Heparin decreases permeability of pig urinary bladder wall preliminarily enhanced by chitosan

Chitosan significantly increases the permeability of the isolated pig urinary bladder wall by causing urothelial desquamation, the extent of which depends also on the concentration of the polymer. By desquamation permeability barriers of the urothelium are removed. To gain additional insight into the mechanism by which chitosan acts an absorption enhancer into urinary bladder mucosa, we evaluated the influence of a polysaccharide heparin on the permeability of isolated pig urinary bladder wall preliminarily treated with chitosan. Moreover, we aimed to establish whether the effect of heparin depends on its concentration and on the degree of urothelial desquamation caused by chitosan. In the permeability studies performed by the use of diffusion cells, transport of a model drug, pipemidic acid, into the isolated pig urinary bladder wall was determined. Heparin did not have a significant effect on the permeability of the intact urothelium. When applied to the urinary bladder wall, whose permeability was preliminarily enhanced by 0.005% or 0.001% w/v chitosan, heparin decreased the permeation of pipemidic acid into the bladder wall to a level not significantly different from the intact tissue. However, the effect of heparin was not significant at the highest concentration of chitosan tested, where the damage to the urothelium was much more intense compared with that found at lower concentrations of the polymer. The formation of complexes between pipemidic acid and heparin cannot be excluded completely, but it seems that they are not the main reason for the decreased permeation of pipemidic acid in the presence of heparin. By application on the urothelium, damaged by chitosan, heparin is supposed to form a layer on the surface of the urothelium that prevents the transport of the model drug into the bladder wall. In this way heparin probably restores the impermeability properties of the urinary bladder wall to a degree dependent on the urothelial damage.     

Optimization of Spectrum Usage and Coexistence Analysis of DVB-T and LTE-800 systems

This paper investigates the possible coexistence issues between the digital video broadcasting-terrestrial (DVB-T) system and the long term evolution (LTE) that operate in adjacent frequency bands. The proposed methodology for interference assessment evaluates the DVB-T performance degradation in presence of aggregate LTE-800 interference targeting the territory of Macedonia as evaluation area. The simulation analysis quantifies the percentage of interference degraded pixels and obtains the probability of pixel DVB-T service degradation. Furthermore, a measurement trial complements the simulation analysis through the evaluation of the influence of active antenna usage by the DVB-T receivers. The simulation and measurement results in this particular case confirm that the alignment of the active DVB-T receiving antenna towards the LTE-800 base station can substantially increase the degradation whereas aligning of the active DVB-T receiving antenna towards the DVB-T transmitter maintains the efficient TV reception. Finally, this paper proposes a simple algorithm for optimal LTE frequency arrangement, resulting in significant reduction of the LTE interference towards the DVB-T system.     

Sub-10 nm device fabrication in a transmission electron microscope

We show that a high-resolution transmission electron microscope can be used to fabricate metal nanostructures and devices on insulating membranes by nanosculpting metal films. Fabricated devices include nanogaps, nanodiscs, nanorings, nanochannels, and nanowires with tailored curvatures and multi-terminal nanogap devices with nanoislands or nanoholes between the terminals. The high resolution, geometrical flexibility, and yield make this fabrication method attractive for many applications including nanoelectronics and nanofluidics.     

Size and surface effects on the MRI relaxivity of manganese ferrite nanoparticle contrast agents

Superparamagnetic MnFe2O4 nanocrystals of different sizes were synthesized in high-boiling ether solvent and transferred into water using three different approaches. First, we applied a ligand exchange in order to form a water soluble polymer shell. Second, the particles were embedded into an amphiphilic polymer shell. Third, the nanoparticles were embedded into large micelles formed by lipids. Although all approaches lead to effective negative contrast enhancement, we observed significant differences concerning the magnitude of this effect. The transverse relaxivity, in particular r2*, is greatly higher for the micellar system compared to the polymer-coated particles using same-sized nanoparticles. We also observed an increase in transverse relaxivities with increasing particle size for the polymer-coated nanocrystals. The results are qualitatively compared with theoretical models describing the dependence of relaxivity on the size of magnetic spheres.     

Design Sensitivity Analysis of a Plate-Finned Air-Cooled Condenser for Low-Temperature Organic Rankine Cycles

ABSTRACT

Due to increasing world energy demand and environmental concerns, sustainable energy production has become crucial. Among sustainable energy sources such as solar, wind, and geothermal, industrial waste heat (heat normally released to the environment) has a big potential. Organic Rankine cycles (ORCs) are promising systems for utilizing low-temperature (100–250°C) waste heat. For an ORC system, the condenser is a key component. An accurate condenser design is important for cycle efficiency and system cost. In the literature, there are in-tube condensation correlations that are used to design condensers. However, they are not necessarily valid for low-temperature ORC conditions and working fluids, and that might lead to inaccurate end designs. This study comprises a summarized literature survey about in-tube condensation correlations. Then an iterative heat exchanger design methodology is proposed that allows performing a design sensitivity analysis on a V-shaped condenser within an input range of geometric parameters and boundary conditions. Nineteen correlations are implemented to calculate rating parameters like pressure drops, total transferred heat, overall heat transfer coefficient, size, cost and degree of subcooling. The deviations at these parameters are represented as the coefficient of variation that indicates the design condition regions where the prediction methods differ or not.     

Macro-azo-initiators having poly(ethylene glycol) units: Synthesis,characterization, and application to AB block copolymerization

Macro-azo-initiators (MAIs) having poly(ethylene glycol) (PEG) units were obtained by various multistep synthetic approaches. In the first stage, macro-azo-initiators of PEG type with azo groups inserted in the main chain were prepared. MAIs were then characterized by chemical analyses, spectral methods, ¹H-NMR, GPC, and DSC techniques. They were used in the free-radical bulk polymerization of dicyclohexylitaconate to synthesize AB block copolymers of poly(ethylene glycol-b-dicyclohexylitaconate) (PEG-b-PDCHI). © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2173–2181, 1997     

Molar Ratio of Phytic Acid and Zinc During Cereal Flake Production

The phytic acid content and distribution of phosphorus during cereal flaking were determined as well as the level of some minerals, and the molar ratios of phytic acid: zinc were calculated. Statistical analyses showed that there were no differences in the amount of total phosphorus, between oats and wheat and between rye and barley. The phytic/non-phytic phosphorus ratio was about 3 in wheat and oats, about 2 in barley and about 13 in rye. The technological processing did not affect ( P< 0·05) phytic acid content. The molar ratio of phytic acid: zinc for the flakes was only slightly below that of the whole grain, indicating that the technological process, primarily a hydrothermal treatment and flaking, did not improve zinc availability.     

Quantitative metallographic assessment of the electromagnetic casting influence on the microstructure of 7075 Al alloy

This study presents an attempt to obtain the better quality of an aluminum super-high strength alloy by application of electromagnetic field during the casting process. The conventional continuous casting process of aluminum alloys causes many defects, such as surface imperfections, grain boundary segregation, non-uniform grain size, and porosity. The better ingot surface along with the homogeneous fine-grained microstructure, and hence the better mechanical properties of the ingot, can be achieved by applying the electromagnetic casting process. The microstructure characterization, accompanied by quantitative metallographic assessment, reveals that it is possible to avoid or decrease many defects of as cast ingots during electromagnetic casting process. In this article, the microstructure of the samples of as cast 7075 aluminum alloy, obtained with and without electromagnetic field influence, was analyzed by optical microscope and the variation of key alloying elements content, i.e., Zn and Mg, through the ingot cross section was examined by chemical analysis. Besides, the microstructural parameters such as dendrite arm spacing, interdendritic space width, as well as eutecticum and intermetallic phases volume fraction, were measured using linear method. The electromagnetic field influence on the microstructure of the as cast 7075 Al alloy was evaluated based on measured quantitative metallographic data.