Search results for "Anna"
showing 10 items of 1027 documents
Über polystannane
1985
Abstract The compound I(t-Bu2Sn)4I has been synthesized by controlled cleavage of the related cyclotetrastannane (t-Bu2Sn)4 with iodine in toluene. Both compounds have been investigated by mass, NMR and vibrational spectra. I(t-Bu2Sn)4I: δ(119Snterminal) 67.7, δ(Sncentral) 17.4 ppm; 1J(SnSn) 2199 (terminal-central) and 1575 (central-central), 2J(SnSn) 20 (terminal-central), 3J (SnSn) 307 Hz (terminal-terminal); ν(SnSn) 119, ν(SnI) 167 cm−1. (t-Bu2Sn)4: δ(Sn) 87.4 ppm; ν(SnSn) 125 cm−1. The crystal structure of I(t-Bu2Sn)4I has been determined (R = 0.071): bond lengths SnSn 289.5(1) (terminal-central) and 292.4(1) (central-central), SnI 275.3(1) pm. The conformation of the chain ISn…
Reactivity of dialkoxydibutylstannanes toward carbon dioxide: A DFT study of electronic and steric effects
2012
Abstract DFT calculations were performed for the reaction of CO 2 with the monomeric species, R′ 2 Sn(OR) 2 , (R = R′ = CH 3 ; R = CH 3 , CH 2 CH 3 , CH(CH 3 ) 2 , R′ = n -Bu) for assessing the role of electronic and steric effects in the kinetics and thermodynamics of CO 2 insertion into Sn–OR bonds. The reaction pathways are exothermic and involve the successive insertion into the two Sn–OR bonds. The driving force for insertion is ascribed to a charge-transfer between the HOMO of the complexes, mainly localized on the oxygen atom of the alkoxy ligands, and the LUMO of CO 2 . Interestingly enough, the energy barrier of the second insertion is much lower by around 27 kJ mol −1 , and quite…
Reactivity of di-tert-butyldimethoxystannane with carbon dioxide and methanol: X-ray structure of the resulting complex
2006
Abstract The synthesis of dimethyl carbonate from carbon dioxide and methanol was studied with ditert-butyldimethoxystannane under pressure at temperatures ⩽423 K. The formation of dimethyl carbonate is accompanied by transformation of the stannane into a trinuclear complex, the structure of which has been determined by single-crystal X-ray diffraction technique. The relevance of this specie in the catalytic cycle is demonstrated by conducting recycling runs. A preliminary kinetic study underlines the steric influence of the tert-butyl ancillary ligands in the stabilisation of intermediates, by comparison with the n-butyl homologue.
Can Green Dimethyl Carbonate Synthesis be More Effective? A Catalyst Recycling Study Benefiting from Experimental Kinetics and DFT Modeling
2014
Dibutyldimethoxystannanes are known to catalyze the reaction between carbon dioxide and methanol leading to dimethyl carbonate. Despite similarities between din-butyl- and ditert-butyldimethoxystannane, the recycled complexes have different structural features. In the din-butyl series, a decatin(IV) complex has been characterized and is less active than the stannane precursor. Kinetic experiments likely indicate that all the tin centers are not active, which is confirmed in comparing with the related dinuclear 1,3-dimethoxytetran-butyldistannoxane complex. In the ditert-butyl series, the tritin(IV) complex isolated upon recycling features the steric effect of bulky tBu ancillary ligands. In…
Real time optical immunosensing with flow-through porous alumina membranes
2014
Through the presentation of analytical data from bioassay experiments, measured by polarimetry, we demonstrate for the first time a real time immunoassay within a free standing macroporous alumina membrane. The 200 nm nominal pore diameter of the membrane enables flow-through, thereby providing an ideal fluidic platform for the targeted delivery of analytes to bioreceptors immobilized on the pore walls, enabling fast sensing response times and the use of small sample volumes (<100 mu L). For the immunoassay, the pore walls were first coated with the functional copolymer, copoly(DMA-NAS) using a novel coupling process, before immobilization of the allergen protein, beta-lactoglobulin, by spo…
Perheyritykset kansantalouden resurssina : keskisuurten ja suurten yritysten omistajuus, toiminnan laajuus ja kannattavuus Suomessa 2000-2005
2009
The first main goal of the research is family business contribution analysis, anexamination of the economic effect of family businesses in Finland. Another topic ofinterest is the relationship between the type of ownership and financial performance ofthe firm, a comparison analysis of profitability between family and non-familybusinesses.On a world-wide basis, the contribution of family businesses to nationaleconomies is considerable. However, the exact extent of the impact of familybusinesses has remained unknown. One reason for this problem is the fact that thereare neither official statistics nor representative performance data available of familybusinesses at the national economic level…
CB(1) signaling in forebrain and sympathetic neurons is a key determinant of endocannabinoid actions on energy balance
2010
The endocannabinoid system (ECS) plays a critical role in obesity development. The pharmacological blockade of cannabinoid receptor type 1 (CB(1)) has been shown to reduce body weight and to alleviate obesity-related metabolic disorders. An unsolved question is at which anatomical level CB(1) modulates energy balance and the mechanisms involved in its action. Here, we demonstrate that CB(1) receptors expressed in forebrain and sympathetic neurons play a key role in the pathophysiological development of diet-induced obesity. Conditional mutant mice lacking CB(1) expression in neurons known to control energy balance, but not in nonneuronal peripheral organs, displayed a lean phenotype and res…
The transcription factor CHOP is critical for WIN-mediated DR5 up-regulation in apoptosis induced by WIN/TRAIL co-treatment in hepatoma cells
2009
TRPV1 channels as putative targets in the cannabinoid-mediated synaptic activity of hippocampal neurons
Endocannabinoids (eCBs) play a critical part in pathophysiological conditions rooted on neuronal excitability such as epilepsy. eCBs seem to be involved in neuroprotection, putatively acting on the cannabinoid receptor type 1 (CB1r), but also on Transient Receptor Potential Vanilloid type 1 channels (TRPV1). Indeed, CB1r and TRPV1 are involved in the transduction of stimuli at synaptic level, though exact molecular mechanisms are far from being unveiled. Thus, we aimed to investigate the role of CB1r/TRPV1 interplay in the rat hippocampal neurotransmission by whole-cell patch clamp technique to evaluate excitatory bioelectric activity in the CA1. We pharmacologically manipulated this pathwa…