La2/3Sr1/3MnO3 and that the thicker the barrier is, the larger is the TMR, while for the negative electric polarization, the thicker the barrier is, the smaller is the TMR. In the mean time, the weak ferromagnetism, arising from spin-orbit coupling in BiFeO3, is found to give a further variation of TMR and TER in these structures. These results agree with recent experimental observation well.
Inexpensive acoustoelectric hydrophone for mapping high intensity ultrasonic fields
Authors: Witte Russell S. , Hall Tim , Olafsson Ragnar , Huang Sheng-Wen , O’Donnell Matthew
Published: September 2008

We describe an inexpensive alternative to conventional hydrophones for measuring ultrasonic fields. The hydrophone, composed of common laboratory supplies, depends on the acoustoelectric (AE) effect, a well-known interaction between electrical current and pressure. Beam patterns of a 540 kHz annular transducer captured using a bowtie-graphite hydrophone were consistent with patterns obtained using conventional, more expensive hydrophones. The AE signal was proportional to both the applied bias current (1.83 μV/mA) and pressure (13.3 μV/MPa) with sensitivity better than 50 kPa. Disposable AE hydrophones may be an attractive alternative for clinical applications that require close monitoring of high intensity acoustic fields.
Low-frequency zone boundary phonons in Li doped ZnO ceramics
Authors: Yadav Harish Kumar , Sreenivas K. , Gupta Vinay , Katiyar R. S.
Published: September 2008

Room temperature Raman spectra of Li doped ZnO (Zn1−xLixO) ceramics with varying Li concentrations (x=0.0, 0.05, 0.10, and 0.15) are investigated in this study. Four peaks were identified at 96.6, 127, 157, and 194 cm−1 in the Li doped samples. The peaks at 127, 157, and 194 cm−1 are assigned to zone boundary phonons in ZnO [J. M. Calleja and M. Cardona, Phys. Rev. B 16, 3753 (1977)], and appear due to disorder in ZnO lattice with Li incorporation. Lithium, owing to its smaller radius, adjusts itself anywhere in the ZnO lattice and breaks the crystal translational symmetry to a large extent, compared to other dopants. Disorder in the lattice is seen to be finely modulated with varying Li content. The peak at 96.6 cm−1 is hypothesized to be a projection of the vibrational motion of Li atoms at lower frequencies, which contributes in a major fashion at higher frequencies, due to its lighter mass than Zn or O atoms.
Erratum: “A Fundamental Equation of State for Sulfur Hexafluoride (SF6) in Extended Equation of State Format” [J. Phys. Chem. Ref. Data 36, 617–662 (2007)]
Authors: Scalabrin G. , Bettio L. , Marchi P. , Stringari P.
Published: September 2008

Typographical errors are corrected in the previously published paper.
Dielectric microwave resonators in TE011 cavities for electron paramagnetic resonance spectroscopy
Authors: Mett Richard R. , Sidabras Jason W. , Golovina Iryna S. , Hyde James S.
Published: September 2008

The coupled system of the microwave cylindrical TE011 cavity and the TE01δ dielectric modes has been analyzed in order to determine the maximum achievable resonator efficiency parameter of a dielectric inserted into a cavity, and whether this value can exceed that of a dedicated TE01δ mode dielectric resonator. The frequency, Q value, and resonator efficiency parameter Λ for each mode of the coupled system were calculated as the size of the dielectric was varied. Other output parameters include the relative field magnitudes and phases. Two modes are found: one with fields in the dielectric parallel to the fields in the cavity center and the other with antiparallel fields. Results closely match those from a computer program that solves Maxwell’s equations by finite element methods. Depending on the relative natural resonance frequencies of the cavity and dielectric, one mode has a higher Q value and correspondingly lower Λ than the other. The mode with the higher Q value is preferentially excited by a coupling iris or loop in or near the cavity wall. However, depending on the frequency separation between modes, either can be excited in this way. A relatively narrow optimum is found for the size of the insert that produces maximum signal for both modes simultaneously. It occurs when the self-resonance frequencies of the two resonators are nearly equal. The maximum signal is almost the same as that of the dedicated TE01δ mode dielectric resonator alone, Λ≅40 G/W1/2 at X-band for a KTaO3 crystal. The cavity is analogous to the second stage of a two-stage coupler. In general, there is no electron paramagnetic resonance (EPR) signal benefit by use of a second stage. However, there is a benefit of convenience. A properly designed sample-mounted resonator inserted into a cavity can give EPR signals as large as what one would expect from the dielectric resonator alone.
The transmission property of the discrete Heisenberg ferromagnetic spin chain
Authors: Ding Qing , Lin Wei
Published: September 2008

We present a mechanism for displaying the transmission property of the discrete Heisenberg ferromagnetic (DHF) spin chain via a geometric approach. With the aid of a discrete nonlinear Schrödinger-like equation which is the discrete gauge equivalent to the DHF, we show that the determination of transmitting coefficients in the transmission problem is always bistable. Thus, a definite algorithm and general stochastic algorithms are presented. A new invariant periodic phenomenon of the nontransmitting behavior for the DHF, with a large probability, is revealed by an adoption of various stochastic algorithms.
A fluid model for ion heating due to ionization in a plasma flow
Authors: Dorf M. A. , Semenov V. E. , Zorin V. G.
Published: September 2008

A mechanism of ion heating due to local ionization in a plasma flow with hot electrons and initially cold ions is described. It is shown that the ion temperature can increase significantly as the ions are accelerated to the ion-acoustic speed, provided there is significant ionization in the acceleration region. The fluid model describing ionization ion heating includes particle, momentum, and energy balance equations for ion species. Using this model with parameters characteristic of gas-dynamic electron cyclotron resonance (ECR) ion source SMIS 37 yields much higher effective ion temperature than can be attributed to the electron-ion collisional energy transfer, typically considered for classical ECR ion sources. This theoretical result is found to be in agreement with findings of recent experiments carried out in SMIS 37.
Dye-sensitized solar cells consisting of dye-bilayer structure stained with two dyes for harvesting light of wide range of wavelength
Authors: Inakazu Fumi , Noma Yusuke , Ogomi Yuhei , Hayase Shuzi
Published: September 2008

Dye-sensitized solar cells (DSCs) containing dye-bilayer structure of black dye and NK3705 (3-carboxymethyl-5-[3-(4-sulfobutyl)-2(3H)-bezothiazolylidene]-2-thioxo-4-thiazolidinone, sodium salt) in one TiO2 layer (2-TiO-BD-NK) are reported. The 2-TiO-BD-NK structure was fabricated by staining one TiO2 layer with these two dyes, step by step, under a pressurized CO2 condition. The dye-bilayer structure was observed by using a confocal laser scanning microscope. The short circuit current (Jsc) and the incident photon to current efficiency of the cell (DSC-2-TiO-BD-NK) was almost the sum of those of DSC stained with black dye only (DSC-1-TiO-BD) and DSC stained with NK3705 only (DSC-1-TiO-NK).
Modeling of the subfilter scalar dissipation rate using the concept of optimal estimators
Authors: Balarac G. , Pitsch H. , Raman V.
Published: September 2008

In this work, modeling of the subfilter scalar dissipation rate is addressed. First, the best set of quantities to write a model is determined using the concept of optimal estimators. This study shows that the best approach is to assume a proportionality between the turbulent time scale and turbulent scalar mixing time scale. It is shown that the turbulent time scale should be defined by the subfilter kinetic energy. To define the coefficient appearing in this model, a dynamic determination based on a global subfilter equilibrium assumption between the dissipation and the production terms leads to the best results.
The theory of variances in equilibrium reconstruction
Authors: Zakharov Leonid E. , Lewandowski Jerome , Foley Elizabeth L. , Levinton Fred M. , Yuh Howard Y. , Drozdov Vladimir , McDonald D. C.
Published: September 2008

The theory of variances of equilibrium reconstruction is presented. It complements existing practices with information regarding what kind of plasma characteristics can be reconstructed, how accurately, and what remains beyond the abilities of diagnostic systems. The σ-curves, introduced by the present theory, give a quantitative assessment of quality of effectiveness of diagnostic systems in constraining equilibrium reconstructions. The theory also suggests a method for aligning the accuracy of measurements of different physical nature and for improvements of numerical algorithms used in reconstruction.
Mixing enhancement in electro-osmotic flows via modulation of electric fields
Authors: Pacheco J. R.
Published: September 2008

The mixing of a passive tracer in a three-dimensional rectangular microchannel is studied numerically. A time-dependent electric field across a microchannel, filled with an electrolyte solution, is applied in order to realize a well-mixed state. Random perturbations to a time-periodic electric field are introduced in order to break the invariant tori of the system and to attain better mixing results. Two types of nonperiodic protocols are used to generate chaotic mixing by modulating the transverse electric field. In each case the quality of mixing is quantified with Lyapunov exponents for nondiffusive tracers and variance in concentration for diffusive tracers. The numerical results suggest that when the Lyapunov exponent is properly scaled, its probability density function measured over various numbers of periods has the same geometrical structure. It was also found that the variance in the concentration of the passive scalar exhibits an exponential decay. For the modulated and periodic systems considered in this investigation, its evolution curves exhibited self-similarity when plotted versus the product of the nondimensional time and the mean Lyapunov exponent of the flow. As the axial flow in this study varies only inside the Debye layer, and the tracers were introduced into the middle pluglike region of the flow, it was found that Taylor dispersion effects are more pronounced for flows (at least in their early stages) with effective mixing in the cross section.
Reduction in critical current density for spin torque transfer switching with composite free layer
Authors: Yen Cheng-Tyng , Chen Wei-Chuan , Wang Ding-Yeong , Lee Yuan-Jen , Shen Chih-Ta , Yang Shan-Yi , Tsai Ching-Hsiang , Hung Chien-Chung , Shen Kuei-Hung , Tsai Ming-Jinn , Kao Ming-Jer
Published: September 2008

A composite free layer (CFL) consisting of a soft layer and a hard layer exchange coupled in parallel is proposed. The experimental results showed that the critical current density (Jc) can be reduced from 7.05×106A∕cm2 of strong coupled CoFeB(12.5Å)∕Ru(4Å)∕NiFe(17.5Å) CFL to 2.65×106A∕cm2 of weak coupled CoFeB(12.5Å)∕Ru(15Å)∕NiFe(17.5Å) CFL. The macrospin simulations showed that the soft layer of CFL can assist the hard layer of CFL to switch at a lower Jc. These results suggest that by using CFL, it is possible to reduce the Jc of spin torque transfer switching without compromising the thermal stability.
Participation in EU Biodiversity Governance: How Far beyond Rhetoric?
Authors: Rauschmayer Felix , van den Hove Sybille , Koetz Thomas
Published: September 2008

We explore the theory and practice of participation in EU biodiversity governance, focusing on the implementation of the Birds and Habitat directives and Natura 2000 at the EU and member-state levels in the cases of France and Germany. We identify three shifts in EU biodiversity governance which potentially lead to intensifying participatory processes, but which may also be induced by more participation: (i) a shift from a top-down state-centred administrative understanding of policy making towards more flexible and bottom-up approaches; (ii) a shift towards more democratic, ‘postnormal’, types of science; and (iii) a shift from a conservation focus towards a more anthropocentric ecosystems goods-and-services approach framed in a normative context of sustainability. We look at whether these shifts happen in practice and also look at the link with participation. At all political levels a big gap remains between the rhetoric on participation and the real-life implementation of participatory processes.
Development of input connections in neural cultures
Authors: Soriano Jordi , Rodríguez Martínez María , Tlusty Tsvi , Moses Elisha
Published: September 2008

We introduce an approach for the quantitative assessment of the connectivity in neuronal cultures, based on the statistical mechanics of percolation on a graph. This allows us to monitor the development of the culture and to see the emergence of connectivity in the network. The culture becomes fully connected at a time equivalent to the expected time of birth. The spontaneous bursting activity that characterizes cultures develops in parallel with the connectivity. The average number of inputs per neuron can be quantitatively determined in units of
m
0
, the number of activated inputs needed to excite the neuron. For
m
0
≃ 15 we find that hippocampal neurons have on average ≈60–120 inputs, whereas cortical neurons have ≈75–150, depending on neuronal density. The ratio of excitatory to inhibitory neurons is determined by using the GABA
A
antagonist bicuculine. This ratio changes during development and reaches the final value at day 7–8, coinciding with the expected time of the GABA switch. For hippocampal cultures the inhibitory cells comprise ≈30% of the neurons in the culture whereas for cortical cultures they are ≈20%. Such detailed global information on the connectivity of networks in neuronal cultures is at present inaccessible by any electrophysiological or other technique.
The A-kinase anchoring protein Yotiao binds and regulates adenylyl cyclase in brain
Authors: Piggott Leslie A. , Bauman Andrea L. , Scott John D. , Dessauer Carmen W.
Published: September 2008

A-kinase anchoring proteins (AKAPs) influence the spatial and temporal regulation of cAMP signaling events. Anchoring of PKA in proximity to certain adenylyl cyclase (AC) isoforms is thought to enhance the phosphorylation dependent termination of cAMP synthesis. Using a combination of immunoprecipitation and enzymological approaches, we show that the plasma membrane targeted anchoring protein AKAP9/Yotiao displays unique specificity for interaction and the regulation of a variety of AC isoforms. Yotiao inhibits AC 2 and 3, but has no effect on AC 1 or 9, serving purely as a scaffold for these latter isoforms. Thus, Yotiao represents an inhibitor of AC2. The N terminus of AC2 (AC2-NT), which binds directly to amino acids 808–957 of Yotiao, mediates this interaction. Additionally, AC2-NT and Yotiao (808–957) are able to effectively inhibit the association of AC2 with Yotiao and, thus, reverse the inhibition of AC2 by Yotiao in membranes. Finally, disruption of Yotiao–AC interactions gives rise to a 40% increase in brain AC activity, indicating that this anchoring protein functions to directly regulate cAMP production in the brain.
Mpv17l protects against mitochondrial oxidative stress and apoptosis by activation of Omi/HtrA2 protease
Authors: Krick Stefanie , Shi Shaolin , Ju Wenjun , Faul Christian , Tsai Su-yi , Mundel Peter , Böttinger Erwin P.
Published: September 2008

Cellular localization determines whether the serine protease HtrA2 exerts pro- or antiapoptotic functions. In contrast to the well-characterized proapoptotic function of cytosolic HtrA2, mechanisms underlying the mitochondrial protective role are poorly understood. Mpv17l is a transmembrane protein previously implicated in peroxisomal reactive oxygen species metabolism and a close homolog of the inner mitochondrial membrane protein Mpv17. Here we demonstrate a previously undescribed direct interaction between Mpv17l and HtrA2 in mitochondria. The interaction is mediated by a PDZ domain and induces protease activation of HtrA2. HtrA2 inhibits mitochondrial superoxide generation, stabilizes mitochondrial membrane potential, and prevents apoptosis at baseline and in response to extracellular inducers of mitochondrial stress. The physiological role of Mpv17l is underscored by the finding that oxidative stress-induced downregulation of Mpv17l is a consistent feature in renal injury models. Our findings identify Mpv17l as a unique interacting protein and regulator of HtrA2 protease mediating antioxidant and antiapoptotic function in mitochondria.
Transmission of Y chromosomes from XY female mice was made possible by the replacement of cytoplasm during oocyte maturation
Authors: Obata Yayoi , Villemure Michele , Kono Tomohiro , Taketo Teruko
Published: September 2008

The B6.Y
TIR
sex-reversed female mouse is anatomically normal at young ages but fails to produce offspring. We have previously shown that its oocytes go through the meiotic cell cycle up to the second metaphase; however, the meiotic spindle is not properly organized, the second meiotic division goes awry after activation or fertilization, and none of the oocytes initiate embryonic development. In the present study, we transferred the nuclei of GV-stage oocytes from XY females into the enucleated GV-stage oocytes from (B6.DBA)F1.XX females. The resultant reconstructed oocytes properly assembled second meiotic spindles after
in vitro
maturation and produced healthy offspring after
in vitro
fertilization. Some male pups inherited maternal Y chromosomes. We conclude that the cytoplasm of the XY oocyte is insufficient to support spindle formation at the second metaphase whereas its replacement with the cytoplasmic material from an XX oocyte allows normal development.
Global synchronous changes in the carbon isotopic composition of carbonate sediments unrelated to changes in the global carbon cycle
Authors: Swart Peter K.
Published: September 2008

The carbon isotopic (δ
13
C) composition of bulk carbonate sediments deposited off the margins of four carbonate platforms/ramp systems (Bahamas, Maldives, Queensland Plateau, and Great Australian Bight) show synchronous changes over the past 0 to 10 million years. However, these variations are different from the established global pattern in the δ
13
C measured in the open oceans over the same time period. For example, from 10 Ma to the present, the δ
13
C of open oceanic carbonate has decreased, whereas platform margin sediments analyzed here show an increase. It is suggested that the δ
13
C patterns in the marginal platform deposits are produced through admixing of aragonite-rich sediments, which have relatively positive δ
13
C values, with pelagic materials, which have lower δ
13
C values. As the more isotopically positive shallow-water carbonate sediments are only produced when the platforms are flooded, there is a connection between changes in global sea level and the δ
13
C of sediments in marginal settings. These data indicate that globally synchronous changes in δ
13
C can take place that are completely unrelated to variations in the global carbon cycle. Fluctuations in the δ
13
C of carbonate sediments measured during previous geological periods may also be subject to similar processes, and global synchroniety of δ
13
C can no longer necessarily be considered an indicator that such changes are related to, or caused by, variations in the burial of organic carbon. Inferences regarding the interpretation of changes in the cycling of organic carbon derived from δ
13
C records should be reconsidered in light of the findings presented here.
Embedded cholesterol in the nicotinic acetylcholine receptor
Authors: Brannigan Grace , Hénin Jérôme , Law Richard , Eckenhoff Roderic , Klein Michael L.
Published: September 2008

The nicotinic acetylcholine receptor (nAChR) is a cation-selective channel central to both neuronal and muscular processes and is considered the prototype for ligand-gated ion channels, motivating a structural determination effort that spanned several decades [Unwin N (2005) Refined structure of the nicotinic acetylcholine receptor at 4 Å resolution.
J Mol Biol
346:967–989]. Purified nAChR must be reconstituted in a mixture containing cholesterol to function. Proposed modes of interaction between cholesterol and the protein range from specific binding to indirect membrane-mediated mechanisms. However, the underlying cause of nAChR sensitivity to cholesterol remains controversial, in part because the vast majority of functional studies were conducted before a medium resolution structure was reported. We show that the nAChR contains internal sites capable of containing cholesterol, whose occupation stabilizes the protein structure. We detect sites at the protein–lipid interface as conventionally predicted from functional data, as well as deeply buried sites that are not usually considered. Molecular dynamics simulations reveal that occupation of both superficial and deeply buried sites most effectively preserves the experimental structure; the structure collapses in the absence of bound cholesterol. In particular, we find that bound cholesterol directly supports contacts between the agonist-binding domain and the pore that are thought to be essential for activation of the receptor. These results likely apply to those other ion channels within the Cys-loop superfamily that depend on cholesterol, such as the GABA receptor.
Middle East coastal ecosystem response to middle-to-late Holocene abrupt climate changes
Authors: Kaniewski D. , Paulissen E. , Van Campo E. , Al-Maqdissi M. , Bretschneider J. , Van Lerberghe K.
Published: September 2008

The Holocene vegetation history of the northern coastal Arabian Peninsula is of long-standing interest, as this Mediterranean/semiarid/arid region is known to be particularly sensitive to climatic changes. Detailed palynological data from an 800-cm alluvial sequence cored in the Jableh plain in northwest Syria have been used to reconstruct the vegetation dynamics in the coastal lowlands and the nearby Jabal an Nuşayriyah mountains for the period 2150 to 550 B.C. Corresponding with the 4.2 to 3.9 and 3.5 to 2.5 cal kyr BP abrupt climate changes (ACCs), two large-scale shifts to a more arid climate have been recorded. These two ACCs had different impacts on the vegetation assemblages in coastal Syria. The 3.5 to 2.5 cal kyr BP ACC is drier and lasted longer than the 4.2 to 3.9 cal kyr BP ACC, and is characterized by the development of a warm steppe pollen-derived biome (1100–800 B.C.) and a peak of hot desert pollen-derived biome at 900 B.C. The 4.2 to 3.9 cal kyr BP ACC is characterized by a xerophytic woods and shrubs pollen-derived biome
ca.
2050 B.C. The impact of the 3.5 to 2.5 cal kyr BP ACC on human occupation and cultural development is important along the Syrian coast with the destruction of Ugarit and the collapse of the Ugarit kingdom at
ca.
1190 to 1185 B.C.
Loss of PIP5KIβ demonstrates that PIP5KI isoform-specific PIP
2
synthesis is required for IP
3
formation
Authors: Wang Yanfeng , Chen Xinsheng , Lian Lurong , Tang Tang , Stalker Timothy J. , Sasaki Takehiko , Brass Lawrence F. , Choi John K. , Hartwig John H. , Abrams Charles S.
Published: September 2008

The three isoforms of PIP5KI (α, β, and γ) synthesize PI4,5P
2
(PIP
2
) by phosphorylating PI4P. Therefore, it is not clear why platelets, like all eukaryotic cells, have more than one isoform. To test the hypothesis that PIP5KI isoforms have nonoverlapping functions, we generated a murine line containing a null mutation of PIP5KIβ and analyzed the effect on platelet signaling. PIP5KIβ-null mice had normal platelet counts. In contrast to platelets lacking PIP5KIα, platelets lacking PIP5KIβ exhibited impaired aggregation accompanied by disaggregation. Although platelets lacking PIP5KIβ had only a moderate deficiency of PIP
2
under basal conditions, they had a striking deficiency in PIP
2
synthesis and IP
3
formation after thrombin stimulation. We have also observed that platelets lacking both PIP5KIα and PIP5KIβ have a complete loss of thrombin-induced IP
3
synthesis even though they still contain PIP5KIγ, the predominant PIP5KI isoform in platelets. These results demonstrate that PIP5KIβ, like PIP5KIα, contributes to the rapid synthesis of a pool of PIP
2
that is required for second-messenger formation, whereas the pool of PIP
2
synthesized by PIP5KIγ does not contribute to this process. Additionally, we found that PIP5KIβ-null platelets failed to form arterial thrombi properly
in vivo
. Together, these data demonstrate that PIP5KIβ is required for rapid PIP
2
synthesis, second-messenger production, and stable platelet adhesion under shear
in vivo
. These results also demonstrate that after stimulation of a G protein-coupled receptor, IP
3
is completely derived from a rapidly synthesized discrete pool of PIP
2
synthesized by PIP5KIα and PIP5KIβ.