PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Švábenská, Eva; Roupcová, Pavla; Havlíček, Lubomír; Schneeweiss, Oldřich
2024 - anglický Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are Fe-Ni-based \nalloys, in particular, the Fe50Ni50 L10 phase (tetrataenite), which has a great perspective for producing hard \nmagnetic materials. Our study explores a promising method for preparing nanoparticles of Fe-Ni alloy from an \niron-nickel oxalate precursor. The coprecipitation method was employed to prepare oxalate precursors, \nfollowed by controlled thermal decomposition in a reducing hydrogen atmosphere. The morphology and \nproperties of the resulting particles were analysed using scanning electron microscopy (SEM) coupled with \nenergy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and \nmagnetic measurements.\nThe SEM analysis revealed that the particles have approximately cube-shaped unit cell morphology with a\nsize in a range of 1 - 2 μm. Upon annealing, the samples contain multiple phases with varying Fe-Ni content.\nMagnetic measurements confirmed the formation of magnetically suitable Fe-Ni phases in the samples after \nannealing. Mössbauer spectroscopy emerged as a highly effective method for characterizing individual phases \nof the Fe-Ni system. Klíčová slova: Magnetic materials; thermal decomposition; Mössbauer spectroscopy Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR. PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS

Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are ...

Švábenská, Eva; Roupcová, Pavla; Havlíček, Lubomír; Schneeweiss, Oldřich
Ústav fyziky materiálů, 2024

Electrochemistry of Acetaminophen
Mikysek, T.; Ludvík, Jiří
2024 - anglický The contribution is focused on electrochemical oxidation of acetaminophen mainly in non-aqueous media. The influence of various organic solvents as well as the pH effect is described herein. The redox properties of acetaminophen were studied by means of cyclic voltammetry, and rotating-disk voltammetry. We found that the protonation/deprotonation of acetaminophen acts as a ratedetermining step, where the stability of phenoxy radical intermediate plays an important role. Klíčová slova: acetaminophen; phenacetine; voltammetry Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd. Electrochemistry of Acetaminophen

The contribution is focused on electrochemical oxidation of acetaminophen mainly in non-aqueous media. The influence of various organic solvents as well as the pH effect is described herein. The redox ...

Mikysek, T.; Ludvík, Jiří
Ústav fyzikální chemie J. Heyrovského, 2024

Temoporfin-conjugated upconversion nanoparticles for NIR-induced photodynamic therapy of pancreatic cancer
Shapoval, Oleksandr; Větvička, D.; Kabešová, M.; Engstová, Hana; Horák, Daniel
2024 - anglický Photodynamic therapy (PDT), a clinically approved cancer treatment strategy, has the potential to cure pancreatic cancer with minimal side effects. PDT primarily uses visible wavelengths to directly activate hydrophobic photosensitizers, which may be insufficient for deep-seated cancer cells in clinical practice due to poor penetration. Upconversion nanoparticles (UCNPs) serve as an indirect excitation source to activate photosensitizers (PSs) in the NIR region, overcoming the limitations of molecular PSs such as hydrophobicity, non-specificity, and excitation in the UV/Vis region. Here, monodisperse upconversion NaYF4:Yb3+, Er3+, Fe2+ nanoparticles (UCNPs) have been surface-engineered with poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) and temoporfin (mTHPC), a clinically used PDT prodrug, for near-infrared (NIR) light-triggered PDT of pancreatic cancer. The incorporation of Fe2+ ions into the particles increased the fluorescence intensity in the red region matching the activation wavelength of mTHPC. Covalent binding of mTHPC to the surface of UCNP@PMVEMA particles provided colloidally stable conjugates enabling generation of singlet oxygen. In vitro cytotoxicity and photodynamic activity of the particles were evaluated using INS-1E rat insulinoma and Capan-2 and PANC-01 human pancreatic adenocarcinoma cell lines. The PDT efficacy of UCNP@PMVEMA-mTHPC conjugates after irradiation with 980 nm NIR light was tested in vivo in a pilot study on Capan-2 human pancreatic adenocarcinoma growing subcutaneously in athymic nude mice. The intratumoral administration of the nanoconjugates significantly hindered tumor growth and demonstrated promising PDT efficacy against human pancreatic cancer. Klíčová slova: photodynamic therapy; temoporfin; upconversion nanoparticles Plné texty jsou dostupné v digitálním repozitáři Akademie Věd. Temoporfin-conjugated upconversion nanoparticles for NIR-induced photodynamic therapy of pancreatic cancer

Photodynamic therapy (PDT), a clinically approved cancer treatment strategy, has the potential to cure pancreatic cancer with minimal side effects. PDT primarily uses visible wavelengths to directly ...

Shapoval, Oleksandr; Větvička, D.; Kabešová, M.; Engstová, Hana; Horák, Daniel
Ústav makromolekulární chemie, 2024

A New Approach to Determining the Drug Guaifenesin Using Voltammetric and Flow Injection Analysis
Kelíšková, P.; Matvieiev, O.; Sokolová, Romana; Janíková, L.; Behúl, M.; Šelešovská, R.
2024 - anglický This study presents a new method for detecting guaifenesin (GFE) in pharmaceutical samples. We employed screen-printed sensors with a boron-doped diamond electrode (BDDE) to develop and validate both voltammetric and flow amperometric methods. These approaches were effectively used to analyze model solutions, pharmaceutical preparations, and serum samples spiked with GFE, producing accurate results comparable to those obtained with HPLC/DAD analysis. The developed methods provide straightforward, sensitive, and selective means for determining GFE in various sample matrices, underscoring the potential of SP/BDDE in electrochemical analysis. Klíčová slova: guaifenesin; screen-printed sensor; boron-doped diamond electrode Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd. A New Approach to Determining the Drug Guaifenesin Using Voltammetric and Flow Injection Analysis

This study presents a new method for detecting guaifenesin (GFE) in pharmaceutical samples. We employed screen-printed sensors with a boron-doped diamond electrode (BDDE) to develop and validate both ...

Kelíšková, P.; Matvieiev, O.; Sokolová, Romana; Janíková, L.; Behúl, M.; Šelešovská, R.
Ústav fyzikální chemie J. Heyrovského, 2024

Optimization of Parameters Used in the Application of Elimination Voltammetry with Linear Scan
Navrátil, Tomáš; Trnková, L.; Hrdlička, Vojtěch; Li, X.
2024 - anglický Elimination Voltammetry with Linear Scan (EVLS) is a well-established mathematical method that aids in understanding an analyzed electrochemical system. In almost 30 years since its derivation, it has become a “black-box” technique that is applied automatically (in most cases due to its incorporation into a voltammetric software) without thinking about its fundamentals. However, the choice of optimum parameters under which DC voltammetric data (from which elimination curves are calculated) is crucial. This contribution deals with revealing the optimum ratio of applied scan rates and their absolute values (i.e., times of recording) in dependence on the character of the investigated system (diffusion-controlled process, adsorption-controlled process, etc.). Klíčová slova: elimination voltammetry with linear scan; optimization; adsorption Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd. Optimization of Parameters Used in the Application of Elimination Voltammetry with Linear Scan

Elimination Voltammetry with Linear Scan (EVLS) is a well-established mathematical method that aids in understanding an analyzed electrochemical system. In almost 30 years since its derivation, it has ...

Navrátil, Tomáš; Trnková, L.; Hrdlička, Vojtěch; Li, X.
Ústav fyzikální chemie J. Heyrovského, 2024

Zoologické dny Brno 2023: sborník abstraktů z konference 9.-10. února 2023
Bryja, Josef; Horsák, M.; Horsáková, V.
2023 - český Klíčová slova: zoology; conference Dokument je dostupný na externích webových stránkách. Zoologické dny Brno 2023: sborník abstraktů z konference 9.-10. února 2023

Bryja, Josef; Horsák, M.; Horsáková, V.
Ústav biologie obratlovců, 2023

Some modifications of the limited-memory variable metric optimization methods
Vlček, Jan; Lukšan, Ladislav
2023 - anglický Several modifications of the limited-memory variable metric (or quasi-Newton) line search methods for large scale unconstrained optimization are investigated. First the block version of the symmetric rank-one (SR1) update formula is derived in a similar way as for the block BFGS update in Vlˇcek and Lukˇsan (Numerical Algorithms 2019). The block SR1 formula is then modified to obtain an update which can reduce the required number of arithmetic operations per iteration. Since it usually violates the corresponding secant conditions, this update is combined with the shifting investigated in Vlˇcek and Lukˇsan (J. Comput. Appl. Math. 2006). Moreover, a new efficient way how to realize the limited-memory shifted BFGS method is proposed. For a class of methods based on the generalized shifted economy BFGS update, global convergence is established. A numerical comparison with the standard L-BFGS and BNS methods is given. Klíčová slova: unconstrained minimization; variable metric methods; limited-memory methods; variationally derived methods; arithmetic operations reduction; global convergence Plné texty jsou dostupné v digitálním repozitáři NUŠL Some modifications of the limited-memory variable metric optimization methods

Several modifications of the limited-memory variable metric (or quasi-Newton) line search methods for large scale unconstrained optimization are investigated. First the block version of the symmetric ...

Vlček, Jan; Lukšan, Ladislav
Ústav informatiky, 2023

Utilization of electrochemically induced cleavage of various sulfonimides
Salvadori, Karolína
2023 - anglický In this work, we describe the unexpected electrochemical cleavage of sulfonimides, providing a direct pathway to corresponding sulfonamides. For this purpose, 16 substances were synthesized and tested, reflecting the influence of different electron effects of -SO2Ph-R substituents, and the impact of the number of nosyl units present in molecules. In the case of octakis-nosylated calixarenes, the electrochemical cleavage via direct potential-controlled electrolysis was compared with conventional organic synthetic procedures. After electrolysis, all prepared sulfonamides were isolated in excellent yields. Klíčová slova: sulfonimides; green chemistry procedures; electrochemisty Plné texty jsou dostupné v digitálním repozitáři NUŠL Utilization of electrochemically induced cleavage of various sulfonimides

In this work, we describe the unexpected electrochemical cleavage of sulfonimides, providing a direct pathway to corresponding sulfonamides. For this purpose, 16 substances were synthesized and ...

Salvadori, Karolína
Ústav chemických procesů, 2023

Green approach for the preparation of biosourced ionic liquids and the study of their thermodynamic properties\n
Souvenir Zafindrajaona, Mahasoa-Salina
2023 - anglický This presentation will address a green approach to the synthesis of ionic liquids qualified as biosourced (monocatenar or bolaform systems) from specific agro-resources, according to several principles of green chemistry. As these solvents could be used to solubilize lignocellulosic biomass and/or extract bioactive compounds (from plant sourcing), the physicochemical characteristics (density, viscosity and heat capacity) of pure ILs or mixtures of IL/water must be determined. Preliminary results concerning this last point will be presented. Klíčová slova: biosourced ionic liquids; lignocellulosic biomass; thermodynamic properties Plné texty jsou dostupné v digitálním repozitáři NUŠL Green approach for the preparation of biosourced ionic liquids and the study of their thermodynamic properties\n

This presentation will address a green approach to the synthesis of ionic liquids qualified as biosourced (monocatenar or bolaform systems) from specific agro-resources, according to several ...

Souvenir Zafindrajaona, Mahasoa-Salina
Ústav chemických procesů, 2023

Cultivation of Limnospira maxima and utilization of its fresh biomass in human nutrition
Vásquez, Claudia
2023 - anglický This work aims to enhance productivity, efficiency and sustainability of L. maxima cultivation as well as to determine the safe microbiological conditions for the nutritional use of fresh spirulina biomass. Various parameters such as light intensity, light spectral composition, temperature, pH, CO2, and culture media composition can be optimized. A series of experiments were performed to find the most suitable configuration to cultivate L. maxima, defined by cyanobacterium productivity and yield as well as other metabolites production such as phycocyanin (C-PC) and carotenoids. Klíčová slova: Limnospira maxima; fresh biomass; human nutrition Plné texty jsou dostupné v digitálním repozitáři NUŠL Cultivation of Limnospira maxima and utilization of its fresh biomass in human nutrition

This work aims to enhance productivity, efficiency and sustainability of L. maxima cultivation as well as to determine the safe microbiological conditions for the nutritional use of fresh spirulina ...

Vásquez, Claudia
Ústav chemických procesů, 2023