8639 research outputs found
Sort by
Comparative investigation of selenium-enriched Pleurotus ostreatus and Ganoderma lucidum as natural sources of selenium supplementation
No full textSelenium (Se) is an essential trace element for human health, but its nutritional supply is insufficient in large parts of the world. Mushrooms can be enriched in selenium and can serve as alternative and natural source of selenium supplementation. In the present study, two common mushroom species (Pleurotus ostreatus and Ganoderma lucidum), were enriched with two selenium compounds (selenite and selenate) to test their suitability as natural sources of selenium supplementation. Sharp differences in the the metabolic patterns of the fortified selenium were observed. Selenium was effectively metabolized in P. ostreatus but remained in inorganic form in G. lucidum. However, mushrooms extracts were effective in enhancing selenoprotein expression in cell lines. The present study highlights the importance of employing selenium speciation analysis with an element-selective technique to examine the metabolic products following mushroom fortification for nutritional purposes due to the different toxicological profile and bioavailability of different selenium biotransformation products
Ru–Co alloy coatings electrodeposited on a MAX phase substrate as efficient catalysts for the hydrogen evolution reaction
No full textThis study investigates the structure, electrochemical behavior and hydrogen evolution reaction (HER) performance of electrodeposited Ru–Co alloy coatings. The alloys were prepared from a 0.75 M Co2+ + 0.025 M Ru3+ solution at various potentials ranging from −0.5 to −1.2 V vs. SCE. Results reveal that the Ru and Co deposition processes are interdependent. The deposition of nobler Ru from the mixed metal solution reaches pure diffusion control already at −0.7 V compared to −1.0 V from a single Ru bath. On the other hand, Co deposition is significantly facilitated in the presence of Ru in the solution. Consequently, as the deposition potential changes from −0.6 to −1.0 V, Ru–Co solid solution coatings characterized by a distinct globular morphology are formed, with their Co content increasing from 22.1/7.4 to 70.2/86.1 wt% for the Cu/Ti2AlC MAX phase substrate applied. The alloy catalysts are found to show much better HER activity and stability in alkaline than in acidic solutions. The best Ru–Co@Ti2AlC sample, electrodeposited at −0.6 V, requires an overpotential of only −95 mV to deliver a current density of −100 mA cm−2 in 1 M KOH, thus outperforming most Ru–Co-based HER electrocatalysts reported to date
Performance prediction and regulation of a tubular solid oxide fuel cell and hydrophilic modified tubular still hybrid system for electricity and freshwater cogeneration
No full textTubular solid oxide fuel cells (TSOFCs) are a promising technology for electricity generation; however, they also generate high-temperature waste heat, leading to reduced efficiency and energy wastage. To address this challenge and unlock the full potential, a novel geometry-matching hybrid system incorporating methane reforming TSOFC and hydrophilic modified tubular still (HMTS) is proposed and modelled. Considering various irreversible losses, vital performance indicators including power output, energy efficiency and exergy efficiency are firstly derived, through which comprehensive thermodynamic performance features of the TSOFC/HMTS hybrid system are predicted. The proposed system design demonstrates a significant advantage by achieving a maximum output power density that is 99.7 % higher and a corresponding energy efficiency that is 57.3 % higher compared to the standalone TSOFC. Extensive parametric analyses reveal that raising the operating temperature or stream/carbon ratio positively enhances the system's performance. Conversely, increasing electrode tortuosity, electrolyte thickness, wind velocity, or tubular shell diameter negatively degrades the system's performance. In addition, the anode thickness is an optimizable parameter. Local sensitivity analyses identify that the operation temperature and electrode tortuosity are, respectively, the most and least sensitive parameters for performance regulation. The findings make a significant step forward in the field of sustainable and innovative energy solutions
Sustainable Removal of Cr(VI) from Wastewater Using Green Composites of Zero-Valent Iron and Natural Clays
No full textComposites for efficient removal of hexavalent chromium Cr(VI) from industrial wastewater were obtained by deposition of nano-zero-valent iron (nZVI), synthesized by environmentally friendly synthesis using oak leaf extract, on inexpensive, natural, readily available and cheap natural raw materials, sepiolite (SEP) or kaolinite/illite (KUb) clay, as support. nZVI particles were deposited from the FeCl3 solution of different concentrations, with the same volume ratio extract/FeCl3 solution (3:1), and with different masses of SEP or KUb. Physico–chemical characterization (SEM/EDS, FTIR, BET, determination of point of zero charge) of the composites and nZVI was performed. The results of SEM and BET analyses suggested more homogeneous deposition of nZVI onto SEP than onto KUb, which ensures greater availability of the nZVI surface for Cr(VI) anions. Therefore, the higher Cr(VI) removal at all investigated initial pH values (pHi) of the solution (3, 4 and 5) was achieved with the SEP composites. The adsorption results indicated that the elimination of Cr(VI) was achieved via the combined effect of reduction and adsorption. The removal of total chromium at pHi = 3 was approximately the same as that of Cr(VI) removal for the KUb composites, but lower for the SEP composites, indicating lower removal of Cr(III) compared to the reduced Cr(VI). The SEP/nZVI composite with the highest removal efficiency was applied for Cr(VI) removal from real wastewater at pHi = 3 and pHi = 5. The results demonstrated the high Cr(VI) removal capacity, validated the assumption that a good dispersion of nZVI particles is beneficial for Cr(VI) removal and showed that the produced green composites can be efficient materials for the removal of Cr(VI) from wastewater
Green Polysaccharide Hydrogels for Wastewater Remediation
No full textIn light of environmental protection and water remediation as important topics nowadays, research in the field of polysaccharide hydrogels as wastewater pollutant sorbents attracts the attention of scientists. Polysaccharides, such as sodium carboxymethylcellulose (CMC) and sodium alginate (SA) are sustainable, biocompatible, biodegradable, non-toxic, and low-cost materials. Despite excellent assets, these polysaccharides have some drawbacks, such as the brittleness of SA hydrogels and the inability of neat CMC to maintain a stable structure in an aqueous environment. An effective method to overcome these drawbacks and improve the performance and physical properties of CMC/SA hydrogels is the mixing of polysaccharides and dual crosslinking1. The topic of this work is the synthesis of green and sustainable CMC/SA hydrogels and their sorption of pollutants from wastewater. Tannic acid together with ZnCl2 is used in a two-step crosslinking process for green CMC/SA hydrogel production. The influence of the CMC/SA ratio and additional crosslinking on hydrogel properties was investigated. Moreover, the CMC/SA hydrogel sorption of various dyes in multiple-dye systems was studied. The eco-friendly green CMC/SA hydrogels obtained by two-step synthesis have excellent sorption properties of the toxic anionic dyes regardless of the presence of other pollutants in the wastewater
Biothermodynamic analysis of the Dengue virus: Empirical formulas, biosynthesis reactions and thermodynamic properties of antigen-receptor binding and biosynthesis
No full textAfter the experience with the COVID-19 pandemic, WHO has issued a warning about the possible causes of future pandemics. One such causative agent is the Dengue virus. Until now, we have had information mostly on biological properties of the Dengue virus and very little information about its chemical and thermodynamic properties. To be better prepared for a potential Dengue pandemic, the goal of this paper is to chemically and thermodynamically characterize the Dengue virus, as well as to describe the biophysical basis of the virus-host interactions of the Dengue virus. To that goal, the empirical formula was determined, as well as biosynthesis reactions and thermodynamic properties of antigen-receptor binding and thermodynamic properties of biosynthesis and multiplication of the Dengue virus. A model was developed of virus-host interactions between the Dengue virus and its host tissues, based on nonequilibrium thermodynamics
Composites Based on Biodegradable Aliphatic Polyesters and Copper Enriched Zeolites with Antibacterial Activity
No full textAliphatic biodegradable polyesters poly(ε-caprolactone), PCL and
poly(lactic acid), PLA with their favorable mechanical and thermal properties
could be environmentally friendly replacement for bio-resistant thermoplastics
currently used for disposable packaging. It would be of interest for packaging
purposes to introduce some “active” properties, such as antibacterial activity, into
these materials. This can be achieved by the addition of different fillers, with
further benefit of increasing mechanical properties of matrix. Special interest is in
the use of fillers of natural origin, such as clays, sepiolites or zeolites. In this study
composites of PLA and PCL with copper-enriched natural zeolite (CuZ) were
prepared, with the aim to obtain materials with antibacterial activity. Thermal and
mechanical properties of composites were characterized by DSC, TG and DMA.
Reinforcing effect of CuZ was achieved, while thermal properties were not
decreased. Antibacterial activity of all composites was investigated toward two
bacterial strains, Echerichia coli DSM 498 and Staphylococcus aureus ATCC
25923. Composites showed good antibacterial activity toward S. aureus. From the
analysis of the amount of released copper it was concluded that antibacterial
activity was achieved not only through the action of the released metal ion, but also
by direct contact with composite. Biodegradability of composites was followed in
accelerated hydrolysis tests in alkaline medium, through evaluation of weight loss
and decrease in thickness of exposed composite films. It was shown that CuZ
presence and its amount in composite had an accelerating effect on degradation
Influence of clove essential oil on the growth of fermentative yeasts
No full textCloves are the aromatic, dried flower buds of the tree Syzygium aromaticum, which are often used as a spice to flavor fermented beverages and as a preservative against oxidative rancidity in food rich in fat. In addition, cloves are traditionally used as a natural remedy to treat various ailments such as gastric irritability, flatulence colic, chronic diarrhea and other gastrointestinal disorders. The biological activities of this spice, such as antioxidant, antimicrobial, anti-inflammatory, anti-carcinogenic, analgesic, insecticidal, and many others, are due to a mixture of different compounds, among which the three main active compounds eugenol, eugenol acetate and β-caryophyllene are stand out. The aim of this study was to evaluate the influence of commercial clove essential oil on the growth of fermentative yeasts from Saccharomyces and non-Saccharomyces groups and to assess its use in the production of fermented beverages such as wine in place of sulfites as a preservative. The antifungal efficacy was investigated by agar well diffusion, agar dilution and broth macrodilution methods, and the results obtained in this study were compared. According to the results of the antifungal activity of clove essential oil, the most sensitive yeast was Kloeckera ssp. from the non-Saccharomyces group with a minimum inhibitory concentration (MIC) of 0.02% (v/v) and a minimum fungicidal concentration (MFC) of 0.1% (v/v). From the Saccharomyces group, the lowest value for MIC and MFC was determined for Saccharomyces boulardii (MIC 0.055% (v/v), MFC 0.08% (v/v), while the other species from this group were slightly more resistant in the following order Saccharomyces cerevisiae>Saccharomyces cerevisiae var. diastaticus>Saccharomyces pastorianus> Saccharomyces cerevisiae var. ellipsoideus. Due to its antioxidant and antimicrobial properties, clove essential oil has the potential to be used as a substitute for sulfites in controlling the growth of surface yeast populations on fruit during spontaneous fermentation and the production of fermented beverages such as wine
Electrochemically synthesized biocomposite poly(vinyl alcohol)/chitosan-based coatings for medical applications
No full textOsteoarticular implants are designed to facilitate
full recovery of lost function and ensure effective
fixation of the implant. However, challenges
may arise, resulting in implant failure, primarily
attributed to infections at the implantation site
and aseptic loosening. Thus, the surface of an
implant must be altered to simultaneously offer
osteoinductive and antibacterial properties.
Synthetic hydroxyapatite (HAP) is frequently
employed to modify metallic implant surfaces
or serve as a bone filler material. To enhance
its biocompatibility, HAP-based polymer composites
were developed. Among most popular
synthetic polymers, poly(vinyl alcohol) (PVA), is
widely used because of its similar structure to
the native extracellular matrix, along with chitosan
(CS), a natural cationic polysaccharide, that
shows biocompatibility, biodegradability and
antimicrobial action, and could act as a carrier
of antibacterial agents. The antibiotic of choice
was Gentamicin (Gent), a water-soluble aminoglycoside,
with very potent antibacterial activity
for the treatment of wide range of infections,
caused by Gram-negative and Gram-positive
bacteria. The original approach of the presented
research is the single-step electrophoretic deposition
(EPD) on Ti plates of thus prepared biocomposite
that would allow for on-site release of the
drug. Obtained hydroxyapatite/chitosan/poly(vinyl
alcohol/gentamicin (HAP/PVA/CS/Gent) biocomposite
coating exhibited strong antibacterial
effect against E. coli and S. aureus. Gentamicin release
study indicated “burst” release in the first 48
h, with ~ 30% of total gentamicin released from
the HAP/PVA/CS/Gent coating which is beneficial
for the blockage of biofilm formation, followed
by slow and steady release in the later period. Cytotoxic
effect of HAP/PVA/CS/Gent coating was
not pronounced in investigated MRC-5 and L929
cell lines. Also, in MRC-5 fibroblast cells, alkaline
phosphatase levels doubled when in contact
with HAP/PVA/CS/Gent, indicating good osteogenic
properties. The overall construct on the
substrate in such a form would be well-advanced
arrangement for future medical device improvement
of skeletal implants
Cavitation resistance of chromium-nickel tool steels obtained by hot isostatic pressing
No full textThe paper presents the results of research into the cavitation resistance of tool steels obtained by
the process of hot isostatic pressing. The compositions of the powder mixture for pressing, as
well as the parameters of the HIP process, primarily temperature and pressure, were investigated.
The pressing temperature ranged from 1000-1150°C, the pressing pressure was 100 to 300 MPa,
and time was 3-4 hours. These steels are used for the production of equipment parts in
metallurgy, mechanical engineering and mining. The cavitation resistance of three series of steels
with different nickel and chromium content was tested using the ultrasonic vibration method with
a stationary sample according to the ASTM G32 standard. The reduction of the nickel content in
the composition of the steel has a favorable effect on the development of the martensitic
transformation and the increase in the hardness of the steel. The presence of chromium improves
the mechanical properties and chemical stability of steel. The obtained cavitation speeds below
0,11mg/min indicate a good cavitation resistance of the samples and the possibility of application
in conditions of exploitation where the presence of cavitation, corrosion and wear is expected