Influence Of Various Preparation Parameters Research Articles

Synergic effect of compositions and processing method on the performance of high strength alkali activated slag foam

Using inorganic porous materials for the insulation of a building improves energy efficiency. Alkali activated slag (AAS) foam concrete with a lower carbon footprint presents to be an alternative to cement-based foam concrete. In this study, the influence of various preparation parameters of AAS foam concrete on setting time, workability, compressive strength, bulk density, drying shrinkage and pore structure were investigated. A modified model was proposed to fit the relationship between compressive strength and geometrical information. Existing six structural models were used for the analytical description of the relationship between thermal conductivity and total porosity. Results show that increasing the mixing time can effectively extend the setting time and improve the workability of AAS foam slurry. The optimized mix proportion of AAS foam concrete exhibited a compressive strength of 24.1 MPa, thermal conductivity of 0.2322 W/(m·K) and adjustable setting time and workability for on-site casting. According to the comparison of the fitting results with other models, the proposed modified model for the relationship between compressive strength and geometrical information provided a better correlation with the experimental data. Analysis of the six structural models for the thermal conductivity showed that AAS foam concrete in this study favored the gaseous phase for heat transfer similar to the characteristic of dry sand.

The Influence of Various Preparation Parameters on the Histological Image of Bone Tissue during Implant Bed Preparation—An In Vitro Study

The purpose of this study was to present the level of bone tissue deformation after drilling under variable conditions in three different dental implant systems in a microscopic analysis. Straumann, Osstem, and S-Wide systems were used to drill boreholes in 27 porcine ribs at three different rotation speeds and under three different cooling conditions. The material was analyzed using a Nikon 80i microscope. The analysis concerned the morphological quality of the obtained boreholes. The statistical analysis revealed that satisfactory results in all drilling systems were obtained when the rotational speed did not exceed 800 revolutions per minute (rpm) regardless of the cooling temperature. However, increased rotational speed and cooling at 4 °C produced better results than without cooling in all the tested systems. Different implant systems have unique drill geometry and therefore generate differences in tissue damage under various conditions. In the experiment, a sufficient required structure was obtained in all systems, but the Straumann system yielded the best results under all the examined conditions.

Removal of Low-concentration Ammonia from Ambient Air by Aluminophosphates

A series of aluminumphosphate materials was prepared and used as adsorbents for the removal of ammonia at low concentrations. The influence of various preparation parameters, including the pH value of sol, calcination temperature and molar ratio of P/Al, on the structure and surface properties as well as adsorption capacity were investigated. The results showed that large amount of P—OH present on the surface of aluminophosphates was suitable for the removal of ammonia. They were the major source of weak Bronsted acid sites and acted as the main active centers for capturing ammonia.

Hydrocracking of residual oil using molybdenum supported over mesoporous alumina as a catalyst

A series of mesoporous alumina catalysts with different textural properties were prepared via the sol–gel method, and the aluminium precursor, chain length of the surfactant and calcination temperatures were varied. The influence of various preparation parameters on the resulted alumina surface area, pore size, pore volume and acidity were investigated. Mesoporous alumina with large surface area of 270–380m2/g and pore size ranging from 3 to 19nm were successfully synthesised. The activity of mesoporous alumina supported molybdenum catalysts with different properties in hydrocracking of residual oil was determined at 400°C. The acidity of the catalyst enhanced the conversion and the production of light gas oil. Higher conversion and higher of liquid products yield were achieved by using catalyst with larger mesopore size as compared to catalyst with smaller pore size and similar acidity.

A modified double-emulsion method for the preparation of daunorubicin-loaded polymeric nanoparticle with enhanced in vitro anti-tumor activity

The encapsulation of hydrophilic drug in polymeric nanoparticles with high loading remains a challenge due to the rapid penetration of the drug to the external aqueous phase. In order to improve the encapsulation efficiency of daunorubicin (DNR) in poly(d,l-lactic-co-glycolic acid (PLGA) and poly(d,l-lactic acid) (PDLLA) nanoparticles, we fabricated a series of DNR-loaded nanoparticles using a modified double-emulsion solvent evaporation/diffusion method, which introduced a partially water-soluble organic solvent into the particle formation. The influence of various preparation parameters was investigated systematically, such as the ratio of organic solvent, the type of surfactant, the type of polymers and the molecular weight. Results showed that regular spherical PLGA nanoparticles with diameters of 200–300 nm could be produced with a remarkably high DNR encapsulation efficiency (>80%) and loading (6.5% (w/w)). Upon encapsulation, the sustained release of DNR could be controlled over 2 weeks. The results of FT-IR and DSC analysis indicated that the encapsulated DNR in polymeric nanoparticles was inclusion, not absorption. Furthermore, optimized DNR/PLGA nanoparticles showed a significant enhancement of cellular uptake, higher cytotoxicity against HL-60 cells compared with free DNR. These results were potentially useful for the nanoparticle formulation of hydrophilic chemotherapeutic drugs that require efficient delivery to cancer cells as well as sustained release at the specific site.

Phospholipid-Coated Gas Bubble Engineering: Key Parameters for Size and Stability Control, as Determined by an Acoustical Method

We have recently reported the sampling of differently sized monomodal populations of microbubbles from a polydisperse lipid-coated bubble preparation. The microbubbles were coated with dimyristoylphosphatidylcholine (DMPC) and stabilized by perfluorohexane (PFH). Such microbubbles are useful as contrast agents and, potentially, for oxygen, drug, and gene delivery and as therapeutic devices. Monomodal populations of small bubbles (approximately 1.6 microm in radius) and large bubbles (approximately 5.4 microm) have been obtained, as assessed by acoustical measurement, static light scattering, and optical microscopy. In this paper, we have determined the influence of various preparation parameters on the initial size characteristics (mean radius and radii distribution) of the microbubbles and on their stability upon time. The bubble size was determined acoustically, with a homemade acoustic setup equipped with a low-power emitter, to avoid altering the bubble stability. We have focused on the effects of the bubble flotation time during the fractionation process and on the DMPC concentration. PFH was indispensable for obtaining stable bubbles. The nature of the buffer [Isoton II vs N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)] used as the continuous phase did not significantly impact the bubble characteristics and stability. In both buffers, the half-lives of small bubbles (approximately 1.6 microm in radius in Isoton II and approximately 2.1 microm in HEPES) were found to be longer than those of larger ones (approximately 5.4 and approximately 5.9 microm in Isoton II and HEPES, respectively). The bubble stability study revealed that in both buffers, the average radius of the population of large bubbles progressively increased with time. On the other hand, the average radius of the population of small bubbles decreased slightly in Isoton II and remained constant in HEPES. This suggests that the dissolution behavior of small and large bubbles is governed by different mechanisms.

XRD studies on the nanosized copper ferrite powders synthesized by sonochemical method

Abstract Nanosized copper ferrite spinel particles have been prepared by a precursor approach with the aid of ultrasound radiation. Influence of various preparation parameters on the formation of copper ferrite was studied. The preparation parameters included concentrations of precipitation agents and copper salt, sonochemical reaction time, calcination temperature and time. The reactions of reaction for the formation of CuFe2O4 were explored by analyzing X-ray diffraction data obtained under different processing conditions.

Effect of formulation parameters on the release characteristics of propranolol from asymmetric membrane coated tablets

Controlled delivery of drugs has been achieved successfully by use of asymmetric membranes. In our study, we have evaluated the influence of various preparation parameters such as concentration of the polymer, concentration of the pore former and temperature of the precipitation bath on the permeability and the release characteristics of propranolol. Propranolol tablets were prepared by direct compression and were coated with varying concentrations of cellulose acetate and glycerin. The coat was precipitated in water, maintained at various temperatures, followed by air drying of the coat. Scanning Electron Microscopy (SEM) was used to characterize the asymmetric structure of the membrane. The influence of various preparation parameters on the release of propranolol from asymmetric coated tablets was evaluated. SEM confirmed the asymmetric nature of the membrane. A zero order release of propranolol was obtained from the coated tablets of propranolol. Various preparation parameters studied significantly affected ( p < 0.05) the release of propranolol hydrochloride from the asymmetric membrane coated tablets and the release was independent of the pH and the rate of agitation of the dissolution medium ( p > 0.05). Asymmetric membranes can be successfully utilized in the controlled delivery of highly water soluble drugs like propranolol and by modifying preparation parameters like polymer concentration, pore former concentration and temperature of the precipitation bath, desired release rates can be obtained.

Preparation of an enteric-soluble solid-state emulsion using oily drugs

To improve the patient's compliance and enhance the stability of oily drugs in the gastric fluid, an enteric-soluble solid-state emulsion (ESE), was developed. The ESE was prepared by spreading liquid o/w-emulsions on a flat glass and drying at the oven maintained at 40 °C. Aerosil 200 was applied as solid carrier and emulsifier. And Eudragit ® L30D-55 was used as enteric coating material. The influence of various preparation parameters on the residual volatile oil and the release behavior was investigated. Droplet size distribution of the primary emulsions and the emulsion after reconstitution of zedoary turmeric oil (ZTO) ESE in the phosphate buffer were also measured. When ZTO ESE was immersed into phosphate buffer (pH 6.8), the stable emulsion was formed in 20 min, but the release was obviously suppressed when it was exposed to the gastric fluid. It was concluded that preparation of enteric-soluble solid-state emulsion by the present method for oral oily drug was feasible.

Preparation and characterization of melittin-loaded poly ( dl-lactic acid) or poly ( dl-lactic-co-glycolic acid) microspheres made by the double emulsion method

The water soluble peptide, melittin, isolated from bee venom and composed of twenty-six amino acids, was encapsulated in poly ( dl-lactic acid, PLA) and poly ( dl-lactic-co-glycolic acid, PLGA) microspheres prepared by a multiple emulsion [(W 1 / O)W 2] solvent evaporation method. The aim of this work was to develop a controlled release injection that would deliver the melittin over a period of about one month. The influence of various preparation parameters, such as the type of polymer, its concentration, stabilizer PVA concentration, volume of internal water phase and level of drug loading on the characteristics of the microspheres and drug release was investigated. It was found that the microspheres of about 5 μm in size can be produced in high encapsulation (up to 90%), and the melittin content in the microspheres was up to 10% (w/w). The drug release profiles in vitro exhibited a significant burst release, followed by a lag phase of little or no release and then a phase of constant melittin release. The type of polymer used was a critical factor in controlling the release of melittin from the microspheres. In this study, the rate of peptide release from the microspheres correlated well with the rate of polymer degradation. Moreover, melittin was released completely during the study period of 30 days, which agreed well with the polymer degradation rate.

Vanadia Supported on Titania Prepared by Grafting: Influence of Support Properties on the Structure and Activity of Vanadia for the Selective Catalytic Reduction of NO by NH3

AbstractThe selective catalytic reduction (SCR) of NO by NH3 has been investigated over vanadia/titania catalysts prepared by grafting of vanadyl alkoxides onto three titania supports which differed in their morphologies (surface area, phase composition) and concentrations of impurities. Neutron activation analysis revealed the presence of chlorine and potassium as major impurities in the titania carriers. The supported catalysts were prepared by the reaction of VO(OR)3 (R = i‐C3H7, i‐C4H9) with support surface hydroxyl groups. Attention was paid to the influence of various preparation parameters (vanadia precursor, support pretreatment, impurities) and their relation to the amount, reducibility and activity of the vanadia deposited. Thermal analysis, X‐ray diffraction and Raman spectroscopy revealed that pre‐conditioning the titania supports before the grafting, if not carried out under mild conditions, results in partial transformation of the anatase phase to rutile. Potassium impurities appear to stabilize the anatase phase with regard to this transformation. For titania containing potassium as impurity, the rutilization occurs at a significantly higher temperature than observed with titania containing chlorine as impurity. Raman spectroscopy showed that within the series of titania supports investigated, the vanadia loading is the most important factor that determines the structure of the immobilized vanadia surface species. Small clusters and ribbons prevail at low coverages (∼ 2μmol V5+/m2). At higher coverages, the catalytically most active two‐dimensional vanadia layers are prevailing. The maximum level of NO turnovers is achieved at coverages exceeding ∼ 3μmol V5+/m2. This behaviour was observed for vanadia deposited on all three titania carriers, irrespective of the largely different BET surface areas and contaminant levels of the supports.