Soft chemistry synthesis of the perovskite CaCu3Ti4O12

The perovskite CaCu3Ti4O12 (CCT) has been obtained after calcination of oxalate precursors at 900–1000 °C in air. Those precursors are prepared using a soft chemistry method, the coprecipitation. The oxalate powders consist of disk-like particles of 2–3 μm diameter and 300–400 nm thickness. By varying the ratio of the initial amounts of metal chlorides, additional phases (CaTiO3, TiO2 and CuO) could be obtained besides CCT. The corresponding multiphased ceramics present improved dielectric properties

Grain Growth-Controlled Giant Permittivity in Soft Chemistry CaCu3Ti4O12 Ceramics

We report a dielectric constant of up to 5.4105 at room temperature and 1 kHz for CaCu3Ti4O12 (CCTO) ceramics, derived from multiphase powders (coprecipitation products), made by a ‘‘chimie douce’’ (coprecipitation) method, and then sintered in air. The sintered products are pure-phase CCTO ceramics. The high dielectric constant is achieved by tuning the size of grains and the thickness of grain boundaries. The grain growth is controlled by varying the concentration of excess CuO in the initial powder (calcined coprecipitation products) between 1 and 3.1 wt%. The dielectric constant of pure CCTO ceramics increases with the initial CuO concentration, reaching its maximum at 2.4 wt% of CuO. A further increase of excess CuO in powders results in a permittivity decrease, accompanied by the formation of CuO as a separate phase in the sintered products. The unusual grain growth behavior is attributed to a eutectic reaction between CuO and TiO2 present in the initial powder

A spatial analysis of African American church attendance in Fresno, California.

This thesis examines African American church attendance in Fresno, California from a spatial perspective. In the 1950s, the majority of Fresno's African American population was concentrated in the southwestern quadrant of the city, but since that time has dispersed throughout the metropolitan area. By administering survey questionnaires in a sample of predominantly African American churches located in the African American "culture hearth" of southwest Fresno, an attempt is made to discover whether or not African Americans return to southwest Fresno for religious purposes. Findings reveal that the area from which African American churches in southwest Fresno collectively draw their members has expanded spatially, and that African Americans residing throughout the city return to southwest Fresno for church services

Effect of T4 modification of host valyl-tRNA synthetase on enzyme action in vivo

It has previously been found that bacteriophage T4 modifies the valyl-tRNA synthetase of its host; in this work we have examined the effects of this modification on the action of the enzyme in vivo. For this purpose we compared the properties of T4-infected cells with those of uninfected cells or cells infected with the amber mutant vs2, which by all available criteria seems to leave the host enzyme completely unmodified.We find that, although the overall rate of transfer of valine into protein is reduced after infection, modification is apparently not the cause of this reduction. Also, modification does not alter the level of aminoacylation of the total valine tRNA pool nor of the invidividual species of valine tRNA. Nor does modification appear to be necessary to maintain these levels after infection. We found no evidence that modification affects any unknown valyl-tRNA synthetase reaction that yields novel valine-containing products. Although the modified enzyme is more stable in vitro than the unmodified enzyme, modification does not seem to facilitate phage growth at temperatures above the optimum.To all appearances, therefore, T4-directed modification of the host valyl-tRNA synthetase does not detectably affect the in vivo catalytic action of the enzyme in any straightforward way, at least under prevailing laboratory conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22178/1/0000609.pd

Antimicrobial activity of metal oxide microspheres: an innovative process for homogeneous incorporation into materials

AIMS:To investigate the potent control of microbial surface contamination of an innovative process which consists in incorporating metal oxide microspheres homogeneously into materials. Spherical microspheres containing zinc and magnesium oxides synthesized via a one-step manufacturing process (Pyrolyse Pulvérisée® ) and incorporated into different plastic matrices were evaluated for their antimicrobial activity according to JIS Z 2801 standard. A significant activity was observed for microsphere-added polyethylene coupons with a reduction of all tested bacteria populations, including Gram negative and Gram positive even expressing acquired antibiotic resistance (Escherichia coli ESBL, Staphylococcus aureus metiR). An antiviral activity higher than 2 log of reduction was also observed on H1N1 and HSV-1 viruses. This antimicrobial effect was dose-dependent and time-dependent for both polyethylene and polypropylene matrices. Antimicrobial activity was maintained after exposition to disinfectants and totally preserved 50 months after the preparation of the coupons. CONCLUSIONS:Incorporated into plastic matrices, metal oxide microspheres showed significant antibacterial and antiviral activities. SIGNIFICANCE AND IMPACT OF STUDY: This is, to our knowledge, the first report on an original process incorporating metal oxide microspheres, which have specific physico-chemical and antimicrobial properties, into materials that could be used for surface contamination prevention

Critical effects of inorganic phosphate at threshold concentrations on cultured aortic valve interstitial cells. Macroautophagocytosis versus procalcific cell degeneration

The conventional threshold values ascribed to inorganic phosphate concentration ([Pi]) in diagnosing normophosphatemia range between 0.8mM and 1.45mM to 2.0mM [Pi]. In cultures mimicking metastatic calcification ([Pi]=3.0mM) a major role was found to be played by [Pi] (Pi-cultures) in priming a procalcific cell degeneration of bovine aortic valve interstitial cells (bAVICs), with mineralization enhancing subsequent to superstimulation with bacterial lipopolysaccharide (LPS) plus conditioned medium from cultured LPS-stimulated macrophages (Pi-LPS-CM-cultures) [1]. Here, bAVIC primary cultures were carried out which contained different [Pi] (0.4, 0.6, and 1.3mM in added solutions, i.e. 0.8, 1.3, and 2.0mM in final cultures), so including border concentrations on respect to hypophosphatemic- and hyperphosphatemic-like conditions. At 0.8mM and 1.3 [Pi] and for each incubation time (3, 9, 15, 21, and 28 days), bAVICs from Pi-cultures and Pi-LPS-CMcultures shared common ultrastructural features showing prominent macroautophagocytosis to occur, consistently with the immunohistochemical detection of the specific marker of mature autophagosomes MAP1-LC3A. Neither cell death signs nor appearance of calcific nodules were observed. At 2.0 [Pi], most bAVICs were affected by degenerative fragmentation as described for severe metastatic-like calcifcation, i.e. the appearence of phthalocianin- positive material outcropping at cell surface, acting as hydroxyapatite nucleator and being source of real calcospherulae. Quantitative spectrophotometric estimation of calcium amounts and alkaline phosphatase activity were consistent with the ultrastructural data, with (i) similar values for Pi-LPS-CM-cultures versus Pi-cultures and control cultures, at 0.8 and 1.3mM [Pi], and (ii) significantly higher values for Pi-LPS-CM-cultures versus Picultures and these latter versus controls, at 2.0mM [Pi]. Restriction of immunopositivity to caspase-8 to very few cells and complete immunonegativity to annexin-V suggested apoptosis to be a negligible epiphenomenon. In conclusion, the propensity of bAVICs to undergo procalcific degeneration resulted to correlate with [Pi] in such a manner that a differential discrimination of this parameter within the conventional normophosphatemic range is suggested for a proper evaluation of the risk for dystrophic valve calcification. Moreover, bacterial-derived inflammation seems to be regarded as an effective trigger for the higher normophosphatemic [Pi]

The Personal Sequence Database: a suite of tools to create and maintain web-accessible sequence databases

Background: Large molecular sequence databases are fundamental resources for modern\ud bioscientists. Whether for project-specific purposes or sharing data with colleagues, it is often\ud advantageous to maintain smaller sequence databases. However, this is usually not an easy task for\ud the average bench scientist.\ud \ud Results: We present the Personal Sequence Database (PSD), a suite of tools to create and\ud maintain small- to medium-sized web-accessible sequence databases. All interactions with PSD\ud tools occur via the internet with a web browser. Users may define sequence groups within their\ud database that can be maintained privately or published to the web for public use. A sequence group\ud can be downloaded, browsed, searched by keyword or searched for sequence similarities using\ud BLAST. Publishing a sequence group extends these capabilities to colleagues and collaborators. In\ud addition to being able to manage their own sequence databases, users can enroll sequences in\ud BLASTAgent, a BLAST hit tracking system, to monitor NCBI databases for new entries displaying\ud a specified level of nucleotide or amino acid similarity.\ud \ud Conclusion: The PSD offers a valuable set of resources unavailable elsewhere. In addition to\ud managing sequence data and BLAST search results, it facilitates data sharing with colleagues,\ud collaborators and public users. The PSD is hosted by the authors and is available at http://\ud bioinfo.cgrb.oregonstate.edu/psd/