Preparation and characterization of stable aqueous suspensions of up-converting Er3+/Yb3+-doped LiNbO3 nanocrystals

The preparation of LiNbO3:Er3+/Yb3+ nanocrystals and their up-conversion properties have been studied. It is demonstrated that polyethyleneimine- (PEI) assisted dispersion procedures allow obtaining stable aqueous LiNbO3:Er3+/Yb3+ powder suspensions, with average size particles well below the micron range (100–200 nm) and the isoelectric point of the suspension reaching values well above pH 7. After excitation of Yb3+ ions at a wavelength of 980 nm, the suspensions exhibit efficient, and stable, IR-to-visible (green and red) up-conversion properties, easily observed by the naked eye, very similar to those of the starting crystalline bulk material

Losses of plasmon surface waves on metallic grating

Abstract . Diffraction and absorption losses of plasmon surface waves (PSW) propagating along a metallic grating are investigated numerically as a function of groove depth . A periodicity of diffraction losses is found to exist . The energy flow distribution (EFD) above and inside the grooves is calculated and a similarity between the PSW on shallow and deep gratings is established above the grooves, while inside the grooves of deep gratings totally hidden curls in EFD are found to form . . Introduction Recently it has been discovered [1] that a close connection exists between different types of phenomena on metallic gratings : plasmon surface waves (PSW) excitation, non-Littrow perfect blazing It is well known that a pole of the scattering matrix corresponds to a solution of the homogeneous problem where nM is the complex refractive index of the substrate . For highly conducting metals Re (aP) > 1 and Im (aP) > 0, the latter corresponding to the energy absorbed in the metal as the PSW propagates along the interface . As the periodic modulation is introduced (h ;0), the PSW may be coupled to a propagating diffraction order(s) in the upper medium provided a suitable wavelength to period ratio 2/d is chosen . Radiation losses appear as a consequence of this and Im (aP) grows rather rapidly (for the results presented in figure 1 d=0. 5 µm and 2=0 . 6328 gm)

Functional and structural leaf plasticity determine photosynthetic performances during drought stress and recovery in two platanus orientalis populations from contrasting habitats.

In the context of climatic change, more severe and long-lasting droughts will modify the fitness of plants, with potentially worse consequences on the relict trees. We have investigated the leaf phenotypic (anatomical, physiological and biochemical) plasticity in well-watered, drought- stressed and re-watered plants of two populations of Platanus orientalis, an endangered species in the west of the Mediterranean area. The two populations originated in contrasting climate (drier and warmer, Italy (IT) population; more humid and colder, Bulgaria (BG) population). The IT control plants had thicker leaves, enabling them to maintain higher leaf water content in the dry environment, and more spongy parenchyma, which could improve water conductivity of these plants and may result in easier CO2 diffusion than in BG plants. Control BG plants were also characterized by higher photorespiration and leaf antioxidants compared to IT plants. BG plants responded to drought with greater leaf thickness shrinkage. Drought also caused substantial reduction in photosynthetic parameters of both IT and BG plants. After re-watering, photosynthesis did not fully recover in either of the two populations. However, IT leaves became thicker, while photorespiration in BG plants further increased, perhaps indicating sustained activation of defensive mechanisms. Overall, our hypothesis, that plants with a fragmented habitat (i.e., the IT population) lose phenotypic plasticity but acquire traits allowing better resistance to the climate where they became adapted, remains confirmed

Microwave plasma torch for wound treatment

Abstract Cold atmospheric pressure plasma (CAP) sources have recently been proven to be an effective therapeutic source regarding wound healing. The most preferred and used plasma devices at this moment are the well-known dielectric barrier discharges (DBD) and free jet devices. In this work, we studied a low temperature plasma torch at atmospheric pressure sustained by a travelling electromagnetic wave excited by surfatron type wave launcher coupled to solid state microwave generator. This plasma source allows variation of discharge conditions: geometric parameters (discharge tube inner diameter and thickness), wave power and gas flow velocity which varies the main plasma parameters (length, gas temperature, concentration of charged particles and reactive species, UV and microwave radiation). Appropriate combination of the parameters lead to the low temperature plasma torch obtaining a gas temperature up to 30–37°C, suitable for in vivo treatment of BALB-C mouse models. The purpose of this research is to study the discharge conditions leading to acceleration of wound healing at short treatment times with relatively low gas flow and microwave power</jats:p