Femtosecond laser studies of CO and NO on Pd(111)

The ultimate goal of any branch of chemistry, including surface chemistry, is to understand the dynamics of reactions. The typical time scale for bond making and breaking is the femtosecond time scale. Femtochemistry has led to enormous progress in the understanding, and even control, of chemical reactions in the gas and solution phases over the past decades. However, a comparable level of sophistication in the analysis of surface chemical reactions has not been achieved due to the complexity of the energy dissipation channels. For this thesis, a new experimental set-up was built with the goal to monitor the femtosecond laser-induced desorption (fs-LID) and femtosecond laser-induced reaction (fs-LIR) of CO and NO co-adsorbed on a Pd(111) surface. In addition, a femtosecond extreme ultraviolet (XUV) source was designed and commissioned. All the femtosecond laser-induced studies were accompanied by temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS). First, fs-LID experiments were performed for pure CO and NO adsorbed on Pd(111) in order to test the apparatus. The CO and NO photodesorption dynamics were compared and the different photoreactivity was explained qualitatively using two theoretical models: electron friction and desorption induced by multiple electronic transitions (DIMET). The power law behaviour was also tested and a new method of fitting proposed. The photodesorption behaviour of CO co-adsorbed with NO on Pd(111) was then studied and compared qualitatively with the photodesorption behaviour of pure CO and NO within the empirical friction model

Post-Modification of the Electronic Properties by Addition of π-Stacking Additives in N-Heterocyclic Carbene Complexes with Extended Polyaromatic Systems

A series of iridium complexes containing phenanthro[4,5-abc]phenazino[11,12-d]imidazol-2-ylidene and acetonaphtho[1,2-b]quinoxaline[11,12-d]imidazol-2-ylidene ligands have been obtained and fully characterized. These complexes display highly extended polyaromatic systems attached to the backbone of the N-heterocyclic carbene. The presence of this extended polyaromatic system makes the electron-donating character of these ligands sensitive to the presence of π-stacking additives, such as pyrene and hexafluorobenzene. The computational studies predict that the addition of pyrene affords an increase of the electron-donating character of the polyaromatic ligand (TEP decreases), while the addition of hexafluorobenzene has the opposite effect (TEP increases). This prediction is experimentally corroborated by IR spectroscopy, by measuring the shift of the CO stretching bands of a series of IrCl(NHC)(CO)2 complexes, where NHC is the N-heterocyclic carbene ligand with the polyaromatic system. Finally, the energy of the π-stacking interaction of one of the key Ir(I) complexes with pyrene and hexafluorobenzene has been estimated by using the Benesi-Hildebrand treat-ment, based on the δ-shifts observed by 1H NMR spectroscopy.MEC of Spain (CTQ2011-24055/BQU

Guiding principles for identification, evaluation and conservation of Vitis vinifera L. subsp. sylvestris

Conservation of grapevine genetic resources is an important and long lasting task. Here, partners of the InWiGrape Activity of the European Cooperative Programme for Plant Genetic Resources have proposed a set of descriptors that will assist in identification, conservation and study of genetic resources of Vitis vinifera L. subsp. sylvestris. A distribution map of Vitis vinifera L. subsp. sylvestris populations in Europe was produced, with on-line access through the European Vitis Database. The several different aspects of conservation of Vitis vinifera L. subsp. sylvestris including bibliographical references, identification in the wild, in situ and ex situ conservation have been discussed. The descriptors and the map will assist different stakeholders, working on biodiversity and ecosystems in more effective conservation of wild grapevine genetic resources

Brazilian cave heritage under siege

info:eu-repo/semantics/publishe

Lyophilized alginate-based microspheres containing Lactobacillus fermentum D12, an exopolysaccharides producer, contribute to the strain\u2019s functionality in vitro

Lactobacillus (Limosilactobacillus) fermentum D12 is an exopolysaccharide (EPS) producing strain whose genome contains a putative eps operon. Whole-genome analysis of D12 was performed to disclose the essential genes correlated with activation of precursor molecules, elongation and export of the polysaccharide chain, and regulation of EPS synthesis. These included the genes required for EPS biosynthesis such as epsA, B, C, D and E, also gt, wzx, and wzy and those involved in the activation of the precursor molecules galE, galT and galU. Both the biosynthesis and export mechanism of EPS were proposed based on functional annotation. When grown on MRS broth with an additional 2% w/v glucose, L. fermentum D12 secreted up to 200\ua0mg/L of a mixture of EPSs, whose porous structure was visualized by scanning electron microscopy (SEM). Structural information obtained by 1HNMR spectroscopy together with composition and linkage analyses, suggested the presence of at least two different EPSs, a branched heteropolysaccharide containing t-Glcp and 2,6-linked Galf, and glycogen. Since recent reports showed that polysaccharides facilitate the probiotic-host interactions, we at first sought to evaluate the functional potential of L. fermentum D12. Strain D12 survived simulated gastrointestinal tract (GIT) conditions, exhibited antibacterial activity against enteropathogenic bacteria, adhered to Caco-2 cells in vitro, and as such showed potential for in vivo functionality. The EPS crude extract positively influenced D12 strain capacity to survive during freeze-drying and to adhere to extracellular matrix (ECM) proteins but did not interfere Caco-2 and mucin adherence when added at concentrations of 0.2, 0.5, and 1.0\ua0mg/mL. Since the viable bacterial count of free D12 cells was 3 logarithmic units lower after the exposure to simulated GIT conditions than the initial count, the bacterial cells had been loaded into alginate for viability improvement. Microspheres of D12 cells, which were previously analyzed at SEM, significantly influenced their survival during freeze-drying and in simulated GIT conditions. Furthermore, the addition of the prebiotic substrates mannitol and lactulose improved the viability of L. fermentum D12 in freeze-dried alginate microspheres during 1-year storage at 4\ua0\ub0C compared to the control. [Figure not available: see fulltext.

A dual-lane flow signal plan for Texas.

Texas Department of Transportation, AustinMode of access: Internet.Author corporate affiliation: Texas Transportation Institute, College StationSubject code: HBEKSubject code: CDKBSubject code: GGCSubject code: GHSubject code: KNSubject code: SDBL

Record summer rains in 2019 led to massive loss of surface and cave ice in SE Europe

Glaciers worldwide are shrinking at an accelerated rate as the climate changes in response to anthropogenic influence. While increasing air temperature is the main factor behind glacier mass and volume loss, variable patterns of precipitation distribution also play a role, though these are not as well understood. Furthermore, while the response of surface glaciers (from large polar ice sheets to small alpine glaciers) to climatic changes is well documented and continuously monitored, little to nothing is known about how cave glaciers (perennial ice accumulations in rock-hosted caves) react to atmospheric warming. In this context, we present here the response of cave and surface glaciers in SE Europe to the extreme precipitation events occurring between May and July 2019 in SE Europe. Surface glaciers in the northern Balkan Peninsula lost between 17 % and 19 % of their total area, while cave glaciers in Croatia, Greece, Romania and Slovenia lost ice at levels higher than any recorded by instrumental observations during the past decades. The melting was likely the result of large amounts of warm water delivered directly to the surface of the glaciers, leading to rapid reduction in the area of surface glaciers and the thickness of cave glaciers. As climate models predict that such extreme precipitation events are set to increase in frequency and intensity, the presence of cave glaciers in SE Europe and the paleoclimatic information they host may be lost in the near future. Moreover, the same projected continuous warming and increase in precipitation extremes could pose an additional threat to the alpine glaciers in southern Europe, resulting in faster-than-predicted melting

Optical position monitoring system for the central muon detector of the CMS experiment at CERN

The CMS experiment (Compact Muon Solenoid) is one of the experiments on the future Large Hadron Collider at CERN (European Organization for Particle Physics). To achieve the best performance in the reconstruction of the particle tracks the knowledge of the positions of the tracking detectors is required. In this paper the optical position monitoring system of the Central Muon part of the CMS Detector is described. (4 refs)