bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ferroelectric crystal with enhanced phase transition temperatures
Authors: Zhang Shujun , Luo Jun , Hackenberger Wesley , Shrout Thomas R.
Published: September 2008

The full set of material constants for relaxor-based ternary single crystals Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN-PMN-PT) were determined and compared to binary Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) crystals. The Curie temperature for rhombohedral compositions of PIN-PMN-PT was found to be in the range of 160–200 °C with ferroelectric rhombohedral to tetragonal phase transition on the order of 120–130 °C, more than 30 °C higher than that found for PMNT. The piezoelectric coefficients (d33) were in the range of 1100–1500 pC/N, with electromechanical coupling factors (k33) about 89%–92% comparable to PMNT crystals. The coercive field of the ternary crystal was found to be 5.5 kV/cm, double the value of the binary counterparts. The dielectric behavior under varying dc bias exhibited a similar trend as observed in PMNT with a much broader usage temperature range. Together with its enhanced field induced phase transition level, the ternary PIN-PMN-PT crystals are promising candidates for high temperature and high drive transducer applications.
Using small angle x-ray scattering to measure the homogeneous nucleation rates of n-propanol, n-butanol, and n-pentanol in supersonic nozzle expansions
Authors: Ghosh David , Manka Alexandra , Strey Reinhard , Seifert Soenke , Winans Randall E. , Wyslouzil Barbara E.
Published: September 2008

In our earlier publication [M. Gharibeh et al., J. Chem. Phys. 122, 094512 (2005)] we determined the temperatures and partial pressures corresponding to the maximum nucleation rate for a series n-alcohols (CiH2i+lOH; i=3–5) during condensation in a supersonic nozzle. Although we were able to determine the characteristic time ΔtJmax corresponding to the peak nucleation rate, we were unable to measure the number density of the aerosol and, thus, unable to directly quantify the nucleation rate J. In this paper we report the results of our pioneering small angle x-ray scattering (SAXS) experiments of n-alcohol droplets formed in a supersonic nozzle together with a new series of complementary pressure trace measurements. By combining the SAXS and pressure trace measurement data we determine the nucleation rates as a function of temperature and supersaturation.
Synchronization in interacting populations of heterogeneous oscillators with time-varying coupling
Authors: So Paul , Cotton Bernard C. , Barreto Ernest
Published: September 2008

In many networks of interest (including technological, biological, and social networks), the connectivity between the interacting elements is not static, but changes in time. Furthermore, the elements themselves are often not identical, but rather display a variety of behaviors, and may come in different classes. Here, we investigate the dynamics of such systems. Specifically, we study a network of two large interacting heterogeneous populations of limit-cycle oscillators whose connectivity switches between two fixed arrangements at a particular frequency. We show that for sufficiently high switching frequency, this system behaves as if the connectivity were static and equal to the time average of the switching connectivity. We also examine the mechanisms by which this fast-switching limit is approached in several nonintuitive cases. The results illuminate novel mechanisms by which synchronization can arise or be thwarted in large populations of coupled oscillators with nonstatic coupling.
Magnetic properties of diluted magnetic semiconductor nanowires CoxSn1−xO2
Authors: Shihui Ge , Jinglei Yin , Huaxin Zhang
Published: September 2008

SnO 2 and CoxSn1−xO2 (x=0.013–0.22) nanowires were fabricated using a catalyzer assisted chemical vapor deposition. The as-grown nanowires are homogeneous along the wire length with diameters ranging from 33 to 250 nm and lengths greater than 15 μm. The morphology of the nanowires is sensitive to the fabrication conditions such as selection of catalyzer, flux rates of O2 and Ar, as well as deposition temperature. The growth mechanism of nanowires can be ascribed to a vapor-liquid-solid [R. S. Wagner and W. C. Ellis, Appl. Phys. Lett. 4, 89 (1964)] process. All CoxSn1−xO2 nanowires exhibit room temperature ferromagnetism. Magnetic moment per Co ion reaches 1.8 μB for the sample of x=0.016 and sharply decreases as x is increased. Nanowires are single crystals and no Co clusters or oxides are found for all samples, implying that the observed ferromagnetism is intrinsic.
Reflectivity and structural evolution of Cr/Sc and nitrogen containing Cr/Sc multilayers during thermal annealing
Authors: Eriksson Fredrik , Ghafoor Naureen , Hultman Lars , Birch Jens
Published: September 2008

It is shown that the thermal stability in vacuum of Cr/Sc multilayer thin films used as reflective optical components in soft x-ray instrumentation has substantial dependence on incorporation of N. The thermal stability is increased by incorporating 34 at.% of N in Cr/Sc multilayers. A pure Cr/Sc multilayer x-ray mirror starts a continuous degradation already at ∼100 °C with a complete destruction of the multilayer at 500 °C. The resulting structure is a mixture of Cr and Sc nanocrystallites. The degradation can be described by linear diffusion theory and is suggested to be due to the formation of uniformly distributed phase-separated nanocrystallites followed by an Ostwald ripening process with an apparent activation energy of 0.5 eV. At the multilayer-substrate interface, a 7 nm thin Sc–Si layer is formed which effectively hinders indiffusion of Si and outdiffusion of Cr and Sc. A nitrided multilayer, initially consisting of crystalline fcc CrNx and fcc ScNy layers (x and y<1), is observed to improve in structural quality up to ∼250 °C where it is stable for more than 12 h. At ∼330 °C, the multilayer separates into regions with two multilayer periods, differing by less than 0.04 nm, which are stable at 420 °C over an extended period of time >40 h. It is proposed that the separation into the different multilayer periods is a consequence of redistribution of N within the Cr layers. Sc is observed to be stabilized in the ScN layers, which, in turn, inhibit the formation of a Sc–Si barrier layer at the substrate leading to a strong exchange of Si and Cr across the film substrate. This leads to a Cr–Si/ScN layered structure close to the substrate and chromium silicide crystallites inside the substrate. Close to the top of the multilayer, a CrN/ScN multilayer appears to be retained.
Iron-filled carbon nanotubes as probes for magnetic force microscopy
Authors: Wolny Franziska , Weissker Uhland , Mühl Thomas , Leonhardt Albrecht , Menzel Siegfried , Winkler Andreas , Büchner Bernd
Published: September 2008

Iron-filled carbon nanotubes (Fe-CNTs) were used to prepare probes for magnetic force microscopy (MFM) by attaching them to the tips of conventional atomic force microscopy cantilevers. An optimized chemical vapor deposition process, employing a two stage furnace and ferrocene as a precursor, supplied the homogeneously filled Fe-CNTs required for the MFM probes. These can be regarded as cylindrically shaped single-domain nanomagnets that are protected from oxidation by a carbon shell. Carbon nanotubes are known to possess both great mechanical stability and elasticity, which lead to a much longer lifetime of these probes compared to conventional magnetically coated probes. It is shown that the prepared probes are suitable for magnetic imaging and so far show no sign of deterioration. Even very long nanotubes can be used as probes, which implies that they are extraordinarily stiff. It is also shown that attached Fe-CNTs can subsequently be tailored by electron-beam induced oxidation (e.g., to remove disturbing empty carbon shell parts) to better fit the requirements of an MFM tip.
Submicron three-dimensional trenched electrodes and capacitors for DRAMs and FRAMs: Fabrication and electrical testing
Authors: Miyake M. , Scott J. F. , Lou X. J. , Morrison F. D. , Nonaka T. , Motoyama S. , Tatsuta T. , Tsuji O.
Published: September 2008

We report conformal deposition of both RuO2 electrodes and PbZrxTi1−xO3 (PZT) capacitors in submicron Si trenches through the same in situ liquid source mist processing. The step coverage for the RuO2 electrodes is 75% at 225 °C. After electroding, we deposited Pb(Zr,Ti)O3 thin films and nanotubes using the same apparatus with remanent polarization of ∼15 μC/cm2. The step coverage was 59% on the sidewall and 79% on the bottom wall. Electrical testing showed charge storage (capacitance/trench) was 13±2 pF, with a breakdown voltage of 11.3±0.2 V and dielectric constant ε=166±30. This shows that a single inexpensive processing can produce fully electroded dynamic random access memory trenched capacitors with high aspect ratios and commercial electrical performance.
Stability diagram of a D− system in quantum dots
Authors: Du Xi , Sheng Weidong
Published: September 2008

We report on a theoretical study of a D− system in noncircular quantum dots by an exact diagonalization method. The stability diagram of the D− center is obtained in the presence of perpendicular magnetic fields. At zero magnetic field, it is found that the D− system would disintegrate if the distance between the donor and the edges of the dot is smaller than one effective Bohr radius. In a finite field, the system is always binding when the donor is localized in the center of the dot. As the donor moves away from the center to the edges of the dot, it is seen that the magnetic field would account for the disintegration of the system. The result reveals the interplay between the electron-impurity and electron-electron interactions, quantum confinement, and external magnetic fields in a few-electron system in quantum dots.
High density patterned quantum dot arrays fabricated by electron beam lithography and wet chemical etching
Authors: Verma V. B. , Coleman J. J.
Published: September 2008

We present a quantum dot (QD) fabrication method which allows for the definition of the explicit location and size of an individual QD. We have obtained high optical quality, high density QD arrays utilizing hydrogen silsesquioxane, a negative tone electron beam resist, as a wet etch mask for an underlying quantum well. Linewidths as small as 24meV from a large ensemble of QDs have been demonstrated in photoluminescence measurements at 77K. The magnitude of the experimentally obtained blueshift due to quantum confinement effects is found to be consistent with that predicted by theory.
Femtosecond time-resolved and two-dimensional vibrational sum frequency spectroscopic instrumentation to study structural dynamics at interfaces
Authors: Ghosh Avishek , Smits Marc , Bredenbeck Jens , Dijkhuizen Niels , Bonn Mischa
Published: September 2008

We present a novel setup to elucidate the dynamics of interfacial molecules specifically, using surface-selective femtosecond vibrational spectroscopy. The approach relies on a fourth-order nonlinear optical interaction at the interface. In the experiments, interfacial molecules are vibrationally excited by an intense, tunable femtosecond midinfrared (2500–3800 cm−1) pump pulse, resonant with the molecular vibrations. The effect of the excitation and the subsequent relaxation to the equilibrium state are probed using broadband infrared+visible sum frequency generation (SFG) light, which provides the transient vibrational spectrum of interfacial molecules specifically. This IR pump-SFG probe setup has the ability to measure both vibrational population lifetimes as well as the vibrational coupling between different chemical moieties at interfaces. Vibrational lifetimes of interfacial molecules are determined in one-dimensional pump-SFG probe experiments, in which the response is monitored as a function of the delay between the pump and probe pulses. Vibrational coupling between molecular groups is determined in two-dimensional pump-SFG probe experiments, which monitor the response as a function of pump and probe frequencies at a fixed delay time. To allow for one setup to perform these multifaceted experiments, we have implemented several instrumentation techniques described here. The detection of the spectrally resolved differential SFG signal using a combination of a charge-coupled device camera and a piezocontrolled optical scanner, computer-controlled Fabry–Pérot etalons to shape and scan the IR pump pulse and the automated sample dispenser and sample trough height corrector are some of the novelties in this setup.
Improved media performance in optimally coupled exchange spring layer media
Authors: Berger A. , Supper N. , Ikeda Y. , Lengsfield B. , Moser A. , Fullerton E. E.
Published: September 2008

We have studied the recording performance of perpendicular exchange spring layer (ESL)-media for hard disk drive recording. In particular, we investigated the role of interlayer coupling by varying the thickness of a nonmagnetic coupling layer (CL). We demonstrate that not only the media writeability is improved upon optimizing the CL thickness, but also that substantial recording performance improvements can be achieved due to improved media noise properties. The potential of these media structures for high areal density recording is demonstrated by performing areal density measurements, which showed a substantial improvement for optimally coupled ESL-media.
High-performance solution-processed triisopropylsilylethynyl pentacene transistors and inverters fabricated by using the selective self-organization technique
Authors: Kim Se Hyun , Choi Danbi , Chung Dae Sung , Yang Chanwoo , Jang Jaeyoung , Park Chan Eon , Park Sang-Hee Ko
Published: September 2008

To obtain selectively self-organized active layers of organic field-effect transistors (OFETs) and inverters from a solution-phased triisopropylsilylethynyl pentacene (TIPS-PEN) semiconductor, we locally patterned an oxide dielectric, covered with a hydrophobic fluoropolymer, using O2 plasma etching. Drop-cast TIPS-PEN molecules were selectively crystallized on the O2-plasma-etched area, where a hydrophilic oxide surface was produced. Modification of the patterned oxide dielectrics with hexamethyldisilazane led to a field-effect mobility of the TIPS-PEN OFETs of 0.185 cm2 V−1 s−1, a substhreshold swing of 0.738 V/decade and an on/off ratio of 107. Moreover, an inverter composed of two of these OFETs showed good device operation and inverter gain of 5.6.
Determination of electron-heated temperatures of petawatt laser-irradiated foil targets with 256 and 68 eV extreme ultraviolet imaging
Authors: Ma T. , MacPhee A. G. , Key M. H. , Hatchett S. P. , Akli K. U. , Barbee T. W. , Chen C. D. , Freeman R. R. , King J. A. , Link A. , Mackinnon A. J. , Offermann D. T. , Ovchinnikov V. , Patel P. K. , Stephens R. B. , Van Woerkom L. D. , Zhang B. , Beg F. N.
Published: September 2008

Measurements of plasma temperature at the rear surface of foil targets due to heating by hot electrons, which were produced in short pulse high intensity laser matter interactions using the 150 J, 0.5 ps Titan laser, are reported. Extreme ultraviolet (XUV) imaging at 256 and 68 eV energies is used to determine spatially resolved target rear surface temperature patterns by comparing absolute intensities to radiation hydrodynamic modeling. XUV mirrors at these two energies were absolutely calibrated at the Advanced Light Source at the Lawrence Berkeley Laboratory. Temperatures deduced from both imagers are validated against each other within the range of 75–225 eV.
Measuring the temperature of microparticles in plasmas
Authors: Maurer Horst , Basner Ralf , Kersten Holger
Published: September 2008

Temperature sensitive features of particular phosphors were utilized for measuring the temperature Tp of microparticles, confined in the sheath of a rf plasma. The experiments were performed under variation of argon pressure and rf power of the process plasma. Tp has been determined by evaluation of characteristic fluorescent lines. The results for Tp measurements are strongly dependent on rf power and gas pressure.
Initial and adhesive contact between a diamond indenter and polydimethylsiloxane
Authors: Shen Yan Xing , Wei Pal Jen , Lin Jen Fin
Published: September 2008

Detailed observations for the initial and adhesive contact of polydimethylsiloxane indentations with sharp indenters are proposed and discussed in this study. In dry experiments, the load-depth results revealed an almost reversible feature, which indicated elastic deformation. Significant initial penetration depths, created during the finding surface process, were found. A power-law relationship was used to illustrate the initial portion of the loading curve and to evaluate the initial penetration depth for correcting depth measurements. An axisymmetrical indenter with a sticky boundary condition was applied to illustrate the results of dry experiments. When the load exceeded a specific value, both loading and unloading results showed an invariant slope. The analysis of the sticky indenter provided a reasonable explanation for the linear load-depth results. By correcting the initial penetration depth, the evaluated Young’s modulus values, obtained from the indenters with different geometries and under different environments, were shown to be unique and accurate.
SI traceable calibration of an instrumented indentation sensor spring constant using electrostatic force
Authors: Chung Koo-Hyun , Scholz Stefan , Shaw Gordon A. , Kramar John A. , Pratt Jon R.
Published: September 2008

We present a measurement scheme for creating reference electrostatic forces that are traceable to the International System of Units. This scheme yields reference forces suitable for calibrating the force sensitivity of instrumented indentation machines and atomic force microscopes. Forces between 10 and 200 μN were created and expressed in terms of the voltage, length, and capacitance between a pair of interacting electrodes. The electrodes comprised an electrically conductive sphere mounted as a tip on an instrumented indentation sensor, and a planar counterelectrode fixed to a sample stage in close proximity to the sphere. For comparison, we applied mechanical forces of similar magnitudes, first using deadweights and then using a reference force sensor. The deflection of the sensor due to the various applied forces was measured using an interferometer. A spring constant for the sensor was computed from the observed records of force versus displacement. Each procedure yielded a relative standard uncertainty of approximately 1%; however, the electrostatic technique is scalable and could provide traceable reference forces as small as a few hundred piconewtons, a range far below anything yet achieved using deadweights.
Deposition sequence dependent variation in interfacial chemical reactions between 8-hydroxyquinolatolithium and Al
Authors: Lee Young Mi , Park Yongsup , Yi Yeonjin , Won Kim Jeong
Published: September 2008

The chemical reactions between 8-hydroxyquinolatolithium (Liq) and Al were investigated by using high resolution synchrotron radiation photoelectron spectroscopy. Unlike the LiF/Al case, two opposite deposition sequences (Al/Liq versus Liq/Al) give different interface reactions. When Al is deposited on a Liq layer, there occurs a strong reaction between Liq and Al, which accounts for a clear peak shift in the Li 1s core level. On the other hand, an interface-localized charge transfer without Li 1s splitting occurs with the reversed deposition sequence. The former strong interface reaction can generate ionic Li as a dopant material in Liq layer, causing band bending.
Structural and optical properties of Cr-doped semi-insulating GaN epilayers
Authors: Mei F. , Wu K. M. , Pan Y. , Han T. , Liu C. , Gerlach J. W. , Rauschenbach B.
Published: September 2008

The properties of Cr-doped GaN epilayers grown by rf-plasma-assisted molecular beam epitaxy were studied. The deep acceptor nature of Cr was used to grow semi-insulating GaN epilayers on sapphire substrates for electronic device applications. The room-temperature (RT) sheet resistivity of the epilayers reached 1010 Ω/square. The activation energy of dark conductivity was about 0.48 eV. Step-graded AlxGa1−xN/GaN (x=0.3−0.2) superlattices (SLs) were designed to filter dislocations. Transmission electron microscopy images showed that the SLs can dramatically reduce dislocation density. Al0.35Ga0.65N/GaN heterostructure grown on Cr-doped semi-insulating GaN epilayer exhibited a RT mobility of 960 cm2/V s and sheet carrier density of 2.1×1013 cm−2.
Cloak for curvilinearly anisotropic media in conduction
Authors: Chen Tungyang , Weng Chung-Ning , Chen Jun-Shan
Published: September 2008

We explore the possibility to cloak a region in curvilinearly anisotropic background materials in the context of conductivity. Materials with curvilinear anisotropy possess constant properties in specific curvilinear coordinate. For cylindrically and spherically anisotropic solids, the cloak center and the origin of material coordinate are generally not collocated. We show that in combination with a rigid-body translation from the cloak center to the material origin, the previous coordinate transformation procedure remains applicable. But now the transformed material specifications depend on the position of cloak center. The validity of the cloak parameters is verified by finite element simulations.
Evolution of defects upon annealing in He-implanted 4H-SiC
Authors: Leclerc S. , Beaufort M. F. , Declémy A. , Barbot J. F.
Published: September 2008

The strain induced by room temperature helium implantation into 4H-SiC below the threshold amorphization dose results from both point and He-related defects. When the helium concentration is lower than 0.5% the strain profile follows the point defect profile, whereas at higher concentrations the He ions have a dominant effect on the strain. Upon annealing, the near surface strain progressively relaxes up to 1500 °C while the maximum strain relaxation stops at a temperature where helium ions agglomerate into platelets. When the vacancies become mobile, the platelets evolve into bubble clusters that expel dislocation loops whose migration is enhanced by the strain.
Electro-optical characteristics of reflective liquid crystal mode using π-cell for low power operation
Authors: Gwag Jin Seog , Park Jaehoon , Lee You-Jin , Kim Jae-Hoon
Published: September 2008

We demonstrated a reflective type of liquid crystal (LC) display with low power consumption using 180° twist and bend states in the π-cell. The driving voltage of the proposed operational mode depends on the cell and the LC parameters, such as the pretilt angle, the sample thickness, and the ratio of the sample thickness to the helical pitch of the LC. Under optimized conditions, this mode operates with less than 1.3 V and it exhibits excellent optical characteristics at all operational wavelengths.
Nanowire grid polarizer for energy efficient and wide-view liquid crystal displays
Authors: Ge Zhibing , Wu Shin-Tson
Published: September 2008

We report a liquid crystal display (LCD) using a nanowire grid polarizer (NWGP) to replace the bottom sheet linear polarizer (LP). The top LP and bottom NWGP configurations enable backlight recycling for enhancing optical efficiency while keeping a high contrast ratio and wide viewing angle. The electro-optic performance of this device configuration is studied based on the effective-medium theory and 4×4 matrix method. Results show that this configuration exhibits a 100:1 contrast ratio over 75° viewing cone in a film-compensated multidomain vertical alignment LCD and 10:1 over 65° viewing cone in a fringe-field switching LCD without any compensation film.
Spin-wave localization between nearest and next-nearest neighboring holes in an antidot lattice
Authors: Neusser S. , Botters B. , Becherer M. , Schmitt-Landsiedel D. , Grundler D.
Published: September 2008

Broadband spectroscopy on spin waves is performed on a square Ni80Fe20 antidot lattice with deep-submicron holes. Depending on the in-plane magnetic field H applied under different angles η, characteristic multiple resonances are resolved. Substantiated by dynamic micromagnetic simulations, these reflect different types of modes, i.e., extended and localized modes. Depending on η, modes are found to localize between nearest or next-nearest neighboring holes. In a small regime of η, they coexist.
Magnetoconductance oscillations in graphene antidot arrays
Authors: Shen T. , Wu Y. Q. , Capano M. A. , Rokhinson L. P. , Engel L. W. , Ye P. D.
Published: September 2008

Epitaxial graphene films have been formed on the C-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. Nanoscale square antidot arrays have been fabricated on these graphene films. At low temperatures, magnetoconductance in these films exhibits pronounced Aharonov–Bohm oscillations with the period corresponding to magnetic flux quanta added to the area of a single antidot. At low fields, weak localization is observed and its visibility is enhanced by intervalley scattering on antidot edges. At high fields, we observe two distinctive minima in magnetoconductance, which can be attributed to commensurability oscillations between classical cyclotron orbits and antidot array. All mesoscopic features, surviving up to 70K, reveal the unique electronic properties of graphene.
In situ tuning of omnidirectional microelectromechanical-systems microphones to improve performance fit in hearing aids
Authors: Je Sang-Soo , Kim Jeonghwan , Harrison Jere C. , Kozicki Michael N. , Chae Junseok
Published: September 2008

Hearing aids are not a one-size-fits-all solution to hearing problems; they must be uniquely tuned for each wearer. There are currently no low-cost and/or effective methods for in situ tuning. This paper describes a microelectromechanical-systems (MEMS)-based dual omnidirectional microphone that can be tuned by growing metallic nanostructures. The nanostructures are grown on integrated solid electrolyte layers on a suspended parylene diaphragm using an external bias and tune the MEMS microphones in situ thereby limiting mismatch. In our tests, this tuning improved the directivity index from 3.5 (fair directionality) to 4.6 dB (excellent directionality) in normal (room temperature) operating environments.
Direct role of dynein motor in stable kinetochore-microtubule attachment, orientation, and alignment
Authors: Varma Dileep , Monzo Pascale , Stehman Stephanie A. , Vallee Richard B.
Published: September 2008

Cytoplasmic dynein has been implicated in diverse mitotic functions, several involving its association with kinetochores. Much of the supporting evidence comes from inhibition of dynein regulatory factors. To obtain direct insight into kinetochore dynein function, we expressed a series of dynein tail fragments, which we find displace motor-containing dynein heavy chain (HC) from kinetochores without affecting other subunits, regulatory factors, or microtubule binding proteins. Cells with bipolar mitotic spindles progress to late prometaphase-metaphase at normal rates. However, the dynein tail, dynactin, Mad1, and BubR1 persist at the aligned kinetochores, which is consistent with a role for dynein in self-removal and spindle assembly checkpoint inactivation. Kinetochore pairs also show evidence of misorientation relative to the spindle equator and abnormal oscillatory behavior. Further, kinetochore microtubule bundles are severely destabilized at reduced temperatures. Dynein HC RNAi and injection of anti-dynein antibody in MG132-arrested metaphase cells produced similar effects. These results identify a novel function for the dynein motor in stable microtubule attachment and maintenance of kinetochore orientation during metaphase chromosome alignment.
Ryk cooperates with Frizzled 7 to promote Wnt11-mediated endocytosis and is essential for Xenopus laevis convergent extension movements
Authors: Kim Gun-Hwa , Her Jung-Hyun , Han Jin-Kwan
Published: September 2008

The single-pass transmembrane protein Ryk (atypical receptor related tyrosine kinase) functions as a Wnt receptor. However, Ryk's correlation with Wnt/Frizzled (Fz) signaling is poorly understood. Here, we report that Ryk regulates Xenopus laevis convergent extension (CE) movements via the β-arrestin 2 (βarr2)-dependent endocytic process triggered by noncanonical Wnt signaling. During X. laevis gastrulation, βarr2-mediated endocytosis of Fz7 and dishevelled (Dvl/Dsh) actually occurs in the dorsal marginal zone tissues, which actively participate in noncanonical Wnt signaling. Noncanonical Wnt11/Fz7-mediated endocytosis of Dsh requires the cell-membrane protein Ryk. Ryk interacts with both Wnt11 and βarr2, cooperates with Fz7 to mediate Wnt11-stimulated endocytosis of Dsh, and signals the noncanonical Wnt pathway in CE movements. Conversely, depletion of Ryk and Wnt11 prevents Dsh endocytosis in dorsal marginal zone tissues. Our study suggests that Ryk functions as an essential regulator for noncanonical Wnt/Fz-mediated endocytosis in the regulation of X. laevis CE movements.
The WAVE2 complex regulates T cell receptor signaling to integrins via Abl- and CrkL–C3G-mediated activation of Rap1
Authors: Nolz Jeffrey C. , Nacusi Lucas P. , Segovis Colin M. , Medeiros Ricardo B. , Mitchell Jason S. , Shimizu Yoji , Billadeau Daniel D.
Published: September 2008

WAVE2 regulates T cell receptor (TCR)–stimulated actin cytoskeletal dynamics leading to both integrin clustering and affinity maturation. Although WAVE2 mediates integrin affinity maturation by recruiting vinculin and talin to the immunological synapse in an Arp2/3-dependent manner, the mechanism by which it regulates integrin clustering is unclear. We show that the Abl tyrosine kinase associates with the WAVE2 complex and TCR ligation induces WAVE2-dependent membrane recruitment of Abl. Furthermore, we show that WAVE2 regulates TCR-mediated activation of the integrin regulatory guanosine triphosphatase Rap1 via the recruitment and activation of the CrkL–C3G exchange complex. Moreover, we demonstrate that although Abl does not regulate the recruitment of CrkL–C3G into the membrane, it does affect the tyrosine phosphorylation of C3G, which is required for its guanine nucleotide exchange factor activity toward Rap1. This signaling node regulates not only TCR-stimulated integrin clustering but also affinity maturation. These findings identify a previously unknown mechanism by which the WAVE2 complex regulates TCR signaling to Rap1 and integrin activation.
NCAM induces CaMKIIα-mediated RPTPα phosphorylation to enhance its catalytic activity and neurite outgrowth
Authors: Bodrikov Vsevolod , Sytnyk Vladimir , Leshchyns'ka Iryna , den Hertog Jeroen , Schachner Melitta
Published: September 2008

Receptor protein tyrosine phosphatase α (RPTPα) phosphatase activity is required for intracellular signaling cascades that are activated in motile cells and growing neurites. Little is known, however, about mechanisms that coordinate RPTPα activity with cell behavior. We show that clustering of neural cell adhesion molecule (NCAM) at the cell surface is coupled to an increase in serine phosphorylation and phosphatase activity of RPTPα. NCAM associates with T- and L-type voltage-dependent Ca2+ channels, and NCAM clustering at the cell surface results in Ca2+ influx via these channels and activation of NCAM-associated calmodulin-dependent protein kinase IIα (CaMKIIα). Clustering of NCAM promotes its redistribution to lipid rafts and the formation of a NCAM–RPTPα–CaMKIIα complex, resulting in serine phosphorylation of RPTPα by CaMKIIα. Overexpression of RPTPα with mutated Ser180 and Ser204 interferes with NCAM-induced neurite outgrowth, which indicates that neurite extension depends on NCAM-induced up-regulation of RPTPα activity. Thus, we reveal a novel function for a cell adhesion molecule in coordination of cell behavior with intracellular phosphatase activity.
Lis1 and Ndel1 influence the timing of nuclear envelope breakdown in neural stem cells
Authors: Hebbar Sachin , Mesngon Mariano T. , Guillotte Aimee M. , Desai Bhavim , Ayala Ramses , Smith Deanna S.
Published: September 2008

Lis1 and Ndel1 are essential for animal development. They interact directly with one another and with cytoplasmic dynein. The developing brain is especially sensitive to reduced Lis1 or Ndel1 levels, as both proteins influence spindle orientation, neural cell fate decisions, and neuronal migration. We report here that Lis1 and Ndel1 reduction in a mitotic cell line impairs prophase nuclear envelope (NE) invagination (PNEI). This dynein-dependent process facilitates NE breakdown (NEBD) and occurs before the establishment of the bipolar spindle. Ndel1 phosphorylation is important for this function, regulating binding to both Lis1 and dynein. Prophase cells in the ventricular zone (VZ) of embryonic day 13.5 Lis1+/− mouse brains show reduced PNEI, and the ratio of prophase to prometaphase cells is increased, suggesting an NEBD delay. Moreover, prophase cells in the VZ contain elevated levels of Ndel1 phosphorylated at a key cdk5 site. Our data suggest that a delay in NEBD in the VZ could contribute to developmental defects associated with Lis1–Ndel1 disruption.
Association between active genes occurs at nuclear speckles and is modulated by chromatin environment
Authors: Brown Jill M. , Green Joanne , das Neves Ricardo Pires , Wallace Helen A.C. , Smith Andrew J.H. , Hughes Jim , Gray Nicki , Taylor Steve , Wood William G. , Higgs Douglas R. , Iborra Francisco J. , Buckle Veronica J.
Published: September 2008

Genes on different chromosomes can be spatially associated in the nucleus in several transcriptional and regulatory situations; however, the functional significance of such associations remains unclear. Using human erythropoiesis as a model, we show that five cotranscribed genes, which are found on four different chromosomes, associate with each other at significant but variable frequencies. Those genes most frequently in association lie in decondensed stretches of chromatin. By replacing the mouse α-globin gene cluster in situ with its human counterpart, we demonstrate a direct effect of the regional chromatin environment on the frequency of association, whereas nascent transcription from the human α-globin gene appears unaffected. We see no evidence that cotranscribed erythroid genes associate at shared transcription foci, but we do see stochastic clustering of active genes around common nuclear SC35-enriched speckles (hence the apparent nonrandom association between genes). Thus, association between active genes may result from their location on decondensed chromatin that enables clustering around common nuclear speckles.
Ero1L, a thiol oxidase, is required for Notch signaling through cysteine bridge formation of the Lin12-Notch repeats in Drosophila melanogaster
Authors: Tien An-Chi , Rajan Akhila , Schulze Karen L. , Ryoo Hyung Don , Acar Melih , Steller Hermann , Bellen Hugo J.
Published: September 2008

Notch-mediated cell–cell communication regulates numerous developmental processes and cell fate decisions. Through a mosaic genetic screen in Drosophila melanogaster, we identified a role in Notch signaling for a conserved thiol oxidase, endoplasmic reticulum (ER) oxidoreductin 1–like (Ero1L). Although Ero1L is reported to play a widespread role in protein folding in yeast, in flies Ero1L mutant clones show specific defects in lateral inhibition and inductive signaling, two characteristic processes regulated by Notch signaling. Ero1L mutant cells accumulate high levels of Notch protein in the ER and induce the unfolded protein response, suggesting that Notch is misfolded and fails to be exported from the ER. Biochemical assays demonstrate that Ero1L is required for formation of disulfide bonds of three Lin12-Notch repeats (LNRs) present in the extracellular domain of Notch. These LNRs are unique to the Notch family of proteins. Therefore, we have uncovered an unexpected requirement for Ero1L in the maturation of the Notch receptor.
Gene associations: true romance or chance meeting in a nuclear neighborhood?
Authors: Lawrence Jeanne B. , Clemson Christine M.
Published: September 2008

Many recent studies have raised interest in the nuclear associations of coregulated genes from different chromosomes, often evoking interpretations of gene–gene interactions, communication, and even “romance.” However, in some cases, the associations may be indirect and infrequent and may reflect the segregation of active and inactive genes into different nuclear compartments. The study by Brown et al. (see p. 1083 of this issue) reports that the apparent association of erythroid genes is not a direct interaction nor colocalization to one tiny transcription factory but arises as a result of the known clustering of many active genes with larger splicing factor–rich speckles (a.k.a., SC35-defined domains). This clustering appears largely stochastic but is impacted by the chromosomal neighborhood of the gene as well as its transcriptional status. The study adds a new twist by examining the same gene in a foreign chromosomal context, providing evidence that this impacts a gene's propensity to form gene–domain (or apparent gene–gene) associations within nuclei.
MS-BID: a Java package for label-free LC-MS-based comparative proteomic analysis
Authors: Hwang Daehee , Zhang Ning , Lee Hookeun , Yi Eugene , Zhang Hui , Lee Inyoul Y. , Hood Leroy , Aebersold Ruedi
Published: September 2008

Summary: MS-BID (MS Biomarker Discovery Platform) is an integrative computational pipeline for biomarker discovery using LC-MS-based comparative proteomic analysis. This platform consists of several computational tools for: (i) detecting peptides in the collected patterns; (ii) matching detected peptides across a number of LC-MS datasets and (iii) selecting discriminatory peptides between classes of samples.

Availability: MS-BID source codes, binaries and documentations are freely available under LGPL from http://tools.proteomecenter.org/msBID.php.

Contact:  dhhwang@postech.ac.kr
Clinical Holistic Medicine: Teaching Orgasm for Females with Chronic Anorgasmia using the Betty Dodson Method
Authors: Struck Pia , Ventegodt Søren
Published: September 2008

The objective of this study was to test the Betty Dodson method of breaking the female orgasm barrier in chronic anorgasmic women. The aim was sexual and existential healing (salutogenesis) through direct confrontation and integration of both the repressed shame, guilt, and other negative feelings associated with body, genitals, and sexuality, and the repressed sexual pleasure and desire. We conducted a retrospective analysis of clinic data from holistic sexological manual therapeutic intervention, an intensive subtype of clinical holistic medicine (CHM). The patients received 3 × 5 h of group therapy, integrating short-term psychodynamic psychotherapy (STPP) and complementary medicine (CAM bodywork, manual sexology similar to the “sexological examination”). The therapy used the advanced tools of reparenting, genital acceptance, acceptance through touch, and direct sexual clitoral stimulation. A clitoral vibrator was used. Participants were 500 female patients between 18 and 88 years of age (mean of 35 years) with chronic anorgasmia (for 12 years on average) who were participating in the “orgasm course for anorgasmic women”; 25% of the patients had never experienced an orgasm. Our results show that 465 patients (93%) had an orgasm during therapy, witnessed by the therapist, and 35 patients (7%) did not. Postmenopausal women were as able to achieve orgasm as fertile women, as were women who never had an orgasm. No patients had detectable negative side effects or adverse effects. NNT: 1.04 < NNT < 1.12, NNH > 500. Therapeutic value: TV = NNH/NNT > 446. Our conclusions are that holistic sexological manual therapy may be rational, safe, ethical, and efficient.
Personal, Social, and Environmental Correlates of Walking to School Behaviors: Case Study in Austin, Texas
Authors: Zhu Xuemei , Arch B. , Lee Chanam
Published: September 2008

Walking is an affordable and environmentally clean mode of transportation that can bring additional benefits as healthy physical activity. This cross-sectional study examines the prevalence and correlates of walking to or from school in eight elementary schools in Austin, Texas, which have high percentages of low-income, Hispanic students. A survey of 1,281 parents was conducted, including questions about personal, social, and environmental factors that may influence their decisions on the children's school transportation. Binary logistic regressions were used to estimate the odds of choosing walking as the children's typical school travel mode. The results showed that walking was a typical mode for 28 and 34% of trips to and from school, respectively, and mostly accompanied by an adult. Parents' education level, family's car ownership, children's and parents' personal barriers, and having the school bus service reduced the likelihood of walking, while positive peer influences encouraged walking. Among the physical environmental factors, living close to school was the strongest positive predictor; safety concerns and the presence of highway or freeway en route were negative correlates. We concluded that the location of school is a key, as it determines the travel distance and the presence of highway or freeway en route. In addition to environmental improvements, educational and other assistance programs are needed for both parents and children to overcome their personal barriers and safety concerns. Health and disparity issues require further attention, as many underprivileged children have no other means of school transportation but walking in unsafe and poor environments.
MAP20, a Microtubule-Associated Protein in the Secondary Cell Walls of Hybrid Aspen, Is a Target of the Cellulose Synthesis Inhibitor 2,6-Dichlorobenzonitrile
Authors: Rajangam Alex S. , Kumar Manoj , Aspeborg Henrik , Guerriero Gea , Arvestad Lars , Pansri Podjamas , Brown Christian J.-L. , Hober Sophia , Blomqvist Kristina , Divne Christina , Ezcurra Ines , Mellerowicz Ewa , Sundberg Björn , Bulone Vincent , Teeri Tuula T.
Published: September 2008

We have identified a gene, denoted PttMAP20, which is strongly up-regulated during secondary cell wall synthesis and tightly coregulated with the secondary wall-associated CESA genes in hybrid aspen (Populus tremula × tremuloides). Immunolocalization studies with affinity-purified antibodies specific for PttMAP20 revealed that the protein is found in all cell types in developing xylem and that it is most abundant in cells forming secondary cell walls. This PttMAP20 protein sequence contains a highly conserved TPX2 domain first identified in a microtubule-associated protein (MAP) in Xenopus laevis. Overexpression of PttMAP20 in Arabidopsis (Arabidopsis  thaliana) leads to helical twisting of epidermal cells, frequently associated with MAPs. In addition, a PttMAP20-yellow fluorescent protein fusion protein expressed in tobacco (Nicotiana tabacum) leaves localizes to microtubules in leaf epidermal pavement cells. Recombinant PttMAP20 expressed in Escherichia coli also binds specifically to in vitro-assembled, taxol-stabilized bovine microtubules. Finally, the herbicide 2,6-dichlorobenzonitrile, which inhibits cellulose synthesis in plants, was found to bind specifically to PttMAP20. Together with the known function of cortical microtubules in orienting cellulose microfibrils, these observations suggest that PttMAP20 has a role in cellulose biosynthesis.
The effects of structural variation in some isoxazolidines on the corrosion inhibition of carbon steel in 0.5 M sulfuric acid
Authors: Al‐Ghamdi R.F. , El‐Shareef A.M. , Saeed M.T. , Ali S.A.
Published: September 2008

Purpose

The aim is to demonstrate corrosion inhibition capabilities of several isoxazolidines, containing hydrophobic substituents and having varying degree of steric congestion around nitrogen.

Design/methodology/approach

A number of isoxazolidines were prepared. Corrosion inhibition efficiencies of these organic compounds were determined by gravimetric and electrochemical methods, using carbon steel as the substrate metal and 0.5 M H2SO4 at 40‐70°C as the corrosive environment. Concentration of inhibitor was varied between 5 and 400 ppm.

Findings

Increase in steric congestion around the nitrogen centre and hydrophobic chain lengths as well as increase in temperature (in the presence of the inhibitor in the higher concentration range 100‐400 ppm) were found to increase the corrosion inhibition efficiency of the isoxazolidines. Electrochemical measurements corroborated these results. Thermodynamic parameters (ΔGads0,ΔHads0,ΔSads0) for the adsorption process and kinetic parameters for the metal dissolution (or hydrogen evolution) reaction were determined.

Originality/value

This is the first time the corrosion inhibition characteristics of isoxazolidines, an important class of readily accessible compounds, have been evaluated in H2SO4 medium.
Turkish academic staffs' perception of organic foods
Authors: Özfer Özc¸elik Ays¸e , Uçar Asli
Published: September 2008

Purpose

This study was planned and carried out among the academic staff working in Ankara (Turkey) in order to determine their perception of organic foods.

Design/methodology/approach

A total of 240 academicians from three institutes at the Ankara University were selected to participate in the research. Data were collected through a survey questionnaire, in which a Likert type scale was used to determine the perception of organic foods. The institutes where the academic staff work are considered as the variables in the study (science, health sciences, and social sciences).

Findings

The research results indicated that there was a significant correlation between the institutes and academicians agreement with 12 statements in the survey questionnaire. Considering the institute variable, no significant difference was found in the organic foods perceptions of individuals from different institutes.

Originality/value

Organic products are widely on the market today. Consumer demand for organic foods has been steadily rising worldwide. Organic food consumption has slightly increased in Turkey in recent years, too. Still, many Turkish consumers do not have enough knowledge about organic foods yet. This study is valuable in that it explores at least some of the Turkish consumers' perception of organic foods whose consumption in the world is increasing fast.
Acceptance of genetically modified food in India: perspectives of gatekeepers
Authors: Knight John , Paradkar Amit
Published: September 2008

Purpose

Consumer and public policy resistance to genetically modified (GM) foods in rich countries has caused governments in many poor countries to withhold official permission for planting GM food crops for fear of damaging export markets for conventional crops. A total of 15 countries are already producing GM food crops. If China and India, the world's two most populous nations, authorise GM food production, then this will account for a large majority of the world's food production coming from GM‐adopting countries. This study sets out to determine perceptions of gatekeepers of the food distribution channel in India towards GM foods.

Design/methodology/approach

Personal interviews were conducted with key informants of a convenience sample of twenty gatekeepers of the food distribution channel in seven main commercial centres in the India. In addition, three agricultural scientists prominent in new crop development in India were interviewed to provide perspectives of likely current and future developments.

Findings

According to gatekeepers interviewed, the GM issue has not achieved great prominence in India, and the public generally seem oblivious to the issue. Activist opposition has been to foreign companies gaining monopoly rights over intellectual property, rather than to GM foods per se. Crop scientists interviewed indicated that biotechnology is widely regarded by the Indian Government as providing the means for a second green revolution. Current Indian government policy appears to be to speed up research and development of a wide range of GM food crops.

Originality/value

These findings are important to public policy makers in food exporting countries as they point to the likelihood of adoption of GM technology in the world's second most populous market.