Roles of SiH4 and SiF4 in growth and structural changes of poly-Si films

The structural properties of polycrystalline silicon films, prepared by plasma enhanced chemical vapor deposition system, with different flow rates of SiH₄/SiF₄ mixtures at 300 °C were investigated. This study indicates that the low hydrogen coverage on the growing surface, under optimum fluorine radicals, will be leaded to an improvement of crystallized area as compared with case of high hydrogen coverage surface. Moreover, the studies of the role of SiH₄ and SiF₄ radicals show that the SiH₄ radicals are important in the nucleation and growth of grains. However, SiF₄ radicals are effective in the structural change of grain boundaries regions and by this way, in the present system, establish the growth of grains under the dominant 〈1 1 0〉 direction. The stress investigation indicates that addition of high flow rate of SiF₄ in amorphous film, results in the nearly stress free films. Finally, we found that the changes in g-value reflect the changes in the intrinsic compressive and tensile stress in the both polycrystalline and amorphous silicon films.     

Symmetry-Breaking Phenomena in an Optimization Problem for some Nonlinear Elliptic Equation

Let $\Omega$ be a bounded domain in ${\bf R^n}$ with Lipschitz boundary, $\lambda >0,$ and $1\le p \le (n+2)/(n-2)$ if $n\ge 3$ and $1\le p< +\infty$ if $n=1,2$. Let $D$ be a measurable subset of $\Omega$ which belongs to the class $ {\cal C}_{\beta}=\{D\subset \Omega \quad | \quad |D|=\beta\} $ for the prescribed $\beta\in (0, |\Omega|).$ For any $D\in{\cal C}_{\beta}$, it is well known that there exists a unique global minimizer $u\in H^1_0(\Omega)$, which we denote by $u_D$, of the functional \[\quad J_{\Omega,D}(v)=\frac12\int_{\Omega}|\nabla v|^2\, dx+\frac{\lambda}{p+1}\int_{\Omega}|v|^{p+1}\, dx -\int_{\Omega}\chi_Dv\,dx \] on $H^1_0(\Omega)$. We consider the optimization problem $ E_{\beta,\Omega}=\inf_{D\in {\cal C}_{\beta}} J_D(u_D) $ and say that a subset $D^*\in {\cal C}_{\beta}$ which attains $E_{\beta,\Omega}$ is an optimal configuration to this problem. In this paper we show the existence, uniqueness and non-uniqueness, and symmetry-preserving and symmetry-breaking phenomena of the optimal configuration $D^*$ to this optimization problem in various settings.     

Design and synthesis of highly sensitive and selective fluorescein-derived magnesium fluorescent probes and application to intracellular 3D Mg2+ imaging

The role of intracellular magnesium ions is of high interest in the fields of pharmacology and cellular biology. To accomplish the dynamic and three-dimensional imaging of intracellular Mg2+, there is a strong desire for the development of optimized Mg2+ fluorescent probes. In this paper we describe the design, synthesis, and cellular application of the three novel Mg2+ fluorescent probes KMG-101, -103, and -104. The compounds of this series feature a charged beta-diketone as a binding site specific for Mg2+ and a fluorescein residue as the fluorophore that can be excited with an Ar+ laser such as is widely used in confocal scanning microscopy. This molecular design leads to an intensive off-on-type fluorescent response toward Mg2+ ions. The two fluorescent probes KMG-103 and -104 showed suitable dissociation constants (Kd,Mg2+ = 2 mM) and nearly a 10-fold fluorescence enhancement over the intracellular magnesium ion concentration range (0.1-6 mM), allowing high-contrast, sensitive, and selective Mg2+ measurements. For intracellular applications, the membrane-permeable probe KMG-104AM was synthesized and successfully incorporated into PC12 cells. Upon application of the mitochondria uncoupler FCCP to the probe-incorporated cells, the resulting increase in the free magnesium ion concentration could be followed over time. By using a confocal microscope, the intracellular 3D magnesium ion concentration distributions were satisfactorily observed.     

Determination of traces of natural brassinosteroids as dansylaminophenylboronates by liquid chromatography with fluorimetric detection

A microanalytical method for the determination of traces of natural brassinosteroids as their dansylaminophenylboronates by liquid chromatography with fluorimetric detection is described. The boronates are easily prepared by the reaction of brassinosteroids with dansylaminophenylboronic acid (DABA), which was newly synthesized as a precolumn fluorogenic reagent for brassinosteroids. The potential of the method is demonstrated by the separation of a standard brassinosteroid mixture and the analysis of a biologically active fraction sample obtained from an extract of Zea mays L. pollen. The detection limit of the DABA derivative was found to be 25 pg for brassinolide, which is superior to that of the phenanthreneboronate derivative.     

Triethylborane as an efficient promoter for palladium-catalyzed allylation of active methylene compounds with allyl alcohols

Without prior activation of allyl alcohols, allylation of a variety of active methylene compounds with allyl alcohols proceeds smoothly at rt-50°C in the presence of catalytic amounts of Pd(OAc)₂ (1-10 mol%), Et₃B (30-240 mol%), a phosphine ligand (1-20 mol%), and a base (0 to 50-60 mol%).     

Remarkably Selective Ag(+) Extraction and Transport by Thiolariat Ethers

Synthesis and metal binding properties of thiolariat ethers, where a sulfide side chain is introduced into a framework of a crown ether, have been performed. Remarkably high Ag(+) selectivity among heavy metal ions was observed in solvent extraction and transport across a liquid membrane using thiolariat ethers with a 15-crown-5 ring as carriers. Thiolariat ethers with a 12-crown-4 or a 18-crown-6 do not exhibit such a high Ag(+) selectivity. The former binds metal ions weakly, and the latter recognizes Pb(2+) as well as Ag(+). The corresponding oxygen analogs, i.e. lariat ethers, do not show Ag(+) selectivity. The Ag(+) binding strength of the sulfoxide and sulfone analogs is much lower than that of thiolariat ethers. Thiolariat ethers with a benzocrown framework containing a sulfide chain at the 4 position of the benzene nucleus showed very low affinity to Ag(+). Extractability and transport ability using various thiolariat ether derivatives strongly suggested that this high Ag(+) selectivity is a result of the synergistic coordination of the ring oxygen and the sulfur atom of the thiolariat ether. NMR chemical shifts of protons and carbons in the proximity of the sulfur atom of the thiolariat ether were changed significantly in accordance with the synergistic coordination described above. 1:1 Complexation between a thiolariat ether and Ag(+) were supported by a Job plot using the chemical shift of the methylene protons adjacent to the sulfur atom.     

Carbonyl reduction with CaH2 and R3SiCl catalyzed by ZnCl2

Ketones and aldehydes were effectively reduced to the corresponding alcohols (or their silyl ethers) by the reaction with CaH₂ and R₃SiCl in the presence of a catalytic amount of ZnCl₂. In the absence of the carbonyl substrate, the reagent reduced R₃SiCl to the corresponding hydrosilane under mild reaction conditions.