Dissolution Behavior of Griseofulvin Solid Dispersions Using Polyethylene Glycol, Talc, and Their Combination as Dispersion Carriers

Griseofulvin solid dispersions were prepared using polyethylene glycol 6000 (PEG), talc, and their combination as carriers by the solvent method. The dissolution of griseofulvin from these dispersions was studied. It was found that in these carriers the drug dissolution rate was a function of drug loading. The dissolution rate from dispersions prepared using PEG was similar to that from PEG/talc dispersions, especially at a low percentage of drug loading. Dispersions of PEG and PEG/talc provided dissolution rates faster than those from dispersions of talc. The incorporation of talc in PEG yielded dispersions with properties of less tackiness and ease for handling. Dissolution kinetics, based on the Hixson-Crowell equation, was used to determine the characteristics of griseofulvin particles in dispersions. Linear relationships were obtained for PEG and PEG/talc dispersions that indicated the presence of a uniformly sized monoparticulate system, whereas deviation from linearity was observed for talc dispersions. This appeared to be a multiparticulate system in which particles were present as free form and adsorbed form on the surface of talc.     

Colour image detection and matching using modified generalisedHough transform

A new approach to 2-dimensional (2D) colour-image detection and matching using a modified version of the generalised Hough transform (GHT) is proposed. In the conventional GHT, the useful colour information existing in the input image and the relationship between each pixel and its neighbourhood are not used. Furthermore, lighting changes in the image are not usually considered. Therefore, the conventional GHT is seldom applied to colour images. In the proposed approach, lighting are removed using normalised colour values. Next, certain critical pixels of an input colour image whose neighbourhoods have larger variances of normalised colour values are extracted. For each critical pixel, a feature vector, which includes the normalised colour values of the pixel as well as those of the pixel's neighbours, is then constructed. A modified voting rule for the GHT is therefore proposed which is based on a similarity-measure function of the feature vectors. High maximum peaks in the cell array are searched finally as the result. The proposed method is robust for colour-image detection and matching in noisy, occlusive, and lighting-change environments, as demonstrated by experimental results     

Effect of oestradiol on ovarian oxytocin secretion rate and luteolysis in the ewe after ovarian auto-transplantation

The release of ovarian oxytocin and uterine prostaglandin (PG)F2alpha in response to an oestradiol stimulus was investigated. On Day 15 post-oestrus, ten ewes with ovarian auto-transplants (n=5 per group) received an intra-muscular injection of either oestradiol benzoate (50 microg) or vehicle. Blood samples were collected from the ovarian and jugular veins at 30 and 0 min before, and at 15-min intervals up to 540 min after, injection. The secretion rate of ovarian progesterone remained elevated in four of five treated ewes and in all control ewes, indicating the presence of a functional corpus luteum. Peripheral oestradiol concentrations were significantly (P < 0.001) higher in treated than in control ewes. The number of ewes that released pulses of ovarian oxytocin > or =240 min following oestradiol benzoate injection was significantly (P < 0 05) greater than that in control ewes. Mean amplitude and area under both ovarian-vein oxytocin and jugular-vein 15 keto-13,14 dihydro prostaglandin F2alpha (PGFM) pulses were significantly increased in the treated ewes. These findings demonstrate that the administration of exogenous oestrogen provides a positive stimulus for the release of ovarian oxytocin and uterine PGF2alpha in the ovarian auto-transplanted ewe.     

Pollination-enhanced expression of a receptor-like protein kinase related gene in tobacco styles

We have isolated a putative serine/threonine receptor kinase gene with an expression pattern indicating that it may play a role in the stylar response to pollination. Differential display PCR was used to select tobacco mRNAs with increased accumulation following pollination. NTS16, a cDNA identified by this method, is homologous to a ca. 2.4 kb mRNA primarily expressed in pistil tissues. Levels of this mRNA increase during floral development and are further increased by pollination reaching maximal accumulation 12-18 hours after pollination and then declining. mRNA levels can also be increased by the application of ethylene to unpollinated flowers. A polypeptide encoded by the NTS 16 open reading frame has sequence similarity to the catalytic domain of several receptor protein kinases from plants including the S-receptor kinases implicated in the rejection of self-pollen in Brassica species and the Pto gene product of tomato which confers resistance to a bacterial pathogen.     

视频编码中的块运动估计算法

在视频压缩的一些国际标准，如Ｈ．２６１，Ｈ．２６３，ＭＰＥＧ０－１，ＭＰＥＧ－２，ＨＤＴＶ中，视频系统编码器的复杂性最主要取决于运动估计。下文以ＭＰＥＧ－２编码器为例，通过计算机模拟实验，得出了一些常用运动估计算法的对比实验结果，以及采用常用的几种匹配函数的对比实验结果。     

Macromers by carbocationic polymerization

Polymer Bulletin - Copolymerization of α-(p-vinylphenyl) polyisobutylene(p-polyisobutenylstyrene, PIB-St) with styrene (St) in emulsion has been investigated. Copolymerization occurs only when...     

Analysis of surface state effect on gate lag phenomena in GaAsMESFET's

A two-dimensional transient simulation of the gate lag phenomenon in GaAs MESFET's has been performed. Our results show that the charge exchanges in the population of the surface states at the ungated access region of FET's are responsible for this slow transient phenomenon. The measured “hole-trap-like” DLTS signal is directly related to the re-emission of the holes, trapped during the filling pulse. Higher gate pulse can cause more serious lag phenomenon due to larger modulation of surface charge density. Devices with shorter N⁺-gate spacing and lower surface state densities are shown to have less gate lag effect     

Nitride-based flip-chip ITO LEDs

Nitride-based flip-chip indium-tin-oxide (ITO) light-emitting diodes (LEDs) were successfully fabricated. It was found that the forward voltage and the 20 mA output power of the flip-chip ITO LED were 3.32 V and 14.5 mW, respectively. Although the operation voltage of such a flip-chip ITO LED was slightly larger, it was found that its output power was much larger than those of conventional nonflip-chip LEDs. It was also found that flip-chip ITO LEDs were more reliable.     

Filtres microondes en microruban suspendu

The authors present the design and the development of integrated microwave filters using suspended substrate microstrip, a technology that provides many advantages. Through quasi-static approximation the propagation structure has been treated using integral equations solved with the method of moments. Thanks to this tool of analysis and to an accurate synthesis method, a series of bandpass filters have been designed and manufactured. The results presented validate the accuracy of our design method.