1,721,026 research outputs found
Enclaves provide new insights on the dynamics of manga mingling: a case study from Salina Island (Southern Thyrrenian Sea, Italy).
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Rheology of bimodal crystals suspensions: Results from analogue experiments and implications for magma ascent
No full textThe effect of crystal size of bimodal suspensions on rheology of magmas at strain rates between 0 and 1 s−1 is studied. Suspensions consist of silicon oil and two populations of natural crystals with size 63–125 and 250–500 µm mixed in different proportions; the total solid fraction ϕ of the mixtures is between 0.25 and 0.5. At ϕ ≤ 0.4, finer, coarser, and bimodal suspensions display comparable viscosities. At ϕ ≥ 0.4, the viscosity of the bimodal suspensions is larger than that of the unimodal ones. The bimodal suspension, made mainly of finer crystals, shows a stronger increase of viscosity with ϕ. The addition of finer crystals to a suspension of coarser ones produces a more pronounced increase of viscosity with respect to suspensions of coarse or fine crystals alone, and of finer crystals with added coarser ones. The bimodal suspensions of coarser crystals develops yield stress at ϕ ≥ 0.25, the others at ϕ ≥ 0.4. It is modeled the ascent velocity in a 20 m wide dike of magmas with bimodal and unimodal populations of crystals of different size. For ϕ ≤ 0.4, the crystal size has not effects on the ascent velocity of magmas. For ϕ ≥ 0.4, the velocity of a magma with growing phenocrystals decreases as ϕ increases less than that of a magma with forming microlites, and more of a magma with microlites and growing phenocrystals. A magma with phenocrystals and forming microlites has the lowest ascent velocity.Published284-2912V. Dinamiche di unrest e scenari pre-eruttivi3V. Dinamiche e scenari eruttiviJCR Journalrestricte
Mechanical erosion of xenoliths by magmatic shear flow
No full textWe focus on the role of mechanical erosion by
magmatic shear flow in the formation of xenoliths
occurring in lava flows. The process is analyzed by
combining the physics of fragmentation and erosion to the
concept of rock mass. The conditions for the country rock
fragmentation are analyzed as a function of the magma
viscosity, strain rate and tensile strength of the rock mass. In
reservoirs, mechanical processes play a subordinate role and
thermal erosion processes prevail. In conduits, intermediate
and silicic magmas may erode and, eventually, fragment
good to poor quality country rock masses. Basalts may erode
poor quality country rocks. A crystal-rich magma has more
chance to break up the conduit walls with respect to a
vesiculated melt. The variety of xenoliths of a lava reflects
a set of wall-rocks with similar mechanical properties and
may not mirror the stratigraphy of the substratum of a
volcanic area.PublishedL093023.6. Fisica del vulcanismoJCR Journalreserve
Technologies and Formulation Design of Polysaccharide-Based Hydrogels for Drug Delivery
No full textPolysaccharide-based hydrogel particles (PbHPs) are very promising carriers aiming to control and target the release of drugs with different physico-chemical properties. Such delivery systems can offer benefits through the proper encapsulation of many drugs (non-steroidal and steroidal anti-inflammatory drugs, antibiotics, etc) ensuring their proper release and targeting. This review discusses the different phases involved in the production of PbHPs in pharmaceutical technology, such as droplet formation (SOL phase), sol-gel transition of the droplets (GEL phase) and drying, as well as the different methods available for droplet production with a special focus on prilling technique. In addition, an overview of the various droplet gelation methods with particular emphasis on ionic cross-linking of several polysaccharides enabling the formation of particles with inner highly porous network or nanofibrillar structure is given. Moreover, a detailed survey of the different inner texture, in xerogels, cryogels or aerogels, each with specific arrangement and properties, which can be obtained with different drying methods, is presented. Various case studies are reported to highlight the most appropriate application of such systems in pharmaceutical field. We also describe the challenges to be faced for the breakthrough towards clinic studies and, finally, the market, focusing on the useful approach of safety-by-design (SbD)
Zinc and calcium cations combination in the production of floating alginate beads as prednisolone delivery systems
No full textThe aim of this research was to verify the application of alginate in combination with Ca2+ and Zn2+ ions to produce a floating and prolonged release system for the oral administration of prednisolone. Hollow and floating gel-beads were designed using prilling/ionotropic gelation as the microencapsulation technique, zinc acetate in the gelling solution as the alginate external crosslinker, and calcium carbonate in the feed as the internal crosslinking agent able to generate gas when in contact with the acidic zinc acetate solution. To achieve this goal, drug/alginate solutions were opportunely combined with different amounts of calcium carbonate. The effect of the addition of calcium carbonate into the feed solution on buoyancy, encapsulation efficiency, morphology, size distribution, as well as in vitro drug release profile of the alginate particles was studied. Moreover, the ability of the floating beads to modulate in vivo the anti-inflammatory response was assayed using the carrageenan-induced acute oedema in rat paw. The proposed strategy allowed obtaining alginate beads with extremely high encapsulation efficiency values (up to 94%) and a very porous inner matrix conferring buoyancy in vitro in simulated gastric fluid up to 5 h. Moreover, in vivo, the best formulation, F4, resulted in the ability to prolong the anti-inflammatory effect up to 15 h compared with raw prednisolone
Pectin and zinc alginate: The right inner/outer polymer combination for core-shell drug delivery systems
No full textCore-shell beads loaded with betamethasone were developed using co-axial prilling as production technique and pectin plus alginate as polymeric carriers. During this study, many operative conditions were intensively investigated to find the best ones necessary to produce uniform core-shell particle systems in a reproducible way. Particularly, feed solutions’ composition, polymers mass ratios and the effect of the main process parameters on particles production, micromeritics, inner structure, drug loading and drug-release/swelling profiles in simulated biological fluids were studied. The optimized core-shell formulation F5 produced with a pectin core concentration of 4.0% w/v and an alginate shell concentration of 2.0% w/v (2:1 core:shell ratio) acted as a sustained drug delivery system. It was able to reduce the early release of the drug in the upper part of the gastro-intestinal tract for the presence of the zinc-alginate gastro-resistant outer layer and to specifically deliver it in the colon, thanks to the selectivity of amidated low methoxy pectin core for this district. Therefore, these particles may be proposed as colon targeted drug delivery systems useful for inflammatory bowel disease (IBD) therapy
METODO DI TRATTAMENTO DI UN MANUFATTO IN MATERIALE FIBROSO, MANUFATTO OTTENUTO MEDIANTE TALE METODO E DISPOSITIVO MEDICO E/O SANITARIO E/O PER LA CURA DELLA PERSONA COMPRENDENTE TALE MANUFATTO
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