Search results for "colloids"
showing 10 items of 89 documents
The effectiveness of Opuntia ficus-indica mucilage edible coating on postharvest maintenance of ‘Dottato’ fig (Ficus carica L.) fruit
2017
Abstract Breba figs are highly perishable and their shelf-life is very short. In this study, breba figs (cv. ‘Dottato’) were treated with a mucilage solution of Opuntia ficus-indica cladodes, sealed in plastic bags, and stored at 4 °C for 14 days. The effect of the edible coating on the shelf-life and qualitative attributes of the fruit were evaluated by colors, content of total soluble solids, titratable acidity, total phenol, total carotenoids. Results showed that coating improves the quality of breba fig during storage. The edible coating was effective in maintaining fruit fresh weight, visual score values, fruit firmness and total carotenoid content. Coated fruit showed a significantly …
Nonclassical crystallization in vivo et in vitro (I): Process-structure-property relationships of nanogranular biominerals.
2016
A distinct nanogranular fine structure is shared by a wealth of biominerals from several species, classes and taxa. This nanoscopic organization affects the properties and behavior of the biogenic ceramic material and confers on them attributes that are essential to their function. We present a set of structure-relationship properties that are rooted in the nanogranular organization and we propose that they rest on a common pathway of formation, a colloid-driven and hence nonclassical mode of crystallization. With this common modus operandi, we reveal the most fundamental and wide spread process-structure-property relationship in biominerals. With the recent increase in our understanding of…
Measurement of elastic forces between iron colloidal particles in a nematic liquid crystal.
2006
The forces that arise between two iron particles in a nematic liquid crystal with a strong homeotropic anchoring were studied. For the first time, the short range repulsive force resulting from the presence of a hedgehog defect between two particles was precisely determined thanks to application of a small magnetic field and observation of the equilibrium position resulting from the balance between the elastic and magnetic forces. Above a given threshold force, the particles stuck together whereas the hedgehog defect was expelled and transformed into a Saturn ring located between the particles. The attractive part of the interparticle force was determined with the same method on the entire …
Effects of confinement and external fields on structure and transport in colloidal dispersions in reduced dimensionality
2012
In this work, we focus on low-dimensional colloidal model systems, via simulation studies and also some complementary experiments, in order to elucidate the interplay between phase behavior, geometric structures and transport properties. In particular, we try to investigate the (nonlinear!) response of these very soft colloidal systems to various perturbations: uniform and uniaxial pressure, laser fields, shear due to moving boundaries and randomly quenched disorder.We study ordering phenomena on surfaces or in monolayers by Monte Carlo computer simulations of binary hard-disk mixtures, the influence of a substrate being modeled by an external potential. Weak external fields allow a control…
Motion, relaxation dynamics, and diffusion processes in two-dimensional colloidal crystals confined between walls
2012
The dynamical behavior of single-component two-dimensional colloidal crystals confined in a slit geometry is studied by Langevin dynamics simulation of a simple model. The colloids are modeled as pointlike particles, interacting with the repulsive part of the Lennard-Jones potential, and the fluid molecules in the colloidal suspension are not explicitly considered. Considering a crystalline strip of triangular lattice structure with n=30 rows, the (one-dimensional) walls confining the strip are chosen as two rigidly fixed crystalline rows at each side, commensurate with the lattice structure and, thus, stabilizing long-range order. The case when the spacing between the walls is incommensura…
Langevin dynamics simulations of a two-dimensional colloidal crystal under confinement and shear
2012
Langevin dynamics simulations are used to study the effect of shear on a two-dimensional colloidal crystal (with implicit solvent) confined by structured parallel walls. When walls are sheared very slowly, only two or three crystalline layers next to the walls move along with them, while the inner layers of the crystal are only slightly tilted. At higher shear velocities, this inner part of the crystal breaks into several pieces with different orientations. The velocity profile across the slit is reminiscent of shear banding in flowing soft materials, where liquid and solid regions coexist; the difference, however, is that in the latter case the solid regions are glassy while here they are …
[99mTc]Ca-Phytate: Some colloidal characteristics related to the optimal preparation conditions
1983
Abstract Some physico-chemical characteristics of the colloidal radiopharmaceutical [ 99 m Tc]Ca-phytate related to optimal preparation conditions have been studied. (1,2) It is demonstrated that the Ca 2+ -phytate stoichiometry is 6:1. Two different Ca-phytate colloids seem to be formed, mainly depending on the Ca 2+ :phytate molar ratio-one of low mycelar size for a 1:1 Ca 2+ :phytate molar ratio ( cmc ∗ = 5.10 −5 M ) , and another one, with a higher mycelar size for a 6:1 molar ratio (cmc = 8.10 −5 M). This last one it probably better for providing a good quality splenic uptake.
Basic properties of the F-type centers in halides, oxides and perovskites
2010
We present a short survey of the optical properties of primary radiation-induced point defects in alkali halides, simple oxides and some ABO3 perovskites. We discuss in details the optical properties of single electron F and F + centers in rock-salt (f.c.c.) alkali halides and oxides and show that the Mollwo–Ivey law well-known for the F-type centers in alkali halides may be extended for other rock-salt structure insulators. We also discuss the major differences in point defect production mechanisms in halides and oxides. We show that the Rabin–Klick diagram may be generalized for a whole family of alkali halides. The F-type center migration and aggregation into metal colloids in alkali hal…
Computer modeling of metal colloid formation in tracks of swift heavy ions in ionic solids
2001
Abstract We present results of computer modelling of the aggregation of primary radiation defects—F centers—in ionic crystals within tracks of swift heavy ions. We study how F-aggregate properties depend on the initial density of primary Frenkel defects in the track and its radius. The mean number of F centers in aggregates is typically very small, about five defects, which greatly complicates detection of expected metal colloids by ESR.
Physical forces in blister formation. The role of colloid osmotic pressure and of total osmolality in fluid migration into the rising blister.
1978
The physical forces operative in the fluid migration from the interstitial spaces into the blister cleft have not been directly measured until now. The colloid osmotic pressure and the total osmolality were determined in suction blister fluid after mild suction blister production by a modified “Dermovac” and in blister fluid of patients with dermatitis herpetiformis, bullous allergic contact dermatitis and pemphigus vulgaris and in the sera of healthy persons. The colloid osmotic pressure was measured by means of a recently developed osmometer with a semipermeable membrane between 2 chambers, one of them filled with Ringer solution, the other with the blister fluid or serum sample. The nega…