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At least 217 records · Page 12Linked to original sources
PubMed2001

Synthesis and Characterization of Basic Catalysts Based on Sodium-Magnesium Mixed Phosphates and Their Use in the Conversion of 2-Hexanol.

Various catalysts consisting of sodium-magnesium mixed orthophosphates were synthesized and characterized in structural terms using X-ray diffraction, thermogravimetric analysis, differential thermal analysis, diffuse reflectance infrared spectroscopy, and solid-state (31)P NMR spectroscopy. In addition, the surface properties of the solids were determined from N(2) adsorption-desorption isotherms and their chemical properties characterized with various titrants. One of the solids obtained consists of NaMgPO(4)/Mg(2)P(2)O(7) and the rest of NaMgPO(4)/MgO. Their surface chemical properties vary depending on the particular synthetic procedure used; thus, the NaMgPO(4)/MgO systems exhibit similar populations of acid and basic sites, whereas the NaMgPO(4)/Mg(2)P(2)O(7) systems contain many more acid sites than basic sites. All the solids obtained exhibit substantial dehydrogenating activity in the conversion of gaseous 2-hexanol; in fact, some of the NaMgPO(4)/MgO systems are even more active and selective than a MgO solid tested under identical reaction conditions. Copyright 2001 Academic Press.

Journal Article↗
PubMed2000

Characterization of the extracellular polysaccharide produced by a marine cyanobacterium, Cyanothece sp. ATCC 51142, and its exploitation toward metal removal from solutions.

Cyanobacterium, Cyanothece sp. ATCC 51142 produces an exopolysaccharide at a high level. Physical analysis of the exopolysaccharide (EPS), such as nuclear magnetic resonance, infrared spectrum, were done to determine its possible structure. Thermal gravimetric analysis, differential scanning calorimeter, and differential thermal analysis of the polymer were done to find out the thermal behavior. Calcium content within the sample was found out. Some of the physicochemical properties, such as relative viscosity, specific viscosity, and intrinsic viscosity of the EPS were studied under different conditions. The phenomenon of gel formation by the EPS was investigated for its potential application in metal removal from solutions.

Calcium↗
PubMed1995

Chemistry and sintering behaviour of thin hydroxyapatite ceramics with controlled porosity.

Hydroxyapatite ceramic tapes (several hundred micrometres thick), have been prepared at different porosity levels, using the tape casting technique. The reactions, which occur during processing and sintering of the tapes, have been characterized by power X-ray diffraction analysis, differential thermal analysis (DTA), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Volume changes have been measured during different stages of heat treatment. These can be attributed to phase transformations of the starting materials, which determine the sintering behaviour and final porosity of the samples. Measurements of the elastic modulus were performed by the resonant frequency method. A cubic dependence on the relative density is found. Finally, some possible improvements for the technique and selection of powders are suggested, based on the reported results.

Ceramics↗
PubMed2006

Preparation of barium strontium titanate Ba(1-x)Sr(x)TiO(3) (0<or= x <or=0.2) single-crystal nanorods by a novel combined method.

An ultrasonic irradiation method was applied to the sol/gel synthesis of the single-crystal cubic barium strontium titanate Ba(1-x)Sr(x)TiO(3) (0<or= x <or=0.2). The characteristics of the composites were examined by X-ray diffraction, thermogravimetric analysis, differential thermal analysis, transmission electron microscopy and high-resolution transmission microscopy. The diameters and lengths of typical resultant Ba(0.8)Sr(0.2)TiO(3) are in the range of 70-100 nm and 650-1000 nm, respectively. In addition, the stoichiometric sonogel formation and its heat-treatment process, the relationship between x of Ba(1-x)Sr(x)TiO (3) and the crystal structure, the relationship between synthesis condition of sonogel and morphology have been discussed.

Journal Article↗
PubMed2003

Determination of Cu and Ni incorporation ratios in Portland cement clinker.

Cu and Ni are metals found in galvanic sludges; these sludges are considered hazardous due to their heavy metal content. The main objective of this work is to determine the incorporation amount of Cu and Ni in Portland clinker when a galvanic sludge containing these metals is added to the clinker raw-material. The influence of this addition on the clinkering reactions is evaluated as well as the possibility of co-incinerating galvanic sludges containing Cu and Ni in rotary cement kilns. This study also characterizes the galvanic sludge. Samples were prepared by additions from 0.25 to 5 wt.% of a galvanic sludge to an industrial clinker raw-material. The clinkering process was simulated in a laboratory device. The following techniques were applied to characterize the raw materials and the products of the tests: chemical analysis, differential thermal analysis (DTA) and thermogravimetric analysis (TG). Leaching tests were performed in the produced clinker samples in order to verify the incorporation of the studied metals in the clinker structure. The results led to the conclusion that additions of up to 2 wt.% of a galvanic sludge containing 2.4 wt.%Cu and 1.2 wt.% Ni to clinker raw-material do not affect the clinkering reactions and that these metals are totally incorporated into the clinker.

Construction Materials↗
PubMed1977

Cold hardiness and deep supercooling in xylem of shagbark hickory.

Differential thermal analysis, differential scanning calorimetry, pulsed nuclear magnetic resonance spectroscopy, and low temperature microscopy are utilized to investigate low temperature freezing points or exotherms which occur near -40 C in the xylem of cold-acclimated shagbark hickory (Carya ovata L.). Experiments using these methods demonstrate that the low temperature exotherm results from the freezing of cellular water in a manner predicted for supercooled dilute aqueous solutions. Heat release on freezing, nuclear magnetic resonance relaxation times, and freezing and thawing curves for hickory twigs all point to a supercooled fraction in the xylem at subfreezing temperatures. Calorimetric and low temperature microscopic analyses indicate that freezing occurs intracellularly in the xylem ray parenchyma. The supercooled fraction is found to be extremely stable, even at temperatures only slightly above the homogeneous nucleation temperature for water (-38 C). Xylem water is also observed to be resistant to dehydration when exposed to 80% relative humidity at 20 C. D(2)O exchange experiments find that only a weak kinetic barrier to water transport exists in the xylem rays of shagbark hickory.

Journal Article↗
PubMed2002

Synthesis of nanoparticles of barium lanthanum hafnium oxide by a modified combustion process.

Barium lanthanum hafnium oxide, a complex perovskite ceramic, has been synthesized as nanoparticles by a modified combustion process for the first time. The Ba, La, and Hf ions required for the formation of Ba2LaHfO5.5 were obtained in solution by dissolving in boiling nitric acid a stoichiometric mixture of BaCO3, La2O3, and HfO2 that had been heated at 1200 degrees C for 4 h. By complexing the ions with citric acid and using ammonia as fuel, it was possible to get Ba2LaHfO5.5 as nanoparticles in a single-step combustion process. The powder obtained by the present combustion process was characterized by X-ray diffraction, BET surface area analysis, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, and scanning and high-resolution transmission electron microscopy. According to the results of X-ray and electron diffraction, the powder synthesized through the combustion process showed single-phase barium lanthanum hafnium oxide. The transmission electron microscopic investigations showed a grain size of 42 nm, with a standard deviation of 8 nm. The nanoparticles of Ba2LaHfO5.5 synthesized by the present combustion technique could be sintered to > 97% of the theoretical density at a relatively low temperature of 1425 degrees C. Scanning electron microscopic studies on the sintered Ba2LaHfO5.5 samples showed that the final grain size of the sintered specimen was < 500 nm.

Calcium Compounds↗
PubMed1994

Contributions of discriminant analysis to differential diagnosis by self-report.

We used discriminant function analyses of the Minnesota Multiphasic Personality Inventory (MMPI; Hathaway & McKinley, 1983), Millon Clinical Multiaxial Inventory (MCMI; Millon, 1983), MCMI-II (Millon, 1987), and Symptom Checklist Ninety-Revised (SCL-90-R; Derogatis, 1983) profiles from a heterogenous group of 272 psychiatric inpatients to classify patients as depressed, manic, and/or psychotic. Most functions generated from these tests significantly discriminated depressed, manic (not MCMI-II), and psychotic (not MCMI) subjects from psychiatric controls. However, there was little improvement in diagnostic efficiency over the use of single scale elevations at specified cut scores. Functions derived from the MCMI for mania and the MCMI-II for psychosis show the most promise but require replication. The difficulty of using group profile differences for the diagnosis of individual psychiatric patients is discussed.

Adult↗
PubMed1978

Study of structural analysis: comparing differential diagnoses based on psychiatric evaluation, the MMPI, and structural analysis of the Hand Test and Rorschach.

Experimental investigation of Structural Analysis compared diagnoses of 30 psychiatric inpatients derived independently from psychiatric evaluations, MMPI analyses, and Structural Analysis interpretation of Hand Test and Rorschach data. Results yielded positive preliminary implications for the use of Structural Analysis in psychodiagnostics.

Adolescent↗
PubMed1995

Polymorphism-structure relationships of rifamexil, an antibiotic rifamycin derivative.

The polymorphism of rifamexil, a rifamycin derivative, has been investigated by thermomicroscopy, differential thermal analysis (differential scanning calorimetry-thermogravimetry), IR spectroscopy, and X-ray powder diffraction. Two crystalline forms, an amorphous material, and three solvates have been studied. The crystal structures of two solvates have also been determined by single-crystal X-ray techniques. Although the overall conformation of rifamexil is very similar in the two compounds, marked differences occur between the two crystal packings, due to differences both in the mutual orientation of the molecules and in the rifamexil-solvent interactions. Multivariate statistical methods have been used to identify the principal structural parameters determining the biological activity of the rifamycins.

Anti-Bacterial Agents↗
PubMed1998

Electroperturbation of human stratum corneum fine structure by high voltage pulses: a freeze-fracture electron microscopy and differential thermal analysis study.

Application of high voltage pulses (HVP) to the skin has been shown to promote the transdermal drug delivery by a mechanism involving skin electroporation. The aim of this study was to detect potential changes in lipid phase and ultrastructure induced in human stratum corneum by various HVP protocols, using differential thermal analysis and freeze-fracture electron microscopy. Due to the time involved between the moment the electric field is switched off and the analysis, only "secondary" phenomena rather than primary events could be observed. A decrease in enthalpies for the phase transitions observed at 70 degrees C and 85 degrees C was detected by differential thermal analysis after HVP treatment. No changes in transition temperature could be seen. The freeze-fracture electron microscopy study revealed a dramatic perturbation of the lamellar ordering of the intercellular lipid after application of HVP. Most of the planes displayed rough surfaces. The lipid lamellae exhibited rounded off steps or a vanished stepwise order. There was no evidence for perturbation of the corneocytes content. In conclusion, the freeze-fracture electron microscopy and differential thermal analysis studies suggest that HVP application induces a general perturbation of the stratum corneum lipid ultrastructure.

Electric Stimulation↗
PubMed1995

Differential display analysis of gene expression in developing embryos of Xenopus laevis.

Differential display (DD), an arbitrarily primed RT-PCR fingerprinting technique, is a novel approach for the search of differentially expressed transcripts. Using our improved DD protocol, reproducible cDNA fingerprints were successfully obtained from RNAs of Xenopus laevis embryos at six representative stages. Parallel comparison among the fingerprints revealed a number of bands with differential expression patterns. Analysis with clones of three randomly chosen bands confirmed that their expression patterns were faithfully reflected on fingerprints, thereby proving the reliability and validity of the approach. Nucleotide sequencing of these clones revealed that one is identical with a known transcript (cardiac actin), the second is a novel developmentally regulated gene showing no significant homology with those reported previously, and the last is a close but unique relative of XK endo B gene showing somewhat different spatial expression pattern. These results indicated that the DD analysis provides a rapid and reliable way for the identification of novel differentially expressed genes as well as a unique 'scope' for the survey of the changes in overall gene expression profiles occurring in the early embryonic development of Xenopus as well as of other organisms.

Amino Acid Sequence↗
PubMed2002

Differential display analysis of breast carcinoma cells enriched by immunomagnetic target cell selection: gene expression profiles in bone marrow target cells.

The red bone marrow (BM) is an important indicator organ of hematogenous micrometastatic spread of carcinomas. Characterization of biological properties specific for BM micrometastatic cells, however, is technically challenging due to the limited number of target cells usually available for the purpose. This report provides referrals to qualitative gene expression profiling of BM micrometastatic cells enriched by immunomagnetic selection. First, an experimental strategy was used to study regulatory mechanisms involved when BM micrometastatic cells colonize distant organs. The MA-11 cells, originating from BM micrometastases in a breast cancer patient clinically devoid of overt metastatic disease, were injected into immunodeficient rats. Metastatic MA-11 cells were subsequently immunoselected from the resulting in vivo lesions. The selected cell populations were compared to the injected cells by differential display analysis, and several genes possibly involved in tumor cell invasion and proliferation were confirmed as differentially expressed among the various MA-11 cell populations. A direct approach to qualitative gene expression profiling of BM micrometastatic cells was also explored. Carcinoma cells were immunoselected from BM and axillary lymph nodes obtained from breast cancer patients, and the isolated cell populations were compared by differential display analysis. Two candidate genes, identified as factors involved in cellular growth control, appeared as differentially expressed by the target cells from BM. Our study provides detailed information on how to combine an immunomagnetic selection procedure and differential display analysis to reveal gene expression profiles that may characterize BM micrometastatic cells.

Animals↗
PubMed1991

Human von Willebrand factor gene and pseudogene: structural analysis and differentiation by polymerase chain reaction.

Structural analysis of the von Willebrand factor gene located on chromosome 12 is complicated by the presence of a partial unprocessed pseudogene on chromosome 22q11-13. The structures of the von Willebrand factor pseudogene and corresponding segment of the gene were determined, and methods were developed for the rapid differentiation of von Willebrand factor gene and pseudogene sequences. The pseudogene is 21-29 kilobases in length and corresponds to 12 exons (exons 23-34) of the von Willebrand factor gene. Approximately 21 kilobases of the gene and pseudogene were sequenced, including the 5' boundary of the pseudogene. The 3' boundary of the pseudogene lies within an 8-kb region corresponding to intron 34 of the gene. The presence of splice site and nonsense mutations suggests that the pseudogene cannot yield functional transcripts. The pseudogene has diverged approximately 3.1% in nucleotide sequence from the gene. This suggests a recent evolutionary origin approximately 19-29 million years ago, near the time of divergence of humans and apes from monkeys. Several repetitive sequences were identified, including 4 Alu, one Line-1, and several short simple sequence repeats. Several of these simple repeats differ in length between the gene and pseudogene and provide useful markers for distinguishing these loci. Sequence differences between the gene and pseudogene were exploited to design oligonucleotide primers for use in the polymerase chain reaction to selectivity amplify sequences corresponding to exons 23-34 from either the von Willebrand factor gene or the pseudogene. This method is useful for the analysis of gene defects in patients with von Willebrand disease, without interference from homologous sequences in the pseudogene.

Amino Acid Sequence↗
PubMed1980

[Reducing activity and differential thermal analysis of enterococci].

The reducing activity of 100 Streptococcus faecalis strains, 100 Streptococcus faecium strains and 100 enterococcal strains were studied by the quantitative method. The study revealed that all mobile enterococci, in contrast to S. faecium, reduce 2,3,5-triphenyltetrazolium chloride with the formation of triphenylformasan. Differential thermal analysis also indicated that S. faecalis, S. faecium and mobile enterococci had thermograms with definite mathematical characteristics and could be best differentiated by the indices of their form and the size of S3 areas. The quantitative methods of the investigation of reducing activity and differential thermal analysis can be used for the differentiation of enterococcal species. Mobile enterococci have definite characteristics allowing one to sharply differentiate them from S. faecium and S. faecalis.

Animals↗
PubMed2001

[Identification of genes related to cell phenotypic transition by differential display analysis].

To identify the genes that are differentially expressed during the phenotypic transition from vascular adventitial fibroblasts to myofibroblasts, the adventitial fibroblasts were cultured from rat thoracic aorta, and myofibroblasts were obtained by treatment of fibroblasts with TGF-beta1. Differential display PCR (DD-PCR) was used to screen for differentially expressed genes by comparison of mRNA extracted from the two cell populations. Bands upregulated or downregulated on DD gels were excised, reamplified, cloned and sequenced. DD results were verified by quantitative PCR and Northern blot analysis.Antisense oligonucleotide was transfected to study the effect of osteopontin on migration of AF. Differential display showed a significant difference in gene expression profile between the two cell types. A transcript that was downregulated in myofibroblasts showed high DNA sequence homology to part of the gene for NADH dehydrogenase subunit 5. An upregulated transcript showed significant sequence homology to osteopontin gene. Quantitative PCR and Northern blot analysis confirmed the DD results. Among the other differential bands detected, 4 candidate sequences showed no homology to the known genes. The AF numbers of migration were significantly decreased by use of OPN antisense oligonucleotide. This study suggests that the downregulation of gene encoding NADH dehydrogenase subunit 5 and upregulation of osteopontin gene and several other unknown genes may be involved in the phenotypic transition of adventitial fibroblasts to myofibroblats. Inhibition of the expression of OPN may play an important role in the process of vascular remodeling.

Animals↗
PubMed2005

WEBSAGE: a web tool for visual analysis of differentially expressed human SAGE tags.

The serial analysis of gene expression (SAGE) is a powerful method to compare gene expression of mRNA populations. To provide quantitative expression levels on a genome-wide scale, the Cancer Genome Anatomy Project (CGAP) uses SAGE. Over 7 million SAGE tags, from 171 human cell types have been assembled. The growing number of laboratories involved in SAGE research necessitates the use of software that provides statistical analysis of raw data, allowing the rapid visualization and interpretation of results. We have created the first simple tool that performs statistical analysis on SAGE data, identifies the tags differentially expressed and shows the results in a scatter plot. It is freely available and accessible at http://bioserv.rpbs.jussieu.fr/websage/index.php.

Cell Line, Tumor↗