bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of spates of different magnitudes on a Phragmites japonica population on a sandbar of a frequently disturbed river
Authors: Asaeda Takashi , Rajapakse Lalith
Published: April 2008

In flow‐regulated rivers, natural flow patterns and related sedimentation processes are disturbed, thus interrupting the magnitude and duration of spates. We hypothesized that this in turn might alter the impact of spates on plant communities inhabiting sandbars along the river channel. In order to test this hypothesis, the effects of spates of different magnitudes and durations on spatial variation and composition of a Phragmites japonica Steud. community on a sandbar during a 2‐year period were investigated. The flow variation of the river was continuously monitored, and the spates were categorized as small, medium or large, based on the magnitude (depth). Growth parameters (shoot length and shoot density), above‐ and belowground biomass of the plant community and the quantity of litter retained within selected quadrats, and ash‐free dry weight (AFDW) of the soil were observed at seven different locations: two each at the extreme upstream, middle and extreme downstream and one location in the downstream reaches of the sandbar. Our results showed that the aboveground biomass declined due to large‐scale spates; however, these spates triggered the formation of secondary shoots if sediments were accumulated as a result of the spates. Conversely, the aboveground biomass did not recover if the substrate was eroded. Accumulated litter beneath shoots was easily washed away due to spates, positively affecting shoot re‐growth. The effects of spates on the P. japonica plant community depended highly on the location of the plants on the sandbar and the magnitude and duration of the spates. The different erosion–sedimentation processes, depending on the local river channel morphology and spate types, significantly affected the growth and morphological characteristics of P. japonica population. Copyright © 2008 John Wiley & Sons, Ltd.
A weighted interference estimation scheme for interface‐switching wireless mesh networks
Authors: Feng Yunxia , Li Minglu , Wu Min‐You
Published: April 2008

The co‐channel interference problem in wireless mesh networks (WMN) is extremely serious due to the heavy aggregated traffic loads and limited available channels. It is preferable for mesh routers to dynamically switch channels according to the accurate estimation of co‐channel interference level in the neighborhood. Most developed interference estimation schemes, however, do not consider the impact of interface switching. Furthermore, the interference in wireless networks has been extensively considered as an all‐or‐nothing event. In this paper, we develop a weighted interference estimation scheme (WIES) for interface‐switching WMN. WIES takes a new version of multi‐interface conflict graph that considers the impacts of frequent interface switching as the interference relationship estimation scheme. Besides, WIES uses a weight to estimate the interference level between links. The weight utilizes two empirical functions to denote the impacts of the relative distance and characteristics of traffic loads in WMN. Extensive NS2 simulations show that WIES achieves significant performance improvements, especially when the interference level of the network is high. We also validate that the interference level of networks is affected by several system parameters such as the number of available channels and the ratio between interference range and transmission range. Copyright © 2008 John Wiley & Sons, Ltd.
Aflatoxin in pecans: Problems and solutions
Authors: Ayres J. L.
Published: April 2008

Abstract and Summary

The aflatoxin contamination potential in pecans has been clearly demonstrated in the literature. No definitive study has been published indicating the extent of aflatoxin contamination in pecans. Good manufacturing practices can be maintained in culture, drying, sizing, storing, and processing which should reduce the possibility of mold growth or aflatoxin production. Sampling of pecans for aflatoxin analysis would be costly due to the great number of pecan sizes and grades as well as to the high cost of pecans. Surveillance costs could be minimized by incorporating chopping with subsampling.
Stabilization of a low-frequency instability in a dipole plasma
Authors: GARNIER D. T. , BOXER A. C. , ELLSWORTH J. L. , HANSEN A. K. , KARIM I. , KESNER J. , MAUEL M. E. , ORTIZ E. E. , ROACH A.
Published: April 2008

Low-frequency fluctuations are observed in a plasma confined by a strong dipole magnet and containing an energetic high-pressure population of trapped electrons. The quasi-coherent fluctuations have frequencies characteristic of drift frequencies of the lower temperature background plasma and have large toroidal and radial extent. They are excited throughout a wide range of plasma conditions determined by the level of neutral gas pressure. However, for a sufficiently high rate of neutral gas fueling, the plasma density profile flattens and the fluctuations disappear.
Anti-cosmopolitanism, pluralism and the cosmopolitan harm principle
Authors: SHAPCOTT RICHARD
Published: April 2008

For anti-cosmopolitan critics, cosmopolitanism is equated with the universalisation of a particular, liberal, account of justice and is therefore problematic for a number of reasons. The liberal principle ‘do no harm’ principle – and the cosmopolitan principle of humanitarianism, can be used to correct the depiction of cosmopolitanism as hostile to ‘pluralism’, to identify the universalism that is latent or undeveloped in much ‘anti-cosmopolitanism’, and to identify further means of reconciling these positions. A cosmopolitan harm principle argues that the absence of a universal conception of justice should not provide an obstacle to the recognition of an obligation to limit transboundary harms.
A matter of drawing boundaries: global democracy and international exclusion
Authors: MARCHETTI RAFFAELE
Published: April 2008

This article defends the case for a global extension of democracy by deploying a cosmo-federalist theory. As a response to the current state of international exclusion, the radical project of stretching the paradigm of democratic inclusion to the extreme limits encompassing the whole of mankind, is here presented. The article begins by taking position for a choice-based version of consequentialism that generates a principle of political justice centred on political participation. From this, a political project is developed that envisages a cosmopolitan system where all world citizens are included within a scheme of a direct representative participation under an overarching authority governing the process of democratising world affairs. Crucial in this is the establishment of an all-inclusive authority to legitimately delineate jurisdictional boundaries and a multilayered system of political interaction.
Minority as inferiority: minority rights in historical perspective
Authors: LIEBICH ANDRE
Published: April 2008

This article argues that minority rights developed as an indemnity offered to defeated parties. As a grudging and begrudged calculus of compensation, considered inadequate by the vanquished and offensive by the victors, minority rights have been unable to compete in terms of legitimacy with either an increasingly robust international human rights regime or with the right of national self-determination. After reviewing some explanations for the weakness of the existing minority rights regime, this article traces the rationale of what may be described anachronistically as minority rights provisions in international treaties from the Peace of Westphalia to the Versailles settlement, concluding with a consideration of present-day implications of the argument elaborated here.
REGIME-SWITCHING AUTOREGRESSIVE COEFFICIENTS AND THE ASYMPTOTICS FOR UNIT ROOT TESTS
Authors: Cavaliere Giuseppe , Georgiev Iliyan
Published: April 2008

Most of the asymptotic results for Markov regime-switching models with possible unit roots are based on specifications implying that the number of regime switches grows to infinity as the sample size increases. Conversely, in this note we derive some new asymptotic results for the case of Markov regime switches that are infrequent in the sense that their number is bounded in probability, even asymptotically. This is achieved by (inversely) relating the probability of regime switching to the sample size. The proposed asymptotic theory is applied to a well-known stochastic unit root model, where the dynamics of the observed variable switches between a unit root regime and a stationary regime.
Extinction, stable pattern and their transition in a diffusive single species population with distributed maturity
Authors: WENG PEIXUAN
Published: April 2008

We consider a single-species structured population with distributed maturity and spatial diffusion in a cylindrical domain subject to Neumann and Robin boundary conditions. We first establish the threshold property of the reaction–diffusion system with distributed delay and non-local interaction in a corresponding lower-dimensional domain, so that the system approaches either an extinction state or a stable spatially varying pattern. We then investigate the transition from the extinction state to the stable pattern of the system in the cylindrical domain.
HUMAN CAPITAL ACCUMULATION AND THE TRANSITION FROM SPECIALIZATION TO MULTITASKING
Authors: BOUCEKKINE RAOUF , CRIFO PATRICIA
Published: April 2008

This paper provides theoretical foundations to the contemporaneous increase in computer usage, human capital, and multitasking observed in many OECD countries during the 1990s. The links among work organization, technology, and human capital is modelled by establishing the conditions under which firms allocate the workers' time among several productive tasks. Organizational change is then analyzed in a dynamic perspective as the transition from specialization toward multitasking emphasizing its technological and educational determinants. We show that large enough “organizational shocks” can trigger a transition from specialization to multitasking, and this transition obviously should be accompanied by gradual increases in human capital.
LÉVY-STABLE PRODUCTIVITY SHOCKS
Authors: GAFFEO EDOARDO
Published: April 2008

In this paper, we analyze the distribution of TFP growth rates at the four-digit sectoral level for the United States. We find that, contrary to the usual assumption employed in the literature on business cycles theory, technological shocks are not normally distributed. Instead, a Lévy-stable distribution with a divergent variance returns a better fit to the data.
Relationship between BMI and blood pressure in girls and boys
Authors: Gundogdu Zuhal
Published: April 2008

Aim

To investigate the relationship between BMI and blood pressure as this is of crucial interest in evaluating both public health and the clinical impact of the so-called obesity epidemic.

Methods

Data were gathered from 1899 children aged between 6 and 14 years, analysing and evaluating a possible relationship between BMI and systolic and diastolic blood pressure values for both girls and boys. Each child was classified on the basis of age- and sex-specific BMI percentile as normal weight (<85th percentile), overweight (≥85th and <95th percentile) or obese (≥95th percentile).

Results

In comparisons among age–sex–BMI percentile groups, systolic and diastolic blood pressure values were higher in obese and overweight groups than in normal weight groups for both sexes. Although BMI among girls was higher than among boys in all three percentile groups, there were no significant differences between sexes with respect to blood pressure values.

Conclusion

The present findings emphasize the importance of the prevention of obesity in order to prevent future related problems such as hypertension in children and adolescents.
Site‐Specific Linking of Biomolecules via Glycan Residues Using Glycosyltransferases
Authors: Qasba Pradman K. , Boeggeman Elizabeth , Ramakrishnan Boopathy
Published: April 2008

The structural information on glycosyltransferases has revealed that the sugar‐donor specificity of these enzymes can be broadened to include modified sugars with a chemical handle that can be utilized for conjugation chemistry. Substitution of Tyr289 to Leu in the catalytic pocket of bovine β‐1,4‐galactosyltransferase generates a novel glycosyltransferase that can transfer not only Gal but also GalNAc or a C2‐modified galactose that has a chemical handle, from the corresponding UDP‐derivatives, to the non‐reducing end GlcNAc residue of a glycoconjugate. Similarly, the wild‐type polypeptide‐ N‐acetyl‐galactosaminyltransferase, which naturally transfers GalNAc from UDP‐GalNAc, can also transfer C2‐modified galactose with a chemical handle from its UDP‐derivative to the Ser/Thr residue of a polypeptide acceptor substrate that is tagged as a fusion peptide to a non‐glycoprotein. The potential of wild‐type and mutant glycosyltransferases to produce glycoconjugates carrying sugar moieties with chemical handle makes it possible to conjugate biomolecules with orthogonal reacting groups at specific sites. This methodology assists in the assembly of bio‐nanoparticles that are useful for developing targeted drug‐delivery systems and contrast agents for magnetic resonance imaging.
Advances in Cell Culture Process Development: Tools and Techniques for Improving Cell Line Development and Process Optimization
Authors: Sharfstein Susan T.
Published: April 2008

At the 234th National Meeting of the American Chemical Society, held in Boston, MA, August 19–23, 2007, the ACS BIOT division held two oral sessions on Cell Culture Process Development. In addition, a number of posters were presented in this area. The critical issues facing cell culture process development today are how to effectively respond to the increase in product demands and decreased process timelines while maintaining robust process performance and product quality and responding to the Quality by Design initiative promulgated by the Food and Drug Administration. Two main areas were addressed in the presentations: first, to understand the effects of process conditions on productivity and product quality, and second, to achieve improved production cell lines. A variety of techniques to achieve these goals were presented, including automated flow cytometric analysis, a high‐throughput cell analysis and selection method, transcriptional and epigenetic techniques for analysis of cell lines and cell culture systems, and novel techniques for glycoform analysis.
Banded tremor at Miyakejima volcano, Japan: Implication for two‐phase flow instability
Authors: Fujita Eisuke
Published: April 2008

Volcanic tremor was recorded during a period of volcanic gas emission from Miyakejima volcano activity from 2001 to 2006. Similar to volcanic earthquakes and long‐period events, the source of banded tremor lies at a shallow depth beneath the summit caldera. Tremor packets occurred every 20 to 45 min for 1 to 2 days. We modeled the source of this phenomenon with a two‐phase hydrothermal instability flow model, consisting of subcool and superheated water regions, and found two modes, an excursion mode and a series of damping oscillations mode. The interval between banded tremor packets can be interpreted in terms of this two‐phase flow oscillation with a heat supply in the order of 10–100 MW from the magma beneath the hydrothermal system.
Subpolar Mode Water in the northeastern Atlantic: 2. Origin and transformation
Authors: Brambilla Elena , Talley Lynne D. , Robbins Paul E.
Published: April 2008

The processes that lead to the transformation and origin of the eastern North Atlantic Subpolar Mode Waters (SPMW) are investigated from observational data using an extended Walin framework. Air‐sea flux data from the National Oceanography Center, Southampton (NOCS), and hydrographic data from the A24 cruise collected during the World Ocean Circulation Experiment (WOCE) are used to estimate the contribution of diapycnal and isopycnal fluxes to the density classes that include SPMW. Surface diapycnal volume flux is the dominant source of waters in the SPMW density. In the North Atlantic subpolar gyre the diapycnal volume flux occurs along the main branches of the North Atlantic Current (NAC) and it has an average transport of 14 ± 6.5 Sv, with a maximum of 21.5 Sv across the 27.35σθ isopycnal. The regional distribution of the diapycnal flux on isopycnal surfaces is computed to identify the areas with the largest diapycnal flux. These regions coincide with the location of SPMW based on potential vorticity. The surface diapycnal flux is associated with obduction and subduction through the permanent pycnocline. Therefore, the water involved in the transformation of SPMWs is continuously exchanged with the ocean interior. In addition, we suggest that subduction is not associated with smooth advection from the mixed layer to the ocean interior, but is water mass loss entrainment into the deep overflows of the subpolar gyre. The isopycnal component of the SPMW throughput is estimated from the geostrophic transport across the A24 section from Greenland to Scotland and is 10% to 40% of the diapycnal flux.
Simulation‐based optimization of dual‐phase vacuum extraction to remove nonaqueous phase liquids in subsurface
Authors: Qin X. S. , Huang G. H. , Zeng G. M. , Chakma A.
Published: April 2008

An integrated simulation‐optimization system was developed for supporting decisions of the dual phase vacuum extraction (DPVE) processes. The system coupled a DPVE process simulator, a multivariate regression tool and a nonlinear optimization model into a general framework. A stepwise‐cluster‐analysis technique was provided for establishing a DPVE process forecasting system for describing the relationships between remediation actions and system responses (i.e., total extracted volume of oil/water, elevation distribution of water table, and specific volume of oil). The forecasting system was then embedded into a multiobjective optimization framework, where the objectives were to minimize the operation cost and maximize the remediation efficiency. The constraints include environmental, hydraulic and technical restrictions to the DPVE processes. A case study was conducted for a petroleum‐contaminated site in western Canada. The results from the stepwise cluster analysis indicated that the generated cluster trees could be used for predicting system responses of the DPVE process, given inputs of the operating conditions. The prediction accuracies of the generated cluster trees were verified using randomly generated data sets. The optimum operating conditions could vary significantly under different cost‐efficiency targets. When a stricter environmental target (i.e., the amount of pollutants in subsurface) was concerned, a higher system cost had to be paid; when the cost became a critical factor, the performance of contaminant removal would have to be compromised. The developed system could be used to analyze tradeoffs between system cost and process efficiency in the DPVE operations; it could also support the formulation of an on‐site process‐control system with vacuum levels and extraction rates being the main control variables.
Recent investigations of the 0–5 Ma geomagnetic field recorded by lava flows
Authors: Johnson C. L. , Constable C. G. , Tauxe L. , Barendregt R. , Brown L. L. , Coe R. S. , Layer P. , Mejia V. , Opdyke N. D. , Singer B. S. , Staudigel H. , Stone D. B.
Published: April 2008

We present a synthesis of 0–5 Ma paleomagnetic directional data collected from 17 different locations under the collaborative Time Averaged geomagnetic Field Initiative (TAFI). When combined with regional compilations from the northwest United States, the southwest United States, Japan, New Zealand, Hawaii, Mexico, South Pacific, and the Indian Ocean, a data set of over 2000 sites with high quality, stable polarity, and declination and inclination measurements is obtained. This is a more than sevenfold increase over similar quality data in the existing Paleosecular Variation of Recent Lavas (PSVRL) data set, and has greatly improved spatial sampling. The new data set spans 78°S to 53°N, and has sufficient temporal and spatial sampling to allow characterization of latitudinal variations in the time‐averaged field (TAF) and paleosecular variation (PSV) for the Brunhes and Matuyama chrons, and for the 0–5 Ma interval combined. The Brunhes and Matuyama chrons exhibit different TAF geometries, notably smaller departures from a geocentric axial dipole field during the Brunhes, consistent with higher dipole strength observed from paleointensity data. Geographical variations in PSV are also different for the Brunhes and Matuyama. Given the high quality of our data set, polarity asymmetries in PSV and the TAF cannot be attributed to viscous overprints, but suggest different underlying field behavior, perhaps related to the influence of long‐lived core‐mantle boundary conditions on core flow. PSV, as measured by dispersion of virtual geomagnetic poles, shows less latitudinal variation than predicted by current statistical PSV models, or by previous data sets. In particular, the Brunhes data reported here are compatible with a wide range of models, from those that predict constant dispersion as a function of latitude to those that predict an increase in dispersion with latitude. Discriminating among such models could be helped by increased numbers of low‐latitude data and new high northern latitude sites. Tests with other data sets, and with simulations, indicate that some of the latitudinal signature previously observed in VGP dispersion can be attributed to the inclusion of low‐quality, insufficiently cleaned data with too few samples per site. Our Matuyama data show a stronger dependence of dispersion on latitude than the Brunhes data. The TAF is examined using the variation of inclination anomaly with latitude. Best fit two‐parameter models have axial quadrupole contributions of 2–4% of the axial dipole term, and axial octupole contributions of 1–5%. Approximately 2% of the octupole signature is likely the result of bias incurred by averaging unit vectors.
MILAMIN: MATLAB‐based finite element method solver for large problems
Authors: Dabrowski M. , Krotkiewski M. , Schmid D. W.
Published: April 2008

The finite element method (FEM) combined with unstructured meshes forms an elegant and versatile approach capable of dealing with the complexities of problems in Earth science. Practical applications often require high‐resolution models that necessitate advanced computational strategies. We therefore developed “Million a Minute” (MILAMIN), an efficient MATLAB implementation of FEM that is capable of setting up, solving, and postprocessing two‐dimensional problems with one million unknowns in one minute on a modern desktop computer. MILAMIN allows the user to achieve numerical resolutions that are necessary to resolve the heterogeneous nature of geological materials. In this paper we provide the technical knowledge required to develop such models without the need to buy a commercial FEM package, programming compiler‐language code, or hiring a computer specialist. It has been our special aim that all the components of MILAMIN perform efficiently, individually and as a package. While some of the components rely on readily available routines, we develop others from scratch and make sure that all of them work together efficiently. One of the main technical focuses of this paper is the optimization of the global matrix computations. The performance bottlenecks of the standard FEM algorithm are analyzed. An alternative approach is developed that sustains high performance for any system size. Applied optimizations eliminate Basic Linear Algebra Subprograms (BLAS) drawbacks when multiplying small matrices, reduce operation count and memory requirements when dealing with symmetric matrices, and increase data transfer efficiency by maximizing cache reuse. Applying loop interchange allows us to use BLAS on large matrices. In order to avoid unnecessary data transfers between RAM and CPU cache we introduce loop blocking. The optimization techniques are useful in many areas as demonstrated with our MILAMIN applications for thermal and incompressible flow (Stokes) problems. We use these to provide performance comparisons to other open source as well as commercial packages and find that MILAMIN is among the best performing solutions, in terms of both speed and memory usage. The corresponding MATLAB source code for the entire MILAMIN, including input generation, FEM solver, and postprocessing, is available from the authors (http://www.milamin.org) and can be downloaded as auxiliary material.
GEOMAGIA50: An archeointensity database with PHP and MySQL
Authors: Korhonen K. , Donadini F. , Riisager P. , Pesonen L. J.
Published: April 2008

The GEOMAGIA50 database stores 3798 archeomagnetic and paleomagnetic intensity determinations dated to the past 50,000 years. It also stores details of the measurement setup for each determination, which are used for ranking the data according to prescribed reliability criteria. The ranking system aims to alleviate the data reliability problem inherent in this kind of data. GEOMAGIA50 is based on two popular open source technologies. The MySQL database management system is used for storing the data, whereas the functionality and user interface are provided by server‐side PHP scripts. This technical brief gives a detailed description of GEOMAGIA50 from a technical viewpoint.
Regional climate models downscaling analysis of general circulation models present climate biases propagation into future change projections
Authors: Liang Xin‐Zhong , Kunkel Kenneth E. , Meehl Gerald A. , Jones Richard G. , Wang Julian X. L.
Published: April 2008

A suite of eighteen simulations over the U.S. and Mexico, representing combinations of two mesoscale regional climate models (RCMs), two driving global general circulation models (GCMs), and the historical and four future anthropogenic forcings were intercompared. The RCMs' downscaling reduces significantly driving GCMs' present‐climate biases and narrows inter‐model differences in representing climate sensitivity and hence in simulating the present and future climates. Very high spatial pattern correlations of the RCM minus GCM differences in precipitation and surface temperature between the present and future climates indicate that major model present‐climate biases are systematically propagated into future‐climate projections at regional scales. The total impacts of the biases on trend projections also depend strongly on regions and cannot be linearly removed. The result suggests that the nested RCM‐GCM approach that offers skill enhancement in representing the present climate also likely provides higher credibility in downscaling the future climate projection.
Mode identification of whistler mode, Z‐mode, and Langmuir/Upper Hybrid mode waves observed in an auroral sounding rocket experiment
Authors: Colpitts C. A. , LaBelle J.
Published: April 2008

The SIERRA (Sounding of the Ion Energization Region – Resolving Ambiguities) rocket was launched to 735 km over an active auroral substorm from Poker Flat, Alaska, on 14 January 2002. A wealth of wave modes at frequencies from below 100 kHz to above 2000 kHz were detected with a dipole electric field antenna that was alternately parallel and perpendicular to Earth's magnetic field. At least two types of whistler mode waves were detected: unstructured broadband whistler waves commonly referred to as auroral hiss occurring at frequencies from <100 kHz up to 1000 kHz, and structured narrowband features in the whistler mode at frequencies of 100 kHz to 600 kHz (Samara and LaBelle, 2006a). Other waves detected in the frequency range 1200 to 2000 kHz were interpreted as Langmuir‐upper hybrid waves and Z‐mode waves. For the unstructured whistler mode waves, comparison of the observed spin dependence of the wave electric fields with Monte Carlo simulations of the expected spin dependence for various polarizations suggests that these waves propagate on or near the resonance cone, which is consistent with previous measurements. Similar analyses of the presumed Langmuir and Z‐mode waves show their electric fields are preferentially parallel and perpendicular to the ambient magnetic field, respectively. These characteristics, together with the relation of the wave frequencies to the Z cutoff frequency, serve to confirm the mode identification of these waves.
Nonlinear dynamics of foreshock structures: Application of nonlinear autoregressive moving average with exogenous inputs model to Cluster data
Authors: Zhu D. , Balikhin M. A. , Gedalin M. , Alleyne H. , Billings S. A. , Hobara Y. , Krasnosel'skikh V. , Dunlop M. W. , Ruderman M.
Published: April 2008

Nonlinear processes identification techniques based on multi‐input nonlinear autoregressive moving average with exogenous inputs model has been applied to four‐point Cluster measurements in order to study nonlinear processes that take place in the terrestrial foreshock. It is shown that both quadratic and cubic processes are involved in the evolution of shocklets in particular in the steepening of their leading edge and generation of whistler precursor. Nonlinear processes do not play an essential role in the dynamics and propagation of small‐amplitude whistler packets. However, for large‐amplitude wave packets, cubic processes lead to the considerable modification of apparent propagation velocity.
Electron scattering by whistler‐mode ELF hiss in plasmaspheric plumes
Authors: Summers Danny , Ni Binbin , Meredith Nigel P. , Horne Richard B. , Thorne Richard M. , Moldwin Mark B. , Anderson Roger R.
Published: April 2008

Nonadiabatic loss processes of radiation belt energetic electrons include precipitation loss to the atmosphere due to pitch‐angle scattering by various magnetospheric plasma wave modes. Here we consider electron precipitation loss due to pitch‐angle scattering by whistler‐mode ELF hiss in plasmaspheric plumes. Using wave observations and inferred plasma densities from the Plasma Wave Experiment on the Combined Release and Radiation Effects Satellite (CRRES), we analyze plume intervals for which well‐determined hiss spectral intensities are available. We then select 14 representative plumes for detailed study, comprising 10 duskside plumes and 4 nonduskside plumes, with local hiss amplitudes ranging from maximum values of above 300 pT to minimum values of less than 1 pT. We estimate the electron loss timescale τloss due to pitch‐angle scattering by hiss in each chosen plume as a function of L‐shell and electron energy; τloss is calculated from quasi‐linear theory as the inverse of the bounce‐averaged diffusion rate evaluated at the equatorial loss cone angle. We find that pitch‐angle scattering by hiss in plumes can be efficient for inducing precipitation loss of outer‐zone electrons with energies throughout the range 100 keV to 1 MeV, though the magnitude of τloss can be highly dependent on wave power, L‐shell, and electron energy. For 100‐ to 200‐keV electrons, typically τloss ∼ 1 day while the minimum loss timescale (τloss)min ∼ hours. For 500‐keV to 1‐MeV electrons, typically (τloss)min ∼ days, while (τloss)min < 1 day in the case of large wave amplitude (∼100's pT). Apart from inducing direct precipitation loss of MeV electrons, scattering by hiss in plumes may reduce the generation of MeV electrons by depleting the lower energy electron seed population. Models of the dynamical variation of the outer‐zone electron flux should incorporate electron precipitation loss induced by ELF hiss scattering in plasmaspheric plumes.
Evidence for significantly greater N2 Lyman‐Birge‐Hopfield emission efficiencies in proton versus electron aurora based on analysis of coincident DMSP SSUSI and SSJ/5 data
Authors: Knight H. K. , Strickland D. J. , Hecht J. H. , Straus P. R. , Morrison D. , Paxton L. J. , Evans D. S.
Published: April 2008

The launch of the Defense Meteorological Satellite Program (DMSP) satellite F16 in 2003 provided the first opportunity to analyze extensive sets of high‐quality coincident auroral particle and FUV data obtained by the onboard sensors Special Sensor Ultraviolet Spectrographic Imager (SSUSI) and Special Sensor Auroral Particle Sensor (SSJ/5). Features of interest are Ly α (121.6 nm), Lyman‐Birge‐Hopfield short (LBHS, the SSUSI 140–150 nm channel), and Lyman‐Birge‐Hopfield long (LBHL, 165–180 nm). We report on comparisons of column emission rates (CERs) by deriving simulated SSUSI values using SSJ/5 electron and ion (treated as proton) spectra. Field‐line tracing is performed to determine the locations of coincidences. CERs are obtained by integrating the products of particle spectra and monoenergetic emission yields. A technique is reported for deriving these yields from nonmonoenergetic CERs obtained by our particle transport model. SSJ/5 ion spectra are extrapolated above 30 keV using a statistical representation based on Polar Orbiting Environmental Satellites particle data. Key quantities of interest are ratios of SSUSI to SSJ/5‐based CERs (S‐S ratios) and corresponding ratios of proton‐produced to total emission (unity for Ly α and from 0 to 1 for LBHS and LBHL). SSJ/5‐based CERs are used to derive the latter ratios. Median ratio values are determined in order to reduce the error budget to primarily calibration and model errors. The median LBH S‐S ratios increase by a factor of ∼2.5 from electron to proton aurora and support significantly higher proton LBH emission efficiencies (3 times the electron efficiencies) assuming reported calibration uncertainties. This calls for significant increases in proton and/or H‐atom LBH cross sections. In turn, FUV auroral remote‐sensing algorithms must explicitly address both electron and proton aurora.
Conditions for a crustal block to be sheared off from the subducted continental lithosphere: What is an essential factor to cause features associated with collision?
Authors: Seno Tetsuzo
Published: April 2008

Crustal blocks are detached from the subducting lithosphere at various depths. I call such phenomena shearing‐off and investigate the mechanical conditions for shearing‐off to occur in the continental lithosphere. The buoyancy of the crustal block does not work selectively as a driving force until it has been sheared off and I suppose that shearing‐off occurs when the shear traction at the thrust, whose maximum value is calculated from the strength along the thrust, overcomes the strength of the boundary faults of the block, and determine the depth of the leading edge of the subducted crustal block when shearing‐off occurs. The temperatures of the slab and at its surface are calculated by the steady state formula of Molnar and England (1990) as a function of the surface heat flow, dip angle, and convergence velocity of the subducted continental plate, as the shear stress and temperature at the ductile part of the thrust zone are consistent with the flow law. The shear stress at the brittle part is a strong function of the pore fluid pressure ratio λ. I show that shearing‐off of an upper crustal block is possible only for a small value of λ such as <∼0.4 when the surface heat flow value is <∼70 mW/m2. I suggest that the essential factor to cause shallow offscraping of crustal blocks in collision zones, is not a buoyancy of the continental crust, but a low value of λ, which would result from a little amount of dehydration from the subducted continental plate.
Identification of seismic precursors before large earthquakes: Decelerating and accelerating seismic patterns
Authors: Papadimitriou Panayotis
Published: April 2008

A useful way of understanding both seismotectonic processes and earthquake prediction research is to conceive seismic patterns as a function of space and time. The present work investigates seismic precursors before the occurrence of an earthquake. It does so by means of a methodology designed to study spatiotemporal characteristics of seismicity in a selected area. This methodology is based on two phenomena: the decelerating moment release (DMR) and the accelerating moment release (AMR), as they occur within a period ranging from several months to a few years before the oncoming event. The combination of these two seismic sequences leads to the proposed decelerating‐accelerating moment release (DAMR) earthquake sequence, which appears as the last stage of loading in the earthquake cycle. This seismic activity appears as a foreshock sequence and can be supported by the stress accumulation model (SAM). The DAMR earthquake sequence constitutes a double seismic precursor identified in space and time before the occurrence of an earthquake and can be used to improve seismic hazard assessment research. In this study, the developed methodology is applied to the data of the 1989 Loma Prieta (California), the 1995 Kobe (Japan), and the 2003 Lefkada (Greece) earthquakes. The last part of this study focuses on the application of the methodology to the Ionian Sea (western Greece) and forecasts two earthquakes in that area.
In situ Raman spectroscopic investigation of the structure of subduction‐zone fluids
Authors: Mibe Kenji , Chou I‐Ming , Bassett William A.
Published: April 2008

In situ Raman spectra of synthetic subduction‐zone fluids (KAlSi3O8−H2O system) were measured to 900°C and 2.3 GPa using a hydrothermal diamond‐anvil cell. The structures of aqueous fluid and hydrous melt become closer when conditions approach the second critical endpoint. Almost no three‐dimensional network was observed in the supercritical fluid above 2 GPa although a large amount of silicate component is dissolved, suggesting that the physical and chemical properties of these phases change drastically at around the second critical endpoint. Our experimental results indicate that the fluids released from a subducting slab change from aqueous fluid to supercritical fluid with increasing depth under the volcanic arcs.
Radiative fluxes from satellites: Focus on aerosols
Authors: Liu Hongqing , Pinker R. T.
Published: April 2008

An existing scheme to derive radiative fluxes from satellite observations has been modified so it can incorporate more detailed information on aerosol properties at a global scale. In this paper we describe the modifications introduced and the experiments performed to learn how to optimally use the new information with available global‐scale satellite data, and we evaluate the impact of the new information and scheme on the accuracy of the satellite‐based estimates of surface fluxes by comparison with ground observations of highest available quality. Specifically, we incorporate a spectral variation of intensive aerosol properties, identify an optimal procedure of coupling aerosol information with satellite observations, and demonstrate improvements achieved in inferring surface fluxes.
Determination of the intrinsic frequency and other wave parameters from a single vertical temperature or density profile measurement
Authors: Gubenko Vladimir N. , Pavelyev Alexander G. , Andreev Vitali E.
Published: April 2008

In order to examine internal gravity wave characteristics we have analyzed small‐scale fluctuations of normalized temperature in the Earth's stratosphere using radio occultation data. An analysis to identify the observed fluctuations as wave‐induced, assuming gravity wave shear saturation, is proposed. This technique is based upon a comparison of the experimental and theoretical values of the relative amplitude threshold which is defined as the wave amplitude required for shear instability. The theoretical amplitude threshold, assuming a minimum Richardson number of 1/4, is a function of f/ω, where f and ω are inertial and intrinsic frequencies, correspondingly. The theoretical threshold values are confined from zero to unity. In the case when this criterion is satisfied for its experimental counterpart and the analyzed fluctuations are positively identified as wave‐induced, then the intrinsic frequency of the monochromatic gravity wave can be determined from only a single vertical temperature (or density) profile measurement. The results of the determination of the intrinsic frequency and other characteristics of internal gravity waves are presented and discussed.
Investigation of stability characteristics of cold‐season convective precipitation events by utilizing the growth rate parameter
Authors: Melick Christopher J. , Market Patrick S. , Smith Larry L. , Pettegrew Brian P. , Becker Amy E. , Lupo Anthony R.
Published: April 2008

The seldom utilized growth rate parameter (σ2), which predicts how rapidly a small‐amplitude disturbance will grow in a conditional symmetrically unstable environment, was applied to study the stability characteristics of convective precipitation case studies across the central United States during the winter seasons of 2003–2004 and 2004–2005. The goals were to improve our understanding of how the environment becomes destabilized over a relatively short period of time, as well as to determine approximately where and when elevated thunderstorms are likely to develop. The comprehensive evaluation comprised a case study example and summary of statistics obtained by tabulations at the initiation site and spatial compositing of all case studies identified. The doubling time for the convection (the time required for a convective element to achieve twice its current depth) was found to be on the order of 1.3 h, which is consistent with the typical timescale for moist slantwise convection resulting from the release of conditional symmetric instability. The development of cold‐season precipitation with lightning (i.e., thundersnow) and any associated banding was correctly and most accurately predicted from trends in plots of σ2 analyzed at the level at which the highest significant growth rates occurred. While this naturally varied from one event to the next, the average elevation tended to be close to 650 hPa. Furthermore, a term‐by‐term diagnosis of the mathematical expression for the growth rate was determined to be quite useful as another means of identifying the type of instability released within instances of wintertime convection. By calculating the individual contributions to the growth rate and observing whether a positive or negative response was obtained, the nature of the stability regime present was also ascertained. The inclusion of a set of non‐thundering snowstorms helped to substantiate the assumption that atmospheres are less stable and more susceptible to vertical motions during those occasions where lightning develops in wintertime scenarios. Thus an outlook for elevated, cold‐season thunderstorms can be more accurately issued by identifying regions where reduced values of equivalent potential vorticity (i.e., small symmetric stability or instability) are collocated with estimates of high σ2 (i.e., where small‐scale slantwise perturbations will grow). Given the overall success, it is hoped that some of the conclusions established by this work will be implemented routinely in an operational environment and provide forecasters an additional, essential tool in dealing with nowcasting situations of hazardous winter weather events.
A comparison of polar mesosphere summer echo at VHF (224 MHz) and UHF (930 MHz) and the effects of artificial electron heating
Authors: Næsheim L. I. , Havnes O. , La Hoz C.
Published: April 2008

A polar mesosphere summer echo (PMSE) campaign with a VHF radar at 224 MHz and UHF radar at 930 MHz was carried out from 30 June to 15 July 2004 at the European Incoherent Scatter (EISCAT) radar facility near Tromsø, Norway. The EISCAT Heating facility was used to produce electron heating with the aim to investigate the effects it produces on PMSE, particularly the overshoot phenomenon. A total of 59 and 28 h of observations were gathered with the VHF and UHF radars, respectively. In this study we concentrate on the 8 d when PMSE was simultaneously looked for with both radars. The occurrence rate over the observation period was 95% for the VHF radar, which is exceptionally large, and 11% for the UHF radar, which observed PMSE on parts of 4 d, always in coincidence with VHF PMSE. On all occasions, the altitude of maximum intensity of the UHF PMSE coincided with the maximum of the VHF PMSE, although it is possible that the maximum of the UHF layer could be slightly below that of the VHF layer. The effects of the heating in reducing the PMSE strength as it was switched on, and a subsequent overshoot effect as it was switched off, were clearly present in both VHF and UHF on only 2 of the 4 d where UHF and VHF PMSE were observed simultaneously. The effects of the heating were identical on the data from both radars. The absence of heating on the other 2 d is connected to the level of electron density which controls the occurrence of the overshoot effect, the latter being stronger when the electron density is lower, in agreement with greater electron heating taking place when the electron density is smaller at the altitude of the PMSE layers and below them. Since all the properties of PMSE that we have extracted from the measurements were identical for both radar wavelengths, we conclude that there is most likely only one mechanism active in creating PMSE at all radar wavelengths.
Effects of aerosol optical properties on deep convective clouds and radiative forcing
Authors: Fan Jiwen , Zhang Renyi , Tao Wei‐Kuo , Mohr Karen I.
Published: April 2008

The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral‐bin cloud‐resolving model coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single‐scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid‐visible SSA of 0.85. Relative to the case without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6 K day−1 higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime‐mean direct forcing induced by black carbon is about 2.2 W m−2 at the top of atmosphere (TOA) and −17.4 W m−2 at the surface for SSA of 0.85. The semi‐direct forcing is positive, about 10 and 11.2 W m−2 at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi‐direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi‐direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.