The structural properties of Co/MCM-41 with pore diameters between 2.9 and 3.6
nm prepared by direct synthesis and impregnation were investigated. For both preparation methods, the size of the metal ...particles decreased with the pore diameter. For Co/MCM-41 with the same pore diameter we observed that the direct synthesis method led to significantly smaller metal clusters compared to the impregnation method. For all Co/MCM-41 samples constraints of the metal cluster sizes were observed, which are speculated to result from influences of the micro structure during the formation of the catalyst precursor.
Background Patients with schizophrenia have an approximately 10-fold higher risk for obsessive–compulsive symptoms (OCS) than the general population. A large subgroup seems to experience OCS as a ...consequence of second-generation antipsychotic agents (SGA), such as clozapine. So far little is known about underlying neural mechanisms. Methods To investigate the role of SGA treatment on neural processing related to OCS in patients with schizophrenia, we stratified patients according to their monotherapy into 2 groups (group I: clozapine or olanzapine; group II: amisulpride or aripiprazole). We used an fMRI approach, applying a go/no-go task assessing inhibitory control and an n-back task measuring working memory. Results We enrolled 21 patients in group I and 19 patients in group II. Groups did not differ regarding age, sex, education or severity of psychotic symptoms. Frequency and severity of OCS were significantly higher in group I and were associated with pronounced deficits in specific cognitive abilities. Whereas brain activation patterns did not differ during working memory, group I showed significantly increased activation in the orbitofrontal cortex (OFC) during response inhibition. Alterations in OFC activation were associated with the severity of obsessions and mediated the association between SGA treatment and co-occurring OCS on a trend level. Limitations The main limitation of this study is its cross-sectional design. Conclusion To our knowledge, this is the first imaging study conducted to elucidate SGA effects on neural systems related to OCS. We propose that alterations in brain functioning reflect a pathogenic mechanism in the development of SGA-induced OCS in patients with schizophrenia. Longitudinal studies and randomized interventions are needed to prove the suggested causal interrelations.
Gas and liquid phase hydrogenation of crotonaldehyde was studied over silica supported promoted Pt catalysts. The influence of reaction temperature and reactant pressure on the activity and ...selectivity of the catalysts and the role of deactivation was investigated. Addition of Ni, Co and Fe to Pt/SiO
2 increased the activity and the selectivity in gas phase hydrogenation. This is attributed to the existence of polar sites in a bimetallic phase favoring the interaction with the carbonyl group and, thus, increasing the rate for the hydrogenation to crotylalcohol. Addition of Ga, Sn and Ge improved the selectivity to crotylalcohol, but decreased the activity of the catalysts. These promoters form catalytically inactive oxides that decorate part of the Pt surface. The electron pair donor–acceptor interaction of the oxygen of the carbonyl group with the Lewis sites present in such oxide clusters is concluded to cause the enhanced selectivity to crotylalcohol. The addition of La, Bi, Pb and Sb to Pt decreased the activity and the selectivity of the parent catalyst by blocking a part of the active surface. With respect to selectivity, catalyst behavior is independent of the reaction medium. In contrast, the highest activities in gas phase were found for catalysts forming a bimetallic phase, while these catalysts showed the lowest activity in liquid phase due to a fast deactivation.
We modeled the behavior of an Austrian alpine forest ecosystem on calcareous soils under changing climate and atmospheric nitrogen deposition scenarios. The change of nitrate leaching, emission rates ...of nitrogen compounds, and forest productivity were calculated using four process-oriented models for the periods 1998-2002 and 2048-2052. Each model reflects with high detail a segment of the ecosystem: PnET-N-DNDC (photosynthesis-evapotranspiration-nitrification-denitrification-decomposition; short-term nitrogen cycling), BROOK90 (water balance for small and homogenous forest watersheds), HYDRUS (water flux in complex and heterogenous soils), and PICUS v1.3 (forest productivity). The nitrogen balance model (NBM) combines the individual results into a comprehensive picture and extends the specific values beyond the limits of the individual models. The evaluation of the findings was outlined with TRACE, a model enabling a long-term prognosis of nitrogen cycling in annual time steps. Temperature increase and nitrogen input are influenced by various components and processes of the forest ecosystem. An increase of the temperature of 2.5 degrees C led to an enhancement of the N2O emission rates and affected the mineralization and the nitrification rates with the consequence of increased nitrate leaching into the subsoil. Enhanced nitrogen input also showed notable effects on nitrate leaching.
We evaluated the soil chemistry, plant species composition, and forest growth rate on a site where a site amelioration project had been realized 30 years earlier. The initial goal of the project was ...the improvement of a site that had been degraded by litter raking. We wanted to know which amelioration method produced a sustainable result and how different treatments might be rated by today's standards. Treatments included fertilization, underplanting with N-fixing plants, and a combination of both. The amelioration was combined with stand conversion by means of natural regeneration and spruce underplanting. In all treatments, a spruce-dominated stand replaced the secondary pine stand. The biomass of the formerly recalcitrant forest floor (143 Mg(.)ha-1) was reduced by 30 to 50% in treated plots, thereby reducing the total soil pool of C, N, and exchangeable cations. The mineral soil of treated plots was enriched with N, Ca, and Mg. An increase in pH was restricted to the forest floor. The C pool of treated soils was much smaller than that of the control plots. However, the loss from the soil was at least partly offset by increased growth rates of the aboveground tree biomass. In treated plots, the stem volume was more than twice that of control plots (38.3 m3). Soil chemical data and the composition of the ground vegetation suggest that even the control plots have changed compared with pre-treatment conditions. Comparison of different blocks of the experiment suggests that the exclusion of roe deer (Capreolus capreolus) by fencing was the most significant treatment required for successful stand conversion. Prior to fencing, deer browsing inhibited the establishment of a new stand.
Since the early eighties air pollution by SO2 and Pb and, to a lesser degree by NOx and NH3, have been significantly reduced in Europe. This was done in part for the protection of forest ecosystems. ...The reductions are reflected in the pollutant impacts and inputs and have been verified through the bioindicator Norway spruce. In contrast, ozone concentrations increased at most of the evaluated measuring locations and trends were calculated based on the results of about 100 stations in Austria and Germany. Despite reduced emissions, large parts of the forest ecosystems are still affected by air-pollution impacts. Negative effects can be assessed using different legal standards and Critical Levels and Critical Loads, respectively: The legal standard for the evaluation of SO2 impact, as used in Austria, is well suited. The provisional European Critical Level for ozone, the AOT40 must, in order to be a meaningful criterion for field applications, be further refined. Continuing the Critical Load concept, the spatial risk of acid depositions in areas of high geomorphic variability were evaluated using the new parameter of 'critical soil depth'. With the help of the newly defined 'lead accumulation index', the accumulation of Pb from air pollution could be evaluated. Air-pollution inputs and the spatial acidification risk is directly related to altitude. Up to altitudes of 1000 m and 1100 m, SO2 impact and acid depositions, respectively were indicated and elevated ozone doses and Pb inputs were observed in the sensitive sub-alpine areas. These results underline the necessity for increased protection of mountain forest ecosystems, among others through a further reduction of emissions or forest-related strategies.
In the framework of this study, nitrogen fluxes on a limestone site are investigated. The major goals are the assessment of the nitrogen status, the estimation of the nitrogen budget and the ...evaluation of the nitrogen saturation. The investigation area, the intensive investigation plot and the research equipment are described.PUBLICATION ABSTRACT
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