bluuebunny/crossref_metadata_2025 huggingface dataset:
High-brightness, high-color-purity, white organic light-emitting diodes featuring multiple emission layers
Authors: Chang Mei-Ying , Wang Chien-Hsiung , Lin Shih-Chin , Chen Yi-Fan
Published: March 2009

We have developed high-brightness, high-color-purity, white organic light-emitting diodes featuring three emission layers: (i) the green light-emitting material 1,3,5-tris(1-pyrenyl)benzene (TPB3), (ii) the host material 1,4-bis(2,2-diphenylvinyl)biphenyl (DPVBi) doped with the blue dye di(4-fluorophenyl)amino-di(styryl)biphenyl (DSB), and (iii) tris(8-hydroxyquinoline)aluminum (Alq3) doped with the red dye 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). A device having the configuration indium tin oxide (1300 Å)/N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (500 Å)/TPB3 (200 Å)/DPVBi: 2 wt % DSB (150 Å)/Alq3: 2 wt % DCJTB (150 Å)/Alq3 (350 Å)/LiF (8 Å)/Al (2000 Å) exhibited a white emission with a maximum luminance at 15 V of 55 800 cd/m2, a maximum current efficiency of 4.06 cd/A at 13 V, a maximum power efficiency of 2.24 lm/W at 5 V, and a maximum external quantum efficiency of 2.45% at 5 V. The Commission Internationale de l’Eclairage coordinates of (0.33, 0.32) changed only slightly upon varying the potential from 9 to 13 V. We attribute the high brightness and color purity of the emitted white light to the high electroluminescence of the hosts and dopants, the relatively high efficiency of the energy transfer from the hosts to the dopants, and the high control over the thicknesses and dopant concentrations of the red-, green-, and blue-emitting layers, resulting in suitable numbers of partial excitons being generated in each of those three layers.
The chemical potential of light in fluorescent solar collectors
Authors: Meyer T. J. J. , Markvart T.
Published: March 2009

The energetic aspect, discussed by the means of the chemical potential, involved into the absorption and radiation processes occurring in the operation of fluorescent solar collectors is of interest in this publication. The chemical potential of the fluorescent light incident on the solar cell is characterized by studying the fluorescence spectrum emitted by a special type of fluorescent collector, where absorption and fluorescence take place in a liquid medium, in effect a liquid fluorescent collector. It is shown that photon reabsorption (known also as photon recycling) gradually brings the emitted photon flux into thermal equilibrium with the collector. The fluorescence photon distribution is then characterized by a specific temperature, obtained from the Kennard–Stepanov law, and a chemical potential given by the generalized Planck’s law. We find that the chemical potential of the fluorescent light incident on the solar cell is nearly equal to the thermodynamical limits imposed by a detailed balance argument. This equality indicates that nonradiative losses do not affect the chemical potential of the light escaping from the collector, a major benefit in comparison to simple semiconductor based solar cells where nonradiative losses significantly affect the open circuit voltage.
Adaptive spatially resolving detector for the extreme ultraviolet with absolute measuring capability
Authors: Benk Markus , Bergmann Klaus
Published: March 2009

A spatially resolving detector for the extreme ultraviolet (XUV) and soft x-ray spectral region is presented. Principle of operation is conversion of XUV radiation to visible light by a scintillator crystal. Luminescence is detected using charge coupled device camera and imaging optics. Single layer and multilayer coatings are applied to match the system to different spectral regions of interest. Field of view and spatial resolution can be adapted to the application. Calibration of the system enables to absolutely measure in-band radiation flux on the scintillator. The setup is designed for the characterization and optimization of XUV sources and XUV optical systems. Measurements, carried out to characterize the focus in a soft x-ray microscope, are presented as an application example.
Interplay between magnetic, electronic, and vibrational effects in monolayer Mn3O4 grown on Pd(100)
Authors: Franchini C. , Zabloudil J. , Podloucky R. , Allegretti F. , Li F. , Surnev S. , Netzer F. P.
Published: March 2009

The surface stabilized MnO(100)-like monolayer, characterized by a regular c(4×2) distribution of Mn vacancies, is studied by hybrid functionals and discussed in the light of available scanning tunneling microscopy and high-resolution electron energy loss spectroscopy data. We show that the use of hybrid functionals is crucial to account for the intermingled nature of magnetic interactions, electron localization, structural distortions, and surface phonons. The proposed Pd(100) supported Mn3O4 structure is excellently compatible with the experiments previously reported in literature.
Strain relaxation properties of InAsyP1−y metamorphic materials grown on InP substrates
Authors: Hudait Mantu K. , Lin Y. , Ringel S. A.
Published: March 2009

The strain relaxation mechanism and defect properties of compositionally step-graded InAsyP1−y buffers grown by molecular beam epitaxy on InP have been investigated. InAsP layers having lattice misfits ranging from 1% to 1.4% with respect to InP, as well as subsequently grown lattice matched In0.69Ga0.31As overlayers on the metamorphic buffers were explored on both (100) and 2° offcut (100) InP substrates. The metamorphic graded buffers revealed very efficient relaxation coupled with low threading dislocation densities on the order of (1–2)×106 cm−2 for the range of misfit values explored here. A detailed analysis via high resolution x-ray diffraction revealed that the strain relaxed symmetrically, with equivalent numbers of α and β dislocations, and to greater than 90% for all cases, regardless of substrate offcut. Further analysis showed the relaxation to always be glide limited in these materials when grown on a graded buffer compared to a single step layer. The threading dislocation density was observed by plan-view transmission electron microscopy to be constant for the range of misfit values studied here in the top layer of the graded structures, which is attributed to the very efficient use of residual dislocations and the dominance of dislocation glide over nucleation in these graded anion metamorphic buffers, suggesting great promise for metamorphic devices with lattice constants greater than that of InP to be enabled by InAsP metamorphic structures on InP.
Comment on “Exchange bias in the layered cobaltite Sr1.5Pr0.5CoO4” [J. Appl. Phys. 104, 023914 (2008)]
Authors: Geshev J.
Published: March 2009

Ang et al. [J. Appl. Phys. 104, 023914 (2008)] recently reported magnetization hysteresis loops shifted along both field and magnetization axes of layered cobaltites. The authors claimed that these shifts are characteristics of the exchange-bias phenomenon associated with coupling between ferromagnetic and spin-glass regions. The present comment affirms that their work shows no proofs supporting the observation of exchange bias since, due to lack of magnetic reversibility at high magnetic fields, all hysteresis loops displaced from the origin are actually minor loops naturally shifted along both axes.
Calculation of the transport and relaxation properties of methane. II. Thermal conductivity, thermomagnetic effects, volume viscosity, and nuclear-spin relaxation
Authors: Hellmann Robert , Bich Eckard , Vogel Eckhard , Dickinson Alan S. , Vesovic Velisa
Published: March 2009

Transport properties of pure methane have been calculated in the rigid-rotor approximation using the recently proposed intermolecular potential energy hypersurface [R. Hellmann et al., J. Chem. Phys. 128, 214303 (2008)] and the classical-trajectory method. Results are reported in the dilute-gas limit for the temperature range of 80–1500 K. The calculated thermal conductivity values are in very good agreement with the measured data and correlations. In the temperature range of 310–480 K the calculated values underestimate the best experimental data by 0.5%–1.0%. We suggest that the calculated values are more accurate, especially at low and high temperatures, than the currently available correlations based on the experimental data. Our results also agree well with measurements of thermal transpiration and of the thermomagnetic coefficients. We have shown that although the dominant contribution to the thermomagnetic coefficients comes from the Wjj¯ polarization in the spherical approximation, the contribution of a second polarization, Wj, cannot be neglected nor can a full description of the Wjj¯ polarization. The majority of the volume viscosity measurements around room temperature are consistent with the calculated values but this is not the case at high and low temperatures. However, for nuclear-spin relaxation the calculated values consistently exceed the measurements, which are mutually consistent within a few percent.
Multipole polarizabilities and long-range interactions of the fluorine atom
Authors: Zatsarinny O. , Bartschat K. , Mitroy J. , Zhang J.-Y.
Published: March 2009

The polarizabilities of the ground state of fluorine are determined by the box-based B-spline configuration-interaction method. The ground-state static and tensor polarizabilities are calculated as αd=3.49a03 and α2=0.303a03, respectively. The resulting excitation matrix elements are employed to compute the interatomic dispersion interactions for the HF and F2 molecules.
Phase-space surface hopping: Nonadiabatic dynamics in a superadiabatic basis
Authors: Shenvi Neil
Published: March 2009

In this paper, we construct a phase-space surface hopping algorithm for use in systems that exhibit strong nonadiabatic coupling. The algorithm is derived from a representation of the electronic basis which is a function of the nuclear phase-space coordinates rather than the nuclear position coordinates. This phase-space adiabatic basis can be understood in the context of Berry’s superadiabatic basis formalism as the first-order superadiabatic correction to the conventional position-space adiabatic basis. This superadiabatic representation leads to nuclear dynamics described not by Newton’s equations of motion but by generalized Hamilton’s equations of motion. The phase-space surface hopping algorithm captures physical effects that cannot be described by traditional algorithms. For a simple model problem, we show that phase-space surface hopping is more accurate than position-space surface hopping, especially when the nonadiabatic coupling is strong.
Tandem demodulation lock-in amplifier based on digital signal processor for dual-modulated spectroscopy
Authors: Qin Jianhuan , Huang Zhiming , Ge Yujian , Hou Yun , Chu Junhao
Published: March 2009

Dual-modulated spectroscopy is one of the most powerful methods in the measurement of modulation spectroscopy. Here we develop a tandem lock-in amplifier (LIA) based on digital signal processor to implement a novel algorithm of tandem demodulation. The theoretical analysis of demodulation algorithm is presented, and the implementation of this tandem LIA is described in detail. Compared to the traditional demodulating way with two LIAs in cascade, this tandem LIA eliminates the extra quantization error of redundant analog-to-digital and digital-to-analog conversions and removes the limitation to the time constant in the commercial LIA, hence lowers the requirement of frequency ratio in dual-modulated spectroscopy. The applications are given as examples in the photoreflectance (PR) measurements of GaAs (100) thin film and GaSb bulk material, respectively, at the different optical energy regions. The experimental results indicate that this tandem is well capable of PR spectra measurement with good PR lineshapes and reasonable signal noise ratio. A brief comparison of GaAs PR results between tandem LIA and two LIAs is made to prove the efficiency and advantages of the tandem LIA.
Nanoparticle-induced resonant tunneling behaviors in small molecule organic light-emitting devices
Authors: Zheng Tianhang , Choy Wallace C. H. , Sun Yuxiu
Published: March 2009

We report a hybrid nanoparticle/organic device with strong resonant tunneling behavior by introducing ligand-capped Ag nanoparticles between indium tin oxide and hole transport layer in small molecule organic light-emitting devices. The dependences of resonant tunneling current on the thickness of the organic layers are investigated. For the optimized device, a peak-to-valley current ratio as high as 4.5 and narrow peak width about 1.8 V are obtained. Combining with the analysis of current-voltage behavior, the mechanism based on the charge trapping effect of Ag nanoparticles is proposed to interpret the operation of the hybrid device. Finally, the emission characteristics of hybrid devices are also studied.
Giant positive magnetoresistance in Co@CoO nanoparticle arrays
Authors: Xing Hui , Kong Wenjie , Kim Chaehyun , Peng Sheng , Sun Shouheng , Xu Zhu-An , Zeng Hao
Published: March 2009

We report the magnetotransport properties of self-assembled Co@CoO nanoparticle arrays at temperatures below 100 K. Resistance shows thermally activated behavior that can be fitted by the general expression of R∝ exp{(T0/T)ν}. Efros–Shklovskii variable range hopping (ν=1/2) and simple activation (hard gap, ν=1) dominate the high and low temperature region, respectively, with a strongly temperature-dependent transition regime in between. A giant positive magnetoresistance (MR) of >1400% is observed at 10 K, which decreases with increasing temperature. The positive MR and most of its features can be explained by the Zeeman splitting of the localized states that suppresses the spin dependent hopping paths in the presence of on-site Coulomb repulsion.
Release melting of shock-loaded single crystal Cu
Authors: Xie Yun , Han Li-Bo , An Qi , Zheng Lianqing , Luo Sheng-Nian
Published: March 2009

We investigate the melting of shock-loaded single crystal Cu during release from solid shock states with molecular dynamics simulations. Cu is subjected to planar shock loading along ⟨100⟩ with a piston velocity (up) of 2–3 km s−1 into the plastic regime. For up≥2.5 km s−1 (above 170 GPa), release melting occurs continuously, and a sustained fully released state (liquid) can be achieved. The shocked crystal may undergo noticeable superheating before release melting. The release path can be regarded as an isentrope regardless of release melting.
Spectral statistics of the quenched normal modes of a network-forming molecular liquid
Authors: Matharoo Gurpreet S. , Razul M. Shajahan G. , Poole Peter H.
Published: March 2009

We evaluate the density of states of the quenched normal modes of ST2 water, and their statistical fluctuations, for a range of densities spanning three regimes of behavior of a hydrogen bonded liquid: a lower-density regime of random tetrahedral network formation, in the vicinity of a liquid-liquid critical point, and in a higher-density regime of fragile glass-forming behavior. For all cases we find that the fluctuations around the mean spectral densities obey the predictions of the Gaussian orthogonal ensemble of random matrix theory. We also measure the participation ratio of the normal modes across the entire frequency range, and find behavior consistent with the majority of modes being of an extended nature, rather than localized.
Optimizing the morphology of metal multilayer films for indium tin oxide (ITO)-free inverted organic solar cells
Authors: Meiss Jan , Riede Moritz K. , Leo Karl
Published: March 2009

We present metal multilayers consisting of aluminum and silver in different combinations serving as semitransparent top contacts for organic solar cells. Scanning electron microscopy, atomic force microscopy, and optical spectroscopy are used to illustrate how ultrathin Al interlayers influence the morphology of Ag layers evaporated on top of organic materials and how closed layers with good conductivity can be achieved. Multilayer metal contacts are used to fabricate top-illuminated small-molecule organic solar cells (SM-OSCs) which reach efficiencies comparable to conventional SM-OSCs that employ tin-doped indium oxide as electrode. It is shown that combinations of Al and Au lead to similar results, suggesting a similar mechanism for the influence on morphological development of both Ag and Au.
Suppression of magnon excitations in Co2MnSi Heusler alloy by Nd doping
Authors: Rajanikanth A. , Takahashi Y. K. , Hono K.
Published: March 2009

We have investigated the effect of Nd doping on the transport and magnetic properties of Co2MnSi. The substitution of 1.25 at. % Nd for Co results in a single L21 phase with a thin layer of Nd enriched phase grain boundaries. However, from resistivity measurements at low temperatures, the suppression of electron-magnon scattering was observed in the alloy with Nd enriched phase. The magnetic moment of Co2MnSi was 5.01μB, whereas that of Co1.95Nd0.05MnSi is 5.35μB, which indicates that the Nd rich phase couples ferromagnetically with the Co1.95Nd0.05MnSi phase. Moreover, point contact Andreev reflection measurements at 4.2 K have shown almost the same spin polarization with (P=0.59) and without Nd doping (P=0.58), indicating that Nd enrichment in the grain boundary does not hamper the spin polarization, but prevents the temperature dependent decay of transport properties.
Effect of thermal processing on silver thin films of varying thickness deposited on zinc oxide and indium tin oxide
Authors: Sivaramakrishnan K. , Ngo A. T. , Iyer S. , Alford T. L.
Published: March 2009

Silver films of varying thicknesses (25, 45, and 60 nm) were deposited on indium tin oxide (ITO) on silicon and zinc oxide (ZnO) on silicon. The films were annealed in vacuum for 1 h at different temperatures (300–650 °C). Four-point-probe measurements were used to determine the resistivity of the films. All films showed an abrupt change in resistivity beyond an onset temperature that varied with thickness. Rutherford backscattering spectrometry measurements revealed agglomeration of the Ag films upon annealing as being responsible for the resistivity change. X-ray pole figure analysis determined that the annealed films took on a preferential ⟨111⟩ texturing; however, the degree of texturing was significantly higher in Ag/ZnO/Si than in Ag/ITO/Si samples. This observation was accounted for by interface energy minimization. Atomic force microscopy (AFM) measurements revealed an increasing surface roughness of the annealed films with temperature. The resistivity behavior was explained by the counterbalancing effects of increasing crystallinity and surface roughness. Average surface roughness obtained from the AFM measurements were also used to model the agglomeration of Ag based on Ostwald ripening theory.
Separation of bulk and interface contributions to electroforming and resistive switching behavior of epitaxial Fe-doped SrTiO3
Authors: Menke T. , Meuffels P. , Dittmann R. , Szot K. , Waser R.
Published: March 2009

We succeeded in the separation of bulk and interface contributions to the electroforming and resistive switching behavior of Pt/STO(Fe)/Nb:STO devices by performing impedance spectroscopy. Two distinctive features observed in the impedance spectra could be assigned to the STO(Fe) bulk and to the depletion layer of the Pt/STO(Fe) Schottky contact. We attribute the resistance change during the dc forming process to a local bypassing of the depletion layer caused by oxygen effusion to the environment. By comparing the impedance spectra in the resistive “on” and “off” states, we propose that the resistance of the STO(Fe)/Nb:STO interface locally changes during the switching process.
Study of electronic structure and dynamics of interacting free radicals influenced by water
Authors: Du Shiyu , Francisco Joseph S. , Kais Sabre
Published: March 2009

We present a study of electronic structure, stability, and dynamics of interaction and recombination of free radicals such as HO2 and OH influenced by water. As simple model calculations, we performed ab initio and density functional calculations for the interaction of HO2 and OH in the presence of water cluster. Results indicate that a significant interaction, overcoming the repulsive Columbic barrier, occurs at a separation distance between the radicals of 5.7Å. This confirms early predictions of the minimum size of molecular dianions stable in the gas phase. It is well known that atomic dianions are unstable in the gas phase but molecular dianions are stable when the size of the molecule is larger than 5.7Å. Ab initio molecular dynamics calculations with Car–Parrinello scheme show that the reaction is very fast and occurs on a time scale of about 1.5ps. The difference in stability and dynamics of the interacting free radicals on singlet and triplet potential energy surfaces is also discussed.
Electronic structures of MoWOy− and MoWOy determined by anion photoelectron spectroscopy and DFT calculations
Authors: Mayhall Nicholas J. , Rothgeb David W. , Hossain Ekram , Raghavachari Krishnan , Jarrold Caroline Chick
Published: March 2009

The anion photoelectron spectra of MoWOy− (y=2–5) and density functional theory (DFT) calculations on MoWOy− and MoWOy are reported and compared to previous comparable studies on Mo2Oy−/Mo2Oy and W2Oy−/W2Oy. The property governing the structure of the lowest energy MoWOy anion and neutral clusters is the stronger W–O bond relative to the Mo–O bond, which results in the stabilization of structures in which the Mo center is in a much lower oxidation state than the W center. Anion PE spectra show a much larger change in structure between anion and neutral states than what was observed in the pure Mo2Oy− and W2Oy− spectra. DFT calculations show increased single-metal localization of spin with respect to the pure metal oxide clusters.
Nucleation mechanism of dislocation half-loop arrays in 4H-silicon carbide homoepitaxial layers
Authors: Zhang N. , Chen Y. , Zhang Y. , Dudley M. , Stahlbush R. E.
Published: March 2009

A model is presented for the formation mechanism of dislocation half-loop arrays formed during the homoepitaxial growth of 4H-SiC. The reorientation during glide of originally screw oriented threading segments of basal plane dislocation (BPD) renders them susceptible to conversion into sessile threading edge dislocations (TEDs), which subsequently pin the motion of the BPD. Continued glide during further growth enables parts of the mobile BPD to escape through the surface leaving arrays of half loops comprising two TEDs and a short BPD segment with significant edge component. The faulting behavior of the arrays under UV excitation is consistent with this model.
Ultralow dielectric losses in pyrochlore films of the PbO–MgO–Nb2O5–TiO2 system
Authors: Zhu X. H. , Defaÿ E. , Suhm A. , Fribourg-blanc E. , Aïd M.
Published: March 2009

( 1 − x ) Pb ( Mg 1 / 3 Nb 2 / 3 ) O 3 - x PbTiO 3 (PMNT) (with x=0.1) thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. A well-crystallized pyrochlore phase structure, which started to nucleate and grow at 450–500 °C, was formed in the PMNT thin films. These pyrochlore-structured PMNT thin films show ultralow dielectric losses with a typical loss tangent as low as 0.001, accompanied by a relatively high dielectric constant (εr=176). Such an extremely low dielectric loss, having never been obtained in thin films of perovskite PMNT, is probably ascribed to the specific structural feature of pyrochlore phase, chemically different from its perovskite counterpart, and ascribed to the avoidance of the polar domain-related losses.
Directional light extraction enhancement from GaN-based film-transferred photonic crystal light-emitting diodes
Authors: Lai Chun-Feng , Chao Chia-Hsin , Kuo Hao-Chung , Yen His-Hsuan , Lee Chia-En , Yeh Wen-Yung
Published: March 2009

Experimental investigation of the directionality in the far-field pattern and light extraction enhancement in collected cone were performed in GaN-based film-transferred photonic crystal (PhC) light-emitting diodes (FTLEDs). Angular-resolved measurement revealed directional profile and azimuthal anisotropy in the far-field distribution with guided modes extraction. Good agreement according to Bragg’s diffraction theory and free photon band structure were achieved. The light enhancement in PhC FTLEDs compared to non-PhC FTLEDs within the collection cone angle was obtained according to measured three-dimensional far-field patterns. In a ±20° collection cone, collected light was enhanced by a factor of ∼2.4 for the collimated PhC FTLED.
Reduction of the spin-torque critical current by partially canceling the free layer demagnetization field
Authors: Liu Luqiao , Moriyama Takahiro , Ralph D. C. , Buhrman R. A.
Published: March 2009

We significantly reduce the critical current Ic0 for the onset of spin torque switching of the free layer in nanometer-scale in-plane magnetized spin valves by partially cancelling its intrinsic demagnetization field through the utilization of Co/Ni multilayer free layers. The out-of-plane magnetic anisotropy arising from the Co/Ni interfaces reduces the effective demagnetization field (Heff) while not significantly affecting the thermal stability of the free layer. A zero-thermal-fluctuation critical current density Jc0∼2×106 A/cm2 is determined through both current ramp rate and nanosecond pulse measurements, and comparisons with large Heff control samples confirm that this strategy is efficient in substantially decreasing Ic0.
Determining ionizing radiation using sensors based on organic semiconducting material
Authors: Raval Harshil N. , Tiwari Shree Prakash , Navan Ramesh R. , Rao V. Ramgopal
Published: March 2009

The use of organic semiconducting material sensors as total dose radiation detectors is proposed, wherein the change in conductivity of an organic material is measured as a function of ionizing radiation dose. The simplest sensor is a resistor made using organic semiconductor. Furthermore, for achieving higher sensitivity, organic field effect transistor (OFET) is used as a sensor. A solution processed organic semiconductor resistor and an OFET were fabricated using poly 3-hexylthiophene (P3HT), a p-type organic semiconductor material. The devices are exposed to Cobalt-60 radiation for different total dose values. The changes in electrical characteristics indicate the potential of these devices as radiation sensors.
Src phosphorylation of RhoGDI2 regulates its metastasis suppressor function
Authors: Wu Yimin , Moissoglu Konstadinos , Wang Hong , Wang Xuejiao , Frierson Henry F. , Schwartz Martin A. , Theodorescu Dan
Published: March 2009

RhoGDI2 is a suppressor of metastasis in human bladder cancer. Although diminished RhoGDI2 expression in tumors is associated with decreased patient survival, normal expression in some metastatic tumors led us to wonder whether other mechanisms regulate RhoGDI2 function. Protein interaction analysis identified Src as a novel RhoGDI2 interaction partner. Gene expression profiling and immunohistochemistry of human tumors revealed that Src levels diminish as a function of bladder cancer stage. In addition, diminished Src levels and RhoGDI2 levels appear mutually exclusive in individual tumors, indicating that both genes are likely involved in the same signaling pathway leading to metastasis suppression. Studies confirmed that activated Src kinase binds and phosphorylates RhoGDI2 in vitro and vivo. Mutagenesis revealed that Tyr-153 and, to a lesser degree, Tyr-24 were the primary Src phosphorylation sites. Phosphorylation decreased the amount of Rac1 in RhoGDI2 complexes and increased RhoGDI2 association with cell membranes. Stable expression of phosphomimetic Tyr-153 RhoGDI2 in metastatic human bladder cancer cell lines had no effect on primary tumor growth but suppressed metastasis more potently than WT RhoGDI2. These data suggest that phosphorylation by Src enhances RhoGDI2 metastasis suppression and that loss of Src relieves metastasis suppression in tumor cells that maintain RhoGDI2 expression. Our findings also suggest caution in using Src inhibitors in the hope of delaying progression in patients with bladder cancer.
Modality effect in false recognition: Evidence from Chinese characters
Authors: Mao Wei Bin , Yang Zhi Liang , Wang Lin Song
Published: March 2009

Using the Deese/Roediger‐McDermott (DRM) false memory method, Smith and Hunt (1998) first reported the modality effect on false memory and showed that false recall from DRM lists was lower following visual study than following auditory study, which led to numerous studies on the mechanism of modality effect on false memory and provided many competing explanations. In the present experiment, the authors tested the modality effect in false recognition by using a blocked presentation condition and a random presentation condition. The present experiment found a modality effect different from the results of the previous research; namely, false recognition was shown to be greater following visual study than following auditory study, especially in the blocked presentation condition rather than in the random presentation condition. The authors argued that this reversed modality effect may be due to different encoding and processing characteristics between Chinese characters and English words. Compared with English words, visual graphemes of critical lures in Chinese lists are likely to be activated and encoded in participants' minds, thus it is more difficult for participants to discriminate later inner graphemes from those items presented in visual modality. Hence visual presentation could lead to more false recognition than auditory presentation in Chinese lists. The results in the present experiment demonstrated that semantic activation occurring during the encoding and retrieve phases played an important role in modality effect in false recognition, and our findings might be explained by the activation‐monitoring account.
Regulation of Mammary Gland Branching Morphogenesis by EphA2 Receptor Tyrosine Kinase
Authors: Vaught David , Chen Jin , Brantley-Sieders Dana M.
Published: March 2009

Eph receptor tyrosine kinases, including EphA2, are expressed in the mammary gland. However, their role in mammary gland development remains poorly understood. Using EphA2-deficient animals, we demonstrate for the first time that EphA2 receptor function is required for mammary epithelial growth and branching morphogenesis. Loss of EphA2 decreased penetration of mammary epithelium into fat pad, reduced epithelial proliferation, and inhibited epithelial branching. These defects appear to be intrinsic to loss of EphA2 in epithelium, as transplantation of EphA2-deficient mammary tissue into wild-type recipient stroma recapitulated these defects. In addition, HGF-induced mammary epithelial branching morphogenesis was significantly reduced in EphA2-deficient cells relative to wild-type cells, which correlated with elevated basal RhoA activity. Moreover, inhibition of ROCK kinase activity in EphA2-deficient mammary epithelium rescued branching defects in primary three-dimensional cultures. These results suggest that EphA2 receptor acts as a positive regulator in mammary gland development, functioning downstream of HGF to regulate branching through inhibition of RhoA. Together, these data demonstrate a positive role for EphA2 during normal mammary epithelial proliferation and branching morphogenesis.
ERp29 Restricts Connexin43 Oligomerization in the Endoplasmic Reticulum
Authors: Das Shamie , Smith Tekla D. , Sarma Jayasri Das , Ritzenthaler Jeffrey D. , Maza Jose , Kaplan Benjamin E. , Cunningham Leslie A. , Suaud Laurence , Hubbard Michael J. , Rubenstein Ronald C. , Koval Michael
Published: March 2009

Connexin43 (Cx43) is a gap junction protein that forms multimeric channels that enable intercellular communication through the direct transfer of signals and metabolites. Although most multimeric protein complexes form in the endoplasmic reticulum (ER), Cx43 seems to exit from the ER as monomers and subsequently oligomerizes in the Golgi complex. This suggests that one or more protein chaperones inhibit premature Cx43 oligomerization in the ER. Here, we provide evidence that an ER-localized, 29-kDa thioredoxin-family protein (ERp29) regulates Cx43 trafficking and function. Interfering with ERp29 function destabilized monomeric Cx43 oligomerization in the ER, caused increased Cx43 accumulation in the Golgi apparatus, reduced transport of Cx43 to the plasma membrane, and inhibited gap junctional communication. ERp29 also formed a specific complex with monomeric Cx43. Together, this supports a new role for ERp29 as a chaperone that helps stabilize monomeric Cx43 to enable oligomerization to occur in the Golgi apparatus.
Larval zebrafish rapidly sense the water flow of a predator's strike
Authors: McHenry M.J. , Feitl K.E. , Strother J.A. , Van Trump W.J.
Published: March 2009

Larval fishes have a remarkable ability to sense and evade the feeding strike of a predator fish with a rapid escape manoeuvre. Although the neuromuscular control of this behaviour is well studied, it is not clear what stimulus allows a larva to sense a predator. Here we show that this escape response is triggered by the water flow created during a predator's strike. Using a novel device, the impulse chamber, zebrafish (Danio rerio) larvae were exposed to this accelerating flow with high repeatability. Larvae responded to this stimulus with an escape response having a latency (mode=13–15 ms) that was fast enough to respond to predators. This flow was detected by the lateral line system, which includes mechanosensory hair cells within the skin. Pharmacologically ablating these cells caused the escape response to diminish, but then recover as the hair cells regenerated. These findings demonstrate that the lateral line system plays a role in predator evasion at this vulnerable stage of growth in fishes.
Sexual conflict and reproductive isolation in flies
Authors: Hosken D.J. , Martin O.Y. , Wigby S. , Chapman T. , Hodgson D.J.
Published: March 2009

Sexual conflict is predicted to generate more rapid reproductive isolation between larger populations. While there is some empirical support for this, the data are inconsistent and, additionally, there has been criticism of some of the evidence. Here we reanalyse two experimental-evolution datasets using an isolation index widely applied in the speciation literature. We find evidence for reproductive isolation through sexual conflict inSepsis cynipsea, but not inDrosophila melanogaster, and this occurred to a greater degree in larger populations, which is consistent with previous findings.
Temperature-responsive intelligent interfaces for biomolecular separation and cell sheet engineering
Authors: Nagase Kenichi , Kobayashi Jun , Okano Teruo
Published: March 2009

Temperature-responsive intelligent surfaces, prepared by the modification of an interface with poly(N-isopropylacrylamide) and its derivatives, have been used for biomedical applications. Such surfaces exhibit temperature-responsive hydrophilic/hydrophobic alterations with external temperature changes, which, in turn, result in thermally modulated interactions with biomolecules and cells. In this review, we focus on the application of these intelligent surfaces to chromatographic separation and cell cultures. Chromatographic separations using several types of intelligent surfaces are mentioned briefly, and various effects related to the separation of bioactive compounds are discussed, including wettability, copolymer composition and graft polymer architecture. Similarly, we also summarize temperature-responsive cell culture substrates that allow the recovery of confluent cell monolayers as contiguous living cell sheets for tissue-engineering applications. The key factors in temperature-dependent cell adhesion/detachment control are discussed from the viewpoint of grafting temperature-responsive polymers, and new methodologies for effective cell sheet culturing and the construction of thick tissues are summarized.
A mathematical model of wound healing and subsequent scarring
Authors: Cumming B. D. , McElwain D. L. S. , Upton Z.
Published: March 2009

Wound healing is a complex process involving the delicate interaction between elements that vary widely in nature and size scales, from the nanometre level, such as molecules, to cells measured in micrometres, and fibres with width and length measured on both scales. Hybrid approaches, where each species is represented by a model on an appropriate size scale, have received attention recently. In this study, we provide a review of earlier work on such hybrid models of wound healing. General models for each of the element types involved in dermal wound healing used in this research are described: cells, modelled as discrete individuals; chemicals, modelled as continua; and fibres, modelled with a novel tensorial representation. Techniques for integrating such disparate models are outlined. A six-species model (fibrin, collagen, macrophages, fibroblasts, transforming growth factor-β (TGF-β) and tissue plasminogen activator) of dermal wound healing is presented. The role of the cytokine TGF-β in the healing cascade is investigated using the model, along with its role in the degree of scarring in the healed tissue.
Going beyond histology. Synchrotron micro-computed tomography as a methodology for biological tissue characterization: from tissue morphology to individual cells
Authors: Zehbe Rolf , Haibel Astrid , Riesemeier Heinrich , Gross Ulrich , Kirkpatrick C. James , Schubert Helmut , Brochhausen Christoph
Published: March 2009

Current light microscopic methods such as serial sectioning, confocal microscopy or multiphoton microscopy are severely limited in their ability to analyse rather opaque biological structures in three dimensions, while electron optical methods offer either a good three-dimensional topographic visualization (scanning electron microscopy) or high-resolution imaging of very thin samples (transmission electron microscopy). However, sample preparation commonly results in a significant alteration and the destruction of the three-dimensional integrity of the specimen. Depending on the selected photon energy, the interaction between X-rays and biological matter provides semi-transparency of the specimen, allowing penetration of even large specimens. Based on the projection-slice theorem, angular projections can be used for tomographic imaging. This method is well developed in medical and materials science for structure sizes down to several micrometres and is considered as being non-destructive. Achieving a spatial and structural resolution that is sufficient for the imaging of cells inside biological tissues is difficult due to several experimental conditions. A major problem that cannot be resolved with conventional X-ray sources are the low differences in density and absorption contrast of cells and the surrounding tissue. Therefore, X-ray monochromatization coupled with a sufficiently high photon flux and coherent beam properties are key requirements and currently only possible with synchrotron-produced X-rays. In this study, we report on the three-dimensional morphological characterization of articular cartilage using synchrotron-generated X-rays demonstrating the spatial distribution of single cells inside the tissue and their quantification, while comparing our findings to conventional histological techniques.
An improved free surface capturing method based on Cartesian cut cell mesh for water-entry and -exit problems
Authors: Wang Wenhua , Wang Yanying
Published: March 2009

The free surface capturing method based on Cartesian cut cell mesh is extended to the water-entry and -exit fields with body–fluid interaction. The governing equations are the incompressible Euler equations for a variable density fluid system with a free surface, which is treated as a contact discontinuity. The solver is based on the artificial compressibility method with a dual time-stepping technique for time advancing and the finite-volume method with a high-resolution Godunov-type upwind scheme on spatial discretization. For solving the numerical problem caused by the extension, the acceleration term of body is introduced for the new pressure condition of moving solid boundary, and the exact Riemann solution is used to calculate the flux of the solid boundary. In addition, a new solution of gradients based on the least-squares idea is presented for simply calculating the gradients. Finally, test cases show that the present method is available and can be successfully applied in various water-entry and -exit phenomena.
The role of nocturnal vision in mate choice: females prefer conspicuous males in the European tree frog (
Hyla arborea
)
Authors: Gomez Doris , Richardson Christina , Lengagne Thierry , Plenet Sandrine , Joly Pierre , Léna Jean-Paul , Théry Marc
Published: March 2009

Nocturnal frog species rely extensively on vocalization for reproduction. But recent studies provide evidence for an important, though long overlooked, role of visual communication. In many species, calling males exhibit a conspicuous pulsing vocal sac, a signal bearing visually important dynamic components. Here, we investigate female preference for male vocal sac coloration—a question hitherto unexplored—and male colour pattern in the European tree frog (
Hyla arborea
). Under nocturnal conditions, we conducted two-choice experiments involving video playbacks of calling males with identical calls and showing various naturally encountered colour signals, differing in their chromatic and brightness components. We adjusted video colours to match the frogs' visual perception, a crucial aspect not considered in previous experiments. Females prefer males with a colourful sac and a pronounced flank stripe. Both signals probably enhance male conspicuousness and facilitate detection and localization by females. This study provides the first experimental evidence of a preference for specific vocal sac spectral properties in a nocturnal anuran species. Vocal sac coloration is based on carotenoids and may convey information about male quality worthwhile for females to assess. The informative content of the flank stripe remains to be demonstrated.
Spatiotemporal Profiling of Starch Biosynthesis and Degradation in the Developing Barley Grain
Authors: Radchuk Volodymyr V. , Borisjuk Ludmilla , Sreenivasulu Nese , Merx Kathleen , Mock Hans-Peter , Rolletschek Hardy , Wobus Ulrich , Weschke Winfriede
Published: March 2009

Barley (Hordeum vulgare) grains synthesize starch as the main storage compound. However, some starch is degraded already during caryopsis development. We studied temporal and spatial expression patterns of genes coding for enzymes of starch synthesis and degradation. These profiles coupled with measurements of selected enzyme activities and metabolites have allowed us to propose a role for starch degradation in maternal and filial tissues of developing grains. Early maternal pericarp functions as a major short-term starch storage tissue, possibly ensuring sink strength of the young caryopsis. Gene expression patterns and enzyme activities suggest two different pathways for starch degradation in maternal tissues. One pathway possibly occurs via α-amylases 1 and 4 and β-amylase 1 in pericarp, nucellus, and nucellar projection, tissues that undergo programmed cell death. Another pathway is deducted for living pericarp and chlorenchyma cells, where transient starch breakdown correlates with expression of chloroplast-localized β-amylases 5, 6, and 7, glucan, water dikinase 1, phosphoglucan, water dikinase, isoamylase 3, and disproportionating enzyme. The suite of genes involved in starch synthesis in filial starchy endosperm is much more complex than in pericarp and involves several endosperm-specific genes. Transient starch turnover occurs in transfer cells, ensuring the maintenance of sink strength in filial tissues and the reallocation of sugars into more proximal regions of the starchy endosperm. Starch is temporally accumulated also in aleurone cells, where it is degraded during the seed filling period, to be replaced by storage proteins and lipids.
Roles of Morphology, Anatomy, and Aquaporins in Determining Contrasting Hydraulic Behavior of Roots
Authors: Bramley Helen , Turner Neil C. , Turner David W. , Tyerman Stephen D.
Published: March 2009

The contrasting hydraulic properties of wheat (Triticum aestivum), narrow-leafed lupin (Lupinus angustifolius), and yellow lupin (Lupinus luteus) roots were identified by integrating measurements of water flow across different structural levels of organization with anatomy and modeling. Anatomy played a major role in root hydraulics, influencing axial conductance (L  ax) and the distribution of water uptake along the root, with a more localized role for aquaporins (AQPs). Lupin roots had greater L  ax than wheat roots, due to greater xylem development. L  ax and root hydraulic conductance (L  r) were related to each other, such that both variables increased with distance from the root tip in lupin roots. L  ax and L  r were constant with distance from the tip in wheat roots. Despite these contrasting behaviors, the hydraulic conductivity of root cells (Lp  c) was similar for all species and increased from the root surface toward the endodermis. Lp  c was largely controlled by AQPs, as demonstrated by dramatic reductions in Lp  c by the AQP blocker mercury. Modeling the root as a series of concentric, cylindrical membranes, and the inhibition of AQP activity at the root level, indicated that water flow in lupin roots occurred primarily through the apoplast, without crossing membranes and without the involvement of AQPs. In contrast, water flow across wheat roots crossed mercury-sensitive AQPs in the endodermis, which significantly influenced L  r. This study demonstrates the importance of examining root morphology and anatomy in assessing the role of AQPs in root hydraulics.
Evolutionary History and Stress Regulation of Plant Receptor-Like Kinase/Pelle Genes
Authors: Lehti-Shiu Melissa D. , Zou Cheng , Hanada Kousuke , Shiu Shin-Han
Published: March 2009

Receptor-Like Kinase (RLK)/Pelle genes play roles ranging from growth regulation to defense response, and the dramatic expansion of this family has been postulated to be crucial for plant-specific adaptations. Despite this, little is known about the history of or the factors that contributed to the dramatic expansion of this gene family. In this study, we show that expansion coincided with the establishment of land plants and that RLK/Pelle subfamilies were established early in land plant evolution. The RLK/Pelle family expanded at a significantly higher rate than other kinases, due in large part to expansion of a few subfamilies by tandem duplication. Interestingly, these subfamilies tend to have members with known roles in defense response, suggesting that their rapid expansion was likely a consequence of adaptation to fast-evolving pathogens. Arabidopsis (Arabidopsis thaliana) expression data support the importance of RLK/Pelles in biotic stress response. We found that hundreds of RLK/Pelles are up-regulated by biotic stress. Furthermore, stress responsiveness is correlated with the degree of tandem duplication in RLK/Pelle subfamilies. Our findings suggest a link between stress response and tandem duplication and provide an explanation for why a large proportion of the RLK/Pelle gene family is found in tandem repeats. In addition, our findings provide a useful framework for potentially predicting RLK/Pelle stress functions based on knowledge of expansion pattern and duplication mechanism. Finally, we propose that the detection of highly variable molecular patterns associated with specific pathogens/parasites is the main reason for the up-regulation of hundreds of RLK/Pelles under biotic stress.