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At least 199 records · Page 11Linked to original sources
PubMed1993

A new rapid air-drying technique for scanning electron microscopy using tetramethylsilane: application to mammalian tissue.

A new rapid air-drying technique for scanning electron microscopy (SEM) with results comparable to critical point drying (CPD) has been developed. In earlier studies a trematode parasite and a fungus were used as test specimens. Here the application of the new method for SEM of some mammalian tissue is described. The method is based on drying the tissues from an organo-silicon compound whose physical and chemical properties make it the most appropriate fluid for tissue drying.

Animals↗
PubMed1995

Mineralogical characteristics of silica polymorphs in relation to their biological activities.

Numerous aspects of silica polymorphs can affect their biological activities, including periodic structures, compositional variations, dissolution characteristics, surface properties, and particle size and shape. For an understanding of mineral-induced pathogenesis from a mechanistic perspective, the links between these properties and biochemical processes must be elucidated. This paper presents some strategies for designing assays to evaluate these properties.

Chemical Phenomena↗
PubMedDate not supplied

[Reconstruction of the floor of the auricle in congenital microtia in children].

The data are presented on 329 children (201 boys and 128 girls) with congenital defects of the external and middle ear. Right-side defect occurred twice as frequently as left-side one. Treatment in 45 children with bilateral defects started with reconstructive meatotympanoplasty. Surgical reconstruction has been performed on 106 floors of the auricle. In 51 cases a rib homocartilage and free skin were used (group 1), in 55 cases alloplastic frames were covered with pedicle tissue (group 2). The following complications occurred in group 1: a complete resorption of the cartilage, necrosis of the skin graft, decubitus (5, 5 and 6 cases, respectively). In group 2 there were 5 cases of the pedicle necrosis, 7 cases of the pedicle self-detachment, 7 cases of the frame sequestration, 2 cases of late frame displacement. The floors formed with the use of neck-chest pedicle and compound silicone frame produced the best cosmetic effects.

Cartilage↗
PubMed2001

1-Boraadamantane: reactivity towards di(1-alkynyl)silicon and -tin compounds: first access to 7-metalla-2,5-diboranorbornane derivatives.

1-Boraadamantane (1) reacts with di(1-alkynyl)silicon and -tin compounds 2 (Me2M(C...CR)2: M=Si; R=Me (a), tBu (b), SiMe3 (c); M=Sn, R=SiMe3 (e)) in a 1:1 ratio by intermolecular 1,1-alkylboration, followed by intramolecular 1,1-vinylboration, to give siloles 5a-c and the stannole 5e, respectively, in which the tricyclic 1-boraadamantane system is enlarged by two carbon atoms. Owing to the high reactivity of 1, a second fast intermolecular 1,1-alkylboration competes with the intramolecular 1,1-vinylboration as the second major step in the reaction if the substituent R at the C...C bond is small (2a) and/or if the M-C... bond is also highly reactive, as in 2d (M=Sn, R= Me) and 2e (M=Sn, R=SiMe3). This leads finally to the novel octacyclic 7-metalla-2,5-diboranorbornane derivatives 8a, 8d, and 8e, of which 8e was characterized by X-ray analysis in the solid state. 1,1,2,2-Tetramethyldi(1-propynyl)disilane, MeC...C-SiMe2SiMe2-C...CMe (3), reacts with 1 to give mainly a 1,2-dihydro-1,2,5-disilaborepine derivative 9 and the octacyclic compound 11, which is analogous to 8a but with an Me4Si2 bridge. All new products were characterized in solution by 1H, 11B, 13C, 29Si, and 119Sn NMR spectroscopy. For 8 and 11, highly resolved 29Si and 119Sn NMR spectra revealed the first two-bond isotope-induced chemical shifts, 2delta10/11B(29Si) and 2delta10/11B(119Sn) respectively, to be reported.

Journal Article↗
PubMed2006

Synthesis, properties, and reactions of a series of stable dialkyl-substituted silicon-chalcogen doubly bonded compounds.

The first dialkyl-substituted silicon-chalcogen doubly bonded compounds [R2Si=X; R2=1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl, X = S (4), Se (5), and Te (6)]were synthesized by the reactions of an isolable dialkylsilylene R2Si: (3) with phosphine sulfide, elemental selenium, and elemental tellurium, respectively. Systematic changes of characteristics of silicon-chalcogen double bonds are elucidated by X-ray analysis, UV-vis spectroscopy, and DFT calculations. In the solid state, the unsaturated silicon atom in 4-6 adopts planar geometry and the extent of the shortening of Si=X double bonds from the corresponding Si-X single bonds decreases in the order 4 > 5 > 6. In the absorption spectra of 4-6, pi -->pi* transition bands are observed distinctly in addition to n -->pi* transition bands. Both the n -->pi* and pi -->pi* transitions are red-shifted in the order 4 < 5 < 6, and the difference between the energies of the two transitions is kept almost constant among 4-6. The tendency is explained using the qualitative perturbation theory and is reproduced by the DFT calculations for model silanechalcogenones. Addition reactions of water, methanol, and isoprene to 4-6 are reported.

Journal Article↗
PubMedDate not supplied

[Use of highly dispersed materials for culturing and isolation of granular Agrobacterium radiobacter preparations ].

The effects of synthetic and natural high-dispersion materials on the growth of Agrobacterium radiobacter were studied. Natural minerals montmorillonite and palygorskite (10 g/l nutrient medium) were more potent than high-dispersion silica and its modified forms in stimulating growth of Agrobacterium radiobacter. The interaction of Agrobacterium radiobacter with clay minerals increased the survival rate of bacteria at supraoptimal temperatures. We elaborated new granular bacterial preparation, which enhanced the productivity of cucumbers by 12-15%.

Bentonite↗
PubMed2006

Reversible photoswitching of the coordination numbers of silicon in organosilicon compounds bearing a 2-(phenylazo)phenyl group.

Several organosilicon compounds bearing a 2-(phenylazo)phenyl group were synthesized from the corresponding chlorosilanes and 2-lithioazobenzene prepared by halogen-lithium transmetalation of 2-iodoazobenzene. Their structures were determined by (1)H, (13)C, (19)F, and (29)Si NMR spectra, UV-vis spectra, and X-ray crystallographic analyses. In the UV-vis spectra, silyl groups caused red shifts of both the n-pi and pi-pi transitions of the azo group compared with the transitions of the unsubstituted azobenzene. The E-isomers of the fluorosilanes showed an intramolecular interaction between a nitrogen atom of the azo group and the silicon atom, leading their intermediate structures between a distorted trigonal bipyramidal structure and a tetrahedral structure around the silicon atoms, which were revealed by the X-ray crystallographic analyses and the NMR spectra. On the other hand, silanes without fluorine atoms showed tetrahedral structures in the absence of such an interaction. The photoirradiation of the E-isomers of the fluorosilanes afforded reversibly the corresponding Z-isomers in good yields. The silicon atoms of the Z-isomers were found to be tetracoordinate in the absence of Si-N interactions by the (29)Si NMR spectra. The coordination numbers of the silicon atom of the fluorosilanes were reversibly switched between four and five by photoirradiation. These properties were compared to those of a tetrafluoro[2-(phenylazo)phenyl]silicate.

Journal Article↗