bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-dimensional magnetotransport in Bi2Te2Se nanoplatelets
Authors: Gehring Pascal , Gao Bo , Burghard Marko , Kern Klaus
Published: July 2012

Single-crystalline Bi2Te2Se nanoplates with thicknesses between 8 and 30 nm and lateral sizes of several micrometers were synthesized by a vapour-solid growth method. Angle-dependent magnetoconductance measurements on individual nanoplates revealed the presence of a two-dimensional weak anti-localization effect. In conjunction with gate-dependent charge transport studies performed at different temperatures, evidence was gained that this effect originates from the topologically protected surface states of the nanoplates.
Elasticity and sound velocities of polycrystalline Mg3Al2(SiO4)3 garnet up to 20 GPa and 1700 K
Authors: Zou Yongtao , Irifune Tetsuo , Gréaux Steeve , Whitaker Matthew L. , Shinmei Toru , Ohfuji Hiroaki , Negishi Ryo , Higo Yuji
Published: July 2012

Elastic wave velocities of synthetic polycrystalline Mg3Al2(SiO4)3 garnet have been successfully measured to 20 GPa and temperatures up to 1700 K by ultrasonic interferometry combined with energy-dispersive synchrotron x-ray diffraction in a Kawai-type multi-anvil apparatus. Compressional (Vp) and shear (Vs) wave velocities as well as the adiabatic bulk (Ks) and shear (G) moduli exhibit monotonic increase with increasing pressure and decrease with increasing temperature, respectively. Two-dimensional (P-T) linear fittings of the present data yield the following parameters: KS0 = 170.0(2) GPa, əKs/əP = 4.51(2), əKs/əT = −0.0170(1) GPa/K, G0 = 93.2(1) GPa, əG/əP = 1.51(2), and əG/əT = −0.0107(1) GPa/K, which is in good agreement with the earlier results by Brillouin scattering and/or ultrasonic measurements at relatively low P-T conditions. The observed linear pressure and temperature dependence in both Vp and Vs is in contrast to the non-linear behavior of Vp and Vs for majorite garnet with the pyrolite composition, in particular for Vs.
Estimating the pressure of laser-induced plasma shockwave by stimulated Raman shift of lattice translational modes
Authors: Li Zhanlong , Shan Xiaoning , Li Zuowei , Cao Junsheng , Zhou Mi , Wang Yiding , Men Zhiwei , Sun Chenglin
Published: July 2012

The current paper investigates stimulated Raman scattering (SRS) when laser-induced plasma is formed in heavy water by focusing an intense pulsed 532 nm Nd:YAG laser beam at room temperature. An unexpected low-frequency SRS line attributed to the lattice translational modes of ice-VII (D2O) is observed. The pressure of the plasma shockwave is estimated using low-frequency SRS line shift.
Electrostatic effects in coupled quantum dot-point contact-single electron transistor devices
Authors: Pelling S. , Otto E. , Spasov S. , Kubatkin S. , Shaikhaidarov R. , Ueda K. , Komiyama S. , Antonov V. N.
Published: July 2012

We study the operation of a system where quantum dot (QD) and point contact (PC) defined in a two-dimensional electron gas of a high-mobility GaAs/AlGaAs heterostructure are capacitively coupled to each other and to metallic single electron transistor (SET). The charge state of the quantum dot can be probed by the point contact or single electron transistor. These can be used for sensitive detection of terahertz radiation. In this work, we explore an electrostatic model of the system. From the model, we determine the sensitivity of the point contact and the single electron transistor to the charge excitation of the quantum dot. Nearly periodic oscillations of the point contact conductance are observed in the vicinity of pinch-off voltage. They can be attributed to Coulomb blockade effect in a quasi-1D channel because of unintentional formation of small quantum dot. The latter can be a result of fluctuations in GaAs quantum well thickness.
Temperature and frequency dependent giant magnetodielectric coupling in DyMn0.33Fe0.67O3
Authors: Hong Fang , Cheng Zhenxiang , Wang Xiaolin
Published: July 2012

Perovskite DyMn0.33Fe0.67O3 experiences a paramagnetism-antiferromagnetism transition at 450 K and spin reorientation at 290 K. Magnetodielectric properties were studied around the spin reorientation transition. Both giant positive and giant negative magnetodielectric coupling (MDC) were observed near room temperature. The MDC shows strong temperature and frequency dependence, and the sign changes from positive to negative when magnetic state transits from a canted antiferromagnetic state to a collinear antiferromagnetic state. Possible mechanisms are proposed based on the Maxwell-Wagner model, phase transition, the magnetoresistance effect, and spin-phonon coupling.
Interparticle coupling of plasmon fields due to reorganization of Au nanoparticles in Langmuir-Blodgett film
Authors: Kundu Sarathi
Published: July 2012

Dodecanethiol-encapsulated Au nanoparticles have been deposited on Si(001) and quartz substrates by Langmuir-Blodgett method at different surface pressures for producing layer-by-layer structure. Out-of-plane structural reorganization and optical absorption spectra have been obtained from x-ray reflectivity and UV-Vis spectroscopy measurements, respectively. With time, positions of the nanoparticles reorganize so that films become more compact and thickness decreases. Localized surface plasmon resonance peaks show that coupling between Au nanoparticles occur as the interparticle distance decreases after reorganization and as a result, a redshift in the plasmon peak wavelength takes place. Variation in redshift depends upon the deposition pressure or layer number.
Electrical measurement of internal quantum efficiency and extraction efficiency of III-N light-emitting diodes
Authors: Kivisaari Pyry , Riuttanen Lauri , Oksanen Jani , Suihkonen Sami , Ali Muhammad , Lipsanen Harri , Tulkki Jukka
Published: July 2012

We propose a direct electrical measurement method for determining the extraction efficiency (EXE) and internal quantum efficiency (IQE) of III-Nitride light-emitting diodes (LEDs). The method is based on measuring the optical output power as a function of injection current at current densities near the external quantum efficiency (EQE) maximum and extracting IQE and EXE from the measurement data. In contrast to conventional methods, our method requires no low temperature measurements or prior knowledge of the device structure. The method is far more convenient than commonly used methods because it enables measuring the EXE and IQE of different LED structures at room temperature directly in a repeatable and consistent way. This enables convenient comparison of LED structures. We apply the method to determine the IQE and EXE of one commercial LED and selected self-grown planar LED chips to compare the effects of different LED structure designs. Our results are in line with published experimental results and also give more insight to our earlier findings regarding the effects of growth parameters on the quantum efficiency. In addition, our measurement method allows estimating the Shockley-Read-Hall and radiative recombination parameters if the Auger parameter is known.
Ultrafast carrier phonon dynamics in NaOH-reacted graphite oxide film
Authors: Lee Dongwook , Zou Xingquan , Zhu Xi , Seo J. W. , Cole Jacqueline M. , Bondino Federica , Magnano Elena , Nair Saritha K. , Su Haibin
Published: July 2012

NaOH-reacted graphite oxide film was prepared by decomposing epoxy groups in graphite oxide into hydroxyl and -ONa groups with NaOH solution. Ultrafast carrier dynamics of the sample were studied by time-resolved transient differential reflection (ΔR/R). The data show two exponential relaxation processes. The slow relaxation process (∼2ps) is ascribed to low energy acoustic phonon mediated scattering. The electron-phonon coupling and first-principles calculation results demonstrate that -OH and -ONa groups in the sample are strongly coupled. Thus, we attribute the fast relaxation process (∼0.17ps) to the coupling of hydroxyl and -ONa groups in the sample.
Aerosol fabrication of thermosensitive nanogels and in situ hybridization with iron nanoparticles
Authors: Byeon Jeong Hoon , Kim Jang-Woo
Published: July 2012

Collison atomized n-isopropylacrylamide (NIPAM) droplets were thermally treated with different furnace wall temperatures to form nanogels in an aerosol state. The size of the aerosol nanogels decreased from 40.3 nm to 32.8 nm by increasing the temperature from 40 °C to 90 °C due to the coil-to-globule transition of the NIPAM. A serial reactor consisting of a spark generator coupled to a collison atomizer was further employed to efficiently (>90% in production yield) fabricate biocompatible (78.8% in cell viability)-magnetic (30.3 emu g−1 in saturation magnetization) hybrid nanogels of NIPAM and iron nanoparticles.
Perpendicular-anisotropy CoFeB-MgO magnetic tunnel junctions with a MgO/CoFeB/Ta/CoFeB/MgO recording structure
Authors: Sato H. , Yamanouchi M. , Ikeda S. , Fukami S. , Matsukura F. , Ohno H.
Published: July 2012

We investigated perpendicular CoFeB-MgO magnetic tunnel junctions (MTJs) with a recording structure consisting of two CoFeB-MgO interfaces, MgO/CoFeB (1.6 nm)/Ta (0.4 nm)/CoFeB (1.0 nm)/MgO. Thermal stability factor of MTJ with the structure having junction size of 70 nmφ was increased by a factor of 1.9 from the highest value of perpendicular MTJs with single CoFeB-MgO interface having the same device structure. On the other hand, intrinsic critical current for spin transfer torque switching of the double- and single-interface MTJs was comparable.
Study of nonlinear interaction between bunched beam and intermediate cavities in a relativistic klystron amplifier
Authors: Wu Y. , Xu Z. , Li Z. H. , Tang C. X.
Published: July 2012

In intermediate cavities of a relativistic klystron amplifier (RKA) driven by intense relativistic electron beam, the equivalent circuit model, which is widely adopted to investigate the interaction between bunched beam and the intermediate cavity in a conventional klystron design, is invalid due to the high gap voltage and the nonlinear beam loading in a RKA. According to Maxwell equations and Lorentz equation, the self-consistent equations for beam-wave interaction in the intermediate cavity are introduced to study the nonlinear interaction between bunched beam and the intermediate cavity in a RKA. Based on the equations, the effects of modulation depth and modulation frequency of the beam on the gap voltage amplitude and its phase are obtained. It is shown that the gap voltage is significantly lower than that estimated by the equivalent circuit model when the beam modulation is high. And the bandwidth becomes wider as the beam modulation depth increases. An S-band high gain relativistic klystron amplifier is designed based on the result. And the corresponding experiment is carried out on the linear transformer driver accelerator. The peak output power has achieved 1.2 GW with an efficiency of 28.6% and a gain of 46 dB in the corresponding experiment.
On the space-charge formation in a collisional magnetized electronegative plasma
Authors: Yasserian Kiomars , Aslaninejad Morteza
Published: July 2012

The plasma sheath formation in the vicinity of a surrounding wall of magnetized plasma is studied in the presence of the electronegative ions and the positive ion-neutral background collisions. Fluid equations are used to treat the plasma particles species. By using the Sagdeev potential, the influence of the collisions and the magnetic field on the Bohm criterion are investigated. The space-charge profiles are obtained in the presence of a magnetic field in different collision frequencies as well as electronegative ions concentration. It is shown that the collision and the magnetic field raise a space-charge peak, while the presence of the electronegative ions results in damping the peaks. Moreover, it is observed that in the case of high magnetic field, some fluctuations emerge in the space-charge profiles. The influences of the magnetic field and electronegative ion concentration as well as negative ion temperature on the positive ion kinetic energy reaching the plasma surrounding wall and positive ion velocity perpendicular to the sheath axis are investigated. Finally, the net current through the sheath region is obtained for different collisionality and magnetic field values in both electropositive and electronegative plasmas.
Stability of the electron-driven fishbone mode
Authors: Merle Antoine , Decker Joan , Garbet Xavier , Sabot Roland , Guimarães-Filho Zwinglio , Nicolas Timothée
Published: July 2012

Electron-driven fishbones provide a good test bed for the linear theory of fast-particle driven instabilities as they exhibit a very high sensitivity to the details of both the equilibrium and the electronic distribution function. Thus, they can help validate the models developed for studying instabilities driven by alpha particles in future fusion reactors such as ITER. The fishbone dispersion relation is extended to properly account for resonance with passing particles by including the contribution of the parallel motion to the resonance condition. Barely passing electrons are found to drive the mode unstable at a lower frequency than barely trapped electrons. Although globally destabilizing, the influence of passing electrons quickly decreases away from the trapped-passing boundary. This is confirmed by an analysis using distributions close to those obtained in electron cyclotron resonance heating experiments. The major effect of this new resonance condition is a reduction of the fast-electron density threshold coupled to a reduction of the frequency of the mode.
Bootstrap current for the edge pedestal plasma in a diverted tokamak geometry
Authors: Koh S. , Chang C. S. , Ku S. , Menard J. E. , Weitzner H. , Choe W.
Published: July 2012

The edge bootstrap current plays a critical role in the equilibrium and stability of the steep edge pedestal plasma. The pedestal plasma has an unconventional and difficult neoclassical property, as compared with the core plasma. It has a narrow passing particle region in velocity space that can be easily modified or destroyed by Coulomb collisions. At the same time, the edge pedestal plasma has steep pressure and electrostatic potential gradients whose scale-lengths are comparable with the ion banana width, and includes a magnetic separatrix surface, across which the topological properties of the magnetic field and particle orbits change abruptly. A drift-kinetic particle code XGC0, equipped with a mass-momentum-energy conserving collision operator, is used to study the edge bootstrap current in a realistic diverted magnetic field geometry with a self-consistent radial electric field. When the edge electrons are in the weakly collisional banana regime, surprisingly, the present kinetic simulation confirms that the existing analytic expressions [represented by O. Sauter et al., Phys. Plasmas 6, 2834 (1999)] are still valid in this unconventional region, except in a thin radial layer in contact with the magnetic separatrix. The agreement arises from the dominance of the electron contribution to the bootstrap current compared with ion contribution and from a reasonable separation of the trapped-passing dynamics without a strong collisional mixing. However, when the pedestal electrons are in plateau-collisional regime, there is significant deviation of numerical results from the existing analytic formulas, mainly due to large effective collisionality of the passing and the boundary layer trapped particles in edge region. In a conventional aspect ratio tokamak, the edge bootstrap current from kinetic simulation can be significantly less than that from the Sauter formula if the electron collisionality is high. On the other hand, when the aspect ratio is close to unity, the collisional edge bootstrap current can be significantly greater than that from the Sauter formula. Rapid toroidal rotation of the magnetic field lines at the high field side of a tight aspect-ratio tokamak is believed to be the cause of the different behavior. A new analytic fitting formula, as a simple modification to the Sauter formula, is obtained to bring the analytic expression to a better agreement with the edge kinetic simulation results.
Thermo-magneto coupling in a dipole plasma
Authors: Yoshida Z. , Yano Y. , Morikawa J. , Saitoh H.
Published: July 2012

We observe the generation of a magnetic moment in a dipole plasma as a levitating magnet-plasma system moves in response to electron cyclotron heating and increasing β (magnetically confined thermal energy). We formulate a thermodynamic model that interprets heating as injection of microscopic magnetic moments; the corresponding chemical potential is the ambient magnetic field.
Erratum: “On a fourth order degenerate parabolic equation in higher space dimension” [J. Math. Phys. 50, 123524 (2009)]
Authors: Li Junjie
Published: July 2012

In this erratum we fix a flaw in the proof of Proposition 3.1 of Li [“On a fourth order degerate parabolic equation in higher space dimensions,” J. Math. Phys. 50, 123524 (2009)]10.1063/1.3272788.
Effects of plasma β on the plasmoid instability
Authors: Ni Lei , Ziegler Udo , Huang Yi-Min , Lin Jun , Mei Zhixing
Published: July 2012

The effects of the initial upstream plasma β on the plasmoid instability are studied via two-dimensional resistive magnetohydrodynamic simulations. For cases with nonuniform β dependent initial plasma mass density and uniform temperature, our numerical results indicate that the critical Lundquist number for onset of the plasmoid instability depends on the initial plasma β. The critical Lundquist number is approximately 2000−3000 for β=50 and is 8000−10 000 for β=0.2. The higher the β, the smaller the critical Lundquist number is. Similar to previous studies of high-β systems, the average reconnection rate in low β systems is found to become weakly dependent on the Lundquist number in the plasmoid-unstable regime. However, the average reconnection rate, normalized to the asymptotic value of upstream BVA, is lower in a low β system than that in a high β system. The magnetic energy spectral index, which characterizes fragmentation of the reconnection layer, is approximately two and is insensitive to β in the high-Lunquist number regime. It is also found that the magnetic reconnection rate becomes similar for different β cases, if the initial force-balance is provided by temperature gradient instead of density gradient. Therefore, it is concluded that the β-dependence mentioned above may be largely attributed to the density variation.
Design and measurements of an electrically small, broad bandwidth, non-Foster circuit-augmented protractor antenna
Authors: Zhu Ning , Ziolkowski Richard W.
Published: July 2012

A broad bandwidth, electrically small, metamaterial-inspired protractor antenna was designed, fabricated and tested around 300 MHz. Its broad bandwidth property was achieved by augmenting the protractor-shaped near-field resonant parasitic (NFRP) element with a non-Foster circuit. The resulting active NFRP element provided the means to surpass the fundamental passive limits. The measurement results for this non-Foster protractor antenna showed more than a 10 times increase of the 10 dB fractional bandwidth (FBW10dB) of the original passive version. The corresponding half-power bandwidth (BW3dB) was more than 8.24 times the passive upper bound.
Spin relaxation mechanism in silver nanowires covered with MgO protection layer
Authors: Idzuchi H. , Fukuma Y. , Wang L. , Otani Y.
Published: July 2012

Spin-flip mechanism in Ag nanowires with MgO surface protection layers has been investigated by nonlocal spin injection using permalloy/Ag lateral spin valves. The spin flip events mediated by surface scattering are effectively suppressed by the MgO capping layer. The spin relaxation process was found to be well described in the framework of Elliott-Yafet mechanism (R. J. Elliott, Phys. Rev. 96, 266 (1954); Y. Yafet, in Solid State Physics, edited by F. Seitz and D. Turnbull (Academic, New York, 1963), pp. 1–98) and then the probabilities of spin-filp scattering for phonon or impurity mediated momentum scattering is precisely determined in the nanowires. The temperature dependent spin-lattice relaxation follows the Bloch-Grüneisen theory (V. F. Bloch, Z. Phys. 59, 208 (1930); V. E. Grüneisen, Ann. Phys. 5, 530 (1933)) and falls on to a universal curve of Ag as in the conduction-electron-spin resonance data for bulk.
Kilohertz magnetic field focusing and force enhancement using a metallic loop array
Authors: Dede Ercan M. , Lee Jaewook , Guo Yuanbo , Qin Zhou Li , Zhang Minjuan , Banerjee Debasish
Published: July 2012

We present a device capable of focusing a kilohertz magnetic field and enhancing the associated magnetic force. The device comprises a two-by-two array of electrically conductive metallic loops embedded in a base substrate. Analytical calculations and numerical simulations verify that the induced electrical current in the loop structure influences the magnetic field distribution thus leading to magnetic force enhancement. Experimental measurements of the magnetic force generated by the device operating at one kilohertz are compared with measurements of a control sample without loops. Such devices have logical applications in electromechanical actuators and transducers.
A thermophone on porous polymeric substrate
Authors: Chitnis G. , Kim A. , Song S. H. , Jessop A. M. , Bolton J. S. , Ziaie B.
Published: July 2012

In this Letter, we present a simple, low-temperature method for fabricating a wide-band (>80 kHz) thermo-acoustic sound generator on a porous polymeric substrate. We were able to achieve up to 80 dB of sound pressure level with an input power of 0.511 W. No significant surface temperature increase was observed in the device even at an input power level of 2.5 W. Wide-band ultrasonic performance, simplicity of structure, and scalability of the fabrication process make this device suitable for many ranging and imaging applications.
Efficient organic light-emitting diodes through up-conversion from triplet to singlet excited states of exciplexes
Authors: Goushi Kenichi , Adachi Chihaya
Published: July 2012

Enhanced electroluminescence efficiency is achieved in organic light-emitting diodes through delayed fluorescence of the exciplex state formed between 4,4′,4′′-tris[3-methylphenyl(phenyl)amino]-triphenylamine (m-MTDATA) as an electron-donating material and 2,8-bis(diphenylphosphoryl)dibenzo-[b,d]thiophene (PPT) as an electron-accepting material. The devices exhibited maximum external electroluminescence quantum and power efficiencies of 10.0% and 47.0 lm/W, respectively.
Epitaxial growth of Ti3SiC2 thin films with basal planes parallel or orthogonal to the surface on α-SiC
Authors: Drevin-Bazin A. , Barbot J. F. , Alkazaz M. , Cabioch T. , Beaufort M. F.
Published: July 2012

The growth of Ti3SiC2 thin films were studied onto α-SiC substrates differently oriented by thermal annealing of TiAl layers deposited by magnetron sputtering. For any substrate’s orientation, transmission electron microscopy coupled with x-ray diffraction showed the coherent epitaxial growth of Ti3SiC2 films along basal planes of SiC. Specifically for the (112¯0) 4H-SiC, Ti3SiC2 basal planes are found to be orthogonal to the surface. The continuous or textured nature of Ti3SiC2 films does not depend of the SiC stacking sequence and is explained by a step-flow mechanism of growth mode. The ohmic character of the contact was confirmed by current-voltage measurements.
Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell and Monte Carlo collision. II. Investigation of acceleration mechanisms
Authors: Tang Hai-Bin , Cheng Jiao , Liu Chang , York Thomas M.
Published: July 2012

The particle-in-cell method previously described in paper (I) has been applied to the investigation of acceleration mechanisms in applied-field magnetoplasmadynamic thrusters. This new approach is an alternative to magnetohydrodynamics models and allows nonlocal dynamic effects of particles and improved transport properties. It was used to model a 100 kW, steady-state, applied-field, argon magnetoplasmadynamic thruster to study the physical acceleration processes with discharge currents of 1000–1500 A, mass flow rates of 0.025–0.1 g/s and applied magnetic field strengths of 0.034–0.102 T. The total thrust calculations were used to verify the theoretical approach by comparison with experimental data. Investigations of the acceleration model offer an underlying understanding of applied-field magnetoplasmadynamic thrusters, including the following conclusions: (1) swirl acceleration mechanism is the dominant contributor to the plasma acceleration, and self-magnetic, Hall, gas-dynamic, and swirl acceleration mechanisms are in an approximate ratio of 1:10:10:100; (2) the Hall acceleration produced mainly by electron swirl is insensitive to the change of externally applied magnetic field and shows only slight increases when the current is raised; (3) self-magnetic acceleration is normally negligible for all cases, while the gas-dynamic acceleration contribution increases with increasing applied magnetic field strength, discharge current, and mass flow rate.
Terahertz radiation from a laser bunched relativistic electron beam in a magnetic wiggler
Authors: Kumar Manoj , Tripathi V. K.
Published: July 2012

We develop a formalism for tunable coherent terahertz radiation generation from a relativistic electron beam, modulated by two laser beams, as it passes through a magnetic wiggler of wave vector kwẑ. The lasers exert a beat frequency ponderomotive force on beam electrons, and modulate their velocity. In the drift space, velocity modulation translates into density modulation. As the beam bunches pass through the wiggler, they acquire a transverse velocity, constituting a transverse current that acts as an antenna to produce coherent THz radiation, when ω1−ω2=kwc/(cosθ−v0b/c), where ω1, ω2 are the frequencies of the lasers, v0bẑ is the beam velocity, and θ is the direction of maximum radiated intensity with respect to the direction of propagation of the beam.
A single-electron probe for buried optically active quantum dot
Authors: Nakaoka T. , Watanabe K. , Kumagai N. , Arakawa Y.
Published: July 2012

We present a simple method that enables both single electron transport through a self-assembled quantum dot and photon emission from the dot. The quantum dot buried in a semiconductor matrix is electrically connected with nanogap electrodes through tunneling junctions formed by a localized diffusion of the nanogap electrode metals. Coulomb blockade stability diagrams for the optically-active dot are clearly resolved at 4.2 K. The position of the quantum dot energy levels with respect to the contact Fermi level is controlled by the kind of metal atoms diffused from the nanogap electrodes.
Unusual dimensional dependence of resonance frequencies of Au nanocantilevers fabricated with self-organized microstructure
Authors: Banerjee Amit , Rajput Nitul S. , Banerjee S. S.
Published: July 2012

Metallic nanocantilevers of gold are fabricated from self-supporting polycrystalline thin film (100 nm) by focused ion beam assisted milling and ion induced manipulation processes. The surfactant assisted growth of the thin film leads to self-organized dendrite like morphology. This self-organized dendrite like morphology of the gold film imposes a new characteristic length scale corresponding to the mean size of gold grains present within the branches of the dendrite pattern in the film. The resonance characteristic investigated on cantilevers having different widths shows a significant drop in energy dissipation and hence an enhancement in the resonance amplitude at a characteristic width. At this width the resonance frequency of a vibrating cantilever approaches the theoretically expected value anticipated from an ideal cantilever treated like an elastic continuum.
Analysis of spherical thermo-acoustic radiation in gas
Authors: Hu Hanping , Wang Zedong , Wu Hao , Wang Yandong
Published: July 2012

A general solution of the spherical thermo-acoustic (TA) radiation from any solid in gas is derived by using a fully thermally-mechanically coupled TA model. Therefore, the characteristics and regularities of spherical TA emission can be studied more completely. It is shown that flat amplitude-frequency response, the most important feature for planar TA emission from technical standpoint, still exists for spherical TA emission, and changes with the radius of a sphere, thickness of TA sample, and the distance from surface. This expression agrees well with experimental and theoretical results of planer TA emission for much larger sphere and lays the foundation to calculate complex TA emission problems.
Focal adhesion kinase-Tyr
407
and -Tyr
397
exhibit antagonistic effects on blood–testis barrier dynamics in the rat
Authors: Lie Pearl P. Y. , Mruk Dolores D. , Mok Ka Wai , Su Linlin , Lee Will M. , Cheng C. Yan
Published: July 2012

Focal adhesion kinase (FAK), a nonreceptor protein tyrosine kinase, displays phosphorylation-dependent localization in the seminiferous epithelium of adult rat testes. FAK is an integrated component of the blood–testis barrier (BTB) involved in regulating Sertoli cell adhesion via its effects on the occludin–zonula occludens-1 complex. Herein, we report that p-FAK-Tyr
407
and p-FAK-Tyr
397
display restricted spatiotemporal and almost mutually exclusive localization in the epithelium, affecting BTB dynamics antagonistically, with the former promoting and the latter disrupting the Sertoli cell tight junction–permeability barrier function. Using primary cultured Sertoli cells as an in vitro model that mimics the BTB in vivo both functionally and ultrastructurally, effects of FAK phosphorylation on BTB function were studied by expressing nonphosphorylatable and phosphomimetic mutants, with tyrosine replaced by phenylalanine (F) and glutamate (E), respectively. Compared with WT FAK, Y407E and Y397F mutations each promoted barrier function, and the promoting effect of the Y407E mutant was abolished in the Y397E-Y407E double mutant, demonstrating antagonism between Tyr
407
and Tyr
397
. Furthermore, Y407E mutation induced the recruitment of actin-related protein 3 to the Sertoli cell-cell interface, where it became more tightly associated with neuronal Wiskott–Aldrich syndrome protein, promoting actin-related protein 2/3 complex activity. Conversely, Y407F mutation reduced the rate of actin polymerization at the Sertoli cell BTB. In summary, FAK-Tyr
407
phosphorylation promotes BTB integrity by strengthening the actin filament-based cytoskeleton. FAK serves as a bifunctional molecular “switch” to direct the cyclical disassembly and reassembly of the BTB during the epithelial cycle of spermatogenesis, depending on its phosphorylation status, to facilitate the transit of preleptotene spermatocytes across the BTB.
Neuroepithelial body microenvironment is a niche for a distinct subset of Clara-like precursors in the developing airways
Authors: Guha Arjun , Vasconcelos Michelle , Cai Yan , Yoneda Mitsuhiro , Hinds Anne , Qian Jun , Li Guihua , Dickel Lauren , Johnson Jane E. , Kimura Shioko , Guo Jinjin , McMahon Jill , McMahon Andrew P. , Cardoso Wellington V.
Published: July 2012

Clara cells of mammalian airways have multiple functions and are morphologically heterogeneous. Although Notch signaling is essential for the development of these cells, it is unclear how Notch influences Clara cell specification and if diversity is established among Clara cell precursors. Here we identify expression of the secretoglobin
Scgb3a2
and Notch activation as early events in a program of secretory cell fate determination in developing murine airways. We show that
Scgb3a2
expression in vivo is Notch-dependent at early stages and ectopically induced by constitutive Notch1 activation, and also that in vitro Notch signaling together with the pan-airway transcription factor Ttf1 (Nkx2.1) synergistically regulate secretoglobin gene transcription. Furthermore, we identified a subpopulation of secretory precursors juxtaposed to presumptive neuroepithelial bodies (NEBs), distinguished by their strong
Scgb3a2
and
uroplakin 3a
(
Upk3a
) signals and reduced Ccsp (Scgb1a1) expression. Genetic ablation of
Ascl1
prevented NEB formation and selectively interfered with the formation of this subpopulation of cells. Lineage labeling of
Upk3a
-expressing cells during development showed that these cells remain largely uncommitted during embryonic development and contribute to Clara and ciliated cells in the adult lung. Together, our findings suggest a role for Notch in the induction of a Clara cell-specific program of gene expression, and reveals that the NEB microenvironment in the developing airways is a niche for a distinct subset of Clara-like precursors.
Localization and quaternary structure of the PKA RIβ holoenzyme
Authors: Ilouz Ronit , Bubis José , Wu Jian , Yim Yun Young , Deal Michael S. , Kornev Alexandr P. , Ma Yuliang , Blumenthal Donald K. , Taylor Susan S.
Published: July 2012

Specificity for signaling by cAMP-dependent protein kinase (PKA) is achieved by both targeting and isoform diversity. The inactive PKA holoenzyme has two catalytic (C) subunits and a regulatory (R) subunit dimer (R
2
:C
2
). Although the RIα, RIIα, and RIIβ isoforms are well studied, little is known about RIβ. We show here that RIβ is enriched selectively in mitochondria and hypothesized that its unique biological importance and functional nonredundancy will correlate with its structure. Small-angle X-ray scattering showed that the overall shape of RIβ
2
:C
2
is different from its closest homolog, RIα
2
:C
2
. The full-length RIβ
2
:C
2
crystal structure allows us to visualize all the domains of the PKA holoenzyme complex and shows how isoform-specific assembly of holoenzyme complexes can create distinct quaternary structures even though the R
1
:C
1
heterodimers are similar in all isoforms. The creation of discrete isoform-specific PKA holoenzyme signaling “foci” paves the way for exploring further biological roles of PKA RIβ and establishes a paradigm for PKA signaling.
Use of Bioelectric Impedance Analysis to Assess Total‐Body Condition and Predict Energy Density in Juvenile Atlantic Croaker
Authors: Garner S. B. , van der Ham J. L. , Boswell K. M. , Cowan J. H.
Published: July 2012

Bioelectric impedance analysis (BIA) uses the conductive properties of biological tissues to provide whole‐body resistance (R) and reactance (Xc) data through direct measurements of intracellular and extracellular water content. The application of BIA to fish remains relatively novel, and the relationship between condition and impedance is not fully understood. We sought to test the efficacy of BIA in assessing total‐body condition and energy content in juvenile fish. We present results from a laboratory tank experiment using juvenile Atlantic croaker Micropogonias undulatus to investigate the BIA‐condition relationship and compare BIA with traditional condition measures (i.e., relative condition and energy‐content analysis). Atlantic croaker were held in large recirculation tanks and subjected to either a starvation or ad libitum feeding treatment for 45 d. Relative condition, energy content, phase angle, and the composition index all showed significant differences between treatments. However, trends observed in the BIA‐derived condition measures (phase angle and the composition index) displayed contradictory results. When regressed against energy content, phase angle yielded consistently lower r2 values than relative condition, while both were much lower than literature‐derived r2 values for predictive equations of proximate components. Two explanations are possible for the weak relationships observed among BIA measures in this experiment: (1) relatively high‐metabolic rates and low energy storage capacities of juvenile fish may have disrupted normal impedance relationships, and (2) an electrode array placed in muscle tissue may not have detected compositional changes if the primary centers for fat storage and mobilization occurred in the liver or viscera.
Feeding Response of Sport Fish after Electrical Immobilization, Chemical Sedation, or Both
Authors: Fredricks Kim T. , Meinertz Jeffery R. , Ambrose Ryan D. , Jackan Leanna M. , Wise Jeremy K. , Gaikowski Mark P.
Published: July 2012

Fishery managers frequently capture wild fish for a variety of fishery management activities. Though some activities can be accomplished without immobilizing the fish, others are accomplished more readily, humanely, and safely (for both the handler and the fish) when fish are immobilized by physical (e.g., electrical immobilization) or chemical sedation. A concern regarding the use of chemical sedatives is that chemical residues may remain in the fillet tissue after the fish recovers from sedation. If those residues are harmful to humans, there is some risk that a postsedated fish released to public waters may be caught and consumed by an angler. To characterize this risk, a series of four trials were conducted. Three trials assessed feeding activity after hatchery-reared fish were electrically immobilized, chemically sedated, or both, and one trial assessed the likelihood of an angler catching a wild fish that had been electrically immobilized and chemically sedated. Results from the first trial indicated that the feeding activity of laboratory habituated fish was variable among and within species after electrical immobilization, chemical sedation, or both. Results from the second trial indicated that the resumption of feeding activity was rapid after being mildly sedated for 45 min. Results from the third trial indicated that the feeding activity of outdoor, hatchery-reared fish was relatively aggressive after fish had been chemically sedated. Results from the fourth trial indicated that the probability of capturing wild fish in a more natural environment by angling after fish had been electrically immobilized and chemically sedated is not likely, i.e., in a group of five fish caught, 3 out of 100 times one would be a fish that had been sedated.

Received October 17, 2011; accepted April 13, 2012
The Relationship between Age-0 Walleye Density and Adult Year-Class Strength across Northern Wisconsin
Authors: Hansen Jonathan F. , Fayram Andrew H. , Hennessy Joseph M.
Published: July 2012

Walleyes Sander vitreus are an important cultural and economic resource in northern Wisconsin, both as a recreational fishery and a tribal subsistence fishery. Understanding the recruitment of age-0 walleyes to the adult population could be of great utility in effectively managing harvest and informing stocking efforts in this mixed-use fishery. Our objective was to determine the relationship between abundance of age-0 walleyes in the fall and the subsequent adult year-class 4 years later and to explain additional residual variation related to environmental variables. Since 1986, fall electrofishing surveys have been conducted to estimate the densities of age-0 walleyes and spring mark–recapture surveys to estimate spawning adult walleyes. We fit a gamma stock–recruitment curve to a data set of 104 paired surveys (age-0 survey with adult survey conducted 4 years later) on 58 lakes and attempted to explain residual variation related to additional environmental variables. Our analysis suggests that the maximum number of age-4 fish (3.36/ha) is not produced by the maximum number of age-0 fish but by a somewhat intermediate density (243/ha) and that this relationship varies with the complexity of the shoreline. This density-dependent relationship should help managers refine models forecasting walleye abundance, as well as optimize stocking rates.

Received December 28, 2011; accepted April 27, 2012
How and Why 1 Year Differs from 365 Days: A Conversational Logic Analysis of Inferences from the Granularity of Quantitative Expressions
Authors: Zhang Y. Charles , Schwarz Norbert
Published: July 2012

The same quantity can be expressed at different levels of granularity, for example, “1 year,” “12 months,” or “365 days.” Consumers attend to the granularity chosen by a communicator and draw pragmatic inferences that influence judgment and choice. They consider estimates expressed in finer granularity more precise and have more confidence in their accuracy (studies 1–4). This effect is eliminated when consumers doubt that the communicator complies with Gricean norms of cooperative conversational conduct (studies 2–3). Based on their pragmatic inferences, consumers perceive products as more likely to deliver on their promises when the promise is described in fine-grained rather than coarse terms and choose accordingly (study 4). These findings highlight the role of pragmatic inferences in consumer judgment and have important implications for the design of marketing communications.
“I Don’t” versus “I Can’t”: When Empowered Refusal Motivates Goal-Directed Behavior
Authors: Patrick Vanessa M. , Hagtvedt Henrik
Published: July 2012

This research is based on the insight that the language we use to describe our choices serves as a feedback mechanism that either enhances or impedes our goal-directed behavior. Specifically, we investigate the influence of a linguistic element of self-talk, in which a refusal may be framed as “I don’t” (vs. “I can’t”), on resisting temptation and motivating goal-directed behavior. We present a set of four studies to demonstrate the efficacy of the “don’t” (vs. “can’t”) framing (studies 1–3) when the source of the goal is internal (vs. external; studies 2A and 2B), as well as the mediating role of psychological empowerment (studies 1, 2A, and 2B). We demonstrate this novel and effective refusal strategy with actual choice (study 1) and with behavioral intent (studies 2A and 2B) and also illustrate its applicability in the real world in a longitudinal intervention-based field study (study 3).
Psychological Distance and Subjective Experience: How Distancing Reduces the Feeling of Difficulty
Authors: Thomas Manoj , Tsai Claire I.
Published: July 2012

Psychological distance can reduce the subjective experience of difficulty caused by task complexity and task anxiety. Four experiments were conducted to test several related hypotheses. Psychological distance was altered by activating a construal mind-set and by varying bodily distance from a given task. Activating an abstract mind-set reduced the feeling of difficulty. A direct manipulation of distance from the task produced the same effect: participants found the task to be less difficult when they distanced themselves from the task by leaning back in their seats. The experiments not only identify psychological distance as a hitherto unexplored but ubiquitous determinant of task difficulty but also identify bodily distance as an antecedent of psychological distance.
Self-Affirmation through the Choice of Highly Aesthetic Products
Authors: Townsend Claudia , Sood Sanjay
Published: July 2012

Just as good looks bestow an unconscious “beauty premium” on people, high aesthetics bestows an unrecognized benefit on consumer goods. Specifically, choosing a product with good design affirms the consumer’s sense of self. Choice of a highly aesthetic product was compared with choice of products superior on other attributes including function, brand, and hedonics to show that only aesthetics influences a consumer’s personal values. In study 1 a prior self-affirming task leads to a decrease in choice share of a highly aesthetic option. Studies 2 and 3 mimic prior research on self-affirmation with, however, choice of a highly aesthetic product replacing a traditional self-affirmation manipulation. Choosing a product with good design resulted in increased openness to counter-attitudinal arguments and reduced propensity to escalate commitment toward a failing course of action. There are numerous implications of this form of self-affirmation, from public policy to retail therapy.
Bayesian sampling of evolutionarily conserved RNA secondary structures with pseudoknots
Authors: Doose Gero , Metzler Dirk
Published: July 2012

Motivation: Today many non-coding RNAs are known to play an active role in various important biological processes. Since RNA's functionality is correlated with specific structural motifs that are often conserved in phylogenetically related molecules, computational prediction of RNA structure should ideally be based on a set of homologous primary structures. But many available RNA secondary structure prediction programs that use sequence alignments do not consider pseudoknots or their estimations consist on a single structure without information on uncertainty.

Results: In this article we present a method that takes advantage of the evolutionary history of a group of aligned RNA sequences for sampling consensus secondary structures, including pseudoknots, according to their approximate posterior probability. We investigate the benefit of using evolutionary history and demonstrate the competitiveness of our method compared with similar methods based on RNase P RNA sequences and simulated data.

Availability: PhyloQFold, a C + + implementation of our method, is freely available from http://evol.bio.lmu.de/_statgen/software/phyloqfold/

Contact: gero@bioinf.uni-leipzig.de, metzler@bio.lmu.de

Supplementary information:  Supplementary data are available at Bioinformatics online.
Gene and translation initiation site prediction in metagenomic sequences
Authors: Hyatt Doug , LoCascio Philip F. , Hauser Loren J. , Uberbacher Edward C.
Published: July 2012

Motivation: Gene prediction in metagenomic sequences remains a difficult problem. Current sequencing technologies do not achieve sufficient coverage to assemble the individual genomes in a typical sample; consequently, sequencing runs produce a large number of short sequences whose exact origin is unknown. Since these sequences are usually smaller than the average length of a gene, algorithms must make predictions based on very little data.

Results: We present MetaProdigal, a metagenomic version of the gene prediction program Prodigal, that can identify genes in short, anonymous coding sequences with a high degree of accuracy. The novel value of the method consists of enhanced translation initiation site identification, ability to identify sequences that use alternate genetic codes and confidence values for each gene call. We compare the results of MetaProdigal with other methods and conclude with a discussion of future improvements.

Availability: The Prodigal software is freely available under the General Public License from http://code.google.com/p/prodigal/.

Contact:  hyattpd@ornl.gov

Supplementary Information: Supplementary data are available at Bioinformatics online.
SQID-XLink: implementation of an intensity-incorporated algorithm for cross-linked peptide identification
Authors: Li Wenzhou , O’Neill Heather A. , Wysocki Vicki H.
Published: July 2012

Summary: Peptide identification algorithm is a major bottleneck for mass spectrometry based chemical cross-linking experiments. Our lab recently developed an intensity-incorporated peptide identification algorithm, and here we implemented this scheme for cross-linked peptide discovery. Our program, SQID-XLink, searches all regular, dead-end, intra and inter cross-linked peptides simultaneously, and its effectiveness is validated by testing a published dataset. This new algorithm provides an alternative approach for high confidence cross-linking identification.

Availability: SQID-XLink program is freely available for download from http://quiz2.chem.arizona.edu/wysocki/bioinformatics.htm

Supplementary information: Supplementary data are available at Bioinformatics online.

Contact:  vwysocki@email.arizona.edu