Search results for "ATAL"
showing 10 items of 10591 documents
Donor-π-acceptors containing the 10-(1,3-dithiol-2-ylidene)anthracene unit for dye-sensitized solar cells
2012
Two donor-acceptor molecular tweezers incorporating the 10-(1,3-dithiol-2-ylidene)anthracene unit as donor group and two cyanoacrylic units as accepting/anchoring groups are reported as metal-free sensitizers for dye-sensitized solar cells. By changing the phenyl spacer with 3,4-ethylenedioxythiophene (EDOT) units, the absorption spectrum of the sensitizer is red-shifted with a corresponding increase in the molar absorptivity. Density functional calculations confirmed the intramolecular charge-transfer nature of the lowest-energy absorption bands. The new dyes are highly distorted from planarity and are bound to the TiO(2) surface through the two anchoring groups in a unidentate binding for…
New simple hydrophobic proline derivatives as highly active and stereoselective catalysts for the direct asymmetric aldol reaction in aqueous medium
2008
New 4-substituted acyloxyproline derivatives with different hydrophobic properties of the acyl group were easily synthesized and used as catalysts in the direct asymmetric aldol reaction between cyclic ketones (cyclohexanone and cyclopentanone) and several substituted benzaldehydes. Reactions were carried out using water, this being the best reaction medium examined. Screening of these catalysts showed that compounds bearing the most hydrophobic acyl chains [4-phenylbutanoate and 4-(pyren-1-yl)butanoate] provided better results. The latter catalysts were successfully used in only 2 mol% at room temperature without additives to give aldol products in excellent stereoselectivities. These resu…
Maankäytön ja maaperäeläinten vaikutus ravinteiden ja torjunta-aineiden valuntaan peltomaasta
2011
Tehomaatalous pyrkii maksimoimaan maan tuottavuutta. Samalla se saattaa kuitenkin vaikuttaa negatiivisesti agroekosysteemien ravinnekiertoon ja maaperän rakenteeseen. Maaperäeläinten toiminnallisen monimuotoisuuden pieneneminen voi osaltaan heikentää maan ravinnekiertoa ja rakennetta. Tässä tutkimuksessa kasvatettiin mikrokosmoksissa vehnää ja verrattiin tehomaatalouskäytössä olleen maan ja laidunmaan kykyä pidättää ravinteita (N) ja torjunta-aineita (metributsiini) sekä tutkittiin, miten änkyrimadot ja lierot vaikuttavat ravinteiden ja torjunta-aineen valuntaan. Laidunmaa pidätti torjunta-ainetta paremmin kuin tehomaatalousmaa, mikä johtui lähinnä laidunmaan suuremmasta orgaanisen aineen p…
Szczegóły konstrukcyjne organów Paula Voelknera na przykładzie unikalnego katalogu firmowego z 1900 roku
2018
This article presents a unique advertising brochure dating from 1900 which was published by the organ building company Voelkner from Duninów and which has been discovered in the State Archives in Wrocław in the files of the Silesian Evangelical Consistory. The catalogue contains 47 pages and is a valuable source for the history of the Voelkner company. By studying this publication, the reader will get acquainted with the trends prevailing in the field of organ building at the turn of the 19th to the 20th centuries. However, the advertising folder does not contain any listing of the works realized by the company, which is probably its greatest shortcoming.
Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges
2021
The study of the electrochemical catalyst conversion of renewable electricity and carbon oxides into chemical fuels attracts a great deal of attention by different researchers. The main role of this process is in mitigating the worldwide energy crisis through a closed technological carbon cycle, where chemical fuels, such as hydrogen, are stored and reconverted to electricity via electrochemical reaction processes in fuel cells. The scientific community focuses its efforts on the development of high-performance polymeric membranes together with nanomaterials with high catalytic activity and stability in order to reduce the platinum group metal applied as a cathode to build stacks of proton …
One-pot cross-enyne metathesis (CEYM)-Diels-Alder reaction of gem-difluoropropargylic alkynes.
2013
Propargylic difluorides 1 were used as starting substrates in a combination of cross-enyne metathesis and Diels–Alder reactions. Thus, the reaction of 1 with ethylene in the presence of 2nd generation Hoveyda–Grubbs catalyst generates a diene moiety which in situ reacts with a wide variety of dienophiles giving rise to a small family of new fluorinated carbo- and heterocyclic derivatives in moderate to good yields. This is a complementary protocol to the one previously described by our research group, which involved the use of 1,7-octadiene as an internal source of ethylene.
Stereoselective aldol reaction catalyzed by a highly recyclable polystyrene supported substituted prolinamide catalyst
2008
Polystyrene supported substituted prolinamide was used as catalyst in the aldol reaction between cyclohexanone or acetone and several substituted benzaldehydes in chloroform/water. This catalyst afforded aldol products in high yields and stereoselectivities, especially in the case of reactions performed with acetone. The catalyst was easily recovered by filtration and reused, after regeneration with formic acid, up to 22 times.
Polystyrene supported L-proline: a recyclable organocatalyst for the asymmetric aldol reaction in the presence of water
2007
Novel Stereoselective Intramolecular Processes for the Generation of New Molecular Entities
2019
La Química Orgánica, además de constituir una fuente inagotable de fascinación académica por su capacidad de generar un número virtualmente infinito de nuevas estructuras moleculares, ha proporcionado una poderosa herramienta, el cribado de librerías de moléculas orgánicas, en el ámbito de la química biológica/médica y el descubrimiento de fármacos que se ha convertido en el caballo de batalla en la identificación de nuevas dianas terapéuticas y sus correspondientes moduladores y potenciales fármacos, con un impacto directo sobre la salud humana. La principal problemática de estas librerías es el aspecto de la diversidad estructural, ya que la probabilidad de dar con un fármaco candidato es…
Catalanes, valencianos y mallorquines en la Ortografía de la lengua castellana (1831) de J. del Castillo y Mayone
2019
Análisis de la obra Ortografía de la lengua castellana para uso de toda clase de personas: con reglas particulares para los catalanes, valencianos y mallorquines deducidas de su propio idioma y observaciones sobre los escollos en que peligran y pueden evitar, en la Imprenta de Corchs, Barcelona, 1831 de Joaquín del Castillo y Mayone. Es una obra general sobre la ortografía de la lengua castellana dirigida y arreglada especialmente para los catalanohablantes, lo que supone una novedad en el panorama de las ortografías peninsulares de la primera mitad del siglo XIX. Este trabajo presenta todas las características de la ortografía contrastiva que contiene, los aspectos historiográficos e ideol…