231 research outputs found
Cyberbullying and digital ethics: A bibliometric analysis from a communication research perspective
No full textThis study examines the phenomenon of cyberbullying and digital ethics through a bibliometric approach using the Biblioshiny application in the R programming environment. The dataset, sourced from Scopus between 2014 and 2024, comprises 73 scientific articles that were systematically extracted and analyzed. The findings indicate a rising trend in cyberbullying, particularly its impact on adolescent mental health. Furthermore, the study highlights the critical role of digital ethics education and the practice of forgiveness as potential solutions for fostering a positive and supportive digital environment. This research uses bibliometric analysis to evaluate various aspects of the research, including an overview of the dataset, the number of annual publications, average citations per year, and author contributions. It also analyzed journals, countries, and identified key trends and themes in research. This approach provides a comprehensive insight into the development of research related to cyberbullying and digital ethics over a period of time
Enzymatic Synthesis of O-Heterocyclic Scaffolds by Cyclization & Ring Expansion Reactions
No full textThe assembly of complex molecular frameworks is one of the major tasks of an organic chemist. Over the past decades, numerous tactics for the construction of such complex entities have emerged. To fulfill these tasks, classical methods often require the use of orthogonal protecting group strategies to preserve the molecular integrity, however, these tactics become more and more challenging and insufficient as the molecule gains in complexity. In this regard, enzymes offer the possibility to manipulate or implement delicate functionalities without the need for protecting groups. With the tremendous developments in the field of protein engineering in order to easily access recombinant enzymes, biocatalysis is increasingly gaining importance in organic synthesis. Heterocycles are key parts of the synthetic-organic target scope and thus, their efficient assembly represents a pivotal task in modern chemistry where particularly the stereoselective construction of these building blocks poses a crucial and recurring challenge. As the general theme of this thesis, the presented work features the application of chemoenzymatic methods for the synthesis of heterocyclic building blocks where novel biocatalytic approaches have been developed that imitate non-natural, classical chemical processes. Especially the so-called Achmatowicz rearrangement, the oxidative ring expansion of furfuryl alcohols and amines to six-membered O- and N-heterocycles, respectively, plays a central role in the thesis. Both synthetic routes to access the required substrates, as well as their application in the Achmatowicz rearrangement to prepare pyranones and piperidinones, is described. Here, a novel method to prepare furfurylamines, as well as a new lipase-mediated Achmatowicz rearrangement, is presented. Moreover, the versatility of the newly developed methods is demonstrated in a multi-catalytic natural product synthesis. Additionally, in the perspective to extend the biocatalytic toolbox, investigations on a biocatalytic decomposition of diazo compounds as a trigger for sigmatropic oxonium ylide rearrangements is presented, where lytic polysaccharide monooxygenases are reported for the first time to act as a catalyst in a protein-mediated Kirmse rearrangement
Biokatalyyttiset ja kemoentsymaattiset O-heterosyklien synteesit allenoleista
No full textOver the last three decades, development of environmentally friendly synthetic methods has become the preeminent objective in contemporary organic chemistry, following the introduction of the Twelve Principles of Green Chemistry. Nature's enzymes offer immense potential for such sustainable synthetic strategies as highly efficient, selective and renewable biocatalysts, operating in mild reaction conditions.
Oxygen heterocycles are important structural units in many high-value synthetic targets such as active pharmaceutical ingredients. Allenes bearing nucleophilic functionalizations have emerged recently as versatile precursors for production of these O-heterocycles.The aim of the research presented in this thesis was the introduction of new, sustainable, biocatalytic methods for allenol cyclizations, to form highly functionalized furan and pyran motifs as valuable synthetic building blocks. Further, we aspired to combine the biocatalytic strategies in economical and ecological chemoenzymatic one-pot processes.
We found that biocatalytic halocyclizations of allenols were efficiently mediated by both heme-dependent and vanadium-dependent haloperoxidase-enzymes, furnishing a wide range of brominated O-heterocycles from alfa-, beta- and gamma-allenols. The bromovinyl structures formed in the haloalkoxylations were an obvious target for further valorizations, prompting applications combining well-established Pd cross-coupling reactions in one-pot processes with the biocatalysis to reach arylated dihydrofurans in step-efficient manner.
In an expansion into heterogeneous catalysis, recently pioneered enzyme-metal nanoparticle biohybrid materials were implemented as dual-active catalysts for the one-pot halocyclization/cross-coupling process, efficiently mediating both reaction steps as a bifunctional catalytic species. Even more remarkably, biohybrids combining lipases and silver nanoparticles together were applied as sole, highly selective, catalysts for cascade processes combining kinetic resolution hydrolysis of an allenic acetate with cycloisomerization of the resulting allenol, producing enantiopure dihydrofurans.Luontoystävällisten synteettisten keinojen kehityksestä on tullut tärkein tavoite orgaanisessa kemiassa viimeisten kolmen vuosikymmenen aikana Vihreän Kemian Kahdentoista Periaatteen julkistuksen seurauksena. Luonnon entsyymit tarjoavat suunnattoman potentiaalin näiden kestävien synteettisten menetelmien kehitykselle erittäin tehokkaina, selektiivisinä ja uusiutuvina biokatalyytteinä, jotka toimivat miedoissa reaktio-olosuhteissa.
Happi-heterosyklit ovat tärkeitä rakenteita monissa arvokkaissa synteettisissä kohdemolekyyleissä, kuten vaikuttavissa lääkeaineissa. Alleenit, joihin on liittyneenä nukleofiilisiä funktionaalisia ryhmiä, ovat hiljattain nousseet esiin näiden O-heterosyklien monipuolisina rakennuspalikoina.Tässä väitöskirjassa esitellyn tutkimuksen tavoite oli kehittää uusia, vihreitä, biokatalyyttisiä allenolien syklisointi-reaktioita synteettisesti hyödyllisten furaani- ja pyraani-rakenteiden muodostamiseksi. Lisäksi, pyrimme yhdistämään kehitettyjä biokatalyyttisiä keinoja taloudellisesti ja ekologisesti kannattavissa kemoentsymaattisissa yhden astian prosesseissa.
Selvitimme, että sekä hemi- että vanadiumhaloperoksidaasi-entsyymit toimivat tehokkaina biokatalyytteinä allenolien halosyklisoinneille, tuottaen laajan valikoiman bromattuja O-heterosyklejä alfa-, beta- ja gamma-allenoleista. Näissä haloalkoksyloinneissa muodostuneet bromivinyylirakenteet ovat ilmiselviä kohteita jatkoreaktioille, mikä johti niiden yhdistämiseen yhden astian prosesseissa hyvin tunnettujen Pd kytkentäreaktioiden kanssa tuottaen aryloituja dihydrofuraaneja prosessivaiheet minimoiden.
Laajennuksena heterogeeniseen katalyysiin, hiljattain innovoituja entsyymejä ja metalli-nanopartikkeleita yhdistäviä biohybridimateriaaleja käytettiin kaksoisaktiivisina katalyytteinä kehitetyssä yhden astian halosyklisointi-ristikytkentäprosessissa. Biohybridejä pystyttiin kaksoistoimintansa ansiosta käyttämään katalyytteinä prosessin molemmissa reaktiovaiheissa. Vielä merkittävämpää oli lipaasit ja hopea-nanopartikkelit yhdistävien biohybridien käyttö ainoina, hyvin selektiivisinä, katalyytteinä yhtäaikaisessa alleenisen asetaatin kineettisen resoluution hydrolyysin ja siinä tuotetun allenolin sykloisomeroinnin yhdistävässä prosessissa, jossa tuotetaan enantiopuhtaita dihydrofuraaneja
Selected RC Elements of Office Building
No full textÚkolem bakalářské práce bylo navrhnout a posoudit lokálně podepřenou stropní desku administrativního objektu s kruhovým otvorem. Řešená stropní deska se nachází nad 1. nadzemním podlažím. Statická analýza konstrukce byla provedena v softwaru Scia Engineer 19. Stropní deska byla posouzena z hlediska mezního stavu únosnosti i použitelnosti. Součástí práce je také návrh a posouzení atypického schodiště.Objective of the bachelor thesis was design and assesment of a flat plate of an administrative building with round hole. The solved ceiling slab is above the first floor. Static analysis of the structure was calculated by Scia Engineer 19 software. The flat plate was assesed to the ultimate limit state and the serviceability limit state. Part of the thesis is also design and assesment of an atypical staircase.
Design of reinforced concrete subway
No full textCílem práce je navrhnout nosnou konstrukci železobetonového podchodu pod dálnicí. Délka přemostění je 4m. Konstrukce je uvažována jako rám vetknutý do základů. V práci bude navržena horní deska rámu, stěna a základový pás.The purpose of this thesis is to design structure of reinforced concrete subway under the highway. Length of the bridge is 4 meters. The structure is concidered as a frame clamped into basis. In this thesis will be designed a slab, wall and the base bend.
Development Kit for 32-bit ARM Micro-controllers with a Focus on Multimedia Applications <br>
No full textBakalářská práce se zabývá návrhem a realizací vývojového kitu, jakožto nástroje pro samotný vývoj v oblasti 32-bitových mikrokontrolérů ARM. Kit obsahuje vývojovou desku a příslušenství potřebné pro její funkci. Samotná deska disponuje standardními funkcemi, což zahrnuje LED diody, uživatelem definovatelná tlačítka, vstupní a výstupní piny, sériové komunikační kanály, USB rozhraní a soket pro paměťové karty. Deska je však navíc osazená zvukovým kodekem, a barevným displejem s vlastním řadičem. Součástí práce na tomto projektu je především návrh a realizace samotné desky po stránce hardwarové, ale i vývoj jednoduchého software, který umožní demonstrovat některé základní funkce tohoto zařízení.This bachelor thesis is concerned with the development and realisation of a development kit for the 32-bit ARM microcontrollers. The kit consists of development board and all the necessary accessories. The board itself offers standard features such as LED diodes, user buttons, input and output pins, serial lines, USB and a memory card sockets. In addition, the board is equipped with an audio codec and a color display with it's own graphics controller. Part of this work is not only the design and realization of the board itself, but also development of a small software application to demonstrate some of the basic board's functions.Ústav automatizace a řídicí technikyobhájen
Design of special antenna rotator
No full textDiplomová práce se zabývá návrhem elektroniky pro řízení anténního rotátoru ve dvou rovinách. Byly navrženy a realizovány budiče pro dva krokové motory. Dále byla navržena a realizována řídicí deska, která umožňuje jak ruční ovládání rotátoru, tak po připojení k PC vzdálené ovládání přes USB. Zároveň vznikl software pro řídicí desku rotátoru a aplikace pro PC na jednoduché ovládání.This master's thesis deals with design electronics for an antenna rotator in two axis. There are designed and implemented drivers for two stepper motors. Was also designed and implemented control panel that allows manual control the rotator and remote control by PC via USB. At the same time created software for control panel and PC application for easy operation.
Solar charger with balancing circuit for 4 cell battery pack working in an IoT network
No full textTato bakalářská práce se zabývá návrhem obvodu pro řízení nabíjení čtyř akumulátorových článků pomocí solární energie. Na jednotlivých článcích je aplikováno pasivní balancování. Je měřeno napětí článků, které by následně mělo být odesláno pomocí sítě LoRa. Návrh bere v potaz především nízkou spotřebu energie, kompaktnost a nezávislost. Správná funkce je poté ověřená pomocí simulací v prostředí MATLAB Simulink a následně otestována také na vývojovém kitu STM32. Výsledkem bude deska plošných spojů a simulace důležitých částí zařízení.This bachelor thesis deals with the design of a circuit for charging control of the four battery cells using solar energy. Passive balancing is applied to the separate cells. The measured cell voltage should then be sent via the LoRa network. The proposal mainly considers low energy consumption, compactness and independence. The appropriate function is then verified using MATLAB Simulink simulations and subsequently tested on the STM32 development kit. The result will be a finished printed circuit board design and simulation of important parts of the device.
Coding Synthetic Chemistry Strategies into Bacterial Designer Cells
No full textFollowing a synthetic chemistry blueprint for the valorization of lignocellulosic platform chemicals, this study showcases a so far unprecedented approach to implement non-natural enzyme modules in vivo. For the design of a novel functional whole cell tool, two purely abiotic transformations were incorporated into a recombinant bacterial host that allows production of complex lactone building blocks. This whole cell system streamlines the synthetic cascade, eliminates isolation and purification steps, and provides a high degree stereoselectivity that has so far been elusive in the chemical methodology.</p
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