bluuebunny/crossref_metadata_2025 huggingface dataset:
Wave gradiometry for USArray: Rayleigh waves
Authors: Liang Chuntao , Langston Charles A.
Published: February 2009

Wave gradiometry (WG) is a new array data processing technique to extract phase velocity, wave directionality, geometrical spreading, and radiation pattern from spatial gradients of waveforms. A weighted inversion method and a reducing velocity method are introduced to compute spatial gradients accurately for irregular arrays. Numerical experiments are conducted to test techniques and to evaluate the parameters determined from the WG method. We apply this method to USArray data for the western United States. In this study, Rayleigh waves from nine earthquakes with varying azimuths are analyzed. The stability of this method is shown by the similarity between the results from two nearly collocated earthquakes from the Kurile Islands. The error check shows the WG results are stable for ambient noise level as high as 10%. Phase velocities determined by WG and two station (TS) methods are statistically consistent, while these determined from beam forming method are systematically higher for wavelength larger than one quarter of the array diameter. Our results show that, first, the average phase velocities of Rayleigh waves range from 3.8 to 4.1 km/s for periods from 60 s to 150 s. This is consistent with average earth models. The prominent feature on the phase velocity map is that the Basin and Range province is dominated by velocity lows while the west coast of the United States and the north and northeastern Snake River plain are dominated by velocity highs. The Snake River plain appears to be a primary tectonic boundary. Second, azimuthal variations represent the accumulated wave directionality changes along the raypath. A velocity contrast of 0.25 km/s across the oceanic‐continental lithosphere boundary along the west coast of the United States is needed to explain the negative azimuth variations. Third, geometrical spreading is slightly anticorrelated with phase velocity, which may suggest that amplitude variations in radial directions are subject to surface wave focusing and defocusing. Fourth, similar to the wave directionality, radiation pattern variations also exhibit strong path dependence. Further theoretical and experimental studies will be conducted to understand the two amplitude parameters: geometrical spreading and radiation pattern and their relations with the local geophysical properties.
Regional cooling in a warming world: Recent temperature trends in the southeast Pacific and along the west coast of subtropical South America (1979–2006)
Authors: Falvey Mark , Garreaud René D.
Published: February 2009

While it is widely accepted that the global mean atmospheric temperature has increased in recent decades, the spatial distribution of global warming has been complex. In this study we comprehensively characterize the spatial pattern, including vertical structure, of temperature trends along the subtropical west coast of South America (continental Chile) for the period 1979–2006 and examine their consistency with expectations based on the CMIP‐3 ensemble of coupled ocean‐atmosphere simulations for the late 20th century. In central and northern Chile (17°–37°S) the most notable feature is a strong contrast between surface cooling at coastal stations (−0.2°C/decade) and warming in the Andes (+0.25°C/decade), only 100–200 km further inland. Coastal radiosonde data imply that the coast‐Andes variation is largely due to strong vertical stratification of temperature trends in the atmosphere west of the Andes. The coastal cooling appears to form part of a larger‐scale, La Niña‐like pattern and may extend below the ocean mixed layer to depths of at least 500 m. Over continental Chile the CMIP‐3 GCM ensemble predicts temperature trends similar to those observed in the Andes. The cooling along the Chilean coast is not reproduced by the models, but the mean SST warming is weaker there than any other part of the world except the Southern Ocean. It is proposed that the intensification of the South Pacific Anticyclone during recent decades, which is also a simulated consequence of global warming, is likely to play a major role in maintaining cooler temperatures off the coast of Chile.
CO retrievals based on MOPITT near‐infrared observations
Authors: Deeter M. N. , Edwards D. P. , Gille J. C. , Drummond James R.
Published: February 2009

We report the first retrieval results of tropospheric carbon monoxide (CO) exclusively using near‐infrared (NIR) radiances in the 2.3 μm CO overtone band observed by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument. For daytime overpasses over land, such observations complement MOPITT's thermal infrared (TIR) observations in the 4.7 μm CO fundamental band, especially for constraining the CO total column. Retrievals are performed in an optimal estimation framework in which effective radiance errors due to geophysical sources are estimated empirically. The new NIR‐based retrievals are evaluated through comparisons with both the standard TIR‐based MOPITT CO product and CO profile measurements.
Recent increases in atmospheric concentrations of Bi, U, Cs, S and Ca from a 350‐year Mount Everest ice core record
Authors: Kaspari Susan , Mayewski Paul A. , Handley Michael , Osterberg Erich , Kang Shichang , Sneed Sharon , Hou Shugui , Qin Dahe
Published: February 2009

High‐resolution major and trace elements (Sr, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, U, Tl, Al, S, Ca, Ti, V, Cr, Mn, Fe, and Co) quantified in a Mount Everest ice core (6518 m above sea level) spanning the period 1650–2002 AD provides the first Asian record of trace element concentrations from the pre‐industrial era, and the first continuous high‐resolution Asian record from which natural baseline concentrations and subsequent changes due to anthropogenic activities can be examined. Modern concentrations of most elements remain within the pre‐industrial range; however, Bi, U, and Cs concentrations and their enrichment factors (EF) have increased since the ∼1950s, and S and Ca concentrations and their EFs have increased since the late 1980s. A comparison of the Bi, U, Cs, S, and Ca data with other ice core records and production data indicates that the increase in atmospheric concentrations of trace elements is widespread, but that enrichment varies regionally. Likely sources for the recent enrichment of these elements include mining, metal smelting, oil and coal combustion, and end uses for Bi, and mining and refinement for U and Cs. The source of the synchronous enrichment of Ca and S is less certain, but may be related to land use and environmental change.
Mid‐Miocene paleoproductivity in the Atlantic Ocean and implications for the global carbon cycle
Authors: Diester‐Haass Liselotte , Billups Katharina , Gröcke Darren R. , François Louis , Lefebvre Vincent , Emeis Kay C.
Published: February 2009

A prominent, middle Miocene (17.5–13.5 Ma) carbon isotope excursion ubiquitously recorded in carbonate sediments has been attributed to enhanced marine productivity and sequestration of 13C depleted organic carbon in marine sediments or enhanced carbon burial in peat/lignite deposits on land. Here we test the hypothesis that the marine δ13C record reflects a change in productivity with proxy records from three Atlantic Ocean sites (Deep Sea Drilling Program Site 608 and Ocean Drilling Program Sites 925 and 1265). Our multiproxy approach is based on benthic foraminiferal accumulation rates, elemental ratios (Ba/Al and P/Al), the δ13C of bulk sedimentary organic matter, and dissolution indices. We compare these proxies to benthic foraminiferal δ13C values measured on the same samples. Our results indicate that marine paleoproductivity in the Atlantic Ocean is not related to the benthic foraminiferal δ13C excursion. A numerical box model confirms that marine productivity cannot account for the δ13C maximum. The model shows that sequestration of 1.5 × 1018 mol C in the terrestrial realm over a period of 3 Ma leads to a 0.9‰ δ13C increase in the deep ocean, which is near the observed records. Therefore, an increase in continental organic carbon sequestration is the most plausible way to enrich the ocean's carbon pool with 13C, which is consistent with coeval lignite deposits worldwide. The δ13C values of bulk sedimentary organic matter parallel the δ13C of dissolved inorganic carbon as reflected by benthic foraminiferal δ13C values suggesting no significant change in atmospheric pCO2 levels over the investigated period.
Niaspan Treatment Increases Tumor Necrosis Factor-α-Converting Enzyme and Promotes Arteriogenesis after Stroke
Authors: Chen Jieli , Cui Xu , Zacharek Alex , Ding Guang Liang , Shehadah Amjad , Jiang Quan , Lu Mei , Chopp Michael
Published: February 2009

We tested the hypothesis that Niaspan (a prolonged release formulation of niacin) increases tumor necrosis factor-α-converting enzyme (TACE) expression and Notch signaling activity and promotes arteriogenesis after stroke. Rats were subjected to middle cerebral artery occlusion and were treated with or without Niaspan. Niaspan significantly elevated local cerebral blood flow, and increased arteriogenesis as indicated by increased arterial diameter and vascular smooth muscle cell (VSMC) proliferation in the ischemic brain after stroke. The increased arteriogenesis significantly correlated with the functional outcome after stroke. Niaspan treatment of stroke upregulated TACE, Notch1, and Notch intracellular domain expression in the ischemic brain. To further investigate the mechanisms of Niaspan-induced arteriogenesis, a primary brain arterial culture was used. Niacin treatment significantly increased arterial sprouting and VSMC migration compared with control nontreated arterial cells. Inhibition of TACE by the TACE inhibitor or knockdown of TACE gene expression in brain arterial culture significantly attenuated Niacin-induced arterial sprouting and VSMC migration. In addition, TACE treatment of arterial culture significantly increased arterial VSMC migration and arterial sprouting. Knockdown of Notch1 marginally decreased arterial sprouting and VSMC migration compared with scrambled control. Niaspan promotes arteriogenesis, which is mediated, in part, by TACE.
Propofol Anesthesia Does Not Alter Regional Rates of Cerebral Protein Synthesis Measured withl-[1-11C]Leucine and PET in Healthy Male Subjects
Authors: Bishu Shrinivas , Schmidt Kathleen C , Burlin Thomas V , Charming Michael A , Horowitz Lisa , Huang Tianjiang , Liu Zhong-hua , Qin Mei , Vuong B-K , Unterman Aaron J , Xia Zengyan , Zametkin Alan , Herscovitch Peter , Quezado Zenaide , Smith Carolyn B
Published: February 2009

We report regional rates of cerebral protein synthesis (rCPS) in 10 healthy young males, each studied under two conditions: awake and anesthetized with propofol. We used the quantitative l-[1-11C]leucine positron emission tomography (PET) method to measure rCPS. The method accounts for the fraction (1) of unlabeled leucine in the precursor pool for protein synthesis that is derived from arterial plasma; the remainder comes from proteolysis of tissue proteins. Across 18 regions and whole brain, mean differences in rCPS between studies ranged from 5% to 5% and were within the variability of rCPS in awake studies (coefficient of variation range: 7% to 14%). Similarly, differences in Λ (range: 1% to 4%) were typically within the variability of Λ (coefficient of variation range: 3% to 6%). Intersubject variances and patterns of regional variation were also similar under both conditions. In propofol-anesthetized subjects, rCPS varied regionally from 0.98 ± 0.12 to 2.39 ± 0.23 nmol g−1min−1in the corona radiata and in the cerebellum, respectively. Our data indicate that the values, variances, and patterns of regional variation in rCPS and Λ measured by the l-[1-11C]leucine PET method are not significantly altered by anesthesia with propofol.
Evolution of the Neurochemical Profile after Transient Focal Cerebral Ischemia in the Mouse Brain
Authors: Lei Hongxia , Berthet Carole , Hirt Lorenz , Gruetter Rolf
Published: February 2009

Evolution of the neurochemical profile consisting of 19 metabolites after 30 mins of middle cerebral artery occlusion was longitudinally assessed at 3, 8 and 24 h in 6 to 8 µL volumes in the striatum using localized 1H-magnetic resonance spectroscopy at 14.1 T. Profound changes were detected as early as 3 h after ischemia, which include elevated lactate levels in the presence of significant glucose concentrations, decreases in glutamate and a transient twofold glutamine increase, likely to be linked to the excitotoxic release of glutamate and conversion into glial glutamine. Interestingly, decreases in N-acetyl-aspartate (NAA), as well as in taurine, exceeded those in neuronal glutamate, suggesting that the putative neuronal marker NAA is rather a sensitive marker of neuronal viability. With further ischemia evolution, additional, more profound concentration decreases were detected, reflecting a disruption of cellular functions. We conclude that early changes in markers of energy metabolism, glutamate excitotoxicity and neuronal viability can be detected with high precision noninvasively in mice after stroke. Such investigations should lead to a better understanding and insight into the sequential early changes in the brain parenchyma after ischemia, which could be used for identifying new targets for neuroprotection.
Spatiotemporal activation of caspase‐dependent and ‐independent pathways in staurosporine‐induced apoptosis of p53wt and p53mt human cervical carcinoma cells
Authors: Nicolier Magali , Decrion‐Barthod Anne‐Zélie , Launay Sophie , Prétet Jean‐Luc , Mougin Christiane
Published: February 2009

Background information. Caspase‐dependent and ‐independent death mechanisms are involved in apoptosis in a variety of human carcinoma cells treated with antineoplastic compounds. Our laboratory has reported that p53 is a key contributor of mitochondrial apoptosis in cervical carcinoma cells after staurosporine exposure. However, higher mitochondrial membrane potential dissipation and greater DNA fragmentation were observed in p53wt (wild‐type p53) HeLa cells compared with p53mt (mutated p53) C‐33A cells. Here, we have studied events linked to the mitochondrial apoptotic pathway.

Results. Staurosporine can induce death of HeLa cells via a cytochrome c/caspase‐9/caspase‐3 mitochondrial‐dependent apoptotic pathway and via a delayed caspase‐independent pathway. In contrast with p53wt cells, p53mt C‐33A cells exhibit firstly caspase‐8 activation leading to caspase‐3 activation and Bid cleavage followed by cytochrome c release. Attenuation of PARP‐1 [poly(ADP‐ribose) polymerase‐1] cleavage as well as oligonucleosomal DNA fragmentation in the presence of z‐VAD‐fmk points toward a major involvement of a caspase‐dependent pathway in staurosporine‐induced apoptosis in p53wt HeLa cells, which is not the case in p53mt C‐33A cells. Meanwhile, the use of 3‐aminobenzamide, a PARP‐1 inhibitor known to prevent AIF (apoptosis‐inducing factor) release, significantly decreases staurosporine‐induced death in these p53mt carcinoma cells, suggesting a preferential implication of caspase‐independent apoptosis. On the other hand, we show that p53, whose activity is modulated by pifithrin‐α, isolated as a suppressor of p53‐mediated transactivation, or by PRIMA‐1 (p53 reactivation and induction of massive apoptosis), that reactivates mutant p53, causes cytochrome c release as well as mitochondrio—nuclear AIF translocation in staurosporine‐induced apoptosis of cervical carcinoma cells.

Conclusions. The present paper highlights that staurosporine engages the intrinsic mitochondrial apoptotic pathway via caspase‐8 or caspase‐9 signalling cascades and via caspase‐independent cell death, as well as through p53 activity.
A method for estimation of stimulated brain sites based on columnar structure of cerebral cortex in transcranial magnetic stimulation
Authors: Hiwaki Osamu , Inoue Tomonori
Published: February 2009

Transcranial magnetic stimulation (TMS) is a noninvasive method to stimulate the cortex. In TMS with a figure-of-eight coil, the induced electric field elicited by the pulsed magnetic fields is gathered beneath the center of the figure-of-eight coil, so the point on the cortex beneath the center of the figure-of-eight coil has been regarded as a stimulating site conventionally. However, the stimulating point determined in this way is not supposed to be plausible because electric field induced in TMS is dispersed over the brain vectorially. The present study proposed the novel method for the accurate estimation of stimulating points of the cortex in TMS. In our proposed method, the cortical structure and property of neural excitation in magnetic nerve stimulation were taken into account. The basic unit of the cerebral cortex is the cylindrical column containing pyramidal neurons perpendicular to the cortical surface, and neural excitation in the magnetic nerve stimulation is determined by the spatial derivative of the electric field parallel to the cablelike neuron such as a pyramidal neuron. According to these understandings, the relative intensity of nerve stimulation in TMS corresponds to the strength of the component of the induced electrical field perpendicular to the cortical surface. We realized the method for the estimation of stimulating sites of the cortex in TMS by using this principle. The component of the electric field perpendicular to the cortical surface at each pixel of magnetic resonance imaging was obtained with computation of the dot product of the electric field and the unit vector perpendicular to the cortex surface. The strength of the component of the electric field perpendicular to the cortical surface was regarded as the stimulating strength at each pixel of the cortical surface in TMS. We conducted the experiments of TMS to confirm the validity of this method. The cortex sites, which innervate muscles of the upper limb, were successfully delineated in primary motor area by the proposed method.
Linear stability of a volatile liquid film flowing over a locally heated surface
Authors: Tiwari Naveen , Davis Jeffrey M.
Published: February 2009

The dynamics and linear stability of a volatile liquid film flowing over a locally heated surface are investigated. The temperature gradient at the leading edge of the heater induces a gradient in surface tension that leads to the formation of a pronounced capillary ridge. Lubrication theory is used to develop a model for the film evolution that contains three key dimensionless groups: a Marangoni parameter (M), an evaporation number (E), and a measure of the vapor pressure driving force for evaporation (K), which behaves as an inverse Biot number. The two-dimensional, steady solutions for the local film thickness are computed as functions of these parameters. A linear stability analysis of these steady profiles with respect to perturbations in the spanwise direction reveals that the operator of the linearized system can have both a discrete and a continuous spectrum. The continuous spectrum exists for all values of the spanwise wave number and is always stable. The discrete spectrum, which corresponds to eigenfunctions localized around the ridge, appears for values of M larger than a critical value for a finite band of wave numbers separated from zero. Above a second, larger critical value of M, a portion of the discrete spectrum becomes unstable, corresponding to rivulet formation at the forward portion of the capillary ridge. For sufficiently large heat transfer at the free surface, due either to phase change or to convection, a second band of unstable discrete modes appears, which is associated with an oscillatory, thermocapillary instability above the heater. The critical Marangoni parameter above which instability develops, Mcrit(K,E), has a nonmonotonic dependence on the steepness of the temperature increase at the heater, in contrast to the monotonic decrease for a nonvolatile film at vanishing Biot number. An energy analysis reveals that the dominant instability mechanism resulting from perturbations to the film thickness is either streamwise capillary flow or gravity for weakly volatile fluids and thermocapillary flow due to spanwise temperature gradients for more volatile fluids. The stability results are rather sensitive to the steepness of the temperature increase and heater width due to the nonlinear coupling of gravity, capillary pressure gradients, thermocapillary flow, and evaporation through the base states.
Low frequency elastic wave propagation in two dimensional locally resonant phononic crystal with asymmetric resonator
Authors: Gu Yongwei , Luo Xudong , Ma Hongru
Published: February 2009

The resonance modes and the related effects to the transmission of elastic waves in a two dimensional phononic crystal formed by periodic arrangements of a two block unit cell in one direction are studied. The unit cell consists of two asymmetric elliptic cylinders coated with silicon rubber and embedded in a rigid matrix. The modes are obtained by the semianalytic method in the least square collocation scheme and confirmed by the finite element method simulations. Two resonance modes, corresponding to the vibration of the cylinder along the long and short axes, give rise to resonance reflections of elastic waves. One mode in between the two modes, related to the opposite vibration of the two cylinders in the unit cell in the direction along the layer, results in the total transmission of elastic waves due to zero effective mass density at the frequency. The resonance frequency of this mode, which has not yet been identified before, changes continuously with the orientation angle of the elliptic resonator.
Anisotropic magnetization reversal in 30 nm triangular FeNi dots
Authors: Niu D. X. , Zou X. , Wu J. , Xu Y. B.
Published: February 2009

We present the room temperature magnetization hysteresis loop measurements of a triangularly shaped Fe64Ni36 dot array with the feature size down to 30 nm using magneto-optical Kerr effect. An in-plane anisotropic magnetization reversal and an enhanced coercivity have been observed in these magnetic dots. In combining with micromagnetic calculations, we found that the magnetization process follows two steps, the rotation of the top corner and the switching of the bottom base, respectively, controlled by the nanometer scale local magnetic shape anisotropy, and the thermal activation is negligible even in this length scale.
Generalized synchronization of chaotic systems: An auxiliary system approach via matrix measure
Authors: He Wangli , Cao Jinde
Published: February 2009

In this paper, generalized synchronization of two chaotic systems is investigated. The auxiliary system approach, which is suggested by H. Abarbanel, N. Rulkov, and M. Sushchik [Phys. Rev. E 53, 4528 (1996)], is used to detect and study generalized synchronization. Based on the Lyapunov method and matrix measure, some less restrictive criteria are obtained to guarantee the asymptotical stability of the error system between the response system and the auxiliary system, which indicates the drive-response systems are synchronized in a general sense. It is shown that the feedback gain can be reduced by means of the matrix measure approach, compared to the norm method. All theoretical results are illustrated by analytical and numerical examples.
Noise-induced transport in a rough ratchet potential
Authors: Mondal Debasish , Ghosh Pulak Kumar , Ray Deb Shankar
Published: February 2009

Several years ago Zwanzig considered the diffusion in a potential that is spatially rough due to hierarchical structure of protein. We extend this idea to the overdamped Brownian dynamics in a one-dimensional periodic and rough ratchet potential. A general expression is obtained for the effective current at the steady state. Variation in both current and efficiency has been studied with respect to the amplitude of the roughness and an external nonequilibrium, nonthermal driving force. It has been shown that roughness hinders current quite significantly. Our analysis is corroborated by detailed numerical simulations and may be useful in the context of laser switching of current through molecular wires.
Photoelectron imaging of multiply charged anions: Effects of intramolecular Coulomb repulsion and photoelectron kinetic energies on photoelectron angular distributions
Authors: Xing Xiao-Peng , Wang Xue-Bin , Wang Lai-Sheng
Published: February 2009

Multiply charged anions possess strong intramolecular Coulomb repulsion (ICR), which has been shown to dictate photoelectron angular distributions (PADs) using photoelectron imaging. Here we report the effects of photoelectron kinetic energies on the PADs of multiply charged anions. Photoelectron images on a series of dicarboxylate dianions, O−2C(CH2)nCO2− (Dn2−, n=3–11) have been measured at two photon energies, 532 and 266 nm. The first photoemission band of Dn2−, which is a perpendicular transition in the absence of the ICR, comes from electron detachment of an O lone pair orbital on the –CO2− end groups. Recent photoelectron imaging studies at 355 nm show that the PADs of Dn2− peak in the directions parallel to the laser polarization for small n due to the ICR, which directs the outgoing electrons along the molecular axis. The current data show much stronger parallel peaking at 532 nm, but much weaker parallel peaking in the 266 nm data, relative to the 355 nm data. These observations indicate that the ICR has greater influence on the trajectories of slow photoelectrons and much reduced effects on faster photoelectrons. This study demonstrates that the PADs of multiply charged anions depend on the interplay between ICR and the outgoing photoelectron kinetic energies.
Temperature dependence of the spectral profile and total intensity of the second-harmonic signal of the fullerene crystal
Authors: Eilmes A. , Pac B. , Petelenz P.
Published: February 2009

The temperature dependence of second-harmonic generation in crystalline fullerene is simulated based on a microscopic model of orientational disorder, with special emphasis on the vicinity of the phase transition. The temperature-induced changes of the total second-harmonic intensity and of the corresponding spectral profile are treated on equal footing within a consistent theoretical framework. In addition to the previously applied approach where superexchange-type exciton transfer via the charge transfer (CT) manifold was described phenomenologically, and alternative model invoking the CT states explicitly is proposed, giving deeper insight into the underlying physics. Both models yield very good agreement with experimental results.
Thermal conductivity of micromachined low-stress silicon-nitride beams from 77 to 325 K
Authors: Sultan Rubina , Avery A. D. , Stiehl G. , Zink B. L.
Published: February 2009

We present thermal conductivity measurements of micromachined 500 nm thick silicon-nitride (Si–N) beams suspended between two Si–N islands, in the temperature range from 77 to 325 K. The measured thermal conductivity, k, of Si–N at high temperatures is in good agreement with previously measured values for Si–N grown by low-pressure chemical vapor deposition, but behaves much differently as temperature is lowered, showing a dependence more similar to polycrystalline materials. Preliminary structural characterization by x-ray diffraction suggests that the material is likely nano- or polycrystalline. The micromachined suspended platform structure is designed to allow highly accurate measurements of the thermal conductivity of deposited metallic, semiconducting, or insulating thin films. As a demonstration, we present measurements of a 200 nm thick sputtered molybdenum film. In the entire temperature range the measured thermal conductivity matches the prediction of the Wiedemann–Franz thermal conductivity determined from measured electrical conductivity.
Thickness and magnetic field dependence of ferroelectric properties in multiferroic BaTiO3–CoFe2O4 nanocomposite films
Authors: Zhong ChongGui , Jiang Qing , Fang JingHuai , Jiang XueFan
Published: February 2009

In the framework of Landau–Devonshire thermodynamic theory, which is used in conventional ferroelectrics, we investigate the ferroelectric properties of the 1–3 type multiferroic BaTiO3–CoFe2O4 nanocomposite films. The films are epitaxial both in plane and out of plane with self-assembled hexagonal arrays of CoFe2O4 nanopillars embedded in a BaTiO3 matrix and present the tantalizing possibility of heteroepitaxy in three dimensions. It is shown that the properties of the BaTiO3 thin films such as polarization, piezoelectric coefficient, dielectric susceptibility, etc., are functions of not only misfit strains but also external magnetic field. The film thickness dependence of epitaxial strains due to relaxation by misfit dislocation during film deposition is incorporated into the model by using effective substrate lattice parameters. Therefore, the thickness dependence of ferroelectric properties and magnetic-field-induced electric polarization (MIEP) in BaTiO3–CoFe2O4 epitaxial thin films are well explained. In addition, the MIEP has also been studied by applying the transversal and longitudinal external magnetic fields to the magnetostrictive phase. Our main results are quantitatively consistent with experimental ones reported for multiferroic BaTiO3–CoFe2O4 nanocomposite films.
C
2
and CN dynamics and pulsed laser deposition of CNx films
Authors: Kushwaha Archana , Mohanta Antaryami , Thareja Raj K.
Published: February 2009

The time-resolved optical emission studies of laser ablated carbon plasma in nitrogen ambient are carried out to understand the dynamic of formation of C2 and CN for depositing quality thin films. An optimum formation of C2 is observed at 3 mm from the target surface and 350 ns after the initiation of plasma. However, CN is formed at comparatively larger distance, 4 mm, and larger delay (850 ns). The expanding plasma plume splits/bifurcates into slow and fast moving two distinct components, with the faster components further splitting up at later times (>350 ns) into two components. The estimated plume front velocity from plume imaging in the nitrogen ambient of 1.2 mbars at a delay of 100 ns is 3.8×106 cm/s, consistent with spectroscopic measurement ∼3.0×106 cm/s. The CNx thin films deposited by pulsed laser deposition technique are characterized by x-ray diffraction, atomic force microscopy, and Raman spectroscopy. The high ID/IG ratio and peak position shift of G band to lower values in the films deposited for longer time indicates the high incorporation of nitrogen and increasing CN concentration within the film.
Optical nonlinearity and structural dynamics of VO2 films
Authors: Lysenko S. , Rua A. , Fernandez F. , Liu H.
Published: February 2009

The degenerate-four-wave-mixing, ultrafast optical pump-probe reflection, and scattering techniques were applied to study the nonlinear optical properties of VO2 in insulating and metallic phases. The third-order nonlinear susceptibility was measured for thin films at different excitation regimes. The VO2 recovery dynamics after light-induced phase transition (PT) shows strong sensitivity to optical pump energy and could be governed by pure electronic relaxation excluding thermal contribution at sufficiently low excitation. Increased light scattering during thermally and light-induced PT demonstrates significant VO2 heterogeneity which appears as a coexistence of insulating and metallic phases accompanied by fluctuations of dielectric constants. Different desorption activity was monitored for insulating and metallic VO2 thin solid films under femtosecond optical excitation.
Modeling germanium diffusion in Si1−xGex/Si superlattice structures
Authors: Hasanuzzaman Mohammad , Haddara Yaser M. , Knights Andrew P.
Published: February 2009

We present a model for the interdiffusion of silicon (Si) and germanium (Ge) in silicon germanium/silicon (Si1−xGex/Si) superlattice (SL) structures. Both a vacancy exchange mechanism and an interstitial diffusion mechanism are considered in the proposed model. The effects of Ge on the diffusion properties of the SL are also considered and the conservation of lattice site constraints is accounted for. Output from the model is compared to experimental Ge interdiffusion profiles for samples annealed in the temperature range 770–1125 °C in inert ambient and in some cases in oxidizing ambient, where the experimental samples contained Ge fractions up to 30%. For anneal temperatures up to 1075 °C a vacancy exchange mechanism is sufficient to describe the interdiffusion mechanism in Si1−xGex/Si SL structures. For higher anneal temperatures interstitial diffusion mechanism dominates the interdiffusion process.
Large piezoresistivity phenomenon in SiCN–(La,Sr)MnO3 composites
Authors: Karmarkar Makarand , Singh Gurpreet , Shah Sandeep , Mahajan Roop L. , Priya Shashank
Published: February 2009

We present the results on SiCN–(La,Sr)MnO3 (LSMO) composites correlating the observed large piezoresistance behavior with the microstructural features and defect chemistry. Scanning electron microscopy characterization revealed the presence of self-assembled periodic microvalleys in the microstructure with width of 1–5 μm and depth of 600–1000 nm. The microvalleys act as stress concentration points providing change in volume with applied stress. High resolution transmission electron microscopy measurements conducted on composites showed that LSMO grains consist of SiCN phase but no inclusions were observed.
High sensitivity resonance frequency measurements of individual microcantilevers using fiber optical interferometry
Authors: Duden Thomas , Radmilovic Velimir
Published: February 2009

We describe a setup for the resonance frequency measurement of individual microcantilevers. The setup displays both high spatial selectivity and sensitivity to specimen vibrations by utilizing a tapered fiber tip. The high sensitivity to specimen vibrations is achieved by the combination of optical Fabry–Perot interferometry and narrow band rf detection. Wave fronts reflected on the specimen and on the fiber tip end face interfere, thus no reference plane on the specimen is needed, as demonstrated with the example of freestanding silicon nitride microcantilevers. The resulting system is integrated in a DB-235 dual beam focused ion beam (FIB) system, thereby allowing the measurement of microcantilever responses during observation in scanning electron microscopy mode. The FIB was used to modify the optical fiber tip. At this point of our rf system development, the microcantilevers used to characterize the detector were not modified in situ.
High performance electrospinning system for fabricating highly uniform polymer nanofibers
Authors: Munir Muhammad Miftahul , Iskandar Ferry , Khairurrijal  , Okuyama Kikuo
Published: February 2009

A high performance electrospinning system has been successfully developed for production of highly uniform polymer nanofibers. The electrospinning system employed a proportional-integral-derivative control action to maintain a constant current during the production of polyvinyl acetate (PVAc) nanofibers from a precursor solution prepared by dissolution of the PVAc powder in dimethyl formamide so that high uniformity of the nanofibers was achieved. It was found that the cone jet length observed at the end of the needle during the injection of the precursor solution and the average diameter of the nanofibers decreased with decreasing Q/I, where Q is the flow rate of the precursor solution of the nanofibers and I is the current flowing through the electrospinning system. A power law obtained from the relation between the average diameter and Q/I is in accordance with the theoretical model.
Dynamics of photoinduced charge transfer between pentacene and a C60-terminated self-assembled monolayer
Authors: Park Byoungnam , Paoprasert Peerasak , Gopalan Padma , Kuech T. F. , Evans Paul G.
Published: February 2009

A C60-terminated self-assembled monolayer can be used to place molecular acceptor states at the interface between the semiconductor and gate insulator of an organic field effect transistor. The time dependence of the photoinduced charge transfer between pentacene and C60 has a fast component with a characteristic time of 1.9 s and slower component with a time constant of 32 and 48 s at the beginning and end of a transient increase in illumination, respectively. Variation in the threshold voltage shift with the thickness of the pentacene results from the competing length scales for light absorption and exciton diffusion.
Light scattering and Fano resonances in high-Q photonic crystal nanocavities
Authors: Galli M. , Portalupi S. L. , Belotti M. , Andreani L. C. , O’Faolain L. , Krauss T. F.
Published: February 2009

The authors show that light scattering from high-Q planar photonic crystal nanocavities can display Fano-like resonances corresponding to the excitation of localized cavity modes. By changing the scattering conditions, we are able to tune the observed lineshapes from strongly asymmetric and dispersivelike resonances to symmetric Lorentzians. Results are interpreted according to the Fano model of quantum interference between two coupled scattering channels. Combined measurements and line shape analysis on a series of silicon L3 nanocavities as a function of nearby hole displacement demonstrate that Q factors as high as 1.1×105 can be directly measured in these structures. Furthermore, a comparison with theoretically calculated Q factors allows to extract the rms deviation of hole radii due to weak disorder of the photonic lattice.
Control of hysteretic behavior in flux concentrators
Authors: Trindade I. G. , Leitão D. C. , Pogorelov Y. , Sousa J. B. , Chaves R. C. , Cardoso S. , Freitas P. P.
Published: February 2009

The magnetic states of flux concentrators (FCs), consisting of poles and yokes with lateral dimensions in the range of 100 μm and integrating either single layer films of amorphous alloys of Cox(Zr–Nb)1−x with x=90 and x=88 or a synthetic antiferromagnet (SAF) of (NiFe/Ru)xn, are analyzed by Bitter pattern and magnetic force microscopy. Magnetic field sensors, placed in the gap of the FC by microfabrication processes, exhibited magnetoresistive responses strongly correlated with the magnetic states of the FC. The hysteresis of the field produced by the FC is reduced to a minimum when the SAF is used.
Realistic adsorption geometries and binding affinities of metal nanoparticles onto the surface of carbon nanotubes
Authors: Park Noejung , Sung Dongchul , Lim Seokho , Moon Seongho , Hong Suklyun
Published: February 2009

Adsorption geometries and binding affinities of metal nanoparticles onto carbon nanotubes (CNTs) are investigated through density-functional-theory calculations. Clusters of 13 metal atoms are used as models for metal nanoparticles. Palladium, platinum, and titanium particles strongly chemisorb to the CNT surface. Unlike the cases of atomic adsorptions the aluminum particle has the weakest binding affinity with the CNT. Aluminum or gold nanoparticles accumulated on the CNT develop the triangular bonding network of the metal surfaces in which the metal-carbon bond is not favored. This suggests that the CNT-Al interface is likely to have many voids and thus susceptible to oxidation damages.
Dielectric relaxation properties of nanostructured Ce0.8Gd0.1Pr0.1O2−δ material at intermediate temperatures
Authors: Baral Ashok Kumar , Sankaranarayanan V.
Published: February 2009

The dielectric relaxation behavior of the fluorite structured nanocrystalline Ce0.8Gd0.1Pr0.1O2−δ compound was studied in the temperature range of 200–550 °C. Two different types of relaxation processes were observed corresponding to (1) defect pairs such as (PrCe′–VO)• and (GdCe′–VO)• and (2) the trimers such as (PrCe′–VO••–GdCe′). The correlation between ionic conduction and the dielectric properties of the nanocrystalline material is discussed. Very low values of the migration energy and association energy of the oxygen vacancies are observed, which are 0.42 and 0.03 eV, respectively. The obtained value of association energy agrees well with the theoretical prediction on doubly doped ceria.
Thinking beyond Homonormativity: Performative Explorations of Diverse Gay Economies
Authors: Brown Gavin
Published: February 2009

This paper performatively decentres the role of mainstream gay consumption in contemporary thought about the economic and social lives of lesbians and gay men in the Global North. It is simultaneously critical and reparative in outlook. This paper critically engages with recent writing on homonormativity, suggesting that this work presents ‘homonormativity’ as an all-encompassing structure that becomes politically unassailable. In parallel with an analysis of contemporary lesbian and gay life as being complicit in the reproduction of various normativities, this paper takes the innovative and reparative stance of considering how such spaces and practices also produce interdependent relationships across social difference. Drawing on the recent work of Gibson-Graham (2006, A Postcapitalist Politics University of Minnesota Press, Minneapolis, MN) this paper considers the prospects for outlining the diversity of lesbian and gay economic practices, with the performative ambition of making existing noncapitalist practices more visible and viable. To this end, the paper examines a number of gay spaces and practices to consider the different forms of enterprise, transactions, and labour that take place within them. On the basis of its preliminary inventory of diverse gay economic practices and spaces, this paper proposes that there are many aspects of contemporary urban gay life that already offer alternatives to the homonormative practices of neoliberalism.
Neighbourhood Mobility in Context: Household Moves and Changing Neighbourhoods in the Netherlands
Authors: van Ham Maarten , Clark William A V
Published: February 2009

Although high levels of population mobility are often viewed as a problem at the neighbourhood level we know relatively little about what makes some neighbourhoods more mobile than others. The main question in this paper is to what extent differences in out-mobility between neighbourhoods can be explained by differences in the share of mobile residents, or whether other neighbourhood characteristics also play a role. To answer this question we focus on the effects of the socioeconomic status and ethnic composition of neighbourhoods and on neighbourhood change. Using data from the Netherlands population registration system and the Housing Demand Survey we model population mobility both at individual and at neighbourhood levels. The aggregate results show that the composition of the housing stock and of the neighbourhood population explain most of the variation in levels of neighbourhood out-mobility. At the same time, although ethnic minority groups in the Netherlands are shown to be relatively immobile, neighbourhoods with higher concentrations of ethnic minority residents have the highest population turnovers. The individual-level models show that people living in neighbourhoods which experience an increase in the percentage of ethnic minorities are more likely to move, except when they belong to an ethnic minority group themselves. The evidence suggests that ‘white flight’ and ‘socio-economic flight’ are important factors in neighbourhood change.
Free-Radical Polymerization and Ring-Expansion of a Cubane Acrylate: a Unique Low-Shrink Polymer
Authors: McGonagle Alison E. , Savage G. Paul
Published: February 2009

A pendant cubane substituent has been incorporated into an acrylate polymer side chain to give poly[methyl 4-(acryloyloxymethyl)cubane carboxylate]. Treating this polymer with a rhodium(i) salt triggers a catalytic, ring-opening rearrangement of the cubane substructure to cyclooctatetraene, with a concomitant expansion in molecular volume. This system offers a unique opportunity to reverse the shrinkage associated with polymerization.
Plant availability of phosphorus from fluid fertiliser is maintained under soil moisture deficit in non-calcareous soils of south-eastern Australia
Authors: Officer S. J. , Armstrong R. D. , Norton R. M.
Published: February 2009

Low soil moisture and phosphorus (P) deficiencies restrict grain production in south-eastern Australia. The effect of the soil moisture regime on the plant availability of P from fluid mono-ammonium phosphate (MAP) fertiliser was examined during vegetative growth of wheat and canola in P-responsive soils from the Wimmera, Mallee, and high rainfall zone (Glenelg) regions of Victoria. Three plant growth experiments were performed. In Experiment 1, wheat growth and P uptake increased synergistically as soil moisture increased above permanent wilting point (PWP) and as P rate increased. In Experiment 2, the uptake of P from MAP fertiliser of wheat growing under a soil moisture deficit was examined using radioactive (32P) labelling. A factorial design compared uptake from intact soil cores of 3 soil types (Vertosol, Sodosol, Chromosol), 2 depths of fertiliser placement (40 and 80 mm), and either 0 or 25 kg P/ha. Results showed distinct plant responses to both the presence and depth of MAP fertiliser. Banding MAP close to the seed was most efficient in terms of recovery of the fertiliser P, regardless of the soil moisture conditions. Soil moisture regime affected the plant uptake of soil P, rather than fertiliser P, with more soil P taken up by the plants when soil moisture increased. The plant availability of the residual MAP fertiliser in the soil was subsequently examined in Experiment 3. The availability of the residual MAP to canola seedlings was equivalent to 8 kg P/ha of freshly applied MAP. Following both crops (9 months), Colwell P values indicated no further residual MAP availability in soil that had been under the wet regime, and only a small residual value in soil from the dry regime. Banded application of fluid MAP close to the seed and into soil that is above PWP is recommended, even when a relatively dry season is expected, although the residual value to following crops may be limited.