ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • sol-gel  (85)
  • RAPD  (66)
  • Springer  (151)
  • American Chemical Society
  • Springer Nature
  • 1995-1999  (151)
  • 1980-1984
  • 1945-1949
  • 1925-1929
  • 1997  (151)
Collection
Keywords
Publisher
Years
  • 1995-1999  (151)
  • 1980-1984
  • 1945-1949
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology reporter 15 (1997), S. 335-354 
    ISSN: 1572-9818
    Keywords: RAPD ; PCR ; Soybean ; Linkage Mapping ; Restriction Enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Random amplified polymorphic DNA (RAPD) is based on DNA amplification by polymerase chain reaction (PCR) of random DNA segments using single arbitrary nucleotide sequences. We have adapted the assay to soybeans by using Stoffel Fragment DNA polymerase and by optimizing the reaction conditions. To increase the percentage of RAPD polymorphisms, the DNA template was digested with restriction enzymes before amplification. The combination of twenty-four primers and five DNA template treatments (Undigested, DraI, EcoRI, HindIII, and TaqI digested) revealed 94 polymorphic DNA fragments differing between soybean lines PI437654 and BSR101. Many polymorphic DNA bands were found unreliable or non-scoreable after re-screening of primers and verification of marker-allele segregation with 20 recombinant inbred lines (RILs). However, 28 RAPD markers were consistently polymorphic between the parental lines and followed Mendelian expectations. The use of DNA templates digested with DraI, EcoRI, HindIII or TaqI increased three times the number of RAPD markers compared to undigested DNA template alone. The 28 RAPD markers obtained were further screened with 72 RILs and placed on an existing RFLP map.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1572-9699
    Keywords: Aspergillus japonicus ; A. aculeatus ; assimilation spectra ; isoenzyme ; mtDNA ; rDNA ; RFLPs ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Forty Aspergillus japonicus and A. aculeatus strains, most of them wild-type isolates, were examined using various molecular and phenotypic techniques. The rDNAs proved to be invariable (even strains of the species A. aculeatus exhibited the same restriction profile), while the strains could be classified into seven different mtDNA RFLP groups. Hybridisation data suggest that six of these mtDNA types have certain common restriction sites, while mtDNA type 7, which was exhibited by some A. aculeatus strains, probably has quite different mtDNA organisation and their size was smallest among the strains studied. The RAPD technique and isoenzyme analysis revealed some variabilities within these RFLP groups and strain specific features could also be recognised. Carbon source assimilation spectra were found to be very distinctive for strains of A. japonicus, A. aculeatus and A. niger, providing a useful tool for pre-characterising new wild-type isolates of black Aspergilli. Only a limited correlation was observed between the dendrograms based on genotypic and phenotypic characters.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 112 (1997), S. 333-339 
    ISSN: 1432-1939
    Keywords: Key words Conservation ; Nassella(Stipa) pulchra ; Population genetics ; RAPD ; Spatial scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the scale of genetic variation of purple needlegrass (Nassella pulchra), a species commonly used in California for grassland restoration. Common garden and field data revealed evidence of genetic differentiation between two intermixed microhabitats characterized by differences in soil depth and community composition. We assessed the genetic variation within a single population using randomly amplified polymorphic DNA (RAPD) data collected from clusters of five individuals in 40 locations. We found no evidence for genetic structure at the whole population level. At smaller spatial scales, however, we found strong evidence that genetic subdivision of the population occurs at the level of the maternal neighborhood. We suggest that the interaction between widespread pollen dispersal and restricted seed dispersal may be the primary factor generating these results; panmictic pollen dispersal will make detection of genetic patterning difficult at larger spatial scales while limited seed dispersal will generate local genetic structure. As a result, the detection of population genetic structure will depend on the spatial scale of analysis. Local selection gradients related to topography and soil depth are also likely to play a role in structuring local genetic variation. Since N. pulchra is widely used in California in grassland and woodland habitat restoration, we suggest that, as a general rule, care should be exercised in transferring germplasm for the purposes of conservation when little is known about the within-population genetic subdivision of a plant species.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant cell reports 17 (1997), S. 119-122 
    ISSN: 1432-203X
    Keywords: Key words Polyamines ; Maize ; Callus culture ; Salt stress ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four callus lines from immature embryos of a self-crossed maize (Zea mays L.) hybrid cultivar were selected for “high” (two lines) and “low” (two lines) polyamine (PA) levels. Each selected line was exposed to culture media containing no (control) or 1% (0.171 m) NaCl and the relative growth rates were compared after subculture. Low-PA lines appeared to be tolerant to salt stress, while high-PA lines were sensitive. Analysis of PA at the end of the subculture showed that treated calli of sensitive lines had increased their putrescine content in comparison with their control, while putrescine remained constant in tolerant lines. Callus lines were analysed by RAPD (random amplification of polymorphic DNA) markers. One polymorphism (550-bp band) was found, demonstrating a genetic difference between the lines.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 989-996 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 48 (1997), S. 1051-1067 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 50 (1997), S. 105-115 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 10 (1997), S. 309-316 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 83-88 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 107-110 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 279-283 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 239-249 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 365-369 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 239-249 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    ISSN: 1573-3017
    Keywords: population genetics ; mosquitofish ; radiation ; RAPD ; allozymes ; evolutionary toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract In 1977, approximately 250 mosquitofish (Gambusia affinis) from a relatively uncontaminated site (Crystal Springs) were transplanted into a small pond on the Department of Energy Oak Ridge Reservation which is heavily contaminated with radionuclides (Pond 3513). Starting in 1992, DNA polymorphism was evaluated using the RAPD (Randomly Amplified Polymorphic DNA) and allozyme genotype techniques to determine if genetic differentiation had occurred between the two populations. Fish from a second radionuclide-contaminated population (White Oak Lake) and another unrelated non-contaminated population (Wolf Creek) were also examined. For the RAPD analyes, 15 RAPD primers (from a total of 40) were found to produce polymorphic banding patterns in at least two of the four populations and subsequently were used to produce a total of 142 bands. Data generated by these RAPD primers indicated an increased genetic diversity in radionuclide-contaminated sites relative to reference sites. Furthermore, the patterns from six RAPD primers produced a higher average number of bands when using DNA from radionuclide- contaminated populations than from non-contaminated, and for three RAPD primers the average number of bands from radionuclide- contaminated populations was lower. In addition, 17 bands occurred at a higher frequency in the radionuclide-contaminated compared to the non-contaminated populations. For the allozyme analyses, it was found that there was a higher percentage of polymorphism and heterozygosity in the radionuclide-contaminated relative to non-contaminated sites. These findings contribute to our understanding of the evolutionary effects of contaminant exposure as well as to the development of population-level biomarkers
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 381-384 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 409-413 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 425-430 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 615-618 
    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).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 663-666 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 681-684 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 721-723 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 729-734 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 735-742 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 759-763 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 819-824 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 895-899 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 927-929 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 931-935 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 979-983 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 991-997 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 999-1005 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1013-1016 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1053-1061 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1063-1066 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1067-1070 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1121-1125 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 29-33 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 83-88 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 365-369 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 381-384 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 409-413 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 23-28 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 29-33 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 615-618 
    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).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 663-666 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 681-684 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 721-723 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 729-734 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 735-742 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 759-763 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 819-824 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 895-899 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 931-935 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 947-951 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 979-983 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 991-997 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 999-1005 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1013-1016 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 947-951 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 107-110 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 425-430 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 927-929 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1063-1066 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 71
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1053-1061 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1067-1070 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 1121-1125 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 5-15 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 17-24 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 65-69 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 95-101 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 78
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 5-15 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 17-24 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 65-69 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 81
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 95-101 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 139-143 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 83
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 183-199 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 139-143 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 183-199 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 9 (1997), S. 279-283 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 10 (1997), S. 91-100 
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 88
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 95 (1997), S. 1080-1083 
    ISSN: 1432-2242
    Keywords: Key wordsMalus ; Apomixis ; RAPD ; Baskatong ; Red-purple pigmentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The lack of red-purple pigmentation in seedlings obtained from crosses between M. cv Baskatong, carrying a dominant homozygous gene for red-purple pigmentation, and other species has been used for the detection of apomictic plants in Malus species. RAPD marker techniques were employed to evaluate the genetic similarity between putative apomictic seedlings and their female parents. From the selected set of 20 (OPA) primers about half were able to detect hybrids from the apomictic seedlings, if present. RAPD analyses confirmed the usefulness of the colour-marker gene in detecting the hybrids in vitro for seedlings of M. toringoides×M. cv Baskatong, but not for crosses involving M. hupehensis×M. cv Baskatong where in vitro colour-based selection was not possible (due to red stems in all cases). The set of primers (OPA-01, 02, 08, 09, 10, 12, 13, 14, 16, 18 and 20) clearly determined the hybrid nature of seedlings and allowed the selection of apomictic ones. Therefore, although cv Baskatong is useful as an indicator, these data show that this technique is not applicable in all cases.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 89
    ISSN: 1432-2242
    Keywords: Key words mtDNA ; RAPD ; Rice ; WA cytoplasm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  RAPD profiles were generated using mitochondrial DNA (mtDNA) isolated from two cytoplasmic male-sterile lines, two restorer lines and four maintainer lines of rice. Of the 40 primers tested, 25 generated consistent and easily scoreable patterns that were used for the computation of pairwise similarities as well as UPGMA analyses. The different lines of rice, including lines IR58025A and IR62829A that contained the same wild abortive (WA) cytoplasm, were distinguishable on the basis of RAPD profiles. These latter two lines were not distinguishable from each other by mtDNA RFLP analyses with as many as 16 mtDNA probes. The data illustrate the utility of the RAPD technique as a powerful tool for distinguishing different cytoplasms that by other techniques appear to be similar. To our knowledge, this is the first report wherein RAPD profiles obtained with isolated mtDNA templates enable the distinction between two or more types of cytoplasms in rice.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 95 (1997), S. 1210-1217 
    ISSN: 1432-2242
    Keywords: Key words Vigna unguiculata ; RFLP ; RAPD ; AFLP ; Linkage map
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have constructed a genetic linkage map within the cultivated gene pool of cowpea (2n=2x=22) from an F8 recombinant inbred population (94 individuals) derived from a cross between the inbreds IT84S-2049 and 524B. These breeding lines, developed in Nigeria and California, show contrasting reactions against several pests and diseases and differ in several morphological traits. Parental lines were screened with 332 random RAPD decamers, 74 RFLP probes (bean, cowpea and mung bean genomic DNA clones), and 17 AFLP primer combinations. RAPD primers were twice as efficient as AFLP primers and RFLP probes in detecting polymorphisms in this cross. The map consists of 181 loci, comprising 133 RAPDs, 19 RFLPs, 25 AFLPs, three morphological/classical markers, and a biochemical marker (dehydrin). These markers identified 12 linkage groups spanning 972 cM with an average distance of 6.4 cM between markers. Linkage groups ranged from 3 to 257 cM in length and included from 2 to 41 markers, respectively. A gene for earliness was mapped on linkage group 2. Seed weight showed a significant association with a RAPD marker on linkage group 5. This map should facilitate the identification of markers that “tag” genes for pest and disease resistance and other traits in the cultivated gene pool of cowpea.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 91
    ISSN: 1432-2242
    Keywords: Key words AMOVA ; Conservation ; Curation ; Genetic markers ; Molecular genetic screening ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To better characterize and conserve crop genetic resources, the assessment of genetic identity, relatedness, and structure among entries and collections becomes a priority. In the present study, a random amplified polymorphic DNA (RAPD) assay was applied as a quick, cost-effective, and preliminary screen to quantify and partition the molecular variation among accessions. Fourteen phenotypically uniform accessions of Brassica oleracea var. capitata L. (cabbage) similarly designated as `Golden Acre' were tested with nine decamer oligonucleotide primers. These amplifications generated 110 fragments, of which 80 were polymorphic ranging in size from 370 to 1720 bp. The 80 polymorphic fragments were sufficient to distinguish between all 14 accessions. Data based on the partitioning of variation among accessions indicated that `Golden Acre' entries could be reduced to as few as four groups, with the potential loss of variation being only 4.6% of the absolute current genetic variation in those holdings as estimated from RAPD analysis. This proposed grouping would concurrently save approximately 70% [$750–1000 (US) per accession] for each cycle of regeneration (approximately 20–25 years at most) which alternatively could then be used for other priorities in B. oleracea conservation and use. This case represents but one example where targeted use of a molecular-marker assay linked with rigorous statistical analysis will be useful for plant genebank management, particularly for questions at the intraspecific level. Molecular markers will provide genebank curators with additional sources of information to better plan and organize collection holdings and use finite financial support in a more effective manner.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 92
    ISSN: 1432-2242
    Keywords: Key wordsBeta vulgaris ; Cytoplasmic male sterility ; RAPD ; Mitochondrial DNA ; Chloroplast DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondrial DNA fragments of two nearly isogenic lines of sugar beet (Beta vulgaris L.) were amplified by RAPD analysis. A number of fragments, most of them unique to either the male-sterile or the male-fertile cytoplasm, were selected for cloning and sequencing. One fragment was present in the PCR fingerprint pattern of both cytoplasms, whereas five of the selected fragments were specifically amplified from only one type of cytoplasm. The mitochondrial origin of all cloned RAPD fragments was confirmed by Southern hybridization. One fragment resulted in a hybridization pattern that suggests its repetitive presence in the mitochondrial genome of sugar beet. Four out of the five cytoplasm-specific RAPD fragments were shown to hybridize specifically to one type of cytoplasm only. One fragment hybridizing with the mtDNA from N-cytoplasm also revealed hybridization signals with both total and nuclear DNAs of N- as well as S-cytoplasm. Sequence alignments of this clone showed strong homologies with a part of the plastidal ndhC gene of higher plants, indicating that the male-fertile-specific mtDNA RAPD fragment is derived from chloroplast DNA. Sequence analysis of an amplified sterile-specific fragment revealed the presence of an open reading frame of 288 bp. Northern hybridization showed a transcription signal specific for the male-sterile cytoplasm. No sequence homology of the open reading frame to any known sequences was found. The results reveal an extremely high degree of sequence variability between the mtDNA of the N- and S-cytoplasm of Beta vulgaris.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 93
    ISSN: 1432-2242
    Keywords: Key words Gene mapping ; RAPD ; RFLP ; Stripe rust ; Triticum dicoccoides ; Triticum durum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The Yr15 gene of wheat confers resistance to the stripe rust pathogen Puccinia striiformis West., which is one of the most devastating diseases of wheat throughout the world. In the present study, molecular markers flanking the Yr15 gene of wheat have been identified using the near-isogenic-lines approach. RFLP screening of 76 probe-enzyme combinations revealed one polymorphic marker (Nor/TaqI) between the susceptible and the resistant lines. In addition, out of 340 RAPD primers tested, six produced polymorphic RAPD bands between the susceptible and the resistant lines. The genetic linkage of the polymorphic markers was tested on segregating F2 population (123 plants) derived from crosses between stripe rust-susceptible Triticum durum wheat, cv D447, and a BC3F9 resistant line carrying Yr15 in a D447 background. A 2.8-kb fragment produced by the Nor RFLP probe and a 1420-bp PCR product generated by the RAPD primer OPB13 showed linkage, in coupling, with the Yr15 gene. Employing the standard maximum-likelihood technique it was found that the order OPB13 1420 –Yr15–Nor1 on chromosome 1B appeared to be no less than 1000-times more probable than the closest alternative. The map distances between OPB13 1420 –Yr15–Nor1 are 27.1 cM and 11.0 cM for the first and second intervals, respectively. The application of marker-assisted selection for the breeding of new wheat cultivars with the stripe rust resistance gene is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 95 (1997), S. 865-873 
    ISSN: 1432-2242
    Keywords: Key words Amaranthus ; Crop evolution ; Isozyme ; Genetic diversity ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic diversity and relationships of 23 cultivated and wild Amaranthus species were examined using both isozyme and RAPD markers. A total of 30 loci encoding 15 enzymes were resolved, and all were polymorphic at the interspecific level. High levels of inter-accessional genetic diversity were found within species, but genetic uniformity was observed within most accessions. In the cultivated grain amaranths (A. caudatus, A. cruentus, and A. hypochondriacus), the mean value of HT was 0.094, HS was 0.003, and GST was 0.977 at the species level. The corresponding values in their putative wild progenitors (A. hybridus, A. powellii, and A. quitensis) were 0.135, 0.004, and 0.963, respectively. More than 600 RAPD fragments were generated with 27 arbitrary 10-base primers. On average, 39.9% of the RAPD fragments were polymorphic among accessions within each crop species; a similar level of polymorphism (42.8%) was present in the putative progenitors, but much higher levels of polymorphism were found in vegetable (51%) and other wild species (69.5%). The evolutionary relationships between grain amaranths and their putative ancestors were investigated, and both the RAPD and isozyme data sets supported a monophyletic origin of grain amaranths, with A. hybridus as the common ancestor. A complementary approach using information from both isozymes and RAPDs was shown to generate more accurate estimates of genetic diversity, and of relationships within and among crop species and their wild relatives, than either data set alone.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 95
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 94 (1997), S. 534-538 
    ISSN: 1432-2242
    Keywords: Key words Zea mays ; B chromosome ; RAPD ; B-A translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Four DNA fragments were amplified specifically from the B chromosome by PCR using random 10-base oligonucleotides as primers. The location of the fragments in the B chromosome was determined based on whether or not they were amplified from the hypo- ploid DNA generated by four B-A translocations, three of which break in the proximal euchromatic region and the fourth in the distal one-third of the heterochromatic region on the B long arm. Since the hypoploid DNA carries the portion of the B chromosome distal to the breakpoint of a translocation, the presence of a fragment in the hypoploid DNA, but not in the control (which is devoid of any B chromatin), indicates that the fragments is located in the B region distal to the breakpoint in the B long arm. Two fragments were mapped to the euchromatic region and two others to either the distal portion of the euchromatic region or the proximal two-thirds of the heterochromatic region. These fragments in turn mapped three B-A translocations whose breakpoints were located in the euchromatic region.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 96
    ISSN: 1432-2242
    Keywords: Key words Medicago truncatula ; Medicago tornata ; RAPD ; Segregation distortion ; DNA content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  About 40% (α=0.05) of the PCR-derived markers scored in a Medicago truncatula and M. tornata intraspecific cross departed from Mendelian expectations at α=0.05. This proportion is among the highest ever documented in the literature, notably for intraspecific crosses. Estimations of DNA amount were also implemented for the parental genotypes or parental lines, and significant variations were observed. Our results suggest that the parental genotypes have diverged for quite a while, and we propose that the level of distortion we documented is correlated with the genome size difference we measured.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 97
    ISSN: 1432-2242
    Keywords: Key words Aegilops markgrafii ; Triticum aestivum ; RAPD ; Addition lines ; Leaf rust ; Powdery mildew
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Aegilops markgrafii contains resistance genes to powdery mildew, leaf rust and stripe rust, and also has high crude protein and lysine contents, which can be useful for wheat improvement. These important traits are localized on different chromosomes. Disomic Triticum aestivum-Ae. markgrafii addition lines and euploid introgression lines showing leaf-rust and powdery mildew resistance were screened with RAPDs to detect chromosome-specific markers which can accelerate the breeding process. RAPD markers for all six available disomic addition lines were obtained. The additional chromosomes B, C, D, E, F and G were identified by three, three, three, two, one and seven primers, respectively. All three chromosome-B-specific RAPD markers demonstrated the presence of alien chromatin in the leaf-rust-resistant 42-chromosome introgression lines as well as in the segregating progeny. The three chromosome-C-identifying primers also demonstrated the presence of that chromosome in powdery mildew-resistant euploid introgression lines. The substitution lines (5A)5C and (5D)5C with different genetic backgrounds for both parents, in comparison to the lines mentioned above, showed the chromosome C-specific band with only two of the three primers. The chromosome F-specific primer and a primer evident on all the Ae. markgrafii chromosomes analysed did not generate the expected fragments on the chromosome Fdel addition line, indicating that the markers are located on the deleted part of chromosome F.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 98
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 94 (1997), S. 1031-1037 
    ISSN: 1432-2242
    Keywords: Key words Genome mapping ; Map length ; Pines ; RAPD ; Microsatellite DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Haploid linkage analysis of eastern white pine, Pinus strobus L., was carried out using mainly RAPD markers and microsatellite, or simple-sequence-repeat, markers. Ninety one loci mapped to 12 linkage groups of three or more markers. The resulting framework genome map, the first for a soft pine species, contained 69 markers. The map covered 58% of the estimated genome length of 2071 cM(K), with a 95% confidence interval of 1828–2242 cM(K). A systematic comparison of linkage data from eastern white pine, longleaf pine (P. palustris Mill.) and maritime pine (P. pinaster Ait.), gave genome-length estimates for all three species very close to either 2000 cM(K) or 2600 cM(H), depending on whether the Kosambi(K) or Haldane(H) map functions, respectively, were employed. Differences among previous pine genome-length estimates were attributed to the divergent criteria used in the methods of estimation, and indicate the need for the adoption of uniform criteria when performing genome-length estimates. Current data suggest that members of the two pine subgenera, which diverged during the late Mesozoic era, have highly conserved rates of recombination.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 99
    ISSN: 1432-2242
    Keywords: Key words Theobroma cacao ; RFLP ; RAPD ; Genetic diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers were used to evaluate genetic relationships within the Theobroma cacao species and to assess the organization of its genetic diversity. Genetic variability was estimated with 18 primers and 43 RFLP probes on 155 cocoa trees belonging to different morphological groups and coming from various geographic origins. The majority of the RFLP probes issued from low-copy DNA sequences. On the basis of on the genetic distance matrices, the two molecular methods gave related estimates of the genetic relationship between genotypes. Although an influence of cocoa morphological groups and geographical origins of trees was observed, a lack of gene differentiation characterized the T. cacao accessions studied. The continuous RFLP variability observed within the species may reflect the hybridization and introgressions between trees of different origins. Nevertheless, the Nacional type was detected to be genetically specific and different from well-known types such as Forastero, Criollo and Trinitario. Some of those genotypes were characterized by a low heterozygosity rate and may constitute the original Nacional pool. These results also provide information for the constitution of a cocoa tree core collection.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 100
    ISSN: 1432-2242
    Keywords: Key words Protoplasts ; Solanum tuberosum ; Solanum ssp. donor ; RAPD ; Chromosome elimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Recipient protoplasts from three Solanum tuberosum genotypes, cv ‘Folva’ (2n=4x=48), cv ‘Matilda’ (4n) and ‘161 : 14’ (2n), were electrofused with X-ray-irradiated donor protoplasts from two wild species S. spegazzinii (2n) or S. microdontum×S. vernei (2n). Prior to fusion, protoplasts were fluorescence-labelled with either fluorescein diacetate or scopoletin. Fusion products were identified by dual fluorescence and selected by micromanipulation or fluorescence-activated cell sorting (FACS). All putative hybrid plants were analysed by the random amplified polymorphic DNA (RAPD) technique. Our analysis demonstrates that each asymmetric hybrid plant has an individual and stable profile of donor-specific RAPD bands. The irradiation of donor protoplasts hampered the growth of selected heterofusion products in a dose-dependent way. Irradiation resulted in donor chromosome elimination, but not in a dose dependent way, in the tested interval. In asymmetric hybrids with the S. spegazzinii donor 33–68% of the donor-specific RAPD bands were missing, indicating a similar level of chromosome elimination. In asymmetric hybrid plants with the S. microdontum×S. vernei donor 74–95% of the donor RAPD bands were missing. Chromosome countings revealed that these hybrids had chromosome numbers equal to or below the chromosome numbers found in the tetraploid recipients. This is the first time that highly asymmetric hybrid plants between two tetraploid potato recipients and the donor S. microdontum×S. vernei have been obtained.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...