Gelatin microparticles containing propolis obtained by spray-drying technique: preparation and characterization

Gelatin microparticles containing propolis extractive solution (PES) were prepared by spray-drying technique. The optimization of the spray-drying operating conditions and the proportions of gelatin and mannitol were investigated. Regular particle morphology was obtained when mannitol was used, whereas mannitol absence produced a substantial number of coalesced and agglomerated microparticles. Microparticles had a mean diameter of 2.70 mum without mannitol and 2.50 mum with mannitol. The entrapment efficiency for propolis of the microparticles was upto 41 % without mannitol and 39% with mannitol. The microencapsulation by spray-drying technique maintained the activity of propolis against Staphylococcus aureus. These gelatin microparticles containing propolis would be useful for developing intermediary or eventual propolis dosage form without the PES' strong and unpleasant taste, aromatic odour, and presence of ethanol. (C) 2003 Elsevier B.V. All rights reserved.

Modeling a system of phosphated cross-linked high amylose for controlled drug release. Part 2: Physical parameters, cross-linking degrees and drug delivery relationships

High amylose cross-linked to different degrees with sodium trimetaphosphate by varying base strength (2% or 4%) and contact time (0.5-4 h) was evaluated as non-compacted systems for sodium diclophenac controlled release. The physical properties and the performance of these products for sodium diclophenac controlled release from non-compacted systems were related to the structures generated at each cross-linking degree. For samples at 2% until 2 h the swelling ability, G' and eta* values increased with the cross-linking degree, because the longer polymer chains became progressively more entangled and linked. This increases water uptake and holding, favoring the swelling and resulting in systems with higher viscosities. Additionally, the increase of cross-linking degree should contribute for a more elastic structure. The shorter chains with more inter-linkages formed at higher cross-linking degrees (2%4h and 4%) make water caption and holding difficult, decreasing the swelling, viscosity and elasticity. For 2% samples, the longer drug release time exhibited for 2%4h sample indicates that the increase of swelling and viscosity contribute for a more sustained drug release, but the mesh size of the polymeric network seems to be determinant for the attachment of drug molecules. For the 4% samples, smaller meshes size should determine less sustained release of drug. (C) 2008 Elsevier B.V. All rights reserved.

Thermal analysis of biodegradable microparticles containing ciprofloxacin hydrochloride obtained by spray drying technique

Thermal analysis has been extensively used to obtain information about drug-polymer interactions and to perform pre-formulation studies of pharmaceutical dosage forms. In this work, biodegradable microparticles of poly(D,L-lactide-co-glycolide) (PLGA) containing ciprofloxacin hydrochloride (CP) in various drug:polymer ratios were obtained by spray drying. The main purpose of this study was to investigate the effect of the spray drying process on the drug-polymer interactions and on the stability of microparticles using differential scanning calorimetry (DSC), thermogravimetry (TG) and derivative thermogravimetry (DTG) and infrared spectroscopy (IR). The results showed that the high levels of encapsulation efficiency were dependant on drug:polymer ratio. DSC and TG/DTG analyses showed that for physical mixtures of the microparticles components the thermal profiles were different from those signals obtained with the pure substances. Thermal analysis data disclosed that physical interaction between CP and PLGA in high temperatures had occurred. The DSC and TG profiles for drug-loaded microparticles were very similar to the physical mixtures of components and it was possible to characterize the thermal properties of microparticles according to drug content. These data indicated that the spray dryer technique does not affect the physicochemical properties of the microparticles. In addition, the results are in agreement with IR data analysis demonstrating that no significant chemical interaction occurs between CP and PLGA in both physical mixtures and microparticles. In conclusion, we have found that the spray drying procedure used in this work can be a secure methodology to produce CP-loaded microparticles. (C) 2007 Elsevier B.V. All rights reserved.

Caracterização farmacognóstica do jambolão (Syzypiam cumini (L.) Skeels)

A padronização de um fitoterápico é etapa imprescindível para garantia da qualidade de medicamentos contendo plantas medicinais. Objetivou-se padronizar Syzygiam cumini (L.) Skeels e para tanto se estabeleceram parametros tais como, avaliação morfoanatômica das folhas, morfológica das flores e dos frutos, avaliação granulométrica da droga rasurada (frutos), determinação da umidade, avaliação dos processos de secagem, determinação do teor de extrativos e do teor de taninos (monômeros e polimeros). O estudo anatômico das folhas revelou a inexistência de pêlos no sistema dérmico, assim como a ocorrência de glândulas secretoras, drusas, colênquima e esclerênquima. As flores são hermafroditas, com androceu polistêmone e gineceu com ovário ínfero, gamocarpelar, bilocular com placentação axial. Observou-se elevado teor extrativo (38,57%). O diâmetro médio de partícula dos frutos secos moídos ficou em 0,630 mm. O processo de secagem dos frutos influenciou o teor de taninos totais. O teor de taninos determinado ficou em 5,10% para monômeros e 11,30% para os polimeros.

Determination of the numerical parameters of a continuous damage model for the structural analysis of clay brick masonry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Artificial neural networks applied in study of atmospheric parameters to high voltage substations concerning lightning

This gaper demonstrates that artificial neural networks can be used effectively for estimation of parameters related to study of atmospheric conditions to high voltage substations design. Specifically, the neural networks are used to compute the variation of electrical field intensity and critical disruptive voltage in substations taking into account several atmospheric factors, such as pressure, temperature, humidity, so on. Examples of simulation of tests are presented to validate the proposed approach. The results that were obtained by experimental evidences and numerical simulations allowed the verification of the influence of the atmospheric conditions on design of substations concerning lightning.

Influence of design parameters on linear induction motor end effect

In this paper, a factor referred to as k(f) for linear induction motor end effect analysis is presented. The mathematical model takes into account the longitudinal entry end effect. The entry end effect produces considerable distortion in magnetic field distribution. It is shown how this influence is derived from the machine-developed force that is calculated through the application of the I-D theory. The k(f) factor establishes the relationship between the longitudinal end effect and machine parameters, mainly the number of magnetic poles, secondary resistivity, and frequency.

Evasive Maneuvers in Space Debris Environment and Technological Parameters

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Determining the Optimum Processing Parameters of Glass-like Carbon Using Weibull Analysis of its Fracture Behaviour

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Alternative parameters for the continuation power flow method

The conventional Newton's method has been considered inadequate to obtain the maximum loading point (MLP) of power systems. It is due to the Jacobian matrix singularity at this point. However, the MLP can be efficiently computed through parameterization techniques of continuation methods. This paper presents and tests new parameterization schemes, namely the total power losses (real and reactive), the power at the slack bus (real or reactive), the reactive power at generation buses, the reactive power at shunts (capacitor or reactor), the transmission lines power losses (real and reactive), and transmission lines power (real and reactive). Besides their clear physical meaning, which makes easier the development and application of continuation methods for power systems analysis, the main advantage of some of the proposed parameters is that its not necessary to change the parameter in the vicinity of the MLP. Studies on the new parameterization schemes performed on the IEEE 118 buses system show that the ill-conditioning problems at and near the MLP are eliminated. So, the characteristics of the conventional Newton's method are not only preserved but also improved. (C) 2003 Elsevier B.V. B.V. All rights reserved.

On the optimum parameters of a device for harvesting energy from running and walking

This paper investigates the feasibility of using an energy harvesting device tuned such that its natural frequency coincides with higher harmonics of the input to capture energy from walking or running human motion more efficiently. The paper starts by reviewing the concept of a linear resonant generator for a tonal frequency input and then derives an expression for the power harvested for an input with several harmonics. The amount of power harvested is estimated numerically using measured data from human subjects. Assuming that the input is periodic, the signal is reconstructed using a Fourier series before being used in the simulation. It is found that although the power output depends on the input frequency, the choice of tuning the natural frequency of the device to coincide with a particular higher harmonic is restricted by the amount of damping that is needed to maximize the amount of power harvested, as well as to comply with the size limit of the device. It is also found that it is not feasible to tune the device to match the first few harmonics when the size of the device is small, because a large amount of damping is required to limit the motion of the mass.