bluuebunny/crossref_metadata_2025 huggingface dataset:
Polar mesosphere and lower thermosphere dynamics: 1. Mean wind and gravity wave climatologies
Authors: Dowdy Andrew J. , Vincent Robert A. , Tsutsumi Masaki , Igarashi Kiyoshi , Murayama Yasuhiro , Singer Werner , Murphy Damian J.
Published: September 2007

Mean wind and gravity wave climatologies are presented for the polar mesosphere and lower thermosphere (MLT). The data were derived using MF radars at Davis (69°S, 78°E) and Syowa (69°S, 40°E) in the Antarctic and Poker Flat (65°N, 147°W) and Andenes (69°N, 16°E) in the Arctic. The dynamics of the Antarctic MLT are found to be significantly different from the Arctic MLT. Summer maxima in both the westward and equatorward winds occur closer to the solstice in the Antarctic than in the Arctic. The greater symmetry around the solstice suggests radiative effects may play a greater role in controlling the state of the Antarctic MLT than in the Arctic, where dynamical effects appear to be more important. Gravity wave observations also suggest that wave drag may be greater in the Arctic than in the Antarctic. The equatorward flow near the mesopause persists later in summer in the Arctic than in the Antarctic, as do observations of polar mesospheric clouds and polar mesospheric summer echoes. All three phenomena begin at about the same time in each hemisphere, but end later in the Arctic than in the Antarctic. It is proposed that the magnitude of the meridional winds can be used as a proxy for gravity wave driving and the consequent adiabatic cooling in the MLT. Seasonal variations in gravity wave activity are predominately combinations of annual and semiannual components. Significant hemispheric differences are observed for both the timing and magnitude of these seasonal variations.
Polar mesosphere and lower thermosphere dynamics: 2. Response to sudden stratospheric warmings
Authors: Dowdy Andrew J. , Vincent Robert A. , Tsutsumi Masaki , Igarashi Kiyoshi , Murayama Yasuhiro , Singer Werner , Murphy Damian J. , Riggin D. M.
Published: September 2007

The dynamical response of the polar mesosphere and lower thermosphere (MLT) to sudden stratospheric warmings is investigated using MF radars at Davis (69°S, 78°E), Syowa (69°S, 40°E) and Rothera (68°S, 68°W) in the Antarctic and Poker Flat (65°N, 147°W) and Andenes (69°N, 16°E) in the Arctic. Mean winds, gravity waves and planetary waves are investigated during sudden stratospheric warmings, and comparisons are made with climatological means. The available MF radar data set includes six major sudden stratospheric warmings in the Northern Hemisphere and the unprecedented 2002 Southern Hemisphere major stratospheric warming. Three of the six northern events are relatively weak and could almost be classed as minor warmings, while the larger three have similar characteristics to the event in the Southern Hemisphere. Zonal wind reversals associated with the major warmings in both hemispheres are generally weaker and earlier by several days in the mesosphere than in the stratosphere. There are, however, significant differences between locations in their response to stratospheric warmings. The zonal winds are remarkably weaker than average during both winter and spring around the time of the southern major warming of 2002, but these effects are not observed for the Northern Hemisphere events. Gravity wave activity is found to vary significantly between individual stratospheric warming events and also between individual locations.
Comparison of AIRS, MODIS, CloudSat and CALIPSO cloud top height retrievals
Authors: Weisz Elisabeth , Li Jun , Menzel W. Paul , Heidinger Andrew K. , Kahn Brian H. , Liu Chian‐Yi
Published: September 2007

Knowledge of cloud properties like cloud top height (CTH) is essential to understand their impact on the earth's radiation budget and on climate change. High spectral resolution measurements from the Atmospheric Infrared Sounder (AIRS) are well suited to reveal valuable information about cloud altitude. The CTH retrievals derived from AIRS single field‐of‐view (FOV) radiance measurements are compared with the operational MODIS (Moderate Resolution Imaging Spectroradiometer) cloud product, and Level 2 products obtained from radar and lidar instruments onboard the EOS (Earth Observing System) CloudSat and the CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellites. Two cases containing a variety of cloud conditions have been studied, and the strengths/shortcomings of CTH products from infrared (IR) sounder radiances are discussed.
Recent extreme near‐surface permafrost temperatures on Svalbard in relation to future climate scenarios
Authors: Isaksen K. , Benestad R. E. , Harris C. , Sollid J. L.
Published: September 2007

Here we report extreme near‐surface permafrost warming resulting from a remarkable temperature anomaly during winter and spring 2005–2006 on Svalbard. We demonstrate that this atmospheric temperature anomaly fell well within the range of predicted warming scenarios for the late 21st Century. The mean December to May air temperature on Svalbard was as high as −4.8°C, some 8.2°C above the 1961–1990 average. The 2006 mean ground temperature at the permafrost table in a monitored borehole in bedrock was 1.8°C higher than the mean for the previous six years, and this corresponded to a 40% reduction in accumulated annual negative degree‐days at that depth. The thermal response was detectable to a depth of at least 15 m. In future, a greater frequency of high‐temperature anomalies such as this, superimposed on a warming trend, is likely to cause potentially hazardous irregular acceleration in near‐surface permafrost thawing.
Azimuthal structures of substorm electron injection and their signatures in riometer observations
Authors: Liang Jun , Liu W. W. , Spanswick E. , Donovan E. F.
Published: September 2007

We propose a theoretical model to investigate the effects of the curvature/gradient (c/g) drift and the finite azimuthal extent of the dipolarization region on the electron injection process associated with the substorm dipolarization. We study the azimuthal structure of high‐energy (>30 keV) electron precipitation flux and compare the result with riometer observations. We are able to reproduce three basic archetypes of riometer responses to substorms, namely, the spike, dispersionless injection, and dispersed injection events catalogued in previous observations. The electron injection near the duskward edge of the dipolarization region is most subject to azimuthal c/g drift loss, appearing in riometer observations as the “spike” feature. The “dispersionless injection” response is seen inside the dipolarization region but some distance away from its western border: or, alternatively, when the substorm has a rapid westward expansion, so that the gain and loss of electrons from the duskside and dawnside of a dipolarizing flux tube roughly balance. The “dispersed injection” feature is seen east of the dipolarization region. Our theory successfully explains the statistical differences in terms of magnetic local time location and peak intensity between spikes and injection events. Through the substorm event on 23 May 1998 we demonstrate that our theoretical predictions of riometer responses are very consistent with the observations. We highlight the potential of riometers in resolving the azimuthal extent and evolution of the dipolarization region, which provides a new ground‐based technique of remote sensing the substorm process.
Energetic neutral atom response to solar wind dynamic pressure enhancements
Authors: Lee D.‐Y. , Ohtani S. , Brandt P. C. , Lyons L. R.
Published: September 2007

We have investigated the response of the ring current to solar wind dynamic pressure (Pdyn) enhancement impacts on the magnetosphere by using energetic neutral atom (ENA) images obtained by the High‐Energy Neutral Atom (HENA) imager on board the IMAGE spacecraft. In this work we present several events by distinguishing between pressure events where only the pure compression effects exist (without substorm effects) and those where the substorm is triggered by the Pdyn enhancement, and we find notable differences between these two types of events. First, for the pure compression events, we present four events where the Pdyn increases by ∼100% to ∼450% under northward interplanetary magnetic field (IMF) conditions. The Pdyn enhancement results in weak‐to‐modest ENA emission increases in both the hydrogen and oxygen channels: The total ENA emission rate increases by ∼25% to ∼40% relative to averages over the 1‐hour period prior to the Pdyn enhancement impact. This ENA enhancement is due to ions adiabatically energized by the compression. The increased ENA emission rate drops as Pdyn decreases, implying that the ENA responses are directly caused by the adiabatic compression and decompression process. Also, the pure compression events lead to overall global, quasi‐simultaneous increases of ENA in contrast to pure substorm‐induced ENA enhancements that are initially localized in the nightside region followed by the drift effect. Next we present two events where the Pdyn enhancement was ∼100% and >300%, respectively, under strongly southward IMF conditions, IMF Bz ≤ −10 nT, and a substorm was triggered. For both events the hydrogen and oxygen ENA emission increase is far more significant than that for the pure compression events, more than 100% even when the low‐altitude contribution was excluded. This is primarily owing to energetic ions generated by the triggered substorm, although the compression effect itself occurs as well. Also, the ENA enhancement appears to be not as global in magnetic local time (MLT) as for the pure compression events, because of the predominant substorm effect that starts near midnight and spreads in MLT.
Identification of a region in the TASK3 two pore domain potassium channel that is critical for its blockade by methanandamide
Authors: Veale E L , Buswell R , Clarke C E , Mathie A
Published: September 2007

Background and purpose:

The TASK subfamily of two pore domain potassium channels (K2P) encodes for leak K currents, contributing to the resting membrane potential of many neurons and regulating their excitability. TASK1 and TASK3 channels are regulated by a number of pharmacological and physiological mediators including cannabinoids such as methanandamide. In this study, we investigate how methanandamide blocks these channels.

Experimental approach:

Currents through wild type and mutated TASK1 and TASK3 channels expressed in modified HEK‐293 cells were measured using whole‐cell electrophysiological recordings in the presence and absence of methanandamide.

Key results:

Methanandamide (3 μM) produced substantial block of hTASK1, hTASK3 and mTASK3 channels but was most potent at blocking hTASK3 channels. Block of these channels was irreversible unless cells were washed with buffer containing bovine serum albumin. Mutation of the distal six amino acids of TASK1 did not alter methanandamide inhibition, whilst C terminal truncation of TASK3 channels caused a small but significant reduction of inhibition. However, deletion of six amino acids (VLRFLT) at the interface between the final transmembrane domain and cytoplasmic C terminus of TASK3 channels gave functional currents that were no longer inhibited by methanandamide or by activation of GPCRs.

Conclusions and implications:

Methanandamide potently blocked TASK3 and TASK1 channels and both methanandamide and G protein‐mediated inhibition converged on the same intracellular gating pathway. Physiologically, methanandamide block of TASK1 and TASK3 channels may underpin a number of CNS effects of cannabinoids that are not mediated through activation of CB1 or CB2 receptors.

British Journal of Pharmacology (2007) 152, 778–786. doi:10.1038/sj.bjp.0707436; published online 10 September 2007
More types than one: multiple muscarinic receptor coupled K+currents undergo remodelling in an experimental model of atrial fibrillation
Authors: James A F , Hancox J C
Published: September 2007

The common cardiac arrhythmia atrial fibrillation (AF) tends to show progression in its severity, which is associated with ‘remodelling’: structural and electrophysiological changes that facilitate arrhythmia induction and maintenance. In this issue of theBJP, Yeh and colleagues demonstrate for the first time, down‐regulation of three types of muscarinic cholinergic receptor (mAChR) coupled K+currents (IKM2,IKM3and IKM4) and of M2, M3and M4mAChR subtype proteins, in a canine model of atrial tachycardia (AT) induced remodelling. The IKMs and their extent of AT‐induced remodelling were similar in left‐atrial and pulmonary vein (PV) myocytes, so remodelling of M2–M4receptor‐linked currents appears not to underlie the unique contribution of PVs to AF. Parasympathetic stimulation can increase susceptibility to AF; thus remodelling of M2–M4receptors and K+currents could be adaptive in AT. Further work is warranted to determine whether or not remodelling of multiple mAChRs and currents also contributes to human AF.

British Journal of Pharmacology(2007)152, 981–983; doi:10.1038/sj.bjp.0707437; published online 10 September 2007
α‐4/β‐1 and α‐L/β‐2 integrins mediate cytokine induced lung leukocyte‐epithelial adhesion and injury
Authors: Parmley L A , Elkins N D , Fini M A , Liu Y‐E , Repine J E , Wright R M
Published: September 2007

Background and purpose:

Injury to the alveolar epithelium is a critical feature of acute lung injury (ALI). Using a cytokine model of ALI we demonstrated previously that newly recruited mononuclear phagocytes (MNP) contributed to lung inflammation and injury. We hypothesized that cytokines delivered into the alveolar airspace would have multiple effects on the lung that may contribute to lung injury.

Experimental approach:

Intratracheal cytokine insufflation and leukocyte adoptive transferin vivowere combined within vitroanalyses of lung epithelial cell‐MNP adhesion and injury. Lung inflammatory injury was assessed by histology, leukocyte infiltration, and release of LDH and RAGE.

Key results:

Cytokine insufflation was associated with apparent MNP‐epithelial adhesion, up‐regulation of alveolar ICAM‐1 and VCAM‐1, and the release of LDH and RAGE into the bronchoalveolar lavage. Insufflation of small molecule integrin antagonists suppressed adhesion of MNP and modulated release of LDH and RAGE. Adoptive transfer of MNP purified from cytokine insufflated lungs into leukopenic rats demonstrated the requirement of MNP for release of LDH that was not induced by cytokine alone. Corroboration that disrupting the ICAM/LFA1 interaction or the VCAM/VLA4 interaction blocked MNP‐epithelial cell interaction and injury was obtainedin vitrousing both blocking monoclonal antibodies and the small molecule integrin antagonists, BIO5192 and XVA143.

Conclusions and implications:

MNP recruited following cytokine insufflation contributed to lung injury. Further, integrin antagonists reduced alveolar epithelial cell injury induced during lung inflammation. Intratracheal delivery of small molecule antagonsists of leukocyte‐epithelial adhesion that prevent lung injury may have significant clinical utility.

British Journal of Pharmacology(2007)152, 915–929; doi:10.1038/sj.bjp.0707443; published online 10 September 2007
CB2 receptors in reproduction
Authors: Maccarrone M
Published: September 2007

Cannabinoids have been always identified as harmful drugs because of their negative effects on male and female reproduction. The discovery of the ‘endocannabinoid system (ECS)’, composed of bioactive lipids (endocannabinoids), their receptors and their metabolic enzymes, and the generation of mouse models missing cannabinoid receptors or other elements of the ECS, has enabled a wealth of information on the significance of endocannabinoid signalling in multiple reproductive events: Sertoli cell survival, spermatogenesis, placentation, fertilization, preimplantation embryo development, implantation and postimplantation embryonic growth. These studies have also opened new perspectives in clinical applications, pointing to the ECS as a new target for correcting infertility and for improving reproductive health in humans. This review will focus on the involvement of type‐2 cannabinoid (CB2) receptors in reproductive biology, covering both the male and female sides. It will also discuss the potential relevance of the immunological activity of CB2 at the maternal/foetal interface, as well as the distinctiveness of CB2 versus type‐1 cannabinoid (CB1) receptors that might be exploited for a receptor subtype‐specific regulation of fertility. In this context, the different signalling pathways triggered by CB1 and CB2 (especially those controlling the intracellular tone of nitric oxide), the different activation of CB1 and CB2 by endogenous agonists (like anandamide and 2‐arachidonoylglycerol) and the different localization of CB1 and CB2 within membrane subdomains, termed ‘lipid rafts’, will be discussed. It is hoped that CB2‐dependent endocannabinoid signalling might become a useful target for correcting infertility, in both men and women.

British Journal of Pharmacology (2008) 153, 189–198; doi:10.1038/sj.bjp.0707444; published online 10 September 2007
ac response of a carbon chain under a finite frequency bias
Authors: Yu Yunjin , Wang Bin , Wei Yadong
Published: September 2007

Based on nonequilibrium Green’s function approach and density functional theory, we report first principles investigation on ac transport of four carbon atom chain connected by two semi-infinite aluminum leads Al–C4–Al. For small alternating external bias voltage, we expanded nonequilibrium Green’s function to the first order in the external voltage and calculated the dynamical conductance. The suppression of the dynamic conductance was obtained near the resonant level while far away from the resonance the giant enhancement of the dynamic conductance was also observed. These behaviors can be well understood under the wide-band limit. By changing the coupling distance between the carbon atom and aluminum leads, the system could change its transport response between capacitivelike and inductivelike.
n
-scroll chaotic attractors from a first-order time-delay differential equation
Authors: Yalçin Müştak E. , Özoguz Serdar
Published: September 2007

In this paper, a novel first-order delay differential equation capable of generating n-scroll chaotic attractor is presented. Hopf bifurcation of the introduced n-scroll chaotic system is analytically and numerically determined. The bifurcation diagram and Lyapunov spectrum of the system are calculated and the results show that the system has a chaotic regime in a wider parameter range. Furthermore, period-3 behavior has been observed on the system. Circuit realizations of two-, three-, four-, and five-scroll chaotic attractors are also presented.
Field-programmable rectification in rutile TiO2 crystals
Authors: Jameson John R. , Fukuzumi Yoshiaki , Wang Zheng , Griffin Peter , Tsunoda Koji , Meijer G. Ingmar , Nishi Yoshio
Published: September 2007

The authors report “field-programmable rectification” in crystals of rutile TiO2. A “programming” voltage is applied between two Pt electrodes on the surface of a crystal. Afterwards, current can pass in the direction of the programming voltage, but not in the reverse direction. The polarity of the rectification can be reversed by applying a programming voltage of opposite sign. The effect was observed on the (110) and (100) surfaces, but not the (001) surface. The proposed mechanism is field-induced motion of oxygen vacancies, which pile up under the negative terminal, eliminating a Schottky barrier, but leaving one at the positive terminal intact.
Enhanced efficiency of multilayer organic light-emitting diodes with a low-refractive index hole-transport layer: An effect of improved outcoupling?
Authors: Köhnen Anne , Gather Malte C. , Riegel Nina , Zacharias Philipp , Meerholz Klaus
Published: September 2007

The authors report on an internal device modification for multilayer organic light-emitting diodes (OLEDs) with enhanced efficiency that promises high compatibility with conventional manufacturing processes. By copolymerization of a hole-conducting monomer with a compound possessing a lower refractive index, a hole-transport layer with reduced optical density but slightly reduced hole-transport properties is formed. Multilayer OLEDs based on this reduced-index layer show a 25% increased efficiency compared to reference devices. The results are compared to optical simulations of the dipole emission from thin organic films. It is found that the efficiency improvement is only to some extent due to enhanced outcoupling resulting directly from the reduced refractive index but primarily due to a change of the width of the emission zone.
Scanning optical pyrometer for measuring temperatures in hollow cathodes
Authors: Polk J. E. , Marrese-Reading C. M. , Thornber B. , Dang L. , Johnson L. K. , Katz I.
Published: September 2007

Life-limiting processes in hollow cathodes are determined largely by the temperature of the electron emitter. To support cathode life assessment, a noncontact temperature measurement technique which employs a stepper motor-driven fiber optic probe was developed. The probe is driven inside the hollow cathode and collects light radiated by the hot interior surface of the emitter. Ratio pyrometry is used to determine the axial temperature profile. Thermocouples on the orifice plate provide measurements of the external temperature during cathode operation and are used to calibrate the pyrometer system in situ with a small oven enclosing the externally heated cathode. The diagnostic method and initial measurements of the temperature distribution in a hollow cathode are discussed.
Polarization characteristics of photonic quantum ring laser with three-dimensional whispering gallery resonances
Authors: Kim D. K. , An S.-J. , Lee E. G. , Kwon O’Dae
Published: September 2007

We report polarization characteristics of light from a photonic quantum ring (PQR) laser of three-dimensional (3D) whispering gallery modes. The 3D polarization states of light from the PQR laser were studied with a home-built solid-angle scanner capable of detecting the spatial intensity distribution in a wide range of solid angles. The analysis shows that the dominant polarization vectors of the PQR laser emitting in the surface normal direction lie always tangential to the PQR perimeter, which means there is a strong carrier-photon coupling.
Long-range surface plasmon-polariton waveguides in silica
Authors: Berini Pierre
Published: September 2007

Metal stripe waveguides in silica, operating in the fundamental long-range mode and at optical free-space wavelengths near 1550nm, are discussed in detail. Straight and curved waveguides having various stripe geometries are modeled. Au, Ag, and Al are compared as metals for the stripe. The wavelength response of waveguides is computed. The impact of index asymmetry is determined and discussed. The results generated and collected herein should be useful to the design of low-loss metal stripe waveguides for integrated plasmonic applications in silica and cladding materials of comparable index.
Selective growth of single-crystalline ZnO nanowires on doped silicon
Authors: Könenkamp R. , Word R. C. , Dosmailov M. , Meiss J. , Nadarajah A.
Published: September 2007

We report the growth of single-crystalline ZnO nanowires on n- and p-type Si wafers by electrodeposition. On strongly doped n-type Si high-quality nanowires can be grown under similar conditions as used for metallic substrates. For low electron concentrations occurring in weakly n-type or in p-type wafers, nanowire growth is inhibited. This difference allows selective growth in strongly n-type areas. The inhibited growth on weakly n-type and p-type wafers can be improved by applying stronger cathodic electrode potentials or by illuminating the growth area. The wires on n-Si show efficient electroluminescence covering the visible and extending into the ultraviolet spectral range.
Ordering, magnetostriction, and elastic properties in Fe-27.5at.% Ga alloy single crystals
Authors: Jayaraman Tanjore V. , Corson Robert P. , Guruswamy Sivaraman
Published: September 2007

Fe–Ga alloys, with composition around 27.5at.% Ga, can be heat treated to obtain α (A2, bcc), α″ (D03-like, ordered bcc), β-Fe3Ga (D019, ordered hexagonal), and α-Fe3Ga (L12 ordered fcc) phases. In this work, the influence of α″ ordering on the magnetostriction coefficient (3∕2) λ100, elastic constants (C11, C12, and C44), and the magnetomechanical coefficients (B1) of the single crystals of α-Fe-27.5at.% Ga and α″-Fe-27.5at.% Ga alloy is examined. Single crystals of Fe-27.5at.% Ga were grown using the vertical Bridgman technique. Magnetostriction measurements were performed using [100]-oriented single crystals. Elastic constants were estimated using resonant ultrasound spectroscopy and analysis technique. It is shown that the α″ ordering in Fe-27.5at.% Ga alloy decreases the (3∕2) λ100 value from that of α phase. This is consistent with our previous work on polycrystalline Fe-27.5at.% Ga alloys. The α-Fe-27.5at.% Ga alloy single crystal was found to have a higher magnetoelastic coupling constant than the α″-Fe-27.5at.% Ga alloy single crystal.
Effect of thermal annealing under vacuum on the crystal structure, size, and magnetic properties of ZnFe2O4 nanoparticles
Authors: Philip John , Gnanaprakash G. , Panneerselvam G. , Antony M. P. , Jayakumar T. , Raj Baldev
Published: September 2007

In this paper, we report the variations in the crystal structure, average particle size, and magnetic properties of ZnFe2O4 nanoparticles on thermal annealing, using in situ high temperature x-ray diffraction (XRD). Fine powder of ZnFe2O4 nanoparticles with an average particle size of 9.3nm, prepared through coprecipitation technique, has been used in these studies. The powder is heated from room temperature to 1000°C, under vacuum in steps of 100°C and the XRD pattern is recorded in situ. A sudden drop in the lattice parameter from 8.478to8.468Å is observed at 800°C, above which it increases with increasing temperature. After annealing at 1000°C, the lattice parameter reduces from 8.441to8.399Å and the magnetization value increases from 5to62emu∕g, suggesting the possibility of a conversion of the cubic structured ZnFe2O4 from normal to inverse spinel structure due to canting of ions between the tetrahedral and octahedral interstitial sites. During annealing, the Zn2+ ions move from tetrahedral site to octahedral site whereas Fe3+ ions redistribute within the octahedral and tetrahedral sites in order to reduce the strain. The increase in the average particle size from 9to27nm, after the thermal annealing at 1000°C, can be attributed to coalescence phenomenon, which starts at 600°C. The estimated value of the activation energy of ZnFe2O4 nanoparticles during the growth is 18.207kJ∕mol.
Integration of GaAs epitaxial layer to Si-based substrate using Ge condensation and low-temperature migration enhanced epitaxy techniques
Authors: Oh Hoon Jung , Choi Kyu Jin , Loh Wei Yip , Htoo Thwin , Chua Soo Jin , Cho Byung Jin
Published: September 2007

A GaAs defect-free epitaxial layer has been grown on Si via a Ge concentration graded SiGe on insulator (SGOI) for application in high channel-mobility metal-oxide-semiconductor field effect transistor. The SGOI layer, 42nm thick, serves as the compliant and intermediate buffer to reduce the lattice and thermal expansion mismatches between Si and GaAs. A modified two-step Ge condensation technique achieves the surface Ge concentration in SGOI as high as 71%. It is also found that low-temperature migration enhanced epitaxy during the initial GaAs nucleation on the SGOI surface is critical to obtain a device quality GaAs layer by epitaxial growth.
Dynamical ultrafast all-optical switching of planar GaAs∕AlAs photonic microcavities
Authors: Harding Philip J. , Euser Tijmen G. , Nowicki-Bringuier Yoanna-Reine , Gérard Jean-Michel , Vos Willem L.
Published: September 2007

The authors study the ultrafast switching-on and -off of planar GaAs∕AlAs microcavities. Up to 0.8% refractive index changes are achieved by optically exciting free carriers at λ=1720nm and pulse energy Epump=1.8±0.18μJ. The cavity resonance is dynamically tracked by measuring reflectivity versus time delay with tunable laser pulses, and is found to shift by as much as 3.3 linewidths within a few picoseconds. The switching-off occurs with a decay time of ∼50ps. They derive the dynamic behavior of the carrier density and of the complex refractive index. They propose that the inferred 10GHz switching rate may be tenfold improved by optimized sample growth.
Relative detection efficiency of back- and front-illuminated charge-coupled device cameras for x-rays between 1keV and 18keV
Authors: Szlachetko J. , Dousse J.-Cl. , Hoszowska J. , Berset M. , Cao W. , Szlachetko M. , Kavčič M.
Published: September 2007

High-resolution x-ray measurements were performed with a von Hamos-type bent crystal spectrometer using for the detection of the diffracted photons either a back-illuminated charge-coupled device (CCD) camera or a front-illuminated one. For each CCD the main x-ray emission lines (e.g., Kα, Kβ, Lα, and Lβ) of a variety of elements were measured in order to probe the performances of the two detectors between 1 and 18keV. From the observed x-ray lines the linearity of the energy response, the noise level, the energy resolution, and the quantum efficiency ratio of the two CCDs were determined.
Iron-phosphate∕platinum∕carbon nanocomposites for enhanced electrocatalytic stability
Authors: Kim Chunjoong , Lee Byungjoo , Park Yejun , Park Byungwoo , Lee Jaeseung , Kim Hasuck
Published: September 2007

The effects of FePO4–Pt∕C nanocomposites on the electrocatalytic properties were examined after 1000 accelerated cycles (up to 1.48V vs normal hydrogen electrode). The FePO4–Pt∕C nanocomposites exhibited similar electrocatalytic properties to Pt∕C without any initial degradation, and also showed enhanced long-term stabilities. By optimizing the synthetic conditions of FePO4–Pt∕C nanocomposites, the well-dispersed FePO4 nanoparticles played important roles in preserving the Pt surface activities, by preventing both the dissolution and agglomeration of Pt nanoparticles.
On resonance diffraction of high frequency radiation at periodically corrugated semiconductor interfaces
Authors: Balakhonova N. A. , Kats A. V. , Gavrikov V. K.
Published: September 2007

It is shown that resonance features analogous to the well known in optics Wood-type anomalies can be observed in the terahertz range on a periodically profiled surface of a highly doped semiconductor at low temperatures. The anomalies are caused by surface plasmon polariton excitation under diffraction on the surface. The results are of interest both from the physical viewpoint and due to a wide field of possible applications in present-day information technologies.
X-ray photoemission spectroscopy determination of the InN/yttria stabilized cubic-zirconia valence band offset
Authors: King P. D. C. , Veal T. D. , Hatfield S. A. , Jefferson P. H. , McConville C. F. , Kendrick C. E. , Swartz C. H. , Durbin S. M.
Published: September 2007

The valence band offset of wurtzite InN(0001)/yttria stabilized cubic-zirconia (YSZ)(111) heterojunctions is determined by x-ray photoemission spectroscopy to be 1.19±0.17eV giving a conduction band offset of 3.06±0.20eV. Consequently, a type-I heterojunction forms between InN and YSZ in the straddling arrangement. The low lattice mismatch and high band offsets suggest potential for use of YSZ as a gate dielectric in high-frequency InN-based electronic devices.
Nanoscale patterning of a conjugated oligomer
Authors: Chandekar Amol , Whitten James E.
Published: September 2007

Vapor-deposited α-sexithiophene is finding important organic electronic device applications. A method of patterning dibutylphosphonate-substituted sexithiophene (DBP-α6T), a soluble version of this conjugated oligomer, with lateral dimensions as small as 50nm is described. It consists of using either microcontact printing or dip-pen nanolithography to form hydrophilic alkanethiol patterns on a gold surface. The remainder of the surface is backfilled with a hydrophobic alkanethiol. When DBP-α6T is spin-coated and annealed, it preferentially adsorbs on the hydrophilic patterns. Photoemission demonstrates the similarity in valence electronic structure of DBP-α6T films to α-sexithiophene. This patterning method may be useful for future nanoscale device fabrication.
Direct-current control of radiation-induced differential magnetoresistance oscillations in two-dimensional electron systems
Authors: Lei X. L.
Published: September 2007

Magnetoresistance oscillations in two-dimensional electron systems driven simultaneously by a strong direct current and a microwave irradiation are analyzed within a unified microscopic scheme treating both excitations on an equal footing. The microwave-induced resistance oscillations are described by a parameter ϵω proportional to the radiation frequency, while the dc-induced resistance oscillations are governed by a parameter ϵj proportional to the current density. In the presence of both a microwave radiation and a strong dc, the combined parameter ϵω+ϵj is shown to control the main resistance oscillations, in agreement with the recent measurement [Zhang et al., Phys. Rev. Lett. 98, 106804 (2007)].
Smallest 90° domains in epitaxial ferroelectric films
Authors: Vlooswijk A. H. G. , Noheda B. , Catalan G. , Janssens A. , Barcones B. , Rijnders G. , Blank D. H. A. , Venkatesan S. , Kooi B. , de Hosson J. T. M.
Published: September 2007

Periodic ferroelectric-ferroelastic 90° domain patterns with an unprecedented small domain periodicity of 27nm were observed in thin PbTiO3 films grown on DyScO3 substrates. These patterns contain the narrowest possible a domains (6nm wide) that allow to preserve the lateral coherence in the films, producing highly ordered patterns visible by x-ray diffraction.
Fiber-optic coupler based refractive index sensor and its application to biosensing
Authors: Tazawa Hidehisa , Kanie Tomohiko , Katayama Makoto
Published: September 2007

A simple and highly sensitive biosensor based on a fiber-optic coupler is developed. The change of refractive index due to biomolecular interaction on the surface of the coupler can be detected as the change of the transmission power. The sensitivity of the sensor is evaluated to be a noise level equivalent to a refractive index variation of 4×10−6. The binding of streptavidin is detected to be concentration dependent over a range of 0.5–2μg∕ml, by immobilizing biotin on the coupler surface via aminosilan treatment. This sensor allows the construction of a low-cost, portable, and label-free biosensing system.
Effective work function modulation of TaN metal gate on HfO2 after postmetallization annealing
Authors: Sugimoto Youhei , Kajiwara Masanari , Yamamoto Keisuke , Suehiro Yuusaku , Wang Dong , Nakashima Hiroshi
Published: September 2007

The effective work function (Φm,eff) of TaN on HfO2 after postmetallization annealing (PMA) was investigated using TaN∕HfO2∕SiO2∕Si as a sample structure. We found that Φm,eff on HfO2 is stable at PMA temperatures of less than 600°C and is 4.6eV, which is approximately 0.2eV higher than that on SiO2. In contrast, Φm,eff is modulated by PMA at temperatures greater than 750°C. An analysis by x-ray photoelectron spectroscopy suggests that the increased Φm,eff is strongly related to Ta oxide formation near the TaN∕HfO2 interface. The modulation of Φm,eff on HfO2 is discussed on the basis of intrinsic and extrinsic Fermi level pinning due to Ta–O bond formation at the TaN∕HfO2 interface.
Separation of long DNA molecules through cleavage of hydrogen bonds under a stretching force
Authors: Gao Lizeng , Wu Jiamin , Gao Di , Wu Jianzhong
Published: September 2007

The authors report that long DNA molecules of different lengths can be separated under a stretching force by cleaving hydrogen bonds that tether one end of the DNA to a substrate. This separation method can be implemented with a simple direct current electric field, does not require separation matrices, and, in principle, has no upper limit on the length of the DNA that can be efficiently separated. Here, they demonstrate efficient separation of lambda DNA (48 502 base pairs) from human genomic DNA (>100000 base pairs) using this method.
Constructing Nature in the Performance of Rural Heterosexualities
Authors: Little Jo
Published: September 2007

In this paper I respond through an exploration of the construction and performance of rural heterosexuality to recent calls for a more nuanced examination of heterosexualities. Using the notion of ‘heteronormativity’, I argue that our understanding of the spatiality of sexuality needs to focus on ‘ordinary’, ‘benign’ forms of family-based heterosexuality, as well as on more deviant forms. I claim that rural spaces provide important sites for the examination of the coconstruction of conventional heterosexuality and place. I demonstrate aspects of rural heterosexuality in the expectations, values, and practices of sexual relationships. I argue that heterosexual relationships are reinforced and sustained through the distancing of the rural from the urban and through associations between rurality and the romantic positioning of nature as central to both of these tactics.
The Art of Doing (Geographies of) Music
Authors: Wood Nichola , Duffy Michelle , Smith Susan J
Published: September 2007

Like every other work of art, music has become the stuff of social research: it has been interrogated for its economy, its politics, and its role in elaborating human life. Music has its geographies too: its cultural landscapes; its positioning in a soundworld; its embodiment; its materiality. But, intriguingly, until recently musical methodologies have remained half formed, fragmentary, hidden, elusive, out of sight, beyond words. This is partly a result of disciplinary histories and an unhelpful division of intellectual labour; it is partly an expression of what music is. This paper is a performance enacted to assemble the field of musical methodologies: to enlarge its scope; to engage with its strengths and limitations; to animate the soundworld; to participate in the art of doing and being (geographies of) music.
Afterimages
Authors: Doel Marcus A , Clarke David B
Published: September 2007

In this paper we argue that montage is at the heart of contemporary human geography. We demonstrate the centrality of montage in a wide variety of domains, including the analysis of modernity, the critique of political economy, and the practice of spatial science, before drawing out the implications of this centrality in the wake of so-called ‘nonrepresentational’ theory. While nonrepresentational styles of thought ordinarily veer off into considerations of performance, practice, and enactment, the ontological and epistemological play of montage plunges theoretical practice into what Agamben, Baudrillard, and Benjamin call ‘imagelessness’, ‘obscenity’, and the ‘optical unconscious’. Each of these is addressed in turn, and each is illustrated with stills taken from the films of Jim Jarmusch. The overall aim of the paper is to sensitize human geographers to the duplicitous operation of the discipline's cinematic optical unconscious, and in so doing to open up a space for a more considered engagement with geography's much-vaunted visuality.
Nonhuman Charisma
Authors: Lorimer Jamie
Published: September 2007

In this paper I outline the parameters of nonhuman charisma in the context of UK biodiversity conservation. Although conservationists frequently discuss charismatic species in their professional discourse there is little existing work that explores the character of this charisma and how it operates in environmental governance. In this paper I map nonhuman charisma and explore its ontological, ethical, and epistemological implications. I first illustrate a three-part typology of nonhuman charisma, comprising ecological, aesthetic, and corporeal charisma. Exploring nonhuman agency through the lens of charisma I contribute to ongoing efforts in geography and cognate disciplines to forge a ‘more-than-human’ understanding of agency and ethics. Nonhuman charisma provides a bounded relational ontology for considering nonhuman difference. Furthermore, nonhuman charisma draws attention to the importance of affect in understanding environmental ethics. Affect provides the vital motivating force that impels people to get involved in conservation. Second, I provide an example of nonhuman charisma in action. I draw on earlier work on human charisma to explore how charismatic organisms, operating as ‘flagship species’, are mobilised as boundary objects to achieve organisation order in the assemblages of UK biodiversity conservation.
Detecting Structure in Glass Patterns: An Interocular Transfer Study
Authors: Vreven Dawn , Berge Jarrod
Published: September 2007

Glass patterns are visual stimuli used here to study how local orientation signals are spatially integrated into global pattern perception. We measured a form aftereffect from adaptation to both static and dynamic Glass patterns and calculated the amount of interocular transfer to determine the binocularity of the detectors responsible for the perception of global structure. Both static and dynamic adaptation produced significant form aftereffects and showed a very high degree of interocular transfer, suggesting that Glass-pattern perception involves cortical processing beyond primary visual cortex. Surprisingly, dynamic adaptation produced significantly greater interocular transfer than static adaptation. Our results suggest a functional interaction between local orientation processing and global motion processing that contributes to form perception.
Learning Sequence of Views of Three-Dimensional Objects: The Effect of Temporal Coherence on Object Memory
Authors: Liu Taosheng
Published: September 2007

How humans recognize objects remains a contentious issue in current research on high-level vision. Here, I test the proposal by Wallis and Bülthoff (1999 Trends in Cognitive Sciences3 22–31) suggesting that object representations can be learned through temporal association of multiple views of the same object. Participants first studied image sequences of novel, three-dimensional objects in a study block. On each trial, the images were from either an orderly sequence of depth-rotated views of the same object (SS), a scrambled sequence of those views (SR), or a sequence of different objects (RR). Recognition memory was assessed in a following test block. A within-object advantage was consistently observed—greater accuracy in the SR than the RR condition in all four experiments, greater accuracy in the SS than the RR condition in two experiments. Furthermore, spatiotemporal coherence did not produce better recognition than temporal coherence alone (similar or less accuracy in the SS compared to the SR condition). These results suggest that the visual system can use temporal regularity to build invariant object representations, via the temporal-association mechanism.
Goodness of Regularity in Dot Patterns: Global Symmetry, Local Symmetry, and Their Interactions
Authors: Nucci Massimo , Wagemans Johan
Published: September 2007

Goodness is a classic Gestalt notion defined as salience or perceptual strength of a given pattern. All operational models of goodness have assigned a central role to mirror symmetry but not much attention has been paid to the distinction between global and local mirror symmetry, and their possible interactions. We designed eight different types of dot patterns (all consisting of 80 dots), combining different numbers (0, 1, and 2) and relative orientations (parallel or orthogonal to each other) of local and global axes of symmetry (affecting 50% or 100% of the dots, respectively) at different absolute orientations (vertical and horizontal). Each of 640 trials consisted of a short presentation of a new dot pattern, which subjects had to classify as regular or random. We hypothesised that the overall goodness of patterns is not the simple sum of the amount of regularity present in them but depends on the cooperation and competition between symmetries. The results confirmed our hypothesis, showing that performance in this regularity-detection task did not increase in a linear way when some symmetries were added to other symmetries.
Carbon sequestration and forest management.
Authors: Jandl R. , Vesterdal L. , Olsson M. , Bens O. , Badeck F. , Roc J.
Published: September 2007

Forest management has the potential to increase the terrestrial C pool. According to the rules of the Kyoto Protocol and of the United Nations Framework Convention on Climate Change, forestry can generate a sink for greenhouse gases that can contribute to meeting the national commitment to emissions reductions. Afforestation is a common strategy that over the course of decades leads to the incorporation of carbon dioxide (CO
2
) in plant biomass. However, site types such as wetlands and peatlands may even be a source of greenhouse gases when they are afforested. Adapted management of existing forests may have a less obvious or slower effect on the terrestrial C pool. It is mainly relevant in countries that already have a large forest cover. We analysed the effects of harvesting, rotation length, thinning, fertilizer application and tree-species selection. All these treatments have an impact on the forest productivity and consequently on C sequestration in the ecosystem. Many forest treatments are already an integral part of sustainable forestry practice. In the context of C sequestration and its accounting in national greenhouse-gas budgets, ecosystem stability is highly rated. Forests that are robust against disturbances up to a certain degree of severity are better suited for political commitments than stands of maximum productivity with a high risk of damages.
Nutrient management and dairy cattle production.
Authors: Harrison J. H. , Nennich T. D. , White R.
Published: September 2007

Nutrient management on dairy operations has become more complex as society demands more attention be placed on environmental stewardship. Although nutrient management has traditionally focused on an individual field basis, there is a need for dairy operations to focus on nutrients at a whole-farm level. The emphasis of contemporary integrated nutrient management should be placed on three areas: reducing imports, enhancing within farm efficiencies (both cropping and cow efficiencies), and seeking export opportunities for excess nutrients not utilized for crop production on the farm. Focusing on the flows of nutrients to, within, and off a farm assists with the development of management strategies of how to best handle nutrients in an environmentally friendly manner. Proper management of nutrients at the whole-farm level needs to be accompanied by an effort to inform the public and environmentally concerned groups about the proactive efforts that producers have adopted to manage nutrients and protect the environment. To be sustainable, integrated nutrient management will require an expanded effort to reconnect the nutrient cycle and link the movement of nutrients between sites of feed production and feed utilization.