In this study, the synthesis, structure and physical properties of two series of thermoplastic polyurethanes based on hydroxypropyl-terminated poly-(dimethylsiloxane) (HP-PDMS) or hydroxyethoxypropyl-terminated poly-(dimethylsiloxane) (EO-PDMS) as soft segments, and 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol as hard segments were investigated. The polyurethanes were synthesized by two-step polyaddition in solution. The effects of the type and content of PDMS segments on the structure, thermal and surface properties of copolymers were studied by 1 H-, 13 C-nuclear magnetic resonance (NMR) spectroscopy and two-dimensional NMR spectroscopies (heteronuclear multiple bond correlation (HMBC) and rotating-frame nuclear Overhauser effect (ROESY)), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide-angle X-ray scattering (WAXS), scanning electron microscopy (SEM) and water contact angle and water absorption measurements. Thermal properties investigated by DSC indicated that the presence of soft PDMS segments lowers the glass transition and melting temperatures of the hard phase as well as the degree of crystallinity. SEM analysis of the copolymers with a lower soft segment content confirmed the presence of spherulite superstructures, which arise from the crystallization of the hard segments. When compared with polyurethanes prepared from HP-PDMS, the copolymers synthesized from EO-PDMS with the same content of the soft segments had a higher degree of crystallinity, better thermal stability and a less hydrophobic surface. The obtained results showed that the synthesized polyurethanes had good thermal and surface
Lactate dehydrogenase (LDH) and lactate are some of the hypoxy biochemical parameters. Extracellular activity of this enzyme increases under the condition of oxidative stress, since the cell integrity can be disrupted during the lipid peroxidation process. Subsequently that leads to the increase level of the lactic acid and lactic acid salts. The objective of this investigation is establishing the level of LDH, LDH1 (HBDH) and the lactate concentration in aqueous humour in patients with primary open-angle glaucoma. Biochemical analysis have been made by enzymatic-colometric method (lactate) and UV-kinetic method (LDH and HBDH) in aqueous humour of 30 patients (42 eyes) with primary open-angle glaucoma (POAG) and 30 patients (40 eyes) with cataract (the control group). The increased values of lactate and the activity of LDH and HBDH enzyme in aqueous humour of POAG patients in correlation with the control group are the results not only of oxidative stress but also of hypoxy and the mitochondry oxidative function (p<0,001). The increased activity of the examined biochemical parameters in the aqueous humour of the POAG patients points to the fact that other mechanisms, besides IOP, have a role in glaucoma pathogenesis.
Entrepreneurs are playing a major role in the economy of each country on the planet. They contribute to national economies by starting up and running small and medium sized enterprises (SMEs), which make more than 95% of the total number of enterprises and which are providing jobs to more than 60% of all employees within each country. The significance of entrepreneurship for economic development oblige goverments and all other relevant institutions within each country to continue to facilitate its growth by all means necessary. In order to do this, these institutions need to be familiar with motives of entrepreneurs to start their own business. In this paper, results of empirical research concerning motivational factors of entrepreneurs in Serbia are presented. This research presents a continuation of serie of research on this topic which were conducted in several countries, by using the same methodological approach.
The results indicate that mutant GSTO2*Asp genotype is associated with increased risk of age-related cataract in smokers and ultraviolet-exposed subjects, suggesting a role of inefficient ascorbate regeneration in cataract development.
Segmented thermoplastic polyurethane copolymers (PURs) were synthesized using 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol as the hard segment and α,ω-dihydroxy-poly(propylene oxide)-b-poly(dimethylsiloxane)-b-poly(propylene oxide) (PPO-PDMS) as the soft segment. The content of incorporated soft segments in PURs varied in the range from 40 to 90 wt.%. The structure, molecular weights and crystallinity of obtained copolymers were monitored by FTIR, 1 Hand 2D-NMR spectroscopy, and GPC and DSC analysis, respectively. Surface free energy analysis indicates the presence of hydrophobic (siloxane) groups on the surface, giving highly hydrophobic nature to the obtained PURs films. Water absorption measurements showed that the increase of the hydrophobic PPO-PDMS segment content led to the decrease of percentage of absorbed water in copolymers. SEM and AFM analysis revealed that copolymers with lower content of PPO-PDMS segments have higher microphase separation between segments. The results obtained in this work indicate that synthesized PURs based on PPO-PDMS demonstrated proper surface and morphological properties with a great potential for variety of applications such as hydrophobic coatings in biomedicine.
BACKGROUND:Recurrence of medulloblastoma appears after 30% to 40% of the surgeries. Different from primary medulloblastoma, in which five-year survival rate is 50%, the survival time of relapses much shorter and only 20% of the patients manage to survive a year. There is a logical need for additional methods of treatment of recurrent medulloblastomas. The aim of the study is to determine the effects of intracavitary and long-term subcutaneous application of Sandostatin (octreotide) on the recurrent medulloblastomas. METHODS: Fourteen children aged 4 to 9 years, in which, despite of craniospinal irradiation and chemotherapy came to a recurrence of medulloblastoma during the first 6 months after the surgery, were treated subcutaneously with Sandostatin (octreotide) in a longer period of time. Cerebellar medulloblastomas with a diameter bigger than 20 mm and spinal over 10 mm were removed operatively and octreotide with Beriplast was applied intracavitary. RESULTS: Magnetic resonance of cranioaxis shows that the application of octreotide has caused the disappearance of spinal drop metastases in all 7 patients and the cerebellar metastases smaller than 5 mm in all 4 patients. Subcutaneous application of octreotide combined with intracavitary expresses an antitumoral effect in 2/3 of the relapses. The application of octreotide results with a transformation of ChangÕs stage M0 into M1 in 71.43% of the patients. CONCLUSION: In the case of in loco or metastatic recurrence of medulloblastomas, intracavitarily and subcutaneously applied octreotide results with a regression of the tumor in a 3 year time within 2/3 of the treated patients.
A novel magnetic polymer/bentonite composite was prepared by suspension copolymerization of glycidyl methacrylate and ethylene glycol dimethacrylate in the presence of magnetic bentonite (MB-PGME) and functionalized with ethylene diamine and hexamethylene diamine (MB-PGME-ED and MB-PGME-HD). The obtained samples were characterized in terms of structure as well as thermal, magnetic and morphological properties. The sorption of rhenium (Re) and tungsten (W) from aqueous solution onto MB-PGME-ED and MB-PGME-HD was investigated considering their contact time and different initial ion concentration, giving possibility for usage of these composites as commercial sorbents. The sorption system follows the pseudo-second order and intraparticle diffusion kinetic models. The results indicated a better fit with the Freundlich isotherm model.
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