731 research outputs found
Sources and sinks of methane and carbon dioxide exchanges in mountain forest in Equatorial Africa
Іван Франко - публіцист
Проаналізовано соціально-економічну і культурно-освітню публіцистику І. Франка,
зокрема, його ставлення до податкової політики Австро-Угорщини, діяльності
банківської системи, еміграції з Галичини, кооперативного руху, майбутнього
української держави.The article analyses social and economic and cultural and educational publications by Ivan
Franko, as well as his attitude to tax policies in Austro-Hungarian Empire, banking system
activities, emigration from Halychyna, co-operative societies movement, and the future of
Ukraine
Conservation et introduction de lémuriens sur l'îlot Mbouzy (Mayotte)
À Mayotte, l'îlot Mbouzi est un lieu remarquable par son milieu naturel en grande partie préservé, alors qu'il se situe à proximité de la ville principale, Mamoudzou. Il fait l'objet d'une demande de classement en réserve naturelle. Nous pensons utile d'apporter quelques éléments pouvant servir à la réflexion sur l'avenir de cet îlot, et d'établir une sorte d'état des lieux concernant son intérêt biologique. Quelles sont les possibilités d'équilibre à long terme entre les populations animales et végétales, sachant qu'une association (loi de 1901) consacr
Conservation et introduction de lémuriens sur l'îlot Mbouzy (Mayotte)
À Mayotte, l'îlot Mbouzi est un lieu remarquable par son milieu naturel en grande partie préservé, alors qu'il se situe à proximité de la ville principale, Mamoudzou. Il fait l'objet d'une demande de classement en réserve naturelle. Nous pensons utile d'apporter quelques éléments pouvant servir à la réflexion sur l'avenir de cet îlot, et d'établir une sorte d'état des lieux concernant son intérêt biologique. Quelles sont les possibilités d'équilibre à long terme entre les populations animales et végétales, sachant qu'une association (loi de 1901) consacr
Monte Carlo simulation of migration of fusion plasma neutrons - optimization and traps
We recall some of the sensitive points and stages in random walk of neutron, frequent solutions and their consequences on quality and duration of MC neutronic and photonic simulations. We present some unconventional approaches we developed to precisely meet the double paramount MC goal: maximal probing at minimal variance, whence minimum CPU time. Instead of the traditional point observation, enhanced probing is used to limit collected random scatter dispersion. Vector probing by shower (through ”nuclear reaction‑channel” space) and drizzle (improved sampling throughout space involving even the deepest parts, with region fragmentation allowed) drastically reduces the collected variance. By treating analogically close‑collision flux-at-a-point tallies, the unphysical pole discontinuity at-the-detecting-point is avoided - this allows the study of even within-detector collisions. For deep shielding treatment the use of the two-step Cascade Monte Carlo is recommended as it reproduces from physical considerations the mathematical approach. Making sure to distinguish volumetric versus local destructive effects, the latter requiring the use of "statistics of extreme values"
Stability and Electronic Properties of TiO2 Nanostructures With and Without B and N Doping
We address one of the main challenges to TiO2-photocatalysis, namely band gap
narrowing, by combining nanostructural changes with doping. With this aim we
compare TiO2's electronic properties for small 0D clusters, 1D nanorods and
nanotubes, 2D layers, and 3D surface and bulk phases using different
approximations within density functional theory and GW calculations. In
particular, we propose very small (R < 0.5 nm) but surprisingly stable
nanotubes with promising properties. The nanotubes are initially formed from
TiO2 layers with the PtO2 structure, with the smallest (2,2) nanotube relaxing
to a rutile nanorod structure. We find that quantum confinement effects - as
expected - generally lead to a widening of the energy gap. However,
substitutional doping with boron or nitrogen is found to give rise to
(meta-)stable structures and the introduction of dopant and mid-gap states
which effectively reduce the band gap. Boron is seen to always give rise to
n-type doping while depending on the local bonding geometry, nitrogen may give
rise to n-type or p-type doping. For under coordinated TiO2 surface structures
found in clusters, nanorods, nanotubes, layers and surfaces nitrogen gives rise
to acceptor states while for larger clusters and bulk structures donor states
are introduced
Resonant Lifetime of Core-Excited Organic Adsorbates from First Principles
We investigate by first-principles simulations the resonant electron-transfer
lifetime from the excited state of an organic adsorbate to a semiconductor
surface, namely isonicotinic acid on rutile TiO(110). The
molecule-substrate interaction is described using density functional theory,
while the effect of a truly semi-infinite substrate is taken into account by
Green's function techniques. Excitonic effects due to the presence of
core-excited atoms in the molecule are shown to be instrumental to understand
the electron-transfer times measured using the so-called core-hole-clock
technique. In particular, for the isonicotinic acid on TiO(110), we find
that the charge injection from the LUMO is quenched since this state lies
within the substrate band gap. We compute the resonant charge-transfer times
from LUMO+1 and LUMO+2, and systematically investigate the dependence of the
elastic lifetimes of these states on the alignment among adsorbate and
substrate states.Comment: 24 pages, 6 figures, to appear in Journal of Physical Chemistry
Status of the SOLEIL femtosecond X-ray source
http://accelconf.web.cern.ch/AccelConf/FEL2012/papers/wepd04.pdfInternational audienceAn electron bunch slicing setup is presently under construction on the SOLEIL storage ring for delivering 100 fs (rms) long photon pulses to two undulator-based beamlines providing soft (TEMPO) and hard X-rays (CRISTAL). Thanks to the non-zero dispersion function present in all straight sections of the storage ring, the sliced bunches can be easily separated from the core bunches. The modulator is a wiggler composed of 20 periods of 164.4 mm. It produces a magnetic field of 1.8 T at a minimum gap of 14.5 mm. To modulate the kinetic energy of the electrons in the wiggler, a Ti:Sa laser will be used, which produces 50 fs pulses at 800 nm with a repetition rate of 2.5 kHz. The laser beam is splitted into two branches in order to provide 2 mJ to the modulator and 0.5 mJ as pump pulse for the CRISTAL and TEMPO end stations. Focusing optics and beam path, from the laser hutch to the inside of the storage ring tunnel are presently under finalization. In this paper, we will report on the specificities of the SOLEIL setup, the status of its installation and the expected performances
LUNEX5 : A FEL PROJECT TOWARDS THE FIFTH GENERATION IN FRANCE
ISBN978-3-95450-117-5 - http://accelconf.web.cern.ch/AccelConf/FEL2011/papers/tupa09.pdfInternational audienc
Contribution to the understanding of tribological properties of graphite intercalation compounds with metal chloride
Intrinsic tribological properties of lamellar compounds are usually attributed to the presence of van der Waals gaps in their structure through which interlayer interactions are weak. The controlled variation of the distances and interactions between graphene layers by intercalation of electrophilic species in graphite is used in order to explore more deeply the friction reduction properties of low-dimensional compounds. Three graphite intercalation compounds with antimony pentachloride, iron trichloride and aluminium trichloride are studied. Their tribological properties are correlated to their structural parameters, and the interlayer interactions are deduced from ab initio bands structure calculations
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