bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas‐aerosol partitioning of semi volatile carbonyls in polluted atmosphere in Hachioji, Tokyo
Authors: Matsunaga Sou N. , Kato Shungo , Yoshino Ayako , Greenberg Jim P. , Kajii Yoshizumi , Guenther Alex B.
Published: June 2005

Gaseous and particulate semi volatile carbonyls have been measured in urban air using an annular denuder sampling system. Three dicarbonyls, five aliphatic aldehydes and two hydroxy carbonyls were observed. Concentrations of other biogenic and anthropogenic volatile organic compounds (VOCs), SO2, CO, NO2 and particle concentration were also measured. Estimated gas‐aerosol equilibrium constants for the carbonyls showed an inverse correlation with the concentrations of anthropogenic pollutants such as benzene, isopentane and SO2. This suggests that the increase in the fraction of non‐polar anthropogenic particles in the atmosphere could change the average property of the ambient aerosols and drive the gas particle equilibrium of the carbonyls to the gas phase. This trend is uncommon in remote forest air. In this study, we examined the factors controlling the equilibrium in the polluted atmosphere and show that there is a difference in gas‐aerosol partition between polluted and clean air.
Analysis techniques for coherent airborne radar sounding: Application to West Antarctic ice streams
Authors: Peters Matthew E. , Blankenship Donald D. , Morse David L.
Published: June 2005

Analysis of coherent radar sounding echoes from polar ice sheets can provide information suitable for classifying the subglacial environment. Echoes from a general interface consist of both specularly reflected and diffusely scattered contributions. Specular reflection results from smooth uniform interfaces, whereas diffuse scattering results from rough nonuniform interfaces and inhomogeneous media. This article discusses how these phenomena are important to the acquisition and analysis of coherent radar sounding data. Reflection results are presented from airborne surveys conducted in 1987 over the downstream portions of Whillans Ice Stream and Ice Stream C, West Antarctica. Additionally, reflection and scattering analyses along with new results are presented for repeat profiles flown in 2001 over Ice Stream C. Analysis methods include using echo amplitudes to compute reflection coefficients which are used for inferring the dielectric properties of the subglacial material. Echo phase analysis provides the locations of dominant scattering centers which relate to reflection or scattering from the interface as well as provide interface roughness estimates. Comparison of low‐ and high‐resolution imaging obtained from synthetic aperture radar techniques indicates a reflecting and/or scattering interface. Combining the results from these independent analyses provides classification of the subglacial environment. Classified regions include smooth seawater, smooth saturated sediments, accreted marine ice, rough bottom crevasses, mixed conditions with partial subglacial water, and dry frozen conditions.
Structure and tectonics of the erosional convergent margin off Antofagasta, north Chile (23°30′S)
Authors: Sallarès Valentí , Ranero César R.
Published: June 2005

Subduction erosion has dominated the evolution of the north Chile convergent continental margin since at least the Mesozoic. We investigate the structure of the Antofagasta (23°S) sector of this margin along a transect using coincident wide‐angle and near‐vertical seismic profiling and gravity data. A 2‐D velocity field of the overriding and subducting plates was obtained using joint refraction and reflection travel time tomography. A velocity‐derived density distribution was used to model marine gravity data and substantiate the velocity model. The gravity and velocity models imply that the overriding plate is mainly made of arc‐type igneous basement. The upper plate is constructed of two main rock bodies separated by a subhorizontal layer defined by a velocity inversion, the top coincident with a reflection in near‐vertical seismic images. The seismic boundary is interpreted as a detachment separating an upper extended domain with large‐scale normal faulting from a lower domain apparently undergoing a different type of deformation. Velocity‐derived porosity indicates that the front of the margin is probably fluid‐saturated and disaggregated by fracturation as a consequence of frontal subduction erosion. Fluids carried into the subduction channel within slope debris filling underthrusting grabens reduce basal friction and probably induce hydrofracturing and basal erosion along the underside of the overriding plate. At depths greater than ∼20 km, porosity and density values imply that most fluids have been exhausted and the lower part of the upper plate is structurally coherent and little fractured. The change in physical properties leads to increased mechanical coupling along the plate boundary and occurs at the updip limit of the distribution of aftershocks of the 1995 Antofagasta earthquake (Mw = 8.0) defining the seismogenic zone.
High‐resolution Rayleigh wave slowness tomography of central Asia
Authors: Maceira Mónica , Taylor Steven R. , Ammon Charles J. , Yang Xiaoning , Velasco Aaron A.
Published: June 2005

We compute short‐period, high‐resolution surface wave slowness maps for central Asia using Bayesian tomography. We focus on the region between 69° and 108°E and 29° and 54°N and used seismograms from more than 1100 events. Using multiple‐filter and phase‐matched filter techniques, we measured the dispersion characteristics of the signals between 6 and 30 s period. These Rayleigh wave group velocity dispersion curves were used to compute high‐resolution, half‐degree cell size, slowness tomographic maps. Because short periods are primarily sensitive to upper crustal structures, the images display low velocities associated with the Tarim, Junggar, and Qaidam basins. Relatively high velocities are associated with mountainous tectonic features such as the Tian Shan. We validated our maps using dispersion curves from 640 events that were not used to construct the tomographic model. The model predictions show a significant variance reduction at short and intermediate periods (6–15 s) with respect to the prior model. Our model also shows 15% improvement in surface wave detection capability with respect to previous one‐dimensional models. These high‐resolution, short‐period tomography maps can help improve regional magnitude estimations for construction of mb:Ms discriminants. Moreover, the short‐period surface wave tomographic results show unprecedented resolution that reveals greater geologic detail than has previously been achieved using surface waves and that give us insight into the shear velocity structure of the crust underlying this part of Asia.
On the determination of the settling flux of cohesive sediments in a turbulent fluid
Authors: Gratiot N. , Michallet H. , Mory M.
Published: June 2005

In this paper we compare the settling flux of a cohesive sediment mixture measured in a quiescent fluid with that achieved in a turbulent flow. Experiments were performed in a mixing tank. The turbulence produced mechanically by an oscillating grid maintains a stationary, highly concentrated fluid mud layer in which the concentration is almost uniform. In this layer the turbulence decay with increasing distance from the grid is similar to that obtained in clear water. For steady conditions the settling flux of the fluid mud mixture is balanced by the upward turbulent flux, and its value can be determined from the measured depth of the fluid mud layer. At high concentrations (10–200 g L−1), we show that the settling flux in a turbulent fluid is much larger than estimated in a quiescent fluid (up to two orders of magnitude). Hindering effects in the settling process of cohesive sediments may thus be considerably reduced by turbulence.
Patterns of ocean current variability on the West Florida Shelf using the self‐organizing map
Authors: Liu Yonggang , Weisberg Robert H.
Published: June 2005

Patterns of ocean current variability are examined on the West Florida Shelf by a neural network analysis based on the self‐organizing map (SOM), using time series of moored velocity data that span the interval October 1998–September 2001. Three characteristic spatial patterns are extracted in a 3 × 4 SOM array: spatially coherent southeastward and northwestward flow patterns with strong currents and a transition pattern of weak currents. On the synoptic weather timescale the variations of these patterns are coherent with the local winds. On the seasonal timescale the variations of the patterns are coherent with both the local winds and complementary sea surface temperature patterns. The currents are predominantly southeastward during fall–winter months (from October to March) and northwestward during summer months (from June to September). The spatial patterns extracted by the (nonlinear) SOM method are asymmetric, a feature that is not captured by the (linear) empirical orthogonal function method. Thus we find for the synoptic weather and longer timescales that (1) southeastward currents are generally stronger than northwestward currents, (2) the coastal jet axis is located further offshore for southeastward currents than for northwestward currents, and (3) the velocity vector rotations with depth are larger in shallower water when the currents are southeastward relative to when the currents are northwestward.
Improved albedo formulation for chemistry transport models based on satellite observations and assimilated snow data and its impact on tropospheric photochemistry
Authors: Laepple T. , Schultz M. G. , Lamarque J. F. , Madronich S. , Shetter R. E. , Lefer B. L. , Atlas E.
Published: June 2005

Present parameterizations of the UV surface albedo in global chemistry transport models are generally based on a crude land cover classification and do not account for interannual variations of the snow‐covered surface or the large variability in the albedo of snow‐covered surfaces. We developed an improved scheme based on 2 years of Moderate‐Resolution Imaging Spectroradiometer (MODIS) albedo data, a fine‐resolution MODIS land cover map, Global Ozone Monitoring Experiment (GOME) albedo data, and daily assimilated snow cover maps from the European Centre for Medium‐Range Weather Forecasts or the National Centers for Environmental Prediction. The new parameterization improves the calculation of photolysis frequencies in particular in the subarctic region as shown by a comparison of the calculated ratio of upwelling and downwelling actinic fluxes with spectral measurements from the Tropospheric Ozone Production About Spring Equinox (TOPSE) campaign (January–May 2000). The impact of surface albedo changes on tropospheric photochemistry has been investigated using the global MOZART‐2 chemistry transport model. Compared with the original model version, the surface albedo changes alter the tropospheric oxidizing capacity (OH concentrations) between −20 and +200% locally and +5% in the global annual mean. About half of this change results from a new value adapted for the ocean UV albedo. Locally, NOx concentrations were found to decrease by up to 40% and were most pronounced where the snow boundary crosses the high‐emission regions in Europe, North America, and Asia. The interannual variability of snow and sea ice cover can lead to changes in the global tropospheric OH‐concentration of 0.5%, which is of similar magnitude compared with the impacts of varying water vapor, transport, ozone column, and emissions as discussed in previous studies.
Using laser‐light scattering to measure impurities, bubbles, and imperfections in ice cores
Authors: Stolz M. R. , Ram M.
Published: June 2005

Laser‐light scattering (LLS) on polar ice, or on polar ice meltwater, is an accepted method for measuring the concentration of water‐insoluble aerosol deposits (dust) in the ice. LLS on polar ice can also be used to measure water‐soluble aerosols, as well as imperfections (air bubbles and cavities) in the ice. LLS was originally used for measuring the dust concentration in polar ice meltwater, but was later also applied to solid ice for measuring the dust concentration profile along the deep, bubble‐free sections of the Greenland Ice Sheet Project 2 (GISP2) ice core from central Greenland. In this paper, we extend the usability of LLS on ice into the realm of the nontransparent, bubbly polar ice, and put previous empirical findings on a theoretical footing. For LLS on clear, bubble‐free polar ice, we studied numerically the scattering of light by soluble and insoluble aerosol particles embedded in the ice to complement previous experimental studies. For air bubbles in polar ice, we calculated the effects of multiple light scattering using Mie theory and Monte Carlo simulations, and found a method for determining the bubble size and number concentration using LLS on bubbly ice. We also demonstrated that LLS can be used on bubbly ice to rapidly measure annual layers.
Evaluation of solar radio bursts' effect on GPS receiver signal tracking within International GPS Service network
Authors: Chen Zhiyu , Gao Yang , Liu Zhizhao
Published: June 2005

The direct interference from solar radio bursts (SRB) has not usually been considered as a potential threat to global positioning system (GPS) signal tracking, since the flux densities of most bursts are below 40,000 solar flux units (sfu), a threat threshold to GPS L1 frequency proposed by Klobuchar et al. (1999). Recent analysis indicated that a much lower threshold should be adopted for codeless or semicodeless dual‐frequency GPS receivers. In this investigation, severe signal corruptions were found at dayside International GPS Service GPS receiver stations during a large solar radio burst that accompanied the super flare of 28 October 2003. Almost no GPS L2 signals were tracked during the solar flux peak time for areas near the subsolar point. Correlation analysis was performed between the rate of loss of lock on GPS L2 frequency and solar radio flux density at different bands, and a correlation index as high as 0.75 is revealed in the 1415 MHz solar radiation band, which is located between the two GPS operating frequencies L2 (1227.60 MHz) and L1 (1575.42 MHz). The correlation analysis indicates that GPS signal losses of lock were primarily caused by microwave in‐band interference and that the threat threshold of SRB effects on the GPS system should be re‐evaluated, since the flux density of the burst at 1415 MHz was just 4,000–12,000 sfu, which is far below the previously proposed threat threshold. The signal‐tracking performance of different types of GPS receivers during such a super flare event is also presented.
Detecting sub‐glacial aquifers in the north polar layered deposits with Mars Express/MARSIS
Authors: Farrell W. M. , Plaut J. J. , Gurnett D. A. , Picardi G.
Published: June 2005

The penetration of the MARSIS radar signal into the polar ice mass is modeled to determine the capability of the instrument to locate sub‐glacial aquifers. As a ground penetrating radar, the orbiting MARSIS transmits a signal >1 W between 1–5 MHz. In this work we will investigate the effect of ice reflective and conductive losses on the radar‐detection of subsurface aquifers using an MGS MOC profile of the ice layering. We find that a basal lake located ∼2.5 km below the surface is at the limit of detectability.
Melting behavior of H2O at high pressures and temperatures
Authors: Lin Jung‐Fu , Gregoryanz Eugene , Struzhkin Viktor V. , Somayazulu Maddury , Mao Ho‐kwang , Hemley Russell J.
Published: June 2005

Water plays an important role in the physics and chemistry of planetary interiors. In situ high pressure‐temperature Raman spectroscopy and synchrotron x‐ray diffraction have been used to examine the phase diagram of H2O. A discontinuous change in the melting curve of H2O is observed at approximately 35 GPa and 1040 K, indicating a triple point on the melting line. The melting curve of H2O increases significantly above the triple point and may intersect the isentropes of Neptune and Uranus. Solid ice could therefore form in stratified layers at depth within these icy planets. The extrapolated melting curve may also intersect with the geotherm of Earth's lower mantle above 60 GPa. The presence of solid H2O would result in a jump in the viscosity of the mid‐lower mantle and provides an additional explanation for the observed higher viscosity of the mid‐lower mantle.
New mean dynamic topography of the Mediterranean calculated from assimilation system diagnostics
Authors: Dobricic Srdjan
Published: June 2005

The use of sea surface height (SSH) measurements by altimeter satellites in the Mediterranean requires an accurate mean dynamic topography (MDT) field with a high horizontal resolution which must be added to observations. This study presents a new Mediterranean MDT estimate calculated from the diagnostics of an existing operational assimilation system in the Mediterranean. The calculation starts from the assumption that the error in the MDT field appears in the assimilation system as a temporally constant and spatially variable observational bias. Therefore, we can reduce this error by calculating long‐term averages of dynamic topography departures and by subtracting them from the previous MDT field. The analysis system statistics show that the assimilation of the SSH in the Mediterranean is more accurate with the new MDT estimate.
Intermediate ion formation in the ship's exhaust
Authors: Gopalakrishnan V. , Pawar S. D. , Siingh Devendraa , Kamra A. K.
Published: June 2005

Measurements of the small‐, intermediate‐ and large‐ion concentrations and atmospheric electric conductivity have been made onboard ORV Sagarkanya off the west coast of India during the Arabian Sea Monsoon Experiment (ARMEX) ‐ 2003. On a few days during the pre‐monsoon season, the intermediate ion concentration is observed to periodically increase by 20–60% of its ambient value with a periodicity of ∼2 hours. An examination of the ion‐concentration variations with respect to cruise pattern and the prevailing wind direction reveals that the observed increases in intermediate ion concentration are caused by the ship's exhaust polluting the air over the measurements site. Formation of intermediate ions in the engine's exhaust has been associated with the generation of chemiions within the engine combustors which provide centers for the rapid growth of molecular clusters and the formation of electrically charged sulphuric acid/water aerosols.
Nitrogen isotopes of the mantle: Insights from mineral separates
Authors: Fischer Tobias P. , Takahata Naoto , Sano Yuji , Sumino Hirochika , Hilton David R.
Published: June 2005

We present the first nitrogen (N) isotope measurements determined by in‐vacuo crushing of mineral separates from arc lavas, OIBs (Ocean Island Basalts), and mantle xenoliths. Measured OIB δ15N values range from ∼−8‰ for the northern rift zone in Iceland to +3.1‰ for a dunite nodule from Hawaii. Most arc‐related olivines show distinctly positive values ‐ up to +6.2‰ (Cerro Negro, Nicaragua). The measured N isotope values in olivine separates are similar to gas samples collected at the same localities, suggesting that both media (olivines and gases) sample volatiles primarily derived from the magma. This observation also implies that N isotope fractionation does not occur during magma degassing, a notion supported by 4He/40Ar* data. Our results indicate a heterogeneous mantle source region, in terms of N isotopic composition, that may have resulted from surface recycling of N at some localities.
First observation of topside ionization ledges using radio beacon measurements from low Earth orbiting satellites
Authors: Thampi Smitha V. , Ravindran Sudha , Devasia C. V. , Pant Tarun K. , Sreelatha P. , Sridharan R.
Published: June 2005

Ionization ledges in the topside ionosphere have been observed from Trivandrum (8.5°N, 77°E, 0.5°N dip) using single station Total Electron Content (TEC) measurements. These measurements are made using a ground based radio beacon receiver. The receiver measures the relative phase between 150 MHz and 400 MHz beacon transmissions from a Low Earth Orbiting Satellite (LEOS). The ionization ledges, which could be observed, using only topside sounders so far, are seen to have their clear signatures in relative TECs derived using differential Doppler measurements. Simulations were also carried out to understand how the ionospheric topside ledges of various intensities would manifest in the latitudinal profiles of the relative TEC. The magnetometer observations indicate the presence of the Equatorial Counter Electrojet (CEJ) on the days when the ledge is observed. The study demonstrates the potential of radio beacon measurements for observing topside ionization ledges, and phenomena similar to it.
Kinetic Modeling of Amyloid Binding in Humans using PET Imaging and Pittsburgh Compound-B
Authors: Price Julie C , Klunk William E , Lopresti Brian J , Lu Xueling , Hoge Jessica A , Ziolko Scott K , Holt Daniel P , Meltzer Carolyn C , DeKosky Steven T , Mathis Chester A
Published: June 2005

A valid quantitative imaging method for the measurement of amyloid deposition in humans could improve Alzheimer's disease (AD) diagnosis and antiamyloid therapy assessment. Our group developed Pittsburgh Compound-B (PIB), an amyloid-binding radiotracer, for positron emission tomography (PET). The current study was aimed to further validate PIB PET through quantitative imaging (arterial input) and inclusion of subjects with mild cognitive impairment (MCI). Pittsburgh Compound-B studies were performed in five AD, five MCI, and five control subjects and five subjects were retested within 20 days. Magnetic resonance images were acquired for partial volume correction and region-of-interest definition (e.g., posterior cingulate: PCG; cerebellum: CER). Data were analyzed using compartmental and graphical approaches. Regional distribution volume (DV) values were normalized to the reference region (CER) to yield DV ratios (DVRs). Good agreement was observed between compartmental and Logan DVR values (e.g., PCG: r = 0.89, slope = 0.91); the Logan results were less variable. Nonspecific PIB retention was similar across subjects ( n = 15, Logan CER DV: 3.63 ± 0.48). Greater retention was observed in AD cortical areas, relative to controls ( P < 0.05). The PIB retention in MCI subjects appeared either ‘AD-like’ or ‘control-like’. The mean test/retest variation was ~6% in primary areas-of-interest. The Logan analysis was the method-of-choice for the PIB PET data as it proved stable, valid, and promising for future larger studies and voxel-based statistical analyses. This study also showed that it is feasible to perform quantitative PIB PET imaging studies that are needed to validate simpler methods for routine use across the AD disease spectrum.
Effects of 5-HT1B/1D Receptor Agonist Rizatriptan on Cerebral Blood Flow and Blood Volume in Normal Circulation
Authors: Okazawa Hidehiko , Tsuchida Tatsuro , Pagani Marco , Mori Tetsuya , Kobayashi Masato , Tanaka Fumiko , Yonekura Yoshiharu
Published: June 2005

To investigate the vasoconstrictor effect of 5-hydroxytryptamine (5-HT1B/1D) receptor agonists for migraine treatment, changes in cerebral blood flow (CBF) and blood volume induced by rizatriptan were assessed by positron emission tomography (PET). Eleven healthy volunteers underwent PET studies before and after rizatriptan administration. Dynamic PET data were acquired after bolus injection of H215O to analyze CBF and arterial-to-capillary blood volume ( V0) images using the three-weighted integral method. After a baseline scan, three further acquisitions were performed at 40 to 50, 60 and 70 to 80 mins after drug administration. Global and regional differences in CBF and V0 between conditions were compared using absolute values in the whole brain and cortical regions, as well as statistical parametric mapping (SPM) analysis. The global and regional values for CBF and V0 decreased significantly after rizatriptan administration compared with the baseline condition. However, both values recovered to baseline within 80 mins after treatment. The maximal reduction in global CBF and V0 was approximately 13% of baseline value. The greatest decrease in CBF was observed approximately 60 mins after drug administration, whereas the maximal reduction in V0 was observed approximately 5 mins earlier. Statistical parametric mapping did not highlight any regional differences between conditions. Thus, in brain circulation, rizatriptan caused significant CBF and V0 decreases, which are consistent with the vasoconstrictor effect of triptans on the large cerebral arteries. The gradual recovery in the late phase from the maximal CBF and V0 decrease suggests that rizatriptan does not affect the cerebral autoregulatory response in small arteries induced by CBF reduction.
Atrial Response to Ventricular Antitachycardia Pacing Discriminates Mechanism of 1:1 Atrioventricular Tachycardia
Authors: RIDLEY DARYL P. , GULA LORNE J. , KRAHN ANDREW D. , SKANES ALLAN C. , YEE RAYMOND , BROWN MARK L. , OLSON WALTER H. , GILLBERG JEFFREY M. , KLEIN GEORGE J.
Published: June 2005

Background: Inappropriate shocks from implantable cardioverter defibrillators (ICD) remain a significant clinical problem despite device discrimination algorithms. The atrial response to antitachycardia pacing (ATP) may determine the mechanism of 1:1 A:V tachycardia.

Methods: For this study we refer to sinus tachycardia, atrial tachycardia (AT), atrial fibrillation, and flutter as atrial tachycardia (AT), and all other tachycardia as “non‐AT.” Three atrial response patterns during the burst of ATP were determined. The atrial cycle length (ACL) may be unchanged (type 1) indicating AT. The ACL may show variation during ATP (type 2) indicating variable VA block and does not discriminate between an AT and a non‐AT mechanism, in which case a default diagnosis of non‐AT is made. The ACL may accelerate to the ATP cycle length (type 3) indicating entrainment. A VAAV response at the end of ATP was considered diagnostic of AT (type 3A) whereas a VAV or VVA response was considered a non‐AT mechanism (type 3B). This algorithm was applied to ICD tracings from 68 episodes of spontaneous 1:1 A:V tachycardia that had 136 sequences of ATP administered. The rhythm “truth” was determined by consensus of two experienced clinicians.

Results: The algorithm correctly identified AT with a sensitivity of 71.9% (95% CI: 67.1–73.6), and specificity of 95% (83.5–99.1). The PPV was 97.2% (90.9–99.5), and NPV 58.5% (51.4–61.0). Kappa was 0.57 (0.43–0.62). If used clinically the algorithm would have aborted 53.3% (8/15) of inappropriate shocks delivered into an AT‐mechanism tachycardia and would not have withheld a shock for any episode of VT.

Conclusion: Analysis of atrial response patterns during and after ventricular ATP can successfully discriminate tachycardia mechanism and may reduce inappropriate ICD shocks.
Effects of Cardiac Resynchronization Therapy on Ventricular Repolarization in Patients with Congestive Heart Failure
Authors: BERGER THOMAS , HANSER FRIEDRICH , HINTRINGER FLORIAN , POELZL GERHARD , FISCHER GERALD , MODRE ROBERT , TILG BERNHARD , PACHINGER OTMAR , ROITHINGER FRANZ X
Published: June 2005

Introduction: Biventricular pacing has been shown to improve the clinical status of patients with congestive heart failure, but little is known about its influence on ventricular repolarization. The aim of our study was to evaluate the effect of biventricular pacing on ECG markers of ventricular repolarization in patients with congestive heart failure.

Methods and Results: Twenty‐five patients with congestive heart failure, sinus rhythm (SR), and complete LBBB (6 females; age 61 ± 8 years; NYHA class II–III; echocardiographic ejection fraction 21 ± 5%; QRS ≥ 130 ms) underwent permanent biventricular DDDR pacemaker implantation. A high‐resolution 65‐lead body‐surface ECG recording was performed at baseline and during right‐, left‐, and biventricular pacing, and the total 65‐lead root mean square curve of the QRST complex and the interlead QT dispersion were assessed. The QRS duration was increased during right (RV)‐ and left ventricular (LV) pacing (127 ± 26% and 117 ± 40%; P < 0.05), as compared to SR (100%) and biventricular pacing (93 ± 16%; ns). The QTc interval was increased during RV and LV pacing (112 ± 12% and 114 ± 14%; P < 0.05) as compared to SR (100%) or biventricular pacing (99 ± 12%). There was no effect on JT interval during all pacing modes. The Tpeak‐end interval was increased during right (120 ± 34%; P < 0.01) and LV pacing (113 ± 29%; P < 0.05) but decreased during biventricular pacing (81 ± 19%; P < 0.01). A similar effect was found for the Tpeak‐end integral and the Tpeak amplitude. QT dispersion was increased during right ventricular (129 ± 16 ms; P < 0.05) and decreased during biventricular pacing (90 ± 12 ms; P < 0.01), as compared to SR (114 ± 22 ms).

Conclusions: Using a high‐resolution surface ECG, biventricular pacing resulted in a significant reduction of ECG markers of ventricular dispersion of repolarization.
Superior Vena Cava Flutter: Electrophysiology and Ablation
Authors: MERINO JOSE L. , PEINADO RAFAEL , ABELLO MAURICIO , GNOATTO MARIANA , VASSEROT MAR G. , SOBRINO JOSE A.
Published: June 2005

Introduction: Reentry within a major thoracic vein has been suggested as a cause of atrial arrhythmias. However, little is known about these potential reentrant circuits.

Methods and Results: Atypical atrial flutter was induced and mapped in 67 out of 225 atrial flutter ablation procedures. Reentry around the superior vena cava (SVC) was suspected in three patients. The suspected SVC flutter was induced and terminated by pacing in all patients. Fusion was demonstrated during flutter entrainment by subeustachian isthmus pacing in all of them. The postpacing interval following entrainment by pacing from different sites of the right atrium (RA) or coronary sinus was longer than the flutter cycle length. Macroreentry within the SVC was demonstrated both by sequential activation and a postpacing interval matching the flutter cycle length when pacing from different sites around the SVC in all patients. Atrial–venous–atrial electrogram sequence was demonstrated following flutter entrainment by atrial pacing. Flutter was terminated by an electrical stimulus delivered to the SVC, which was not propagated to the trabeculated RA, in one patient, and linear radiofrequency application from the distal SVC to the posterior wall of the RA, or to the superoseptal portion of the crista terminalis, in the other two.

Conclusion: Macroreentry within the SVC is a distinctive mechanism responsible for rapid atrial activation, which is different from other reported flutter mechanisms, such as upper loop reentry. SVC longitudinal radiofrequency application can eliminate the arrhythmia without the need for complete electrical disconnection of the vein.
Role of Repolarization Restitution in the Development of Coarse and Fine Atrial Fibrillation in the Isolated Canine Right Atria
Authors: BURASHNIKOV ALEXANDER , ANTZELEVITCH CHARLES
Published: June 2005

Introduction: Although the role of action potential duration restitution (APD‐R) in the initiation and maintenance of ventricular fibrillation (VF) has been the subject of numerous investigations, its role in the generation of atrial fibrillation (AF) is less well studied. The cellular and ionic basis for coarse versus fine AF is not well delineated. Methods and Results: We measured APD‐R during acetylcholine‐mediated AF as well as during pacing (standard and dynamic protocols) in crista teriminalis, pectinate muscle, superior vena cava, and appendage of isolated canine arterially perfused right atria (n = 15). Transmembrane action potential (TAP), pseudo‐ECG, and isometric tension development were simultaneously recorded. Acetylcholine flattened APD‐R measured by both standard and dynamic protocols, but promoted induction of AF. AF was initially coarse, converting to fine within 3–15 minutes of AF. Coarse, but not fine AF was associated with dramatic fluctuations in tension development, reflecting wide variations in intracellular calcium activity ([Ca2+]i). During coarse AF, APD‐R data displayed a cloud‐like distribution pattern, with a wide range of maximum APD‐R slope (from 1.21 to 0.35). A maximum APD‐R slope >1 was observed only in crista terminalis (3/10). The APD‐R relationship was relatively linear and flat during fine AF. Reduction of [Ca2+]i was associated with fine AF whereas augmentation of [Ca2+]i with coarse AF. Conclusions: Our data indicate that while APD‐R may have a limited role in the maintenance of coarse AF, it is unlikely to contribute to the maintenance of fine AF and that [Ca2+]i dynamics determine the degree to which AF is coarse or fine.
Ventricular Tachycardia Duration and Form Are Associated with Electrical Discontinuities Bounding the Core of the Reentrant Circuit
Authors: CIACCIO EDWARD J.
Published: June 2005

Background: Successful prediction of reentrant ventricular tachycardia duration and form from sinus‐rhythm electrogram signals in canine hearts is relevant to clinical studies, to potentially improve catheter ablation treatment during EP study.

Methods/Results: Following LAD ligation of canine hearts, activation maps were constructed from 312 border zone sites 4–5 days postinfarction. When reentrant ventricular tachycardia was inducible via programmed stimulation, the core of the circuit was defined on the maps as the enclosed area formed by the adjoining lines of slowest conduction and block bounding the protected region of the reentrant circuit. The number, location, and width of points of entrance or exit of the activation wavefront about the core were determined. Core perimeter location was then marked on the sinus‐rhythm activation map, and the difference in activation time at opposite recording sites along the core perimeter was measured. Mean sinus‐rhythm activation was highly discontinuous along the core perimeter in 10 transient reentry experiments (30.1 ± 4.4 ms), moderately discontinuous in 13 sustained experiments (16.7 ± 1.8 ms), and only slightly discontinuous in 5 noninducible experiments (9.7 ± 1.7 ms). For transient versus sustained experiments, the entrance/exit points were narrower (mean: 6.5 ± 1.0 mm vs 9.5 ± 1.8 mm) with larger sinus‐rhythm discontinuity across them (mean: 23.8 ± 6.0 ms vs 11.8 ± 2.1 ms). As core size increased, so did the number of entrance/exits present during reentry (P < 0.001). With increasing core size, four‐loop (quatrefoil) reentry was frequently observed.

Conclusions: Whether reentrant ventricular tachycardia will be inducible in the canine infarct border zone, and its duration and form, is associated with the characteristics of electrical discontinuities present about the core perimeter.
Mechanistic and kinetic study of the CH3CO+O2 reaction
Authors: Hou Hua , Li Aixiao , Hu Hongyi , Li Yuzhen , Li Hui , Wang Baoshan
Published: June 2005

Potential-energy surface of the CH3CO+O2 reaction has been calculated by ab initio quantum chemistry methods. The geometries were optimized using the second-order Moller–Plesset theory (MP2) with the 6-311G(d,p) basis set and the coupled-cluster theory with single and double excitations (CCSD) with the correlation consistent polarized valence double zeta (cc-pVDZ) basis set. The relative energies were calculated using the Gaussian-3 second-order Moller–Plesset theory with the CCSD/cc-pVDZ geometries. Multireference self-consistent-field and MP2 methods were also employed using the 6-311G(d,p) and 6-311++G(3df,2p) basis sets. Both addition/elimination and direct abstraction mechanisms have been investigated. It was revealed that acetylperoxy radical [CH3C(O)OO] is the initial adduct and the formation of OH and α-lactone [CH2CO2(A′1)] is the only energetically accessible decomposition channel. The other channels, e.g., abstraction, HO2+CH2CO, O+CH3CO2, CO+CH3O2, and CO2+CH3O, are negligible. Multichannel Rice–Ramsperger–Kassel–Marcus theory and transition state theory (E-resolved) were employed to calculate the overall and individual rate coefficients and the temperature and pressure dependences. Fairly good agreement between theory and experiments has been obtained without any adjustable parameters. It was concluded that at pressures below 3 Torr, OH and CH2CO2(A′1) are the major nascent products of the oxidation of acetyl radials, although CH2CO2(A′1) might either undergo unimolecular decomposition to form the final products of CH2O+CO or react with OH and Cl to generate H2O and HCl. The acetylperoxy radicals formed by collisional stabilization are the major products at the elevated pressures. In atmosphere, the yield of acetylperoxy is nearly unity and the contribution of OH is only marginal.
Multiple reflectance interference spectroscopy measurements made in parallel for binding studies
Authors: Gauglitz Guenter
Published: June 2005

Reflectometric interference spectroscopy (RIfS) for the direct optical detection of biomolecular interaction has gained increasing interest in recent years compared to fluorophore based assays. The method has been established in the last decade as a robust and simple optical tool to perform such binding studies taking advantage of low temperature dependence and its capability of time-resolved monitoring of binding processes. Therefore various single-channel setups are given in review. In addition, the capability of parallel measurements and miniaturisation is discussed. The different properties of the setups are presented and the theoretical background is outlined. Many applications are given for this method in comparison to other direct optical detection methods; concentrating on a number of applications that have not yet been published. The capability of using this method in the area of high throughput screening of libraries and the application to combinatorial chemistry is demonstrated.
Fabrication of elliptically figured mirror for focusing hard x rays to size less than 50nm
Authors: Yumoto Hirokatsu , Mimura Hidekazu , Matsuyama Satoshi , Hara Hideyuki , Yamamura Kazuya , Sano Yasuhisa , Ueno Kazumasa , Endo Katsuyoshi , Mori Yuzo , Yabashi Makina , Nishino Yoshinori , Tamasaku Kenji , Ishikawa Tetsuya , Yamauchi Kazuto
Published: June 2005

In this study, we designed, fabricated, and evaluated a hard x-ray focusing mirror having an ideally focused beam with a full width at half maximum in the intensity profile of 36nm at an x-ray energy of 15keV. The designed elliptically curved shape was fabricated by a computer-controlled fabrication system using plasma chemical vaporization machining and elastic emission machining, on the basis of surface profiles accurately measured by combining microstitching interferometry with relative angle determinable stitching interferometry. A platinum-coated surface was employed for hard x-ray focusing with a large numerical aperture. Line-focusing tests on the fabricated elliptical mirror are carried out at the 1-km-long beamline of SPring-8. A full width at half maximum of 40nm was achieved in the focused beam intensity profile under the best focus conditions.
Effects of strain rate and curvature on surface density function transport in turbulent premixed flames in the thin reaction zones regime
Authors: Chakraborty Nilanjan , Cant R. S.
Published: June 2005

Strain rate and curvature effects on Surface Density Function (SDF) transport in the thin reaction zones regime are studied using a three-dimensional direct numerical simulations (DNS) with a single-step Arrhenius type chemistry. It is shown that if the tangential strain rate on a flame isosurface exceeds a critical value, then a negative normal strain rate is induced, which acts to bring the isoscalar lines closer to each other and hence leads to a higher value of SDF. This is reflected in a positive correlation between SDF and tangential strain rate. Curvature is also found to affect SDF through the correlation between tangential strain rate and curvature on a given flame isosurface. Strain rate and curvature are found to have an appreciable effect on various terms of the SDF transport equation. The SDF straining term is correlated positively with tangential strain rate as expected and is also correlated negatively with the curvature. The combined SDF curvature and propagation terms operate as a source near the fresh gas side of the flame and as a sink towards the burned gas side. The SDF propagation term is found to correlate negatively with flame curvature towards the fresh gas side and positively towards the burned gas side. The variation of the SDF curvature term with local flame curvature is found to be nonlinear due to the additional stretch induced by the tangential diffusion component of the displacement speed.
Phase transitions in the liquid-vapor interface of dilute alloys of Bi in Ga: New experimental studies
Authors: Li Dongxu , Jiang Xu , Yang Bin , Rice Stuart A.
Published: June 2005

We report the results of measurements of x-ray reflectivity and grazing incidence x-ray diffraction from the liquid-vapor interfaces of four dilute alloys of Bi in Ga with mole fractions xBi=0.0032, 0.0023, 0.000 37, and 0.000 037. The monolayer coverage of the alloys with xBi=0.0023, and xBi=0.00037 is about 0.85 and only very slightly temperature dependent. The monolayer coverage in the lowest-concentration alloy, with xBi=0.000037, ranged from 0.82 at 29°C to 0.58 at 110°C. In none of these alloys, down to the lowest temperature used, 29°C, can we find any evidence for crystallization of the Bi monolayer that segregates as the outermost stratum of the liquid-vapor interface. Drawing on theoretical arguments we propose that the transitions inferred from the second-harmonic generation and plasma generation studies of dilute Bi in Ga alloys are from the liquid state to the hexatic state of the Bi monolayer. The data for the alloy with xBi=0.000037 suggest that near 80°C there is a disordered phase-to-disordered phase transition.
Supersonically cooled hydronium ions in a slit-jet discharge: High-resolution infrared spectroscopy and tunneling dynamics of HD2O+
Authors: Dong Feng , Uy Dairene , Davis Scott , Child Mark , Nesbitt David J.
Published: June 2005

Jet-cooled high-resolution infrared spectra of partially deuterated hydronium ion (HD2O+) in the O–H stretch region (ν3 band) are obtained for the first time, exploiting the high ion densities, long absorption path lengths, and concentration modulation capabilities of the slit-jet discharge spectrometer. Least-squares analysis with a Watson asymmetric top Hamiltonian yields rovibrational constants and provides high level tests of ab initio molecular structure predictions. Transitions out of both the lower (ν3+←0+) and the upper (ν3−←0−) tunneling levels, as well as transitions across the tunneling gap (ν3−←0+) are observed. The ν3−←0+ transitions in HD2O+ acquire oscillator strength by loss of D3h symmetry, and permit both ground-state-[27.0318(72)cm−1] and excited-state-[17.7612(54)cm−1]-tunneling splittings to be determined to spectroscopic precision from a single rovibrational band. The splittings and band origins calculated with recent high level ab initio six-dimensional potential surface predictions for H3O+ and isotopomers [X. C. Huang, S. Carter, and J. M. Bowman, J. Chem. Phys. 118, 5431 (2003); T. Rajamaki, A. Miani, and L. Halonen, J. Chem. Phys. 118, 10929 (2003)] are in very good agreement with the current experimental results.
Shear viscosity of molten alkali halides from equilibrium and nonequilibrium molecular-dynamics simulations
Authors: Galamba N. , Nieto de Castro C. A. , Ely James F.
Published: June 2005

The shear viscosity of molten NaCl and KCl was calculated through equilibrium (EMD) and nonequilibrium molecular-dynamics (NEMD) simulations in the canonical (N,V,T) ensemble. Two rigid-ion potentials were investigated, namely, the Born–Mayer–Huggins–Tosi–Fumi potential and the Michielsen–Woerlee–Graaf–Ketelaar potential with the parameters proposed by Ladd. The NEMD simulations were performed using the SLLOD equations of motion [D. J. Evans and G. P. Morriss, Phys. Rev. A 30, 1528 (1984)] with a Gaussian isokinetic thermostat and the results are compared with those obtained from Green–Kubo EMD (N,V,T) simulations and experimental shear viscosity data. The NEMD zero strain rate shear viscosity, η(0), was obtained by fitting a simplified Carreau-type equation and by application of mode-coupling theory, i.e., a η-γ1∕2 linear relationship. The values obtained from the first method are found to be significantly lower than those predicted by the second. The agreement between the EMD and NEMD results with experimental data is satisfactory for the two potentials investigated. The ion-ion radial distribution functions obtained with the two rigid-ion potentials for both molten salts are discussed in terms of the differences between the two models.
Stochastic potential switching algorithm for Monte Carlo simulations of complex systems
Authors: Mak C. H.
Published: June 2005

This paper describes a new Monte Carlo method based on a novel stochastic potential switching algorithm. This algorithm enables the equilibrium properties of a system with potential V to be computed using a Monte Carlo simulation for a system with a possibly less complex stochastically altered potential Ṽ. By proper choices of the stochastic switching and transition probabilities, it is shown that detailed balance can be strictly maintained with respect to the original potential V. The validity of the method is illustrated with a simple one-dimensional example. The method is then generalized to multidimensional systems with any additive potential, providing a framework for the design of more efficient algorithms to simulate complex systems. A near-critical Lennard-Jones fluid with more than 20 000 particles is used to illustrate the method. The new algorithm produced a much smaller dynamic scaling exponent compared to the Metropolis method and improved sampling efficiency by over an order of magnitude.
Observability of the scattering cross-section through phase decoherence
Authors: Field Timothy R.
Published: June 2005

We derive the stochastic dynamics for scattering of a wavelike field from a large population of scatterers whose dynamics is arbitrary. This leads to a result concerning the observability of the scattering cross section in terms of the resultant phase fluctuations that is independent of the population dynamics. An emergent concept is a certain notion of an ideal filter. The diffusion based model of K-scattering arises as a special case. The experimental implications of the results in a variety of contexts are discussed.
Critical comparison of various connected quadruple excitation approximations in the coupled-cluster treatment of bond breaking
Authors: Musiał Monika , Bartlett Rodney J.
Published: June 2005

To assess the limits of single-reference coupled-cluster (CC) methods for potential-energy surfaces, several methods have been considered for the inclusion of connected quadruple excitations. Most are based upon the factorized inclusion of the connected quadruple contribution (Qf) [J. Chem. Phys. 108, 9221 (1998)]. We compare the methods for the treatment of potential-energy curves for small molecules. These include CCSD(TQf), where the initial contributions of triple (T) and factorized quadruple excitations are added to coupled-cluster singles (S) and doubles (D), its generalization to CCSD(T̃Q̃f), where instead of measuring their first contribution from orders in H, it is measured from orders in H̃=e−(T1+T2)He(T1+T2); renormalized approximations of both, and CCSD(2) defined in [J. Chem. Phys. 115, 2014 (2001)]. We also consider CCSDT, CCSDT(Qf), CCSDTQ, and CCSDTQP for comparison, where T, Q, and P indicate full triple, quadruple, and pentuple excitations, respectively. Illustrations for F2, the double bond breaking in water, and N2 are shown, including effects of quadruples on equilibrium geometries and vibrational frequencies. Despite the fact that no perturbative approximation, as opposed to an iterative approximation, should be able to separate a molecule correctly for a restricted-Hartree–Fock reference function, some of these higher-order approximations have a role to play in developing new, more robust procedures.