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Sample records for 10kwth calcium looping

  1. Integration of calcium and chemical looping combustion using composite CaO/CuO-based materials.

    PubMed

    Manovic, Vasilije; Anthony, Edward J

    2011-12-15

    Calcium looping cycles (CaL) and chemical looping combustion (CLC) are two new, developing technologies for reduction of CO(2) emissions from plants using fossil fuels for energy production, which are being intensively examined. Calcium looping is a two-stage process, which includes oxy-fuel combustion for sorbent regeneration, i.e., generation of a concentrated CO(2) stream. This paper discuss the development of composite materials which can use copper(II)-oxide (CuO) as an oxygen carrier to provide oxygen for the sorbent regeneration stage of calcium looping. In other words, the work presented here involves integration of calcium looping and chemical looping into a new class of postcombustion CO(2) capture processes designated as integrated CaL and CLC (CaL-CLC or Ca-Cu looping cycles) using composite pellets containing lime (CaO) and CuO together with the addition of calcium aluminate cement as a binder. Their activity was tested in a thermogravimetric analyzer (TGA) during calcination/reduction/oxidation/carbonation cycles. The calcination/reduction typically was performed in methane (CH(4)), and the oxidation/carbonation stage was carried out using a gas mixture containing both CO(2) and O(2). It was confirmed that the material synthesized is suitable for the proposed cycles; with the very favorable finding that reduction/oxidation of the oxygen carrier is complete. Various schemes for the Ca-Cu looping process have been explored here that would be compatible with these new composite materials, along with some different possibilities for flow directions among carbonator, calciner, and air reactor.

  2. Class and Home Problems: Carbon Dioxide Capture from Coal-Fired Power Plants Using Calcium Looping

    ERIC Educational Resources Information Center

    Deshpande, Niranjani; Phalak, Nihar; Fan, Liang-Shih; Sundaresan, Sankaran

    2015-01-01

    Calcium looping is based on the simple premise of the reversible reaction between CO[subscript 2] and CaO. This reaction can be used for separation of CO2 from a mixture of gases; most notably the technology finds applications in CO[subscript 2] removal from gas streams in fossil fuel-based energy systems. This article gives a brief overview of…

  3. Class and Home Problems: Carbon Dioxide Capture from Coal-Fired Power Plants Using Calcium Looping

    ERIC Educational Resources Information Center

    Deshpande, Niranjani; Phalak, Nihar; Fan, Liang-Shih; Sundaresan, Sankaran

    2015-01-01

    Calcium looping is based on the simple premise of the reversible reaction between CO[subscript 2] and CaO. This reaction can be used for separation of CO2 from a mixture of gases; most notably the technology finds applications in CO[subscript 2] removal from gas streams in fossil fuel-based energy systems. This article gives a brief overview of…

  4. Cdk9 T-loop Phosphorylation is Regulated by the Calcium Signaling Pathway

    PubMed Central

    Ramakrishnan, Rajesh; Rice, Andrew P.

    2011-01-01

    Eukaryotic RNA polymerase II transcriptional elongation is a tightly regulated process and is dependent upon positive transcription elongation factor-b (P-TEFb). The core P-TEFb complex is composed of Cdk9 and Cyclin T and is essential for the expression of most protein coding genes. Cdk9 kinase function is dependent upon phosphorylation of Thr186 in its T-loop. In this study, we examined kinases and signaling pathways that influence Cdk9 T-loop phosphorylation. Using an RNAi screen in HeLa cells, we found that Cdk9 T-loop phosphorylation is regulated by Calcium/Calmodulin- dependent kinase 1D (CaMK1D). Using small molecules inhibitors in HeLa cells and primary CD4+ T lymphocytes, we found that the Ca2+ signaling pathway is required for Cdk9 T-loop phosphorylation. Inhibition of Ca2+ signaling led to dephosphorylation of Thr186 on Cdk9. In reporter plasmid assays, inhibition of the Ca2+ signaling pathway repressed the PCNA promoter and HIV-1 Tat transactivation of the HIV-1 LTR, but not HTLV-1 Tax transactivation of the HTLV-1 LTR, suggesting that perturbation of the Ca2+ pathway and reduction of Cdk9 T-loop phosphorylation inhibits transcription units that have a rigorous requirement for P-TEFb function. PMID:21448926

  5. Quantum Chemical Studies on Stability and Chemical Activities in Calcium Ion Bound Calmodulin Loops.

    PubMed

    Sikdar, Samapan; Ghosh, Mahua; De Raychaudhury, Molly; Chakrabarti, J

    2015-11-19

    Quantum chemical (QC) calculations for macromolecules require truncation of the molecule, highlighting the portion of interest due to heavy computation cost. As a result, an estimation of the effects of truncation is important to interpret the energy spectrum of such calculations. We perform density functional theory based QC calculations on calcium ion bound EF-hand loops of Calmodulin isolated from the crystal structure in an implicit solvent. We find that the terminal contributions of neutral capping are negligible across the entire ground-state energy spectrum. The coordination energy range and the nature of hybridization of the coordination state molecular orbitals remain qualitatively similar across these loops. While the HOMO and LUMO of loops in the N-terminal domain are dominated by the acidic aspartates, and the polar/hydrophobic residues, respectively, these levels of the C-terminal domain loops show strong localized electron density on the phenyl rings of the tyrosines. The Fukui index calculation identifies the hydroxyl oxygen in the phenyl ring of Y99 as a potent nucleophile. Our analysis indicates a general way of interpreting the electronic energy spectra to understand stability and functions of large biomolecules where the truncation of the molecule and, hence, the terminal capping effects are inevitable.

  6. Calcium looping spent sorbent as a limestone replacement in the manufacture of portland and calcium sulfoaluminate cements.

    PubMed

    Telesca, Antonio; Marroccoli, Milena; Tomasulo, Michele; Valenti, Gian Lorenzo; Dieter, Heiko; Montagnaro, Fabio

    2015-06-02

    The calcium looping (CaL) spent sorbent (i) can be a suitable limestone replacement in the production of both ordinary Portland cement (OPC) and calcium sulfoaluminate (CSA) cement, and (ii) promotes environmental benefits in terms of reduced CO2 emission, increased energy saving and larger utilization of industrial byproducts. A sample of CaL spent sorbent, purged from a 200 kWth pilot facility, was tested as a raw material for the synthesis of two series of OPC and CSA clinkers, obtained from mixes heated in a laboratory electric oven within temperature ranges 1350°-1500 °C and 1200°-1350 °C, respectively. As OPC clinker-generating mixtures, six clay-containing binary blends were investigated, three with limestone (reference mixes) and three with the CaL spent sorbent. All of them showed similar burnability indexes. Moreover, three CSA clinker-generating blends (termed RM, MA and MB) were explored. They included, in the order: (I) limestone, bauxite and gypsum (reference mix); (II) CaL spent sorbent, bauxite and gypsum; (III) CaL spent sorbent plus anodization mud and a mixture of fluidized bed combustion (FBC) fly and bottom ashes. The maximum conversion toward 4CaO·3Al2O3·SO3, the chief CSA clinker component, was the largest for MB and almost the same for RM and MA.

  7. The calcium feedback loop and T cell activation: how cytoskeleton networks control intracellular calcium flux.

    PubMed

    Joseph, Noah; Reicher, Barak; Barda-Saad, Mira

    2014-02-01

    During T cell activation, the engagement of a T cell with an antigen-presenting cell (APC) results in rapid cytoskeletal rearrangements and a dramatic increase of intracellular calcium (Ca(2+)) concentration, downstream to T cell antigen receptor (TCR) ligation. These events facilitate the organization of an immunological synapse (IS), which supports the redistribution of receptors, signaling molecules and organelles towards the T cell-APC interface to induce downstream signaling events, ultimately supporting T cell effector functions. Thus, Ca(2+) signaling and cytoskeleton rearrangements are essential for T cell activation and T cell-dependent immune response. Rapid release of Ca(2+) from intracellular stores, e.g. the endoplasmic reticulum (ER), triggers the opening of Ca(2+) release-activated Ca(2+) (CRAC) channels, residing in the plasma membrane. These channels facilitate a sustained influx of extracellular Ca(2+) across the plasma membrane in a process termed store-operated Ca(2+) entry (SOCE). Because CRAC channels are themselves inhibited by Ca(2+) ions, additional factors are suggested to enable the sustained Ca(2+) influx required for T cell function. Among these factors, we focus here on the contribution of the actin and microtubule cytoskeleton. The TCR-mediated increase in intracellular Ca(2+) evokes a rapid cytoskeleton-dependent polarization, which involves actin cytoskeleton rearrangements and microtubule-organizing center (MTOC) reorientation. Here, we review the molecular mechanisms of Ca(2+) flux and cytoskeletal rearrangements, and further describe the way by which the cytoskeletal networks feedback to Ca(2+) signaling by controlling the spatial and temporal distribution of Ca(2+) sources and sinks, modulating TCR-dependent Ca(2+) signals, which are required for an appropriate T cell response. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters

  8. A mechanistic investigation of a calcium-based oxygen carrier for chemical looping combustion

    SciTech Connect

    Shen, Laihong; Zheng, Min; Xiao, Jun; Xiao, Rui

    2008-08-15

    Chemical looping combustion (CLC) has been suggested as an energy-efficient method for the capture of carbon dioxide from combustion. It is indirect combustion by the use of an oxygen carrier, which can be used for CO{sub 2} capture in power-generating processes. The possibility of CLC using a calcium-based oxygen carrier is investigated in this paper. In the air reactor air is supplied to oxidize CaS to CaSO{sub 4}, where oxygen is transferred from air to the oxygen carrier; the reduction of CaSO{sub 4} to CaS takes place in the fuel reactor. The exit gas from the fuel reactor is CO{sub 2} and H{sub 2}O. After condensation of water, almost pure CO{sub 2} could be obtained. The thermodynamic and kinetic problem of the reduction reactions of CaSO{sub 4} with CO and H{sub 2} and the oxidization reactions of CaS with O{sub 2} is discussed in the paper to investigate the technique possibility. To prevent SO{sub 2} release from the process of chemical looping combustion using a calcium-based oxygen carrier, thermochemical CaSO{sub 4} reduction and CaS oxidation are discussed. Thermal simulation experiments are carried out using a thermogravimetric analyzer (TGA). The properties of the products are characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD), and the optimal reaction parameters are evaluated. The effects of reaction temperature, reductive gas mixture, and oxygen partial pressure on the composition of flue gas are discussed. The suitable temperature of the air reactor is between 1050 and 1150 C and the optimal temperature of the fuel reactor between 900 and 950 C. (author)

  9. Mitochondrial fission forms a positive feedback loop with cytosolic calcium signaling pathway to promote autophagy in hepatocellular carcinoma cells.

    PubMed

    Huang, Qichao; Cao, Haiyan; Zhan, Lei; Sun, Xiacheng; Wang, Gang; Li, Jibin; Guo, Xu; Ren, Tingting; Wang, Zhe; Lyu, Yinghua; Liu, Bingrong; An, Jiaze; Xing, Jinliang

    2017-09-10

    Both mitochondrial morphology and the level of cytosolic calcium [Ca(2+)]c are actively changed and play critical roles in a number of malignancies. However, whether communications existed between these two processes to ingeniously control the malignant phenotype are far from clear. We investigated the reciprocal regulation between mitochondrial fission and cytosolic calcium signaling in human hepatocellular carcinoma (HCC) cells. Furthermore, the underlying molecular mechanisms and the synergistic effect on autophagy were explored. Our results showed that mitochondrial fission increased the [Ca(2+)]c and calcium oscillation in HCC cells. We further found that mitochondrial fission-mediated calcium signaling was dependent on ROS-activated NF-κB pathways, which facilitated the expression of STIM1 and subsequent store-operated calciumentry. Additionally, we also demonstrated that increase in [Ca(2+)]c promoted mitochondrial fission by up-regulating expression of Drp1 and FIS1 via transcription factors NFATC2 and c-Myc, respectively. Moreover, the positive feedback loop significantly promoted HCC cell global autophagy by Ca(2+)/CAMKK/AMPK pathway. Our data demonstrate a positive feedback loop between mitochondrial fission and cytosolic calcium signaling and their promoting role in autophagy of HCC cells, which provides evidence for this loop as a potential drug target in tumor treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. All three Ca[superscript 2+]-binding loops of photoproteins bind calcium ions: The crystal structures of calcium-loaded apo-aequorin and apo-obelin

    SciTech Connect

    Deng, Lu; Vysotski, Eugene S.; Markova, Svetlana V.; Liu, Zhi-Jie; Lee, John; Rose, John; Wang, Bi-Cheng

    2010-07-13

    The crystal structures of calcium-loaded apoaequorin and apo-obelin have been determined at resolutions 1.7 {angstrom} and 2.2 {angstrom}, respectively. A calcium ion is observed in each of the three EF-hand loops that have the canonical calcium-binding sequence, and each is coordinated in the characteristic pentagonal bipyramidal configuration. The calcium-loaded apo-proteins retain the same compact scaffold and overall fold as the unreacted photoproteins containing the bound substrate, 2-hydroperoxycoelenterazine, and also the same as the Ca{sup 2+}-discharged obelin bound with the product, coelenteramide. Nevertheless, there are easily discerned shifts in both helix and loop regions, and the shifts are not the same between the two proteins. It is suggested that these subtle shifts are the basis of the ability of these photoproteins to sense Ca{sup 2+} concentration transients and to produce their bioluminescence response on the millisecond timescale. A mechanism of intrastructural transmission of the calcium signal is proposed.

  11. CO₂ capture from cement plants using oxyfired precalcination and/or calcium looping.

    PubMed

    Rodríguez, Nuria; Murillo, Ramón; Abanades, J Carlos

    2012-02-21

    This paper compares two alternatives to capture CO(2) from cement plants: the first is designed to exploit the material and energy synergies with calcium looping technologies, CaL, and the second implements an oxyfired circulating fluidized bed precalcination step. The necessary mass and heat integration balances for these two options are solved and compared with a common reference cement plant and a cost analysis exercise is carried out. The CaL process applied to the flue gases of a clinker kiln oven is substantially identical to those proposed for similar applications to power plants flue gases. It translates into avoided cost of of 23 $/tCO(2) capturing up to 99% of the total CO(2) emitted in the plant. The avoided cost of an equivalent system with an oxyfired CFBC precalcination only, goes down to 16 $/tCO(2) but only captures 89% of the CO(2) emitted in the plant. Both cases reveal that the application of CaL or oxyfired CFBC for precalcination of CaCO(3) in a cement plant, at scales in the order of 50 MWth (referred to the oxyfired CFB calciner) is an important early opportunity for the development of CaL processes in large scale industrial applications as well as for the development of zero emissions cement plants.

  12. Chemical looping coal gasification with calcium ferrite and barium ferrite via solid--solid reactions

    SciTech Connect

    Siriwardane, Ranjani; Tian, Hanjing; Richards, George

    2016-01-01

    Coal gasification to produce synthesis gas by chemical looping was investigated with two oxygen carriers, barium ferrite (BaFe2O4) and calcium ferrite (CaFe2O4). Thermo-gravimetric analysis (TGA) and fixed-bed flow reactor data indicated that a solid–solid interaction occurred between oxygen carriers and coal to produce synthesis gas. Both thermodynamic analysis and experimental data indicated that BaFe2O4 and CaFe2O4 have high reactivity with coal but have a low reactivity with synthesis gas, which makes them very attractive for the coal gasification process. Adding steam increased the production of hydrogen (H2) and carbon monoxide (CO), but carbon dioxide (CO2) remained low because these oxygen carriers have minimal reactivity with H2 and CO. Therefore, the combined steam–oxygen carrier produced the highest quantity of synthesis gas. It appeared that neither the water–gas shift reaction nor the water splitting reaction promoted additional H2 formation with the oxygen carriers when steam was present. Wyodak coal, which is a sub-bituminous coal, had the best gasification yield with oxygen carrier–steam while Illinois #6 coal had the lowest. The rate of gasification and selectivity for synthesis gas production was significantly higher when these oxygen carriers were present during steam gasification of coal. The rates and synthesis gas yields during the temperature ramps of coal–steam with oxygen carriers were better than with gaseous oxygen.

  13. Directly irradiated fluidized bed reactors for thermochemical processing and energy storage: Application to calcium looping

    NASA Astrophysics Data System (ADS)

    Tregambi, Claudio; Montagnaro, Fabio; Salatino, Piero; Solimene, Roberto

    2017-06-01

    Directly irradiated fluidized bed reactors are very promising in the context of concentrated solar power applications, as they can be operated at process temperatures high enough to perform thermochemical storage reactions with high energy density. Limestone calcination-carbonation is an appealing reaction for thermochemical storage applications due to the cheapness of the raw material, and the interesting value of the reaction enthalpy at fairly high process temperatures. Moreover, limestone calcination-carbonation is intensively studied in Calcium Looping (CaL) application for post combustion CO2 capture and sequestration. In this work, the dynamics of a directly irradiated 0.1 m ID fluidized bed reactor exposed to a 12 kWel simulated solar furnace is analyzed with specific reference to temperature distribution at the surface and in the bulk of the bed. Simulation of the solar radiation was performed through an array of three short arc Xe-lamps coupled with elliptical reflectors, yielding a peak flux of nearly 3000 kW m-2 and a total power of nearly 3 kW incident on the bed surface. Moreover, the directly irradiated fluidized bed reactor has been used to perform CaL tests by alternating solar-driven limestone calcination and autothermal recarbonation of lime. CaL has been investigated with the twofold perspective of: a) accomplishing energy storage by solar-driven calcination of limestone; b) perform solar-aided CO2 capture from flue gas to be embodied in carbon capture and sequestration schemes.

  14. Selectivity filters and cysteine-rich extracellular loops in voltage-gated sodium, calcium, and NALCN channels

    PubMed Central

    Stephens, Robert F.; Guan, W.; Zhorov, Boris S.; Spafford, J. David

    2015-01-01

    How nature discriminates sodium from calcium ions in eukaryotic channels has been difficult to resolve because they contain four homologous, but markedly different repeat domains. We glean clues from analyzing the changing pore region in sodium, calcium and NALCN channels, from single-cell eukaryotes to mammals. Alternative splicing in invertebrate homologs provides insights into different structural features underlying calcium and sodium selectivity. NALCN generates alternative ion selectivity with splicing that changes the high field strength (HFS) site at the narrowest level of the hourglass shaped pore where the selectivity filter is located. Alternative splicing creates NALCN isoforms, in which the HFS site has a ring of glutamates contributed by all four repeat domains (EEEE), or three glutamates and a lysine residue in the third (EEKE) or second (EKEE) position. Alternative splicing provides sodium and/or calcium selectivity in T-type channels with extracellular loops between S5 and P-helices (S5P) of different lengths that contain three or five cysteines. All eukaryotic channels have a set of eight core cysteines in extracellular regions, but the T-type channels have an infusion of 4–12 extra cysteines in extracellular regions. The pattern of conservation suggests a possible pairing of long loops in Domains I and III, which are bridged with core cysteines in NALCN, Cav, and Nav channels, and pairing of shorter loops in Domains II and IV in T-type channel through disulfide bonds involving T-type specific cysteines. Extracellular turrets of increasing lengths in potassium channels (Kir2.2, hERG, and K2P1) contribute to a changing landscape above the pore selectivity filter that can limit drug access and serve as an ion pre-filter before ions reach the pore selectivity filter below. Pairing of extended loops likely contributes to the large extracellular appendage as seen in single particle electron cryo-microscopy images of the eel Nav1 channel. PMID

  15. Determinants of chymotrypsin C cleavage specificity in the calcium binding loop of human cationic trypsinogen

    PubMed Central

    Szabó, András; Sahin-Tóth, Miklós

    2013-01-01

    SUMMARY The pancreatic serine protease chymotrypsin C (CTRC) cleaves the Leu81-Glu82 peptide bond in the calcium binding loop of human cationic trypsinogen and thereby promotes its degradation. This serves as a protective mechanism against ectopic trypsinogen activation in the pancreas. In the present study we demonstrate that cleavage of the Leu81-Glu82 peptide bond by CTRC is highly specific and other human pancreatic chymotrypsins (CTRB1, CTRB2, CTRL1) and elastases (ELA2A, ELA3A, ELA3B) do not catalyze this reaction. To elucidate the mechanistic basis for CTRC specificity, we surveyed the primary (P1) cleavage preference of these pancreatic proteases on peptide substrates. We found that CTRC cleaved after a P1 Leu with at least 10-fold higher catalytic efficiency than other enzymes tested. To assess extended subsite interactions, we introduced Ala-mutations into human cationic trypsinogen at the P3, P1' P3' and P4' amino-acid positions, where P1-P1' corresponds to Leu81-Glu82. Interestingly, CTRC mediated cleavage was stimulated 3-fold by mutation E82A and unaffected by mutations E79A and N84A, but all three mutations compromised specificity and resulted in increased cleavage by ELA2A. Mutation E85A decreased CTRC cleavage by 2-fold. Remarkably, other chymotrypsins and elastases did not cleave human cationic trypsinogen even with the L81F or L81A mutations, which introduced favorable P1 residues for these enzymes. We conclude that specific cleavage of the Leu81-Glu82 peptide bond in human cationic trypsinogen by CTRC is primarily determined by its distinctively high activity on leucyl peptide bonds, whereas the P1' Glu82, P3' Asn84 and P4' Glu85 residues serve as additional specificity determinants. PMID:23035638

  16. Calcium

    MedlinePlus

    ... You'll also find calcium in broccoli and dark green, leafy vegetables (especially collard and turnip greens, ... can enjoy good sources of calcium such as dark green, leafy vegetables, broccoli, chickpeas, and calcium-fortified ...

  17. An amphipathic α-helix directs palmitoylation of the large intracellular loop of the sodium/calcium exchanger.

    PubMed

    Plain, Fiona; Congreve, Samitha Dilini; Yee, Rachel Sue Zhen; Kennedy, Jennifer; Howie, Jacqueline; Kuo, Chien-Wen; Fraser, Niall J; Fuller, William

    2017-06-23

    The electrogenic sodium/calcium exchanger (NCX) mediates bidirectional calcium transport controlled by the transmembrane sodium gradient. NCX inactivation occurs in the absence of phosphatidylinositol 4,5-bisphosphate and is facilitated by palmitoylation of a single cysteine at position 739 within the large intracellular loop of NCX. The aim of this investigation was to identify the structural determinants of NCX1 palmitoylation. Full-length NCX1 (FL-NCX1) and a YFP fusion protein of the NCX1 large intracellular loop (YFP-NCX1) were expressed in HEK cells. Single amino acid changes around Cys-739 in FL-NCX1 and deletions on the N-terminal side of Cys-739 in YFP-NCX1 did not affect NCX1 palmitoylation, with the exception of the rare human polymorphism S738F, which enhanced FL-NCX1 palmitoylation, and D741A, which modestly reduced it. In contrast, deletion of a 21-amino acid segment enriched in aromatic amino acids on the C-terminal side of Cys-739 abolished YFP-NCX1 palmitoylation. We hypothesized that this segment forms an amphipathic α-helix whose properties facilitate Cys-739 palmitoylation. Introduction of negatively charged amino acids to the hydrophobic face or of helix-breaking prolines impaired palmitoylation of both YFP-NCX1 and FL-NCX1. Alanine mutations on the hydrophilic face of the helix significantly reduced FL-NCX1 palmitoylation. Of note, when the helix-containing segment was introduced adjacent to cysteines that are not normally palmitoylated, they became palmitoylation sites. In conclusion, we have identified an amphipathic α-helix in the NCX1 large intracellular loop that controls NCX1 palmitoylation. NCX1 palmitoylation is governed by a distal secondary structure element rather than by local primary sequence. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. An amphipathic α-helix directs palmitoylation of the large intracellular loop of the sodium/calcium exchanger

    PubMed Central

    Plain, Fiona; Congreve, Samitha Dilini; Yee, Rachel Sue Zhen; Kennedy, Jennifer; Howie, Jacqueline; Kuo, Chien-Wen

    2017-01-01

    The electrogenic sodium/calcium exchanger (NCX) mediates bidirectional calcium transport controlled by the transmembrane sodium gradient. NCX inactivation occurs in the absence of phosphatidylinositol 4,5-bisphosphate and is facilitated by palmitoylation of a single cysteine at position 739 within the large intracellular loop of NCX. The aim of this investigation was to identify the structural determinants of NCX1 palmitoylation. Full-length NCX1 (FL-NCX1) and a YFP fusion protein of the NCX1 large intracellular loop (YFP-NCX1) were expressed in HEK cells. Single amino acid changes around Cys-739 in FL-NCX1 and deletions on the N-terminal side of Cys-739 in YFP-NCX1 did not affect NCX1 palmitoylation, with the exception of the rare human polymorphism S738F, which enhanced FL-NCX1 palmitoylation, and D741A, which modestly reduced it. In contrast, deletion of a 21-amino acid segment enriched in aromatic amino acids on the C-terminal side of Cys-739 abolished YFP-NCX1 palmitoylation. We hypothesized that this segment forms an amphipathic α-helix whose properties facilitate Cys-739 palmitoylation. Introduction of negatively charged amino acids to the hydrophobic face or of helix-breaking prolines impaired palmitoylation of both YFP-NCX1 and FL-NCX1. Alanine mutations on the hydrophilic face of the helix significantly reduced FL-NCX1 palmitoylation. Of note, when the helix-containing segment was introduced adjacent to cysteines that are not normally palmitoylated, they became palmitoylation sites. In conclusion, we have identified an amphipathic α-helix in the NCX1 large intracellular loop that controls NCX1 palmitoylation. NCX1 palmitoylation is governed by a distal secondary structure element rather than by local primary sequence. PMID:28432123

  19. Calprotectin S100A9 calcium-binding loops I and II are essential for keratinocyte resistance to bacterial invasion.

    PubMed

    Champaiboon, Chantrakorn; Sappington, Kaia J; Guenther, Brian D; Ross, Karen F; Herzberg, Mark C

    2009-03-13

    Epithelial cells expressing calprotectin, a heterodimer of S100A8 and S100A9 proteins, are more resistant to bacterial invasion. To determine structural motifs that affect resistance to bacterial invasion, mutations were constructed in S100A9 targeting the calcium-binding loops I and II (E36Q, E78Q, E36Q,E78Q) and the C terminus (S100A9(1-99) and S100A9(1-112)), which contains putative antimicrobial zinc-binding and phosphorylation sites. The S100A8 and mutated S100A9 encoding plasmids were transfected into calprotectin-negative KB carcinoma cells. All transfected cells (except KB-sham) expressed 27E10-reactive heterodimers. In bacterial invasion assays with Listeria monocytogenes and Salmonella enterica serovar Typhimurium (Salmonella typhimurium), cell lines expressing S100A8 in complex with S100A9E36Q, S100A9E78Q, S100A9(1-99), or S100A9(1-112) mutants or the S100A9(1-114) (full-length) calprotectin resisted bacterial invasion better than KB-sham. When compared with KB-S100A8/A9(1-114), cells expressing truncated S100A9(1-99) or S100A9(1-112) with S100A8 also showed increased resistance to bacterial invasion. In contrast, glutamic acid residues 36 and 78 in calcium-binding loops I and II promote resistance in epithelial cells, because cells expressing S100A9E36Q,E78Q with S100A8 were unable to resist bacterial invasion. Mutations in S100A9 E36Q, E78Q were predicted to cause loss of the calcium-induced positive face in calprotectin, reducing interactions with microtubules and appearing to be crucial for keratinocyte resistance to bacterial invasion.

  20. Cdk9 T-loop phosphorylation is regulated by the calcium signaling pathway.

    PubMed

    Ramakrishnan, Rajesh; Rice, Andrew P

    2012-02-01

    Eukaryotic RNA polymerase II transcriptional elongation is a tightly regulated process and is dependent upon positive transcription elongation factor-b (P-TEFb). The core P-TEFb complex is composed of Cdk9 and Cyclin T and is essential for the expression of most protein coding genes. Cdk9 kinase function is dependent upon phosphorylation of Thr186 in its T-loop. In this study, we examined kinases and signaling pathways that influence Cdk9 T-loop phosphorylation. Using an RNAi screen in HeLa cells, we found that Cdk9 T-loop phosphorylation is regulated by Ca(2+)/calmodulin-dependent kinase 1D (CaMK1D). Using small molecules inhibitors in HeLa cells and primary CD4(+) T lymphocytes, we found that the Ca(2+) signaling pathway is required for Cdk9 T-loop phosphorylation. Inhibition of Ca(2+) signaling led to dephosphorylation of Thr186 on Cdk9. In reporter plasmid assays, inhibition of the Ca(2+) signaling pathway repressed the PCNA promoter and HIV-1 Tat transactivation of the HIV-1 LTR, but not HTLV-1 Tax transactivation of the HTLV-1 LTR, suggesting that perturbation of the Ca(2+) pathway and reduction of Cdk9 T-loop phosphorylation inhibits transcription units that have a rigorous requirement for P-TEFb function.

  1. Protein conformational changes studied by diffusion NMR spectroscopy: Application to helix-loop-helix calcium binding proteins

    PubMed Central

    Weljie, Aalim M.; Yamniuk, Aaron P.; Yoshino, Hidenori; Izumi, Yoshinobu; Vogel, Hans J.

    2003-01-01

    Pulsed-field gradient (PFG) diffusion NMR spectroscopy studies were conducted with several helix-loop-helix regulatory Ca2+-binding proteins to characterize the conformational changes associated with Ca2+-saturation and/or binding targets. The calmodulin (CaM) system was used as a basis for evaluation, with similar hydrodynamic radii (Rh) obtained for apo- and Ca2+-CaM, consistent with previously reported Rh data. In addition, conformational changes associated with CaM binding to target peptides from myosin light chain kinase (MLCK), phosphodiesterase (PDE), and simian immunodeficiency virus (SIV) were accurately determined compared with small-angle X-ray scattering results. Both sets of data demonstrate the well-established collapse of the extended Ca2+-CaM molecule into a globular complex upon peptide binding. The Rh of CaM complexes with target peptides from CaM-dependent protein kinase I (CaMKI) and an N-terminal portion of the SIV peptide (SIV-N), as well as the anticancer drug cisplatin were also determined. The CaMKI complex demonstrates a collapse analogous to that observed for MLCK, PDE, and SIV, while the SIV-N shows only a partial collapse. Interestingly, the covalent CaM–cisplatin complex shows a near complete collapse, not expected from previous studies. The method was extended to related calcium binding proteins to show that the Rh of calcium and integrin binding protein (CIB), calbrain, and the calcium-binding region from soybean calcium-dependent protein kinase (CDPK) decrease on Ca2+-binding to various extents. Heteronuclear NMR spectroscopy suggests that for CIB and calbrain this is likely because of shifting the equilibrium from unfolded to folded conformations, with calbrain forming a dimer structure. These results demonstrate the utility of PFG-diffusion NMR to rapidly and accurately screen for molecular size changes on protein–ligand and protein–protein interactions for this class of proteins. PMID:12538886

  2. Suggestive Evidence for the Involvement of the Second Calcium and Surface Loop in Interfacial Binding: Monoclinci and Trigonal Crystal Structures of a Quadruple Mutant of Phospholipase A2

    SciTech Connect

    Sekar,K.; Yogavel, M.; Kanaujia, S.; Sharma, A.; Velmurugan, D.; Poi, M.; Dauter, Z.; Tsai, M.

    2006-01-01

    The crystal structures of the monoclinic and trigonal forms of the quadruple mutant K53,56,120,121M of recombinant bovine pancreatic phospholipase A{sub 2} (PLA{sub 2}) have been solved and refined at 1.9 and 1.1 Angstroms resolution, respectively. Interestingly, the monoclinic form reveals the presence of the second calcium ion. Furthermore, the surface-loop residues are ordered and the conformation of residues 62-66 is similar to that observed in other structures containing the second calcium ion. On the other hand, in the trigonal form the surface loop is disordered and the second calcium is absent. Docking studies suggest that the second calcium and residues Lys62 and Asp66 from the surface loop could be involved in the interaction with the polar head group of the membrane phospholipid. It is hypothesized that the two structures of the quadruple mutant, monoclinic and trigonal, represent the conformations of PLA2 at the lipid interface and in solution, respectively. A docked structure with a phospholipid molecule and with a transition-state analogue bound, one at the active site coordinating to the catalytic calcium and the other at the second calcium site, but both at the i-face, is presented.

  3. Calcium

    MedlinePlus

    ... in luck if you like sardines and canned salmon with bones. Almond milk. previous continue Working Calcium ... drinks, and cereals. Other Considerations for Building Bones Vitamin D is essential for calcium absorption, so it's ...

  4. Calcium

    MedlinePlus

    ... such as canned sardines and salmon Calcium-enriched foods such as breakfast cereals, fruit juices, soy and rice drinks, and tofu. Check the product labels. The exact amount of calcium you need depends on your age and other factors. Growing children and teenagers need more calcium than ...

  5. Two helices in the third intracellular loop determine anoctamin 1 (TMEM16A) activation by calcium.

    PubMed

    Lee, Jesun; Jung, Jooyoung; Tak, Min Ho; Wee, Jungwon; Lee, Byeongjoon; Jang, Yongwoo; Chun, Hyeyeon; Yang, Dong-Jin; Yang, Young Duk; Park, Sang Ho; Han, Byung Woo; Hyun, Soonsil; Yu, Jaehoon; Cho, Hawon; Hartzell, H Criss; Oh, Uhtaek

    2015-08-01

    Anoctamin 1 (ANO1)/TMEM16A is a Cl(-) channel activated by intracellular Ca(2+) mediating numerous physiological functions. However, little is known of the ANO1 activation mechanism by Ca(2+). Here, we demonstrate that two helices, "reference" and "Ca(2+) sensor" helices in the third intracellular loop face each other with opposite charges. The two helices interact directly in a Ca(2+)-dependent manner. Positively and negatively charged residues in the two helices are essential for Ca(2+)-dependent activation because neutralization of these charges change the Ca(2+) sensitivity. We now predict that the Ca(2+) sensor helix attaches to the reference helix in the resting state, and as intracellular Ca(2+) rises, Ca(2+) acts on the sensor helix, which repels it from the reference helix. This Ca(2+)-dependent push-pull conformational change would be a key electromechanical movement for gating the ANO1 channel. Because chemical activation of ANO1 is viewed as an alternative means of rescuing cystic fibrosis, understanding its gating mechanism would be useful in developing novel treatments for cystic fibrosis.

  6. Calcium.

    PubMed

    Williams, Robert J P

    2002-01-01

    This chapter describes the chemical and biological value of the calcium ion. In calcium chemistry, our main interest is in equilibria within static, nonflowing systems. Hence, we examined the way calcium formed precipitates and complex ions in solution. We observed thereafter its uses by humankind in a vast number of materials such as minerals, e.g., marble, concrete, mortars, which parallel the biological use in shells and bones. In complex formation, we noted that many combinations were of anion interaction with calcium for example in the uses of detergents and medicines. The rates of exchange of calcium from bound states were noted but they had little application. Calcium ions do not act as catalysts of organic reactions. In biological systems, interest is in the above chemistry, but extends to the fact that Ca2+ ions can carry information by flowing in one solution or from one solution to another through membranes. Hence, we became interested in the details of rates of calcium exchange. The fast exchange of this divalent ion from most organic binding sites has allowed it to develop as the dominant second messenger. Now the flow can be examined in vitro as calcium binds particular isolated proteins, which it activates as seen in physical mechanical changes or chemical changes and this piece-by-piece study of cells is common. Here, however, we have chosen to stress the whole circuit of Ca2+ action indicating that the cell is organized both at a basal and an activated state kinetic level by the steady state flow of the ion (see Fig. 11). Different time constants of exchange utilizing very similar binding constants lead to: 1) fast responses as in the muscle of an animal; or 2) slower change as in differentiation of an egg or seed. Many other changes of state may relate to Ca2+ steady-state levels of flow in the circuitry and here we point to two: 1) dormancy in reptiles and animals; and 2) sporulation in both bacteria and lower plants. In the other chapters of

  7. Effect of dolomite decomposition under CO2 on its multicycle CO2 capture behaviour under calcium looping conditions.

    PubMed

    de la Calle Martos, Antonio; Valverde, Jose Manuel; Sanchez-Jimenez, Pedro E; Perejón, Antonio; García-Garrido, Cristina; Perez-Maqueda, Luis A

    2016-06-28

    One of the major drawbacks that hinder the industrial competitiveness of the calcium looping (CaL) process for CO2 capture is the high temperature (∼930-950 °C) needed in practice to attain full calcination of limestone in a high CO2 partial pressure environment for short residence times as required. In this work, the multicycle CO2 capture performance of dolomite and limestone is analysed under realistic CaL conditions and using a reduced calcination temperature of 900 °C, which would serve to mitigate the energy penalty caused by integration of the CaL process into fossil fuel fired power plants. The results show that the fundamental mechanism of dolomite decomposition under CO2 has a major influence on its superior performance compared to limestone. The inert MgO grains resulting from dolomite decomposition help preserve a nanocrystalline CaO structure wherein carbonation in the solid-state diffusion controlled phase is promoted. The major role played by the dolomite decomposition mechanism under CO2 is clearly demonstrated by the multicycle CaO conversion behaviour observed for samples decomposed at different preheating rates. Limestone decomposition at slow heating rates yields a highly crystalline and poorly reactive CaCO3 structure that requires long periods to fully decarbonate and shows a severely reduced capture capacity in subsequent cycles. On the other hand, the nascent CaCO3 produced after dolomite half-decomposition consists of nanosized crystals with a fast decarbonation kinetics regardless of the preheating rate, thus fully decomposing from the very first cycle at a reduced calcination temperature into a CaO skeleton with enhanced reactivity as compared to limestone derived CaO.

  8. Variomics screen identifies the re-entrant loop of the calcium-activated chloride channel ANO1 that facilitates channel activation.

    PubMed

    Bill, Anke; Popa, M Oana; van Diepen, Michiel T; Gutierrez, Abraham; Lilley, Sarah; Velkova, Maria; Acheson, Kathryn; Choudhury, Hedaythul; Renaud, Nicole A; Auld, Douglas S; Gosling, Martin; Groot-Kormelink, Paul J; Gaither, L Alex

    2015-01-09

    The calcium-activated chloride channel ANO1 regulates multiple physiological processes. However, little is known about the mechanism of channel gating and regulation of ANO1 activity. Using a high-throughput, random mutagenesis-based variomics screen, we generated and functionally characterized ∼6000 ANO1 mutants and identified novel mutations that affected channel activity, intracellular trafficking, or localization of ANO1. Mutations such as S741T increased ANO1 calcium sensitivity and rendered ANO1 calcium gating voltage-independent, demonstrating a critical role of the re-entrant loop in coupling calcium and voltage sensitivity of ANO1 and hence in regulating ANO1 activation. Our data present the first unbiased and comprehensive study of the structure-function relationship of ANO1. The novel ANO1 mutants reported have diverse functional characteristics, providing new tools to study ANO1 function in biological systems, paving the path for a better understanding of the function of ANO1 and its role in health and diseases.

  9. Variomics Screen Identifies the Re-entrant Loop of the Calcium-activated Chloride Channel ANO1 That Facilitates Channel Activation*

    PubMed Central

    Bill, Anke; Popa, M. Oana; van Diepen, Michiel T.; Gutierrez, Abraham; Lilley, Sarah; Velkova, Maria; Acheson, Kathryn; Choudhury, Hedaythul; Renaud, Nicole A.; Auld, Douglas S.; Gosling, Martin; Groot-Kormelink, Paul J.; Gaither, L. Alex

    2015-01-01

    The calcium-activated chloride channel ANO1 regulates multiple physiological processes. However, little is known about the mechanism of channel gating and regulation of ANO1 activity. Using a high-throughput, random mutagenesis-based variomics screen, we generated and functionally characterized ∼6000 ANO1 mutants and identified novel mutations that affected channel activity, intracellular trafficking, or localization of ANO1. Mutations such as S741T increased ANO1 calcium sensitivity and rendered ANO1 calcium gating voltage-independent, demonstrating a critical role of the re-entrant loop in coupling calcium and voltage sensitivity of ANO1 and hence in regulating ANO1 activation. Our data present the first unbiased and comprehensive study of the structure-function relationship of ANO1. The novel ANO1 mutants reported have diverse functional characteristics, providing new tools to study ANO1 function in biological systems, paving the path for a better understanding of the function of ANO1 and its role in health and diseases. PMID:25425649

  10. Calcium - urine

    MedlinePlus

    ... Monitor someone who has a problem with the parathyroid gland , which helps control calcium levels in the blood ... much production of parathyroid hormone (PTH) by the parathyroid glands in the neck (hyperparathyroidism) Use of loop diuretics ...

  11. Malignant hyperthermia-associated mutations in the S2-S3 cytoplasmic loop of type 1 ryanodine receptor calcium channel impair calcium-dependent inactivation.

    PubMed

    Gomez, Angela C; Holford, Timothy W; Yamaguchi, Naohiro

    2016-11-01

    Channel activities of skeletal muscle ryanodine receptor (RyR1) are activated by micromolar Ca(2+) and inactivated by higher (∼1 mM) Ca(2+) To gain insight into a mechanism underlying Ca(2+)-dependent inactivation of RyR1 and its relationship with skeletal muscle diseases, we constructed nine recombinant RyR1 mutants carrying malignant hyperthermia or centronuclear myopathy-associated mutations and determined RyR1 channel activities by [(3)H]ryanodine binding assay. These mutations are localized in or near the RyR1 domains which are responsible for Ca(2+)-dependent inactivation of RyR1. Four RyR1 mutations (F4732D, G4733E, R4736W, and R4736Q) in the cytoplasmic loop between the S2 and S3 transmembrane segments (S2-S3 loop) greatly reduced Ca(2+)-dependent channel inactivation. Activities of these mutant channels were suppressed at 10-100 μM Ca(2+), and the suppressions were relieved by 1 mM Mg(2+) The Ca(2+)- and Mg(2+)-dependent regulation of S2-S3 loop RyR1 mutants are similar to those of the cardiac isoform of RyR (RyR2) rather than wild-type RyR1. Two mutations (T4825I and H4832Y) in the S4-S5 cytoplasmic loop increased Ca(2+) affinities for channel activation and decreased Ca(2+) affinities for inactivation, but impairment of Ca(2+)-dependent inactivation was not as prominent as those of S2-S3 loop mutants. Three mutations (T4082M, S4113L, and N4120Y) in the EF-hand domain showed essentially the same Ca(2+)-dependent channel regulation as that of wild-type RyR1. The results suggest that nine RyR1 mutants associated with skeletal muscle diseases were differently regulated by Ca(2+) and Mg(2+) Four malignant hyperthermia-associated RyR1 mutations in the S2-S3 loop conferred RyR2-type Ca(2+)- and Mg(2+)-dependent channel regulation. Copyright © 2016 the American Physiological Society.

  12. Computational fluid dynamics modeling of chemical looping combustion process with calcium sulphate oxygen carrier - article no. A19

    SciTech Connect

    Baosheng Jin; Rui Xiao; Zhongyi Deng; Qilei Song

    2009-07-01

    To concentrate CO{sub 2} in combustion processes by efficient and energy-saving ways is a first and very important step for its sequestration. Chemical looping combustion (CLC) could easily achieve this goal. A chemical-looping combustion system consists of a fuel reactor and an air reactor. Two reactors in the form of interconnected fluidized beds are used in the process: (1) a fuel reactor where the oxygen carrier is reduced by reaction with the fuel, and (2) an air reactor where the reduced oxygen carrier from the fuel reactor is oxidized with air. The outlet gas from the fuel reactor consists of CO{sub 2} and H{sub 2}O, while the outlet gas stream from the air reactor contains only N{sub 2} and some unused O{sub 2}. The water in combustion products can be easily removed by condensation and pure carbon dioxide is obtained without any loss of energy for separation. Until now, there is little literature about mathematical modeling of chemical-looping combustion using the computational fluid dynamics (CFD) approach. In this work, the reaction kinetic model of the fuel reactor (CaSO{sub 4}+ H{sub 2}) is developed by means of the commercial code FLUENT and the effects of partial pressure of H{sub 2} (concentration of H{sub 2}) on chemical looping combustion performance are also studied. The results show that the concentration of H{sub 2} could enhance the CLC performance.

  13. Calcium looping process for high purity hydrogen production integrated with capture of carbon dioxide, sulfur and halides

    DOEpatents

    Ramkumar, Shwetha; Fan, Liang-Shih

    2015-11-04

    A process for producing hydrogen comprising the steps of: (i) gasifying a fuel into a raw synthesis gas comprising CO, hydrogen, steam, sulfur and halide contaminants in the form of H.sub.2S, COS, and HX, wherein X is a halide; (ii) passing the raw synthesis gas through a water gas shift reactor (WGSR) into which CaO and steam are injected, the CaO reacting with the shifted gas to remove CO.sub.2, sulfur and halides in a solid-phase calcium-containing product comprising CaCO.sub.3, CaS and CaX.sub.2; (iii) separating the solid-phase calcium-containing product from an enriched gaseous hydrogen product; and (iv) regenerating the CaO by calcining the solid-phase calcium-containing product at a condition selected from the group consisting of: in the presence of steam, in the presence of CO.sub.2, in the presence of synthesis gas, in the presence of H.sub.2 and O.sub.2, under partial vacuum, and combinations thereof.

  14. Calcium looping process for high purity hydrogen production integrated with capture of carbon dioxide, sulfur and halides

    DOEpatents

    Ramkumar, Shwetha; Fan, Liang-Shih

    2013-07-30

    A process for producing hydrogen comprising the steps of: (i) gasifying a fuel into a raw synthesis gas comprising CO, hydrogen, steam, sulfur and halide contaminants in the form of H.sub.2S, COS, and HX, wherein X is a halide; (ii) passing the raw synthesis gas through a water gas shift reactor (WGSR) into which CaO and steam are injected, the CaO reacting with the shifted gas to remove CO.sub.2, sulfur and halides in a solid-phase calcium-containing product comprising CaCO.sub.3, CaS and CaX.sub.2; (iii) separating the solid-phase calcium-containing product from an enriched gaseous hydrogen product; and (iv) regenerating the CaO by calcining the solid-phase calcium-containing product at a condition selected from the group consisting of: in the presence of steam, in the presence of CO.sub.2, in the presence of synthesis gas, in the presence of H.sub.2 and O.sub.2, under partial vacuum, and combinations thereof.

  15. A calcium-redox feedback loop controls human monocyte immune responses: The role of ORAI Ca2+ channels.

    PubMed

    Saul, Stephanie; Gibhardt, Christine S; Schmidt, Barbara; Lis, Annette; Pasieka, Bastian; Conrad, David; Jung, Philipp; Gaupp, Rosmarie; Wonnenberg, Bodo; Diler, Ebru; Stanisz, Hedwig; Vogt, Thomas; Schwarz, Eva C; Bischoff, Markus; Herrmann, Mathias; Tschernig, Thomas; Kappl, Reinhard; Rieger, Heiko; Niemeyer, Barbara A; Bogeski, Ivan

    2016-03-08

    In phagocytes, pathogen recognition is followed by Ca(2+) mobilization and NADPH oxidase 2 (NOX2)-mediated "oxidative burst," which involves the rapid production of large amounts of reactive oxygen species (ROS). We showed that ORAI Ca(2+) channels control store-operated Ca(2+) entry, ROS production, and bacterial killing in primary human monocytes. ROS inactivate ORAI channels that lack an ORAI3 subunit. Staphylococcal infection of mice reduced the expression of the gene encoding the redox-sensitive Orai1 and increased the expression of the gene encoding the redox-insensitive Orai3 in the lungs or in bronchoalveolar lavages. A similar switch from ORAI1 to ORAI3 occurred in primary human monocytes exposed to bacterial peptides in culture. These alterations in ORAI1 and ORAI3 abundance shifted the channel assembly toward a more redox-insensitive configuration. Accordingly, silencing ORAI3 increased the redox sensitivity of the channel and enhanced oxidation-induced inhibition of NOX2. We generated a mathematical model that predicted additional features of the Ca(2+)-redox interplay. Our results identified the ORAI-NOX2 feedback loop as a determinant of monocyte immune responses.

  16. Exocytosis of serotonin from the neuronal soma is sustained by a serotonin and calcium-dependent feedback loop

    PubMed Central

    Leon-Pinzon, Carolina; Cercós, Montserrat G.; Noguez, Paula; Trueta, Citlali; De-Miguel, Francisco F.

    2014-01-01

    The soma of many neurons releases large amounts of transmitter molecules through an exocytosis process that continues for hundreds of seconds after the end of the triggering stimulus. Transmitters released in this way modulate the activity of neurons, glia and blood vessels over vast volumes of the nervous system. Here we studied how somatic exocytosis is maintained for such long periods in the absence of electrical stimulation and transmembrane Ca2+ entry. Somatic exocytosis of serotonin from dense core vesicles could be triggered by a train of 10 action potentials at 20 Hz in Retzius neurons of the leech. However, the same number of action potentials produced at 1 Hz failed to evoke any exocytosis. The 20-Hz train evoked exocytosis through a sequence of intracellular Ca2+ transients, with each transient having a different origin, timing and intracellular distribution. Upon electrical stimulation, transmembrane Ca2+ entry through L-type channels activated Ca2+-induced Ca2+ release. A resulting fast Ca2+ transient evoked an early exocytosis of serotonin from sparse vesicles resting close to the plasma membrane. This Ca2+ transient also triggered the transport of distant clusters of vesicles toward the plasma membrane. Upon exocytosis, the released serotonin activated autoreceptors coupled to phospholipase C, which in turn produced an intracellular Ca2+ increase in the submembrane shell. This localized Ca2+ increase evoked new exocytosis as the vesicles in the clusters arrived gradually at the plasma membrane. In this way, the extracellular serotonin elevated the intracellular Ca2+ and this Ca2+ evoked more exocytosis. The resulting positive feedback loop maintained exocytosis for the following hundreds of seconds until the last vesicles in the clusters fused. Since somatic exocytosis displays similar kinetics in neurons releasing different types of transmitters, the data presented here contributes to understand the cellular basis of paracrine neurotransmission

  17. Limestone calcination under calcium-looping conditions for CO2 capture and thermochemical energy storage in the presence of H2O: an in situ XRD analysis.

    PubMed

    Valverde, Jose Manuel; Medina, Santiago

    2017-03-15

    This work reports an in situ XRD analysis of whether the calcination/carbonation behavior of natural limestone (CaCO3) is affected by the addition of H2O to the calciner at a very low concentration under relevant Calcium-Looping (CaL) conditions for CO2 capture in coal fired power plants (CFPP) and Thermochemical Energy Storage (TCES) in Concentrated Solar Power plants (CSP). Previous studies have demonstrated that the presence of steam in the calciner at a high concentration yields a significant increase in the reaction rate. However, a further undesired consequence is the serious deterioration of the CaO mechanical strength, which would lead to particle attrition and mass loss in any CaL process based on the use of circulating fluidized beds. The results presented in this manuscript on the time evolution of the wt% and crystallite size of the phases involved in the calcination/carbonation reactions indicate that the calcination rate is still notably increased by the presence of H2O at very low concentrations whereas the reactivity toward carbonation and crystal structure of the formed CaO are not essentially affected, which suggests that the CaO mechanical strength is not impaired. Thus, the benefit of using steam for calcination in the CaL process could be still retained while at the same time particle attrition would not be promoted.

  18. Solid-phase synthesis of the non-calcium-binding loop of cod allergen M. Direct evidence of the reactivity of the amino-terminal segment.

    PubMed

    Elsayed, S; Ragnarsson, U; Netteland, B

    1983-03-01

    The synthesis of the non-calcium-binding AB loop of the assembly 13-32 of cod Allergen M (Mr 2122.1) was accomplished by solid-phase peptide synthesis. This peptide and the previously synthesized ones [12, 13, 14] have significant amino acid sequence homology. The synthetic crude preparation was obtained at relatively high recovery and purity. Further purification on a Bio-Gel P-2 column and a reversed-phase high-performance liquid chromatography column improved the grade of homogeneity, as demonstrated by high-voltage electrophoresis, end-terminal analysis, and amino acid composition. The peptide could, although to a much weaker extent than the intact Allergen M, directly bind IgE antibodies from the sera of cod-allergic individuals. At identical molar concentrations, a ratio of 1:6 for the in vitro reactivity of the peptide relative to the intact Allergen M was obtained. A similar reactivity was shown in the in vivo system used. The peptide also reacted with rabbit anti-Allergen M antibodies in rocket immunoelectrophoresis. The peptide appears to function as a divalent molecule in its primary interaction with antibodies.

  19. The CaVβ Subunit Protects the I-II Loop of the Voltage-gated Calcium Channel CaV2.2 from Proteasomal Degradation but Not Oligoubiquitination*

    PubMed Central

    Page, Karen M.; Rothwell, Simon W.; Dolphin, Annette C.

    2016-01-01

    CaVβ subunits interact with the voltage-gated calcium channel CaV2.2 on a site in the intracellular loop between domains I and II (the I-II loop). This interaction influences the biophysical properties of the channel and leads to an increase in its trafficking to the plasma membrane. We have shown previously that a mutant CaV2.2 channel that is unable to bind CaVβ subunits (CaV2.2 W391A) was rapidly degraded (Waithe, D., Ferron, L., Page, K. M., Chaggar, K., and Dolphin, A. C. (2011) J. Biol. Chem. 286, 9598–9611). Here we show that, in the absence of CaVβ subunits, a construct consisting of the I-II loop of CaV2.2 was directly ubiquitinated and degraded by the proteasome system. Ubiquitination could be prevented by mutation of all 12 lysine residues in the I-II loop to arginines. Including a palmitoylation motif at the N terminus of CaV2.2 I-II loop was insufficient to target it to the plasma membrane in the absence of CaVβ subunits even when proteasomal degradation was inhibited with MG132 or ubiquitination was prevented by the lysine-to-arginine mutations. In the presence of CaVβ subunit, the palmitoylated CaV2.2 I-II loop was protected from degradation, although oligoubiquitination could still occur, and was efficiently trafficked to the plasma membrane. We propose that targeting to the plasma membrane requires a conformational change in the I-II loop that is induced by binding of the CaVβ subunit. PMID:27489103

  20. Regulative Loops, Step Loops and Task Loops

    ERIC Educational Resources Information Center

    VanLehn, Kurt

    2016-01-01

    This commentary suggests a generalization of the conception of the behavior of tutoring systems, which the target article characterized as having an outer loop that was executed once per task and an inner loop that was executed once per step of the task. A more general conception sees these two loops as instances of regulative loops, which…

  1. Regulative Loops, Step Loops and Task Loops

    ERIC Educational Resources Information Center

    VanLehn, Kurt

    2016-01-01

    This commentary suggests a generalization of the conception of the behavior of tutoring systems, which the target article characterized as having an outer loop that was executed once per task and an inner loop that was executed once per step of the task. A more general conception sees these two loops as instances of regulative loops, which…

  2. Repositioning of charged I-II loop amino acid residues within the electric field by beta subunit as a novel working hypothesis for the control of fast P/Q calcium channel inactivation.

    PubMed

    Sandoz, Guillaume; Lopez-Gonzalez, Ignacio; Stamboulian, Séverine; Weiss, Norbert; Arnoult, Christophe; De Waard, Michel

    2004-04-01

    We have investigated the contribution of the Ca(v)beta subunits to the process of inactivation dependent of the I-II loop of Ca(v)alpha(2.1). Two amino acid residues located in the alpha1 interaction domain (AID) of the I-II loop of Ca(v)alpha(2.1) (Arg(387) and Glu(388)) have been directly implicated in voltage-dependent inactivation of this channel. Various point mutations of these residues disrupt the interaction between the I-II loop and the III-IV loop, and thereby modify the inactivation properties of the channel by accelerating its kinetics and shifting the steady-state inactivation curve towards hyperpolarized potentials. A similar disruption is produced by Ca(v)beta(4) subunit association with the I-II loop. Moreover, in the presence of Ca(v)beta(4) subunit, introducing negatively charged residues at positions 387 or 388 slows inactivation kinetics down, whereas introducing positive charges has the opposite effect. The shift of the steady-state inactivation curve is also amino acid charge-dependent. In contrast, mutation of Arg(387) or Glu(388) does not alter the differential regulation of the different Ca(v)beta isoforms on inactivation. These results suggest that the expression of Ca(v)beta(4) alters the contribution of charged residues at positions 387 and 388 to inactivation. We discuss these results with regard to the actual hypotheses on the mechanisms of calcium channel inactivation. We introduce the working concept that Ca(v)beta-subunits produce a conformational repositioning of charged AID residues within the electric field.

  3. Characterization of superoxide overproduction by the D-Loop(Nox4)-Nox2 cytochrome b(558) in phagocytes-Differential sensitivity to calcium and phosphorylation events.

    PubMed

    Carrichon, Laure; Picciocchi, Antoine; Debeurme, Franck; Defendi, Federica; Beaumel, Sylvain; Jesaitis, Algirdas J; Dagher, Marie-Claire; Stasia, Marie-José

    2011-01-01

    NADPH oxidase is a crucial element of phagocytes involved in microbicidal mechanisms. It becomes active when membrane-bound cytochrome b(558), the redox core, is assembled with cytosolic p47(phox), p67(phox), p40(phox), and rac proteins to produce superoxide, the precursor for generation of toxic reactive oxygen species. In a previous study, we demonstrated that the potential second intracellular loop of Nox2 was essential to maintaining NADPH oxidase activity by controlling electron transfer from FAD to O(2). Moreover, replacement of this loop by the Nox4-D-loop (D-loop(Nox4)-Nox2) in PLB-985 cells induced superoxide overproduction. In the present investigation, we demonstrated that both soluble and particulate stimuli were able to induce this superoxide overproduction. Superoxide overproduction was also observed after phosphatidic acid activation in a purified cell-free-system assay. The highest oxidase activity was obtained after ionomycin and fMLF stimulation. In addition, enhanced sensitivity to Ca(2+) influx was shown by thapsigargin, EDTA, or BTP2 treatment before fMLF activation. Mutated cytochrome b(558) was less dependent on phosphorylation triggered by ERK1/2 during fMLF or PMA stimulation and by PI3K during OpZ stimulation. The superoxide overproduction of the D-loop(Nox4)-Nox2 mutant may come from a change of responsiveness to intracellular Ca(2+) level and to phosphorylation events during oxidase activation. Finally the D-loop(Nox4)-Nox2-PLB-985 cells were more effective against an attenuated strain of Pseudomonas aeruginosa compared to WT-Nox2 cells. The killing mechanism was biphasic, an early step of ROS production that was directly bactericidal, and a second oxidase-independent step related to the amount of ROS produced in the first step.

  4. Loop quantization

    SciTech Connect

    Nicolau, A.

    1988-10-01

    Loop unwinding is a known technique for reducing loop overhead, exposing parallelism, and increasing the efficiency of pipelining. Traditional loop unwinding is limited to the innermost loop in a group of nested loops and the amount of unwinding either is fixed or must be specified by the user, on a case by case basis. In this paper the authors present a general technique for automatically unwinding multiply nested loops, explain its advantages over other transformation techniques, and illustrate its practical effectiveness. Lopp Quantization could be beneficial by itself or coupled with other loop transformations.

  5. Voltage- and calcium-dependent gating of TMEM16A/Ano1 chloride channels are physically coupled by the first intracellular loop

    PubMed Central

    Xiao, Qinghuan; Yu, Kuai; Perez-Cornejo, Patricia; Cui, Yuanyuan; Arreola, Jorge; Hartzell, H. Criss

    2011-01-01

    Ca2+-activated Cl− channels (CaCCs) are exceptionally well adapted to subserve diverse physiological roles, from epithelial fluid transport to sensory transduction, because their gating is cooperatively controlled by the interplay between ionotropic and metabotropic signals. A molecular understanding of the dual regulation of CaCCs by voltage and Ca2+ has recently become possible with the discovery that Ano1 (TMEM16a) is an essential subunit of CaCCs. Ano1 can be gated by Ca2+ or by voltage in the absence of Ca2+, but Ca2+- and voltage-dependent gating are very closely coupled. Here we identify a region in the first intracellular loop that is crucial for both Ca2+ and voltage sensing. Deleting 448EAVK in the first intracellular loop dramatically decreases apparent Ca2+ affinity. In contrast, mutating the adjacent amino acids 444EEEE abolishes intrinsic voltage dependence without altering the apparent Ca2+affinity. Voltage-dependent gating of Ano1 measured in the presence of intracellular Ca2+ was facilitated by anions with high permeability or by an increase in [Cl−]e. Our data show that the transition between closed and open states is governed by Ca2+ in a voltage-dependent manner and suggest that anions allosterically modulate Ca2+-binding affinity. This mechanism provides a unified explanation of CaCC channel gating by voltage and ligand that has long been enigmatic. PMID:21555582

  6. Calcium supplements

    MedlinePlus

    ... TYPES OF CALCIUM SUPPLEMENTS Forms of calcium include: Calcium carbonate: Over-the-counter (OTC) antacid products, such as Tums and Rolaids, contain calcium carbonate. These sources of calcium do not cost much. ...

  7. The voltage dependence of the TMEM16B/anoctamin2 calcium-activated chloride channel is modified by mutations in the first putative intracellular loop

    PubMed Central

    Cenedese, Valentina; Betto, Giulia; Celsi, Fulvio; Cherian, O. Lijo; Pifferi, Simone

    2012-01-01

    Ca2+-activated Cl− channels (CaCCs) are involved in several physiological processes. Recently, TMEM16A/anoctamin1 and TMEM16B/anoctamin2 have been shown to function as CaCCs, but very little information is available on the structure–function relations of these channels. TMEM16B is expressed in the cilia of olfactory sensory neurons, in microvilli of vomeronasal sensory neurons, and in the synaptic terminals of retinal photoreceptors. Here, we have performed the first site-directed mutagenesis study on TMEM16B to understand the molecular mechanisms of voltage and Ca2+ dependence. We have mutated amino acids in the first putative intracellular loop and measured the properties of the wild-type and mutant TMEM16B channels expressed in HEK 293T cells using the whole cell voltage-clamp technique in the presence of various intracellular Ca2+ concentrations. We mutated E367 into glutamine or deleted the five consecutive glutamates 386EEEEE390 and 399EYE401. The EYE deletion did not significantly modify the apparent Ca2+ dependence nor the voltage dependence of channel activation. E367Q and deletion of the five glutamates did not greatly affect the apparent Ca2+ affinity but modified the voltage dependence, shifting the conductance–voltage relations toward more positive voltages. These findings indicate that glutamates E367 and 386EEEEE390 in the first intracellular putative loop play an important role in the voltage dependence of TMEM16B, thus providing an initial structure–function study for this channel. PMID:22412191

  8. Varietal Loops

    NASA Image and Video Library

    2016-09-15

    A series of active regions stretched along the right side of the sun exhibited a wide variety of loops cascading above them (Sept. 12-14, 2016). The active region near the center has tightly coiled loops, while the region rotating over the right edge has some elongated and some very stretched loops above it. The loops are actually charged particles spiraling along magnetic field lines, observed here in a wavelength of extreme ultraviolet light. Near the middle of the video the Earth quickly passes in front of a portion of the sun as viewed by SDO. http://photojournal.jpl.nasa.gov/catalog/PIA16997

  9. Calcium Carbonate

    MedlinePlus

    Calcium carbonate is a dietary supplement used when the amount of calcium taken in the diet is not ... for healthy bones, muscles, nervous system, and heart. Calcium carbonate also is used as an antacid to relieve ...

  10. Stretched Loops

    NASA Image and Video Library

    2017-03-16

    When an active region rotated over to the edge of the sun, it presented us with a nice profile view of its elongated loops stretching and swaying above it (Mar. 8-9, 2017). These loops are actually charged particles (made visible in extreme ultraviolet light) swirling along the magnetic field lines of the active region. The video covers about 30 hours of activity. Also of note is a darker twisting mass of plasma to the left of the active region being pulled and spun about by magnetic forces. Video is available at http://photojournal.jpl.nasa.gov/catalog/PIA21562

  11. Loop-to-loop coupling.

    SciTech Connect

    Warne, Larry Kevin; Lucero, Larry Martin; Langston, William L.; Salazar, Robert Austin; Coleman, Phillip Dale; Basilio, Lorena I.; Bacon, Larry Donald

    2012-05-01

    This report estimates inductively-coupled energy to a low-impedance load in a loop-to-loop arrangement. Both analytical models and full-wave numerical simulations are used and the resulting fields, coupled powers and energies are compared. The energies are simply estimated from the coupled powers through approximations to the energy theorem. The transmitter loop is taken to be either a circular geometry or a rectangular-loop (stripline-type) geometry that was used in an experimental setup. Simple magnetic field models are constructed and used to estimate the mutual inductance to the receiving loop, which is taken to be circular with one or several turns. Circuit elements are estimated and used to determine the coupled current and power (an equivalent antenna picture is also given). These results are compared to an electromagnetic simulation of the transmitter geometry. Simple approximate relations are also given to estimate coupled energy from the power. The effect of additional loads in the form of attached leads, forming transmission lines, are considered. The results are summarized in a set of susceptibility-type curves. Finally, we also consider drives to the cables themselves and the resulting common-to-differential mode currents in the load.

  12. Adding calcium improves lithium ferrite core

    NASA Technical Reports Server (NTRS)

    Lessoff, H.

    1969-01-01

    Adding calcium increases uniformity of grain growth over a wide range of sintering temperatures and reduces porosity within the grain. Ferrite cores containing calcium have square hysteresis loops and high curie temperatures, making them useful in coincident current memories of digital electronic computers.

  13. Calcium Test

    MedlinePlus

    ... Hyperthyroidism Sarcoidosis Tuberculosis Prolonged immobilization Excess vitamin D intake Thiazide diuretics Kidney transplant HIV/AIDS Low total calcium (hypocalcemia) The most common cause of low total calcium is: Low blood protein levels, especially a low level of albumin , which ...

  14. Diuretics and disorders of calcium homeostasis.

    PubMed

    Grieff, Marvin; Bushinsky, David A

    2011-11-01

    Diuretics commonly are administered in disorders of sodium balance. Loop diuretics inhibit the Na-K-2Cl transporter and also increase calcium excretion. They are often used in the treatment of hypercalcemia. Thiazide diuretics block the thiazide-sensitive NaCl transporter in the distal convoluted tubule, and can decrease calcium excretion. They are often used in the treatment of nephrolithiasis. Carbonic anhydrase inhibitors decrease bicarbonate absorption and the resultant metabolic acidosis can increase calcium excretion. Their use can promote nephrocalcinosis and nephrolithiasis. This review will address the use of diuretics on disorders of calcium homeostasis. Copyright © 2011 Elsevier Inc. All rights reserved.

  15. Water Stream "Loop-the-Loop"

    ERIC Educational Resources Information Center

    Jefimenko, Oleg

    1974-01-01

    Discusses the design of a modified loop-the-loop apparatus in which a water stream is used to illustrate centripetal forces and phenomena of high-velocity hydrodynamics. Included are some procedures of carrying out lecture demonstrations. (CC)

  16. Water Stream "Loop-the-Loop"

    ERIC Educational Resources Information Center

    Jefimenko, Oleg

    1974-01-01

    Discusses the design of a modified loop-the-loop apparatus in which a water stream is used to illustrate centripetal forces and phenomena of high-velocity hydrodynamics. Included are some procedures of carrying out lecture demonstrations. (CC)

  17. Looping: An Empirical Evaluation

    ERIC Educational Resources Information Center

    Cistone, Peter; Shneyderman, Aleksandr

    2004-01-01

    Looping is the practice in which a teacher instructs the same group of students for at least two school years, following them from one grade level to the next. Once a "loop" of two or more years is completed, the teacher may start a new loop teaching a new group of students. This evaluation study of the practice of looping in a large…

  18. Hybrid Combustion-Gasification Chemical Looping

    SciTech Connect

    Herbert Andrus; Gregory Burns; John Chiu; Gregory Lijedahl; Peter Stromberg; Paul Thibeault

    2009-01-07

    For the past several years Alstom Power Inc. (Alstom), a leading world-wide power system manufacturer and supplier, has been in the initial stages of developing an entirely new, ultra-clean, low cost, high efficiency power plant for the global power market. This new power plant concept is based on a hybrid combustion-gasification process utilizing high temperature chemical and thermal looping technology The process consists of the oxidation, reduction, carbonation, and calcination of calcium-based compounds, which chemically react with coal, biomass, or opportunity fuels in two chemical loops and one thermal loop. The chemical and thermal looping technology can be alternatively configured as (i) a combustion-based steam power plant with CO{sub 2} capture, (ii) a hybrid combustion-gasification process producing a syngas for gas turbines or fuel cells, or (iii) an integrated hybrid combustion-gasification process producing hydrogen for gas turbines, fuel cells or other hydrogen based applications while also producing a separate stream of CO{sub 2} for use or sequestration. In its most advanced configuration, this new concept offers the promise to become the technology link from today's Rankine cycle steam power plants to tomorrow's advanced energy plants. The objective of this work is to develop and verify the high temperature chemical and thermal looping process concept at a small-scale pilot facility in order to enable AL to design, construct and demonstrate a pre-commercial, prototype version of this advanced system. In support of this objective, Alstom and DOE started a multi-year program, under this contract. Before the contract started, in a preliminary phase (Phase 0) Alstom funded and built the required small-scale pilot facility (Process Development Unit, PDU) at its Power Plant Laboratories in Windsor, Connecticut. Construction was completed in calendar year 2003. The objective for Phase I was to develop the indirect combustion loop with CO{sub 2

  19. The preprocessed doacross loop

    NASA Technical Reports Server (NTRS)

    Saltz, Joel H.; Mirchandaney, Ravi

    1990-01-01

    Dependencies between loop iterations cannot always be characterized during program compilation. Doacross loops typically make use of a-priori knowledge of inter-iteration dependencies to carry out required synchronizations. A type of doacross loop is proposed that allows the scheduling of iterations of a loop among processors without advance knowledge of inter-iteration dependencies. The method proposed for loop iterations requires that parallelizable preprocessing and postprocessing steps be carried out during program execution.

  20. Fast flux locked loop

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-09-10

    A flux locked loop for providing an electrical feedback signal, the flux locked loop employing radio-frequency components and technology to extend the flux modulation frequency and tracking loop bandwidth. The flux locked loop of the present invention has particularly useful application in read-out electronics for DC SQUID magnetic measurement systems, in which case the electrical signal output by the flux locked loop represents an unknown magnetic flux applied to the DC SQUID.

  1. OPE for super loops

    NASA Astrophysics Data System (ADS)

    Sever, Amit; Vieira, Pedro; Wang, Tianheng

    2011-11-01

    We extend the Operator Product Expansion for Null Polygon Wilson loops to the Mason-Skinner-Caron-Huot super loop dual to non MHV gluon amplitudes. We explain how the known tree level amplitudes can be promoted into an infinite amount of data at any loop order in the OPE picture. As an application, we re-derive all one loop NMHV six gluon amplitudes by promoting their tree level expressions. We also present some new all loops predictions for these amplitudes.

  2. Calcium - ionized

    MedlinePlus

    ... 245. Read More Acute kidney failure Albumin - blood (serum) test Bone tumor Calcium blood test Hyperparathyroidism Hypoparathyroidism Malabsorption Milk-alkali syndrome Multiple myeloma Osteomalacia Paget disease of the bone Rickets Sarcoidosis Vitamin D Review ...

  3. Calcium Carbonate.

    PubMed

    Al Omari, M M H; Rashid, I S; Qinna, N A; Jaber, A M; Badwan, A A

    2016-01-01

    Calcium carbonate is a chemical compound with the formula CaCO3 formed by three main elements: carbon, oxygen, and calcium. It is a common substance found in rocks in all parts of the world (most notably as limestone), and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. CaCO3 exists in different polymorphs, each with specific stability that depends on a diversity of variables. © 2016 Elsevier Inc. All rights reserved.

  4. Calcium orthophosphates

    PubMed Central

    Dorozhkin, Sergey V.

    2011-01-01

    The present overview is intended to point the readers’ attention to the important subject of calcium orthophosphates. This type of materials is of special significance for human beings, because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with calcium orthophosphates, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenphosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of calcium orthophosphates. Similarly, dental caries and osteoporosis might be considered an in vivo dissolution of calcium orthophosphates. Thus, calcium orthophosphates hold a great significance for humankind, and in this paper, an overview on the current knowledge on this subject is provided. PMID:23507744

  5. Calcium Hydroxylapatite

    PubMed Central

    Yutskovskaya, Yana Alexandrovna; Philip Werschler, WM.

    2015-01-01

    Background: Calcium hydroxylapatite is one of the most well-studied dermal fillers worldwide and has been extensively used for the correction of moderate-to-severe facial lines and folds and to replenish lost volume. Objectives: To mark the milestone of 10 years of use in the aesthetic field, this review will consider the evolution of calcium hydroxylapatite in aesthetic medicine, provide a detailed injection protocol for a global facial approach, and examine how the unique properties of calcium hydroxylapatite provide it with an important place in today’s market. Methods: This article is an up-to-date review of calcium hydroxylapatite in aesthetic medicine along with procedures for its use, including a detailed injection protocol for a global facial approach by three expert injectors. Conclusion: Calcium hydroxylapatite is a very effective agent for many areas of facial soft tissue augmentation and is associated with a high and well-established safety profile. Calcium hydroxylapatite combines high elasticity and viscosity with an ability to induce long-term collagen formation making it an ideal agent for a global facial approach. PMID:25610523

  6. Calcium and Calcium Supplements: Achieving the Right Balance

    MedlinePlus

    ... calcium. Common calcium supplements may be labeled as: Calcium carbonate (40 percent elemental calcium) Calcium citrate (21 percent ... forms of calcium supplements are carbonate and citrate. Calcium carbonate is cheapest and therefore often a good first ...

  7. PTH-independent regulation of blood calcium concentration by the calcium-sensing receptor

    PubMed Central

    Loupy, Alexandre; Ramakrishnan, Suresh Krishna; Wootla, Bharath; Chambrey, Régine; de la Faille, Renaud; Bourgeois, Soline; Bruneval, Patrick; Mandet, Chantal; Christensen, Erik Ilso; Faure, Hélène; Cheval, Lydie; Laghmani, Kamel; Collet, Corinne; Eladari, Dominique; Dodd, Robert H.; Ruat, Martial; Houillier, Pascal

    2012-01-01

    Tight regulation of calcium levels is required for many critical biological functions. The Ca2+-sensing receptor (CaSR) expressed by parathyroid cells controls blood calcium concentration by regulating parathyroid hormone (PTH) secretion. However, CaSR is also expressed in other organs, such as the kidney, but the importance of extraparathyroid CaSR in calcium metabolism remains unknown. Here, we investigated the role of extraparathyroid CaSR using thyroparathyroidectomized, PTH-supplemented rats. Chronic inhibition of CaSR selectively increased renal tubular calcium absorption and blood calcium concentration independent of PTH secretion change and without altering intestinal calcium absorption. CaSR inhibition increased blood calcium concentration in animals pretreated with a bisphosphonate, indicating that the increase did not result from release of bone calcium. Kidney CaSR was expressed primarily in the thick ascending limb of the loop of Henle (TAL). As measured by in vitro microperfusion of cortical TAL, CaSR inhibitors increased calcium reabsorption and paracellular pathway permeability but did not change NaCl reabsorption. We conclude that CaSR is a direct determinant of blood calcium concentration, independent of PTH, and modulates renal tubular calcium transport in the TAL via the permeability of the paracellular pathway. These findings suggest that CaSR inhibitors may provide a new specific treatment for disorders related to impaired PTH secretion, such as primary hypoparathyroidism. PMID:22886306

  8. Pseudonoise code tracking loop

    NASA Technical Reports Server (NTRS)

    Laflame, D. T. (Inventor)

    1980-01-01

    A delay-locked loop is presented for tracking a pseudonoise (PN) reference code in an incoming communication signal. The loop is less sensitive to gain imbalances, which can otherwise introduce timing errors in the PN reference code formed by the loop.

  9. Blind Loop Syndrome

    MedlinePlus

    ... breeding ground for bacteria. The bacteria may produce toxins as well as block the absorption of nutrients. The greater the length of small bowel involved in the blind loop, the greater the chance of bacterial overgrowth. What triggers blind loop syndrome? Blind loop ...

  10. Calcium cyanide

    Integrated Risk Information System (IRIS)

    Jump to main content . Integrated Risk Information System Recent Additions | Contact Us Search : All EPA IRIS • You are here : EPA Home • Research • Environmental Assessment • IRIS • IRIS Summaries Redirect Page As of September 28 , 2010 , the assessment summary for calcium cyanide is included in th

  11. Calcium and bone disease

    PubMed Central

    Blair, Harry C.; Robinson, Lisa J.; Huang, Christopher L.-H.; Sun, Li; Friedman, Peter A.; Schlesinger, Paul H.; Zaidi, Mone

    2013-01-01

    Calcium transport and calcium signaling are of basic importance in bone cells. Bone is the major store of calcium and a key regulatory organ for calcium homeostasis. Bone, in major part, responds to calcium-dependent signals from the parathyroids and via vitamin D metabolites, although bone retains direct response to extracellular calcium if parathyroid regulation is lost. Improved understanding of calcium transporters and calcium-regulated cellular processes has resulted from analysis of genetic defects, including several defects with low or high bone mass. Osteoblasts deposit calcium by mechanisms including phosphate and calcium transport with alkalinization to absorb acid created by mineral deposition; cartilage calcium mineralization occurs by passive diffusion and phosphate production. Calcium mobilization by osteoclasts is mediated by acid secretion. Both bone forming and bone resorbing cells use calcium signals as regulators of differentiation and activity. This has been studied in more detail in osteoclasts, where both osteoclast differentiation and motility are regulated by calcium. PMID:21674636

  12. Calcium and Vitamin D

    USDA-ARS?s Scientific Manuscript database

    Calcium is required for the bone formation phase of bone remodeling. Typically about 5 nmol (200 mg) of calcium is removed from the adult skeleton and replaced each day. To supply this amount, one would need to consume about 600 mg of calcium, since calcium is not very efficiently absorbed. Calcium ...

  13. Testing loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Wilson-Ewing, Edward

    2017-03-01

    Loop quantum cosmology predicts that quantum gravity effects resolve the big-bang singularity and replace it by a cosmic bounce. Furthermore, loop quantum cosmology can also modify the form of primordial cosmological perturbations, for example by reducing power at large scales in inflationary models or by suppressing the tensor-to-scalar ratio in the matter bounce scenario; these two effects are potential observational tests for loop quantum cosmology. In this article, I review these predictions and others, and also briefly discuss three open problems in loop quantum cosmology: its relation to loop quantum gravity, the trans-Planckian problem, and a possible transition from a Lorentzian to a Euclidean space-time around the bounce point.

  14. Calcium and Vitamin D

    MedlinePlus

    ... A calcium-rich diet (including dairy, nuts, leafy greens and fish) helps to build and protect your ... yogurt and cheese are high in calcium. Certain green vegetables and other foods contain calcium in smaller ...

  15. Multiprotein DNA Looping

    NASA Astrophysics Data System (ADS)

    Vilar, Jose M. G.; Saiz, Leonor

    2006-06-01

    DNA looping plays a fundamental role in a wide variety of biological processes, providing the backbone for long range interactions on DNA. Here we develop the first model for DNA looping by an arbitrarily large number of proteins and solve it analytically in the case of identical binding. We uncover a switchlike transition between looped and unlooped phases and identify the key parameters that control this transition. Our results establish the basis for the quantitative understanding of fundamental cellular processes like DNA recombination, gene silencing, and telomere maintenance.

  16. Thermal power loops

    NASA Technical Reports Server (NTRS)

    Gottschlich, Joseph M.; Richter, Robert

    1991-01-01

    The concept of a thermal power loop (TPL) to transport thermal power over relatively large distances is presented as an alternative to heat pipes and their derivatives. The TPL is compared to heat pipes, and capillary pumped loops with respect to size, weight, conservation of thermal potential, start-up, and 1-g testing capability. Test results from a proof of feasibility demonstrator at the NASA JPL are discussed. This analysis demonstrates that the development of specific thermal power loops will result in substantial weight and cost savings for many spacecraft.

  17. Large lithium loop experience

    SciTech Connect

    Kolowith, R.; Owen, T.J.; Berg, J.D.; Atwood, J.M.

    1981-10-01

    An engineering design and operating experience of a large, isothermal, lithium-coolant test loop are presented. This liquid metal coolant loop is called the Experimental Lithium System (ELS) and has operated safely and reliably for over 6500 hours through September 1981. The loop is used for full-scale testing of components for the Fusion Materials Irradiation Test (FMIT) Facility. Main system parameters include coolant temperatures to 430/sup 0/C and flow to 0.038 m/sup 3//s (600 gal/min). Performance of the main pump, vacuum system, and control system is discussed. Unique test capabilities of the ELS are also discussed.

  18. Introduction to Loop Heat Pipes

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    2015-01-01

    This is the presentation file for the short course Introduction to Loop Heat Pipes, to be conducted at the 2015 Thermal Fluids and Analysis Workshop, August 3-7, 2015, Silver Spring, Maryland. This course will discuss operating principles and performance characteristics of a loop heat pipe. Topics include: 1) pressure profiles in the loop; 2) loop operating temperature; 3) operating temperature control; 4) loop startup; 4) loop shutdown; 5) loop transient behaviors; 6) sizing of loop components and determination of fluid inventory; 7) analytical modeling; 8) examples of flight applications; and 9) recent LHP developments.

  19. Dynamic Loops in Profile

    NASA Image and Video Library

    2017-03-28

    As an active region rotated into view, NASA Solar Dynamics Observatory was able to observe well-defined magnetic loops gyrating above the sun between Mar, 23-24, 2017. These loops appear because charged particles spinning along the magnetic field lines above this active region are made visible in this wavelength of extreme ultraviolet light. The video clip covers about a day and a half of activity. Movies are available at https://photojournal.jpl.nasa.gov/catalog/PIA21583

  20. Calcium and Calcium-Base Alloys

    DTIC Science & Technology

    1949-01-01

    alloys have •been made in electrical contacts. Little is known of’ the high - calcium alloys,» The aluminum-calcium diagram from Hansen^1) is shown in...list is still incom- plete« No use has been suggested for high calcium -aluminum alloys, ..•Arsenic-pal’c-iüm- Alloys •K.. Calcium arsenide, OajAsg...hot CaCUy, by X-ray determination of the structure. The probability of finding a useful high - calcium alloy in this system is based-on-the-validity

  1. Explaining Warm Coronal Loops

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.; Karpen, Judy T.; Patsourakos, Spiros

    2008-01-01

    One of the great mysteries of coronal physics that has come to light in the last few years is the discovery that warn (- 1 INK) coronal loops are much denser than expected for quasi-static equilibrium. Both the excess densities and relatively long lifetimes of the loops can be explained with bundles of unresolved strands that are heated impulsively to very high temperatures. Since neighboring strands are at different stages of cooling, the composite loop bundle is multi-thermal, with the distribution of temperatures depending on the details of the "nanoflare storm." Emission hotter than 2 MK is predicted, but it is not clear that such emission is always observed. We consider two possible explanations for the existence of over-dense warm loops without corresponding hot emission: (1) loops are bundles of nanoflare heated strands, but a significant fraction of the nanoflare energy takes the form of a nonthermal electron beam rather then direct plasma heating; (2) loops are bundles of strands that undergo thermal nonequilibrium that results when steady heating is sufficiently concentrated near the footpoints. We present numerical hydro simulations of both of these possibilities and explore the observational consequences, including the production of hard X-ray emission and absorption by cool material in the corona.

  2. Explaining Warm Coronal Loops

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.; Karpen, Judy T.; Patsourakos, Spiros

    2008-01-01

    One of the great mysteries of coronal physics that has come to light in the last few years is the discovery that warn (- 1 INK) coronal loops are much denser than expected for quasi-static equilibrium. Both the excess densities and relatively long lifetimes of the loops can be explained with bundles of unresolved strands that are heated impulsively to very high temperatures. Since neighboring strands are at different stages of cooling, the composite loop bundle is multi-thermal, with the distribution of temperatures depending on the details of the "nanoflare storm." Emission hotter than 2 MK is predicted, but it is not clear that such emission is always observed. We consider two possible explanations for the existence of over-dense warm loops without corresponding hot emission: (1) loops are bundles of nanoflare heated strands, but a significant fraction of the nanoflare energy takes the form of a nonthermal electron beam rather then direct plasma heating; (2) loops are bundles of strands that undergo thermal nonequilibrium that results when steady heating is sufficiently concentrated near the footpoints. We present numerical hydro simulations of both of these possibilities and explore the observational consequences, including the production of hard X-ray emission and absorption by cool material in the corona.

  3. Imaging calcium in neurons.

    PubMed

    Grienberger, Christine; Konnerth, Arthur

    2012-03-08

    Calcium ions generate versatile intracellular signals that control key functions in all types of neurons. Imaging calcium in neurons is particularly important because calcium signals exert their highly specific functions in well-defined cellular subcompartments. In this Primer, we briefly review the general mechanisms of neuronal calcium signaling. We then introduce the calcium imaging devices, including confocal and two-photon microscopy as well as miniaturized devices that are used in freely moving animals. We provide an overview of the classical chemical fluorescent calcium indicators and of the protein-based genetically encoded calcium indicators. Using application examples, we introduce new developments in the field, such as calcium imaging in awake, behaving animals and the use of calcium imaging for mapping single spine sensory inputs in cortical neurons in vivo. We conclude by providing an outlook on the prospects of calcium imaging for the analysis of neuronal signaling and plasticity in various animal models.

  4. Classical Physics and Quantum Loops

    SciTech Connect

    Barry R. Holstein; John F. Donoghue

    2004-05-01

    The standard picture of the loop expansion associates a factor of h-bar with each loop, suggesting that the tree diagrams are to be associated with classical physics, while loop effects are quantum mechanical in nature. We discuss examples wherein classical effects arise from loop contributions and display the relationship between the classical terms and the long range effects of massless particles.

  5. Shape of Cosmic String Loops

    NASA Astrophysics Data System (ADS)

    Copi, Craig J.; Vachaspati, Tanmay

    2010-11-01

    Complicated cosmic string loops will fragment until they reach simple, non-intersecting ("stable") configurations. Through extensive numerical study we characterize these attractor loop shapes including their length, velocity, kink, and cusp distributions. We find that an initial loop containing M harmonic modes will, on average, split into 3M stable loops. These stable loops are approximately described by the degenerate kinky loop, which is planar and rectangular, independently of the number of modes on the initial loop. This is confirmed by an analytic construction of a stable family of perturbed degenerate kinky loops. The average stable loop is also found to have a 40% chance of containing a cusp. We examine the properties of stable loops of different lengths and find only slight variation. Finally we develop a new analytic scheme to explicitly solve the string constraint equations.

  6. Shape of cosmic string loops

    NASA Astrophysics Data System (ADS)

    Copi, Craig J.; Vachaspati, Tanmay

    2011-01-01

    Complicated cosmic string loops will fragment until they reach simple, nonintersecting (“stable”) configurations. Through extensive numerical study we characterize these attractor loop shapes including their length, velocity, kink, and cusp distributions. We find that an initial loop containing M harmonic modes will, on average, split into 3M stable loops. These stable loops are approximately described by the degenerate kinky loop, which is planar and rectangular, independently of the number of modes on the initial loop. This is confirmed by an analytic construction of a stable family of perturbed degenerate kinky loops. The average stable loop is also found to have a 40% chance of containing a cusp. We examine the properties of stable loops of different lengths and find only slight variation. Finally we develop a new analytic scheme to explicitly solve the string constraint equations.

  7. Efficient Algorithms to Explore Conformation Spaces of Flexible Protein Loops

    PubMed Central

    Yao, Peggy; Dhanik, Ankur; Marz, Nathan; Propper, Ryan; Kou, Charles; Liu, Guanfeng; van den Bedem, Henry; Latombe, Jean-Claude; Halperin-Landsberg, Inbal; Altman, Russ Biagio

    2009-01-01

    Several applications in biology—e.g., incorporation of protein flexibility in ligand docking algorithms, interpretation of fuzzy X-ray crystallographic data, and homology modeling—require computing the internal parameters of a flexible fragment (usually, a loop) of a protein in order to connect its termini to the rest of the protein without causing any steric clash inside the loop and with the rest of the protein. One must often sample many such conformations in order to explore and adequately represent the conformational range of the studied loop. While sampling must be fast, it is made difficult by the fact that two conflicting constraints—kinematic closure and clash avoidance—must be satisfied concurrently. This paper describes two efficient and complementary sampling algorithms to explore the space of closed clash-free conformations of a flexible protein loop. The “seed sampling” algorithm samples broadly from this space, while the “deformation sampling” algorithm uses seed conformations as starting points to explore the conformation space around them at a finer grain. Computational results are presented for various loops ranging from 5 to 25 residues. More specific results also show that the combination of the sampling algorithms with a functional site prediction software (FEATURE) makes it possible to compute and recognize calcium-binding loop conformations. The sampling algorithms are implemented in a toolkit, called LoopTK, which is available at https://simtk.org/home/looptk. PMID:18989041

  8. Loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Chiou, Dah-Wei

    2015-12-01

    This paper presents an "in-a-nutshell" yet self-contained introductory review on loop quantum gravity (LQG) — a background-independent, nonperturbative approach to a consistent quantum theory of gravity. Instead of rigorous and systematic derivations, it aims to provide a general picture of LQG, placing emphasis on the fundamental ideas and their significance. The canonical formulation of LQG, as the central topic of the paper, is presented in a logically orderly fashion with moderate details, while the spin foam theory, black hole thermodynamics, and loop quantum cosmology are covered briefly. Current directions and open issues are also summarized.

  9. Wilson-loop instantons

    NASA Technical Reports Server (NTRS)

    Lee, Kimyeong; Holman, Richard; Kolb, Edward W.

    1987-01-01

    Wilson-loop symmetry breaking is considered on a space-time of the form M4 x K, where M4 is a four-dimensional space-time and K is an internal space with nontrivial and finite fundamental group. It is shown in a simple model that the different vacua obtained by breaking a non-Abelian gauge group by Wilson loops are separated in the space of gauge potentials by a finite energy barrier. An interpolating gauge configuration is then constructed between these vacua and shown to have minimum energy. Finally some implications of this construction are discussed.

  10. Livermore Compiler Analysis Loop Suite

    SciTech Connect

    Hornung, R. D.

    2013-03-01

    LCALS is designed to evaluate compiler optimizations and performance of a variety of loop kernels and loop traversal software constructs. Some of the loop kernels are pulled directly from "Livermore Loops Coded in C", developed at LLNL (see item 11 below for details of earlier code versions). The older suites were used to evaluate floating-point performances of hardware platforms prior to porting larger application codes. The LCALS suite is geared toward assissing C++ compiler optimizations and platform performance related to SIMD vectorization, OpenMP threading, and advanced C++ language features. LCALS contains 20 of 24 loop kernels from the older Livermore Loop suites, plus various others representative of loops found in current production appkication codes at LLNL. The latter loops emphasize more diverse loop constructs and data access patterns than the others, such as multi-dimensional difference stencils. The loops are included in a configurable framework, which allows control of compilation, loop sampling for execution timing, which loops are run and their lengths. It generates timing statistics for analysis and comparing variants of individual loops. Also, it is easy to add loops to the suite as desired.

  11. [Effect of phosphate upon calcium intestinal absorption (author's transl)].

    PubMed

    Fournier, P; Dupuis, Y; Digaud, A; Fournier, A

    1976-11-01

    Adult rats receive 5 to 50 mM CaCl2 solutions in which glycerophosphate or sodium diacid phosphate may be added in variable quantity. These solutions are administered by gavage or in situ ligatured jejunal loop. The inhibition of calcium absorption dependent on simultaneously administered phosphate doses is well characterized: high for the lowest concentration, the inhibiting effect of phosphate doses decreases more and more reaching a limit from which phosphate supplementation has no effect. These observations discarding an intervention of phosphate by calcium insolubilization seem to demonstrate that the control supplied by phosphates on calcium absorption is of enzymatic character. Facts related to the respective effects of calcium and phosphates on the action of alkaline phosphatases lead to discuss a possible intervention of these enzymes upon calcium transfer.

  12. CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING IN CENTER, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING IN CENTER, CALCIUM CHLORIDE STORAGE BUILDING ON RIGHT WITH SA (SODA ASH) BUILDING IN RIGHT BACKGROUND. - Solvay Process Company, Calcium Chloride Plant, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

  13. Mashup the OODA Loop

    DTIC Science & Technology

    2008-06-01

    MTR070365 MITRE TECHNICAL REPORT Mashup the OODA Loop June 2008 Jeffrey E. Heier-E305 C2C Center – MITRE New Jersey Sponsor: Sponsor Name...ES) The MITRE Corporation, C2C Center,260 Industrial Way West,Eatontown,NJ,07724 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING

  14. Closing the Loop Sampler.

    ERIC Educational Resources Information Center

    California Integrated Waste Management Board, Sacramento.

    Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

  15. Closing the Loop Sampler.

    ERIC Educational Resources Information Center

    California Integrated Waste Management Board, Sacramento.

    Closing the Loop (CTL) is a science curriculum designed to introduce students to integrated waste management through awareness. This document presents five lesson plans focusing on developing an understanding of natural resources, solid wastes, conservation, and the life of landfills. Contents include: (1) "What Are Natural Resources?"; (2)…

  16. Reversible hysteresis loop tuning

    NASA Astrophysics Data System (ADS)

    Berger, A.; Binek, Ch.; Margulies, D. T.; Moser, A.; Fullerton, E. E.

    2006-02-01

    We utilize antiferromagnetically coupled bilayer structures to magnetically tune hysteresis loop properties. Key element of this approach is the non-overlapping switching field distribution of the two magnetic layers that make up the system: a hard magnetic CoPtCrB layer (HL) and a soft magnetic CoCr layer (SL). Both layers are coupled antiferromagnetically through an only 0.6-nm-thick Ru interlayer. The non-overlapping switching field distribution allows the measurement of magnetization reversal in the SL at low fields while keeping the magnetization state of the HL unperturbed. Applying an appropriate high field or high field sequence changes the magnetic state of the HL, which then influences the SL magnetization reversal due to the interlayer coupling. In this way, the position and shape of the SL hysteresis loop can be changed or tuned in a fully reversible and highly effective manner. Here, we study specifically how the SL hysteresis loop characteristics change as we move the HL through an entire high field hysteresis loop sequence.

  17. Closing the Assessment Loop

    ERIC Educational Resources Information Center

    Banta, Trudy W.; Blaich, Charles

    2011-01-01

    Accreditors, speakers at assessment conferences, and campus leaders all decry the fact that too few faculty are closing the loop--that is, studying assessment findings to see what improvements might be suggested and taking the appropriate steps to make them. This is difficult enough with locally developed measures; adding the need to interpret…

  18. NETL - Chemical Looping Reactor

    SciTech Connect

    2013-07-24

    NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.

  19. NETL - Chemical Looping Reactor

    ScienceCinema

    None

    2016-07-12

    NETL's Chemical Looping Reactor unit is a high-temperature integrated CLC process with extensive instrumentation to improve computational simulations. A non-reacting test unit is also used to study solids flow at ambient temperature. The CLR unit circulates approximately 1,000 pounds per hour at temperatures around 1,800 degrees Fahrenheit.

  20. [Do cows drink calcium?].

    PubMed

    Geishauser, T; Lechner, S; Plate, I; Heidemann, B

    2008-03-01

    The objective of this study was to investigate how well cows drink the Propeller calcium drink, and it's effect on blood calcium concentration. Drinking was tested in 120 cows right after calving, before cows drank anything else. 60 cows each were offered 20 liters of Propeller calcium drink or 20 liters of water. Cows drank the Propeller as good as water. 72% of all cows drank all 20 liters, 18% drank on average 8.2 liters and 10% drank less than 1 liter. Blood calcium concentration was studied in 16 cows right after calving. Eight cows each were offered 20 liters of Propeller calcium drink or no calcium drink. Blood calcium significantly increased ten minutes after Propeller intake and stayed significantly elevated for 24 hours. Without calcium drink blood calcium levels decreased significantly. Advantages of the new Propeller calcium drink over calcium gels or boli could be that cows now drink calcium themselves and that the Propeller increases blood calcium concentration rapidly and long lasting.

  1. Effect of cadmium administration on intestinal calcium absorption and vitamin D-dependent calcium-binding protein

    SciTech Connect

    Fullmer, C.S.; Oku, T.; Wasserman, R.H.

    1980-08-01

    The effects of cadmium on intestinal calcium absorption and calcium-binding protein (CaBP) were investigated in chicks by means of the in situ ligated duodenal loop technique. Dietary cadmium, administered in the feed or by gastric intubation, resulted in significant declines in intestinal calcium absorption and mucosal calcium-binding protein concentrations. Cadmium chloride injected directly into the ligated loop of naive chicks also diminished calcium absorption and CaBP concentrations in an apparently dose-response related fashion. No adverse effects of cadmium administration on either the 25- or 1..cap alpha..-hydroxylation reactions of vitamin D were observed. While the general effect of cadmium administration was a reduction in intestinal calcium absorption, plasma calcium levels were consistently elevated in Cd-treated chicks, with the exception of those also maintained on diets low in Ca. The results indicate that cadmium toxicity exerts at least two effects on Ca metabolism, one at the intestinal level and another at the level of the bone, kidney, or both.

  2. Operation of a cyclonic preheater in the Ca-looping for CO2 capture.

    PubMed

    Martínez, Ana; Lara, Yolanda; Lisbona, Pilar; Romeo, Luis M

    2013-10-01

    Calcium looping is an emerging technology for CO2 capture that makes use of the calcium oxide as a sorbent. One of its main issues is the significant energy consumption in the calciner, where the regeneration of the sorbent takes place. Nevertheless, as a high temperature looping technology, the surplus heat flows may be used to reduce the energy needs in this reactor. The addition of a cyclonic preheater similar to those used in the cement industry is proposed in this work. A calcium looping system was modeled and simulated to assess the advantages and disadvantages of the inclusion of a cyclonic preheater. Despite the negative effect on the maximum average capture capacity of the sorbent, a reduction on the coal and oxygen consumptions and on the extra CO2 generated in the calciner is obtained.

  3. Calcium in diet

    MedlinePlus

    ... Salmon and sardines canned with their soft bones Almonds, Brazil nuts, sunflower seeds, tahini, and dried beans ... greens = 100 mg of calcium ¼ cup of almonds = 100 mg of calcium 1 medium orange = 50 ...

  4. Integumentary loss of calcium.

    PubMed

    Chu, J Y; Margen, S; Calloway, D H; Costa, F M

    1979-08-01

    Integumentary calcium loss was studied in 16 healthy young men. The daily loss by the 16 ambulatory but relatively sedentary young men in 52 determinations of 6-day periods each was 8.7 +/- 1.9 mg/m2 per day (average 15.8 mg/man per day). The amount lost was not influenced by calcium intake (0.1 to 2.3 g/day). In contrast to urinary calcium excretion, which is directly related to protein intake, there was no significant change in integumentary calcium loss with varying protein intakes (1 to 96 g nitrogen per day). No compensatory relationship between urinary and integumentary calcium excretion was noted. During strenuous exercise calcium loss increased to an average of 25 mg in 40 min. There was no compensatory decrease in urinary excretion on the day of strenuous exercise. It was also noted that integumentary calcium loss was not affected by general calcium balance.

  5. Calcium Pyrophosphate Deposition (CPPD)

    MedlinePlus

    ... too. Proper diagnosis depends on detecting calcium pyrophosphate crystals in the fluid of an affected joint. CPPD ... using a microscope to see small calcium pyrophosphate crystals in joint fluid. Anti-inflammatory medications reduce pain ...

  6. COLD TEST LOOP INTEGRATED TEST LOOP RESULTS

    SciTech Connect

    Abraham, TJ

    2003-10-22

    A testing facility (Cold Test Loop) was constructed and operated to demonstrate the efficacy of the Accelerated Waste Retrieval (AWR) Project's planned sluicing approach to the remediation of Silos 1 and 2 at the Fernald Environmental Management Project near Cincinnati, Ohio. The two silos contain almost 10,000 tons of radium-bearing low-level waste, which consists primarily of solids of raffinates from processing performed on ores from the Democratic Republic of Congo (commonly referred to as ''Belgium Congo ores'') for the recovery of uranium. These silos are 80 ft in diameter, 36 ft high to the center of the dome, and 26.75 ft to the top of the vertical side walls. The test facility contained two test systems, each designed for a specific purpose. The first system, the Integrated Test Loop (ITL), a near-full-scale plant including the actual equipment to be installed at the Fernald Site, was designed to demonstrate the sluicing operation and confirm the selection of a slurry pump, the optimal sluicing nozzle operation, and the preliminary design material balance. The second system, the Component Test Loop (CTL), was designed to evaluate many of the key individual components of the waste retrieval system over an extended run. The major results of the initial testing performed during July and August 2002 confirmed that the AWR approach to sluicing was feasible. The ITL testing confirmed the following: (1) The selected slurry pump (Hazleton 3-20 type SHW) performed well and is suitable for AWR application. However, the pump's motor should be upgraded to a 200-hp model and be driven by a 150-hp variable-frequency drive (VFD). A 200-hp VFD is not much more expensive and would allow the pump to operate at full speed. (2) The best nozzle performance was achieved by using 15/16-in. nozzles operated alternately. This configuration appeared to most effectively mine the surrogate. (3) The Solartron densitometer, which was tested as an alternative mass flow measurement

  7. Role of claudins in renal calcium handling.

    PubMed

    Negri, Armando Luis

    2015-01-01

    Paracellular channels occurring in tight junctions play a major role in transepithelial ionic flows. This pathway includes a high number of proteins, such as claudins. Within renal epithelium, claudins result in an ionic selectivity in tight junctions. Ascending thick limb of loop of Henle (ATLH) is the most important segment for calcium reabsorption in renal tubules. Its cells create a water-proof barrier, actively transport sodium and chlorine through a transcellular pathway, and provide a paracellular pathway for selective calcium reabsorption. Several studies have led to a model of paracellular channel consisting of various claudins, particularly claudin-16 and 19. Claudin-16 mediates cationic paracellular permeability in ATLH, whereas claudin-19 increases cationic selectivity of claudin-16 by blocking anionic permeability. Recent studies have shown that claudin-14 promoting activity is only located in ATLH. When co-expressed with claudin-16, claudin-14 inhibits the permeability of claudin-16 and reduces paracellular permeability to calcium. Calcium reabsorption process in ATLH is closely regulated by calcium sensor receptor (CaSR), which monitors circulating Ca levels and adjusts renal excretion rate accordingly. Two microRNA, miR-9 and miR-374, are directly regulated by CaSR. Thus, miR-9 and miR-374 suppress mRNA translation for claudin-14 and induce claudin-14 decline. Copyright © 2015 The Author. Published by Elsevier España, S.L.U. All rights reserved.

  8. Calcium and Mitosis

    NASA Technical Reports Server (NTRS)

    Hepler, P.

    1983-01-01

    Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

  9. Calcium and Mitosis

    NASA Technical Reports Server (NTRS)

    Hepler, P.

    1983-01-01

    Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

  10. Efficient algorithms to explore conformation spaces of flexible protein loops.

    PubMed

    Yao, Peggy; Dhanik, Ankur; Marz, Nathan; Propper, Ryan; Kou, Charles; Liu, Guanfeng; van den Bedem, Henry; Latombe, Jean-Claude; Halperin-Landsberg, Inbal; Altman, Russ Biagio

    2008-01-01

    Several applications in biology - e.g., incorporation of protein flexibility in ligand docking algorithms, interpretation of fuzzy X-ray crystallographic data, and homology modeling - require computing the internal parameters of a flexible fragment (usually, a loop) of a protein in order to connect its termini to the rest of the protein without causing any steric clash. One must often sample many such conformations in order to explore and adequately represent the conformational range of the studied loop. While sampling must be fast, it is made difficult by the fact that two conflicting constraints - kinematic closure and clash avoidance - must be satisfied concurrently. This paper describes two efficient and complementary sampling algorithms to explore the space of closed clash-free conformations of a flexible protein loop. The "seed sampling" algorithm samples broadly from this space, while the "deformation sampling" algorithm uses seed conformations as starting points to explore the conformation space around them at a finer grain. Computational results are presented for various loops ranging from 5 to 25 residues. More specific results also show that the combination of the sampling algorithms with a functional site prediction software (FEATURE) makes it possible to compute and recognize calcium-binding loop conformations. The sampling algorithms are implemented in a toolkit (LoopTK), which is available at https://simtk.org/home/looptk.

  11. Classical physics and quantum loops.

    PubMed

    Holstein, Barry R; Donoghue, John F

    2004-11-12

    The standard picture of the loop expansion associates a factor of variant Planck's over 2pi with each loop, suggesting that the tree diagrams are to be associated with classical physics, while loop effects are quantum mechanical in nature. We discuss counterexamples wherein classical effects arise from loop diagrams and display the relationship between the classical terms and the long range effects of massless particles.

  12. Loop Heat Pipes and Capillary Pumped Loops: An Applications Perspective

    NASA Technical Reports Server (NTRS)

    Butler, Dan; Ku, Jentung; Swanson, Theodore; Obenschain, Arthur F. (Technical Monitor)

    2001-01-01

    Capillary pumped loops (CPLS) and loop heat pipes (LHPS) are versatile two-phase heat transfer devices which have recently gained increasing acceptance in space applications. Both systems work based on the same principles and have very similar designs. Nevertheless, some differences exist in the construction of the evaporator and the hydro-accumulator, and these differences lead to very distinct operating characteristics for each loop. This paper presents comparisons of the two loops from an applications perspective, and addresses their impact on spacecraft design, integration, and test. Some technical challenges and issues for both loops are also addressed.

  13. Aurora Australis, Sinuous Loop

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This view of the Aurora Australis or Southern Lights (location unknown) shows a sinuous looping band of airglow above the Earth Limb. Calculated to be in the 80 - 120 km altitude region, auroral activity is due to exitation of atomic oxygen in the upper atmosphere by radiation from the van Allen Radiation Belts and is most common above the 65 degree north and south latitude range during the spring and fall of the year.

  14. Loop Quantum Cosmology.

    PubMed

    Bojowald, Martin

    2005-01-01

    Quantum gravity is expected to be necessary in order to understand situations where classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical space-time inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding space-time is then modified. One particular realization is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. Main effects are introduced into effective classical equations which allow to avoid interpretational problems of quantum theory. They give rise to new kinds of early universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function which allows to extend space-time beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of space-time arising in loop quantum gravity and its application to cosmology sheds new light on more general issues such as time.

  15. Loop Quantum Cosmology.

    PubMed

    Bojowald, Martin

    2008-01-01

    Quantum gravity is expected to be necessary in order to understand situations in which classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical spacetime inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding spacetime is then modified. One particular theory is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. The main effects are introduced into effective classical equations, which allow one to avoid the interpretational problems of quantum theory. They give rise to new kinds of early-universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function, which allows an extension of quantum spacetime beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of spacetime arising in loop quantum gravity and its application to cosmology sheds light on more general issues, such as the nature of time.

  16. Calcium bioavailability from calcium fortified food products.

    PubMed

    Kohls, K

    1991-08-01

    The calcium balance of 12 presumed healthy human young adult subjects was assessed. Subjects consumed a constant laboratory-controlled diet supplemented with one of four calcium-fortified food products: orange juice (OJ), milk (M), experimental pasteurized processed cheese (T), soda (S), or a calcium carbonate plus vitamin D tablet (CC). Study length was 6 weeks with seven-day experimental periods (2-days allowed for adjustment with 5-days combined for purposes of analysis). All urine and fecal samples were collected by the subjects for the duration of the study. Blood samples were drawn at the end of each experimental period. Urine and fecal calcium contents were determined. Blood samples were analyzed for alkaline phosphatase. Results of this study indicate a higher fecal calcium content (mg/day) when subjects consumed CC and T, and when subjects consumed self-selected diets, than when given S, M, or OJ. Urinary calcium excretion was significantly lower when subjects consumed OJ than when they consumed M, T, or their self-selected diets. A significantly larger positive calcium balance was demonstrated when subjects consumed OJ as compared to T. Fecal transmit time did not vary significantly. Serum alkaline phosphatase was significantly lower when subjects consumed T than when they consumed self-selected diets.

  17. Cosmic string loop microlensing

    NASA Astrophysics Data System (ADS)

    Bloomfield, Jolyon K.; Chernoff, David F.

    2014-06-01

    Cosmic superstring loops within the galaxy microlens background point sources lying close to the observer-string line of sight. For suitable alignments, multiple paths coexist and the (achromatic) flux enhancement is a factor of two. We explore this unique type of lensing by numerically solving for geodesics that extend from source to observer as they pass near an oscillating string. We characterize the duration of the flux doubling and the scale of the image splitting. We probe and confirm the existence of a variety of fundamental effects predicted from previous analyses of the static infinite straight string: the deficit angle, the Kaiser-Stebbins effect, and the scale of the impact parameter required to produce microlensing. Our quantitative results for dynamical loops vary by O(1) factors with respect to estimates based on infinite straight strings for a given impact parameter. A number of new features are identified in the computed microlensing solutions. Our results suggest that optical microlensing can offer a new and potentially powerful methodology for searches for superstring loop relics of the inflationary era.

  18. Verification of Loop Diagnostics

    NASA Technical Reports Server (NTRS)

    Winebarger, A.; Lionello, R.; Mok, Y.; Linker, J.; Mikic, Z.

    2014-01-01

    Many different techniques have been used to characterize the plasma in the solar corona: density-sensitive spectral line ratios are used to infer the density, the evolution of coronal structures in different passbands is used to infer the temperature evolution, and the simultaneous intensities measured in multiple passbands are used to determine the emission measure. All these analysis techniques assume that the intensity of the structures can be isolated through background subtraction. In this paper, we use simulated observations from a 3D hydrodynamic simulation of a coronal active region to verify these diagnostics. The density and temperature from the simulation are used to generate images in several passbands and spectral lines. We identify loop structures in the simulated images and calculate the loop background. We then determine the density, temperature and emission measure distribution as a function of time from the observations and compare with the true temperature and density of the loop. We find that the overall characteristics of the temperature, density, and emission measure are recovered by the analysis methods, but the details of the true temperature and density are not. For instance, the emission measure curves calculated from the simulated observations are much broader than the true emission measure distribution, though the average temperature evolution is similar. These differences are due, in part, to inadequate background subtraction, but also indicate a limitation of the analysis methods.

  19. Loops of Jupiter

    NASA Astrophysics Data System (ADS)

    Opolski, Antoni

    2014-12-01

    Professor Antoni Opolski was actively interested in astronomy after his retirement in 1983. He especially liked to study the works of the famous astronomer Copernicus getting inspiration for his own work. Opolski started his work on planetary loops in 2011 continuing it to the end of 2012 . During this period calculations, drawings, tables, and basic descriptions of all the planets of the Solar System were created with the use of a piece of paper and a pencil only. In 2011 Antoni Opolski asked us to help him in editing the manuscript and preparing it for publication. We have been honored having the opportunity to work on articles on planetary loops with Antoni Opolski in his house for several months. In the middle of 2012 the detailed material on Jupiter was ready. However, professor Opolski improved the article by smoothing the text and preparing new, better drawings. Finally the article ''Loops of Jupiter'', written by the 99- year old astronomer, was published in the year of his 100th birthday.

  20. Chemical Looping Combustion Kinetics

    SciTech Connect

    Edward Eyring; Gabor Konya

    2009-03-31

    One of the most promising methods of capturing CO{sub 2} emitted by coal-fired power plants for subsequent sequestration is chemical looping combustion (CLC). A powdered metal oxide such as NiO transfers oxygen directly to a fuel in a fuel reactor at high temperatures with no air present. Heat, water, and CO{sub 2} are released, and after H{sub 2}O condensation the CO{sub 2} (undiluted by N{sub 2}) is ready for sequestration, whereas the nickel metal is ready for reoxidation in the air reactor. In principle, these processes can be repeated endlessly with the original nickel metal/nickel oxide participating in a loop that admits fuel and rejects ash, heat, and water. Our project accumulated kinetic rate data at high temperatures and elevated pressures for the metal oxide reduction step and for the metal reoxidation step. These data will be used in computational modeling of CLC on the laboratory scale and presumably later on the plant scale. The oxygen carrier on which the research at Utah is focused is CuO/Cu{sub 2}O rather than nickel oxide because the copper system lends itself to use with solid fuels in an alternative to CLC called 'chemical looping with oxygen uncoupling' (CLOU).

  1. Coronal Loops: Isothermal or Multithermal?

    NASA Astrophysics Data System (ADS)

    Kimble, Jason; Schmelz, J. T.; Nasraoui, K.; Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E.

    2007-05-01

    The coronal loop data used for this analysis were taken on 2003 January 17 at 14:24:45 UT by the Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric Observatory. We use the Chianti atomic physics data base and the hybrid coronal abundances to determine temperatures and densities for positions along several loops. The traditional method used to create our differential emission measure (DEM) curves has been forward folding, but we are now using both emission measure loci plots and DEM automatic inversion to support and confirm the original conclusions. In this poster, we will look specifically at the emission measure loci analysis of three loops visible in the CDS data set. We find different results for each of these loops. One of the loops seems to be composed of isothermal plasma with Log T = 5.8 MK. The temperature does not appear to change with position, from the footpoint to the loop leg. Unfortunately, the loop top is outside the CDS field of view. Each pixel examined in the second loop seems to require a multithermal DEM distribution. For the third loop, the temperature increases and the density appears to decrease with loop height, reminiscent of traditional hydrostatic loop models. Solar physics research at the University of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G.

  2. An excitatory GABA loop operating in vivo

    PubMed Central

    Astorga, Guadalupe; Bao, Jin; Marty, Alain; Augustine, George J.; Franconville, Romain; Jalil, Abdelali; Bradley, Jonathan; Llano, Isabel

    2015-01-01

    While it has been proposed that the conventional inhibitory neurotransmitter GABA can be excitatory in the mammalian brain, much remains to be learned concerning the circumstances and the cellular mechanisms governing potential excitatory GABA action. Using a combination of optogenetics and two-photon calcium imaging in vivo, we find that activation of chloride-permeable GABAA receptors in parallel fibers (PFs) of the cerebellar molecular layer of adult mice causes parallel fiber excitation. Stimulation of PFs at submaximal stimulus intensities leads to GABA release from molecular layer interneurons (MLIs), thus creating a positive feedback loop that enhances excitation near the center of an activated PF bundle. Our results imply that elevated chloride concentration can occur in specific intracellular compartments of mature mammalian neurons and suggest an excitatory role for GABAA receptors in the cerebellar cortex of adult mice. PMID:26236197

  3. Coupled dual loop absorption heat pump

    DOEpatents

    Sarkisian, Paul H.; Reimann, Robert C.; Biermann, Wendell J.

    1985-01-01

    A coupled dual loop absorption system which utilizes two separate complete loops. Each individual loop operates at three temperatures and two pressures. This low temperature loop absorber and condenser are thermally coupled to the high temperature loop evaporator, and the high temperature loop condenser and absorber are thermally coupled to the low temperature generator.

  4. Stretch-activated calcium channels relay fast calcium waves propagated by calcium-induced calcium influx.

    PubMed

    Jaffe, Lionel F

    2007-03-01

    For nearly 30 years, fast calcium waves have been attributed to a regenerative process propagated by CICR (calcium-induced calcium release) from the endoplasmic reticulum. Here, I propose a model containing a new subclass of fast calcium waves which is propagated by CICI (calcium-induced calcium influx) through the plasma membrane. They are called fast CICI waves. These move at the order of 100 to 1000 microm/s (at 20 degrees C), rather than the order of 3 to 30 microm/s found for CICR. Moreover, in this proposed subclass, the calcium influx which drives calcium waves is relayed by stretch-activated calcium channels. This model is based upon reports from approx. 60 various systems. In seven of these reports, calcium waves were imaged, and, in five of these, evidence was presented that these waves were regenerated by CICI. Much of this model involves waves that move along functioning flagella and cilia. In these systems, waves of local calcium influx are thought to cause waves of local contraction by inducing the sliding of dynein or of kinesin past tubulin microtubules. Other cells which are reported to exhibit waves, which move at speeds in the fast CICI range, include ones from a dozen protozoa, three polychaete worms, three molluscs, a bryozoan, two sea urchins, one arthropod, four insects, Amphioxus, frogs, two fish and a vascular plant (Equisetum), together with numerous healthy, as well as cancerous, mammalian cells, including ones from human. In two of these systems, very gentle local mechanical stimulation is reported to initiate waves. In these non-flagellar systems, the calcium influxes are thought to speed the sliding of actinomyosin filaments past each other. Finally, I propose that this mechanochemical model could be tested by seeing if gentle mechanical stimulation induces waves in more of these systems and, more importantly, by imaging the predicted calcium waves in more of them.

  5. Closing the loop.

    PubMed

    Dassau, E; Atlas, E; Phillip, M

    2011-02-01

    Closed-loop algorithms can be found in every aspect of everyday modern life. Automation and control are used constantly to provide safety and to improve quality of life. Closed-loop systems and algorithms can be found in home appliances, automobiles, aviation and more. Can one imagine nowadays driving a car without ABS, cruise control or even anti-sliding control? Similar principles of automation and control can be used in the management of diabetes mellitus (DM). The idea of an algorithmic/technological way to control glycaemia is not new and has been researched for more than four decades. However, recent improvements in both glucose-sensing technology and insulin delivery together with advanced control and systems engineering made this dream of an artificial pancreas possible. The artificial pancreas may be the next big step in the treatment of DM since the use of insulin analogues. An artificial pancreas can be described as internal or external devices that use continuous glucose measurements to automatically manage exogenous insulin delivery with or without other hormones in an attempt to restore glucose regulation in individuals with DM using a control algorithm. This device as described can be internal or external; can use different types of control algorithms with bi-hormonal or uni-hormonal design; and can utilise different ways to administer them. The different designs and implementations have transitioned recently from in silico simulations to clinical evaluation stage with practical applications in mind. This may mark the beginning of a new era in diabetes management with the introduction of semi-closed-loop systems that can prevent or minimise nocturnal hypoglycaemia, to hybrid systems that will manage blood glucose (BG) levels with minimal user intervention to finally fully automated systems that will take the user out of the loop. More and more clinical trials will be needed for the artificial pancreas to become a reality but initial encouraging

  6. Bright Loops at 171

    NASA Technical Reports Server (NTRS)

    2007-01-01

    STEREO was able to capture bright loops in exquisite detail as they were arcing above an active region (May 26, 2007) over an 18 hour period. What we are actually seeing are charged particles spinning along magnetic field lines that extend above the Sun's surface. Active regions are areas of intense magnetic activity and often the source of solar storms. In fact, the clip ends with a flourish in which a small coronal mass ejection (CME) blows out into space. This is from the STEREO Ahead spacecraft at the 171 Angstroms wavelength in extreme ultraviolet light.

  7. Bright Arcing Loops

    NASA Image and Video Library

    2016-06-27

    Several arcing loops rotated into view and swirled above an active region, which gave us a nice profile view of the action (June 26-27, 2016). The arcing plasma is tracing magnetic field lines extending out from the active region. Some darker matter also jiggled back and forth near the active region as well, pulled about by magnetic forces. At one point a lick of plasma pushed its way out from the region but quickly fell back into the sun. The images were taken in a wavelength of extreme ultraviolet light. Movies are also available at the Photojournal. http://photojournal.jpl.nasa.gov/catalog/PIA20882

  8. Optical parametric loop mirror

    NASA Astrophysics Data System (ADS)

    Mori, K.; Morioka, T.; Saruwatari, M.

    1995-06-01

    A novel configuration for four-wave mixing (FWM) is proposed that offers the remarkable feature of inherently separating the FWM wave from the input pump and signal waves and suppressing their background amplified stimulated emission without optical filtering. In the proposed configuration, an optical parametric loop mirror, two counterpropagating FWM waves generated in a Sagnac interferometer interfere with a relative phase difference that is introduced deliberately. FWM frequency-conversion experiments in a polarization-maintaining fiber achieved more than 35 dB of input-wave suppression against the FWM wave.

  9. Bright Loops at 171

    NASA Technical Reports Server (NTRS)

    2007-01-01

    STEREO was able to capture bright loops in exquisite detail as they were arcing above an active region (May 26, 2007) over an 18 hour period. What we are actually seeing are charged particles spinning along magnetic field lines that extend above the Sun's surface. Active regions are areas of intense magnetic activity and often the source of solar storms. In fact, the clip ends with a flourish in which a small coronal mass ejection (CME) blows out into space. This is from the STEREO Ahead spacecraft at the 171 Angstroms wavelength in extreme ultraviolet light.

  10. Loop expansion and the bosonic representation of loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Bianchi, E.; Guglielmon, J.; Hackl, L.; Yokomizo, N.

    2016-10-01

    We introduce a new loop expansion that provides a resolution of the identity in the Hilbert space of loop quantum gravity on a fixed graph. We work in the bosonic representation obtained by the canonical quantization of the spinorial formalism. The resolution of the identity gives a tool for implementing the projection of states in the full bosonic representation onto the space of solutions to the Gauss and area matching constraints of loop quantum gravity. This procedure is particularly efficient in the semiclassical regime, leading to explicit expressions for the loop expansions of coherent, heat kernel and squeezed states.

  11. Ekpyrotic loop quantum cosmology

    SciTech Connect

    Wilson-Ewing, Edward

    2013-08-01

    We consider the ekpyrotic paradigm in the context of loop quantum cosmology. In loop quantum cosmology the classical big-bang singularity is resolved due to quantum gravity effects, and so the contracting ekpyrotic branch of the universe and its later expanding phase are connected by a smooth bounce. Thus, it is possible to explicitly determine the evolution of scalar perturbations, from the contracting ekpyrotic phase through the bounce and to the post-bounce expanding epoch. The possibilities of having either one or two scalar fields have been suggested for the ekpyrotic universe, and both cases will be considered here. In the case of a single scalar field, the constant mode of the curvature perturbations after the bounce is found to have a blue spectrum. On the other hand, for the two scalar field ekpyrotic model where scale-invariant entropy perturbations source additional terms in the curvature perturbations, the power spectrum in the post-bounce expanding cosmology is shown to be nearly scale-invariant and so agrees with observations.

  12. High temperature storage loop :

    SciTech Connect

    Gill, David Dennis; Kolb, William J.

    2013-07-01

    A three year plan for thermal energy storage (TES) research was created at Sandia National Laboratories in the spring of 2012. This plan included a strategic goal of providing test capability for Sandia and for the nation in which to evaluate high temperature storage (>650ÀC) technology. The plan was to scope, design, and build a flow loop that would be compatible with a multitude of high temperature heat transfer/storage fluids. The High Temperature Storage Loop (HTSL) would be reconfigurable so that it was useful for not only storage testing, but also for high temperature receiver testing and high efficiency power cycle testing as well. In that way, HTSL was part of a much larger strategy for Sandia to provide a research and testing platform that would be integral for the evaluation of individual technologies funded under the SunShot program. DOEs SunShot program seeks to reduce the price of solar technologies to 6/kWhr to be cost competitive with carbon-based fuels. The HTSL project sought to provide evaluation capability for these SunShot supported technologies. This report includes the scoping, design, and budgetary costing aspects of this effort

  13. Accelerating the loop expansion

    SciTech Connect

    Ingermanson, R.

    1986-07-29

    This thesis introduces a new non-perturbative technique into quantum field theory. To illustrate the method, I analyze the much-studied phi/sup 4/ theory in two dimensions. As a prelude, I first show that the Hartree approximation is easy to obtain from the calculation of the one-loop effective potential by a simple modification of the propagator that does not affect the perturbative renormalization procedure. A further modification then susggests itself, which has the same nice property, and which automatically yields a convex effective potential. I then show that both of these modifications extend naturally to higher orders in the derivative expansion of the effective action and to higher orders in the loop-expansion. The net effect is to re-sum the perturbation series for the effective action as a systematic ''accelerated'' non-perturbative expansion. Each term in the accelerated expansion corresponds to an infinite number of terms in the original series. Each term can be computed explicitly, albeit numerically. Many numerical graphs of the various approximations to the first two terms in the derivative expansion are given. I discuss the reliability of the results and the problem of spontaneous symmetry-breaking, as well as some potential applications to more interesting field theories. 40 refs.

  14. 2 π -flux loop semimetals

    NASA Astrophysics Data System (ADS)

    Li, Linhu; Chesi, Stefano; Yin, Chuanhao; Chen, Shu

    2017-08-01

    We introduce a model of 2 π -flux loop semimetals which holds nodal loops described by a winding number ν =2 . By adding some extra terms, this model can be transformed into a recently discovered Hopf-link semimetal, and the symmetries distinguishing these two types of semimetals are studied. We also propose a simpler physical implementation of 2 π -flux loops and of Hopf-link semimetals which only involves nearest-neighbor hoppings, although in the presence of spin-orbit interactions. Finally, we investigate the Floquet properties of the 2 π -flux loop, and find that such a loop may be driven into two separated π -flux loops or four Weyl points by light with circular polarization in certain directions.

  15. Calcium hydroxide poisoning

    MedlinePlus

    These products contain calcium hydroxide: Cement Limewater Many industrial solvents and cleaners (hundreds to thousands of construction products, flooring strippers, brick cleaners, cement thickening products, and many ...

  16. Calcium Channel Blockers

    MedlinePlus

    ... calcium channel blockers interact with grapefruit products. References Kaplan NM, et al. Treatment of hypertension: Drug therapy. In: Kaplan's Clinical Hypertension. 11th ed. Philadelphia, Pa.: Wolters Kluwer ...

  17. Calcium: total or ionized?

    PubMed

    Schenck, Patricia A; Chew, Dennis J

    2008-05-01

    Measurement of serum total calcium (tCa) has been relied on for assessment of calcium status, despite the fact that it is the ionized calcium (iCa) fraction that has biologic activity. Serum tCa does not accurately predict iCa status in many clinical conditions. For accurate assessment of iCa status, iCa should be directly measured. Anaerobic measurement of serum iCa under controlled conditions provides the most reliable assessment of calcium status; aerobic measurement of iCa with species-specific pH correction is highly correlated with anaerobic measurements.

  18. The double loop mattress suture

    PubMed Central

    Biddlestone, John; Samuel, Madan; Creagh, Terry; Ahmad, Tariq

    2014-01-01

    An interrupted stitch type with favorable tissue characteristics will reduce local wound complications. We describe a novel high-strength, low-tension repair for the interrupted closure of skin, cartilage, and muscle, the double loop mattress stitch, and compare it experimentally with other interrupted closure methods. The performance of the double loop mattress technique in porcine cartilage and skeletal muscle is compared with the simple, mattress, and loop mattress interrupted sutures in both a novel porcine loading chamber and mechanical model. Wound apposition is assessed by electron microscopy. The performance of the double loop mattress in vivo was confirmed using a series of 805 pediatric laparotomies/laparoscopies. The double loop mattress suture is 3.5 times stronger than the loop mattress in muscle and 1.6 times stronger in cartilage (p ≤ 0.001). Additionally, the double loop mattress reduces tissue tension by 66% compared with just 53% for the loop mattress (p ≤ 0.001). Wound gapping is equal, and wound eversion appears significantly improved (p ≤ 0.001) compared with the loop mattress in vitro. In vivo, the double loop mattress performs as well as the loop mattress and significantly better than the mattress stitch in assessments of wound eversion and dehiscence. There were no episodes of stitch extrusion in our series of patients. The mechanical advantage of its intrinsic pulley arrangement gives the double loop mattress its favorable properties. Wound dehiscence is reduced because this stitch type is stronger and exerts less tension on the tissue than the mattress stitch. We advocate the use of this novel stitch wherever a high-strength, low-tension repair is required. These properties will enhance wound repair, and its application will be useful to surgeons of all disciplines. PMID:24698436

  19. Enhancement of surface nonwettability by grafting loops.

    PubMed

    Pei, Han-Wen; Liu, Xiao-Li; Liu, Hong; Zhu, You-Liang; Lu, Zhong-Yuan

    2017-02-08

    We present a computer simulation study on the nonwettability of a flat surface tethered with deformable looped polymer chains. Two kinds of loops are studied: monodispersed loops (loops with the same length) and polydispersed loops (loops with different lengths). Both kinds of loops include two arrangements: with regularly tethered sites and with randomly tethered sites. Regularly grafted loops form typical grooves on the surface, while randomly grafted loops form a more rugged surface. For monodispersed loops, we analyze the factors that influence the nonwettability when varying the rigidity of the loops. The loops are divided into two categories based on their rigidity according to our previous analysis procedure (Phys. Chem. Chem. Phys., 2016, 18, 18767-18775): rigid loops and flexible loops. It is found that the loop can partially form a re-entrant-like structure, which is helpful to increase the nonwettability of the surface. The surfaces with grafted loops have increased nonwettability, especially those grafted with flexible chains. However, the contact angle on the loop structure cannot further increase for the rigid chains due to a large top layer density (Phys. Chem. Chem. Phys., 2016, 18, 18767-18775). For polydispersed loops, the contact angle is highly related to the rigidity of the long loops that contact the droplet. Different from monodispersed loops, the mechanism of the nonwettability of polydispersed loops is attributed to the supporting ability (rigidity) of long loops.

  20. Unstable anisotropic loop quantum cosmology

    SciTech Connect

    Nelson, William; Sakellariadou, Mairi

    2009-09-15

    We study stability conditions of the full Hamiltonian constraint equation describing the quantum dynamics of the diagonal Bianchi I model in the context of loop quantum cosmology. Our analysis has shown robust evidence of an instability in the explicit implementation of the difference equation, implying important consequences for the correspondence between the full loop quantum gravity theory and loop quantum cosmology. As a result, one may question the choice of the quantization approach, the model of lattice refinement, and/or the role of the ambiguity parameters; all these should, in principle, be dictated by the full loop quantum gravity theory.

  1. Loop Heat Pipe Startup Behaviors

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    2016-01-01

    A loop heat pipe must start successfully before it can commence its service. The startup transient represents one of the most complex phenomena in the loop heat pipe operation. This paper discusses various aspects of loop heat pipe startup behaviors. Topics include the four startup scenarios, the initial fluid distribution between the evaporator and reservoir that determines the startup scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power startup, and methods to enhance the startup success. Also addressed are the pressure spike and pressure surge during the startup transient, and repeated cycles of loop startup and shutdown under certain conditions.

  2. Loop-the-Loop: Bringing Theory into Practice

    ERIC Educational Resources Information Center

    Suwonjandee, N.; Asavapibhop, B.

    2012-01-01

    During the Thai high-school physics teacher training programme, we used an aluminum loop-the-loop system built by the Institute for the Promotion of Teaching Science and Technology (IPST) to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. There were 27 high-school teachers from three provinces,…

  3. Loop-the-Loop: Bringing Theory into Practice

    ERIC Educational Resources Information Center

    Suwonjandee, N.; Asavapibhop, B.

    2012-01-01

    During the Thai high-school physics teacher training programme, we used an aluminum loop-the-loop system built by the Institute for the Promotion of Teaching Science and Technology (IPST) to demonstrate a circular motion and investigate the concept of the conservation of mechanical energy. There were 27 high-school teachers from three provinces,…

  4. Vortex loops and Majoranas

    SciTech Connect

    Chesi, Stefano; Jaffe, Arthur; Loss, Daniel; Pedrocchi, Fabio L.

    2013-11-15

    We investigate the role that vortex loops play in characterizing eigenstates of interacting Majoranas. We give some general results and then focus on ladder Hamiltonian examples as a test of further ideas. Two methods yield exact results: (i) A mapping of certain spin Hamiltonians to quartic interactions of Majoranas shows that the spectra of these two examples coincide. (ii) In cases with reflection-symmetric Hamiltonians, we use reflection positivity for Majoranas to characterize vortices in the ground states. Two additional methods suggest wider applicability of these results: (iii) Numerical evidence suggests similar behavior for certain systems without reflection symmetry. (iv) A perturbative analysis also suggests similar behavior without the assumption of reflection symmetry.

  5. Dynamic PID loop control

    SciTech Connect

    Pei, L.; Klebaner, A.; Theilacker, J.; Soyars, W.; Martinez, A.; Bossert, R.; DeGraff, B.; Darve, C.; /Fermilab

    2011-06-01

    The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters oscillation.

  6. Pulse thermal loop

    NASA Technical Reports Server (NTRS)

    Weislogel, Mark M. (Inventor)

    2002-01-01

    A pulse thermal loop heat transfer system includes a means to use pressure rises in a pair of evaporators to circulate a heat transfer fluid. The system includes one or more valves that iteratively, alternately couple the outlets the evaporators to the condenser. While flow proceeds from one of the evaporators to the condenser, heating creates a pressure rise in the other evaporator, which has its outlet blocked to prevent fluid from exiting the other evaporator. When the flow path is reconfigured to allow flow from the other evaporator to the condenser, the pressure in the other evaporator is used to circulate a pulse of fluid through the system. The reconfiguring of the flow path, by actuating or otherwise changing the configuration of the one or more valves, may be triggered when a predetermined pressure difference between the evaporators is reached.

  7. Uranyl Nitrate Flow Loop

    SciTech Connect

    Ladd-Lively, Jennifer L

    2008-10-01

    The objectives of the work discussed in this report were to: (1) develop a flow loop that would simulate the purified uranium-bearing aqueous stream exiting the solvent extraction process in a natural uranium conversion plant (NUCP); (2) develop a test plan that would simulate normal operation and disturbances that could be anticipated in an NUCP; (3) use the flow loop to test commercially available flowmeters for use as safeguards monitors; and (4) recommend a flowmeter for production-scale testing at an NUCP. There has been interest in safeguarding conversion plants because the intermediate products [uranium dioxide (UO{sub 2}), uranium tetrafluoride (UF{sub 4}), and uranium hexafluoride (UF{sub 6})] are all suitable uranium feedstocks for producing special nuclear materials. Furthermore, if safeguards are not applied virtually any nuclear weapons program can obtain these feedstocks without detection by the International Atomic Energy Agency (IAEA). Historically, IAEA had not implemented safeguards until the purified UF{sub 6} product was declared as feedstock for enrichment plants. H. A. Elayat et al. provide a basic definition of a safeguards system: 'The function of a safeguards system on a chemical conversion plant is in general terms to verify that no useful nuclear material is being diverted to use in a nuclear weapons program'. The IAEA now considers all highly purified uranium compounds as candidates for safeguarding. DOE is currently interested in 'developing instruments, tools, strategies, and methods that could be of use to the IAEA in the application of safeguards' for materials found in the front end of the nuclear fuel cycle-prior to the production of the uranium hexafluoride or oxides that have been the traditional starting point for IAEA safeguards. Several national laboratories, including Oak Ridge, Los Alamos, Lawrence Livermore, and Brookhaven, have been involved in developing tools or techniques for safeguarding conversion plants. This study

  8. Loop gravity string

    NASA Astrophysics Data System (ADS)

    Freidel, Laurent; Perez, Alejandro; Pranzetti, Daniele

    2017-05-01

    In this work we study canonical gravity in finite regions for which we introduce a generalization of the Gibbons-Hawking boundary term including the Immirzi parameter. We study the canonical formulation on a spacelike hypersurface with a boundary sphere and show how the presence of this term leads to an unprecedented type of degrees of freedom coming from the restoration of the gauge and diffeomorphism symmetry at the boundary. In the presence of a loop quantum gravity state, these boundary degrees of freedom localize along a set of punctures on the boundary sphere. We demonstrate that these degrees of freedom are effectively described by auxiliary strings with a three-dimensional internal target space attached to each puncture. We show that the string currents represent the local frame field, that the string angular momenta represent the area flux, and that the string stress tensor represents the two-dimensional metric on the boundary of the region of interest. Finally, we show that the commutators of these broken diffeomorphism charges of quantum geometry satisfy, at each puncture, a Virasoro algebra with central charge c =3 . This leads to a description of the boundary degrees of freedom in terms of a CFT structure with central charge proportional to the number of loop punctures. The boundary S U (2 ) gauge symmetry is recovered via the action of the U (1 )3 Kac-Moody generators (associated with the string current) in a way that is the exact analog of an infinite dimensional generalization of the Schwinger spin representation. We finally show that this symmetry is broken by the presence of background curvature.

  9. Loop Quantum Gravity.

    PubMed

    Rovelli, Carlo

    2008-01-01

    The problem of describing the quantum behavior of gravity, and thus understanding quantum spacetime, is still open. Loop quantum gravity is a well-developed approach to this problem. It is a mathematically well-defined background-independent quantization of general relativity, with its conventional matter couplings. Today research in loop quantum gravity forms a vast area, ranging from mathematical foundations to physical applications. Among the most significant results obtained so far are: (i) The computation of the spectra of geometrical quantities such as area and volume, which yield tentative quantitative predictions for Planck-scale physics. (ii) A physical picture of the microstructure of quantum spacetime, characterized by Planck-scale discreteness. Discreteness emerges as a standard quantum effect from the discrete spectra, and provides a mathematical realization of Wheeler's "spacetime foam" intuition. (iii) Control of spacetime singularities, such as those in the interior of black holes and the cosmological one. This, in particular, has opened up the possibility of a theoretical investigation into the very early universe and the spacetime regions beyond the Big Bang. (iv) A derivation of the Bekenstein-Hawking black-hole entropy. (v) Low-energy calculations, yielding n-point functions well defined in a background-independent context. The theory is at the roots of, or strictly related to, a number of formalisms that have been developed for describing background-independent quantum field theory, such as spin foams, group field theory, causal spin networks, and others. I give here a general overview of ideas, techniques, results and open problems of this candidate theory of quantum gravity, and a guide to the relevant literature.

  10. ModLoop: automated modeling of loops in protein structures.

    PubMed

    Fiser, András; Sali, Andrej

    2003-12-12

    ModLoop is a web server for automated modeling of loops in protein structures. The input is the atomic coordinates of the protein structure in the Protein Data Bank format, and the specification of the starting and ending residues of one or more segments to be modeled, containing no more than 20 residues in total. The output is the coordinates of the non-hydrogen atoms in the modeled segments. A user provides the input to the server via a simple web interface, and receives the output by e-mail. The server relies on the loop modeling routine in MODELLER that predicts the loop conformations by satisfaction of spatial restraints, without relying on a database of known protein structures. For a rapid response, ModLoop runs on a cluster of Linux PC computers. The server is freely accessible to academic users at http://salilab.org/modloop

  11. Calcium fluoride window mounting

    NASA Astrophysics Data System (ADS)

    Berger, D. Douglas

    1982-10-01

    A technique has been developed for joining a large calcium fluoride crystal to a stainless-steel flange by means of a silver transition ring. The process involves both vacuum brazing using a copper-silver alloy and air brazing using silver chloride. This paper describes the procedure used in fabricating a high-vacuum leak-tight calcium fluoride window assembly.

  12. Calcium and bones (image)

    MedlinePlus

    ... for the growth, maintenance, and reproduction of the human body. Bones, like other tissues in the body, are continually being re-formed and incorporate calcium into their structure. Calcium is essential for the formation of and maintenance of healthy teeth.

  13. Open-Loop Control of Oxidative Phosphorylation in Skeletal and Cardiac Muscle Mitochondria by Ca2+

    PubMed Central

    Vinnakota, Kalyan C.; Singhal, Abhishek; Van den Bergh, Françoise; Bagher-Oskouei, Masoumeh; Wiseman, Robert W.; Beard, Daniel A.

    2016-01-01

    In cardiac muscle, mitochondrial ATP synthesis is driven by demand for ATP through feedback from the products of ATP hydrolysis. However, in skeletal muscle at higher workloads there is an apparent contribution of open-loop stimulation of ATP synthesis. Open-loop control is defined as modulation of flux through a biochemical pathway by a moiety, which is not a reactant or a product of the biochemical reactions in the pathway. The role of calcium, which is known to stimulate the activity of mitochondrial dehydrogenases, as an open-loop controller, was investigated in isolated cardiac and skeletal muscle mitochondria. The kinetics of NADH synthesis and respiration, feedback from ATP hydrolysis products, and stimulation by calcium were characterized in isolated mitochondria to test the hypothesis that calcium has a stimulatory role in skeletal muscle mitochondria not apparent in cardiac mitochondria. A range of respiratory states were obtained in cardiac and skeletal muscle mitochondria utilizing physiologically relevant concentrations of pyruvate and malate, and flux of respiration, NAD(P)H fluorescence, and rhodamine 123 fluorescence were measured over a range of extra mitochondrial calcium concentrations. We found that under these conditions calcium stimulates NADH synthesis in skeletal muscle mitochondria but not in cardiac mitochondria. PMID:26910432

  14. Kidney and calcium homeostasis.

    PubMed

    Jeon, Un Sil

    2008-12-01

    Plasma calcium concentration is maintained within a narrow range (8.5-10.5 mg/dL) by the coordinated action of parathyroid hormone (PTH), 1,25(OH)2D3, calcitonin, and ionized calcium (iCa(2+)) itself. The kidney plays a key role in this process by the fine regulation of calcium excretion. More than 95% of filtered calcium is reabsorbed along the renal tubules. In the proximal tubules, 60% of filtered calcium is reabsorbed by passive mechanisms. In the thick ascending limb, 15% of calcium is reabsorbed by paracellular diffusion through paracellin-1 (claudin-16). The calcium sensing receptor (CaSR) in the basolateral membrane of the thick ascending limb senses the change in iCa(2+) and inhibits calcium reabsorption independent to PTH and 1,25(OH)2D3. The fine regulation of calcium excretion occurs in the distal convoluted tubules and connecting tubules despite the fact that only 10-15% of filtered calcium is reabsorbed there. Transient receptor potential vanilloid 5 (TRPV5) and 6 (TRPV6) in the apical membrane act as the main portal of entry, calbindin-D28K delivers Ca(2+) in the cytoplasm, and then Na(2+)/Ca(2+) exchanger (NCX1) and plasma membrane Ca(2+)-ATPase in the basolateral membrane serve as an exit. In the cortical collecting duct, TRPV6 is expressed, but the role might be negligible. In addition to PTH and 1,25(OH)2D3, acid-base disturbance, diuretics, and estrogen affect on these calcium channels. Recently, klotho and fibroblast growth factor 23 (FGF23) are suggested as new players in the calcium metabolism. Klotho is exclusively expressed in the kidney and co-localized with TRPV5, NCX1, and calbindin-D28K. Klotho increases calcium reabsorption through trafficking of TRPV5 to the plasma membrane, and also converts FGF receptor to the specific FGF23 receptor. FGF23:klotho complex bound to FGF receptor inhibits 1α-hydroxylase of vitamin D, and contributes to calcium reabsorption and phosphate excretion in the kidney.

  15. Improved code-tracking loop

    NASA Technical Reports Server (NTRS)

    Laflame, D. T.

    1980-01-01

    Delay-locked loop tracks pseudonoise codes without introducing dc timing errors, because it is not sensitive to gain imbalance between signal processing arms. "Early" and "late" reference codes pass in combined form through both arms, and each arm acts on both codes. Circuit accomodates 1 dB weaker input signals with tracking ability equal to that of tau-dither loops.

  16. The Projectile Inside the Loop

    ERIC Educational Resources Information Center

    Varieschi, Gabriele U.

    2006-01-01

    The loop-the-loop demonstration can be easily adapted to study the kinematics of projectile motion, when the moving body falls inside the apparatus. Video capturing software can be used to reveal peculiar geometrical effects of this simple but educational experiment.

  17. RCD+: Fast loop modeling server.

    PubMed

    López-Blanco, José Ramón; Canosa-Valls, Alejandro Jesús; Li, Yaohang; Chacón, Pablo

    2016-07-08

    Modeling loops is a critical and challenging step in protein modeling and prediction. We have developed a quick online service (http://rcd.chaconlab.org) for ab initio loop modeling combining a coarse-grained conformational search with a full-atom refinement. Our original Random Coordinate Descent (RCD) loop closure algorithm has been greatly improved to enrich the sampling distribution towards near-native conformations. These improvements include a new workflow optimization, MPI-parallelization and fast backbone angle sampling based on neighbor-dependent Ramachandran probability distributions. The server starts by efficiently searching the vast conformational space from only the loop sequence information and the environment atomic coordinates. The generated closed loop models are subsequently ranked using a fast distance-orientation dependent energy filter. Top ranked loops are refined with the Rosetta energy function to obtain accurate all-atom predictions that can be interactively inspected in an user-friendly web interface. Using standard benchmarks, the average root mean squared deviation (RMSD) is 0.8 and 1.4 Å for 8 and 12 residues loops, respectively, in the challenging modeling scenario in where the side chains of the loop environment are fully remodeled. These results are not only very competitive compared to those obtained with public state of the art methods, but also they are obtained ∼10-fold faster. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  18. RCD+: Fast loop modeling server

    PubMed Central

    López-Blanco, José Ramón; Canosa-Valls, Alejandro Jesús; Li, Yaohang; Chacón, Pablo

    2016-01-01

    Modeling loops is a critical and challenging step in protein modeling and prediction. We have developed a quick online service (http://rcd.chaconlab.org) for ab initio loop modeling combining a coarse-grained conformational search with a full-atom refinement. Our original Random Coordinate Descent (RCD) loop closure algorithm has been greatly improved to enrich the sampling distribution towards near-native conformations. These improvements include a new workflow optimization, MPI-parallelization and fast backbone angle sampling based on neighbor-dependent Ramachandran probability distributions. The server starts by efficiently searching the vast conformational space from only the loop sequence information and the environment atomic coordinates. The generated closed loop models are subsequently ranked using a fast distance-orientation dependent energy filter. Top ranked loops are refined with the Rosetta energy function to obtain accurate all-atom predictions that can be interactively inspected in an user-friendly web interface. Using standard benchmarks, the average root mean squared deviation (RMSD) is 0.8 and 1.4 Å for 8 and 12 residues loops, respectively, in the challenging modeling scenario in where the side chains of the loop environment are fully remodeled. These results are not only very competitive compared to those obtained with public state of the art methods, but also they are obtained ∼10-fold faster. PMID:27151199

  19. The Projectile Inside the Loop

    ERIC Educational Resources Information Center

    Varieschi, Gabriele U.

    2006-01-01

    The loop-the-loop demonstration can be easily adapted to study the kinematics of projectile motion, when the moving body falls inside the apparatus. Video capturing software can be used to reveal peculiar geometrical effects of this simple but educational experiment.

  20. Loop-bed combustion apparatus

    DOEpatents

    Shang, Jer-Yu; Mei, Joseph S.; Slagle, Frank D.; Notestein, John E.

    1984-01-01

    The present invention is directed to a combustion apparatus in the configuration of a oblong annulus defining a closed loop. Particulate coal together with a sulfur sorbent such as sulfur or dolomite is introduced into the closed loop, ignited, and propelled at a high rate of speed around the loop. Flue gas is withdrawn from a location in the closed loop in close proximity to an area in the loop where centrifugal force imposed upon the larger particulate material maintains these particulates at a location spaced from the flue gas outlet. Only flue gas and smaller particulates resulting from the combustion and innerparticle grinding are discharged from the combustor. This structural arrangement provides increased combustion efficiency due to the essentially complete combustion of the coal particulates as well as increased sulfur absorption due to the innerparticle grinding of the sorbent which provides greater particle surface area.

  1. Loop Heat Pipe Startup Behaviors

    NASA Technical Reports Server (NTRS)

    Ku, Jentung

    2014-01-01

    A loop heat pipe must start successfully before it can commence its service. The start-up transient represents one of the most complex phenomena in the loop heat pipe operation. This paper discusses various aspects of loop heat pipe start-up behaviors. Topics include the four start-up scenarios, the initial fluid distribution between the evaporator and reservoir that determines the start-up scenario, factors that affect the fluid distribution between the evaporator and reservoir, difficulties encountered during the low power start-up, and methods to enhance the start-up success. Also addressed are the thermodynamic constraint between the evaporator and reservoir in the loop heat pipe operation, the superheat requirement for nucleate boiling, pressure spike and pressure surge during the start-up transient, and repeated cycles of loop start-up andshutdown under certain conditions.

  2. Higher dimensional loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong

    2016-07-01

    Loop quantum cosmology (LQC) is the symmetric sector of loop quantum gravity. In this paper, we generalize the structure of loop quantum cosmology to the theories with arbitrary spacetime dimensions. The isotropic and homogeneous cosmological model in n+1 dimensions is quantized by the loop quantization method. Interestingly, we find that the underlying quantum theories are divided into two qualitatively different sectors according to spacetime dimensions. The effective Hamiltonian and modified dynamical equations of n+1 dimensional LQC are obtained. Moreover, our results indicate that the classical big bang singularity is resolved in arbitrary spacetime dimensions by a quantum bounce. We also briefly discuss the similarities and differences between the n+1 dimensional model and the 3+1 dimensional one. Our model serves as a first example of higher dimensional loop quantum cosmology and offers the possibility to investigate quantum gravity effects in higher dimensional cosmology.

  3. Wilson Loop Diagrams and Positroids

    NASA Astrophysics Data System (ADS)

    Agarwala, Susama; Marin-Amat, Eloi

    2017-03-01

    In this paper, we study a new application of the positive Grassmannian to Wilson loop diagrams (or MHV diagrams) for scattering amplitudes in N= 4 Super Yang-Mill theory ( N = 4 SYM). There has been much interest in studying this theory via the positive Grassmannians using BCFW recursion. This is the first attempt to study MHV diagrams for planar Wilson loop calculations (or planar amplitudes) in terms of positive Grassmannians. We codify Wilson loop diagrams completely in terms of matroids. This allows us to apply the combinatorial tools in matroid theory used to identify positroids (non-negative Grassmannians) to Wilson loop diagrams. In doing so, we find that certain non-planar Wilson loop diagrams define positive Grassmannians. While non-planar diagrams do not have physical meaning, this finding suggests that they may have value as an algebraic tool, and deserve further investigation.

  4. Stability of solar coronal loops

    NASA Astrophysics Data System (ADS)

    Goedbloed, J. P.

    1990-05-01

    The equations of magnetohydrodynamics do not contain an intrinsic length scale determining the size of phenomena. Hence, size only enters through the external geometrical properties of the configurations considered. This is one of the reasons why tokamaks and solar coronal loops may be considered as similar objects. The equations of MHD do not distinguish between the two. It is only the geometry and, hence, the boundary conditions that discriminate between them. Whereas for tokamaks toroidal periodicity and normal confinement provide the appropriate boundary conditions, for coronal loops line-tying at the photosphere and some prescription for the behavior across the ``edge'' of the loop determine the solutions. The latter is a more complicated problem and gives rise to even more complex dynamics than encountered in tokamaks. Here, we consider the influence of the two mentioned groups of boundary conditions for the problem of the stability and disruption of a solar coronal loop. We consider the stability properties of a single loop with twisted magnetic field lines under the simultaneous influence of photospheric line-tying and constraining by neighboring flux loops. The loops would be violently unstable without these two ingredients (i.e. for the corresponding tokamak problem). It is shown that line-tying alone in not sufficient for stability, but the neighboring flux tubes provide a normal boundary condition similar to a conducting shell in tokamaks. This stabilization gets lost on the time scale associated with reconnection of the tangetial magnetic field discontinuities present in the many-loop system. On this time scale the magnetic energy, which has been built up during the twisting of the field lines, gets released, resulting in a disruption of the loop. This process may be considered as the single loop variant of Parker's solar flare model.

  5. Calcium and osteoporosis.

    PubMed

    Nordin, B E

    1997-01-01

    Calcium is an essential nutrient that is involved in most metabolic processes and the phosphate salts of which provide mechanical rigidity to the bones and teeth, where 99% of the body's calcium resides. The calcium in the skeleton has the additional role of acting as a reserve supply of calcium to meet the body's metabolic needs in states of calcium deficiency. Calcium deficiency is easily induced because of the obligatory losses of calcium via the bowel, kidneys, and skin. In growing animals, it may impair growth, delay consolidation of the skeleton, and in certain circumstances give rise to rickets but the latter is more often due to deficiency of vitamin D. In adult animals, calcium deficiency causes mobilization of bone and leads sooner or later to osteoporosis, i.e., a reduction in the "amount of bone in the bone" or apparent bone density. The effects of calcium deficiency and oophorectomy (ovariectomy) are additive. In humans, osteoporosis is a common feature of aging. Loss of bone starts in women at the time of the menopause and in men at about age 55 and leads to an increase in fracture rates in both sexes. Individual fracture risk is inversely related to bone density, which in turn is determined by the density achieved at maturity (peak bone density) and the subsequent rate of bone loss. At issue is whether either or both of these variables is related to calcium intake. The calcium requirement of adults may be defined as the mean calcium intake needed to preserve calcium balance, i.e., to meet the significant obligatory losses of calcium through the gastrointestinal tract, kidneys, and skin. The calcium allowance is the higher intake recommended for a population to allow for individual variation in the requirement. The mean requirement defined in this way, calculated from balance studies, is about 20 mmol (800 mg) a day on Western diets, implying an allowance of 25 mmol (1000 mg) or more. Corresponding requirements and allowances have been calculated for

  6. Bile salts and calcium absorption.

    PubMed

    Webling, D D; Holdsworth, E S

    1966-09-01

    1. The study of the effect of bile salts on enhancing calcium absorption in the rachitic chick has been extended to bile salts not present in chick bile, e.g. glycine conjugates and bile alcohol sulphates. 2. Bile and bile salts cause an increase in calcium absorption from sparingly soluble calcium hydrogen phosphate when compared with a suspension of calcium hydrogen phosphate in saline. 3. If the bile ducts of normal rats are tied the absorption of calcium from calcium hydrogen phosphate decreases but can be restored by giving bile salts with the calcium salt. 4. Bile salts increase solubility in water of the sparingly soluble calcium salts, phytate and phosphate at pH values between 6 and 8. 5. Bile salts increase the solubility in lipid solvents of calcium in approximately the same proportion as they increase the absorption of calcium from the gut. 6. The physiological role of bile in calcium absorption and its mode of action are discussed.

  7. [Calcium and health].

    PubMed

    Ortega Anta, Rosa M; Jiménez Ortega, Ana I; López-Sobaler, Ana M

    2015-04-07

    An adequate intake of calcium is only not limited to avoid the risk of osteoporosis and its benefits in longterm bone health, but also it has been linked to protection against various major diseases, such as hypertension, cancer, kidney stones, insulin resistance, diabetes... and several investigations suggest its importance in preventing and controlling obesity. Studies conducted in Spanish representative samples show that a high percentage of adults and children (> 75%) don't achieve the recommended intake of calcium. Moreover, are growing trends among the population suggesting that calcium intake and dairy consumption (main food source of the mineral) are high, and even excessive, in many individuals. This misconception results in that the calcium intake is increasingly far from the recommended one. The maximum tolerable intake of the mineral is fixed at 2.500 mg/day, but this intake is unusual, and it's more disturbing and frequent, to find intakes below the recommended calcium intakes (1.000 and 1.200 mg/day in adults, men and women, respectively). Data from different studies highlight the risk of an inadequate calcium intake and the damages that may affect the health in a long term. It is not about transmitting indiscriminate guidelines in order to increase the intake of calcium / dairy, but the recommended intakes must be met to achieve both the nutritional and health benefits. Also activities for demystification of misconceptions are need, increasingly frequent, that may impair health population.

  8. Calcium Signaling and Neurodegeneration

    PubMed Central

    2010-01-01

    Neurodegenerative disorders, such as Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS), Huntington’s disease (HD), and spinocerebellar ataxias (SCA) are very important both for fundamental science and for practical medicine. Despite extensive research into the causes of these diseases, clinical researchers have had very limited progress and, as of now, there is still no cure for any of these diseases. One of the main obstacles in the way of creating treatments for these disorders is the fact that their etiology and pathophysiology still remain unclear. This paper reviews results that support the so–called “calcium hypothesis of neurodegenerative diseases.” The calcium hypothesis states that the atrophic and degenerative processes in the neurons of AD, PD, ALS, HD, and SCA patients are accompanied by alterations in calcium homeostasis. Moreover, the calcium hypothesis states that this deregulation of calcium signaling is one of the early–stage and key processes in the pathogenesis of these diseases. Based on the results we reviewed, we conclude that the calcium channels and other proteins involved in the neuronal calcium signaling system are potential drug targets for AD, PD, ALS, HD, and SCA therapy. PMID:22649630

  9. 21 CFR 184.1191 - Calcium carbonate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... soda process”; (2) By precipitation of calcium carbonate from calcium hydroxide in the “Carbonation process”; or (3) By precipitation of calcium carbonate from calcium chloride in the “Calcium...

  10. 21 CFR 184.1191 - Calcium carbonate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... soda process”; (2) By precipitation of calcium carbonate from calcium hydroxide in the “Carbonation process”; or (3) By precipitation of calcium carbonate from calcium chloride in the “Calcium...

  11. 21 CFR 184.1191 - Calcium carbonate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... soda process”; (2) By precipitation of calcium carbonate from calcium hydroxide in the “Carbonation process”; or (3) By precipitation of calcium carbonate from calcium chloride in the “Calcium...

  12. 21 CFR 184.1191 - Calcium carbonate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... soda process”; (2) By precipitation of calcium carbonate from calcium hydroxide in the “Carbonation process”; or (3) By precipitation of calcium carbonate from calcium chloride in the “Calcium...

  13. CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING ON LEFT, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    CALCIUM CHLORIDE PLANT LOOKING EAST. CALCIUM CHLORIDE BUILDING ON LEFT, CALCIUM CHLORIDE STORAGE BUILDING ON RIGHT OF CENTER WITH TOP OF SA (SODA ASH) BUILDING IN RIGHT BACKGROUND. - Solvay Process Company, Calcium Chloride Plant, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

  14. Modeling loop entropy.

    PubMed

    Chirikjian, Gregory S

    2011-01-01

    Proteins fold from a highly disordered state into a highly ordered one. Traditionally, the folding problem has been stated as one of predicting "the" tertiary structure from sequential information. However, new evidence suggests that the ensemble of unfolded forms may not be as disordered as once believed, and that the native form of many proteins may not be described by a single conformation, but rather an ensemble of its own. Quantifying the relative disorder in the folded and unfolded ensembles as an entropy difference may therefore shed light on the folding process. One issue that clouds discussions of "entropy" is that many different kinds of entropy can be defined: entropy associated with overall translational and rotational Brownian motion, configurational entropy, vibrational entropy, conformational entropy computed in internal or Cartesian coordinates (which can even be different from each other), conformational entropy computed on a lattice, each of the above with different solvation and solvent models, thermodynamic entropy measured experimentally, etc. The focus of this work is the conformational entropy of coil/loop regions in proteins. New mathematical modeling tools for the approximation of changes in conformational entropy during transition from unfolded to folded ensembles are introduced. In particular, models for computing lower and upper bounds on entropy for polymer models of polypeptide coils both with and without end constraints are presented. The methods reviewed here include kinematics (the mathematics of rigid-body motions), classical statistical mechanics, and information theory.

  15. Loop heat pipe radiator

    SciTech Connect

    Sarraf, D.B.; Gernert, N.J.

    1996-03-01

    This paper describes the design and testing of a Loop Heat Pipe Radiator (LHPR) which was developed as an alternative to state-of-the-art axially-grooved heat pipes for space-based heat rejection which would be usable with tubing made of aluminum foil covered with a carbon-epoxy composite. The LHPR had an aluminum envelope and a polymer wick, and used ammonia as a working fluid. It was 4 meters long with a mass of 1.4 kg. The LHPR transported 500 watts at a 2.3 meter adverse inclination and 1500 watts when horizontal. This non-optimized LHPR had a 3000 watt-meter capability, which is four times greater than an axially-grooved heat pipe of similar power-handling capability and mass. In addition to a higher power handling capability, the LHPR has a much higher capillary margin than axially-grooved pipes. That high capillary margin simplifies ground testing in a 1-g environment by reducing the need for the careful levelling and vibration reduction required by axially-grooved pipes. {copyright} {ital 1996 American Institute of Physics.}

  16. Modeling Loop Entropy

    PubMed Central

    Chirikjian, Gregory S.

    2011-01-01

    Proteins fold from a highly disordered state into a highly ordered one. Traditionally, the folding problem has been stated as one of predicting ‘the’ tertiary structure from sequential information. However, new evidence suggests that the ensemble of unfolded forms may not be as disordered as once believed, and that the native form of many proteins may not be described by a single conformation, but rather an ensemble of its own. Quantifying the relative disorder in the folded and unfolded ensembles as an entropy difference may therefore shed light on the folding process. One issue that clouds discussions of ‘entropy’ is that many different kinds of entropy can be defined: entropy associated with overall translational and rotational Brownian motion, configurational entropy, vibrational entropy, conformational entropy computed in internal or Cartesian coordinates (which can even be different from each other), conformational entropy computed on a lattice; each of the above with different solvation and solvent models; thermodynamic entropy measured experimentally, etc. The focus of this work is the conformational entropy of coil/loop regions in proteins. New mathematical modeling tools for the approximation of changes in conformational entropy during transition from unfolded to folded ensembles are introduced. In particular, models for computing lower and upper bounds on entropy for polymer models of polypeptide coils both with and without end constraints are presented. The methods reviewed here include kinematics (the mathematics of rigid-body motions), classical statistical mechanics and information theory. PMID:21187223

  17. Wilson loops in minimal surfaces

    SciTech Connect

    Drukker, Nadav; Gross, David J.; Ooguri, Hirosi

    1999-04-27

    The AdS/CFT correspondence suggests that the Wilson loop of the large N gauge theory with N = 4 supersymmetry in 4 dimensions is described by a minimal surface in AdS{sub 5} x S{sup 5}. The authors examine various aspects of this proposal, comparing gauge theory expectations with computations of minimal surfaces. There is a distinguished class of loops, which the authors call BPS loops, whose expectation values are free from ultra-violet divergence. They formulate the loop equation for such loops. To the extent that they have checked, the minimal surface in AdS{sub 5} x S{sup 5} gives a solution of the equation. The authors also discuss the zig-zag symmetry of the loop operator. In the N = 4 gauge theory, they expect the zig-zag symmetry to hold when the loop does not couple the scalar fields in the supermultiplet. They will show how this is realized for the minimal surface.

  18. Extra EF hand unit (DX) mediated stabilization and calcium independency of α-amylase.

    PubMed

    Sadeghi, Leila; Khajeh, Khosro; Mollania, Nasrin; Dabirmanesh, Bahareh; Ranjbar, Bijan

    2013-03-01

    It is the common feature of α-amylases that calcium ion is required for their structural integrity and thermal stability. All amylases have at least one Ca(2+) per molecule; therefore amino acids involved in calcium binding are specific and conserved. In this study, sequence analysis revealed the presence of EF-hand-like motif in calcium-binding loop of Bacillus megaterium WHO (BMW)-amylase that was previously isolated from BMW. The EF-hand motif and its variants (EF-hand-like motif) are the most common calcium-binding motifs found in a large number of protein families. To investigate the effect of calcium ion on the thermal stability and activity of BMW-amylase, we used site-directed mutagenesis to replace histidine 58 with Asp (D), Ile (I), Tyr (Y), Phe (F), and Arg (R) at the seventh position of EF-hand-like motif. Upon the addition of an extra DX unit to the calcium-binding loop in H58D variant, thermal stability, catalytic activity, and chelating power of the enzyme improved due to higher affinity toward calcium. H58D variant demonstrated calcium independency compared to the wild type and other created mutants. Conformational changes in the presence and absence of Ca(2+) were monitored using fluorescence technique.

  19. Open loop distribution system design

    SciTech Connect

    Glamocanin, V. ); Filipovic, V. . Elektrotechnicki fakulet)

    1993-10-01

    The ability to supply consumers of an urban area, with minimum interruption during a feeder segment or substation transformer outage, is assured by a uniform cable size of the feeder segments along the entire loop. Based on the criterion of the uniform cable size, a loop configuration is obtained first by minimizing the installation costs, and then an open loop solution is found by minimizing the power losses. Heuristic rules are proposed and used to obtain an initial solution, as well as to improve current solutions.

  20. Digital phase-locked loop

    NASA Technical Reports Server (NTRS)

    Cliff, R. A. (Inventor)

    1975-01-01

    An digital phase-locked loop is provided for deriving a loop output signal from an accumulator output terminal. A phase detecting exclusive OR gate is fed by the loop digital input and output signals. The output of the phase detector is a bi-level digital signal having a duty cycle indicative of the relative phase of the input and output signals. The accumulator is incremented at a first rate in response to a first output level of the phase detector and at a second rate in response to a second output level of the phase detector.

  1. Stoichiometry of Calcium Medicines

    ERIC Educational Resources Information Center

    Pinto, Gabriel

    2005-01-01

    The topic of calcium supplement and its effects on human lives is presented in the way of questions to the students. It enables the students to realize the relevance of chemistry outside the classroom surrounding.

  2. Get Enough Calcium

    MedlinePlus

    ... like: Fat-free or low-fat (1%) milk, yogurt, and cheese Soymilk with added calcium Broccoli and ... Milk with added vitamin D Some breakfast cereals, yogurt, and juices with added vitamin D Mushrooms Vitamin ...

  3. Stoichiometry of Calcium Medicines

    ERIC Educational Resources Information Center

    Pinto, Gabriel

    2005-01-01

    The topic of calcium supplement and its effects on human lives is presented in the way of questions to the students. It enables the students to realize the relevance of chemistry outside the classroom surrounding.

  4. Calcium and bones

    MedlinePlus

    ... Your body also needs calcium (as well as phosphorus) to make healthy bones. Bones are the main ... nlm.nih.gov/pubmed/25182228 . De Paula FJA, Black DM, Rosen CJ. Osteoporosis and bone biology. In: ...

  5. Calcium-D-glucarate.

    PubMed

    2002-08-01

    Calcium-D-glucarate is the calcium salt of D-glucaric acid, a substance produced naturally in small amounts by mammals, including humans. Glucaric acid is also found in many fruits and vegetables with the highest concentrations to be found in oranges, apples, grapefruit, and cruciferous vegetables. Oral supplementation of calcium-D-glucarate has been shown to inhibit beta-glucuronidase, an enzyme produced by colonic microflora and involved in Phase II liver detoxification. Elevated beta-glucuronidase activity is associated with an increased risk for various cancers, particularly hormone-dependent cancers such as breast, prostate, and colon cancers. Other potential clinical applications of oral calcium-D-glucarate include regulation of estrogen metabolism and as a lipid-lowering agent.

  6. Coronary Calcium Scan

    MedlinePlus

    ... Intramural Research Research Resources Research Meeting Summaries Technology ... complete. A coronary calcium scan uses a special scanner such as an electron beam CT or a multidetector CT (MDCT) machine. ...

  7. Optical loop framing

    SciTech Connect

    Kalibjian, R.; Chong, Y.P.; Prono, D.S.; Cavagnolo, H.R.

    1984-06-01

    The ATA provides an electron beam pulse of 70-ns duration at a 1-Hz rate. Our present optical diagnostics technique involve the imaging of the visible light generated by the beam incident onto the plant of a thin sheet of material. It has already been demonstrated that the light generated has a sufficiently fast temporal reponse in performing beam diagnostics. Notwithstanding possible beam emittance degradation due to scattering in the thin sheet, the observation of beam spatial profiles with relatively high efficiencies has provided data complementary to that obtained from beam wall current monitors and from various x-ray probes and other electrical probes. The optical image sensor consists of a gated, intensified television system. The gate pulse of the image intensifier can be appropriately delayed to give frames that are time-positioned from the head to the tail of the beam with a minimum gate time of 5-ns. The spatial correlation of the time frames from pulse to pulse is very good for a stable electron beam; however, when instabilities do occur, it is difficult to properly assess the spatial composition of the head and the tail of the beam on a pulse-to-pulse basis. Multiple gating within a pulse duration becomes desirable but cannot be performed because the recycle time (20-ms) of the TV system is much longer than the beam pulse. For this reason we have developed an optical-loop framing technique that will allow the recording of two frames within one pulse duration with our present gated/intensified TV system.

  8. Calcium-sensing receptors.

    PubMed

    Goodman, William G

    2004-01-01

    It is now known that variations in extracellular calcium concentration exert diverse physiologic effects in a variety of tissues that are mediated by a calcium-sensing receptor (CaSRs). In parathyroid tissue, the CaSR represents the molecular mechanism by which parathyroid cells detect changes in blood ionized calcium concentration, modulate parathyroid hormone (PTH) secretion accordingly, and thus maintain serum calcium levels within a narrow physiologic range. In the kidney, the CaSR regulates renal calcium excretion and influences the transepithelial movement of water and other electrolytes. More generally, activation of the CaSR represents an important signal transduction pathway in intestine, placenta, brain, and perhaps bone. Some of these actions involve cell cycle regulation, changes that may be relevant to understanding the pathogenesis of parathyroid gland hyperplasia in secondary hyperparathyroidism caused by chronic kidney disease. The CaSR represents an appealing target for therapeutic agents designed to modify parathyroid gland function in vivo, offering the prospect of novel therapies for selected disorders of bone and mineral metabolism. Other receptors capable of responding to extracellular calcium ions also have been identified, but the functional importance of these interactions remains to be determined.

  9. SDO Sees Brightening Magnetic Loops

    NASA Image and Video Library

    Two active regions sprouted arches of bundled magnetic loops in this video from NASA’s Solar Dynamics Observatory taken on Nov. 11-12, 2015. Charged particles spin along the magnetic field, tracing...

  10. Automatic blocking of nested loops

    NASA Technical Reports Server (NTRS)

    Schreiber, Robert; Dongarra, Jack J.

    1990-01-01

    Blocked algorithms have much better properties of data locality and therefore can be much more efficient than ordinary algorithms when a memory hierarchy is involved. On the other hand, they are very difficult to write and to tune for particular machines. The reorganization is considered of nested loops through the use of known program transformations in order to create blocked algorithms automatically. The program transformations used are strip mining, loop interchange, and a variant of loop skewing in which invertible linear transformations (with integer coordinates) of the loop indices are allowed. Some problems are solved concerning the optimal application of these transformations. It is shown, in a very general setting, how to choose a nearly optimal set of transformed indices. It is then shown, in one particular but rather frequently occurring situation, how to choose an optimal set of block sizes.

  11. Integrated optical phase locked loop.

    SciTech Connect

    Lentine, Anthony L.; Kim, Jungwon; Trotter, Douglas Chandler; DeRose, Christopher T.; Kartner, Franz X.; Byun, Hyunil; Nejadmalayeri, Amir H.; Watts, Michael R.; Zortman, William A.

    2010-12-01

    A silicon photonics based integrated optical phase locked loop is utilized to synchronize a 10.2 GHz voltage controlled oscillator with a 509 MHz mode locked laser, achieving 32 fs integrated jitter over 300 kHz bandwidth.

  12. SDO Sees Flourishing Magnetic Loops

    NASA Image and Video Library

    A bright set of loops near the edge of the sun’s face grew and shifted quickly after the magnetic field was disrupted by a small eruption on Nov. 25, 2015. Charged particles emitting light in extre...

  13. Loop Electrosurgical Excision Procedure (LEEP)

    MedlinePlus

    ... that acts like a scalpel (surgical knife). An electric current is passed through the loop, which cuts away ... A procedure in which an instrument works with electric current to destroy tissue. Local Anesthesia: The use of ...

  14. Loop Electrosurgical Excision Procedure (LEEP)

    MedlinePlus

    ... that acts like a scalpel (surgical knife). An electric current is passed through the loop, which cuts away ... A procedure in which an instrument works with electric current to destroy tissue. Local Anesthesia: The use of ...

  15. Oxidative calcium release from catechol.

    PubMed

    Riley, Patrick A; Stratford, Michael R L

    2015-04-01

    Oxidation of 4-methylcatechol previously exposed to aqueous calcium chloride was shown by ion chromatography to be associated with release of calcium ions. The catechol was oxidised to the corresponding orthoquinone by the use of tyrosinase from Agaricus bisporus. The oxidative release of calcium from the catechol is ascribed to the diminution of the available hydroxyl functions able to act as chelating groups. Our results suggest that the redox status of melanin may regulate calcium binding and influence calcium levels in pigmented cells.

  16. Observations of loops and prominences

    NASA Technical Reports Server (NTRS)

    Strong, Keith T.

    1994-01-01

    We review recent observations by the Yohkoh-SXT (Soft X-ray Telescope) in collaboration with other spacecraft and ground-based observatories of coronal loops and prominences. These new results point to problems that SoHO will be able to address. With a unique combination of rapid-cadence digital imaging (greater than or equal to 32 s full-disk and greater than or equal to 2 s partial-frame images), high spatial resolution (greater than or equal to 2.5 arcsec pixels), high sensitivity (EM less than or equal to 10(exp 42) cm(exp -3)), a low-scatter mirror, and large dynamic range, SXT can observe a vast range of targets on the Sun. Over the first 21 months of Yohkoh operations SXT has taken over one million images of the corona and so is building up an invaluable long-term database on the large-scale corona and loop geometry. The most striking thing about the SXT images is the range of loop sizes and shapes. The active regions are a bright tangle of magnetic field lines, surrounded by a network of large-scale quiet-Sun loops stretching over distances in excess of 105 km. The cross-section of most loops seems to be constant. Loops displaying significant Gamma's are the exception, not the rule, implying the presence of widespread currents in the corona. All magnetic structures show changes. Time scales range from seconds to months. The question of how these structures are formed, become filled with hot plasma, and are maintained is still open. While we see the propagation of brightenings along the length of active-region loops and in X-ray jets with velocities of several hundred km/s, much higher velocities are seen in the quiet Sun. In XBP flares, for example, velocities of over 1000 km/s are common. Active-region loops seem to be in constant motion, moving slowly outward, carrying plasma with them. During flares, loops often produce localized brightenings at the base and later at the apex of the loop. Quiescent filaments and prominences have been observed regularly

  17. Closed loop spray cooling apparatus

    NASA Technical Reports Server (NTRS)

    Alger, D. L.; Schwab, W. B.; Furman, E. R. (Inventor)

    1979-01-01

    A closed loop apparatus for jet spraying coolant against the back of a radiation target is described. The coolant is circulated through a closed loop with a bubble of inert gas being maintained around the spray. Mesh material is disposed between the bubble and the surface of the liquid coolant which is below the bubble at a predetermined level. In a second arrangement no inert gas is used, the bubble consists of vapor produced when the coolant is sprayed against the target.

  18. LETS: An Expressional Loop Notation.

    DTIC Science & Technology

    1982-10-01

    r - ..’ -rI- x- - r ,11 V~ The Expressional Metaphor 2- Waters i "The Expressional Metaphor ’lhe key property of expressions which makes them...development of a notation which has the property of decomposability. Viewing Loops as Expressions Involving Sequences In order to represent loops as...a DEFUNS or LETS. For example, the function EPLIST takes in a discnbodied plist and returns two values: a sequence of the property names. and a

  19. The role of uncoupling protein 3 regulating calcium ion uptake into mitochondria during sarcopenia

    NASA Astrophysics Data System (ADS)

    Nikawa, Takeshi; Choi, Inho; Haruna, Marie; Hirasaka, Katsuya; Maita Ohno, Ayako; Kondo Teshima, Shigetada

    Overloaded mitochondrial calcium concentration contributes to progression of mitochondrial dysfunction in aged muscle, leading to sarcopenia. Uncoupling protein 3 (UCP3) is primarily expressed in the inner membrane of skeletal muscle mitochondria. Recently, it has been reported that UCP3 is associated with calcium uptake into mitochondria. However, the mechanisms by which UCP3 regulates mitochondrial calcium uptake are not well understood. Here we report that UCP3 interacts with HS-1 associated protein X-1 (Hax-1), an anti-apoptotic protein that is localized in mitochondria, which is involved in cellular responses to calcium ion. The hydrophilic sequences within the loop 2, matrix-localized hydrophilic domain of mouse UCP3 are necessary for binding to Hax-1 of the C-terminal domain in adjacent to mitochondrial innermembrane. Interestingly, these proteins interaction occur the calcium-dependent manner. Indeed, overexpression of UCP3 significantly enhanced calcium uptake into mitochondria on Hax-1 endogenously expressing C2C12 myoblasts. In addition, Hax-1 knock-down enhanced calcium uptake into mitochondria on both UCP3 and Hax-1 endogenously expressing C2C12 myotubes, but not myoblasts. Finally, the dissociation of UCP3 and Hax-1 enhances calcium uptake into mitochondria in aged muscle. These studies identify a novel UCP3-Hax-1 complex regulates the influx of calcium ion into mitochondria in muscle. Thus, the efficacy of UCP3-Hax-1 in mitochondrial calcium regulation may provide a novel therapeutic approach against mitochondrial dysfunction-related disease containing sarcopenia.

  20. THE CORONAL LOOP INVENTORY PROJECT

    SciTech Connect

    Schmelz, J. T.; Pathak, S.; Christian, G. M.; Dhaliwal, R. S. S.; Paul, K. S.

    2015-11-01

    Most coronal physicists now seem to agree that loops are composed of tangled magnetic strands and have both isothermal and multithermal cross-field temperature distributions. As yet, however, there is no information on the relative importance of each of these categories, and we do not know how common one is with respect to the other. In this paper, we investigate these temperature properties for all loop segments visible in the 171-Å image of AR 11294, which was observed by the Atmospheric Imaging Assembly (AIA) on 2011 September 15. Our analysis revealed 19 loop segments, but only 2 of these were clearly isothermal. Six additional segments were effectively isothermal, that is, the plasma emission to which AIA is sensitive could not be distinguished from isothermal emission, within measurement uncertainties. One loop had both isothermal transition region and multithermal coronal solutions. Another five loop segments require multithermal plasma to reproduce the AIA observations. The five remaining loop segments could not be separated reliably from the background in the crucial non-171-Å AIA images required for temperature analysis. We hope that the direction of coronal heating models and the efforts modelers spend on various heating scenarios will be influenced by these results.

  1. The Structure of Coronal Loops

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.

    2009-01-01

    It is widely believed that the simple coronal loops observed by XUV imagers, such as EIT, TRACE, or XRT, actually have a complex internal structure consisting of many (perhaps hundreds) of unresolved, interwoven "strands". According to the nanoflare model, photospheric motions tangle the strands, causing them to reconnect and release the energy required to produce the observed loop plasma. Although the strands, themselves, are unresolved by present-generation imagers, there is compelling evidence for their existence and for the nanoflare model from analysis of loop intensities and temporal evolution. A problem with this scenario is that, although reconnection can eliminate some of the strand tangles, it cannot destroy helicity, which should eventually build up to observable scales. we consider, therefore, the injection and evolution of helicity by the nanoflare process and its implications for the observed structure of loops and the large-scale corona. we argue that helicity does survive and build up to observable levels, but on spatial and temporal scales larger than those of coronal loops. we discuss the implications of these results for coronal loops and the corona, in general .

  2. Loop Models from SOHO Observations

    NASA Astrophysics Data System (ADS)

    Landini, M.; Brković , A.; Landi, E.; Rüedi, I.; Solanki, S.

    1999-01-01

    The Coronal Diagnostic Spectrometer (CDS) on SOHO is a grazing/normal incidence spectrograph, aimed to produce stigmatic spectra of selected regions of the solar surface in six spectral windows of the extreme ultraviolet from 150 Å to 785 Å (Harrison et al. 1995). In the present work, CDS, EIT, MDI and Yohkoh observations of active region lops have been analyzed. These observations are part of JOP 54. CDS monochromatic images from lines at different temperatures have been co-aligned with EIT and MDI images, and loop structures have been clearly identified using Fe XVI emission lines. Density sensitive lines and lines from adjacent stages of ionization of Fe ions have been used to measure electron density and temperature along the loop length; these measurements have been used to determine the electron pressure along the loop and test the constant pressure assumption commonly used in loop modeling. The observations have been compared with a static, isobaric loop model (Landini and Monsignori Fossi 1975) assuming a temperature-constant heating function in the energy balance equation. Good agreement is found for the temperature distribution along the loop at the coronal level. The model pressure is somewhat higher than obtained from density sensitive line ratios.

  3. High temperature loop heat pipes

    SciTech Connect

    Anderson, W.G.; Bland, J.J.; Fershtater, Y.; Goncharov, K.A.; Nikitkin, M.; Juhasz, A.

    1995-12-31

    Advantages of loop heat pipes over conventional heat pipes include self-priming during start-up, improved tolerance for noncondensible gas, and ability for ground testing in any orientation. The applications for high temperature, alkali-metal working fluid loop heat pipes include space radiators, and bimodal systems. A high temperature loop heat pipe was fabricated and tested at 850 K, using cesium as the working fluid. Previous loop heat pipes were tested with ambient temperature working fluids at temperatures below about 450 K. The loop heat pipe had a titanium envelope, and a titanium aluminide wick. The maximum cesium loop heat pipe power was only about 600 watts, which was lower the predicted 1,000 W power. The power limitation may be due to a wettability problem with the cesium not completely wetting the titanium aluminide wick. This would reduce the pumping capability of the wick, and the maximum power that the heat pipe could carry. This problem could be solved by using a refractory metal powder wick, since the alkali metals are known to wet refractory metal wicks.

  4. [Microbial geochemical calcium cycle].

    PubMed

    Zavarzin, G A

    2002-01-01

    The participation of microorganisms in the geochemical calcium cycle is the most important factor maintaining neutral conditions on the Earth. This cycle has profound influence on the fate of inorganic carbon, and, thereby, on the removal of CO2 from the atmosphere. The major part of calcium deposits was formed in the Precambrian, when prokaryotic biosphere predominated. After that, calcium recycling based on biogenic deposition by skeletal organisms became the main process. Among prokaryotes, only a few representatives, e.g., cyanobacteria, exhibit a special calcium function. The geochemical calcium cycle is made possible by the universal features of bacteria involved in biologically mediated reactions and is determined by the activities of microbial communities. In the prokaryotic system, the calcium cycle begins with the leaching of igneous rock predominantly through the action of the community of organotrophic organisms. The release of carbon dioxide to the soil air by organotrophic aerobes leads to leaching with carbonic acid and soda salinization. Under anoxic conditions, of major importance is the organic acid production by primary anaerobes (fermentative microorganisms). Calcium carbonate is precipitated by secondary anaerobes (sulfate reducers) and to a smaller degree by methanogens. The role of the cyanobacterial community in carbonate deposition is exposed by stromatolites, which are the most common organo-sedimentary Precambrian structures. Deposition of carbonates in cyanobacterial mats as a consequence of photoassimilation of CO2 does not appear to be a significant process. It is argued that carbonates were deposited at the boundary between the "soda continent", which emerged as a result of subaerial leaching with carbonic acid, and the ocean containing Ca2+. Such ecotones provided favorable conditions for the development of the benthic cyanobacterial community, which was a precursor of stromatolites.

  5. Filter for third order phase locked loops

    NASA Technical Reports Server (NTRS)

    Crow, R. B.; Tausworthe, R. C. (Inventor)

    1973-01-01

    Filters for third-order phase-locked loops are used in receivers to acquire and track carrier signals, particularly signals subject to high doppler-rate changes in frequency. A loop filter with an open-loop transfer function and set of loop constants, setting the damping factor equal to unity are provided.

  6. Kalman Orbit Optimized Loop Tracking

    NASA Technical Reports Server (NTRS)

    Young, Lawrence E.; Meehan, Thomas K.

    2011-01-01

    Under certain conditions of low signal power and/or high noise, there is insufficient signal to noise ratio (SNR) to close tracking loops with individual signals on orbiting Global Navigation Satellite System (GNSS) receivers. In addition, the processing power available from flight computers is not great enough to implement a conventional ultra-tight coupling tracking loop. This work provides a method to track GNSS signals at very low SNR without the penalty of requiring very high processor throughput to calculate the loop parameters. The Kalman Orbit-Optimized Loop (KOOL) tracking approach constitutes a filter with a dynamic model and using the aggregate of information from all tracked GNSS signals to close the tracking loop for each signal. For applications where there is not a good dynamic model, such as very low orbits where atmospheric drag models may not be adequate to achieve the required accuracy, aiding from an IMU (inertial measurement unit) or other sensor will be added. The KOOL approach is based on research JPL has done to allow signal recovery from weak and scintillating signals observed during the use of GPS signals for limb sounding of the Earth s atmosphere. That approach uses the onboard PVT (position, velocity, time) solution to generate predictions for the range, range rate, and acceleration of the low-SNR signal. The low- SNR signal data are captured by a directed open loop. KOOL builds on the previous open loop tracking by including feedback and observable generation from the weak-signal channels so that the MSR receiver will continue to track and provide PVT, range, and Doppler data, even when all channels have low SNR.

  7. Lattice calculation of the Polyakov loop and Polyakov loop correlators

    NASA Astrophysics Data System (ADS)

    Weber, Johannes Heinrich

    2017-03-01

    We discuss calculations of the Polyakov loop and of Polyakov loop correlators using lattice gauge theory. We simulate QCD with 2+1 flavors and almost physical quark masses using the highly improved staggered quark action (HISQ).We demonstrate that the entropy derived from the Polyakov loop is a good probe of color screening. In particular, it allows for scheme independent and quantitative conclusions about the deconfinement aspects of the crossover and for a rigorous study of the onset of weak-coupling behavior at high temperatures. We examine the correlators for small and large separations and identify vacuum-like and screening regimes in the thermal medium. We demonstrate that gauge-independent screening properties can be obtained even from gauge-fixed singlet correlators and that we can pin down the asymptotic regime.

  8. Study of the Open Loop and Closed Loop Oscillator Techniques

    SciTech Connect

    Imel, George R.; Baker, Benjamin; Riley, Tony; Langbehn, Adam; Aryal, Harishchandra; Benzerga, M. Lamine

    2015-04-11

    This report presents the progress and completion of a five-year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques.The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this report we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign to measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems.

  9. Study of the open loop and closed loop oscillator techniques

    SciTech Connect

    Baker, Benjamin; Riley, Tony; Langbehn, Adam; Imel, George R.; Benzerga, M. Lamine; Aryal, Harishchandra

    2015-07-01

    This paper presents some aspects of a five year study undertaken at Idaho State University of the measurement of very small worth reactivity samples comparing open and closed loop oscillator techniques. The study conclusively demonstrated the equivalency of the two techniques with regard to uncertainties in reactivity values, i.e., limited by reactor noise. As those results are thoroughly documented in recent publications, in this paper we will concentrate on the support work that was necessary. For example, we describe in some detail the construction and calibration of a pilot rod for the closed loop system. We discuss the campaign to measure the required reactor parameters necessary for inverse-kinetics. Finally, we briefly discuss the transfer of the open loop technique to other reactor systems. (authors)

  10. Calcium metabolism and correcting calcium deficiencies.

    PubMed

    Emkey, Ronald D; Emkey, Gregory R

    2012-09-01

    Calcium is the most abundant cation in the human body, of which approximately 99% occurs in bone, contributing to its rigidity and strength. Bone also functions as a reservoir of Ca for its role in multiple physiologic and biochemical processes. This article aims to provide a thorough understanding of the absorptive mechanisms and factors affecting these processes to enable one to better appreciate an individual's Ca needs, and to provide a rationale for correcting Ca deficiencies. An overview of Ca requirements and suggested dosing regimens is presented, with discussion of various Ca preparations and potential toxicities of Ca treatment.

  11. Constraints on Nonuniform Expansion in Coronal Loops

    NASA Astrophysics Data System (ADS)

    Kucera, Therese A.; DeForest, Craig; Klimchuk, James A.; Young, Peter R.

    2017-08-01

    We use measurements of coronal loop properties to constrain the hypothesis that coronal loops expand differently in different directions. A long standing problem in understanding coronal loops is that although the magnetic field is expected to expand with altitude and does indeed seem to do so on scales of active regions, individual loops seem to have fairly uniform diameters along the length of the loop. Malanushenko & Schrijver (2013) have suggested that loops may be expanding, but with a non-circular cross section. In this scenario a loop might have a constant width in the plane of the sky, but expand along the line of sight. Furthermore, such loops might be easier to see from the point of view that does not show expansion. We use Hinode/EIS and SDO/AIA data to measure loop intensities, electron densities, temperatures and dimensions in order to determine the extent to which loops may be expanding along the line of sight.

  12. Inositol trisphosphate and calcium signalling

    NASA Astrophysics Data System (ADS)

    Berridge, Michael J.

    1993-01-01

    Inositol trisphosphate is a second messenger that controls many cellular processes by generating internal calcium signals. It operates through receptors whose molecular and physiological properties closely resemble the calcium-mobilizing ryanodine receptors of muscle. This family of intracellular calcium channels displays the regenerative process of calcium-induced calcium release responsible for the complex spatiotemporal patterns of calcium waves and oscillations. Such a dynamic signalling pathway controls many cellular processes, including fertilization, cell growth, transformation, secretion, smooth muscle contraction, sensory perception and neuronal signalling.

  13. Loop coupled resonator optical waveguides.

    PubMed

    Song, Junfeng; Luo, Lian-Wee; Luo, Xianshu; Zhou, Haifeng; Tu, Xiaoguang; Jia, Lianxi; Fang, Qing; Lo, Guo-Qiang

    2014-10-06

    We propose a novel coupled resonator optical waveguide (CROW) structure that is made up of a waveguide loop. We theoretically investigate the forbidden band and conduction band conditions in an infinite periodic lattice. We also discuss the reflection- and transmission- spectra, group delay in finite periodic structures. Light has a larger group delay at the band edge in a periodic structure. The flat band pass filter and flat-top group delay can be realized in a non-periodic structure. Scattering matrix method is used to calculate the effects of waveguide loss on the optical characteristics of these structures. We also introduce a tunable coupling loop waveguide to compensate for the fabrication variations since the coupling coefficient of the directional coupler in the loop waveguide is a critical factor in determining the characteristics of a loop CROW. The loop CROW structure is suitable for a wide range of applications such as band pass filters, high Q microcavity, and optical buffers and so on.

  14. Bandwidth controller for phase-locked-loop

    NASA Technical Reports Server (NTRS)

    Brockman, Milton H. (Inventor)

    1992-01-01

    A phase locked loop utilizing digital techniques to control the closed loop bandwidth of the RF carrier phase locked loop in a receiver provides high sensitivity and a wide dynamic range for signal reception. After analog to digital conversion, a digital phase locked loop bandwidth controller provides phase error detection with automatic RF carrier closed loop tracking bandwidth control to accommodate several modes of transmission.

  15. Calcium revisited: part I

    PubMed Central

    Burckhardt, Peter

    2013-01-01

    In February 2013, the US Preventive Services Task Force (see www.uspreventiveservicestaskforce.org) recommended ‘against daily supplementation with 400 IU or less of vitamin D3 and 1000, mg or less of calcium for the primary prevention of fractures in non institutionalized postmenopausal women', which illustrates the divergence of opinions. This review wants to shed an objective light on the importance of calcium for bone health. It cannot compete with an exhaustive analysis of the literature by an institute. It does not mention all significant references. But it highlights some pivotal studies from the past and it refers to recent studies that opened new views or added essential data to known facts. It also reflects the personal perception of the author. The first part deals mainly with intake, absorption, needs and recommendations; the second part will discuss the effects of calcium and its supplements on bone. PMID:24422133

  16. Calcium revisited: part I.

    PubMed

    Burckhardt, Peter

    2013-10-16

    In February 2013, the US Preventive Services Task Force (see www.uspreventiveservicestaskforce.org) recommended 'against daily supplementation with 400 IU or less of vitamin D3 and 1000, mg or less of calcium for the primary prevention of fractures in non institutionalized postmenopausal women', which illustrates the divergence of opinions. This review wants to shed an objective light on the importance of calcium for bone health. It cannot compete with an exhaustive analysis of the literature by an institute. It does not mention all significant references. But it highlights some pivotal studies from the past and it refers to recent studies that opened new views or added essential data to known facts. It also reflects the personal perception of the author. The first part deals mainly with intake, absorption, needs and recommendations; the second part will discuss the effects of calcium and its supplements on bone.

  17. Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.

    ERIC Educational Resources Information Center

    Henrickson, Charles H.; Robinson, Paul R.

    1979-01-01

    The gravimetric determination of calcium as calcium carbonate is described. This experiment is suitable for undergraduate quantitative analysis laboratories. It is less expensive than determination of chloride as silver chloride. (BB)

  18. Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.

    ERIC Educational Resources Information Center

    Henrickson, Charles H.; Robinson, Paul R.

    1979-01-01

    The gravimetric determination of calcium as calcium carbonate is described. This experiment is suitable for undergraduate quantitative analysis laboratories. It is less expensive than determination of chloride as silver chloride. (BB)

  19. Direct Demonstration That Loop1 of Scap Binds to Loop7

    PubMed Central

    Zhang, Yinxin; Lee, Kwang Min; Kinch, Lisa N.; Clark, Lindsay; Grishin, Nick V.; Rosenbaum, Daniel M.; Brown, Michael S.; Goldstein, Joseph L.; Radhakrishnan, Arun

    2016-01-01

    Cholesterol homeostasis is mediated by Scap, a polytopic endoplasmic reticulum (ER) protein that transports sterol regulatory element-binding proteins from the ER to Golgi, where they are processed to forms that activate cholesterol synthesis. Scap has eight transmembrane helices and two large luminal loops, designated Loop1 and Loop7. We earlier provided indirect evidence that Loop1 binds to Loop7, allowing Scap to bind COPII proteins for transport in coated vesicles. When ER cholesterol rises, it binds to Loop1. We hypothesized that this causes dissociation from Loop7, abrogating COPII binding. Here we demonstrate direct binding of the two loops when expressed as isolated fragments or as a fusion protein. Expressed alone, Loop1 remained intracellular and membrane-bound. When Loop7 was co-expressed, it bound to Loop1, and the soluble complex was secreted. A Loop1-Loop7 fusion protein was also secreted, and the two loops remained bound when the linker between them was cleaved by a protease. Point mutations that disrupt the Loop1-Loop7 interaction prevented secretion of the Loop1-Loop7 fusion protein. These data provide direct documentation of intramolecular Loop1-Loop7 binding, a central event in cholesterol homeostasis. PMID:27068746

  20. Calcium Handling and Arrhythmogenesis.

    PubMed

    Bompotis, Georgios C; Pappas, Loukas K; Angelidis, Christos; Kossyvakis, Charalampos; Giannopoulos, Georgios; Deftereos, Spyridon

    2016-01-01

    Intracellular calcium homeostasis plays a fundamental role in the electric and mechanical function of the heart by modulating action potential pattern and duration, by linking cell membrane depolarization to myocardial contraction and by regulating cardiac automaticity. Abnormalities of intracellular calcium regulation disrupt the electrophysiological properties of the heart and create an arrhythmogenic milieu, which promotes atrial and ventricular arrhythmogenesis and impairs cardiac automaticity and atrioventricular conduction. In this brief review, we summarize the basic genetic, molecular and electrophysiological mechanisms linking inherited or acquired intracellular Ca(2+) dysregulation to arrhythmogenesis.

  1. Calcium metabolism in microgravity.

    PubMed

    Heer, M; Kamps, N; Biener, C; Korr, C; Boerger, A; Zittermann, A; Stehle, P; Drummer, C

    1999-09-09

    Unloading of weight bearing bones as induced by microgravity or immobilization has significant impacts on the calcium and bone metabolism and is the most likely cause for space osteoporosis. During a 4.5 to 6 month stay in space most of the astronauts develop a reduction in bone mineral density in spine, femoral neck, trochanter, and pelvis of 1%-1.6% measured by Dual Energy X-ray Absorption (DEXA). Dependent on the mission length and the individual turnover rates of the astronauts it can even reach individual losses of up to 14% in the femoral neck. Osteoporosis itself is defined as the deterioration of bone tissue leading to enhanced bone fragility and to a consequent increase in fracture risk. Thinking of long-term missions to Mars or interplanetary missions for years, space osteoporosis is one of the major concerns for manned spaceflight. However, decrease in bone density can be initiated differently. It either can be caused by increases in bone formation and bone resorption resulting in a net bone loss, as obtained in fast looser postmenopausal osteoporosis. On the other hand decrease in bone formation and increase in bone resorption also leads to bone losses as obtained in slow looser postmenopausal osteoporosis or in Anorexia Nervosa patients. Biomarkers of bone turnover measured during several missions indicated that the pattern of space osteoporosis is very similar to the pattern of Anorexia Nervosa patients or slow looser postmenopausal osteoporosis. However, beside unloading, other risk factors for space osteoporosis exist such as stress, nutrition, fluid shifts, dehydration and bone perfusion. Especially nutritional factors may contribute considerably to the development of osteoporosis. From earthbound studies it is known that calcium supplementation in women and men can prevent bone loss of 1% bone per year. Based on these results we studied the calcium intake during several European missions and performed an experiment during the German MIR 97 mission

  2. Digital phase-lock loop

    NASA Technical Reports Server (NTRS)

    Thomas, Jr., Jess B. (Inventor)

    1991-01-01

    An improved digital phase lock loop incorporates several distinctive features that attain better performance at high loop gain and better phase accuracy. These features include: phase feedback to a number-controlled oscillator in addition to phase rate; analytical tracking of phase (both integer and fractional cycles); an amplitude-insensitive phase extractor; a more accurate method for extracting measured phase; a method for changing loop gain during a track without loss of lock; and a method for avoiding loss of sampled data during computation delay, while maintaining excellent tracking performance. The advantages of using phase and phase-rate feedback are demonstrated by comparing performance with that of rate-only feedback. Extraction of phase by the method of modeling provides accurate phase measurements even when the number-controlled oscillator phase is discontinuously updated.

  3. Calcium channels, external calcium concentration and cell proliferation.

    PubMed

    Borowiec, Anne-Sophie; Bidaux, Gabriel; Pigat, Natascha; Goffin, Vincent; Bernichtein, Sophie; Capiod, Thierry

    2014-09-15

    Evidence for a role for calcium channel proteins in cell proliferation is numerous suggesting that calcium influx is essential in this physiological process. Several studies in the past thirty years have demonstrated that calcium channel expression levels are determinant in cell proliferation. Voltage-gated, store-operated, second messengers and receptor-operated calcium channels have been associated to cell proliferation. However, the relationship between calcium influx and cell proliferation can be uncoupled in transformed and cancer cells, resulting in an external calcium-independent proliferation. Thus, protein expression could be more important than channel function to trigger cell proliferation suggesting that additional channel functions may be responsible to reconcile calcium channel expression and cell proliferation. When needed, external calcium concentration is obviously important for calcium channel function but it also regulates calcium sensing receptor (CaSR) activity. CaSR can up- or down-regulate cell proliferation depending on physiological conditions. CaSR sensitivity to external calcium is within the 0.5 to 5 mM range and therefore, the role of these receptors in cell proliferation must be taken into account. We therefore suggest here that cell proliferation rates could depend on the relative balance between calcium influx and CaSR activation.

  4. All digital pulsewidth control loop

    NASA Astrophysics Data System (ADS)

    Huang, Hong-Yi; Jan, Shiun-Dian; Pu, Ruei-Iun

    2013-03-01

    This work presents an all-digital pulsewidth control loop (ADPWCL). The proposed system accepts a wide range of input duty cycles and performs a fast correction to the target output pulsewidth. An all-digital delay-locked loop (DLL) with fast locking time using a simplified time to digital converter and a new differential two-step delay element is proposed. The area of the delay element is much smaller than that in conventional designs, while having the same delay range. A test chip is verified in a 0.18-µm CMOS process. The measured duty cycle ranges from 4% to 98% with 7-bit resolution.

  5. LISA Pathfinder: OPD loop characterisation

    NASA Astrophysics Data System (ADS)

    Born, Michael; LPF Collaboration

    2017-05-01

    The optical metrology system (OMS) of the LISA Pathfinder mission is measuring the distance between two free-floating test masses with unprecedented precision. One of the four OMS heterodyne interferometers reads out the phase difference between the reference and the measurement laser beam. This phase from the reference interferometer is common to all other longitudinal interferometer read outs and therefore subtracted. In addition, the phase is fed back via the digital optical pathlength difference (OPD) control loop to keep it close to zero. Here, we analyse the loop parameters and compare them to on-ground measurement results.

  6. Reionization from cosmic string loops

    SciTech Connect

    Olum, Ken D.; Vilenkin, Alexander

    2006-09-15

    Loops formed from a cosmic string network at early times would act as seeds for early formation of halos, which would form galaxies and lead to early reionization. With reasonable guesses about astrophysical and string parameters, the cosmic string scale G{mu} must be no more than about 3x10{sup -8} to avoid conflict with the reionization redshift found by WMAP. The bound is much stronger for superstring models with a small string reconnection probability. For values near the bound, cosmic string loops may explain the discrepancy between the WMAP value and theoretical expectations.

  7. Contraception with intrauterine plastic loops.

    PubMed

    Lippes, J

    1965-12-01

    Intrauterine plastic loops were inserted 2179 times into 1713 patients of the Planned Parenthood Center of Buffalo, New York and from the author's private practice between November 1, 1961 and June 30, 1964 to evaluate the acceptability, effectiveness, reversibility, and side effects of this contraceptive method. Median age of the patients was 26 and their median parity 3. At the Planned Parenthood Center, patients are offered a choice of oral contraception (OC), condoms, diaphragms, jellies, rhythm, and the loop. During 1962, 30% of the new patients chose the loop. In 1963, 48% of new patients chose intrauterine contraception, and this proportion continued through June 1964. It rose to 55% early in 1965. 41 pregnancies occurred giving an overall pregnancy rate of 2.2/100 woman years for all loops. Loop D had a rate of 1.0/100 woman years. The pregnancy rate was calculated according to Potter's life table procedure. These rates compared favorably with a diaphragm failure rate of 4/100 woman years reported in the Indianapolis study or the diaphragm failure rate of 14.4 reported by Westoff and Potter, as well as with the rate of 2.1 for OC reported by Cook, Gamble, and Satterthwaite. 23 patients became pregnant with a loop in situ. There were 20 loop failures where location of the device was undetermined. Before November 30, 1964, 32 patients had discontinued intrauterine contraception because they wanted a child. All but 3 became pregnant. There were no abortions. The devices are not tolerated by all patients. Side effects consisted primarily of expulsions and bleeding, but pain and the possibility of infection were sometimes present. The monthly expulsion rate decreased with continued use. Most expulsions occurred in the 1st 6 months of use, and the largest and heaviest device had the lowest expulsion rate. 90% of the patients exhibited some alteration of their menstrual pattern. Cramps or pain were only a minor reason for terminating intrauterine contraception

  8. Many Ways to Loop DNA

    PubMed Central

    Griffith, Jack D.

    2013-01-01

    In the 1960s, I developed methods for directly visualizing DNA and DNA-protein complexes using an electron microscope. This made it possible to examine the shape of DNA and to visualize proteins as they fold and loop DNA. Early applications included the first visualization of true nucleosomes and linkers and the demonstration that repeating tracts of adenines can cause a curvature in DNA. The binding of DNA repair proteins, including p53 and BRCA2, has been visualized at three- and four-way junctions in DNA. The trombone model of DNA replication was directly verified, and the looping of DNA at telomeres was discovered. PMID:24005675

  9. Cascading Post-coronal Loops

    NASA Image and Video Library

    2017-04-24

    An active region that had just rotated into view blasted out a coronal mass ejection, which was immediately followed by a bright series of post-coronal loops seeking to reorganize that region's magnetic field (April 19, 2017). We have observed this phenomenon numerous times, but this one was one of the longest and clearest sequences we have seen in years. The bright loops are actually charged particles spinning along the magnetic field lines. The action was captured in a combination of two wavelengths of extreme ultraviolet light over a period of about 20 hours. Movies are available at https://photojournal.jpl.nasa.gov/catalog/PIA21598

  10. moco: Fast Motion Correction for Calcium Imaging.

    PubMed

    Dubbs, Alexander; Guevara, James; Yuste, Rafael

    2016-01-01

    Motion correction is the first step in a pipeline of algorithms to analyze calcium imaging videos and extract biologically relevant information, for example the network structure of the neurons therein. Fast motion correction is especially critical for closed-loop activity triggered stimulation experiments, where accurate detection and targeting of specific cells in necessary. We introduce a novel motion-correction algorithm which uses a Fourier-transform approach, and a combination of judicious downsampling and the accelerated computation of many L 2 norms using dynamic programming and two-dimensional, fft-accelerated convolutions, to enhance its efficiency. Its accuracy is comparable to that of established community-used algorithms, and it is more stable to large translational motions. It is programmed in Java and is compatible with ImageJ.

  11. moco: Fast Motion Correction for Calcium Imaging

    PubMed Central

    Dubbs, Alexander; Guevara, James; Yuste, Rafael

    2016-01-01

    Motion correction is the first step in a pipeline of algorithms to analyze calcium imaging videos and extract biologically relevant information, for example the network structure of the neurons therein. Fast motion correction is especially critical for closed-loop activity triggered stimulation experiments, where accurate detection and targeting of specific cells in necessary. We introduce a novel motion-correction algorithm which uses a Fourier-transform approach, and a combination of judicious downsampling and the accelerated computation of many L2 norms using dynamic programming and two-dimensional, fft-accelerated convolutions, to enhance its efficiency. Its accuracy is comparable to that of established community-used algorithms, and it is more stable to large translational motions. It is programmed in Java and is compatible with ImageJ. PMID:26909035

  12. Combined chemical looping for energy storage and conversion

    NASA Astrophysics Data System (ADS)

    Galvita, Vladimir V.; Poelman, Hilde; Marin, Guy B.

    2015-07-01

    Combined chemical looping was demonstrated as novel concept of energy storage in a laboratory scale test. The proposed technology is able to store and release energy from redox chemical looping reactions combined with calcium looping. This process uses Fe3O4 and CaO, two low cost and environmentally friendly materials, while CH4 + CO2 serve as feed. During the reduction of Fe3O4 by CH4, both formation of carbon and metallic iron occur. CO2 acts as mediation gas to facilitate the metal/metal oxide redox reaction and carbon gasification into CO. CaO, on the other hand, is used for storage of CO2. Upon temperature rise, CaCO3 releases CO2, which re-oxidizes the carbon deposits and reduced Fe, thus producing carbon monoxide. The amount of produced CO is higher than the theoretical amount for Fe3O4, because carbon deposits from CH4 equally contribute to the CO yield. After each redox cycle, the material is regenerated, so that it can be used repeatedly, providing a stable process.

  13. High Blood Calcium (Hypercalcemia)

    MedlinePlus

    ... as sarcoidosis • Hormone disorders, such as overactive thyroid (hyperthyroidism) • A genetic condition called familial hypocalciuric hypercalcemia • Kidney ... topics: www.hormone.org (search for PHPT, calcium, hyperthyroidism, or osteoporosis) • MedlinePlus (National Institutes of Health-NIH): ...

  14. Calcium silicate insulation structure

    DOEpatents

    Kollie, Thomas G.; Lauf, Robert J.

    1995-01-01

    An insulative structure including a powder-filled evacuated casing utilizes a quantity of finely divided synthetic calcium silicate having a relatively high surface area. The resultant structure-provides superior thermal insulating characteristics over a broad temperature range and is particularly well-suited as a panel for a refrigerator or freezer or the insulative barrier for a cooler or a insulated bottle.

  15. Calcium biofortification of crops

    USDA-ARS?s Scientific Manuscript database

    More than half of the world's population is deficient in calcium (Ca), iron (Fe), iodine (I), magnesium (Mg), selenium (Se), or zinc (Zn). The consumption of plants, directly or via livestock, containing inadequate concentrations of particular minerals causes these deficiencies. Agronomic and geneti...

  16. Diet and calcium stones.

    PubMed Central

    Hughes, J; Norman, R W

    1992-01-01

    OBJECTIVE: To review the current literature on the dietary modification of urinary risk factors as a means of reducing the likelihood of recurrent stone formation and to develop practical dietary recommendations that might be useful to this end. DATA SOURCES: MEDLINE was searched for English-language articles published from 1983 to 1990. Additional references were selected from the bibliographies of identified articles. STUDY SELECTION: Nonrandomized trials and retrospective reviews were included because of a paucity of randomized controlled trials. DATA SYNTHESIS: Information on the dietary intake of calcium, oxalate, protein, sodium and fibre and on alcohol and fluid intake was used to develop practical guidelines on dietary modification. CONCLUSION: Dietary modification plays an important role in the reduction of urinary risk factors in patients with calcium stone disease of the urinary tract. As an initial form of prevention attention should be directed toward moderating the intake of calcium, oxalate, protein, sodium and alcohol and increasing the intake of fibre and water. Future research should include an assessment of the long-term reduction of dietary and urinary risk factors and the rates of recurrence of calcium stones. PMID:1310430

  17. Calcium and Vitamin D

    USDA-ARS?s Scientific Manuscript database

    Adequate intakes of vitamin D and calcium are essential preventative measures and essential components of any therapeutic regimen for osteoporosis. Vitamin D is also important for the prevention of falls. Current evidence suggests that a 25-hydroxyvitamin D level of 75 nmol/L (30 ng/ml) or higher ...

  18. Assay for calcium channels

    SciTech Connect

    Glossmann, H.; Ferry, D.R.

    1985-01-01

    This chapter focuses on biochemical assays for Ca/sup 2 +/-selective channels in electrically excitable membranes which are blocked in electrophysiological and pharmacological experiments by verapamil, 1,4-dihydropyridines, diltiazen (and various other drugs), as well as inorganic di- or trivalent cations. The strategy employed is to use radiolabeled 1,4-dihydropyridine derivatives which block calcium channels with ED/sub 50/ values in the nanomolar range. Although tritiated d-cis-diltiazem and verapamil can be used to label calcium channels, the 1,4-dihydropyridines offer numerous advantages. The various sections cover tissue specificity of channel labeling, the complex interactions of divalent cations with the (/sup 3/H)nimodipine-labeled calcium channels, and the allosteric regulation of (/sup 3/H)nimodipine binding by the optically pure enantiomers of phenylalkylamine and benzothiazepine calcium channel blockers. A comparison of the properties of different tritiated 1,4-dihydropyridine radioligands and the iodinated channel probe (/sup 125/I)iodipine is given.

  19. Antenatal calcium intake in Malaysia.

    PubMed

    Mahdy, Zaleha Abdullah; Basri, Hashimah; Md Isa, Zaleha; Ahmad, Shuhaila; Shamsuddin, Khadijah; Mohd Amin, Rahmah

    2014-04-01

    To determine the adequacy of antenatal calcium intake in Malaysia, and the influencing factors. A cross-sectional study was conducted among postnatal women who delivered in two tertiary hospitals. Data were collected from antenatal cards, hospital documents and diet recall on daily milk and calcium intake during pregnancy. SPSS version 19.0 was used for statistical analyses. A total of 150 women were studied. The total daily calcium intake was 834 ± 43 mg (mean ± standard error of the mean), but the calcium intake distribution curve was skewed to the right with a median intake of 725 mg daily. When calcium intake from milk and calcium supplements was excluded, the daily dietary calcium intake was only 478 ± 25 mg. Even with inclusion of milk and calcium supplements, more than a third (n=55 or 36.7%) of the women consumed less than 600 mg calcium in their daily diet. The adequacy of daily calcium intake was not influenced by maternal age, ethnicity, income or maternal job or educational status as well as parity. The daily dietary calcium intake of the Malaysian antenatal population is far from adequate without the addition of calcium supplements and milk. © 2013 The Authors. Journal of Obstetrics and Gynaecology Research © 2013 Japan Society of Obstetrics and Gynecology.

  20. The Plasma Membrane Calcium Pump

    NASA Technical Reports Server (NTRS)

    Rasmussen, H.

    1983-01-01

    Three aspect of cellular calcium metabolism in animal cells was discussed including the importance of the plasma membrane in calcium homeostasis, experiments dealing with the actual mechanism of the calcium pump, and the function of the pump in relationship to the mitochondria and to the function of calmodulin in the intact cell.

  1. The Plasma Membrane Calcium Pump

    NASA Technical Reports Server (NTRS)

    Rasmussen, H.

    1983-01-01

    Three aspect of cellular calcium metabolism in animal cells was discussed including the importance of the plasma membrane in calcium homeostasis, experiments dealing with the actual mechanism of the calcium pump, and the function of the pump in relationship to the mitochondria and to the function of calmodulin in the intact cell.

  2. Impregnating Coal With Calcium Carbonate

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Voecks, Gerald E.; Gavalas, George R.

    1991-01-01

    Relatively inexpensive process proposed for impregnating coal with calcium carbonate to increase rates of gasification and combustion of coal and to reduce emission of sulfur by trapping sulfur in calcium sulfide. Process involves aqueous-phase reactions between carbon dioxide (contained within pore network of coal) and calcium acetate. Coal impregnated with CO2 by exposing it to CO2 at high pressure.

  3. Bioceramics of calcium orthophosphates.

    PubMed

    Dorozhkin, Sergey V

    2010-03-01

    A strong interest in use of ceramics for biomedical applications appeared in the late 1960's. Used initially as alternatives to metals in order to increase a biocompatibility of implants, bioceramics have become a diverse class of biomaterials, presently including three basic types: relatively bioinert ceramics, bioactive (or surface reactive) and bioresorbable ones. Furthermore, any type of bioceramics could be porous to provide tissue ingrowth. This review is devoted to bioceramics prepared from calcium orthophosphates, which belong to the categories of bioresorbable and bioactive compounds. During the past 30-40 years, there have been a number of major advances in this field. Namely, after the initial work on development of bioceramics that was tolerated in the physiological environment, emphasis was shifted towards the use of bioceramics that interacted with bones by forming a direct chemical bond. By the structural and compositional control, it became possible to choose whether the bioceramics of calcium orthophosphates was biologically stable once incorporated within the skeletal structure or whether it was resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics, which is able to regenerate bone tissues, has been developed. Current biomedical applications of calcium orthophosphate bioceramics include replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Potential future applications of calcium orthophosphate bioceramics will include drug-delivery systems, as well as they will become effective carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes.

  4. Variations of intestinal calcium absorption in adult frogs (Rana esculenta). Effect of lysine.

    PubMed

    el Maraghi-Ater, H; Hourdry, J; Mesnard, J; Dupuis, Y

    1987-01-01

    Intestinal calcium absorption was investigated in an adult frog (Rana esculenta) by injecting a CaCl2 solution containing 45Ca into the lumen. The 45Ca absorption coefficient in the proximal loop was higher than in the distal loop, only when the CaCl2 solution was left for 4 h. This coefficient increased both in the proximal and distal loops when a 4-h treatment was substituted for a 1-h treatment. The coefficient increased in the whole intestine during the first 2 h of treatment (1 h: 21%; 2 h: 55%) and remained stable afterwards in our experimental conditions. The intestinal calcium absorption increase occurred early in the presence of L-lysine (100 mM), since the coefficient already reached its maximum value (52%) after a 1-h treatment.

  5. Loop quantum cosmology gravitational baryogenesis

    NASA Astrophysics Data System (ADS)

    Odintsov, S. D.; Oikonomou, V. K.

    2016-11-01

    Loop quantum cosmology is an appealing quantum completion of classical cosmology, which brings along various theoretical features which in many cases offer a remedy for or modify various classical cosmology aspects. In this paper we address the gravitational baryogenesis mechanism in the context of loop quantum cosmology. As we demonstrate, when loop quantum cosmology effects are taken into account in the resulting Friedmann equations for a flat Friedmann-Robertson-Walker Universe, then even for a radiation-dominated Universe, the predicted baryon-to-entropy ratio from the gravitational baryogenesis mechanism is non-zero, in contrast to the Einstein-Hilbert case, in which case the baryon-to-entropy ratio is zero. We also discuss various other cases apart from the radiation domination case, and we discuss how the baryon-to-entropy ratio is affected from the parameters of the quantum theory. In addition, we use illustrative exact solutions of loop quantum cosmology and we investigate under which circumstances the baryon-to-entropy ratio can be compatible with the observational constraints.

  6. Loop quantum cosmology and singularities.

    PubMed

    Struyve, Ward

    2017-08-15

    Loop quantum gravity is believed to eliminate singularities such as the big bang and big crunch singularity. This belief is based on studies of so-called loop quantum cosmology which concerns symmetry-reduced models of quantum gravity. In this paper, the problem of singularities is analysed in the context of the Bohmian formulation of loop quantum cosmology. In this formulation there is an actual metric in addition to the wave function, which evolves stochastically (rather than deterministically as the case of the particle evolution in non-relativistic Bohmian mechanics). Thus a singularity occurs whenever this actual metric is singular. It is shown that in the loop quantum cosmology for a homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker space-time with arbitrary constant spatial curvature and cosmological constant, coupled to a massless homogeneous scalar field, a big bang or big crunch singularity is never obtained. This should be contrasted with the fact that in the Bohmian formulation of the Wheeler-DeWitt theory singularities may exist.

  7. Closed-Loop Neuromorphic Benchmarks

    PubMed Central

    Stewart, Terrence C.; DeWolf, Travis; Kleinhans, Ashley; Eliasmith, Chris

    2015-01-01

    Evaluating the effectiveness and performance of neuromorphic hardware is difficult. It is even more difficult when the task of interest is a closed-loop task; that is, a task where the output from the neuromorphic hardware affects some environment, which then in turn affects the hardware's future input. However, closed-loop situations are one of the primary potential uses of neuromorphic hardware. To address this, we present a methodology for generating closed-loop benchmarks that makes use of a hybrid of real physical embodiment and a type of “minimal” simulation. Minimal simulation has been shown to lead to robust real-world performance, while still maintaining the practical advantages of simulation, such as making it easy for the same benchmark to be used by many researchers. This method is flexible enough to allow researchers to explicitly modify the benchmarks to identify specific task domains where particular hardware excels. To demonstrate the method, we present a set of novel benchmarks that focus on motor control for an arbitrary system with unknown external forces. Using these benchmarks, we show that an error-driven learning rule can consistently improve motor control performance across a randomly generated family of closed-loop simulations, even when there are up to 15 interacting joints to be controlled. PMID:26696820

  8. Bimodal loop-gap resonator

    NASA Astrophysics Data System (ADS)

    Piasecki, W.; Froncisz, W.; Hyde, James S.

    1996-05-01

    A bimodal loop-gap resonator for use in electron paramagnetic resonance (EPR) spectroscopy at S band is described. It consists of two identical one-loop-one-gap resonators in coaxial juxtaposition. In one mode, the currents in the two loops are parallel and in the other antiparallel. By introducing additional capacitors between the loops, the frequencies of the two modes can be made to coincide. Details are given concerning variable coupling to each mode, tuning of the resonant frequency of one mode to that of the other, and adjustment of the isolation between modes. An equivalent circuit is given and network analysis carried out both experimentally and theoretically. EPR applications are described including (a) probing of the field distributions with DPPH, (b) continuous wave (cw) EPR with a spin-label line sample, (c) cw electron-electron double resonance (ELDOR), (d) modulation of saturation, and (e) saturation-recovery (SR) EPR. Bloch induction experiments can be performed when the sample extends half way through the structure, but microwave signals induced by Mx and My components of magnetization cancel when it extends completely through. This latter situation is particularly favorable for SR, modulation of saturation, and ELDOR experiments, which depend on observing Mz indirectly using a second weak observing microwave source.

  9. Ponderomotive Acceleration in Coronal Loops

    NASA Astrophysics Data System (ADS)

    Dahlburg, R. B.; Laming, J. M.; Taylor, B. D.; Obenschain, K.

    2016-11-01

    Ponderomotive acceleration has been asserted to be a cause of the first ionization potential (FIP) effect, the well-known enhancement in abundance by a factor of 3-4 over photospheric values of elements in the solar corona with FIP less than about 10 eV. It is shown here by means of numerical simulations that ponderomotive acceleration occurs in solar coronal loops, with the appropriate magnitude and direction, as a “by-product” of coronal heating. The numerical simulations are performed with the HYPERION code, which solves the fully compressible three-dimensional magnetohydrodynamic equations including nonlinear thermal conduction and optically thin radiation. Numerical simulations of coronal loops with an axial magnetic field from 0.005 to 0.02 T and lengths from 25,000 to 75,000 km are presented. In the simulations the footpoints of the axial loop magnetic field are convected by random, large-scale motions. There is a continuous formation and dissipation of field-aligned current sheets, which act to heat the loop. As a consequence of coronal magnetic reconnection, small-scale, high-speed jets form. The familiar vortex quadrupoles form at reconnection sites. Between the magnetic footpoints and the corona the reconnection flow merges with the boundary flow. It is in this region that the ponderomotive acceleration occurs. Mirroring the character of the coronal reconnection, the ponderomotive acceleration is also found to be intermittent.

  10. Telomeres thrown for a loop.

    PubMed

    Haber, James E

    2004-11-19

    A remarkable paper from the de Lange lab (Wang et al., 2004) in a recent issue of Cell reveals that homologous recombination can result in the abrupt shortening of telomeres in a process that appears to involve reciprocal crossing over within the t-loop structure that protects chromosome ends.

  11. Ponderomotive Acceleration in Coronal Loops

    NASA Astrophysics Data System (ADS)

    Dahlburg, Russell B.; Laming, J. Martin; Taylor, Brian; Obenschain, Keith

    2017-08-01

    Ponderomotive acceleration has been asserted to be a cause of the First Ionization Potential (FIP) effect, the by now well known enhancement in abundance by a factor of 3-4 over photospheric values of elements in the solar corona with FIP less than about 10 eV. It is shown here by means of numerical simulations that ponderomotive acceleration occurs in solar coronal loops, with the appropriate magnitude and direction, as a ``byproduct'' of coronal heating. The numerical simulations are performed with the HYPERION code, which solves the fully compressible three-dimensional magnetohydrodynamic equations including nonlinear thermal conduction and optically thin radiation. Numerical simulations of a coronal loops with an axial magnetic field from 0.005 Teslas to 0.02 Teslas and lengths from 25000 km to 75000 km are presented. In the simulations the footpoints of the axial loop magnetic field are convected by random, large-scale motions. There is a continuous formation and dissipation of field-aligned current sheets which act to heat the loop. As a consequence of coronal magnetic reconnection, small scale, high speed jets form. The familiar vortex quadrupoles form at reconnection sites. Between the magnetic footpoints and the corona the reconnection flow merges with the boundary flow. It is in this region that the ponderomotive acceleration occurs. Mirroring the character of the coronal reconnection, the ponderomotive acceleration is also found to be intermittent.

  12. Voltage-Gated Calcium Channels

    NASA Astrophysics Data System (ADS)

    Zamponi, Gerald Werner

    Voltage Gated Calcium Channels is the first comprehensive book in the calcium channel field, encompassing over thirty years of progress towards our understanding of calcium channel structure, function, regulation, physiology, pharmacology, and genetics. This book balances contributions from many of the leading authorities in the calcium channel field with fresh perspectives from risings stars in the area, taking into account the most recent literature and concepts. This is the only all-encompassing calcium channel book currently available, and is an essential resource for academic researchers at all levels in the areas neuroscience, biophysics, and cardiovascular sciences, as well as to researchers in the drug discovery area.

  13. Calcium Phosphates and Human Beings

    NASA Astrophysics Data System (ADS)

    Dorozhkin, Sergey V.

    2006-05-01

    This article describes the general importance of calcium phosphates for human beings. The basic information on the structure and chemical properties of the biologically relevant calcium phosphates is summarized. Basic facts on the natural occurrence and the industrial use of natural calcium phosphates are discussed. Fundamental details on the presence of calcium phosphates in major calcified tissues (bones and teeth) of humans and mammals, as well as on biomaterials made of calcium phosphates are discussed. The article will be of value for chemistry teachers for expansion of their general background and point the students' attention to the rapidly growing topic of bone-substituting biomaterials.

  14. Calcium signaling in taste cells.

    PubMed

    Medler, Kathryn F

    2015-09-01

    The sense of taste is a common ability shared by all organisms and is used to detect nutrients as well as potentially harmful compounds. Thus taste is critical to survival. Despite its importance, surprisingly little is known about the mechanisms generating and regulating responses to taste stimuli. All taste responses depend on calcium signals to generate appropriate responses which are relayed to the brain. Some taste cells have conventional synapses and rely on calcium influx through voltage-gated calcium channels. Other taste cells lack these synapses and depend on calcium release to formulate an output signal through a hemichannel. Beyond establishing these characteristics, few studies have focused on understanding how these calcium signals are formed. We identified multiple calcium clearance mechanisms that regulate calcium levels in taste cells as well as a calcium influx that contributes to maintaining appropriate calcium homeostasis in these cells. Multiple factors regulate the evoked taste signals with varying roles in different cell populations. Clearly, calcium signaling is a dynamic process in taste cells and is more complex than has previously been appreciated. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

  15. Bile salts and calcium absorption

    PubMed Central

    Webling, D. D'A.; Holdsworth, E. S.

    1966-01-01

    1. The study of the effect of bile salts on enhancing calcium absorption in the rachitic chick has been extended to bile salts not present in chick bile, e.g. glycine conjugates and bile alcohol sulphates. 2. Bile and bile salts cause an increase in calcium absorption from sparingly soluble calcium hydrogen phosphate when compared with a suspension of calcium hydrogen phosphate in saline. 3. If the bile ducts of normal rats are tied the absorption of calcium from calcium hydrogen phosphate decreases but can be restored by giving bile salts with the calcium salt. 4. Bile salts increase solubility in water of the sparingly soluble calcium salts, phytate and phosphate at pH values between 6 and 8. 5. Bile salts increase the solubility in lipid solvents of calcium in approximately the same proportion as they increase the absorption of calcium from the gut. 6. The physiological role of bile in calcium absorption and its mode of action are discussed. PMID:4291037

  16. Characterization of a helix-loop-helix (EF hand) motif of silver hake parvalbumin isoform B.

    PubMed Central

    Revett, S. P.; King, G.; Shabanowitz, J.; Hunt, D. F.; Hartman, K. L.; Laue, T. M.; Nelson, D. J.

    1997-01-01

    Parvalbumins are a class of calcium-binding proteins characterized by the presence of several helix-loop-helix (EF-hand) motifs. It is suspected that these proteins evolved via intragene duplication from a single EF-hand. Silver hake parvalbumin (SHPV) consists of three EF-type helix-loop-helix regions, two of which have the ability to bind calcium. The three helix-loop-helix motifs are designated AB, CD, and EF, respectively. In this study, native silver hake parvalbumin isoform B (SHPV-B) has been sequenced by mass spectrometry. The sequence indicates that this parvalbumin is a beta-lineage parvalbumin. SHPV-B was cleaved into two major fragments, consisting of the ABCD and EF regions of the native protein. The 33-amino acid EF fragment (residues 76-108), containing one of the calcium ion binding sites in native SHPV-B, has been isolated and studied for its structural characteristics, ability to bind divalent and trivalent cations, and for its propensity to undergo metal ion-induced self-association. The presence of Ca2+ does not induce significant secondary structure in the EF fragment. However, NMR and CD results indicate significant secondary structure promotion in the EF fragment in the presence of the higher charge-density trivalent cations. Sedimentation equilibrium analysis results show that the EF fragment exists in a monomer-dimer equilibrium when complexed with La3+. PMID:9385642

  17. Characterization of a helix-loop-helix (EF hand) motif of silver hake parvalbumin isoform B.

    PubMed

    Revett, S P; King, G; Shabanowitz, J; Hunt, D F; Hartman, K L; Laue, T M; Nelson, D J

    1997-11-01

    Parvalbumins are a class of calcium-binding proteins characterized by the presence of several helix-loop-helix (EF-hand) motifs. It is suspected that these proteins evolved via intragene duplication from a single EF-hand. Silver hake parvalbumin (SHPV) consists of three EF-type helix-loop-helix regions, two of which have the ability to bind calcium. The three helix-loop-helix motifs are designated AB, CD, and EF, respectively. In this study, native silver hake parvalbumin isoform B (SHPV-B) has been sequenced by mass spectrometry. The sequence indicates that this parvalbumin is a beta-lineage parvalbumin. SHPV-B was cleaved into two major fragments, consisting of the ABCD and EF regions of the native protein. The 33-amino acid EF fragment (residues 76-108), containing one of the calcium ion binding sites in native SHPV-B, has been isolated and studied for its structural characteristics, ability to bind divalent and trivalent cations, and for its propensity to undergo metal ion-induced self-association. The presence of Ca2+ does not induce significant secondary structure in the EF fragment. However, NMR and CD results indicate significant secondary structure promotion in the EF fragment in the presence of the higher charge-density trivalent cations. Sedimentation equilibrium analysis results show that the EF fragment exists in a monomer-dimer equilibrium when complexed with La3+.

  18. Evolution in a Braided Loop Ensemble

    NASA Image and Video Library

    This braided loop has several loops near the 'base' that appear to be unwinding with significant apparent outflow. This is evidence of untwisting, and the braided structure also seeming to unwind w...

  19. Crystal packing effects on protein loops.

    PubMed

    Rapp, Chaya S; Pollack, Rena M

    2005-07-01

    The effects of crystal packing on protein loop structures are examined by (1) a comparison of loops in proteins that have been crystallized in alternate packing arrangements, and (2) theoretical prediction of loops both with and without the inclusion of the crystal environment. Results show that in a minority of cases, loop geometries are dependent on crystal packing effects. Explicit representation of the crystal environment in a loop prediction algorithm can be used to model these effects and to reconstruct the structures, and relative energies, of a loop in alternative packing environments. By comparing prediction results with and without the inclusion of the crystal environment, the loop prediction algorithm can further be used to identify cases in which a crystal structure does not represent the most stable state of a loop in solution. We anticipate that this capability has implications for structural biology.

  20. Fruit Calcium: Transport and Physiology

    PubMed Central

    Hocking, Bradleigh; Tyerman, Stephen D.; Burton, Rachel A.; Gilliham, Matthew

    2016-01-01

    Calcium has well-documented roles in plant signaling, water relations and cell wall interactions. Significant research into how calcium impacts these individual processes in various tissues has been carried out; however, the influence of calcium on fruit ripening has not been thoroughly explored. Here, we review the current state of knowledge on how calcium may impact the development, physical traits and disease susceptibility of fruit through facilitating developmental and stress response signaling, stabilizing membranes, influencing water relations and modifying cell wall properties through cross-linking of de-esterified pectins. We explore the involvement of calcium in hormone signaling integral to the physiological mechanisms behind common disorders that have been associated with fruit calcium deficiency (e.g., blossom end rot in tomatoes or bitter pit in apples). This review works toward an improved understanding of how the many roles of calcium interact to influence fruit ripening, and proposes future research directions to fill knowledge gaps. Specifically, we focus mostly on grapes and present a model that integrates existing knowledge around these various functions of calcium in fruit, which provides a basis for understanding the physiological impacts of sub-optimal calcium nutrition in grapes. Calcium accumulation and distribution in fruit is shown to be highly dependent on water delivery and cell wall interactions in the apoplasm. Localized calcium deficiencies observed in particular species or varieties can result from differences in xylem morphology, fruit water relations and pectin composition, and can cause leaky membranes, irregular cell wall softening, impaired hormonal signaling and aberrant fruit development. We propose that the role of apoplasmic calcium-pectin crosslinking, particularly in the xylem, is an understudied area that may have a key influence on fruit water relations. Furthermore, we believe that improved knowledge of the calcium

  1. Complexometric Determination of Calcium

    NASA Astrophysics Data System (ADS)

    Nielsen, S. Suzanne

    Ethylenediaminetetraacetate (EDTA) complexes with numerous mineral ions, including calcium and magnesium. This reaction can be used to determine the amount of these minerals in a sample by a complexometric titration. Endpoints in the titration are detected using indicators that change color when they complex with mineral ions. Calmagite and eriochrome black T (EBT) are such indicators that change from blue to pink when they complex with calcium and magnesium. In the titration of a mineral-containing solution with EDTA, the solution turns from pink to blue at the endpoint with either indicator. The pH affects a complexometric EDTA titration in several ways, and must be carefully controlled. A major application of EDTA titration is testing the hardness of water, for which the method described is an official one (Standard Methods for the Examination of Water and Wastewater, Method 2340C; AOAC Method 920.196).

  2. Nutrition in calcium nephrolithiasis

    PubMed Central

    2013-01-01

    Idiopathic calcium nephrolithiasis is a multifactorial disease with a complex pathogenesis due to genetic and environmental factors. The importance of social and health effects of nephrolithiasis is further highlighted by the strong tendency to relapse of the disease. Long-term prospective studies show a peak of disease recurrence within 2–3 years since onset, 40-50% of patients have a recurrence after 5 years and more than 50-60% after 10 years. International nutritional studies demonstrated that nutritional habits are relevant in therapy and prevention approaches of nephrolithiasis. Water, right intake of calcium, low intake of sodium, high levels of urinary citrate are certainly important for the primary and secondary prevention of nephrolithiasis. In this review is discussed how the correction of nutritional mistakes can reduce the incidence of recurrent nephrolithiasis. PMID:23634702

  3. DISTILLATION OF CALCIUM

    DOEpatents

    Barton, J.

    1954-07-27

    This invention relates to an improvement in the process for the purification of caicium or magnesium containing an alkali metal as impurity, which comprises distiiling a batch of the mixture in two stages, the first stage distillation being carried out in the presence of an inert gas at an absolute pressure substantially greater than the vapor pressure of calcium or maguesium at the temperature of distillation, but less than the vaper pressure at that temperature of the alkali metal impurity so that only the alkali metal is vaporized and condensed on a condensing surface. A second stage distilso that substantially only the calcium or magnesium distills under its own vapor pressure only and condenses in solid form on a lower condensing surface.

  4. Synthesis of calcium superoxide

    NASA Technical Reports Server (NTRS)

    Rewick, R. T.; Blucher, W. G.; Estacio, P. L.

    1972-01-01

    Efforts to prepare Ca(O2) sub 2 from reactions of calcium compounds with 100% O3 and with O(D-1) atoms generated by photolysis of O3 at 2537 A are described. Samples of Ca(OH) sub 2, CaO, CaO2, Ca metal, and mixtures containing suspected impurities to promote reaction have been treated with excess O3 under static and flow conditions in the presence and absence of UV irradiation. Studies with KO2 suggest that the superoxide anion is stable to radiation at 2537 A but reacts with oxygen atoms generated by the photolysis of O3 to form KO3. Calcium superoxide is expected to behave in an analogous.

  5. Optimum design of hybrid phase locked loops

    NASA Technical Reports Server (NTRS)

    Lee, P.; Yan, T.

    1981-01-01

    The design procedure of phase locked loops is described in which the analog loop filter is replaced by a digital computer. Specific design curves are given for the step and ramp input changes in phase. It is shown that the designed digital filter depends explicitly on the product of the sampling time and the noise bandwidth of the phase locked loop. This technique of optimization can be applied to the design of digital analog loops for other applications.

  6. Fragmentation of cosmic-string loops

    NASA Technical Reports Server (NTRS)

    York, Thomas

    1989-01-01

    The fragmentation of cosmic string loops is discussed, and the results of a simulation of this process are presented. The simulation can evolve any of a large class of loops essentially exactly, including allowing fragments that collide to join together. Such reconnection enhances the production of small fragments, but not drastically. With or without reconnections, the fragmentation process produces a collection of nonself-intersecting loops whose typical length is on the order of the persistence length of the initial loop.

  7. Calcium antagonists and vasospasm.

    PubMed

    Meyer, F B

    1990-04-01

    A critical review of the clinical data supports the conclusion that nimodipine decreases the severity of neurologic deficits and improves outcome after subarachnoid hemorrhage. The mechanisms by which mortality and morbidity are reduced are still controversial. First, the frequency of vasospasm is not altered (Figs. 5 and 6). Second, the consistent reversal of vasospasm once present has not been demonstrated either angiographically or by noninvasive cerebral blood flow studies. These observations suggest that there is either modification of microcirculatory flow (i.e., dilation of pial conducting vessels or decreased platelet aggregation) or a direct neuronal protective effect. As suggested previously, support for either mechanism is not resolute, and further investigation is necessary. Currently, nimodipine has been the most thoroughly investigated calcium antagonist both from an experimental and clinical perspective. Oral administration has had few reported complications. Therefore, the benefit/risk ratio clearly supports the prophylactic use of this calcium antagonist in patients of all clinical grades after subarachnoid hemorrhage. Evidence also indicates that starting nimodipine after the onset of delayed ischemic deficits is of benefit. Finally, it can be predicted that in the future additional calcium antagonists with more selective vascular or neuronal effects will be developed for use in neurologic disorders.

  8. Availability of calcium from skim milk, calcium sulfate and calcium carbonate for bone mineralization in pigs.

    PubMed

    Pointillart, A; Coxam, V; Sève, B; Colin, C; Lacroix, C H; Guéguen, L

    2000-01-01

    Dairy products provide abundant, accessible calcium for humans, while some calcium sulfate-rich mineral waters could provide appreciable amounts of calcium. But there is little evidence that this calcium is as available as milk calcium for making bone. The availability of calcium was studied by monitoring bone parameters in 2-month-old pigs fed restricted amounts of calcium (70% RDA) for 2.5 months. The 3 main (> or = 50% Ca intake) Ca sources were either CaCO3 or CaSO4 or skim milk powder (29% of the diet). The bones of the pigs fed the "milk" diet had higher (P < 0.01) ash contents, breaking strength and density (DEXA) than those of the two others groups, in which the bone values were similar. Thus, the calcium provided by a diet containing milk appears to ensure better bone mineralization than do calcium salts included in a non-milk diet. The calcium restriction may have enhanced some milk properties to stimulate calcium absorption in these young, rapidly growing pigs.

  9. Data-aided carrier tracking loops

    NASA Technical Reports Server (NTRS)

    Lindsey, W. C.; Simon, M. K.

    1973-01-01

    Power in composite signal sidebands is used to enhance signal-to-noise ratio in carrier tracking loop, thereby reducing radio loss and decreasing probability of receiver error. By adding quadrature channel to phase-lock-loop detector circuit of receiver, dc component can be fed back into carrier tracking loop.

  10. Teachers' Perception of Looping in Secondary Schools

    ERIC Educational Resources Information Center

    Chakey, Dennis J.

    2014-01-01

    The purpose of this qualitative study was to gain an understanding of secondary teachers' perception of the looping process. The research questions revealed teachers' opinions of the looping process and its impact on the overall educational experience. Participants within this study had experiences teaching within the looping process and within a…

  11. Measurement of cytosolic calcium: fluorescent calcium indicators.

    PubMed

    Rink, T J

    1988-01-01

    The invention of intracellularly trappable fluorescent indicators of [Ca2+i] has provided an important new way to answer many key questions about the role of Ca2+ and of other messengers in cell activation. Perhaps equally important, the results of these investigations have thrown up many interesting new questions. The suitability of this, or any other method of measuring [Ca2+]i, naturally depends on the tissue, the experimenter, the facilities available and the particular question to be asked. For simply measuring [Ca2+]i, fura-2 and indo-1 are likely to be preferable to quin2, although right now more is known about quin2, its behaviour and its calibration in cells. Anecdotal evidence suggests that indo-1 may have advantages over fura-2 although many more people are presently using fura-2. For manipulating [Ca2+]i by deliberately adding Ca2+ buffering power, quin2 may have advantages and is certainly the tried and tested method. For epithelial cell work, where the relation of the cells to the rest of the tissue and their polarity are critical, suspensions and even monolayer measurements will seldom be adequate. Calcium microelectrodes or single-cell fluorescence techniques will surely be required and rewarding.

  12. Loop Variables in String Theory

    NASA Astrophysics Data System (ADS)

    Sathiapalan, B.

    The loop variable approach is a proposal for a gauge-invariant generalization of the sigma-model renormalization group method of obtaining equations of motion in string theory. The basic guiding principle is space-time gauge invariance rather than world sheet properties. In essence it is a version of Wilson's exact renormalization group equation for the world sheet theory. It involves all the massive modes and is defined with a finite world sheet cutoff, which allows one to go off the mass-shell. On shell the tree amplitudes of string theory are reproduced. The equations are gauge-invariant off shell also. This paper is a self-contained discussion of the loop variable approach as well as its connection with the Wilsonian RG.

  13. Grain boundary loops in graphene

    NASA Astrophysics Data System (ADS)

    Cockayne, Eric; Rutter, Gregory M.; Guisinger, Nathan P.; Crain, Jason N.; First, Phillip N.; Stroscio, Joseph A.

    2011-05-01

    Topological defects can affect the physical properties of graphene in unexpected ways. Harnessing their influence may lead to enhanced control of both material strength and electrical properties. Here we present a class of topological defects in graphene composed of a rotating sequence of dislocations that close on themselves, forming grain boundary loops that either conserve the number of atoms in the hexagonal lattice or accommodate vacancy or interstitial reconstruction, while leaving no unsatisfied bonds. One grain boundary loop is observed as a “flower” pattern in scanning tunneling microscopy studies of epitaxial graphene grown on SiC(0001). We show that the flower defect has the lowest energy per dislocation core of any known topological defect in graphene, providing a natural explanation for its growth via the coalescence of mobile dislocations.

  14. Loop connectors in dentogenic diastema

    PubMed Central

    Nayar, Sanjna; Jayesh, Raghevendra; Venkateshwaran; Dinakarsamy, V.

    2015-01-01

    Patients with a missing tooth along with diastema have limited treatment options to restore the edentulous space. The use of a conventional fixed partial denture (FPD) to replace the missing tooth may result in too wide anterior teeth leading to poor esthetics. Loss of anterior teeth with existing diastema may result in excess space available for pontic. This condition presents great esthetic challenge for prosthodontist. If implant supported prosthesis is not possible because of inadequate bone support, FPD along with loop connector may be a treatment option to maintain the diastema and provide optimal esthetic restoration. Here, we report a clinical case where FPD along with loop connector was used to achieve esthetic rehabilitation in maxillary anterior region in which midline diastema has been maintained. PMID:26015732

  15. The Statistical Loop Analyzer (SLA)

    NASA Technical Reports Server (NTRS)

    Lindsey, W. C.

    1985-01-01

    The statistical loop analyzer (SLA) is designed to automatically measure the acquisition, tracking and frequency stability performance characteristics of symbol synchronizers, code synchronizers, carrier tracking loops, and coherent transponders. Automated phase lock and system level tests can also be made using the SLA. Standard baseband, carrier and spread spectrum modulation techniques can be accomodated. Through the SLA's phase error jitter and cycle slip measurements the acquisition and tracking thresholds of the unit under test are determined; any false phase and frequency lock events are statistically analyzed and reported in the SLA output in probabilistic terms. Automated signal drop out tests can be performed in order to trouble shoot algorithms and evaluate the reacquisition statistics of the unit under test. Cycle slip rates and cycle slip probabilities can be measured using the SLA. These measurements, combined with bit error probability measurements, are all that are needed to fully characterize the acquisition and tracking performance of a digital communication system.

  16. Microgyroscope with closed loop output

    NASA Technical Reports Server (NTRS)

    Challoner, A. Dorian (Inventor); Gutierrez, Roman C. (Inventor); Tang, Tony K. (Inventor); Cargille, Donald R. (Inventor)

    2002-01-01

    A micro-gyroscope (10) having closed loop operation by a control voltage (V.sub.TY), that is demodulated by an output signal of the sense electrodes (S1, S2), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope (10) on the output axis (y-axis). The present invention provides wide-band, closed-loop operation for a micro-gyroscope (10) and allows the drive frequency to be closely tuned to a high Q sense axis resonance. A differential sense signal (S1-S2) is compensated and fed back by differentially changing the voltage on the drive electrodes to rebalance Coriolis torque. The feedback signal is demodulated in phase with the drive axis signal (K.sub..omega..crclbar..sub.x) to produce a measure of the Coriolis force.

  17. DNA Looping, Supercoiling and Tension

    NASA Astrophysics Data System (ADS)

    Finzi, Laura

    2007-11-01

    In complex organisms, activation or repression of gene expression by proteins bound to enhancer or silencer elements located several kilobases away from the promoter is a well recognized phenomenon. However, a mechanistic understanding of any of these multiprotein interactions is still incomplete. Part of the difficulty in characterizing long-range interactions is the complexity of the regulatory systems and also an underestimation of the effect of DNA supercoiling and tension. Supercoiling is expected to promote interactions between DNA sites because it winds the DNA into compact plectonemes in which distant DNA segments more frequently draw close. The idea that DNA is also under various levels of tension is becoming more widely accepted. Forces that stretch the double helix in vivo are the electrostatic repulsion among the negatively charged phosphate groups along the DNA backbone, the action of motor enzymes perhaps acting upon a topologically constrained sequence of DNA or chromosome segregation during cell mitosis following DNA replication. Presently, little is known about the tension acting on DNA in vivo, but characterization of how physiological regulatory processes, such as loop formation, depend on DNA tension in vitro will indicate the stretching force regimes likely to exist in vivo. In this light, the well studied CI protein of bacteriophage l, which was recently found to cause a of 3.8 kbp loop in DNA, is an ideal system in which to characterize long-range gene regulation. The large size of the loop lends itself to single-molecule techniques, which allow characterization of the dynamics of CI-mediated l DNA looping under controlled levels of supercoiling and tension. Such experiments are being used to discover the principles of long-range interactions in l and in more complex systems.

  18. A model of propagating calcium-induced calcium release mediated by calcium diffusion

    PubMed Central

    1989-01-01

    The effect of sudden local fluctuations of the free sarcoplasmic [Ca++]i in cardiac cells on calcium release and calcium uptake by the sarcoplasmic reticulum (SR) was calculated with the aid of a simplified model of SR calcium handling. The model was used to evaluate whether propagation of calcium transients and the range of propagation velocities observed experimentally (0.05-15 mm s(-1)) could be predicted. Calcium fluctuations propagate by virtue of focal calcium release from the SR, diffusion through the cytosol (which is modulated by binding to troponin and calmodulin and sequestration by the SR), and subsequently induce calcium release from adjacent release sites of the SR. The minimal and maximal velocities derived from the simulation were 0.09 and 15 mm s(-1) respectively. The method of solution involved writing the diffusion equation as a difference equation in the spatial coordinates. Thus, coupled ordinary differential equations in time with banded coefficients were generated. The coupled equations were solved using Gear's sixth order predictor-corrector algorithm for stiff equations with reflective boundaries. The most important determinants of the velocity of propagation of the calcium waves were the diastolic [Ca++]i, the rate of rise of the release, and the amount of calcium released from the SR. The results are consistent with the assumptions that calcium loading causes an increase in intracellular calcium and calcium in the SR, and an increase in the amount and rate of calcium released. These two effects combine to increase the propagation velocity at higher levels of calcium loading. PMID:2738577

  19. Calcium bioavailability and kinetics of calcium ascorbate and calcium acetate in rats.

    PubMed

    Cai, Jianwei; Zhang, Qinmin; Wastney, Meryl E; Weaver, Connie M

    2004-01-01

    The objective was to investigate the bioavailability and mechanism of calcium absorption of calcium ascorbate (ASC) and calcium acetate (AC). A series of studies was performed in adult Sprague-Dawley male rats. In the first study, each group of rats (n = 10/group) was assigned to one of the five test meals labeled with (45)Ca: (i) 25 mg calcium as heated ASC or (ii) unheated ASC, (iii) 25 mg calcium as unheated AC, (iv) 3.6 mg Ca as unheated ASC, or (v) unheated AC. Femur uptake indicated better calcium bioavailability from ASC than AC at both calcium loads. A 5-min heat treatment partly reduced bioavailability of ASC. Kinetic studies were performed to further investigate the mechanism of superior calcium bioavailability from ASC. Two groups of rats (n = 10/group) received oral doses of 25 mg Ca as ASC or AC. Each dose contained 20 micro Ci (45)Ca. Two additional groups of rats (n = 10/group) received an intravenous injection (iv) of 10 micro Ci (45)Ca after receiving an unlabeled oral dose of 25 mg calcium as ASC or AC. Sequential blood samples were collected over 48 hrs. Urine and fecal samples were collected every 12 hrs for 48 hrs and were analyzed for total calcium and (45)Ca content. Total calcium and (45)Ca from serum, urine, and feces were fitted by a compartment kinetics model with saturable and nonsaturable absorption pathways by WinSAAM (Windows-based Simulation Analysis and Modeling). The difference in calcium bioavailability between the two salts was due to differences in saturable rather than passive intestinal absorption and not to endogenous secretion or calcium deposition rate. The higher bioavailability of calcium ascorbate was due to a longer transit time in the small intestine compared with ASC.

  20. Calcium signalling and calcium channels: evolution and general principles.

    PubMed

    Verkhratsky, Alexei; Parpura, Vladimir

    2014-09-15

    Calcium as a divalent cation was selected early in evolution as a signaling molecule to be used by both prokaryotes and eukaryotes. Its low cytosolic concentration likely reflects the initial concentration of this ion in the primordial soup/ocean as unicellular organisms were formed. As the concentration of calcium in the ocean subsequently increased, so did the diversity of homeostatic molecules handling calcium. This includes the plasma membrane channels that allowed the calcium entry, as well as extrusion mechanisms, i.e., exchangers and pumps. Further diversification occurred with the evolution of intracellular organelles, in particular the endoplasmic reticulum and mitochondria, which also contain channels, exchanger(s) and pumps to handle the homeostasis of calcium ions. Calcium signalling system, based around coordinated interactions of the above molecular entities, can be activated by the opening of voltage-gated channels, neurotransmitters, second messengers and/or mechanical stimulation, and as such is all-pervading pathway in physiology and pathophysiology of organisms.

  1. Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

    PubMed Central

    Wilson, Rosamund J; Copley, J Brian

    2017-01-01

    Background Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease. Scope A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent-to-treat population (N=2520), 752 patients with recorded dose data for calcium acetate (n=551)/calcium carbonate (n=201) at baseline and lanthanum carbonate at week 16 were studied. Elemental calcium intake, serum phosphate, corrected serum calcium, and serum intact parathyroid hormone levels were analyzed. Findings Of the 551 patients with calcium acetate dose data, 271 (49.2%) had an elemental calcium intake of at least 1.5 g/day at baseline, and 142 (25.8%) had an intake of at least 2.0 g/day. Mean (95% confidence interval [CI]) serum phosphate levels were 6.1 (5.89, 6.21) mg/dL at baseline and 6.2 (6.04, 6.38) mg/dL at 16 weeks; mean (95% CI) corrected serum calcium levels were 9.3 (9.16, 9.44) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Of the 201 patients with calcium carbonate dose data, 117 (58.2%) had an elemental calcium intake of at least 1.5 g/day, and 76 (37.8%) had an intake of at least 2.0 g/day. Mean (95% CI) serum phosphate levels were 5.8 (5.52, 6.06) mg/dL at baseline and 5.8 (5.53, 6.05) mg/dL at week 16; mean (95% CI) corrected serum calcium levels were 9.7 (9.15, 10.25) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Conclusion Calcium acetate/calcium carbonate phosphate binders, taken to control serum phosphate levels, may result in high levels of elemental calcium intake. This may lead to complications related to calcium balance. PMID:28182142

  2. Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia.

    PubMed

    Wilson, Rosamund J; Copley, J Brian

    2017-01-01

    Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease. A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent-to-treat population (N=2520), 752 patients with recorded dose data for calcium acetate (n=551)/calcium carbonate (n=201) at baseline and lanthanum carbonate at week 16 were studied. Elemental calcium intake, serum phosphate, corrected serum calcium, and serum intact parathyroid hormone levels were analyzed. Of the 551 patients with calcium acetate dose data, 271 (49.2%) had an elemental calcium intake of at least 1.5 g/day at baseline, and 142 (25.8%) had an intake of at least 2.0 g/day. Mean (95% confidence interval [CI]) serum phosphate levels were 6.1 (5.89, 6.21) mg/dL at baseline and 6.2 (6.04, 6.38) mg/dL at 16 weeks; mean (95% CI) corrected serum calcium levels were 9.3 (9.16, 9.44) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Of the 201 patients with calcium carbonate dose data, 117 (58.2%) had an elemental calcium intake of at least 1.5 g/day, and 76 (37.8%) had an intake of at least 2.0 g/day. Mean (95% CI) serum phosphate levels were 5.8 (5.52, 6.06) mg/dL at baseline and 5.8 (5.53, 6.05) mg/dL at week 16; mean (95% CI) corrected serum calcium levels were 9.7 (9.15, 10.25) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Calcium acetate/calcium carbonate phosphate binders, taken to control serum phosphate levels, may result in high levels of elemental calcium intake. This may lead to complications related to calcium balance.

  3. Quantum reduced loop gravity and the foundation of loop quantum cosmology

    NASA Astrophysics Data System (ADS)

    Alesci, Emanuele; Cianfrani, Francesco

    2016-06-01

    Quantum reduced loop gravity is a promising framework for linking loop quantum gravity and the effective semiclassical dynamics of loop quantum cosmology. We review its basic achievements and its main perspectives, outlining how it provides a quantum description of the Universe in terms of a cuboidal graph which constitutes the proper framework for applying loop techniques in a cosmological setting.

  4. Loops in inflationary correlation functions

    NASA Astrophysics Data System (ADS)

    Tanaka, Takahiro; Urakawa, Yuko

    2013-12-01

    We review the recent progress regarding the loop corrections to the correlation functions in the inflationary universe. A naive perturbation theory predicts that the loop corrections generated during inflation suffer from various infrared (IR) pathologies. Introducing an IR cutoff by hand is neither satisfactory nor enough to fix the problem of a secular growth, which may ruin the predictive power of inflation models if the inflation lasts sufficiently long. We discuss the origin of the IR divergences and explore the regularity conditions of the loop corrections for the adiabatic perturbation, the iso-curvature perturbation, and the tensor perturbation, in turn. These three kinds of perturbations have qualitative differences, but in discussing the IR regularity there is a feature common to all cases, which is the importance of the proper identification of observable quantities. Genuinely, observable quantities should respect the gauge invariance from the view point of a local observer. Interestingly, we find that the requirement of the IR regularity restricts the allowed quantum states.

  5. Two-loop quantum gravity

    NASA Astrophysics Data System (ADS)

    van de Ven, Anton E. M.

    1992-07-01

    We prove the existence of a nonrenormalizable infinity in the two-loop effective action of perturbative quantum gravity by means of an explicit calculation. Our final result agrees with that obtained by earlier authors. We use the background-field method in coordinate space, combined with dimensional regularization and a heat kernel representation for the propagators. General covariance is manifestly preserved. Only vacuum graphs in the presence of an on-shell background metric need to be calculated. We extend the background covariant harmonic gauge to include terms nonlinear in the quantum gravitational fields and allow for general reparametrizations of those fields. For a particular gauge choice and field parametrization only two three-graviton and six four-graviton vertices are present in the action. Calculational labor is further reduced by restricting to backgrounds, which are not only Ricci-flat, but satisfy an additional constraint bilinear in the Weyl tensor. To handle the still formidable amount of algebra, we use the symbolic manipulation program FORM. We checked that the on-shell two-loop effective action is in fact independent of all gauge and field redefinition parameters. A two-loop analysis for Yang-Mills fields is included as well, since in that case we can give full details as well as simplify earlier analyses.

  6. Calcium and Iron Regulate Swarming and Type III Secretion in Vibrio parahaemolyticus▿ †

    PubMed Central

    Gode-Potratz, Cindy J.; Chodur, Daniel M.; McCarter, Linda L.

    2010-01-01

    Here, we probe the response to calcium during growth on a surface and show that calcium influences the transcriptome and stimulates motility and virulence of Vibrio parahaemolyticus. Swarming (but not swimming) gene expression and motility were enhanced by calcium. Calcium also elevated transcription of one of the organism's two type III secretion systems (T3SS1 but not T3SS2) and heightened cytotoxicity toward host cells in coculture. Calcium stimulation of T3SS gene expression has not been reported before, although low calcium is an inducing signal for the T3SS of many organisms. EGTA was also found to increase T3SS1 gene expression and virulence; however, this was demonstrated to be the consequence of iron rather than calcium chelation. Ectopic expression of exsA, encoding the T3SS1 AraC-type regulator, was used to define the extent of the T3SS1 regulon and verify its coincident induction by calcium and EGTA. To begin to understand the regulatory mechanisms modulating the calcium response, a calcium-repressed, LysR-type transcription factor named CalR was identified and shown to repress swarming and T3SS1 gene expression. Swarming and T3SS1 gene expression were also demonstrated to be linked by LafK, a σ54-dependent regulator of swarming, and additionally connected by a negative-feedback loop on the swarming regulon propagated by ExsA. Thus, calcium and iron, two ions pertinent for a marine organism and pathogen, play a signaling role with global consequences on the regulation of gene sets that are relevant for surface colonization and infection. PMID:20851895

  7. Calcium and bone health--goodbye, calcium supplements?

    PubMed

    Ströhle, A; Hadji, P; Hahn, A

    2015-10-01

    This review assesses (1) the potential role of calcium supplements in the prevention and treatment of osteoporosis and osteoporotic fractures, and (2) the safety of calcium supplements with respect to cardiovascular health as well. With regard to (1), a total calcium intake of < 800 mg/day is associated with increased loss of bone mineral density in peri- and postmenopausal women with an increase in fracture risk. Hereby, the effect of calcium supplements on fracture prevention is dependent primary on baseline calcium intake. The strongest protective effect has been reported in individuals with a calcium intake < 700 mg/day and in high-risk groups. A calcium intake of about 1000-1200 mg/day seems to be sufficient for general fracture prevention. With regard to (2), an analysis of the data based on the Hill criteria does not demonstrate convincing evidence that calcium supplements increase cardiovascular risk. In the long term, total calcium intake of 2500 mg/day (from food and supplements) continues to be classified as safe. This value should not be exceeded for an extended period of time.

  8. Dynamic Aperture-based Solar Loop Segmentation

    NASA Technical Reports Server (NTRS)

    Lee, Jon Kwan; Newman, Timothy S.; Gary, G. Allen

    2006-01-01

    A new method to automatically segment arc-like loop structures from intensity images of the Sun's corona is introduced. The method constructively segments credible loop structures by exploiting the Gaussian-like shape of loop cross-sectional intensity profiles. The experimental results show that the method reasonably segments most of the well-defined loops in coronal images. The method is only the second published automated solar loop segmentation method. Its advantage over the other published method is that it operates independently of supplemental time specific data.

  9. Synaptotagmin restores kinetic properties of a syntaxin-associated N-type voltage sensitive calcium channel.

    PubMed

    Wiser, O; Tobi, D; Trus, M; Atlas, D

    1997-03-10

    The voltage sensitive N-type calcium channel interacts functionally and biochemically with synaptotagmin (p65). N-type channel interaction with p65 is demonstrated in the Xenopus oocyte expression system, where p65 alters the steady state voltage inactivation of the N-channel, and fully restores the syntaxin-modified current amplitude and inactivation kinetics in a calcium dependent manner. In agreement with the functional results, GST-p65 fusion protein binds to a cytosolic region, amino acids 710-1090 of the N-type channel (N-loop(710-1090)). The results of the combined approach provide a functional and biochemical basis for proposing that p65 interaction with the N-type channel brings p65 into a close association with a syntaxin-coupled channel. In turn, calcium entry through the liberated channel initiates fusion of the primed vesicles with the cell membrane at a short distance from the site of calcium entry.

  10. Magnetic Helicity Injection and Sigmoidal Coronal Loops

    NASA Astrophysics Data System (ADS)

    Yamamoto, Tetsuya T.; Kusano, K.; Maeshiro, T.; Yokoyama, T.; Sakurai, T.

    2005-05-01

    We studied the relationship between magnetic helicity injection and the formation of sigmoidal loops. We analyzed seven active regions: three regions showed coronal loops similar to the potential field, and four regions showed the sigmoidal loops. The magnetic helicity injection rate was evaluated using the method proposed by Kusano et al. In order to compare the helicity of regions of various sizes, we defined the normalized helicity injection rate as the magnetic helicity injection rate divided by the magnetic flux squared. We found that the sigmoidal regions and nonsigmoidal regions have comparable normalized helicity injection rates. Next, we calculated the magnetic helicity content of the sigmoidal loops by using the magnetic flux tube model (Longcope & Welsch) and compared it with the magnetic helicity injected from around the footpoints of three sigmoidal loops. For two sigmoidal loops, it is found that these values are comparable. Another loop showed significant disagreement between helicity injection rate and its magnetic helicity content. Excluding this region on the basis of its complexity (perhaps multiple loops forming a sigmoidal loop), we can conclude that geometric twist of the sigmoidal loops is consistent with the magnetic helicity injected from around the footpoints of the sigmoidal loops.

  11. Orientability of loop processes in relative locality

    NASA Astrophysics Data System (ADS)

    Chen, Lin-Qing

    2013-12-01

    Inspired by recent results of unusual properties of loop processes in relative locality, we introduce a way to classify loops in the case of κ-Poincaré momentum space. We show that the notion of orientability is deeply connected to a few essential properties of loop processes. Nonorientable loops have effective curvature, which explicitly breaks translation symmetry, and can lead to a breaking of causality and global momentum conservation. Orientable loops, on the other hand, are “flat.” Causality and global momentum conservation are all well preserved in these kinds of loops. We comment that the nontrivial classical loops in relative locality might be understood as dual effects from general relativity, and some physical implications are discussed.

  12. Hyperstaticity and loops in frictional granular packings

    NASA Astrophysics Data System (ADS)

    Tordesillas, Antoinette; Lam, Edward; Metzger, Philip T.

    2009-06-01

    The hyperstatic nature of granular packings of perfectly rigid disks is analyzed algebraically and through numerical simulation. The elementary loops of grains emerge as a fundamental element in addressing hyperstaticity. Loops consisting of an odd number of grains behave differently than those with an even number. For odd loops, the latent stresses are exterior and are characterized by the sum of frictional forces around each loop. For even loops, the latent stresses are interior and are characterized by the alternating sum of frictional forces around each loop. The statistics of these two types of loop sums are found to be Gibbsian with a "temperature" that is linear with the friction coefficient μ when μ<1.

  13. Chemical Looping Technology: Oxygen Carrier Characteristics.

    PubMed

    Luo, Siwei; Zeng, Liang; Fan, Liang-Shih

    2015-01-01

    Chemical looping processes are characterized as promising carbonaceous fuel conversion technologies with the advantages of manageable CO2 capture and high energy conversion efficiency. Depending on the chemical looping reaction products generated, chemical looping technologies generally can be grouped into two types: chemical looping full oxidation (CLFO) and chemical looping partial oxidation (CLPO). In CLFO, carbonaceous fuels are fully oxidized to CO2 and H2O, as typically represented by chemical looping combustion with electricity as the primary product. In CLPO, however, carbonaceous fuels are partially oxidized, as typically represented by chemical looping gasification with syngas or hydrogen as the primary product. Both CLFO and CLPO share similar operational features; however, the optimum process configurations and the specific oxygen carriers used between them can vary significantly. Progress in both CLFO and CLPO is reviewed and analyzed with specific focus on oxygen carrier developments that characterize these technologies.

  14. High-temperature helium-loop facility

    SciTech Connect

    Tokarz, R.D.

    1981-09-01

    The high-temperature helium loop is a facility for materials testing in ultrapure helium gas at high temperatures. The closed loop system is capable of recirculating high-purity helium or helium with controlled impurities. The gas loop maximum operating conditions are as follows: 300 psi pressure, 500 lb/h flow rate, and 2100/sup 0/F temperature. The two test sections can accept samples up to 3.5 in. diameter and 5 ft long. The gas loop is fully instrumented to continuously monitor all parameters of loop operation as well as helium impurities. The loop is fully automated to operate continuously and requires only a daily servicing by a qualified operator to replenish recorder charts and helium makeup gas. Because of its versatility and high degree of parameter control, the helium loop is applicable to many types of materials research. This report describes the test apparatus, operating parameters, peripheral systems, and instrumentation system.

  15. Theoretical aspects of calcium signaling

    NASA Astrophysics Data System (ADS)

    Pencea, Corneliu Stefan

    2001-08-01

    Experiments investigating intracellular calcium dynamics have revealed that calcium signals differentially affect a variety of intracellular processes, from fertilization and cell development and differentiation to subsequent cellular activity, ending with cell death. As an intracellular messenger, calcium transmits information within and between cells, thus regulating their activity. To control such a variety of processes, calcium signals have to be very flexible and also precisely regulated. The cell uses a calcium signaling ``toolkit'', where calcium ions can act in different contexts of space, amplitude and time. For different tasks, the cell selects the particular signal, or combination of signals, that triggers the appropriate physiological response. The physical foundations of such a versatile cellular signaling toolkit involving calcium are not completely understood, despite important experimental and theoretical progress made recently. The declared goal of this work is to investigate physical mechanisms on which the propagation of differential signals can be based. The dynamics of calcium near a cluster of inositol trisphosphate (IP3) activated calcium channels has been investigated analytically and numerically. Our work has demonstrated that clusters of different IP3 receptors can show similar bistable behavior, but differ in both the transient and long term dynamics. We have also investigated the conditions under which a calcium signal propagates between a pair of localized stores. We have shown that the propagation of the signal across a random distribution of such stores shows a percolation transition manifested in the shape of the wave front. More importantly, our work indicates that specific distribution of stores can be interpreted as calcium circuits that can perform important signal analyzing task, from unidirectional propagation and coincidence detection to a complete set of logic gates. We believe that phenomena like the ones described are

  16. Calcium nutrition and metabolism during infancy.

    PubMed

    Bass, J Kirk; Chan, Gary M

    2006-10-01

    Calcium is a vital mineral for the developing newborn infant. This review discusses perinatal and neonatal calcium metabolism, with an emphasis on enteral calcium absorption and the nutritional factors affecting calcium bioavailability including the three major endocrine hormones involved in calcium metabolism: parathyroid hormone, vitamin D, and calcitonin. The placenta transports calcium to the fetus throughout pregnancy, with the largest amount of fetal calcium accumulation occurring in the third trimester. At birth, the newborn transitions to intestinal absorption to meet the body's calcium needs. Most calcium is absorbed by paracellular passive diffusion in the small intestine. Calcium intestinal absorption is affected by the type and amount of calcium ingested. It is also affected by the amount of intestinal calcium that is bound to dietary fats and proteins. One major consequence of decreased calcium absorption is metabolic bone disease in which there is a failure of complete mineralization of the bone osteoid.

  17. Thiosulfate Reduces Calcium Phosphate Nephrolithiasis

    PubMed Central

    Asplin, John R.; Donahue, Susan E.; Lindeman, Christina; Michalenka, Anne; Strutz, Kelly Laplante; Bushinsky, David A.

    2009-01-01

    An uncontrolled trial reported that sodium thiosulfate reduces formation of calcium kidney stones in humans, but this has not been established in a controlled human study or animal model. Using the genetic hypercalciuric rat, an animal model of calcium phosphate stone formation, we studied the effect of sodium thiosulfate on urine chemistries and stone formation. We fed genetic hypercalciuric rats normal food with or without sodium thiosulfate for 18 wk and measured urine chemistries, supersaturation, and the upper limit of metastability of urine. Eleven of 12 untreated rats formed stones compared with only three of 12 thiosulfate-treated rats (P < 0.002). Urine calcium and phosphorus were higher and urine citrate and volume were lower in the thiosulfate-treated rats, changes that would increase calcium phosphate supersaturation. Thiosulfate treatment lowered urine pH, which would lower calcium phosphate supersaturation. Overall, there were no statistically significant differences in calcium phosphate supersaturation or upper limit of metastability between thiosulfate-treated and control rats. In vitro, thiosulfate only minimally affected ionized calcium, suggesting a mechanism of action other than calcium chelation. In summary, sodium thiosulfate reduces calcium phosphate stone formation in the genetic hypercalciuric rat. Controlled trials testing the efficacy and safety of sodium thiosulfate for recurrent kidney stones in humans are needed. PMID:19369406

  18. Cardiovascular effects of calcium supplements.

    PubMed

    Reid, Ian R

    2013-07-05

    Calcium supplements reduce bone turnover and slow the rate of bone loss. However, few studies have demonstrated reduced fracture incidence with calcium supplements, and meta-analyses show only a 10% decrease in fractures, which is of borderline statistical and clinical significance. Trials in normal older women and in patients with renal impairment suggest that calcium supplements increase the risk of cardiovascular disease. To further assess their safety, we recently conducted a meta-analysis of trials of calcium supplements, and found a 27%-31% increase in risk of myocardial infarction, and a 12%-20% increase in risk of stroke. These findings are robust because they are based on pre-specified analyses of randomized, placebo-controlled trials and are consistent across the trials. Co-administration of vitamin D with calcium does not lessen these adverse effects. The increased cardiovascular risk with calcium supplements is consistent with epidemiological data relating higher circulating calcium concentrations to cardiovascular disease in normal populations. There are several possible pathophysiological mechanisms for these effects, including effects on vascular calcification, vascular cells, blood coagulation and calcium-sensing receptors. Thus, the non-skeletal risks of calcium supplements appear to outweigh any skeletal benefits, and are they appear to be unnecessary for the efficacy of other osteoporosis treatments.

  19. Revisiting intracellular calcium signaling semantics.

    PubMed

    Haiech, Jacques; Audran, Emilie; Fève, Marie; Ranjeva, Raoul; Kilhoffer, Marie-Claude

    2011-12-01

    Cells use intracellular free calcium concentration changes for signaling. Signal encoding occurs through both spatial and temporal modulation of the free calcium concentration. The encoded message is detected by an ensemble of intracellular sensors forming the family of calcium-binding proteins (CaBPs) which must faithfully translate the message using a new syntax that is recognized by the cell. The cell is home to a significant although limited number of genes coding for proteins involved in the signal encoding and decoding processes. In a cell, only a subset of this ensemble of genes is expressed, leading to a genetic regulation of the calcium signal pathways. Calmodulin (CaM), the most ubiquitous expressed intracellular calcium-binding protein, plays a major role in calcium signal translation. Similar to a hub, it is central to a large and finely tuned network, receiving information, integrating it and dispatching the cognate response. In this review, we examine the different steps starting with an external stimulus up to a cellular response, with special emphasis on CaM and the mechanism by which it decodes calcium signals and translates it into exquisitely coordinated cellular events. By this means, we will revisit the calcium signaling semantics, hoping that we will ease communication between scientists dealing with calcium signals in different biological systems and different domains.

  20. The bioavailability of dietary calcium.

    PubMed

    Guéguen, L; Pointillart, A

    2000-04-01

    This update focuses on the bioavailability of dietary calcium for humans. Fundamentals of calcium metabolism, intestinal absorption, urinary excretion and balance are recalled. Dietary factors, especially lactose and other milk components, influencing calcium bioavailability at intestinal and renal levels are reviewed. A critical examination of all the methods used for evaluating calcium bioavailability is made. This includes in vitro assays, classical and isotopic balances, urinary excretion, isotope labeling in the urine, plasma and bones, long term evaluation of bone mineralization and the use of biological bone markers. Importance and advantages of animal models are discussed. The state of the art in the comparative bioavailability of calcium in foods is detailed including a comparison of sources of calcium (dairy products and calcium salts) in human studies and in some animal studies, casein phosphopeptides, proteins, lactose and lactase and their relation with calcium bioavailability (in humans and rats). An update on the consumption of dairy products and bone mass is presented. Emphasis on peculiarities and advantages of calcium in milk and dairy products is given.

  1. 21 CFR 184.1201 - Calcium glycerophosphate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... neutralizing glycerophosphoric acid with calcium hydroxide or calcium carbonate. The commercial product is a... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium glycerophosphate. 184.1201 Section 184... as GRAS § 184.1201 Calcium glycerophosphate. (a) Calcium glycerophosphate (C3H7CaO6P, CAS Reg. No...

  2. Extracellular calcium sensing and extracellular calcium signaling

    NASA Technical Reports Server (NTRS)

    Brown, E. M.; MacLeod, R. J.; O'Malley, B. W. (Principal Investigator)

    2001-01-01

    , localized changes in Ca(o)(2+) within the ECF can originate from several mechanisms, including fluxes of calcium ions into or out of cellular or extracellular stores or across epithelium that absorb or secrete Ca(2+). In any event, the CaR and other receptors/sensors for Ca(o)(2+) and probably for other extracellular ions represent versatile regulators of numerous cellular functions and may serve as important therapeutic targets.

  3. Why oral calcium supplements may reduce renal stone disease: report of a clinical pilot study

    PubMed Central

    Williams, C; Child, D; Hudson, P; Davies, G; Davies, M; John, R; Anandaram, P; De Bolla, A R

    2001-01-01

    calcium and urine phosphate was relevant to the interpretation of the study. Conclusions—Regular calcium supplementation does not raise the product of calcium and oxalate in urine and the proportion of oxalate to calcium is reduced. The underlying mechanisms of the changes seen in phosphate, calcium, and PTH and the observations on 1,25-(OH)2-cholecalciferol are not clear. Observed changes in phosphate could possibly be part of a calcium regulating feedback loop operating over a period of weeks. In evaluating these mechanisms background seasonal effects are important. It is possible that "programming" of the gut mucosa in terms of calcium transport is a major determinant of the relation between calcium and oxalate concentrations in urine and their relative abundance. Increased oral calcium, in association with a reduction of the relative proportion absorbed, may be pertinent to the prevention of calcium oxalate rich stones. Key Words: renal stones • calcium oxalate product • dietary calcium • renal tubular reabsorption of phosphate PMID:11271790

  4. Singularities in loop quantum cosmology.

    PubMed

    Cailleteau, Thomas; Cardoso, Antonio; Vandersloot, Kevin; Wands, David

    2008-12-19

    We show that simple scalar field models can give rise to curvature singularities in the effective Friedmann dynamics of loop quantum cosmology (LQC). We find singular solutions for spatially flat Friedmann-Robertson-Walker cosmologies with a canonical scalar field and a negative exponential potential, or with a phantom scalar field and a positive potential. While LQC avoids big bang or big rip type singularities, we find sudden singularities where the Hubble rate is bounded, but the Ricci curvature scalar diverges. We conclude that the effective equations of LQC are not in themselves sufficient to avoid the occurrence of curvature singularities.

  5. Dirac Loops in Carbon Allotropes

    NASA Astrophysics Data System (ADS)

    Mullen, Kieran; Uchoa, Bruno; Glatzhofer, D.

    2015-03-01

    We propose a family of structures that have ``Dirac loops'': closed lines in momentum space with Dirac-like quasiparticles, on which the density of states vanishes linearly with energy. The structures all possess the planar trigonal connectivity present in graphene, but are three dimensional. We discuss the consequences of their multiply-connected Fermi surface for transport, including the presence of three dimensional Integer Quantum Hall effect. In the presence of spin-orbit coupling, we show that those structures may have topological surface states. We discuss the feasibility of realizing the structures as an allotrope of carbon. Work supported by NSF Grants DMR-1310407 and DMR-1352604.

  6. Loop Virasoro Lie conformal algebra

    SciTech Connect

    Wu, Henan Chen, Qiufan; Yue, Xiaoqing

    2014-01-15

    The Lie conformal algebra of loop Virasoro algebra, denoted by CW, is introduced in this paper. Explicitly, CW is a Lie conformal algebra with C[∂]-basis (L{sub i} | i∈Z) and λ-brackets [L{sub i} {sub λ} L{sub j}] = (−∂−2λ)L{sub i+j}. Then conformal derivations of CW are determined. Finally, rank one conformal modules and Z-graded free intermediate series modules over CW are classified.

  7. Using the Meeting Graph Framework to Minimise Kernel Loop Unrolling for Scheduled Loops

    NASA Astrophysics Data System (ADS)

    Bachir, Mounira; Gregg, David; Touati, Sid-Ahmed-Ali

    This paper improves our previous research effort [1] by providing an efficient method for kernel loop unrolling minimisation in the case of already scheduled loops, where circular lifetime intervals are known. When loops are software pipelined, the number of values simultaneously alive becomes exactly known giving better opportunities for kernel loop unrolling. Furthermore, fixing circular lifetime intervals allows us to reduce the algorithmic complexity of our method compared to [1] by computing a new research space for minimal kernel loop unrolling. The meeting graph (MG) is one of the [3] frameworks proposed in the literature which models loop unrolling and register allocation together in a common formal framework for software pipelined loops. Although MG significantly improves loop register allocation, the computed loop unrolling may lead to unpractical code growth.

  8. 21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium pantothenate, calcium chloride double salt..., calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may... information required by the Act, the following: (1) The name of the additive “calcium chloride double salt...

  9. 21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium pantothenate, calcium chloride double salt..., calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may... information required by the Act, the following: (1) The name of the additive “calcium chloride double salt...

  10. 21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium pantothenate, calcium chloride double salt..., calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may... information required by the Act, the following: (1) The name of the additive “calcium chloride double salt...

  11. 21 CFR 172.330 - Calcium pantothenate, calcium chloride double salt.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium pantothenate, calcium chloride double salt..., calcium chloride double salt. The food additive calcium chloride double salt of calcium pantothenate may... information required by the Act, the following: (1) The name of the additive “calcium chloride double salt...

  12. Thermal Analysis of CDS Coronal Loops

    NASA Astrophysics Data System (ADS)

    Kimble, J. A.; Schmelz, J. T.; Nasraoui, K.; Rightmire, L. A.; Andrews, J. M.; Cirtain, J. W.

    2008-05-01

    The coronal loop data used for this analysis was obtained using the Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric Observatory on 2003 January 17 at 14:24:43 UT. We use the Chianti atomic physics database and the hybrid coronal abundances to determine temperatures and densities for positions along several loops. We chose six pixels along each loop as well as background pixels. The intensities of the background pixels are subtracted from each loop pixel to isolate the emission from the loop pixel, and then spectral lines with significant contributions to the loop intensities are selected. The loops were then analyzed with a forward folding process to produce differential emission measure (DEM) curves. Emission measure loci plots and DEM automatic inversions are then used to verify those conclusions. We find different results for each of these loops. One appears to be isothermal at each loop position, and the temperature does not change with height. The second appears to be multithermal at each position and the third seems to be consistent with two DEM spikes, which might indicate that there are two isothermal loops so close together, that they are not resolved by CDS. Solar physics research at the University of Memphis is supported by a Hinode subcontract from NASA/SAO as well as NSF ATM-0402729.

  13. Calcium channels and migraine.

    PubMed

    Pietrobon, Daniela

    2013-07-01

    Missense mutations in CACNA1A, the gene that encodes the pore-forming α1 subunit of human voltage-gated Ca(V)2.1 (P/Q-type) calcium channels, cause a rare form of migraine with aura (familial hemiplegic migraine type 1: FHM1). Migraine is a common disabling brain disorder whose key manifestations are recurrent attacks of unilateral headache that may be preceded by transient neurological aura symptoms. This review, first, briefly summarizes current understanding of the pathophysiological mechanisms that are believed to underlie migraine headache, migraine aura and the onset of a migraine attack, and briefly describes the localization and function of neuronal Ca(V)2.1 channels in the brain regions that have been implicated in migraine pathogenesis. Then, the review describes and discusses i) the functional consequences of FHM1 mutations on the biophysical properties of recombinant human Ca(V)2.1 channels and native Ca(V)2.1 channels in neurons of knockin mouse models carrying the mild R192Q or severe S218L mutations in the orthologous gene, and ii) the functional consequences of these mutations on neurophysiological processes in the cerebral cortex and trigeminovascular system thought to be involved in the pathophysiology of migraine, and the insights into migraine mechanisms obtained from the functional analysis of these processes in FHM1 knockin mice. This article is part of a Special Issue entitled: Calcium channels.

  14. Calcium transporters: From fields to the table

    USDA-ARS?s Scientific Manuscript database

    Calcium transporters regulate calcium fluxes within cells. Plants, like all organisms, contain channels, pumps, and exchangers to carefully modulate intracellular calcium levels. This review presents a summary of the recent advances in cloning and characterizing of these transporters and highlight...

  15. Vitamin D, Calcium, and Bone Health

    MedlinePlus

    ... in Balance › Vitamin D, Calcium, and Bone Health Vitamin D, Calcium, and Bone Health March 2012 Download ... also helps keep your bones strong. Why are vitamin D and calcium important to bone health? Vitamin ...

  16. An Improved Calcium Flame Test.

    ERIC Educational Resources Information Center

    Pearson, Robert S.

    1985-01-01

    Indicates that the true red color of calcium can be obtained (using the procedure described by Sorm and Logowski) if the calcium ion solution is mixed with an equal volume of saturated ammonium bromide solution. Suggestions for flame tests of other elements are also noted. (JN)

  17. Calcium Intake: A Lifelong Proposition.

    ERIC Educational Resources Information Center

    Amschler, Denise H.

    1985-01-01

    This article reviews the current problem of low calcium intake in the United States among all age groups, the role of calcium in the formation and maintenance of bone mass, and major factors influencing absorption. Osteoporosis is discussed, and current recommendations for Recommended Dietary allowance are provided. (Author/MT)

  18. Major Minerals - Calcium, Magnesium, Phosphorus

    USDA-ARS?s Scientific Manuscript database

    Calcium, magnesium and phosphorus are essential elements critically important for the function of the musculoskeletal system, including the formation and transduction of energy and the maintenance of healthy bone. The major calcium concern for physically active healthy middle-aged adults is to consu...

  19. Electrochemical cell with calcium anode

    DOEpatents

    Cooper, John F.; Hosmer, Pamela K.; Kelly, Benjamin E.

    1979-01-01

    An electrochemical cell comprising a calcium anode and a suitable cathode in an alkaline electrolyte consisting essentially of an aqueous solution of an hydroxide and a chloride. Specifically disclosed is a mechanically rechargeable calcium/air fuel cell with an aqueous NaOH/NaCl electrolyte.

  20. Calcium Intake: A Lifelong Proposition.

    ERIC Educational Resources Information Center

    Amschler, Denise H.

    1985-01-01

    This article reviews the current problem of low calcium intake in the United States among all age groups, the role of calcium in the formation and maintenance of bone mass, and major factors influencing absorption. Osteoporosis is discussed, and current recommendations for Recommended Dietary allowance are provided. (Author/MT)

  1. Factors affecting ex-situ aqueous mineral carbonation using calcium and magnesium silicate minerals

    SciTech Connect

    Gerdemann, Stephen J.; Dahlin, David C.; O'Connor, William K.; Penner, Larry R.; Rush, G.E.

    2004-01-01

    Carbonation of magnesium- and calcium-silicate minerals to form their respective carbonates is one method to sequester carbon dioxide. Process development studies have identified reactor design as a key component affecting both the capital and operating costs of ex-situ mineral sequestration. Results from mineral carbonation studies conducted in a batch autoclave were utilized to design and construct a unique continuous pipe reactor with 100% recycle (flow-loop reactor). Results from the flow-loop reactor are consistent with batch autoclave tests, and are being used to derive engineering data necessary to design a bench-scale continuous pipeline reactor.

  2. Effect of calcium on lead in soft-water distribution systems

    SciTech Connect

    Bisogni, J.J. Jr.; Nassar, I.S.; Menegaux, A.M.

    2000-05-01

    Meeting the lead rule action level for drinking water can be difficult for soft-water systems. One concern in these systems is the formation of particulate or colloidal lead that is difficult to remove from the aqueous phase. In this preliminary study, batch and pipe-loop systems are used to assess the effect of calcium addition on lowering the concentration of particulate or colloidal lead. The addition of calcium at levels as low as 5 mg/L reduced zeta potential of lead-bound colloids and in some cases resulted in a reduction of total Pb concentration.

  3. Stable prenucleation calcium carbonate clusters.

    PubMed

    Gebauer, Denis; Völkel, Antje; Cölfen, Helmut

    2008-12-19

    Calcium carbonate forms scales, geological deposits, biominerals, and ocean sediments. Huge amounts of carbon dioxide are retained as carbonate ions, and calcium ions represent a major contribution to water hardness. Despite its relevance, little is known about the precipitation mechanism of calcium carbonate, and specified complex crystal structures challenge the classical view on nucleation considering the formation of metastable ion clusters. We demonstrate that dissolved calcium carbonate in fact contains stable prenucleation ion clusters forming even in undersaturated solution. The cluster formation can be characterized by means of equilibrium thermodynamics, applying a multiple-binding model, which allows for structural preformation. Stable clusters are the relevant species in calcium carbonate nucleation. Such mechanisms may also be important for the crystallization of other minerals.

  4. Calcium concentration dependent collagen mineralization.

    PubMed

    Niu, Xufeng; Fan, Rui; Tian, Feng; Guo, Xiaolin; Li, Ping; Feng, Qingling; Fan, Yubo

    2017-04-01

    Mineralization of collagen fibrils is a regular combination process of organic and mineral components mainly involving calcium, phosphate and collagen. We report the influence of calcium to the self-assembly of collagen by changing the concentration of calcium ion in the process of mineralization. Low concentration of calcium results in the well collagen self-assembly while poor mineral crystallization. Relatively, high concentration of calcium can hinder collagen self-assembly, whereas it is benefited to mineral crystallization. We also reveal that collagen self-assembly happens in advance of the formation of better mineral crystals. These results interpret the mechanism of collagen mineralization further. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. LMFBR with booster pump in pumping loop

    DOEpatents

    Rubinstein, H.J.

    1975-10-14

    A loop coolant circulation system is described for a liquid metal fast breeder reactor (LMFBR) utilizing a low head, high specific speed booster pump in the hot leg of the coolant loop with the main pump located in the cold leg of the loop, thereby providing the advantages of operating the main pump in the hot leg with the reliability of cold leg pump operation.

  6. Magnetic monopole in the loop representation

    SciTech Connect

    Leal, Lorenzo; Lopez, Alexander

    2006-01-15

    We quantize, within the Loop Representation formalism, the electromagnetic field in the presence of a static magnetic pole. It is found that the loop-dependent physical wave functionals of the quantum Maxwell theory become multivalued, through a topological phase factor depending on the solid angle subtended at the monopole by a surface bounded by the loop. It is discussed how this fact generalizes what occurs in ordinary quantum mechanics in multiply connected spaces.

  7. Wilson Loops in Open String Theory

    NASA Astrophysics Data System (ADS)

    Shiraishi, Kiyoshi

    Wilson loop elements on torus are introduced into the partition function of open strings as Polyakov’s path integral at one-loop level. Mass spectra from compactification and expected symmetry breaking are illustrated by choosing the correct weight for the contributions from annulus and Möbius strip. We show that Jacobi’s imaginary transformation connects the mass spectra with the Wilson loops. The application to thermopartition function and cosmological implications are briefly discussed.

  8. Spectra of sparse regular graphs with loops.

    PubMed

    Metz, F L; Neri, I; Bollé, D

    2011-11-01

    We derive exact equations that determine the spectra of undirected and directed sparsely connected regular graphs containing loops of arbitrary lengths. The implications of our results for the structural and dynamical properties of network models are discussed by showing how loops influence the size of the spectral gap and the propensity for synchronization. Analytical formulas for the spectrum are obtained for specific lengths of the loops.

  9. Catheterization of Intestinal Loops in Ruminants Does Not Adversely Affect Loop Function

    PubMed Central

    Inglis, G Douglas; Kastelic, John P; Uwiera, Richard R E

    2010-01-01

    Catheterized intestinal loops may be a valuable model to elucidate key components of the host response to various treatments within the small intestine of ruminants. We examined whether catheterizing ileal loops in sheep affected the overall health of animals and intestinal function, whether a bacterial treatment could be introduced into the loops through the catheters, and whether broad-spectrum antibiotics could sterilize the loops. Escherichia coli cells transformed to express the GFP gene were introduced readily into the loops through the catheters, and GFP E. coli cells were localized within the injected loops. Catheterized loops, interspaces, and intact ileum exhibited no abnormalities in tissue appearance or electrical resistance. Expression of the IFNγ, IL1α, IL4, IL6, IL12p40, IL18, TGFβ1, and TNFα cytokine genes did not differ significantly among the intact ileum, catheterized loops, and interspaces, nor did the expression of the gene for inducible nitric oxide synthase. Broad-spectrum antibiotics administered during surgery did not sterilize the loops or interspaces and did not substantively change the composition of the microbiota. However, antibiotics reduced the overall number of bacterial cells within the loop and the relative abundance of community constituents. We concluded that catheterization of intestinal loops did not adversely affect health or loop function in sheep. Furthermore, allowing animals to recover fully from surgery and to clear pharmaceuticals will remove any confounding effects due to these factors, making catheterized intestinal loops a feasible model for studying host responses in ruminants. PMID:21262134

  10. The bioavailability of calcium in spinach and calcium-oxalate to calcium-deficient rats.

    PubMed

    Kikunaga, S; Arimori, M; Takahashi, M

    1988-04-01

    We estimated the utilization of calcium in spinach and calcium-oxalate to calcium-deficient rats, and the effect of oxalic acid on absorption of dietary calcium by using calcium-deficient rats. The body weight gain of the calcium-deficient rats for 8 days receiving a calcium-deficient diet supplemented with raw-powdered spinach (R-sp), boiled-powdered spinach (B-sp), or calcium-oxalate (Ca-ox), and a control diet supplemented with oxalic acid (OX-C) were 4.8, 2.8, 4.9, and 5.1 g, respectively. The calcium content in the liver and kidney of the rats receiving R-sp, B-sp, Ca-ox, and OX-C diets significantly increased as compared with the calcium-deficient rats. Significant differences in the liver calcium levels were not observed among the rats receiving various additional diets, though the content in the kidneys of the rats receiving R-sp, B-sp, Ca-ox, and OX-C diets were 28.0, 21.5, 0.11, and 0.59 mg, respectively. An especially large amount of calcium was accumulated in the kidneys of the rats receiving R-sp and B-sp diets. The calcium concentration in the serum of the rats receiving Ca-ox and OX-C diets was higher than the calcium concentration in the serum of the R-sp, B-sp, and calcium-deficient rats. The calcium content in the left tibiae of the rats receiving Ca-ox and OX-C diets was higher than that of the rats receiving R-sp and B-sp diets. The breaking force of the right tibiae of the rats was highest in the OX-C group, and higher in the R-sp and Ca-ox groups than the breaking force of the right tibiae of the rats fed on B-sp diet. The alkaline phosphatase activity in the small intestines of the rats rose in the order of the R-sp, B-sp, and Ca-ox groups, although significant differences of the activity were not observed between the Ca-ox and the OX-C groups. The calcium retention of the rats receiving the calcium-deficient, R-sp, B-sp, Ca-ox, and OX-C diets was -18.5, 35.2, 25.6, 41.6, and 45.8%, respectively. About 35% of the calcium in the spinach was

  11. Binary phase locked loops for Omega receivers

    NASA Technical Reports Server (NTRS)

    Chamberlin, K.

    1974-01-01

    An all-digital phase lock loop (PLL) is considered because of a number of problems inherent in an employment of analog PLL. The digital PLL design presented solves these problems. A single loop measures all eight Omega time slots. Memory-aiding leads to the name of this design, the memory-aided phase lock loop (MAPLL). Basic operating principles are discussed and the superiority of MAPLL over the conventional digital phase lock loop with regard to the operational efficiency for Omega applications is demonstrated.

  12. M-Brane Models and Loop Spaces

    NASA Astrophysics Data System (ADS)

    Sämann, Christian

    2012-06-01

    I review an extension of the ADHMN construction of monopoles to M-brane models. This extended construction gives a map from solutions to the Basu-Harvey equation to solutions to the self-dual string equation transgressed to loop space. Loop spaces appear in fact quite naturally in M-brane models. This is demonstrated by translating a recently proposed M5-brane model to loop space. Finally, I comment on some recent developments related to the loop space approach to M-brane models.

  13. Polyakov loop modeling for hot QCD

    NASA Astrophysics Data System (ADS)

    Fukushima, Kenji; Skokov, Vladimir

    2017-09-01

    We review theoretical aspects of quantum chromodynamics (QCD) at finite temperature. The most important physical variable to characterize hot QCD is the Polyakov loop, which is an approximate order parameter for quark deconfinement in a hot gluonic medium. Additionally to its role as an order parameter, the Polyakov loop has rich physical contents in both perturbative and non-perturbative sectors. This review covers a wide range of subjects associated with the Polyakov loop from topological defects in hot QCD to model building with coupling to the Polyakov loop.

  14. Coronal Diagnostics Spectrometer Observations of Coronal Loops

    NASA Astrophysics Data System (ADS)

    Nasraoui, Kaouther; Schmelz, J. T.; Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E.

    2007-05-01

    Two side by side loops from the solar disk were analyzed. These two loops were observed with the Coronal Diagnostics Spectrometer on SOHO on 2003 January 17. The first loop was best seen in Mg IX at a wavelength of 368 angstroms and a peak formation temperature of Log T = 6.0. Seven pixels on the loop and one background pixel were chosen. The intensity of the background pixel was subtracted from each of the loop pixels. Only the lines that had a significant intensity after background subtraction were considered. A differential emission measure (DEM) curve was constructed for the background subtracted data using the forward folding technique. The DEM for most of these pixels had a spike shape at Log T equal to 5.85. This result shows that the loop is isothermal at most of these pixels. The second loop was best seen in Si XII at a wavelength of 520 angstroms and a peak formation temperature of Log T = 6.3. The same procedure was followed for the data analysis. After background subtraction only some hot lines had a significant intensity and a DEM curve was constructed for each loop pixel. This time the DEM is broader with a shape that shows that the loop plasma is multithermal with a log temperature range of 6.1 to 6.5. Solar physics research at the University of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G.

  15. Conservation law for linked cosmic string loops

    NASA Astrophysics Data System (ADS)

    Bekenstein, Jacob D.

    1992-05-01

    Taking a cue from the connection between fluid helicity and the linkage between closed vortices in ordinary turbulent flow, we examine topological restrictions on the linkage of cosmic string loops (or superfluid quantum vortex rings). The analog of helicity in these cases vanishes, but loops (and vortex rings) can link together, the extent of linkage (knotting included) being related to the contorsion of the loops or rings by a topological conservation law. This law is respected by intercommunication. One consequence is that total loop contorsion is quantized in integers.

  16. Multi-instrument observations of coronal loops

    NASA Astrophysics Data System (ADS)

    Scott, Jason Terrence

    This document exhibits results of analysis from data collected with multiple EUV satellites (SOHO, TRACE, STEREO, Hinode, and SDO). The focus is the detailed observation of coronal loops using multiple instruments, i.e. filter imagers and spectrometers. Techniques for comparing the different instruments and deriving loop parameters are demonstrated. Attention is given to the effects the different instruments may introduce into the data and their interpretation. The assembled loop parameters are compared to basic energy balance equations and scaling laws. Discussion of the blue-shifted, asymmetric, and line broadened spectral line profiles near the footpoints of coronal loops is made. The first quantitative analysis of the anti-correlation between intensity and spectral line broadening for isolated regions along loops and their footpoints is presented. A magnetic model of an active region shows where the separatrices meet the photospheric boundary. At the boundary, the spectral data reveal concentrated regions of increased blue-shifted outflows, blue wing asymmetry, and line broadening. This is found just outside the footpoints of bright loops. The intensity and line broadening in this region are anti-correlated. A comparison of the similarities in the spectroscopic structure near the footpoints of the arcade loops and more isolated loops suggests the notion of consistent structuring for the bright loops forming an apparent edge of an active region core.

  17. Unified framework for systematic loop transformations

    SciTech Connect

    Lu, L.C.; Chen, M.

    1990-10-01

    This paper presents a formal mathematical framework which unifies the existing loop transformations. This framework also includes more general classes of loop transformations, which can extract more parallelism from a class of programs than the existing techniques. We classify schedules into three classes: uniform, subdomain-variant, and statement-variant. Viewing from the degree of parallelism to be gained by loop transformation, the schedules can also be classified as single-sequential level, multiple-sequential level, and mixed schedules. We also illustrate the usefulness of the more general loop transformation with an example program.

  18. Calcium in Plants

    PubMed Central

    WHITE, PHILIP J.; BROADLEY, MARTIN R.

    2003-01-01

    Calcium is an essential plant nutrient. It is required for various structural roles in the cell wall and membranes, it is a counter‐cation for inorganic and organic anions in the vacuole, and the cytosolic Ca2+ concentration ([Ca2+]cyt) is an obligate intracellular messenger coordinating responses to numerous developmental cues and environmental challenges. This article provides an overview of the nutritional requirements of different plants for Ca, and how this impacts on natural flora and the Ca content of crops. It also reviews recent work on (a) the mechanisms of Ca2+ transport across cellular membranes, (b) understanding the origins and specificity of [Ca2+]cyt signals and (c) characterizing the cellular [Ca2+]cyt‐sensors (such as calmodulin, calcineurin B‐like proteins and calcium‐dependent protein kinases) that allow plant cells to respond appropriately to [Ca2+]cyt signals. PMID:12933363

  19. Limestone reaction in calcium aluminate cement–calcium sulfate systems

    SciTech Connect

    Bizzozero, Julien Scrivener, Karen L.

    2015-10-15

    This paper reports a study of ternary blends composed of calcium aluminate cement, calcium sulfate hemihydrate and limestone. Compressive strength tests and hydration kinetics were studied as a function of limestone and calcium sulfate content. The phase evolution and the total porosity were followed and compared to thermodynamic simulation to understand the reactions involved and the effect of limestone on these binders. The reaction of limestone leads to the formation of hemicarboaluminate and monocarboaluminate. Increasing the ratio between sulfate and aluminate decreases the extent of limestone reaction.

  20. Closed-Loop Neuroscience and Non-Invasive Brain Stimulation: A Tale of Two Loops

    PubMed Central

    Zrenner, Christoph; Belardinelli, Paolo; Müller-Dahlhaus, Florian; Ziemann, Ulf

    2016-01-01

    Closed-loop neuroscience is receiving increasing attention with recent technological advances that enable complex feedback loops to be implemented with millisecond resolution on commodity hardware. We summarize emerging conceptual and methodological frameworks that are available to experimenters investigating a “brain in the loop” using non-invasive brain stimulation and briefly review the experimental and therapeutic implications. We take the view that closed-loop neuroscience in fact deals with two conceptually quite different loops: a “brain-state dynamics” loop, used to couple with and modulate the trajectory of neuronal activity patterns, and a “task dynamics” loop, that is the bidirectional motor-sensory interaction between brain and (simulated) environment, and which enables goal-directed behavioral tasks to be incorporated. Both loops need to be considered and combined to realize the full experimental and therapeutic potential of closed-loop neuroscience. PMID:27092055

  1. The diversity of H3 loops determines the antigen‐binding tendencies of antibody CDR loops

    PubMed Central

    2016-01-01

    Abstract Of the complementarity‐determining regions (CDRs) of antibodies, H3 loops, with varying amino acid sequences and loop lengths, adopt particularly diverse loop conformations. The diversity of H3 conformations produces an array of antigen recognition patterns involving all the CDRs, in which the residue positions actually in contact with the antigen vary considerably. Therefore, for a deeper understanding of antigen recognition, it is necessary to relate the sequence and structural properties of each residue position in each CDR loop to its ability to bind antigens. In this study, we proposed a new method for characterizing the structural features of the CDR loops and obtained the antigen‐binding ability of each residue position in each CDR loop. This analysis led to a simple set of rules for identifying probable antigen‐binding residues. We also found that the diversity of H3 loop lengths and conformations affects the antigen‐binding tendencies of all the CDR loops. PMID:26749247

  2. R-loopDB: a database for R-loop forming sequences (RLFS) and R-loops

    PubMed Central

    Jenjaroenpun, Piroon; Wongsurawat, Thidathip; Sutheeworapong, Sawannee; Kuznetsov, Vladimir A.

    2017-01-01

    R-loopDB (http://rloop.bii.a-star.edu.sg) was originally constructed as a collection of computationally predicted R-loop forming sequences (RLFSs) in the human genic regions. The renewed R-loopDB provides updates, improvements and new options, including access to recent experimental data. It includes genome-scale prediction of RLFSs for humans, six other animals and yeast. Using the extended quantitative model of RLFSs (QmRLFS), we significantly increased the number of RLFSs predicted in the human genes and identified RLFSs in other organism genomes. R-loopDB allows searching of RLFSs in the genes and in the 2 kb upstream and downstream flanking sequences of any gene. R-loopDB exploits the Ensembl gene annotation system, providing users with chromosome coordinates, sequences, gene and genomic data of the 1 565 795 RLFSs distributed in 121 056 genic or proximal gene regions of the covered organisms. It provides a comprehensive annotation of Ensembl RLFS-positive genes including 93 454 protein coding genes, 12 480 long non-coding RNA and 7 568 small non-coding RNA genes and 7 554 pseudogenes. Using new interface and genome viewers of R-loopDB, users can search the gene(s) in multiple species with keywords in a single query. R-loopDB provides tools to carry out comparative evolution and genome-scale analyses in R-loop biology. PMID:27899586

  3. UWB communication receiver feedback loop

    DOEpatents

    Spiridon, Alex; Benzel, Dave; Dowla, Farid U.; Nekoogar, Faranak; Rosenbury, Erwin T.

    2007-12-04

    A novel technique and structure that maximizes the extraction of information from reference pulses for UWB-TR receivers is introduced. The scheme efficiently processes an incoming signal to suppress different types of UWB as well as non-UWB interference prior to signal detection. Such a method and system adds a feedback loop mechanism to enhance the signal-to-noise ratio of reference pulses in a conventional TR receiver. Moreover, sampling the second order statistical function such as, for example, the autocorrelation function (ACF) of the received signal and matching it to the ACF samples of the original pulses for each transmitted bit provides a more robust UWB communications method and system in the presence of channel distortions.

  4. Delay locked loop integrated circuit.

    SciTech Connect

    Brocato, Robert Wesley

    2007-10-01

    This report gives a description of the development of a Delay Locked Loop (DLL) integrated circuit (IC). The DLL was developed and tested as a stand-alone IC test chip to be integrated into a larger application specific integrated circuit (ASIC), the Quadrature Digital Waveform Synthesizer (QDWS). The purpose of the DLL is to provide a digitally programmable delay to enable synchronization between an internal system clock and external peripherals with unknown clock skew. The DLL was designed and fabricated in the IBM 8RF process, a 0.13 {micro}m CMOS process. It was designed to operate with a 300MHz clock and has been tested up to 500MHz.

  5. Closed loop steam cooled airfoil

    DOEpatents

    Widrig, Scott M.; Rudolph, Ronald J.; Wagner, Gregg P.

    2006-04-18

    An airfoil, a method of manufacturing an airfoil, and a system for cooling an airfoil is provided. The cooling system can be used with an airfoil located in the first stages of a combustion turbine within a combined cycle power generation plant and involves flowing closed loop steam through a pin array set within an airfoil. The airfoil can comprise a cavity having a cooling chamber bounded by an interior wall and an exterior wall so that steam can enter the cavity, pass through the pin array, and then return to the cavity to thereby cool the airfoil. The method of manufacturing an airfoil can include a type of lost wax investment casting process in which a pin array is cast into an airfoil to form a cooling chamber.

  6. Coronal Loops Reveal Magnetic Dance

    NASA Image and Video Library

    2017-09-28

    Magnetic Dance: Solar material traces out giant magnetic fields soaring through the sun to create what's called coronal loops. Here they can be seen as white lines in a sharpened AIA image from Oct. 24, 2014, laid over data from SDO's Helioseismic Magnetic Imager, which shows magnetic fields on the sun's surface in false color. Credit: NASA/SDO/HMI/AIA/LMSAL Read more: www.nasa.gov/content/goddard/sdo-telescope-collects-its-1... NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  7. Closed Loop Fire Control System

    DTIC Science & Technology

    1976-11-01

    bD 0 C 0 0 0 r- C0 - 1 u 0 z 2-5 F-t WI > zI C 0 t V). /- 0 LLI I 2-56 in the case of Vu . The estimation of V is...2-57 1! F𔃻 5 ’E-4 LMOSOW - - - 4 c- 44- <L V) L 0: 0 < ~ * ~ L., 0 I I I2-5 2.5 OPEN LOOP FIREl CONTROL COMIPUTATIION The objetctivye of tilt opel ...ELECTRONICS ASSY ITEM QTY FrQ N i N FAMILY 7Qx N 1 6 Connector Sets - 70 Pin PW BD , Solder Cup 1.0 1. 7 10.2 Airborne 2 7 Double Sided Printed

  8. DNA looping mediates nucleosome transfer

    PubMed Central

    Brennan, Lucy D.; Forties, Robert A.; Patel, Smita S.; Wang, Michelle D.

    2016-01-01

    Proper cell function requires preservation of the spatial organization of chromatin modifications. Maintenance of this epigenetic landscape necessitates the transfer of parental nucleosomes to newly replicated DNA, a process that is stringently regulated and intrinsically linked to replication fork dynamics. This creates a formidable setting from which to isolate the central mechanism of transfer. Here we utilized a minimal experimental system to track the fate of a single nucleosome following its displacement, and examined whether DNA mechanics itself, in the absence of any chaperones or assembly factors, may serve as a platform for the transfer process. We found that the nucleosome is passively transferred to available dsDNA as predicted by a simple physical model of DNA loop formation. These results demonstrate a fundamental role for DNA mechanics in mediating nucleosome transfer and preserving epigenetic integrity during replication. PMID:27808093

  9. Closing the loop with blur

    NASA Astrophysics Data System (ADS)

    Tani, Jacopo

    A great variety of systems use image sensors to provide measurements for closed loop operation. A drawback of using image sensors in real-time feedback is that they provide measurements at slower sampling rates as compared to the actuators, typically around 30 Hz for CCD cameras, hence acting as the bottleneck for closed loop control bandwidths. While high speed cameras exist, higher frame rates imply an upper bound on exposures which lowers the signal-to-noise-ratio (SNR), reducing measurements accuracy. The integrative nature of image sensors though offers the opportunity to prolong the exposure window and collect motion blurred measurements. This research describes how to exploit the dynamic information of observed system outputs, encoded in motion blur, to control fast systems at the fast rate through slow rate image sensors. In order to achieve this objective it is necessary to (a) design a controller providing fast rate input to the system based on the slow image measurements. Ideally such a controller would require a fast rate estimate of the system's state variables in order to provide the necessary control action, therefore an (b) image blur based estimator is to be developed. State estimators typically need a model of the system in order to provide their estimates, so (c) a system identification problem has to be addressed, where a reliable model describing the frequency content of the system, up to frequencies corresponding to the fast rate, has to be determined through slow rate image sensor measurements. Alternatively when such a procedure is not possible for lack, e.g., of knowledge of the input to the system, then (d) a method to reconstruct the output signal frequency content up to frequencies above those set by the limitations of the sampling theorem is to be devised. Therefore in order to "close the loop with blur", this work describes how to pose and solve the problems of, namely: system identification , state estimation, closed loop control and

  10. Three-loop cusp anomalous dimension and a conjecture for n loops

    NASA Astrophysics Data System (ADS)

    Kidonakis, Nikolaos

    2016-05-01

    I present analytical expressions for the massive cusp anomalous dimension in QCD through three loops, first calculated in 2014, in terms of elementary functions and ordinary polylogarithms. I observe interesting relations between the results at different loops and provide a conjecture for the n-loop cusp anomalous dimension in terms of the lower-loop results. I also present numerical results and simple approximate formulas for the cusp anomalous dimension relevant to top-quark production.

  11. Calcium homeostasis in diabetes mellitus.

    PubMed

    Heath, H; Lambert, P W; Service, F J; Arnaud, S B

    1979-09-01

    Experimentally diabetic rats have low serum 1,25-dihydroxyvitamin D, intestinal malabsorption of calcium, secondary hyperparathyroidism, and bone loss. To examine the hypothesis that abnormalities similar to those in the diabetic rat might explain human diabetic osteopenia, we studied calcium metabolism in 40 healthy control and 82 diabetic patients aged 18--75 yr [47 untreated: fasting plasma glucose (mean +/- SE), 267 +/- 8 mg/dl; 19 treated but hyperglycemic: glucose 305 +/- 24 mg/dl; 16 treated and in better control: glucose, 146 +/- 8 mg/dl]. Serum total calcium, ionic calcium, immunoreactive parathyroid hormone (Arnaud method, GP-1M and CH-12M antisera), 25-hydroxyvitamin D (Haddad method), and 1,25-dihydroxyvitamin D (Lambert method) concentrations were normal in all 3 groups of diabetics and were not significantly different from values in the control group. We determined absorption of calcium from the intestine by a double isotope method (100 mg Ca carrier; normal range, 40--80%) in 11 control and 13 untreated, uncontrolled diabetics (mean plasma glucose, 285 +/- 17 mg/dl). Absorption of calcium in controls was 60 +/- 3% and in diabetics was 56 +/- 3% (not significantly different). We have found no derangement of calcium metabolism in adults with insulin-requiring juvenile- and adult-onset diabetes regardless of treatment status. The experimental diabetic rat model does not appear to be useful for determining the pathogenesis of adult human diabetic osteopenia.

  12. Defoaming effect of calcium soap.

    PubMed

    Zhang, Hui; Miller, Clarence A; Garrett, Peter R; Raney, Kirk H

    2004-11-15

    The effect of calcium oleate on foam stability was studied for aqueous solutions of two commonly used surfactants (anionic and nonionic) under alkaline conditions in the absence of oil. For the anionic surfactant, defoaming by calcium oleate appears to involve two mechanisms. One is that oleate and calcium ions are presumably incorporated into the surfactant monolayers with a resulting decrease in the maximum of the disjoining pressure curve and therefore produces less stable thin films. The other is bridging of the films by calcium oleate particles. The latter mechanism was especially important in freshly made solutions where precipitation in the aqueous phase was still occurring when the foam was generated. Foams generated after aging (hours) when precipitation was nearly complete were more stable even though solution turbidities were greater. Foams of the nonionic surfactant were less stable than those of the anionic surfactant but were also destabilized by sufficient amounts of calcium oleate and exhibited a similar aging effect. A simplified model was developed for estimating the sodium oleate concentration at which precipitation commences in solutions of the anionic surfactant containing dissolved calcium. It includes enhancement of calcium content in the electrical double layers of the surfactant micelles. Predictions of the model were in agreement with experiment.

  13. Gravitational steady states of solar coronal loops

    NASA Astrophysics Data System (ADS)

    Sugiyama, Linda E.; Asgari-Targhi, M.

    2017-02-01

    Coronal loops on the surface of the sun appear to consist of curved, plasma-confining magnetic flux tubes or "ropes," anchored at both ends in the photosphere. Toroidal loops carrying current are inherently unstable to expansion in the major radius due to toroidal-curvature-induced imbalances in the magnetic and plasma pressures. An ideal MHD analysis of a simple isolated loop with density and pressure higher than the surrounding corona, based on the theory of magnetically confined toroidal plasmas, shows that the radial force balance depends on the loop internal structure and varies over parameter space. It provides a unified picture of simple loop steady states in terms of the plasma beta βo, the inverse aspect ratio ɛ =a /Ro , and the MHD gravitational parameter G ̂≡g a /vA2 , all at the top of the loop, where g is the acceleration due to gravity, a the average minor radius, and vA the shear Alfvén velocity. In the high and low beta tokamak orderings, βo=2 noT /(Bo2/2 μo)˜ɛ1 and ɛ2 , that fit many loops, the solar gravity can sustain nonaxisymmetric steady states at G ̂˜ɛ βo that represent the maximum stable height. At smaller G ̂≤ɛ2βo , the loop is axisymmetric to leading order and stabilized primarily by the two fixed loop ends. Very low beta, nearly force-free, steady states with βo˜ɛ3 may also exist, with or without gravity, depending on higher order effects. The thin coronal loops commonly observed in solar active regions have ɛ ≃0.02 and fit the high beta steady states. G ̂ increases with loop height. Fatter loops in active regions that form along magnetic neutral lines and may lead to solar flares and Coronal Mass Ejections have ɛ ≃0.1 -0.2 and may fit the low beta ordering. Larger loops tend to have G ̂>ɛ βo and be unstable to radial expansion because the exponential hydrostatic reduction in the density at the loop-top reduces the gravitational force -ρG ̂ R ̂ below the level that balances expansion, in agreement with

  14. On the Properties of Cosmic String Loops

    NASA Astrophysics Data System (ADS)

    Casper, Paul Henry

    1996-01-01

    When coupled with the prevailing ideas of cosmology, the standard model of particle physics implies that the early universe underwent a sequence of phase transitions. Such phase transitions can lead to topological defects such as magnetic monopoles, domain walls and cosmic strings. The formation and subsequent evolution of a network of cosmic strings may have played a key role in the development of the early universe. One of the most crucial elements in the evolution of the cosmic string network is the formation and decay of closed loops of cosmic string. After formation, the loops lose their energy by emitting gravitational radiation. This provides the primary energy loss mechanism for the cosmic string network. In addition, the cosmic string loops may display a number of observable features through which the cosmic string model may be constrained. In this dissertation a number of the key properties of cosmic string loops are investigated. A general method for determining the rates at which cosmic string loops radiate both energy and linear momentum is developed and implemented. Exact solutions for the radiation rates of a several new classes of loops are derived and used to test the validity of using the piecewise linear method on smooth loop trajectories. A large set of representative loop trajectories is produced using the method of loop fragmentation. These trajectories are analyzed to provide useful information on the properties of realistic cosmic string loops. The fraction of cosmic string loops which would collapse to form black holes is determined and used to place a new observational limit on the mass per unit length of cosmic strings.

  15. Progress in Super Long Loop Prediction

    PubMed Central

    Zhao, Suwen; Zhu, Kai; Li, Jianing; Friesner, Richard A.

    2011-01-01

    Sampling errors are very common in super long loop (referring here to loops that have more than thirteen residues) prediction, simply because the sampling space is vast. We have developed a dipeptide segment sampling algorithm to solve this problem. As a first step in evaluating the performance of this algorithm, it was applied to the problem of reconstructing loops in native protein structures. With a newly constructed test set of 89 loops ranging from 14 to 17 residues, this method obtains average/median global backbone root-mean-square deviations (RMSDs) to the native structure (superimposing the body of the protein, not the loop itself) of 1.46/0.68 Å. Specifically, results for loops of various lengths are 1.19/0.67 Å for 36 fourteen-residue loops, 1.55/0.75 Å for 30 fifteen-residue loops, 1.43/0.80 Å for 14 sixteen-residue loops, and 2.30/1.92 Å for 9 seventeen-residue loops. In the vast majority of cases, the method locates energy minima that are lower than or equal to that of the minimized native loop, thus indicating that the new sampling method is successful and rarely limits prediction accuracy. Median RMSDs are substantially lower than the averages because of a small number of outliers. The causes of these failures are examined in some detail, and some can be attributed to flaws in the energy function, such as pi-pi interactions are not accurately accounted for by the OPLS-AA force field we employed in this study. By introducing a new energy model which has a superior description of pi-pi interactions, significantly better results were achieved for quite a few former outliers. Crystal packing is explicitly included in order to provide a fair comparison with crystal structures. PMID:21905115

  16. Glycoprotein Degradation in the Blind Loop Syndrome

    PubMed Central

    Prizont, Roberto

    1981-01-01

    Contents obtained from jejunum of normal controls, self-emptying and self-filling blind loop rats were analyzed for the presence of glycoprotein-degrading glycosidases. The blind loop syndrome was documented by the increased fat excretion and slower growth rate of self-filling blind loop rats 6 wk after surgery. With p-nitrophenylglycosides as substrate, the specific activity of α-N-acetylgalactosaminidase, a potential blood group A destroying glycosidase, was 0.90±0.40 mU/mg of protein. This level was 23-fold higher than the specific activity of normal controls. In partially purified self-filling blind loop contents, the activity of α-N-acetylgalactosaminidase was 9- to 70-fold higher than activities of self-emptying and normal controls. Antibiotic treatment with chloromycetin and polymyxin decreased 24-fold the glycosidase levels in self-filling blind loops. In experiments with natural substrate, the blood group A titer of a20,000g supernate from normal jejunal homogenates decreased 128-fold after 24-h incubation with blind loop contents. Normal contents failed to diminish the blood group reactivity of the natural substrate. Furthermore, blind loop contents markedly decreased the blood group A titer of isolated brush borders. Incubation between blind loop bacteria and mucosal homogenates or isolated brush borders labeled with d-[U-14C]glucosamine revealed increased production of labeled ether extractable organic acids. Likewise, intraperitoneal injection of d-[U-14C]glucosamine into self-filling blind loop rats resulted in incorporation of the label into luminal short chain fatty acids. These results suggest that glycosidases may provide a mechanism by which blind loop bacteria obtain sugars from intestinal glycoproteins. The released sugars are used and converted by bacteria into energy and organic acids. This use of the host's glycoproteins would allow blind loop bacteria to grow and survive within the lumen independent of exogenous sources. PMID:6257760

  17. Dihedral-like constructions of automorphic loops

    NASA Astrophysics Data System (ADS)

    Aboras, Mouna

    In this dissertation we study dihedral-like constructions of automorphic loops. Automorphic loops are loops in which all inner mappings are automorphisms. We start by describing a generalization of the dihedral construction for groups. Namely, if (G, +) is an abelian group, m > 1 and alpha ∈2 Aut(G), let Dih(m, G, alpha) on Zm x G be defined by. (i, u)(j, v) = (i + j, ((--1)ju + v)alpha ij). We prove that the resulting loop is automorphic if and only if m = 2 or (alpha2 = 1 and m is even) or (m is odd, alpha = 1 and exp(G) ≤ 2). In the last case, the loop is a group. The case m = 2 was introduced by Kinyon, Kunen, Phillips, and Vojtechovsky. We study basic structural properties of dihedral-like automorphic loops. We describe certain subloops, including: nucleus, commutant, center, associator subloop and derived subloop. We prove theorems for dihedral-like automorphic loops analogous to the Cauchy and Lagrange theorems for groups, and further we discuss the coset decomposition in dihedral-like automorphic loops. We show that two finite dihedral-like automorphic loops Dih( m, G, alpha) and Dih(m¯, G¯, [special character omitted]) are isomorphic if and only if m = m¯, G ≅ G¯ and alpha is conjugate to [special character omitted] in Aut(G). We describe the automorphism group of Q and its subgroup consisting of inner mappings of Q. Finally, due to the solution to the isomorphism problem, we are interested in studying conjugacy classes of automorphism groups of finite abelian groups. Then we describe all dihedral-like automorphic loops of order < 128 up to isomorphism. We conclude with a description of all dihedral-like automorphic loops of order < 64 up to isotopism.

  18. Core-Shell Collagen Peptide Chelated Calcium/Calcium Alginate Nanoparticles from Fish Scales for Calcium Supplementation.

    PubMed

    Guo, Honghui; Hong, Zhuan; Yi, Ruizao

    2015-07-01

    We report simple methods for preparing collagen peptide chelated calcium (cpcc) and a novel cpcc-loaded nanoparticle from marine fish scales for calcium supplementation. Cpcc nanoparticles have an average diameter of approximately 150 nm and a calcium content of up to 130.4 g/kg. Calcium alginate was selected to encapsulate cpcc for the preparation of core-shell cpcc/calcium alginate nanoparticles. The core-shell nanoparticles were mainly 200 to 500 nm in diameter. The ratio of calcium to sulfur was approximately 1.6:1. In vivo experiments indicated both cpcc and core-shell cpcc were able to improve calcium absorption and prevent calcium deficiency. Especially core-shell cpcc worked well to increase femur bone mineral density and femur calcium content in rats significantly. The study demonstrated that cpcc and core-shell cpcc nanoparticles were ideal for calcium supplementation. Calcium deficiency has become an increasingly relevant health concern in the food industry. There is an urgent need for new effective calcium supplements. This study consisted of preparing and characterizing alginate nanoparticles loaded with collagen peptide chelated calcium. These nanoparticles can enhance calcium absorption significantly and prevent calcium deficiency. The data presented in this study can aid the food industry in developing a new ideal calcium supplement. © 2015 Institute of Food Technologists®

  19. Calcium signals in olfactory neurons.

    PubMed

    Tareilus, E; Noé, J; Breer, H

    1995-11-09

    Laser scanning confocal microscopy in combination with the fluorescent calcium indicators Fluo-3 and Fura-Red was employed to estimate the intracellular concentration of free calcium ions in individual olfactory receptor neurons and to monitor temporal and spatial changes in the Ca(2+)-level upon stimulation. The chemosensory cells responded to odorants with a significant increase in the calcium concentration, preferentially in the dendritic knob. Applying various stimulation paradigma, it was found that in a population of isolated cells, subsets of receptor neurons display distinct patterns of responsiveness.

  20. Influence of dietary calcium on bone calcium utilization

    SciTech Connect

    Farmer, M.; Roland, D.A. Sr.; Clark, A.J.

    1986-02-01

    In Experiment 1, 10 microCi /sup 45/Ca/day were administered to 125 hens for 10 days. Hens were then allocated to five treatments with calcium levels ranging from .08 to 3.75% of the diet. In Experiment 2, hens with morning oviposition times were randomly allocated to 11 treatments that were periods of time postoviposition ranging from 6 hr to 24 hr, in 2-hr increments (Experiment 2). At the end of each 2-hr period, eggs from 25 hens were removed from the uterus. The 18-, 20-, and 22-hr treatments were replicated three times. In Experiment 3, hens were fed either ad libitum or feed was withheld the last 5 or 6 hr before oviposition. In Experiment 4, hens were fed 10 microCi of /sup 45/Ca for 15 days to label skeletal calcium. Hens were divided into two groups and fed a .08 or 3.75% calcium diet for 2 days. On the second day, 25 hens fed the 3.75% calcium diet were intubated with 7 g of the same diet containing .5 g calcium at 1700, 2100, 0100, 0500, and 0700 hr. The measurements used were egg weight, shell weight, and /sup 45/Ca content of the egg shell. Results indicated a significant linear or quadratic regression of dietary calcium levels on /sup 45/Ca accumulation in eggshells and eggshell weight (Experiment 1). As the calcium level of the diet increased, eggshell weight increased and /sup 45/Ca recovery decreased. Utilization of skeletal calcium for shell formation ranged from 28 to 96%. In Experiment 2, the rate of shell calcification was not constant throughout the calcification process but varied significantly.

  1. Calcium carbonate and calcium sulfate in Martian meteorite EETA79001

    NASA Technical Reports Server (NTRS)

    Gooding, J. L.; Wentworth, S. J.

    1987-01-01

    Chips of glassy Lithology C of EETA79001 were studied by scanning electron microscopy and energy dispersive X-ray spectroscopy to determine the mineralogy and petrogenesis of the glass that was shown by others to contain trapped Mars-like gases. Calcium carbonite was identified as massive to acicular crystals for which Ca, C, and O were the major elements. Calcium sulfate was identified as prismatic-acicular crystals with Ca and S as the major elements.

  2. Three loop balanced bridge feedback pointing control

    NASA Technical Reports Server (NTRS)

    Lurie, Boris J.

    1988-01-01

    The balanced bridge feedback (BBF) technique developed in communication engineering is applied to the multiloop pointing control problem. Using colocated sensors, BBF decouples the motor loop from the mechanical plant and increases the feedback bandwidth in the motor and plant loops.

  3. Vacuum Energy Sequestering and Graviton Loops.

    PubMed

    Kaloper, Nemanja; Padilla, Antonio

    2017-02-10

    We recently formulated a local mechanism of vacuum energy sequester. This mechanism automatically removes all matter loop contributions to vacuum energy from the stress energy tensor which sources the curvature. Here we adapt the local vacuum energy sequestering mechanism to also cancel all the vacuum energy loops involving virtual gravitons, in addition to the vacuum energy generated by matter fields alone.

  4. Kopra during EMU Cooling Loop Maintenance

    NASA Image and Video Library

    2016-04-01

    ISS047e032108 (04/01/2016) --- NASA astronaut and Expedition 47 commander Tim Kopra conducts a loop scrub on two U.S. spacesuits inside the Quest airlock. Periodic cleaning and sampling of the spacesuit cooling loops is conducted to ensure the suits are in working order and ready to support future spacewalks.

  5. On Novice Loop Boundaries and Range Conceptions

    ERIC Educational Resources Information Center

    Ginat, David

    2004-01-01

    The paper presents a study of novice difficulties with range conceptions in loop design. CS2 students were asked to solve four related enumeration tasks, which required various loop boundary specifications. The student solutions varied considerably in conciseness and efficiency. The solution diversity reveals significant differences in range…

  6. Loop calculus for lattice gauge theories

    SciTech Connect

    Gambini, R.; Leal, L.; Trias, A.

    1989-05-15

    Hamiltonian calculations are performed using a loop-labeled basis where the full set of identities for the SU(/ital N/) gauge models has been incorporated. The loops are classified as clusterlike structures and the eigenvalue problem leads to a linear set of finite-difference equations easily amenable to numerical treatment. Encouraging results are reported for SU(2) at spatial dimension 2.

  7. External Tank CIL Closed Loop Verification System

    NASA Technical Reports Server (NTRS)

    Hartley, Eugene A., Jr.

    2005-01-01

    Lockheed Martin was requested to develop a closed loop CIL system following the Challenger accident. The system that was developed has proven to be very robust with minimal problems since implementation, having zero escapes in the last 7 years (27 External Tanks). We are currently investigating expansion of the CIL Closed Loop system to include "MI" CILs.

  8. Three loop balanced bridge feedback pointing control

    NASA Technical Reports Server (NTRS)

    Lurie, Boris J.

    1988-01-01

    The balanced bridge feedback (BBF) technique developed in communication engineering is applied to the multiloop pointing control problem. Using colocated sensors, BBF decouples the motor loop from the mechanical plant and increases the feedback bandwidth in the motor and plant loops.

  9. Active Region Loop Models and Observations

    NASA Astrophysics Data System (ADS)

    Landi, E.; Landini, M.

    2004-01-01

    The analysis of broad band images from EIT and TRACE and spectra from SUMER and CDS have triggered a heated debate on 1) whether the loops are isothermal for most of their length 2) whether they are multithermal across their section and 3) what is the shape of their heating function. Our work describes a detailed comparison between SOHO-CDS observations of an active region loop with a standard RTV-like loop model developed assuming a temperature-independent heating function in the energy balance equation and a variable loop cross-section. Observations of an active region loop recorded by CDS have been analyzed. Additional data from EIT MDI and Yohkoh-SXT have been considered. Electron density temperature and pressure along the selected loop structure have been measured by means of line ratio techniques and an emission measure analysis. Comparison with CDS data has shown that 1) the RTV-like model is not able to reproduce the observations 2) the loop is isothermal along most of its length 3) the loop is isothermal across its section.

  10. The Cygnus Loop: An Older Supernova Remnant.

    ERIC Educational Resources Information Center

    Straka, William

    1987-01-01

    Describes the Cygnus Loop, one of brightest and most easily studied of the older "remnant nebulae" of supernova outbursts. Discusses some of the historical events surrounding the discovery and measurement of the Cygnus Loop and makes some projections on its future. (TW)

  11. R-loops in bacterial transcription

    PubMed Central

    Gowrishankar, J; Leela, J Krishna; Anupama, K

    2013-01-01

    Nascent untranslated transcripts in bacteria are prone to generating RNA-DNA hybrids (R-loops); Rho-dependent transcription termination acts to reduce their prevalence. Here we discuss the mechanisms of R-loop formation and growth inhibition in bacteria. PMID:23756343

  12. Formation of Chromosomal Domains by Loop Extrusion.

    PubMed

    Fudenberg, Geoffrey; Imakaev, Maxim; Lu, Carolyn; Goloborodko, Anton; Abdennur, Nezar; Mirny, Leonid A

    2016-05-31

    Topologically associating domains (TADs) are fundamental structural and functional building blocks of human interphase chromosomes, yet the mechanisms of TAD formation remain unclear. Here, we propose that loop extrusion underlies TAD formation. In this process, cis-acting loop-extruding factors, likely cohesins, form progressively larger loops but stall at TAD boundaries due to interactions with boundary proteins, including CTCF. Using polymer simulations, we show that this model produces TADs and finer-scale features of Hi-C data. Each TAD emerges from multiple loops dynamically formed through extrusion, contrary to typical illustrations of single static loops. Loop extrusion both explains diverse experimental observations-including the preferential orientation of CTCF motifs, enrichments of architectural proteins at TAD boundaries, and boundary deletion experiments-and makes specific predictions for the depletion of CTCF versus cohesin. Finally, loop extrusion has potentially far-ranging consequences for processes such as enhancer-promoter interactions, orientation-specific chromosomal looping, and compaction of mitotic chromosomes.

  13. The Cygnus Loop: An Older Supernova Remnant.

    ERIC Educational Resources Information Center

    Straka, William

    1987-01-01

    Describes the Cygnus Loop, one of brightest and most easily studied of the older "remnant nebulae" of supernova outbursts. Discusses some of the historical events surrounding the discovery and measurement of the Cygnus Loop and makes some projections on its future. (TW)

  14. Complete renormalization of QCD at five loops

    NASA Astrophysics Data System (ADS)

    Luthe, Thomas; Maier, Andreas; Marquard, Peter; Schröder, York

    2017-03-01

    We present new analytical five-loop Feynman-gauge results for the anomalous dimensions of ghost field and -vertex, generalizing the known values for SU(3) to a general gauge group. Together with previously published results on the quark mass and -field anomalous dimensions and the Beta function, this completes the 5-loop renormalization program of gauge theories in that gauge.

  15. Spring control of wire harness loops

    NASA Technical Reports Server (NTRS)

    Curcio, P. J.

    1979-01-01

    Negator spring control guides wire harness between movable and fixed structure. It prevents electrical wire harness loop from jamming or being severed as wire moves in response to changes in position of aircraft rudder. Spring-loaded coiled cable controls wire loop regardless of rudder movement.

  16. Vacuum Energy Sequestering and Graviton Loops

    NASA Astrophysics Data System (ADS)

    Kaloper, Nemanja; Padilla, Antonio

    2017-02-01

    We recently formulated a local mechanism of vacuum energy sequester. This mechanism automatically removes all matter loop contributions to vacuum energy from the stress energy tensor which sources the curvature. Here we adapt the local vacuum energy sequestering mechanism to also cancel all the vacuum energy loops involving virtual gravitons, in addition to the vacuum energy generated by matter fields alone.

  17. Acquisition performance of various QPSK carrier tracking loops

    NASA Technical Reports Server (NTRS)

    Hinedi, S.; Shah, B.

    1992-01-01

    The frequency and phase acquisition performance of three quadrature phase shift keying (QPSK) carrier tracking loops, the MAP estimation loop, the Costas crossover loop, and the generalized Costas loop, is described. Acquisition time and probability of acquisition as a function of both loop signal-to-noise ratio and frequency offset to loop bandwidth ratio are obtained via computer simulations for type II and III loops. It is shown that the MAP loop, which results in the smallest squaring loss for all signal-to-noise ratios, is sometimes outperformed by the other two loops in terms of acquisition time and acquisition probability.

  18. Damped transverse oscillations of interacting coronal loops

    NASA Astrophysics Data System (ADS)

    Soler, Roberto; Luna, Manuel

    2015-10-01

    Damped transverse oscillations of magnetic loops are routinely observed in the solar corona. This phenomenon is interpreted as standing kink magnetohydrodynamic waves, which are damped by resonant absorption owing to plasma inhomogeneity across the magnetic field. The periods and damping times of these oscillations can be used to probe the physical conditions of the coronal medium. Some observations suggest that interaction between neighboring oscillating loops in an active region may be important and can modify the properties of the oscillations. Here we theoretically investigate resonantly damped transverse oscillations of interacting nonuniform coronal loops. We provide a semi-analytic method, based on the T-matrix theory of scattering, to compute the frequencies and damping rates of collective oscillations of an arbitrary configuration of parallel cylindrical loops. The effect of resonant damping is included in the T-matrix scheme in the thin boundary approximation. Analytic and numerical results in the specific case of two interacting loops are given as an application.

  19. REVIEWS OF TOPICAL PROBLEMS: Coronal magnetic loops

    NASA Astrophysics Data System (ADS)

    Zaitsev, Valerii V.; Stepanov, Alexander V.

    2008-11-01

    The goal of this review is to outline some new ideas in the physics of coronal magnetic loops, the fundamental structural elements of the atmospheres of the Sun and flaring stars, which are involved in phenomena such as stellar coronal heating, flare energy release, charged particle acceleration, and the modulation of optical, radio, and X-ray emissions. The Alfvén-Carlqvist view of a coronal loop as an equivalent electric circuit allows a good physical understanding of loop processes. Describing coronal loops as MHD-resonators explains various ways in which flaring emissions from the Sun and stars are modulated, whereas modeling them by magnetic mirror traps allows one to describe the dynamics and emission of high-energy particles. Based on these approaches, loop plasma and fast particle parameters are obtained and models for flare energy release and stellar corona heating are developed.

  20. The cut-closed-reconnected Roux loop.

    PubMed

    Kummer, E W; Gerritsen, J J; Brummelkamp, W H

    2000-02-01

    Motility disturbances in the Roux loop can negatively influence the outcome of reflux gastritis; the uncut Roux loop does not have these disadvantages, but is less suitable for clinical application because of staple dehiscence. The reported "cut-closed-reconnected" Roux loop has the same physiological starting points as the uncut Roux loop, but a difference is an extra closure at the site of the seromuscular level. The technique of the cut-closed-reconnected Roux loop is described. After 1 year, the clinical findings in 8 patients were as follows: 1 patient free of symptoms, 4 with gastric pain, 2 patients vomited (1 bilious), and 1 felt fullness. Dehiscence of the closure could not be demonstrated by endoscopy, barium contrast roentgenography, and HIDA scan.

  1. Leaping of a flexible loop on water

    NASA Astrophysics Data System (ADS)

    Kim, Ho-Young; Yang, Eun Jin; Lee, Min-Hee; Shin, Bongsu

    2008-11-01

    Small aquatic arthropods, such as water striders and fishing spiders, are able to leap on water to a height several times their body length. We study a simple model using a floating flexible loop to provide fundamental understanding and mimicking principle of the leaping on water. Motion of a loop, initially bent into an ellipse from equilibrium circular shape using a thin thread, is visualized with a high speed camera upon cutting the thread with a laser. We find that the loop may merely oscillate while afloat, penetrate into the water, or soar into air depending on the hydrophobicity, the bending stiffness, the weight and the degree of initial deflection of the loop. We also construct a scaling law for the leaping height by balancing the initial elastic bending energy with the loop's translational and vibrational energy and a loss imparted to the water in the forms of interfacial, kinetic and viscous energy.

  2. Osmotic mechanism of the loop extrusion process

    NASA Astrophysics Data System (ADS)

    Yamamoto, Tetsuya; Schiessel, Helmut

    2017-09-01

    The loop extrusion theory assumes that protein factors, such as cohesin rings, act as molecular motors that extrude chromatin loops. However, recent single molecule experiments have shown that cohesin does not show motor activity. To predict the physical mechanism involved in loop extrusion, we here theoretically analyze the dynamics of cohesin rings on a loop, where a cohesin loader is in the middle and unloaders at the ends. Cohesin monomers bind to the loader rather frequently and cohesin dimers bind to this site only occasionally. Our theory predicts that a cohesin dimer extrudes loops by the osmotic pressure of cohesin monomers on the chromatin fiber between the two connected rings. With this mechanism, the frequency of the interactions between chromatin segments depends on the loading and unloading rates of dimers at the corresponding sites.

  3. 21 CFR 184.1187 - Calcium alginate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium alginate. 184.1187 Section 184.1187 Food... Specific Substances Affirmed as GRAS § 184.1187 Calcium alginate. (a) Calcium alginate (CAS Reg. No. 9005.... Calcium alginate is prepared by the neutralization of purified alginic acid with appropriate pH...

  4. 21 CFR 184.1201 - Calcium glycerophosphate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... carbonate. The commercial product is a mixture of calcium β-, and D-, and L-α-glycerophosphate. (b) The... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium glycerophosphate. 184.1201 Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1201 Calcium glycerophosphate. (a) Calcium...

  5. 21 CFR 184.1199 - Calcium gluconate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... neutralization of gluconic acid with lime or calcium carbonate. (b) The ingredient meets the specifications of... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium gluconate. 184.1199 Section 184.1199 Food... Specific Substances Affirmed as GRAS § 184.1199 Calcium gluconate. (a) Calcium gluconate ([CH2OH(CHOH)4COO...

  6. 21 CFR 184.1201 - Calcium glycerophosphate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... carbonate. The commercial product is a mixture of calcium β-, and D-, and L-α-glycerophosphate. (b) The... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium glycerophosphate. 184.1201 Section 184.1201... Listing of Specific Substances Affirmed as GRAS § 184.1201 Calcium glycerophosphate. (a) Calcium...

  7. 21 CFR 184.1201 - Calcium glycerophosphate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... carbonate. The commercial product is a mixture of calcium β-, and D-, and L-α-glycerophosphate. (b) The... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium glycerophosphate. 184.1201 Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1201 Calcium glycerophosphate. (a) Calcium...

  8. 21 CFR 184.1201 - Calcium glycerophosphate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... carbonate. The commercial product is a mixture of calcium β-, and D-, and L-α-glycerophosphate. (b) The... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium glycerophosphate. 184.1201 Section 184... Listing of Specific Substances Affirmed as GRAS § 184.1201 Calcium glycerophosphate. (a) Calcium...

  9. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  10. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  11. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Calcium silicate. 172.410 Section 172.410 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used in food in accordance with...

  12. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  13. 21 CFR 172.410 - Calcium silicate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be...

  14. Direct loop gain and bandwidth measurement of phase-locked loop

    NASA Astrophysics Data System (ADS)

    Ye, P.; Ren, R.; Kou, Y.; Sun, F.; Hu, J.; Chen, S.; Hou, D.

    2017-08-01

    A simple and robust technique for directly measuring the loop gain and bandwidth of a phase-locked loop (PLL) is proposed. This technique can be used for the real-time measurement of the real loop gain in a closed PLL without breaking its locking state. The agreement of the measured loop gain and theoretical calculations proves the validity of the proposed measurement technique. This technique with a simple configuration can be easily expanded to other phase-locking systems whose loop gain and bandwidth should be measured precisely.

  15. Loop heat pipes and capillary pumped loops-an applications perspective

    NASA Astrophysics Data System (ADS)

    Butler, Dan; Ku, Jentung; Swanson, Theodore

    2002-01-01

    Capillary pumped loops (CPLs) and loop heat pipes (LHPs) are versatile two-phase heat transfer devices which have recently gained increasing acceptance in space applications. Both systems work based on the same principles and have very similar designs. Nevertheless, some differences exist in the construction of the evaporator and the hydro-accumulator, and these differences lead to very distinct operating characteristics for each loop. This paper presents comparisons of the two loops from an applications perspective, and addresses their impact on spacecraft design, integration, and test. Some technical challenges and issues for both loops are also addressed. .

  16. A communication scheme for the distrubted execution of loop nests with while loops

    SciTech Connect

    Griebl, M.; Lengauer, C.

    1995-10-01

    The mathematical model for the parallelization, or {open_quotes}space-time mapping,{close_quotes} of loop nests is the polyhedron model. The presence of while loops in the nest complicates matters for two reasons: (1) the parallelized loop nest does not correspond to a polyhedron but instead to a subset that resembles a (multi-dimensional) comb and (2) it is not clear when the entire loop nest has terminated. We describe a communication scheme which can deal with both problems and which can be added to the parallel target loop nest by a compiler.

  17. Children's Bone Health and Calcium

    MedlinePlus

    ... Research Information Clinical Trials Resources and Publications Children's Bone Health and Calcium: Condition Information Skip sharing on ... media links Share this: Page Content What is bone health and how do you build strong bones? ...

  18. Calcium Phosphate Nanoparticle Adjuvant

    PubMed Central

    He, Qing; Mitchell, Alaina R.; Johnson, Stacy L.; Wagner-Bartak, Claus; Morcol, Tulin; Bell, Steve J. D.

    2000-01-01

    Vaccination to protect against human infectious diseases may be enhanced by using adjuvants that can selectively stimulate immunoregulatory responses. In a murine model, a novel nanoparticulate adjuvant composed of calcium phosphate (CAP) was compared with the commonly used aluminum (alum) adjuvants for its ability to induce immunity to herpes simplex virus type 2 (HSV-2) and Epstein-Barr virus (EBV) infections. Results indicated that CAP was more potent as an adjuvant than alum, elicited little or no inflammation at the site of administration, induced high titers of immunoglobulin G2a (IgG2a) antibody and neutralizing antibody, and facilitated a high percentage of protection against HSV-2 infection. Additional benefits of CAP include (i) an insignificant IgE response, which is an important advantage over injection of alum compounds, and (ii) the fact that CAP is a natural constituent of the human body. Thus, CAP is very well tolerated and absorbed. These studies were performed with animal models. By virtue of the potency of this CAP adjuvant and the relative absence of side effects, we believe that this new CAP formulation has great potential for use as an adjuvant in humans. PMID:11063495

  19. Calcium and Arrhythmogenesis

    PubMed Central

    Ter Keurs, Henk E. D. J.; Boyden, Penelope A.

    2010-01-01

    Triggered activity in cardiac muscle and intracellular Ca2+ have been linked in the past. However, today not only are there a number of cellular proteins that show clear Ca2+ dependence but also there are a number of arrhythmias whose mechanism appears to be linked to Ca2+-dependent processes. Thus we present a systematic review of the mechanisms of Ca2+ transport (forward excitation-contraction coupling) in the ventricular cell as well as what is known for other cardiac cell types. Second, we review the molecular nature of the proteins that are involved in this process as well as the functional consequences of both normal and abnormal Ca2+ cycling (e.g., Ca2+ waves). Finally, we review what we understand to be the role of Ca2+ cycling in various forms of arrhythmias, that is, those associated with inherited mutations and those that are acquired and resulting from reentrant excitation and/or abnormal impulse generation (e.g., triggered activity). Further solving the nature of these intricate and dynamic interactions promises to be an important area of research for a better recognition and understanding of the nature of Ca2+ and arrhythmias. Our solutions will provide a more complete understanding of the molecular basis for the targeted control of cellular calcium in the treatment and prevention of such. PMID:17429038

  20. Calcium metabolism in sarcoidosis

    PubMed Central

    Dent, C. E.

    1970-01-01

    Fifteen patients with hypercalcaemia and sarcoidosis have been studied. Twelve were males of average age 34; the three females averaged 53. Cases included widely varying sarcoid manifestations, but five gave a clear history of rather excessive ingestion of low-dosage vitamin D preparations. The data confirm that in most cases there is an undue sensitivity to all the actions of vitamin D, the situation therefore mimicking vitamin D intoxication. Two patients volunteered to receive ultra-violet irradiation and became hypercalcaemic with corresponding clinical and biochemical changes. Steroids make normal the calcium abnormalities just as they do in straight vitamin D intoxication. However, in three further patients the hypercalcaemia did not respond to steroids and was shown to be due to the presence of an over-acting parathyroid gland, removal of which corrected the abnormality. There are a sufficient number of other similar cases in the literature to suggest that the development of parathyroid adenomas is another even rarer complication of sarcoidosis which must be carefully distinguished from vitamin D sensitivity. PMID:5481094

  1. Cygnus Loop Supernova Blast Wave

    NASA Technical Reports Server (NTRS)

    1993-01-01

    This is an image of a small portion of the Cygnus Loop supernova remnant, which marks the edge of a bubble-like, expanding blast wave from a colossal stellar explosion, occurring about 15,000 years ago. The HST image shows the structure behind the shock waves, allowing astronomers for the first time to directly compare the actual structure of the shock with theoretical model calculations. Besides supernova remnants, these shock models are important in understanding a wide range of astrophysical phenomena, from winds in newly-formed stars to cataclysmic stellar outbursts. The supernova blast is slamming into tenuous clouds of insterstellar gas. This collision heats and compresses the gas, causing it to glow. The shock thus acts as a searchlight revealing the structure of the interstellar medium. The detailed HST image shows the blast wave overrunning dense clumps of gas, which despite HST's high resolution, cannot be resolved. This means that the clumps of gas must be small enough to fit inside our solar system, making them relatively small structures by interstellar standards. A bluish ribbon of light stretching left to right across the picture might be a knot of gas ejected by the supernova; this interstellar 'bullet' traveling over three million miles per hour (5 million kilometres) is just catching up with the shock front, which has slowed down by ploughing into interstellar material. The Cygnus Loop appears as a faint ring of glowing gases about three degrees across (six times the diameter of the full Moon), located in the northern constellation, Cygnus the Swan. The supernova remnant is within the plane of our Milky Way galaxy and is 2,600 light-years away. The photo is a combination of separate images taken in three colors, oxygen atoms (blue) emit light at temperatures of 30,000 to 60,000 degrees Celsius (50,000 to 100,000 degrees Farenheit). Hydrogen atoms (green) arise throughout the region of shocked gas. Sulfur atoms (red) form when the gas cools to

  2. Quantitation of interactions between two DNA loops demonstrates loop domain insulation in E. coli cells

    PubMed Central

    Priest, David G.; Kumar, Sandip; Yan, Yan; Dunlap, David D.; Dodd, Ian B.; Shearwin, Keith E.

    2014-01-01

    Eukaryotic gene regulation involves complex patterns of long-range DNA-looping interactions between enhancers and promoters, but how these specific interactions are achieved is poorly understood. Models that posit other DNA loops—that aid or inhibit enhancer–promoter contact—are difficult to test or quantitate rigorously in eukaryotic cells. Here, we use the well-characterized DNA-looping proteins Lac repressor and phage λ CI to measure interactions between pairs of long DNA loops in E. coli cells in the three possible topological arrangements. We find that side-by-side loops do not affect each other. Nested loops assist each other’s formation consistent with their distance-shortening effect. In contrast, alternating loops, where one looping element is placed within the other DNA loop, inhibit each other’s formation, thus providing clear support for the loop domain model for insulation. Modeling shows that combining loop assistance and loop interference can provide strong specificity in long-range interactions. PMID:25288735

  3. Sequence–structure relationships in RNA loops: establishing the basis for loop homology modeling

    PubMed Central

    Schudoma, Christian; May, Patrick; Nikiforova, Viktoria; Walther, Dirk

    2010-01-01

    The specific function of RNA molecules frequently resides in their seemingly unstructured loop regions. We performed a systematic analysis of RNA loops extracted from experimentally determined three-dimensional structures of RNA molecules. A comprehensive loop-structure data set was created and organized into distinct clusters based on structural and sequence similarity. We detected clear evidence of the hallmark of homology present in the sequence–structure relationships in loops. Loops differing by <25% in sequence identity fold into very similar structures. Thus, our results support the application of homology modeling for RNA loop model building. We established a threshold that may guide the sequence divergence-based selection of template structures for RNA loop homology modeling. Of all possible sequences that are, under the assumption of isosteric relationships, theoretically compatible with actual sequences observed in RNA structures, only a small fraction is contained in the Rfam database of RNA sequences and classes implying that the actual RNA loop space may consist of a limited number of unique loop structures and conserved sequences. The loop-structure data sets are made available via an online database, RLooM. RLooM also offers functionalities for the modeling of RNA loop structures in support of RNA engineering and design efforts. PMID:19923230

  4. Role of loop-loop interactions in coordinating motions and enzymatic function in triosephosphate isomerase.

    PubMed

    Wang, Yan; Berlow, Rebecca B; Loria, J Patrick

    2009-06-02

    The enzyme triosephosphate isomerase (TIM) has been used as a model system for understanding the relationship between protein sequence, structure, and biological function. The sequence of the active site loop (loop 6) in TIM is directly correlated with a conserved motif in loop 7. Replacement of loop 7 of chicken TIM with the corresponding loop 7 sequence from an archaeal homologue caused a 10(2)-fold loss in enzymatic activity, a decrease in substrate binding affinity, and a decrease in thermal stability. Isotope exchange studies performed by one-dimensional (1)H NMR showed that the substrate-derived proton in the enzyme is more susceptible to solvent exchange for DHAP formation in the loop 7 mutant than for WT TIM. TROSY-Hahn Echo and TROSY-selected R(1rho) experiments indicate that upon mutation of loop 7, the chemical exchange rate for active site loop motion is nearly doubled and that the coordinated motion of loop 6 is reduced relative to that of the WT. Temperature dependent NMR experiments show differing activation energies for the N- and C-terminal hinges in this mutant enzyme. Together, these data suggest that interactions between loop 6 and loop 7 are necessary to provide the proper chemical context for the enzymatic reaction to occur and that the interactions play a significant role in modulating the chemical dynamics near the active site.

  5. Calcium transport in turtle bladder

    SciTech Connect

    Sabatini, S.; Kurtzman, N.A. )

    1987-12-01

    Unidirectional {sup 45}Ca fluxes were measured in the turtle bladder under open-circuit and short-circuit conditions. In the open-circuited state net calcium flux (J{sup net}{sub Ca}) was secretory (serosa to mucosa). Ouabain reversed J{sup net}{sub Ca} to an absorptive flux. Amiloride reduced both fluxes such that J{sup net}{sub Ca} was not significantly different from zero. Removal of mucosal sodium caused net calcium absorption; removal of serosal sodium caused calcium secretion. When bladders were short circuited, J{sup net}{sub Ca} decreased to approximately one-third of control value but remained secretory. When ouabain was added under short-circuit conditions, J{sup net}{sub Ca} was similar in magnitude and direction to ouabain under open-circuited conditions (i.e., absorptive). Tissue {sup 45}Ca content was {approx equal}30-fold lower when the isotope was placed in the mucosal bath, suggesting that the apical membrane is the resistance barrier to calcium transport. The results obtained in this study are best explained by postulating a Ca{sup 2+}-ATPase on the serosa of the turtle bladder epithelium and a sodium-calcium antiporter on the mucosa. In this model, the energy for calcium movement would be supplied, in large part, by the Na{sup +}-K{sup +}-ATPase. By increasing cell sodium, ouabain would decrease the activity of the mucosal sodium-calcium exchanger (or reverse it), uncovering active calcium transport across the serosa.

  6. Medical therapy, calcium oxalate urolithiasis

    NASA Technical Reports Server (NTRS)

    Ruml, L. A.; Pearle, M. S.; Pak, C. Y.

    1997-01-01

    The development of diagnostic protocols that identify specific risk factors for calcium oxalate nephrolithiasis has led to the formulation of directed medical regimens that are aimed at correcting the underlying metabolic disturbances. Initiation of these treatment programs has reduced markedly the rate of stone formation in the majority of patients who form stones. This article discusses the rationale that underlies the choice of medical therapy for the various pathophysiologic causes of calcium oxalate nephrolithiasis and the appropriate use of available medications.

  7. Medical therapy, calcium oxalate urolithiasis

    NASA Technical Reports Server (NTRS)

    Ruml, L. A.; Pearle, M. S.; Pak, C. Y.

    1997-01-01

    The development of diagnostic protocols that identify specific risk factors for calcium oxalate nephrolithiasis has led to the formulation of directed medical regimens that are aimed at correcting the underlying metabolic disturbances. Initiation of these treatment programs has reduced markedly the rate of stone formation in the majority of patients who form stones. This article discusses the rationale that underlies the choice of medical therapy for the various pathophysiologic causes of calcium oxalate nephrolithiasis and the appropriate use of available medications.

  8. The effect of bile, bile acids and detergents on calcium absorption in the chick

    PubMed Central

    Webling, D. D'A.; Holdsworth, E. S.

    1965-01-01

    1. Bile from rachitic or normal chicks causes an immediate increase in the intestinal absorption of soluble calcium in rachitic and vitamin D3-treated chicks as tested in vivo by intestinal-loop and oral-dosing methods. 2. This effect is apparently solely due to the taurine-conjugated bile acids present in the bile and is independent of the action of vitamin D. 3. Chick bile and bile acids can increase the solubility and the absorption of calcium presented as sparingly soluble calcium hydrogen phosphate. 4. In addition, bile is necessary to some extent at least for the intestinal absorption of vitamin D3 in the chick and this would indirectly enhance the absorption of calcium. 5. Thus bile is capable of a threefold action in the absorption of calcium in the chick. It is suggested that the direct action on sparingly soluble forms of calcium is of considerable physiological importance since most of the calcium in the normal bird's diet would be in this form. 6. Bile acids enhance the absorption of calcium in all regions of the small intestine of the chick. 7. Of a range of bile acids and detergents tested for enhancement of calcium absorption, various taurine-conjugated bile acids and sodium lauryl sulphate, an anionic detergent, are effective. A non-ionic detergent (Tween 80) and a cationic detergent (Zephiran) are without effect. 8. The ability of a substance to increase directly the intestinal absorption of soluble calcium appears to depend to some extent on an anionic detergent action, i.e. the ability to form a salt or complex soluble to some extent in both aqueous and lipid phases. 9. In chicks the immediate deposition of calcium (45Ca) in the bones closely reflects any increase in plasma calcium radioactivity regardless of the cause of the increase and regardless of the vitamin D3 status. Although sodium lauryl sulphate can increase markedly the calcium absorption from the gut and the immediate deposition in the bones it has no significant effect on rickets

  9. The effect of aminoacetonitrile on calcium metabolism and bone in the rat.

    PubMed Central

    Kemm, J R

    1976-01-01

    1. The effect of the osteolathyrogen aminoacetonitrile (AAN) on plasma calcium, phosphate and alkaline phosphatase, on bone, on growth rates, on absorption of calcium and phosphate in the gut and on their urinary excretion, has been examined in rats. 2. AAN caused a general deterioration in the health of the rat and reduced its rate of growth. 3. AAN reduced plasma calcium and increased plasma alkaline phosphatase but did not affect plasma phosphate. 4. AAN caused obvious deformity of the long bones with large exostoses. The femurs of the lathyritic rats had an increased fat-free weight and increased fat-free weight to ash weight ratio. 5. AAN increased true and apparent absorption of calcium but did not consistently affect urinary excretion of phosphate or apparent absorption of phosphate. 6. AAN did not produce a significant reduction in the plasma calcium of parathyroidectomized or thyroparathyroidectomized rats. 7. Absorption of calcium from ligated jejunal loops was increased in AAN-treated parathyroidectomized rats. 8. In some experiments parathyroidectomy or thyroparathyroidectomy protected the bones from the effect of AAN. Images Plate 1 Plate 2 Plate 3 PMID:994026

  10. Calcium Orthophosphate Cements and Concretes

    PubMed Central

    Dorozhkin, Sergey V.

    2009-01-01

    In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA) or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone), calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

  11. Looping charged elastic rods: applications to protein-induced DNA loop formation.

    PubMed

    Cherstvy, A G

    2011-01-01

    We analyze looping of thin charged elastic filaments under applied torques and end forces, using the solution of linear elasticity theory equations. In application to DNA, we account for its polyelectrolyte character and charge renormalization, calculating electrostatic energies stored in the loops. We argue that the standard theory of electrostatic persistence is only valid when the loop's radius of curvature and close-contact distance are much larger than the Debye screening length. We predict that larger twist rates are required to trigger looping of charged rods as compared with neutral ones. We then analyze loop shapes formed on charged filaments of finite length, mimicking DNA looping by proteins with two DNA-binding domains. We find optimal loop shapes at different salt amounts, minimizing the sum of DNA elastic, DNA electrostatic, and protein elastic energies. We implement a simple model where intercharge repulsions do not affect the loop shape directly but can choose the energy-optimized shape from the allowed loop types. At low salt concentrations more open loops are favored due to enhanced repulsion of DNA charges, consistent with the results of computer simulations on formation of DNA loops by lac repressor. Then, we model the precise geometry of DNA binding by the lac tetramer and explore loop shapes, varying the confined DNA length and protein opening angle. The characteristics of complexes obtained, such as the total loop energy, stretching forces required to maintain its shape, and the reduction of electrostatic energy with increment of salt, are in good agreement with the outcomes of more elaborate numerical calculations for lac-repressor-induced DNA looping.

  12. Calcium in plant defence-signalling pathways.

    PubMed

    Lecourieux, David; Ranjeva, Raoul; Pugin, Alain

    2006-01-01

    In plant cells, the calcium ion is a ubiquitous intracellular second messenger involved in numerous signalling pathways. Variations in the cytosolic concentration of Ca2+ ([Ca2+]cyt) couple a large array of signals and responses. Here we concentrate on calcium signalling in plant defence responses, particularly on the generation of the calcium signal and downstream calcium-dependent events participating in the establishment of defence responses with special reference to calcium-binding proteins.

  13. 21 CFR 184.1195 - Calcium citrate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... acid with calcium hydroxide or calcium carbonate. It occurs as a fine white, odorless powder and... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Calcium citrate. 184.1195 Section 184.1195 Food... Specific Substances Affirmed as GRAS § 184.1195 Calcium citrate. (a) Calcium citrate (Ca3(C6H5O7)2·4H2O...

  14. 21 CFR 184.1195 - Calcium citrate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... acid with calcium hydroxide or calcium carbonate. It occurs as a fine white, odorless powder and... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Calcium citrate. 184.1195 Section 184.1195 Food... Specific Substances Affirmed as GRAS § 184.1195 Calcium citrate. (a) Calcium citrate (Ca3(C6H5O7)2·4H2O...

  15. 21 CFR 184.1195 - Calcium citrate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... calcium hydroxide or calcium carbonate. It occurs as a fine white, odorless powder and usually contains... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium citrate. 184.1195 Section 184.1195 Food and... Substances Affirmed as GRAS § 184.1195 Calcium citrate. (a) Calcium citrate (Ca3(C6H5O7)2·4H2O, CAS Reg. No...

  16. 21 CFR 184.1195 - Calcium citrate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... acid with calcium hydroxide or calcium carbonate. It occurs as a fine white, odorless powder and... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Calcium citrate. 184.1195 Section 184.1195 Food... Specific Substances Affirmed as GRAS § 184.1195 Calcium citrate. (a) Calcium citrate (Ca3(C6H5O7)2·4H2O...

  17. Loop Heat Pipe Development Overview

    NASA Astrophysics Data System (ADS)

    Riehl, Roger R.; dos Santos, Nadjara

    2008-01-01

    Over the last 4 years, the loop heat pipe (LHP) technology has been under development by this institute, focusing on future applications for this passive thermal control device, specially related to instruments' thermal control in satellites. Such a development has been focused on designing, manufacturing, assembling, charging and testing LHPs for Space applications using acetone as working fluid. Several procedures were specially conceived during the development program, which resulted in reliable apparatuses that have been extensively tested for potential applications. Repeatability on the processes used during the manufacturing of the LHPs was established as the key parameter to qualify this technology, as well as suppliers and techniques for charging and testing procedures. As a result, several LHPs were manufactured and are operational presenting reliable results related to the thermal control, according to the parameters established by the project. In parallel, two mathematical models were developed based on the experimental data gathered in laboratory conditions, which were then validated and have been applied on the design of LHPs for Earth orbit operation.

  18. Simulation methods for looping transitions.

    PubMed

    Gaffney, B J; Silverstone, H J

    1998-09-01

    Looping transitions occur in field-swept electron magnetic resonance spectra near avoided crossings and involve a single pair of energy levels that are in resonance at two magnetic field strengths, before and after the avoided crossing. When the distance between the two resonances approaches a linewidth, the usual simulation of the spectra, which results from a linear approximation of the dependence of the transition frequency on magnetic field, breaks down. A cubic approximation to the transition frequency, which can be obtained from the two resonance fields and the field-derivatives of the transition frequencies, along with linear (or better) interpolation of the transition-probability factor, restores accurate simulation. The difference is crucial for accurate line shapes at fixed angles, as in an oriented single crystal, but the difference turns out to be a smaller change in relative intensity for a powder spectrum. Spin-3/2 Cr3+ in ruby and spin-5/2 Fe3+ in transferrin oxalate are treated as examples.

  19. Packing loops into annular cavities

    NASA Astrophysics Data System (ADS)

    Sobral, T. A.; Gomes, M. A. F.

    2017-02-01

    The continuous packing of a flexible rod in two-dimensional cavities yields a countable set of interacting domains that resembles nonequilibrium cellular systems and belongs to a new class of lightweight material. However, the link between the length of the rod and the number of domains requires investigation, especially in the case of non-simply connected cavities, where the number of avoided regions emulates an effective topological temperature. In the present article we report the results of an experiment of injection of a single flexible rod into annular cavities in order to find the total length needed to insert a given number of loops (domains of one vertex). Using an exponential model to describe the experimental data we quite minutely analyze the initial conditions, the intermediary behavior, and the tight packing limit. This method allows the observation of a new fluctuation phenomenon associated with instabilities in the dynamic evolution of the packing process. Furthermore, the fractal dimension of the global pattern enters the discussion under a novel point of view. A comparison with the classical problems of the random close packing of disks and jammed disk packings is made.

  20. Curcumin improves synaptic plasticity impairment induced by HIV-1gp120 V3 loop

    PubMed Central

    Shen, Ling-ling; Jiang, Ming-liang; Liu, Si-si; Cai, Min-chun; Hong, Zhong-qiu; Lin, Li-qing; Xing, Yan-yan; Chen, Gui-lin; Pan, Rui; Yang, Li-juan; Xu, Ying; Dong, Jun

    2015-01-01

    Curcumin has been shown to significantly improve spatial memory impairment induced by HIV-1 gp120 V3 in rats, but the electrophysiological mechanism remains unknown. Using extracellular microelectrode recording techniques, this study confirmed that the gp120 V3 loop could suppress long-term potentiation in the rat hippocampal CA1 region and synaptic plasticity, and that curcumin could antagonize these inhibitory effects. Using a Fura-2/AM calcium ion probe, we found that curcumin resisted the effects of the gp120 V3 loop on hippocampal synaptosomes and decreased Ca2+ concentration in synaptosomes. This effect of curcumin was identical to nimodipine, suggesting that curcumin improved the inhibitory effects of gp120 on synaptic plasticity, ameliorated damage caused to the central nervous system, and might be a potential neuroprotective drug. PMID:26199609

  1. Calcium metabolism and cardiovascular function after spaceflight

    NASA Technical Reports Server (NTRS)

    Hatton, Daniel C.; Yue, Qi; Dierickx, Jacqueline; Roullet, Chantal; Otsuka, Keiichi; Watanabe, Mitsuaki; Coste, Sarah; Roullet, Jean Baptiste; Phanouvang, Thongchan; Orwoll, Eric; Orwoll, Shiela; McCarron, David A.

    2002-01-01

    To determine the influence of dietary calcium on spaceflight-induced alterations in calcium metabolism and blood pressure (BP), 9-wk-old spontaneously hypertensive rats, fed either high- (2%) or low-calcium (0.02%) diets, were flown on an 18-day shuttle flight. On landing, flight animals had increased ionized calcium (P < 0.001), elevated parathyroid hormone levels (P < 0.001), reduced calcitonin levels (P < 0.05), unchanged 1,25(OH)(2)D(3) levels, and elevated skull (P < 0.01) and reduced femur bone mineral density. Basal and thrombin-stimulated platelet free calcium (intracellular calcium concentration) were also reduced (P < 0.05). There was a tendency for indirect systolic BP to be reduced in conscious flight animals (P = 0.057). However, mean arterial pressure was elevated (P < 0.001) after anesthesia. Dietary calcium altered all aspects of calcium metabolism (P < 0.001), as well as BP (P < 0.001), but the only interaction with flight was a relatively greater increase in ionized calcium in flight animals fed low- compared with high-calcium diets (P < 0.05). The results indicate that 1) flight-induced disruptions of calcium metabolism are relatively impervious to dietary calcium in the short term, 2) increased ionized calcium did not normalize low-calcium-induced elevations of BP, and 3) parathyroid hormone was paradoxically increased in the high-calcium-fed flight animals after landing.

  2. Calcium metabolism and cardiovascular function after spaceflight

    NASA Technical Reports Server (NTRS)

    Hatton, Daniel C.; Yue, Qi; Dierickx, Jacqueline; Roullet, Chantal; Otsuka, Keiichi; Watanabe, Mitsuaki; Coste, Sarah; Roullet, Jean Baptiste; Phanouvang, Thongchan; Orwoll, Eric; hide

    2002-01-01

    To determine the influence of dietary calcium on spaceflight-induced alterations in calcium metabolism and blood pressure (BP), 9-wk-old spontaneously hypertensive rats, fed either high- (2%) or low-calcium (0.02%) diets, were flown on an 18-day shuttle flight. On landing, flight animals had increased ionized calcium (P < 0.001), elevated parathyroid hormone levels (P < 0.001), reduced calcitonin levels (P < 0.05), unchanged 1,25(OH)(2)D(3) levels, and elevated skull (P < 0.01) and reduced femur bone mineral density. Basal and thrombin-stimulated platelet free calcium (intracellular calcium concentration) were also reduced (P < 0.05). There was a tendency for indirect systolic BP to be reduced in conscious flight animals (P = 0.057). However, mean arterial pressure was elevated (P < 0.001) after anesthesia. Dietary calcium altered all aspects of calcium metabolism (P < 0.001), as well as BP (P < 0.001), but the only interaction with flight was a relatively greater increase in ionized calcium in flight animals fed low- compared with high-calcium diets (P < 0.05). The results indicate that 1) flight-induced disruptions of calcium metabolism are relatively impervious to dietary calcium in the short term, 2) increased ionized calcium did not normalize low-calcium-induced elevations of BP, and 3) parathyroid hormone was paradoxically increased in the high-calcium-fed flight animals after landing.

  3. The antiatherogenic potential of calcium antagonists.

    PubMed

    Weinstein, D B

    1988-01-01

    Atherosclerosis is an arterial disease characterized by focal accumulation of collagen, elastin, lipids, and calcium at sites associated with macrophage infiltration and altered smooth muscle metabolic function. Studies in several types of animal models, especially cholesterol-fed rabbits, have shown that calcium competitors, calcium chelators, anticalcifying agents, and calcium channel blockers can reduce the accumulation of atherogenic lesion components and thus apparently decrease the progression of lesions. Although there are some conflicting data in the animal model studies using calcium channel antagonists, as a result of differences in experimental designs, it is now apparent that several classes of calcium channel blockers inhibit the progression of early arterial lesions induced by cholesterol feeding. The dihydropyridine calcium channel blockers appear to be more potent antiatherosclerotic agents than other classes of calcium channel antagonists. Several mechanisms involving regulation of endothelial cell, smooth muscle cell, and macrophage metabolic functions may be responsible for the calcium channel blocker effects on early lesion progression. For example, recent studies in cell culture model systems suggest that calcium channel blockers may significantly alter activities that regulate lipoprotein-derived cholesterol accumulation by cells. Some of these activities are independent of calcium flux across voltage-operated calcium channels. Thus, calcium channel blockers may reduce the progression of atherogenic lesions by a combination of decreasing calcium accumulation within arterial wall cells and by altering calcium-independent metabolic activities.

  4. Biophysical investigation of retinal calcium sensor function.

    PubMed

    Koch, Karl-Wilhelm

    2012-08-01

    Neuronal calcium sensor proteins represent a subgroup of the family of EF-hand calcium binding proteins. Members of this subgroup are the guanylate cyclase-activating proteins and recoverin, which operate as important calcium sensors in retinal photoreceptor cells. Physiological and biochemical data indicate that these proteins participate in shaping the photoreceptor light response. Biophysical methods have been widely applied to investigate the molecular properties of retinal calcium binding proteins like the guanylate cyclase-activating proteins and recoverin. Properties include the determination of calcium affinities by isotope techniques and spectroscopical approaches. Conformational changes are investigated for example by tryptophan fluorescence emission. A special focus of this review is laid on a new experimental approach to study conformational changes in calcium binding proteins by surface plasmon resonance spectroscopy. In addition this technique has been employed for measuring the calcium-dependent binding of calcium sensors to membranes. Biophysical approaches provide valuable information about key properties of calcium sensor proteins involved in intracellular signalling. Parameters of their molecular properties like calcium binding and conformational changes help to define their physiological role derived from cellular, genetic or physiological studies. Calcium is an important second messenger in intracellular signaling. Calcium signals are propagated via calcium binding proteins that are able to discriminate between incremental differences in intracellular calcium and that regulate their targets with high precision and specificity. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signalling. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Calcium in the pathomechanism of amyotrophic lateral sclerosis - Taking center stage?

    PubMed

    Patai, Roland; Nógrádi, Bernát; Engelhardt, József I; Siklós, László

    2017-02-19

    Amyotrophic lateral sclerosis is an incurable, relentlessly progressive disease primarily affecting motor neurons. The cause of the disease, except for the mutations identified in a small fraction of patients, is unknown. The major mechanisms contributing to the degeneration of motor neurons have already been disclosed and characterized, including excitotoxicity, oxidative stress, mitochondrial dysfunction, and immune/inflammatory processes. During the progression of the disease these toxic processes are not discrete, but each facilitates the deleterious effect of the other. However, due to their common reciprocal calcium dependence, calcium ions may act as a common denominator and through a positive feedback loop may combine the individual pathological processes into a unified escalating mechanism of neuronal destruction. This mini-review provides an overview of the mutual calcium dependence of the major toxic mechanisms associated with amyotrophic lateral sclerosis. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Disruption of the IS6-AID Linker Affects Voltage-gated Calcium Channel Inactivation and Facilitation

    PubMed Central

    Findeisen, Felix

    2009-01-01

    Two processes dominate voltage-gated calcium channel (CaV) inactivation: voltage-dependent inactivation (VDI) and calcium-dependent inactivation (CDI). The CaVβ/CaVα1-I-II loop and Ca2+/calmodulin (CaM)/CaVα1–C-terminal tail complexes have been shown to modulate each, respectively. Nevertheless, how each complex couples to the pore and whether each affects inactivation independently have remained unresolved. Here, we demonstrate that the IS6–α-interaction domain (AID) linker provides a rigid connection between the pore and CaVβ/I-II loop complex by showing that IS6-AID linker polyglycine mutations accelerate CaV1.2 (L-type) and CaV2.1 (P/Q-type) VDI. Remarkably, mutations that either break the rigid IS6-AID linker connection or disrupt CaVβ/I-II association sharply decelerate CDI and reduce a second Ca2+/CaM/CaVα1–C-terminal–mediated process known as calcium-dependent facilitation. Collectively, the data strongly suggest that components traditionally associated solely with VDI, CaVβ and the IS6-AID linker, are essential for calcium-dependent modulation, and that both CaVβ-dependent and CaM-dependent components couple to the pore by a common mechanism requiring CaVβ and an intact IS6-AID linker. PMID:19237593

  7. Closed-loop neurostimulation: the clinical experience.

    PubMed

    Sun, Felice T; Morrell, Martha J

    2014-07-01

    Neurostimulation is now an established therapy for the treatment of movement disorders, pain, and epilepsy. While most neurostimulation systems available today provide stimulation in an open-loop manner (i.e., therapy is delivered according to preprogrammed settings and is unaffected by changes in the patient's clinical symptoms or in the underlying disease), closed-loop neurostimulation systems, which modulate or adapt therapy in response to physiological changes, may provide more effective and efficient therapy. At present, few such systems exist owing to the complexities of designing and implementing implantable closed-loop systems. This review focuses on the clinical experience of four implantable closed-loop neurostimulation systems: positional-adaptive spinal cord stimulation for treatment of pain, responsive cortical stimulation for treatment of epilepsy, closed-loop vagus nerve stimulation for treatment of epilepsy, and concurrent sensing and stimulation for treatment of Parkinson disease. The history that led to the development of the closed-loop systems, the sensing, detection, and stimulation technology that closes the loop, and the clinical experiences are presented.

  8. Mitotic chromosome compaction via active loop extrusion

    NASA Astrophysics Data System (ADS)

    Goloborodko, Anton; Imakaev, Maxim; Marko, John; Mirny, Leonid; MIT-Northwestern Team

    During cell division, two copies of each chromosome are segregated from each other and compacted more than hundred-fold into the canonical X-shaped structures. According to earlier microscopic observations and the recent Hi-C study, chromosomes are compacted into arrays of consecutive loops of ~100 kilobases. Mechanisms that lead to formation of such loop arrays are largely unknown. Here we propose that, during cell division, chromosomes can be compacted by enzymes that extrude loops on chromatin fibers. First, we use computer simulations and analytical modeling to show that a system of loop-extruding enzymes on a chromatin fiber self-organizes into an array of consecutive dynamic loops. Second, we model the process of loop extrusion in 3D and show that, coupled with the topo II strand-passing activity, it leads to robust compaction and segregation of sister chromatids. This mechanism of chromosomal condensation and segregation does not require additional proteins or specific DNA markup and is robust against variations in the number and properties of such loop extruding enzymes. Work at NU was supported by the NSF through Grants DMR-1206868 and MCB-1022117, and by the NIH through Grants GM105847 and CA193419. Work at MIT was supported by the NIH through Grants GM114190 R01HG003143.

  9. Are Coronal Loops Isothermal Or Multithermal? Yes!

    NASA Astrophysics Data System (ADS)

    Schmelz, Joan T.; Nasraoui, K.; Rightmire, L.; Garst, J.; Kimble, J.; Cirtain, J.; DeLuca, E. E.; Del Zanna, G.; Mason, H.

    2007-05-01

    Analysis of loops observed with the Coronal Diagnostics Spectrometer (CDS) and the Transition Region and Coronal Explorer (TRACE) reveal examples of both isothermal and multithermal plasma. These data were taken on 2003 January 17, and since the loops are on the disk, a lot of work was done on the details of background subtraction. The background-subtracted CDS intensities were analyzed using three methods: (1) Emission Measure Loci, (2) Forward-Folding DEM, and (3) Automatic-Inversion DEM. The first loop appears to be isothermal, with Log T = 5.8 MK. The forward-folding DEM shows a spike at this temperature and the EM Loci curves all intersect at this point. The automatic-inversion DEM results are broadened, however, as a result of the smoothing required for this method. This loop has a uniform temperature along the segment visible in the CDS field of view, and this result is confirmed using the TRACE data. The pixels along the second loop do not appear to be isothermal. The EM Loci curves do not intersect at a single point and both DEM methods show a broad curve. Other loops in this data set as well as loop evolution will be investigated if time permits. Solar physics research at the University of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G.

  10. A novel monoclonal antibody against the second extracellular loop of occludin disrupts epithelial cell polarity.

    PubMed

    Tokunaga, Yuichi; Kojima, Takashi; Osanai, Makoto; Murata, Masaki; Chiba, Hideki; Tobioka, Hirotoshi; Sawada, Norimasa

    2007-07-01

    The tight junction (TJ) regulates epithelial cell polarity and paracellular permeability. In the present study, to investigate whether the second extracellular loop of occludin affects the localization of carcinoembryonic antigen (CEA) and CD26 expressed on apical membranes, and the fence function of the TJ, the human intestinal epithelial cell line T84 was treated with the monoclonal anti-occludin antibody (MAb) 1H8, corresponding to the second extracellular loop of occludin. In T84 cells treated with MAb 1H8, occludin disappeared, and CEA and CD26 were observed to diffuse from the apical membrane to the basolateral membrane. Furthermore, a decrease in the fence function of TJ was observed without changes in the TJ strands and barrier function. When T84 cells precultured in low calcium (Ca) medium were recultured in normal Ca medium in the presence of MAb 1H8, recruitment of occludin to the apical-most membranes and recovery in distribution of CEA and CD26 were markedly retarded compared with the control. These results suggested that MAb 1H8 against the second extracellular loop of occludin selectively affected formation of the apical/basolateral intramembrane diffusion barrier and that the second extracellular loop of occludin plays a crucial role in the maintenance of epithelial cell polarity by the TJ.

  11. Bootstrapping an NMHV amplitude through three loops

    NASA Astrophysics Data System (ADS)

    Dixon, Lance J.; von Hippel, Matt

    2014-10-01

    We extend the hexagon function bootstrap to the next-to-maximally-helicity-violating (NMHV) configuration for six-point scattering in planar = 4 super-Yang-Mills theory at three loops. Constraints from the differential equation, from the operator product expansion (OPE) for Wilson loops with operator insertions, and from multi-Regge factorization, lead to a unique answer for the three-loop ratio function. The three-loop result also predicts additional terms in the OPE expansion, as well as the behavior of NMHV amplitudes in the multi-Regge limit at one higher logarithmic accuracy (NNLL) than was used as input. Both predictions are in agreement with recent results from the flux-tube approach. We also study the multi-particle factorization of multi-loop amplitudes for the first time. We find that the function controlling this factorization is purely logarithmic through three loops. We show that a function U , which is closely related to the parity-even part of the ratio function V , is remarkably simple; only five of the nine possible final entries in its symbol are non-vanishing. We study the analytic and numerical behavior of both the parity-even and parity-odd parts of the ratio function on simple lines traversing the space of cross ratios ( u, v, w), as well as on a few two-dimensional planes. Finally, we present an empirical formula for V in terms of elements of the coproduct of the six-gluon MHV remainder function R 6 at one higher loop, which works through three loops for V (four loops for R 6).

  12. Calcium signaling and cytotoxicity.

    PubMed Central

    Kass, G E; Orrenius, S

    1999-01-01

    The divalent calcium cation Ca(2+) is used as a major signaling molecule during cell signal transduction to regulate energy output, cellular metabolism, and phenotype. The basis to the signaling role of Ca(2+) is an intricate network of cellular channels and transporters that allow a low resting concentration of Ca(2+) in the cytosol of the cell ([Ca(2+)]i) but that are also coupled to major dynamic and rapidly exchanging stores. This enables extracellular signals from hormones and growth factors to be transduced as [Ca(2+)]i spikes that are amplitude and frequency encoded. There is considerable evidence that a number of toxic environmental chemicals target these Ca(2+) signaling processes, alter them, and induce cell death by apoptosis. Two major pathways for apoptosis will be considered. The first one involves Ca(2+)-mediated expression of ligands that bind to and activate death receptors such as CD95 (Fas, APO-1). In the second pathway, Ca(2+) has a direct toxic effect and its primary targets include the mitochondria and the endoplasmic reticulum (ER). Mitochondria may respond to an apoptotic Ca(2+) signal by the selective release of cytochrome c or through enhanced production of reactive oxygen species and opening of an inner mitochondrial membrane pore. Toxic agents such as the environmental pollutant tributyltin or the natural plant product thapsigargin, which deplete the ER Ca(2+) stores, will induce as a direct result of this effect the opening of plasma membrane Ca(2+) channels and an ER stress response. In contrast, under some conditions, Ca(2+) signals may be cytoprotective and antagonize the apoptotic machinery. Images Figure 1 Figure 2 Figure 3 PMID:10229704

  13. Looping circuit: a novel mechanism for prolonged spontaneous [Ca2+]i increases in developing embryonic mouse brainstem

    PubMed Central

    Watari, Hirofumi; Tose, Amanda J; Bosma, Martha M

    2014-01-01

    Most cells maintain [Ca2+]i at extremely low levels; calcium entry usually occurs briefly, and within seconds it is cleared. However, at embryonic day 12.5 in the mouse brainstem, trains of spontaneous events occur with [Ca2+]i staying close to peak value, well above baseline, for minutes; we termed this ‘bash bursts’. Here, we investigate the mechanism of this unusual activity using calcium imaging and electrophysiology. Bash bursts are triggered by an event originating at the mid-line of the rostral hindbrain and are usually the result of that event propagating repeatedly along a defined circular path. The looping circuit can either encompass both the midbrain and hindbrain or remain in the hindbrain only, and the type of loop determines the duration of a single lap time, 5 or 3 s, respectively. Bash bursts are supported by high membrane excitability of mid-line cells and are regulated by persistent inward ‘window current’ at rest, contributing to spontaneous activity. This looping circuit is an effective means for increasing [Ca2+]i at brief, regular intervals. Bash bursts disappear by embryonic day 13.5 via alteration of the looping circuit, curtailing the short epoch of bash bursts. The resulting sustained [Ca2+]i may influence development of raphe serotonergic and ventral tegmental dopaminergic neurons by modulating gene expression. PMID:24366258

  14. Looping circuit: a novel mechanism for prolonged spontaneous [Ca2+]i increases in developing embryonic mouse brainstem.

    PubMed

    Watari, Hirofumi; Tose, Amanda J; Bosma, Martha M

    2014-02-15

    Most cells maintain [Ca(2+)]i at extremely low levels; calcium entry usually occurs briefly, and within seconds it is cleared. However, at embryonic day 12.5 in the mouse brainstem, trains of spontaneous events occur with [Ca(2+)]i staying close to peak value, well above baseline, for minutes; we termed this 'bash bursts'. Here, we investigate the mechanism of this unusual activity using calcium imaging and electrophysiology. Bash bursts are triggered by an event originating at the mid-line of the rostral hindbrain and are usually the result of that event propagating repeatedly along a defined circular path. The looping circuit can either encompass both the midbrain and hindbrain or remain in the hindbrain only, and the type of loop determines the duration of a single lap time, 5 or 3 s, respectively. Bash bursts are supported by high membrane excitability of mid-line cells and are regulated by persistent inward 'window current' at rest, contributing to spontaneous activity. This looping circuit is an effective means for increasing [Ca(2+)]i at brief, regular intervals. Bash bursts disappear by embryonic day 13.5 via alteration of the looping circuit, curtailing the short epoch of bash bursts. The resulting sustained [Ca(2+)]i may influence development of raphe serotonergic and ventral tegmental dopaminergic neurons by modulating gene expression.

  15. Randall’s plaque of patients with nephrolithiasis begins in basement membranes of thin loops of Henle

    PubMed Central

    Evan, Andrew P.; Lingeman, James E.; Coe, Fredric L.; Parks, Joan H.; Bledsoe, Sharon B.; Shao, Youzhi; Sommer, Andre J.; Paterson, Ryan F.; Kuo, Ramsay L.; Grynpas, Marc

    2003-01-01

    Our purpose here is to test the hypothesis that Randall’s plaques, calcium phosphate deposits in kidneys of patients with calcium renal stones, arise in unique anatomical regions of the kidney, their formation conditioned by specific stone-forming pathophysiologies. To test this hypothesis, we performed intraoperative biopsies of plaques in kidneys of idiopathic-calcium-stone formers and patients with stones due to obesity-related bypass procedures and obtained papillary specimens from non–stone formers after nephrectomy. Plaque originates in the basement membranes of the thin loops of Henle and spreads from there through the interstitium to beneath the urothelium. Patients who have undergone bypass surgery do not produce such plaque but instead form intratubular hydroxyapatite crystals in collecting ducts. Non–stone formers also do not form plaque. Plaque is specific to certain kinds of stone-forming patients and is initiated specifically in thin-limb basement membranes by mechanisms that remain to be elucidated. PMID:12618515

  16. Calcium signalling and calcium channels: Evolution and general principles

    PubMed Central

    Verkhratsky, Alexei; Parpura, Vladimir

    2014-01-01

    Calcium as a divalent ion was selected early in evolution as a signaling molecule to be used by both prokaryotes and eukaryotes. Its low cytosolic concentration likely reflects the initial concentration of this ion in the primordial soup/ocean as unicellular organisms were formed. As the concentration of calcium in the ocean subsequently increased, so did the diversity of homeostatic molecules. This includes the plasma membrane channels that allowed the calcium entry, as well as extrusion mechanisms, i.e., exchangers and pumps. Further diversification occurred with the evolution of intracellular organelles, in particular the endoplasmic reticulum and mitochondria, which also contain channels, exchanger(s) and pumps to handle the homeostasis of calcium ions. Calcium signalling system, based around coordinated interactions of the above molecular entities, can be activated by the opening of voltage-gated channels, by neurotransmitters, by second messengers and/or mechanical stimulation, and as such is all-pervading pathway in physiology and pathophysiology of organisms. PMID:24291103

  17. Dopaminergic regulation of dendritic calcium: fast multisite calcium imaging.

    PubMed

    Zhou, Wen-Liang; Oikonomou, Katerina D; Short, Shaina M; Antic, Srdjan D

    2013-01-01

    Optimal dopamine tone is required for the normal cortical function; however it is still unclear how cortical-dopamine-release affects information processing in individual cortical neurons. Thousands of glutamatergic inputs impinge onto elaborate dendritic trees of neocortical pyramidal neurons. In the process of ensuing synaptic integration (information processing), a variety of calcium transients are generated in remote dendritic compartments. In order to understand the cellular mechanisms of dopaminergic modulation it is important to know whether and how dopaminergic signals affect dendritic calcium transients. In this chapter, we describe a relatively inexpensive method for monitoring dendritic calcium fluctuations at multiple loci across the pyramidal dendritic tree, at the same moment of time (simultaneously). The experiments have been designed to measure the amplitude, time course and spatial extent of action potential-associated dendritic calcium transients before and after application of dopaminergic drugs. In the examples provided here the dendritic calcium transients were evoked by triggering the somatic action potentials (backpropagation-evoked), and puffs of exogenous dopamine were applied locally onto selected dendritic branches.

  18. Increased calcium bioavailability in mice fed genetically engineered plants lacking calcium oxalate

    USDA-ARS?s Scientific Manuscript database

    Bioavailable calcium affects bone formation and calcification. Here we investigate how a single gene mutation altering calcium partitioning in the model forage crop Medicago truncatula affects calcium bioavailability. Previously, the cod5 M. truncatula mutant was identified which contains identical ...

  19. Polyakov loop correlator in perturbation theory

    NASA Astrophysics Data System (ADS)

    Berwein, Matthias; Brambilla, Nora; Petreczky, Péter; Vairo, Antonio

    2017-07-01

    We study the Polyakov loop correlator in the weak coupling expansion and show how the perturbative series reexponentiates into singlet and adjoint contributions. We calculate the order g7 correction to the Polyakov loop correlator in the short distance limit. We show how the singlet and adjoint free energies arising from the reexponentiation formula of the Polyakov loop correlator are related to the gauge invariant singlet and octet free energies that can be defined in pNRQCD, namely we find that the two definitions agree at leading order in the multipole expansion, but differ at first order in the quark-antiquark distance.

  20. Loop-quantum-gravity vertex amplitude.

    PubMed

    Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo

    2007-10-19

    Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity.

  1. Detecting neutrino magnetic moments with conducting loops

    NASA Astrophysics Data System (ADS)

    Apyan, Aram; Apyan, Armen; Schmitt, Michael

    2008-02-01

    It is well established that neutrinos have mass, yet it is very difficult to measure those masses directly. Within the standard model of particle physics, neutrinos will have an intrinsic magnetic moment proportional to their mass. We examine the possibility of detecting the magnetic moment using a conducting loop. According to Faraday’s law of induction, a magnetic dipole passing through a conducting loop induces an electromotive force in the loop. We compute this electromotive force for neutrinos in several cases, based on a fully covariant formulation of the problem. We discuss prospects for a real experiment, as well as the possibility to test the relativistic formulation of intrinsic magnetic moments.

  2. Parallel Digital Phase-Locked Loops

    NASA Technical Reports Server (NTRS)

    Sadr, Ramin; Shah, Biren N.; Hinedi, Sami M.

    1995-01-01

    Wide-band microwave receivers of proposed type include digital phase-locked loops in which band-pass filtering and down-conversion of input signals implemented by banks of multirate digital filters operating in parallel. Called "parallel digital phase-locked loops" to distinguish them from other digital phase-locked loops. Systems conceived as cost-effective solution to problem of filtering signals at high sampling rates needed to accommodate wide input frequency bands. Each of M filters process 1/M of spectrum of signal.

  3. Relevance of metal ions for lipase stability: structural rearrangements induced in the Burkholderia glumae lipase by calcium depletion.

    PubMed

    Invernizzi, Gaetano; Papaleo, Elena; Grandori, Rita; De Gioia, Luca; Lotti, Marina

    2009-12-01

    We have studied the accessibility of the structural calcium ion in the Burkholderia glumae lipase and the consequences of its removal on the protein conformation by different biophysical techniques (circular dichroism, fluorimetry, and mass spectrometry) and by molecular-dynamics simulations. We show that, in the native protein, calcium is not accessible unless specific flexible loops are displaced, for example, by a temperature increase. Such movements concern the whole calcium-binding pocket and particularly the environment of the coordinating aspartate residue 241. As a consequence of metal depletion the protein unfolds irreversibly and undergoes aggregation. The removal of the metal ion causes major structural transitions and leads to an increase in beta-structure, in particular in protein regions that are largely unstructured in the native protein and encompass the calcium coordination residues.

  4. Calcium wave of tubuloglomerular feedback.

    PubMed

    Peti-Peterdi, János

    2006-08-01

    ATP release from macula densa (MD) cells into the interstitium of the juxtaglomerular (JG) apparatus (JGA) is an integral component of the tubuloglomerular feedback (TGF) mechanism that controls the glomerular filtration rate. Because the cells of the JGA express a number of calcium-coupled purinergic receptors, these studies tested the hypothesis that TGF activation triggers a calcium wave that spreads from the MD toward distant cells of the JGA and glomerulus. Ratiometric calcium imaging of in vitro microperfused isolated JGA-glomerulus complex dissected from rabbits was performed with fluo-4/fura red and confocal fluorescence microscopy. Activation of TGF by increasing tubular flow rate at the MD rapidly produced a significant elevation in intracellular Ca(2+) concentration ([Ca(2+)](i)) in extraglomerular mesangial cells (by 187.6 +/- 45.1 nM) and JG renin granular cells (by 281.4 +/- 66.6 nM). Subsequently, cell-to-cell propagation of the calcium signal at a rate of 12.6 +/- 1.1 microm/s was observed upstream toward proximal segments of the afferent arteriole and adjacent glomeruli, as well as toward intraglomerular elements including the most distant podocytes (5.9 +/- 0.4 microm/s). The same calcium wave was observed in nonperfusing glomeruli, causing vasoconstriction and contractions of the glomerular tuft. Gap junction uncoupling, an ATP scavenger enzyme cocktail, and pharmacological inhibition of P(2) purinergic receptors, but not adenosine A(1) receptor blockade, abolished the changes in [Ca(2+)](i) and propagation of the calcium wave. These studies provided evidence that both gap junctional communication and extracellular ATP are integral components of the TGF calcium wave.

  5. [Calcium metabolism characteristics in microgravity].

    PubMed

    Grigor'ev, A I; Larina, I M; Morukov, B V

    1999-06-01

    The results of research of calcium exchange parameters at cosmonauts taken part in long space flights (SF) onboard of orbital stations "SALUT" and "MIR" within 1978-1998 were generalized. The analysis of data received during observation of 44 cosmonauts (18 of them have taken part in long SF twice) was done. The observation was carried out before and after SF by duration 30-438 days. The content of a total calcium in blood serum was increased basically by the increase of its ionized fraction after flights of moderate (3-6 months) and large duration (6-14 months) along with the significant increase of PTH and decrease of calcitonin levels. The content of osteocalcin after SF was increased. Three cosmonauts participated in research of calcium kinetics using stable isotopes before, in time and after a 115-day SF. Reduction of intestinal absorption, excretion through a gastrointestinal tract, and increase of calcium excretion with urine were marked in time of SF. In early postflight period a level of intestinal absorption, on the average, was much lower than in SF, and the calcium removal through intestine was increased. Both renal and intestinal excretion of calcium were not normalized in 3.5-4.5 months after end of SF. Increase of resorbtive processes in bone tissues which induced negative bone balance during flight was observed in all test subjects, proceeding from estimations of speed of the basic calcium flows made on the basis of mathematical modeling. The conclusion about decrease in speed of bone tissue remodeling and strengthening of its resorption proves to be true by data of research of biochemical and endocrine markers.

  6. Modeling Calcium Microdomains using Homogenisation

    PubMed Central

    Higgins, Erin R.; Goel, Pranay; Puglisi, Jose L.; Bers, Donald M.; Cannell, Mark; Sneyd, James

    2007-01-01

    Microdomains of calcium (i.e., areas on the nanometer scale that have qualitatively different calcium concentrations from that in the bulk cytosol) are known to be important in many situations. In cardiac cells, for instance, a calcium microdomain between the L-type channels and the ryanodine receptors, the so-called diadic cleft, is where the majority of the control of calcium release occurs. In other cell types that exhibit calcium oscillations and waves, the importance of microdomains in the vicinity of clusters of inositol trisphosphate receptors, or between the endoplasmic reticulum (ER) and other internal organelles or the plasma membrane, is clear. Given the limits of computational power, it is not currently realistic to model an entire cellular cytoplasm by incorporating detailed structural information about the ER throughout the entire cytoplasm. Hence, most models use a homogenised approach, assuming that both cytoplasm and ER coexist at each point of the domain. Conversely, microdomain models can be constructed, in which detailed structural information can be incorporated, but, until now, methods have not been developed for linking such a microdomain model to a model at the level of the entire cell. Using the homogenisation approach we developed in an earlier paper (Goel P., A. Friedman and J. Sneyd. 2006. Homogenization of the cell cytoplasm: the calcium bidomain equations. SIAM J. on Multiscale Modeling and Simulation, in press) we show how a multiscale model of a calcium microdomain can be constructed. In this model a detailed model of the microdomain (in which the ER and the cytoplasm are separate compartments) is coupled to a homogenised model of the entire cell in a rigorous way. Our method is illustrated by a simple model of the diadic cleft of a cardiac half-sarcomere. PMID:17499276

  7. Calcium binding domains and calcium-induced conformational transition of SPARC/BM-40/osteonectin, an extracellular glycoprotein expressed in mineralized and nonmineralized tissues

    SciTech Connect

    Engel, J.; Taylor, W.; Paulsson, M.; Sage, H.; Hogan, B.

    1987-11-03

    PSARC, BM-40, and osteonectin are identical or very closely related extracellular proteins of apparent M/sub r/ 43,000 (M/sub r/ 33,000 predicted from sequence). They were originally isolated from parietal endoderm cells, basement membrane producing tumors, and bone, respectively, but are rather widely distributed in various tissues. In view of the calcium binding activity reported for osteonectin, the authors analyzed the SPARC sequence and found two putative calcium binding domains. One is an N-terminal acid region with clusters of glutamic acid residues. This region, although neither ..gamma..-carboxylated nor homologous, resembles the ..gamma..-carboxyglutamic acid (Gla) domain of vitamin K dependent proteins of the blood clotting system in charge density, size of negatively charged clusters, and linkage to the rest of the molecule by a cysteine-rich domain. The other region is an EF-hand calcium binding domain located near the C-terminus. A disulfide bond between the E and F helix is predicted from modeling the EF-hand structure with the known coordinates of intestinal calcium binding protein. The disulfide bridge apparently serves to stabilize the isolated calcium loop in the extracellular protein. As observed for cytoplasmic EF-hand-containing proteins and for Gla domain containing proteins, a major conformational transition is induced in BM-40 upon binding of several Ca/sup 2 +/ ions. This is accompanied by a 35% increase in ..cap alpha..-helicity. A pronounced sigmoidicity of the dependence of the circular dichroism signal at 220 nm on calcium concentration indicates that the process is cooperative. In view of its properties, abundance, and wide distribution, it is proposed that SPARC/BM-40/osteonectin has a rather general regulatory function in calcium-dependent processes of the extra-cellular matrix.

  8. Calcium binding domains and calcium-induced conformational transition of SPARC/BM-40/osteonectin, an extracellular glycoprotein expressed in mineralized and nonmineralized tissues.

    PubMed

    Engel, J; Taylor, W; Paulsson, M; Sage, H; Hogan, B

    1987-11-03

    SPARC, BM-40, and osteonectin are identical or very closely related extracellular proteins of apparent Mr 43,000 (Mr 33,000 predicted from sequence). They were originally isolated from parietal endoderm cells, basement membrane producing tumors, and bone, respectively, but are rather widely distributed in various tissues. In view of the calcium binding activity reported for osteonectin, we analyzed the SPARC sequence and found two putative calcium binding domains. One is an N-terminal acidic region with clusters of glutamic acid residues. This region, although neither gamma-carboxylated nor homologous, resembles the gamma-carboxyglutamic acid (Gla) domain of vitamin K dependent proteins of the blood clotting system in charge density, size of negatively charged clusters, and linkage to the rest of the molecule by a cysteine-rich domain. The other region is an EF-hand calcium binding domain located near the C-terminus. A disulfide bond between the E and F helix is predicted from modeling the EF-hand structure with the known coordinates of intestinal calcium binding protein. The disulfide bridge apparently serves to stabilize the isolated calcium loop in the extracellular protein. As observed for cytoplasmic EF-hand-containing proteins and for Gla domain containing proteins, a major conformational transition is induced in BM-40 upon binding of several Ca2+ ions. This is accompanied by a 35% increase in alpha-helicity. A pronounced sigmoidicity of the dependence of the circular dichroism signal at 220 nm on calcium concentration indicates that the process is cooperative. In view of its properties, abundance, and wide distribution, it is proposed that SPARC/BM-40/osteonectin has a rather general regulatory function in calcium-dependent processes of the extracellular matrix.

  9. Calcium supplement: humanity's double-edged sword.

    PubMed

    Bunyaratavej, Narong; Buranasinsup, Shutipen

    2011-10-01

    The principle aim of the present study is to investigate the dark side of calcium, pollutions in calcium preparation especially lead (Pb), mercury (Hg) and cadmium (Cd). The collected samples were the different calcium salts in the market and 18 preparations which were classified into 3 groups: Calcium carbonate salts, Chelated calcium and natural-raw calcium. All samples were analyzed for lead, cadmium and mercury by inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique, in house method based on AOAC (2005) 999.10 by ICP-MS. The calcium carbonate and the natural-raw calcium in every sample contained lead at 0.023-0.407 mg/kg of calcium powder. Meanwhile, the natural-raw calcium such as oyster, coral and animal bone showed amount of lead at 0.106-0.384 mg/kg with small amounts of mercury and cadmium. The chelated calcium such as calcium gluconate, calcium lactate and calcium citrate are free of lead.

  10. Calcium bioavailability and its relation to osteoporosis.

    PubMed

    Weaver, C M

    1992-06-01

    The balance of data suggests that calcium intake has a positive influence on bone mass in premenopausal women and has a preventive effect on the rate of bone loss in postmenopausal women. Even small advantages in bone mass provide great reductions in fracture rates. However, the majority of studies have tested the relationship of calcium intake and bone mass using calcium supplements. Few intervention studies have manipulated calcium intake through foods. Calcium is only useful to the skeleton once it is absorbed. Therefore, the bioavailability of dietary calcium becomes important in the prevention and treatment of osteoporosis. Isotopic tracer techniques have only recently been employed in the labeling of foods with calcium isotopes for evaluation of calcium absorption. Milk calcium is usually the referent food which is typically absorbed at 20-40% depending on the calcium status of the subject. The absorptive efficiency of most vegetable sources is as good or better than for dairy foods, unless they have high concentrations of oxalic acid (spinach, for example) or phytic acid (wheat bran cereal, for example). Few vegetable sources are concentrated sources of calcium. Therefore, it would be difficult to obtain adequate intakes of calcium to protect against osteoporosis without liberal use of dairy products in the diet. Alternately, calcium supplements provide concentrated amounts of absorbable calcium, but they do not provide other nutrients necessary for skeletal growth and maintenance.

  11. Calcium fortification systems differ in bioavailability.

    PubMed

    Heaney, Robert P; Rafferty, Karen; Dowell, M Susan; Bierman, June

    2005-05-01

    The objective of this study was to compare the bioavailability of calcium from two fortification systems used in orange juice. The design was randomized crossover, within-subject. The subjects were 25 healthy premenopausal women in an academic health sciences center. Two commercially marketed calcium-fortified orange juices, ingested in an amount providing 500 mg calcium, were taken at breakfast after an overnight fast. The two fortification systems tested were calcium citrate malate and a combination of tricalcium phosphate and calcium lactate (tricalcium phosphate/calcium lactate). The main outcome measure was the area under the curve (AUC) for the increase in serum calcium from 0 to 9 hours after ingesting the test calcium source. Statistical analyses performed were repeated measures analysis of variance, testing source, and sequence. AUC 9 was 48% greater for calcium citrate malate than for tricalcium phosphate/calcium lactate ( P < .001); absorbed calcium calculated from AUC 9 values (mean+/-standard error of the mean) was 148+/-9.0 mg and 100+/-8.9 mg for calcium citrate malate and tricalcium phosphate/calcium lactate, respectively. The results indicate that equivalent calcium contents on a nutritional label do not guarantee equivalent nutritional value. Nutritionists and dietetics professionals should encourage manufacturers of fortified products to provide information on bioavailability.

  12. A role for voltage gated T-type calcium channels in mediating "capacitative" calcium entry?

    PubMed

    Gackière, Florian; Bidaux, Gabriel; Lory, Philippe; Prevarskaya, Natalia; Mariot, Pascal

    2006-04-01

    Calcium entry through plasma membrane calcium channels is one of the most important cell signaling mechanism involved in such diverse functions as secretion, contraction and cell growth by regulating gene expression, proliferation and apoptosis. The identity of plasma membrane calcium channels, the main regulators of calcium entry, involved in cell proliferation has been thus extensively sought. Among these, a calcium entry pathway called capacitative calcium entry (CCE), activated by calcium store depletion, is particularly important in non-excitable cells. Though this capacitative calcium entry is generally supposed to occur through TRP channels there is some evidence that voltage-dependent T-type calcium channels may contribute to calcium entry after store depletion. Here we show that though mibefradil, a T-type calcium channel blocker, is able to reduce capacitative calcium entry induced by either thapsigargin or ATP, this was not mimicked by any other T-type calcium channel inhibitors even in cells overexpressing alpha(1H) T-type calcium channels, leading us to conclude that T-type calcium channels are not responsible for the capacitative calcium entry observed in different cancer cell lines. On the contrary, we show that the action of mibefradil on capacitative calcium entry is due to an action on store-operated calcium channels.

  13. Influence of phosvitin and calcium gluconate concentration on permeation and intestinal absorption of calcium ions.

    PubMed

    Dolińska, Barbara; Łopata, Katarzyna; Mikulska, Agnieszka; Leszczyńska, Lucyna; Ryszka, Florian

    2012-06-01

    The effect of egg yolk phosvitin on the permeation and absorption of calcium was investigated in vitro in relation to calcium gluconate concentration. Obtained results indicate that phosvitin significantly reduces the intestinal calcium absorption from 1 and 10 mM of calcium gluconate solution. It is associated with the formation of the complex of Ca (II) ions with phosvitin. The process of calcium permeation increases under phosvitin influence when calcium gluconate concentrations rise up to 10 mM. At a higher concentration of calcium gluconate (20 mM), no effect of phosvitin was seen on permeation of calcium ions.

  14. Review of current loop coalescence process.

    NASA Astrophysics Data System (ADS)

    Sakai, J.-I.

    This paper concentrates on the developments since the review by Sakai and Ohsawa (1987) dealing with particle acceleration by magnetic reconnection and shocks during current loop coalescence in solar flares.

  15. Four-loop screened perturbation theory

    NASA Astrophysics Data System (ADS)

    Andersen, Jens O.; Kyllingstad, Lars

    2008-10-01

    We study the thermodynamics of massless ϕ4-theory using screened perturbation theory. In this method, the perturbative expansion is reorganized by adding and subtracting a thermal mass term in the Lagrangian. We calculate the free energy through four loops expanding in a double power expansion in m/T and g2, where m is the thermal mass and g is the coupling constant. The expansion is truncated at order g7 and the loop expansion is shown to have better convergence properties than the weak-coupling expansion. The free energy at order g6 involves the four-loop triangle sum-integral evaluated by Gynther, Laine, Schröder, Torrero, and Vuorinen using the methods developed by Arnold and Zhai. The evaluation of the free energy at order g7 requires the evaluation of a nontrivial three-loop sum-integral, which we calculate by the same methods.

  16. Loop Diuretics in the Treatment of Hypertension.

    PubMed

    Malha, Line; Mann, Samuel J

    2016-04-01

    Loop diuretics are not recommended in current hypertension guidelines largely due to the lack of outcome data. Nevertheless, they have been shown to lower blood pressure and to offer potential advantages over thiazide-type diuretics. Torsemide offers advantages of longer duration of action and once daily dosing (vs. furosemide and bumetanide) and more reliable bioavailability (vs. furosemide). Studies show that the previously employed high doses of thiazide-type diuretics lower BP more than furosemide. Loop diuretics appear to have a preferable side effect profile (less hyponatremia, hypokalemia, and possibly less glucose intolerance). Studies comparing efficacy and side effect profiles of loop diuretics with the lower, currently widely prescribed, thiazide doses are needed. Research is needed to fill gaps in knowledge and common misconceptions about loop diuretic use in hypertension and to determine their rightful place in the antihypertensive arsenal.

  17. The Effect of Loops in Connectivity Percolation

    NASA Astrophysics Data System (ADS)

    Hagh, Varda F.; Thorpe, M. F.

    We introduce a new method that employs the concepts of redundancy and stress from rigidity theory to study the effect of loops in connectivity percolation. In the rigidity percolation redundant bonds are not necessary to maintain the rigidity of a network. These redundant bonds cause internal stress in some regions and as a result those regions carry finite forces that characterize them as over-constrained. In connectivity percolation the bonds that cause a loop correspond to redundant bonds in rigidity and all the bonds that are part of a loop are equivalent to over-constrained bonds in rigidity. To illustrate this we start with a network in 2D where all the bonds are present and remove the bonds randomly. Then using renormalization groups and numerical simulations we study the behavior of loops near percolation transition in hierarchical networks and lattices.

  18. Mathematical Modeling of Loop Heat Pipes

    NASA Technical Reports Server (NTRS)

    Kaya, Tarik; Ku, Jentung; Hoang, Triem T.; Cheung, Mark L.

    1998-01-01

    The primary focus of this study is to model steady-state performance of a Loop Heat Pipe (LHP). The mathematical model is based on the steady-state energy balance equations at each component of the LHP. The heat exchange between each LHP component and the surrounding is taken into account. Both convection and radiation environments are modeled. The loop operating temperature is calculated as a function of the applied power at a given loop condition. Experimental validation of the model is attempted by using two different LHP designs. The mathematical model is tested at different sink temperatures and at different elevations of the loop. Tbc comparison of the calculations and experimental results showed very good agreement (within 3%). This method proved to be a useful tool in studying steady-state LHP performance characteristics.

  19. Hierarchical loop detection for mobile outdoor robots

    NASA Astrophysics Data System (ADS)

    Lang, Dagmar; Winkens, Christian; Häselich, Marcel; Paulus, Dietrich

    2012-01-01

    Loop closing is a fundamental part of 3D simultaneous localization and mapping (SLAM) that can greatly enhance the quality of long-term mapping. It is essential for the creation of globally consistent maps. Conceptually, loop closing is divided into detection and optimization. Recent approaches depend on a single sensor to recognize previously visited places in the loop detection stage. In this study, we combine data of multiple sensors such as GPS, vision, and laser range data to enhance detection results in repetitively changing environments that are not sufficiently explained by a single sensor. We present a fast and robust hierarchical loop detection algorithm for outdoor robots to achieve a reliable environment representation even if one or more sensors fail.

  20. A magnetohydrodynamic theory of coronal loop transients

    NASA Technical Reports Server (NTRS)

    Yeh, T.

    1982-01-01

    The physical and geometrical characteristics of solar coronal loop transients are described in an MHD model based on Archimedes' MHD buoyancy force. The theory was developed from interpretation of coronagraphic data, particularly from Skylab. The brightness of a loop is taken to indicate the electron density, and successive pictures reveal the electron enhancement in different columns. The forces which lift the loop off the sun surface are analyzed as an MHD buoyancy force affecting every mass element by imparting an inertial force necessary for heliocentrifugal motion. Thermal forces are responsible for transferring the ambient stress to the interior of the loop to begin the process. The kinematic and hydrostatic buoyancy overcome the gravitational force, and a flux rope can then curve upward, spiralling like a corkscrew with varying cross section around the unwinding solar magnetic field lines.

  1. A magnetohydrodynamic theory of coronal loop transients

    NASA Technical Reports Server (NTRS)

    Yeh, T.

    1982-01-01

    The physical and geometrical characteristics of solar coronal loop transients are described in an MHD model based on Archimedes' MHD buoyancy force. The theory was developed from interpretation of coronagraphic data, particularly from Skylab. The brightness of a loop is taken to indicate the electron density, and successive pictures reveal the electron enhancement in different columns. The forces which lift the loop off the sun surface are analyzed as an MHD buoyancy force affecting every mass element by imparting an inertial force necessary for heliocentrifugal motion. Thermal forces are responsible for transferring the ambient stress to the interior of the loop to begin the process. The kinematic and hydrostatic buoyancy overcome the gravitational force, and a flux rope can then curve upward, spiralling like a corkscrew with varying cross section around the unwinding solar magnetic field lines.

  2. Open-loop digital frequency multiplier

    NASA Technical Reports Server (NTRS)

    Moore, R. C.

    1977-01-01

    Monostable multivibrator is implemented by using digital integrated circuits where multiplier constant is too large for conventional phase-locked-loop integrated circuit. A 400 Hz clock is generated by divide-by-N counter from 1 Hz timing reference.

  3. CHY loop integrands from holomorphic forms

    NASA Astrophysics Data System (ADS)

    Gomez, Humberto; Mizera, Sebastian; Zhang, Guojun

    2017-03-01

    Recently, the Cachazo-He-Yuan (CHY) approach for calculating scattering amplitudes has been extended beyond tree level. In this paper, we introduce a way of constructing CHY integrands for Φ3 theory up to two loops from holomorphic forms on Riemann surfaces. We give simple rules for translating Feynman diagrams into the corresponding CHY integrands. As a complementary result, we extend the Λ-algorithm, originally introduced in arXiv:1604.05373, to two loops. Using this approach, we are able to analytically verify our prescription for the CHY integrands up to seven external particles at two loops. In addition, it gives a natural way of extending to higher-loop orders.

  4. A multiple-pass ring oscillator based dual-loop phase-locked loop

    NASA Astrophysics Data System (ADS)

    Danfeng, Chen; Junyan, Ren; Jingjing, Deng; Wei, Li; Ning, Li

    2009-10-01

    A dual-loop phase-locked loop (PLL) for wideband operation is proposed. The dual-loop architecture combines a coarse-tuning loop with a fine-tuning one, enabling a wide tuning range and low voltage-controlled oscillator (VCO) gain without poisoning phase noise and reference spur suppression performance. An analysis of the phase noise and reference spur of the dual-loop PLL is emphasized. A novel multiple-pass ring VCO is designed for the dual-loop application. It utilizes both voltage-control and current-control simultaneously in the delay cell. The PLL is fabricated in Jazz 0.18-μm RF CMOS technology. The measured tuning range is from 4.2 to 5.9 GHz. It achieves a low phase noise of -99 dBc/Hz @ 1 MHz offset from a 5.5 GHz carrier.

  5. Calcium-induced calcium release and gap junctions mediate large-scale calcium waves in olfactory ensheathing cells in situ.

    PubMed

    Stavermann, Maren; Meuth, Patrick; Doengi, Michael; Thyssen, Anne; Deitmer, Joachim W; Lohr, Christian

    2015-08-01

    Olfactory ensheathing cells (OECs) are a specialised type of glial cells, supporting axon growth and guidance during development and regeneration of the olfactory nerve and the nerve layer of the olfactory bulb. We measured calcium signalling in OECs in olfactory bulb in-toto preparations using confocal and epifluorescence microscopy and the calcium indicator Fluo-4. We identified two subpopulations of olfactory bulb OECs: OECs in the outer sublamina of the nerve layer responded to purinergic neurotransmitters such as adenosine triphosphate with calcium transients, while OECs in the inner sublamina of the nerve layer did not respond to neurotransmitters. However, the latter generated spontaneous calcium waves that covered hundreds of cells. These calcium waves persisted in the presence of tetrodotoxin and in calcium-free saline, but were abolished after calcium store depletion with cyclopiazonic acid or inositol trisphosphate receptor blockage with 2-APB. Calcium waves could be triggered by laser photolysis of caged inositol trisphosphate. Blocking purinoceptors with PPADS had no effect on calcium wave propagation, whereas blocking gap junctions with carbenoxolone or meclofenamic acid entirely suppressed calcium waves. Increasing calcium buffer capacity in OECs with NP-EGTA ("caged" Ca(2+)) prevented calcium wave generation, and laser photolysis of NP-EGTA in a small group of OECs resulted in a calcium increase in the irradiated cells followed by a calcium wave. We conclude that calcium waves in OECs can be initiated by calcium-induced calcium release via InsP3 receptors and propagate through gap junctions, while purinergic signalling is not involved. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Simple system for locating ground loops.

    PubMed

    Bellan, P M

    2007-06-01

    A simple low-cost system for rapid identification of the cables causing ground loops in complex instrumentation configurations is described. The system consists of an exciter module that generates a 100 kHz ground loop current and a detector module that determines which cable conducts this test current. Both the exciter and detector are magnetically coupled to the ground circuit so there is no physical contact to the instrumentation system under test.

  7. Loop quantum cosmology in 2 +1 dimension

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangdong

    2014-12-01

    As a first step to generalize the structure of loop quantum cosmology to the theories with the spacetime dimension other than four, the isotropic model of loop quantum cosmology in 2 +1 dimension is studied in this paper. We find that the classical big bang singularity is again replaced by a quantum bounce in the model. The similarities and differences between the (2 +1 )-dimensional model and the (3 +1 )-dimensional one are also discussed.

  8. Onset of inflation in loop quantum cosmology

    SciTech Connect

    Germani, Cristiano; Nelson, William; Sakellariadou, Mairi

    2007-08-15

    Using a Liouville measure, similar to the one proposed recently by Gibbons and Turok, we investigate the probability that single-field inflation with a polynomial potential can last long enough to solve the shortcomings of the standard hot big bang model, within the semiclassical regime of loop quantum cosmology. We conclude that, for such a class of inflationary models and for natural values of the loop quantum cosmology parameters, a successful inflationary scenario is highly improbable.

  9. Miniature loops in the solar corona

    NASA Astrophysics Data System (ADS)

    Barczynski, K.; Peter, H.; Savage, S. L.

    2017-03-01

    Context. Magnetic loops filled with hot plasma are the main building blocks of the solar corona. Usually they have lengths of the order of the barometric scale height in the corona that is 50 Mm. Aims: Previously it has been suggested that miniature versions of hot loops exist. These would have lengths of only 1 Mm barely protruding from the chromosphere and spanning across just one granule in the photosphere. Such short loops are well established at transition region temperatures (0.1 MK), and we investigate if such miniature loops also exist at coronal temperatures (>1 MK). Methods: We used extreme UV (EUV) imaging observations from the High-resolution Coronal Imager (Hi-C) at an unprecedented spatial resolution of 0.3'' to 0.4''. Together with EUV imaging and magnetogram data from the Solar Dynamics Observatory (SDO) and X-Ray Telescope (XRT) data from Hinode we investigated the spatial, temporal and thermal evolution of small loop-like structures in the solar corona above a plage region close to an active region and compared this to a moss area within the active region. Results: We find that the size, motion and temporal evolution of the loop-like features are consistent with photospheric motions, suggesting a close connection to the photospheric magnetic field. Aligned magnetograms show that one of their endpoints is rooted at a magnetic concentration. Their thermal structure, as revealed together with the X-ray observations, shows significant differences to moss-like features. Conclusions: Considering different scenarios, these features are most probably miniature versions of hot loops rooted at magnetic concentrations at opposite sides of a granule in small emerging magnetic loops (or flux tubes).

  10. Deployable radiator with flexible line loop

    NASA Technical Reports Server (NTRS)

    Keeler, Bryan V. (Inventor); Lehtinen, Arthur Mathias (Inventor); McGee, Billy W. (Inventor)

    2003-01-01

    Radiator assembly (10) for use on a spacecraft (12) is provided including at least one radiator panel assembly (26) repeatably movable between a panel stowed position (28) and a panel deployed position (36), at least two flexible lines (40) in fluid communication with the at least one radiator panel assembly (26) and repeatably movable between a stowage loop (42) and a flattened deployed loop (44).

  11. Quantum Kinematics of Bosonic Vortex Loops

    SciTech Connect

    Goldin, G.A.; Owczarek, R.; Sharp, D.H.

    1999-05-06

    Poisson structure for vortex filaments (loops and arcs) in 2D ideal incompressible fluid is analyzed in detail. Canonical coordinates and momenta on coadjoint orbits of the area-preserving diffeomorphism group, associated with such vortices, are found. The quantum space of states in the simplest case of ''bosonic'' vortex loops is built within a geometric quantization approach to the description of a quantum fluid. Fock-like structure and non-local creation and annihilation operators of quantum vortex filaments are introduced.

  12. A Heuristic for Deriving Loop Functions.

    DTIC Science & Technology

    1981-10-01

    At m, Air )-- ,n Thefc-,ni)= A(m,A(.ira ,n)) . ....... .... c ,rogra ccmputes Ac -nrn ff’unt’.on us ".’ a A Heuristic For Deriving Loop Functions...8217 be a loop functicn w;’ich :,a’ "inconsistent" across al! values of the Ioon inputs "’icn" coulP : only be in7errel fron the ccnstraint "unctions with

  13. Simple system for locating ground loops

    NASA Astrophysics Data System (ADS)

    Bellan, P. M.

    2007-06-01

    A simple low-cost system for rapid identification of the cables causing ground loops in complex instrumentation configurations is described. The system consists of an exciter module that generates a 100kHz ground loop current and a detector module that determines which cable conducts this test current. Both the exciter and detector are magnetically coupled to the ground circuit so there is no physical contact to the instrumentation system under test.

  14. Can Chemical Looping Combustion Use CFB Technology?

    SciTech Connect

    Gamwo, I.K.

    2006-11-01

    Circulating Fluidized Bed (CFB) technology has demonstrated an unparalleled ability to achieve low SO2 and NOx emissions for coal-fired power plants without CO2 capture. Chemical Looping combustion (CLC) is a novel fuel combustion technology which appears as a leading candidate in terms of competitiveness for CO2 removal from flue gas. This presentaion deals with the adaptation of circulating fluidized bed technology to Chemical looping combustion

  15. Pathogenesis and treatment of calcium stones.

    PubMed

    Parks, J H; Coe, F L

    1996-09-01

    Calcium stones arise from imbalances between urinary excretions of insoluble salts and water. Idiopathic hypercalciuria and hyperparathyroidism are the calcium disorders usually associated with elevated levels of calcium in the urine. Renal tubular acidosis is associated with a disordered acid-base status that results in low urine citrate. Hypocitraturia itself is a cause of calcium stones because it leaves urine calcium free to complex with either oxalate or phosphate. Elevated urine oxalate is commonly associated with dietary excesses, bowel disease, and, rarely, primary hyperoxaluria. Hyperuricosuria, usually of dietary origin, when reversed can cause a fall in new calcium stones.

  16. Multiple Flow Loop SCADA System Implemented on the Production Prototype Loop

    SciTech Connect

    Baily, Scott A.; Dalmas, Dale Allen; Wheat, Robert Mitchell; Woloshun, Keith Albert; Dale, Gregory E.

    2015-11-16

    The following report covers FY 15 activities to develop supervisory control and data acquisition (SCADA) system for the Northstar Moly99 production prototype gas flow loop. The goal of this effort is to expand the existing system to include a second flow loop with a larger production-sized blower. Besides testing the larger blower, this system will demonstrate the scalability of our solution to multiple flow loops.

  17. Space Station evolution study oxygen loop closure

    NASA Technical Reports Server (NTRS)

    Wood, M. G.; Delong, D.

    1993-01-01

    In the current Space Station Freedom (SSF) Permanently Manned Configuration (PMC), physical scars for closing the oxygen loop by the addition of oxygen generation and carbon dioxide reduction hardware are not included. During station restructuring, the capability for oxygen loop closure was deferred to the B-modules. As such, the ability to close the oxygen loop in the U.S. Laboratory module (LAB A) and the Habitation A module (HAB A) is contingent on the presence of the B modules. To base oxygen loop closure of SSF on the funding of the B-modules may not be desirable. Therefore, this study was requested to evaluate the necessary hooks and scars in the A-modules to facilitate closure of the oxygen loop at or subsequent to PMC. The study defines the scars for oxygen loop closure with impacts to cost, weight and volume and assesses the effects of byproduct venting. In addition, the recommended scenarios for closure with regard to topology and packaging are presented.

  18. Modeling the Cooling of Postflare Loops

    NASA Astrophysics Data System (ADS)

    Reeves, Katharine K.; Warren, Harry P.

    2002-10-01

    We present a model for the cooling of postflare loops. In our model, we form an arcade that consists of hundreds of loops with offset formation times to simulate a rising reconnection site. An initial temperature and density is assumed in each loop, and then the scaling laws of Cargill, Mariska, & Antiochos are used to determine the evolution of the temperature and density in the loop. Once these quantities are found, they are passed through the instrument response functions for TRACE and the Yohkoh Soft X-Ray Telescope (SXT) to obtain intensities, which are integrated over the arcade to give a simulated light curve. This light curve is then compared to observed light curves from the 2000 July 14 X6 flare. We find that this multiloop, multithermal approach to simulating the flare cooling fits the observed data much better than a single-loop model. There are some discrepancies between our simulations and the observed data in the decay phase of the flare, however, which may be due to residual late-phase heating. We also find that the temperatures calculated by using SXT filter ratios are generally lower than the initial loop temperatures needed in the simulation to give a good fit to the observed data.

  19. Antibody binding loop insertions as diversity elements

    PubMed Central

    Kiss, Csaba; Fisher, Hugh; Pesavento, Emanuele; Dai, Minghua; Valero, Rosa; Ovecka, Milan; Nolan, Rhiannon; Phipps, M. Lisa; Velappan, Nileena; Chasteen, Leslie; Martinez, Jennifer S.; Waldo, Geoffrey S.; Pavlik, Peter; Bradbury, Andrew R.M.

    2006-01-01

    In the use of non-antibody proteins as affinity reagents, diversity has generally been derived from oligonucleotide-encoded random amino acids. Although specific binders of high-affinity have been selected from such libraries, random oligonucleotides often encode stop codons and amino acid combinations that affect protein folding. Recently it has been shown that specific antibody binding loops grafted into heterologous proteins can confer the specific antibody binding activity to the created chimeric protein. In this paper, we examine the use of such antibody binding loops as diversity elements. We first show that we are able to graft a lysozyme-binding antibody loop into green fluorescent protein (GFP), creating a fluorescent protein with lysozyme-binding activity. Subsequently we have developed a PCR method to harvest random binding loops from antibodies and insert them at predefined sites in any protein, using GFP as an example. The majority of such GFP chimeras remain fluorescent, indicating that binding loops do not disrupt folding. This method can be adapted to the creation of other nucleic acid libraries where diversity is flanked by regions of relative sequence conservation, and its availability sets the stage for the use of antibody loop libraries as diversity elements for selection experiments. PMID:17023486

  20. Flare Half-Loops: What Are They?

    NASA Astrophysics Data System (ADS)

    McKenzie, David Eugene; Guidoni, S. E.; Longcope, D. W.; Yoshimura, K.

    2012-05-01

    The M1.4 flare of 28 January 2011 has a remarkable resemblance to the famous "Tsuneta candle-flame" flare of 1992. It was observed with Hinode/XRT, SDO/AIA, and STEREO (A)/EUVI, resulting in higher resolution, greater temperature coverage, and stereoscopic views of this iconic structure. The high temperature images reveal a brightening that grows in size to form a tower-like structure at the top of the arcade. They also show that loops which are successively connected to this tower develop a density increase in one of their legs that can exceed twice the density of the other leg, giving the appearance of "half loops". These jumps in density last for an extended period of time. On the other hand, XRT filter ratios suggest that temperature is approximately uniform along the entire loop. XRT filter-ratio density maps corroborate that the brighter legs have higher density than the fainter halves. The tower is associated with a localized density increase, with even higher densities than either leg of the loop. This spatial variation of density may correspond to a shock at the top of the loops. We use STEREO images to show that the half loop brightening is not a line-of-sight projection effect of the type suggested by Forbes & Acton. This work is supported under contract SP02H3901R from Lockheed-Martin to MSU, and under contract NNM07AB07C with the Harvard-Smithsonian Astrophysical Observatory.

  1. [Regulatory mechanism of calcium metabolism.

    PubMed

    Ozono, Keiichi

    It is often difficult for terrestrial animals to take enough calcium. To maintain serum or extracellular calcium levels is very important for muscle and nerve function. Two major regulators to increase the serum calcium levels are parathyroid hormone(PTH)and vitamin D. PTH binds to the G protein coupling receptor, PTH1R, and increases intracellular cAMP levels. Impirement in the PTH signalling causes many diseases such as pseudohypoparathyroidism and acrodysostosis with hormone resistance. Vitamin D is activated to 1,25-dihydroxyvitamin D[1,25(OH)2D]by two steps of hydroxylation which occurs in the Liver and Kidney. Then, 1,25(OH)2D binds to vitamin D receptor(VDR), which works as a ligand-dependent transcription factor. Hypocalcemia and hypercalcemia are caused by various disorders including abnormal regulation of PTH and vitamin D production and their signal transduction.

  2. Efficient chromosomal-scale DNA looping in Escherichia coli using multiple DNA-looping elements.

    PubMed

    Hao, Nan; Sneppen, Kim; Shearwin, Keith E; Dodd, Ian B

    2017-05-19

    Genes are frequently regulated by interactions between proteins that bind to the DNA near the gene and proteins that bind to DNA sites located far away, with the intervening DNA looped out. But it is not understood how efficient looping can occur when the sites are very far apart. We develop a simple theoretical framework that relates looping efficiency to the energetic cost and benefit of looping, allowing prediction of the efficiency of single or multiple nested loops at different distances. Measurements of absolute loop efficiencies for Lac repressor and λ CI using gene expression reporters in Escherichia coli cells show that, as predicted by the model, long-range DNA looping between a pair of sites can be strongly enhanced by the use of nested DNA loops or by the use of additional protein-binding sequences. A combination of these approaches was able to generate efficient DNA looping at a 200 kb distance. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  3. Two-loop polygon Wilson loops in Script N = 4 SYM

    NASA Astrophysics Data System (ADS)

    Anastasiou, C.; Brandhuber, A.; Heslop, P.; Khoze, V. V.; Spence, B.; Travaglini, G.

    2009-05-01

    We compute for the first time the two-loop corrections to arbitrary n-gon lightlike Wilson loops in Script N = 4 supersymmetric Yang-Mills theory, using efficient numerical methods. The calculation is motivated by the remarkable agreement between the finite part of planar six-point MHV amplitudes and hexagon Wilson loops which has been observed at two loops. At n = 6 we confirm that the ABDK/BDS ansatz must be corrected by adding a remainder function, which depends only on conformally invariant ratios of kinematic variables. We numerically compute remainder functions for n = 7,8 and verify dual conformal invariance. Furthermore, we study simple and multiple collinear limits of the Wilson loop remainder functions and demonstrate that they have precisely the form required by the collinear factorisation of the corresponding two-loop n-point amplitudes. The number of distinct diagram topologies contributing to the n-gon Wilson loops does not increase with n, and there is a fixed number of ``master integrals", which we have computed. Thus we have essentially computed general polygon Wilson loops, and if the correspondence with amplitudes continues to hold, all planar n-point two-loop MHV amplitudes in the Script N = 4 theory.

  4. The effect of variable calcium and very low calcium diets on human calcium metabolism. Ph.D. Thesis. Final Report

    NASA Technical Reports Server (NTRS)

    Chu, J.

    1971-01-01

    The effects of a very low calcium diet, with variable high and low protein intake, on the dynamics of calcium metabolism and the mechanism of calciuretics, are examined. The experiment, using male subjects, was designed to study the role of intestinal calcium absorption on urinary calcium excretion, and the rate of production of endogeneously secreted calcium in the gastrointestinal tract. The study showed an average of 70% fractional absorption rate during very low calcium intake, and that a decrease in renal tubular reabsorption of calcium is responsible for calciuretic effects of high protein intake. The study also indicates that there is a tendency to develop osteoporosis after long periods of low calcium intake, especially with a concurrent high protein intake.

  5. Calcium regulation of muscle contraction.

    PubMed Central

    Szent-Györgyi, A G

    1975-01-01

    Calcium triggers contraction by reaction with regulatory proteins that in the absence of calcium prevent interaction of actin and myosin. Two different regulatory systems are found in different muscles. In actin-linked regulation troponin and tropomyosin regulate actin by blocking sites on actin required for complex formation with myosin; in myosin-linked regulation sites on myosin are blocked in the absence of calcium. The major features of actin control are as follows: there is a requirement for tropomyosin and for a troponin complex having three different subunits with different functions; the actin displays a cooperative behavior; and a movement of tropomyosin occurs controlled by the calcium binding on troponin. Myosin regulation is controlled by a regulatory subunit that can be dissociated in scallop myosin reversibly by removing divalent cations with EDTA. Myosin control can function with pure actin in the absence of tropomyosin. Calcium binding and regulation of molluscan myosins depend on the presence of regulatory light chains. It is proposed that the light chains function by sterically blocking myosin sites in the absence of calcium, and that the "off" state of myosin requires cooperation between the two myosin heads. Both myosin control and actin control are widely distributed in different organisms. Many invertebrates have muscles with both types of regulation. Actin control is absent in the muscles of molluscs and in several minor phyla that lack troponin. Myosin control is not found in striated vertebrate muscles and in the fast muscles of crustacean decapods, although regulatory light chains are present. While in vivo myosin control may not be excluded from vertebrate striated muscles, myosin control may be absent as a result of mutations of the myosin heavy chain. PMID:806311

  6. Vitamin D and intestinal calcium absorption.

    PubMed

    Christakos, Sylvia; Dhawan, Puneet; Porta, Angela; Mady, Leila J; Seth, Tanya

    2011-12-05

    The principal function of vitamin D in calcium homeostasis is to increase calcium absorption from the intestine. Calcium is absorbed by both an active transcellular pathway, which is energy dependent, and by a passive paracellular pathway through tight junctions. 1,25Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) the hormonally active form of vitamin D, through its genomic actions, is the major stimulator of active intestinal calcium absorption which involves calcium influx, translocation of calcium through the interior of the enterocyte and basolateral extrusion of calcium by the intestinal plasma membrane pump. This article reviews recent studies that have challenged the traditional model of vitamin D mediated transcellular calcium absorption and the crucial role of specific calcium transport proteins in intestinal calcium absorption. There is also increasing evidence that 1,25(OH)(2)D(3) can enhance paracellular calcium diffusion. The influence of estrogen, prolactin, glucocorticoids and aging on intestinal calcium absorption and the role of the distal intestine in vitamin D mediated intestinal calcium absorption are also discussed.

  7. The effect of calcium gluconate and other calcium supplements as a dietary calcium source on magnesium absorption in rats.

    PubMed

    Chonan, O; Takahashi, R; Yasui, H; Watanuki, M

    1997-01-01

    The effects of commercially available calcium supplements (calcium carbonate, calcium gluconate, oyster shell preparation and bovine bone preparation) and gluconic acid on the absorption of calcium and magnesium were evaluated for 30 days in male Wistar rats. There were no differences in the apparent absorption ratio of calcium among rats fed each calcium supplement; however, the rats fed the calcium gluconate diet had a higher apparent absorption ratio of magnesium than the rats fed the other calcium supplements. Dietary gluconic acid also more markedly stimulated magnesium absorption than the calcium carbonate diet, and the bone (femur and tibia) magnesium contents of rats fed the gluconic acid diet were significantly higher than those of the rats fed the calcium carbonate diet. Furthermore, the weight of cecal tissue and the concentrations of acetic acid and butyric acid in cecal digesta of rats fed the calcium gluconate diet or the gluconic acid diet were significantly increased. We speculate that the stimulation of magnesium absorption in rats fed the calcium gluconate diet is a result of the gluconic acid component and the effect of gluconic acid on magnesium absorption probably results from cecal hypertrophy, magnesium solubility in the large intestine and the effects of volatile fatty acids on magnesium absorption.

  8. Calcium fertilization increases the concentration of calcium in sapwood and calcium oxalate in foliage of red spruce

    Treesearch

    Kevin T. Smith; Walter C. Shortle; Jon H. Connolly; Rakesh Minocha; Jody Jellison

    2009-01-01

    Calcium cycling plays a key role in the health and productivity of red spruce forests in the northeastern US. A portion of the flowpath of calcium within forests includes translocation as Ca2+ in sapwood and accumulation as crystals of calcium oxalate in foliage. Concentrations of Ca in these tree tissues have been used as markers of...

  9. Capacitative calcium entry is colocalised with calcium release in Xenopus oocytes: evidence against a highly diffusible calcium influx factor.

    PubMed

    Petersen, C C; Berridge, M J

    1996-06-01

    Depletion of intracellular calcium stores activates the plasma membrane capacitative calcium entry pathway in many cell types. The nature of the signal that couples the depletion of the intracellular calcium stores to the activation of the plasma membrane calcium influx pathway is as yet unknown. It has recently been suggested that a highly diffusible calcium influx factor is involved in the activation of capacitative calcium entry, and that its action is potentiated by the protein phosphatase inhibitor okadaic acid. Depletion of intracellular calcium stores in a localised region of a Xenopus oocyte was found to evoke capacitative calcium entry exclusively colocalised across the stimulated area of the plasma membrane, arguing against the involvement of a highly diffusible calcium influx factor. Equally, no evidence could be found for the presence of a soluble calcium influx factor in the bulk cytosol of Xenopus oocytes. The potentiation of capacitative calcium entry by okadaic acid resembled that mediated by the activation of protein kinase C, thus suggesting that okadaic acid activity may not necessarily be related to the action of a putative calcium influx factor.

  10. Extra-intestinal calcium handling contributes to normal serum calcium levels when intestinal calcium absorption is suboptimal.

    PubMed

    Lieben, Liesbet; Verlinden, Lieve; Masuyama, Ritsuko; Torrekens, Sophie; Moermans, Karen; Schoonjans, Luc; Carmeliet, Peter; Carmeliet, Geert

    2015-12-01

    The active form of vitamin D, 1,25(OH)2D, is a crucial regulator of calcium homeostasis, especially through stimulation of intestinal calcium transport. Lack of intestinal vitamin D receptor (VDR) signaling does however not result in hypocalcemia, because the increased 1,25(OH)2D levels stimulate calcium handling in extra-intestinal tissues. Systemic VDR deficiency, on the other hand, results in hypocalcemia because calcium handling is impaired not only in the intestine, but also in kidney and bone. It remains however unclear whether low intestinal VDR activity, as observed during aging, is sufficient for intestinal calcium transport and for mineral and bone homeostasis. To this end, we generated mice that expressed the Vdr exclusively in the gut, but at reduced levels. We found that ~15% of intestinal VDR expression greatly prevented the Vdr null phenotype in young-adult mice, including the severe hypocalcemia. Serum calcium levels were, however, in the low-normal range, which may be due to the suboptimal intestinal calcium absorption, renal calcium loss, insufficient increase in bone resorption and normal calcium incorporation in the bone matrix. In conclusion, our results indicate that low intestinal VDR levels improve intestinal calcium absorption compared to Vdr null mice, but also show that 1,25(OH)2D-mediated fine-tuning of renal calcium reabsorption and bone mineralization and resorption is required to maintain fully normal serum calcium levels.

  11. LOOP CALCULUS AND BELIEF PROPAGATION FOR Q-ARY ALPHABET: LOOP TOWER

    SciTech Connect

    CHERTKOV, MICHAEL; CHERNYAK, VLADIMIR

    2007-01-10

    Loop calculus introduced in [1], [2] constitutes a new theoretical tool that explicitly expresses symbol Maximum-A-Posteriori (MAP) solution of a general statistical inference problem via a solution of the Belief Propagation (BP) equations. This finding brought a new significance to the BP concept, which in the past was thought of as just a loop-free approximation. In this paper they continue a discussion of the Loop Calculus, partitioning the results into three Sections. In Section 1 they introduce a new formulation of the Loop Calculus in terms of a set of transformations (gauges) that keeping the partition function of the problem invariant. The full expression contains two terms referred to as the 'ground state' and 'excited states' contributions. The BP equations are interpreted as a special (BP) gauge fixing condition that emerges as a special orthogonality constraint between the ground state and excited states, which also selects loop contributions as the only surviving ones among the excited states. In Section 2 they demonstrate how the invariant interpretation of the Loop Calculus, introduced in Section 1, allows a natural extension to the case of a general q-ary alphabet, this is achieved via a loop tower sequential construction. The ground level in the tower is exactly equivalent to assigning one color (out of q available) to the 'ground state' and considering all 'excited' states colored in the remaining (q-1) colors, according to the loop calculus rule. Sequentially, the second level in the tower corresponds to selecting a loop from the previous step, colored in (q-1) colors, and repeating the same ground vs excited states splitting procedure into one and (q-2) colors respectively. The construction proceeds till the full (q-1)-levels deep loop tower (and the corresponding contributions to the partition function) are established. In Section 3 they discuss an ultimate relation between the loop calculus and the Bethe-Free energy variational approach of [3].

  12. An Antibody Loop Replacement Design Feasibility Study and a Loop-Swapped Dimer Structure

    SciTech Connect

    Clark, L.; Boriack-Sjodin, P; Day, E; Eldredge, J; Fitch, C; Jarpe, M; Miller, S; Li, Y; Simon, K; van Vlijmen, H

    2009-01-01

    A design approach was taken to investigate the feasibility of replacing single complementarity determining region (CDR) antibody loops. This approach may complement simpler mutation-based strategies for rational antibody design by expanding conformation space. Enormous crystal structure diversity is available, making CDR loops logical targets for structure-based design. A detailed analysis for the L1 loop shows that each loop length takes a distinct conformation, thereby allowing control on a length scale beyond that accessible to simple mutations. The L1 loop in the anti-VLA1 antibody was replaced with the L2 loop residues longer in an attempt to add an additional hydrogen bond and fill space on the antibody-antigen interface. The designs expressed well, but failed to improve affinity. In an effort to learn more, one design was crystallized and data were collected at 1.9 {angstrom} resolution. The designed L1 loop takes the qualitatively desired conformation; confirming that loop replacement by design is feasible. The crystal structure also shows that the outermost loop (residues Leu51-Ser68) is domain swapped with another monomer. Tryptophan fluorescence measurements were used to monitor unfolding as a function of temperature and indicate that the loop involved in domain swapping does not unfold below 60C. The domain-swapping is not directly responsible for the affinity loss, but is likely a side-effect of the structural instability which may contribute to affinity loss. A second round of design was successful in eliminating the dimerization through mutation of a residue (Leu51Ser) at the joint of the domain-swapped loop.

  13. Phase-lock loop frequency control and the dropout problem

    NASA Technical Reports Server (NTRS)

    Attwood, S.; Kline, A. J.

    1968-01-01

    Technique automatically sets the frequency of narrow band phase-lock loops within automatic lock-in-range. It presets a phase-lock loop to a desired center frequency with a closed loop electronic frequency discriminator and holds the phase-lock loop to that center frequency until lock is achieved.

  14. Calcium release from experimental dental materials.

    PubMed

    Okulus, Zuzanna; Buchwald, Tomasz; Voelkel, Adam

    2016-11-01

    The calcium release from calcium phosphate-containing experimental dental restorative materials was examined. The possible correlation of ion release with initial calcium content, solubility and degree of curing (degree of conversion) of examined materials was also investigated. Calcium release was measured with the use of an ion-selective electrode in an aqueous solution. Solubility was established by the weighing method. Raman spectroscopy was applied for the determination of the degree of conversion, while initial calcium content was examined with the use of energy-dispersive spectroscopy. For examined materials, the amount of calcium released was found to be positively correlated with solubility and initial calcium content. It was also found that the degree of conversion does not affect the ability of these experimental composites to release calcium ions.

  15. 21 CFR 582.1199 - Calcium gluconate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Additives § 582.1199 Calcium gluconate. (a) Product. Calcium gluconate. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or feeding...

  16. 21 CFR 582.1205 - Calcium hydroxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Additives § 582.1205 Calcium hydroxide. (a) Product. Calcium hydroxide. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or feeding...

  17. 21 CFR 582.1193 - Calcium chloride.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Additives § 582.1193 Calcium chloride. (a) Product. Calcium chloride. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or feeding practice. ...

  18. 21 CFR 582.1195 - Calcium citrate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Additives § 582.1195 Calcium citrate. (a) Product. Calcium citrate. (b) Conditions of use. This substance is generally recognized as safe when used in accordance with good manufacturing or feeding practice. ...

  19. Decalcification of calcium polycarbophil in rats.

    PubMed

    Yamada, T; Saito, T; Takahara, E; Nagata, O; Tamai, I; Tsuji, A

    1997-03-01

    The in vivo decalcification of calcium polycarbophil was examined. The decalcification ratio of [45Ca]calcium polycarbophil in the stomach after oral dosing to rats was more than 70% at each designated time and quite closely followed in the in vitro decalcification curve, indicating that the greater part of the calcium ion is released from calcium polycarbophil under normal gastric acidic conditions. The residual radioactivity in rat gastrointestine was nearly equal to that after oral administration of either [45Ca]calcium chloride + polycarbophil. The serum level of radioactivity was nearly equal to that after oral dosing of [45Ca]calcium lactate. These results indicate that the greater part of orally administered calcium polycarbophil released calcium ions to produce polycarbophil in vivo.

  20. Magnesium/Calcium Competition at Excitable Membranes.

    ERIC Educational Resources Information Center

    Belzer, Bill; Fry, Panni

    1998-01-01

    Considers some consequences of altering intracellular calcium supply by magnesium concentration changes. Focuses on using this procedure as an exercise with allied health students as they witness therapeutic uses of magnesium and other calcium entry inhibitors. (DDR)