Search results for " Light scattering"
showing 10 items of 265 documents
Acs aberāciju un gaismas izkliedes ietekme uz redzes kvalitāti.
2020
Darbs ir uzrakstīts angļu valodā 66 lapām. Tā satur 33 attēlus, 3 tabulas, 8 grafiki un 121 atsauces uz literatūras avotiem. Mērķis. Izpētīt saistību starp cilvēka redzi un acs iekšējo gaismas izkliedi un mēģināt saprast, vai intraokulārā gaismas izkliede ietekmē acs aberācijas. Izpētīta Strehl koeficientu normalitāte. Metodes. Redzes asumu un jutīgumu pret kontrastu novērtē parastā stāvoklī un ar 3 dažādiem izkliedes filtriem 10 jaunu un veselīgu acu grupai. Pašizveidota modeļa acs viļņu frontes kļūdas tiek izmeklētas ar izkliedes filtriem un bez tiem. Rezultāti. Redzes asums un jutība pret kontrastu ir sliktāka, ja izkliedēšanas filtri tiek novietoti subjekta acu priekšā (p <.05). VA iete…
Relation between structural and release properties in a polysaccharide gel system.
2007
Abstract The potential utility of κ-carrageenan gels for preparing drug release devices is here shown. Structural properties of κ-carrageenan gels prepared with different salt composition and containing Ketoprofen sodium salt, as model drug, have been evaluated with static light scattering and rheological measurements. These properties have been correlated with release profiles in vitro at pH 5.5. Release properties from gelled matrices have been compared with those obtained by two commercial products containing the same drug. Results show that: i) in this system it is possible to easily control the gel texture by using different cationic concentration; ii) the kinetics of drug release by κ…
Synthesis, characterization and study of covalently modified triazole LAPONITE® edges
2020
Abstract LAPONITE® (Lap) clay mineral was successful functionalized by triazole groups in a two steps procedure. First, the Lap edges were modified with 3-azidopropyltrimethoxysilane by traditional heating and microwave irradiation. Microwave irradiation allowed us to obtain high loading onto the Lap edges in lower times compared to those obtained through conventional method. Afterwards, the triazole moieties were obtained by reaction between azido functionalized Lap and propargyl alcohol. The successful functionalization of Lap was proved by thermogravimetric analysis, FT-IR spectroscopy, dynamic light scattering and ζ-potential measurements. Finally, the effects of the surface modificatio…
Modification of calix[4]arenes with CMPO-functions at the wide rim. Synthesis, solution behavior, and separation of actinides from lanthanides
2003
Two calix[4]arene tetraethers (Y = C5H11, C14H29) bearing on their wide rim four –N(Me)–CO–CH2–P(O)Ph2 residues were synthesized for the first time. Their ability to extract lanthanides and actinides from an acidic aqueous phase to organic phases (CH2Cl2, NPHE) was studied. In comparison to the corresponding –NH-analogs, they are less efficient extractants, the selectivity for the light over the heavy lanthanides is less pronounced, while there is still an interesting selectivity of Am3+ over Eu3+. Stability constants for selected lanthanide salts were determined also in homogenous phase (methanol, acetonitrile) but do not account for the different extraction results. The complexation of Gd…
An Improved Empirical Relation to Determine the Particle Number Density of Fluid-Like Ordered Charge-Stabilized Suspensions
2001
Polystyrene as an archetypal charge-stabilized colloid model system was used in this work under well defined preparation conditions. A continuous preparation technique was used to control the suspension parameters salt concentration c and particle number density n. Measurements of n were performed using both conductivity in the completely deionized state and static light scattering. We found a significant deviation between the position of the first maximum of the static structure factor qmax=2π/L and an estimate identifying the relevant length scale L with the average inter-particle distance d¯=n−1/3. Instead, qmax was observed to follow the relation qmax=(2.20±0.03)π/d¯, which is equivalen…
Liposome Formation from Bile Salt–Lipid Micelles in the Digestion and Drug Delivery Model FaSSIFmod Estimated by Combined Time-Resolved Neutron and D…
2011
The flow of bile secretion into the human digestive system was simulated by the dilution of a bile salt-lipid micellar solution. The structural development upon the dilution of the fed state bile model FeSSIF(mod6.5) to the fasted state bile model FaSSIF(mod) was investigated by small-angle neutron scattering (SANS) and dynamic light scattering (DLS) in crossed beam experiments to observe small and large structures in a size range of 1 nm to 50 μm in parallel. Because of the physiologically low lipid and surfactant concentrations of 2.625 mM egg-phosphatidylcholine and 10.5 mM taurocholate the sensitivity of the neutron-structural investigations was improved by partial solvent deuteration w…
Synergistic behavior of poly(aspartic acid) and Pluronic F127 in aqueous solution as studied by viscometry and dynamic light scattering.
2012
Abstract Pluronic F127/poly(aspartic acid) mixtures were investigated in dilute solutions by viscometry and dynamic light scattering. The two polymers were chosen due to well known applications in biomedical field, taking into account the final purpose (the use of the complex structure as drug delivery systems). The central item was to identify the possibility of complexation between the poly(carboxylic acid) and a non-ionic polymer and to investigate the conditions of the interpolymer complex formation. The ability of Pluronic F127 to form micelle is well known. Poly(aspartic acid), as a polycarboxylic acid with resemblance with polyacrylic acid, can act as dispersant, antiscalant, superab…
An Artificial Neural Network Assisted Dynamic Light Scattering Procedure for Assessing Living Cells Size in Suspension
2020
Dynamic light scattering (DLS) is an essential technique used for assessing the size of the particles in suspension, covering the range from nanometers to microns. Although it has been very well established for quite some time, improvement can still be brought in simplifying the experimental setup and in employing an easier to use data processing procedure for the acquired time-series. A DLS time series processing procedure based on an artificial neural network is presented with details regarding the design, training procedure and error analysis, working over an extended particle size range. The procedure proved to be much faster regarding time-series processing and easier to use than fitti…
Formation of two-dimensional crystals of icosahedral RNA viruses.
2007
International audience; The formation of 2D arrays of three small icosahedral RNA viruses with known 3D structures (tomato bushy stunt virus, turnip yellow mosaic virus and bromegrass mosaic virus) has been investigated to determine the role of each component of a negative staining solution containing ammonium molybdate and polyethylene glycol. Virion association was monitored by dynamic light scattering (DLS) and virus array formation was visualised by conventional transmission electron microscopy and cryo-electron microscopy after negative staining. The structural properties of viral arrays prepared in vitro were compared to those of microcrystals found in the leaves of infected plants. A…
Potential dopamine prodrug-loaded liposomes: preparation, characterization, andin vitrostability studies
2010
Dopamine delivery to the central nervous system (CNS) undergoes the permeability limitations of the blood-brain barrier (BBB). Condensation of dopamine with neutral amino acids could afford potential pro- drugs able to interact with the BBB endogenous transporters and easily enter the brain. To improve the bio-availability of the dopamine prodrug, 2-amino-N-[2-(3,4-dihydroxy-phenyl)-ethyl]-3-phenyl-propionamide (DOPH), it was encapsulated in unilamellar liposomes of dimiristoylphosphatidylcholine (DMPC)and cholesterol. Vesicles were characterized by dynamic light scattering in order to evaluate their dimensions and vesicle stability, by zeta-potential measurements, by means of electronic mi…