2,051 research outputs found
DNA Nanorobotics
This paper presents a molecular mechanics study for new nanorobotic
structures using molecular dynamics (MD) simulations coupled to virtual reality
(VR) techniques. The operator can design and characterize through molecular
dynamics simulation the behavior of bionanorobotic components and structures
through 3-D visualization. The main novelty of the proposed simulations is
based on the mechanical characterization of passive/active robotic devices
based on double stranded DNA molecules. Their use as new DNA-based nanojoint
and nanotweezer are simulated and results discussed.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Fine structure of the dorsal lingual epithelium in Tarentola annularis and Crocodylus niloticus
The present study examined the morphological features, histological and histochemical aspect of the tongue of two reptilian species, Tarentola annularis (family: Gekkonidae) and Crocodylus niloticus (family: Crocodylidea), with different habitats, feeding patterns and behaviours, by light and scanning electron microscope. It was observed, that the bifurcation of the tongue was more visible in Tarentola annularis. Conical and filamentous papillae were observed on the lingual body of Tarentola annularis, while in Crocodylus niloticus both mechanical filiform and gustatory papillae appeared. The lingual mucosa in Tarentola annularis is covered by stratified squamous epithelium and keratinised but in Crocodylus niloticus it is highly folded and more heavily keratinised in the folded region and have a localised thickenings structure resembling taste buds. Mucous glands appeared in Tarentola annularis and compound tubular glands in Crocodylus niloticus. At scanning electron microscopy, abundant microridges and microvilli in both species were exhibited on papillae surface facilitated feeding habits. Histochemically, the tongue of two species is strongly positive for carbohydrate stain but with variable degree with others stains. In conclusion, there is a marked correlation between the structure of the tongue of the present reptilian species, habitats and feeding mechanism of the two species.
On the existence of positive solutions for generalized fractional boundary value problems
The existence of positive solutions is established for boundary value problems defined within generalized Riemann–Liouville and Caputo fractional operators. Our approach is based on utilizing the technique of fixed point theorems. For the sake of converting the proposed problems into integral equations, we construct Green functions and study their properties for three different types of boundary value problems. Examples are presented to demonstrate the validity of theoretical findings.Scopu
Selective Reflection Spectroscopy on the UV Third Resonance Line of Cs : Simultaneous Probing of a van der Waals Atom-Surface Interaction Sensitive to Far IR Couplings and of Interatomic Collisions
We report on the analysis of FM selective reflection experiments on the
6S1/2->8P3/2 transition of Cs at 388 nm, and on the measurement of the surface
van der Waals interaction exerted by a sapphire interface on Cs(8P3/2). Various
improvements in the systematic fitting of the experiments have permitted to
supersede the major difficulty of a severe overlap of the hyperfine components,
originating on the one hand in a relatively small natural structure, and on the
other hand on a large pressure broadening imposed by the high atomic density
needed for the observation of selective reflection on a weak transition. The
strength of the van der Waals surface interaction is evaluated to be 7310
kHz.m3. An evaluation of the pressure shift of the transition is also
provided as a by-product of the measurement. We finally discuss the
significance of an apparent disagreement between the experimental measurement
of the surface interaction, and the theoretical value calculated for an
electromagnetic vacuum at a null temperature. The possible influence of the
thermal excitation of the surface is evoked, because, the dominant
contributions to the vW interaction for Cs(8P3/2) lie in the far infrared
range.Comment: submitted to Laser Physics - issue in the memory of Herbert Walther
Exploring the van der Waals Atom-Surface attraction in the nanometric range
The van der Waals atom-surface attraction, scaling as C3 z-3 for z the
atom-surface distance, is expected to be valid in the distance range 1-1000 nm,
covering 8-10 orders of magnitudes in the interaction energy. A Cs vapour
nanocell allows us to analyze the spectroscopic modifications induced by the
atom-surface attraction on the 6P3/2->6D5/2 transition. The measured C3 value
is found to be independent of the thickness in the explored range 40-130 nm,
and is in agreement with an elementary theoretical prediction. We also discuss
the specific interest of exploring short distances and large interaction
energy.Comment: to appear in Europhysics Letter
Strain and Damage Measurements in Ion Implanted Al_xGa_(1−x)As/GaAs Superlattices
Strain measurements in Al_xGa_(1−x) As/GaAs superlattices have been carried out before and after Si ion implantation. For doses up to 5 × 10^(15) cm^(−2), no atomic intermixing of the sublayers is observed by backscattering spectrometry. However, with x-ray rocking curve measurements, significant changes in the strain profiles are detected for implantations with doses as low as 7 × 10^(12) cm^(−2). Interpretation of the rocking curves suggests that low-dose implantations release strain in the Al_xGa_(1−x) As sublayers. The strain profile recovery of the implanted samples, upon annealing at ∼ 420°C, implies that the damage caused by implantation is largely reversible
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