Particle Size Modification Research Articles

Particle size modification of curcumin in relation to its pharmacokinetics and tissue distribution profile

Particle size modification of curcumin in relation to its pharmacokinetics and tissue distribution profile

Synthesis and characterization of nano-sized α-alumina powder from kaolin by acid leaching process

α- alumina powder with particle size <100nm and spherical shape was prepared from calcined kaolin by acid leaching method. Here hydrochloric acid was used as a leaching agent. The amorphous white powders formed after precipitation, washing and drying were characterised by the different technique like XRD, TG-DSC and FTIR. Particle size distribution, specific surface area and microstructural analysis of the 1200°C calcined powder were also carried out to ascertain the size, shape and distribution of the particles. The phase pure α-alumina with a size range <100nm, was formed at 1200°C. The presence of a surfactant during processing also exhibited a positive effect on modification of particle size.

Fractal crushing of granular materials under confined compression at different strain rates

Quasi-static and dynamic compression experiments are conducted on quartz sand, to study the stress-induced gradation evolution of granular materials under confined comminution. The particle size distributions obtained from laser diffractometry show three regimes, and the second regime is found to satisfy a power law or fractal distribution. The fractal dimension increases exponentially/linearly with increasing stress/breakage extent, indicating an increasingly sophisticated packing geometry due to increasing fragmentation and fractal arrangement of particles. The fractal dimension, and normalized characteristic size of particles both exhibit generality, the asymptotic values of which are independent of loading rates. Particle size distributions with these three regimes have also been revealed in discrete element modeling. The third regime, mainly for fine particles, is attributed to the existence of a crushing size limit. The transition particle size between the second and third regime decreases significantly when the crushing size limit is reduced.

Electronic excitation induced structural modification of FeCo nanoparticles embedded in silica matrix

Electronic excitation mediated energy loss by 120 MeV Au9+ swift heavy ions (SHIs) results in significant structural modifications of FeCo nanoparticles embedded in thin SiO2 matrix. The variations in local atomic structure and particle size/shape at different irradiation fluences are probed by extended x-ray absorption fine structure spectroscopy (EXAFS) and grazing incidence small angle x-ray scattering (GISAXS). The crystallinity and ordering of the films are found to first decrease and then increase with fluence. The observed alterations in co-ordination number of Fe/Co from EXAFS are correlated primarily with particle size modifications due to a transient thermal spike generated in the embedded nanoparticles by SHIs. The role of hydrogen desorption from nanoparticles is also highlighted.

Organic matter content and particle size modifications in mangrove sediments as responses to sea level rise

Mangroves sediments contain large reservoirs of organic material (OM) as mangrove ecosystems produce large quantities and rapidly burial OM. Sediment accumulation rates of approximately 2.0 mm year−1, based on 210Pbex dating, were estimated at the margin of two well-developed mangrove forest in southern Brazil. Regional data point to a relative sea level (RSL) rise of up to ∼4.0 mm year−1. This RSL rise in turn, may directly influence the origin and quantity of organic matter (OM) deposited along mangrove sediments. Lithostratigraphic changes show that sand deposition is replacing the mud (<63 μm) fraction and OM content is decreasing in successively younger sediments. Sediment accumulation in coastal areas that are not keeping pace with sea level rise is potentially conducive to the observed shifts in particle size and OM content.

Formulation of poorly water-soluble Gemfibrozil applying power ultrasound

The dissolution properties of a drug and its release from the dosage form have a basic impact on its bioavailability. Solubility problems are a major challenge for the pharmaceutical industry as concerns the development of new pharmaceutical products. Formulation problems may possibly be overcome by modification of particle size and morphology. The application of power ultrasound is a novel possibility in drug formulation. This article reports on solvent diffusion and melt emulsification, as new methods supplemented with drying in the field of sonocrystallization of poorly water-soluble Gemfibrozil. During thermoanalytical characterization, a modified structure was detected. The specific surface area of the drug was increased following particle size reduction and the poor wettability properties could also be improved. The dissolution rate was therefore significantly increased.

A semi-empirical model of aerosol deposition in the human respiratory tract for mouth inhalation.

A mathematical model for regional deposition of aerosols following inhalations via mouth has been developed. The model is in the form of algebraic equations which make it particularly efficient for computation of deposition of polydisperse aerosols. The parameters of the model were derived from average experimental data for "head' and tracheobronchial deposition which were supplemented by results of previous theoretical calculations and mass balance considerations. An example is presented to illustrate an application of the model to a problem in formulation of inhalation aerosols. To make the calculations more reliable for particular patho-physiological groups of patients, some modifications of the parameters used in the model are necessary. The model may be suitable, e.g. for testing the changes in regional deposition which would be likely to result from modification of particle size and related formulation properties of inhalation aerosols.

Physical dynamics of sludges during wine fermentation in liquid phase

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aims&lt;/strong&gt;: The aim of this work was to study the dynamics of the sludge particles during wine fermentation in liquid phase.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Ninety L of Sauvignon blanc enriched with 1.8% (v/v) of sludges, inoculated with a commercial strain of S. cerevisiae, were fermented in a transparent 100 L-fermentation tank. Results showed that the physical behavior of the sludge particles is dependent on the yeast CO2 production activity. Sludge dynamics can be divided in three phases clearly linked to the yeast fermentative activity. Although a complete dispersion of the sludges occurred during the fermentation, it could be observed that either at the surface or at the bottom of the tank, the medium turbidity never ranges the initial turbidity level, due to the disruption of the medium/gross particles into fine particles during the growth phase. Fine particles rapidly re-aggregated into medium/gross particles during the stationary phase.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusions&lt;/strong&gt;: From these results, it appears that the evolution of must turbidity during fermentation is much more complex than previously expected. Sludges are only dispersed in the fermenting must during a very short phase after the initiation of cell growth.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: This study raises the questioning of the relationship between initial must turbidity and nutrient availability in trouble musts, since sludges are completely deposited at the onset of both cell growth and fermentation. Further research works are therefore needed to study the factors which can impact sludge particle size modification and consequently sludge nutrient accessibility for yeast growth.&lt;/p&gt;

Particle Size Modification of Thermally Stable Secondary Explosives for IM Applications

AbstractAs well as improving the survivability of weapons and platforms, insensitive munitions (IM) reduce both casualty rates and mission losses. Their use also leads to improved safety during storage and transportation. For a munition to fulfil IM criteria, each of its energetic sub‐sections must be IM compliant. The initiator and explosive train are the most critical of these sub‐systems as their safety and reliability are of paramount importance if the weapon is to be suitable for service use, yet they are generally the most difficult part of a weapon to protect from inadvertent initiation. As part of an ongoing study into initiation methods suitable for use in IM systems, an investigation into the behaviour of energetic materials when impacted by laser‐driven flyers was performed. Laser‐based detonators exhibit increased safety characteristics over conventional initiation methods as they can be based on insensitive secondary explosives rather than sensitive primary explosives. Also, they are less susceptible to accidental initiation due to an external hazard threat. Single pulses from a high‐powered Q‐switched Nd:YAG laser were used to launch flyers from substrate‐backed aluminium films to velocities up to 6 km s−1 across a short stand‐off to impact explosive targets. Several novel energetic materials have been selected for investigation as potential candidates for inclusion within flyer‐based initiation systems and explosive train applications. The materials are of interest due to their increased thermal stability and power output over conventional explosives currently in service. Attempts were made to increase the flyer responsiveness of the materials by tuning their particle size using ultrasound. The effect of particle size on the initiation threshold energy was investigated for three materials.

Deformation yield of Co nanoparticles in SiO 2 irradiated with 200 MeV 127I ions

Cobalt ions of 160 keV have been implanted into SiO 2 layers at a fluence of 10 17 at cm −2 at 873 K. The resulting spherical metallic Co nanoparticles have been in their turn irradiated by 200 MeV 127I ions at between 10 11 and 10 14 ions cm −2 at 300 K. The latter procedure induces an increase of the particle size for lower fluences and a deformation for higher fluences. The modification of particle size and shape has been followed by transmission electron microscopy. An incubation fluence for Co nanoparticle deformation of a few 10 12 ions cm −2 and deformation yields of 1.7 × 10 −14 and 3.3 × 10 −14 cm 2 have been measured for Co nanoparticles of 7.2 and 15.6 mean diameters, respectively. The results are compared with existing models.

Irradiations of implanted cobalt nanoparticles in silica layers

Cobalt ions have been implanted at an energy of 160 keV at fluences of 2×10 16, 5×10 16 and 10 17 Co + cm −2 in silica layers and at temperatures of 77, 295 and 873 K. The nanocomposites formed have further been irradiated with electrons and swift heavy ions. Magnetic properties of the nanoparticles studied by a SQUID magnetometer at 295 and 5 K have been related to the modification of particle size and size distribution, which have been observed by transmission electron microscopy.

A new white light photosedimentometer for solid-liquid dispersion study: device description, stability and settling behaviour

This paper describes a new photosedimentation device that monitors and measures the settling rate, hindered settling, constant, flocculation factor, sediment volume and rate of coagulation of monodisperse samples of solid particulates in dispersant liquids. First we examine the well-known theoretical aspects of sedimentation as well as some sedimentation and turbidity applications. Then we introduce the K200 photosedimentometer and most of its technical features and advantages with respect to existing devices. Finally, we give the results of several turbidimetric (particle size modification, concentration determination) and settling measurements (stability parameters).

The particle size of Martian aeolian dunes

The effective particle size of unconsolidated materials on the Martian surface can be determined from thermal inertia, due to a pore size dependence of thermal conductivity at Martian atmospheric pressures. Because dunes consist of a narrow range of well‐sorted, unconsolidated particles, they provide for a test of the relationship between particle size and thermal inertia calculated from midinfrared emission data for the Martian surface. We use two independent approaches. First, thermal inertia data indicate that Martian dunes have an average particle size of about 500±100 μm, or medium to coarse sand. Second, we determine expected dune particle sizes from grain trajectory calculations and the particle size transition from suspension to saltation. On Earth, the transition occurs for a grain when the ratio of the terminal fall velocity to the wind friction speed (u*t) is near unity; for grains at u*t, this occurs at about 52 μm. Terrestrial dune sands have a mean of 250 μm and are composed entirely of grains &gt;52 μm. The corresponding Martian transition grain size is about 210 μm, suggesting that Martian dunes should be significantly coarser than terrestrial dunes. Grain saltation path length as a function of particle size also shows that under Martian conditions, larger grains than on Earth will become suspended. Both approaches indicate that Martian dune sand should be coarser than terrestrial dune sand. Thus, while terrestrial dune grains are in the fine to medium sand range, the average Martian dune sediments are probably medium to coarse sands. These results closely match the grain sizes determined from thermal inertia models, providing the first direct test of the validity of these models for actual Martian surface materials.

Pollution Prevention

The role of engineers in the design of environmentally compatible products and industrial plants is discussed. Research is needed in the fields of waste reduction, development of biodegradable plastics, and in the reduction of particulate emissions by modification of particle size of pulverized coal. It is recommended that pollution control concepts be included in the normal engineering curricula of the separate disciplines and that selection and design of manufacturing processes and products include environmental constraints right from the start.

Spectroscopic characterization of superparamagnetic particles of thermolytic products of ferric sulphate hydrates

Superparamagnetic particles of chemically pure samples, in the system Fe(OH)SO 4/Fe(OH)SO 4·(H 2O), are produced by thermal decomposition of ferric sulphate hydrates. The control of particle size distribution is achieved by successive hydration and dehydration processes monitored by X-ray diffraction, electron microscopy, Mössbauer and IR spectroscopy. The particle size modification is related for the particle growth and two mechanisms are suggested thereon.

Effect of modification of particle size of emulsions of venezuelan crude oil on feeding, survival and growth of marine zooplankton

Variations in the natural particle size spectra following the addition of Venezuelan crude oil in seawater ( ⋍ 6 μ l litre −1 ) were related to the mixing speeds of the emulsion and were independent of the oil concentration. The particle spectrum and feeding behaviour of Meganyctiphanes norvegica and Calanus hyperboreus were both modified. Artificially created oil droplets were suitable in size for ready ingestion by zooplankton. The growth and survival of contaminated Acartia hudsonica were rapidly and significantly reduced. Groups under starvation conditions showed similar decreases to those exposed to oil. During a depuration period, treated copepods exhibited growth rates similar to those of untreated specimens. The input and noxious effects of crude oil are discussed with special reference to particle size distribution and chemosensory feeding behaviour.

Preparation and hard magnetic properties of Co-Zn-P films for high-density recording

The digital recording density of magnetic media can be improved by the development of thin ferromagnetic coatings having a high coercive force. An experimental study of the influence of zinc on the coercive force of chemically reduced cobalt-phosphorus films is presented. Incorporation of zinc increases the coercive force of cobalt-phosphorus films on Mylar substrates by a factor of 2 to 60. Cobalt-zinc-phosphorus films exhibited coercivities ranging from 300 to 1200 Oe, depending on the preparation conditions. The influence of substrate and solution parameters, such as hypophosphite ion concentration, zinc concentration, and pH are discussed with respect to the hysteresis properties of the films. The influence of zinc on the coercivity is attributed to increased magnetic isolation of the cobalt particles and to a modification of particle size.