Polyimide surface modification by RF plasma for biocide attachment

This article has been retracted.     

Explicit min–max polynomials on the disc

Denote by ${\Pi }_{n+m?1}^2?\{{\sum }_{0\le i+j\le n+m?1}{c}_{i,j}{x}^i{y}^j:c_{i,j}\in \mathbb{R}\}$ the space of polynomials of two variables with real coefficients of total degree less than or equal to $n+m?1$. Let $b_0,b_1,\dots ,b_l\in \mathbb{R}$ be given. For $n,m\in \mathbb{N},n\ge l+1$ we look for the polynomial $b_0{x}^n{y}^m+b_1{x}^{n?1}{y}^{m+1}+?+b_l{x}^{n?l}{y}^{m+l}+q(x,y),q(x,y)\in {\Pi }_{n+m?1}^2$, which has least maximum norm on the disc and call such a polynomial a min–max polynomial. First we introduce the polynomial $2P_{n,m}(x,y)=x{G}_{n?1,m}(x,y)+y{G}_{n,m?1}(x,y)=2x^n{y}^m+q(x,y)$ and $q(x,y)\in {\Pi }_{n+m?1}^2$, where $G_{n,m}(x,y)?1/2^{n+m}(U_n\left(x\right)U_m\left(y\right)+U_{n?2}\left(x\right)U_{m?2}\left(y\right))$, and show that it is a min–max polynomial on the disc. Then we give a sufficient condition on the coefficients $b_j,j=0,\dots ,l,l$ fixed, such that for every $n,m\in \mathbb{N},n\ge l+1$, the linear combination ${\sum }_{\nu =0}^l{b}_{\nu }{P}_{n?\nu ,m+\nu }(x,y)$ is a min–max polynomial. In fact the more general case, when the coefficients $b_j$ and $l$ are allowed to depend on $n$ and $m$, is considered. So far, up to very special cases, min–max polynomials are known only for $x^n{y}^m$,$n,m\in {\mathbb{N}}_0$.     

An allelochemical from Myrica gale with strong phytotoxic activity against highly invasive Fallopia x bohemica taxa

We report the identification of the allelochemical 3-(1-oxo-3-phenylpropyl)-1,1,5-trimethylcyclo-hexane-2,4,6-trione, known as myrigalone A, from the fruits and leaves of Myrica gale. The structure of the compound was confirmed by high-resolution techniques (UV, MS and NMR analysis). The compound is phytotoxic towards classical plant species used for allelochemical assays and also against Fallopia x bohemica, a highly invasive plant. Application of either powdered dry leaves or dry fruits of M. gale also showed in vitro phytotoxic activity. We hypothesize that M. gale could be used as a green allelopathic shield to control Fallopia x bohemica invasion, in addition to its potential use as an environmentally friendly herbicide.     

Investigation of thermal decomposition of yttrium–aluminum-based precursors for YAG phosphors

Three types of precursors were prepared using the wet-chemical synthesis route, starting from yttrium?Ceuropium?Caluminum nitrate solution and different precipitating agents (urea, oxalic acid, and ammonium carbonate). The precursors were fired at 1200?°C in nitrogen atmosphere in order to obtain europium-doped yttrium aluminate Y₃Al₅O₁₂:Eu³⁺ phosphor with garnet structure (YAG:Eu). The processes involved in the thermal decomposition of precursors and their composition were put in evidence using thermal analysis (TG?CDTA) and FT-IR spectroscopy. The GA?CDTA curves possess typical features for basic-oxalate, -nitrate, and -carbonates as formed with oxalic acid, urea, and ammonium carbonate, respectively. Correlation between the thermal decomposition steps, mass loss, and composition of gases evolved during the thermal treatment was established using TG?CDTA?CFT-IR coupling. It was found that the different composition of precursors reflects on the luminescent characteristics of the corresponding phosphors. Urea and ammonium carbonate lead to the formation of YAG type phosphors, with garnet structure and specific red emission. As for the oxalic acid, this precipitating agent generates a non-homogeneous powder that contains yttrium oxide as impurity phase. This phosphor is a mixture of Y₂O₃:Eu³⁺, Y₄Al₂O₉:Eu³⁺, and Y₃Al₅O₁₂:Eu³⁺ that explain the relative higher emission intensity.     

Growth and structural characterization of YMnO3 thin films grown by pulsed liquid injection MOCVD on Si and SrTiO3 substrates

Optimum parameters for the growing of YMnO₃ films by pulsed liquid injection metalorganic chemical vapor deposition have been studied. Si substrates were used for the optimization of the deposition process. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that polycrystalline single phase YMnO₃ films can be obtained for an optimal ratio of Y and Mn on the injected solution and either amorphous, metastable orthorhombic, and/or hexagonal YMnO₃ phases can be obtained depending on the deposition temperature and precursors ratio. In a second stage, YMnO₃ films were grown on SrTiO₃ substrates. Pure epitaxial orthorhombic YMnO₃ phase was confirmed by XRD. The films microstructure, characterized by scanning electron microscopy and TEM, shows a columnar growth. Each columnar grain grows epitaxially with three possible orientations.     

Stability of Strongly Gauduchon Manifolds Under Modifications

In our previous works on deformation limits of projective and Moishezon manifolds, we introduced and made crucial use of the notion of strongly Gauduchon metrics as a reinforcement of the earlier notion of Gauduchon metrics. Using direct and inverse images of closed positive currents of type (1,1) and regularization, we now show that compact complex manifolds carrying strongly Gauduchon metrics are stable under modifications. This stability property, known to fail for compact Kähler manifolds, mirrors the modification stability of balanced manifolds proved by Alessandrini and Bassanelli.     

Development of systems for the laser synthesis of nanoparticles starting from liquid precursors

The laser synthesis of nanoparticles starting from liquid precursors is particularly suitable as synthesis technique for obtaining nanoparticles. In the present work the laser pyrolysis is performed in a novel setup where the liquid precursor is brought with the aid of an original evaporator system to temperatures in excess of the boiling point and is finally fed into the reactor under the form of heated vapors.The process occurs in the gas phase and ensures the avoidance of the condensation. The temperature control system allows for the maintaining of the overall system temperature below the decomposition temperature and above the boiling. Temperatures up to 500 °C are assured for the mixed precursors. The control of the amount of the active substances is performed upstream, in the liquid phase. The set-up is able to offer safety conditions at the synthesis of substances with high toxicity. This experimental set-up was proposed in order to synthesize TiO₂ nanoparticles from TTIP because its boiling temperature is relatively high (239 °C grades). Different analytical techniques such as EDX, TEM, XRD and HRTEM were used in order to evaluate the structural characteristics of the produced nanopowders.     

Study on the retention of uranyl ions on modified clays with titanium oxide

Four analytical techniques—instrumental neutron activation analysis (INAA), inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscope energy dispersive X-ray fluorescence (SEM-EDXRF), and proton induced X-ray emission (PIXE)—were evaluated in the context of air pollution biomonitoring studies. Three combinations INAA/ICP-MS, ICP-MS/PIXE and ICP-MS/SEM-EDXRF are illustrated by experimental results.     

Structure and orbital ordering of ultrathin LaVO3 probed by atomic resolution electron microscopy and Raman spectroscopy

Orbital ordering has been less investigated in epitaxial thin films, due to the difficulty to evidence directly the occurrence of this phenomenon in thin film samples. Atomic resolution electron microscopy enabled us to observe the structural details of the ultrathin LaVO₃ films. The transition to orbital ordering of epitaxial layers as thin as ≈4 nm was probed by temperature‐dependent Raman scattering spectroscopy of multilayer samples. From the occurrence and temperature dependence of the 700 cm^–1 Raman active mode it can be inferred that the structural phase transition associated with orbital ordering takes place in ultrathin LaVO₃ films at about 130 K.