Interactive mixing between agglomerated drug particles and coarse carrier particles

Abstract

The equation of Egermann¹ was used to calculate the theoretical coefficient of variation in drug content of completely random interactive mixtures containing furosemide and sodium chloride. These coefficients of variation (CV) were compared to that obtained experimentally. Although no free furosemide agglomerates or aggregates were present in the mixtures, the experimental values were consistently higher. This could only be explained if small furosemide aggregates accumulated in clefts and crevices in the sodium chloride particle surfaces. For the system examined random interactive mixtures were produced with furosemide concentrations between 0.05 and 4%     

Dissolution Rate A Measurement of the Deaggregation of Furosemide Agglomerates During An Interactive Mixing Process

Agglomerates of drug particles must be broken down and single particles attached to the carrier to ensure a completely random interactive mixture. Here it was found that the dissolution rates of samples from interactive mixtures compared to suspended furosemide was an indication of the deaggregation of furosemide agglomerates during an interactive mixing process. Deaggregation depended on the forces generated during mixing and was quicker when a high density carrier such as sodium chloride was used.     

Dissolution Rate A Measurement of the Deaggregation of Furosemide Agglomerates During An Interactive Mixing Process

Abstract

Agglomerates of drug particles must be broken down and single particles attached to the carrier to ensure a completely random interactive mixture. Here it was found that the dissolution rates of samples from interactive mixtures compared to suspended furosemide was an indication of the deaggregation of furosemide agglomerates during an interactive mixing process. Deaggregation depended on the forces generated during mixing and was quicker when a high density carrier such as sodium chloride was used.     

On the polymer modified cement mortars with different lightweight aggregates in marine environment

Having a light weight is a design objective for offshore and coastal structures and in order to reach this aim, use of lightweight concrete consisting lightweight aggregates and polymers is a feasible solution. In this study, materials obtained from locally available crushed volcanic scoria as main aggregate and some additional lightweight aggregates with ceramic, perlite and andesite as well polymers were used in the mixtures with different proportions (totally 14 mixtures) to propose feasible alternatives for coastal structure designers. To evaluate the design performances of the mixtures, their properties such as density, cylinder compressive strength, capillarity, loss of mass under the effects of the agents in marine environment such as sodium sulphate and sodium chloride were obtained experimentally. It was found that mixtures with scoria aggregates showed more favourable results and additional aggregates gave flexibility to the designer to lower densities up to 40 % ‐ 60 % of normal‐weight mixtures. Polymer modification also improved the performance of the related materials.     

Compressive strength and durability properties of ceramic wastes based concrete

This paper presents an experimental study on the properties and on the durability of concrete containing ceramic wastes. Several concrete mixes possessing a target mean compressive strength of 30 MPa were prepared with 20% cement replacement by ceramic powder (W/B = 0.6). A concrete mix with ceramic sand and granite aggregates were also prepared as well as a concrete mix with natural sand and coarse ceramic aggregates (W/B = 0.5). The mechanical and durability performance of ceramic waste based concrete are assessed by means of mechanical tests, water performance, permeability, chloride diffusion and also accelerated aging tests. Results show that concrete with partial cement replacement by ceramic powder although it has minor strength loss possess increase durability performance. Results also shows that concrete mixtures with ceramic aggregates perform better than the control concrete mixtures concerning compressive strength, capillarity water absorption, oxygen permeability and chloride diffusion. The replacement of cement and aggregates in concrete by ceramic wastes will have major environmental benefits.     

Metal-coated colloidal particles

Procedures are described for coating of submicrometre ceramic powders with copper and nickel. The process required precoating of the core particles with a palladium catalyst. A precoating procedure was developed in which palladium chloride is reduced by sodium hypophosphite or stannous chloride on the powder surface in aqueous suspensions. Commercial electroless solutions were used to deposit copper and nickel on the catalysed powders. The effect of various experimental parameters on the effectiveness of the surface conditioning of the particles was also investigated.     

Impact of bitumen and aggregate composition on stripping in bituminous mixtures

The impact of bitumen and aggregate composition on stripping was investigated using four bitumens and four aggregates. Moisture sensitivity was assessed based on retained resilient modulus and tensile strength ratio (MRR and TSR, respectively). The results indicate that mixtures from the bitumen with a high acid number exhibited high resilient modulus and tensile strength in the dry condition for all the aggregates. In wet condition, this conclusion did also hold except for one aggregate. Regarding penetration grade, mixtures made with lower penetration grade bitumen exhibited higher resilient modulus and tensile strength, in dry and wet conditions, than those of higher penetration grade. Bitumen characteristics like acid number, penetration grade and molecular size distribution did not influence moisture sensitivity. Mixtures with aggregates containing alkali metals (sodium and potassium) exhibited relatively high moisture sensitivity, regardless of the bitumen used. In contrast, indications of moisture sensitivity were not apparent in mixtures made with aggregates containing calcium, magnesium and iron. Data analysis revealed that variability in moisture sensitivity is attributed to aggregate rather than bitumen. No significant interaction effect between bitumen and aggregate was found on moisture sensitivity. The results indicated good correlation between MRR and TSR in ranking mixtures for stripping.     

AGGREGATION DURING THE DISSOLUTION OF DIAZEPAM IN INTERACTIVE MIXTURES

The dissolution of micronized diazepam (1.0-10.0%) in interactive mixtures with lactose-povidone, Emdex®, TabBase® and Compactrol® as carriers was investigated using the USP paddle method and distilled water as the dissolution medium. Dissolution rate of the binary diazepam-carrier mixtures increased using more soluble carriers such as lactose-povidone and decreased as the diazepam concentration of the mixtures increased. The data were interpreted by considering dissolution from both dispersed and aggregated particles and modelled using monoexponential and biexponential equations allowing the estimation of reciprocal dissolution rate constants for dispersed and aggregated particles (k_d and k_a and initial aggregate concentrations (C_a). The estimated k_d parameters were independent of carrier and diazepam concentration while the ka. parameters varied and were dependent on the aggregate size distribution in the interactive mixtures studied. The degree of aggregation increased markedly with increasing diazepam concentration and was greatest for the less soluble carrier, Compactrol®. Ternary surfactant interactive mixtures containing diazepam and sodium lauryl sulphate (100:2) adhered to the carrier surface were developed and demonstrated improved dissolution rates which were attributed to the deaggregation effect of the surfactant in the aggregate microenvironment. The effect was most noticeable at 10 percent drug loadings where the surfactant concentration was greatest and where both the k_a and C_a parameters were minimized.     

The Tensile Strength of Tablets of Binary Mixtures Lubricated with Magnesium Stearate

Abstract

The influence of magnesium stearate on the tensile strength of tablets prepared from binary mixtures of materials lubricated with magnesium stearate have been studied. Mixtures of which both components (lactose and Emcompress) compact by fragmentation are largely unaffected. For a mixture of materials with dissimilar compaction mechanisms, (lactose and sodium chloride) magnesium stearate has a significant effect in that the originally high tensile strength of the sodium chloride is reduced to the level of lactose and the strengths of the mixtures and independent of the proportion of the components.     

Fluid transport in high volume fly ash mixtures with and without internal curing

The transport of fluid and ions in concrete mixtures is central to many aspects of concrete deterioration. As a result, transport properties are frequently measured as an indication of the durability that a concrete mixture may be expected to have. This paper is the second in a series investigating the performance of high volume fly ash (HVFA) mixtures with low water-to-cementitious ratios (w/cm) that are internally cured. While the first paper focused on strength and shrinkage, this paper presents the evaluation of the transport properties of these mixtures. Specifically, the paper presents results from: rapid chloride migration (RCM), rapid chloride penetration test (RCPT), apparent chloride diffusion coefficient, surface electrical resistivity, and water absorption. The test matrix consisted of mortar samples with two levels of class C fly ash replacement (40% and 60% by volume) with and without internal curing provided with pre-wetted lightweight fine aggregates (LWA). These mixtures are compared to plain ordinary portland cement (OPC) mortars. The results indicate that HVFA mixtures with and without internal curing provide benefits in terms of reduced transport coefficients compared to the OPC mixtures.     

应用纳滤膜分离糖和盐的实验研究

选择NF-45纳滤膜进行糖和盐单组分和混合体系的分离实验研究,考察了纳滤膜分离性能随着操作压力、循环流量及料液浓度的变化所受到的影响。讨论了葡萄糖-氯化钠、蔗糖-氯化纳混合体系中糖和盐的相互影响作用,认为可以运用NF-45纳滤膜在适宜的操作条件（如操作压力、料液浓度）实现糖和盐的较好分离。     

Effects of Interparticulate Interactions on Mixing Homogeneity

Abstract

By theoretical approach, the highest degree of mixing of cohesive, interactive powders was derived to conform to the homogeneity of the random mixture of free-flowing, non-interactive constituents. Particulate interactions like adherence of a cohesive drug ingredient to the diluent component, cannot yield ordered mixtures of higher degree of homogeneity under real mixing conditions.

These conclusions were confirmed by mixing experiments, using minor proportions of free-flowing and of cohesive drug constituents, and diluents in excess. With both types of drug powders, the quality of the random mixture was attained. Ordered mixtures of higher degree of homogeneity could not be produced.     

Effect of sodium alterations on hepatic cytochrome P450 3A2 and 2C11 and renal function in rats

Numerous dietary supplements are known to modulate cytochrome P450 (CYP)-mediated metabolism and subsequently alter drug toxicity or efficacy in animals and humans. In the present study we investigated the effect of varying amounts of sodium intake on renal function and the metabolic activity of the hepatic CYP3A2 and CYP2C11 isoforms. Rats were maintained on standard rodent chow or a low-salt rice diet. Within each of these groups rats received either a single intraperitoneal injection of furosemide to initiate salt depletion, or saline. Additional groups included salt supplementation of 500 mg/300 g body weight/day and 1.25 g/300 g body weight/day of sodium chloride solution. Rats receiving the low-salt diet, both with and without a concomitant furosemide administration, had a significant reduction in creatinine clearance without changes in serum creatinine. In addition, urine flow rate was markedly reduced in rats maintained on the low-salt diet. Western blot analysis indicated that neither sodium supplementation nor deprivation altered hepatic microsomal CYP3A2 levels; however, hepatic CYP2C11 levels significantly increased in rats receiving the largest sodium supplement. In vitro metabolic activity of CYP3A2 was unchanged as compared with controls. Activity of CYP2C11 was significantly reduced in both rat groups receiving additional sodium supplements. Acute manipulation of daily sodium intake does alter renal function and specific hepatic CYP isoforms and should be considered when using these rat models.     

AGGREGATION DURING THE DISSOLUTION OF DIAZEPAM IN INTERACTIVE MIXTURES

ABSTRACT

The dissolution of micronized diazepam (1.0-10.0%) in interactive mixtures with lactose-povidone, Emdex®, TabBase® and Compactrol® as carriers was investigated using the USP paddle method and distilled water as the dissolution medium. Dissolution rate of the binary diazepam-carrier mixtures increased using more soluble carriers such as lactose-povidone and decreased as the diazepam concentration of the mixtures increased. The data were interpreted by considering dissolution from both dispersed and aggregated particles and modelled using monoexponential and biexponential equations allowing the estimation of reciprocal dissolution rate constants for dispersed and aggregated particles (k_d and k_a and initial aggregate concentrations (C_a). The estimated k_d parameters were independent of carrier and diazepam concentration while the ka. parameters varied and were dependent on the aggregate size distribution in the interactive mixtures studied. The degree of aggregation increased markedly with increasing diazepam concentration and was greatest for the less soluble carrier, Compactrol®. Ternary surfactant interactive mixtures containing diazepam and sodium lauryl sulphate (100:2) adhered to the carrier surface were developed and demonstrated improved dissolution rates which were attributed to the deaggregation effect of the surfactant in the aggregate microenvironment. The effect was most noticeable at 10 percent drug loadings where the surfactant concentration was greatest and where both the k_a and C_a parameters were minimized.     

Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

In this study, the fresh and hardened properties of self-compacting concrete (SCC) using recycled concrete aggregate as both coarse and fine aggregates were evaluated. Three series of SCC mixtures were prepared with 100% coarse recycled aggregates, and different levels of fine recycled aggregates were used to replace river sand. The cement content was kept constant for all concrete mixtures. The SCC mixtures were prepared with 0, 25, 50, 75 and 100% fine recycled aggregates, the corresponding water-to-binder ratios (W/B) were 0.53 and 0.44 for the SCC mixtures in Series I and II, respectively. The SCC mixtures in Series III were prepared with 100% recycled concrete aggregates (both coarse and fine) but three different W/B ratios of 0.44, 0.40 and 0.35 were used. Different tests covering fresh, hardened and durability properties of these SCC mixtures were executed. The results indicate that the properties of the SCCs made from river sand and crushed fine recycled aggregates showed only slight differences. The feasibility of utilizing fine and coarse recycled aggregates with rejected fly ash and Class F fly ash for self-compacting concrete has been demonstrated.     

Effect of a new functional double-hydrophilic block copolymer PAAL on the morphology of calcium carbonate particles

Calcium carbonate (CaCO₃) particles with various shapes were prepared by the reaction of sodium carbonate with calcium chloride in the presence of a new functional double-hydrophilic block copolymer poly (acrylic acid)-block-(acrylic hydroxy lactide) (PAAL) at room temperature. The as-prepared products were characterized with scanning electron microscopy and X-ray diffraction. The effects of pH, concentration of PAAL and CaCO₃ on the crystal form and morphologies of the as-prepared CaCO₃ were investigated. The results show that pH, concentration of PAAL and CaCO₃ are important parameters for the control of morphologies of CaCO₃. Depending on the experimental conditions, various morphologies of CaCO₃, such as plate-like aggregates, poly-nucleated spheres, ellipsoids, monodispersed spheres, rhombohedras, etc., can be obtained. Especially, the optimal experimental conditions for the production of monodispersed spherical CaCO₃ particles were determined.     

Dissolution from ordered mixtures: The effect of stirring rate and particle characteristics on the dissolution rate.

Different particle size fractions of three carriers were used to prepare ordered mixtures of frusemide. The dissolution of these mixtures were compared with a frusemide suspension and pure frusemide agglomerates by the USP XXI paddle method at three rotational speeds.

The dissolution of mixtures containing a highly soluble carrier (sodium chloride) were comparable to the suspension depending on the particle size of the carrier. Insoluble carriers (dicalciumphosphatedihydrate and microcrystalline cellulose) increased the dissolution, but the enhancement depended on the rotational speed, the particle size and the density of the carrier.     

The combined effect of chlorides and sulphates present in water and aggregates on properties of concrete

The combined effect of sulphates present in aggregates and high levels of chloride ions in the mixing water on some properties of concrete was studied. Different amounts of sulphates in sand (0.38, 0.50, 0.75 and 1.0% SO₃) with chloride contents in water (50, 750, 1000, 3000 and 6000 p.p.m. as Cl⁻) were used. The compressive strength was lower for concrete with higher sulphate contents at early ages. Small additions of sodium chloride to the mixing water decreased the compressive strength of concrete, particularly those with a low sulphate content.     

Molecular dynamics simulation to assess the effect of temperature on diffusion coefficients of different ions and water molecules in C-S-H

Diffusion is a particle transportation process beginning from one point of a system to another through random molecular motion. This process depends on various parameters like temperature, concentration gradient, and particle size. The objective of this article is to assess the variation of diffusion coefficients of water molecules, chloride and sodium ions against different temperatures in calcium silicate hydrates (C-S-H) through molecular dynamics simulation. A uniform sodium chloride solution is modeled between cement hydrate layers with no concentration gradient. In such a solution, temperature could affect diffusion process in a significant manner. The two most important crystalline mineral analogues of C-S-H, tobermorite and jennite, are applied in this simulation. Diffusion coefficients of different ions and water molecules are found in different temperatures. It is revealed that diffusion coefficient is higher at high temperatures. Activation energies of chloride and sodium ions transport in cement hydrates are calculated through Arrhenius law. Output values of diffusion coefficients and activation energies are compared to previous experimental and simulation results in the related literature. A multi-scale analysis is run to estimate the penetration depth of \(\mbox{Cl}^{-}\) ions in cement paste through Fick’s second law.     

Preparation and mesostructure control of highly ordered zirconia particles having crystalline walls

Mesostructured zirconia particles having monoclinic-type crystalline walls were prepared using a low-temperature crystallization technique. Crystalline zirconia particles with highly-ordered mesostructures were obtained through the sol–gel process of zirconium sulfate tetrahydrate at 333 K in the presence of molecular self-assemblies of cetyltrimethylammonium bromide (CTAB) or mixtures of CTAB and anionic molecules such as sodium dodecyl sulfate and sodium p-toluenesulfonate. Variations in the molar ratios of CTAB and the chemical species of anionic molecules led to the variations in the periods of highly-ordered zirconia having crystalline walls. Calcination of the mesostructured zirconia particles prepared using templates consisting solely of CTAB yielded crystalline mesoporous zirconia particles.