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  • sol-gel  (85)
  • gene expression  (69)
  • Springer  (154)
  • American Meteorological Society
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  • 1995-1999  (154)
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  • Springer  (154)
  • American Meteorological Society
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  • 1995-1999  (154)
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  • 1935-1939
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  • 1
    Electronic Resource
    Electronic Resource
    Thermal treatment of a modified alkoxide gel precursor for the preparation of the YBa2Cu4O8 superconductor (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 989-996 
    Details
    ISSN: 1572-8943
    Keywords: sol-gel ; TG ; thermal decomposition ; Y-Ba-Cu superconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A precursor of Y-Ba-Cu oxides was prepared by a modified alkoxide sol-gel method and its thermal decomposition in air was studied by on-line coupled TG-FTIR and High Resolution Thermogravimetric measurements. A continuous more or less stepwise weight loss was observed between room temperature and 600°C at which all organic compounds had evolved and were progressively oxidized as the temperature increased leaving only Y and Cu oxides and bariumcarbonate. Between 700 and 800°C a final weight loss was observed due to the decomposition of bariumcarbonate into oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979148
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  • 2
    Electronic Resource
    Electronic Resource
    Thermoanalytical investigations on the sol-gel synthesis of YBa2Cu3O72212;δ (1997)
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 1051-1067 
    Details
    ISSN: 1572-8943
    Keywords: reaction mechanisms ; sol-gel ; superconductors ; thermoanalytical techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The high temperature superconducting compound YBa2Cu3O72212;δ (Y-123) is synthesised by sol-gel process using various precursors viz., acetate, acetate-citrate, nitrate-citrate and acrylamide. The phase purity of the final product depends on the homogeneity of the gels which intern depends on the bonding of the metal ions in the gels. The samples prepared by acrylamide and nitrate-citrate gel routes yielded phase pure Y-123 compound with better superconducting properties. The mechanism of formation of Y-123 in all these four gel routes is established by characterising the gels and intermediate phases using TG, DTA and XRD techniques. Kinetic analysis is carried out on the mass loss data using the method proposed by Phadni's and Deshpande. Avrami-Erofeev nuclei growth in case of acrylamide, diffusion controlled process in nitrate-citrate and phase boundary reaction mechanisms in case of acetate-citrate gels are found to be responsible for the formation of Y-123 phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979153
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  • 3
    Electronic Resource
    Electronic Resource
    Sol-gel preparation and fluorine substitution of BiSCCO high-T c superconductors (1997)
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 105-115 
    Details
    ISSN: 1572-8943
    Keywords: BiSCCO synthesis ; fluorine substitution ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel citrate technology was used to prepare BiSCCO 2223 and 2212 superconducting phases. Fluorine in the initial mixture was shown to enhance considerably formation of the 2223 phase. Fluorine substitution of up to three F atoms per Bi(Pb)SCCO 2223 formula was achieved by treatment of the sample in 80 Torr ClF3 atmosphere. A number of experimental methods have been used to characterize the samples and to trace the phase transformations in the sol-gel process: DTA/TG, XRD, atomic absorption, potentiometry with fluoride selective electrode, magnetic susceptibility measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979553
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  • 4
    Electronic Resource
    Electronic Resource
    Immobilization and Characterization of Lactate Dehydrogenase on TEOS Derived Sol-Gel Films (1997)
    Springer
    Journal of sol gel science and technology 10 (1997), S. 309-316 
    Details
    ISSN: 1573-4846
    Keywords: lactate dehydrogenase ; sol-gel ; biosensor ; lactic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Physical adsorption and physical entrapment techniques have been utilized for the immobilization of lactate dehydrogenase (LDH) on tetraethylorthosilicate (TEOS) derived sol-gel films. The enzyme (LDH) activity has been assayed as a function of time, temperature, pH and pyruvate concentration. The results of photometric measurements used for monitoring the reaction yield a response time of about 1 min, linearity over a concentration range of 0–1.5 × 10-3 M and detection limit of 5 × 10-5 M. The TEOS sol-gel films containing LDH have been found to be stable for about 30 days at temperatures 4 to 10°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018329518938
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  • 5
    Electronic Resource
    Electronic Resource
    Selective Formation of Spinel Iron Oxide in Thin Films by Complexing Agent-Assisted Sol-Gel Processing (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 77-81 
    Details
    ISSN: 1573-4846
    Keywords: iron oxide ; structural control ; complexing agent ; thin film ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α -Fe2O3 with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400° C, γ -Fe2O3 with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α -Fe2O3 appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of γ -Fe2O3 could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel film at 350° C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026407306265
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrolysis and Condensation of Transition Metal Alkoxide: Experiments and Simulations (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 83-88 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; gelation modelling ; TiO2 gels ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We present here an experimental and numerical study of the chemical and aggregative mechanisms for titanium alkoxide in a reverse micellar medium. NMR experiments were done to study the first step of the sol-gel process: hydrolysis of titanium isopropoxide. Light and X-ray scattering experiments were then conducted to characterize the clustering of aggregates and aggregation kinetics. Fractal dimension, measured by U.S.A.X.S., varies with the hydrolysis ratio and the hydration of the surfactant. This evolution was explained by polydispersity of the hydrolysis which depends on the surfactant concentration. This hypothesis was tested through a numerical simulation of irreversible aggregation using a chemically limited aggregation model. The hydrolyzed sites are distributed among the monomers by a random procedure governed by a polydispersity parameter p , varying from 0 to 1. The total number of hydrolyzed sites is governed by a parameter q belonging to the interval [0, 1]. The p -q evolution of the fractal dimension coincides rather well with the experimental data in all the region of the two dimensional phase space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026459323103
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison Between Sol-Gel, Coprecipitation and Wet Mixing Synthesis of ZnAl2O4 (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 107-110 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; zinc aluminate ; spinel structure ; catalyst support
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract ZnAl2O4 was prepared by hydrolyzing a mixture of aluminum alkoxide with zinc nitrate dissolved in hexylene glycol and calcining at 800°C. The results are compared with those obtained by wet mixing and coprecipitation. The sol-gel method produces solids whose surface areas and pore volumes are 100% larger and with a more homogeneous pore size distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026471709899
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Organic Ligands Used in Sol-Gel Process on the Formation of Mullite (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 101-106 
    Details
    ISSN: 1573-4846
    Keywords: mullite ; organic ligand ; hydrolytic polymerization ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The preparation of mullite by the sol-gel method using organic polydentate ligands and the effect of the raw materials and organic polydentate ligands on the formation of mullite were investigated. Two series of samples were prepared using tetraethoxyorthosilicate (TEOS) and aluminum nitrate nonahydrate, or dibutoxyethylacetoacetatoaluminum (Al(OBu)2(AcAcEt)) as the silica and alumina sources, respectively, and using ethylene glycol (EG), 1,3-propanediol (PD), 1,3-butanediol (BD), 2-methyl-2, 4-pentanediol (MPD), diethlene glycol monoethyl ether (DEME) and ethoxyethanol as the ligands. When the alumina source was aluminum nitrate nonahydrate, mullite was apt to appear in the order of EG 〉 PD 〉 MPD. When Al(OBu)2(AcAcEt) was the alumina source, the tendency toward the appearance of mullite crystalline phase was EG 〉 BD 〉 DEME 〉 MPD. Between the two alumina sources, aluminum nitrate nonahydrate gave mullite much easier than Al(OBu)2(AcAcEt). These relationships were discussed from the viewpoints of the coordination ability of the ligands and the miscibility between the silica and alumina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026467608991
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation and Photochromic Behavior of Ormosil Containing Encapsulated AgTCNQ Molecules (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 279-283 
    Details
    ISSN: 1573-4846
    Keywords: AgTCNQ ; photochromism ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Preparation and photochromic behavior of ormosil containing encapsulated AgTCNQ molecules were studied in this paper. The ormosil resulted from hydrolysis and polycondensation of glycidoxypropyltrimethoxysilane, dimethyldimethoxysilane and methyltrimethoxysilane. The time to add AgNO3 water solution into the resultant sol was a key factor to synthesize AgTCNQ molecules inside ormosil matrix. AgTCNQ molecules encapsulated in the ormosil showed different photochromic behavior compared with pure AgTCNQ film: normal photochromic reaction can be realized, while reverse photochromic reaction can not. The “cage” model was used to explain this phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018311428500
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  • 10
    Electronic Resource
    Electronic Resource
    Sol-Gel transition and structural evolution on multicomponent gels derived from the alumina-silica system (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 239-249 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; alumina-gel ; multicomponent ; mullite ; phase transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The capacity of the sol-gel process of producing highly pure, homogeneous alumina-silica based materials had been demonstrated in the last few years. However, a full understanding on the mechanisms associated to sol formation and sol to gel transition has not yet been achieved and is required for the development of a new generation of nano-structurally tailored materials that will significantly enhance the technological importance of the sol-gel process. In this work, tetraethyl orthosilicate (TEOS) and aluminum isopropoxide were used to prepare materials within the entire silica-alumina system. Process parameters, such as gelation time, were correlated to variables of the initial stage of the process, such as pH, temperature of hydrolysis and water/alkoxide ratio. The obtained gels were dried at 105°C and subsequently heat treated at 500 and 1100°C for 3 hours. X-ray diffraction and infrared spectroscopy were used to characterize the materials and phase transformations. Structural information obtained from phase characterization and phase transformations was correlated to the effects of the process variables on sol formation and gelation, providing insights related to the mechanisms involved. The influence of temperature of aluminum isopropoxide hydrolysis on peptization and gelation of the mixtures was noted. The different behavior of mixtures hydrolyzed at low and high temperatures was suggested to be caused by different mechanisms of surface charge formation on the structurally different aluminum hydroxides. Monophasic and diphasic mullite xerogels were produced by changing temperature of aluminum isopropoxide hydrolysis, and led to formation of mullite and Al−Si spinel phases respectively, when treated at 1100°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02437187
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  • 11
    Electronic Resource
    Electronic Resource
    Calreticulin inhibits glucocorticoid– but not cAMP–sensitive expression of tyrosine aminotransferase gene in cultured McA–RH7777 hepatocytes (1997)
    Springer
    Molecular and cellular biochemistry 171 (1997), S. 37-43 
    Details
    ISSN: 1573-4919
    Keywords: calreticulin ; gene expression ; steroid receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Calreticulin is a ubiquitously expressed Ca2+ binding protein of the endoplasmic reticulum which inhibits DNA binding and transcriptional activation by steroid hormone receptors. In this study the effects of calreticulin on tyrosine aminotransferase (TAT) gene expression in cultured McA–RH7777 hepatocytes was investigated. McA–RH7777 cells were stably transfected with calreticulin expression vector to generate cells overexpressing the protein. The transcriptional activity of the TAT gene, which is glucocorticoid–sensitive and cAMP–dependent, was investigated in the mock transfected McA–RH7777 and in cells overexpressing calreticulin (designated McA–11 and McA–17). In the presence of dexamethasone or the cAMP analog (CTP–cAMP) expression of the TAT gene was induced in mock transfected McA–RH7777 cells by approximately 4.5 and 5 fold, respectively. In McA–11 and McA–17 cells, overexpressing calreticulin, glucocorticoi ever, the CTP–cAMP–dependent expression of the TAT gene was not affected. The ability of calreticulin to inhibit glucocorticoid–sensitive TAT gene expression but not the cAMP–dependent expression of the gene suggests that the protein affects specifically the action of transcription pathways involving steroid receptors or transcription factors containing KxFF(K/R)R–like motifs. Calreticulin may play an important role in the regulation of glucocorticoid–sensitive pathway of expression of the hepatocytes specific genes during development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006865108833
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  • 12
    Electronic Resource
    Electronic Resource
    Densification of Sol-Gel Thin Films by Ultraviolet and Vacuum Ultraviolet Irradiations (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 365-369 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; SiO2 ; TiO2 ; ultraviolet ; densification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural changes in SiO2 and TiO2 gel films were investigated using ultraviolet (UV) and vacuum ultraviolet (VUV) irradiations. A significant compaction with dehydration of SiO2 gel films was induced by irradiation of photons in the range of 9–18 eV. The refractive index and the shrinkage of the irradiated SiO2 gel films were comparable to those obtained by sintering at 1000°C. Densification of TiO2 gel films was also observed with irradiation of 5–14 eV photons. However, effects of the irradiation on TiO2 gel were smaller that those on SiO2 gel. The structural changes in the gel films are attributed to electronic excitations which are induced by irradiation with photons having higher energies than the bandgap of the oxides. The photo-induced effects are presumed to depend on the optical properties and structure of the gels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026411724863
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  • 13
    Electronic Resource
    Electronic Resource
    Sol-Gel Transition and Structural Evolution on Multicomponent Gels Derived from the Alumina-Silica System (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 239-249 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; alumina-gel ; multicomponent ; mullite ; phase transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The capacity of the sol-gel process of producing highly pure, homogeneous alumina-silica based materials had been demonstrated in the last few years. However, a full understanding on the mechanisms associated to sol formation and sol to gel transition has not yet been achieved and is required for the development of a new generation of nano-structurally tailored materials that will significantly enhance the technological importance of the sol-gel process. In this work, tetraethyl orthosilicate (TEOS) and aluminum isopropoxide were used to prepare materials within the entire silica-alumina system. Process parameters, such as gelation time, were correlated to variables of the initial stage of the process, such as pH, temperature of hydrolysis and water/alkoxide ratio. The obtained gels were dried at 105°C and subsequently heat treated at 500 and 1100°C for 3 hours. X-ray diffraction and infrared spectroscopy were used to characterize the materials and phase transformations. Structural information obtained from phase characterization and phase transformations was correlated to the effects of the process variables on sol formation and gelation, providing insights related to the mechanisms involved. The influence of temperature of aluminum isopropoxide hydrolysis on peptization and gelation of the mixtures was noted. The different behavior of mixtures hydrolyzed at low and high temperatures was suggested to be caused by different mechanisms of surface charge formation on the structurally different aluminum hydroxides. Monophasic and diphasic mullite xerogels were produced by changing temperature of aluminum isopropoxide hydrolysis, and led to formation of mullite and Al-Si spinel phases respectively, when treated at 1100°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018303226682
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  • 14
    Electronic Resource
    Electronic Resource
    Hepatic calcium-binding protein regucalcin concentration is decreased by streptozotocin-diabetic state and ethanol ingestion in rats (1997)
    Springer
    Molecular and cellular biochemistry 168 (1997), S. 67-72 
    Details
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; gene expression ; diabetic state ; ethanol ; liver injury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The alteration in calcium-binding protein regucalcin in the liver and serum of rats with streptozotocin (STZ)-diabetic state or ethanol ingestion was investigated. STZ (6.0 mg/100 g body weight) was subcutaneously administered in rats, and 1 or 3 weeks later they were sacrificed by bleeding. Liver regucalcin mRNA levels were not clearly altered by the diabetic state, as evidenced by Northern blotting using regucalcin cDNA (0.9 kb of open reading frame). Based on enzyme-linked immunoadsorbent assay (ELISA) with rabbit-anti-regucalcin IgG, hepatic regucalcin concentration was decreased about 50% of control levels by STZ treatment. However, serum regucalcin concentration was not significantly altered by STZ treatment. Meanwhile, when rats ingested ethanol (10 and 30%) in the drinking water for 2 weeks, liver regucalcin mRNA levels were clearly increased, although hepatic regucalcin concentration was significantly decreased. Serum regucalcin concentration was not appreciably altered. Serum transaminases (GOT and GPT) activities were significantly increased at 1 or 3 weeks after STZ administration in rats, while their activities were not altered by ethanol ingestion. The present study demonstrates that hepatic regucalcin concentration is decreased independent of mRNA expression in the STZ-diabetes and during ethanol ingestion in rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006822606198
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  • 15
    Electronic Resource
    Electronic Resource
    Tamoxifen enhances interferon-regulated gene expression in breast cancer cells (1997)
    Springer
    Molecular and cellular biochemistry 167 (1997), S. 169-177 
    Details
    ISSN: 1573-4919
    Keywords: tamoxifen ; interferon ; gene expression ; breast cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The molecular basis for the enhanced growth inhibition of MCF-7 human breast cancer xenografts by a combination of human interferon-β (IFN-β) and tamoxifen was investigated. Treatment of MCF-7, MDA-MB-231, and BT-20 cells with the combination of IFN-β and tamoxifen resulted in enhanced antiproliferative effects in vitro. Treatment with the combination of IFN-β and tamoxifen enhanced the expression of several IFN-β-inducible genes in human breast carcinoma cell lines relative to levels induced by IFN-β alone. Tamoxifen alone did not induce transcription of IFN-stimulated genes (ISGs). Augmentation of ISG expression by the combination of IFN-β and tamoxifen was noted in breast tumor cell lines irrespective of their functional estrogen receptor (ER) status or their dependence on estradiol for growth, suggesting that upregulation of ISGs was independent of ER status. Enhancement of IFN-stimulated gene expression by tamoxifen occurred at the transcripti onal level. Expression of transfected reporter genes under the control of IFN-α/β regulated promoters was also enhanced in IFN-β and tamoxifen-treated cells. Similarly, transcriptional induction of chimeric reporter plasmids driven by an IFN-γ inducible promoter (GAS; IFN-γ activated site) was also enhanced by the combination of IFN-γ and tamoxifen. In tamoxifen treated cells, IFN-β and IFN-γ readily activated transcription factors ISGF-3 and GAF, respectively. Therefore, augmentation of ISG expression by tamoxifen is an early event in the antitumoral activity of this drug combination. (Mol Cell Biochem 167: 169-177, 1997)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006854110122
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  • 16
    Electronic Resource
    Electronic Resource
    Use of a hammerhead ribozyme with cationic liposomes to reduce leukocyte type 12-lipoxygenase expression in vascular smooth muscle (1997)
    Springer
    Molecular and cellular biochemistry 172 (1997), S. 47-57 
    Details
    ISSN: 1573-4919
    Keywords: smooth muscle ; gene transfer ; DNA ; RNA ; ribozyme ; liposome ; lipoxygenase ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Chemically synthesized hammerhead-type ribozymes targeted against the porcine leukocyte-type 12-lipoxygenase (LO) have been developed and studied. One chimeric ribozyme consists of DNA in the non-enzymatic portions, and RNA in the enzymatic core as well as two phosphorothioate internucleotide linkages at 3′ terminus. The second ribozyme consists of ribonucleotide sequences generated by in vitro transcription. In this chapter we describe methodologies to first analyze the ribozyme catalytic activity in vitro by studying cleavage of target RNA in vitro. The subsequent sections will describe how to target the catalytic ribozyme and deliver it to porcine vascular smooth muscle cells (PVSMC) by a liposome-mediated method. Finally ways to evaluate its activity to inhibit expression of the 12-LO mRNA will be presented. These results demonstrate the feasibility of using ribozymes as novel candidates for therapeutic agents to block specific gene expression in vascular cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006855219018
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  • 17
    Electronic Resource
    Electronic Resource
    Construction of a human heart cDNA library and identification of cardiovascular based genes (CVBest) (1997)
    Springer
    Molecular and cellular biochemistry 172 (1997), S. 81-87 
    Details
    ISSN: 1573-4919
    Keywords: heart ; DNA ; library ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The availability of high quality cDNA libraries is often crucial to the successful identification and characterization of genes. The concepts and potential pitfalls of constructing cDNA libraries are presented. Various applications requiring high quality cDNA libraries are outlined, including large-scale single pass sequencing of cDNA clones to generate expressed sequence tags (ESTs) and differential screening of cDNA libraries. The usefulness of combining such approaches for the discovery of novel disease-related and cardiovascular-based ESTs (CVBest) is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006811403996
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  • 18
    Electronic Resource
    Electronic Resource
    Hydrogen peroxide-induced expression of the proto-oncogenes, c-jun, c-fos and c-myc in rabbit lens epithelial cells (1997)
    Springer
    Molecular and cellular biochemistry 173 (1997), S. 59-69 
    Details
    ISSN: 1573-4919
    Keywords: hydrogen peroxide ; oxidative stress ; gene expression ; lens epithelial cells ; N-acetylcysteine ; pyrrolidine dithiocarbamate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The involvement of H2O2 in cataract development has been established inboth human patients and animal models. At the molecular level H2O2 has beenobserved to cause damage to DNA, protein and lipid. To explore the oxidativestress response of the lens system at the gene expression level, we haveexamined the effects of H2O2 on the mRNA change of the proto-oncogenes,c-jun, c-fos and c-myc in a rabbit lens cell line, N/N1003A. H2O2 treatmentof the rabbit lens epithelial cells for 60 min induces quick up-regulationof both c-jun and c-fos mRNAs. The maximal induction is 38 fold for c-jun at150 µM and 72 fold for c-fos at 250 µM H2O2. Treatment ofN/N1003A cells with 50-250 µM H2O2 for 60 min leads to a 2-5 foldincrease of the c-myc mRNA level. H2O2 also induces an up-regulation intransactivity of the activating protein-1 (AP-1) as shown with a reportergene driven by a prolactin gene promoter with 4 copies of AP-1 binding sitesinserted in the upstream of the promoter. Maximal induction occurs with 150µM H2O2. In the same system, the antioxidants, N-acetyl-cysteine (NAC)and pyrrolidine dithiocarbamate (PDTC) at concentrations shown toup-regulate the mRNAs of both c-jun and c-fos, also enhance thetransactivity of AP-1. NAC and PDTC have different effects in modulating theinduction of AP-1 activity by H2O2 and TPA. These results reveal thatoxidative stress regulates expression of various regulatory genes in lenssystems, which likely affects cell proliferation, differentiation andviability and thus affect normal lens functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006828402225
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  • 19
    Electronic Resource
    Electronic Resource
    Molecular cloning of the cDNA coding for regucalcin and its mRNA expression in mouse liver: The expression is stimulated by calcium administration (1997)
    Springer
    Molecular and cellular biochemistry 173 (1997), S. 127-133 
    Details
    ISSN: 1573-4919
    Keywords: regucalcin ; calcium-binding protein ; cDNA cloning ; gene expression ; mouse liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The molecular cloning of the cDNA coding for a Ca2+-binding proteinregucalcin and its mRNA expression in mouse liver were investigated. ThecDNA clone encoding a regucalcin was isolated from a mouse liver cDNAlibrary and sequenced. Analysis of the sequence of the cloned cDNA showedthat the cDNA encoded the complete amino acid sequence of the mouseregucalcin molecule; the cDNA had an open reading frame of 897 bp. Mouseregucalcin was composed of 299 amino acid residues, and its molecular weightwas estimated to be 33,406 Da. The amino acid sequence of mouse regucalcinhad 94% homology, as compared with that of rat regucalcin. Northernblot analysis with the mouse liver cDNA probe revealed that mouse regucalcinmRNA was mainly present in the liver but only slightly in the kidney with asize of 1.8 kb. Hepatic regucalcin mRNA level of male mouse was higher thanthat of female mouse. A single intraperitoneal administration of calciumchloride (5, 15, and 30 mg Ca2+/100 g body weight) to mice induced aremarkable increase in regucalcin mRNA in the liver; the increase inregucalcin mRNA levels at 30 min after calcium administration wasdose-dependent. The present results demonstrate that regucalcin mRNA in miceis uniquely expressed in the liver, and that its expression is stimulated bycalcium administration.
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    URL: http://dx.doi.org/10.1023/A:1006887929369
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    Cardiac hypertrophy: Old concepts, new perspectives (1997)
    Springer
    Molecular and cellular biochemistry 176 (1997), S. 273-279 
    Details
    ISSN: 1573-4919
    Keywords: cardiac hypertrophy ; myosin heavy chain ; gene expression ; adrenergic system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Growth of the heart in hypertrophy is accompanied by changes in the phenotypic expression of cardiac genes. To explore the molecular basis of cardiac hypertrophy, we have analyzed the regulation of myosin heavy chain gene (MHC) expression. In one set of experiments, pressure overload on the rat heart was produced by constriction of the abdominal aorta. Changes in the α and β-MHC mRNA were then studied in overloaded hearts and following load removal. Pressure overload resulted in down-regulation of the α-MHC with corresponding up-regulation of the steady state level of β-MHC mRNA. Load removal (debanding) resulted in regression of cardiac hypertrophy and a rapid return of α-MHC mRNA to normal values. In contrast, the recovery in β-MHC mRNA was much slower to the extent that it remained substantially elevated compared to respective sham controls even after 7 weeks of post-debanding. These results suggest that putative load-related signals independently regulate two genes. Several lines of evidence indicate that adrenergic nervous system plays an important role in the induction and maintenance of cardiac hypertrophy and in the redistribution of myosin isoforms. We have analyzed the effect of cAMP inducing agents on the regulation of a-MHC gene in primary cultures of the fetal (18 day) rat cardiac myocyte. Inclusion of 8 Br-cAMP in the culture media increased the expression of α-MHC promoter/reporter construct comprising of 2.9 kb upstream sequence of the α-MHC gene. Several deletion mutations in the α- MHC gene promoter defined the cAMP responsive boundaries to be a 32 bp region comprising of -71 to -40 bp sequences. Deletion of this region resulted in loss of cAMP response as well as in basal expression of α-MHC promoter/reporter construct. These data suggest a role of β-adrenergic pathway in the modulation of α-MHC gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006865515646
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    The Glycophorin A Gene Family in Gorillas: Structure, Expression, and Comparison with the Human and Chimpanzee Homologues (1997)
    Springer
    Biochemical genetics 35 (1997), S. 59-76 
    Details
    ISSN: 1573-4927
    Keywords: glycophorins ; gorilla ; evolution ; gene family ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Homologues of MN blood group antigens, encoded by members of the glycophorin A (GPA) gene family, are expressed in man, anthropoid apes, and some species of Old World monkeys. Previous studies had shown that a three-gene framework, most closely related to that in man, is present in the chimpanzee. Here we report the genomic structure, transcript map, and protein expression of the GYPA locus in gorillas. Compared to the corresponding human and chimpanzee homologues, gorilla GPA, GPB, and GPB/E genes each showed a high degree of sequence identity, with the same exon-intron organization. However, the expression of exons III, IV, or V encoding the extracellular or membrane domains of homologous glycophorins varied among the three species. Gorilla GPA and GPB/E genes were unique in that the former occurred in two allelic forms with or without the expression of exon III, whereas the latter contained one (ψ exon III) instead of two silenced exons (ψ exons III and IV). Differences from human but not chimpanzee GPA also included the presence of a hybrid M/N epitope and the absence of the sequon for N-glycosylation. Owing to the retention of a functional exon III, gorilla GPB was more similar to chimpanzee GPB than human GPB. A transspecies allele was identified in the gorilla that gave rise to the Henshaw (He)-like antigen similar to that found in man. These results provide further insight into the model for evolution of the GPA gene family, indicating that the mechanisms underlying inter- and intraspecific polymorphism of glycophorins could predate the divergence of gorillas as the consequence of gene duplication and diversification.
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    URL: http://dx.doi.org/10.1023/A:1022212630370
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    Novel methods for adenovirus-mediated gene transfer to blood vessels in vivo (1997)
    Springer
    Molecular and cellular biochemistry 172 (1997), S. 37-46 
    Details
    ISSN: 1573-4919
    Keywords: gene transfer ; gene expression ; adenovirus ; blood vessel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Adenovirus-mediated gene transfer is a promising method for studies of vascular biology and potentially for gene therapy. Intravascular approaches for gene transfer to blood vessels in vivo generally require interruption of blood flow and have several limitations. We have used two alternative approaches for gene transfer to blood vessels in vivo using perivascular application of vectors. First, replication-deficient adenovirus expressing nuclear-targeted bacterial b-galactosidase was injected into cerebrospinal fluid via the cisterna magna of rats. Leptomeningeal cells over the major arteries were efficiently transfected, and adventitial cells of large vessels and smooth muscle cells of small vessels were occasionally stained. When viral suspension was injected with the rat in a lateral position, the reporter gene was expressed extensively on the ipsilateral surface of the brain. Thus, adenovirus injected into cerebrospinal fluid provides gene transfer in vivo to cerebral blood vessels and, with greater efficiency, to perivascular tissue. Furthermore, positioning of the head may ‘target’ specific regions of the brain. Second, vascular gene delivery was accomplished by perivascular injection of virus in peripheral vessels. Injection of the adenoviral vector within the periarterial sheath of monkeys resulted in gene transfer to the vessel wall that was substantial in magnitude although limited to cells in the adventitia. Approximately20% of adventitial cells expressed the transgene, with no gene transfer to cells in the intima or media. These approaches may provide alternative approaches for gene transfer to blood vessels, and may be useful for studies of vascular biology and perhaps vascular gene therapy.
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    URL: http://dx.doi.org/10.1023/A:1006803202179
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    Differential display: Identifying genes involved in cardiomyocyte proliferation (1997)
    Springer
    Molecular and cellular biochemistry 172 (1997), S. 111-120 
    Details
    ISSN: 1573-4919
    Keywords: differential display ; cardiac development ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract An estimated 15,000 different mRNA species are expressed in a typical mammalian cell. The differential expression of mRNAs in both a temporal and cell-specific manner determines the fate of the cell and creates the organism. Analysis of this differential gene expression has become a central aim of many laboratories attempting to understand the mechanisms underlying various biological processes. Currently, we are using a technique called differential display to analyze the differential expression of genes in cardiomyocytes. Differential display is a rapid and powerful technique that was introduced by Liang and Pardee in 1992. Since that time, it has been successfully applied by several groups, and it is quickly becoming a standard method for studying differential gene expression. Here, we present a detailed article discussing the differential display methodology and how we have utilized it to identify potential genes involved in cardiomyocyte proliferation. Furthermore, we have provided a list of materials and supplied examples of data obtained, in an effort to allow the reader to perform the technique with success in their own laboratory.
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    URL: http://dx.doi.org/10.1023/A:1006819705814
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    Increased gene expression of plasminogen activators and inhibitors in left ventricular hypertrophy (1997)
    Springer
    Molecular and cellular biochemistry 176 (1997), S. 265-271 
    Details
    ISSN: 1573-4919
    Keywords: plasminogen activators ; plasminogen activator inhibitors ; gene expression ; left ventricular hypertrophy ; pressure overload
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In the early stages of left ventricular hypertrophy (LVH) acute adaptive changes occur in the coronary vasculature as it remodels. Plasminogen activators (PAs) and inhibitors (PAIs) have the potential effects of proteolytic degradation that is relevant to tissue remodeling and angiogenesis. Our study focused on the possible roles of PAI-1, PAI-2, uPA and tPA in myocyte hypertrophy and angiogenesis in the early and late stages of pressure overload induced left ventricular hypertrophy (LVH). We divided seventeen adult swine, weighing 24.2 ± 6.5 kg, into four groups: control, sham-operated, early LVH and late heart failure LVH group. At surgery we placed a fixed constrictor on the ascending aorta immediately above the aortic valve. This increased LV systolic pressure from 133 ± 15 to 193 ± 24 mm Hg after the surgery. We subdivided the early group into groups of 3 animals each that we euthanized at 8, 24 and 72 h after operation and obtained heart samples for analysis. In the late heart failure group individual animals were euthanized at 55, 59, 62 and 72 days after the detection of congestive heart failure. We also obtained tissue samples from the control and sham-operated swine. Sections for histologic analysis were fixed in 10% buffered formalin. We isolated RNA, size fractionated it using 1% formaldehyde-agarose gel electrophoresis and then did Northern blots. The mRNAs from both PAI-1 and PAI-2 showed a remarkable increase at 8 and 24 h after acute aortic constriction and returned to control by 72 h. Regional differences showed that most of the increases were in the endocardium. Three animals in the late heart failure LVH group were determined to be in congestive heart failure at about 2 months after the onset of aortic constriction. In these animals PAI-1 and PAI-2 were increased in both the left and right ventricles but remained low in an animal of the same elevation in aortic pressure seen by the LV who did not have congestive failure. These data suggest that PA and PAI gene expressions change before morphologic changes occur in the early stages of developing LVH. Also at the time of onset of congestive heart failure this increased expression reappears. PAs and PA inhibitors mRNA levels vary in the different regions of the heart reflecting changing wall stresses. Thus, the PAs and PA inhibitors may play an important role in angiogenesis that occurs during the early stages of LVH. The increased expression in the late stage of LVH may reflect further changes in wall stresses since these animals also showed overt clinical signs of heart failure.
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    URL: http://dx.doi.org/10.1023/A:1006813531576
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    Microstructures of Alkoxide-Derived Barium Osumilite (BaMg2Al6Si9O30) Glass Ceramics (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 381-384 
    Details
    ISSN: 1573-4846
    Keywords: barium osumilite ; sol-gel ; alkoxide ; crystallisation ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystallisation sequence of stoichiometric barium osumilite prepared by partial-alkoxide (PAR) and all-alkoxide routes (AAR) and the microstructure of the fully crystallised glass ceramic were examined. Comparing the crystallisation behaviours of the gel-glasses obtained revealed that the first phase to crystallise was mullite in PAR but hexacelsian in AAR. Barium osumilite crystals grew randomly and more homogeneously in PAR while in AAR larger barium osumilite crystals grew in clusters. Cordierite formed as a secondary phase in both routes and it crystallised on and between the osumilite lamellae. Mullite and hexacelsian also persisted up to the stage when full crystallisation had taken place.
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    URL: http://dx.doi.org/10.1023/A:1026424110750
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    Crystallization Behavior of SiO2-TiO2 Sol-Gel Thin Films (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 409-413 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; thin films ; crystallization ; anatase ; rutile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aim of this work was to investigate the crystallization behavior of thin films of SiO2-TiO2 made by the sol-gel process as function of the TiO2 content and the temperature and time of heat treatment. Precursor solutions were prepared by hydrolysis of TEOS (tetraethoxysilane) and TPOT (titanium tetraisopropoxide). Multilayer films were spun on single crystal silicon wafers. The compositions studied were (on a molar percentage basis) 20TiO2-80SiO2, 30TiO2-70SiO2, 40TiO2-60SiO2 and pure TiO2. The films were heat treated at different temperatures between 300°C and 1200°C, for different periods of time (30 s–90 h). The crystallization kinetics were followed by micro-Raman spectrometry. Grazing incidence X-ray diffraction showed that the films crystallized into one or both of two crystalline phases of TiO2: anatase and rutile (for pure TiO2 only). The volume fractions of the crystalline phase varied from very low values (〈1%), up to 100%, for a TiO2 sample heat treated at 800°C for 8 hours. The results show that the volume fraction of crystalline phase is strongly influenced by the heat treatment temperature and also, to a smaller extent, by the heat treatment time. The most important parameter, however, is the composition of the films: the higher their TiO2 concentration, the lower is the crystallization temperature and the larger is the crystallized fraction.
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    URL: http://dx.doi.org/10.1023/A:1026444615293
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    Crystallization and Microstructure of (Sm, Pb)TiO3 Thin Films Prepared from Sol-Gel Synthesized Solutions (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 425-430 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; thin films ; lead titanate ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A sol-gel route is developed for the synthesis of samarium modified lead titanate precursor solutions. The solutions are used for the deposition of thin films. After thermal treatment of the films, two crystalline phases are observed by X-ray diffraction analysis: an undesirable pyrochlore phase and a ferroelectric perovskite. These two phases are clearly distinguished in the film microstructure, showing a fined grained fraction of pyrochlore and a-axis oriented rosette grains of perovskite. The development of these phases as well as the evolution of the perovskite/pyrochlore ratio in the films is related to the chemistry of the synthesized solutions and the thermal treatment used for crystallization.
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    URL: http://dx.doi.org/10.1023/A:1026457002089
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    Chemistry of Hybrid Organic-Inorganic. Access to Silica Materials through Chemical Selectivity (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 603-607 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; silsesquioxanes ; hybrid organic-inorganic materials ; silicas ; pore structure ; Si–C bond cleavage ; alkynyl silanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hybrid organic-inorganic materials containing labile organic fragments with various structural features have been prepared. The mild cleavage of Si–C bonds allowed removal of the organic moities. It led to silica which pore structure varied according to the nature of the organic component eliminated.
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    URL: http://dx.doi.org/10.1023/A:1018355822987
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    Nanocomposites Fe2O3/SiO2-Preparation by Sol-Gel Method and Physical Properties (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 615-618 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; magnetic nanocomposite ; iron oxide ; Mössbauer spectroscopy ; Kerr effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Magnetic nanocomposites γ-Fe2O3/silica were prepared by a one-step sol-gel method. The sol was prepared by TEOS (tetraethyl orthosilicate) acid hydrolysis in the presence of an iron salt soluble in methanol. After gelation and drying, the transparent samples were characterized after treatment at different temperatures. The particle size, observed by HR TEM, was in the range of 2–10 nm and depended on Fe-concentration and heating temperature. Magnetic measurements showed either a ferromagnetic or a superparamagnetic behaviour and could be explained by the particle size. The dependence of the magnetic behaviour on the particle size was also studied by Mössbauer spectroscopy. The samples in which the Fe2O3 particle size was approximately 10 nm showed magnetic splitting (sextet) at room temperature, while smaller particles (2–3 nm) showed this splitting only at the temperature of liquid helium. The optomagnetic properties of the samples were also measured (Kerr effect).
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    URL: http://dx.doi.org/10.1023/A:1018359923896
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    Antibody-Antigen Reactions in Porous Sol-Gel Matrices (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 663-666 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; immunoassays ; antigen ; antibody
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Porous silica gels, synthesized via the acid hydrolysis and basic condensation of TMOS, have been used for the encapsulation of antigens. The pores of the matrix are large enough to allow the diffusion of antibodies through the gel. Antigen-antibody specific fixation occurs within the sol-gel matrix. It can be detected via the so-called enzyme linked immunosorbent assays (ELISA). Antigen-antibody associations occurring in the gel are optically detected via the reaction of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. Immunoassays have been performed using the hydatid cyst fluid as the source of antigens and sera from human patients as the source of antibodies. Specific fixation appears to be as good in the sol-gel matrix as in antigen solutions.
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    URL: http://dx.doi.org/10.1023/A:1018380512509
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    Contributions to the Gelling Process in the Bi-Sr-Ca-Cu-O System, Via Acetate Route (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 681-684 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; acetates ; Bi-based superconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Metal acetates represent suitable precursors in the sol-gel method. Generally, acetates are used in multicomponent systems with alkoxides or other carboxylic salts. However, Bi-Sr-Ca-Cu-O superconductors have been obtained by the sol-gel method starting only from acetate mixture. This work was intended to study the gelling process of acetates involved in the formation of bismuth-based superconducting phases, both individually and in the bi- and multicomponent systems. Probably, copper acetate is mainly responsible for the gel formation in these systems. The gelling process was monitored by measuring the pH, density and viscosity changes. The gels obtained were characterized by UV-VIS and IR spectra, DTA/TGA and powder X-ray diffraction.
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    URL: http://dx.doi.org/10.1023/A:1018388730256
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    Processing and Characterization of Sol-Gel Derived Modified PbTiO3 for Ferroelectric Composite Applications (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 721-723 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; lead titanate ; ferroelectric ; electroactive material ; composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Powders of (Pb0.8Ca0.2)(Ti0.99Mn0.01)O3 have been prepared by sol-gel processing. A tetragonal phase is formed after heat treatment at as low as 800°C. The tetragonality was found to be 1.053 ± 0.005 and Curie temperature 315°C. Composite films with 0–3 connectivity were prepared from 800°C heat treated powders and P(VDF-TrFE) by the solvent casting technique. Composites poled at 20 MV/m, exhibited a pyroelectric coefficient of 17.4 μC/m2K and a pyroelectric figure of merit (FOMp = p/ɛ) of 0.51 μ C/m2K.
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    Preparation of Ferroelectric Thin Films from Water-Soluble Titanate-Based Gels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 729-734 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; thin films ; titanate perovskites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A description is made of a wet chemical method for obtaining ferroelectric thin films. The processing is based on a twofold synthetic scheme: the synthesis of a titanate gel from a sol-gel process and the rehydration of this gel during the incorporation into the system of other ions as water-soluble salts. The versatility of this route has made possible preparation of modified lead titanate precursor solutions. Alkaline earth ions or lanthanides such as Ca2+ or Sm3+, have been used as modifier elements. Physico-chemical properties of the solutions are studied as well as the reaction mechanisms that make possible the rehydration of the titanate gel. The solutions obtained are used for the deposition and crystallization of titanate based thin films. Crystallinity, microstructure and polarization-electrid field characteristics of the films are shown.
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    URL: http://dx.doi.org/10.1023/A:1018313502940
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    Photoelectrochemical Properties of Sol-Gel Nb2O5 Films (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 735-742 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; Nb2O5 ; film ; photoconductivity ; photoelectrochemistry ; semiconductor ; solar cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural, optical, electro and photoelectrochemical properties of amorphous and crystalline sol-gel Nb2O5 coatings have been determined. The coatings are n-type semiconductor with indirect allowed transition and present an overall low quantum efficiency (φ 〈 4%) for UV light to electric conversion. The photoconducting behavior of the coatings is discussed within the framework of the Gärtner and Södergren models. Improvement can be foreseen if Nb2O5 coatings can be made of 10–20 nm size nanoparticles.
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    Bi4Ti3O12 Thin Films from Mixed Bismuth-Titanium Alkoxides (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 759-763 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; bismuth titanate ; spin-coating ; thin films ; ferroelectric
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bi4Ti3O12 thin films were obtained by the sol-gel method. The precursor solution was prepared by allowing the two metallic alkoxides, Bi(OC2H4OCH3)3 and Ti(OC2H4OCH3)4, to react in 2-methoxy-ethanol to form the mixed alkoxide. This stable sol was deposited by spin-coating onto platinized silicon substrates. X-Ray diffraction patterns indicate that the perovskite initial crystallization temperature is 460°C for powder samples and it ranges between 400 and 500°C, for thin films, as a function of the number of coating layers. Dense, smooth and crack free thin films with grain sizes ranging from 20 nm to 500 nm are obtained, depending on the number of coating layers and on the post-deposition temperature annealing.
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    URL: http://dx.doi.org/10.1023/A:1018321721596
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    Effect of Cluster Deformations in the DLCA Modeling of the Sol-Gel Process (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 819-824 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; diffusion limited cluster-cluster aggregation ; theory of gelation ; fluctuating bond aggregation ; numerical simulations ; aggregation ; chemical gels formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The diffusion limited cluster-cluster aggregation (DLCA) model is modified by including cluster deformations during aggregation, with a tuning flexibility parameter F. A three-dimensional computer simulation is presented, which starts from a collection of f-functional monomers randomly distributed in a cubic box with a volumic fraction c (concentration) and which uses the highly efficient bond fluctuation algorithm to describe the cluster deformations. It is shown that, for F ≠ 0, there exists a well defined threshold value of the volumic fraction below which the realization of all intra-aggregate bonding possibilities prevents the formation of a gelling network. For c 〉 c g , a true sol-gel transition occurs at a characteristic time t g , after which an infinite cluster (which is self connected via the boundary conditions) appears. In contrast to DLCA, t g does not increase as the box size increases. The transition at c g is characterized by a divergence of the final clusters size for c〈c g and a divergence of the gel time for c〉c g . Several other numerical results are reported.
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    URL: http://dx.doi.org/10.1023/A:1018350527956
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    Fluorescence of Pyranine in Sol-Gel Based Silica and Hybrid Thin Films (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 895-899 
    Details
    ISSN: 1573-4846
    Keywords: luminescence ; pyranine ; sol-gel ; hybrid coatings ; emission anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The sensitivity of the pyranine fluorescence to protonation/deprotonation is used to follow modifications in cured sol-gel thin films. The acid concentration in the sol-gel solution is varied for TEOS-based coatings and a series of organically modified silanes Si(OR)3R′ are added to the TEOS solution. The concentration of the organically modified silane is varied as well as the chain length of the alkylgroup (R′). The stationary fluorescence measurements show that the equilibrium between the protonated and the deprotonated form of pyranine changes depending on the type of silica matrix. The deprotonated form is dominant in the cured SiO2 films and the protonation/deprotonation ratio of pyranine is constant for the different acid concentrations used. The protonated form becomes dominant as the concentration of Si(OR)3R′ is increased and as the alkyl chain length (R′) of the organically modified silanes is augmented. Emission anisotropy measurements of pyranine in the same coatings show that the rotational freedom of the molecule changes due to modifications in the cages for the TEOS-based coatings. These modifications are produced by the acid concentration used to prepare the coatings. An increase in the rotational freedom of pyranine is observed in the TEOS-Si(OR)3R′ systems.
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    Enhancement of the Photochromic Performance of Spirooxazine in Sol-Gel Derived Organic-Inorganic Hybrid Matrices by Additives (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 927-929 
    Details
    ISSN: 1573-4846
    Keywords: organic-inorganic hybrids ; sol-gel ; photochromic performance ; spirooxazine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Organic-inorganic hybrid materials synthesized via sol-gel processing are excellent solid matrices for photochromic dyes like spirooxazine, and the photochromic performance can be further enhanced by introducing suitable additives. This work describes the effects of additives on the photochromic intensity (Δ A 0), decolouration rate (k) and photostability of spirooxazine in sol-gel derived organic-inorganic hybrid matrices. They include fluoro-alkylsilane (FAS), bisphenol A (BPA) and methyl-imidazole (MI). FAS enhances both Δ A 0 and photostability, but has little effect on k. The higher the content of BPA, the higher the Δ A 0 and the higher the photostability, but the lower the k. The effect of MI on Δ A 0 and k is not so considerable as that of BPA and is a little complicated, while significant improvement in photostability is achieved by the addition of MI at an optimum concentration with the presence of BPA at a higher content.
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    URL: http://dx.doi.org/10.1023/A:1018337030198
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    Photochromic Doped Sol-Gel Materials for Fiber-Optic Devices (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 931-935 
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    ISSN: 1573-4846
    Keywords: photochromic ; fiber optic ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Photochromic-doped sol-gel materials have been prepared by adding a spiropyran photochromic dye to a solution of ethoxy silane monomers containing non-reacting ethyl radicals. After polymerization, normal photochromism (i.e., colored material upon UV irradiation) is obtained in the resulting matrix. The sol-gel matrix hinders the organic molecule rotations, thus giving two stable states, which can be reversibly switched by UV and green-blue irradiation respectively. If these materials are attached to optical fibers, the properties of the light throughput may be modified. Simple fiber-optic/photochromic devices made of two optical fibers placed in a V-groove removable connector have been prepared. Once cured, these devices behave as optically addressed variable delay generators. The same devices can be used for preparing simple optical switches and routing systems.
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    URL: http://dx.doi.org/10.1023/A:1018389014269
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    The Photophysical Properties of Ruthenium Polypyridyl Complexes within a Sol-Gel Matrix (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 979-983 
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    ISSN: 1573-4846
    Keywords: fluorescence ; pH ; ruthenium polypyridyl ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tetraethoxysilane (TEOS) sol-gel monoliths impregnated with three different luminescent [Ru(L)3]2+ complexes (where L = 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,7-diphenyl,1,10-phenanthroline (dpp)) have been prepared. The photoluminescence properties of these complexes were followed as a function of time, as the sol-gel reactions proceeded. Clear differences were observed in the emission energies and the emission lifetimes of the complexes upon gel formation. These differences can be explained by the different extent of electrostatic interaction between the surface of the siloxane polymer and the immobilised complex.
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    URL: http://dx.doi.org/10.1023/A:1018361702882
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    Sol-Gel Glass Waveguides (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 991-997 
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    ISSN: 1573-4846
    Keywords: sol-gel ; optical waveguides ; semiconductor-doped glass ; nonlinear optics ; laser writing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel processes show many promises for the development of low-loss, high-performance glass integrated optical circuits. Special attention is being paid to the preparation of composite glass films, where the properties of organic or inorganic dopant compounds included in the glass matrix are fully exploited. Nonlinear optical glass film waveguides have the potential to become key devices in the future, leading to further technical advances of fiber optic communication systems. This paper briefly reviews current activities in sol-gel glasses for integrated optics, with particular focus on silica-titania and semiconductor-doped films.
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    URL: http://dx.doi.org/10.1023/A:1018365803791
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    Planar ZrO2 Waveguides Prepared by the Sol-Gel Process: Structural and Optical Properties (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 999-1005 
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    ISSN: 1573-4846
    Keywords: ZrO2 ; sol-gel ; planar waveguide ; Raman scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract ZrO2 waveguides are prepared by the sol-gel process from a solution containing zirconium n-propoxide and acetylacetone in propanol-2. Structural characterizations are investigated for different annealing temperatures using suitable techniques including Waveguide Raman Spectroscopy, Electron Microscopy and Atomic Force Microscopy. Films are amorphous at 300°C and the pure ZrO2 tetragonal crystalline phase appears beyond 400°C. Crystallized films present a dense, uniform and polycrystalline structure made up by randomly oriented nanocrystallites, the diameter of which increases from 38 Å at 400°C to 53 Å at 600°C. Waveguides are at least monomode TE0 at 632.8 nm. At this wavelength, optical losses are about 0.8 ± 0.2 dB/cm for amorphous layers and increase up to 2.5 ± 0.4 dB/cm for 600°C heat-treated waveguides.
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    URL: http://dx.doi.org/10.1023/A:1018317920629
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    Improved Composition for Sol-Gel Rare-Earth Doped Planar Waveguides (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1013-1016 
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    ISSN: 1573-4846
    Keywords: sol-gel ; neodymium and erbium doped planar waveguide ; fluorescence lifetime measurement ; phosphorous and aluminium codoping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A multilayer sol-gel process has been developed in order to make highly doped rare-earth planar waveguides on silica or silicon substrates. Starting with a small range of constituents, such as SiO2, TiO2, P2O5 and Al2O3, we show that a large variety of gel compositions, with different spectroscopic behaviour, can be made when doped with rare-earths. We have doped the sol-gel films with neodymium and we have optimized their compositions by measuring the neodymium fluorescence lifetime. For a composition with 10 atom% of phosphorous, the lifetime evolution with neodymium concentration was studied and a quenching concentration was found at 1% of neodymium. We have also shown the strong influence of phosphorous or aluminium in the sol composition on the fluorescence lifetime, for a given neodymium concentration. First results on similar planar waveguides, doped with erbium, are also presented. The stability of the fluorescence lifetime over a long period of time is an other important point to be checked for these new materials: the lifetime evolution over a 9 months measurement period is presented.
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    URL: http://dx.doi.org/10.1023/A:1018374005608
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    Optical Chemical Sensors Based on Sol-Gel Materials: Recent Advances and Critical Issues (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1053-1061 
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    ISSN: 1573-4846
    Keywords: sol-gel ; optical chemical sensor ; waveguide sensor ; fibre optic sensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The use of the sol-gel process to produce materials for optical chemical sensors and biosensors is attracting considerable interest. This interest derives mainly from the design flexibility of the sol-gel process and the ease of fabrication. In most applications the sol-gel material is used to provide a microporous support matrix in which analyte-sensitive species are entrapped and into which smaller analyte molecules may diffuse. Sensors based on entrapped organic and inorganic dyes, enzymes and other biomolecules have been reported. A range of sensor configurations has been employed, including monoliths, thin films, as well as more elaborate structures. In this paper a selection is presented of recent significant developments in optical chemical sensors which employ sol-gel-derived materials. These developments include the tailoring of sol-gel materials to optimise sensor response, advanced waveguide structures and novel probe-tip sensors. Those issues which remain critical to the eventual deployment of sol-gel sensors are examined. In particular, the problems of leaching, microstructural stability, diffusion-limited response time, and susceptibility to interferents are discussed and some solutions proposed.
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    URL: http://dx.doi.org/10.1023/A:1018338426081
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    Color Displays with Gel-Glass Dispersed Liquid Crystals (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1063-1066 
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    ISSN: 1573-4846
    Keywords: GDLC ; color display ; liquid crystal ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Liquid crystal microdroplets trapped into silica gel-glasses by sol-gel processes may be used for display applications. Gel-glass dispersed liquid crystals (GDLC) are switched between opaque and transparent states by applying external AC-voltage signals; no polarizers are required. The feasibility of applying these materials to colored displays has been explored. A comparative study of different dyes for GDLC color displays, which were either embedded in the sol-gel matrix or dissolved in the liquid crystal microdroplets is presented.
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    URL: http://dx.doi.org/10.1023/A:1018394611060
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    Spectroscopic Determination of Cholinesterase Activity and Inhibition in Sol-Gel Media (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1067-1070 
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    ISSN: 1573-4846
    Keywords: cholinesterase ; sol-gel ; pesticide ; THA ; enzyme activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Biological activity of cholinesterases can be determined by optically monitoring the enzymatic reaction with indophenyl acetate, (N-4′-acetoxyphenyl)-4-quinone imine. At pH 8.0 cholinesterases hydrolyze this yellow dye to yield a blue reaction product. Cholinesterase inhibitors reduce the rate of this hydrolysis. Thus, by monitoring absorbance of the hydrolysis product at its maximum (630 nm) as a function of time, reaction rates of both cholinesterase activity and cholinesterase inhibition may be quantified spectroscopically. Using this technique, we measured the enzymatic activity of butyrylcholinesterase (BuChE) molecules encapsulated in tetramethyl orthosilicate (TMOS) silicate gel-glass prepared by hydrolysis and condensation. This activity is reduced, in a concentration-dependent manner, by the reversible cholinesterase inhibitors 1,5-bis(4-allyldimethyl-ammoniumphenyl) pentan- 3-one dibromide (BADAPP) and 9-amino-1,2,3,4-tetrahydroacridine (THA; tacrine, Cognex). The gel-glasses are rigid and compact, transparent, and porous enough to allow reagents to diffuse in and out.
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    URL: http://dx.doi.org/10.1023/A:1018350828807
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    Optimisation of Sol-Gel-Derived Silica Films for Optical Oxygen Sensing (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1121-1125 
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    ISSN: 1573-4846
    Keywords: sol-gel ; thin films ; oxygen sensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel-derived silica films were fabricated by dip-coating onto planar and optical fibre substrates. The films were pre-doped with the oxygen-sensitive ruthenium complex [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline)], whose fluorescence is quenched in the presence of oxygen. The structure and behaviour of sol-gel films is related to the fabrication parameters. In order to optimise the films for oxygen sensing in gaseous and in aqueous media, the quenching behaviour was monitored as a function of dip-speed and water : precursor ratio. By adjusting the above parameters, film properties can be tailored to optimise oxygen quenching in particular concentration ranges and environments.
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    Sol-gel processing of functional and structural ceramic oxide fibers (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 29-33 
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    ISSN: 1573-4846
    Keywords: ceramic fibers ; spinnability ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural ceramic oxide fibers like α-Al2O3, MgAl2O4 (spinel), Y3Al5O12 (YAG) and eutectic Al2O3−Y3Al5O12 as well as the functional Pb(Zr1−xTix)O3 (PZT) fibers were successfully prepared by sol-gel processing. All precursors are based on metal oxohydroxopropionates. A comparative study of sol-gel routes leading to spinnable sols demonstrates the key role of propionic acid as an excellent agent for controlling hydrolysis and condensation reactions.
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    URL: http://dx.doi.org/10.1007/BF02436813
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    Selective formation of spinel iron oxide in thin films by complexing agent-assisted sol-gel processing (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 77-81 
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    ISSN: 1573-4846
    Keywords: iron oxide ; structural control ; complexing agent ; thin film ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α-Fe2O3 with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400°C, ψ-Fe2O3 with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α-Fe2O3 appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of γ-Fe2O3 could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel film at 350°C.
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    URL: http://dx.doi.org/10.1007/BF02436821
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    Hydrolysis and condensation of transition metal alkoxide: Experiments and simulations (1997)
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    Journal of sol gel science and technology 8 (1997), S. 83-88 
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    ISSN: 1573-4846
    Keywords: sol-gel ; gelation modelling ; TiO2 gels ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We present here an experimental and numerical study of the chemical and aggregative mechanisms for titanium alkoxide in a reverse micellar medium. NMR experiments were done to study the first step of the sol-gel process: hydrolysis of titanium isopropoxide. Light and X-ray scattering experiments were then conducted to characterize the clustering of aggregates and aggregation kinetics. Fractal dimension, measured by U.S.A.X.S., varies with the hydrolysis ratio and the hydration of the surfactant. This evolution was explained by polydispersity of the hydrolysis which depends on the surfactant concentration. This hypothesis was tested through a numerical simulation of irreversible aggregation using a chemically limited aggregation model. The hydrolyzed sites are distributed among the monomers by a random procedure governed by a polydispersity parameterp, varying from 0 to 1. The total number of hydrolyzed sites is governed by a parameterq belonging to the interval [0, 1]. Thep-q evolution of the fractal dimension coincides rather well with the experimental data in all the region of the two dimensional phase space.
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    Effect of organic ligands used in sol-gel process on the formation of mullite (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 101-106 
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    ISSN: 1573-4846
    Keywords: mullite ; organic ligand ; hydrolytic polymerization ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The preparation of mullite by the sol-gel method using organic polydentate ligands and the effect of the raw materials and organic polydentate ligands on the formation of mullite were investigated. Two series of samples were prepared using tetraethoxyorthosilicate (TEOS) and aluminum nitrate nonahydrate, or dibutoxyethylacetoacetatoaluminum (Al(OBu)2(AcAcEt)) as the silica and alumina sources, respectively, and using ethylene glycol (EG), 1,3-propanediol (PD), 1,3-butanediol (BD), 2-methyl-2, 4-pentanediol (MPD), diethlene glycol monoethyl ether (DEME) and ethoxyethanol as the ligands. When the alumina source was aluminum nitrate nonahydrate, mullite was apt to appear in the order of EG〉PD〉MPD. When Al(OBu)2(AcAcEt) was the alumina source, the tendency toward the appearance of mullite crystalline phase was EG〉BD〉DEME〉MPD. Between the two alumina sources, aluminum nitrate nonahydrate gave mullite much easier than Al(OBu)2(AcAcEt). These relationships were discussed from the viewpoints of the coordination ability of the ligands and the miscibility between the silica and alumina.
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    Densification of sol-gel thin films by ultraviolet and vacuum ultraviolet irradiations (1997)
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    Journal of sol gel science and technology 8 (1997), S. 365-369 
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    ISSN: 1573-4846
    Keywords: sol-gel ; SiO2 ; TiO2 ; ultraviolet ; densification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural changes in SiO2 and TiO2 gel films were investigated using ultraviolet (UV) and vacuum ultraviolet (VUV) irradiations. A significant compaction with dehydration of SiO2 gel films was induced by irradiation of photons in the range of 9–18 eV. The refractive index and the shrinkage of the irradiated SiO2 gel films were comparable to those obtained by sintering at 1000°C. Densification of TiO2 gel films was also observed with irradiation of 5–14 eV photons. However, effects of the irradiation on TiO2 gel were smaller than those on SiO2 gel. The structural changes in the gel films are attributed to electronic excitations which are induced by irradiation with photons having higher energies than the bandgap of the oxides. The photo-induced effects are presumed to depend on the optical properties and structure of the gels.
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    Microstructures of alkoxide-derived barium osumilite (BaMg2Al6Si9O30) glass ceramics (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 381-384 
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    ISSN: 1573-4846
    Keywords: barium osumilite ; sol-gel ; alkoxide ; crystallisation ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystallisation sequence of stoichiometric barium osumilite prepared by partial-alkoxide (PAR) and all-alkoxide routes (AAR) and the microstructure of the fully crystallised glass ceramic were examined. Comparing the crystallisation behaviours of the gel-glasses obtained revealed that the first phase to crystallise was mullite in PAR but hexacelsian in AAR. Barium osumilite crystals grew randomly and more homogeneously in PAR while in AAR larger barium osumilite crystals grew in clusters. Cordierite formed as a secondary phase in both routes and it crystallised on and between the osumilite lamellae. Mullite and hexacelsian also persisted up to the stage when full crystallisation and taken place.
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    Crystallization behavior of SiO2−TiO2 sol-gel thin films (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 409-413 
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    ISSN: 1573-4846
    Keywords: sol-gel ; thin films ; crystallization ; anatase ; rutile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aim of this work was to investigate the crystallization behavior of thin films of SiO2−TiO2 made by the sol-gel process as function of the TiO2 content and the temperature and time of heat treatment. Precursor solutions were prepared by hydrolysis of TEOS (tetraethoxysilane) and TPOT (titaniums tetraisopropoxide). Multilayer films were spun on single crystal silicon wafers. The compositions studied were (on a molar percentage basis) 20TiO2−80SiO2, 30TiO2−70SiO2, 40TiO2−60SiO2 and pure TiO2. The films were heat treated at different temperatures between 300°C and 1200°C, for different periods of time (30 s-90 h). The crystallization kinetics were followed by micro-Raman spectrometry. Grazing incidence X-ray diffraction showed that the films crystallized into one or both of two crystalline phase of TiO2: anatase and rutile (for pure TiO2 only). The volume fractions of the crystalline phase varied from very low values (〈1%), up to 100%, for a TiO2 sample heat treated at 800°C for 8 hours. The results show that the volume fraction of crystalline phase is strongly influenced by the heat treatment temperature and also, to a smaller extent, by the heat treatment time. The most important parameter, however, is the composition of the films: the higher their TiO2 concentration, the lower is the crystallization temperature and the larger is the crystallized fraction.
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    A Study of the Hydrolysis-Condensation Pathways of a Hetero Bimetallic Alkoxide, Ni2Sb4(OEt)16 (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 23-28 
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    ISSN: 1573-4846
    Keywords: hydrolysis pathway ; Ni-Sb-ethoxides ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrolysis-condensation pathways of Ni-Sb-ethoxides in different toluene-ethanol solvents have been studied. The hydrolysis was performed by slow addition of controlled amounts of water, diluted in toluene-ethanol solvents. Characterization of the hydrolysis products was performed with single crystal X-ray determinations, IR-spectroscopy, UV-Vis spectroscopy and TGA. In this way, a number of different Ni-Sb-(oxo)-ethoxides have been isolated and characterized. It was thereby shown that the Ni:Sb ratio of the hetero bimetallic oxo-alkoxides varied much depending on the degree of hydrolysis and that the species formed vary with the solvent used and the speed at which the water is added.
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    Sol-Gel Processing of Functional and Structural Ceramic Oxide Fibers (1997)
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    Journal of sol gel science and technology 8 (1997), S. 29-33 
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    ISSN: 1573-4846
    Keywords: ceramic fibers ; spinnability ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural ceramic oxide fibers like α-Al2O3, MgAl2O4 (spinel), Y3Al5O12 (YAG) and eutectic Al2O3-Y3Al5O12 as well as the functional Pb(Zr1−xTix)O3 (PZT) fibers were successfully prepared by sol-gel processing. All precursors are based on metal oxohydroxopropionates. A comparative study of sol-gel routes leading to spinnable sols demonstrates the key role of propionic acid as an excellent agent for controlling hydrolysis and condensation reactions.
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    URL: http://dx.doi.org/10.1023/A:1026457913109
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    Chemistry of hybrid organic-inorganic. Access to silica materials through chemical selectivity (1997)
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    Journal of sol gel science and technology 8 (1997), S. 603-607 
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    ISSN: 1573-4846
    Keywords: sol-gel ; silsesquioxanes ; hybrid organic-inorganic materials ; silicas ; pore structure ; Si−C bond cleavage ; alkynyl silanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hybrid organic-inorganic materials containing labile organic fragments with various structural features have been prepared. The mild cleavage of Si−C bonds allowed removal of the organic moities. It led to silica which pore structure varied according to the nature of the organic component eliminated.
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    Nanocomposites Fe2O3/SiO2-preparation by sol-gel method and physical properties (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 615-618 
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    ISSN: 1573-4846
    Keywords: sol-gel ; magnetic nanocomposite ; iron oxide ; Mössbauer spectroscopy ; Kerr effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Magnetic nanocomposites γ-Fe2O3/silica were prepared by a one-step sol-gel method. The sol was prepared by TEOS (tetraethyl orthosilicate) acid hydrolysis in the presence of an iron salt soluble in methanol. After gelation and drying, the transparent samples were characterized after treatment at different temperatures. The particle size, observed by HR TEM, was in the range of 2–10 nm and depended on Fe-concentration and heating temperature. Magnetic measurements showed either a ferromagnetic or a superparamagnetic behaviour and could be explained by the particle size. The dependence of the magnetic behaviour on the particle size was also studied by Mössbauer spectroscopy. The samples in which the Fe2O3 particle size was approximately 10 nm showed magnetic splitting (sextet) at room temperature, while smaller particles (2–3 nm) showed this splitting only at the temperature of liquid helium. The optomagnetic properties of the samples were also measured (Kerr effect).
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    Antibody-antigen reactions in porous sol-gel matrices (1997)
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    Journal of sol gel science and technology 8 (1997), S. 663-666 
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    ISSN: 1573-4846
    Keywords: sol-gel ; immunoassays ; antigen ; antibody
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Porous silica gels, synthesized via the acid hydrolysis and basic condensation of TMOS, have been used for the encapsulation of antigens. The pores of the matrix are large enough to allow the diffusion of antibodies through the gel. Antigen-antibody specific fixation occurs within the sol-gel matrix. It can be detected via the so-called enzyme linked immunosorbent assays (ELISA). Antigen-antibody associations occurring in the gel are optically detected via the reaction of a peroxidase conjugate with ortho-phenylenediamine leading to the formation of a yellow coloration. Immunoassays have been performed using the hydatid cyst fluid as the source of antigens and sera from human patients as the source of antibodies. Specific fixation appears to be as good in the sol-gel matrix as in antigen solutions.
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    URL: http://dx.doi.org/10.1007/BF02436919
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    Contributions to the gelling process in the Bi−Sr−Ca−Cu−O system, via acetate route (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 681-684 
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    ISSN: 1573-4846
    Keywords: sol-gel ; acetates ; Bi-based superconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Metal acetates represent suitable precursors in the sol-gel method. Generally, acetates are used in multicomponent systems with alkoxides or other carboxylic salts. However, Bi−Sr−Ca−Cu−O superconductors have been obtained by the sol-gel method starting only from acetate mixture. This work was intended to study the gelling process of acetates involved in the formation of bismuth-based superconducting phases, both individually and in the bi-and multicomponent systems. Probably, copper acetate is mainly responsible for the gel formation in these systems. The gelling process was monitored by measuring the pH, density and viscosity changes. The gels obtained were characterized by UV-VIS and IR spectra, DTA/TGA and powder X-ray diffraction.
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    URL: http://dx.doi.org/10.1007/BF02436922
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    Processing and characterization of sol-gel derived modified PbTiO3 for ferroelectric composite applications (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 721-723 
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    ISSN: 1573-4846
    Keywords: sol-gel ; lead titanate ; ferroelectric ; electroactive material ; composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Powders of (Pb0.8Ca0.2)(Ti0.99Mn0.01)O3 have been prepared by sol-gel processing. A tetragonal phase is formed after heat treatment at as low as 800°C. The tetragonality was found to be 1.053±0.005 and Curie temperature 315°C. Composite films with 0–3 connectivity were prepared from 800°C heat treated powders and P(VDF-TrFE) by the solvent casting technique. Composites poled at 20 MV/m, exhibited a pyroelectric coefficient of 17.4 μC/m2K and a pyroelectric figure of merit (FOMp=p/ε) of 0.51 μC/m2K.
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    URL: http://dx.doi.org/10.1007/BF02436929
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    Preparation of ferroelectric thin films from water-soluble titanate-based gels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 729-734 
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    ISSN: 1573-4846
    Keywords: sol-gel ; thin films ; titanate perovskites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A description is made of a wet chemical method for obtaining ferroelectric thin films. The processing is based on a twofold synthetic scheme: the synthesis of a titanate gel from a sol-gel process and the rehydration of this gel during the incorporation into the system of other ions as water-soluble salts. The versability of this route has made possible preparation of modified elements. Physico-chemical properties of the solutions are studied as well as the reaction mechanisms that make possible the rehydration of the titanate gel. The solutions obtained are used for the deposition and crystallization of titanate based thin films. Crystallinity, microstructure and polarization-electrid field characteristics of the films are shown.
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    Photoelectrochemical properties of sol-gel Nb2O5 films (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 735-742 
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    ISSN: 1573-4846
    Keywords: sol-gel ; Nb2O5 ; film ; photoconductivity ; photoelectrochemistry ; semiconductor ; solar cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural, optical, electro and photoelectrochemical properties of amorphous and crystalline sol-gel Nb2O5 coatings have been determined. The coatings aren-type semiconductor with indirect allowed transition and present an overall low quantum efficiency (ϕ〈4%) for UV light to electric conversion. The photoconducting behavior of the coatings is discussed within the framework of the Gärtner and Södergren models. Improvement can be foreseen if Nb2O5 coatings can be made of 10–20 nm size nanoparticles.
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    Bi4Ti3O12 thin films from mixed bismuth-titanium alkoxides (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 759-763 
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    ISSN: 1573-4846
    Keywords: sol-gel ; bismuth titanate ; spin-coating ; thin films ; ferroelectric
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bi4Ti3O12 thin films were obtained by the sol-gel method. The precursor solution was prepared by allowing the two metallic alkoxides, Bi(OC2H4OCH3)3 and Ti(OC2H4OCH3)4, to react in 2-methoxy-ethanol to form the mixed alkoxide. This stable sol was deposited by spin-coating onto platinized silicon substrates. X-Ray diffraction patterns indicate that the perovskite initial crystallization temperature is 460°C for powder samples and it ranges between 400 and 500°C, for thin films, as a function of the number of coating layers. Dense, smooth and crack free thin films with grain sizes ranging from 20 nm to 500 nm are obtained, depending on the number of coating layers and on the post-deposition temperature annealing.
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    Effect of cluster deformations in the DLCA modeling of the sol-gel process (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 819-824 
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    ISSN: 1573-4846
    Keywords: sol-gel ; diffusion limited cluster-cluster aggregation ; theory of gelation ; fluctuating bond aggregation ; numerical simulations ; aggregation ; chemical gels formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The diffusion limited cluster-cluster aggregation (DLCA) model is modified by including cluster deformations during aggregation, with a tuningflexibility parameterF. A three-dimensional computer simulation is presented, which starts from a collection off-functional monomers randomly distributed in a cubic box with a volumic fractionc (concentration) and which uses the highly efficientbond fluctuation algorithm to describe the cluster deformations. It is shown that, forF≠0, there exists a well defined threshold value of the volumic fraction below which the realization of all intra-aggregate bonding possibilities prevents the formation of a gelling network. Forc〉c g , atrue sol-gel transition occurs at a characteristic timet g , after which an infinite cluster (which is self connected via the boundary conditions) appears. In contrast to DLCA,t g does not increase as the box size increases. The transition atc g is characterized by a divergence of the final clusters size forc〈c g and a divergence of the gel time forc〉c g . Several other numerical results are reported.
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    Fluorescence of pyranine in sol-gel based silica and hybrid thin films (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 895-899 
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    ISSN: 1573-4846
    Keywords: luminescence ; pyranine ; sol-gel ; hybrid coatings ; emission anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The sensitivity of the pyranine fluorescence to protonation/deprotonation is used to follow modifications in cured sol-gel thin films. The acid concentration in the sol-gel solution is varied for TEOS-based coatings and a series of organically modified silanes Si(OR)3R’ are added to the TEOS solution. The concentration of the organically modified silane is varied as well as the chain length of the alkylgroup (R’). The stationary fluorescence measurements show that the equilibrium between the protonated and the deprotonated form of pyranine changes depending on the type of silica matrix. The deprotonated form is dominant in the cured SiO2 films and the protonation/deprotonation ratio of pyranine is constant for the different acid concentrations used. The protonated form becomes dominant as the concentration of Si(OR)3R’ is increased and as the alkyl chain length (R’) of the organically modified silanes is augmented. Emission anisotropy measurements of pyranine in the same coatings show that the rotational freedom of the molecule changes due to modifications in the cages for the TEOS-based coatings. These modifications are produced by the acid concentration used to prepare the coatings. An increase in the rotational freedom of pyranine is observed in the TEOS-Si(OR)3R’ systems.
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    Photochromic doped sol-gel materials for fiber-optic devices (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 931-935 
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    ISSN: 1573-4846
    Keywords: photochromic ; fiber optic ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Photochromic-doped sol-gel materials have been prepared by adding a spiropyran photochromic dye to a solution of ethoxy silane monomers containing non-reacting ethyl radicals. After polymerization, normal photochromism (i.e., colored material upon UV irradiation) is obtained in the resulting matrix. The sol-gel matrix hinders the organic molecule rotations, thus giving two stable states, which can be reversibly switched by UV and green-blue irradiation respectively. If these materials are attached to optical fibers, the properties of the light throughput may be modified. Simple fiber-optic/photochromic devices made of two optical fibers placed in a V-groove removable connector have been prepared. Once cured, these devices behave as optically addressed variable delay generators. The same devices can be used for preparing simple optical switches and routing systems.
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    URL: http://dx.doi.org/10.1007/BF02436963
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    Magneto-optical characteristics of Co, Ti-substituted barium hexaferrite films deposited by the dip-coating method (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 947-951 
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    ISSN: 1573-4846
    Keywords: hexagonal ferrites ; thin films ; sol-gel ; magneto-optics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pure and Co, Ti-substituted hexagonal barium ferrite (BaFe12O19, BaM) films were prepared by the dip-coating method from alkoxides. After repeated dipping, drying and calcining at 500°C for about 15 minutes in an oxygen atmosphere, polycrystalline films with a thickness of 1–1.8 μm on SiO2 substrates were obtained. Spectral dependencies of the Faraday rotation and the optical transmission of BaCo x Ti x Fe12−2x O19(0≤x≤0.8) films were measured in the range from 500 to 2500 nm at room temperature. The absorption coefficient did not display much structure, but specific Faraday rotation spectra of Co, Ti-ferrite films showed local maxima at 720, 1475 and 1750 nm. At those wavelengths, the magneto-optical figure of merit attains its maximum values. For comparison of the crystallization and magnetic properties, Ba(CoTi) x Fe12−2x O19 (x=0.9) powder has also been prepared by the sol-gel method.
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    The photophysical properties of ruthenium polypyridyl complexes within a sol-gel matrix (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 979-983 
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    ISSN: 1573-4846
    Keywords: fluorescence ; pH ; ruthenium polypyridyl ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tetraethoxysilane (TEOS) sol-gel monoliths impregnated with three different luminescent [Ru(L)3]2+ complexes (whereL=2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), or 4,7-diphenyl,1,10-phenanthroline (dpp)) have been prepared. The photoluminescence properties of these complexes were followed as a function of time, as the sol-gel reactions proceeded. Clear differences were observed in the emission energies and the emission lifetimes of the complexes upon gel formation. These differences can be explained by the different extent of electrostatic interaction between the surface of the siloxane polymer and the immobilised complex.
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    Sol-gel glass waveguides (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 991-997 
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    ISSN: 1573-4846
    Keywords: sol-gel ; optical waveguides ; semiconductor-doped glass ; nonlinear optics ; laser writing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel processes show many promises for the development of low-loss, high-performance glass integrated optical circuits. Special attention is being paid to the preparation of composite glass film, where the properties of organic or inorganic dopant compounds included in the glass matrix are fully exploited. Nonlinear optical glass film waveguides have the potential to become key devices in the future, leading to further technical advances of fiber optic communication systems. This paper briefly reviews current activities in sol-gel glasses for integrated optics, with particular focus on silica-titania and semiconductor-doped films.
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    URL: http://dx.doi.org/10.1007/BF02436973
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    Planar ZrO2 waveguides prepared by the sol-gel process: Structural and optical properties (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 999-1005 
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    ISSN: 1573-4846
    Keywords: ZrO2 ; sol-gel ; planar waveguide ; Raman scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract ZrO2 waveguides are prepared by the sol-gel process from a solution containing zirconiumn-propoxide and acetylacetone in propanol-2. Structural characterizations are investigated for different annealing temperatures using suitable techniques including Waveguide Raman Spectroscopy, Electron Microscopy and Atomic Force Microscopy. Films are amorphous at 300°C and the pure ZrO2 tetragonal crystalline phase appears beyond 400°C. Crystallized films present a dense, uniform and polycrystalline structure made up by randomly oriented nanocrystallites, the diameter of which increases from 38 Å at 400°C to 53 Å at 600°C. Waveguides are at least monomode TE0 at 632.8 nm. At this wavelength, optical losses are about, 0.8±0.2dB/cm for amorphous layers and increase up to 2.5±0.4 dB/cm for 600°C heat-treated waveguides.
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    Improved composition for sol-gel rare-earth doped planar waveguides (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1013-1016 
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    ISSN: 1573-4846
    Keywords: sol-gel ; neodymium and erbium doped planar waveguide ; fluorescence lifetime measurement ; phosphorous and aluminium codoping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A multilayer sol-gel process has been developed in order to make highly doped rare-earth planar waveguides on silica or silicon substrates. Starting with a small range of constituents, such as SiO2, TiO2, P2O5 and Al2O3, we show that a large variety of gel compositions, with different spectroscopic behaviour, can be made when doped with rare-earths. We have doped the sol-gel films with neodymium and we have optimized their compositions by measuring the neodymium fluorescence lifetime. For a composition with 10 atom% of phosphorous, the lifetime evolution with neodymium concentration was studied and a quenching concentration was found at 1% of neodymium. We have also shown the strong influence of phosphorous or aluminium in the sol composition on the fluorescence lifetime, for a given neodymium concentration. First results on similar planar waveguides, doped with erbium, are also presented. The stability of the fluorescence lifetime over a long period of time is an other important point to be checked for these new materials: the lifetime evolution over a 9 months measurement period is presented.
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    Magneto-Optical Characteristics of Co, Ti-Substituted Barium Hexaferrite Films Deposited by the Dip-Coating Method (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 947-951 
    Details
    ISSN: 1573-4846
    Keywords: hexagonal ferrites ; thin films ; sol-gel ; magneto-optics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pure and Co, Ti-substituted hexagonal barium ferrite (BaFe12O19, BaM) films were prepared by the dip-coating method from alkoxides. After repeated dipping, drying and calcining at 500°C for about 15 minutes in an oxygen atmosphere, polycrystalline films with a thickness of 1–1.8 μm on SiO2 substrates were obtained. Spectral dependencies of the Faraday rotation and the optical transmission of BaCoxTixFe12-2xO19 (0 ≤ x ≤ 0.8) films were measured in the range from 500 to 2500 nm at room temperature. The absorption coefficient did not display much structure, but specific Faraday rotation spectra of Co, Ti-ferrite films showed local maxima at 720, 1475 and 1750 nm. At those wavelengths, the magneto-optical figure of merit attains its maximum values. For comparison of the crystallization and magnetic properties, Ba(CoTi)xFe12-2xO19 (x = 0.9) powder has also been prepared by the sol-gel method.
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    URL: http://dx.doi.org/10.1023/A:1018352421519
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    Comparison between sol-gel, coprecipitation and wet mixing synthesis of ZnAl2O4 (1997)
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    Journal of sol gel science and technology 8 (1997), S. 107-110 
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    ISSN: 1573-4846
    Keywords: sol-gel ; zinc aluminate ; spinel structure ; catalyst support
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract ZnAl2O4 was prepared by hydrolyzing a mixture of aluminum alkoxide with zinc nitrate dissolved in hexylene glycol and calcining at 800°C. The results are compared with those obtained by wet mixing and coprecipitation. The sol-gel method produces solids whose surface areas and pore volumes are 100% larger and with a more homogeneous pore size distribution.
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    Crystallization and microstructure of (Sm, Pb)TiO3 thin films prepared from sol-gel synthesized solutions (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 425-430 
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    ISSN: 1573-4846
    Keywords: sol-gel ; thin films ; lead titanate ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A sol-gel route is developed for the synthesis of samarium modified lead titanate precursor solutions. The solutions are used for the deposition of thin films. After thermal treatment of the films, two crystalline phases are observed by X-ray diffraction analysis: an undesirable pyrochlore phase and a ferroelectric perovskite. These two phases are clearly distinguished in the film microstructure, showing a fined grained fraction of pyrochlore anda-axis oriented rosette grains of perovskite. The development of these phases as well as the evolution of the perovskite/pyrochlore ratio in the films is related to the chemistry of the synthesized solutions and the thermal treatment used for crystallization.
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    Enhancement of the photochromic performance of spirooxazine in sol-gel derived organic-inorganic hybrid matrices by additives (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 927-929 
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    ISSN: 1573-4846
    Keywords: organic-inorganic hybrids ; sol-gel ; photochromic performance ; spirooxazine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Organic-inorganic hybrid materials synthesized via sol-gel processing are excellent solid matrices for photochromic dyes like spirooxazine, and the photochromic performance can be further enhanced by introducing suitable additives. This work describes the effects of additives on the photochromic intensity (ΔA 0), decolouration rate (k) and photostability of spirooxazine in sol-gel derived organic-inorganic hybrid matrices. They include fluoroalkylsilane (FAS), bisphenolA (BPA) and methyl-imidazole (MI). FAS enhances both ΔA 0 and photostability, but has little effect onk. The higher the content of BPA, the higher the ΔA 0 and the higher the photostability, but the lower thek. The effect of MI on ΔA 0 andk is not so considerable as that of BPA and is a little complicated, while significant improvement in photostability is achieved by the addition of MI at an optimum concentration with the presence of BPA at a higher content.
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    Color displays with gel-glass dispersed liquid crystals (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1063-1066 
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    ISSN: 1573-4846
    Keywords: GDLC ; color display ; liquid crystal ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Liquid crystal microdroplets trapped into silica gel-glasses by sol-gel processes may be used for display applications. Gel-glass dispersed liquid crystals (GDLC) are switched between opaque and transparent states by applying external AC-voltage signals; no polarizers are required. The feasibility of applying these materials to colored displays has been explored. A comparative study of different dyes for GDLC color displays, which were either embedded in the sol-gel matrix or dissolved in the liquid crystal microdroplets is presented.
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    Optical chemical sensors based on sol-gel materials: Recent advances and critical issues (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1053-1061 
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    ISSN: 1573-4846
    Keywords: sol-gel ; optical chemical sensor ; waveguide sensor ; fibre optic sensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The use of the sol-gel process to produce materials for optical chemical sensors and biosensors is attracting considerable interest. This interest derives mainly from the design flexibility of the sol-gel process and the ease of fabrication. In most applications the sol-gel material is used to provide a microporous support matrix in which analyte-sensitive species are entrapped and into which smaller analyte molecules may diffuse. Sensors based on entrapped organic and inorganic dyes, enzymes and other biomolecules have been reported. A range of sensor configurations has been employed, including monoliths, thin films, as well as more elaborate structures. In this paper a selection is presented of recent significant developments in optical chemical sensors which employ solgel-derived materials. These developments include the tailoring of sol-gel materials to optimise sensor response, advanced waveguide structures and novel probe-tip sensors. Those issues which remain critical to the eventual deployment of sol-gel sensors are examined. In particular, the problems of leaching, microstructural stability, diffusion-limited response time, and susceptibility to interferents are discussed and some solutions proposed.
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    Spectroscopic determination of cholinesterase activity and inhibition in sol-gel media (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1067-1070 
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    ISSN: 1573-4846
    Keywords: cholinesterase ; sol-gel ; pesticide ; THA ; enzyme activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Biological activity of cholinesterases can be determined by optically monitoring the enzymatic reaction with indophenyl acetate, (N-4′-acetoxyphenyl)-4-quinone imine. At pH 8.0 cholinesterases hydrolyze this yellow dye to yield a blue reaction product. Cholinesterase inhibitors reduce the rate of this hydrolysis. Thus, by monitoring absorbance of the hydrolysis product at its maximum (630 nm) as a function of time, reaction rates of both cholinesterase activity and cholinesterase inhibition may be quantified spectroscopically. Using this technique, we measured the enzymatic activity of butyrylcholinesterase (BuChE) molecules encapsulated in tetramethyl orthosilicate (TMOS) silicate gel-glass prepared by hydrolysis and condensation. This activity is reduced, in a concentration-dependent manner, by the reversible cholinesterase inhibitors 1,5-bis(4-allyldimethyl-ammoniumphenyl) pentan 3-one dibromide (BADAPP) and 9-amino-1,2,3,4-tetrahydroacridine (THA; tacrine, Cognex). The gel-glasses are rigid, and compact, transparent and porous enough to allow reagents to diffuse in and out.
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    Optimisation of sol-gel-derived silica films for optical oxygen sensing (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1121-1125 
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    ISSN: 1573-4846
    Keywords: sol-gel ; thin films ; oxygen sensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-gel-derived silica films were fabricated by dip-coating onto planar and optical fibre substrates. The films were pre-doped with the oxygen-sensitive ruthenium complex [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline)], whose fluorescence is quenched in the presence of oxygen. The structure and behaviour of sol-gel films is related to the fabrication parameters. In order to optimise the films for oxygen sensing in gaseous and in aqueous media, the quenching behaviour was monitored as a function of dip-speed and water: precursor ratio. By adjusting the above parameters, film properties can be tailored to optimise oxygen quenching in particular concentration ranges and environments.
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    Rheological Characterization of BaTiO3 Sol-Gel Transition (1997)
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    Journal of sol gel science and technology 9 (1997), S. 5-15 
    Details
    ISSN: 1573-4846
    Keywords: rheology ; sol-gel ; barium titanate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract BaTiO3 gels were prepared by hydrolysis and polycondensation reactions between titanium isopropoxide and barium hydroxide in presence of methoxyethanol, methanol and water. The rheology of the sol-gel transition was studied with a rheometer allowing low amplitude sinusoidal oscillations. Experimental data show a continuous increase in the complex viscosity along with time, showing the progressive character of the transition. The influence of synthesis operating variables was studied. The gelation time, which definition is based on viscoelastic measurements, increases exponentially when the water content is increased, when the dilution due to the methoxyethanol is reduced or when the temperature is lowered. Different growth models were used for the characterization of the particles in the solution. These models suggest that the polymerisation first produces spherical particles (mass fractals) and that these spherical particles then agglomerate to form a linear network.
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    URL: http://dx.doi.org/10.1023/A:1026496104827
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  • 82
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    Fourier Transform and Multi Dimensional EPR Spectroscopy for the Characterization of Sol-Gel Derived Hydroxyapatite (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 17-24 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; hydroxyapatite ; FT-EPR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Calcium hydroxyapatite powder was prepared by sol-gel method using calcium acetate and PO(OC2H5)3 as initial compounds, and alcohol (methyl, ethyl, and propyl-alcohol) as solvent. Homogeneous solution and gels were prepared using a molar ratio of Ca/P = 1.67. The evolution of the structure was detected by X-ray diffraction, IR, and FT-n(=1,2,3)D-EPR spectroscopy. The dried gels exhibit a signal characterized by a central line and two satellites. The 2D spectrum (ESEEM vs. field sweep) showed the same modulation for the central line. The FT-EPR spectrum vs. field sweep 2D-spectrum indicated that the satellites are due to an hfs splitting with water. The central region of this 2D spectrum is influenced by P and H in a concentration ratio of [H]/[P]=2.5. The ESEEM spectrum was simulated assuming the equation $$V_{\bmod } = V_{\bmod } (P)^m V_{\bmod } (H)^n $$ for two spin systems S = 1/2 and I = 1/2. This simulation gave for m and n the values of 2 and 5, respectively. This finding suggests the structure: $$\begin{gathered} {\text{ O = P}}---{\text{O}}---{\text{CH}}_{\text{2}} ---{\text{CH}}_{\text{3}} \hfill \\ {\text{ |}} \hfill \\ {\text{ O}} \hfill \\ {\text{O}}---*{\text{P}}---{\text{O}}---{\text{CH}}_{\text{2}} ---{\text{CH}}_{\text{3}} \hfill \\ {\text{ |}} \hfill \\ {\text{ O}} \hfill \\ {\text{ O = P}}---{\text{O}}---{\text{CH}}_{\text{2}} ---{\text{CH}}_{\text{3}} \hfill \\ \end{gathered} $$ for the unpaired state. It appears that one ethyl group does not hydrolyse in the gelation process. The ESEEM spectra of hydroxyapatite exhibit a modulation generated by P, H and Ca atoms.
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    URL: http://dx.doi.org/10.1023/A:1026452021666
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  • 83
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    Spectroscopic Study of Cerium-Doped Silica Gel Monoliths and Their Densified Derivatives (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 65-69 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; cerium ; silica gel ; rehydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cerium is exploited as a probe cation for elucidating the structure of an alkoxide-derived silica gel and its progressive evolution to a glass network as a function of heat-treatment up to 1000°C. At intermediate temperatures, the host structure exhibits inhomogeneity due to insufficient formation of siloxane bonds, which is reflected by at least two different sites and co-ordination spheres (termed “high” and “low” water ligation) for cerium. This is proved by the response of the gels heated up to 700°C to rehydration. Further formation of Si-O-Si network (900°C) leads to the destruction of the “high water” sites of cerium and progression towards a glassy structure. It is, however, only after heat-treatment at 1000°C that a dense silica glass network, not responding to rehydration, is finally obtained with cerium ions embedded in it.
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  • 84
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    Alkoxide Derived SrBi2Ta2O9 Phase Pure Powder and Thin Films (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 95-101 
    Details
    ISSN: 1573-4846
    Keywords: SrBi2Ta2O9 ; sol-gel ; thin films ; ferroelectric non-volatile memories
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Phase pure powder and thin films of the novel ferroelectric materials SrBi2Ta2O9 (SBT) have been prepared using the organic precursors. The xero-gel formed was dried and characterized using TGA and DTA to determine the organic burn out and crystallization temperature of SBT. Powder X-ray diffraction was used systematically to check the crystallinity of SBT. Phase pure SBT powder was formed as low as 650°C and thin films at 600°C in comparison to other earlier reported work. SEM micrographs show a grain size of ∼0.1 μm and show crack free films with a film thickness of 2 μm.
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    URL: http://dx.doi.org/10.1023/A:1026468525300
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  • 85
    Electronic Resource
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    Rheological characterization of BaTiO3 sol-gel transition (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 5-15 
    Details
    ISSN: 1573-4846
    Keywords: rheology ; sol-gel ; barium titanate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract BaTiO3 gels were prepared by hydrolysis and polycondensation reactions between titanium isopropoxide and barium hydroxide in presence of methoxyethanol, methanol and water. The rheology of the sol-gel transition was studied with a rheometer allowing low amplitude sinusoidal oscillations. Experimental data show a continuous increase in the complex viscosity along with time, showing the progressive character of the transition. The influence of synthesis operating variables was studied. The gelation time, which definition is based on viscoelastic measurements, increases exponentially when the water content is increased, when the dilution due to the methoxyethanol is reduced or when the temperature is lowered. Different growth models were used for the characterization of the particles in the solution. These models suggest that the polymerisation first produces spherical particles (mass fractals) and that these spherical particles then agglomerate to form a linear network.
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    URL: http://dx.doi.org/10.1007/BF02439331
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  • 86
    Electronic Resource
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    Fourier transform and multi dimensional EPR spectroscopy for the characterization of sol-gel derived hydroxyapatite (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 17-24 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; hydroxyapatite ; FT-EPR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Calcium hydroxyapatite powder was prepared by sol-gel method using calcium acetate and PO(OC2H5)3 as initial compounds, and alcohol (methyl, ethyl, and propyl-alcohol) as solvent. Homogeneous solution and gels were prepared using a molar ratio of Ca/P=1.67. The evolution of the structure was detected by X-ray diffraction, IR, and FT-n(=1,2,3)D-EPR spectroscopy. The dried gels exhibit a signal characterized by a central line and two satellites. The 2D spectrum (ESEEM vs. field sweep) showed the same modulation for the central line. The FT-EPR spectrum vs. field sweep 2D-spectrum indicated that the satellites are due to an hfs splitting with water. The central region of this 2D spectrum is influenced by P and H in a concentration ratio of [H]/[P]=2.5. The ESEEM spectrum was simulated assuming the equation Vmod=Vmod(P)mVmod(H)n for two spin systems S=1/2 and I=1/2. This simulation gave form andn the values of 2 and 5, respectively. This finding suggests the structure: for the unpaired state. It appears that one ethyl group does not hydrolyse in the gelation process. The ESEEM spectra of hydroxyapatite exhibit a modulation generated by P, H and Ca atoms.
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    URL: http://dx.doi.org/10.1007/BF02439332
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  • 87
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    Spectroscopic study of cerium-doped silica gel monoliths and their densified derivatives (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 65-69 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; cerium ; silica gel ; rehydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cerium is exploited as a probe cation for elucidating the structure of an alkoxide-derived silica gel and its progressive evolution to a glass network as a function of heat-treatment up to 1000°C. At intermediate temperatures, the host structure exhibits inhomogeneity due to insufficient formation of siloxane bonds, which is reflected by at least two different sites and co-ordination spheres (termed “high” and “low” water ligation) for cerium. This is proved by the response of the gels heated up to 700°C to rehydration. Further formation of Si−O−Si network (900°C) leads to the destruction of the “high water” sites of cerium and progression towards a glassy structure. It is, however, only after heat-treatment at 1000°C that a dense silica glass network, not responding to rehydration, is finally obtained with cerium ions embedded in it.
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    URL: http://dx.doi.org/10.1007/BF02439337
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  • 88
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    Alkoxide derived SrBi2Ta2O9 phase pure powder and thin films (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 95-101 
    Details
    ISSN: 1573-4846
    Keywords: SrBi2Ta2O9 ; sol-gel ; thin films and ferroelectric non-volatile memories
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Phase pure powder and thin films of the novel ferroelectric materials SrBi2Ta2O9 (SBT) have been prepared using the organic precursors. The xero-gel formed was dried and characterized using TGA and DTA to determine the organic burn out and crystallization temperature of SBT. Powder X-ray diffraction was used systematically to check the crystallinity of SBT. Phase pure SBT powder was formed as low as 650°C and thin films at 600°C in comparison to other earlier reported work. SEM micrographs show a grain size of ≈0.1 μm and show crack free films with a film thickness of 2 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02439340
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  • 89
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    Sol-Gel Synthesis of Ge Nanocrystals-Doped Glass and Its Photoluminescence (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 139-143 
    Details
    ISSN: 1573-4846
    Keywords: Ge nano-crystal ; photoluminescence ; doped glass ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ge nanocrystal-embedded SiO2 glasses were prepared by a sol-gel process. The glasses synthesized through the hydrolysis of Si(OC2H5)4 and GeCl4 were heated in H2 gas atmosphere at 500 to 800°C, in which Ge4+ ions were reduced to precipitate nanosized Ge crystals with the size smaller than 10 nm diameter. Glasses doped with Ge nanocrystals of diameter of ∼5nm showed the optical absorption edge at ∼2.8 eV and a broad photoluminescence exhibiting the peak at around 2.2 eV. Large Ge crystals precipitated by heating above 800°C showed no photoluminescence.
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    URL: http://dx.doi.org/10.1023/A:1026461029767
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  • 90
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    Sol-Gel Synthesis of Potassium Titanyl Phosphate: Solution Chemistry and Gelation (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 183-199 
    Details
    ISSN: 1573-4846
    Keywords: KTP ; sol-gel ; non-linear optics ; solution chemistry ; mixed metal oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The solution chemistry and aggregation mechanisms involved in sol-gel synthesis of potassium titanyl phosphate (KTP) are studied in detail. The chemistry of the metal precursors are shown to be critical for the formation of the desired KTP phase. The precursor solution as well as some preparation intermediates were studied by several spectroscopic methods to determine the structure of the organometallic species present in these solutions. The structural evolution taking place in the solution after hydrolysis was studied using photon correlation spectroscopy and small angle X-ray scattering techniques. The influence on the gelation of several preparation parameters such as, the precursors chemistry, the mixing order of the metal alkoxides, the solvent/KTP ratio and the water/KTP molar ratio was also examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026421415654
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  • 91
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    Sol-gel synthesis of ge nanocrystals-doped glass and its photoluminescence (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 139-143 
    Details
    ISSN: 1573-4846
    Keywords: Ge nano-crystal ; photoluminescence ; doped glass ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ge nanocrystal-embedded SiO2 glasses were prepared by a sol-gel process. The glasses synthesized through the hydrolysis of Si(OC2H5)4 and GeCl4 were heated in H2 gas atmosphere at 500 to 800°C, in which Ge4+ ions were reduced to precipitate nanosized Ge crystals with the size smaller than 10 nm diameter. Glasses doped with Ge nanocrystals of diameter of ≈5 nm showed the optical absorption edge at ≈2.8 eV and a broad photoluminescence exhibiting the peak at around 2.2 eV. Large Ge crystals precipitated by heating above 800°C showed no photoluminescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02439394
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  • 92
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    Sol-gel synthesis of potassium titanyl phosphate: Solution chemistry and gelation (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 183-199 
    Details
    ISSN: 1573-4846
    Keywords: KTP ; sol-gel ; nonlinear optics ; solution chemistry ; mixed metal oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The solution chemistry and aggregation mechanisms involved in sol-gel synthesis of potassium titanyl phosphate (KTP) are studied in detail. The chemistry of the metal precursors are shown to be critical for the formation of the desired KTP phase. The precursor solution as well as some preparation intermediates were studied by several spectroscopic methods to determine the structure of the organometallic species present in these solutions. The structural evolution taking place in the solution after hydrolysis was studied using photon correlation spectroscopy and small angle X-ray scattering techniques. The influence on the gelation of several preparation parameters such as, the precursors chemistry, the mixing order of the metal alkoxides, the solvent/KTP ratio and the water/KTP molar ratio was also examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02439398
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  • 93
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    Preparation and photochromic behavior of ormosil containing encapsulated AgTCNQ molecules (1997)
    Springer
    Journal of sol gel science and technology 9 (1997), S. 279-283 
    Details
    ISSN: 1573-4846
    Keywords: AgTCNQ ; photochromism ; sol-gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Preparation and photochromic behavior of ormosil containing encapsulated AgTCNQ molecules were studied in this paper. The ormosil resulted from hydrolysis and polycondensation of glycidoxypropyltrimethoxysilane, dimethyldimethoxysilane and methyltrimethoxysilane. The time to add AgNO3 water solution into the resultant sol was a key factor to synthesize AgTCNQ molecules inside ormosil matrix. AgTCNQ molecules encapsulated in the ormosil showed different photochromic behavior compared with pure AgTCNQ film: normal photochromic reaction can be realized, while reverse photochromic reaction can not. The “cage” model was used to explain this phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02437191
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  • 94
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    Regulation of lipoprotein metabolism by estrogen in inbred strains of mice occurs primarily by posttranscriptional mechanisms (1997)
    Springer
    Molecular and cellular biochemistry 173 (1997), S. 161-168 
    Details
    ISSN: 1573-4919
    Keywords: estrogen ; apolipoprotein ; gene expression ; mice ; atherosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Estrogen protects against developing premature coronary artery disease.However, the mechanism of protective effects of estrogen still remainspoorly understood. One mechanism by which estrogen can have protectiveeffects apppears to be through modulation of plasma lipoproteins. We showedthat the mouse can be used as animal model to study estrogen-mediatedsynthesis and secretion of lipoproteins since, unlike the rat, the mousedoes not up-regulate LDL receptors (Srivastava et al. [4]). Since inbredstrains of mice differ in their genetic background and show differingresponsiveness to dietary lipids, we examined how various inbred strains ofmice respond to estradiol administration, and whether some mouse strainsshow responses similar to rats. 17b-estradiol was administered to male micefrom 15 different inbred strains, and the changes in plasma levels oflipids, apoB, apoAI, and apoE were examined. Total cholesterol decreased inall but one strain, apoAI levels decreased in all but 3 strains while apoBlevels and apoB/apoAI ratios increased in all but 2 strains, suggesting thatin contrast to rats, the apoB-containing lipoproteins increased relative toHDL in all strains of mice examined. Basal and estradiol-induced changes intotal cholesterol were significantly correlated with changes in apoAI, butnot apoB, reflecting the predominance of HDL over other lipoproteins inmouse plasma. The effects of estrogen on plasma apoE levels varied amongvarious inbred strains of mice tested. Plasma apoE levels increased in sevenstrains treated with estrogen, and remained unchanged in the rest. Toexamine whether changes of plasma apoproteins are associated with thechanges in the respective hepatic mRNA levels, apoAI, B and E mRNA werequantified by RNase protection assay. Hepatic apoE mRNA did not showcorrelation with either basal or post treatment plasma apoE levels in any ofthe strains. Similarly, most of the mouse strains did not show correlationof plasma apoAI and apoB levels with the corresponding hepatic mRNA levels.These results suggest that estrogen regulates plasma lipoproteinconcentrations primarily by posttranscriptional mechansims, and there werestrain-related differences in the estrogen-mediated regulation oflipoprotein metabolism.
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  • 95
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    Expression of calcium-binding protein regucalcin mRNA in the cloned human hepatoma cells (HegG2): Stimulation by insulin (1997)
    Springer
    Molecular and cellular biochemistry 175 (1997), S. 163-168 
    Details
    ISSN: 1573-4919
    Keywords: regucalcin ; Ca2+-binding protein ; insulin ; gene expression ; HepG2 cells ; transformed cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The expression of hepatic Ca2+-binding protein regucalcin in the cloned human hepatoma cells (HepG2) was investigated. The change in regucalcin mRNA levels was analyzed by Northern blotting using rat liver regucalcin complementary DNA (0.9 kb of open reading frame). Regucalcin mRNA was expressed in HepG2 cells, although the mRNA was markedly expressed in normal rat liver. Moreover, regucalcin protein in HepG2 cells was detected by Western blot analysis using a polyclonal rabbit anti-regucalcin antibody. Regucalcin mRNA expression in HepG2 cells was clearly stimulated by the culture with insulin (10-8 M) of the effective concentration. Regucalcin protein in HepG2 cells was also increased by the treatment of insulin (10-8 M). The present results demonstrate that regucalcin is expressed in the transformed HepG2 cells, and that the expression is stimulated by insulin.
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    URL: http://dx.doi.org/10.1023/A:1006844815743
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  • 96
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    Intrinsic secondary structure of human TNFR-I mRNA influences the determination of gene expression by RT-PCR (1997)
    Springer
    Molecular and cellular biochemistry 177 (1997), S. 1-6 
    Details
    ISSN: 1573-4919
    Keywords: gene expression ; mRNA secondary structure ; single tube RT-PCR ; TNF receptor I
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The secondary structure of human tumor necrosis factor receptor I (TNFR-I) mRNA based on its lowest folding energy was predicted. Three combinations of primers selected from open-regions and four combinations of primers from closed-regions of TNFR-I mRNA structure were employed for single-tube reverse transcription-polymerase chain reaction (RT-PCR) for the determination of TNFR-I gene expression in U937 cell. All the primers were designed with the same criteria. However, the different primers generated distinct quantities of RT-PCR products from the same concentration of TNFR-I mRNA, implying that the determination of gene expression by RT-PCR was affected by the mRNA secondary structure. In addition, the sensitivity of the open-region RT-PCR was approximately one hundred-fold higher than that in the closed-regions of TNFR-I mRNA. The low efficiency of the closed-region RT-PCR was not correlated with the G/C content of the TNFR-I mRNA structure. These results suggest that consideration of the influence of intrinsic mRNA structure of a gene is essential prior to the determination of gene expression by quantitative RT-PCR, and this open-region strategy of primer design may yield an efficient primer for in vitro amplification of cDNA by RT-PCR.
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    URL: http://dx.doi.org/10.1023/A:1006862304381
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  • 97
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    Alternative splicing of human plasma cholesteryl ester transfer protein mRNA in Caco-2 cells and its modulation by oleic acid (1997)
    Springer
    Molecular and cellular biochemistry 177 (1997), S. 107-112 
    Details
    ISSN: 1573-4919
    Keywords: cholesteryl ester ; CETP ; Caco-2 ; polymerase chain reaction ; gene expression ; mRNA ; alternative splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Cholesteryl ester transfer protein (CETP) is a plasma protein involved in the reverse cholesterol transport and expressed in several human tissues and cell lines. We studied CETP expression in Caco-2 cell line, a model of the human enterocyte epithelium. By reverse-transcriptase polymerase chain reaction, we could demonstrate that in basal condition Caco-2 cells have a low rate of expression of active CETP mRNA. Furthermore, we found that even in this cell line CETP mRNA alternative splicing occurs with deletion of exon 9 sequence. Densitometric analysis of the in vitro amplified fragments showed that under basal conditions about 60% of reverse transcribed CETP cDNA corresponds to exon 9-deleted transcripts. After challenge with 50 µM sodium oleate, there is a ∼2 fold increase in the transcription rate of the full-length CETP cDNA, as measured by competitive PCR, which is accompanied to an increased activity measured in the cell-conditioned medium. On the contrary, no significant change is seen in the amount of exon 9-deleted cDNA. Consequently, an inversion in the ratio of full-length and exon 9-deleted CETP cDNA is evident, suggesting that sodium oleate selectively enhances the expression of full-length CETP mRNA.
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    URL: http://dx.doi.org/10.1023/A:1006823601032
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  • 98
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    Expression of mouse RNase MRP RNA in human embryonic kidney 293 cells (1997)
    Springer
    Molecular biology reports 24 (1997), S. 221-230 
    Details
    ISSN: 1573-4978
    Keywords: gene expression ; ribonucleoprotein ; RNase MRP ; RNase P ; transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report on the expression of mouse RNase MRP RNA in human embryonic kidney 293 cells upon DNA transfection. Stable cell lines were selected by cotransfection with a neo r gene. Transcription of wild-type and deletion mutants of MRP RNA and ribonucleoprotein formation were assessed by RNase protection and immunoprecipitation experiments. Mouse MRP RNA as expressed in 293 cells readily associates with human proteins to form a chimeric Th ribonucleoprotein. 5' truncated MRP RNAs, however, failed to associate with Th antigen(s) and deletion of the 3' sequences of MRP RNA greatly reduced the expression in stable as well as in transient transfectants. Abbreviations: nt(s) – nucleotide(s); RNP – ribonucleoprotein.
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    URL: http://dx.doi.org/10.1023/A:1006882704481
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  • 99
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    Sol Gel Processing of Low Permittivity, Fiber-Reinforced SiO2-Polyimide Substrates (1997)
    Springer
    Journal of sol gel science and technology 10 (1997), S. 91-100 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel ; composite ; substrate ; permittivity ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Low permittivity ceramic substrates with a sandwich structure consisting of a porous, fiber-reinforced SiO2 core and two thin polymer plates were fabricated by sol-gel processing, and polymer infiltration. The rheological behavior of an aqueous colloidal SiO2 sol, containing short SiO2 fibers was studied as a function of particle loading, fiber loading and gelation time. Short SiO2 fibers were introduced to limit drying shrinkage and thus minimize substrate cracking during drying. After the psuedoplastic sol was tape cast and sintered at 1150°C for 2 h, a polyimide solution was infiltrated into the porous SiO2 core. Permittivities ranging from 1.81 to 3.08 could be obtained by using 32–42% SiO2, 5–50% polyimide and 63 to 8% porosity. The substrate strength was increased from 1.93 MPa to 3.83 MPa after polyimide infiltration.
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    URL: http://dx.doi.org/10.1023/A:1018392407583
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  • 100
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    Characterization of two cDNA clones for mRNAs expressed during ripening of melon (Cucumis melo L.) fruits (1997)
    Springer
    Plant molecular biology 33 (1997), S. 313-322 
    Details
    ISSN: 1573-5028
    Keywords: cDNA cloning ; ethylene ; fruit ripening ; gene expression ; melon ; wounding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro translation of mRNAs and polyacrylamide gel electrophoresis of proteins from melons revealed that several mRNAs increased in amount during ripening, indicating the existence of other ripening genes in addition to those cloned previously. To identify ripening-related genes we have screened a ripe melon cDNA library and isolated two novel cDNA clones (MEL2 and MEL7) encoding unidentified proteins. Southern analysis revealed that MEL2 and MEL7 are encoded by low-copy-number genes. The MEL2 cDNA clone is near full-length, corresponds to a 1600 nucleotide mRNA that accumulates during ripening and encodes a predicted protein rich in hydrophobic amino acids. The MEL7 cDNA clone is full-length, corresponds to a mRNA of 0.7 kb which accumulates during early ripening stages and is also present at low levels in other organs of the melon plant. The MEL7 predicted polypeptide is 17 kDa and shows significant homology with the major latex protein from opium-poppy. Wounding and ethylene treatment of unripe melon fruits 20 days after anthesis showed that MEL2 and MEL7 mRNAs are only induced by ethylene.
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    URL: http://dx.doi.org/10.1023/A:1005701730598
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