bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrostatic pressure effects on electron states in GaAs–(Ga,Al)As double quantum rings
Authors: Culchac F. J. , Porras-Montenegro N. , Latgé A.
Published: May 2009

Here we address a theoretical analysis of the effects of applied hydrostatic pressure on electron states in concentric GaAs–(Ga,Al)As double quantum rings, under axial magnetic fields. Emphasis is put on the dependence of such effects on the system geometry confinement described within a hard potential model and following an effective-mass approximation. The energy of the ground and excited electronic states were found to decrease with the applied hydrostatic pressure, due mainly to an effective reduction in the barrier potential confinement. Also, while the increase in the magnetic field opens the electron states degeneracy with different angular momenta, the increase in the applied hydrostatic pressure does not alter significantly the energy of these states. For both symmetric and asymmetric double quantum rings, one found that the electron-heavy hole transition energies augment with the applied hydrostatic pressure, mainly due to the increase in the GaAs gap.
Frequency response of acoustic-assisted Ni–Mn–Ga ferromagnetic-shape-memory-alloy actuator
Authors: Techapiesancharoenkij Ratchatee , Kostamo Jari , Allen Samuel M. , O’Handley Robert C.
Published: May 2009

A prototype of Ni–Mn–Ga based ferromagnetic-shape-memory-alloy (FSMA) actuator was designed and built; an acoustic-assist technique was applied to the actuator to enhance its performance. A piezoelectric stack actuator was attached to the Ni–Mn–Ga sample to generate acoustic energy to enhance twin-boundary mobility and, hence, reduce the magnetic threshold field required for activating twin-boundary motion. The dynamic response of the acoustic-assist FSMA actuator was measured up to 1 kHz actuation. The acoustic assistance improves the actuator performance by increasing the reversible magnetic-field-induced strain (MFIS) by up to 100% (increase from 0.017 to 0.03 at 10 Hz) for drive frequencies below 150 Hz. For frequencies above 150 Hz, the acoustic-assist effect becomes negligible and the resonant characteristic of the actuator takes over the actuator response. Even though the acoustic assist does not improve the actuation at high frequencies, the MFIS output of 5% can be obtained at the resonant frequency of 450 Hz without acoustic assistance. The FSMA actuator is shown to be ideal for applications that require large strain at a specific high frequency
Axial buckling of multiwall carbon nanotubes with heterogeneous boundaries
Authors: Tong F. M. , Wang C. Y. , Adhikari S.
Published: May 2009

The finite element method has been employed to study the effects of different boundary conditions on the axial buckling of multiwall carbon nanotubes (MWCNTs). Unlike previous works, both homogeneous and heterogeneous end constraints are considered for the constituent tubes of various MWCNTs comprising shell-type (i.e., the length-to-diameter ratio L/D<10), beam-type (i.e., L/D>10), and the two different types of constituent tubes. The results show that clamping the individual tubes of simply supported or free MWCNTs exerts a variety of influences on their buckling behaviors depending on the type of the MWCNTs, the position, and the number of the clamped tubes. Clamping the outermost tube can enhance the critical buckling strain up to four times of its original value and can shift the buckling modes of those MWCNTs consisting both shell- and beam-type tubes. In contrast, little difference can be observed when simply supported ends of MWCNTs are replaced by free ends or vice versa. Explicit buckling mode shapes obtained using the finite element method for various physically realistic cases have been shown in the paper.
Highly selective electroplated nickel mask for lithium niobate dry etching
Authors: Benchabane Sarah , Robert Laurent , Rauch Jean-Yves , Khelif Abdelkrim , Laude Vincent
Published: May 2009

A sulfur hexafluoride based reactive ion etching process allowing to etch several micron deep holes with diameters of the order of a few microns in lithium niobate is reported. Etching of deep structures with aspect ratios up to 1.5 was made possible through the use of an electroplated nickel mask exhibiting a selectivity as high as 20 with respect to lithium niobate. Several crystallograpic orientations were investigated, although particular interest was paid to Y-axis oriented substrates. Photoresist as well as metal masks were also tested and their selectivity was compared. The influence of process parameters such as applied rf power or operating pressure on the sidewall slope angle of the etched patterns was investigated. The technique has been successfully applied to the fabrication of phononic crystals consisting of periodical arrays of 9 μm diameter, 10 μm deep holes, with a 10 μm period, and presenting sidewall angles as high as 73° etched in Y-axis oriented lithium niobate.
Voltage response of current carrying Y–Ba–Cu–O tapes to alternating magnetic fields
Authors: Uksusman A. , Wolfus Y. , Friedman A. , Shaulov A. , Yeshurun Y.
Published: May 2009

We present a study of the alternating voltage generated in YBa2Cu3O7−δ (YBCO) tapes in response to sinusoidal magnetic fields applied perpendicular to the tapes. The alternating field induces a strongly nonlinear voltage response with various waveforms that drastically change upon changing the bias current, the bias magnetic field, and the amplitude and frequency of the alternating field. In particular, one observes transitions from waveforms including double peaks to waveforms including a single peak in one cycle of the alternating field. We attribute these effects to modulation of the vortex pinning energy by both the alternating magnetic field and the alternating current induced by it. Our model allows separation of these two contributions to the total response, thus revealing the dominating source of the nonlinear response and its accompanied steady component at different experimental conditions.
Experimental study of surface-wave-assisted microwave transmission through a single subwavelength slit
Authors: Wang Liang , Cao Jin-Xiang , Lv You , Liu Lei , Niu Tian-Ye , Du Yin-Chang
Published: May 2009

In this study, we made a systematic investigation in the enhanced transmission of X-band microwaves through a single subwavelength slit aperture surrounded by periodic grooves in metallic aluminum plates. The influence of the grooves’ number, width, and depth on the transmission spectra was examined. By tuning these geometrical parameters, the transmission enhancement could be maximally optimized. The transmission spectra at s-polarization was also measured and compared to those at p-polarization. It is shown that the extraordinarily enhanced transmission at p-polarization is associated with the surface waves of Brewster–Zenneck modes on the metal-air interface. Our experimental results will be helpful to the control of the propagation of electromagnetic waves in the microwave regime.
Nonlinear optical properties of Si nanocrystals embedded in SiO2 prepared by a cosputtering method
Authors: Imakita Kenji , Ito Masahiko , Fujii Minoru , Hayashi Shinji
Published: May 2009

Nonlinear optical properties of Si nanocrystals (Si-ncs) doped SiO2 prepared by a cosputtering method were studied by z-scan technique in a femtosecond regime at around 1.6 eV. The nonlinear refractive index (n2) and nonlinear absorption coefficient (β) were strongly enhanced compared to those of bulk Si and found to be about ∼2×10−13 cm2/W and ∼0.8 cm/GW, respectively. In the photon energy region from 1.48 to 1.65 eV, the n2 and β spectra followed the absorption spectra and no enhancement was observed in the band-edge photoluminescence region. In the diameter range of 2.7–5.4 nm, the size dependence of n2 coincided well with that calculated by a pseudopotential approach, suggesting that the discrete energy states of Si-ncs are responsible for the observed enhanced optical nonlinearity.
Second-order Møller–Plesset perturbation theory applied to extended systems. I. Within the projector-augmented-wave formalism using a plane wave basis set
Authors: Marsman M. , Grüneis A. , Paier J. , Kresse G.
Published: May 2009

We present an implementation of the canonical formulation of second-order Møller–Plesset (MP2) perturbation theory within the projector-augmented-wave method under periodic boundary conditions using a plane wave basis set. To demonstrate the accuracy of our approach we show that our result for the atomization energy of a LiH molecule at the Hartree-Fock+MP2 level is in excellent agreement with well converged Gaussian-type-orbital calculations. To establish the feasibility of employing MP2 perturbation theory in its canonical form to systems that are periodic in three dimensions we calculated the cohesive energy of bulk LiH.
Phase transition of [Cn-mim][PF6] under high pressure up to 1.0 GPa
Authors: Su Lei , Li Liangbin , Hu Yun , Yuan Chaosheng , Shao Chunguang , Hong Shiming
Published: May 2009

Behavior of the phase transition of an ionic liquid, [Cn-mim][PF6], has been investigated under pressures up to 1.0 GPa by using a high-pressure differential thermal analysis (DTA) apparatus. The T versus P phase diagrams of [BMIM][PF6] and [EMIM][PF6] are constructed. The DTA curve of [BMIM][PF6] shows one endothermal valley in heating course at each given pressure, which indicates that a simple phase transition from solid to liquid has taken place under high pressure and that the melting point is an increase function of pressure. However, the DTA curve of [EMIM][PF6] shows two endothermal valleys in the heating course within the tested pressure range, implying that there may exist another phase. After treatment of [EMIM][PF6] at different temperatures under high pressure, the structures of the recovered samples are also investigated by wide-angle x-ray scattering. By considering the results above, it indicates that another crystalline phase exists between the solid and liquid of [EMIM][PF6].
Controlled formation of colloidal structures by an alternating electric field and its mechanisms
Authors: Zhang Ke-Qin , Liu Xiang Y.
Published: May 2009

A detailed phase diagram, revealing a variety of processes including various colloidal structures of monodisperse charged colloidal particles from the colloidal chains, vortex rings, three-dimensional aggregation to a two-dimensional crystal under different frequencies, and strengths of an alternating electric field, is obtained for the first time. The occurrence of different colloidal structures is driven by the electrohydrodynamic interaction and induced dipolar interaction near the polarized layer on the electrode. This simple colloidal system can be employed as a model system to understand the complex phase behavior of the assembly/aggregation of the nanoparticles and biomacromolecules under external perturbation. Detailed phase diagram provides vital guidance for the fabrication of desired colloidal structures with single-particle resolution, which could be employed as a sort of templates for nanolithography or imprinting. Moreover, the sensitivity of the electrohydrodynamic interaction on the particle size and the dependence of the convective flow on the frequency and strength could be utilized in microfluidic devices for manipulating nanoparticles, biomacromolecules, and vesicles.
Inertia dominated drop collisions. II. An analytical solution of the Navier–Stokes equations for a spreading viscous film
Authors: Roisman Ilia V.
Published: May 2009

This study is devoted to a theoretical description of an unsteady laminar viscous flow in a spreading film of a Newtonian fluid. Such flow is generated by normal drop impact onto a dry substrate with high Weber and Reynolds numbers. An analytical self-similar solution for the viscous flow in the spreading drop is obtained which satisfies the full Navier–Stokes equations. The characteristic thickness of a boundary layer developed near the wall uniformly increases as a square root of time. An expression for the thickness of the boundary layer is used for the estimation of the residual film thickness formed by normal drop impact and the maximum spreading diameter. The theoretical predictions agree well with the existing experimental data. A possible explanation of the mechanism of formation of an uprising liquid sheet leading to splash is also proposed.
Field-induced transition from parallel to perpendicular parametric pumping for a microstrip transducer
Authors: Neumann T. , Serga A. A. , Vasyuchka V. I. , Hillebrands B.
Published: May 2009

Microstrip transducers used for the excitation of spin waves in magnetic films possess two characteristic properties: high spatial localization of the microwave magnetic field and the presence of field components parallel and perpendicular to the bias field. Here, the effects of these features on the process of parametric pumping are presented. By microwave measurements of the spin-wave instability threshold a transition from parallel pumping to perpendicular pumping at the critical field with the minimal threshold is observed. This transition is accompanied by a sharp threshold increase above the critical field due to the spatial confinement of the pump region.
Comment on “The single-wall carbon nanotube waveguides and excitation of their σ+π plasmons by an electron beam” [Phys. Plasmas 16, 022108 (2009)]
Authors: Moradi Afshin
Published: May 2009

In a recent article [M. Nejati, C. Javaherian, B. Shokri, and B. Jazi, Phys. Plasmas 16, 022108 (2009)], Nejati et al. studied the propagation of plasma wave in the single-wall carbon nanotubes in the presence of the electron beam and showed that the frequency of the σ+π plasma wave strongly depends on the nanotube radius in the short-wavelength region. Here we derive the correct form of the dispersion relation for the transverse magnetic wave in the system and show that the frequency of the plasma wave is quite sensitive to the radius of the tube in the long-wavelength limit.
Entropy change and effect of magnetic field on martensitic transformation in a metamagnetic Ni–Co–Mn–In shape memory alloy
Authors: Kustov S. , Corró M. L. , Pons J. , Cesari E.
Published: May 2009

We studied the entropy change and the shift of the martensitic transformation temperatures with magnetic field in samples of a polycrystalline Ni–Co–Mn–In alloy having different degrees of long-range atomic order due to different heat treatments. We found, for the samples of the same composition, strong variations of the entropy change with the degree of atomic order, mediated by the difference between the Curie and martensitic transformation temperatures. Calculations of the field-induced shift of the transformation using data of entropy variations show good agreement with experimental results.
Effective control of ion fluxes over large areas by magnetic fields: From narrow beams to highly uniform fluxes
Authors: Baranov O. , Romanov M. , Ostrikov Kostya (Ken)
Published: May 2009

An effective control of the ion current distribution over large-area (up to 103 cm2) substrates with the magnetic fields of a complex structure by using two additional magnetic coils installed under the substrate exposed to vacuum arc plasmas is demonstrated. When the magnetic field generated by the additional coils is aligned with the direction of the magnetic field generated by the guiding and focusing coils of the vacuum arc source, a narrow ion density distribution with the maximum current density 117 A m−2 is achieved. When one of the additional coils is set to generate the magnetic field of the opposite direction, an area almost uniform over the substrate of 103 cm2 ion current distribution with the mean value of 45 A m−2 is achieved. Our findings suggest that the system with the vacuum arc source and two additional magnetic coils can be effectively used for the effective, high throughput, and highly controllable plasma processing.
Resonance energy transfer: When a dipole fails
Authors: Andrews David L. , Leeder Jamie M.
Published: May 2009

The Coulombic coupling of electric dipole (E1) transition moments is the most commonly studied and widely operative mechanism for energy migration in multichromophore systems. However a significant number of exceptions exist, in which donor decay and/or acceptor excitation processes are E1-forbidden. The alternative transfer mechanisms that can apply in such cases include roles for higher multipole transitions, exciton- or phonon-assisted interactions, and non-Coulombic interactions based on electron exchange. A quantum electrodynamical formulation provides a rigorous basis to assess the first of these, specifically addressing the relative significance of higher multipole contributions to the process of energy transfer in donor-acceptor systems where electric dipole transitions are precluded by symmetry. Working within the near-zone limit, where donor-acceptor separations are small in comparison to the chromophore scale, the analysis highlights the contributions of both electric quadrupole-electric quadrupole (E2-E2) coupling and the seldom considered second-order electric dipole-electric dipole (E12-E12) coupling. For both forms of interaction, experimentally meaningful rate equations are secured by the use of orientational averaging, and the mechanisms are analyzed with reference to systems in which E1-forbidden transitions are commonly reported.
Distribution of the decay rate constants of individual excited probes surrounded by randomly distributed quenchers
Authors: Hilczer Maria , Tachiya M.
Published: May 2009

Recent development in single molecule spectroscopy enabled us to measure the decay kinetics of individual excited probes surrounded by randomly distributed quenchers. Since the distribution of quenchers around individual excited probes change from one excited probe to another, the quenching rate constant also changes from one excited probe to another. We calculated the distribution of quenching rate constants of individual excited probes theoretically and analyzed the observed distributions of quenching rate constants, which were recently measured by Lupton et al. [J. Phys. Chem. C 111, 11511 (2007)] by using single molecule spectroscopy.
Dramatic efficiency improvement in phosphorescent organic light-emitting diodes with ultraviolet-ozone treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)
Authors: Benor Amare , Takizawa Shin-ya , Chen Ping , Pérez-Bolívar César , Anzenbacher Pavel
Published: May 2009

The treatment of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films by ultraviolet (UV) light-ozone to improve device efficiency was investigated utilizing two simple phosphorescent organic light-emitting diodes (PHOLEDs) architectures. The maximum external quantum efficiency in the first device increased from 3.5% for the untreated anode to 10.5%, while in the second device comprising an exciton blocking layer increased from 15.8% to 18.5%. The time dependence of the UV-ozone treatment on the performance was studied. The dramatic improvement in the PHOLED performance is attributed to the change in the PEDOT:PSS work function and more balanced charge injection, suggesting promising easy-to-do method to improve PHOLED performance.
Deformation mechanisms during large strain deformation of nanocrystalline nickel
Authors: Gurao N. P. , Suwas Satyam
Published: May 2009

In this letter, a conclusive evidence of the operation of planar slip along with grain boundary mediated mechanisms has been reported during large strain deformation of nanocrystalline nickel. Dislocation annihilation mechanism such as mechanical recovery has been found to play an important role during the course of deformation. The evidences rely on x-ray based techniques, such as dislocation density determination and crystallographic texture measurement as well as microstructural observation by electron microscopy. The characteristic texture evolution in this case is an indication of normal slip mediated plasticity in nanocrystalline nickel.
Cross-phase modulation between lasers in a tunnel ionizing gas
Authors: Liu C. S. , Pathak Vishwa Bandhu , Tripathi V. K.
Published: May 2009

The phase modulation of a low power long pulse probe laser beam in a rapidly tunnel ionizing gas (helium) under a relativistic short pulse laser is investigated. The relativistic pulse creates a fast increasing plasma density at its front, far ahead of the intensity peak. The probe pulse sees these changes as modulation in its phase and undergoes large frequency upshift. The spectral content of the blueshifted potion of the probe pulse is large when its intensity peak commoves with the ionization front. There are two ionization front created by first and second ionizations, and the separation between the two increases as laser propagates through the gas. The rate of density variation by first and second ionizations, however, is fairly the same and varies little as the spot size of the laser beam increases up to three times its initial value. The ionization front velocity, as well as the upshift in probe pulse frequency, is bigger for sharper laser pulse.
The intrinsic domain wall resistance of Fe films with a periodic domain pattern
Authors: Vandezande Stijn , Van Haesendonck Chris , Temst Kristiaan
Published: May 2009

The intrinsic domain wall resistance (DWR) of 180° Néel walls in a polycrystalline Fe film is determined by creating a periodic domain pattern, obtained by locally inducing exchange bias. After field cooling, the coercivity is spatially modulated, resulting in periodic 180° domain walls. To determine the intrinsic DWR, a rotating magnetic field is used to reversibly create and annihilate the domain walls. After correcting for the anisotropic magnetoresistance, the extracted DWR is positive.
Enhanced quantum efficiency of Ge solar cells by a two-dimensional photonic crystal nanostructured surface
Authors: Prieto I. , Galiana B. , Postigo P. A. , Algora C. , Martínez L. J. , Rey-Stolle I.
Published: May 2009

A single-junction germanium solar cell with a photonic crystal nanostructured surface has been developed. The solar cell comprises a Ge p-n junction and an InGaP window layer. The InGaP window layer has been nanopatterned with an extended photonic crystal structure consisting on a triangular lattice of holes with submicronic sizes. Enhancements of the external quantum efficiency of 22% for a wide range of wavelengths and up to a 46% for specific wavelengths have been measured, which implies an increase in photocurrent between 11% and 22%. A clear correlation with the area of photonic crystal patterned has been observed.
The relationship of current transfer ratio and input light wavelengths in the organic photocoupler
Authors: Wang Zhongqiang , Deng Jiachun , Wu Xiaoming , Jing Na , Hu Ziyang , Cheng Xiaoman , Hua Yulin , Wei Jun , Yin Shougen
Published: May 2009

In this article we have fabricated an organic photocoupler with different wavelengths of organic light-emitting diodes as light source (input unit) and photodiode based on poly(3-hexylthiophene):1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)-C61 as detector (output unit). The relationship between the current transfer ratio (CTR) and input light wavelengths was studied. The output current and CTR are increasing with the input light wavelengths decreasing from 624 to 470 nm, and the CTR value with 470 nm input wavelength is 3–12 times higher than that with other longer input wavelengths, indicating that the short wavelength input light generates photocurrent and CTR efficiently.
High performance In0.7Ga0.3As metal-oxide-semiconductor transistors with mobility >4400 cm2/V s using InP barrier layer
Authors: Zhao Han , Chen Yen-Ting , Yum Jung Hwan , Wang Yanzhen , Goel Niti , Lee Jack C.
Published: May 2009

We have investigated device performance for In0.7Ga0.3As and In0.53Ga0.47As metal-oxide-semiconductor transistors (MOSFETs) with and without InP barrier layer using atomic layer deposited Al2O3 gate dielectric. InP barrier layer was found to provide higher transconductance for both In0.7Ga0.3As and In0.53Ga0.47As MOSFETs, especially for In0.7Ga0.3As. In0.7Ga0.3As MOSFETs with InP barrier layer show much higher transconductance and lower subthreshold swing than other MOSFETs studied. These In0.7Ga0.3As MOSFETs exhibit high drive current of 98 mA/mm (L=20 μm), subthreshold swing of 106 mV/decade and maximum effective channel mobility of 4402 cm2/V s.
Thermal tuning of phononic bandstructure in ferroelectric ceramic/epoxy phononic crystal
Authors: Jim K. L. , Leung C. W. , Lau S. T. , Choy S. H. , Chan H. L. W.
Published: May 2009

Thermal tuning of phononic bandgaps in megahertz range was demonstrated in ferroelectric ceramic-based phononic crystal structure. Temperature variation across ferroelectric phase transition, accompanied by substantial changes in acoustic velocities, leads to a shift in the phononic bandstructure of a two-dimensional (Ba,Sr)TiO3/epoxy composite sample over a range of 10 °C. Experimental results are supported by modelings based on plane-wave expansion calculations. The high tunability of phononic bandstructure is advantageous for active control of ultrasound transmissions.
Dopamine-induced proliferation of adult neural precursor cells in the mammalian subventricular zone is mediated through EGF
Authors: O'Keeffe Gráinne C. , Tyers Pam , Aarsland Dag , Dalley Jeffrey W. , Barker Roger A. , Caldwell Maeve A.
Published: May 2009

A reduction in dopaminergic innervation of the subventricular zone (SVZ) is responsible for the impaired proliferation of its resident precursor cells in this region in Parkinson's disease (PD). Here, we show that this effect involves EGF, but not FGF2. In particular, we demonstrate that dopamine increases the proliferation of SVZ-derived cells by releasing EGF in a PKC-dependent manner in vitro and that activation of the EGF receptor (EGFR) is required for this effect. We also show that dopamine selectively expands the GFAP
+
multipotent stem cell population in vitro by promoting their self-renewal. Furthermore, in vivo dopamine depletion leads to a decrease in precursor cell proliferation in the SVZ concomitant with a reduction in local EGF production, which is reversed through the administration of the dopamine precursor levodopa (
l
-DOPA). Finally, we show that EGFR
+
cells are depleted in the SVZ of human PD patients compared with age-matched controls. We have therefore demonstrated a unique role for EGF as a mediator of dopamine-induced precursor cell proliferation in the SVZ, which has potential implications for future therapies in PD.
Brain systems mediating semantic and syntactic processing in deaf native signers: Biological invariance and modality specificity
Authors: Capek Cheryl M. , Grossi Giordana , Newman Aaron J. , McBurney Susan L. , Corina David , Roeder Brigitte , Neville Helen J.
Published: May 2009

Studies of written and spoken language suggest that nonidentical brain networks support semantic and syntactic processing. Event-related brain potential (ERP) studies of spoken and written languages show that semantic anomalies elicit a posterior bilateral N400, whereas syntactic anomalies elicit a left anterior negativity, followed by a broadly distributed late positivity. The present study assessed whether these ERP indicators index the activity of language systems specific for the processing of aural-oral language or if they index neural systems underlying any natural language, including sign language. The syntax of a signed language is mediated through space. Thus the question arises of whether the comprehension of a signed language requires neural systems specific for this kind of code. Deaf native users of American Sign Language (ASL) were presented signed sentences that were either correct or that contained either a semantic or a syntactic error (1 of 2 types of verb agreement errors). ASL sentences were presented at the natural rate of signing, while the electroencephalogram was recorded. As predicted on the basis of earlier studies, an N400 was elicited by semantic violations. In addition, signed syntactic violations elicited an early frontal negativity and a later posterior positivity. Crucially, the distribution of the anterior negativity varied as a function of the type of syntactic violation, suggesting a unique involvement of spatial processing in signed syntax. Together, these findings suggest that biological constraints and experience shape the development of neural systems important for language.
The
Drosophila
DPP signal is produced by cleavage of its proprotein at evolutionary diversified furin-recognition sites
Authors: Künnapuu Jaana , Björkgren Ida , Shimmi Osamu
Published: May 2009

Maturation of bone morphogenetic proteins (BMPs) requires cleavage of their precursor proteins by furin-type proprotein convertases. Here, we find that cleavage sites of the BMP2/4/decapentaplegic (DPP) subfamily have been evolutionary diversified and can be categorized into 4 different types. Cnidaria BMP2/4/DPP is considered to be a prototype containing only 1 furin site. Bilateria BMP2/4/DPP acquired an additional cleavage site with either the combination of minimal–optimal or optimal–optimal furin sites. DPPs belonging to Diptera, such as
Drosophila
and mosquito, and Lepidoptera of silkworm contain a third cleavage site between the 2 optimal furin sites. We studied how the 3 furin sites (FSI–III) of
Drosophila
DPP coordinate maturation of ligands and contribute to signals in vivo. Combining mutational analysis of furin-recognition sites and RNAi experiments, we found that the
Drosophila
DPP precursor is initially cleaved at an upstream furin-recognition site (FSII), with consequent cleavages at 2 furin sites (FSI and FSIII). Both Dfurin1 and Dfurin2 are involved in the processing of DPP proproteins. Biochemical and genetic analyses using cleavage mutants of DPP suggest the first cleavage at FSII to be critical and sufficient for long-range DPP signaling. Our data suggest that the
Drosophila
DPP precursor is cleaved in a different manner from vertebrate BMP4 even though they are functional orthologs. This indicates that the furin-cleavage sites in BMP2/4/DPP precursors are tolerant to mutations acquired through evolution and have adapted to different systems in diversified species.
Controlling the fluorescence of ordinary oxazine dyes for single-molecule switching and superresolution microscopy
Authors: Vogelsang Jan , Cordes Thorben , Forthmann Carsten , Steinhauer Christian , Tinnefeld Philip
Published: May 2009

Fluorescent molecular switches have widespread potential for use as sensors, material applications in electro-optical data storages and displays, and superresolution fluorescence microscopy. We demonstrate that adjustment of fluorophore properties and environmental conditions allows the use of ordinary fluorescent dyes as efficient single-molecule switches that report sensitively on their local redox condition. Adding or removing reductant or oxidant, switches the fluorescence of oxazine dyes between stable fluorescent and nonfluorescent states. At low oxygen concentrations, the off-state that we ascribe to a radical anion is thermally stable with a lifetime in the minutes range. The molecular switches show a remarkable reliability with intriguing fatigue resistance at the single-molecule level: Depending on the switching rate, between 400 and 3,000 switching cycles are observed before irreversible photodestruction occurs. A detailed picture of the underlying photoinduced and redox reactions is elaborated. In the presence of both reductant and oxidant, continuous switching is manifested by “blinking” with independently controllable on- and off-state lifetimes in both deoxygenated and oxygenated environments. This “continuous switching mode” is advantageously used for imaging actin filament and actin filament bundles in fixed cells with subdiffraction-limited resolution.
IL-9 induces differentiation of T
H
17 cells and enhances function of FoxP3
+
natural regulatory T cells
Authors: Elyaman Wassim , Bradshaw Elizabeth M. , Uyttenhove Catherine , Dardalhon Valérie , Awasthi Amit , Imitola Jaime , Bettelli Estelle , Oukka Mohamed , van Snick Jacques , Renauld Jean-Christophe , Kuchroo Vijay K. , Khoury Samia J.
Published: May 2009

The development of T helper (T
H
)17 and regulatory T (T
reg
) cells is reciprocally regulated by cytokines. Transforming growth factor (TGF)-β alone induces FoxP3
+
T
reg
cells, but together with IL-6 or IL-21 induces T
H
17 cells. Here we demonstrate that IL-9 is a key molecule that affects differentiation of T
H
17 cells and T
reg
function. IL-9 predominantly produced by T
H
17 cells, synergizes with TGF-β1 to differentiate naïve CD4
+
T cells into T
H
17 cells, while IL-9 secretion by T
H
17 cells is regulated by IL-23. Interestingly, IL-9 enhances the suppressive functions of FoxP3
+
CD4
+
T
reg
cells in vitro, and absence of IL-9 signaling weakens the suppressive activity of nT
regs
in vivo, leading to an increase in effector cells and worsening of experimental autoimmune encephalomyelitis. The mechanism of IL-9 effects on T
H
17 and T
regs
is through activation of STAT3 and STAT5 signaling. Our findings highlight a role of IL-9 as a regulator of pathogenic versus protective mechanisms of immune responses.
Experience sampling during fMRI reveals default network and executive system contributions to mind wandering
Authors: Christoff Kalina , Gordon Alan M. , Smallwood Jonathan , Smith Rachelle , Schooler Jonathan W.
Published: May 2009

Although mind wandering occupies a large proportion of our waking life, its neural basis and relation to ongoing behavior remain controversial. We report an fMRI study that used experience sampling to provide an online measure of mind wandering during a concurrent task. Analyses focused on the interval of time immediately preceding experience sampling probes demonstrate activation of default network regions during mind wandering, a finding consistent with theoretical accounts of default network functions. Activation in medial prefrontal default network regions was observed both in association with subjective self-reports of mind wandering and an independent behavioral measure (performance errors on the concurrent task). In addition to default network activation, mind wandering was associated with executive network recruitment, a finding predicted by behavioral theories of off-task thought and its relation to executive resources. Finally, neural recruitment in both default and executive network regions was strongest when subjects were unaware of their own mind wandering, suggesting that mind wandering is most pronounced when it lacks meta-awareness. The observed parallel recruitment of executive and default network regions—two brain systems that so far have been assumed to work in opposition—suggests that mind wandering may evoke a unique mental state that may allow otherwise opposing networks to work in cooperation. The ability of this study to reveal a number of crucial aspects of the neural recruitment associated with mind wandering underscores the value of combining subjective self-reports with online measures of brain function for advancing our understanding of the neurophenomenology of subjective experience.
ERIS, an endoplasmic reticulum IFN stimulator, activates innate immune signaling through dimerization
Authors: Sun Wenxiang , Li Yang , Chen Lu , Chen Huihui , You Fuping , Zhou Xiang , Zhou Yi , Zhai Zhonghe , Chen Danying , Jiang Zhengfan
Published: May 2009

We report here the identification and characterization of a protein, ERIS, an endoplasmic reticulum (ER) IFN stimulator, which is a strong type I IFN stimulator and plays a pivotal role in response to both non–self-cytosolic RNA and dsDNA. ERIS (also known as STING or MITA) resided exclusively on ER membrane. The ER retention/retrieval sequence RIR was found to be critical to retain the protein on ER membrane and to maintain its integrity. ERIS was dimerized on innate immune challenges. Coumermycin-induced ERIS dimerization led to strong and fast IFN induction, suggesting that dimerization of ERIS was critical for self-activation and subsequent downstream signaling.
Implications for complex cognition from the hafting of tools with compound adhesives in the Middle Stone Age, South Africa
Authors: Wadley Lyn , Hodgskiss Tamaryn , Grant Michael
Published: May 2009

Compound adhesives made from red ochre mixed with plant gum were used in the Middle Stone Age (MSA), South Africa. Replications reported here suggest that early artisans did not merely color their glues red; they deliberately effected physical transformations involving chemical changes from acidic to less acidic pH, dehydration of the adhesive near wood fires, and changes to mechanical workability and electrostatic forces. Some of the steps required for making compound adhesive seem impossible without multitasking and abstract thought. This ability suggests overlap between the cognitive abilities of modern people and people in the MSA. Our multidisciplinary analysis provides a new way to recognize complex cognition in the MSA without necessarily invoking the concept of symbolism.
Thalidomide induces limb defects by preventing angiogenic outgrowth during early limb formation
Authors: Therapontos Christina , Erskine Lynda , Gardner Erin R. , Figg William D. , Vargesson Neil
Published: May 2009

Thalidomide is a potent teratogen that induces a range of birth defects, most commonly of the developing limbs. The mechanisms underpinning the teratogenic effects of thalidomide are unclear. Here we demonstrate that loss of immature blood vessels is the primary cause of thalidomide-induced teratogenesis and provide an explanation for its action at the cell biological level. Antiangiogenic but not antiinflammatory metabolites/analogues of thalidomide induce chick limb defects. Both in vitro and in vivo, outgrowth and remodeling of more mature blood vessels is blocked temporarily, whereas newly formed, rapidly developing, angiogenic vessels are lost. Such vessel loss occurs upstream of changes in limb morphogenesis and gene expression and, depending on the timing of drug application, results in either embryonic death or developmental defects. These results explain both the timing and relative tissue specificity of thalidomide embryopathy and have significant implications for its use as a therapeutic agent.
Genetic and pharmacological inhibition of JNK ameliorates hypoxia-induced retinopathy through interference with VEGF expression
Authors: Guma Monica , Rius Jordi , Duong-Polk Karen X. , Haddad Gabriel G. , Lindsey James D. , Karin Michael
Published: May 2009

Many ocular pathologies, including retinopathy of prematurity (ROP), diabetic retinopathy, and age-related macular degeneration, result in vision loss because of aberrant neoangiogenesis. A common feature of these conditions is the presence of hypoxic areas and overexpression of the proangiogenic vascular endothelial growth factor (VEGF). The prevailing current treatment, laser ablation of the retina, is destructive and only partially effective. Preventive and less destructive therapies are much more desirable. Here, we show that mice lacking c-Jun N-terminal kinase 1 (JNK1) exhibit reduced pathological angiogenesis and lower levels of retinal VEGF production in a murine model of ROP. We found that hypoxia induces JNK activation and regulates VEGF expression by enhancing the binding of phospho-c-Jun to the VEGF promoter. Intravitreal injection of a specific JNK inhibitor decreases retinal VEGF expression and reduces pathological retinal neovascularization without obvious side effects. These results strongly suggest that JNK1 plays a key role in retinal neoangiogenesis and that it represents a new pharmacological target for treatment of diseases where excessive neoangiogenesis is the underlying pathology.
Analysis of genomic diversity in Mexican Mestizo populations to develop genomic medicine in Mexico
Authors: Silva-Zolezzi Irma , Hidalgo-Miranda Alfredo , Estrada-Gil Jesus , Fernandez-Lopez Juan Carlos , Uribe-Figueroa Laura , Contreras Alejandra , Balam-Ortiz Eros , del Bosque-Plata Laura , Velazquez-Fernandez David , Lara Cesar , Goya Rodrigo , Hernandez-Lemus Enrique , Davila Carlos , Barrientos Eduardo , March Santiago , Jimenez-Sanchez Gerardo
Published: May 2009

Mexico is developing the basis for genomic medicine to improve healthcare of its population. The extensive study of genetic diversity and linkage disequilibrium structure of different populations has made it possible to develop tagging and imputation strategies to comprehensively analyze common genetic variation in association studies of complex diseases. We assessed the benefit of a Mexican haplotype map to improve identification of genes related to common diseases in the Mexican population. We evaluated genetic diversity, linkage disequilibrium patterns, and extent of haplotype sharing using genomewide data from Mexican Mestizos from regions with different histories of admixture and particular population dynamics. Ancestry was evaluated by including 1 Mexican Amerindian group and data from the HapMap. Our results provide evidence of genetic differences between Mexican subpopulations that should be considered in the design and analysis of association studies of complex diseases. In addition, these results support the notion that a haplotype map of the Mexican Mestizo population can reduce the number of tag SNPs required to characterize common genetic variation in this population. This is one of the first genomewide genotyping efforts of a recently admixed population in Latin America.
Cyclodepsipeptide toxin promotes the degradation of Hsp90 client proteins through chaperone-mediated autophagy
Authors: Shen Shensi , Zhang Pengtao , Lovchik Martin A. , Li Ying , Tang Liuya , Chen Zhimin , Zeng Rong , Ma Dawei , Yuan Junying , Yu Qiang
Published: May 2009

Promoting the degradation of Hsp90 client proteins by inhibiting Hsp90, an important protein chaperone, has been shown to be a promising new anticancer strategy. In this study, we show that an oxazoline analogue of apratoxin A (oz-apraA), a cyclodepsipeptide isolated from a marine cyanobacterium, promotes the degradation of Hsp90 clients through chaperone-mediated autophagy (CMA). We identify a KFERQ-like motif as a conserved pentapeptide sequence in the kinase domain of epidermal growth factor receptor (EGFR) necessary for recognition as a CMA substrate. Mutation of this motif prevents EGFR degradation by CMA and promotes the degradation of EGFR through the proteasomal pathway in oz-apraA–treated cells. Oz-apraA binds to Hsc70/Hsp70. We propose that apratoxin A inhibits Hsp90 function by stabilizing the interaction of Hsp90 client proteins with Hsc70/Hsp70 and thus prevents their interactions with Hsp90. Our study provides the first examples for the ability of CMA to mediate degradation of membrane receptors and cross talks of CMA and proteasomal degradation mechanisms.
Segregation of sphingolipids and sterols during formation of secretory vesicles at the trans-Golgi network
Authors: Klemm Robin W. , Ejsing Christer S. , Surma Michal A. , Kaiser Hermann-Josef , Gerl Mathias J. , Sampaio Julio L. , de Robillard Quentin , Ferguson Charles , Proszynski Tomasz J. , Shevchenko Andrej , Simons Kai
Published: May 2009

The trans-Golgi network (TGN) is the major sorting station in the secretory pathway of all eukaryotic cells. How the TGN sorts proteins and lipids to generate the enrichment of sphingolipids and sterols at the plasma membrane is poorly understood. To address this fundamental question in membrane trafficking, we devised an immunoisolation procedure for specific recovery of post-Golgi secretory vesicles transporting a transmembrane raft protein from the TGN to the cell surface in the yeast Saccharomyces cerevisiae. Using a novel quantitative shotgun lipidomics approach, we could demonstrate that TGN sorting selectively enriched ergosterol and sphingolipid species in the immunoisolated secretory vesicles. This finding, for the first time, indicates that the TGN exhibits the capacity to sort membrane lipids. Furthermore, the observation that the immunoisolated vesicles exhibited a higher membrane order than the late Golgi membrane, as measured by C-Laurdan spectrophotometry, strongly suggests that lipid rafts play a role in the TGN-sorting machinery.
Regulation of glutamate receptor subunit availability by microRNAs
Authors: Karr Julie , Vagin Vasia , Chen Kaiyun , Ganesan Subhashree , Olenkina Oxana , Gvozdev Vladimir , Featherstone David E.
Published: May 2009

The efficacy of synaptic transmission depends, to a large extent, on postsynaptic receptor abundance. The molecular mechanisms controlling receptor abundance are poorly understood. We tested whether abundance of postsynaptic glutamate receptors (GluRs) in Drosophila neuromuscular junctions is controlled by microRNAs, and provide evidence that it is. We show here that postsynaptic knockdown of dicer-1, the endoribonuclease necessary for microRNA synthesis, leads to large increases in postsynaptic GluR subunit messenger RNA and protein. Specifically, we measured increases in GluRIIA and GluRIIB but not GluRIIC. Further, knockout of MiR-284, a microRNA predicted to bind to GluRIIA and GluRIIB but not GluRIIC, increases expression of GluRIIA and GluRIIB but not GluRIIC proportional to the number of predicted binding sites in each transcript. Most of the de-repressed GluR protein, however, does not appear to be incorporated into functional receptors, and only minor changes in synaptic strength are observed, which suggests that microRNAs primarily regulate Drosophila receptor subunit composition rather than overall receptor abundance or synaptic strength.
Milk fat globule epidermal growth factor–8 blockade triggers tumor destruction through coordinated cell-autonomous and immune-mediated mechanisms
Authors: Jinushi Masahisa , Sato Marimo , Kanamoto Akira , Itoh Akihiko , Nagai Shigenori , Koyasu Shigeo , Dranoff Glenn , Tahara Hideaki
Published: May 2009

Carcinogenesis reflects the dynamic interplay of transformed cells and normal host elements, but cancer treatments typically target each compartment separately. Within the tumor microenvironment, the secreted protein milk fat globule epidermal growth factor–8 (MFG-E8) stimulates disease progression through coordinated αvβ3 integrin signaling in tumor and host cells. MFG-E8 enhances tumor cell survival, invasion, and angiogenesis, and contributes to local immune suppression. We show that systemic MFG-E8 blockade cooperates with cytotoxic chemotherapy, molecularly targeted therapy, and radiation therapy to induce destruction of various types of established mouse tumors. The combination treatments evoke extensive tumor cell apoptosis that is coupled to efficient dendritic cell cross-presentation of dying tumor cells. This linkage engenders potent antitumor effector T cells but inhibits FoxP3+ T reg cells, thereby achieving long-term protective immunity. Collectively, these findings suggest that systemic MFG-E8 blockade might intensify the antitumor activities of existing therapeutic regimens through coordinated cell-autonomous and immune-mediated mechanisms.