bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical and biogeochemical transports structure in the North Atlantic subpolar gyre
Authors: Álvarez Marta , Pérez Fiz F. , Bryden Harry , Ríos Aida F.
Published: March 2004

Physical (mass, heat, and salt) and biogeochemical (nutrients, oxygen, alkalinity, total inorganic carbon, and anthropogenic carbon) transports across the transoceanic World Ocean Circulation Experiment (WOCE) A25 section in the subpolar North Atlantic (4x line) obtained previously [Álvarez et al., 2002, 2003] are reanalyzed to describe their regional and vertical structure. The water mass distribution in the section is combined with the transport fields to provide the relative contribution from each water mass to the final transport values. The water mass circulation pattern across the section is discussed within the context of the basin‐scale thermohaline circulation in the North Atlantic. Eastern North Atlantic Central, influenced Antarctic Intermediate, Mediterranean, and Subarctic Intermediate Waters flow northward with 10.3, 5.6, 1.7, and 2.9 Sv, respectively. The total flux of Lower Deep Water (LDW) across the section is 1 Sv northward. A portion of LDW flowing northward in the Iberian Basin recirculates southward within the eastern basin and about 0.7 Sv flow into the western North Atlantic. About 7 Sv of Labrador Seawater (LSW) from the Labrador Sea cross the 4x section within the North Atlantic Current, and 12 Sv of LSW from the Irminger Sea flow southward within the East Greenland Current. Denmark Strait Overflow Water flows over the western flank of the Irminger basin (1.5 Sv), and Iceland Scotland Overflow Water (ISOW) is mainly transported in the Charlie Gibbs Fracture Zone (6 Sv). ISOW remnants flow southward to the eastern basin, contributing to the eastern basin deep ventilation. LSW and the overflows transport CANT southward across the section. This southward CANT transport is overcome by the northward transport in upper layers; finally, CANT is injected into the subpolar gyre where it accumulates.
Scotian Slope circulation and eddy variability from TOPEX/Poseidon and frontal analysis data
Authors: Han Guoqi
Published: March 2004

Sea level observations from TOPEX/Poseidon (T/P) altimetry, in conjunction with concurrent frontal analysis data from infrared imagery, are used to study temporal and spatial variability of sea‐surface currents over the Scotian Slope. Geostrophic surface current anomalies normal to ground tracks are derived from the sea level anomalies relative to local means for the study period. The altimetric results reveal prominent spatial variability of cross‐track currents with an overall intensification toward the west and south, typically 20–30 cm/s over the upper and lower slope, 20–50 cm over the continental rise, and up to 70–75 cm/s near the Gulf Stream northern wall. A rapid westward intensification on the western slope contrasts with nearly uniform distribution on the eastern slope. The intensification seems to be associated with the high occurrence of Gulf Stream warm core rings (WCR) and with the close proximity to the Gulf Stream. Crossover analyses of altimetric current anomalies indicate that the total current variability can be estimated by a factor of 1.5 from the cross‐track current variability and the variance is isotropic to within 14%. The rotational speed of the Gulf Stream rings can reach 1–2 m/s over the Scotian Slope, with the root‐mean‐square variability of ∼60 cm/s. The relative vorticity of the interior core is estimated to be ∼1.5 ×10−5 1/s. When combined with CTD data, T/P observations can produce the vertical profile of the total geostrophic current that is in approximate agreement with ADCP measurements.
Comparison of radiative transfer models for limb‐viewing scattered sunlight measurements
Authors: Loughman R. P. , Griffioen E. , Oikarinen L. , Postylyakov O. V. , Rozanov A. , Flittner D. E. , Rault D. F.
Published: March 2004

This study compares the limb scattered radiances calculated by six radiative transfer models for a variety of viewing conditions. Atmospheres that include molecular scattering, aerosol scattering, and ozone absorption are considered. All models treat single scattering accurately in full spherical geometry. Two “approximate spherical” models (CDI and LIMBTRAN) rely on the plane‐parallel atmosphere approximation to calculate the diffuse radiance field; the remaining four “spherical” models (Siro, MCC++, GSLS, and CDIPI) treat multiple scattering in a spherical atmosphere. Only three of the models (Siro, MCC++, and GSLS) have vector treatment with polarization. A brief comparison of vector radiances with the limb scattered radiances measured by the SOLSE and LORE instruments demonstrates agreement usually within 15% and always within 30%. The inclusion of polarization appears to have little effect on the level of agreement among the models (which agree to within 2% for this sample case). A more general comparison among calculated scalar radiances follows, including four solar zenith angles (20°, 60°, 80°, and 90°), three relative azimuth angles (20°, 90°, and 160°), and two surface albedos (0 and 0.95). The single scattered radiances agree to within 1% for almost every case. Comparisons of the total radiance show larger differences, with 2–4% spread among the results of the spherical models. The approximate spherical models show a positive radiance difference relative to the other models that increases with tangent height, reaching as much as 8% at 60 km. The rule used to divide the model atmosphere into discrete layers is shown to affect the calculated radiance, causing a height‐dependent difference of up to 1% for 1 km layer thickness.
Improved 11‐year solar signal in the Freie Universität Berlin Climate Middle Atmosphere Model (FUB‐CMAM)
Authors: Matthes Katja , Langematz Ulrike , Gray Lesley L. , Kodera Kunihiko , Labitzke Karin
Published: March 2004

So far, general circulation model studies have not been able to capture the magnitude and characteristics of the observed 11‐year solar signal in the stratosphere satisfactorily. Here results from model experiments with the Freie Universität Berlin Climate Middle Atmosphere Model are presented that are in considerable agreement with observations. The experiments used realistic spectral solar irradiance changes, ozone changes from a two‐dimensional radiative‐chemical‐transport model, and a relaxation toward observed equatorial wind profiles throughout the stratosphere. During Northern Hemisphere winter a realistic poleward downward propagation of the polar night jet (PNJ) anomalies, significantly weaker planetary wave activity, and a weaker mean meridional circulation under solar maximum conditions are reproduced in the model. The observed interaction between the Sun and the Quasi‐Biennial Oscillation (QBO) is captured and stratospheric warmings occur preferentially in the west phase of the QBO. Only the magnitude of the anomalies during the dynamically active season improves, whereas the summer signal and the signal at low latitudes are still too weak. The results emphasize the important role of equatorial winds in achieving a more realistic solar signal by producing a more realistic wind climatology. Furthermore, they confirm recent results that equatorial winds in the upper stratosphere, the region dominated by the Semiannual Oscillation, are an important factor in determining interannual variability of the PNJ.
Observations of solar spectral irradiance change during cycle 22 from NOAA‐9 Solar Backscattered Ultraviolet Model 2 (SBUV/2)
Authors: DeLand Matthew T. , Cebula Richard P. , Hilsenrath Ernest
Published: March 2004

The NOAA‐9 Solar Backscatter Ultraviolet Model 2 (SBUV/2) instrument is one of a series of instruments providing daily solar spectral irradiance measurements in the middle and near ultraviolet since 1978. The SBUV/2 instruments are primarily designed to measure the stratospheric profile and total column amount of ozone, using the directional albedo as the input to the ozone retrieval algorithm. Almost all optical components are common to both radiance and irradiance measurements, whose ratio forms the directional albedo, so that most response changes cancel out. As a result, the SBUV/2 instrument does not require onboard monitoring of time‐dependent sensitivity changes for production of ozone data. We use vicarious comparisons with coincident Shuttle SBUV (SSBUV) solar irradiance measurements during 1989–1996, combined with observed calibration drift during the solar activity minimum in 1985–1986, to determine the long‐term instrument characterization for NOAA‐9 SBUV/2. This approach allows us to derive more accurate solar spectral irradiances for the period from March 1985 to May 1997, spanning two solar cycle minima with a single instrument. The NOAA‐9 irradiance data show an amplitude of approximately 9.3% at 200–205 nm for solar cycle 22. This is consistent with the result of ΔF200–205 = 8.3% for cycle 21 from Nimbus‐7 SBUV and ΔF200–205 = 10% for cycle 23 from UARS SUSIM. NOAA‐9 data at 245–250 nm show a solar cycle amplitude of ∼5.7%. The observed irradiance change at 200–205 nm between the minima of solar cycles 21 and 22 is not consistent with the UV irradiance change expected from the total solar irradiance trend suggested by Willson and Mordvinov [2003]. NOAA‐9 SBUV/2 data can be combined with data from other instruments to create a 25‐year record of solar UV irradiance.
Modeling of surface energy partitioning, surface temperature, and soil wetness in the Tibetan prairie using the Simple Biosphere Model 2 (SiB2)
Authors: Gao Zhiqiu , Chae Namyi , Kim Joon , Hong Jinkyu , Choi Taejin , Lee Heechoon
Published: March 2004

This paper examines the performance of a stand‐alone version of the Simple Biosphere Model 2 (SiB2) to investigate the accuracy of the modeled surface energy components, surface effective radiative temperature, and soil wetness in a Tibetan short grass prairie from 15 July to 14 September 1998. During this monsoon period the mean canopy height and the leaf area index were 0.05 m and 0.5, respectively. The study site represented the prevailing conditions of the high Tibetan plateau with an average elevation of 4500 m. The model was initialized using in situ measurements and was driven by half‐hourly atmospheric observations. The modeled values for the two months period were compared with micrometeorological field measurements made through the Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment (GAME)‐Tibet project. Results show that (1) when underestimating net radiation by 11%, the model overestimated sensible, latent, and soil heat fluxes by 8, 3, and 13% respectively; (2) the model generated warmer (colder) ground surface in daytime (nighttime); and (3) soil wetness was estimated reasonably.
Particulate polycyclic aromatic hydrocarbons in the Atlantic and Indian Ocean atmospheres during the Indian Ocean Experiment and Aerosols99: Continental sources to the marine atmosphere
Authors: Crimmins Bernard S. , Dickerson Russell R. , Doddridge Bruce G. , Baker Joel E.
Published: March 2004

Polycyclic aromatic hydrocarbons (PAHs), mutagenic compounds predominantly derived from combustion, have been used as markers of combustion sources to the atmosphere. Marine aerosol collected aboard the NOAA R/V Ronald Brown during the Aerosols99 and the Indian Ocean Experiment (INDOEX) projects was analyzed for PAHs to assess the continental impact of combustion‐derived particulate matter on the Atlantic and Indian Ocean atmospheres. PAH concentrations in the Atlantic and southern Indian Ocean atmospheres were consistent and low, ranging from <0.45 pg/m3 for coronene to 30 pg/m3 for 9, 10‐dimethylanthracene. PAH concentrations increased ten fold as the ship crossed the Intertropical Convergence Zone (ITCZ) into the northern Indian Ocean, indicating an increased anthropogenic influence. PAH concentrations over the northern Indian Ocean atmosphere were approximately an order of magnitude greater than those in the northern Atlantic Ocean atmosphere. PAH composition profiles over the northern Indian Ocean were specific to wind regimes and influenced by a combination of biomass and fossil fuel combustion. This was supported by significant correlations between select PAHs and organic carbon (OC), elemental carbon (EC), SO4−2 and K+ for particular wind regimes. Indeno[1,2,3‐cd]pyrene/EC ratios used as a combustion source marker suggest that fossil fuel combustion, rather than biomass burning, is the predominant source of PAHs to the Northern Hemisphere Indian Ocean atmosphere. Interestingly, fossil fuel consumption in the Indian sub‐continent is a fraction of that in Europe and the United States but the soot and PAH levels in the adjacent Northern Indian Ocean atmosphere are significantly greater than those in the Northern Atlantic atmosphere.
Sensitivity of global biogenic isoprenoid emissions to climate variability and atmospheric CO2
Authors: Naik Vaishali , Delire Christine , Wuebbles Donald J.
Published: March 2004

Isoprenoids (isoprene and monoterpenes) are the most dominant class of biogenic volatile organic compounds (BVOCs) and have been shown to significantly affect global tropospheric chemistry and composition, climate, and the global carbon cycle. In this study we assess the sensitivity of biogenic isoprene and monoterpene emissions to combined and isolated fluctuations in observed global climate and atmospheric carbon dioxide (CO2) concentration during the period 1971–1990. We integrate surface emission algorithms within the framework of a dynamic global ecosystem model, the Integrated Biospheric Simulator (IBIS), to simulate biogenic fluxes of isoprenoids as a component of the climate‐vegetation dynamics. IBIS predicts global land surface isoprene emissions of 454 Tg C and monoterpenes of 72 Tg C annually and captures the spatial and temporal patterns well. The combined fluctuations in climate and atmospheric CO2 during 1971–1990 caused significant interannual and seasonal variability in global biogenic isoprenoid fluxes that was somewhat related to the El Niño‐Southern Oscillation. Furthermore, an increasing trend in the simulated emissions was seen during this period that is attributed partly to the warming trend and partly to CO2 fertilization effect. The isolated effect of increasing CO2 during this period was to steadily increase emissions as a result of increases in foliar biomass. These fluctuations in biogenic emissions could have significant impacts on regional and global atmospheric chemistry and the global carbon budget.
Nitric acid uptake on subtropical cirrus cloud particles
Authors: Popp P. J. , Gao R. S. , Marcy T. P. , Fahey D. W. , Hudson P. K. , Thompson T. L. , Kärcher B. , Ridley B. A. , Weinheimer A. J. , Knapp D. J. , Montzka D. D. , Baumgardner D. , Garrett T. J. , Weinstock E. M. , Smith J. B. , Sayres D. S. , Pittman J. V. , Dhaniyala S. , Bui T. P. , Mahoney M. J.
Published: March 2004

The redistribution of HNO3 via uptake and sedimentation by cirrus cloud particles is considered an important term in the upper tropospheric budget of reactive nitrogen. Numerous cirrus cloud encounters by the NASA WB‐57F high‐altitude research aircraft during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers‐Florida Area Cirrus Experiment (CRYSTAL‐FACE) were accompanied by the observation of condensed‐phase HNO3 with the NOAA chemical ionization mass spectrometer. The instrument measures HNO3 with two independent channels of detection connected to separate forward and downward facing inlets that allow a determination of the amount of HNO3 condensed on ice particles. Subtropical cirrus clouds, as indicated by the presence of ice particles, were observed coincident with condensed‐phase HNO3 at temperatures of 197–224 K and pressures of 122–224 hPa. Maximum levels of condensed‐phase HNO3 approached the gas‐phase equivalent of 0.8 ppbv. Ice particle surface coverages as high as 1.4 × 1014 molecules cm−2 were observed. A dissociative Langmuir adsorption model, when using an empirically derived HNO3 adsorption enthalpy of −11.0 kcal mol−1, effectively describes the observed molecular coverages to within a factor of 5. The percentage of total HNO3 in the condensed phase ranged from near zero to 100% in the observed cirrus clouds. With volume‐weighted mean particle diameters up to 700 μm and particle fall velocities up to 10 m s−1, some observed clouds have significant potential to redistribute HNO3 in the upper troposphere.
Testing the physical oceanographic implications of the suggested sudden Black Sea infill 8400 years ago
Authors: Siddall M. , Pratt Lawrence J. , Helfrich Karl R. , Giosan L.
Published: March 2004

We apply a shock‐capturing numerical model based on the single‐layer shallow water equations to an idealized geometry of the Black Sea and the Sea of Marmara in order to test the implications of a suggested sudden Black Sea infill 8400 years ago. The model resolves the two‐dimensional flow upstream and downstream of the hydraulic jump provoked by the cascade of water from the Sea of Marmara into the Black Sea, which would occur during a sudden Black Sea infill. The modeled flow downstream of the hydraulic jump in the Black Sea would consist of a jet that is in part constrained by bathymetric contours. Guided by the Bosporus Canyon, the modeled jet reaches depths of up to 2000 m and could explain the origin of the sediment waves observed at this depth. At a late stage of the infill the modeled jet is attached to the coast and might account for the course of a submerged channel at the mouth of the Bosporus. The preservation of continuous barrier‐washover‐lagoonal fill systems occurring on the Black Sea shelf is, however, not easily reconcilable with the large flows over the southwest Black Sea shelf predicted by the model. Intensified flow in the upstream basin (Sea of Marmara) is restricted to the immediate vicinity of the Bosporus, suggesting that a sudden reconnection need not have disturbed sediments in the wider Sea of Marmara.
Intermediate depth warming in the tropical Atlantic related to weakened thermohaline circulation: Combining paleoclimate data and modeling results for the last deglaciation
Authors: Rühlemann Carsten , Mulitza Stefan , Lohmann Gerrit , Paul André , Prange Matthias , Wefer Gerold
Published: March 2004

Benthic foraminiferal oxygen isotope ratios from two sediment cores recovered at 426 and 1299 m water depth in the eastern and western tropical Atlantic show that a slowdown of the thermohaline circulation (THC) during Heinrich event H1 and the Younger Dryas was accompanied by rapid and intense warming of intermediate depth waters. Millennial‐scale covariations of low paleosalinities in the subpolar North Atlantic with decreased benthic oxygen isotope ratios in the eastern tropical Atlantic throughout the past 10,000 years suggest that THC weakening might be related to middepth warming during the Holocene period as well. Climate model experiments simulating a strong reduction of the THC in the Atlantic Ocean under present‐day and glacial conditions reveal that the increase of temperature in the middepth tropical and South Atlantic is a common feature for both climatic states, caused by a reduced ventilation of cold intermediate and deep waters in conjunction with downward mixing of heat from the thermocline. From the similarity of the paleoclimatic records with the model simulations, we infer that the characteristic pattern of temperature change in the Atlantic Ocean related to weakened thermohaline circulation can serve as an indicator of present‐day and future THC slowdown.
Late Cenozoic reorganization of the Arabia‐Eurasia collision and the comparison of short‐term and long‐term deformation rates
Authors: Allen Mark , Jackson James , Walker Richard
Published: March 2004

The Arabia‐Eurasia collision deforms an area of ∼3,000,000 km2 of continental crust, making it one of the largest regions of convergent deformation on Earth. There are now estimates for the active slip rates, total convergence and timing of collision‐related deformation of regions from western Turkey to eastern Iran. This paper shows that extrapolating the present day slip rates of many active fault systems for ∼3–7 million years accounts for their total displacement. This result means that the present kinematics of the Arabia‐Eurasia collision are unlikely be the same as at its start, which was probably in the early Miocene (16–23 Ma) or earlier. In some, but not all, active fault systems, short‐term (∼10 year) and long‐term (∼5 million year) average deformation rates are consistent. There is little active thickening across the Turkish‐Iranian plateau and, possibly, the interior of the Greater Caucasus. These are two areas where present shortening rates would need more than 7 million years to account for the total crustal thickening, and where there are structural and/or stratigraphic data for pre‐late Miocene deformation. We suggest that once thick crust (up to 60 km) built up in the Turkish‐Iranian plateau and the Greater Caucasus, convergence took place more easily by crustal shortening in less elevated regions, such as the Zagros Simple Folded Zone, the South Caspian region and foothills of the Greater Caucasus, or in other ways, such as westward transport of Turkey between the North and East Anatolian faults. The time and duration of this changeover are not known for certain and are likely be diachronous, although deformation started or intensified in many of the currently active fault systems at ∼5 ± 2 Ma.
Real‐time data received from Mount Erebus Volcano, Antarctica
Authors: Aster R. , MacIntosh W. , Kyle P. , Esser R. , Bartel B. , Dunbar N. , Johnson J. , Karstens R. , Kurnik C. , McGowan M. , McNamara S. , Meertens C. , Pauly B. , Richmond M. , Ruiz M.
Published: March 2004

Internal and eruptive volcano processes involve complex interactions of multi‐phase fluids with the solid Earth and the atmosphere, and produce diverse geochemical, visible, thermal, elastic, and anelastic effects. Multidisciplinary experimental agendas are increasingly being employed to meet the challenge of understanding active volcanoes and their hazards [e.g.,Ripepe et al., 2002; Wallace et al., 2003].

Mount Erebus is a large (3794 m) stratovolcano that forms the centerpiece of Ross Island, Antarctica, the site of the principal US. (McMurdo) and New Zealand (Scott) Antarctic bases. With an elevation of 3794 m and a volume of ∼1670 km3, Erebus offers exceptional opportunities for extended study of volcano processes because of its persistent, low‐level, strombolian activity (Volcano Explosivity Index 0–1) and exposed summit magma reservoir (manifested as a long‐lived phonolitic lava lake). Key scientific questions include linking conduit processes to near‐field deformations [e.g., Aster et al., 2003] ,explosion physics [ e.g., Johnson et al., 2003], magmatic differentiation and residence [e.g., Kyle et al., 1992], and effects on Antarctic atmospheric and ice geochemistry [e.g., Zreda‐Gostynska et al., 1997]. The close proximity of Erebus (35 km) to McMurdo, and its characteristic dry, windy, cold, and high‐elevation Antarctic environment, make the volcano a convenient test bed for the general development of volcano surveillance and other instrumentation under extreme conditions.
Call to protect deep‐sea coral, sponge ecosystems
Authors: Showstack Randy
Published: March 2004

More than 1100 scientists are signatories to a 15 February consensus statement calling for the protection of deep‐sea coral and sponge ecosystems.

The statement indicates that “the greatest human threat” to these ecosystems “is commercial fishing, especially bottom trawling.”
Creating an article template
Authors: Anonymous
Published: March 2004

The Publications Committee is seeking volunteers to develop an electronic template for providing production‐ready article files. The template would allow authors to create their accepted manuscripts in XML, the language used by AGU to produce online journals. If authors could use this template to produce XML files according to AGU specifications, in much the same way as they previously provided camera‐ready copy, and the costs of article production could correspondingly be lowered, the savings could be passed on to authors. The Information Technology Committee will be advising the Publications Committee and staff throughout the experiment.
Results of a VSP experiment at the Resurgent Dome, Long Valley caldera, California
Authors: Gritto Roland , Romero Arturo E. , Daley Thomas M.
Published: March 2004

A vertical seismic profiling experiment has been conducted at the DOE well LVF 51–20 at the resurgent dome at Long Valley caldera, California. The current paper is intended to report the velocity results derived from this experiment to seismically constrain the area around the resurgent dome. We report the results of velocity logs, Vp/Vs ratios, and VpVs products for the depth interval from 880–1980 m. The Bishop tuff can be divided into three zones (top‐to‐bottom) of intermediate velocities (Vp ≈ 4.0 km/s, Vs ≈ 2.3 km/s), followed by higher velocities (Vp = 4.7 km/s, Vs = 2.9 km/s) in the lower‐central part, and a decrease back to the lower values at the bottom of the sequence. The analysis of VpVs data suggested a decrease in porosity in the lower‐central section of the tuff as a possible explanation, which was supported by direct density measurements from a nearby location.
Investigation of a high Tc piezoelectric system: (1−x)Bi(Mg1/2Ti1/2)O3–(x)PbTiO3
Authors: Randall C. A. , Eitel R. , Jones B. , Shrout T. R. , Woodward D. I. , Reaney I. M.
Published: March 2004

(1−x) Bi(Mg 1/2 Ti 1/2 ) O 3 –x PbTiO 3 polycrystalline ceramics were investigated for potential as high-temperature piezoelectric materials. A morphotropic phase boundary (MPB) between tetragonal (T) and rhombohedral (R) ferroelectric (FE) phases, which exhibited enhanced piezoelectric activity and a ferroelectric–paraelectric phase transition at 478 °C was observed at x≈0.37. Electron diffraction patterns (x⩽0.37) contained discrete superlattice reflections at 12{hkl} positions arising from antiphase rotations of the O octahedra, consistent with R3c space group symmetry. These reflections were diffuse at the MPB (x=0.38) and absent in the T phase (x=0.5). In the unpoled state, FE R (x=0.35) ceramics revealed a polar microdomain structure whereas the T phase (x=0.5) contained classic {110} twin domain boundaries. However, poled R samples underwent a field-induced transformation to an aligned domain structure with {110} twin boundaries similar to those in the T phase. Correlations are made between structure and properties for these piezoelectric materials.
Cell parameter measurement of a twisted-nematic liquid crystal cell by the spectroscopic method
Authors: Chae Jong Seok , Moon Soo Gil
Published: March 2004

We propose a measurement method to determine the cell parameters which are a cell gap thickness, a twist angle and dispersion for a twisted-nematic liquid crystal cell by the spectral method. This method finds the variation point of transmission with respect to the wavelength λ. The proposed method can be applied to the determination of cell thickness and twist angle in the low cell gap as well as to the high cell gap.
Observation of electrostatically released DNA from gold electrodes with controlled threshold voltages
Authors: Takeishi Shunsaku , Rant Ulrich , Fujiwara Tsuyoshi , Buchholz Karin , Usuki Tatsuya , Arinaga Kenji , Takemoto Kazuya , Yamaguchi Yoshitaka , Tornow Marc , Fujita Shozo , Abstreiter Gerhard , Yokoyama Naoki
Published: March 2004

DNA oligo-nucleotides, localized at Au metal electrodes in aqueous solution, are found to be released when applying a negative bias voltage to the electrode. The release was confirmed by monitoring the intensity of the fluorescence of cyanine dyes (Cy3) linked to the 5′ end of the DNA. The threshold voltage of the release changes depending on the kind of linker added to the DNA 3′-terminal. The amount of released DNA depends on the duration of the voltage pulse. Using this technique, we can retain DNA at Au electrodes or Au needles, and release the desired amount of DNA at a precise location in a target. The results suggest that DNA injection into living cells is possible with this method.
Enhanced carrier velocity to early impact ionization
Authors: Hambleton P. J. , David J. P. R. , Rees G. J.
Published: March 2004

Numerical simulations predict that carriers which impact ionize shortly after their dead space travel to their ionization event with an average velocity much greater than their saturated drift velocity. The effect is argued to result from the fortuitously reduced phonon scattering which leads to this early ionization. Analytical models constructed using pictures of impact ionization similar to those of both Wolff and Shockley give good agreement with Monte Carlo simulations of the effect.
Thermoelectric properties of layered oxyselenides La1−xSrxCuOSe (x=0 to 0.2)
Authors: Yasukawa Masahiro , Ueda Kazushige , Hosono Hideo
Published: March 2004

Thermoelectric properties of layered oxyselenides La1−xSrxCuOSe (x=0.00 to 0.20) were investigated to evaluate the potential as thermoelectric material. Temperature dependence of the electrical conductivity and Seebeck coefficient measured in a temperature range of 373 to 673 K indicated that nondoped LaCuOSe was a p-type degenerate semiconductor due to Cu vacancies, while Sr-doped materials with x=0.05 to 0.20 were p-type metals. The electrical conductivity increased and Seebeck coefficient decreased with increasing Sr concentration up to x=0.10 in La1−xSrxCuOSe, suggesting that the effective hole carriers increase with increasing Sr content up to x=0.10. Thermoelectric power factors were drastically enhanced by the Sr doping, and the value reached 1.0−1.4×10−4 W m−1 K−2 for La0.95Sr0.05CuOSe. Thermal conductivities measured for the materials with x=0.00 and 0.05 were 2.1 W m−1 K−1 and 2.3 W m−1 K−1 at room temperature, respectively. These results lead to an estimation of Z value of 4.4×10−5 K−1 for La0.95Sr0.05CuOSe.
High-mobility transparent conducting Mo-doped In2O3 thin films by pulsed laser deposition
Authors: Warmsingh C. , Yoshida Y. , Readey D. W. , Teplin C. W. , Perkins J. D. , Parilla P. A. , Gedvilas L. M. , Keyes B. M. , Ginley D. S.
Published: March 2004

Highly conductive and transparent Mo-doped indium oxide (IMO) thin films were grown on glass and (100) yttria-stabilized zirconia (YSZ) single-crystal substrates by pulsed laser deposition. The electrical, optical, and structural properties were measured for films grown from 0, 1, 2, and 4 wt % Mo-doped targets. Films grown from the 2 wt % Mo-doped target had the best overall properties. In particular, for biaxially textured 2 wt % Mo IMO films grown on (100) YSZ, the conductivity was ∼3000 S cm−1 with a mobility greater than 95 cm2 V−1 s−1. In the visible, the optical transmittance normalized to the substrate was greater than 90%.
Coordination imperfection enhanced electron-phonon interaction
Authors: Pan L. K. , Sun Chang Q.
Published: March 2004

Correlation between the size-enhanced Stokes shift and the size-enlarged band gap expansion of porous silicon has been derived, which allows us to discriminate the effect of electron-phonon coupling from the effect of crystal binding on the blueshift in photoemission and photoabsorption of nanosolid silicon. Matching predictions to the measured peak shift of both photoemission and absorption and to the measured band gap expansion evidences the essentiality and validity of the recent bond order-length-strength correlation mechanism which suggests that the atomic coordination imperfection dictates the shape and size dependency of a nanosolid.
First stretching overtone of BiH3: An extreme local-mode case for XH3-type molecule?
Authors: Jerzembeck W. , Bürger H. , Hänninen V. , Halonen L.
Published: March 2004

The first stretching overtone region of short-lived, formerly inaccessible BiH3 near 3405 cm−1 has been measured by Fourier-transform infrared spectroscopy with a resolution of 0.0066 cm−1. Only the 2ν1(A1)/ν1+ν3(E) band system has been observed. Rotational analysis, with transitions reaching Jmax′=14, has revealed almost perfect local-mode behavior for the upper states denoted as (200A1/E) in the local-mode notation. Ratios of vibration–rotation interaction parameters q̄eff/αeff(BB) and reff/αeff(BC), and the appropriate rotational constant differences, are in good agreement with theoretical local-mode limit values. A simple stretching vibrational model reproduces the observed vibrational term values well, and the potential parameters obtained are close to true values.
Viscosity of network liquids within Doremus approach
Authors: Ojovan Michael I. , Lee William E.
Published: March 2004

Defect-mediated diffusion and viscous flow of network forming liquids have been investigated. An analytical formula of viscosity has been derived with two-exponential forms demonstrating high activation energy at low temperatures and low activation energy at high temperatures with Arrhenius-type behavior for both high and low temperature limits. Calculated data for the viscosity of silica glass are in excellent agreement with the experimental data.
Quantal density functional theory of the hydrogen molecule
Authors: Pan Xiao-Yin , Sahni Viraht
Published: March 2004

In this paper we perform a quantal density functional theory (Q-DFT) study of the hydrogen molecule in its ground state. In common with traditional Kohn–Sham density functional theory, Q-DFT transforms the interacting system as described by Schrödinger theory, to one of noninteracting fermions—the S system—such that the equivalent density, total energy, and ionization potential are obtained. The Q-DFT description of the S system is in terms of “classical” fields and their quantal sources that are quantum-mechanical expectations of Hermitian operators taken with respect to the interacting and S system wave functions. The sources, and hence the fields, are separately representative of all the many-body effects the S system must account for, viz. electron correlations due to the Pauli exclusion principle, Coulomb repulsion, and correlation-kinetic effects. The local electron-interaction potential energy of each model fermion is the work done to move it in the force of a conservative effective field that is the sum of the individual fields. The Hartree, Pauli, Coulomb, and correlation-kinetic energy components of the total energy are also expressed in virial form in terms of the corresponding fields. The highest occupied eigenvalue of the S system is the negative of the ionization potential energy. The Q-DFT analysis of the hydrogen molecule is performed employing the highly accurate correlated wave function of Kolos and Roothaan.
Non-Born–Oppenheimer trajectories with self-consistent decay of mixing
Authors: Zhu Chaoyuan , Jasper Ahren W. , Truhlar Donald G.
Published: March 2004

A semiclassical trajectory method, called the self-consistent decay of mixing (SCDM) method, is presented for the treatment of electronically nonadiabatic dynamics. The SCDM method is a modification of the semiclassical Ehrenfest (SE) method (also called the semiclassical time-dependent self-consistent-field method) that solves the problem of unphysical mixed final states by including decay-of-mixing terms in the equations for the evolution of the electronic state populations. These terms generate a force, called the decoherent force (or dephasing force), that drives the electronic component of each trajectory toward a pure state. Results for several mixed quantum–classical methods, in particular the SCDM, SE, and natural-decay-of-mixing methods and several trajectory surface hopping methods, are compared to the results of accurate quantum mechanical calculations for 12 cases involving five different fully dimensional triatomic model systems. The SCDM method is found to be the most accurate of the methods tested. The method should be useful for the simulation of photochemical reactions.
The dielectrophoresis of cylindrical and spherical particles submerged in shells and in semi-infinite media
Authors: Liu Hui , Bau Haim H.
Published: March 2004

The dielectrophoretic forces acting on and the resulting velocities of cylindrical and spherical particles embedded in perfectly dielectric viscous fluids are calculated analytically. The fluids are confined in cylindrical/spherical shells and in semi-infinite media with prescribed potential distributions along the surfaces of the media. The forces are calculated by evaluating the Maxwell stress tensor. The velocities of the particles are obtained by solving the Stokes equation for creeping flow. The range of validity of force calculations based on the dipole-moment approximation is estimated.
Density of phonon states in solid parahydrogen from inelastic neutron scattering
Authors: Colognesi D. , Celli M. , Zoppi M.
Published: March 2004

We have measured the inelastic neutron scattering spectrum of solid parahydrogen (at low pressure and T=13.3 K) using the thermal original spectrometer with cylindrical analyzers spectrometer at the ISIS pulsed neutron source (UK). From the experimental spectrum we have obtained the parahydrogen density of phonon states which has been compared with the estimates available in the literature. The present determination improves substantially the previous experimental scenario from the point of view of both statistics and accuracy. The comparison with the most recent estimate obtained from a quantum mechanical simulation of the molecular dynamics calls for an improvement of the computational methods.
Dynamics of ring vortices impinging on planar shock waves
Authors: Pirozzoli Sergio
Published: March 2004

In the present paper the encounter of vortex rings with planar shock waves is studied in a three-dimensional environment, with the objective to assess the influence of shock and vortex strength and vortex orientation on the dynamics of the process. The study relies on numerical simulations performed by means of a state-of-the-art hybrid compact/WENO (weighted essentially nonoscillatory) shock-capturing algorithm to solve the Euler equations of gas dynamics. The study focuses on the characterization of the interaction in terms of the evolution of the geometrical parameters of the vortex and the mean flow properties such as kinetic energy and enstrophy. The vortex is compressed as it passes through the shock, and its characteristic dimensions decrease; at the same time its axis is deflected and the ring follows a complex dynamic evolution, even though a nearly steady state is reached for the global quantities. In particular, it has been found that the total vortex kinetic energy is generally nonincreasing after the interaction, while the enstrophy always increases. A simple theory is developed here to shed some light onto the physical phenomena involved, which is found to compare reasonably well with the results of the computations. Some final comments are made regarding the extension of the results reported in the present study to the analysis of shock-compressed turbulence.
A variational analysis of flow-reversal condition in a turbulent swirling pipe flow using the bulk-helicity concept
Authors: Yokoi Nobumitsu , Yoshizawa Akira , Itoh Kimitaka , Itoh Sanae-I.
Published: March 2004

The magnitude of axial-flow retardation near the center of a turbulent swirling flow is estimated from the results of the variational analysis with the aid of the helicity concept. It is analytically shown that the axial-flow reversal in a swirl occurs if the bulk helicity imparted to the mean flow exceeds the critical value, which is proportional to the square of the flux. It is suggested that the bulk helicity in the center region plays an important role in determining the flow-reversal condition. Through the comparison with the experimental observations in a turbulent swirling pipe flow, the reliability of the theoretically-derived reversal condition is confirmed.
Low-frequency, low-field dielectric spectroscopy of living cell suspensions
Authors: Prodan C. , Mayo F. , Claycomb J. R. , Miller J. H. , Benedik M. J.
Published: March 2004

We have developed a dielectric spectroscopy technique for low-frequencies and low-electric field amplitudes. The excellent sensitivity of this method enables us to apply field amplitudes that are below the linear threshold. The dielectric constants of inorganic and organic liquids are found to be consistent with the previously reported experimental data and theoretical predictions.
Structural characterization of GaInNAs/GaAs double quantum well structures
Authors: Nakashima Kiichi , Tateno Kouta
Published: March 2004

We performed a structural analysis of strained GaInNAs/GaAs double quantum well samples (about 2% N content) having various well-layer thicknesses and investigated the relaxation process beyond the critical thickness. We used photoluminescence (PL) measurements, x-ray diffraction measurements, and transmission electron microscopy (TEM) analysis. PL measurement reveals deterioration of crystal quality as the well thickness increases. X-ray diffraction reveals that no serious relaxation occurs even when the deterioration proceeds. Cross-sectional and plan-view TEM analysis clarify the deterioration process in detail. In a sample with thin well layers, local dark spots are first generated only at the first well layer, whereas no such dark spots are observed in the second well layer. Through careful observation, the dark spots are identified as local defects (dislocation loop), not the quantum dot structures reported for other materials. For samples with thicker wells, large dark spots penetrating both well layers are observed. Furthermore, threading dislocations and/or stacking faults, which derive from the dark spots, are also observed in the upper GaAs cladding layers. However, no misfit dislocations are observed in any samples, although two-dimensional growth is confirmed. These results indicate a different type of deterioration from that conventionally reported in InGaAs/GaAs material systems. The relationships between the deterioration process and growth process are discussed based on the interface smoothness. The discussion clarifies that dynamical processes play essential roles in the deterioration.
Pyroelectric response of ferroelectric thin films
Authors: Sharma A. , Ban Z.-G. , Alpay S. P. , Mantese J. V.
Published: March 2004

A thermodynamic formalism is developed to calculate the pyroelectric coefficients of epitaxial (001) Ba0.6Sr0.4TiO3 (BST 60/40) and Pb0.5Zr0.5O3 (PZT 50/50) thin films on (001) LaAlO3, 0.29 LaAlO3:0.35(Sr2TaAlO6) (LSAT), MgO, Si, and SrTiO3 substrates as a function of film thickness by taking into account the formation of misfit dislocations at the growth temperature. The role of internal stress is discussed in detail with respect to epitaxy-induced misfit and thermal stresses arising from the difference between the thermal expansion coefficients of the film and the substrates. It is shown that the pyroelectric coefficients steadily increase with increasing film thickness for BST 60/40 and PZT 50/50 on LSAT and SrTiO3 substrates due to stress relaxation by misfit dislocations. Large pyroelectric responses (∼1.1 μC/cm2 K for BST 60/40 and ∼0.3 μC/cm2 K for PZT 50/50) are theoretically predicted for films on MgO substrates at critical film thicknesses (∼52 nm for BST 60/40 and ∼36 nm for PZT 50/50) corresponding to the ferroelectric to paraelectric phase transformation. Analysis shows that the pyroelectric coefficients of both BST 60/60 and PZT 50/50 epitaxial films on Si substrates are an order of magnitude smaller than corresponding films on LaAlO3, LSAT, MgO, and SrTiO3 substrates.
Study of strain fields at a-Si/c-Si interface
Authors: Yu Zhiheng , Muller David A. , Silcox John
Published: March 2004

The contrast due to a strain field at an amorphous silicon/crystalline silicon (a-Si/c-Si) interface relative to the bulk crystal is studied with a scanning transmission electron microscope equipped with a low angle annular dark field (LAADF) detector and a high angle ADF (HAADF) detector. Experimental observations suggest that strain contrast depends closely on sample thickness and collection angle. For a thin sample (<100 Å) strain contrast is negative in both the LAADF and HAADF images. For a thick sample (>150 Å) strain contrast is positive in the LAADF image and negative in the HAADF image. Theoretical calculations of the effect of a random strain field are carried out. First, a simple model based on atomic scattering with an extra Debye–Waller factor is employed. It predicts a positive strain contrast in the LAADF image and no contrast in the HAADF image. The simple model fails for the HAADF contrast because it does not consider the propagation process of the electron beam inside the sample. Therefore multislice simulations including propagation details are carried out. The multislice simulation results agree well with the experimental observations. A measure of the strain amplitude is attained by comparing the experimental data with multislice simulation results. Quantitative measurements of strain contrast are only possible if the sample thickness is known.
Determination of the optical dispersion in ferroelectric vinylidene fluoride (70%)/trifluoroethylene (30%) copolymer Langmuir–Blodgett films
Authors: Bai Mengjun , Sorokin A. V. , Thompson Daniel W. , Poulsen Matt , Ducharme Stephen , Herzinger C. M. , Palto S. , Fridkin V. M. , Yudin S. G. , Savchenko V. E. , Gribova L. K.
Published: March 2004

We report measurements of the optical dispersion in ferroelectric Langmuir–Blodgett films of polyvinylidene fluoride (70%)-trifluoroethylene (30%) copolymer, using variable-angle spectroscopic ellipsometry over a wide spectral range from infrared to ultraviolet. Film thickness averaged 1.78±0.07 nm per deposition layer for films ranging from 5 to 125 deposition layers as determined from multi-sample analysis. This deposition rate was consistent with capacitance measurements, yielding a dielectric constant of 9.9±0.4 normal to the film, by quartz microbalance measurements, and by atomic force microscopy.
Inelastic collisions of molecular hydrogen: A comparison of results from quantum and classical mechanics
Authors: Mandy M. E. , Pogrebnya S. K.
Published: March 2004

Full-dimensional quantum and classical calculations have been carried out for inelastic (nonreactive) energy transfer in H2+H2 on the ab initio potential energy surface of Boothroyd et al. [J. Chem. Phys. 116, 666 (2002)]. State-to-state cross sections are determined and compared for transitions from H2(0,jab)+H2(1,jcd). While there is excellent agreement for transitions involving small Δj, for larger Δj and for vibrational relaxation, significant differences are observed which exhibit no systematic trends. Reasons for this disagreement are discussed.
An alternative multipolar expansion for intermolecular potential functions
Authors: Chao Sheng Der , Kress Joel D. , Redondo Antonio
Published: March 2004

We have derived a new multipolar expansion for intermolecular potential-energy functions with applications in molecular physics, theoretical chemistry, and mathematical physics. The new formulation employs a separation of radial and angular terms with a simple index structure that leads to computational efficiency and ease of physical interpretation. For the case of the Coulomb interaction, we compare the present formulation with two conventional multipole expansions: the Cartesian tensor and the irreducible spherical tensor expansions. The new formalism leads to efficient numerical algorithms that are useful for general applications beyond intermolecular potentials. In addition to the electrostatic Coulomb interaction, we illustrate the formalism with applications to special function theory and a bipolar expansion involved in potential theory.