bluuebunny/crossref_metadata_2025 huggingface dataset:
MODELING OCCURRENCES OF OBJECTS IN RELATIONS
Authors: LEO JOOP
Published: January 2010

We study the logical structure of ‘real’ relations, and in particular the notion of occurrences of objects in a state. We start with formulating a number of principles for occurrences and defining corresponding mathematical models. These models are analyzed to get more insight in the formal properties of occurrences. In particular, we prove uniqueness results that tell us more about the possible logical structures relations might have.
Contribution of land surface initialization to subseasonal forecast skill: First results from a multi‐model experiment
Authors: Koster R. D. , Mahanama S. P. P. , Yamada T. J. , Balsamo Gianpaolo , Berg A. A. , Boisserie M. , Dirmeyer P. A. , Doblas‐Reyes F. J. , Drewitt G. , Gordon C. T. , Guo Z. , Jeong J.‐H. , Lawrence D. M. , Lee W.‐S. , Li Z. , Luo L. , Malyshev S. , Merryfield W. J. , Seneviratne S. I. , Stanelle T. , van den Hurk B. J. J. M. , Vitart F. , Wood E. F.
Published: January 2010

The second phase of the Global Land‐Atmosphere Coupling Experiment (GLACE‐2) is aimed at quantifying, with a suite of long‐range forecast systems, the degree to which realistic land surface initialization contributes to the skill of subseasonal precipitation and air temperature forecasts. Results, which focus here on North America, show significant contributions to temperature prediction skill out to two months across large portions of the continent. For precipitation forecasts, contributions to skill are much weaker but are still significant out to 45 days in some locations. Skill levels increase markedly when calculations are conditioned on the magnitude of the initial soil moisture anomaly.
Correlations between cloud thickness and sub‐cloud water abundance on Venus
Authors: Tsang Constantine C. C. , Wilson Colin F. , Barstow Joanna K. , Irwin Patrick G. J. , Taylor Fredric W. , McGouldrick Kevin , Piccioni Giuseppe , Drossart Pierre , Svedhem Håkan
Published: January 2010

Past spacecraft observations of Venus have found considerable spatial and temporal variations of water vapour abundance above the clouds. Previous searches for variability below the clouds at 30–45 km altitude found no large scale latitudinal gradients, but lacked the spatial resolution to detect smaller scale variations. Here we interpret results from the VIRTIS imaging spectrometer on Venus Express, remotely sounding at near‐infrared ‘spectral window’ wavelengths, as indicating that the water vapour abundance at 30–40 km altitude varies from 22 to 35 ppmv (±4 ppmv). Furthermore, this variability is correlated with cloud opacity, supporting the hypothesis that its genesis is linked to cloud convection. It is also possible to fit the observations without requiring spatial variation of water abundance, but this places a strong constraint on the spectral dependence of the refractive index data assumed for the lower cloud particles, for which there is as yet no supporting evidence.
Generation of quasi‐isotropic electron population during nonlinear beam‐plasma interaction
Authors: Pavan J. , Ziebell L. F. , Yoon P. H. , Gaelzer R.
Published: January 2010

The nonlinear interaction of a single or a bidirectional electron beam and a background plasma is analyzed on the basis of electrostatic weak turbulence theory. It is found that for a sufficiently high electron beam density, the nonlinear interaction produces quasi‐isotropic electron population. This is in contrast to our previous finding in which a relatively low electron beam density was adopted, and for which complete isotropization was not achieved. The present finding may thus provide a possible explanation for the observed isotropic solar wind electron distribution within the context of electrostatic nonlinear theory involving Langmuir and ion‐sound turbulence, without the resorting to additional mechanisms such as the pitch angle scattering by electromagnetic whistler turbulence.
Effect of strain localization on frictional behavior of sheared granular materials
Authors: Rathbun Andrew P. , Marone Chris
Published: January 2010

We performed laboratory experiments to investigate shear localization and the evolution of frictional behavior as a function of shear strain. Experiments were conducted on water‐saturated layers, 0.3–1 cm thick, of Caesar till, a granular material analogous to fault gouge. We used the double‐direct shear configuration at normal stresses ranging from 0.5 to 5 MPa and shearing velocities of 10–100 μm/s. Shear localization was assessed via strain markers and two proxies: (1) macroscopic layer dilation in response to perturbations in shear stress and (2) rate/state friction response to shear velocity perturbations. In creep mode experiments, at constant shear stress, we monitored dilation for perturbations in shear stress. In standard friction tests, we measured the coefficient of friction during perturbations in macroscopic strain rate. We find evidence of strain localization beginning at shear strain γ ≈ 0.15 and continuing until γ ≈ 1. Analysis of strain markers supports interpretations based on the proxies for localization and shows that strain is localized in zones of finite thickness. We also investigate symmetry of the friction response to step changes in imposed slip velocity and find that the behavior is symmetric. Our results favor the Ruina law for friction state evolution in which slip is the fundamental variable rather than the Dieterich law. The critical slip distance for friction evolution, Dc, is ∼140 μm. The Dieterich state evolution law requires different values of Dc for velocity increases/decreases, 100 μm versus 175 μm, respectively, and would imply strain localization/delocalization associated with shear in a finite zone.
Can thin cirrus clouds in the tropics provide a solution to the faint young Sun paradox?
Authors: Rondanelli Roberto , Lindzen Richard S.
Published: January 2010

In this paper we present radiative‐convective simulations to test the idea that tropical cirrus clouds, acting as a negative feedback on climate, can provide a solution to the faint young Sun paradox. We find that global mean surface temperatures above freezing can indeed be found for luminosities larger than about 0.8 (corresponding to ∼2.9 Ga and nearly complete tropical cirrus coverage). For luminosities smaller than 0.8, even though global mean surface temperatures are below freezing, tropical mean temperatures are still above freezing, indicating the possibility of a partially ice‐free Earth for the Early Archean. We discuss possible mechanisms for the functioning of this negative feedback. While it is feasible for tropical cirrus to completely eliminate the paradox, it is similarly possible for tropical cirrus to reduce the amounts of other greenhouse gases needed for solving the paradox and therefore easing the constraints on CO2 and CH4 that appear to be in disagreement with geological evidence.
Validation of QuikSCAT wind vectors by dropwindsonde data from Dropwindsonde Observations for Typhoon Surveillance Near the Taiwan Region (DOTSTAR)
Authors: Chou Kun‐Hsuan , Wu Chun‐Chieh , Lin Po‐Hsiung , Majumdar Sharanya
Published: January 2010

The accuracy of 10 m wind vectors derived from the QuikSCAT satellite near tropical cyclones is validated against soundings from 457 GPS dropwindsondes deployed by Dropwindsonde Observations for Typhoon Surveillance Near the Taiwan Region (DOTSTAR) during 2003–2007. To maximize the database, the surface to 40 m wind speed in the dropwindsondes is averaged and interpolated to the 10 m wind speed by linear regression. After removing rain‐flagged data, the root‐mean‐square differences between QuikSCAT and dropwindsonde data were 2.6 m s−1 or 18% (wind speed) and 17° (wind direction) on the basis of 896 matching samples. Further analyses also indicate that the QuikSCAT data slightly underestimates the wind speed of medium‐wind regime (between 10 and 17.2 m s−1) and possesses some clockwise directional bias in the high‐wind regime (above 17.2 m s−1). In summary, this study suggests that the QuikSCAT wind vectors below tropical storm wind strength (17.2 m s−1) are accurate enough for forecasters to determine the critical wind radius of 34 knot wind, while a new error bound of the QuikSCAT wind estimate in high‐wind regimes near tropical cyclones is suggested to be set at about 4 m s−1.
Arctic System Reanalysis: Call for Community Involvement
Authors: Bromwich David , Kuo Ying‐Hwa , Serreze Mark , Walsh John , Bai Le‐Sheng , Barlage Michael , Hines Keith , Slater Andrew
Published: January 2010

Arctic climate encompasses multiple feedbacks, the most important of which is the ice‐albedo feedback. Enhanced Arctic changes, first recognized in the nineteenth century, increasingly are being observed across terrestrial, oceanic, atmospheric, and human systems, inspiring interdisciplinary research efforts, including the Study of Environmental Arctic Change (SEARCH) program, to understand the nature and future development of the Arctic system.

In response to the need for enhanced understanding outlined in the 2005 SEARCH Implementation Plan [Arctic Research Consortium of the United States, 2005], an ongoing Arctic System Reanalysis (ASR) project builds on previous programs to observe the Arctic climate. The ASR is a multi‐institutional, interdisciplinary collaboration that optimally merges measurements and modeling to provide a high‐resolution description of the region's atmosphere/sea ice/land system by assimilating a diverse suite of observations into a regional model. The project builds upon lessons learned from past reanalyses by optimizing model physics parameterizations and methods of data assimilation for Arctic conditions. The ASR, which is a partnership with the broader Arctic research community, represents a synthesis tool for assessing and monitoring variability and change in the Arctic system.
Climate Monitoring of the Indonesian Throughflow
Authors: You Yuzhu , Sanford Tom , Liu Cho‐Teng
Published: January 2010

Despite growing recognition of the need to monitor the global ocean circulation, existing sensor networks are unable to observe certain key parts of the world ocean (see Figure 1). One such choke point is in the Indonesian seas, where the Indonesian Throughflow (ITF) flows from the Pacific Ocean to the Indian Ocean as an upper branch of the overturning circulation. To properly understand the role the ITF plays in the climate system, longer‐term measurements are required on decadal time scales and beyond. The Indonesian seas currently are not sampled on a regular basis because the Argo float network is not able to operate in this extremely complicated marginal sea environment.

Since 2008, an international program called the Indonesian Throughflow: Pacific Source Water Investigation (PACSWIN [You et al., 2010]) has sought to fill this gap in the global ocean observing network. PACSWIN is a coordinated multinational ocean climate program that will be active in the Indonesian seas and adjacent regions for the coming decade and beyond. The cable component of PACSWIN, which also has other components, promises to meet the need for a cost‐effective long‐term monitoring system, in addition to providing a more diverse set of supporting and supplementary measurements. This cable component was the subject of a 9–10 September 2009 workshop, the Climate Variability and Predictability (CLIVAR)‐endorsed First PACSWIN Submarine Cable Workshop, held in Taipei, Taiwan (for more information, visit http://sol.oc/ntu.edu.tw/PACSWIN/index.htm). An implementation plan currently is being developed.
Paleointensity Database Updated and Upgraded
Authors: Biggin Andrew John , McCormack Alan , Roberts Andrew
Published: January 2010

The global absolute paleointensity (PINT) database, sponsored by the International Association of Geomagnetism and Aeronomy, recently was updated with new data and published alongside a new queryable interface at http://earth.liv.ac.uk/pint/.

Absolute paleointensity determinations are spot readings of the strength of the geomagnetic field at the time and place at which a rock cooled down from elevated temperatures. The time generally can be estimated using an independent dating technique applied to the rock itself, and the place (or at least the paleolatitude) of the rock often can be estimated from the associated paleomagnetic direction.
Barbara A. Romanowicz Receives 2009 Inge Lehmann Medal
Authors: Romanowicz Barbara A. , Dziewonski Adam M.
Published: January 2010

Barbara A. Romanowicz was awarded the 2009 Inge Lehmann Medal at the AGU Fall Meeting Honors Ceremony, held on 16 December 2009 in San Francisco, Calif. The medal is for “outstanding contributions to the understanding of the structure, composition, and dynamics of the Earth's mantle and core.”
Sense and nonsense from a systems biology approach to microbial recombinant protein production
Authors: Sevastsyanovich Yanina R. , Alfasi Sara N. , Cole Jeffrey A.
Published: January 2010

The ‘Holy Grail’ of recombinant protein production remains the availability of generic protocols and hosts for the production of even the most difficult target products. The present review provides first an explanation why the shock imposed on bacteria using a standard induction protocol not only arrests growth, but also decreases the number of colony‐forming units by several orders of magnitude. Particular emphasis is placed on findings of numerous genome‐wide transcriptomic studies that highlight cellular stress, in which the general stress, heat‐shock and stringent responses are the underlying basis for the manifestation of the deterioration of cell physiology. We then review common approaches used to solve bottlenecks in protein folding and post‐translational modification that result in recombinant protein deposition in cytoplasmic inclusion bodies. Finally, we suggest a generic approach to process design that minimizes stress on the production host and a strategy for isolating improved hosts.
Selection of affibody molecules to the ligand‐binding site of the insulin‐like growth factor‐1 receptor
Authors: Li Jingjing , Lundberg Emma , Vernet Erik , Larsson Barbro , Höidén‐Guthenberg Ingmarie , Gräslund Torbjörn
Published: January 2010

Affibody molecules binding to the site of hormone interaction in IGF‐1R (insulin‐like growth factor‐1 receptor) were successfully selected by phage‐display technology employing a competitive‐elution strategy during biopanning, whereby release of receptor‐bound phagemids was accomplished by competition with IGF‐1 (insulin‐like growth factor‐1). In non‐competitive selections, the elution of receptor‐bound phagemids was performed by imidazole or low‐pH incubation, which also resulted in the isolation of affibody molecules that could bind to the receptor. An ELISA‐based assay showed that the affibody molecules generated by IGF‐1 competition during elution, in addition to affibody molecules generated in the non‐competitive selections, could compete with IGF‐1 for binding to the receptor. The affinities of the isolated variants to IGF‐1R‐overexpressing MCF‐7 cells were determined and ranged from high nanomolar to 2.3 nM. The most promising variant, Z4:40, was shown to recognize IGF‐1R efficiently in several different contexts: in analyses based on flow cytometry, fluorescence microscopy and receptor pull‐down from cell extracts. In addition, when Z4:40was added to the medium of MCF‐7 cells that were dependent on IGF‐1 for efficient growth, it was found to have a dose‐dependent growth‐inhibitory effect on the cells. Applications of affibody‐based reagents for quantitative and qualitative analyses of IGF‐1R status, as well as applications of affibody‐based reagents for therapy, are discussed.
Intranuclear sphingomyelin is associated with transcriptionally active chromatin and plays a role in nuclear integrity
Authors: Scassellati Catia , Albi Elisabetta , Cmarko Dusan , Tiberi Cinzia , Cmarkova Jana , Bouchet‐Marquis Cedric , Verschure Pernette J. , van Driel Roel , Magni Mariapia Viola , Fakan Stanislav
Published: January 2010

Background information. Sphingomyelin is one of the major phospholipids in the cell nucleus. However, its intranuclear distribution with regard to different functional nuclear domains as well as its possible involvement in the nuclear functional architecture remains to be elucidated.

Results. We carried out an ultrastructural cytochemical study of the intranuclear distribution of SM (sphingomyelin) using an in situ binding assay of neutral SMase (sphingomyelinase) conjugated to colloidal gold particles. The enzymatic labelling was carried out on ultrathin sections of different mammalian cells prepared by means of various fixation and resin‐embedding protocols. Transmission electron microscopic analysis revealed preferential localization of SM within the PR (perichromatin region), a functionally important nucleoplasmic domain containing sites of pre‐mRNA synthesis and processing. In the nucleolus, SM is mostly associated with the dense fibrillar component containing transcriptionally active ribosomal genes. Microinjection of enzymatically active SMase into living cells resulted in a rapid degradation of intranuclear structure.

Conclusions. Our observations, supported by biochemical data, provide evidence for the involvement of SM in important nuclear functions. They bring additional information pointing out the PR as an essential functional nuclear domain. Furthermore, they suggest a role for SM in the internal nuclear architecture.
S165F mutation of junctophilin 2 affects Ca2+ signalling in skeletal muscle
Authors: Woo Jin Seok , Hwang Ji-Hye , Ko Jae-Kyun , Weisleder Noah , Kim Do Han , Ma Jianjie , Lee Eun Hui
Published: January 2010

JPs (junctophilins) contribute to the formation of junctional membrane complexes in muscle cells by physically linking the t-tubule (transverse-tubule) and SR (sarcoplasmic reticulum) membranes. In humans with HCM (hypertrophic cardiomyopathy), mutations in JP2 are linked to altered Ca2+ signalling in cardiomyocytes; however, the effects of these mutations on skeletal muscle function have not been examined. In the present study, we investigated the role of the dominant-negative JP2-S165F mutation (which is associated with human HCM) in skeletal muscle. Consistent with the hypertrophy observed in human cardiac muscle, overexpression of JP2-S165F in primary mouse skeletal myotubes led to a significant increase in myotube diameter and resting cytosolic Ca2+ concentration. Single myotube Ca2+ imaging experiments showed reductions in both the excitation–contraction coupling gain and RyR (ryanodine receptor) 1-mediated Ca2+ release from the SR. Immunoprecipitation assays revealed defects in the PKC (protein kinase C)-mediated phosphorylation of the JP2-S165F mutant protein at Ser165 and in binding of JP2-S165F to the Ca2+ channel TRPC3 (transient receptor potential cation canonical-type channel 3) on the t-tubule membrane. Therefore both the hypertrophy and altered intracellular Ca2+ signalling in the JP2-S165F-expressing skeletal myotubes can be linked to altered phosphorylation of JP2 and/or altered cross-talk among Ca2+ channels on the t-tubule and SR membranes.
The cathepsin L gene is a direct target of FOXO1 in skeletal muscle
Authors: Yamazaki Yoshihiro , Kamei Yasutomi , Sugita Satoshi , Akaike Fumiko , Kanai Sayaka , Miura Shinji , Hirata Yukio , Troen Bruce R. , Kitamura Tadahiro , Nishino Ichizo , Suganami Takayoshi , Ezaki Osamu , Ogawa Yoshihiro
Published: January 2010

FOXO1 (forkhead box O1), a forkhead-type transcription factor whose gene expression is up-regulated in the skeletal muscle during starvation, appears to be a key molecule of energy metabolism and skeletal muscle atrophy. Cathepsin L, a lysosomal proteinase whose expression is also up-regulated in the skeletal muscle during starvation, is induced in transgenic mice overexpressing FOXO1 relative to wild-type littermates. In the present study, we conducted in vivo and in vitro experiments focusing on FOXO1 regulation of Ctsl (cathepsin L gene; CTSL1 in humans) expression in the skeletal muscle. During fasting and refeeding of C57BL/6 mice, Ctsl was regulated in parallel with FOXO1 in the skeletal muscle. Fasting-induced Ctsl expression was attenuated in transgenic mice overexpressing a dominant-negative form of FOXO1 or in skeletal-muscle-specific Foxo1-knockout mice relative to respective wild-type controls. Using C2C12 mouse myoblasts overexpressing a constitutively active form of FOXO1, we showed that FOXO1 induces Ctsl expression. Moreover, we found FOXO1-binding sites in both the mouse Ctsl and human CTSL1 promoters. The luciferase reporter analysis revealed that the mouse Ctsl and human CTSL1 promoters are activated by FOXO1, which is abolished by mutations in the consensus FOXO1-binding sites. Gel mobility-shift and chromatin immunoprecipiation assays showed that FOXO1 is recruited and binds to the Ctsl promoter. The present study provides in vivo and in vitro evidence that Ctsl is a direct target of FOXO1 in the skeletal muscle, thereby suggesting a role for the FOXO1/cathepsin L pathway in fasting-induced skeletal muscle metabolic change and atrophy.
Electrophysiological characterization of ATPases in native synaptic vesicles and synaptic plasma membranes
Authors: Obrdlik Petr , Diekert Kerstin , Watzke Natalie , Keipert Christine , Pehl Ulrich , Brosch Catrin , Boehm Nicole , Bick Inga , Ruitenberg Maarten , Volknandt Walter , Kelety Bela
Published: January 2010

Vesicular V-ATPase (V-type H+-ATPase) and the plasma membrane-bound Na+/K+-ATPase are essential for the cycling of neurotransmitters at the synapse, but direct functional studies on their action in native surroundings are limited due to the poor accessibility via standard electrophysiological equipment. We performed SSM (solid supported membrane)-based electrophysiological analyses of synaptic vesicles and plasma membranes prepared from rat brains by sucrose-gradient fractionation. Acidification experiments revealed V-ATPase activity in fractions containing the vesicles but not in the plasma membrane fractions. For the SSM-based electrical measurements, the ATPases were activated by ATP concentration jumps. In vesicles, ATP-induced currents were inhibited by the V-ATPase-specific inhibitor BafA1 (bafilomycin A1) and by DIDS (4,4′-di-isothiocyanostilbene-2,2′-disulfonate). In plasma membranes, the currents were inhibited by the Na+/K+-ATPase inhibitor digitoxigenin. The distribution of the V-ATPase- and Na+/K+-ATPase-specific currents correlated with the distribution of vesicles and plasma membranes in the sucrose gradient. V-ATPase-specific currents depended on ATP with a K0.5 of 51±7 μM and were inhibited by ADP in a negatively co-operative manner with an IC50 of 1.2±0.6 μM. Activation of V-ATPase had stimulating effects on the chloride conductance in the vesicles. Low micromolar concentrations of DIDS fully inhibited the V-ATPase activity, whereas the chloride conductance was only partially affected. In contrast, NPPB [5-nitro-2-(3-phenylpropylamino)-benzoic acid] inhibited the chloride conductance but not the V-ATPase. The results presented describe electrical characteristics of synaptic V-ATPase and Na+/K+-ATPase in their native surroundings, and demonstrate the feasibility of the method for electrophysiological studies of transport proteins in native intracellular compartments and plasma membranes.
Myopathy-causing actin mutations promote defects in serum-response factor signalling
Authors: Visegrády Balázs , Machesky Laura M.
Published: January 2010

Mutations in the gene encoding skeletal muscle α-actin (ACTA1) account for approx. 20% of patients with the muscular disorder nemaline myopathy. Nemaline myopathy is a muscular wasting disease similar to muscular dystrophy, but distinguished by deposits of actin and actin-associated proteins near the z-line of the sarcomere. Approx. one-third of the over 140 myopathy actin mutations have been characterized either biochemically or in cultured cells to determine their effects on the actin cytoskeleton. However, the actin defects causing myopathy are likely to be heterogeneous, with only a few common trends observed among the actin mutants, such as reduced polymerization capacity or an inability to fold properly. Notably, the transcriptional programme regulated by serum-response factor, which is instrumental in muscle development and maintenance, is directly controlled by the balance of actin assembly and disassembly in cells. In the present study, we explored the impact of myopathy mutations in actin on the control of the transcriptional response by serum-response factor and found that the majority of mutants examined have altered serum-response factor signalling. We propose that altered serum-response factor signalling could be a major factor in actin-based nemaline myopathy, and that this area could be exploited to develop therapies for sufferers.
Mechanical loading modulates chondrocyte primary cilia incidence and length
Authors: McGlashan Susan R. , Knight Martin M. , Chowdhury Tina T. , Joshi Purva , Jensen Cynthia G. , Kennedy Sarah , Poole Charles A.
Published: January 2010

The pathways by which chondrocytes of articular cartilage sense their mechanical environment are unclear. Compelling structural evidence suggests that chondrocyte primary cilia are mechanosensory organelles. This study used a 3D agarose culture model to examine the effect of compressive strain on chondrocyte cilia. Chondrocyte/agarose constructs were subjected to cyclic compression (0–15%; 1 Hz) for 0.5–48 h. Additional constructs were compressed for 48 h and allowed to recover for 72 h in uncompressed free‐swelling conditions. Incidence and length of cilia labelled with anti‐acetylated α‐tubulin were examined using confocal microscopy. In free‐swelling chondrocytes, these parameters increased progressively, but showed a significant decrease following 24 or 48 h compression. A 72 h recovery partially reversed this effect. The reduced cilia incidence and length were not due to increased cell division. We therefore propose that control of primary cilia length is an adaptive signalling mechanism in response to varying levels and duration of mechanical loads during joint activity.
In situ method for real time measurement of dielectric film thickness in plasmas
Authors: Jang Sung-Ho , Kim Gun-Ho , Chung Chin-Wook
Published: January 2010

An in situ thickness measurement method of dielectric films (dual frequency method) was developed, and the thicknesses were measured in an inductively coupled plasma. This method uses a small ac bias voltage with two frequencies for thickness measurement. The dielectric thickness is obtained from measuring the amplitudes of the two frequency ac currents through a sensor, as well as using an equivalent circuit model describing impedance of the dielectric film and the plasma sheath. In the experiment, the thicknesses of Al2O3 film could be accurately measured in real time. To check the measurement reliability, the dual frequency method was compared with reflection spectrophotometry as a technique for optical thickness diagnostics. It was found that the dual frequency method agrees closely with reflection spectrophotometry at various rf powers and pressures. In addition, this method is very simple and can be installed anywhere in plasma reactors, in contrast with optical methods; therefore, it is expected to be applied to in situ surface diagnostics for various processing plasmas.
On Young’s Paradox, and the attractions of immersed parallel plates
Authors: Finn Robert
Published: January 2010

A seemingly paradoxical prediction for behavior of objects with nonconstant contact angles when dipped into fluids is clarified in a new way. The method is then applied to the problem of determining the attraction (or repulsion) of parallel vertical plates dipped into an infinite liquid bath. A criterion is given for determining whether the plates attract or repel each other, and estimates for the forces are obtained, which are asymptotically exact for small plate separations. It is shown that the attracting force is asymptotically proportional inversely to the square of the distance between the plates; however the repelling force remains under a fixed bound in magnitude. In all cases the net forces are independent of the contact angles of the exterior fluid with the plates, although that is not the case for the individual forces ascribable to pressure differences and to surface tensions. It is shown that regardless of the data, each of the plates experiences the same net force as does the other. Finally a new and more precise and inclusive clarification is given for a phenomenon described in 1806 by Laplace, who noted conditions under which repelling forces can change abruptly into (much larger) attracting forces.
An electrostatic autoresonant ion trap mass spectrometer
Authors: Ermakov A. V. , Hinch B. J.
Published: January 2010

A new method for ion extraction from an anharmonic electrostatic trap is introduced. Anharmonicity is a common feature of electrostatic traps which can be used for small scale spatial confinement of ions, and this feature is also necessary for autoresonant ion extraction. With the aid of ion trajectory simulations, novel autoresonant trap mass spectrometers (ART-MSs) have been designed based on these very simple principles. A mass resolution ∼60 is demonstrated for the prototypes discussed here. We report also on the pressure dependencies, and the (mV) rf field strength dependencies of the ART-MS sensitivity. Importantly the new MS designs do not require heavy magnets, tight manufacturing tolerances, introduction of buffer gases, high power rf sources, nor complicated electronics. The designs described here are very inexpensive to implement relative to other instruments, and can be easily miniaturized. Possible applications are discussed.
Wurtzite-to-tetragonal structure phase transformation and size effect in ZnO nanorods
Authors: Wang J. , Xiao P. , Zhou M. , Wang Z. R. , Ke F. J.
Published: January 2010

The deformation of [0001]-oriented ZnO nanorods with hexagonal cross sections under uniaxial tensile loading is analyzed through molecular statistical thermodynamics (MST) simulations. The focus is on the size dependence of mechanical behavior in ZnO nanorods with diameters ranging from 1.95 to 17.5 nm. An irreversible phase transformation from the wurtzite (P63mc space group) structure to a tetragonal structure (P42/mnm space group) occurs during the tensile loading process. Young’s modulus before the transformation demonstrates a size dependence consistent with what is observed in experiments. A stronger size dependence of response is seen after the transformation and is attributed to the polycrystalline nature of the transformed structure. A comparison of the MST and molecular dynamics (MD) methods shows that MST is 60 times faster than MD and yields results consistent with the results of MD.
Transport properties and electronic states of anatase Ti1−xWxO2 epitaxial thin films
Authors: Takeuchi Utahito , Chikamatsu Akira , Hitosugi Taro , Kumigashira Hiroshi , Oshima Masaharu , Hirose Yasushi , Shimada Toshihiro , Hasegawa Tetsuya
Published: January 2010

We have investigated the transport properties and electronic states of W-doped anatase TiO2 (Ti1−xWxO2) fabricated by pulsed-laser deposition. Based on transport and photoemission spectroscopy (PES) measurements, we discuss the conduction mechanism of Ti1−xWxO2, focusing on the valence state of W. The Ti0.95W0.05O2 film deposited under optimized conditions showed a resistivity of 2×10−3 Ω cm at room temperature, which is approximately ten times higher than that of Ti0.94Nb0.06O2. This is mainly due to the lower carrier density in Ti1−xWxO2 films. From PES measurements of Ti0.91W0.09O2 films, we observed the finite density of states originating from O 2p hybridized with W near the top of the valence band. However, we could not find any states at the same position in the Ti0.94Nb0.06O2 films. In addition, the density of states near the Fermi level [N(EF)] was found to be quite low in the Ti0.91W0.09O2 films. Indeed, this is in sharp contrast to Ti0.94Nb0.06O2, which indicates a remarkably high N(EF) value assigned to the bottom of the Ti 3d conduction band. The difference in transport properties between Ti1−xWxO2 and Ti1−xNbxO2 can be attributed to the existence of impurity states that trap carriers associated with doped W atoms.
Note: Highly sensitive superconducting quantum interference device microsusceptometers operating at high frequencies and very low temperatures inside the mixing chamber of a dilution refrigerator
Authors: Martínez-Pérez M. J. , Sesé J. , Luis F. , Drung D. , Schurig T.
Published: January 2010

We report the experimental results that show the operation of superconducting quantum interference device (SQUID) microsusceptometers immersed in the H3e–H4e mixture inside the mixing chamber of a dilution refrigerator at high frequency (1 MHz) and down to very low temperatures (13 mK). The devices are based on highly sensitive and easy-to-use commercial SQUID sensors. The integrated susceptometers are fabricated by rerouting some connections of the SQUID’s input circuit. Examples of measurements on molecular magnets Mn12 and HoW10 are shown.
Single-gate accumulation-mode InGaAs quantum dot with a vertically integrated charge sensor
Authors: Croke E. T. , Borselli M. G. , Gyure M. F. , Bui S. S. , Milosavljevic I. I. , Ross R. S. , Schmitz A. E. , Hunter A. T.
Published: January 2010

We report on the fabrication and characterization of a few-electron quantum dot controlled by a single gate electrode. Our device has a double-quantum-well design, in which the doping controls the occupancy of the lower well while the upper well remains empty under the free surface. Electrons tunneling between this accumulation-mode dot and the lower well are detected using a quantum point contact, located slightly offset from the dot gate. Addition spectra starting with N=0 were observed as a function of gate voltage. DC sensitivity to single electrons was determined to be as high as 8.6%.
Emission characteristics and dynamics of the stagnation layer in colliding laser produced plasmas
Authors: Hough P. , McLoughlin C. , Harilal S. S. , Mosnier J. P. , Costello J. T.
Published: January 2010

The expansion dynamics of ion and neutral species in laterally colliding laser produced aluminum plasmas have been investigated using time and space resolved optical emission spectroscopies and spectrally and angularly resolved fast imaging. The emission results highlight a difference in neutral atom and ion distributions in the stagnation layer where, at a time delay of 80 ns, the neutral atoms are localized in the vicinity of the target surface (<1 mm from the target surface) while singly and doubly charged ions lie predominantly at larger distances, <1.5 and <2 mm, respectively. The imaging results show that the ions were found to form a well defined, but compressed, stagnation layer at the collision front between the two seed plasmas at early times (Δt<80 ns). On the other hand, the excited neutrals were observed to form a V-shaped emission feature at the outer regions of the collision front with enhanced neutral emission in the less dense, cooler regions of the stagnation layer.
Powder formation in SiH4–H2 discharge in large area capacitively coupled reactors: A study of the combined effect of interelectrode distance and pressure
Authors: Strahm B. , Hollenstein Ch.
Published: January 2010

One of the main challenges for silicon thin film deposition for solar cell applications is to achieve high rate deposition in order to reduce the manufacturing costs. However, when silane and hydrogen are used as precursor gas in parallel plate plasma-enhanced chemical vapor deposition, high rate deposition is generally synonymous of powdery discharge. In this work, time- and space-resolved light scattering experiments are presented. These were performed in an industrial-type large area reactor with a variable interelectrode distance. Results show that with a standard 25 mm interelectrode distance, the fraction of silane transformed into powder can be as high as 50% and that reducing the interelectrode distance shifts to higher pressure the appearance of powder in the discharge. From a standard 25 mm interelectrode distance to a 10 mm narrow gap reactor, the threshold pressure was increased from 2 to 7 mbars. More generally, it is proposed that the onset of powder formation depends mainly on the product of the interelectrode distance and the gas residence time in the discharge.
Multiferroic properties of Bi0.9Gd0.1Fe0.9Mn0.1O3 thin film
Authors: Lahmar A. , Habouti S. , Solterbeck C-H. , Dietze M. , Es-Souni M.
Published: January 2010

Monolithic oxides whose lattice structures exhibit both ferroelectric and magnetic ordering and eventually intrinsic coupling between them are known as multiferroics. The possibility to switch magnetization by an electric field and reciprocally polarization by a magnetic field may allow new applications spanning the fields from new memory devices to medical measuring technology. Until now, the only monolithic oxide that has been shown to exhibit both (weak) magnetism and ferroelectric polarization at room temperature is BiFeO3 (BFO). However, as this material is a line compound, i.e., with sharply defined stoichiometry, its properties largely depend on defects and parasitic phases that could arise during processing. In the present work, we report on a new compound based on the solid solution GdMnO3–BiFeO3 (GdMBFO) that exhibit a fairly high magnetization coupled with moderate ferroelectric polarization at room temperature. Using conductive-tip atomic force microscopy, we show the highly electrically homogeneous microstructure. Ferroelectric polarization switching is obtained both as P-E hysteresis (or I-E) and capacitance-voltage butterfly curves. The effects of space charge on ferroelectric polarization that often bias polarization measurements reported for pure BFO are shown to be marginal. The high magnetization obtained for GdMBFO has allowed us to determine the Néel temperature (TN) directly from magnetic measurements. This results bears novelty as it is the first time that TN is reported for BFO-base thin films. The origin of magnetization improvement is discussed in terms of Gd substitution effects on octahedral distortion and tilting.
Shock Hugoniot of single crystal copper
Authors: Chau R. , Stölken J. , Asoka-Kumar P. , Kumar M. , Holmes N. C.
Published: January 2010

The shock Hugoniot of single crystal copper is reported for stresses below 66 GPa. Symmetric impact experiments were used to measure the Hugoniots of three different crystal orientations of copper, [100], [110], and [111]. The photonic doppler velocimetry (PDV) diagnostic was adapted into a very high precision time of arrival detector for these experiments. The measured Hugoniots along all three crystal directions were nearly identical to the experimental Hugoniot for polycrystalline Cu. The predicted orientation dependence of the Hugoniot from molecular dynamics calculations was not observed. At the lowest stresses, the sound speed in Cu was extracted from the PDV data. The measured sound speeds are in agreement with values calculated from the elastic constants for Cu.
Near-infrared electroluminescence and stimulated emission from semiconducting nonconjugated polymer thin films
Authors: Kobayashi Takeyuki , Djiango Martin , Blau Werner J.
Published: January 2010

We present the results of a study on near-infrared electroluminescence and optical amplification in semiconductor thin films based on a nonconjugated polymer doped with luminescent and electron-transport molecules. A single-layer light-emitting diode is fabricated on an indium tin oxide-coated glass substrate with poly(9-vinylcarbazole) containing an electron-transport material, 2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole and a near-infrared-emitting compound, 2-(6-(p-dimethylaminophenyl)-2,4-neopentylene-1,3,5-hexatrienyl)-3-ethylbenzothiazolium perchlorate. The single-layer structure shows near-infrared electroluminescence with a turn-on voltage of 13 V. The same structure is characterized under transversal pulsed photopumping with a frequency-doubled Nd: yttrium aluminum garnet laser. With increasing pump fluence, the edge emission at 0.82 μm shows both significant gain narrowing and superlinear intensity increase, which indicate the existence of optical gain by stimulated emission. Our results provide impetus for the development of near-infrared polymer lasers and optical amplifiers.
Epitaxial growth, electrical and optical properties of a-plane InN on r-plane sapphire
Authors: Ajagunna A. O. , Iliopoulos E. , Tsiakatouras G. , Tsagaraki K. , Androulidaki M. , Georgakilas A.
Published: January 2010

The heteroepitaxy of a-plane (112¯0) InN films on r-plane (11¯02) sapphire substrates, by nitrogen radio frequency plasma-assisted molecular beam epitaxy, has been investigated and compared to that of c-plane (0001) InN. The epitaxial growth of a-plane InN proceeded through the nucleation, growth, and coalescence of three-dimensional islands, resulting in surface roughness that increased monotonically with epilayer thickness. The full width at half maximum of (112¯0) x-ray diffraction rocking curves decreased significantly with increasing InN thickness, characteristic of structural improvement, and it reached the value of 24 arcmin for a 1 μm thick film. Hall-effect measurements exhibited a similar dependence of electron concentration and mobility on thickness for both the a- and c-plane InN films. The analysis of the Hall-effect measurements, by considering the contribution of two conducting layers, indicates a similar accumulation of low mobility electrons with Ns>1014 cm−2 at the films’ surface/interfacial region for both the a- and c-plane InN films. From optical transmittance measurements, the absorption edge of 0.768 eV was determined for the 1 μm a-plane film, consistent with the expected Burstein–Moss effect. Photoluminescence spectra exhibited a lower energy peak at 0.631 eV, suggesting defect-related transitions.
Note: A technique to capture and compose streak images of explosive events with unpredictable timing
Authors: Parker Gary R. , Asay Blaine W. , Dickson Peter M.
Published: January 2010

The authors describe a method to capture optical data and construct digitized streak images for analysis of high-speed phenomena with unpredictable timing by using a high-speed video camera and software routines. Advances in high-speed video camera technology have led to development of cameras with frame rates (1×106 frames per second) and spatial resolution (1280×800 pixels) suitable to capture fast phenomena, such as detonation in high explosives (≤10 km s−1), on small enough scales to be convenient for laboratory experiments. Further, relatively long-duration recordings (≥1 s) are maintained in a rolling buffer in volatile memory allowing the entire frame sequence to be recorded pretrigger, thus obviating the need for precisely located diagnostic triggers. The method described was used to capture the progression of luminous reaction during the deflagration-to-detonation transition of the HMX-based (octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine) plastic bonded explosive (PBX) formulation during cookoff.
Design and validation of a novel bioreactor principle to combine online micro-computed tomography monitoring and mechanical loading in bone tissue engineering
Authors: Hagenmüller Henri , Hitz Marco , Merkle Hans P. , Meinel Lorenz , Müller Ralph
Published: January 2010

Mechanical loading plays an important role in bone remodeling in vivo and, therefore, has been suggested as a key parameter in stem cell-based engineering of bone-like tissue in vitro. However, the optimization of loading protocols during stem cell differentiation and subsequent bone-like tissue formation is challenged by multiple input factors, which are difficult to control and validate. These include the variable cellular performance of cells harvested from different patients, nonstandardized culture media components, the choice of the biomaterial forming the scaffold, and its morphology, impacting a broader validity of mechanical stimulation regimens. To standardize the cell culture of bone-like tissue constructs, we suggest the involvement of time-lapsed feedback loops. For this purpose we present a prototype bioreactor that combines online, nondestructive monitoring using micro-computed tomography and direct mechanical loading of three-dimensional tissue engineering constructs. Validation of this system showed displacement steps down to 1 μm and cyclic sinusoidal loadings of up to 10 Hz. Load detection resolution was 0.01 N, and micro-computed tomography data were of high quality. For the first time, the developed bioreactor links time-lapsed, nondestructive, and dynamic imaging with mechanical stimulation, designed for cell culture under sterile conditions. This system is believed to substantially improve today’s experimental options to study and optimize osteogenic stem cell culture and differentiation at the interface with mechanical stimulation.
Theoretical studies on electronic and magnetic properties of ultrathin Mo nanowires
Authors: Bala Anu , Singh Poorva , Nautiyal Tashi , Auluck Sushil
Published: January 2010

We present a detailed theoretical study on electronic and magnetic properties of Mo nanowires with different structures. The ultrathin nanowires of this 4d transition metal show a unique behavior for the stability. We notice that zigzag structure is stable at the lower values of nearest neighbor distance. On slightly stretching the nanowire, the ladder structure is preferred while the dimerized structure, with the highest value of cohesive energy, is the most stable structure at larger nearest neighbor distances. This work suggests that magnetic ordering of Mo nanowires can be tuned with structure. The linear and ladder structures of Mo nanowires show antiferromagnetic ordering. Equilateral zigzag structure prefers a nonmagnetic state whereas the planar zigzag structure is ferromagnetic. The dimerized structure stands out showing degenerate nonmagnetic and ferromagnetic states. The highest value of magnetic moment (∼1.16 μB/atom) is predicted for linear chains. Relative break force values suggest that these nanowires would be difficult to be realized. The density of states and band structure shine light on engineering the electronic properties with structural tailoring. We notice that dimerized structure is the only one which can be used in semiconducting applications with a band gap of 1.1 eV. Interestingly, all these Mo nanowires show a signature of covalent bonding coexisting with metallic charge sharing, the former getting enhanced with the stretching of the wire.
Grain size dependence of properties in lead nickel niobate-lead zirconate titanate films
Authors: Griggio F. , Trolier-McKinstry S.
Published: January 2010

A chemical solution deposition procedure was developed for lead nickel niobate-lead zirconate titanate (0.3)Pb(Ni0.33Nb0.67)O3–(0.7)Pb(Zr0.45Ti0.55O3) ferroelectric thin films. On tailoring the heat-treatment conditions and excess lead content, the average grain diameters could be varied from 110 to 270 nm. Dielectric permittivities ranging from 1350 to 1520 and a transverse piezoelectric coefficient e31,f as high as −9.7 C/m2 were observed for films of about 0.25 μm in thickness. The permittivity and piezoelectric response increased for samples with larger grain size. Higher thermal budgets also imposed higher levels of in-plane tensile stress on the perovskite layer; the imposed stress reduced the remanent polarization for the samples. Nonetheless, samples processed at higher temperatures showed larger average grain diameters and higher extrinsic contributions to the properties.