The present study describes degradable polyurethane (PU) microspheres fabricated using toluene diisocyanate, polycaprolactone, polyethylene glycol, 2, 2-hydroxymethyl-2-propionic acid and triethylamine for drug delivery. The novel microspheres were synthesized using self-emulsion and condensed phase separation method. Fourier-Transform Infrared Spectrum analysis (FTIR) was performed revealing the chemical structure of polyurethane microspheres with special chains changing. Swelling properties influenced by solvent polarity, PEG content, PEG molecular weight, were evaluated, suggesting that the swelling ratio (SR) of PU microspheres increased with the increase in solvent polarity, PEG content and PEG molecular weight respectively.
Ultrasonic velocity tomography is a novel technique for velocity field measurement with the advantages of being non-invasive and insensitive to fluid properties. But its application is limited by poor spatial resolution. Thus, a novel ultrasonic velocity tomography method based on an interlaced chord network is proposed in this paper. To form the interlaced chord network, transducers are installed at two mounting planes of the pipe with N transducers on each plane, and 2×N transducers are equally spaced along the pipe circumference. In particular, N is selected to be an odd number to avoid blind zone. The average velocity on each chord is scanned in a fan-beam mode and used as projection data for velocity field reconstruction. The projection data are rearranged into a parallel beam mode and interpolated at a uniform interval. A filtered back projection algorithm is employed for 2-dimensional reconstruction of the velocity field. Numerical simulation experiments show that, the spatial resolution is improved obviously by the interlaced chord network without introducing extra transducers and 13 transducers on each mounting plane are enough for actual velocity field imaging downstream a single-bend pipe.
To study the relationship between the molecular main chain structure and the properties of amine based tetra-functional epoxy resins, especially for the thermal stabilities and the mechanical properties, N,N,N',N'-Tetraglycidyl-2,2-Bis[4-(4-aminophenoxy)phenyl]propane (TGBAPP) and N,N,N',N'-Tetraglycidyl-4,4'-diamino diphenyl ether (TGDDE) were cured with Methyl nadic anhydride (MNA). The thermal behavior of the cured epoxy resins were studied with the thermo-gravimetric analysis (TGA), and the glass transition temperature (Tg) were determined with the Dynamic Mechanical Analysis (DMA). Additionally, the mechanical properties of them were tested. The results indicated that the cured epoxy resin based on TGBAPP had better thermal stabilities and toughness.
The experiments of artificial heart valves were divided into in vivo and in vitro experiments; in vivo experiments provide accurate experimental parameters serving in vitro research. Simulation experiment used in vitro usually goes like this, firstly design a similar model or prototype phenomenon, then analysis the model working out the regular parameters related to the process, ruled out the possibility of impact on the study of individual exist in vivo experiment. In vitro experiments are likely designed; performance can be simplified and prominently concerned about contents, even designed some extreme conditions to test. A number of means related to fluid experimental measurement are included, such as the Particle Image Velocimetry(PIV)[1], Dual Catheter Method [2],and ultrasonic method[3] and so on. However, these methods have different kinds of limitations, for example the Dual Catheter Method cannot be used as a routine determination for clinic due to its destructiveness, and PIV test requires expensive equipment. This study was designed by the image processing technology of high-speed photography aiming at the production of a reliable, simple, economic, injury-free and non-contact measurement method.
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