bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heads and tails: 30 million years of the Afar plume
Authors: Furman T. , Bryce J. , Rooney T. , Hanan B. , Yirgu G. , Ayalew D. 
Published: September 2007

Abstract

Primitive recent mafic lavas from the Main Ethiopian Rift provide insight into the structure, composition and long-term history of the Afar plume. Modern rift basalts are mildly alkalic in composition, and were derived by moderate degrees of melting of fertile peridotite at depths corresponding to the base of the modern lithosphere (
c.
100 km). They are typically more silica-undersaturated than Oligocene lavas from the Ethiopia-Yemen continental flood basalt province, indicating derivation by generally smaller degrees of melting than were prevalent during the onset of plume head activity in this region. Major and trace element differences between the Oligocene and modern suites can be interpreted in terms of melting processes, including melt-induced binary mixing of melts from the Afar plume and those from three mantle end-member compositions (the convecting upper mantle and two enriched mantle sources). The Afar plume composition itself has remained essentially constant over the past 30 million years, indicating that the plume is a long-lived feature of the mantle. The geochemical and isotopic compositions of mafic lavas derived from the Afar plume support a modified single plume model in which multiple plume stems rise from a common large plume originating at great depth in the mantle (i.e. the South African superplume).
Temporal compositional variation of syn-rift rhyolites along the western margin of the southern Red Sea and northern Main Ethiopian Rift
Authors: Ayalew D. , Ebinger C. , Bourdon E. , Wolfenden E. , Yirgu G. , Grassineau N. 
Published: September 2007

Abstract

Structural and geochronological relations indicate that the felsic rocks at the top of the Oligocene flood basalt sequences in the Afar volcanic province were erupted coevally with the initial rifting in the Red Sea and Gulf of Aden. In this study, we use the newly established volcanic-tectonic history to examine the geochemical evolution with time of felsic volcanics as rifting has progressed to seafloor spreading in the southern Red Sea and northern Main Ethiopian Rift. Geochemical analyses (major and trace elements; Sr, Nd and O isotopic compositions) of syn-rift rhyolites ranging in age from 28 to 2.5 Ma indicate that the rhyolites can be derived from mantle-sourced basaltic magma through fractional crystallization accompanied by variable amounts of crustal contamination (e.g.
87
Sr/
86
Sr = 0.70489−0.70651;
143
Nd/
144
Nd = 0.51254−0.51283; δ
18
O = +4.5 to +6.4‰). The input of crust tends to increase with time, which suggests the weakening and heating of the crust in response to lithospheric thinning and magma injection in the past
c.
30 Ma. These results support earlier structural and thermomechanical models for rift formation in the southern Red Sea rift and the younger, less-evolved northern Main Ethiopian Rift system.
New evidence for Afro-Arabian plate separation in southern Afar
Authors: Ayele Atalay , Nyblade Andrew A. , Langston Charles A. , Cara Michel , Leveque Jean-J. 
Published: September 2007

Abstract
The May 2000 earthquake cluster, around 10° N and 41° E in southern Afar, has been studied using high quality data from 12 temporary and permanent broadband seismic stations deployed in the area. 140 earthquakes have been located using P- and S-wave arrival times, a well-constrained velocity model, and a double-difference location algorithm. Source mechanisms and moment magnitudes for the four largest events (M > 4) have been obtained from moment tensor inversion. There is no clear alignment of the epicentres along a fault zone; however, the events are clustered slightly southeast of Mount Amoissa along WNW-ESE extension of the Ayelu-Amoissa (Abida/Dabita) lineament. Focal mechanisms show fault motion along WNW-ESE to east-west striking normal faults, with extension oblique to the orientation of the Main Ethiopian Rift. The non-double-couple components of the source mechanisms range from 18–25%, suggesting that the seismic activity is of tectonic origin and not volcanic. Source depths are ≤7 km, in good agreement with estimates of the elastic thickness of the Afar lithosphere. We suggest that the Gewane earthquake swarm represents remnant strain accommodation along a previous line of weakness in southern Afar related to the separation of Arabia from Africa because the focal mechanisms show north-south extension similar to many of the events in central Afar at the triple junction where Arabia is presently rifting away from Africa.
The Wonji fault belt (Main Ethiopian Rift): structural and geomorphological constraints and GPS monitoring
Authors: Pizzi Alberto , Coltorti Mauro , Abebe Bekele , Disperati Leonardo , Sacchi Giorgio , Salvini Riccardo 
Published: September 2007

Abstract

The Wonji Fault Belt (WFB), Main Ethiopian Rift, forms a network of faults oriented NNE-SSW with a Quaternary direction of extension oriented
c
. N95° E. Faults are spaced between 0.5 and 2 km, show a fresh steep scarp, recent activity and slip rates of up to 2.0 mm a
−1
. This high value of deformation along the rift floor with respect to the plate separation rates suggests that most of the active strain could be accommodated by magma-induced faulting within the rift. However, the mountain front morphology associated with a displacement of 300–400 m since the Middle Pleistocene, tilted-blocks, brittle-seismic fault rock fabric and historical earthquakes with
M
>6 support a tectonic origin of the Asela boundary fault. Therefore, we propose a model that considers the possible coexistence of both magmatic deformation at the rift floor and brittle faulting at the rift margin. We also report the data relative to a GPS network installed in December 2004, along two transects across the WFB, between Asela and the Ziway Lake.
Magnetic Separation Research: A Survey of Some Activitiesin The Netherlands
Authors: Kerkdijk C. B. W. , van Kleef R. P. A. R. , Roeterdink J. A. 
Published: September 2007

A survey of magnetic separation research at FDO
Engineering consultants, the University of Nijmegen, and
the Energy Research Foundation (ECN) will be given.FDO efforts were primarily on coal cleaning using the high
gradient magnetic separation (HGMS) technique.
The Institute for Materials of the University of Nijmegen
performs fundamental studies on magnetic flocculation. A
continuous flow magnetic separator is briefly described.
The Energy Research Foundation has built and operates an
HGMS–system with superconducting magnets. Auxiliary
equipment enables the execution of well controlled HGMS
pilot scale tests.Intensive contacts and cooperation exist between scientists
of the 3 research organisations, and with other industries
which are interested in magnetic separation applications.
Magnetic Characterization of Sulphide Ores: Examples From Sweden
Authors: Jirestig J. , Forssberg E. 
Published: September 2007

Diagrams of accumulativemagnetic susceptibility distribution are
used to evaluate the suitability of four sulphide ores for magnetic methods of
beneficiation. The investigated materials are Garpenberg, Aitik and
Kedtrask. The samples were divided into susceptibility classes each of which
was characterized by its mineral content. The results are presented as
diagrams showing mineral appearance in the whole susceptibility range of
the ore. The obtained accumulative susceptibility diagrams can be used to
predict the outcome of magnetic separation.The accumulative susceptibility diagrams indicate that the Garpenberg and
possibly the Kedtrask materials are suited for magnetic separation, possibly
as the primary concentration method. The other investigated materials
contain iron‐bearing silicates magnetic susceptibility of which is higher than
that of valuable mineral and will thus report into the magnetic product
making further separation necessary.
Application of Magstream in Mineral Sands Separation
Authors: Kojovic T. 
Published: September 2007

The Magstream separation process, developed by Intermagnetics
General corporation, offers an alternative method for both laboratory and
plant mineral separations. It is based on the concept of using a fluid whose
effective density is magnetically derived. The separator can be applied to
both purely gravimetric separation of non–magnetic materials and
magnetic–gravimetric separation of paramagnetic material.The separation density can be easily adjusted by changing the speed of
rotation or process fluid concentration. A separation band can be drawn on
a plot of particle density and magnetic susceptibility to illustrate the
separation of particles that would be achieved. The process fluid is a
non–toxic, water–based bio–degradable magnetic fluid, and relatively
inexpensive compared to heavy liquids and sodium polytungstates.The Model 100 separator available at the Julius Kruttschnitt Mineral
Research Centre is portable and suitable for analysing small batch samples.
The separator selectivity is at best ± 0.1 SG units, which may cause a lower
grade of products in separations of materials with a small SG differential.The separator has been evaluated for mineral sands applications. Several
good applications of Magstream have been identified. Particularly effective
separations were quartz/heavy mineral concentrate, kyanite/zircon,
monazite/zircon and rutile/zircon (multiple passes required).This paper describes the Magstream process, operation, the mathematical
model of separation, and presents the results of the separation case studies
in detail.
The Effect of Irrigation With MagneticallyTreated Water on The Translocation ofMinerals in The Soil
Authors: Noran Rami , Shani Uri , Lin Israel 
Published: September 2007

Magnetically treated water (MTW) is water passed through a
magnetic field before being used. Applications of MTW are abundant in
industry where it is used to prevent scaling on inner walls of pipes
conveying fluids, especially water. In recent years scientists investigating
the subject have concluded that the magnetic field interacts with the
surface charges of particles in the fluid solutions affecting the crystallisation
and precipitation of the solids in them. These processes are of significant
effect on the translocation of minerals in irrigated soil.In this work the concentrations of K, N, P, Na and Ca+Mg, as well as the
total mineral content in the MTW—irrigated soil were compared with the
same data in soil irrigated with ordinary water. The soil was sampled at
three different locations at three different distances from the dripper line,
representing three different leaching states of the soil. Differences in
concentrations were found in at least one of the three locations with
respect to each mineral and including the total mineral content. Most of
the differences appeared in the less leached parts of the soil, in the bed
margin. It appears that there is a general tendency of minerals to
precipitate out of the solution faster in MTW conditions.
Electrical Separation of Metals From Mineral Wastes Using Gradient Forces
Authors: Lungu Mihail , Schlett Zeno 
Published: September 2007

This paper presents a method for recovery nonferromagnetic components
(Au, Ag) in reduced concentration from mineral wastes, using gradient forces.
First the main up‐to‐date electrical dry separation techniques for recovery
useful materials from wastes are presented which are based on different electrical
properties of the waste components.Then, the main theoretical considerations reffering to electric gradient forces
(typical for nonuniform fields) are presented. The theory shows how these
forces together with other forces act on the particles of a mixture subjected
to the separation process. Owing to combined actions of all these forces a
superficial layer is obtained, consisting in metallic particles concentrated on
the surface of mixture. Finally, the experimental results are presented, based
on chemical analysis of the obtained superficial layer.
Dynamics of Eddy-Driven Low-Frequency Dipole Modes. Part III: Meridional Displacement of Westerly Jet Anomalies during Two Phases of NAO
Authors: Luo Dehai , Gong Tingting , Diao Yina 
Published: September 2007

Abstract
In this paper, the north–south variability of westerly jet anomalies during the two phases of the North Atlantic Oscillation (NAO) is examined in a theoretical model. It is found that the north–south variability of the zonal mean westerly anomaly results from the interaction between the eddy-driven anomalous stationary waves with a dipole meridional structure (NAO anomalies) and topographically induced climatological stationary waves with a monopole structure, which is dependent upon the phase of the NAO. The westerly jet anomaly tends to shift northward during the positive NAO phase but southward during the negative phase. Synoptic-scale eddies tend to maintain westerly jet anomalies through the excitation of NAO anomalies, but the climatological stationary wave and its position relative to the eddy-driven anomalous stationary wave appear to dominate the north–south shift of westerly jet anomalies.
On the other hand, it is shown that when the climatological stationary wave ridge is located downstream of the eddy-driven anomalous stationary wave, the storm track modulated by the NAO pattern splits into two branches for the negative phase, in which the northern branch is generally stronger than the southern one. However, the southern one can be dominant as the relative position between anomalous and climatological stationary waves is within a moderate range. The storm track for the positive phase tends to drift northeastward when there is a phase difference between the NAO anomaly and climatological stationary wave ridge downstream. Thus, it appears that the relationship between the NAO jets and storm tracks can be clearly seen from the present theoretical model.
Observations of Freezing Drizzle in Extratropical Cyclonic Storms during IMPROVE-2
Authors: Ikeda Kyoko , Rasmussen Roy M. , Hall William D. , Thompson Gregory 
Published: September 2007

Abstract
Observations of supercooled drizzle aloft within two storms impacting the Oregon Cascades during the second Improvement of Microphysical Parameterization through Observational Verification Experiment (IMPROVE-2) field project are presented. The storms were characterized by a structure and evolution similar to the split-front model of synoptic storms. Both storms were also characterized by strong cross-barrier flow. An analysis of aircraft and radar data indicated the presence of supercooled drizzle during two distinct storm periods: 1) the intrafrontal period immediately following the passage of an upper cold front and 2) the postfrontal period. The conditions associated with these regions of supercooled drizzle included 1) temperatures between −3° and −19°C, 2) ice crystal concentrations between 1 and 2 L−1, and 3) bimodal cloud droplet distributions of low concentration [cloud condensation nuclei (CCN) concentration between 20 and 30 cm−3 and cloud drop concentration &lt;35 cm−3].
Unique to this study was the relatively cold cloud top (&lt;−15°C) and relatively high ice crystal concentrations in the drizzle region. These conditions typically hinder drizzle formation and survival; however, the strong flow over the mountain barrier amplified vertical motions (up to 2 m s−1) above local ridges, the mountain crest, and updrafts in embedded convection. These vertical motions produced high condensate supply rates that were able to overcome the depletion by the higher ice crystal concentrations. Additionally, the relatively high vertical motions resulted in a near balance of ice crystal fall speed (0.5–1.0 m s−1), leading to nearly terrain-parallel trajectories of the ice particles and a reduction of the flux of ice crystals from the higher levels into the low-level moisture-rich cloud, allowing the low-level cloud water and drizzle to be relatively undepleted.
One of the key observations in the current storms was the persistence of drizzle drops in the presence of significant amounts of ice crystals over the steepest portion of the mountain crest. Despite the high radar reflectivity produced by the ice crystals (&gt;15 dBZ) in this region, the relatively high condensate supply rate led to hazardous icing conditions. The current study reveals that vertical motions generated by local topographic features are critical in precipitation processes such as drizzle formation and thus it is essential that microphysical models predict these motions.
Two-Layer Baroclinic Eddy Heat Fluxes: Zonal Flows and Energy Balance
Authors: Thompson Andrew F. , Young William R. 
Published: September 2007

Abstract
The eddy heat flux generated by statistically equilibrated baroclinic turbulence supported on a uniform, horizontal temperature gradient is examined using a two-layer β-plane quasigeostrophic model. The dependence of the eddy diffusivity of temperature, Dτ, on external parameters such as β, bottom friction κ, the deformation radius λ, and the velocity jump 2U, is provided by numerical simulations at 110 different points in the parameter space β* = βλ2/U and κ* = κλ/U. There is a special “pivot” value of β*, βpiv* ≈ 11/16, at which Dτ depends weakly on κ*. But otherwise Dτ has a complicated dependence on both β* and κ*, highlighted by the fact that reducing κ* leads to increases (decreases) in Dτ if β is less than (greater than) βpiv*. Existing heat-flux parameterizations, based on Kolmogorov cascade theories, predict that Dτ is nonzero and independent of κ* in the limit κ* → 0. Simulations show indications of this regime provided that κ* ≤ 0.04 and 0.25 ≤ β* ≤ 0.5.
All important length scales in this problem, namely the mixing length, the scale of the energy containing eddies, the Rhines scale, and the spacing of the zonal jets, converge to a common value as bottom friction is reduced. The mixing length and jet spacing do not decouple in the parameter regime considered here, as predicted by cascade theories. The convergence of these length scales is due to the formation of jet-scale eddies that align along the eastward jets. The baroclinic component of these eddies helps force the zonal mean flow, which occurs through nonzero Reynolds stress correlations in the upper layer, as opposed to the barotropic mode. This behavior suggests that the dynamics of the inverse barotropic cascade are insufficient to fully describe baroclinic turbulence.
Dependence of Polar Low Development on Baroclinicity and Physical Processes: An Idealized High-Resolution Numerical Experiment
Authors: Yanase Wataru , Niino Hiroshi 
Published: September 2007

Abstract
Polar low dynamics in an idealized atmosphere in which baroclinicity, stratification, and average temperature are varied in the typically observed range is investigated using a 5-km-resolution nonhydrostatic model. The baroclinicity is found to be the most important factor that strongly controls the polar low dynamics.
When the baroclinicity is weak, a small, nearly axisymmetric vortex develops through a cooperative interaction between the vortex flow and cumulus convection. The surface friction promotes the vortex dynamics by transporting the sensible heat and moisture into the vortex center. The vortex development has a strong sensitivity to the initial perturbation.
As the baroclinicity is increased, most of the characteristics of polar low dynamics change smoothly without showing any significant regime shift. The vortex for an intermediate baroclinicity, however, moves northward, which is a unique behavior. This is caused by vortex stretching on the northern side of the vortex where intense convection produces a stronger updraft.
When the baroclinicity is strong, a larger vortex with a comma-shaped cloud pattern develops. The condensational heating, baroclinic conversion from the basic available potential energy, and conversion from the basic kinetic energy through the vertical shear all contribute to the vortex development, which depends little on the initial perturbation. The above relations between baroclinicity and vortex dynamics are proved to be robust in the typically observed range of stratification and average temperature.
Forced-Dissipative Shallow-Water Turbulence on the Sphere and the Atmospheric Circulation of the Giant Planets
Authors: Scott R. K. , Polvani L. M. 
Published: September 2007

Abstract
Although possibly the simplest model for the atmospheres of the giant planets, the turbulent forced-dissipative shallow-water system in spherical geometry has not, to date, been investigated; the present study aims to fill this gap. Unlike the freely decaying shallow-water system described by Cho and Polvani, equilibrium states in the forced-dissipative system are highly dependent on details of the forcing and the dissipation. For instance, it is found that for a given equilibrated energy level, the steadiness of zonal jets depends crucially on the balance between forcing and dissipation.
With long (up to 100 000 days) high-resolution (T170) calculations, the dependence of the equilibrium states on Rossby number Ro and Rossby deformation radius LD is explored, for the case when the dissipation takes the form of hypodiffusion (acting predominantly at large scales) and the random forcing at small scales is δ correlated in time. When LD is large compared to the planetary radius, zonal jets are verified to scale closely with the Rhines scale over a wide range of Ro; furthermore, the jets at the equator are found to be both prograde and retrograde with approximately equal likelihood. As LD is decreased, the equatorial jets become increasingly and consistently retrograde, in agreement with the freely decaying turbulence results. Also, the regime recently discussed by Theiss, where zonal jets are confined to low latitudes, is illustrated to emerge robustly in the limit of small LD. Finally, specific calculations with parameter values typical of the giant planets are presented, confirming many of the earlier results obtained in the freely decaying case.
Eddy–Zonal Flow Interactions and the Persistence of the Zonal Index
Authors: Gerber Edwin P. , Vallis Geoffrey K. 
Published: September 2007

Abstract
An idealized atmospheric general circulation model is used to investigate the factors controlling the time scale of intraseasonal (10–100 day) variability of the extratropical atmosphere. Persistence on these time scales is found in patterns of variability that characterize meridional vacillations of the extratropical jet. Depending on the degree of asymmetry in the model forcing, patterns take on similar properties to the zonal index, annular modes, and North Atlantic Oscillation. It is found that the time scale of jet meandering is distinct from the obvious internal model time scales, suggesting that interaction between synoptic eddies and the large-scale flow establish a separate, intraseasonal time scale. A mechanism is presented by which eddy heat and momentum transport couple to retard motion of the jet, slowing its meridional variation and thereby extending the persistence of zonal index and annular mode anomalies. The feedback is strong and quite sensitive to model parameters when the model forcing is zonally uniform. However, the time scale of jet variation drops and nearly all sensitivity to parameters is lost when zonal asymmetries, in the form of topography and thermal perturbations that approximate land–sea contrast, are introduced. A diagnostic on the zonal structure of the zonal index provides intuition on the physical nature of the index and annular modes and hints at why zonal asymmetries limit the eddy–mean flow interactions.