Electrochemical performance of La2O3/Li2O/TiO2 nano-particle coated cathode material LiFePO4.

PubMed

Wang, Hong; Yang, Chi; Liu, Shu-Xin

2014-09-01

Cathode material, LiFePO4 was modified by coating with a thin layer of La2O3/Li2O/TiO2 nano-particles for improving its performance for lithium ion batteries. The morphology and structure of the modified cathode material were characterized by powder X-ray diffraction, scanning electron microcopy and AES. The performance of the battery with the modified cathode material, including cycling stability, C-rate discharge was examined. The results show that the battery composed of the coated cathode materials can discharge at a large current density and show stable cycling performance in the range from 2.5 to 4.0 V. The rate of Li ion diffusion increases in the battery with the La2O3/Li2O/TiO2-coated LiFePO4 as a cathode and the coating layer may acts as a faster ion conductor (La(2/3-x)Li(3x)TiO3).

Highly efficient photocatalytic degradation of methylene blue by PoPD/TiO2 nanocomposite

PubMed Central

Dong, Wenping; Cui, Guanwei; Ren, Zongming

2017-01-01

The poly-o-phenylenediamine (PoPD)/TiO2 nanocomposite was successfully synthesized via ‘in situ’ oxidative polymerization method. The modified photocatalysts were characterized by BET, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrarad spectra (FT-IR), thermogravimrtic analysis (TGA), X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible diffuse reflectance spectrum (UV-Vis DRS) and Photocurrent Test. The results showed that the PoPD exists on the surface of TiO2, the presence of PoPD does not impact on the lattice structure and grain size of TiO2, and the presence of PoPD enhances the visible response and photoelectric property. The photocatalytic degradation of methylene blue (MB) was chosen as a model reaction to evaluate the photocatalytic activities of TiO2 and PoPD/TiO2. The optimal preparation condition was the molar ratio of oPD to TiO2 = 3:1, HCl concentration = 1.2 mol/L, the molar ratio of APS to oPD = 1:1. The apparent first-order rate constant kapp of PoPD/TiO2 nanocomposite was 0.0098 min-1, which is 6 times higher than TiO2 (0.0016 min-1). Meanwhile, the PoPD/TiO2 nanocomposites showed excellent photocatalytic stability, and the photocatalytic stability was depended on the stability of structure. At last, the photocatalytic mechanism of POPD/TiO2 nanocomposites was also proposed based on the synergetic effect between TiO2 and PoPD. PMID:28329007

Properties and Crystallization Phenomena in Li2Si2O5–Ca5(PO4)3F and Li2Si2O5–Sr5(PO4)3F Glass–Ceramics Via Twofold Internal Crystallization

PubMed Central

Rampf, Markus; Dittmer, Marc; Ritzberger, Christian; Schweiger, Marcel; Höland, Wolfram

2015-01-01

The combination of specific mechanical, esthetic, and chemical properties is decisive for the application of materials in prosthodontics. Controlled twofold crystallization provides a powerful tool to produce special property combinations for glass–ceramic materials. The present study outlines the potential of precipitating Ca5(PO4)3F as well as Sr5(PO4)3F as minor crystal phases in Li2Si2O5 glass–ceramics. Base glasses with different contents of CaO/SrO, P2O5, and F− were prepared within the glasses of the SiO2–Li2O–K2O–CaO/SrO–Al2O3–P2O5–F system. Preliminary studies of nucleation by means of XRD and scanning electron microscopy (SEM) of the nucleated base glasses revealed X-ray amorphous phase separation phenomena. Qualitative and quantitative crystal phase analyses after crystallization were conducted using XRD in combination with Rietveld refinement. As a main result, a direct proportional relationship between the content of apatite-forming components in the base glasses and the content of apatite in the glass–ceramics was established. The microstructures of the glass–ceramics were investigated using SEM. Microstructural and mechanical properties were found to be dominated by Li2Si2O5 crystals and quite independent of the content of the apatite present in the glass–ceramics. Biaxial strengths of up to 540 MPa were detected. Ca5(PO4)3F and Sr5(PO4)3F influence the translucency of the glass–ceramics and, hence, help to precisely tailor the properties of Li2Si2O5 glass–ceramics. The authors conclude that the twofold crystallization of Li2Si2O5–Ca5(PO4)3F or Li2Si2O5–Sr5(PO4)3F glass–ceramics involves independent solid-state reactions, which can be controlled via the chemical composition of the base glasses. The influence of the minor apatite phase on the optical properties helps to achieve new combinations of features of the glass–ceramics and, hence, displays new potential for dental applications. PMID:26389112

Syntheses and characterization of phosphonates and diphosphonates of molybdenum, A4[(MoO3)5(O3PR)2]·xH2O, A2[Mo2O5(O3PR)2] and A2[Mo2O5(O3P-R-PO3)] (A = K, Rb, Cs, Tl, NH4).

PubMed

Elias Jesu Packiam, D; Vidyasagar, Kanamaluru

2017-11-28

Twenty new molybdenum phosphonates and diphosphonates have been synthesized and structurally characterized by single crystal and powder X-ray diffraction, CHN analyses, spectroscopic and thermal studies. Four of them are molecular phenyl- and benzyl-phosphonates containing discrete [(MoO 3 ) 5 (O 3 PR) 2 ] 4- (R = Ph or CH 2 Ph) cyclic anions. The sixteen non-molecular compounds are layered isostructural phenylphosphonates, A 2 [Mo 2 O 5 (O 3 PPh) 2 ] (A = NH 4 , Tl, Rb, Cs) and K 1.5 (H 3 O) 0.5 [Mo 2 O 5 (O 3 PPh) 2 ] and the corresponding diphosphonate compounds with pillared anionic layers, A 2 [Mo 2 O 5 (O 3 P(CH 2 ) 3 PO 3 )], A 2 [Mo 2 O 5 (O 3 P(CH 2 ) 4 PO 3 )] and A 2 [Mo 2 O 5 (O 3 P(C 6 H 4 )PO 3 )]. The A + ions reside in the interlayer region as well as in the cavities within the anionic layers.

Application of phosphorescence quenching by O2 to the investigation of O2 delivery to ocular tissues

NASA Astrophysics Data System (ADS)

Chamot, Stephane R.; Petrig, Benno L.; Pournaras, Constantin J.; Percicot, Christine L.; Lambrou, George N.; Riva, Charles E.

2001-10-01

The technique of phosphorescence quenching by O2 (PQ) allows the non-invasive measurement of the partial pressure of oxygen in blood (pO2blood). This technique and its application to the investigation of the pO2blood in the microvasculature of the retina and optic nerve head (ONH) of two animal species is described. Using the imaging mode of PQ, 2-dimensional pO2blood maps were obtained to investigate the response of the pO2blood to various physiological stimuli in miniature pigs and the effect of experimental glaucoma in monkeys. Applied in its focal mode, PQ allows measurements of the pO2blood with a time resolution of 1 second and is adequate to investigate the pO2blood time course during light stimulation.

pO(2) measurements by phosphorescence quenching: characteristics and applications of an automated system.

PubMed

Kerger, Heinz; Groth, Gesine; Kalenka, Armin; Vajkoczy, Peter; Tsai, Amy G; Intaglietta, Marcos

2003-01-01

An automated system for pO(2) analysis based upon phosphorescence quenching was tested. The system was calibrated in vitro with capillary samples of saline and blood. Results were compared to a conventional measuring procedure wherein pO(2) was calculated off-line by computer fitting of phosphorescence decay signals. PO(2) measurements obtained by the automated system were correlated (r(2) = 0.98) with readings simultaneously generated by a blood gas analyzer, accuracy being highest in the low (0-20 mm Hg) and medium pO(2) ranges (21-70 mm Hg). Measurements in in vivo studies in the hamster skin-fold preparation were similar to previously reported results. The automated system fits the phosphorescence decay data to a single exponential and allows repeated pO(2) measurements in rapid sequence.

A second polymorph with composition Co3(PO4)2·H2O

PubMed Central

Lee, Young Hoon; Clegg, Jack K.; Lindoy, Leonard F.; Lu, G. Q. Max; Park, Yu-Chul; Kim, Yang

2008-01-01

Single crystals of Co3(PO4)2·H2O, tricobalt(II) bis­[ortho­phosphate(V)] monohydrate, were obtained under hydro­thermal conditions. The compound is the second polymorph of this composition and is isotypic with its zinc analogue, Zn3(PO4)2·H2O. Three independent Co2+ cations are bridged by two independent orthophosphate anions. Two of the metal cations exhibit a distorted tetra­hedral coordination while the third exhibits a considerably distorted [5 + 1] octa­hedral coordination environment with one very long Co—O distance of 2.416 (3) Å. The former cations are bonded to four different phosphate anions, and the latter cation is bonded to four anions (one of which is bidentate) and one water mol­ecule, leading to a framework structure. Additional hydrogen bonds of the type O—H⋯O stabilize this arrangement. PMID:21200979

Special hydrogen bonds observed in two monovalent metal carboxylate-phosphinates: {NaH(Phsbnd PO2sbnd C2H4sbnd COOH)2}∞ and {[KH(Phsbnd PO2sbnd C2H4sbnd COOH)2]·H2O}∞

NASA Astrophysics Data System (ADS)

Zhao, Cui-Cui; Zhang, Jian-Wei; Zhou, Zhong-Gao; Du, Zi-Yi

2013-02-01

The addition of strong base such as sodium hydroxide or potassium hydroxide to the aqueous solution of (2-carboxyethyl)(phenyl)phosphinic acid afforded two novel monovalent metal carboxylate-phosphinates, namely, {NaH(Phsbnd PO2sbnd C2H4sbnd COOH)2}∞ (1) and {[KH(Phsbnd PO2sbnd C2H4sbnd COOH)2]·H2O}∞ (2). They represent the first examples of phosphinate containing short, symmetric or almost symmetric O⋯H⋯O hydrogen bonds.

Detailing the relation between renal T2* and renal tissue pO2 using an integrated approach of parametric magnetic resonance imaging and invasive physiological measurements.

PubMed

Pohlmann, Andreas; Arakelyan, Karen; Hentschel, Jan; Cantow, Kathleen; Flemming, Bert; Ladwig, Mechthild; Waiczies, Sonia; Seeliger, Erdmann; Niendorf, Thoralf

2014-08-01

This study was designed to detail the relation between renal T2* and renal tissue pO2 using an integrated approach that combines parametric magnetic resonance imaging (MRI) and quantitative physiological measurements (MR-PHYSIOL). Experiments were performed in 21 male Wistar rats. In vivo modulation of renal hemodynamics and oxygenation was achieved by brief periods of aortic occlusion, hypoxia, and hyperoxia. Renal perfusion pressure (RPP), renal blood flow (RBF), local cortical and medullary tissue pO2, and blood flux were simultaneously recorded together with T2*, T2 mapping, and magnetic resonance-based kidney size measurements (MR-PHYSIOL). Magnetic resonance imaging was carried out on a 9.4-T small-animal magnetic resonance system. Relative changes in the invasive quantitative parameters were correlated with relative changes in the parameters derived from MRI using Spearman analysis and Pearson analysis. Changes in T2* qualitatively reflected tissue pO2 changes induced by the interventions. T2* versus pO2 Spearman rank correlations were significant for all interventions, yet quantitative translation of T2*/pO2 correlations obtained for one intervention to another intervention proved not appropriate. The closest T2*/pO2 correlation was found for hypoxia and recovery. The interlayer comparison revealed closest T2*/pO2 correlations for the outer medulla and showed that extrapolation of results obtained for one renal layer to other renal layers must be made with due caution. For T2* to RBF relation, significant Spearman correlations were deduced for all renal layers and for all interventions. T2*/RBF correlations for the cortex and outer medulla were even superior to those between T2* and tissue pO2. The closest T2*/RBF correlation occurred during hypoxia and recovery. Close correlations were observed between T2* and kidney size during hypoxia and recovery and for occlusion and recovery. In both cases, kidney size correlated well with renal vascular conductance

The influence of Na + and Ca 2+ ions on the SiO 2-AlPO 4 materials structure — IR and Raman studies

NASA Astrophysics Data System (ADS)

Rokita, M.; Mozgawa, W.; Handke, M.

2001-09-01

The series of samples containing 0-20 mol% of NaCaPO4 and 20-0 mol% of AlPO4, respectively, with the constant amount of SiO2 (80 mol%) have been selected. The materials were prepared using both sol-gel as well as aerosil pseudo-aqua solution method. The AlPO4·SiO2 and NaCaPO4·SiO2 (80 mol% of SiO2) samples have been prepared. IR and Raman spectra of these samples are presented. The spectra of materials from NaCaPO4-AlPO4-SiO2 system are compared to those of NaCaPO4·SiO2 and AlPO4·SiO2 sample (samples without Al3+ or Na+ and Ca2+ cations, respectively). The studies have enabled us to identify the bands arising from the internal and lattice vibrations. The slight differences between the spectra of sol-gel and aerosil pseudo-aqua solution materials are pointed out and discussed. The influence of Na+ and Ca2+ ions on the AlPO4-SiO2 materials structure is analysed.

Na7Cr4(P2O7)4PO4

PubMed Central

Bourguiba Fakhar, Noura; Zid, Mohamed Faouzi; Driss, Ahmed

2013-01-01

The title compound, hepta­sodium tetra­chromium(III) tetra­kis­(diphosphate) orthophosphate, was synthesized by solid-state reaction. Its structure is isotypic with that of Na7 M 4(P2O7)4PO4 (M = In, Al) compounds and is made up from a three-dimensional [(CrP2O7)4PO4]7− framework with channels running along [001]. The three Na+ cations are located in the voids of the framework. One of the cations is situated on a general position, one is equally disordered around a twofold rotation axis and one is on a fourfold rotoinversion axis. The isolated PO4 tetra­hedron of the anionic framework is also situated on the -4 axis. Structural relationships between the title compound and different diphosphates containing MP2O11 units (M = Mo, V) are discussed. PMID:23723751

Photocatalytic activity of Ag3PO4 nanoparticle/TiO2 nanobelt heterostructures

NASA Astrophysics Data System (ADS)

Liu, Ruoyu; Hu, Peiguang; Chen, Shaowei

2012-10-01

Heterostructures based on Ag3PO4 nanoparticles and TiO2 nanobelts were prepared by a coprecipitation method. The crystalline structures were characterized by X-ray diffraction measurements. Electron microscopic studies showed that the Ag3PO4 nanoparticles and TiO2 nanobelts were in intimate contact which might be exploited to facilitate charge transfer between the two semiconductor materials. In fact, the heterostructures exhibited markedly enhanced photocatalytic activity as compared with unmodified TiO2 nanobelts or commercial TiO2 colloids in the photodegradation of methyl orange under UV irradiation. This was accounted for by the improved efficiency of interfacial charge separation thanks to the unique alignments of their band structures. Remarkably, whereas the photocatalytic activity of the heterostructure was comparable to that of Ag3PO4 nanoparticles alone, the heterostructures exhibited significantly better stability and reusability in repeated tests than the Ag3PO4 nanoparticles.

K2Ho(PO4)(WO4)

PubMed Central

Terebilenko, Katherina V.; Zatovsky, Igor V.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.; Shishkin, Oleg V.

2008-01-01

A new compound, dipotassium holmium(III) phosphate(V) tungstate(VI), K2Ho(PO4)(WO4), has been obtained during investigation of the K2O–P2O5–WO3–HoF3 phase system using the flux technique. The compound is isotypic with K2Bi(PO4)(WO4). Its framework structure consists of flat ∞ 2[HoPO4] layers parallel to (100) that are made up of ∞ 1[HoO8] zigzag chains inter­linked via slightly distorted PO4 tetra­hedra. WO4 tetra­hedra are attached above and below these layers, leaving space for the K+ counter-cations. The HoO8, PO4 and WO4 units exhibit 2 symmetry. PMID:21580811

Study on the Visible-Light Photocatalytic Performance and Degradation Mechanism of Diclofenac Sodium under the System of Hetero-Structural CuBi2O4/Ag3PO4 with H2O2

PubMed Central

Chen, Xiaojuan; Li, Ning; Xu, Song; Cai, Yumin

2018-01-01

Two kinds of CuBi2O4/Ag3PO4 with different heterojunction structures were prepared based on the combination of hydrothermal and in-situ precipitation methods with surfactant additives (sodium citrate and sodium stearate), and their characteristics were systematically resolved by X-ray Diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM)/ High-resolution Transmission Electron Microscopy (HRTEM), UV-vis Diffuse Reflectance Spectra (DRS) and Photoluminescence (PL). Meanwhile, the photocatalytic properties of the catalysts were determined for diclofenac sodium (DS) degradation and the photocatalytic mechanism was also explored. The results indicate that both of the two kinds of CuBi2O4/Ag3PO4 exhibit higher photocatalytic efficiency, mineralization rate, and stability than that of pure CuBi2O4 or Ag3PO4. Moreover, the catalytic activity of CuBi2O4/Ag3PO4 can be further enhanced by adding H2O2. The free radical capture experiments show that in the pure CuBi2O4/Ag3PO4 photocatalytic system, the OH• and O2•− are the main species participating in DS degradation; however, in the CuBi2O4/Ag3PO4 photocatalytic system with H2O2, all OH•, h+, and O2•− take part in the DS degradation, and the contribution order is OH• > h+ > O2•−. Accordingly, the photocatalytic mechanism of CuBi2O4/Ag3PO4 could be explained by the Z-Scheme theory, while the catalysis of CuBi2O4/Ag3PO4 with H2O2 follows the heterojunction energy band theory. PMID:29597267

Cherenkov excited phosphorescence-based pO2 estimation during multi-beam radiation therapy: phantom and simulation studies

NASA Astrophysics Data System (ADS)

Holt, Robert W.; Zhang, Rongxiao; Esipova, Tatiana V.; Vinogradov, Sergei A.; Glaser, Adam K.; Gladstone, David J.; Pogue, Brian W.

2014-09-01

Megavoltage radiation beams used in External Beam Radiotherapy (EBRT) generate Cherenkov light emission in tissues and equivalent phantoms. This optical emission was utilized to excite an oxygen-sensitive phosphorescent probe, PtG4, which has been developed specifically for NIR lifetime-based sensing of the partial pressure of oxygen (pO2). Phosphorescence emission, at different time points with respect to the excitation pulse, was acquired by an intensifier-gated CCD camera synchronized with radiation pulses delivered by a medical linear accelerator. The pO2 distribution was tomographically recovered in a tissue-equivalent phantom during EBRT with multiple beams targeted from different angles at a tumor-like anomaly. The reconstructions were tested in two different phantoms that have fully oxygenated background, to compare a fully oxygenated and a fully deoxygenated inclusion. To simulate a realistic situation of EBRT, where the size and location of the tumor is well known, spatial information of a prescribed region was utilized in the recovery estimation. The phantom results show that region-averaged pO2 values were recovered successfully, differentiating aerated and deoxygenated inclusions. Finally, a simulation study was performed showing that pO2 in human brain tumors can be measured to within 15 mmHg for edge depths less than 10-20 mm using the Cherenkov Excited Phosphorescence Oxygen imaging (CEPhOx) method and PtG4 as a probe. This technique could allow non-invasive monitoring of pO2 in tumors during the normal process of EBRT, where beams are generally delivered from multiple angles or arcs during each treatment fraction.

Cherenkov excited phosphorescence-based pO2 estimation during multi-beam radiation therapy: phantom and simulation studies.

PubMed

Holt, Robert W; Zhang, Rongxiao; Esipova, Tatiana V; Vinogradov, Sergei A; Glaser, Adam K; Gladstone, David J; Pogue, Brian W

2014-09-21

Megavoltage radiation beams used in External Beam Radiotherapy (EBRT) generate Cherenkov light emission in tissues and equivalent phantoms. This optical emission was utilized to excite an oxygen-sensitive phosphorescent probe, PtG4, which has been developed specifically for NIR lifetime-based sensing of the partial pressure of oxygen (pO2). Phosphorescence emission, at different time points with respect to the excitation pulse, was acquired by an intensifier-gated CCD camera synchronized with radiation pulses delivered by a medical linear accelerator. The pO2 distribution was tomographically recovered in a tissue-equivalent phantom during EBRT with multiple beams targeted from different angles at a tumor-like anomaly. The reconstructions were tested in two different phantoms that have fully oxygenated background, to compare a fully oxygenated and a fully deoxygenated inclusion. To simulate a realistic situation of EBRT, where the size and location of the tumor is well known, spatial information of a prescribed region was utilized in the recovery estimation. The phantom results show that region-averaged pO2 values were recovered successfully, differentiating aerated and deoxygenated inclusions. Finally, a simulation study was performed showing that pO2 in human brain tumors can be measured to within 15 mmHg for edge depths less than 10-20 mm using the Cherenkov Excited Phosphorescence Oxygen imaging (CEPhOx) method and PtG4 as a probe. This technique could allow non-invasive monitoring of pO2 in tumors during the normal process of EBRT, where beams are generally delivered from multiple angles or arcs during each treatment fraction.

H2O2 rejuvenation-mediated synthesis of stable mixed-morphology Ag3PO4 photocatalysts.

PubMed

Agbe, Henry; Raza, Nadeem; Dodoo-Arhin, David; Chauhan, Aditya; Kumar, Ramachandran Vasant

2018-04-01

Ag 3 PO 4 photocatalyst has attracted interest of the scientific community in recent times due to its reported high efficiency for water oxidation and dye degradation. However, Ag 3 PO 4 photo-corrodes if electron accepter such as AgNO 3 is not used as scavenger. Synthesis of efficient Ag 3 PO 4 followed by a simple protocol for regeneration of the photocatalyst is therefore a prerequisite for practical application. Herein, we present a facile method for the synthesis of a highly efficient Ag 3 PO 4 , whose photocatalytic efficiency was demonstrated using 3 different organic dyes: Methylene Blue (MB), Methyl orange (MO) and Rhodamine B (RhB) organic dyes for degradation tests. Approximately, 19 % of Ag 3 PO 4 is converted to Ag 0 after 4.30 hours of continuous UV-Vis irradiation in presence of MB organic dye. We have shown that the Ag/Ag 3 PO 4 composite can be rejuvenated by a simple chemical oxidation step after several cycles of photocatalysis tests. At an optimal pH of 6.5, a mixture of cubic, rhombic dodecahedron, nanosphere and nanocrystals morphologies of the photocatalyst was formed. H 2 O 2 served as the chemical oxidant to re-insert the surface metallic Ag into the Ag 3 PO 4 photocatalyst but also as the agent that can control morphology of the regenerated as-prepared photocatalyst without the need for any other morphology controlling Agent (MCA). Surprisingly, the as- regenerated Ag 3 PO 4 was found to have higher photocatalytic reactivity than the freshly made material and superior at least 17 times in comparison with the conventional Degussa TiO 2 , and some of TiO 2 composites tested in this work.

Protonic Conductors for Intermediate Temperature Fuel Cell Electrolytes: Superprotonic CsH2PO4 Stabilization and in-Doped SnP2O7 Structure Study

NASA Astrophysics Data System (ADS)

Martinez Salinas, Heber Jair

monoclinic structure, characteristic of room temperature CsH 2PO4, was the only phase present even after the samples had been heated for over 40 hours at a temperature of 250 °C. By using this novel contraption, this has been the first time that undoped CsH2PO 4 has achieved its high conductivity phase and maintained a stable conductivity for a significant amount of time in air, without the use of a humidified environment, and without high pressure in an AC impedance spectroscopy study. Finally, in-house and synchrotron X-ray diffraction studies performed in the Sn1-xInxP2O7 series showed the cubic structure characteristic of the undoped compound at room temperature remains present up to temperatures of 250 °C. Sn0.9In 0.1P2O7, which is known to have the highest conductivity of the compound series, presented an increased unit cell as compared to the rest of the series when measured in air. However, the increased unit cell was not observed when measured under vacuum or an inert gas. Doping did not produce any major distortions on the P2O7 tetrahedra.

Mechanical properties and in vitro bioactivity of Ca5(PO4)2SiO4 bioceramic.

PubMed

Lu, Wenhao; Duan, Wei; Guo, Yaping; Ning, Congqin

2012-02-01

Pure Ca(5)(PO(4))(2)SiO(4) bioceramic was first prepared by a sol-gel method using triethyl phosphate, tetraethoxysilane, and calcium nitrate tetrahydrate as original materials. Simulated body fluid (SBF) immersion tests revealed that Ca(5)(PO(4))(2)SiO(4) samples had a greater in vitro apatite-forming ability than hydroxyapatite (HA). After soaking Ca(5)(PO(4))(2)SiO(4) samples in the SBF for 1 day, bone-like apatite precipitated on the surfaces and the apatite layer became thicker with increasing the soaking time. However, few bone-like apatites precipitated on the HA samples even after soaking in the SBF for 7 days. The good in vitro bioactivity of Ca(5)(PO(4))(2)SiO(4) samples was attributed to the silanol (Si-OH) groups and greater solubility of Ca(5)(PO(4))(2)SiO(4). In addition, hot-pressed Ca(5)(PO(4))(2)SiO(4) ceramic exhibited lower bending strength and elastic modulus than hot-pressed HA, since the former had a lower relative density than the latter. The results have shown that Ca(5)(PO(4))(2)SiO(4) is a potential candidate material for bone repair. © The Author(s), 2010.

A V(IV) Hydroxyhydrogenomonophosphate with an Intersecting Tunnel Structure: HK 4[V 10O 10(H 2O) 2(OH) 4(PO 4) 7]·9H 2O

NASA Astrophysics Data System (ADS)

Berrah, F.; Guesdon, A.; Leclaire, A.; Borel, M. M.; Provost, J.; Raveau, B.

1999-12-01

A V(IV) hydroxyhydrogenomonophosphate HK4[V10O10(H2O)2(OH)4(PO4)7]·9H2O has been obtained, using hydrothermal conditions. Its structure, closely related to that of (CH3)2NH2K4[V10O10(H2O)2(OH)4(PO4)7]·4H2O, differs from the latter by its I41/a space group (instead of P43). This difference corresponds to a "disordering" of the vanadium atoms, with respect to the dimethyl ammonium phase. It is shown that this disorder, which appears in the form of "V5O22" units distributed at random, does not affect the oxygen framework. The analysis of this complex structure shows that it can be described from the stacking along c of [V8P7O38(OH)4(H2O)2]∞ layers interconnected through layers of isolated VO6 octahedra. In this structure, built up of VO6, VO5OH, and VO4(OH)(H2O) octahedra, of VO4OH pyramids, and of PO4 tetrahedra, large "toffee" tunnels and smaller ones with a tulip-shape section are running along a (or b). The first ones are stuffed with H2O molecules forming aquo tubes, where protons are likely "delocalized," whereas the second ones are occupied by K+ cations.

Vibrational spectroscopy of the phosphate mineral kovdorskite - Mg2PO4(OH)ṡ3H2O

NASA Astrophysics Data System (ADS)

Frost, Ray L.; López, Andrés; Xi, Yunfei; Granja, Amanda; Scholz, Ricardo; Lima, Rosa Malena Fernandes

2013-10-01

The mineral kovdorskite Mg2PO4(OH)ṡ3H2O was studied by electron microscopy, thermal analysis and vibrational spectroscopy. A comparison of the vibrational spectroscopy of kovdorskite is made with other magnesium bearing phosphate minerals and compounds. Electron probe analysis proves the mineral is very pure. The Raman spectrum is characterized by a band at 965 cm-1 attributed to the PO43- ν1 symmetric stretching mode. Raman bands at 1057 and 1089 cm-1 are attributed to the PO43- ν3 antisymmetric stretching modes. Raman bands at 412, 454 and 485 cm-1 are assigned to the PO43- ν2 bending modes. Raman bands at 536, 546 and 574 cm-1 are assigned to the PO43- ν4 bending modes. The Raman spectrum in the OH stretching region is dominated by a very sharp intense band at 3681 cm-1 assigned to the stretching vibration of OH units. Infrared bands observed at 2762, 2977, 3204, 3275 and 3394 cm-1 are attributed to water stretching bands. Vibrational spectroscopy shows that no carbonate bands are observed in the spectra; thus confirming the formula of the mineral as Mg2PO4(OH)ṡ3H2O.

Solid state coordination chemistry: structural consequences of variations in tether length in the oxovanadium-copper-bisterpy-[O3P(CH2)nPO3]4- system, n= 1-6 (bisterpy = 2,2':4',4'':2'',2'''-quarterpyridyl-6',6''-di-2-pyridine).

PubMed

Ouellette, Wayne; Koo, Bon-Kweon; Burkholder, Eric; Golub, Vladimir; O'Connor, C J; Zubieta, Jon

2004-05-21

Hydrothermal reactions of Na3VO4, an appropriate Cu(II) source, bisterpy and an organodiphosphonate, H2O3P(CH2)nPO3H2 (n = 1-6) yielded a family of materials of the type [Cu2(bisterpy)]4+/VxOy(n-)/[O3P(CH2)nPO3]4-. This family of bimetallic oxides is characterized by an unusual structural diversity. The oxides [[Cu2(bisterpy)]V2O4[O3PCH2PO3H]2] (1), [[Cu2(bisterpy)(H2O)]VO2[O3P(CH2)3PO3][HO3P(CH2)3PO3H2

Synthesis, structure and NMR characterization of a new monomeric aluminophosphate [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4 containing four different types of monophosphates

NASA Astrophysics Data System (ADS)

Chen, Peng; Li, Jiyang; Xu, Jun; Duan, Fangzheng; Deng, Feng; Xu, Ruren

2009-03-01

A new zero-dimensional (0D) aluminophosphate monomer [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4 (designated AlPO-CJ38) with Al/P ratio of 1/6 has been solvothermally prepared by using racemic cobalt complex dl-Co(en) 3Cl 3 as the template. The Al atom is octahedrally linked to six P atoms via bridging oxygen atoms, forming a unique [Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2] 6- monomer. Notably, there exists intramolecular symmetrical O⋯H⋯O bonds, which results in pseudo-4-rings stabilized by the strong H-bonding interactions. The structure is also featured by the existence of four different types of monophosphates that have been confirmed by 31P NMR and 1H NMR spectra. The crystal data are as follows: AlPO-CJ38, [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4, M = 1476.33, monoclinic, C2/ c (No. 15), a = 36.028(7) Å, b = 8.9877(18) Å, c = 16.006(3) Å, β = 100.68(3)°, U = 5093.2(18) Å 3,Z = 4, R1 = 0.0509 ( I > 2 σ( I)) and wR2 = 0.1074 (all data). CCDC number 689491.

Ab initio study of phase stability of NaZr{sub 2}(PO{sub 4}){sub 3} under pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chinnappan, Ravi; Kaur, Gurpreet; Panigrahi, B. K.

2016-05-23

The elastic constants of NaZr{sub 2}(PO{sub 4}){sub 3} were computed as a function of pressure through Density Functional Theory calculations. The behavior of elastic constants show that the rhombohedral (R-3c) NaZr{sub 2}(PO{sub 4}){sub 3} becomes unstable above 8 GPa and is driven by softening of C{sub 44} through one of the Born stability criteria. High pressure equation of state and enthalpy show further that the ambient rhombohedral (R-3c)) NaZr{sub 2}(PO{sub 4}){sub 3} transforms first to another rhombohedral (R3) phase and subsequently to LiZr{sub 2}(PO{sub 4}){sub 3}-type orthorhombic phase at pressures above 6 and 8 GPa respectively which are in agreement with recentmore » X-ray diffraction study.« less

Coating effect of LiFePO4 and Al2O3 on Li1.2Mn0.54Ni0.13Co0.13O2 cathode surface for lithium ion batteries

NASA Astrophysics Data System (ADS)

Seteni, Bonani; Rapulenyane, Nomasonto; Ngila, Jane Catherine; Mpelane, Siyasanga; Luo, Hongze

2017-06-01

Lithium-manganese-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by combustion method, and then coated with nano-sized LiFePO4 and nano-sized Al2O3 particles via a wet chemical process. The as-prepared Li1.2Mn0.54Ni0.13Co0.13O2, LiFePO4-coated Li1.2Mn0.54Ni0.13Co0.13O2 and Al2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The scanning electron microscopy shows the agglomeration of the materials and their nanoparticle size ∼100 nm. The transmission electron microscopy confirms that LiFePO4 forms a rough mat-like surface and Al2O3 remain as islandic particles on the surface of the Li1.2Mn0.54Ni0.13Co0.13O2 material. The Li1.2Mn0.54Ni0.13Co0.13O2 coated with LiFePO4 and Li1.2Mn0.54Ni0.13Co0.13O2 coated with Al2O3 exhibits improved electrochemical performance. The initial discharge capacity is enhanced to 267 mAhg-1 after the LiFePO4 coating and 285 mAhg-1 after the Al2O3 coating compared to the as-prepared Li1.2Mn0.54Ni0.13Co0.13O2 material that has an initial discharge capacity of 243 mAhg-1. Galvanostatic charge-discharge tests at C/10 display longer activation of Li2MnO3 phase and higher capacity retention of 88% after 20 cycles for Li1.2Mn0.54Ni0.13Co0.13O2-LiFePO4 compared to Li1.2Mn0.54Ni0.13Co0.13O2-Al2O3 of 80% after 20 cycles and LMNC of 80% after 20 cycles. Meanwhile Li1.2Mn0.54Ni0.13Co0.13O2-LiFePO4 also shows higher rate capability compared to Li1.2Mn0.54Ni0.13Co0.13O2-Al2O3.

Conjugation of TbPO4·H2O-Based Nanowires with Immunoglobulin G for Bioimaging

NASA Astrophysics Data System (ADS)

Huong, Nguyen Thanh; Lien, Pham Thi; Hung, Nguyen Manh; Van, Nguyen Duc; Thuy, Tran Thi; Binh, Nguyen Thanh; Minh, Le Quoc

2016-05-01

The surface modification, functionalization, and conjugation of undoped and 11 at.% Eu3+-doped TbPO4 ·H2O nanowires by using silica, a thyocyanate functional group, and immunoglobulin G, respectively, are described in this paper. For the core layer of obtained conjugated nanowires, the undoped TbPO4 ·H2O exhibited characteristic photoluminescent green emission corresponding to 5 D 4 → 7 F J transitions ( J = 6, 5, 4, 3) while the incorporation of Eu3+ into TbPO4 ·H2O lattice was evidenced by Starks splitting transitions at 590, 615, 693 nm of Eu3+ ions for the case of 11 at.% Eu3+-doped TbPO4 ·H2O. The results also indicated that both immunoglobulin G-conjugated undoped and Eu3+-doped TbPO4 ·H2O nanowires can be used in the fluorescent immune analysis as a biomedical label maker to identify measles viruses in vaccine testing.

Cs2Bi(PO4)(WO4)

PubMed Central

Terebilenko, Kateryna V.; Zatovsky, Igor V.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.

2009-01-01

Dicaesium bis­muth(III) phosphate(V) tungstate(VI), Cs2Bi(PO4)(WO4), has been synthesized during complex investigation in a molten pseudo-quaternary Cs2O–Bi2O3–P2O5–WO3 system. It is isotypic with K2Bi(PO4)(WO4). The three-dimensional framework is built up from [Bi(PO4)(WO4)] nets, which are organized by adhesion of [BiPO4] layers and [WO4] tetra­hedra above and below of those layers. The inter­stitial space is occupied by Cs atoms. Bi, W and P atoms lie on crystallographic twofold axes. PMID:21577386

Real-time monitoring of ischemic and contralateral brain pO2 during stroke by variable length multisite resonators

PubMed Central

Hou, Huagang; Li, Hongbin; Dong, Ruhong; Khan, Nadeem; Swartz, Harold

2014-01-01

Purpose Electron paramagnetic resonance (EPR) oximetry using variable length multi-probe implantable resonator (IR), was used to investigate the temporal changes in the ischemic and contralateral brain pO2 during stroke in rats. Material and Methods The EPR signal to noise ratio (S/N) of the IR with four sensor loops at a depth of up to11 mm were compared with direct implantation of lithium phthalocyanine (LiPc, oximetry probe) deposits in vitro. These IRs were used to follow the temporal changes in pO2 at two sites in each hemisphere during ischemia induced by left middle cerebral artery occlusion (MCAO) in rats breathing 30% O2 or 100% O2. Results The S/N ratios of the IRs were significantly greater than the LiPc deposits. A similar pO2 at two sites in each hemisphere prior to the onset of ischemia was observed in rats breathing 30% O2. However, a significant decline in the pO2 of the left cortex and striatum occurred during ischemia but no change in the pO2 of the contralateral brain was observed. A significant increase in the pO2 of only the contralateral non-ischemic brain was observed in the rats breathing 100% O2. No significant difference in the infarct volume was evident between the animals breathing 30% O2 or 100% O2 during ischemia. Conclusions EPR oximetry with IRs can repeatedly assess temporal changes in the brain pO2 at four sites simultaneously during stroke. This oximetry approach can be used to test and develop interventions to rescue ischemic tissue by modulating cerebral pO2 during stroke. PMID:24629514

Preparation and characterization of SnO2 and Carbon Co-coated LiFePO4 cathode materials.

PubMed

Wang, Haibin; Liu, Shuxin; Huang, Yongmao

2014-04-01

The SnO2 and carbon co-coated LiFePO4 cathode materials were successfully synthesized by solid state method. The microstructure and morphology of LiFePO4 composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscope. The results showed that the SnO2 and carbon co-coated LiFePO4 cathode materials exhibited more uniform particle size distribution. Compared with the uncoated LiFePO4/C, the structure of LiFePO4 with SnO2 and carbon coating had no change. The existence of SnO2 and carbon coating layer effectively enhanced the initial discharge capacity. Among the investigated samples, the one with DBTDL:LiFePO4 molar ratios of 7:100 exhibited the best electrochemical performance.

AgPO2F2 and Ag9(PO2F2)14: the first Ag(i) and Ag(i)/Ag(ii) difluorophosphates with complex crystal structures.

PubMed

Malinowski, Przemysław J; Kurzydłowski, Dominik; Grochala, Wojciech

2015-12-07

The reaction of AgF2 with P2O3F4 yields a mixed valence Ag(I)/Ag(II) difluorophosphate salt with AgAg(PO2F2)14 stoichiometry - the first Ag(ii)-PO2F2 system known. This highly moisture sensitive brown solid is thermally stable up to 120 °C, which points at further feasible extension of the chemistry of Ag(ii)-PO2F2 systems. The crystal structure shows a very complex bonding pattern, comprising of polymeric Ag(PO2F2)14(4-) anions and two types of Ag(I) cations. One particular Ag(II) site present in the crystal structure of Ag9(PO2F2)14 is the first known example of square pyramidal penta-coordinated Ag(ii) in an oxo-ligand environment. Ag(i)PO2F2 - the product of the thermal decomposition of Ag9(PO2F2)14 - has also been characterized by thermal analysis, IR spectroscopy and X-ray powder diffraction. It has a complicated crystal structure as well, which consists of infinite 1D [Ag(I)O4/2] chains which are linked to more complex 3D structures via OPO bridges. The PO2F2(-) anions bind to cations in both compounds as bidentate oxo-ligands. The terminal F atoms tend to point inside the van der Waals cavities in the crystal structure of both compounds. All important structural details of both title compounds were corroborated by DFT calculations.

Targeted partial surface modification with nano-SiO2@Li2CoPO4F as high-voltage cathode material for LIBs

NASA Astrophysics Data System (ADS)

Chang, Caiyun; Huang, Zhipeng; Tian, Runsai; Jiang, Xinyu; Li, Chunsheng; Feng, Jijun

2017-10-01

Tuning whole/partial surface modification on cathode material with oxide material is a sought-after method to enhance the electrochemical performance in power storage field. Herein, nano-SiO2 targeted partial surface modified high voltage cathode material Li2CoPO4F has been successfully fabricated via a facile self-assembly process in silica dispersion at ambient temperature. With the aid of polar -OH groups attracted on the surface of SiO2 micelles, the nano-SiO2 preferentially nestle up along the borders and boundaries of Li2CoPO4F particles, where protection should be deployed with emphasis against the undesirable interactions between materials and electrolytes. Compared with pristine Li2CoPO4F, the SiO2 selectively modified Li2CoPO4F cathode materials, especially LCPF-3S, exhibit desirable electrochemical performances with higher discharge capacity, more outstanding cycle stability and favorable rate capability without any additional carbon involved. The greatly enhanced electrochemical properties can be attributed to the improved lithium-ion diffusion kinetics and structure tolerance during repeated lithiation/delithiation process. Such findings reveal a great potential of nano-SiO2 modified Li2CoPO4F as high energy cathode material for lithium ion batteries.

Brain parenchyma PO2, PCO2, and pH during and after hypoxic, ischemic brain insult in dogs.

PubMed

McKinley, B A; Morris, W P; Parmley, C L; Butler, B D

1996-11-01

1) The investigation of fiberoptic PO2, PCO2, and pH sensor technology as a monitor of brain parenchyma during and after brain injury, and 2) the comparison of brain parenchyma PO2, PCO2, and pH with intracranial pressure during and after hypoxic, ischemic brain insult. Prospective, controlled, animal study in an acute experimental preparation. Physiology laboratory in a university medical school. Fourteen mongrel dogs (20 to 35 kg), anesthetized, room-air ventilated. Anesthesia was induced with thiopental and maintained after intubation using 1% to 1.5% halothane in room air (FiO2 0.21). Mechanical ventilation was established to maintain end-tidal PCO2 approximately 35 torr (-4.7 kPa). Intravenous, femoral artery, and pulmonary artery catheters were placed. The common carotid arteries were surgically exposed, and ultrasonic blood flow probes were applied. A calibrated intracranial pressure probe was placed through a right-side transcranial bolt, and a calibrated intracranial chemistry probe with optical sensors for PO2, PCO2, and pH was placed through a left-side bolt into brain parenchyma. Brain insult was induced in the experimental group (n = 6) by hypoxia (FiO2 0.1), ischemia (bilateral carotid artery occlusion), and hypotension (mean arterial pressure [MAP] approximately 40 mm Hg produced with isoflurane approximately 4%). After 45 mins, carotid artery occlusion was released, FiO2 was reset to 0.21, and anesthetic was returned to halothane (approximately 1.25%). The control group (n = 5) had the same surgical preparation and sequence of anesthetic agent exposure but no brain insult. Monitored variables included brain parenchyma PO2, PCO2, and pH, which were monitored at 1-min intervals, and intracranial pressure, MAP, arterial hemoglobin oxygen saturation (by pulse oximetry), end-tidal PCO2, and carotid artery blood flow rate, for which data were collected at 15-min intervals for 7 hrs. Arterial and mixed venous blood gas analyses were done at approximately 1

O2(a1Δ) quenching in O/O2/O3/CO2/He/Ar mixtures

NASA Astrophysics Data System (ADS)

Azyazov, V. N.; Mikheyev, P. A.; Postell, D.; Heaven, M. C.

2010-02-01

The development of discharge singlet oxygen generators (DSOG's) that can operate at high pressures is required for the power scaling of the discharge oxygen iodine laser. In order to achieve efficient high-pressure DSOG operation it is important to understand the mechanisms by which singlet oxygen (O2(a1Δ)) is quenched in these devices. It has been proposed that three-body deactivation processes of the type O2(a1Δ))+O+M-->2O2+M provide significant energy loss channels. To further explore these reactions the physical and reactive quenching of O2(a1Δ)) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a1Δ)) quenching were followed by observing the 1268 nm fluorescence of the O2 a1Δ-X3Ε transition. Fast quenching of O2(a1Δ)) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

Continuous arterial PO2 profiles in unrestrained, undisturbed aquatic turtles during routine behaviors

PubMed Central

Hicks, James W.

2016-01-01

ABSTRACT Mammals and birds maintain high arterial partial pressure of oxygen (PO2) values in order to preserve near-complete hemoglobin (Hb) oxygen (O2) saturation. In diving mammals and birds, arterial O2 follows a primarily monotonic decline and then recovers quickly after dives. In laboratory studies of submerged freshwater turtles, arterial O2 depletion typically follows a similar pattern. However, in these studies, turtles were disturbed, frequently tethered to external equipment and confined either to small tanks or breathing holes. Aquatic turtles can alter cardiac shunting patterns, which will affect arterial PO2 values. Consequently, little is known about arterial O2 regulation and use in undisturbed turtles. We conducted the first study to continuously measure arterial PO2 using implanted microelectrodes and a backpack logger in undisturbed red-eared sliders during routine activities. Arterial PO2 profiles during submergences varied dramatically, with no consistent patterns. Arterial PO2 was also lower than previously reported during all activities, with values rarely above 50 mmHg (85% Hb saturation). There was no difference in mean PO2 between five different activities: submerged resting, swimming, basking, resting at the surface and when a person was present. These results suggest significant cardiac shunting occurs during routine activities as well as submergences. However, the lack of relationship between PO2 and any activity suggests that cardiac shunts are not regulated to maintain high arterial PO2 values. These data support the idea that cardiac shunting is the passive by-product of regulation of vascular resistances by the autonomic nervous system. PMID:27618860

Three-Dimensional Ordered Macroporous FePO4 as High-Efficiency Catalyst for Rechargeable Li-O2 Batteries.

PubMed

Li, Chao; Guo, Ziyang; Pang, Ying; Sun, Yunhe; Su, Xiuli; Wang, Yonggang; Xia, Yongyao

2016-11-23

The Li-O 2 battery is receiving much recent attention because of its superhigh theoretical energy density. However, its performance is limited by the irreversible formation/decomposition of Li 2 O 2 on the cathode and the undesired electrolyte decomposition. In this work, low-cost three-dimensional ordered macroporous (3DOM) FePO 4 is synthesized by using polystyrene (PS) spheres template in a facile experimental condition and applied as a high-efficiency catalyst for rechargeable Li-O 2 batteries, including good rate performance, high specific capacity, and perfect cycling stability. The superior performances can be attributed to the unique structure of 3DOM FePO 4 cathodes, which can provide an efficient buffer space for O 2 /Li 2 O 2 conversion. In addition, it is demonstrated that the Li + intercalation/deintercalation behavior of 3DOM FePO 4 in ether-based electrolyte can contribute to capacity for Li-O 2 batteries over cycling. As a result, when there is no O 2 in the environment, the Li-O 2 cell can also be operated as a rechargeable Li-FePO 4 cell with a perfect cycle capability.

Experimental ammonia-free phosphate-bonded investments using Mg(H2PO4)2.

PubMed

Zhang, Z; Tamaki, Y; Miyazaki, T

2001-12-01

In previous study, we found that Mg(H2PO4)2 instead of NH4H2PO4 was available as a binder material for phosphate-bonded investments and possibly could be used to develop the phosphate-bonded investment without ammonia gas release. The purpose of the present study was to develop the experimental ammonia-free phosphate-bonded investments by investigating suitable refractories. Mg(H2PO4)2.nH2O and MgO were prepared as a binder. Cristobalite and quartz were selected as refractories. The power ratio of MgO/Mg(H2PO4)2.nH2O was set constant at 1.2 according to our previous findings. Fundamental properties of dental investment such as strength, manipulation and expansion were evaluated. Using cristobalite as the refractory material, further investigations were performed. The refractory/binder ratio was definitely effective. The increase of this ratio led to low mold strength and large mold expansion. The present findings suggested that C5 was desirable for dental investment.

The porous TiO2 nanotubes/Ag3PO4 heterojunction for enhancing sunlight photocatalytic activity

NASA Astrophysics Data System (ADS)

Chi, Chunyan; Pan, Jiaqi; You, Mingzhu; Dong, Zongjun; Zhao, Weijie; Song, Changsheng; Zheng, Yingying; Li, Chaorong

2018-03-01

The porous TiO2 nanotubes/Ag3PO4 heterojunction are synthesized via simple electrospining and chemical co-deposition method. The results of SEM, XRD, TEM and XPS imply that the Ag3PO4 nanoparticles have been introduced on to the surface of TiO2 nanotubes successfully. Compared with the unmodified samples, the photocatalytic activity of the as-prepared porous TiO2 nanotubes/Ag3PO4 heterojunction exhibit a remarkable enhancement by the degradation of methylene blue (MB) under the sunlight. Further, the Z-Scheme structure of the samples and the porous-tubular structure of the TiO2 are considered as the main reasons for the enhancement.

Structure and properties of hopeites (Mg xZn 1- x) 3(PO 4) 2 · 4H 2O

NASA Astrophysics Data System (ADS)

Haussühl, S.; Middendorf, B.; Dörffel, M.

1991-07-01

Mg-hopeites (Mg xZn 1- x) 3(PO 4) 2 · 4H 2O were prepared by crystallization from hot aqueous solutions (70°C). The structure of (Mg 0.206Zn 0.794) 3(PO 4) 2 · 4H 2O has been determined from 1612 unique reflections (MoKα, R = 0.033): Pnma, a1 = 10.594(2), a2 = 18.333(2), a3 = 5.029(2)Å, Z = 4, Dcalc = 2.943g cm -3. The structure resembles that of pure hopeite. However, the magnesium atoms occupy only the sixcoordinated site. The thermal behavior of hopeites is strongly influenced by the substitution of Zn by Mg. The dehydration range is shifted to higher temperatures with increasing Mg content. A strongly anisotropic thermal expansion was measured by X-ray diffraction in a temperature range of -40° to 50°C. Experiments to substitute Zn by Ca, Sr, and Ba in the hopeite failed. A hitherto unknown monoclinic phase with the composition BaZn 2(PO 4) 2 · H 2O and a1 = 4.707(2), a2 = 7.840(2), a3 = 8.061(3)Å, and α 2 = 88.99(4)° was found.

Self-assembly of red-blood-cell-like (NH4)[Fe2(OH)(PO4)2]·2H2O architectures from 2D nanoplates by sonochemical method.

PubMed

Wu, Kaipeng; Liu, Diwei; Tang, Yun

2018-01-01

Red-blood-cell-like (RBC-like) (NH 4 )[Fe 2 (OH)(PO 4 ) 2 ]·2H 2 O architectures assembled from 2D nanoplates are successfully synthesized via a facile sonochemical method. XRD measurement indicates that the as-prepared sample is well crystallized with a monoclinic structure. The morphology of the sample is characterized by SEM analysis, which shows that the (NH 4 )[Fe 2 (OH)(PO 4 ) 2 ]·2H 2 O particles exhibit a unique biconcave red blood cell morphology with an average diameter of 4um and thickness of 1.5um. The detailed time-dependent experiments are conducted to investigate the morphological evolution process. It reveals that the ultrasonic time is crucial to the morphology of the products, and the RBC-like (NH 4 )[Fe 2 (OH)(PO 4 ) 2 ]·2H 2 O proceeds in steps of crystallization, formation of thin plates, and the subsequent self-assembly. Compared to the available methods that are typically time-consuming and complicated, this smart sonochemical strategy proposed herein is efficient and simple. Moreover, these obtained special RBC-like architectures will be more fascinating for application in many areas. Copyright © 2017 Elsevier B.V. All rights reserved.

Selective detection of Fe2+ by combination of CePO4:Tb3+ nanocrystal-H2O2 hybrid system with synchronous fluorescence scan technique.

PubMed

Chen, Hongqi; Ren, Jicun

2012-04-21

A new method for quenching kinetic discrimination of Fe(2+) and Fe(3+), and sensitive detection of trace amount of Fe(2+) was developed by using synchronous fluorescence scan technique. The principle of this assay is based on the quenching kinetic discrimination of Fe(2+) and Fe(3+) in CePO(4):Tb(3+) nanocrytals-H(2)O(2) hybrid system and the Fenton reaction between Fe(2+) and H(2)O(2). Stable, water-soluble and well-dispersible CePO(4):Tb(3+) nanocrystals were synthesized in aqueous solutions, and characterized by transmission electron microscopy (TEM) and electron diffraction spectroscopy (EDS). We found that both Fe(2+) and Fe(3+) could quench the synchronous fluorescence of CePO(4):Tb(3+) nanocrytals-H(2)O(2) system, but their quenching kinetics velocities were quite different. In the presence of Fe(3+), the synchronous fluorescent intensity was unchanged after only one minute, but in the presence of Fe(2+), the synchronous fluorescent intensity decreased slowly until 28 min later. The Fenton reaction between Fe(2+) and H(2)O(2) resulted in hydroxyl radicals which effectively quenched the synchronous fluorescence of the CePO(4):Tb(3+) nanocrystals due to the oxidation of Ce(3+) into Ce(4+) by hydroxyl radicals. Under optimum conditions, the linear range for Fe(2+) is 3 nM-2 μM, and the limit of detection is 2.0 nM. The method was used to analyze water samples.

64Cu-ATSM Reflects pO2 Levels in Human Head and Neck Cancer Xenografts but Not in Colorectal Cancer Xenografts: Comparison with 64CuCl2.

PubMed

Li, Fan; Jørgensen, Jesper T; Forman, Julie; Hansen, Anders E; Kjaer, Andreas

2016-03-01

The hypoxia PET tracer (64)Cu-diacetyl-bis(N(4)-methylthiosemicarbazonate) ((64)Cu-ATSM) has shown promising results in clinical studies. However, concerns have been raised with regard to the possible effect of copper metabolism and free copper on tumor uptake and thereby the robustness of (64)Cu-ATSM as a hypoxia marker. In this study, accumulation and distribution of (64)Cu-ATSM and (64)CuCl2 in tumor tissue were compared with partial pressure of oxygen (pO2) probe measurements. One-hour dynamic PET scans were performed on nude mice bearing subcutaneous human head and neck tumors (FaDu) and human colorectal tumors (HT29) after administration of either (64)Cu-ATSM or (64)CuCl2. Subsequently, tracks were generated and track markers were positioned in tumors to allow for registration of their exact location on the high-resolution CT scan. After completion of the CT scan, pO2 probe measurements were performed along each track. PET and CT images were coregistered and ROIs drawn on the basis of the location of track markers and pO2 probe measurement depth. A linear mixed model for repeated measures was applied for the comparison of PET tracer uptake to corresponding pO2 values. Comparable uptake of (64)Cu-ATSM and (64)CuCl2 was found in the kidney, muscle, and liver of all animals, but (64)CuCl2 showed a higher uptake 10-60 min after injection in both tumor models. Significant differences were also found for both tumor-to-muscle and tumor-to-liver ratios. The intratumoral distribution of (64)Cu-ATSM, but not (64)CuCl2, showed a significant negative relationship with pO2 measurements in FaDu tumors. However, this relationship was not found in HT29 tumors. (64)Cu-ATSM and (64)CuCl2 displayed different uptake in tumors. In human head and neck xenografts, (64)Cu-ATSM but not (64)CuCl2 reflected pO2 measurements, indicating that (64)Cu-ATSM is a hypoxia-specific marker in this tumor type. However, data from colorectal cancer xenografts indicated that (64)Cu-ATSM may not be

Pressure, O2, and CO2, in aquatic Closed Ecological Systems

NASA Astrophysics Data System (ADS)

Taub, Frieda B.; McLaskey, Anna K.

2013-03-01

Pressure increased during net photosynthetic O2 production in the light and decreased during respiratory O2 uptake during the dark in aquatic Closed Ecological Systems (CESs) with small head gas volumes. Because most CO2 will be in the liquid phase as bicarbonate and carbonate anions, and CO2 is more soluble than O2, volumes of gaseous CO2 and gaseous O2 will not change in a compensatory manner, leading to the development of pressure. Pressure increases were greatest with nutrient rich medium with NaHCO3 as the carbon source. With more dilute media, pressure was greatest with NaHCO3, and less with cellulose or no-added carbon. Without adequate turbulence, pressure measurements lagged dissolved O2 concentrations by several hours and dark respiration would have been especially underestimated in our systems (250-1000 ml). With adequate turbulence (rotary shaker), pressure measurements and dissolved O2 concentrations generally agreed during lights on/off cycles, but O2 measurements provided more detail. At 20 °C, 29.9 times as much O2 will distribute into the gas phase as in the liquid, per unit volume, as a result of the limited solubility of O2 in water and according to Henry's Law. Thus even a small head gas volume can contain more O2 than a larger volume of water. When both dissolved and gaseous O2 and CO2 are summed, the changes in Total O2 and CO2 are in relatively close agreement when NaHCO3 is the carbon source. These findings disprove an assumption made in some of Taub's earlier research that aquatic CESs would remain at approximately atmospheric pressure because approximately equal molar quantities of O2 and CO2 would exchange during photosynthesis and respiration; this assumption neglected the distribution of O2 between water and gas phases. High pressures can occur when NaHCO3 is the carbon source in nutrient rich media and if head-gas volumes are small relative to the liquid volume; e.g., one "worse case" condition developed 800 mm Hg above atmospheric

Interplay of tumor vascular oxygenation and pO2 in tumors using NIRS and needle electrode

NASA Astrophysics Data System (ADS)

Kim, Jae Gwan; Song, Yulin; Zhao, Dawen; Constantinescu, Anca; Mason, Ralph P.; Liu, Hanli

2001-06-01

The effective measurement of dynamic changes of blood and tissue oxygenation of tumors could be valuable for optimizing tumor treatment plans. For this study, a near- infrared spectroscopy system and pO2 needle electrode were used to measure simultaneously changes in total hemoglobin concentration ([Hb]total), oxygenated hemoglobin concentration ([HbO2[) and local oxygen tension (pO2) in the vascular bed of prostate tumors implanted in rats in response to respiratory challenge. The inhaled gas was alternated between air and carbogen (95% oxygen, 5% CO2). Significant changes in tumor vascular oxygenation were observed with an apparent threshold for variation in [HbO2]/[HbO2]max. For comparison, a phantom study was undertaken with 1% intralipid solution and blood. The slope of [HbO2]/[HbO2[max vs. pO2 in the phantom was ten times larger than in the tumor indicating that tumor cells are relatively resistant to oxygenation. This study demonstrates that the NIR technology can provide an efficient, real-time, non-invasive approach to monitoring tumor physiology and is compatible with additional techniques.

Visible light induced H2PO(4)(-) removal over CuAlO2 catalyst.

PubMed

Benreguia, N; Omeiri, S; Bellal, B; Trari, M

2011-09-15

The delafossite CuAlO(2) is successfully used for the visible light driven H(2)PO(4)(-) reduction. It is prepared from the nitrates decomposition in order to increase the ratio of reaction surface per given mass. CuAlO(2) is a narrow band gap semiconductor which exhibits a good chemical stability with a corrosion rate of 1.70 μmol year(-1) at neutral pH. The flat band potential (+0.25 V(SCE)) is determined from the Mott-Schottky characteristic. Hence, the conduction band, positioned at (-1.19 V(SCE)), lies below the H(2)PO(4)(-) level yielding a spontaneous reduction under visible illumination. The photocatalytic process is investigated under mild conditions and 30% conversion occurs in less than ~6h with a quantum efficiency of 0.04% under full light. The concentration decreases by a factor of 39% after a second cycle. The photoactivity follows a first order kinetic with a rate constant of 6.6 × 10(-2)h(-1). The possibility of identifying the reaction products via the intensity-potential characteristics is explored. The decrease of the conversion rate over illumination time is due to the competitive water reduction. Copyright © 2011 Elsevier B.V. All rights reserved.

Experimental ammonia-free phosphate-bonded investments using Mg(H2PO4)2 solution.

PubMed

Takashiba, Shigeyuki; Zhang, Zutai; Tamaki, Yukimichi

2002-12-01

In our previous study, we investigated ammonia-free phosphate-bonded investments using Mg (H2PO4)2 powder. The purpose of the present study was to attempt usage of 50 wt% Mg (H2PO4)2 solution instead of powder. Magnesium oxide (MgO) was prepared as a binder and cristobalite was selected as a refractory. After arranging six kinds of experimental investments (A-F) with different cristobalite/MgO ratios, the fundamental properties of the dental investments were examined. The properties of the molds were influenced by the amount of MgO. Decreases in MgO showed lower mold strengths, longer setting time and larger setting expansion. According to XRD analysis, the peaks of MgH(PO4)3 x 3H2O newly formed, cristobalite and MgO were detected in the A set, but MgO peaks in F set were reduced. On the other hand, the surface of F was entirely covered by phosphorus. From these results, it was found that the usage of Mg(H2PO4)2 solution was possible for ammonia-free investments.

LiFePO4 Nanostructures Fabricated from Iron(III) Phosphate (FePO4 x 2H2O) by Hydrothermal Method.

PubMed

Saji, Viswanathan S; Song, Hyun-Kon

2015-01-01

Electrode materials having nanometer scale dimensions are expected to have property enhancements due to enhanced surface area and mass/charge transport kinetics. This is particularly relevant to intrinsically low electronically conductive materials such as lithium iron phosphate (LiFePO4), which is of recent research interest as a high performance intercalation electrode material for Li-ion batteries. Many of the reported works on LiFePO4 synthesis are unattractive either due to the high cost of raw materials or due to the complex synthesis technique. In this direction, synthesis of LiFePO4 directly from inexpensive FePO4 shows promise.The present study reports LiFePO4 nanostructures prepared from iron (III) phosphate (FePO4 x 2H2O) by precipitation-hydrothermal method. The sintered powder was characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Inductive coupled plasma-optical emission spectroscopy (ICP-OES), and Electron microscopy (SEM and TEM). Two synthesis methods, viz. bulk synthesis and anodized aluminum oxide (AAO) template-assisted synthesis are reported. By bulk synthesis, micro-sized particles having peculiar surface nanostructuring were formed at precipitation pH of 6.0 to 7.5 whereas typical nanosized LiFePO4 resulted at pH ≥ 8.0. An in-situ precipitation strategy inside the pores of AAO utilizing the spin coating was utilized for the AAO-template-assisted synthesis. The template with pores filled with the precipitate was subsequently subjected to hydrothermal process and high temperature sintering to fabricate compact rod-like structures.

Selective Metal Exsolution in BaFe 2-yMy(PO 4) 2 (M = Co 2+, Ni 2+) Solid Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alcover, Ignacio Blazquez; Daviero-Minaud, Sylvie; David, Rénald

2015-08-19

The 2D-Ising ferromagnetic phase BaFe 2+ 2(PO 4) 2 shows exsolution of up to one-third of its iron content (giving BaFe 3+ 1.33(PO 4) 2) under mild oxidation conditions, leading to nanosized Fe 2O 3 exsolved clusters. Here we have prepared BaFe 2–yMy(PO 4) 2 (M = Co 2+, Ni 2+; y = 0, 0.5, 1, 1.5) solid solutions to investigate the feasibility and selectivity of metal exsolution in these mixed metallic systems. For all the compounds, after 600 °C thermal treatment in air, a complete oxidation of Fe 2+ to Fe 3+ leaves stable M 2+ ions, as verifiedmore » by 57Fe Mössbauer spectroscopy, TGA, TEM, microprobe, and XANES. Furthermore, the size of the nanometric α-Fe 2O 3clusters coating the main phase strongly depends on the y M metal concentration. For M-rich phases the iron diffusion is hampered so that a significant fraction of superparamagnetic α-Fe2O3 particles (100% for BaFe 0.5–xCo 1.5(PO 4) 2) was detected even at 78 K. Although Ni 2+and Co 2+ ions tend to block Fe diffusion, the crystal structure of BaFe 0.67Co 1(PO 4) 2demonstrates a fully ordered rearrangement of Fe 3+ and Co 2+ ions after Fe exsolution. We found that the magnetic behaviors of the Fe-depleted materials are mostly dominated by antiferromagnetic exchange, while Co 2+-rich compounds show metamagnetic transitions reminiscent of the BaCo 2(PO 4) 2 soft helicoidal magnet.« less

A sodium gallophosphate with an original tunnel structure: NaGa 2(OH)(PO 4) 2

NASA Astrophysics Data System (ADS)

Guesdon, A.; Monnin, Y.; Raveau, B.

2003-05-01

A new sodium gallophosphate, NaGa 2(OH)(PO 4) 2, has been obtained by hydrothermal synthesis under autogeneous pressure at 473 K. It crystallizes in the P2 1/ n space group with the cell parameters a=8.9675(8) Å, b=8.9732(5) Å, c=9.2855(7) Å, β=114.812(6)°, V=678.2 Å 3 ( Z=4). In its original three-dimensional framework, monophosphate groups share their apices with [Ga 4O 16(OH) 2] tetrameric units, which are built from two GaO 5(OH) octahedra and two GaO 4(OH) trigonal bipyramids. The sodium cations are located in tunnels running along a, whereas the tunnels running along b are empty.

O2(a1Δ) Quenching In The O/O2/O3 System

NASA Astrophysics Data System (ADS)

Azyazov, V. N.; Mikheyev, P. A.; Postell, D.; Heaven, M. C.

2010-10-01

The development of discharge singlet oxygen generators (DSOG's) that can operate at high pressures is required for the power scaling of the discharge oxygen iodine laser. In order to achieve efficient high-pressure DSOG operation it is important to understand the mechanisms by which singlet oxygen (O2(a1Δ)) is quenched in these devices. It has been proposed that three-body deactivation processes of the type O2(a1Δ)+O+M→2O2+M provide significant energy loss channels. To further explore these reactions the physical and reactive quenching of O2(a1Δ) in O(3P)/O2/O3/CO2/He/Ar mixtures has been investigated. Oxygen atoms and singlet oxygen molecules were produced by the 248 nm laser photolysis of ozone. The kinetics of O2(a1Δ) quenching were followed by observing the 1268 nm fluorescence of the O2a1Δ-X3∑ transition. Fast quenching of O2(a1Δ) in the presence of oxygen atoms and molecules was observed. The mechanism of the process has been examined using kinetic models, which indicate that quenching by vibrationally excited ozone is the dominant reaction.

PH2O and simulated hypobaric hypoxia.

PubMed

Conkin, Johnny

2011-12-01

Some manufacturers of reduced oxygen (O2) breathing devices claim a comparable hypobaric hypoxia (HH) training experience by providing F1O2 < 0.209 at or near sea level pressure to match the ambient oxygen partial pressure (iso-PO2) of the target altitude. I conclude after a review of literature from investigators and manufacturers that these devices may not properly account for the 47 mmHg of water vapor partial pressure that reduces the inspired partial pressure of oxygen (P1O2), which is substantial at higher altitude relative to sea level. Consequently, some devices claiming an equivalent HH experience under normobaric conditions would significantly overestimate the HH condition, especially when simulating altitudes above 10,000 ft (3048 m). At best, the claim should be that the devices provide an approximate HH experience since they only duplicate the ambient PO2 at sea level as at altitude. An approach to reduce the overestimation and standardize the operation is to at least provide machines that create the same P1O2 conditions at sea level as at the target altitude, a simple software upgrade.

Composited reduced graphene oxide into LiFePO4/Li2SiO3 and its electrochemical impedance spectroscopy properties

NASA Astrophysics Data System (ADS)

Arifin, M.; Rus, Y. B.; Aimon, A. H.; Iskandar, F.; Winata, T.; Abdullah, M.; Khairurrijal, K.

2017-03-01

LiFePO4 is commonly used as cathode material for Li-ion batteries due to its stable operational voltage and high specific capacity. However, it suffers from certain disadvantages such as low intrinsic electronic conductivity and low ionic diffusion. This study was conducted to analyse the effect of reduced graphene oxide (rGO) on the electrochemical properties of LiFePO4/Li2SiO3 composite. This composite was synthesized by a hydrothermal method. Fourier transform infrared spectroscopy measurement identified the O-P-O, Fe-O, P-O, and O-Si-O- bands in the LiFePO4/Li2SiO3 composite. X-ray diffraction measurement confirmed the formation of LiFePO4. Meanwhile, Raman spectroscopy confirmed the number of rGO layers. Further, scanning electron microscopy images showed that rGO was distributed around the LiFePO4/Li2SiO3 particles. Finally, the electrochemical impedance spectroscopy results showed that the addition of 1 wt% of rGO to the LiFePO4/Li2SiO3 composite reduced charge transfer resistance. It may be concluded that the addition of 1 wt% rGO to LiFePO4/Li2SiO3 composite can enhance its electrochemical performance as a cathode material.

Color-tunable photoluminescence and energy transfer properties of single-phase Ba{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+}, Mn{sup 2+} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Qingfeng; Liao, Libing, E-mail: clayl@cugb.edu.cn; Mei, Lefu, E-mail: mlf@cugb.edu.cn

2015-12-15

Single-phase Ba{sub 10−x−y}(PO{sub 4}){sub 6}O:xEu{sup 2+},yMn{sup 2+} samples with apatite structure have been synthesized via a solid-state reaction method. The phase structure, luminescence properties, lifetime, PL thermal stability, as well as fluorescence decay curves of the samples were investigated. Effective energy transfer occurs from Eu{sup 2+} to Mn{sup 2+} in Ba{sub 10}(PO{sub 4}){sub 6}O and a possible mechanism of the energy-transfer from Eu{sup 2+} to Mn{sup 2+} is proposed. The critical distances R{sub c} was calculated by concentration quenching and turned out to be about 0.817 nm (x{sub c}=0.21). The CIE and thermally stable luminescence behaviors of Ba{sub 9.94}(PO{sub 4}){submore » 6}O:0.06Eu{sup 2+} phosphor were also studied in detail. All the results indicate that Ba{sub 10−x−y}(PO{sub 4}){sub 6}O:xEu{sup 2+}, yMn{sup 2+} phosphors have potential applications as near UV-convertible phosphors for white light-emitting diodes. - Graphical abstract: Crystal structure and luminescence property of Ba{sub 10−x−y}(PO{sub 4}){sub 6}O:xEu{sup 2+},yMn{sup 2+} have been discussed. - Highlights: • Ba{sub 10−x−y}(PO{sub 4}){sub 6}O:xEu{sup 2+},yMn{sup 2+} was firstly reported. • Ba{sub 9.94}(PO{sub 4}){sub 6}O:0.06Eu{sup 2+} exhibits high thermal quenching resistance. • The energy transfer between Eu{sup 2+} and Mn{sup 2+} was investigated.« less

Heterometallic cerium(IV) perrhenate, permanganate, and molybdate complexes supported by the imidodiphosphinate ligand [N(i-Pr2PO)2]-.

PubMed

Wang, Guo-Cang; Sung, Herman H Y; Dai, Feng-Rong; Chiu, Wai-Hang; Wong, Wai-Yeung; Williams, Ian D; Leung, Wa-Hung

2013-03-04

Heterometallic cerium(IV) perrhenate, permanganate, and molybdate complexes containing the imidodiphosphinate ligand [N(i-Pr2PO)2](-) have been synthesized, and their reactivity was investigated. Treatment of Ce[N(i-Pr2PO)2]3Cl (1) with AgMO4 (M = Re, Mn) afforded Ce[N(i-Pr2PO)2]3(ReO4) (2) or Ce2[N(i-Pr2PO)2]6(MnO4)2 (3). In the solid state, 3 is composed of a [Ce2{N(i-Pr2PO)2}6(MnO4)](+) moiety featuring a weak Ce-OMn interaction [Ce-OMn distance = 2.528(8) Å] and a noncoordinating MnO4(-) counteranion. While 3 is stable in the solid state and acetonitrile solution, it decomposes readily in other organic solvents, such as CH2Cl2. 3 can oxidize ethylbenzene to acetophenone at room temperature. Treatment of 1 with AgBF4, followed by reaction with [n-Bu4N]2[MoO4], afforded [Ce{N(i-Pr2PO)2}3]2(μ-MoO4) (4). Reaction of trans-Ce[N(i-Pr2PO)2]2(NO3)2 (5), which was prepared from (NH4)2Ce(NO3)6 and K[N(i-Pr2PO)2], with 2 equiv of [n-Bu4N][Cp*MoO3] yielded trans-Ce[N(i-Pr2PO)2]2(Cp*MoO3)2 (6). 4 can catalyze the oxidation of methyl phenyl sulfide with tert-butyl hydroperoxide with high selectivity. The crystal structures of complexes 3-6 have been determined.

The effect of hypoxia and hyperoxia on nucleoside triphosphate/inorganic phosphate, pO2 and radiation response in an experimental tumour model.

PubMed Central

Nordsmark, M.; Maxwell, R. J.; Horsman, M. R.; Bentzen, S. M.; Overgaard, J.

1997-01-01

This study has evaluated the effect of breathing 100% oxygen, carbogen and carbon monoxide (at 660 p.p.m.) on the bioenergetic and oxygenation status and the radiation response of 200-mm3 C3H mammary carcinomas grown in the feet of CDF mice. Bioenergetic status was assessed by 31P magnetic resonance spectroscopy (MRS) using a 7-tesla spectrometer with both short (2 s) and long (6 s) pulse repetition times. Tumour partial pressure of oxygen (PO2) was measured with an Eppendorf polarographic electrode; the oxygenation parameters were the median pO2 and fraction of pO2 values < or = 2.5 mmHg. The radiation response was estimated using a tumour growth delay assay (time to grow three times treatment volume). Carbon monoxide breathing decreased tumour pO2 and compromised the radiation response, but the beta-nucleoside triphosphate (NTP)/Pi ratio was unchanged. Both carbogen and oxygen (100%) increased tumour pO2 and beta-NTP/Pi and enhanced the radiation response, the effects being similar under the two gassing conditions and dependent on the gas breathing time. Thus, in this tumour model, 31P-MRS can detect hyperoxic changes, but because cells can remain metabolically active even at low oxygen tensions the beta-NTP/Pi did not correlate with low tissue oxygenation. An analysis of variance showed that gas breathing time induced a significant systematic effect on beta-NTP/Pi, the MRS pulse repetition time had a significant effect on beta-NTP/Pi change under hypoxic but not under hyperoxic conditions and the type of gas that was inhaled had a significant effect on beta-NTP/Pi. Images Figure 4 PMID:9400939

[Preliminary study on DNA damage of ZrO(2)/LaPO(4) diphase ceramics on human peripheral blood lymphocytes in vitro].

PubMed

Zhu, Hui-fang; Chen, Li-ping; Zhang, Xiu-li; Zhang, Bao-wei

2009-06-01

To detect the genotoxicity of dental machinable ZrO(2)/LaPO(4) diphase ceramics on human peripheral blood lymphocytes in vitro. The evaluation of DNA damage on human lymphocytes was performed by comet assay for three groups of ZrO(2)/LaPO(4) diphase ceramics with 30wt% of LaPO(4) (with 3wt% and 5wt% of Y(2)O(3)) and 40wt% of LaPO(4) (with 5wt% of Y(2)O(3)). The results were analyzed with SPSS16.0 software package for one-factor ANOVA and LSD. Three experimental groups with different concentration of LaPO(4) of ZrO(2)/LaPO(4) diphase ceramics, the negative control of IPS Empress II ceramics and the blank behaved little migration of the DNA strands respectively after six-day test, and there was no significant difference in all the groups except the positive control (P>0.05). The study indicates little effect of DNA damage of ZrO(2)/LaPO(4) diphase ceramics.

Synthesis, structure, and properties of nickel complexes with nitrilotris(methylenephosphonic acid) [Ni(H{sub 2}O)3N(CH2PO{sub 3}H){sub 3}] and Na{sub 4}[Ni(H{sub 2}O)N(CH{sub 2}PO{sub 3}){sub 3}] ∙ 11H{sub 2}O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: chaus@yandex.ru; Zakirova, R. M.

2016-03-15

Nitrilotris(methylenephosphonato)triaquanickel and tetrasodium nitrilotris(methylenephosphonato) aquanickelate undecahydrate were synthesized and characterized. The crystal of [Ni(H{sub 2}O){sub 3}N(CH{sub 2}PO{sub 3}H){sub 3}] is composed of linear coordination polymers and belongs to sp. gr. P2{sub 1}/c, Z = 4, a = 9.17120(10) Å, b = 16.05700(10) Å, c = 9.70890(10) Å, β = 115.830(2)°. The Ni atom is in an octahedral coordination formed by two oxygen atoms of one phosphonate ligand, one oxygen atom of another ligand molecule, and three water molecules in a meridional configuration. The crystal of Na{sub 4}[Ni(H{sub 2}O)N(CH{sub 2}PO{sub 3}){sub 3}] ∙ 11H{sub 2}O has an island dimeric chelate structuremore » and belongs to sp. gr. C2/c, Z = 8, a = 18.7152(2) Å, b = 12.05510(10) Å, c = 21.1266(2) Å, β = 104.4960(10)°. The Ni atom has a slightly distorted octahedral coordination involving one nitrogen atom and closes three five-membered N–C–P–O–Ni rings sharing the Ni–N bond.« less

Luminescence Spectroscopy and Crystal Field Simulations of Europium Propylenediphosphonate EuH[O 3P(CH 2) 3PO 3] and Europium Glutarate [Eu(H 2O)] 2[O 2C(CH 2) 3CO 2] 3·4H 2O

NASA Astrophysics Data System (ADS)

Serpaggi, F.; Férey, G.; Antic-Fidancev, E.

1999-12-01

The results of investigations on the photoluminescence of two europium hybrid compounds, EuH[O3P(CH2)3PO3] (Eu[diph]) and [Eu(H2O)]2[O2C(CH2)3CO2]3·4H2O (Eu[glut]), are presented. In both compounds one local environment is found for the rare earth (Re) ion and the symmetry of the Re polyhedron is low (Cs) as evidenced by the Eu3+ luminescence studies. The electrostatic crystal field (cf) parameters of the 7F multiplet are obtained by the application of the phenomenological cf theory. The simulations using C2v symmetry for the rare earth ion give good agreement between the calculated and the experimental 7F0-4 energy level schemes. The observed optical data are discussed in relation to the crystal structure of the compounds.

Synthesis of LiFePO4/Li2SiO3/reduced Graphene Oxide (rGO) Composite via Hydrothermal Method

NASA Astrophysics Data System (ADS)

Arifin, M.; Iskandar, F.; Aimon, A. H.; Munir, M. M.; Nuryadin, B. W.

2016-08-01

LiFePO4 is a type of cathode active material used for lithium ion batteries. It has a high electrochemical performance. However, it suffers from certain disadvantages such as a very low intrinsic electronic conductivity and low ionic diffusion. This study was conducted to increase the conductivity of LiFePO4. We have investigated the addition of Li2SiO3 and reduced graphene oxide (rGO) to LiFePO4. The objective of this research was to synthesize LiFePO4/Li2SiO3/rGO via hydrothermal method. Fourier transform infrared spectroscopy (FTIR) measurement showed that the peaks corresponded to the vibration of LiFePO4/Li2SiO3. Further, X-ray diffraction (XRD) measurement confirmed a single phase of LiFePO4. Finally, scanning electron microscopy (SEM) images showed that rGO was distributed on the LiFePO4/Li2SiO3 structure.

Non-aqueous synthesis of water-dispersible Fe3O4-Ca3(PO4)2 core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Liu, HongLing; Wu, JunHua; Min, Ji Hyun; Hou, Peng; Song, Ah-Young; Kim, Young Keun

2011-02-01

The Fe3O4-Ca3(PO4)2 core-shell nanoparticles were prepared by one-pot non-aqueous nanoemulsion with the assistance of a biocompatible triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEO-PPO-PEO), integrating the magnetic properties of Fe3O4 and the bioactive functions of Ca3(PO4)2 into single entities. The Fe3O4 nanoparticles were pre-formed first by thermal reduction of Fe(acac)3 and then the Ca3(PO4)2 layer was coated by simultaneous deposition of Ca2 + and PO43 - . The characterization shows that the combination of the two materials into a core-shell nanostructure retains the magnetic properties and the Ca3(PO4)2 shell forms an hcp phase (a = 7.490 Å, c = 9.534 Å) on the Fe3O4 surface. The magnetic hysteresis curves of the nanoparticles were further elucidated by the Langevin equation, giving an estimation of the effective magnetic dimension of the nanoparticles and reflecting the enhanced susceptibility response as a result of the surface covering. Fourier transform infrared (FTIR) analysis provides the characteristic vibrations of Ca3(PO4)2 and the presence of the polymer surfactant on the nanoparticle surface. Moreover, the nanoparticles could be directly transferred to water and the aqueous dispersion-collection process of the nanoparticles was demonstrated for application readiness of such core-shell nanostructures in an aqueous medium. Thus, the construction of Fe3O4 and Ca3(PO4)2 in the core-shell nanostructure has conspicuously led to enhanced performance and multi-functionalities, offering various possible applications of the nanoparticles.

Chemical and Electrochemical Asymmetric Dihydroxylation of Olefins in I(2)-K(2)CO(3)-K(2)OsO(2)(OH)(4) and I(2)-K(3)PO(4)/K(2)HPO(4)-K(2)OsO(2)(OH)(4) Systems with Sharpless' Ligand.

PubMed

Torii, Sigeru; Liu, Ping; Bhuvaneswari, Narayanaswamy; Amatore, Christian; Jutand, Anny

1996-05-03

Iodine-assisted chemical and electrochemical asymmetric dihydroxylation of various olefins in I(2)-K(2)CO(3)-K(2)OsO(2)(OH)(4) and I(2)-K(3)PO(4)/K(2)HPO(4)-K(2)OsO(2)(OH)(4) systems with Sharpless' ligand provided the optically active glycols in excellent isolated yields and high enantiomeric excesses. Iodine (I(2)) was used stoichiometrically for the chemical dihydroxylation, and good results were obtained with nonconjugated olefins in contrast to the case of potassium ferricyanide as a co-oxidant. The potentiality of I(2) as a co-oxidant under stoichiometric conditions has been proven to be effective as an oxidizing mediator in electrolysis systems. Iodine-assisted asymmetric electro-dihydroxylation of olefins in either a t-BuOH/H(2)O(1/1)-K(2)CO(3)/(DHQD)(2)PHAL-(Pt) or t-BuOH/H(2)O(1/1)-K(3)PO(4)/K(2)HPO(4)/(DHQD)(2)PHAL-(Pt) system in the presence of potassium osmate in an undivided cell was investigated in detail. Irrespective of the substitution pattern, all the olefins afforded the diols in high yields and excellent enantiomeric excesses. A plausible mechanism is discussed on the basis of cyclic voltammograms as well as experimental observations.

Controllable synthesis of (NH4)Fe2(PO4)2(OH)·2H2O using two-step route: Ultrasonic-intensified impinging stream pre-treatment followed by hydrothermal treatment.

PubMed

Dong, Bin; Li, Guang; Yang, Xiaogang; Chen, Luming; Chen, George Z

2018-04-01

(NH 4 )Fe 2 (PO 4 ) 2 (OH)·2H 2 O samples with different morphology are successfully synthesized via two-step synthesis route - ultrasonic-intensified impinging stream pre-treatment followed by hydrothermal treatment (UIHT) method. The effects of the adoption of ultrasonic-intensified impinging stream pre-treatment, reagent concentration (C), pH value of solution and hydrothermal reaction time (T) on the physical and chemical properties of the synthesised (NH 4 )Fe 2 (PO 4 ) 2 (OH)·2H 2 O composites and FePO 4 particles were systematically investigated. Nano-seeds were firstly synthesized using the ultrasonic-intensified T-mixer and these nano-seeds were then transferred into a hydrothermal reactor, heated at 170 °C for 4 h. The obtained samples were characterized by utilising XRD, BET, TG-DTA, SEM, TEM, Mastersizer 3000 and FTIR, respectively. The experimental results have indicated that the particle size and morphology of the obtained samples are remarkably affected by the use of ultrasonic-intensified impinging stream pre-treatment, hydrothermal reaction time, reagent concentration, and pH value of solution. When such (NH 4 )Fe 2 (PO 4 ) 2 (OH)·2H 2 O precursor samples were transformed to FePO 4 products after sintering at 650 °C for 10 h, the SEM images have clearly shown that both the precursor and the final product still retain their monodispersed spherical microstructures with similar particle size of about 3 μm when the samples are synthesised at the optimised condition. Copyright © 2017 Elsevier B.V. All rights reserved.

P-T phase diagram and structural transformations of molten P2O5 under pressure

NASA Astrophysics Data System (ADS)

Brazhkin, V. V.; Katayama, Y.; Lyapin, A. G.; Saitoh, H.

2014-03-01

The P2O5 compound is an archetypical glass-forming oxide with a record high hygroscopicity, which makes its study extremely difficult. We present the in situ x-ray diffraction study of the pressure-temperature phase diagram of P2O5 and, particularly, of the liquid P2O5 structure under high pressure up to 10 GPa. Additionally, quenching from the melt has been used to extend the melting curve up to 15 GPa. We found that structural transformation in the liquid P2O5 under pressure is unique and includes three stages: first, the disappearance of the intermediate range order of the melt together with a slow increase in the average first-coordination number (P-O and O-P neighbors) up to 4 GPa; second, the "normal" compression almost without structural modification at higher pressures up to 8-9 GPa; and, finally, the abrupt change of the short-range order structure of the liquid with the jumplike increase at 9-10 GPa. The last stage correlates with the melting curve maximum (≈1250 °C) at ≈10 GPa and can be interpreted as a transformation to the liquid phase with entirely fivefold-coordinated phosphorus and twofold-coordinated oxygen atoms.

Effect of administration of water enriched in O2 by injection or electrolysis on transcutaneous oxygen pressure in anesthetized pigs.

PubMed

Charton, Antoine; Péronnet, François; Doutreleau, Stephane; Lonsdorfer, Evelyne; Klein, Alexis; Jimenez, Liliana; Geny, Bernard; Diemunsch, Pierre; Richard, Ruddy

2014-01-01

Oral administration of oxygenated water has been shown to improve blood oxygenation and could be an alternate way for oxygen (O2) supply. In this experiment, tissue oxygenation was compared in anesthetized pigs receiving a placebo or water enriched in O2 by injection or a new electrolytic process. Forty-two pigs randomized in three groups received either mineral water as placebo or water enriched in O2 by injection or the electrolytic process (10 mL/kg in the stomach). Hemodynamic parameters, partial pressure of oxygen in the arterial blood (PaO2), skin blood flow, and tissue oxygenation (transcutaneous oxygen pressure, or TcPO2) were monitored during 90 minutes of general anesthesia. Absorption and tissue distribution of the three waters administered were assessed using dilution of deuterium oxide. Mean arterial pressure, heart rate, PaO2, arteriovenous oxygen difference, and water absorption from the gut were not significantly different among the three groups. The deuterium to protium ratio was also similar in the plasma, skin, and muscle at the end of the protocol. Skin blood flow decreased in the three groups. TcPO2 slowly decreased over the last 60 minutes of the experiment in the three groups, but when compared to the control group, the values remained significantly higher in animals that received the water enriched in O2 by electrolysis. In this protocol, water enriched in O2 by electrolysis lessened the decline of peripheral tissue oxygenation. This observation is compatible with the claim that the electrolytic process generates water clathrates which trap O2 and facilitate O2 diffusion along pressure gradients. Potential applications of O2-enriched water include an alternate method of oxygen supply.

Effect of administration of water enriched in O2 by injection or electrolysis on transcutaneous oxygen pressure in anesthetized pigs

PubMed Central

Charton, Antoine; Péronnet, François; Doutreleau, Stephane; Lonsdorfer, Evelyne; Klein, Alexis; Jimenez, Liliana; Geny, Bernard; Diemunsch, Pierre; Richard, Ruddy

2014-01-01

Background Oral administration of oxygenated water has been shown to improve blood oxygenation and could be an alternate way for oxygen (O2) supply. In this experiment, tissue oxygenation was compared in anesthetized pigs receiving a placebo or water enriched in O2 by injection or a new electrolytic process. Methods Forty-two pigs randomized in three groups received either mineral water as placebo or water enriched in O2 by injection or the electrolytic process (10 mL/kg in the stomach). Hemodynamic parameters, partial pressure of oxygen in the arterial blood (PaO2), skin blood flow, and tissue oxygenation (transcutaneous oxygen pressure, or TcPO2) were monitored during 90 minutes of general anesthesia. Absorption and tissue distribution of the three waters administered were assessed using dilution of deuterium oxide. Results Mean arterial pressure, heart rate, PaO2, arteriovenous oxygen difference, and water absorption from the gut were not significantly different among the three groups. The deuterium to protium ratio was also similar in the plasma, skin, and muscle at the end of the protocol. Skin blood flow decreased in the three groups. TcPO2 slowly decreased over the last 60 minutes of the experiment in the three groups, but when compared to the control group, the values remained significantly higher in animals that received the water enriched in O2 by electrolysis. Conclusions In this protocol, water enriched in O2 by electrolysis lessened the decline of peripheral tissue oxygenation. This observation is compatible with the claim that the electrolytic process generates water clathrates which trap O2 and facilitate O2 diffusion along pressure gradients. Potential applications of O2-enriched water include an alternate method of oxygen supply. PMID:25210438

Kinetics of solution crystal growth of strengite, FePO4,2H2O

NASA Astrophysics Data System (ADS)

Lundager Madsen, Hans E.; Koch, Christian Bender

2018-01-01

The iron(III) phosphate strengite, FePO4,2H2O, has been precipitated at 25 °C by mixing solutions of iron alum and ammonium phosphate. The rate of crystallization has been determined by pH recording. Three stages of crystal growth kinetics could be distinguished: (1) mononuclear growth, (2) polynuclear growth and, in a few cases, (3) spiral growth (BCF mechanism). From the first two, the value of edge free energy λ = 87 ± 1 pJ/m was found. The identity of the precipitate was verified by SEM, XRD and Mössbauer spectroscopy.

Paramagnetic defects in KH{sub 2}PO{sub 4} crystals with high concentration of embedded TiO{sub 2} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grachev, Valentin G., E-mail: grachev@physics.montana.edu; Tse, Romand; Malovichko, Galina I.

2016-01-21

Qualitative transformations of spectra of Electron Paramagnetic Resonance, EPR, were found in KH{sub 2}PO{sub 4} crystals grown from liquor with 10{sup −5}–10{sup −1 }wt. % of anatase TiO{sub 2} nanoparticles in comparison with nominally pure KH{sub 2}PO{sub 4}. The nanoparticles have larger segregation coefficient for prismatic parts of the crystals than for pyramidal ones. Significant decrease in resonance absorption, complete disappearance of EPR lines of Fe{sup 3+} and Cr{sup 3+} centers, and appearance of four weak lines of equal intensities together with broad asymmetric lines with g-factors about 2.07–2.5 was observed in pyramidal parts grown with concentration of TiO{sub 2} nanoparticlesmore » larger than the threshold value 10{sup −2 }wt. %. The four lines were attributed to non-controlled impurity As substituted for P. In the presence of TiO{sub 2} nanoparticles, non-paramagnetic AsO{sub 4}{sup 3−} clusters trap electrons becoming AsO{sub 4}{sup 4−}. Disappearance of Fe{sup 3+} and Cr{sup 3+} centers was explained by their recharge to “EPR-silent” states and/or pairing at the surface of TiO{sub 2} nanoparticles.« less

Crystallization of a Li2O2SiO2 Glass under High Hydrostatic Pressures

NASA Technical Reports Server (NTRS)

Fuss, T.; Day, D. E.; Lesher, C. E.; Ray, C. S.

2004-01-01

The crystallization behavior of a Li2O.2SiO2 (LS2) glass subjected to a uniform hydrostatic pressure of 4.5 or 6 GPa was investigated between 550 and 800 C using XRD, IR, Raman, TEM, NMR, and DTA. The density of the glass subjected to 6 GPa was between 2.52 plus or minus 0.01 and 2.57 plus or minus 0.01 grams per cubic centimeters, depending upon the processing temperatures, and was higher than that of the stoichiometric LS2 crystals, 2.46 plus or minus 0.01 grams per cubic centimeter. Thus, crystallization in 6 GPa glass occurred in a condition of negative volume dilatation, deltaV = V(sub glass) - V(sub crystal), while that for the 4.5 GPa glass occurred in the condition deltaV greater than 0. For deltaV greater than 0, which also includes the control glass at ambient (one atmosphere) pressure, the glasses always crystallize Li2Si2O5 (orthorhombic, Ccc2) crystals, but for deltaV less than 0 (6 GPa), the glasses crystallize Li2SiO3 crystals with a slightly deformed structure. The crystal growth rate vs. temperature curve moved to higher temperature with increasing pressure, and was independent of the sign of deltaV. These results for the effect of hydrostatic pressure on the crystallization of LS2 glass were discussed from thermodynamic considerations.

Pressure-induced Ge coordination change in SiO2-GeO2 glasses

NASA Astrophysics Data System (ADS)

Majérus, O.; Cormier, L.; Itié, J.-P.; Calas, G.

2003-04-01

Among the parameters controlling igneous processes in Earth, the density and transport properties of silicate melts are playing a major role. These properties are strongly dependent upon pressure, in a way that can significantly differ from the crystalline phases. The study of the pressure-induced structural changes can give a further understanding of the peculiar microscopic origins of these properties in molten phases. As in silicate minerals, the coordination change IVSi towards VISi is expected to be the major transformation occurring in melts at mantle conditions, yielding amorphous phases with properties distinct to those corresponding to a tetrahedral framework. This change is predicted by molecular dynamics simulations, but experimental evidences are scarce because of difficult technical constraints. The binary SiO_2-GeO_2 system allows a further insight into the compression mechanism of a tetrahedral framework glass structure. The Ge coordination change and its composition dependence can be assessed by using XAS spectroscopy at Ge K-edge with a diamond anvil cell. In this study, we report an in situ investigation carried out on well characterized glasses of the SiO_2-GeO_2 system. Experiments were preformed on the D11 beamline which is a unique dispersive experimental setup developed at the Laboratoire pour l’Utilisation du Rayonnement Magnétique (LURE, Orsay, France). Pressures up to 25 GPa have been obtained. With increasing SiO_2 content, both Ge-O distances extracted from EXAFS data and XANES features indicate the regular increase of the pressure threshold for the Ge coordination change (from 4 in pure GeO_2 to 12 Gpa in 80 mol% SiO_2-bearing glass), which corresponds to the end of the elastic compression regime, and the achievement of the transformation on a broader pressure range as predicted in pure SiO_2. These data are compared to results on slightly depolymerised glasses of Na_2O-GeO_2 composition, where a greater variety of compression

Pressure induced phase transformations in NaZr{sub 2}(PO{sub 4}){sub 3} studied by X-ray diffraction and Raman spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamali, K.; Ravindran, T.R., E-mail: trr@igcar.gov.in; Chandra Shekar, N.V.

2015-01-15

Raman spectroscopic and x-ray diffraction measurements on NaZr{sub 2}(PO{sub 4}){sub 3} were carried out up to 30 GPa at close intervals of pressure, revealing two structural phase transformations around 5 and 6.6 GPa. The second phase at 5.4 GPa is indexed to R3 space group similar to that of RbTi{sub 2}(PO{sub 4}){sub 3}. Bulk modulus decreases abruptly from 53 GPa (B′=4) to 36 GPa (B′=4) in the second phase above 5 GPa. The structure of the phase III at 8.2 GPa is indexed as orthorhombic similar to the case of high temperature phase of monoclinic LiZr{sub 2}(PO{sub 4}){sub 3}. Bulkmore » modulus of this phase III is found to be 65 GPa (B′=4), which is higher than that of the ambient phase. In high pressure Raman studies, modes corresponding to 72 and 112 cm{sup −1} soften in the ambient phase whereas around 5 GPa, the ones at 60, 105, 125 and 190 cm{sup −1} soften with pressure contributing negatively to overall thermal expansion. - Graphical abstract: High pressure study of NaZr{sub 2}(PO{sub 4}){sub 3} shows a reversible phase transition from R-3c to R3 structure at 5 GPa accompanied by an increase in compressibility signaling a polyhedral tilt transition. - Highlights: • NaZr{sub 2}(PO{sub 4}){sub 3} undergoes two reversible phase transitions at 5 and 6.7 GPa. • The transition at 5 is from rhombohedral R-3c to R3 structure. • Bulk modulus of NaZr{sub 2}(PO{sub 4}){sub 3} is lower than that for the isostructural RbTi{sub 2}(PO{sub 4}){sub 3.} • Compressibility increases with substitution of a smaller cation (Na). • Zr-translational and PO{sub 4} librational modes contribute to phase transition.« less

Erratum to: Blood HbO2 and HbCO2 dissociation curves at varied O2, CO2, pH, 2,3-DPG and temperature levels.

PubMed

Dash, Ranjan K; Bassingthwaighte, James B

2010-04-01

New mathematical model equations for O(2) and CO(2) saturations of hemoglobin (S(HbO)(2) and S(HbCO)(2) are developed here from the equilibrium binding of O(2) and CO(2) with hemoglobin inside RBCs. They are in the form of an invertible Hill-type equation with the apparent Hill coefficients KHbO(2) and KHbCO(2) in the expressions for SHbO(2) and SHbCO(2) dependent on the levels of O(2) and CO(2) partial pressures (P(O)(2) and P(CO)(2)), pH, 2,3-DPG concentration, and temperature in blood. The invertibility of these new equations allows PO(2) and PCO(2) to be computed efficiently from S(HbO)(2) and S(HbCO)(2) and vice versa. The oxyhemoglobin (HbO(2)) and carbamino-hemoglobin (HbCO(2)) dissociation curves computed from these equations are in good agreement with the published experimental and theoretical curves in the literature. The model solutions describe that, at standard physiological conditions, the hemoglobin is about 97.2% saturated by O(2) and the amino group of hemoglobin is about 13.1% saturated by CO(2). The O(2) and CO(2) content in whole blood are also calculated here from the gas solubilities, hematocrits, and the new formulas for S(HbO)(2) and S(HbCO)(2). Because of the mathematical simplicity and invertibility, these new formulas can be conveniently used in the modeling of simultaneous transport and exchange of O(2) and CO(2) in the alveoli-blood and blood-tissue exchange systems.

Synthesis, structure, and magnetic properties of new layered phosphate halides Sr2Cu5(PO4)4X2·8H2O (X = Cl, Br) with a crown-like building unit.

PubMed

Qiu, Chaoqun; He, Zhangzhen; Cui, Meiyan; Tang, Yingying; Chen, Sihuai

2017-03-27

Two new compounds Sr 2 Cu 5 (PO 4 ) 4 X 2 ·8H 2 O (X = Cl and Br) are synthesized by a conventional hydrothermal method. Sr 2 Cu 5 (PO 4 ) 4 Cl 2 ·8H 2 O crystallizes in the tetragonal system with a space group of P42 1 2, while Sr 2 Cu 5 (PO 4 ) 4 Br 2 ·8H 2 O crystallizes in the space group P4/nmm, which are found to have a similar framework of layered structure, in which the crown-like {Cu 5 (PO 4 ) 4 X 2 } building units connect to each other forming a 2D corrugated sheet with vacancies, while the Sr 2+ cations are located along the vacancies. The spin lattice of two compounds built by Cu 2+ ions shows a new type of corrugated square. Magnetic measurements confirmed that both Sr 2 Cu 5 (PO 4 ) 4 X 2 ·8H 2 O (X = Cl and Br) exhibit antiferromagnetic ordering at low temperatures. A fit of theoretical model shows exchange interaction J = -25.62 K for the Cl-analogue and J/k B = -26.47 K for the Br-analogue.

40 CFR 721.9675 - Titanate [Ti6O13 (2-)], di-po-tas-sium.

Code of Federal Regulations, 2013 CFR

2013-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9675 Titanate [Ti6O13 (2-)], di-po-tas-sium. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as titanate [Ti6O13 (2-)], dipotassium (CAS No...

40 CFR 721.9675 - Titanate [Ti6O13 (2-)], di-po-tas-sium.

Code of Federal Regulations, 2010 CFR

2010-07-01

... SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.9675 Titanate [Ti6O13 (2-)], di-po-tas-sium. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as titanate [Ti6O13 (2-)], dipotassium (CAS No...

KH2PO4 single crystals activated with the Ti4+ ions in the form of TiO2-x × nH2O nanoparticles: Structural peculiarities, point defects, and dielectric properties

NASA Astrophysics Data System (ADS)

Kuz'micheva, Galina M.; Timaeva, Olesya I.; Kaurova, Irina A.; Svetogorov, Roman D.; Mühlbauer, Martin J.

2018-03-01

Potassium dihydrogen phosphate KH2PO4 (KDP) single crystals activated with Ti4+ ions in the form of TiO2-x × nH2O nanoparticles in the η-phase, synthesized by the sulfate method using TiOSO4 × xH2SO4 × yH2O, have been first grown by the temperature lowering method and cut from pyramidal (P) and prismatic (Pr) growth sectors. The first-performed neutron powder diffraction investigation of P and Pr samples cut from the KDP:Ti4+ crystal allowed us to reveal vacancies in the K and H sites for both samples, their number being larger in the Pr structure compared to the P one. Taking into account the deficiency of the K and H sites, full occupation of the O site, presence of Ti4+ ions in the structure, and the electroneutrality condition, a partial substitution of (PO4)3- anion by the (SO4)2- one, larger for the Pr sample, was observed. The real compositions of P and Pr samples, correlated with the cation-anion internuclear distances, were refined. The dielectric permittivity of the Pr sample was significantly lower than that of the P one; it decreases with decreasing K-O, P-O, and O...H distances and increasing deficiency of the K and H sites.

Crystal structure, thermally stability and photoluminescence properties of novel Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Qingfeng; Liao, Libing, E-mail: clayl@cugb.edu.cn; Mei, Lefu

2015-03-15

A series of novel luminescent phosphors Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} with apatite structure were synthesized via a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples, and the selected Sr{sub 9.97}(PO{sub 4}){sub 6}O:0.03Eu{sup 2+} phosphor exhibits strong thermal quenching resistance, retaining the luminance of 88.73% at 150 °C. The quenching concentration of Eu{sup 2+} in Sr{sub 10}(PO{sub 4}){sub 6}O was about 0.03 attributing to the dipole–quadrupole interaction. The Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphor exhibited a broad-bandmore » blue emission at 439 nm upon excitation at 346 nm. The results indicate that Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. - Graphical abstract: Sr{sub 10}(PO{sub 4}){sub 6}O:Eu{sup 2+} phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. - Highlights: • Sr{sub 9.97}(PO{sub 4}){sub 6}O:0.03Eu{sup 2+} phosphor exhibits strong thermal quenching resistance. • Two different Eu{sup 2+} emission centers exists in Sr{sub 10}(PO{sub 4}){sub 6}O. • The activation energy was also estimated for the Eu{sup 2+} luminescence center.« less

High pressure behavior of complex phosphate K2Ce[PO4]2: Grüneisen parameter and anharmonicity properties

NASA Astrophysics Data System (ADS)

Mishra, Karuna Kara; Bevara, Samatha; Ravindran, T. R.; Patwe, S. J.; Gupta, Mayanak K.; Mittal, Ranjan; Krishnan, R. Venkata; Achary, S. N.; Tyagi, A. K.

2018-02-01

Herein we reported structural stability, vibrational and thermal properties of K2Ce[PO4]2, a relatively underexplored complex phosphate of tetravalent Ce4+ from in situ high-pressure Raman spectroscopic investigations up to 28 GPa using a diamond anvil cell. The studies identified the soft phonons that lead to a reversible phase transformation above 8 GPa, and a phase coexistence of ambient (PI) and high pressure (PII) phases in a wider pressure region 6-11 GPa. From a visual representation of the computed eigen vector displacements, the Ag soft mode at 82 cm-1 is assigned as a lattice mode of K+ cation. Pressure-induced positional disorder is apparent from the substantial broadening of internal modes and the disappearance of low frequency lattice and external modes in phase PII above 18 GPa. Isothermal mode Grüneisen parameters γi of the various phonon modes are calculated and compared for several modes. Using these values, thermal properties such as average Grüneisen parameter, and thermal expansion coefficient are estimated as 0.47, and 2.5 × 10-6 K-1, respectively. The specific heat value was estimated from all optical modes obtained from DFT calculations as 314 J-mol-1 K-1. Our earlier reported temperature dependence of phonon frequencies is used to decouple the "true anharmonic" (explicit contribution at constant volume) and "quasi harmonic" (implicit contribution brought out by volume change) contributions from the total anharmonicity. In addition to the 81 cm-1 Ag lattice mode, several other lattice and external modes of PO43- ions are found to be strongly anharmonic.

Kinetic study of the thermal decomposition of uranium metaphosphate, U(PO3)4, into uranium pyrophosphate, UP2O7

NASA Astrophysics Data System (ADS)

Yang, Hee-Chul; Kim, Hyung-Ju; Lee, Si-Young; Yang, In-Hwan; Chung, Dong-Yong

2017-06-01

The thermochemical properties of uranium compounds have attracted much interest in relation to thermochemical treatments and the safe disposal of radioactive waste bearing uranium compounds. The characteristics of the thermal decomposition of uranium metaphosphate, U(PO3)4, into uranium pyrophosphate, UP2O7, have been studied from the view point of reaction kinetics and acting mechanisms. A mixture of U(PO3)4 and UP2O7 was prepared from the pyrolysis residue of uranium-bearing spent TBP. A kinetic analysis of the reaction of U(PO3)4 into UP2O7 was conducted using an isoconversional method and a master plot method on the basis of data from a non-isothermal thermogravimetric analysis. The thermal decomposition of U(PO3)4 into UP2O7 followed a single-step reaction with an activation energy of 175.29 ± 1.58 kJ mol-1. The most probable kinetic model was determined as a type of nucleation and nuclei-growth models, the Avrami-Erofeev model (A3), which describes that there are certain restrictions on nuclei growth of UP2O7 during the solid-state decomposition of U(PO3)4.

Photocatalytic activity of attapulgite-TiO2-Ag3PO4 ternary nanocomposite for degradation of Rhodamine B under simulated solar irradiation

NASA Astrophysics Data System (ADS)

He, Hongcai; Jiang, Zhuolin; He, Zhaoling; Liu, Tao; Li, Enzhu; Li, Bao-Wen

2018-01-01

An excellent ternary composite photocatalyst consisting of silver orthophosphate (Ag3PO4), attapulgite (ATP), and TiO2 was synthesized, in which heterojunction was formed between dissimilar semiconductors to promote the separation of photo-generated charges. The ATP/TiO2/Ag3PO4 composite was characterized by SEM, XRD, and UV-vis diffuse reflectance spectroscopy. The co-deposition of Ag3PO4 and TiO2 nanoparticles onto the surface of ATP forms a lath-particle structure. Compared with composite photocatalysts consisting of two phases, ATP/TiO2/Ag3PO4 ternary composite exhibits greatly improved photocatalytic activity for degradation of rhodamine B under simulated solar irradiation. Such ternary composite not only improves the stability of Ag3PO4, but also lowers the cost by reducing application amount of Ag3PO4, which provides guidance for the design of Ag3PO4- and Ag-based composites for photocatalytic applications.

Occlusion pressures in men rebreathing CO2 under methoxyflurane anesthesia.

PubMed

Derenne, J P; Couture, J; Iscoe, S; Whitelaw, A; Milic-Emili, J

1976-05-01

The effect of general anesthesia on control of breathing was studied by CO2 rebreathing and occlusion pressure measurements in six normal human subjects under methoxyflurane anesthesia. CO2 was found to increase the amplitude of the occlusion pressure wave without changing its shape, so that CO2 responses in terms of the occlusion pressure developed 100 ms after the onset of inspiration (Po/0.1) gave results equivalent to the responses in terms of Po/1.o or any other parameter of the pressure wave. Methoxyflurane depressed the ventilatory response to CO2 but not the occlusion pressure response, implying that the most important action of the anesthetic was to increase the effective elastance of the respiratory system rather than to depress the respiratory centers. The elastance was further increased by CO2, and this mechanical change had the effect of shifting the "apneic threshold" extrapolated from the ventilatory response curve to a lower PAco2. Frequency of breathing, inspiratory and expiratory times were not altered by CO2 in anesthetized subjects.

New crystals of the CsHSO{sub 4}–CsH{sub 2}PO{sub 4}–H{sub 2}O system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makarova, I. P., E-mail: makarova@crys.ras.ru; Grebenev, V. V.; Komornikov, V. A.

2016-11-15

Cs{sub 6}H(HSO{sub 4}){sub 3}(H{sub 2}PO{sub 4}){sub 4} crystals, grown for the first time based on an analysis of the phase diagram of the CsHSO{sub 4}–CsH{sub 2}PO{sub 4}–H{sub 2}O ternary system, have been investigated by structural analysis using synchrotron radiation. The atomic structure of the crystals is determined and its specific features are analyzed.

Synthesis and Electrocatalytic Activity of Ammonium Nickel Phosphate, [NH4]NiPO4·6H2O, and β-Nickel Pyrophosphate, β-Ni2P2O7: Catalysts for Electrocatalytic Decomposition of Urea.

PubMed

Meguerdichian, Andrew G; Jafari, Tahereh; Shakil, Md R; Miao, Ran; Achola, Laura A; Macharia, John; Shirazi-Amin, Alireza; Suib, Steven L

2018-02-19

Electrocatalytic decomposition of urea for the production of hydrogen, H 2, for clean energy applications, such as in fuel cells, has several potential advantages such as reducing carbon emissions in the energy sector and environmental applications to remove urea from animal and human waste facilities. The study and development of new catalyst materials containing nickel metal, the active site for urea decomposition, is a critical aspect of research in inorganic and materials chemistry. We report the synthesis and application of [NH 4 ]NiPO 4 ·6H 2 O and β-Ni 2 P 2 O 7 using in situ prepared [NH 4 ] 2 HPO 4 . The [NH 4 ]NiPO 4 ·6H 2 O is calcined at varying temperatures and tested for electrocatalytic decomposition of urea. Our results indicate that [NH 4 ]NiPO 4 ·6H 2 O calcined at 300 °C with an amorphous crystal structure and, for the first time applied for urea electrocatalytic decomposition, had the greatest reported electroactive surface area (ESA) of 142 cm 2 /mg and an onset potential of 0.33 V (SCE) and was stable over a 24-h test period.

Batagayite, CaZn2(Zn,Cu)6(PO4)4(PO3OH)3·12H2O, a new phosphate mineral from Këster tin deposit (Yakutia, Russia): occurrence and crystal structure

NASA Astrophysics Data System (ADS)

Yakovenchuk, Victor N.; Pakhomovsky, Yakov A.; Konopleva, Nataliya G.; Panikorovskii, Taras L.; Bazai, Ayya; Mikhailova, Julia A.; Bocharov, Vladimir N.; Ivanyuk, Gregory Yu.; Krivovichev, Sergey V.

2017-12-01

Batagayite, CaZn2(Zn,Cu)6(PO4)4(PO3OH)3·12H2O, is a new secondary phosphate mineral from the Këster deposit, Arga-Ynnykh-Khai massif, NE Yakutia, Russia. It is monoclinic, P21, a = 8.4264(4), b = 12.8309(6), c = 14.6928(9) Å, β = 98.514(6)o, V = 1571.05(15) Å3 and Z = 2 (from single-crystal X-ray diffraction data). Batagayite crystals are blades up to 2 mm long, flattened on {001} and elongated on [100]; blades often grow in radial aggregates. Associated minerals are arsenolite, native copper, epifanovite, fluorapatite, libethenite, Na-analogue of batagayite, pseudomalachite, quartz, sampleite, tobermorite, and Mg-analogue of hopeite. The streak is white and the luster is vitreous. The mineral is brittle and has a perfect cleavage on {001}, no parting was observed. The Mohs hardness is 3. Density, determined by the float-sink method in Clerici solution, is 2.90(3) g/cm3, and the calculated density is 3.02 g/cm3 (using the empirical formula and single-crystal unit-cell parameters). Batagayite is biaxial, optically negative, α = 1.566 ± 0.002, β = 1.572 ± 0.002, γ = 1.573 ± 0.002 at 589 nm. 2V meas. = 40(5)°, 2V calc = 44.3°. Optical orientation: Z is perpendicular to (001), further details unclear. No dispersion or pleochroism were observed. The mean chemical composition determined by electron microprobe is: Na2O 0.31, MgO 1.39, Al2O3 0.55, SiO2 0.48, P2O5 34.37, K2O 0.17, CaO 2.76, MnO 1.03, CuO 5.80, ZnO 35.62, CdO 0.24 wt%. The H2O content estimated from the crystal-structure refinement is 16.83 wt%, giving a total of 99.55 wt%. The empirical formula calculated on the basis of P + Si = 7 is (Zn6.22Cu1.04Ca0.70Mg0.49Mn0.21Al0.15Na0.14K0.05Cd0.03)Σ9.03(P6.89Si0.11)Σ7.00O24.91(OH)3.09·12.10H2O. The mineral easily dissolves in 10% room-temperature HCl. The eight diagnostic lines in the X-ray powder-diffraction pattern are (I-d[Å]-hkl): 100-14.59-001, 25-6.34-012, 11-6.02-111, 37-4.864-003, 13-4.766-112, 20-3.102-1 \\overline {2} \\overline {4} , 11-2.678-2

Compositions of supersaturated solutions for enhanced growth of {alpha}-NiSO{sub 4} . 6H{sub 2}O, Me{sub 2}Ni(SO{sub 4}){sub 2} . 6H{sub 2}O, MeH{sub 2}PO{sub 4} [Me = Li, Na, K, Rb, Cs, NH{sub 4}], and K(H{sub x}D{sub 1-x}){sub 2}PO{sub 4} single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soboleva, L. V., E-mail: afkonst@ns.crys.ras.ru

2008-05-15

The possibility of determining the optimal compositions and temperatures of supersaturated solutions for enhanced growth of single crystals of congruently and incongruently dissolving solid phases from the solubility diagrams of ternary systems is shown, and this approach is justified. The NiSO{sub 4}-H{sub 2}SO{sub 4}-H{sub 2}O, Me{sub 2}SO{sub 4}-NiSO{sub 4}-H{sub 2}O, and Me{sub 2}O-P{sub 2}O{sub 5}-H{sub 2}O(D{sub 2}O) systems have been used to determine the optimal compositions and temperatures of supersaturated solutions for growth of {alpha}-NiSO{sub 4} . 6H{sub 2}O, Me{sub 2}Ni(SO{sub 4}){sub 2} . 6H{sub 2}O, MeH{sub 2}PO{sub 4} [Me = Li, Na, K, Rb, Cs, NH{sub 4}], and Kmore » (H{sub x} D{sub 1-x}){sub 2}PO{sub 4} (D is deuterium) single crystals.« less

Influence of under pressure dissolved oxygen on trichloroethylene degradation by the H2O2/TiO2 process.

PubMed

Hoseini, Mohammad; Nabizadeh, Ramin; Nazmara, Shahrokh; Safari, Gholam Hossein

2013-12-20

The widespread use of trichloroethylene (TCE) and its frequent release into the environment has caused many environmental and health problems. In this study the degradation of TCE at different micromolar concentrations was investigated in a stainless steel reactor with various concentrations of H2O2 and TiO2 at different oxygen pressures and three different pHs. To examine the synergistic effect of under pressure oxygen on TCE degradation, the concentrations of H2O2 and TiO2 as well as pH were first optimized, and then the experiments were performed under optimal conditions. Gas chromatography with a flame ionization detector (FID) was used to measure TCE concentrations. Results showed that the percentage of TCE degradation without pressurized oxygen was low and it increased with increasing pressure of oxygen at all initial concentrations of TCE. The degradation percentages without oxygen pressure were 48.27%, 51.22%, 58.13% and 64.33% for TCE concentrations of 3000, 1500, 300 and 150 μg/L respectively. At an oxygen pressure of 2.5 atmospheres (atm) the percent degradation of TCE reached 84.85%, 89.14%, 93.13% and 94.99% respectively for the aforementioned TCE concentrations. The results of this study show that the application of dissolved oxygen under pressure increases the efficiency of the H2O2/TiO2 process on the degradation of TCE and can be used along with other oxidants as an effective method for the removal of this compound from aqueous solutions.

Influence of under pressure dissolved oxygen on trichloroethylene degradation by the H2O2/TiO2 process

PubMed Central

2013-01-01

Background The widespread use of trichloroethylene (TCE) and its frequent release into the environment has caused many environmental and health problems. In this study the degradation of TCE at different micromolar concentrations was investigated in a stainless steel reactor with various concentrations of H2O2 and TiO2 at different oxygen pressures and three different pHs. Methods To examine the synergistic effect of under pressure oxygen on TCE degradation, the concentrations of H2O2 and TiO2 as well as pH were first optimized, and then the experiments were performed under optimal conditions. Gas chromatography with a flame ionization detector (FID) was used to measure TCE concentrations. Results Results showed that the percentage of TCE degradation without pressurized oxygen was low and it increased with increasing pressure of oxygen at all initial concentrations of TCE. The degradation percentages without oxygen pressure were 48.27%, 51.22%, 58.13% and 64.33% for TCE concentrations of 3000, 1500, 300 and 150 μg/L respectively. At an oxygen pressure of 2.5 atmospheres (atm) the percent degradation of TCE reached 84.85%, 89.14%, 93.13% and 94.99% respectively for the aforementioned TCE concentrations. Conclusions The results of this study show that the application of dissolved oxygen under pressure increases the efficiency of the H2O2/TiO2 process on the degradation of TCE and can be used along with other oxidants as an effective method for the removal of this compound from aqueous solutions. PMID:24359702

Fabrication and Characterization of Luminescent Magnetic Bifunctional Nanocomposite Based on TbPO4·H2O Nanowires and Fe3O4 Nanoparticles

NASA Astrophysics Data System (ADS)

Huong, Nguyen Thanh; Hung, Nguyen Manh; Lien, Pham Thi; Van, Nguyen Duc; Nam, Pham Hong; Binh, Nguyen Thanh; Minh, Le Quoc

2016-07-01

The fabrication and properties of luminescent magnetic bifunctional nanocomposites comprised of TbPO4·H2O nanowires as a core and magnetite nanoparticles as a shell are presented. TbPO4·H2O nanowires were synthesized by a microwave-assisted method while the grafting process of freshly-formed superparamagnetic magnetite nanoparticles on the surface of luminescent nanowires was carried out by a co-precipitate method. The effects of the Fe3O4/TbPO4·H2O mass ratio on the luminescent and magnetic properties of the obtained nanocomposite were also investigated. The results showed that, for the optimized bifunctional nanocomposites, green luminescent emissions at 488 nm, 542 nm, 585 nm, 620 nm and superparamagnetic behavior with saturation magnetization M s of 6 emu/g were achieved. With a hyperthermia temperature of ~43.5°C under an alternating current (AC) magnetic field, the obtained TbPO4·H2O/Fe3O4 nanocomposite was expected to be used for both optical probing and hyperthermia cancer treatments in biomedical applications.

High-pressure Phase Relation In The MgAl2O4-Mg2SiO4 System

NASA Astrophysics Data System (ADS)

Kojitani, H.; Hisatomi, R.; Akaogi, M.

2005-12-01

High-pressure and high-temperature experiments indicate that high-pressure phases of oceanic basalts contain Al-rich phases. MgAl2O4 with calcium ferrite-type crystal structure is considered as a main component of such the Al-rich phases. Since the calcium ferrite-type MgAl2O4 can be synthesized at only the maximum pressure of a Kawai-type high-pressure apparatus with tungsten carbide (WC) anvils, the amount of a synthesized sample is very limited. Therefore, the crystal structure of the calcium ferrite-type MgAl2O4 has been hardly known in detail due to these difficulties in sample synthesis. In our high-pressure experiments in the MgO-Al2O3-SiO2 system, it was shown that Mg2SiO4 component could be dissolved in the MgAl2O4 calcium ferrite. In this study, we tried to synthesize a single phase MgAl2O4 calcium ferrite sample and to make the Rietveld refinement of the XRD pattern of the sample. The high-pressure phase relations in the MgAl2O4-Mg2SiO4 system were studied to know the stability field of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions. Lattice parameters-composition relation of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions was also determined. High-pressure and high-temperature experiments were performed by using a Kawai-type high-pressure apparatus at Gakushuin University. WC anvils with truncated edge length of 1.5 mm were used. Heating was made by a Re heater. Temperature was measured by a Pt/Pt-13%Rh thermocouple. Starting materials for the phase relation experiments were the mixture of MgO, Al2O3 and SiO2 with bulk compositions of MgAl2O4:Mg2SiO4 = 90:10, 78:22, 70:30 and 50:50. The starting materials were held at 21-27 GPa and 1600 °C for 3 hours and then were recovered by the quenching method. The MgAl2O4 calcium ferrite sample for the Rietveld analysis was prepared by heating MgAl2O4 spinel at 27 GPa and about 2200 °C for one hour. Powder X-ray diffraction (XRD) profiles of obtained samples were measured by using a X-ray diffractometer

Increased hemoglobin O2 affinity protects during acute hypoxia

PubMed Central

Yalcin, Ozlem

2012-01-01

Acclimatization to hypoxia requires time to complete the adaptation mechanisms that influence oxygen (O2) transport and O2 utilization. Although decreasing hemoglobin (Hb) O2 affinity would favor the release of O2 to the tissues, increasing Hb O2 affinity would augment arterial O2 saturation during hypoxia. This study was designed to test the hypothesis that pharmacologically increasing the Hb O2 affinity will augment O2 transport during severe hypoxia (10 and 5% inspired O2) compared with normal Hb O2 affinity. RBC Hb O2 affinity was increased by infusion of 20 mg/kg of 5-hydroxymethyl-2-furfural (5HMF). Control animals received only the vehicle. The effects of increasing Hb O2 affinity were studied in the hamster window chamber model, in terms of systemic and microvascular hemodynamics and partial pressures of O2 (Po2). Pimonidazole binding to hypoxic areas of mice heart and brain was also studied. 5HMF decreased the Po2 at which the Hb is 50% saturated with O2 by 12.6 mmHg. During 10 and 5% O2 hypoxia, 5HMF increased arterial blood O2 saturation by 35 and 48% from the vehicle group, respectively. During 5% O2 hypoxia, blood pressure and heart rate were 58 and 30% higher for 5HMF compared with the vehicle. In addition, 5HMF preserved microvascular blood flow, whereas blood flow decreased to 40% of baseline in the vehicle group. Consequently, perivascular Po2 was three times higher in the 5HMF group compared with the control group at 5% O2 hypoxia. 5HMF also reduced heart and brain hypoxic areas in mice. Therefore, increased Hb O2 affinity resulted in hemodynamics and oxygenation benefits during severe hypoxia. This acute acclimatization process may have implications in survival during severe environmental hypoxia when logistic constraints prevent chronic acclimatization. PMID:22636677

Incorporation of thorium in the rhabdophane structure: Synthesis and characterization of Pr1-2xCaxThxPO4·nH2O solid solutions

NASA Astrophysics Data System (ADS)

Qin, Danwen; Mesbah, Adel; Gausse, Clémence; Szenknect, Stéphanie; Dacheux, Nicolas; Clavier, Nicolas

2017-08-01

Thorium incorporation in the rhabdophane structure as Pr1-2xCaxThxPO4·nH2O solid solutions was successfully achieved and resulted in the preparation of a low temperature precursor of the monazite-cheralite type Pr1-2xCaxThxPO4. The rhabdophane compounds are considered as potential neoformed phases in case of release of actinides from the phosphate-based ceramic wasteforms envisaged to host radionuclides in the back-end of the nuclear fuel cycle. A multiparametric study was thus undertaken to specify the wet chemistry conditions (starting stoichiometry, temperature, heating time) leading to single phase Pr1-2xCaxThxPO4·nH2O powdered samples. The excess of calcium appeared to be a prevailing factor with a suggested initial Ca:Th ratio being equal to 10. Similarly, the recommended heating time should exceed 4 days while the optimal temperature of synthesis is 110 °C. Under these conditions, the stability domain of Pr1-2xCaxThxPO4·nH2O ranged from x = 0.00 to x = 0.15. After heating at 1100 °C under air during 6 h, rhabdophane-type samples were fully converted into the highly durable Pr1-2xCaxThxPO4 cheralite ceramic wasteform.

Synthesis and structure of cesium complexes of nitrilotris(methylenephosphonic) acid [Cs-μ6-NH(CH2PO3)3H4] and [Cs2-μ10-NH(CH2PO3H)3] · H2O

NASA Astrophysics Data System (ADS)

Somov, N. V.; Chausov, F. F.; Zakirov, R. M.

2017-07-01

3D coordination polymers cesium nitrilotris(methylenephosphonate) and dicesium nitrilotris( methylenephosphonate) are synthesized and their crystal structure is determined. In the crystal of [Cs-μ6-NH(CH2PO3)3H4] (space group P, Z = 2), cesium atoms occupy two crystallographically inequivalent positions with c.n. = 10 and c.n. = 14. The phosphonate ligand plays the bridging function; its denticity is nine. The crystal packing consists of alternating layers of Cs atoms in different environments with layers of ligand molecules between them. A ligand is bound to three Cs atoms of one layer and three Cs atoms of another layer. In the crystal of [Cs2-μ10-NH(CH2PO3H)3] · H2O (space group P, Z = 2), the complex has a dimeric structure: the bridging phosphonate ligand coordinates Cs to form a three-dimensional Cs4O6 cluster. The denticity of the ligand is equal to nine; the coordination numbers of cesium atoms are seven and nine. Two-dimensional corrugated layers of Cs4O6 clusters lie in the (002) plane, and layers of ligand molecules are located between them. Each ligand molecule coordinates eight Cs atoms of one layer and two Cs atoms of the neighboring layer.

Investigation of the system ThO 2-NpO 2-P 2O 5. Solid solutions of thorium-neptunium (IV) phosphate-diphosphate

NASA Astrophysics Data System (ADS)

Dacheux, N.; Thomas, A. C.; Brandel, V.; Genet, M.

1998-11-01

Considering that phosphate matrices could be potential candidates for the immobilization of actinides or for the final disposal of the excess plutonium from dismantled nuclear weapons, the chemistry of thorium phosphates has been re-examined. In the ThO 2-P 2O 5 system, the thorium phosphate-diphosphate Th 4(PO 4) 4P 2O 7 (TPD) can be synthesized by wet and dry chemical processes. The substitution of thorium by other tetravalent actinides like uranium or plutonium can be obtained for 0 < x < 3.0 and 0 < x < 1.63, respectively. In this work, we report the chemical conditions of synthesis of thorium-neptunium (IV) phosphate-diphosphate solid solutions Th 4- xNp x(PO 4) 4P 2O 7 (TNPD) with 0 < x < 1.6 from a mixture of thorium and neptunium (IV) nitrates and concentrated phosphoric acid. From the variation of the cell parameters and volume, the maximum substitution of Th 4+ by Np 4+ in the TPD structure is evaluated to 2.08 (which corresponds to about 52 mol% of thorium replaced by neptunium (IV)). The field of existence of solid solutions Th 4- xU- xNp- xPuU xUNp xNpPu xPu(PO 4)4P 2O 7 has been calculated. These solid solutions should be synthesized for 5 xU+7 xNp+9 xPu⩽15. In the NpO 2-P 2O 5 system, the unit cell parameters of Np 2O(PO 4) 2 were refined by analogy with U 2O(PO 4) 2 which crystallographic data have been published recently. For Np 2O(PO 4) 2 the unit cell is orthorhombic with the following cell parameters: a=7.033(2) Å, b=9.024(3) Å, c=12.587(6) Å and V=799(1) Å 3. The unit cell parameter obtained for α-NpP 2O 7 ( a=8.586(1) Å) is in good agreement with those already reported in literature.

A vibrational spectroscopic study of the silicate mineral lomonosovite Na5Ti2(Si2O7)(PO4)O2

NASA Astrophysics Data System (ADS)

Frost, Ray L.; López, Andrés; Theiss, Frederick L.; Graça, Leonardo M.; Scholz, Ricardo

2015-01-01

The mineral lomonosovite has been studied using a combination of scanning electron microscopy with energy dispersive X-ray analysis and vibrational spectroscopy. Qualitative chemical analysis gave Si, P, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and Al. The mineral lomonosovite has a formula Na5Ti2(Si2O7)(PO4)O2. Raman bands observed at 909, 925 and 939 cm-1 are associated with phosphate units. Raman bands found at 975, 999, 1070, 1080 and 1084 cm-1 are attributed to siloxane stretching vibrations. The observation of multiple bands in both the phosphate stretching and bending regions supports the concept that the symmetry of the phosphate anion in the structure of lomonosovite is significantly reduced. Infrared spectroscopy identifies bands in the water stretching and bending regions, thus suggesting that water is involved with the structure of lomonosovite either through adsorption on the surface or by bonding to the phosphate units.

In pursuit of the rhabdophane crystal structure: from the hydrated monoclinic LnPO{sub 4}.0.667H{sub 2}O to the hexagonal LnPO{sub 4} (Ln = Nd, Sm, Gd, Eu and Dy)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mesbah, Adel, E-mail: adel.mesbah@cea.fr; Clavier, Nicolas; Elkaim, Erik

The dehydration process of the hydrated rhabdophane LnPO{sub 4}.0.667H{sub 2}O (Ln = La to Dy) was thoroughly studied over the combination of in situ high resolution synchrotron powder diffraction and TGA experiments. In the case of SmPO{sub 4}.0.667H{sub 2}O (monoclinic, C2), a first dehydration step was identified around 80 °C leading to the formation of SmPO{sub 4}.0.5H{sub 2}O (Monoclinic, C2) with Z =12 and a =17.6264(1) Å, b =6.9704(1) Å, c =12.1141(1) Å, β=133.74(1) °, V =1075.33(1) Å{sup 3}. In agreement with the TGA and dilatometry experiments, all the water molecules were evacuated above 220 °C yielding to the anhydrousmore » form, which crystallizes in the hexagonal P3{sub 1}21 space group with a =7.0389(1) Å, c =6.3702(1) Å and V =273.34(1) Å{sup 3}. This study was extended to selected LnPO{sub 4}.0.667H{sub 2}O samples (Ln= Nd, Gd, Eu, Dy) and the obtained results confirmed the existence of two dehydration steps before the stabilization of the anhydrous form, with the transitory formation of LnPO{sub 4}.0.5H{sub 2}O. - Graphical abstract: The dehydration process of the rhabdophane SmPO{sub 4}.0.667H{sub 2}O was studied over combination of in situ high resolution synchrotron powder diffraction and TGA techniques, a first dehydration was identified around 80 °C leading to the formation of SmPO{sub 4}.0.5H{sub 2}O (Monoclinic, C2). Then above 220 °C, the anhydrous form of the rhabdophane SmPO{sub 4} was stabilized and crystallizes in the hexagonal P3{sub 1}21 space group. - Highlights: • In situ synchrotron powder diffraction was carried out during the dehydration of the rhabdopahe LnPO{sub 4}.0.667H{sub 2}O. • The heat of the rhabdophane LnPO{sub 4}.0.667H{sub 2}O leads to LnPO{sub 4}.0.5H{sub 2}O then to anhydrous rhabdophane LnPO{sub 4}. • LnPO{sub 4}.0.5H{sub 2}O (monoclinic, C2) and LnPO{sub 4} (Hexagonal, P3{sub 1}21) were solved over the use of direct methods.« less

Estimates of atmospheric O2 in the Paleoproterozoic from paleosols

NASA Astrophysics Data System (ADS)

Kanzaki, Yoshiki; Murakami, Takashi

2016-02-01

A weathering model was developed to constrain the partial pressure of atmospheric O2 (PO2) in the Paleoproterozoic from the Fe records in paleosols. The model describes the Fe behavior in a weathering profile by dissolution/precipitation of Fe-bearing minerals, oxidation of dissolved Fe(II) to Fe(III) by oxygen and transport of dissolved Fe by water flow, in steady state. The model calculates the ratio of the precipitated Fe(III)-(oxyhydr)oxides from the dissolved Fe(II) to the dissolved Fe(II) during weathering (ϕ), as a function of PO2 . An advanced kinetic expression for Fe(II) oxidation by O2 was introduced into the model from the literature to calculate accurate ϕ-PO2 relationships. The model's validity is supported by the consistency of the calculated ϕ-PO2 relationships with those in the literature. The model can calculate PO2 for a given paleosol, once a ϕ value and values of the other parameters relevant to weathering, namely, pH of porewater, partial pressure of carbon dioxide (PCO2), water flow, temperature and O2 diffusion into soil, are obtained for the paleosol. The above weathering-relevant parameters were scrutinized for individual Paleoproterozoic paleosols. The values of ϕ, temperature, pH and PCO2 were obtained from the literature on the Paleoproterozoic paleosols. The parameter value of water flow was constrained for each paleosol from the mass balance of Si between water and rock phases and the relationships between water saturation ratio and hydraulic conductivity. The parameter value of O2 diffusion into soil was calculated for each paleosol based on the equation for soil O2 concentration with the O2 transport parameters in the literature. Then, we conducted comprehensive PO2 calculations for individual Paleoproterozoic paleosols which reflect all uncertainties in the weathering-relevant parameters. Consequently, robust estimates of PO2 in the Paleoproterozoic were obtained: 10-7.1-10-5.4 atm at ∼2.46 Ga, 10-5.0-10-2.5 atm at ∼2

Repeated assessment of orthotopic glioma pO2 by multi-site EPR oximetry: A technique with the potential to guide therapeutic optimization by repeated measurements of oxygen

PubMed Central

Khan, Nadeem; Mupparaju, Sriram; Hou, Huagang; Williams, Benjamin B.; Swartz, Harold

2011-01-01

Tumor hypoxia plays a vital role in therapeutic resistance. Consequently, measurements of tumor pO2 could be used to optimize the outcome of oxygen-dependent therapies, such as, chemoradiation. However, the potential optimizations are restricted by the lack of methods to repeatedly and quantitatively assess tumor pO2 during therapies, particularly in gliomas. We describe the procedures for repeated measurements of orthotopic glioma pO2 by multi-site electron paramagnetic resonance (EPR) oximetry. This oximetry approach provides simultaneous measurements of pO2 at more than one site in the glioma and contralateral cerebral tissue. The pO2 of intracerebral 9L, C6, F98 and U251 tumors, as well as contralateral brain, were measured repeatedly for five consecutive days. The 9L glioma was well oxygenated with pO2 of 27 - 36 mm Hg, while C6, F98 and U251 glioma were hypoxic with pO2 of 7 - 12 mm Hg. The potential of multi-site EPR oximetry to assess temporal changes in tissue pO2 was investigated in rats breathing 100% O2. A significant increase in F98 tumor and contralateral brain pO2 was observed on day 1 and day 2, however, glioma oxygenation declined on subsequent days. In conclusion, EPR oximetry provides the capability to repeatedly assess temporal changes in orthotopic glioma pO2. This information could be used to test and optimize the methods being developed to modulate tumor hypoxia. Furthermore, EPR oximetry could be potentially used to enhance the outcome of chemoradiation by scheduling treatments at times of increase in glioma pO2. PMID:22079559

Preparation of orthophosphate glasses in the MgO-CaO-SiO2-Nb2O5-P2O5 system.

PubMed

Lee, Sungho; Ueda, Kyosuke; Narushima, Takayuki; Nakano, Takayoshi; Kasuga, Toshihiro

2017-01-01

Niobia/magnesia-containing orthophosphate invert glasses were successfully prepared in our earlier work. Orthophosphate groups in the glasses were cross-linked by tetrahedral niobia (NbO4) and magnesia. The aim of this work is to prepare calcium orthophosphate invert glasses containing magnesia and niobia, incorporating silica, and to evaluate their structures and releasing behaviors. The glasses were prepared by melt-quenching, and their structures and ion-releasing behaviors were evaluated. 31P solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies showed the glasses consist of orthophosphate (PO4), orthosilicate (SiO4), and NbO4 tetrahedra. NbO4 and MgO in the glasses act as network formers. By incorporating SiO2 into the glasses, the chemical durability of the glasses was slightly improved. The glasses reheated at 800°C formed the orthophosphate crystalline phases, such as β-Ca3(PO4)2, Mg3(PO4)2 and Mg3Ca3(PO4)4 in the glasses. The chemical durability of the crystallized glasses was slightly improved. Orthosilicate groups and NbO4 in the glasses coordinated with each other to form Si-O-Nb bonds. The chemical durability of the glasses was slightly improved by addition of SiO2, since the field strength of Si is larger than that of Ca or Mg.

High pressure synthesis of amorphous TiO2 nanotubes

NASA Astrophysics Data System (ADS)

Li, Quanjun; Liu, Ran; Wang, Tianyi; Xu, Ke; Dong, Qing; Liu, Bo; Liu, Jing; Liu, Bingbing

2015-09-01

Amorphous TiO2 nanotubes with diameters of 8-10 nm and length of several nanometers were synthesized by high pressure treatment of anatase TiO2 nanotubes. The structural phase transitions of anatase TiO2 nanotubes were investigated by using in-situ high-pressure synchrotron X-ray diffraction (XRD) method. The starting anatase structure is stable up to ˜20GPa, and transforms into a high-density amorphous (HDA) form at higher pressure. Pressure-modified high- to low-density transition was observed in the amorphous form upon decompression. The pressure-induced amorphization and polyamorphism are in good agreement with the previous results in ultrafine TiO2 nanoparticles and nanoribbons. The relationship between the LDA form and α-PbO2 phase was revealed by high-resolution transmission electron microscopy (HRTEM) study. In addition, the bulk modulus (B0 = 158 GPa) of the anatase TiO2 nanotubes is smaller than those of the corresponding bulks and nanoparticles (180-240 GPa). We suggest that the unique open-ended nanotube morphology and nanosize play important roles in the high pressure phase transition of TiO2 nanotubes.

New polymorphs of Ru IIIP 3O 9: Cyclo-hexaphosphate Ru 2P 6O 18 and metaphosphate Ru(PO 3) 3 with a novel structure

NASA Astrophysics Data System (ADS)

Fukuoka, Hiroshi; Imoto, Hideo; Saito, Taro

1995-10-01

Two new polymorphs of ruthenium phosphate with RuP 3O 9 composition were prepared and their crystal structures were determined by single-crystal X-ray diffraction. They are cyclo-hexaphosphate Ru 2P 6O 18 and metaphosphate Ru(PO 3) 3. Ru 2P 6O 18 crystallizes in the monoclinic space group P2 1/ c with a = 6.292(2) Å, b = 15.276(2) Å, c = 8.365(2) Å, β = 106.54(2)°, V = 770.6(3) Å 3, Z = 2, R = 0.043, RW = 0.035. The structure contains cyclo-hexaphosphate rings stacking obliquely along the [100] direction and is isotypic with B-form cyclo-phosphates. Ru(PO 3) 3 has a novel structure and crystallizes in the triclinic space group P overline1 with a = 6.957(1) Å, b = 10.324(2) Å, c = 5.030(1) Å, α = 92.45(2)°, β = 92.31(2)°, γ = 98.61(1)°, V = 356.5(1) Å 3, Z = 2, R = 0.030, RW = 0.027. It is built up of a network of infinite [PO 3-] ∞ chains and RuO 6 octahedra. The configuration of the metaphosphate chains is different from that in the C-form Ru(PO 3) 3. While the chains in the C-form consisting of PO 3OPO 3 units are condensed in nearly staggered configurations, the units in the new phosphate are eclipsed.

High pressure phase transitions and compressibilities of Er2Zr2O7 and Ho2Zr2O7

NASA Astrophysics Data System (ADS)

Zhang, F. X.; Lang, M.; Becker, U.; Ewing, R. C.; Lian, J.

2008-01-01

Phase stability and compressibility of rare earth zirconates with the defect-fluorite structure were investigated by in situ synchrotron x-ray diffraction. A sluggish defect-fluorite to a cotunnitelike phase transformation occurred at pressures of ˜22 and ˜30GPa for Er2Zr2O7 and Ho2Zr2O7, respectively. Enhanced compressibility was found for the high pressure phase as a result of increasing cation coordination number and cation-anion bond length.

Efficient UV-emitting X-ray phosphors: octahedral Zr(PO 4) 6 luminescence centers in potassium hafnium-zirconium phosphates K 2Hf 1- xZr x(PO 4) 2 and KHf 2(1- x) Zr 2 x(PO 4) 3

NASA Astrophysics Data System (ADS)

Torardi, C. C.; Miao, C. R.; Li, J.

2003-02-01

Potassium hafnium-zirconium phosphates, K 2Hf 1- xZr x(PO 4) 2 and KHf 2(1- x) Zr 2 x(PO 4) 3, are broad-band UV-emitting phosphors. At room temperature, they have emission peak maxima at approximately 322 and 305 nm, respectively, under 30 kV peak molybdenum X-ray excitation. Both phosphors demonstrate luminescence efficiencies that make them up to ˜60% as bright as commercially available CaWO 4 Hi-Plus. The solid-state and flux synthesis conditions, and X-ray excited UV luminescence of these two phosphors are discussed. Even though the two compounds have different atomic structures, they contain zirconium in the same active luminescence environment as that found in highly efficient UV-emitting BaHf 1- xZr x(PO 4) 2. All the three materials have hafnium and zirconium in octahedral coordination via oxygen-atom corner sharing with six separate PO 4 tetrahedra. This octahedral Zr(PO 4) 6 moiety appears to be an important structural element for efficient X-ray excited luminescence, as are the edge-sharing octahedral TaO 6 chains for tantalate emission.

Molten salt flux synthesis and crystal structure of a new open-framework uranyl phosphate Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}: Spectroscopic characterization and cationic mobility studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yagoubi, S., E-mail: said.yagoubi@cea.fr; Renard, C.; Abraham, F.

2013-04-15

The reaction of triuranyl diphosphate tetrahydrate precursor (UO{sub 2}){sub 3}(PO{sub 4}){sub 2}(H{sub 2}O){sub 4} with a CsI flux at 750 °C yields a yellow single crystals of new compound Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}. The crystal structure (monoclinic, space group C2/c, a=13.6261 (13) Å, b=8.1081(8) Å, c=12.3983(12) Å, β=114.61(12)°, V=1245.41(20) Å{sup 3} with Z=4) has been solved using direct methods and Fourier difference techniques. A full-matrix least-squares refinement on the basis of F{sup 2} yielded R1=0.028 and wR2=0.071 for 79 parameters and 1352 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a charge-coupledmore » device detector. The crystal structure is built by two independent uranium atoms in square bipyramidal coordination, connected by two opposite corners to form infinite chains {sup 1}{sub ∞}[UO{sub 5}] and by one phosphorus atom in a tetrahedral environment PO{sub 4}. The two last entities {sup 1}{sub ∞}[UO{sub 5}] and PO{sub 4} are linked by sharing corners to form a three-dimensional structure presenting different types of channels occupied by Cs{sup +} alkaline cations. Their mobility within the tunnels were studied between 280 and 800 °C and compared with other tunneled uranyl minerals. The infrared spectrum shows a good agreement with the values inferred from the single crystal structure analysis of uranyl phosphate compound. - Graphical abstract: Arrhenius plot of the electrical conductivity of tunneled compounds Cs{sub 3}U{sub 2}PO{sub 10} and CsU{sub 2}Nb{sub 2}O{sub 11.5}. Highlights: ► The reaction of (UO{sub 2}){sub 3}(PO{sub 4}){sub 2}(H{sub 2}O){sub 4} in excess of molten CsI leads to single-crystals of new tunneled compound Cs{sub 3}(UO{sub 2}){sub 2}(PO{sub 4})O{sub 2}. ► Ionic conductivity measurements and crystal structure analysis indicate a strong connection of the Cs{sup +} cations to the tunnels. ► A low symmetry in Cs{sub 3

O(2)-dependent K(+) fluxes in trout red blood cells: the nature of O(2) sensing revealed by the O(2) affinity, cooperativity and pH dependence of transport.

PubMed

Berenbrink, M; Völkel, S; Heisler, N; Nikinmaa, M

2000-07-01

The effects of pH and O(2) tension on the isotonic ouabain-resistant K(+) (Rb+) flux pathway and on haemoglobin O2 binding were studied in trout red blood cells (RBCs) in order to test for a direct effect of haemoglobin O(2) saturation on K(+) transport across the RBC membrane. At pH values corresponding to in vivo control arterial plasma pH and higher, elevation of the O(2) partial pressure (PO(2)) from 7.8 to 157 mmHg increased unidirectional K(+) influx across the RBC membrane several-fold. At lower extracellular pH values, stimulation of K(+) influx by O(2) was depressed, exhibiting an apparent pK(a) (pK'(a)) for the process of 8.0. Under similar conditions the pK'(a) for acid-induced deoxygenation of haemoglobin (Hb) was 7.3. When trout RBCs were exposed to PO(2) values between 0 and 747 mmHg, O(2) equilibrium curves typical of Hb O(2) saturation were also obtained for K(+) influx and efflux. However, at pH 7.9, the PO(2) for half-maximal K(+) efflux and K(+) influx (P50) was about 8- to 12-fold higher than the P(50) for Hb-O(2) binding. While K(+) influx and efflux stimulation by O(2) was essentially non-cooperative, Hb-O(2) equilibrium curves were distinctly sigmoidal (Hill parameters close to 1 and 3, respectively). O(2)-stimulated K(+) influx and efflux were strongly pH dependent. When the definition of the Bohr factor for respiratory pigments (Phi = delta logP50 x delta pH(-1)) was extended to the effect of pH on O(2)-dependent K(+) influx and efflux, extracellular Bohr factors (Phi(o) of -2.00 and -2.06 were obtained, values much higher than that for Hb (Phi(o) = -0.49). The results of this study are consistent with an O(2) sensing mechanism differing markedly in affinity and cooperativity of O(2) binding, as well as in pH sensitivity, from bulk Hb.

Micro-Raman observation on the H2PO4- association structures in a supersaturated droplet of potassium dihydrogen phosphate (KH2PO4)

NASA Astrophysics Data System (ADS)

Syed, Kamran Ajmal; Pang, Shu-Feng; Zhang, Yun; Zhang, Yun-Hong

2013-01-01

The efflorescence of an individual KH2PO4 droplet on Teflon substrate was investigated by micro-Raman spectroscopy. With the decrease of relative humidity (RH) from 98.0% to 73.0%, the KH2PO4 droplet lost water gradually and entered into supersaturated state, which was reflected by the area ratio between the water stretching band to the sum of νs-PO2 and νs-P(OH)2 bands of the H2PO4- (A_{H_2 O} /(A_{(ν _s -PO_2 } {+ A}_{ν _s -P(OH)_2 {)}} {)}). In 1.0 mol l-1 KH2PO4 solution, the νs-P(OH)2 and νs-PO2 bands appeared at 877 and 1077 cm-1. In the KH2PO4 droplet, the two bands shifted to 894 and 1039 cm-1 at 98.0% RH, to 899 and 1031 cm-1 at 89.6% RH, and then to 904 and 997 cm-1 at 73.0% RH. Moreover, the aggregation process between the H2PO4- ions was observed from the spectral characteristic of the νs-P(OH)2 band in the concentration process, including the transitions of the H2PO4- ions from monomer in bulk solutions (0.5-1.0 mol l-1) to possible dimers at 98.0% RH and then further to oligomers in the droplet with the RH decrease, which were indicated by the blueshift of the νs-P(OH)2 band and its full width at half-height as a function of the RH. When the RH reached at 72.0%, the anhydrous crystal was obtained. A strong peak appeared at 928 cm-1, implying that the four oxygen atoms of the H2PO4- were all hydrogen bonding through the bridge hydrogen atoms to get the extensive hydrogen-bonded network structure of the H2PO4- association, leading to the symmetric increase of the H2PO4- ion from C2v in dilute solution to quasi-Td in the anhydrous crystal.

Repeated assessment of orthotopic glioma pO(2) by multi-site EPR oximetry: a technique with the potential to guide therapeutic optimization by repeated measurements of oxygen.

PubMed

Khan, Nadeem; Mupparaju, Sriram; Hou, Huagang; Williams, Benjamin B; Swartz, Harold

2012-02-15

Tumor hypoxia plays a vital role in therapeutic resistance. Consequently, measurements of tumor pO(2) could be used to optimize the outcome of oxygen-dependent therapies, such as, chemoradiation. However, the potential optimizations are restricted by the lack of methods to repeatedly and quantitatively assess tumor pO(2) during therapies, particularly in gliomas. We describe the procedures for repeated measurements of orthotopic glioma pO(2) by multi-site electron paramagnetic resonance (EPR) oximetry. This oximetry approach provides simultaneous measurements of pO(2) at more than one site in the glioma and contralateral cerebral tissue. The pO(2) of intracerebral 9L, C6, F98 and U251 tumors, as well as contralateral brain, were measured repeatedly for five consecutive days. The 9L glioma was well oxygenated with pO(2) of 27-36 mm Hg, while C6, F98 and U251 glioma were hypoxic with pO(2) of 7-12mm Hg. The potential of multi-site EPR oximetry to assess temporal changes in tissue pO(2) was investigated in rats breathing 100% O(2). A significant increase in F98 tumor and contralateral brain pO(2) was observed on day 1 and day 2, however, glioma oxygenation declined on subsequent days. In conclusion, EPR oximetry provides the capability to repeatedly assess temporal changes in orthotopic glioma pO(2). This information could be used to test and optimize the methods being developed to modulate tumor hypoxia. Furthermore, EPR oximetry could be potentially used to enhance the outcome of chemoradiation by scheduling treatments at times of increase in glioma pO(2). Copyright © 2011 Elsevier B.V. All rights reserved.

Structure of complexes of nitrilo tris methylene phosphonic acid with copper, [CuN(CH{sub 2}PO{sub 3}){sub 3}(H{sub 2}O){sub 3}] and Na{sub 4}[CuN(CH{sub 2}PO{sub 3}){sub 3}]{sub 2} · 19H{sub 2}O, as bactericides and inhibitors of scaling and corrosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: chaus@uni.udm.ru

2015-03-15

Nitrilotris methylene phosphonate triaqua copper and octasodium bis(nitrilotris methylene phosphonate cuprate(II)) nonadecahydrate have been synthesized and investigated. [CuN(CH{sub 2}PO{sub 3}){sub 3}(H{sub 2}O){sub 3}] is crystallized in the sp. gr. P2{sub 1}/c, Z = 4, a = 9.2506(2) Å, b = 15.9815(2) Å, c = 9.5474(2) Å, β = 113.697(2)°. The copper atom is coordinated by oxygen atoms in the configuration of elongated octahedron; the ligand (of bridge type) links neighboring copper atoms. Na{sub 8}[CuN(CH{sub 2}PO{sub 3}){sub 3}]{sub 2} · 19H{sub 2}O is crystallized in the sp. gr. P2{sub 1}/c, Z = 2, a = 11.24550(10) Å, b = 17.38980(10) Å,more » c = 13.5852(2) Å, β = 127.8120(10)°. This complex is chelating; the copper atom closes three five-membered N-C-P-O-Cu cycles with a shared Cu-N bond. Copper is coordinated in a distorted trigonal-bipyramidal configuration.« less

Facile synthesis of hierarchical Ag3PO4/TiO2 nanofiber heterostructures with highly enhanced visible light photocatalytic properties

NASA Astrophysics Data System (ADS)

Xie, Jinlei; Yang, Yefeng; He, Haiping; Cheng, Ding; Mao, Minmin; Jiang, Qinxu; Song, Lixin; Xiong, Jie

2015-11-01

Heterostructured semiconductor nanostructures have provoked great interest in the areas of energy, environment and catalysis. Herein, we report a novel hierarchical Ag3PO4/TiO2 heterostructure consisting of nearly spherical Ag3PO4 particles firmly coupled on the surface of TiO2 nanofibers (NFs). The construction of Ag3PO4/TiO2 heterostructure with tailored morphologies, compositions and optical properties was simply achieved via a facile and green synthetic strategy involving the electrospinning and solution-based processes. Owing to the synergetic effects of the components, the resulting hybrid heterostructures exhibited much improved visible light photocatalytic performance, which could degrade the RhB dye completely in 7.5 min. In addition, the coupling of Ag3PO4 particles with UV-light-sensitive TiO2 NFs enabled full utilization of solar energy and less consumption of noble metals, significantly appealing for their practical use in new energy sources and environmental issues. The developed synthetic strategy was considered to be applicable for the rational design and construction of other heterostructured catalysts.

In vivo PO2 imaging in the porcine model with perfluorocarbon F-19 NMR at low field.

PubMed

Thomas, S R; Pratt, R G; Millard, R W; Samaratunga, R C; Shiferaw, Y; McGoron, A J; Tan, K K

1996-01-01

Quantitative pO2 imaging in vivo has been evaluated utilizing F-19 NMR in the porcine model at 0.14 T for the lungs, liver, and spleen following i.p. administration of the commercial perfluorotributylamine (FC-43)-based perfluorocarbon (PFC) emulsion, Oxypherol-ET. Calculated T1 maps obtained from a two spin-echo saturation recovery/inversion recovery (SR/IR) pulse protocol are converted into quantitative pO2 images through a temperature-dependent calibration curve relating longitudinal relaxation rate (1/T1) to pO2. The uncertainty in pO2 for a T1 measurement error of +/- 5% as encountered in establishing the calibration curves ranges from +/- 10 torr (+/- 40%) at 25 torr to +/- 16 torr (+/- 11%) at 150 torr for FC-43 (37 degrees C). However, additional uncertainties in T1 dependent upon the signal-to-noise ratio may be introduced through the SR/IR calculated T1 pulse protocol, which might severely degrade the pO2 accuracy. Correlation of the organ image calculated pO2 with directly measured pO2 in airway or blood pools in six pigs indicate that the PFC resident in lung is in near equilibrium with arterialized blood and not with airway pO2, suggesting a location distal to the alveolar epithelium. For the liver, the strongest correlation implying equilibrium was evident for venous blood (hepatic vein). For the spleen, arterial blood pO2 (aorta) was an unreliable predictor of pO2 for PFC resident in splenic tissue. The results have demonstrated the utility and defined the limiting aspects quantitative pO2 imaging in vivo using F-19 MRI of sequestered PFC materials.

Bulk and grain-boundary ionic conductivity in sodium zirconophosphosilicate Na3Zr2(SiO4)2PO4 (NASICON)

NASA Astrophysics Data System (ADS)

Lunghammer, S.; Ma, Q.; Rettenwander, D.; Hanzu, I.; Tietz, F.; Wilkening, H. M. R.

2018-06-01

Sodium zirconophosphosilicates (Na1+x Zr2(P1-x SixO4)3 (0 < x < 3)) currently experience a kind of renaissance as promising ceramic electrolytes for safe all-solid-state Na batteries. Such energy storage systems are an emerging option for next-generation technologies with attractive cost due to the use of abundant elements as sodium. To identify the right candidates their ion transport properties need to be precisely studied. In many cases less is known about the contributions of blocking grain boundaries to the overall charge carrier transport. Here, we took advantage of broadband impedance and conductivity spectroscopy carried out at sufficiently low temperature to make visible these two contributions for polycrystalline Na3Zr2(SiO4)2PO4. It turned out that ion transport across the grain boundaries of a sintered pellet do not greatly hinder long-range ion dynamics. While bulk ion dynamics in Na3Zr2(SiO4)2PO4 is characterized by 1.0 mS cm-1, the grain boundary ionic conductivity is only slightly lower viz. 0.7 mS cm-1. The latter value is of large practical interest as it allows the realization of all-solid-state Na batteries without strong interfering resistances from grain boundaries.

Crystal structure and ion conductivity of a new mixed-anion phosphate LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sung-Chul; Lee, Mi-Sun; Kang, Jinyeong

2015-05-15

A new lithium-containing phosphate, LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7}, was prepared by a solid-state reaction, and it was characterized by an ab initio structure determination method on the basis of synchrotron powder X-ray diffraction data. LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} was found to be orthorhombic (space group Pnma) with lattice parameters a=9.0387(1) Å, b=10.6072(1) Å, c=8.3065(1) Å, and V=796.39(1) Å{sup 3}. The structure features infinite [Mg{sub 3}O{sub 10}]{sub ∞} layers that are parallel to the bc plane and that are interconnected along the a axis by PO{sub 4} and P{sub 2}O{sub 7} groups. The [Mg{sub 3}O{sub 10}]{sub ∞} layer containsmore » Mg{sub 3}O{sub 14} trimers that are formed by three edge-shared MgO{sub 6} octahedra. The PO{sub 4} and P{sub 2}O{sub 7} groups are located alternatively between [Mg{sub 3}O{sub 10}]{sub ∞} layers. This gives rise to a three-dimensional framework that contains large tunnels along the directions [1 0 0] and [0 1 0]; the Li{sup +} ions are stabilized in these tunnels. AC impedance spectroscopy shows that LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} has an ionic conductivity of 3.40×10{sup −5} S cm{sup −1} at 769 K, with an activation energy of 1.17 eV. - Graphical abstract: Polyhedral view of LiMg3(PO4)P2O7. Li+ ions are represented by orange spheres, MgO6 groups by octahedra, and PO4 groups by tetrahedra. - Highlights: • New compound LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} is reported. • The crystal structure is investigated by synchrotron XRD analysis. • The structure features [Mg{sub 3}O{sub 10}]{sub ∞} layers with interconnecting PO{sub 4} and P{sub 2}O{sub 7} groups. • Correlation between the crystal structure and ionic conductivity is discussed.« less

Studies on the structural stability of Co2P2O7 under pressure

NASA Astrophysics Data System (ADS)

Wang, W. P.; Pang, H.; Jin, M. L.; Shen, X.; Yao, Y.; Wang, Y. G.; Li, Y. C.; Li, X. D.; Jin, C. Q.; Yu, R. C.

2018-05-01

The crystal structural evolution of Co2P2O7 was studied by using in situ high pressure angle dispersive x-ray diffraction with synchrotron radiation. The results demonstrate that the α phase of Co2P2O7 goes through a partially irreversible structural transformation to β phase under pressure. The pressure is conductive to reduce the longest Cosbnd O bond length of the α phase, and then more uniform Cosbnd O bonds and regular hexagonal arrangement of CoO6 octahedra of the β phase are favored. According to the Birch-Murnaghan equation, the fitted bulk modulus B0 is 158.1(±5.6) GPa for α phase and 276.5(±6.5) GPa for β phase. Furthermore, the first-principles calculations show that these two phases of Co2P2O7 have almost equal total energies, and also have similar band structures and spin-polarized density of states at their ground states. This may be the reason why these two phases of Co2P2O7 can coexist in the pressure released state. It is found that the band gap energies decrease with increasing pressure for both phases.

In pursuit of the rhabdophane crystal structure: from the hydrated monoclinic LnPO4.0.667H2O to the hexagonal LnPO4 (Ln = Nd, Sm, Gd, Eu and Dy)

NASA Astrophysics Data System (ADS)

Mesbah, Adel; Clavier, Nicolas; Elkaim, Erik; Szenknect, Stéphanie; Dacheux, Nicolas

2017-05-01

The dehydration process of the hydrated rhabdophane LnPO4.0.667H2O (Ln = La to Dy) was thoroughly studied over the combination of in situ high resolution synchrotron powder diffraction and TGA experiments. In the case of SmPO4.0.667H2O (monoclinic, C2), a first dehydration step was identified around 80 °C leading to the formation of SmPO4.0.5H2O (Monoclinic, C2) with Z =12 and a =17.6264(1) Å, b =6.9704(1) Å, c =12.1141(1) Å, β=133.74(1) °, V =1075.33(1) Å3. In agreement with the TGA and dilatometry experiments, all the water molecules were evacuated above 220 °C yielding to the anhydrous form, which crystallizes in the hexagonal P3121 space group with a =7.0389(1) Å, c =6.3702(1) Å and V =273.34(1) Å3. This study was extended to selected LnPO4.0.667H2O samples (Ln= Nd, Gd, Eu, Dy) and the obtained results confirmed the existence of two dehydration steps before the stabilization of the anhydrous form, with the transitory formation of LnPO4.0.5H2O.

Ferrous Iron Oxidation under Varying pO2 Levels: The Effect of Fe(III)/Al(III) Oxide Minerals and Organic Matter.

PubMed

Chen, Chunmei; Thompson, Aaron

2018-01-16

Abiotic Fe(II) oxidation by O 2 commonly occurs in the presence of mineral sorbents and organic matter (OM) in soils and sediments; however, this tertiary system has rarely been studied. Therefore, we examined the impacts of mineral surfaces (goethite and γ-Al 2 O 3 ) and organic matter [Suwannee River fulvic acid (SRFA)] on Fe(II) oxidation rates and the resulting Fe(III) (oxyhydr)oxides under 21 and 1% pO 2 at pH 6. We tracked Fe dynamics by adding 57 Fe(II) to 56 Fe-labeled goethite and γ-Al 2 O 3 and characterized the resulting solids using 57 Fe Mössbauer spectroscopy. We found Fe(II) oxidation was slower at low pO 2 and resulted in higher-crystallinity Fe(III) phases. Relative to oxidation of Fe(II) (aq) alone, both goethite and γ-Al 2 O 3 surfaces increased Fe(II) oxidation rates regardless of pO 2 levels, with goethite being the stronger catalyst. Goethite surfaces promoted the formation of crystalline goethite, while γ-Al 2 O 3 favored nano/small particle or disordered goethite and some lepidocrocite; oxidation of Fe(II) aq alone favored lepidocrocite. SRFA reduced oxidation rates in all treatments except the mineral-free systems at 21% pO 2 , and SRFA decreased Fe(III) phase crystallinity, facilitating low-crystalline ferrihydrite in the absence of mineral sorbents, low-crystalline lepidocrocite in the presence of γ-Al 2 O 3 , but either crystalline goethite or ferrihydrite when goethite was present. This work highlights that the oxidation rate, the types of mineral surfaces, and OM control Fe(III) precipitate composition.

Na3Tb(PO4)2: Synthesis, crystal structure and greenish emitting properties

NASA Astrophysics Data System (ADS)

Zhao, Dan; Ma, Zhao; Liu, Bao-Zhong; Zhang, Rui-Juan; Wu, Zhi-Qiang; Wang, Jian; Duan, Pei-Gao

2018-03-01

A anhydrous orthoborate Na3Tb(PO4)2 has been prepared and its crystal structure was determined by X-Ray diffraction of a non-merohedral twinned single crystal. The results show that the compound crystallizes in monoclinic space group C2/c and the structure features a 3D framework containing PO4, NaO6, NaO7, NaO8 and TbO8 polyhedra. Under near-UV excitation (370 nm), Na3Tb(PO4)2 shows intense characteristic emission bands of Tb3+ (490 nm, 543 nm, 585 nm and 620 nm) with the CIE coordinate of (0.3062, 0.5901), corresponding to greenish color. The excitation spectrum covers a wide range from 340 nm to 390 nm, which indicates that phosphor Na3Tb(PO4)2 can be efficiently activated by near-UV LED ship.

Defect phase diagram for doping of Ga2O3

NASA Astrophysics Data System (ADS)

Lany, Stephan

2018-04-01

For the case of n-type doping of β-Ga2O3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association of dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO2) conditions. Considering further the stability constraints due to sublimation of molecular Ga2O, specific predictions of optimized pO2 and Si dopant concentrations are given. The incomplete passivation of dopant-defect complexes in β-Ga2O3 suggests a design rule for metastable doping above the solubility limit.

"Artificial lymphatic system": a new approach to reduce interstitial hypertension and increase blood flow, pH and pO2 in solid tumors.

PubMed

DiResta, G R; Lee, J; Healey, J H; Levchenko, A; Larson, S M; Arbit, E

2000-05-01

A mechanical drainage system, the "artificial lymphatic system" (ALS), consisting of a vacuum source and drain, is evaluated for its ability to aspirate the interstitial fluids responsible for the elevated interstitial fluid pressure (IFP) observed in solid tumors. IFP, pH, and pO2 radial profiles were measured before and after aspiration using wick-in-needle (WIN) probes, needle pH and oxygen electrodes, respectively. Laser Doppler flowmetry measured temporal changes in blood flow rate (BFR) at the tumor surface during aspiration. The WIN probe and IFP profile data were analyzed using numerical simulation and distributed mathematical models, respectively. The model parameter, P(E), reflecting central tumor IFP, was reduced from 15.3 to 5.7 mm Hg in neuroblastoma and from 13.3 to 12.1 mm Hg in Walker 256, respectively, following aspiration. The simulation demonstrated that spatial averaging inherent in WIN measurements reduced the calculated magnitude of the model parameter changes. IFP was significantly lower (p<0.05), especially in regions surrounding the drain, and BFR was significantly higher (p<0.05) following 25 and 45 min of aspiration, respectively; pH and pO2 profiles increased following aspiration. The experimental and mathematical findings suggest that ALS aspiration may be a viable way of reducing IFP and increasing BFR, pO2, and pH and should enhance solid tumor chemo and radiation therapy.

Synthesis and performances of 2LiFePO4·Li3V2(PO4)3/C cathode materials via spray drying method with double carbon sources

NASA Astrophysics Data System (ADS)

Zhang, Jia-feng; Shen, Chao; Zhang, Bao; Zheng, Jun-chao; Peng, Chun-li; Wang, Xiao-wei; Yuan, Xin-bo; Li, Hui; Chen, Guo-min

2014-12-01

The 2LiFePO4·Li3V2(PO4)3/C samples are synthesized through spray drying method. Glucose and oxalic acid are used as collaborative carbon sources to improve the electrochemical performance of 2LiFePO4·Li3V2(PO4)3/C composites. XRD results reveal the LiFePO4·Li3V2(PO4)3/C samples are composed of orthorhombic LiFePO4 and monoclinic Li3V2(PO4)3 phases. SEM results reveal that the nano-spherical Fe4(VO4)4·5H2O are about 80 nm and the 2LiFePO4·Li3V2(PO4)3/C composites possess a micro-nano spherical morphology with carbon coating layer. The samples show the best electrochemical performance when the mass ration of glucose and oxalic is 6:4, it can deliver a capacity of 147.6 mAh g-1, 145.0 mAh g-1, 134.1 mAh g-1 and 123.0 mAh g-1 at the rates of 0.1C, 1C, 5C and 10C, respectively.

Chromium incorporation into TiO{sub 2} at high pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Escudero, Alberto, E-mail: aescudero@icmse.csic.es; Langenhorst, Falko; Institut fuer Geowissenschaften, Friedrich-Schiller-Universitaet Jena, Carl-Zeiss-Promenade 10, D-07745 Jena

2012-06-15

Chromium incorporation into TiO{sub 2} up to 3 GPa at 1300 Degree-Sign C and 900 Degree-Sign C has been studied by XRD as well as TEM. A CaCl{sub 2} type TiO{sub 2} polymorph has been observed in the quenched samples from high pressure. Two different mechanisms of solubility occur in the recovered samples. Chromium replaces titanium on normal octahedral sites but it also occupies interstitial octahedral sites, especially in the samples recovered from higher pressures. Interstitial chromium is responsible for an orthorhombic distortion of the TiO{sub 2} rutile structure in the quenched samples and gives rise to a (1 1more » 0) twinned CaCl{sub 2}-structured polymorph. This phase is very likely the result of temperature quench at high pressure. The formation of this phase is directly related to the chromium content of the TiO{sub 2} grains. Chromium solubility in TiO{sub 2} increases with increasing the synthesis pressure. TiO{sub 2} is able to accommodate up to 15.3 wt% Cr{sub 2}O{sub 3} at 3 GPa and 1300 Degree-Sign C, compared to 5.7 wt% at atmospheric pressure at the same temperature. - Graphical abstract: Microstructure consisting of twins domains of recovered Cr-doped CaCl{sub 2} type TiO{sub 2} grains synthesised at high pressure. Highlights: Black-Right-Pointing-Pointer Chromium solubility in TiO{sub 2} increases at high pressure. Black-Right-Pointing-Pointer Chromium occupies substitutional and interstitial positions in the rutile structure. Black-Right-Pointing-Pointer Interstitial chromium causes a decrease of the rutile symmetry. Black-Right-Pointing-Pointer An orthorhombic CaCl{sub 2} type structure is observed in the quenched samples.« less

Fe2 PO5 -Encapsulated Reverse Energetic ZnO/Fe2 O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water.

PubMed

Qin, Dong-Dong; He, Cai-Hua; Li, Yang; Trammel, Antonio C; Gu, Jing; Chen, Jing; Yan, Yong; Shan, Duo-Liang; Wang, Qiu-Hong; Quan, Jing-Jing; Tao, Chun-Lan; Lu, Xiao-Quan

2017-07-10

Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe 2 O 3 shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm -2 ), a maximal photocurrent of 1.0 mA cm -2 is achieved with ZnO/Fe 2 O 3 core-shell NWs and 2.3 mA cm -2 was achieved for the PH 3 -treated NWs at 1.23 V versus RHE. The PH 3 low-temperature treatment creates a dual function, passivation and catalyst layer (Fe 2 PO 5 ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mn{sub 0.95}I{sub 0.02}[PO{sub 3}(OH)] · 2H{sub 2}O phosphate–iodate, an inorganic analogue of phosphonates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belokoneva, E. L., E-mail: elbel@geol.msu.ru; Dimitrova, O. V.; Volkov, A. S.

2015-09-15

The new Mn{sub 0.95}I{sub 0.02}[PO{sub 3}(OH)] · 2H{sub 2}O phosphate–iodate (space group Pnam = Pnma, D{sub 2h}{sup 16}) is obtained under hydrothermal conditions. The crystal structure is determined without preliminary knowledge of the chemical formula. The structure consists of layers of MnO{sub 6} octahedra connected with PO{sub 4} tetrahedra. Water molecules are located between the layers. [IO3]{sup –} groups having a typical umbrella-like coordination are statistically implanted in layers of MnO{sub 6} octahedra at a distance of 1.2 Å from Mn atoms. Their content in the crystal is minor. The structures of the phosphate–iodate coincides with the structures of phosphonatesmore » with consideration for the replacement of one (OH) vertex of the PO{sub 4} tetrahedron by the organic methyl radical CH{sub 3}. In the structures of phosphonates and earlier studied phosphates, identical layers are distinguished and the cause of the existence of two MDO varieties is established based on the analysis within the OD theory. Possible hybrid structures derived from the prototypes under consideration are predicted.« less

KMg0.09Fe1.91(PO4)2

PubMed Central

Yatskin, Michael M.; Zatovsky, Igor V.; Baumer, Vyacheslav N.; Ogorodnyk, Ivan V.; Slobodyanik, Nikolay S.

2012-01-01

KMg0.09Fe1.91(PO4)2, potassium [iron(II)/magnesium] iron(III) bis(orthophosphate), is a solid solution derived from compounds with general formula KM IIFe(PO4)2 (M II = Fe, Cu), in which the Mg atoms substitute Fe atoms only in the octa­hedrally surrounded sites. The framework of the structure is built up from [FeO5] trigonal bipyramids and [MO6] (M = (Fe, Mg) octa­hedra sharing corners and edges and connected by two types of bridging PO4 tetra­hedra. The K+ cations are nine-coordinated and are situated in channels running along [101]. PMID:22719280

Monoclinic structure of hydroxylpyromorphite Pb10(PO4)6(OH)2 - hydroxylmimetite Pb10(AsO4)6(OH)2 solid solution series

NASA Astrophysics Data System (ADS)

Giera, Alicja; Manecki, Maciej; Borkiewicz, Olaf; Zelek, Sylwia; Rakovan, John; Bajda, Tomasz; Marchlewski, Tomasz

2016-04-01

Seven samples of hydroxyl analogues of pyromorphite-mimetite solid solutions series were synthesized from aqueous solutions at 80° C in a computer-controlled chemistate: 200 mL aqueous solutions of 0.05M Pb(NO3)2 and 0.03M KH2AsO4 and/or KH2PO4 were dosed with a 0.25 mL/min rate to a glass beaker, which initially contained 100 mL of distilled water. Constant pH of 8 was maintained using 2M KOH. The syntheses yielded homogeneous fine-grained white precipitates composition of which was close to theoretical Pb10[(PO4)6-x(AsO4)x](OH)2, where x = 0, 1, 2, 3, 4, 5, 6. High-resolution powder X-ray diffraction data were obtained in transmission geometry at the beamline 11-BM at the Advanced Photon Source (Argonne National Laboratory in Illinois, USA). The structure Rietveld refinements based on starting parameters of either hexagonal hydroxylpyromorphite or monoclinic mimetite-M were performed using GSAS+EXPGUI software. Apatite usually crystallizes in the hexagonal crystal system with the space group P63/m. For the first time, however, the lowering of the hexagonal to monoclinic crystal symmetry was observed in the hydroxyl variety of pyromorphite-mimetite solid solution series. This is indicated by better fitting of the modeled monoclinic structure to the experimental data. The same is not the case for analogous calcium hydroxylapatite series Ca5(PO4)3OH - Ca5(AsO4)3OH (Lee et al. 2009). Systematical linear increase of unit cell parameters is observed with As substitution from a=9.88, b=19.75, and c=7.43 for Pb10(PO4)6(OH)2 to a=10.23, b=20.32, and c=7.51 for Pb10(AsO4)6(OH)2. A strong pseudohexagonal character (γ ≈ 120° and b ≈ 2a) of the analyzed monoclinic phases was established. This work is partially funded by AGH research grant no 11.11.140.319 and partially by Polish NCN grant No 2011/01/M/ST10/06999. Lee Y.J., Stephens P.W., Tang Y., Li W., Philips B.L., Parise J.B., Reeder R.J., 2009. Arsenate substitution in hydroxylapatite: Structural characterization

Defect phase diagram for doping of Ga 2O 3

DOE PAGES

Lany, Stephan

2018-04-01

For the case of n-type doping of β-Ga 2O 3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO 2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association ofmore » dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO 2) conditions. Considering further the stability constraints due to sublimation of molecular Ga 2O, specific predictions of optimized pO 2 and Si dopant concentrations are given. To conclude, the incomplete passivation of dopant-defect complexes in β-Ga 2O 3 suggests a design rule for metastable doping above the solubility limit.« less

Defect phase diagram for doping of Ga 2O 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lany, Stephan

For the case of n-type doping of β-Ga 2O 3 by group 14 dopants (C, Si, Ge, Sn), a defect phase diagram is constructed from defect equilibria calculated over a range of temperatures (T), O partial pressures (pO 2), and dopant concentrations. The underlying defect levels and formation energies are determined from first-principles supercell calculations with GW bandgap corrections. Only Si is found to be a truly shallow donor, C is a deep DX-like (lattice relaxed donor) center, and Ge and Sn have defect levels close to the conduction band minimum. The thermodynamic modeling includes the effect of association ofmore » dopant-defect pairs and complexes, which causes the net doping to decline when exceeding a certain optimal dopant concentration. The optimal doping levels are surprisingly low, between about 0.01% and 1% of cation substitution, depending on the (T, pO 2) conditions. Considering further the stability constraints due to sublimation of molecular Ga 2O, specific predictions of optimized pO 2 and Si dopant concentrations are given. To conclude, the incomplete passivation of dopant-defect complexes in β-Ga 2O 3 suggests a design rule for metastable doping above the solubility limit.« less

Synthesis and structure of heptaaqua(nitrilotris(methylenephosphonato))(dibarium)sodium monohydrate [Na(H{sub 2}O){sub 3}(μ{sup 6}-NH(CH{sub 2}PO{sub 3}){sub 3})(μ-H{sub 2}O){sub 3}Ba{sub 2}(H{sub 2}O)] · H{sub 2}O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: xps@ftiudm.ru; Zakirova, R. M., E-mail: ftt@udsu.ru

Crystals of the monohydrate form of heptaaqua(nitrilotris(methylenephosphonato))(dibarium) sodium [Na(H{sub 2}O{sub )3}(µ{sup 6}-NH(CH{sub 2}PO{sub 3}){sub 3})(µ-H{sub 2}O){sub 3}Ba{sub 2}(H{sub 2}O)] · H{sub 2}O are obtained; space group P2{sub 1}/c, Z = 4; a = 13.9117(10) Å, b = 11.54030(10) Å, and c = 24.1784(17) Å, ß = 148.785(18)°. The Na atom is coordinated octahedrally by one oxygen atom of a phosphonate group and five water molecules, including two bridging molecules. Ba atoms occupy two inequivalent crystallographic positions with coordination number eight and nine. The coordination spheres of both Ba atoms include two water molecules. Each ligand is bound to one Namore » atom and five Ba atoms forming three Ba–O–P–O and five Ba–O–P–C–N–C–P–O chelate cycles. In addition to the coordination bonds, molecules, including the solvate water molecule, are involved in hydrogen bonds in the crystal packing.« less

Raman spectroscopy of newberyite Mg(PO3OH)·3H2O: a cave mineral.

PubMed

Frost, Ray L; Palmer, Sara J; Pogson, Ross E

2011-09-01

Newberyite Mg(PO3OH)·3H2O is a mineral found in caves such as from Moorba Cave, Jurien Bay, Western Australia, the Skipton Lava Tubes (SW of Ballarat, Victoria, Australia) and in the Petrogale Cave (Madura, Eucla, Western Australia). Because these minerals contain oxyanions, hydroxyl units and water, the minerals lend themselves to spectroscopic analysis. Raman spectroscopy can investigate the complex paragenetic relationships existing between a number of 'cave' minerals. The intense sharp band at 982 cm(-1) is assigned to the PO4(3-)ν1 symmetric stretching mode. Low intensity Raman bands at 1152, 1263 and 1277 cm(-1) are assigned to the PO4(3-)ν3 antisymmetric stretching vibrations. Raman bands at 497 and 552 cm(-1) are attributed to the PO4(3-)ν4 bending modes. An intense Raman band for newberyite at 398 cm(-1) with a shoulder band at 413 cm(-1) is assigned to the PO4(3-)ν2 bending modes. The values for the OH stretching vibrations provide hydrogen bond distances of 2.728 Å (3267 cm(-1)), 2.781 Å (3374 cm(-1)), 2.868 Å (3479 cm(-1)), and 2.918 Å (3515 cm(-1)). Such hydrogen bond distances are typical of secondary minerals. Estimates of the hydrogen-bond distances have been made from the position of the OH stretching vibrations and show a wide range in both strong and weak bonds. Copyright © 2011 Elsevier B.V. All rights reserved.

Two-photon microscopy measurement of CMRO2 using periarteriolar PO2 gradients(Conference Presentation)

NASA Astrophysics Data System (ADS)

Sakadžić, Sava; Yaseen, Mohammad A.; Jaswal, Rajeshwer S.; Roussakis, Emmanuel; Dale, Anders M.; Buxton, Richard B.; Vinogradov, Sergei A.; Boas, David A.; Devor, Anna

2017-02-01

The cerebral metabolic rate of oxygen (CMRO2) is an essential parameter for evaluating brain function and pathophysiology. Measurements of CMRO2 with high spatio-temporal resolution are critically important for understanding how the brain copes with metabolic and blood perfusion changes associated with various clinical conditions, such as stroke, periinfarct depolarizations, and various microvasculopathies (e.g., Alzheimer's disease, chronic hypertension). CMRO2 measurements are also important for understanding the physiological underpinnings of functional Magnetic Resonance Imaging signals. However, the currently available approaches for quantifying CMRO2 rely on complex multimodal imaging and mathematical modeling. Here, we introduce a novel method that allows estimation of CMRO2 based on a single measurement modality - two-photon phosphorescence lifetime microscopy (2PLM) imaging of the partial pressure of oxygen (PO2) in cortical tissue. CMRO2 is estimated by fitting the changes of tissue PO2 around cortical penetrating arterioles with the Krogh cylinder model of oxygen diffusion. We measured the baseline CMRO2 in anesthetized rats, and modulated tissue PO2 levels by manipulating the depth of anesthesia. This method has a spatial resolution of approximately 200 μm and it may provide CMRO2 measurements in individual cortical layers or within confined cortical regions such as in ischemic penumbra and the foci of functional activation.

Density functional theory study of 3R- and 2H-CuAlO2 under pressure

NASA Astrophysics Data System (ADS)

Liu, Qi-Jun; Liu, Zheng-Tang; Feng, Li-Ping; Tian, Hao; Liu, Wen-Ting; Yan, Feng

2010-10-01

We present a first-principles density-functional theory based study of the impact of pressure on the structural and elastic properties of bulk 3R- and 2H-CuAlO2. The ground state properties of 3R- and 2H-CuAlO2 are obtained, which are in good agreement with previous experimental and theoretical data. The analysis of enthalpy variation with pressure indicates the phase transition pressure between 3R and 2H is 15.4 GPa. The independent elastic constants of 3R- and 2H-CuAlO2 are calculated. As the applied pressure increases, the calculations show the presences of mechanical instability at 26.2 and 27.8 GPa for 3R- and 2H-CuAlO2, which are possibly related with the phase transitions.

Structural and physical properties of transparent conducting, amorphous Zn-doped SnO2 films

NASA Astrophysics Data System (ADS)

Zhu, Q.; Ma, Q.; Buchholz, D. B.; Chang, R. P. H.; Bedzyk, M. J.; Mason, T. O.

2014-01-01

The structural and physical properties of conducting amorphous Zn-doped SnO2 (a-ZTO) films, prepared by pulsed laser deposition, were investigated as functions of oxygen deposition pressure (pO2), composition, and thermal annealing. X-ray scattering and X-ray absorption spectroscopy measurements reveal that at higher pO2, the a-ZTO films are highly transparent and have a structural framework similar to that found in crystalline (c-), rutile SnO2 in which the Sn4+ ion is octahedrally coordinated by 6 O2- ions. The Sn4+ ion in these films however has a coordination number (CN) smaller by 2%-3% than that in c-SnO2, indicating the presence of oxygen vacancies, which are the likely source of charge carriers. At lower pO2, the a-ZTO films show a brownish tint and contain some 4-fold coordinated Sn2+ ions. Under no circumstances is the CN around the Zn2+ ion larger than 4, and the Zn-O bond is shorter than the Sn-O bond by 0.07 Å. The addition of Zn has no impact on the electroneutrality but improves significantly the thermal stability of the films. Structural changes due to pO2, composition, and thermal annealing account well for the changes in the physical properties of a-ZTO films.

Crystal structures and electronic properties for the over-lithiated and Li–Ag substituted phases of Li{sub 9}V{sub 3}(P{sub 2}O{sub 7}){sub 3}(PO{sub 4}){sub 2} insertion electrode system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onoda, Masashige, E-mail: onoda.masashige.ft@u.tsukuba.ac.jp; Inagaki, Makoto; Saito, Hiroaki

2014-11-15

For the Li{sub 9}V{sub 3}(P{sub 2}O{sub 7}){sub 3}(PO{sub 4}){sub 2} insertion electrode system with a multiple-electron reaction, the over-lithiated phase Li{sub x}V{sub 3}(P{sub 2}O{sub 7}){sub 3}(PO{sub 4}){sub 2} with 99) and Li{sub 9−y}Ag{sub y}V{sub 3}(P{sub 2}O{sub 7}){sub 3}(PO{sub 4}){sub 2} (0

Assessment of the Changes in 9L and C6 Glioma pO2 by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy

PubMed Central

Hou, Huagang; Mupparaju, Sriram P.; Lariviere, Jean P.; Hodge, Sassan; Gui, Jiang; Swartz, Harold M.; Khan, Nadeem

2013-01-01

Tumor hypoxia impedes the outcome of radiotherapy. As the extent of hypoxia in solid tumors varies during the course of radiotherapy, methods that can provide repeated assessment of tumor pO2 such as EPR oximetry may enhance the efficacy of radiotherapy by scheduling irradiations when the tumors are oxygenated. The repeated measurements of tumor pO2 may also identify responders, and thereby facilitate the design of better treatment plans for nonresponding tumors. We have investigated the temporal changes in the ectopic 9L and C6 glioma pO2 irradiated with single radiation doses less than 10 Gy by EPR oximetry. The 9L and C6 tumors were hypoxic with pO2 of approximately 5–9 mmHg. The pO2 of C6 tumors increased significantly with irradiation of 4.8–9.3 Gy. However, no change in the 9L tumor pO2 was observed. The irradiation of the oxygenated C6 tumors with a second dose of 4.8 Gy resulted in a significant delay in growth compared to hypoxic and 2 Gy × 5 treatment groups. The C6 tumors with an increase in pO2 of greater than 50% from the baseline of irradiation with 4.8 Gy (responders) had a significant tumor growth delay compared to nonresponders. These results indicate that the ectopic 9L and C6 tumors responded differently to radiotherapy. We propose that the repeated measurement of the oxygen levels in the tumors during radiotherapy can be used to identify responders and to design tumor oxygen guided treatment plans to improve the outcome. PMID:23391148

Pressure-induced Structural Transformations in LanthanideTitanates: La2TiO5 and Nd2TiO5

DOE Office of Scientific and Technical Information (OSTI.GOV)

F Zhang; J Wang; M Lang

The structure of orthorhombic rare earth titanates of La{sub 2}TiO{sub 5} and Nd{sub 2}TiO{sub 5}, where Ti cations are in five-fold coordination with oxygen, has been studied at high pressures by X-ray diffraction (XRD), Raman scattering measurements, and quantum mechanical calculations. Both XRD and Raman results indicated two pressure-induced phase transitions during the process. An orthorhombic super cell (a x b x 2c) formed at a pressure between 6 and 10 GPa, and then transformed to a hexagonal high-pressure phase accompanied by partial decomposition. The hexagonal high-pressure phase is quenchable. Detailed structural analysis indicated that the five-coordinated TiO{sub 5} polyhedramore » remain during the formation of super cell, but the orthorhombic-to-hexagonal phase transition at high pressures is a reconstructive process, and the five-fold Ti-O coordination increased to more than 6. This phase transition sequence was verified by quantum mechanical calculations.« less

Bonding Transition in SiO2 Glass at High Pressures: Applications to SiO2 Liquid in Earth's Interior

NASA Astrophysics Data System (ADS)

Yoo, C.; Lin, J.; Fukui, H.; Prendergast, D.; Okuchi, T.; Cai, Y.; Hiraoka, N.; Trave, A.; Eng, P.; Hu, M. Y.; Chow, P.

2006-12-01

SiO2 and MgSiO3 liquids are two major components in the magma deep inside the Earth. Knowledge of their electronic bonding characters at high pressures is essential to understanding the complex properties of the materials in the melts. The nature of pressure-induced bonding change in amorphous SiO2 has been an intriguing and long-standing problem that remains to be further understood. For example, previous infrared and X-ray diffraction studies suggested that a continuous transformation from the four- to six-fold coordinated silicon occurred in amorphous SiO2 at high pressures, whereas separate optical Raman studies attributed to a pressure-induced shift in the local ring statistics and a breakdown in the intermediate-range order. Here we have studied the oxygen near K-edge spectra of SiO2 glass to 51 GPa obtained using X-ray Raman scattering in a diamond-anvil cell, which directly probes the electronic bonding character of the sample. Our results provide conclusive evidence for a pressure-induced electronic bonding transition in SiO2 glass at high pressures. Although a progressive decrease in the mean Si-O-Si angle in the SiO4 tetrahedra is believed to be responsible for the irreversible densification in SiO2 glass at high pressures, our observed transition is reversible upon decompression. A similar transformation is also expected to occur in silicate glasses and melts, which will most definitely alter their physical, mechanical and transport properties in the magma chamber deep in the Earth's interior. This work was performed under the auspices of the U.S. DOE by UC/LLNL under Contract W-7405-Eng-48.

Comparison of the high-pressure behavior of the cerium oxides C e 2 O 3 and Ce O 2

DOE PAGES

Lipp, M. J.; Jeffries, J. R.; Cynn, H.; ...

2016-02-09

We studied the high-pressure behavior of Ce 2O 3 using angle-dispersive x-ray diffraction to 70 GPa and compared with that of CeO 2. Up to the highest pressure Ce 2O 3 remains in the hexagonal phase (space group 164, P ¯32/m1) typical for the lanthanide sesquioxides. We did not observe a theoretically predicted phase instability for 30 GPa. The isothermal bulk modulus and its pressure derivative for the quasihydrostatic case are B 0 = 111 ± 2 GPa, B' 0 = 4.7 ± 0.3, and for the case without pressure-transmitting medium B 0 = 104 ±4 GPa, B' 0 =more » 6.5 ± 0.4. Starting from ambient-pressure magnetic susceptibility measurements for both oxides in highly purified form,we find that the Ce atom in Ce 2O 3 behaves like a trivalent Ce 3+ ion (2.57μB per Ce atom) in contrast to previously published data. Since x-ray emission spectroscopy of the Lγ (4d 3/2 → 2p 1/2) transition is sensitive to the 4f -electron occupancy, we also followed the high-pressure dependence of this line for both oxides up to 50 GPa. We observed no change of the respective line shape, indicating that the 4f -electron configuration is stable for both materials. We posit from this data that the 4f electrons do not drive the volume collapse of CeO 2 from the high-symmetry, low-pressure fluorite structure to the lower-symmetry orthorhombic phase.« less

High pressure experimental studies on Na3Fe(PO4)(CO3) and Na3Mn(PO4)(CO3): Extensive pressure behaviors of carbonophosphates family

NASA Astrophysics Data System (ADS)

Gao, Jing; Huang, Weifeng; Wu, Xiang; Qin, Shan

2018-04-01

Carbon-bearing phases in the Earth's interior have profound implications for the long-term Earth carbon cycle. Here we investigate high-pressure behaviors of carbonophosphates bonshtedtite Na3Fe(PO4)(CO3) and sidorenkite Na3Mn(PO4)(CO3) in diamond anvil cells up to ∼12 GPa at room temperature. Modifications in in situ synchrotron X-ray diffraction patterns and Raman spectra confirm the structural stability of carbonophosphates within the pressure region. Fitting the third-order Birch-Murnaghan equation of state to the volume compression curve, the isothermal bulk modulus parameters are obtained to be K0 = 56(1) GPa, K0' = 3.3(1), V0 = 303.3(3) Å3 for Na3Fe(PO4)(CO3) and K0 = 54(1) GPa, K0' = 3.4(1), V0 = 313.4(2) Å3 for Na3Mn(PO4)(CO3). Crystallographic axes exhibit an elastic anisotropy with a more compressible c-axis relative to the ab-plane. An inverse linear correlation between the K0 value and the ionic radius of M2+ (M = Mg, Fe, Mn) is well determined for carbonophosphates. The pressure-dependence responsiveness of [PO4] and [CO3] in carbonophosphates show a negative relationship to the M2+ radius. We also discussed the effect of [PO4] group on the structural variations and high-pressure behaviors of carbonates. Furthermore, the geochemical properties of carbonophosphates hold implications to diamond genesis.

EPR Oximetry for Investigation of Hyperbaric O2 Pre-treatment for Tumor Radiosensitization.

PubMed

Williams, Benjamin B; Hou, Huagang; Coombs, Rachel; Swartz, Harold M

A number of studies have reported benefits associated with the application of hyperbaric oxygen treatment (HBO) delivered immediately prior to radiation therapy. While these studies provide evidence that pre-treatment with HBO may be beneficial, no measurements of intratumoral pO2 were carried out and they do not directly link the apparent benefits to decreased hypoxic fractions at the time of radiation therapy. While there is empirical evidence and some theoretical basis for HBO to enhance radiation therapy, without direct and repeated measurements of its effects on pO2, it is unlikely that the use of HBO can be understood and optimized for clinical applications. In vivo EPR oximetry is a technique uniquely capable of providing repeated direct measurements of pO2 through a non-invasive procedure in both animal models and human patients. In order to evaluate the ability of pretreatment with HBO to elevate tumor pO2, a novel small animal hyperbaric chamber system was constructed that allows simultaneous in vivo EPR oximetry. This chamber can be placed within the EPR magnet and is equipped with a variety of ports for multiplace gas delivery, thermoregulation, delivery of anesthesia, physiologic monitoring, and EPR detection. Initial measurements were performed in a subcutaneous RIF-1 tumor model in C3H/HeJ mice. The mean baseline pO2 value was 6.0 ± 1.2 mmHg (N = 7) and responses to two atmospheres absolute pressure HBO varied considerably across subjects, within tumors, and over time. When an increase in pO2 was observed, the effect was transient in all but one case, with durations lasting from 5 min to over 20 min, and returned to baseline levels during HBO administration. These results indicate that without direct measurements of pO2 in the tissue of interest, it is likely to be difficult to know the effects of HBO on actual tissue pO2.

Facile solution-precipitation assisted synthesis and luminescence property of greenish-yellow emitting Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Haipeng; Huang, Zhaohui, E-mail: huang118@cugb.edu.cn; Xia, Zhiguo, E-mail: xiazg@ustb.edu.cn

2016-03-15

Highlights: • Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor was prepared by the solution-precipitation assisted route. • The phosphors have satisfactory smooth grain surface and particle size. • It shows greenish-yellow color emission (maximum at 540 nm) upon blue light excitation. • Eu{sup 2+} is coordinated with isolated oxygen atoms and those from PO{sub 4} polyhedra. - Abstract: Greenish-yellow emitting microcrystalline Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphor was successfully prepared by a solution-precipitation assisted high temperature reaction method. Phase structure, morphology and/or luminescence properties of the precursor and the as-prepared phosphors were characterized. The phase-pure Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} phosphorsmore » were obtained with smooth grain surface and particle size of 2–8 μm. Ca{sub 6}Ba(PO{sub 4}){sub 4}O:Eu{sup 2+} exhibits bright greenish-yellow color emission with its maximum at 540 nm upon UV-blue light excitation. The maximum position of the broad emission band is independent on the calcination temperature. The emission intensity increases with increasing calcination temperature due to improved crystallinity. Besides, the presence of two Eu{sup 2+} emission centers in the Ca{sub 6}Ba(PO{sub 4}){sub 4}O crystal lattice was confirmed and the coordination effects are considered concerning the roles of isolated O atoms and those from the PO{sub 4} tetrahedra.« less

Phase equilibria in the NaF-CdO-NaPO{sub 3} system at 873 K and crystal structure and physico-chemical characterizations of the new Na{sub 2}CdPO{sub 4}F fluorophosphate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aboussatar, Mohamed; Laboratoire de Physico-Chimie de l’État Solide, Faculté des Sciences de Sfax, Université de Sfax, BP 1171, 3000 Sfax; Mbarek, Aïcha

Isothermal sections of the diagram representing phase relationships in the NaF-CdO-NaPO{sub 3} system have been investigated by solid state reactions and powder X-ray diffraction. This phase diagram investigation confirms the polymorphism of the NaCdPO{sub 4} side component and the structure of the ß high temperature polymorph (orthorhombic, space group Pnma and unit cell parameters a=9.3118(2), b=7.0459(1), c=5.1849(1) Å has been refined. A new fluorophosphate, Na{sub 2}CdPO{sub 4}F, has been discovered and its crystal structure determined and refined from powder X-ray diffraction data. It exhibits a new 3D structure with orthorhombic symmetry, space group Pnma and unit cell parameters a=5.3731(1), b=6.8530(1),more » c=12.2691(2) Å. The structure is closely related to those of the high temperature polymorph of the nacaphite Na{sub 2}CaPO{sub 4}F and the fluorosilicate Ca{sub 2}NaSiO{sub 4}F but differs essentially in the cationic repartition since the structure is fully ordered with one Na site (8d) and one Cd site (4c). Relationships with other Na{sub 2}M{sup II}PO{sub 4}F (M{sup II}=Mg, Ca, Mn, Fe, Co, Ni) have been examined and the crystal-chemical and topographical analysis of these fluorophosphates is briefly reviewed. IR, Raman, optical and {sup 19}F, {sup 23}Na, {sup 31}P MAS NMR characterizations of Na{sub 2}CdPO{sub 4}F have been investigated. - Graphical abstract: The structure of the compound Na{sub 2}CdPO{sub 4}F, discovered during the study of the phase relationships in the NaF-CdO-NaPO{sub 3} system, has been determined and compared with other Na{sub 2}M{sup II}PO{sub 4}F fluorophosphates. - Highlights: • XRD analysis of the isothermal section of the NaF-CdO-NaPO{sub 3} system at 923 K. • Rietveld refinement of the high temperature polymorph β-NaCdPO{sub 4}. • Crystal structure of the new Na{sub 2}CdPO{sub 4}F fluorophosphate determined from powder XRD. • Crystal structure - composition relationships of Na{sub 2}M{sup II}PO{sub 4}F

SiO2 Solubility in Rutile at High Pressure and Temperature

NASA Astrophysics Data System (ADS)

Ren, Y.; Fei, Y.; Yang, J.; Bai, W. J.; Xu, Z. Q.

2005-12-01

Silicon-bearing rutile has been found in nature. The extent of SiO2 solubility in rutile and the nature of its origin are still not clear. At high pressure, SiO2 takes rutile structure with 6-coordinated Si. The high-pressure phase of SiO2 may enhance its solubility in rutile because possible isovalent exchange in octahedral site. In this study, we report new experimental results on SiO2 solubility in rutile up to 23 GPa and 2273 K. Starting materials are mixtures of powdered TiO2 and SiO2, with compositions of (Ti0.5Si0.5)O2, (Ti0.93Si0.07)O2, and (Ti0.75Si0.25)O2. The mixtures were loaded into either a platinum capsules (for a 10/5 assembly) or a rhenium capsules (for an 8/3 assembly). The experiments were carried out using multi-anvil high-pressure apparatus with rhenium resistance heater. Sample temperatures were measured with a type-C thermocouple. The quenched samples were recovered and prepared for electron microprobe analyses. TiO2-rich and SiO2-rich phases are produced in all the quenched samples. The analyses showed that the solubility of SiO2 in rutile increases with increasing pressure, from 1.5 wt% SiO2 at 10 GPa to 3.8 wt% SiO2 at 23 GPa for a given temperature of 2073 K. The solubility also increases with increasing temperature, from 0.5 wt% SiO2 at 1773 K to 4.5 wt% SiO2 at 2273 K for a given pressure of 18 GPa. On the other hand, the solubility of TiO2 in coesite or stishovite is very limited, with an average of 0.6 wt% TiO2 over the experimental P-T ranges. Lower oxygen fugacity decreases the solubility of SiO2 in rutile, whereas water has little effect on the solubility of SiO2 in rutile. Our experimental data are extreme useful for determine the depth of origin for the SiO2-bearing rutile in nature.

A novel amido-pyrophosphate Mn(II) chelate complex with the synthetic ligand O{P(O)[NHC(CH3)3]2}2 (L): [Mn(L)2{OC(H)N(CH3)2}2]Cl2·2H2O.

PubMed

Tarahhomi, Atekeh; Pourayoubi, Mehrdad; Fejfarová, Karla; Dušek, Michal

2013-03-01

The title complex, trans-bis(dimethylformamide-κO)bis{N,N'-N'',N'''-tetra-tert-butyl[oxybis(phosphonic diamide-κO)]}manganese(II) dichloride dihydrate, [Mn(C16H40N4O3P2)2(C3H7NO)2]Cl2·2H2O, is the first example of a bis-chelate amido-pyrophosphate (pyrophosphoramide) complex containing an O[P(O)(NH)2]2 fragment. Its asymmetric unit contains half of the complex dication, one chloride anion and one water molecule. The Mn(II) atom, located on an inversion centre, is octahedrally coordinated, with a slight elongation towards the monodentate dimethylformamide ligand. Structural features of the title complex, such as the P=O bond lengths and the planarity of the chelate ring, are compared with those of previously reported complexes with six-membered chelates involving the fragments C(O)NHP(O), (X)NP(O) [X = C(O), C(S), S(O)2 and P(O)] and O[P(O)(N)2]2. This analysis shows that the six-membered chelate rings are less puckered in pyrophosphoramide complexes containing a P(O)OP(O) skeleton, such as the title compound. The extended structure of the title complex involves a linear aggregate mediated by N-H...O and N-H...Cl hydrogen bonds, in which the chloride anion is an acceptor in two additional O-H...Cl hydrogen bonds.

SiO2 Glass Density to Lower-Mantle Pressures

NASA Astrophysics Data System (ADS)

Petitgirard, Sylvain; Malfait, Wim J.; Journaux, Baptiste; Collings, Ines E.; Jennings, Eleanor S.; Blanchard, Ingrid; Kantor, Innokenty; Kurnosov, Alexander; Cotte, Marine; Dane, Thomas; Burghammer, Manfred; Rubie, David C.

2017-11-01

The convection or settling of matter in the deep Earth's interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60 GPa. The density data present two discontinuities at ˜17 and ˜60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5 /6 coordination and from 5 /6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at ˜40 GPa , and its density becomes identical to that of MgSiO3 glass above 80 GPa. Our results on SiO2 glass may suggest that a variation of SiO2 content in a basaltic or pyrolitic melt with pressure has at most a minor effect on the final melt density, and iron partitioning between the melts and residual solids is the predominant factor that controls melt buoyancy in the lowermost mantle.

High-pressure X-ray diffraction and Raman spectroscopy of CaFe2O4-type β-CaCr2O4

NASA Astrophysics Data System (ADS)

Zhai, Shuangmeng; Yin, Yuan; Shieh, Sean R.; Shan, Shuangming; Xue, Weihong; Wang, Ching-Pao; Yang, Ke; Higo, Yuji

2016-04-01

In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic studies of orthorhombic CaFe2O4-type β-CaCr2O4 chromite were carried out up to 16.2 and 32.0 GPa at room temperature using multi-anvil apparatus and diamond anvil cell, respectively. No phase transition was observed in this study. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a zero-pressure volume of V 0 = 286.8(1) Å3, an isothermal bulk modulus of K 0 = 183(5) GPa and the first pressure derivative of isothermal bulk modulus K 0' = 4.1(8). Analyses of axial compressibilities show anisotropic elasticity for β-CaCr2O4 since the a-axis is more compressible than the b- and c-axis. Based on the obtained and previous results, the compressibility of several CaFe2O4-type phases was compared. The high-pressure Raman spectra of β-CaCr2O4 were analyzed to determine the pressure dependences and mode Grüneisen parameters of Raman-active bands. The thermal Grüneisen parameter of β-CaCr2O4 is determined to be 0.93(2), which is smaller than those of CaFe2O4-type CaAl2O4 and MgAl2O4.

Structural and spectral properties of undoped and tungsten doped Zn3(PO4)2ZnO nanopowders

NASA Astrophysics Data System (ADS)

Satyavathi, K.; Subba Rao, M.; Nagabhaskararao, Y.; Cole, Sandhya

2018-01-01

Pure and tungsten doped Zn3(PO4)2ZnO nanopowders (NPs) are prepared using sol-gel method. It has the longest track record of used in dentistry. It is used for cementation of inlays, crowns and orthodontic appliances. The systematic investigations like X-ray Diffraction (XRD), Scanning electron microscope (SEM) with energy dispersive X-ray (EDX) spectroscope, Transmission electron microscope (TEM), Fourier transform infrared (FT-IR) spectroscopy, Optical absorption, Photoluminescence (PL) and Electron Paramagnetic Resonance (EPR) spectroscopic techniques are carried out for the prepared NPs. XRD pattern reveals that the prepared samples are in crystalline nature in which Zn3(PO4)2 corresponding to monoclinic phase and ZnO corresponding to hexagonal wurtzite phase, the average crystallite size of prepared nanopowders is in the range of 20-30 nm. The lattice strain, lattice cell parameters, unit cell volume and dislocation density of the prepared NPs are also calculated. The morphology of the prepared NPs is analyzed with SEM and TEM images. The distribution of Zn, P, O and W species in the prepared samples are identified by the chemical composition mapping through EDX. IR spectra of prepared samples exhibit the characteristic sharp absorption band peaks. The sharp absorption bands observed in the region 1200-900 cm-1 are due to complex stretching of characteristic PO43- groups. The absorption spectra exhibit a broad band around 696 nm is recognized due to 2B2g → 2B1g (dxy → dx2- y2) transition of tungsten ions. The PL spectra exhibit four emission peaks in the visible region indicating the quantum-confinement-induced photoluminescence. The CIE chromaticity diagram suggests that the prepared NPs have good color purity. The EPR spectra indicate that the W5+ ions occupy octahedral site symmetry in the host lattice.

1D nanostructured Na7V4(P2O7)4(PO4) as high-potential and superior-performance cathode material for sodium-ion batteries.

PubMed

Deng, Chao; Zhang, Sen

2014-06-25

Tailoring materials into nanostructure offers unprecedented opportunities in the utilization of their functional properties. High-purity Na7V4(P2O7)4(PO4) with 1D nanostructure is prepared as a cathode material for rechargeable Na-ion batteries. An efficient synthetic approach is developed by carefully controlling the crystal growth in the molten sodium phosphate. Based on the XRD, XPS, TG, and morphological characterization, a molten-salt assisted mechanism for nanoarchitecture formation is revealed. The prepared Na7V4(P2O7)4(PO4) nanorod has rectangle sides and preferential [001] growth orientation. GITT evaluation indicates that the sodium de/intercalation of Na7V4(P2O7)4(PO4) nanorod involves V(3+)/V(4+) redox reaction and Na5V(3.5+)4(P2O7)4(PO4) as intermediate phase, which results in two pairs of potential plateaus at the equilibrium potentials of 3.8713 V (V(3+)/V(3.5+)) and 3.8879 V (V(3.5+)/V(4+)), respectively. The unique nanoarchitecture of the phase-pure Na7V4(P2O7)4(PO4) facilitates its reversible sodium de/intercalation, which is beneficial to the high-rate capability and the cycling stability. The Na7V4(P2O7)4(PO4) cathode delivers 80% of the capacity (obtained at C/20) at the 10 C rate and 95% of the initial capacity after 200 cycles. Therefore, it is feasible to design and fabricate an advanced rechargeable sodium-ion battery by employment of 1D nanostructured Na7V4(P2O7)4(PO4) as the cathode material.

SiO_{2} Glass Density to Lower-Mantle Pressures.

PubMed

Petitgirard, Sylvain; Malfait, Wim J; Journaux, Baptiste; Collings, Ines E; Jennings, Eleanor S; Blanchard, Ingrid; Kantor, Innokenty; Kurnosov, Alexander; Cotte, Marine; Dane, Thomas; Burghammer, Manfred; Rubie, David C

2017-11-24

The convection or settling of matter in the deep Earth's interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past and present Earth. SiO_{2} is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO_{2} glass up to 110 GPa, doubling the pressure range for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO_{2} minerals above 60 GPa. The density data present two discontinuities at ∼17 and ∼60  GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO_{2} glass becomes denser than MgSiO_{3} glass at ∼40  GPa, and its density becomes identical to that of MgSiO_{3} glass above 80 GPa. Our results on SiO_{2} glass may suggest that a variation of SiO_{2} content in a basaltic or pyrolitic melt with pressure has at most a minor effect on the final melt density, and iron partitioning between the melts and residual solids is the predominant factor that controls melt buoyancy in the lowermost mantle.

Explaining the Paleoproterozoic Rise of O2

NASA Astrophysics Data System (ADS)

Anbar, A. D.; Rye, R.; Kaufman, A. J.

2001-12-01

The Paleoproterozoic rise of atmospheric O2 is not understood. Geochemical evidence indicates pO2 \\leq 5 x 10-4 atm before ~ 2.2 Ga and >= 0.03 atm by 2.0 Ga [1]. Most models of this rapid oxygenation account for the timing in an ad hoc manner. In contrast, we suggest oxygenation was driven by rising solar luminosity, a hypothesis consistent with emerging geochemical evidence. Solar luminosity was { ~} 80 % of present value 2.75 Ga. Climate models indicate that pCO2 > 0.2 atm was required before 2.75 Ga if CO2 alone accounted for greenhouse enhancement that averted global glaciation [2]. Paleosols reveal pCO2 <= 10-1.4 atm between 2.75 and 2.2 Ga [3]. This constraint may extend earlier [4]. Given insufficient CO2, CH4 likely helped maintain surface temperature. pCH4 > 10-4 atm would have been adequate 2.75 Ga; Methanogens could sustain this level as long as pO2 was negligible [5]. Atmospheric CH4 and O2 are incompatible. If CH4 was a critical greenhouse gas, increases in pO2 caused global cooling. Temperature and photosynthetic O2 production are probably positively correlated between 273 and 300 K. Combined, these effects constituted a negative feedback on pO2: Excess O2 production cooled the surface, decreasing O2 production until pCH4 was restored. Methanogenesis was decoupled from this feedback as the bulk of Archean methanogens presumably lived in the deep ocean, insulated from surface temperature. Hence, the CH4 greenhouse acted as a cap on pO2 in the Archean. This cap would have eased as rising solar luminosity permitted "titration" of CH4 by increased O2 production; pO2 increased slowly as pCH4 decreased. This feedback suppressed pO2 until solar luminosity allowed the CO2-H2O greenhouse to maintain equable temperatures without appreciable CH4. This threshold was crossed { ~} 2.5 to 2.0 Ga [2], explaining Paleoproterozoic oxygenation. As Earth approached the threshold the CH4 buffer shrank and the likelihood of the feedback being temporarily overwhelmed by

Folic acid-conjugated GdPO4:Tb3+@SiO2 Nanoprobe for folate receptor-targeted optical and magnetic resonance bi-modal imaging

NASA Astrophysics Data System (ADS)

Xu, Xianzhu; Zhang, Xiaoying; Wu, Yanli

2016-11-01

Both fluorescent and magnetic nanoprobes have great potential applications for diagnostics and therapy. In the present work, a folic acid-conjugated and silica-modified GdPO4:Tb3+ (GdPO4:Tb3+@SiO2-FA) dual nanoprobe was strategically designed and synthesized for the targeted dual-modality optical and magnetic resonance (MR) imaging via a facile aqueous method. Their structural, optical, and magnetic properties were determined using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), ultraviolet-visible spectra (UV-Vis), photoluminescence (PL), and superconducting quantum interference device (SQUID). These results indicated that GdPO4:Tb3+@SiO2-FA were uniform monodisperse core-shell structured nanorods (NRs) with an average length of 200 nm and an average width of 25 nm. The paramagnetic property of the synthesized GdPO4:Tb3+@SiO2-FA NRs was confirmed with its linear hysteresis plot (M-H). In addition, the NRs displayed an obvious T1-weighted effect and thus it could potentially serve as a T1-positive contrast agent. The NRs emitted green lights due to the 5D4 → 7F5 transition of the Tb3+. The in vitro assays with NCI-H460 lung cancer cells and human embryonic kidney cell line 293T cells indicated that the GdPO4:Tb3+@SiO2-FA nanoprobe could specifically bind the cells bearing folate receptors (FR). The MTT assay of the NRs revealed that its cytotoxicity was very low. Further in vivo MRI experiments distinctively depict enhanced anatomical features in a xenograft tumor. These results suggest that the GdPO4:Tb3+@SiO2-FA NPs have excellent imaging and cell-targeting abilities for the folate receptor-targeted dual-modality optical and MR imaging and can be potentially used as the nanoprobe for bioimaging.

Cerebral formation of free radicals during hypoxia does not cause structural damage and is associated with a reduction in mitochondrial PO2; evidence of O2-sensing in humans?

PubMed

Bailey, Damian M; Taudorf, Sarah; Berg, Ronan M G; Lundby, Carsten; Pedersen, Bente K; Rasmussen, Peter; Møller, Kirsten

2011-04-01

Cellular hypoxia triggers a homeostatic increase in mitochondrial free radical signaling. In this study, blood was obtained from the radial artery and jugular venous bulb in 10 men during normoxia and 9  hours hypoxia (12.9% O(2)). Mitochondrial oxygen tension (p(O(2))(mit)) was derived from cerebral blood flow and blood gases. The ascorbate radical (A(•-)) was detected by electron paramagnetic resonance spectroscopy and neuron-specific enolase (NSE), a biomarker of neuronal injury, by enzyme-linked immunosorbent assay. Hypoxia increased the cerebral output of A(•-) in proportion to the reduction in p(O(2))(mit), but did not affect NSE exchange. These findings suggest that neuro-oxidative stress may constitute an adaptive response.

Degradation of microcystin-LR by highly efficient AgBr/Ag3PO4/TiO2 heterojunction photocatalyst under simulated solar light irradiation

NASA Astrophysics Data System (ADS)

Wang, Xin; Utsumi, Motoo; Yang, Yingnan; Li, Dawei; Zhao, Yingxin; Zhang, Zhenya; Feng, Chuanping; Sugiura, Norio; Cheng, Jay Jiayang

2015-01-01

A novel photocatalyst AgBr/Ag3PO4/TiO2 was developed by a simple facile in situ deposition method and used for degradation of mirocystin-LR. TiO2 (P25) as a cost effective chemical was used to improve the stability of AgBr/Ag3PO4 under simulated solar light irradiation. The photocatalytic activity tests for this heterojunction were conducted under simulated solar light irradiation using methyl orange as targeted pollutant. The results indicated that the optimal Ag to Ti molar ratio for the photocatalytic activity of the resulting heterojunction AgBr/Ag3PO4/TiO2 was 1.5 (named as 1.5 BrPTi), which possessed higher photocatalytic capacity than AgBr/Ag3PO4. The 1.5 BrPTi heterojunction was also more stable than AgBr/Ag3PO4 in photocatalysis. This highly efficient and relatively stable photocatalyst was further tested for degradation of the hepatotoxin microcystin-LR (MC-LR). The results suggested that MC-LR was much more easily degraded by 1.5 BrPTi than by AgBr/Ag3PO4. The quenching effects of different scavengers proved that reactive h+ and •OH played important roles for MC-LR degradation.

Toward a stable solid-electrolyte-interfaces on nickel-rich cathodes: LiPO2F2 salt-type additive and its working mechanism for LiNi0.5Mn0.25Co0.25O2 cathodes

NASA Astrophysics Data System (ADS)

Zhao, Weimin; Zheng, Guorui; Lin, Min; Zhao, Wengao; Li, Dongjiang; Guan, Xiaoyun; Ji, Yajuan; Ortiz, Gregorio F.; Yang, Yong

2018-03-01

Although the LiNi0.5Mn0.25Co0.25O2 holds the merits of high theoretical capacities and a relatively high operating voltage, the battery performance suffers from the severe cycling decay due to the unstable solid electrolyte interface on the cathode. Herein, we present LiPO2F2 as a salt-type electrolyte additive to enhance the cycling stability of large-size crystallite LiNi0.5Mn0.25Co0.25O2 cathodes. Results demonstrate that 1 wt% LiPO2F2 can significantly improve not only the initial coulombic efficiency by 3%, but also the cycling stability and rate capability at 25 °C. Furthermore, the discharge capacity of LiNi0.5Mn0.25Co0.25O2 cathodes still maintain 156 mAh g-1 after 100 cycles even when the temperature increases to 55 °C. In-depth experimental characterization and theoretical calculation indicate that a new stable and thin (e.g. 15-20 nm) film formed on the surface of the cathodes, with composition of LiPO2F2, LiF, etc., which significantly reduces charge transfer impedance of the electrodes, and therefore significantly improves the cycling and rate performance of LiNi0.5Mn0.25Co0.25O2.

A new set of K3Fe3(PO4)4·yH2O (0 ≤ y ≤ 1) layered phases obtained by topotactic reactions

NASA Astrophysics Data System (ADS)

Trad, Khiem; Wattiaux, Alain; Ben Amara, Mongi; Delmas, Claude; Carlier, Dany

2018-06-01

K3Fe3(PO4)4·H2O powder was synthesized by Na+/K+ exchange reaction from Na3Fe3(PO4)4 in aqueous medium. The replacement of the sodium cations by the potassium larger ones and water molecules causes a structural distortion leading to P2/n monoclinic K3Fe3(PO4)4·H2O. This new layered phase was characterized by XRD, Mössbauer spectroscopy and magnetic measurements. The study of its thermal stability reveals that other new layered K3Fe3(PO4)4·yH2O with (0 ≤ y ≤ 1) phases can be stabilized up to 600 °C and finally at higher temperature a new K3Fe3(PO4)4 polymorph with a different structural type is irreversibility formed.

Geometry of α-Cr2O3(0001) as a Function of H2O Partial Pressure

PubMed Central

2015-01-01

Surface X-ray diffraction has been employed to elucidate the surface structure of α-Cr2O3(0001) as a function of water partial pressure at room temperature. In ultra high vacuum, following exposure to ∼2000 Langmuir of H2O, the surface is found to be terminated by a partially occupied double layer of chromium atoms. No evidence of adsorbed OH/H2O is found, which is likely due to either adsorption at minority sites, or X-ray induced desorption. At a water partial pressure of ∼30 mbar, a single OH/H2O species is found to be bound atop each surface Cr atom. This adsorption geometry does not agree with that predicted by ab initio calculations, which may be a result of some differences between the experimental conditions and those modeled. PMID:26877825

Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yahia, H. Ben; Essehli, R., E-mail: ressehli@qf.org.qa; Avdeev, M.

The new compounds NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} crystallize with a stuffed α-CrPO{sub 4}-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structuresmore » of NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} a statistical disorder Ni{sup 2+}/Cr{sup 3+} was observed on both the 8g and 4a atomic positions, whereas in NaCoCr{sub 2}(PO{sub 4}){sub 3} the statistical disorder Co{sup 2+}/Cr{sup 3+} was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} delivered specific capacities of 352, 385, and 368 mA h g{sup −1}, respectively, which attests to the electrochemical activity of sodium in these compounds. - Highlights: • NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} were synthesized by sol-gel method. • The crystal structures were determined by using neutron powder diffraction data. • The three compounds crystallize with a stuffed α-CrPO{sub 4}-type structure. • The three compounds were tested as anodes in sodium-ion batteries. • Relatively high specific capacities were obtained for these compounds.« less

Kinetics of struvite to newberyite transformation in the precipitation system MgCl2-NH4H2PO4NaOH-H2O.

PubMed

Babić-Ivancić, Vesna; Kontrec, Jasminka; Brecević, Ljerka; Kralj, Damir

2006-10-01

The influence of the initial reactant concentrations on the composition of the solid phases formed in the precipitation system MgCl(2)-NH(4)H(2)PO(4)-NaOH-H(2)O was investigated. The precipitation diagram constructed shows the approximate concentration regions within which struvite, newberyite, and their mixtures exist at 25 degrees C and an aging time of 60 min. It was found that immediately after mixing the reactant solutions, struvite (MgNH(4)PO(4).6H(2)O) precipitated in nearly the whole concentration area, while newberyite (MgHPO(4).3H(2)O) appeared mostly within the region of the excess of magnesium concentration. It was also found that after aging time of 60 min the precipitation domain of struvite alone is much broader than that of newberyite or the domain of their coexistence, and shows that struvite is more abundant in the systems in which the initial concentration of ammonium phosphate is higher than that of magnesium. The kinetics of struvite to newberyite transformation (conversion) was systematically studied under the conditions of different initial reactant concentrations and different initial pH in the systems in which a mixture of both phases precipitated spontaneously. The struvite to newberyite conversion period was found to be strongly related to the ratio of initial supersaturations, S(N)/S(S), rather than to the any particular physical quantity that can describe and predict the behavior of the precipitation system. Experimental data suggest a solution-mediated process as a most possible transformation mechanism. Along with a continuous monitoring of the changes in the liquid phase, the content of struvite in the solid phase was estimated by means of a Fourier transform infrared (FT-IR) method, developed for this particular precipitation system.

Applications of Novel Carbon/AlPO4 Hybrid-Coated H2Ti12O25 as a High-Performance Anode for Cylindrical Hybrid Supercapacitors.

PubMed

Lee, Jeong-Hyun; Lee, Seung-Hwan

2016-10-26

The hybrid supercapacitor using carbon/AlPO 4 hybrid-coated H 2 Ti 12 O 25 /activated carbon is fabricated as a cylindrical cell and investigated against electrochemical performances. The hybrid coating shows that the conductivity for the electron and Li ion is superior and it prevented active material from HF attack. Consequently, carbon/AlPO 4 hybrid-coated H 2 Ti 12 O 25 shows enhanced rate capability and long-term cycle life. Also, the hybrid coating inhibits swelling phenomenon caused by gas generated as decomposition reaction of electrolyte. Therefore, the hybrid supercapacitor using carbon/AlPO 4 hybrid-coated H 2 Ti 12 O 25 /activated carbon can be applied to an energy storage system that requires a long-term life.

Influence of temperature and frequency on ionic conductivity of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

El Moudane, M., E-mail: m.elmoudane@gmail.com; El Maniani, M.; Sabbar, A.

2015-12-15

Highlights: • Results of ionic conductivities of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses. • Determination of glass transition temperature using DSC method. • Study of temperature and frequency on ionic conductivity of Li{sub 3}PO{sub 4}–Pb{sub 3}(PO{sub 4}){sub 2}–BiPO{sub 4} phosphate glasses. - Abstract: Lithium–Lead–Bismuth phosphates glasses having, a composition 30Li{sub 3}PO{sub 4}–(70 − x)Pb{sub 3}(PO{sub 4}){sub 2}–xBiPO{sub 4} (45 ≤ x ≤ 60 mol%) were prepared by using the melt quenching method 1000 °C. The thermal stability of theses glasses increases with the substitution of Bi{sub 2}O{sub 3} with PbO. The ionic conductivity of all compositions havemore » been measured over a wide temperature (200–500 °C) and frequency range (1–106 Hz). The ionic conductivity data below and above T{sub g} follows Arrhenius and Vogel–Tamman–Fulcher (VTF) relationship, respectively. The activation energies are estimated and discussed. The dependence in frequency of AC conductivity is found to obey Jonscher’s relation.« less

Network rigidity and properties of SiO2 and GeO2 glasses under pressure.

PubMed

Trachenko, Kostya; Dove, Martin T; Brazhkin, Vadim; El'kin, F S

2004-09-24

We report in situ studies of SiO2 glass under pressure and find that temperature-induced densification takes place in a pressure window. To explain this effect, we study how rigidity of glasses changes under pressure, with rigidity percolation affecting the dynamics of local relaxation events. We link rigidity percolation in glasses to other effects, including a large increase of crystallization temperature and logarithmic relaxation under pressure.

Mn0.95I0.02[PO3(OH)] · 2H2O phosphate-iodate, an inorganic analogue of phosphonates

NASA Astrophysics Data System (ADS)

Belokoneva, E. L.; Dimitrova, O. V.; Volkov, A. S.

2015-09-01

The new Mn0.95I0.02[PO3(OH)] · 2H2O phosphate-iodate (space group Pnam = Pnma, D {2/h 16}) is obtained under hydrothermal conditions. The crystal structure is determined without preliminary knowledge of the chemical formula. The structure consists of layers of MnО6 octahedra connected with PO4 tetrahedra. Water molecules are located between the layers. [IO3]- groups having a typical umbrella-like coordination are statistically implanted in layers of MnО6 octahedra at a distance of 1.2 Å from Mn atoms. Their content in the crystal is minor. The structures of the phosphate-iodate coincides with the structures of phosphonates with consideration for the replacement of one (OH) vertex of the РО4 tetrahedron by the organic methyl radical СН3. In the structures of phosphonates and earlier studied phosphates, identical layers are distinguished and the cause of the existence of two MDO varieties is established based on the analysis within the OD theory. Possible hybrid structures derived from the prototypes under consideration are predicted.

Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

PubMed

Li, H C; Wang, D G; Meng, X G; Chen, C Z

2014-06-01

A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and β-CaSiO(3). (β-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of β-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell. Copyright © 2014 Elsevier B.V. All rights reserved.

Pressure-induced structural transformations in lanthanide titanates: La{sub 2}TiO{sub 5} and Nd{sub 2}TiO{sub 5}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, F.X., E-mail: zhangfx@umich.ed; Wang, J.W.; Lang, M.

The structure of orthorhombic rare earth titanates of La{sub 2}TiO{sub 5} and Nd{sub 2}TiO{sub 5}, where Ti cations are in five-fold coordination with oxygen, has been studied at high pressures by X-ray diffraction (XRD), Raman scattering measurements, and quantum mechanical calculations. Both XRD and Raman results indicated two pressure-induced phase transitions during the process. An orthorhombic super cell (axbx2c) formed at a pressure between 6 and 10 GPa, and then transformed to a hexagonal high-pressure phase accompanied by partial decomposition. The hexagonal high-pressure phase is quenchable. Detailed structural analysis indicated that the five-coordinated TiO{sub 5} polyhedra remain during the formationmore » of super cell, but the orthorhombic-to-hexagonal phase transition at high pressures is a reconstructive process, and the five-fold Ti-O coordination increased to more than 6. This phase transition sequence was verified by quantum mechanical calculations. - Graphical abstract: At high pressures, La{sub 2}TiO{sub 5} and Nd{sub 2}TiO{sub 5} transform from the orthorhombic phase to an axbx2c superlattice of the orthorhombic structure and then to a hexagonal high-pressure phase. Display Omitted« less

Li3PO4 surface coating on Ni-rich LiNi0.6Co0.2Mn0.2O2 by a citric acid assisted sol-gel method: Improved thermal stability and high-voltage performance

NASA Astrophysics Data System (ADS)

Lee, Suk-Woo; Kim, Myeong-Seong; Jeong, Jun Hui; Kim, Dong-Hyun; Chung, Kyung Yoon; Roh, Kwang Chul; Kim, Kwang-Bum

2017-08-01

A surface coating of Li3PO4 was applied to a Ni-rich LiNi0.6Co0.2Mn0.2O2 (NCM) material to improve its thermal stability and electrochemical properties via a citric acid assisted sol-gel method. The addition of citric acid effectively suppressed the instant formation of Li3PO4 in solution, resulting in successful coating of the NCM surface. The improved thermal stability of NCM after Li3PO4 surface coating was demonstrated by differential scanning calorimetry (DSC) analysis and in situ time-resolved X-ray diffraction (TR-XRD). In particular, the TR-XRD results showed that the improved thermal stability after Li3PO4 surface coating originates from suppression of the phase transition of charged NCM at high temperatures. Furthermore, the charge-discharge tests demonstrated that Li3PO4-coated LiNi0.6Co0.2Mn0.2O2 (LP-NCM) has excellent electrochemical properties. LP-NCM exhibited a specific capacity of 192.7 mAh g-1, a capacity retention of 44.1% at 10 C, and a capacity retention of 79.7% after 100 cycles at a high cut-off voltage of 4.7 V; these values represent remarkably improved electrochemical properties compared with those of bare NCM. These improved thermal and electrochemical properties were mainly attributed to the improvement of the structural stability of the material and the suppression of the interface reaction between the cathode and the electrolyte owing to the Li3PO4 coating.

Ionothermal synthesis, crystal structure, and magnetic study of Co2PO4OH isostructural with caminite.

PubMed

Wang, Guangmei; Valldor, Martin; Spielberg, Eike T; Mudring, Anja-Verena

2014-03-17

A new framework cobalt(II) hydroxyl phosphate, Co2PO4OH, was prepared by ionothermal synthesis using 1-butyl-4-methyl-pyridinium hexafluorophosphate as the ionic liquid. As the formation of Co2PO4F competes in the synthesis, the synthesis conditions have to be judiciously chosen to obtain well-crystallized, single phase Co2PO4OH. Single-crystal X-ray diffraction analyses reveal Co2PO4OH crystallizes with space group I41/amd (a = b = 5.2713(7) Å, c = 12.907(3) Å, V = 358.63(10) Å(3), and Z = 4). Astonishingly, it does not crystallize isotypically with Co2PO4F but rather isotypically with the hydroxyl minerals caminite Mg1.33[SO4(OH)0.66(H2O)0.33] and lipscombite Fe(2–y)PO4(OH) (0 ≤ y ≤ 2/3). Phosphate tetrahedra groups interconnect four rod-packed face-sharing ∞(1){CoO(6/2)} octahedra chains to form a three-dimensional framework structure. The compound Co2PO4OH was further characterized by powder X-ray diffraction, Fourier transform–infrared, and ultraviolet–visible spectroscopy, confirming the discussed structure. The magnetic measurement reveals that Co2PO4OH undergoes a magnetic transition and presents at low temperatures a canted antiferromagnetic spin order in the ground state.

Novel high-pressure phase of ZrO{sub 2}: An ab initio prediction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durandurdu, Murat, E-mail: murat.durandurdu@agu.edu.tr

2015-10-15

The high-pressure behavior of the orthorhombic cotunnite type ZrO{sub 2} is explored using an ab initio constant pressure technique. For the first time, a novel hexagonal phase (Ni{sub 2}In type) within P6{sub 3}/mmc symmetry is predicted through the simulation. The Ni{sub 2}In type crystal is the densest high-pressure phase of ZrO{sub 2} proposed so far and has not been observed in other metal dioxides at high pressure before. The phase transformation is accompanied by a small volume drop and likely to occur around 380 GPa in experiment. - Graphical abstract: Post-cotunnite Ni{sub 2}In type hexagonal phase forms in zirconia atmore » high pressure. - Highlights: • A post-cotunnite phase is predicted for ZrO{sub 2} through an ab initio simulation. • Cotunnite ZrO{sub 2} adopts the Ni{sub 2}In type structure at high pressure. • The Ni{sub 2}In type structure is the densest high-pressure phase of ZrO{sub 2} proposed so far. • The preferred mechanism in ZrO{sub 2} differs from the other metal dioxides.« less

Signature of quantum entanglement in NH{sub 4}CuPO{sub 4}·H{sub 2}O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, Tanmoy, E-mail: tanmoy@iiserkol.ac.in; Singh, Harkirat; Mitra, Chiranjib, E-mail: chiranjib@iiserkol.ac.in

2014-01-21

Entangled solid state systems have gained a great deal of attention due to their fruitful applications in modern quantum technologies. Herein, detection of entanglement content from experimental magnetic susceptibility and specific heat data is reported for NH{sub 4}CuPO{sub 4}·H{sub 2}O in its solid state crystalline form. NH{sub 4}CuPO{sub 4}·H{sub 2}O is a prototype of Heisenberg spin 1/2 dimer system. Temperature dependent magnetic susceptibility and specific data are fitted to an isolated dimer model and the exchange coupling constant is determined. Field dependent magnetization isotherms taken at different temperatures are plotted in a three dimensional plot. Subsequently, entanglement is detected bothmore » from susceptibility and specific heat through two different entanglement measures; entanglement witness and entanglement of formation. The temperature evolution of entanglement is studied and the critical temperature is determined up to which entanglement exists. Temperature dependent nature of entanglement extracted from susceptibility and specific heat shows good consistency with each other. Moreover, the field dependent entanglement is also investigated.« less

Toward pressure-induced multiferroicity in PrMn2O5

NASA Astrophysics Data System (ADS)

Peng, W.; Balédent, V.; Chattopadhyay, S.; Lepetit, M.-B.; Yahia, G.; Colin, C. V.; Gooch, M. J.; Pasquier, C. R.; Auban-Senzier, P.; Greenblatt, M.; Foury-Leylekian, P.

2017-08-01

The series of multiferroics R Mn2O5 is extensively studied for its quasicollinear spin arrangement, which results in an electrical polarization according to the exchange-striction model. Variations of the interatomic distances modified by the external pressure can strongly influence the multiferroic properties. Understanding this influence is of great importance, especially for the future realization of multiferroic devices. As PrMn2O5 is paraelectric at ambient pressure, it is the most suitable candidate to search for pressure induced multiferroicity. In this paper, we report the emergence of a new pressure induced magnetic phase in PrMn2O5 determined by powder neutron diffraction under pressure. This new magnetic phase presenting at relatively low pressure becomes completely exclusive at 8 GPa. The determination of its magnetic structure has thus been possible for the first time. More importantly, the magnetic structure stabilized under pressure should induce a strong spontaneous electric polarization due to the nearly perfect collinearity of the Mn3 + and Mn4 + spins.

Pnicogen bonded complexes of PO2X (X = F, Cl) with nitrogen bases.

PubMed

Alkorta, Ibon; Elguero, José; Del Bene, Janet E

2013-10-10

An ab initio MP2/aug'-cc-pVTZ study has been carried out on complexes formed between PO2X (X = F and Cl) as the Lewis acids and a series of nitrogen bases ZN, including NH3, H2C═NH, NH2F, NP, NCH, NCF, NF3, and N2. Binding energies of these complexes vary from -10 to -150 kJ/mol, and P-N distances from 1.88 to 2.72 Å. Complexes ZN:PO2F have stronger P(...)N bonds and shorter P-N distances than the corresponding complexes ZN:PO2Cl. Charge transfer from the N lone pair through the π-hole to the P-X and P-O σ* orbitals leads to stabilization of these complexes, although charge-transfer energies can be evaluated only for complexes with binding energies less than -71 kJ/mol. Complexation of PO2X with the strongest bases leads to P···N bonds with a significant degree of covalency, and P-N distances that approach the P-N distances in the molecules PO2NC and PO2NH2. In these complexes, the PO2X molecules distort from planarity. Changes in (31)P absolute chemical shieldings upon complexation do not correlate with changes in charges on P, although they do correlate with the binding energies of the complexes. EOM-CCSD spin-spin coupling constants (1p)J(P-N) are dominated by the Fermi-contact term, which is an excellent approximation to total J. (1p)J(P-N) values are small at long distances, increase as the distance decreases, but then decrease at short P-N distances. At the shortest distances, values of (1p)J(P-N) approach (1)J(P-N) for the molecules PO2NC and PO2NH2.

Electron excitation cross sections for the 2s(2)2p(3)4S(O) -- 2s(2)2p(3)2D(O) (forbidden) and 4S(O) -- 2s2p(4) 4P (resonance) transitions in O II

NASA Technical Reports Server (NTRS)

Zuo, M.; Smith, Steven J.; Chutjian, A.; Williams, I. D.; Tayal, S. S.; Mclaughlin, Brendan M.

1995-01-01

Experimental and theoretical excitation cross sections are reported for the first forbidden transition 4S(O) -- 2S(2)2p(3) 2D(O) (lambda-lambda 3726, 3729) and the first allowed (resonance) transition 4S(O) -- 2s2p(4) 4P(lambda-833) in O II. Use is made of electron energy loss and merged-beams methods. The electron energy range covered is 3.33 (threshold) to 15 eV for the S -- D transition, and 14.9 (threshold) to 40 eV for the S -- P transition. Care was taken to assess and minimize the metastable fraction of the O II beam. An electron mirror was designed and tested to reflect inelastically backscattered electrons into the forward direction to account for the full range of polar scattering angles. Comparisons are made between present experiments and 11-state R-matrix calculations. Calculations are also presented for the 4S(O) -- 2s(2)2p(3)2P(O) (lambda-2470) transition.

Synthesis, crystal structure, and ionic conductivity of a new layered metal phosphate, Li{sub 2}Sr{sub 2}Al(PO{sub 4}){sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sung-Chul; Kwak, Hyun-Jung; Yoo, Chung-Yul

2016-11-15

A new layered metal phosphate, Li{sub 2}Sr{sub 2}Al(PO{sub 4}){sub 3}, was synthesized in the form of either a single-crystal or polycrystalline powder using the molten hydroxide flux method or a solid-state reaction, respectively. Li{sub 2}Sr{sub 2}Al(PO{sub 4}){sub 3} crystallizes to the P2{sub 1}/n (Z=4) monoclinic space group with lattice parameters a≈4.95 Å, b≈22.06 Å, c≈8.63 Å, and β≈91.5°. The structure is composed of stacked [LiSrAl(PO{sub 4}){sub 2}] layers alternating regularly with [LiSrPO{sub 4}] layers. In the [LiSrAl(PO{sub 4}){sub 2}] sublattice, the AlO{sub 6} octahedra and PO{sub 4} tetrahedra are tilted cooperatively to form an anionic, corrugated, two-dimensional [Al(PO{sub 4}){sub 2}]{supmore » 3−} framework that can be regarded as a “distorted-glaserite” structure. The [LiSrPO{sub 4}] sublattice is that of a layered block containing a six-membered ring formed from alternating linkages of LiO{sub 4} and PO{sub 4} tetrahedra. The six-membered rings show a boat-type arrangement with the up(U) or down(D) pointing sequence, UUDUUD. The interspace between the two sublattices generates a two-dimensional pathway for Li{sup +} ion conduction. The impedance measurement indicated that Li{sub 2}Sr{sub 2}Al(PO{sub 4}){sub 3} had a moderate ion conductivity (σ≈1.30×10{sup −4} S cm{sup −1} at 667 K), with an activation energy E{sub a}≈1.02 eV. - Graphical abstract: Polyhedral view of Li{sub 2}Sr{sub 2}Al(PO{sub 4}){sub 3}. Li{sup +} ions are represented by green spheres, Sr atoms by white spheres, AlO{sub 6} groups by octahedra, and PO{sub 4} groups by tetrahedra. - Highlights: • New compound Li{sub 2}Sr{sub 2}Al(PO{sub 4}){sub 3} is reported. • The crystal structure is investigated by single-crystal XRD analysis. • The structure is formed by the alternate stacking of two different sublattices. • Correlation between the crystal structure and ionic conductivity is discussed.« less

A 2 TiO 5 (A = Dy, Gd, Er, Yb) at High Pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Sulgiye; Rittman, Dylan R.; Tracy, Cameron L.

The structural evolution of lanthanide A2TiO5 (A = Dy, Gd, Yb, and Er) at high pressure is investigated using synchrotron X-ray diffraction. The effects of A-site cation size and of the initial structure are systematically examined by varying the composition of the isostructural lanthanide titanates, and the structure of dysprosium titanate polymorphs (orthorhombic, hexagonal and cubic), respectively. All samples undergo irreversible high pressure phase transformations, but with different onset pressures depending on the initial structure. While individual phase exhibits different phase transformation histories, all samples commonly experience a sluggish transformation to a defect cotunnite-like (Pnma) phase for a certain pressuremore » range. Orthorhombic Dy2TiO5 and Gd2TiO5 form P21am at pressures below 9 GPa and Pnma above 13 GPa. Pyrochlore-type Dy2TiO5 and Er2TiO5 as well as defect-fluorite-type Yb2TiO5 form Pnma at ~ 21 GPa, followed by Im-3m. Hexagonal Dy2TiO5 forms Pnma directly, although a small amount of remnants of hexagonal Dy2TiO5 is observed even at the highest pressure (~ 55 GPa) reached, indicating a kinetic limitations in the hexagonal Dy2TiO5 phase transformations at high pressure. Decompression of these materials leads to different metastable phases. Most interestingly, a high pressure cubic X-type phase (Im-3m) is confirmed using highresolution transmission electron microscopy on recovered pyrochlore-type Er2TiO5. The kinetic constraints on this metastable phase yield a mixture of both the X-type phase and amorphous domains upon pressure release. This is the first observation of an X-type phase for an A2BO5 composition at high pressure.« less

PO2 cycling reduces diaphragm fatigue by attenuating ROS formation.

PubMed

Zuo, Li; Diaz, Philip T; Chien, Michael T; Roberts, William J; Kishek, Juliana; Best, Thomas M; Wagner, Peter D

2014-01-01

Prolonged muscle exposure to low PO2 conditions may cause oxidative stress resulting in severe muscular injuries. We hypothesize that PO2 cycling preconditioning, which involves brief cycles of diaphragmatic muscle exposure to a low oxygen level (40 Torr) followed by a high oxygen level (550 Torr), can reduce intracellular reactive oxygen species (ROS) as well as attenuate muscle fatigue in mouse diaphragm under low PO2. Accordingly, dihydrofluorescein (a fluorescent probe) was used to monitor muscular ROS production in real time with confocal microscopy during a lower PO2 condition. In the control group with no PO2 cycling, intracellular ROS formation did not appear during the first 15 min of the low PO2 period. However, after 20 min of low PO2, ROS levels increased significantly by ∼30% compared to baseline, and this increase continued until the end of the 30 min low PO2 condition. Conversely, muscles treated with PO2 cycling showed a complete absence of enhanced fluorescence emission throughout the entire low PO2 period. Furthermore, PO2 cycling-treated diaphragm exhibited increased fatigue resistance during prolonged low PO2 period compared to control. Thus, our data suggest that PO2 cycling mitigates diaphragm fatigue during prolonged low PO2. Although the exact mechanism for this protection remains to be elucidated, it is likely that through limiting excessive ROS levels, PO2 cycling initiates ROS-related antioxidant defenses.

Colorimetric and fluorescent chemosensor for highly selective and sensitive relay detection of Cu2 + and H2PO4- in aqueous media

NASA Astrophysics Data System (ADS)

Su, Jun-Xia; Wang, Xiao-Ting; Chang, Jing; Wu, Gui-Yuan; Wang, Hai-Ming; Yao, Hong; Lin, Qi; Zhang, You-Ming; Wei, Tai-Bao

2017-07-01

In this manuscript, a new colorimetric and fluorescent chemosensor (T) was designed and synthesized, it could successively detect Cu2 + and H2PO4- in DMSO/H2O (v/v = 9:1, pH = 7.2) buffer solution with high selectivity and sensitivity. When added Cu2 + ions into the solution of T, it showed a color changes from yellow to colorless, meanwhile, the green fluorescence of sensor T quenched. This recognition behavior was not affected in the presence of other cations, including Hg2 +, Ag+, Ca2 +, Co2 +, Ni2 +, Cd2 +, Pb2 +, Zn2 +, Cr3 +, and Mg2 + ions. More interestingly, the Cu2 + ions contain sensor T solution could recover the color and fluorescence upon the addition of H2PO4- anions in the same medium. And other surveyed anions (including F-, Cl-, Br-, I-, AcO-, HSO4-, ClO4-, CN- and SCN-) had nearly no influence on the recognition behavior. The detection limits of T to Cu2 + and T-Cu2 + to H2PO4- were evaluated to be 1.609 × 10- 8 M and 0.994 × 10- 7 M, respectively. In addition, the sensor T also could be served as a recyclable component and the logic gate output was also defined in sensing materials. The test strips based on sensor T were fabricated, which acted as a convenient and efficient Cu2 + and H2PO4- test kits.

Phase equilibria in the NaF-CdO-NaPO3 system at 873 K and crystal structure and physico-chemical characterizations of the new Na2CdPO4F fluorophosphate

NASA Astrophysics Data System (ADS)

Aboussatar, Mohamed; Mbarek, Aïcha; Naili, Houcine; El-Ghozzi, Malika; Chadeyron, Geneviève; Avignant, Daniel; Zambon, Daniel

2017-04-01

Isothermal sections of the diagram representing phase relationships in the NaF-CdO-NaPO3 system have been investigated by solid state reactions and powder X-ray diffraction. This phase diagram investigation confirms the polymorphism of the NaCdPO4 side component and the structure of the ß high temperature polymorph (orthorhombic, space group Pnma and unit cell parameters a=9.3118(2), b=7.0459(1), c=5.1849(1) Å has been refined. A new fluorophosphate, Na2CdPO4F, has been discovered and its crystal structure determined and refined from powder X-ray diffraction data. It exhibits a new 3D structure with orthorhombic symmetry, space group Pnma and unit cell parameters a=5.3731(1), b=6.8530(1), c=12.2691(2) Å. The structure is closely related to those of the high temperature polymorph of the nacaphite Na2CaPO4F and the fluorosilicate Ca2NaSiO4F but differs essentially in the cationic repartition since the structure is fully ordered with one Na site (8d) and one Cd site (4c). Relationships with other Na2MIIPO4F (MII=Mg, Ca, Mn, Fe, Co, Ni) have been examined and the crystal-chemical and topographical analysis of these fluorophosphates is briefly reviewed. IR, Raman, optical and 19F, 23Na, 31P MAS NMR characterizations of Na2CdPO4F have been investigated.

FirefOx Design Reference fO2 Sensor for Hot, Deep Atmospheres

NASA Astrophysics Data System (ADS)

Izenberg, N.; Papadakis, S.; Deglau, D.; Francomacaro, A. S.

2016-12-01

Understanding the composition of the lowest portion of Venus' atmosphere is critical to knowing the stable mineralogy of the rocks there. Oxygen gas is a critical trace component, with fugacity, or partial pressure, estimated in the range of 10-19 to 10-22 from early probe measurements down to 22km altitude (Pioneer Venus, Venera), chemical equilibrium measurements, and other modeling. "FirefOx" is a simple oxygen fugacity sensor with the express purpose of determining the partial pressure of oxygen in the lowest scale heights of the Venus atmosphere, and especially the lowest hundreds of meters; the surface atmosphere interface, where the atmosphere and surface move to thermodynamic equilibrium. Knowledge of the fO2 at the surface atmosphere interface is crucial to determining the stable mineralogy of surface materials (e.g. magnetite vs. hematite) and gas chemistry in the near-surface atmosphere FirefOx is a Metal/Metal Oxide oxygen fugacity sensor intended to be mounted on the outside of a Venus descent probe, with electronics housed inside a thermally controlled environment. The sole sensor capability is the precise, accurate detection of the partial pressure of oxygen gas (fO2) in the near-surface environment of Venus, at up to 95-bar pressure (predominantly CO2. Surface temperatures at mean planetary elevation are near 735 K, thus a required operational temperature range of 710-740 K covers a range of near-surface elevations. FirefOx system requirements are low ( 100-200 grams, mass, milliwatt power, several kilobytes total science data). A design reference sensor, composed of custom, Yittria-ZrO ceramic electrolyte, with an encapsulated Pd/PdO standard and patterned Pt electrodes has demonstrated scientifically useful signal-to-noise millivolt level potential at temperatures as low as 620 K, relatable to fO2 by a Nernst equation E = RT/4F ln(PO2/PrefO2) where E = open circuit potential across the sensor electrolyte, R = universal gas constant, T

A method for measuring brain partial pressure of oxygen in unanesthetized unrestrained subjects: the effect of acute and chronic hypoxia on brain tissue PO(2).

PubMed

Ortiz-Prado, E; Natah, Siraj; Srinivasan, Sathyanarayanan; Dunn, Jeff F

2010-11-30

The level of tissue oxygenation provides information related to the balance between oxygen delivery, oxygen utilization, tissue reactivity and morphology during physiological conditions. Tissue partial pressure of oxygen (PtO(2)) is influenced by the use of anesthesia or restraint. These factors may impact the absolute level of PtO(2). In this study we present a novel fiber optic method to measure brain PtO(2). This method can be used in unanesthetized, unrestrained animals, provides absolute values for PO(2), has a stable calibration, does not consume oxygen and is MRI compatible. Brain PtO(2) was studied during acute hypoxia, as well as before and after 28 days of high altitude acclimatization. A sensor was chronically implanted in the frontal cortex of eight Wistar rats. It is comprised of a fiber optic probe with a tip containing material that fluoresces with an oxygen dependent lifetime. Brain PtO(2) declines by 80% and 76% pre- and post-acclimatization, respectively, when the fraction of inspired oxygen declines from 0.21 to 0.08. In addition, a linear relationship between brain PtO(2) and inspired O(2) levels was demonstrated r(2)=0.98 and r(2)=0.99 (pre- and post-acclimatization). Hypoxia acclimatization resulted in an increase in the overall brain PtO(2) by approximately 35%. This paper demonstrates the use of a novel chronically implanted fiber optic based sensor for measuring absolute PtO(2). It shows a very strong linear relationship in awake animals between inspired O(2) and tissue O(2), and shows that there is a proportional increase in PtO(2) over a range of inspired values after exposure to chronic hypoxia. Copyright © 2010 Elsevier B.V. All rights reserved.

X-ray-induced dissociation of H.sub.2O and formation of an O.sub.2-H.sub.2 alloy at high pressure

DOEpatents

Mao, Ho-kwang [Washington, DC; Mao, Wendy L [Washington, DC

2011-11-29

A novel molecular alloy of O.sub.2 and H.sub.2 and a method of producing such a molecular alloy are provided. When subjected to high pressure and extensive x-radiation, H.sub.2O molecules cleaved, forming O--O and H--H bonds. In the method of the present invention, the O and H framework in ice VII was converted into a molecular alloy of O.sub.2 and H.sub.2. X-ray diffraction, x-ray Raman scattering, and optical Raman spectroscopy demonstrate that this crystalline solid differs from previously known phases.

Internally consistent thermodynamic data for high-pressure and ultrahigh-pressure phases in the system CaO-MgO-Al2O3-SiO2-H2O

NASA Astrophysics Data System (ADS)

Grevel, K. D.

2008-12-01

In order to enable reliable calculations of phase relations among high-pressure phases the Berman [1] data set was augmented by data for the high-pressure phases stishovite (stv), topaz-OH (toz-OH), phase pi (pi), Mg-staurolite (Mg-st), Mg-sursassite (Mg-sur), and Mg-chloritoid (Mg-cld) using a similar optimization technique as described by Berman et al. [2]. The data of several other phases of the system CaO-MgO- Al2O3-SiO2-H2O obtained in the Berman data base were slightly refined to keep the consistency to the reversal brackets and the originally measured data: andalusite (and), clinochlore (chl), coesite (cs), diaspore (dsp), kaolinite (kln), kyanite (ky), lawsonite (lws), pyrophyllite (prl), sillimanite (sil), zoisite (zo). CP-data were kept constant [1] or estimated [3]. phase; ΔfH0298 (kJ mol-1); S0298 (J K-1 mol-1); V0298 (J K-1 mol-1); v1×105 (bar-1); v2×1012 (bar-2); v3×105 (K-1); v4×108 (K-2) and; -2589.857; 91.47; 5.146; -0.0653; 0.000; 2.291; 0.170 chl; -8903.532; 437.92; 21.000; -0.1328; 3.837; 2.142; 0.962 Mg-cld; -3551.657; 142.20; 6.874; -0.0692; 0.000; 2.544; 0.000 cs; -907.510; 39.63; 2.064; -0.0998; 1.823; 0.620; 0.960 dsp; -999.115; 35.22; 1.776; -0.0719; 0.629; 3.245; 0.684 kln; -4119.400; 204.18; 9.952; -0.1200; 0.000; 3.200; 0.000 ky; -2593.767; 82.71; 4.408; -0.0593; 1.021; 1.730; 0.787 lws; -4866.665; 228.04; 10.155; -0.0825; 0.000; 3.339; 0.000 Mg-sur; -13907.329; 608.39; 26.888; -0.0826; 0.923; 3.187; 0.087 pi; -9586.742; 403.23; 18.559; -0.0678; 0.000; 2.254; 0.000 prl; -5640.501; 239.43; 12.782; -0.1800; 0.000; 2.621; 0.000 sil; -2586.169; 95.40; 4.984; -0.0601; 1.341; 1.138; 0.605 Mg-st; -24998.289; 944.53; 44.260; -0.0579; 0.000; 2.017; 0.000 stv; -870.861; 25.59; 1.401; -0.0318; 0.000; 1.849; 0.000 toz-OH; -2885.939; 117.40; 5.352; -0.0630; 0.000; 1.938; 0.000 zo; -6889.494; 297.20; 13.565; -0.0695; 0.000; 2.752; 0.000 References [1] R.G. Berman, J. Petrol., 1988, 29, 445 [2] R.G. Berman et al., J. Petrol., 1986, 27, 1331 [3] R

Phase Equilibria of ``Cu2O''-``FeO''-CaO-MgO-Al2O3 Slags at PO2 of 10-8.5 atm in Equilibrium with Metallic Copper for a Copper Slag Cleaning Production

NASA Astrophysics Data System (ADS)

Henao, Hector M.; Pizarro, Claudio; Font, Jonkion; Moyano, Alex; Hayes, Peter C.; Jak, Evgueni

2010-12-01

Limited data are available on phase equilibria of the multicomponent slag system at the oxygen partial pressures used in the copper smelting, converting, and slag-cleaning processes. Recently, experimental procedures have been developed and have been applied successfully to characterize several complex industrial slags. The experimental procedures involve high-temperature equilibration on a substrate and quenching followed by electron probe X-ray microanalysis. This technique has been used to construct the liquidus for the “Cu2O”-“FeO”-SiO2-based slags with 2 wt pct of CaO, 0.5 wt pct of MgO, and 4.0 wt pct of Al2O3 at controlled oxygen partial pressures in equilibrium with metallic copper. The selected ranges of compositions and temperatures are directly relevant to the copper slag-cleaning processes. The new experimental equilibrium results are presented in the form of ternary sections and as a liquidus temperature vs Fe/SiO2 weight ratio diagram. The experimental results are compared with the FactSage thermodynamic model calculations.

Hydrothermal synthesis and structural analysis of new mixed oxyanion borates: Ba11B26O44(PO4)2(OH)6, Li9BaB15O27(CO3) and Ba3Si2B6O16

NASA Astrophysics Data System (ADS)

Heyward, Carla; McMillen, Colin D.; Kolis, Joseph

2013-07-01

Several new borate compounds, Ba11B26O44(PO4)2(OH)6 (1), Li9BaB15O27(CO3) (2), and Ba3Si2B6O16 (3) were synthesized containing other hetero-oxyanion building blocks in addition to the borate frameworks. They were all prepared under hydrothermal conditions and characterized by single crystal and powder X-ray diffraction, and IR spectroscopy. Crystal data: For 1; space group P21/c, a=6.8909 (14) Å, b=13.629 (3) Å, c=25.851 (5) Å, β=90.04 (3)°; For 2; space group P-31c, a=8.8599 (13) Å, c=15.148 (3) Å; For 3; space group P-1, a=5.0414 (10) Å, b=7.5602 (15) Å, c=8.5374 (17) Å, α=77.15 (3)°, β=77.84 (3)°, γ=87.41 (3)° for 3. Compounds 1 and 2 contain isolated oxyanions [PO4]3- and [CO3]2- respectively, sitting in channels created by the borate framework, while structure 3 has the [SiO4]4- groups directly bonded to the borate groups creating a B-O-Si framework.

Melting and subsolidus reactions in the system K2O-CaO-Al2O3-SiO2-H2O

NASA Astrophysics Data System (ADS)

Johannes, Wilhelm

1980-09-01

Beginning of melting and subsolidus relationships in the system K2O-CaO-Al2O3-SiO2-H2O have been experimentally investigated at pressures up to 20 kbars. The equilibria discussed involve the phases anorthite, sanidine, zoisite, muscovite, quartz, kyanite, gas, and melt and two invariant points: Point [Ky] with the phases An, Or, Zo, Ms, Qz, Vapor, and Melt; point [Or] with An, Zo, Ms, Ky, Qz, Vapor, and Melt. The invariant point [Ky] at 675° C and 8.7 kbars marks the lowest solidus temperature of the system investigated. At pressures above this point the hydrated phases zoisite and muscovite are liquidus phases and the solidus temperatures increase with increasing pressure. At 20 kbars beginning of melting occurs at 740 °C. The solidus temperatures of the quinary system K2O-CaO-Al2O3-SiO2-H2O are almost 60° C (at 20 kbars) and 170° C (at 2kbars) below those of the limiting quaternary system CaO-Al2O3-SiO2-H2O. The maximum water pressure at which anorthite is stable is lowered from 14 to 8.7 kbars in the presence of sanidine. The stability limits of anorthite+ vapor and anorthite+sanidine+vapor at temperatures below 700° C are almost parallel and do not intersect. In the wide temperature — pressure range at pressures above the reaction An+Or+Vapor = Zo+Ms+Qz and temperatures below the melting curve of Zo+Ms+Ky+Qz+Vapor, the feldspar assemblage anorthite+sanidine is replaced by the hydrated phases zoisite and muscovite plus quartz. CaO-Al2O3-SiO2-H2O. Knowledge of the melting relationships involving the minerals zoisite and muscovite contributes to our understanding of the melting processes occuring in the deeper parts of the crust. Beginning of melting in granites and granodiorites depends on the composition of plagioclase. The solidus temperatures of all granites and granodiorites containing plagioclases of intermediate composition are higher than those of the Ca-free alkali feldspar granite system and below those of the Na-free system discussed in this

Electrode Reaction Mechanism of Ag 2VO 2PO 4 Cathode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ruibo; Abtew, Tesfaye A.; Quackenbush, Nicholas F.

In this study, the high capacity of primary lithium-ion cathode Ag 2VO 2PO 4 is facilitated by both displacement and insertion reaction mechanisms. Whether the Ag extrusion (specifically, Ag reduction with Ag metal displaced from the host crystal) and V reduction are sequential or concurrent remains unclear. A microscopic description of the reaction mechanism is required for developing design rules for new multimechanism cathodes, combining both displacement and insertion reactions. However, the amorphization of Ag 2VO 2PO 4 during lithiation makes the investigation of the electrode reaction mechanism difficult with conventional characterization tools. For addressing this issue, a combination ofmore » local probes of pair-distribution function and X-ray spectroscopy were used to obtain a description of the discharge reaction. We determine that the initial reaction is dominated by silver extrusion with vanadium playing a supporting role. In addition, once sufficient Ag has been displaced, the residual Ag + in the host can no longer stabilize the host structure and V–O environment (i.e., onset of amorphization). After amorphization, silver extrusion continues but the vanadium reduction dominates the reaction. As a result, the crossover from primarily silver reduction displacement to vanadium reduction is facilitated by the amorphization that makes vanadium reduction increasingly more favorable.« less

Electrode Reaction Mechanism of Ag 2VO 2PO 4 Cathode

DOE PAGES

Zhang, Ruibo; Abtew, Tesfaye A.; Quackenbush, Nicholas F.; ...

2016-05-09

In this study, the high capacity of primary lithium-ion cathode Ag 2VO 2PO 4 is facilitated by both displacement and insertion reaction mechanisms. Whether the Ag extrusion (specifically, Ag reduction with Ag metal displaced from the host crystal) and V reduction are sequential or concurrent remains unclear. A microscopic description of the reaction mechanism is required for developing design rules for new multimechanism cathodes, combining both displacement and insertion reactions. However, the amorphization of Ag 2VO 2PO 4 during lithiation makes the investigation of the electrode reaction mechanism difficult with conventional characterization tools. For addressing this issue, a combination ofmore » local probes of pair-distribution function and X-ray spectroscopy were used to obtain a description of the discharge reaction. We determine that the initial reaction is dominated by silver extrusion with vanadium playing a supporting role. In addition, once sufficient Ag has been displaced, the residual Ag + in the host can no longer stabilize the host structure and V–O environment (i.e., onset of amorphization). After amorphization, silver extrusion continues but the vanadium reduction dominates the reaction. As a result, the crossover from primarily silver reduction displacement to vanadium reduction is facilitated by the amorphization that makes vanadium reduction increasingly more favorable.« less

Temperature dependence of partial conductivities of the BaZr0.7Ce0.2Y0.1O3-δ proton conductor

NASA Astrophysics Data System (ADS)

Heras-Juaristi, Gemma; Pérez-Coll, Domingo; Mather, Glenn C.

2017-10-01

Partial conductivities are presented for BaZr0.7Ce0.2Y0.1O3-δ, an important proton conductor for protonic-ceramic fuel cells and membrane reactors. Atmospheric dependencies of impedance performed in humidified and dry O2, air, N2 and H2(10%)/N2(90%) in the temperature range 300-900 °C, supported by the modified emf method, confirm significant electron-hole and protonic contributions to transport. For very reducing and wet atmospheres, the conductivity is predominantly ionic, with a higher participation of protons with decreasing temperature and increasing water-vapour partial pressure (pH2O). From moderately reducing conditions of wet N2 to wet O2, however, the conductivity is considerably influenced by electron holes as revealed by a significant dependence of total conductivity on oxygen partial pressure (pO2). With higher pH2O, proton transport increases, with a concomitant decrease of holes and oxygen vacancies. However, the effect of pH2O is also influenced by temperature, with a greater protonic contribution at both lower temperature and pO2. Values of proton transport number tH ≈ 0.63 and electronic transport number th ≈ 0.37 are obtained at 600 °C for pH2O = 0.022 atm and pO2 = 0.2 atm, whereas tH ≈ 0.95 and th ≈ 0.05 for pO2 = 10-5 atm. A hydration enthalpy of -109 kJ mol-1 is obtained in the range 600-900 °C.

Crystal structures of lazulite-type oxidephosphates Ti IIITi IV3O 3(PO 4) 3 and MIII4Ti IV27O 24(PO 4) 24 ( MIII=Ti, Cr, Fe)

NASA Astrophysics Data System (ADS)

Schöneborn, M.; Glaum, R.; Reinauer, F.

2008-06-01

Single crystals of the oxidephosphates Ti IIITi IV3O 3(PO 4) 3 (black), Cr III4Ti IV27O 24(PO 4) 24 (red-brown, transparent), and Fe III4Ti IV27O 24(PO 4) 24 (brown) with edge-lengths up to 0.3 mm were grown by chemical vapour transport. The crystal structures of these orthorhombic members (space group F2 dd ) of the lazulite/lipscombite structure family were refined from single-crystal data [Ti IIITi IV3O 3(PO 4) 3: Z=24, a=7.3261(9) Å, b=22.166(5) Å, c=39.239(8) Å, R1=0.029, w R2=0.084, 6055 independent reflections, 301 variables; Cr III4Ti IV27O 24(PO 4) 24: Z=1, a=7.419(3) Å, b=21.640(5) Å, c=13.057(4) Å, R1=0.037, w R2=0.097, 1524 independent reflections, 111 variables; Fe III4Ti IV27O 24(PO 4) 24: Z=1, a=7.4001(9) Å, b=21.7503(2) Å, c=12.775(3) Å, R1=0.049, w R2=0.140, 1240 independent reflections, 112 variables). For Ti IIITi IVO 3(PO 4) 3 a well-ordered structure built from dimers [Ti III,IV2O 9] and [Ti IV,IV2O 9] and phosphate tetrahedra is found. The metal sites in the crystal structures of Cr 4Ti 27O 24(PO 4) 24 and Fe 4Ti 27O 24(PO 4) 24, consisting of dimers [ MIIITi IVO 9] and [Ti IV,IV2O 9], monomeric [Ti IVO 6] octahedra, and phosphate tetrahedra, are heavily disordered. Site disorder, leading to partial occupancy of all octahedral voids of the parent lipscombite/lazulite structure, as well as splitting of the metal positions is observed. According to Guinier photographs Ti III4Ti IV27O 24(PO 4) 24 ( a=7.418(2) Å, b=21.933(6) Å, c=12.948(7) Å) is isotypic to the oxidephosphates MIII4Ti IV27O 24(PO 4) 24 ( MIII: Cr, Fe). The UV/vis spectrum of Cr 4Ti 27O 24(PO 4) 24 reveals a rather small ligand-field splitting Δ o=14,370 cm -1 and a very low nephelauxetic ratio β=0.72 for the chromophores [Cr IIIO 6] within the dimers [Cr IIITi IVO 9].

The structure of MgO-SiO2 glasses at elevated pressure.

PubMed

Wilding, Martin; Guthrie, Malcolm; Kohara, Shinji; Bull, Craig L; Akola, Jaakko; Tucker, Matt G

2012-06-06

The magnesium silicate system is an important geophysical analogue and neutron diffraction data from glasses formed in this system may also provide an initial framework for understanding the structure-dependent properties of related liquids that are important during planetary formation. Neutron diffraction data collected in situ for a single composition (38 mol% SiO(2)) magnesium silicate glass sample shows local changes in structure as pressure is increased from ambient conditions to 8.6 GPa at ambient temperature. A method for obtaining the fully corrected, total structure factor, S(Q), has been developed that allows accurate structural characterization as this weakly scattering glass sample is compressed. The measured S(Q) data indicate changes in chemical ordering with pressure and the real-space transforms show an increase in Mg-O coordination number and a distortion of the local environment around magnesium ions. We have used reverse Monte Carlo methods to compare the high pressure and ambient pressure structures and also compare the high pressure form with a more silica-poor glass (Mg(2)SiO(4)) that represents the approach to a more dense, void-free and topologically ordered structure. The Mg-O coordination number increases with pressure and we also find that the degree of continuous connectivity of Si-O bonds increases via a collapse of interstices.

Abnormal Pressure-Induced Photoluminescence Enhancement and Phase Decomposition in Pyrochlore La2 Sn2 O7.

PubMed

Zhao, Yongsheng; Li, Nana; Xu, Cong; Li, Yan; Zhu, Hongyu; Zhu, Pinwen; Wang, Xin; Yang, Wenge

2017-09-01

La 2 Sn 2 O 7 is a transparent conducting oxide (TCO) material and shows a strong near-infrared fluorescent at ambient pressure and room temperature. By in situ high-pressure research, pressure-induced visible photoluminescence (PL) above 2 GPa near 2 eV is observed. The emergence of unusual visible PL behavior is associated with the seriously trigonal lattice distortion of the SnO 6 octehedra, under which the Sn-O1-Sn exchange angle θ is decreased below 22.1 GPa, thus enhancing the PL quantum yield leading to Sn 3 P 1 → 1 S 0 photons transition. Besides, bandgap closing followed by bandgap opening and the visible PL appearing at the point of the gap reversal, which is consistent with high-pressure phase decomposition, are discovered. The high-pressure PL results demonstrate a well-defined pressure window (7-17 GPa) with flat maximum PL yielding and sharp edges at both ends, which may provide a great calibration tool for pressure sensors for operation in the deep sea or at extreme conditions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of photocoagulation on intraretinal PO2 in cat.

PubMed

Budzynski, Ewa; Smith, Jennifer H; Bryar, Paul; Birol, Gulnur; Linsenmeier, Robert A

2008-01-01

To test the hypothesis that intraretinal Po(2) increases after photocoagulation. Anesthetized cats underwent retinal argon laser photocoagulation. At least 4 weeks after treatment, Po(2)-sensitive microelectrodes were used to record intraretinal Po(2) profiles from healed photocoagulation lesions in anesthetized cats breathing air. Histopathologic examination of the retinas was used to confirm that the photoreceptors were destroyed and that the inner retinal layers were preserved, though somewhat disorganized, as in human panretinal photocoagulation (PRP). The retina and tapetum were thinner in the lesioned retina than in the nonphotocoagulated retina. Average Po(2) across the inner 50% of the retina was higher (22 +/- 10 mm Hg) in photocoagulated retina than in untreated retina (14 +/- 7 mm Hg; P < 0.01; n = 13 cats). The minimum Po(2) was also significantly higher, whereas choroidal Po(2) was significantly lower in the photocoagulated retina than in untreated retina. No significant difference was found in the preretinal vitreous. After lesions, inner retinal Po(2) could also be maintained above zero, even in the absence of retinal circulation. Previous measurements showed increased Po(2) in the preretinal vitreous of rabbits and pigs (but not cats) after photocoagulation of the outer retina. These intraretinal measurements in cats provide further evidence for a chronic increase in inner retinal Po(2) in lesioned areas during air breathing.

Electrical conductivity of cobalt doped La 0.8Sr 0.2Ga 0.8Mg 0.2O 3- δ

NASA Astrophysics Data System (ADS)

Wang, Shizhong; Wu, Lingli; Liang, Ying

La 0.8Sr 0.2Ga 0.8Mg 0.2O 3- δ (LSGM8282), La 0.8Sr 0.2Ga 0.8Mg 0.15Co 0.05O 3- δ (LSGMC5) and La 0.8Sr 0.2Ga 0.8Mg 0.115Co 0.085O 3- δ (LSGMC8.5) were prepared using a conventional solid-state reaction. Electrical conductivities and electronic conductivities of the samples were measured using four-probe impedance spectrometry, four-probe dc polarization and Hebb-Wagner polarization within the temperature range of 973-1173 K. The electrical conductivities in LSGMC5 and LSGMC8.5 increased with decreasing oxygen partial pressures especially in the high (>10 -5 atm) and low oxygen partial pressure regions (<10 -15 atm). However, the electrical conductivity in LSGM8282 had no dependency on the oxygen partial pressure. At temperatures higher than 1073 K, PO2 dependencies of the free electron conductivities in LSGM8282, LSGMC5 and LSGMC8.5 were about -1/4, and PO2 dependencies of the electron hole conductivities were about 0.25, 0.12 and 0.07, respectively. Oxygen ion conductivities in LSGMC5 and LSGMC8.5 increased with decreasing oxygen partial pressures especially in the high and low oxygen partial pressure regions, which was due to the increase in the concentration of oxygen vacancies. The change in the concentration of oxygen vacancies and the valence of cobalt with oxygen partial pressure were determined using a thermo-gravimetric technique. Both the electronic conductivity and oxygen ion conductivity in cobalt doped lanthanum gallate samples increased with increasing concentration of cobalt, suggesting that the concentration of cobalt should be optimized carefully to maintain a high electrical conductivity and close to 1 oxygen ion transference number.

Evidence for a pressure-induced spin transition in olivine-type LiFePO4 triphylite

NASA Astrophysics Data System (ADS)

Núñez Valdez, Maribel; Efthimiopoulos, Ilias; Taran, Michail; Müller, Jan; Bykova, Elena; McCammon, Catherine; Koch-Müller, Monika; Wilke, Max

2018-05-01

We present a combination of first-principles and experimental results regarding the structural and magnetic properties of olivine-type LiFePO4 under pressure. Our investigations indicate that the starting P b n m phase of LiFePO4 persists up to 70 GPa. Further compression leads to an isostructural transition in the pressure range of 70-75 GPa, inconsistent with a former theoretical study. Considering our first-principles prediction for a high-spin to low-spin transition of Fe2 + close to 72 GPa, we attribute the experimentally observed isostructural transition to a change in the spin state of Fe2 + in LiFePO4. Compared to relevant Fe-bearing minerals, LiFePO4 exhibits the largest onset pressure for a pressure-induced spin state transition.

Measurement of differences in pO2 in response to perfluorocarbon/carbogen in FSa and NFSa murine fibrosarcomas with low-frequency electron paramagnetic resonance oximetry.

PubMed

Halpern, H J; Yu, C; Peric, M; Barth, E D; Karczmar, G S; River, J N; Grdina, D J; Teicher, B A

1996-05-01

We have used very low-frequency electron paramagnetic resonance (EPR) oximetry to measure the change in oxygen concentration (delta pO2) due to change in breathing atmosphere in FSa and NFSa fibrosarcomas implanted in the legs of C3H mice infused with perfluoro-octylbromine (PFOB). Measurements in each tumor were made before and after the administration of the high-density (47% v/v) perfluorocarbon PFOB, perflubron (Alliance Pharmaceutical Corporation, San Diego, CA). Measurements in each tumor were also made, after the administration of the PFOB, both before (PFOB/air) and after the administration of carbogen (95% O2 + 5% CO2, PFOB/carbogen). Large changes (delta p02) relative to PFOB/air oxygenation were seen with the administration of PFOB/carbogen. No significant difference in oxygen concentration was seen between air-breathing mice with and without PFOB. The mean delta pO2 for FSa tumors was 13 +/- 6 torr, while the mean for NFSa fibrosarcomas was 28 +/- 7 torr. There were such large intertumor differences that the trend toward a smaller change in the more hypoxic FSa tumors was not significant (P = 0.13). This paper describes a novel method of measuring differences in oxygenation in tumor tissues. The results of such measurements indicate large differences in pO2 response to different breathing atmospheres in PFOB-infused tumors of similar histology. The intertumor delta pO2 differences may correlate with differences in radiation response.

Antiferromagnetism in pressure-amorphized Fe2SiO4

USGS Publications Warehouse

Kruger, M.B.; Jeanloz, R.; Pasternak, M.P.; Taylor, R.D.; Snyder, B.S.; Stacy, A.M.; Bohlen, S.R.

1992-01-01

Amorphous Fe2SiO4 synthesized at elevated pressures exhibits a Ne??el transition at a temperature identical to that observed in the crystalline form, TN = 65 (??2) kelvin at zero pressure. This behavior contrasts sharply with observations on other disordered systems, such as spin glasses, which characteristically exhibit strong "frustration" of the spins and consequent marked suppression of the Ne??el transition.

Sodium intercalation in the phosphosulfate cathode NaFe2(PO4)(SO4)2

NASA Astrophysics Data System (ADS)

Ben Yahia, Hamdi; Essehli, Rachid; Amin, Ruhul; Boulahya, Khalid; Okumura, Toyoki; Belharouak, Ilias

2018-04-01

The compound NaFe2(PO4)(SO4)2 is successfully synthesized via a solid state reaction route and its crystal structure is determined using powder X-ray diffraction data. NaFe2(PO4)(SO4)2 phase is also characterized by cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. NaFe2(PO4)(SO4)2 crystallizes with the well-known NASICON-type structure. SAED and HRTEM experiments confirm the structural model, and no ordering between the PO4-3 and SO4-2 polyanions is detected. The electrochemical tests indicate that NaFe2(PO4)(SO4)2 is a 3 V sodium intercalating cathode. The electrical conductivity is relatively low (2.2 × 10-6 Scm-1 at 200 °C) and the obtained activation energy is ∼0.60eV. The GITT experiments indicate that the diffusivity values are in the range of 10-11-10-12 cm2/s within the measured sodium concentrations.

Measurement of pO2 and pH in Living Breast Tumor Models with Three-Dimensional Resolution by Multiphoton Microscopy during Combined Therapy with Herceptin

DTIC Science & Technology

2007-04-01

contact with a freshly spin-coated NC–titania pre- polymer , which was transferred to a hot plate to initiate polymerization . The pattern of the PDMS stamp...to quantify pO2 and pH in vivo with high three-dimensional resolution (~1 µm3) and significant depth penetration (up to 400 µm) with MPLSM. The...proposed to develop techniques for measuring in vivo pO2 and pH of HER2-positive and negative primary tumors in murine models of breast cancer using

Mahlmoodite, FeZr(PO4).4H2O, a new iron zirconium phosphate mineral from Wilson Springs, Arkansas

USGS Publications Warehouse

Milton, C.; McGee, J.J.; Evans, H.T.

1993-01-01

Small (<0.5 mm) cream white spheres observed in V ore have been identified as ferrous zirconium phosphate tetrahedrate, FeZr(PO4)2.4H2O. This new mineral, named mahlmoodite, occurs as spherules of radiating fibers usually perched on crystals of pyroxene in vugs. The optical and crystallographic properties of mahlmoodite are described. -after Authors

Influence of Ar/O2/H2O Feed Gas and N2/O2/H2O Environment on the Interaction of Time Modulated MHz Atmospheric Pressure Plasma Jet (APPJ) with Model Polymers

NASA Astrophysics Data System (ADS)

Oehrlein, Gottlieb; Luan, Pingshan; Knoll, Andrew; Kondeti, Santosh; Bruggeman, Peter

2016-09-01

An Ar/O2/H2O fed time modulated MHz atmospheric pressure plasma jet (APPJ) in a sealed chamber was used to study plasma interaction with model polymers (polystyrene, poly-methyl methacrylate, etc.). The amount of H2O in the feed gas and/or present in the N2, O2, or N2/O2 environment was controlled. Short lived species such as O atoms and OH radicals play a crucial role in polymer etching and surface modifications (obtained from X-ray photoelectron spectroscopy of treated polymers without additional atmospheric exposure). Polymer etching depth for Ar/air fed APPJ mirrors the decay of gas phase O atoms with distance from the APPJ nozzle in air and is consistent with the estimated O atom flux at the polymer surface. Furthermore, whereas separate O2 or H2O admixture to Ar enhances polymer etching, simultaneous addition of O2 and H2O to Ar quenches polymer etching. This can be explained by the mutual quenching of O with OH, H and HO2 in the gas phase. Results where O2 and/or H2O in the environment were varied are consistent with these mechanisms. All results will be compared with measured and simulated species densities reported in the literature. We gratefully acknowledge funding from US Department of Energy (DE-SC0001939) and National Science Foundation (PHY-1415353).

High pressure studies of A2Mo3O12 negative thermal expansion materials (A2=Al2, Fe2, FeAl, AlGa)

NASA Astrophysics Data System (ADS)

Young, Lindsay; Gadient, Jennifer; Gao, Xiaodong; Lind, Cora

2016-05-01

High pressure powder X-ray diffraction studies of several A2Mo3O12 materials (A2=Al2, Fe2, FeAl, and AlGa) were conducted up to 6-7 GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversible on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga2Mo3O12 suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations.

Redox process catalysed by growing crystal-strengite, FePO4,2H2O, crystallizing from solution with iron(II) and hydroxylamine

NASA Astrophysics Data System (ADS)

Lundager Madsen, Hans Erik

2014-09-01

In an attempt to grow pure crystals of the iron(II) phosphate vivianite, Fe3(PO4)2,8H2O, from a solution of Mohr's salt, Fe(NH4)2(SO4)2,6H2O, added to a solution of ammonium phosphate, hydroxylammonium chloride, NH3OHCl, was added to the iron(II) stock solution to eliminate oxidation of iron(II) by oxygen from the air. However, the effect turned out to be the opposite of the expected: whereas hydroxylamine reduces iron(III) in bulk solution, it acted as a strong oxidant in the presence of growing iron phosphate crystals, causing the crystallization of the iron(III) phosphate strengite, FePO4,2H2O, as the only solid phase. Evidently the crystal surface catalyses oxidation of iron(II) by hydroxylamine. The usual composite kinetics of spiral growth and surface nucleation was found. The surface-nucleation part yielded edge free energy λ in the range 12-45 pJ/m, virtually independent of temperature and in the range typical for phosphates of divalent metals. The scatter of values for λ presumably arises from contributions from different crystal forms to the overall growth rate. The low mean value points to strong adsorption of iron(II), which is subsequently oxidized at the crystal surface, forming strengite. The state of the system did not tend to thermodynamic equilibrium, but to a metastable state, presumably controlled by the iron(II) rich surface layer of the crystal. In addition to crystal growth, it was possible to measure nucleation kinetics by light scattering (turbidimetry). A point of transition from heterogeneous to homogeneous nucleation was found, and from the results for the homogeneous domain a rather precise value of crystal surface free energy γ=55 mJ/m2 was found. This is a relatively low value as well, indicating that the redox process plays a role already at the nucleation stage.

The lower-temperature-pressure stability of pyrope in the presence of quartz in the system MgO-Al2O3-SiO2

NASA Astrophysics Data System (ADS)

Cheng, N.; Jenkins, D. M.

2017-12-01

Pyrope (Mg3Al2Si3O12) is the dominant component in garnets from type A eclogites. Determining the lower-pressure-temperature (P-T) stability of pyrope in the presence of quartz helps put constraints on the stability of quartz-bearing eclogites and therefore the depths to which crustal rocks in high pressure/ultra-high pressure (HP/UHP) terranes can be transferred. It also defines the lower-pressure stability of the nearly pure pyrope-bearing quartzites of the Dora Maira massif of the Western Alps (Chopin, 1984, Contrib. Min. Pet.). Aside from the approximate boundary proposed by Hensen & Essene (1971, Contrib. Min. Pet.), there has been no detailed study of the lower P-T stability of pyrope + quartz. A reversed determination of the reaction 3 enstatite + 2 kyanite = 2 pyrope + 2 quartz has been done in the system MgO-Al2O3-SiO2 over the P-T range of 900-1100 °C and 1.6-2.5 GPa for durations of 24 hours. Double capsules, one using pure enstatite and the other Al-rich (10 wt% Al2O3) enstatite in the starting mixtures, were used to obtain reversals on the Al content in the orthopyroxene (Opx). Experiments were done using a ½-inch diameter piston-cylinder press and NaCl-pyrex-MgO pressure media. Run products were analyzed using powder XRD and electron microprobe. Reaction direction was readily determined from peak height changes on XRD patterns. The reaction has been bracketed at 1.65 GPa at 1100 °C with > 12 wt% Al2O3 in Opx; 2.05 GPa at 1000 °C with 10 wt% Al2O3 in Opx; and 2.4 GPa at 930 °C with 5 wt% Al2O3 in Opx. The reaction boundary is slightly curved to higher P with increasing T caused by increasing Al in Opx. The boundary observed in this study is about 100 °C or 0.4 GPa higher than previously proposed by Hensen & Essene (1971) and 70-170 °C or 0.6-0.7 GPa higher than the boundary calculated in this system using THERMOCALC ds6.22 (Holland & Powell, 2011, J. Meta. Geol.) and about 1-4 wt% higher Al2O3 contents in Opx. Higher pressure runs in the field

The model of nano-scale copper particle removal from silicon surface in high pressure CO2 + H2O and CO2 + H2O + IPA cleaning solutions.

PubMed

Tan, Xin; Chai, Jiajue; Zhang, Xiaogang; Chen, Jiawei

2011-12-01

This study focuses on the description of the static forces in CO2-H2O and CO2-H2O-IPA cleaning solutions with a separate fluid phase entrapped between nano-scale copper particles and a silicon surface. Calculations demonstrate that increasing the pressure of the cleaning system decreases net adhesion force (NAF) between the particle and silicon. The NAF of a particle for in CO2-H2O-IPA system is less than that in CO2-H2O system, suggesting that the particles enter into bulk layer more easily as the CO2-H2O cleaning system is added IPA.

The effect of PO 4 doping on the luminescent properties of Sr 3-3zEu 2zV 2-xP xO 8

NASA Astrophysics Data System (ADS)

Cao, S.; Ma, Y. Q.; Yang, K.; Zhu, W. L.; Yin, W. J.; Zheng, G. H.; Wu, M. Z.; Sun, Z. Q.

2010-07-01

The luminescent properties of Sr 3V 2-xP xO 8 (0 ⩽ x ⩽ 2), Eu 3+ doped Sr 2.7Eu 0.2V 2-yP yO 8 (0 ⩽ y ⩽ 2) and Sr 3-3zEu 2zV 0.8P 1.2O 8 (0 < z ⩽ 0.3) have been investigated. For the Sr 3V 2-xP xO 8 (0 ⩽ x ⩽ 2) samples, the VO43- activation and emission intensity reaches the strongest as x = 1.6. For the Sr 2.7Eu 0.2V 2-yP yO 8 (0 ⩽ y ⩽ 2) samples, an appropriate amount of phosphorus doping enhances the Eu 3+ emission with the strongest emission occurring at y = 1.2. For the Sr 3-3zEu 2zV 0.8P 1.2O 8 (0 < z ⩽ 0.3) sample with the phosphorus content fixed at 1.2, it exhibits the most intense emission as Eu 3+ concentration reaches at z = 0.2. Our results indicate that the introduction of the PO43- plays an important role in the photoluminescence properties of the studied samples and the relevant mechanism has been discussed.

Effects of training on muscle O2 transport at VO2max

NASA Technical Reports Server (NTRS)

Roca, J.; Agusti, A. G.; Alonso, A.; Poole, D. C.; Viegas, C.; Barbera, J. A.; Rodriguez-Roisin, R.; Ferrer, A.; Wagner, P. D.

1992-01-01

To quantify the relative contributions of convective and peripheral diffusive components of O2 transport to the increase in leg O2 uptake (VO2leg) at maximum O2 uptake (VO2max) after 9 wk of endurance training, 12 sedentary subjects (age 21.8 +/- 3.4 yr, VO2max 36.9 +/- 5.9 ml.min-1.kg-1) were studied. VO2max, leg blood flow (Qleg), and arterial and femoral venous PO2, and thus VO2leg, were measured while the subjects breathed room air, 15% O2, and 12% O2. The sequence of the three inspirates was balanced. After training, VO2max and VO2leg increased at each inspired O2 concentration [FIO2; mean over the 3 FIO2 values 25.2 +/- 17.8 and 36.5 +/- 33% (SD), respectively]. Before training, VO2leg and mean capillary PO2 were linearly related through the origin during hypoxia but not during room air breathing, suggesting that, at 21% O2, VO2max was not limited by O2 supply. After training, VO2leg and mean capillary PO2 at each FIO2 fell along a straight line with zero intercept, just as in athletes (Roca et al. J. Appl. Physiol. 67: 291-299, 1989). Calculated muscle O2 diffusing capacity (DO2) rose 34% while Qleg increased 19%. The relatively greater rise in DO2 increased the DO2/Qleg, which led to 9.9% greater O2 extraction. By numerical analysis, the increase in Qleg alone (constant DO2) would have raised VO2leg by 35 ml/min (mean), but that of DO2 (constant Qleg) would have increased VO2leg by 85 ml/min, more than twice as much. The sum of these individual effects (120 ml/min) was less (P = 0.013) than the observed rise of 164 ml/min (mean). This synergism (explained by the increase in DO2/Qleg) seems to be an important contribution to increases in VO2max with training.

High-pressure phases transitions in SnO2 to 117 GPa: Implications for silica

NASA Astrophysics Data System (ADS)

Shieh, S. R.; Kubo, A.; Duffy, T. S.; Prakapenka, V. B.; Shen, G.

2005-12-01

Cassiterite (SnO2) is regarded to be a good analog material for silica as both SnO2 and SiO2 are group IV-B metal dioxides. The high-pressure behavior of SnO2 has been the subject of many previous investigations extending up to 49 GPa and in addition to the rutile structure, three high-pressure phases, CaCl2-type, α-PbO2-type, and pyrite-type were observed. Better knowledge of high-pressure phases of SnO2 will be useful to understand the behavior of silica at deep mantle conditions. In addition, high-pressure metal dioxide phases may qualify as superhard solids. Our study will also provide insights into interpretation of shock compression data. Pure natural cassiterite (SnO2) powder was compressed in a diamond anvil cell using an argon medium. Pressure was determined from the equation of state of platinum. In situ monochromatic x-ray diffraction at high pressure was carried out at the GSECARS, Advanced Photon Source. High temperatures were achieved using double-sided laser heating . Three heating cycles were conducted with total heating times up to 30 minutes. Our diffraction results on SnO2 demonstrate the existence of four phase transitions to 117 GPa. The observed sequence of high-pressure phases for SnO2 is rutile-type, CaCl2-type, pyrite-type, ZrO2 orthorhombic phase I (Pbca), cotunnite-type. Our observations of the first three phases are generally in agreement with earlier studies. The orthorhombic phase I and cotunnite-type structures were observed in SnO2 for the first time. The Pbca phase is found at 50-74 GPa during room-temperature compression. The cotunnite-type structure was synthesized when SnO2 was heated at 74 GPa and 1200 K. The cotunnite-type form was observed during compression between 54-117 GPa. Fitting the pressure-volume data for the high-pressure phases to the second-order Birch-Murnaghan equation of state yields a bulk modulus of 259(26) GPa for the Pbca phase and 417(7) GPa for the cotunnite-type phase. Rietveld profile refinements were

Hierarchical Fe3O4@MoS2/Ag3PO4 magnetic nanocomposites: Enhanced and stable photocatalytic performance for water purification under visible light irradiation

NASA Astrophysics Data System (ADS)

Guo, Na; Li, Haiyan; Xu, Xingjian; Yu, Hongwen

2016-12-01

Novel hierarchical Fe3O4@MoS2/Ag3PO4 magnetic nanophotocatalyst with remarkable photocatalytic capability were prepared by simply depositing the Ag3PO4 onto the surface of crumpled Fe3O4@MoS2 nanosphere. The nanocomposites were characterized by XRD, TEM, HRTEM, XPS, BET, and UV-vis DRS. The outcome of the photocatalytic experiments demonstrated that Fe3O4@MoS2/Ag3PO4 with 6 wt% content of Ag3PO4 (FM/A-6%) showed the highest photocatalytic activity upon the degradation Congo red (CR) and Rhodamine B (RhB) under both visible light and simulated sunlight irradiation. In addition, FM/A-6% possessed larger specific surface area (76.56 m2/g) and excellent optical property. The possible Z-scheme charge carriers transfer mechanism for the enhanced photocatalytic properties of the FM/A-6% was also discussed. The Z-scheme charge carriers transfer mechanism established between MoS2 and Ag3PO4 facilitate the charge separation efficiency. Moreover, FM/A-6% can be separated and collected easily by external magnetic field and maintain high activity after five times photoreaction cycles. Given the remarkable photocatalytic performance and high stability of FM/A-6% nanocomposite, it is looking forward to exhibit great potential for applications in water purification.

Effect of high-pressure H{sub 2}O treatment on elimination of interfacial GeO{sub X} layer between ZrO{sub 2} and Ge stack

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Chen-Shuo; Liu, Po-Tsun

2011-08-22

This investigation demonstrates the effect of high-pressure H{sub 2}O treatment on the elimination of the interfacial germanium suboxide (GeO{sub X}) layer between ZrO{sub 2} and Ge. The formation of GeO{sub X} interlayer increases the gate-leakage current and worsen the controllability of the gate during deposition or thermal cycles. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy reveal that high-pressure H{sub 2}O treatment eliminates the interfacial GeO{sub X} layer. The physical mechanism involves the oxidation of non-oxidized Zr with H{sub 2}O and the reduction of GeO{sub X} by H{sub 2}. Treatment with H{sub 2}O reduces the gate-leakage current of a ZrO{submore » 2}/Ge capacitor by a factor of 1000.« less

The kinetics of the O2/CO2 reaction in molten carbonate - Reaction orders for O2 and CO2 on NiO. [in fuel cells

NASA Technical Reports Server (NTRS)

Winnick, J.; Ross, P. N.

1980-01-01

The kinetics of the O2/CO2 reaction in molten carbonate is investigated using paste electrolytes and nickel sinter electrodes. A two-step approach to the determination of reaction orders is employed. First, exchange currents at various P(CO2) and P(O2) were measured using the low polarization method. Second, alpha(+) and alpha(-) values were obtained from the slope of the Allen-Hickling plot for current densities low enough so that concentration polarization within the electrode can be neglected. The reaction orders are + 1/4 in CO2 and + 5/8 in O2 in the cathodic direction, and - 3/4 in CO2 and + 1/8 in O2 in the anodic direction.

Study on crystallization kinetics and phase evolution in Li2O-Al2O3-GeO2-P2O5 glass-ceramics system

NASA Astrophysics Data System (ADS)

Das, Anurup; Dixit, Anupam; Goswami, Madhumita; Mythili, R.; Hajra, R. N.

2018-04-01

To address the safety issues related to liquid electrolyte and improve the battery performance, Solid State Electrolytes (SSEs) are now in frontier area of research interest. We report here synthesis of Li-SSE based on Li2O-Al2O3-GeO2-P2O5 (LAGP) system with NASICON structure. Glass sample with nominal composition Li1.5Al0.5Ge1.5P2.5Si0.5O12 was prepared by melt-quenching technique. Non-isothermal crystallization kinetics was studied using DSC and activation energy of crystallisation was calculated to be ˜ 246 kJ/mol using Kissinger's equation. XRD of heat treated samples show the formation of required LiGe2(PO4)3 phase along with other minor phases. Compositional analysis using SEM-EDX confirms enrichment of Ge and Si along the grain boundaries.

Double-walled structure of anodic TiO2 nanotubes in H3PO4/NH4F mixed electrolyte

NASA Astrophysics Data System (ADS)

Chen, Siyu; Chen, Ying; Li, Chengyuan; Ouyang, Huijun; Qin, Shuai; Song, Ye

2018-04-01

Normally, the well-ordered anodic TiO2 nanotubes (ATNTs) are obtained in NH4F electrolyte, after annealing, the double-walled structure of nanotubes will appear. Here, after adding H3PO4 into NHF4 electrolyte, we got the double-walled structure of nanotubes by anodizing without annealing, which means the direct existence of anion-contaminated layer in ATNTs. Influence of H3PO4 content on anodizing voltage and morphology of ATNTs were compared in detail. The XRD pattern illustrated that the crystallinity decreases with increasing H3PO4 concentration, and the anion-contaminated layer thickens with the increase of H3PO4 concentration. Meanwhile, the existence of the anion-contaminated layer also proved the limitations of the filed-assisted dissolution theory, while the double-walled structure can be explained by oxygen bubble model and plastic flow model.

Change of oxygen pressure in glioblastoma tissue under various conditions.

PubMed

Beppu, Takaaki; Kamada, Katsura; Yoshida, Yuki; Arai, Hiroshi; Ogasawara, Kuniaki; Ogawa, Akira

2002-05-01

Measurement of oxygen pressure (pO2) in tumor tissue is important, because pO2 is a major factor for radiosensitivity in malignant glioma treatment. We attempted to elucidate the changes in pO2 level in glioblastoma tissue of patients under various conditions. Eighteen patients with newly diagnosed glioblastoma were recruited to this study. Disposable Clark-type electrodes were inserted using CT guided stereotactic surgery under local anesthesia and left in the intra- and peritumoral regions. pO2 was measured in patients under conditions of being awake and asleep, inhaling 100% O2, being administered osmotic diuretics and following hyperbaric oxygen exposure (HBO). Peritumoral tissue had a significantly higher pO2 value in both awake and sleeping patients. O2 inhalation could not significantly increase the pO2 level, whereas administration of osmotic diuretics induced an increase in pO2 levels in peritumoral tissue alone. The pO2 levels were significantly increased in both regions after HBO, and a high pO2 level was maintained until 15 min after HBO in both regions. It is possible that the pO2 level in peritumoral tissue is affected by intracranial pressure, whereas that in the intratumoral tissue is usually low. HBO was the optimal procedure for oxygenation, but its benefit was reduced over time.

Topological insulators double perovskites: A2TePoO6 (A = Ca, Sr, Ba)

NASA Astrophysics Data System (ADS)

Lee, Po-Han; Zhou, Jian; Pi, Shu-Ting; Wang, Yin-Kuo

2017-12-01

Based on first-principle calculations and direct density functional theory calculations of surface bands, we predict a new class of three-dimensional (3D) Z2 topological insulators (TIs) with larger bulk bandgaps up to 0.4 eV in double perovskite materials A2TePoO6 (A = Ca, Sr, and Ba). The larger nontrivial gaps are induced by the symmetry-protected band contact along with band inversion occurring in the absence of spin-orbit coupling (SOC) making the SOC more effective than conventional TIs. The proposed materials are chemically inert and more robust to surface perturbations due to its intrinsic protection layer. This study provides the double perovskite material as a rich platform to design new TI-based electronic devices.

Luminescence properties of long-lasting phosphor SrMg2(PO4)2:Eu2+, Ho3+, Zr4+

NASA Astrophysics Data System (ADS)

Tang, Wei; Wang, Mingwen; Lin, Wei; Ye, Yaping; Wu, Xue

2016-12-01

Novel long lasting phosphors SrMg2(PO4)2:Eu2+, SrMg2(PO4)2:Eu2+, Zr4+, SrMg2(PO4)2:Eu2+, Ho3+ and SrMg2(PO4)2:Eu2+, Ho3+, Zr4+ were synthesized by conventional solid-state reaction method. The luminescent properties were systematically characterized by X-ray diffraction, photoluminescent excitation and emission spectra, as well as thermoluminescence spectrum and decay curves. The XRD patterns indicated that the samples belonged to monoclinic phase and co-doping Eu2+, Ho3+ and Zr4+ ions had no effect on the basic crystal structure. These phosphors emitting purplish blue light is related to the characteristic emission of Eu2+. The afterglow time of Eu2+ activated SrMg2(PO4)2 can be greatly enhanced by the co-doping of Ho3+, Zr4+. After the 365 nm UV light excitation source switching off, the Sr0.92Mg1.95(PO4)2:Eu2+0.01, Zr4+0.05, Ho3+0.07 phosphorescence can be observed for more than 1013 s in the limit of light perception of dark-adapted human eyes (0.32 mcd/m2). Different kinds of TL peaks at 423, 448 and 473 K have appeared, and traps densities have increased compared with the Eu2+ single doped SrMg2(PO4)2 phosphor. By analyzing the TL curve the depths of traps were calculated to be 0.846, 0.896 and 0.946 eV, respectively, which suggested that the co-doping of Ho3+, Zr4+ improved the electron storage ability of material. Besides, the mechanism was discussed in this report.