Infinitesimal bending of curves on the ruled surfaces

In this paper we study infinitesimal bending of curves that lie on the ruled surfaces in Euclidean 3-dimensional space. We obtain an infinitesimal bending field under whose effect all bent curves remain on the same ruled surface as the initial curve. Specially, we consider infinitesimal bending of the curves which belong to the cylinder as well as to the hyperbolic paraboloid and find corresponding infinitesimal bending fields. We examine the variation of the curvature of a curve under infinitesimal bending on the hyperbolic paraboloid. Some examples are visualized using program packet Mathematica

Tissue response to different implanted biomaterials in models in vivo

Данашњи приступ репарацији и регенерацији ткива често подразумева употребу различитих биоматеријала, самостално или у комбинацији са ћелијама и/или факторима раста. Сви материјали, без обзира да ли су природног порекла или синтетисани, изазивају реакцију околног ткива након имплантације. Ова реакција подразумева низ повезаних догађаја од којих коначно зависи да ли ће имплантирани материјал бити добро прихваћен и обавити своју примарну улогу. Сваки материјал за организам представља страно тело и иницира пролазну инфламаторну реакцију, чија дужина трајања и интензитет умногоме одређују његову даљу судбину. На то утиче хемијски састав материјала, величина и облик његових гранула, порозност, компактност, као и степен биодеградабилности. Тако, судбина материјала може кренути једним од два пута: ка доброј интеграцији са околним ткивом, подршци ћелијама са којима интерагује и, код биодеградабилних материјала, замени здравим, функционалним ткивом, или ће пак изазвати снажан и продужен инфламаторни одговор који резултује потпуном изолацијом материјала од остатка ткива дебелом фиброзном капсулом. In vivo испитивања одговора ткива на имплантирани биоматеријал подразумевају истраживања на различитим анималним моделима и у различитим ткивима, са ортопичним или ектопичним имплантацијама. У овом раду ће бити дат преглед наших in vivo истраживања на различитим моделима имплантација. Користили смо ортопичне моделе за формирање кости код пацова и кунића и моделе супкутаних имплантација различитих биоматеријала мишевима и пацовима. За анализу импланата и околног ткива у временским периодима раног и касног одговора коришћене су бројне методе као што су хистолошка бојења, хистоморфометрија, имунохистохемија, СЕМ, радиографске методе, анализа специфичне експресије гена и друге. In vivo анимални модели у сврху претклиничких испитивања важни су за добијање смерница за клиничку примену.Today's approach to tissue repair and regeneration often involves application of different biomaterials, alone or in combination with cells and/or growth factors. All materials, regardless of whether they are of natural origin or synthesized, cause a reaction in the surrounding tissue after implantation. This reaction involves a series of related events on which ultimately depends whether the implanted material will be well accepted and perform its primary role. Each material represents a foreign body for the organism and initiates a transient inflammatory reaction, the duration and intensity of which largely determine materil's further fate. Inflammatory reaction is influenced by material's chemical composition, the size and shape of its granules, porosity, compactness, as well as the degree of material's biodegradability. Thus, the fate of the material can go one of two ways: towards good integration with the surrounding tissue, supporting the cells with which it interacts and, in the case of biodegradable materials, replacement by healthy, functional tissue, or it will cause a strong inflammatory response resulting in the complete isolation of the material from the rest of the tissue with thick fibrous capsule. In vivo research of tissue response to implanted biomaterial involves investigation in different animal models and in different tissues, with orthotopic or ectopic implantations. We used orthotopic models for bone formation in rats and rabbits and models of subcutaneous implantation of various biomaterials in mice and rats. Numerous methods were used for the analysis of implants and surrounding tissue in the time periods of early and late response, such as histological staining, histomorphometry, immunohistochemistry, SEM, radiographic methods, analysis of specific gene expression and others. In vivo animal models for the purpose of preclinical studies are important in order to obtain guidelines for clinical application

Actual contamination of the Danube and Sava Rivers at Belgrade (2013)

This study was focussed on a comprehensive investigation on the state of pollution of the Danube and Sava Rivers in the region of Belgrade. Different complementary analytical approaches were employed covering both i) organic contaminants in the river water by target analyses of hormones and neonicotinoids as well as non-target screening analyses and ii) heavy metals in the sediments. Finally, some common water quality parameters were analysed. The overall state of pollution is on a moderate level. Bulk parameters did not reveal any unusual observations. Moreover, quantification of preselected organic contaminants did not indicate to elevated pollution. More significant contaminations were registered for chromium, nickel, zinc and partially copper in sediments with values above the target values according to Serbian regulations. Lastly, non-target screening analysis revealed a wider spectrum of organic contaminants comprising pharmaceuticals, technical additives, personal care products and pesticides. The study presented a comprehensive view on the state of pollution of the Sava and Danube Rivers and is the base for setting up further monitoring programs. As a superior outcome, it was illustrated how different chemical analyses can result in different assessments of the river quality. A comparison of target and non-target analyses pointed to potential misinterpretation of the real state of pollution

Electrochemically synthesized Molybdenum oxides for enhancement of atmospheric pressure non-thermal pulsating corona plasma induced degradation of an organic compound

MoO2 and MoO3 were applied as catalysts for plasma degradation of organic compound. They were prepared by electrodeposition (MoO2) and electrodeposition followed by thermal treatment (MoO3), and then characterized by the cyclic voltammetry, SEM, EDX, XRD, and FTIR. The RB 19 was degraded by self-made non-thermal atmospheric pressure pulsating plasma corona reactor. Decolourization mechanism, parameters, kinetics, and influence of the catalysts were examined. Mo-oxides enhanced degradation reactions rate constants by 45% – 50%, increased decolourization rate at all the tested pHs, discharged current densities, and decreased energy consumption. Degradation followed the pseudo-first kinetics order and proceeded via plasma-generated ⋅OH radical, which attacked dye molecule; MoO2 and MoO3, excited by plasma-generated UV radiation and high-energy chemical species bombardment, enhanced decomposition of plasma-generated H2O2 into ⋅OH radicals, thus enhancing production of degradation agent. Higher percentage of mineralization was attained in the presence of catalysts, which maintained their degradation activity after 5 uses

Osteogenic effect of inflammatory macrophages loaded onto mineral bone substitute in subcutaneous implants

We analyzed the influence of inflammatory macrophages on the osteogenic process in subcutaneous implants composed of mineral bone substitute. Thioglycollate-elicited peritoneal macrophages (TEPMs) were characterized as inflammatory. This was confirmed microscopically by the nitroblue tetrazolium (NBT) test and the production of tumor necrosis factor α (TNF-α). The implants (M-type) were made of mineral bone substitute (Bio-Oss®) mixed with TEPMs and blood clot. Implants without macrophages served as the control (C-type). Subcutaneous implantation in the interscapular area was performed on BALB/c mice. Implants were extracted after 2 and 8 weeks. In M-type implants, phagocytosis and angiogenesis were more pronounced, and osteoblast-like cells aligned onto granules of implanted material and osteoid structures can be seen. The observed higher osteocalcin and lower osteopontin immunoexpression in M-type implants when compared to the control after 8 weeks suggest a more advanced osteogenic process. Our results indicate that the presence of inflammatory macrophages in the composition of an implant may have a beneficial effect on the osteogenic process. [Projekat Ministarstva nauke Republike Srbije, br. III41017

Effects of bone tissue engineering triad components on vascularization process: comparative gene expression and histological evaluation in an ectopic bone-forming model

Vascular development has a great significance in the osteogenic process and in bone tissue engineering (BTE). BTE is based on various combinations of three principal types of components: biomaterials as scaffolds, regulatory signals and cells. The aim of our study was to evaluate, at gene expression and histological level, the effect of BTE triad components on the vascularization process in an ectopic bone-forming model in mice. Bone mineral matrix (BMM) was used as a scaffold and a carrier, platelet-rich plasma (PRP) as a source of regulatory signals and adipose stem cells (ASCs) as a source of cells for endothelial differentiation, in order to show how and to what extent the biological enrichment of BMM influences the outcome of the osteogenic process and its key precondition, vascularization. Implants composed of BMM, PRP and ASCs in vitro induced into endothelial cells (EPB implants) and implants composed of BMM and PRP (PB implants) were compared with implants composed of BMM only (B implants). More pronounced endothelial-related gene expression and stronger VCAM-1 (vascular cell adhesion molecule-1) immunoexpression were observed in EPB implants in comparison with PB and B ones at later time points of the in vivo experimental period. Osteopontin gene expression and immunoexpression of osteopontin were significantly higher in EPB compared to PB and B implants. Therefore, addition of ASCs combined with PRP to BMM improved the vascularization process in the ectopic bone-forming model, which makes this BTE composition the most favourable among the examined types of implants for application in BTE

A New Photocatalyst Bismuth Oxo Citrate: Synthesis, Characterization, and Photocatalytic Performance

A new photocatalyst bismuth oxo citrate was synthesized by facile precipitation process with calcination at 200 8C. The photocatalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fouriertransform infrared (FTIR) spectroscopy, N2 sorptometry, and elemental analysis. Morphologically, it is composed of polyhedral particles with different, irregular shapes and sizes. The specific surface area (SSA) of the photocatalyst was 8.92 m2 g-1. It showed very good photocatalytic performance and reusability. Total decolorization of Reactive Blue 19 (RB19) was achieved in less than 10 minutes, which is much faster in comparison with TiO2 P25. Also, bismuth oxo citrate showed higher photocatalytic activity than other photocatalysts based on bismuth compounds reported by other authors. Optimal photocatalysis parameters were pH 2 and photocatalyst dose of 250 mg dm-3. The decolorization rate was found to decrease as initial dye concentration increased. The photocatalytic data best fitted to L-H kinetic model with pseudo-first order reaction rate. Chrastil diffusion model showed that diffusion has not influence on the process. Water Environ. Res., 90, 719 (2018). © 2018 Water Environment Federation