Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Silicon Compounds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1975

Ferromagnetic silicone necrosis of hypernephromas by selective vascular occlusion to the tumor: a new technique.

Arterial vascular occlusion of hypernephromas may be performed by obstructiing the tumor vascular tree with the injection of ferromagnetic silicone microspheres. The powerful superconducting electromagnet confines the embolized iron-silicone compound to the neoplastic target organ. Radioactive material may or may not be added to the iron-silicone compound to give local direct radioactive radiation therapy to the tumor area. In experimental dogs up to 70,000 rad of beta radiation from the P32 source had been delivered homogeneously within the kidney when mixed with the ferrosilicone. This technique may well be used in cases in which a major operation is contraindicated or when preoperative necrosis of the tumor is advisable. Since the entire procedure can be done with the patient under local anesthesia in a radiology department it may be a valuable new technique in the future management of urological tumors, unilateral renal hypertension, solitary kidney pathology and so forth. Ferrosilicone material has not been found to be toxic. The application of a powerful superconducting electromagnet to the technique provides a means of confining the embolized iron-silicone compound to the target organ.

Adenocarcinoma↗
PubMed2002

Spectra and structure of silicon-containing compounds. XXX. Raman and infrared spectra, conformational stability, vibrational assignment of chloromethyl silyl dichloride.

The Raman spectra (3200-30 cm(-1)) of liquid and solid, and infrared spectra of gaseous and solid chloromethyl silyl dichloride, ClCH2SiHCl2, have been recorded. Variable temperature (-105 to -150 degrees C) studies of the infrared spectra of the sample dissolved in liquid krypton have been carried out. From these data, the enthalpy difference was determined to be 363 +/- 40 cm(-1) (4.34 +/- 0.48 kJ mol(-1)), with the more stable form being the gauche conformer, which is consistent with the prediction from ab initio calculations at both the Hartree-Fock level and with full electron correlation by the perturbation method to second order. It is estimated that 92% of the sample is in the gauche form at ambient temperature. A complete vibrational assignment is proposed for the gauche conformer and several of fundamentals of the trans conformer based on infrared band contours, relative intensities, depolarization values, and group frequencies, which is supported by normal coordinate calculations utilizing the force constants from the ab initio MP2/6-31G(d) calculations. The r0 SiH bond distances of 1.476 and 1.472 A have been obtained for the trans and gauche conformers, respectively, from the silicon-hydrogen stretching frequencies. The optimized geometries have also been obtained from ab initio calculations utilizing several different basis sets with full electron correlation by the perturbation method up to MP2/6-311 + G(2d,2p). The results are discussed and compared to some corresponding results for several related molecules.

Molecular Conformation↗
PubMed2003

Spectra and structure of silicon containing compounds. XXXII. Raman and infrared spectra, conformational stability, vibrational assignment and ab initio calculations of n-propylsilane-d0 and Si-d3.

The infrared (3100-40 cm(-1)) and Raman (3100-20 cm(-1)) spectra of gaseous and solid n-propylsilane, CH(3)CH(2)CH(2)SiH(3) and the Si-d(3) isotopomer, CH(3)CH(2)CH(2)SiD(3), have been recorded. Additionally, the Raman spectra of the liquids have been recorded and qualitative depolarization values obtained. Both the anti and gauche conformers have been identified in the fluid phases but only the anti conformer remains in the solid. Variable temperature (-105 to -150 degrees C) studies of the infrared spectra of n-propylsilane dissolved in liquid krypton have been recorded and the enthalpy difference has been determined to be 220+/-22 cm(-1) (2.63+/-0.26 kJ mol(-1)) with the anti conformer the more stable form. A similar value of 234+/-23 cm(-1) (2.80+/-0.28 kJ mol(-1)) was obtained for deltaH for the Si-d(3) isotopomer. At ambient temperature it is estimated that there is 30+/-2% of the gauche conformer present. The potential function governing the conformation interchange has been estimated from the far infrared spectral data, the enthalpy difference, and the dihedral angle of the gauche conformer, which is compared to the one predicted from ab initio MP2/6-31G(d) calculations. The barriers to conformational interchange are: 942, 970 and 716 cm(-1) for the anti to gauche, gauche to gauche, and gauche to anti conformers, respectively. Relatively complete vibrational assignments are proposed for both the n-propylsilane-d(0) and Si-d(3) molecules based on the relative infrared and Raman spectral intensities, infrared band contours, depolarization ratios, and normal coordinate calculations. The geometrical parameters, harmonic force constants, vibrational frequencies, infrared intensities, Raman activities and depolarization ratios, and energy differences have been obtained for the anti and gauche conformers from ab initio MP2/6-31G(d) calculations. Structural parameters and energy differences have also been obtained utilizing the larger 6-311 + G(d,p) and 6-311 + G(2d,2p) basis sets. From the isolated Si-H stretching frequency from the Si-d(2) isotopomer the r(0) distances of 1.484 and 1.485 A have been determined for the SiH(s) and SiH(a) bonds, respectively, for the anti conformer, and 1.486 A for the SiH bond for the gauche conformer. Utilizing previously reported microwave rotational constants for the anti conformer and the determined SiH distances along with ab initio predicted parameters 'adjusted r(0)' parameters have been obtained for the anti conformer. The results are discussed and compared to those obtained for some similar molecules.

Silicon Compounds↗
PubMed2003

Superconductivity of metal deficient silicon clathrate compounds, Ba8-xSi46 (0< x < or = 1.4).

Single crystals of the Ba-containing silicon clathrate superconductor Ba(7.76)Si(46) were prepared using a high-pressure and high-temperature condition (3 GPa, 1300 degrees C). It crystallized in the cubic space group Pm-3n with a = 10.3141(7) A and Z = 1. There are two crystallographically different types of Ba sites, at the centers of Si dodecahederal (Ba@Si(20)) and Si tetrakaidecahedral (Ba@Si(24)) cages. On evacuation at 527 degrees C, a part of Ba atoms were removed from the Ba@Si(20) sites. The superconducting transition temperature (T(c)) decreased from 9.0 to 6.0 K with the decrease of the Ba content from 7.76 to 6.63 Ba/Si(46). The Ba deficient sites and the deficiency were determined by the structural refinement in the single-crystal X-ray analyses.

Journal Article↗
PubMed2000

Analysis of silicon in human tissues with special reference to silicone breast implants.

The increase, in the last two decades, in the application of silicones (polysiloxanes) and inorganic silicon compounds in medicine and the food industry, has exposed the human body to extensive contacts with these substances. Most silicone breast implants contain a gel consisting of a crosslinked silicone elastomer swollen by silicone oil (PDMS). Diffusion of PDMS through the silicone elastomer envelope and rupture of the envelope with release of the gel contents both occur clinically. The amount and distribution of silicone compounds in various tissues are key issues in the assessment of health problems connected with silicone implants. We have measured by GFAAS the Si content of tissues from normal and implant patients and the organic solvent extractable Si levels (assumed to be silicone), using careful control of sample collection and preparation. Whole blood levels were: implant patients mean 38.8 (SD 25.6) (microg/kg), controls mean 24.2 (SD 26.7) (microg/kg) in one study and subsequently 103.8 (SD 112.1) and 74.3 (SD 86.5) (microg/kg) in another study. Capsular tissue levels were: gel implants 25047 (SD 39313) (mg/kg of dry tissue), saline implants 20.0 (SD 27.3) (mg/kg of dry tissue) and controls 0.24 (SD 0.39) (mg/kg of dry tissue). Breast milk levels were: implant patients mean 58.7 (SD 33.8) (microg/kg), controls mean 51.1 (SD 31.0) (microg/kg); infant formula mean was 4.40 (mg/kg). Various precautions were undertaken to avoid Si contamination in this work, the most important being a) the use of a Class 100 laboratory for sample preparation and b) application of strict and elaborate washing procedure for specimen collection tools and laboratory plasticware. This data demonstrated that to properly interpret the importance of these numbers for human health, a larger study of "normal" levels of Si in human tissues should be undertaken and factors such as diet, water, race and geographical location should be considered.

Breast Implants↗
PubMed1975

Pulmonary deposits of titanium dioxide in cytologic and lung biopsy specimens. Light and electron microscopic x-ray analysis.

Although titanium dioxide (TiO2) is widely used in industry, its biologic effects have not been determined. In the present investigation, open lung biopsy samples and sputum specimens from three former TiO2 factory workers and bronchial aspirations from seven TiO2 factory workers were analyzed by conventional and x-ray microanalytic light and electron microscopic methods. These studies showed that in the alveolar macrophages, lysosomes contained a significant amount of titanium as well as smaller amounts of silicon, aluminum, iron, and potassium. It appeared that titanium dioxide was situated in round or oval-shaped particles whereas silica or silicon compounds were localized in separate, more rectangular structures. There fore, the adverse effects may be induced by such quartz or silicon compounds. The latter are utilized as covering substances in the manufacture of TiO2 pigment.

Adult↗
PubMed2005

Novel phthalocyaninatobis(alkylcarboxylato)silicon(IV) compounds: NMR data and X-ray structures to study the spacing provided by long hydrocarbon tails that enhance their solubility.

The reaction between trans-PcSiCl2 (1) and the potassium salts of six fatty acids (2 a-2 f) led to the trans-PcSi[OOC(CH2)nCH3]2 compounds (3 a-3 f), which were characterised by elemental analysis, IR, UV/Vis and 1H, 13C, and 29Si NMR spectroscopy. From a detailed study of the NMR spectra, the strong anisotropic currents of the Pc macrocycle were found to have an effect on up to the sixth methylenic group. As expected, the length of the hydrocarbon tail does not affect the chemical shift of the 29Si nucleus of any of the compounds, appearing at around -222.6. The structures of PcSi[OOC(CH2)nCH3]2, where n = 7, 10, 12, 13 and 20, were determined by X-ray crystallography. All the compounds were found to be triclinic with a P1 space group. In all cases the observed crystallographic pseudosymmetry is Ci and the asymmetric unit consists of half a molecule. The silicon atom is at the centre of a distorted octahedron and hence its coordination number is six. The carboxylate fragments are in a trans configuration with respect to the Pc macrocycle. The supramolecular structures are discussed in detail herein. The correlation between the 1H NMR chemical shifts and the position of the corresponding carbon atoms in the hydrocarbon tail reveals that the dicarboxylate substituents exhibit a spacer-like behaviour that enhances the solubility. A detailed study of the tail variable allowed us to evaluate the loss of radial shielding along the Pc2- ligand.

Journal Article↗
PubMed2006

Role of silicon contamination on calcification of hydrophilic acrylic intraocular lenses.

PURPOSE: To verify the presence of the element silicon on hydrophilic acrylic intraocular lenses (IOLs) explanted because of calcification. DESIGN: Interventional case series with clinicopathological correlation. METHODS: Twenty explanted IOLs with surface deposits (MemoryLens), and 20 with deposits mostly within their optic substance (SC60B-OUV and Aqua-Sense; 10 each) were used. After gross, microscopic, and histochemical analyses to confirm the presence of deposits, the lenses underwent scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) for elemental composition, on the external surface of MemoryLens IOLs, and on the surface and internal substance of SC60B-OUV and Aqua-Sense IOLs. The weight percentage of the element silicon was obtained at the level of deposits, and at adjacent deposit-free areas in all lenses. RESULTS: Scanning electron microscopy (SEM) coupled with EDS confirmed that the composition of the deposits was calcium/phosphate in all cases. The element silicon was found in all 40 lenses, on all areas analyzed. The silicon weight percentage was higher at the level of the deposits. The presence of aluminum on five MemoryLens IOLs, and in most of the SC60B-OUV and Aqua-Sense lenses might be related to scattering from the aluminum mounting stubs used for surface analyses. CONCLUSIONS: Silicone compounds have been implicated in the calcification of another hydrophilic acrylic design (Hydroview). They may also have a role in the calcification of other hydrophilic acrylic IOLs. Further investigation on the relationship between the presence of the element silicon and the silicone compounds found on calcified hydrophilic acrylic lenses is necessary.

Acrylic Resins↗
PubMed2003

Spectra and structure of silicon-containing compounds. Part XXXVIII: Infrared and Raman spectra, vibrational assignment, conformational stability, and ab initio calculations of vinyldifluorosilane.

Infrared spectra (3500-50 cm(-1)) of gaseous and solid, and Raman spectrum (3500-30 cm(-1)) of liquid vinyldifluorosilane, CH(2)z.dbnd6;CHSiF(2)H, are reported. Both the cis and gauche rotamers have been identified in the fluid phases. From temperature-dependent FT-infrared spectra of krypton solutions, it is shown that the cis conformer is more stable than the gauche form by 119+/-12 cm(-1) (1.42+/-0.14 kJ mol(-1)). At ambient temperature there is 53+/-2% of the gauche conformer present. Complete vibrational assignments are provided for the cis conformer and several modes are identified for the gauche form. Harmonic force constants, fundamental frequencies, infrared intensities, and Raman activities have been obtained from MP2/6-31G(d) calculations with full electron correlation. The optimized geometries and conformational stabilities have also been obtained from ab initio MP2/6-31G(d), MP2/6-311+G(d,p), and MP2/6-311+G(2d,2p) calculations with full electron correlation as well as from density functional theory calculations (DFT) by the B3LYP method. The SiH bond distances (r(0)) of 1.472 and 1.471 A have been obtained for the cis and gauche conformers, respectively, from the silicon-hydrogen stretching frequencies. These results are compared to the corresponding quantities of the corresponding carbon analogue as well as with some similar molecules.

Molecular Conformation↗
PubMed2004

Stereocontrol in organic synthesis using silicon-containing compounds. Studies directed towards the synthesis of ebelactone A.

Several approaches to the synthesis of ebelactone A 2 are described, culminating in the synthesis of the benzenesulfonate of 2-epi-ebelactone A 161. All the approaches were based on three fragments A, B and C, originally defined in general terms in, but eventually used as the aldehyde 72, the allenylsilane 3 and the aldehyde 139, respectively. They were joined, first B with C, and then B+C with A. In the main routes to fragments A and C, the relative stereochemistry was controlled by highly stereoselective enolate methylations 67-->67, 68-->69, and 135-->136, in each case anti to an adjacent silyl group, and by a highly stereoselective hydroboration of an allylsilane 137-->138, also anti to the silyl group. The hydroxyl groups destined to be on C-3 and C-11 were unmasked by silyl-to-hydroxy conversions 69-->70 and 138-->139 with retention of configuration. The stereochemistry created in the coupling of fragment B to C was controlled by the stereospecifically anti S(E)2' reaction between the enantiomerically enriched allenylsilane 3 and the aldehyde 139. The double bond geometry was controlled by syn stereospecific silylcupration 148-->151, and preserved by iododesilylation 151-->152 of the vinylsilane with retention of configuration, and Nozaki-Hiyama-Kishi coupling with the aldehyde 72 gave the whole carbon skeleton 153 of ebelactone A with the correct relative configuration, all of which had been controlled by organosilicon chemistry. In the steps to remove the superfluous allylic hydroxyl, an intermediate allyllithium species 156 abstracted the proton on C-2, and its reprotonation inverted the configuration at that atom. Other routes to the fragments A and C were also explored, both successful and unsuccessful, both silicon-based and conventional, and a number of unexpected side reactions were investigated.

Journal Article↗
PubMed2003

Spectra and structure of silicon containing compounds. XXXIX. Raman and infrared spectra, conformational stability, vibrational assignment and ab initio calculations of n-propyltrifluorosilane.

The infrared (3100-40 cm(-1)) spectra of gaseous and solid and Raman (3200-20 cm(-1)) spectra of liquid with qualitative depolarization values and solid n-propyltrifluorosilane, CH(3)CH(2)CH(2)SiF(3), have been recorded. Additionally the infrared spectra of the sample in nitrogen and argon matrices have been recorded. Both the anti and gauche conformers have been identified in the fluid phases but only the anti conformer remains in the solid. Variable temperature (-105 to -150 degrees C) studies of the infrared spectra of the sample dissolved in liquid krypton have been recorded and the enthalpy difference has been determined to be 135+/-14 cm(-1) (1.62+/-0.17 kJ mol(-1)) with the anti conformer the more stable form. At ambient temperature it is estimated that there is 51+/-2% of the gauche conformer present. Also the enthalpy difference in the liquid was obtained from variable temperature studies of the Raman spectra and from three conformer pairs an average value of 179+/-18 cm(-1) (2.14+/-0.22 kJ mol(-1)) was obtained again with the anti form the more stable conformer. Relatively complete vibrational assignments are proposed for both conformers based on the relative infrared and Raman spectral intensities, infrared band contours, depolarization ratios which are supported by normal coordinate calculations. The geometrical parameters, harmonic force constants, vibrational frequencies, infrared intensities, Raman activities, depolarization ratios, and energy differences have been obtained for the anti and gauche conformers from ab initio MP2/6-31G(d) calculations. Structural parameters and energy differences have also been obtained utilizing the larger 6-311+G(d, p) and 6-311+G(2d, 2p) basis sets. By utilizing the previously reported microwave rotational constants for five isotopomers of CH(3)SiF(3) along with ab initio predicted structural values, r(0) parameters have been obtained for methyltrifluorosilane. Similarly, from the ab initio predicted parameters "adjusted r(0)" parameters have been estimated for both conformers of n-propyltrifluorosilane. The results are discussed and compared with those obtained for some similar molecules.

Cold Temperature↗
PubMed1999

Silicon assays in women with and without silicone gel breast implants--a review.

During the past 5 years, as the failure properties of silicone gel breast implants have emerged, there has been considerable interest in measuring the levels of silicone and silicon in blood, serum, breast milk, and body tissues. Assays have been done in control patients without implant exposure, and in patients with silicone gel implants in an attempt to predict implant failure. Nuclear magnetic resonance measurements of silicone compounds have not been helpful because of their low sensitivity of detection. However, all compounds containing the element silicon, which includes silicone, have been measured accurately. Modern techniques, such as electrothermal atomic absorption spectrometry, direct-current plasma emission spectrometry, and inductively coupled plasma emission spectroscopy have allowed precise measurement of silicon in body fluids and tissues. Using these techniques, recent studies have demonstrated consistent levels of silicon in the blood and plasma of control women without exposure to implants. In one study, plasma silicon was shown to be 140 +/- 10 ng per milliliter. In four other studies, serum silicon levels in control patients were the following: mean, 130 +/- 70 ng per milliliter; mean, 170 +/- 100 ng per milliliter; median, 100 ng per milliliter (range, 30-209 ng per milliliter); and 10 to 250 ng per milliliter. Three independent studies have shown that women with silicone gel implants have higher blood and serum silicon levels than control subjects, but their values were still within the range of control subjects. One study has shown that the mean silicon level in breast milk was not significantly different between 15 implant patients and 34 control patients. The measurement of silicon in control breast tissue has shown consistent results in three different studies, with most tests varying from <0.2 to 2.2 microg per gram dry weight. Three studies have shown that capsules from women with silicone gel breast implants had markedly elevated silicon levels compared with control breast tissue. Median silicon levels varied from 9,980 to 14,390 microg per gram dry weight. There was no significant difference in capsule silicon level between intact and ruptured implants or associated with implant duration in situ or year of implantation. Four studies have shown that capsules from saline implants had elevated levels of silicon compared with control tissue, but their silicon levels were much lower than those of gel implants. The median levels of silicon in the capsules of these studies were as follows: 7.7, 71.5, 198, and 1,100 microg per gram dry weight. Based on current knowledge, because of the large variability among patients, the use of silicon measurements in blood, serum, breast milk, or implant capsule tissue has no clinical role for the effective monitoring of implant leakage in women with silicone gel breast implants.

Breast Implants↗