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Computational fluid dynamics implementation and optimization of electrohydrodynamics' two-phase leaky dielectric model
No full textThe leaky dielectric model from electrohydrodynamics (EHD) was incorporated into the computational fluid dynamics (CFD) software called OpenFOAM®. Based on the used literature, it can be said that this implementation of the mentioned model is the most complete. Three sets of two-phase simulations were done. The first set was one-dimensional. In the second set, a stationary drop surrounded by another fluid deformed under the influence of an electric field. The deformations were both positive and negative. These two sets were used in order to optimize the implementation. Different expressions were tested. A new way for calculating the electrostrictive force when there are two fluids is presented. It resolves the previously encountered issue concerning drop deformations. Recommendations for expressions used in OpenFOAM® for all three electric forces are given. Finally, a settling drop within an electric field was simulated. The final set of simulations more obviously shows the usability of this implementation in practice. Conclusions that are presented in this paper can be transferred to other EHD models and their implementations
Reduction of fines in recycled paper white water via cellulase enzymes
No full textDue to the high wastepaper recyclability and water-loop system closure, packaging paper mills struggle with increased fines, causing runnability issues. Cellulase enzymes are a preferred treatment choice for the improvement of the pulp refining in stock preparation area but are not widely used or easy to introduce in the production process. Different cellulase enzymes were tested, and those with the highest activity were introduced to the white-water (WW) samples with the aim to reduce fines content as potentially new enzyme applications on the paper machine. The first portion of the study involved the development of an experiment model to find and confirm the optimal enzyme process parameters (40 °C, pH 5.7, reaction time 3 h, and 0.18% v/v enzyme addition) for laboratory made white-water. The second portion of the study included turbidity, colloidal charge, flow cytometry (FCM), and chemical oxygen demand (COD) analysis on industrial and laboratory made white-water samples at optimized process parameters. Obtained results corresponded to reduced fines content in white-water samples, which justified commercial usage of cellulase enzymes on recycled paper machine short loop and potentially increased machine runnability without negative influence on wastewater treatment plant
Microwave extraction of modulators of microbial growth from medicinal plant waste [Predavanje po pozivu štampano u izvodu]
No full textMicrowave-assisted extraction (MAE) has been efficaciously applied for the extraction of
bioactive compounds (such as polyphenols) from various plants. When compared to traditional
extraction methods, MAE reduces both extraction time and solvent usage while enhancing the
yield and quality of the resulting extracts. Ethanol and water mixtures are usually used in the
preparation of extracts in the MAE, ensuring that the extracts are safe for human consumption.
The addition of iodine during MAE, as a catalyst, enables the production of extracts with enhanced biological activity compared to extracts without iodine. The catalytic properties of iodine are
exhibited through its ability to form halogen intermolecular bonds with electron-rich atoms within
various functional groups, which facilitates nucleophilic attack, enabling the synthesis of various
compounds. Waste generated from the processing of medicinal plants can be used as a starting
material for extract preparation. Although this waste is not suitable for infusion preparation due to
its fine particle size, which can easily pass through filter bags, the small particle size increases the
contact area between the solvent and the sample. This facilitates deeper microwave penetration
into the sample, thus improving the extraction efficiency of polyphenols. Polyphenols are
bioactive compounds present in medicinal plants, vegetables, fruits, and spices. They exhibit
a diverse range of biological activities, such as antioxidant, antimicrobial, anticancer, and antiinflammatory effects. Regular consumption of polyphenols has been related to the prevention of
cardiovascular diseases, certain types of cancer, and metabolic disorders. Polyphenols may exert
a doubly positive effect - simultaneous inhibition of pathogens, while promoting the growth of
beneficial bacteria and yeast. Probiotic bacteria such as Lactobacillus and Bifidobacterium, and
probiotic yeast Saccharomyces boulardii show increased growth in the presence of polyphenols,
while the polyphenols often exhibit antimicrobial properties against various pathogenic bacteria
and yeast. Polyphenols support microbial growth by providing carbon sources, acting as electronic
acceptors or generating proton motive forces during metabolization. Their antimicrobial effects
can be attributed to several mechanisms, including disrupting the microbial cell membrane and
cell wall, inhibiting enzyme activity and nucleic acid synthesis, preventing biofilm formation, and
chelating essential metals.Predavanje po poziv
Analiza površinske strukture, termičkih svojstava i studija bubrenja poli(vinilpirolidon-ko-vinil acetat) kopolimera
No full textThe goal of this study was to synthesize chemically cross-linked copolymeric hydrogels based on vinylpyrrolidone monomer and vinyl acetate comonomer, with
varying crosslinker content (ethanediol dimethacrylate) using the free radical polymerization mechanism, as well as to characterize them. Surface morphology
was conducted using scanning electron microscopy (SEM). SEM micrographs
reveal macroporous, amorphous-crystalline crosslinked structures of p(VP/VA)
copolymers with an average pore diameter in the swollen state ranging approximately from 50 μm to 100 μm. DSC method was applied to detect the glass transition and melting temperatures of the p(VP/VA) copolymers. The obtained data
indicates good comonomers miscibility within the homogenous polymer network
and enhanced thermal stability (up to about 130 °C), which increases with increasing crosslinking density. A swelling study was conducted to assess the copolymer
behaviour in solutions of different pH values. The highest equilibrium swelling ratio
value (αe
=123.42) was achieved for the sample with 2.0 mol% of crosslinker in
alkaline solution with a pH value of 8. The lowest swelling capacity (αe
=14.42)
was observed for the sample with 3.0 mol% of crosslinker in an acidic medium
(pH=2.0). These thermosensitive hydrogels showed also pH sensitivity.Cilj ovog rada je sinteza hemijski umreženih kopolimernih hidrogelova na bazi
monomera vinilpirolidona i komonomera vinil acetata, sa promenljivim sadržajem
umreživača (etandiol dimetakrilata) mehanizmom slobodno-radikalne polimerizacije, kao i njihova karakterizacija. Morfologija površine je sprovedena korišćenjem
skenirajuće elektronske mikroskopije (SEM). SEM mikrografije otkrivaju makroporozne, amorfno-kristalne umrežene strukture p(VP/VA) hidrogelova sa prosečnim
prečnikom pora u nabubrenom stanju u rasponu od približno 50-100 mm. DSC
metoda je primenjena za detekciju temperature staklastog prelaza i temperature topljenja p(VP/VA) hidrogelova. Dobijeni podaci ukazuju na dobru mešljivost komonomera unutar homogene polimerne mreže i poboljšanu termičku stabilnost (do oko
130 °C) koja se povećava sa povećanjem gustine umreženja. Studija bubrenja je
sprovedena da bi se procenilo ponašanje kopolimera u rastvorima različitih pH vrednosti. Najveća vrednost ravnotežnog stepena bubrenja (αe
=123,42) postignuta je
za uzorak sa 2,0 mol% umreživača u alkalnom rastvoru pH vrednosti 8. Najmanji kapacitet bubrenja (αe
=14,42) je zabeležen za uzorak sa 3,0 mol% umreživača u kiseloj
sredini (pH=2,0). Ovi termoosetljivi hidrogelovi su takođe pokazali pH osetljivost
Solar-driven thermo-photocatalytic CO2 methanation over a structured RuO2:TiO2/SBA-15 nanocomposite at low temperature
No full textA new hybrid catalyst composed of mesostructured silica SBA-15 functionalized with TiO2 and further loaded with RuO2 was developed to efficiently promote thermo-photocatalytic CO2 hydrogenation into methane at low temperatures. The catalytic activity was assessed with respect to TiO2:RuO2 loading, catalyst dosage, illumination source (polychromatic sunlight and monochromatic LEDs) and power, [H2]:[CO2] molar ratio, temperature, and catalyst reusability. The best methanation yields were attained for the RuO2(6.4%):TiO2(16.9%)/SBA-15 nanocomposite at 150 ºC, under simulated sunlight (0.21 W) and stoichiometric [H2]:[CO2] molar ratio, reaching: a specific CH4 production rate of 13.6 mmol gcat-1 h-1; 99.8 % selectivity; 96.8 % CO2 conversion (110-min; 40 mL); and apparent photonic efficiency/quantum yield of 39.5 %/42.1 %. Considering only the active RuO2:TiO2 photocatalyst mass (23.3 %), the CH4 production rate increased to 58.6 mmol gactive_cat-1 h-1. Besides, this highly-active photocatalyst featured excellent UV-Vis-IR light absorbance, high surface area, and stability for reuse when moist gas was removed between cycles
Synthesis of hydrogels based on poly (methacryl acid) using an environmental Friendly initiator based on hydrogen Peroxide, peroxidase isolated from waste Material and vitamin c
No full textPredmetnim pronalaskom postignuto je da se hidrogelovi na bazi poli(metakrilne kiseline) dobiju jednostavnim postupkom koji je finansijski isplativ i u skladu sa principima cirkularne ekonomije. Takođe, predmetnim pronalaskom je postignuto da se ovi hidrogelovi dobiju korišćenjem inicijatora na bazi male količine vodonik-peroksida, peroksidaze izolovane iz kore krompira ili ljuspica soje i vitamina C i da se sinteza izvede na sobnoj temperaturi i u prisustvu kiseonika. Predmetni pronalazak obezbeđuje i da hidrogelovi na bazi poli(metakrilne kiseline) dobijeni ovom metodom imaju optimalna svojstva. Takođe, dobijeni hidrogelovi na bazi poli(metakrilne kiseline) mogu da se koriste za ciljanu dostavu, produženo i kontrolisano otpuštanje aniinflamatornih lekova.Broj prijave: P-2023/039
The influence of design conditions on the failure of the universal cross joint (ucj) of the cardan coupling
No full textIn the system of power transmission from the driving to the operating machine, cardan couplings are
components of vital importance. Due to the ability to transmit power over long distances, as well as insensitivity to the
coaxiality of the connecting shafts, they have found wide application in all branches of mechanical engineering. In the
plant for the production of profiled semi-finished steel products, a volumetric failure of the sleeve on the universal cross
joint (UCJ) of the cardan coupling occured. This type of failure occurs very rarely with cardan couplings. In order to
understand the real reason for the failure of the sleeve, analytical and numerical models were formed, and tests of
materials and fracture surfaces were carried out. The influence of the line load distribution at the mating surfaces and
the geometric stress concentration on the load capacity of the UCJ was analyzed using the developed models. With the
increase in the unevenness of the line load distribution, the influence of tangential stresses on the stress state in the
critical cross-section significantly increases. It is concluded that the simultaneous influence of the uneven line load
distribution and the geometric stress concentration led to the failure of the UCJ sleeve
Spent Coffee Grounds, Plant Growth Promoting Bacteria, and Medicinal Plant Waste: The Biofertilizing Effect of High-Value Compost
No full textComposting of mixed medicinal plant waste was performed with the addition of mixture of plant growth promoting bacteria (PGPB), including Streptomyces sp., Paenybacillus sp., Bacillus sp., and Hymenobacter sp., and portions of spent coffee grounds (SCG). To assess the maturity and quality parameters of the compost, chemical and biological parameters (C/N ratio, loss of organic matter, CO2 production, dehydrogenase activity (DHA), and phytotoxicity) were evaluated during the three months of the composting process. The results revealed that the control sample (without the addition of SCG and PGPB) had evidently lower values of DHA during the entire monitoring period in comparison to other samples, indicating lower microbial activity in the compost mixture. Also, according to the released CO2, the composting process was accelerated in all samples where the SCG and PGPB were added, enabling a reduction in time needed for mixed plant waste to decompose. The germination index (GI) of the tested seeds indicated that the produced compost was acceptable and safe, with regard to all of the evaluated samples. However, at the end of the process the samples contained SCG and PGPB, which caused an increase of more than 50% of the GI in comparison to the control sample, expressing a high phyto-stimulant effect and improving the biofertilization impact.Supplementary information: [https://technorep.tmf.bg.ac.rs/handle/123456789/7345
GC-MS/MS and LC-MS/MS analysis followed by risk ranking of mepiquat and pyrethroids in coffee
No full textPesticides used in coffee cultivation may remain behind and pose a risk to humans even after various processing stages of coffee beans (washing, drying, roasting, and grinding). In addition to pesticides applied to battle pests and diseases, mepiquat formation occurs during roasting. A comprehensive LC-MS/MS and GC-MS/MS multi-residue screening approach to determine pesticides in coffee was used in this study. Residues were extracted using the QuEChERS method and analyzed using multiple reaction monitoring (MRM) mass spectrometry after chromatographic separations. Good linearity (r2˃0.9919), recovery (80.2–118%), and RSD (≤19%) were obtained for the procedure including sample preparation and both instrumental techniques. Nine residues were identified as commonly present in coffee samples collected from supermarkets in Serbia. The human intake risk of pesticides was categorized and prioritized using the matrix ranking scheme. Also, health risk assessment was conducted by calculating acute and chronic hazard indices. Multi-residues were present in 79.2% of samples, whereas mepiquat chloride (88.9%) and permethrin (81.9%) were the most detected residues. Risk ranking classified mepiquat chloride, permethrin, and methiocarb sulfone in a high-risk group. On the other hand, the human health risk assessment indicated no risks in the short- and long-term and no cumulative chronic risk
Nanotechnology in Delivery and Targeting of Phytochemicals for Lifestyle Diseases
No full textIn many cases, conventional therapeutics are not able to cure diseases in a proper and safe manner. Conversely, plants and their derivatives have been successfully used for the treatment of numerous diseases and disorders for centuries and have proven themselves as efficient, inexpensive, environmentally friendly, faster, and less toxic. However, their use is sometimes connected to some issues, mainly due to inefficient systemic delivery and bioavailability, which prevent to translate their promising in vitro and in vivo effects into clinical use. During the past decade, nanotechnology has made big progress in developing different nanocarriers for drug delivery formulations. In the case of phytopharmaceuticals their encapsulation in nanoparticles can help in improving drug solubility, physical and chemical stability, pharmacological activity, reducing its toxicity and side effects, and providing targeted and sustained delivery which all leads to better bioavailability. The current review highlights the main problems connected to the delivery of phytopharmaceuticals, the main properties of different types of plant drugs, and gives a critical review of properties and limitations connected to the application of numerous lipid, polymer, and inorganic nanoparticles as phytodrug carriers. It also provides information about up-to-date investigated combinations of phytopharmaceuticals and nanocarriers