Spatial Distribution Of Oxygen In Luminescent Porous Silicon Films

Transmission electron microscopy associated with electron energy loss spectroscopy imaging was used to determine structural spatial variations and compositional variation in heavily doped (0.006 Ω cm) and lightly doped (0.4 Ω cm) luminescent porous silicon films.64151986198

A common and unstable copy number variant is associated with differences in Glo1 expression and anxiety-like behavior

Glyoxalase 1 (Glo1) has been implicated in anxiety-like behavior in mice and in multiple psychiatric diseases in humans. We used mouse Affymetrix exon arrays to detect copy number variants (CNV) among inbred mouse strains and thereby identified a approximately 475 kb tandem duplication on chromosome 17 that includes Glo1 (30,174,390-30,651,226 Mb; mouse genome build 36). We developed a PCR-based strategy and used it to detect this duplication in 23 of 71 inbred strains tested, and in various outbred and wild-caught mice. Presence of the duplication is associated with a cis-acting expression QTL for Glo1 (LOD>30) in BXD recombinant inbred strains. However, evidence for an eQTL for Glo1 was not obtained when we analyzed single SNPs or 3-SNP haplotypes in a panel of 27 inbred strains. We conclude that association analysis in the inbred strain panel failed to detect an eQTL because the duplication was present on multiple highly divergent haplotypes. Furthermore, we suggest that non-allelic homologous recombination has led to multiple reversions to the non-duplicated state among inbred strains. We show associations between multiple duplication-containing haplotypes, Glo1 expression and anxiety-like behavior in both inbred strain panels and outbred CD-1 mice. Our findings provide a molecular basis for differential expression of Glo1 and further implicate Glo1 in anxiety-like behavior. More broadly, these results identify problems with commonly employed tests for association in inbred strains when CNVs are present. Finally, these data provide an example of biologically significant phenotypic variability in model organisms that can be attributed to CNVs.These studies were funded by MH070933, MH79103 and MH020065

Isolated Submicrometer Filaments Formed By Silicon Anodization In Hf Solutions

Porous silicon nanocolumn formation is the result of the merging of nearest-neighbor nanopores. In this paper we describe isolated submicrometer filaments formed by silicon anodization in HF solutions. The merging of nearest-neighbor pores may result in the formation of isolated submicrometer silicon filaments. The filament formation is explained by a model which takes into account filament wall layer passivation by hydrogen atoms. The formation of one isolated wire structure is a consequence of the pore diameter enlargement resulting from the available area decrease with etching time.1435L100L102Uhlir, A., (1956) Bell Sys. Tech. J., 35, p. 333Canham, L.T., (1990) Appl. Phys. Lett., 57, p. 1046Beale, M.I.J., Benjamin, J.D., Uren, M.J., Chew, N.G., Cullis, A.G., (1985) J. Cryst. Growth, 73, p. 622Earwaker, L.G., Farr, J.P.G., Grzeszezyk, P.E., Sturland, I., Keen, J.M., (1985) Nucl. Instrum. Methods Phys. Rev., B9, p. 317Bomchil, G., Halimaoui, A., Herino, R., (1988) Microelectron. Eng., 8, p. 293Smith, R.L., Chuang, S.F., Collins, S.D., (1988) J. Electron. Mater., 17, p. 533Memming, R., Schwandt, G., (1966) Surf. Sci., 4, p. 109Cullis, A.G., Canham, L.T., (1991) Nature, 353, p. 335Teschke, O., Alvarez, F., Tessler, L.R., Kleinke, M.U., (1993) Appl. Phys. Lett., 63, p. 1927Teschke, O., Galembeck, F., Gonçalves, M.C., Davanzo, C.U., (1994) Appl. Phys. Lett., 64, p. 3590Teschke, O., Gonçalves, M.C., Galembeck, F., (1993) Appl. Phys. Lett., 63, p. 1348Scares, D.M., Dos Santos, M.C., Teschke, O., (1995) Chem. Phys. Lett., 242, p. 202Teschke, O., Dos Santos, M.C., Kleinke, M.U., Scares, D.M., Galvão, P.S., (1995) J. Appl. Phys., 78, p. 590Trucks, G.W., Raghavachari, K., Higashi, G.S., Chabal, Y.J., (1990) Phys. Rev. Lett., 65, p. 50

Method For Measuring Ohmic Resistance Of Solution Layers At Gas-evolving Electrodes

A method for measuring ohmic resistance of solution layers at gas-evolving electrodes was developed and tested. The method was applied to hydrogen and oxygen-evolving electrodes, and the resistance of their adjacent solution layers (for a 9 mm electrode separator gap) causes a negligible IR drop. For 3 mm gaps at a current density of 300 mA/cm2, the IR drop of the solution layer increases to 25 mV. Contact resistance at the various electrode connections are shown to have a measurable contribution which increases with electrolysis time.13841028103

Pattern Formation On Aluminum Electrodes

The mechanisms of pattern formation on anodized aluminum electrodes in contact with various acid solutions were investigated. The mechanism is related to solute concentration inhomogeneities at the film-solution interface. The size of cells forming the structure was determined experimentally and successfully matched with a recently developed model.13892763277

Time Resolved Photoluminescence Of Porous Silicon: Evidence For Tunneling Limited Recombination In A Band Of Localized States

Time resolved photoluminescence of porous silicon at room temperature was measured for several emission energies under 2 ns nitrogen laser excitation. For each emission energy studied there is a broad distribution of lifetimes extending over a few decades. The mean value of the distribution varies with the emission energy, from 3 (2.77 eV) to 50 μs (1.96 eV). The results can be explained by assuming a tunneling limited recombination mechanism between bands of localized states. We associate this behavior with a superficial disordered Si:O:H compound rather than with quantum confinement effects.62192381238

Etching Technique For Transmission Electron Microscopy Observation Of Nanostructure Of Visible Luminescent Porous Silicon

We present a special configuration for the electrochemical etching of silicon, in which thin samples suitable for direct transmission electron microscopy observation are produced. This technique allows the observation of images of an irregular matrix of pores and individual columnlike structures with a ∼15 Å cross-sectional diameter. These images show that the preferential etching directions are the projections of the {100} planes on the (111) plane for the etched <111≳-oriented silicon. The large pore (≳50 nm diam) axis orientation is independent of the preferential etching direction and is parallel to the etching current direction.63101348135

Wettability Gradients On Anodized Aluminum Effects Of Surface Chemical Reactions

Wettability variation of aluminum electrode surfaces was determined using a Wilhemly-type apparatus, in which the pull force exerted by the electrolyte solution on the electrode was measured at each switching of the electrode potential, for a periodically reversed step potential. The data obtained for aluminum and amalgamated electrodes show that metal-liquid surface tension is sensitive to the applied potential mainly through its effect on the chemical composition of the interface. The gradient of wettability induced by chemical reactions generates a displacement of the meniscus during the periodic polarization pulses. Wettability of aluminum surfaces in contact with H2SO4 solutions depends on the acid concentration, in agreement with previous results for iron-sulfuric acid systems.137378178

Accelerated Projected Gradient Method for Linear Inverse Problems with Sparsity Constraints

Regularization of ill-posed linear inverse problems via $\ell_1$ penalization has been proposed for cases where the solution is known to be (almost) sparse. One way to obtain the minimizer of such an $\ell_1$ penalized functional is via an iterative soft-thresholding algorithm. We propose an alternative implementation to $\ell_1$-constraints, using a gradient method, with projection on $\ell_1$-balls. The corresponding algorithm uses again iterative soft-thresholding, now with a variable thresholding parameter. We also propose accelerated versions of this iterative method, using ingredients of the (linear) steepest descent method. We prove convergence in norm for one of these projected gradient methods, without and with acceleration.Comment: 24 pages, 5 figures. v2: added reference, some amendments, 27 page