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Viscosity of biodiesel: experiments and modeling
No full textA model has been developed to predict the viscosity of biodiesel fuel. It is based on the extended hard-sphere (EHS) model that assumes conformal viscosity behavior and makes use of the mole average mixing rules. The relevant mixture parameters for unsaturated esters were obtained by means of the effective molecular mass concept, while those for saturated esters were obtained by recourse to previously published correlations. In order to validate the developed model, the density and viscosity of three synthetic biodiesel mixtures, composed of up to five components, were measured at atmospheric pressure at temperatures between (288.15 and 353.15) K. The density was measured by means of a vibrating U-tube densimeter with the combined expanded uncertainty (k ≈ 2) of 2.5 kg⋅m−3. The viscosity was measured with a Stabinger viscometer, with a relative uncertainty of 3.5 %. The data measured in this work, together with the literature viscosity data on both synthetic biodiesel mixtures and real biodiesel fuel was used to validate the developed EHS model. The experimental data, consisting of 84 data points, were represented with the average absolute deviation of 3.5 % and a maximum deviation of 12 %
Effects along the epithelial-mesenchymal biointerface in direct cell self-organisation: Multiscale theoretical analysis
No full textEpithelial cancer ranks among the most deadly types of cancer globally. Focusing on the disease's early stages could lead to significant enhancements in the survival rates of cancer patients. The initial phase of the disease is associated with the dissemination of cancer cells into the adjacent healthy epithelium. Therefore, a more profound understanding of cell dynamics at the biointerface between epithelial and cancer (mesenchymal) cells is essential for managing the disease promptly. The dynamics of cells at this epithelial-cancer biointerface arises through interplay between a variety of biological and physical mechanisms. Although considerable research has been dedicated to examining the spread of cancer cells across the epithelium, the physical mechanisms that govern the dynamics at the biointerface remain poorly understood. The main goal of this multi-scale theoretical consideration is to emphasize the influence of physical factors, such as the viscoelasticity of the subpopulations and the dilational viscoelasticity of the biointerface, on the efficiency with which cancer spreads through the epithelium. We do so by consideration of the mechanical coupling between the epithelial and cancer mesenchymal-like subpopulations. In this review, we consider this complex phenomenon from a multiscale mechanical perspective that has not been explicitly addressed in earlier studies, using model systems such as the segregation of co-cultured epithelial–mesenchymal spheroids. The mechanical-coupling between the subpopulations arising from the system's viscoelasticity is discussed from the cellular to supracellular levels in order to recognize the main physical factors responsible for the spreading of cancer
Identification of priority sources of potentially hazardous elements from public drinking water fountains in Zaječar/East Serbia
No full textAccess to clean drinking water is essential for human health, economic development, and environmental sustainability. To effectively preserve water quality and ensure a safe and stable water supply, it is essential to determine the priority control factors of potentially hazardous elements in water. This study focused on public drinking water fountains in Zaječar City (Serbia), examining water hydrochemistry, quality, potential sources of hazardous elements, and the health risks associated with consumption or dermal exposure. Among all potentially hazardous elements, iron showed a deviation from the limit in drinking water prescribed by the World Health Organization, reaching 631 µg/L. However, all samples were categorized as excellent quality for drinking. Water composition was governed by water-rock interactions, distinguishing Na-HCO3 as the dominant water type. A total of 3.3 % and 6.6 % of samples exceeded the threshold of 1 for non-carcinogenic health risk for adults and children, respectively, with the mean HIa value of 0.35 and the mean HIc value of 0.57. However, the carcinogenic risk was within the allowable limits for children, whereas it surpassed the threshold of 1.0 × 10–4 for adults in 10 % of the samples. The positive matrix factorization model identified four sources responsible for water quality, i.e., natural source, industrial source, sewage source, and agricultural source, with contributions of 37.1 %, 35.0 %, 17.8 %, and 10.1 %, respectively. The Monte Carlo simulation of source-specific health risks revealed that the industrial source was the main contributor to both non-carcinogenic and carcinogenic risks, attributed to its high arsenic load
Mathematical model for the exergy of the system ammonium nitrate–water
No full textThe exergy balance has recently been used more frequently for the energy analysis of technological processes and represents a considerable improvement over the evaluation according to the First law of thermodynamics, in which completely convertible and incompletely convertible forms of energy are taken into account equally. In order to carry out the exergy balance, the exergy values of the material flows involved in the process must be known. This article presents a mathematical model for calculating the exergy of ammonium nitrate in aqueous solution in the production of fertilizers. When carrying out the exergy model, it was assumed that the conditions are: ambient temperature 20 °C, pressure 101.325 kPa and that it consists of liquid water and crystalline ammonium nitrate, which has an exergy value of zero under these conditions. The model is based on Pitzer's ion-interaction type equations for the dependence of the activity coefficient on the composition of the solution at a given temperature and pressure. This mathematical model is valid for aqueous solutions of ammonium nitrate up to saturation in the temperature range from 20 °C to 170 °C and offers the possibility to estimate the NH4NO3(aq) enthalpies at different temperatures and different compositions
Uticaj teksture i nanomaterijala na karakteristike proizvedenih prirodnih vlakana
No full textIn this study, pyrophyllite was used for the first time in the composition of protective refractory coatings together with supplementary waste resources. The proposed refractory coatings are applicable for metallic and non-metallic structures, with the option of using them to protect machinery components in the chemical industry, metallurgy, and mining. Given that pyrophyllite has a low hardness, the goal was to improve the coating's resistance to cavitation erosion by adding 20 wt.% of hard refractory materials, i.e., crushed and micronized waste bricks based on mullite and corundum, respectively. Previous studies have demonstrated that protective coatings using a pyrophyllite filler have refractory qualities but insufficient resistance to cavitation erosion. As a result, the composition of refractory coatings, the preparation techniques, and the coating manufacturing process were altered. This study presents a simple method for combining conventional coatings made of refractory fillers (primary resource: pyrophyllite) with waste materials (mullite brick and corundum brick) used as reinforcement in protective refractory coatings for metal and non-metal structural elements that are highly resistant to cavitation erosion.U ovoj studiji pirofilit je prvi put korišćen u sastavu zaštitnih premaza zajedno sa dodatnim
otpadnim resursima. Predloženi vatrostalni premazi su primenljivi za metalne i nemetalne
konstrukcije, sa mogućnošću upotrebe za zaštitu komponenti mašina u hemijskoj
industriji, metalurgiji i rudarstvu. S obzirom na to da pirofilit ima malu tvrdoću, cilj je bio
da se poboljša otpornost premaza na kavitacionu eroziju dodavanjem 20 tež. % tvrdih
vatrostalnih materijala, odnosno drobljene i mikronizovane opeke na bazi mulita i
korunda. Predhodne studije su pokazale da zaštitni premazi sa pirofilitnim puniocem
imaju zadovoljavajuću vatrostalnost, ali nedovoljnu otpornost na kavitacionu eroziju. Kao
rezultat toga, sastav vatrostalnih premaza, tehnike pripreme i proces proizvodnje
premaza su izmenjeni. Ova studija predstavlja jednostavnu metodu kombinovanja
konvencionalnih premaza od vatrostalnih punioca (primarni resurs: pirofilit) sa otpadnim
sirovinama (opeke na bazi mulita i korunda) koji se koriste kao ojačivači u zaštitnim
vatrostalnim premazima za metalne i nemetane elemente konstrukcija koji su visoko
otporni na kavitacionu eroziju
Enhancement of the Biological Potential of Herbal Extracts through Fermentation, Microwave-Assisted Extraction, and Iodine Catalysis
No full textIntroduction: The biological potential of herbal extracts can be significantly
enhanced through fermentation, followed by microwave-assisted extraction
(MAE). The selection of microorganisms capable of producing enzymes
such as hemicellulase, cellulase, tannase, and glucosidase facilitates the
release of polyphenols from the plant matrix, the depolymerization of
tannins, and the conversion of glycosides into aglycones. This enzymatic
activity results in fermented extracts with superior biological properties
compared to non-fermented counterparts. Moreover, the addition of iodine
during MAE, as a catalyst, enables the production of extracts with enhanced
biological activity. The catalytic properties of iodine arise from its ability to
form intermolecular bonds with electron-rich atoms within various functional
groups, thereby facilitating nucleophilic reactions and enabling the synthesis
of new compounds. ..
Antimicrobial properties of probiotic edible films based on whey proteins
No full textThe development of biodegradable food packaging materials
has gained widespread attention due to growing environmental concerns
associated with plastic pollution. Additionally, food safety remains a serious
global issue, resulting in numerous deaths annually. Consequently,
development of not only biodegradable, but also active packaging materials
based on natural components, that would guarantee food safety and prolong
food shelf-life became an imperative. Incorporation of probiotic bacteria in
protein-based films presents a promising way to create edible active food
packaging that also enables consumption of health-promoting probiotics.
Namely, probiotics within films produce numerous bioactive compounds that
contribute to improved functional properties of films, particularly their
antioxidative and antimicrobial activities. However, controlling the synthesis
and release of bioactive compounds in probiotic films presents a difficult
task. In this paper, films obtained from whey protein concentrate (WPC) and
inulin were used as carriers for the probiotic strain Lactiplantibacillus
plantarum 299v
Cost-Effective and Sustainable Activation of Carbon Felt
No full textThis study presents an eco-friendly and cost-effective method for activating and functionalizing pristine carbon felt (CF) through immersion in a commercial 5 wt.% hypochlorite solution. The electrochemical performance of the activated CF was significantly improved, exhibiting a twenty-fold enhancement compared to the untreated material. Characterization techniques, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), contact angle measurements, and water uptake tests, confirmed substantial modifications to the material’s properties. Notably, the activation process introduced oxygen-containing functional groups, expanded mesopores and macropores, and reduced C–C bonds, with a more than 22% decrease in sp3 and sp2 bonding, alongside a 20% increase in C–O groups. These changes led to enhanced water uptake and improved electrochemical behavior. Additionally, galvanostatic electrodeposition of polypyrrole (PPy) onto both pristine and activated CF demonstrated that the treated CF exhibited four times the capacitance of the untreated sample, underscoring its potential for advanced applications. The results suggest that this low-cost, eco-friendly activation method is a promising approach for the large-scale functionalization of carbon felt for energy storage and other electrochemical applications
Mathematical Optimization in Machine Learning for Computational Chemistry
No full textMachine learning (ML) is transforming computational chemistry by accelerating molecular simulations, property prediction, and inverse design. Central to this transformation is mathematical optimization, which underpins nearly every stage of model development, from training neural networks and tuning hyperparameters to navigating chemical space for molecular discovery. This review presents a structured overview of optimization techniques used in ML for computational chemistry, including gradient-based methods (e.g., SGD and Adam), probabilistic approaches (e.g., Monte Carlo sampling and Bayesian optimization), and spectral methods. We classify optimization targets into model parameter optimization, hyperparameter selection, and molecular optimization
and analyze their application across supervised, unsupervised, and reinforcement learning frameworks. Additionally, we examine key challenges such as data scarcity, limited generalization, and computational cost, outlining how mathematical strategies like active learning, meta-learning, and hybrid physics-informed models can address these issues. By bridging optimization methodology with domain-specific challenges, this review highlights how tailored optimization strategies enhance the accuracy, efficiency, and scalability of ML models in computational chemistry
Nitro derivatives of N-phenylsuccinimide: a microwave-assisted synthetic approach and in silico evaluation of the pharmalogical potential
No full textPrimena mikrotalasne tehnike u sintezi organskih molekula predstavlja efikasnu i održivu alternativu
klasičnim metodama, jer omogućava kraće vreme reakcije, veći prinos i bolju selektivnost.
Usaglašenost sa principima zelene hemije čini ovu tehniku posebno pogodnom za brzu i efikasnu
sintezu različitih organskih jedinjenja. N-fenilsukcinimid i njegovi derivati privlače posebnu pažnju
zbog širokog spektra bioloških aktivnosti, uključujući antikonvulzivno, antiinflamatorno i antimikrobno
dejstvo. Strukturna raznovrsnost ovih jedinjenja čini ih perspektivnim u medicinskoj hemiji, naročito
za razvoj agenasa koji imaju uticaj na centralni nervni sistem. Dalja funkcionalizacija može
doprineti sintezi jedinjenja sa poboljšanim farmakološkim svojstvima. Polazeći od sukcinske kiseline
i odgovarajućih o- i/ili p-nitro supstituisanih anilina, sintetisani su derivati N-fenilsukcinimida primenom
mikrotalasnog zračenja kao brze i efikasne metode. Struktura sintetisanih jedinjenja potvrđena
je primenom različitih spektroskopskih metoda. Njihov farmakološki potencijal procenjen je
korišćenjem različitih empirijskih pravila i savremenih in silico metoda. Dobijeni podaci doprinose
razvoju sintetskih strategija zasnovanih na mikrotalasnoj tehnologiji, usmerenih ka pronalaženju novih
organskih molekula sa potencijalnom biološkom aktivnošću.Microwave-assisted synthesis has emerged as a powerful and sustainable alternative to conventional
methods, offering reduced reaction times, improved yields, and enhanced selectivity. Its
alignment with green chemistry principles makes it particularly attractive for the rapid and efficient
preparation of various organic compounds. N-Phenylsuccinimide and its derivatives have attracted considerable attention due to their diverse biological activities, including anticonvulsant, anti-inflammatory,
and antimicrobial effects. Their structural versatility makes them promising scaffolds in
medicinal chemistry, particularly for the development of central nervous system active agents. Continued
research into their functionalization may yield compounds with enhanced pharmacological
profiles. Using succinic acid and corresponding o- and/or p-nitro substituted anilines as starting
materials, N-phenylsuccinimide derivatives were efficiently synthesized under microwave irradiation.
The obtained compounds were characterized by different spectroscopic methods. The pharmacological
potential of these compounds was assessed using a combination of empirical rules and in silico
methods. The obtained data contribute to the development of microwave-assisted synthetic strategies
aimed at discovering new organic molecules with potential biological activity