gas phase vibrational spectroscopy of V3O6-8+

We present gas phase vibrational spectra of the trinuclear vanadium oxide cations V3O6+·He1–4, V3O7+·Ar0,1, and V3O8+·Ar0,2 between 350 and 1200 cm−1. Cluster structures are assigned based on a comparison of the experimental and simulated IR spectra. The latter are derived from B3LYP/TZVP calculations on energetically low-lying isomers identified in a rigorous search of the respective configurational space, using higher level calculations when necessary. V3O7+ has a cage-like structure of C3v symmetry. Removal or addition of an O-atom results in a substantial increase in the number of energetically low-lying structural isomers. V3O8+ also exhibits the cage motif, but with an O2 unit replacing one of the vanadyl oxygen atoms. A chain isomer is found to be most stable for V3O6+. The binding of the rare gas atoms to V3O6–8+ clusters is found to be strong, up to 55 kJ/mol for Ar, and markedly isomer-dependent, resulting in two interesting effects. First, for V3O7+·Ar and V3O8+·Ar an energetic reordering of the isomers compared to the bare ion is observed, making the ring motif the most stable one. Second, different isomers bind different number of rare gas atoms. We demonstrate how both effects can be exploited to isolate and assign the contributions from multiple isomers to the vibrational spectrum. The present results exemplify the structural variability of vanadium oxide clusters, in particular, the sensitivity of their structure on small perturbations in their environment

Backup über das Netzwerk – neue Systeme

Der CMS betreibt einen Backupservice auf Basis des Tivoli Storage Managers. Die Infrastruktur wurde im Jahr 2009 erneuert und wird im Folgenden vorgestellt

Building Service Platforms using OpenStack and CEPH

For providing Infrastructure as a Service to the institutes, OpenStack was selected as a platform at the Computer and Media Service of Humboldt University. CEPH was chosen as the storage backend within this platform. The paper describes the project and first results. An overview to OpenStack is given and the results of initial CEPH performance tests are shown. The technical setup is depicted. Moving from traditional data center management to IaaS involves organizational changes as well as changes to service and business models. The first findings of this process are discussed and an outlook is providedPeer Reviewe

Comparison of anticoagulation strategies for veno-venous ECMO support in acute respiratory failure

BACKGROUND Extracorporeal membrane oxygenation (ECMO) support in acute respiratory failure may be lifesaving, but bleeding and thromboembolic complications are common. The optimal anticoagulation strategy balancing these factors remains to be determined. This retrospective study compared two institutional anticoagulation management strategies focussing on oxygenator changes and both bleeding and thromboembolic events. METHODS We conducted a retrospective observational cohort study between 04/2015 and 02/2020 in two ECMO referral centres in Germany in patients receiving veno-venous (VV)-ECMO support for acute respiratory failure for > 24 h. One centre routinely applied low-dose heparinization aiming for a partial thromboplastin time (PTT) of 35-40 s and the other routinely used a high-dose therapeutic heparinization strategy aiming for an activated clotting time (ACT) of 140-180 s. We assessed number of and time to ECMO oxygenator changes, 15-day freedom from oxygenator change, major bleeding events, thromboembolic events, 30-day ICU mortality, activated clotting time and partial thromboplastin time and administration of blood products. Primary outcome was the occurrence of oxygenator changes depending on heparinization strategy; main secondary outcomes were the occurrence of severe bleeding events and occurrence of thromboembolic events. The transfusion strategy was more liberal in the low-dose centre. RESULTS Of 375 screened patients receiving VV-ECMO support, 218 were included in the analysis (117 high-dose group; 101 low-dose group). Disease severity measured by SAPS II score was 46 (IQR 36-57) versus 47 (IQR 37-55) and ECMO runtime was 8 (IQR 5-12) versus 11 (IQR 7-17) days (P = 0.003). There were 14 oxygenator changes in the high-dose group versus 48 in the low-dose group. Freedom from oxygenator change at 15 days was 73% versus 55% (adjusted HR 3.34 [95% confidence interval 1.2-9.4]; P = 0.023). Severe bleeding events occurred in 23 (19.7%) versus 14 (13.9%) patients (P = 0.256) and thromboembolic events occurred in 8 (6.8%) versus 19 (19%) patients (P = 0.007). Mortality at 30 days was 33.3% versus 30.7% (P = 0.11). CONCLUSIONS In this retrospective study, ECMO management with high-dose heparinization was associated with lower rates of oxygenator changes and thromboembolic events when compared to a low-dose heparinization strategy. Prospective, randomized trials are needed to determine the optimal anticoagulation strategy in patients receiving ECMO support

Vibrational spectra of alumina- and silica-supported vanadia revisited: An experimental and theoretical model catalyst study

Oxide-supported vanadia particles were prepared via evaporation of vanadium metal in an oxygen ambient. As support oxides, we have employed thin, well-ordered alumina and silica films grown on top of NiAl(110) and Mo(112) surfaces. According to our analysis, the vanadia particles exhibit very similar morphology on both supports but differ in the extent of particle–support interactions. It is shown that these differences in the vanadia–support interface region strongly affect the CO adsorption behavior of the particles. The measured vibrational spectra of the model systems are interpreted on the basis of DFT calculations for model compounds and surface models for both the vanadia/silica and the vanadia/alumina system. The combined information is then compared with Raman spectra of real catalytic materials such as vanadia supported over -Al2O3 and mesoporous SiO2 (MCM-41) taken at different laser wavelengths. A consistent interpretation is developed, which shows that the accepted interpretation of vibrational spectra from vanadia catalysts must be revised

Infrared spectroscopic characterization of the oxidative dehydrogenation of propane by v4o10+

Contains fulltext : 99085.pdf (preprint version ) (Open Access