bluuebunny/crossref_metadata_2025 huggingface dataset:
Contribution of continental water to sea level variations during the 1997–1998 El Niño–Southern Oscillation event: Comparison between Atmospheric Model Intercomparison Project simulations and TOPEX/Poseidon satellite data
Authors: Ngo‐Duc T. , Laval K. , Polcher J. , Cazenave A.
Published: May 2005

Satellite altimetry from TOPEX/Poseidon (T/P) is used to estimate the variation of the global sea level. This signal, once corrected for steric effects, reflects water mass exchange with the atmosphere and land reservoirs (mainly ice caps, soils and snowpack). It can thus be used to test the capacity of general circulations models (GCMs) to estimate change in land water storage. In this study, we compare the land hydrology contribution to global mean sea level variations during the major 1997–1998 El Niño–Southern Oscillation event from two data sets: (1) the results of the Organizing Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface scheme, developed at the Institute Pierre Simon Laplace, coupled to the Laboratoire de Météorologie Dynamique Atmospheric General Circulation Model (LMD AGCM) and (2) the T/P‐based estimates. We show that the seasonal variation of the continental water storage is well represented in the model. The drastic amplitude change between the two contrasted years, 1997 and 1998, observed from satellite altimetry, is also simulated. We analyze the role of each component of simulated water fluxes (precipitation, evaporation, and runoff) in determining the range of annual continental water mass variation and its interannual variability. The difference between the two years, 1997 and 1998, is, for an essential part, due to land precipitation in the 20°N–20°S domain. This analysis emphasizes the important role of tropical regions in interannual variability of climate.
Asian continental aerosol persistence above the marine boundary layer over the eastern North Pacific: Continuous aerosol measurements from Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2)
Authors: VanCuren Richard A. , Cliff Steven S. , Perry Kevin D. , Jimenez‐Cruz Michael
Published: May 2005

We report analyses of aerosols collected for the 2002 Intercontinental Transport and Chemical Transformation experiment (ITCT‐2K2). Sampling was conducted 15 April to 25 May 2002. Data are from three sites: a sea level site at Trinidad Head, California, a coastal mountain site 1 km altitude (Trinity Alps), and an inland mountain site near 2 km altitude (Mount Lassen). Aerosols were continuously collected in eight size bins (0.09 to 10 micrometers aerodynamic diameter) using eight‐stage rotating drum impactors. Samples were analyzed in 3‐hour time steps by synchrotron x‐ray fluorescence. We find the following. (1) Aerosol chemical composition at Trinidad Head was generally dominated by marine aerosols with varying minor contributions from local sources. Despite the presence of Asian continental aerosol above the marine boundary layer, significant concentrations of Asian aerosols were observed at sea level only during a strong frontal passage between 22 and 25 April. (2) At the elevated sites, aerosol elemental composition was predominantly Asian despite wide swings in concentration. Analysis of soil‐forming elements shows that Asian continental dust and associated combustion products overwhelmed local‐source aerosols through the first half of the sampling period; in the latter half, Asian aerosols present in the free troposphere were regularly delivered to the mountain sampling sites by nocturnal subsidence. (3) Asian aerosols in the lower free troposphere, although highly variable, were very persistent, not arriving only in discrete “transport events.” We conclude that throughout the experiment the aerosols in the lower free troposphere over the northeastern Pacific Ocean and western North America were dominated by continental outflow from Asia, with little marine or North American continental influence. Viewed in the context of previously published analyses of the long‐term aerosol history for Mount Lassen that showed frequent, strong Asian influence throughout spring, summer, and fall, the Asian impact appears likely to be quasi‐continuous for much of the year.
Regional and global trace gas distributions and inferred transports in the upper troposphere and lower stratosphere
Authors: Schaeler B. , Offermann D. , Kuell V. , Jarisch M. , Feldmann H. , Ebel A.
Published: May 2005

Trace gas mixing ratios were measured in the upper troposphere and lower stratosphere during the second mission of the Cryogenic Infrared Spectrometers and Telescopes (CRISTA) experiment in August 1997. Water vapor data at high vertical and horizontal resolution are presented here. Respective data for CFC 11 (CFCl3) are given in a future paper by V. Kuell et al. (Tropopause region temperatures and CFC 11 mixing ratios from CRISTA 2, submitted to Journal of Geophysical Research, 2004). Some ozone data are also available. Zonal mean mixing ratios of water vapor are compared to several other measurements, and good agreement is obtained. Data variance of all three gases is high and is mostly attributable to atmospheric fluctuations rather than instrument noise. Diffusive (“eddy”) fluxes were derived from these fluctuations for all three gases. They were converted to meridional eddy coefficients Kyy by means of respective mixing ratio gradients. Kyy values obtained from CFC 11 and H2O show a close correlation (r = 0.62). This suggests that water vapor may be a usable tracer at medium latitudes. (This does not include the tropics, where our Kyy values appear to be unreliable.) Our Kyy values are substantially higher than those frequently used in the literature. Another difference is that our summer values are larger on average than the winter ones (by a factor of 2). A similar result, however, is seen in the effective diffusivities Keff of Haynes and Shuckburgh (2000a, 2000b) (hereinafter referred to as HS a,b). There are other agreements of the two data sets Kyy and Keff: HS a,b discuss a number of transport barriers (equator and tropopause). These are found in a very similar way in our data. The latitude structures of the Kyy and Keff coefficients can be compared at three altitude levels. These patterns are also found to be quite similar.
Comparing clouds and their seasonal variations in 10 atmospheric general circulation models with satellite measurements
Authors: Zhang M. H. , Lin W. Y. , Klein S. A. , Bacmeister J. T. , Bony S. , Cederwall R. T. , Del Genio A. D. , Hack J. J. , Loeb N. G. , Lohmann U. , Minnis P. , Musat I. , Pincus R. , Stier P. , Suarez M. J. , Webb M. J. , Wu J. B. , Xie S. C. , Yao M.‐S. , Zhang J. H.
Published: May 2005

To assess the current status of climate models in simulating clouds, basic cloud climatologies from ten atmospheric general circulation models are compared with satellite measurements from the International Satellite Cloud Climatology Project (ISCCP) and the Clouds and Earth's Radiant Energy System (CERES) program. An ISCCP simulator is employed in all models to facilitate the comparison. Models simulated a four‐fold difference in high‐top clouds. There are also, however, large uncertainties in satellite high thin clouds to effectively constrain the models. The majority of models only simulated 30–40% of middle‐top clouds in the ISCCP and CERES data sets. Half of the models underestimated low clouds, while none overestimated them at a statistically significant level. When stratified in the optical thickness ranges, the majority of the models simulated optically thick clouds more than twice the satellite observations. Most models, however, underestimated optically intermediate and thin clouds. Compensations of these clouds biases are used to explain the simulated longwave and shortwave cloud radiative forcing at the top of the atmosphere. Seasonal sensitivities of clouds are also analyzed to compare with observations. Models are shown to simulate seasonal variations better for high clouds than for low clouds. Latitudinal distribution of the seasonal variations correlate with satellite measurements at >0.9, 0.6–0.9, and −0.2–0.7 levels for high, middle, and low clouds, respectively. The seasonal sensitivities of cloud types are found to strongly depend on the basic cloud climatology in the models. Models that systematically underestimate middle clouds also underestimate seasonal variations, while those that overestimate optically thick clouds also overestimate their seasonal sensitivities. Possible causes of the systematic cloud biases in the models are discussed.
Fire effects on net radiation and energy partitioning: Contrasting responses of tundra and boreal forest ecosystems
Authors: Chambers S. D. , Beringer J. , Randerson J. T. , Chapin F. S.
Published: May 2005

The net radiation available to drive surface‐atmosphere exchange is strongly influenced by albedo and surface temperature. Tower‐based microclimatic and eddy covariance measurements in typical Alaskan black spruce and tundra ecosystems before and immediately after fire indicated a 10% decrease in net radiation over the burned spruce stand but a 12% increase in net radiation over the burned tundra surface. In both cases, there was increased partitioning of net radiation into sensible heat flux. In terms of absolute fluxes, however, fire increased average sensible heating over tundra by ∼50 W m−2 but caused little change in average sensible heat flux over the black spruce forest. This difference in fire effects occurred because fire altered the canopy characteristics (including surface roughness) more strongly in the forest than in the tundra, leading to a greater reduction in surface‐atmosphere coupling over the forest.
Cloud‐to‐ground lightning in Austria: A 10‐year study using data from a lightning location system
Authors: Schulz W. , Cummins K. , Diendorfer G. , Dorninger M.
Published: May 2005

In this paper we present lightning statistics for more than three million cloud‐to‐ground (CG) flashes located during the 10‐year operation period 1992–2001 of the Austrian lightning location system (LLS) called ALDIS (Austrian Lightning Detection and Information System). Like a majority of other LLS operated worldwide, ALDIS underwent configuration changes and continuous performance improvement. Since these changes can alter the lightning statistics, we also relate the variation of the individual lightning parameters during the period of operation to changes in ALDIS configuration and performance. This analysis should be useful to other network operators and data users. Flash densities in Austria are normally between 0.5 and 4 flashes km−2 yr−1 depending on terrain. Flashes are classified as negative, positive, or bipolar. Seventeen percent of the flashes were classified as positive, and 2.3% of the total number of flashes were bipolar. Fifty percent of the positive multiple‐stroke flashes were bipolar flashes with positive first stroke; this influences the positive flash multiplicity and interstroke interval statistics. Compared to many other networks, the ALDIS network reports much lower median negative peak currents. For 2001, the median first‐stroke peak current for negative flashes was 10 kA. Estimated multiplicity of negative flashes for the 10‐year period is affected by the algorithm that groups strokes into flashes, as well as the improved DE of the network as a result of the integration of ALDIS into the European LLS (EUCLID). This performance improvement also resulted in a higher number of single‐stroke flashes. Interstroke interval and median first‐stroke peak current show a clear correlation with multiplicity for negative flashes, irrespective of detection efficiency. Negative flashes with higher multiplicity show smaller average interstroke intervals and larger first stroke median peak currents. No correlation between interstroke interval and stroke order was found. On average, regions with higher flash density show slightly higher flash multiplicity.
Odin/SMR limb observations of stratospheric trace gases: Validation of N2O
Authors: Urban J. , Lautié N. , Le Flochmoën E. , Jiménez C. , Eriksson P. , de La Noë J. , Dupuy E. , El Amraoui L. , Frisk U. , Jégou F. , Murtagh D. , Olberg M. , Ricaud P. , Camy‐Peyret C. , Dufour G. , Payan S. , Huret N. , Pirre M. , Robinson A. D. , Harris N. R. P. , Bremer H. , Kleinböhl A. , Küllmann K. , Künzi K. , Kuttippurath J. , Ejiri M. K. , Nakajima H. , Sasano Y. , Sugita T. , Yokota T. , Piccolo C. , Raspollini P. , Ridolfi M.
Published: May 2005

The Sub‐Millimetre Radiometer (Odin/SMR) on board the Odin satellite, launched on 20 February 2001, performs regular measurements of the global distribution of stratospheric nitrous oxide (N2O) using spectral observations of the J = 20 → 19 rotational transition centered at 502.296 GHz. We present a quality assessment for the retrieved N2O profiles (level 2 product) by comparison with independent balloonborne and aircraftborne validation measurements as well as by cross‐comparing with preliminary results from other satellite instruments. An agreement with the airborne validation experiments within 28 ppbv in terms of the root mean square (RMS) deviation is found for all SMR data versions (v222, v223, and v1.2) under investigation. More precisely, the agreement is within 19 ppbv for N2O volume mixing ratios (VMR) lower than 200 ppbv and within 10% for mixing ratios larger than 150 ppbv. Given the uncertainties due to atmospheric variability inherent to such comparisons, these values should be interpreted as upper limits for the systematic error of the Odin/SMR N2O measurements. Odin/SMR N2O mixing ratios are systematically slightly higher than nonvalidated data obtained from the Improved Limb Atmospheric Spectrometer‐II (ILAS‐II) on board the Advanced Earth Observing Satellite‐II (ADEOS‐II). Root mean square deviations are generally within 23 ppbv (or 20% for VMR‐N2O > 100 ppbv) for versions 222 and 223. The comparison with data obtained from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the Envisat satellite yields a good agreement within 9–17 ppbv (or 10% for VMR‐N2O > 100 ppbv) for the same data versions. Odin/SMR version 1.2 data show somewhat larger RMS deviations and a higher positive bias.
Biomass burning emission inventory from burnt area data given by the SPOT‐VEGETATION system in the frame of TRACE‐P and ACE‐Asia campaigns
Authors: Michel C. , Liousse C. , Grégoire J.‐M. , Tansey K. , Carmichael G. R. , Woo J.‐H.
Published: May 2005

One of the main uncertainties in the estimation of the climatic impact of aerosols is linked to our knowledge of gas and aerosol emissions. This is particularly crucial over Asia, where a strong regional fingerprint is observed, with different emission types, depending on the various vegetation and climate conditions (biomass burning emissions) and on the very fast changes of the population and industrialization (biofuel and fossil fuel emissions). The main contribution of this work is to derive a biomass burning inventory of 1° × 1° over Asia (the Asian biomass burning inventory (ABBI)) for gases and particles for the Aerosol Characterization Experiment‐Asia (ACE‐Asia) and Transport and Chemical Evolution Over the Pacific (TRACE‐P) campaign period (March to May 2001) in 2001. In this paper we apply new estimates of burnt biomass area to estimate emissions. The method is based on burnt areas (GBA2000 project; Tansey et al. (2002) and Grégoire et al. (2003)) obtained from 1 km resolution SPOT‐VEGETATION satellite data. Regional‐scale maps of burnt areas are produced, and then spatial and temporal emission distribution are obtained from biomass density and emission factors. Strength and weaknesses associated with the use of satellite products are discussed, including the problem of subpixel classification and the lack of validation data for the accuracy assessment of the products for the studied area. Estimated emissions are compared with ACE‐Asia and TRACE‐P Modeling and Emission Support System (ACESS) climatological estimates. In addition, interannual variability is estimated by preparing inventories for the years 2000 and 2001.
Origin and evolution of a cold‐based tropical mountain glacier on Mars: The Pavonis Mons fan‐shaped deposit
Authors: Shean David E. , Head James W. , Marchant David R.
Published: May 2005

Each of the large Tharsis Montes volcanoes in the equatorial region of Mars has an unusual Amazonian‐aged fan‐shaped deposit on its west‐northwestern flank. On the basis of Viking Orbiter data, the origin of these deposits has been variously ascribed to volcanic, mass‐wasting, tectonic, and glacial processes. Using new MGS and Odyssey data, combined with recent developments in the study of cold‐based glaciers, we reassess the geology and mode of origin for these deposits with particular emphasis on Pavonis Mons. The deposits share three characteristic facies, including (1) a ridged facies, consisting of tens to >100 parallel, concentric ridges around the margins of the deposits, (2) a knobby facies composed of irregular hills and hummocks, and (3) a smooth facies of broad, lobate plains that superposes all other units within the deposits. On the basis of morphology, topography, superposition relationships, and close terrestrial analogs in the Dry Valleys of Antarctica, we interpret the Pavonis fan‐shaped deposit as the depositional remains of a cold‐based glacier that formed on the northwestern flank in recent Martian history. We interpret the ridged facies as drop moraines formed around the margins of a retreating cold‐based glacier, the knobby facies as a sublimation till derived from in situ down‐wasting of cold‐based glacial ice, and the smooth facies as extant debris‐covered glacial ice. In addition to the three main facies, the fan‐shaped deposit at Pavonis Mons contains several unique features, including arcuate scarps, high‐relief flow‐like features, and radial ridges, which suggest that volcanism played a role during its formation. Using recent results from Mars general circulation model simulations, we outline a model of glacier formation involving atmospheric deposition of water ice on the northwestern flanks of the Tharsis Montes during periods of high mean obliquity. Reconstructed ice sheet profiles for each of the Tharsis Montes glaciers suggest that the ice sheets attained average thicknesses of ∼1.6–2.4 km, values that are consistent with a cold‐based glacial origin. Analysis of crater size‐frequency distributions using new data indicates that the age of the glaciation lies within the Late Amazonian (∼10–200 Ma). Thus our results suggest that multiple phases of tropical mountain glaciation occurred on Mars within the past few hundred Myr and that significant amounts of near‐surface, equatorial ice may remain within the deposit today.
Radio frequency interference mitigation for detection of extended sources with an interferometer
Authors: Bower Geoffrey C.
Published: May 2005

Radio frequency interference (RFI) is a significant problem for current and future radio telescopes. We describe here a method for postcorrelation cancellation of RFI for the special case of an extended source observed with an interferometer that spatially resolves the astronomical signal. In this circumstance the astronomical signal is detected through the autocorrelations of each antenna but is not present in the cross correlations between antennas. We assume that the RFI is detected in both autocorrelations and cross correlations, which is true for many cases. The large number of cross correlations can provide a very high interference‐to‐noise ratio reference signal which can be adaptively subtracted from the autocorrelation signals. The residual signal is free of interference to significant levels. We discuss the application of this technique for detection of the spin‐flip transition of interstellar deuterium with the Allen Telescope Array. The technique may also be of use for epoch of reionization experiments and with multibeam feeds on single‐dish telescopes.
Nonlinear left‐handed metamaterials
Authors: Shadrivov Ilya V. , Zharov Alexander A. , Zharova Nina A. , Kivshar Yuri S.
Published: May 2005

We analyze nonlinear properties of microstructured materials with the negative refractive index, the so‐called left‐handed metamaterials. We demonstrate that the hysteresis‐type dependence of the magnetic permeability on the field intensity allows changing the material properties from left to right handed and back. Using the finite difference time domain simulations, we study the wave reflection from a slab of a nonlinear left‐handed material and observe generation and propagation of temporal solitons in such materials. We demonstrate also that the nonlinear left‐handed metamaterials can support both transverse electric– and transverse magnetic–polarized self‐trapped localized beams, spatial electromagnetic solitons. Such solitons appear as single‐hump and multihump beams, being either symmetric or antisymmetric, and they can exist because of the hysteresis‐type magnetic nonlinearity and the effective domains of negative magnetic permeability.
Kinematics of long‐lasting Paleoproterozoic transpression within the Thompson Nickel Belt, Manitoba, Canada
Authors: Gapais Denis , Potrel Alain , Machado Nuno , Hallot Erwan
Published: May 2005

This paper presents a reappraisal of kinematics and tectonic history of the Thompson Nickel Belt, a major Paleoproterozoic deformation zone along the western boundary of the Archean Superior Province in Manitoba. The study, based on the analysis of foliation trajectory maps and associated shear zone arrays, emphasizes that the overall strain pattern results from transpression. Strains are large, marked by strong subvertical stretch and NW‐SE subhorizontal shortening, combined with along‐strike stretch. From these, we infer distributed crustal shortening, involving steeply plunging flow rather than large horizontal displacements, although kinematic indicators show that top‐to‐the‐west motions were dominant. Along‐strike shear indicators are poorly expressed but suggest a component of bulk dextral strike‐slip. Synkinematic thermal indicators and new geochronological data indicate that transpression could have been a long‐lasting, circa 100 Ma, event in the area.
Paleocene–Eocene record of ophiolite obduction and initial India‐Asia collision, south central Tibet
Authors: Ding Lin , Kapp Paul , Wan Xiaoqiao
Published: May 2005

Uppermost Cretaceous to Eocene marine sedimentary sequences occur both to the south and north of the Yarlung Zangbo suture in south central Tibet. They consist of Indian‐margin strata of the northern Tethyan Himalaya and Asian‐margin strata of the Gangdese forearc. Both assemblages are characterized by major changes in depositional environment and sedimentary provenance at ∼65 Ma and an appearance of detrital chromium‐rich spinel of ophiolite affinity (TiO2 generally <0.1 wt%) during the Paleocene. Ophiolitic melange exposed along the suture could have provided a source for detrital spinel. The melange occurs in the hanging wall of a north dipping, south directed mylonitic shear zone which includes a tectonic sliver of mafic schist. Amphibole from the schist yields 40Ar/39Ar ages of ∼63 Ma, which we attribute to cooling during slip along the shear zone and southward obduction of the melange. Melange obduction was coeval with the development of an angular unconformity within the Gangdese forearc basin to the north (between late Maastrichtian time and ∼62 Ma). Upper Paleocene to middle Eocene sandstones in the northern Tethyan Himalaya yield 200–120 Ma U‐Pb detrital zircon ages and 190–170 Ma 40Ar/39Ar detrital mica ages. These detrital grains were most likely sourced from regions north of the Yarlung Zangbo suture, suggesting that onset of India‐Asia collision in south central Tibet is middle Eocene or older in age. Collectively, our results support previous suggestions that oceanic rocks were obducted onto the northern margin of India during latest Cretaceous–earliest Tertiary time. Coeval changes in Gangdese forearc sedimentation raise the possibility that this obduction event marks onset of tectonic interaction between India and Asia at ∼65 Ma. Alternatively, in concert with the conventional view of Eocene collision initiation, the obducted oceanic rocks may be of intraoceanic origin, while coeval changes in Gangdese forearc sedimentation may be a consequence of an increase in the rate of ocean‐continent convergence following the demise of the intraoceanic subduction zone.
Stochastic analysis of contaminant transport through nonstationary fractured porous media: A dual‐permeability approach
Authors: Xu Jie , Hu Bill X.
Published: May 2005

A Eulerian moment expansion through the first order of σp2(p = f, m) (σp2 is the velocity variance in the fracture, p = f, or matrix, p = m, domain) is developed for solute transport in a nonstationary, fractured medium. A dual‐permeability model is applied to describe the conceptualized fractured medium where solute convection and dispersion in both the fracture and matrix domains are considered. Hydraulic conductivity distrbutions in both fracture and matrix domains are nonstationary. The stochastic governing equations for the mean concentration and concentration covariance are analytically derived. A numerical method (a finite difference method) is applied to obtain the solutions. The developed method is applied to study solute transport in stationary and nonstationary fractured media. The study results indicate that medium nonstationarity significantly influences the solute transport process. The nonstationary transport theory relaxes many assumptions adopted in stationary theories and paves the way for applying the theory to many environmental projects, especially for uncertainty analysis of solute transport.
Observations of stratospheric warmings and mesospheric coolings by the TIMED SABER instrument
Authors: Siskind D. E. , Coy L. , Espy P.
Published: May 2005

We used temperature data from the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER) on the the NASA TIMED satellite to quantify the connection between temperatures in the stratosphere and in the mesosphere and lower thermosphere. Specifically, we studied three winter periods where stratospheric temperatures were dynamically disturbed: February 2002, August, 2002, and February 2003. The SABER temperatures show a clear signature of mesospheric coolings in concert with stratospheric warmings. Mesospheric temperatures between 0.7 hPa and 0.01 hPa show a significant anticorrelation with stratospheric temperatures. For pressures <0.01 hPa, this anticorrelation breaks down, in disagreement with recent model results from a thermosphere‐ionosphere‐mesosphere general circulation model that suggest mesospheric coolings persist up to 110 km. Also, the lack of a clear correlation between stratospheric temperatures and those at 83–90 km suggests that measurements of the OH Meinel band temperatures at those altitudes may not be representative of the entire mesosphere.
Ambient infrasound noise
Authors: Bowman J. Roger , Baker G. Eli , Bahavar Manochehr
Published: May 2005

The ambient infrasound noise environment is characterized for 21 globally distributed infrasound arrays in the frequency band of 0.03 to 7 Hz. Power Spectral Density (PSD) is measured for one site of each array for 21 intervals at each of four times of day from January 2003 through January 2004. The ambient noise at infrasound stations is highly variable by season, time of day and station. Noise spectra for an individual station may vary by four orders of magnitude at any given frequency. Preliminary infrasound noise models are defined, which can be used as baselines for evaluating ambient noise at current and new infrasound stations. Median noise levels in the microbarom band centered on 0.2 Hz vary smoothly in an annual pattern, with most stations observing maximum noise during local winter. Noise amplitudes do not have a normal or log‐normal distribution, but rather are skewed to larger amplitudes.
Unfolding the relation between global temperature and ENSO
Authors: Tsonis A. A. , Elsner J. B. , Hunt A. G. , Jagger T. H.
Published: May 2005

An analysis of global temperature and ENSO data indicates that their relationship is more complicated than currently thought. Indeed, it appears that there are two complimenting aspects to this relation. The first (and known) aspect expresses the fact that global temperature increases after an El Nino event and a La Nina event follows an El Nino event. Thus, El Nino forces global temperature. While this is an important result, it is not the entire picture. If it were, ENSO would be independent of global temperature. The second aspect, which is proposed here, suggests a deeper connection between global temperature and ENSO. We find that ENSO is not independent and that positive (negative) global temperature tendency tends to trigger an El Nino (La Nina). Thus, in a warming climate El Nino events will be more frequent than La Nina events. The methodology presented in this paper may elucidate how realistically coupled ocean‐atmosphere models simulate the response of climate to global change.
Long‐Term Incidence of Malignant Ventricular Arrhythmia and Shock Therapy in Patients with Primary Defibrillator Implantation Does Not Differ from Event Rates in Patients Treated for Survived Cardiac Arrest
Authors: BACKENKÖHLER ULRICH , ERDOGAN ALI , STEEN‐MUELLER MARY‐KAY , KUHLMANN CHRISTOPH , MOST ASTRID , SCHAEFER CHRISTIAN , STERTMANN WILHELM , WAAS WOLFGANG , TILLMANNS HARALD , WALDECKER BERND
Published: May 2005

Introduction: Recent trials have demonstrated benefit of prophylactic defibrillator (ICD) implantation compared to conventional treatment in high‐risk patients. However, many patients have rare or no sustained arrhythmias following implantation. Our study addresses the question, whether patients with prophylactic defibrillator implantation have a lower risk for life‐threatening ventricular tachycardia (VT) or ventricular fibrillation (VF) compared to sudden cardiac death (SCD) survivors.

Methods and Results: Over 7 years we enrolled 245 patients. Occurrence of spontaneous sustained VT/VF resulting in adequate ICD treatment was the endpoint. Incidence, type, and treatment of sustained arrhythmia in 43 previously asymptomatic ICD recipients (group B) were compared to data of 202 survivors of imminent SCD (group A). All patients had severely impaired left ventricular ejection fraction (<45%). Group B patients had long runs (>6 cycles, <30 s) of VT during Holter monitoring and inducible sustained arrhythmia. Incidence of rapid VT and VF (cycle length <240 ms/heart rate >250 bpm) after 4 years (35% in both groups, P = ns) and adequate defibrillator therapies (57% vs 55%, P = ns) were similar in both groups after univariate and multivariate analysis. Cumulative mortality tended to be lower in group B compared to group A, but the difference was not statistically significant.

Conclusion: During long‐term follow‐up, incidence of sustained rapid ventricular arrhythmia in prophylactically treated patients is as high as that of SCD survivors. Benefit from defibrillator implantation for primary prevention (group B) appears to be comparable to that for survived cardiac arrest (group A).
An Unusual Accessory Pathway: Anteroseptal to Ventricular Outflow Region Connection
Authors: PETRELLIS BASILIOS , SKANES ALLAN C , KLEIN GEORGE J , GOLLOB MICHAEL H , KRAHN ANDREW D , YEE RAYMOND
Published: May 2005

Accessory pathways are typically located along the left or right atrioventricular junction. Distinct ventricular pre‐excitation patterns determined by surface electrocardiography can provide reasonable pathway localization prior to invasive mapping and catheter ablation. We report an accessory pathway producing an unusual electrocardiographic appearance suggestive of ventricular outflow region pre‐excitation. Pacing maneuvers and standard intracardiac recordings confirmed an atrial insertion immediately adjacent to the atrioventricular (AV) node and supported a ventricular insertion at the outflow tract region well away from the AV junction. The elimination of pathway conduction was achieved with radiofrequency (RF) energy at the atrial insertion after successful ice mapping excluded AV block at the target site. This is the second such pathway observed at our institution over a 20‐year period.
Cooled Needle Catheter Ablation Creates Deeper and Wider Lesions Than Irrigated Tip Catheter Ablation
Authors: THIAGALINGAM ARAVINDA , POULIOPOULOS JIM , ANTHONY (TONY) BARRY MICHAEL , BOYD ANITA C. , EIPPER VICKI , YUNG TERESA , ROSS DAVID L. , KOVOOR PRAMESH
Published: May 2005

Objectives: To design and test a catheter that could create deeper ablation lesions.

Background: Endocardial radiofrequency (RF) ablation is unable to reliably create transmural ventricular lesions. We designed an intramural needle ablation catheter with an internally cooled 1.1‐mm diameter straight needle that could be advanced up to 14 mm into the myocardium. The prototype catheter was compared with an irrigated tip ablation catheter.

Methods: Ablation lesions were created under general anesthesia in 14 male sheep (weight 44 ± 7.3 kg) with fluoroscopic guidance. Each of the catheters was used to create two ablation lesions at randomly allocated positions within the left ventricle. The irrigation rate, target temperature, and maximum power were: 20 mL/min, 85°C, 50 W for the intramural needle catheter and 20 mL/min, 50°C, 50 W for the irrigated tip catheter, respectively. All ablations were performed for 2 minutes. After the last ablation, blue tetrazolium (12.5 mg/kg) was infused intravenously. The heart was removed via a left thoracotomy after monitoring the sheep for one hour.

Results: There was no evidence of cardiac tamponade in any sheep. The intramural needle catheter lesions were significantly wider (10.9 ± 2.8 mm vs 10.1 ± 2.4 mm, P = 0.01), deeper (9.6 ± 2.0 mm vs 7.0 ± 1.3 mm, P = 0.01), and more likely to be transmural (38% vs 0%, P = 0.03).

Conclusions: Cooled intramural needle ablation creates lesions that are significantly deeper and wider than endocardial RF ablation using an irrigated tip catheter in sheep hearts. This technology may be useful in treating ventricular tachycardia resistant to conventional ablation techniques.
Sex Modulates the Arrhythmogenic Substrate in Prepubertal Rabbit Hearts with Long QT 2
Authors: LIU TONG , CHOI BUM‐RAK , DRICI MILOU‐DANIEL , SALAMA GUY
Published: May 2005

Females have a greater susceptibility to Torsade de Pointes in congenital and drug‐induced long QT syndrome (LQTS) that has been attributed to the modulation of ion channel expression by sex hormones. However, little is known regarding sex differences in pre‐puberty, that is, before the surge of sexual hormones. In patients with congenital LQTS types 1 and 2, male children tend to have a greater occurrence of adverse events, especially in 10–15 year olds, than their female counterpart. To evaluate whether the rabbit model of drug‐acquired LQTS exhibits similar age dependences, hearts of prepubertal rabbits were perfused, mapped optically to record action potentials (APs) and treated with an IKr blocker, E4031 to elicit LQTS2. As expected, AP durations (APD) were significantly longer in female (n = 18) than male hearts (n = 10), at long cycle length. Surprisingly, E4031 (50–250 nM) induced a greater prolongation of APDs in male than in female hearts, and in both genders reversed the direction of repolarization (apex → base to base → apex), enhancing dispersions of repolarization. Furthermore, in male hearts, E4031 (0.5 μM) elicited early afterdepolarizations (EADs) that progressed to polymorphic ventricular tachycardia (PVT) (n = 7/10) and were interrupted by isoproterenol (40 nM) and prevented by propranolol (0.5–2.5 μM). In female hearts, E4031 (0.5 μM) produced marked prolongations of APDs yet few EADs with no progression to PVT (n = 16/18). Thus, sex differences are opposite in prepubertal versus adult rabbits with respect to E4031‐induced APD prolongation, EADs and PVT, underscoring the fact that APD prolongation alone is insufficient to predict arrhythmia susceptibility.
Manipulating current-induced magnetization switching (invited)
Authors: Urazhdin S. , Kurt H. , AlHajDarwish M. , Birge Norman O. , Pratt W. P. , Bass J.
Published: May 2005

We summarize our recent findings on how current-driven magnetization switching and magnetoresistance in nanofabricated magnetic multilayers are affected by varying the spin-scattering properties of the nonmagnetic spacers, the relative orientations of the magnetic layers, and the spin-dependent scattering properties of the interfaces and the bulk of the magnetic layers. We show how our data are explained in terms of a current-dependent effective magnetic temperature.
Spin-dependent Peltier effect in Co∕Cu multilayer nanowires
Authors: Gravier Laurent , Serrano-Guisan Santiago , Ansermet J.-Ph.
Published: May 2005

Heat transport perpendicular to the plane of magnetic multilayers is monitored with ac temperature gradients in the presence of a direct charge current. A very strong dependence on the applied magnetic field of the voltage response to the ac gradient is observed using Co∕Cu multilayered nanowires. The effect is interpreted as a Peltier effect for a one-dimensional heat flux.
The structure, magnetism, and electrical-transport properties of the Heusler alloys Co2Cr1−xFexAl(x=0.2–0.6)
Authors: Zhang Ming , Wolf Anne L. , Zhang L. , Tegus O. , Brück Ekkes , Wu Guangheng , de Boer Frank R.
Published: May 2005

We synthesize the polycrystalline Heusler compounds Co2Cr1−xFexAl(x=0.2−0.6). The x-ray diffraction patterns show A2 structure rather than L21 structure. The magnetic moment and the Curie temperature increase with increasing x. The electrical resistivity characterizes the Co2Cr1−xFexAl compounds to be not typical metals and the temperature dependence of the resistivity changes from metallic to semiconductinglike behavior with increasing Cr concentrations. We attribute the fact, which we observe for most of the compounds smaller magnetic moments than the theoretical values and the low magnetoresistance in these alloys, to the considerably high level of Co-(Cr, Fe)-type disorder.
Magnetotransport in NiMnGa thin films
Authors: Vovk Andriy , Malkinski Leszek , Golub Vladimir , O’Connor Charles , Wang Zhenjun , Tang Jinke
Published: May 2005

The influence of substrate temperature and annealing conditions on structure, magnetic, and magnetotransport properties of NiMnGa films was investigated, and the crucial effect of substrate temperature was confirmed. It was found that amorphous disordered films are formed during deposition on a substrate held at room temperature. Postdeposition annealing leads to partial recrystallization and recovery of magnetic properties. Annealing at 773 K does not allow the formation of crystal structure, which is created during deposition on substrates held at the same temperature. The highest values of magnetoresistance were observed in the films with a well-defined crystal structure.
Magnetoresistance of polycrystalline Fe3O4 films prepared by reactive sputtering at room temperature
Authors: Park Chando , Peng Yingguo , Zhu Jian-Gang , Laughlin David E. , White Robert M.
Published: May 2005

The magnetic, structural, and transport properties of single-layer magnetite (Fe3O4) films prepared by reactive sputtering were investigated. Magnetoresistance (MR) was measured at various thicknesses and temperatures. The increase in MR with thickness is related to grain crystallinity and size, as confirmed by transmission electron microscopy. MR arises from intergranular tunneling, which is supported by the temperature dependence of resistivity (logρ∼T−1∕2). Field-dependent MR correlates with the M curve. Magnetoresistance versus magnetization curves clearly show that the MR effects come from the surface spin arrangement near the grain boundaries. The dependence of MR on the magnetic field observed in polycrystalline Fe3O4 films can be attributed to a surface magnetization near the grain boundary, which will be discussed.
Application of magnetostriction measurements for the computation of deformation in electrical steel
Authors: Hilgert Tom , Vandevelde Lieven , Melkebeek Jan
Published: May 2005

In this paper, a method is presented to calculate the deformation of electrical steel due to magnetic forces and magnetostriction by using the finite element method. The magnetostrictive properties of the steel are determined experimentally in a small single-sheet tester with strain gauges fitted on the sheet. This method is applied to an inductor with a small airgap. The results from the computations are verified with measurements on the test object.
Magnetic properties of V-doped ZnO thin films
Authors: Hong Nguyen Hoa , Sakai Joe , Hassini Awatef
Published: May 2005

Ferromagnetic V-doped ZnO films were fabricated by the conventional pulsed-laser deposition technique on R-cut sapphire substrates from a ceramic target that was made by sol-gel method. All films are highly crystallized to be wurtzite. V-doped ZnO thin films grown at 600–650°C show room-temperature ferromagnetism along with a spin-glass-like behavior at low temperatures. It is found that V atoms were distributed very uniformly in the ZnO matrix. However, different growth conditions could result in different values of the saturation magnetic moment, and an increase of the substrate temperature above 650°C seems to favor a secondary phase, which is antiferromagnetic.
Generalized reversible susceptibility tensor
Authors: Dumitru I. , Stancu A. , Cimpoesu D. , Spinu L.
Published: May 2005

A theory of reversible susceptibility tensor based on magnetization vector dynamics, as described by the Landau–Lifshitz equation of motion, is given. It is shown that the reversible transverse susceptibility (RTS) is in fact the zero frequency limit of the ferromagnetic resonance (FMR). Thus, the methods which have been developed previously for the theoretical description of FMR may be applied to predict the RTS behavior. The importance of these results resides in the generality of the approach which allows one to find the reversible susceptibility tensor for virtually any magnetic system if an expression for the magnetic free energy density is known.
High-temperature ferromagnetism in dilute magnetic oxides
Authors: Coey J. M. D.
Published: May 2005

High temperature ferromagnetism in thin films of dilute magnetic oxides is a widespread phenomenon, of which there appear to be two sources. One is the contribution of the 3d dopant ions themselves, the other is related to crystal defects in the interface region. The latter contributes a magnetic moment of 100–400μB per square nanometer of substrate area, which is largely independent of film thickness or dopant concentration. It is suggested that the defects are two-electron or two-hole centers which have a spin triplet as ground state or low-lying excited state. HfO2, an example of the former, is ferromagnetic even when undoped. In ZnO or SnO2, examples of the latter, the magnetic dopant may stabilize the spin triplet by exchange.
Manipulating a domain wall in (Ga,Mn)As
Authors: Holleitner A. W. , Knotz H. , Myers R. C. , Gossard A. C. , Awschalom D. D.
Published: May 2005

By using a focused beam of gallium ions, we define magnetization pinning lines in a ferromagnetic epilayer of (Ga,Mn)As. We are able to resolve the arrival of a domain wall at a pinning line through transport spectroscopy. This technique enables us to manipulate a pinned domain wall via the influence of an external magnetic field. Temperature dependent measurements elucidate the disappearance of these effects above the (Ga,Mn)As Curie temperature.
The effects of biaxial strain on stability and half-metallicity of zinc blende CrSb
Authors: Miao M. S. , Lambrecht Walter R. L.
Published: May 2005

Biaxial (tetragonal) strain effects on metastable zinc blende CrSb are investigated using full-potential linearized muffin-tin orbital calculations in order to simulate the in-plane matching to a [001] oriented substrate. The relaxed equilibrium volume is found to stay close to the equilibrium volume of zinc blende. Compared to an isotropic expansion of the volume, this distortion greatly reduces the energy cost. The effects of the strains on the spin-flip gap, the minority band gap, and partial density of states are investigated.
Magnetic interactions in Zn1−xMnxO studied by electron paramagnetic resonance spectroscopy
Authors: Chikoidze E. , von Bardeleben H. J. , Dumont Y. , Galtier P. , Cantin J. L.
Published: May 2005

Zn 1 − x Mn x O layers with x varying between 0.006 and 0.22, have been prepared by metal-organic chemical-vapor deposition technique and analyzed by electron paramagnetic resonance spectroscopy. The layers show an exchange narrowed single line spectrum of Mn2+ ions; its temperature dependence demonstrates antiferromagnetic coupling with an effective exchange constant of J1∕kB=−14.9K.
Low resistance spin-valve-type current-perpendicular-to-plane giant magnetoresistance with Co75Fe25
Authors: Aoshima Ken-ichi , Funabashi Nobuhiko , Machida Kenji , Miyamoto Yasuyoshi , Kuga Kiyoshi
Published: May 2005

Spin-valve-type current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) read sensors containing Co75Fe25 have been investigated. This type of sensor exhibits a MR ratio of 2.88%, which is a factor of 1.5 times larger than that of the conventional CPP-GMR sensor containing Co90Fe10 (1.98%). Three types of Co75Fe25-CPP-GMR structures were fabricated, with the following sequence of increasing etching depths: through the capping layer only (type A), through the CoFe∕Cu∕CoFe trilayer (type B) and through the IrMn antiferromagnetic layer (type C). The MR ratio increases with the etching depth, and a MR ratio of 3.31% was achieved for the type C sample, which is one of the largest reported MR ratios for low-resistance area product-CPP-GMR sensors.
Micromagnetic calculation of the magnetization process in nanocontacts
Authors: Komine Takashi , Takahashi Tomohiro , Sugita Ryuji , Muranoi Tetsuo , Hasegawa Yasuhiro
Published: May 2005

We report herein the micromagnetic calculations of the magnetic domain walls in nanoconstrictions of various shapes for H-shaped samples and estimate the domain wall widths. The length and width of the nanoconstriction and the exchange stiffness constant in the nanoconstriction was varied for each case. In the case of a uniform exchange stiffness constant at the nanoconstriction, the domain wall width depends on the length and width of the nanoconstriction. Each domain wall width D calculated herein is longer than the constriction length L, and the exchange stiffness constant is 1.05×10−6erg∕cm. The small exchange stiffness at the nanoconstriction leads to the small domain wall width. These results imply the possibility of the large domain wall scattering only for nanoconstrictions with a small effective exchange coupling between the two magnetic materials.
The governing electrodynamic equations of electromagnetic acoustic transducers
Authors: Jafari-Shapoorabadi R. , Konrad A. , Sinclair A. N.
Published: May 2005

This paper presents the governing electrodynamic equations of electromagnetic acoustic transducers (EMATs) and extends them to the derivation of the magnetic- and acoustic-field equations in terms of the magnetic vector potential (MVP) and the acoustic wave particle displacement vector (PDV), respectively. It also provides formulations for calculating forces and current densities in the case of two-dimensional (2D) models of EMAT configurations in Cartesian coordinates. Existing methods solve the governing electrodynamic equations for field quantities to analyze EMATs. However, they ignore skin and proximity effects and rely on simple 2D configurations for EMAT coils. Taking into account skin and proximity effects in complex 2D EMAT coil configurations requires the application of the finite element method (FEM). The FEM can be applied to solve the equations stated in terms of the MVP and PDV in the modeling of EMATs. These formulations and expressions facilitate the development and presentation of the FEM for the modeling and analysis of EMATs.