bluuebunny/crossref_metadata_2025 huggingface dataset:
Hautausschlag und Flankenschmerzen bei einer jungen Frau
Authors: Miedinger
Published: April 2006

Wir berichten über eine junge Patientin mit den Leitsymptomen Arthralgien, Exanthem und Flankenschmerzen. Neben infektiösen Erkrankungen sollte bei der Kombination von Exanthem und Arthralgien unter anderem auch an Kollagenosen oder medikamenteninduzierte Nebenwirkungen gedacht werden. Flankenschmerzen lassen vor allem an Erkrankungen der Niere, der ableitenden Harnwege und der Wirbelsäule denken. Bei der Patientin konnte mittels Sonographie und MRT-Untersuchung des Abdomens eine symptomatische pyelourethrale Abgangsstenose mit Dilatation des Nierenbeckens sowie mittels serologischer Untersuchung eine akute Parvovirus B19-Infektion diagnostiziert werden. Nach Einlage eines Doppel-J-Katheters wurde die Patientin zur elektiven retroperitoneoskopischen Korrektur der pyelourethralen Abgangsstenose aufgeboten.
Boundary flow on a lake slope during Ekman layer arrest
Authors: Pálmarsson Sveinn Ó. , Schladow S. Geoffrey
Published: April 2006

The disruption of an arrested bottom Ekman layer on a lake boundary slope is initiated when buoyancy enters the balance between the Coriolis force and the pressure gradient. This process is shown to behave in a lake in a qualitatively similar manner to the ocean. A greater bottom slope and stronger stratification are found to dramatically shorten the shutdown timescale of the Ekman flux compared to typical values on the continental shelf and slope. Convergence of the flow at the density front, where the thermocline intersects the bottom, leads to a detrainment of bottom boundary layer water into the interior of the lake and thus facilitates the transport of mass and heat independent of turbulence generation in the boundary layer by internal wave interactions. Internal waves complicate the flow structure. The boundary water detrainment and gravitational instability due to Ekman layer dynamics and the critical reflection and vertical overturns associated with the internal waves combine in effective boundary mixing.
Aerosol iron and aluminum solubility in the northwest Pacific Ocean: Results from the 2002 IOC cruise
Authors: Buck Clifton S. , Landing William M. , Resing Joseph A. , Lebon Geoffrey T.
Published: April 2006

Dust aerosol samples were collected across the western North Pacific Ocean during May–June 2002. Samples were analyzed for soluble aerosol Fe(II), Fe(II) + Fe(III), and Al as well as major cations and anions. The aerosol samples were leached using a 10 second exposure to either filtered surface seawater or ultrapure deionized water yielding a measure of the “instantaneous” soluble fraction. A variety of analytical methods were employed, including 57Fe isotope dilution high‐resolution ICP‐MS, energy dispersive X‐ray fluorescence, graphite furnace AAS, ion chromatography, and the FeLume chemiluminescent technique. Fe was found to be more soluble in ultrapure deionized water leaches, especially during periods of higher dust concentrations. Fe solubility averaged 9 ± 8% in ultrapure water leaches and 6 ± 5% in seawater leaches. Significant correlations were found between both soluble aerosol FeT and soluble Fe(II) concentrations and aerosol acidity; however, the percentages of soluble aerosol FeT and Fe(II) did not correlate with aerosol acidity We also did not observe significant correlations between total and soluble aerosol Fe concentrations and the concentrations of either particulate Fe or dissolved Fe in surface waters.
Comparison of foraminiferal cleaning procedures for Mg/Ca paleothermometry on core material deposited under varying terrigenous‐input and bottom water conditions
Authors: Weldeab Syee , Schneider Ralph R. , Kölling Martin
Published: April 2006

A down‐core comparison of two commonly applied foraminiferal cleaning procedures for Mg/Ca paleothermometry has been conducted using well‐preserved Globigerinoides ruber white (250–300 μm) from core material deposited under varying terrigenous‐input and bottom water conditions. This study demonstrates that in the majority of investigated core materials, both cleaning methods yield fairly comparable results of Mg/Ca ratios. However, Fe and Mn phases are effectively removed by the cleaning procedure containing a reductive step. In a core interval indicating gradual transition of terrigenous deposition and pore water conditions, the cleaning procedure without a reductive step results in anomalously higher Mg/Ca ratios accompanied by high Fe/Ca and Mn/Ca ratios, indicating the presence of high‐Mg contaminants. Considering that the Mg/Ca deviation of the comparison study is the cumulative sum of (1) the difference in cleaning efficiency of the applied methods, (2) the cleaning‐method‐dependent partial dissolution of Mg, and (3) the heterogeneity of subsamples, we suggest that selective Mg loss from well‐preserved Globigerinoides ruber shells caused by the reductive sample treatment is not substantial enough to significantly bias paleotemperature estimation. Thus, for core material deposited under varying sources and amounts of terrigenous material and bottom water conditions favorable for formation of authigenic mineral phases, the use of cleaning methods that do include a reductive step yields more effective cleaning results by successful removal of mineral phases that may contain high Mg.
Modeling open system metamorphic decarbonation of subducting slabs
Authors: Gorman P. J. , Kerrick D. M. , Connolly J. A. D.
Published: April 2006

Fluids derived from the devolatilization of subducting slabs play a critical role in the melting of the mantle wedge and global geochemical cycles. However, in spite of evidence for the existence and mobility of an aqueous fluid phase during subduction metamorphism, the effect of this fluid on decarbonation reactions in subducting lithologies remains largely unquantified. In this study we present results from thermodynamic modeling of metamorphic devolatilization of subducted lithologies for pressures up to 6 GPa using an approach which considers fluid fractionation from source lithologies and infiltration from subjacent lithologies. This open system approach in which fluid flow is an intrinsic component of the chemical model offers an alternative to closed system models of subduction zone decarbonation. In general, our models simulating pervasive fluid flow in subducting lithologies predict CO2 fluxes measured from volcanic arcs more closely than models which assume purely channelized flow. Despite the enhanced effect of H2O‐rich fluid infiltration on subduction decarbonation, our results support the hypothesis that CO2 is returned to the deep mantle at convergent margins, particularly in cool and intermediate subduction zones. Our results demonstrate that for most subduction zones, a significant proportion of the CO2 derived from the slab is lost beneath the fore arc, and therefore CO2 flux estimates based on measurements within the volcanic arc alone may significantly underestimate the slab‐derived CO2 flux for individual margins. Nevertheless, our predicted global slab‐derived CO2 flux from convergent margins of 0.35–3.12 × 1012 mols CO2/yr is in good agreement with previous estimates of global arc volcanic flux. Because our predicted global slab‐derived CO2 flux is significantly less than atmospheric CO2 drawdown by chemical weathering, significant CO2 emission from other geologic regimes (e.g., hot spots) would be required to balance the global carbon cycle.
High‐temperature mixtures of magmatic and atmospheric gases
Authors: Martin R. S. , Mather T. A. , Pyle D. M.
Published: April 2006

Recent measurements of BrO, NOx, and near‐source sulfate in volcanic plumes suggest that volcanic vents might not simply act as point sources of emissions into the troposphere, but may also act as high‐temperature reaction sites where mixtures of magmatic and ambient atmospheric gases may combine, giving new and previously unexpected reaction products. The detection of such species demands that a more complex model be developed for the interaction of volcanoes and atmospheres. We show that general thermodynamic models can be applied successfully to volcanic gas equilibria by comparing the results from HSC Chemistry with those from two volcanic gas equilibrium models (Solvgas and Gasmix). Using a thermodynamic model optimized for volcanic gas chemistry (C‐O‐S‐H‐F‐Cl‐Br‐I‐N‐Ar speciation), we show that the volume ratio of atmospheric gas to magmatic gas in a high‐temperature mixture is an important parameter of the volcanic plume chemistry, and our results suggest that even small amounts of air (a few % for an H2O‐rich magmatic gas) in the high‐temperature mixture are sufficient to yield elevated levels of reactive nitrogen, halogen (Cl, Br, and I), and sulfur species within the volcanic plume. Further modifications of the plume chemistry may also occur due to low‐temperature reactions, and chemical schemes for the modification of halogen (Cl, Br, I), nitrogen, and sulfur chemistry are suggested, within the constraints imposed by recent measurements.
Lightning‐rainfall relationships in Mediterranean winter thunderstorms
Authors: Price Colin , Federmesser Bela
Published: April 2006

Space‐based instruments on the Tropical Rain Measuring Mission (TRMM) have been used to study rainfall and lightning over the central and eastern Mediterranean Sea. Data from six winters (1998 until 2003) were analyzed. Rainfall amounts increase during the winter months, with the maximum precipitation occurring during December, while lightning activity has a maximum during November. Analysis of seasonal rainfall and lightning activity showed a strong correlation with ENSO events. Instantaneous (90 second) analysis of the rain and lightning in individual storms reveals a strong correlation between rain rate and total flash rate. Monthly and seasonal correlation coefficients between rainfall and lightning were found to vary between 0.81 and 0.98, with the rainfall yield (kg/flash) found to vary between 2.5 × 108 and 9.7 × 108 kg/flash. Due to these high correlations we suggest the possibility to use lightning data over the Mediterranean Sea as a proxy for instantaneous rain rate in thunderstorms.
A new probe of ULVZ S‐wave velocity structure: Array stacking of ScS waveforms
Authors: Avants Megan , Lay Thorne , Garnero Edward J.
Published: April 2006

S‐wave velocity reductions in thin layers above the core‐mantle boundary (CMB) are resolved by modeling precursors to the tangential‐components of core‐reflected ScS phases. Unlike most phases used to study ultra‐low velocity zone (ULVZ) structure, ScS provides direct sensitivity to shear velocity structure, VS. Recordings of deep earthquakes in the Tonga‐Fiji and South American subduction zones at broadband seismic networks in western North America are used to map small‐scale ULVZ variability. A two‐layer low‐VS structure exists under the central Pacific: an abrupt 0.8–2.0% decrease 60–86 km above the CMB is underlain by a 24–30 km thick ULVZ layer having reductions of 3.3–7.4% (with respect to PREM). No corresponding velocity reductions are found under the Cocos plate. The structure above the ULVZ may be associated with reverse transformation of post‐perovskite to perovskite in a steep thermal gradient in a boundary layer above the CMB.
Bottom scour observed under Hurricane Ivan
Authors: Teague William J. , Jarosz Ewa , Keen Timothy R. , Wang David W. , Hulbert Mark S.
Published: April 2006

Observations that extensive bottom scour along the outer continental shelf under Hurricane Ivan resulted in the displacement of more than 100 million cubic meters of sediment from a 35 × 15 km region directly under the storm's path are presented. Sediment resuspension was accomplished by the extreme waves generated by Ivan and transported by strong near‐bottom wind‐driven currents. The sediment transport was primarily westward along the shelf, but also contained a significant offshore component, suggesting sediment was transported toward the Mississippi Delta and that it may have accumulated near the shelf break and on the upper continental slope. The maximum observed scour of about 32 and 36 cm took place at two locations approximately 17 km apart along the 60 m isobath over which the maximum wind stress occurred.
Evidence for an infrasound waveguide
Authors: Herrin Eugene T. , Kim Tae Sung , Stump Brian W.
Published: April 2006

On May 30, 2005 eight strongly dispersed infrasound signals were recorded at one seismo‐acoustic array in the Republic of Korea. Phase‐matched filtering and a forward modeling technique were used to determine the nature of the dispersion. The most likely explanation for these dispersed infrasound signals are that the dispersion is due to propagation down a low‐velocity waveguide. This can be characterized as an ephemeral “SOFAR” layer in the atmosphere.
Theory of energetic particle transport in the magnetosphere: A noncanonical approach
Authors: Zhang Ming
Published: April 2006

This paper presents a new transport theory suitable for the study of energetic particles in the magnetospheric environment. A Fokker‐Planck diffusion equation governing the variation of the particle distribution function, along with its isotropic and bounce average approximations, is established in the phase space of location and momentum, which is similar to how cosmic rays are treated by the heliospheric community. The equation includes essentially all the particle transport mechanisms: streaming, convection, drift, adiabatic energy change, acceleration by parallel electric field, focusing, and diffusions in location, momentum, and pitch angle. All the coefficients of the equation are directly linked to plasma and magnetic configurations including electromagnetic fluctuations. The theory can form a base for developing full‐scale numerical models of energetic particle transport including acceleration in the magnetosphere. Unlike the conventional theory using canonical variables which is only applicable to the radiation belt of the inner magnetosphere, this theory includes the effects of nonuniform magnetospheric convection and thus is valid for the entire magnetosphere. The derivation of the transport equation has identified some important particle transport mechanisms that have not received careful study by the magnetospheric community. It is found that the compression of magnetospheric plasma can play a significant role in particle acceleration and trapping. The compressional acceleration is the first‐order particle acceleration mechanism, very similar to particle acceleration at shock waves in other space plasma environments. This acceleration mechanism is operable to both electrons and ions. A model map of magnetospheric convection flow shows that the compressional particle acceleration is a large‐scale phenomenon and it is the strongest in the near‐Earth nightside plasma sheet. Magnetospheric compression can also drive particles toward the 90° equatorial pitch angle, which is ideal for trapping them in the geomagnetic field.
Rupture characteristics of the 2003 Mw 7.6 mid‐Indian Ocean earthquake: Implications for seismic properties of young oceanic lithosphere
Authors: Antolik Michael , Abercrombie Rachel E. , Pan Jianfeng , Ekström Göran
Published: April 2006

Analysis of broadband seismograms from the 15 July 2003 large earthquake (M 7.6) in the central Indian Ocean reveals an unusual source process. The source duration of longer than a minute is more than twice as long as expected from earthquake scaling relations, yet ∼80% of the moment release occurred in two energetic asperities near the end of the rupture. These two asperities were located in lithosphere with an age of 7 Ma or greater. A previous study has suggested that strike‐slip earthquakes in oceanic lithosphere having much longer than expected source durations also have a slow, dissipative rupture process characterized by low radiated seismic energy (and therefore low apparent stress). We find no evidence for a slow rupture process to the 2003 earthquake. Instead, the long duration appears to be due only to nucleation close to the actively spreading Carlsberg Ridge, in lithosphere younger than 7 Ma. Younger oceanic lithosphere may be able to generate small to moderate earthquakes but be unable to sustain slip in a large event due to steady release of strain in aseismic creep events. Large strike‐slip earthquakes within oceanic lithosphere may occur only in the central portions of long transform faults or in intraplate regions, rupturing energetic asperities like those that failed in the mid‐Indian Ocean earthquake and leading to the observation that oceanic strike‐slip earthquakes have the largest apparent stresses among the global population of shallow earthquakes.
VP and VS structure of the Yellowstone hot spot from teleseismic tomography: Evidence for an upper mantle plume
Authors: Waite Gregory P. , Smith Robert B. , Allen Richard M.
Published: April 2006

The movement of the lithosphere over a stationary mantle magmatic source, often thought to be a mantle plume, explains key features of the 16 Ma Yellowstone–Snake River Plain volcanic system. However, the seismic signature of a Yellowstone plume has remained elusive because of the lack of adequate data. We employ new teleseismic P and S wave traveltime data to develop tomographic images of the Yellowstone hot spot upper mantle. The teleseismic data were recorded with two temporary seismograph arrays deployed in a 500 km by 600 km area centered on Yellowstone. Additional data from nearby regional seismic networks were incorporated into the data set. The VP and VS models reveal a strong low‐velocity anomaly from ∼50 to 200 km directly beneath the Yellowstone caldera and eastern Snake River Plain, as has been imaged in previous studies. Peak anomalies are −2.3% for VP and −5.5% for VS. A weaker, anomaly with a velocity perturbation of up to −1.0% VP and −2.5% VS continues to at least 400 km depth. This anomaly dips 30° from vertical, west‐northwest to a location beneath the northern Rocky Mountains. We interpret the low‐velocity body as a plume of upwelling hot, and possibly wet rock, from the mantle transition zone that promotes small‐scale convection in the upper ∼200 km of the mantle and long‐lived volcanism. A high‐velocity anomaly, 1.2% VP and 1.9% VS, is located at ∼100 to 250 km depth southeast of Yellowstone and may represent a downwelling of colder, denser mantle material.
Dynamic fracture of granular material under quasi‐static loading
Authors: Sagy Amir , Cohen Gil , Reches Ze'ev , Fineberg Jay
Published: April 2006

The dynamics of rapid fracturing of heterogeneous grainy media are studied in laboratory experiments in which artificial rock slabs are fractured under uniaxial tension. By performing detailed measurements of the instantaneous fracture velocity and the fracture surface topography, we quantitatively relate fracture morphology with the dynamics of the surface formation. We show that fracture dynamics in these materials is strongly influenced by the interaction of the fracture front with material heterogeneities and by the formation of microbranches. The instantaneous fracture velocity is characterized by abrupt fluctuations, whose amplitudes increase with the average velocity and which are correlated with the surface roughness. The surfaces of the fractures display aligned grooves and ridges, which extend large distances in the propagation direction and are localized in the transverse direction. These features, interpreted as lines of aligned microbranches, are observed solely when the fracture velocity is above 0.3 of the Rayleigh wave speed. In addition, small‐scale striations corresponding to fracture front waves are identified. The overall similarity between fracture dynamics in these heterogeneous materials and those in ideal amorphous materials suggests that universal processes control the dynamics. The heterogeneity of the grainy medium, however, strongly amplifies the velocity fluctuations and enhances both the deflection and segmentation of fracture fronts.
Dislocation pileup as a representation of strain accumulation on a strike‐slip fault
Authors: Savage J. C.
Published: April 2006

The conventional model of strain accumulation on a vertical transform fault is a discrete screw dislocation in an elastic half‐space with the Burgers vector of the dislocation increasing at the rate of relative plate motion. It would be more realistic to replace that discrete dislocation by a dislocation distribution, presumably a pileup in which the individual dislocations are in equilibrium. The length of the pileup depends upon the applied stress and the amount of slip that has occurred at depth. I argue here that the dislocation pileup (the transition on the fault from no slip to slip at the full plate rate) occupies a substantial portion of the lithosphere thickness. A discrete dislocation at an adjustable depth can reproduce the surface deformation profile predicted by a pileup so closely that it will be difficult to distinguish between the two models. The locking depth (dislocation depth) of that discrete dislocation approximation is substantially (∼30%) larger than that (depth to top of the pileup) in the pileup model. Thus, in inverting surface deformation data using the discrete dislocation model, the locking depth in the model should not be interpreted as the true locking depth. Although dislocation pileup models should provide a good explanation of the surface deformation near the fault trace, that explanation may not be adequate at greater distances from the fault trace because approximating the expected horizontally distributed deformation at subcrustal depths by uniform slip concentrated on the fault is not justified.
Application of normalized biomass size spectra to laser optical plankton counter net intercomparisons of zooplankton distributions
Authors: Herman A. W. , Harvey M.
Published: April 2006

The optical plankton counter (OPC) and recently the laser OPC (LOPC) have been used primarily in two measurement applications: (1) identification of specific zooplankton species and (2) changes in zooplankton community structure using size‐based spectral measurements. The normalized biomass size spectra (NBSS) are one representation of the size‐based approach. The present study is based on utilizing the NBSS to describe the conditions or characteristics of the zooplankton community that allow a reasonable intercomparison of net samples and LOPC measurements made simultaneously for data collected during two oceanographic cruises carried out in the Lower Estuary and the Gulf of St. Lawrence in spring 2001 and 2002, respectively. NBSS linear slopes <−0.7 indicate the presence of additional plankton material such as diatom aggregates and gelatinous material (present during or immediately following blooms) that are less present in nets and are not intercomparable with LOPC measurements. Conversely, slopes >−0.7, or more “blue water” conditions, indicate the potential for reasonable intercomparison of the two methods. This observation applies to smaller‐sized zooplankton such as copepodites of Calanus spp. with equivalent spherical diameter <900 μm. The measurement of larger Calanus spp. stages (IV–VI) did not seem affected by the presence of additional aggregates or gelatinous material and reasonable intercomparisons between LOPC and net were obtained for both sampling years. The LOPC signals produced by Calanus spp. (IV–VI) were larger and more easily separated.
Does the Taiwan Warm Current originate in the Taiwan Strait in wintertime?
Authors: Chen Chen‐Tung Arthur , Sheu David D.
Published: April 2006

There is no doubt that the Taiwan Warm Current (TWC) flows through the Taiwan Strait in summer and it reaches the East China Sea (ECS) proper, bringing with it a great deal of nutrients. Here satellite temperature, as well as hydrological, satellite‐tracked drifter, and 18O data, are used to show that in winter, warm waters from the South China Sea and a branch of the Kuroshio south of Taiwan reach only the southern part of the Taiwan Strait and that in no way do they flow up freely through the northern part of the Taiwan Strait. This is a clear sign that in winter most of the TWC must originate in the Kuroshio, which moves onto the ECS shelf northeast of Taiwan.
Sea surface temperatures of southern midlatitudes 0–160 kyr B.P.
Authors: Pahnke Katharina , Sachs Julian P.
Published: April 2006

Late Quaternary climate fluctuated between extremes of glaciations, lasting ∼90 kyr on average, and interglacial episodes, lasting ∼10 kyr. Still largely unknown are the spatial and temporal evolution of these global climate states, with vigorous debate still underway on the mechanisms responsible for glacial inceptions and terminations. Though it is widely believed that the Southern Hemisphere oceans play a central role in global climate changes, few paleoclimate records exist from there. Here we present three new alkenone‐derived SST records from the midlatitude Southern Hemisphere spanning the last 160 kyr, a full glacial‐interglacial cycle. Our subtropical SST records from the last glacial period are characterized by (1) warming 47–23 kyr B.P., when high latitudes in both hemispheres cooled, and (2) milder temperatures during the penultimate glacial period than during the last glacial interval. These SST features are found to be of tropical‐ to subtropical‐wide extent, implying increased thermal gradients at times of high‐latitude ice sheet growth. This has implications for the vigor of atmospheric and upper ocean circulation and the transport of heat and moisture to the poles that may have been instrumental in the growth and maintenance of polar ice sheets during glacial periods.
Aspects of data assimilation peculiar to space weather forecasting
Authors: Siscoe George , Solomon Stanley C.
Published: April 2006

Data assimilation in space weather forecasting is necessary but differs in important respects from terrestrial weather forecasting. These differences arise in part from the relative sparsity of data in space weather and from relatively direct driving of space weather phenomena. They present opportunities for space weather forecasting to add new data assimilation techniques to those developed in terrestrial weather forecasting.
A new parameterization of the effective temperature for L band radiometry
Authors: Holmes T. R. H. , de Rosnay P. , de Jeu R. , Wigneron R. J.‐P. , Kerr Y. , Calvet J.‐C. , Escorihuela M. J. , Saleh K. , Lemaître F.
Published: April 2006

An accurate value of the effective temperature is critical for soil emissivity retrieval, and hence soil moisture content retrieval, from passive microwave observations. Computation of the effective temperature needs fine profile measurements of soil temperature and soil moisture. The availability of a two year long data set of these surface variables from SMOSREX (Surface Monitoring Of the Soil Reservoir EXperiment) makes it possible to study the effective temperature at the seasonal to interannual scale. This study shows that present parameterizations do not adequately describe the seasonal variations in sensing depth. Therefore, a new parameterization is proposed that is stable at the seasonal to interannual scales while retaining simplicity.
Scavenging of pollutant acid substances by Asian mineral dust particles
Authors: Matsumoto Jun , Takahashi Kenshi , Matsumi Yutaka , Yabushita Akihiro , Shimizu Atsushi , Matsui Ichiro , Sugimoto Nobuo
Published: April 2006

Uptakes of sulfate and nitrate onto Asian dust particles during transport from the Asian continent to the Pacific Ocean were analyzed by using a single‐particle time‐of‐flight mass spectrometer. Observation was conducted at Tsukuba in Japan in the springtime of 2004. Sulfate‐rich dust particles made their largest contribution during the ‘dust event’ in the middle of April 2004. As a result of detailed analysis including backward trajectory calculations, it was confirmed that sulfate components originating from coal combustion in the continent were internally mixed with dust particles. Even in the downstream of the outflow far from the continental coastline, significant contribution of Asian dust to sulfate was observed. Asian dust plays critical roles as the carrier of sulfate over the Pacific Ocean.
Mapping attenuation beneath North America using waveform cross‐correlation and cluster analysis
Authors: Lawrence Jesse F. , Shearer Peter M. , Masters Guy
Published: April 2006

We measure seismic attenuation beneath North America using waveform cross‐correlation and cluster analysis, and obtain images of the laterally varying anelastic structure of the upper mantle. Cluster analysis improves attenuation measurements by systematically comparing only highly similar waveforms, which reduces bias from scattering, directional differences in source functions, and source‐side structure. While lacking station coverage in many areas, the P‐ and S‐wave results are correlated (R2 ≥ 0.5) in both travel time and attenuation. Much weaker correlations are observed between travel‐time and attenuation measurements. Similarities and differences between attenuation and travel times may be used to infer the source of the observed anomalies. The observed anelastic structure has a long‐wavelength pattern crudely similar to that of seismic velocity, which likely indicates higher temperatures beneath western North America than in the east. Shorter‐wavelength structure suggests complex variations requiring alternate explanations such as variable water content.
Dynamic response to mountain breeze circulation in Alchichica, a crater lake in Mexico
Authors: Filonov Anatoliy , Tereshchenko Iryna , Alcocer Javier
Published: April 2006

In this paper we discuss the dynamic response to mountain breeze circulation in Alchichica, a deep crater lake in Mexico. A numerical model was used to simulate integrated drift currents based on wind data sampled at 1‐h intervals. The results are compared with those measured by an ADCP. Measurements taken with a level recorder demonstrate that the mountain breeze is coordinated with diurnal level inclinations up to 11 cm and that it simulates free seiches with a period of 2.7 and 2.1 min with amplitudes equal to 7 mm and 4 mm. Measurements carried out with a SBE‐19 profiler show that in the second half of day the breeze blowing from the north causes a sinking of the thermocline by 3 meters in the southern part of the lake. It appears that periodic inclinations of the thermocline serve as the main mechanism in the generation of internal waves in Lake Alchichica.
Cloud types associated with the Asian summer monsoons as determined from MODIS/TERRA measurements and a comparison with surface observations
Authors: Tang Xu , Chen Baode
Published: April 2006

Using a 6‐year June‐July‐August MODIS/Terra‐measured cloud properties data set, the characteristics of clouds associated with the Asian summer monsoons are examined. The results indicate that a large amount of high clouds exists in the Indian monsoon region and account for approximately 65% of all cloud grids. Moreover, the interannual variation of high clouds is not apparent. In the East Asian monsoon region, high clouds show a relatively strong interannual variation and account for roughly 38.5% of all cloud grids. The overall percentages of middle and low clouds are comparable to each other within the East Asian monsoon region. Moreover three high cloud types have been identified to coexist in the Indian monsoon regions, i.e., cirrus, cirrostratus and deep convective clouds. Among them, cirrostratus has the largest percentage. In the East Asian monsoon region, the most frequently occurring cloud type is stratocumulus. However, compared with cloud climatology of surface observations, middle and low clouds are severely underestimated in the Asian monsoon regions by the MODIS/Terra measurements; in particular, the underestimation for low clouds is up to 80% in the Indian monsoon region. Therefore, great caution is needed when using the MODIS data to analyze middle and low clouds, especially when high and thick clouds exist.
Cation electric field is related to hydration energy
Authors: Chipman Daniel M. , Chen Feiwu
Published: April 2006

Electronic structure calculations on ions that use dielectric continuum theory to mimic solvent around the bare ionic solutes are often prone to make large errors in the hydration energies. It is found for cations that much of the error can be accounted for by a simple linear correlation with the maximum value found anywhere on the dielectric cavity surface of the solute potential or, even better, the outgoing normal electric field, thus mirroring analogous results previously obtained for anions. This correlation allows for significantly improved estimates of cation hydration energies while still retaining cavities of physically reasonable size in determination of the bulk dielectric contributions.
Digital feedback controller for force microscope cantilevers
Authors: Degen C. L. , Meier U. , Lin Q. , Hunkeler A. , Meier B. H.
Published: April 2006

We present a fast, digital signal processor (DSP)-based feedback controller that allows active motion damping of low-k, high-Q cantilevers in magnetic resonance force microscopy. A setup using a piezoelement attached to the cantilever base for actuation and a beam deflection sensor for tip motion detection is employed for controller demonstration. Controller parameters, derived according to stochastic optimal control theory, are formulated in a simple form readily implemented on a DSP, and extensions to other detection and actuation schemes are indicated. The controller is combined with an automated calibration scheme allowing for adaptive parameter adjustment. With the digital device operating at a sampling rate of 625kHz and 16bits of dynamic range, we were able to obtain closed-loop quality factors Qcl<5 for cantilevers with Q≈10000 and resonance frequencies up to 15kHz. This corresponds to an increase in bandwidth of >103 at undiminished signal to noise, and reduces response time and vibration amplitude by the same factor.
Dynamic coupling between coordinates in a model for biomolecular isomerization
Authors: Ma Ao , Nag Ambarish , Dinner Aaron R.
Published: April 2006

To understand a complex reaction, it is necessary to project the dynamics of the system onto a low-dimensional subspace of physically meaningful coordinates. We recently introduced an automatic method for identifying coordinates that relate closely to stable-state commitment probabilities and successfully applied it to a model for biomolecular isomerization, the C7eq→αR transition of the alanine dipeptide [A. Ma and A. R. Dinner, J. Phys. Chem. B 109, 6769 (2005)]. Here, we explore approximate means for estimating diffusion tensors for systems subject to restraints in one and two dimensions and then use the results together with an extension of Kramers theory for unimolecular reaction rates [A. Berezhkovskii and A. Szabo, J. Chem. Phys. 122, 014503 (2005)] to show explicitly that both the potential of mean force and the diffusion tensor are essential for describing the dynamics of the alanine dipeptide quantitatively. In particular, the signficance of off-diagonal elements of the diffusion tensor suggests that the coordinates of interest are coupled by the hydrodynamic-like response of the bath of remaining degrees of freedom.
Dielectric response of a polar fluid trapped in a spherical nanocavity
Authors: Blaak Ronald , Hansen Jean-Pierre
Published: April 2006

We present extensive molecular dynamics simulation results for the structure and the static and dynamical responses of a droplet of 1000 soft spheres carrying extended dipoles and confined to spherical cavities of radii R=2.5, 3, and 4nm embedded in a dielectric continuum of permittivity ϵ′⩾1. The polarization of the external medium by the charge distribution inside the cavity is accounted for by appropriate image charges. We focus on the influence of the external permittivity ϵ′ on the static and dynamic properties of the confined fluid. The density profile and local orientational order parameter of the dipoles turn out to be remarkably insensitive to ϵ′. Permittivity profiles ϵ(r) inside the spherical cavity are calculated from a generalized Kirkwood formula. These profiles oscillate in phase with the density profiles and go to a “bulk” value ϵb away from the confining surface; ϵb is only weakly dependent on ϵ′, except for ϵ′=1 (vacuum), and is strongly reduced compared to the permittivity of a uniform (bulk) fluid under comparable thermodynamic conditions. The dynamic relaxation of the total dipole moment of the sample is found to be strongly dependent on ϵ′ and to exhibit oscillatory behavior when ϵ′=1; the relaxation is an order of magnitude faster than in the bulk. The complex frequency-dependent permittivity ϵ(ω) is sensitive to ϵ′ at low frequencies, and the zero-frequency limit ϵ(ω=0) is systematically lower than the bulk value ϵb of the static permittivity.
Pressure dependence of local structure in liquid carbon disulfide
Authors: Yamamoto Sekika , Ishibashi Yasuhiko , Inamura Yasuhiro , Katayama Yoshinori , Mishina Tomobumi , Nakahara Jun’ichiro
Published: April 2006

High pressure x-ray diffraction measurements on liquid carbon disulfide up to 1.2GPa are performed by using an energy dispersion method. The results are compared with a molecular dynamics calculation with usual Lennard-Jones potential. They give very good agreement for all pressures measured. It becomes clear that the liquid structure changes like hard core liquid up to the pressure just below crystallizing point. The relation between structural change and optical response at high pressure is discussed.
Aggregation of [70]fullerene in presence of acetonitrile: A chemical kinetic experiment
Authors: Datta Kakali , Mukherjee Asok K.
Published: April 2006

[70]fullerene solutions in carbon tetrachloride and o-xylene exhibit a noteworthy spectral variation with time when acetonitrile is added. This has been ascribed to self-aggregation of [70]fullerene caused by the repulsion between polar acetonitrile and hydrophobic [70]fullerene, and the aggregation numbers have been determined from a kinetic scheme and also from a scanning electron microscopic study. The numbers thus obtained follow a cuboctahedral stacking pattern proposed recently and also agree with the magic formula n=55+3m (m=1 to 14) proposed by Branz et al. for [60]fullerene clusters [Phys. Rev. B. 66, 094107 (2002)].
Solvent reorganization of electron transitions in viscous solvents
Authors: Ghorai Pradip K. , Matyushov Dmitry V.
Published: April 2006

We develop a model of electron transfer reactions at conditions of nonergodicity when the time of solvent relaxation crosses the observation time window set up by the reaction rate. Solvent reorganization energy of intramolecular electron transfer in a charge-transfer molecule dissolved in water and acetonitrile is studied by molecular dynamics simulations at varying temperatures. We observe a sharp decrease of the reorganization energy at a temperature identified as the temperature of structural arrest due to cage effect, as discussed by the mode-coupling theory. This temperature also marks the onset of the enhancement of translational diffusion relative to rotational relaxation signaling the breakdown of the Stokes-Einstein relation. The change in the reorganization energy at the transition temperature reflects the dynamical arrest of the slow, collective relaxation of the solvent related to the relaxation of the solvent dipolar polarization. An analytical theory proposed to describe this effect agrees well with both the simulations and experimental Stokes shift data. The theory is applied to the analysis of charge-transfer kinetics in a low-temperature glass former. We show that the reorganization energy is substantially lower than its equilibrium value for the low-temperature portion of the data. The theory predicts the possibility of discontinuous changes in the dependence of the electron transfer rate on the free energy gap when the reaction switches between ergodic and nonergodic regimes.
Rovibrational characterization of XΣ+2B11H+ by the extrapolation of photoselected high Rydberg series in B11H
Authors: Ricardo Viteri C. , Gilkison Andrew T. , Rixon Scott J. , Grant Edward R.
Published: April 2006

Optical-optical-optical triple-resonance spectroscopy of B11H isolates high Rydberg states that form series converging to rotational state specific ionization potentials in the vibrational levels of B11H+ from ν+=0 through 4. Limits defined by a comprehensive fit of these series to state-detailed thresholds yield rovibrational constants describing the XΣ+2 state of B11H+. The data provide a first determination of the vibrational-rotational interaction parameter αe=0.4821cm−1 and a more accurate estimate of ωe=2526.58cm−1 together with the higher-order anharmonic terms ωexe=61.98cm−1 and ωeye=−1.989cm−1. The deperturbation and global fit of series to state-detailed limits also yield a precise value of the adiabatic ionization potential of B11H of 79120.3±0.1cm−1, or 9.81033±1×10−5eV. High precision is afforded here by the use of graphical analysis techniques, narrow-bandwidth laser systems, and an analysis of newly observed, high principal quantum number Rydberg states that conform well with Hund’s case (d) electron-core coupling limit.
Anisotropic colloidal particles interacting with polymers in a good solvent
Authors: Eisenriegler E.
Published: April 2006

We study the consequences of chain self-avoidance for the interaction between nonadsorbing polymers and colloidal particles of anisotropic shape, such as ellipsoids, lenses, and dumbbells. In the framework of a field theoretic operator expansion for small mesoscopic particles, we obtain exact results for self-avoiding polymers in d=2 spatial dimensions and we compare ideal and self-avoiding polymers in 2<d<4. Changing the orientation of a particle, with a given size and shape, near a boundary wall requires less free energy if the chains are self-avoiding. The distance dependence of the anisotropic interation, mediated by the polymers between particle and wall, is changed both qualitatively and quantitatively by self-avoidance.
Trace functions as Laplace transforms
Authors: Hansen Frank
Published: April 2006

We study trace functions on the form t→Trf(A+tB) where f is a real function defined on the positive half-line, and A and B are matrices such that A is positive definite and B is positive semidefinite. If f is non-negative and operator monotone decreasing, then such a trace function can be written as the Laplace transform of a positive measure. The question is related to the Bessis-Moussa-Villani conjecture.
Space-time matter inflation
Authors: Anabitarte Mariano , Bellini Mauricio
Published: April 2006

We study a model of power-law inflationary inflation using the space-time-matter theory of gravity for a five-dimensional canonical metric that describes an apparent vacuum. In this approach the expansion is governed by a single scalar (neutral) quantum field. In particular, we study the case where the power of expansion of the universe is p⪢1. This kind of model is more successful than others in accounting for galaxy formation.
Beyond time-dependent exact exchange: The need for long-range correlation
Authors: Bruneval Fabien , Sottile Francesco , Olevano Valerio , Reining Lucia
Published: April 2006

In the description of the interaction between electrons beyond the classical Hartree picture, bare exchange often yields a leading contribution. Here we discuss its effect on optical spectra of solids, comparing three different frameworks: time-dependent Hartree-Fock, a recently introduced combined density-functional and Green’s function approaches applied to the bare exchange self-energy, and time-dependent exact exchange within time-dependent density-functional theory (TD-EXX). We show that these three approximations give rise to identical excitonic effects in solids; these effects are drastically overestimated for semiconductors. They are partially compensated by the usual overestimation of the quasiparticle band gap within Hartree-Fock. The physics that lacks in these approaches can be formulated as screening. We show that the introduction of screening in TD-EXX indeed leads to a formulation that is equivalent to previously proposed functionals derived from many-body perturbation theory. It can be simulated by reducing the long-range part of the Coulomb interaction: this produces absorption spectra of semiconductors in good agreement with experiment.
Interatomic decay of inner-valence-excited states in clusters
Authors: Gokhberg Kirill , Averbukh Vitali , Cederbaum Lorenz S.
Published: April 2006

In an isolated atom, excitation of an inner valence electron above the outer valence subshell leads to creation of an autoionizing state. Recently, it has been demonstrated experimentally that in a cluster, the inner-valence-excited states can decay also by an interatomic mechanism which has been called resonant interatomic Coulombic decay (RICD). Here we show that RICD is indeed the leading but not the only possible interatomic decay mode of the inner-valence excitations in clusters. Using Ne (2s→3p) excitation in MgNe cluster as an example, we explore the possible decay mechanisms and draw conclusions on their relative importance and on the nature of the corresponding decay products.
Structure and effective interactions in polymer nanocomposite melts: An integral equation theory study
Authors: Zhao Lei , Li Yi-Gui , Zhong Chongli , Mi Jianguo
Published: April 2006

The polymer reference interaction site model from integral equation theory is used to investigate the structure and effective interactions in polymer nanocomposite melts where strong nanoparticle-monomer interactions are principally considered in this work. For finite particle volume fraction, the compromise for the interference between polymers and nanoparticles results in an optimum particle volume fraction for nanoparticle dispersion in polymer melts. At constant particle volume fraction, the effects of degree of polymerization become insignificant when it reaches a threshold value, below which quantitative effects on the organization states of polymer nanocomposite melts are found and help nanoparticles to well disperse in polymer. The aggregation of large nanoparticles decreases with the increase of the nanoparticle-monomer attraction strength. These observations may provide useful information for the development of new polymer materials.
The electronic structure of oxo-Mn(salen): Single-reference and multireference approaches
Authors: Sears John S. , Sherrill C. David
Published: April 2006

Using single- and multireference approaches we have examined many of the low-lying electronic states of oxo-Mn(salen), several of which have not been explored previously. Large complete-active-space self-consistent-field (CASSCF) computations have been performed in pursuit of an accurate ordering for the lowest several electronic states. Basis set and relativistic effects have also been considered. For the geometry considered, our best results indicate the ground spin state to be a closed-shell singlet, followed by a pair of low-lying triplet states, with additional singlet states and the lowest quintet state lying significantly higher in energy. Hartree-Fock and density functional theory (DFT) results are obtained and are compared to the more robust CASSCF results. The Hartree-Fock results are qualitatively incorrect for the relative energies of the states considered. Popular density functionals such as BP86 and B3LYP are superior to Hartree-Fock for this problem, but they give inconsistent answers regarding the ordering of the lowest singlet and triplet states and they greatly underestimate the singlet-quintet gap. We obtained multiple Hartree-Fock and DFT solutions within a given spin multiplicity, and these solutions have been subjected to wave function stability analysis.