bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of magnetospheric line radiation and power line harmonic radiation: A systematic survey using the DEMETER spacecraft
Authors: Němec F. , Santolík O. , Parrot M. , Berthelier J. J.
Published: April 2007

Results of a systematic search for magnetospheric line radiation (MLR) observed by the DEMETER spacecraft since the beginning of the mission are presented. DEMETER is a French microsatellite (altitude of orbit about 700 km, inclination 98°) designed to study electromagnetic phenomena connected with seismic or man‐made activity that has been launched in June 2004. An automatic identification procedure of possible MLR events has been used in order to analyze a large amount of measured data. It is shown that there are two principally different classes of events: (1) events with frequency spacing of 50/100 or 60/120 Hz (power line harmonic radiation, PLHR) and (2) events with a different frequency spacing. The first class of events is generated by power systems on the Earth's surface, with frequency spacing well corresponding to the fundamental frequency of the radiating power system. On the other hand, the second class is most probably generated in a completely natural way. All the detected events are thoroughly analyzed, and different properties of the two classes are statistically demonstrated. We have found that PLHR events occur both during low and high geomagnetic activity, with none of them significantly preferred. However, MLR events occur more frequently under disturbed conditions. Most of the PLHR events are observed at frequencies of 2 to 3 kHz. On the other hand, MLR events most frequently occur at frequencies below 2 kHz and seem to be more intense than PLHR. Additionally, PLHR events are more intense during the night than during the day, and there is about the same number of PLHR events observed during the day and during the night. On the contrary, no dependence of MLR peak intensities on magnetic local time was found, and more MLR events were observed during the day than during the night, although this difference is not statistically very significant. Finally, there is a group of MLR events with characteristics corresponding to the previous spacecraft observations of equatorial noise.
An intense gravity wave near the mesopause region observed by a Fabry‐Perot interferometer and an airglow imager
Authors: Shiokawa K. , Suzuki S. , Otsuka Y. , Ogawa T. , Nakamura T. , Horinouchi T.
Published: April 2007

We report an intense gravity wave event observed at Shigaraki, Japan, at 1500–2000 UT (0000–0500 LT) on 22 December 2001 using a Fabry‐Perot interferometer, which measures the Doppler shift of nocturnal airglow emission at a wavelength of 557.7 nm (emission altitude: 90–100 km). The wave had a period of 1.5 hours and a peak‐to‐peak amplitude of 68 m/s in the horizontal wind velocity. The hodograph of the east‐west and north‐south wind oscillations showed a polarization direction of the wave of ENE‐WSW. An all‐sky airglow imager at Shigaraki also recorded a similar southwestward moving wave with a period of ∼1.5 hours and a velocity of 146 m/s in the 557.7‐nm airglow images. The horizontal wavelength was estimated to be 790 km from the images. These facts indicate that the wave was generated in the northeast of Japan, where a well‐developed low‐pressure cell (968 hPa) and a distortion of the jet stream were observed in the troposphere. However, the large horizontal wavelength, the fast phase velocity, and the possible source location apart from the exit of the jet streak are different from those predicted from previous numerical simulations.
Development of a simple groundwater model for use in climate models and evaluation with Gravity Recovery and Climate Experiment data
Authors: Niu Guo‐Yue , Yang Zong‐Liang , Dickinson Robert E. , Gulden Lindsey E. , Su Hua
Published: April 2007

Groundwater interacts with soil moisture through the exchanges of water between the unsaturated soil and its underlying aquifer under gravity and capillary forces. Despite its importance, groundwater is not explicitly represented in climate models. This paper developed a simple groundwater model (SIMGM) by representing recharge and discharge processes of the water storage in an unconfined aquifer, which is added as a single integration element below the soil of a land surface model. We evaluated the model against the Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage change (ΔS) data. The modeled total water storage (including unsaturated soil water and groundwater) change agrees fairly well with GRACE estimates. The anomaly of the modeled groundwater storage explains most of the GRACE ΔS anomaly in most river basins where the water storage is not affected by snow water or frozen soil. For this reason, the anomaly of the modeled water table depth agrees well with that converted from the GRACE ΔS in most of the river basins. We also investigated the impacts of groundwater dynamics on soil moisture and evapotranspiration through the comparison of SIMGM to an additional model run using gravitational free drainage (FD) as the model's lower boundary condition. SIMGM produced much wetter soil profiles globally and up to 16% more annual evapotranspiration than FD, most obviously in arid‐to‐wet transition regions.
A study of the vertical scale of halogen chemistry in the Arctic troposphere during Polar Sunrise at Barrow, Alaska
Authors: Tackett Philip J. , Cavender Aubrey E. , Keil Adam D. , Shepson Paul B. , Bottenheim Jan W. , Morin Samuel , Deary John , Steffen Alexandra , Doerge Chris
Published: April 2007

The vertical extent and impact of halogen chemistry in the Arctic springtime was investigated through balloon‐based measurement of several atmospheric chemical components. Various chemical species, including volatile organic compounds (VOCs), ozone, and elemental mercury, that are modified by halogen chemistry were measured from the surface to ∼300 m during late March through mid‐April 2005 in Barrow, Alaska. It is observed that the halogen chemistry appears to be most active in the lowest 100–200 m of the atmosphere. The Hg vertical concentration profiles are consistent with destruction by chemistry that evolves from a species emitted from the snowpack, most likely Br2 and BrCl, and the VOC profiles also demonstrate the limited vertical scale of halogen‐initiated chemistry taking place above the Arctic snowpack.
Interference with energy metabolism by 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside induces HPV suppression in cervical carcinoma cells and apoptosis in the absence of LKB1
Authors: Nafz Julia , De-Castro Arce Johanna , Fleig Verena , Patzelt Andrea , Mazurek Sybille , Rösl Frank
Published: April 2007

Carcinogenesis is a dynamic and stepwise process, which is accompanied by a variety of somatic and epigenetic alterations in response to a changing microenvironment. Hypoxic conditions will select for cells that have adjusted their metabolic profile and can maintain proliferation by successfully competing for scarce nutritional and oxygen resources. In the present study we have investigated the effects of energy depletion in the context of HPV (human papillomavirus)-induced pathogenesis. We show that cervical carcinoma cell lines are susceptible to undergoing either growth arrest or cell death under conditions of metabolic stress induced by AICAR (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside), a known activator of the AMPK (AMP-activated protein kinase). Our results reveal that AICAR treatment leads to a reduced binding affinity of the transcription factor AP-1 (activator protein-1) and in turn to a selective suppression of HPV transcription. Moreover, the outcome of AICAR on proliferation and survival was dependent on p53 activation and the presence of LKB1, the major upstream kinase of AMPK. Using non-malignant LKB1-expressing somatic cell hybrids, which lose expression after tumorigenic segregation, as well as small interfering RNA LKB1 knockdown approaches, we could further demonstrate that expression of LKB1 protects cells from cytotoxicity induced by agents which modulate the ATP/AMP ratio. Since simulation of low energy status can selectively eradicate LKB1-negative cervical carcinoma cells, AICAR may represent a novel drug in the treatment of cervical cancer.
Distinct roles of the C2A and the C2B domain of the vesicular Ca2+ sensor synaptotagmin 9 in endocrine β-cells
Authors: Grise Florence , Taib Nada , Monterrat Carole , Lagrée Valérie , Lang Jochen
Published: April 2007

Synaptotagmins form a family of calcium-sensor proteins implicated in exocytosis, and these vesicular transmembrane proteins are endowed with two cytosolic calcium-binding C2 domains, C2A and C2B. Whereas the isoforms syt1 and syt2 have been studied in detail, less is known about syt9, the calcium sensor involved in endocrine secretion such as insulin release from large dense core vesicles in pancreatic β-cells. Using cell-based assays to closely mimic physiological conditions, we observed SNARE (soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor)-independent translocation of syt9C2AB to the plasma membrane at calcium levels corresponding to endocrine exocytosis, followed by internalization to endosomes. The use of point mutants and truncations revealed that initial translocation required only the C2A domain, whereas the C2B domain ensured partial pre-binding of syt9C2AB to the membrane and post-stimulatory localization to endosomes. In contrast with the known properties of neuronal and neuroendocrine syt1 or syt2, the C2B domain of syt9 did not undergo calcium-dependent membrane binding despite a high degree of structural homology as observed through molecular modelling. The present study demonstrates distinct intracellular properties of syt9 with different roles for each C2 domain in endocrine cells.
Evolutionary tinkering: birth of a novel chloroplast protein
Authors: Kleine Tatjana , Leister Dario
Published: April 2007

The term ‘evolutionary tinkering’ refers to evolutionary innovation by recombination of functional units, and includes the creation of novel proteins from pre-existing modules. A novel instance of evolutionary tinkering was recently discovered in the flowering plant genus Nicotiana: the conversion of a nuclear transcription factor into the plastid-resident protein WIN4 (wound-induced clone 4) involved in environmental stress responses. In this issue of the Biochemical Journal, Kodama and Sano now show that two steps are necessary for the establishment of the novel plastid protein: the acquisition of an internal translation initiation site and the use of multiple transcription starts to produce short mRNA variants that encode the plastid-targeted protein form.
Tail resonances of Fermi-Pasta-Ulam q-breathers and their impact on the pathway to equipartition
Authors: Penati Tiziano , Flach Sergej
Published: April 2007

Upon initial excitation of a few normal modes the energy distribution among all modes of a nonlinear atomic chain (the Fermi-Pasta-Ulam model) exhibits exponential localization on large time scales. At the same time, resonant anomalies (peaks) are observed in its weakly excited tail for long times preceding equipartition. We observe a similar resonant tail structure also for exact time-periodic Lyapunov orbits, coined q-breathers due to their exponential localization in modal space. We give a simple explanation for this structure in terms of superharmonic resonances. The resonance analysis agrees very well with numerical results and has predictive power. We extend a previously developed perturbation method, based essentially on a Poincaré-Lindstedt scheme, in order to account for these resonances, and in order to treat more general model cases, including truncated Toda potentials. Our results give a qualitative and semiquantitative account for the superharmonic resonances of q-breathers and natural packets.
Influence of trapped magnetic flux quantum on two-dimensional magnetic field dependence of a Josephson junction
Authors: Watanabe Norimichi , Nakayama Akiyoshi , Abe Susumu
Published: April 2007

We have measured the change in two-dimensional magnetic field dependence of a Josephson junction by magnetic flux quantum trapped in a superconducting thin film. When the external magnetic field (Hx,Hy) was applied in the two directions parallel to the junction plane, Josephson junction showed two Fraunhofer diffraction pattern in the Hx and Hy directions. However, when the magnetic flux was trapped within a Josephson junction by cooling through the transition temperature in the presence of environmental magnetic field noises, Josephson current was not periodically modulated to the external magnetic field (Hx,Hy). We have investigated the influence of trapped magnetic flux quantum on two-dimensional magnetic field dependence of a Josephson junction.
Nanogranular BaTiO3–CoFe2O4 thin films deposited by pulsed laser ablation
Authors: Barbosa J. , Almeida B. G. , Mendes J. A. , Rolo A. G. , Araújo J. P. , Sousa J. B.
Published: April 2007

Detailed structural and magnetic measurements were performed on nanostructured composite thin films of cobalt ferrite (CoFe2O4-magnetostrictive) dispersed in a barium titanate (BaTiO3-piezoelectric) matrix, with different CoFe2O4 concentrations (ranging from x=20% to x=70%). The films were deposited by laser ablation on platinum covered Si(100). Their structure was studied by x-ray diffraction and Raman spectroscopy. The magnetic properties were measured with a superconducting quantum inteference device magnetometer. The nanocomposite films were polycrystalline and composed by a mixture of tetragonal-BaTiO3 and CoFe2O4 with the cubic spinel structure. The lattice parameter of the CoFe2O4 phase varied from 8.26Å (x=20%) to 8.35Å (x=70%), and, compared with bulk CoFe2O4, it was under compressive stress that relaxed as its concentration progressively increased. In the tetragonal-BaTiO3 phase, the lattice parameter a was contracted relative to the bulk phase and decreases with x. The lattice parameter c increased from 4.088Å (x=20%) to 4.376Å (x=70%), so that the BaTiO3 c axes were increasingly expanded as the quantity of the barium titanate phase was reduced. This behavior was the opposite of that observed in CoFe2O4. The magnetic measurements showed that the coercive fields decreased from 6.6kOe (x=20%) to 2.3kOe (x=70%), which was attributed to the progressive relaxation of the stress in the films as well as to the increase of particle agglomeration in bigger polycrystalline clusters with increasing cobalt ferrite concentration. For higher temperatures T=300K, the reduction of magnetocrystalline anisotropy induced a strong reduction of the coercive field.
Dynamics of quantum dissipation systems interacting with fermion and boson grand canonical bath ensembles: Hierarchical equations of motion approach
Authors: Jin Jinshuang , Welack Sven , Luo JunYan , Li Xin-Qi , Cui Ping , Xu Rui-Xue , Yan YiJing
Published: April 2007

A hierarchical equations of motion formalism for a quantum dissipation system in a grand canonical bath ensemble surrounding is constructed on the basis of the calculus-on-path-integral algorithm, together with the parametrization of arbitrary non-Markovian bath that satisfies fluctuation-dissipation theorem. The influence functionals for both the fermion or boson bath interaction are found to be of the same path integral expression as the canonical bath, assuming they all satisfy the Gaussian statistics. However, the equation of motion formalism is different due to the fluctuation-dissipation theories that are distinct and used explicitly. The implications of the present work to quantum transport through molecular wires and electron transfer in complex molecular systems are discussed.
Stress in silicon interlayers at the SiOx∕Ge interface
Authors: O’Callaghan S. , Monaghan S. , Elliott S. D. , Greer J. C.
Published: April 2007

Materials such as germanium display an advantage relative to silicon in terms of carrier mobilities but form poor quality interfaces to oxides. By sandwiching silicon layers between a germanium substrate and the oxide, advantages of the silicon oxide/silicon (SiOx∕Si) interface can be retained combined with the advantage of a high mobility germanium substrate. Using density functional theory calculations, stress within the silicon interlayer is quantified for different interlayer thicknesses revealing that for up to three silicon layers, the stress in the interlayer is compensated for by the energy gained by forming silicon-oxygen bonds at the interface.
Couplings between electronic transitions in a subsystem formulation of time-dependent density functional theory
Authors: Neugebauer Johannes
Published: April 2007

A subsystem formulation of time-dependent density functional theory (TDDFT) within the frozen-density embedding (FDE) framework and its practical implementation are presented, based on the formal TDDFT generalization of the FDE approach by Casida and Wesolowski [Int. J. Quantum Chem. 96, 577 (2004)]. It is shown how couplings between electronic transitions on different subsystems can be seamlessly incorporated into the formalism to overcome some of the shortcomings of the approximate TDDFT-FDE approach in use so far, which was only applicable for local subsystem excitations. In contrast to that, the approach presented here allows to include couplings between excitations on different subsystems, which become very important in aggregates composed of several similar chromophores, e.g., in biological or biomimetic light-harvesting systems. A connection to Förster- and Dexter-type excitation energy coupling expressions is established. A hybrid approach is presented and tested, in which excitation energy couplings are selectively included between different chromophore fragments, but neglected for inactive parts of the environment. It is furthermore demonstrated that the coupled TDDFT-FDE approach can cure the inability of the uncoupled FDE approach to describe induced circular dichroism in dimeric chromophores, a feature known as a “couplet,” which is also related to couplings between (nearly) degenerate electronic transitions.
Far-infrared and dielectric spectroscopy of relaxor ferroelectric (Pb1−xLax)(Zr0.4Ti0.6)O3
Authors: Buixaderas E. , Nuzhnyy D. , Veljko S. , Kamba S. , Savinov M. , Petzelt J. , Kosec M.
Published: April 2007

The dielectric behavior of tetragonal (Pb1−xLax)(Zr0.4Ti0.6)O3 (PLZT x∕40∕60) ceramics doped with lanthanum (x=12% and 15%) has been investigated from 102to1014Hz in the temperature range of 20–800K. Relaxor ferroelectric behavior, together with a first-order ferroelectric phase transition at TC below the dielectric maximum, was revealed. The lowest-frequency phonon partially softens to TC and splits into two components in the ferroelectric phase. It is shown that similar splitting is typical for all relaxors even for samples without ferroelectric phase transitions, because the TO1 splitting occurs due to a local distortion in the polar clusters. A relaxational mode, assigned to the dynamics of polar clusters, was revealed in the teraherz spectra below 800K. This mode slows down to the microwave range on cooling and finally anomalously broadens below TC, which appears to be characteristic for all relaxors. In comparison to the rhombohedral (Pb1−xLa0.095)(Zr0.65Ti0.35)O3, the low-temperature permittivity and dielectric losses are lower in the tetragonal PLZT as expected from the presence of the ferroelectric phase transition.
Ab initio study of hydrated potassium halides KX(H2O)1–6 (X=F,Cl,Br,I)
Authors: Olleta Adriana C. , Lee Han Myoung , Kim Kwang S.
Published: April 2007

The ionic dissociation of salts was examined with a theoretical study of KX (X=F,Cl,Br,I) hydrated by up to six water molecules KX(H2O)n (n=1–6). Calculations were done using the density functional theory and second order Møller-Plesset (MP2) perturbational theory. To provide more conclusive results, single point energy calculations using the coupled cluster theory with single, double, and perturbative triple excitations were performed on the MP2 optimized geometries. The dissociation feature of the salts was examined in terms of K–X bond lengths and K–X stretch frequencies. In general, the successive incorporation of water molecules to the cluster lengthens the K–X distance, and consequently the corresponding frequency decreases. Near 0K, the KX salt ion pairs can be partly separated by more than five water molecules. The pentahydrated KX salt is partly dissociated, though these partly dissociated structures are almost isoenergetic to the undissociated ones for KF∕KCl. For the hexahydrated complexes, KF is undissociated, KCl∕KBr is partly dissociated, and KI is dissociated (though this dissociated structure is nearly isoenergetic to a partly dissociated one). On the other hand, at room temperature, the penta- and hexahydrated undissociated structures which have less hydrogen bonds are likely to be more stable than the partly dissociated ones because of the entropy effect. Therefore, the dissociation at room temperature could take place for higher clusters than the hexahydrated ones.
Higher-order equation-of-motion coupled-cluster methods for electron attachment
Authors: Kamiya Muneaki , Hirata So
Published: April 2007

High-order equation-of-motion coupled-cluster methods for electron attachment (EA-EOM-CC) have been implemented with the aid of the symbolic algebra program TCE into parallel computer programs. Two types of size-extensive truncation have been applied to the electron-attachment and cluster excitation operators: (1) the electron-attachment operator truncated after the 2p-1h, 3p-2h, or 4p-3h level in combination with the cluster excitation operator after doubles, triples, or quadruples, respectively, defining EA-EOM-CCSD, EA-EOM-CCSDT, or EA-EOM-CCSDTQ; (2) the combination of up to the 3p-2h electron-attachment operator and up to the double cluster excitation operator [EA-EOM-CCSD(3p-2h)] or up to 4p-3h and triples [EA-EOM-CCSDT(4p-3h)]. These methods, capable of handling electron attachment to open-shell molecules, have been applied to the electron affinities of NH and C2, the excitation energies of CH, and the spectroscopic constants of all these molecules with the errors due to basis sets of finite sizes removed by extrapolation. The differences in the electron affinities or excitation energies between EA-EOM-CCSD and experiment are frequently in excess of 2eV for these molecules, which have severe multideterminant wave functions. Including higher-order operators, the EA-EOM-CC methods predict these quantities accurate to within 0.01eV of experimental values. In particular, the 3p-2h electron-attachment and triple cluster excitation operators are significant for achieving this accuracy.
Theory of radiative shocks in optically thick media
Authors: Drake R. P.
Published: April 2007

The theory of radiative shocks in optically thick media is discussed, using exact relations for the fluid dynamics quantities. A quantitative, semianalytic approach to the radiation transport is presented here, based on the observation that the mean intensity is essentially constant through the cooling layer. This permits a self-consistent three-layer solution, in which the temperature upstream of the density jump never strictly equals the final downstream temperature. The development of the diffusive structure in the precursor is not fundamentally tied to the downstream properties. Portions of the precursor may be transmissive or diffusive.
Temperature dependent shape transformation of Ge nanostructures by the vapor-liquid-solid method
Authors: Das K. , Chakraborty A. K. , NandaGoswami M. L. , Shingha R. K. , Dhar A. , Coleman K. S. , Ray S. K.
Published: April 2007

A vapor-liquid-solid method has been used to study the temperature dependent growth mechanism of Ge nanostructures on Au-coated Si (100) substrates. The formation of Ge nanodots, nanorods, and nanowires has been observed at different growth temperatures. The diameter of grown nanowires is found to be varying from 40 to 80 nm and that of nanorods from 70 to 90 nm, respectively. A comparative study has been done on three types of samples using x-ray diffraction and Raman spectroscopy. Photoluminescence spectra of grown nanostructures exhibit a broad emission band around 2.6 eV due to oxide related defect states.
How surface stresses lead to size-dependent mechanics of tensile deformation in nanowires
Authors: Shankar M. Ravi , King Alexander H.
Published: April 2007

It has been proposed that surface and interface stresses can modify the elastic behavior in nanomaterials such as nanowires. The authors show that surface stresses modify the tensile response of nanowires only when nonlinear elastic effects become important leading to cross terms between the applied stress and the surface stress. These effects are only significant when the radius of the nanowire is of the order of a few nanometers. The resulting alteration of tensile stiffness, though effected in part by the nonlinear elastic modulus, is particularly wrought by a modification of the stress state in the deformed nanowire.
Superconductivity in doped cubic silicon: An ab initio study
Authors: Bourgeois E. , Blase X.
Published: April 2007

The authors study within a first-principles approach the band structure, vibrational modes, and electron-phonon coupling in boron-, aluminum-, and phosphorus-doped silicon in the diamond phase. Their results provide evidences that the recently discovered superconducting transition in boron-doped cubic silicon, with a transition temperature of ∼0.34K, can be explained within a standard phonon-mediated mechanism. The importance of lattice compression and dopant related stretching modes are emphasized. The authors find that TC can be increased by one order of magnitude by adopting aluminum doping instead of boron.
Double and triple junction polymer solar cells processed from solution
Authors: Gilot Jan , Wienk Martijn M. , Janssen René A. J.
Published: April 2007

Multiple junction solar cells incorporating polymer:fullerene bulk heterojunctions as active layers and solution processed electron and hole transport layers are presented. The recombination layer, deposited between the active layers, is fabricated by spin coating ZnO nanoparticles from acetone, followed by spin coating neutral pH poly(3,4-ethylenedioxythiophene) from water and short UV illumination of the completed device. The key advantage of this procedure is that each step does not affect the integrity of previously deposited layers. The open-circuit voltage (Voc) for double and triple junction solar cells is close to the sum of the Voc’s of individual cells.
Broadband coherent anti-Stokes Raman scattering spectroscopy in supercontinuum optical trap
Authors: Shi Kebin , Li Peng , Liu Zhiwen
Published: April 2007

The authors report on a supercontinuum tweezer which combines tweezing with broadband (∼3000cm−1) coherent anti-Stokes Raman scattering (CARS) spectroscopy by taking advantage of the high spatial coherence and broad bandwidth of pulsed supercontinuum generated in a nonlinear photonic crystal fiber. Polarization-discriminated and time-resolved CARS is investigated to suppress the nonresonant four-wave-mixing background.
Separation of dielectric and space charge polarizations in CaCu3Ti4O12∕CaTiO3 composite polycrystalline systems
Authors: Bueno Paulo R. , Ribeiro William C. , Ramírez Miguel A. , Varela José A. , Longo Elson
Published: April 2007

The complex analysis of dielectric/capacitance is a very useful approach to separate different polarization contributions existing in polycrystalline ceramics. In this letter, the authors use this type of spectroscopic analysis to separate the bulk’s dielectric dipolar relaxation contributions from the polarization contribution due to space charge in the grain boundaries of a CaCu3Ti4O12∕CaTiO3 polycrystalline composite system. The bulk dielectric dipolar relaxation was attributed to the self-intertwined domain structures from the CaCu3Ti4O12 phase coupled to the dipole relaxation from the CaTiO3 phase, while the space charge relaxation was attributed to the Schottky-type potential barrier responsible for the highly non-Ohmic properties observed in this composite polycrystalline system.
Photoluminescence study of semipolar {101¯1} InGaN∕GaN multiple quantum wells grown by selective area epitaxy
Authors: Yu Hongbo , Lee L. K. , Jung Taeil , Ku P. C.
Published: April 2007

Semipolar InGaN∕GaN multiple quantum wells (MQWs) were fabricated on the {101¯1} facets of GaN pyramidal structures by selective area epitaxy. Optical properties of the MQWs were investigated by photoluminescence (PL) in comparison with (0001) MQWs. Compared with (0001) MQWs, the internal electric field in the {101¯1} MQWs was remarkably reduced, the PL peak redshifted monotonically with the increasing temperature, and the internal quantum efficiency was estimated to be improved by a factor of 3. These results suggest that the {101¯1} planes are promising for improving the performance of III-nitride light emitters owing to their surface stability and suppression of polarization effects.
Fabrication of Ta2O5∕GeNx gate insulator stack for Ge metal-insulator-semiconductor structures by electron-cyclotron-resonance plasma nitridation and sputtering deposition techniques
Authors: Otani Yohei , Itayama Yasuhiro , Tanaka Takuo , Fukuda Yukio , Toyota Hiroshi , Ono Toshiro , Mitsui Minoru , Nakagawa Kiyokazu
Published: April 2007

The authors have fabricated germanium (Ge) metal-insulator-semiconductor (MIS) structures with a 7-nm-thick tantalum pentaoxide (Ta2O5)∕2-nm-thick germanium nitride (GeNx) gate insulator stack by electron-cyclotron-resonance plasma nitridation and sputtering deposition. They found that pure GeNx ultrathin layers can be formed by the direct plasma nitridation of the Ge surface without substrate heating. X-ray photoelectron spectroscopy revealed no oxidation of the GeNx layer after the Ta2O5 sputtering deposition. The fabricated MIS capacitor with a capacitance equivalent thickness of 4.3nm showed excellent leakage current characteristics. The interface trap density obtained by the modified conductance method was 4×1011cm−2eV−1 at the midgap.
Magnetic and transport behaviors in Ge1−xMnxTe with high Mn composition
Authors: Chen W. Q. , Teo K. L. , Lim S. T. , Jalil M. B. A. , Liew T. , Chong T. C.
Published: April 2007

The authors investigate the magnetic and transport behaviors of Ge1−xMnxTe thin films with high Mn composition (x=0.98) grown by solid-source molecular-beam epitaxy. The temperature-dependent magnetization (M-T) gives a Curie paramagnetic temperature θp∼120K, in contrast to the Curie temperature of TC∼95K obtained from the Arrott plot and temperature-dependent resistivity measurement. The resistivity and M-T behaviors can be attributed to weak localization effect of disordering. The authors discussed the ferromagnetism in Ge0.02Mn0.98Te on the basis of the Ruderman-Kittel-Kasuya-Yoshida interaction and clustering effect.
ZnO nanowires and nanobelts: Shape selection and thermodynamic modeling
Authors: Fan Hong Jin , Barnard Amanda S. , Zacharias Margit
Published: April 2007

The authors show that, during a steady-state vapor phase growth of ZnO nanomaterials, indium doping causes the structural change from usual [0001]-axial short nanowires to [112¯0]-axial nanobelts of much larger aspect ratio. They used an analytical thermodynamic model based on geometric summation of the Gibbs free energy to predict the dimension dependence of the nanowires and nanobelts for both pure and In-doped ZnO. The calculation result agrees with the experiment observation that in situ indium doping influences the nucleation and supports the dominating growth of a-axial nanobelts over c-axial nanowires.
On the nature of the spin-polarized hole states in a quasi-two-dimensional GaMnAs ferromagnetic layer
Authors: Dias Cabral E. , Boselli M. A. , da Cunha Lima A. T. , Ghazali A. , da Cunha Lima I. C.
Published: April 2007

A self-consistent calculation of the density of states and the spectral density function is performed in a two-dimensional spin-polarized hole system based on a multiple-scattering approximation. Using parameters corresponding to GaMnAs thin layers, a wide range of Mn concentrations and hole densities have been explored to understand the nature, localized or extended, of the spin-polarized holes at the Fermi level for several values of the average magnetization of the Mn system. The authors show that, for a certain interval of Mn and hole densities, an increase on the magnetic order of the Mn ions come together with a change of the nature of the states at the Fermi level. This fact provides a delocalization of spin-polarized extended states antialigned to the average Mn magnetization and a higher spin polarization of the hole gas. This nonmetal-to-metal transition caused by the increase of Mn concentration once the ferromagnetic phase is reached was observed experimentally since the first samples were produced. These results are consistent with the occurrence of ferromagnetism with relatively high transition temperatures observed in some thin film samples and multilayered structures of this material.
Integrated reactive ion etching to pattern cross-linked hydrophilic polymer structures for protein immobilization
Authors: Bhatnagar Parijat , Strickland Aaron D. , Kim Il , Malliaras George G. , Batt Carl A.
Published: April 2007

Patterning of cross-linked hydrophilic polymer features using reactive ion etching (RIE) capable of covalently immobilizing proteins has been achieved. Projection photolithography was used to pattern photoresist to create micromolds. Vapor phase molecular self-assembly of polymerizable monolayer in molds allowed covalent binding of hydrogel on surface during free-radical polymerization. Excess hydrogel blanket film was consumed with oxygen RIE resulting into hydrogel pattern of 1μm size aligned to prefabricated silicon oxide structures. Proteins were finally coupled through their primary amine groups selectively to acid functionalized hydrogel features through stable amide linkages using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride and N-hydroxysulfosuccinimide.
Nanotracks as transport routes for enhanced and reversible hydrogen diffusion in swift heavy ion irradiated Pd–Pr layers
Authors: Kala Shubhra , Mehta B. R. , Khan S. A. , Avasthi D. K.
Published: April 2007

This study reports an all-round enhancement in the hydrogenation properties of Pd–Pr layers due to ion tracks formed on irradiation with 120MeV Ag+10 ions. About 17.8% increase in the hydrogen stoichiometry value during loading, near maximal removal (about 31%) during deloading, and increase in the active layer thickness are observed on ion irradiation. Nonequilibrium structural change during ion-induced shock wave generation results in the formation of nanotracks throughout the film thickness, which provide two-way transport routes for H diffusion. This study thus provides an effective methodology of improving the hydrogenation properties of materials.
Dynamin 2 is required for the enhancement of HIV-1 infectivity by Nef
Authors: Pizzato Massimo , Helander Anna , Popova Elena , Calistri Arianna , Zamborlini Alessia , Palù Giorgio , Göttlinger Heinrich G.
Published: April 2007

Nef is a virulence factor of HIV-1 and other primate lentiviruses that is crucial for rapid progression to AIDS. In cell culture, Nef increases the infectivity of HIV-1 progeny virions by an unknown mechanism. We now show that dynamin 2 (Dyn2), a key regulator of vesicular trafficking, is a binding partner of Nef that is required for its ability to increase viral infectivity. Dominant-negative Dyn2 or the depletion of Dyn2 by small interfering RNA potently inhibited the effect of Nef on HIV-1 infectivity. Furthermore, in Dyn2-depleted cells, this function of Nef could be rescued by ectopically expressed Dyn2 but not by Dyn1, a closely related isoform that does not bind Nef. The infectivity enhancement by Nef also depended on clathrin, because it was diminished in clathrin-depleted cells and profoundly inhibited in cells expressing the clathrin-binding domain of AP180, which blocks clathrin-coated pit formation but not clathrin-independent endocytosis. Together, these findings imply that the infectivity enhancement activity of Nef depends on Dyn2- and clathrin-mediated membrane invagination events.
Effect of light scattering from source optics in goniometric diffuse reflectance measurements
Authors: Holopainen Silja , Manoocheri Farshid , Nevas Saulius , Ikonen Erkki
Published: April 2007

The significance of light scattering around the main beam in a gonioreflectometer based measurement of spectral diffuse reflectance is discussed. This kind of scatter is always present in goniometric measurement systems that use a shaped measurement beam. Furthermore, errors due to this effect are a potential cause of discrepancies between goniometer and integrating-sphere based measurement methods. Procedures used to determine such errors and the required corrections are presented. At the Helsinki University of Technology, the determined wavelength-dependent correction in the worst case was as high as −1.6% and could be reduced to −0.2% with improvements in the optical setup of the gonioreflectometer. The measurement results for our diffuse reflectance reference materials with the appropriate corrections in each case are in good agreement, which gives a new view on some measurements reported earlier.
Germ of a synthesis: space–time is spinorial, extra dimensions are time-like
Authors: Sparling George A.J
Published: April 2007

A pressing issue for modern physics is the possibility of extra dimensions of space–time. Here, a novel approach to this question is put forward, with three facets:

First, an integral transform is introduced into Einstein's general relativity that is non-local and spinorial. For Minkowskian space–time, the transform intertwines three spaces of six dimensions, whicha prioriare on an equal footing, linked by the octavic triality of Cartan. Two of these spaces are interpreted as null twistor spaces; the third may be regarded as giving space–time two extra time-like dimensions, for which the ordinary space–time is an axis of symmetry.

Second, it is suggested that the extra dimensions perdure for a general space–time: the overall structure is controlled by a generalized Fefferman tensor. Accordingly, it is posited that the additional time-like dimensions arise naturally and constitute an aspect of space–time reality that ultimately will be amenable to experimental investigation. Conceivably, devices such as the Large Hadron Collider will uncover this reality.

Third, it is argued that the structure hints at a synthesis of ideas deriving from general relativity, string theory, condensed matter physics, category theory and non-commutative geometry.
Birth order and male androphilia in Samoanfa'afafine
Authors: Vasey Paul L , VanderLaan Doug P
Published: April 2007

The manner in which male androphilia is publicly expressed varies cross-culturally. As such, it is unclear whether distinct or common underlying causal processes characterize male androphilia in different cultures. Establishing the existence of cross-cultural universals in male androphilia is one means of ascertaining whether common biological bases underlie this phenomenon despite its culturally distinct forms. The evidence that the number of older biological brothers increases the odds of androphilia in later-born males has been well documented for Western samples (i.e. thefraternal birth order effect); but there is little evidence for this effect in non-Western samples. Here, we compare the birth order of androphilic males (i.e.fa'afafine) and gynephilic males from the politically autonomous Polynesian nation of Independent Samoa. Results indicate that relative to gynephilic males,fa'afafinetend to have more siblings and are generally later born when birth order is quantified using Slater, fraternal and sororal indices. More specifically,fa'afafinetend to have a greater number of older brothers, older sisters and younger brothers. We discuss the observed effects in relation to the differing reproductive patterns exhibited by the mothers offa'afafineand gynephilic males, and to existing social and biological theories for sexual orientation.
Stoats (Mustela erminea) provide evidence of natural overland colonization of Ireland
Authors: Martínková Natália , McDonald Robbie A , Searle Jeremy B
Published: April 2007

The current Irish biota has controversial origins. Ireland was largely covered by ice at the Last Glacial Maximum (LGM) and may not have had land connections to continental Europe and Britain thereafter. Given the potential difficulty for terrestrial species to colonize Ireland except by human introduction, we investigated the stoat (Mustela erminea) as a possible cold-tolerant model species for natural colonization of Ireland at the LGM itself. The stoat currently lives in Ireland and Britain and across much of the Holarctic region including the high Arctic. We studied mitochondrial DNA variation (1771 bp) over the whole geographical range of the stoat (186 individuals and 142 localities), but with particular emphasis on the British Isles and continental Europe. Irish stoats showed considerably greater nucleotide and haplotype diversity than those in Britain. Bayesian dating is consistent with an LGM colonization of Ireland and suggests that Britain was colonized later. This later colonization probably reflects a replacement event, which can explain why Irish and British stoats belong to different mitochondrial lineages as well as different morphologically defined subspecies. The molecular data strongly indicate that stoats colonized Ireland naturally and that their genetic variability reflects accumulation of mutations during a population expansion on the island.
Levels of processing during non-conscious perception: a critical review of visual masking
Authors: Kouider Sid , Dehaene Stanislas
Published: April 2007

Understanding the extent and limits of non-conscious processing is an important step on the road to a thorough understanding of the cognitive and cerebral correlates of conscious perception. In this article, we present a critical review of research on subliminal perception during masking and other related experimental conditions. Although initially controversial, the possibility that a broad variety of processes can be activated by a non-reportable stimulus is now well established. Behavioural findings of subliminal priming indicate that a masked word or digit can have an influence on perceptual, lexical and semantic levels, while neuroimaging directly visualizes the brain activation that it evokes in several cortical areas. This activation is often attenuated under subliminal presentation conditions compared to consciously reportable conditions, but there are sufficiently many exceptions, in paradigms such as the attentional blink, to indicate that high activation,
per se
, is not a sufficient condition for conscious access to occur. We conclude by arguing that for a stimulus to reach consciousness, two factors are jointly needed: (i) the input stimulus must have enough strength (which can be prevented by masking) and (ii) it must receive top-down attention (which can be prevented by drawing attention to another stimulus or task). This view leads to a distinction between two types of non-conscious processes, which we call subliminal and preconscious. According to us, maintaining this distinction is essential in order to make sense of the growing neuroimaging data on the neural correlates of consciousness.
The control and monitoring system for the Adour 900
Authors: Harris P.J.H. , Swain B.A. , Webb K.P.
Published: April 2007

Looks at an aircraft engine manufacturer’s use of an electronic system to enhance an existing product. During the early 1990s Rolls‐Royce studied the changing military market and compared its range of engines with potential business opportunities. The trainer/light combat powerplant was one area where there was potential to develop its position. As a result of the continuing success of the BAe Hawk and Boeing Goshawk aircraft and the expectation of new sales well into the next century, the decision was taken to launch a new version of the Adour engine. Thus in 1996 Rolls‐Royce launched the Adour 900, based on the current, well‐proven Mark 871, but offering thrust growth, improved life cycle costs and enhanced functionality. Central to the concept of the Adour 900 is a new Full Authority Digital Engine Controller with integrated Engine Health Monitoring. Examines the features of the FADEC and EHM System, showing how they have been tailored to meet the needs of a modern trainer aircraft without sacrificing retrofit capability. Attention is also given to the development process which had to ensure the demanding design targets were met within the cost and timescale constraints.
Measuring the rates and impact of corrosion damage
Authors: Kinzie Richard C.
Published: April 2007

This paper focuses on corrosion maintenance on both commercial and military aircraft, which is based on finding and fixing the damage prior to its becoming a structural or safety concern.
New tools for aircraft maintenance
Authors: Komorowski Jerzy P.
Published: April 2007

An overview of the advances in understanding the impact of corrosion on structural integrity and the associated tools available for inspection, assessment and repair is presented. A comprehensive set of these tools would allow for a significant shift in aircraft maintenance concepts.
Fusible coring ‐ practical for forming one‐off structures
Authors: Morgan Glyn
Published: April 2007

Reviews the state of fusible‐core technology and describes various techniques: core casting, overmoulding and melt‐out. Suggests that fusible coring for small runs can make a product financially viable.
Corrosion control on CN‐235 aircraft
Authors: Sutika Ananta Wayan , Setiawan Wahyu , Shuko Widodo Hari , Kirmanto Dwi
Published: April 2007

Presents a model of how an Indonesian aircraft manufacturer, Industri Pesawat Terbang Nusantara (PT. IPTN), evaluates the causes of stress corrosion in CN‐235 aircraft and how it resolves these problems. Describes the different types of corrosion encountered and how it analyses each.
Head up designing with today’s technology
Authors: Inglesby Tom
Published: April 2007

Reports on the design and installation of a Head Up Display unit from Flight Visions, the FV‐2000 HUD, which has been fitted into Beachcraft’s King Air for private and commercial pilots. However, with the many models and revision levels of this popular aircraft, Flight Visions found it was spending too much time cutting and fitting styrofoam mockups of the HUD in sample aircraft. So it turned to modern technology in the form of the FaroArm digitizer from FARO Technologies (Lake Mary, FL) and CADKEY, a computer‐aided design (CAD) system from Cadkey (Windsor, CT).
Towards a scheduling and timing analysis solution for integrated modular avionic systems
Authors: Grigg Alan , Audsley Neil C.
Published: April 2007

Integrated modular avionics (IMA) aims to provide highly flexible, reliable and integrated solutions for future aircraft systems which can readily exploit new advances in processor and networking technologies. In this paper, we discuss the problems involved in the provision of appropriate scheduling and timing analysis techniques for IMA systems and suggest a potential solution.
Boeing 777 thrust reverser actuation system
Authors: O’Brien Mike
Published: April 2007

Outlines some of the features and design issues surrounding the thrust reverser actuation system (TRAS).
Trends in high temperature alloys: selection and manufacture
Authors: Rohrbach Kurt P.
Published: April 2007

Guidelines for making a wise choice when selecting high temperature alloys are provided. Four groups of alloys are discussed, along with helpful selection criteria. Substantial benefits accrue from contemporary alloy manufacturing techniques. Process databases and state‐of‐the‐art forging equipment significantly impact product quality, consistency and cost effectiveness. Finally, the author suggests that the elimination of unnecessary test requirements offers potential for savings in time and money. He feels that alloy integrity can be assured by any producer who can demonstrate narrow limits of compositional control, as well as melting, remelting and hot working controls.