2,971 research outputs found
Stability of an oscillating tip in Non-Contact Atomic Force Microscopy: theoretical and numerical investigations
This paper is a theoretical and a numerical investigation of the stability of
a tip-cantilever system used in Non-Contact Atomic Force Microscopy (NC-AFM)
when it oscillates close to a surface. No additional dissipative force is
considered. The theoretical approach is based on a variationnal method
exploiting a coarse grained operation that gives the temporal dependence of the
nonlinear coupled equations of motion in amplitude and phase of the oscillator.
Stability criterions for the resonance peak are deduced and predict a stable
behavior of the oscillator in the vicinity of the resonance. The numerical
approach is based on results obtained with a virtual NC-AFM developped in our
group. The effect of the size of the stable domain in phase is investigated.
These results are in particularly good agreement with the theoretical
predictions. Also they show the influence of the phase shifter in the feedback
loop and the way it can affect the damping signal
Influence of noncontact dissipation in the tapping mode: Attempt to extract quantitative information on the surface properties with the local force probe method
In the Tapping mode, a variation of the oscillation amplitude and phase as a
function of the tip sample distance is the necessary measurement to access
quantitatively to the properties of the surface. In the present work, we give a
systematic comparison between experimental data recorded on two surfaces, phase
and amplitude, and theoretical curves. With an interaction between the tip and
the surface taking into account an attractive and a repulsive term, the
analytical approach is unable to properly describe the relationship between the
phase variation and the oscillation amplitude variation. When an additional
dissipation term is involved, due to the attractive interaction between the tip
and the surface, the model gives a good agreement with the recorded data.
Particularly, the trends in the phase variations related to the noncontact
situations have been found to be amenable to an analysis based upon a simple
viscoelastic behavior of the surface
Trophic relationships between palms and bruchids (Coleoptera: Bruchidae: Pachymerini) in Peruvian Amazonia
Qualitative and quantitative host plant data are provided for palm bruchids in a part of Amazonia from where previously few or no data were available. The host range and geographical distribution of several species are extended. The role of fruit structure on susceptibility to bruchid infestation and fruit maturity on oviposition site selection is discussed. The importance of mesologic conditions, particularly in areas subjected to flooding, on population dynamics of palm seed beetles is stressed. A specialist parasitoid of Caryoborus serripes, which is a specific predator of Astrocaryum nuts, is recorded for the first time; a trichogrammatid parasitic on the eggs of the same bruchid is also identified
Trophic relationships between palms and bruchids (Coleoptera: Bruchidae: Pachymerini) in Peruvian Amazonia
Qualitative and quantitative host plant data are provided for palm bruchids in a part of Amazonia from where previously few or no data were available. The host range and geographical distribution of several species are extended. The role of fruit structure on susceptibility to bruchid infestation and fruit maturity on oviposition site selection is discussed. The importance of mesologic conditions, particularly in areas subjected to flooding, on population dynamics of palm seed beetles is stressed. A specialist parasitoid of Caryoborus serripes, which is a specific predator of Astrocaryum nuts, is recorded for the first time; a trichogrammatid parasitic on the eggs of the same bruchid is also identified
Cochonilhas que vivem sobre o camu camu, (Myrciaria dubia H.B.K. Myrtaceae) no Estado do Pará.
Insetos visitantes e polinizadores em palmeiras nativas da AmazĂ´nia.
bitstream/item/57864/1/Oriental-PA1.pd
Entomofauna fitĂłfaga em palmeiras nativas da AmazĂ´nia.
bitstream/item/52974/1/PesquisaAnd020001.pd
Optical and Electrical Properties of SnO 2
Tin oxide films were deposited on glass substrates by reactive and non reactive r.f. sputtering using
different types of targets corresponding to various Sn/F atomic ratio: hot pressed Sn–SnF2 or
SnO2–SnF2 mixtures, ceramics obtained by casting either an aqueous SnO2–SnF2 slurry or a suspension
of tin oxide in molten tin fluoride. The samples were prepared in oxygen-argon gas mixtures in which
the oxygen concentration was varied from 0 mole % up to 30 mole% depending on the target. The
optical and electrical properties of the obtained thin films have been studied and compared to those of
the films obtained by spray technique
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