bluuebunny/crossref_metadata_2025 huggingface dataset:
Waste management modeling with PC‐based model — EASEWASTE
Authors: Bhander Gurbakhash S. , Hauschild Michael Z. , Christensen Thomas H.
Published: February 2008

As life‐cycle‐thinking becomes more integrated into waste management, quantitative tools are needed for assessing waste management systems and technologies. This article presents a decision support model to deal with integrated solid waste management planning problems at a regional or national level. The model is called EASEWASTE (environmental assessment of solid waste systems and technologies). The model consists of a number of modules (submodels), each describing a process in a real waste management system, and these modules may combine to represent a complete waste management system in a scenario. EASEWASTE generates data on emissions (inventory), which are translated and aggregated into different environmental impact categories, e.g. the global warming, acidification, and toxicity. To facilitate a “first level” screening evaluation, default values for process parameters have been provided, wherever possible.

The EASEWASTE model for life‐cycle‐assessment of waste management is described and applied to a case study for illustrative purposes. The case study involving hypothetical but realistic data demonstrates the functionality, usability, and flexibilities of the model. The design and implementation of the software successfully address the substantial challenges in integrating process modeling, life‐cycle inventory (LCI), and impact assessment (LCIA) modeling, and optimization into an interactive decision support platform. © 2008 American Institute of Chemical Engineers Environ Prog, 2008
Rejoinder to Goldberg, Lee and Ashton (2008): explaining counterintuitive findings
Authors: Anderson Neil , Ones Deniz S.
Published: February 2008

In their critique of our erratum and addendum (Anderson & Ones, 2008), Goldberg, Lee, and Ashton (2008) allege clerical errors (1) where participants' HPI scores were incorrectly matched to other inventory scale scores and (2) in scoring of the OPQ and BPI scales. The first point was fully addressed by our erratum and addendum and Goldberg et al. do not present any new evidence that was not already considered. In this response, we further demonstrate that Goldberg et al. do not and cannot prove clerical errors in scoring OPQ and BPI scales. The circumstantial arguments presented by Goldberg et al. are shown to be fallacious. We respond to all conjectures and criticisms raised by their paper. We acknowledge, as we did in our previous publication (Anderson & Ones, 2003) that some of the specific convergent correlations and findings reported are not normative, but nonetheless explainable given psychometric and statistical artefacts that influence individual primary study results. Even basing our analyses upon the ‘reconstituted’ dataset generated and preferred by Goldberg et al., we demonstrate that our original conclusions do not change substantially. Responsible science requires the publication of all results, not only those confirming extant hypotheses and expectations. We continue to stand by the findings and conclusions reported in our previous publications (Anderson & Ones, 2003; Ones & Anderson, 2002). Copyright © 2008 John Wiley & Sons, Ltd.
Chitin synthesis inhibitor effect on Aedes aegypti populations susceptible and resistant to organophosphate temephos
Authors: Martins Ademir Jesus , Belinato Thiago Affonso , Lima José Bento Pereira , Valle Denise
Published: February 2008

BACKGROUND: In Brazil, dengue vector control is hampered by the resistance of Aedes aegypti L. populations to organophosphates (OPs). Insect growth regulators (IGRs) are a promising alternative, as their mechanisms of action are different from those of conventional insecticides. The authors analysed the effect of the IGR triflumuron, a chitin synthesis inhibitor, on the Ae. aegypti insecticide‐susceptible strain Rockefeller, as well as on field populations both susceptible (TemS) and resistant (TemR) to the OP temephos.

RESULTS: Triflumuron arrested development and inhibited adult emergence of the Rockefeller strain in a dose‐dependent way (EI50 and EI90 of 0.8 and 1.8 µg L−1 respectively). A direct relationship between triflumuron concentration and the precocity of its effects was evident. TemS and TemR temephos resistance ratios (RR90) were 4.5 and 13.8, triflumuron RR90 being 1.0 and 1.3 respectively.

CONCLUSION: The IGR triflumuron exhibited a dose‐dependent effect against the reference Ae. aegypti Rockefeller strain. It was also effective against two field populations, regardless of their OP resistance status. The present results are discussed in the context of utilization of chitin synthesis inhibitors as potential alternatives in the control of Ae. aegypti in Brazil. Copyright © 2008 Society of Chemical Industry
Hopping energy relaxation of localized excitons in GaP(N)
Authors: Niebling T. , Rubel O. , Heimbrodt W. , Stolz W. , Baranovskii S. D. , Klar P. J. , Geisz J. F.
Published: February 2008

Low‐temperature kinetics of the energy transfer of localized optical excitations in a nitrogen‐doped GaP bulk sample with a nitrogen content of 2.1 % is studied by means of time‐resolved spectroscopy. Both spectral and time dependence of the photoluminescence decay are described quantitatively in a time range from nanoseconds to microsecond by a phenomenological theory of hopping and energy relaxation of localized excitons. The density of localized states and their energy distribution are determined by comparison of experiment and theory. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hopping transport of interacting carriers in disordered organic materials
Authors: Novikov Sergey V.
Published: February 2008

Computer simulation of the hopping charge transport in disordered organic materials has been carried out explicitly taking into account charge‐charge interactions. This approach provides a possibility to take into account dynamic correlations that are neglected by more traditional approaches like mean field theory. It was found that the effect of interaction is no less significant than the usually considered effect of filling of deep states by noninteracting carriers. It was found too that carrier mobility generally increases with the increase of carrier density, but the effect of interaction is opposite for two models of disordered organic materials: for the non‐correlated random distribution of energies with Gaussian DOS mobility decreases with the increase of the interaction strength, while for the model with long range correlated disorder mobility increases with the increase of interaction strength. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoconductivity in amorphous selenium blocking structures
Authors: Reznik A. , Baranovskii S. D. , Rubel O. , Jandieri K. , Rowlands J. A.
Published: February 2008

Photoconductive properties of the first practical a‐Se avalanche photosensor (hole drift mobility, photocurrent response time, quantum yield of charge photogeneration and avalanche multiplication gain) have been studied. It has been shown that hole transport and avalanche multiplication mechanisms in multilayered a‐Se blocking structure used in practical photosensors are similar to those observed in a‐Se monolayers confined between insulating layers and used for the first manifestation of avalanche effect in this material by Juska and Arlauskas, phys. stat. sol. (a) 59, 389 (1980). It is suggested that combination of high avalanche gain (up to 1000) with high quantum efficiency of charge photogeneration (almost 100%) and fast photocurrent time response (∼ 1 ns) makes a‐Se avalanche photosensor a promising candidate to replace vacuum photomultiplier tubes for application in medical radiation imaging. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of screening on slow relaxation of excess conductance in two‐dimensional array of tunnel‐coupled quantum dots
Authors: Stepina N. P. , Koptev E. C. , Nenashev A. V. , Dvurechenskii A. V. , Nikiforov A. I.
Published: February 2008

The excess conductivity relaxation in two‐dimensional array of tunnel‐coupled Ge/Si quantum dots (QDs) was studied for the samples with Coulomb and screened‐Coulomb interaction in hopping regime. The screening of long‐range electron‐electron (e‐e) interaction in the sample with metal plane, put close to the dot layer, was revealed in the crossover from Efros‐Shklovskii variable‐range hopping to the Mott one. It was shown that the relaxation both in interacting and non‐interacting systems is described by stretched exponential law. Characteristic time for the unscreened sample linearly scales with the exciting field. Screening of the electron‐electron interaction suppresses the dependence of the relaxation behavior on the bias voltage and accelerates the relaxation process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tribological and electrical study of fluorinated diazonium films as dry lubricants for electrical contacts
Authors: Alamarguy David , Benedetto Alessandro , Balog Mirela , Noël Sophie , Viel Pascal , Derf Franck Le , Houzé Frédéric , Sallé Marc , Palacin Serge
Published: February 2008

The need to operate in extreme environmental conditions (ultra high vacuum, high temperatures, aerospatial, etc.) and the miniaturisation toward microelectromechanical system is demanding new materials in the field of low‐level electrical contacts lubrication. A dry and chemically immobilised layer avoiding the traditional wet lubricating fluids would have many advantages.

We report here the first results on films obtained by the electrochemical reduction of different diazonium salts and their use as protective coatings able to lubricate the metallic surfaces of an electrical contact while preserving at the same time electrical conduction.

The physicochemical properties of the films, elaborated from various diazonium salts, were studied by cyclic voltammetry and ATR FT‐IR spectroscopy. Atomic force microscope was combined with a home‐made wide‐range current measurement system to investigate simultaneously the mechanical and electrical interactions between the doped diamond conductive tips and the evaporated gold surfaces coated with the diazonium films. The analysis of the simultaneous mechanical and electrical properties of the films in a nanocontact situation is shown to bring much insight into the electrical contact application. Copyright © 2008 John Wiley & Sons, Ltd.
Cervical length for prediction of preterm birth in women with multiple prior induced abortions
Authors: Visintine J. , Berghella V. , Henning D. , Baxter J.
Published: February 2008

Objective

To determine whether transvaginal sonographic cervical length predicts preterm birth in women with multiple prior induced abortions.

Methods

This was a retrospective cohort study using the Thomas Jefferson University Prematurity Database. Patients with a singleton pregnancy and a history of more than one induced abortion were identified. Exclusion criteria were cerclage and indicated preterm birth. Subjects were followed with transvaginal ultrasound measurement of the cervix between 14 and 24 weeks' gestation and grouped into those with and those without a short cervix; a cervical length of < 25 mm was considered short. The primary outcome was spontaneous preterm birth at < 35 weeks.

Results

Fifteen of the 65 (23%) women with more than one induced abortion included in the study had a short cervix. The demographics and risk factors were similar between those with and those without a short cervix. The overall incidence of preterm birth was 21.5% (14/65); in women with a short cervix the incidence was 47% (7/15) and in women without a short cervix it was 14% (7/50). The sensitivity, specificity and positive and negative predictive values of a short cervix in the prediction of preterm birth were 50%, 84%, 47% and 86%, respectively. The relative risk of a short cervix for spontaneous preterm birth was 3.3 (95% CI, 1.4–7.4).

Conclusion

A cervical length of < 25 mm on transvaginal ultrasound is predictive of preterm birth in women with more than one prior induced abortion. Women with multiple prior induced abortions and a short cervix have a 3.3‐fold greater chance of spontaneous preterm birth compared with those with a cervical length of ≥ 25mm. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Psychosocial Conditions of Women Awaiting Genetic Counseling: A Population‐based Study
Authors: Mikkelsen Ellen M. , Sunde Lone , Johansen Christoffer , Johnsen Søren P.
Published: February 2008

The decision whether to undergo genetic counseling for hereditary breast and ovarian cancer is complex. Knowledge about the psychosocial conditions of women who are awaiting counseling is sparse. We aimed to compare the psychosocial conditions of women awaiting genetic counseling with those of women in two reference groups. We included 567 women referred to genetic counseling for hereditary risk of breast or ovarian cancer (Genetic Group), 689 women referred to mammography (Mammography Group) and a random sample of 2,000 women from the general population (Population Group). One to 4 weeks before the first counseling session or mammography, data were collected by questionnaires. Both women affected with cancer and unaffected women in the Genetic Group appeared to have a somewhat higher prevalence of cancer‐specific‐distress than the corresponding reference groups. Further research on the effect of pre‐ counseling interventions appear warranted in addition with exploring a potential association between waiting time and cancer‐specific distress.
Early capital cities
Authors: Qi DONG
Published: February 2008

The early capital cities are the key symbols of early Chinese civilization. By comparing the Erlitou site, Shang city in Zhengzhou, Shang city in Yanshi with Niuheliang site, Mojiaoshan site, Shijiahe site, Taosi site, and Wangchenggang site, the characteristics of the early capital cities could be drawn: First, it should have palace or palace city in big sizes; Second, the palace or palace city should be surrounded by living quarters for noble families, working areas for melting bronze, and quarters for sacrifice.
The popularization of bicycles and modern Shanghai
Authors: Tao XU
Published: February 2008

Taking the popularization of bicycles in modern Shanghai as an example, this article discussed the interrelationship between the development of instruments and the users by analyzing the expansion of city space, formation of the city time rhythm, changes in consumption mode of different social classes, and the competition of various transportation tools, etc. The influences on the transformation of social life in Shanghai and other cities of China were also revealed.
Radiative transfer modeling of near‐infrared spectra of lunar mare soils: Theory and measurement
Authors: Denevi B. W. , Lucey P. G. , Sherman S. B.
Published: February 2008

We examine the ability of a radiative transfer model based on the theory of Hapke (1981, 1993, 2001) to reproduce reflectance spectra of known composition, as well as extract compositional information from reflectance spectra. We test this model using spectra of two‐component mineral mixtures, spectra of lunar mare soils studied by the Lunar Soil Characterization Consortium (LSCC), and a telescopic spectrum of the Apollo 11 landing site. The model is able to accurately reproduce spectra of two‐component mineral mixtures and can be used to accurately predict mineral abundances, mineral chemistry, and particle size. Reflectance spectra of the lunar mare soils are modeled using the mineral abundances and chemistries reported for each soil. We collect our own mineral and chemical information for one of these samples, 12001, in order to examine the effects of several simplifying assumptions employed by the LSCC and conclude that the classification of glass (volcanic/impact versus agglutinitic) can have large consequences on the predicted spectra. Model spectra can generally mimic the lunar mare sample spectra, though with consistent errors in contrast and continuum slope, and absorption bands offset to shorter wavelengths. The Apollo 11 telescopic spectrum is successfully modeled with mineralogy and chemistry from sample 10084, though the fit is improved with slight variations in mineralogy or mineral chemistry. We find that varying pyroxene chemistry can have as large an effect on spectral shape as varying mineral abundance.
Plasma transport in the Io torus: The importance of microscopic diffusion
Authors: Mei Yi , Thorne Richard M.
Published: February 2008

We consider the question of whether the distribution of mass in the Io plasma torus is consistent with the concept of interchange eddy transport. Specifically, the flux tube content exhibits a gradual decrease with increasing radial distance from the source near Io without any evidence for substantial density irregularity associated with the plasma source or loss. Using a simple one dimensional numerical model to simulate macroscopic interchange eddy transport, we demonstrate that this smooth equilibrium distribution of mass can occur but only with the inclusion of a minimal level of small scale microscopic mixing at a rate approaching Bohm diffusion. Otherwise the system exhibits a chaotic appearance which never approaches an equilibrium distribution. We discuss various physical mechanisms for the microscopic diffusion process which is required to provide a sufficiently rapid mixing of material between the macroscopic eddies.
Balloon borne observations of backscatter, frost point and ozone in polar stratospheric clouds at the South Pole
Authors: Rosen James M. , Kjome Norman T. , Oltmans Samuel J.
Published: February 2008

Concurrent backscatter and ozone measurements were made with near‐simultaneous frost point soundings over the South Pole when the center of the 1990 winter vortex was at or very near that location. The initial water vapor concentration in the stratosphere was ∼5ppmv and decreased to ∼1.5–2.0 ppmv as cooling took place. By mid‐July the stratospheric temperature had decreased to the frost point and heavy polar stratospheric cloud (PSC) activity was observed presumably due to the condensation of water vapor. The lowest water vapor concentrations observed correspond to saturated air at the lowest temperatures encountered. The slow recovery of the water vapor concentration during spring warming indicates that the 12 to 22 km altitude region in the vortex is not readily penetrated by outside air.

The observed large decrease in PSC backscatter above ∼14 km before the stratosphere began to warm is consistent with loss of particles by sedimentation leading to significant dehydration and denitrification, The region of PSC activity in July is noted to be in the same region in which ozone depletion and the persistent dehydration is observed later in the year. At the end of August heavy PSC activity was observed in the lower stratosphere and upper troposphere, consistent with earlier observations from NASA aircraft. These lower clouds were in a region that apparently was still experiencing cooling. No compelling evidence was found supporting earlier claims that PSC layers are anti‐correlated with ozone inside the vortex.
A study of slow‐mode structures in the dayside magnetosheath
Authors: Lee L. C. , Yan M. , Hawkins J. G.
Published: February 2008

Recent observations indicate that a region of enhanced plasma pressure and decreased magnetic field intensity frequently occurs in front of the plasma depletion layer at the dayside magnetopause [Song et al., 1990]. This inverse relationship is characteristic of a slow‐mode wave. We have simulated this phenomenon with a two‐dimensional incompressible MHD simulation code. When a normal component of the interplanetary magnetic field is present (Bx≠0), the total magnetic field intensity tends to decrease in front of the depletion layer due to the bending of the magnetic field lines, and the plasma pressure is enhanced in this region. On the other hand, when Bx =0, this slow‐mode structure is not present in the simulation and only the plasma depletion layer is observed.
Mapping using the Tsyganenko Long Magnetospheric Model and its relationship to Viking auroral images
Authors: Elphinstone R. D. , Hearn D. , Murphree J. S. , Cogger L. L.
Published: February 2008

The Tsyganenko long magnetospheric model (1987) has been used in conjunction with ultraviolet images taken by the Viking spacecraft to investigate the relationship of the auroral distribution to different magnetospheric regions. The model describes the large‐scale structure of the magnetosphere reasonably well for dipole tilt angles near zero, but it appears to break down at higher tilt angles. Even so, a wide variety of auroral configurations can be accurately described by the model. It appears that the open‐closed field line boundary is a poor indicator of auroral arc systems with the possible exception of high‐latitude polar arcs. The auroral distribution typically called the “oval” maps to a region in the equatorial plane quite close to the Earth and can be approximately located by mapping the model current density maximum from the equatorial plane into the ionosphere. Although the model may break down along the flanks of the magnetotail, the large‐scale auroral distribution generally reflects variations in the near‐Earth region and can be modeled quite effectively.
Mesosphere‐ thermosphere tidal coupling during the September 21–25, 1987, LTCS 1 Campaign
Authors: Forbes Jeffrey M. , Salah Joseph E.
Published: February 2008

The thermosphere (≥ 90 km) is dynamically coupled to the mesosphere and lower atmospheric regions by gravity waves, tides, and planetary waves which propagate upward from below and often undergo dissipation in the 80 to 150‐km region. This paper focuses on the mesosphere‐thermosphere coupling due to the solar semidiurnal atmospheric tide during the first Lower Thermosphere Coupling Study (LTCS) campaign interval of September 21–25, 1987. During this period, determinations of semidiurnal eastward (u) and northward (υ) velocity components and temperature (δT) are available within the 80 to 150‐km region from a total of 13 incoherent scatter, meteor, and spaced antenna radars. A new method is developed and reported here for assimilating such data sets into a self‐consistent global empirical description of the tidal dynamics between 80 and 150 km. Using a set of numerically generated ‘Hough mode extension’ (HME) functions for u, v, and δT corresponding to the (2,2), (2,3), (2,4), and (2,5) semidiurnal tidal modes, a least squares fit to the radar data is performed. The fit results in a single (complex) normalizing factor for each HME from which globally continuous and internally consistent semidiurnal oscillations in u, v, and δT (as well as vertical velocity and density) can be derived. The quality of fit to these data from various height regions including both northern and southern hemispheres establishes the internal consistency between these measurements as well as the applicability of the method to future data sets. The resulting empirical model reproduces the data significantly better than recent theoretical models, suggesting use of the method for deriving tidal boundary conditions for thermospheric general circulation models.
A large‐amplitude rotational wave in the Venusian ionosheath
Authors: Fedorov A. O. , Vaisberg O. L. , Intriligator D. S. , Sagdeev R. Z. , Galeev A. A.
Published: February 2008

We report the results of a preliminary analysis of a large‐amplitude rotational wave in the Venusian ionosheath. Our results are based on an analysis of the Pioneer Venus Orbiter plasma and magnetic field observations from six orbits in the first (1979) tail season. This wave appears to be the standing superalfvenic wing. It is located within the shocked plasma flow outside the boundary of the tail. The rotation of the magnetic field by about 90 deg across the wave occurs through several successive cycles making the wave similar to the group velocity wing consisting of phase velocity waves. The transition through the wave is accompanied by the vector change of the plasma velocity with the magnitude of the plasma velocity jump comparable to the vector jump of the Alfven velocity. The observed super‐Alfvenic wing appears to originate upstream and closer to the planet, possibly near the upper boundary of the magnetic barrier on the dayside.
Comparison between the polar cap index, PC, and the auroral electrojet indices AE, AL, and AU
Authors: Vennerstrøm S. , Friis‐Christensen E. , Troshichev O. A. , Andersen V. G.
Published: February 2008

The newly introduced index PC for magnetic activity in the polar cap has been examined to establish to which extent it can serve as an indicator of auroral electrojet activity. PC is derived from a single nearpole station, as a 15‐min average index. We have derived it for two stations, one in the northern hemisphere (Thule) and one in the southern hemisphere (Vostok). The simplicity of the PC index enables us to make a large data base for statistical investigations. We have thus used 7 years of PC values for the two stations to analyze the relationship between PC and the auroral zone indices AE, AU, and AL statistically. We find a very high correlation between PC and AE during winter and equinox, the linear correlation coefficient being ≈0.8–0.9 for Thule and ≈0.7–0.8 for Vostok. During summer the correlation is less because the PC index is then disturbed by polar cap currents controlled by the northward and east‐west components of the interplanetary magnetic field. We therefore stress the importance of having PC available from both the northern and southern hemisphere. From event studies we find that PC is sensitive both to DP 2 type electrojet activity and to substorm intensifications of the westward electrojet in the midnight or postmidnight sector but less sensitive to substorm intensifications of the westward electrojet in the premidnight sector. We conclude that PC can serve as a fast available indicator of DP 2 and DP 1 activity in the polar regions, excluding intrusions of the westward electrojet in the premidnight sector.
Kinetic theory of geomagnetic pulsations: 1. Internal excitations by energetic particles
Authors: Chen Liu , Hasegawa Akira
Published: February 2008

Motivated by recent satellite observations, we have carried out a comprehensive theoretical analysis on the generation of hydromagnetic Alfvén waves in a realistic magnetospheric plasma environment consisting of a core (∼100 eV) component and an energetic (∼10 keV) component. Our theoretical formulation employs the gyrokinetic equations and, thus, retains anisotropy, finite Larmor radii, magnetic trapping, and wave‐particle interactions in addition to nonuniform plasma equilibria. A set of coupled equations for transverse and compressional magnetic perturbations is derived and analyzed for its stabilities assuming equilibrium distribution functions which are interchange stable. Our findings are as follows: (1) compressional and transverse shear Alfvén oscillations are generally coupled in realistic plasmas; (2) in the decoupled limit, for the compressional wave branch, one recovers the drift mirror instability due to the Landau resonances and τ ≡ 1 + 4π(∂P⊥/B∂B) < 0; here, P⊥ = P⊥(ψ, B) is the perpendicular pressure and ψ is the magnetic flux function; (3) for the decoupled transverse shear Alfvén branch, one obtains the drift Alfvén ballooning instability due to the Landau resonances and free energy of the pressure gradient for τ > 0; (4) for both branches, the most unstable modes have antisymmetric structures and propagate in the diamagnetic drift direction of the energetic ions; and (5) finite coupling can be shown to further enhance the drift Alfvén ballooning instabilities. Thus we conclude that for τ ≥ 0, the coupled drift Alfvén ballooning mirror instability constitutes an important internal generating mechanism of geomagnetic pulsations. The various predicted features of this instability are consistent with satellite observations.
Detailed analysis of broadband electrostatic noise in the dayside auroral zone
Authors: Dubouloz N. , Pottelette R. , Malingre M. , Holmgren G. , Lindqvist P. A.
Published: February 2008

The great number of bursts of broadband electrostatic noise (BEN) recorded during crossings of the dayside auroral zone by the Viking satellite enables their statistical study. The angular distribution of BEN with respect to the Earth's magnetic field is shown to be most likely isotropic, implying that it cannot consist of a unique linear plasma mode. Most of the bursts evidence a power law spectrum from the lower hybrid and ion plasma frequencies up to frequencies sometimes much higher than the electron plasma frequency, suggesting the presence of nonlinear effects. This is confirmed by their high intensity, and by the correlation between their amplitude and their frequency extension. BEN emissions are associated with ion conical distributions and with field‐aligned electron beams. Although most of the power is concentrated at very low frequencies and around the lower hybrid and ion plasma frequencies, electron acoustic and beam mode waves may contribute to the high‐frequency extension of BEN. The most intense BEN emissions are also correlated with sharp cold plasma density gradients and probably involve drift instabilities. Strong quasi‐static perpendicular electric fields, which induce high‐speed plasma flows, are also measured, so that the Doppler effect may contribute to the broadening of the BEN spectrum.
The relationship between plate curvature and elastic plate thickness: A study of the Peru‐Chile Trench
Authors: Judge Anne V. , McNutt Marcia K.
Published: February 2008

The age of the Nazca plate where it enters the Peru and northern Chile trenches varies from 30 Ma in the north to 45 Ma in the south as its dip beneath the South American continent steepens from 13° to 30°. If the elastic thickness Te of oceanic lithosphere depends only on its age, and therefore thermal state, we would expect that Te determined from fitting the flexure of the lithosphere over the outer rise as revealed in the depth, geoid, and gravity anomalies would increase from the Peru Trench in the north to the northern Chile Trench further south. We find that the opposite is true: the lithosphere appears suffer outboard of the Peru Trench than it does offshore Chile. To explain deflections of the lithosphere seaward of Peru, the isotherm controlling the elastic/ductile transition must be near 800°C, providing the thermal structure of the plate is that predicted by the standard thermal plate model. Because the decrease in plate stiffness to the south is correlated with an increase of plate curvature over the outer rise and outer trench wall, we interpret our result in terms of inelastic yielding of the oceanic lithosphere when bent to high strains. The magnitude of the reduction in strength, however, suggests that the standard oceanic yield strength envelope underestimates the amount of failure for lithosphere bent to high strains unless the stress field off northern Chile is characterized by 100‐MPa‐level tension. The more highly bent segment of subducting lithosphere at this trench also dips at a steeper angle at greater depth beneath the continent, but detailed analysis of plate geometry does not support a relationship between slab dip as determined by earthquake hypocenters and elastic behavior over the outer rise.
Thermoluminescence dating of fault‐scarp‐derived colluvium: Deciphering the timing of paleoearthquakes on the Weber Segment of the Wasatch Fault Zone, north central Utah
Authors: Forman Steven L. , Nelson Alan R. , McCalpin James P.
Published: February 2008

The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine‐grained, fault‐related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine‐grained colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and 14C age estimates indicate that these three faulting events occurred sometime between 4500 and 3500, between 3200 and 2500, and between 1400 and 1000 years ago. Detailed investigation of a sequence of fine‐grained, scarp‐derived distal colluvium shows that much of the sediment was deposited during <600‐year intervals immediately after faulting. The sedimentation rate of colluvium is inferred to increase shortly after faulting, and TL dating of these sediments provides additional information to constrain the timing of faulting events.
Magnetic polarity stratigraphy and carboniferous paleopole positions from the Joggins Section, Cumberland Structural Basin, Nova Scotia
Authors: DiVenere V. J. , Opdyke N. D.
Published: February 2008

One hundred seventy‐seven samples were taken in stratigraphic sequence in redbeds from approximately 2100 m of Namurian‐Westphalian strata from the Shepody, Enragé, Boss Point, and lower Joggins formations between Minudie and Joggins, Nova Scotia, for the purpose of constructing a magnetic polarity stratigraphy. In addition, five samples from each of four sites were taken from north dipping strata of the Cumberland Group for the purpose of conducting a fold test for the Joggins Formation. This yields a total coverage of 412 samples from approximately 2400 m of south dipping strata in the composite section when combined with previous results from the Maringouin Peninsula (DiVenere and Opdyke, 1990) and 88 samples from north‐dipping strata collected for the purpose of conducting fold tests. Two components of magnetization are identified in these sediments: a prefolding component, termed C, and a synfolding component, termed B. The present results extend the mid‐Carboniferous magnetic polarity stratigraphy to include eight normal and eight reversed magnetozones in the Namurian A through early Westphalian A interval. The results are dominantly to completely reversed in samples from the remainder of the Westphalian A and the Westphalian B, but because of the complication of varying degrees of remagnetization and an 800 m sampling gap it is not possible to verify the base of the Permo‐Carboniferous reversed superchron in this time period. Northward plate motion is inferred from an observed shallowing of inclinations upsection. A 5–7 cm/yr average poleward drift rate is calculated for this time period from these results, yielding a low‐latitude southern hemisphere paleogeographic position.
The Salt Dome problem: A multilayered approach
Authors: Römer Mathias‐M. , Neugebauer Horst J.
Published: February 2008

The dynamical evolution of buoyancy‐driven geological systems is mainly influenced by two physical parameters: density and equivalent viscosity. Salt structures are an appropriate geological representation of these systems. Important variations of these parameters are directly related to changes in mass, and thus the internal structures themselves and their changes in time become significant parameters. In order to decipher these structures in nature by means of experiments it is therefore necessary to extend model calculations on intrusion processes to multilayer systems. A two‐dimensional finite element program has been developed to simulate the rise of individual diapirs through multi‐layered overburdens exhibiting Newtonian‐viscous rheologies. This program includes the following features: arbitrarily shaped interfaces between different fluid boundaries, layers of finite thickness and subsidence of the model within the model‐frame as well as time‐ and depth‐dependent material properties. This paper is concerned with single diapirs intruding upbuilt multilayered overburdens, the effect of a subsiding salt base due to pure downbuilding, and differential loading of gravitationally unstable distributions of mass. Variable density and viscosity of the overburden with depth control the shape and ascent rates of diapiric bodies. The subsidence history of “salt structures” dominates the development of maximum horizontal pressure gradients with time and thus the ascend histories of diapirs.
Magnetic, structural and geochronologic evidence bearing on volcanic sources and Oligocene Deformation of Ash Flow Tuffs, northeast Nevada
Authors: Palmer H. C. , MacDonald W. D. , Hayatsu A.
Published: February 2008

Magnetic properties of mid‐Tertiary volcanic rocks west of Jiggs in northeast Nevada were investigated for the purposes of interpreting igneous, structural, and tectonic processes in this part of the Basin and Range province. Anisotropy of magnetic susceptibility (AMS) patterns reflect flow fabrics and suggest previously unknown sources for these ash flow tuffs. Paleomagnetic and structural evidence suggest counterclockwise relative rotation of the southern part of the area with respect to the north. New stratigraphic, chemical and K‐Ar isotopic data support these interpretations. Dacite to rhyolite ash flow tuffs of the Indian Well Formation were subdivided into two main units: the lower and predominant tuff of Jiggs (35.8–37.0 Ma) and the unconformably overlying but areally restricted tuff of Hackwood (30.8 Ma). The Jiggs unit has two polarities whereas the Hackwood has only a reversed polarity remanence. Together these units with tilt correction define a pole (92°E, 87°N, dp = 6°, dm = 8°) for approximately 30–37 Ma. This pole is concordant with coeval North American reference poles, indicating that this zone of approximately 30 km NS extent has not undergone significant vertical axis rotation relative to the North American reference. Andesite lavas of normal magnetic polarity and of 32.5‐Ma age characterize the Diamond Hills immediately to the south. We interpret this region, from both structural evidence and discordant paleomagnetic direction, to have rotated approximately 25° counterclockwise relative to the Indian Well volcanic units to the north. The apparent rotation of the Diamond Hills is possibly the result of drag on the left‐lateral Garcia fault which limits the Diamond Hills on the southwest. Analysis of AMS data suggests, by patterns of the K1 axes, two distinct sources for the Jiggs unit: a northern buried source and a central partially buried source. Lithologic evidence consistent with proximal vent facies is found near the latter source. An unusual pattern in the AMS K3 axes, suggested as resulting from the tilt correction applied to initial dip, is consistent with the interpreted flow directions. Tight age constraints can be placed on the deformation of the main ash flows of the Jiggs unit, in the 35.8‐ to 30.8‐Ma interval. Because the Diamond Hills unit is slightly younger and appears to have been affected by the same deformative episode as the Jiggs, the regional deformation affecting both units can be more narrowly confined to the 32.5–30.8 Ma interval. This deformation is inferred to coincide with the major early Tertiary episode of crustal extension in this region of the Basin and Range.
Reversals of the Earth's magnetic field and temporal variations of the dynamo families
Authors: McFadden P. L. , Merrill R. T. , McElhinny M. W. , Lee Sunhee
Published: February 2008

A recent model for polarity reversals suggested that reversals involve critical interactions between the primary (dipole) and secondary (quadrupole) dynamo families. This model predicted that the relative secondary family contribution to the field would be smaller when the reversal rate is low than when the reversal rate is high. In particular, therefore, it was predicted that the contribution from the secondary family would have been low during the Cretaceous Normal Superchron. This prediction is tested using model G for the paleosecular variation of lavas to estimate the relative contributions of the two families back through time. It is found that the data support the prediction. It is also found that a decrease in the contribution from the secondary family is associated with an increase in the contribution from the primary family, and vice versa.
Separating multidomain and single‐domain‐like remanences in pseudo‐single‐domain magnetites (215–540 nm) by low‐temperature demagnetization
Authors: Dunlop David J. , Argyle Kenneth S.
Published: February 2008

It has long been hypothesized that the pseudo‐single‐domain properties of submicron magnetites are a result of coexisting multidomain and single‐domain‐like remanences. We have separated these two types of remanence by low‐temperature demagnetization (LTD), in which samples are cooled through the low‐temperature magnetite isotropic point and rewarmed to room temperature, all in zero field. At the isotropic point, the first crystalline anisotropy constant vanishes, and multidomain remanence due to displaced domain walls will be unpinned. We measured stepwise alternating field (AF) and thermal demagnetization curves of weak‐field thermoremanent magnetization (TRM) and anhysteretic remanent magnetization and of saturation isothermal remanent magnetization (IRMs), both with and without prior LTD, for magnetites with mean particle sizes of 215, 390, and 540 nm. The memory fraction of remanence recovered after LTD, which represents the single‐domain‐like component, decreased from 44% for 215‐nm grains to 23% for 540‐nm grains in the case of IRMs. Memory of TRM was approximately twice as large. AF decay curves were soft and multidomain‐like before LTD but became harder and single‐domain‐like in shape after LTD. LTD removed most low unblocking temperature TRM and IRMs. Distributed low unblocking temperatures are therefore a multidomain phenomenon, probably resulting from successive adjustments of domain walls to changing internal fields and pinning strengths during heating.
Anomalous cyclicity in climate and stratigraphy and modeling nonlinear oscillations
Authors: Gaffin Stuart R. , Maasch Kirk A.
Published: February 2008

For geological periods lacking evidence of extensive glaciation, such as the Cretaceous, the presence of anomalously large, globally synchronous, cycles in coastal onlap stratigraphy (Haq et al., 1987) may be a new example of a nonlinear geophysical response to weak external forcing. A number of analogies can be drawn between this situation and the anomalously large 100‐kyr late Pleistocene ice volume cycle vis‐à‐vis weak 100‐kyr Milankovitch insolation changes. Apropos of these analogies we discuss formal models for evolving, free, sedimentary or glacial surfaces, subject to lateral mass transport and subsidence, and observe that nonlinear diffusivity obtains in each case. In particular, the systems both involve retarded transport. We then define equilibrium surfaces and show them to be closely related to either the subsidence profile or the ablation profile. In the absence of mass supply feedback, these equilibrium surfaces should be unconditionally stable, and amplified reponses to external forcing are unlikely. We then consider feedbacks on mass supply and show first how to construct a three‐variable glacial wedge that freely oscillates. Glacial models of this type suggest that a fundamental role is played in the oscillation by isostatic relaxation times. This effect should be considered for sedimentary systems as well. We finish with a speculation about a simple sediment supply feedback that might be associated with relative sea level changes and illustrate graphically how the multiple equilibrium points introduced by this feedback could lead to large coastal onlap shifts from relatively small perturbations to the system. Much more work will be needed, however, to determine the parameter values required to achieve such behavior and if such values are physically realistic.
Refractive index and elastic properties of MgO up to 1900 K
Authors: Zouboulis E. S. , Grimsditch M.
Published: February 2008

The refractive index and elastic constants of MgO have been measured up to 1900 K using Brillouin scattering. The refractive index shows a monotonic increase with temperature. Our elastic constant measurements slightly extend the temperature range previously covered in ultrasonic and resonance experiments; although overall agreement is good, small differences exist between the different determinations.
Characteristics of seismic waves composing Hawaiian volcanic tremor and gas‐piston events observed by a near‐source array
Authors: Ferrazzini Valerie , Aki Keiiti , Chouet Bernard
Published: February 2008

A correlation method, specifically designed for describing the characteristics of a complex wave field, is applied to volcanic tremor and gas‐piston events recorded by a semicircular array of GEOS instruments set at the foot of the Puu Oo crater on the east rift of Kilauea volcano, Hawaii. The spatial patterns of correlation coefficients obtained as functions of frequency for the three components of motion over the entire array are similar for gas‐piston events and tremor, and clearly depict dispersive waves propagating across the array from the direction of Puu Oo. The wave fields are composed of comparable amounts of Rayleigh and Love waves propagating with similar and extremely slow phase velocities ranging from 700 m/s at 2 Hz to 300 m/s at 8 Hz. The highly cracked solidified lava flow on which the array was deployed, and subjacent structure of alternating lava and ash layers formed during repeated eruptions of Puu Oo since 1983, appear to be responsible for the low velocities observed. The results from Puu Oo stand in sharp contrast to those obtained in an experiment conducted in 1976 on the partially solidified lava lake of Kilauea Iki. Rayleigh waves were not observed in Kilauea Iki, but well‐developed trains of Love waves were seen to propagate there with velocities twice as high as those observed near Puu Oo. These differences in the propagation characteristics of surface waves at the two sites may be attributed to the presence of a soft horizontal layer of molten rock in Kilauea Iki, which may have lowered the phase velocity of Rayleigh waves more drastically than that of Love waves, resulting in severe scattering of the Rayleigh wave mode. On the other hand, the thin superficial pahoehoe flow under our array at Puu Oo may have favored the development of vertical columnar joints more extensively at this location than at Kilauea Iki, which may have reduced the shear moduli controlling the Love wave mode. The average phase velocities in the frequency band from 2 to 5 Hz found at Puu Oo are roughly similar to those determined for tremor at Klyuchevskoy volcano, Kamchatka, but the frequency dependence appears much stronger at Puu Oo.
A Comparison of ship drift, drifting buoy, and current meter mooring velocities in the Pacific South Equatorial Current
Authors: McPhaden M. J. , Hansen D. V. , Richardson P. L.
Published: February 2008

In this note we compare mean seasonal cycles of zonal and meridional velocity in the Pacific South Equatorial Current based on current meter mooring data, drifting buoy data, and ship drift data. Monthly averages of ship drift and drifting buoy data were computed over 2° latitude by 10° longitude rectangles centered at the positions of multiyear current meter moorings near 0°, 110°W, and 0°, 140°W. All three representations of the flow field show the basic character of the annual mean and its variations, provided that the sampling characteristics associated with each measurement technique are taken into account. In particular we find that more than 15 days of drifter data (regardless of year) are required on a 2° latitude by 10° longitude basis to produce monthly mean estimates that agree with moored estimates to within about 5–10 cm s−1 rms. We also infer that windage affects climatological monthly mean ship drift velocities, although uncertainties in the data limit a precise determination of the windage magnitude. An upper bound appears to be about 3% of the surface wind speed, though the actual effect of windage may be considerably smaller.