Search results for "Dissolution"
showing 10 items of 333 documents
Nanostructure Formation on ZnSe Crystal Surface by Electrochemical Etching
2021
The article describes a simple method for nanostructuring the surface of monocrystalline zinc selenide. It is shown that the traditional electrochemical etching of n-ZnSe (111) samples in a concentrated solution of nitric acid leads to the appearance of massive etching pits and small pores on the surface. The dynamics of the process and stages of crystal dissolution has been studied. It is assumed that the porous zinc selenide obtained in this way can be used in optoelectronic structures, as well as as buffer layers for growing zinc oxide.
Change of arsenite adsorption mechanism during aging of 2-line ferrihydrite in the absence of oxygen
2018
Abstract Arsenite was effectively immobilized by 2-line ferrihydrite at different pH values (4.0, 5.5 and 7.4) and adsorbent dosages (0.4, 1, and 2 g/L) in the absence of oxygen, showing an initial surface diffusion-controlled period (Stage I, 2 h). Dissolved δ 56 Fe increased during Stage I and decreased during Stage II, resulting from aging of ferrihydrite and equilibrium isotopic exchange, respectively. The ferrihydrite aging was hampered by both high As concentrations and high pH values close to the pH zpc , due to inhibition of mineral dissolution as a prerequisite for mineral transformation. During Stage I, As was adsorbed by both bidentate binuclear corner-sharing ( 2 C ) and monoden…
Development and Optimization of Pre-Concentration Procedure of Rare-Earth Elements (REEs) in Their Minerals, Using Microwave - Assisted Sample Dissol…
2015
Abstract The aim of this research was to develop and optimize a procedure for determination of REEs in xenotime and monazite samples collected from Bangka Island, which were compared to Standard Monazite (71 AG) of Bureau of Analyzed Samples, London. ICP-OES method was used for the determination. The samples were dried and sterilized by heating for a week at 110 °C, before digesting with nitric acid and hydrofluoric acid, using a microwave-assisted digestion system. After a careful line selection, at the detection limits for all REEs in the ng/mL the REEs were reliably obtained at the 0.09 – 38% level.
Calcification is not the Achilles'heel of cold-water corals in an acidifying ocean
2015
Ocean acidification is thought to be a major threat to coral reefs: laboratory evidence and CO2 seep research has shown adverse effects on many coral species, although a few are resilient. There are concerns that cold-water corals are even more vulnerable as they live in areas where aragonite saturation (Omega ara) is lower than in the tropics and is falling rapidly due to CO2 emissions. Here, we provide laboratory evidence that net (gross calcification minus dissolution) and gross calcification rates of three common cold-water corals, Caryophyllia smithii, Dendrophyllia cornigera, and Desmophyllum dianthus, are not affected by pCO2 levels expected for 2100 (pCO2 1058 µatm, Omega ara 1.29),…
On the interlayer spacing collaps of the Cloisite® 30B organoclay
2011
Oral Solid Dosage Form Disintegration Testing — The Forgotten Test
2014
Since its inception in the 1930s, disintegration testing has become an important quality control (QC) test in pharmaceutical industry, and disintegration test procedures for various dosage forms have been described by the different pharmacopoeias, with harmonization among them still not quite complete. However, because of the fact that complete disintegration does not necessarily imply complete dissolution, much more research has been focused on dissolution rather than on disintegration testing. Nevertheless, owing to its simplicity, disintegration testing seems to be an attractive replacement to dissolution testing as recognized by the International Conference on Harmonization guidelines, …
New binary solid dispersion of indomethacin with surfactant polymer: From physical characterization to in vitro dissolution enhancement
2009
This article investigated preparation of solid dispersions containing a poor water-soluble drug, indomethacin (IND), and a new surfactant polymer, polyoxyethylene 32 distearate (POED). Solid dispersions were prepared by the melting method and characterized by DSC, hot-stage microscopy (HSM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). DSC and HSM analyses performed on IND/POED physical mixtures indicated that IND could dissolve in liquid POED. The materials showed complete miscibility at liquid state. Combination of DSC, XRD, and SEM revealed that these materials had limited miscibility at the solid state. Up to 20% w/w IND in POED, we did not detect significant modifica…
Effect of thickener on disintegration, dissolution and permeability of common drug products for elderly patients
2019
Dysphagia is a very common problem suffered by elderly patients. The use of thickeners during administration in these patients helps to prevent difficulties with swallowing larger solid dosage forms. However, there are several indications when the thickeners may influence disintegration and dissolution processes of solid dosage forms, potentially affecting therapeutic efficacy. In this paper the effects of a commonly used thickener on tablet disintegration, dissolution and subsequent absorption of 6 formulated drugs frequently used in elderly patients (Aspirin, Atenolol, Acenocumarol, Candesartan, Ramipril and Valsartan) in two different administration conditions (intact tablet and crushed …
Novel inulin-based mucoadhesive micelles loaded with corticosteroids as potential transcorneal permeation enhancers
2017
In this work a new copolymer of inulin (INU) derivatized with ethylendiamine (EDA) and retinoic acid (RA), named INU-EDA-RA, was synthetized, characterized and employed to produce micelles as carriers for topical administration of corticosteroids for the potential treatment of diseases of posterior eye segment. Spectroscopic analysis confirmed a molar derivatization degree of 11.30 and 4.30% in EDA and RA, respectively. INU-EDA-RA micelles are capable of strong mucoadhesive interactions which result time-independent and stable over time but concentration depending. Moreover micelles are able to encapsulate efficiently from 3 to 13% (w/w) of lipophilic drugs, as dexamethasone, triamcinolone …
Amorphous Ropinirole-Loaded Mucoadhesive Buccal Film: A Potential Patient-Friendly Tool to Improve Drug Pharmacokinetic Profile and Effectiveness
2020
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