190 research outputs found
Utjecaj razliÄitih povrÅ”inski aktivnih tvari i njihovih koncentracija na kontrolirano oslobaÄanje kaptoprila iz polimernih matriksa
Various methods are available to formulate water soluble drugs into sustained release dosage forms by retarding the dissolution rate. One of the methods used to control drug release and thereby prolong therapeutic activity is to use hydrophilic and lipophilic polymers. In this study, the effects of various polymers such as hydroxypropyl methylcellulose (HPMC), ethylcellulose (EC) and sodium carboxymethylcellulose (CMC) and surfactants (sodium lauryl sulphate, cetyltrimethylammonium bromide and Arlacel 60) on the release rate of captopril were investigated. The results showed that an increase in the amount of HPMC K15M resulted in reduction of the release rate of captopril from these matrices. When HPMC was partly replaced by NaCMC (the ratio of HPMC/NaCMC was 5:1), the release rate of the drug significantly decreased. However, there was no significant difference in release rate of captopril from matrices produced with ratios of 5:1 and 2:1 of HPMC/NaCMC. The presence of lactose in matrices containing HPMC and NaCMC increased the release rate of captopril. It was interesting to note that although partial replacement of HPMC by EC reduced the release rate of the drug (ratio of HPMC/EC 2:1), the release rate was increased when the ratio of HPMC/EC was reduced to 1:1. The effects of various surfactants on the release rate of captopril from HPMC/EC 1:1 matrices were also investigated. The results showed that the surfactants did not significantly change the release rate of the drug. Release data were examined kinetically and the ideal kinetic models were estimated for the drug release. The kinetic analysis of drug release data from various formulations showed that incorporation of surfactants in HPMC/EC matrices did not produce a zero-order release pattern.Postoje razliÄite metode formuliranja vodotopljivih lijekova u dozirane ljekovite oblike s polaganim oslobaÄanjem. Jedan od naÄina postizanja kontroliranog otpuÅ”tanja, a prema tome i produljenog uÄinka je upotreba hidrofilnih i lipofilnih polimera. U ovom radu prouÄavan je utjecaj razliÄitih polimera poput hidroksipropil metilceluloze (HPMC), etilceluloze (EC) i natrijeve soli karboksimetilceluloze (NaCMC) i povrÅ”inski aktivnih tvari (natrijevog lauril-sulfata, cetiltrimetilamonijevog bromida i Arlacela 60) na oslobaÄanje kaptoprila. Rezultati pokazuju da poveÄanje koliÄine HPMC K15M ima za posljedicu smanjenje oslobaÄanja kaptoprila iz matriksa. Ako se HPMC djelomiÄno zamijeni s NaCMC (omjer HPMC/NaCMC 5:1), oslobaÄanje ljekovite tvari znaÄajno se smanjuje. MeÄutim, nema znaÄajne razlike u oslobaÄanju kaptoprila iz matriksa s omjerom HPMC/NaCMC 5:1 i 2:1. Prisutnost laktoze u matriksu koji sadrži HPMC i NaCMC poveÄalo je oslobaÄanje kaptoprila. Iako djelomiÄna zamjena HPMC s EC smanjuje oslobaÄanje ljekovite tvari (omjer HPMC/EC 2:1), oslobaÄanje se poveÄava uz omjer HPMC/EC 1:1. Nadalje, ispitivan je utjecaj povrÅ”inski aktivnih tvari na oslobaÄanje kaptoprila iz matriksa u kojima je omjer HPMC/EC (1:1). Može se zakljuÄiti da povrÅ”inski aktivne tvari ne utjeÄu znaÄajno na oslobaÄanje ljekovite tvari. U sklopu istraživanja odreÄen je i kinetiÄki model oslobaÄanja kaptoprila. Analiza kinetiÄkih podataka ukazuje da dodatak povrÅ”inski aktivnih tvari u HPMC/EC matrikse ne slijedi kinetiku nultog reda
Further Insight into Mechanisms of Ventricular Tachycardia from the Clinical Electrophysiology Laboratory
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72003/1/j.1540-8167.1991.tb01319.x.pd
Intraventricular Electrogram Analysis for Ventricular Tachycardia Detection: Statistical Validation
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72298/1/j.1540-8159.1990.tb06860.x.pd
The Bin Area Method: A Computationally Efficient Technique for Analysis of Ventricular and Atrial Intracardiac Electrograms
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74901/1/j.1540-8159.1990.tb02028.x.pd
Soil sedimentology at Gusev Crater from Columbia Memorial Station to Winter Haven
A total of 3140 individual particles were examined in 31 soils along Spirit’s traverse. Their size, shape, and texture were quantified and classified. They represent a unique record of 3 years of sedimentologic exploration from landing to sol 1085 covering the Plains Unit to Winter Haven where Spirit spent the Martian winter of 2006. Samples in the Plains Unit and Columbia Hills appear as reflecting contrasting textural domains. One is heterogeneous, with a continuum of angular-to-round particles of fine sand to pebble sizes that are generally dust covered and locally cemented in place. The second shows the effect of a dominant and ongoing dynamic aeolian process that redistributes a uniform population of medium-size sand. The texture of particles observed in the samples at Gusev Crater results from volcanic, aeolian, impact, and water-related processes
Prediction of inter-particle adhesion force from surface energy and surface roughness
Fine powder flow is a topic of great interest to industry, in particular for the pharmaceutical industry; a major concern being their poor flow behavior due to high cohesion. In this study, cohesion reduction, produced via surface modification, at the particle scale as well as bulk scale is addressed. The adhesion force model of Derjaguin-Muller-Toporov (DMT) was utilized to quantify the inter-particle adhesion force of both pure and surface modified fine aluminum powders (ā¼8 Ī¼m in size). Inverse Gas Chromatography was utilized for the determination of surface energy of the samples, and Atomic Force Microscopy was utilized to evaluate surface roughness of the powders. Surface modification of the original aluminum powders was done for the purpose of reduction in cohesiveness and improvement in flowability, employing either silane surface treatment or dry mechanical coating of nano-particles on the surface of original powders. For selected samples, the AFM was utilized for direct evaluation of the particle pull-off force. The results indicated that surface modification reduced the surface energy and altered the surface nano-roughness, resulting in drastic reduction of the inter-particle adhesion force. The particle bond number values were computed based on either the inter-particle adhesion force from the DMT model or the inter-particle pull-off force obtained from direct AFM measurements. Surface modification resulted in two to three fold reductions in the Bond number. In order to examine the influence of the particle scale property such as the Bond number on the bulk-scale flow characterization, Angle of Repose measurements were done and showed good qualitative agreements with the Bond number and acid/base surface characteristics of the powders. The results indicate a promising method that may be used to predict flow behavior of original (cohesive) and surface modified (previously cohesive) powders utilizing very small samples
Impact of tunable oligophosphonates on barium sulfate crystallization
Calixarenes can be used as well-defined scaffolds for investigating structureāactivity relationships of additives and their impact on crystallization. In this work, we present the crystal growth modification of barium sulfate by p-phosphonic acid calix[n]arenes that vary in size (n = 4, 5, 6, and 8) and thus vary in the size of the internal cavity for the same functionality in the upper rim. The tetrameric, hexameric, and octameric macrocycles induce nanoparticle formation with clear superstructure. In the case of the hexameric calix[6]arene, the initial mesocrystalline superstructure fuses over time to form almost hollow spheres, while the mesocrystals formed in the presence of the tetramer and octamer are stable over an extended period. The pentameric calix[5]arene forms more disordered aggregates of single crystals. Thermogravimetric data shows that a significant proportion of the mass of the barium sulfate-containing solid is the macrocycle, regardless of the choice of macrocycle
Defining strawberry shape uniformity using 3D imaging and genetic mapping
Strawberry shape uniformity is a complex trait, influenced by multiple genetic and environmental components. To complicate matters further, the phenotypic assessment of strawberry uniformity is confounded by the difficulty of quantifying geometric parameters āby eyeā and variation between assessors. An in-depth genetic analysis of strawberry uniformity has not been undertaken to date, due to the lack of accurate and objective data. Nonetheless, uniformity remains one of the most important fruit quality selection criteria for the development of a new variety. In this study, a 3D-imaging approach was developed to characterise berry shape uniformity. We show that circularity of the maximum circumference had the closest predictive relationship with the manual uniformity score. Combining five or six automated metrics provided the best predictive model, indicating that human assessment of uniformity is highly complex. Furthermore, visual assessment of strawberry fruit quality in a multi-parental QTL mapping population has allowed the identification of genetic components controlling uniformity. A āregular shapeā QTL was identified and found to be associated with three uniformity metrics. The QTL was present across a wide array of germplasm, indicating a potential candidate for marker-assisted breeding, while the potential to implement genomic selection is explored. A greater understanding of berry uniformity has been achieved through the study of the relative impact of automated metrics on human perceived uniformity. Furthermore, the comprehensive definition of strawberry shape uniformity using 3D imaging tools has allowed precision phenotyping, which has improved the accuracy of trait quantification and unlocked the ability to accurately select for uniform berries
Colorimetric Humidity Sensor Based on Liquid Composite Materials for the Monitoring of Food and Pharmaceuticals
Influence of fines on the surface energy heterogeneity of lactose for pulmonary drug delivery
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