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Significance of the Water-Yield Relation in Water Deficit
Georgieva Stoyanka Eneva Korean National Committee on Irrigation and Draina 1997 한국관개배수논문집 Vol.4 No.1
농업에서의 용수부족 문제는 불가리아 뿐만 아니라, 여러나라에서 발생하고 있다. 그리고 에너지 비용이 커지므로 관개에 소요되는 비용도 점점 증가하고 있다. 용수 부족과 고비용은 용수의 효율적 이용을 요하며 이 문제를 위해서는 용수와 수량관계가 중요하다. 여기에서는 전통적으로 불가리아에서 재배되는 옥수수, 사탕무우, 자주개자리 및 포도의 증발산량대 수량 관계와 관개에 의한 중수량대 관개량 관계에 대하여 검토하였다. 용수부족시의 수량을 구하기 위해서는 FAO
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Reactive Compatibilization of Ethylene-co-Vinyl Acetate/Starch Blends
Piming Ma,Denka Georgieva Hristova-Bogaerds,Pauline Schmit,Johannes Gerardus Petrus Goossens,Pieter Jan Lemstra 한국고분자학회 2012 Macromolecular Research Vol.20 No.10
The dispersion of starch as a filler in hydrophobic ethylene-co-vinyl acetate (EVA) rubber is an issue. To obtain a fine dispersion of starch in EVA rubber, EVA/starch blends were prepared by reactive extrusion in the presence of maleic anhydride (MA), benzoyl peroxide (BPO), and glycerol. MA, BPO, and glycerol play the role of coupling agent, free-radical initiator, and plasticizer, respectively. Molau experiment and Fourier transform infrared spectroscopy (FTIR) results showed that EVA chains were grafted onto the surface of starch particles during reactive extrusion via a free-radical grafting mechanism. As a result, EVA-g-starch copolymers acted as a compatibilizer,leading to fine dispersion of starch and strong interfacial adhesion between the starch and the EVA matrix. Scanning electron microscope (SEM) images showed that the starch particle size reduced from hundreds micrometers in the case of physical blending to approximately 1 micrometer in the case of reactive blending, and consequently, the EVA rubber was effectively reinforced by the incorporation of starch and the reactive compatibilization (e.g., the tensile strength of the EVA/starch (50/50, wt/wt) was increased by a factor of 6 after the addition of 0.9-1.8 wt% MA). The property stability of starch compounds is usually an issue, while the mechanical properties of the (compatibilized)EVA/starch blends reported in this article were stable during storage
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Rheological behavior of sun protection compositions during formulation
Maria Karsheva,Silviya Georgieva,Silvia Alexandrova 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.12
Rheological properties of cosmetic products are related to the products’ sensory attributes and to performance. In literature there is a lack of information on the influence of physicochemical interactions during processing of complex systems. This study is focussed on the interactions between the ingredients of cosmetic compositions during formulation in respect to their flow behavior. The rheological behavior of model cosmetic compositions based on polyvinyl alcohol solutions and containing natural plant extracts in glycerol and olive oil, UV screens (TiO2), synthetic UV absorber, emulsifier (Carbopol 2050), preservative (Bronopol) and fragrance was studied. The flow properties of compositions containing natural UV absorbers were compared to those of compositions with synthetic ones. All the compositions exhibited shear thinning rheological behavior that can be described by the power-law rheological model. It was proved that the emulsifier’s addition thickens the compositions; the addition of Bronopol leads to slight degree of thixotropy avoided by pre-shearing the samples for one minute. The fragrance addition in EtOH solution lowers the composition’s apparent viscosity; the addition of fine TiO2 as UV-screen even in quite tiny quantity of 0.2% mass increases the consistency of basic 10% PVA samples, lowering in the same time the flow index. The compositions containing glycerol extracts are more stable than those with olive oil extracts and they preserve their properties longer.
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Curcumin-PVP Loaded Electrospun Membranes with Conferred Antibacterial and Antitumoral Activities
Gyuldzhan Yakub,Antoniya Toncheva,Veselin Kussovski,Reneta Toshkova,Ani Georgieva,Elena Nikolova,Nevena Manolova,Iliya Rashkov 한국섬유공학회 2020 Fibers and polymers Vol.21 No.1
Electrospun membranes containing curcumin were prepared from poly(L-co-D,L-lactic) acid and polyvinylpyrrolidone. The effect of curcumin concentration on the solution viscosity and the morphology of fiber was studied. Curcumin solubility in aqueous solutions was enhanced by the formation of curcumin/polyvinylpyrrolidone watersoluble complex. Curcumin physico-chemical and therapeutic properties within the membranes were preserved upon UV-Vislight irradiation, as a part of the membranes sterilization. The biomaterials showed antibacterial activity against pathogenic microorganisms such as Staphylococcus aureus and Candida albicans. In-vitro experiments against HeLa and Graffi tumor cells and white blood cells (peritoneal macrophages and spleen lymphocytes) revealed potential biomedical application of the membranes.
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