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Articles de revues sur le sujet "CAZ PHOSPHOR"
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Zhang, Xing Hua, Zun Ming Lu, Fan Bin Meng, Long Hu, Xue Wen Xu, Jing Lin et Cheng Chun Tang. « The Structure and Photoluminescence Properties of Ca3Si2O7 : Eu2+ Phosphor ». Advanced Materials Research 509 (avril 2012) : 192–96. http://dx.doi.org/10.4028/www.scientific.net/amr.509.192.
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A series of yellow-emitting phosphors based on a silicate host matrix, Ca3-xSi2O7: xEu2+, were prepared by solid-state reaction method. The structure and photoluminescent properties of the phosphors were investigated. The XRD results show that the Eu2+ substitution of Ca2+ does not change the structure of Ca3Si2O7 host. The SEM images display that phosphors aggregate obviously and the shape of the phosphor particle is irregular. The EDX results reveal that the phosphors consist of Ca, Si, O, and Eu elements. The Ca3-xSi2O7: xEu2+ phosphors can be excited at wavelength of 300-490 nm, which is suitable for the emission band of near ultraviolet or blue light-emitting-diode (LED) chips. The phosphors exhibit a broad emission region from 520 to 650 nm and the emission peak centered at 568 nm. The phosphor for has the strongest excitation and emission intensity, and the energy transfer style between Eu2+ ions is quadrupole-quadrupole interaction for higher concentration Eu2+ doped Ca3Si2O7 phosphor. The Ca3-xSi2O7: xEu2+ phosphors can be used as candidates for white LEDs.
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MORI, KENTAROU, YOSHIYUKI KOJIMA et NOBUYUKI NISHIMIYA. « EFFECT OF REDUCING ATMOSPHERE ON THE AFTERGLOW PROPERTIES OF RED-EMITTING CaS:Eu2+,Pr3+ PHOSPHORS ». Functional Materials Letters 05, no 02 (juin 2012) : 1260012. http://dx.doi.org/10.1142/s1793604712600120.
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The afterglow time of typical red-emitting phosphors is much shorter than those of green- or blue-emitting phosphors which afterglow time were longer than 1000 min. CaS has been used as an effective host material for afterglow phosphors because trapping centers can be easily created in the host by doping with an activator. This study reports on the effect of a reducing atmosphere on the afterglow properties of a red-emitting CaS:Eu2+,Pr3+ phosphor. The phosphor was prepared by reduction under an Ar-H2 (5%) or H2S atmosphere from a CaSO4:Eu3+,Pr3+ phosphor prepared using a liquid phase method. Heating the CaSO4:Eu3+,Pr3+ phosphor for 2 h under an Ar-H2 (5%) atmosphere at 1050°C gave CaO as by-product in addition to CaS . The resulting phosphor exhibited red-emission at 646 nm originating from Eu2+ ions upon visible light irradiation, and gave some afterglow after cessation of visible light irradiation. Addition of Li+ ions extended the afterglow time of the phosphor as a result of a slight change in the CaS host structure. For preparation of a CaSO4:Eu3+,Pr3+ phosphor under a H2S atmosphere, a CaS monophase was obtained. The emission and afterglow of the phosphor were similar to that prepared under the Ar-H2 (5%) atmosphere, but the afterglow time resulting from the CaS monophase was longer. The longest afterglow time obtained was about 60 min for a phosphor prepared under a H2S atmosphere with an initial Li/Ca atomic ratio of 0.04.
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Liu, Sheng, Bei Ying Zhou, Shi Jia Gu, Lian Jun Wang, Wan Jiang et Wei Luo. « A Promising Energy-Saving and Environmental-Friendly Lighting Device : High CRI White LED with Phosphor Materials ». Materials Science Forum 848 (mars 2016) : 446–53. http://dx.doi.org/10.4028/www.scientific.net/msf.848.446.
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Two kinds of commercial LED phosphors (green phosphor LuAG:Ce3+ and red phosphor CaAlSiN3:Eu2+) with polymethyl methacrylate (PMMA) powders were mixed to prepare film phosphors with tunable emission peak in photoluminescence spectrum by flat vulcanizing machine under the temperature of 170 oC and pressure of 2 MPa. The physical phase, surface morphology, transmittance, luminescence spectra of samples were characterized by means of X-ray diffraction (XRD), Environmental scanning electron microscopy (ESEM), Ultraviolet-Visible (UV-Vis) spectrophotometry and Fluorescence spectrometer. The results show that the film phosphors phase was consistent with raw phosphors, phosphor particles were uniformly distributed, and fluorescence spectra with different proportions of phosphors in different position can be adjusted. Tested by HSP 3000 spectrum analyzer, the white LEDs fabricated by blue chip and composite film phosphor containing 5 wt% green phosphor and 1.5 wt.% red phosphor, which refers to the remote excitation technique, possessed color coordinate of (0.3715, 0.3280) and color rendering index (CRI) of 87 when it was driven at power of 36 V/140 mA, reaching the international advanced level.
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Ye, Shenrui, Yukun Li, Ming Qiang, Wenhui Lou, Bo Dai, Hui Lin, Zhaoxia Han, Ruijin Hong et Dawei Zhang. « Color Tunable Composite Phosphor Ceramics Based on SrAlSiN3:Eu2+/Lu3Al5O12:Ce3+ for High-Power and High-Color-Rendering-Index White LEDs/LDs Lighting ». Materials 16, no 17 (31 août 2023) : 6007. http://dx.doi.org/10.3390/ma16176007.
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Lu3Al5O12:Ce3+ phosphor ceramics were fabricated by vacuum sintering. On this basis, a bi-layer composite phosphor was prepared by low-temperature sintering to cover the phosphor ceramics with a layer of SrAlSiN3:Eu2+-phosphor-in-glass (PiG). The optical, thermal, and colorimetric properties of LuAG:Ce3+ phosphor ceramics, SrAlSiN3:Eu2+ phosphors and SrAlSiN3:Eu2+-PiG were studied individually. Combining the bi-layer composite phosphors with the blue LED chip, it is found that the spectrum can be adjusted by varying the doping concentration of SrAlSiN3:Eu2+-PiG and the thickness of Lu3Al5O12:Ce3+ phosphor ceramics. The maximal color rendering index value of the white LED is 86, and the R9 is 61. Under the excitation of a laser diode, the maximum phosphor conversion efficacy of the bi-layer composite phosphors is 120 lm/W, the Ra is 83, and the correlated color temperature is 4534 K. These results show that the bi-layer composite phosphor ceramic is a candidate material to achieve high color rendering index for high brightness lighting.
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Rodionova, Anna V., Victor I. Kuular, Tamara S. Minakova, Parviz Sh Ustabaev et Vadim V. Bakhmetyev. « Acid-Base and Luminescent Properties of Gd2O2S : Tb Luminescent Phosphors Synthesized in a Reducing Atmosphere ». Key Engineering Materials 854 (juillet 2020) : 57–63. http://dx.doi.org/10.4028/www.scientific.net/kem.854.57.
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Gd2O2S:Tb phosphors with different terbium content are prepared in a reducing atmosphere at various synthesis conditions. The effect of an activator and Na4P2O7 flux concentrations upon photo-and X-ray induced luminescence of the synthesized samples as well as on their acid-base properties and morphology is studied. The addition of Na4P2O7 flux into the charge mixture leads to a significant increase of the phosphor particle size. A positive correlation is found between the particle size and pH value of the phosphor aqueous slurry. The photoluminescence intensity is found to mostly depend on the activator concentration, while X-ray luminescence intensity primarily depends on the particle size and crystal structure perfectness of the phosphor matrix. Charge mixture compositions and synthesis conditions providing Gd2O2S:Tb phosphors with the highest photo-and X-ray luminescence intensity are determined. A Gd2O2S:Tb phosphor with X-ray luminescence intensity exceeding the values for the commercial phosphor KEP-45 of a similar composition is developed. The obtained phosphors can be used for the manufacture of intensifying screens applied in industrial X-ray flaw detection.
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Tatte, S. P., N. S. Dhoble, G. C. Mishra et S. J. Dhoble. « Synthesis characterization and Luminescence Properties of B2BiMg2V3O12 based phosphors with rare earth activated Dy3+ phosphor for solid state lighting ». IOP Conference Series : Materials Science and Engineering 1258, no 1 (1 octobre 2022) : 012016. http://dx.doi.org/10.1088/1757-899x/1258/1/012016.
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Highly new efficient vanadate based phosphor B2BiMg2V3O12 (B= K & Na) material incapacitated through rare-earth Dysprosium (Dy) and it was characterized by high temperature solid-state synthesis. Equipped phosphor was established by X-ray diffraction method. In Photo-luminescence measurements shows that the prepared phosphors doped by Dy is excited by near UV ultraviolet light reaching after 300 nm to 380 nm efficiently acceptable to recognize the emission in visible spectrum (in the range 400 nm –570 nm. The highly efficient prepared phosphor doped with lanthanide doped with Dy phosphor likewise showed the exact emission point at 487 nm and 571 nm at the excitation point at 325 nm. Hence, these prepared phosphors can find numerous applications as green emitting phosphor in the field of solid-state lighting area.
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Chen, Yi Bo, Wei Cai, Yong Qiao Liu et Meng Lian Gong. « Ca3Sc2Si3O12:1%Ce3+, x%Ba2+ Green Phosphors for White Light-Emitting Diodes ». Advanced Materials Research 557-559 (juillet 2012) : 776–80. http://dx.doi.org/10.4028/www.scientific.net/amr.557-559.776.
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Low temperature-quenching and high-efficiency Ca3Sc2Si3O12:1%Ce3+, x%Ba2+ phosphors were prepared by solid state method and the properties of these phosphors were investigated. The results showed that co-doping of Ba2+ ions can improve the photoluminescence properties and decrease temperature-quenching of Ca3Sc2Si3O12:Ce3+ phosphor obviously. High-efficiency blue-green light-emitting diode was fabricated with the prepared phosphor and an InGaN blue-emitting (~460 nm) chip. Good performance of the prepared LED indicates that Ca3Sc2Si3O12:1%Ce3+, 0.5%Ba2+ phosphor is a suitable candidate for the fabrication of high-efficiency white LEDs.
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Segal, Ohad, Avner Shultzman, Yaniv Kurman et Ido Kaminer. « Optimizing the spontaneous-emission of far-UVC phosphors ». Applied Physics Letters 120, no 23 (6 juin 2022) : 231902. http://dx.doi.org/10.1063/5.0092109.
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Far-UVC light can enable virus-deactivation while remaining harmless to human tissues. This triggered great efforts to create far-UVC light sources with sufficient emission power and efficiency. However, current sources, such as mercury lamps, KrCl excimer lamps, and LEDs, are made from hazardous chemicals or are limited by low efficiency. Consequently, an alternative approach for reaching the far-UVC is now receiving renewed interest: using phosphors for converting higher frequencies to the desired range of far-UVC. However, this concept is limited by the phosphor's conversion efficiency. In this paper, we propose to utilize principles of nanophotonics to create far-UVC sources. Specifically, we design a phosphor-dielectric multilayer that increases the efficiency of far-UVC light conversion and controls the intrinsic emission properties, including the angular spectrum and emission rate, by shaping the local density of photonic states. To exemplify our approach, we design an aperiodic multilayer nanostructure made of the phosphor material YPO4:Pr3+, showing an increase in light extraction by a factor of 3 compared to naïve bulk structures. Our approach can be applied to any phosphor material and any emitter geometry, opening avenues for engineering nanophotonic light sources in the far-UVC and other spectral regimes.
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Yadav, Pooja J. « Long Persistent Afterglow Luminescence in Gd<sub>3</sub>Al<sub>3</sub>Ga<sub>2</sub>O<sub>12</sub> ;:Ce<sup>3+</sup>, Green Emitting Aluminate Phosphor ». Materials Science Forum 1072 (25 octobre 2022) : 163–68. http://dx.doi.org/10.4028/p-t5bm75.
Texte intégralRésumé :
Green LL is observed in Ce doped Gd3Al5O12: Ce, Ga garnet phosphors. LL is well correlated with Ce3+ emission and a peak around 150°C in the TL glow curve. In comparison with the commercial phosphor YAG, the Gd3Al5O12: Ce, Ga (GAG) is more stable and shows more intense TL properties, this phosphor can be used for dosimetry detections and measurements. Gd3Al5O12 activated with Ce (0.7 mol.%) phosphors were prepared by combustion synthesis. The long-lasting luminescence (LL) is also reported in Pr3+ and Ce3+ doped in reducing atmosphere in YAG phosphor. But YAG: Ce gives yellow emission which doesn’t suit LL applications. On the other hand, Ga substituted GdAG: Ce phosphor gives green emission at shorter wavelengths. In this paper we explored Ga substituted GdAG: Ce phosphor prepared by combustion synthesis for LL, results of these investigations are reported in this paper.
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Sun, Jia Yue, Jin Li Lai et Hai Yan Du. « Synthesis and Luminescence Properties of Red Emitting Phosphors Na3CaB5O10:Eu3+ ». Advanced Materials Research 295-297 (juillet 2011) : 547–50. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.547.
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A series of new Na3CaB5O10:Eu3+ phosphor was synthesized by a solid-state reaction method, and its luminescent properties were investigated. The phase formation of phosphors was confirmed by X-ray powder diffraction (XRD). The excitation spectra exhibited that the phosphors could be effectively excited by near ultraviolet (392 nm) and blue (464 nm) light, which perfectly match the emission wavelength of near-UV light-emitting diodes (LEDs). The emission spectra showed that two characteristic red emission lines peaking at 592 and 613 nm can be obtained upon 394 and 463 excitation with the chromaticity coordinates of (0.6347, 0.3649), which are due to 5D0- 7F1 and 5D0-7F2transitions of Eu3+ ions. The effect of Eu3+ concentration on the emission spectrum of Na3CaB5O10:Eu3+ phosphor was studied. The results showed that the emission intensity increased with increasing Eu3+ concentration, and then decreased because of concentration quenching. The obtained results indicated that this phosphor could be a promising candidate for near-UV white LEDs.
Thèses sur le sujet "CAZ PHOSPHOR"
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Rennie, J. « Dosimetry and electroluminescence properties of doped calcium sulphide ». Thesis, Robert Gordon University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382850.
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Marrano, C. A. « PHOSPHO-REGULATION OF ACA8, A PLASMA MEMBRANE CA2+-ATPASE OF ARABIDOPSIS THALIANA ». Doctoral thesis, Università degli Studi di Milano, 2013. http://hdl.handle.net/2434/215592.
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ACA8 is a plasma membrane-localized isoform of calmodulin (CaM)-regulated Ca2+-ATPase of Arabidopsis thaliana. Phospho-proteomic studies identified several phosphopeptides corresponding to portions of its regulatory N-terminus. Each of the Ser found to be phosphorylated in those studies (S19, S22, S27, S29, S57, and S99) has been mutated to Asp, to mimic phosphorylation of the ACA8 N-terminus, and to Ala to prevent phosphorylation. Mutants have been expressed in Saccharomyces cerevisiae and characterized: as shown by the low activation by CaM, mutants S19D, S57D, S22D and S27D are deregulated. Moreover, the low response to CaM of ACA8 mutants S22A, S27A, and S29A points the relevance of these serine residues per se in determining the amplitude of the response of ACA8 to CaM. To analyse the effect of S to D mutation on the kinetic of CaM binding, His-tagged N-termini of wild-type and mutant ACA8 (6His-1M-I116) were expressed in Escherichia coli, affinity-purified and used in surface plasmon resonance experiments. All the analysed mutations affect the kinetics of interaction with CaM to some extent: in most cases, the altered kinetics result in marginal changes in affinity, with the exception of mutants S57D (KD 10-fold higher than wild-type ACA8) and S99D (KD about half that of wild-type ACA8). Since S19 is in a consensus motive for calcium-dependent protein kinases (CDPKs) the ACA8 N-terminus has been subjected to in vitro phosphorylation assays with two isoforms of A. thaliana CDPKs: CDPK1, that phosphorylates ACA2 (an endoplasmic reticulum localised isoform of A. thaliana ACA) and CDPK16, a plasma membrane localised isoform of CDPK. Results show that both kinases are able to phosphorylate ACA8 N-terminus, but CDPK16 with higher extent. Phosphorylation of mutant 6His-1M-I116 peptides mapped CDPK16 phosphorylation site at S19 and at S22. Furthermore, we identified by two-hybrid screening two isoforms of CBL-interacting protein kinases (CIPKs) as putative interactors of ACA8 N-terminus region: CIPK9 and CIPK14. BiFC analysis in Nicotiana benthamiana confirmed the two-hybrid results, showing that interaction between ACA8 full length and CIPK9 or CIPK14 occurs in planta at the plasma membrane. Moreover, phosphorylation assay demonstrate that both kinases phosphorylate ACA8 N-terminus in vitro. Implications of these results are discussed.
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McLellan, Ross. « Synthesis and novel chemistry of phospha(car)boranes and arsaboranes ». Thesis, Heriot-Watt University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548744.
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Proux, Corinne. « Enlèvement du phosphore par procédé d'électrocoagulation. Le cas d'une unité de traitement pour résidences isolées ». Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25465/25465.pdf.
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Zaim, Wadghiri Youssef. « Méthodologies pour l'utilisation clinique de la spectroscopie RMN : cas du phosphore-31 ; quantification ; mesures thermométriques ». Lyon 1, 1994. http://www.theses.fr/1994LYO10349.
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Le chapitre i du manuscrit fait un appel succinct des bases physiques de la spectroscopie rmn. Les methodes recentes employees et les applications medicales de la spectroscopie rmn du 31p in vivo y sont egalement decrites et une attention particuliere est portee sur l'etude du muscle et du cerveau. Le chapitre ii concerne les developpements techniques elabores pour l'observation in vivo du phosphore-31 dans un aimant a 4,7 tesla de diametre utile 36 cm. Cette partie du travail a porte notamment sur la realisation d'un ergometre permettant de correler travail musculaire et spectres rmn et sur la conception d'une antenne adaptee a une couveuse pour l'observation du cerveau chez le nouveau-ne. Le chapitre iii est consacre a l'optimisation d'une methode parametrique de quantification des signaux rmn in vivo developpee au laboratoire. Cette methode est actuellement utilisee pour l'analyse automatique des spectres rmn obtenus au cours de cinetiques. Le dernier chapitre aborde les effets d'echauffements radiofrequence pouvant etre occasionnees au cours d'une experience de rmn a champ eleve, notamment en spectroscopie in vivo. Une methode de cartographie de temperature mettant a profit la dependance du deplacement chimique du noyau de cobalt-59 vis a vis de la temperature est proposee
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Susser, Jessica R. « Can we reduce phosphorus runoff into Lake Erie by stimulating soil biota ? » University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1515756009087471.
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FAILLENET, ANNE-FRANCOISE. « Etat du metabolisme phospho-calcique dans l'hyperthyroidie du sujet age : a propos de 35 cas ». Besançon, 1992. http://www.theses.fr/1992BESA3091.
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Lebecq, Isabelle. « Etude de bioverres à base de SiO2, CaO, Na2O non dopés et dopés par le phosphore ». Valenciennes, 2002. https://ged.uphf.fr/nuxeo/site/esupversions/628f0255-e6b4-4af0-a060-ac6b163d2fa1.
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Le but est de trouver les verres les plus bioactifs de SiO2-CaO-Na2O non dopés et dopés avec du phosphore (P). L'immersion dans du fluide physiologique simulé permet d'étudier la formation d'hydroxyapatite cristallisée (HAC). Cette couche permet un accrochage chimique implant-os naturel. Les verres les plus bioactifs sont riches en Na2O et pauvres en SiO2. Ils forment une couche d'HAC dès 12 heures. Pour ces mêmes verres dopés avec P, l'ajout n'améliore pas la bioactivité. Pour les verres inversés au P moins riches en Na2O, correspondants aux verres du ternaire les moins bioactifs, plus le taux de P est grand plus l'HAC se forme vite (6 heures à 6 % molaire de P2O5). Dans les verres traditionnels au P, la bioactivité reste moyenne (2-3 jours) comme pour les verres conventionnels du ternaire. Des études de cytoxicité et cytocompatibilité sur le verre le plus riche en Na2O sans et avec P montrent que ces verres forment l'HAC rapidement mais rendent le milieu trop agressif pour les cellulesThe aim is to determine the most bioactive glasses of SiO2-CaO-Na2O ternary, and of this system doped with phosphorus. Soaking glasses in the simulated body fluid allowed to study the formation of crystalline hydroxycarbonate apatite (HCA). This layer allows a chemical anchoring implant-natural bone. The most bioactive glasses are Na2O-rich and SiO2-poor glasses. They forms an HCA layer within 12 hours. For this same glasses doped with phosphorus, adding phosphorus don't improve bioactivity. For less Na2O-rich invert glasses with phosphorus, corresponding to the less bioactive glasses of the ternary, the higher rate of P the faster HCA forms (6 hours with 6 mol % of P2O5). In conventional glasses, bioactivity stays middle (2-3 days). Some studies of cytotoxicity and cytocompatibility on the most Na-rich glass without and with phosphorus showed that these glasses form rapidly the HCA but make the environment too aggressive for the cells
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Perrault, Edith. « Intoxications par l'herbicide Roundup : à propos de deux cas, nouvelle méthode de dosage du glyphosate ». Bordeaux 2, 1995. http://www.theses.fr/1995BOR2M017.
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Lagoudakis, Laura. « Ca2+ et régénération du foie : impact de la signalisation calcique intracellulaire sur la prolifération hépatocytaire ». Paris 6, 2009. http://www.theses.fr/2009PA066471.
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LE FOIE possède une capacité exceptionnelle à régénérer à la suite d’une lésion induite soit chirurgicalement soit par des agents toxiques. Parmi les agonistes impliqués dans le processus régénératif, nombreux sont ceux qui mobilisent le calcium (Ca2+) intracellulaire, sans que l’impact physiologique de cette voie de signalisation soit déterminé. Pour l’étudier, nous avons interféré in vivo avec la signalisation calcique par transfert de gène grâce à un vecteur adénoviral. La parvalbumine (PV), une protéine tamponnant le Ca2+, a été adressée sélectivement dans le cytosol ou le noyau des hépatocytes, et la régénération du foie a été analysée après hépatectomie partielle (Hx) chez le rat. Nous avons ainsi mis en évidence un ralentissement de la régénération hépatique chez les animaux exprimant la PV cytosolique (PV-NES-DsR). En effet, nous avons observé, après Hx, un retard dans la prise de poids du foie ainsi que dans la progression des hépatocytes dans le cycle cellulaire. Ce retard était associé à une transcription altérée du gène précoce c-fos, fortement impliqué dans le démarrage du processus régénératif, ainsi que des gènes des cyclines E et A et la kinase associée cdk2. Nous avons également observé un retard d’activation de la voie ERK 1/2, impliquée dans la prolifération hépatocytaire au cours de la régénération, et connue pour sa dépendance vis-à-vis du Ca2+. Une moindre activation de la réponse cytokinique a également été observée après Hx chez les animaux PV-NES-DsR, dont les mécanismes restent à préciser. Par ailleurs, nous avons observé in vitro, sur des cultures primaires d’hépatocytes exprimant PV-NES-DsR, un retard de prolifération et mis en évidence une altération de la phosphorylation de CREB, un facteur de transcription activé par le Ca2+. Ces résultats nous indiquent que le calcium cytosolique régule de manière positive la régénération hépatique. Des résultats préliminaires après expression nucléaire de la PV (PV-NLS-DsR) dans les hépatocytes, in vivo et in vitro, indiquent que le tamponnement du Ca2+ dans ce compartiment conduit à l’apoptose des hépatocytes. L’ensemble de ces données indiquent que la signalisation calcique contribue à réguler les processus de croissance et de survie hépatocytaire.
Livres sur le sujet "CAZ PHOSPHOR"
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Bossche, Hugues Vanden. Devenir du phosphore apporté sur les sols et risques de contamination des eaux de surface : Cas des boues de stations d'épuration. Rennes, France : Géosciences Rennes, UMR 6118, CNRS-Université de Rennes I, Campus de Beaulieu, 2002.
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Emery-Coderre, J. Jurisprudence médicale : Examen médico-légal des procès d'Anaïs Toussaint, de Joseph Bérubé et de Césarée Thériault, et précis de procèdures à suivre dans les cas d'empoisonnements par l'arsenic et le phosphore. [Montréal ? : s.n.], 1985.
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Phosphate Coatings Suitable for Personal Protective Equipment. Materials Research Forum LLC, 2021. http://dx.doi.org/10.21741/9781644901113.
Texte intégralRésumé :
Phosphate coatings can improve the corrosion resistance of carbon steel equipment such as carabiners. The specific porosity of the phosphate layer allows the deposition of an elastomer-based paint for absorbing mechanical shocks. The book is relevant for fundamental and applied research in the field of protective phosphate layers and their industrial applications. It also describes how to design and develop phosphating solutions that differ in the type and concentration of metal ions dissolved in phosphoric acid.
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Bardin, Thomas, et Tilman Drüeke. Renal osteodystrophy. Oxford University Press, 2013. http://dx.doi.org/10.1093/med/9780199642489.003.0149.
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Renal osteodystrophy (ROD) is a term that encompasses the various consequences of chronic kidney disease (CKD) for the bone. It has been divided into several entities based on bone histomorphometry observations. ROD is accompanied by several abnormalities of mineral metabolism: abnormal levels of serum calcium, phosphorus, parathyroid hormone (PTH), vitamin D metabolites, alkaline phosphatases, fibroblast growth factor-23 (FGF-23) and klotho, which all have been identified as cardiovascular risk factors in patients with CKD. ROD can presently be schematically divided into three main types by histology: (1) osteitis fibrosa as the bony expression of secondary hyperparathyroidism (sHP), which is a high bone turnover disease developing early in CKD; (2) adynamic bone disease (ABD), the most frequent type of ROD in dialysis patients, which is at present most often observed in the absence of aluminium intoxication and develops mainly as a result of excessive PTH suppression; and (3) mixed ROD, a combination of osteitis fibrosa and osteomalacia whose prevalence has decreased in the last decade. Laboratory features include increased serum levels of PTH and bone turnover markers such as total and bone alkaline phosphatases, osteocalcin, and several products of type I collagen metabolism products. Serum phosphorus is increased only in CKD stages 4-5. Serum calcium levels are variable. They may be low initially, but hypercalcaemia develops in case of severe sHP. Serum 25-OH-vitamin D (25OHD) levels are generally below 30 ng/mL, indicating vitamin D insufficiency or deficiency. The international KDIGO guideline recommends serum PTH levels to be maintained in the range of approximately 2-9 times the upper normal normal limit of the assay and to intervene only in case of significant changes in PTH levels. It is generally recommended that calcium intake should be up to 2 g per day including intake with food and administration of calcium supplements or calcium-containing phosphate binders. Reduction of serum phosphorus towards the normal range in patients with endstage kidney failure is a major objective. Once sHP has developed, active vitamin D derivatives such as alfacalcidol or calcitriol are indicated in order to halt its progression.
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Geerse, Daniël A., et Marcus J. Schultz. Disorders of phosphate in the critically ill. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0254.
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Phosphorus plays an important role in many cellular processes and hypophosphataemia can result from a number of causes. Critically-ill patients are at increased risk for developing hypophosphataemia due to the presence of multiple causal factors. Hypophosphataemia may lead to a multitude of symptoms and frequent monitoring of serum phosphate is advised in critically-ill patients is recommended and should be corrected in patients with associated symptoms. It is uncertain whether correction in apparently asymptomatic patients affects outcome, although treatment is generally recommended for severe hypophosphataemia. Multiple strategies of intravenous phosphate administration have been described, but it is unknown which strategy is superior. Hyperphosphataemia is most often caused by renal insufficiency, but can also be caused by increased intake or release from damaged cells. Symptoms are mainly associated with subsequent hypocalcaemia and correction of hyperphosphataemia can be achieved by minimizing the intake of phosphate, increasing renal phosphate excretion, and renal replacement therapy.
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Gluckman, Sir Peter, Mark Hanson, Chong Yap Seng et Anne Bardsley. Vitamin D in pregnancy and breastfeeding. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780198722700.003.0015.
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Vitamin D, which is synthesized in skin exposed to UV light, or is consumed in the diet, plays a key role in maintaining bone integrity via the regulation of calcium and phosphorus homeostasis. It also influences a number of extra-skeletal processes, including immune function and blood glucose homeostasis. Maternal vitamin D deficiency in pregnancy leads to poor fetal skeletal mineralization in utero that can manifest as rickets in newborns. In addition to skeletal effects, women with very low vitamin D status face increased risks of other adverse pregnancy outcomes and possible long-term effects on their own health and that of their offspring. However, controversy remains over definitions of vitamin D sufficiency and deficiency, complicating recommendations on maternal intakes. At a minimum, all pregnant women should take a supplement of 400 IU/day, in addition to sensible sun exposure and increasing their intake of food sources.
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Jurisprudence médicale : Examen médico-l'egal des procès d'Anaïs Toussaint, de Joseph Bérubé et de Césarée Thériault, et précis de procèdures à suivre dans les cas d'empoisonnements par l'arsenic et le phosphore. [Montréal ? : s.n.], 1985.
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Sprague, Stuart M., et Menaka Sarav. Chronic kidney disease-mineral and bone disorder. Sous la direction de David J. Goldsmith. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199592548.003.0115_update_001.
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The kidneys play a critical role in maintaining normal serum calcium and phosphorus concentrations, under the regulation of three main hormones: parathyroid hormone, calcitriol, and fibroblast growth factor 23. With the progression of chronic kidney disease (CKD), most patients develop CKD–mineral and bone disorder (CKD-MBD), which is a systemic disorder involving derangement in mineral metabolism, renal osteodystrophy, and extraskeletal calcification. Disturbances in mineral metabolism develop early in CKD and include phosphate retention, hypocalcaemia, vitamin D deficiency, and hyperparathyroidism. Renal osteodystrophy involves pathologic changes of bone morphology related to progressive CKD and is quantifiable by histomorphometry, based on bone biopsy. CKD-MBD is associated with significant morbidity, including bone loss, fractures, cardiovascular disease, immune suppression, as well as increased mortality. As the disorder begins early in the course of CKD, a proactive approach with intervention is important. Therapeutic strategies could then be employed to prevent and correct these disturbances, aiming to improve cardiovascular outcomes and survival. Current practice guidelines for CKD-MBD are based on insufficient data and high-quality studies are required before specific treatment can be advocated strongly.
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Voinescu, Alexandra, Nadia Wasi Iqbal et Kevin J. Martin. Management of chronic kidney disease-mineral and bone disorder. Sous la direction de David J. Goldsmith. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199592548.003.0118_update_001.
Texte intégralRésumé :
In all patients with chronic kidney disease (CKD) stages 3–5, regular monitoring of serum markers of CKD-mineral and bone disorder, including calcium (Ca), phosphorus (P), parathyroid hormone (PTH), 25-hydroxyvitamin D, and alkaline phosphatase, is recommended. Target ranges for these markers are endorsed by guidelines. The principles of therapy for secondary hyperparathyroidism include control of hyperphosphataemia, correction of hypocalcaemia, use of vitamin D sterols, use of calcimimetics, and parathyroidectomy. of hyperphosphataemia is crucial and may be achieved by means of dietary P restriction, use of P binders, and P removal by dialysis. Dietary P restriction requires caution, as it may be associated with protein malnutrition. Aluminium salts are effective P binders, but they are not recommended for long-term use, as Aluminium toxicity (though from contaminated dialysis water rather than oral intake) may cause cognitive impairment, osteomalacia, refractory microcytic anaemia, and myopathy. Ca-based P binders are also quite effective, but should be avoided in patients with hypercalcaemia, vascular calcifications, or persistently low PTH levels. Non-aluminium, non-Ca binders, like sevelamer and lanthanum carbonate, may be more adequate for such patients; however, they are expensive and may have several side effects. Furthermore, comparative trials have failed so far to provide conclusive evidence on the superiority of these newer P binders over Ca-based binders in terms of preventing vascular calcifications, bone abnormalities, and mortality. P removal is about 1800–2700 mg per week with conventional thrice-weekly haemodialysis, but may be increased by using haemodiafiltration or intensified regimens, such as short daily, extended daily or three times weekly nocturnal haemodialysis. Several vitamin D derivatives are currently used for the treatment of secondary hyperparathyroidism. In comparison with the natural form calcitriol, the vitamin D analogue paricalcitol seems to be more fast-acting and less prone to induce hypercalcaemia and hyperphosphataemia, but whether these advantages translate into better clinical outcomes is unknown. Calcimimetics such as cinacalcet can significantly reduce PTH, Ca, and P levels, but they have failed to definitively prove any benefits in terms of mortality and cardiovascular events in dialysis patients. Parathyroidectomy is often indicated in CKD patients with severe persistent hyperparathyroidism, refractory to aggressive medical treatment with vitamin D analogues and/or calcimimetics. This procedure usually leads to rapid improvements in biochemical markers (i.e. significant lowering of serum Ca, P, and PTH) and clinical manifestations (such as pruritus and bone pain); however, the long-term benefits are still unclear.
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Kirchman, David L. Microbial primary production and phototrophy. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789406.003.0006.
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This chapter is focused on the most important process in the biosphere, primary production, the turning of carbon dioxide into organic material by higher plants, algae, and cyanobacteria. Photosynthetic microbes account for roughly 50% of global primary production while the other half is by large, terrestrial plants. After reviewing the basic physiology of photosynthesis, the chapter discusses approaches to measuring gross and net primary production and how these processes affect fluxes of oxygen and carbon dioxide into and out of aquatic ecosystems. It then points out that terrestrial plants have high biomass but relatively low growth, while the opposite is the case for aquatic algae and cyanobacteria. Primary production varies greatly with the seasons in temperate ecosystems, punctuated by the spring bloom when the biomass of one algal type, diatoms, reaches a maximum. Other abundant algal types include coccolithophorids in the oceans and filamentous cyanobacteria in freshwaters. After the bloom, small algae take over and out-compete larger forms for limiting nutrients because of superior uptake kinetics. Abundant types of small algae include two coccoid cyanobacteria, Synechococcus and Prochlorococcus, the latter said to be the most abundant photoautotroph on the planet because of its large numbers in oligotrophic oceans. Other algae, often dinoflagellates, are toxic. Many algae can also graze on other microbes, probably to obtain limiting nitrogen or phosphorus. Still other microbes are mainly heterotrophic but are capable of harvesting light energy. Primary production in oxic environments is carried out by oxygenic photosynthetic organisms, whereas in anoxic environments with sufficient light, it is anaerobic anoxygenic photosynthesis in which oxygen is not produced. Although its contribution to global primary production is small, anoxygenic photosynthesis helps us understand the biophysics and biochemistry of photosynthesis and its evolution on early Earth. These microbes as well as aerobic phototrophic and heterotrophic microbes make up microbial mats. These mats can provide insights into early life on the planet when a type of mat, “stromatolites,” covered vast areas of primordial seas in the Proterozoic.
Chapitres de livres sur le sujet "CAZ PHOSPHOR"
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Shaber, G. S., J. M. Boone et R. Shlansky-Goldberg. « Detectability Evaluation of a Photostimulable Phosphor Digital Radiographic System ». Dans CAR’89 Computer Assisted Radiology / Computergestützte Radiologie, 124–31. Berlin, Heidelberg : Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-52311-3_23.
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Gur, D., J. C. Weiser, M. Deutsch et R. Schaetzing. « Verification of Electron Beam Therapy with Conventional and Storage Phosphor Images ». Dans CAR’89 Computer Assisted Radiology / Computergestützte Radiologie, 251–53. Berlin, Heidelberg : Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-52311-3_44.
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Mushtaq, Umer, Irfan Ayoub, Nisar Hussain, Vishal Sharma, Hendrik C. Swart et Vijay Kumar. « Luminescence Properties of Rare-Earth-Doped CaO Phosphors ». Dans Advanced Materials for Solid State Lighting, 149–76. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-4145-2_6.
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Tian, Fuwei, Jiangyu Dai, Jiayi Xu, Xiufeng Wu, Shiqiang Wu, Yu Zhang, Fangfang Wang et Ang Gao. « Do the Short-Term Water Diversion from Yangtze River Increase Phosphorus Bioavailability in the Water-Receiving Area ? » Dans Lecture Notes in Civil Engineering, 1098–112. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-6138-0_96.
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AbstractWater diversion projects have an important role in coping with water shortage and improving water quality, but they also have an impact on the ecological environment of lakes that cannot be ignored. As an important biogenic element for evaluating the primary productivity and eutrophication of lake water bodies, the influence of phosphorus by water diversion activities and its impact on the production and elimination of phytoplankton is lacking attention. In this study, we analyzed the phosphorus composition and bioavailability of the water channel and the Gonghu Bay of Lake Taihu under the influence of seasonal water diversion, revealed the spatio-temporal distribution patterns of phytoplankton communities in the water receiving river and lake, and analyzed the contribution of phosphorus to the variations of phytoplankton communities and their quantitative coupling relationships. The results showed that short-term water diversion in autumn and winter did not significantly increase the concentrations of particulate phosphorus in the receiving waters, but there was a risk of increasing the concentration of dissolved reactive phosphorus and dissolved organic phosphorus. The difference in total phosphorus concentrations between the diversion and non-diversion periods in Gonghu Bay was an important environmental factor influencing the phytoplankton community, and the bioavailable phosphorus could better fit the logarithm of algal cell density in all seasons, which was significantly and positively correlated with the phytoplankton cell densities. This study implies that the control of bioavailable phosphorus in the water channel can reduce the ecological risks of the water diversion project on the cyanobacterial blooms to some extent.
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Imai, T. « Calcination Technology for Manufacturing Mineral Fertilizer Using CaO-Enriched Sewage Sludge Ash ». Dans Phosphorus Recovery and Recycling, 179–87. Singapore : Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-8031-9_11.
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Williams, R. J. P. « Can the Availability of Phosphorus be Critical for Mankind ? » Dans Ciba Foundation Symposium 57 - Phosphorus in the Enviroment : Its Chemistry and Biochemistry, 285–307. Chichester, UK : John Wiley & Sons, Ltd., 2008. http://dx.doi.org/10.1002/9780470720387.ch16.
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Kufel, Lech, et Teresa Ozimek. « Can Chara control phosphorus cycling in Lake Łuknajno (Poland) ? » Dans Nutrient Dynamics and Biological Structure in Shallow Freshwater and Brackish Lakes, 277–83. Dordrecht : Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-017-2460-9_24.
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Kawamura, Hiroaki, Yutaka Yanaba, Takeshi Yoshikawa et Kazuki Morita. « Reductive Removal of Phosphorus in Silicon Using CaO-CaF2Slag ». Dans EPD Congress 2013, 227–36. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118658468.ch26.
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Oestmann, Joerg W., Christopher S. Walsh, Stephan Reichelt, C. C. Wang, Mary Austin-Seymour, Noah C. Choi, John E. Munzenrider, Herman D. Suit et Reginald Greene. « Digital Images of Treatment Ports Acquired with Storage Phosphors : Comparison with Conventional Film Technique in a Phantom Model ». Dans CAR’89 Computer Assisted Radiology / Computergestützte Radiologie, 164–70. Berlin, Heidelberg : Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-52311-3_30.
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Zhou, Zhiqiang, Zizong Zhu, Yuchuan Ding et Shengnan Zhou. « Effect of Silicon on Removal of Phosphorus from High Phosphorus Si–Mn Alloy by CaO-Based Slag ». Dans The Minerals, Metals & ; Materials Series, 559–69. Cham : Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-51340-9_55.
Texte intégralActes de conférences sur le sujet "CAZ PHOSPHOR"
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Crim, P. R., D. G. Walker et S. W. Allison. « Transient Thermal Measurements Using Thermographic Phosphors for Temperature Rate Estimates ». Dans ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72464.
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This paper addresses the potential for predicting heat flux from thermographic phosphor measurements. Temperature can be measured using thermographic phosphors by extracting the intensity decay of the phosphor, which is temperature dependent. This measured temperature can then be used to estimate boundary heat fluxes, which is often called the inverse heat conduction problem. Heating rate can also be estimated with the use of thermographic phosphors, from which heat flux can also be determined. In this case, the solution to the inverse problem appears more stable. The purpose of this work is to demonstrate the feasibility of measuring change in decay rates and the ability to determine the first derivative of temperature from these measurements. Preliminary analysis shows that by determining dT/dt instead of temperature, a better estimate of heat flux can be made. The experiment uses a millisecond phosphor, excited by an LED pulsed at 100 Hz. The phosphor is painted on a tungsten filament, which can be heated to hundreds of degrees in under a second. The temperature change during a single pulse is significant enough to affect the decay rate, which is necessary to achieve reasonable heating rate measurement. The measurements of heating rate are used to determine the volumetric generation rate (Joule heating) and the heat transfer loss from the system by convection and radiation. Early data show that estimates from heating rate data, as opposed to temperature data, result more accurate predictions with less error.
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Noel, B. W., H. M. Borella, W. Lewis, W. D. Turley, D. L. Beshears, G. J. Capps, M. R. Cates, J. D. Muhs et K. W. Tobin. « Evaluating Thermographic Phosphors in an Operating Turbine Engine ». Dans ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-266.
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The results of a field test in a commercial turbine engine showed that we can remotely measure the temperature of engine components in operating engines using thermographic phosphors. The remote-measurement method exploits the temperature dependence of the characteristic decay time of the laser-induced fluorescence of thermographic phosphors. This paper summarizes recent work leading up to and including a successful test of the thermographic-phosphor method in an operating turbine engine.
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Chyu, M. K., et D. J. Bizzak. « Measurement of Surface Temperature Using a Laser-Induced Fluorescence Thermal Imaging System ». Dans ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/93-gt-214.
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This paper describes a novel, non-intrusive thermal imaging system based on the fluorescence properties of an europium-doped lanthanum oxysulfide (Eu+3:La2O2S) thermographic phosphor. In this system the phosphor coating on a test surface is excited by a pulsed Nd:YAG laser. The resulting fluorescent emission of the temperature-sensitive 512 nm transition, along with that of the relatively temperature independent 620 nm transition, is acquired using an image-intensified charged coupled device (ICCD) camera. The ratio of the 512- and 620-nm emissions, integrated over a set gating period, is then correlated with temperature. Quality data obtained from a calibration procedure have demonstrated that the present approach can be more advantageous than many existing thermal imaging techniques. The system has been specifically designed to provide two-dimensional temperature measurements with high accuracy and exceptional spatial resolution. Because of the extremely short fluorescent lifetimes of various thermographic phosphors (∼μs), applicability of the technique to fast-moving or rotating surfaces is very promising.
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Allison, Stephen W., David L. Beshears, Michael R. Cates, Bruce W. Noel et W. D. Turley. « Phosphor Thermometry of Gas Turbine Surfaces ». Dans ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-385.
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This paper describes a nondestructive method for thermometry applicable to ceramic surfaces and coatings. To date our primary application has been to turbine engine and air vehicle surfaces. This method makes use of thermally sensitive phosphors many of which, as it turns out, are also ceramics. These materials fluoresce when suitably illuminated by ultraviolet light. The fluorescence intensity and decay time are well-behaved functions of temperature and therefore serve as reliable indicators of the temperature of the substrate to which the fluorescing material is attached. It is a non-contact method in that the light delivery and collection optics can be remotely located. A range of phosphor materials have been tested and any temperature ranging from 8 to 1900 K can be measured by selection of the appropriate phosphor. Turbine blades, vanes, thermal barrier coatings, and panels are examples of surfaces which have been diagnosed to date in either engine or engine-simulation facilities. A variety of coating methods are used, including electron-beam deposition, radio-frequency sputtering, and curing with inorganic binders. This paper summarizes the results to date and status of this technology.
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Yu, Xingjian, Weicheng Shu, Bofeng Shang, Bin Xie, Yanhua Cheng et Xiaobing Luo. « Color Uniformity Enhancement of White Light-Emitting Diodes With Novel Bell Shape Phosphor Layer ». Dans ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2017 Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ipack2017-74195.
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In this study, we proposed a bell shape phosphor layer geometry and the corresponding dual-step phosphor coating method for enhancing the angular color uniformity (ACU) of phosphor-converted white light-emitting diodes (pcLEDs). Numerical simulation based on Volume of Fluid (VOF) model was applied to predict phosphor geometries. Based on the simulated results, experiments were conducted to realize the phosphor geometries. The simulated results show that the VOF model can predict the phosphor geometries with an acceptable geometric deviation within 5%. The experimental results show that compared with the spherical cap phosphor layer geometry, the bell shape geometry can achieve better ACU performance, an optimal bell phosphor layer geometry with equal coating volume above and around the LED chip was achieved, for the corrected color temperature (CCT) of 4000 K, the angular CCT deviation of the optimal geometry is 62 K, while it is 382 K for the spherical cap geometry.
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Taikar, D. R., P. D. Belsare et S. V. Moharil. « Study of thermoluminescence in Cu doped CaO phosphor ». Dans INTERNATIONAL CONFERENCE ON “MULTIDIMENSIONAL ROLE OF BASIC SCIENCE IN ADVANCED TECHNOLOGY” ICMBAT 2018. Author(s), 2019. http://dx.doi.org/10.1063/1.5100461.
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Heyes, A. L., A. Rabhiou, J. P. Feist et A. M. Kempf. « Phosphor Based Temperature Indicating Paints ». Dans ASME Turbo Expo 2012 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69811.
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The ability to measure temperature in extreme environments such as the hot sections of gas turbines is critically important. Several on-line techniques exist but it is often not possible to measure in real-time the temperature of all surfaces of interest. Indeed, some surfaces are so inaccessible as to require complex, costly and intrusive instrumentation for on-line temperature measurement. Here, off-line sensors, also called thermal history sensors, can be used to record the temperatures to which they are exposed, in such a way that they can be extracted later off-line, at room temperature. Probably the best-known types of thermal history sensor are the colour changing thermal paints, that are widely used in gas turbine development. These have been valuable tools of engine developers for many years, but their use presents a number of challenges so that alternatives would be welcome. This paper reports the latest developments of a thermal history sensor based on phosphors that undergo permanent changes in their luminescence properties when exposed to high temperatures. Such thermal history sensors have several advantages over and address many of the shortcomings of existing sensors. The paper contains details of the application of a phosphor-based temperature indicating paint based on Y2SiO5:Tb suspended in a chemical binder. The binder was found to influence the optical properties of the phosphor but despite this, a viable sensor paint for temperatures in the range 400°C to 900°C was formed. A thermal history coating was installed using a thermal barrier coating architecture, applied on various components of a Royce-Rolls Viper 201 engine owned by STS and operated for a number of hours at Cranfield University. Post-operation analysis revealed a temperature distribution on the surfaces/components and enabled hotspots to be identified. Overall the results suggest that phosphor-based temperature indicating paints have the potential to surpass the capability of existing paints.
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Huihua Liu, Rong Zhang, Jeffery C. C. Lo et S. W. Ricky Lee. « LED wafer level packaging with a remote phosphor cap ». Dans 2012 14th International Conference on Electronic Materials and Packaging (EMAP). IEEE, 2012. http://dx.doi.org/10.1109/emap.2012.6507885.
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Nanto, H., Y. Douguchi, J. Nishishita, M. Kadota, N. Kashiwagi, T. Shinkawa et S. Nasu. « A Novel Erasable and Rewritable Optical Memory Utilizing Photostimulated Luminescence in Eu and Sm Co-doped SrS Phosphor Ceramics ». Dans Symposium on Optical Memory. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/isom.1996.otub.9.
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New systems to optical memory, which are based on the photostimulated luminescence (PSL) phenomenon in electron trapping phosphor materials for optical storage, have been studied in the fields of optical parallel Boolean logic operation [1], two-dimensional optical associative memory [2] and optical neural networks [3,4], The electron trapping phosphor materials can emit different output photons that correlate spatially in intensity with input photons. Consequently, the phosphor materials can be used to store optical information as trapped electrons and the information stored can be read out by a laser beam scanning of the phosphor material. The unique features of the electron trapping phosphor materials that exhibit the PSL phenomenon provide the potential for high bit storage densities, high data transfer, and fast recovery speeds. [5] Important characteristics of a good electron trapping phosphor materials for optical memory are high PSL brightness for low noise, short luminescent lifetime for minimum readout time, and low light scattering for high bit densities. Especially, the electron trapping phosphor materials using transparent thin film provides an efficient PSL and low light scattering.
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Nau, Patrick, Zhiyao Yin, Oliver Lammel et Wolfgang Meier. « Wall Temperature Measurements in Gas Turbine Combustors With Thermographic Phosphors ». Dans ASME Turbo Expo 2018 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75293.
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Phosphor thermometry has been developed for wall temperature measurements in gas turbines and gas turbine model combustors. An array of phosphors has been examined in detail for spatially and temporally resolved surface temperature measurements. Two examples are provided, one at high pressure (8 bar) and high temperature and one at atmospheric pressure with high time resolution. To study the feasibility of this technique for full scale gas turbine applications a high momentum confined jet combustor at 8 bar was used. Successful measurements up to 1700 K on a ceramic surface are shown with good accuracy. In the same combustor, temperatures on the combustor quartz walls were measured, which can be used as boundary conditions for numerical simulations. An atmospheric swirl-stabilized flame was used to study transient temperature changes on the bluff body. For this purpose, a high-speed setup (1 kHz) was used to measure the wall temperatures at an operating condition where the flame switches between being attached (M-flame) and being lifted (V-flame) (bistable). The influence of a precessing vortex core (PVC) present during M-flame periods is identified on the bluff body tip, but not at positions further inside the nozzle.
Rapports d'organisations sur le sujet "CAZ PHOSPHOR"
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Hackbarth, Carolyn, et Rebeca Weissinger. Water quality in the Northern Colorado Plateau Network : Water years 2016–2018 (revised with cost estimate). National Park Service, novembre 2023. http://dx.doi.org/10.36967/nrr-2279508.
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Water-quality monitoring in National Park Service units of the Northern Colorado Plateau Network (NCPN) is made possible through partnerships between the National Park Service Inventory & Monitoring Division, individual park units, the U.S. Geological Survey, and the Utah Division of Water Quality. This report evaluates data from site visits at 62 different locations on streams, rivers, and reservoirs in or near ten NCPN park units between October 1, 2015 and September 30, 2018. Data are compared to state water-quality standards for the purpose of providing information to park managers about potential water-quality problems. The National Park Service does not determine the regulatory status of surface waters; state water quality agencies determine whether waters comply with the Clean Water Act. Evaluation of water-quality parameters relative to state water-quality standards indicated that 17,997 (96.8%) of the 18,583 total designated beneficial-use evaluations completed for the period covered in this report met state water-quality standards. The most common exceedances or indications of impairment, in order of abundance, were due to elevated nutrients, elevated bacteria (E. coli), elevated water temperature, elevated trace metals, elevated total dissolved solids (and sulfate), elevated pH, and low dissolved oxygen. While some exceedances were recurring and may have been caused by human activities in the watersheds, many were due to naturally occurring conditions characteristic of the geographic setting. This is most apparent with phosphorus, which can be introduced into surface water bodies at elevated levels by natural weathering of the geologic strata found throughout the Colorado Plateau. Higher phosphorus concentrations could also be attributed to anthropogenic activities that can accelerate erosion and transport of phosphorus. Some activities that can increase erosional processes include grazing, logging, mining, pasture irrigation, and off-highway vehicle (OHV) use. Exceedances for total phosphorus were common occurrences at nine out of ten NCPN park units, where at least one site in each of these parks had elevated phosphorus concentrations. At these sites, high levels of nutrients have not led to algal blooms or other signs of eutrophication. Sites monitored in Arches National Park (NP), Black Canyon of the Gunnison NP (BLCA), Bryce Canyon NP (BRCA), Capitol Reef NP (CARE), Curecanti National Recreation Area (CURE), Dinosaur National Monument (DINO), and Zion NP (ZION) all had E. coli ex-ceedances that could be addressed by management actions. While many of these sites already have management actions underway, some of the actions necessary to bring these waters into compliance are beyond the control of the National Park Service. Changes to agricultural practices to improve water quality involves voluntary participation by landowners and/or grazing permittees and their respective states. This could be the case with lands upstream of several parks with E. coli contamination issues, including Red Rock Canyon (BLCA); Sul-phur, Oak, and Pleasant creeks (CARE); Blue Creek and Cimarron River (CURE); Brush and Pot creeks (DINO); and North Fork Virgin River (ZION). Issues with E. coli contamination at Yellow Creek (BRCA) seemed to be resolved after the park boundary fence downstream of the site was repaired, keeping cattle out of the park. At North Fork Virgin River, E. coli exceedances have been less frequent since the State of Utah worked with landowners and grazing permittees to modify agricultural practices. Continued coordination between the National Park Service, state agencies, and local landowners will be necessary to further re-duce E. coli exceedances and, in turn, improve public health and safety in these streams. Selenium concentrations in Red Rock Canyon (BLCA) continued to exceed the state aquat-ic-life standard at both the upstream and downstream sites. Although selenium weathers naturally from bedrock and...
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Litaor, Iggy, James Ippolito, Iris Zohar et Michael Massey. Phosphorus capture recycling and utilization for sustainable agriculture using Al/organic composite water treatment residuals. United States Department of Agriculture, janvier 2015. http://dx.doi.org/10.32747/2015.7600037.bard.
Texte intégralRésumé :
Objectives: 1) develop a thorough understanding of the sorption mechanisms of Pi and Po onto the Al/O- WTR; 2) determine the breakthrough range of the composite Al/O-WTR during P capturing from agro- wastewaters; and 3) critically evaluate the performance of the composite Al/O-WTR as a fertilizer using selected plants grown in lysimeters and test-field studies. Instead of lysimeters we used pots (Israel) and one- liter cone-tainers (USA). We conducted one field study but in spite of major pretreatments the soils still exhibited high enough P from previous experiments so no differences between control and P additions were noticeable. Due to time constrains the field study was discontinued. Background: Phosphorous, a non-renewable resource, has been applied extensively in fields to increase crop yield, yet consequently has increased the potential of waterway eutrophication. Our proposal impetus is the need to develop an innovative method of P capturing, recycling and reuse that will sustain agricultural productivity while concurrently reducing the level of P discharge from and to agricultural settings. Major Conclusions & Achievements: An innovative approach was developed for P removal from soil leachate, dairy wastewater (Israel), and swine effluents (USA) using Al-based water treatment residuals (Al- WTR) to create an organic-Al-WTR composite (Al/O-WTR), potentially capable of serving as a P fertilizer source. The Al-WTR removed 95% inorganic-P, 80% to 99.9% organic P, and over 60% dissolved organic carbon from the agro-industrial waste streams. Organic C accumulation on particles surfaces possibly enhanced weak P bonding and facilitated P desorption. Analysis by scanning electron microscope (SEM- EDS), indicated that P was sparsely sorbed on both calcic and Al (hydr)oxide surfaces. Sorption of P onto WW-Al/O-WTR was reversible due to weak Ca-P and Al-P bonds induced by the slight alkaline nature and in the presence of organic moieties. Synchrotron-based microfocused X-ray fluorescence (micro-XRF) spectrometry, bulk P K-edge X-ray absorption near edge structure spectroscopy (XANES), and P K-edge micro-XANES spectroscopy indicated that adsorption was the primary P retention mechanism in the Al- WTR materials. However, distinct apatite- or octocalciumphosphatelike P grains were also observed. Synchrotron micro-XRF mapping further suggested that exposure of the aggregate exteriors to wastewater caused P to diffuse into the porous Al-WTR aggregates. Organic P species were not explicitly identified via P K-edge XANES despite high organic matter content, suggesting that organic P may have been predominantly associated with mineral surfaces. In screen houses experiments (Israel) we showed that the highest additions of Al/O-WTR (5 and 7 g kg⁻¹) produced the highest lettuce (Lactuca sativa L. var. longifolial) yield. Lettuce yield and P concentration were similar across treatments, indicating that Al/O- WTR can provide sufficient P to perform similarly to common fertilizers. A greenhouse study (USA) was utilized to compare increasing rates of swine wastewater derived Al/O-WTR and inorganic P fertilizer (both applied at 33.6, 67.3, and 134.5 kg P₂O₅ ha⁻¹) to supply plant-available P to spring wheat (TriticumaestivumL.) in either sandy loam or sandy clay loam soil. Spring wheat straw and grain P uptake were comparable across all treatments in the sandy loam, while Al/O-WTR application to the sandy clay loam reduced straw and grain P uptake. The Al/O-WTR did not affect soil organic P concentrations, but did increase phosphatase activity in both soils; this suggests that Al/O-WTR application stimulated microorganisms and enhance the extent to which microbial communities can mineralize Al/O-WTR-bound organic P. Implications: Overall, results suggest that creating a new P fertilizer from Al-WTR and agro-industrial waste sources may be a feasible alternative to mining inorganic P fertilizer sources, while protecting the environment from unnecessary waste disposal.
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Shenker, Moshe, Paul R. Bloom, Abraham Shaviv, Adina Paytan, Barbara J. Cade-Menun, Yona Chen et Jorge Tarchitzky. Fate of Phosphorus Originated from Treated Wastewater and Biosolids in Soils : Speciation, Transport, and Accumulation. United States Department of Agriculture, juin 2011. http://dx.doi.org/10.32747/2011.7697103.bard.
Texte intégralRésumé :
Beneficial use of reclaimed wastewater (RW) and biosolids (BS) in soils is accompanied by large input of sewage-originated P. Prolonged application may result in P accumulation up to levelsBeneficial use of reclaimed wastewater (RW) and biosolids (BS) in soils is accompanied by large input of sewage-originated P. Prolonged application may result in P accumulation up to levels that impair plant nutrition, increase P loss, and promote eutrophication in downstream waters. This study aims to shed light on the RW- and BS-P forms in soils and to follow the processes that determine P reactivity, solubility, availability, and loss in RW and BS treated soils. The Technion group used sequential P extraction combined with measuring stable oxygen isotopic composition in phosphate (δ18OP) and with 31P-NMR studies to probe P speciation and transformations in soils irrigated with RW or fresh water (FW). The application of the δ18OP method to probe inorganic P (Pi) speciation and transformations in soils was developed through collaboration between the Technion and the UCSC groups. The method was used to trace Pi in water-, NaHCO3-, NaOH-, and HCl- P fractions in a calcareous clay soil (Acre, Israel) irrigated with RW or FW. The δ18OP signature changes during a month of incubation indicated biogeochemical processes. The water soluble Pi (WSPi) was affected by enzymatic activity yielding isotopic equilibrium with the water molecules in the soil solution. Further it interacted rapidly with the NaHCO3-Pi. The more stable Pi pools also exhibited isotopic alterations in the first two weeks after P application, likely related to microbial activity. Isotopic depletion which could result from organic P (PO) mineralization was followed by enrichment which may result from biologic discrimination in the uptake. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with RW. Specific P compounds were identified by the Technion group, using solution-state 31P-NMR in wastewater and in soil P extracts from Acre soils irrigated by RW and FW. Few identified PO compounds (e.g., D-glucose-6-phosphate) indicated coupled transformations of P and C in the wastewater. The RW soil retained higher P content, mainly in the labile fractions, but lower labile PO, than the FW soil; this and the fact that P species in the various soil extracts of the RW soil appear independent of P species in the RW are attributed to enhanced biological activity and P recycling in the RW soil. Consistent with that, both soils retained very similar P species in the soil pools. The HUJ group tested P stabilization to maximize the environmental safe application rates and the agronomic beneficial use of BS. Sequential P extraction indicated that the most reactive BS-P forms: WSP, membrane-P, and NaHCO3-P, were effectively stabilized by ferrous sulfate (FeSul), calcium oxide (CaO), or aluminum sulfate (alum). After applying the stabilized BS, or fresh BS (FBS), FBS compost (BSC), or P fertilizer (KH2PO4) to an alluvial soil, P availability was probed during 100 days of incubation. A plant-based bioassay indicated that P availability followed the order KH2PO4 >> alum-BS > BSC ≥ FBS > CaO-BS >> FeSul-BS. The WSPi concentration in soil increased following FBS or BSC application, and P mineralization further increased it during incubation. In contrast, the chemically stabilized BS reduced WSPi concentrations relative to the untreated soil. It was concluded that the chemically stabilized BS effectively controlled WSPi in the soil while still supplying P to support plant growth. Using the sequential extraction procedure the persistence of P availability in BS treated soils was shown to be of a long-term nature. 15 years after the last BS application to MN soils that were annually amended for 20 years by heavy rates of BS, about 25% of the added BS-P was found in the labile fractions. The UMN group further probed soil-P speciation in these soils by bulk and micro X-ray absorption near edge structure (XANES). This newly developed method was shown to be a powerful tool for P speciation in soils. In a control soil (no BS added), 54% of the total P was PO and it was mostly identified as phytic acid; 15% was identified as brushite and 26% as strengite. A corn crop BS amended soil included mostly P-Fe-peat complex, variscite and Al-P-peat complex but no Ca-P while in a BS-grass soil octacalcium phosphate was identified and o-phosphorylethanolamine or phytic acid was shown to dominate the PO fraction that impair plant nutrition, increase P loss, and promote eutrophication in downstream waters. This study aims to shed light on the RW- and BS-P forms in soils and to follow the processes that determine P reactivity, solubility, availability, and loss in RW and BS treated soils. The Technion group used sequential P extraction combined with measuring stable oxygen isotopic composition in phosphate (δ18OP) and with 31P-NMR studies to probe P speciation and transformations in soils irrigated with RW or fresh water (FW). The application of the δ18OP method to probe inorganic P (Pi) speciation and transformations in soils was developed through collaboration between the Technion and the UCSC groups. The method was used to trace Pi in water-, NaHCO3-, NaOH-, and HCl- P fractions in a calcareous clay soil (Acre, Israel) irrigated with RW or FW. The δ18OP signature changes during a month of incubation indicated biogeochemical processes. The water soluble Pi (WSPi) was affected by enzymatic activity yielding isotopic equilibrium with the water molecules in the soil solution. Further it interacted rapidly with the NaHCO3-Pi. The more stable Pi pools also exhibited isotopic alterations in the first two weeks after P application, likely related to microbial activity. Isotopic depletion which could result from organic P (PO) mineralization was followed by enrichment which may result from biologic discrimination in the uptake. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with RW. Specific P compounds were identified by the Technion group, using solution-state 31P-NMR in wastewater and in soil P extracts from Acre soils irrigated by RW and FW. Few identified PO compounds (e.g., D-glucose-6-phosphate) indicated coupled transformations of P and C in the wastewater. The RW soil retained higher P content, mainly in the labile fractions, but lower labile PO, than the FW soil; this and the fact that P species in the various soil extracts of the RW soil appear independent of P species in the RW are attributed to enhanced biological activity and P recycling in the RW soil. Consistent with that, both soils retained very similar P species in the soil pools. The HUJ group tested P stabilization to maximize the environmental safe application rates and the agronomic beneficial use of BS. Sequential P extraction indicated that the most reactive BS-P forms: WSP, membrane-P, and NaHCO3-P, were effectively stabilized by ferrous sulfate (FeSul), calcium oxide (CaO), or aluminum sulfate (alum). After applying the stabilized BS, or fresh BS (FBS), FBS compost (BSC), or P fertilizer (KH2PO4) to an alluvial soil, P availability was probed during 100 days of incubation. A plant-based bioassay indicated that P availability followed the order KH2PO4 >> alum-BS > BSC ≥ FBS > CaO-BS >> FeSul-BS. The WSPi concentration in soil increased following FBS or BSC application, and P mineralization further increased it during incubation. In contrast, the chemically stabilized BS reduced WSPi concentrations relative to the untreated soil. It was concluded that the chemically stabilized BS effectively controlled WSPi in the soil while still supplying P to support plant growth. Using the sequential extraction procedure the persistence of P availability in BS treated soils was shown to be of a long-term nature. 15 years after the last BS application to MN soils that were annually amended for 20 years by heavy rates of BS, about 25% of the added BS-P was found in the labile fractions. The UMN group further probed soil-P speciation in these soils by bulk and micro X-ray absorption near edge structure (XANES). This newly developed method was shown to be a powerful tool for P speciation in soils. In a control soil (no BS added), 54% of the total P was PO and it was mostly identified as phytic acid; 15% was identified as brushite and 26% as strengite. A corn crop BS amended soil included mostly P-Fe-peat complex, variscite and Al-P-peat complex but no Ca-P while in a BS-grass soil octacalcium phosphate was identified and o-phosphorylethanolamine or phytic acid was shown to dominate the PO fraction.
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Berkowitz, Jacob, Christine VanZomeren, Nia Hurst et Kristina Sebastian. An evaluation of soil phosphorus storage capacity (SPSC) at proposed wetland restoration locations in the western Lake Erie Basin. Engineer Research and Development Center (U.S.), septembre 2021. http://dx.doi.org/10.21079/11681/42108.
Texte intégralRésumé :
Historical loss of wetlands coupled with excess phosphorus (P) loading at watershed scales have degraded water quality in portions of the western Lake Erie Basin (WLEB). In response, efforts are underway to restore wetlands and decrease P loading to surface waters. Because wetlands have a finite capacity to retain P, researchers have developed techniques to determine whether wetlands function as P sources or sinks. The following technical report evaluates the soil P storage capacity (SPSC) at locations under consideration for wetland restoration in collaboration with the Great Lakes Restoration Initiative (GLRI) and the H2Ohio initiative. Results indicate that the examined soils display a range of P retention capacities, reflecting historic land-use patterns and management regimes. However, the majority of study locations exhibited some capacity to sequester additional P. The analysis supports development of rankings and comparative analyses of areas within a specific land parcel, informing management through design, avoidance, removal, or remediation of potential legacy P sources. Additionally, the approaches described herein support relative comparisons between multiple potential wetland development properties. These results, in conjunction with other data sources, can be used to target, prioritize, justify, and improve decision-making for wetland management activities in the WLEB.
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Mitchell, Brian G., Amir Neori, Charles Yarish, D. Allen Davis, Tzachi Samocha et Lior Guttman. The use of aquaculture effluents in spray culture for the production of high protein macroalgae for shrimp aqua-feeds. United States Department of Agriculture, janvier 2013. http://dx.doi.org/10.32747/2013.7597934.bard.
Texte intégralRésumé :
The FAO has projected a doubling in world demand for seafood during the 21 ed from aquaculture of marine fish and shrimps fed primarily on fishmeal-based aquafeeds. However, current practices of high intensity monoculture of shrimp in coastal ponds and fish in offshore pens have been strongly criticized as being ecologically and socially unsustainable. This view derives from un- checked eutrophication of coastal marine ecosystems from fish farm effluents, and the destruction of coastal estuarine ecosystems by shrimp farm constructions, plus aquaculture’s reliance on wild-caught small fish - which are excellent food for humans, but instead are rendered into fishmeal and fish oil for formulating aquafeeds. Fishmeal-sparing and waste- reduction aquafeeds can only delay the time when fed aquaculture product are priced out of affordability for most consumers. Additionally, replacement of fishmeal protein and fish oil by terrestrial plant sources such as soybean meal and oil directly raises food costs for human communities in developing nations. New formulations incorporating sustainably-produced marine algal proteins and oils are growing in acceptance as viable and practical alternatives. This BARD collaborative research project investigated a sustainable water-sparing spray/drip culture method for producing high-protein marine macrophyte meals for incorporation into marine shrimp and fish diets. The spray culture work was conducted at laboratory-scale in the USA (UCSD-SIO) using selected Gracilariaand Ulvastrains isolated and supplied by UCONN, and outdoors at pilot-scale in Israel (IOLR-NCM) using local strains of Ulvasp., and nitrogen/phosphorus-enriched fish farm effluent to fertilize the spray cultures and produce seaweed biomass and meals containing up to 27% raw protein (dry weight content). Auburn University (USA) in consultation with TAMUS (USA) used the IOLR meals to formulate diets and conduct marine shrimp feeding trials, which resulted in mixed outcomes, indicating further work was needed to chemically identify and remove anti-nutritional elements present in the IOLR-produced seaweed meals.
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Cytryn, Eddie, Mark R. Liles et Omer Frenkel. Mining multidrug-resistant desert soil bacteria for biocontrol activity and biologically-active compounds. United States Department of Agriculture, janvier 2014. http://dx.doi.org/10.32747/2014.7598174.bard.
Texte intégralRésumé :
Control of agro-associated pathogens is becoming increasingly difficult due to increased resistance and mounting restrictions on chemical pesticides and antibiotics. Likewise, in veterinary and human environments, there is increasing resistance of pathogens to currently available antibiotics requiring discovery of novel antibiotic compounds. These drawbacks necessitate discovery and application of microorganisms that can be used as biocontrol agents (BCAs) and the isolation of novel biologically-active compounds. This highly-synergistic one year project implemented an innovative pipeline aimed at detecting BCAs and associated biologically-active compounds, which included: (A) isolation of multidrug-resistant desert soil bacteria and root-associated bacteria from medicinal plants; (B) invitro screening of bacterial isolates against known plant, animal and human pathogens; (C) nextgeneration sequencing of isolates that displayed antagonistic activity against at least one of the model pathogens and (D) in-planta screening of promising BCAs in a model bean-Sclerotiumrolfsii system. The BCA genome data were examined for presence of: i) secondary metabolite encoding genes potentially linked to the anti-pathogenic activity of the isolates; and ii) rhizosphere competence-associated genes, associated with the capacity of microorganisms to successfully inhabit plant roots, and a prerequisite for the success of a soil amended BCA. Altogether, 56 phylogenetically-diverse isolates with bioactivity against bacterial, oomycete and fungal plant pathogens were identified. These strains were sent to Auburn University where bioassays against a panel of animal and human pathogens (including multi-drug resistant pathogenic strains such as A. baumannii 3806) were conducted. Nineteen isolates that showed substantial antagonistic activity against at least one of the screened pathogens were sequenced, assembled and subjected to bioinformatics analyses aimed at identifying secondary metabolite-encoding and rhizosphere competence-associated genes. The genome size of the bacteria ranged from 3.77 to 9.85 Mbp. All of the genomes were characterized by a plethora of secondary metabolite encoding genes including non-ribosomal peptide synthase, polyketidesynthases, lantipeptides, bacteriocins, terpenes and siderophores. While some of these genes were highly similar to documented genes, many were unique and therefore may encode for novel antagonistic compounds. Comparative genomic analysis of root-associated isolates with similar strains not isolated from root environments revealed genes encoding for several rhizospherecompetence- associated traits including urea utilization, chitin degradation, plant cell polymerdegradation, biofilm formation, mechanisms for iron, phosphorus and sulfur acquisition and antibiotic resistance. Our labs are currently writing a continuation of this feasibility study that proposes a unique pipeline for the detection of BCAs and biopesticides that can be used against phytopathogens. It will combine i) metabolomic screening of strains from our collection that contain unique secondary metabolite-encoding genes, in order to isolate novel antimicrobial compounds; ii) model plant-based experiments to assess the antagonistic capacities of selected BCAs toward selected phytopathogens; and iii) an innovative next-generation-sequencing based method to monitor the relative abundance and distribution of selected BCAs in field experiments in order to assess their persistence in natural agro-environments. We believe that this integrated approach will enable development of novel strains and compounds that can be used in large-scale operations.
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Crowley, David E., Dror Minz et Yitzhak Hadar. Shaping Plant Beneficial Rhizosphere Communities. United States Department of Agriculture, juillet 2013. http://dx.doi.org/10.32747/2013.7594387.bard.
Texte intégralRésumé :
PGPR bacteria include taxonomically diverse bacterial species that function for improving plant mineral nutrition, stress tolerance, and disease suppression. A number of PGPR are being developed and commercialized as soil and seed inoculants, but to date, their interactions with resident bacterial populations are still poorly understood, and-almost nothing is known about the effects of soil management practices on their population size and activities. To this end, the original objectives of this research project were: 1) To examine microbial community interactions with plant-growth-promoting rhizobacteria (PGPR) and their plant hosts. 2) To explore the factors that affect PGPR population size and activity on plant root surfaces. In our original proposal, we initially prqposed the use oflow-resolution methods mainly involving the use of PCR-DGGE and PLFA profiles of community structure. However, early in the project we recognized that the methods for studying soil microbial communities were undergoing an exponential leap forward to much more high resolution methods using high-throughput sequencing. The application of these methods for studies on rhizosphere ecology thus became a central theme in these research project. Other related research by the US team focused on identifying PGPR bacterial strains and examining their effective population si~es that are required to enhance plant growth and on developing a simulation model that examines the process of root colonization. As summarized in the following report, we characterized the rhizosphere microbiome of four host plant species to determine the impact of the host (host signature effect) on resident versus active communities. Results of our studies showed a distinct plant host specific signature among wheat, maize, tomato and cucumber, based on the following three parameters: (I) each plant promoted the activity of a unique suite of soil bacterial populations; (2) significant variations were observed in the number and the degree of dominance of active populations; and (3)the level of contribution of active (rRNA-based) populations to the resident (DNA-based) community profiles. In the rhizoplane of all four plants a significant reduction of diversity was observed, relative to the bulk soil. Moreover, an increase in DNA-RNA correspondence indicated higher representation of active bacterial populations in the residing rhizoplane community. This research demonstrates that the host plant determines the bacterial community composition in its immediate vicinity, especially with respect to the active populations. Based on the studies from the US team, we suggest that the effective population size PGPR should be maintained at approximately 105 cells per gram of rhizosphere soil in the zone of elongation to obtain plant growth promotion effects, but emphasize that it is critical to also consider differences in the activity based on DNA-RNA correspondence. The results ofthis research provide fundamental new insight into the composition ofthe bacterial communities associated with plant roots, and the factors that affect their abundance and activity on root surfaces. Virtually all PGPR are multifunctional and may be expected to have diverse levels of activity with respect to production of plant growth hormones (regulation of root growth and architecture), suppression of stress ethylene (increased tolerance to drought and salinity), production of siderophores and antibiotics (disease suppression), and solubilization of phosphorus. The application of transcriptome methods pioneered in our research will ultimately lead to better understanding of how management practices such as use of compost and soil inoculants can be used to improve plant yields, stress tolerance, and disease resistance. As we look to the future, the use of metagenomic techniques combined with quantitative methods including microarrays, and quantitative peR methods that target specific genes should allow us to better classify, monitor, and manage the plant rhizosphere to improve crop yields in agricultural ecosystems. In addition, expression of several genes in rhizospheres of both cucumber and whet roots were identified, including mostly housekeeping genes. Denitrification, chemotaxis and motility genes were preferentially expressed in wheat while in cucumber roots bacterial genes involved in catalase, a large set of polysaccharide degradation and assimilatory sulfate reduction genes were preferentially expressed.