38 research outputs found
Full Quantum Analysis of Two-Photon Absorption Using Two-Photon Wavefunction: Comparison with One-Photon Absorption
For dissipation-free photon-photon interaction at the single photon level, we
analyze one-photon transition and two-photon transition induced by photon pairs
in three-level atoms using two-photon wavefunctions. We show that the
two-photon absorption can be substantially enhanced by adjusting the time
correlation of photon pairs. We study two typical cases: Gaussian wavefunction
and rectangular wavefunction. In the latter, we find that under special
conditions one-photon transition is completely suppressed while the high
probability of two-photon transition is maintained.Comment: 6 pages, 4 figure
Recent changes in the abundance of Common Pochard Aythya ferina breeding in Europe
National accounts suggest that the Common Pochard Aythya ferina was an uncommon
breeding bird throughout western Europe before 1850. Extensions to the breeding
range in the late 19th century were potentially aided by the rapid development of
managed fish-ponds in eastern Europe, which provided suitable novel habitat at that
time. Expansion into western Europe followed in subsequent decades. Wetland and
waterbody eutrophication throughout Europe, which likely provided food and cover
for the birds, may have accelerated the rapid expansion from the 1950s until the early
1980s. Widespread declines in the last 30 years, especially in eastern Europe, where
breeding numbers are highest, are possibly linked to intensification and/or
abandonment of freshwater fish farming and changes in water quality. Studies show
that Pochard gain fitness benefits from nesting in Black-headed Gull Chroicocephalus
ridibundus colonies and hence has been affected by major losses of European gull
colonies in the last 30 years. The spread of alien fish species such as the Carp Cyprinus
carpio, which compete with Pochard for food resources, is a problem in the
Mediterranean region. Changing predation pressures (in some cases linked to invasive
alien mammals) are also implicated in some areas. Relatively modest numbers breeding
in the UK, France and the Netherlands have remained stable or increased over the
same recent span of years, confirming that different factors currently affect Pochard
breeding abundance throughout its range. We urgently need better information
relating to key factors affecting Pochard breeding success and abundance, which is
currently showing an unfavourable conservation status throughout much of EuropePeer reviewe
Efeito da bactéria diazotrófica em mudas micropropagadas de abacaxizeiros Cayenne Champac em diferentes substratos
Effects of interface-layers composition and strain distribution on the optical transitions of InAs quantum dots on InP
International audienc
Towards Active Applications: the Virtual Virtual Machine Approach.
With the wide acceptance of distributed computing a rapidly growing number of application domains are emerging, leading to a growing number of ad hoc solutions that are rigid and poorly interoperable. Our response to this situation is a platform for building flexible and interoperable execution environments called the Virtual Virtual Machine. This article presents our approach, the architecture of the VVM and some of its primary applications
Influence of germ cells upon Sertoli cells during continuous low-dose rate gama-irradiation of adult rats
International audienc
Influence of germ cells upon Sertoli cells during continuous low-dose rate gama-irradiation of adult rats
International audienc