Magnetic and relaxation properties of vanadium(iv) complexes: an integrated H-1 relaxometric, EPR and computational study

We report a detailed study of the magnetic and relaxation properties of a series of oxovanadium(IV) complexes comprising the aqua ion [VO(H2O)5]2+ and [VO(ox)2]2- (ox = oxalate), [VO(nta)]- (nta = nitrilotriacetate), [VO(dtpa)] 3- (dtpa = diethylenetriaminepentaacetate) and [VO(acac)2] (acac = acetylacetonato) in solution. The complexes were characterized using continuous wave (X-band) and pulsed (Q-band) EPR measurements and 1H nuclear magnetic relaxation dispersion (NMRD) studies in the 0.01-120 MHz 1H Larmor frequency range. The 51V A-tensor parameters obtained from the analysis of EPR spectra are in good agreement with those obtained using theoretical calculations at the DFT and coupled-cluster levels (DLPNO-CCSD), while g-tensors were obtained with CASSCF/NEVPT2 calculations. EPR measurements reveal significant differences in the electronic Te1 and Te m relaxation times, with [VO(acac)2] showing a markedly different behaviour due to the trans coordination geometry. The NMRD profiles measured at different temperatures have contributions from both the outer- and inner-sphere mechanisms, with the latter showing contributions from the dipolar and scalar mechanisms. The rotational correlation times ( tR) obtained from the fitting of NMRD and EPR data are in good mutual agreement. The scalar mechanism depends on the hyperfine coupling constants of the coordinated water molecule Haiso, which were obtained from the fitting of the NMRD profiles and DFT calculations. Finally, the analysis of the data provided information on the exchange rate of coordinated water molecules, which display mean residence times of similar to 7-17 mu s at 298 K

The European Photon Imaging Camera on XMM-Newton: The MOS Cameras

The EPIC focal plane imaging spectrometers on XMM-Newton use CCDs to record the images and spectra of celestial X-ray sources focused by the three X-ray mirrors. There is one camera at the focus of each mirror; two of the cameras contain seven MOS CCDs, while the third uses twelve PN CCDs, defining a circular field of view of 30 arcmin diameter in each case. The CCDs were specially developed for EPIC, and combine high quality imaging with spectral resolution close to the Fano limit. A filter wheel carrying three kinds of X-ray transparent light blocking filter, a fully closed, and a fully open position, is fitted to each EPIC instrument. The CCDs are cooled passively and are under full closed loop thermal control. A radio-active source is fitted for internal calibration. Data are processed on-board to save telemetry by removing cosmic ray tracks, and generating X-ray event files; a variety of different instrument modes are available to increase the dynamic range of the instrument and to enable fast timing. The instruments were calibrated using laboratory X-ray beams, and synchrotron generated monochromatic X-ray beams before launch; in-orbit calibration makes use of a variety of celestial X-ray targets. The current calibration is better than 10% over the entire energy range of 0.2 to 10 keV. All three instruments survived launch and are performing nominally in orbit. In particular full field-of-view coverage is available, all electronic modes work, and the energy resolution is close to pre-launch values. Radiation damage is well within pre-launch predictions and does not yet impact on the energy resolution. The scientific results from EPIC amply fulfil pre-launch expectations.Comment: 9 pages, 11 figures, accepted for publication in the A&A Special Issue on XMM-Newto

Photocatalytic generation of H2 by photoreforming of organics in aqueous suspension of Nb2O5/C3N4 composites

Bare and composite materials based on C3N4 and Nb2O5 have been used as photocatalysts for the photoreforming of aqueous solutions of oxygenated compounds. Both Nb2O5 and Nb2O5/C3N4 composites have been prepared by hydrothermal synthesis and all of them were physical-chemically characterized. In this work two different carbon nitride species i.e. graphitic (g-C3N4) or thermo-etched (TE-C3N4) were used both alone or coupled with Nb2O5. The photo-reforming activity has been measured under UV irradiation by using the semiconductors in the presence of Pt as co-catalysts and, in the case of the best material, it was, for the first time, measured and compared also under natural solar irradiation. It was found that the highest activity was achieved with the Nb2O5/TE-C3N4 10:1-200 photocatalyst for which the hydrogen formation under UV irradiation resulted of ca. 46 mmol·h-1·g-1 with an apparent quantum yield of ca. 14 %. The maximum solar hydrogen productivity was 1.8 mmol·kJ-1·g-1 or 0.81 mmol·h-1·g-1

Fly iDNA suggests strict reliance of the causative agent of sylvatic anthrax on rainforest ecosystems

Abstract Metabarcoding of invertebrate‐derived DNA (iDNA) is increasingly used to describe vertebrate diversity in terrestrial ecosystems. Fly iDNA has also shown potential as a tool for detecting pathogens. Combining these approaches makes fly iDNA a promising tool for understanding the ecology and distribution of novel pathogens or emerging infectious diseases. Here, we use fly iDNA to explore the geographic distribution of Bacillus cereus biovar anthracis (Bcbva) along a gradient from the forest within Taï National Park, Côte d'Ivoire, out to surrounding villages. We tested fly pools (N = 100 pools of 5 flies) collected in the forest (N = 25 pools), along the forest edge (N = 50 pools), and near surrounding villages (N = 25 pools) for Bcbva. Using the same iDNA, we sought to reconstruct fly and mammal communities with metabarcoding, with the aim of investigating potential links with Bcbva detection. We detected Bcbva in 5/100 fly pools and positivity varied significantly across the habitat types (forest = 4/25, edge = 1/50, village = 0/25). It was possible to culture Bcbva from all positive fly pools, confirming their positivity, while sequencing of their whole genomes revealed a considerable portion of known genomic diversity for this pathogen. iDNA generated data about the mammal and fly communities in these habitats, revealing the highest mammal diversity in the forest and considerable changes in fly community composition along the gradient. Bcbva host range estimates from fly iDNA were largely identical to the results of long‐term carcass monitoring efforts in the region. We show that fly iDNA can generate data on the geographic distribution and host range of a pathogen at kilometer scales, as well as reveal the pathogen's phylogenetic diversity. Our results highlight the power of fly iDNA for mammal biomonitoring and pathogen surveillance