bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulsating dayside aurora in relation to ion upflow events during a northward interplanetary magnetic field (IMF) dominated by a strongly negative IMF BY
Authors: Lorentzen D. A. , Kintner P. M. , Moen J. , Sigernes F. , Oksavik K. , Ogawa Y. , Holmes J.
Published: March 2007

We report a study of ion upflow as seen by the European Incoherent Scatter (EISCAT) Svalbard Radar (ESR), initiated by a rotation from interplanetary magnetic field (IMF) BZ negative to IMF BZ positive, under the influence of a strongly negative IMF BY. We combine ground‐based instruments, such as meridian scanning photometers (MSP), all‐sky imager (ASI) data, and radars, with solar wind data from the Advanced Composition Explorer (ACE) spacecraft and low‐altitude particle precipitation data from the Defense Meteorological Satellite Program (DMSP) F‐13 spacecraft as well as wave data from the Svalbard EISCAT Rocket Study of Ion Outflows (SERSIO) sounding rocket flight. Following a coronal mass ejection, the solar wind data showed high dynamic pressures (up to 20 n Pa) and a strongly varying IMF. The observed ion upflow was seen to be of a pulsed nature and sustained by pulsed soft electron precipitation. The data findings indicated pulsed lobe reconnection as the mechanism funneling energy and momentum down to the northern polar hemisphere.
Reduced sea ice concentrations in the Arctic Ocean during the last interglacial period revealed by sediment cores off northern Greenland
Authors: Nørgaard‐Pedersen Niels , Mikkelsen Naja , Lassen Susanne Juul , Kristoffersen Yngve , Sheldon Emma
Published: March 2007

We present a record encompassing marine isotope stages 7‐1 from a hitherto unexplored and heavily ice‐covered area of the Arctic Ocean, the Lomonosov Ridge off the northern Greenland‐Canada continental margin, using nannofossil and benthic foraminifera stratigraphy. Planktic foraminifera assemblages are used as a key paleoceanographic proxy, and a surprisingly large variability is found for an interior Arctic Ocean site. Abundant small (63–125 μm) subpolar Turborotalita quinqueloba occur in two sections, possibly representing substages 5e (last interglacial) and 5a (warm interstadial). However, the present‐day circulation pattern and the very distant location of high productive regions cannot explain such high abundances of subpolar specimens in the interior, perennially sea ice–covered Arctic Ocean. Hence our proxy record indicates that last interglacial sea ice concentrations were reduced off some areas of northern Greenland‐Canada. Whether this was part of a larger regional pattern or it represents the influence of polynya areas with locally increased productivity remains to be solved. With respect to glacial conditions, increased ice‐rafted debris (IRD) deposition in the area appears to be associated with glacial stages 6, 4, and late 3. Stage 2 sediments (including the Last Glacial Maximum) are condensed with a sparse IRD content only.
Effect of Nd3+ concentration quenching in highly doped lead lanthanum zirconate titanate transparent ferroelectric ceramics
Authors: de Camargo A. S. S. , Jacinto C. , Nunes L. A. O. , Catunda T. , Garcia D. , Botero É. R. , Eiras J. A.
Published: March 2007

The concentration dependence of the fluorescence quantum efficiency in Nd3+ doped lead lanthanum zirconate titanate (PLZT), transparent ceramics, is presented. The total emission decay of the emitting level F3∕24 is close to exponential, even for high Nd3+ concentration Nt, due to the very low probability of the cross relaxation energy transfer processes among ions. Owing to this low probability, it was inferred that Nd:PLZT presents lower concentration quenching than other laser materials as Nd:YAG. The figure of merit ηNt, where η is the fluorescence quantum efficiency, presents a maximum around 6.0wt% Nd2O3, indicating the good prospects of concentrated samples for miniaturization of the laser medium (microchip laser).
Spectral mode changes in an alkali rf discharge
Authors: Camparo J. C. , Mackay R.
Published: March 2007

As a result of observations made by Shaw (M.S. thesis, Cornell University, 1964) in the mid-1960s, alkali rf discharges are known to operate in two spectral modes, the so-called ring mode and the red mode. Experience has shown that the ring mode is best for discharge lamps used in quantum-electronic devices such as atomic clocks and optically pumped magnetometers and that the performance of these devices seriously degrades when the lamp operates in the red mode. Understanding the origin of these modes therefore has application to understanding and improving various quantum-electronic devices. Here we show that Shaw’s model for these modes is inconsistent with observation, and we propose an alternate model based on the role of radiation trapping in multistep ionization.
In situ determination and imaging of physical properties of metastable and equilibrium precipitates using valence electron energy-loss spectroscopy and energy-filtering transmission electron microscopy
Authors: Oleshko Vladimir P. , Howe James M.
Published: March 2007

The physical (elastic, cohesive, and electronic) properties of precipitates are important in determining factors such as their equilibrium shape, coarsening, and strengthening behavior in alloys. In this work, we use valence electron energy-loss spectroscopy (VEELS) and energy-filtering transmission electron microscopy (EFTEM) to determine quantitatively and image the elastic moduli, cohesive energy, and interstitial electron density of both metastable and equilibrium precipitates in two different metal alloys. We show that the elastic properties of θ′ and θ precipitates in Al–Cu alloys can be measured in situ as a function of temperature and during transformation from θ′ and θ phases. We also measure and image in situ the elastic and cohesive properties of metastable TiHx precipitates in a Ti–H alloy. These results demonstrate the capability of VEELS∕EFTEM for real-time nanoscale determination and imaging of multiple physical properties of precipitates in solid-solid phase transformations.
Underwater streamer propagation analyzed from detailed measurements of pressure release
Authors: An Wladimir , Baumung Kurt , Bluhm Hansjoachim
Published: March 2007

In this paper we describe experimental observations connected with the propagation of primary and secondary streamers in water. Using a Mach-Zehnder interferometer we determined the pressure field surrounding the streamer channel at a given instant in time with high temporal and spatial resolution. This pressure field contains information on the time evolution of the pressure pulse inside the discharge channel. The pressure history in the channel has been reconstructed by comparing the experimentally obtained fringe shifts in the interferograms with those derived from one-dimensional hydrodynamic calculations in cylindrical geometry. Assuming different trial pressure pulses, it has been possible to establish the channel pressure iteratively. A reproduction of the experimental data from secondary streamers requires short (2–3ns) pressure pulses with amplitudes of 2–3GPa. These findings are inconsistent with the assumption of bubble-initiated propagation of secondary streamers. It has also been inferred from estimates of the channel diameter that self-propagation of secondary streamers occurs at field strengths at the streamer tip of more than 2GV∕m. We can therefore conclude that field induced dissociation and ionization of molecules in the bulk liquid are the most likely mechanism for secondary streamer propagation. Rather high electrical conductivity (>0.2S∕m) is achieved at fields of 2GV∕m and an ionization wave is launched from the streamer tip into the liquid. To advance the streamer the electric field must be expelled from the newly generated section. This occurs with the Maxwellian relaxation time of a few nanoseconds. During this time the region of high conductivity is transformed into a plasma channel of lower density and a pressure wave is launched into the liquid. A different mechanism is suggested for primary streamer formation. Because of the low conductivity in the channels it is more likely that gas bubbles or phase instabilities are involved in this case.
Crystallization of amorphous silicon by self-propagation of nanoengineered thermites
Authors: Hossain Maruf , Subramanian Senthil , Bhattacharya Shantanu , Gao Yuanfang , Apperson Steve , Shende Rajesh , Guha Suchi , Arif Mohammad , Bai Mengjun , Gangopadhyay Keshab , Gangopadhyay Shubhra
Published: March 2007

Crystallization of amorphous silicon (a-Si) thin film occurred by the self-propagation of copper oxide/aluminum thermite nanocomposites. Amorphous Si films were prepared on glass at a temperature of 250°C by plasma enhanced chemical vapor deposition. The platinum heater was patterned on the edge of the substrate and the CuO∕Al nanoengineered thermite was spin coated on the substrate that connects the heater and the a-Si film. A voltage source was used to ignite the thermites followed by a piranha solution (4:1 of H2SO4:H2O2) etch for the removal of residual products of thermite reaction. Raman spectroscopy was used to confirm the crystallization of a-Si.
All-electrical indentation shear modulus and elastic modulus measurement using a piezoelectric cantilever with a tip
Authors: Yegingil Hakki , Shih Wan Y. , Shih Wei-Heng
Published: March 2007

We have investigated an all-electrical indentation shear modulus and elastic modulus measurement technique using piezoelectric cantilever sensors with a tip for potential in vivo applications. A piezoelectric cantilever with a tip was capable of carrying out compression, shear, indentation, and indentation shear tests, where compression and shear tests refer to those where the sample is not confined by a container and the contact area of the cantilever is the same as or larger than the sample surface area and the indentation and indentation shear tests are those where the contact area of the cantilever is smaller than the sample surface area. Because the cantilever could measure both the elastic modulus and the shear modulus, Poisson’s ratio of a sample could be determined from the ratio of the shear modulus to the elastic modulus with no presumption. We showed that the experimental elastic moduli and shear moduli obtained from the indentation and indentation shear tests agree with those obtained from the compression and shear tests. Furthermore, we showed that the same elastic moduli and the same shear moduli could be obtained either by using the displacement measurements or by the induced voltage measurements across the sensing piezoelectric layer. With a model tissue consisting of modeling clay embedded in gelatin, we demonstrated that the indentation compression and indentation shear tests could produce two-dimensional elastic and shear moduli maps or images that accurately showed the size and location of the modeling clay inclusion.
Nonlinear study of photoelectrothermal modulated optical reflectance for active dopant profile extraction
Authors: Dortu Fabian , Bogdanowicz Janusz , Clarysse Trudo , Vandervorst Wilfried
Published: March 2007

Carrier illumination (CI) is a photoelectrothermal modulated optical reflectance (PMOR) technique for the one dimensional active doping profile characterization of ultrashallow junctions. The specificity of CI as a PMOR technique is to exploit the probe differential reflectance nonlinearity as a function of the pump laser irradiance (104–106W∕cm2). The probe differential reflectance as function of the pump power is called a power curve, and its interpretation provides information on the underlying active doping profile. In a previous work [F. Dortu et al., J. Vac. Sci. Technol. 24, 375 (2006)], the independent extraction of the active doping concentration (N) and the metallurgical junction (Xj) of a chemical vapor deposited boxlike profile was based on two features of the power curve, namely, the inflexion power and the signal at end of range power. However, this method suffers from the difficulty to extract accurately the second derivative and has a limited extraction range (Xj=20–40nm, N=1019–1020∕cm3). In the present work, we present a method making use of the power curve’s first derivative at low and high illumination powers. This method, in principle, allows a much broader extraction range (Xj=10–70nm, N=1018–1020∕cm3) provided that the signal time dependence due to the native silicon oxide charging under intense illumination is taken into account properly. The present work is supported by a two-layer diffusionless nonlinear analytical model, which provides the basic insights of the method, and three dimensional axisymmetric numerical simulations in the framework of the drift-diffusion equations. A procedure to remove the time dependent charging effect is also presented.
A planar-geometry platform for the experimental investigation of Be jets
Authors: Keiter P. A. , Laffite S. C. , Kyrala G. A. , Fincke J. R. , Cooley J. H. , Wilson D. C.
Published: March 2007

Initial experiments were performed at the OMEGA laser [J. Soures et al., Phys. Plasmas 3, 2108 (1996)] to investigate the physics associated with inertial confinement fusion capsule fill tubes and holes. These experiments were performed in planar geometry and examined the hydrodynamics of a 6.7:1 aspect ratio fill-hole. X-ray radiographs at 310eV show a jet has formed due to the interaction between the temperature drive and the beryllium (Be) washer.
Contact angle influence on the pull-in voltage of microswitches in the presence of capillary and quantum vacuum effects
Authors: Palasantzas George
Published: March 2007

Capillary condensation between the electrodes of microswitches influences the effective pull-in voltage in a manner that depends on the contact angle of the capillary meniscus and the presence of plate surface roughness. Indeed, surface roughening is shown to have a stronger influence on the pull-in potential for relatively small contact angles with respect to that of a flat surface when capillary condensation takes place. For long wavelength roughness ratios w∕ξ⪡1 with w the rms roughness amplitude and ξ the in-plane correlation length, the pull-in voltage increases with increasing theoretical contact angle θ0 for flat surfaces. With decreasing correlation length ξ (increasing roughness), the pull-in potential decreases faster for smaller contact angles θ0 In addition, with decreasing roughness exponent H (0<H<1), which characterizes short wavelength roughness fluctuation at short length scales (<ξ), the pull-in potential shows a steeper decrease with decreasing correlation length ξ. Finally, with increasing relative humidity, the sensitivity of the pull-in voltage at small correlation lengths attenuates significantly with increasing contact angle θ0.
Fractional embedding of differential operators and Lagrangian systems
Authors: Cresson Jacky
Published: March 2007

This paper is a contribution to the general program of embedding theories of dynamical systems. Following our previous work on the stochastic embedding theory developed with Darses [C. R. Acad. Sci. Ser. I: Math 342, 333 (2006); (preprint IHES 06/27, p. 87, 2006)], we define the fractional embedding of differential operators and ordinary differential equations. We construct an operator combining in a symmetric way the left and right (Riemann-Liouville) fractional derivatives. For Lagrangian systems, our method provides a fractional Euler-Lagrange equation. We prove, developing the corresponding fractional calculus of variations, that such equation can be derived via a fractional least-action principle. We then obtain naturally a fractional Noether theorem and a fractional Hamiltonian formulation of fractional Lagrangian systems. All these constructions are coherents, i.e., the embedding procedure is compatible with the fractional calculus of variations. We then extend our results to cover the Ostrogradski formalism. Using the fractional embedding and following a previous work of Riewe [Phys. Rev. E 53, 1890 (1996); Phys. Rev. E 55, 3581 (1997)], we obtain a fractional Ostrogradski formalism which allows us to derive nonconservative dynamical systems via a fractional generalized least-action principle. We also discuss the Whittaker equations and obtain a fractional Lagrangian formulation. Last, we discuss the fractional embedding of continuous Lagrangian systems. In particular, we obtain a fractional Lagrangian formulation of the classical fractional wave equation introduced by Schneider and Wyss [J. Math. Phys. 30, 134 (1989)] as well as the fractional diffusion equation.
An experimental investigation of turbulent flows over a hilly surface
Authors: Poggi D. , Katul G. G. , Albertson J. D. , Ridolfi L.
Published: March 2007

Gentle topographic variations significantly alter the mass and momentum exchange rates between the land surface and the atmosphere from their flat-world state. This recognition is now motivating basic studies on how a wavy surface impacts the flow dynamics near the ground for high bulk Reynolds numbers (Reh). Using detailed flume experiments on a train of gentle hills, we explore the spatial structure of the mean longitudinal (u) and vertical (w) velocities at high Reh. We show that classical analytical theories proposed by Jackson and Hunt (JH75) for isolated hills can be extended to a train of gentle hills if the background velocity is appropriately defined. We also show that these theories can reproduce the essential 2D structure of the Reynolds stresses. The basic assumptions in the derivation of the JH75 model are also experimentally investigated. We found that the linearization of the advective acceleration term and the mixing length proposed in JH75 are reasonable within the inner layer. We also show that the measured variability in the linearized mean longitudinal advective acceleration term can explain much of the measured variability in the entire nonlinear advective acceleration term for the longitudinal mean momentum balance.
Enhancement of vacuum polarization effects in a plasma
Authors: Di Piazza A. , Hatsagortsyan K. Z. , Keitel C. H.
Published: March 2007

The dispersive effects of vacuum polarization on the propagation of a strong circularly polarized electromagnetic wave through a cold collisional plasma are studied analytically. It is found that, due to the singular dielectric features of the plasma, the vacuum effects on the wave propagation in a plasma are qualitatively different and much larger than those in pure vacuum in the regime when the frequency of the propagating wave approaches the plasma frequency. A possible experimental setup to detect these effects in plasma is described.
Artificial submicron or nanometer speckle fabricating technique and electron microscope speckle photography
Authors: Liu Zhanwei , Xie Huimin , Fang Daining , Dai Fulong , Wang Weining , Fang Yan
Published: March 2007

In this article, a novel artificial submicro- or nanometer speckle fabricating technique is proposed by taking advantage of submicro or nanometer particles. In the technique, submicron or nanometer particles were adhered to an object surface by using ultrasonic dispersing technique. The particles on the object surface can be regarded as submicro or nanometer speckle by using a scanning electronic microscope at a special magnification. In addition, an electron microscope speckle photography (EMSP) method is developed to measure in-plane submicron or nanometer deformation of the object coated with the artificial submicro or nanometer speckles. The principle of artificial submicro or nanometer speckle fabricating technique and the EMSP method are discussed in detail in this article. Some typical applications of this method are offered. The experimental results verified that the artificial submicro or nanometer speckle fabricating technique and EMSP method is feasible.
Magnetic compound refractive lens for focusing and polarizing cold neutron beams
Authors: Littrell K. C. , te Velthuis S. G. E. , Felcher G. P. , Park S. , Kirby B. J. , Fitzsimmons M. R.
Published: March 2007

Biconcave cylindrical lenses are used to focus beams of x rays or neutrons using the refractive properties of matter. In the case of neutrons, the refractive properties of magnetic induction can similarly focus and simultaneously polarize the neutron beam without the concomitant attenuation of matter. This concept of a magnetic refractive lens was tested using a compound lens consisting of 99 pairs of cylindrical permanent magnets. The assembly successfully focused the intensity of a white beam of cold neutrons of one spin state at the detector, while defocusing the other. This experiment confirmed that a lens of this nature may boost the intensity locally by almost an order of magnitude and create a polarized beam. An estimate of the performance of a more practically dimensioned device suitable for incorporation in reflectometers and slit-geometry small angle scattering instruments is given.
Room temperature emission from CdSe∕ZnSSe∕MgS single quantum dots
Authors: Arians R. , Kümmell T. , Bacher G. , Gust A. , Kruse C. , Hommel D.
Published: March 2007

The authors report on room temperature photoluminescence from single CdSe quantum dots. The quantum dots, realized by self-organized epitaxial growth, are embedded in ZnSSe∕MgS barriers. The integrated intensity of the emission drops by less than a factor of 3 between 4K and room temperature. Microphotoluminescence with a spatial resolution of 200nm exhibits single dot emission that remains visible up to 300K. The linewidth of the single dot emission increases thereby from 340μeVto25meV at room temperature, which the authors attribute to the interaction of excitons with optical phonons.
Kinetically constraint zero- and one-dimensional heteroepitaxial island growth
Authors: Li Zhipeng , Singh Manish Kumar , Tok Eng Soon , Tan Joyce Pei Ying , Lin Ming , Foo Yong-Lim
Published: March 2007

Direct observation of the dynamics, formation, and selective growth of low dimensional epitaxial Fe13Ge8 structures [zero-dimensional (0D) compact islands or one-dimensional (1D) wires of different aspect ratios] was conducted in real time using in situ ultra high vacuum transmission electron microscopy at 350, 430, 480, and 510°C. Both types of island (0D/1D) share the same epitaxial relation to the underlying Ge substrate. The compact islands are formed preferentially at lower deposition temperature while wires, which are kinetically constrained, at higher temperature. The effective Ea for growth along two orthogonal azimuths of an Fe13Ge8 island are 0.17 and 0.95eV. The temperature dependence in morphological evolution is due to anisotropy in corner barriers and ledge diffusion on orthogonal azimuths during growth.
Physical mechanisms of in situ surface gettering of metals in ribbon silicon for solar cells
Authors: Khanal D. R. , Buonassisi T. , Marcus M. A. , Istratov A. A. , Weber E. R.
Published: March 2007

The authors have employed synchrotron-based x-ray absorption near-edge spectroscopy and x-ray fluorescence microscopy to identify the chemical state and distribution of metals gettered to the surface of String Ribbon silicon grown with CO-ambient gas. Copper and nickel precipitates were observed in their equilibrium silicide phases, indicating a dominant relaxation gettering mechanism. In addition, microwave photoconductive decay measurements show a decrease in bulk iron concentration and a tenfold increase in minority carrier lifetime in CO-ambient grown material. Implications of the observed gettering mechanism on ribbon-type solar cells are discussed.
Electrophosphorescence from triplet excimers in poly-(N-vinylcarbazole)
Authors: Qian Lei , Bera Debasis , Holloway Paul H.
Published: March 2007

The authors have observed electrophosphorescence from triplet excimer in poly-(N-vinylcarbazole) (PVK) polymer at room temperature. The triplet excimer appears to be influenced by the PVK molecular conformation. This observation is very important to the understanding of the mechanism of triplet exciton formation in PVK. It is, therefore, an important consideration in selecting materials for phosphor-doped organic light-emitting diode applications.
Voltage- and light-induced hysteresis effects at the high-k dielectric—poly(3-hexylthiophene) interface
Authors: Lancaster J. , Taylor D. M. , Sayers P. , Gomes H. L.
Published: March 2007

Capacitance-voltage (C-V) measurements have been undertaken on metal-insulator-semiconductor capacitors formed from atomic-layer-deposited films of aluminium titanium oxide as the insulator and poly(3-hexylthiophene) as the insulator. Upon cycling from −30to+30V in the dark, the C-V plots show large, temperature-dependent, reversible shifts in the flatband voltage to more negative voltages consistent with reversible, shallow hole trapping at or near the insulator-semiconductor interface. When illuminated with photons of energy exceeding the polymer band gap, even larger shifts to positive voltages are observed accompanied by inversion layer formation. This latter effect has potential applications in optical sensing.
Origins of shallow level and hole mobility in codoped p-type ZnO thin films
Authors: Ye H. B. , Kong J. F. , Shen W. Z. , Zhao J. L. , Li X. M.
Published: March 2007

A combination study of structural, optical, and electrical properties has been carried out on N–In codoped p-type ZnO thin films for the origins of shallow level and hole mobility. The observed small activation energy of ∼20meV for the hole concentration corresponds well to the results from photoluminescence and conductivity data, revealing the grain boundary trapping nature of the shallow level. The achieved hole mobility is mainly due to the lack of grain boundary barrier effect, and the codoping yielded weak ionized impurity scattering. The authors have also revealed the scattering and conduction mechanisms in these p-ZnO films.
Transformation-induced plasticity in an ultrafine-grained steel: An in situ neutron diffraction study
Authors: Tao Kaixiang , Choo Hahn , Li Hongqi , Clausen Bjørn , Jin Jae-Eun , Lee Young-Kook
Published: March 2007

An ultrafine-grained steel with an average grain size of about 350nm was developed. The tensile testing at ambient temperature shows a threefold increase in the yield strength compared to its coarse-grained counterpart. Moreover, the increase in the strength was achieved without the sacrifice of the ductility due to strain-induced martensitic transformation. The evolution of lattice strains and phase fractions of the austenite and martensite phases during the deformation was investigated using in situ neutron diffraction to provide a micromechanical understanding of the transformation-induced plasticity responsible for the combination of high strength and ductility.
Enhanced flux pinning in YBa2Cu3O7 layers by the formation of nanosized BaHfO3 precipitates using the chemical deposition method
Authors: Engel S. , Thersleff T. , Hühne R. , Schultz L. , Holzapfel B. , Engel S. , Thersleff T. , Schultz L. , Holzapfel B. , Schultz L.
Published: March 2007

Both a high critical current density and a cost-competitive, easily upscalable procedure are among the most critical requirements for coated conductors. In this work, a low-cost method based on the trifluoroacetic acid process was used to prepare nanosized BaHfO3 particles inside a YBa2Cu3O7 film matrix. The inclusions have a perovskite structure and grow epitaxially in a cube-on-cube relationship. A drastically improved pinning force density and high irreversibility fields in the YBa2Cu3O7 layers were found and are discussed in respect to the Hf doping level in the precursor solutions, which resulted in an increased nanoinclusion content.
Noise properties of superconducting coplanar waveguide microwave resonators
Authors: Gao Jiansong , Zmuidzinas Jonas , Mazin Benjamin A. , LeDuc Henry G. , Day Peter K.
Published: March 2007

The authors have measured noise in thin-film superconducting coplanar waveguide resonators. This noise appears entirely as phase noise, equivalent to a jitter of the resonance frequency. In contrast, amplitude fluctuations are not observed at the sensitivity of their measurement. The ratio between the noise power in the phase and amplitude directions is large, in excess of 30dB. These results have important implications for resonant readouts of various devices such as detectors, amplifiers, and qubits. They suggest that the phase noise is due to two-level systems in dielectric materials.
Fabrication and characterization of microcavity lasers in rhodamine B doped SU8 using high energy proton beam
Authors: Venugopal Rao S. , Bettiol A. A. , Vishnubhatla K. C. , Bhaktha S. N. B. , Narayana Rao D. , Watt F.
Published: March 2007

The authors present their results on the characterization of individual dye-doped microcavity polymer lasers fabricated using a high energy proton beam. The lasers were fabricated in rhodamine B doped SU8 resist with a single exposure step followed by chemical processing. The resulting trapezoidal shaped cavities had dimensions of ∼250×250μm2. Physical characterization of these structures was performed using a scanning electron microscope while the optical characterization was carried out by recording the emission subsequent to pumping the lasers with 532nm, 6 nanosecond pulses. The authors observed intense, narrow emission near 624nm with the best emission linewidth full width at half maximum of ∼9nm and a threshold ∼150μJ∕mm2.
Standardising terrestrial invertebrate biomonitoring techniques across natural and agricultural systems
Authors: Neville Peter J. , Yen Alan L.
Published: March 2007

Invertebrate biomonitoring is often cited as a means to assess ecological sustainability. This paper surveys the use of sampling techniques to assess invertebrate abundance and diversity within natural and agricultural systems. Results found that fewer sampling techniques were used in natural systems, with the emphasis being placed on pitfall traps, than in agricultural systems, where multiple techniques and a wide range of techniques were used to document the abundance and distribution of invertebrates. A detailed examination of pitfall trap techniques demonstrated inconsistencies in use, leading to recommendations for standardised sampling regimes to document bioindicators in natural and agricultural systems.
Phylogenetic analysis and reclassification of the genus Priochirus Sharp (Coleoptera:Staphylinidae:Osoriinae)
Authors: Wu Jie , Zhou Hong-Zhang
Published: March 2007

The genus Priochirus Sharp (Coleoptera : Staphylinidae) is a rove beetle group with great variation in cephalic structures, especially the teeth on the frontal margin of head. In this paper, phylogenetic relationships among ten subgenera of the genus Priochirus sensu lato, and of Priochirus and other genera of the tribe Leptochirini are analysed. A cladistic analysis was conducted based on 62 characters of adult morphology. Results indicate that the genus Priochirus is not a monophyletic group and is divided into two lineages (called here Lineages I and II respectively). The subgenus Euleptarthrus Jakobson, which included three species-groups (japonicus, longicornis and malayanus), is shown to be polyphyletic. Lineage I corresponds with the Leiochirus + (Exochirus + Syncampsochirus) + (Eutriacanthus + (Plastus + (japonicus-group of Euleptarthrus + (Barychirus + Stigmatochirus)))) clade and forms a sister group to the genus Thoracochirus Bernhauer. Lineage II corresponds with the Priochirus, s. str. + (Cephalomerus + (longicornis- and malayanus-group of the Euleptarthrus)) clade. In addition, the analysis reveals sister relationships between representatives of Lineage I and the genus Thoracochirus. On the basis of phylogenetic inference, the genus Plastus Bernhauer, stat. nov. is proposed to include the subgenera of Lineage I and a new subgenus Sinumandibulus, subgen. nov., which is erected for the japonicus-group of the former subgenus Euleptarthrus. The genus Priochirus Sharp sensu novo is redefined to include the subgenera of Lineage II. Seven new species are described from China: Plastus (Sinumandibulus) curvaticornis, sp. nov. from Sichuan; Plastus (Sinumandibulus) recticornis, sp. nov. from Hubei; Priochirus (Euleptarthrus) amblyodontus, sp. nov. from Hunan; Priochirus (Euleptarthrus) baoxingensis, sp. nov. from Sichuan, Priochirus (Euleptarthrus) elongates, sp. nov. from Guizhou, Priochirus (Euleptarthrus) parvicornis, sp. nov. from Fujian and Priochirus (Euleptarthrus) oxygonus, sp. nov. from Hainan.
Developmental vision determines the reference frame for the multisensory control of action
Authors: Röder Brigitte , Kusmierek Anna , Spence Charles , Schicke Tobias
Published: March 2007

Both animal and human studies suggest that action goals are defined in external coordinates regardless of their sensory modality. The present study used an auditory-manual task to test whether the default use of such an external reference frame is innately determined or instead acquired during development because of the increasing dominance of vision over manual control. In Experiment I, congenitally blind, late blind, and age-matched sighted adults had to press a left or right response key depending on the bandwidth of pink noise bursts presented from either the left or right loudspeaker. Although the spatial location of the sounds was entirely task-irrelevant, all groups responded more efficiently with uncrossed hands when the sound was presented from the same side as the responding hand (“Simon effect”). This effect reversed with crossed hands only in the congenitally blind: They responded faster with the hand that was located contralateral to the sound source. In Experiment II, the instruction to the participants was changed: They now had to respond with the hand located next to the sound source. In contrast to Experiment I (“Simon-task”), this task required an explicit matching of the sound's location with the position of the responding hand. In Experiment II, the congenitally blind participants showed a significantly larger crossing deficit than both the sighted and late blind adults. This pattern of results implies that developmental vision induces the default use of an external coordinate frame for multisensory action control; this facilitates not only visual but also auditory–manual control.
Impaired NFAT nuclear translocation results in split exhaustion of virus-specific CD8
+
T cell functions during chronic viral infection
Authors: Agnellini Paola , Wolint Petra , Rehr Manuela , Cahenzli Julia , Karrer Urs , Oxenius Annette
Published: March 2007

In persistent viral infections, the host's immune system is challenged by the constant exposure to antigen, potentially causing continuous activation of CD8
+
T cells with subsequent immunopathology. Here we demonstrate, for experimental chronic lymphocytic choriomeningitis virus and human HIV infection, that upon prolonged
in vivo
exposure to antigen, TCR-triggered Ca
2+
flux, degranulation, and cytotoxicity are maintained on a cellular level, whereas cytokine production is severely impaired because of a selective defect in activation-induced NFAT nuclear translocation. During chronic infection, this differential regulation of pathways leading to diverse effector functions may allow CD8
+
T cells to sustain some degree of local viral control by direct cytotoxicity while limiting systemic immune pathology by silencing cytokine production.
Differential localization of coatomer complex isoforms within the Golgi apparatus
Authors: Moelleken Jörg , Malsam Jörg , Betts Matthew J. , Movafeghi Ali , Reckmann Ingeborg , Meissner Ingrid , Hellwig Andrea , Russell Robert B. , Söllner Thomas , Brügger Britta , Wieland Felix T.
Published: March 2007

Coatomer, the coat protein of coat protein complex (COP)I-vesicles, is a soluble protein complex made up of seven subunits, α-, β-, β′-, γ-, δ-, ε-, and ζ-COP. Higher eukaryotes have two paralogous versions of the γ- and ζ- subunits, termed γ1- and γ2-COP and ζ1- and ζ2-COP. Different combinations of these subunits are known to exist within coatomer complexes, and γ1/ζ1-, γ1/ζ2-, and γ2/ζ1-COP represent the major coatomer populations in mammals. The role of COPI vesicles in the early secretory pathway is the subject of considerable debate. To help to resolve this discussion, we used quantitative immunoelectron microscopy and found that significant localization differences for COPI-isoforms do exist, with a preference for γ1ζ1- and γ1ζ2-coatomer in the early Golgi apparatus and γ2ζ1-coatomer in the late Golgi apparatus. These differences suggest distinct functions for coatomer isoforms in a manner similar to clathrin/adaptor vesicles, where different adaptor proteins serve particular transport routes.
Impaired angiogenesis in aminopeptidase N-null mice
Authors: Rangel Roberto , Sun Yan , Guzman-Rojas Liliana , Ozawa Michael G. , Sun Jessica , Giordano Ricardo J. , Van Pelt Carolyn S. , Tinkey Peggy T. , Behringer Richard R. , Sidman Richard L. , Arap Wadih , Pasqualini Renata
Published: March 2007

Aminopeptidase N (APN, CD13; EC 3.4.11.2) is a transmembrane metalloprotease with several functions, depending on the cell type and tissue environment. In tumor vasculature, APN is overexpressed in the endothelium and promotes angiogenesis. However, there have been no reports ofin vivoinactivation of the APN gene to validate these findings. Here we evaluated, by targeted disruption of the APN gene, whether APN participates in blood vessel formation and function under normal conditions. Surprisingly, APN-null mice developed with no gross or histological abnormalities. Standard neurological, cardiovascular, metabolic, locomotor, and hematological studies revealed no alterations. Nonetheless, in oxygen-induced retinopathy experiments, APN-deficient mice had a marked and dose-dependent deficiency of the expected retinal neovascularization. Moreover, gelfoams embedded with growth factors failed to induce functional blood vessel formation in APN-null mice. These findings establish that APN-null mice develop normally without physiological alterations and can undergo physiological angiogenesis but show a severely impaired angiogenic response under pathological conditions. Finally, in addition to vascular biology research, APN-null mice may be useful reagents in other medical fields such as malignant, cardiovascular, immunological, or infectious diseases.
Defective DNA repair and increased genomic instability in Cernunnos-XLF-deficient murine ES cells
Authors: Zha Shan , Alt Frederick W. , Cheng Hwei-Ling , Brush James W. , Li Gang
Published: March 2007

Nonhomologous DNA end-joining (NHEJ) is a major pathway of DNA double-strand break (DSB) repair in mammalian cells, and it functions to join both specifically programmed DSBs that occur in the context of V(D)J recombination during early lymphocyte development as well as general DSBs that occur in all cells. Thus, defects in NHEJ impair V(D)J recombination and lead to general genomic instability. In human patients, mutations of Cernunnos-XLF (also called NHEJ1), a recently identified NHEJ factor, underlie certain severe combined immune deficiencies associated with defective V(D)J recombination and radiosensitivity. To characterize Cernunnos-XLF function in mouse cells, we used gene-targeted mutation to delete exons 4 and 5 from both copies of the
Cernunnos-XLF
gene in ES cell (referred to as Cer
Δ/Δ
ES cells). Analyses of Cer
Δ/Δ
ES cells showed that they produce no readily detectable Cernunnos-XLF protein. Based on transient V(D)J recombination assays, we find that Cer
Δ/Δ
ES cells have dramatic impairments in ability to form both V(D)J coding joins and joins of their flanking recombination signal sequences (RS joins). Cer
Δ/Δ
ES cells are highly sensitive to ionizing radiation and have intrinsic DNA DSB repair defects as measured by pulse field gel electrophoresis. Finally, the
Cernunnos-XLF
mutations led to increased spontaneous genomic instability, including translocations. We conclude that, in mice, Cernunnos-XLF is essential for normal NHEJ-mediated repair of DNA DSBs and that Cernunnos-XLF acts as a genomic caretaker to prevent genomic instability.
Gαi2-mediated signaling events in the endothelium are involved in controlling leukocyte extravasation
Authors: Pero Ralph S. , Borchers Michael T. , Spicher Karsten , Ochkur Sergei I. , Sikora Lyudmila , Rao Savita P. , Abdala-Valencia Hiam , O'Neill Katie R. , Shen Huahao , McGarry Michael P. , Lee Nancy A. , Cook-Mills Joan M. , Sriramarao P. , Simon Melvin I. , Birnbaumer Lutz , Lee James J.
Published: March 2007

The trafficking of leukocytes from the blood to sites of inflammation is the cumulative result of receptor-ligand-mediated signaling events associated with the leukocytes themselves as well as with the underlying vascular endothelium. Our data show that Gαisignaling pathways in the vascular endothelium regulate a critical step required for leukocyte diapedesis.In vivostudies using knockout mice demonstrated that a signaling event in a non-lymphohematopoietic compartment of the lung prevented the recruitment of proinflammatory leukocytes. Intravital microscopy showed that blockade was at the capillary endothelial surface andex vivostudies of leukocyte trafficking demonstrated that a Gαi-signaling event in endothelial cells was required for transmigration. Collectively, these data suggest that specific Gαi2-mediated signaling between endothelial cells and leukocytes is required for the extravasation of leukocytes and for tissue-specific accumulation.
FOXP3 interactions with histone acetyltransferase and class II histone deacetylases are required for repression
Authors: Li Bin , Samanta Arabinda , Song Xiaomin , Iacono Kathryn T. , Bembas Kathryn , Tao Ran , Basu Samik , Riley James L. , Hancock Wayne W. , Shen Yuan , Saouaf Sandra J. , Greene Mark I.
Published: March 2007

The forkhead family protein FOXP3 acts as a repressor of transcription and is both an essential and sufficient regulator of the development and function of regulatory T cells. The molecular mechanism by which FOXP3-mediated transcriptional repression occurs remains unclear. Here, we report that transcriptional repression by FOXP3 involves a histone acetyltransferase–deacetylase complex that includes histone acetyltransferase TIP60 (Tat-interactive protein, 60 kDa) and class II histone deacetylases HDAC7 and HDAC9. The N-terminal 106–190 aa of FOXP3 are required for TIP60–FOXP3, HDAC7–FOXP3 association, as well as for the transcriptional repression of FOXP3 via its forkhead domain. FOXP3 can be acetylated in primary human regulatory T cells, and TIP60 promotes FOXP3 acetylationin vivo. Overexpression of TIP60 but not its histone acetyltransferase-deficient mutant promotes, whereas knockdown of endogenous TIP60 relieved, FOXP3-mediated transcriptional repression. A minimum FOXP3 ensemble containing native TIP60 and HDAC7 is necessary for IL-2 production regulation in T cells. Moreover, FOXP3 association with HDAC9 is antagonized by T cell stimulation and can be restored by the protein deacetylation inhibitor trichostatin A, indicating a complex dynamic aspect of T suppressor cell regulation. These findings identify a previously uncharacterized complex-based mechanism by which FOXP3 actively mediates transcriptional repression.
Compact non-orientable hyperbolic surfaces with an extremal metric disc
Authors: Girondo Ernesto , Nakamura Gou
Published: March 2007

The size of a metric disc embedded in a compact non-orientable hyperbolic surface is bounded by some constant depending only on the genus

g
≥
3

g \ge 3

. We show that a surface of genus greater than six contains at most one metric disc of the largest radius. For the case

g
=
3

g=3

, we carry out an exhaustive study of all the extremal surfaces, finding the location of every extremal disc inside them.
R-Ras Regulates Exocytosis by Rgl2/Rlf-mediated Activation of RalA on Endosomes
Authors: Takaya Akiyuki , Kamio Takahiro , Masuda Michitaka , Mochizuki Naoki , Sawa Hirofumi , Sato Mami , Nagashima Kazuo , Mizutani Akiko , Matsuno Akira , Kiyokawa Etsuko , Matsuda Michiyuki
Published: March 2007

R-Ras is a Ras-family small GTPase that regulates various cellular functions such as apoptosis and cell adhesion. Here, we demonstrate a role of R-Ras in exocytosis. By the use of specific anti-R-Ras antibody, we found that R-Ras was enriched on both early and recycling endosomes in a wide range of cell lines. Using a fluorescence resonance energy transfer-based probe for R-Ras activity, R-Ras activity was found to be higher on endosomes than on the plasma membrane. This high R-Ras activity on the endosomes correlated with the accumulation of an R-Ras effector, the Rgl2/Rlf guanine nucleotide exchange factor for RalA, and also with high RalA activity. The essential role played by R-Ras in inducing high levels of RalA activity on the endosomes was evidenced by the short hairpin RNA (shRNA)-mediated suppression of R-Ras and by the expression of R-Ras GAP. In agreement with the reported role of RalA in exocytosis, the shRNA of either R-Ras or RalA was found to suppress calcium-triggered exocytosis in PC12 pheochromocytoma cells. These data revealed that R-Ras activates RalA on endosomes and that it thereby positively regulates exocytosis.
The Transcriptional Repressor Glis2 Is a Novel Binding Partner for p120 Catenin
Authors: Hosking Catherine Rose , Ulloa Fausto , Hogan Catherine , Ferber Emma C. , Figueroa Angélica , Gevaert Kris , Birchmeier Walter , Briscoe James , Fujita Yasuyuki
Published: March 2007

In epithelial cells, p120 catenin (p120) localizes at cell–cell contacts and regulates adhesive function of the cadherin complex. In addition, p120 has been reported to localize in the nucleus, although the nuclear function of p120 is not fully understood. Here, we report the identification of Gli-similar 2 (Glis2) as a novel binding protein for p120. Glis2 is a Krüppel-like transcriptional repressor with homology to the Gli family, but its physiological function has not been well characterized. In this study, we show that coexpression of Glis2 and Src induces nuclear translocation of p120. Furthermore, p120 induces the C-terminal cleavage of Glis2, and this cleavage is further enhanced by Src. The cleaved form of Glis2 loses one of its five zinc finger domains, but it is still able to bind DNA. Functional studies in chick neural tube indicate that full-length Glis2 can affect neuronal differentiation, whereas the cleaved form requires coexpression of p120 to have a similar effect. These data indicate that p120 has additional novel functions in the nucleus together with Glis2.
Specialized Roles of the Two Mitotic Cyclins in Somatic Cells: Cyclin A as an Activator of M Phase–promoting Factor
Authors: Fung Tsz Kan , Ma Hoi Tang , Poon Randy Y.C.
Published: March 2007

The role of cyclin B-CDC2 as M phase-promoting factor (MPF) is well established, but the precise functions of cyclin A remain a crucial outstanding issue. Here we show that down-regulation of cyclin A induces a G2 phase arrest through a checkpoint-independent inactivation of cyclin B-CDC2 by inhibitory phosphorylation. The phenotype is rescued by expressing cyclin A resistant to the RNA interference. In contrast, down-regulation of cyclin B disrupts mitosis without inactivating cyclin A-CDK, indicating that cyclin A-CDK acts upstream of cyclin B-CDC2. Even when ectopically expressed, cyclin A cannot replace cyclin B in driving mitosis, indicating the specific role of cyclin B as a component of MPF. Deregulation of WEE1, but not the PLK1-CDC25 axis, can override the arrest caused by cyclin A knockdown, suggesting that cyclin A-CDK may tip the balance of the cyclin B-CDC2 bistable system by initiating the inactivation of WEE1. These observations show that cyclin A cannot form MPF independent of cyclin B and underscore a critical role of cyclin A as a trigger for MPF activation.