bluuebunny/crossref_metadata_2025 huggingface dataset:
Physico-mechanical and microstructural characteristics of historic and restoration mortars based on gypsum: current knowledge and perspective
Authors: Middendorf Bernhard
Published: September 2007

The use of gypsum based mortar can be traced back over 4500 years. In Germany, in the vicinity of natural gypsum outcrops, in addition to lime mortars, calcium sulphate based mortars were widely used for joints in exterior walls of sacred buildings. There are several medieval buildings with well-preserved calcium sulphate-based mortars. The high water solubility of gypsum (CaSO
4
•2H
2
O) is a disadvantage that makes it difficult in general to handle calcium sulphate based building materials in areas exposed to weathering. Physico-mechanical as well as mineralogical investigations of historic calcium sulphate based mortars have shown that long-term weathered mortars have a much denser microstructure, larger average grain sizes, and a higher compressive strength than laboratory prepared mortars. Porosity models of these mortars will be presented which are helpful to prepare calcium sulphate based mortars with a higher water resistance for restoration purposes. The reason for the change of crystal size and morphology as well as of porosity and strength can be explained by crystallization and recrystallization processes of these calcium sulphate based mortars, as a consequence of long-term weathering. Since it is obvious that crystal size and its distribution have an enormous effect on the weathering resistance, the development of mortars with comparable structural properties is of present interest. In current use are chemical additives which modify the morphology and size of gypsum crystals of set mortars. Another possibility to influence the weathering resistance is the addition of hydraulic and/or latent hydraulic admixtures.
Thermal behaviour of weathered and consolidated marbles
Authors: Ruedrich J. , Weiss T. , Siegesmund S.
Published: September 2007

To optimize stone consolidation it is necessary to understand the mechanisms of weathering in marbles, and its control by the mineralogical composition and the rock fabric. A knowledge of how the stone consolidants affect the weathering mechanisms and if they are compatible with the stone is also an important consideration. The weathering of marble can begin with thermal stress whereby cracks are generated. To verify whether consolidation influences the thermal behaviour of marbles, we compared the behaviour of weathered and consolidated marbles. For the investigations four marbles were selected with various fabrics (e.g. texture, grain size, grain boundary geometry, etc.) and different weathering conditions. Three consolidation approaches were adopted: a solved polymethyl-methacrylate (PMMA
sol
) dissolved in xylenes, a polysilicic acid ester (PSAE) and a total impregnation with a monomer methyl-methacrylate (PMMA
poly
). Measurements of the porosity and effective pore size distribution evidenced a strong modification of the pore space by consolidation. Both PMMA approaches show a re-establishment of cohesion which can be determined by ultrasonic velocity measurements. By reaching the respective glass transition temperatures of PMMA
sol
and PMMA
poly
, a strong modification of thermal behaviour occurs. The PSAE consolidated marbles show only minor changes of dilatation, but due to its low bonding effect no significant cohesion between the crystals occurs.
The influence of petrographic, architectural and environmental factors in decay patterns and durability of granite stones in Braga monuments (NW Portugal)
Authors: Matias J. M. S. , Alves C. A. S.
Published: September 2007

In order to discuss decay patterns and susceptibility of granite types used in architectural works, the decay features of 39 monuments built with granite stones and presenting diverse architectural characteristics, date of construction and environmental characteristics (including exposition conditions, traffic intensity, etc.) are compared. Decay patterns of biotite-rich medium- to fine-grained (frequently porphyritic) granite stones are related to weathering inherited from the quarry (expressed by yellowing), to the presence of heterogeneous elements (enclaves and phenocrysts) and to grain size variations. Fine-grained leucogranitic stone decay is mainly controlled by tectonic foliation. The characteristics of stone application, including how and where stone was used, influence decay patterns by favouring salt pollution concentration, biological colonization and fixation of atmospheric pollutants. Erosive decay features (linked mainly to salt pollution) and stone coatings (linked to biological action and atmospheric and organic pollution) are wide-spread decay forms that affect granite stones in Braga monuments.
Bowing of marble panels: on-site damage analysis from the Oeconomicum Building at Göttingen (Germany)
Authors: Koch A. , Siegesmund S.
Published: September 2007

The use of natural stone panels or cladding material for building facades has led to some durability problems, especially with marble slabs. To examine the effects of intrinsic and extrinsic parameters on bowing, a very detailed study was performed on the Oeconomicum Building at the University of Goettingen. In total 1556 panels from the whole building were measured with respect to bowing using a bow-meter. The variation of bowing ranges from concave (up to 23 mm/m) to convex (up to −11 mm/m). The variation is not controlled by the position with respect to the geographical coordinates, height above ground, shadows, temperature etc. On the north facade the different rock structures visible on the panel surfaces are a result of the marble slabs being cut in different directions. The different degrees of bowing are associated with the structure of the marble since all other influencing factors are relatively constant (position, temperature, moisture content, building physics). Experimental data on the expansion behaviour under dry and/or wet conditions reveal different degrees of bowing with respect to the rock fabric and may help to explain the observed differences in bowing. The effect of the rock fabric, especially of the lattice preferred orientation in this case, clearly controls the deterioration of the marble and the degree of bowing. The bowing is also characterized by an increase in the porosity, decreasing values of ultrasonic wave velocities and flexural strength. The loss of cohesion in the strongly deteriorated panels is clearly visible in the microstructure by the open grain boundaries which are interconnected to intergranular microcracks.
Principal decay patterns on Venetian monuments
Authors: Fassina Vasco , Favaro Monica , Naccari Andrea
Published: September 2007

In most Venetian monuments studied, the stone decay was ascribed to the transformation of calcium carbonate into calcium sulphate. This phenomenon is commonly observed elsewhere and has been pointed out by many authors. In order to explain why different forms of decay are present on a building facade, samples were taken from different areas of many monuments. Analytical results were related to different forms of decay, defined respectively as white washing, dirt accumulation and dirt wetting. A simplified model of stone decay is presented and its validity tested on several Venetian monuments. Results showed that the features visible on stone surfaces corresponded to different degrees of deterioration. Sulphate formation is greatest in the black dendrite-shaped crusts, which are generally formed at the interface between the white washing areas and the sheltered ones, which were defined as dirt wetting area.

The decay forms of the most common lithotypes used in Venetian monuments were also studied. Results obtained showed that in compact limestone, gypsum formation affects the stone only on the surface. In contrast, on marble a different mechanism of decay takes place: the decohesion of calcite crystals, due to thermal changes, favours the penetration of sulphuric acid solution into intergranular spaces, thus causing the transformation of calcium carbonate into calcium sulphate, not only on the surface, but also inside the marble.
Implications of future climate change for stone deterioration
Authors: Viles Heather A.
Published: September 2007

Climate change over the next 100 years is likely to have a range of direct and indirect impacts on many natural and physical environments, including the built environment. Important influences on the built environment will include alterations in temperature, precipitation, extreme climatic events, soil conditions, groundwater and sea level. Some processes of building stone decay will be accelerated or worsened by climate change, whilst others will be retarded. The impacts on individual processes can be conceptualized, but it is difficult to assess or quantify the overall risk posed by climate change given currently available data. Linking global-scale changes to the response of individual walls or buildings remains a challenge. Overall changes in decay rates could also be related to climatic change. As an example downscaled climate predictions, knowledge of stock at risk and long-term decay rates can be used to assess the future of building stone decay in the UK. Using the UK Climatic Impacts Programme’s (UKCIP98) regional climate change projections an increasing NW-SE climatic gradient is predicted, which should enhance chemical weathering of silicate building materials in the NW and increase crystallization damage of limestones in the SE.
A rapid method for the determination of cation exchange capacities of sandstones: preliminary data
Authors: Schäfer Mathias , Steiger Michael
Published: September 2007

A rapid and efficient single-extraction procedure for measuring cation exchange capacities in sandstones has been developed and tested. The method is based on the use of a SrCl
2
(0.25 mol l
−1
) solution to displace the exchangeable cations. The cation exchange capacities (CEC) of three types of natural building stones were analysed, both in freshly quarried material and in weathered samples. Large differences in the sorptive properties of these materials were observed. The measurement of profiles of CEC in weathered sandstones revealed a significant decrease of CEC in the weathered zone close to the exposed surface, most likely reflecting the partial dissolution of clay minerals due to acid attack. CEC measurements appear to be a very sensitive indicator of chemical weathering profiles.
The role of magma in the development of the Afro-Arabian Rift System
Authors: Buck W. R.
Published: September 2007

The initiation of the Afro-Arabian Rift System on three nearly straight segments occurred shortly after massive amounts of basalt poured out of the triple junction of those segments in Afar. The synchroneity of magmatism and rifting may reflect the fact that normal continental lithosphere is too strong to rift without magmatic dyke intrusions and the straightness of rifts reflects a localized source for the magma feeding those dykes. Simple relations are derived for the minimum extensional force needed for lithosphere cutting dyke intrusions as functions of the density structure and thickness of the lithosphere. As long as the density contrast between continental crust and magma is small compared to the density contrast between the mantle and magma, then the force needed to rift scales with the square of the thickness of the mantle lithosphere. Thus, continental regions with normal-thickness lithosphere may rift when reasonable levels of extensional force and sufficient magma are available. Very thick mantle lithosphere may not rift at levels of force that are likely to arise on Earth. Two main sections of the Afro-Arabian Rift System, the Red Sea and the Ethiopian Rift, appear to have developed as magma-assisted rifts in normal continental lithosphere. The northern and southern ends of the system are bounded by regions of very thick mantle lithosphere where dykes could not open. In the south, the Tanzanian Craton, with normal-thickness crust and a very deep lithospheric root, was also not split by the rift. In the north, the rift opened along a nearly straight line from the centre of the flood basalt province 2000 km to the edge of the Mediterranean Sea. The old oceanic lithosphere of this margin may be no thicker than the adjacent continental lithosphere of Egypt, but the thinner oceanic crust means that Mediterranean lithosphere may be too thick and dense to rift magmatically. The role of magma in the third branch, the Gulf of Aden, is not so clear given the lack of syn-rift dykes.
Basaltic magmatism and the geodynamics of the East African Rift System
Authors: Rogers N.W.
Published: September 2007

The major and trace element and radiogenic isotope compositions of basalts from throughout the East African rift system are reviewed in the context of constraints from previous geophysical studies. The data indicate the presence of two mantle plumes, the East African and Afar plumes, which dynamically support the East African and Ethiopian plateaus. Rifting across the plateaus is accompanied by the generation of large volumes of basaltic magma and associated evolved derivatives. Relatively few mafic magmas have an unambiguous Afar mantle plume signature, notably the MgO-rich picrites and ankaramites from the 29–31 Ma Ethiopian traps, and the most recent basalts (<5 Ma) from Afar. The Eocene Amaro basalts from southern Ethiopia also have a plume source but their lower source temperatures and isotopic characteristics are distinct from those of Afar. The remaining basalts from the Ethiopian rift, and throughout the Kenya and Western rifts, have a lithospheric source region as reflected in both radiogenic isotope and trace element characteristics. The Amaro basalts are suggested as the first manifestations of magmatism from the East African plume; subsequent magmatic activity being represented by progressively younger episodes further south through Turkana, Kenya and into Northern. Tanzania, as the African plate migrated north. Despite their clear lithospheric characteristics, U-series data on geologically recent basalts from the axis of the Kenya rift show that they were generated in a dynamic melting regime. Melting is effected when lithospheric mantle heats up and becomes incorporated into the convecting mantle, hence leading to greater degrees of lithospheric thinning than are indicated by extension across individual rift basins.
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

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

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

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

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.
Expression of adrenomedullin in human epicardial adipose tissue: role of coronary status
Authors: Silaghi Alina , Achard Vincent , Paulmyer-Lacroix Odile , Scridon Traian , Tassistro Virginie , Duncea Ileana , Clément Karine , Dutour Anne , Grino Michel
Published: September 2007

Epicardial white adipose tissue (eWAT) is in close contact with coronary vessels and therefore could alter coronary homeostasis. Adrenomedullin (AM) is a potent vasodilatator and antioxidative peptide which has been shown to play a cytoprotective role in experimental models of acute myocardial infarction. We studied, using immunohistochemistry and qRT-PCR, the expression of AM and its receptors calcitonin receptor-like receptor (CRLR), and receptor activity-modifying protein (RAMP)2 and -3 in paired biopsies of subcutaneous WAT (sWAT) and eWAT obtained from patients with coronary artery disease (CAD) or without CAD (NCAD). In eWAT obtained from NCAD or CAD patients, immunoreactivity for AM, CRLR, and RAMP2 and -3 was detected in blood vessel walls and isolated stromal cells close to adipocytes. Some of the AM positive stromal cells colocalized CD68 immunoreactivity. eWAT from CAD patients showed increased AM immunoreactivity and AM gene expression. CRLR mRNA levels were comparable in sWAT of both groups and decreased by 40–50% in eWAT, irrespectively of the coronary status. RAMP2 mRNA concentrations did not change while RAMP3 mRNA levels increased in sWAT from CAD patients. There was a positive linear relationship between eWAT 11β-hydroxysteroid dehydrogenase type 1 mRNA (11β-HSD-1, the enzyme that converts inactive to active glucocorticoids) and AM mRNA. In conclusion, we demonstrate that AM and its receptors are expressed in eWAT. Our data suggest that eWAT AM, which could originate from macrophages, is related to 11β-HSD-1 expression. AM synthesis, which is increased in eWAT during chronic CAD in humans, can play a cardioprotective role.
Carbenoxolone treatment attenuates symptoms of metabolic syndrome and atherogenesis in obese, hyperlipidemic mice
Authors: Nuotio-Antar Alli M. , Hachey David L. , Hasty Alyssa H.
Published: September 2007

Glucocorticoids, which are well established to regulate body fat mass distribution, adipocyte lipolysis, hepatic gluconeogenesis, and hepatocyte VLDL secretion, are speculated to play a role in the pathology of metabolic syndrome. Recent focus has been on the activity of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which is capable of regenerating, and thus amplifying, glucocorticoids in key metabolic tissues such as liver and adipose tissue. To determine the effects of global 11β-HSD1 inhibition on metabolic syndrome risk factors, we subcutaneously injected “Western”-type diet-fed hyperlipidemic mice displaying moderate or severe obesity [LDL receptor (LDLR)-deficient (LDLR−/−) mice and mice derived from heterozygous agouti ( Ay/a) and homozygous LDLR−/−breeding pairs ( Ay/a;LDLR−/−mice)] with the nonselective 11β-HSD inhibitor carbenoxolone for 4 wk. Body composition throughout the study, end-point fasting plasma, and extent of hepatic steatosis and atherosclerosis were assessed. This route of treatment led to detection of high levels of carbenoxolone in liver and fat and resulted in decreased weight gain due to reduced body fat mass in both mouse models. However, only Ay/a;LDLR−/−mice showed an effect of 11β-HSD1 inhibition on fasting insulin and plasma lipids, coincident with a reduction in VLDL due to mildly increased VLDL clearance and dramatically decreased hepatic triglyceride production. Ay/a;LDLR−/−mice also showed a greater effect of the drug on reducing atherosclerotic lesion formation. These findings indicate that subcutaneous injection of an 11β-HSD1 inhibitor allows for the targeting of the enzyme in not only liver, but also adipose tissue, and attenuates many metabolic syndrome risk factors, with more pronounced effects in cases of severe obesity and hyperlipidemia.
Dendrite-to-Soma Input/Output Function of Continuous Time-Varying Signals in Hippocampal CA1 Pyramidal Neurons
Authors: Cook Erik P. , Guest Jennifer A. , Liang Yong , Masse Nicolas Y. , Colbert Costa M.
Published: September 2007

We examined how hippocamal CA1 neurons process complex time-varying inputs that dendrites are likely to receive in vivo. We propose a functional model of the dendrite-to-soma input/output relationship that combines temporal integration and static-gain control mechanisms. Using simultaneous dual whole cell recordings, we injected 50 s of subthreshold and suprathreshold zero-mean white-noise current into the primary dendritic trunk along the proximal 2/3 of stratum radiatum and measured the membrane potential at the soma. Applying a nonlinear system-identification analysis, we found that a cascade of a linear filter followed by an adapting static-gain term fully accounted for the nonspiking input/output relationship between the dendrite and soma. The estimated filters contained a prominent band-pass region in the 1- to 10-Hz frequency range that remained constant as a function of stimulus variance. The gain of the dendrite-to-soma input/output relationship, in contrast, varied as a function of stimulus variance. When the contribution of the voltage-dependent current Ih was eliminated, the estimated filters lost their band-pass properties and the gain regulation was substantially altered. Our findings suggest that the dendrite-to-soma input/output relationship for proximal apical inputs to CA1 pyramidal neurons is well described as a band-pass filter in the theta frequency range followed by a gain-control nonlinearity that dynamically adapts to the statistics of the input signal.
Osteopenia in Sparc (osteonectin)-deficient mice: characterization of phenotypic determinants of femoral strength and changes in gene expression
Authors: Mansergh Fiona C. , Wells Timothy , Elford Carole , Evans Samuel L. , Perry Mark J. , Evans Martin J. , Evans Bronwen A. J.
Published: September 2007

Sparc null mutants have been generated independently via targeted mutations in exons 4 and 6. Previous studies have identified low-turnover osteopenia in the 129Sv/C57BL/6 exon 4 knockout. Since both Sparc null mutations result in complete absence of Sparc protein, similar phenotypic outcomes are likely. However, genetic background (strain) and/or linkage disequilibrium effects can influence phenotype. Different inactivating mutations should be tested in various mouse strains; similar phenotypic outcomes can then confidently be assigned to the mutated gene. We have evaluated the bone phenotype in the 129Sv/EvSparc tm1cam exon 6 knockout at 4 and 9 mo, using physical measurement, mechanical strength tests, and DXA scanning. We have also quantified bone marrow adiposity and circulating leptin levels to assess adipose tissue metabolism. 129Sv/EvSparc tm1cam null mice show decreased bone mineral density and bone mineral content and increased mechanical fragility of bone, in line with previous studies. Differences were also noted. Increased body weight and levels of bone marrow adiposity but decreased circulating leptin concentrations were identified at 4, but not 9 mo, and 129Sv/EvSparc tm1cam null mice also had shorter femurs. Molecular phenotyping was carried out using mouse HGMP NIA microarrays with cortical femur samples at various ages, using semiquantitative RT-PCR validation. We identified 429 genes highly expressed in normal bone. Six genes (Sparc, Zfp162, Bysl, E2F4, two ESTs) are differentially regulated in 129Sv/EvSparc tm1cam cortical femur vs. 129Sv/Ev controls. We confirm low-turnover osteopenia as a feature of the Sparc null phenotype, identifying the usefulness of this mouse as a model for human osteoporosis.
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.
A New Mathematical Model for the Performanceof Axial Magnetic Filters
Authors: Collan H. K. , Kokkala M. A. , Toikka O. E.
Published: September 2007

A mathematical model to describe the macroscopic
behaviour of an axial magnetic filter is developed. The
model takes into account the long range of absorption
forces. Partial mixing of the particles in the fluid is
included by introducing the concept of “mixing length”.
Behaviour of an axial filter under different conditions is
numerically simulated. Experiments with colloidal ferrite
particles indicate that for an axial filter composed of 12
μm steel wires with a packing factor of 4.8% the mixing
length is of the order of 4 mm.
High Gradient Magnetic Gas Filtration
Authors: Lua Aik Chong , Boucher Robert F.
Published: September 2007

Highly successful tests have shown that high
gradient magnetic filtration can provide a viable alternative
to conventional filtration to curb the amount of stack gas
particulate emissions from iron‐based industries, especially
steelmaking processes. Using basic oxygen furnace dust in our
work at Sheffield University, filtration efficiencies of 99%
and greater were obtained for submicron particles down to an
optically measurable 0.24 μm diameter; for particles of 1 μm
and above, 100% filtration efficiency was achieved. High gas
throughput, together with low pressure losses, low applied
magnetic fields and good filter matrix loadability all further
indicate the potential commercial practicality of HGMF in the
steelmaking industry.
Magnetic Separation in South Africa
Authors: Corrans Ian James , Svoboda Jan
Published: September 2007

The use of magnetic separators in the various mineral
processing facilities in South Africa is described. A large
number are used to recover medium in dense medium plants. The
manufacture of various types of magnetic separation machines by
three local suppliers is highlighted. The potential use of highgradient
and/or high–intensity magnetic separation in the recovery
of gold, uranium, and phosphate minerals is discussed.
The Magnetic Beneficiation of Coal
Authors: Male S. E.
Published: September 2007

The magnetic demineralization of coal can produce a fuel containing lower leveIs of sulphur and ash forming minerals. The ability of the magnetic separation technique to process material over a wide range of particle sizes (I‐1000 µm) and to operate on either liquid or gaseous feed enables a number of possible coal processing applications. These range from dry desulphurization of power station pulverized fuel to the cleaning of solvent refined coals. This article reviews work on the development of magnetic separation as applied to coal processing.
Analysis of Magnetic and Hydraulic Forcesin an Oriented Real Matrix of a HighGradient Magnetic Separator
Authors: Hencl V. , Jahoda K. , Madai E.
Published: September 2007

The application of existing theoretical models for
the computation of magnetic and hydraulic forces in a real
oriented matrix consisting of regularly arranged rods and
wires indicates that these models produce no exact results.
The differences between computations and measurements of
force effects documented by Maxwell lead to the conclusion
that it is necessary to start with different physical assumptions
when modelling a high–gradient separation process.
First of all, the magnetic field of the rods or wires system
differs from the magnetic field of a single rod. Second,
the particle need not be attracted to the rod surface, it is
brought there by the suspension stream and the magnetic force
must hold it, so that it is not entrained by the streaming
suspension. As the layer of attracted particles grows, the
magnetic attractive force on the surface of the growing layer
decreases until the magnetic attractive force is in equilibrium
with the entraining force of suspension flow.
Application of High‐Gradient Magnetic Separation
Authors: Svoboda J.
Published: September 2007

Some problems of practical applications of magnetic separation, primarily in mineral industry, are outlined. The work shows that current theoretical models are inadequate in accounting for the magnetic separation of valuable mineral components. The negative impact of a lack of cost‐effective separators in the mining industry is discussed.
A Precaution on Using 316L Stainless Wire in Hgms Matrices
Authors: Graham Marshall D.
Published: September 2007

Use of unannealed 316L stainless wire as HGMS matrix material in an application requiring frequent reversals of the magnetizing field has been noted to result in slow degradation of matrix magnetization characteristics, with attendant reductions in magnetic filtration efficiency. This alloy should be restricted to applications where field reversals are seldom required, particularly if it is exposed to corroding fluids. A similar precaution probably applies to other austenitic alloys.
Optimization of a Magnetic Separator Air‐Gap
Authors: Adamiak Kazimierz
Published: September 2007

The paper describes a method of optimization of a magnetic separator air‐gap which serves to separate
magnetic particles from volatile power plant dust. The method consists in seeking the air‐gap dimensions, assuming
that the shape of poles is known on the basis of magnetic force field analysis, or in seeking the shape of poles for the assumed force field distribution. In the second case the problem is reduced to solving a certain inverse boundary problem of the Dirichlet type.
Concentration of Cupriferous Micas by Hgms
Authors: Top J. L. , Agricola J. N.M. , Fort A. F.
Published: September 2007

High Gradient Magnetic Separation tests have been carried out on low grade refractory copper ores, consisting mainly of cupriferous micas. An effective concentration of copper was obtained for two types of ores. The copper grade was improved 2 and 1.5 times at a recovery of about 90%. In particular, the amount of quartz in the concentrate could be reduced. This indicates that HGMS could be a successful method for concentration of these ores.
Magnetic Field Effect in the Process of Rinsing a Magnetic Separator Matrix
Authors: Galas Jiri
Published: September 2007

This paper surveys fundamental aspects of the problem of rinsing matrices in high gradient magnetic
separators. This is done, for the first time, in terms of the magnetic circuit design. Equations have been constructed
to describe the effects of spurious remanent magnetic fields on the rinsing process.
Treatment of Drinking and Irrigation Water in Animal and Plant Husbandry by Electromagnetic Technology
Authors: Lin Israel , Yotvat Jacob
Published: September 2007

A survey is given of recent preliminary results of a broadbased investigation in Israel of the potentially beneficial effects of the magnetic treatment of water on plant and animal husbandry.
Magnetic Separation of Weakly Magnatic Copper Minerals
Authors: Agricola J. N.M. , Top J. L. , Fort A. F.
Published: September 2007

High Gradient Magnetic Separation of small (5‐38 µm) weakly magnetic copper mineral particles from a
copper concentrate and ore has been performed. In previous work coarser fractions of these minerals, bornite and chalcopyrite, were separated successfully. The recovery of the smaller particles in the magnetic fraction decreases but
their grade increases compared to the results obtained on the larger particles. At a magnetic background field of 1.3 T the concentrate was upgraded from 72% bornite and chalcopyrite to 86% with a recovery of 82% and the ore from 16% magnetic minerals to 44% with a recovery of 72%.
Development of H.G.M.S. Techniques for Biological Cell Separation
Authors: Parker M. R. , Tsang E.
Published: September 2007

High Gradient Magnetic Separation (HGMS) for biological specimens is reviewed. Selective tagging for the enhancement of cell capture is discussed. A detailed survey of major improvements in HGMS techniques ‐‐ filter matrix designs and magnet designs aimed specifically at bench‐top experiments in bioseparation ‐‐ is also given.
Magnetic Separation in Czechoslovakia
Authors: Hencl Vladimir
Published: September 2007

The use of magnetic separation in various
mineral processing facilities in Czechoslovakia is
described. The manufacture of assorted types of magnetic
separation machines is highlighted. Potential
applications and research and development activities
are discussed.
Superconducting Magnetic Separators
Authors: Kopp Juergen
Published: September 2007

The fields available with conventional
electromagnets are limited to 2 Tesla by the saturation
of iron. In addition, the creation of large field
volumes is costly in terms of copper, iron and electric
power. For these reasons superconducting separator magnets
were proposed as early as 1970. This paper deals
with the special requirements of cryomagnets in the
mineral processing industry, and the relatively slow
rate of replacement of conventional magnets. Finally,
the impact of the new high‐temperature superconductors
is examined briefly.
Development and Performance of the 6 ERM‐35/315Separator With a High Intensity Magnehc Field
Authors: Ulubabov R. S. , Karmazin V. I.
Published: September 2007

Design and operational experience with a new rotor high‐intensity
magnetic separator are discussed. Improved metallurgical efficiency and a
greater resistance against the matrix clogging were found to be the main
advantages of the new design. Comparison with the Jones separator is
outlined.
Hidden Momentum and the Force on a Magnetic Dipole
Authors: Hnizdo V.
Published: September 2007

The problem of the correct expression for the force on a magnetic
dipole in vacuum is discussed. Different models of magnetic dipole are considered
and particular attention is given to the presence of hidden momentum,
which modifies the usual expression for the force on a current‐loop dipole when
the external electromagnetic field is not static.
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.
Water Exposed to Magnetic Treatment: Muskmelon (Cantaloupe) Growing
Authors: Harari M. , Lih I. J.
Published: September 2007

This paper surveys recent experimental results of investigation of
the influence of an exposure of irrigation water to magnetic field on yield,
quality parameters and duration of fruit‐bearing of cantaloupe.
Changes in Magnetic Susceptibility of Chalcopyrite Induced by Vibration Grinding
Authors: Baláž Peter , Tkáčová Klára
Published: September 2007

Changes in magnetic susceptibility of chalcopyrite brought about by
vibration grinding in air and methanol were investigated. Significant increase
in magnetic susceptibility is ascribed to plastic strain that results in
destruction of the long‐range order.
Borates in the Argentine Puna: A New Application of Magnetic Separation
Authors: Flores H. R. , Villagran P.
Published: September 2007

Large, highly marketable deposits of borate are situated in the
north‐western Argentina. The exploitation of these deposits started in the
beginning of this century. The exploitation and industrialization of some of
these deposits during the 1980s turned the region into an important trading
centre for export of raw borates and of boric acid. Technical specifications, as regards the iron content in those products, are
very rigorous, particularly if they are used in manufacture of high‐quality
glass. This paper presents a survey of the borate industry in the Puna region
of Argentina. A purification technique for "hard borates", based on magnetic
separation is described. The study has been carried out using pilot‐ plant
magnetic separators at the IN BE MI, The Salta National University.
Effects of Surface Finish and Material of Construction of the Separating Surface on High–TensionElectrical Separation
Authors: Rozelaar A. J.W. , Wells I. S.
Published: September 2007

Tests with a roll type electrostatic separator have shown that the
separation of minerals is affected by the material from which the roll is
constructed as well as the surface finish of the roll. Experiments have been
carried out with single mineral species on roll constructed of titanium,
chromium–plated mild steel and aluminium with differing surface finishes.
The results indicate that the surface finish influences the separation of the
minerals. The effect is attributed to alteration either to the field
configuration in proximity of the roll or to the particle–roll
capacitance resistance.
Carrier Coagulation of Chromite Fines in Wet Magnetic Separation
Authors: Wang Yanmin , Pugh Robert J. , Forssberg Eric
Published: September 2007

A "carrier" or "piggy–back" coagulation process was applied to
improve the separation efficiency of chromite slimes in wet high–gradient
magnetic separation. This was achieved by the addition of a coarse
chromite fraction to the slime fraction (< 10 mm). Three coarse chromite
fractions were investigated in the present study with size ranges <106>75,
<75>53 and <53>38 μm. The results suggested that the <53>38 μm coarse
fraction was the most effective in improving the process efficiency. Superior
performance was also found to occur between pH 5 and 6. The results were
discussed by computing the various components for potential energy of
interaction between the slime particles and the "carrier" or "piggy‐back"
particles at a range of surface potentials in the absence or presence of the
magnetic field.
Charge‐Neutralization Electrodes for High‐Tension Separators
Authors: Dascalescu L. , Morar R. , Iuga Al. , Neamtu V. , Suarasan I.
Published: September 2007

Safe and efficient operation of industrial high‐tension separators
requires a strict control of residual electric charge of the particles
emerging the process. Principles of charge neutralization in a roll‐type
electroseparator are briefly discussed, in order to establish the
general features of the corona electrodes that might accomplish this
task. A new electrode design is suggested. Its spacific features:
small cross‐section (neglectable perturbation of the material
stream), low corona on‐set voltage, good stability of corona
discharge during long‐time operation, short maintenance time, have
been tested on a laboratory model, prior to industrial application.
Several design considerations have been formulated, based on a
critical evaluation of the experimental results.
The Separation Performance of the Pulsating High–Gradient Magnetic Separator
Authors: Peng Yang , Shuyi Liu , Jin Chen
Published: September 2007

In order to develop the pulsating high–gradient magnetic
separation technology, a laboratory pulsating high–gradient magnetic
separator (PHGMS) has been manufactured.. Experiments on its separation
performance were carried out. The results show that PHGMS can
significantly increase the grade of the magnetic product and it can eliminate
the matrix clogging. The characteristic curve of the pulsating fluid was
measured and a formula for estimating the grade of the magnetic product
from PHGMS was established.
Magnetic Treatment of Water–A Theoretical Quantum Model
Authors: Srebrenik S. , Nadiv S. , Lin I. J.
Published: September 2007

It is claimed that magnetic treatment of water can prevent
formation of hard calcite scale on the walls of hot–water containers, and
devices based on this phenomenon are already commercially for industrial
use. The present paper puts forward and examines a theoretical model with
a view to explain why the low–energy magnetic field of a permanent
magnet is effective at all and why the phenomenon persists for some time
after the treatment (memory effect).
A New Type of Corona Electrode for High ‐ Tension Separators
Authors: Iuga Al. , Morar R. , Dascalescu L. , Samuila A. , Rafiroiu D.
Published: September 2007

The corona discharge represents the main physical mechanism
involved in the charging of granular materials in high‐tension
separators. This is why an attempt has been made to formulate
several criteria for choosing the most adequate electrode. A crude
evaluation of the required corona current for an efficient charging
has been considered as a necessary starting point for a wellgrounded
decision on the type of electrode to be employed with a
certain application. The specific features of several models of
corona electrodes are briefly discussed, in order to justify the need
for a new design. The original corona electrode proposed by the
authors is characterized by lower corona on‐set voltage, better
stability of the corona discharge during long‐time operation, and
shorter maintenance time, as compared to "classical" solutions.
Systematic experiments made on a laboratory model of this
electrode enable several design considerations that could be easily
extended to other similar devices. Two industrial high‐tension
separators are already provided with the new type of electrode.
The Application of High–Gradient Magnetic Separation to Water Treatment by Means of ChemicallyPrecipitated Magnetite
Authors: Hencl V. , Mucha P.
Published: September 2007

Conditions of high–gradient magnetic separation (HGMS) of
chemically precipitated magnetite, prepared from a waste material of the
titanium white production were studied. The magnetite was used as a
sorption material for the treatment of water from the Vltava River.
Detailed experimental research resulted in a proposal for a technology of
water treatment, schematic description of which is presented. The results of
HGMS of chemically precipitated magnetite together with those of water
treatment are discussed.