bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between structural style, overpressures, and modern stress, Baram Delta Province, northwest Borneo
Authors: Morley Christopher K. , Tingay Mark , Hillis Richard , King Rosalind
Published: September 2008

The Baram Delta differs from most large (passive margin) deltas because of its location on an active postcollisional margin. Structural style and evolution is influenced both by gravity‐driven deformation and regional stress. Key structural features of the delta include (1) late development of the toe fold and thrust belt (latest Miocene‐Recent) with respect to 17 Ma recent development of growth faults on the shelf; (2) a narrow active region of extension on the outer shelf upper slope; (3) absence of well‐developed shale diapirs; and (4) inner shelf onshore folding, thrusting, and growth fault inversion. Overpressure magnitude, type, distribution, and principal stress orientation and magnitude for the shelfal area were determined from well data. The inner shelf onshore area of inversion displays decreasing vertical stress gradient offshore and pronounced transfer of disequilibrium compaction overpressure from the Setap (shale) Formation into the overlying Belait Formation. This loss of overpressure permitted partial recoupling of once detached deltaic sediments with basement. Evidence for partial recoupling includes decreasing minimum horizontal stress gradient from NE (area of maximum inversion) to SW across the shelf and coast‐perpendicular inner shelf Shmax directions appropriate for inversion, but with stress magnitudes insufficient to cause deformation. These observations constrain models to explain why toe fold‐thrust belt activity occurred relatively late, while inner shelf folding developed early and is inactive today. During delta progradation disequilibrium compaction overpressures developed in the outer shelf slope area and helped decouple the section from basement late in the delta history, hence compressional deformation shifted further offshore. Conversely onshore inner shelf inversion caused late overpressure loss, resulting in partial recoupling of the deltaic section with basement.
Inner‐core fine‐scale structure from scattered waves recorded by LASA
Authors: Peng Zhigang , Koper Keith D. , Vidale John E. , Leyton Felipe , Shearer Peter
Published: September 2008

Recent observations of inner‐core scattering (ICS) waves provide evidence that the outermost 300 km of the inner‐core has strong heterogeneities with a length scale of a few kilometers. These waves follow a path similar to that of the inner‐core–reflected waves PKiKP and were originally observed in data from 16 events in the distance range 58° to 73° recorded by the Large Aperture Seismic Array (LASA). Here we present additional observations of the ICS waves from a total of 78 events recorded by LASA at distances from 18° to 98°. We use a modified version of the Generic Array Processing software package to identify ICS waves on the basis of travel time, back azimuth, ray parameter, amplitude, and coherence. There are 44 events that produce clear ICS waves. We then perform forward modeling of the observed ICS waves using a Monte Carlo seismic phonon method that allows for multiple scattering along the raypath. Most of the ICS waves appear without a visible PKiKP phase, initially grow in time, and have a spindle‐shaped envelope. The duration, risetime, and decay rates of the observed ICS waves can be best explained by small‐scale volumetric heterogeneities in the outermost few hundred kilometers of the inner core. The average Qc value for the 44 events is ∼600. Most clear ICS waves are found for raypaths sampling the Pacific Ocean and Asia, and relatively few observations are from the Atlantic Ocean, roughly consistent with the recently observed hemispheric difference in the inner‐core structure.
Seasonal cycle of averages of nitrous oxide and ozone in the Northern and Southern Hemisphere polar, midlatitude, and tropical regions derived from ILAS/ILAS‐II and Odin/SMR observations
Authors: Khosrawi F. , Müller R. , Proffitt M. H. , Urban J. , Murtagh D. , Ruhnke R. , Grooß J.‐U. , Nakajima H.
Published: September 2008

Northern and Southern Hemispheric monthly averages of ozone (O3) and nitrous oxide (N2O) have been suggested as a tool for evaluating atmospheric photochemical models. An adequate data set for such an evaluation can be derived from measurements made by satellites which, in general, have a high spatial and temporal coverage. Here, we use measurements made by the Improved Limb Atmospheric Spectrometers (ILAS and ILAS‐II) which use the solar occultation technique and by the Odin‐Sub‐Millimetre Radiometer (Odin/SMR) which passively observes thermal emissions from the Earth's limb. From ILAS/ILAS‐II and Odin/SMR observations, 1‐year data sets of monthly averaged O3 and N2O, covering a full seasonal cycle, were derived for the latitude range between 60–90°N and 60–90°S, respectively, by partitioning the data into equal bins of altitude or potential temperature. A comparison between both data sets in this latitude region shows a good agreement and verifies that limited sampling from satellite occultation experiments does not constitute a problem for deriving such a full seasonal cycle of monthly averaged N2O and O3. Since Odin/SMR provides measurements globally, a 1‐year data set of monthly averaged N2O and O3 is reported here for both the entire Northern and Southern Hemispheres from these measurements. Further, these hemispheric data sets from Odin/SMR are separated into data sets of monthly averaged N2O and O3 for the low latitudes, midlatitudes, and high latitudes. The resulting families of curves help to differentiate between O3 changes due to photochemistry from those due to transport. These 1‐year hemispheric data sets of monthly averaged N2O and O3 from Odin/SMR and ILAS/ILAS‐II as well as the data sets of monthly averaged N2O and O3 for the specific latitude regions from Odin/SMR provide a potentially important tool for the evaluation of atmospheric photochemical models. An example of how such an evaluation can be performed is given using data from two chemical transport models (CTMs), the Chemical Lagrangian Model of the Stratosphere (CLaMS) and the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA). We find a good agreement between Odin/SMR and the CTMs CLaMS and KASIMA with differences generally less than ±20%.
Meteorological conditions in the Arctic Ocean in spring and summer 2007 as recorded on the drifting ice station Tara
Authors: Vihma Timo , Jaagus Jaak , Jakobson Erko , Palo Timo
Published: September 2008

Meteorological observations were made at the drifting ice station Tara in the central Arctic Ocean from 23 March to 19 September 2007, constituting a unique data set from the season preceding the record‐low sea ice extent. Comparisons of the Tara data with observations at the Russian drifting ice stations in 1937–1938 and 1950–1991 and at SHEBA in 1998 indicated that at Tara and SHEBA the atmospheric transmissivity for shortwave radiation was smaller than at the Russian stations, suggesting a higher cloud fraction or optical thickness. Compared to the mean conditions at the Russian stations, at Tara the melting season was twice as long and in April the 2‐m air temperature was 7.0°C higher, but in July the 2‐m temperature difference disappeared. The Tara tethersonde sounding data suggest that the air temperature at the altitudes of 200–1000 m was approximately 1°C higher than the mean of 1954–1985.
Dynamic models of earthquakes on the North Anatolian fault zone under the Sea of Marmara: Effect of hypocenter location
Authors: Oglesby David D. , Mai P. Martin , Atakan Kuvvet , Pucci Stefano
Published: September 2008

We perform three‐dimensional spontaneous dynamic rupture models of potential earthquakes on the geometrically complex North Anatolian fault zone (NAFZ) under the Marmara Sea, Turkey. The NAFZ south of the city of Istanbul consists of a large‐scale extensional stepover, with right lateral strike‐slip segments linked by an oblique normal segment. We find that earthquakes nucleating near the stepover do not propagate across the entire fault system due to the statically unfavorable stress field on the oblique fault, and lead to moderate‐size events only. However, earthquakes initiating a significant distance from the stepover cause significant dynamic unclamping of the oblique fault, and thus generate large through‐going ruptures. Dynamic unclamping also produces supershear rupture propagation in the vicinity of fault discontinuities. The results emphasize that estimations of earthquake size, rupture propagation, and slip distribution cannot be decoupled from the location of the hypocenter and the orientation of the geometrically complex fault system within the tectonic stress field.
Effects of magnetospheric activity on the current sheet energy resonance ion distribution function signature
Authors: Holland D. L. , Bush C. J. , Paterson W. R.
Published: September 2008

In this paper, we discuss the effects of magnetospheric activity (as measured by Kp) on an ion distribution function signature of nonlinear particle dynamics in current sheet‐like magnetic fields. The signature manifests itself as a series of peaks in the ion distribution function whose separation depends on the fourth root of the energy and parameters that describe the current sheet structure. We have found that the signature is evident in Geotail CPI data for Kp ≤ 3+ and that the larger the value of Kp, the closer the peaks are together. We have also used the energy resonance signature in conjunction with measurements of the magnetic field to determine a lower bound on the current sheet thickness and have found that this lower bound decreases for increasing levels of magnetospheric activity. For values of Kp > 4−, there are frequently peaks in the ion distribution function; however, their separations do not follow a simple rule.
A Markov chain model for characterizing medium heterogeneity and sediment layering structure
Authors: Ye Ming , Khaleel Raziuddin
Published: September 2008

By leveraging use of “soft” data (e.g., initial moisture content, θi), this study applies the transition probability (TP) based Markov chain (MC) model to sediment textural classes for characterizing the medium heterogeneity and sediment layering structure. The TP/MC method is evaluated by simulating the vadose zone moisture movement at a field site, where the stratigraphy consists of imperfectly stratified soil layers. Soil heterogeneity is characterized via spatial variability of the geometry of soil textural classes. When the θimeasurements, which carry signature about medium heterogeneity and stratigraphy, are not included in the TP/MC model, it is not possible to identify the horizontal TP. The θimeasurements, when transformed into soil classes, are necessary in mapping the soil layering structure prevalent at the site. The soil hydraulic parameters for each soil class are treated deterministically and are estimated on the basis of core samples. To evaluate uncertainty in characterizing geometry of the soil classes, multiple conditional realizations of the soil classes are generated. A Monte Carlo simulation shows that the simulated mean moisture contents agree well with corresponding field observations. The observed splitting of the moisture plume in a coarse sand layer that is sandwiched between two fine‐textured layers, the southeastward movement of the plume during the redistribution period, and the near‐zero fluid flux below the bottom fine layer are adequately simulated. Spatial variability of the field‐measured moisture content is sufficiently captured by the 95% confidence intervals calculated from the Monte Carlo simulations. Investigating the effect of data conditioning on the simulated results shows that a reduction of conditioning data does not necessarily deteriorate simulation results if other conditioning data exist within the mean length of the soil classes. The TP/MC method is flexible so that other types of site characterization data (e.g., geophysical data) can be incorporated as they become available.
Numerical simulation of hydrodynamics and bank erosion in a river bend
Authors: Rinaldi Massimo , Mengoni Beatrice , Luppi Laura , Darby Stephen E. , Mosselman Erik
Published: September 2008

We present an integrated analysis of bank erosion in a high‐curvature bend of the gravel bed Cecina River (central Italy). Our analysis combines a model of fluvial bank erosion with groundwater flow and bank stability analyses to account for the influence of hydraulic erosion on mass failure processes, the key novel aspect being that the fluvial erosion model is parameterized using outputs from detailed hydrodynamic simulations. The results identify two mechanisms that explain how most bank retreat usually occurs after, rather than during, flood peaks. First, in the high curvature bend investigated here the maximum flow velocity core migrates away from the outer bank as flow discharge increases, reducing sidewall boundary shear stress and fluvial erosion at peak flow stages. Second, bank failure episodes are triggered by combinations of pore water and hydrostatic confining pressures induced in the period between the drawdown and rising phases of multipeaked flow events.
Function and regulation of protein neddylation
Authors: Rabut Gwénaël , Peter Matthias
Published: September 2008

Neddylation is the post‐translational protein modification that is most closely related to ubiquitination. However, ubiquitination is known to regulate a myriad of processes in eukaryotic cells, whereas only a limited number of neddylation substrates have been described to date. Here, we review the principles of protein neddylation and highlight the mechanisms that ensure the specificity of neddylation over ubiquitination. As numerous neddylation substrates probably remain to be discovered, we propose some criteria that could be used as guidelines for the characterization of neddylated proteins.
A diaphragmless shock tube for high temperature kinetic studies
Authors: Tranter Robert S. , Giri Binod R.
Published: September 2008

A novel, diaphragmless shock tube (DFST) has been developed for use in high temperature chemical kinetic studies. The design of the apparatus is presented along with performance data that demonstrate the range and reproducibility of reaction conditions that can be generated. The ability to obtain data in the fall off region, confined to much narrower pressure ranges than can be obtained with a conventional shock tube is shown, and results from laser schlieren densitometry experiments on the unimolecular dissociation of phenyl iodide (P2=57±9 and 122±7 torr, T2=1250–1804 K) are presented. These are compared with results similar to those that would be obtained from a classical shock tube and the implications for extrapolation by theoretical methods are discussed. Finally, the use of the DFST with an online mass spectrometer to create reproducible experiments that can be signal averaged to improve signal/noise and the quality of mass peaks is demonstrated; something that is not possible with a conventional shock tube where each experiment has to be considered unique.
Structure and growth mechanism of ZnSe nanowires
Authors: Basu Joysurya , Divakar R. , Nowak Julia , Hofmann Stephan , Colli Alan , Franciosi A. , Carter C. Barry
Published: September 2008

ZnSe nanowires were grown onto Mo transmission electron microscopy (TEM) grids by MBE by suitably varying the growth parameters. In situ and high-resolution TEM studies were carried out to understand the structure, defects, and growth mechanism of this nanowire. The nanowire morphology is very sensitive to the growth parameters involved. Twin boundaries are the most commonly occurring defects in the nanowires grown under Zn-rich condition and catalytic gold particles of irregular shape are observed along the nanowire body. In the course of in situ heating the shape of the nanowire tip is observed to change at ∼178 °C. Definite growth of the nanowire starts at ∼235 °C. The diameter of the grown nanowire is almost equal to that of the catalyst gold particle present at the tip of the nanowire. In situ experimental observation and available phase-diagram information strongly suggests that nanowire growth should be possible with a solid catalyst particle though it does not rule out the possibility of the existence of a VLS mechanism.
Low-temperature molecular beam epitaxy of a ferromagnetic full-Heusler alloy Fe2MnSi on Ge(111)
Authors: Ueda K. , Hamaya K. , Yamamoto K. , Ando Y. , Sadoh T. , Maeda Y. , Miyao M.
Published: September 2008

We demonstrate the epitaxial growth of ferromagnetic full-Heusler alloy Fe2MnSi layers on group-IV semiconductor Ge(111) using molecular beam epitaxy at the growth temperatures of 130 and 200 °C. The Fe2MnSi/Ge(111) layers have an atomic-scale abrupt interface and include the ordered L21 phase. We also show ferromagnetic features with a saturation magnetization of ∼2.2 μB/f.u. and a Curie temperature of ∼210 K, which are nearly comparable to those of bulk Fe2MnSi.
Photoluminescence properties of highly dispersed ZnO quantum dots in polyvinylpyrrolidone nanotubes prepared by a single capillary electrospinning
Authors: Li X. H. , Shao C. L. , Liu Y. C. , Chu X. Y. , Wang C. H. , Zhang B. X.
Published: September 2008

Highly dispersed ZnO quantum dots (QDs) in polyvinylpyrrolidone (PVP) nanotubes have been prepared by a single capillary electrospinning. The structure and optical properties characterizations were performed by x-ray diffraction, scanning and transmission electron microscopy, absorption, photoluminescence, and resonant Raman spectra. In the composites, PVP molecules passivate the surface defects of ZnO QDs and prevent the aggregations of ZnO QDs. As a result, the composites exhibit narrower band edge emissions and less laser thermal effects. Blueshifted band gap, enlarged exciton energy, and less exciton-longitudinal optical (LO) phonon interaction due to the quantum confinement effect have also been observed.
Anomalous transport properties of Co-site impurity doped NaxCoO2
Authors: Mandal P.
Published: September 2008

The effect of substitution of Cu, Zn, Ga, Mn, and Ni for Co in layered NaxCoO2 (x∼0.85) on its resistivity (ρ), magnetization (M), and thermopower (S) has been investigated. At low temperature, ρ remains metallic (dρ/dT>0) for Cu, Zn, and Ga impurities up to a maximum doping of 15%, while for Mn and Ni a metal-insulator transition occurs at 3% and 6% doping, respectively. For the Cu-doped samples, ρ(T) shows a strong anomaly and a hysteresis around 280 K where a first-order structural phase transition occurs due to long-range ordering of the Na-vacancy clusters. Well above the antiferromagnetic transition temperature, the magnetic susceptibility exhibits the Curie–Weiss law. The Neel temperature is insensitive to impurity while both the Curie constant and Weiss constant (θ) depend on the nature of impurity. A small enhancement in magnetization above 280 K and an increase of θ with Cu doping are the signatures of superior Na-vacancy ordering in the Cu-doped samples. In contrast to ρ and M, S changes systematically with doping and temperature, and does not show any anomalous behavior around 280 K.
Thickness dependence of electronic phase transitions in epitaxial V2O3 films on (0001) LiTaO3
Authors: Allimi B. S. , Aindow M. , Alpay S. P.
Published: September 2008

Single crystal epitaxial thin films of V2O3 were grown on (0001) LiTaO3 by pulsed laser deposition. X-ray diffraction and atomic force microscopy data show that the deposits were initially pseudomorphic, that they underwent plastic relaxation at a critical thickness of ≈16 nm, and that relaxation is accompanied by the development of surface roughness, increasing with deposit thickness. These effects lead to changes in electrical properties of the films as a function of temperature. As film thickness increases the properties go from insulator-insulator to metal-insulator, then metal-metal transitions. The thickest films (>200 nm) remained metallic over the temperature range of the measurements.
Influence of interlayer dipolar coupling on magnetization reversal and high-frequency dynamics in asymmetric NiFe/Cu/NiFe circular nanorings
Authors: Madami M. , Tacchi S. , Gubbiotti G. , Carlotti G. , Pandana H. , Gomez R. D. , Tanigawa H. , Ono T.
Published: September 2008

The magnetization reversal process and the spectrum of magnetic excitations of NiFe(10 nm)/Cu(10 nm)/NiFe(20 nm) circular nanorings have been investigated by magneto-optic Kerr effect, magnetic force microscopy (MFM), and Brillouin light scattering (BLS). These measurements reveal several magnetic ground states as a function of the applied field strength, corresponding to the different magnetization distributions in the two ferromagnetic layers with switching fields influenced by the sizable interlayer dipolar coupling. A satisfactory reproduction of the measured hysteresis loop as well as of the main features of the MFM images was achieved by the combined use of three-dimensional micromagnetic simulations and analytical calculations of the dipolar stray field felt by the magnetic tip. The spectrum of thermal spin waves reveals the presence of several discrete and stationary modes, whose frequency evolution with the applied field was measured by BLS, encompassing different magnetic ground states. The frequency and the spatial distribution of the dynamical magnetization of each mode were calculated by micromagnetic simulations. The presence of dipolar coupling between the layers causes the appearance of modes, which are either in-phase (acoustic) or out-of-phase (optical) in the two layers, as well as the presence of complicated mode profiles when the ground states in the two layers are different.
Investigating the effect of oxygen vacancy on the dielectric and electromechanical properties in ferroelectric ceramics
Authors: Lo Veng-cheong , Chung Winnie Wing-yee , Cao Haixia , Dai Xiao
Published: September 2008

The effect of oxygen vacancy on the dielectric and electromechanical properties in lead titanate zirconate based ferroelectric ceramics is discussed in this paper. The presence of oxygen vacancy forms a defect-dipole inside a perovskite cell. This defect-dipole contributes to the unswitchable polarization and influences the alignment of the ferroelectric dipole in the same cell as well. The latter is due to the displacement of the B-site cation, which contributes to the switchable polarization. It is found that a double hysteresis emerges when the alignment of defect-dipole conforms with the crystal orientation, which is perpendicular to the measured polarization. Moreover, the optimal electromechanical property can be obtained by careful adjustment of c-domain volume fraction and the alignment of defect dipoles. Monte Carlo simulation based on the four-state Potts model is presented. Calculation results are compared with experiments.
Numerical analysis of negative refraction of transverse waves in an elastic material
Authors: Hladky-Hennion Anne-Christine , Vasseur Jérôme , Dubus Bertrand , Djafari-Rouhani Bahram , Ekeom Didace , Morvan Bruno
Published: September 2008

A numerical analysis of negative refraction process is reported using a phononic crystal with an elastic solid matrix. The phononic crystal considered in this study is made of a periodic arrangement of holes in aluminum. Dispersion curves are discussed and conditions for which negative refraction can appear are identified. These conditions are obtained for the transverse waves, whereas the longitudinal waves are evanescent. A calculation is performed with a prism shaped phononic crystal, and it clearly exhibits a negative refraction angle. Several analyses are provided with a view to characterize the wave going out of the phononic crystal. Finally, improvements, with respect to the impedance matching and index tuning, are discussed.
A simple and flexible thin film evaporating device for energetic materials
Authors: Zhang Gengxin , Pitchimani Rajasekar , Weeks Brandon L.
Published: September 2008

A thin film evaporation device has been developed to prepare energetic materials at atmospheric pressure. The device is intuitive, simple, and easy to manipulate. The application of the device is demonstrated for pentaerythritol tetranitrate but can be extended to other explosives and organic materials that have low saturation pressures.
Proximity effect in ferromagnetic semiconductor/superconductor junctions
Authors: Tao Y. C. , Hu J. G.
Published: September 2008

We study how the proximity effect in a ferromagnetic semiconductor (FS)/superconductor (SC) junction is manipulated by the mismatches of the band and mass between the FS and SC, as well as the strength of potential scattering at the interface. It is demonstrated that they have different influences on the superconducting order parameter and density of states in the FS and SC induced by the proximity effect, particularly on the features of gapless superconductivity and transition from the “0 state” to the “π state,” which is different from those in ferromagnet/SC junctions.
A mathematical model of turbulent drag reduction by high-molecular-weight polymeric additives in a shear flow
Authors: Barenblatt Grigory Isaakovich
Published: September 2008

Drag reduction, or the mean velocity increase in a turbulent flow at a fixed pressure drop through the addition of tiny amounts (several parts per million) of high-molecular-weight polymers (Thoms effect), has been known already for more than 60 years. Long ago it was understood that this effect is related to supramolecular structures formed in the flow. Recent experiments by Chu, Shaqfeh, and associates, where the motion of supramolecular structures was directly observed, made it possible to understand and quantify the dynamic interaction of the polymeric structures with the solvent (water) flow. These results lead to the construction of a mathematical model of the Thoms effect, based on the Kolmogorov (1942)–Prandtl (1945) semiempirical theory of shear flow turbulence. This is the subject of the present letter.
Impurity bands and the character of the electronic states in ferromagnetic GaMnAs layers
Authors: Dias Cabral E. , da Cunha Lima I. C. , Boselli M. A. , da Cunha Lima A. T.
Published: September 2008

The interplay between disorder and spin polarization in a GaMnAs thin layer results into spin-polarized impurity hole bands. A figure of merit is defined to label the nature of the sample as metallic or nonmetallic. It is shown that samples with the highest figures of merit have a ratio between the extended hole density and the Mn concentration near 0.2, in agreement with the ratio of 0.1–0.25 known to occur among samples produced with the highest Curie temperatures. Both the nonmetal-to-metal and the metal-to-nonmetal transitions experimentally observed in the ferromagnetic regime are obtained as the Mn concentration increases.
A versatile magnetic refrigeration test device
Authors: Bahl C. R. H. , Petersen T. F. , Pryds N. , Smith A.
Published: September 2008

A magnetic refrigeration test device has been built and tested. The device allows variation and control of many important experimental parameters, such as the type of heat transfer fluid, the movement of the heat transfer fluid, the timing of the refrigeration cycle, and the magnitude of the applied magnetic field. An advanced two-dimensional numerical model has previously been implemented in order to help in the optimization of the design of a refrigeration test device. Qualitative agreement between the results from model and the experimental results is demonstrated for each of the four different parameter variations mentioned above.
Voltage polarity dependent low-power and high-speed resistance switching in CoO resistance random access memory with Ta electrode
Authors: Shima Hisashi , Takano Fumiyoshi , Muramatsu Hidenobu , Akinaga Hiro , Tamai Yukio , Inque Isao H. , Takagi Hidenori
Published: September 2008

Structural and resistance switching properties were investigated in the CoO resistance random access memory (RRAM) with the Ta electrode. The intermediate layer consisting of Co and Ta oxides was confirmed at the interface by the transmission electron microscopy and electron energy loss spectroscopy. The great affinity with oxygen in Ta together with a high resistivity of the Ta oxide improves the operational performance of RRAM. The controllability of the resistance after forming and the low-current operation property were substantially improved by using the load resistor connected in series with CoO RRAM with the Ta electrode. The reset current less than 0.2 mA and the switching speed faster than 20 ns were demonstrated.
Improved thermal management of GaN/sapphire light-emitting diodes embedded in reflective heat spreaders
Authors: Horng R. H. , Chiang C. C. , Hsiao H. Y. , Zheng X. , Wuu D. S. , Lin H. I.
Published: September 2008

Using maskless lithography and electroforming techniques, we have demonstrated an enhanced performance of GaN/sapphire light-emitting diode (LED) embedded in a reflective copper heat spreader. The chip size and dominant wavelength of the blue emitter used in this research is 1×1 mm2 and 455 nm, respectively. The cup-shaped LED heat sink is electroformed on sapphire directly using the spin-coated photoresist coated with the Au/Cr/Ag mirror as a mold and dicing into the embedded LED with a Cu base dimension of 3×3 mm2, which effectively enhances the heat dissipation down to the metal frame and reaps the light flux generated from the side emission. With the aid of a reflective heat spreader, the encapsulated LED sample driven at 1 A yields the light output power of 700 mW and around 2.7-times increase in the wall-plug efficiency compared to that of the conventional GaN/sapphire LED. Infrared thermal images confirm the GaN/sapphire LED with more efficient heat extraction and better temperature uniformity. These results exhibit an alternative solution to thermal management of high power LED-on-sapphire samples besides the laser lift-off technique.
In situ measurement of stress generation arising from dislocation inclination in AlxGa1−xN:Si thin films
Authors: Acord Jeremy D. , Manning Ian C. , Weng Xiaojun , Snyder David W. , Redwing Joan M.
Published: September 2008

The effect of Si-doping on the stress and microstructure of AlxGa1−xN (x≈0.39–0.45) films grown by metalorganic chemical vapor deposition on SiC substrates was investigated. In situ measurements revealed a compressive-to-tensile transition of the stress state at the film surface upon the addition of SiH4 during growth, which correlated with a change in the angle of inclination of threading dislocations in the film. The magnitude of the in situ measured stress gradient was comparable to that predicted by the dislocation effective climb model, suggesting that dislocation inclination is the dominant mechanism responsible for tensile stress generation in the films.
Defect-controlled growth of GaN nanorods on (0001)sapphire by molecular beam epitaxy
Authors: Cherns D. , Meshi L. , Griffiths I. , Khongphetsak S. , Novikov S. V. , Farley N. R. S. , Campion R. P. , Foxon C. T.
Published: September 2008

Transmission electron microscopy is used to reveal threading defects in single crystal c-oriented GaN nanorods grown on (0001)sapphire by molecular beam epitaxy. The defects are shown to be planar faults lying on {101¯0} planes and bounded by opposite partial screw dislocations with Burgers vectors of 1/2⟨0001⟩. The faults nucleate, as dislocation half-loops, from points close to the GaN/(0001)sapphire interface. It is proposed that the spiral growth of the partial atomic step joining the emerging dislocations controls nanorod growth and accounts for the growth surface morphology. The significance of these defects for nanorod growth and applications is discussed.
Oscillator circuit based on a single organic transistor
Authors: Dost René , Ray Sumon K. , Das Arindam , Grell Martin
Published: September 2008

We design and demonstrate an oscillator circuit based on feedback and controlled by a single organic transistor. Oscillations are assisted by standard operational amplifiers. The oscillator frequency f partly depends on the parameters of the circuit, but also on the transistor’s channel length and charge carrier mobility. Monitoring f provides a fast and simple tool in following the change in semiconductor mobility under changing environmental conditions. We demonstrate the application of the circuit for cheap, portable organic transistor-based odor sensors.
p
-
p
isotype organic heterojunction and ambipolar field-effect transistors
Authors: Wang Haibo , Wang Xiujin , Yu Bo , Geng Yanhou , Yan Donghang
Published: September 2008

We realized ambipolar transport behavior in field-effect transistors by using p-p isotype heterojunction films as active layers, which consisted of two p-type semiconductor materials, 2, 2′; 7′, 2″-terphenanthrenyl (Ph3) and vanadyl-phthalocyanine (VOPc). The ambipolar charge transport was attributed to the interfacial electronic structure of Ph3-VOPc isotype heterojunction, and electrons and holes were accumulated at both sides of the narrow band-gap VOPc and the wide band-gap Ph3, respectively, which were confirmed by the capacitance-voltage relationship of metal-oxide-semiconductor diodes. The accumulation thickness of carriers was also obtained by changing the heterojunction active layer thickness. Furthermore, the results indicate that the device performance is relative to interfacial electronic structures.
Plastic distributed feedback laser biosensor
Authors: Lu M. , Choi S. S. , Irfan U. , Cunningham B. T.
Published: September 2008

A replica-molded plastic-based vertically emitting distributed feedback (DFB) laser has been demonstrated for label-free chemical and biomolecular detection in which the emission wavelength is modulated by changes in bulk and surface-adsorbed material permittivity. A one-dimensional surface grating formed in UV-curable polymer on a flexible plastic substrate is coated with a thin polymer film incorporating organic laser dye. When optically pumped with a ∼10 ns pulse at λ=532 nm, the DFB laser exhibits stimulated emission in the λ=585–620 nm wavelength range with a linewidth as narrow as δλ=0.09 nm. While exposed to chemical solutions with different refractive indices and adsorbed charged polymer monolayers, the laser sensor demonstrates single mode emission over a tuning range of ∼14 nm and the ability to perform kinetic monitoring of surface-adsorbed mass. A protein-protein interaction experiment is used to demonstrate the capability to characterize antibody-antigen affinity binding constants.
Exciting circular TEmn modes at low terahertz region
Authors: Chang T. H. , Li C. H. , Wu C. N. , Yu C. F.
Published: September 2008

This work proposes an approach to generate circular TEmn modes at low terahertz region through sidewall couplings. With proper arrangement of the couplings on the circumference of the waveguide, they then jointly excite the desired mode. A model is developed to calculate the coupling strength and to analyze the mode purity. Accordingly, three mode converters TE21, TE01, and TE41, were designed, built, and tested at W-band. Back-to-back transmission measurements exhibit excellent agreement with the results of simulations. The measured optimal transmissions are 91%, 95%, and 89% with 3 dB bandwidths of 18.3, 24.0, and 20.2 GHz, respectively.
Tuning electrical properties of transparent p-NiO/n-MgZnO heterojunctions with band gap engineering of MgZnO
Authors: Chen Xinman , Ruan Kaibin , Wu Guangheng , Bao Dinghua
Published: September 2008

Transparent p-n heterojunctions composed of p-type NiO and n-type MgZnO thin films were fabricated on indium-tin-oxide-coated glass substrates by sol-gel spin coating technique. The p-n junctions exhibit typical current-voltage behaviors with good rectifying characteristics, and their electrical properties can be effectively tuned by band gap engineering of n-MgZnO. With increment of Mg content in n-MgZnO layer, enlarging band gap can lead to the higher forward threshold voltage, higher breakdown voltage, and lower reverse saturation current. The electrical behaviors of the p-n junctions can be further improved by using compositionally graded n-MgZnO layer instead of single n-MgZnO layer. These results suggest that the transparent all-oxide p-NiO/n-MgZnO heterojunctions can find applications in transparent electronic devices.
Large tunnel magnetoresistance in magnetic tunnel junctions using a Co2MnSi Heusler alloy electrode and a MgO barrier
Authors: Tsunegi Sumito , Sakuraba Yuya , Oogane Mikihiko , Takanashi Koki , Ando Yasuo
Published: September 2008

A large tunnel magnetoresistance (TMR) ratio of 753% has been observed at 2 K in a magnetic tunnel junction (MTJ) using a Co2MnSi Heusler alloy electrode and a crystalline MgO tunnel barrier. This TMR ratio is the largest reported to date in MTJs using a Heusler alloy electrode. Moreover, we have observed a large TMR ratio of 217% at room temperature (RT). This TMR at RT is much larger than that of MTJs using an amorphous Al-oxide tunnel barrier. However, the temperature dependence of the TMR ratio is still large because of inelastic tunneling in the antiparallel magnetic configuration.
Solution-processable organic-capped titanium oxide nanoparticle dielectrics for organic thin-film transistors
Authors: Cai Qin Jia , Gan Ye , Chan-Park Mary B. , Yang Hong Bin , Lu Zhi Song , Song Qun Liang , Li Chang Ming , Li Dong Zhi
Published: September 2008

Oleic acid-capped titanium dioxide (OA-TiO2) nanoparticles were solution-processed to form homogeneous dielectrics for organic thin-film transistors (TFTs) of top-gate and bottom-gate configurations. The OA-TiO2 nanoparticles were well-dispersed into the organic solvent and spin-coated to give homogeneous films. These nanoparticle films showed a dielectric constant of about 5.3 and low leakage current density of ∼3×10−8 A/cm2 under an electric field of 1 MV/cm. Poly(3,3‴-didodecylquaterthiophene) and pentacene TFTs with OA-TiO2 dielectrics exhibited mobilities of 0.05±0.02 and 0.2±0.05 cm2 V−1 s−1, respectively, with on/off ratios of 103–105. This material appears to be useful for applications in printable organic TFTs.
Inflammation and autoimmunity caused by a SHP1 mutation depend on IL-1, MyD88, and a microbial trigger
Authors: Croker Ben A. , Lawson Brian R. , Rutschmann Sophie , Berger Michael , Eidenschenk Celine , Blasius Amanda L. , Moresco Eva Marie Y. , Sovath Sosathya , Cengia Louise , Shultz Leonard D. , Theofilopoulos Argyrios N. , Pettersson Sven , Beutler Bruce Alan
Published: September 2008

A recessive phenotype calledspin(spontaneous inflammation) was induced byN-ethyl-N-nitrosourea (ENU) mutagenesis in C57BL/6J mice. Homozygotes display chronic inflammatory lesions affecting the feet, salivary glands and lungs, and antichromatin antibodies. They are immunocompetent and show enhanced resistance to infection byListeria monocytogenes. TLR-induced TNF and IL-1 production are normal in macrophages derived fromspinmice. The autoinflammatory phenotype ofspinmice is fully suppressed by compound homozygosity forMyd88poc,Irak4otiose, andIl1r1-null mutations, but notTicam1Lps2,Stat1m1Btlr, orTnf-null mutations. Both autoimmune and autoinflammatory phenotypes are suppressed whenspinhomozygotes are derived into a germ-free environment. Thespinphenotype was ascribed to a viable hypomorphic allele ofPtpn6, which encodes the tyrosine phosphatase SHP1, mutated in mice with the classicalmotheatenallelesmeandme-v. Inflammation and autoimmunity caused by SHP1 deficiency are thus conditional. The SHP1-deficient phenotype is driven by microbes, which activate TLR signaling pathways to elicit IL-1 production. IL-1 signaling via MyD88 elicits inflammatory disease.
Functional modules integrating essential cellular functions are predictive of the response of leukaemia cells to DNA damage
Authors: Sameith Katrin , Antczak Philipp , Marston Elliot , Turan Nil , Maier Dieter , Stankovic Tanja , Falciani Francesco
Published: September 2008

Motivation: Childhood B-precursor lymphoblastic leukaemia (ALL) is the most common paediatric malignancy. Despite the fact that 80% of ALL patients respond to anti-cancer drugs, the patho-physiology of this disease is still not fully understood. mRNA expression-profiling studies that have been performed have not yet provided novel insights into the mechanisms behind cellular response to DNA damage. More powerful data analysis techniques may be required for identifying novel functional pathways involved in the cellular responses to DNA damage.

Results: In order to explore the possibility that unforeseen biological processes may be involved in the response to DNA damage, we have developed and applied a novel procedure for the identification of functional modules in ALL cells. We have discovered that the overall activity of functional modules integrating protein degradation and mRNA processing is predictive of response to DNA damage.

Availability:  Supplementary material including R code, additional results, experimental datasets, as well as a detailed description of the methodology are available at http://www.bip.bham.ac.uk/vivo/fumo.html.

Contact:  f.falciani@bham.ac.uk

Supplementary information:  Supplementary data are available at Bioinformatics online.
Pre-tension generates strongly reversible adhesion of a spatula pad on substrate
Authors: Chen Bin , Wu Peidong , Gao Huajian
Published: September 2008

Motivated by recent studies on reversible adhesion mechanisms of geckos and insects, we investigate the effect of pre-tension on the orientation-dependent adhesion strength of an elastic tape adhering on a substrate. Our analysis shows that the pre-tension can significantly increase the peel-off force at small peeling angles while decreasing it at large peeling angles, leading to a strongly reversible adhesion. More interestingly, we find that there exists a critical value of pre-tension beyond which the peel-off force plunges to zero at a force-independent critical peeling angle. We further show that the level of pre-tension required for such force-independent detachment at a critical angle can be induced by simply dragging a spatula pad along a substrate at sufficiently low angles. These results provide a feasible explanation of relevant experimental observations on gecko adhesion and suggest possible strategies to design strongly reversible adhesives via pre-tension.
Fibrin gels and their clinical and bioengineering applications
Authors: Janmey Paul A , Winer Jessamine P , Weisel John W
Published: September 2008

Fibrin gels, prepared from fibrinogen and thrombin, the key proteins involved in blood clotting, were among the first biomaterials used to prevent bleeding and promote wound healing. The unique polymerization mechanism of fibrin, which allows control of gelation times and network architecture by variation in reaction conditions, allows formation of a wide array of soft substrates under physiological conditions. Fibrin gels have been extensively studied rheologically in part because their nonlinear elasticity, characterized by soft compliance at small strains and impressive stiffening to resist larger deformations, appears essential for their function as haemostatic plugs and as matrices for cell migration and wound healing. The filaments forming a fibrin network are among the softest in nature, allowing them to deform to large extents and stiffen but not break. The biochemical and mechanical properties of fibrin have recently been exploited in numerous studies that suggest its potential for applications in medicine and bioengineering.
Improving the realism of deterministic multi-strain models: implications for modelling influenza A
Authors: Minayev Pavlo , Ferguson Neil
Published: September 2008

Understanding the interaction between epidemiological and evolutionary dynamics for antigenically variable pathogens remains a challenge, particularly if analytical insight is wanted. In particular, while a variety of relatively complex simulation models have reproduced the evolutionary dynamics of influenza, simpler models have given less satisfying descriptions of the patterns seen in data. Here, we develop a set of relatively simple deterministic models of the transmission dynamics of multi-strain pathogens which give increased biological realism compared with past work. We allow the intensity of cross-immunity generated against one strain given exposure to a different strain to depend on the extent of genetic difference between the strains. We show that the dynamics of this model are determined by the interplay of parameters defining the cross-immune response function and can include fully symmetric equilibria, self-organized strain structures, regular periodic and chaotic regimes. We then extend the model by incorporating transient strain-transcending immunity that acts as a density-dependent mechanism to lower overall infection prevalence and thus pathogen diversity. We conclude that while some aspects of the evolution of influenza can be captured by deterministic models, overall, the description obtainable using a purely deterministic framework is unsatisfactory, implying that stochasticity of strain generation (via mutation) and extinction needs to be captured to appropriately capture influenza dynamics.
Culture, embodiment and genes: unravelling the triple helix
Authors: Wheeler Michael , Clark Andy
Published: September 2008

Much recent work stresses the role of embodiment and action in thought and reason, and celebrates the power of transmitted cultural and environmental structures to transform the problem-solving activity required of individual brains. By apparent contrast, much work in evolutionary psychology has stressed the selective fit of the biological brain to an ancestral environment of evolutionary adaptedness, with an attendant stress upon the limitations and cognitive biases that result. On the face of it, this suggests either a tension or, at least, a mismatch, with the symbiotic dyad of cultural evolution and embodied cognition. In what follows, we explore this mismatch by focusing on three key ideas: cognitive niche construction; cognitive modularity; and the existence (or otherwise) of an evolved universal human nature. An appreciation of the power and scope of the first, combined with consequently more nuanced visions of the latter two, allow us to begin to glimpse a much richer vision of the combined interactive potency of biological and cultural evolution for active, embodied agents.
Cultural evolution: implications for understanding the human language faculty and its evolution
Authors: Smith Kenny , Kirby Simon
Published: September 2008

Human language is unique among the communication systems of the natural world: it is socially learned and, as a consequence of its recursively compositional structure, offers open-ended communicative potential. The structure of this communication system can be explained as a consequence of the evolution of the human biological capacity for language or the cultural evolution of language itself. We argue, supported by a formal model, that an explanatory account that involves some role for cultural evolution has profound implications for our understanding of the biological evolution of the language faculty: under a number of reasonable scenarios, cultural evolution can shield the language faculty from selection, such that strongly constraining language-specific learning biases are unlikely to evolve. We therefore argue that language is best seen as a consequence of cultural evolution in populations with a weak and/or domain-general language faculty.