Tuneable properties of carbon quantum dots by different synthetic methods

Carbon quantum dots (CQD) were prepared from three different precursors and by three bottom-up synthesis methods: classical pyrolysis of citric acid (CAP), microwave irradiation of glucose (GM), and hydrothermal treatment of glucosamine hydrochloride (GAH). CQD were further functionalized using various nitrogen-containing compounds: 6-aminohexanoic acid, 1,6-diaminohexane, N-octylamine, dimethylamine, and tryptophan. Special attention was dedicated to investigate how the combination of synthetic method and starting material affected the nature and properties of CQD. The analysis indicated that CAP were good candidates for covalent post-functionalization, GM allowed an easy passivation, and GAH permitted the direct introduction of nitrogen into the core. The size distribution showed a core–shell structure for CQD functionalized with an aminoacid by microwave irradiation, whereas the thermal decomposition evidenced the degradation of functionalizing molecules and the presence of pyridinic and pyrrolic nitrogen after hydrothermal synthesis. Photoluminescence spectra revealed important differences between the synthesis techniques, related to the occurrence of surface states, and the highest fluorescence quantum yield for hydrothermally prepared CQD. These approaches led to CQD with properties that can be exploited in many fields from energy conversion to sensing.

Nickel-catalyzed oxidative fluoroalkylation of aryl halides via paired electrolysis

The paired electrolysis triggers multiple oxidative and reductive processes to occur simultaneously, which ensures the steady transformation of the intermediates to the desired coupling products. However, fluoroalkyl radicals have not been harnessed for metal-catalyzed cross-coupling with aryl halides under electrochemical conditions. This work describes a general strategy for rapid access to various fluoromethyl and difluoromethyl aromatics by paired electrolysis. The contradiction between anodic oxidation of fluoroalkyl sulfinates and cathodic reduction of low-valent nickel catalysts can be well addressed under mild cell conditions, allowing for direct introduction of fluorinated functionalities into aromatic systems.

Solvent-Driven Chirality Switching of a Pillar[4]arene[1]quinone Having a Chiral Amine-Substituted Quinone Subunit

Several new chiral pillar[4]arene[1]quinone derivatives were synthesized by reacting pillar[4]arene[1]quinone (EtP4Q1), containing four 1,4-diethoxybenzene units and one benzoquinone unit, with various chiral amines via Michael addition. Due to the direct introduction of chiral substituents on the rim of pillar[n]arene and the close location of the chiral center to the rim of EtP4Q1, the newly prepared compounds showed unique chiroptical properties without complicated chiral resolution processes, and unprecedented high anisotropy factor of up to −0.018 at the charge transfer absorption band was observed. Intriguingly, the benzene sidearm attached pillar[4]arene[1]quinone derivative 1a showed solvent- and complexation-driven chirality inversion. This work provides a promising potential for absolute asymmetric synthesis of pillararene-based derivatives.

Biologická konverze energeticky bohatých plynů na biometan

Přechod ze stávajících neobnovitelných zdrojů elektrické energie na zdroje obnovitelné se jeví jako vhodné řešení pro celosvětově narůstající spotřebu energie. Udržitelná technologie pro zpracování organických odpadů formou anaerobní fermentace produkuje bioplyn, z kterého se odstraněním oxidu uhličitého získává biometan – energeticky bohatý plyn kompatibilní se zemním plynem a využitelný jako biopalivo. Zaváděním externího vodíku, získaného z přebytečné energie z obnovitelných zdrojů, do procesu anaerobní fermentace dochází pomocí hydrogenotrofních metanogenů k redukci oxidu uhličitého na metan, čímž se zvyšuje výhřevnost bioplynu v ideálním případě až na biometan. V rámci této práce byla zkoumána technologie obohacování bioplynu pomocí vodíku přímým zaváděním do fermentoru tzv. metoda in-situ a s využitím externího bioreaktoru tzv. metoda ex-situ Získané výsledky z provozu laboratorních modelů insitu a ex-situ bioreaktoru poslouží k sestrojení poloprovozního modelu této technologie pro následné převedení do praxe. Abstract - EN The transition from existing sources of electricity to renewables seems to be a suitable solution for the global increase of energy consumption. Sustainable technology of anaerobic fermentation for the treatment of organic wastes produces biogas, from which is by removing carbon dioxide obtained biomethane – energy-rich gas compatible with natural gas and can be used as biofuel. Hydrogen obtained by using excess energy production from renewable sources, can be introduce into the anaerobic fermentation process. Hydrogenotrophic methanogens use external hydrogen for reduction of carbon dioxide to methane, which increases energetical potencial of biogas, ideally up to the level of biomethane. In this work, the technology of enrichment of biogas with hydrogen by direct introduction into the fermenter, the “in-situ” method and with the use of an external bioreactor, the “ex-situ method,” was investigated. The results obtained from the operation of laboratory models of insitu and ex-situ bioreactors will be used to build a pilot model of this technology for subsequent implementation in practice.

POLA ASUH ORANG TUA TERHADAP PERKEMBANGAN ANAK BERDASARKAN GENDER

Children need education to increase their roles in society. Children education through formal, non-formal, and/or informal education is held to improve the quality of children's skills. Given the huge and importance of the process of parenting education, hence this study aims to determine the influence of parenting on children. Children are great blessings people must be grateful for, hence they deserve the best parenting by their parents. However, parents still treat their children differently. This discussion aims to identify various styles or methods of parenting and their impacts on children. This discussion consisted of four types of parenting proposed by Eisenburg et al. These parenting types are more specific and focused on children’s gender development than other parenting styles that are more general. The four types of parenting are channeling/shaping, direct introduction, differential treatment, and models. There are four types of parenting model according to some psychologists, which are authoritative parenting, neglectful parenting, permissive parenting, and democratic parenting. These four types have their own impacts. While some other opinions believe that authoritative parenting style has 6 (six) parenting styles, which are: Accept children's opinion, Ask about children's mistakes without accusing them, Give advice upon their mistakes, Give appreciation, Give presents, and Facilitate their hobbies.

A Zooarchaeological and Molecular Assessment of Ancient Chicken Remains from Russia

We here conduct ancient DNA analyses on 58 chicken bones from 15 archaeological sites (from the 9th to the 18th century AD) across the Volga region, the Leningrad region, the Pskov region, and the north of the Krasnoyarsk region to investigate genetic diversity of past chicken populations within this geographical area. We find all samples belong to sub-haplogroup E1, ubiquitous throughout the world and dominant in Europe, Africa and the Americas. This supports an introduction of chickens from the west, rather than a direct introduction from East Asia. Our study also demonstrates good endogenous DNA content, confirming species identification and sex of the individuals, thus highlighting the potential of genetic studies on archaeological remains in that region.

Alloying working surface during electroslag surfacing

Parts subject to intense abrasive wear have a short service life. In the manufacture or restoration of such parts by electroslag surfacing, strengthening of the deposited metal is required. The use of ready-made alloying powders in surfacing increases the cost of the finished part, which necessitates the search for cheaper materials for alloying the parts being welded. The study of the efficiency of alloying the deposited metal through the melted insert, as well as by direct introduction of alloying powders into the slag bath has been carried out. Mixtures based on enriched mineral scheelite concentrate and graphite are used as alloying powders