Particle Size Research Papers - Academia.edu (original) (raw)

O presente trabalho teve por objetivos avaliar a composição de rizomas do lírio-do-bejo (Hedychium coronarium) e isolar e caracterizar seu amido, por meio de análises físicas e físico-químicas. A composição química dos grânulos de amido... more

O presente trabalho teve por objetivos avaliar a composição de rizomas do lírio-do-bejo (Hedychium coronarium) e isolar e caracterizar seu amido, por meio de análises físicas e físico-químicas. A composição química dos grânulos de amido isolados dos rizomas também foi determinada, bem como o formato, tamanho, distribuição de tamanho de partícula por difração a laser, viscosidade de pasta em analisador rápido de viscosidade, poder de inchamento, índice de solubilidade em água, propriedade térmica por calorimetria diferencial de varredura e cristalinidade por difração de raios X. Observou-se que os rizomas apresentaram elevado teor de água e baixos teores de matéria graxa, carboidratos, cinzas, proteínas e fibras. Os rizomas de lírio-do-brejo apresentam-se inadequados para produção de amido, devido ao baixo teor de matéria seca (17,3%), com 21,97% de amido, bem como fibras longas e látex, que dificultam a extração do amido. O amido extraído apresentou pureza de 99,2%, com 37,2% de ami...

Minkowski famously introduced the concept of a space-time continuum in 1908, merging the three dimensions of space with an imaginary time dimension $ i c t ,withtheunitimaginaryproducingthecorrectspacetimedistance, with the unit imaginary producing the correct spacetime distance ,withtheunitimaginaryproducingthecorrectspacetimedistance x^2 - c^2... more

Minkowski famously introduced the concept of a space-time continuum in 1908, merging the three dimensions of space with an imaginary time dimension $ i c t ,withtheunitimaginaryproducingthecorrectspacetimedistance, with the unit imaginary producing the correct spacetime distance ,withtheunitimaginaryproducingthecorrectspacetimedistance x^2 - c^2 t^2 ,andtheresultsofEinstein′sthenrecentlydevelopedtheoryofspecialrelativity,thusprovidinganexplanationforEinstein′stheoryintermsofthestructureofspaceandtime.AsanalternativetoaplanarMinkowskispace−timeoftwospacedimensionsandonetimedimension,wereplacetheunitimaginary, and the results of Einstein's then recently developed theory of special relativity, thus providing an explanation for Einstein's theory in terms of the structure of space and time. As an alternative to a planar Minkowski space-time of two space dimensions and one time dimension, we replace the unit imaginary ,andtheresultsofEinstein′sthenrecentlydevelopedtheoryofspecialrelativity,thusprovidinganexplanationforEinstein′stheoryintermsofthestructureofspaceandtime.AsanalternativetoaplanarMinkowskispace−timeoftwospacedimensionsandonetimedimension,wereplacetheunitimaginary i = \sqrt{-1} ,withtheCliffordbivector, with the Clifford bivector ,withtheCliffordbivector \iota = e_1 e_2 $ for the plane that also squares to minus one, but which can be included without the addition of an extra dimension, as it is an integral part of the real Cartesian plane with the orthonormal basis $ e_1 $ and $ e_2 $. We find that with this model of planar spacetime, using a two-dimensional Clifford multivector, the spacetime metric and the Lorentz transformations follow immediately as properties of the algebra. This also leads to momentum and energy being represented as components of a multivector and we give a new efficient derivation of Compton's scattering formula, and a simple formulation of Dirac's and Maxwell's equations. Based on the mathematical structure of the multivector, we produce a semi-classical model of massive particles, which can then be viewed as the origin of the Minkowski spacetime structure and thus a deeper explanation for relativistic effects. We also find a new perspective on the nature of time, which is now given a precise mathematical definition as the bivector of the plane.

Successful use of liposomes as immunological adjuvants in vaccines requires simple, easy to scale up technology capable of high-yield antigen entrapment. Recent work from this laboratory has led to the development of techniques that can... more

Successful use of liposomes as immunological adjuvants in vaccines requires simple, easy to scale up technology capable of high-yield antigen entrapment. Recent work from this laboratory has led to the development of techniques that can generate liposomes of various sizes containing soluble antigens such as proteins or particulate antigens such as whole, live, or attenuated bacteria or viruses. Entrapment of proteins is carried out by the dehydration-rehydration procedure, which entails freeze-drying of a mixture of "empty" small unilamellar vesicles and free antigens. Upon rehydration, the large multilamellar vesicles that are formed incorporate up to 80% of the antigen used. When such liposomes are microfluidized in the presence of nonentrapped material, their size is reduced to about 100 nm in diameter, with much of the originally entrapped antigen still associated with the vesicles. A similar technique applied to the entrapment of particulate antigens (e.g., Bacillus s...

Spray drying techniques have been applied to improve the solubility and dissolution rate of poorly water-soluble salicylic acid. Spray drying of the acid dispersed in acacia solutions resulted in as much as a 50% improvement in the... more

Spray drying techniques have been applied to improve the solubility and dissolution rate of poorly water-soluble salicylic acid. Spray drying of the acid dispersed in acacia solutions resulted in as much as a 50% improvement in the solubility of the product. Solubility improvement was closely related not only to the concentration of acacia but also the amount of amorphous material in the spray-dried products. The heat of solution was inversely related to these parameters. The dissolution rate of spray-dried product was almost instantaneous being about 60 times faster than that of the original powder. A great improvement in the wettability of the spray-dried material seemed to be mainly responsible for the increase of dissolution rate.

Synthesis of metallic and semiconductor nanoparticles through physical and chemical routes has been extensively reported. However, green synthesized metal nanoparticles are currently in the limelight due to the simplicity,... more

Synthesis of metallic and semiconductor nanoparticles through physical and chemical routes has been extensively reported. However, green synthesized metal nanoparticles are currently in the limelight due to the simplicity, cost-effectiveness and eco-friendliness of their synthesis. This study explored the use of aqueous leaf extract of Costus afer in the synthesis of silver nanoparticles (CA-AgNPs). The optical and structural properties of the resulting silver nanoparticles were studied using UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infra-red spectrophotometer (FTIR). TEM images of the silver nanoparticles confirmed the existence of monodispersed spherical nanoparticles with a mean size of 20 nm. The FTIR spectra affirmed the presence of phytochemicals from the Costus afer leaf extract on the surface of the silver nanoparticles. The electrochemical characterization of a CA-AgNPs/multiwalled carbon nanot...

The possibility of producing titanium alloy Ti ? 6Al ? 4V with minimal residual porosity from mixtures of elemental powders by the method of pressing and sintering without hot deformation during or after sintering was investigated.... more

The possibility of producing titanium alloy Ti ? 6Al ? 4V with minimal residual porosity from mixtures of elemental powders by the method of pressing and sintering without hot deformation during or after sintering was investigated. Various powder mixtures based on titanium and titanium hydride with alloying additions of either elemental powders having different particle sizes, or master alloys, were studied. It was shown that the synthesis of Ti ? 6Al ? 4V from mixtures of titanium hydride and master alloys is optimal with respect to the attainment of high relative density. In this case the sintered material has density up to 99%, homogeneous microstructure with relatively small (100-120 µm) ß-phase grains, and a low concentration of impurities, in particular oxygen, which provide a high level of mechanical properties s(ten = 970 MPa, d = 6%).

The effect of six different preservatives on the production process and stability of resveratrol nanosuspensions was investigated. Nanosuspensions of the anti-oxidant resveratrol were prepared by high pressure homogenization (1,500 bar,... more

The effect of six different preservatives on the production process and stability of resveratrol nanosuspensions was investigated. Nanosuspensions of the anti-oxidant resveratrol were prepared by high pressure homogenization (1,500 bar, 20 homogenization cycles). The preservatives used were: caprylyl glycol (0.75%), Euxyl PE 9010 (1.0%), Hydrolite-5 (2.0), Phenonip (0.75%), Rokonsal PB-5 (0.5%) and MultiEx Naturotics (2.0%). Preservation is essential for oral and dermal nanosuspensions, but can impair the stability. The effect of the preservatives on stability as a function of cycle numbers was determined by size measurements (photon correlation spectroscopy (PCS), laser diffraction (LD) and light microscopy). Zeta potential measurements were performed for determination of the Stern potential (measurements in water) and as stability criterion (measurements in original dispersion medium), to elucidate the mechanism of destabilization. The preservatives could be placed into three grou...

Dry powder formulations are often composed of fine drug particles and coarser carrier particles, typically alpha-lactose monohydrate. However, the performance of a powder formulation may be highly dependent on the lactose quality and... more

Dry powder formulations are often composed of fine drug particles and coarser carrier particles, typically alpha-lactose monohydrate. However, the performance of a powder formulation may be highly dependent on the lactose quality and source. This study investigated the characteristics of lactose that influence the drug-to-carrier interaction and the performance of lactose-based dry powder inhaler formulations. The selected lactoses differed in the preparation processes and the content of fine lactose particles. Efficiency testing was done using fluticasone propionate and terbutaline sulphate as model drugs. Inverse gas chromatography was used to determine the surface heterogeneity distribution of different energy sites of the lactose and to understand the mechanism by which the fine carrier particles can improve the performance of dry powder inhalers. To assess the adhesion of respirable-sized drug to carrier particles, a simple method was developed based on aspiration and consideri...