bluuebunny/crossref_metadata_2025 huggingface dataset:
A reduced crustal magnetization zone near the first observed active hydrothermal vent field on the Southwest Indian Ridge
Authors: Zhu Jian , Lin Jian , Chen Yongshun J. , Tao Chunhui , German Christopher R. , Yoerger Dana R. , Tivey Maurice A.
Published: September 2010

Inversion of near‐bottom magnetic data reveals a well‐defined low crustal magnetization zone (LMZ) near a local topographic high (37°47′S, 49°39′E) on the ultraslow‐spreading Southwest Indian Ridge (SWIR). The magnetic data were collected by the autonomous underwater vehicle ABE on board R/V DaYangYiHao in February‐March 2007. The first active hydrothermal vent field observed on the SWIR is located in Area A within and adjacent to the LMZ at the local topographic high, implying that this LMZ may be the result of hydrothermal alteration of magnetic minerals. The maximum reduction in crustal magnetization is 3 A/M. The spatial extent of the LMZ is estimated to be at least 6.7 × 104 m2, which is larger than that of the LMZs at the TAG vent field on the Mid‐Atlantic Ridge (MAR), as well as the Relict Field, Bastille, Dante‐Grotto, and New Field vent‐sites on the Juan de Fuca Ridge (JdF). The calculated magnetic moment, i.e., the product of the spatial extent and amplitude of crustal magnetization reduction is at least −3 × 107 Am2 for the LMZ on the SWIR, while that for the TAG field on the MAR is −8 × 107 Am2 and that for the four individual vent fields on the JdF range from −5 × 107 to −3 × 107 Am2. Together these results indicate that crustal demagnetization is a common feature of basalt‐hosted hydrothermal vent fields at mid‐ocean ridges of all spreading rates. Furthermore, the crustal demagnetization of the Area A on the ultraslow‐spreading SWIR is comparable in strength to that of the TAG area on the slow‐spreading MAR.
Pulse‐like dynamic earthquake rupture propagation under rate‐, state‐ and temperature‐dependent friction
Authors: Bizzarri Andrea
Published: September 2010

Healing of faults is an important process in earthquake source physics since it accounts for a rapid restrengthening of the fault traction and for a consequent short slip duration, as indicated by slip inversions of seismic data. In this paper we show that a laboratory‐derived constitutive model, with an explicit dependence on the temperature developed by frictional heat, can provide a suitable explanation for the generation of self‐healing slip pulses. The model requires neither special modifications at low or high speeds nor the introduction of heterogeneities in the material properties, as previously proposed. We also demonstrate through numerical experiments of 3‐D ruptures that the temperature evolution can discriminate between crack‐like and slip pulses mode of propagation. In particular, we find that for a moderate level of strain localization (slipping zone width larger than 20 mm) ruptures behave as classical enlarging cracks.
Diagnosing radio plasma heating in the polar summer mesosphere using cross modulation: Theory and observations
Authors: Senior A. , Rietveld M. T. , Kosch M. J. , Singer W.
Published: September 2010

Radio heating of the free electrons in the mesosphere is an important diagnostic technique for the phenomenon of polar mesosphere summer echoes (PMSE). Due to a lack of suitable observations, the heating must be modeled when studying its effect on PMSE. In order to try to validate these models, the cross‐modulation technique was implemented at the EISCAT facility near Tromsø, Norway to compare the absorption of a diagnostic radio wave in the heated and unheated plasma. The results are compared to predictions from a model similar to that used for estimating the heating in PMSE studies. It is found that, after allowing for certain instrumental effects, the model overestimates the change in absorption of the diagnostic wave by a factor of 1.5–2.5. It is suggested that the assumption that the electron distribution function remains Maxwellian during heating could contribute to this discrepancy.
Seasonal to decadal variations of water vapor in the tropical lower stratosphere observed with balloon‐borne cryogenic frost point hygrometers
Authors: Fujiwara M. , Vömel H. , Hasebe F. , Shiotani M. , Ogino S.‐Y. , Iwasaki S. , Nishi N. , Shibata T. , Shimizu K. , Nishimoto E. , Valverde Canossa J. M. , Selkirk H. B. , Oltmans S. J.
Published: September 2010

We investigated water vapor variations in the tropical lower stratosphere on seasonal, quasi‐biennial oscillation (QBO), and decadal time scales using balloon‐borne cryogenic frost point hygrometer data taken between 1993 and 2009 during various campaigns including the Central Equatorial Pacific Experiment (March 1993), campaigns once or twice annually during the Soundings of Ozone and Water in the Equatorial Region (SOWER) project in the eastern Pacific (1998–2003) and in the western Pacific and Southeast Asia (2001–2009), and the Ticosonde campaigns and regular sounding at Costa Rica (2005–2009). Quasi‐regular sounding data taken at Costa Rica clearly show the tape recorder signal. The observed ascent rates agree well with the ones from the Halogen Occultation Experiment (HALOE) satellite sensor. Average profiles from the recent five SOWER campaigns in the equatorial western Pacific in northern winter and from the three Ticosonde campaigns at Costa Rica (10°N) in northern summer clearly show two effects of the QBO. One is the vertical displacement of water vapor profiles associated with the QBO meridional circulation anomalies, and the other is the concentration variations associated with the QBO tropopause temperature variations. Time series of cryogenic frost point hygrometer data averaged in a lower stratospheric layer together with HALOE and Aura Microwave Limb Sounder data show the existence of decadal variations: The mixing ratios were higher and increasing in the 1990s, lower in the early 2000s, and probably slightly higher again or recovering after 2004. Thus linear trend analysis is not appropriate to investigate the behavior of the tropical lower stratospheric water vapor.
Factors Determining Hotel Selection: Online Behaviour by Leisure Travellers
Authors: Jones Peter , Chen Meng-Mei
Published: September 2010

This paper reviews the considerable literature on hotel selection. It demonstrates that this body of literature has been developed, for the most part, outside of the context of a widely endorsed consumer decision-making model based on set formulation. It then reports on a study that uses an experimental design aimed at understanding hotel consumer consideration set formation and modification, rather than the previous traditional emphasis on choice sets and attributes. For a specific market segment selecting a hotel for a leisure stay the paper reports on the size of the consideration and choice set, and identifies the different factors that influence choice at these two stages in the process.
A plasma needle for generating homogeneous discharge in atmospheric pressure air
Authors: Li Xuechen , Yuan Ning , Jia Pengying , Chen Junying
Published: September 2010

Homogeneous discharge in air is often considered to be the ultimate low-temperature atmospheric pressure plasmas for industrial applications. In this paper, we present a method whereby stable homogeneous discharge in open air can be generated by a simple plasma needle. The discharge mechanism is discussed based on the spatially resolved light emission waveforms from the plasma. Optical emission spectroscopy is used to determine electron energy and rotational temperature, and results indicate that both electron energy and rotational temperature increase with increasing the applied voltage. The results are analyzed qualitatively based on the discharge mechanism.
Correcting magnetic probe perturbations on current density measurements of current carrying plasmas
Authors: Knoblauch P. , Raspa V. , Di Lorenzo F. , Lazarte A. , Clausse A. , Moreno C.
Published: September 2010

A method to infer the current density distribution in the current sheath of a plasma focus discharge from a magnetic probe is formulated and then applied to experimental data obtained in a 1.1 kJ device. Distortions on the magnetic probe signal caused by current redistribution and by a time-dependent total discharge current are considered simultaneously, leading to an integral equation for the current density. Two distinct, easy to implement, numerical procedures are given to solve such equation. Experimental results show the coexistence of at least two maxima in the current density structure of a nitrogen sheath.
Two-photon-excited luminescence from a Eu3+-doped lithium niobate crystal pumped by a near-infrared femtosecond laser
Authors: Li Ai-Hua , Zheng Zhi-Ren , Lü Qiang , Xu Zhao-Peng , Sun Liang , Liu Wei-Long , Wu Wen-Zhi , Lü Tian-Quan
Published: September 2010

Red upconversion luminescence (UCL) is observed using an 800 nm femtosecond laser to irradiate a Eu3+-doped LiNbO3 single crystal. Power-dependent and polarization-dependent experiments demonstrate that the red UCL originates from Eu3+ two-photon simultaneous absorption rather than second harmonic generation of nonlinear optical crystal followed by reabsorption of Eu3+. Two different kinds of Eu3+-centers, called Eu3+-pairs, are revealed via emission spectra. Besides using femtosecond laser excitation to simulate diode laser excitation with broad line, the efficient two-photon simultaneous absorption can populate more Eu3+ to upper levels, these are beneficial to the study of cross relaxation with submicrosecond resolution between Eu3+-pairs occurred in practical application. Transient UCL spectra and decay curves suggest that the luminescent state D50 is fed by way of both multiphonon relaxation through state D51 and cross relaxation of D52+F70→D50+F75.
Nonlinear optical properties of silicon nanoclusters/nanocrystals doped SiO2 films: Annealing temperature dependence
Authors: Ito Masahiko , Imakita Kenji , Fujii Minoru , Hayashi Shinji
Published: September 2010

Comprehensive studies on nonlinear refractive indices (n2) of SiO2 films containing Si nanocrystals and/or nanoclusters (SiO2:Si-ncs) are performed. The comparison of the nonlinear refractive indices with the electron spin resonance signals reveals that defect states play a major role in the large n2 when the annealing temperature is low, i.e., when Si nanoclusters exist in films. On the other hand, when Si nanocrystals are grown by high-temperature annealing, the contribution of defect states becomes small and that of the quantized electronic states of Si nanocrystals becomes large. The present results demonstrate that both the defect states and the quantized electronic states should be taken into account to explain the origin of large n2 of SiO2:Si-ncs and to optimize the structure to maximize n2.
Low Reynolds number Couette flow facility for drag measurements
Authors: Johnson Tyler J. , Lang Amy W. , Wheelus Jennifer N. , Westcott Matthew
Published: September 2010

For this study a new low Reynolds number Couette facility was constructed to investigate surface drag. In this facility, mineral oil was used as the working fluid to increase the shear stress across the surface of the experimental models. A mounted conveyor inside a tank creates a flow above which an experimental model of a flat plate was suspended. The experimental plate was attached to linear bearings on a slide system that connects to a force gauge used to measure the drag. Within the gap between the model and moving belt a Couette flow with a linear velocity profile was created. Digital particle image velocimetry was used to confirm the velocity profile. The drag measurements agreed within 5% of the theoretically predicted Couette flow value.
Glycine in aqueous solution: solvation shells, interfacial water, and vibrational spectroscopy from ab initio molecular dynamics
Authors: Sun Jian , Bousquet David , Forbert Harald , Marx Dominik
Published: September 2010

An aqueous glycine solution is studied with ab initio molecular dynamics to investigate the structural aspects of the different solvation shells within the zwitterion and their impact on the infrared spectrum. The individual contributions to the total IR spectrum from glycine and solvation water are decomposed systematically using the standard schemes in terms of maximally localized Wannier orbitals to define approximate molecular dipole moments in solution. The IR spectra of the aqueous solution and of the solvated zwitterionic glycine molecule itself are compared to those stemming from neutral glycine in the gas phase and a virtual “isolated” zwitterionic glycine molecule vertically transferred from solution into vacuum. Furthermore, electronic polarization effects due to solute-solvent coupling are discussed in detail for the solute and for the interfacial solvent molecules based on dipole moment distribution functions.
Estimation of plasma position from tangentially viewed images on a toroidally symmetric device
Authors: Nam Y. U. , Chung J. , Jeon Y. M.
Published: September 2010

Images of plasma from a fast-framing camera are the most intuitive and reliable data to understand the status of tokamak plasmas. Generation, movement, size variation, and disruptions of plasmas can be clearly observed from these images. However, it is not a simple task to obtain the exact positions and sizes of plasmas using these images because measured two-dimensional images inevitably lose the three-dimensional position information of their targets. In this paper, the exact positions and sizes of plasmas have been calculated from tangentially viewed images using the toroidal symmetry of the plasma in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The positions and sizes of the plasmas have been manually determined with displayed cursors on images and automatically determined using a correlation factor with calculated virtual plasma images as well. These two results correspond well with each other. The estimated positions have also been compared with those obtained from magnetic diagnostics analysis.
Coating of tips for electrochemical scanning tunneling microscopy by means of silicon, magnesium, and tungsten oxides
Authors: Salerno Marco
Published: September 2010

Different combinations of metal tips and oxide coatings have been tested for possible operation in electrochemical scanning tunneling microscopy. Silicon and magnesium oxides have been thermally evaporated onto gold and platinum-iridium tips, respectively. Two different thickness values have been explored for both materials, namely, 40 and 120 nm for silicon oxide and 20 and 60 nm for magnesium oxide. Alternatively, tungsten oxide has been grown on tungsten tips via electrochemical anodization. In the latter case, to seek optimal results we have varied the pH of the anodizing electrolyte between one and four. The oxide coated tips have been first inspected by means of scanning electron microscopy equipped with microanalysis to determine the morphological results of the coating. Second, the coated tips have been electrically characterized ex situ for stability in time by means of cyclic voltammetry in 1 M aqueous KCl supporting electrolyte, both bare and supplemented with K3[Fe(CN)6] complex at 10 mM concentration in milliQ water as an analyte. Only the tungsten oxide coated tungsten tips have shown stable electrical behavior in the electrolyte. For these tips, the uncoated metal area has been estimated from the electrical current levels, and they have been successfully tested by imaging a gold grating in situ, which provided stable results for several hours. The successful tungsten oxide coating obtained at pH=4 has been assigned to the WO3 form.
Nonuniform fiber networks and fiber-based composites: Pore size distributions and elastic moduli
Authors: Chatterjee Avik P.
Published: September 2010

An excluded-volume approach is developed for modeling the distribution of pore sizes and the specific surface area in isotropic networks of cylindrical fibers. The effect of accounting for nonuniformities in the spatial distribution of the fibers upon the mean pore size and effective surface area is examined. Fluctuations in the fiber volume fraction are shown to increase the mean pore radius and to reduce the specific surface area relative to their values for a spatially uniform network. A method is suggested for addressing the impact of spatial nonuniformities in the fiber volume fraction within mean-field and semiempirical models for the elastic moduli of fiber-based composites.
The effect of thickness and/or doping on the nonlinear and saturable absorption behaviors in amorphous GaSe thin films
Authors: Kürüm Ulaş , Yüksek Mustafa , Yaglioglu H. Gul , Elmali Ayhan , Ateş Aytunç , Karabulut Mevlüt , Mamedov Gasan M.
Published: September 2010

We investigated the nonlinear and saturable absorption characteristics of very thin amorphous undoped GaSe, Ge (0.01 at. %), and Sn (0.5 at. %) doped GaSe films by pump-probe and open aperture Z-scan techniques. Linear absorption measurements indicate blueshift in energy with increasing film thickness. Thinner films exhibit saturable absorption while thicker films exhibit nonlinear absorption for 4 ns and 65 ps pulse durations. The films exhibit competing effects between nonlinear and saturable absorption. Saturable absorption behavior weakens while nonlinear absorption appears with increasing film thickness. In addition to that, saturable absorption behavior is very sensitive to doping. Doping causes absorption behaviors to appear in thinner films compared to undoped films. These behaviors are attributed to increasing localized defect states with increasing film thickness and doping. To derive the transmission in open aperture Z-scan data, a theoretical model incorporating one photon, two photon, and free carrier absorptions and their saturations were considered. The experimental curves were fitted to the theory of open aperture Gaussian beam Z-scan based on the Adomian decomposition method. Nonlinear absorption coefficients and saturation intensity thresholds were extracted from the fitting of the experimental results for both pulse durations used for the experiments. Saturation intensity threshold values increased with increasing film thickness and doping. The lowest saturation intensity threshold for undoped GaSe film was found to be 1.9×10−3 GW/cm2 for 45 nm film thickness and increased about two orders of magnitude for 74 nm film thickness.
Particle simulation of femtosecond laser stimulation of electrical discharges in small gaps
Authors: Chen J. , He L. N. , Farson D. F. , Rokhlin S. I.
Published: September 2010

A particle-in-cell/Monte Carlo collision simulation study of femtosecond laser stimulation of electrical discharges in submicron gaps between platinum scanning tunneling microscope cathode tips and gold film anodes in atmospheric pressure argon gas is described. The breakdown potential of gaps containing either preloaded electrons or preloaded neutral and ionized platinum atoms and electrons at various densities were compared to the breakdown potential of gaps with background argon gas alone. It was found that gaps preloaded with sufficient densities of either electrons or partially ionized electrode materials broke down at cathode potential of −80 V while gaps with background argon gas alone required applied cathode potentials between −200 to −250 V to cause a breakdown. Also, partially ionized material was much more effective at stimulating breakdown than electrons alone. The density of preloaded partially ionized platinum required to lower breakdown cathode potential to −80 V was approximately 12.5 times smaller than that required for the preloaded electrons alone in the same size gap. Analysis of the mechanism by which the preloaded partially ionized material promoted breakdown showed that laser ablated ions located near the cathode tip increased the local field at the cathode surface and the field-emitted electron flux from the cathode. This higher electron flux ionized background argon gas and preloaded platinum which resulted in gap breakdown. The threshold density of partially ionized platinum for gap breakdown varied approximately linearly with applied cathode potential.
Hysteretic current-voltage characteristic in polycrystalline ceramic ferrites
Authors: Cai Kunpeng , Wang Rui , Li Bo , Zhou Ji
Published: September 2010

Electric transport properties of sintered polycrystalline Zn0.6Mn0.4Fe2O4 ferrite prepared by traditional solid reaction method were studied. A hysteretic current-voltage characteristic was found, and it could be tuned by both relatively low electric field and magnetic field at room temperature. A magnetic hysteresis related electron transmission model was proposed to explain the results. The tunable electric transport properties are potentially significant for electronic applications, such as nonvolatile random access memories, memristors, and other circuit elements with memory.
Nanomechanical biosensing with immunomagnetic separation
Authors: Icoz Kutay , Savran Cagri
Published: September 2010

We report a biosensing method that combines immunomagnetic separation and nanomechanical detection. In this method, same magnetic beads that are used to “fish” biomolecules from complex mixtures enable deflection of a cantilever structure upon excitation by an oscillating magnetic field. Biotin-coated magnetic beads were used to capture and separate streptavidin from serum. Streptavidin loaded magnetic beads were exposed to a differential cantilever system whose sensing arm was functionalized with biotin. The magnetic force applied on the streptavidin-beads resulted in differential cantilever deflections that could be detected down to 0.26 Årms in air.
Nanocheckerboard modulations in (NaNd)(MgW)O6
Authors: Licurse Mark W. , Davies Peter K.
Published: September 2010

Data is presented for a complex structural and compositional modulation in the perovskite (NaNd)(MgW)O6. This modulation creates a large 14ap×14ap×2ap supercell (ap≈3.9 Å is the lattice parameter of the cubic perovskite aristotype) containing ordered regions with doubled (110) d-spacings in the a-b plane separated by two-dimensional periodic antiphase boundaries and accompanied by a nanocheckerboard pattern. Faint periodic modulations in Z-contrast images suggest an associated periodic variation in composition. The presence of a sodium rich impurity implies the composition of the stable perovskite is nonstoichiometric.
Photoluminescence from colloids containing aluminum hydroxide nanocrystals with uniform size
Authors: Li T. H. , Liu L. Z. , Wu X. L. , Shen J. C. , Gao F. , Chu Paul K.
Published: September 2010

Aluminum hydroxide nanocrystals consisting of an amorphous shell and crystalline core are fabricated by pulsed laser ablation of an aluminum target in water. The colloid consisting of nanocrystals with a uniform size exhibits a size-independent photoluminescence (PL) band at ∼383 nm. According to the PL excitation spectra and time-resolved PL decay analysis, this PL band originates from oxygen vacancies in the amorphous shell and Förster energy transfer occurs between the oxygen vacancy levels in the crystalline core and amorphous shell. These phenomena are found to alter the PL excitation spectra.
Linear-scaling density-functional simulations of charged point defects in Al2O3 using hierarchical sparse matrix algebra
Authors: Hine N. D. M. , Haynes P. D. , Mostofi A. A. , Payne M. C.
Published: September 2010

We present calculations of formation energies of defects in an ionic solid (Al2O3) extrapolated to the dilute limit, corresponding to a simulation cell of infinite size. The large-scale calculations required for this extrapolation are enabled by developments in the approach to parallel sparse matrix algebra operations, which are central to linear-scaling density-functional theory calculations. The computational cost of manipulating sparse matrices, whose sizes are determined by the large number of basis functions present, is greatly improved with this new approach. We present details of the sparse algebra scheme implemented in the ONETEP code using hierarchical sparsity patterns, and demonstrate its use in calculations on a wide range of systems, involving thousands of atoms on hundreds to thousands of parallel processes.
Calibration sets and the accuracy of vibrational scaling factors: A case study with the X3LYP hybrid functional
Authors: Teixeira Filipe , Melo André , Cordeiro M. Natália D. S.
Published: September 2010

A linear least-squares methodology was used to determine the vibrational scaling factors for the X3LYP density functional. Uncertainties for these scaling factors were calculated according to the method devised by Irikura et al. [J. Phys. Chem. A 109, 8430 (2005)]. The calibration set was systematically partitioned according to several of its descriptors and the scaling factors for X3LYP were recalculated for each subset. The results show that the scaling factors are only significant up to the second digit, irrespective of the calibration set used. Furthermore, multivariate statistical analysis allowed us to conclude that the scaling factors and the associated uncertainties are independent of the size of the calibration set and strongly suggest the practical impossibility of obtaining vibrational scaling factors with more than two significant digits.
Port Governance Reforms in Diversified Institutional Frameworks: Generic Solutions, Implementation Asymmetries
Authors: Ng Adolf K Y , Pallis Athanasios A
Published: September 2010

Bringing in neo-institutional perspectives, this paper investigates the recent corporatisation process of three seaports in Asia and Europe. We focus on whether the newly established seaport governance structures follow a path largely affected by the local/national institutional frameworks and the political traditions in place. Findings confirm that path-dependent decisions largely preserve the institutional characteristics of local/national systems, resulting in implementation asymmetries when different countries seek generic governance solutions.
‘Full-Cost Recovery’: Producing Differentiated Water Collection Practices and Responses to Centralized Water Networks in Jaipur, India
Authors: Birkenholtz Trevor
Published: September 2010

This paper examines the political ecological effects of the expansion of an urban centralized water-supply network and the transformation of it into a full-cost-recovery system in Jaipur, Rajasthan, India. It draws on data collected through a 2007 household survey of six Jaipur neighborhoods stratified by class; follow-up household interviews in 2007 and 2009; and interviews with public water supply managers and private water tanker vendors in both 2007 and 2009. The investigation concludes that the spatially uneven integration of network expansion and the intermittent flow of water circulating through it, combined with historical axes of political economic difference produces uneven adaptive responses to maintain access to water, such as waiting on water, private tubewell construction, and private water tanker operations, while transforming social power relations. It is concluded, first, that these uneven flows and cost-recovery initiatives are exacerbating current disparities in access to drinking water and, second, that the current public water-supply system has only been partially reformed and that these policy changes have rendered the public supplier unable to recover costs. This makes the need for a private sector rescue of an incapacitated and inefficient public institution seem obvious to planners, yet the public utility's inability to set costs or to set infrastructure priorities draws into question the need for the private sector and full-cost-recovery reforms.
Learning and Generalization in Haptic Classification of 2-D Raised-Line Drawings of Facial Expressions of Emotion by Sighted and Adventitiously Blind Observers
Authors: Abramowicz Aneta , Klatzky Roberta L , Lederman Susan J
Published: September 2010

Sighted blindfolded individuals can successfully classify basic facial expressions of emotion (FEEs) by manually exploring simple 2-D raised-line drawings (Lederman et al 2008, IEEE Transactions on Haptics1 27–38). The effect of training on classification accuracy was assessed by sixty sighted blindfolded participants (experiment 1) and by three adventitiously blind participants (experiment 2). We further investigated whether the underlying learning process(es) constituted token-specific learning and/or generalization. A hybrid learning paradigm comprising pre/post and old/new test comparisons was used. For both participant groups, classification accuracy for old (ie trained) drawings markedly increased over study trials (mean improvement = 76%, and 88%, respectively). Additionally, RT decreased by a mean of 30% for the sighted, and 31% for the adventitiously blind. Learning was mostly token-specific, but some generalization was also observed for both groups. The sighted classified novel drawings of all six FEEs faster with training (mean RT decrease = 20%). Accuracy also improved significantly (mean improvement = 20%), but this improvement was restricted to two FEEs (anger and sadness). Two of three adventitiously blind participants classified new drawings more accurately (mean improvement = 30%); however, RTs for this group did not reflect generalization. Based on a limited number of blind subjects, our results tentatively suggest that adventitiously blind individuals learn to haptically classify FEEs as well as, or even better than, sighted persons.
An Atg9-containing compartment that functions in the early steps of autophagosome biogenesis
Authors: Mari Muriel , Griffith Janice , Rieter Ester , Krishnappa Lakshmi , Klionsky Daniel J. , Reggiori Fulvio
Published: September 2010

Eukaryotes use the process of autophagy, in which structures targeted for lysosomal/vacuolar degradation are sequestered into double-membrane autophagosomes, in numerous physiological and pathological situations. The key questions in the field relate to the origin of the membranes as well as the precise nature of the rearrangements that lead to the formation of autophagosomes. We found that yeast Atg9 concentrates in a novel compartment comprising clusters of vesicles and tubules, which are derived from the secretory pathway and are often adjacent to mitochondria. We show that these clusters translocate en bloc next to the vacuole to form the phagophore assembly site (PAS), where they become the autophagosome precursor, the phagophore. In addition, genetic analyses indicate that Atg1, Atg13, and phosphatidylinositol-3-phosphate are involved in the further rearrangement of these initial membranes. Thus, our data reveal that the Atg9-positive compartments are important for the de novo formation of the PAS and the sequestering vesicle that are the hallmarks of autophagy.
Two distinct secretory vesicle–priming steps in adrenal chromaffin cells
Authors: Liu Yuanyuan , Schirra Claudia , Edelmann Ludwig , Matti Ulf , Rhee JeongSeop , Hof Detlef , Bruns Dieter , Brose Nils , Rieger Heiko , Stevens David R. , Rettig Jens
Published: September 2010

Priming of large dense-core vesicles (LDCVs) is a Ca2+-dependent step by which LDCVs enter a release-ready pool, involving the formation of the soluble N-ethyl-maleimide sensitive fusion protein attachment protein (SNAP) receptor complex consisting of syntaxin, SNAP-25, and synaptobrevin. Using mice lacking both isoforms of the calcium-dependent activator protein for secretion (CAPS), we show that LDCV priming in adrenal chromaffin cells entails two distinct steps. CAPS is required for priming of the readily releasable LDCV pool and sustained secretion in the continued presence of high Ca2+ concentrations. Either CAPS1 or CAPS2 can rescue secretion in cells lacking both CAPS isoforms. Furthermore, the deficit in the readily releasable LDCV pool resulting from CAPS deletion is reversed by a constitutively open form of syntaxin but not by Munc13-1, a priming protein that facilitates the conversion of syntaxin to the open conformation. Our data indicate that CAPS functions downstream of Munc13s but also interacts functionally with Munc13s in the LDCV-priming process.
Cdc48/p97 and Shp1/p47 regulate autophagosome biogenesis in concert with ubiquitin-like Atg8
Authors: Krick Roswitha , Bremer Sebastian , Welter Evelyn , Schlotterhose Petra , Muehe Yvonne , Eskelinen Eeva-Liisa , Thumm Michael
Published: September 2010

The molecular details of the biogenesis of double-membraned autophagosomes are poorly understood. We identify the Saccharomyces cerevisiae AAA–adenosine triphosphatase Cdc48 and its substrate-recruiting cofactor Shp1/Ubx1 as novel components needed for autophagosome biogenesis. In mammals, the Cdc48 homologue p97/VCP and the Shp1 homologue p47 mediate Golgi reassembly by extracting an unknown monoubiquitinated fusion regulator from a complex. We find no requirement of ubiquitination or the proteasome system for autophagosome biogenesis but detect interaction of Shp1 with the ubiquitin-fold autophagy protein Atg8. Atg8 coupled to phosphatidylethanolamine (PE) is crucial for autophagosome elongation and, in vitro, mediates tethering and hemifusion. Interaction with Shp1 requires an FK motif within the N-terminal non–ubiquitin-like Atg8 domain. Based on our data, we speculate that autophagosome formation, in contrast to Golgi reassembly, requires a complex in which Atg8 functionally substitutes ubiquitin. This, for the first time, would give a rationale for use of the ubiquitin-like Atg8 during macroautophagy and would explain why Atg8-PE delipidation is necessary for efficient macroautophagy.
Fibrillin-1 and -2 differentially modulate endogenous TGF-β and BMP bioavailability during bone formation
Authors: Nistala Harikiran , Lee-Arteaga Sui , Smaldone Silvia , Siciliano Gabriella , Carta Luca , Ono Robert N. , Sengle Gerhard , Arteaga-Solis Emilio , Levasseur Regis , Ducy Patricia , Sakai Lynn Y. , Karsenty Gerard , Ramirez Francesco
Published: September 2010

Extracellular regulation of signaling by transforming growth factor (TGF)–β family members is emerging as a key aspect of organ formation and tissue remodeling. In this study, we demonstrate that fibrillin-1 and -2, the structural components of extracellular microfibrils, differentially regulate TGF-β and bone morphogenetic protein (BMP) bioavailability in bone. Fibrillin-2–null (Fbn2−/−) mice display a low bone mass phenotype that is associated with reduced bone formation in vivo and impaired osteoblast maturation in vitro. This Fbn2−/− phenotype is accounted for by improper activation of latent TGF-β that selectively blunts expression of osterix, the transcriptional regulator of osteoblast maturation, and collagen I, the structural template for bone mineralization. Cultured osteoblasts from Fbn1−/− mice exhibit improper latent TGF-β activation as well, but mature faster because of increased availability of otherwise matrix-bound BMPs. Additional in vitro evidence excludes a direct role of microfibrils in supporting mineral deposition. Together, these findings identify the extracellular microfibrils as critical regulators of bone formation through the modulation of endogenous TGF-β and BMP signaling.
Mechanical Integrity of Hemodialysis Catheters after Exposure to a Novel Catheter Lock Solution
Authors: Aslam Saima , Darouiche Rabih O.
Published: September 2010

Objective.

To examine the mechanical integrity of hemodialysis catheters after exposure to the combination of N-acetylcysteine, ti-gecycline, and heparin, compared with that of catheters exposed to heparin alone.

Methods.

We used 3 types of hemodialysis catheters: polyurethane, silicone, and carbothane catheters. Catheter segments were incubated in vitro for various time intervals of up to 2 weeks either in a novel catheter lock solution (novel CLS), which consisted of N-acetylcysteine, tigecycline, and heparin, or in heparin alone (as a control). At the time of testing, each segment was rinsed and cut longitudinally into 2 sections. All catheter sections were scanned using an optical dissecting microscope to check for surface abnormalities and to measure wall thickness. We also carried out tensile strength testing of another set of catheters using a universal testing machine. Tested parameters included stress at yield, strain at yield, stress at break, strain at break, modulus of elasticity, and force at break.

Results.

The surfaces of catheters in both groups appeared similar by microscopy. The mean thickness of the catheter wall was not significantly different for the catheters exposed to the novel CLS and the catheters exposed to heparin (P >.05). Results for most of the tensile strength parameters tested were similar in the 2 groups of catheters at the end of 2 weeks of incubation. In particular, the force-at-break value of all tested catheters remained much greater than that recommended by industry standards.

Conclusions.

The use of the novel catheter lock solution did not impair the mechanical integrity or increase the propensity for fracture of hemodialysis catheters.
Objective determination of the sea age of Atlantic salmon from the sizes and dates of capture of individual fish
Authors: Bacon Philip J. , Gurney William S. C. , McKenzie Eddie , Whyte Bryce , Campbell Ronald , Laughton Robert , Smith Gordon , MacLean Julian
Published: September 2010

Bacon, P. J., Gurney, W. S. C., McKenzie, E., Whyte, B., Campbell, R., Laughton, R., Smith, G., and MacLean, J. 2011. Objective determination of the sea age of Atlantic salmon from the sizes and dates of capture of individual fish. – ICES Journal of Marine Science, 68: 130–143. The sea ages of Atlantic salmon indicate crucial differences between oceanic feeding zones that have important implications for conservation and management. Historical fishery-catch records go back more than 100 years, but the reliability with which they discriminate between sea-age classes is uncertain. Research data from some 188 000 scale-aged Scottish salmon that included size (length, weight) and seasonal date of capture on return to the coast were investigated to devise a means of assigning sea age to individual fish objectively. Two simple bivariate probability distributions are described that discriminate between 1SW and 2SW fish with 97% reliability, and between 2SW and 3SW fish with 70% confidence. The same two probability distributions achieve this accuracy across five major east coast Scottish rivers and five decades. They also achieve the same exactitude for a smaller recent dataset from the Scottish west coast, from the River Tweed a century ago (1894/1895), and for salmon caught by rod near the estuary. More surprisingly, they also achieve the same success for rod-caught salmon taken at beats remote from the estuary and including capture dates when some fish could have been in the river for a few months. The implications of these findings for fishery management and conservation are discussed.
Identification of Genes Involved in the Response of Banana to Crown Rot Disease
Authors: Lassois Ludivine , Frettinger Patrick , de Lapeyre de Bellaire Luc , Lepoivre Philippe , Jijakli Haissam
Published: September 2010

Variations in banana susceptibility to crown rot disease have been observed but the molecular mechanisms underlying these quantitative host–pathogen relationships are still unknown. This study was designed to compare gene expression between crowns of banana fruit showing a high susceptibility (S+) and crowns showing a low susceptibility (S–) to the disease. Comparisons were performed at two situation times: i) between crowns (S+and S–) collected 1 h before inoculation and ii) between crowns (S+ and S–) collected 13 days after inoculation. Gene expression comparisons were performed with cDNA-amplified fragment length polymorphism (AFLP) and results were confirmed by real-time reverse-transcription polymerase chain reaction. Among genes identified as differentially expressed between S+and S–crowns, two were involved in signal transduction, three in proteolytic machinery, two had similarity to pathogenesis-related protein 14, one to a CCR4-associated factor protein, and one to a cellulose synthase. Paradoxically, the overexpression of the cellulose synthase gene was associated with banana showing a high susceptibility in both pre- and post-inoculation situations. Finally, the cDNA-AFLP identified a gene that seems to be associated with the quantitative banana responses to crown rot disease; this gene encodes a dopamine-β-monooxygenase, which is involved in the catecholamine pathway. To our knowledge, this work is the first to address both pre- and post-infection gene expression with the same host–pathogen combination and distinct susceptibility levels.
Development of a Novel Rolling-Circle Amplification Technique to Detect Banana streak virus that also Discriminates Between Integrated and Episomal Virus Sequences
Authors: James A. P. , Geijskes R. J. , Dale J. L. , Harding R. M.
Published: September 2010

Banana plants are hosts to a large number of Banana streak virus (BSV) species. However, diagnostic methods for BSV are inadequate because of the considerable genetic and serological diversity among BSV isolates and the presence of integrated BSV sequences in some banana cultivars which leads to false positives. In this study, a sequence-nonspecific, rolling-circle amplification (RCA) technique was developed and shown to overcome these limitations for the detection and subsequent characterization of BSV isolates infecting banana. This technique was shown to discriminate between integrated and episomal BSV DNA, specifically detecting the latter in several banana cultivars known to contain episomal or integrated sequences of Banana streak Mysore virus (BSMyV), Banana streak OL virus (BSOLV), and Banana streak GF virus (BSGFV). Using RCA, the presence of BSMyV and BSOLV was confirmed in Australia, while BSOLV, BSGFV, Banana streak Uganda I virus (BSUgIV), Banana streak Uganda L virus (BSUgLV), and Banana streak Uganda M virus (BSUgMV) were detected in Uganda. This is the first confirmed report of episomally-derived BSUglV, BSUgLV, and BSUgMV in Uganda. As well as its ability to detect BSV, RCA was shown to detect two other pararetroviruses, Sugarcane bacilliform virus in sugarcane and Cauliflower mosaic virus in turnip.
Self-organization at the frictional interface for green tribology
Authors: Nosonovsky Michael
Published: September 2010

Despite the fact that self-organization during friction has received relatively little attention from tribologists so far, it has the potential for the creation of self-healing and self-lubricating materials, which are important for green or environment-friendly tribology. The principles of the thermodynamics of irreversible processes and of the nonlinear theory of dynamical systems are used to investigate the formation of spatial and temporal structures during friction. The transition to the self-organized state with low friction and wear occurs through destabilization of steady-state (stationary) sliding. The criterion for destabilization is formulated and several examples are discussed: the formation of a protective film, microtopography evolution and slip waves. The pattern formation may involve self-organized criticality and reaction–diffusion systems. A special self-healing mechanism may be embedded into the material by coupling the corresponding required forces. The analysis provides the structure–property relationship, which can be applied for the design optimization of composite self-lubricating and self-healing materials for various ecologically friendly applications and green tribology.
Influence of boric acid additive size on green lubricant performance
Authors: Lovell Michael R. , Kabir M. A. , Menezes Pradeep L. , Higgs C. Fred
Published: September 2010

As the industrial community moves towards green manufacturing processes, there is an increased demand for multi-functional, environmentally friendly lubricants with enhanced tribological performance. In the present investigation, green (environmentally benign) lubricant combinations were prepared by homogeneously mixing nano- (20 nm), sub-micrometre- (600 nm average size) and micrometre-scale (4 μm average size) boric acid powder additives with canola oil in a vortex generator. As a basis for comparison, lubricants of base canola oil and canola oil mixed with MoS
2
powder (ranging from 0.5 to 10 μm) were also prepared. Friction and wear experiments were carried out on the prepared lubricants using a pin-on-disc apparatus under ambient conditions. Based on the experiments, the nanoscale (20 nm) particle boric acid additive lubricants significantly outperformed all of the other lubricants with respect to frictional and wear performance. In fact, the nanoscale boric acid powder-based lubricants exhibited a wear rate more than an order of magnitude lower than the MoS
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and larger sized boric acid additive-based lubricants. It was also discovered that the oil mixed with a combination of sub-micrometre- and micrometre-scale boric acid powder additives exhibited better friction and wear performance than the canola oil mixed with sub-micrometre- or micrometre-scale boric acid additives alone.
Green waxes, adhesives and lubricants
Authors: Li W. , Kong X. H. , Ruan M. , Ma F. M. , Jiang Y. F. , Liu M. Z. , Chen Y. , Zuo X. H.
Published: September 2010

General characteristics of waxes, adhesives and lubricants as well as the recent fundamental investigations on their physical and mechanical behaviour are introduced. The current R&D status for new type/generation of waxes, adhesives and lubricants from natural products is reviewed, with an emphasis on their tribological applications. In particular, some crucial issues and challenges relating to technological improvement and materials development are discussed. Based on the current predicted shortage of energy resources and environmental concerns, prospective research on the development of green waxes, adhesives and lubricants is suggested.
Arboreality, terrestriality and bipedalism
Authors: Crompton Robin Huw , Sellers William I. , Thorpe Susannah K. S.
Published: September 2010

The full publication ofArdipithecus ramidushas particular importance for the origins of hominin bipedality, and strengthens the growing case for an arboreal origin. Palaeontological techniques however inevitably concentrate on details of fragmentary postcranial bones and can benefit from a whole-animal perspective. This can be provided by field studies of locomotor behaviour, which provide a real-world perspective of adaptive context, against which conclusions drawn from palaeontology and comparative osteology may be assessed and honed. Increasingly sophisticated dynamic modelling techniques, validated against experimental data for living animals, offer a different perspective where evolutionary and virtual ablation experiments, impossible for living mammals, may be runin silico, and these can analyse not only the interactions and behaviour of rigid segments but increasingly the effects of compliance, which are of crucial importance in guiding the evolution of an arboreally derived lineage.