Search results for "Zen"
showing 10 items of 3479 documents
A Dendrimer Chiroptical Switch Based on the Reversible Intramolecular Photoreaction of Anthracene and Benzene Rings
2010
A series of Fréchet-type dendrimers with 9-benzyloxymethylanthracene cores were synthesized and characterized. The chiral source for the dendrimers was an (S)-2-methyl-1-butoxy group in the 3-position of the benzene ring. Irradiation at 366 nm of a dilute benzene solution led to the formation of two diastereomers (1:1) through a quantitative intramolecular [4pi+4pi] cycloaddition between the central anthracene ring and the neighboring benzene ring. The process can be reversed with 254 nm UV light or heat. The benzene rings in the dendrons work as a light-harvesting system. The optical rotation values measured for the reversible process showed fatigue resistance. Thus, a promising new type o…
Reversible and Efficient Light-Induced Molecular Switching on an Insulator Surface
2018
Prototypical molecular switches such as azobenzenes exhibit two states, i.e., trans and cis, with different characteristic physical properties. In recent years various derivatives were investigated on metallic surfaces. However, bulk insulators as supporting substrate reveal important advantages since they allow electronic decoupling from the environment, which is key to control the switching properties. Here, we report on the light-induced isomerization of an azobenzene derivative on a bulk insulator surface, in this case calcite (101̅4), studied by atomic force microscopy with submolecular resolution. Surprisingly, cis isomers appear on the surface already directly after preparation, indi…
Novel Domino Oxidative Coupling: C−C Bond Formation Sequence to Highly Functionalized Dibenzo[a,c]cycloheptenes
2011
A domino sequence involving various MoCl(5)-mediated oxidations followed by trapping and supposed [3,3]-sigmatropic rearrangement provides a fast access to the full carbon skeleton of metasequirin-B. A variety of different moieties R(1) and R(2) are tolerated.
Preparation of organic monolithic columns in polytetrafluoroethylene tubes for reversed-phase liquid chromatography
2017
[EN] In this work, a method for the preparation and anchoring of polymeric monoliths in a polytetrafluoroethylene (PTFE) tubing as a column housing for microbore HPLC is described. In order to assure a covalent attachment of the monolith to the inner wall of the PTFE tube, a two-step procedure was developed. Two surface etching reagents, a commercial sodium naphthalene solution (Fluoroetch®), or mixtures of H2O2 and H2SO4, were tried and compared. Then, the obtained hydroxyl groups on the PTFE surface were modified by methacryloylation. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed the successful modification…
L'immagine-montaggio
2011
L'articolo descrive la teoria ejzenstejniana del montaggio, alla luce delle più recenti interpretazioni
The role of water in the photocatalytic degradation of acetonitrile and toluene in gas-solid and liquid-solid regimes
2006
Photocatalytic degradation of acetonitrile and toluene was carried out both in gas-solid and in liquid-solid regimes by using commercialTiO2samples (Merck and Degussa P25). The investigation was mainly aimed to study the influence of water present in the reaction environment on the mechanism and degradation rate of two probe molecules. In gas-solid regime, the reacting mixture consisted of toluene or acetonitrile, oxygen, nitrogen, and water vapour. The main degradation product of toluene wasCO2with small amounts of benzaldehyde. In the presence of water vapour, the activity ofTiO2Merck remained stable but greatly decreased if water was absent.TiO2Degussa P25 continuously deactivated, even …
A Successful Crowdsourcing Approach for Bird Sound Classification
2023
Automated recorders are increasingly used in remote sensing of wildlife, yet automated methods of processing the audio remains challenging. Identifying animal sounds with machine learning provides a solution, but optimizing the models requires annotated training data. Producing such data can require much manual effort, which could be alleviated by engaging masses to contribute to research and share the workload. Birdwatchers are experts on identifying bird vocalizations and form an ideal focal audience for a citizen science project aiming for the required multitudes of annotated avian audio data. For this purpose, we launched a web portal that was targeted and advertised to Finnish birdwatc…
Citizen consultations on science communication: A citizen science approach
2021
La ciencia ciutadana forma part d’una tendencia cientifica i social mes amplia que promou el dialeg bidireccional i la implicacio dels cientifics i el public a forca d’involucrar la ciutadania en el proces d’investigacio. Aquest article examina els esforcos de CONCISE (un projecte internacional en el qual participen Espanya, Italia, Portugal, Polonia i Eslovaquia) per a comprendre, mitjancant consultes publiques, com adquireix i utilitza la informacio cientifica la ciutadania. Les consultes, celebrades en 2019, van incloure prop de 500 persones. CONCISE intenta posar la participacio de la ciutadania en el centre del proces d’investigacio demanant-li suggeriments sobre com millorar la comuni…
Ciudadanía y transformación social: Nuevos discursos y acción contra el cambio climático
2021
El canvi climatic protagonitza el debat mediambiental des de fa tres decades. Malgrat els acords internacionals adoptats, la humanitat no ha aconseguit frenar l’augment de la temperatura planetaria. La crisi del coronavirus ha relegat el debat sobre l’emergencia climatica a un segon pla, encara que les connexions entre canvi climatic i pandemia demostren les multiples raons que tenim per a actuar pel clima. Les politiques publiques han afavorit regulacions, instruments de mercat i estrategies de modernitzacio ecologica que consoliden un capitalisme verd que agreuja el problema i el despolititza. La lluita contra el canvi climatic necessita un nou enfocament, basat en la politica ciutadana i…
Between idiosyncratic self-interests and professional standards: A contribution to the understanding of participatory journalism in Web 2.0. Results …
2012
Not much is known about participatory journalists in Germany or further afield. We conducted a standardized quantitative online survey of participatory journalists at the German-language website myheimat, a German-based hyperlocal participatory journalism portal with about 37,000 contributors (as at September 2010). The purpose of the survey was to examine the individual characteristics of participatory journalists (sociodemographics, expertise, qualification and gender aspects). The survey also explored why they write articles for myheimat (societal/individual motivations), what they think about their role and function as grassroots journalists (identity/self-concept), what they know and …