The Influence of Annealing on Optical and Humidity Sensing Properties of Poly(Vinyl Alcohol-Co-Vinyl Acetal) Thin Films

Hydrophobically modified poly(vinyl alcohol)s of varied copolymer composition were tested as active media for optical sensing of humidity. Copolymer thin films were deposited on silicon substrate using water-methanol solution in a volume ratio of 20:80 and concentration of 1 wt%. Films were subjected to low (60 °C) and moderate (180 °C) temperature annealing in order to study the temperature influence on optical and humidity sensing properties. Refractive index, extinction coefficient along with thickness of the films were determined by non-linear minimization of the goal function comprising measured and calculated reflectance spectra at normal light incidence. The humidity sensing ability of the films was studied through reflectance measurements at different humidity levels in the range 5–95 %RH. The influence of temperature annealing on optical and sensing properties was demonstrated and discussed

Effect of Milling Time on the Sensing Properties of Fly Ash Zeolite Composite Thin Films

Thin films, consisting of a sol–gel Nb2O5 matrix doped with zeolite Na-X synthesized from fly ash through ultrasonic-assisted double-stage fusion-hydrothermal alkaline activation, were deposited by the spin-coating method. In order to improve the optical quality and sensing properties of the thin films, zeolites were wet milled for 60, 120 and 540 s prior to incorporation in the film. The liquid adsorption ability of thin films was tested by measuring the reflectance spectra prior to and after exposure to liquid acetone and the change in the reflection coefficient ∆R of the films was calculated. The influence of milling time of zeolites on the sensing and optical properties of the films was studied

Progress in the Utilization of Coal Fly Ash by Conversion to Zeolites with Green Energy Applications

Fly ash (FA) from lignite coal combusted in different Thermal Power Plants (TPPs) was used for the synthesis of zeolites (FAZs) of the Na-X type by alkaline activation via three laboratory procedures. FAZs were characterized with respect to their morphology, phase composition and surface properties, which predetermine their suitability for applications as catalysts and adsorbents. FAZs were subsequently modified with metal oxides (CuO) to improve their catalytic properties. The catalytic activity of non-modified and CuO-modified FAZs in the total oxidation of volatile organic compounds was investigated. FAZs were studied for their potential to retain CO2, as their favorable surface characteristics and the presence of iron oxides make them suitable for carbon capture technologies. Thin films of FAZs were deposited by in situ crystallization, and investigated for their morphology and optical sensitivity when exposed to pollutants in the gas phase, e.g., acetone. This study contributes to the development of novel technological solutions for the smart and valuable utilization of FA in the context of the circular economy and green energy production

Application of fluoride in children (advantages and disadvantages)

Aim: The purpose of this study was to demonstrate the use of fluoride in children’s dentistry,the ways in which they act and who are pozitive and negative characteristics from treatment with fluorides and the same time to prove that treatment with a dental fluoride is one of the most effective ways to prevent tooth decay and mentaining excellent dental health in children. Material and method: For this study, we compared a group of children that started using fluoride from an early age (during growth and development of permanent dentition) and a group of children in whom the application of fluoride started later. (in permanent dentition) Conclusion: The conclusion is that fluoride treatments are effective in decreasing the prevalence of cavities in children, by 95% specifically, when combined with dental sealants.They are especially active when they start using them since early childhood. However, fluoride overdoses, that is, the so-called fluorosis, should be avoided, where excessive use of fluoride results in tooth decay. We conclude that it is necessary to apply fluoride in children at a moderate dose. Key words: fluoride; caries; caries prevention; children; treatment; fluorosi

Processing of high-grade zeolite nanocomposites from solid fuel combustion by-products as critical raw materials substitutes

High-grade zeolite nanocomposites are synthesized utilizing solid by-products from combustion of coal for energy production in Thermal Power Plants applying alkaline aging, hydrothermal and fusion-hydrothermal activation procedures. The obtained coal ash zeolites were studied with respect to their chemical and phase composition, morphology, surface parameters and thermal properties. It was found that they are distinguished in nanocrystalline morphology and significant content of iron oxide nanoparticles (γ-Fe2O3, α-Fe2O3, γ-Fe3O4) and doping elements (Cu, Co, Mn, V, W, etc.) transferred from the raw coal ash, and therefore they are assumed as nanocomposites. Coal fly ash zeolite nanocomposites are characterized by a mixed micro-mesoporous texture, significant concentration of acidic Brønsted centers due to their high surface insaturation, high chemical and thermal stabilty. This unique combination of compositional and textural properties predetermines the application of these materials as catalysts for thermal oxidation processes, anticorrosion barrier coatings, carbon capture adsorbents, matrices for hosting functional groups, detergents etc. Examples for coal fly ash zeolite applications for substitution of critical raw materials in practice are provided

Вовед во стоматолошка протетика - практикум

Практикумот Вовед во стоматолошка протетика е наменет за студентите на стручните студии за забни техничари – протетичари, на Факултетот за медицински науки при Универзитетот „Гоце Делчев“ – Штип. Овој практикум ги содржи описите на анатомските делови на стоматогнатниот систем, како и нивните основни функции. Дадени се основите за мобилно и парцијално протезирање, основи на фиксното протезирање, како и запознавање со импланто-протетика и максилофацијална протетика

Вовед во стоматолошка протетика - скрипта

Скриптата “Вовед во стоматолошка протетика” е наменета за студентите на Стручните студии за забни техничари – протетичари, на Факултетот за медицински науки при Универзитетот “Гоце Делчев” – Штип. Оваа скрипта ги содржи описите на анатомските делови на стоматогнатниот систем, како и нивните основни функции. Дадени се основите за мобилно и парцијално протезирање, основи на фиксното протезирање, како и запознавање со имплантопротетика и максилофацијална протетика

Hard-Templated Porous Niobia Films for Optical Sensing Applications

Porous Nb2O5 films obtained by a modified hard-template method were studied and their optical and sensing properties were optimized in order to find applications in chemo-optical sensing. Porous films were prepared by following three steps: liquid mixing of niobium sol and SiO2 colloids in different volume fractions, thermal annealing of spin-coated films for formation of a rigid niobia matrix, and selective removal of silica phase by wet etching thus generating free volume in the films. The morphology and structure of the films were studied using transmission electron microscopy and selected area electron diffraction, while their optical and sensing properties were estimated using UV-VIS-NIR reflectance measurements in different ambiences such as air, argon and acetone vapors and nonlinear curve fitting of the measured reflectance spectra. Bruggeman effective medium approximation was applied for determination of the volume fraction of silica and air in the films, thus revealing the formation of porosity inside the films. For further characterization of composite films, their water contact angles were measured and finally conclusions about the impact of initial chemical composition and etching duration on properties of the films were drawn

All Ceramics Bridge for Perfect Smile (Case Report)

Background: The best make up on our face is smiling. All ceramics crown or bridges is the solutions for a beautiful smile that we all wish. All ceramics represent the highest achievements of modern dentistry. Aesthetic dentistry would be unthinkable without all ceramics. The purpose of this study was to show our management of smile design with all ceramics bridge. Case report: A 37 years old male patient visit our dental office searching for solution for his unsatisfactory smile appearance. Thought clinical examination, missing tooth, tooth discoloration after root canal treatment, low smile line and caries were found. All the solutions were offered to the patient, and a bridge was chosen all ceramics dental bridge as the best solution. A preparation on the three frontal teeth was made. Impressions were taken and sent to the laboratory where dental bridge with three anchor crown and one lateral pontic were made. After try-in the bridge were cemented by light curing cement. After follow-up there were no signs of changes in the bridge. Conclusion: А patient was satisfied with the restoration done. All-ceramic systems achieving the esthetic results and cover all indications in fixed prosthodontics while. Key words: Aesthetic, ceramics, dental bridge, fixed prosthodontics

Influence of the Size of Coal Ash FAU Zeolites Used as Dopants on the Sensing Properties of Nb2O5 Thin Films

In this study, solid waste from coal combustion in thermal power plants (TPPs) was used for the synthesis of zeolite Na-X samples. They were prepared by the long-term alkaline atmospheric conversion of coal ash collected from the electrostatic precipitators in the TPP “AES Galabovo”. When used in the form of thin films/layers, the optical detection of volatile organic compounds (VOCs) is possible due to a change in their reflectance spectra and color. In order to improve the sensing properties of synthesized zeolites, they were wet milled for 60 s and both milled and unmilled zeolites were used as dopants for the niobium oxide matrix in the form of thin films deposited by the spin-coating method on a silicon substrate. The surface morphology and structure of both zeolite powders were studied by scanning electron microscopy, while their size was determined by dynamic light scattering (DLS) spectra. Optical constants (refractive index, n, and extinction coefficient, k) and the thickness of the films were calculated from reflectance measurements. The change in the reflection coefficient ∆R of the films was determined from measured reflectance spectra prior to and after exposure to probe acetone molecules. An increase in the reaction of the films with milled zeolites to acetone, compared to the samples with unmilled zeolites, is demonstrated