bluuebunny/crossref_metadata_2025 huggingface dataset:
Geology of the Gusev cratered plains from the Spirit rover transverse
Authors: Golombek M. P. , Crumpler L. S. , Grant J. A. , Greeley R. , Cabrol N. A. , Parker T. J. , Rice J. W. , Ward J. G. , Arvidson R. E. , Moersch J. E. , Fergason R. L. , Christensen P. R. , Castaño A. , Castaño R. , Haldemann A. F. C. , Li R. , Bell J. F. , Squyres S. W.
Published: January 2006

The cratered plains of Gusev traversed by Spirit are generally low‐relief rocky plains dominated by impact and eolian processes. Ubiquitous shallow, soil‐filled, circular depressions, called hollows, are modified impact craters. Rocks are dark, fine‐grained basalts, and the upper 10 m of the cratered plains appears to be an impact‐generated regolith developed over intact basalt flows. Systematic field observations across the cratered plains identified vesicular clasts and rare scoria similar to original lava flow tops, consistent with an upper inflated surface of lava flows with adjacent collapse depressions. Crater and hollow morphometry are consistent with most being secondaries. The size‐frequency distribution of rocks >0.1 m diameter generally follows exponential functions similar to other landing sites for total rock abundances of 5–35%. Systematic clast counts show that areas with higher rock abundance and more large rocks have higher thermal inertia. Plains with lower thermal inertia have fewer rocks and substantially more pebbles that are well sorted and evenly spaced, similar to a desert pavement or lag. Eolian bed forms (ripples and wind tails) have coarse surface lags, and many are dust covered and thus likely inactive. Deflation of the surface ∼5–25 cm likely exposed two‐toned rocks and elevated ventifacts and transported fines into craters creating the hollows. This observed redistribution yields extremely slow average erosion rates of ∼0.03 nm/yr and argues for very little long‐term net change of the surface and a dry and desiccating environment similar to today's since the Hesperian (or ∼3 Ga).
Implantation of a New Porous Gelatin–Siloxane Hybrid into a Brain Lesion as a Potential Scaffold for Tissue Regeneration
Authors: Deguchi Kentaro , Tsuru Kanji , Hayashi Takeshi , Takaishi Mikiro , Nagahara Mitsuyuki , Nagotani Shoko , Sehara Yoshihide , Jin Guang , Zhang HanZhe , Hayakawa Satoshi , Shoji Mikio , Miyazaki Masahiro , Osaka Akiyoshi , Huh Nam-Ho , Abe Koji
Published: January 2006

For brain tissue regeneration, any scaffold for migrated or transplanted stem cells with supportive angiogenesis is important once necrotic brain tissue has formed a cavity after injury such as cerebral ischemia. In this study, a new porous gelatin–siloxane hybrid derived from the integration of gelatin and 3-(glycidoxypropyl) trimethoxysilane was implanted as a three-dimensional scaffold into a defect of the cerebral cortex. The porous hybrid implanted into the lesion remained at the same site for 60 days, kept integrity of the brain shape, and attached well to the surrounding brain tissues. Marginal cavities of the scaffolds were occupied by newly formed tissue in the brain, where newly produced vascular endothelial, astroglial, and microglial cells were found with bromodeoxyuridine double positivity, and the numbers of those cells were dose-dependently increased with the addition of basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). Extension of dendrites was also found from the surrounding cerebral cortex to the newly formed tissue, especially with the addition of bFGF and EGF. The present study showed that a new porous gelatin–siloxane hybrid had biocompatibility after implantation into a lesion of the central nervous system, and thus provided a potential scaffold for cell migration, angiogenesis and dendrite elongation with dose-dependent effects of additive bFGF and EGF.
Redox behavior of tumor-inhibiting ruthenium(iii) complexes and effects of physiological reductants on their binding to GMP
Authors: Schluga Petra , Hartinger Christian G. , Egger Alexander , Reisner Erwin , Galanski Mathea S. , Jakupec Michael A. , Keppler Bernhard K.
Published: January 2006

The redox properties and GMP-binding of antitumor Ru(iii) complexes were studied by capillary electrophoresis, NMR spectroscopy and square wave voltammetry with regard to the activation of such compounds in tumor tissue.
Measurement of the runaway electrons in the HT-7 tokamak
Authors: Chen Z. Y. , Wan B. N. , Lin S. Y. , Shi Y. J. , Hu L. Q. , Gong X. Z. , Lin H. , Asif M.
Published: January 2006

A thermographic camera and four hard x-ray detectors have been developed to measure the runaway electrons in the HT-7 tokamak. The synchrotron radiation originated from the runaway electrons was measured by an infrared (IR) camera working in the wavelength ranges of 7.5–13μm. With a tangential viewing into the plasma in the direction of the electron approach on the equatorial plane, the synchrotron radiation from the runaway electrons was measured in a full poloidal cross section. Three NaI scintillators are used to monitor the hard x-ray radiation (HXR) in the energy ranges of 0.5–7MeV, and a CdTe detector is used to monitor the low-energy HXR in the energy ranges of 0.3–1.2MeV. The combination of infrared camera and hard x-ray detectors provides a powerful tool to investigate the runaway electron dynamics in HT-7. Runaways in the core and edge regions are monitored simultaneously. The parameters of runaway beam in the core are deduced from the IR pictures. The interaction of runway electrons with toroidal magnetic field ripple is monitored from the HXR emission.
From cluster to bulk: Size dependent energetics of silica and silica-water interaction
Authors: He Yao , Cao Chao , Wan Ying-Xia , Cheng Hai-Ping
Published: January 2006

We present our computational investigations on the energetics of clusters that consist of H2O and SiO2 using first-principles Born-Oppenheimer molecular dynamics method. Cohesive energy and hydration energy of both pure (or dry) and hydroxylated (or wet) ring-structured clusters have been investigated as functions of system size. We have found clear trends of energy as the cluster size increases. Energetics of a small silica nano-rod that contains 108 atoms is also obtained as a middle reference point for size evolution. Results from cluster and nano-rod calculations are compared with values from bulk quartz calculations using the same level of theoretical treatments.
Photodissociation dynamics of ketene at 157.6nm
Authors: Lu I-Chung , Lee Shih-Huang , Lee Yuan T. , Yang Xueming
Published: January 2006

Photodissociation dynamics of ketene at 157.6nm has been investigated using the photofragment translational spectroscopic technique based on photoionization detection using vacuum-ultraviolet synchrotron radiation. Three dissociation channels have been observed: CH2+CO, CH+HCO, and HCCO+H. The product translational energy distributions and angular anisotropy parameters were measured for all three observed dissociation channels, and the relative branching ratios for different channels were also estimated. The experimental results show that the direct C–C bond cleavage (CH2+CO) is the dominant channel, while H migration and elimination channels are very minor. The results in this work show that direct dissociation on excited electronic state is much more significant than the indirect dissociation via the ground state in the ketene photodissociation at 157.6nm.
System for detecting acoustic emissions in multianvil experiments: Application to deep seismicity in the Earth
Authors: Jung Haemyeong , Fei Yingwei , Silver Paul G. , Green Harry W.
Published: January 2006

One of the major goals in the experimental study of deep earthquakes is to identify slip instabilities at high pressure and high temperature (HPHT) that might be responsible for the occurrence of earthquakes. Detecting acoustic emissions from a specimen during faulting provides unique constraints on the instability process. There are few experimental studies reporting acoustic emissions under HPHT conditions, due to technical challenges. And those studies have used only one or at most two acoustic sensors during the experiments. Such techniques preclude the accurate location of the acoustic emission source region and thus the ability to distinguish real signal from noise that may be coming from outside the sample. We have developed a system for detecting acoustic emissions at HPHT. Here we present a four-channel acoustic emission detecting system working in the HPHT octahedral multianvil apparatus. Each channel has high resolution (12 bits) and a sampling rate of 30 MHz. In experiments at the pressures up to 6 GPa and temperatures up to 770 °C, we have observed acoustic emissions under various conditions. Analyzing these signals, we are able to show that this system permits us to distinguish between signal and noise, locate the source of the acoustic emission, and obtain reliable data on the radiation pattern. This system has greatly improved our ability to study faulting instabilities under high pressure and high temperature.
Magnetically filtered Faraday probe for measuring the ion current density profile of a Hall thruster
Authors: Rovey Joshua L. , Walker Mitchell L. R. , Gallimore Alec D. , Peterson Peter Y.
Published: January 2006

The ability of a magnetically filtered Faraday probe (MFFP) to obtain the ion current density profile of a Hall thruster is investigated. The MFFP is designed to eliminate the collection of low-energy, charge-exchange (CEX) ions by using a variable magnetic field as an ion filter. In this study, a MFFP, Faraday probe with a reduced acceptance angle (BFP), and nude Faraday probe are used to measure the ion current density profile of a 5kW Hall thruster operating over the range of 300–500V and 5–10mg∕s. The probes are evaluated on a xenon propellant Hall thruster in the University of Michigan Large Vacuum Test Facility at operating pressures within the range of 4.4×10−4Pa Xe (3.3×10−6Torr Xe) to 1.1×10−3Pa Xe (8.4×10−6Torr Xe) in order to study the ability of the Faraday probe designs to filter out CEX ions. Detailed examination of the results shows that the nude probe measures a greater ion current density profile than both the MFFP and BFP over the range of angular positions investigated for each operating condition. The differences between the current density profiles obtained by each probe are attributed to the ion filtering systems employed. Analysis of the results shows that the MFFP, operating at a +5A solenoid current, provides the best agreement with flight-test data and across operating pressures.
Control system for 5MW neutral beam ion source for SST1
Authors: Patel G. B. , Onali Raja , Sharma Vivek , Suresh S. , Tripathi V. , Bandyopadhyay M. , Singh N. P. , Thakkar Dipal , Gupta L. N. , Singh M. J. , Patel P. J. , Chakraborty A. K. , Baruah U. K. , Mattoo S. K.
Published: January 2006

This article describes the control system for a 5MW ion source of the NBI (neutral beam injector) for steady-state superconducting tokamak-1 (SST-1). The system uses both hardware and software solutions. It comprises a DAS (data acquisition system) and a control system. The DAS is used to read the voltage and current signals from eight filament heater power supplies and 24 discharge power supplies. The control system is used to adjust the filament heater current in order to achieve an effective control on the discharge current in the plasma box. The system consists of a VME (Verse Module Eurocard) system and C application program running on a VxWorks™ real-time operating system. A PID (proportional, integral, and differential) algorithm is used to control the filament heater current. Experiments using this system have shown that the discharge current can be controlled within 1% accuracy for a PID loop time of 20ms. Response of the control system to the pressure variation of the gas in the chamber has also been studied and compared with the results obtained from those of an uncontrolled system. The present approach increases the flexibility of the control system. It not only eases the control of the plasma but also allows an easy changeover to various operation scenarios.
The scaling properties of two-dimensional compressible magnetohydrodynamic turbulence
Authors: Merrifield J. A. , Arber T. D. , Chapman S. C. , Dendy R. O.
Published: January 2006

Understanding the phenomenology captured in direct numerical simulation (DNS) of magnetohydrodynamic (MHD) turbulence rests upon models and assumptions concerning the scaling of field variables and dissipation. Here compressible MHD turbulence is simulated in two spatial dimensions by solving the isothermal equations of resistive MHD on a periodic square grid. In these simulations it is found that the energy spectrum decreases more slowly with k, and the viscous cutoff length is larger, than would be expected from the 1941 phenomenology of Kolmogorov (K41). Both these effects suggest that the cascade time is modified by the presence of Alfvén waves as in the phenomenology of Iroshnikov and Kraichnan (IK). Motivated by this, these scaling exponents are compared with those of the IK-based model of Politano and Pouquet [Phys. Rev. E 52, 636 (1995)], which is an extension of the model of She and Leveque [Phys. Rev. Lett. 72, 336 (1994)]. However, the scaling exponents from these simulations are not consistent with the model of Politano and Pouquet, so that neither IK nor K41 models would appear to describe the simulations. The spatial intermittency of turbulent activity in such simulations is central to the observed phenomenology and relates to the geometry of structures that dissipate most intensely via the scaling of the local rate of dissipation. The framework of She and Leveque implies a scaling relation that links the scaling of the local rate of dissipation to the scaling exponents of the pure Elsässer field variables (z±=v±B∕μoρ). This scaling relation is conditioned by the distinct phenomenology of K41 and IK. These distinct scaling relations are directly tested using these simulations and it is found that neither holds. This deviation suggests that additional measures of the character of the dissipation may be required to fully capture the turbulent scaling, for example, pointing towards a refinement of the phenomenological models. It may also explain why previous attempts to predict the scaling exponents of the pure Elsässer fields in two-dimensional magnetohydrodynamic turbulence by extending the theory of She and Leveque have proved unsuccessful.
Distinctive features of photoionized plasma from short x-ray-pulse interaction with gaseous medium
Authors: Bychenkov V. Yu. , Romanov D. V. , Rozmus W. , Capjack C. E. , Fedosejevs R.
Published: January 2006

The study of a photoionized plasma created through the interaction of a short linearly polarized x-ray pulse with a gaseous medium is presented in the context of the future design of experiments involving femtosecond free-electron laser pulses. The dispersion properties and instabilities of such x-ray-produced plasma are studied. It is shown that a two-stream type of instability can be obtained with a growth rate comparable to the plasma frequency. This is expected to have a dramatic effect on the evolution of an x-ray laser-produced plasma. A model for describing electromagnetic-field generation and emission resulting from the interaction of a short x-ray laser pulse with a gas jet is proposed. Issues addressed include the effect of the thermal electromotive force at the edge of a plasma driven by the anisotropic electron energy distribution that arises from the photoionization of a gas. Terahertz pulse emission from these photoionized plasma is also predicted.
Nonlinear propagation of ion-acoustic waves in electron-positron-ion plasma with trapped electrons
Authors: Alinejad H. , Sobhanian S. , Mahmoodi J.
Published: January 2006

A theoretical investigation has been made for ion-acoustic waves in an unmagnetized electron-positron-ion plasma. A more realistic situation in which plasma consists of a negatively charged ion fluid, free positrons, and trapped as well as free electrons is considered. The properties of stationary structures are studied by the reductive perturbation method, which is valid for small but finite amplitude limit, and by pseudopotential approach, which is valid for large amplitude. With an appropriate modified form of the electron number density, two new equations for the ion dynamics have been found. When deviations from isothermality are finite, the modified Korteweg-deVries equation has been found, and for the case that deviations from isothermality are small, calculations lead to a generalized Korteweg-deVries equation. It is shown from both weakly and highly nonlinear analysis that the presence of the positrons may allow solitary waves to exist. It is found that the effect of the positron density changes the maximum value of the amplitude and M (Mach number) for which solitary waves can exist. The present theory is applicable to analyze arbitrary amplitude ion-acoustic waves associated with positrons which may occur in space plasma.
Giant anisotropy of carrier mobility in electroluminescent conjugated polymer
Authors: Meng Hsin-Fei , Chen Bo-Lun , Tzeng Kuo-Chen , Horng Sheng-Fu
Published: January 2006

The horizontal and vertical hole mobility of amorphous spin-coated electroluminescent conjugated films are studied. It is found that the horizontal mobility is about four orders of magnitude larger than the vertical mobility. The horizontal mobility increases daily with the aging of the polymer solution from which the film is spun. Low temperature and photoluminescence study reveal that the giant mobility anisotropy is a result of the alignment of the aggregates, formed during aging, by the centrifugal force of the spin.
Kinetic simulation of secondary electron emission effects in Hall thrusters
Authors: Sydorenko D. , Smolyakov A. , Kaganovich I. , Raitses Y.
Published: January 2006

The particle-in-cell code has been developed for kinetic simulations of Hall thrusters with a focus on plasma-wall interaction. It is shown that the effect of secondary electron emission on wall losses is different from predictions of previous fluid and kinetic studies. In simulations, the electron velocity distribution function is strongly anisotropic, depleted at high energy, and nonmonotonic. Secondary electrons form two beams propagating between the walls of a thruster channel in opposite radial directions. The beams produce secondary electron emission themselves depending on their energy at the moment of impact with the wall, which is defined by the electric and magnetic fields in the thruster as well as by the electron transit time between the walls. The condition for the space-charge-limited secondary electron emission depends not only on the energy of bulk plasma electrons but also on the energy of beam electrons. The contribution of the beams to the particles and energy wall losses may be much larger than that of the plasma bulk electrons. Recent experimental studies may indirectly support the results of these simulations, in particular, with respect to the electron temperature saturation and the channel width effect on the thruster discharge.
Implantation of labelled single nitrogen vacancy centers in diamond using N15
Authors: Rabeau J. R. , Reichart P. , Tamanyan G. , Jamieson D. N. , Prawer S. , Jelezko F. , Gaebel T. , Popa I. , Domhan M. , Wrachtrup J.
Published: January 2006

Nitrogen-vacancy (NV−) color centers in diamond were created by implantation of 7 keV N15(I=1∕2) ions into type IIa diamond. Optically detected magnetic resonance was employed to measure the hyperfine coupling of single NV− centers. The hyperfine spectrum from NV−15 arising from implanted N15 can be distinguished from NV−14 centers created by native N14(I=1) sites. Analysis indicates 1 in 40 implanted N15 atoms give rise to an optically observable NV−15 center. This report ultimately demonstrates a mechanism by which the yield of NV− center formation by nitrogen implantation can be measured.
Fragmentation dynamics of ionized neon clusters (Nen,n=3–14) embedded in helium nanodroplets
Authors: Bonhommeau David , Halberstadt Nadine , Viel Alexandra
Published: January 2006

We report a theoretical study of the nonadiabatic fragmentation dynamics of ionized neon clusters embedded in helium nanodroplets for cluster sizes up to n=14 atoms. The dynamics of the neon atoms is modeled using the molecular dynamics with quantum transitions method of Tully [J. Chem. Phys. 93, 1061 (1990)] with the nuclei treated classically and transitions between electronic states quantum mechanically. The potential-energy surfaces are derived from a diatomics-in-molecules model to which induced dipole-induced dipole interactions are added. The effect of the spin-orbit interaction is also discussed. The helium environment is modeled by a friction force acting on charged atoms whose speed exceeds the critical Landau velocity. The dependence of the fragment size distribution on the friction strength and on the initial nanodroplet size is investigated. By comparing with the available experimental data obtained for Ne3+ and Ne4+, a reasonable value for the friction coefficient, the only parameter of the model, is deduced. This value is then used to predict the effect of the helium environment on the dissociation dynamics of larger neon clusters, n=5–14. The results show stabilization of larger fragments than in the gas phase, but fragmentation is not completely caged. In addition, two types of dynamics are characterized for Ne4+: fast and explosive, therefore leaving no time for friction to cool down the process when dynamics starts on one of the highest electronic states, and slower, therefore leading to some stabilization by helium when it starts on one of the lowest electronic states.
High-pressure torsion-induced grain growth in electrodeposited nanocrystalline Ni
Authors: Liao X. Z. , Kilmametov A. R. , Valiev R. Z. , Gao Hongsheng , Li Xiaodong , Mukherjee A. K. , Bingert J. F. , Zhu Y. T.
Published: January 2006

Deformation-induced grain growth has been reported in nanocrystalline (nc) materials under indentation and severe cyclic loading, but not under any other deformation mode. This raises an issue on critical conditions for grain growth in nc materials. This study investigates deformation-induced grain growth in electrodeposited nc Ni during high-pressure torsion (HPT). Our results indicate that high stress and severe plastic deformation are required for inducing grain growth, and the upper limit of grain size is determined by the deformation mode and parameters. Also, texture evolution suggests that grain-boundary-mediated mechanisms played a significant role in accommodating HPT strain.
Measurements of plasma-wave generation using a short-pulse high-intensity laser beat wave
Authors: Walton B. , Najmudin Z. , Wei M. S. , Marle C. , Kingham R. J. , Krushelnick K. , Dangor A. E. , Clarke R. J. , Poulter M. J. , Hernandez-Gomez C. , Hawkes S. , Neely D. , Collier J. L. , Danson C. N. , Fritzler S. , Malka V.
Published: January 2006

Experiments to examine the generation of relativistic plasma waves via a high-intensity short-pulse beat-wave scheme are described in detail. The pulse stretcher of the Vulcan chirped-pulse amplification (CPA) laser system was modified to produce two frequency, 3ps pulses focusable to intensities up to 1018Wcm−2. Short high-intensity pulses were used to avoid limitations to the plasma-wave amplitude due to the modulational instability. Two experiments were undertaken, at 3 and 10TW, with the generation of plasma waves diagnosed by measuring the sidebands produced in the spectrum of the forward scattered beam. A resonance in the sideband signal was observed for an initial plasma density higher than expected for the given beat frequency. This resonance shift can be attributed to transverse ponderomotive expulsion of plasma electrons from the laser focal region. A monotonically increasing background was also observed, which was due to nonresonant cross-phase modulation.
Neoclassical momentum transport in an impure rotating tokamak plasma
Authors: Newton S. , Helander P.
Published: January 2006

It is widely believed that transport barriers in tokamak plasmas are caused by radial electric-field shear, which is governed by angular momentum transport. Turbulence is suppressed in the barrier, and ion thermal transport is comparable to the neoclassical prediction, but experimentally angular momentum transport has remained anomalous. With this motivation, the collisional transport matrix is calculated for a low collisionality plasma with collisional impurity ions. The bulk plasma toroidal rotation velocity is taken to be subsonic, but heavy impurities undergo poloidal redistribution due to the centrifugal force. The impurities give rise to off-diagonal terms in the transport matrix, which cause the plasma to rotate spontaneously. At conventional aspect ratio, poloidal impurity redistribution increases the angular momentum flux by a factor up to ε−3∕2 over previous predictions, making it comparable to the “banana” regime heat flux. The flux is primarily driven by radial pressure and temperature gradients.
Control of radio-frequency atmospheric pressure argon plasma characteristics by helium gas mixing
Authors: Moon Se Youn , Han Jewoo , Choe W.
Published: January 2006

The control of plasma characteristics is one of the important issues in many atmospheric pressure plasma applications. In order to accomplish this control, a feasibility study was performed by investigating the role of helium gas in an argon glow plasma that were produced in ambient air by 13.56MHz radio-frequency power. Optical emission spectroscopy was used to measure rotational temperature and emission spectra acquired between 300 and 840nm. Based on electrical and optical measurements, parameters such as gas temperature, breakdown voltage, power coupling efficiency, spatial uniformity of rotational temperature, and the sum of the emission intensity were controlled by varying the argon and helium gas mixing ratio. The addition of helium gas (from 0to10ℓpm) to the argon flow (of 10ℓpm) lowered the breakdown voltage (from 430to300Vpk) and the rotational temperature (from 465to360K). However, an excessive addition of helium resulted in a reduction of the spatial uniformity and efficiency of power coupling. When the ratio of helium to argon flow was between 0.3 and 0.5, a high spatial uniformity with a relatively low gas temperature and breakdown voltage was achieved. This suggests that mixing of the supply gas is a useful way of controlling the plasma characteristics that may be utilized for applications with specific required discharge conditions.
Numerical and experimental exploration of phase control of chaos
Authors: Zambrano Samuel , Allaria Enrico , Brugioni Stefano , Leyva Immaculada , Meucci Riccardo , Sanjuán Miguel A. F. , Arecchi Fortunato T.
Published: January 2006

A well-known method to suppress chaos in a periodically forced chaotic system is to add a harmonic perturbation. The phase control of chaos scheme uses the phase difference between a small added harmonic perturbation and the main driving to suppress chaos, leading the system to different periodic orbits. Using the Duffing oscillator as a paradigm, we present here an in-depth study of this technique. A thorough numerical exploration has been made focused in the important role played by the phase, from which new interesting patterns in parameter space have appeared. On the other hand, our novel experimental implementation of phase control in an electronic circuit confirms both the well-known features of this method and the new ones detected numerically. All this may help in future implementations of phase control of chaos, which is globally confirmed here to be robust and easy to implement experimentally.
Principal physics of rotating magnetic-field current drive of field reversed configurations
Authors: Hoffman A. L. , Guo H. Y. , Miller K. E. , Milroy R. D.
Published: January 2006

After extensive experimentation on the Translation, Confinement, and Sustainment rotating magnetic-field (RMF)-driven field reversed configuration (FRC) device [A. L. Hoffman et al., Fusion Sci. Technol. 41, 92 (2002)], the principal physics of RMF formation and sustainment of standard prolate FRCs inside a flux conserver is reasonably well understood. If the RMF magnitude Bω at a given frequency ω is high enough compared to other experimental parameters, it will drive the outer electrons of a plasma column into near synchronous rotation, allowing the RMF to penetrate into the plasma. If the resultant azimuthal current is strong enough to reverse an initial axial bias field Bo a FRC will be formed. A balance between the RMF applied torque and electron-ion friction will determine the peak plasma density nm∝Bω∕η1∕2ω1∕2rs, where rs is the FRC separatrix radius and η is an effective weighted plasma resistivity. The plasma total temperature Tt is free to be any value allowed by power balance as long as the ratio of FRC diamagnetic current, I′dia≈2Be∕μo, is less than the maximum possible synchronous current, I′sync=⟨ne⟩eωrs2∕2. The RMF will self-consistently penetrate a distance δ* governed by the ratio ζ=I′dia∕I′sync. Since the FRC is a diamagnetic entity, its peak pressure pm=nmkTt determines its external magnetic field Be≈(2μopm)1∕2. Higher FRC currents, magnetic fields, and poloidal fluxes can thus be obtained, with the same RMF parameters, simply by raising the plasma temperature. Higher temperatures have also been noted to reduce the effective plasma resistivity, so that these higher currents can be supported with surprisingly little increase in absorbed RMF power.
Temperature and electron density measurements on laser driven radiative shocks
Authors: Vinci T. , Koenig M. , Benuzzi-Mounaix A. , Michaut C. , Boireau L. , Leygnac S. , Bouquet S. , Peyrusse O. , Batani D.
Published: January 2006

In this paper, new results on radiative shocks generated by a high power laser in a xenon gas cell are presented. Several shock parameters were measured: temperature, radial expansion and velocity, as well as the electron density in the radiative precursor and its velocity. Multiple laser shot allowed the investigation of physical trends changing initial conditions (laser energy and initial gas pressure). Results are compared with one- and two-dimensional radiative hydrodynamic simulations. The experiments were carried out at the LULI Laboratory.
Mechanical characteristic of ssDNA∕dsDNA molecule under external loading
Authors: Chiang K. N. , Yuan C. A. , Han C. N. , Chou C. Y. , Cui Yujia
Published: January 2006

The elasticity and extensibility behaviors of sequence-dependent single stranded and double stranded DNA (ssDNA∕dsDNA) under various external loading conditions are studied by the clustered atomistic-continuum mechanics (CACM). The proposed numerical CACM is based on the finite element method, and it comprises both the atomistic-continuum and clustered atomistic-continuum (the clustered atoms are treated as a single super atom) mechanics. Through the CACM simulation, the transient mechanical response of the DNA could be revealed, including the stretching and rotating of the DNA backbone. Moreover, good agreement was achieved between the numerical simulation and single molecule experimental results.
Quantum computing based on vibrational eigenstates: Pulse area theorem analysis
Authors: Cheng Taiwang , Brown Alex
Published: January 2006

In a recent paper [D. Babikov, J. Chem. Phys. 121, 7577 (2004)], quantum optimal control theory was applied to analyze the accuracy of quantum gates in a quantum computer based on molecular vibrational eigenstates. The effects of the anharmonicity parameter of the molecule, the target time of the pulse, and the penalty function on the accuracy of the qubit transformations were investigated. We demonstrate that the effects of all the molecular and laser-pulse parameters can be explained utilizing the analytical pulse area theorem, which originates from the standard two-level model. Moreover, by analyzing the difference between the optimal control theory results and those obtained using the pulse area theorem, it is shown that extremely high quantum gate fidelity can be achieved for a qubit system based on vibrational eigenstates.
van der Waals interactions between the air-bearing surface and a lubricated glass disk: A comparative study
Authors: Crone Robert , Dagastine Raymond R. , White Lee. R. , Jones Paul M. , Hsia Yiao-Tee
Published: January 2006

Lifshitz theory has been used to calculate the van der Waals (vdW) force between a magnetic storage read-write head over both a lubricated glass disk and a magnetic disk. These forces were then incorporated into an air-bearing simulation that calculates the flying height of the slider as a function of disk revolutions per minute (rpm) for both types of media. A sharp decrease in the flying height of the slider over the magnetic disk was calculated at approximately 1950 rpm, whereas a similar decrease is observed at 150 rpm slower over the glass disk. These differences were ascribed to a significantly larger vdW force acting between the slider and the magnetic media, when compared to the glass disk. The magnitude of the vdW force, acting on the slider, over both glass and magnetic media, is described and its relevance to the reliability of the head-disk interface is discussed.
Determination of dc Kerr coefficients of polymer filmswith prism-optical waveguide configuration
Authors: Zhou Jianhong , Deng Xiaoxu , Cao Zhuangqi , Shen Qishun , Wei Wei , Zhang Zhijian , Xie Shixiang
Published: January 2006

A prism-optical waveguide coupling system, which consists of a prism and a symmetrical metal-cladding polymer optical waveguide, is used to analyze the field-induced intensity variation due to the quadratic electro-optic (QEO) effect. As a result, not only the dc Kerr coefficient, but also the whole components of the QEO tensor of the polymer film are determined experimentally.
Intermodulation gain in nonlinear NbN superconducting microwave resonators
Authors: Abdo Baleegh , Segev Eran , Shtempluck Oleg , Buks Eyal
Published: January 2006

We report the measurement of intermodulation gain greater than unity in NbN superconducting stripline resonators. In the intermodulation measurements we inject two unequal tones into the oscillator—the pump and signal—both lying within the resonance band. At the onset of instability of the reflected pump we obtain a simultaneous gain of both the idler and the reflected signal. The measured gain in both cases can be as high as 15dB.
Collective movement of three million plus Au atoms on a silicon bicrystal
Authors: Liu C. H. , Wu W. W. , Chen L. J.
Published: January 2006

The movement of nanosized Au clusters on Si bicrystal was found to be critically influenced by strained fields of the buried twist-dislocation network by in situ ultrahigh vacuum transmission electronic microscopy. Collective movement of Au atoms was observed. Most strikingly, clusters of more than three million atoms move concertedly by one dislocation spacing (7–45 nm) within 1∕30s at a substrate temperature of 250 °C. The “jumping” mechanism is attributed to the viscous flow. The observation shall serve as a good reference to refine the theory to realize the control of self-organized nanoparticles on silicon bicrystals.
Effect of tensile strain on grain connectivity and flux pinning in Bi2Sr2Ca2Cu3Ox tapes
Authors: van der Laan D. C. , Ekin J. W. , van Eck H. J. N. , Dhallé M. , ten Haken B. , Davidson M. W. , Schwartz J.
Published: January 2006

The grain-to-grain connectivity in Bi2Sr2Ca2Cu3Ox tapes is still poorly understood, even though they have been commercially available in long lengths for several years. This letter explains the effects of tensile strain on the grain-to-grain connectivity in Bi2Sr2Ca2Cu3Ox tapes. The different length scales at which damage to the grain structure occurs are studied with magneto-optical imaging, scanning-electron microscopy, and transport current. These data show that the initial degradation in critical current when strain exceeds the irreversible strain limit is caused by microcracks (∼100–500nm in width) that form mainly at high-angle grain boundaries. Filament-wide cracks (∼5–10μm in width) form at locations of lower grain density in the filaments at strains far exceeding the irreversible strain limit. However, in contrast to previous reports, a careful analysis of the pinning force as a function of tensile strain, taking into account current sharing with the normal matrix by using the offset criterion, shows that intragranular flux pinning is not affected by strain in any significant way.
Giant enhancement of room-temperature magnetoresistance in La0.67Sr0.33MnO3∕Nd0.67Sr0.33MnO3 multilayers
Authors: Mukhopadhyay Soumik , Das I.
Published: January 2006

The metal-insulator transition temperature in colossal magnetoresistance manganites has been altered and brought close to the room temperature by preparing La0.67Sr0.33MnO3 (LSMO)∕Nd0.67Sr0.33MnO3 (NSMO) multilayers with ultrathin individual layers of LSMO and NSMO. The LSMO/NSMO multilayers with ultrathin individual layers of thickness of about 10 Å exhibits 150% magnetoresistance at 270 K whereas LSMO/NSMO multilayers with moderate individual layer thickness of about 40 Å each exhibits a mere 15% magnetoresistance at the same temperature. We have shown that the reduction in thickness of the individual layers leads to increased spin fluctuation which results in the enhancement of magnetoresistance.
Soil nitrogen mineralisation and organic matter composition revealed by 13C NMR spectroscopy under repeated prescribed burning in eucalypt forests of south-east Queensland
Authors: Guinto D. F. , Xu Z. H. , Saffigna P. G. , House A. P. N. , Perera M. C. S.
Published: January 2006

The effects of burning on in situ extractable nitrogen
(NH+4-N+NO-3-N)
and net Nmineralisation following scheduled fuel reduction burns in repeatedly
burnt dry and wet sclerophyll forest sites in south-east Queensland were
assessed. In addition, soil organic matter composition in the wet sclerophyll
site was assessed by 13C NMR spectroscopy. The results
showed that at the dry sclerophyll site, extractable N and net N
mineralisation for 1 year were largely unaffected by burning, while at the wet
sclerophyll site, these parameters decreased. 13C NMR
analysis of soil samples from the wet sclerophyll site revealed that there was
a significant reduction in the proportion of O-alkyl (alkoxy/carbohydrate)
C with increasing burning frequency. Statistically significant effects on the
other chemical shift regions were not detected. The ratio of alkyl C to
O-alkyl C, a proposed index of organic matter decomposition, increased with
increasing burning frequency. A high ratio of alkyl C to O-alkyl C suggests
low amounts of carbohydrates relative to waxes and cutins, which could in turn
lead to slower mineralisation. The findings are in accord with this
hypothesis. There were significant linear relationships between cumulative N
mineralisation for 1 year and the proportions of alkyl C and O-alkyl C, and
the ratio of alkyl C/O-alkyl C. Thus, in addition to reductions in
substrate quantity (low organic C and total N for burnt soils), there was also
an alteration of substrate quality as revealed by 13C
NMR spectroscopy which is reflected in low N mineralisation.
Polymer effects on surface mechanical strength of a crusting loessial soil
Authors: Levy G. J. , Rapp I.
Published: January 2006

Addition of synthetic polymers to crusting soils generally improves seedling
emergence and this is thought to be caused by lower mechanical strength of the
crusted soil surfaces. The objective of the present study was to evaluate the
mechanism by which polymer addition contributes to the reduction in crust
mechanical strength. Three polymers were used, 2 anionic polyacrylamides
differing in their molecular weight, and a cationic polysaccharide. Samples of
a silty loam calcareous loess (Calcic Haploxeralf) were packed to a depth of
78 mm in round pots having an internal diameter of 120 mm at the top. Polymer
was added to the soil surface, at a rate of 20 or 40 kg/ha, by spraying a
concentrated polymer solution. The pots were then exposed to 40 mm of
simulated rainfall comprising either distilled water or tap water (electrical
conductivity 0·97 dS/m). In an additional study, polymer was added
to the tap water to form a dilute (20 or 40 g/m3)
polymer solution which was then used in the 40-mm rain event. After the
exposure to rain, the pots were transferred to a temperature-controlled room
(30°C). Weight of the pots, moisture content of the upper 10 mm of the
soil, and crust strength (impedance) determined with a 3·24-mm diameter
probe were measured periodically up to 95% water loss in the soil. In
most of the polymer treatments, moisture content immediately after the rain
was in the range of 32–39%, which was significantly higher than
that in the control (27–29%). In general, for a given moisture
content, crust strength did not differ significantly between the control and
the polymer treatments. However, moisture content for a given cumulative
drying time was higher in the polymer treatments than in the control,
indicating that polymer application delayed crust drying and maintained a
crust with a lower mechanical strength for a longer period of time.
Polyacrylamide with a low molecular weight, applied at a rate of 40 kg/ha,
emerged as the most effective treatment for maintaining high moisture content
in the upper soil layer, and hence a crust with a low mechanical strength.
Application of a physically based soil erosion model, GUEST, in the absence of data on runoff rates II.
Authors: Yu B. , Rose C. W. , Sajjapongse A. , Yin D. , Eusof Z. , Anecksamphant C. , Cakurs U.
Published: January 2006

Runoff rates were estimated from rainfall rates and runoff amounts for 4
experimental sites in China, Malaysia, and Thailand before a physically based
erosion model GUEST was used to determine the soil erodibility parameter and
evaluate the potential to use the erosion model to predict the amount of soil
loss on an event basis. We also examined 3 different ways of determining the
soil erodibility parameter for the same storm event using:
(i) hydrographs estimated from rainfall intensities and
runoff amounts; (ii) an effective runoff rate calculated
from the hydrograph; (iii) an estimate of the effective
runoff rate based on a scaling technique involving the peak rainfall intensity
and the gross runoff coefficient. All 3 methods can produce consistent soil
erodibility parameters for a given runoff event. The calculated soil
erodibility for individual storm events for all sites shows considerable
temporal variation and for most sites a decreasing trend over time, as
observed elsewhere in the same region. Among the 4 soils examined, the average
soil erodibility tends to decrease as the ratio of coarse to fine materials
decreases. When the erosion model GUEST is used to predict event soil loss
using estimated soil erodibility parameters, an average model efficiency of
0·68 is achieved for the sites tested.
Extracting soil-landscape rules from previous soil surveys
Authors: Bui Elisabeth N. , Loughhead Andrew , Corner Robert
Published: January 2006

Where map legends and map unit definitions reflect the mental models used by
soil surveyors to map soils in the past, the association between soil map
units and other environmental spatial data can be re-modelled to infer formal
survey rules. These rules then can be used to guide subsequent
re-interpretations of spatial information for the same area or for another
area judged to be similar. Classification trees and Bayesian statistical
modelling were used to extract soil mapping rules from an existing map using
the Toowoomba area in south-eastern Queensland, Australia, as a case study. In
the Toowoomba map area, regional soil-landscape rules could be extracted by
combining geology and DEM-derived attributes. The two approaches achieved
comparable success.
Soil organic carbon dynamics under long-term sugarcane monoculture
Authors: Skjemstad J. O. , Taylor J. A. , Janik L. J. , Marvanek S. P.
Published: January 2006

Comparisons of soil samples from virgin sites or sites recently planted to
sugarcane (new) with sites that had been under cane production for many years
(old) were made to investigate the potential impact of cane production on soil
organic carbon (OC) levels and chemistry. The comparisons showed that very
little change had occurred in total OC and in ‘light’ fraction
(<1·6 Mg/m3). Increasing pyrophosphate
extractability throughout the profile at some sites, as a result of
cultivation, however, suggested that the organic matter generally became more
‘humified’ with long-term cane production. Evidence is presented
for a redistribution of OC within profiles under cane production. Old,
well-established cane sites had soils with lower OC levels in the surface
horizons and higher levels in the subsoils relative to new sites. The overall
chemistry of the soil organic matter, as indicated by solid state
13C nuclear magnetic resonance spectroscopy, did not
change significantly at each site even though between site differences were
large. Some soils contained substantial amounts of charcoal which was of
pre-cane origin. In some of the coarse-textured soils, smaller amounts of
charcoal produced during the burning of cane appeared to accumulate below the
A1 horizons in the profiles. It also appeared likely that the redistribution
of carbon in the upper horizons of some soils resulted from the movement of
charcoal within the profile, probably as a result of tillage.
Using active fractions of soil organic matter as indicators of the sustainability of Ferrosol farming systems
Authors: Bell M. J. , Moody P. W. , Yo S. A. , Connolly R. D.
Published: January 2006

Chemical and physical degradation of Red Ferrosols in eastern Australia is a
major issue necessitating the development of more sustainable cropping
systems. This paper derives critical concentrations of the active
(permanganate-oxidisable) fraction of soil organic matter (C1) which maximise
soil water recharge and minimise the likelihood of surface runoff in these
soils.
Ferrosol soils were collected from commercial properties in both north and
south Queensland, while additional data were made available from a similar
collection of Tasmanian Ferrosols. Sites represented a range of management
histories, from grazed and ungrazed grass pastures to continuously cropped
soil under various tillage systems. The concentration of both total carbon (C)
and C1 varied among regions and farming systems.
C1 was the primary factor controlling aggregate breakdown, measured by the
percentage of aggregates <0·125 mm (P125) in the surface crust after
simulated rainfall. The rates of change in P125 per unit change in C1 were not
significantly different (P < 0·05) for soils
from the different localities. However, soils from the coastal Burnett
(south-east Queensland) always produced lower P125 (i.e. less aggregate
breakdown) than did soils from the inland Burnett and north Queensland
locations given the same concentration of C1. This difference was not
associated with a particular land use.
The ‘critical’ concentrations of C1 for each region were taken as
the C1 concentrations that would allow an infiltration rate greater than or
equal to the intensity of a 1 in 1 or 1 in 10 year frequency rainfall event of
30 min duration. This analysis also provided an indication of the risk
associated with the concentrations of C1 currently characterising each farming
system in each rainfall environment. None of the conventionally tilled
Queensland Ferrosols contained sufficient C1 to cope with rainfall events
expected to occur with a 1 in 10 frequency, while in many situations the C1
concentration was sufficiently low that runoff events would be expected on an
annual basis.
Our data suggest that management practices designed both to maximise C inputs
and to maintain a high proportion of active C should be seen as essential
steps towards developing a more sustainable cropping system.