96 research outputs found
Resonant Auger spectroscopy at the L2,3 shake-up thresholds as a probe of electron correlation effects in nickel
The excitation energy dependence of the three-hole satellites in the
L3-M4,5M4,5 and L2-M4,5M4,5 Auger spectra of nickel metal has been measured
using synchrotron radiation. The satellite behavior in the non-radiative
emission spectra at the L3 and L2 thresholds is compared and the influence of
the Coster-Kronig channel explored. The three-hole satellite intensity at the
L3 Auger emission line reveals a peak structure at 5 eV above the L3 threshold
attributed to resonant processes at the 2p53d9 shake-up threshold. This is
discussed in connection with the 6-eV feature in the x-ray absorption spectrum.Comment: 8 pages, 4 figures; http://prb.aps.org/abstract/PRB/v58/i7/p3677_
Oldest known pantherine skull and evolution of the tiger
The tiger is one of the most iconic extant animals, and its origin and evolution have been intensely debated. Fossils attributable to extant pantherine species-lineages are less than 2 MYA and the earliest tiger fossils are from the Calabrian, Lower Pleistocene. Molecular studies predict a much younger age for the divergence of modern tiger subspecies at <100 KYA, although their cranial morphology is readily distinguishable, indicating that early Pleistocene tigers would likely have differed markedly anatomically from extant tigers. Such inferences are hampered by the fact that well-known fossil tiger material is middle to late Pleistocene in age. Here we describe a new species of pantherine cat from Longdan, Gansu Province, China, Panthera zdanskyi sp. nov. With an estimated age of 2.55–2.16 MYA it represents the oldest complete skull of a pantherine cat hitherto found. Although smaller, it appears morphologically to be surprisingly similar to modern tigers considering its age. Morphological, morphometric, and cladistic analyses are congruent in confirming its very close affinity to the tiger, and it may be regarded as the most primitive species of the tiger lineage, demonstrating the first unequivocal presence of a modern pantherine species-lineage in the basal stage of the Pleistocene (Gelasian; traditionally considered to be Late Pliocene). This find supports a north-central Chinese origin of the tiger lineage, and demonstrates that various parts of the cranium, mandible, and dentition evolved at different rates. An increase in size and a reduction in the relative size of parts of the dentition appear to have been prominent features of tiger evolution, whereas the distinctive cranial morphology of modern tigers was established very early in their evolutionary history. The evolutionary trend of increasing size in the tiger lineage is likely coupled to the evolution of its primary prey species
Hydrogen sensors based on electrophoretically deposited Pd nanoparticles onto InP
Electrophoretic deposition of palladium nanoparticles prepared by the reverse micelle technique onto InP substrates is addressed. We demonstrate that the substrate pre-deposition treatment and the deposition conditions can extensively influence the morphology of the deposited palladium nanoparticle films. Schottky diodes based on these films show notably high values of the barrier height and of the rectification ratio giving evidence of a small degree of the Fermi level pinning. Moreover, electrical characteristics of these diodes are exceptionally sensitive to the exposure to gas mixtures with small hydrogen content
Hydrogen Sensors Made on InP or GaN with Electrophoretically Deposited Pd or Pt Nanoparticles
High quality Schottky diodes were prepared by printing colloidal graphite on the polished wafers of n-type InP or n-type GaN. The wafers were earlier sparsely covered with palladium or platinum nanoparticles by electrophoresis from prepared colloid solutions in isooctane. Deposited contacts and nanoparticles were observed by scanning electron mictroscopy. Current voltage characteristics of the Schottky diodes showed high rectification ratios and the barrier heights close to the value of vacuum-level-alignment of the Schottky-Mott limit. The sensitivity to hydrogen of the diodes was measured in the flow of hydrogen/nitrogen mixtures of various hydrogen concentrations in the range from 1 ppm to 1000 ppm. The estimated detection limits of the diodes were in the sub-ppm range. The diodes represent orders-of-magnitude improvement over the best hydrogen sensors reported previously
Hydrogen Sensors Made on InP or GaN with Electrophoretically Deposited Pd or Pt Nanoparticles
High quality Schottky diodes were prepared by printing colloidal graphite on the polished wafers of n-type InP or n-type GaN. The wafers were earlier sparsely covered with palladium or platinum nanoparticles by electrophoresis from prepared colloid solutions in isooctane. Deposited contacts and nanoparticles were observed by scanning electron mictroscopy. Current voltage characteristics of the Schottky diodes showed high rectification ratios and the barrier heights close to the value of vacuum-level-alignment of the Schottky-Mott limit. The sensitivity to hydrogen of the diodes was measured in the flow of hydrogen/nitrogen mixtures of various hydrogen concentrations in the range from 1 ppm to 1000 ppm. The estimated detection limits of the diodes were in the sub-ppm range. The diodes represent orders-of-magnitude improvement over the best hydrogen sensors reported previously
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