Search results for "surface"
showing 10 items of 9345 documents
Time-resolving Analysis of Cryotropic Gelation of Water/Poly(Vinyl Alcohol) Solutions via Small Angle Neutron Scattering
2007
The structural transformations occurring in initially homogeneous aqueous solutions of poly(vinyl alcohol) (PVA) through application of freezing (-13 degrees C) and thawing (20 degrees C) cycles is investigated by time resolving small-angle neutron scattering (SANS). These measurements indicate that formation of gels of complex hierarchical structure arises from occurrence of different elementary processes, involving different length and time scales. The fastest process that could be detected by our measurements during the first cryotropic treatment consists of the crystallization of the solvent. However, solvent crystallization is incomplete, and an unfrozen liquid microphase more concentr…
Mesoscopic and Microscopic Investigation on Poly(vinyl alcohol) Hydrogels in the Presence of Sodium Decylsulfate
2007
The structure of poly(vinyl alcohol) (PVA) hydrogels formed as a result of freeze/thaw treatments of aqueous solutions of the polymer (11 wt % PVA) in the freshly prepared state is analyzed through the combined use of small (SANS) and ultrasmall (USANS) angle neutron scattering techniques. The structure of these hydrogels may be described in terms of polymer rich regions, with dimensions of the order of 1-2 microm, dispersed in a water rich phase, forming two bicontinuous phases. The PVA chains in the polymer rich phase form a network where the cross-linking points are mainly crystalline aggregates of PVA having average dimensions of approximately 45 A. The structural organization of freeze…
Resist-based silver nanocomposites synthesized by lithographic methods
2010
In this work, the formation of silver metal nanoparticles inside a negative-tone resist based on poly(vinyl alcohol) is achieved by electron beam lithography. The chemistry of this sensitive resist allows the production of nanoparticles as well as the polymer crosslinking by the electron radiation. Due to the presence of the silver nanoparticles, the final composite exhibits a plasmonic behavior, which was characterized by measuring the absorbance. The lithographic properties of the resist have been characterized. The technique has also been exported to UV lithography, where silver nanoparticles are obtained inside the polymeric patterns after optical lithography.
ISFET drawbacks minimization using a novel electronic compensation
2004
Ion sensitive field effect transistor (ISFET) and membrane field effect transistor (MEMFET) have some drawbacks related to: long-term drift, hysteresis and thermal drift. These factors limit the accuracy of ISFET/MEMFET based measurements systems, specially for continuous or long period measurements. Due to its accuracy, repeatability and easy-to-use features, electronic instrumentation systems are the best tools to design ISFET/MEMFET based measurement systems. A well-designed hardware and a qualified virtual instrumentation software are the key factors to overcome and compensate hysteresis, thermal and long-term drifts ISFET/MEMFET limitations. The paper is dedicated to show an instrument…
Lactococcal 949 group phages recognize a carbohydrate receptor on the host cell surface
2015
ABSTRACT Lactococcal bacteriophages represent one of the leading causes of dairy fermentation failure and product inconsistencies. A new member of the lactococcal 949 phage group, named WRP3, was isolated from cheese whey from a Sicilian factory in 2011. The genome sequence of this phage was determined, and it constitutes the largest lactococcal phage genome currently known, at 130,008 bp. Detailed bioinformatic analysis of the genomic region encoding the presumed initiator complex and baseplate of WRP3 has aided in the functional assignment of several open reading frames (ORFs), particularly that for the receptor binding protein required for host recognition. Furthermore, we demonstrate th…
Viscoelastic properties of concentrated dispersions in water of soy lecithin
2003
Abstract Viscoelastic properties of soy lecithin dispersions at 60, 120, 180 and 240 g l−1 in water have been studied as a function of ionic strength (NaCl concentrations in the range 10−5–10−2 mol l−1) and of preparation method (sonication, freezing–unfreezing). Viscosity measurements of sonicated dispersions in a rotatory viscometer show Newtonian and plastic (Bingham) behavior, whereas the frozen–unfrozen dispersions show a spectacular change in their viscoelastic properties, that is, a non-Newtonian behavior with pseudoplastic characteristics and rheopexy. These properties have been related to electrokinetic characteristics of the segregated vesicles in each case. A decrease in ζ-potent…
La adaptación al uso turístico del patrimonio cultural : una propuesta metodológica de evaluación
2020
El patrimoni és una construcció sociocultural i la seva funció depèn dels valors, interessos, tradicions i identitats de cada societat i de cada moment, de manera que queda subjecta tant al seu valor intrínsec com a allò que representa. Quan aquest patrimoni desperta l'interès en el turisme, apareix una nova funció, però, com que cap patrimoni ha nascut amb la finalitat d'oci, el seu condicionament resulta una tasca indiscutible. Aquesta investigació se centra en aquest procés de transformació per a l'ús turístic del patrimoni cultural immoble, amb l'ànim d'identificar quins elements són necessaris perquè l'activitat turística sigui adequada. L'acadèmia (via Delphi) i els visitants cultural…
Effects of Dissolved Complexation on REE Fate During Interactions between Volcanic Ash and Coexisting Fluids
2013
AbstractThis work analyzes REE behavior during the delivery of volcanic ash into a marine system and highlights the effects induced by dissolved carbonate and humate complexes on REE release. Kinetic experiments were carried out during a 6-month period using a batch method approach. Results show that the highest degree of REE leaching occurs during the early stage. Altered phases that crystallize induce REE sorption and dissolved complexation towards surface complexation, concurrent processes that are enhanced by Y/Ho, La/Yb, and Ce/Ce* changes, whereas dissolved humates and carbonates influence the dissolution rate of ash and the dissolved REE behavior.
Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring
2016
OVSICORI Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high‐frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2‐rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are acc…
Fractal approach in petrology: Small-angle neutron scattering experiments with volcanic rocks.
1988
Following Mandelbrot's pioneering work in 1977, we attempt to use the concept of fractal dimension in petrology. Fractal dimension is an intensive property of matter which offers a quantitative measure of the degree of surface roughness. Neutron scattering experiments have been performed on 18 volcanic rocks from different localities. The scattered intensity as a function of the momentum transfer obeys a power law whose exponent varies, for the rock samples presented, between -3 and -4. We conclude that, at the molecular level, our volcanic rocks are not fractal volumes. With regard to the particle-matrix interface, it is not possible to provide a determination at the present stage of resea…