bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in subduction in the South Atlantic Ocean during the 21st century in the CCSM3
Authors: Goes Marlos , Wainer Ilana , Gent Peter R. , Bryan Frank O.
Published: March 2008

The Community Climate System Model version 3 is used to analyse changes in water mass subduction rates in the South Atlantic Ocean over the 21st century. The model results are first compared to observations over 1950–2000, and shown to be rather good. The subduction rates do not change significantly over the 21st century, but the densities at which water masses form become significantly lighter. The strong westerly winds in this region do not change much, which suggests small changes to the rate at which the Atlantic sector of the Southern Ocean takes up heat and carbon dioxide over the 21st century.
Driving the TING model with GAIM electron densities: Ionospheric effects on the thermosphere
Authors: Jee G. , Burns A. G. , Wang W. , Solomon S. C. , Schunk R. W. , Scherliess L. , Thompson D. C. , Sojka J. J. , Zhu L.
Published: March 2008

In order to study the effects of ionospheric plasma densities on the thermosphere, the electron and O+ densities in the Thermosphere Ionosphere Nested Grid (TING) model were replaced by electron densities from the Global Assimilation of Ionospheric Measurements (GAIM) model at pressure level z = 0 (about 210 ∼ 230 km altitude) and above. This GAIM‐derived TING model (G‐TING) was then run for the period 1–4 April 2004. The TING model was also run as a stand‐alone coupled model (S‐TING), without using the GAIM electron densities, for the same period. The resulting thermospheric responses from the two simulations were compared at around the F region peak altitude. There was an extended quiet period during this interval followed by a moderate geomagnetic storm (Kp ∼ 6.0). The ingestion of the GAIM electron densities had little effect on the neutral temperature and composition during the quiet period before the storm, but there were noticeable global effects on the neutral winds, mainly as a result of changes in the ion drag force. During disturbed periods, changed electron densities produced much more significant effects on the global thermosphere. The increased auroral electron densities enhanced the Joule heating rate, in addition to the ion drag, which resulted in significant global changes not only in the neutral winds, but also in the neutral temperature and composition. The results of our study confirm that having correct ionospheric plasma densities is critical to accurately predicting the thermosphere in the coupled thermosphere‐ionosphere model.
Dam breaking by wave‐induced erosional incision
Authors: Balmforth N. J. , von Hardenberg J. , Provenzale A. , Zammett R.
Published: March 2008

We present an experimental and theoretical study of whether a large displacement wave can lead to catastrophic erosional incision of a moraine damming a glacial lake. The laboratory experiments consist of reservoirs held by barriers of granular materials in a glass tank; the theoretical model combines the Saint‐Venant equations of hydraulic engineering with an empirical prescription for erosion. The results of both the laboratory experiments and the numerical simulations indicate that a single wave is generally unable to break the dam, but a sufficiently large disturbance in an almost‐filled reservoir creates a seiche that can repeatedly overtop the dam. In such a case, the combined effect of the multiple erosion events ultimately breaks the dam.
How can man‐made water reservoirs be accounted for in a lumped rainfall‐runoff model?
Authors: Payan Jean‐Luc , Perrin Charles , Andréassian Vazken , Michel Claude
Published: March 2008

The evaluation of diffuse impacts far downstream of man‐made reservoirs is complex but useful for water resources management and impact studies. The influence of reservoirs is usually modeled using a spatially distributed approach. To date lumped approaches have not been used to address this problem, probably because the lumped mode is seen as a major obstacle to accounting for water works that are at specific locations within the watershed. Here we propose a way to explicitly account for artificial storages in a lumped hydrological model. The method was tested on a large set of 46 watersheds (in France, the United States and Brazil) influenced by 26 reservoirs representing various types of management objectives. The results indicate that the method developed can effectively account for reservoirs despite the lumped modeling approach, with significant improvements in the simulation of low flows, but more limited for high flows.
Atomistic insight into the origin of the temperature-dependence of kinetic isotope effects and H-tunnelling in enzyme systems is revealed through combined experimental studies and biomolecular simulation
Authors: Hay Sam , Pudney Christopher , Hothi Parvinder , Johannissen Linus O. , Masgrau Laura , Pang Jiayun , Leys David , Sutcliffe Michael J. , Scrutton Nigel S.
Published: March 2008

The physical basis of the catalytic power of enzymes remains contentious despite sustained and intensive research efforts. Knowledge of enzyme catalysis is predominantly descriptive, gained from traditional protein crystallography and solution studies. Our goal is to understand catalysis by developing a complete and quantitative picture of catalytic processes, incorporating dynamic aspects and the role of quantum tunnelling. Embracing ideas that we have spearheaded from our work on quantum mechanical tunnelling effects linked to protein dynamics for H-transfer reactions, we review our recent progress in mapping macroscopic kinetic descriptors to an atomistic understanding of dynamics linked to biological H-tunnelling reactions.
Molecular probes: insights into design and analysis from computational and physical chemistry
Authors: Mitchell Felicity L. , Marks Gabriel E. , Bichenkova Elena V. , Douglas Kenneth T. , Bryce Richard A.
Published: March 2008

The application of new molecular diagnostics to probe cellular process in vivo is leading to a greater understanding of molecular cytology at a sub-nanoscale level and is opening the way to individualized medicines. We review here three distinct fluorescence-based molecular probes, HyBeacons™, split-probe exciplexes and GFP (green fluorescent protein)-based FRET (fluorescence resonance energy transfer) systems. Through this, we highlight the insights into the mechanism and design that a combined computational and experimental approach can yield.
Insights into adaptor binding to the AAA protein p97
Authors: Yeung Heidi O. , Kloppsteck Patrik , Niwa Hajime , Isaacson Rivka L. , Matthews Steve , Zhang Xiaodong , Freemont Paul S.
Published: March 2008

The AAA (ATPase associated with various cellular activities) p97 [also known as VCP (valosin-containing protein)] participates in numerous biological activities and is an essential component of the ubiquitin signalling pathway. A plethora of adaptors have been reported for p97, and increasing evidence is suggesting that it is through adaptor binding that p97 is diverted into different cellular pathways. Studying the interaction between p97 and its adaptors is therefore crucial to our understanding of the physiological roles of the protein. The interactions between p97 and the PUB [PNGase (peptide N-glycosidase)/ubiquitin-associated] domain of PNGase, the UBX (ubiquitin regulatory X) domain of p47, and the UBD (ubiquitin D) domain of Npl4 have been structurally characterized. UBX and UBD are structural homologues that share similar p97-binding modes; it is plausible that other proteins that contain a UBX/UBX-like domain also interact with p97 via similar mechanisms. In addition, several short p97-interacting motifs, such as VBM (VCP-binding motif), VIM (VCP-interacting motif) and SHP, have been identified recently and are also shared between p97 adaptors, hinting that proteins possessing the same p97-binding motif might also share common p97-binding mechanisms. In this review, we aim to summarize our current knowledge on adaptor binding to p97.
From the common molecular basis of the AAA protein to various energy-dependent and -independent activities of AAA proteins
Authors: Ogura Teru , Matsushita-Ishiodori Yuka , Johjima Ai , Nishizono Masayo , Nishikori Shingo , Esaki Masatoshi , Yamanaka Kunitoshi
Published: March 2008

AAA (ATPase associated with various cellular activities) proteins remodel substrate proteins and protein complexes upon ATP hydrolysis. Substrate remodelling is diverse, e.g. proteolysis, unfolding, disaggregation and disassembly. In the oligomeric ring of the AAA protein, there is a conserved aromatic residue which lines the central pore. Functional analysis indicates that this conserved residue in AAA proteases is involved in threading unfolded polypeptides. Katanin and spastin have microtubule-severing activity. These AAA proteins also possess a conserved aromatic residue at the central pore, suggesting its importance in their biological activity. We have constructed pore mutants of these AAA proteins and have obtained in vivo and in vitro results indicating the functional importance of the pore motif. Degradation of casein by the Escherichia coli AAA protease, FtsH, strictly requires ATP hydrolysis. We have constructed several chimaeric proteases by exchanging domains of FtsH and its homologues from Caenorhabditis elegans mitochondria, and examined their ATPase and protease activities in vitro. Interestingly, it has been found that some chimaeras are able to degrade casein in an ATP-independent manner. The proteolysis is supported by either ATP[S] (adenosine 5′-[γ-thio]triphosphate) or ADP, as well as ATP. It is most likely that substrate translocation in these chimaeras occurs by facilitated diffusion. We have also investigated the roles of C. elegans p97 homologues in aggregation/disaggregation of polyglutamine repeats, and have found that p97 prevents filament formation of polyglutamine proteins in an ATP-independent fashion.
Using x-ray diffraction to identify precipitates in transition metal doped semiconductors
Authors: Zhou Shengqiang , Potzger K. , Talut G. , von Borany J. , Skorupa W. , Helm M. , Fassbender J.
Published: March 2008

In the past decade, room temperature ferromagnetism was often observed in transition metal doped semiconductors, which were claimed as diluted magnetic semiconductors (DMS). Nowadays intensive activities are devoted to clarify wether the observed ferromagnetism stems from carrier mediated magnetic impurities, ferromagnetic precipitates, or spinodal decomposition. In this paper, we have correlated the structural and magnetic properties of transition metal doped ZnO, TiO2, and Si, prepared by ion implantation. Crystalline precipitates, i.e., transition metal (Co, Ni) and Mn-silicide nanocrystals, are responsible for the magnetism. Additionally due to their orientation nature with respect to the host, these nanocrystals in some cases are not detectable by conventional x-ray diffraction (XRD). This nature results in the pitfall of using XRD to exclude magnetic precipitates in DMS materials.
Improvement of chemical ordering of FePt (001) oriented films by MgO buffer layer
Authors: Lim B. C. , Chen J. S. , Hu J. F. , Lim Y. K. , Liu B. , Chow G. M. , Ju G.
Published: March 2008

Chemically ordered L10 FePt layer was obtained at temperature as low as 280°C by in situ heating by using MgO buffer layer on CrRu (200) underlayer. The chemical ordering and magnetocrystalline anisotropy, Ku, increased with increasing deposition temperature from 280to400°C. The out-of-plane coercivity Hc⊥ also increased significantly from 2.7to9.0kOe. All the films showed perpendicular anisotropy. The reason for the increase in the coercivity was investigated by reducing the thickness of the FePt layer to 4nm and varying the thickness of the MgO buffer layer at 1, 2, and 4nm. Well isolated FePt islands were formed. When the MgO layer was 1nm, the Hc⊥ of the 4nm FePt layer was as high as 12kOe. However, it reduced to 6.3kOe when the MgO was 4nm. The change in Hc⊥ was due to the improved chemical ordering and thus higher magnetocrystalline anisotropy.
Hundred-nanometer sized biomagnetic beads with large magnetization using ferrite nanoparticles grown by hydrothermal process
Authors: Matsushita Nobuhiro , Nakagawa Kazunori , Taniguchi Takaaki , Handa Hiroshi , Tada Masaru , Abe Masanori , Yoshimura Masahiro
Published: March 2008

Biomagnetic beads, 300nm in average diameter, were prepared by encapsulating large numbers of ferrite nanoparticles in nonspecific absorption polymer. The coprecipitated ferrite particles, 9.2nm in diameter, were grown to 12.9nm by the hydrothermal process (200°C for 3h) adding sodium oleate in water. The grown-up ferrite nanoparticles were highly dispersed due to the existence of oleate on the particle surface. The saturation magnetization of ferrite particles increased from 56to74emu∕g with the growth of ferrite particles. These ferrite nanoparticles were encapsulated in a copolymer of polystyrene and poly(glycidyl methacrylate) by an emulsion polymerization method. The polymer coated ferrite beads having sphere shape of 300nm in average diameter exhibited a saturation magnetization of 55emu∕g, which was five to six times larger than those of commercialized magnetic beads, in which ferrite (maghemite) nanoparticles are dispersed in polystyrene and SiO2 matrix.
Magnetic reversal phenomena of perpendicular magnetic islands fabricated by block copolymer lithography
Authors: Ilievski Filip , Ross C. A. , Vancso G. J.
Published: March 2008

Templated block copolymer lithography has been proposed as a method of fabricating patterned magnetic media. This paper discusses the magnetic properties of perpendicular CoCrPt magnetic uniaxial islands in a range of sizes (5–15nm thick, 20–35nm diameter) fabricated by this method. Sputter-deposited films of perpendicular CoCrPt films were patterned in a series of reactive and ion beam etches. The magnetic islands maintain the perpendicular magnetization from the film, but show increased coercivity (800–1650Oe) as compared to the film (150Oe). Time-scale-dependent magnetic measurements show switching volumes (V*) on the order of the physical volume of the dots (∼5000nm3), suggesting that the dots switch their magnetization coherently and independently of each other. Last, we demonstrate selectively removable topographic templates for imposing long-range order to the system.
Experimental and mechanistic description of merging and bouncing in head-on binary droplet collision
Authors: Pan Kuo-Long , Law Chung K. , Zhou Biao
Published: March 2008

The dynamics of head-on collision between two identical droplets was experimentally and computationally investigated, with emphasis on the transitions from merging to bouncing and to merging again, as the collision Weber number was increased. Experimentally the stroboscopically illuminated microphotographic images of two colliding droplet streams, generated through the ink-jet printing technique, were acquired with adequate temporal resolution of the collision event such that the instant at which the droplets merged for both soft and hard collisions was identified. Using this empirical information as an input, the simulated collision images were found to agree well with the experimental observations and allowed investigation of the collision flow field including the energy budget and the fundamental differences between the soft and hard collisions that lead to merging. It is further shown that the merging instant can be computationally assessed through the use of an augmented van der Waals force to effect merging through rupturing of the surfaces, with the associated Hamaker constant empirically but consistently extracted from the experimental observations.
First-order perturbation solutions of faceted nanostructures in an electric field
Authors: Chiu Cheng-hsin , Huang Zhijun
Published: March 2008

This paper presents the first-order perturbation solution to the two-dimensional electrostatics problems of faceted wires on a film-substrate system under the influence of a patterned electric plate. The solutions are accurate to the first order of the characteristic slopes of the wire and the pattern; the expressions of the solutions are concise, and the solutions are valid for single and multiple wires and patterns. The perturbation solutions provide an efficient scheme for studying the effects of a patterned electric plate on the formation of wires on the film-substrate systems.
A modified Vegard’s law for multisite occupancy of Ca in BaTiO3–CaTiO3 solid solutions
Authors: Lee Soonil , Randall Clive A.
Published: March 2008

The site occupancy of Ca in the CaTiO3–BaTiO3 solid solution has been investigated through an analysis of the lattice parameters and ferroelectric phase transition temperature variation. The lattice volume was found to vary in a nonlinear manner with different amounts of Ca2+ ions occupying the Ba and Ti sites near the pure BaTiO3 end member. To model the lattice volume trends in this complex case, we modify the classical Vegard’s law and incorporate a lattice volume correction to account for the ionic compensation of the acceptor charge CaTi″, with oxygen vacancies VO••. The paraelectric-ferroelectric phase transition temperature shows further evidence of a non-linear variation with composition. This is also consistent with site occupancy changes. From lattice volume and phase transition temperature variations on the Ba-site occupancy compositions, the maximum concentration of Ti-site occupancy (y) was determined and found to be approximately 0.007±0.002 and then found to remain constant for higher concentrations of Ca, specifically (0.03<x+y<0.1,Ba1−xCax+yTi1−yO3−y).
Tuning of intraband absorption and photoresponse in self-assembled InAs∕GaAs quantum dots by thermal annealing
Authors: Ng W. H. , Zibik E. A. , Wilson L. R. , Skolnick M. S. , Cockburn J. W. , Steer M. J.
Published: March 2008

The effects of the thermal annealing on the conduction band states in self-assembled quantum dots (QDs) have been investigated using midinfrared absorption and photocurrent spectroscopies. We demonstrate a significant tuning of the intraband electron transition energies (∼15%) upon annealing due to the reduction in the confinement energy, observed both in intraband absorption and photocurrent spectra. More uniform QD size distribution in the growth direction after annealing results in narrowing of the absorption peak. We also observe additional intersublevel transitions arising after QD annealing.
The mechanism of nickel sulfide induced rapid crystallization of highly textured tungsten disulfide (WS2) thin films: An in situ real-time diffraction study
Authors: Brunken S. , Mientus R. , Seeger S. , Ellmer K.
Published: March 2008

Highly (001)-textured, photoactive tungsten disulfide (WS2) thin films have been grown by nickel sulfide induced rapid crystallization of amorphous sulfur rich tungsten sulfide (WS3+x) films. This paper focuses on the mechanism of the crystal growth. The rapid crystallization was monitored by real-time in situ energy dispersive x-ray diffraction. Provided that a thin nickel film is deposited prior to the deposition of WS3+x, the films crystallize rapidly (>20nm∕s). The crystallization takes place at a temperature of about 650°C, i.e., slightly above the Ni–S eutectic temperature of 637°C. After crystallization, isolated hexagonal NiSx crystallites are located on the surface of the WS2 layer, which was observed by scanning and transmission electron microscopy. These results lead to the model that the rapid crystallization occurs by liquid-phase crystal growth from NiSx droplets floating on top of the crystallized WS2 films. Nickel sulfide induced crystallized WS2 layers exhibit a pronounced (001) orientation with crystallite sizes up to 3μm diameter.
Three regularization models of the Navier–Stokes equations
Authors: Pietarila Graham Jonathan , Holm Darryl D. , Mininni Pablo D. , Pouquet Annick
Published: March 2008

We determine how the differences in the treatment of the subfilter-scale physics affect the properties of the flow for three closely related regularizations of Navier–Stokes. The consequences on the applicability of the regularizations as subgrid-scale (SGS) models are also shown by examining their effects on superfilter-scale properties. Numerical solutions of the Clark-α model are compared to two previously employed regularizations, the Lagrangian-averaged Navier–Stokes α-model (LANS-α) and Leray-α, albeit at significantly higher Reynolds number than previous studies, namely, Re≈3300, Taylor Reynolds number of Reλ≈790, and to a direct numerical simulation (DNS) of the Navier–Stokes equations. We derive the de Kármán–Howarth equation for both the Clark-α and Leray-α models. We confirm one of two possible scalings resulting from this equation for Clark-α as well as its associated k−1 energy spectrum. At subfilter scales, Clark-α possesses similar total dissipation and characteristic time to reach a statistical turbulent steady state as Navier–Stokes, but exhibits greater intermittency. As a SGS model, Clark-α reproduces the large-scale energy spectrum and intermittency properties of the DNS. For the Leray-α model, increasing the filter width α decreases the nonlinearity and, hence, the effective Reynolds number is substantially decreased. Therefore, even for the smallest value of α studied Leray-α was inadequate as a SGS model. The LANS-α energy spectrum ∼k1, consistent with its so-called “rigid bodies,” precludes a reproduction of the large-scale energy spectrum of the DNS at high Re while achieving a large reduction in numerical resolution. We find, however, that this same feature reduces its intermittency compared to Clark-α (which shares a similar de Kármán–Howarth equation). Clark-α is found to be the best approximation for reproducing the total dissipation rate and the energy spectrum at scales larger than α, whereas high-order intermittency properties for larger values of α are best reproduced by LANS-α.
Charge and doping distributions by capacitance profiling in Cu(In,Ga)Se2 solar cells
Authors: Cwil Michal , Igalson Małgorzata , Zabierowski Paweł , Siebentritt Susanne
Published: March 2008

Doping distributions in the Cu(In,Ga)Se2 solar cells with various gallium contents are analyzed by the use of capacitance-voltage and drive-level capacitance profiling. The influence of deep traps on the evaluation of the spatial-doping distribution in the bulk of Cu(In,Ga)Se2 absorbers is discussed. An analysis is presented, which shows that traps labeled N1, commonly observed in these devices, are interface states or compensating donors and their input to the capacitance is related only to the width of the depleted n-type insulating layer. We attribute the apparent increase of doping density toward the back electrode to the accumulation of the electrostatic charge in deep bulk acceptors with a concentration at an order of magnitude higher than net shallow doping. The metastable changes of doping distributions induced by light or reverse bias are also investigated and interpreted in terms of the Lany–Zunger model of VSe-VCu divacancies with negative-U property. All conclusions have been tested by numerical modeling. Conductivity of thin films prepared in the same process as absorbers of investigated cells in relaxed and light-soaked states have also been measured. The results provide additional arguments that capacitance methods, if interpreted with care, give credible estimation of doping level in the absorber of Cu(In,Ga)Se2 devices.
Characterization of manganese-doped BaTiO3–(Bi1∕2Na1∕2)TiO3 positive temperature coefficient of resistivity ceramics using impedance spectroscopy
Authors: Xiang Ping-Hua , Takeda Hiroaki , Shiosaki Tadashi
Published: March 2008

Small amount of manganese (Mn)-doped BaTiO3–(Bi1∕2Na1∕2)TiO3 (BT-BNT) positive temperature coefficient of resistivity ceramics are investigated by impedance analyses. The impedance/modulus spectroscopic plots reveal that a third resistance-capacitance (RC) response besides grains and grain boundaries is exhibited in the Mn-free BT-BNT ceramic with 4mol% BNT, but is not observed in the Mn-doped samples. The third RC element can be attributed to a barium vacancy-rich layer in the outer grain region. The evidence of impedance spectroscopy indicates that the highly Bi donor is partially compensated by the Mn acceptor and the predominant charge compensation defect shifts from barium vacancies to electrons with doping small amount of Mn dopant.
In situ switch of boron nanowire growth mode from vapor-liquid-solid to oxide-assisted growth
Authors: Li Zhuangzhi , Baca Javier , Wu Judy
Published: March 2008

A two-step process was developed to explore ways for massive production of inorganic nanowires (NWs) with well-defined morphology. The first-step vapor-liquid-solid (VLS) growth defined the lateral dimension of boron NWs using Au–B catalytic tips, which was terminated with a quench to solidify the Au–B tip. The second-step oxide-assisted (OA) growth continued the NW growth from the BOx sheath formed around the tip at growth rates more than an order of magnitude higher than in the first step. This two-step process combines the merits of the VLS and OA growths and is promising for massive production of boron and other inorganic NW.
Effects of postdeposition annealing on the structure and optical properties of YOxNy films
Authors: Wang X. J. , Zhang L. D. , He G. , Zhang J. P. , Liu M. , Zhu L. Q.
Published: March 2008

High-k gate dielectric YOxNy films were prepared by reactive sputtering. The effects of postdeposition annealing on the structure and optical properties of YOxNy films have been investigated. The x-ray diffraction result shows that the crystallization starts at the annealing temperature of 500°C. Spectroscopic ellipsometry was employed to determine the optical properties of a set of YOxNy films annealed at various temperatures. It was found that the refractive index (n) of YOxNy films decreased with the increase of annealing temperature below 600°C, whereas it increased with increasing annealing temperature above 600°C. The annealing-temperature dependence of the optical band gap of YOxNy films was also discussed in detail. It has indicated that the optical band gap of YOxNy films shifts to higher energy after higher temperature annealing, which is likely due to the reduction of N content and the change of crystalline structure in YOxNy films.
Ruelle–Takens–Newhouse scenario in reaction-diffusion-convection system
Authors: Budroni Marcello Antonio , Masia Marco , Rustici Mauro , Marchettini Nadia , Volpert Vitaly , Cresto Pier Carlo
Published: March 2008

Direct numerical simulations of the transition process from periodic to chaotic dynamics are presented for two variable Oregonator-diffusion model coupled with convection. Numerical solutions to the corresponding reaction-diffusion-convection system of equations show that natural convection can change in a qualitative way, the evolution of concentration distribution, as compared with convectionless conditions. The numerical experiments reveal distinct bifurcations as the Grashof number is increased. A transition to chaos similar to Ruelle–Takens–Newhouse scenario is observed. Numerical results are in agreement with the experiments.
Thermal stability of dysprosium scandate thin films
Authors: Adelmann C. , Van Elshocht S. , Franquet A. , Conard T. , Richard O. , Bender H. , Lehnen P. , De Gendt S.
Published: March 2008

The thermal stability of DyScO3 thin films in contact with SiO2 or HfO2 during annealing up to 1000°C has been studied. It is found that DyScO3∕SiO2 stacks react during annealing and a phase separation into polycrystalline Sc-rich (and relatively Si-poor) DySc silicate on top of an amorphous Dy-rich DySc silicate is observed. In contrast, DyScO3 is found to be thermodynamically stable in contact with HfO2 and to recrystallize upon annealing. These results demonstrate that the previously reported high crystallization temperature of >1000°C for DyScO3 is not an intrinsic material property but caused by silicate formation.
Low-frequency noise in GaN nanowire transistors
Authors: Rumyantsev S. L. , Shur M. S. , Levinshtein M. E. , Motayed A. , Davydov A. V.
Published: March 2008

Noise in nanostructures is one of the key problems impeding their applications in electronic devices. We show that the level of 1∕f and recombination-generation noise in GaN nanowire field effect transistors can be suppressed by ultraviolet radiation by up to an order of magnitude. This strong suppression of the noise is explained by the illumination changing the occupancy of traps responsible for noise.
Nanogaps with very large aspect ratios for electrical measurements
Authors: Fursina A. , Lee S. , Sofin R. G. S. , Shvets I. V. , Natelson D.
Published: March 2008

For nanoscale electrical characterization and device fabrication, it is often desirable to fabricate planar metal electrodes separated by large aspect ratio gaps with interelectrode distances well below 100nm. We demonstrate a self-aligned process to accomplish this goal using a thin Cr film as a sacrificial etch layer. The resulting gaps can be as small as 10nm and have aspect ratios exceeding 1000, with excellent interelectrode isolation. Such Ti∕Au electrodes are demonstrated on Si substrates and are used to examine a voltage-driven transition in magnetite nanostructures. This shows the utility of this fabrication approach even with relatively reactive substrates.
Dielectric response of structured multilayered polymer films fabricated by forced assembly
Authors: Wolak Mason A. , Pan Ming-Jen , Wan Alan , Shirk James S. , Mackey Matt , Hiltner Anne , Baer Eric , Flandin Lionel
Published: March 2008

The effect of introducing a multilayer microstructure on the dielectric properties of polymer materials is evaluated in 32- and 256-layer films with alternating polycarbonate (PC) and polyvinylidene-hexafluoropropylene (coPVDF) layers. The permittivity, dielectric loss, dielectric strength, and energy density were measured as a function of the relative PC/coPVDF volume concentrations. The permittivity follows an effective medium model while the dielectric strength was typically higher than that predicted by a volume fraction based weighted average of the components. Energy densities as high as ∼14J∕cm3, about 60% greater than that of the component polymers, are measured for 50% PC/50% coPVDF films.
Re-examination of Casimir limit for phonon traveling in semiconductor nanostructures
Authors: Zhu Yong Fu , Lian Jian She , Jiang Qing
Published: March 2008

A simple and unified model is developed to predict the effective phonon mean free path (MFP) of semiconductor nanostructures based on Casimir’s work [Physica (Amsterdam) 5, 495 (1938)]. The effective MFP of nanofilms is found to be larger than that of nanowires, where the Casimir limit for nanofilms equals twice its thickness, or two times of the limit for nanowires. The theoretical formula agrees approximately with available experimental and computer simulation results for heat conduction along semiconducting nanowires, nanofilms, and superlattices.
Magnetic behavior and thickness dependence in Co-doped BaTiO3 thin films
Authors: Lin Yuan-Hua , Zhang Songyin , Deng Chaoyong , Zhang Yi , Wang Xiaohui , Nan Ce-Wen
Published: March 2008

We fabricated epitaxial Co-doped BaTiO3 thin films (4–80nm thick) on Nb-doped SrTiO3 substrates. Our results indicate that Co ions exist in the form of Co3+ and that no Co metal clusters appear. All of the Co-doped BaTiO3 thin films show ferromagnetic behavior and the saturated magnetization increases as the film thickness decreases, which may be attributed to the effective exchange coupling interaction between oxygen vacancies and Co 3d spins. However, as the film thickness further decreases (∼4nm), the magnetization decreases, which may be mainly ascribed to surface effects.
Reconstructing a radiation: the chiton genus Mopalia in the north Pacific
Authors: Kelly Ryan P. , Eernisse Douglas J.
Published: March 2008

The chiton genus Mopalia Gray, 1847 is highly speciose despite showing little morphological differentiation. Many of the 24 extant species are conspicuous, large-bodied and ecologically important today, but pre-Pleistocene fossils for the genus are rare. Here, we use a combined analysis of four gene regions (16S and COI mtDNA, 18S and 28S rDNA) to estimate the phylogenetic relationships for Mopalia species and use the inferred phylogeny to analyse the group’s biogeography and patterns of speciation. We then use these molecular data to distinguish between two alternative interpretations of the fossil record, as there is a large temporal gap between the oldest fossils tentatively identified as Mopalia and the next oldest fossils (Miocene versus Plio-Pleistocene). Based on the estimated substitution rates from a wide variety of other marine animals, we conclude that the observed rates in Mopalia are consistent with a Miocene origin for the genus. Given this age for the group and assuming a molecular clock, most speciation events in Mopalia are inferred to have occurred on average ~5 Mya. The phylogenetic results indicate that most of the speciation events leading to extant species must have occurred along the western North American coast, though there appear to have been multiple spreading events across the Pacific. When considered along with results for the many other near-shore taxa that have similar distributions to Mopalia, our findings suggest the emergence of a coherent historical biogeography of the northern Pacific.
Nicarbazin bait reduces reproduction by pigeons (Columba livia)
Authors: Avery Michael L. , Keacher Kandy L. , Tillman Eric A.
Published: March 2008

Development of effective methods for reducing populations of overabundant nuisance bird species continues to challenge wildlife biologists. Reproductive inhibition, although conceptually pleasing, has been difficult to implement because of the lack of a safe, approved avian contraceptive. Recently, however, nicarbazin received regulatory approval in the United States for use as a bait to decrease hatchability of resident Canada goose (Branta canadensis) and feral pigeon (Columba livia) eggs. In anticipation of the feral pigeon registration, we evaluated efficacy by exposing captive pairs of nesting pigeons to nicarbazin bait for 4 h daily. Egg production was unaffected, but only 9 of 22 eggs hatched, a 59% reduction from pre-treatment when each of the 11 test pairs produced 2 nestlings. In the recovery phase, when treated bait was removed, the 11 pairs produced 18 nestlings. All nestlings produced during the study appeared healthy and normal, and there was no mortality among the adult pairs. Nicarbazin is an effective and safe means of reducing hatchability of feral pigeon eggs that can be used within an integrated management plan to reduce feral pigeon populations.
Citizenship education in Denmark: reinventing the nation and/or conducting multiculturalism(s)?
Authors: Haas Claus
Published: March 2008

Article & 2008 In 2007 the concept of citizenship was officially incorporated into teacher education in Denmark, as part of a compulsory subject called 'Christianity studies, life enlightenment, and citizenship'. Thus, at least to some extent, the notion of citizenship is expected
to find its way into the educational and political vocabulary of future teachers and pupils/students of the Danish educational system, and probably into the public discussions about the meaning of democratic education in general. The subject itself is only described in very general terms within
the legal framework. In order to understand the meaning and purpose of the new subject it is necessary to position it within a broader discourse of citizenship education, as it has been launched by the Danish nation state since 1999. First, citizenship education seems to be exclusively about
responding to cultural diversity; secondly, articulated as part of a nation state driven strategy of the sociocultural integration of foreigners, migrants and ethnic minorities. From this follow the questions: What does integration mean, and integration into what? I will make use of four different
versions of multiculturalism as my analytical framework – assimilationism, cosmopolitanism, fragmented pluralism, interactive pluralism, and pointing to the fact that the first seems to be the hegemonic understanding of the purpose of citizenship education.
Studies in Spaced and Massed Learning: III. Paired-Associate and Serial Learning
Authors: Tsao J. C.
Published: March 2008

An experiment on paired-associate learning was carried out to test Hovland's prediction that spaced practice should be more advantageous than massed if the order of presenting the pairs of nonsense syllables were fixed.

In the results, spaced and massed practice showed little difference in learning efficiency. Hovland's prediction was not confirmed.

In a previous experiment of this series of studies it had been found that spaced practice was more efficient than massed in serial learning when syllables of “low-meaningfulness” value were used; but that there was little difference in efficiency between the two forms of distribution when “high-meaningfulness” syllables were used. The results of the two experiments naturally suggested that, as regards the relative efficiency of spaced and massed practice, paired-associate learning of low-meaningfulness syllables differed from serial learning of similar syllables, but matched serial learning of high-meaningfulness syllables. It seems justifiable to draw the conclusion that the relative efficiency of spaced and massed practice is different in paired-associate and serial learning, not because remote associations can be formed in the one case and not in the other, as Hovland (1939a, 1939b) assumed; but because the organization of the material and the learning processes are different in the two forms of learning.
The Effect of One Experience upon the Recall of Another
Authors: Davis D. Russell , Sinha Durganand
Published: March 2008

An exploratory experiment was made to show how one experience may exert an influence upon the recall of another, and how both may lose their separate identities in memory, to become merged into what Bartlett has described as an active organization of related experiences. The original material was a story, and the experience interpolated between it and its recall was a picture which illustrated part of it, in some respects correctly, in others incorrectly. Some subjects were asked to recall the story, others the picture, after from one to four weeks, or in a few cases a year.

The picture was viewed under the influence of the attitudes induced by the story. These determined its selection from a number of other unrelated pictures, to be perceived as a related experience. In consequence only few details gained attention, and these were interpreted in terms of the attitudes induced by the story, in some cases contrary to the meaning given to them by the rest of the picture. Other details without significance in the theme of the story were neglected. In its turn, seeing the picture favoured the recall of some aspects of the theme of the story, details not reinforced by the picture tending to be left out in recall. Many picture details intruded into the reproductions of the story. This tendency was progressive, and at the end of a year picture and story details were not separated. Especially, the picture brought about changes in the points of emphasis in the story.
Perceptual Anticipation and Reaction Time
Authors: Poulton E. C.
Published: March 2008

To determine the effect of perceptual anticipation upon reaction time, two different types of experiment were carried out. In the first a skilled response had occasionally to be altered at a given point after a variable warning period. In the second the subject had to react to two auditory signals separated by a short time interval which was systematically varied, the second signal being expected or unexpected.

It was found that lack of readiness to respond to a signal, as revealed by a lengthened reaction time, may be due either to the subject not having prepared himself, as he was not expecting the signal; or to the subject not being able to prepare himself in time. Preparation for reacting to the second of the two signals, when both are expected and have to be reacted to, never appears to take more than between 0·2 and 0·4 seconds, as judged by reaction time. On the majority of occasions it appears to be complete in 0·2 seconds. These times are shorter than those usually given, because the extra delay due to incorrect anticipation has been excluded. With intervals of 0·1 seconds or less, delay in the second reaction may be due to the mechanical difficulty of responding quickly enough, especially when the two reactions have to be made in opposite directions.

The finding that lack of readiness might be due to the subject not expecting the signal, and the further finding that preparation took longer when a skilled response had to be extended than when it had to be stopped, both suggest that so-called Psychological refractoriness is due to lack of fore period in which to prepare for the response, rather than to a “Psychological refractory phase” comparable to the refractory phase of nerves. If, by dividing his attention, the subject was able to prepare for his next response while making his previous one, so-called Psychological refractoriness could be completely absent.
The Influence of an Interpolated Experience upon Recognition
Authors: Davis D. Russell , Sinha Durganand
Published: March 2008

It was demonstrated in a previous experiment that an experience interpolated between an original experience and its recall may bring about changes in the points of emphasis in the recall of the original experience. Moreover, details of the interpolated experience may be recalled as if they had formed part of the original experience. These results were taken to mean that two experiences of a related kind may become merged in memory into something akin to Bartlett's notion of an organized mass of past experiences. In the experiment here reported, the original experience was the hearing of a story, and the interpolated experience the seeing of a picture which illustrated part of the story. When in a recognition test subjects were asked to select from three alternatives (including the original) the one version which was “most like the original story,” a proportion of them preferred to the original story a version which differed from the original by including a number of details from the picture. Asked about details, all the subjects tended to place details from the picture in the story, even if they had not been mentioned there. The results of the two experiments are thought to show that irreversible changes are brought about in the memory of an experience by subsequent experiences of a related kind.
Perceiving and Naming a Series of Figures
Authors: Hall K. R. L.
Published: March 2008

Bartlett (1932) observed in one of his experiments that his subjects, when presented with a series of figures, tended to name them with reference to their general trend of development, sometimes anticipating the outcome rather than making an immediate identification. Two recent experiments have studied the effect of verbal “set” upon perception, and the present study was designed to show both the effect of the objective frame of reference and of verbal suggestions upon the naming of a series of figures. A series of 10 figures was presented to one group with instructions to name them. A second group was shown the same figures in exactly the reverse order. The distribution of responses was significantly different for the two groups, showing the effect of the different settings. Other groups were given the same figures, but with preliminary suggestions as to what they were to see, and their responses show some modifications. Individual variations in quality of response are also discussed, and the general implications of the method and materials for research on conceptual thinking are briefly surveyed.
The Relation between Angle of Display and Performance in a Prolonged Visual Task
Authors: Fraser D. C.
Published: March 2008

An experiment is described to test the relation between angle of display and performance in prolonged visual tasks, using the Clock Test in three positions of display surface, vertical, at an angle of 45 degrees to the horizontal, and horizontal. In every case the line of regard was kept at right-angles to the display surface. The results indicate that significantly fewer stimuli are missed in the vertical position of the display surface than in the other two.

The deterioration observed in the second half-hour of the original Clock Test experiments was not found in the present experiment, and two possible reasons for this are discussed briefly.
The Effects of Repeated Retesting: III. Further Experiments and General Conclusions
Authors: Cane V. R. , Heim A. W.
Published: March 2008

This is the third of a series of papers dealing with the effects of repeated retesting on intelligence test scores. It comprises an account of two further experiments, and a discussion of the four so far performed, since each throws light on the results of the others and it is their joint interpretation which is thought to be of value.

The two earlier experiments consisted in repeated testing of a group of W.E.A. students and a group of mentally defective boys by an intelligence test (AH 4) designed for an unselected population. In the two later experiments, a group of Technical College students and a group of Naval Ratings were repeatedly tested on another intelligence test (AH 5), designed for a population of high-grade intelligence, such as university students. Examination of all the results confirms the artificiality of the “ceiling effect” which was suspected in the first experiment; it suggests that, given sufficient scope, subjects of all levels of intelligence would, with repeated trials on the same test, continue to improve their score up to and beyond 10 testing; and that, given comparable opportunity, subjects with initially higher scores will tend to improve more than those with initially lower scores. All these results concern short-term experiments with testing at weekly intervals.

The four sets of results considered jointly indicate that conclusions on these problems should be drawn only in terms of the relation between the level of the test and that of the group tested: this offers some resolution of the conflicting findings of earlier investigators.
Experimental Finger Dyspraxia
Authors: Jackson C. V. , Zangwill O. L.
Published: March 2008

Subjects were required to perform discrete finger movements in accordance with a pre-arranged sequence of instructions. In all cases, any movement made by any finger was recorded by means of a constant-speed kymograph equipped with levers designed to record separately the movements of the individual fingers. This experiment was carried out under three conditions: (a) with no vision of the hand; (b) with direct vision of the hand; and (c) with the hand presented in mirror-image. It was found that, whereas deprivation of visual control was without effect on the efficiency of finger movements, presentation of the hand in mirror-image gave rise to significant increases in reaction time of three fingers and to an increase in the percentages of prior and substitute movements of other digits. Phenomena akin to depersonalisation were reported in some cases. It was also found that the rank order of mean reaction times of the five digits was approximately constant under all conditions and that the two fingers with the shortest reaction times were preceded by the fewest movements of other digits. These two digits were also the most frequently moved in advance when movements of other digits were requested and it is suggested that they have a certain “signpost function” in guiding identification of the remaining fingers. Some implications of these results for an understanding of “finger agnosia” are briefly indicated in an Appendix.