bluuebunny/crossref_metadata_2025 huggingface dataset:
Climatology of Arctic polar stratospheric clouds as measured by lidar in Ny‐Ålesund, Spitsbergen (79°N, 12°E)
Authors: Massoli P. , Maturilli M. , Neuber R.
Published: May 2006

Polar stratospheric clouds (PSCs) are observed by lidar at the Koldewey Station in Ny‐Ålesund, Spitsbergen (79°N, 12°E). Here we present a PSC climatology for the period 1995/1996–2003/2004, when the Arctic stratosphere was not disturbed by the presence of volcanic aerosols. The study is restricted to only five of these winters, i.e., when the stratospheric temperatures over Spitsbergen were cold enough for PSC formation. The typical altitude range where PSCs are found is 20–24 km, with a downward shifting of the cloud altitude level occurring during the season. Liquid PSCs, the majority of the observations, are usually detected from mid‐January onward; nitric acid trihydrate (NAT) is more frequent in early winter. Furthermore, NAT is generally located at lower altitudes than the liquid clouds. In this data set we rarely observe NAT enhanced PSCs, and ice clouds are entirely absent. In addition to the traditional PSC classification scheme (types Ia/Ib and II) the detected clouds are distinguished according to their vertical thickness, and they are grouped in two categories (thick and thin PSCs), as in a previous study performed on the Antarctic McMurdo PSC data set. The analysis reveals that in Ny‐Ålesund the spatial‐temporal distribution of thick and thin PSCs corresponds to NAT and liquid cloud signatures, respectively. Comparison between the Ny‐Ålesund and the McMurdo PSC climatologies is also reported. In both records, thick and thin PSCs show similar altitude distribution, while discrepancies between the Arctic and Antarctic cases exist for the appearance of NAT and liquid PSCs during the polar winter.
Climatology and trends in some adverse and fair weather conditions in Canada, 1953–2004
Authors: Wang Xiaolan L.
Published: May 2006

This study characterizes the climatology and trends of some adverse and fair weather occurrence in Canada, on the basis of reliable long‐term records of hourly weather and bright sunshine observations at about 90 Canadian stations for the period 1953–2004. The results show that fair or no‐weather (i.e., no precipitation or visibility obscuration) trends are generally consistent with the sunshine trends, showing significant increases in southern Canada, with decreases in the Canadian Arctic. The increase of no‐weather is most extensive in spring and summer, while the decrease is most extensive in autumn. For the same period, freezing precipitation has become more frequent in the region north of 50°N (especially in spring and autumn) but less frequent in southern British Columbia (BC), central Prairies, and the Great Lakes area in autumn‐winter, as well as in northeastern Canada in winter. Blowing snow occurrence has decreased significantly almost everywhere across Canada, with the most significant decline in southwestern Canada in winter. In every season, fog occurrence has significantly increased in the Prairies‐Yukon‐Northwest Territories and northern BC but decreased in eastern Canada and southern BC. The frequency of low ceiling conditions (<304.8 m, i.e., 1000 feet) has increased in Alberta‐BC interior and the Great Lakes area, with the most significant increases in Alberta‐BC interior in autumn‐winter and in the Great Lakes area in spring; while the other regions have experienced a negative trend, which prevails across the country in summer.
Accuracy of geophysical parameters derived from Atmospheric Infrared Sounder/Advanced Microwave Sounding Unit as a function of fractional cloud cover
Authors: Susskind Joel , Barnet Chris , Blaisdell John , Iredell Lena , Keita Fricky , Kouvaris Lou , Molnar Gyula , Chahine Moustafa
Published: May 2006

AIRS was launched on EOS Aqua on 4 May 2002, together with AMSU A and HSB, to form a next generation polar orbiting infrared and microwave atmospheric sounding system. The primary products of AIRS/AMSU are twice daily global fields of atmospheric temperature‐humidity profiles, ozone profiles, sea/land surface skin temperature, and cloud related parameters including OLR. The sounding goals of AIRS are to produce 1 km tropospheric layer mean temperatures with an RMS error of 1 K, and layer precipitable water with an RMS error of 20%, in cases with up to 80% effective cloud cover. The basic theory used to analyze AIRS/AMSU/HSB data in the presence of clouds, called the at‐launch algorithm, was described previously. Prelaunch simulation studies using this algorithm indicated that these results should be achievable. Some modifications have been made to the at‐launch retrieval algorithm as described in this paper. Sample fields of parameters retrieved from AIRS/AMSU/HSB data are presented and validated as a function of retrieved fractional cloud cover. As in simulation, the degradation of retrieval accuracy with increasing cloud cover is small and the RMS accuracy of lower‐tropospheric temperature retrieved with 80% cloud cover is about 0.5 K poorer than for clear cases. HSB failed in February 2003, and consequently, HSB channel radiances are not used in the results shown in this paper. The AIRS/AMSU retrieval algorithm described in this paper, called version 4, become operational at the Goddard DAAC (Distributed Active Archive Center) in April 2003 and is being used to analyze near‐real time AIRS/AMSU data. Historical AIRS/AMSU data, going backward from March 2005 through September 2002, is also being analyzed by the DAAC using the version 4 algorithm.
Impact of three‐dimensional radiative effects on satellite retrievals of cloud droplet sizes
Authors: Marshak Alexander , Platnick Steven , Várnai Tamás , Wen Guoyong , Cahalan Robert F.
Published: May 2006

There are several dozen papers that study the effects of cloud horizontal inhomogeneity on the retrievals of cloud optical thickness, but only a few of them deal with cloud droplet sizes. This paper is one of the first comprehensive attempts to fill this gap: It takes a close theoretical look at the radiative effects of cloud 3‐D structure in retrievals of droplet effective radii. Under some general assumptions, it was found that ignoring subpixel (unresolved) variability produces a negative bias in the retrieved effective radius, while ignoring cloud inhomogeneity at scales larger than a pixel scale (resolved variability), on the contrary, leads to overestimation of the domain average droplet size. The theoretical results are illustrated with examples from Large Eddy Simulations (LES) of cumulus (Cu) and stratocumulus (Sc) cloud fields. The analysis of cloud drop size distributions retrieved from both LES fields confirms that ignoring shadowing in 1‐D retrievals results in substantial overestimation of effective radii which is more pronounced for broken Cu than for Sc clouds. Collocated measurements of broken Cu clouds by Moderate Resolution Imaging Spectrometer (MODIS) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) are used to check simulations and theory with observations. The analysis of ASTER and MODIS data and associated derived products recommends against blindly using retrieved effective radii for broken cloud fields, especially if one wants to relate aerosol amounts to cloud droplet sizes.
Basin topology in dissipative chaotic scattering
Authors: Seoane Jesús M. , Aguirre Jacobo , Sanjuán Miguel A.F. , Lai Ying-Cheng
Published: May 2006

Chaotic scattering in open Hamiltonian systems under weak dissipation is not only of fundamental interest but also important for problems of current concern such as the advection and transport of inertial particles in fluid flows. Previous work using discrete maps demonstrated that nonhyperbolic chaotic scattering is structurally unstable in the sense that the algebraic decay of scattering particles immediately becomes exponential in the presence of weak dissipation. Here we extend the result to continuous-time Hamiltonian systems by using the Hénon-Heiles system as a prototype model. More importantly, we go beyond to investigate the basin structure of scattering dynamics. A surprising finding is that, in the common case where multiple destinations exist for scattering trajectories, Wada basin boundaries are common and they appear to be structurally stable under weak dissipation, even when other characteristics of the nonhyperbolic scattering dynamics are not. We provide numerical evidence and a geometric theory for the structural stability of the complex basin topology.
Wave-particle interaction and Hamiltonian dynamics investigated in a traveling wave tube
Authors: Doveil Fabrice , Macor Alessandro
Published: May 2006

For wave-particle interaction studies, the one-dimensional (1-D) beam-plasma system can be advantageously replaced by a Traveling Wave Tube (TWT). This led us to a detailed experimental analysis of the self-consistent interaction between unstable waves and a small either cold or warm beam. More recently, a test electron beam has been used to observe its non-self-consistent interaction with externally excited wave(s). The velocity distribution function of the electron beam is investigated with a trochoidal energy analyzer that records the beam energy distribution at the output of the TWT. An arbitrary waveform generator is used to launch a prescribed spectrum of waves along the slow wave structure (a 4m long helix) of the TWT. The nonlinear synchronization of particles by a single wave responsible for Landau damping is observed. The resonant velocity domain associated to a single wave is also observed, as well as the transition to large-scale chaos when the resonant domains of two waves and their secondary resonances overlap leading to a typical “devil’s staircase” behavior. A new strategy for the control of chaos is tested.
Physics of zonal flows
Authors: Itoh K. , Itoh S.-I. , Diamond P. H. , Hahm T. S. , Fujisawa A. , Tynan G. R. , Yagi M. , Nagashima Y.
Published: May 2006

Zonal flows, which means azimuthally symmetric band-like shear flows, are ubiquitous phenomena in nature and the laboratory. It is now widely recognized that zonal flows are a key constituent in virtually all cases and regimes of drift wave turbulence, indeed, so much so that this classic problem is now frequently referred to as “drift wave-zonal flow turbulence.” In this review, new viewpoints and unifying concepts are presented, which facilitate understanding of zonal flow physics, via theory, computation and their confrontation with the results of laboratory experiment. Special emphasis is placed on identifying avenues for further progress.
Neoclassical tearing modes and their control
Authors: La Haye R. J.
Published: May 2006

A principal pressure limit in tokamaks is set by the onset of neoclassical tearing modes (NTMs), which are destabilized and maintained by helical perturbations to the pressure-gradient driven “bootstrap” current. The resulting magnetic islands break up the magnetic surfaces that confine the plasma. The NTM is linearly stable but nonlinearly unstable, and generally requires a “seed” to destabilize a metastable state. In the past decade, NTM physics has been studied and its effects identified as performance degrading in many tokamaks. The validation of NTM physics, suppressing the NTMs, and/or avoiding them altogether are areas of active study and considerable progress. Recent joint experiments give new insight into the underlying physics, seeding, and threshold scaling of NTMs. The physics scales toward increased NTM susceptibility in ITER, underlying the importance of both further study and development of control strategies. These strategies include regulation of “sawteeth” to reduce seeding, using static “bumpy” magnetic fields to interfere with the perturbed bootstrap current, and/or applying precisely located microwave power current drive at an island to stabilize (or avoid destabilization of) the NTM. Sustained stable operation without the highly deleterious m=2, n=1 island has been achieved at a pressure consistent with the no-wall n=1 ideal kink limit, by using electron cyclotron current drive at the q=2 rational surface, which is found by real-time accurate equilibrium reconstruction. This improved understanding of NTM physics and stabilization strategies will allow design of NTM control methods for future burning-plasma experiments like ITER.
Operation of Alcator C-Mod with high-Z plasma facing components and implications
Authors: Lipschultz B. , Lin Y. , Reinke M. L. , Hubbard A. , Hutchinson I. H. , Irby J. , LaBombard B. , Marmar E. S. , Marr K. , Terry J. L. , Wolfe S. M. , Alcator C-Mod group the , Whyte D.
Published: May 2006

Studies of potential plasma facing component (PFC) materials for a magnetic fusion reactor generally conclude that tungsten is the best choice due to its low tritium (T) retention, capability to handle high heat fluxes with low erosion, and robustness to nuclear damage and activation. ITER [F. Perkins et al., Nucl. Fusion 39, 2137 (1999)] may operate with all tungsten PFCs to provide the necessary operational experience for a reactor. Alcator C-Mod [I. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] operates with molybdenum (Mo) high-Z PFCs, which have very similar properties to tungsten. The experiments described herein have provided a unique comparison of operation with or without in situ boron coatings applied to the molybdenum PFCs; the latter are likely most relevant to ITER and beyond. ICRF-heated H-modes were readily achieved without boron coatings although the resultant enhancement in energy confinement was typically small (HITER,89∼1). Molybdenum concentrations, nMo∕ne, rise rapidly after the H-mode transition up to 0.1%, cooling the plasma by line radiation, reducing energy confinement, and/or causing a back H∕L transition. Surprisingly, the primarily molybdenum PFC surfaces retain 3.5−5.0×1020 of injected D2 molecules per discharge, corresponding to 50% of the injected gas. Plasma current disruptions, both randomly occurring over the course of a day, or planned, reduce the retained D long term. After applying boron coatings, nMo∕ne was reduced by a factor of 10–20 with HITER,89 approaching 2. A world-record volume-average plasma pressure of 1.8 atm at 5.4T was achieved at the ITER normalized β. The effects of each boronization are found to be limited in time, correlated to time-integrated input energy. Intra- and inter-discharge boronization techniques have been developed with the latter being the most successful. This initial study indicates that a low-Z coating over at least a fraction of the Mo PFCs in C-Mod is needed to reduce core molybdenum levels and achieve the best energy confinement. This, together with the larger than expected D retention, raises concerns for the performance of uncoated tungsten surfaces in ITER and beyond.
Terahertz radiation as a bunch diagnostic for laser-wakefield-accelerated electron bunches
Authors: van Tilborg J. , Schroeder C. B. , Filip C. V. , Tóth Cs. , Geddes C. G. R. , Fubiani G. , Esarey E. , Leemans W. P.
Published: May 2006

Experimental results are reported from two measurement techniques (semiconductor switching and electro-optic sampling) that allow temporal characterization of electron bunches produced by a laser-driven plasma-based accelerator. As femtosecond electron bunches exit the plasma-vacuum interface, coherent transition radiation (at THz frequencies) is emitted. Measuring the properties of this radiation allows characterization of the electron bunches. Theoretical work on the emission mechanism is presented, including a model that calculates the THz wave form from a given bunch profile. It is found that the spectrum of the THz pulse is coherent up to the 200 μm thick crystal (ZnTe) detection limit of 4THz, which corresponds to the production of sub-50fs (rms) electron bunch structure. The measurements demonstrate both the shot-to-shot stability of bunch parameters that are critical to THz emission (such as total charge and bunch length), as well as femtosecond synchronization among bunch, THz pulse, and laser beam.
Advanced tokamak research on long time scales in JT-60 Upgrade
Authors: Fujita T. ,   JT-60 Team
Published: May 2006

The duration of advanced tokamak plasma operation in JT-60 Upgrade (JT-60U) [A. Kitsunezaki et al., Fusion Sci. Technol. 42, 179 (2002)] has been extended on long time scales exceeding the current diffusion time (τR) and close to the wall saturation time. A very high bootstrap current fraction (fBS) of 75% was maintained for 7.4s (2.7τR), while a normalized beta of 2.5 was maintained for 15.5s (∼9.5τR). The current profile reaches stationary conditions in ∼τR for the small fBS regime, while a longer time is required for the large fBS regime. A plasma with a weak shear q profile, similar to requirements for the ITER steady-state operational scenario, was successfully maintained. The particle inventory in the wall was observed to saturate in repeated long-pulse (∼30s) H-mode discharges with edge localized modes. The analysis of neutral particles in the scrape-of-layer plasma indicates different time scales are involved for the wall saturation. Ferritic steel tiles have been installed in the vacuum vessel to reduce the toroidal field ripple towards extending the advanced tokamak regime further in the coming operational campaign.
Protein folding in a force clamp
Authors: Cieplak Marek , Szymczak P.
Published: May 2006

Kinetics of folding of a protein held in a force clamp are compared to an unconstrained folding. The comparison is made within a simple topology-based dynamical model of ubiquitin. We demonstrate that the experimentally observed variations in the end-to-end distance reflect microscopic events during folding. However, the folding scenarios in and out of the force clamp are distinct.
A simple, direct derivation and proof of the validity of the SLLOD equations of motion for generalized homogeneous flows
Authors: Daivis Peter J. , Todd B. D.
Published: May 2006

We present a simple and direct derivation of the SLLOD equations of motion for molecular simulations of general homogeneous flows. We show that these equations of motion (1) generate the correct particle trajectories, (2) conserve the total thermal momentum without requiring the center of mass to be located at the origin, and (3) exactly generate the required energy dissipation. These equations of motion are compared with the g-SLLOD and p-SLLOD equations of motion, which are found to be deficient. Claims that the SLLOD equations of motion are incorrect for elongational flows are critically examined and found to be invalid. It is confirmed that the SLLOD equations are, in general, non-Hamiltonian. We derive a Hamiltonian from which they can be obtained in the special case of a symmetric velocity gradient tensor. In this case, it is possible to perform a canonical transformation that results in the well-known DOLLS tensor Hamiltonian.
Dynamics of water confined in single- and double-wall carbon nanotubes
Authors: Mamontov E. , Burnham C. J. , Chen S.-H. , Moravsky A. P. , Loong C.-K. , de Souza N. R. , Kolesnikov A. I.
Published: May 2006

Using high-resolution quasielastic neutron scattering, we investigated the temperature dependence of single-particle dynamics of water confined in single- and double-wall carbon nanotubes with the inner diameters of 14±1 and 16±3Å, respectively. The temperature dependence of the alpha relaxation time for water in the 14Å nanotubes measured on cooling down from 260to190K exhibits a crossover at 218K from a Vogel-Fulcher-Tammann law behavior to an Arrhenius law behavior, indicating a fragile-to-strong dynamic transition in the confined water. This transition may be associated with a structural transition from a high-temperature, low-density (<1.02g∕cm3) liquid to a low-temperature, high-density (>1.14g∕cm3) liquid found in molecular dynamics simulation at about 200K. However, no such dynamic transition in the investigated temperature range of 240–195K was detected for water in the 16Å nanotubes. In the latter case, the dynamics of water simply follows a Vogel-Fulcher-Tammann law. This suggests that the fragile-to-strong crossover for water in the 16Å nanotubes may be shifted to a lower temperature.
Water dynamics in n-propylene glycol aqueous solutions
Authors: Cerveny S. , Schwartz G. A. , Alegría A. , Bergman R. , Swenson J.
Published: May 2006

The relaxation dynamics of dipropylene glycol and tripropylene glycol (nPG—n=2,3) water solutions on the nPG-rich side has been studied by broadband dielectric spectroscopy and differential scanning calorimetry in the temperature range of 130–280K. Two relaxation processes are observed for all the hydration levels; the slower process (I) is related to the α relaxation of the solution whereas the faster one (II) is associated with the reorientation of water molecules in the mixture. Dielectric data for process (II) at temperatures between 150 and 200K indicate the existence of a critical water concentration (xc) below which water mobility is highly restricted. Below xc, nPG-water domains drive the dielectric signal whereas above xc, water-water domains dominate the dielectric response at low temperatures. The results also show that process (II) at low temperatures is due to local motions of water molecules in the glassy frozen matrix. Additionally, we will show that the glass transition temperatures (Tg) for aqueous PG, 2PG, and 3PG solutions do not extrapolate to ∼136K, regardless of the extrapolation method. Instead, we find that the extrapolated Tg value for water from these solutions lies in the neighborhood of 165K.
Gravitational radiation, vorticity and the electric and magnetic part of Weyl tensor
Authors: Herrera L. , Santos N. O. , Carot J.
Published: May 2006

The electric and the magnetic part of the Weyl tensor, as well as the invariants obtained from them, are calculated for the Bondi vacuum metric. One of the invariants vanishes identically and the other only exhibits contributions from terms of the Weyl tensor containing the static part of the field. It is shown that the necessary and sufficient condition for the spacetime to be purely electric is that such spacetime be static. It is also shown that the vanishing of the electric part implies Minkowski spacetime. Unlike the electric part, the magnetic part does not contain contributions from the static field. Finally a speculation about the link between the vorticity of world lines of observers at rest in a Bondi frame, and gravitational radiation, is presented.
Fluid theory for quasistatic magnetic field generation in intense laser plasma interaction
Authors: Qiao Bin , He X. T. , Zhu Shao-ping
Published: May 2006

Based on the ten-moment Grad system of hydrodynamic equations, a self-consistent fluid model is presented for the generation of quasistatic magnetic fields in relativistic intense laser plasma interaction. In this model, the nondiagonal stress tensor is taken into account and the generalized vorticity is proved to be not conserved, which are different from previous ideal fluid models. In the quasistatic approximation, where the low-frequency phase speed vp is much smaller than the electron thermal speed vte, the axial magnetic field Bz and the azimuthal one Bθ are derived. It is found that the condition vp⪢vte used as the cold fluid approximation by previous papers is improper, where the derived Bz is incomplete and one magnetization current for Bz associated with the electron thermal motion does not appear. The profiles of both Bz and Bθ are analyzed. Their dependence on the laser intensity is discussed.
Geometries and magnetisms of the Zrn (n=2–8) clusters: The density functional investigations
Authors: Wang Chun-Cheng , Zhao Run-Ning , Han Ju-Guang
Published: May 2006

The geometries, stabilities, and electronic and magnetic properties of small-sized Zrn (n=2–8) clusters with different spin configurations were systematically investigated by using density functional approach. Emphasis is placed on studies that focus on the total energies, equilibrium geometries, growth-pattern behaviors, fragmentation energies, and magnetic characteristics of zirconium clusters. The optimized geometries show that the large-sized low-lying Zrn (n=5–8) clusters become three-dimensional structures. Particularly, the relative stabilities of Zrn clusters in terms of the calculated fragmentation energies and second-order difference of energies are discussed, exhibiting that the magic numbers of stabilities are n=2, 5, and 7 and that the pentagonal bipyramidal D5h Zr7 geometry is the most stable isomer and a nonmagnetic ground state. Furthermore, the investigated magnetic moments confirm that the atomic averaged magnetic moments of the Zrn (n≠2) display an odd-even oscillation features and the tetrahedron Cs Zr4 structure has the biggest atomic averaged magnetic moment of 1.5μB∕at. In addition, the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital gaps indicate that the Zrn (n=2 and 7) clusters have dramatically enhanced chemical stabilities.
Anomalous positive magnetoresistance at low temperatures in nanocrystalline Ni3Al
Authors: Abhyankar A. C. , Kaul S. N.
Published: May 2006

Reducing the crystallite size to ≅45nm drives the weak itinerant-electron ferromagnet Ni3Al to magnetic instability, where long-range ferromagnetic order collapses. Non-Fermi-liquid behavior of resistivity, ρ(T), at temperatures 4K⩽T⩽22K, an abrupt drop in ρ(T), and a sudden increase in positive magnetoresistance at T≲4K (presumably due to antiferromagnetic-spin fluctuation-mediated superconductivity) in nanocrystalline Ni3Al indicates that the crossover region near the magnetic quantum critical point extends to temperatures as high as 4K.
Simulation of disk- and band-like voids in dusty plasma systems
Authors: Liu Y. H. , Chen Z. Y. , Huang F. , Yu M. Y. , Wang L. , Bogaerts A.
Published: May 2006

The minimum-energy configurations of systems of multispecies charged grains of different mass and charge with an interaction potential including long-range repulsive as well as short-range attractive components are studied by molecular dynamics simulation. The grains are also subject to a radial drag force and a quadratic confining potential. It is found that central as well as band-like void regions separating grains of different species can exist as well as coexist, depending on the species parameters. The results are consistent with the horizontal cross-sections of the structures found in a recent experiment on self-organization of chemically synthesizing grains [Huang et al. Chin. Phys. Lett. 21, 121 (2004)].
In situformation of recombinant humanlike collagen-hydroxyapatite nanohybrid through bionic approach
Authors: Murugan R. , Ramakrishna S.
Published: May 2006

Processing bone graft materials that mimic the chemical composition and structure of natural bone is a good option for the treatment of bone defects. This investigation reports a processing condition for the in situ formation of recombinant humanlike collagen-hydroxyapatite (CHA) nanohybrid with chemical composition and crystal structure quite similar to natural bone through bionic approach. The processed CHA was characterized by various physicochemical methods and the results suggested that HA crystals are nucleated on the collagen domain with an average size of 32nm, relatively similar to that of biological apatite. The CHA has enhanced bioresorption than HA and mimics the natural bone in composition and structure; thereby it may be considered for bone applications.
Anomalous Hall effect and origin of magnetism in Zn1−xCoxO thin films at low Co content
Authors: Peng Y. Z. , Liew T. , Chong T. C. , An C. W. , Song W. D.
Published: May 2006

A small anomalous Hall effect signal of a Zn1−xCoxO (x=0.05) thin film was observed, indicating that there presents sp-d interactions in the Zn1−xCoxO thin film. However, under a self-held setup, we did not obtain observable differences between the M-H curves when the near band electrons were changed. Integrated with our previous results, possible mechanisms for the magnetism of Zn1−xCoxO thin films were proposed based on a picture of spins in a carrier sea.
Orthogonal exchange bias field directions in exchange bias microstructures
Authors: Candeloro P. , Schultheiß H. , Nembach H. T. , Hillebrands B. , Trellenkamp S. , Dautermann C. , Wolff S.
Published: May 2006

We report on the realization of microstructures exhibiting the coexistence of two exchange bias fields with orthogonal directions. The microstructures are made of Fe50Mn50∕Ni81Fe19 bilayers and have L-like and crosslike shapes. Above the Néel temperature the magnetic elements are initially saturated along the diagonal of the structures and then cooled down in zero external field. This causes the exchange bias field to be initialized along two different axes. Magneto-optical measurements confirm the simultaneous presence of orthogonal biasing directions.
Field emission image uniformity improvement by laser treating carbon nanotube powders
Authors: Chen K. F. , Chen K. C. , Jiang Y. C. , Jiang L. Y. , Chang Y. Y. , Hsiao M. C. , Chan L. H.
Published: May 2006

Carbon nanotube powders were synthesized by arc discharge method and incorporated into the paste to be applied in the screen printing process. It was investigated that the field emission image uniformity was efficiently improved by laser treating carbon nanotube powders. The laser energy burned out carbon particles to reveal more carbon nanotubes and graphitized carbon nanotubes. In addition to uniformity improvement, field emission properties were also reinforced after laser treating. For instance, turn-on voltage decreased from 3.2to2.2V∕μm, while field enhancement factor increased from 2200 to 2900.
Optical knife-edge technique for nanomechanical displacement detection
Authors: Karabacak D. , Kouh T. , Huang C. C. , Ekinci K. L.
Published: May 2006

We describe an optical knife-edge technique for nanomechanical displacement detection. Here, one carefully focuses a laser spot on a moving edge and monitors the reflected power as the edge is displaced sideways. To demonstrate nanomechanical displacement detection using the knife-edge technique, we have measured in-plane resonances of nanometer scale doubly clamped beams. The obtained displacement sensitivity is in the ∼1pm∕Hz range—in close agreement with a simple analytical model.
Gold-nanoparticles-induced pattern metallization on high-roughness diamond film surfaces
Authors: Tian Ruhai , Zhi Jinfang
Published: May 2006

In this letter, we report an approach toward the pattern metallization of high roughness diamond film surfaces under mild experimental conditions. First, hydrogen-terminated diamond film surfaces were activated through bonding with allylamine molecules under 254nm UV light irradiation. Then, amino prepatterns on the diamond surfaces were constructed by a photolithography process. Subsequently, gold nanoparticle (AuNP) patterns were obtained through the immobilization of 15±3nm AuNPs on the amino prepatterns and the remnant photoresist was removed by rinsing with acetone. Finally, the AuNP patterns were enhanced through silver deposition and intact silver-gold micropatterns were constructed on diamond surfaces.
Model for mode locking in quantum dot lasers
Authors: Viktorov E. A. , Mandel Paul , Vladimirov Andrei G. , Bandelow Uwe
Published: May 2006

We propose a model for passive mode locking in quantum dot lasers and report on specific dynamical properties of the regime which is characterized by a fast gain recovery. No Q-switching instability has been found accompanying the mode locking. Bistability can occur between the mode locking regime and the nonlasing state.
Stimulation of lateral branch formation on Ilex paraguariensis (Aquifoliaceae) seedlings
Authors: Sansberro P. , Mroginski L. , Bottini R.
Published: May 2006

Intensive yerba mate (Ilex paraguariensis St. Hil.) orchard management is needed to improve productivity. Full size trees with strong apical dominance are being replaced by smaller, more efficient trees, planted at higher densities for mechanical harvest. The production potential of a high-density field is maximised when cultural methods that control tree size and induce a significant number of well-distributed branches are used. The application of chemical pruning agents to shape the architecture of the seedling may be a viable alternative to induce lateral shoot development in replacement of the hand pruning technique. Nursery grown yerba mate seedlings were treated with a single foliar spray of aqueous solutions containing either benzyladenine (BA), 2,3:4,6-di-o-isopropylidene-2-keto-L-gulonic acid sodium salt (dikegulac) or 2,3,5-triiodobenzoic acid (TIBA), at the beginning of the second flash of growth (summer). A hand-pruned treatment was also included. BA-treated plants produced more new shoots than untreated controls or plants that received other treatments. BA treatment at 8.8 mmol/L increased the number of branches to up to 8 branches per single stem. Control plants sprayed with distilled water did not branch, while hand-pruned plants rarely showed more than 1 branch. Dikegulac was less effective than BA at promoting lateral branch development and its phytotoxicity was concentration dependent. TIBA did not stimulate budbreak; in addition, primary shoot development was delayed and leaf indentations were apparent. The results suggest that BA can be used to obtain high quality multiply-branched yerba mate plants.
Soil and tissue tests to predict the potassium requirements of canola in south-western Australia
Authors: Brennan R. F. , Bolland M. D. A.
Published: May 2006

The predominantly sandy soils of south-western Australia have become potassium (K) deficient for spring wheat (Triticum aestivum L.) production due to the removal of K from soil in grain and hay. The K requirements of canola (rape, Brassica napus L.) grown in rotation with wheat on these soils are not known and were determined in the study reported here. Seed (grain) yield increases (responses) of canola to applications of fertiliser K occurred at sites where Colwell soil test K values (top 10 cm of soil) were <60 mg/kg soil. Grain yield responses to applied K occurred when concentrations of K in dried shoots were <45 g/kg for young plants 7 and 10 weeks after sowing and <35 g/kg for 18 weeks after sowing. Application of fertiliser K had no significant effects on either oil or K concentrations in grain.
Do some naturalised legumes have the potential to improve pasture production in the Victorian Mallee?
Authors: Robertson S. M. , Smith J. G.
Published: May 2006

Some naturalised (not commercialised or deliberately sown) annual pasture legumes may be valuable pasture components, but their production relative to commercial species is poorly defined. This study aimed to determine the relative productivity, morphology, nutritive value, ecotype variation and sulfonylurea tolerance of some naturalised species in the Victorian Mallee. A series of 3 glasshouse and 2 ungrazed field experiments compared the production of haresfoot clover (Trifolium arvense L.), little woolly burr medic (Medicago minima L.), spineless M. minima, and M. monspeliaca (L.) Trautv. with the commercial species strand medic (M. littoralis Loisel cv. Herald) and barrel medic (M. truncatula Gaertn cv. Paraggio). The crude protein and in vitro digestibility of leaf and stem components were similar among species. The proportion of leaf was associated with species maturity, with later maturing species having a greater proportion of leaf at each harvest. There was a range of 52 days among species for date of first flowering. T. arvense produced similar or more biomass than the commercial species in spring, but had lower winter production. A 38-day range in days to first flower and a 2-fold range in winter biomass production among T. arvense ecotypes indicate potential for selection within this species. T. arvense also appears to have greater tolerance of triasulfuron residues than M. littoralis. Spineless M. minima requires further evaluation for persistence in this environment, but the low production of M. monspeliaca limits its value as a component of pastures. T. arvense, spineless and spiny M. minima all have some characteristics which could enhance pasture production in low-rainfall, low-input mixed farming systems.
The origin of European cattle: Evidence from modern and ancient DNA
Authors: Beja-Pereira Albano , Caramelli David , Lalueza-Fox Carles , Vernesi Cristiano , Ferrand Nuno , Casoli Antonella , Goyache Felix , Royo Luis J. , Conti Serena , Lari Martina , Martini Andrea , Ouragh Lahousine , Magid Ayed , Atash Abdulkarim , Zsolnai Attila , Boscato Paolo , Triantaphylidis Costas , Ploumi Konstantoula , Sineo Luca , Mallegni Francesco , Taberlet Pierre , Erhardt Georg , Sampietro Lourdes , Bertranpetit Jaume , Barbujani Guido , Luikart Gordon , Bertorelle Giorgio
Published: May 2006

Cattle domestication from wild aurochsen was among the most important innovations during the Neolithic agricultural revolution. The available genetic and archaeological evidence points to at least two major sites of domestication in India and in the Near East, where zebu and the taurine breeds would have emerged independently. Under this hypothesis, all present-day European breeds would be descended from cattle domesticated in the Near East and subsequently spread during the diffusion of herding and farming lifestyles. We present here previously undescribed genetic evidence in contrast with this view, based on mtDNA sequences from five Italian aurochsen dated between 7,000 and 17,000 years B.P. and >1,000 modern cattle from 51 breeds. Our data are compatible with local domestication events in Europe and support at least some levels of introgression from the aurochs in Italy. The distribution of genetic variation in modern cattle suggest also that different south European breeds were affected by introductions from northern Africa. If so, the European cattle may represent a more variable and valuable genetic resource than previously realized, and previous simple hypotheses regarding the domestication process and the diffusion of selected breeds should be revised.
Rethinking Urban Incivility Research: Strangers, Bodies and Circulations
Authors: Phillips Timothy , Smith Philip
Published: May 2006

Research on urban incivility has made progress but has limited scope thanks to a stereotyped and policy-relevant focus on problem neighbourhoods and urban renewal. It also lacks benchmark comparative data, has almost nothing to say about interpersonal incivility and is experiencing diminishing returns to effort. A new agenda is proposed that explores everyday life incivility as this is experienced over the broader population in the course of daily routine. The Everyday Life Incivility in Australia Survey is introduced. This was a random national sample survey collecting systematic narrative information on interpersonal encounters involving a rude stranger. Findings from the study are reported here, documenting the range of low-level incivilities experienced in daily life and outlining some of their properties. The results challenge received wisdom about the corrosive effects of urban incivility on society.
USA's Destiny? Regulating Space and Creating Community in American Shopping Malls
Authors: Staeheli Lynn A. , Mitchell Don
Published: May 2006

In North American cities, shopping malls are heralded as the new town square. Historically, the town square was a place where diverse people came together and where politics, economics and sociability were intermingled. However, shopping centres, which are separated from the old downtown by distance or design, seem for many people to be the new heart of public and social life. It is argued in this article that the regulation of the spaces of the mall is intended to create 'community' rather than a 'public'. In the process of creating community, the political potential of public space and the quality of publicity created are contorted so as to muffle political opposition and critique in the name of civility. This argument is illustrated through an examination of the Carousel Center Mall in Syracuse, New York.
Active Citizenship and Effective Public Services and Programmes: How Can We Know What Really Works?
Authors: Brannan Tessa , John Peter , Stoker Gerry
Published: May 2006

This paper is a review of the aims and practice of active citizenship in England. It sets out the key concepts and gives an account of the developing policy agenda in crime, regeneration and housing, education, health and local government. It reviews the current state of scientific knowledge in this area, in particular summarising research commissioned by the Home Office Civil Renewal Research Programme, 2004-05. Whilst the research findings show the positive contribution of government initiatives in this area, a key theme that emerges is that the policy context and the causal relationships are often more complex than advocates sometimes claim.
The Good City
Authors: Amin Ash
Published: May 2006

Can the contemporary city qualify as the topos of the good life, as it has in classical literature on human emancipation? As geographical entities, cities are hardly discernible places with distinct identities. They have become an endless inhabited sprawl without clear boundaries and they have become sites of extraordinary circulation and translocal connectivity. Similarly, sociologically, contemporary cities do not spring to mind as the sites of community and well-being. For the vast majority of people, cities are polluted, unhealthy, tiring, overwhelming, confusing, alienating. Politically, too, the contemporary city bears little resemblance to imaginings of the times when urbanism stood for citizenship, the ideal republic, good government, civic behaviour and the ideal public sphere. The politics of emancipation with a big 'P' is no longer a particularly urban affair in either genesis or practice, having given way to national and global institutions and movements. What remains of the urban as demos in these circumstances? At one level, clearly very little, as one instance in a wider demos or demon that pulls in many directions. This said, the urban remains an enormously significant formative arena, not only as the daily space of over half of the world's population, but also as the supremely visible manifestation of difference and heterogeneity placed together. Urbanism highlights the challenges of negotiating class, gender and ethnic or racial differences placed in close proximity. It also profiles the newness that arises from spatial juxtaposition and global flow and connectivity, forever forcing responses of varying type and intensity in the face of negotiating strangers, strangeness and continuous change. Possibilities thus remain for continuing to ask about the nature of the 'good city'. This paper outlines the elements of an urban ethic imagined as an ever-widening habit of solidarity built around different dimensions of the urban common weal. It offers a practical urban utopianism based around four registers of solidarity woven around the collective basics of everyday urban life. These are 'repair', 'relatedness', 'rights' and 're-enchantment'.
Types and Patterns of Response in the Larynx Following Inhalation
Authors: Renne Roger A. , Gideon Katherine M.
Published: May 2006

The laryngeal mucosa responds to insult similarly to other epithelial tissues but the response depends on location within the larynx since important anatomic differences exist, even within rodent species. Although dogs and nonhuman primates are also utilized for inhalation toxicology studies, little published information is available regarding sites of injury from inhaled toxicants in these species. Accurate and consistent fixation, trimming, and microtomy of laryngeal sections allow the pathologist to compare the morphology of laryngeal mucosa from exposed and control animals and detect and interpret subtle differences resulting from inhalation exposure. There are anatomic landmarks that are keys to providing consistent sections through important areas of the laryngeal mucosa. Repeated inhalation of toxic concentrations of chemicals, drugs, or environmental contaminants induces a wide range of responses, depending on the physical properties and concentration of the toxic substance and duration of exposure. Responses include edema, acute to chronic inflammation, fibrosis, mucosal ulceration, degeneration, and necrosis. Attempts at repair include regeneration, hyperplasia, squamous metaplasia, hyperkeratosis, and neoplasia. Awareness of normal histology and zones of transition from squamous to respiratory epithelium in different areas of the larynx in different species is critical to avoid confusing normal epithelium with metaplasia or hyperplasia. Microscopic examination of laryngeal mucosa from animals exposed via inhalation and necropsied following a recovery period provides the opportunity to determine the degree of regression or progression of exposure-induced laryngeal lesions.
Existence of No Hepatocarcinogenic Effect Levels of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline with or without Coadministration with Ethanol
Authors: Wanibuchi Hideki , Wei Min , Karim M. Rezaul , Morimura Keiichirou , Doi Kenichiro , Kinoshita Anna , Fukushima Shoji
Published: May 2006

There is increasing evidence of the existence of no effect levels for genotoxic carcinogens. However, only limited information is available regarding dose-response curves for combination effects of multiple carcinogens at low dose. In the present study, 280 male F344 rats were divided into 14 groups to determine the effects of co-administration of various doses of 2-amino-3,8-dimethylimidazo[4,5- f]quinoxaline (MeIQx) and 10% ethanol on the development of glutathione S-transferase placental form (GST-P)-positive foci in the liver. The results provided concrete evidence for the existence of no effect levels for hepatocarcinogenicity of MeIQx either in presence or absence of ethanol and, therefore, for a practical threshold for this genotoxic carcinogen.
Reasoning about the Relations between Relations
Authors: Goodwin Geoffrey P. , Johnson-Laird P. N.
Published: May 2006

Relations can hold between relations, as in assertions such as: Cordelia loves Lear more than Goneril does. Naïve reasoners can make inferences that depend on these higher order relations, which are vital for science and mathematics, but no existing theory explains such inferences. The present paper presents a theory based on mental models of the situations under description, and it reports four experiments corroborating the theory. Experiment 1a showed that the difficulty of such inferences from two premises depends on the integration of the information from the premises into a single model. The same result held in Experiment 1b, even when individuals were not permitted to make written workings. Experiment 2 required the participants to think aloud, and their protocols revealed that they developed three main strategies. Experiment 3 biased the development of these strategies, showing that individuals assemble them “bottom up” from various tactical steps.
The fear of necrotizing enterocolitis versus achieving optimal growth in preterm infants—an opinion
Authors: Flidel‐Rimon Orna , Branski David , Shinwell Eric S.
Published: May 2006

Very‐low‐birthweight (VLBW) infants suffer marked growth delay despite well‐intentioned efforts at combining enteral and parenteral nutrition. Fear of necrotizing enterocolitis (NEC) has traditionally influenced neonatologists toward delaying and progressing slowly with enteral feeding, while supporting the infant with parenteral nutrition. Current evidence suggests significant benefits of enteral feeding that is started early and advanced at rates of 20–35 ml/kg/d.

Conclusion: We conclude that fear of inadequate growth should replace the fear of NEC in guiding nutritional strategies for these infants.