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Sample records for amelogenin null dental

  1. Amelogenins as potential buffers during secretory-stage amelogenesis

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    Guo, J.; Lyaruu, D.M.; Takano, Y.; Gibson, C.W.; Denbesten, P.K.; Bronckers, A.L.

    2015-01-01

    Amelogenins are the most abundant protein species in forming dental enamel, taken to regulate crystal shape and crystal growth. Unprotonated amelogenins can bind protons, suggesting that amelogenins could regulate the pH in enamel in situ. We hypothesized that without amelogenins the enamel would

  2. Amelogenin and Enamel Biomimetics

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    Ruan, Qichao; Moradian-Oldak, Janet

    2015-01-01

    Mature tooth enamel is acellular and does not regenerate itself. Developing technologies that rebuild tooth enamel and preserve tooth structure is therefore of great interest. Considering the importance of amelogenin protein in dental enamel formation, its ability to control apatite mineralization in vitro, and its potential to be applied in fabrication of future bio-inspired dental material this review focuses on two major subjects: amelogenin and enamel biomimetics. We review the most recent findings on amelogenin secondary and tertiary structural properties with a focus on its interactions with different targets including other enamel proteins, apatite mineral, and phospholipids. Following a brief overview of enamel hierarchical structure and its mechanical properties we will present the state-of-the-art strategies in the biomimetic reconstruction of human enamel. PMID:26251723

  3. Distribution of the amelogenin protein in developing, injured and carious human teeth

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    Thimios eMitsiadis

    2014-12-01

    Full Text Available Amelogenin is the major enamel matrix protein with key roles in amelogenesis. Although for many decades amelogenin was considered to be exclusively expressed by ameloblasts, more recent studies have shown that amelogenin is also expressed in other dental and no-dental cells. However, amelogenin expression in human tissues remains unclear. Here, we show that amelogenin protein is not only expressed during human embryonic development but also in pathological conditions such as carious lesions and injuries after dental cavity preparation. In developing embryonic teeth, amelogenin stage-specific expression is found in all dental epithelia cell populations but with different instensities. In the different layers of enamel matrix, waves of positive versus negative immunostaining for amelogenin are detected suggesting that the secretion of amelogenin protein is orchestreted by a biological clock. Amelogenin is also expressed transiently in differentiating odontoblasts during predentin formation, but was absent in mature functional odontoblasts. In intact adult teeth, amelogenin was not present in dental pulp, odontoblasts, and dentin. However, in injured and carious adult human teeth amelogenin is strongly re-expressed in newly differentiated odontoblasts and is distributed in the dentinal tubuli under the lesion site. In an in vitro culture system, amelogenin is expressed preferentially in human dental pulp cells that start differentiating into odontoblast-like cells and form mineralization nodules. These data suggest that amelogenin plays important roles not only during cytodifferentiation, but also during tooth repair processes in humans.

  4. An amelogenin mutation leads to disruption of the odontogenic apparatus and aberrant expression of Notch I

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    Chen, Xu; Li, Yong; Alawi, Faizan; Bouchard, Jessica R.; Kulkarni, Ashok B.; Gibson, Carolyn W.

    2012-01-01

    BACKGROUND Amelogenins are highly conserved proteins secreted by ameloblasts in the dental organ of developing teeth. These proteins regulate dental enamel thickness and structure in humans and mice. Mice that express an amelogenin transgene with a P70T mutation (TgP70T) develop abnormal epithelial proliferation in an amelogenin null (KO) background. Some of these cellular masses have the appearance of proliferating stratum intermedium, which is the layer adjacent to the ameloblasts in unerupted teeth. As Notch proteins are thought to constitute the developmental switch that separates ameloblasts from stratum intermedium, these signaling proteins were evaluated in normal and proliferating tissues. METHODS Mandibles were dissected for histology and immunohistochemistry using Notch I antibodies. Molar teeth were dissected for western blotting and RT-PCR for evaluation of Notch levels through imaging and statistical analyses. RESULTS Notch I was immunolocalized to ameloblasts of TgP70TKO mice, KO ameloblasts stained, but less strongly, and wild-type teeth had minimal staining. Cells within the proliferating epithelial cell masses were positive for Notch I and had an appearance reminiscent of calcifying epithelial odontogenic tumor with amyloid-like deposits. Notch I protein and mRNA were elevated in molar teeth from TgP70TKO mice. CONCLUSION Expression of TgP70T leads to abnormal structures in mandibles and maxillae of mice with the KO genetic background and these mice have elevated levels of Notch I in developing molars. As cells within the masses also express transgenic amelogenins, development of the abnormal proliferations suggests communication between amelogenin producing cells and the proliferating cells, dependent on the presence of the mutated amelogenin protein. PMID:20923441

  5. Weaker dental enamel explains dental decay.

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    Vieira, Alexandre R; Gibson, Carolyn W; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution.

  6. Amelogenins as potential buffers during secretory-stage amelogenesis.

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    Guo, J; Lyaruu, D M; Takano, Y; Gibson, C W; DenBesten, P K; Bronckers, A L J J

    2015-03-01

    Amelogenins are the most abundant protein species in forming dental enamel, taken to regulate crystal shape and crystal growth. Unprotonated amelogenins can bind protons, suggesting that amelogenins could regulate the pH in enamel in situ. We hypothesized that without amelogenins the enamel would acidify unless ameloblasts were buffered by alternative ways. To investigate this, we measured the mineral and chloride content in incisor enamel of amelogenin-knockout (AmelX(-/-)) mice and determined the pH of enamel by staining with methyl-red. Ameloblasts were immunostained for anion exchanger-2 (Ae2), a transmembrane pH regulator sensitive for acid that secretes bicarbonate in exchange for chloride. The enamel of AmelX(-/-) mice was 10-fold thinner, mineralized in the secretory stage 1.8-fold more than wild-type enamel and containing less chloride (suggesting more bicarbonate secretion). Enamel of AmelX(-/-) mice stained with methyl-red contained no acidic bands in the maturation stage as seen in wild-type enamel. Secretory ameloblasts of AmelX(-/-) mice, but not wild-type mice, were immunopositive for Ae2, and stained more intensely in the maturation stage compared with wild-type mice. Exposure of AmelX(-/-) mice to fluoride enhanced the mineral content in the secretory stage, lowered chloride, and intensified Ae2 immunostaining in the enamel organ in comparison with non-fluorotic mutant teeth. The results suggest that unprotonated amelogenins may regulate the pH of forming enamel in situ. Without amelogenins, Ae2 could compensate for the pH drop associated with crystal formation. © International & American Associations for Dental Research 2014.

  7. Matching 4.7-Å XRD spacing in amelogenin nanoribbons and enamel matrix.

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    Sanii, B; Martinez-Avila, O; Simpliciano, C; Zuckermann, R N; Habelitz, S

    2014-09-01

    The recent discovery of conditions that induce nanoribbon structures of amelogenin protein in vitro raises questions about their role in enamel formation. Nanoribbons of recombinant human full-length amelogenin (rH174) are about 17 nm wide and self-align into parallel bundles; thus, they could act as templates for crystallization of nanofibrous apatite comprising dental enamel. Here we analyzed the secondary structures of nanoribbon amelogenin by x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) and tested if the structural motif matches previous data on the organic matrix of enamel. XRD analysis showed that a peak corresponding to 4.7 Å is present in nanoribbons of amelogenin. In addition, FTIR analysis showed that amelogenin in the form of nanoribbons was comprised of β-sheets by up to 75%, while amelogenin nanospheres had predominantly random-coil structure. The observation of a 4.7-Å XRD spacing confirms the presence of β-sheets and illustrates structural parallels between the in vitro assemblies and structural motifs in developing enamel. © International & American Associations for Dental Research.

  8. Interaction between the enamel matrix proteins amelogenin and ameloblastin

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    Ravindranath, Hanumanth H.; Chen, Li-Sha; Zeichner-David, Margaret; Ishima, Rieko; Ravindranath, Rajeswari M.H.

    2004-01-01

    Enamel matrix consists of amelogenin and non-amelogenins. Though amelogenin is not involved in nucleation of minerals, the enamel mineralization is impaired when amelogenin or other matrix protein (ameloblastin/enamelin) genes are mutated. We hypothesize that amelogenin may promote enamel mineralization by interacting with the calcium-binding matrix proteins. Specific binding of amelogenin to N-acetylglucosamine (GlcNAc), GlcNAc-mimicking peptides (GMps), and their carrier proteins and the identification of amelogenin-trityrosyl-motif-peptide (ATMP) as a GlcNAc/GMp-binding domain in amelogenin favor the hypothesis. This study tested the interaction of amelogenin with ameloblastin, a carrier of GMp sequence at intermittent sites. Neither GlcNAc nor sialic acids were identified in the recombinant-ameloblastin. Amelogenin bound to recombinant-ameloblastin in both Western blots and in ELISA. More specifically, [ 3 H]ATMP bound to both recombinant and native ameloblastins. Dosimetry and Scatchard analyses showed the specific interaction between ATMP and ameloblastin, suggesting that amelogenin may interact with ameloblastin to form a heteromolecular assembly

  9. Interaction between the enamel matrix proteins amelogenin and ameloblastin.

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    Ravindranath, Hanumanth H; Chen, Li-Sha; Zeichner-David, Margaret; Ishima, Rieko; Ravindranath, Rajeswari M H

    2004-10-22

    Enamel matrix consists of amelogenin and non-amelogenins. Though amelogenin is not involved in nucleation of minerals, the enamel mineralization is impaired when amelogenin or other matrix protein (ameloblastin/enamelin) genes are mutated. We hypothesize that amelogenin may promote enamel mineralization by interacting with the calcium-binding matrix proteins. Specific binding of amelogenin to N-acetylglucosamine (GlcNAc), GlcNAc-mimicking peptides (GMps), and their carrier proteins and the identification of amelogenin-trityrosyl-motif-peptide (ATMP) as a GlcNAc/GMp-binding domain in amelogenin favor the hypothesis. This study tested the interaction of amelogenin with ameloblastin, a carrier of GMp sequence at intermittent sites. Neither GlcNAc nor sialic acids were identified in the recombinant-ameloblastin. Amelogenin bound to recombinant-ameloblastin in both Western blots and in ELISA. More specifically, [(3)H]ATMP bound to both recombinant and native ameloblastins. Dosimetry and Scatchard analyses showed the specific interaction between ATMP and ameloblastin, suggesting that amelogenin may interact with ameloblastin to form a heteromolecular assembly.

  10. Amelogenin as a promoter of nucleation and crystal growth of apatite

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    Uskoković, Vuk; Li, Wu; Habelitz, Stefan

    2011-02-01

    Human dental enamel forms over a period of 2-4 years by substituting the enamel matrix, a protein gel mostly composed of a single protein, amelogenin with fibrous apatite nanocrystals. Self-assembly of amelogenin and the products of its selective proteolytic digestion are presumed to direct the growth of apatite fibers and their organization into bundles that eventually comprise the mature enamel, the hardest tissue in the mammalian body. This work aimed to establish the physicochemical and biochemical conditions for the growth of apatite crystals under the control of a recombinant amelogenin matrix (rH174) in combination with a programmable titration system. The growth of apatite substrates was initiated in the presence of self-assembling amelogenin particles. A series of constant titration rate experiments was performed that allowed for a gradual increase of the calcium and/or phosphate concentrations in the protein suspensions. We observed a significant amount of apatite crystals formed on the substrates following the titration of rH174 sols that comprised the initial supersaturation ratio equal to zero. The protein layers adsorbed onto the substrate apatite crystals were shown to act as promoters of nucleation and growth of calcium phosphates subsequently formed on the substrate surface. Nucleation lag time experiments have showed that rH174 tends to accelerate precipitation from metastable calcium phosphate solutions in proportion to its concentration. Despite their mainly hydrophobic nature, amelogenin nanospheres, the size and surface charge properties of which were analyzed using dynamic light scattering, acted as a nucleating agent for the crystallization of apatite. The biomimetic experimental setting applied in this study proves as convenient for gaining insight into the fundamental nature of the process of amelogenesis.

  11. Enamel protein regulation and dental and periodontal physiopathology in MSX2 mutant mice.

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    Molla, Muriel; Descroix, Vianney; Aïoub, Muhanad; Simon, Stéphane; Castañeda, Beatriz; Hotton, Dominique; Bolaños, Alba; Simon, Yohann; Lezot, Frédéric; Goubin, Gérard; Berdal, Ariane

    2010-11-01

    Signaling pathways that underlie postnatal dental and periodontal physiopathology are less studied than those of early tooth development. Members of the muscle segment homeobox gene (Msx) family encode homeoproteins that show functional redundancy during development and are known to be involved in epithelial-mesenchymal interactions that lead to crown morphogenesis and ameloblast cell differentiation. This study analyzed the MSX2 protein during mouse postnatal growth as well as in the adult. The analysis focused on enamel and periodontal defects and enamel proteins in Msx2-null mutant mice. In the epithelial lifecycle, the levels of MSX2 expression and enamel protein secretion were inversely related. Msx2+/- mice showed increased amelogenin expression, enamel thickness, and rod size. Msx2-/- mice displayed compound phenotypic characteristics of enamel defects, related to both enamel-specific gene mutations (amelogenin and enamelin) in isolated amelogenesis imperfecta, and cell-cell junction elements (laminin 5 and cytokeratin 5) in other syndromes. These effects were also related to ameloblast disappearance, which differed between incisors and molars. In Msx2-/- roots, Malassez cells formed giant islands that overexpressed amelogenin and ameloblastin that grew over months. Aberrant expression of enamel proteins is proposed to underlie the regional osteopetrosis and hyperproduction of cellular cementum. These enamel and periodontal phenotypes of Msx2 mutants constitute the first case report of structural and signaling defects associated with enamel protein overexpression in a postnatal context.

  12. Amelogenin-cytokeratin 14 interaction in ameloblasts during enamel formation.

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    Ravindranath, R M; Tam, W Y; Bringas, P; Santos, V; Fincham, A G

    2001-09-28

    The enamel protein amelogenin binds to the GlcNAc-mimicking peptide (GMp) (Ravindranath, R. M. H., Tam, W., Nguyen, P., and Fincham, A. G. (2000) J. Biol. Chem. 275, 39654-39661). The GMp motif is found in the N-terminal region of CK14, a differentiation marker for ameloblasts. The binding affinity of CK14 and amelogenin was confirmed by dosimetric binding of CK14 to recombinant amelogenin (rM179), and to the tyrosine-rich amelogenin polypeptide. The specific binding site for CK14 was identified in the amelogenin trityrosyl motif peptide (ATMP) of tyrosine-rich amelogenin polypeptide and specific interaction between CK14 and [(3)H]ATMP was confirmed by Scatchard analysis. Blocking rM179 with GlcNAc, GMp, or CK14 with ATMP abrogates the CK14-amelogenin interaction. CK14 failed to bind to ATMP when the third proline was substituted with threonine, as in some cases of human X-linked amelogenesis imperfecta or when tyrosyl residues were substituted with phenylalanine. Morphometry of developing teeth distinguished three phases of enamel formation; growth initiation phase (days 0-1), prolific growth phase (days 1-7), and growth cessation phase (post-day 7). Confocal microscopy revealed co-assembly of CK14/amelogenin in the perinuclear region of ameloblasts on day 0, migration of the co-assembled CK14/amelogenin to the apical region of the ameloblasts from day 1, reaching a peak on days 3-5, and a collapse of the co-assembly. Autoradiography with [(3)H]ATMP and [(3)H]GMp corroborated the dissociation of the co-assembly at the ameloblast Tomes' process. It is proposed that CK14 play a chaperon role for nascent amelogenin polypeptide during amelogenesis.

  13. Amelogenin interacts with cytokeratin-5 in ameloblasts during enamel growth.

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    Ravindranath, Rajeswari M H; Basilrose, Rajam M; Ravindranath, Naren H; Vaitheesvaran, Bhavapriya

    2003-05-30

    The enamel protein amelogenin binds to GlcNAc (Ravindranath, R. M. H., Moradian-Oldak, R., and Fincham, A.G. (1999) J. Biol. Chem. 274, 2464-2471) and to the GlcNAc-mimicking peptide (GMp) (Ravindranath, R. M. H., Tam, W., Nguyen, P., and Fincham, A. G. (2000) J. Biol. Chem. 275, 39654-39661). The GMp motif in the N-terminal region of the cytokeratin 14 of ameloblasts binds to trityrosyl motif peptide (ATMP) of amelogenin (Ravindranath, R. M. H., Tam, W., Bringas, P., Santos, V., and Fincham, A. G. (2001) J. Biol. Chem. 276, 36586 - 36597). K14 (Type I) pairs with K5 (Type II) in basal epithelial cells; GlcNAc-acylated K5 is identified in ameloblasts. Dosimetric analysis showed the binding affinity of amelogenin to K5 and to GlcNAc-acylated-positive control, ovalbumin. The specific binding of [3H]ATMP with K5 or ovalbumin was confirmed by Scatchard analysis. [3H]ATMP failed to bind to K5 after removal of GlcNAc. Blocking K5 with ATMP abrogates the K5-amelogenin interaction. K5 failed to bind to ATMP when the third proline was substituted with threonine, as in some cases of human X-linked amelogenesis imperfecta or when tyrosyl residues were substituted with phenylalanine. Confocal laser scan microscopic observations on ameloblasts during postnatal (PN) growth of the teeth showed that the K5-amelogenin complex migrated from the cytoplasm to the periphery (on PN day 1) and accumulated at the apical region on day 3. Secretion of amelogenin commences from day 1. K5, similar to K14, may play a role of chaperone during secretion of amelogenin. Upon secretion of amelogenin, K5 pairs with K14. Pairing of K5 and K14 commences on day 3 and ends on day 9. The pairing of K5 and K14 marks the end of secretion of amelogenin.

  14. Matrix metalloproteinase-20 mediates dental enamel biomineralization by preventing protein occlusion inside apatite crystals.

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    Prajapati, Saumya; Tao, Jinhui; Ruan, Qichao; De Yoreo, James J; Moradian-Oldak, Janet

    2016-01-01

    Reconstruction of enamel-like materials is a central topic of research in dentistry and material sciences. The importance of precise proteolytic mechanisms in amelogenesis to form a hard tissue with more than 95% mineral content has already been reported. A mutation in the Matrix Metalloproteinase-20 (MMP-20) gene results in hypomineralized enamel that is thin, disorganized and breaks from the underlying dentin. We hypothesized that the absence of MMP-20 during amelogenesis results in the occlusion of amelogenin in the enamel hydroxyapatite crystals. We used spectroscopy and electron microscopy techniques to qualitatively and quantitatively analyze occluded proteins within the isolated enamel crystals from MMP-20 null and Wild type (WT) mice. Our results showed that the isolated enamel crystals of MMP-20 null mice had more organic macromolecules occluded inside them than enamel crystals from the WT. The crystal lattice arrangements of MMP-20 null enamel crystals analyzed by High Resolution Transmission Electron Microscopy (HRTEM) were found to be significantly different from those of the WT. Raman studies indicated that the crystallinity of the MMP-20 null enamel crystals was lower than that of the WT. In conclusion, we present a novel functional mechanism of MMP-20, specifically prevention of unwanted organic material entrapped in the forming enamel crystals, which occurs as the result of precise amelogenin cleavage. MMP-20 action guides the growth morphology of the forming hydroxyapatite crystals and enhances their crystallinity. Elucidating such molecular mechanisms can be applied in the design of novel biomaterials for future clinical applications in dental restoration or repair. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Remineralization of initial enamel caries in vitro using a novel peptide based on amelogenin

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    Li, Danxue; Lv, Xueping; Tu, Huanxin; Zhou, Xuedong; Yu, Haiyang; Zhang, Linglin

    2015-09-01

    Dental caries is the most common oral disease with high incidence, widely spread and can seriously affect the health of oral cavity and the whole body. Current caries prevention measures such as fluoride treatment, antimicrobial agents, and traditional Chinese herbal, have limitations to some extent. Here we design and synthesize a novel peptide based on the amelogenin, and assess its ability to promote the remineralization of initial enamel caries lesions. We used enamel blocks to form initial lesions, and then subjected to 12-day pH cycling in the presence of peptide, NaF and HEPES buffer. Enamel treated with peptide or NaF had shallower, narrower lesions, thicker remineralized surfaces and less mineral loss than enamel treated with HEPES. This peptide can promote the remineralization of initial enamel caries and inhibit the progress of caries. It is a promising anti-caries agent with various research prospects and practical application value.

  16. Identification of a novel splicing form of amelogenin gene in a reptile, Ctenosaura similis.

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    Xinping Wang

    Full Text Available Amelogenin, the major enamel matrix protein in tooth development, has been demonstrated to play a significant role in tooth enamel formation. Previous studies have identified the alternative splicing of amelogenin in many mammalian vertebrates as one mechanism for amelogenin heterogeneous expression in teeth. While amelogenin and its splicing forms in mammalian vertebrates have been cloned and sequenced, the amelogenin gene, especially its splicing forms in non-mammalian species, remains largely unknown. To better understand the mechanism underlying amelogenin evolution, we previously cloned and characterized an amelogenin gene sequence from a squamate, the green iguana. In this study, we employed RT-PCR to amplify the amelogenin gene from the black spiny-tailed iguana Ctenosaura similis teeth, and discovered a novel splicing form of the amelogenin gene. The transcript of the newly identified iguana amelogenin gene (named C. Similis-T2L is 873 nucleotides long encoding an expected polypeptide of 206 amino acids. The C. Similis-T2L contains a unique exon denominated exon X, which is located between exon 5 and exon 6. The C. Similis-T2L contains 7 exons including exon 1, 2, 3, 5, X, 6, and 7. Analysis of the secondary and tertiary structures of T2L amelogenin protein demonstrated that exon X has a dramatic effect on the amelogenin structures. This is the first report to provide definitive evidence for the amelogenin alternative splicing in non-mammalian vertebrates, revealing a unique exon X and the splicing form of the amelogenin gene transcript in Ctenosaura similis.

  17. Preparative SDS PAGE as an Alternative to His-Tag Purification of Recombinant Amelogenin

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    Claire M. Gabe

    2017-06-01

    Full Text Available Recombinant protein technology provides an invaluable source of proteins for use in structure-function studies, as immunogens, and in the development of therapeutics. Recombinant proteins are typically engineered with “tags” that allow the protein to be purified from crude host cell extracts using affinity based chromatography techniques. Amelogenin is the principal component of the developing enamel matrix and a frequent focus for biomineralization researchers. Several groups have reported the successful production of recombinant amelogenins but the production of recombinant amelogenin free of any tags, and at single band purity on silver stained SDS PAGE is technically challenging. This is important, as rigorous structure-function research frequently demands a high degree of protein purity and fidelity of protein sequence. Our aim was to generate His-tagged recombinant amelogenin at single band purity on silver stained SDS PAGE for use in functionality studies after His-tag cleavage. An acetic acid extraction technique (previously reported to produce recombinant amelogenin at 95% purity directly from E. coli followed by repeated rounds of nickel column affinity chromatography, failed to generate recombinant amelogenin at single band purity. This was because following an initial round of nickel column affinity chromatography, subsequent cleavage of the His-tag was not 100% efficient. A second round of nickel column affinity chromatography, used in attempts to separate the cleaved His-tag free recombinant from uncleaved His-tagged contaminants, was still unsatisfactory as cleaved recombinant amelogenin exhibited significant affinity for the nickel column. To solve this problem, we used preparative SDS PAGE to successfully purify cleaved recombinant amelogenins to single band purity on silver stained SDS PAGE. The resolving power of preparative SDS PAGE was such that His-tag based purification of recombinant amelogenin becomes redundant. We

  18. Latex allergy and filaggrin null mutations

    DEFF Research Database (Denmark)

    Carlsen, Berit C; Meldgaard, Michael; Hamann, Dathan

    2011-01-01

    to aeroallergens and it is possible that filaggrin null mutations also increase the risk of latex allergy. The aim of this paper was to examine the association between filaggrin null mutations and type I latex allergy. Methods Twenty latex allergic and 24 non-latex allergic dentists and dental assistants...... in the cases in this study may not have occurred through direct skin contact but through the respiratory organs via latex proteins that are absorbed in glove powder and aerosolized...

  19. Effects of amelogenins on angiogenesis-associated processes of endothelial cells

    DEFF Research Database (Denmark)

    Almqvist, S; Kleinman, H K; Werthén, M

    2011-01-01

    To study the effects of an amelogenin mixture on integrin-dependent adhesion, DNA synthesis and apoptosis of cultured human dermal microvascular endothelial cells and angiogenesis in an organotypic assay.......To study the effects of an amelogenin mixture on integrin-dependent adhesion, DNA synthesis and apoptosis of cultured human dermal microvascular endothelial cells and angiogenesis in an organotypic assay....

  20. Amelogenin Affects Brushite Crystal Morphology and Promotes Its Phase Transformation to Monetite

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    Ren, Dongni; Ruan, Qichao; Tao, Jinhui; Lo, Jonathan; Nutt, Steven; Moradian-Oldak, Janet

    2016-09-07

    Amelogenin protein is involved in organized apatite crystallization during enamel formation. Brushite (CaHPO4·2H2O), which is one of the precursors for hydroxyapatite in in vitro mineralization, has been used for fabrication of biomaterials for hard tissue repair. In order to explore its potential application in biomimetic material synthesis, we studied the influence of amelogenin on brushite morphology and phase transformation to monetite. Our results show that amelogenin can adsorb onto surface of brushite, leading to the formation of layered structures on the (010) face. Amelogenin promoted the phase transformation of brushite into monetite (CaHPO4) in the dry state, presumably by interacting with crystalline water layers in brushite unit cell. Changes to the crystal morphology by amelogenin continued even after the phase transformation to monetite forming an organized nanotextured structure of nano-sticks resembling the bundle structure in enamel.

  1. Nance-Horan syndrome: a contiguous gene syndrome involving deletion of the amelogenin gene? A case report and molecular analysis.

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    Franco, E; Hodgson, S; Lench, N; Roberts, G J

    1995-03-01

    A case of Nance-Horan syndrome in a male is presented, with some features of the condition in his carrier mother and her mother. It is proposed that Nance-Horan syndrome might be a contiguous gene syndrome mapping to chromosome Xp21.2-p22.3. The proband had congenital cataract microphthalmia and dental abnormalities including screwdriver shaped incisors and evidence of enamel pitting hypoplasia. The region Xp21.2-p22.3 also contains the tooth enamel protein gene, amelogenin (AMGX). Using molecular genetic techniques, we have shown that there is no evidence that the AMGX gene is deleted in this case of the Nance-Horan syndrome.

  2. Analysis of Co-assembly and Co-localization of Ameloblastin and Amelogenin

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    Prichita eMazumder

    2014-07-01

    Full Text Available Epithelially-derived ameloblasts secrete extracellular matrix proteins including amelogenin, enamelin and ameloblastin. Complex intermolecular interactions among these proteins are believed to be important in controlling enamel formation. Here we provide in vitro and in vivo evidence of co-assembly and co-localization of ameloblastin with amelogenin using both biophysical and immunohistochemical methods. We performed co-localization studies using immunofluorescence confocal microscopy with paraffin-embedded tissue sections from mandibular molars of mice at 1, 5 and 8 days of age. Commercially-available ameloblastin antibody (M300 against mouse ameloblastin residues 107-407 and an antibody against full-length recombinant mouse (rM179 amelogenin were used. Ameloblastin-M300 clearly reacted along the secretory face of ameloblasts from days 1-8. Quantitative co-localization was analyzed (QCA in several configurations by choosing appropriate regions of interest (ROIs. Analysis of ROIs along the secretory face of ameloblasts revealed that at day 1, very high percentages of both the ameloblastin and amelogenin co-localized. At day 8 along the ameloblast cells the percentage of co-localization remained high for the ameloblastin whereas co-localization percentage was reduced for amelogenin. Analysis of the entire thickness on day 8 revealed no significant co-localization of amelogenin and ameloblastin. With the progress of amelogenesis and ameloblastin degradation, there was a segregation of ameloblastin and co-localization with the C-terminal region decreased. CD spectra indicated that structural changes in ameloblastin occurred upon addition of amelogenin. Our data suggest that amelogenin-ameloblastin complexes may be the functional entities at the early stage of enamel mineralization.

  3. Amelogenesis Imperfecta and Screening of Mutation in Amelogenin Gene

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    Fernanda Veronese Oliveira

    2014-01-01

    Full Text Available The aim of this study was to report the clinical findings and the screening of mutations of amelogenin gene of a 7-year-old boy with amelogenesis imperfecta (AI. The genomic DNA was extracted from saliva of patient and his family, followed by PCR and direct DNA sequencing. The c.261C>T mutation was found in samples of mother, father, and brother, but the mutation was not found in the sequence of the patient. This mutation is a silent mutation and a single-nucleotide polymorphism (rs2106416. Thus, it is suggested that the mutation found was not related to the clinical presence of AI. Further research is necessary to examine larger number of patients and genes related to AI.

  4. Dose-Dependent Rescue of KO Amelogenin Enamel by Transgenes in Vivo.

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    Bidlack, Felicitas B; Xia, Yan; Pugach, Megan K

    2017-01-01

    Mice lacking amelogenin (KO) have hypoplastic enamel. Overexpression of the most abundant amelogenin splice variant M180 and LRAP transgenes can substantially improve KO enamel, but only ~40% of the incisor thickness is recovered and the prisms are not as tightly woven as in WT enamel. This implies that the compositional complexity of the enamel matrix is required for different aspects of enamel formation, such as organizational structure and thickness. The question arises, therefore, how important the ratio of different matrix components, and in particular amelogenin splice products, is in enamel formation. Can optimal expression levels of amelogenin transgenes representing both the most abundant splice variants and cleavage product at protein levels similar to that of WT improve the enamel phenotype of KO mice? Addressing this question, our objective was here to understand dosage effects of amelogenin transgenes ( Tg ) representing the major splice variants M180 and LRAP and cleavage product CTRNC on enamel properties. Amelogenin KO mice were mated with M180 Tg , CTRNC Tg and LRAP Tg mice to generate M180 Tg and CTRNC Tg double transgene and M180 Tg , CTRNC Tg , LRAP Tg triple transgene mice with transgene hemizygosity (on one allelle) or homozygosity (on both alleles). Transgene homo- vs. hemizygosity was determined by qPCR and relative transgene expression confirmed by Western blot. Enamel volume and mineral density were analyzed by microCT, thickness and structure by SEM, and mechanical properties by Vickers microhardness testing. There were no differences in incisor enamel thickness between amelogenin KO mice with three or two different transgenes, but mice homozygous for a given transgene had significantly thinner enamel than mice hemizygous for the transgene ( p structure, but only up to a maximum of ~80% that of molar and ~40% that of incisor wild-type enamel.

  5. Dose-Dependent Rescue of KO Amelogenin Enamel by Transgenes in Vivo

    Directory of Open Access Journals (Sweden)

    Felicitas B. Bidlack

    2017-11-01

    Full Text Available Mice lacking amelogenin (KO have hypoplastic enamel. Overexpression of the most abundant amelogenin splice variant M180 and LRAP transgenes can substantially improve KO enamel, but only ~40% of the incisor thickness is recovered and the prisms are not as tightly woven as in WT enamel. This implies that the compositional complexity of the enamel matrix is required for different aspects of enamel formation, such as organizational structure and thickness. The question arises, therefore, how important the ratio of different matrix components, and in particular amelogenin splice products, is in enamel formation. Can optimal expression levels of amelogenin transgenes representing both the most abundant splice variants and cleavage product at protein levels similar to that of WT improve the enamel phenotype of KO mice? Addressing this question, our objective was here to understand dosage effects of amelogenin transgenes (Tg representing the major splice variants M180 and LRAP and cleavage product CTRNC on enamel properties. Amelogenin KO mice were mated with M180Tg, CTRNCTg and LRAPTg mice to generate M180Tg and CTRNCTg double transgene and M180Tg, CTRNCTg, LRAPTg triple transgene mice with transgene hemizygosity (on one allelle or homozygosity (on both alleles. Transgene homo- vs. hemizygosity was determined by qPCR and relative transgene expression confirmed by Western blot. Enamel volume and mineral density were analyzed by microCT, thickness and structure by SEM, and mechanical properties by Vickers microhardness testing. There were no differences in incisor enamel thickness between amelogenin KO mice with three or two different transgenes, but mice homozygous for a given transgene had significantly thinner enamel than mice hemizygous for the transgene (p < 0.05. The presence of the LRAPTg did not improve the phenotype of M180Tg/CTRNCTg/KO enamel. In the absence of endogenous amelogenin, the addition of amelogenin transgenes representing the most

  6. Amelogenin is phagocytized and induces changes in integrin configuration, gene expression and proliferation of cultured normal human dermal fibroblasts

    DEFF Research Database (Denmark)

    Almqvist, Sofia; Werthén, Maria; Johansson, Anna

    2010-01-01

    Fibroblasts are central in wound healing by expressing important mediators and producing and remodelling extracellular matrix (ECM) components. This study aimed at elucidating possible mechanisms of action of the ECM protein amelogenin on normal human dermal fibroblasts (NHDF). Amelogenin at 100...

  7. Chronic fluoride toxicity: dental fluorosis.

    Science.gov (United States)

    Denbesten, Pamela; Li, Wu

    2011-01-01

    Dental fluorosis occurs as a result of excess fluoride ingestion during tooth formation. Enamel fluorosis and primary dentin fluorosis can only occur when teeth are forming, and therefore fluoride exposure (as it relates to dental fluorosis) occurs during childhood. In the permanent dentition, this would begin with the lower incisors, which complete mineralization at approximately 2-3 years of age, and end after mineralization of the third molars. The white opaque appearance of fluorosed enamel is caused by a hypomineralized enamel subsurface. With more severe dental fluorosis, pitting and a loss of the enamel surface occurs, leading to secondary staining (appearing as a brown color). Many of the changes caused by fluoride are related to cell/matrix interactions as the teeth are forming. At the early maturation stage, the relative quantity of amelogenin protein is increased in fluorosed enamel in a dose-related manner. This appears to result from a delay in the removal of amelogenins as the enamel matures. In vitro, when fluoride is incorporated into the mineral, more protein binds to the forming mineral, and protein removal by proteinases is delayed. This suggests that altered protein/mineral interactions are in part responsible for retention of amelogenins and the resultant hypomineralization that occurs in fluorosed enamel. Fluoride also appears to enhance mineral precipitation in forming teeth, resulting in hypermineralized bands of enamel, which are then followed by hypomineralized bands. Enhanced mineral precipitation with local increases in matrix acidity may affect maturation stage ameloblast modulation, potentially explaining the dose-related decrease in cycles of ameloblast modulation from ruffle-ended to smooth-ended cells that occur with fluoride exposure in rodents. Specific cellular effects of fluoride have been implicated, but more research is needed to determine which of these changes are relevant to the formation of fluorosed teeth. As further

  8. Topical application of amelogenin extracellular matrix protein in non-healing venous ulcers

    Directory of Open Access Journals (Sweden)

    Burçin Abud

    2014-12-01

    Full Text Available Background and Design: Treatment of chronic venous ulcers of the lower extremity is still an important difficulty. The principal treatment of these ulcers includes compression therapy, local wound care and surgery. Unresponsiveness to these standard treatments is a frequent situation with negative effects on life quality and reductions in personal productivity. Therefore, there is a need for new applications to increase the effectiveness of treatment in treatment-resistant cases. In the present study, we retrospectively evaluated the results of topical application of amelogenin extracellular matrix protein in resistant venous ulcers. Materials and Methods: We analyzed the records of patients with treatment-resistant venous ulceration who were treated with amelogenin extracellular matrix protein between June 2011 and December 2012.. Results: 26 patients (21 male and 5 female with a total number of 28 ulcers (24 patients with 1 ulcer, 2 patients with two ulcers were evaluated. The patients were treated with topically applied amelogenin extracellular matrix protein and regional four bandage compression. Bandages were changed weekly. Each cure continued for six weeks. In fourteen patients (15 ulcers, we observed a complete healing by the end of the first cure. In another twelve cases (13 ulcers, the same period resulted with a reduction in wound diameter. We continued to the second cure for these patients. By the end of the second cure, complete healing was achieved in five cases (6 ulcers. Conclusion: Topical application of amelogenin extracellular matrix protein may be considered as an effective therapeutic choice for refractory venous ulcers.

  9. Effect of Amelogenin Coating of a Nano-Modified Titanium Surface on Bioactivity

    Directory of Open Access Journals (Sweden)

    Chisato Terada

    2018-04-01

    Full Text Available The interactions between implants and host tissues depend on several factors. In particular, a growing body of evidence has demonstrated that the surface texture of an implant influences the response of the surrounding cells. The purpose of this study is to develop new implant materials aiming at the regeneration of periodontal tissues as well as hard tissues by coating nano-modified titanium with amelogenin, which is one of the main proteins contained in Emdogain®. We confirmed by quartz crystal microbalance evaluation that amelogenin is easy to adsorb onto the nano-modified titanium surface as a coating. Scanning electron microscopy, scanning probe microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy analyses confirmed that amelogenin coated the nano-modified titanium surface following alkali-treatment. In vitro evaluation using rat bone marrow and periodontal ligament cells revealed that the initial adhesion of both cell types and the induction of hard tissue differentiation such as cementum were improved by amelogenin coating. Additionally, the formation of new bone in implanted surrounding tissues was observed in in vivo evaluation using rat femurs. Together, these results suggest that this material may serve as a new implant material with the potential to play a major role in the advancement of clinical dentistry.

  10. Identification and characterization of amelogenin genes in monotremes, reptiles, and amphibians

    Science.gov (United States)

    Toyosawa, Satoru; O’hUigin, Colm; Figueroa, Felipe; Tichy, Herbert; Klein, Jan

    1998-01-01

    Two features make the tooth an excellent model in the study of evolutionary innovations: the relative simplicity of its structure and the fact that the major tooth-forming genes have been identified in eutherian mammals. To understand the nature of the innovation at the molecular level, it is necessary to identify the homologs of tooth-forming genes in other vertebrates. As a first step toward this goal, homologs of the eutherian amelogenin gene have been cloned and characterized in selected species of monotremes (platypus and echidna), reptiles (caiman), and amphibians (African clawed toad). Comparisons of the homologs reveal that the amelogenin gene evolves quickly in the repeat region, in which numerous insertions and deletions have obliterated any similarity among the genes, and slowly in other regions. The gene organization, the distribution of hydrophobic and hydrophilic segments in the encoded protein, and several other features have been conserved throughout the evolution of the tetrapod amelogenin gene. Clones corresponding to one locus only were found in caiman, whereas the clawed toad possesses at least two amelogenin-encoding loci. PMID:9789040

  11. Null cone superspace supergravity

    International Nuclear Information System (INIS)

    Downes-Martin, S.G.

    1980-03-01

    The null cone formalism is used to derive a 2(N-1) parameter family of constraints for O(N) extended superspace supergravity. The invariance groups of these constraints is analysed and is found to be [subgroup U submanifold] contains GL(4,R) for N = 1, the submanifold being eliminated for N > 1. The invariance group defines non-Weyl rotations on the superbein which combine to form Weyl transformations on the supertangent space metric. The invariance of the supergravity Lagrangian under these transformations is discussed. (Auth.)

  12. The Small Alternatively Spliced Amelogenin LRAP Modulates Early Stage Ameloblast Differentiation

    Science.gov (United States)

    2014-01-30

    proteins are cleaved and degraded, mineral deposition in the form of hydroxyapatite crystals occurs in a well-ordered pattern (Wen et al., 2001). It...differentiation. In additional studies I developed cell culture models to further investigate LRAP function and used LRAP overexpression compare the molar...occurs. 15 The removal of amelogenins from the enamel matrix directs matrix mineralization and creates space for the hydroxyapatite crystals to expand

  13. Sex determination based on amelogenin DNA by modified electrode with gold nanoparticle.

    Science.gov (United States)

    Mazloum-Ardakani, Mohammad; Rajabzadeh, Nooshin; Benvidi, Ali; Heidari, Mohammad Mehdi

    2013-12-15

    We have developed a simple and renewable electrochemical biosensor based on carbon paste electrode (CPE) for the detection of DNA synthesis and hybridization. CPE was modified with gold nanoparticles (AuNPs), which are helpful for immobilization of thiolated bioreceptors. AuNPs were characterized by scanning electron microscopy (SEM). Self-assembled monolayers (SAMs) of thiolated single-stranded DNA (SH-ssDNA) of the amelogenin gene was formed on CPE. The immobilization of the probe and its hybridization with the target DNA was optimized using different experimental conditions. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical response of ssDNA hybridization and DNA synthesis was measured using differential pulse voltammetry (DPV) with methylene blue (MB) as an electroactive indicator. The new biosensor can distinguish between complementary and non-complementary strands of amelogenin ssDNA. Genomic DNA was extracted from blood and was detected based on changes in the MB reduction signal. These results demonstrated that the new biosensor could be used for sex determination. The proposed biosensor in this study could be used for detection and discrimination of polymerase chain reaction (PCR) products of amelogenin DNA. Copyright © 2013 Elsevier Inc. All rights reserved.

  14. Protein Phosphorylation and Mineral Binding Affect the Secondary Structure of the Leucine-Rich Amelogenin Peptide

    Directory of Open Access Journals (Sweden)

    Hajime Yamazaki

    2017-06-01

    Full Text Available Previously, we have shown that serine-16 phosphorylation in native full-length porcine amelogenin (P173 and the Leucine-Rich Amelogenin Peptide (LRAP(+P, an alternative amelogenin splice product, affects protein assembly and mineralization in vitro. Notably, P173 and LRAP(+P stabilize amorphous calcium phosphate (ACP and inhibit hydroxyapatite (HA formation, while non-phosphorylated counterparts (rP172, LRAP(−P guide the growth of ordered bundles of HA crystals. Based on these findings, we hypothesize that the phosphorylation of full-length amelogenin and LRAP induces conformational changes that critically affect its capacity to interact with forming calcium phosphate mineral phases. To test this hypothesis, we have utilized Fourier transform infrared spectroscopy (FTIR to determine the secondary structure of LRAP(−P and LRAP(+P in the absence/presence of calcium and selected mineral phases relevant to amelogenesis; i.e., hydroxyapatite (HA: an enamel crystal prototype and (ACP: an enamel crystal precursor phase. Aqueous solutions of LRAP(−P or LRAP(+P were prepared with or without 7.5 mM of CaCl2 at pH 7.4. FTIR spectra of each solution were obtained using attenuated total reflectance, and amide-I peaks were analyzed to provide secondary structure information. Secondary structures of LRAP(+P and LRAP(−P were similarly assessed following incubation with suspensions of HA and pyrophosphate-stabilized ACP. Amide I spectra of LRAP(−P and LRAP(+P were found to be distinct from each other in all cases. Spectra analyses showed that LRAP(−P is comprised mostly of random coil and β-sheet, while LRAP(+P exhibits more β-sheet and α-helix with little random coil. With added Ca, the random coil content increased in LRAP(−P, while LRAP(+P exhibited a decrease in α-helix components. Incubation of LRAP(−P with HA or ACP resulted in comparable increases in β-sheet structure. Notably, however, LRAP(+P secondary structure was more affected by

  15. Enamel formation in vitro in mouse molar explants exposed to amelogenin polypeptides ATMP and LRAP on enamel development.

    Science.gov (United States)

    Ravindranath, Rajeswari M H; Devarajan, Asokan; Bringas, Pablo

    2007-12-01

    The enamel matrix contains amelogenin, leucine-rich amelogenin-polypeptide (LRAP), resulting from alternative splicing of the primary amelogenin-RNA transcript and tyrosine-rich amelogenin-polypeptide (TRAP), a proteolytic product of amelogenin. Presence of amelogenin-trityrosyl-motif peptide (ATMP) distinguishes TRAP from LRAP. The roles of these polypeptides in the formation of enamel remain to be elucidated. The mouse in vitro molar tooth-organ developed from bud stage (E16) was exposed to LRAP, ATMP, and mutated ATMP (T-ATMP, third proline replaced by threonine). The histology and morphometry of the explants on day-12 in culture was examined using Mallory's stain. Guanidine-HCl soluble protein concentrations of explants were compared. The enamel width and protein solubility indicate that the explant on day-12 is comparable to postnatal molar on day-3 in vivo. The enamel of both untreated explants as well as that in vivo is fuchinophilic (acid fuchsin, AF+). ATMP reduced the ameloblast-height, accumulated AF+ spherules at the apical end of ameloblasts, and disrupted enamel-dentin bonding. T-ATMP abrogated deposition of AF+ material on the aniline blue positive (AB+) enamel matrix. LRAP reduced ameloblast-height, increased the enamel-width without disruption (at 17.25 nmol) and increased the density of AF+ dentinal tubules. AF+ substance from the tubules is released onto the surface of the dentin. The Guanidine-HCl-soluble protein is elevated in ATMP-treated explants but decreased in LRAP-treated explants. Exogenous ATMP, T-ATMP and LRAP have divergent effects on developing enamel. Exogenous ATMP, but not LRAP, abrogates enamel-dentin bonding at 17.25 nmol. LRAP may play a role in the differentiation of ameloblasts, growth of enamel and formation of dentinal tubules.

  16. Regeneration of bone and periodontal ligament induced by recombinant amelogenin after periodontitis.

    Science.gov (United States)

    Haze, Amir; Taylor, Angela L; Haegewald, Stefan; Leiser, Yoav; Shay, Boaz; Rosenfeld, Eli; Gruenbaum-Cohen, Yael; Dafni, Leah; Zimmermann, Bernd; Heikinheimo, Kristiina; Gibson, Carolyn W; Fisher, Larry W; Young, Marian F; Blumenfeld, Anat; Bernimoulin, Jean P; Deutsch, Dan

    2009-06-01

    Regeneration of mineralized tissues affected by chronic diseases comprises a major scientific and clinical challenge. Periodontitis, one such prevalent disease, involves destruction of the tooth-supporting tissues, alveolar bone, periodontal-ligament and cementum, often leading to tooth loss. In 1997, it became clear that, in addition to their function in enamel formation, the hydrophobic ectodermal enamel matrix proteins (EMPs) play a role in the regeneration of these periodontal tissues. The epithelial EMPs are a heterogeneous mixture of polypeptides encoded by several genes. It was not clear, however, which of these many EMPs induces the regeneration and what mechanisms are involved. Here we show that a single recombinant human amelogenin protein (rHAM(+)), induced in vivo regeneration of all tooth-supporting tissues after creation of experimental periodontitis in a dog model. To further understand the regeneration process, amelogenin expression was detected in normal and regenerating cells of the alveolar bone (osteocytes, osteoblasts and osteoclasts), periodontal ligament, cementum and in bone marrow stromal cells. Amelogenin expression was highest in areas of high bone turnover and activity. Further studies showed that during the first 2 weeks after application, rHAM(+) induced, directly or indirectly, significant recruitment of mesenchymal progenitor cells, which later differentiated to form the regenerated periodontal tissues. The ability of a single protein to bring about regeneration of all periodontal tissues, in the correct spatio-temporal order, through recruitment of mesenchymal progenitor cells, could pave the way for development of new therapeutic devices for treatment of periodontal, bone and ligament diseases based on rHAM(+).

  17. Visible Nulling Coronagraph Progress Report

    Science.gov (United States)

    Lyon, R. G.; Clampin, M.; Woodruff, R. A.; Vasudevan, G.; Thompson, P.; Petrone, P.; Madison, T.; Rizzo, M.; Melnick, G.; Tolls, V.

    2010-10-01

    We report on recent laboratory results with the NASA Goddard Space Flight Center Visible Nulling Coronagraph (VNC) testbed. We have achieved focal plane contrasts of 108 and approaching 109 at inner working angles of 2 λ/D and 4 λ/D, respectively. Results were obtained with a broadband source and 40 nm filter centered on 630 nm. A null control breadboard (NCB) was also developed to assess and quantify MEMS based deformable mirror technology (DM), and to develop and assess closed-loop null control algorithms. We have demonstrated closed-loop performance at 27 Hz.

  18. Null lifts and projective dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Cariglia, Marco, E-mail: marco@iceb.ufop.br

    2015-11-15

    We describe natural Hamiltonian systems using projective geometry. The null lift procedure endows the tangent bundle with a projective structure where the null Hamiltonian is identified with a projective conic and induces a Weyl geometry. Projective transformations generate a set of known and new dualities between Hamiltonian systems, as for example the phenomenon of coupling-constant metamorphosis. We conclude outlining how this construction can be extended to the quantum case for Eisenhart–Duval lifts.

  19. Structural analysis of a repetitive protein sequence motif in strepsirrhine primate amelogenin.

    Directory of Open Access Journals (Sweden)

    Rodrigo S Lacruz

    2011-03-01

    Full Text Available Strepsirrhines are members of a primate suborder that has a distinctive set of features associated with the development of the dentition. Amelogenin (AMEL, the better known of the enamel matrix proteins, forms 90% of the secreted organic matrix during amelogenesis. Although AMEL has been sequenced in numerous mammalian lineages, the only reported strepsirrhine AMEL sequences are those of the ring-tailed lemur and galago, which contain a set of additional proline-rich tandem repeats absent in all other primates species analyzed to date, but present in some non-primate mammals. Here, we first determined that these repeats are present in AMEL from three additional lemur species and thus are likely to be widespread throughout this group. To evaluate the functional relevance of these repeats in strepsirrhines, we engineered a mutated murine amelogenin sequence containing a similar proline-rich sequence to that of Lemur catta. In the monomeric form, the MQP insertions had no influence on the secondary structure or refolding properties, whereas in the assembled form, the insertions increased the hydrodynamic radii. We speculate that increased AMEL nanosphere size may influence enamel formation in strepsirrhine primates.

  20. Different effects of 25-kDa amelogenin on the proliferation, attachment and migration of various periodontal cells

    International Nuclear Information System (INIS)

    Li, Xiting; Shu, Rong; Liu, Dali; Jiang, Shaoyun

    2010-01-01

    Previous studies have assumed that amelogenin is responsible for the therapeutic effect of the enamel matrix derivative (EMD) in periodontal tissue healing and regeneration. However, it is difficult to confirm this hypothesis because both the EMD and the amelogenins are complex mixtures of multiple proteins. Further adding to the difficulties is the fact that periodontal tissue regeneration involves various types of cells and a sequence of associated cellular events including the attachment, migration and proliferation of various cells. In this study, we investigated the potential effect of a 25-kDa recombinant porcine amelogenin (rPAm) on primarily cultured periodontal ligament fibroblasts (PDLF), gingival fibroblasts (GF) and gingival epithelial cells (GEC). The cells were treated with 25-kDa recombinant porcine amelogenin at a concentration of 10 μg/mL. We found that rPAm significantly promoted the proliferation and migration of PDLF, but not their adhesion. Similarly, the proliferation and adhesion of GF were significantly enhanced by treatment with rPAm, while migration was greatly inhibited. Interestingly, this recombinant protein inhibited the growth rate, cell adhesion and migration of GEC. These data suggest that rPAm may play an essential role in periodontal regeneration through the activation of periodontal fibroblasts and inhibition of the cellular behaviors of gingival epithelial cells.

  1. Bare Quantum Null Energy Condition.

    Science.gov (United States)

    Fu, Zicao; Marolf, Donald

    2018-02-16

    The quantum null energy condition (QNEC) is a conjectured relation between a null version of quantum field theory energy and derivatives of quantum field theory von Neumann entropy. In some cases, divergences cancel between these two terms and the QNEC is intrinsically finite. We study the more general case here where they do not and argue that a QNEC can still hold for bare (unrenormalized) quantities. While the original QNEC applied only to locally stationary null congruences in backgrounds that solve semiclassical theories of quantum gravity, at least in the formal perturbation theory at a small Planck length, the quantum focusing conjecture can be viewed as the special case of our bare QNEC for which the metric is on shell.

  2. Visible nulling coronagraph testbed results

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Woodruff, Robert A.; Vasudevan, Gopal; Thompson, Patrick; Petrone, Peter; Madison, Timothy; Rizzo, Maxime; Melnick, Gary; Tolls, Volker

    2009-08-01

    We report on our recent laboratory results with the NASA/Goddard Space Flight Center (GSFC) Visible Nulling Coronagraph (VNC) testbed. We have experimentally achieved focal plane contrasts of 1 x 108 and approaching 109 at inner working angles of 2 * wavelength/D and 4 * wavelength/D respectively where D is the aperture diameter. The result was obtained using a broadband source with a narrowband spectral filter of width 10 nm centered on 630 nm. To date this is the deepest nulling result with a visible nulling coronagraph yet obtained. Developed also is a Null Control Breadboard (NCB) to assess and quantify MEMS based segmented deformable mirror technology and develop and assess closed-loop null sensing and control algorithm performance from both the pupil and focal planes. We have demonstrated closed-loop control at 27 Hz in the laboratory environment. Efforts are underway to first bring the contrast to > 109 necessary for the direct detection and characterization of jovian (Jupiter-like) and then to > 1010 necessary for terrestrial (Earth-like) exosolar planets. Short term advancements are expected to both broaden the spectral passband from 10 nm to 100 nm and to increase both the long-term stability to > 2 hours and the extent of the null out to a ~ 10 * wavelength / D via the use of MEMS based segmented deformable mirror technology, a coherent fiber bundle, achromatic phase shifters, all in a vacuum chamber at the GSFC VNC facility. Additionally an extreme stability textbook sized compact VNC is under development.

  3. Amelogenin, an extracellular matrix protein, in the treatment of venous leg ulcers and other hard-to-heal wounds: Experimental and clinical evidence  ||FREE PAPER||

    Directory of Open Access Journals (Sweden)

    Marco Romanelli

    2008-06-01

    Full Text Available Marco Romanelli1, Valentina Dini1, Peter Vowden2, Magnus S Ågren31Department of Dermatology, University of Pisa, Pisa, Italy; 2Vascular Unit, Bradford Royal Infirmary, Bradford, United Kingdom; 3Department of Surgery K, Bispebjerg Hospitals, Copenhagen University Hospital, Copenhagen, DenmarkAbstract: Amelogenins are extracellular matrix proteins that, under physiological conditions, self-assemble into globular aggregates up to micron-sizes. Studies with periodontal fibroblasts indicate that attachment to these structures increases the endogenous secretion of multiple growth factors and cell proliferation. Pre-clinical and clinical studies indicate that cutaneous wounds benefit from treatment with amelogenins. A randomized controlled trial (RCT involving patients with hard-to-heal venous leg ulcers (VLUs (ie, ulcers with a surface area ≥10 cm2 and duration of ≥6 months showed that the application of amelogenin (Xelma®, Molnlycke Health Care, Gothenburg, Sweden as an adjunct treatment to compression results in significant reduction in ulcer size, improvement in the state of ulcers, reduced pain, and a larger proportion of ulcers with low levels of exudate, compared with treatment with compression alone. Amelogenin therapy was also shown to be safe to use in that there were no significant differences in adverse events noted between patients treated with amelogenin plus compression and those treated with compression alone. Case study evaluations indicate that the benefits of amelogenin therapy demonstrated in the RCT are being repeated in “real life” situations and that amelogenin therapy may also have a role to play in the treatment of other wound types such as diabetic foot ulcers.Keywords: extracellular matrix, amelogenin, venous leg ulcers, diabetic foot ulcers, pyoderma gangrenosum

  4. Dental Enamel Development: Proteinases and Their Enamel Matrix Substrates

    Science.gov (United States)

    Bartlett, John D.

    2013-01-01

    This review focuses on recent discoveries and delves in detail about what is known about each of the proteins (amelogenin, ameloblastin, and enamelin) and proteinases (matrix metalloproteinase-20 and kallikrein-related peptidase-4) that are secreted into the enamel matrix. After an overview of enamel development, this review focuses on these enamel proteins by describing their nomenclature, tissue expression, functions, proteinase activation, and proteinase substrate specificity. These proteins and their respective null mice and human mutations are also evaluated to shed light on the mechanisms that cause nonsyndromic enamel malformations termed amelogenesis imperfecta. Pertinent controversies are addressed. For example, do any of these proteins have a critical function in addition to their role in enamel development? Does amelogenin initiate crystallite growth, does it inhibit crystallite growth in width and thickness, or does it do neither? Detailed examination of the null mouse literature provides unmistakable clues and/or answers to these questions, and this data is thoroughly analyzed. Striking conclusions from this analysis reveal that widely held paradigms of enamel formation are inadequate. The final section of this review weaves the recent data into a plausible new mechanism by which these enamel matrix proteins support and promote enamel development. PMID:24159389

  5. Standard and Null Weak Values

    OpenAIRE

    Zilberberg, Oded; Romito, Alessandro; Gefen, Yuval

    2013-01-01

    Weak value (WV) is a quantum mechanical measurement protocol, proposed by Aharonov, Albert, and Vaidman. It consists of a weak measurement, which is weighed in, conditional on the outcome of a later, strong measurement. Here we define another two-step measurement protocol, null weak value (NVW), and point out its advantages as compared to WV. We present two alternative derivations of NWVs and compare them to the corresponding derivations of WVs.

  6. Simple and label-free electrochemical impedance Amelogenin gene hybridization biosensing based on reduced graphene oxide.

    Science.gov (United States)

    Benvidi, Ali; Rajabzadeh, Nooshin; Mazloum-Ardakani, Mohammad; Heidari, Mohammad Mehdi; Mulchandani, Ashok

    2014-08-15

    The increasing desire for sensitive, easy, low-cost, and label free methods for the detection of DNA sequences has become a vital matter in biomedical research. For the first time a novel label-free biosensor for sensitive detection of Amelogenin gene (AMEL) using reduced graphene oxide modified glassy carbon electrode (GCE/RGO) has been developed. In this work, detection of DNA hybridization of the target and probe DNA was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The optimum conditions were found for the immobilization of probe on RGO surface and its hybridization with the target DNA. CV and EIS carried out in an aqueous solution containing [Fe(CN)6](3-/4-) redox pair have been used for the biosensor characterization. The biosensor has a wide linear range from 1.0×10(-20) to 1.0×10(-14)M with the lower detection limit of 3.2×10(-21)M. Moreover, the present electrochemical detection offers some unique advantages such as ultrahigh sensitivity, simplicity, and feasibility for apparatus miniaturization in analytical tests. The excellent performance of the biosensor is attributed to large surface-to-volume ratio and high conductivity of RGO, which enhances the probe absorption and promotes direct electron transfer between probe and the electrode surface. This electrochemical DNA sensor could be used for the detection of specific ssDNA sequence in real biological samples. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. [Experimental study on human periodontal ligament cells transfected with human amelogenin gene].

    Science.gov (United States)

    Yu, Guang; Shu, Rong; Sun, Ying; Cheng, Lan; Song, Zhong-Chen; Zhang, Xiu-Li

    2008-02-01

    To construct the recombinant lentiviral vector of human amelogenin gene, infect human periodontal ligament cells with the recombinant lentivirus, and evaluate the feasibility of applying modified PDLCs as seeds for a further periodontal reconstruction. The mature peptide of hAm cDNA was cloned and linked into the vector plasmid, the recombinant plasmid FUAmW was confirmed by double enzyme digestion and sequence analysis. Recombinant lentivirus was prepared from 293T cells by polytheylenimine (PEI)-mediated transient cotransfection. The hPDLCs and 293T cells were infected with the generated lentivirus. The infection efficiency was analysed by detection of green fluorescence protein (GFP) with fluorescent microscope and flow cytometer 72 hours later. The expression of hAm gene was detected by reverse transcription polymerase chain reaction (RT-PCR). The sequence of inserted fragment in recombinant plasmid was identical to the hAm sequence reported in Genebank. Green fluorescence was visible under fluorescent microscope, FCM assay showed that positive percentage was 69.46% and 33.99% in 293T and hPDLCs, respectively. The targeted gene was obtained in the experimental groups by RT-PCR. The recombinan lentiviral vector of hAm gene is constructed successfully and it could be transfected into cultured hPDLCs. hAm gene and seed cells may be used for further study in the fields periodontal tissue engineering. Supported by National Natural Science Foundation of China (Grant No. 30672315).

  8. Multicolor-based discrimination of 21 short tandem repeats and amelogenin using four fluorescent universal primers.

    Science.gov (United States)

    Asari, Masaru; Okuda, Katsuhiro; Hoshina, Chisato; Omura, Tomohiro; Tasaki, Yoshikazu; Shiono, Hiroshi; Matsubara, Kazuo; Shimizu, Keiko

    2016-02-01

    The aim of this study was to develop a cost-effective genotyping method using high-quality DNA for human identification. A total of 21 short tandem repeats (STRs) and amelogenin were selected, and fluorescent fragments at 22 loci were simultaneously amplified in a single-tube reaction using locus-specific primers with 24-base universal tails and four fluorescent universal primers. Several nucleotide substitutions in universal tails and fluorescent universal primers enabled the detection of specific fluorescent fragments from the 22 loci. Multiplex polymerase chain reaction (PCR) produced intense FAM-, VIC-, NED-, and PET-labeled fragments ranging from 90 to 400 bp, and these fragments were discriminated using standard capillary electrophoretic analysis. The selected 22 loci were also analyzed using two commercial kits (the AmpFLSTR Identifiler Kit and the PowerPlex ESX 17 System), and results for two loci (D19S433 and D16S539) were discordant between these kits due to mutations at the primer binding sites. All genotypes from the 100 samples were determined using 2.5 ng of DNA by our method, and the expected alleles were completely recovered. Multiplex 22-locus genotyping using four fluorescent universal primers effectively reduces the costs to less than 20% of genotyping using commercial kits, and our method would be useful to detect silent alleles from commercial kit analysis. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Dental Amalgam

    Science.gov (United States)

    ... Products and Medical Procedures Dental Devices Dental Amalgam Dental Amalgam Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Dental amalgam is a dental filling material which is ...

  10. Amelogenin, an extracellular matrix protein, in the treatment of venous leg ulcers and other hard-to-heal wounds: experimental and clinical evidence

    DEFF Research Database (Denmark)

    Romanelli, M.; Dini, V.; Vowden, P.

    2008-01-01

    Amelogenins are extracellular matrix proteins that, under physiological conditions, self-assemble into globular aggregates up to micron-sizes. Studies with periodontal fibroblasts indicate that attachment to these structures increases the endogenous secretion of multiple growth factors and cell...... that the application of amelogenin (Xelma, Molnlycke Health Care, Gothenburg, Sweden) as an adjunct treatment to compression results in significant reduction in ulcer size, improvement in the state of ulcers, reduced pain, and a larger proportion of ulcers with low levels of exudate, compared with treatment...... therapy demonstrated in the RCT are being repeated in "real life" situations and that amelogenin therapy may also have a role to play in the treatment of other wound types such as diabetic foot ulcers Udgivelsesdato: 2008...

  11. A new multiplex assay of 17 autosomal STRs and Amelogenin for forensic application.

    Directory of Open Access Journals (Sweden)

    Suhua Zhang

    Full Text Available This paper describes a newly devised autosomal short tandem repeat (STR multiplex polymerase chain reaction (PCR systems for 17 autosomal loci (D1S1656, D2S441, D3S1358, D3S3045, D6S477, D7S3048, D8S1132, D10S1435, D10S1248, D11S2368, D13S325, D14S608, D15S659, D17S1290, D18S535, D19S253 and D22-GATA198B05 and Amelogenin. Primers for the loci were designed and optimized so that all of the amplicons were distributed from 50 base pairs (bp to less than 500 bp within a five-dye chemistry design with the fifth dye reserved for the sizing standard. Strategies were developed to overcome challenges that encountered in creating the final assay. The limits of the multiplex were tested, resulting in the successful amplification of genomic DNA range from 0.25-4 ng with 30 PCR cycles. A total of 681 individuals from the Chinese Han population were studied and forensic genetic data were present. No significant deviations from Hardy-Weinberg equilibrium were observed. A total of 180 alleles were detected for the 17 autosomal STRs. The cumulative mean exclusion chance in duos (CMECD was 0.999967, and cumulative mean exclusion chance in trios (CMECT was 0.99999995. We conclude that the present 17plex autosomal STRs assay provides an additional powerful tool for forensic applications.

  12. The Importance of Proving the Null

    Science.gov (United States)

    Gallistel, C. R.

    2009-01-01

    Null hypotheses are simple, precise, and theoretically important. Conventional statistical analysis cannot support them; Bayesian analysis can. The challenge in a Bayesian analysis is to formulate a suitably vague alternative, because the vaguer the alternative is (the more it spreads out the unit mass of prior probability), the more the null is…

  13. Conformal symmetry inheritance in null fluid spacetimes

    International Nuclear Information System (INIS)

    Tupper, B O J; Keane, A J; Hall, G S; Coley, A A; Carot, J

    2003-01-01

    We define inheriting conformal Killing vectors for null fluid spacetimes and find the maximum dimension of the associated inheriting Lie algebra. We show that for non-conformally flat null fluid spacetimes, the maximum dimension of the inheriting algebra is seven and for conformally flat null fluid spacetimes the maximum dimension is eight. In addition, it is shown that there are two distinct classes of non-conformally flat generalized plane wave spacetimes which possess the maximum dimension, and one class in the conformally flat case

  14. Null solution of the Yang-Mills equations

    International Nuclear Information System (INIS)

    Tafel, J.

    1986-05-01

    We investigate the correspondence between null solutions of the Yang-Mills equations and shearfree geodesic null congruences. We give an example of a non-Abelian null solution with twisting rays. (orig.)

  15. Null-strut calculus. II. Dynamics

    International Nuclear Information System (INIS)

    Kheyfets, A.; LaFave, N.J.; Miller, W.A.

    1990-01-01

    In this paper, we continue from the preceding paper to develop a fully functional Regge calculus geometrodynamic algorithm from the null-strut-calculus construction. The developments discussed include (a) the identification of the Regge calculus analogue of the constraint and evolution equations on the null-strut lattice, (b) a description of the Minkowski solid geometry for the simplicial blocks of the null-strut lattice, (c) a description of the evolution algorithm for the geometrodynamic scheme and an analysis of its consistency, and (d) a presentation of the dynamical degrees of freedom for a simplicial hypersurface and the description of an initial-value prescription. To demonstrate qualitatively this new approach to geometrodynamics, we present the most simple application of null-strut calculus that we know of---the Friedmann cosmology using the three-boundary of a 600-cell simplicial polytope to model the simplicial hypersurface

  16. Null structure groups in eleven dimensions

    International Nuclear Information System (INIS)

    Cariglia, Marco; Mac Conamhna, Oisin A. P.

    2006-01-01

    We classify all the structure groups which arise as subgroups of the isotropy group (Spin(7)xR 8 )xR, of a single null Killing spinor in 11 dimensions. We construct the spaces of spinors fixed by these groups. We determine the conditions under which structure subgroups of the maximal null structure group (Spin(7)xR 8 )xR may also be embedded in SU(5), and hence the conditions under which a supersymmetric spacetime admits only null, or both timelike and null, Killing spinors. We discuss how this purely algebraic material will facilitate the direct analysis of the Killing spinor equation of 11 dimensional supergravity, and the classification of supersymmetric spacetimes therein

  17. On smoothness-asymmetric null infinities

    International Nuclear Information System (INIS)

    Valiente Kroon, Juan Antonio

    2006-01-01

    We discuss the existence of asymptotically Euclidean initial data sets for the vacuum Einstein field equations which would give rise (modulo an existence result for the evolution equations near spatial infinity) to developments with a past and a future null infinity of different smoothness. For simplicity, the analysis is restricted to the class of conformally flat, axially symmetric initial data sets. It is shown how the free parameters in the second fundamental form of the data can be used to satisfy certain obstructions to the smoothness of null infinity. The resulting initial data sets could be interpreted as those of some sort of (nonlinearly) distorted Schwarzschild black hole. Their developments would be that they admit a peeling future null infinity, but at the same time have a polyhomogeneous (non-peeling) past null infinity

  18. High-contrast Nulling Interferometry Techniques Project

    Data.gov (United States)

    National Aeronautics and Space Administration — "We are developing rotating-baseline nulling-interferometry techniques and algorithms on the single-aperture Hale and Keck telescopes at near-infrared wavelengths,...

  19. Null-plane quantization of fermions

    International Nuclear Information System (INIS)

    Mustaki, D.

    1990-01-01

    Massive Dirac fermions are canonically quantized on the null plane using the Dirac-Bergmann algorithm. The procedure is carried out in the framework of quantum electrodynamics as an illustration of a rigorous treatment of interacting fermion fields

  20. Globoside accelerates the differentiation of dental epithelial cells into ameloblasts

    Institute of Scientific and Technical Information of China (English)

    Takashi Nakamura; Yuta Chiba; Masahiro Naruse; Kan Saito; Hidemitsu Harada; Satoshi Fukumoto

    2016-01-01

    Tooth crown morphogenesis is tightly regulated by the proliferation and differentiation of dental epithelial cells. Globoside (Gb4), a globo-series glycosphingolipid, is highly expressed during embryogenesis as well as organogenesis, including tooth development. We previously reported that Gb4 is dominantly expressed in the neutral lipid fraction of dental epithelial cells. However, because its functional role in tooth development remains unknown, we investigated the involvement of Gb4 in dental epithelial cell differentiation. The expression of Gb4 was detected in ameloblasts of postnatal mouse molars and incisors. A cell culture analysis using HAT-7 cells, a rat-derived dental epithelial cell line, revealed that Gb4 did not promote dental epithelial cell proliferation. Interestingly, exogenous administration of Gb4 enhanced the gene expression of enamel extracellular matrix proteins such as ameloblastin, amelogenin, and enamelin in dental epithelial cells as well as in developing tooth germs. Gb4 also induced the expression of TrkB, one of the key receptors required for ameloblast induction in dental epithelial cells. In contrast, Gb4 downregulated the expression of p75, a receptor for neurotrophins (including neurotrophin-4) and a marker of undifferentiated dental epithelial cells. In addition, we found that exogenous administration of Gb4 to dental epithelial cells stimulated the extracellular signal-regulated kinase and p38 mitogen-activated protein kinase signalling pathways. Furthermore, Gb4 induced the expression of epiprofin and Runx2, the positive regulators for ameloblastin gene transcription. Thus, our results suggest that Gb4 contributes to promoting the differentiation of dental epithelial cells into ameloblasts.

  1. IDENTIFIKASI DAGING BABI MENGGUNAKAN METODE PCR-RFLP GEN Cytochrome b DAN PCR PRIMER SPESIFIK GEN AMELOGENIN (Pork Identification Using PCR-RFLP of Cytochrome b Gene and Species Specific PCR of Amelogenin Gene

    Directory of Open Access Journals (Sweden)

    Yuny Erwanto

    2013-03-01

    Full Text Available A polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP and species specific PCR methods had been applied for identifying pork in mixture of meat. Pork sample in various levels (1, 3, 5 and 10% was prepared in mixture with beef, chicken and mutton. The primary CYTb1 and CYTb2 were designed in the mitochondrial cytochrome b b (cytochrome b gene and PCR successfully amplified fragments of 359 bp. To distinguish pig species existence, the amplified PCR products of mitochondrial DNA were cut by BseDI restriction enzyme. The result showed that pig mitochondrial DNA was cut into 131 and 228 bp fragments. A polymerase chain reaction (PCR method based on the nucleotide sequence variation in the amelogenin gene has been chosen for the specific identification of pork DNAs in mixture meat. The primers designed generated specific fragments of 353 and 312 bp length for pork. The specificity of the primary designed was tested on 4 animal species including pig, cattle, chicken and goat species. Analysis of experimental mixture meat demonstrated that 1% of raw pork tissues could be detected using PCR-RFLP with BseDI restriction enzyme but detection using species-specific PCR showed the cross reactivity to beef, chicken and mutton. The cytochrome b PCR-RFLP species identification assay yielded excellent results for identification of pig species. PCR-RFLP is a potentially reliable technique for detection of the existence of pork in animal food product for Halal authentication. Keywords: Pork identification, cytochrome b, amelogenin, polymerase chain reaction   ABSTRAK   Penelitian ini dilakukan untuk mengaplikasikan metode deteksi daging babi dalam campuan daging dengan sapi, kambing dan ayam melalui PCR-RFLP dan PCR dengan primer spesifik untuk babi. Level kontaminasi daging babi dibuat sebesar 1, 3, 5 dan 10% dari total daging dalam campuran. Metode PCR-RFLP menggunakan sepasang primer yaitu gen cytochrome b dari mitokondria yang

  2. On the Penrose inequality along null hypersurfaces

    International Nuclear Information System (INIS)

    Mars, Marc; Soria, Alberto

    2016-01-01

    The null Penrose inequality, i.e. the Penrose inequality in terms of the Bondi energy, is studied by introducing a functional on surfaces and studying its properties along a null hypersurface Ω extending to past null infinity. We prove a general Penrose-type inequality which involves the limit at infinity of the Hawking energy along a specific class of geodesic foliations called Geodesic Asymptotically Bondi (GAB), which are shown to always exist. Whenever this foliation approaches large spheres, this inequality becomes the null Penrose inequality and we recover the results of Ludvigsen–Vickers (1983 J. Phys. A: Math. Gen. 16 3349–53) and Bergqvist (1997 Class. Quantum Grav. 14 2577–83). By exploiting further properties of the functional along general geodesic foliations, we introduce an approach to the null Penrose inequality called the Renormalized Area Method and find a set of two conditions which imply the validity of the null Penrose inequality. One of the conditions involves a limit at infinity and the other a restriction on the spacetime curvature along the flow. We investigate their range of applicability in two particular but interesting cases, namely the shear-free and vacuum case, where the null Penrose inequality is known to hold from the results by Sauter (2008 PhD Thesis Zürich ETH ), and the case of null shells propagating in the Minkowski spacetime. Finally, a general inequality bounding the area of the quasi-local black hole in terms of an asymptotic quantity intrinsic of Ω is derived. (paper)

  3. Oriented and Ordered Biomimetic Remineralization of the Surface of Demineralized Dental Enamel Using HAP@ACP Nanoparticles Guided by Glycine

    Science.gov (United States)

    Wang, Haorong; Xiao, Zuohui; Yang, Jie; Lu, Danyang; Kishen, Anil; Li, Yanqiu; Chen, Zhen; Que, Kehua; Zhang, Qian; Deng, Xuliang; Yang, Xiaoping; Cai, Qing; Chen, Ning; Cong, Changhong; Guan, Binbin; Li, Ting; Zhang, Xu

    2017-01-01

    Achieving oriented and ordered remineralization on the surface of demineralized dental enamel, thereby restoring the satisfactory mechanical properties approaching those of sound enamel, is still a challenge for dentists. To mimic the natural biomineralization approach for enamel remineralization, the biological process of enamel development proteins, such as amelogenin, was simulated in this study. In this work, carboxymethyl chitosan (CMC) conjugated with alendronate (ALN) was applied to stabilize amorphous calcium phosphate (ACP) to form CMC/ACP nanoparticles. Sodium hypochlorite (NaClO) functioned as the protease which decompose amelogenin in vivo to degrade the CMC-ALN matrix and generate HAP@ACP core-shell nanoparticles. Finally, when guided by 10 mM glycine (Gly), HAP@ACP nanoparticles can arrange orderly and subsequently transform from an amorphous phase to well-ordered rod-like apatite crystals to achieve oriented and ordered biomimetic remineralization on acid-etched enamel surfaces. This biomimetic remineralization process is achieved through the oriented attachment (OA) of nanoparticles based on non-classical crystallization theory. These results indicate that finding and developing analogues of natural proteins such as amelogenin involved in the biomineralization by natural macromolecular polymers and imitating the process of biomineralization would be an effective strategy for enamel remineralization. Furthermore, this method represents a promising method for the management of early caries in minimal invasive dentistry (MID).

  4. Targeted overexpression of amelotin disrupts the microstructure of dental enamel.

    Science.gov (United States)

    Lacruz, Rodrigo S; Nakayama, Yohei; Holcroft, James; Nguyen, Van; Somogyi-Ganss, Eszter; Snead, Malcolm L; White, Shane N; Paine, Michael L; Ganss, Bernhard

    2012-01-01

    We have previously identified amelotin (AMTN) as a novel protein expressed predominantly during the late stages of dental enamel formation, but its role during amelogenesis remains to be determined. In this study we generated transgenic mice that produce AMTN under the amelogenin (Amel) gene promoter to study the effect of AMTN overexpression on enamel formation in vivo. The specific overexpression of AMTN in secretory stage ameloblasts was confirmed by Western blot and immunohistochemistry. The gross histological appearance of ameloblasts or supporting cellular structures as well as the expression of the enamel proteins amelogenin (AMEL) and ameloblastin (AMBN) was not altered by AMTN overexpression, suggesting that protein production, processing and secretion occurred normally in transgenic mice. The expression of Odontogenic, Ameloblast-Associated (ODAM) was slightly increased in secretory stage ameloblasts of transgenic animals. The enamel in AMTN-overexpressing mice was much thinner and displayed a highly irregular surface structure compared to wild type littermates. Teeth of transgenic animals underwent rapid attrition due to the brittleness of the enamel layer. The microstructure of enamel, normally a highly ordered arrangement of hydroxyapatite crystals, was completely disorganized. Tomes' process, the hallmark of secretory stage ameloblasts, did not form in transgenic mice. Collectively our data demonstrate that the overexpression of amelotin has a profound effect on enamel structure by disrupting the formation of Tomes' process and the orderly growth of enamel prisms.

  5. Targeted overexpression of amelotin disrupts the microstructure of dental enamel.

    Directory of Open Access Journals (Sweden)

    Rodrigo S Lacruz

    Full Text Available We have previously identified amelotin (AMTN as a novel protein expressed predominantly during the late stages of dental enamel formation, but its role during amelogenesis remains to be determined. In this study we generated transgenic mice that produce AMTN under the amelogenin (Amel gene promoter to study the effect of AMTN overexpression on enamel formation in vivo. The specific overexpression of AMTN in secretory stage ameloblasts was confirmed by Western blot and immunohistochemistry. The gross histological appearance of ameloblasts or supporting cellular structures as well as the expression of the enamel proteins amelogenin (AMEL and ameloblastin (AMBN was not altered by AMTN overexpression, suggesting that protein production, processing and secretion occurred normally in transgenic mice. The expression of Odontogenic, Ameloblast-Associated (ODAM was slightly increased in secretory stage ameloblasts of transgenic animals. The enamel in AMTN-overexpressing mice was much thinner and displayed a highly irregular surface structure compared to wild type littermates. Teeth of transgenic animals underwent rapid attrition due to the brittleness of the enamel layer. The microstructure of enamel, normally a highly ordered arrangement of hydroxyapatite crystals, was completely disorganized. Tomes' process, the hallmark of secretory stage ameloblasts, did not form in transgenic mice. Collectively our data demonstrate that the overexpression of amelotin has a profound effect on enamel structure by disrupting the formation of Tomes' process and the orderly growth of enamel prisms.

  6. Null Subjects in European and Brazilian Portuguese

    Directory of Open Access Journals (Sweden)

    Pilar Barbosa

    2005-12-01

    Full Text Available The goals of this paper are twofold: a to provide a structural account of the effects of the informal ‘Avoid Pronoun Principle’, proposed in Chomsky (1981: 65 for the Null Subject Languages (NSLs, and b to compare, in European and Brazilian Portuguese (EP and BP, the distribution of the third person pronouns in its full and null forms, to check whether in written corpora BP incorporates signs of the ongoing loss of the null subject, largely attested in its contemporary spoken language. The strong theoretical claim is that in the Romance non-NSLs the pre-verbal subject is sitting in Spec of IP, while in the Romance NSLs it is Clitic Left-Dislocated (or is extracted by A-bar movement if it belongs to a restricted set of non-referential quantified expressions. The paper provides quantitative evidence that BP is losing the properties associated with the Null Subject Parameter. In its qualitative analysis, it shows that the contrasts between EP and BP are easily accounted for if the two derivations are assumed and if the null subjects in the two varieties are considered to be of a different nature: a pronoun in EP and a pronominal anaphor in BP.

  7. Supersymmetric null-like holographic cosmologies

    International Nuclear Information System (INIS)

    Lin Fengli; Wen Wenyu

    2006-01-01

    We construct a new class of 1/4-BPS time dependent domain-wall solutions with null-like metric and dilaton in type II supergravities, which admit a null-like big bang singularity. Based on the domain-wall/QFT correspondence, these solutions are dual to 1/4-supersymmetric quantum field theories living on a boundary cosmological background with time dependent coupling constant and UV cutoff. In particular we evaluate the holographic c function for the 2-dimensional dual field theory living on the corresponding null-like cosmology. We find that this c function runs in accordance with the c-theorem as the boundary universe evolves, this means that the number of degrees of freedom is divergent at big bang and suggests the possible resolution of big bang singularity

  8. Null-strut calculus. I. Kinematics

    International Nuclear Information System (INIS)

    Kheyfets, A.; LaFave, N.J.; Miller, W.A.

    1990-01-01

    This paper describes the kinematics of null-strut calculus---a 3+1 Regge calculus approach to general relativity. We show how to model the geometry of spacetime with simplicial spacelike three-geometries (TET's) linked to ''earlier'' and ''later'' momentumlike lattice surfaces (TET * ) entirely by light rays or ''null struts.'' These three-layered lattice spacetime geometries are defined and analyzed using combinatorial formulas for the structure of polytopes. The following paper in this series describes how these three-layered spacetime lattices are used to model spacetimes in full conformity with Einstein's theory of gravity

  9. X- and Y-chromosome specific variants of the amelogenin gene allow sex determination in sheep (Ovis aries and European red deer (Cervus elaphus

    Directory of Open Access Journals (Sweden)

    Brenig B

    2005-03-01

    Full Text Available Abstract Background Simple and precise methods for sex determination in animals are a pre-requisite for a number of applications in animal production and forensics. However, some of the existing methods depend only on the detection of Y-chromosome specific sequences. Therefore, the abscence of a signal does not necessarily mean that the sample is of female origin, because experimental errors can also lead to negative results. Thus, the detection of Y- and X-chromosome specific sequences is advantageous. Results A novel method for sex identification in mammals (sheep, Ovis aries and European red deer, Cervus elaphus is described, using a polymerase chain reaction (PCR and sequencing of a part of the amelogenin gene. A partial sequence of the amelogenin gene of sheep and red deer was obtained, which exists on both X and Y chromosomes with a deletion region on the Y chromosome. With a specific pair of primers a DNA fragment of different length between the male and female mammal was amplified. Conclusion PCR amplification using the amelogenin gene primers is useful in sex identification of samples from sheep and red deer and can be applied to DNA analysis of micro samples with small amounts of DNA such as hair roots as well as bones or embryo biopsies.

  10. Fine art of computing nulling interferometer maps

    Science.gov (United States)

    Hénault, F.

    2008-07-01

    Spaceborne nulling interferometers are often characterized by means of their nulling ratio, which is defined as the deepest possible extinction of one target star supposed to harbor an extra-solar system. Herein is shown that another parameter, which is the transmitting efficiency of nearby bright fringes, is also of prime importance. More generally, "nulling maps" formed by the whole destructive and constructive fringe pattern projected on-sky, are found to be very sensitive on the design of some subsystems constituting the interferometer. In particular, we consider Spatial Filtering (SF) and Achromatic Phase Shifter (APS) devices, both required achieving planet detection and characterization. Consequences of the SF choice (pinhole or single-mode optical fiber) and APS properties (with or without induced pupil-flip) are discussed, for both monochromatic and polychromatic cases. Examples of numerical simulations are provided for single Bracewell interferometer, Angel cross and X-array configurations, demonstrating noticeable differences in the aspect of resulting nulling maps. It is concluded that both FS and APS designs exhibit variable capacities for serendipitous planet discovery.

  11. Matter sources for a null big bang

    International Nuclear Information System (INIS)

    Bronnikov, K A; Zaslavskii, O B

    2008-01-01

    We consider the properties of stress-energy tensors compatible with a null big bang, i.e., cosmological evolution starting from a Killing horizon rather than a singularity. For Kantowski-Sachs cosmologies, it is shown that if matter satisfies the null energy condition, then (i) regular cosmological evolution can only start from a Killing horizon, (ii) matter is absent at the horizon and (iii) matter can only appear in the cosmological region due to interaction with vacuum. The latter is understood phenomenologically as a fluid whose stress tensor is insensitive to boosts in a particular direction. We also argue that matter is absent in a static region beyond the horizon. All this generalizes the observations recently obtained for a mixture of dust and a vacuum fluid. If, however, we admit the existence of phantom matter, its certain special kinds (with the parameter w ≤ -3) are consistent with a null big bang without interaction with vacuum (or without vacuum fluid at all). Then in the static region there is matter with w ≥ -1/3. Alternatively, the evolution can begin from a horizon in an infinitely remote past, leading to a scenario combining the features of a null big bang and an emergent universe

  12. Instabilities and the null energy condition

    International Nuclear Information System (INIS)

    Buniy, Roman V.; Hsu, Stephen D.H.

    2006-01-01

    We show that violation of the null energy condition implies instability in a broad class of models, including gauge theories with scalar and fermionic matter as well as any perfect fluid. When applied to the dark energy, our results imply that w=p/ρ is unlikely to be less than -1. than -1

  13. Covariant quantum mechanics on a null plane

    International Nuclear Information System (INIS)

    Leutwyler, H.; Stern, J.

    1977-03-01

    Lorentz invariance implies that the null plane wave functions factorize into a kinematical part describing the motion of the system as a whole and an inner wave function that involves the specific dynamical properties of the system - in complete correspondence with the non-relativistic situation. Covariance is equivalent to an angular condition which admits non-trivial solutions

  14. Null vectors in superconformal quantum field theory

    International Nuclear Information System (INIS)

    Huang Chaoshang

    1993-01-01

    The superspace formulation of the N=1 superconformal field theory and superconformal Ward identities are used to give a precise definition of fusion. Using the fusion procedure, superconformally covariant differential equations are derived and consequently a complete and straightforward algorithm for finding null vectors in Verma modules of the Neveu-Schwarz algebra is given. (orig.)

  15. Gravitational collapse of a cylindrical null shell in vacuum

    Directory of Open Access Journals (Sweden)

    S. Khakshournia

    2008-03-01

    Full Text Available   Barrabès-Israel null shell formalism is used to study the gravitational collapse of a thin cylindrical null shell in vacuum. In general the lightlike matter shell whose history coincides with a null hypersurface is characterized by a surface energy density. In addition, a gravitational impulsive wave is present on this null hypersurface whose generators admit both the shear and expansion. In the case of imposing the cylindrical flatness the surface energy-momentum tensor of the matter shell on the null hypersurface vanishes and the null hyper- surface is just the history of the gravitational wave .

  16. Functional role of EMMPRIN in the formation and mineralisation of dental matrix in mouse molars.

    Science.gov (United States)

    Xie, Ming; Xing, Guofang; Hou, Liwen; Bao, Jing; Chen, Yuqing; Jiao, Ting; Zhang, Fuqiang

    2015-02-01

    Our previous research has shown that the extracellular matrix metalloproteinase inducer (EMMPRIN) is expressed during and may function in the early development of tooth germs. In the present study, we observed the specific expression of EMMPRIN in ameloblasts and odontoblasts during the middle and late stages of tooth germ development using immunohistochemistry. Furthermore, to extend our understanding of the function of EMMPRIN in odontogenesis, we used an anti-EMMPRIN function-blocking antibody to remove EMMPRIN activity in tooth germ culture in vitro. Both the formation and mineralisation of dental hard tissues were suppressed in the tooth germ culture after the abrogation of EMMPRIN. Meanwhile, significant reductions in VEGF, MMP-9, ALPL, ameloblastin, amelogenin and enamelin expression were observed in antibody-treated tooth germ explants compared to control and normal serum-treated explants. The current results illustrate that EMMPRIN may play a critical role in the processing and maturation of the dental matrix.

  17. Nulling tomography with weak gravitational lensing

    International Nuclear Information System (INIS)

    Huterer, Dragan; White, Martin

    2005-01-01

    We explore several strategies of eliminating (or nulling) the small-scale information in weak lensing convergence power spectrum measurements in order to protect against undesirable effects, for example, the effects of baryonic cooling and pressure forces on the distribution of large-scale structures. We selectively throw out the small-scale information in the convergence power spectrum that is most sensitive to the unwanted bias, while trying to retain most of the sensitivity to cosmological parameters. The strategies are effective in the difficult but realistic situations when we are able to guess the form of the contaminating effect only approximately. However, we also find that the simplest scheme of simply not using information from the largest multipoles works about as well as the proposed techniques in most, although not all, realistic cases. We advocate further exploration of nulling techniques and believe that they will find important applications in the weak lensing data mining

  18. Collapse and bounce of null fluids

    OpenAIRE

    Creelman, Bradley; Booth, Ivan

    2016-01-01

    Exact solutions describing the spherical collapse of null fluids can contain regions which violate the energy conditions. Physically the violations occur when the infalling matter continues to move inwards even when non-gravitational repulsive forces become stronger than gravity. In 1991 Ori proposed a resolution for these violations: spacetime surgery should be used to replace the energy condition violating region with an outgoing solution. The matter bounces. We revisit and implement this p...

  19. Null balance type electrostatic generating voltmeters

    International Nuclear Information System (INIS)

    Mahant, A.K.; Sidhu, N.P.S.; Gupta, U.C.

    1977-01-01

    A description is given of a null balance type generating voltmeter for measuring high D.C. voltage upto about 400 kV. The paper discusses the principle of operation, design, calibration and performance of the instrument. Main advantages of the device are: (1) it does not load the high voltage source, (2) no physical connection is required with the H.T. terminal and (3) calibration is independent of the rotor's frequency and amplifier's gain. (author)

  20. Null controllability of the viscous Camassa–Holm equation with ...

    Indian Academy of Sciences (India)

    In this paper, we study the null controllability of the viscous Camassa–. Holm equation on the one-dimensional torus. By using a moving distributed control, we obtain that the system is null controllable for a given data with certain regularity. Keywords. Viscous Camassa–Holm equation; null controllability; moving control;.

  1. About Dental Amalgam Fillings

    Science.gov (United States)

    ... and Medical Procedures Dental Devices Dental Amalgam About Dental Amalgam Fillings Share Tweet Linkedin Pin it More ... should I have my fillings removed? What is dental amalgam? Dental amalgam is a dental filling material ...

  2. Dental cavities

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/001055.htm Dental cavities To use the sharing features on this page, please enable JavaScript. Dental cavities are holes (or structural damage) in the ...

  3. Dental sealants

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000779.htm Dental sealants To use the sharing features on this ... case a sealant needs to be replaced. How Dental Sealants are Applied Your dentist applies sealants on ...

  4. Dental negligence.

    Science.gov (United States)

    Tay, C S

    2000-02-01

    Medical and dental errors and negligence are again in the spotlight in recent news report. Dead because of doctor's bad handwriting Prescribing drug overdoses Germ-infested soap pumps--infections in hospitals This articles explains dental negligence including dental duty of care and the standard of care expected of dentists in relation to the Bolam principle.

  5. Clausius entropy for arbitrary bifurcate null surfaces

    International Nuclear Information System (INIS)

    Baccetti, Valentina; Visser, Matt

    2014-01-01

    Jacobson’s thermodynamic derivation of the Einstein equations was originally applied only to local Rindler horizons. But at least some parts of that construction can usefully be extended to give meaningful results for arbitrary bifurcate null surfaces. As presaged in Jacobson’s original article, this more general construction sharply brings into focus the questions: is entropy objectively ‘real’? Or is entropy in some sense subjective and observer-dependent? These innocent questions open a Pandora’s box of often inconclusive debate. A consensus opinion, though certainly not universally held, seems to be that Clausius entropy (thermodynamic entropy, defined via a Clausius relation dS=đQ/T) should be objectively real, but that the ontological status of statistical entropy (Shannon or von Neumann entropy) is much more ambiguous, and much more likely to be observer-dependent. This question is particularly pressing when it comes to understanding Bekenstein entropy (black hole entropy). To perhaps further add to the confusion, we shall argue that even the Clausius entropy can often be observer-dependent. In the current article we shall conclusively demonstrate that one can meaningfully assign a notion of Clausius entropy to arbitrary bifurcate null surfaces—effectively defining a ‘virtual Clausius entropy’ for arbitrary ‘virtual (local) causal horizons’. As an application, we see that we can implement a version of the generalized second law (GSL) for this virtual Clausius entropy. This version of GSL can be related to certain (nonstandard) integral variants of the null energy condition. Because the concepts involved are rather subtle, we take some effort in being careful and explicit in developing our framework. In future work we will apply this construction to generalize Jacobson’s derivation of the Einstein equations. (paper)

  6. Generalized frame of reference with null congruence

    International Nuclear Information System (INIS)

    Ferrarese, G.; Antonelli, R.

    2000-01-01

    The paper derives the main properties of a generalized frame of reference with a null congruence (light flux), by means of adapted non-holonomic techniques; then it studies the geometry of the space-time in terms of non-orthogonal projection: longitudinal and transverse covariant derivatives and corresponding commutation formulae, decomposition of the Riemann and gravitational tensors, lie derivatives of the Ricci rotation coefficients, transverse Bianchi identity. Application to the (absolute and relative) light flux: kinematical characteristics and screen, Sachs theorems etc. are also given

  7. Towards enamel biomimetics: Structure, mechanical properties and biomineralization of dental enamel

    Science.gov (United States)

    Fong, Hanson Kwok

    Dental enamel is the most mineralized tissue in the human body. This bioceramic, composed largely of hydroxyapatite (HAp), is also one of the most durable tissues despite a lifetime of masticatory loading and bacterial attack. The biosynthesis of enamel, which occurs in physiological conditions is a complex orchestration of protein assembly and mineral formation. The resulting product is the hardest tissue in the vertebrate body with the longest and most organized arrangement of hydroxyapatite crystals known to biomineralizing systems. Detail understanding of the structure of enamel in relationship to its mechanical function and the biomineralization process will provide a framework for enamel regeneration as well as potential lessons in the design of engineering materials. The objective of this study, therefore, is twofold: (1) establish the structure-function relationship of enamel as well as the dentine-enamel junction (DEJ) and (2) determine the effect of proteins on the enamel biomineralization process. A hierarchy in the enamel structure was established by means of various microscopy techniques (e.g. SEM, TEM, AFM). Mechanical properties (hardness and elastic modulus) associated with the microstructural features were also determined by nanoindentation. Furthermore, the DEJ was found to have a width in the range of micrometers to 10s of micrometers with continuous change in structure and mechanical properties. Indentation tests and contact fatigue tests using a spherical indenter have revealed that the structural features in the enamel and the DEJ played important roles in containing crack propagation emanating from the enamel tissue. To further understand the effect of this protein on the biominerailzation process, we have studied genetically engineered animals that express altered amelogenin which lack the known self-assembly properties. This in vivo study has revealed that, without the proper self-assembly of the amelogenin protein as demonstrated by the

  8. Dall-Null tester for spaceborne applications

    Science.gov (United States)

    Wingler, R. L.

    1984-12-01

    This is a study to design a self correcting primary mirror system for a space telescope. The design is centered around a Dall-Null tester (a Foucault knife-edge tester with compensating lens). An indepth study of the theory of the Foucault test from Foucault's original publications to current work is presented. Also short comings of the diffraction approach are shown. The findings of a simple experiment showed the way to the correct explanation as to the workings of the test. Based on this new explanation, a computer program to find the error in the surface of the mirror from the irradiance pattern provided by the Dall-Null tester was developed. The computer program with a sample run is included in the appendixes A and B. The basic design of an adaptive optic system for a spaceborne application is also presented in the paper. This design has the desired quality of being able to correct the mirror while the telescope is in use. The equations being independent of wavelength allows for the design to be applied to systems working outside of the visible spectrum as well as the systems working in the visible.

  9. Averaged null energy condition from causality

    Science.gov (United States)

    Hartman, Thomas; Kundu, Sandipan; Tajdini, Amirhossein

    2017-07-01

    Unitary, Lorentz-invariant quantum field theories in flat spacetime obey mi-crocausality: commutators vanish at spacelike separation. For interacting theories in more than two dimensions, we show that this implies that the averaged null energy, ∫ duT uu , must be non-negative. This non-local operator appears in the operator product expansion of local operators in the lightcone limit, and therefore contributes to n-point functions. We derive a sum rule that isolates this contribution and is manifestly positive. The argument also applies to certain higher spin operators other than the stress tensor, generating an infinite family of new constraints of the form ∫ duX uuu··· u ≥ 0. These lead to new inequalities for the coupling constants of spinning operators in conformal field theory, which include as special cases (but are generally stronger than) the existing constraints from the lightcone bootstrap, deep inelastic scattering, conformal collider methods, and relative entropy. We also comment on the relation to the recent derivation of the averaged null energy condition from relative entropy, and suggest a more general connection between causality and information-theoretic inequalities in QFT.

  10. Recent developments with the visible nulling coronagraph

    Science.gov (United States)

    Hicks, Brian A.; Lyon, Richard G.; Bolcar, Matthew R.; Clampin, Mark; Petrone, Peter; Helmbrecht, Michael A.; Howard, Joseph M.; Miller, Ian J.

    2016-08-01

    A wide array of general astrophysics studies including detecting and characterizing habitable exoplanets could be enabled by a future large segmented telescope with sensitivity in the UV, optical, and infrared bands. When paired with a starshade or coronagraph, such an observatory could enable direct imaging and detailed spectroscopic observations of nearby Earth-like habitable zone planets. Over the past several years, a laboratory-based Visible Nulling Coronagraph (VNC) has evolved to reach requisite contrasts over a 1 nm bandwidth at narrow source angle separation using a segmented deformable mirror in one arm of a Mach-Zehnder layout. More recent efforts targeted broadband performance following the addition of two sets of half-wave Fresnel rhomb achromatic phase shifters (APS) with the goal of reaching 10-9 contrast, at a separation of 2λ/D, using a 40 nm (6%) bandwidth single mode fiber source. Here we present updates on the VNC broadband nulling effort, including approaches to addressing system contrast limitations.

  11. Singular Null Hypersurfaces in General Relativity

    International Nuclear Information System (INIS)

    Dray, T

    2006-01-01

    Null hypersurfaces are a mathematical consequence of the Lorentzian signature of general relativity; singularities in mathematical models usually indicate where the interesting physics takes place. This book discusses what happens when you combine these ideas. Right from the preface, this is a no-nonsense book. There are two principal approaches to singular shells, one distributional and the other 'cut and paste'; both are treated in detail. A working knowledge of GR is assumed, including familiarity with null tetrads, differential forms, and 3 + 1 decompositions. Despite my own reasonably extensive, closely related knowledge, there was material unfamiliar to me already in chapter 3, although I was reunited with some old friends in later chapters. The exposition is crisp, with a minimum of transition from chapter to chapter. In fact, my main criticism is that there is no clear statement of the organization of the book, nor is there an index. Everything is here, and the story is compelling if you know what to look for, although it is less easy to follow the story if you are not already familiar with it. But this is really a book for experts, and the authors certainly qualify, having played a significant role in developing and extending the results they describe. It is also entirely appropriate that the book is dedicated to Werner Israel, who pioneered the thin-shell approach to (non-null) singular surfaces and later championed the use of similar methods for analysing null shells. After an introductory chapter on impulsive signals, the authors show how the Bianchi identities can be used to classify spacetimes with singular null hypersurfaces. This approach, due to the authors, generalizes the framework originally proposed by Penrose. While astrophysical applications are discussed only briefly, the authors point out that detailed physical characteristics of signals from isolated sources can be determined in this manner. In particular, they describe the behaviour of

  12. On the null origin of the ambitwistor string

    Energy Technology Data Exchange (ETDEWEB)

    Casali, Eduardo [Mathematical Institute, University of Oxford,Woodstock Road, Oxford, OX2 6GG (United Kingdom); Tourkine, Piotr [Department of Applied Mathematics and Theoretical Physics,Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)

    2016-11-07

    In this paper we present the null string origin of the ambitwistor string. Classically, the null string is the tensionless limit of string theory, and so too is the ambitwistor string. Both have as constraint algebra the Galilean Conformal Algebra in two dimensions. But something interesting happens in the quantum theory since there is an ambiguity in quantizing the null string. We show that, given a particular choice of quantization scheme and a particular gauge, the null string coincides with the ambitwistor string both classically and quantum mechanically. We also show that the same holds for the spinning versions of the null string and ambitwistor string. With these results we clarify the relationship between the ambitwistor string, the null string, the usual string and the Hohm-Siegel-Zwiebach theory.

  13. Mechanical Forces Exacerbate Periodontal Defects in Bsp-null Mice

    Science.gov (United States)

    Soenjaya, Y.; Foster, B.L.; Nociti, F.H.; Ao, M.; Holdsworth, D.W.; Hunter, G.K.; Somerman, M.J.

    2015-01-01

    Bone sialoprotein (BSP) is an acidic phosphoprotein with collagen-binding, cell attachment, and hydroxyapatite-nucleating properties. BSP expression in mineralized tissues is upregulated at onset of mineralization. Bsp-null (Bsp-/-) mice exhibit reductions in bone mineral density, bone turnover, osteoclast activation, and impaired bone healing. Furthermore, Bsp-/- mice have marked periodontal tissue breakdown, with a lack of acellular cementum leading to periodontal ligament detachment, extensive alveolar bone and tooth root resorption, and incisor malocclusion. We hypothesized that altered mechanical stress from mastication contributes to periodontal destruction observed in Bsp-/- mice. This hypothesis was tested by comparing Bsp-/- and wild-type mice fed with standard hard pellet diet or soft powder diet. Dentoalveolar tissues were analyzed using histology and micro–computed tomography. By 8 wk of age, Bsp-/- mice exhibited molar and incisor malocclusion regardless of diet. Bsp-/- mice with hard pellet diet exhibited high incidence (30%) of severe incisor malocclusion, 10% lower body weight, 3% reduced femur length, and 30% elevated serum alkaline phosphatase activity compared to wild type. Soft powder diet reduced severe incisor malocclusion incidence to 3% in Bsp-/- mice, supporting the hypothesis that occlusal loading contributed to the malocclusion phenotype. Furthermore, Bsp-/- mice in the soft powder diet group featured normal body weight, long bone length, and serum alkaline phosphatase activity, suggesting that tooth dysfunction and malnutrition contribute to growth and skeletal defects reported in Bsp-/- mice. Bsp-/- incisors also erupt at a slower rate, which likely leads to the observed thickened dentin and enhanced mineralization of dentin and enamel toward the apical end. We propose that the decrease in eruption rate is due to a lack of acellular cementum and associated defective periodontal attachment. These data demonstrate the importance of BSP

  14. Technology Advancement of the Visible Nulling Coronagraph

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Petrone, Peter; Thompson, Patrick; Bolcar, Matt; Madison, Timothy; Woodruff, Robert; Noecker, Charley; Kendrick, Steve

    2010-01-01

    The critical high contrast imaging technology for the Extrasolar Planetary Imaging Coronagraph (EPIC) mission concept is the visible nulling coronagraph (VNC). EPIC would be capable of imaging jovian planets, dust/debris disks, and potentially super-Earths and contribute to answering how bright the debris disks are for candidate stars. The contrast requirement for EPIC is 10(exp 9) contrast at 125 milli-arseconds inner working angle. To advance the VNC technology NASA/Goddard Space Flight Center, in collaboration with Lockheed-Martin, previously developed a vacuum VNC testbed, and achieved narrowband and broadband suppression of the core of the Airy disk. Recently our group was awarded a NASA Technology Development for Exoplanet Missions to achieve two milestones: (i) 10(exp 8) contrast in narrowband light, and, (ii) 10(ecp 9) contrast in broader band light; one milestone per year, and both at 2 Lambda/D inner working angle. These will be achieved with our 2nd generation testbed known as the visible nulling testbed (VNT). It contains a MEMS based hex-packed segmented deformable mirror known as the multiple mirror array (MMA) and coherent fiber bundle, i.e. a spatial filter array (SFA). The MMA is in one interferometric arm and works to set the wavefront differences between the arms to zero. Each of the MMA segments is optically mapped to a single mode fiber of the SFA, and the SFA passively cleans the sub-aperture wavefront error leaving only piston, tip and tilt error to be controlled. The piston degree of freedom on each segment is used to correct the wavefront errors, while the tip/tilt is used to simultaneously correct the amplitude errors. Thus the VNT controls both amplitude and wavefront errors with a single MMA in closed-loop in a vacuum tank at approx.20 Hz. Herein we will discuss our ongoing progress with the VNT.

  15. [Dilemma of null hypothesis in ecological hypothesis's experiment test.

    Science.gov (United States)

    Li, Ji

    2016-06-01

    Experimental test is one of the major test methods of ecological hypothesis, though there are many arguments due to null hypothesis. Quinn and Dunham (1983) analyzed the hypothesis deduction model from Platt (1964) and thus stated that there is no null hypothesis in ecology that can be strictly tested by experiments. Fisher's falsificationism and Neyman-Pearson (N-P)'s non-decisivity inhibit statistical null hypothesis from being strictly tested. Moreover, since the null hypothesis H 0 (α=1, β=0) and alternative hypothesis H 1 '(α'=1, β'=0) in ecological progresses are diffe-rent from classic physics, the ecological null hypothesis can neither be strictly tested experimentally. These dilemmas of null hypothesis could be relieved via the reduction of P value, careful selection of null hypothesis, non-centralization of non-null hypothesis, and two-tailed test. However, the statistical null hypothesis significance testing (NHST) should not to be equivalent to the causality logistical test in ecological hypothesis. Hence, the findings and conclusions about methodological studies and experimental tests based on NHST are not always logically reliable.

  16. Broadband Active Segmented Aperture and Radial Shear Nulling

    Data.gov (United States)

    National Aeronautics and Space Administration — The Visible Nulling Coronagraph (VNC) is a starlight suppression system for enabling exoplanet detectionand atmospheric measurement. Conceptual space telescope...

  17. MAGNETIC NULL POINTS IN KINETIC SIMULATIONS OF SPACE PLASMAS

    International Nuclear Information System (INIS)

    Olshevsky, Vyacheslav; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni; Deca, Jan; Divin, Andrey; Peng, Ivy Bo; Markidis, Stefano

    2016-01-01

    We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic particle-in-cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind, and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly (LMA) and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3–9. We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and LMA simulations are rather stable and do not exhibit any energy dissipation. Energy dissipation is more powerful in the vicinity of spiral nulls enclosed by magnetic flux ropes with strong currents at their axes (their cross sections resemble 2D magnetic islands). These null lines reminiscent of Z-pinches efficiently dissipate magnetic energy due to secondary instabilities such as the two-stream or kinking instability, accompanied by changes in magnetic topology. Current enhancements accompanied by spiral nulls may signal magnetic energy conversion sites in the observational data

  18. Visual and Plastic Arts in Teaching Literacy: Null Curricula?

    Science.gov (United States)

    Wakeland, Robin Gay

    2010-01-01

    Visual and plastic arts in contemporary literacy instruction equal null curricula. Studies show that painting and sculpture facilitate teaching reading and writing (literacy), yet such pedagogy has not been formally adopted into USA curriculum. An example of null curriculum can be found in late 19th - early 20th century education the USA…

  19. Euclidean null controllability of nonlinear infinite delay systems with ...

    African Journals Online (AJOL)

    Sufficient conditions for the Euclidean null controllability of non-linear delay systems with time varying multiple delays in the control and implicit derivative are derived. If the uncontrolled system is uniformly asymptotically stable and if the control system is controllable, then the non-linear infinite delay system is Euclidean null ...

  20. Null infinity and extremal horizons in AdS-CFT

    International Nuclear Information System (INIS)

    Hickling, Andrew; Wiseman, Toby; Lucietti, James

    2015-01-01

    We consider AdS gravity duals to CFT on background spacetimes with a null infinity. Null infinity on the conformal boundary may extend to an extremal horizon in the bulk. For example it does so for Poincaré–AdS, although does not for planar Schwarzschild–AdS. If null infinity does extend into an extremal horizon in the bulk, we show that the bulk near-horizon geometry is determined by the geometry of the boundary null infinity. Hence the ‘infra-red’ geometry of the bulk is fixed by the large scale behaviour of the CFT spacetime. In addition the boundary stress tensor must have a particular decay at null infinity. As an application, we argue that for CFT on asymptotically flat backgrounds, any static bulk dual containing an extremal horizon extending from the boundary null infinity, must have the near-horizon geometry of Poincaré–AdS. We also discuss a class of boundary null infinity that cannot extend to a bulk extremal horizon, although we give evidence that they can extend to an analogous null surface in the bulk which possesses an associated scale-invariant ‘near-geometry’. (paper)

  1. Logarithmic corrections to gravitational entropy and the null energy condition

    Energy Technology Data Exchange (ETDEWEB)

    Parikh, Maulik, E-mail: maulik.parikh@asu.edu; Svesko, Andrew

    2016-10-10

    Using a relation between the thermodynamics of local horizons and the null energy condition, we consider the effects of quantum corrections to the gravitational entropy. In particular, we find that the geometric form of the null energy condition is not affected by the inclusion of logarithmic corrections to the Bekenstein–Hawking entropy.

  2. Logarithmic corrections to gravitational entropy and the null energy condition

    Directory of Open Access Journals (Sweden)

    Maulik Parikh

    2016-10-01

    Full Text Available Using a relation between the thermodynamics of local horizons and the null energy condition, we consider the effects of quantum corrections to the gravitational entropy. In particular, we find that the geometric form of the null energy condition is not affected by the inclusion of logarithmic corrections to the Bekenstein–Hawking entropy.

  3. A new dynamic null model for phylogenetic community structure

    NARCIS (Netherlands)

    Pigot, Alex L; Etienne, Rampal S

    Phylogenies are increasingly applied to identify the mechanisms structuring ecological communities but progress has been hindered by a reliance on statistical null models that ignore the historical process of community assembly. Here, we address this, and develop a dynamic null model of assembly by

  4. ENERGY DISSIPATION IN MAGNETIC NULL POINTS AT KINETIC SCALES

    International Nuclear Information System (INIS)

    Olshevsky, Vyacheslav; Lapenta, Giovanni; Divin, Andrey; Eriksson, Elin; Markidis, Stefano

    2015-01-01

    We use kinetic particle-in-cell and MHD simulations supported by an observational data set to investigate magnetic reconnection in clusters of null points in space plasma. The magnetic configuration under investigation is driven by fast adiabatic flux rope compression that dissipates almost half of the initial magnetic field energy. In this phase powerful currents are excited producing secondary instabilities, and the system is brought into a state of “intermittent turbulence” within a few ion gyro-periods. Reconnection events are distributed all over the simulation domain and energy dissipation is rather volume-filling. Numerous spiral null points interconnected via their spines form null lines embedded into magnetic flux ropes; null point pairs demonstrate the signatures of torsional spine reconnection. However, energy dissipation mainly happens in the shear layers formed by adjacent flux ropes with oppositely directed currents. In these regions radial null pairs are spontaneously emerging and vanishing, associated with electron streams and small-scale current sheets. The number of spiral nulls in the simulation outweighs the number of radial nulls by a factor of 5–10, in accordance with Cluster observations in the Earth's magnetosheath. Twisted magnetic fields with embedded spiral null points might indicate the regions of major energy dissipation for future space missions such as the Magnetospheric Multiscale Mission

  5. On the Robinson theorem and shearfree geodesic null congruences

    International Nuclear Information System (INIS)

    Tafel, J.

    1985-01-01

    Null electromagnetic fields and shearfree geodesic null congruences in curved and flat spacetimes are studied. We point out some mathematical problems connected with the validity of the Robinson theorem. The problem of finding nonanalytic twisting congruences in the Minkowski space is reduced to the construction of holomorphic functions with specific boundary conditions. (orig.)

  6. An omnibus test for the global null hypothesis.

    Science.gov (United States)

    Futschik, Andreas; Taus, Thomas; Zehetmayer, Sonja

    2018-01-01

    Global hypothesis tests are a useful tool in the context of clinical trials, genetic studies, or meta-analyses, when researchers are not interested in testing individual hypotheses, but in testing whether none of the hypotheses is false. There are several possibilities how to test the global null hypothesis when the individual null hypotheses are independent. If it is assumed that many of the individual null hypotheses are false, combination tests have been recommended to maximize power. If, however, it is assumed that only one or a few null hypotheses are false, global tests based on individual test statistics are more powerful (e.g. Bonferroni or Simes test). However, usually there is no a priori knowledge on the number of false individual null hypotheses. We therefore propose an omnibus test based on cumulative sums of the transformed p-values. We show that this test yields an impressive overall performance. The proposed method is implemented in an R-package called omnibus.

  7. The Visible Nulling Coronagraph--Architecture Definition and Technology Development

    Science.gov (United States)

    Shao, Michael; Levine, B. Martin; Wallace, J. Kent; Liu, Duncan T.; Schmidtlin, Edouard; Serabyn, Eugene; Mennesson, Bertrand; Green, Joseph J.; Aguayo, Francisco; Fregoso, S. Felipe; hide

    2005-01-01

    This paper describes the advantages of visible direct detection and spectroscopy of Earth-like extrasolar planets using a nulling coronagraph instrument behind a moderately sized single aperture space telescope. Our concept synthesizes a nulling interferometer by shearing the telescope pupil, with the resultant producing a deep null. We describe nulling configurations that also include methods to mitigate stellar leakage, such as spatial filtering by a coherent array of single mode fibers, and post-starlight suppression wavefront sensing and control. With diffraction limited telescope optics and similar quality components in the optical train (lambda/20), suppression of the starlight to 1e-10 is readily achievable. We describe key features of the architecture and analysis, present latest results of laboratory measurements demonstrating achievable null depth and component development, and discuss future key technical milestones.

  8. Wormholes minimally violating the null energy condition

    Energy Technology Data Exchange (ETDEWEB)

    Bouhmadi-López, Mariam [Departamento de Física, Universidade da Beira Interior, 6200 Covilhã (Portugal); Lobo, Francisco S N; Martín-Moruno, Prado, E-mail: mariam.bouhmadi@ehu.es, E-mail: fslobo@fc.ul.pt, E-mail: pmmoruno@fc.ul.pt [Centro de Astronomia e Astrofísica da Universidade de Lisboa, Campo Grande, Edifício C8, 1749-016 Lisboa (Portugal)

    2014-11-01

    We consider novel wormhole solutions supported by a matter content that minimally violates the null energy condition. More specifically, we consider an equation of state in which the sum of the energy density and radial pressure is proportional to a constant with a value smaller than that of the inverse area characterising the system, i.e., the area of the wormhole mouth. This approach is motivated by a recently proposed cosmological event, denoted {sup t}he little sibling of the big rip{sup ,} where the Hubble rate and the scale factor blow up but the cosmic derivative of the Hubble rate does not [1]. By using the cut-and-paste approach, we match interior spherically symmetric wormhole solutions to an exterior Schwarzschild geometry, and analyse the stability of the thin-shell to linearized spherically symmetric perturbations around static solutions, by choosing suitable properties for the exotic material residing on the junction interface radius. Furthermore, we also consider an inhomogeneous generalization of the equation of state considered above and analyse the respective stability regions. In particular, we obtain a specific wormhole solution with an asymptotic behaviour corresponding to a global monopole.

  9. Bodyweight Assessment of Enamelin Null Mice

    Directory of Open Access Journals (Sweden)

    Albert H.-L. Chan

    2013-01-01

    Full Text Available The Enam null mice appear to be smaller than wild-type mice, which prompted the hypothesis that enamel defects negatively influence nutritional intake and bodyweight gain (BWG. We compared the BWG of Enam−/− and wild-type mice from birth (D0 to Day 42 (D42. Wild-type (WT and Enam−/− (N mice were given either hard chow (HC or soft chow (SC. Four experimental groups were studied: WTHC, WTSC, NHC, and NSC. The mother’s bodyweight (DBW and the average litter bodyweight (ALBW were obtained from D0 to D21. After D21, the pups were separated from the mother and provided the same type of food. Litter bodyweights were measured until D42. ALBW was compared at 7-day intervals using one-way ANOVA, while the influence of DBW on ALBW was analyzed by mixed-model analyses. The ALBW of Enam−/− mice maintained on hard chow (NHC was significantly lower than the two WT groups at D21 and the differences persisted into young adulthood. The ALBW of Enam−/− mice maintained on soft chow (NSC trended lower, but was not significantly different than that of the WT groups. We conclude that genotype, which affects enamel integrity, and food hardness influence bodyweight gain in postnatal and young adult mice.

  10. Dental OCT

    Science.gov (United States)

    Wilder-Smith, Petra; Otis, Linda; Zhang, Jun; Chen, Zhongping

    This chapter describes the applications of OCT for imaging in vivo dental and oral tissue. The oral cavity is a diverse environment that includes oral mucosa, gingival tissues, teeth and their supporting structures. Because OCT can image both hard and soft tissues of the oral cavity at high resolution, it offers the unique capacity to identity dental disease before destructive changes have progressed. OCT images depict clinically important anatomical features such as the location of soft tissue attachments, morphological changes in gingival tissue, tooth decay, enamel thickness and decay, as well as the structural integrity of dental restorations. OCT imaging allows for earlier intervention than is possible with current diagnostic modalities.

  11. Infant dental care (image)

    Science.gov (United States)

    ... sugar water. As the child grows, establishing proper dental hygiene will promote healthy teeth and gums which are essential to overall good health. Poor dental development, dental disease, and dental trauma can result ...

  12. Tensionless branes and the null string critical dimension

    International Nuclear Information System (INIS)

    Bozhilov, P.

    1998-01-01

    BRST quantization is carried out for a model of p-branes with second class constraints. After extension of the phase space the constraint algebra coincides with the one of null string when p=1. It is shown that in this case one can or cannot obtain critical dimension for the null string, depending on the choice of the operator ordering and corresponding vacuum states. When p>1, operator orderings leading to critical dimension in the p=1 case are not allowed. Admissible orderings give no restrictions on the dimension of the embedding space-time. Finally, a generalization to supersymmetric null branes is proposed

  13. Dental Calculus Arrest of Dental Caries

    OpenAIRE

    Keyes, Paul H.; Rams, Thomas E.

    2016-01-01

    Background An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human t...

  14. Emission and null coordinates: geometrical properties and physical construction

    International Nuclear Information System (INIS)

    Coll, Bartolome; Ferrando, Joan J; Morales-Lladosa, Juan A

    2011-01-01

    A Relativistic Positioning System is defined by four clocks (emitters) broadcasting their proper time. Then, every event reached by the signals is naturally labeled by these four times which are the emission coordinates of this event. The coordinate hypersurfaces of the emission coordinates are the future light cones based on the emitter trajectories. For this reason the emission coordinates have been also named null coordinates or light coordinates. Nevertheless, other coordinate systems used in different relativistic contexts have the own right to be named null or light coordinates. Here we analyze when one can say that a coordinate is a null coordinate and when one can say that a coordinate system is null. Moreover, we examine the physical construction and the geometrical properties of several n ull coordinate systems : the emission and the reception coordinates, the radar coordinates, and the Bondi-Sachs coordinates, among others.

  15. Relative null controllability of linear systems with multiple delays in ...

    African Journals Online (AJOL)

    varying multiple delays in state and control are developed. If the uncontrolled system is uniformly asymptotically stable, and if the linear system is controllable, then the linear system is null controllable. Journal of the Nigerian Association of ...

  16. Null canonical formalism 1, Maxwell field. [Poisson brackets, boundary conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wodkiewicz, K [Warsaw Univ. (Poland). Inst. Fizyki Teoretycznej

    1975-01-01

    The purpose of this paper is to formulate the canonical formalism on null hypersurfaces for the Maxwell electrodynamics. The set of the Poisson brackets relations for null variables of the Maxwell field is obtained. The asymptotic properties of the theory are investigated. The Poisson bracket relations for the news-functions of the Maxwell field are computed. The Hamiltonian form of the asymptotic Maxwell equations in terms of these news-functions is obtained.

  17. Null controllability of a cascade system of Schrodinger equations

    Directory of Open Access Journals (Sweden)

    Marcos Lopez-Garcia

    2016-03-01

    Full Text Available This article presents a control problem for a cascade system of two linear N-dimensional Schrodinger equations. We address the problem of null controllability by means of a control supported in a region not satisfying the classical geometrical control condition. The proof is based on the application of a Carleman estimate with degenerate weights to each one of the equations and a careful analysis of the system in order to prove null controllability with only one control force.

  18. Sequential weak continuity of null Lagrangians at the boundary

    Czech Academy of Sciences Publication Activity Database

    Kalamajska, A.; Kraemer, S.; Kružík, Martin

    2014-01-01

    Roč. 49, 3/4 (2014), s. 1263-1278 ISSN 0944-2669 R&D Projects: GA ČR GAP201/10/0357 Institutional support: RVO:67985556 Keywords : null Lagrangians * nonhomogeneous nonlinear mappings * sequential weak/in measure continuity Subject RIV: BA - General Mathematics Impact factor: 1.518, year: 2014 http://library.utia.cas.cz/separaty/2013/MTR/kruzik-sequential weak continuity of null lagrangians at the boundary.pdf

  19. On the geometry of null congruences in general relativity

    International Nuclear Information System (INIS)

    Ahsan, Zafar; Malik, N.P.

    1977-01-01

    Some theorems for the null congruences within the framework of general theory of relativity are given. These theorems are important in themselves as they illustrate the geometric meaning of the spin coefficients. The newly developed Geroch-Held-Penrose (GHP) formalism has been used throughout the investigations. The salient features of GHP formalism that are necessary for the present work are given and these techniques are applied to a pair of null congruences C(l) and C(n). (author)

  20. A parameter set for a double-null DEMO reactor

    International Nuclear Information System (INIS)

    Cooke, P.I.H.

    1987-01-01

    The present study is aimed at commenting on the reactor-relevance of the design principles and technology being proposed for NET. The authors propose that a double-null device serve as a basis for a NET-based demonstration reactor. Calculations are carried out to determine the parameter set for reactors based on the double-null NET design, and the results are presented in tabular form. (U.K.)

  1. Vortical null orbits, repulsive barriers, energy confinement in Kerr metric

    Energy Technology Data Exchange (ETDEWEB)

    Calvani, M [Padua Univ. (Italy). Ist. di Astronomia; De Felice, F

    1978-10-01

    The complete analytical description of the null trajectories in the field of a Kerr naked singularity is given. Two peculiar phenomena are described: the existence of repulsive barriers in the r < O world and the existence of null circular bound orbits which surround the singularity in 'shells'. They distribute around the surface at r = m, which is the position of the horizon in the extreme black-hole case; this suggests that a naked singularity 'remembers' the position of the last horizon.

  2. Ambitwistor strings at null infinity and (subleading) soft limits

    International Nuclear Information System (INIS)

    Geyer, Yvonne; Lipstein, Arthur E; Mason, Lionel

    2015-01-01

    The relationship between BMS symmetries at null infinity and Weinberg's soft theorems for gravitons and photons together with their subleading extensions are developed using ambitwistor string theory. Ambitwistor space is the phase space of complex null geodesics in complexified space-time. We show how it can be canonically identified with the cotangent bundle of complexified null infinity. BMS symmetries of null infinity lift to give a Hamiltonian action on ambitwistor space, both in general dimension and in its twistorial four-dimensional representation. General vertex operators arise from Hamiltonians generating diffeomorphisms of ambitwistor space that determine the scattering from past to future null infinity. When a momentum eigenstate goes soft, the diffeomorphism defined by its leading and its subleading part are extended BMS generators realized in the world sheet conformal field theory of the ambitwistor string. More generally, this gives an explicit perturbative correspondence between the scattering of null geodesics and that of the gravitational field via ambitwistor string theory. (paper)

  3. Dental caries

    DEFF Research Database (Denmark)

    Pitts, Nigel B; Zero, Domenick T; Marsh, Phil D

    2017-01-01

    Dental caries is a biofilm-mediated, sugar-driven, multifactorial, dynamic disease that results in the phasic demineralization and remineralization of dental hard tissues. Caries can occur throughout life, both in primary and permanent dentitions, and can damage the tooth crown and, in later life......, exposed root surfaces. The balance between pathological and protective factors influences the initiation and progression of caries. This interplay between factors underpins the classification of individuals and groups into caries risk categories, allowing an increasingly tailored approach to care. Dental...... caries is an unevenly distributed, preventable disease with considerable economic and quality-of-life burdens. The daily use of fluoride toothpaste is seen as the main reason for the overall decline of caries worldwide over recent decades. This Primer aims to provide a global overview of caries...

  4. Dental Calculus Arrest of Dental Caries.

    Science.gov (United States)

    Keyes, Paul H; Rams, Thomas E

    An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human teeth for the presence and location of dental caries, dental calculus, and dental plaque biofilms. A total of 1,200 teeth were preserved in 10% buffered formal saline, and viewed while moist by a single experienced examiner using a research stereomicroscope at 15-25× magnification. Representative teeth were sectioned and photographed, and their dental plaque biofilms subjected to gram-stain examination with light microscopy at 100× magnification. Dental calculus was observed on 1,140 (95%) of the extracted human teeth, and no dental carious lesions were found underlying dental calculus-covered surfaces on 1,139 of these teeth. However, dental calculus arrest of dental caries was found on one (0.54%) of 187 evaluated teeth that presented with unrestored proximal enamel caries. On the distal surface of a maxillary premolar tooth, dental calculus mineralization filled the outer surface cavitation of an incipient dental caries lesion. The dental calculus-covered carious lesion extended only slightly into enamel, and exhibited a brown pigmentation characteristic of inactive or arrested dental caries. In contrast, the tooth's mesial surface, without a superficial layer of dental calculus, had a large carious lesion going through enamel and deep into dentin. These observations further document the potential protective effects of dental calculus mineralization against dental caries.

  5. Dental Calculus Arrest of Dental Caries

    Science.gov (United States)

    Keyes, Paul H.; Rams, Thomas E.

    2016-01-01

    Background An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human teeth for the presence and location of dental caries, dental calculus, and dental plaque biofilms. Materials and methods A total of 1,200 teeth were preserved in 10% buffered formal saline, and viewed while moist by a single experienced examiner using a research stereomicroscope at 15-25× magnification. Representative teeth were sectioned and photographed, and their dental plaque biofilms subjected to gram-stain examination with light microscopy at 100× magnification. Results Dental calculus was observed on 1,140 (95%) of the extracted human teeth, and no dental carious lesions were found underlying dental calculus-covered surfaces on 1,139 of these teeth. However, dental calculus arrest of dental caries was found on one (0.54%) of 187 evaluated teeth that presented with unrestored proximal enamel caries. On the distal surface of a maxillary premolar tooth, dental calculus mineralization filled the outer surface cavitation of an incipient dental caries lesion. The dental calculus-covered carious lesion extended only slightly into enamel, and exhibited a brown pigmentation characteristic of inactive or arrested dental caries. In contrast, the tooth's mesial surface, without a superficial layer of dental calculus, had a large carious lesion going through enamel and deep into dentin. Conclusions These observations further document the potential protective effects of dental calculus mineralization against dental caries. PMID:27446993

  6. Resistivity at the field null of the FRC plasma

    International Nuclear Information System (INIS)

    Gerwin, R.A.

    1989-01-01

    In the absence of the major destructive instabilities, the configuration time is ultimately determined by particle and flux containment. If the profiles are ''gentle,'' then the anomalous flux-loss rate depends essentially on the anomalous resistivity at the field null. Conventional electrostatic quasi-linear models of anomalous cross-field resistive diffusivity are based upon the use of rvec E x rvec B drift velocities, and hence break down at the magnetic field null. In this paper, an electromagnetic treatment valid at the field null is developed, based upon the presence of flute-parity perturbations. An expression for anomalous resistivity at the field null in the quasi-linear approximation is derived by averaging in the ignorable direction over the random phases of the perturbations. The expression is valid for arbitrary (non-local) radial shapes of the perturbing modes (for example, the eigenfunctions need not be centered at the field null), and for an arbitrary ratio of real frequency to growth rate. The effective resistivity due to flute perturbations of the MHD type will be considered. 1 ref

  7. Evaluation of null-point detection methods on simulation data

    Science.gov (United States)

    Olshevsky, Vyacheslav; Fu, Huishan; Vaivads, Andris; Khotyaintsev, Yuri; Lapenta, Giovanni; Markidis, Stefano

    2014-05-01

    We model the measurements of artificial spacecraft that resemble the configuration of CLUSTER propagating in the particle-in-cell simulation of turbulent magnetic reconnection. The simulation domain contains multiple isolated X-type null-points, but the majority are O-type null-points. Simulations show that current pinches surrounded by twisted fields, analogous to laboratory pinches, are formed along the sequences of O-type nulls. In the simulation, the magnetic reconnection is mainly driven by the kinking of the pinches, at spatial scales of several ion inertial lentghs. We compute the locations of magnetic null-points and detect their type. When the satellites are separated by the fractions of ion inertial length, as it is for CLUSTER, they are able to locate both the isolated null-points, and the pinches. We apply the method to the real CLUSTER data and speculate how common are pinches in the magnetosphere, and whether they play a dominant role in the dissipation of magnetic energy.

  8. Visible nulling coronagraphy testbed development for exoplanet detection

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Woodruff, Robert A.; Vasudevan, Gopal; Thompson, Patrick; Chen, Andrew; Petrone, Peter; Booth, Andrew; Madison, Timothy; Bolcar, Matthew; Noecker, M. Charley; Kendrick, Stephen; Melnick, Gary; Tolls, Volker

    2010-07-01

    Three of the recently completed NASA Astrophysics Strategic Mission Concept (ASMC) studies addressed the feasibility of using a Visible Nulling Coronagraph (VNC) as the prime instrument for exoplanet science. The VNC approach is one of the few approaches that works with filled, segmented and sparse or diluted aperture telescope systems and thus spans the space of potential ASMC exoplanet missions. NASA/Goddard Space Flight Center (GSFC) has a well-established effort to develop VNC technologies and has developed an incremental sequence of VNC testbeds to advance the this approach and the technologies associated with it. Herein we report on the continued development of the vacuum Visible Nulling Coronagraph testbed (VNT). The VNT is an ultra-stable vibration isolated testbed that operates under high bandwidth closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence of three visible light nulling milestones of sequentially higher contrasts of 108, 109 and 1010 at an inner working angle of 2*λ/D and ultimately culminate in spectrally broadband (>20%) high contrast imaging. Each of the milestones, one per year, is traceable to one or more of the ASMC studies. The VNT uses a modified Mach-Zehnder nulling interferometer, modified with a modified "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters. Discussed will be the optical configuration laboratory results, critical technologies and the null sensing and control approach.

  9. Tolerance analysis of null lenses using an end-use system performance criterion

    Science.gov (United States)

    Rodgers, J. Michael

    2000-07-01

    An effective method of assigning tolerances to a null lens is to determine the effects of null-lens fabrication and alignment errors on the end-use system itself, not simply the null lens. This paper describes a method to assign null- lens tolerances based on their effect on any performance parameter of the end-use system.

  10. Null but not void: considerations for hypothesis testing.

    Science.gov (United States)

    Shaw, Pamela A; Proschan, Michael A

    2013-01-30

    Standard statistical theory teaches us that once the null and alternative hypotheses have been defined for a parameter, the choice of the statistical test is clear. Standard theory does not teach us how to choose the null or alternative hypothesis appropriate to the scientific question of interest. Neither does it tell us that in some cases, depending on which alternatives are realistic, we may want to define our null hypothesis differently. Problems in statistical practice are frequently not as pristinely summarized as the classic theory in our textbooks. In this article, we present examples in statistical hypothesis testing in which seemingly simple choices are in fact rich with nuance that, when given full consideration, make the choice of the right hypothesis test much less straightforward. Published 2012. This article is a US Government work and is in the public domain in the USA.

  11. sirt1-null mice develop an autoimmune-like condition

    International Nuclear Information System (INIS)

    Sequeira, Jedon; Boily, Gino; Bazinet, Stephanie; Saliba, Sarah; He Xiaohong; Jardine, Karen; Kennedy, Christopher; Staines, William; Rousseaux, Colin; Mueller, Rudi; McBurney, Michael W.

    2008-01-01

    The sirt1 gene encodes a protein deacetylase with a broad spectrum of reported substrates. Mice carrying null alleles for sirt1 are viable on outbred genetic backgrounds so we have examined them in detail to identify the biological processes that are dependent on SIRT1. Sera from adult sirt1-null mice contain antibodies that react with nuclear antigens and immune complexes become deposited in the livers and kidneys of these animals. Some of the sirt1-null animals develop a disease resembling diabetes insipidus when they approach 2 years of age although the relationship to the autoimmunity remains unclear. We interpret these observations as consistent with a role for SIRT1 in sustaining normal immune function and in this way delaying the onset of autoimmune disease

  12. Unicorns do exist: a tutorial on "proving" the null hypothesis.

    Science.gov (United States)

    Streiner, David L

    2003-12-01

    Introductory statistics classes teach us that we can never prove the null hypothesis; all we can do is reject or fail to reject it. However, there are times when it is necessary to try to prove the nonexistence of a difference between groups. This most often happens within the context of comparing a new treatment against an established one and showing that the new intervention is not inferior to the standard. This article first outlines the logic of "noninferiority" testing by differentiating between the null hypothesis (that which we are trying to nullify) and the "nill" hypothesis (there is no difference), reversing the role of the null and alternate hypotheses, and defining an interval within which groups are said to be equivalent. We then work through an example and show how to calculate sample sizes for noninferiority studies.

  13. ISCO and Principal Null Congruences in Extremal Kerr Spacetime

    International Nuclear Information System (INIS)

    Pradhan, Parthapratim

    2012-01-01

    The effective potential in universal like coordinates(U, V, θ, φ), which are smooth across the event horizon is derived and investigated the ISCO(Innermost Stable Circular Orbits) explicitly in these coordinates for extremal Kerr spacetime. Extremization of the effective potential for timelike circular orbit shows that the existence of a stable circular geodesics in the extremal spacetime for direct orbit, precisely on the event horizon in terms of the radial coordinate which coincides with the principal null geodesic congruences of the event horizon. These null geodesic congruences mold themselves to the spacetime curvature in such a way that Weyl conformal tensor and its dual are vanished, that is why they are in-fact doubly degenerate principal null congruences.

  14. Phase-space lagrangians for null spinning strings

    International Nuclear Information System (INIS)

    Barcelos-Neto, J.; Ruiz-Altaba, M.; Ramirez, C.

    1990-01-01

    The striking fact that normal-ordered null strings have the same critical dimension as their usual non-zero tension siblings can be understood from the observation that one must, in the tensionless case, keep all the conjugate momenta as independent dynamical variables, thus doubling the number of physical degrees of freedom. The fermionic momenta give rise to a second-class constraint which cannot be solved covariantly, but can be successfully incorporated into the first-class constraint algebra after gauge-fixing. The ghost contributions to the anomaly consist of two b-c (and also two β-γ systems in the supersymmetric case), of the single Virasoro sub(super)algebra for the closed null (spinning) string. In the appropriate gauge, the null (super)string is (super)chiral. (orig.)

  15. Combined effect of fluoride and 2,3,7,8-tetrachlorodibenzo-p-dioxin on mouse dental hard tissue formation in vitro.

    Science.gov (United States)

    Salmela, Eija; Lukinmaa, Pirjo-Liisa; Partanen, Anna-Maija; Sahlberg, Carin; Alaluusua, Satu

    2011-08-01

    Fluoride interferes with enamel matrix secretion and mineralization and dentin mineralization. The most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), also impairs dental hard tissue formation and mineralization in vitro and in vivo. Our aim was to investigate in vitro whether the combined effect of sodium fluoride (NaF) and TCDD on dental hard tissue formation is potentiative. For this purpose, mandibular first and second molar tooth germs of E18 mouse embryos were cultured for 5-12 days with NaF and TCDD alone at various concentrations (2.5, 5, 10, 12.5, 15, and 20 μM and 5, 10, 12.5, and 15 nM, respectively) to determine the highest concentrations, which alone cause no or negligible effects. Morphological changes were studied from the whole tooth photographs and histological tissue sections. The concentrations found were 15 μM for NaF and 10 nM for TCDD. While at these concentrations, the effects of NaF and TCDD alone were barely detectable, the effect of simultaneous exposure on dentin and enamel formation was overt; mineralization of predentin to dentin and enamel matrix secretion and mineralization were impaired. Immunohistochemical analysis revealed that the combined exposure modified amelogenin expression by odontoblasts. Morphology of ameloblasts and the expression of amelogenin indicated that ameloblasts were still secretory. The results show that NaF and TCDD have potentiative, harmful effects on the formation of dental hard tissues. Since children can be exposed to subclinical levels of fluoride and dioxins during early childhood, coincidently with mineralization of the first permanent teeth, this finding may have clinical significance.

  16. Clareamento Dental

    OpenAIRE

    Sossai, Najara; Universidade Paranaense - UNIPAR; Verdinelli, Ellen Carla; Universidade Paranaense - UNIPAR; Bassegio, Wagner; Universidade Paranaense - UNIPAR

    2011-01-01

    O clareamento dental já é utilizado há bastante tempo na Odontologia e atualmente é um dos tratamentos odontológicos mais solicitados para obtenção de um sorriso mais estético. Classificado em clareamento caseiro e/ou de consultório, ambas as técnicas são motivo de polêmica quanto aos seus benefícios, riscos, limitações e efeito clareador, bem como sobre qual é a melhor técnica existente para a promoção de um clareamento dental eficaz e seguro. Neste contexto, o presente estudo tem por objeti...

  17. Sex Determination from Fragmented and Degenerated DNA by Amplified Product-Length Polymorphism Bidirectional SNP Analysis of Amelogenin and SRY Genes

    Science.gov (United States)

    Masuyama, Kotoka; Shojo, Hideki; Nakanishi, Hiroaki; Inokuchi, Shota; Adachi, Noboru

    2017-01-01

    Sex determination is important in archeology and anthropology for the study of past societies, cultures, and human activities. Sex determination is also one of the most important components of individual identification in criminal investigations. We developed a new method of sex determination by detecting a single-nucleotide polymorphism in the amelogenin gene using amplified product-length polymorphisms in combination with sex-determining region Y analysis. We particularly focused on the most common types of postmortem DNA damage in ancient and forensic samples: fragmentation and nucleotide modification resulting from deamination. Amplicon size was designed to be less than 60 bp to make the method more useful for analyzing degraded DNA samples. All DNA samples collected from eight Japanese individuals (four male, four female) were evaluated correctly using our method. The detection limit for accurate sex determination was determined to be 20 pg of DNA. We compared our new method with commercial short tandem repeat analysis kits using DNA samples artificially fragmented by ultraviolet irradiation. Our novel method was the most robust for highly fragmented DNA samples. To deal with allelic dropout resulting from deamination, we adopted “bidirectional analysis,” which analyzed samples from both sense and antisense strands. This new method was applied to 14 Jomon individuals (3500-year-old bone samples) whose sex had been identified morphologically. We could correctly identify the sex of 11 out of 14 individuals. These results show that our method is reliable for the sex determination of highly degenerated samples. PMID:28052096

  18. Sex Determination from Fragmented and Degenerated DNA by Amplified Product-Length Polymorphism Bidirectional SNP Analysis of Amelogenin and SRY Genes.

    Directory of Open Access Journals (Sweden)

    Kotoka Masuyama

    Full Text Available Sex determination is important in archeology and anthropology for the study of past societies, cultures, and human activities. Sex determination is also one of the most important components of individual identification in criminal investigations. We developed a new method of sex determination by detecting a single-nucleotide polymorphism in the amelogenin gene using amplified product-length polymorphisms in combination with sex-determining region Y analysis. We particularly focused on the most common types of postmortem DNA damage in ancient and forensic samples: fragmentation and nucleotide modification resulting from deamination. Amplicon size was designed to be less than 60 bp to make the method more useful for analyzing degraded DNA samples. All DNA samples collected from eight Japanese individuals (four male, four female were evaluated correctly using our method. The detection limit for accurate sex determination was determined to be 20 pg of DNA. We compared our new method with commercial short tandem repeat analysis kits using DNA samples artificially fragmented by ultraviolet irradiation. Our novel method was the most robust for highly fragmented DNA samples. To deal with allelic dropout resulting from deamination, we adopted "bidirectional analysis," which analyzed samples from both sense and antisense strands. This new method was applied to 14 Jomon individuals (3500-year-old bone samples whose sex had been identified morphologically. We could correctly identify the sex of 11 out of 14 individuals. These results show that our method is reliable for the sex determination of highly degenerated samples.

  19. Comparative expression of the four enamel matrix protein genes, amelogenin, ameloblastin, enamelin and amelotin during amelogenesis in the lizard Anolis carolinensis.

    Science.gov (United States)

    Gasse, Barbara; Sire, Jean-Yves

    2015-01-01

    In a recent study, we have demonstrated that amelotin (AMTN) gene structure and its expression during amelogenesis have changed during tetrapod evolution. Indeed, this gene is expressed throughout enamel matrix deposition and maturation in non-mammalian tetrapods, while in mammals its expression is restricted to the transition and maturation stages of amelogenesis. Previous studies of amelogenin (AMEL) gene expression in a lizard and a salamander have shown similar expression pattern to that in mammals, but to our knowledge there are no data regarding ameloblastin (AMBN) and enamelin (ENAM) expression in non-mammalian tetrapods. The present study aims to look at, and compare, the structure and expression of four enamel matrix protein genes, AMEL, AMBN, ENAM and AMTN during amelogenesis in the lizard Anolis carolinensis. We provide the full-length cDNA sequence of A. carolinensis AMEL and AMBN, and show for the first time the expression of ENAM and AMBN in a non-mammalian species. During amelogenesis in A. carolinensis, AMEL, AMBN and ENAM expression in ameloblasts is similar to that described in mammals. It is noteworthy that AMEL and AMBN expression is also found in odontoblasts. Our findings indicate that AMTN is the only enamel matrix protein gene that is differentially expressed in ameloblasts between mammals and sauropsids. Changes in AMTN structure and expression could be the key to explain the structural differences between mammalian and reptilian enamel, i.e. prismatic versus non-prismatic.

  20. Dental Implant Surgery

    Science.gov (United States)

    ... here to find out more. Dental Implant Surgery Dental Implant Surgery Dental implant surgery is, of course, ... to find out more. Wisdom Teeth Management Wisdom Teeth Management An impacted wisdom tooth can damage neighboring ...

  1. American Dental Education Association

    Science.gov (United States)

    ... Interest Groups ADEA Governance Documents and Publications ADEA Dental Faculty Code of Conduct ADEA Bylaws ADEAGies Foundation ... Benefits for Faculty ADEA Member Benefits for Allied Dental Programs ADEA Member Benefits for Dental Schools ADEA ...

  2. Dental Holography

    Science.gov (United States)

    Dirtoft, Ingegerd

    1983-12-01

    Ten years have passed since the first articles appeared in this new field. The qualities of the laser light together with the need of contactless 3-D measurements for different dental purposes seemed to be extremely promising, but still just a few scientists have used the method and mostly for laboratory studies. For some reason there has been a preponderance for orthodontic measurements. This seems to be a bit peculiar from holographic view compared with measurements for engineering purposes, which usually are made on metals. So naturally holography can become a clinical tool for measurements in the field of fixed bridges, removable partial dentures and implants. One of the problems is that the need for holography in dental research must be fulfilled in collaboration with physicists. Only a two-way communication during an entire experiment can balance both technical and odontological demands and thus give practical and clinical important results. The need for an easy way of handling the evaluation to get all required information is another problem and of course the holographic equipment must be converted to a box easy to handle for everyone. At last the position of dental holography today is going to be carefully examined together with an attempt to look into the hopefully exciting and not to utopic future for this research field.

  3. Danish dental education:

    DEFF Research Database (Denmark)

    Moore, Rod

    1985-01-01

    The effects of Danish cultural traditions on dental education in Denmark are described, as well as the system's current structure and developing issues. Some Danish ideas for future exports of dental education programs and dental personnel are also discussed.......The effects of Danish cultural traditions on dental education in Denmark are described, as well as the system's current structure and developing issues. Some Danish ideas for future exports of dental education programs and dental personnel are also discussed....

  4. Dental students--dental advocates.

    Science.gov (United States)

    Bensch, Brittany

    2010-01-01

    Student advocacy and involvement in the political process is built into the structure of the American Student Dental Association (ASDA), especially in its Legislative Grassroots Network and an internal communication network among students to ensure political awareness. Students are concerned with such issues as a universally accepted, non-patient-based licensure process, mid-level providers, loan availability and tax deductibility, financial support for schools, and service early in one's professional career (giving forward rather than giving back). Through collaboration with the American Dental Education Association and with many state associations, students participate in lobbying, awareness campaigns, and behind the scenes as legislative aids. Although students share the same love for the profession that animates established practitioners, they are perceived by legislators as being different. Students are involved in the legislative process because it represents their future.

  5. Testing the null hypothesis: the forgotten legacy of Karl Popper?

    Science.gov (United States)

    Wilkinson, Mick

    2013-01-01

    Testing of the null hypothesis is a fundamental aspect of the scientific method and has its basis in the falsification theory of Karl Popper. Null hypothesis testing makes use of deductive reasoning to ensure that the truth of conclusions is irrefutable. In contrast, attempting to demonstrate the new facts on the basis of testing the experimental or research hypothesis makes use of inductive reasoning and is prone to the problem of the Uniformity of Nature assumption described by David Hume in the eighteenth century. Despite this issue and the well documented solution provided by Popper's falsification theory, the majority of publications are still written such that they suggest the research hypothesis is being tested. This is contrary to accepted scientific convention and possibly highlights a poor understanding of the application of conventional significance-based data analysis approaches. Our work should remain driven by conjecture and attempted falsification such that it is always the null hypothesis that is tested. The write up of our studies should make it clear that we are indeed testing the null hypothesis and conforming to the established and accepted philosophical conventions of the scientific method.

  6. Euclidean null controllability of perturbed infinite delay systems with ...

    African Journals Online (AJOL)

    Euclidean null controllability of perturbed infinite delay systems with limited control. ... Open Access DOWNLOAD FULL TEXT ... The results are established by placing conditions on the perturbation function which guarantee that, if the linear control base system is completely Euclidean controllable, then the perturbed system ...

  7. Euclidean null controllability of linear systems with delays in state ...

    African Journals Online (AJOL)

    Sufficient conditions are developed for the Euclidean controllability of linear systems with delay in state and in control. Namely, if the uncontrolled system is uniformly asymptotically stable and the control equation proper, then the control system is Euclidean null controllable. Journal of the Nigerian Association of ...

  8. Future null infinity of Robertson-Walker spacetimes

    International Nuclear Information System (INIS)

    Moreschi, O.M.

    1988-08-01

    The future null infinity for all non-contracting Robertson-Walker space time is studied systematically. A theorem is proved which establishes the expected relation between the nature of J + and the appearance or absence of cosmic event horizons. (author). 7 refs, 1 tab

  9. The Many Null Distributions of Person Fit Indices.

    Science.gov (United States)

    Molenaar, Ivo W.; Hoijtink, Herbert

    1990-01-01

    Statistical properties of person fit indices are reviewed as indicators of the extent to which a person's score pattern is in agreement with a measurement model. Distribution of a fit index and ability-free fit evaluation are discussed. The null distribution was simulated for a test of 20 items. (SLD)

  10. Spatial and null infinity via advanced and retarded conformal factors

    International Nuclear Information System (INIS)

    Hayward, Sean A.

    2003-01-01

    A new approach to space-time asymptotics is presented, refining Penrose's idea of conformal transformations with infinity represented by the conformal boundary of space-time. It is proposed that the Penrose conformal factor be a product of advanced and retarded conformal factors, which asymptotically relate physical and conformal null coordinates and vanish at future and past null infinity respectively. A refined definition of asymptotic flatness at both spatial and null infinity is given, including that the conformal boundary is locally a light cone, with spatial infinity as the vertex. It is shown how to choose the conformal factors so that this asymptotic light cone is locally a metric light cone. The theory is implemented in the spin-coefficient (or null-tetrad) formalism by a joint transformation of the spin-metric and spin-basis (or metric and tetrad). Asymptotic regularity conditions are proposed, based on the conformal boundary locally being a smoothly embedded metric light cone. These conditions ensure that the Bondi-Sachs energy-flux integrals of ingoing and outgoing gravitational radiation decay at spatial infinity such that the total radiated energy is finite, and that the Bondi-Sachs energy-momentum has a unique limit at spatial infinity, coinciding with the uniquely rendered ADM energy-momentum

  11. Red hair is the null phenotype of MC1R.

    Science.gov (United States)

    Beaumont, Kimberley A; Shekar, Sri N; Cook, Anthony L; Duffy, David L; Sturm, Richard A

    2008-08-01

    The Melanocortin-1 Receptor (MC1R) is a G-protein coupled receptor, which is responsible for production of the darker eumelanin pigment and the tanning response. The MC1R gene has many polymorphisms, some of which have been linked to variation in pigmentation phenotypes within human populations. In particular, the p.D84E, p.R151C, p.R160W and p.D294 H alleles have been strongly associated with red hair, fair skin and increased skin cancer risk. These red hair colour (RHC) variants are relatively well described and are thought to result in altered receptor function, while still retaining varying levels of signaling ability in vitro. The mouse Mc1r null phenotype is yellow fur colour, the p.R151C, p.R160W and p.D294 H alleles were able to partially rescue this phenotype, leading to the question of what the true null phenotype of MC1R would be in humans. Due to the rarity of MC1R null alleles in human populations, they have only been found in the heterozygous state until now. We report here the first case of a homozygous MC1R null individual, phenotypic analysis indicates that red hair and fair skin is found in the absence of MC1R function.

  12. On the null distribution of Bayes factors in linear regression

    Science.gov (United States)

    We show that under the null, the 2 log (Bayes factor) is asymptotically distributed as a weighted sum of chi-squared random variables with a shifted mean. This claim holds for Bayesian multi-linear regression with a family of conjugate priors, namely, the normal-inverse-gamma prior, the g-prior, and...

  13. Magnetic Reconnection at a Three-dimensional Solar Null Point

    DEFF Research Database (Denmark)

    Frederiksen, Jacob Trier; Baumann, Gisela; Galsgaard, Klaus

    2012-01-01

    Using a specific solar null point reconnection case studied by Masson et al (2009; ApJ 700, 559) we investigate the dependence of the reconnection rate on boundary driving speed, numerical resolution, type of resistivity (constant or numerical), and assumed stratification (constant density or sol...

  14. Null point of discrimination in crustacean polarisation vision.

    Science.gov (United States)

    How, Martin J; Christy, John; Roberts, Nicholas W; Marshall, N Justin

    2014-07-15

    The polarisation of light is used by many species of cephalopods and crustaceans to discriminate objects or to communicate. Most visual systems with this ability, such as that of the fiddler crab, include receptors with photopigments that are oriented horizontally and vertically relative to the outside world. Photoreceptors in such an orthogonal array are maximally sensitive to polarised light with the same fixed e-vector orientation. Using opponent neural connections, this two-channel system may produce a single value of polarisation contrast and, consequently, it may suffer from null points of discrimination. Stomatopod crustaceans use a different system for polarisation vision, comprising at least four types of polarisation-sensitive photoreceptor arranged at 0, 45, 90 and 135 deg relative to each other, in conjunction with extensive rotational eye movements. This anatomical arrangement should not suffer from equivalent null points of discrimination. To test whether these two systems were vulnerable to null points, we presented the fiddler crab Uca heteropleura and the stomatopod Haptosquilla trispinosa with polarised looming stimuli on a modified LCD monitor. The fiddler crab was less sensitive to differences in the degree of polarised light when the e-vector was at -45 deg than when the e-vector was horizontal. In comparison, stomatopods showed no difference in sensitivity between the two stimulus types. The results suggest that fiddler crabs suffer from a null point of sensitivity, while stomatopods do not. © 2014. Published by The Company of Biologists Ltd.

  15. Null Lens Assembly for X-Ray Mirror Segments

    Science.gov (United States)

    Robinson, David W.

    2011-01-01

    A document discusses a null lens assembly that allows laser interferometry of 60 deg. slumped glass mirror segments used in x-ray mirrors. The assembly consists of four lenses in precise alignment to each other, with incorporated piezoelectric nanometer stepping actuators to position the lenses in six degrees of freedom for positioning relative to each other.

  16. Self-Nulling Beam Combiner Using No External Phase Inverter

    Science.gov (United States)

    Bloemhof, Eric E.

    2010-01-01

    A self-nulling beam combiner is proposed that completely eliminates the phase inversion subsystem from the nulling interferometer, and instead uses the intrinsic phase shifts in the beam splitters. Simplifying the flight instrument in this way will be a valuable enhancement of mission reliability. The tighter tolerances on R = T (R being reflection and T being transmission coefficients) required by the self-nulling configuration actually impose no new constraints on the architecture, as two adaptive nullers must be situated between beam splitters to correct small errors in the coatings. The new feature is exploiting the natural phase shifts in beam combiners to achieve the 180 phase inversion necessary for nulling. The advantage over prior art is that an entire subsystem, the field-flipping optics, can be eliminated. For ultimate simplicity in the flight instrument, one might fabricate coatings to very high tolerances and dispense with the adaptive nullers altogether, with all their moving parts, along with the field flipper subsystem. A single adaptive nuller upstream of the beam combiner may be required to correct beam train errors (systematic noise), but in some circumstances phase chopping reduces these errors substantially, and there may be ways to further reduce the chop residuals. Though such coatings are beyond the current state of the art, the mechanical simplicity and robustness of a flight system without field flipper or adaptive nullers would perhaps justify considerable effort on coating fabrication.

  17. Visible Nulling Coronagraphy for Exo-Planetary Detection and Characterization

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Woodruff, Robert; Vasudevan, Gopal; Shao, Mike; Levine, Martin; Melnick, Gary; Tolls, Volker; Petrone, Peter; Dogoda, Peter; Duval, Julia; Ge, Jian

    Visible Nulling Coronagraphy (VNC) is the proposed method of detecting and characterizing exo-solar Jovian planets (null depth 10-9) for the proposed NASA's Extrasolar Planetary Imaging Coronagraph (EPIC) Clampin & Lyon 2004 and is an approach under evaluation for NASA's Terrestrial Planet Finder (TPF) mission. The VNC approach uses a single unobscured filled-aperture telescope and splits, via a 50:50 beamsplitter, its re-imaged pupil into two paths within a Mach-Zender interferometer. An achromatic PI phase shift is imposed onto one beam path and the two paths are laterally sheared with respect to each other. The two beams are recombined at a second 50:50 beamsplitter. The net effect is that the on axis (stellar) light is transmitted out of the bright interferometer arm while the off-axis (planetary) light is transmitted out of the nulled interferometer arm. The bright output is used for fine pointing control and coarse wavefront control. The nulled output is relayed to the science camera for science imagery and fine wavefront control. The actual transmission pattern, projected on the sky, follows a θ^2 pattern for a single shear, θ^4 for a double shear, with the spacing of the successive maxima proportional to the inverse of the relative lateral shear. Combinations of shears and spacecraft rolls build up the spatial frequency content of the sky transmission pattern in the same manner as imaging interferometer builds up the spatial frequency content of the image.

  18. Shaping Up the Practice of Null Hypothesis Significance Testing.

    Science.gov (United States)

    Wainer, Howard; Robinson, Daniel H.

    2003-01-01

    Discusses criticisms of null hypothesis significance testing (NHST), suggesting that historical use of NHST was reasonable, and current users should read Sir Ronald Fisher's applied work. Notes that modifications to NHST and interpretations of its outcomes might better suit the needs of modern science. Concludes that NHST is most often useful as…

  19. Relative controllability and null controllability of linear delay systems ...

    African Journals Online (AJOL)

    Necessary and sufficient conditions are established for the relative, absolute controllability and null controllability of the generalized linear delay system and its discrete prototype. The paper presents illuminating examples on previous controllability results by Manitius and Olbrot [7] and carries over the results of Onwuatu [8] ...

  20. A model for electron currents near a field null

    International Nuclear Information System (INIS)

    Stark, R.A.; Miley, G.H.

    1987-01-01

    The fluid approximation is invalid near a field null, since the local electron orbit size and the magnetic scale length are comparable. To model the electron currents in this region we propose a single equation of motion describing the bulk electron dynamics. The equation applies to the plasma within one thermal orbit size of the null. The region is treated as unmagnetized; electrons are accelerated by the inductive electric field and drag on ions; damping is provided by viscosity due to electrons and collisions with ions. Through variational calculations and a particle tracking code for electrons, the size of the terms in the equation of motion have been estimated. The resulting equation of motion combines with Faraday's Law to produce a governing equation which implicitly contains the self inductive field of the electrons. This governing equation predicts that viscosity prevents complete cancellation of the ion current density by the electrons in the null region. Thus electron dynamics near the field null should not prevent the formation and deepening of field reversal using neutral-beam injection

  1. A comment on the null geodesic equations in Schwarzschild geometry

    International Nuclear Information System (INIS)

    Rosa, M.A.F.; Rodrigues Junior, W.A.

    1986-01-01

    An integration of the null geodesic equations in the Schwarzschild geometry, which is valid to first order in GM/Rc 2 is presented. The solution is compared with others published in the literature and their range of validity is analysed. Some misunderstandings are also clarified. (Author) [pt

  2. Maxwell fields and shear-free null geodesic congruences

    International Nuclear Information System (INIS)

    Newman, Ezra T

    2004-01-01

    We study and report on the class of vacuum Maxwell fields in Minkowski space that possess a non-degenerate, diverging, principal null vector field (null eigenvector field of the Maxwell tensor) that is tangent to a shear-free null geodesics congruence. These congruences can be either surface forming (the tangent vectors being proportional to gradients) or not, i.e., the twisting congruences. In the non-twisting case, the associated Maxwell fields are precisely the Lienard-Wiechert fields, i.e., those Maxwell fields arising from an electric monopole moving on an arbitrary worldline. The null geodesic congruence is given by the generators of the light-cones with apex on the worldline. The twisting case is much richer, more interesting and far more complicated. In a twisting subcase, where our main interests lie, the following strange interpretation can be given. If we allow the real Minkowski space to be complexified so that the real Minkowski coordinates x a take complex values, i.e., x a → z a = x a + iy a with complex metric g η ab dz a dz b , the real vacuum Maxwell equations can be extended into the complex space and rewritten as curl W=i W radical, div W=0 with W=E+iB. This subcase of Maxwell fields can then be extended into the complex space so as to have as source, a complex analytic worldline, i.e., to now become complex Lienard-Wiechart fields. When viewed as real fields on the real Minkowski space (z a = x a ), they possess a real principal null vector that is shear-free but twisting and diverging. The twist is a measure of how far the complex worldline is from the real 'slice'. Most Maxwell fields in this subcase are asymptotically flat with a time-varying set of electric and magnetic moments, all depending on the complex displacements and the complex velocities

  3. Dental radiography

    International Nuclear Information System (INIS)

    Shekhdar, J.

    1993-01-01

    Dental radiography must comply with the same regulations with which conventional radiography complies. Radiation doses to individual patients are low but, because of the large number of patients X-rayed, the collective dose to the population is not negligible. Care in siting and regular maintenance of the equipment will reduce doses to both staff and patients. To produce X-ray films with a good image quality using a low radiation dose requires attention to film processing; this is often a neglected area. (Author)

  4. Dental erozyon

    NARCIS (Netherlands)

    Özen, B.; Yönel, N.; Çetiner, S.

    2015-01-01

    Dental erozyon, plak içermeyen diş yüzeyleri üzerinde içsel ve dışsal asitlerin veya şelatların etkileriyle oluşan kimyasal bir aşınmadır. İçsel ve/veya dışsal kaynaklar nedensel faktörler olarak tanımlanırken tükürük ve pelikıl gibi biyolojik faktörler, yeme ve içme alışkanlıkları ve ağız hijyeni

  5. A Comparison of Plasma Performance Between Single-Null and Double-Null Configurations During Elming H-Mode

    International Nuclear Information System (INIS)

    Petrie, T.W.; Fenstermacher, M.E.; Allen, S.L.; Carlstrom, T.N.; Gohil, P.; Groebner, R.J.; Greenfield, C.M.; Hyatt, A.W.; Lasnier, C.J.; La Haye, R.J.; Leonard, A.W.; Mahdavi, M.A.; Osborne, T.H.; Porter, G.D.; Rhodes, T.L.; Thomas, D.M.; Watkins, J.G.; West, W.P.; Wolf, N.S.

    1999-01-01

    Tokamak plasma performance generally improves with increased shaping of the plasma cross section, such as higher elongation and higher triangularity. The stronger shaping, especially higher triangularity, leads to changes in the magnetic topology of the divertor. Because there are engineering and divertor physics issues associated with changes in the details of the divertor flux geometry, especially as the configuration transitions from a single-null (SN) divertor to a marginally balanced double-null (DN) divertor, we have undertaken a systematic evaluation of the plasma characteristics as the magnetic geometry is varied, particularly with respect to (1) energy confinement, (2) the response of the plasma to deuterium gas fueling, (3) the operational density range for the ELMing H-mode, and (4) heat flux sharing by the diverters. To quantify the degree of divertor imbalance (or equivalently, to what degree the shape is double-null or single-null), we define a parameter DRSEP. DRSEP is taken as the radial distance between the upper divertor separatrix and the lower divertor separatrix, as determined at the outboard midplane. For example, if DRSEP=O, the configuration is a magnetically balanced DN; if DRSEP = +1.0 cm, the divertor configuration is biased toward the upper divertor. Three examples are shown in Fig. 1. In the following discussions, VB drift is directed toward the lower divertor

  6. Detection of long nulls in PSR B1706-16, a pulsar with large timing irregularities

    Science.gov (United States)

    Naidu, Arun; Joshi, Bhal Chandra; Manoharan, P. K.; Krishnakumar, M. A.

    2018-04-01

    Single pulse observations, characterizing in detail, the nulling behaviour of PSR B1706-16 are being reported for the first time in this paper. Our regular long duration monitoring of this pulsar reveals long nulls of 2-5 h with an overall nulling fraction of 31 ± 2 per cent. The pulsar shows two distinct phases of emission. It is usually in an active phase, characterized by pulsations interspersed with shorter nulls, with a nulling fraction of about 15 per cent, but it also rarely switches to an inactive phase, consisting of long nulls. The nulls in this pulsar are concurrent between 326.5 and 610 MHz. Profile mode changes accompanied by changes in fluctuation properties are seen in this pulsar, which switches from mode A before a null to mode B after the null. The distribution of null durations in this pulsar is bimodal. With its occasional long nulls, PSR B1706-16 joins the small group of intermediate nullers, which lie between the classical nullers and the intermittent pulsars. Similar to other intermediate nullers, PSR B1706-16 shows high timing noise, which could be due to its rare long nulls if one assumes that the slowdown rate during such nulls is different from that during the bursts.

  7. Nonparametric Regression Estimation for Multivariate Null Recurrent Processes

    Directory of Open Access Journals (Sweden)

    Biqing Cai

    2015-04-01

    Full Text Available This paper discusses nonparametric kernel regression with the regressor being a \\(d\\-dimensional \\(\\beta\\-null recurrent process in presence of conditional heteroscedasticity. We show that the mean function estimator is consistent with convergence rate \\(\\sqrt{n(Th^{d}}\\, where \\(n(T\\ is the number of regenerations for a \\(\\beta\\-null recurrent process and the limiting distribution (with proper normalization is normal. Furthermore, we show that the two-step estimator for the volatility function is consistent. The finite sample performance of the estimate is quite reasonable when the leave-one-out cross validation method is used for bandwidth selection. We apply the proposed method to study the relationship of Federal funds rate with 3-month and 5-year T-bill rates and discover the existence of nonlinearity of the relationship. Furthermore, the in-sample and out-of-sample performance of the nonparametric model is far better than the linear model.

  8. Pair of null gravitating shells: III. Algebra of Dirac's observables

    International Nuclear Information System (INIS)

    Kouletsis, I; Hajicek, P

    2002-01-01

    The study of the two-shell system started in 'pair of null gravitating shells I and II' is continued. The pull back of the Liouville form to the constraint surface, which contains complete information about the Poisson brackets of Dirac observables, is computed in the singular double-null Eddington-Finkelstein (DNEF) gauge. The resulting formula shows that the variables conjugate to the Schwarzschild masses of the intershell spacetimes are simple combinations of the values of the DNEF coordinates on these spacetimes at the shells. The formula is valid for any number of in- and outgoing shells. After applying it to the two-shell system, the symplectic form is calculated for each component of the physical phase space; regular coordinates are found, defining it as a symplectic manifold. The symplectic transformation between the initial and final values of observables for the shell-crossing case is given

  9. Local modular Hamiltonians from the quantum null energy condition

    Science.gov (United States)

    Koeller, Jason; Leichenauer, Stefan; Levine, Adam; Shahbazi-Moghaddam, Arvin

    2018-03-01

    The vacuum modular Hamiltonian K of the Rindler wedge in any relativistic quantum field theory is given by the boost generator. Here we investigate the modular Hamiltonian for more general half-spaces which are bounded by an arbitrary smooth cut of a null plane. We derive a formula for the second derivative of the modular Hamiltonian with respect to the coordinates of the cut which schematically reads K''=Tv v . This formula can be integrated twice to obtain a simple expression for the modular Hamiltonian. The result naturally generalizes the standard expression for the Rindler modular Hamiltonian to this larger class of regions. Our primary assumptions are the quantum null energy condition—an inequality between the second derivative of the von Neumann entropy of a region and the stress tensor—and its saturation in the vacuum for these regions. We discuss the validity of these assumptions in free theories and holographic theories to all orders in 1 /N .

  10. Segmented Aperture Interferometric Nulling Testbed (SAINT) II: component systems update

    Science.gov (United States)

    Hicks, Brian A.; Bolcar, Matthew R.; Helmbrecht, Michael A.; Petrone, Peter; Burke, Elliot; Corsetti, James; Dillon, Thomas; Lea, Andrew; Pellicori, Samuel; Sheets, Teresa; Shiri, Ron; Agolli, Jack; DeVries, John; Eberhardt, Andrew; McCabe, Tyler

    2017-09-01

    This work presents updates to the coronagraph and telescope components of the Segmented Aperture Interferometric Nulling Testbed (SAINT). The project pairs an actively-controlled macro-scale segmented mirror with the Visible Nulling Coronagraph (VNC) towards demonstrating capabilities for the future space observatories needed to directly detect and characterize a significant sample of Earth-sized worlds around nearby stars in the quest for identifying those which may be habitable and possibly harbor life. Efforts to improve the VNC wavefront control optics and mechanisms towards repeating narrowband results are described. A narrative is provided for the design of new optical components aimed at enabling broadband performance. Initial work with the hardware and software interface for controlling the segmented telescope mirror is also presented.

  11. Lovelock vacua with a recurrent null vector field

    Czech Academy of Sciences Publication Activity Database

    Ortaggio, Marcello

    2018-01-01

    Roč. 97, č. 4 (2018), č. článku 044051. ISSN 2470-0010 R&D Projects: GA ČR GA13-10042S Institutional support: RVO:67985840 Keywords : Lovelock gravity * recurrent null vector field Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 4.568, year: 2016 https://journals.aps.org/prd/abstract/10.1103/PhysRevD.97.044051

  12. Spherical null geodesics of rotating Kerr black holes

    International Nuclear Information System (INIS)

    Hod, Shahar

    2013-01-01

    The non-equatorial spherical null geodesics of rotating Kerr black holes are studied analytically. Unlike the extensively studied equatorial circular orbits whose radii are known analytically, no closed-form formula exists in the literature for the radii of generic (non-equatorial) spherical geodesics. We provide here an approximate formula for the radii r ph (a/M;cosi) of these spherical null geodesics, where a/M is the dimensionless angular momentum of the black hole and cos i is an effective inclination angle (with respect to the black-hole equatorial plane) of the orbit. It is well-known that the equatorial circular geodesics of the Kerr spacetime (the prograde and the retrograde orbits with cosi=±1) are characterized by a monotonic dependence of their radii r ph (a/M;cosi=±1) on the dimensionless spin-parameter a/M of the black hole. We use here our novel analytical formula to reveal that this well-known property of the equatorial circular geodesics is actually not a generic property of the Kerr spacetime. In particular, we find that counter-rotating spherical null orbits in the range (3√(3)−√(59))/4≲cosi ph (a/M;cosi=const) on the dimensionless rotation-parameter a/M of the black hole. Furthermore, it is shown that spherical photon orbits of rapidly-rotating black holes are characterized by a critical inclination angle, cosi=√(4/7), above which the coordinate radii of the orbits approach the black-hole radius in the extremal limit. We prove that this critical inclination angle signals a transition in the physical properties of the spherical null geodesics: in particular, it separates orbits which are characterized by finite proper distances to the black-hole horizon from orbits which are characterized by infinite proper distances to the horizon.

  13. The quantum null energy condition in curved space

    Science.gov (United States)

    Fu, Zicao; Koeller, Jason; Marolf, Donald

    2017-11-01

    The quantum null energy condition (QNEC) is a conjectured bound on components (Tkk = Tab ka k^b) of the stress tensor along a null vector k a at a point p in terms of a second k-derivative of the von Neumann entropy S on one side of a null congruence N through p generated by k a . The conjecture has been established for super-renormalizeable field theories at points p that lie on a bifurcate Killing horizon with null tangent k a and for large-N holographic theories on flat space. While the Koeller-Leichenauer holographic argument clearly yields an inequality for general ( p, k^a) , more conditions are generally required for this inequality to be a useful QNEC. For d≤slant 3 , for arbitrary backgroud metric we show that the QNEC is naturally finite and independent of renormalization scheme when the expansion θ of N at the point p vanishes. This is consistent with the original QNEC conjecture which required θ and the shear σab to satisfy θ \\vert _p= \\dotθ\\vert p =0 , σab\\vert _p=0 . But for d=4, 5 more conditions than even these are required. In particular, we also require the vanishing of additional derivatives and a dominant energy condition. In the above cases the holographic argument does indeed yield a finite QNEC, though for d≥slant6 we argue these properties to fail even for weakly isolated horizons (where all derivatives of θ, σab vanish) that also satisfy a dominant energy condition. On the positive side, a corrollary to our work is that, when coupled to Einstein-Hilbert gravity, d ≤slant 3 holographic theories at large N satisfy the generalized second law (GSL) of thermodynamics at leading order in Newton’s constant G. This is the first GSL proof which does not require the quantum fields to be perturbations to a Killing horizon.

  14. Null half-supersymmetric solutions in five-dimensional supergravity

    International Nuclear Information System (INIS)

    Grover, Jai; Gutowski, Jan B.; Sabra, Wafic

    2008-01-01

    We classify half-supersymmetric solutions of gauged N = 2, D = 5 supergravity coupled to an arbitrary number of abelian vector multiplets for which all of the Killing spinors generate null Killing vectors. We show that there are four classes of solutions, and in each class we find the metric, scalars and gauge field strengths. When the scalar manifold is symmetric, the solutions correspond to a class of local near horizon geometries recently found by Kunduri and Lucietti.

  15. Yang-Mills theory in null path space

    International Nuclear Information System (INIS)

    Kent, S.L.

    1982-01-01

    A reformulation of classical GL(n,c) Yang-Mills theory is presented. The reformulation is in terms of a single matrix-valued function G on a six-dimensional subspace of the space of paths in Minkowski space, M. This subspace is defined as the null paths beginning at each point, (X/sup a/), of M and ending at future null infinity. A convenient parametrization of these paths is to give the Minkowski coordinates x/sup a/ of the starting point and the (complex) stereographic coordinates (xi, antixi) on S 2 which label the light cone generators of x/sup a/. A path is thus labeled by (x/sup a/,xi, antixi). The function G(x/sup a/,xi, antixi) is defined by the parallel propagation (with a given connection) of n linearly independent fiber vectors from x/sup a/ to null infinity along the (xi, antixi) generator. From knowledge of G(x/sup a/,xi, antixi) the connection one-form γ/sub a/ at the point x/sup a/ can be obtained is shown. Furthermore how the vacuum Yang-Mills equations can be imposed on the G is shown. This results in a rather complicated integro-differential equation for G which involves the characteristic initial data (essentially the radiation field) acting as the driving term. Two simple special cases are immediately obtainable; in the case of self-dual (or anti-self dual) fields the author obtains a simple derivation of the Sparling equation, namely delta G = -GA, while for Abelian (Maxwell) theories obtained the equation delta anti delta log G = -anti delta A-anti delta A, where A and its conjugate anti A are the characteristic free data given on null infinity. The latter equation is equivalent to the vacuum Maxwell equations

  16. Shearfree congruences of null geodesics and Killing tensors

    International Nuclear Information System (INIS)

    Dietz, W.; Ruediger, R.

    1980-01-01

    In this communication, the mutual connections between quantities that are generalizations of the notion of a a Killing vector field are investigated. A classification of these quantities in terms of a complex vector field αsub(a) is given. A common feature of all these quantities is that they imply the existence of a pair of shearfree geodetic null congruences. There are no explicit restrictions posed on the Ricci tensor. (author)

  17. Lovelock vacua with a recurrent null vector field

    Czech Academy of Sciences Publication Activity Database

    Ortaggio, Marcello

    2018-01-01

    Roč. 97, č. 4 (2018), č. článku 044051. ISSN 2470-0010 R&D Projects: GA ČR GA13-10042S Institutional support: RVO:67985840 Keywords : Lovelock gravity * recurrent null vector field Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 4.568, year: 2016 https://journals. aps .org/prd/abstract/10.1103/PhysRevD.97.044051

  18. In Search of the Null: The NCSA 2003 Presidential Address

    Directory of Open Access Journals (Sweden)

    Beth Davison

    2003-10-01

    Full Text Available Sociologists usually publish articles where the results show statistically significant differences between two groups of people. Results which show the opposite are generally called 'negative findings,' and are not considered publishable. Davison argues that we really ought to be looking for and encouraging the null finding, especially when social inequality and poverty are the issue. In addition, society as a whole should be working to eliminate poverty and inequality

  19. Zero emission city. Preliminary study; Null-Emissions-Stadt. Sondierungsstudie

    Energy Technology Data Exchange (ETDEWEB)

    Diefenbach, N; Enseling, A; Werner, P; Flade, A; Greiff, R; Hennings, D; Muehlich, E; Wullkopf, U; Sturm, P; Kieslich, W; Born, R; Grossklos, M; Hatteh, R; Mueller, K; Ratschow, A; Valouch-Fornoff, C

    2002-10-01

    The idea of a 'zero emission city' is investigated by the Institut Wohnen und Umwelt on behalf of the Federal Minister of Education and Research. After describing the current situation and defining the key parameters of a 'zero emission city', settlement structures, power supply, production processes and transportation are analyzed and linked with the communal action level to obtain a framework for research, activities and actions. The study ends with recommendations for a research programme 'zero emission city'. (orig.) [German] Die von den Staedten der Industrielaender ausgehenden Emissionen stellen im Hinblick auf die globalen Belastungen wie z.B. Treibhauseffekt, Ozonabbau und Versauerung das Hauptproblem dar. Aus diesem Grunde bietet es sich an, den Gedanken der 'Null-Emissions-Stadt', der Vision einer moeglichst emissionsfreien Stadt, aufzugreifen und auf seine Tragfaehigkeit fuer innovative Handlungsmodelle forschungsstrategisch zu ueberpruefen. Das Bundesministerium fuer Bildung und Forschung hat das Institut Wohnen und Umwelt beauftragt, in einer Sondierungsstudie dieser Fragestellung nachzugehen. Nach der Festlegung der Ausgangsbedingungen und Eckpunkte der Vision 'Null-Emissions-Stadt' und der Analyse der vier Handlungsfelder Siedlungsstrukturen, Energieversorgung, Produktionsprozesse (Kreislaufwirtschaft) und Verkehr werden diese aufgegriffen und mit der kommunalen Handlungsebene verknuepft und zu einem Forschungs-, Handlungs- und moeglichen Aktionsrahmen zusammengefuegt. Die Studie schliesst mit Hinweisen fuer die Gestaltung eines Forschungsprogramms 'Null-Emissions-Stadt'. (orig.)

  20. The Quantum Focussing Conjecture and Quantum Null Energy Condition

    Science.gov (United States)

    Koeller, Jason

    Evidence has been gathering over the decades that spacetime and gravity are best understood as emergent phenomenon, especially in the context of a unified description of quantum mechanics and gravity. The Quantum Focussing Conjecture (QFC) and Quantum Null Energy Condition (QNEC) are two recently-proposed relationships between entropy and geometry, and energy and entropy, respectively, which further strengthen this idea. In this thesis, we study the QFC and the QNEC. We prove the QNEC in a variety of contexts, including free field theories on Killing horizons, holographic theories on Killing horizons, and in more general curved spacetimes. We also consider the implications of the QFC and QNEC in asymptotically flat space, where they constrain the information content of gravitational radiation arriving at null infinity, and in AdS/CFT, where they are related to other semiclassical inequalities and properties of boundary-anchored extremal area surfaces. It is shown that the assumption of validity and vacuum-state saturation of the QNEC for regions of flat space defined by smooth cuts of null planes implies a local formula for the modular Hamiltonian of these regions. We also demonstrate that the QFC as originally conjectured can be violated in generic theories in d ≥ 5, which led the way to an improved formulation subsequently suggested by Stefan Leichenauer.

  1. Zero emission city. Preliminary study; Null-Emissions-Stadt. Sondierungsstudie

    Energy Technology Data Exchange (ETDEWEB)

    Diefenbach, N.; Enseling, A.; Werner, P.; Flade, A.; Greiff, R.; Hennings, D.; Muehlich, E.; Wullkopf, U.; Sturm, P.; Kieslich, W.; Born, R.; Grossklos, M.; Hatteh, R.; Mueller, K.; Ratschow, A.; Valouch-Fornoff, C.

    2002-10-01

    The idea of a 'zero emission city' is investigated by the Institut Wohnen und Umwelt on behalf of the Federal Minister of Education and Research. After describing the current situation and defining the key parameters of a 'zero emission city', settlement structures, power supply, production processes and transportation are analyzed and linked with the communal action level to obtain a framework for research, activities and actions. The study ends with recommendations for a research programme 'zero emission city'. (orig.) [German] Die von den Staedten der Industrielaender ausgehenden Emissionen stellen im Hinblick auf die globalen Belastungen wie z.B. Treibhauseffekt, Ozonabbau und Versauerung das Hauptproblem dar. Aus diesem Grunde bietet es sich an, den Gedanken der 'Null-Emissions-Stadt', der Vision einer moeglichst emissionsfreien Stadt, aufzugreifen und auf seine Tragfaehigkeit fuer innovative Handlungsmodelle forschungsstrategisch zu ueberpruefen. Das Bundesministerium fuer Bildung und Forschung hat das Institut Wohnen und Umwelt beauftragt, in einer Sondierungsstudie dieser Fragestellung nachzugehen. Nach der Festlegung der Ausgangsbedingungen und Eckpunkte der Vision 'Null-Emissions-Stadt' und der Analyse der vier Handlungsfelder Siedlungsstrukturen, Energieversorgung, Produktionsprozesse (Kreislaufwirtschaft) und Verkehr werden diese aufgegriffen und mit der kommunalen Handlungsebene verknuepft und zu einem Forschungs-, Handlungs- und moeglichen Aktionsrahmen zusammengefuegt. Die Studie schliesst mit Hinweisen fuer die Gestaltung eines Forschungsprogramms 'Null-Emissions-Stadt'. (orig.)

  2. PERSEE: a nulling interferometer with dynamic correction of external perturbations

    Science.gov (United States)

    Jacquinod, S.; Houairi, K.; Le Duigou, J.-M.; Barillot, M.; Cassaing, F.; Réess, J.-M.; Hénault, F.; Sorrente, B.; Morinaud, G.; Amans, J.-P.; Coudé du Foresto, V.; Ollivier, M.

    2017-11-01

    Nulling interferometry is one of the direct detection methods assessed to find and characterize extrasolar planets and particularly telluric ones. Several projects such as Darwin [1;2], TPF-I [3;4], PEGASE [5;6] or FKSI [7], are currently considered. One of the main issues is the feasibility of a stable polychromatic null despite the presence of significant disturbances, induced by vibrations, atmospheric turbulence on the ground or satellite drift. Satisfying all these requirements is a great challenge and a key issue of these missions. In the context of the PEGASE mission, it was decided (in 2006), to build a laboratory demonstrator named PERSEE. It is the first laboratory setup which couples deep nulling interferometry with a free flying GNC simulator [8]. It is developed by a consortium composed of CNES, IAS, LESIA, OCA, ONERA, and TAS. In this paper, we detail the main objectives, the set-up and the function of the bench. We describe all the subsystems and we focus particularly on two key points of PERSEE: the beam combiner and the Fringe tracker.

  3. Kastor-Traschen black holes, null geodesics and conformal circles

    International Nuclear Information System (INIS)

    Casey, Stephen

    2012-01-01

    The Kastor-Traschen metric is a time-dependent solution of the Einstein-Maxwell equations with positive cosmological constant Λ which can be used to describe an arbitrary number of charged dynamical black holes. In this paper, we consider the null geodesic structure of this solution, in particular, focusing on the projection to the space of orbits of the timelike conformal retraction. It is found that these projected light rays arise as integral curves of a system of third-order ordinary differential equations. This system is not uniquely defined, however, and we use the inherent freedom to construct a new system whose integral curves coincide with the projection of distinguished null curves of Kastor-Traschen arising from a magnetic flow. We discuss our results in the one-centre case and demonstrate a link to conformal circles in the limit Λ → 0. We also show how to construct analytic expressions for the projected null geodesics of this metric by exploiting a well-known diffeomorphism between the K-T metric and extremal Reissner-Nordstrom-de Sitter. We make some remarks about the two-centre solution and demonstrate a link with the one-centre case. (paper)

  4. "Time sweet time": circadian characterization of galectin-1 null mice

    Directory of Open Access Journals (Sweden)

    Rabinovich Gabriel A

    2010-04-01

    Full Text Available Abstract Background Recent evidence suggests a two-way interaction between the immune and circadian systems. Circadian control of immune factors, as well as the effect of immunological variables on circadian rhythms, might be key elements in both physiological and pathological responses to the environment. Among these relevant factors, galectin-1 is a member of a family of evolutionarily-conserved glycan-binding proteins with both extracellular and intracellular effects, playing important roles in immune cell processes and inflammatory responses. Many of these actions have been studied through the use of mice with a null mutation in the galectin-1 (Lgals1 gene. To further analyze the role of endogenous galectin-1 in vivo, we aimed to characterize the circadian behavior of galectin-1 null (Lgals1-/- mice. Methods We analyzed wheel-running activity in light-dark conditions, constant darkness, phase responses to light pulses (LP at circadian time 15, and reentrainment to 6 hour shifts in light-dark schedule in wild-type (WT and Lgals1-/- mice. Results We found significant differences in free-running period, which was longer in mutant than in WT mice (24.02 vs 23.57 h, p alpha (14.88 vs. 12.35 circadian h, p Conclusions Given the effect of a null mutation on circadian period and entrainment, we indicate that galectin-1 could be involved in the regulation of murine circadian rhythmicity. This is the first study implicating galectin-1 in the mammalian circadian system.

  5. Variational principle for gravity with null and non-null boundaries: a unified boundary counter-term

    Energy Technology Data Exchange (ETDEWEB)

    Parattu, Krishnamohan; Chakraborty, Sumanta; Padmanabhan, T. [IUCAA, Post Bag 4, Pune (India)

    2016-03-15

    It is common knowledge that the Einstein-Hilbert action does not furnish a well-posed variational principle. The usual solution to this problem is to add an extra boundary term to the action, called a counter-term, so that the variational principle becomes well-posed. When the boundary is spacelike or timelike, the Gibbons-Hawking-York counter-term is the most widely used. For null boundaries, we had proposed a counter-term in a previous paper. In this paper, we extend the previous analysis and propose a counter-term that can be used to eliminate variations of the ''off-the-surface'' derivatives of the metric on any boundary, regardless of its spacelike, timelike or null nature. (orig.)

  6. Left cardiac isomerism in the Sonic hedgehog null mouse.

    Science.gov (United States)

    Hildreth, Victoria; Webb, Sandra; Chaudhry, Bill; Peat, Jonathan D; Phillips, Helen M; Brown, Nigel; Anderson, Robert H; Henderson, Deborah J

    2009-06-01

    Sonic hedgehog (Shh) is a secreted morphogen necessary for the production of sidedness in the developing embryo. In this study, we describe the morphology of the atrial chambers and atrioventricular junctions of the Shh null mouse heart. We demonstrate that the essential phenotypic feature is isomerism of the left atrial appendages, in combination with an atrioventricular septal defect and a common atrioventricular junction. These malformations are known to be frequent in humans with left isomerism. To confirm the presence of left isomerism, we show that Pitx2c, a recognized determinant of morphological leftness, is expressed in the Shh null mutants on both the right and left sides of the inflow region, and on both sides of the solitary arterial trunk exiting from the heart. It has been established that derivatives of the second heart field expressing Isl1 are asymmetrically distributed in the developing normal heart. We now show that this population is reduced in the hearts from the Shh null mutants, likely contributing to the defects. To distinguish the consequences of reduced contributions from the second heart field from those of left-right patterning disturbance, we disrupted the movement of second heart field cells into the heart by expressing dominant-negative Rho kinase in the population of cells expressing Isl1. This resulted in absence of the vestibular spine, and presence of atrioventricular septal defects closely resembling those seen in the hearts from the Shh null mutants. The primary atrial septum, however, was well formed, and there was no evidence of isomerism of the atrial appendages, suggesting that these features do not relate to disruption of the contributions made by the second heart field. We demonstrate, therefore, that the Shh null mouse is a model of isomerism of the left atrial appendages, and show that the recognized associated malformations found at the venous pole of the heart in the setting of left isomerism are likely to arise from

  7. Apoptosis in spermatogonia irradiated P53 null mice

    International Nuclear Information System (INIS)

    Streit-Bianchi, M.; Hendry, J.H.; Roberts, S.A.; Morris, J.D.; Durgaryan, A.A.

    2007-01-01

    Complete text of publication follows. The exposure of germ cells to ionizing radiations is of concern both from high-dose therapeutic exposures and from low doses causing deleterious trans-generational mutations. P53 protein plays an important role in cellular damage and is expressed in the testis normally during meiosis, its expression being localised to the preleptotene and early/mid pachytene spermatocytes. P53 null mice, heterozygotes possessing a 129 Sv/C57BL6 genetic background and B6D2F1 mice have been irradiated to 1 and 2 Gy single doses. Fractionated exposures of 1+1 Gy at 4 hours interval were also carried out. Apoptosis induction, spermatogonia and spermatocytes survival were assessed by microscope analysis of histological samples at 4 to 96 hours after irradiation in time-course experiments. The same end-points were also assessed at 72 and 96 hours after irradiation to single doses in the region between 20cGy to 2Gy. A dose dependent level of p53 expression was observed at 4 hours after irradiation to 1 and 2 Gy which returned to normal level by 24 hours. Our data support a two process mode of apoptosis with a first wave around 12 hours followed by a second wave at 2-3 days. The first wave apoptosis is substantially reduced in p53 null mice whereas the second wave is reduced in B6D2F1 mice. The initial increase in apoptosis was delayed in some stages of the of germ cells development which were identified by the spermatids shape. Clear correlation exists between apoptosis and survival assessed in stage XI-XII Tubules 72 hours after irradiation. The data are in agreement with other data in literature indicating that irradiated spermatogonia die through apoptosis. The lack of apoptosis observed in p53 null mice results in a very high survival rate of daughter cells assessed later. Theses spermatocytes and the following progenitor cells are likely to carry mutations as most will not die in the smaller second wave of apoptosis observed 3 days after

  8. Dental Sealants Prevent Cavities

    Science.gov (United States)

    ... Digital Press Kit Read the MMWR Science Clips Dental Sealants Prevent Cavities Effective protection for children Language: ... more use of sealants and reimbursement of services. Dental care providers can Apply sealants to children at ...

  9. Dental Care in Scleroderma

    Science.gov (United States)

    Dental Care in Scleroderma People living with scleroderma face unique challenges while trying to maintain their oral ... They are more likely to be affected by dental conditions such as small mouth, dry mouth, jaw ...

  10. American Dental Association

    Science.gov (United States)

    ... CE providers and find CE courses. Commission on Dental Accreditation Explore CODA's role and find accredited schools and programs Joint Commission on National Dental Examinations Learn about the examinations used in licensing ...

  11. Diabetes: Dental Tips

    Science.gov (United States)

    Diabetes: Dental Tips For more copies contact: National Institute of Dental and Craniofacial Research National Oral Health Information Clearinghouse ... damage the gum and bone that hold your teeth in place and may lead to painful chewing ...

  12. American Dental Hygienists' Association

    Science.gov (United States)

    ... Now Autumn Giving: ‘Fall’ into the Future of Dental Hygiene Support the Institute for Oral Health! Give ... best for your patients! Learn More Sidebar Menu Dental Hygiene Programs Continuing Education Career Center Annual Conference ...

  13. Dental Effluent Guidelines

    Science.gov (United States)

    Overview and documents for Dental Office Category regulation (40 CFR Part 441); comprising pretreatment standards for discharges of dental amalgam pollutants, including mercury, into publicly owned treatment works (POTWs).

  14. Dental Encounter System (DES)

    Data.gov (United States)

    Department of Veterans Affairs — Dental Encounter System (DES) is an automated health care application designed to capture critical data about the operations of VA Dental Services. Information on...

  15. Dental Caries (Tooth Decay)

    Science.gov (United States)

    ... Materials Contact Us Home Research Data & Statistics Dental Caries (Tooth Decay) Dental caries (tooth decay) remains the most prevalent chronic disease ... adults, even though it is largely preventable. Although caries has significantly decreased for most Americans over the ...

  16. Dental Caries (Tooth Decay)

    Science.gov (United States)

    ... Contact Us Home Research Data & Statistics Share Dental Caries (Tooth Decay) Dental caries (tooth decay) remains the most prevalent chronic disease ... adults, even though it is largely preventable. Although caries has significantly decreased for most Americans over the ...

  17. The dynamics of TGF-β in dental pulp, odontoblasts and dentin.

    Science.gov (United States)

    Niwa, Takahiko; Yamakoshi, Yasuo; Yamazaki, Hajime; Karakida, Takeo; Chiba, Risako; Hu, Jan C-C; Nagano, Takatoshi; Yamamoto, Ryuji; Simmer, James P; Margolis, Henry C; Gomi, Kazuhiro

    2018-03-13

    Transforming growth factor-beta (TGF-β) is critical for cell proliferation and differentiation in dental pulp. Here, we show the dynamic mechanisms of TGF-β in porcine dental pulp, odontoblasts and dentin. The mRNA of latent TGF-β1 and TGF-β3 is predominantly expressed in odontoblasts, whereas the mRNA expression level of latent TGF-β2 is high in dental pulp. TGF-β1 is a major isoform of TGF-β, and latent TGF-β1, synthesized in dental pulp, is primarily activated by matrix metalloproteinase 11 (MMP11). Activated TGF-β1 enhances the mRNA expression levels of MMP20 and full-length dentin sialophosphoprotein (DSPP) in dental pulp cells, coinciding with the induction of odontoblast differentiation. Latent TGF-β1 synthesized in odontoblasts is primarily activated by MMP2 and MMP20 in both odontoblasts and dentin. The activity level of TGF-β1 was reduced in the dentin of MMP20 null mice, although the amount of latent TGF-β1 expression did not change between wild-type and MMP20 null mice. TGF-β1 activity was reduced with the degradation of DSPP-derived proteins that occurs with ageing. We propose that to exert its multiple biological functions, TGF-β1 is involved in a complicated dynamic interaction with matrix metalloproteinases (MMPs) and/or DSPP-derived proteins present in dental pulp, odontoblasts and dentin.

  18. Vacuum Nuller Testbed Performance, Characterization and Null Control

    Science.gov (United States)

    Lyon, R. G.; Clampin, M.; Petrone, P.; Mallik, U.; Madison, T.; Bolcar, M.; Noecker, C.; Kendrick, S.; Helmbrecht, M. A.

    2011-01-01

    The Visible Nulling Coronagraph (VNC) can detect and characterize exoplanets with filled, segmented and sparse aperture telescopes, thereby spanning the choice of future internal coronagraph exoplanet missions. NASA/Goddard Space Flight Center (GSFC) has developed a Vacuum Nuller Testbed (VNT) to advance this approach, and assess and advance technologies needed to realize a VNC as a flight instrument. The VNT is an ultra-stable testbed operating at 15 Hz in vacuum. It consists of a MachZehnder nulling interferometer; modified with a "W" configuration to accommodate a hexpacked MEMS based deformable mirror (DM), coherent fiber bundle and achromatic phase shifters. The 2-output channels are imaged with a vacuum photon counting camera and conventional camera. Error-sensing and feedback to DM and delay line with control algorithms are implemented in a real-time architecture. The inherent advantage of the VNC is that it is its own interferometer and directly controls its errors by exploiting images from bright and dark channels simultaneously. Conservation of energy requires the sum total of the photon counts be conserved independent of the VNC state. Thus sensing and control bandwidth is limited by the target stars throughput, with the net effect that the higher bandwidth offloads stressing stability tolerances within the telescope. We report our recent progress with the VNT towards achieving an incremental sequence of contrast milestones of 10(exp 8) , 10(exp 9) and 10(exp 10) respectively at inner working angles approaching 2A/D. Discussed will be the optics, lab results, technologies, and null control. Shown will be evidence that the milestones have been achieved.

  19. A visualization of null geodesics for the bonnor massive dipole

    Directory of Open Access Journals (Sweden)

    G. Andree Oliva Mercado

    2015-08-01

    Full Text Available In this work we simulate null geodesics for the Bonnor massive dipole metric by implementing a symbolic-numerical algorithm in Sage and Python. This program is also capable of visualizing in 3D, in principle, the geodesics for any given metric. Geodesics are launched from a common point, collectively forming a cone of light beams, simulating a solid-angle section of a point source in front of a massive object with a magnetic field. Parallel light beams also were considered, and their bending due to the curvature of the space-time was simulated.

  20. Do electromagnetic waves always propagate along null geodesics?

    International Nuclear Information System (INIS)

    Asenjo, Felipe A; Hojman, Sergio A

    2017-01-01

    We find exact solutions to Maxwell equations written in terms of four-vector potentials in non–rotating, as well as in Gödel and Kerr spacetimes. We show that Maxwell equations can be reduced to two uncoupled second-order differential equations for combinations of the components of the four-vector potential. Exact electromagnetic waves solutions are written on given gravitational field backgrounds where they evolve. We find that in non–rotating spherical symmetric spacetimes, electromagnetic waves travel along null geodesics. However, electromagnetic waves on Gödel and Kerr spacetimes do not exhibit that behavior. (paper)

  1. Two-loop string theory on null compactifications

    International Nuclear Information System (INIS)

    Cove, Henry C.D.; Szabo, Richard J.

    2006-01-01

    We compute the two-loop contributions to the free energy in the null compactification of perturbative string theory at finite temperature. The cases of bosonic, type II and heterotic strings are all treated. The calculation exploits an explicit reductive parametrization of the moduli space of infinite-momentum frame string worldsheets in terms of branched cover instantons. Various arithmetic and physical properties of the instanton sums are described. Applications to symmetric product orbifold conformal field theories and to the matrix string theory conjecture are also briefly discussed

  2. Twisting null geodesic congruences and the Einstein-Maxwell equations

    International Nuclear Information System (INIS)

    Newman, Ezra T; Silva-Ortigoza, Gilberto

    2006-01-01

    In a recent article, we returned to the study of asymptotically flat solutions of the vacuum Einstein equations with a rather unconventional point of view. The essential observation in that work was that from a given asymptotically flat vacuum spacetime with a given Bondi shear, one can find a class of asymptotically shear-free (but, in general, twisting) null geodesic congruences where the class was uniquely given up to the arbitrary choice of a complex analytic 'worldline' in a four-dimensional complex space. By imitating certain terms in the Weyl tensor that are found in the algebraically special type II metrics, this complex worldline could be made unique and given-or assigned-the physical meaning as the complex centre of mass. Equations of motion for this case were found. The purpose of the present work is to extend those results to asymptotically flat solutions of the Einstein-Maxwell equations. Once again, in this case, we get a class of asymptotically shear-free null geodesic congruences depending on a complex worldline in the same four-dimensional complex space. However in this case there will be, in general, two distinct but uniquely chosen worldlines, one of which can be assigned as the complex centre of charge while the other could be called the complex centre of mass. Rather than investigating the situation where there are two distinct complex worldlines, we study instead the special degenerate case where the two worldlines coincide, i.e., where there is a single unique worldline. This mimics the case of algebraically special Einstein-Maxwell fields where the degenerate principle null vector of the Weyl tensor coincides with a Maxwell principle null vector. Again we obtain equations of motion for this worldline-but explicitly found here only in an approximation. Though there are ambiguities in assigning physical meaning to different terms it appears as if reliance on the Kerr and charged Kerr metrics and classical electromagnetic radiation theory helps

  3. The null-event method in computer simulation

    International Nuclear Information System (INIS)

    Lin, S.L.

    1978-01-01

    The simulation of collisions of ions moving under the influence of an external field through a neutral gas to non-zero temperatures is discussed as an example of computer models of processes in which a probe particle undergoes a series of interactions with an ensemble of other particles, such that the frequency and outcome of the events depends on internal properties of the second particles. The introduction of null events removes the need for much complicated algebra, leads to a more efficient simulation and reduces the likelihood of logical error. (Auth.)

  4. Null geodesic deviation II. Conformally flat space--times

    International Nuclear Information System (INIS)

    Peters, P.C.

    1975-01-01

    The equation of geodesic deviation is solved in conformally flat space--time in a covariant manner. The solution is given as an integral equation for general geodesics. The solution is then used to evaluate second derivatives of the world function and derivatives of the parallel propagator, which need to be known in order to find the Green's function for wave equations in curved space--time. A method of null geodesic limits of two-point functions is discussed, and used to find the scalar Green's function as an iterative series

  5. DENTAL SCHOOL PLANNING.

    Science.gov (United States)

    GALAGAN, DONALD J.

    THIS DISCUSSION PRESENTS A COMPLETE PICTURE OF THE CURRENT STATE OF DENTAL EDUCATION WITH SUGGESTIONS FOR MEETING THE DEMANDS FOR DENTAL STAFF AND FACILITIES. THE AREAS INVESTIGATED ARE (1) OBJECTIVES IN DENTAL EDUCATION--COURSES, TEACHING MODES, INNOVATIONS IN CURRICULUM, COORDINATION OF BASIC AND CLINICAL INSTRUCTION, (2) FACILITY…

  6. Stress Among Dental Students

    NARCIS (Netherlands)

    A.M. Alzahem (Abdullah)

    2015-01-01

    markdownabstractAbstract Dental students are facing many stressors in dental education, causing many negative outcomes. The most common are the exams and the clinical requirements. We suggest exposing the dental students to patient care as early as possible in their curriculum. This can help to

  7. Marketing Dental Services | Tuominen | Tanzania Dental Journal

    African Journals Online (AJOL)

    Tanzania Dental Journal. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 9, No 1 (2000) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. Marketing Dental Services. R Tuominen. Abstract. No Abstract.

  8. Dental Radiographs Ordered by Dental Professionals: an ...

    African Journals Online (AJOL)

    Conclusions: Even in resource limited settings dental caries is still the regular indication for taking dental radiographs, and periapical views are the most frequent type of radiograph ordered. Maxillary central incisors and mandibular molars were types of teeth commonly x-rayed mainly due to the aesthetic importance of the ...

  9. The new null testing method for the special optical window

    Science.gov (United States)

    Huang, Changchun

    2009-07-01

    The high speed, high precision and wide range specifications are requirement for the modern aircraft, which the traditional hemispherical dome can't achieve now, and the novel conformal window instead can enhance the aerodynamic performance of the aircraft obviously. To reduce the aerodynamic drag and radar cross-section, the window geometry is generally aspheric in shape. As a result, the involved fabrication and testing processes are much more challenging than that of conventional optics and must be mastered before these windows and systems can be implemented at an acceptable cost and risk. Metrology is one of the critical areas required to advance the conformal window technology. But as the surface of these conformal windows is not the traditional sphere lens, the measurement method for it is infeasible with the conventional optics measurement processes. This paper we express the development of testing technology for the special conformal windows in brief, and emphatically introduces one available novel testing method- a new null testing, and here based on the theory of compensation methods, The principle of Offner's refractive null lens has been extended to test the transmission wavefront through conformal window optics and provide feedback during surface fabrication. a compensator system for the was designed for the conformal window is given which parameters are 100mm for its aperture and two parabolic surface as conformal window, the final residual wavefront error(RMS) of which is less than 1/20λ(λ=632.8nm).

  10. Pituitary null cell adenoma in a domestic llama (Lama glama).

    Science.gov (United States)

    Chalkley, M D; Kiupel, M; Draper, A C E

    2014-07-01

    Pituitary gland neoplasia has been reported rarely in camelids. A 12-year-old neutered male llama (Lama glama) presented with lethargy, inappetence and neurological signs. On physical examination, the llama was mentally dull and exhibited compulsive pacing and circling to the left. Complete blood count and serum biochemistry revealed haemoconcentration, mild hypophosphataemia, hyperglycaemia, hypercreatininaemia and hyperalbuminaemia. Humane destruction was elected due to rapid clinical deterioration and poor prognosis. Post-mortem examination revealed a pituitary macroadenoma and bilateral internal hydrocephalus. Microscopically, the pituitary tumour was composed of neoplastic chromophobic pituitary cells. Ultrastructural studies revealed similar neoplastic cells to those previously described in human null cell adenomas. Immunohistochemically, the neoplastic cells were strongly immunoreactive for neuroendocrine markers (synaptophysin and chromogranin A), but did not exhibit immunoreactivity for epithelial, mesenchymal, neuronal and all major pituitary hormone markers (adrenocorticotropic hormone, follicle stimulating hormone, growth hormone, luteinizing hormone, melanocyte-stimulating hormone, prolactin and thyroid stimulating hormone), consistent with the diagnosis of a pituitary null cell adenoma. This is the first report of pituitary neoplasia in a llama. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Randomizing growing networks with a time-respecting null model

    Science.gov (United States)

    Ren, Zhuo-Ming; Mariani, Manuel Sebastian; Zhang, Yi-Cheng; Medo, Matúš

    2018-05-01

    Complex networks are often used to represent systems that are not static but grow with time: People make new friendships, new papers are published and refer to the existing ones, and so forth. To assess the statistical significance of measurements made on such networks, we propose a randomization methodology—a time-respecting null model—that preserves both the network's degree sequence and the time evolution of individual nodes' degree values. By preserving the temporal linking patterns of the analyzed system, the proposed model is able to factor out the effect of the system's temporal patterns on its structure. We apply the model to the citation network of Physical Review scholarly papers and the citation network of US movies. The model reveals that the two data sets are strikingly different with respect to their degree-degree correlations, and we discuss the important implications of this finding on the information provided by paradigmatic node centrality metrics such as indegree and Google's PageRank. The randomization methodology proposed here can be used to assess the significance of any structural property in growing networks, which could bring new insights into the problems where null models play a critical role, such as the detection of communities and network motifs.

  12. Geometry of extended null supersymmetry in M theory

    International Nuclear Information System (INIS)

    Conamhna, Oisin A.P. Mac

    2006-01-01

    For supersymmetric spacetimes in 11 dimensions admitting a null Killing spinor, a set of explicit necessary and sufficient conditions for the existence of any number of arbitrary additional Killing spinors is derived. The necessary and sufficient conditions are comprised of algebraic relationships, linear in the spinorial components, between the spinorial components and their first derivatives, and the components of the spin connection and four-form. The integrability conditions for the Killing spinor equation are also analyzed in detail, to determine which components of the field equations are implied by arbitrary additional supersymmetries and the four-form Bianchi identity. This provides a complete formalism for the systematic and exhaustive investigation of all spacetimes with extended null supersymmetry in 11 dimensions. The formalism is employed to show that the general bosonic solution of 11 dimensional supergravity admitting a G 2 structure defined by four Killing spinors is either locally the direct product of R 1,3 with a seven-manifold of G 2 holonomy, or locally the Freund-Rubin direct product of AdS 4 with a seven-manifold of weak G 2 holonomy. In addition, all supersymmetric spacetimes admitting a (G 2 xR 7 )xR 2 structure are classified

  13. Extrasolar Planetary Imaging Coronagraph (EPIC): visible nulling cornagraph testbed results

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Melnick, Gary; Tolls, Volker; Woodruff, Robert; Vasudevan, Gopal

    2008-07-01

    The Extrasolar Planetary Imaging Coronagraph (EPIC) is a NASA Astrophysics Strategic Mission Concept under study for the upcoming Exoplanet Probe. EPIC's mission would be to image and characterize extrasolar giant planets, and potential super-Earths, in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys and potentially some transits, determine orbital inclinations and masses, characterize the atmospheres of gas giants around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched into a heliocentric Earth trailing drift-away orbit, with a 3-year mission lifetime (5 year goal) and will revisit planets at least three times. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables high order starlight suppression in broadband light. To demonstrate the VNC approach and advance it's technology readiness the NASA/Goddard Space Flight Center and Lockheed-Martin have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed.

  14. Extrasolar Planetary Imaging Coronagraph: Visible Nulling Coronagraph Testbed Results

    Science.gov (United States)

    Lyon, Richard G.

    2008-01-01

    The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 3-year mission lifetime ( 5 year goal) and will revisit planets at least three times at intervals of 9 months. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables high order starlight suppression in broadband light. To demonstrate the VNC approach and advance it's technology readiness the NASA Goddard Space Flight Center and Lockheed-Martin have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed,

  15. Non-dissipative electromagnetic media with two Lorentz null cones

    International Nuclear Information System (INIS)

    Dahl, Matias F.

    2013-01-01

    We study Maxwell’s equations on a 4-manifold where the electromagnetic medium is modeled by an antisymmetric (2/2 )-tensor with 21 real coefficients. In this setting the Fresnel surface is a fourth-order polynomial surface that describes the dynamical response of the medium in the geometric optics limit. For example, in an isotropic medium the Fresnel surface is a Lorentz null cone. The contribution of this paper is the pointwise description of all electromagnetic medium tensors κ with real coefficients that satisfy the following three conditions: (i)medium κ is invertible, (ii)medium κ is skewon-free, or non-dissipative, (iii)the Fresnel surface of κ is the union of two distinct Lorentz null cones. We show that there are only three classes of media with these properties and give explicit expressions in local coordinates for each class. - Highlights: ► We find two new electromagnetic media classes for which the Fresnel surface decomposes into two light cones. ► In a suitable setting we classify all electromagnetic media where this is the case. ► We find an electromagnetic medium tensor with three different signal speeds in one direction. ► The work is related to [5], which classifies all media with one light cone (in a suitable setting).

  16. Plate with a hole obeys the averaged null energy condition

    International Nuclear Information System (INIS)

    Graham, Noah; Olum, Ken D.

    2005-01-01

    The negative energy density of Casimir systems appears to violate general relativity energy conditions. However, one cannot test the averaged null energy condition (ANEC) using standard calculations for perfectly reflecting plates, because the null geodesic would have to pass through the plates, where the calculation breaks down. To avoid this problem, we compute the contribution to ANEC for a geodesic that passes through a hole in a single plate. We consider both Dirichlet and Neumann boundary conditions in two and three space dimensions. We use a Babinet's principle argument to reduce the problem to a complementary finite disk correction to the perfect mirror result, which we then compute using scattering theory in elliptical and spheroidal coordinates. In the Dirichlet case, we find that the positive correction due to the hole overwhelms the negative contribution of the infinite plate. In the Neumann case, where the infinite plate gives a positive contribution, the hole contribution is smaller in magnitude, so again ANEC is obeyed. These results can be extended to the case of two plates in the limits of large and small hole radii. This system thus provides another example of a situation where ANEC turns out to be obeyed when one might expect it to be violated

  17. Meterwavelength Single-pulse Polarimetric Emission Survey. III. The Phenomenon of Nulling in Pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Basu, Rahul; Mitra, Dipanjan; Melikidze, George I., E-mail: rahulbasu.astro@gmail.com [Janusz Gil Institute of Astronomy, University of Zielona Góra, ul. Szafrana 2, 65–516 Zielona Góra (Poland)

    2017-09-10

    A detailed analysis of nulling was conducted for the pulsars studied in the Meterwavelength Single-pulse Polarimetric Emission Survey. We characterized nulling in 36 pulsars including 17 pulsars where the phenomenon was reported for the first time. The most dominant nulls lasted for a short duration, less than five periods. Longer duration nulls extending to hundreds of periods were also seen in some cases. A careful analysis showed the presence of periodicities in the transition from the null to the burst states in 11 pulsars. In our earlier work, fluctuation spectrum analysis showed multiple periodicities in 6 of these 11 pulsars. We demonstrate that the longer periodicity in each case was associated with nulling. The shorter periodicities usually originate from subpulse drifting. The nulling periodicities were more aligned with the periodic amplitude modulation, indicating a possible common origin for both. The most prevalent nulls last for a single period and can be potentially explained using random variations affecting the plasma processes in the pulsar magnetosphere. On the other hand, longer-duration nulls require changes in the pair-production processes, which need an external triggering mechanism for the changes. The presence of periodic nulling puts an added constraint on the triggering mechanism, which also needs to be periodic.

  18. Dental education in Peru.

    Science.gov (United States)

    Komabayashi, Takashi; Sato, Manuel; Rodiguez, Lyly; Sato, Doris; Bird, William F

    2008-09-01

    This paper provides information about Peru's dental history and dental school system, including the curriculum and dental licensure. With the increase in the number of dental schools in Peru, the number of dentists is also increasing. Until 1965, Peru had only three dental schools; currently, there are 14. Four of these dental schools are public, and ten are private. A five- or six-year dental program leads to the B.D.S. degree. After successful completion of a thesis defense or competency examination, the D.D.S. degree is awarded. The D.D.S. is mandatory for practicing dentistry in Peru. Currently, there are approximately 14,000 active dentists, with a dentist-patient ratio of approximately 1:2,000.

  19. Description and Documentation of the Dental School Dental Delivery System.

    Science.gov (United States)

    Chase, Rosen and Wallace, Inc., Alexandria, VA.

    A study was undertaken to describe and document the dental school dental delivery system using an integrated systems approach. In late 1976 and early 1977, a team of systems analysts and dental consultants visited three dental schools to observe the delivery of dental services and patient flow and to interview administrative staff and faculty.…

  20. WITHDRAWN: Hypnosis for children undergoing dental treatment.

    Science.gov (United States)

    Al-Harasi, Sharifa; Ashley, Paul F; Moles, David R; Parekh, Susan; Walters, Val

    2017-06-20

    Managing children is a challenge that many dentists face. Many non-pharmacological techniques have been developed to manage anxiety and behavioural problems in children, such us: 'tell, show & do', positive reinforcement, modelling and hypnosis. The use of hypnosis is generally an overlooked area, hence the need for this review. This systematic review attempted to answer the question: What is the effectiveness of hypnosis (with or without sedation) for behaviour management of children who are receiving dental care in order to allow successful completion of treatment?Null hypothesis: Hypnosis has no effect on the outcome of dental treatment of children. We searched the Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE (OVID), EMBASE (OVID), and PsycINFO. Electronic and manual searches were performed using controlled vocabulary and free text terms with no language restrictions. Date of last search: 11th June 2010. All children and adolescents aged up to 16 years of age. Children having any dental treatment, such as: simple restorative treatment with or without local anaesthetic, simple extractions or management of dental trauma. Information regarding methods, participants, interventions, outcome measures and results were independently extracted, in duplicate, by two review authors. Authors of trials were contacted for details of randomisation and withdrawals and a quality assessment was carried out. The methodological quality of randomised controlled trials (RCTs) was assessed using the criteria described in the Cochrane Handbook for Systematic Reviews of Interventions 5.0.2. Only three RCTs (with 69 participants) fulfilled the inclusion criteria. Statistical analysis and meta-analysis were not possible due to insufficient number of studies. Although there are a considerable number of anecdotal accounts indicating the benefits of using hypnosis in paediatric dentistry, on the basis of the three studies meeting the inclusion criteria for this review there

  1. Mice null for the deubiquitinase USP18 spontaneously develop leiomyosarcomas

    International Nuclear Information System (INIS)

    Chinyengetere, Fadzai; Sekula, David J.; Lu, Yun; Giustini, Andrew J.; Sanglikar, Aarti; Kawakami, Masanori; Ma, Tian; Burkett, Sandra S.; Eisenberg, Burton L.; Wells, Wendy A.; Hoopes, Paul J.; Demicco, Elizabeth G.; Lazar, Alexander J; Torres, Keila E.; Memoli, Vincent; Freemantle, Sarah J.; Dmitrovsky, Ethan

    2015-01-01

    USP18 (ubiquitin-specific protease 18) removes ubiquitin-like modifier interferon stimulated gene 15 (ISG15) from conjugated proteins. USP18 null mice in a FVB/N background develop tumors as early as 2 months of age. These tumors are leiomyosarcomas and thus represent a new murine model for this disease. Heterozygous USP18 +/− FVB/N mice were bred to generate wild-type, heterozygous and homozygous cohorts. Tumors were characterized immunohistochemically and two cell lines were derived from independent tumors. Cell lines were karyotyped and their responses to restoration of USP18 activity assessed. Drug testing and tumorigenic assays were also performed. USP18 immunohistochemical staining in a large series of human leiomyosacomas was examined. USP18 −/− FVB/N mice spontaneously develop tumors predominantly on the back of the neck with most tumors evident between 6–12 months (80 % penetrance). Immunohistochemical characterization of the tumors confirmed they were leiomyosarcomas, which originate from smooth muscle. Restoration of USP18 activity in sarcoma-derived cell lines did not reduce anchorage dependent or independent growth or xenograft tumor formation demonstrating that these cells no longer require USP18 suppression for tumorigenesis. Karyotyping revealed that both tumor-derived cell lines were aneuploid with extra copies of chromosomes 3 and 15. Chromosome 15 contains the Myc locus and MYC is also amplified in human leiomyosarcomas. MYC protein levels were elevated in both murine leiomyosarcoma cell lines. Stabilized P53 protein was detected in a subset of these murine tumors, another feature of human leiomyosarcomas. Immunohistochemical analyses of USP18 in human leiomyosarcomas revealed a range of staining intensities with the highest USP18 expression in normal vascular smooth muscle. USP18 tissue array analysis of primary leiomyosarcomas from 89 patients with a clinical database revealed cases with reduced USP18 levels had a significantly

  2. Fibrillin levels in a severely affected Marfan syndrome patient with a null allele

    Energy Technology Data Exchange (ETDEWEB)

    Boxer, M.; Withers, A.P.; Al-Ghaban, Z. [Univ. of Wales, Cardiff (United Kingdom)]|[Ninewells Hospital and Medical School, Dundee (United Kingdom)] [and others

    1994-09-01

    Marfan syndrome is an autosomal dominantly inherited connective tissue disorder characterized by defects in the cardiovascular, skeletal and ocular systems. A patient was first examined in 1992 having survived an acute sortic dissection with subsequent composite repair and insertion of a prosthetic aortic valve. Clinical examination revealed arachnodactyly, narrow, high arched palate with dental crowding, an arm span exceeding her height by 10.5 cm, joint laxity and bilateral lens subluxation. Analysis of the family showed affected members in three generations and the fibrillin gene, FBN1, was shown to segregate with the disease when using polymorphic markers including an RsaI polymorphism in the 3{prime}-untranslated region of the gene. Analysis of patient mRNA for this RsaI polymorphism by RT-PCR (reverse transcriptase-PCR) amplification and restriction enzyme digestion of the PCR products showed that the copy of the gene segregating with the disease was not transcribed. No low level expression of this allele was observed despite RT-PCR amplification incorporating radioactively labelled dCTP, thus revealing a null allele phenotype. Western blotting analysis of fibrillin secreted by the patient`s dermal fibroblasts using fibrillin-specific antibodies showed only normal sized fibrillin protein. However, immunohistochemical studies of the patient`s tissue and fibroblasts showed markedly lowered levels in staining of microfibrillar structures compared with age-matched controls. This low level of expression of the protein affected in Marfan syndrome in a patient with such severe clinical manifestations is surprising since current understanding would suggest that this molecular phenotype should lead to a mild clinical disorder.

  3. Radiation Hardened NULL Convention Logic Asynchronous Circuit Design

    Directory of Open Access Journals (Sweden)

    Liang Zhou

    2015-10-01

    Full Text Available This paper proposes a radiation hardened NULL Convention Logic (NCL architecture that can recover from a single event latchup (SEL or single event upset (SEU fault without deadlock or any data loss. The proposed architecture is analytically proved to be SEL resistant, and by extension, proved to be SEU resistant. The SEL/SEU resistant version of a 3-stage full-word pipelined NCL 4 × 4 unsigned multiplier was implemented using the IBM cmrf8sf 130 nm 1.2 V process at the transistor level and simulated exhaustively with SEL fault injection to validate the proposed architectures. Compared with the original version, the SEL/SEU resilient version has 1.31× speed overhead, 2.74× area overhead, and 2.79× energy per operation overhead.

  4. The simple map for a single-null divertor tokamak

    International Nuclear Information System (INIS)

    Punjabi, A.; Verma, A.; Boozer, A.

    1996-01-01

    We present the simple map for a single-null divertor tokamak. The simple map is an area-preserving map based on the idea that magnetic field lines are a single-degree-of-freedom time-dependent Hamiltonian system, and that the basic features of such systems near the X-point are generic. We obtain the properties of this map and the resulting footprints of field lines on the divertor plate. These include the width of the stochastic layer, the edge safety factor, the area of the footprint and the amount of magnetic flux diverted. We give the safety factor profile, the average and median values of strike angles, lengths and the Liapunov exponents. We describe how the effects of magnetic perturbations can be included in the simple map. We show how the map can be applied to the problem of the determination of heat flux on the divertor plate in tokamaks. (Author)

  5. Status of the Visible Nulling Coronagraph Technology Demonstration Program

    Science.gov (United States)

    Clampin, M.; Lyon, R.

    2012-01-01

    We report on the development, sensing and control of the Vacuum Nuller Testbed to realize a Visible Nulling Coronagraphy (VNC) for exoplanet detection and characterization. The VNC is one of the few approaches that works with filled, segmented and sparse or diluted-aperture telescope systems. It thus spans a range of potential future NASA telescopes and could be flown as a separate instrument on such a future mission. NASA/Goddard Space Flight Center has an established effort to develop VNC technologies, and an incremental sequence of testbeds to advance this approach and its critical technologies. We will highlight results demonstrating the achievement of our TDEM contrast milestones, and highlight the performance of our wavefront sensing and control concept.

  6. Horizons in Matter:. Black Hole Hair Versus Null Big Bang

    Science.gov (United States)

    Bronnikov, K. A.; Zaslavskii, Oleg B.

    It is shown that only particular kinds of matter (in terms of the "radial" pressure-to-density ratio w) can coexist with Killing horizons in black hole or cosmological space-times. Thus, for arbitrary (not necessarily spherically symmetric) static black holes, admissible are vacuum matter (w = -1, i.e. the cosmological constant or its generalization with the same value of w) and matter with certain values of w between 0 and -1, in particular a gas of disordered cosmic strings (w = -1/3). If the cosmological evolution starts from a horizon (the so-called null big bang scenarios), this horizon can coexist with vacuum matter and certain kinds of phantom matter with w ≤ -3. It is concluded that normal matter in such scenarios is entirely created from vacuum.

  7. Cadmium modulates adipocyte functions in metallothionein-null mice

    Energy Technology Data Exchange (ETDEWEB)

    Kawakami, Takashige; Nishiyama, Kaori; Kadota, Yoshito; Sato, Masao; Inoue, Masahisa; Suzuki, Shinya, E-mail: suzukis@ph.bunri-u.ac.jp

    2013-11-01

    Our previous study has demonstrated that exposure to cadmium (Cd), a toxic heavy metal, causes a reduction of adipocyte size and the modulation of adipokine expression. To further investigate the significance of the Cd action, we studied the effect of Cd on the white adipose tissue (WAT) of metallothionein null (MT{sup −/−}) mice, which cannot form atoxic Cd–MT complexes and are used for evaluating Cd as free ions, and wild type (MT{sup +/+}) mice. Cd administration more significantly reduced the adipocyte size of MT{sup −/−} mice than that of MT{sup +/+} mice. Cd exposure also induced macrophage recruitment to WAT with an increase in the expression level of Ccl2 (MCP-1) in the MT{sup −/−} mice. The in vitro exposure of Cd to adipocytes induce triglyceride release into culture medium, decrease in the expression levels of genes involved in fatty acid synthesis and lipid hydrolysis at 24 h, and at 48 h increase in phosphorylation of the lipid-droplet-associated protein perilipin, which facilitates the degradation of stored lipids in adipocytes. Therefore, the reduction in adipocyte size by Cd may arise from an imbalance between lipid synthesis and lipolysis. In addition, the expression levels of leptin, adiponectin and resistin decreased in adipocytes. Taken together, exposure to Cd may induce unusually small adipocytes and modulate the expression of adipokines differently from the case of physiologically small adipocytes, and may accelerate the risk of developing insulin resistance and type 2 diabetes. - Highlights: • Cd causes a marked reduction in adipocyte size in MT-null mice. • Cd enhances macrophage migration into adipose tissue and disrupt adipokine secretion. • MT gene alleviates Cd-induced adipocyte dysfunctions. • Cd enhances the degradation of stored lipids in adipocytes, mediated by perilipin. • Cd induces unusually small adipocytes and the abnormal expression of adipokines.

  8. Dinucleotide controlled null models for comparative RNA gene prediction

    Directory of Open Access Journals (Sweden)

    Gesell Tanja

    2008-05-01

    Full Text Available Abstract Background Comparative prediction of RNA structures can be used to identify functional noncoding RNAs in genomic screens. It was shown recently by Babak et al. [BMC Bioinformatics. 8:33] that RNA gene prediction programs can be biased by the genomic dinucleotide content, in particular those programs using a thermodynamic folding model including stacking energies. As a consequence, there is need for dinucleotide-preserving control strategies to assess the significance of such predictions. While there have been randomization algorithms for single sequences for many years, the problem has remained challenging for multiple alignments and there is currently no algorithm available. Results We present a program called SISSIz that simulates multiple alignments of a given average dinucleotide content. Meeting additional requirements of an accurate null model, the randomized alignments are on average of the same sequence diversity and preserve local conservation and gap patterns. We make use of a phylogenetic substitution model that includes overlapping dependencies and site-specific rates. Using fast heuristics and a distance based approach, a tree is estimated under this model which is used to guide the simulations. The new algorithm is tested on vertebrate genomic alignments and the effect on RNA structure predictions is studied. In addition, we directly combined the new null model with the RNAalifold consensus folding algorithm giving a new variant of a thermodynamic structure based RNA gene finding program that is not biased by the dinucleotide content. Conclusion SISSIz implements an efficient algorithm to randomize multiple alignments preserving dinucleotide content. It can be used to get more accurate estimates of false positive rates of existing programs, to produce negative controls for the training of machine learning based programs, or as standalone RNA gene finding program. Other applications in comparative genomics that require

  9. Dinucleotide controlled null models for comparative RNA gene prediction.

    Science.gov (United States)

    Gesell, Tanja; Washietl, Stefan

    2008-05-27

    Comparative prediction of RNA structures can be used to identify functional noncoding RNAs in genomic screens. It was shown recently by Babak et al. [BMC Bioinformatics. 8:33] that RNA gene prediction programs can be biased by the genomic dinucleotide content, in particular those programs using a thermodynamic folding model including stacking energies. As a consequence, there is need for dinucleotide-preserving control strategies to assess the significance of such predictions. While there have been randomization algorithms for single sequences for many years, the problem has remained challenging for multiple alignments and there is currently no algorithm available. We present a program called SISSIz that simulates multiple alignments of a given average dinucleotide content. Meeting additional requirements of an accurate null model, the randomized alignments are on average of the same sequence diversity and preserve local conservation and gap patterns. We make use of a phylogenetic substitution model that includes overlapping dependencies and site-specific rates. Using fast heuristics and a distance based approach, a tree is estimated under this model which is used to guide the simulations. The new algorithm is tested on vertebrate genomic alignments and the effect on RNA structure predictions is studied. In addition, we directly combined the new null model with the RNAalifold consensus folding algorithm giving a new variant of a thermodynamic structure based RNA gene finding program that is not biased by the dinucleotide content. SISSIz implements an efficient algorithm to randomize multiple alignments preserving dinucleotide content. It can be used to get more accurate estimates of false positive rates of existing programs, to produce negative controls for the training of machine learning based programs, or as standalone RNA gene finding program. Other applications in comparative genomics that require randomization of multiple alignments can be considered. SISSIz

  10. Does horizon entropy satisfy a quantum null energy conjecture?

    Science.gov (United States)

    Fu, Zicao; Marolf, Donald

    2016-12-01

    A modern version of the idea that the area of event horizons gives 4G times an entropy is the Hubeny-Rangamani causal holographic information (CHI) proposal for holographic field theories. Given a region R of a holographic QFTs, CHI computes A/4G on a certain cut of an event horizon in the gravitational dual. The result is naturally interpreted as a coarse-grained entropy for the QFT. CHI is known to be finitely greater than the fine-grained Hubeny-Rangamani-Takayanagi (HRT) entropy when \\partial R lies on a Killing horizon of the QFT spacetime, and in this context satisfies other non-trivial properties expected of an entropy. Here we present evidence that it also satisfies the quantum null energy condition (QNEC), which bounds the second derivative of the entropy of a quantum field theory on one side of a non-expanding null surface by the flux of stress-energy across the surface. In particular, we show CHI to satisfy the QNEC in 1  +  1 holographic CFTs when evaluated in states dual to conical defects in AdS3. This surprising result further supports the idea that CHI defines a useful notion of coarse-grained holographic entropy, and suggests unprecedented bounds on the rate at which bulk horizon generators emerge from a caustic. To supplement our motivation, we include an appendix deriving a corresponding coarse-grained generalized second law for 1  +  1 holographic CFTs perturbatively coupled to dilaton gravity.

  11. 3D Solar Null Point Reconnection MHD Simulations

    Science.gov (United States)

    Baumann, G.; Galsgaard, K.; Nordlund, Å.

    2013-06-01

    Numerical MHD simulations of 3D reconnection events in the solar corona have improved enormously over the last few years, not only in resolution, but also in their complexity, enabling more and more realistic modeling. Various ways to obtain the initial magnetic field, different forms of solar atmospheric models as well as diverse driving speeds and patterns have been employed. This study considers differences between simulations with stratified and non-stratified solar atmospheres, addresses the influence of the driving speed on the plasma flow and energetics, and provides quantitative formulas for mapping electric fields and dissipation levels obtained in numerical simulations to the corresponding solar quantities. The simulations start out from a potential magnetic field containing a null-point, obtained from a Solar and Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) magnetogram magnetogram extrapolation approximately 8 hours before a C-class flare was observed. The magnetic field is stressed with a boundary motion pattern similar to - although simpler than - horizontal motions observed by SOHO during the period preceding the flare. The general behavior is nearly independent of the driving speed, and is also very similar in stratified and non-stratified models, provided only that the boundary motions are slow enough. The boundary motions cause a build-up of current sheets, mainly in the fan-plane of the magnetic null-point, but do not result in a flare-like energy release. The additional free energy required for the flare could have been partly present in non-potential form at the initial state, with subsequent additions from magnetic flux emergence or from components of the boundary motion that were not represented by the idealized driving pattern.

  12. Molecular bass for a malic enzyme null mutation

    International Nuclear Information System (INIS)

    Brown, M.L.; Wise, L.S.; Rubin, C.S.

    1987-01-01

    Many tissues from normal (wt) mice have cytosolic malic enzyme (ME) activity and express two mRNAs (2 and 3.1 kb) that code for a single ME polypeptide. Mod-1 null (M-n) mice lack cytosolic ME activity, but express 2.5 and 3.6 kb mRNAs that hybridize with wt ME cDNAs. To investigate the basis for the ME deficiency cDNAs corresponding to M-n ME RNA were cloned. A λgt11 library was prepared using M-n liver mRNA as a template. Wt ME cDNA probes hybridized with several recombinant phages and a 2kb insert with an atypical (non-wt) restriction pattern was subcloned in pGEM 1 and sequenced. The M-n ME cDNA contains an internal directly repeated sequence that corresponds to nts 1109-1617 in the coding region of wt ME cDNA. A restriction fragment from M-n ME cDNA that includes the first 204 bp of repeated sequence and 306 bp of contiguous 5' sequence was subcloned into pGEM 1 and used as a template for synthesizing 32 P-labeled anti-sense RNA. After hybridization with M-n liver RNA the 510 nt transcript was resistant to RNA digestion; after hybridization with wt RNA only fragments corresponding to the normally non-contiguous 204 bp and 306 bp segments of the insert were protected. Thus the partial duplication of coding sequence in M-n ME mRNA is confirmed. Analyses of intron-exon organization in the relevant regions of the wt and M-n ME genes will provide further insights into the mechanism underlying the ME null mutation

  13. Surprising structures hiding in Penrose’s future null infinity

    Science.gov (United States)

    Newman, Ezra T.

    2017-07-01

    Since the late1950s, almost all discussions of asymptotically flat (Einstein-Maxwell) space-times have taken place in the context of Penrose’s null infinity, I+. In addition, almost all calculations have used the Bondi coordinate and tetrad systems. Beginning with a known asymptotically flat solution to the Einstein-Maxwell equations, we show first, that there are other natural coordinate systems, near I+, (analogous to light-cones in flat-space) that are based on (asymptotically) shear-free null geodesic congruences (analogous to the flat-space case). Using these new coordinates and their associated tetrad, we define the complex dipole moment, (the mass dipole plus i times angular momentum), from the l  =  1 harmonic coefficient of a component of the asymptotic Weyl tensor. Second, from this definition, from the Bianchi identities and from the Bondi-Sachs mass and linear momentum, we show that there exists a large number of results—identifications and dynamics—identical to those of classical mechanics and electrodynamics. They include, among many others, {P}=M{v}+..., {L}= {r} × {P} , spin, Newton’s second law with the rocket force term (\\dotM v) and radiation reaction, angular momentum conservation and others. All these relations take place in the rather mysterious H-space rather than in space-time. This leads to the enigma: ‘why do these well known relations of classical mechanics take place in H-space?’ and ‘What is the physical meaning of H-space?’

  14. Is PMI the Hypothesis or the Null Hypothesis?

    Science.gov (United States)

    Tarone, Aaron M; Sanford, Michelle R

    2017-09-01

    Over the past several decades, there have been several strident exchanges regarding whether forensic entomologists estimate the postmortem interval (PMI), minimum PMI, or something else. During that time, there has been a proliferation of terminology reflecting this concern regarding "what we do." This has been a frustrating conversation for some in the community because much of this debate appears to be centered on what assumptions are acknowledged directly and which are embedded within a list of assumptions (or ignored altogether) in the literature and in case reports. An additional component of the conversation centers on a concern that moving away from the use of certain terminology like PMI acknowledges limitations and problems that would make the application of entomology appear less useful in court-a problem for lawyers, but one that should not be problematic for scientists in the forensic entomology community, as uncertainty is part of science that should and can be presented effectively in the courtroom (e.g., population genetic concepts in forensics). Unfortunately, a consequence of the way this conversation is conducted is that even as all involved in the debate acknowledge the concerns of their colleagues, parties continue to talk past one another advocating their preferred terminology. Progress will not be made until the community recognizes that all of the terms under consideration take the form of null hypothesis statements and that thinking about "what we do" as a null hypothesis has useful legal and scientific ramifications that transcend arguments over the usage of preferred terminology. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. Observation of a 3D Magnetic Null Point

    Energy Technology Data Exchange (ETDEWEB)

    Romano, P.; Falco, M. [INAF—Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania (Italy); Guglielmino, S. L.; Murabito, M., E-mail: prom@oact.inaf.it [Dipartimento di Fisica e Astronomia—Sezione Astrofisica, Università di Catania, Via S. Sofia 78, I-95123 Catania (Italy)

    2017-03-10

    We describe high-resolution observations of a GOES B-class flare characterized by a circular ribbon at the chromospheric level, corresponding to the network at the photospheric level. We interpret the flare as a consequence of a magnetic reconnection event that occurred at a three-dimensional (3D) coronal null point located above the supergranular cell. The potential field extrapolation of the photospheric magnetic field indicates that the circular chromospheric ribbon is cospatial with the fan footpoints, while the ribbons of the inner and outer spines look like compact kernels. We found new interesting observational aspects that need to be explained by models: (1) a loop corresponding to the outer spine became brighter a few minutes before the onset of the flare; (2) the circular ribbon was formed by several adjacent compact kernels characterized by a size of 1″–2″; (3) the kernels with a stronger intensity emission were located at the outer footpoint of the darker filaments, departing radially from the center of the supergranular cell; (4) these kernels started to brighten sequentially in clockwise direction; and (5) the site of the 3D null point and the shape of the outer spine were detected by RHESSI in the low-energy channel between 6.0 and 12.0 keV. Taking into account all these features and the length scales of the magnetic systems involved in the event, we argue that the low intensity of the flare may be ascribed to the low amount of magnetic flux and to its symmetric configuration.

  16. Genes expressed in dental enamel development are associated with molar-incisor hypomineralization.

    Science.gov (United States)

    Jeremias, Fabiano; Koruyucu, Mine; Küchler, Erika C; Bayram, Merve; Tuna, Elif B; Deeley, Kathleen; Pierri, Ricardo A; Souza, Juliana F; Fragelli, Camila M B; Paschoal, Marco A B; Gencay, Koray; Seymen, Figen; Caminaga, Raquel M S; dos Santos-Pinto, Lourdes; Vieira, Alexandre R

    2013-10-01

    Genetic disturbances during dental development influence variation of number and shape of the dentition. In this study, we tested if genetic variation in enamel formation genes is associated with molar-incisor hypomineralization (MIH), also taking into consideration caries experience. DNA samples from 163 cases with MIH and 82 unaffected controls from Turkey, and 71 cases with MIH and 89 unaffected controls from Brazil were studied. Eleven markers in five genes [ameloblastin (AMBN), amelogenin (AMELX), enamelin (ENAM), tuftelin (TUFT1), and tuftelin-interacting protein 11 (TFIP11)] were genotyped by the TaqMan method. Chi-square was used to compare allele and genotype frequencies between cases with MIH and controls. In the Brazilian data, distinct caries experience within the MIH group was also tested for association with genetic variation in enamel formation genes. The ENAM rs3796704 marker was associated with MIH in both populations (Brazil: p=0.03; OR=0.28; 95% C.I.=0.06-1.0; Turkey: p=1.22e-012; OR=17.36; 95% C.I.=5.98-56.78). Associations between TFIP11 (p=0.02), ENAM (p=0.00001), and AMELX (p=0.01) could be seen with caries independent of having MIH or genomic DNA copies of Streptococcus mutans detected by real time PCR in the Brazilian sample. Several genes involved in enamel formation appear to contribute to MIH. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Genetic variation may explain why females are less susceptible to dental erosion.

    Science.gov (United States)

    Uhlen, Marte-Mari; Stenhagen, Kjersti R; Dizak, Piper M; Holme, Børge; Mulic, Aida; Tveit, Anne B; Vieira, Alexandre R

    2016-10-01

    Not all individuals at risk for dental erosion (DE) display erosive lesions. The prevalence of DE is higher among male subjects. The occurrence of DE may depend on more than just acidic challenge, with genetics possibly playing a role. The aim of this study was to investigate the association of enamel-formation genes with DE. One premolar and a saliva sample were collected from 90 individuals. Prepared teeth were immersed in 0.01 M HCl (pH 2.2), and enamel loss (μm) was measured using white light interferometry. DNA was extracted from saliva, and 15 single-nucleotide polymorphisms were analysed. Allele and genotype frequencies were related to the enamel loss of the specimens. Single-marker and haplotype analyses were performed using sex as a covariate. Mean enamel loss was higher for male donors than for female donors (P = 0.047). Significant associations were found between enamel loss and amelogenin, X-linked (AMELX), tuftelin 1 (TUFT1), and tuftelin-interacting protein 11 (TFIP11). Analyses showed significant associations between variation in enamel-formation genes and a lower susceptibility to DE in female subjects. The results indicate that susceptibility to DE is influenced by genetic variation, and may, in part, explain why some individuals are more susceptible than others to DE, including differences between female subjects and male subjects. © 2016 Eur J Oral Sci.

  18. An experimental bioactive dental ceramic for metal-ceramic restorations: Textural characteristics and investigation of the mechanical properties.

    Science.gov (United States)

    Goudouri, Ourania-Menti; Kontonasaki, Eleana; Papadopoulou, Lambrini; Manda, Marianthi; Kavouras, Panagiotis; Triantafyllidis, Konstantinos S; Stefanidou, Maria; Koidis, Petros; Paraskevopoulos, Konstantinos M

    2017-02-01

    The aim of this study was the evaluation of the textural characteristics of an experimental sol-gel derived feldspathic dental ceramic, which has already been proven bioactive and the investigation of its flexural strength through Weibull Statistical Analysis. The null hypothesis was that the flexural strength of the experimental and the commercial dental ceramic would be of the same order, resulting in a dental ceramic with apatite forming ability and adequate mechanical integrity. Although the flexural strength of the experimental ceramics was not statistically significant different compared to the commercial one, the amount of blind pores due to processing was greater. The textural characteristics of the experimental ceramic were in accordance with the standard low porosity levels reported for dental ceramics used for fixed prosthetic restorations. Feldspathic dental ceramics with typical textural characteristics and advanced mechanical properties as well as enhanced apatite forming ability can be synthesized through the sol-gel method. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. 75 FR 33169 - Dental Devices: Classification of Dental Amalgam, Reclassification of Dental Mercury, Designation...

    Science.gov (United States)

    2010-06-11

    .... FDA-2008-N-0163] (formerly Docket No. 2001N-0067) RIN 0910-AG21 Dental Devices: Classification of Dental Amalgam, Reclassification of Dental Mercury, Designation of Special Controls for Dental Amalgam... the Federal Register of August 4, 2009 (74 FR 38686) which classified dental amalgam as a class II...

  20. Case based dental radiology.

    Science.gov (United States)

    Niemiec, Brook A

    2009-02-01

    Dental radiology is quickly becoming integral to the standard of care in veterinary dentistry. This is not only because it is critical for proper patient care, but also because client expectations have increased. Furthermore, providing dental radiographs as a routine service can create significant practice income. This article details numerous conditions that are indications for dental radiographs. As you will see, dental radiographs are often critical for proper diagnosis and treatment. These conditions should not be viewed as unusual; they are present within all of our practices. When you choose not to radiograph these teeth, you leave behind painful pathology. Utilizing the knowledge gained from dental radiographs will both improve patient care and increase acceptance of treatment recommendations. Consequently, this leads to increased numbers of dental procedures performed at your practice.

  1. The 'simple' general dental anaesthetic

    African Journals Online (AJOL)

    Dental anaesthesia should not be underestimated. Eddie Oosthuizen .... dental surgeon has limited training in airway management. ... primary teeth to hours for extensive dental conservation .... options after the extraction of permanent teeth ...

  2. Dental pulp stem cells

    DEFF Research Database (Denmark)

    Ashri, N. Y.; Ajlan, S. A.; Aldahmash, Abdullah M.

    2015-01-01

    scaffold, and guided through signaling molecules. Dental pulp stem cells have been used in an increasing number of studies in dental tissue engineering. Those cells show mesenchymal (stromal) stem cell-like properties including self-renewal and multilineage differentiation potentials, aside from...... an updated review on dental pulp stem cells and their applications in periodontal regeneration, in combination with different scaffolds and growth factors....

  3. Dental radiology for children

    International Nuclear Information System (INIS)

    Myers, D.R.

    1984-01-01

    The benefit for the child from the judicious use of diagnostic dental radiography is improved dental health. The risk to the child from dental diagnostic radiation exposure appears to be extremely low. Despite the low risk, the dentist must minimize the child's exposure to ionizing radiation by using sound clinical judgment to determine what radiographs are necessary and to provide children with optimal protection from ionizing radiation

  4. Dental magnetic resonance imaging

    International Nuclear Information System (INIS)

    Hilgenfeld, Tim; Bendszus, Martin; Haehnel, Stefan

    2016-01-01

    Growing distribution and utilization of digital volume tomography (DVT) extend the spectrum of clinical dental imaging. Additional diagnostic value, however, comes along with an increasing amount of radiation. In contrast, magnetic resonance imaging is a radiation free imaging technique. Furthermore, it offers a high soft tissue contrast. Morphological and numerical dental anomalies, differentiation of periapical lesions and exclusion of complications of dental diseases are field of applications for dental MRI. In addition, detection of caries and periodontal lesions and injury of inferior alveolar nerve are promising application areas in the future.

  5. Biocompatibility of dental alloys

    Energy Technology Data Exchange (ETDEWEB)

    Braemer, W. [Heraeus Kulzer GmbH and Co. KG, Hanau (Germany)

    2001-10-01

    Modern dental alloys have been used for 50 years to produce prosthetic dental restorations. Generally, the crowns and frames of a prosthesis are prepared in dental alloys, and then veneered by feldspar ceramics or composites. In use, the alloys are exposed to the corrosive influence of saliva and bacteria. Metallic dental materials can be classified as precious and non-precious alloys. Precious alloys consist of gold, platinum, and small amounts of non-precious components such as copper, tin, or zinc. The non-precious alloys are based on either nickel or cobalt, alloyed with chrome, molybdenum, manganese, etc. Titanium is used as Grade 2 quality for dental purposes. As well as the dental casting alloys, high purity electroplated gold (99.8 wt.-%) is used in dental technology. This review discusses the corrosion behavior of metallic dental materials with saliva in ''in vitro'' tests and the influence of alloy components on bacteria (Lactobacillus casei and Streptococcus mutans). The test results show that alloys with high gold content, cobalt-based alloys, titanium, and electroplated gold are suitable for use as dental materials. (orig.)

  6. Human dental pulp pluripotent-like stem cells promote wound healing and muscle regeneration.

    Science.gov (United States)

    Martínez-Sarrà, Ester; Montori, Sheyla; Gil-Recio, Carlos; Núñez-Toldrà, Raquel; Costamagna, Domiziana; Rotini, Alessio; Atari, Maher; Luttun, Aernout; Sampaolesi, Maurilio

    2017-07-27

    Dental pulp represents an easily accessible autologous source of adult stem cells. A subset of these cells, named dental pulp pluripotent-like stem cells (DPPSC), shows high plasticity and can undergo multiple population doublings, making DPPSC an appealing tool for tissue repair or maintenance. DPPSC were harvested from the dental pulp of third molars extracted from young patients. Growth factors released by DPPSC were analysed using antibody arrays. Cells were cultured in specific differentiation media and their endothelial, smooth and skeletal muscle differentiation potential was evaluated. The therapeutic potential of DPPSC was tested in a wound healing mouse model and in two genetic mouse models of muscular dystrophy (Scid/mdx and Sgcb-null Rag2-null γc-null). DPPSC secreted several growth factors involved in angiogenesis and extracellular matrix deposition and improved vascularisation in all three murine models. Moreover, DPPSC stimulated re-epithelialisation and ameliorated collagen deposition and organisation in healing wounds. In dystrophic mice, DPPSC engrafted in the skeletal muscle of both dystrophic murine models and showed integration in muscular fibres and vessels. In addition, DPPSC treatment resulted in reduced fibrosis and collagen content, larger cross-sectional area of type II fast-glycolytic fibres and infiltration of higher numbers of proangiogenic CD206 + macrophages. Overall, DPPSC represent a potential source of stem cells to enhance the wound healing process and slow down dystrophic muscle degeneration.

  7. Qualification of a Null Lens Using Image-Based Phase Retrieval

    Science.gov (United States)

    Bolcar, Matthew R.; Aronstein, David L.; Hill, Peter C.; Smith, J. Scott; Zielinski, Thomas P.

    2012-01-01

    In measuring the figure error of an aspheric optic using a null lens, the wavefront contribution from the null lens must be independently and accurately characterized in order to isolate the optical performance of the aspheric optic alone. Various techniques can be used to characterize such a null lens, including interferometry, profilometry and image-based methods. Only image-based methods, such as phase retrieval, can measure the null-lens wavefront in situ - in single-pass, and at the same conjugates and in the same alignment state in which the null lens will ultimately be used - with no additional optical components. Due to the intended purpose of a Dull lens (e.g., to null a large aspheric wavefront with a near-equal-but-opposite spherical wavefront), characterizing a null-lens wavefront presents several challenges to image-based phase retrieval: Large wavefront slopes and high-dynamic-range data decrease the capture range of phase-retrieval algorithms, increase the requirements on the fidelity of the forward model of the optical system, and make it difficult to extract diagnostic information (e.g., the system F/#) from the image data. In this paper, we present a study of these effects on phase-retrieval algorithms in the context of a null lens used in component development for the Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission. Approaches for mitigation are also discussed.

  8. An equation satisfied by the tangent to a shear-free, geodesic, null congruence

    International Nuclear Information System (INIS)

    Hogan, P.A.; Dublin Inst. for Advanced Studies

    1987-01-01

    A tensorial equation satisfied by the tangent to a shear-free geodesic, null congruence is presented. If the congruence is neither twist-free nor expansion-free then the equation defines a second, unique, null direction previously obtained, using the spinor formalism, by Somers. Some further properties of the equation are discussed. (orig.)

  9. Education About Dental Hygienists' Roles in Public Dental Prevention Programs: Dental and Dental Hygiene Students' and Faculty Members' and Dental Hygienists' Perspectives.

    Science.gov (United States)

    Pervez, Anushey; Kinney, Janet S; Gwozdek, Anne; Farrell, Christine M; Inglehart, Marita R

    2016-09-01

    In 2005, Public Act No. 161 (PA 161) was passed in Michigan, allowing dental hygienists to practice in approved public dental prevention programs to provide services for underserved populations while utilizing a collaborative agreement with a supervising dentist. The aims of this study were to assess how well dental and dental hygiene students and faculty members and practicing dental hygienists have been educated about PA 161, what attitudes and knowledge about the act they have, and how interested they are in additional education about it. University of Michigan dental and dental hygiene students and faculty members, students in other Michigan dental hygiene programs, and dental hygienists in the state were surveyed. Respondents (response rate) were 160 dental students (50%), 63 dental hygiene students (82%), 30 dental faculty members (26%), and 12 dental hygiene faculty members (52%) at the University of Michigan; 143 dental hygiene students in other programs (20%); and 95 members of the Michigan Dental Hygienists' Association (10%). The results showed that the dental students were less educated about PA 161 than the dental hygiene students, and the dental faculty members were less informed than the dental hygiene faculty members and dental hygienists. Responding dental hygiene faculty members and dental hygienists had more positive attitudes about PA 161 than did the students and dental faculty members. Most of the dental hygiene faculty members and dental hygienists knew a person providing services in a PA 161 program. Most dental hygiene students, faculty members, and dental hygienists wanted more education about PA 161. Overall, the better educated about the program the respondents were, the more positive their attitudes, and the more interested they were in learning more.

  10. Causal null hypotheses of sustained treatment strategies: What can be tested with an instrumental variable?

    Science.gov (United States)

    Swanson, Sonja A; Labrecque, Jeremy; Hernán, Miguel A

    2018-05-02

    Sometimes instrumental variable methods are used to test whether a causal effect is null rather than to estimate the magnitude of a causal effect. However, when instrumental variable methods are applied to time-varying exposures, as in many Mendelian randomization studies, it is unclear what causal null hypothesis is tested. Here, we consider different versions of causal null hypotheses for time-varying exposures, show that the instrumental variable conditions alone are insufficient to test some of them, and describe additional assumptions that can be made to test a wider range of causal null hypotheses, including both sharp and average causal null hypotheses. Implications for interpretation and reporting of instrumental variable results are discussed.

  11. Continuous development of current sheets near and away from magnetic nulls

    International Nuclear Information System (INIS)

    Kumar, Sanjay; Bhattacharyya, R.

    2016-01-01

    The presented computations compare the strength of current sheets which develop near and away from the magnetic nulls. To ensure the spontaneous generation of current sheets, the computations are performed congruently with Parker's magnetostatic theorem. The simulations evince current sheets near two dimensional and three dimensional magnetic nulls as well as away from them. An important finding of this work is in the demonstration of comparative scaling of peak current density with numerical resolution, for these different types of current sheets. The results document current sheets near two dimensional magnetic nulls to have larger strength while exhibiting a stronger scaling than the current sheets close to three dimensional magnetic nulls or away from any magnetic null. The comparative scaling points to a scenario where the magnetic topology near a developing current sheet is important for energetics of the subsequent reconnection.

  12. Nulling interferometry for the darwin mission: laboratory demonstration experiment

    Science.gov (United States)

    Ollivier, Marc; Léger, Alain; Sekulic, Predrag; Labèque, Alain; Michel, Guy

    2017-11-01

    The DARWIN mission is a project of the European Space Agency that should allow around 2012 the search for extrasolar planets and a spectral analysis of their potential atmosphere in order to evidence gases and particularly tracers of life. The principle of the instrument is based on the Bracewell nulling interferometer. It allows high angular resolution and high dynamic range. However, this concept, proposed more than 20 years ago, has never been experimentally demonstrated in the thermal infrared with high levels of extinction. We present here a laboratory monochromatic experiment dedicated to this goal. A theoretical and numerical approach of the question highlights a strong difficulty: the need for very clean and homogeneous wavefronts, in terms of intensity, phase and polarisation distribution. A classical interferometric approach appears to be insufficient to reach our goals. We have shown theoretically then numerically that this difficulty can be surpassed if we perform an optical filtering of the interfering beams. This technique allows us to decrease strongly the optical requirements and to view very high interferometric contrast measurements with commercial optical pieces. We present here a laboratory interferometer working at 10,6 microns, and implementing several techniques of optical filtering (pinholes and single-mode waveguides), its realisation, and its first promising results. We particularly present measurements that exhibit stable visibility levels better than 99,9% that is to say extinction levels better than 1000.

  13. Constrained Null Space Component Analysis for Semiblind Source Separation Problem.

    Science.gov (United States)

    Hwang, Wen-Liang; Lu, Keng-Shih; Ho, Jinn

    2018-02-01

    The blind source separation (BSS) problem extracts unknown sources from observations of their unknown mixtures. A current trend in BSS is the semiblind approach, which incorporates prior information on sources or how the sources are mixed. The constrained independent component analysis (ICA) approach has been studied to impose constraints on the famous ICA framework. We introduced an alternative approach based on the null space component (NCA) framework and referred to the approach as the c-NCA approach. We also presented the c-NCA algorithm that uses signal-dependent semidefinite operators, which is a bilinear mapping, as signatures for operator design in the c-NCA approach. Theoretically, we showed that the source estimation of the c-NCA algorithm converges with a convergence rate dependent on the decay of the sequence, obtained by applying the estimated operators on corresponding sources. The c-NCA can be formulated as a deterministic constrained optimization method, and thus, it can take advantage of solvers developed in optimization society for solving the BSS problem. As examples, we demonstrated electroencephalogram interference rejection problems can be solved by the c-NCA with proximal splitting algorithms by incorporating a sparsity-enforcing separation model and considering the case when reference signals are available.

  14. A null relationship between media multitasking and well-being.

    Directory of Open Access Journals (Sweden)

    Shui-I Shih

    Full Text Available There is a rapidly increasing trend in media-media multitasking or MMM (using two or more media concurrently. In a recent conference, scholars from diverse disciplines expressed concerns that indulgence in MMM may compromise well-being and/or cognitive abilities. However, research on MMM's impacts is too sparse to inform the general public and policy makers whether MMM should be encouraged, managed, or minimized. The primary purpose of the present study was to develop an innovative computerized instrument--the Survey of the Previous Day (SPD--to quantify MMM as well as media-nonmedia and nonmedia-nonmedia multitasking and sole-tasking. The secondary purpose was to examine whether these indices could predict a sample of well-being related, psychosocial measures. In the SPD, participants first recalled (typed what they did during each hour of the previous day. In later parts of the SPD, participants analysed activities and their timing and duration for each hour of the previous day, while relevant recall was on display. Participants also completed the Media Use Questionnaire. The results showed non-significant relationship between tasking measures and well-being related measures. Given how little is known about the associations between MMM and well-being, the null results may offer some general reassurance to those who are apprehensive about negative impacts of MMM.

  15. A Null Relationship between Media Multitasking and Well-Being

    Science.gov (United States)

    Shih, Shui-I

    2013-01-01

    There is a rapidly increasing trend in media-media multitasking or MMM (using two or more media concurrently). In a recent conference, scholars from diverse disciplines expressed concerns that indulgence in MMM may compromise well-being and/or cognitive abilities. However, research on MMM's impacts is too sparse to inform the general public and policy makers whether MMM should be encouraged, managed, or minimized. The primary purpose of the present study was to develop an innovative computerized instrument – the Survey of the Previous Day (SPD) – to quantify MMM as well as media-nonmedia and nonmedia-nonmedia multitasking and sole-tasking. The secondary purpose was to examine whether these indices could predict a sample of well-being related, psychosocial measures. In the SPD, participants first recalled (typed) what they did during each hour of the previous day. In later parts of the SPD, participants analysed activities and their timing and duration for each hour of the previous day, while relevant recall was on display. Participants also completed the Media Use Questionnaire. The results showed non-significant relationship between tasking measures and well-being related measures. Given how little is known about the associations between MMM and well-being, the null results may offer some general reassurance to those who are apprehensive about negative impacts of MMM. PMID:23691236

  16. Conical twist fields and null polygonal Wilson loops

    Science.gov (United States)

    Castro-Alvaredo, Olalla A.; Doyon, Benjamin; Fioravanti, Davide

    2018-06-01

    Using an extension of the concept of twist field in QFT to space-time (external) symmetries, we study conical twist fields in two-dimensional integrable QFT. These create conical singularities of arbitrary excess angle. We show that, upon appropriate identification between the excess angle and the number of sheets, they have the same conformal dimension as branch-point twist fields commonly used to represent partition functions on Riemann surfaces, and that both fields have closely related form factors. However, we show that conical twist fields are truly different from branch-point twist fields. They generate different operator product expansions (short distance expansions) and form factor expansions (large distance expansions). In fact, we verify in free field theories, by re-summing form factors, that the conical twist fields operator product expansions are correctly reproduced. We propose that conical twist fields are the correct fields in order to understand null polygonal Wilson loops/gluon scattering amplitudes of planar maximally supersymmetric Yang-Mills theory.

  17. Lovelock vacua with a recurrent null vector field

    Science.gov (United States)

    Ortaggio, Marcello

    2018-02-01

    Vacuum solutions of Lovelock gravity in the presence of a recurrent null vector field (a subset of Kundt spacetimes) are studied. We first discuss the general field equations, which constrain both the base space and the profile functions. While choosing a "generic" base space puts stronger constraints on the profile, in special cases there also exist solutions containing arbitrary functions (at least for certain values of the coupling constants). These and other properties (such as the p p - waves subclass and the overlap with VSI, CSI and universal spacetimes) are subsequently analyzed in more detail in lower dimensions n =5 , 6 as well as for particular choices of the base manifold. The obtained solutions describe various classes of nonexpanding gravitational waves propagating, e.g., in Nariai-like backgrounds M2×Σn -2. An Appendix contains some results about general (i.e., not necessarily Kundt) Lovelock vacua of Riemann type III/N and of Weyl and traceless-Ricci type III/N. For example, it is pointed out that for theories admitting a triply degenerate maximally symmetric vacuum, all the (reduced) field equations are satisfied identically, giving rise to large classes of exact solutions.

  18. Tanzania Dental Association

    African Journals Online (AJOL)

    Committee of Tanzania Dental. Association would like to Thank. [fUfNJfNJU[[j)~ for its magnanimity towards meeting the cost of this Journal ... ceps is token out of the dental kit and the tooth is removed out of its socket. The tooth is dropped into the waste bucket. The fareceps is placed in the water basin. The socket site is ...

  19. Nigerian Dental Journal

    African Journals Online (AJOL)

    ... needs of dental practitioners in Nigeria, Africa and international community interested in the dental practice in the developing world. The NDJ is published biannually and accepts reports of original research, review articles, clinical case reports and innovations in surgical techniques related to dentistry and allied subjects ...

  20. Acute dental pain II

    DEFF Research Database (Denmark)

    Jonasson, Peter; Kirkevang, Lise-Lotte; Rosen, Annika

    2016-01-01

    Acute dental pain most often occurs in relation to inflammatory conditions in the dental pulp or in the periradicular tissues surrounding a tooth, but it is not always easy to reach a diagnose and determine what treatment to perform. The anamnesis and the clinical examination provide valuable...

  1. Evaluation of dental age and associated developmental anomalies in subjects with impacted mandibular canines.

    Science.gov (United States)

    Jain, Shikha; Shetty, K Sadashiva; Jain, Shweta; Jain, Sachin; Prakash, A T; Agrawal, Mamta

    2015-07-01

    To assess the null hypothesis that there is no difference in the rate of dental development and the occurrence of selected developmental anomalies related to shape, number, structure, and position of teeth between subjects with impacted mandibular canines and those with normally erupted canines. Pretreatment records of 42 subjects diagnosed with mandibular canines impaction (impaction group: IG) were compared with those of 84 subjects serving as a control reference sample (control group: CG). Independent t-tests were used to compare mean dental ages between the groups. Intergroup differences in distribution of subjects based on the rate of dental development and occurrence of selected dental anomalies were assessed using χ(2) tests. Odds of late, normal, and early developers and various categories of developmental anomalies between the IG and the CG were evaluated in terms of odds ratios. Mean dental age for the IG was lower than that for the CG in general. Specifically, this was true for girls (P dental development and occurrence of positional anomalies also reached statistical significance (P anomalies compared with controls (odds ratios 3.00 and 2.82, respectively; P dental development compared with the female orthodontic patients. Increased frequency of positional developmental anomalies was also remarkable in the IG.

  2. Patients' satisfaction with dental care provided by public dental ...

    African Journals Online (AJOL)

    Background: In Tanzania, patient satisfaction with dental services has received only minor attention. Objective: To assess patients' satisfaction with public dental health services in Dar es Salaam. Design: A cross-sectional study. Setting: Five public dental clinics randomly selected from a list of all the nine public dental ...

  3. Dental fluorosis and dental caries prevalence among 12 and 15 ...

    African Journals Online (AJOL)

    Background: Fluoride is a double edged sword. The assessment of dental caries and fluorosis in endemic fluoride areas will facilitate in assessing the relation between fluoride concentrations in water with dental caries, dental fluorosis simultaneously. Aim: The objective of the following study is to assess the dental caries ...

  4. Awareness of dental implants among dental patients in Nigeria ...

    African Journals Online (AJOL)

    The aim of this study was to determine the level of awareness of dental implant in Nigerian patients and their willingness to choose dental implant as a tooth replacement option. A survey was conducted among patients presenting for dental treatment in 3 teaching hospitals and private dental clinics in 3 urban cities of ...

  5. What is dental ecology?

    Science.gov (United States)

    Cuozzo, Frank P; Sauther, Michelle L

    2012-06-01

    Teeth have long been used as indicators of primate ecology. Early work focused on the links between dental morphology, diet, and behavior, with more recent years emphasizing dental wear, microstructure, development, and biogeochemistry, to understand primate ecology. Our study of Lemur catta at the Beza Mahafaly Special Reserve, Madagascar, has revealed an unusual pattern of severe tooth wear and frequent tooth loss, primarily the result of consuming a fallback food for which these primates are not dentally adapted. Interpreting these data was only possible by combining our areas of expertise (dental anatomy [FC] and primate ecology [MS]). By integrating theoretical, methodological, and applied aspects of both areas of research, we adopted the term "dental ecology"-defined as the broad study of how teeth respond to the environment. Specifically, we view dental ecology as an interpretive framework using teeth as a vehicle for understanding an organism's ecology, which builds upon earlier work, but creates a new synthesis of anatomy and ecology that is only possible with detailed knowledge of living primates. This framework includes (1) identifying patterns of dental pathology and tooth use-wear, within the context of feeding ecology, behavior, habitat variation, and anthropogenic change, (2) assessing ways in which dental development and biogeochemical signals can reflect habitat, environmental change and/or stress, and (3) how dental microstructure and macro-morphology are adapted to, and reflect feeding ecology. Here we define dental ecology, provide a short summary of the development of this perspective, and place our new work into this context. Copyright © 2012 Wiley Periodicals, Inc.

  6. 75 FR 16511 - Pentron Clinical Technologies, a Wholly-Owned Subsidiary of Kerr Dental/Sybron Dental...

    Science.gov (United States)

    2010-04-01

    ... produce dental materials such as dental prosthetics, dental composites, dental impressions, dental... materials such as dental prosthetics, dental composites, dental impressions, dental adhesives, and other... Technologies, a Wholly-Owned Subsidiary of Kerr Dental/Sybron Dental Specialities, Formally Known as Customedix...

  7. Measurement of high-departure aspheres using subaperture stitching with the Variable Optical Null (VON)

    Science.gov (United States)

    Kulawiec, Andrew; Murphy, Paul; DeMarco, Michael

    2010-10-01

    Aspheric surfaces are proven to provide significant benefits to a wide variety of optical systems, but the ability to produce high-precision aspheric surfaces has historically been limited by the ability (or lack thereof) to measure them. Traditionally, aspheric measurements have required dedicated null optics, but the cost, lead time, and calibration difficulty of using null optics has made the use of aspheres more challenging and less attractive. In the past three years, QED has developed the Subaperture Stitching Interferometer for Aspheres (SSI-A®) to help address this limitation, providing flexible aspheric measurement capability of up to 200 waves of aspheric departure from best-fit sphere. Some aspheres, however, have thousands of waves of departure. We have recently developed Variable Optical Null (VON) technology that can null much of the aspheric departure in a subaperture. The VON is automatically configurable and is adjusted to nearly null each specific subaperture of an asphere. This ability to nearly null a local subaperture of an asphere provides a significant boost in aspheric measurement capability, enabling aspheres with up to 1000 waves of departure to be measured, without the use of dedicated null optics. We outline the basic principles of subaperture stitching and VON technology, demonstrate the extended capability provided by the VON, and present measurement results from the new Aspheric Stitching Interferometer (ASI®).

  8. Shocks and currents in stratified atmospheres with a magnetic null point

    Science.gov (United States)

    Tarr, Lucas A.; Linton, Mark

    2017-08-01

    We use the resistive MHD code LARE (Arber et al 2001) to inject a compressive MHD wavepacket into a stratified atmosphere that has a single magnetic null point, as recently described in Tarr et al 2017. The 2.5D simulation represents a slice through a small ephemeral region or area of plage. The strong gradients in field strength and connectivity related to the presence of the null produce substantially different dynamics compared to the more slowly varying fields typically used in simple sunspot models. The wave-null interaction produces a fast mode shock that collapses the null into a current sheet and generates a set of outward propagating (from the null) slow mode shocks confined to field lines near each separatrix. A combination of oscillatory reconnection and shock dissipation ultimately raise the plasma's internal energy at the null and along each separatrix by 25-50% above the background. The resulting pressure gradients must be balanced by Lorentz forces, so that the final state has contact discontinuities along each separatrix and a persistent current at the null. The simulation demonstrates that fast and slow mode waves localize currents to the topologically important locations of the field, just as their Alfvenic counterparts do, and also illustrates the necessity of treating waves and reconnection as coupled phenomena.

  9. Modular Hamiltonians on the null plane and the Markov property of the vacuum state

    Science.gov (United States)

    Casini, Horacio; Testé, Eduardo; Torroba, Gonzalo

    2017-09-01

    We compute the modular Hamiltonians of regions having the future horizon lying on a null plane. For a CFT this is equivalent to regions with a boundary of arbitrary shape lying on the null cone. These Hamiltonians have a local expression on the horizon formed by integrals of the stress tensor. We prove this result in two different ways, and show that the modular Hamiltonians of these regions form an infinite dimensional Lie algebra. The corresponding group of unitary transformations moves the fields on the null surface locally along the null generators with arbitrary null line dependent velocities, but act non-locally outside the null plane. We regain this result in greater generality using more abstract tools on the algebraic quantum field theory. Finally, we show that modular Hamiltonians on the null surface satisfy a Markov property that leads to the saturation of the strong sub-additive inequality for the entropies and to the strong super-additivity of the relative entropy.

  10. Magnetoacoustic Waves in a Stratified Atmosphere with a Magnetic Null Point

    Energy Technology Data Exchange (ETDEWEB)

    Tarr, Lucas A.; Linton, Mark; Leake, James, E-mail: lucas.tarr.ctr@nrl.navy.mil [U.S. Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375 (United States)

    2017-03-01

    We perform nonlinear MHD simulations to study the propagation of magnetoacoustic waves from the photosphere to the low corona. We focus on a 2D system with a gravitationally stratified atmosphere and three photospheric concentrations of magnetic flux that produce a magnetic null point with a magnetic dome topology. We find that a single wavepacket introduced at the lower boundary splits into multiple secondary wavepackets. A portion of the packet refracts toward the null owing to the varying Alfvén speed. Waves incident on the equipartition contour surrounding the null, where the sound and Alfvén speeds coincide, partially transmit, reflect, and mode-convert between branches of the local dispersion relation. Approximately 15.5% of the wavepacket’s initial energy ( E {sub input}) converges on the null, mostly as a fast magnetoacoustic wave. Conversion is very efficient: 70% of the energy incident on the null is converted to slow modes propagating away from the null, 7% leaves as a fast wave, and the remaining 23% (0.036 E {sub input}) is locally dissipated. The acoustic energy leaving the null is strongly concentrated along field lines near each of the null’s four separatrices. The portion of the wavepacket that refracts toward the null, and the amount of current accumulation, depends on the vertical and horizontal wavenumbers and the centroid position of the wavepacket as it crosses the photosphere. Regions that refract toward or away from the null do not simply coincide with regions of open versus closed magnetic field or regions of particular field orientation. We also model wavepacket propagation using a WKB method and find that it agrees qualitatively, though not quantitatively, with the results of the numerical simulation.

  11. An improved null model for assessing the net effects of multiple stressors on communities.

    Science.gov (United States)

    Thompson, Patrick L; MacLennan, Megan M; Vinebrooke, Rolf D

    2018-01-01

    Ecological stressors (i.e., environmental factors outside their normal range of variation) can mediate each other through their interactions, leading to unexpected combined effects on communities. Determining whether the net effect of stressors is ecologically surprising requires comparing their cumulative impact to a null model that represents the linear combination of their individual effects (i.e., an additive expectation). However, we show that standard additive and multiplicative null models that base their predictions on the effects of single stressors on community properties (e.g., species richness or biomass) do not provide this linear expectation, leading to incorrect interpretations of antagonistic and synergistic responses by communities. We present an alternative, the compositional null model, which instead bases its predictions on the effects of stressors on individual species, and then aggregates them to the community level. Simulations demonstrate the improved ability of the compositional null model to accurately provide a linear expectation of the net effect of stressors. We simulate the response of communities to paired stressors that affect species in a purely additive fashion and compare the relative abilities of the compositional null model and two standard community property null models (additive and multiplicative) to predict these linear changes in species richness and community biomass across different combinations (both positive, negative, or opposite) and intensities of stressors. The compositional model predicts the linear effects of multiple stressors under almost all scenarios, allowing for proper classification of net effects, whereas the standard null models do not. Our findings suggest that current estimates of the prevalence of ecological surprises on communities based on community property null models are unreliable, and should be improved by integrating the responses of individual species to the community level as does our

  12. OBSERVATION OF MAGNETIC RECONNECTION AT A 3D NULL POINT ASSOCIATED WITH A SOLAR ERUPTION

    International Nuclear Information System (INIS)

    Sun, J. Q.; Yang, K.; Cheng, X.; Ding, M. D.; Zhang, J.

    2016-01-01

    Magnetic null has long been recognized as a special structure serving as a preferential site for magnetic reconnection (MR). However, the direct observational study of MR at null-points is largely lacking. Here, we show the observations of MR around a magnetic null associated with an eruption that resulted in an M1.7 flare and a coronal mass ejection. The Geostationary Operational Environmental Satellites X-ray profile of the flare exhibited two peaks at ∼02:23 UT and ∼02:40 UT on 2012 November 8, respectively. Based on the imaging observations, we find that the first and also primary X-ray peak was originated from MR in the current sheet (CS) underneath the erupting magnetic flux rope (MFR). On the other hand, the second and also weaker X-ray peak was caused by MR around a null point located above the pre-eruption MFR. The interaction of the null point and the erupting MFR can be described as a two-step process. During the first step, the erupting and fast expanding MFR passed through the null point, resulting in a significant displacement of the magnetic field surrounding the null. During the second step, the displaced magnetic field started to move back, resulting in a converging inflow and subsequently the MR around the null. The null-point reconnection is a different process from the current sheet reconnection in this flare; the latter is the cause of the main peak of the flare, while the former is the cause of the secondary peak of the flare and the conspicuous high-lying cusp structure.

  13. Dental Anomalies: An Update

    Directory of Open Access Journals (Sweden)

    Fatemeh Jahanimoghadam

    2016-01-01

    Full Text Available Dental anomalies are usual congenital malformation that can happen either as isolated findings or as a part of a syndrome. Developmental anomalies influencing the morphology exists in both deciduous and permanent dentition and shows different forms such as gemination, fusion, concrescence, dilaceration, dens evaginatus (DE, enamel pearls, taurodontism or peg-shaped laterals. All These anomalies have clinical significance concerning aesthetics, malocclusion and more necessary preparing of the development of dental decays and oral diseases. Through a search in PubMed, Google, Scopus and Medline, a total of eighty original research papers during 1928-2016 were found with the keywords such as dental anomaly, syndrome, tooth and hypodontia. One hundred review titles were identified, eighty reviews were retrieved that were finally included as being relevant and of sufficient quality. In this review, dental anomalies including gemination, fusion, concrescence, dilaceration, dens invaginatus, DE, taurodontism, enamel pearls, fluorosis, peg-shaped laterals, dentinal dysplasia, regional odontodysplasia and hypodontia are discussed. Diagnosing dental abnormality needs a thorough evaluation of the patient, involving a medical, dental, familial and clinical history. Clinical examination and radiographic evaluation and in some of the cases, specific laboratory tests are also needed. Developmental dental anomalies require careful examination and treatment planning. Where one anomaly is present, clinicians should suspect that other anomalies may also be present. Moreover, careful clinical and radiographical examination is required. Furthermore, more complex cases need multidisciplinary planning and treatment.

  14. Transgenic Expression of Dspp Partially Rescued the Long Bone Defects of Dmp1-null Mice

    Science.gov (United States)

    Jani, Priyam H.; Gibson, Monica P.; Liu, Chao; Zhang, Hua; Wang, Xiaofang; Lu, Yongbo; Qin, Chunlin

    2016-01-01

    Dentin matrix protein 1 (DMP1) and dentin sialophosphoprotein (DSPP) belong to the Small Integrin-Binding Ligand N-linked Glycoprotein (SIBLING) family. In addition to the features common to all SIBLING members, DMP1 and DSPP share several unique similarities in chemical structure, proteolytic activation and tissue localization. Mutations in, or deletion of DMP1, cause autosomal recessive hypophosphatemic rickets along with dental defects; DSPP mutations or its ablation are associated with dentinogenesis imperfecta. While the roles and functional mechanisms of DMP1 in osteogenesis have been extensively studied, those of DSPP in long bones have been studied only to a limited extent. Previous studies by our group revealed that transgenic expression of Dspp completely rescued the dentin defects of Dmp1-null (Dmp1−/−) mice. In this investigation, we assessed the effects of transgenic Dspp on osteogenesis by analyzing the formation and mineralization of the long bones in Dmp1−/− mice that expresses a transgene encoding full-length DSPP driven by a 3.6-kb rat Col1a1 promoter (referred as “Dmp1−/−;Dspp-Tg mice”). We characterized the long bones of the Dmp1−/−;Dspp-Tg mice at different ages and compared them with those from Dmp1−/− and Dmp1+/− (normal control) mice. Our analyses showed that the long bones of Dmp1−/−;Dspp-Tg mice had a significant increase in cortical bone thickness, bone volume and mineral density along with a remarkable restoration of trabecular thickness compared to those of the Dmp1−/− mice. The long bones of Dmp1−/−;Dspp-Tg mice underwent a dramatic reduction in the amount of osteoid, significant improvement of the collagen fibrillar network, and better organization of the lacunocanalicular system, compared to the Dmp1−/− mice. The elevated levels of biglycan, bone sialoprotein and osteopontin in Dmp1−/− mice were also noticeably corrected by the transgenic expression of Dspp. These findings suggest that

  15. Equine dental advances.

    Science.gov (United States)

    Greene, S K

    2001-08-01

    The reintroduction and development of safe motorized instruments, the increased availability of continuing education, and the understanding and implementation of appropriate procedures allow practitioners to provide better dental care. Veterinarians realize that sedation, analgesia, a full-mouth speculum, and proper instrumentation are necessary to provide these services. Continued instrument design, future research, and new treatment and prophylactic protocols should have a positive impact on the future of equine dental health. New and rediscovered procedures for equilibrating equine occlusion are allowing horses to masticate more efficiently, carry a bit more comfortably, and experience improved performance. The horse, the horse owner, and the veterinary profession all benefit from providing complete equine dental care.

  16. Dental biofilm infections

    DEFF Research Database (Denmark)

    Larsen, Tove; Fiehn, Nils-Erik

    2017-01-01

    and cause gingival inflammation and breakdown of supporting periodontal fibers and bone and ultimately tooth loss, i.e., gingivitis, chronic or aggressive periodontitis, and around dental implants, peri-implantitis. Furthermore, bacteria from the dental biofilm may spread to other parts of the body......-fermenting bacteria causing demineralization of teeth, dental caries, which may further lead to inflammation and necrosis in the pulp and periapical region, i.e., pulpitis and periapical periodontitis. In supra- and subgingival biofilms, predominantly gram-negative, anaerobic proteolytic bacteria will colonize...

  17. Dental Trauma Guide

    DEFF Research Database (Denmark)

    Andreasen, Jens Ove; Lauridsen, Eva; Gerds, Thomas Alexander

    2012-01-01

    Diagnosis and treatment for traumatic dental injuries are very complex owing to the multiple trauma entities represented by six luxation types and nine fracture types affecting both the primary and the permanent dentition. When it is further considered that fracture and luxation injuries are often...... problems in selecting proper treatment for some of these trauma types. To remedy this situation, an Internet-based knowledge base consisting of 4000 dental trauma cases with long-term follow up is now available to the public and the professions on the Internet using the address http://www.Dental...

  18. Optimization of dental implantation

    Science.gov (United States)

    Dol, Aleksandr V.; Ivanov, Dmitriy V.

    2017-02-01

    Modern dentistry can not exist without dental implantation. This work is devoted to study of the "bone-implant" system and to optimization of dental prostheses installation. Modern non-invasive methods such as MRI an 3D-scanning as well as numerical calculations and 3D-prototyping allow to optimize all of stages of dental prosthetics. An integrated approach to the planning of implant surgery can significantly reduce the risk of complications in the first few days after treatment, and throughout the period of operation of the prosthesis.

  19. Economic impact of dental hygienists on solo dental practices.

    Science.gov (United States)

    Lazar, Vickie F; Guay, Albert H; Beazoglou, Tryfon J

    2012-08-01

    The fact that a significant percentage of dentists employ dental hygienists raises an important question: Are dental practices that utilize a dental hygienist structurally and operationally different from practices that do not? This article explores differences among dental practices that operate with and without dental hygienists. Using data from the American Dental Association's 2003 Survey of Dental Practice, a random sample survey of U.S. dentists, descriptive statistics were used to compare selected characteristics of solo general practitioners with and without dental hygienists. Multivariate regression analysis was used to estimate the effect of dental hygienists on the gross billings and net incomes of solo general practitioners. Differences in practice characteristics--such as hours spent in the practice and hours spent treating patients, wait time for a recall visit, number of operatories, square feet of office space, net income, and gross billings--were found between solo general practitioners who had dental hygienists and those who did not. Solo general practitioners with dental hygienists had higher gross billings. Higher gross billings would be expected, as would higher expenses. However, net incomes of those with dental hygienists were also higher. In contrast, the mean waiting time for a recall visit was higher among dentists who employed dental hygienists. Depending on personal preferences, availability of qualified personnel, etc., dentists who do not employ dental hygienists but have been contemplating that path may want to further research the benefits and opportunities that may be realized.

  20. Dental education in Kuwait.

    Science.gov (United States)

    Behbehani, J M

    2003-01-01

    For a long time there has been a need to establish a dental school in Kuwait, due to the fact that the majority of dentists working in Kuwait are expatriates from various countries. An Amiri decree in 1996 made it possible, and the first dental students were admitted to the Kuwait University Faculty of Dentistry in 1998. The mission of the Faculty of Dentistry is 'to promote oral health in Kuwait through education, research and cooperation with other professional health care institutions as well as the community at large'. A 6.5-year dental curriculum was completed after 2 years of committee work and was accepted by the University Council in 2001. This curriculum incorporates current trends in medical and dental education, such as the evidence-based and community-based approaches, problem-solving methodology for outcome-based learning, and competency achieved through comprehensive patient care. Copyright 2003 S. Karger AG, Basel

  1. Xilitol and dental caries.

    NARCIS (Netherlands)

    Smits, Marten Titus

    1987-01-01

    Dental caries is a widespread multifactoral disease. The main sympthons are minaral loss from tooth enemal and dentine, eventually leading to total destruction of the teeth, pain, impairment of mastication and problems with facial esthetics. ... Zie: Summary

  2. Advances in dental imaging.

    Science.gov (United States)

    Brown, J E

    2001-04-01

    The number of dental radiographs taken in the UK has steadily increased over the past 20 years--recently estimating around 18 million taken in the general dental services alone, and dental radiographs now account for nearly 25% of all medical radiographic exposures. Radiographs remain our most useful diagnostic aid. Their strength is in demonstrating hard tissue pathology, which makes radiographs particularly effective in the maxillofacial region. Although well accepted in this capacity, there remain a number of limitations and drawbacks to conventional radiographs which recent developments have begun to overcome. There have been improvements in the scope and capabilities of dental imaging equipment. There has also been a continuing effort to reduce radiation-induced harm by limiting our exposure to it. This has been possible both through the introduction of new methods and protocols for reducing individual radiation exposures and by the creation of guidelines for selecting radiographs more effectively and thereby reducing the total number of radiographs taken.

  3. Glossary of Dental Terms

    Science.gov (United States)

    ... more... Coffee and Doughnuts: A Disastrous Combo for Teeth? The sugars in doughnuts have been identified as ... More print this article enlarge text Glossary of Dental Terms Oral Health Defined Amalgam silver/mercury alloy ...

  4. Dental care - child

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002213.htm Dental care - child To use the sharing features on ... please enable JavaScript. Proper care of your child's teeth and gums includes brushing and rinsing daily. It ...

  5. Dental Exam for Children

    Science.gov (United States)

    ... risks associated with tobacco, substance abuse and oral piercings. Why it's done Regular dental exams help protect ... sugary beverages Smoking Chewing tobacco Eating disorders Oral piercings Not wearing a mouthguard during contact sports The ...

  6. Nigerian Dental Journal: Submissions

    African Journals Online (AJOL)

    INSTRUCTIONS FOR AUTHORS AND CONTRIBUTORS The Nigerian Dental ... review articles, clinical case reports and innovations in surgical techniques ... figures and illustrations, including one copy stored in a 3.5” floppy should be sent to ...

  7. Dental Assisting Program Standards.

    Science.gov (United States)

    Georgia Univ., Athens. Dept. of Vocational Education.

    This publication contains statewide standards for the dental assisting program in Georgia. The standards are divided into 12 categories: foundations (philosophy, purpose, goals, program objectives, availability, evaluation); admissions (admission requirements, provisional admission requirements, recruitment, evaluation and planning); program…

  8. Argonaute-2-null embryonic stem cells are retarded in self-renewal ...

    Indian Academy of Sciences (India)

    Present address: Institute of Stem Cells and Regenerative Medicine, Bangalore, India ... [Chandra Shekar P, Naim A, Partha Sarathi D and Kumar S 2011 Argonaute-2-null embryonic stem cells are retarded in self-renewal ..... Research, India.

  9. Possible Solution to Publication Bias Through Bayesian Statistics, Including Proper Null Hypothesis Testing

    NARCIS (Netherlands)

    Konijn, Elly A.; van de Schoot, Rens; Winter, Sonja D.; Ferguson, Christopher J.

    2015-01-01

    The present paper argues that an important cause of publication bias resides in traditional frequentist statistics forcing binary decisions. An alternative approach through Bayesian statistics provides various degrees of support for any hypothesis allowing balanced decisions and proper null

  10. Vacuum non-expanding horizons and shear-free null geodesic congruences

    International Nuclear Information System (INIS)

    Adamo, T M; Newman, E T

    2009-01-01

    We investigate the geometry of a particular class of null surfaces in spacetime called vacuum non-expanding horizons (NEHs). Using the spin-coefficient equation, we provide a complete description of the horizon geometry, as well as fixing a canonical choice of null tetrad and coordinates on a NEH. By looking for particular classes of null geodesic congruences which live exterior to NEHs but have the special property that their shear vanishes at the intersection with the horizon, a good cut formalism for NEHs is developed which closely mirrors asymptotic theory. In particular, we show that such null geodesic congruences are generated by arbitrary choice of a complex worldline in a complex four-dimensional space, each such choice induces a CR structure on the horizon, and a particular worldline (and hence CR structure) may be chosen by transforming to a privileged tetrad frame.

  11. ON THE NATURE OF RECONNECTION AT A SOLAR CORONAL NULL POINT ABOVE A SEPARATRIX DOME

    International Nuclear Information System (INIS)

    Pontin, D. I.; Priest, E. R.; Galsgaard, K.

    2013-01-01

    Three-dimensional magnetic null points are ubiquitous in the solar corona and in any generic mixed-polarity magnetic field. We consider magnetic reconnection at an isolated coronal null point whose fan field lines form a dome structure. Using analytical and computational models, we demonstrate several features of spine-fan reconnection at such a null, including the fact that substantial magnetic flux transfer from one region of field line connectivity to another can occur. The flux transfer occurs across the current sheet that forms around the null point during spine-fan reconnection, and there is no separator present. Also, flipping of magnetic field lines takes place in a manner similar to that observed in the quasi-separatrix layer or slip-running reconnection

  12. Are eikonal quasinormal modes linked to the unstable circular null geodesics?

    Directory of Open Access Journals (Sweden)

    R.A. Konoplya

    2017-08-01

    Full Text Available In Cardoso et al. [6] it was claimed that quasinormal modes which any stationary, spherically symmetric and asymptotically flat black hole emits in the eikonal regime are determined by the parameters of the circular null geodesic: the real and imaginary parts of the quasinormal mode are multiples of the frequency and instability timescale of the circular null geodesics respectively. We shall consider asymptotically flat black hole in the Einstein–Lovelock theory, find analytical expressions for gravitational quasinormal modes in the eikonal regime and analyze the null geodesics. Comparison of the both phenomena shows that the expected link between the null geodesics and quasinormal modes is violated in the Einstein–Lovelock theory. Nevertheless, the correspondence exists for a number of other cases and here we formulate its actual limits.

  13. Are eikonal quasinormal modes linked to the unstable circular null geodesics?

    Science.gov (United States)

    Konoplya, R. A.; Stuchlík, Z.

    2017-08-01

    In Cardoso et al. [6] it was claimed that quasinormal modes which any stationary, spherically symmetric and asymptotically flat black hole emits in the eikonal regime are determined by the parameters of the circular null geodesic: the real and imaginary parts of the quasinormal mode are multiples of the frequency and instability timescale of the circular null geodesics respectively. We shall consider asymptotically flat black hole in the Einstein-Lovelock theory, find analytical expressions for gravitational quasinormal modes in the eikonal regime and analyze the null geodesics. Comparison of the both phenomena shows that the expected link between the null geodesics and quasinormal modes is violated in the Einstein-Lovelock theory. Nevertheless, the correspondence exists for a number of other cases and here we formulate its actual limits.

  14. Vlasov Fluid stability of a 2-D plasma with a linear magnetic field null

    International Nuclear Information System (INIS)

    Kim, J.S.

    1984-01-01

    Vlasov Fluid stability of a 2-dimensional plasma near an O type magnetic null is investigated. Specifically, an elongated Z-pinch is considered, and applied to Field Reversed Configurations at Los Alamos National Laboratory by making a cylindrical approximation of the compact torus. The orbits near an elliptical O type null are found to be very complicated; the orbits are large and some are stochastic. The kinetic corrections to magnetohydrodynamics (MHD) are investigated by evaluating the expectation values of the growth rates of a Vlasov Fluid dispersion functional by using a set of trial functions based on ideal MHD. The dispersion functional involves fluid parts and orbit dependent parts. The latter involves phase integral of two time correlations. The phase integral is replaced by the time integral both for the regular and for the stochastic orbits. Two trial functions are used; one has a large displacement near the null and the other away from the null

  15. Panoramic dental radiography

    International Nuclear Information System (INIS)

    Cushman, R.H.; Kircher, D.R.; Hart, F.W.; Ciavattoni, A.

    1980-01-01

    Apparatus is described for improving the handling rate of patients in panoramic dental radiography when tube head-camera assembly of a low silhouette panoramic dental X-ray machine is rotated for a scan in one direction only. This is effected by fast return of the tube head-camera assembly with its simultaneous elevation, thus facilitating the radiographed patient's exit from the machine and the entrance of another patient. Fast speed is about twice the scanning speed. (author)

  16. Saliva and dental erosion

    Directory of Open Access Journals (Sweden)

    Marília Afonso Rabelo Buzalaf

    2012-10-01

    Full Text Available Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. Objective: This review discusses the role of salivary factors on the development of dental erosion. Material and Methods: A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Results: Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Conclusions: Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

  17. Saliva and dental erosion.

    Science.gov (United States)

    Buzalaf, Marília Afonso Rabelo; Hannas, Angélicas Reis; Kato, Melissa Thiemi

    2012-01-01

    Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. This review discusses the role of salivary factors on the development of dental erosion. A search was undertaken on MeDLINe website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects.

  18. Managing dental erosion.

    Science.gov (United States)

    Curtis, Donald A; Jayanetti, Jay; Chu, Raymond; Staninec, Michal

    2012-01-01

    The clinical signs of dental erosion are initially subtle, yet often progress because the patient remains asymptomatic, unaware and uninformed. Erosion typically works synergistically with abrasion and attrition to cause loss of tooth structure, making diagnosis and management complex. The purpose of this article is to outline clinical examples of patients with dental erosion that highlight the strategy of early identification, patient education and conservative restorative management. Dental erosion is defined as the pathologic chronic loss of dental hard tissues as a result of the chemical influence of exogenous or endogenous acids without bacterial involvement. Like caries or periodontal disease, erosion has a multifactorial etiology and requires a thorough history and examination for diagnosis. It also requires patient understanding and compliance for improved outcomes. Erosion can affect the loss of tooth structure in isolation of other cofactors, but most often works in synergy with abrasion and attrition in the loss of tooth structure (Table 1). Although erosion is thought to be an underlying etiology of dentin sensitivity, erosion and loss of tooth structure often occurs with few symptoms. The purpose of this article is threefold: first, to outline existing barriers that may limit early management of dental erosion. Second, to review the clinical assessment required to establish a diagnosis of erosion. And third, to outline clinical examples that review options to restore lost tooth structure. The authors have included illustrations they hope will be used to improve patient understanding and motivation in the early management of dental erosion.

  19. Hypersensitivities for acetaldehyde and other agents among cancer cells null for clinically relevant Fanconi anemia genes.

    Science.gov (United States)

    Ghosh, Soma; Sur, Surojit; Yerram, Sashidhar R; Rago, Carlo; Bhunia, Anil K; Hossain, M Zulfiquer; Paun, Bogdan C; Ren, Yunzhao R; Iacobuzio-Donahue, Christine A; Azad, Nilofer A; Kern, Scott E

    2014-01-01

    Large-magnitude numerical distinctions (>10-fold) among drug responses of genetically contrasting cancers were crucial for guiding the development of some targeted therapies. Similar strategies brought epidemiological clues and prevention goals for genetic diseases. Such numerical guides, however, were incomplete or low magnitude for Fanconi anemia pathway (FANC) gene mutations relevant to cancer in FANC-mutation carriers (heterozygotes). We generated a four-gene FANC-null cancer panel, including the engineering of new PALB2/FANCN-null cancer cells by homologous recombination. A characteristic matching of FANCC-null, FANCG-null, BRCA2/FANCD1-null, and PALB2/FANCN-null phenotypes was confirmed by uniform tumor regression on single-dose cross-linker therapy in mice and by shared chemical hypersensitivities to various inter-strand cross-linking agents and γ-radiation in vitro. Some compounds, however, had contrasting magnitudes of sensitivity; a strikingly high (19- to 22-fold) hypersensitivity was seen among PALB2-null and BRCA2-null cells for the ethanol metabolite, acetaldehyde, associated with widespread chromosomal breakage at a concentration not producing breaks in parental cells. Because FANC-defective cancer cells can share or differ in their chemical sensitivities, patterns of selective hypersensitivity hold implications for the evolutionary understanding of this pathway. Clinical decisions for cancer-relevant prevention and management of FANC-mutation carriers could be modified by expanded studies of high-magnitude sensitivities. Copyright © 2014 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

  20. American Academy of Dental Sleep Medicine

    Science.gov (United States)

    ... New Research AADSM Highlights Members More news... Dental Sleep Medicine: An area of dental practice that focuses on ... SomnoMed Silver Sponsors Copyright © American Academy of Dental Sleep Medicine, All Rights Reserved. American Academy of Dental Sleep ...

  1. Dental patients' use of the Internet.

    LENUS (Irish Health Repository)

    2009-12-19

    To determine the use of the Internet by patients attending a range of dental clinics to search for information regarding dental procedures, and also to investigate their interest in online dental consultations and \\'dental tourism\\'.

  2. Null geodesics and embedding diagrams of the interior Schwarzschild--de Sitter spacetimes with uniform density

    International Nuclear Information System (INIS)

    Stuchlik, Zdenek; Hledik, Stanislav; Soltes, Jiri; Ostgaard, Erlend

    2001-01-01

    Null geodesics and embedding diagrams of central planes in the ordinary space geometry and the optical reference geometry of the interior Schwarzschild--de Sitter spacetimes with uniform density are studied. For completeness, both positive and negative values of the cosmological constant are considered. The null geodesics are restricted to the central planes of these spacetimes, and their properties can be reflected by an 'effective potential.' If the interior spacetime is extremely compact, the effective potential has a local maximum corresponding to a stable circular null geodesic around which bound null geodesics are concentrated. The upper limit on the size of the interior spacetimes containing bound null geodesics is R=3M, independently of the value of the cosmological constant. The embedding diagrams of the central planes of the ordinary geometry into three-dimensional Euclidean space are well defined for the complete interior of all spacetimes with a repulsive cosmological constant, but the planes cannot be embedded into the Euclidean space in the case of spacetimes with subcritical values of an attractive cosmological constant. On the other hand, the embedding diagrams of the optical geometry are well defined for all of the spacetimes, and the turning points of these diagrams correspond to the radii of the circular null geodesics. All the embedding diagrams, for both the ordinary and optical geometry, are smoothly matched to the corresponding embedding diagrams of the external vacuum Schwarzschild--de Sitter spacetimes

  3. pyNSMC: A Python Module for Null-Space Monte Carlo Uncertainty Analysis

    Science.gov (United States)

    White, J.; Brakefield, L. K.

    2015-12-01

    The null-space monte carlo technique is a non-linear uncertainty analyses technique that is well-suited to high-dimensional inverse problems. While the technique is powerful, the existing workflow for completing null-space monte carlo is cumbersome, requiring the use of multiple commandline utilities, several sets of intermediate files and even a text editor. pyNSMC is an open-source python module that automates the workflow of null-space monte carlo uncertainty analyses. The module is fully compatible with the PEST and PEST++ software suites and leverages existing functionality of pyEMU, a python framework for linear-based uncertainty analyses. pyNSMC greatly simplifies the existing workflow for null-space monte carlo by taking advantage of object oriented design facilities in python. The core of pyNSMC is the ensemble class, which draws and stores realized random vectors and also provides functionality for exporting and visualizing results. By relieving users of the tedium associated with file handling and command line utility execution, pyNSMC instead focuses the user on the important steps and assumptions of null-space monte carlo analysis. Furthermore, pyNSMC facilitates learning through flow charts and results visualization, which are available at many points in the algorithm. The ease-of-use of the pyNSMC workflow is compared to the existing workflow for null-space monte carlo for a synthetic groundwater model with hundreds of estimable parameters.

  4. The data-driven null models for information dissemination tree in social networks

    Science.gov (United States)

    Zhang, Zhiwei; Wang, Zhenyu

    2017-10-01

    For the purpose of detecting relatedness and co-occurrence between users, as well as the distribution features of nodes in spreading path of a social network, this paper explores topological characteristics of information dissemination trees (IDT) that can be employed indirectly to probe the information dissemination laws within social networks. Hence, three different null models of IDT are presented in this article, including the statistical-constrained 0-order IDT null model, the random-rewire-broken-edge 0-order IDT null model and the random-rewire-broken-edge 2-order IDT null model. These null models firstly generate the corresponding randomized copy of an actual IDT; then the extended significance profile, which is developed by adding the cascade ratio of information dissemination path, is exploited not only to evaluate degree correlation of two nodes associated with an edge, but also to assess the cascade ratio of different length of information dissemination paths. The experimental correspondences of the empirical analysis for several SinaWeibo IDTs and Twitter IDTs indicate that the IDT null models presented in this paper perform well in terms of degree correlation of nodes and dissemination path cascade ratio, which can be better to reveal the features of information dissemination and to fit the situation of real social networks.

  5. Losses at magnetic nulls in pulsed-power transmission line systems

    International Nuclear Information System (INIS)

    Mendel, C.W. Jr.; Pointon, T.D.; Savage, M.E.; Seidel, D.B.; Magne, I.; Vezinet, R.

    2006-01-01

    Pulsed-power systems operating in the terawatt regime must deal with large electron flows in vacuum transmission lines. In most parts of these transmission lines the electrons are constrained by the self-magnetic field to flow parallel to the conductors. In very low impedance systems, such as those used to drive Z-pinch radiation sources, the currents from multiple transmission lines are added together. This addition necessarily involves magnetic nulls that connect the positive and negative electrodes. The resultant local loss of magnetic insulation results in electron losses at the anode in the vicinity of the nulls. The lost current due to the magnetic null might or might not be appreciable. In some cases the lost current due to the null is not large, but is spatially localized, and may create a gas and plasma release from the anode that can lead to an excessive loss, and possibly to catastrophic damage to the hardware. In this paper we describe an analytic model that uses one geometric parameter (aside from straightforward hardware size measurements) that determines the loss to the anode, and the extent of the loss region when the driving source and load are known. The parameter can be calculated in terms of the magnetic field in the region of the null calculated when no electron flow is present. The model is compared to some experimental data, and to simulations of several different hardware geometries, including some cases with multiple nulls, and unbalanced feeds

  6. Premeiotic germ cell defect in seminiferous tubules of Atm-null testis

    International Nuclear Information System (INIS)

    Takubo, Keiyo; Hirao, Atsushi; Ohmura, Masako; Azuma, Masaki; Arai, Fumio; Nagamatsu, Go; Suda, Toshio

    2006-01-01

    Lifelong spermatogenesis is maintained by coordinated sequential processes including self-renewal of stem cells, proliferation of spermatogonial cells, meiotic division, and spermiogenesis. It has been shown that ataxia telangiectasia-mutated (ATM) is required for meiotic division of the seminiferous tubules. Here, we show that, in addition to its role in meiosis, ATM has a pivotal role in premeiotic germ cell maintenance. ATM is activated in premeiotic spermatogonial cells and the Atm-null testis shows progressive degeneration. In Atm-null testicular cells, differing from bone marrow cells of Atm-null mice, reactive oxygen species-mediated p16 Ink4a activation does not occur in Atm-null premeiotic germ cells, which suggests the involvement of different signaling pathways from bone marrow defects. Although Atm-null bone marrow undergoes p16 Ink4a -mediated cellular senescence program, Atm-null premeiotic germ cells exhibited cell cycle arrest and apoptotic elimination of premeiotic germ cells, which is different from p16 Ink4a -mediated senescence

  7. 42 CFR Appendix G to Part 75 - Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography G Appendix G to Part 75 Public Health PUBLIC HEALTH SERVICE...—Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography The following section...

  8. Collaborative Dental Hygiene Practice in New Mexico and Minnesota.

    Science.gov (United States)

    Hodges, Kathleen O; Rogo, Ellen J; Cahoon, Allison C; Neill, Karen

    2016-06-01

    This descriptive, comparative study was conducted to examine characteristics, services, models and opinions among collaborative dental hygiene practitioners in New Mexico and Minnesota. A self-designed online questionnaire, distributed via SurveyMonkey®, was utilized to collect data from 73 subjects who met the inclusion criteria. A multi-phase administration process was followed. Content validity and reliability was established. Descriptive statistics were used for analysis of 6 research questions. The Mann-Whitney U, Pearson Chi-Square and Fisher's Exact tests were employed to analyze 4 null hypotheses (p=0.05). Most participants (n=36) were experienced clinicians who chose to work in an alternative setting after 28 years or more in the field and reported increased access to care as the reason for practicing collaboratively. A variety of services were offered and private insurance and Medicaid were accepted, although many practitioners did not receive direct reimbursement. The majority of New Mexico participants worked in private dental hygiene practices, earned advanced degrees and serviced Health Provider Shortage Areas. The majority of Minnesota respondents worked in various facilities, earned associate's degrees and were uncertain if Health Provider Shortage Areas were served. There were no significant differences in the variables between practitioners in both states. New Mexico and Minnesota collaborative dental hygiene practitioners are similar in characteristics, services, and opinions although models of practice vary. Collaborative dental hygiene practice is a viable answer to increasing access to care and is an option for patients who might otherwise go without care, including the unserved, underserved, uninsured and underinsured. Copyright © 2016 The American Dental Hygienists’ Association.

  9. Dental school finances: current status.

    Science.gov (United States)

    Crawford, W H

    1986-05-01

    Total expenditures and revenues of 58 US dental school were derived from reports of the ADA Division of Educational Measurements. These financial data were studied by type of dental school (public, state-related private, and private) and by expenditure/revenue categories. Dental schools showed little diversity in expenditures: most were directed toward instruction; few were directed toward research or continuing education. Several distinctive patterns among the three types of dental schools in revenues were observed. Two configurations emerged: public and state-related private dental schools receive more than 75% of their revenues from government and tuition, and private dental schools, more than 50%.

  10. Patient Satisfaction in Military Dental Treatment Facilities

    Science.gov (United States)

    2006-03-07

    the variance in regards to overall satisfaction. 15. SUBJECT TERMS Dentistry, Patient Satisfaction, Military, Consumer Satisfaction, Dental... patient satisfaction in military dental treatment facilities. Dental health is extremely important for the military as dental assets are not always... customer satisfaction is an important component of military dental care. Quarterly patient satisfaction reports are generated for each dental treatment

  11. History of dental hygiene research.

    Science.gov (United States)

    Bowen, Denise M

    2013-01-01

    Dental hygiene is defined as the science and practice of the recognition, treatment and prevention of oral diseases. The history of dental hygiene research is considered in the context of the development of the discipline and an emerging infrastructure. Research-related events supporting the growth and maturation of the profession are considered from the early years to the most recent. The benefits of preventive oral health services provided by dental hygienists have been supported by research, and the practice of dental hygiene has expanded as a result of research findings since its inception 100 years ago. Dental hygienists' engagement in research, however, did not begin until the 1960s as research associates or administrators, primarily with dental researchers as primary investigators. The Journal of Dental Hygiene (JDH) has provided information for dental hygiene practice since 1927, and has been the primary venue for dissemination of dental hygiene research since 1945. Graduate education in dental hygiene at the master's degree level and the work of early dental hygiene researchers led to the first conference on dental hygiene research in 1982. Over 30 years later, dental hygiene has established a meta-paradigm and defined conceptual models, built an initial infrastructure to support research endeavors and contributed much to the development of dental hygiene as a unique discipline. A doctoral degree in the discipline, continued theory-based research, initiatives to foster collaborations between dental hygiene and other researchers and enhanced capabilities to attract funding to support large scale studies are goals that must be attained through the efforts of future researchers to address the needs for additional development in the discipline of dental hygiene. Dental hygiene research supports the growing discipline and its value to society.

  12. Bruxism and Dental Implants: A Meta-Analysis.

    Science.gov (United States)

    Chrcanovic, Bruno Ramos; Albrektsson, Tomas; Wennerberg, Ann

    2015-10-01

    To test the null hypothesis of no difference in the implant failure rates, postoperative infection, and marginal bone loss after the insertion of dental implants in bruxers compared with the insertion in non-bruxers against the alternative hypothesis of a difference. An electronic search was undertaken in June 2014. Eligibility criteria included clinical studies, either randomized or not. Ten publications were included with a total of 760 implants inserted in bruxers (49 failures; 6.45%) and 2989 in non-bruxers (109 failures; 3.65%). Due to lack of information, meta-analyses for the outcomes "postoperative infection" and "marginal bone loss" were not possible. A risk ratio of 2.93 was found (95% confidence interval, 1.48-5.81; P = 0.002). These results cannot suggest that the insertion of dental implants in bruxers affects the implant failure rates due to a limited number of published studies, all characterized by a low level of specificity, and most of them deal with a limited number of cases without a control group. Therefore, the real effect of bruxing habits on the osseointegration and survival of endosteal dental implants is still not well established.

  13. Bulimia and Anorexia Nervosa in Dental and Dental Hygiene Curricula.

    Science.gov (United States)

    Gross, Karen B. W.; And Others

    1990-01-01

    Dentists and dental hygienists are in a unique position to identify an eating disorder patient from observed oral manifestations and to refer the patient for psychological therapy. The inclusion of information on general and oral complications of bulimia and anorexia nervosa in dental and dental hygiene curriculum was examined. (MLW)

  14. Hand hygiene amongst dental professionals in a tertiary dental clinic ...

    African Journals Online (AJOL)

    Objective: To evaluate hand washing attitude and practices among Dentists and Dental Students treating patients in a Nigerian Tertiary Dental Clinic. Materials and Methods: A cross-sectional survey of Dentists and Dental Students treating patients in University of Benin Teaching Hospital was conducted between February ...

  15. Reasons for late seeking of dental care among dental patients ...

    African Journals Online (AJOL)

    Reasons for delayed reporting for oral care were negligence (53.5%); poor dental services or visited but not treated (19.4%); financial reasons (14.8%); and dental fear (12.3%). Seventy seven percent of respondents who had toothache due to advanced dental caries were aware that the aching tooth was decayed, of which, ...

  16. Diagnostic methods for dental caries used by private dental ...

    African Journals Online (AJOL)

    Objectives: This study aimed to investigate the preference profiles of various types of diagnostic tools and methods used by private dental practitioners in Ankara for detecting dental caries. Methods: Private dental practitioners, in five districts of Ankara, were provided with questionnaires comprising demographic ...

  17. Dental Education in the Netherlands.

    Science.gov (United States)

    Nash, David A.; And Others

    1981-01-01

    Dental education in the Netherlands is reviewed in terms of dental practice, overall development, structure and functioning of a typical school of dentistry, admissions, student finances, curriculum, certification, postgraduate education, and education for related professions. (MSE)

  18. Medical and Dental Patient Issues

    Science.gov (United States)

    ... A RadiationAnswers.org Ask the Experts Medical and Dental Patient Issues What's My Risk? The risks of ... developed by our topic editors for this category: Dental-Patient Issues Medical CT Reference Books and Articles ...

  19. Dental Care - Medicaid and Chip

    Data.gov (United States)

    U.S. Department of Health & Human Services — Dental health is an important part of peoples overall health. States are required to provide dental benefits to children covered by Medicaid and the Childrens Health...

  20. Dental modification in the past

    DEFF Research Database (Denmark)

    Bennike, Pia; Alexandersen, Verner

    2003-01-01

    Skeleton remains from Denmark, Greenland, Faeroe Islands, dental care, drillling in the past, tooth extraction......Skeleton remains from Denmark, Greenland, Faeroe Islands, dental care, drillling in the past, tooth extraction...

  1. Dental Health: The Basic Facts

    Science.gov (United States)

    Dental Health THE BASIC FACTS MULTIPLE SCLEROSIS Kim, diagnosed in 1986 People with a chronic disease may neglect their general health and wellness, research shows. Dental care is no exception. A tendency to focus ...

  2. Dental plaque identification at home

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003426.htm Dental plaque identification at home To use the sharing ... a sticky substance that collects around and between teeth. The home dental plaque identification test shows where ...

  3. Radiation protection in dental practice

    International Nuclear Information System (INIS)

    This guide provides the dentist and dental support personnel with basic information on the safe use of x-rays in dental radiography. Included in this CODE are specific recommendations for eliminating unnecessary radiation exposure of both patients and staff

  4. Visualisation of dental images

    International Nuclear Information System (INIS)

    Md Saion Salikin; Azuhar Ripin; Wan Hazlinda Ismail; Asmaliza Hashim; Norriza Mohd Isa; Suriany Sarmid

    2005-01-01

    Since the invention and the discovery of x-rays, physicians, surgeons and life scientists have been using images to diagnose and subsequently treat diseases. X-ray is also widely used in many imaging techniques to better understand basics anatomy, physiology and biology as well as testing and analytical work in physical science. In dentistry, x-ray technique has been employed to get a panoramic view of the whole teeth of a particular patient. A panoramic dental radiograph is very useful in dentistry for diagnostic purpose, denture preparation, as well as for orthodontic. Image visualisation is an important aspect especially for the dentists to analyse and proceed with a particulate dental treatment. In this project panoramic dental image obtained by using a standard phantom is visualised by using Interactive Data Language (IDL) software. A panoramic dental x-ray machine, Cranex3, is used to get a panoramic radiograph, which is subsequently digitized, by using Vidar digitizer (Sierra Plus). The 2D digitized image is enhance and apply other visualising techniques such as surface rendering and volume rendering technique using Interactive Data Language (IDL) software as a first step in 3D visualisation. In this paper, visualising of panoramic dental radiograph by using IDL is discussed in brief. (Author)

  5. Influence of choice of null network on small-world parameters of structural correlation networks.

    Directory of Open Access Journals (Sweden)

    S M Hadi Hosseini

    Full Text Available In recent years, coordinated variations in brain morphology (e.g., volume, thickness have been employed as a measure of structural association between brain regions to infer large-scale structural correlation networks. Recent evidence suggests that brain networks constructed in this manner are inherently more clustered than random networks of the same size and degree. Thus, null networks constructed by randomizing topology are not a good choice for benchmarking small-world parameters of these networks. In the present report, we investigated the influence of choice of null networks on small-world parameters of gray matter correlation networks in healthy individuals and survivors of acute lymphoblastic leukemia. Three types of null networks were studied: 1 networks constructed by topology randomization (TOP, 2 networks matched to the distributional properties of the observed covariance matrix (HQS, and 3 networks generated from correlation of randomized input data (COR. The results revealed that the choice of null network not only influences the estimated small-world parameters, it also influences the results of between-group differences in small-world parameters. In addition, at higher network densities, the choice of null network influences the direction of group differences in network measures. Our data suggest that the choice of null network is quite crucial for interpretation of group differences in small-world parameters of structural correlation networks. We argue that none of the available null models is perfect for estimation of small-world parameters for correlation networks and the relative strengths and weaknesses of the selected model should be carefully considered with respect to obtained network measures.

  6. Influence of Choice of Null Network on Small-World Parameters of Structural Correlation Networks

    Science.gov (United States)

    Hosseini, S. M. Hadi; Kesler, Shelli R.

    2013-01-01

    In recent years, coordinated variations in brain morphology (e.g., volume, thickness) have been employed as a measure of structural association between brain regions to infer large-scale structural correlation networks. Recent evidence suggests that brain networks constructed in this manner are inherently more clustered than random networks of the same size and degree. Thus, null networks constructed by randomizing topology are not a good choice for benchmarking small-world parameters of these networks. In the present report, we investigated the influence of choice of null networks on small-world parameters of gray matter correlation networks in healthy individuals and survivors of acute lymphoblastic leukemia. Three types of null networks were studied: 1) networks constructed by topology randomization (TOP), 2) networks matched to the distributional properties of the observed covariance matrix (HQS), and 3) networks generated from correlation of randomized input data (COR). The results revealed that the choice of null network not only influences the estimated small-world parameters, it also influences the results of between-group differences in small-world parameters. In addition, at higher network densities, the choice of null network influences the direction of group differences in network measures. Our data suggest that the choice of null network is quite crucial for interpretation of group differences in small-world parameters of structural correlation networks. We argue that none of the available null models is perfect for estimation of small-world parameters for correlation networks and the relative strengths and weaknesses of the selected model should be carefully considered with respect to obtained network measures. PMID:23840672

  7. Abnormal Activation of BMP Signaling Causes Myopathy in Fbn2 Null Mice.

    Directory of Open Access Journals (Sweden)

    Gerhard Sengle

    2015-06-01

    Full Text Available Fibrillins are large extracellular macromolecules that polymerize to form the backbone structure of connective tissue microfibrils. Mutations in the gene for fibrillin-1 cause the Marfan syndrome, while mutations in the gene for fibrillin-2 cause Congenital Contractural Arachnodactyly. Both are autosomal dominant disorders, and both disorders affect musculoskeletal tissues. Here we show that Fbn2 null mice (on a 129/Sv background are born with reduced muscle mass, abnormal muscle histology, and signs of activated BMP signaling in skeletal muscle. A delay in Myosin Heavy Chain 8, a perinatal myosin, was found in Fbn2 null forelimb muscle tissue, consistent with the notion that muscle defects underlie forelimb contractures in these mice. In addition, white fat accumulated in the forelimbs during the early postnatal period. Adult Fbn2 null mice are already known to demonstrate persistent muscle weakness. Here we measured elevated creatine kinase levels in adult Fbn2 null mice, indicating ongoing cycles of muscle injury. On a C57Bl/6 background, Fbn2 null mice showed severe defects in musculature, leading to neonatal death from respiratory failure. These new findings demonstrate that loss of fibrillin-2 results in phenotypes similar to those found in congenital muscular dystrophies and that FBN2 should be considered as a candidate gene for recessive congenital muscular dystrophy. Both in vivo and in vitro evidence associated muscle abnormalities and accumulation of white fat in Fbn2 null mice with abnormally activated BMP signaling. Genetic rescue of reduced muscle mass and accumulation of white fat in Fbn2 null mice was accomplished by deleting a single allele of Bmp7. In contrast to other reports that activated BMP signaling leads to muscle hypertrophy, our findings demonstrate the exquisite sensitivity of BMP signaling to the fibrillin-2 extracellular environment during early postnatal muscle development. New evidence presented here suggests that

  8. Averaged null energy condition and difference inequalities in quantum field theory

    International Nuclear Information System (INIS)

    Yurtsever, U.

    1995-01-01

    For a large class of quantum states, all local (pointwise) energy conditions widely used in relativity are violated by the renormalized stress-energy tensor of a quantum field. In contrast, certain nonlocal positivity constraints on the quantum stress-energy tensor might hold quite generally, and this possibility has received considerable attention in recent years. In particular, it is now known that the averaged null energy condition, the condition that the null-null component of the stress-energy tensor integrated along a complete null geodesic is non-negative for all states, holds quite generally in a wide class of spacetimes for a minimally coupled scalar field. Apart from the specific class of spacetimes considered (mainly two-dimensional spacetimes and four-dimensional Minkowski space), the most significant restriction on this result is that the null geodesic over which the average is taken must be achronal. Recently, Ford and Roman have explored this restriction in two-dimensional flat spacetime, and discovered that in a flat cylindrical space, although the stress energy tensor itself fails to satisfy the averaged null energy condition (ANEC) along the (nonachronal) null geodesics, when the ''Casimir-vacuum'' contribution is subtracted from the stress-energy the resulting tensor does satisfy the ANEC inequality. Ford and Roman name this class of constraints on the quantum stress-energy tensor ''difference inequalities.'' Here I give a proof of the difference inequality for a minimally coupled massless scalar field in an arbitrary (globally hyperbolic) two-dimensional spacetime, using the same techniques as those we relied on to prove the ANEC in an earlier paper with Wald. I begin with an overview of averaged energy conditions in quantum field theory

  9. Does dental caries affect dental development in children and adolescents?

    Science.gov (United States)

    Dhamo, Brunilda; Elezi, Besiana; Kragt, Lea; Wolvius, Eppo B; Ongkosuwito, Edwin M

    2018-01-01

    Although a link between dietary changes, caries, and dental development has been observed, the literature provides little insight about this relationship. The aim of our study was to investigate the association between dental caries and dental development in a clinical sample of Albanian children and adolescents. In total, 118 children and adolescents, born between 1995 and 2004 and aged 6–15 years, were included. Dental caries in the deciduous dentition was assessed using the Decayed, Filled Teeth (dft) index and dental caries in the permanent dentition was assessed using the Decayed, Missing, Filled Teeth (DMFT) index. Dental development during the permanent dentition was determined using the Demirjian method. Linear and ordinal regression models were applied to analyze the associations of dental caries with dental age and developmental stages of each left mandibular tooth. Dental caries in the deciduous dentition, estimated as a median dft of 2.0 (90% range, 0.0–9.1), was significantly associated with lower dental age (β = -0.21; 90% CI: -0.29, -0.12) and with delayed development of the canine, both premolars, and the second molar. Untreated dental caries (dt) was associated with lower dental age (β = -0.19; 90% CI: -0.28, -0.10). Dental caries in the permanent dentition, estimated as a median DMFT of 1.0 (90% range, 0.0–8.0), was not significantly associated with dental age (β = 0.05; 90% CI: -0.04, 0.14). However, the DMFT was associated with the advanced stages of development of both premolars and the second molar. The untreated dental caries in the deciduous dentition delays the development of permanent teeth. PMID:29659350

  10. Dental ethics and emotional intelligence.

    Science.gov (United States)

    Rosenblum, Alvin B; Wolf, Steve

    2014-01-01

    Dental ethics is often taught, viewed, and conducted as an intell enterprise, uninformed by other noncognitive factors. Emotional intelligence (EQ) is defined distinguished from the cognitive intelligence measured by Intelligence Quotient (IQ). This essay recommends more inclusion of emotional, noncognitive input to the ethical decision process in dental education and dental practice.

  11. The Primary Dental Care Workforce.

    Science.gov (United States)

    Neenan, M. Elaine; And Others

    1993-01-01

    A study describes the characteristics of the current primary dental care workforce (dentists, hygienists, assistants), its distribution, and its delivery system in private and public sectors. Graduate dental school enrollments, trends in patient visits, employment patterns, state dental activities, and workforce issues related to health care…

  12. Dental Hygiene Realpolitik Affecting Education.

    Science.gov (United States)

    Bader, James D.

    1991-01-01

    Current conditions in dental hygiene influencing professional education are discussed. Workplace/practice issues include dental hygiene care as a component of dental practice, content, effects, and quality of care, hygienist supply and demand, and job satisfaction. Professional issues include the knowledge base, definitions of practice, and…

  13. 76 FR 14600 - Dental Conditions

    Science.gov (United States)

    2011-03-17

    ... qualify for VHA dental treatment, including any claim for treatment of periodontal disease or calculus... DEPARTMENT OF VETERANS AFFAIRS 38 CFR Part 3 RIN 2900-AN28 Dental Conditions AGENCY: Department of... its adjudication regulations regarding service connection of dental conditions for treatment purposes...

  14. Panoramic Dental X-Ray

    Science.gov (United States)

    ... Physician Resources Professions Site Index A-Z Panoramic Dental X-ray Panoramic dental x-ray uses a very small dose of ... x-ray , is a two-dimensional (2-D) dental x-ray examination that captures the entire mouth ...

  15. 77 FR 4469 - Dental Conditions

    Science.gov (United States)

    2012-01-30

    ... DEPARTMENT OF VETERANS AFFAIRS 38 CFR Part 3 RIN 2900-AN28 Dental Conditions AGENCY: Department of... rule the proposal to amend its adjudication regulations regarding service connection of dental... Veterans Benefits Administration (VBA) for service connection of dental conditions for the purpose of...

  16. Dental therapists: a global perspective.

    Science.gov (United States)

    Nash, David A; Friedman, Jay W; Kardos, Thomas B; Kardos, Rosemary L; Schwarz, Eli; Satur, Julie; Berg, Darren G; Nasruddin, Jaafar; Mumghamba, Elifuraha G; Davenport, Elizabeth S; Nagel, Ron

    2008-04-01

    In 1921, New Zealand began training school dental nurses, subsequently deploying them throughout the country in school-based clinics providing basic dental care for children. The concept of training dental nurses, later to be designated dental therapists, was adopted by other countries as a means of improving access to care, particularly for children. This paper profiles six countries that utilise dental therapists, with a description of the training that therapists receive in these countries, and the context in which they practice. Based on available demographic information, it also updates the number of dental therapists practising globally, as well as the countries in which they practice. In several countries, dental therapy is now being integrated with dental hygiene in training and practice to create a new type of professional complementary to a dentist. Increasingly, dental therapists are permitted to treat adults as well as children. The paper also describes the status of a current initiative to introduce dental therapy to the United States. It concludes by suggesting that dental therapists can become valued members of the dental team throughout the world, helping to improve access to care and reducing existing disparities in oral health.

  17. Stereoscopy in Dental Education

    DEFF Research Database (Denmark)

    Murakami, Shumei; Verdonschot, Rinus G; Kreiborg, Sven

    2017-01-01

    The aim of this study was to investigate whether stereoscopy can play a meaningful role in dental education. The study used an anaglyph technique in which two images were presented separately to the left and right eyes (using red/cyan filters), which, combined in the brain, give enhanced depth...... perception. A positional judgment task was performed to assess whether the use of stereoscopy would enhance depth perception among dental students at Osaka University in Japan. Subsequently, the optimum angle was evaluated to obtain maximum ability to discriminate among complex anatomical structures. Finally...... practice, they did recognize its merits for education. These results suggest that using stereoscopic images in dental education can be quite valuable as stereoscopy greatly helped these students' understanding of the spatial relationships in complex anatomical structures....

  18. Risks from dental radiology

    International Nuclear Information System (INIS)

    Costa, Tamara Goularte

    2013-01-01

    The objective of this research is to demonstrate the risks and consequences of exposure to dental X-ray. The methodology used was the survey of bibliographic literature on this matter. First, we tried to understand the operation and characteristics of dental X-rays. Afterwards, we tried to know about the risks that this procedure offers to workers and patients. And concluded with the consequences of such exposure. The results showed that dental x-rays only offer risks in prolonged exposure, can affect the worker or patient to pathologies such as cancer or a life-time decreased due to the stochastic effect. Therefore, radiological protection standards must be respected and practised. (author)

  19. Dental implants: A review.

    Science.gov (United States)

    Guillaume, B

    2016-12-01

    A high number of patients have one or more missing tooth and it is estimated that one in four American subjects over the age of 74 have lost all their natural teeth. Many options exist to replace missing teeth but dental implants have become one of the most used biomaterial to replace one (or more) missing tooth over the last decades. Contemporary dental implants made with titanium have been proven safe and effective in large series of patients. This review considers the main historical facts concerned with dental implants and present the different critical factors that will ensure a good osseo-integration that will ensure a stable prosthesis anchorage. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  20. Dental formulations for the prevention of dental erosion

    DEFF Research Database (Denmark)

    2010-01-01

    The invention relates to a therapeutic method for preventing and/or inhibiting dental erosion in a mammalian subject, and the provision of a dental care product for performing the method. The dental care product of the invention comprises a starch-degrading enzyme of E. C. 3.2.1.1, wherein said...... product comprises less than 1 wt.% ionic surfactant, and preferably is substantially free of endoprotease and/or lipase. The properties of the dental care product serve to prevent and/or inhibit dental erosion in a subject that typically results from repeated exposure of the patient's tooth surfaces...

  1. Vacuum Nuller Testbed (VNT) Performance, Characterization and Null Control: Progress Report

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Petrone, Peter; Mallik, Udayan; Madison, Timothy; Bolcar, Matthew R.; Noecker, M. Charley; Kendrick, Stephen; Helmbrecht, Michael

    2011-01-01

    Herein we report on the development. sensing and control and our first results with the Vacuum Nuller Testbed to realize a Visible Nulling Coronagraph (VNC) for exoplanet coronagraphy. The VNC is one of the few approaches that works with filled. segmented and sparse or diluted-aperture telescope systems. It thus spans a range of potential future NASA telescopes and could be Hown as a separate instrument on such a future mission. NASA/Goddard Space Flight Center (GSFC) has a well-established effort to develop VNC technologies. and has developed an incremental sequence of VNC testbeds to advance this approach and the enabling technologies associated with it. We discuss the continued development of the vacuum Visible Nulling Coronagraph testbed (VNT). Tbe VNT is an ultra-stable vibration isolated testbed that operates under closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence of three visible-light nulling milestones with sequentially higher contrasts of 10(sup 8), 10(sup 9) and ideally 10(sup 10) at an inner working angle of 2*lambda/D. The VNT is based on a modified Mach-Zehnder nulling interferometer, with a "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters. We discuss the initial laboratory results, the optical configuration, critical technologies and the null sensing and control approach.

  2. A Null Space Control of Two Wheels Driven Mobile Manipulator Using Passivity Theory

    Science.gov (United States)

    Shibata, Tsuyoshi; Murakami, Toshiyuki

    This paper describes a control strategy of null space motion of a two wheels driven mobile manipulator. Recently, robot is utilized in various industrial fields and it is preferable for the robot manipulator to have multiple degrees of freedom motion. Several studies of kinematics for null space motion have been proposed. However stability analysis of null space motion is not enough. Furthermore, these approaches apply to stable systems, but they do not apply unstable systems. Then, in this research, base of manipulator equips with two wheels driven mobile robot. This robot is called two wheels driven mobile manipulator, which becomes unstable system. In the proposed approach, a control design of null space uses passivity based stabilizing. A proposed controller is decided so that closed-loop system of robot dynamics satisfies passivity. This is passivity based control. Then, control strategy is that stabilizing of the robot system applies to work space observer based approach and null space control while keeping end-effector position. The validity of the proposed approach is verified by simulations and experiments of two wheels driven mobile manipulator.

  3. Time asymmetric spacetimes near null and spatial infinity: I. Expansions of developments of conformally flat data

    International Nuclear Information System (INIS)

    Kroon, Juan Antonio Valiente

    2004-01-01

    The conformal Einstein equations and the representation of spatial infinity as a cylinder introduced by Friedrich are used to analyse the behaviour of the gravitational field near null and spatial infinity for the development of data which are asymptotically Euclidean, conformally flat and time asymmetric. Our analysis allows for initial data whose second fundamental form is more general than the one given by the standard Bowen-York ansatz. The conformal Einstein equations imply, upon evaluation on the cylinder at spatial infinity, a hierarchy of transport equations which can be used to calculate asymptotic expansions for the gravitational field in a recursive way. It is found that the solutions to these transport equations develop logarithmic divergences at the critical sets where null infinity meets spatial infinity. Associated with these, there is a series of quantities expressible in terms of the initial data (obstructions), which if zero, preclude the appearance of some of the logarithmic divergences. The obstructions are, in general, time asymmetric. That is, the obstructions at the intersection of future null infinity with spatial infinity are in general different from those obtained at the intersection of past null infinity with spatial infinity. The latter allows for the possibility of having spacetimes where future and past null infinity have different degrees of smoothness. Finally, it is shown that if both sets of obstructions vanish up to a certain order, then the initial data have to be asymptotically Schwarzschildean in a certain sense

  4. Vacuum nuller testbed (VNT) performance, characterization and null control: progress report

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Petrone, Peter; Mallik, Udayan; Madison, Timothy; Bolcar, Matthew R.; Noecker, M. Charley; Kendrick, Stephen; Helmbrecht, Michael

    2011-10-01

    Herein we report on the development, sensing and control and our first results with the Vacuum Nuller Testbed to realize a Visible Nulling Coronagraph (VNC) for exoplanet coronagraphy. The VNC is one of the few approaches that works with filled, segmented and sparse or diluted-aperture telescope systems. It thus spans a range of potential future NASA telescopes and could be flown as a separate instrument on such a future mission. NASA/Goddard Space Flight Center (GSFC) has a well-established effort to develop VNC technologies, and has developed an incremental sequence of VNC testbeds to advance this approach and the enabling technologies associated with it. We discuss the continued development of the vacuum Visible Nulling Coronagraph testbed (VNT). The VNT is an ultra-stable vibration isolated testbed that operates under closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence of three visible-light nulling milestones with sequentially higher contrasts of 108, 109, and ideally 1010 at an inner working angle of 2*λ/D. The VNT is based on a modified Mach-Zehnder nulling interferometer, with a "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters. We discuss the initial laboratory results, the optical configuration, critical technologies and the null sensing and control approach.

  5. Current singularities at finitely compressible three-dimensional magnetic null points

    International Nuclear Information System (INIS)

    Pontin, D.I.; Craig, I.J.D.

    2005-01-01

    The formation of current singularities at line-tied two- and three-dimensional (2D and 3D, respectively) magnetic null points in a nonresistive magnetohydrodynamic environment is explored. It is shown that, despite the different separatrix structures of 2D and 3D null points, current singularities may be initiated in a formally equivalent manner. This is true no matter whether the collapse is triggered by flux imbalance within closed, line-tied null points or driven by externally imposed velocity fields in open, incompressible geometries. A Lagrangian numerical code is used to investigate the finite amplitude perturbations that lead to singular current sheets in collapsing 2D and 3D null points. The form of the singular current distribution is analyzed as a function of the spatial anisotropy of the null point, and the effects of finite gas pressure are quantified. It is pointed out that the pressure force, while never stopping the formation of the singularity, significantly alters the morphology of the current distribution as well as dramatically weakening its strength. The impact of these findings on 2D and 3D magnetic reconnection models is discussed

  6. Syllabus of Dental Materials

    Science.gov (United States)

    1984-07-01

    Rubberloid Van R Dental Prod. Surgident Lactona Corp. Alginates Coe Alginate Coe Labs o Jeltrate L.D. Caulk Kerr Alginate Kerr/Sybron Alginate S.S. White Co...Surgident- Alginate Lactona Corp. Unijel II Unitek Corp. O Combination Agar/a ig inate Colloid 80 U.S. Shiza Corp. Dentloid Denterials, Ltd...66061 (215) 277-3800 (913) 782-2200 Shofu Dental Corp. Lactona Corp. (subsidary of 4025 Bohannon Dr. Warner-Lambert Co.) Menlo Park, CA 94025 . Academy

  7. Dental Trauma Guide

    DEFF Research Database (Denmark)

    Andreasen, Jens Ove; Lauridsen, Eva Fejerskov; Christensen, Søren Steno Ahrensburg

    2012-01-01

    Diagnose and treatment of traumatic dental injuries is very complex due to the multiple trauma entities represented by 6 lunation types and 9 fracture types affecting both the primary and the permanent dentition. When it is further considered that fracture and lunation injuries are often combined...... problems in selecting proper treatment for some of these trauma types. To remedy this situation, an internet based knowledge base consisting of 4000 dental trauma cases with long term follow up is now available to the public and professionals, on the internet using the address www...

  8. Perceived Dentist and Dental Hygienist Task Distribution After Dental and Dental Hygiene Students' Team Intervention

    NARCIS (Netherlands)

    Reinders, Jan J.; Krijnen, Wim P.; Stegenga, Boudewijn; van der Schans, Cees P.

    2017-01-01

    Attitudes of dental students regarding the provision of treatment tend to be dentist-centered; however, facilitating mixed student group formation could change such perceptions. The aim of this study was to investigate the perceived scope of practice of dental and dental hygiene students and whether

  9. Perceived dentist and dental hygienist task distribution after dental and dental hygiene students' team intervention

    NARCIS (Netherlands)

    Reinders, Jan J; Krijnen, Wim P; Stegenga, Boudewijn; van der Schans, Cees P

    Attitudes of dental students regarding the provision of treatment tend to be dentist-centered; however, facilitating mixed student group formation could change such perceptions. The aim of this study was to investigate the perceived scope of practice of dental and dental hygiene students and whether

  10. Anti-optic-null medium: Achieving the optic-null medium effect by enclosing an air region with relatively low-anisotropy media

    Science.gov (United States)

    Sun, Fei; Liu, Yichao; He, Sailing

    2016-07-01

    A so-called anti-optic-null medium (anti-ONM), which can be utilized to cancel the optic-null medium (ONM) and create many novel optical illusions, is introduced and designed by transformation optics (TO). Optical separation illusions can be achieved with an anti-ONM. With the help of the anti-ONM, we can achieve the same optical illusions where ONM is required via a shelled structure filled with low anisotropic medium, which is easier to realize for some novel optical devices designed by TO and optical surface transformation. The special function of the anti-ONM will lead to a new way to design optical devices or simplify the material requirements. Overlapping illusions, and wave-front reshapers are designed to demonstrate the function of the proposed method.

  11. The null hypothesis of GSEA, and a novel statistical model for competitive gene set analysis

    DEFF Research Database (Denmark)

    Debrabant, Birgit

    2017-01-01

    MOTIVATION: Competitive gene set analysis intends to assess whether a specific set of genes is more associated with a trait than the remaining genes. However, the statistical models assumed to date to underly these methods do not enable a clear cut formulation of the competitive null hypothesis....... This is a major handicap to the interpretation of results obtained from a gene set analysis. RESULTS: This work presents a hierarchical statistical model based on the notion of dependence measures, which overcomes this problem. The two levels of the model naturally reflect the modular structure of many gene set...... analysis methods. We apply the model to show that the popular GSEA method, which recently has been claimed to test the self-contained null hypothesis, actually tests the competitive null if the weight parameter is zero. However, for this result to hold strictly, the choice of the dependence measures...

  12. A few insights into the nature of classical and quantum gravity via null-strut calculus

    International Nuclear Information System (INIS)

    Kheyfets, Arkady

    1989-01-01

    Null-strut calculus is a 3 + 1 formulation of standard Regge calculus, wherein the dynamics of 3-geometry is propagated in time along light rays, or 'null struts'. However, just as Regge calculus is a discrete and geometric tool for the description of Einstein's theory of gravitation, so too NSC offers itself as a discrete and geometric tool for the description of Einstein's spacetime as the dynamics of discrete spacelike 3-geometries in time, or discrete geometrodynamics. It has for its objectives to provide a discrete model of a 3 + 1 split of spacetime into space plus time, while in so doing to preserve and illuminate the geometric content of Einstein's theory of gravity. The feature of 'light-cone-produced duality' is central to null-strut calculus. This paper will capitalise on this feature, and will attempt to provide some insights into the nature of classical and quantum gravity. (Author)

  13. Maxwell, Yang-Mills, Weyl and eikonal fields defined by any null shear-free congruence

    Science.gov (United States)

    Kassandrov, Vladimir V.; Rizcallah, Joseph A.

    We show that (specifically scaled) equations of shear-free null geodesic congruences on the Minkowski space-time possess intrinsic self-dual, restricted gauge and algebraic structures. The complex eikonal, Weyl 2-spinor, SL(2, ℂ) Yang-Mills and complex Maxwell fields, the latter produced by integer-valued electric charges (“elementary” for the Kerr-like congruences), can all be explicitly associated with any shear-free null geodesic congruence. Using twistor variables, we derive the general solution of the equations of the shear-free null geodesic congruence (as a modification of the Kerr theorem) and analyze the corresponding “particle-like” field distributions, with bounded singularities of the associated physical fields. These can be obtained in a straightforward algebraic way and exhibit nontrivial collective dynamics simulating physical interactions.

  14. The (2, 0) superalgebra, null M-branes and Hitchin's system

    Science.gov (United States)

    Kucharski, P.; Lambert, N.; Owen, M.

    2017-10-01

    We present an interacting system of equations with sixteen supersymmetries and an SO(2) × SO(6) R-symmetry where the fields depend on two space and one null dimensions that is derived from a representation of the six-dimensional (2, 0) superalgebra. The system can be viewed as two M5-branes compactified on {S}-^1× T^2 or equivalently as M2-branes on R+× R^2 , where ± refer to null directions. We show that for a particular choice of fields the dynamics can be reduced to motion on the moduli space of solutions to the Hitchin system. We argue that this provides a description of intersecting null M2-branes and is also related by U-duality to a DLCQ description of four-dimensional maximally supersymmetric Yang-Mills.

  15. Alaska Dental Health Aide Program.

    Science.gov (United States)

    Shoffstall-Cone, Sarah; Williard, Mary

    2013-01-01

    In 1999, An Oral Health Survey of American Indian and Alaska Native (AI/AN) Dental Patients found that 79% of 2- to 5-year-olds had a history of tooth decay. The Alaska Native Tribal Health Consortium in collaboration with Alaska's Tribal Health Organizations (THO) developed a new and diverse dental workforce model to address AI/AN oral health disparities. This paper describes the workforce model and some experience to date of the Dental Health Aide (DHA) Initiative that was introduced under the federally sanctioned Community Health Aide Program in Alaska. These new dental team members work with THO dentists and hygienists to provide education, prevention and basic restorative services in a culturally appropriate manner. The DHA Initiative introduced 4 new dental provider types to Alaska: the Primary Dental Health Aide, the Expanded Function Dental Health Aide, the Dental Health Aide Hygienist and the Dental Health Aide Therapist. The scope of practice between the 4 different DHA providers varies vastly along with the required training and education requirements. DHAs are certified, not licensed, providers. Recertification occurs every 2 years and requires the completion of 24 hours of continuing education and continual competency evaluation. Dental Health Aides provide evidence-based prevention programs and dental care that improve access to oral health care and help address well-documented oral health disparities.

  16. Alaska Dental Health Aide Program

    Directory of Open Access Journals (Sweden)

    Sarah Shoffstall-Cone

    2013-08-01

    Full Text Available Background. In 1999, An Oral Health Survey of American Indian and Alaska Native (AI/AN Dental Patients found that 79% of 2- to 5-year-olds had a history of tooth decay. The Alaska Native Tribal Health Consortium in collaboration with Alaska’s Tribal Health Organizations (THO developed a new and diverse dental workforce model to address AI/AN oral health disparities. Objectives. This paper describes the workforce model and some experience to date of the Dental Health Aide (DHA Initiative that was introduced under the federally sanctioned Community Health Aide Program in Alaska. These new dental team members work with THO dentists and hygienists to provide education, prevention and basic restorative services in a culturally appropriate manner. Results. The DHA Initiative introduced 4 new dental provider types to Alaska: the Primary Dental Health Aide, the Expanded Function Dental Health Aide, the Dental Health Aide Hygienist and the Dental Health Aide Therapist. The scope of practice between the 4 different DHA providers varies vastly along with the required training and education requirements. DHAs are certified, not licensed, providers. Recertification occurs every 2 years and requires the completion of 24 hours of continuing education and continual competency evaluation. Conclusions. Dental Health Aides provide evidence-based prevention programs and dental care that improve access to oral health care and help address well-documented oral health disparities.

  17. Dental PACS development in Korea

    International Nuclear Information System (INIS)

    Kim, Eun Kyung

    2008-01-01

    Picture archiving and communication system (PACS) is an image information technology system for the transmission and storage of medical images. In Korea the first full PACS was installed at Samsung Medical Center in 1994, but, the rate of distribution was very slow. The government's approval for the medical insurance reimbursement for full PACS examinations in November 1999 became the turning point. Thereafter the number of hospitals with full PACS has steeply increased. In September of this year, PACS was installed at 906 medical institutes, including most of university hospitals and general hospitals. The first full dental PACS was installed at Wonkwang University Dental Hospital in 2002. Now ten out of eleven university dental hospitals implemented full dental PACS. The current status and technological factors of dental PACS in Korean university dental hospitals and the future perspectives of dental PACS are described.

  18. Dental Hygiene Student Attrition.

    Science.gov (United States)

    Young, Lynda J.; Fellows, Avis L.

    1981-01-01

    A study to determine differences between graduating and withdrawing students in the University of Minnesota Dental Hygiene program is discussed. The identification of differences may prove useful in the selection process for future classes through identification of students likely to complete their education. (MLW)

  19. Fatigue of dental ceramics.

    Science.gov (United States)

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-12-01

    Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Advances in dental materials.

    Science.gov (United States)

    Fleming, Garry J P

    2014-05-01

    The dental market is replete with new resorative materials marketed on the basis of novel technological advances in materials chemistry, bonding capability or reduced operator time and/or technique sensitivity. This paper aims to consider advances in current materials, with an emphasis on their role in supporting contemporary clinical practice.

  1. [Instruction in dental radiology

    NARCIS (Netherlands)

    Sanden, W.J.M. van der; Kreulen, C.M.; Berkhout, W.E.

    2016-01-01

    The diagnostic use of oral radiology is an essential part of daily dental practice. Due to the potentially harmful nature of ionising radiation, the clinical use of oral radiology in the Netherlands is framed by clinical practice guidelines and regulatory requirements. Undergraduate students receive

  2. Dental Implant Surgery

    Science.gov (United States)

    ... more impressions made of your mouth and remaining teeth. These impressions are used to make the crown — your realistic-looking artificial tooth. The crown can't be placed until your jawbone is strong ... and your dental specialist can choose artificial teeth that are either ...

  3. Mouth and dental disorders

    NARCIS (Netherlands)

    de Baat, C.; van der Waal, I.; Jackson, S.H.D.; Jansen, P.A.F.; Mangoni, A.A.

    2009-01-01

    Summary This chapter contains sections titled: • Introduction • Periodontal disease • Dental caries • Odontogenic infections • Alveolar osteitis • Xerostomia and hyposalivation • Candidiasis • Angular cheilitis • Denture stomatitis • Burning mouth syndrome • Recurrent aphthous stomatitis • Recurrent

  4. Dental Health - Multiple Languages

    Science.gov (United States)

    ... Health Resource Center Burmese (myanma bhasa) Expand Section Betel Nut - English PDF Betel Nut - myanma bhasa (Burmese) PDF Orange County North ... California Dental Association Karen (S’gaw Karen) Expand Section Betel Nut - English PDF Betel Nut - S’gaw Karen (Karen) ...

  5. From GLC to double-null coordinates and illustration with static black holes

    Energy Technology Data Exchange (ETDEWEB)

    Nugier, Fabien, E-mail: fnugier@ntu.edu.tw [Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei, 10617 Taiwan (China)

    2016-09-01

    We present a system of coordinates deriving directly from the so-called Geodesic Light-Cone (GLC) coordinates and made of two null scalars intersecting on a 2-dimensional sphere parameterized by two constant angles along geodesics. These coordinates are shown to be equivalent to the well-known double-null coordinates. As GLC, they present interesting properties for cosmology and astrophysics. We discuss this latter topic for static black holes, showing simple descriptions for the metric or particles and photons trajectories. We also briefly comment on the time of flight of ultra-relativistic particles.

  6. The Segmented Aperture Interferometric Nulling Testbed (SAINT) I: overview and air-side system description

    Science.gov (United States)

    Hicks, Brian A.; Lyon, Richard G.; Petrone, Peter; Ballard, Marlin; Bolcar, Matthew R.; Bolognese, Jeff; Clampin, Mark; Dogoda, Peter; Dworzanski, Daniel; Helmbrecht, Michael A.; Koca, Corina; Shiri, Ron

    2016-07-01

    This work presents an overview of the Segmented Aperture Interferometric Nulling Testbed (SAINT), a project that will pair an actively-controlled macro-scale segmented mirror with the Visible Nulling Coronagraph (VNC). SAINT will incorporate the VNC's demonstrated wavefront sensing and control system to refine and quantify end-to-end high-contrast starlight suppression performance. This pathfinder testbed will be used as a tool to study and refine approaches to mitigating instabilities and complex diffraction expected from future large segmented aperture telescopes.

  7. Noncolocated Time-Reversal MUSIC: High-SNR Distribution of Null Spectrum

    Science.gov (United States)

    Ciuonzo, Domenico; Rossi, Pierluigi Salvo

    2017-04-01

    We derive the asymptotic distribution of the null spectrum of the well-known Multiple Signal Classification (MUSIC) in its computational Time-Reversal (TR) form. The result pertains to a single-frequency non-colocated multistatic scenario and several TR-MUSIC variants are here investigated. The analysis builds upon the 1st-order perturbation of the singular value decomposition and allows a simple characterization of null-spectrum moments (up to the 2nd order). This enables a comparison in terms of spectrums stability. Finally, a numerical analysis is provided to confirm the theoretical findings.

  8. In vivo time-gated diffuse correlation spectroscopy at quasi-null source-detector separation.

    Science.gov (United States)

    Pagliazzi, M; Sekar, S Konugolu Venkata; Di Sieno, L; Colombo, L; Durduran, T; Contini, D; Torricelli, A; Pifferi, A; Mora, A Dalla

    2018-06-01

    We demonstrate time domain diffuse correlation spectroscopy at quasi-null source-detector separation by using a fast time-gated single-photon avalanche diode without the need of time-tagging electronics. This approach allows for increased photon collection, simplified real-time instrumentation, and reduced probe dimensions. Depth discriminating, quasi-null distance measurement of blood flow in a human subject is presented. We envision the miniaturization and integration of matrices of optical sensors of increased spatial resolution and the enhancement of the contrast of local blood flow changes.

  9. A class of algebraically general solutions of the Einstein-Maxwell equations for non-null electromagnetic fields

    International Nuclear Information System (INIS)

    Tupper, B.O.J.

    1976-01-01

    In a previous article (Gen. Rel. Grav.; 6 : 345 (1975)) the Einstein-Maxwell field equations for non-null electromagnetic fields were studied under the conditions that the null tetrad is parallel-propagated along both principal null congruences. A solution with twist and shear, but no expansion, was found and was conjectured to be the only expansion-free solution. Here it is shown that this conjecture is false; the general expansion-free solution is found to be a family of space-times depending on a single constant parameter which is the ratio of the (constant) twists of the two principal null congruences. (author)

  10. Dental anxiety and salivary cortisol levels before urgent dental care.

    Science.gov (United States)

    Kanegane, Kazue; Penha, Sibele S; Munhoz, Carolina D; Rocha, Rodney G

    2009-12-01

    Dental anxiety is still prevalent, despite advances in treatment, and affects the utilization of health care services. The purpose of this cross-sectional study was to determine if patients with different degrees of dental anxiety and pain undergoing emergency dental care have different stress reactions as measured by salivary cortisol. Seventy three patients completed the modified dental anxiety scale (MDAS), and described any previous dental traumatic experience. Their socio-demographic characteristics were also recorded. They also rated pain intensity on a 100 mm visual analogue scale (VAS). A saliva sample was collected before the procedure, and analyzed by enzyme immunoassay. Thirty patients were dentally anxious and forty one complained of pain. In this sample, dental anxiety was not related to gender, age, educational level and family income; however, a previous traumatic event was related to dental anxiety. There was no association between salivary cortisol concentrations and gender or dental anxiety. Patients with pain showed higher cortisol levels. When gathering patient information, the dentist should note patients' negative dental experiences in order to provide more effective, less traumatic treatment.

  11. Exploring Dental Providers' Workflow in an Electronic Dental Record Environment.

    Science.gov (United States)

    Schwei, Kelsey M; Cooper, Ryan; Mahnke, Andrea N; Ye, Zhan; Acharya, Amit

    2016-01-01

    A workflow is defined as a predefined set of work steps and partial ordering of these steps in any environment to achieve the expected outcome. Few studies have investigated the workflow of providers in a dental office. It is important to understand the interaction of dental providers with the existing technologies at point of care to assess breakdown in the workflow which could contribute to better technology designs. The study objective was to assess electronic dental record (EDR) workflows using time and motion methodology in order to identify breakdowns and opportunities for process improvement. A time and motion methodology was used to study the human-computer interaction and workflow of dental providers with an EDR in four dental centers at a large healthcare organization. A data collection tool was developed to capture the workflow of dental providers and staff while they interacted with an EDR during initial, planned, and emergency patient visits, and at the front desk. Qualitative and quantitative analysis was conducted on the observational data. Breakdowns in workflow were identified while posting charges, viewing radiographs, e-prescribing, and interacting with patient scheduler. EDR interaction time was significantly different between dentists and dental assistants (6:20 min vs. 10:57 min, p = 0.013) and between dentists and dental hygienists (6:20 min vs. 9:36 min, p = 0.003). On average, a dentist spent far less time than dental assistants and dental hygienists in data recording within the EDR.

  12. Radiographic Assessment of Dental Maturation in Children With Dental Agenesis.

    Science.gov (United States)

    Medina, Aida Carolina; Pozo, Rodrigo Del; de Cedres, Lucila Blanco

    Dental agenesis is the most common developmental anomaly in humans, frequently associated with disorders in dental development and maturation. The purpose of this study is to determine radiographic variations in dental maturation in a group of Venezuelan children with dental agenesis. 1,188 panoramic radiographs, from healthy patients ages 5 to 12 years old were studied for agenesis of permanent teeth. Dental maturation was assessed by relative eruption and dental age according to Nolla, comparing children affected with dental agenesis to a stratified control group selected from the same population, excluding children with premature loss of primary teeth in the left quadrants and unclear radiographs. Descriptive analysis, and differences between means and medians (Student t test, Kruskall-Wallis p=0.05) were performed. Medians for Nolla stages were similar between groups, with delay in tooth formation in the agenesis group for second molars (p<0.05) and maxillary lateral incisors and second premolars. Dental age was significantly underestimated for both groups, -0.89 (±0.78) for the control group and -1.20 (±0.95) for the study group. Tooth eruption was similar between groups. Dental age was significantly delayed in Venezuelan children with dental agenesis, with variable significance for tooth formation of studied teeth.

  13. 21 CFR 872.3240 - Dental bur.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental bur. 872.3240 Section 872.3240 Food and... DENTAL DEVICES Prosthetic Devices § 872.3240 Dental bur. (a) Identification. A dental bur is a rotary... materials intended for use in the fabrication of dental devices. (b) Classification. Class I (general...

  14. 21 CFR 872.3700 - Dental mercury.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental mercury. 872.3700 Section 872.3700 Food and... DENTAL DEVICES Prosthetic Devices § 872.3700 Dental mercury. (a) Identification. Dental mercury is a... dental cavity or a broken tooth. (b) Classification. Class I. ...

  15. Dental Care for Medicaid and CHIP Enrollees

    Science.gov (United States)

    ... FAQs Home › Medicaid › Benefits › Dental Care Dental Care Dental Care Related Resources Learn How to Report the ... services and opportunities and challenges to obtaining care. Dental Benefits for Children in Medicaid Medicaid covers dental ...

  16. Developing a flexible core Dental Public Health curriculum for predoctoral dental and dental hygiene schools.

    Science.gov (United States)

    Atchison, Kathryn; Mascarenhas, Ana Karina; Bhoopathi, Vinodh

    2015-01-01

    The curriculum for graduating dental and dental hygiene students must prepare them to contribute to the improvement or maintenance of health for individual patient's and the public's health. The objective is to describe the background for and the process used to develop a core Dental Public Health Curriculum for such students. The process used was to solicit and review existing dental public health curriculum in dental and dental hygiene schools; review curriculum for other health professionals; identify the themes needed to frame the curriculum; select usable materials and identify gaps in existing curricular materials; and develop appropriate curriculum materials that would embody the competencies developed for undergraduate dental and dental hygiene education. Twenty-three topics were identified as embodying the eight competencies. Based on these topics, six courses, Principles of Dental Public Health, Evidence-Based Dentistry, Ethics and Dental Public Health, Dental Public Health Policy and Advocacy, Oral Health Promotion and Disease Prevention, and Oral Health Literacy and Dental Public Health, were prepared. Each course includes syllabus, PowerPoint presentations, student assignments and activities, instructor guide, and classroom discussion points. Depending on the hours available in the existing curriculum at the dental or hygiene school, lecture presentations and take home assignments/discussions may be used independently or in combination with presentations from other courses. In addition, individual discussions and activities may be used to integrate dental public health materials into other courses. A flexible curriculum is available at the AAPHD website to enable the incorporation of DPH topics into the curriculum. © 2015 American Association of Public Health Dentistry.

  17. Prevalence of Dental Fear and Anxiety amongst Patients in Selected Dental Clinics in Ghana

    Science.gov (United States)

    Ofori, Marian A.; Adu-Ababio, F.; Nyako, E. A.; Ndanu, Tom A.

    2009-01-01

    Objective: To find out the prevalence of dental anxiety and fear amongst patients in various selected dental clinics in Accra, Ghana. Study design: Dental patients (n = 279) who had either been exposed to dental treatments or had no prior dental exposure, attending four selected dental clinics in Accra were randomly sampled. They were interviewed…

  18. Advancing education in dental hygiene.

    Science.gov (United States)

    Battrell, Ann; Lynch, Ann; Steinbach, Pam; Bessner, Sue; Snyder, Josh; Majeski, Jean

    2014-06-01

    The changing health care environment and societal imperatives indicate the need for transformative change within the dental hygiene profession to serve the emerging needs of the public. The American Dental Hygienists' Association is leading the way toward meaningful change. The American Dental Hygienists' Association (ADHA) has as its vision the integration of dental hygienists into the health care delivery system as essential primary care providers to expand access to oral health care. This article provides data on current dental hygiene education programs and those in development. Also included is a discussion regarding how the dental hygiene profession can better serve the health and wellness needs of society by transforming the way graduates are prepared for the future. ADHA's dental hygiene survey center data, policies and a futuristic analysis plus a review of the professional literature describe the current state of dental hygiene education and the profession. A discussion of societal, health care and educational trends that creates the imperative for transformation of the dental hygiene profession is provided. Ultimately, the purpose of advancing education in dental hygiene is to achieve better oral and overall health for more people. The profession's responsibility to the public includes evaluating its own ability to provide care and taking the steps necessary to ensure its maximum effectiveness. ADHA is leading this process for dental hygienists in diverse ways. It is imperative that the dental hygiene profession understands and embraces the changing health care environment. Through open dialog and the sharing of evidence the professional path will be determined along with forward movement for the benefit of society and the dental hygiene profession. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Propagation of errors from a null balance terahertz reflectometer to a sample's relative water content

    International Nuclear Information System (INIS)

    Hadjiloucas, S; Walker, G C; Bowen, J W; Zafiropoulos, A

    2009-01-01

    The THz water content index of a sample is defined and advantages in using such metric in estimating a sample's relative water content are discussed. The errors from reflectance measurements performed at two different THz frequencies using a quasi-optical null-balance reflectometer are propagated to the errors in estimating the sample water content index.

  20. Partial null astigmatism-compensated interferometry for a concave freeform Zernike mirror

    Science.gov (United States)

    Dou, Yimeng; Yuan, Qun; Gao, Zhishan; Yin, Huimin; Chen, Lu; Yao, Yanxia; Cheng, Jinlong

    2018-06-01

    Partial null interferometry without using any null optics is proposed to measure a concave freeform Zernike mirror. Oblique incidence on the freeform mirror is used to compensate for astigmatism as the main component in its figure, and to constrain the divergence of the test beam as well. The phase demodulated from the partial nulled interferograms is divided into low-frequency phase and high-frequency phase by Zernike polynomial fitting. The low-frequency surface figure error of the freeform mirror represented by the coefficients of Zernike polynomials is reconstructed from the low-frequency phase, applying the reverse optimization reconstruction technology in the accurate model of the interferometric system. The high-frequency surface figure error of the freeform mirror is retrieved from the high-frequency phase adopting back propagating technology, according to the updated model in which the low-frequency surface figure error has been superimposed on the sag of the freeform mirror. Simulations verified that this method is capable of testing a wide variety of astigmatism-dominated freeform mirrors due to the high dynamic range. The experimental result using our proposed method for a concave freeform Zernike mirror is consistent with the null test result employing the computer-generated hologram.

  1. The Harm Done to Reproducibility by the Culture of Null Hypothesis Significance Testing.

    Science.gov (United States)

    Lash, Timothy L

    2017-09-15

    In the last few years, stakeholders in the scientific community have raised alarms about a perceived lack of reproducibility of scientific results. In reaction, guidelines for journals have been promulgated and grant applicants have been asked to address the rigor and reproducibility of their proposed projects. Neither solution addresses a primary culprit, which is the culture of null hypothesis significance testing that dominates statistical analysis and inference. In an innovative research enterprise, selection of results for further evaluation based on null hypothesis significance testing is doomed to yield a low proportion of reproducible results and a high proportion of effects that are initially overestimated. In addition, the culture of null hypothesis significance testing discourages quantitative adjustments to account for systematic errors and quantitative incorporation of prior information. These strategies would otherwise improve reproducibility and have not been previously proposed in the widely cited literature on this topic. Without discarding the culture of null hypothesis significance testing and implementing these alternative methods for statistical analysis and inference, all other strategies for improving reproducibility will yield marginal gains at best. © The Author(s) 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  2. High Contrast Vacuum Nuller Testbed (VNT) Contrast, Performance and Null Control

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Petrone, Peter; Mallik, Udayan; Madison, Timothy; Bolcar, Matthew R.

    2012-01-01

    Herein we report on our Visible Nulling Coronagraph high-contrast result of 109 contrast averaged over a focal planeregion extending from 14 D with the Vacuum Nuller Testbed (VNT) in a vibration isolated vacuum chamber. TheVNC is a hybrid interferometriccoronagraphic approach for exoplanet science. It operates with high Lyot stopefficiency for filled, segmented and sparse or diluted-aperture telescopes, thereby spanning the range of potential futureNASA flight telescopes. NASAGoddard Space Flight Center (GSFC) has a well-established effort to develop the VNCand its technologies, and has developed an incremental sequence of VNC testbeds to advance this approach and itsenabling technologies. These testbeds have enabled advancement of high-contrast, visible light, nulling interferometry tounprecedented levels. The VNC is based on a modified Mach-Zehnder nulling interferometer, with a W configurationto accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters.We give an overview of the VNT and discuss the high-contrast laboratory results, the optical configuration, criticaltechnologies and null sensing and control.

  3. Modelling the electromechanical interactions in a null-flux EDS Maglev system

    NARCIS (Netherlands)

    Boeij, de J.; Steinbuch, M.; Gutierrez, H.M.; Fair, H.D.

    2004-01-01

    The fundamental electromechanical interactionsin a passive null-ux EDS maglev system aremediated by the voltages induced in the levita-tion coils by the sled magnets, and by the forcesexerted on the sled as a result of the inducedcurrents. This paper presents a reliable andcompact method to

  4. Parallel-propagated frame along null geodesics in higher-dimensional black hole spacetimes

    International Nuclear Information System (INIS)

    Kubiznak, David; Frolov, Valeri P.; Connell, Patrick; Krtous, Pavel

    2009-01-01

    In [arXiv:0803.3259] the equations describing the parallel transport of orthonormal frames along timelike (spacelike) geodesics in a spacetime admitting a nondegenerate principal conformal Killing-Yano 2-form h were solved. The construction employed is based on studying the Darboux subspaces of the 2-form F obtained as a projection of h along the geodesic trajectory. In this paper we demonstrate that, although slightly modified, a similar construction is possible also in the case of null geodesics. In particular, we explicitly construct the parallel-transported frames along null geodesics in D=4, 5, 6 Kerr-NUT-(A)dS spacetimes. We further discuss the parallel transport along principal null directions in these spacetimes. Such directions coincide with the eigenvectors of the principal conformal Killing-Yano tensor. Finally, we show how to obtain a parallel-transported frame along null geodesics in the background of the 4D Plebanski-Demianski metric which admits only a conformal generalization of the Killing-Yano tensor.

  5. Diversity-Multiplexing-Nulling Trade-Off Analysis of Multiuser MIMO System for Intercell Interference Coordination

    Directory of Open Access Journals (Sweden)

    Jinwoo Kim

    2017-01-01

    Full Text Available A fundamental performance trade-off of multicell multiuser multiple-input multiple-output (MU-MIMO systems is explored for achieving intercell and intracell interference-free conditions. In particular, we analyze the three-dimensional diversity-multiplexing-nulling trade-off (DMNT among the diversity order (i.e., the slope of the error performance curve, multiplexing order (i.e., the number of users that are simultaneously served by MU-MIMO, and nulling order (i.e., the number of users with zero interference in a victim cell. This trade-off quantifies the performance of MU-MIMO in terms of its diversity and multiplexing order, while nulling the intercell interference toward the victim cell in the neighbor. First, we design a precoding matrix to mitigate both intercell and intracell interference for a linear precoding-based MU-MIMO system. Then, the trade-off relationship is obtained by analyzing the distribution of the signal-to-noise ratio (SNR at the user terminals. Furthermore, we demonstrate how DMNT can be applied to estimate the long-term throughput for each mobile station, which allows for determining the optimal number of multiplexing order and throughput loss due to the interference nulling.

  6. Exact null distributions of quadratic distribution-free statistics for two-way classification

    NARCIS (Netherlands)

    Wiel, van de M.A.

    2004-01-01

    Abstract We present new techniques for computing exact distributions of `Friedman-type¿ statistics. Representing the null distribution by a generating function allows for the use of general, not necessarily integer-valued rank scores. Moreover, we use symmetry properties of the multivariate

  7. Pattern Nulling of Linear Antenna Arrays Using Backtracking Search Optimization Algorithm

    Directory of Open Access Journals (Sweden)

    Kerim Guney

    2015-01-01

    Full Text Available An evolutionary method based on backtracking search optimization algorithm (BSA is proposed for linear antenna array pattern synthesis with prescribed nulls at interference directions. Pattern nulling is obtained by controlling only the amplitude, position, and phase of the antenna array elements. BSA is an innovative metaheuristic technique based on an iterative process. Various numerical examples of linear array patterns with the prescribed single, multiple, and wide nulls are given to illustrate the performance and flexibility of BSA. The results obtained by BSA are compared with the results of the following seventeen algorithms: particle swarm optimization (PSO, genetic algorithm (GA, modified touring ant colony algorithm (MTACO, quadratic programming method (QPM, bacterial foraging algorithm (BFA, bees algorithm (BA, clonal selection algorithm (CLONALG, plant growth simulation algorithm (PGSA, tabu search algorithm (TSA, memetic algorithm (MA, nondominated sorting GA-2 (NSGA-2, multiobjective differential evolution (MODE, decomposition with differential evolution (MOEA/D-DE, comprehensive learning PSO (CLPSO, harmony search algorithm (HSA, seeker optimization algorithm (SOA, and mean variance mapping optimization (MVMO. The simulation results show that the linear antenna array synthesis using BSA provides low side-lobe levels and deep null levels.

  8. On the geometry of null cones to infinity under curvature flux bounds

    International Nuclear Information System (INIS)

    Alexakis, Spyros; Shao, Arick

    2014-01-01

    The main objective of this paper is to control the geometry of a future outgoing truncated null cone extending smoothly toward infinity in an Einstein-vacuum spacetime. In particular, we wish to do this under minimal regularity assumptions, namely, at the (weighted) L 2 -curvature level. We show that if the curvature flux and the data on an initial sphere of the cone are sufficiently close to the corresponding values in a standard Minkowski or Schwarzschild null cone, then we can obtain quantitative bounds on the geometry of the entire infinite cone. The same bounds also imply the existence of limits at infinity, along the null cone, of naturally scaled geometric quantities. In Alexakis and Shao (2013 Bounds on the Bondi energy by a flux of curvature arXiv:1308.4170), we will apply these results in order to control various physical quantities—e.g., the Bondi energy and (linear and angular) momenta—associated with such infinite null cones in vacuum spacetimes. (paper)

  9. Altered extracellular matrix remodeling and angiogenesis in sponge granulomas of thrombospondin 2-null mice.

    Science.gov (United States)

    Kyriakides, T R; Zhu, Y H; Yang, Z; Huynh, G; Bornstein, P

    2001-10-01

    The matricellular angiogenesis inhibitor, thrombospondin (TSP) 2, has been shown to be an important modulator of wound healing and the foreign body response. Specifically, TSP2-null mice display improved healing with minimal scarring and form well-vascularized foreign body capsules. In this study we performed subcutaneous implantation of sponges and investigated the resulting angiogenic and fibrogenic responses. Histological and immunohistochemical analysis of sponges, excised at 7, 14, and 21 days after implantation, revealed significant differences between TSP2-null and wild-type mice. Most notably, TSP2-null mice exhibited increased angiogenesis and fibrotic encapsulation of the sponge. However, invasion of dense tissue was compromised, even though its overall density was increased. Furthermore, histomorphometry and biochemical assays demonstrated a significant increase in the extracellular distribution of matrix metalloproteinase (MMP) 2, but no change in the levels of active transforming growth factor-beta(1). The alterations in neovascularization, dense tissue invasion, and MMP2 in TSP2-null mice coincided with the deposition of TSP2 in the extracellular matrix of wild-type animals. These observations support the proposed role of TSP2 as a modulator of angiogenesis and matrix remodeling during tissue repair. In addition, they provide in vivo evidence for a newly proposed function of TSP2 as a modulator of extracellular MMP2 levels.

  10. A Coding of Real Null Four-Momenta into World-Sheet Coordinates

    Directory of Open Access Journals (Sweden)

    David B. Fairlie

    2009-01-01

    Full Text Available The results of minimizing the action for string-like systems on a simply connected world sheet are shown to encode the Cartesian components of real null momentum four-vectors into coordinates on the world sheet. This identification arises consistently from different approaches to the problem.

  11. A Coding of Real Null Four-Momenta into World-Sheet Co-ordinates

    OpenAIRE

    Fairlie, David B.

    2008-01-01

    The results of minimizing the action for string-like systems on a simply-connected world sheet are shown to encode the Cartesian components of real null momentum four-vectors into co-ordinates on the world sheet. This identification arises consistently from different approaches to the problem.

  12. A Panel Test of Purchasing Power Parity Under the Null of Stationarity

    OpenAIRE

    Hunter, J; Simpson, M

    2001-01-01

    Purchasing Power Parity (PPP) is tested using a sample of real exchange rate data for twelve European countries. Acknowledging that Augmented Dickey Fuller tests have low power, we apply a Panel test that considers the null of stationarity and corrects for serial dependence using a non-parametric kernel based method.

  13. Null alleles and sequence variations at primer binding sites of STR loci within multiplex typing systems.

    Science.gov (United States)

    Yao, Yining; Yang, Qinrui; Shao, Chengchen; Liu, Baonian; Zhou, Yuxiang; Xu, Hongmei; Zhou, Yueqin; Tang, Qiqun; Xie, Jianhui

    2018-01-01

    Rare variants are widely observed in human genome and sequence variations at primer binding sites might impair the process of PCR amplification resulting in dropouts of alleles, named as null alleles. In this study, 5 cases from routine paternity testing using PowerPlex ® 21 System for STR genotyping were considered to harbor null alleles at TH01, FGA, D5S818, D8S1179, and D16S539, respectively. The dropout of alleles was confirmed by using alternative commercial kits AGCU Expressmarker 22 PCR amplification kit and AmpFℓSTR ® . Identifiler ® Plus Kit, and sequencing results revealed a single base variation at the primer binding site of each STR locus. Results from the collection of previous reports show that null alleles at D5S818 were frequently observed in population detected by two PowerPlex ® typing systems and null alleles at D19S433 were mostly observed in Japanese population detected by two AmpFℓSTR™ typing systems. Furthermore, the most popular mutation type appeared the transition from C to T with G to A, which might have a potential relationship with DNA methylation. Altogether, these results can provide helpful information in forensic practice to the elimination of genotyping discrepancy and the development of primer sets. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Stitching interferometry of high numerical aperture cylindrical optics without using a fringe-nulling routine.

    Science.gov (United States)

    Peng, Junzheng; Wang, Qingquan; Peng, Xiang; Yu, Yingjie

    2015-11-01

    Stitching interferometry is a common method for measuring the figure error of high numerical aperture optics. However, subaperture measurement usually requires a fringe-nulling routine, thus making the stitching procedure complex and time-consuming. The challenge when measuring a surface without a fringe-nulling routine is that the rays no longer perpendicularly hit the surface. This violation of the null-test condition can lead to high fringe density and introduce high-order misalignment aberrations into the measurement result. This paper demonstrates that the high-order misalignment aberrations can be characterized by low-order misalignment aberrations; then, an efficient method is proposed to separate the high-order misalignment aberrations from subaperture data. With the proposed method, the fringe-nulling routine is not required. Instead, the subaperture data is measured under a nonzero fringe pattern. Then, all possible misalignment aberrations are removed with the proposed method. Finally, the full aperture map is acquired by connecting all subaperture data together. Experimental results showing the feasibility of the proposed procedure are presented.

  15. No association of GSTM1 null polymorphism with endometriosis in women from central and southern Iran

    Directory of Open Access Journals (Sweden)

    Razieh Dehghani Firouzabadi

    2012-01-01

    Full Text Available Background: Endometriosis is one of the most common gynecologic disorders. It is a complex trait and both genetic and environmental factors have been implicated in its pathogenesis. There is growing evidence indicating that exposure to environmental contaminants is a risk factor for endometriosis. Glutathione-S-Transferase M1 (GSTM1 is one of the genes involved in detoxification of endogenous and exogenous compounds. Objective: Several studies have indicated an association between GSTM1 null mutation and endometriosis. In this study, the possible association between the GSTM1 gene null genotype and susceptibility to endometriosis in woman from central and southern Iran was investigated.Materials and Methods: One hundred and one unrelated premenopausal women with endometriosis and 142 unrelated healthy premenopausal women without endometriosis were enrolled in the study. Genomic DNA was extracted from Peripheral blood in all subjects. GSTM1 null genotyping was performed by polymerase chain reaction (PCR.Results: There was no significant difference between frequencies of GSTM1 null genotype in case and control groups (50.5% Vs. 52.1%, p=0.804. Furthermore, this genotype was not associated with severity of endometriosis in our sample (p=0.77. Conclusion: further studies involving gene-environment and gene-gene interactions, particularly combination of GSTM1 and other GST gene family polymorphisms are needed.

  16. High contrast vacuum nuller testbed (VNT) contrast, performance, and null control

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Petrone, Peter; Mallik, Udayan; Madison, Timothy; Bolcar, Matthew R.

    2012-09-01

    Herein we report on our Visible Nulling Coronagraph high-contrast result of 109 contrast averaged over a focal plane region extending from 1 - 4 λ/D with the Vacuum Nuller Testbed (VNT) in a vibration isolated vacuum chamber. The VNC is a hybrid interferometric/coronagraphic approach for exoplanet science. It operates with high Lyot stop efficiency for filled, segmented and sparse or diluted-aperture telescopes, thereby spanning the range of potential future NASA flight telescopes. NASA/Goddard Space Flight Center (GSFC) has a well-established effort to develop the VNC and its technologies, and has developed an incremental sequence of VNC testbeds to advance this approach and its enabling technologies. These testbeds have enabled advancement of high-contrast, visible light, nulling interferometry to unprecedented levels. The VNC is based on a modified Mach-Zehnder nulling interferometer, with a “W” configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters. We give an overview of the VNT and discuss the high-contrast laboratory results, the optical configuration, critical technologies and null sensing and control.

  17. Cell therapy of congenital corneal diseases with umbilical mesenchymal stem cells: lumican null mice.

    Directory of Open Access Journals (Sweden)

    Hongshan Liu

    Full Text Available BACKGROUND: Keratoplasty is the most effective treatment for corneal blindness, but suboptimal medical conditions and lack of qualified medical personnel and donated cornea often prevent the performance of corneal transplantation in developing countries. Our study aims to develop alternative treatment regimens for congenital corneal diseases of genetic mutation. METHODOLOGY/PRINCIPAL FINDINGS: Human mesenchymal stem cells isolated from neonatal umbilical cords were transplanted to treat thin and cloudy corneas of lumican null mice. Transplantation of umbilical mesenchymal stem cells significantly improved corneal transparency and increased stromal thickness of lumican null mice, but human umbilical hematopoietic stem cells failed to do the same. Further studies revealed that collagen lamellae were re-organized in corneal stroma of lumican null mice after mesenchymal stem cell transplantation. Transplanted umbilical mesenchymal stem cells survived in the mouse corneal stroma for more than 3 months with little or no graft rejection. In addition, these cells assumed a keratocyte phenotype, e.g., dendritic morphology, quiescence, expression of keratocyte unique keratan sulfated keratocan and lumican, and CD34. Moreover, umbilical mesenchymal stem cell transplantation improved host keratocyte functions, which was verified by enhanced expression of keratocan and aldehyde dehydrogenase class 3A1 in lumican null mice. CONCLUSIONS/SIGNIFICANCE: Umbilical mesenchymal stem cell transplantation is a promising treatment for congenital corneal diseases involving keratocyte dysfunction. Unlike donated corneas, umbilical mesenchymal stem cells are easily isolated, expanded, stored, and can be quickly recovered from liquid nitrogen when a patient is in urgent need.

  18. Development of IR single mode optical fibers for DARWIN-nulling interferometry

    NARCIS (Netherlands)

    Chakkalakkal Abdulla, S.M.; Cheng, L.K.; Bosch, B. van den; Dijkhuizen, N.; Nieuwland, R.A.; Gielesen, W.L.M.; Lucas, J.; Boussard-Plédel, C.; Conseil, C.; Bureau, B.; Carmo, J.P. do

    2014-01-01

    The DARWIN mission aims to detect weak infra-red emission lines from distant orbiting earth-like planets using nulling interferometry. This requires filtering of wavefront errors using single mode waveguides operating at a wavelength range of 6.5-20 μm. This article describes the optical design of

  19. The Need for Nuance in the Null Hypothesis Significance Testing Debate

    Science.gov (United States)

    Häggström, Olle

    2017-01-01

    Null hypothesis significance testing (NHST) provides an important statistical toolbox, but there are a number of ways in which it is often abused and misinterpreted, with bad consequences for the reliability and progress of science. Parts of contemporary NHST debate, especially in the psychological sciences, is reviewed, and a suggestion is made…

  20. Integrable structures and the quantization of free null initial data for gravity

    Science.gov (United States)

    Fuchs, Andreas; Reisenberger, Michael P.

    2017-09-01

    Variables for constraint free null canonical vacuum general relativity are presented which have simple Poisson brackets that facilitate quantization. Free initial data for vacuum general relativity on a pair of intersecting null hypersurfaces has been known since the 1960s. These consist of the ‘main’ data which are set on the bulk of the two null hypersurfaces, and additional ‘surface’ data set only on their intersection 2-surface. More recently the complete set of Poisson brackets of such data has been obtained. However the complexity of these brackets is an obstacle to their quantization. Part of this difficulty may be overcome using methods from the treatment of cylindrically symmetric gravity. Specializing from general to cylindrically symmetric solutions changes the Poisson algebra of the null initial data surprisingly little, but cylindrically symmetric vacuum general relativity is an integrable system, making powerful tools available. Here a transformation is constructed at the cylindrically symmetric level which maps the main initial data to new data forming a Poisson algebra for which an exact deformation quantization is known. (Although an auxiliary condition on the data has been quantized only in the asymptotically flat case, and a suitable representation of the algebra of quantum data by operators on a Hilbert space has not yet been found.) The definition of the new main data generalizes naturally to arbitrary, symmetryless gravitational fields, with the Poisson brackets retaining their simplicity. The corresponding generalization of the quantization is however ambiguous and requires further analysis.

  1. Reduced infarct size in neuroglobin-null mice after experimental stroke in vivo

    DEFF Research Database (Denmark)

    Raida, Zindy; Hundahl, Christian Ansgar; Kelsen, Jesper

    2012-01-01

    Neuroglobin is considered to be a novel important pharmacological target in combating stroke and neurodegenerative disorders, although the mechanism by which this protection is accomplished remains an enigma. We hypothesized that if neuroglobin is directly involved in neuroprotection, then perman......, then permanent cerebral ischemia would lead to larger infarct volumes in neuroglobin-null mice than in wild-type mice....

  2. Interpretation of Chinese Overt and Null Embedded Arguments by English-Speaking Learners

    Science.gov (United States)

    Zhao, Lucy Xia

    2012-01-01

    It has been proposed that external interfaces are vulnerable to residue optionality, whereas pure syntax and internal interfaces are acquirable in second language (L2) acquisition (Sorace, 2005, 2011; Sorace and Filiaci, 2006). The proposal was tested in this article through the interpretation of overt and null embedded arguments in L2 Chinese…

  3. Simple Fourier optics formalism for high-angular-resolution systems and nulling interferometry.

    Science.gov (United States)

    Hénault, François

    2010-03-01

    Reviewed are various designs of advanced, multiaperture optical systems dedicated to high-angular-resolution imaging or to the detection of exoplanets by nulling interferometry. A simple Fourier optics formalism applicable to both imaging arrays and nulling interferometers is presented, allowing their basic theoretical relationships to be derived as convolution or cross-correlation products suitable for fast and accurate computation. Several unusual designs, such as a "superresolving telescope" utilizing a mosaicking observation procedure or a free-flying, axially recombined interferometer are examined, and their performance in terms of imaging and nulling capacity are assessed. In all considered cases, it is found that the limiting parameter is the diameter of the individual telescopes. A final section devoted to nulling interferometry shows an apparent superiority of axial versus multiaxial recombining schemes. The entire study is valid only in the framework of first-order geometrical optics and scalar diffraction theory. Furthermore, it is assumed that all entrance subapertures are optically conjugated with their associated exit pupils.

  4. Hamilton-Jacobi formalism for Podolsky's electromagnetic theory on the null-plane

    Science.gov (United States)

    Bertin, M. C.; Pimentel, B. M.; Valcárcel, C. E.; Zambrano, G. E. R.

    2017-08-01

    We develop the Hamilton-Jacobi formalism for Podolsky's electromagnetic theory on the null-plane. The main goal is to build the complete set of Hamiltonian generators of the system as well as to study the canonical and gauge transformations of the theory.

  5. What Constitutes Science and Scientific Evidence: Roles of Null Hypothesis Testing

    Science.gov (United States)

    Chang, Mark

    2017-01-01

    We briefly discuss the philosophical basis of science, causality, and scientific evidence, by introducing the hidden but most fundamental principle of science: the similarity principle. The principle's use in scientific discovery is illustrated with Simpson's paradox and other examples. In discussing the value of null hypothesis statistical…

  6. Predicting Anxiety Among Patients In LPU Clinical Dispensary During Dental Treatment: Towards Student’s Clinical Performance Enhancement

    Directory of Open Access Journals (Sweden)

    Maribel D. Mayuga-Barrion

    2013-12-01

    Full Text Available The study aimed to determine the respondents’ profile in terms of age, gender, frequency of dental visit, and type of patient whether dental phobic or not; to determine the dental anxiety of patients in LPU dental dispensary; to identify the causes and severity of anxiety of the patients in LPU dental dispensary; to determine if there is a significant difference between the respondents’ demographic profile and their level of anxiety; and lastly, to propose a program that will help the patients cope with dental anxiety and a program that will enhance the students’ clinical performance. The study used the descriptive research design with the combination of content analysis of documents and related materials. Results showed that majority of the respondents belonged to age range of 14-18 years old range whereas for gender or sex, majority who avail of the clinic’s services are males. This is because women are more afraid than men in terms of dental problems. Further, younger people are more afraid than older ones. The weighted mean distribution of the level of anxiety showed that the level of anxiety of patients varies on moderately to not anxious. Feeling or experiencing pain during dental treatment ranked first followed by the fear or worry of not working the proposed treatment and thirdly, the dentist is in a hurry while treating also made the patients moderately anxious. Overall, the level of anxiety of patients is moderately anxious. Probing to asses gum disease, dislike the numb feeling and injection were the top three causes of dental anxiety. Only type of patient shows significant difference, thus the null hypothesis of no significant difference on the level of anxiety when grouped according to profile variables is rejected. This means that the level of anxiety of both phobic and not phobic differs.

  7. THE NATURE OF FLARE RIBBONS IN CORONAL NULL-POINT TOPOLOGY

    International Nuclear Information System (INIS)

    Masson, S.; Aulanier, G.; Pariat, E.; Schrijver, C. J.

    2009-01-01

    Flare ribbons are commonly attributed to the low-altitude impact, along the footprints of separatrices or quasi-separatrix layers (QSLs), of particle beams accelerated through magnetic reconnection. If reconnection occurs at a three-dimensional coronal magnetic null point, the footprint of the dome-shaped fan surface would map a closed circular ribbon. This paper addresses the following issues: does the entire circular ribbon brighten simultaneously, as expected because all fan field lines pass through the null point? And since the spine separatrices are singular field lines, do spine-related ribbons look like compact kernels? What can we learn from these observations about current sheet formation and magnetic reconnection in a null-point topology? The present study addresses these questions by analyzing Transition Region and Coronal Explorer and Solar and Heliospheric Observatory/Michelson Doppler Imager observations of a confined flare presenting a circular ribbon. Using a potential field extrapolation, we linked the circular shape of the ribbon with the photospheric mapping of the fan field lines originating from a coronal null point. Observations show that the flare ribbon outlining the fan lines brightens sequentially along the counterclockwise direction and that the spine-related ribbons are elongated. Using the potential field extrapolation as initial condition, we conduct a low-β resistive magnetohydrodynamics simulation of this observed event. We drive the coronal evolution by line-tied diverging boundary motions, so as to emulate the observed photospheric flow pattern associated with some magnetic flux emergence. The numerical analysis allows us to explain several observed features of the confined flare. The vorticity induced in the fan by the prescribed motions causes the spines to tear apart along the fan. This leads to formation of a thin current sheet and induces null-point reconnection. We also find that the null point and its associated topological

  8. Reversing hypomyelination in BACE1-null mice with Akt-DD overexpression.

    Science.gov (United States)

    Hu, Xiangyou; Schlanger, Rita; He, Wanxia; Macklin, Wendy B; Yan, Riqiang

    2013-05-01

    β-Site amyloid precursor protein convertase enzyme 1 (BACE1), a type I transmembrane aspartyl protease required to cleave amyloid precursor protein for releasing a toxic amyloid peptide, also cleaves type I and type III neuregulin-1 (Nrg-1). BACE1 deficiency in mice causes hypomyelination during development and impairs remyelination if injured. In BACE1-null mice, the abolished cleavage of neuregulin-1 by BACE1 is speculated to cause reduced myelin sheath thickness in both the central nervous system and peripheral nervous system because reduced cleavage of Nrg-1 correlates with reduced Akt phosphorylation, a downstream signaling molecule of the Nrg-1/ErbB pathway. Here we tested specifically whether increasing Akt activity alone in oligodendrocytes would be sufficient to reverse the hypomyelination phenotype in BACE1-null mice. BACE1-null mice were bred with transgenic mice expressing constitutively active Akt (Akt-DD; mutations with D(308)T and D(473)S) in oligodendrocytes. Relative to littermate BACE1-null controls, BACE1(-/-)/Akt-DD mice exhibited enhanced expression of myelin basic protein and promoter of proteolipid protein. The elevated expression of myelin proteins correlated with a thicker myelin sheath in optic nerves; comparison of quantified g ratios with statistic significance was used to confirm this reversion. However, it appeared that myelin sheath thickness in the sciatic nerves was not increased in BACE1(-/-)/Akt-DD mice, as the g ratio was not significantly different from the control. Hence, increased Akt activity in BACE1-null myelinating cells only compensates for the loss of BACE1 activity in the central nervous system, which is consistent with the observation that overexpression of Akt-DD in Schwann cells did not induce hypermyelination. Our results suggest that signaling activity other than Akt may also contribute to proper myelination in peripheral nerves.

  9. Orexin Receptor Antagonism Improves Sleep and Reduces Seizures in Kcna1-null Mice.

    Science.gov (United States)

    Roundtree, Harrison M; Simeone, Timothy A; Johnson, Chaz; Matthews, Stephanie A; Samson, Kaeli K; Simeone, Kristina A

    2016-02-01

    Comorbid sleep disorders occur in approximately one-third of people with epilepsy. Seizures and sleep disorders have an interdependent relationship where the occurrence of one can exacerbate the other. Orexin, a wake-promoting neuropeptide, is associated with sleep disorder symptoms. Here, we tested the hypothesis that orexin dysregulation plays a role in the comorbid sleep disorder symptoms in the Kcna1-null mouse model of temporal lobe epilepsy. Rest-activity was assessed using infrared beam actigraphy. Sleep architecture and seizures were assessed using continuous video-electroencephalography-electromyography recordings in Kcna1-null mice treated with vehicle or the dual orexin receptor antagonist, almorexant (100 mg/kg, intraperitoneally). Orexin levels in the lateral hypothalamus/perifornical region (LH/P) and hypothalamic pathology were assessed with immunohistochemistry and oxygen polarography. Kcna1-null mice have increased latency to rapid eye movement (REM) sleep onset, sleep fragmentation, and number of wake epochs. The numbers of REM and non-REM (NREM) sleep epochs are significantly reduced in Kcna1-null mice. Severe seizures propagate to the wake-promoting LH/P where injury is apparent (indicated by astrogliosis, blood-brain barrier permeability, and impaired mitochondrial function). The number of orexin-positive neurons is increased in the LH/P compared to wild-type LH/P. Treatment with a dual orexin receptor antagonist significantly increases the number and duration of NREM sleep epochs and reduces the latency to REM sleep onset. Further, almorexant treatment reduces the incidence of severe seizures and overall seizure burden. Interestingly, we report a significant positive correlation between latency to REM onset and seizure burden in Kcna1-null mice. Dual orexin receptor antagonists may be an effective sleeping aid in epilepsy, and warrants further study on their somnogenic and ant-seizure effects in other epilepsy models. © 2016 Associated

  10. Diabetes, Gum Disease, and Other Dental Problems

    Science.gov (United States)

    ... Diabetes, Sexual, & Bladder Problems Diabetes, Gum Disease, & Other Dental Problems How can diabetes affect my mouth? Too ... What if my mouth is sore after my dental work? A sore mouth is common after dental ...

  11. Teething & Dental Hygiene for Young Children

    Science.gov (United States)

    ... Living Listen Español Text Size Email Print Share Dental Health & Hygiene for Young Children Page Content Article ... and lead to future dental problems. Teaching Good Dental Habits The best way to protect your child's ...

  12. Milestones of dental history

    OpenAIRE

    Rajesh Mahant; S Vineet Agrawal; Sonali Kapoor; Isha Agrawal

    2017-01-01

    Since ages, human beings suffer from the dental problems. With the journey as time elapsed the person treating the teeth changed (i.e., from barbers and monks to present dentists), equipment changed (i.e., from bow drills to airotor and laser handpieces), materials changed (i.e., from ground mastic alum/honey to tooth colored composite and ceramics). There has been drastic change in treatment planning from extraction to the conservation of teeth and from manual restoration to computerized res...

  13. Ergonomics in dental pratice

    Directory of Open Access Journals (Sweden)

    Lucas Quaresemin de Oliveira

    2017-08-01

    Full Text Available The application of ergonomics is critical so that you can get a suitable working environment for professional, it is safe, healthy and comfortable. The objective was to identify whether the dental students followed the principles of ergonomics during clinical visits, evaluating, through photographs, compliance with ergonomic principles applied in dental practice, and finally identify the most affected sites by RSI / WMSDs of students enrolled in the dental clinic of the Faculdade IMED. Snapshots were made and only considered the position of the student operator, the same taken by the researcher using the mobile device. For each clinical procedure were taken two photographs in hidden angles to the student operator so that it did not change its ergonomic position to be observed. After obtaining the photos, they were evaluated and classified in scores from 0 to 3 according to the adequacy of the work placement, and then inserted into Excel and later in a database (SPSS 15.0. The following work is a cross-sectional, observational study, they were conducted in dental clinics IMED college. Among the 66 respondents, 14 were male and 52 female. It was found that 57 (86,3% reported feeling pain somewhere in the body, being the most affected sites neck (36.4%, and consecutively lower back (30.3% and higher than the back (27.3%. The results of the 63 procedures performed by the photographic shots were classified as “inadequate” in 49 procedures, “partially adequate” in 12 and “impossible to evaluate” in 2 procedures. The research results have shown a high prevalence of musculoskeletal pain and do not follow the ergonomic principles, emphasizing the need for more attention to ergonomics of the students.

  14. Ethical checklist for dental practice.

    Science.gov (United States)

    Rinchuse, D J; Rinchuse, D J; Deluzio, C

    1995-01-01

    A checklist for verification of unethical business practices, originally formulated by Drs. Blanchard and Peale, is adapted to dental practice. A scenario is used as a model to demonstrate the applicability of this instrument to dental practice. The instrument asks three questions in regards to an ethical dilemma: 1) Is it legal? 2) Is it fair? 3) How does it make you feel? The paper concludes the giving of gifts to general dentists by dental specialists for the referral of patients is unethical.

  15. Isolation of two independent allyl alcohol resistant Adh-1 null mutants following selection of pollen and seeds.

    NARCIS (Netherlands)

    Wisman, E.; Ramanna, M.S.; Zabel, P.

    1993-01-01

    The Adh-1 null mutant (B15-1-8) isolated previously was used to establish conditions that allow the selection of ADH-deficient pollen grains and seeds of tomato. New Adh-1 null mutants were then selected among the progenies derived from crosses between the genetically unstable tomato lines Yvms,

  16. Increased Oocyte Degeneration and Follicular Atresia during the Estrous Cycle in Anti-Müllerian Hormone Null Mice

    NARCIS (Netherlands)

    Visser, Jenny A.; Durlinger, Alexandra L.L.; Peters, Isolde J.J.; Heuvel, Edwin R. van den; Rose, Ursula M.; Kramer, Piet; Jong, Frank H. de; Themmen, Axel P.N.

    2007-01-01

    Anti-Müllerian hormone (AMH) plays an important role in folliculogenesis. AMH null mice display an increased recruitment of primordial follicles. Nevertheless, these mice do not have proportionally more preovulatory follicles. Therefore, AMH null mice provide an interesting genetic model to study

  17. Population estimators or progeny tests: what is the best method to assess null allele frequencies at SSR loci?

    NARCIS (Netherlands)

    Oddou-Muratorio, S.; Vendramin, G.G.; Buiteveld, J.; Fady, B.

    2009-01-01

    Nuclear SSRs are notorious for having relatively high frequencies of null alleles, i.e. alleles that fail to amplify and are thus recessive and undetected in heterozygotes. In this paper, we compare two kinds of approaches for estimating null allele frequencies at seven nuclear microsatellite

  18. Confronting shibboleths of dental education.

    Science.gov (United States)

    Masella, Richard S

    2005-10-01

    Shibboleths are common expressions presented as indisputable truths. When used in educational discussions, they reflect "motherhood and apple pie" viewpoints and tend to bring debate to a halt. Use of shibboleths may precede a desired imposition of "locksteps" in educational programming and are easily perceived as paternalistic by recipients. Nine shibboleths are presented as common beliefs of dental faculty and administrators. Evidence contradicting the veracity of the "obvious truths" is offered. The traditional "splendid isolation" of dentistry contributes to parochialism and belief in false shibboleths. Sound principles of higher and health professions education, student learning, and dental practice apply to dental education as to all health disciplines. Student passivity in dental education is not the best preparation for proficiency in dental practice. The master teacher possesses a repertoire of methodologies specific to meeting defined educational objectives. Active learning experiences bear close resemblances to professional duties and responsibilities and internally motivate future doctors of dental medicine. The difficulty in achieving curricular change leads to curricular entrenchment. Dentistry and dental education should not trade their ethical high ground for the relatively low ethical standards of the business world. Principles of professional ethics should govern relationships between dentists, whether within the dental school workplace or in practice. Suggestions are made on how to confront shibboleths in dental school settings.

  19. Children's experiences of dental anxiety.

    Science.gov (United States)

    Morgan, Annie G; Rodd, Helen D; Porritt, Jenny M; Baker, Sarah R; Creswell, Cathy; Newton, Tim; Williams, Chris; Marshman, Zoe

    2017-03-01

    Dental anxiety is common among children. Although there is a wealth of research investigating childhood dental anxiety, little consideration has been given to the child's perspective. This qualitative study sought to explore with children their own experiences of dental anxiety using a cognitive behavioural therapy assessment model. Face-to-face, semi-structured interviews were conducted with dentally anxious children aged 11-16 years. The Five Areas model was used to inform the topic guide and analysis. Data were analysed using a framework approach. In total, 13 children were interviewed. Participants described their experiences of dental anxiety across multiple dimensions (situational factors and altered thoughts, feelings, physical symptoms, and behaviours). Participants placed considerable value on communication by dental professionals, with poor communication having a negative influence on dental anxiety and the dentist-patient relationship. This study confirms the Five Areas model as an applicable theoretical model for the assessment of childhood dental anxiety. Children provided insights about their own dental anxiety experiences that have not previously been described. © 2016 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  20. Medical emergencies in dental practice.

    LENUS (Irish Health Repository)

    Wilson, M H

    2009-06-01

    Serious medical emergencies are fortunately a rare occurrence in the dental practice environment; however, if an emergency situation is encountered a delay in treatment may result in potentially avoidable consequences. The risk of mortality or serious morbidity can be reduced by ensuring that basic emergency equipment and medications are in place, and that the dental team is appropriately trained in basic life support measures. This article aims to provide an overview of the basic emergency medications and equipment that should be present in dental practices, and to discuss specific responses to some of the more common adverse medical events that can present while providing dental treatment.

  1. Diagnosis and treatment of abnormal dental pain

    OpenAIRE

    Fukuda, Ken-ichi

    2016-01-01

    Most dental pain is caused by an organic problem such as dental caries, periodontitis, pulpitis, or trauma. Diagnosis and treatment of these symptoms are relatively straightforward. However, patients often also complain of abnormal dental pain that has a non-dental origin, whose diagnosis is challenging. Such abnormal dental pain can be categorized on the basis of its cause as referred pain, neuromodulatory pain, and neuropathic pain. When it is difficult to diagnose a patient's dental pain, ...

  2. On Bäcklund transformation and vortex filament equation for null Cartan curve in Minkowski 3-space

    Energy Technology Data Exchange (ETDEWEB)

    Grbović, Milica, E-mail: milica.grbovic@kg.ac.rs; Nešović, Emilija, E-mail: nesovickg@sbb.rs [University of Kragujevac, Faculty of Science, Department of Mathematics and Informatics (Serbia)

    2016-12-15

    In this paper we introduce Bäcklund transformation of a null Cartan curve in Minkowski 3-space as a transformation which maps a null Cartan helix to another null Cartan helix, congruent to the given one. We also give the sufficient conditions for a transformation between two null Cartan curves in the Minkowski 3-space such that these curves have equal constant torsions. By using the Da Rios vortex filament equation, based on localized induction approximation, we derive the vortex filament equation for a null Cartan curve and obtain evolution equation for it’s torsion. As an application, we show that Cartan’s frame vectors generate new solutions of the Da Rios vortex filament equation.

  3. Mandatory Clinical Practice for Dental and Dental Hygiene Faculty.

    Science.gov (United States)

    Cameron, Cheryl A.; And Others

    1982-01-01

    Dental and dental hygiene faculty should maintain their clinical skills through regular practice, to improve their ability to relate to students through instruction, provide an additional source of income, and improve their image in the community. Institutional policies fostering and regulating faculty practice plans are suggested. (Author/MSE)

  4. Pattern of dental caries in Mulago Dental School clinic, Uganda ...

    African Journals Online (AJOL)

    Information on dental caries among patients attending Mulago Hospital is scarce. Yet knowledge of the pattern of caries can be used to plan preventive and treatment interventions. This study describes the pattern of dental caries (in terms of age group, tooth and tooth surface and gender) among patients attending the ...

  5. The Swedish national dental insurance and dental health care policy

    DEFF Research Database (Denmark)

    Moore, Rod

    1981-01-01

    Sweden initiated a dental health care insurance in 1973. The health insurance is outlined, current problems and political issues are described. The benefits and limitations are described.......Sweden initiated a dental health care insurance in 1973. The health insurance is outlined, current problems and political issues are described. The benefits and limitations are described....

  6. Inhibition of urethane-induced genotoxicity and cell proliferation in CYP2E1-null mice

    International Nuclear Information System (INIS)

    Hoffler, Undi; Dixon, Darlene; Peddada, Shyamal; Ghanayem, Burhan I.

    2005-01-01

    Urethane is a multi-site animal carcinogen and was classified as 'reasonably anticipated to be a human carcinogen.' Urethane is a fermentation by-product and found at appreciable levels in alcoholic beverages and foods such as bread and cheese. Recent work in this laboratory demonstrated for the first time that CYP2E1 is the principal enzyme responsible for urethane metabolism. The current studies were undertaken to assess the relationships between CYP2E1-mediated metabolism and urethane-induced genotoxicity and cell proliferation as determined by induction of micronucleated erythrocytes (MN) and expression of Ki-67, respectively, using CYP2E1-null and wild-type mice. Urethane was administered at 0 (vehicle), 1, 10, or 100 mg/kg/day (p.o.), 5 days/week for 6 weeks. A significant dose-dependent increase in MN was observed in wild-type mice; however, a slight increase was measured in the MN-polychromatic erythrocytes in CYP2E1-null mice treated with 100 mg/kg. A significant increase in the expression of Ki-67 was detected in the livers and the lungs (terminal bronchioles, alveoli, and bronchi) of wild-type mice administered 100 mg urethane/kg in comparison to controls. In contrast, CYP2E1-null mice administered this dose exhibited negligible alterations in Ki-67 expression in the livers and lungs compared to controls. Interestingly, while Ki-67 expression in the forestomach decreased in wild-type mice, it increased in CYP2E1-null mice. Subsequent comparative metabolism studies demonstrated that total urethane-derived radioactivity in the plasma, liver, and lung was significantly higher in CYP2E1-null versus wild-type mice and un-metabolized urethane constituted greater than 83% of the radioactivity in CYP2E1-null mice. Un-metabolized urethane was not detectable in the plasma, liver, and lung of wild-type mice. In conclusion, these data demonstrated that CYP2E1-mediated metabolism of urethane, presumably via epoxide formation, is necessary for the induction of

  7. Exploring Dental Providers’ Workflow in an Electronic Dental Record Environment

    Science.gov (United States)

    Schwei, Kelsey M; Cooper, Ryan; Mahnke, Andrea N.; Ye, Zhan

    2016-01-01

    Summary Background A workflow is defined as a predefined set of work steps and partial ordering of these steps in any environment to achieve the expected outcome. Few studies have investigated the workflow of providers in a dental office. It is important to understand the interaction of dental providers with the existing technologies at point of care to assess breakdown in the workflow which could contribute to better technology designs. Objective The study objective was to assess electronic dental record (EDR) workflows using time and motion methodology in order to identify breakdowns and opportunities for process improvement. Methods A time and motion methodology was used to study the human-computer interaction and workflow of dental providers with an EDR in four dental centers at a large healthcare organization. A data collection tool was developed to capture the workflow of dental providers and staff while they interacted with an EDR during initial, planned, and emergency patient visits, and at the front desk. Qualitative and quantitative analysis was conducted on the observational data. Results Breakdowns in workflow were identified while posting charges, viewing radiographs, e-prescribing, and interacting with patient scheduler. EDR interaction time was significantly different between dentists and dental assistants (6:20 min vs. 10:57 min, p = 0.013) and between dentists and dental hygienists (6:20 min vs. 9:36 min, p = 0.003). Conclusions On average, a dentist spent far less time than dental assistants and dental hygienists in data recording within the EDR. PMID:27437058

  8. Dentistry and Dental Hygiene Handbook.

    Science.gov (United States)

    New York State Education Dept., Albany. Office of the Professions.

    The handbook contains laws, rules, and regulations of the New York State Education Department that govern dentistry and dental hygiene practice in the state. It describes licensure requirements and includes complete application forms and instructions for obtaining license and first registration as a dentist and dental hygienist. Applicants are…

  9. Dental Chairside Technique. Student's Manual.

    Science.gov (United States)

    Apfel, Maura; Weaver, Trudy Karlene

    This manual is part of a series dealing with skills and information needed by students in dental assisting. The individualized student materials are suitable for classroom, laboratory, or cooperative training programs. This student manual contains four units covering the following topics: local anesthesia; dental office emergencies; oral hygiene;…

  10. Dental technician of the future

    NARCIS (Netherlands)

    Derksen, W.; Wismeijer, D.; Hanssen, S.; Tahmaseb, A.

    2015-01-01

    The new technologies in the field of dental science have not only changed the way in which dentists run their practice but have also dramatically changed the procedures carried out in dental laboratories. Mechanical engineering, incorporated CMM, laser milling, 3D printing and 3D design in a

  11. New dental applications with LEDs

    DEFF Research Database (Denmark)

    Argyraki, A.; Ou, Yiyu; Petersen, Paul Michael

    Visible and ultraviolet LEDs will in the future give rise to new dental applications. Fluorescence imaging, photodynamic therapy and photoactivated disinfection are important future candidates for diagnostics and treatment in dentistry.......Visible and ultraviolet LEDs will in the future give rise to new dental applications. Fluorescence imaging, photodynamic therapy and photoactivated disinfection are important future candidates for diagnostics and treatment in dentistry....

  12. EAMJ Jan. Dental 10.indd

    African Journals Online (AJOL)

    2010-01-01

    Jan 1, 2010 ... Oral diseases qualify as a major public health concern owing to their high prevalence and incidence in all regions of the world (1). Dental caries and gingivitis are the two most common dental diseases affecting children worldwide. These two diseases are, to a large extent, the result of the presence of ...

  13. Drawing Links within Dental Education

    Science.gov (United States)

    Wright, J.

    2017-01-01

    This study examines results of a practical drawing task given to a cohort of first year dental surgery students at Kings College Dental Institute, London. It compares and relates their success in drilling and removing caries and pulp tissue from a virtual tooth using the hapTEL virtual learning system, with each individuals' drawing skills.…

  14. Music interventions for dental anxiety.

    Science.gov (United States)

    Bradt, J; Teague, A

    2018-04-01

    Anxiety is a significant issue in the dental care of adults and children. Dental anxiety often leads to avoidance of dental care which may result in significant deterioration of oral and dental health. Non-pharmacological anxiety management interventions such as music listening are increasingly used in dental care. Although efficacy for music's anxiolytic effects has been established for pre-operative anxiety, findings regarding the use of music listening for dental anxiety are inconclusive, especially for children. The use of music for passive distraction may not be adequate for children and highly anxious adults. Instead, interventions offered by a trained music therapist may be needed to optimize music's anxiolytic impact. Music therapy interventions are individualized to the patient's presenting needs and geared at enhancing patients' active engagement in the management of their anxiety. Interventions may include (i) active refocusing of attention, (ii) music-guided deep breathing, (iii) music-assisted relaxation, and (iv) music-guided imagery. In addition, music therapists can teach patients music-based anxiety management skills prior to dental treatments, offer them the opportunity to express emotions related to the upcoming procedure, and help them gain a sense of control and safety. Clinical guidelines for the use of music listening by dental practitioners are offered. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  15. [The impact of dental implants

    NARCIS (Netherlands)

    Meijer, G.J.

    2013-01-01

    The importance of the introduction of dental implants can only be understood when the historical context is clarified. In the past, the main treatment carried out by dentists consisted of filling or, in unfortunate cases, removal of painful teeth. Only since the introduction of dental implants did

  16. Dental, Dental Hygiene, and Advanced Dental Students' Use, Knowledge, and Beliefs Regarding Tobacco Products.

    Science.gov (United States)

    Shearston, Jenni A; Shah, Krina; Cheng, Eric; Moosvi, Rizvan; Park, Su Hyun; Patel, Naiya; Spielman, Andrew I; Weitzman, Michael L

    2017-11-01

    Using cigarettes and alternative tobacco products (ATPs) is associated with negative oral health outcomes, and dental health professionals are poised to help patients quit. The aim of this study was to determine dental, dental hygiene, and advanced dental students' use, knowledge, and beliefs about cigarettes and ATPs, including perceptions about their education in tobacco dependence treatment and counseling experience. All 1,783 students enrolled in the dental, dental hygiene, and postdoctoral dental programs at the New York University College of Dentistry were invited to participate in the survey in 2016. A total of 708 students at least partially completed the survey, for a response rate of 39.7%. In the results, 146 of the students (20.1%) reported ever using cigarettes, while 253 (35.7%) reported ever using any ATP. Regarding tobacco use intervention, the students reported they had not received enough training on ATPs, were neutral about cigarettes, and were somewhat confident and not so confident counseling a cigarette smoker or ATP user, respectively. By their fourth year, 77.8% of the dental students reported they had counseled someone to stop smoking cigarettes, but only 40.7% had counseled someone to stop using ATPs. Overall, all groups of students reported feeling more confident and had received more education on interventions for cigarettes than for ATPs (ptobacco and did not perceive they had received enough training on intervening with patients on use of cigarettes and ATPs. These findings call for a revised tobacco education curriculum for dental, dental hygiene, and advanced dental students, focused on building knowledge and confidence for promoting tobacco dependence treatment.

  17. Competition and dental services.

    Science.gov (United States)

    Grytten, J; Sørensen, R

    2000-07-01

    Dental services for adults are different from all other Norwegian health services in that they are provided by private producers (dentists) who have full freedom to establish a practice. They have had this freedom since the end of World War II. A further liberalization of the market for dental services occurred in November 1995, when the so-called normal tariff was repealed. The system changed from a fixed fee system to a deregulated fee system. In principle, the market for dental services for adults operates as a free competitive market, in which dentists must compete for a market share. The aim of this study was to study the short-term effects of competition. A comprehensive set of data on fees, practice characteristics, treatment profiles and factors that dentists take into account when determining fees was analysed. The main finding was that competition has a weak effect. No support was found for the theory that the level of fees is the result of monopolistic competition or monopoly. The results also provided some evidence against the inducement hypothesis. At this stage, it is interesting to notice that dentists do not seem to exploit the power they have to control the market. One explanation, which is consistent with the more recent literature, is that physicians' behaviour to a large extent is influenced by professional norms and caring concerns about their patients. Financial incentives are important, but these incentives are constrained by norms other than self-interest. The interpretation of the results should also take into account that the deregulation has operated for a short time and that dentists and patients may not yet have adjusted to changes in the characteristics of the market. Copyright 2000 John Wiley & Sons, Ltd.

  18. Nanotechnology for dental implants.

    Science.gov (United States)

    Tomsia, Antoni P; Lee, Janice S; Wegst, Ulrike G K; Saiz, Eduardo

    2013-01-01

    With the advent of nanotechnology, an opportunity exists for the engineering of new dental implant materials. Metallic dental implants have been successfully used for decades, but they have shortcomings related to osseointegration and mechanical properties that do not match those of bone. Absent the development of an entirely new class of materials, faster osseointegration of currently available dental implants can be accomplished by various surface modifications. To date, there is no consensus regarding the preferred method(s) of implant surface modification, and further development will be required before the ideal implant surface can be created, let alone become available for clinical use. Current approaches can generally be categorized into three areas: ceramic coatings, surface functionalization, and patterning on the micro- to nanoscale. The distinctions among these are imprecise, as some or all of these approaches can be combined to improve in vivo implant performance. These surface improvements have resulted in durable implants with a high percentage of success and long-term function. Nanotechnology has provided another set of opportunities for the manipulation of implant surfaces in its capacity to mimic the surface topography formed by extracellular matrix components of natural tissue. The possibilities introduced by nanotechnology now permit the tailoring of implant chemistry and structure with an unprecedented degree of control. For the first time, tools are available that can be used to manipulate the physicochemical environment and monitor key cellular events at the molecular level. These new tools and capabilities will result in faster bone formation, reduced healing time, and rapid recovery to function.

  19. Ergonomic design for dental offices.

    Science.gov (United States)

    Ahearn, David J; Sanders, Martha J; Turcotte, Claudia

    2010-01-01

    The increasing complexity of the dental office environment influences productivity and workflow for dental clinicians. Advances in technology, and with it the range of products needed to provide services, have led to sprawl in operatory setups and the potential for awkward postures for dental clinicians during the delivery of oral health services. Although ergonomics often addresses the prevention of musculoskeletal disorders for specific populations of workers, concepts of workflow and productivity are integral to improved practice in work environments. This article provides suggestions for improving workflow and productivity for dental clinicians. The article applies ergonomic principles to dental practice issues such as equipment and supply management, office design, and workflow management. Implications for improved ergonomic processes and future research are explored.

  20. Null geodesics and wave front singularities in the Gödel space-time

    Science.gov (United States)

    Kling, Thomas P.; Roebuck, Kevin; Grotzke, Eric

    2018-01-01

    We explore wave fronts of null geodesics in the Gödel metric emitted from point sources both at, and away from, the origin. For constant time wave fronts emitted by sources away from the origin, we find cusp ridges as well as blue sky metamorphoses where spatially disconnected portions of the wave front appear, connect to the main wave front, and then later break free and vanish. These blue sky metamorphoses in the constant time wave fronts highlight the non-causal features of the Gödel metric. We introduce a concept of physical distance along the null geodesics, and show that for wave fronts of constant physical distance, the reorganization of the points making up the wave front leads to the removal of cusp ridges.

  1. Luxembourg in the Early Days of the EEC: Null Player or Not?

    Directory of Open Access Journals (Sweden)

    Alexander Mayer

    2018-05-01

    Full Text Available Voters whose yes-or-no decision never makes a difference to the outcome in a simple voting game are known as “null players”. Luxembourg’s role in the Council of Ministers during the first period of the European Economic Community (EEC is often cited as a real-world case. The paper contrasts the textbook claim that Luxembourg was a null player with a more comprehensive picture of Luxembourg’s role in EEC’s voting system. The assessment of Luxembourg’s voting power is sensitive to the role played by the European Commission in the decision-making procedure and the measurement concepts underlying power evaluations.

  2. Enhanced endotoxin sensitivity in fps/fes-null mice with minimal defects in hematopoietic homeostasis.

    Science.gov (United States)

    Zirngibl, Ralph A; Senis, Yotis; Greer, Peter A

    2002-04-01

    The fps/fes proto-oncogene encodes a cytoplasmic protein tyrosine kinase implicated in growth factor and cytokine receptor signaling and thought to be essential for the survival and terminal differentiation of myeloid progenitors. Fps/Fes-null mice were healthy and fertile, displayed slightly reduced numbers of bone marrow myeloid progenitors and circulating mature myeloid cells, and were more sensitive to lipopolysaccharide (LPS). These phenotypes were rescued using a fps/fes transgene. This confirmed that Fps/Fes is involved in, but not required for, myelopoiesis and that it plays a role in regulating the innate immune response. Bone marrow-derived Fps/Fes-null macrophages showed no defects in granulocyte-macrophage colony-stimulating factor-, interleukin 6 (IL-6)-, or IL-3-induced activation of signal transducer and activator of transcription 3 (Stat3) and Stat5A or LPS-induced degradation of I kappa B or activation of p38, Jnk, Erk, or Akt.

  3. Magnetic Nulls and Super-radial Expansion in the Solar Corona

    Energy Technology Data Exchange (ETDEWEB)

    Gibson, Sarah E.; Dalmasse, Kevin; Tomczyk, Steven; Toma, Giuliana de; Burkepile, Joan; Galloy, Michael [National Center for Atmospheric Research, 3080 Center Green Drive, Boulder, CO 80301 (United States); Rachmeler, Laurel A. [NASA Marshall Space Flight Center, Huntsville, AL 35811 (United States); Rosa, Marc L. De, E-mail: sgibson@ucar.edu [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street B/252, Palo Alto, CA 94304 (United States)

    2017-05-10

    Magnetic fields in the Sun’s outer atmosphere—the corona—control both solar-wind acceleration and the dynamics of solar eruptions. We present the first clear observational evidence of coronal magnetic nulls in off-limb linearly polarized observations of pseudostreamers, taken by the Coronal Multichannel Polarimeter (CoMP) telescope. These nulls represent regions where magnetic reconnection is likely to act as a catalyst for solar activity. CoMP linear-polarization observations also provide an independent, coronal proxy for magnetic expansion into the solar wind, a quantity often used to parameterize and predict the solar wind speed at Earth. We introduce a new method for explicitly calculating expansion factors from CoMP coronal linear-polarization observations, which does not require photospheric extrapolations. We conclude that linearly polarized light is a powerful new diagnostic of critical coronal magnetic topologies and the expanding magnetic flux tubes that channel the solar wind.

  4. Local differential geometry of null curves in conformally flat space-time

    International Nuclear Information System (INIS)

    Urbantke, H.

    1989-01-01

    The conformally invariant differential geometry of null curves in conformally flat space-times is given, using the six-vector formalism which has generalizations to higher dimensions. This is then paralleled by a twistor description, with a twofold merit: firstly, sometimes the description is easier in twistor terms, sometimes in six-vector terms, which leads to a mutual enlightenment of both; and secondly, the case of null curves in timelike pseudospheres or 2+1 Minkowski space we were only able to treat twistorially, making use of an invariant differential found by Fubini and Cech. The result is the expected one: apart from stated exceptional cases there is a conformally invariant parameter and two conformally invariant curvatures which, when specified in terms of this parameter, serve to characterize the curve up to conformal transformations. 12 refs. (Author)

  5. Bursty, Broadband Electromagnetic Waves Associated with Three-Dimensional Nulls Observed in Turbulent Magnetosheath Reconnection

    Science.gov (United States)

    Adrian, Mark L.; Wendel, D. E.

    2012-01-01

    We investigate observations of intense bursts of electromagnetic wave energy in association with the thin current layers of turbulent magnetosheath reconnection. These observed emissions - typically detected in the layers immediately outside of the current layer proper - form two distinct types: (i) broadband emissions that extend continuously to lOs of Hertz; and (ii) structured bursts of emitted energy that occur above 80-Hz, often displaying features reminiscent of absorption bands and are observed near the local minima in the magnetic field. We present detailed analyses of these intense bursts of electromagnetic energy and quantify their proximity to X-IO-nulls and magnetic spine connected null pairs, as well as their correlation - if any - to the amount of magnetic energy converted by the process of magnetic reconnection.

  6. Vacuum solutions admitting a geodesic null congruence with shear proportional to expansion

    International Nuclear Information System (INIS)

    Kupeli, A.H.

    1988-01-01

    Algebraically general, nontwisting solutions for the vacuum to vacuum generalized Kerr--Schild (GKS) transformation are obtained. These solutions admit a geodesic null congruence with shear proportional to expansion. In the Newman--Penrose formalism, if l/sup μ/ is chosen to be the null vector of the GKS transformation, this property is stated as σ = arho and Da = 0. It is assumed that a is a constant, and the background is chosen as a pp-wave solution. For generic values of a, the GKS metrics consist of the Kasner solutions. For a = +- (1 +- (2)/sup 1/2/), there are solutions with less symmetries including special cases of the Kota--Perjes and Lukacs solutions

  7. Kinetic modeling of particle acceleration in a solar null point reconnection region

    DEFF Research Database (Denmark)

    Baumann, Gisela; Haugbølle, Troels; Nordlund, Åke

    2013-01-01

    The primary focus of this paper is on the particle acceleration mechanism in solar coronal 3D reconnection null-point regions. Starting from a potential field extrapolation of a SOHO magnetogram taken on 2002 November 16, we first performed MHD simulations with horizontal motions observed by SOHO...... particles and 3.5 billion grid cells of size 17.5\\,km --- these simulations offer a new opportunity to study particle acceleration in solar-like settings....... applied to the photospheric boundary of the computational box. After a build-up of electric current in the fan-plane of the null-point, a sub-section of the evolved MHD data was used as initial and boundary conditions for a kinetic particle-in-cell model of the plasma. We find that sub...

  8. The american dental dream.

    Science.gov (United States)

    Hodges, Nathan

    2015-01-01

    The American Dental Dream-the cultural desire for straight, white teeth-is difficult, if not impossible, for poor and working-class people to achieve. Using ethnographic fiction, autoethnography, poetry, and qualitative interviewing, I brush away the taken-for-granted assumptions about teeth. I explore the personal, relational, and structural consequences of this cultural desire, and show how social class writes itself on our bodies. I write these culture-centered teeth tales to show how one might cope with their teeth.

  9. Adhesive dental materials

    International Nuclear Information System (INIS)

    Unlu, N.

    2005-01-01

    Two main classes of material are involved, the glass-ionomer cements and the composite resins. This investigation describes the way they are bonded to the tooth and highlights their differences. Glass ionomers develop a zone of interaction with the tooth as they age which ultimately gives an extremely strong bond, and results in excellent retention rates. By contrast, bonding of composite resins is more complicated and possibly less effective, though these materials have better wear resistance and better aesthetics than glass ionomers. Assessment of bond durability is difficult. This is because a dental restorative can fail by a number of mechanisms apart from de bonding: for example, through wear or fracture

  10. IMPROVING INTERFEROMETRIC NULL DEPTH MEASUREMENTS USING STATISTICAL DISTRIBUTIONS: THEORY AND FIRST RESULTS WITH THE PALOMAR FIBER NULLER

    International Nuclear Information System (INIS)

    Hanot, C.; Riaud, P.; Absil, O.; Mennesson, B.; Martin, S.; Liewer, K.; Loya, F.; Mawet, D.; Serabyn, E.

    2011-01-01

    A new 'self-calibrated' statistical analysis method has been developed for the reduction of nulling interferometry data. The idea is to use the statistical distributions of the fluctuating null depth and beam intensities to retrieve the astrophysical null depth (or equivalently the object's visibility) in the presence of fast atmospheric fluctuations. The approach yields an accuracy much better (about an order of magnitude) than is presently possible with standard data reduction methods, because the astrophysical null depth accuracy is no longer limited by the magnitude of the instrumental phase and intensity errors but by uncertainties on their probability distributions. This approach was tested on the sky with the two-aperture fiber nulling instrument mounted on the Palomar Hale telescope. Using our new data analysis approach alone-and no observations of calibrators-we find that error bars on the astrophysical null depth as low as a few 10 -4 can be obtained in the near-infrared, which means that null depths lower than 10 -3 can be reliably measured. This statistical analysis is not specific to our instrument and may be applicable to other interferometers.

  11. A mycobacterial smc null mutant is proficient in DNA repair and long-term survival.

    Science.gov (United States)

    Güthlein, Carolin; Wanner, Roger M; Sander, Peter; Böttger, Erik C; Springer, Burkhard

    2008-01-01

    SMC (structural maintenance of chromosomes) proteins play fundamental roles in various aspects of chromosome organization and dynamics, including repair of DNA damage. Mutant strains of Mycobacterium smegmatis and Mycobacterium tuberculosis defective in SMC were constructed. Surprisingly, inactivation of smc did not result in recognizable phenotypes in hallmark assays characteristic for the function of these genes. This is in contrast to data for smc null mutants in other species.

  12. A Mycobacterial smc Null Mutant Is Proficient in DNA Repair and Long-Term Survival▿

    OpenAIRE

    Güthlein, Carolin; Wanner, Roger M.; Sander, Peter; Böttger, Erik C.; Springer, Burkhard

    2007-01-01

    SMC (structural maintenance of chromosomes) proteins play fundamental roles in various aspects of chromosome organization and dynamics, including repair of DNA damage. Mutant strains of Mycobacterium smegmatis and Mycobacterium tuberculosis defective in SMC were constructed. Surprisingly, inactivation of smc did not result in recognizable phenotypes in hallmark assays characteristic for the function of these genes. This is in contrast to data for smc null mutants in other species.

  13. Null Geodesic Congruences, Asymptotically-Flat Spacetimes and Their Physical Interpretation

    Directory of Open Access Journals (Sweden)

    Timothy M. Adamo

    2009-09-01

    Full Text Available A priori, there is nothing very special about shear-free or asymptotically shear-free null geodesic congruences. Surprisingly, however, they turn out to possess a large number of fascinating geometric properties and to be closely related, in the context of general relativity, to a variety of physically significant effects. It is the purpose of this paper to try to fully develop these issues. This work starts with a detailed exposition of the theory of shear-free and asymptotically shear-free null geodesic congruences, i.e., congruences with shear that vanishes at future conformal null infinity. A major portion of the exposition lies in the analysis of the space of regular shear-free and asymptotically shear-free null geodesic congruences. This analysis leads to the space of complex analytic curves in complex Minkowski space. They in turn play a dominant role in the applications. The applications center around the problem of extracting interior physical properties of an asymptotically-flat spacetime directly from the asymptotic gravitational (and Maxwell field itself, in analogy with the determination of total charge by an integral over the Maxwell field at infinity or the identification of the interior mass (and its loss by (Bondi’s integrals of the Weyl tensor, also at infinity. More specifically, we will see that the asymptotically shear-free congruences lead us to an asymptotic definition of the center-of-mass and its equations of motion. This includes a kinematic meaning, in terms of the center-of-mass motion, for the Bondi three-momentum. In addition, we obtain insights into intrinsic spin and, in general, angular momentum, including an angular-momentum–conservation law with well-defined flux terms. When a Maxwell field is present, the asymptotically shear-free congruences allow us to determine/define at infinity a center-of-charge world line and intrinsic magnetic dipole moment.

  14. Potential of balloon payloads for in flight validation of direct and nulling interferometry concepts

    Science.gov (United States)

    Demangeon, Olivier; Ollivier, Marc; Le Duigou, Jean-Michel; Cassaing, Frédéric; Coudé du Foresto, Vincent; Mourard, Denis; Kern, Pierre; Lam Trong, Tien; Evrard, Jean; Absil, Olivier; Defrere, Denis; Lopez, Bruno

    2010-07-01

    While the question of low cost / low science precursors is raised to validate the concepts of direct and nulling interferometry space missions, balloon payloads offer a real opportunity thanks to their relatively low cost and reduced development plan. Taking into account the flight capabilities of various balloon types, we propose in this paper, several concepts of payloads associated to their flight plan. We also discuss the pros and cons of each concepts in terms of technological and science demonstration power.

  15. Tooth development in a model reptile: functional and null generation teeth in the gecko Paroedura picta

    Czech Academy of Sciences Publication Activity Database

    Zahradníček, Oldřich; Horáček, I.; Tucker, A. S.

    2012-01-01

    Roč. 221, č. 3 (2012), s. 195-208 ISSN 0021-8782 R&D Projects: GA ČR(CZ) GAP305/12/1766 Grant - others:GA AV ČR(CZ) KJB601110910 Program:KJ Institutional research plan: CEZ:AV0Z50390703 Institutional support: RVO:68378041 Keywords : cusps * gecko * null generation teeth Subject RIV: EA - Cell Biology Impact factor: 2.357, year: 2012

  16. Vascular Response to Intra-arterial Injury in the Thrombospondin-1 Null Mouse

    OpenAIRE

    Budhani, Faisal; Leonard, Katherine A.; Bergdahl, Andreas; Gao, Jimin; Lawler, Jack; Davis, Elaine C.

    2007-01-01

    Thrombospondin-1 (TSP-1) is a multifunctional, extracellular matrix protein that has been implicated in the regulation of smooth muscle cell proliferation, migration and differentiation during vascular development and injury. Vascular injury in wildtype and TSP-1 null mice was carried out by insertion of a straight spring guidewire into the femoral artery via a muscular arterial branch. Blood flow was restored after the muscular branch was ligated. The injury completely denuded the endotheliu...

  17. Null strings and complex Einstein-Maxwell fields with cosmological constant

    International Nuclear Information System (INIS)

    Garcia, A.; Plebanski, J.F.; Robinson, I.

    1977-01-01

    Previous results of Plebanski and Robinson (Phys. Rev. Lett.; 37:493 (1976)) concerning left-degenerate Einstein-flat complex space-times and preliminary results concerning the electromagnetic field, are here generalized and worked out in some detail for the system of Einstein-Maxwell equations with a cosmological constant. On the assumption that there exists a congruence of totally null surfaces, the system is reduced to a pair of equations for the two unknown functions. (author)

  18. The root infinitive stage in a null subject language: Romance in the Balkans

    Directory of Open Access Journals (Sweden)

    Larisa Avram

    2007-01-01

    Full Text Available The aim of the present paper is to determine which early non-finite verbal form is the Root Infinitive analogue in Romanian, an Inflection-licensed null subject language. In particular, we investigate whether the RI-analogue is the imperative, as predicted by Salustri and Hyams’s (2003 hypothesis, or whether it is a language specific underspecified form, overused during the early stages of acquisition, as predicted by Wexler et al. (2004.

  19. Null Geodesic Congruences, Asymptotically-Flat Spacetimes and Their Physical Interpretation

    Directory of Open Access Journals (Sweden)

    Timothy M. Adamo

    2012-01-01

    Full Text Available A priori, there is nothing very special about shear-free or asymptotically shear-free null geodesic congruences. Surprisingly, however, they turn out to possess a large number of fascinating geometric properties and to be closely related, in the context of general relativity, to a variety of physically significant effects. It is the purpose of this paper to try to fully develop these issues. This work starts with a detailed exposition of the theory of shear-free and asymptotically shear-free null geodesic congruences, i.e., congruences with shear that vanishes at future conformal null infinity. A major portion of the exposition lies in the analysis of the space of regular shear-free and asymptotically shear-free null geodesic congruences. This analysis leads to the space of complex analytic curves in an auxiliary four-complex dimensional space, H-space. They in turn play a dominant role in the applications. The applications center around the problem of extracting interior physical properties of an asymptotically-flat spacetime directly from the asymptotic gravitational (and Maxwell field itself, in analogy with the determination of total charge by an integral over the Maxwell field at infinity or the identification of the interior mass (and its loss by (Bondi's integrals of the Weyl tensor, also at infinity. More specifically, we will see that the asymptotically shear-free congruences lead us to an asymptotic definition of the center-of-mass and its equations of motion. This includes a kinematic meaning, in terms of the center-of-mass motion, for the Bondi three-momentum. In addition, we obtain insights into intrinsic spin and, in general, angular momentum, including an angular-momentum--conservation law with well-defined flux terms. When a Maxwell field is present, the asymptotically shear-free congruences allow us to determine/define at infinity a center-of-charge world line and intrinsic magnetic dipole moment.

  20. Likelihood of Null Effects of Large NHLBI Clinical Trials Has Increased over Time.

    Directory of Open Access Journals (Sweden)

    Robert M Kaplan

    Full Text Available We explore whether the number of null results in large National Heart Lung, and Blood Institute (NHLBI funded trials has increased over time.We identified all large NHLBI supported RCTs between 1970 and 2012 evaluating drugs or dietary supplements for the treatment or prevention of cardiovascular disease. Trials were included if direct costs >$500,000/year, participants were adult humans, and the primary outcome was cardiovascular risk, disease or death. The 55 trials meeting these criteria were coded for whether they were published prior to or after the year 2000, whether they registered in clinicaltrials.gov prior to publication, used active or placebo comparator, and whether or not the trial had industry co-sponsorship. We tabulated whether the study reported a positive, negative, or null result on the primary outcome variable and for total mortality.17 of 30 studies (57% published prior to 2000 showed a significant benefit of intervention on the primary outcome in comparison to only 2 among the 25 (8% trials published after 2000 (χ2=12.2,df= 1, p=0.0005. There has been no change in the proportion of trials that compared treatment to placebo versus active comparator. Industry co-sponsorship was unrelated to the probability of reporting a significant benefit. Pre-registration in clinical trials.gov was strongly associated with the trend toward null findings.The number NHLBI trials reporting positive results declined after the year 2000. Prospective declaration of outcomes in RCTs, and the adoption of transparent reporting standards, as required by clinicaltrials.gov, may have contributed to the trend toward null findings.

  1. Null Geodesic Congruences, Asymptotically-Flat Spacetimes and Their Physical Interpretation.

    Science.gov (United States)

    Adamo, Timothy M; Newman, Ezra T; Kozameh, Carlos

    2012-01-01

    A priori, there is nothing very special about shear-free or asymptotically shear-free null geodesic congruences. Surprisingly, however, they turn out to possess a large number of fascinating geometric properties and to be closely related, in the context of general relativity, to a variety of physically significant effects. It is the purpose of this paper to try to fully develop these issues. This work starts with a detailed exposition of the theory of shear-free and asymptotically shear-free null geodesic congruences, i.e., congruences with shear that vanishes at future conformal null infinity. A major portion of the exposition lies in the analysis of the space of regular shear-free and asymptotically shear-free null geodesic congruences. This analysis leads to the space of complex analytic curves in an auxiliary four-complex dimensional space, [Formula: see text]-space. They in turn play a dominant role in the applications. The applications center around the problem of extracting interior physical properties of an asymptotically-flat spacetime directly from the asymptotic gravitational (and Maxwell) field itself, in analogy with the determination of total charge by an integral over the Maxwell field at infinity or the identification of the interior mass (and its loss) by (Bondi's) integrals of the Weyl tensor, also at infinity. More specifically, we will see that the asymptotically shear-free congruences lead us to an asymptotic definition of the center-of-mass and its equations of motion. This includes a kinematic meaning, in terms of the center-of-mass motion, for the Bondi three-momentum. In addition, we obtain insights into intrinsic spin and, in general, angular momentum, including an angular-momentum-conservation law with well-defined flux terms. When a Maxwell field is present, the asymptotically shear-free congruences allow us to determine/define at infinity a center-of-charge world line and intrinsic magnetic dipole moment.

  2. Hypersensitivities for Acetaldehyde and Other Agents among Cancer Cells Null for Clinically Relevant Fanconi Anemia Genes

    OpenAIRE

    Ghosh, Soma; Sur, Surojit; Yerram, Sashidhar R.; Rago, Carlo; Bhunia, Anil K.; Hossain, M. Zulfiquer; Paun, Bogdan C.; Ren, Yunzhao R.; Iacobuzio-Donahue, Christine A.; Azad, Nilofer A.; Kern, Scott E.

    2014-01-01

    Large-magnitude numerical distinctions (>10-fold) among drug responses of genetically contrasting cancers were crucial for guiding the development of some targeted therapies. Similar strategies brought epidemiological clues and prevention goals for genetic diseases. Such numerical guides, however, were incomplete or low magnitude for Fanconi anemia pathway (FANC) gene mutations relevant to cancer in FANC-mutation carriers (heterozygotes). We generated a four-gene FANC-null cancer panel, inclu...

  3. Nav 1.8-null mice show stimulus-dependent deficits in spinal neuronal activity

    Directory of Open Access Journals (Sweden)

    Wood John N

    2006-02-01

    Full Text Available Abstract Background The voltage gated sodium channel Nav 1.8 has a highly restricted expression pattern to predominantly nociceptive peripheral sensory neurones. Behaviourally Nav 1.8-null mice show an increased acute pain threshold to noxious mechanical pressure and also deficits in inflammatory and visceral, but not neuropathic pain. Here we have made in vivo electrophysiology recordings of dorsal horn neurones in intact anaesthetised Nav 1.8-null mice, in response to a wide range of stimuli to further the understanding of the functional roles of Nav 1.8 in pain transmission from the periphery to the spinal cord. Results Nav 1.8-null mice showed marked deficits in the coding by dorsal horn neurones to mechanical, but not thermal, -evoked responses over the non-noxious and noxious range compared to littermate controls. Additionally, responses evoked to other stimulus modalities were also significantly reduced in Nav 1.8-null mice where the reduction observed to pinch > brush. The occurrence of ongoing spontaneous neuronal activity was significantly less in mice lacking Nav 1.8 compared to control. No difference was observed between groups in the evoked activity to electrical activity of the peripheral receptive field. Conclusion This study demonstrates that deletion of the sodium channel Nav 1.8 results in stimulus-dependent deficits in the dorsal horn neuronal coding to mechanical, but not thermal stimuli applied to the neuronal peripheral receptive field. This implies that Nav 1.8 is either responsible for, or associated with proteins involved in mechanosensation.

  4. Congruences of null strings in complex space-times and some Cauchy--Kovalevski-like problems

    International Nuclear Information System (INIS)

    Robinson, I.; Rozga, K.

    1984-01-01

    It is shown that a problem of construction of a local congruence of null strings is equivalent to a natural Cauchy--Kovalevski-like problem, related to an equation for a spinor field k/sub A/ defining the congruence. Initial data are specified on two-dimensional submanifolds. In left-conformally-flat spaces, the solution of that problem exists for arbitrary initial data

  5. Chronic Toxoplasma gondii in Nurr1-Null Heterozygous Mice Exacerbates Elevated Open Field Activity

    OpenAIRE

    Eells, Jeffrey B.; Varela-Stokes, Andrea; Guo-Ross, Shirley X.; Kummari, Evangel; Smith, Holly M.; Cox, Erin; Lindsay, David S.

    2015-01-01

    Latent infection with Toxoplasma gondii is common in humans (approximately 30% of the global population) and is a significant risk factor for schizophrenia. Since prevalence of T. gondii infection is far greater than prevalence of schizophrenia (0.5-1%), genetic risk factors are likely also necessary to contribute to schizophrenia. To test this concept in an animal model, Nurr1-null heterozygous (+/-) mice and wild-type (+/+) mice were evaluate using an emergence test, activity in an open fie...

  6. Internalizing Null Extraterrestrial "Signals": An Astrobiological App for a Technological Society

    OpenAIRE

    Chaisson, Eric J.

    2014-01-01

    One of the beneficial outcomes of searching for life in the Universe is that it grants greater awareness of our own problems here on Earth. Lack of contact with alien beings to date might actually comprise a null "signal" pointing humankind toward a viable future. Astrobiology has surprising practical applications to human society; within the larger cosmological context of cosmic evolution, astrobiology clarifies the energetic essence of complex systems throughout the Universe, including tech...

  7. On the dependence of energy confinement on elongation in Single Null divertor plasmas

    International Nuclear Information System (INIS)

    Weisen, H.; Martin, Y.; Moret, J. M.; Others

    2002-03-01

    An analysis of the effect of magnetic geometry on heat flux in a wide range of Single Null diverted discharge configurations with 1.5 κ ∼ 74, based on the configurations in the study. This is very close to dependences from the ITER database for discharge conditions, such as ELMy H-modes, obtained from a large number of experiments in various tokamak devices. (author)

  8. Bi-dimensional null model analysis of presence-absence binary matrices.

    Science.gov (United States)

    Strona, Giovanni; Ulrich, Werner; Gotelli, Nicholas J

    2018-01-01

    Comparing the structure of presence/absence (i.e., binary) matrices with those of randomized counterparts is a common practice in ecology. However, differences in the randomization procedures (null models) can affect the results of the comparisons, leading matrix structural patterns to appear either "random" or not. Subjectivity in the choice of one particular null model over another makes it often advisable to compare the results obtained using several different approaches. Yet, available algorithms to randomize binary matrices differ substantially in respect to the constraints they impose on the discrepancy between observed and randomized row and column marginal totals, which complicates the interpretation of contrasting patterns. This calls for new strategies both to explore intermediate scenarios of restrictiveness in-between extreme constraint assumptions, and to properly synthesize the resulting information. Here we introduce a new modeling framework based on a flexible matrix randomization algorithm (named the "Tuning Peg" algorithm) that addresses both issues. The algorithm consists of a modified swap procedure in which the discrepancy between the row and column marginal totals of the target matrix and those of its randomized counterpart can be "tuned" in a continuous way by two parameters (controlling, respectively, row and column discrepancy). We show how combining the Tuning Peg with a wise random walk procedure makes it possible to explore the complete null space embraced by existing algorithms. This exploration allows researchers to visualize matrix structural patterns in an innovative bi-dimensional landscape of significance/effect size. We demonstrate the rational and potential of our approach with a set of simulated and real matrices, showing how the simultaneous investigation of a comprehensive and continuous portion of the null space can be extremely informative, and possibly key to resolving longstanding debates in the analysis of ecological

  9. Null Geodesics and Strong Field Gravitational Lensing in a String Cloud Background

    International Nuclear Information System (INIS)

    Iftikhar, Sehrish; Sharif, M.

    2015-01-01

    This paper is devoted to studying two interesting issues of a black hole with string cloud background. Firstly, we investigate null geodesics and find unstable orbital motion of particles. Secondly, we calculate deflection angle in strong field limit. We then find positions, magnifications, and observables of relativistic images for supermassive black hole at the galactic center. We conclude that string parameter highly affects the lensing process and results turn out to be quite different from the Schwarzschild black hole

  10. A Model of Oxidative Stress Management: Moderation of Carbohydrate Metabolizing Enzymes in SOD1-Null Drosophila melanogaster

    Science.gov (United States)

    Bernard, Kristine E.; Parkes, Tony L.; Merritt, Thomas J. S.

    2011-01-01

    The response to oxidative stress involves numerous genes and mutations in these genes often manifest in pleiotropic ways that presumably reflect perturbations in ROS-mediated physiology. The Drosophila melanogaster SOD1-null allele (cSODn108) is proposed to result in oxidative stress by preventing superoxide breakdown. In SOD1-null flies, oxidative stress management is thought to be reliant on the glutathione-dependent antioxidants that utilize NADPH to cycle between reduced and oxidized form. Previous studies suggest that SOD1-null Drosophila rely on lipid catabolism for energy rather than carbohydrate metabolism. We tested these connections by comparing the activity of carbohydrate metabolizing enzymes, lipid and triglyceride concentration, and steady state NADPH:NADP+ in SOD1-null and control transgenic rescue flies. We find a negative shift in the activity of carbohydrate metabolizing enzymes in SOD1-nulls and the NADP+-reducing enzymes were found to have significantly lower activity than the other enzymes assayed. Little evidence for the catabolism of lipids as preferential energy source was found, as the concentration of lipids and triglycerides were not significantly lower in SOD1-nulls compared with controls. Using a starvation assay to impact lipids and triglycerides, we found that lipids were indeed depleted in both genotypes when under starvation stress, suggesting that oxidative damage was not preventing the catabolism of lipids in SOD1-null flies. Remarkably, SOD1-nulls were also found to be relatively resistant to starvation. Age profiles of enzyme activity, triglyceride and lipid concentration indicates that the trends observed are consistent over the average lifespan of the SOD1-nulls. Based on our results, we propose a model of physiological response in which organisms under oxidative stress limit the production of ROS through the down-regulation of carbohydrate metabolism in order to moderate the products exiting the electron transport chain. PMID

  11. On the Penrose inequality for dust null shells in the Minkowski spacetime of arbitrary dimension

    International Nuclear Information System (INIS)

    Mars, Marc; Soria, Alberto

    2012-01-01

    A particular, yet relevant, case of the Penrose inequality involves null shells propagating in the Minkowski spacetime. Despite previous claims in the literature, the validity of this inequality remains open. In this paper, we rewrite this inequality in terms of the geometry of the surface obtained by intersecting the past null cone of the original surface S with a constant time hyperplane and the 'time height' function of S over this hyperplane. We also specialize to the case when S lies in the past null cone of a point and show the validity of the corresponding inequality in any dimension (in four dimensions this inequality was proved by Tod (1985 Class. Quantum Grav. 2 L65-8). Exploiting properties of convex hypersurfaces in the Euclidean space, we write down the Penrose inequality in the Minkowski spacetime of an arbitrary dimension n + 2 as an inequality for two smooth functions on the sphere S n . We finally obtain a sufficient condition for the validity of the Penrose inequality in the four-dimensional Minkowski spacetime and show that this condition is satisfied by a large class of surfaces. (paper)

  12. A robust null hypothesis for the potential causes of megadrought in western North America

    Science.gov (United States)

    Ault, T.; St George, S.; Smerdon, J. E.; Coats, S.; Mankin, J. S.; Cruz, C. C.; Cook, B.; Stevenson, S.

    2017-12-01

    The western United States was affected by several megadroughts during the last 1200 years, most prominently during the Medieval Climate Anomaly (MCA: 800 to 1300 CE). A null hypothesis is developed to test the possibility that, given a sufficiently long period of time, these events are inevitable and occur purely as a consequence of internal climate variability. The null distribution of this hypothesis is populated by a linear inverse model (LIM) constructed from global sea-surface temperature anomalies and self-calibrated Palmer Drought Severity Index data for North America. Despite being trained only on seasonal data from the late 20th century, the LIM produces megadroughts that are comparable in their duration, spatial scale, and magnitude as the most severe events of the last 12 centuries. The null hypothesis therefore cannot be rejected with much confidence when considering these features of megadrought, meaning that similar events are possible today, even without any changes to boundary conditions. In contrast, the observed clustering of megadroughts in the MCA, as well as the change in mean hydroclimate between the MCA and the 1500-2000 period, are more likely to have been caused by either external forcing or by internal climate variability not well sampled during the latter half of the Twentieth Century. Finally, the results demonstrate the LIM is a viable tool for determining whether paleoclimate reconstructions events should be ascribed to external forcings, "out of sample" climate mechanisms, or if they are consistent with the variability observed during the recent period.

  13. Null-point titration measurements of free magnesium in stored erythrocytes

    International Nuclear Information System (INIS)

    Bock, J.L.; Yusuf, Y.; Puntillo, E.

    1987-01-01

    Free intracellular magnesium concentration (Mg/sub i/) was measured in stored human erythrocytes, using null-point titration with ionophore A23187. For cells stored 31 P NMR spectroscopy, which showed a decrease in Mg/sub i/ with storage. However, the NMR measurements are performed with no pretreatment of the cells, while the null-point method requires an initial washing step, which alters pH/sub i/ and may also alter Mg/sub i/. The titration-measured Mg/sub i/ values are still surprisingly low for long-stored cells, considering that depletion of ATP and 2,3-DPG should release bound Mg. Using the titration-measured Mg/sub i/ values along with measurements of total Mg, ATP, and 2,3-DPG, they estimate that an additional buffer contains about 47% of total Mg in cells stored 21 days. Mg/sub i/ determinations by both 31 P NMR and null-point titration thus indicate that erythrocyte Mg is largely bound to a high-capacity, low-affinity buffer whose relative importance increases during cell storage. Discrepancies between the methods require further investigation

  14. Asymptotic symmetries of Rindler space at the horizon and null infinity

    International Nuclear Information System (INIS)

    Chung, Hyeyoun

    2010-01-01

    We investigate the asymptotic symmetries of Rindler space at null infinity and at the event horizon using both systematic and ad hoc methods. We find that the approaches that yield infinite-dimensional asymptotic symmetry algebras in the case of anti-de Sitter and flat spaces only give a finite-dimensional algebra for Rindler space at null infinity. We calculate the charges corresponding to these symmetries and confirm that they are finite, conserved, and integrable, and that the algebra of charges gives a representation of the asymptotic symmetry algebra. We also use relaxed boundary conditions to find infinite-dimensional asymptotic symmetry algebras for Rindler space at null infinity and at the event horizon. We compute the charges corresponding to these symmetries and confirm that they are finite and integrable. We also determine sufficient conditions for the charges to be conserved on-shell, and for the charge algebra to give a representation of the asymptotic symmetry algebra. In all cases, we find that the central extension of the charge algebra is trivial.

  15. Percentiles of the null distribution of 2 maximum lod score tests.

    Science.gov (United States)

    Ulgen, Ayse; Yoo, Yun Joo; Gordon, Derek; Finch, Stephen J; Mendell, Nancy R

    2004-01-01

    We here consider the null distribution of the maximum lod score (LOD-M) obtained upon maximizing over transmission model parameters (penetrance values, dominance, and allele frequency) as well as the recombination fraction. Also considered is the lod score maximized over a fixed choice of genetic model parameters and recombination-fraction values set prior to the analysis (MMLS) as proposed by Hodge et al. The objective is to fit parametric distributions to MMLS and LOD-M. Our results are based on 3,600 simulations of samples of n = 100 nuclear families ascertained for having one affected member and at least one other sibling available for linkage analysis. Each null distribution is approximately a mixture p(2)(0) + (1 - p)(2)(v). The values of MMLS appear to fit the mixture 0.20(2)(0) + 0.80chi(2)(1.6). The mixture distribution 0.13(2)(0) + 0.87chi(2)(2.8). appears to describe the null distribution of LOD-M. From these results we derive a simple method for obtaining critical values of LOD-M and MMLS. Copyright 2004 S. Karger AG, Basel

  16. General dental practitioner's views on dental general anaesthesia services.

    Science.gov (United States)

    Threlfall, A G; King, D; Milsom, K M; Blinkhom, A S; Tickle, M

    2007-06-01

    Policy has recently changed on provision of dental general anaesthetic services in England. The aim of this study was to investigate general dental practitioners' views about dental general anaesthetics, the reduction in its availability and the impact on care of children with toothache. Qualitative study using semi-structured interviews and clinical case scenarios. General dental practitioners providing NHS services in the North West of England. 93 general dental practitioners were interviewed and 91 answered a clinical case scenario about the care they would provide for a 7-year-old child with multiple decayed teeth presenting with toothache. Scenario responses showed variation; 8% would immediately refer for general anaesthesia, 25% would initially prescribe antibiotics, but the majority would attempt to either restore or extract the tooth causing pain. Interview responses also demonstrated variation in care, however most dentists agree general anaesthesia has a role for nervous children but only refer as a last resort. The responses indicated an increase in inequalities, and that access to services did not match population needs, leaving some children waiting in pain. Most general dental practitioners support moving dental general anaesthesia into hospitals but some believe that it has widened health inequalities and there is also a problem associated with variation in treatment provision. Additional general anaesthetic services in some areas with high levels of tooth decay are needed and evidence based guidelines about caring for children with toothache are required.

  17. Intergrated dental care in nursing homes

    NARCIS (Netherlands)

    Gerritsen, P.F.M.

    2015-01-01

    The thesis deals with integrated dental care in nursing homes. First, the dental treatment needs were ascertained of 432 residents in three Dutch nursing homes that offer integrated dental care. Dentist researchers intra-orally examined the residents and found that 72% required dental treatment.

  18. Involving Parents in Their Children's Dental Care.

    Science.gov (United States)

    Becker, Donna

    1998-01-01

    Asserts that parent education is vital to good dental hygiene for the whole family. Discusses what Head Start staffers can do to ensure that children's dental needs are being met, particularly in assisting parents with taking responsibility for children's dental hygiene. Covers dental care tips for parents, questions and answers about dental…

  19. Dental photography today. Part 1: basic concepts.

    Science.gov (United States)

    Casaglia, A; DE Dominicis, P; Arcuri, L; Gargari, M; Ottria, L

    2015-01-01

    This paper is the first article in a new series on digital dental photography. Part 1 defines the aims and objectives of dental photography for examination, diagnosis and treatment planning, legal and forensic documentation, publishing, education, marketing and communication with patients, dental team members, colleagues and dental laboratory.

  20. 21 CFR 872.6390 - Dental floss.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental floss. 872.6390 Section 872.6390 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6390 Dental floss. (a) Identification. Dental floss is a...

  1. 21 CFR 872.3275 - Dental cement.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental cement. 872.3275 Section 872.3275 Food and... DENTAL DEVICES Prosthetic Devices § 872.3275 Dental cement. (a) Zinc oxide-eugenol—(1) Identification... filling or as a base cement to affix a temporary tooth filling, to affix dental devices such as crowns or...

  2. Dental Curriculum Development in Developing Countries.

    Science.gov (United States)

    Phantumvanit, Prathip

    1996-01-01

    Since establishment of formal dental education in Southeast Asia, changes stemming from research and technology have led to dental curriculum changes. Development of the dental curriculum can be divided into three phases: disease oriented; health oriented; and community oriented. Evolution of these phases is traced in the dental curricula of Laos,…

  3. [Maintenance care for dental implant].

    Science.gov (United States)

    Kamoi, K

    1989-10-01

    Dental implant has tried at the early stage in 19th century recovering an oral function and esthetics. Technological revolutions in biochemical and new materials have developed on the remarkable change in the dental implants, nowadays we call the three generation therapy for dental implantology. There are many kinds of methods and techniques in dental implants, however a lot of troublesome complication on the process of surgical phase, construction of prothodontics and prognosis of maintenance care. In the proceedings of this symposium, I would like to propose you how to manage the maintenance care for various kind of dental implants through the methodology and case presentations. Tendenay and future for dental implants The current outlook of dental implant has increasing supply and demand not only dentists but also patients. According to Japanese Welfare Ministry's report in 1987, average missing teeth over sixty years old generations are approximately 42% in accordance with NIDR (U.S.A.) research. They are missed on ten over teeth in full 28th teeth dentitions owing to dental caries and periodontal diseases. Generally speaking, latent implant patients are occupied on the same possibility of needs for dental implants both Japan and U.S.A. Management of maintenance care The patients hardly recognized the importance of plaque control for the maintenance care in the intraoral condition after implantation. Dentists and dental staffs must be instruct patients for importance of plaque removal and control, because they already had forgotten the habit of teeth cleaning, especially in the edenturous conditions. 1) Concept of establishment in oral hygiene. Motivation and instruction for patients include very important factors in dental implants as well as in periodontal diseases. Patients who could not achieve on good oral hygiene levels obtained no good results in the long term observations. To establish good oral hygiene are how to control supra plaque surrounding tissues

  4. Cones for dental radiography

    Energy Technology Data Exchange (ETDEWEB)

    Butler, M J [National Radiological Protection Board, Harwell (UK)

    1977-04-01

    Dental radiographic techniques are summarized. The advantages and disadvantages of the use of both the conventional plastic pointer cone and the open-ended cylinders or divergent cones favoured both by the ICRP (Protection against Ionizing Radiation from External Sources, Oxford, Pergamon Press, 1973, ICRP Publication 15), and in the Code of Practice for the Protection of Persons against Ionizing Radiation arising from Medical and Dental Use (1972, 3rd edition, London, HMSO) are discussed. The use of the word 'should' in these recommendations to signify a desirable requirement, not an essential one, is noted. This wording is currently of interest both nationally and internationally in relation to regulations, standards and notes for guidance. The National Radiological Protection Board (NRPB) has been reviewing the position, and has concluded that open-ended cones have disadvantages which may sometimes outweigh their advantages. Although open-ended cones are preferable under some circumstances, the recommendation that they should be used ought not to be followed without an understanding of the issues involved. The hazards associated with the use of interchangeable cones are considered. The NRPB now proposes that the requirement for the replacement of pointer cones (for both new and existing equipment) should be withdrawn.

  5. On dental caries and dental erosion in Swedish young adults.

    Science.gov (United States)

    Isaksson, Helén

    2013-01-01

    All children in Sweden are entitled to regular, free dental care up to 20 years of age. While dental caries generally continues to decline, still there is a pronounced skewness in caries prevalence. Furthermore, the reported increase in dental erosion in young adults is cause for concern. The aim was to study the prevalence of dental caries and dental erosion in a cohort of Swedish 20 year-olds, with special reference to the influence of previous caries experience and lifestyle as well as parental, socioeconomic and psychosocial factors. The study was prospective, longitudinal and cross-sectional in design and based on registration of caries lesions, dental erosion, body adiposity status, saliva sampling, interviews, and questionnaires at 20 years of age. Data were available for the same cohort at 1, 3, 6 and 15 years of age. 499 subjects (74 percent of the original cohort) were included. Five individuals were subsequently excluded, leaving a final sample of 494. 74 percent of the subjects had initial and/or manifest caries lesions and/or restorations. The mean number of DimFS was 5.8 and the mean number of DmFS on occlusal surfaces of molars was 1.1. There was a strong relationship between caries activity at 3 and 6 years of age and approximal caries prevalence in premolars and molars at 20 years of age. Overweight/obese individuals had significantly higher caries prevalence than normal weight individuals. Parental, socioeconomic and psychosocial factors during infancy were related to approximal caries at age 20. Dental erosion was found in 75 percent of the individuals: 18 percent of these had extensive erosion. There was a significant association between caries and dental erosion. A relationship was found between dental erosion and lifestyle factors and overweight/obesity. There is a strong relationship between caries prevalence at age 20 and caries experience in early childhood. Young adults show a high prevalence of dental erosion, but the severity is

  6. Clinical use of dental classification.

    Science.gov (United States)

    Jones, Gordon

    2008-01-01

    The Dental Classification system used by the uniformed services is supposed to predict the incidence of dental emergencies in the operational setting, at least on the unit level. Since most Sailors and Marines are deployed without close dental support, the sea services have adopted a policy of early treatment of class 3 dental conditions during recruit training. The other services are beginning to do the same. Recently, two factors have emerged that are affecting this early dental class 3 treatment. These factors must be considered when planning to provide early dental treatment. First, changing population and dentist provider demographics in the civilian sector are beginning to affect the class 3 treatment needs of incoming military recruits. Second, attrition from recruit training results in treatment provided to recruits who leave military service before finishing their training. Some view this as a waste of resources, others as a cost of doing business. As operational jointness increases, the three services must develop and use a single dental classification terminology, as well as unified standards and guidelines, both for better research in this area and for the readiness and well-being of our patients.

  7. Dental imaging characterization of micropigs

    International Nuclear Information System (INIS)

    Lee, H.Y.; Choi, M.H.; Chang, J.H.; Jung, J.H.; Kim, M.E.; Lee, N.S.; Kim, J.Y.; Choi, M.C.

    2010-01-01

    Recently the micropig has been developed as human disease model. The dental and orofacial region of micropig is similar to that of humans, so it has been used for testing implant materials and techniques. The purpose of this study is on dental image at each age using radiography and computed tomography. Total twenty-two male micropigs, two or three animals of each 1, 3, 5, 7, 9, 12, 18 and 24 months old, were given radiographic examinations. After general anesthesia, extra- and intra-oral radiographic technique and computed tomographic scans were performed to assess the dental characterization of micropigs. The total deciduous dental formula comprised 28 teeth and was depicted as Di 3/3, Dc 1/1, Dp 3/3. The total permanent dental formula comprised 44 teeth and was depicted as I 3/3, C 1/1, P 4/4, M 3/3. Hypodontia of the first premolars was common in the micropig. The permanent teeth erupted from 3 to 24 month after birth. The sequence of eruption of the permanent teeth was M1, P1, I3, C, M2, I1 + P3 + P4, P2, I2, M3. Dental imaging enables visualization of the unerupted teeth and gives more information about the development of the teeth. The growth pattern of the teeth obtained through radiographic and computed tomographic examination provides basic data in the micropig as animal model for dental research

  8. Multi-Segment Radius Measurement Using an Absolute Distance Meter Through a Null Assembly

    Science.gov (United States)

    Merle, Cormic; Wick, Eric; Hayden, Joseph

    2011-01-01

    This system was one of the test methods considered for measuring the radius of curvature of one or more of the 18 segmented mirrors that form the 6.5 m diameter primary mirror (PM) of the James Webb Space Telescope (JWST). The assembled telescope will be tested at cryogenic temperatures in a 17-m diameter by 27-m high vacuum chamber at the Johnson Space Center. This system uses a Leica Absolute Distance Meter (ADM), at a wavelength of 780 nm, combined with beam-steering and beam-shaping optics to make a differential distance measurement between a ring mirror on the reflective null assembly and individual PM segments. The ADM is located inside the same Pressure-Tight Enclosure (PTE) that houses the test interferometer. The PTE maintains the ADM and interferometer at ambient temperature and pressure so that they are not directly exposed to the telescope s harsh cryogenic and vacuum environment. This system takes advantage of the existing achromatic objective and reflective null assembly used by the test interferometer to direct four ADM beamlets to four PM segments through an optical path that is coincident with the interferometer beam. A mask, positioned on a linear slide, contains an array of 1.25 mm diameter circular subapertures that map to each of the 18 PM segments as well as six positions around the ring mirror. A down-collimated 4 mm ADM beam simultaneously covers 4 adjacent PM segment beamlets and one ring mirror beamlet. The radius, or spacing, of all 18 segments can be measured with the addition of two orthogonally-oriented scanning pentaprisms used to steer the ADM beam to any one of six different sub-aperture configurations at the plane of the ring mirror. The interferometer beam, at a wavelength of 687 nm, and the ADM beamlets, at a wavelength of 780 nm, pass through the objective and null so that the rays are normally incident on the parabolic PM surface. After reflecting off the PM, both the ADM and interferometer beams return to their respective

  9. Low-dose Dental-CT

    International Nuclear Information System (INIS)

    Gahleitner, A.; Imhof, H.; Homolka, P.; Fuerhauser, R.; Freudenthaler, J.; Watzek, G.

    2000-01-01

    Dental-CT is a relatively new, increasingly used investigation technique in dental radiology. Several authors have stated that the indication for Dental-CT has to be chosen on a strict basis, due to high dose values. This article describes the technique of performing dental-CT and calculates the effective dose based on published data and own measurements as well as the dose reduction potential to achieve an optimized protocol for Dental-CT investigations. (orig.) [de

  10. Current State of Dental Education: Executive Summary.

    Science.gov (United States)

    Formicola, Allan J

    2017-08-01

    This executive summary for Section 1 of the "Advancing Dental Education in the 21 st Century" project provides a composite picture of information from 12 background articles on the current state of dental education in the United States. The summary includes the following topics: the current status of the dental curriculum, the implications of student debt and dental school finances, the expansion of enrollment, student diversity, pre- and postdoctoral education, safety net status of dental school clinics, and trends in faculty.

  11. Dental implants in growing children

    Directory of Open Access Journals (Sweden)

    S K Mishra

    2013-01-01

    Full Text Available The replacement of teeth by implants is usually restricted to patients with completed craniofacial growth. The aim of this literature review is to discuss the use of dental implants in normal growing patients and in patients with ectodermal dysplasia and the influence of maxillary and mandibular skeletal and dental growth on the stability of those implants. It is recommended that while deciding the optimal individual time point of implant insertion, the status of skeletal growth, the degree of hypodontia, and extension of related psychological stress should be taken into account, in addition to the status of existing dentition and dental compliance of a pediatric patient.

  12. Advances in dental public health.

    Science.gov (United States)

    Holt, R D

    2001-07-01

    Dental public health has been defined as 'the science and art of preventing oral diseases, promoting oral health and improving the quality of life through the organised efforts of society'. Dental practitioners most often have the oral health of individual patients as their primary focus but the aim of public health is to benefit populations. Early developments in dental public health were concerned largely with demonstrating levels of disease and with treatment services. With greater appreciation of the nature of oral health and disease, and of their determinants has come recognition of the need for wider public health action if the effects of prevention and oral health promotion are to be maximized.

  13. The Dental Trauma Internet Calculator

    DEFF Research Database (Denmark)

    Gerds, Thomas Alexander; Lauridsen, Eva Fejerskov; Christensen, Søren Steno Ahrensburg

    2012-01-01

    Background/Aim Prediction tools are increasingly used to inform patients about the future dental health outcome. Advanced statistical methods are required to arrive at unbiased predictions based on follow-up studies. Material and Methods The Internet risk calculator at the Dental Trauma Guide...... provides prognoses for teeth with traumatic injuries based on the Copenhagen trauma database: http://www.dentaltraumaguide.org The database includes 2191 traumatized permanent teeth from 1282 patients that were treated at the dental trauma unit at the University Hospital in Copenhagen (Denmark...

  14. Bioinspired design of dental multilayers.

    Science.gov (United States)

    Huang, M; Wang, R; Thompson, V; Rekow, D; Soboyejo, W O

    2007-01-01

    This paper considers the use of bioinspired functionally graded structures in the design of dental multi-layers that are more resistant to sub-surface crack nucleation. Unlike existing dental crown restorations that give rise to high stress concentration, the functionally graded layers (between crown materials and the joins that attach them to dentin) are shown to promote significant reductions in stress and improvements in the critical crack size. Special inspiration is drawn from the low stress concentrations associated with the graded distributions in the dentin-enamel-junction (DEJ). The implications of such functionally graded structures are also discussed for the design of dental restorations.

  15. Entrepreneurship in continuing dental education: a dental school perspective.

    Science.gov (United States)

    Liberto, Vincent N

    2005-01-01

    The definition of continuing dental education is presented, along with its benefits to the profession. The preeminence of dental schools in providing lifelong learning opportunities and freedom from commercial involvement that existed even twenty years ago has changed. Less than a quarter of CE takes place in school, and the focus there is increasingly on material with deep scientific background and hands-on learning. The newest innovations and those with the greatest commercial potential are taught elsewhere. Proposed changes in the ADA CERP standards would take on a "purist" approach that could place dental schools at a severe disadvantage while allowing "for profit" institutes to flourish and thus further undermine the role dental schools can play in providing quality professional development experiences.

  16. Dental anxiety among patients visiting a University Dental Centre ...

    African Journals Online (AJOL)

    Nigerian Dental Journal. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 19, No 1 (2011) >. Log in or Register to get access to full text downloads.

  17. An audit of dental prescriptions between clinics and dental laboratories.

    Science.gov (United States)

    Stewart, C A

    2011-08-12

    To discover the quality of written instructions from dentists to dental technicians and the nature of non-compliant prescriptions. An audit of laboratory prescription compliance was conducted within an NHS Trust Dental Teaching Hospital to determine the level of communication between dentists and dental technicians. One hundred and fifty prescriptions were audited from dental undergraduates and qualified dentists throughout the different departments. A total of two-thirds of prescriptions were considered non-compliant and failed to meet relevant ethical and legal guidelines. This problem was seen throughout all departments and at all professional levels. A breakdown in communication between dentists and technicians through the use of prescriptions is evident even within a close working environment.

  18. The Fourier-Kelvin Stellar Interferometer (FKSI) Nulling Testbed II: Closed-loop Path Length Metrology And Control Subsystem

    Science.gov (United States)

    Frey, B. J.; Barry, R. K.; Danchi, W. C.; Hyde, T. T.; Lee, K. Y.; Martino, A. J.; Zuray, M. S.

    2006-01-01

    The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for an imaging and nulling interferometer in the near to mid-infrared spectral region (3-8 microns), and will be a scientific and technological pathfinder for upcoming missions including TPF-I/DARWIN, SPECS, and SPIRIT. At NASA's Goddard Space Flight Center, we have constructed a symmetric Mach-Zehnder nulling testbed to demonstrate techniques and algorithms that can be used to establish and maintain the 10(exp 4) null depth that will be required for such a mission. Among the challenges inherent in such a system is the ability to acquire and track the null fringe to the desired depth for timescales on the order of hours in a laboratory environment. In addition, it is desirable to achieve this stability without using conventional dithering techniques. We describe recent testbed metrology and control system developments necessary to achieve these goals and present our preliminary results.

  19. Nickel reactivity and filaggrin null mutations--evaluation of the filaggrin bypass theory in a general population

    DEFF Research Database (Denmark)

    Ross-Hansen, Katrine; Menné, Torkil; Johansen, Jeanne D

    2011-01-01

    It was recently shown that filaggrin null mutation carrier status was associated with nickel allergy and self-reported intolerance to costume jewellery. Because of the biochemical characteristics of filaggrin, it may show nickel barrier properties in the stratum corneum....

  20. Dental Pulp Defence and Repair Mechanisms in Dental Caries

    OpenAIRE

    Farges, Jean-Christophe; Alliot-Licht, Brigitte; Renard, Emmanuelle; Ducret, Maxime; Gaudin, Alexis; Smith, Anthony J.; Cooper, Paul R.

    2015-01-01

    Dental caries is a chronic infectious disease resulting from the penetration of oral bacteria into the enamel and dentin. Microorganisms subsequently trigger inflammatory responses in the dental pulp. These events can lead to pulp healing if the infection is not too severe following the removal of diseased enamel and dentin tissues and clinical restoration of the tooth. However, chronic inflammation often persists in the pulp despite treatment, inducing permanent loss of normal tissue and red...