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[en] Processes of thermal dehydration of Ln2(Cr2O7)3x10H2O where Ln=Sm-Er were studied by the methods of differential thermal and thermogravimetric analyses. It was established that dichromate decahydrates of the mentioned rare earths form on heating a series of intermediate forms: Sm-Gd dichromates form penta-, tetra-, tri- and monhydrates; Dy dichromate forms penta-, tetra-, and monohydrates; Ho and Er dichromates - only pentahydrates. The complete dehydration takes place at temperatures of above 240eg C
[en] A key issue concerning environmental impacts from cooling tower operation is the interception of drift by vegetation and the efficiency of plants in retaining the residue scavenged from the atmosphere. Chromated drift water, typical of the cooling towers of the Department of Energy's uranium enrichment facilities at Oak Ridge, Tennessee, was prepared using radio-labelled chromium. A portable aerosol generator was used to produce a spectrum of droplets with diameters (100 to 1300 μ) characteristic of cooling towers using state-of-the-art drift eliminators. Efficiency of interception by foliage varied according to leaf morphology with yellow poplar seedlings intercepting 72% of the deposition mass in contrast to 45% by loblolly pine and 24% by fescue grass. Retention patterns of intercepted deposition consisted of a short-time component (0 to 3 days) and a long-time component (3 to 63 days). Retention times, estimated from the regression equation of the long component, indicated that drift contamination from any deposition event may persist from between 8 and 12 weeks. In field situations adjacent to cooling towers, the average annual concentration of drift on vegetation at any distance remains relatively constant, with losses from weathering being compensated by chronic deposition
[en] Spectroscopic constants and potential energy curves of 21 electronic states of CrH are obtained using the all-electron complete active space multiconfiguration self-consistent field (CASMCSCF) followed by first-order configuration interaction (FOCI) and full second-order CI (SOCI) and multireference CI including Rydberg states calculations. The ground state of CrH is found to be of 6 summation + symmetry with re = 1.690 angstrom, ωe = 1592 cm-1, De = 2.11 eV, and μe = 3.864 D at the SOCI level. Several optical transitions for CrH are predicted. The computations support the reassignment of the state perturbing the A-X system to 4 summation + suggested by Ram et al. The computed spectroscopic constants for the A, X, and a 4 summation + state are in excellent agreement with the experimental values reported by Ram et al
[en] We present nulling interferometric observations of six nearby main-sequence stars (α CrB, α Lyr, β Leo, γ Ser, ε Eri, and ζ Lep). None of the stars show evidence for a positive detection of warm debris in the habitable zone of the systems. Using a scaled up model of solar zodiacal emission, the 3σ upper limits on dust density range from 220 to 104 Zody (1 Zody = the density of our own solar zodiacal cloud) depending on the particular star, corresponding to mass limits of 10-7 to 10-5 M + of micron-sized dust. These limits contrast with the presence of dust at greater separations from the star, implying a clearing in dust in the inner system. This suggests that the inner circumstellar environment around nearby intermediate-mass main-sequence stars more than several tens of millions of years old are generally cleared of dusty debris. Finally, the well studied nature of the debris disks around Vega, ε Eridani, and ζ Leporis allows us to place these 10 μm nulling observations in the context of previous studies to determine the physical processes responsible for shaping the debris disk in these particular systems.