108 research outputs found

    Crystal chemical significance of chemical zoning in dissakisite-(Ce)

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    Dissakisites from Trimouns dolomite mine,France, have two kinds of single crystals: chemical-zonedand homogeneous types. Back-scattered electron microprobe(BSE) images of these dissakisites reveal both Ca–Al rich dark zones and Fe-RREE rich bright zones.Crystal structures of three dark and two bright zones in achemical-zoned dissakisite and of a homogeneous zone inunzoned dissakisite were refined to individual R indices(about 3.0–5.0%) based on 1,400 observed [F0[4rF0]reflections measured with MoKa X-radiation using thesingle crystal diffractometer. The differences in brightnessbetween their BSE images arise from those in coupledsubstitutions of the elements occupying A2 and M3 sites.The main reason for these differences is that ten-coordinatedA2 polyhedra and M3 octahedra are directly linkedthrough their shared edge, which creates a great potentialfor making this coupled substitution. This zoning indicatesthat formation of the whole zoned crystal, where eachzone could be grown steadily with its crystallographicaxes mutually parallel to each other, may be identified asautoepitaxy

    Synergistic effect of sulfonation followed by precipitation of amorphous calcium phosphate on the bone-bonding strength of carbon fiber reinforced polyetheretherketone

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    Sulfonation and applications of amorphous calcium phosphate are known to make polyetheretherketone (PEEK) bioactive. Sulfonation followed by precipitation of amorphous calcium phosphate (AN-treatment) may provide PEEK with further bone-bonding strength. Herein, we prepared a carbon-fiber-reinforced PEEK (CPEEK) with similar tensile strength to cortical bone and a CPEEK subjected to AN-treatment (CPEEK-AN). The effect of AN-treatment on the bone-bonding strength generated at the interface between the rabbit’s tibia and a base material was investigated using a detaching test at two time-points (4 and 8 weeks). At 4 weeks, the strength of CPEEK-AN was significantly higher than that of CPEEK due to the direct bonding between the interfaces. Between 4 and 8 weeks, the different bone forming processes showed that, with CPEEK-AN, bone consolidation was achieved, thus improving bone-bonding strength. In contrast, with CPEEK, a new bone was absorbed mainly on the interface, leading to poor strength. These observations were supported by an in vitro study, which showed that pre-osteoblast on CPEEK-AN caused earlier maturation and mineralization of the extracellular matrix than on CPEEK. Consequently, AN-treatment, comprising a combination of two efficient treatments, generated a synergetic effect on the bonding strength of CPEEK

    Impact of the Ce 4f4f states in the electronic structure of the intermediate-valence superconductor CeIr3_3

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    The electronic structure of the ff-based superconductor CeIr3\mathrm{CeIr_3} was studied by photoelectron spectroscopy. The energy distribution of the Ce 4f\mathrm{Ce}~4f states were revealed by the Ce 3d4f\mathrm{Ce}~3d-4f resonant photoelectron spectroscopy. The Ce 4f\mathrm{Ce}~4f states were mostly distributed in the vicinity of the Fermi energy, suggesting the itinerant character of the Ce 4f\mathrm{Ce}~4f states. The contribution of the Ce 4f\mathrm{Ce}~4f states to the density of states (DOS) at the Fermi energy was estimated to be nearly half of that of the Ir 5d\mathrm{Ir}~5d states, implying that the Ce 4f\mathrm{Ce}~4f states have a considerable contribution to the DOS at the Fermi energy. The Ce 3d\mathrm{Ce}~3d core-level and Ce 3d\mathrm{Ce}~3d X-ray absorption spectra were analyzed based on a single-impurity Anderson model. The number of the Ce 4f\mathrm{Ce}~4f states in the ground state was estimated to be 0.80.90.8-0.9, which is much larger than the values obtained in the previous studies (i.e., 00.40-0.4).Comment: 9 pages, 4 figures, accepted to Electronic Structur

    A noncoding RNA gene on chromosome 10p15.3 may function upstream of hTERT

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    <p>Abstract</p> <p>Background</p> <p>We attempted to clone candidate genes on 10p14–15 which may regulate hTERT expression, through exon trapping using 3 BAC clones covering the region. After obtaining 20 exons, we examined the function of RGM249 (RGM: RNA gene for miRNAs) we cloned from primary cultured human hepatocytes and hepatoma cell lines. We confirmed approximately 20 bp products digested by Dicer, and investigated the function of this cloned gene and its involvement in hTERT expression by transfecting the hepatoma cell lines with full-length dsRNA, gene-specific designed siRNA, and shRNA-generating plasmid.</p> <p>Results</p> <p>RGM249 showed cancer-dominant intense expression similar to hTERT in cancer cell lines, whereas very weak expression was evident in human primary hepatocytes without telomerase activity. This gene was predicted to be a noncoding precursor RNA gene. Interestingly, RGM249 dsRNA, siRNA, and shRNA inhibited more than 80% of hTERT mRNA expression. In contrast, primary cultured cells overexpressing the gene showed no significant change in hTERT mRNA expression; the overexpression of the gene strongly suppressed hTERT mRNA in poorly differentiated cells.</p> <p>Conclusion</p> <p>These findings indicate that RGM249 might be a microRNA precursor gene involved in the differentiation and function upstream of hTERT.</p

    WDR55 Is a Nucleolar Modulator of Ribosomal RNA Synthesis, Cell Cycle Progression, and Teleost Organ Development

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    The thymus is a vertebrate-specific organ where T lymphocytes are generated. Genetic programs that lead to thymus development are incompletely understood. We previously screened ethylnitrosourea-induced medaka mutants for recessive defects in thymus development. Here we report that one of those mutants is caused by a missense mutation in a gene encoding the previously uncharacterized protein WDR55 carrying the tryptophan-aspartate-repeat motif. We find that WDR55 is a novel nucleolar protein involved in the production of ribosomal RNA (rRNA). Defects in WDR55 cause aberrant accumulation of rRNA intermediates and cell cycle arrest. A mutation in WDR55 in zebrafish also leads to analogous defects in thymus development, whereas WDR55-null mice are lethal before implantation. These results indicate that WDR55 is a nuclear modulator of rRNA synthesis, cell cycle progression, and embryonic organogenesis including teleost thymus development

    Glenoid Stress Distribution in Baseball Players Using Computed Tomography Osteoabsorptiometry: A Pilot Study

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    Background: It is important to understand the loading conditions when considering the pathology of shoulder disorders in overhead athletes. However, because throwing is a complicated motion, direct measurement of the stress distribution across the glenohumeral joint is difficult. Subchondral bone density reportedly reflects the cumulative stress acting on a joint surface under actual loading conditions. Questions/Purposes: To assess alterations in stress distribution across the glenoid cavity caused by pitching, we investigated the distribution of subchondral bone density in nonathletic volunteers and asymptomatic baseball players, including fielders and pitchers. Methods: We collected computed tomography (CT) imaging data from the dominant-side shoulder of 10 nonathletic volunteers (controls), 10 fielders, and 10 pitchers in a competitive college baseball league (all men aged 19-24 years, mean 20.7 years). We measured the distribution of subchondral bone density of the glenoid cavity using CT osteoabsorptiometry. The obtained stress distribution map was divided into four segments: anterosuperior, anteroinferior, posteroinferior, and posterosuperior regions. The location and percentages of high-density regions on the articular surface were analyzed quantitatively. Results: The percentages of high-density regions, including the anteroinferior, and posterior segments, were greater in pitchers and fielders than in controls. The percentages of high-density regions did not differ significantly between pitchers and fielders. Conclusions: The bicentric density patterns indicate that the cumulative force of pitching activity affected the long-term stress distribution across the glenoid cavity. Clinical Relevance: The current results provide useful information for analyzing pitching activity and clarifying the pathology of shoulder disorders associated with throwing

    Effect of periacetabular osteotomy on the distribution pattern of subchondral bone mineral density in patients with hip dysplasia

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    Despite the availability of long-term follow-up data, the effect of pelvic osteotomy on the natural history of osteoarthritis is not yet fully understood, partly because there is untapped potential for radiographs to better describe osteoarthritis. Therefore, this study aimed to assess the distribution of subchondral bone mineral density (BMD) across the acetabulum in patients with hip dysplasia immediately (2 weeks) and 1 year after undergoing periacetabular osteotomy (PAO). To that end, we reviewed 40 hips from 33 patients with developmental dysplasia of the hip who underwent PAO between January 2016 and July 2019 at our institution. We measured subchondral BMD through the articular surface of the acetabulum using computed tomography osteoabsorptiometry, dividing the distribution map into nine segments. We then compared the subchondral BMD between 2 weeks and 1 year after PAO in each area. At 2 weeks after PAO, the high-density area tended to be localized particularly in the lateral part of the acetabulum, whereas 1 year after PAO, the high-density area moved to the central and lateral parts. The percentage ratios of the subchondral BMD for the central-posterior, lateral-central, and lateral-posterior areas relative to the central-central area were significantly decreased at 1 year after PAO, as compared to those at 2 weeks after PAO. These findings suggest that loading was altered by PAO to be more similar to physiological loading. A long follow-up observational study is warranted to confirm the association between early changes in subchondral BMD by PAO and joint degeneration
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