Magnetic hardening mechanisms in Nd-Fe-B nanocrystalline material

Microstructural and magnetic measurements of the evolution by heat treatment of initially amorphous Nd16Fe76B8 alloys prepared by melt spinning are presented. Evidence of magnetic hardening above a threshold temperature induced by magnetic isolation of the Nd2Fe14B grains is provided. A thermodynamic and kinetic explanation of local melting of the intergranular nanostructured Nd¿rich eutectic phase at temperatures below 900 K based on capillary effects is presented. A subsequent Ostwald ripening process moves Nd to wet intimately the hard magnetic grains, becoming, on cooling, a real paramagnetic isolating thin film (~2.5 nm). By using a simple analogy, it is shown that the switching magnetization field in a single¿domain crystal can be drastically affected through the exchange coupling to neighboring grains with different orientation of the easy axis. This effect should be important enough to reinforce the coercive field of polycrystalline hard magnetic materials and explains the observed enhancement from 0.9 to 1.9 T.

Use of steel slag to neutralize acid mine drainage (AMD) in sulfidic material from a uranium mine

Acid Mine Drainage (AMD) is one of the main environmental impacts caused by mining. Thus, innovative mitigation strategies should be exploited, to neutralize acidity and prevent mobilization of trace elements in AMD. The use of industrial byproducts has been considered an economically and environmentally effective alternative to remediate acid mine drainage. Therefore, the objective of this study was to evaluate the use of steel slag to mitigate acid mine drainage in a sulfidic material from a uranium mine, as an alternative to the use of limestone. Thus, increasing doses of two neutralizing agents were applied to a sulfidic material from the uranium mine Osamu Utsumi in Caldas, Minas Gerais State. A steel slag from the company ArcelorMittal Tubarão and a commercial limestone were used as neutralizing agents. The experiment was conducted in leaching columns, arranged in a completely randomized, [(2 x 3) + 1] factorial design, consisting of two neutralizing agents, three doses and one control, in three replications, totaling 21 experimental units. Electrical conductivity (EC), pH and the concentrations of Al, As, Ca, Cd, Cu, Fe, Mn, Ni, S, Se, and Zn were evaluated in the leached solutions. The trace element concentration was evaluated by ICP-OES. Furthermore, the CO2 emission was measured at the top of the leaching columns by capturing in NaOH solution and titration with HCl, in the presence of BaCl2. An increase in the pH of the leachate was observed for both neutralizing agents, with slightly higher values for steel slag. The EC was lower at the higher lime dose at an early stage of the experiment, and CO2 emission was greater with the use of limestone compared to steel slag. A decrease in trace element mobilization in the presence of both neutralizing agents was also observed. Therefore, the results showed that the use of steel slag is a suitable alternative to mitigate AMD, with the advantage of reducing CO2 emissions to the atmosphere compared to limestone.

Electrical colonic stimulation reduces mean transit time in a porcine model.

Abstract Electrical stimulation is a new way to treat digestive disorders such as constipation. Colonic propulsive activity can be triggered by battery operated devices. This study aimed to demonstrate the effect of direct electrical colonic stimulation on mean transit time in a chronic porcine model. The impact of stimulation and implanted material on the colonic wall was also assessed. Three pairs of electrodes were implanted into the caecal wall of 12 anaesthetized pigs. Reference colonic transit time was determined by radiopaque markers for each pig before implantation. It was repeated 4 weeks after implantation with sham stimulation and 5 weeks after implantation with electrical stimulation. Aboral sequential trains of 1-ms pulse width (10 V; 120 Hz) were applied twice daily for 6 days, using an external battery operated stimulator. For each course of markers, a mean value was computed from transit times obtained from individual pig. Microscopic examination of the caecum was routinely performed after animal sacrifice. A reduction of mean transit time was observed after electrical stimulation (19 +/- 13 h; mean +/- SD) when compared to reference (34 +/- 7 h; P = 0.045) and mean transit time after sham stimulation (36 +/- 9 h; P = 0.035). Histological examination revealed minimal chronic inflammation around the electrodes. Colonic transit time measured in a chronic porcine model is reduced by direct sequential electrical stimulation. Minimal tissue lesion is elicited by stimulation or implanted material. Electrical colonic stimulation could be a promising approach to treat specific disorders of the large bowel.

Magnetic properties and domain-wall motion in single-crystal BaFe10.2Sn0.74Co0.66O19

The magnetic properties of BaFe12O19 and BaFe10.2Sn0.74Co0.66O19 single crystals have been investigated in the temperature range (1.8 to 320 K) with a varying field from -5 to +5 T applied parallel and perpendicular to the c axis. Low-temperature magnetic relaxation, which is ascribed to the domain-wall motion, was performed between 1.8 and 15 K. The relaxation of magnetization exhibits a linear dependence on logarithmic time. The magnetic viscosity extracted from the relaxation data, decreases linearly as temperature goes down, which may correspond to the thermal depinning of domain walls. Below 2.5 K, the viscosity begins to deviate from the linear dependence on temperature, tending to be temperature independent. The near temperature independence of viscosity suggests the existence of quantum tunneling of antiferromagnetic domain wall in this temperature range.

Three-dimensional black-blood cardiac magnetic resonance coronary vessel wall imaging detects positive arterial remodeling in patients with nonsignificant coronary artery disease.

BACKGROUND: Direct noninvasive visualization of the coronary vessel wall may enhance risk stratification by quantifying subclinical coronary atherosclerotic plaque burden. We sought to evaluate high-resolution black-blood 3D cardiovascular magnetic resonance (CMR) imaging for in vivo visualization of the proximal coronary artery vessel wall. METHODS AND RESULTS: Twelve adult subjects, including 6 clinically healthy subjects and 6 patients with nonsignificant coronary artery disease (10% to 50% x-ray angiographic diameter reduction) were studied with the use of a commercial 1.5 Tesla CMR scanner. Free-breathing 3D coronary vessel wall imaging was performed along the major axis of the right coronary artery with isotropic spatial resolution (1.0x1.0x1.0 mm(3)) with the use of a black-blood spiral image acquisition. The proximal vessel wall thickness and luminal diameter were objectively determined with an automated edge detection tool. The 3D CMR vessel wall scans allowed for visualization of the contiguous proximal right coronary artery in all subjects. Both mean vessel wall thickness (1.7+/-0.3 versus 1.0+/-0.2 mm) and wall area (25.4+/-6.9 versus 11.5+/-5.2 mm(2)) were significantly increased in the patients compared with the healthy subjects (both P<0.01). The lumen diameter (3.6+/-0.7 versus 3.4+/-0.5 mm, P=0.47) and lumen area (8.9+/-3.4 versus 7.9+/-3.5 mm(2), P=0.47) were similar in both groups. CONCLUSIONS: Free-breathing 3D black-blood coronary CMR with isotropic resolution identified an increased coronary vessel wall thickness with preservation of lumen size in patients with nonsignificant coronary artery disease, consistent with a "Glagov-type" outward arterial remodeling. This novel approach has the potential to quantify subclinical disease.

Task 6: Material Thermal Input for Iowa Materials, May 2008

The present research project was designed to determine thermal properties, such as coefficient of thermal expansion (CTE) and thermal conductivity, of Iowa concrete pavement materials. These properties are required as input values by the Mechanistic-Empirical Pavement Design Guide (MEPDG). In this project, a literature review was conducted to determine the factors that affect thermal properties of concrete and the existing prediction equations for CTE and thermal conductivity of concrete. CTE tests were performed on various lab and field samples of portland cement concrete (PCC) at the Iowa Department of Transportation and Iowa State University. The variations due to the test procedure, the equipment used, and the consistency of field batch materials were evaluated. The test results showed that the CTE variations due to test procedure and batch consistency were less than 5%, and the variation due to the different equipment was less than 15%. Concrete CTE values were significantly affected by different types of coarse aggregate. The CTE values of Iowa concrete made with limestone+graval, quartzite, dolomite, limestone+dolomite, and limestone were 7.27, 6.86, 6.68, 5.83, and 5.69 microstrain/oF (13.08, 12.35, 12.03, 10.50, and 10.25 microstrain/oC), respectively, which were all higher than the default value of 5.50 microstrain/oF in the MEPDG program. The thermal conductivity of a typical Iowa PCC mix and an asphalt cement concrete (ACC) mix (both with limestone as coarse aggregate) were tested at Concrete Technology Laboratory in Skokie, Illinois. The thermal conductivity was 0.77 Btu/hr•ft•oF (1.33 W/m•K) for PCC and 1.21 Btu/hr•ft•oF (2.09 W/m•K) for ACC, which are different from the default values (1.25 Btu/hr•ft•oF or 2.16 W/m•K for PCC and 0.67 Btu/hr•ft•oF or 1.16 W/m•K for ACC) in the MEPDG program. The investigations onto the CTE of ACC and the effects of concrete materials (such as cementitious material and aggregate types) and mix proportions on concrete thermal conductivity are recommended to be considered in future studies.

Material Thermal Inputs of Iowa Materials for MEPDG, 2011

The thermal properties of concrete materials, such as coeffi cient of thermal expansion (CTE), thermal conductivity, and heat capacity, are required by the MEPDG program as the material inputs for pavement design. However, a limited amount of test data is available on the thermal properties of concrete in Iowa. The default values provided by the MEPDG program may not be suitable for Iowa concrete, since aggregate characteristics have signifi cant infl uence on concrete thermal properties.

Post-Plutonic Magmatism: from the Source to the Emplacement of an Upper Crustal Dyke Swarm, Adamello Massif, Italy

Magmas of the arc-tholeiitic and calc-alkaline differentiation suites contribute substantially to the formation of continental crust in subduction zones. Different geochemical-petrological models have been put forward to achieve evolved magmas forming large volumes of tonalitic to granitic plutons, building an important part of the continental crust. Primary magmas produced in the mantle wedge overlying the subducted slab migrate through the mantle and the crust. During the transfer, magma can accumulate in intermediate reservoirs at different levels where crystallization leads to differentiation and the heat transfer from the magma, together with gained heat from solidification, lead to partial melting of the crust. Partial melts can be assimilated and mix with more primitive magma. Moreover, already formed crystal cumulates or crystal mushes can be recycled and reactivated to transfer to higher crustal levels. Magma transport in the crust involves fow through fractures within a brittle elastic rock. The solidified magma filled crack, a dyke, can crosscut previously formed geological structures and thus serves as a relative or absolute time marker. The study area is situated in the Adamello massif. The Adamello massif is a composite of plutons that were emplaced between 42 and 29 million years. A later dyke swarm intruded into the southern part of the Adamello Batholith. A fractionation model covering dyke compositions from picrobasalts to dacites results in the cummulative crystallization of 17% olivine, 2% Cr-rich spinel, 18% clinopyroxene, 41% amphibole, 4% plagioclase and 0.1% magnetite to achieve an andesitic composition out of a hydrous primitive picrobasalt. These rocks show a similar geochemical evolution as experimental data simulating fractional crystallization and associated magma differentiation at lower crustal depth (7-10 kbar). The peraluminous, corundum normative composition is one characteristic of more evolved dacitic magmas, which has been explained in a long lasting debate with two di_erent models. Melting of mafic crust or politic material provides one model, whereas an alternative is fractionation from primary mantle derived melts. Amphibole occurring in basaltic-andesitic and andesitic dyke rocks as fractionating cumulate phase extracted from lower crustal depth (6-7.5 kbar) is driving the magmas to peraluminous, corundum normative compositions, which are represented by tonalites forming most of the Adamello Batholith. Most primitive picrobasaltic dykes have a slightly steepened chondrite normalized rare earth elements (REE) pattern and the increased enrichment of light-REE (LREE) for andesites and dacites can be explained by the fractional crystallization model originating from a picrobasalt, taking the changing fractionating phase assemblage and temperature into account. The injection of hot basaltic magma (~1050°C) in a closely spaced dyke swarm increases the surface of the contact to the mainly tonalitic wallrock. Such a setting induces partial melting of the wall rock and selective assimilation. Partial melting of the tonalite host is further expressed through intrusion breccias from basaltic dykes. Heat conduction models with instantaneous magma injection for such a dyke swarm geometry can explain features of partial melting observed in the field. Geochemical data of minerals and bulk rock further underline the selective or bulk assimilation of the tonalite host rock at upper crustal levels (~2-3 kbar), in particular with regard to light ion lithophile elements (LILE) such as Sr, Ba and Rb. Primitive picrobasalts carry an immiscible felsic assimilant as enclaves that bring along refractory rutile and zircon with textures typically found in oceanic plagiogranites or high pressure/low-temperature metamorphic rocks in general. U-Pb data implies a lower Cretaceous age for zircon not yet described as assimilant in Eocene to Oligocene magmatic rocks of the Central Southern Alps. The distribution of post-plutonic dykes in large batholiths such as the Adamello is one of the key features for understanding the regional stress field during the post-batholith emplacement cooling history. The emplacement of the regional dyke swarm covering the southern part of the Adamello massif was associated with consistent left lateral strike-slip movement along magma dilatation planes, leading to en echelon segmentation of dykes. Through the dilation by magma of pre-existing weaknesses and cracks in an otherwise uniform host rock, the dyke propagation and according orientation in the horizontal plane adjusted continuously perpendicular to least compressive remote stress σ3, resulting in an inferred rotation of the remote principal stress field. Les magmas issus des zones de subduction contribuent substantiellement à la formation de la croûte continentale. Les plutons tonalitiques et granitiques représentent, en effet, une partie importante de la croûte continentale. Des magmas primaires produits dans le 'mantle wedge ', partie du manteau se trouvant au-dessus de la plaque plongeante dans des zones de subduction, migrent à travers le manteau puis la croûte. Pendant ce transfert, le magma peut s'accumuler dans des réservoirs intermédiaires à différentes profondeurs. Le stockage de magma dans ces réservoirs engendre, d'une part, la différentiation des magmas par cristallisation fractionnée et, d'autre part, une fusion partielle la croûte continentale préexistante associée au transfert de la chaleur des magmas vers l'encaissant. Ces liquides magmatiques issus de la croûte peuvent, ensuite, se mélanger avec des magmas primaires. Le transport du magma dans la croûte implique notamment un flux de magma à travers différentes fractures recoupant les roches encaissantes élastiques. Au cours de ce processus de migration, des cumulats de cristaux ou des agrégats de cristaux encore non-solidifiés, peuvent être recyclés et réactivés pour être transportés à des niveaux supérieures de la croûte. Le terrain d'étude est situé dans le massif d'Adamello. Celui-ci est composé de plusieurs plutons mis en place entre 42 et 29 millions d'années. Dans une phase tardive de l'activité magmatique liée à ce batholite, une série de filons de composition variable allant de picrobasalte à des compositions dacitiques s'est mise en place la partie sud du massif. Deux modèles sont proposés dans la littérature, pour expliquer la formation des magmas dacitiques caractérisés par des compositions peralumineux (i.e. à corindon normatif). Le premier modèle propose que ces magmas soient issus de la fusion de matériel mafique et pélitique présent dans la partie inférieur de la croûte, alors que le deuxième modèle suggère une évolution par cristallisation fractionnée à partir de liquides primaires issus du manteau. Un modèle de cristallisation fractionnée a pu être développé pour expliquer l'évolution des filons de l'Adamello. Ce modèle explique la formation des filons dacitiques par la cristallisation fractionnée de 17% olivine, 2% spinelle riche en Cr, 18% clinopyroxène, 41% amphibole, 4% plagioclase et 0.1% magnetite à partir de liquide de compositions picrobasaltiques. Ce modèle prend en considération les contraintes pétrologiques déduites de l'observation des différents filons ainsi que du champ de stabilité des différentes phases en fonction de la température. Ces roches montrent une évolution géochimique similaire aux données expérimentales simulant la cristallisation fractionnée de magmas évoluant à des niveaux inférieurs de la croûte (7-10 kbar). Le modèle montre, en particulier, le rôle prépondérant de l'amphibole, une phase qui contrôle en particulier le caractère peralumineux des magmas différentiés ainsi que leurs compositions en éléments en traces. Des phénomènes de fusion partielle de l'encaissant tonalitique lors de la mise en place de _lons mafiques sont observée sur le terrain. L'injection du magma basaltique chaud (~1050°C) sous forme de filons rapprochés augmente la surface du contact avec l'encaissante tonalitique. Une telle situation produit la fusion partielle des roches encaissantes nécessaire à l'incorporation d'enclaves mafiques observés au sein des tonalites. Pour comprendre les conditions nécessaires pour la fusion partielle des roches encaissantes, des modèles de conduction thermique pour une injection simultanée d'une série de filons ont été développées. Des données géochimiques sur les minéraux et sur les roches totales soulignent qu'au niveau supérieur de la croûte, l'assimilation sélective ou totale de l'encaissante tonalitique modifie la composition du liquide primaire pour les éléments lithophiles tel que le Sr, Ba et Rb. Un autre aspect important concernant la pétrologie des filons de l'Adamello est la présence d'enclaves felsiques dans les filons les plus primitifs. Ces enclaves montrent, en particulier, des textures proches de celles rencontrées dans des plagiogranites océaniques ou dans des roches métamorphiques de haute pression/basse température. Ces enclaves contiennent du zircon et du rutile. La datations de ces zircons à l'aide du géochronomètre U-Pb indique un âge Crétacé inférieur. Cet âge est important, car aucune roche de cet âge n'a été considérée comme un assimilant potentiel pour des roches magmatiques d'âge Eocène à Oligocène dans les Alpes Sud Centrales. La réparation spatiale des filons post-plutoniques dans des grands batholites tel que l'Adamello, est une caractéristique clé pour la compréhension des champs de contraintes lors du refroidissement du batholite. L'orientation des filons va, en particulier, indiqué la contrainte minimal au sein des roches encaissante. La mise en place de la série de filon recoupant la partie Sud du massif de l'Adamello est associée à un décrochement senestre, un décrochement que l'on peut lié aux contraintes tectoniques régionales auxquelles s'ajoutent l'effet de la dilatation produite par la mise en place du batholite lui-même. Ce décrochement senestre produit une segmentation en échelon des filons.

Posterior vaginal wall repair with synthetic absorbable mesh: A new technique for and old procedure

The objective of this study was to assess the applicability of posterior wall repair with a synthetic absorbable mesh. Between January and September 1996, five posterior repairs using absorbable synthetic meshes were performed. Five posterior wall repairs in patients matched for age, parity, and rectocele degree were performed according to usual procedures during the same period, and were used as controls. No febrile morbidity, cuff or posterior vaginal wall infections, thrombophlebitis, rectal injury, or hemorrhagic complications were observed in the 10 women who entered the study. In summary, posterior wall repair can be easily performed with an absorbable soft tissue patch, theoretically preserving sexual activity, and probably offers better functional results with longer experience, thus providing a safe and useful procedure in sexually active women.

Progression of human carotid and femoral atherosclerosis: a prospective follow-up study by magnetic resonance vessel wall imaging.

AIMS: The time course of atherosclerosis burden in distinct vascular territories remains poorly understood. We longitudinally evaluated the natural history of atherosclerotic progression in two different arterial territories using high spatial resolution magnetic resonance imaging (HR-MRI), a powerful, safe, and non-invasive tool. METHODS AND RESULTS: We prospectively studied a cohort of 30 patients (mean age 68.3, n = 9 females) with high Framingham general cardiovascular disease 10-year risk score (29.5%) and standard medical therapy with mild-to-moderate atherosclerosis intra-individually at the level of both carotid and femoral arteries. A total of 178 HR-MRI studies of carotid and femoral arteries performed at baseline and at 1- and 2-year follow-up were evaluated in consensus reading by two experienced readers for lumen area (LA), total vessel area (TVA), vessel wall area (VWA = TVA - LA), and normalized wall area index (NWI = VWA/TVA). At the carotid level, LA decreased (-3.19%/year, P = 0.018), VWA increased (+3.83%/year, P = 0.019), and TVA remained unchanged. At the femoral level, LA remained unchanged, VWA and TVA increased (+5.23%/year and +3.11%/year, both P < 0.01), and NWI increased for both carotid and femoral arteries (+2.28%/year, P = 0.01, and +1.8%/year, P = 0.033). CONCLUSION: The atherosclerotic burden increased significantly in both carotid and femoral arteries. However, carotid plaque progression was associated with negative remodelling, whereas the increase in femoral plaque burden was compensated by positive remodelling. This finding could be related to anatomic and flow differences and/or to the distinct degree of obstruction in the two arterial territories.