Linear thermal expansion coefficient of MgAl2O4(s)

International Nuclear Information System (INIS)

Dash, A.; Samui, P.; Naik, Y.P.; Chaudhary, Z.S.

2011-01-01

The coefficient of linear thermal expansion (α av ) of MgAl 2 O 4 (s) has been determined using a Netzsch 402 PC dilatometer with Al 2 O 3 (s) as the push-rod. The change in length per unit length was recorded as a function of temperature between room temperature to 1273 K at a heating rate of 8 K.min /1 , in argon flowing atmosphere. The average of three measurements was quoted as the α av for MgAl 2 O 4 (s). The linear thermal expansion was measured to an accuracy of ±3%. (author)

A wheel-shaped single-molecule magnet of [MnII 3MnIII 4]: quantum tunneling of magnetization under static and pulse magnetic fields.

Science.gov (United States)

Koizumi, Satoshi; Nihei, Masayuki; Shiga, Takuya; Nakano, Motohiro; Nojiri, Hiroyuki; Bircher, Roland; Waldmann, Oliver; Ochsenbein, Stefan T; Güdel, Hans U; Fernandez-Alonso, Felix; Oshio, Hiroki

2007-01-01

The reaction of N-(2-hydroxy-5-nitrobenzyl)iminodiethanol (=H3(5-NO2-hbide)) with Mn(OAc)2* 4 H2O in methanol, followed by recrystallization from 1,2-dichloroethane, yielded a wheel-shaped single-molecule magnet (SMM) of [MnII 3MnIII 4(5-NO2-hbide)6].5 C2H4Cl2 (1). In 1, seven manganese ions are linked by six tri-anionic ligands and form the wheel in which the two manganese ions on the rim and the one in the center are MnII and the other four manganese ions are MnIII ions. Powder magnetic susceptibility measurements showed a gradual increase with chimT values as the temperature was lowered, reaching a maximum value of 53.9 emu mol(-1) K. Analyses of magnetic susceptibility data suggested a spin ground state of S=19/2. The zero-field splitting parameters of D and B 0 4 were estimated to be -0.283(1) K and -1.64(1)x10(-5) K, respectively, by high-field EPR measurements (HF-EPR). The anisotropic parameters agreed with those estimated from magnetization and inelastic neutron scattering experiments. AC magnetic susceptibility measurements showed frequency-dependent in- and out-of-phase signals, characteristic data for an SMM, and an Arrhenius plot of the relaxation time gave a re-orientation energy barrier (DeltaE) of 18.1 K and a pre-exponential factor of 1.63x10(-7) s. Magnetization experiments on aligned single crystals below 0.7 K showed a stepped hysteresis loop, confirming the occurrence of quantum tunneling of the on magnetization (QTM). QTM was, on the other hand, suppressed by rapid sweeps of the magnetic field even at 0.5 K. The sweep-rate dependence of the spin flips can be understood by considering the Landau-Zener-Stückelberg (LZS) model.

Graphitic carbon nitride induced activity enhancement of OMS-2 catalyst for pollutants degradation with peroxymonosulfate

Science.gov (United States)

Li, Jun; Fang, Jia; Gao, Long; Zhang, Jingwen; Ruan, Xinchao; Xu, Aihua; Li, Xiaoxia

2017-04-01

Low valent manganese species and surface oxygen vacancies in OMS-2 play an important role in catalytic reactions, and it is highly desirable and challenging to develop a feasible strategy of increasing the Mn(II) and Mn(III) species concentration in the oxide. Herein, the OMS-2/g-C3N4 hybrids (OMS-2/CN) were prepared by a facile refluxing approach. It was found that the MnOx precursor from the reaction of KMnO4 and MnSO4 was transformed into OMS-2 nanofibers with the formation of more Mn(II) and Mn(III) species in OMS-2 and the destruction and oxidation of g-C3N4. The hybrids exhibited higher efficiency for pollutants degradation in the presence of PMS than the pure OMS-2 or g-C3N4. There was a linear correlation between the specific initial rate and the ratio of Mn(II + III)/Mn(IV). Mechanism investigation indicated that high active manganese species or caged radicals were produced through the oxidation of Mn(II) and Mn(III) by PMS and contributed to the degradation reaction. During five consecutive cycles, the catalyst exhibited good reusability and stability. Therefore, the OMS-2/CN hybrids are promising catalysts for wastewater treatment with PMS as the oxidant.

Incorporation of μ3-CO3 into an MnIII/MnIV Mn12 cluster: {[(cyclam)MnIV(μ-O)2MnIII(H2O)(μ-OH)]6(μ3-CO3)2}Cl8·24H2O

Science.gov (United States)

Levaton, Ben B.; Olmstead, Marilyn M.

2010-01-01

The centrosymmetric title cluster, hexa­aquadi-μ3-carbonato-hexa­cyclamhexa-μ2-hydroxido-dodeca-μ2-oxido-hexa­mang­an­ese(IV)hexa­manganese(III) octa­chloride tetra­cosa­hydrate, [Mn12(CO3)2O12(OH)6(C10H24N4)6(H2O)6]Cl8·24H2O, has two μ3-CO3 groups that not only bridge octahedrally coordinated MnIII ions but also act as acceptors to two different kinds of hydrogen bonds. The carbonate anion is planar within experimental error and has an average C—O distance of 1.294 (4) Å. The crystal packing is stabilized by O—H⋯Cl, O—H⋯O, N—H⋯Cl and N—H⋯O hydrogen bonds. Two of the four independent chloride ions are disordered over five positions, and eight of the 12 independent water mol­ecules are disordered over 21 positions. PMID:21587382

Single-molecule magnets: structure and properties of [Mn18O14(O2CMe)18(hep)4(hepH)2(H2O)2](ClO4)2 with spin S = 13.

Science.gov (United States)

Brechin, E K; Sañudo, E C; Wernsdorfer, W; Boskovic, C; Yoo, J; Hendrickson, D N; Yamaguchi, A; Ishimoto, H; Concolino, T E; Rheingold, A L; Christou, G

2005-02-07

The reaction of 2-(hydroxyethyl)pyridine (hepH) with a 2:1 molar mixture of [Mn3O(O2CMe)6(py)3]ClO4 and [Mn3O(O2CMe)6(py)3] in MeCN afforded the new mixed-valent (16Mn(III), 2Mn(II)), octadecanuclear complex [Mn18O14(O2CMe)18(hep)4(hepH)2(H2O)2](ClO4)2 (1) in 20% yield. Complex 1 crystallizes in the triclinic space group P. Direct current magnetic susceptibility studies in a 1.0 T field in the 5.0-300 K range, and variable-temperature variable-field dc magnetization studies in the 2.0-4.0 K and 2.0-5.0 T ranges were obtained on polycrystalline samples. Fitting of magnetization data established that complex 1 possesses a ground-state spin of S = 13 and D = -0.18 K. This was confirmed by the value of the in-phase ac magnetic susceptibility signal. Below 3 K, the complex exhibits a frequency-dependent drop in the in-phase signal, and a concomitant increase in the out-of-phase signal, consistent with slow magnetization relaxation on the ac time scale. This suggests the complex is a single-molecule magnet (SMM), and this was confirmed by hysteresis loops below 1 K in magnetization versus dc field sweeps on a single crystal. Alternating current and direct current magnetization data were combined to yield an Arrhenius plot from which was obtained the effective barrier (U(eff)) for magnetization reversal of 21.3 K. Below 0.2 K, the relaxation becomes temperature-independent, consistent with relaxation only by quantum tunneling of the magnetization (QTM) through the anisotropy barrier via the lowest-energy MS = +/-13 levels of the S = 13 spin manifold. Complex 1 is thus the SMM with the largest ground-state spin to display QTM.

Microstructural dependence on relevant physical-mechanical properties on SiO2-Na2O-CaO-P2O5 biological glasses.

Science.gov (United States)

Rajendran, V; Begum, A Nishara; Azooz, M A; el Batal, F H

2002-11-01

Bioactive glasses of the system SiO2-Na2O-CaO-P2O5 have been prepared by the normal melting and annealing technique. The elastic moduli, attenuation, Vickers hardness, fracture toughness and fracture surface energy have been obtained using the known method at room temperature. The temperature dependence of elastic moduli and attenuation measurements have been extended over a wide range of temperature from 150 to 500 K. The SiO2 content dependence of velocities, attenuation, elastic moduli, and other parameters show an interesting observation at 45 wt% of SiO2 by exhibiting an anomalous behaviour. A linear relation is developed for Tg, which explores the influence of Na2O on SiO2-Na2O-CaO-P2O5 bioactive glasses. The measured hardness, fracture toughness and fracture surface energy show a linear relation with Young's modulus. It is also interesting to note that the observed results are functions of polymerisation and the number of non-bridging oxygens (NBO) prevailing in the network with change in SiO2 content. The temperature dependence of velocities, attenuation and elastic moduli show the existence of softening in the glass network structure as temperature increases.

Bis{μ-4,4′-dimethoxy-2,2′-[propane-1,2-diylbis(nitrilomethylidyne]diphenolato}bis({4,4′-dimethoxy-2,2′-[propane-1,2-diylbis(nitrilomethylidyne]diphenol}manganese(III bis(hexafluoridophosphate

Directory of Open Access Journals (Sweden)

Mohammad Hossein Habibi

2009-08-01

Full Text Available In the title complex, [Mn2(C19H20N2O42(C19H22N2O42](PF62, the MnIII ion is coordinated by two O [Mn—O = 1.855 (2 and 1.887 (2 Å] and two N [Mn—N = 1.982 (3 and 1.977 (3 Å] atoms from the tetradentate Schiff base ligand and a coordinated axial ligand [Mn—O = 2.129 (2 Å]. The centrosymmetric dimer contains two Jahn–Teller-distorted MnIII ions, each in a nearly octahedral geometry, connected through two phenolate bridges from two ligands. There are two stereogenic centers. The methyl group and the H atom attached to the middle propane C atom are disordered over two positions with occupancy factors in the ratio 0.58:0.42. The crystal is therefore a mixture of two diasteroisomers, viz. RS/SR and RR/SS. In the axial ligand, the two benzene rings form a dihedral angle of 56.97 (5° and the dihedral angle between the two MnNC3O chelate rings is 2.98 (12°

Mechanism of potentiostatic deposition of MnO2 and electrochemical characteristics of the deposit in relation to carbohydrate oxidation

International Nuclear Information System (INIS)

Das, Debasmita; Sen, Pratik Kumar; Das, Kaushik

2008-01-01

Cyclic voltammetric (CV) and chronoamperometric (CA) studies on potentiostatic deposition of MnO 2 on Pt from Mn(II) solution in very weakly alkaline media show the process to be controlled by a one-electron transfer step, which means that the deposition proceeds through the generation of Mn(III). The electrocatalytic activity of the deposited electrode towards carbohydrate oxidation is found to be maximum at an optimum amount of deposition. Chronopotentiometric (CP) and CV measurements show that the oxidation of carbohydrates on the deposited electrodes follows a catalytic EC (electrochemical-chemical) mechanism via electrolytic formation of Mn(V) and its subsequent consumption either by disproportionation or by chemical reaction in the presence of carbohydrates. The rate constants of the reaction of Mn(V) with dextrose and fructose have been obtained from CA results. The relative order of the oxidation currents for dextrose and fructose as well as their dependence on carbohydrate concentration has been discussed. Replacement of Pt by carbon as the electrode support material does not affect the electrocatalytic activity of the MnO 2 deposit. The observed linear variation of the steady state oxidation currents with carbohydrate concentration can be exploited for analytical application

Monoclinic form of (cyanato-κN{2,2′-[ethane-1,2-diylbis(nitrilomethylidyne]diphenolato-κ4O,N,N′,O′}manganese(III

Directory of Open Access Journals (Sweden)

Daopeng Zhang

2010-12-01

Full Text Available The title compound, [Mn(C16H14N2O2(NCO], is a monoclinic polymorph of the previously published orthorhombic form [Lu et al. (2006. Inorg. Chem. 45, 3538–3548]. The MnIII ion is chelated by a tetradentate Schiff base ligand and coordinated by the N atom of a cyanate ligand in a distorted square-pyramidal arrangement. In the crystal, there are short intermolecular Mn...Ophenolate distances of 2.752 (3 Å between pairs of inversion-related molecules.

Improved linearity and reliability in GaN metal-oxide-semiconductor high-electron-mobility transistors using nanolaminate La2O3/SiO2 gate dielectric

Science.gov (United States)

Hsu, Ching-Hsiang; Shih, Wang-Cheng; Lin, Yueh-Chin; Hsu, Heng-Tung; Hsu, Hisang-Hua; Huang, Yu-Xiang; Lin, Tai-Wei; Wu, Chia-Hsun; Wu, Wen-Hao; Maa, Jer-Shen; Iwai, Hiroshi; Kakushima, Kuniyuki; Chang, Edward Yi

2016-04-01

Improved device performance to enable high-linearity power applications has been discussed in this study. We have compared the La2O3/SiO2 AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) with other La2O3-based (La2O3/HfO2, La2O3/CeO2 and single La2O3) MOS-HEMTs. It was found that forming lanthanum silicate films can not only improve the dielectric quality but also can improve the device characteristics. The improved gate insulation, reliability, and linearity of the 8 nm La2O3/SiO2 MOS-HEMT were demonstrated.

Investigation of non linear optical properties in glasses. Case of the Na2O - TiO2 - P2O5 system

International Nuclear Information System (INIS)

Duchesne, Claire

1993-01-01

The research thesis is part of collaborative work between research laboratories on optical nonlinearities in glasses. The first part proposes an overview, in terms of optics as well as solid chemistry, of relevant criteria for the design of such materials which leads to the choice of the Na 2 O-TiO 2 -P 2 O 5 system. Characterizations means are then presented, notably X ray absorption spectroscopy (Extended X-Ray Absorption Fine Structure spectroscopy or EXAFS, and X-ray Absorption Near Edge Structure or XANES) for the glass structure analysis, and Kerr-type nonlinearity measurements by means of a Mach-Zender interferometer modified for nonlinear optics and operating in the sub-picosecond range. The next part highlights the influence of structure entities formed about the titanium atom on the noticed optical nonlinearities. The author finally reports an attempt of modelling of the linear and nonlinear response in mineral glasses under the effect of an electric perturbation [fr

Organic carbonates as solvents in macrocyclic Mn(III) salen catalyzed asymmetric epoxidation of non-functionalized olefins

Czech Academy of Sciences Publication Activity Database

Maity, N. Ch.; Rao, G. V. S.; Prathap, Kaniraj Jeya; Abdi, S. H. R.; Kureshy, R. I.; Khan, N. H.; Bajaj, H. C.

2013-01-01

Roč. 366, January (2013), s. 380-389 ISSN 1381-1169 Institutional support: RVO:61388963 Keywords : asymmetric epoxidation * organic carbonate * macrocyclic Mn(III) salen complex Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.679, year: 2013

O2 Activation and Double C-H Oxidation by a Mononuclear Manganese(II) Complex.

Science.gov (United States)

Deville, Claire; Padamati, Sandeep K; Sundberg, Jonas; McKee, Vickie; Browne, Wesley R; McKenzie, Christine J

2016-01-11

A Mn(II) complex, [Mn(dpeo)2](2+) (dpeo=1,2-di(pyridin-2-yl)ethanone oxime), activates O2, with ensuing stepwise oxidation of the methylene group in the ligands providing an alkoxide and ultimately a ketone group. X-ray crystal-structure analysis of an intermediate homoleptic alkoxide Mn(III) complex shows tridentate binding of the ligand via the two pyridyl groups and the newly installed alkoxide moiety, with the oxime group no longer coordinated. The structure of a Mn(II) complex of the final ketone ligand, cis-[MnBr2(hidpe)2] (hidpe=2-(hydroxyimino)-1,2-di(pyridine-2-yl)ethanone) shows that bidentate oxime/pyridine coordination has been resumed. H2(18)O and (18)O2 labeling experiments suggest that the inserted O atoms originate from two different O2 molecules. The progress of the oxygenation was monitored through changes in the resonance-enhanced Raman bands of the oxime unit. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Properties of phases in HfO2-TiO2 system

International Nuclear Information System (INIS)

Red'ko, V.P.; Terekhovskij, P.B.; Majster, I.M.; Shevchenko, A.V.; Lopato, L.M.; Dvernyakova, A.A.

1990-01-01

A study was made on axial and linear coefficients of thermal expansion (CTE) of HfO 2 -TiO 2 system samples in concentration range of 25-50 mol% TiO 2 . Samples, containing 35 and 37 mol% TiO 2 , are characterized by the lowest values of linear CTE. Dispersion of the basic substances doesn't affect CTE value. Correlation with axial and linear CTE of samples in ZrO 2 -TiO 2 system was conducted. Presence of anisotropy of change of lattice parameters was supported for samples, containing 37.5 and 40 mol% TiO 2 . Polymorphous transformations for hafnium titanate were not revealed

Phase relations and linear thermal expansion of cubic solid solutions in the Th1-xMxO2-x/2 (M=Eu, Gd, Dy) systems

International Nuclear Information System (INIS)

Mathews, M.D.; Ambekar, B.R.; Tyagi, A.K.

2005-01-01

Cell parameters and linear thermal expansion studies of the Th-M oxide systems with general compositions Th 1-x M x O 2-x/2 (M=Eu 3+ , Gd 3+ and Dy 3+ , 0.0= 1.5 in the ThO 2 lattice. The upper solid solubility limits of EuO 1.5 , GdO 1.5 and DyO 1.5 in the ThO 2 lattice under conditions of slow cooling from 1673K are represented as Th 0.50 Eu 0.50 O 1.75 , Th 0.60 Gd 0.40 O 1.80 and Th 0.85 Dy 0.15 O 1.925 , respectively. The linear thermal expansion (293-1123K) of MO 1.5 and their single-phase solid solutions with thoria were investigated by dilatometery. The average linear thermal expansion coefficients (α-bar ) of the compounds decrease on going from EuO 1.5 to DyO 1.5 . The values of α-bar for EuO 1.5 , GdO 1.5 and DyO 1.5 containing solid solutions showed a downward trend as a function of the dopant concentration. The linear thermal expansion (293-1473K) of the solid solutions investigated by high-temperature XRD also showed a similar trend

Melts in the Deep Earth: Calculating the Densities of CaO-FeO-MgO-Al2O3-SiO2 Liquids

Science.gov (United States)

Thomas, C.; Guo, X.; Agee, C. B.; Asimow, P. D.; Lange, R. A.

2012-12-01

We present new equation of state (EOS) measurements for hedenbergite (Hd, CaFeSi2O6) and forsterite (Fo, Mg2SiO4) liquids. These liquid EOS add to the basis set in the CaO-FeO-MgO-Al2O3-SiO2 (CMASF) oxide space at elevated temperatures and pressures; other liquids include: enstatite (En, MgSiO3), anorthite (An, CaAl2Si2O8), diopside (Di, CaMgSi2O6), and fayalite (Fa, Fe2SiO4). The Hd EOS measurement was a multi-technique collaboration using 1-atm double-bob Archimedean, ultrasonic, sink/float, and shock wave techniques. Un-weighted linear fitting of the shock data in shock velocity (US)-particle velocity (up) space defines a pre-heated (1400 °C) Hugoniot US = 2.628(0.024) + 1.54(0.01)up km/s. The slope corresponds to a K' of 5.16(0.04), consistent with piston-cylinder and multi-anvil sink/float experiments. The intercept is fixed at the ultrasonic sound speed (Co) since the unconstrained intercept is within the stated error. This behavior demonstrates consistency across methods and that the liquid is relaxed during shock compression. Shock compression of pre-heated (2000°C) single crystal Fo gives an un-weighted linear Hugoniot of US = 2.674(0.188) + 1.64(0.06)up km/s. The unconstrained Co falls below estimates based on extrapolation in both temperature and composition from two published partial molar sound speed models, 3.195m/s [1] and 3.126 m/s [2]. The shock-derived Co indicates that dC/dT is negative for Fo liquid, contrary to the positive [1] and zero [2] temperature dependences derived over relatively narrow temperature intervals. CMASF liquid isentropes were calculated using five end-members (En, Fo, Fa, An, Di). For modeling crystallization of a fictive magma ocean, we examined two liquids: peridotite [3] (P=.33En+.56Fo+.07Fa+.03An+.007Di) and simplified chondrite [4] (Ch=.62En+.24Fo+.08Fa+.04An+.02Di). Each end-member is defined by a 3rd or 4th order Birch-Murnaghan isentrope, Mie-Grüneisen thermal pressure and a constant heat capacity. The volumes are

The influence of SiO2 Addition on 2MgO-Al2O3-3.3P2O5 Glass

DEFF Research Database (Denmark)

Larsen, P.H.; Poulsen, F.W.; Berg, Rolf W.

1999-01-01

2MgO-Al2O3-3.3P2O5 glasses with increasing amounts of SiO2 are considered for sealing applications in Solid Oxide Fuel Cells (SOFC). The change in chemical durability under SOFC anode conditions and the linear thermal expansion is measured as functions of the SiO2 concentration. Raman spectroscopy...... analysis of the glasses reveals no sign of important changes in the glass structure upon SiO2 addition. Some increase in glass durability with SiO2 concentration is reported and its cause is discussed....

PENGEMBANGAN BAHAN AJAR MATA KULIAH ALJABAR LINEAR BERBASIS OPEN ENDED

Directory of Open Access Journals (Sweden)

Nurul Farida

2017-01-01

Full Text Available Teaching materials is one important component in learning because teaching materials can be used for independent study. On the other hand, the lack of teaching materials are on open-ended problems leads to an underdevelopment of creativity in learning. With the open-ended problems, students are expected to have more than one solution to solve problems in everyday life, especially in mathematical problem solving. The purpose of this study is to develop teaching materials based on open-ended valildly, practically and effectively in the subject of linear algebra. This research is the development by using Plomp models which consists of three stages: preliminary research, prototyping, and assessment. Data collection technique through observation, questionnaires and tests. The instruments used were observation sheet, questionnaire sheet and a test sheet. Based on result of the research that has been done shows that the teaching materials is based on open-ended in the subject linear algebra that have been developed otherwise valid with a value of 3.43, practice with a value 3,11 or in the percentage reached 77,75%, and effective with value of learning outcomes experiment class (use teaching materials developed higher than control class.

The effects of the physical states of a simulated fission product on the linear thermal expansion of (U0.924Ce0.076)O2

International Nuclear Information System (INIS)

Kim, Dong-Joo; Kim, Yong-Soo; Yang, Jae-Ho; Kim, Si-Hyung; Lee, Young-Woo; Kim, Han-Soo

2006-01-01

The linear thermal expansions of an (U 0.924 Ce 0.076 )O 2 pellet, doped a simulated fission product (Nd 2 O 3 or Ru), were measured from room temperature to 1673 K in a flowing argon atmosphere using TMA. Nd 2 O 3 and Ru represent the physical states of a fission product, a dissolved oxide and a metallic precipitate, respectively. Using the measured data, the mean coefficients of a linear thermal expansion was obtained as a function of the temperature, and the effects of the physical states of a simulated fission product on the thermal expansion were investigated. In the case of the Nd 2 O 3 forming a dissolved oxide, the thermal expansion of the sample increased and the increment was proportional to the Nd contents, because the melting point of the Nd 2 O 3 was lower than that of UO 2 and although the metallic precipitate hardly affected the crystal structure, the linear thermal expansion also increased with an increasing Ru contents

A wideband high-linearity RF receiver front-end in CMOS

NARCIS (Netherlands)

Arkesteijn, V.J.; Klumperink, Eric A.M.; Nauta, Bram

This paper presents a wideband high-linearity RF receiver-front-end, implemented in standard 0.18 μm CMOS technology. The design employs a noise-canceling LNA in combination with two passive mixers, followed by lowpass-filtering and amplification at IF. The achieved bandwidth is >2 GHz, with a noise

Voltage linearity modulation and polarity dependent conduction in metal-insulator-metal capacitors with atomic-layer-deposited Al{sub 2}O{sub 3}/ZrO{sub 2}/SiO{sub 2} nano-stacks

Energy Technology Data Exchange (ETDEWEB)

Zhu, Bao; Liu, Wen-Jun; Wei, Lei; Zhang, David Wei; Jiang, Anquan; Ding, Shi-Jin, E-mail: sjding@fudan.edu.cn [State Key Laboratory of ASIC and System, School of Microelectronics, Fudan University, Shanghai 200433 (China)

2015-07-07

Excellent voltage linearity of metal-insulator-metal (MIM) capacitors is highly required for next generation radio frequency integration circuits. In this work, employing atomic layer deposition technique, we demonstrated how the voltage linearity of MIM capacitors was modulated by adding different thickness of SiO{sub 2} layer to the nano-stack of Al{sub 2}O{sub 3}/ZrO{sub 2}. It was found that the quadratic voltage coefficient of capacitance (α) can be effectively reduced from 1279 to −75 ppm/V{sup 2} with increasing the thickness of SiO{sub 2} from zero to 4 nm, which is more powerful than increasing the thickness of ZrO{sub 2} in the Al{sub 2}O{sub 3}/ZrO{sub 2} stack. This is attributed to counteraction between the positive α for Al{sub 2}O{sub 3}/ZrO{sub 2} and the negative one for SiO{sub 2} in the MIM capacitors with Al{sub 2}O{sub 3}/ZrO{sub 2}/SiO{sub 2} stacks. Interestingly, voltage-polarity dependent conduction behaviors in the MIM capacitors were observed. For electron bottom-injection, the addition of SiO{sub 2} obviously suppressed the leakage current; however, it abnormally increased the leakage current for electron top-injection. These are ascribed to the co-existence of shallow and deep traps in ZrO{sub 2}, and the former is in favor of the field-assisted tunnelling conduction and the latter contributes to the trap-assisted tunnelling process. The above findings will be beneficial to device design and process optimization for high performance MIM capacitors.

A Structural Molar Volume Model for Oxide Melts Part I: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Binary Systems

Science.gov (United States)

Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

2016-04-01

A structural molar volume model was developed to accurately reproduce the molar volume of molten oxides. As the non-linearity of molar volume is related to the change in structure of molten oxides, the silicate tetrahedral Q-species, calculated from the modified quasichemical model with an optimized thermodynamic database, were used as basic structural units in the present model. Experimental molar volume data for unary and binary melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system were critically evaluated. The molar volumes of unary oxide components and binary Q-species, which are model parameters of the present structural model, were determined to accurately reproduce the experimental data across the entire binary composition in a wide range of temperatures. The non-linear behavior of molar volume and thermal expansivity of binary melt depending on SiO2 content are well reproduced by the present model.

TiO2 nanorods/PMMA copolymer-based nanocomposites: highly homogeneous linear and nonlinear optical material

International Nuclear Information System (INIS)

Sciancalepore, C; Agostiano, A; Cassano, T; Valentini, A; Curri, M L; Striccoli, M; Mecerreyes, D; Tommasi, R

2008-01-01

Original nanocomposites have been obtained by direct incorporation of pre-synthesized oleic acid capped TiO 2 nanorods into properly functionalized poly(methyl methacrylate) copolymers, carrying carboxylic acid groups on the repeating polymer unit. The presence of carboxylic groups on the alkyl chain of the host functionalized copolymer allows an highly homogeneous dispersion of the nanorods in the organic matrix. The prepared TiO 2 /PMMA-co-MA nanocomposites show high optical transparency in the visible region, even at high TiO 2 nanorod content, and tunable linear refractive index depending on the nanoparticle concentration. Finally measurements of nonlinear optical properties of TiO 2 polymer nanocomposites demonstrate a negligible two-photon absorption and a negative value of nonlinear refractive index, highlighting the potential of the nanocomposite for efficient optical devices operating in the visible region

TiO2 nanorods/PMMA copolymer-based nanocomposites: highly homogeneous linear and nonlinear optical material

Science.gov (United States)

Sciancalepore, C.; Cassano, T.; Curri, M. L.; Mecerreyes, D.; Valentini, A.; Agostiano, A.; Tommasi, R.; Striccoli, M.

2008-05-01

Original nanocomposites have been obtained by direct incorporation of pre-synthesized oleic acid capped TiO2 nanorods into properly functionalized poly(methyl methacrylate) copolymers, carrying carboxylic acid groups on the repeating polymer unit. The presence of carboxylic groups on the alkyl chain of the host functionalized copolymer allows an highly homogeneous dispersion of the nanorods in the organic matrix. The prepared TiO2/PMMA-co-MA nanocomposites show high optical transparency in the visible region, even at high TiO2 nanorod content, and tunable linear refractive index depending on the nanoparticle concentration. Finally measurements of nonlinear optical properties of TiO2 polymer nanocomposites demonstrate a negligible two-photon absorption and a negative value of nonlinear refractive index, highlighting the potential of the nanocomposite for efficient optical devices operating in the visible region.

Synthesis, structure, and electrochemistry and magnetic properties of a novel 1D homochiral MnIII(5-Brsalen) coordination polymer with left-handed helical character

Science.gov (United States)

Dong, Dapeng; Yu, Naisen; Zhao, Haiyan; Liu, Dedi; Liu, Jia; Li, Zhenghua; Liu, Dongping

2016-01-01

A novel homochiral manganese (III) Mn(5-Brsalen) coordination polymer with left-handed helical character by spontaneous resolution on crystallization by using Mn(5-Brsalen) and 4,4-bipyridine, [MnIII(5-Brsalen)(4,4-bipy)]·ClO4·CH3OH (1) (4,4-bipy = 4,4-bipyridine) has been synthesized and structurally characterized by X-ray single-crystal diffraction, elemental analysis and infrared spectroscopy. In compound 1, each manganese(III) anion is six-coordinate octahedral being bonded to four atoms of 5-Brsalen ligand in an equatorial plane and two nitrogen atoms from a 4,4-bipyridine ligand in axial positions. The structure of compound 1 can be described a supramolecular 2D-like structure which was formed by the intermolecular π-stacking interactions between the neighboring chains of the aromatic rings of 4,4-bipyridine and 5-Brsalen molecules. UV-vis absorption spectrum, electrochemistry and magnetic properties of the compound 1 have also been studied.

End effect braking force reduction in high-speed single-sided linear induction machine

International Nuclear Information System (INIS)

Shiri, Abbas; Shoulaie, Abbas

2012-01-01

Highlights: ► A new analytical equation to model the end effect braking force of SLIM is derived. ► Equations for efficiency, power factor and output thrust are analytically derived. ► The effect of design variables on the performance of the motor is analyzed. ► An optimization method is employed to minimize the end effect braking force (EEBF). ► The results show that EEBF is minimized by appropriate selection of motor parameters. - Abstract: Linear induction motors have been widely employed in industry because of their simple structure and low construction cost. However, they suffer from low efficiency and power factor. In addition, existence of so called end effect influences their performance especially in high speeds. The end effect deteriorates the performance of the motor by producing braking force. So, in this paper, by using Duncan equivalent circuit model, a new analytical equation is proposed to model end effect braking force. Employing the proposed equation and considering all phenomena involved in the single-sided linear induction motor, a simple design procedure is presented and the effect of different design variables on the performance of the motor is analyzed. A multi-objective optimization method based on genetic algorithm is introduced to maximize efficiency and power factor, as well as to minimize the end effect braking force, simultaneously. Finally, to validate the optimization results, 2D finite element method is employed.

Combined use of O3/H2O2 and O3/Mn2+ in flotation of dairy wastewater

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Marta Cristina Silva Carvalho

2018-05-01

Full Text Available This work investigated the degradation of organic matter present in synthetic dairy wastewater by the combination of ozonation (ozone (O3/hydrogen peroxide (H2O2 and catalytic ozonation (ozone (O3/manganese (Mn2+ associated with dispersed air flotation process. The effect of independent factors such as O3 concentration, pH and H2O2 and Mn2+ concentration was evaluated. For the flotation/O3/H2O2 treatment, the significant variables (p ≤ 0.05 were: O3 concentration (linear and quadratic effect, H2O2 concentration linear and quadratic effect, pH values (linear and quadratic effect and interaction O3 concentration versus pH. For catalytic ozonation, it was observed that the significant variable was the linear effect of O3 concentration. According to the desirability function, it was concluded that the optimal condition for the treatment of flotation/O3/H2O2 can be obtained in acidic solution using O3 concentrations greater than 42.9 mg L-1 combined with higher concentrations of H2O2 to 1071.5 mg L-1. On other hand, at pH values higher than 9.0, the addition of O3 may be neglected when using higher concentrations than 1071.5 mg L-1 of H2O2. For flotation/ozonation catalyzed by Mn2+, it was observed that metal addition did not affect treatment, resulting in an optimum condition: 53.8 mg L-1 of O3 and pH 3.6.

MnO2-x nanosheets on stainless steel felt as a carbon- and binder-free cathode for non-aqueous lithium-oxygen batteries

Science.gov (United States)

Wei, Z. H.; Zhao, T. S.; Zhu, X. B.; Tan, P.

2016-02-01

Manganese dioxide (MnO2) has been recognized as an effective catalyst for the oxygen reduction and oxygen evolution reactions in non-aqueous lithium-oxygen batteries. However, a further improvement in battery performance with the MnO2 catalyst is limited by its low electronic conductivity and catalytic activity, which strongly depend on the morphology and composition. In this work, we develop a carbon- and binder-free MnO2-x nanosheets/stainless steel (SS) cathode via a simple and effective electrodeposition-solvothermal route. The created Mn(III) and oxygen vacancy in MnO2-x nanosheets allows an significant increase in the electronic conductivity and catalytic activity. It is experimentally shown that the use of the present nanostructure MnO2-x/SS cathode in a non-aqueous lithium-oxygen battery results in a rechargeable specific capacity of 7300 mAh g-1 at a current density of 200 mA g-1, which is 39% higher than that with the MnO2/SS cathode. In addition, the specific capacities at 400 mA g-1 and 800 mA g-1 reach 5249 mAh g-1 and 2813 mAh g-1, respectively, which are over 30% higher than that with the MnO2/SS cathode. Furthermore, the discharge/charge cycle test shows no degradation for 120 cycles. All the results show that the present nanostructure MnO2-x/SS cathode is a promising candidate for high-performance lithium-oxygen batteries.

A Note on Ko-Type O-Ending Syllables in Old Japanese

Science.gov (United States)

Unger, J. Marshall

1975-01-01

Further evidence is offered to support the argument that ko-type o-ending syllables may have been secondary in nature in Old Japanese. Pre-Old Japanese indicates the */uwa/ sequence was manifested as /uwe/ and /uwu/ endings of o-ending syllable verbs. (SCC)

Use of linear free energy relationship to predict Gibbs free energies of formation of zirconolite phases (MZrTi2O7 and MHfTi2O7)

International Nuclear Information System (INIS)

Xu, H.

1999-01-01

In this letter, the Sverjensky-Molling equation derived from a linear free energy relationship is used to calculate the Gibbs free energies of formation of zirconolite crystalline phases (MZrTi 2 O 7 and MHfTi 2 O 7 ) from the known thermodynamic properties of the corresponding aqueous divalent cations (M 2+ ). Sverjensky-Molling equation is expressed as ΔG 0 f,M v X =a M v X ΔG 0 n,M 2+ +b M v X +β M v X r M 2+ , where the coefficients a M v X , b M v X , and β M v X characterize a particular structural family of M v X, r M 2+ is the ionic radius of M 2+ cation, ΔG f,M v X 0 is the standard Gibbs free energy of formation of M v X, and ΔG 0 n,M 2+ is the standard non-solvation energy of cation M 2+ . This relationship can be used to predict the Gibbs free energies of formation of various fictive phases (such as BaZrTi 2 O 7 , SrZrTi 2 O 7 , PbZrTi 2 O 7 , etc.) that may form solid solution with CaZrTi 2 O 7 in actual Synroc-based nuclear waste forms. Based on obtained linear free energy relationships, it is predicted that large cations (e.g., Ba and Ra) prefer to be in perovskite structure, and small cations (e.g., Ca, Zn, and Cd) prefer to be in zirconolite structure. (orig.)

Kinetic approach to plasma end loss from linear devices

International Nuclear Information System (INIS)

Dreicer, H.

1976-01-01

A first step in the direction of a kinetic approach to end loss has been presented. This approach brings to light some fundamental processes not uncovered by the magnetohydrodynamic or guiding center approach. Attention was focused on the basically transient phenomenon in a way that describes the quite different behavior of collision dominated and collisionless ions, but ignores the magnetic nozzle effects near the ends of the system. The treatment illuminates some of the roles played by the parameter l/sub ii//L, and suggests the direction for more detailed investigations. End loss from linear systems is a very many faceted problem. Kinetic effects, magnetic effects, heat flow, etc. are all intermixed, and it will require a strong long term experimental and theoretical program to unravel all of its mysteries

Study of the O(N) linear σ model at finite temperature using the 2PPI expansion

International Nuclear Information System (INIS)

Verschelde, H.; De Pessemier, J.

2002-01-01

We show that a new expansion, which sums seagull and bubble graphs to all orders, can be applied to the O(N) linear σ-model at finite temperature. We prove that this expansion can be renormalized with the usual counterterms in a mass independent scheme and that Goldstone's theorem is satisfied at each order. At the one loop order of this expansion, the Hartree result for the effective potential (daisy and superdaisy graphs) is recovered. We show that at one loop 2PPI order, the self-energy of the σ-meson can be calculated exactly and that diagrams are summed beyond the Hartree approximation. (orig.)

End-functional silicone coupling agent modified PEO/P(VDF-HFP)/SiO2 nanocomposite polymer electrolyte DSSC

International Nuclear Information System (INIS)

Zhang Jing; Yang Ying; Wu Sujuan; Xu Sheng; Zhou Conghua; Hu Hao; Chen Bolei; Xiong Xiaodong; Sebo, Bobby; Han Hongwei; Zhao Xingzhong

2008-01-01

The end-functional silicone coupling agent (dodecyl-trimethoxysilane, DTMS for short) was used to modify the PEO/P(VDF-HFP)/SiO 2 nanocomposite polymer electrolyte (CPE) and the different amounts of DTMS modification effects were studied. The experiments showed the silicone coupling agent with hydrophobic alkyl chains (-C 12 H 25 ) chemically engineered on the SiO 2 nanoparticles, and formed a Si-O-Si cross-linked network in the new nanocomposite polymer electrolyte. Proper content of DTMS modified CPE exhibited improved ionic conductivity and the connection with the photoanode and counter electrode. However, much higher content of the DTMS modification changed the conformation of the polymer network and reduced the ionic movement. Compared with the performance (3.84%) of the original DSSC, the DSSC with functional silicone coupling agent modified CPE (DTMS:SiO 2 = 2:1, mol ratio) exhibited improved J sc (7.94 mA cm -2 ), V oc (0.624 V) and optimal efficiency (5.2%) (measured at AM1.5, light intensity of 58.4 mW cm -2 ). The V oc of the silicone coupling agent modified polymer electrolyte DSSC is obviously improved, which is mainly due to that the hydrophobic alkyl chain end groups formed an insulating layer that retarded the electron recombination at the TiO 2 nanoporous photoanode/polymer electrolyte interface. The DTMS:SiO 2 = 2:1 modified CPE type DSSC exhibited a performance of 6.42% at a light intensity of 32.1 mW cm -2 and 4.94% at 99.2 mW cm -2

Experimental Investigation on Ductile Mode Micro-Milling of ZrO2 Ceramics with Diamond-Coated End Mills

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Rong Bian

2018-03-01

Full Text Available ZrO2 ceramics are currently used in a broad range of industrial applications. However, the machining of post-sintered ZrO2 ceramic is a difficult task, due to its high hardness and brittleness. In this study, micro-milling of ZrO2 with two kinds of diamond-coated end mills has been conducted on a Kern MMP 2522 micro-milling center (Kern Microtechnik GmbH, Eschenlohe, Germany. To achieve a ductile mode machining of ZrO2, the feed per tooth and depth of cut was set in the range of a few micrometers. Cutting force and machined surface roughness have been measured by a Kistler MiniDynamometer (Kistler Group, Winterthur, Switzerland and a Talysurf 120 L profilometer (Taylor Hobson Ltd., Leicester, UK, respectively. Machined surface topography and tool wear have been examined under SEM. Experiment results show that the material can be removed in ductile mode, and mirror quality surface with Ra low as 0.02 μm can be achieved. Curled and smooth chips have been collected and observed. The axial cutting force Fz is always bigger than Fx and Fy, and presents a rising trend with increasing of milling length. Tool wear includes delamination of diamond coating and wear of tungsten carbide substrate. Without the protection of diamond coating, the tungsten carbide substrate was worn out quickly, resulting a change of tool tip geometry.

Dependence of glass-forming ability on starting compositions in Y2O3–Al2O3–SiO2 system

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Yixiang Chen

2011-09-01

Full Text Available The dependence of glass-forming ability on starting compositions in Y2O3–Al2O3–SiO2 (YAS system has been investigated by melting experiment. Transparent YAS glasses have been prepared under the condition of furnace cooling instead of quenching. It is found that, in the YAS ternary phase diagram, the compositions on the Y3Al5O12–SiO2 line and with 52-68 mol% SiO2 have a higher glass-forming ability to produce pure glass. For the compositions with too much or less SiO2 or with Y/Al = 5/3, 1/1, or 1/3, crystallization occurs with the formation of Y3Al5O12, Y2Si2O7, Al6Si2O13, or SiO2. The densities of the YAS glasses increase with decreasing SiO2 contents and increasing Y/Al ratios, and for the samples with Y/Al = 3/5 there is a good linear relationship between the density and SiO2 content.

"Switching on" the properties of single-molecule magnetism in triangular manganese(III) complexes.

Science.gov (United States)

Stamatatos, Theocharis C; Foguet-Albiol, Dolos; Lee, Sheng-Chiang; Stoumpos, Constantinos C; Raptopoulou, Catherine P; Terzis, Aris; Wernsdorfer, Wolfgang; Hill, Stephen O; Perlepes, Spyros P; Christou, George

2007-08-01

The reaction between oxide-centered, triangular [MnIII3O(O2CR)6(py)3](ClO4) (R = Me (1), Et (2), Ph (3)) compounds and methyl 2-pyridyl ketone oxime (mpkoH) affords a new family of Mn/carboxylato/oximato complexes, [MnIII3O(O2CR)3(mpko)3](ClO4) [R = Me (4), Et (5), and Ph (6)]. As in 1-3, the cations of 4-6 contain an [MnIII3(mu3-O)]7+ triangular core, but with each Mn2 edge now bridged by an eta1:eta1:mu-RCO2- and an eta1:eta1:eta1:mu-mpko- group. The tridentate binding mode of the latter causes a buckling of the formerly planar [MnIII3(mu3-O)]7+ core, resulting in a relative twisting of the three MnIII octahedra and the central O2- ion now lying approximately 0.3 A above the Mn3 plane. This structural distortion leads to ferromagnetic exchange interactions within the molecule and a resulting S = 6 ground state. Fits of dc magnetization data for 4-6 collected in the 1.8-10.0 K and 10-70 kG ranges confirmed S = 6 ground states, and gave the following D and g values: -0.34 cm(-1) and 1.92 for 4, -0.34 cm(-1) and 1.93 for 5, and -0.35 cm(-1) and 1.99 for 6, where D is the axial zero-field splitting (anisotropy) parameter. Complexes 4-6 all exhibit frequency-dependent out-of-phase (chi" M) ac susceptibility signals suggesting them possibly to be single-molecule magnets (SMMs). Relaxation rate vs T data for complex 4 down to 1.8 K obtained from the chi" M vs T studies were supplemented with rate vs T data measured to 0.04 K via magnetization vs time decay studies, and these were used to construct Arrhenius plots from which was obtained the effective barrier to relaxation (Ueff) of 10.9 K. Magnetization vs dc field sweeps on single-crystals of 4.3CH2Cl2 displayed hysteresis loops exhibiting steps due to quantum tunneling of magnetization (QTM). The loops were essentially temperature-independent below approximately 0.3 K, indicating only ground-state QTM between the lowest-lying Ms = +/-6 levels. Complexes 4-6 are thus confirmed as the first triangular SMMs. High

High Dynamic Range RF Front End with Noise Cancellation and Linearization for WiMAX Receivers

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J.-M. Wu

2012-06-01

Full Text Available This research deals with verification of the high dynamic range for a heterodyne radio frequency (RF front end. A 2.6 GHz RF front end is designed and implemented in a hybrid microwave integrated circuit (HMIC for worldwide interoperability for microwave access (WiMAX receivers. The heterodyne RF front end consists of a low-noise amplifier (LNA with noise cancellation, an RF bandpass filter (BPF, a downconverter with linearization, and an intermediate frequency (IF BPF. A noise canceling technique used in the low-noise amplifier eliminates a thermal noise and then reduces the noise figure (NF of the RF front end by 0.9 dB. Use of a downconverter with diode linearizer also compensates for gain compression, which increases the input-referred third-order intercept point (IIP3 of the RF front end by 4.3 dB. The proposed method substantially increases the spurious-free dynamic range (DRf of the RF front end by 3.5 dB.

High temperature X-ray diffraction studies on HfO2-Gd2O3 system

International Nuclear Information System (INIS)

Panneerselvam, G.; Antony, M.P.; Ananthasivan, K.; Joseph, M.

2016-01-01

High temperature X-ray diffraction (HTXRD) technique is an important experimental tool for measuring thermal expansion of materials of interest. A series of solid solutions containing GdO 1.5 in HfO 2 ,Hf 1-y Gd y )O 2 (y = 0.15, 0.2, 0.3, 0.41 and 0.505) were prepared by solid state method. Structural characterization and computation of lattice parameter was carried out by using room temperature X-ray diffraction measurements. The room temperature lattice parameter estimated for (Hf 1-y Gd y )O 2 (y=0.15, 0.2, 0.3, 0.41 and 0.505) are 0.51714 nm, 0.51929 nm, 0.52359nm, 0.52789nm and 0.53241 nm, respectively. Thermal expansion coefficients and percentage linear thermal expansion of the HfO 2 -Gd 2 O 3 solid solutions containing 20 and 41 mol% GdO 1.5 were determined using HTXRD in the temperature range 298 to 1673K. The mean linear thermal expansion coefficients of the solid solutions containing 20 and 41 mol. %Gd are 11.65 x 10 -6 K -1 and 12.07 x 10 -6 K -1 , respectively. (author)

Crystal structure of 2-hydroxy-N-(2-hydroxyethyl-N-{2-hydroxy-3-[(E-N-hydroxyethanimidoyl]-5-methylbenzyl}ethanaminium acetate monohydrate

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Gary S. Nichol

2015-03-01

Full Text Available The structure of the title hydrated molecular salt, C14H23N2O4+·C2H3O2−·H2O, was determined as part of a wider study on the use of the molecule as a polydentate ligand in the synthesis of MnIII clusters with magnetic properties. The cation features intramolecular O—H...N and N—H...O hydrogen-bond interactions. The crystal structure features a range of intermolecular hydrogen-bonding interactions, principally O—H...O interactions between all three species in the asymmetric unit. An R24(8 graph-set hydrogen-bonding motif between the anion and water molecules serves as a unit which links to the cation via the diethanolamine group. Each O atom of the acetate anion accepts two hydrogen bonds.

Association behaviour of 241Am(III) on SiO2(amorphous) and SiO2(quartz) colloids

International Nuclear Information System (INIS)

Degueldre, C.; Wernli, B.

1993-01-01

SiO 2 colloids have been identified as a potential vector for enhancing radionuclide transport in granitic groundwater and in concrete pore water. The sorption behaviour of 241 Am(III) on SiO 2 colloids was studied as a function of americium concentration pH (5-12), colloid concentration, ionic strength, temperature and SiO 2 allotropic species. The Am(III) sorption mechanism on amorphous silica is different from that on quartz. For SiO 2(amorphous) solution, the variation of log K p (ml g -1 ) with pH is linear (pH=5-9) with a slope of +1 indicating a one proton exchange mechanism. The colloid concentration (ppm) affects the sorption and log K p 3.7-0.67 log [SiO 2 ] (pH = 6). K p increases insignificantly when the ionic strength decreases. It shows no significant variation, however, with the Am concentration. On amorphous silica, the Am(III) sorption is driven by proton exchange from the silanol groups. For SiO 2 (quartz), log K p is constant over a large range of quartz concentration in suspension and the variation of log K p with pH is about linear (pH = 5-12), with a slope of 0.28, indicating a more complex exchange mechanism. Reactions taking into account the interaction of positive Am(OH) w (3-w)+ species on to the negatively charged quartz surface are suggested. (author)

Constraints on superoxide mediated formation of manganese oxides

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Deric R. Learman

2013-09-01

Full Text Available Manganese (Mn oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2- (both of biogenic and abiogenic origin as an effective oxidant of Mn(II leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III and Mn(III/IV oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide, a product of the reaction of O2- with Mn(II, inhibits the oxidation process presumably through the reduction of Mn(III. Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III-ligand complexes. While complexing ligands played a role in stabilizing Mn(III, they did not eliminate the inhibition of net Mn(III formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation.

Determination and analysis of non-linear index profiles in electron-beam-deposited MgOAl2O3ZrO2 ternary composite thin-film optical coatings

International Nuclear Information System (INIS)

Sahoo, N.K.; Thakur, S.; Senthilkumar, M.; Das, N.C.

2005-01-01

Thickness-dependent index non-linearity in thin films has been a thought provoking as well as intriguing topic in the field of optical coatings. The characterization and analysis of such inhomogeneous index profiles pose several degrees of challenges to thin-film researchers depending upon the availability of relevant experimental and process-monitoring-related information. In the present work, a variety of novel experimental non-linear index profiles have been observed in thin films of MgOAl 2 O 3 ZrO 2 ternary composites in solid solution under various electron-beam deposition parameters. Analysis and derivation of these non-linear spectral index profiles have been carried out by an inverse-synthesis approach using a real-time optical monitoring signal and post-deposition transmittance and reflection spectra. Most of the non-linear index functions are observed to fit polynomial equations of order seven or eight very well. In this paper, the application of such a non-linear index function has also been demonstrated in designing electric-field-optimized high-damage-threshold multilayer coatings such as normal- and oblique-incidence edge filters and a broadband beam splitter for p-polarized light. Such designs can also advantageously maintain the microstructural stability of the multilayer structure due to the low stress factor of the non-linear ternary composite layers. (orig.)

Study of the critical behavior of the O(N) linear and nonlinear sigma models

International Nuclear Information System (INIS)

Graziani, F.R.

1983-01-01

A study of the large N behavior of both the O(N) linear and nonlinear sigma models is presented. The purpose is to investigate the relationship between the disordered (ordered) phase of the linear and nonlinear sigma models. Utilizing operator product expansions and stability analyses, it is shown that for 2 - (lambda/sub R/(M) is the dimensionless renormalized quartic coupling and lambda* is the IR fixed point) limit of the linear sigma model which yields the nonlinear sigma model. It is also shown that stable large N linear sigma models with lambda 0) and nonlinear models are trivial. This result (i.e., triviality) is well known but only for one and two component models. Interestingly enough, the lambda< d = 4 linear sigma model remains nontrivial and tachyonic free

Statistical modeling of the reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2.

Science.gov (United States)

Ushakov, Vladimir G; Troe, Jürgen; Johnson, Ryan S; Guo, Hua; Ard, Shaun G; Melko, Joshua J; Shuman, Nicholas S; Viggiano, Albert A

2015-08-14

The rates of the reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2 are modeled by statistical rate theory accounting for energy- and angular momentum-specific rate constants for formation of the primary and secondary cationic adducts and their backward and forward reactions. The reactions are both suggested to proceed on sextet and quartet potential energy surfaces with efficient, but probably not complete, equilibration by spin-inversion of the populations of the sextet and quartet adducts. The influence of spin-inversion on the overall reaction rate is investigated. The differences of the two reaction rates mostly are due to different numbers of entrance states (atom + linear rotor or linear rotor + linear rotor, respectively). The reaction Fe(+) + N2O was studied either with (6)Fe(+) or with (4)Fe(+) reactants. Differences in the rate constants of (6)Fe(+) and (4)Fe(+) reacting with N2O are attributed to different contributions from electronically excited potential energy surfaces, such as they originate from the open-electronic shell reactants.

Thermal expansion of ThO2-2 wt% UO2 by HT-XRD

International Nuclear Information System (INIS)

Tyagi, A.K.; Mathews, M.D.

2000-01-01

The linear thermal expansion of polycrystalline ThO 2 -2 wt% UO 2 has been investigated from room temperature to 1473 K in flowing helium atmosphere using high temperature X-ray diffractometry. ThO 2 -2 wt% UO 2 shows a marginally higher linear thermal expansion as compared to pure ThO 2 . The average linear and volume thermal expansion coefficients of ThO 2 -2 wt% UO 2 are found to be α-bar a =9.74x10 -6 K -1 and α-bar v =29.52x10 -6 K -1 (298-1473 K). This study will be useful in designing the nuclear reactor fuel assembly based on ThO 2

Modelos lineares e não lineares da curva de Phillips para previsão da taxa de inflação no Brasil

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Elano Ferreira Arruda

2011-09-01

Full Text Available Este trabalho compara previsões da taxa de inflação mensal brasileira a partir de diferentes modelos lineares e não lineares de séries temporais e da curva de Phillips. Em geral, os modelos não lineares apresentaram um melhor desempenho preditivo. Um modelo VAR produziu o menor erro quadrático médio de previsão (EQM entre os modelos lineares, enquanto as melhores previsões, entre todos os modelos, foram geradas pela curva de Phillips ampliada com threshold, a qual apresentou um EQM 20% menor do que a do modelo VAR. Essa diferença é significante de acordo com o teste de Diebold e Mariano (1995.

Vitrification and some physical and chemical properties of glass in the BaO-B2O3-GeO2 system

International Nuclear Information System (INIS)

Dzhavadyan, V.G.; Kostanyan, K.A.

1977-01-01

The results are presented of the determination of the areas of glass-transition in RO-B 2 O-GeO 2 systems (where R=Mg, Ca, Sr, Ba) and of the study of the density, the refraction index and the coefficient of linear thermal expansion of glasses of the BaO-B 2 O 3 -GeO 2 system as a function of the composition. It is shown that the substitution of the glass forming agent in the borogermanate component by BaO leads to a non-linear growth of the density. A negative deviation is observed of the experimental variation of the molar volume from the ideal and the positive deviation of the refraction indices from the ideal values. A content of 30 % and over of BaO brings about a sharp increase in the value of the coefficient of linear thermal expansion. Changes of the m lar volume, refraction index and coefficient of linear thermal expansion of glasses as a function of their compositions is due to the variation of the coordination number of boron on charge of the BaO/B 2 O 3 ratio

Linearization Method and Linear Complexity

Science.gov (United States)

Tanaka, Hidema

We focus on the relationship between the linearization method and linear complexity and show that the linearization method is another effective technique for calculating linear complexity. We analyze its effectiveness by comparing with the logic circuit method. We compare the relevant conditions and necessary computational cost with those of the Berlekamp-Massey algorithm and the Games-Chan algorithm. The significant property of a linearization method is that it needs no output sequence from a pseudo-random number generator (PRNG) because it calculates linear complexity using the algebraic expression of its algorithm. When a PRNG has n [bit] stages (registers or internal states), the necessary computational cost is smaller than O(2n). On the other hand, the Berlekamp-Massey algorithm needs O(N2) where N(≅2n) denotes period. Since existing methods calculate using the output sequence, an initial value of PRNG influences a resultant value of linear complexity. Therefore, a linear complexity is generally given as an estimate value. On the other hand, a linearization method calculates from an algorithm of PRNG, it can determine the lower bound of linear complexity.

SPoRT - An End-to-End R2O Activity

Science.gov (United States)

Jedlovec, Gary J.

2009-01-01

Established in 2002 to demonstrate the weather and forecasting application of real-time EOS measurements, the Short-term Prediction Research and Transition (SPoRT) program has grown to be an end-to-end research to operations activity focused on the use of advanced NASA modeling and data assimilation approaches, nowcasting techniques, and unique high-resolution multispectral observational data applications from EOS satellites to improve short-term weather forecasts on a regional and local scale. SPoRT currently partners with several universities and other government agencies for access to real-time data and products, and works collaboratively with them and operational end users at 13 WFOs to develop and test the new products and capabilities in a "test-bed" mode. The test-bed simulates key aspects of the operational environment without putting constraints on the forecaster workload. Products and capabilities which show utility in the test-bed environment are then transitioned experimentally into the operational environment for further evaluation and assessment. SPoRT focuses on a suite of data and products from MODIS, AMSR-E, and AIRS on the NASA Terra and Aqua satellites, and total lightning measurements from ground-based networks. Some of the observations are assimilated into or used with various versions of the WRF model to provide supplemental forecast guidance to operational end users. SPoRT is enhancing partnerships with NOAA / NESDIS for new product development and data access to exploit the remote sensing capabilities of instruments on the NPOESS satellites to address short term weather forecasting problems. The VIIRS and CrIS instruments on the NPP and follow-on NPOESS satellites provide similar observing capabilities to the MODIS and AIRS instruments on Terra and Aqua. SPoRT will be transitioning existing and new capabilities into the AWIIPS II environment to continue the continuity of its activities.

B2O3/SiO2 substitution effect on structure and properties of Na2O-CaO-SrO-P2O5-SiO2 bioactive glasses from molecular dynamics simulations.

Science.gov (United States)

Ren, Mengguo; Lu, Xiaonan; Deng, Lu; Kuo, Po-Hsuen; Du, Jincheng

2018-05-23

The effect of B2O3/SiO2 substitution in SrO-containing 55S4.3 bioactive glasses on glass structure and properties, such as ionic diffusion and glass transition temperature, was investigated by combining experiments and molecular dynamics simulations with newly developed potentials. Both short-range (such as bond length and bond angle) and medium-range (such as polyhedral connection and ring size distribution) structures were determined as a function of glass composition. The simulation results were used to explain the experimental results for glass properties such as glass transition temperature and bioactivity. The fraction of bridging oxygen increased linearly with increasing B2O3 content, resulting in an increase in overall glass network connectivity. Ion diffusion behavior was found to be sensitive to changes in glass composition and the trend of the change with the level of substitution is also temperature dependent. The differential scanning calorimetry (DSC) results show a decrease in glass transition temperature (Tg) with increasing B2O3 content. This is explained by the increase in ion diffusion coefficient and decrease in ion diffusion energy barrier in glass melts, as suggested by high-temperature range (above Tg) ion diffusion calculations as B2O3/SiO2 substitution increases. In the low-temperature range (below Tg), the Ea for modifier ions increased with B2O3/SiO2 substitution, which can be explained by the increase in glass network connectivity. Vibrational density of states (VDOS) were calculated and show spectral feature changes as a result of the substitution. The change in bioactivity with B2O3/SiO2 substitution is discussed with the change in pH value and release of boric acid into the solution.

Beam-Mode Piezoelectric Properties of Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals for Medical Linear Array Applications

Science.gov (United States)

Wang, Wei; Wang, Sheng; Zhang, Yaoyao; Zhao, Xiangyong; Luo, Haosu

2011-11-01

In this work, the dielectric and beam-mode piezoelectric properties of ternary 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PIMNT35/35/30) piezoelectric single crystals were investigated. The Curie temperature ( T C) and rhombohedral-to-tetragonal phase-transition temperature ( T rt) are 187°C and 127°C, about 30°C higher than those of PMNT crystals. The beam-mode coupling coefficient k {33/ w } was found to be 90.3%. Furthermore, 3.5-MHz linear arrays based on PIMNT35/35/30 crystals and Pb(Zr1- x Ti x )O3 ceramic (PZT-5H) were simulated using PiezoCAD software. The results indicate that the sensitivity and -6 dB bandwidth of a PIMNT35/35/30 transducer would be approximately 4 dB and 20% higher, respectively, compared with a traditional PZT transducer.

Equação de difusão não linear, soluções e difusão anômala - DOI: 10.4025/actascitechnol.v29i2.702

Directory of Open Access Journals (Sweden)

Renata Ferreira Colli Badini

2008-02-01

Full Text Available Neste trabalho, investigaremos uma equação de difusão não linear considerando a presença de termos convectivos, absorventes e um coeficiente de difusão dependente do tempo. Os termos não lineares presentes na equação serão uma conseqüência do emprego de uma generalização não linear da Lei de Darcy ou da presença de um termo absorvente não linear que pode, por exemplo, representar um processo de difusão com reação. Em particular, para esta equação de difusão obteremos uma nova classe de soluções e analisaremos os efeitos produzidos por tais termos, assim como relação com processos difusivos anômalos.

Thermal, optical and structural properties of glasses within the TeO{sub 2}-TiO{sub 2}-ZnO system

Energy Technology Data Exchange (ETDEWEB)

Ghribi, N. [CNRS-Université de Limoges, Science des Procédés Céramiques et de Traitements de Surface, UMR7315 CNRS, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex (France); Sciences des Matériaux et de l’Environnement Laboratory, Sfax University, Route de Soukra km 4, 3038 Sfax (Tunisia); Dutreilh-Colas, M.; Duclère, J.-R. [CNRS-Université de Limoges, Science des Procédés Céramiques et de Traitements de Surface, UMR7315 CNRS, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex (France); Hayakawa, T. [Field of Advanced Energy Conversion, Department of Frontier Materials, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555 (Japan); Carreaud, J. [CNRS-Université de Limoges, Science des Procédés Céramiques et de Traitements de Surface, UMR7315 CNRS, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges Cedex (France); Karray, R.; Kabadou, A. [Sciences des Matériaux et de l’Environnement Laboratory, Sfax University, Route de Soukra km 4, 3038 Sfax (Tunisia); and others

2015-02-15

Highlights: • This paper reports on original results on new tellurium oxide-based glasses which are actually very promising glasses in the field of nonlinear optics. • We present for the first time the determination of a new glassy system and the structure of the glasses has been investigated using Raman spectroscopy which is actually the most adapted method in laboratory to study the local structure of tellurite glasses, a detail linear and non-linear optical study is also presented. - Abstract: A glass-forming domain was evidenced and studied within the TeO{sub 2}-TiO{sub 2}-ZnO system. Density, glass transition temperature (T{sub g}) and onset crystallization temperature (T{sub 0}) were measured and interpreted as a function of the zinc oxide mole fraction for relevant glasses. It was concluded that the zinc oxide favors the thermal stability of glasses. On the other hand, the impact of TiO{sub 2} addition is even more pronounced on the enhancement of the thermal stability. The optical transmission was recorded for series of glasses in the UV-Visible-NIR range. Refractive index and optical band gap were extracted from these measurements and studied as a function of the ZnO content. Linear refractive indices and optical band gap were found to decrease and increase respectively, with increasing ZnO content. The third-order non-linear susceptibility Re (χ{sup 3}), measured for two series of glasses (TiO{sub 2} content was fixed either to 5 or 10 mol%), was found to progressively decrease when the ZnO concentration increases. The impact of ZnO modifier on the glass structure was discussed based on Raman spectroscopy data. We evidenced that TiO{sub 2} does not change drastically the glass network, whereas ZnO leads in a first step to the breaking of the Te-O-Te bridges, inducing network depolymerization. A further addition in ZnO leads to the formation of new Te-O-Zn and Zn-O-Zn linkages.

Diffusive charge transport in graphene on SiO 2

Science.gov (United States)

Chen, J.-H.; Jang, C.; Ishigami, M.; Xiao, S.; Cullen, W. G.; Williams, E. D.; Fuhrer, M. S.

2009-07-01

We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO 2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density ( σ(n)∝n) in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates; increased dielectric screening reduces the scattering from charged impurities, but increases the scattering from short-range scatterers. We evaluate the effects of the corrugations (ripples) of graphene on SiO 2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity that is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO 2 substrate give rise to an activated, carrier density-dependent resistivity. Together the results paint a complete picture of charge carrier transport in graphene on SiO 2 in the diffusive regime.

Na2MoO2As2O7

Directory of Open Access Journals (Sweden)

Raja Jouini

2012-12-01

Full Text Available Disodium molybdenum dioxide diarsenate, Na2MoO2As2O7, has been synthesized by a solid-state reaction. The structure is built up from MoAs2O12 linear units sharing corners to form a three-dimensional framework containing tunnels running along the a-axis direction in which the Na+ cations are located. In this framework, the AsV atoms are tetrahedrally coordinated and form an As2O7 group. The MoVI atom is displaced from the center of an octahedron of O atoms. Two Na+ cations are disordered about inversion centres. Structural relationships between different compounds: A2MoO2As2O7 (A = K, Rb, AMOP2O7 (A = Na, K, Rb; M = Mo, Nb and MoP2O7 are discussed.

The Front-End Readout as an Encoder IC for Magneto-Resistive Linear Scale Sensors

Directory of Open Access Journals (Sweden)

Trong-Hieu Tran

2016-09-01

Full Text Available This study proposes a front-end readout circuit as an encoder chip for magneto-resistance (MR linear scales. A typical MR sensor consists of two major parts: one is its base structure, also called the magnetic scale, which is embedded with multiple grid MR electrodes, while another is an “MR reader” stage with magnets inside and moving on the rails of the base. As the stage is in motion, the magnetic interaction between the moving stage and the base causes the variation of the magneto-resistances of the grid electrodes. In this study, a front-end readout IC chip is successfully designed and realized to acquire temporally-varying resistances in electrical signals as the stage is in motions. The acquired signals are in fact sinusoids and co-sinusoids, which are further deciphered by the front-end readout circuit via newly-designed programmable gain amplifiers (PGAs and analog-to-digital converters (ADCs. The PGA is particularly designed to amplify the signals up to full dynamic ranges and up to 1 MHz. A 12-bit successive approximation register (SAR ADC for analog-to-digital conversion is designed with linearity performance of ±1 in the least significant bit (LSB over the input range of 0.5–2.5 V from peak to peak. The chip was fabricated by the Taiwan Semiconductor Manufacturing Company (TSMC 0.35-micron complementary metal oxide semiconductor (CMOS technology for verification with a chip size of 6.61 mm2, while the power consumption is 56 mW from a 5-V power supply. The measured integral non-linearity (INL is −0.79–0.95 LSB while the differential non-linearity (DNL is −0.68–0.72 LSB. The effective number of bits (ENOB of the designed ADC is validated as 10.86 for converting the input analog signal to digital counterparts. Experimental validation was conducted. A digital decoder is orchestrated to decipher the harmonic outputs from the ADC via interpolation to the position of the moving stage. It was found that the displacement

Linear and nonlinear intraband optical properties of ZnO quantum dots embedded in SiO2 matrix

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Deepti Maikhuri

2012-03-01

Full Text Available In this work we investigate some optical properties of semiconductor ZnO spherical quantum dot embedded in an amorphous SiO2 dielectric matrix. Using the framework of effective mass approximation, we have studied intraband S-P, and P-D transitions in a singly charged spherical ZnO quantum dot. The optical properties are investigated in terms of the linear and nonlinear photoabsorption coefficient, the change in refractive index, and the third order nonlinear susceptibility and oscillator strengths. Using the parabolic confinement potential of electron in the dot these parameters are studied with the variation of the dot size, and the energy and intensity of incident radiation. The photoionization cross sections are also obtained for the different dot radii from the initial ground state of the dot. It is found that dot size, confinement potential, and incident radiation intensity affects intraband optical properties of the dot significantly.

Thermal expansion of lanthanum silicate oxyapatite (La9.33+2x(SiO4)6O2+3x), lanthanum oxyorthosilicate (La2SiO5) and lanthanum sorosilicate (La2Si2O7)

International Nuclear Information System (INIS)

Fukuda, Koichiro; Asaka, Toru; Uchida, Tomohiro

2012-01-01

Four types of powder specimens of La 9.33 (SiO 4 ) 6 O 2 (space group P6 3 /m and Z=1), La 9.33+2x (SiO 4 ) 6 O 2+3x with 0.06≤x≤0.13 (P6 3 /m and Z=1), La 2 SiO 5 (P2 1 /c and Z=4) and La 2 Si 2 O 7 (P2 1 /c and Z=4) were examined by high-temperature X-ray powder diffractometry to determine the changes in unit-cell dimensions up to 1473 K. The anisotropy of thermal expansion was demonstrated for the former two crystals to clarify the thermal behaviors of the highly c-axis-oriented polycrystals. With La 9.33 (SiO 4 ) 6 O 2 , the linear expansion coefficient of the a-axis (α a ) was 4.8×10 −6 K −1 and that of the c-axis (α c ) was 1.8×10 −6 K −1 in the temperature range from 298 to 1473 K. The α a - and α c -values of La 9.33+2x (SiO 4 ) 6 O 2+3x (0.06≤x≤0.13) were, respectively, 5.9×10 −6 K −1 and 2.3×10 −6 K −1 . The coefficients of mean linear thermal expansion were 4.9×10 −6 K −1 for La 2 SiO 5 and 6.0×10 −6 K −1 for La 2 Si 2 O 7 , which describe the thermal expansion behaviors of the randomly grain-oriented polycrystalline materials. - Graphical abstarct: Temperature dependence of the coefficients of thermal expansion (CTE). The linear CTE along the a-axes for La 9.33 (SiO 4 ) 6 O 2 and La 9.33+2x (SiO 4 ) 6 O 2+3x with 0.06≤x≤0.13. The mean linear CTE for La 2 SiO 5 and La 2 Si 2 O 7 . Highlights: ► We examined the thermal expansion of La 9.33+2x (SiO 4 ) 6 O 2+3x (x=0 and 0.06≤x≤0.13), La 2 SiO 5 and La 2 Si 2 O 7 ► Unit-cell dimensions were determined up to 1473 K by high-temperature X-ray diffraction ► Anisotropic expansion was clarified for La 9.33+2x (SiO 4 ) 6 O 2+3x (x=0 and 0.06≤x≤0.13) ► Mean linear thermal expansion was determined for La 2 SiO 5 and La 2 Si 2 O 7.

Linear electro-optical properties of tetragonal BaTiO 3

Indian Academy of Sciences (India)

Linear optical susceptibility and clamped linear electro-optical tensor coefficients of tetragonal BaTiO3 are calculated using a formalism based on bond charge theory. Calculated values are in close agreement with experimental data. The covalent Ti–O bonds constituting distorted TiO6 octahedral groups are found to be ...

Indolenine meso-substituted dibenzotetraaza[14]annulene and its coordination chemistry toward the transition metal ions Mn(III), Fe(III), Co(II), Ni(II), Cu(II), and Pd(II).

Science.gov (United States)

Khaledi, Hamid; Olmstead, Marilyn M; Ali, Hapipah Mohd; Thomas, Noel F

2013-02-18

A new dibenzotetraaza[14]annulene bearing two 3,3-dimethylindolenine fragments at the meso positions (LH(2)), has been synthesized through a nontemplate method. X-ray crystallography shows that the whole molecule is planar. The basicity of the indolenine ring permits the macrocycle to be protonated external to the core and form LH(4)(2+)·2Cl(-). Yet another structural modification having strong C-H···π interactions was found in the chloroform solvate of LH(2). The latter two modifications are accompanied by a degree of nonplanar distortion. The antiaromatic core of the macrocycle can accommodate a number of metal ions, Mn(III), Fe(III), Co(II), Ni(II) and Cu(II), to form complexes of [Mn(L)Br], [Mn(L)Cl], [Fe(LH(2))Cl(2)](+)·Cl(-), [Co(L)], [Ni(L)], and [Cu(L)]. In addition, the reaction of LH(2) with the larger Pd(II) ion leads to the formation of [Pd(2)(LH(2))(2)(OAc)(4)] wherein the macrocycle acts as a semiflexible ditopic ligand to coordinate pairs of metal ions via its indolenine N atoms into dinuclear metallocycles. The compounds LH(2), [Co(L)], and [Ni(L)] are isostructural and feature close π-stacking as well as linear chain arrangements in the case of the metal complexes. Variable temperature magnetic susceptibility measurements showed thermally induced paramagnetism in [Ni(L)].

Mixed Alkali Effect in (40-x)K2O-xLi2O-10Na2O-50B2O3 Glasses - Physical and Optical Absorption Studies

Science.gov (United States)

Samee, M. A.; Ahmmad, Shaikh Kareem; Taqiullah, Sair. Md.; Edukondalu, A.; Bale, Shashidhar; Rahman, Syed

So far only a handful of publications have been concerned with the study of the mixed alkali effect in borate glasses containing three types of alkali ions. In the present work, the mixed alkali effect (MAE) has been investigated in the glass system (40-x) K2O-x Li2O -10Na2O-50B2O3.(0≤x≤40 mol%) through density and modulated DSC studies. The density and glass transition temperature of the present glasses varies non-linearly exhibiting mixed alkali effect. We report the mixed alkali effect in the present glasses through optical properties. From the absorption edge studies, the various values of optical band gap (Eo) and Urbach energy (ΔE) have been evaluated. The values of Eo and ΔE show non-linear behavior with compositional parameter showing the mixed alkali effect. The band gap energy based average electronic polarizability of oxide ions αO2-(Eo), optical basicity A(Eo), and Yamashita-Kurosawa’s interaction parameter A(Eo) have been examined to check the correlations among them and bonding character. Based on good correlation among electronic polarizability of oxide ions, optical basicity and interaction parameter, the present K2O- Li2O-Na2O-B2O3 glasses are classified as normal ionic (basic) oxides.

Detection of nicotine based on molecularly imprinted TiO{sub 2}-modified electrodes

Energy Technology Data Exchange (ETDEWEB)

Wu, C.-T.; Chen, P.-Y.; Chen, J.-G.; Suryanarayanan, Vembu [Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Ho, K.-C. [Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan (China); Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)], E-mail: kcho@ntu.edu.tw

2009-02-02

Amperometric detection of nicotine (NIC) was carried out on a titanium dioxide (TiO{sub 2})/poly(3,4-ethylenedioxythiophene) (PEDOT)-modified electrode by a molecular imprinting technique. In order to improve the conductivity of the substrate, PEDOT was coated onto the sintered electrode by in situ electrochemical polymerization of the monomer. The sensing potential of the NIC-imprinted TiO{sub 2} electrode (ITO/TiO{sub 2}[NIC]/PEDOT) in a phosphate-buffered saline (PBS) solution (pH 7.4) containing 0.1 M KCl was determined to be 0.88 V (vs. Ag/AgCl/saturated KCl). The linear detection range for NIC oxidation on the so-called ITO/TiO{sub 2}[NIC]/PEDOT electrode was 0-5 mM, with a sensitivity and limit of detection of 31.35 {mu}A mM{sup -1} cm{sup -2} and 4.9 {mu}M, respectively. When comparing with the performance of the non-imprinted one, the sensitivity ratio was about 1.24. The sensitivity enhancement was attributed to the increase in the electroactive area of the imprinted electrode. The at-rest stability of the ITO/TiO{sub 2}[NIC]/PEDOT electrode was tested over a period of 3 days. The current response remained about 85% of its initial value at the end of 2 days. The ITO/TiO{sub 2}[NIC]/PEDOT electrode showed reasonably good selectivity in distinguishing NIC from its major interferent, (-)-cotinine (COT). Moreover, scanning electrochemical microscopy (SECM) was employed to elucidate the surface morphology of the imprinted and non-imprinted electrodes using Fe(CN){sub 6}{sup 3-}/Fe(CN){sub 6}{sup 4-} as a redox probe on a platinum tip. The imprinted electrode was further characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR)

Modelos lineares e não lineares inteiros para problemas da mochila bidimensional restrita a 2 estágios Linear and nonlinear integer models for constrained two-stage two-dimensional knapsack problems

Directory of Open Access Journals (Sweden)

Horacio Hideki Yanasse

2013-01-01

Full Text Available Neste trabalho revemos alguns modelos lineares e não lineares inteiros para gerar padrões de corte bidimensionais guilhotinados de 2 estágios, incluindo os casos exato e não exato e restrito e irrestrito. Esses problemas são casos particulares do problema da mochila bidimensional. Apresentamos também novos modelos para gerar esses padrões de corte, baseados em adaptações ou extensões de modelos para gerar padrões de corte bidimensionais restritos 1-grupo. Padrões 2 estágios aparecem em diferentes processos de corte, como, por exemplo, em indústrias de móveis e de chapas de madeira. Os modelos são úteis para a pesquisa e o desenvolvimento de métodos de solução mais eficientes, explorando estruturas particulares, a decomposição do modelo, relaxações do modelo etc. Eles também são úteis para a avaliação do desempenho de heurísticas, já que permitem (pelo menos para problemas de tamanho moderado uma estimativa do gap de otimalidade de soluções obtidas por heurísticas. Para ilustrar a aplicação dos modelos, analisamos os resultados de alguns experimentos computacionais com exemplos da literatura e outros gerados aleatoriamente. Os resultados foram produzidos usando um software comercial conhecido e mostram que o esforço computacional necessário para resolver os modelos pode ser bastante diferente.In this work we review some linear and nonlinear integer models to generate two stage two-dimensional guillotine cutting patterns, including the constrained, non constrained, exact and non exact cases. These problems are particular cases of the two dimensional knapsack problems. We also present new models to generate these cutting patterns, based on adaptations and extensions of models that generate one-group constrained two dimensional cutting patterns. Two stage patterns arise in different cutting processes like, for instance, in the furniture industry and wooden hardboards. The models are useful for the research and

Minimizing End-to-End Interference in I/O Stacks Spanning Shared Multi-Level Buffer Caches

Science.gov (United States)

Patrick, Christina M.

2011-01-01

This thesis presents an end-to-end interference minimizing uniquely designed high performance I/O stack that spans multi-level shared buffer cache hierarchies accessing shared I/O servers to deliver a seamless high performance I/O stack. In this thesis, I show that I can build a superior I/O stack which minimizes the inter-application interference…

Ajuste de modelos estocásticos lineares e não-lineares para a descrição do perfil longitudinal de árvores Fitting linear and nonlinear stochastic models to describe longitudinal tree profile

Directory of Open Access Journals (Sweden)

Leonardo Machado Pires

2007-10-01

Full Text Available Os modelos polinomiais são mais difundidos no meio florestal brasileiro na descrição do perfil de árvores devido à sua facilidade de ajuste e precisão. O mesmo não ocorre com os modelos não-lineares, os quais possuem maior dificuldade de ajuste. Dentre os modelos não-lineares clássicos, na descrição do perfil, podem-se citar o de Gompertz, o Logístico e o de Weibull. Portanto, este estudo visou comparar os modelos lineares e não lineares para a descrição do perfil de árvores. As medidas de comparação foram o coeficiente de determinação (R², o erro-padrão residual (s yx, o coeficiente de determinação corrigido (R²ajustado, o gráfico dos resíduos e a facilidade de ajuste. Os resultados ressaltaram que, dentre os modelos não-lineares, o que obteve melhor desempenho, de forma geral, foi o modelo Logístico, apesar de o modelo de Gompertz ser melhor em termos de erro-padrão residual. Nos modelos lineares, o polinômio proposto por Pires & Calegario foi superior aos demais. Ao comparar os modelos não-lineares com os lineares, o modelo Logístico foi melhor em razão, principalmente, do fato de o comportamento dos dados ser não-linear, à baixa correlação entre os parâmetros e à fácil interpretação deles, facilitando a convergência e o ajuste.Polynomial models are most commonly used in Brazilian forestry for taper modeling due to its straightforwardly fitting and precision. The use of nonlinear regression classic models, like Gompertz, Logistic and Weibull, is not very common in Brazil. Therefore, this study aimed to verify the best nonlinear and linear models, and among these the best model to describe the longitudinal tree profile. The comparison measures were: R², syx, R²adjusted, residual graphics and fitting convergence. The results pointed out that among the non-linear models the best behavior, in general, was given by the Logistic model, although the Gompertz model was superior compared with the Weibull

Mechanism of Selenite Removal by a Mixed Adsorbent Based on Fe–Mn Hydrous Oxides Studied Using X-ray Absorption Spectroscopy

KAUST Repository

Chubar, Natalia

2014-11-18

© 2014 American Chemical Society. Selenium cycling in the environment is greatly controlled by various minerals, including Mn and Fe hydrous oxides. At the same time, such hydrous oxides are the main inorganic ion exchangers suitable (on the basis of their chemical nature) to sorb (toxic) anions, separating them from water solutions. The mechanism of selenite adsorption by the new mixed adsorbent composed of a few (amorphous and crystalline) phases [maghemite, MnCO3, and X-ray amorphous Fe(III) and Mn(III) hydrous oxides] was studied by extended X-ray absorption fine structure (EXAFS) spectroscopy [supported by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data]. The complexity of the porous adsorbent, especially the presence of the amorphous phases of Fe(III) and Mn(III) hydrous oxides, is the main reason for its high selenite removal performance demonstrated by batch and column adsorption studies shown in the previous work. Selenite was bound to the material via inner-sphere complexation (via oxygen) to the adsorption sites of the amorphous Fe(III) and Mn(III) oxides. This anion was attracted via bidentate binuclear corner-sharing coordination between SeO3 2- trigonal pyramids and both FeO6 and MnO6 octahedra; however, the adsorption sites of Fe(III) hydrous oxides played a leading role in selenite removal. The contribution of the adsorption sites of Mn(III) oxide increased as the pH decreased from 8 to 6. Because most minerals have a complex structure (they are seldom based on individual substances) of various crystallinity, this work is equally relevant to environmental science and environmental technology because it shows how various solid phases control cycling of chemical elements in the environment.

Mechanism of Selenite Removal by a Mixed Adsorbent Based on Fe–Mn Hydrous Oxides Studied Using X-ray Absorption Spectroscopy

KAUST Repository

Chubar, Natalia; Gerda, Vasyl; Szlachta, Małgorzata

2014-01-01

© 2014 American Chemical Society. Selenium cycling in the environment is greatly controlled by various minerals, including Mn and Fe hydrous oxides. At the same time, such hydrous oxides are the main inorganic ion exchangers suitable (on the basis of their chemical nature) to sorb (toxic) anions, separating them from water solutions. The mechanism of selenite adsorption by the new mixed adsorbent composed of a few (amorphous and crystalline) phases [maghemite, MnCO3, and X-ray amorphous Fe(III) and Mn(III) hydrous oxides] was studied by extended X-ray absorption fine structure (EXAFS) spectroscopy [supported by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data]. The complexity of the porous adsorbent, especially the presence of the amorphous phases of Fe(III) and Mn(III) hydrous oxides, is the main reason for its high selenite removal performance demonstrated by batch and column adsorption studies shown in the previous work. Selenite was bound to the material via inner-sphere complexation (via oxygen) to the adsorption sites of the amorphous Fe(III) and Mn(III) oxides. This anion was attracted via bidentate binuclear corner-sharing coordination between SeO3 2- trigonal pyramids and both FeO6 and MnO6 octahedra; however, the adsorption sites of Fe(III) hydrous oxides played a leading role in selenite removal. The contribution of the adsorption sites of Mn(III) oxide increased as the pH decreased from 8 to 6. Because most minerals have a complex structure (they are seldom based on individual substances) of various crystallinity, this work is equally relevant to environmental science and environmental technology because it shows how various solid phases control cycling of chemical elements in the environment.

Studies of the local distortions and the EPR parameters for Cu{sup 2+} in xLi{sub 2}O-(30-x)Na{sub 2}O-69.5B{sub 2}O glasses

Energy Technology Data Exchange (ETDEWEB)

Ding, Chang-Chun; Wu, Shao-Yi; Kuang, Min-Quan; Hu, Xian-Fen; Li, Guo-Liang [Univ. of Electronic Science and Technology of China, Chengdu (China). Dept. of Applied Physics

2016-07-01

The local distortions and electron paramagnetic resonance (EPR) parameters for Cu2+ in lithium sodium borate (LNB) glasses xLi{sub 2}O.(30-x).Na{sub 2}O.69.5B{sub 2}O{sub 3} (5 ≤ x ≤ 25 mol%) are theoretically studied at various concentrations x in a consistent way. Owing to the Jahn-Teller effect, the [CuO{sub 6}]{sup 10-} clusters are found to experience the significant tetragonal elongations of 16% along C{sub 4} axis. Despite the nearly unchanging observed g factors, measured d-d transition band (or cubic field parameter Dq) shows remarkable linear increases with concentration x, whose influences on g {sub parallel} and g {sub perpendicular} {sub to} are actually cancelled by the linearly increasing covalency factor N and relative elongation ratio η with x. The almost unvarying hyperfine structure constants are attributed to the fact that the influences of the linearly increasing N and the linearly decreasing core polarisation constant κ largely cancel one another. The microscopic mechanisms of the above concentration dependences for these quantities are illustrated from mixed alkali effect (modification of B{sub 2}O{sub 3} network by transforming some BO{sub 3} units into BO{sub 4} ones with variations in modifier Li{sub 2}O concentration).

Synthesis, characterization and thermal expansion studies on ThO2-SmO1.5 solid solutions

International Nuclear Information System (INIS)

Panneerselvam, G.; Antony, M.P.

2008-01-01

Full text: A highly homogeneous Th 1-x Sm x O 2 ; 0 ≤ x ≤ 0.8 solid solutions were synthesized by co-precipitation technique and the co-precipitated samples were sintered at 1473 K. Compositions of the solid solutions were characterized by standard wet-chemical analysis. X-ray diffraction measurements were performed in the sintered pellets for structural analysis, lattice parameter calculation and determination of solid solubility of SmO 1.5 in ThO 2 matrix. Bulk and theoretical densities of solid solutions were also determined. A fluorite structure was observed for ThO 2 -SmO 1.5 solid solutions with 0-55.2 mol % SmO 1.5 . Their thermal expansion coefficients were measured using high temperature X-ray diffraction technique. The mean linear thermal expansivity, αm for ThO 2 -SmO 1.5 solid solutions containing 17.9, 41.7 and 52.0 mole percent of SmO 1.5 were determined in the temperature range 298 to 2000 K for the first time. The mean linear thermal expansion coefficients for ThO 2 -SmO 1.5 solid solutions are 10.47x10 -6 K -1 , 11.16x10 -6 K -1 and 11.45x10 -6 K -1 , respectively. The percentage linear thermal expansion in this temperature range, for ThO 2 -SmO 1.5 solid solutions containing 17.9, 41.7 and 52.0 mol % SmO 1.5 are 1.82,1.94 and 1.99 respectively. It is suggested that the solid solutions are stable up to 2000 K. It is also suggested that the effect and nature of the dopant are the important parameters influenced in the thermal expansion of the ThO 2

Linearity enhancement design of a 16-channel low-noise front-end readout ASIC for CdZnTe detectors

International Nuclear Information System (INIS)

Zeng, Huiming; Wei, Tingcun; Wang, Jia

2017-01-01

A 16-channel front-end readout application-specific integrated circuit (ASIC) with linearity enhancement design for cadmium zinc telluride (CdZnTe) detectors is presented in this paper. The resistors in the slow shaper are realized using a high-Z circuit to obtain constant resistance value instead of using only a metal–oxide–semiconductor (MOS) transistor, thus the shaping time of the slow shaper can be kept constant for different amounts of input energies. As a result, the linearity of conversion gain is improved significantly. The ASIC was designed and fabricated in a 0.35 µm CMOS process with a die size of 2.60 mm×3.53 mm. The tested results show that a typical channel provides an equivalent noise charge (ENC) of 109.7e − +16.3e − /pF with a power consumption of 4 mW and achieves a conversion gain of 87 mV/fC with a nonlinearity of <0.4%. The linearity of conversion gain is improved by at least 86.6% as compared with the traditional approaches using the same front-end readout architecture and manufacture process. Moreover, the inconsistency among channels is <0.3%. An energy resolution of 2.975 keV (FWHM) for gamma rays of 59.5 keV was measured by connecting the ASIC to a 5 mm×5 mm ×2 mm CdZnTe detector at room temperature. The front-end readout ASIC presented in this paper achieves an outstanding linearity performance without compromising the noise, power consumption, and chip size performances.

Linearity enhancement design of a 16-channel low-noise front-end readout ASIC for CdZnTe detectors

Energy Technology Data Exchange (ETDEWEB)

Zeng, Huiming; Wei, Tingcun, E-mail: weitc@nwpu.edu.cn; Wang, Jia

2017-03-01

A 16-channel front-end readout application-specific integrated circuit (ASIC) with linearity enhancement design for cadmium zinc telluride (CdZnTe) detectors is presented in this paper. The resistors in the slow shaper are realized using a high-Z circuit to obtain constant resistance value instead of using only a metal–oxide–semiconductor (MOS) transistor, thus the shaping time of the slow shaper can be kept constant for different amounts of input energies. As a result, the linearity of conversion gain is improved significantly. The ASIC was designed and fabricated in a 0.35 µm CMOS process with a die size of 2.60 mm×3.53 mm. The tested results show that a typical channel provides an equivalent noise charge (ENC) of 109.7e{sup −}+16.3e{sup −}/pF with a power consumption of 4 mW and achieves a conversion gain of 87 mV/fC with a nonlinearity of <0.4%. The linearity of conversion gain is improved by at least 86.6% as compared with the traditional approaches using the same front-end readout architecture and manufacture process. Moreover, the inconsistency among channels is <0.3%. An energy resolution of 2.975 keV (FWHM) for gamma rays of 59.5 keV was measured by connecting the ASIC to a 5 mm×5 mm ×2 mm CdZnTe detector at room temperature. The front-end readout ASIC presented in this paper achieves an outstanding linearity performance without compromising the noise, power consumption, and chip size performances.

Effect of Ga2O3 addition on the properties of Y2O3-doped AlN ceramics

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Shin H.

2015-01-01

Full Text Available Effect Ga2O3 addition on the densification and properties of Y2O3-doped AlN ceramics was investigated under the constraint of total sintering additives (Y2O3 and Ga2O3 of 4.5 wt%. Ga was detected in the AlN grain as well as the grain boundary phases. YAlO3 and Y4Al2O9 were observed as the secondary crystalline phases in all of the investigated compositions. As the substitution of Ga2O3 for Y2O3 increased, the quantity of the Y4Al2O9 phase decreased while that of YAlO3 was more or less similar. Neither additional secondary phases was identified, nor was the sinterability inhibited by the Ga2O3 addition; the linear shrinkage and apparent density were above 20 percent and 3.34-3.37 g/cm3, respectively. However, the optical reflectance and the elastic modulus generally decreased whereas the Poisson ratio increased significantly. The dielectric constant and the loss tangent of 4.0Y2O3-0.5Ga2O3-95.5Y2O3 at the resonant frequency of 8.22 GHz were 8.63 and 0.003, respectively.

The Effects of Anchor Groups on (1) TiO2-Catalyzed Photooxidation and (2) Linker-Assisted Assembly on TiO2

Science.gov (United States)

Anderson, Ian Mark

Quantum dot-sensitized solar cells (QDSSCs) are a popular target for research due to their potential for highly efficient, easily tuned absorption. Typically, light is absorbed by quantum dots attached to a semiconductor substrate, such as TiO2, via bifunctional linker molecules. This research aims to create a patterned monolayer of linker molecules on a TiO2 film, which would in turn allow the attachment of a patterned layer of quantum dots. One method for the creation of a patterned monolayer is the functionalization of a TiO2 film with a linker molecule, followed by illumination with a laser at 355 nm. This initiates a TiO 2-catalyzed oxidation reaction, causing loss of surface coverage. A second linker molecule can then be adsorbed onto the TiO2 surface in the illuminated area. Towards that end, the behaviors of carboxylic and phosphonic acids adsorbed on TiO2 have been studied. TiO2 films were functionalized by immersion in solutions a single adsorbate and surface coverage was determined by IR spectroscopy. It is shown that phosphonic acids attain higher surface coverage than carboxylic acids, and will displace them from TiO2 when in a polar solvent. Alkyl chain lengths, which can influence stabilities of monolayers, are shown not to have an effect on this relationship. Equilibrium binding data for the adsorption of n-hexadecanoic acid to TiO2 from a THF solution are presented. It is shown that solvent polarity can affect monolayer stability; carboxylates and phosphonates undergo more desorption into polar solvents than nonpolar. Through illumination, it was possible to remove nearly all adsorbed linkers from TiO2. However, the illuminated areas were found not to be receptive to attachment by a second adsorbate. A possible reason for this behavior is presented. I also report on the synthesis and characterization of a straight-chain, thiol-terminated phosphonic acid. Initial experiments involving monolayer formation and quantum dot attachment are presented

Crystallization of rare earth germanates in the K2O-Ln2O3-GeO2-H2O at 280 deg C

International Nuclear Information System (INIS)

Panasenko, E.B.; Begunova, R.G.; Sklokina, N.F.

1980-01-01

Crystallization of rare earth germanates in potassium hydroxide solutions is studied at 280 deg C. Stability limits for different crystalline phases are established. Diorthogermanates Ln 2 O 3 x2GeO 3 (three structural modifications) are formed with all lanthanides except lanthanum. Germanates-apatites 7Ln 2 O 3 x9GeO 2 are characteristic for ''large'' lanthanides La-Nd. Alkali germanate of the composition 0.5 K 2 OxLn 2 O 3 xGeO 2 xnH 2 O is realized with the elements of the end of rare earth series, i.e., Tm-Lu. Some properties of the germanates synthesized are considered [ru

Anisotropic pressure effects on the Kagome Cu3Bi(SeO3)2O2Cl metamagnet

Science.gov (United States)

Wu, H. C.; Tseng, W. J.; Yang, P. Y.; Chandrasekhar, K. D.; Berger, H.; Yang, H. D.

2017-07-01

The anisotropic spin-flip-induced multiferroic property of the Kagome single-crystal Cu3Bi(SeO3)2O2Cl was recently investigated. The doping effects on the structural and magnetic properties of Cu3Bi(Se1-x Te x O3)2O2Cl (0 ≤slant x≤slant 0.6) polycrystalline samples were studied to further explore and manipulate the metamagnetic spin-flip transition. With higher Te concentration, the lattice constants a and b exhibit a linear increase, whereas the lattice constant c gradually decreases, which indicates that the anisotropic expansion and compression effect is induced by Te substitution in the Se site. Subsequently, the antiferromagnetic transition (T N) shifts to a higher temperature, the critical field ({{H}\\text{c}} ) of the metamagnetic spin-flip transition increases, and the value of the saturation magnetisation ({{M}\\text{s}} ) diminishes. Meanwhile, the effects of isotropic expansion (with Br doping) and compression (with external pressure) do not show a clear influence on the spin-flip phenomena. Our results emphasise the introduction of anisotropic pressure in Cu3Bi(SeO3)2O2Cl, which modulates the magnetic interaction of Cu (I)-O1-Cu (I) and Cu (I)-O1-Cu (II) and, consequently, enhances the {{H}\\text{c}} of the spin-flip transition.

A wideband large dynamic range and high linearity RF front-end for U-band mobile DTV

International Nuclear Information System (INIS)

Liu Rongjiang; Liu Shengyou; Guo Guiliang; Cheng Xu; Yan Yuepeng

2013-01-01

A wideband large dynamic range and high linearity U-band RF front-end for mobile DTV is introduced, and includes a noise-cancelling low-noise amplifier (LNA), an RF programmable gain amplifier (RFPGA) and a current communicating passive mixer. The noise/distortion cancelling structure and RC post-distortion compensation are employed to improve the linearity of the LNA. An RFPGA with five stages provides large dynamic range and fine gain resolution. A simple resistor voltage network in the passive mixer decreases the gate bias voltage of the mixing transistor, and optimum linearity and symmetrical mixing is obtained at the same time. The RF front-end is implemented in a 0.25 μm CMOS process. Tests show that it achieves an IIP3 (third-order intercept point) of −17 dBm, a conversion gain of 39 dB, and a noise figure of 5.8 dB. The RFPGA achieves a dynamic range of −36.2 to 23.5 dB with a resolution of 0.32 dB. (semiconductor integrated circuits)

Optical properties of nanocrystalline potassium lithium niobate in the glass system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5).

Science.gov (United States)

Ahamad, M Niyaz; Varma, K B R

2009-08-01

Optically clear glasses of various compositions in the system (100-x) TeO2-x(1.5K2O-Li2O-2.5Nb2O5) (2 glasses comprising potassium lithium niobate (K3Li2Nb5O15) microcrystallites on the surface and nanocrystallites within the glass were obtained by controlled heat-treatment of the as-quenched glasses just above the glass transition temperature (T(g)). The optical transmission spectra of these glasses and glass-crystal composites of various compositions were recorded in the 200-2500 nm wavelength range. Various optical parameters such as optical band gap, Urbach energy, refractive index were determined. Second order optical non-linearity was established in the heat-treated samples by employing the Maker-Fringe method.

Analysis and design of a high-linearity receiver RF front-end with an improved 25%-duty-cycle LO generator for WCDMA/GSM applications

International Nuclear Information System (INIS)

Hu Song; Li Weinan; Huang Yumei; Hong Zhiliang

2012-01-01

A fully integrated receiver RF front-end that meets WCDMA/GSM system requirements is presented. It supports SAW-less operation for WCDMA. To improve the linearity in terms of both IP3 and IP2, the RF front-end is comprised of multiple-gated LNAs with capacitive desensitization, current-mode passive mixers with the proposed IP2 calibration circuit and reconfigurable Tow-Thomas-like biquad TIAs. A new power-saving multi-mode divider with low phase noise is proposed to provide the 4-phase 25%-duty-cycle LO. In addition, a constant-g m biasing with a non-chip resistor is adopted to make the conversion gain invulnerable to the process and temperature variations of the transimpedance. This RF front-end is integrated in a receiver with an on-chip frequency synthesizer in 0.13 μm CMOS. The measurement results show that owing to this high-linearity RF front-end, the receiver achieves −6 dBm IIP3 and better than +60 dBm IIP2 for all modes and bands. (semiconductor integrated circuits)

Mechanistic and Kinetic Study of Singlet O2 Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry.

Science.gov (United States)

Liu, Fangwei; Lu, Wenchao; Yin, Xunlong; Liu, Jianbo

2016-01-01

We report a reaction apparatus developed to monitor singlet oxygen ((1)O2) reactions in solution using on-line ESI mass spectrometry and spectroscopy measurements. (1)O2 was generated in the gas phase by the reaction of H2O2 with Cl2, detected by its emission at 1270 nm, and bubbled into aqueous solution continuously. (1)O2 concentrations in solution were linearly related to the emission intensities of airborne (1)O2, and their absolute scales were established based on a calibration using 9,10-anthracene dipropionate dianion as an (1)O2 trapping agent. Products from (1)O2 oxidation were monitored by UV-Vis absorption and positive/negative ESI mass spectra, and product structures were elucidated using collision-induced dissociation-tandem mass spectrometry. To suppress electrical discharge in negative ESI of aqueous solution, methanol was added to electrospray via in-spray solution mixing using theta-glass ESI emitters. Capitalizing on this apparatus, the reaction of (1)O2 with methionine was investigated. We have identified methionine oxidation intermediates and products at different pH, and measured reaction rate constants. (1)O2 oxidation of methionine is mediated by persulfoxide in both acidic and basic solutions. Persulfoxide continues to react with another methionine, yielding methionine sulfoxide as end-product albeit with a much lower reaction rate in basic solution. Density functional theory was used to explore reaction potential energy surfaces and establish kinetic models, with solvation effects simulated using the polarized continuum model. Combined with our previous study of gas-phase methionine ions with (1)O2, evolution of methionine oxidation pathways at different ionization states and in different media is described.

Linear series of stellar models. Pt. 4. Helium-carbon stars of 3.5Msub(o) and 1Msub(o)

International Nuclear Information System (INIS)

Kozlowski, M.; Paczynski, B.; Popova, K.

1973-01-01

One linear series of models for a star of 3.5Msub(o) and two linear series of models for a star of 1Msub(o) are constructed. Models consist of helium rich envelopes (Y = 0.97, Z = 0.03) and pure carbon cores, and they have a rectangular helium profile, Y(Msub(r)). The linear series for a star of 3.5Msub(o) begins on the normal branch of the helium main sequence and terminates on the normal branch of the carbon main sequence. This series has eight turning points at which the core mass attains a local extremum. One of the two linear series for a star of 1Msub(o) begins on the normal branch of the helium main sequence, terminates on the high density branch of the helium main sequence, and has one turning point. The second linear series for a star of 1Msub(o) begins on the normal branch of the carbon main sequence, terminates on the high density branch of the carbon main sequence, and has three turning points. Two such linear series may have a common bifurcation point for a star of about 1.26Msub(o). (author)

Paralelização e comparação de métodos iterativos na solução de sistemas lineares grandes e esparsos

Directory of Open Access Journals (Sweden)

Lauro Cássio Martins de Paula

2013-11-01

Full Text Available Apresenta-se neste trabalho uma comparação de desempenho computacional entre métodos iterativos utilizados para solução de sistemas lineares. O objetivo é mostrar que a utilização de processamento paralelo fornecido por uma Graphics Processing Unit (GPU pode ser viável, por viabilizar a solução rápida de sistemas de equações lineares, para que sistemas grandes e esparsos possam ser solucionados em um espaço curto de tempo. Para a validação do trabalho, utilizou-se uma GPU, por meio da arquitetura Compute Unified Device Architecture (CUDA, e comparou-se o desempenho computacional dos métodos iterativos de Jacobi, Gauss-Seidel, BiCGStab e BiCGStab(2 paralelizado na solução de sistemas lineares de tamanhos variados. Foi possível observar uma aceleração significativa nos testes com o método paralelizado, que se acentua consideravelmente na medida em que os sistemas aumentam. Os resultados mostraram que a aplicação de processamento paralelo em um método robusto e eficiente, tal como o BiCGStab(2, se torna muitas vezes indispensável, para que simulações sejam realizadas com qualidade e em tempo não proibitivo.Palavras-chave: CUDA. GPU. BiCGStab(2.Parallelization and comparison of interative methods in solving large and sparse linear systemsAbstractThis paper presents a computational performance comparison between some iterative methods used for linear systems solution. The goal is to show that the use of parallel processing provided by a Graphics Processing Unit (GPU may be more feasible, for making possible the fast solution of linear equations systems in order that complex and sparse problems can be solved in a short time. To validate the paper a GPU through the NVIDIA's Compute Unified Device Architecture (CUDA was employed and the computational performance was compared with Jacobi, Gauss-Seidel, BiCGStab iterative methods and BiCGStab(2 parallelized in the solution of linear systems of varying sizes. There was a

Quantization of O(N) non-linear sigma models as the stochastic motion on Ssup(N-1)

International Nuclear Information System (INIS)

Aldazabal, G.; Parga, N.

1983-09-01

We obtain the Langevin equations for the stochastic quantization of the O(N) non-linear sigma model by studying the random (Gaussian) motion on the sphere Ssup(N-1). We prove the equivalence of this procedure with a different one where the random forces are elements of the O(N) algebra. A proof that our approach yields in the equilibrium regime the quantum field theory is also given. (author)

Studies on the retention mechanism of solutes in hydrophilic interaction chromatography using stoichiometric displacement theory I. The linear relationship of lgk' vs. lg[H2O].

Science.gov (United States)

Wang, Fei; Yang, Fan; Tian, Yang; Liu, Jiawei; Shen, Jiwei; Bai, Quan

2018-01-01

A stoichiometric displacement model for retention (SDM-R) of small solutes and proteins based on hydrophilic interaction chromatography (HILIC) was presented. A linear equation that related the logarithm of the capacity factor of the solute to the logarithm of the concentration of water in the mobile phase was derived. The stoichiometric displacement parameters, Z (the number of water molecules required to displace a solute from ligands) and lgI (containing a number of constants that relate to the affinity of solute to the ligands) could be obtained from the slope and the intercept of the linear plots of lgk' vs. lg[H 2 O]. The retention behaviors and retention mechanism of 15 kinds of small solutes and 6 kinds of proteins on 5 kinds HILIC columns with different ligands were investigated with SDM-R in typical range of water concentration in mobile phase. A good linear relationship between lgk' and lg[H 2 O] demonstrated that the most rational retention mechanism of solute in HILIC was a stoichiometric displacement process between solute and solvent molecules with water as displacing agents, which was not only valid for small solutes, but also could be used to explain the retention mechanism of biopolymers in HILIC. Comparing with the partition and adsorption models in HILIC, SDM-R was superior to them. Copyright © 2017 Elsevier B.V. All rights reserved.

A GEM-TPC prototype with low-Noise highly integrated front-end electronics for linear collider studies

CERN Document Server

Kappler, Steffen; Kaminski, Jochen; Ledermann, Bernhard; Müller, Thomas; Ronan, Michael T; Ropelewski, Leszek; Sauli, Fabio; Settles, Ronald

2004-01-01

Connected to the linear collider project, studies on the readout of time projection chambers (TPCs) based on the gas electron multiplier (GEM) are ongoing. Higher granularity and intrinsically suppressed ion feedback are the major advantages of this technology. After a short discussion of these issues, we present the design of a small and very flexible TPC prototype, whose cylindrical drift volume can be equipped with endcaps of different gas detector types. An endcap with multi-GEM readout is currently set up and successfully operated with a low-noise highly integrated front-end electronics. We discuss results of measurements with this system in high intensity particle beams at CERN, where 99.3 plus or minus 0.2% single-pad-row efficiency could be achieved at an effective gain of 2.5 multiplied by 10**3 only, and spatial resolutions down to 63 plus or minus 3 mum could be demonstrated. Finally, these results are extrapolated to the high magnetic field in a linear collider TPC. 5 Refs.

Simulating maize phenology as a function of air temperature with a linear and a nonlinear model Simulação da fenologia do milho em função da temperatura do ar por um modelo linear e um não linear

Directory of Open Access Journals (Sweden)

Nereu Augusto Streck

2008-04-01

Full Text Available The objective of this study was to adapt a nonlinear model (Wang and Engel - WE for simulating the phenology of maize (Zea mays L., and to evaluate this model and a linear one (thermal time, in order to predict developmental stages of a field-grown maize variety. A field experiment, during 2005/2006 and 2006/2007 was conducted in Santa Maria, RS, Brazil, in two growing seasons, with seven sowing dates each. Dates of emergence, silking, and physiological maturity of the maize variety BRS Missões were recorded in six replications in each sowing date. Data collected in 2005/2006 growing season were used to estimate the coefficients of the two models, and data collected in the 2006/2007 growing season were used as independent data set for model evaluations. The nonlinear WE model accurately predicted the date of silking and physiological maturity, and had a lower root mean square error (RMSE than the linear (thermal time model. The overall RMSE for silking and physiological maturity was 2.7 and 4.8 days with WE model, and 5.6 and 8.3 days with thermal time model, respectively.O objetivo deste trabalho foi adaptar um modelo não linear (Wang e Engel - WE, para simular a fenologia do milho (Zea mays L., e avaliar esse modelo e um modelo linear (soma térmica, para estimar os estágios de desenvolvimento de uma variedade de milho cultivada em campo. Um experimento de dois anos, com sete datas anuais de semeadura cada ano, foi conduzido em Santa Maria, RS, durante os anos agrícolas 2005/2006 e 2006/2007. Foram registradas as datas de emergência, espigamento e maturação fisiológica da variedade de milho BRS Missões, em seis repetições, em cada data de semeadura. Os dados coletados no ano agrícola 2005/2006 foram usados para estimar os coeficientes dos dois modelos, e os dados coletados no ano agrícola 2006/2007 foram usados como dados independentes para avaliar os modelos. O modelo não linear (WE estimou com precisão as datas de espigamento

Flux pinning by heavy-ion-irradiation induced linear defects in YBa2Cu3O7 epitaxial films

International Nuclear Information System (INIS)

Budhani, R.C.; Zhu, Y.; Suenaga, M.

1992-01-01

We report some transport measurements carried out to study flux pinning by heavy-ion-irradiation induced linear defects in Y 1 Ba 2 Cu 3 O 7 films. Our results show that in these in situ deposited films containing a large concentration of defects frozen-in at the time of film growth, a marginal enhancement in critical current density occurs when the density of linear defects 10 /cm 2 , and their diameter of the order of coherence length. This criterion is satisfied by Ag +21 ions. The damage due to Au +24 ions is much too severe to improve the J c

An Experimental Study on What Controls the Ratios of 18O/16O and 17O/16O of O2 During Microbial Respiration

Science.gov (United States)

Stolper, D. A.; Ward, B. B.; Fischer, W. W.; Bender, M. L.

2015-12-01

18O/16O and 17O/16O ratios of atmospheric and dissolved oceanic O2 are key biogeochemical tracers of total photosynthesis and respiration on global to local length scales and glacial/interglacial time scales (Luz et al., 1999). Critical to the use of these ratios as biogeochemical tracers is knowledge of how they are affected by production, consumption, and transport of O2. We present new measurements of O2 respiration by E. coli and N. oceanus, an ammonia oxidizing bacterium, to test three assumptions of isotopically enabled models of the O2 cycle: (i) laboratory-measured respiratory 18O/16O isotope effects (18α) of microorganisms are constant under all experimental and natural conditions (e.g., temperature and growth rate); (ii) the respiratory 'mass law' relationship between 18O/16O and 17O/16O [17α = (18α)β] is universal; and (iii) 18α and β for aerobic ammonia and organic carbon oxidation are identical. For E. coli, we find that both 18α and β are variable. From 37°C to 15°C, 18α varies linearly with temperature from 17 to 14‰, and β varies linearly from 0.513 to 0.508. 18α and β do not appear to vary with growth rate (as tested using different carbon sources). Both 18α and β are lower than previous observations for bacteria: 18α = 17-20‰ (Kiddon et al., 1993) and β = 0.515 (Luz and Barkan, 2005). We were able to simulate the observed temperature dependence of 18α and β using a model of respiration with two isotopically discriminating steps: O2 binding to cytochrome bo oxidase (the respiratory enzyme) and reduction of O2 to H2O. Finally, initial results on N. oceanus suggest it has similar values for 18α and β as previously studied aerobic bacteria that consume organic carbon, providing the first support for assumption (iii). Based on these results, isotopically constrained biogeochemical models of O2 cycling may need to consider a temperature dependence for 18α and β for microbial respiration. For example, these results may

Linear Chromosome-generating System of Agrobacterium tumefaciens C58: Protelomerase Generates and Protects Hairpin Ends

Energy Technology Data Exchange (ETDEWEB)

Huang, Wai Mun; DaGloria, Jeanne; Fox, Heather; Ruan, Qiurong; Tillou, John; Shi, Ke; Aihara, Hideki; Aron, John; Casjens, Sherwood (Utah); (UMM)

2012-09-05

Agrobacterium tumefaciens C58, the pathogenic bacteria that causes crown gall disease in plants, harbors one circular and one linear chromosome and two circular plasmids. The telomeres of its unusual linear chromosome are covalently closed hairpins. The circular and linear chromosomes co-segregate and are stably maintained in the organism. We have determined the sequence of the two ends of the linear chromosome thus completing the previously published genome sequence of A. tumefaciens C58. We found that the telomeres carry nearly identical 25-bp sequences at the hairpin ends that are related by dyad symmetry. We further showed that its Atu2523 gene encodes a protelomerase (resolvase) and that the purified enzyme can generate the linear chromosomal closed hairpin ends in a sequence-specific manner. Agrobacterium protelomerase, whose presence is apparently limited to biovar 1 strains, acts via a cleavage-and-religation mechanism by making a pair of transient staggered nicks invariably at 6-bp spacing as the reaction intermediate. The enzyme can be significantly shortened at both the N and C termini and still maintain its enzymatic activity. Although the full-length enzyme can uniquely bind to its product telomeres, the N-terminal truncations cannot. The target site can also be shortened from the native 50-bp inverted repeat to 26 bp; thus, the Agrobacterium hairpin-generating system represents the most compact activity of all hairpin linear chromosome- and plasmid-generating systems to date. The biochemical analyses of the protelomerase reactions further revealed that the tip of the hairpin telomere may be unusually polymorphically capable of accommodating any nucleotide.

Thermal expansion of UO2-Gd2O3 fuel pellets

International Nuclear Information System (INIS)

Une, Katsumi

1986-01-01

In recent years, more consideration has been given to the application of UO 2 -Gd 2 O 3 burnable poison fuel to LWRs in order to improve the core physics and to extend the burnup. It has been known that UO 2 forms a single phase cubic fluorite type solid solution with Gd 2 O 3 up to 20 - 30 wt.% above 1300 K. The addition of Gd 2 O 3 to UO 2 lattices changes the properties of the fuel pellets. The limited data on the thermal expansion of UO 2 -Gd 2 O 3 fuel exist, but those are inconsistent. UO 2 -Gd 2 O 3 fuel pellets were fabricated, and the linear thermal expansion of UO 2 and UO 2 -(5, 8 and 10 wt.%)Gd 2 O 3 fuel pellets was measured with a differential dilatometer over the temperature range of 298 - 1973 K. A sapphire rod of 6 mm diameter and 15.5 mm length was used as the reference material. After the preheating cycle, the measurement was performed in argon atmosphere. The results for UO 2 pellets showed excellent agreement with the data in literatures. The linear thermal expansion of UO 2 -Gd 2 O 3 fuel pellets showed the increase with increasing the Gd 2 O 3 content. Consideration must be given to this excessive expansion in the fuel design of UO 2 -Gd 2 O 3 pellets. The equations for the linear thermal expansion and density of UO 2 -Gd 2 O 3 fuel pellets were derived by the method of least squares. (Kako, I.)

Thermal expansion of Cr2xFe2-2xMo3O12, Al2xFe2-2xMo3O12 and Al2xCr2-2xMo3O12 solid solutions

International Nuclear Information System (INIS)

Ari, M.; Jardim, P.M.; Marinkovic, B.A.; Rizzo, F.; Ferreira, F.F.

2008-01-01

The transition temperature from monoclinic to orthorhombic and the thermal expansion of the orthorhombic phase were investigated for three systems of the family A 2 M 3 O 12 : Cr 2x Fe 2-2x Mo 3 O 12 , Al 2x Fe 2-2x Mo 3 O 12 and Al 2x Cr 2-2x Mo 3 O 12 . It was possible to obtain a single-phase solid solution in all studied samples (x=0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1). A linear relationship between the transition temperature and the fraction of A 3+ cations (x) was observed for each system. In all orthorhombic solid solutions studied here the observed thermal expansion was anisotropic. These anisotropic thermal expansion properties of crystallographic axes a, b and c result in a low positive or near-zero overall linear coefficient of thermal expansion (α l =α V /3). The relationship between the size of A 3+ cations in A 2 M 3 O 12 and the coefficient of thermal expansion is discussed. Near-zero thermal expansion of Cr 2 Mo 3 O 12 is explained by the behavior of Cr-O and Mo-O bond distances, Cr-Mo non-bond distances and Cr-O-Mo bond angles with increasing temperature, estimated by Rietveld analysis of synchrotron X-ray powder diffraction data. - Graphical abstract: In this figure, all published overall linear coefficients of thermal expansion for orthorhombic A 2 M 3 O 12 family obtained through diffraction methods as a function of A 3+ cation radii size, together with dilatometric results, are plotted. Our results indicate that Cr 2 Mo 3 O 12 does not exactly follow the established relationship

New Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 Quaternary Ceramics: Morphotropic Phase Boundary Design and Electrical Properties.

Science.gov (United States)

Luo, Nengneng; Zhang, Shujun; Li, Qiang; Xu, Chao; Yang, Zhanlue; Yan, Qingfeng; Zhang, Yiling; Shrout, Thomas R

2016-06-22

Four series of Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 (PMN-PIN-PZ-PT) quaternary ceramics with compositions located at the morphotropic phase boundary (MPB) regions were prepared. The MPBs of the multicomponent system were predicted using a linear combination rule and experimentally confirmed by X-ray powder diffraction and electrical measurement. The positions of MPBs in multicomponent systems were found in linear correlation with the tolerance factor and ionic radii of non-PT end-members. The phase structure, piezoelectric coefficient, electromechanical coupling coefficient, unipolar strains, and dielectric properties of as-prepared ceramics were systematically investigated. The largest d33s were obtained at S36.8, L37.4, M39.6, and N35.8, with the corresponding values of 580, 450, 420, and 530 pC/N, respectively, while the largest kps were found at S34.8, L37.4, M39.6, and N35.8, with the respective values of 0.54, 0.50, 0.47, and 0.53. The largest unipolar strain Smax and high-field piezoelectric strain coefficients d33* were also observed around the respective MPB regions. The rhombohedral-to-tetragonal phase transition temperature Trt increased with increasing PIN and PZ contents. Of particular importance is that high Trt of 140-197 °C was achieved in the M series with PZ and PIN contents being around 0.208 and 0.158, which will broaden the temperature usage range.

Linear-to-λ-Shape P-O-P Bond Transmutation in Polyphosphates with Infinite (PO3)∞ Chain.

Science.gov (United States)

Wang, Ying; Li, Lin; Han, Shujuan; Lei, Bing-Hua; Abudoureheman, Maierhaba; Yang, Zhihua; Pan, Shilie

2017-09-05

A new metal polyphosphate, α-CsBa 2 (PO 3 ) 5 , exhibiting the first example of a linear P-O-P bond angle in a one-dimensional (PO 3 ) ∞ chain has been reported. Interestingly, α → β phase transition occurs in CsBa 2 (PO 3 ) 5 along with the P-O-P bonds varying from linear to λ-shape, suggesting that α-CsBa 2 (PO 3 ) 5 with unfavorable linear P-O-P bonds is more stable at ambient temperature.

Energy-band alignment of (HfO2)x(Al2O3)1-x gate dielectrics deposited by atomic layer deposition on β-Ga2O3 (-201)

Science.gov (United States)

Yuan, Lei; Zhang, Hongpeng; Jia, Renxu; Guo, Lixin; Zhang, Yimen; Zhang, Yuming

2018-03-01

Energy band alignments between series band of Al-rich high-k materials (HfO2)x(Al2O3)1-x and β-Ga2O3 are investigated using X-Ray Photoelectron Spectroscopy (XPS). The results exhibit sufficient conduction band offsets (1.42-1.53 eV) in (HfO2)x(Al2O3)1-x/β-Ga2O3. In addition, it is also obtained that the value of Eg, △Ec, and △Ev for (HfO2)x(Al2O3)1-x/β-Ga2O3 change linearly with x, which can be expressed by 6.98-1.27x, 1.65-0.56x, and 0.48-0.70x, respectively. The higher dielectric constant and higher effective breakdown electric field of (HfO2)x(Al2O3)1-x compared with Al2O3, coupled with sufficient barrier height and lower gate leakage makes it a potential dielectric for high voltage β-Ga2O3 power MOSFET, and also provokes interest in further investigation of HfAlO/β-Ga2O3 interface properties.

Ab initio studies of O-2(-) (H2O)(n) and O-3(-) (H2O)(n) anionic molecular clusters, n

DEFF Research Database (Denmark)

Bork, Nicolai Christian; Kurten, T.; Enghoff, Martin Andreas Bødker

2011-01-01

that anionic O-2(-)(H2O)n and O-3(-)(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding....... Although clustering up to 12 H2O, we find that the O-2 and O-3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O-2(-) and O-3(-) speicies are thus accessible for further reactions. We consider the distributions of cluster sizes as function of altitude before...

Effect of TiO2 on thermal, structural and third-order nonlinear optical properties of Ca-La-B-O glass system

International Nuclear Information System (INIS)

Biswas, Kaushik; Sontakke, Atul D.; Annapurna, K.

2010-01-01

A series of calcium lanthanum metaborate glasses in the composition (wt%) of 23.88CaO-28.33La 2 O 3 -47.79B 2 O 3 modified with TiO 2 up to 20 wt% are prepared by a melt quenching technique to study the influence of TiO 2 on their thermal, structural, linear and nonlinear optical properties. The differential thermal analysis (DTA) studies have demonstrated significant effects due to the presence of TiO 2 on the glass forming ability and crystallization situations. The glass with 15 wt% TiO 2 has achieved a eutectic composition and also exhibited a better glass forming ability among the glasses studied. The FT-IR spectra of these glasses show mainly vibration modes corresponding to stretching of BO 3 trigonal, BO 4 tetrahedral units and of B-O-B bending bonds. At higher concentrations of TiO 2 , development of vibration band around 400 cm -1 has indicated the formation of TiO 6 structural units in the glass network. The red shift of optical absorption edge (UV cutoff) shows a monotonous decrease in direct and indirect optical band gap energies (E opt ) with an increase of TiO 2 content in the glasses based on their absorption spectra. The optical transparency of these glasses is found to be varied from 64 to 87% within the wavelength range 450-1100 nm depending on the TiO 2 content. Besides these studies, linear refractive indices, the nonlinear optical properties of these glasses have also been evaluated.

A 1.2-V CMOS front-end for LTE direct conversion SAW-less receiver

International Nuclear Information System (INIS)

Wang Riyan; Li Zhengping; Zhang Weifeng; Zeng Longyue; Huang Jiwei

2012-01-01

A CMOS RF front-end for the long-term evolution (LTE) direct conversion receiver is presented. With a low noise transconductance amplifier (LNA), current commutating passive mixer and transimpedance operational amplifier (TIA), the RF front-end structure enables high-integration, high linearity and simple frequency planning for LTE multi-band applications. Large variable gain is achieved using current-steering transconductance stages. A current commutating passive mixer with 25% duty-cycle LO improves gain, noise and linearity. A direct coupled current-input filter (DCF) is employed to suppress the out-of-band interferer. Fabricated in a 0.13-μm CMOS process, the RF front-end achieves a 45 dB conversion voltage gain, 2.7 dB NF, −7 dBm IIP3, and +60 dBm IIP2 with calibration from 2.3 to 2.7 GHz. The total RF front end with divider draws 40 mA from a single 1.2-V supply. (semiconductor integrated circuits)

RuO 2 nanoparticles supported on MnO 2 nanorods as high efficient bifunctional electrocatalyst of lithium-oxygen battery

Energy Technology Data Exchange (ETDEWEB)

Xu, Yue-Feng; Chen, Yuan; Xu, Gui-Liang; Zhang, Xiao-Ru; Chen, Zonghai; Li, Jun-Tao; Huang, Ling; Amine, Khalil; Sun, Shi-Gang

2016-10-01

RuO2 nanoparticles supported on MnO2 nanorods (denoted as np-RuO2/nr-MnO2) were synthesized via a two-step hydrothermal reaction. SEM and TEM images both illustrated that RuO2 nanoparticles are well dispersed on the surface of MnO2 nanorods in the as-prepared np-RuO2/nr-MnO2 material. Electrochemical results demonstrated that the np-RuO2/nr-MnO2 as oxygen cathode of Li-O-2 batteries could maintain a reversible capacity of 500 mA h g(-1) within 75 cycles at a rate of 50 mA g(-1), and a higher capacity of 4000 mA h g(-1) within 20 cycles at a rate as high as 200 mA g(-1). Moreover, the cell with the np-RuO2/nr-MnO2 catalyst presented much lower voltage polarization (about 0.58 V at a rate of 50 mA g(-1)) than that measured with only MnO2 nanorods during charge/discharge processes. The catalytic property of the np-RuO2/nr-MnO2 and MnO2 nanorods were further compared by conducting studies of using rotating disk electrode (RDE), chronoamperommetry and linear sweep voltammetry. The results illustrated that the np-RuO2/nr-MnO2 exhibited excellent bifunctional electrocatalytic activities towards both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Furthermore, in-situ high-energy X-ray diffraction was employed to trace evolution of species on the np-RuO2/nr-MnO2 cathode during the discharge processes. In-situ XRD patterns demonstrated the formation process of the discharge products that consisted of mainly Li2O2. Ex-situ SEM images were recorded to investigate the morphology and decomposition of the sphere-like Li2O2, which could be observed clearly after discharge process, while are decomposed almost after charge process. The excellent electrochemical performances of the np-RuO2/nr-MnO2 as cathode of Li-O-2 battery could be contributed to the excellent bifunctional electrocatalytic activities for both the ORR and OER, and to the one-dimensional structure which would benefit the diffusion of oxygen and the storage of Li2O2 in the discharge process of

Armazenamento refrigerado sob atmosfera modificada de pedúnculos de cajueiro-anão-precoce dos clones CCP-76, end-157, end-183 e end-189 Storage of cashew apples from dwarf clones CCP-76, end-157, end-183 and end-189 under refrigeration and modified atmosphere

Directory of Open Access Journals (Sweden)

Auricélia de Souza Morais

2002-12-01

Full Text Available Pedúnculos de clones de cajueiro-anão-precoce, dos clones CCP-76, END-157, END-183 e END-189, foram armazenados durante 25 dias, sob refrigeração associada a atmosfera modificada, com o objetivo de avaliar o efeito das condições atualmente utilizadas (5ºC e 85-90% de UR para conservação, transporte e comercialização de cajus in natura. Os pedúnculos foram avaliados a cada 5 dias quanto às seguintes características: perda de peso, firmeza, cor (antocianinas, sólidos e açúcares solúveis, acidez, pH, vitamina C e compostos fenólicos. O uso da refrigeração (5ºC e 85% U.R, associada a atmosfera modificada, proporcionou uma vida útil pós-colheita de 10 dias para o clone END 189, de até 15 dias para o clone END 157 e de até 25 dias para os clones CCP 76 e END 183. A temperatura de 5ºC não se mostrou adequada para armazenamento de pedúnculos de coloração mais intensa (END 157 e END 189 que a testemunha (CCP 76, provocando perda de cor (antocianinas a partir do 10º dia de armazenamento. A atmosfera modificada reduziu significativamente a perda de peso, favorecendo a aparência do produto para comercialização, independentemente do clone estudado.Apples or false fruits from early dwarf cashew clones CCP-76, END-157, END-183 and END-189 were stored for 25 days under refrigeration associated to modified atmosphere with the aim of evaluating the effect of the conditions presently adopted (5ºC and 85-90% RH for conservation, storage and commercialization of fresh cashew apples. The cashew apples were evaluated every 5 days for the following characteristics: weight loss, pulp firmness, color (anthocyannins, acidity, pH, soluble solids, vitamin C and phenolic contents. With the use of refrigeration and modified atmosphere it was possible to attain postharvest storage life of 10 days for clone END 189, 15 days for clone END 157 and up to 25 days for clones CCP 76 and END 183. It was found that 5ºC was not an adequate

An educational overview of the chemistry, biochemistry and therapeutic aspects of Mn porphyrins--From superoxide dismutation to H2O2-driven pathways.

Science.gov (United States)

Batinic-Haberle, Ines; Tovmasyan, Artak; Spasojevic, Ivan

2015-08-01

Most of the SOD mimics thus far developed belong to the classes of Mn-(MnPs) and Fe porphyrins(FePs), Mn(III) salens, Mn(II) cyclic polyamines and metal salts. Due to their remarkable stability we have predominantly explored Mn porphyrins, aiming initially at mimicking kinetics and thermodynamics of the catalysis of O2(-) dismutation by SOD enzymes. Several MnPs are of potency similar to SOD enzymes. The in vivo bioavailability and toxicity of MnPs have been addressed also. Numerous in vitro and in vivo studies indicate their impressive therapeutic efficacy. Increasing insight into complex cellular redox biology has been accompanied by increasing awareness of complex redox chemistry of MnPs. During O2(-) dismutation process, the most powerful Mn porphyrin-based SOD mimics reduce and oxidize O2(-) with close to identical rate constants. MnPs reduce and oxidize other reactive species also (none of them specific to MnPs), acting as reductants (antioxidant) and pro-oxidants. Distinction must be made between the type of reactions of MnPs and the favorable therapeutic effects we observe; the latter may be of either anti- or pro-oxidative nature. H2O2/MnP mediated oxidation of protein thiols and its impact on cellular transcription seems to dominate redox biology of MnPs. It has been thus far demonstrated that the ability of MnPs to catalyze O2(-) dismutation parallels all other reactivities (such as ONOO(-) reduction) and in turn their therapeutic efficacies. Assuming that all diseases have in common the perturbation of cellular redox environment, developing SOD mimics still seems to be the appropriate strategy for the design of potent redox-active therapeutics. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Microstructure, Thermal, Mechanical, and Dielectric Properties of BaO-CaO-Al2O3-B2O3-SiO2 Glass-Ceramics

Science.gov (United States)

Li, Bo; Bian, Haibo; Fang, Yi

2017-12-01

BaO-CaO-Al2O3-B2O3-SiO2 (BCABS) glass-ceramics were prepared via the method of controlled crystallization. The effect of CaO modification on the microstructure, phase evolution, as well as thermal, mechanical, and dielectric properties was investigated. XRD identified that quartz is the major crystal phase; cristobalite and bazirite are the minor crystal phases. Moreover, the increase of CaO could inhibit the phase transformation from quartz to cristobalite, but excessive CaO would increase the porosity of the ceramics. Additionally, with increasing the amount of CaO, the thermal expansion curve tends to be linear, and subsequently the CTE value decreases gradually, which is attributed to the decrease of cristobalite with high CTE and the formation of CaSiO3 with low CTE. The results indicated that a moderate amount of CaO helps attaining excellent mechanical, thermal, and dielectric properties, that is, the specimen with 9 wt% CaO sintered at 950 °C has a high CTE value (11.5 × 10-6/°C), a high flexural strength (165.7 MPa), and good dielectric properties (ɛr = 6.2, tanδ = 1.8 × 10-4, ρ = 4.6 × 1011 Ω•cm).

Ab initio studies of O2-(H2O)n and O3-(H2O)n anionic molecular clusters, n≤12

DEFF Research Database (Denmark)

Bork, Nicolai Christian; Kurtén, T.; Enghoff, Martin Andreas Bødker

2011-01-01

that anionic O2−(H2O)n and O3−(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding. Although...... clustering up to 12 H2O, we find that the O2 and O3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O2− and O3− speicies are thus accessible for further reactions. Finally, the thermodynamics of a few relevant cluster reactions are considered....

Viscosity and Structure of CaO-SiO2-P2O5-FetO System with Varying P2O5 and FeO Content

Science.gov (United States)

Diao, Jiang; Gu, Pan; Liu, De-Man; Jiang, Lu; Wang, Cong; Xie, Bing

2017-10-01

A rotary viscosimeter and Raman spectrum were employed to measure the viscosity and structural information of the CaO-SiO2-P2O5-FetO system at 1673 K. The experimental data have been compared with the calculated results using different viscosity models. It shows that the National Physical Laboratory (NPL) and Pal models fit the CaO-SiO2-P2O5-FeOt system better. With the P2O5 content increasing from 5% to 14%, the viscosity increases from 0.12 Pa s to 0.27 Pa s. With the FeO content increasing from 30% to 40%, the viscosity decreases from 0.21 Pa s to 0.12 Pa s. Increasing FeO content makes the complicated molten melts become simple, and increasing P2O5 content will complicate the molten melts. The linear relation between viscosity and structure parameter Q(Si + P) was obtained by regression analysis. The calculated viscosity by using the optimized NPL and Pal model are almost identical with the fitted values.

The Study on Thermal Expansion of Ceramic Composites with Addition of ZrW[2]O]8

OpenAIRE

Dedova, Elena Sergeevna; Shadrin, V. S.; Petrushina, M. Y.; Kulkov, Sergey Nikolaevich

2016-01-01

The studies on structure, phase composition and thermal properties of (Al[2]O[3] - 20 wt% ZrO[2]) - ZrW[2]O[8] ceramic composites obtained using nanosized, initial powders were conducted. Homogeneously distributed white particles on the polished surface of composites were observed. Phase composition of the composites was represented with corundum, monoclinic ZrO[2] and two modifications of ZrW[2]O[8] (tetragonal and cubic). Linear thermal expansion coefficient values of the composites were de...

Dosimetric UV Exposure Effect on the Optical Properties of Ag2O Doped P2O5-ZnO-CuO Glass

Directory of Open Access Journals (Sweden)

K. S. Al Mugren

2016-01-01

Full Text Available Silver phosphate glass types within composition 60P2O5-30ZnO-10CuO-100000 ppm Ag2O were prepared by melt-quenching technique. The optical properties of these glass types were studied under UV exposure at different times, 0, 20, 80, 105, and 115 minutes. The optical absorbance spectra were measured in the range of wavelength from 190 to 3200 nm. The absorbance bandwidth decreases with increasing the time of UV exposure. The optical energy gap, Eg, linear refractive index, n, ratio between molar refraction, Rm, and molar volume, Vm, and metallization criterion (M were estimated. The value of Eg decreases from 2.132 to 1.91 eV with increasing the time of UV exposure from 0 to 115 min. Otherwise n value and metallization increase with increase in the time of UV exposure. The results indicated that these glass types are promising for using an ultraviolet radiation dosimeter.

Flexible End2End Workflow Automation of Hit-Discovery Research.

Science.gov (United States)

Holzmüller-Laue, Silke; Göde, Bernd; Thurow, Kerstin

2014-08-01

The article considers a new approach of more complex laboratory automation at the workflow layer. The authors purpose the automation of end2end workflows. The combination of all relevant subprocesses-whether automated or manually performed, independently, and in which organizational unit-results in end2end processes that include all result dependencies. The end2end approach focuses on not only the classical experiments in synthesis or screening, but also on auxiliary processes such as the production and storage of chemicals, cell culturing, and maintenance as well as preparatory activities and analyses of experiments. Furthermore, the connection of control flow and data flow in the same process model leads to reducing of effort of the data transfer between the involved systems, including the necessary data transformations. This end2end laboratory automation can be realized effectively with the modern methods of business process management (BPM). This approach is based on a new standardization of the process-modeling notation Business Process Model and Notation 2.0. In drug discovery, several scientific disciplines act together with manifold modern methods, technologies, and a wide range of automated instruments for the discovery and design of target-based drugs. The article discusses the novel BPM-based automation concept with an implemented example of a high-throughput screening of previously synthesized compound libraries. © 2014 Society for Laboratory Automation and Screening.

Physico-chemical properties of (U,Ce)O2

International Nuclear Information System (INIS)

Yamada, K.; Yamanaka, S.; Katsura, M.

1998-01-01

The high-temperature X-ray diffraction analysis of (U,Ce)O 2 with CeO 2 contents ranging from 0 to 20 mol.% CeO 2 was performed to obtain the variation of the linear thermal expansion coefficient with the CeO 2 content. Ultrasonic pulse-echo measurements were also carried out from room temperature to 673 K to estimate the change in the mechanical properties of (U,Ce)O 2 with the CeO 2 content. The variation in the linear thermal expansion coefficient at the low CeO 2 content region is more steep than that expected from the linear thermal expansion coefficient of UO 2 and CeO 2 . The Young's and shear moduli of all (U,Ce)O 2 were found to decrease with rising temperature. This was due to the increase of the bond length accompanied by the thermal expansion. Although the lattice parameter decreased with CeO 2 content, the moduli of (U,Ce)O 2 were found to decrease with increasing CeO 2 content at room temperature. These results show that in the range from 0 to 20 mol.% of CeO 2 , as CeO 2 content increases, the bottom of the potential energy in (U,Ce)O 2 is shallower and broader. (orig.)

Linear Accelerator Reactors (LARs) year end report, FY 1977--September 30, 1977

International Nuclear Information System (INIS)

Powell, J.R.; Steinberg, M.; Takahashi, H.

1977-01-01

Under the Nuclear Alternative Systems Assessment Program (NASAP), Brookhaven National Laboratory has initiated a study of Linear Accelerator Assisted Reactors to assess their potential and feasibility in a nuclear energy scenario which will minimize the risk of weapons proliferation. This report covers the period from the inception of the project to the end of FY 1977

Dye-sensitized solar cells employing doubly or singly open-ended TiO2 nanotube arrays: structural geometry and charge transport.

Science.gov (United States)

Choi, Jongmin; Song, Seulki; Kang, Gyeongho; Park, Taiho

2014-09-10

We systematically investigated the charge transport properties of doubly or singly open-ended TiO2 nanotube arrays (DNT and SNT, respectively) for their utility as electrodes in dye-sensitized solar cells (DSCs). The SNT or DNT arrays were transferred in a bottom-up (B-up) or top-up (T-up) configuration onto a fluorine-doped tin oxide (FTO) substrate onto which had been deposited a 2 μm thick TiO2 nanoparticle (NP) interlayer. This process yielded four types of DSCs prepared with SNTs (B-up or T-up) or DNT (B-up or T-up). The photovoltaic performances of these DSCs were analyzed by measuring the dependence of the charge transport on the DSC geometry. High resolution scanning electron microscopy techniques were used to characterize the electrode cross sections, and electrochemical impedance spectroscopy was used to characterize the electrical connection at the interface between the NT array and the TiO2 NP interlayer. We examined the effects of decorating the DNT or SNT arrays with small NPs (sNP@DNT and sNP@SNT, respectively) in an effort to increase the extent of dye loading. The DNT arrays decorated with small NPs performed better than the decorated SNT arrays, most likely because the Ti(OH)4 precursor solution flowed freely into the array through the open ends of the NTs in the DNT case but not in the SNT case. The sNP@DNT-based DSC exhibited a better PCE (10%) compared to the sNP@SNT-based DSCs (6.8%) because the electrolyte solution flow was not restricted, direct electron transport though the NT arrays was possible, the electrical connection at the interface between the NT array and the TiO2 NP interlayer was good, and the array provided efficient light harvesting.

Quantitative analysis of Ni2+/Ni3+ in Li[NixMnyCoz]O2 cathode materials: Non-linear least-squares fitting of XPS spectra

Science.gov (United States)

Fu, Zewei; Hu, Juntao; Hu, Wenlong; Yang, Shiyu; Luo, Yunfeng

2018-05-01

Quantitative analysis of Ni2+/Ni3+ using X-ray photoelectron spectroscopy (XPS) is important for evaluating the crystal structure and electrochemical performance of Lithium-nickel-cobalt-manganese oxide (Li[NixMnyCoz]O2, NMC). However, quantitative analysis based on Gaussian/Lorentzian (G/L) peak fitting suffers from the challenges of reproducibility and effectiveness. In this study, the Ni2+ and Ni3+ standard samples and a series of NMC samples with different Ni doping levels were synthesized. The Ni2+/Ni3+ ratios in NMC were quantitatively analyzed by non-linear least-squares fitting (NLLSF). Two Ni 2p overall spectra of synthesized Li [Ni0.33Mn0.33Co0.33]O2(NMC111) and bulk LiNiO2 were used as the Ni2+ and Ni3+ reference standards. Compared to G/L peak fitting, the fitting parameters required no adjustment, meaning that the spectral fitting process was free from operator dependence and the reproducibility was improved. Comparison of residual standard deviation (STD) showed that the fitting quality of NLLSF was superior to that of G/L peaks fitting. Overall, these findings confirmed the reproducibility and effectiveness of the NLLSF method in XPS quantitative analysis of Ni2+/Ni3+ ratio in Li[NixMnyCoz]O2 cathode materials.

Electrical conduction of glasses in the system Fe2O3-Sb2O3-TeO2; Fe2O3-Sb2O3-TeO2 kei garasu no denki dendo

Energy Technology Data Exchange (ETDEWEB)

Qiu, Honghua; Mori, H; Sakata, H; Hirayama, T [Tokai Univ., Tokyo (Japan). Faculty of Engineering

1995-01-01

In this study, taking into consideration that TeO2 is a component of the glass network and Sb2O3 shows the redox effect in the glasses reducing its possibility of transformation of Sb{sup 3+} to Sb{sup 5+} as well as glass basicity, highly conductive tellurite based glasses have been prepared by the press-quenching method selecting the Fe2O3-Sb2O3-TeO2 system, and the electroconductive mechanism of the glasses has been examined by measuring its D.C. conductivity {sigma}. Part of the obtained information is as follows; the glass formation range of the Fe2O3-Sb2O3-TeO2 system has been 0 {le} Fe2O3 {le} 15mol%, 0 {le} Sb2O3 {le} 18mol% and 78 {le} TeO2 {le} 100mol% and about 15mol% of the additional amount of Fe2O3 has been the limit of glass formation. As the amount of Fe2O3 has increased, C{sub Fe} has also increased and with this, the linear electroconductivity of the glasses has increased from 1.86 {times} 10{sup -7}S{center_dot}cm{sup -1} to 1.62 {times} 10{sup -6}S{center_dot}cm{sup -1} and the glasses have been confirmed as the n-type semiconductor. The factor determining {sigma} of the glasses has been C{sub Fe} which has increased as the amount of Fe2O3 has increased. 34 refs., 8 figs., 2 tabs.

Cathodic detection of H2O2 based on nanopyramidal gold surface with enhanced electron transfer of myoglobin.

Science.gov (United States)

Xia, Peipei; Liu, Haiqing; Tian, Yang

2009-04-15

Direct and reversible electron transfer of myoglobin (Mb), for the first time, is achieved at nanopyramidal gold surface, which was fabricated by one-step electrodeposition, with redox formal potential of 0.21+/-0.01 V (vs. Ag/AgCl) and an apparent heterogeneous electron-transfer rate constant (k(s)) of 1.6+/-0.2 s(-1). Electrochemical investigation indicates that Mb is stably confined on the nanopyramidal gold surface and maintains electrocatalytic activity toward hydrogen peroxide (H(2)O(2)). The facilitated electron transfer combined with the intrinsic catalytical activity of Mb substantially construct the third-generation biosensor for H(2)O(2). The positive redox potential of Mb at the nanostructured gold electrode gives a strong basis for determination of H(2)O(2) with high selectivity. Besides this advantage, the present biosensor also exhibits quick response time, broad linear range, and good sensitivity. The dynamic detection linear range is from 1 microM to 1.4 mM with a detection limit of 0.5 microM at 3sigma. The striking analytical performance of the present biosensor, as well as the biocompatibility of gold nanostructures provided a potential for continuous, on-line detection of H(2)O(2) in the biological system.

Lung recruitability is better estimated according to the Berlin definition of acute respiratory distress syndrome at standard 5 cm H2O rather than higher positive end-expiratory pressure: a retrospective cohort study.

Science.gov (United States)

Caironi, Pietro; Carlesso, Eleonora; Cressoni, Massimo; Chiumello, Davide; Moerer, Onner; Chiurazzi, Chiara; Brioni, Matteo; Bottino, Nicola; Lazzerini, Marco; Bugedo, Guillermo; Quintel, Michael; Ranieri, V Marco; Gattinoni, Luciano

2015-04-01

The Berlin definition of acute respiratory distress syndrome has introduced three classes of severity according to PaO2/FIO2 thresholds. The level of positive end-expiratory pressure applied may greatly affect PaO2/FIO2, thereby masking acute respiratory distress syndrome severity, which should reflect the underlying lung injury (lung edema and recruitability). We hypothesized that the assessment of acute respiratory distress syndrome severity at standardized low positive end-expiratory pressure may improve the association between the underlying lung injury, as detected by CT, and PaO2/FIO2-derived severity. Retrospective analysis. Four university hospitals (Italy, Germany, and Chile). One hundred forty-eight patients with acute lung injury or acute respiratory distress syndrome according to the American-European Consensus Conference criteria. Patients underwent a three-step ventilator protocol (at clinical, 5 cm H2O, or 15 cm H2O positive end-expiratory pressure). Whole-lung CT scans were obtained at 5 and 45 cm H2O airway pressure. Nine patients did not fulfill acute respiratory distress syndrome criteria of the novel Berlin definition. Patients were then classified according to PaO2/FIO2 assessed at clinical, 5 cm H2O, or 15 cm H2O positive end-expiratory pressure. At clinical positive end-expiratory pressure (11±3 cm H2O), patients with severe acute respiratory distress syndrome had a greater lung tissue weight and recruitability than patients with mild or moderate acute respiratory distress syndrome (pBerlin definition of acute respiratory distress syndrome assessed at 5 cm H2O allows a better evaluation of lung recruitability and edema than at higher positive end-expiratory pressure clinically set.

Use of linear free energy relationship to predict Gibbs free energies of formation of pyrochlore phases (CaMTi2O7)

International Nuclear Information System (INIS)

Xu, H.; Wang, Y.

1999-01-01

In this letter, a linear free energy relationship is used to predict the Gibbs free energies of formation of crystalline phases of pyrochlore and zirconolite families with stoichiometry of MCaTi 2 O 7 (or, CaMTi 2 O 7 ,) from the known thermodynamic properties of aqueous tetravalent cations (M 4+ ). The linear free energy relationship for tetravalent cations is expressed as ΔG f,M v X 0 =a M v X ΔG n,M 4+ 0 +b M v X +β M v X r M 4+ , where the coefficients a M v X , b M v X , and β M v X characterize a particular structural family of M v X, r M 4+ is the ionic radius of M 4+ cation, ΔG f,M v X 0 is the standard Gibbs free energy of formation of M v X, and ΔG n,M 4+ 0 is the standard non-solvation energy of cation M 4+ . The coefficients for the structural family of zirconolite with the stoichiometry of M 4+ CaTi 2 O 7 are estimated to be: a M v X =0.5717, b M v X =-4284.67 (kJ/mol), and β M v X =27.2 (kJ/mol nm). The coefficients for the structural family of pyrochlore with the stoichiometry of M 4+ CaTi 2 O 7 are estimated to be: a M v X =0.5717, b M v X =-4174.25 (kJ/mol), and β M v X =13.4 (kJ/mol nm). Using the linear free energy relationship, the Gibbs free energies of formation of various zirconolite and pyrochlore phases are calculated. (orig.)

Optically stimulated luminescence study on gamma-irradiated ice frozen from H sub 2 O and D sub 2 O

CERN Document Server

Yada, T; Hirai, M; Yamanaka, C; Ikeya, M

2002-01-01

Optically stimulated luminescence (OSL) and thermoluminescence (TL) for gamma-irradiated ice samples have been investigated as future dating techniques for icy bodies in the solar system. The OSL around 400nm lasted more than 600s for gamma-irradiated H sub 2 O ice and D sub 2 O ice under 623-nm-light stimulation at 90 K; the latter was used to study the migration of hydrogen atoms. A defect containing trapped electrons is the most suitable explanation of the OSL emissions. The intensity of the TL peak at 120 K increased linearly with gamma-dosage increasing up to 15 kGy for both D sub 2 O ice and H sub 2 O ice. Intensities of both OSL and TL for D sub 2 O ice were larger than those for H sub 2 O ice. The TL peak related to H sub 2 O was observed but its thermal characteristics did not agree with those of OH and HO sub 2 radicals measured by ESR. The OSL method should be employed in future surveys in the solar system.

Thermophysical properties and oxygen transport in (Thx,Pu1-x)O2.

Science.gov (United States)

Galvin, C O T; Cooper, M W D; Rushton, M J D; Grimes, R W

2016-10-31

Using Molecular Dynamics, this paper investigates the thermophysical properties and oxygen transport of (Th x ,Pu 1-x )O 2 (0 ≤ x ≤ 1) between 300-3500 K. In particular, the superionic transition is investigated and viewed via the thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure. Oxygen diffusivity and activation enthalpy are also investigated. Below the superionic temperature an increase of oxygen diffusivity for certain compositions of (Th x ,Pu 1-x )O 2 compared to the pure end members is predicted. Oxygen defect formation enthalpies are also examined, as they underpin the superionic transition temperature and the increase in oxygen diffusivity. The increase in oxygen diffusivity for (Th x ,Pu 1-x )O 2 is explained in terms of lower oxygen defect formation enthalpies for (Th x ,Pu 1-x )O 2 than PuO 2 and ThO 2 , while links are drawn between the superionic transition temperature and oxygen Frenkel disorder.

Mn(II,III) oxidation and MnO2 mineralization by an expressed bacterial multicopper oxidase

Science.gov (United States)

Butterfield, Cristina N.; Soldatova, Alexandra V.; Lee, Sung-Woo; Spiro, Thomas G.; Tebo, Bradley M.

2013-01-01

Reactive Mn(IV) oxide minerals are ubiquitous in the environment and control the bioavailability and distribution of many toxic and essential elements and organic compounds. Their formation is thought to be dependent on microbial enzymes, because spontaneous Mn(II) to Mn(IV) oxidation is slow. Several species of marine Bacillus spores oxidize Mn(II) on their exosporium, the outermost layer of the spore, encrusting them with Mn(IV) oxides. Molecular studies have identified the mnx (Mn oxidation) genes, including mnxG, encoding a putative multicopper oxidase (MCO), as responsible for this two-electron oxidation, a surprising finding because MCOs only catalyze single-electron transfer reactions. Characterization of the enzymatic mechanism has been hindered by the lack of purified protein. By purifying active protein from the mnxDEFG expression construct, we found that the resulting enzyme is a blue (absorption maximum 590 nm) complex containing MnxE, MnxF, and MnxG proteins. Further, by analyzing the Mn(II)- and (III)-oxidizing activity in the presence of a Mn(III) chelator, pyrophosphate, we found that the complex facilitates both electron transfers from Mn(II) to Mn(III) and from Mn(III) to Mn(IV). X-ray absorption spectroscopy of the Mn mineral product confirmed its similarity to Mn(IV) oxides generated by whole spores. Our results demonstrate that Mn oxidation from soluble Mn(II) to Mn(IV) oxides is a two-step reaction catalyzed by an MCO-containing complex. With the purification of active Mn oxidase, we will be able to uncover its mechanism, broadening our understanding of Mn mineral formation and the bioinorganic capabilities of MCOs. PMID:23818588

Influence of exercise intensity on skeletal muscle blood flow, O2 extraction and O2 uptake on-kinetics

Science.gov (United States)

Jones, Andrew M; Krustrup, Peter; Wilkerson, Daryl P; Berger, Nicolas J; Calbet, José A; Bangsbo, Jens

2012-01-01

Following the start of low-intensity exercise in healthy humans, it has been established that the kinetics of skeletal muscle O2 delivery is faster than, and does not limit, the kinetics of muscle O2 uptake (). Direct data are lacking, however, on the question of whether O2 delivery might limit kinetics during high-intensity exercise. Using multiple exercise transitions to enhance confidence in parameter estimation, we therefore investigated the kinetics of, and inter-relationships between, muscle blood flow (), a– difference and following the onset of low-intensity (LI) and high-intensity (HI) exercise. Seven healthy males completed four 6 min bouts of LI and four 6 min bouts of HI single-legged knee-extension exercise. Blood was frequently drawn from the femoral artery and vein during exercise and , a– difference and were calculated and subsequently modelled using non-linear regression techniques. For LI, the fundamental component mean response time (MRTp) for kinetics was significantly shorter than kinetics (mean ± SEM, 18 ± 4 vs. 30 ± 4 s; P exercise intensities; however, the MRTp for a– difference was significantly shorter for HI compared with LI (17 ± 3 vs. 28 ± 4 s; P exercise and remained unaltered thereafter, with no differences between LI and HI. These results indicate that bulk O2 delivery does not limit kinetics following the onset of LI or HI knee-extension exercise. PMID:22711961

Current linearity and operation stability in Al2O3-gate AlGaN/GaN MOS high electron mobility transistors

Science.gov (United States)

Nishiguchi, Kenya; Kaneki, Syota; Ozaki, Shiro; Hashizume, Tamotsu

2017-10-01

To investigate current linearity and operation stability of metal-oxide-semiconductor (MOS) AlGaN/GaN high electron mobility transistors (HEMTs), we have fabricated and characterized the Al2O3-gate MOS-HEMTs without and with a bias annealing in air at 300 °C. Compared with the as-fabricated (unannealed) MOS HEMTs, the bias-annealed devices showed improved linearity of I D-V G curves even in the forward bias regime, resulting in increased maximum drain current. Lower subthreshold slope was also observed after bias annealing. From the precise capacitance-voltage analysis on a MOS diode fabricated on the AlGaN/GaN heterostructure, it was found that the bias annealing effectively reduced the state density at the Al2O3/AlGaN interface. This led to efficient modulation of the AlGaN surface potential close to the conduction band edge, resulting in good gate control of two-dimensional electron gas density even at forward bias. In addition, the bias-annealed MOS HEMT showed small threshold voltage shift after applying forward bias stress and stable operation even at high temperatures.

Study of flow and loss processes at the ends of a linear theta pinch. Progress report, June 1, 1978--May 31, 1979

International Nuclear Information System (INIS)

York, T.M.; Klevans, E.H.

1979-02-01

Experimental and analytical studies of end loss from a linear theta pinch have been carried out. Analysis of reduced data on loss from a 25 cm long theta pinch has indicated: rotation at the end of pinch collapse, which appears to persist; ejection of the plasma in two modes, the first of which includes reversed, trapped fields; unique patterns of radial and axial variation of electron density in the end loss flow; substantial inaccuracies in plasma properties indicated by spectroscopy as compared to Thomson scattering. Studies of loss in a 50 cm long pinch with 50 eV, 2 x 10 16 cm -3 plasma are underway

Effect of temperature on the structural, linear, and nonlinear optical properties of MgO-doped graphene oxide nanocomposites

Science.gov (United States)

Kimiagar, Salimeh; Abrinaei, Fahimeh

2018-01-01

Magnesium oxide (MgO)-graphene oxide (GO) nanocomposites were prepared by the hydrothermal method at different temperatures. The effect of growth temperature on the structural, linear, and nonlinear optical (NLO) parameters was investigated. The decoration of MgO on GO sheets was confirmed by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and UV-visible (UV-vis) spectroscopy analyses. The energy band-gaps of MgO-GO nanocomposites were calculated from UV-vis spectrum using Tauc plot. The NLO parameters of MgO-GO nanocomposites were calculated for the first time by the simple Z-scan technique with nanosecond Nd:YAG laser at 532 nm. The nonlinear absorption coefficient β and nonlinear refractive index n2 for MgO-GO nanocomposites at the laser intensity of 1.1×108 W/cm2 were measured to be in the order of 10-7 cm/W and 10-12 cm2/W, respectively. The third-order NLO susceptibility of MgO-GO nanocomposites was measured in the order of 10-9 esu. The results showed that MgO-GO structures have negative nonlinearity as well as good nonlinear two-photon absorption at 532 nm. Furthermore, the NLO parameters increased by the enhancement of the growth temperature. As the investigation of new materials plays an important role in the advancement of optoelectronics, MgO-GO nanocomposites possess potential applications in NLO devices.

In2Mo3O12: A low negative thermal expansion compound

International Nuclear Information System (INIS)

Marinkovic, Bojan A.; Ari, Monica; Jardim, Paula Mendes; Avillez, Roberto R. de; Rizzo, Fernando; Ferreira, Fabio Furlan

2010-01-01

Orthorhombic In 2 Mo 3 O 12 has low negative linear coefficient of thermal expansion (α l = -1.85 x 10 -6 o C -1 ) as evaluated by X-ray powder diffraction using a synchrotron facility. The linear coefficient of thermal expansion for orthorhombic In 2 Mo 3 O 12 is directly dependent on the inherent volume distortion parameter (υ) of InO 6 . This finding strongly corroborates the recently proposed relationship between the linear coefficient of thermal expansion in A 2 M 3 O 12 compounds (α l ) and the distortion level of AO 6 polyhedra. With the increase of inherent distortion parameter (υ) of AO 6 polyhedra, the linear coefficient of thermal expansion becomes more negative. Another important feature of AO 6 polyhedra, including InO 6 , is that their distortion increases as a function of temperature. Orthorhombic In 2 Mo 3 O 12 is stable in the studied temperature range, 370-760 o C.

MCD spectroscopy of hexanuclear Mn(III) salicylaldoxime single-molecule magnets

DEFF Research Database (Denmark)

Bradley, Justin M; Thomson, Andrew J; Inglis, Ross

2010-01-01

The hexanuclear cages [Mn(6)O(2)(R-sao)(6)L(2)(EtOH)(x)(H(2)O)(y)] "Mn(6)" behave as single-molecule magnets (SMMs) below a characteristic blocking temperature. As with [Mn(12)O(12)(O(2)CR)(16)(H(2)O)(4)] "Mn(12)" the electronic absorption spectra are rather featureless, yielding little information......)(MeOH)(3)](ClO(4)) (4) cast into polymer film. SMM behaviour has previously been observed using magnetic susceptibility measurements on powder and single-crystal samples. The ligand field environment of the magnetic ions is assumed to be similar in (1) and (2) and their different blocking temperatures...

TBA equations for the mass gap in the O(2r) non-linear σ-models

International Nuclear Information System (INIS)

Balog, Janos; Hegedues, Arpad

2005-01-01

We propose TBA integral equations for 1-particle states in the O(n) non-linear σ-model for even n. The equations are conjectured on the basis of the analytic properties of the large volume asymptotics of the problem, which is explicitly constructed starting from Luscher's asymptotic formula. For small volumes the mass gap values computed numerically from the TBA equations agree very well with results of three-loop perturbation theory calculations, providing support for the validity of the proposed TBA system

Low-temperature specific heat of single-crystal Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10

Science.gov (United States)

Urbach, J. S.; Mitzi, D. B.; Kapitulnik, A.; Wei, J. Y. T.; Morris, D. E.

1989-06-01

We report specific-heat measurements from 2 to 15 K on single crystals of Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10 We find low-temperature deviations from the Debye law that can be attributed to spin-glass behavior of a small concentration of isolated impurity copper moments. At higher temperatures, we observe contributions to the specific heat that can be attributed to a soft-phonon mode, possibly associated with the superstructure in the Bi-O and Tl-O layers. From our single-crystal data, we conclude that the thallium- and bismuth-based copper oxide superconductors show no measurable linear term in the specific heat [γ(0)<=1 mJ/mole K2].

Photon Irradiation Response on Ge and Al-Doped SiO2 Optical Fibres

Science.gov (United States)

Yaakob, Nor Haliza; Wagiran, Husin; Ramli, Ahmad Termizi; Ali, Hassan; Asni, Hazila

2010-07-01

Recently, research groups have reported a number of radiation effects on the applications of SiO2 optical fibres with possible use as dosimeter material because these optical fibre provide a good basis for medical radiation dosimetry. The objective of this study is to investigate the thermoluminescence response and fading characteristic for germanium and aluminium doped SiO2 optical fibres with photon irradiation. These optical fibres are placed in solid phantom and irradiated to 6 and 10 MV photon beam at dose ranging from 0.06 Gy to 0.24 Gy using Primus MLC 3339 linear accelerator at Hospital Sultan Ismail, Johor Bahru. In fading studies, the TL measurements were continued up to 14 days period. The optical fibres will produce glow curves whereby the information is then analyzed. Al and Ge-doped optical fibres have a linear dose-TL signal relationship that is proportionality between the TL signal and the doses. Comparison for TL response between different linear accelerator showed a good agreement because these optical fibres also have a linear dose-TL signal relationship even using different equipments.

Métodos do tipo dual simplex para problemas de otimização linear canalizados

Directory of Open Access Journals (Sweden)

Ricardo Silveira Sousa

2005-12-01

Full Text Available Neste artigo estudamos o problema de otimização linear canalizado (restrições e variáveis canalizadas, chamado formato geral e desenvolvemos métodos do tipo dual simplex explorando o problema dual, o qual é linear por partes, num certo sentido não-linear. Várias alternativas de busca unidimensional foram examinadas. Experimentos computacionais revelam que a busca unidimensional exata na direção dual simplex apresenta melhor desempenho.In this paper we study the linear optimization problem lower and upper constrained (i.e., there are lower and upper bounds on constraints and variables and develop dual simplex methods that explore the dual problem, which is piecewise linear, in some sense nonlinear. Different one-dimensional searches were examined. Computational experiments showed that the exact one-dimensional search in the dual simplex direction has the best performance.

The denitrification paradox: The role of O2 in sediment N2O production

Science.gov (United States)

Barnes, Jonathan; Upstill-Goddard, Robert C.

2018-01-01

We designed a novel laboratory sediment flux chamber in which we maintained the headspace O2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (∼3 cm depth) and headspace O2 regulation (headspace: sediment/water ratio ∼9:1), net N2O production was highest at 1.2% O2 (sub-oxic; 32.3 nmol N2O m-2 d-1), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m-2 d-1) or 20.85% (ambient; 2.3 nmol N2O m-2 d-1) O2. In a longer-term sealed incubation (∼490 h) without O2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O2 or N2O up to ∼ 100 h; (ii) a quasi-linear, inverse correlation between O2 and N2O to ∼360 h, in which O2 declined to ∼2.1% and N2O rose to ∼7800 natm; (iii) over the following 50 h a slower O2 decline, to ∼1.1%, and a more rapid N2O increase, to ∼12000 natm; (iv) over the next 24 h a slowed O2 decline towards undetectable levels and a sharp fall in N2O to ∼4600 natm; (iv) a continued N2O decrease at zero O2, to ∼3000 natm by ∼ 490 h. These results show clearly that rapid N2O consumption (∼115 nmol m-2 d-1), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m-2 d-1 (NH4+ addition) and 0.4-2.2 nmol N2O m-2 d-1 (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O

Thermophysical properties and oxygen transport in (Thx,Pu1−x)O2

Science.gov (United States)

Galvin, C. O. T.; Cooper, M. W. D.; Rushton, M. J. D.; Grimes, R. W.

2016-01-01

Using Molecular Dynamics, this paper investigates the thermophysical properties and oxygen transport of (Thx,Pu1−x)O2 (0 ≤ x ≤ 1) between 300–3500 K. In particular, the superionic transition is investigated and viewed via the thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure. Oxygen diffusivity and activation enthalpy are also investigated. Below the superionic temperature an increase of oxygen diffusivity for certain compositions of (Thx,Pu1−x)O2 compared to the pure end members is predicted. Oxygen defect formation enthalpies are also examined, as they underpin the superionic transition temperature and the increase in oxygen diffusivity. The increase in oxygen diffusivity for (Thx,Pu1−x)O2 is explained in terms of lower oxygen defect formation enthalpies for (Thx,Pu1−x)O2 than PuO2 and ThO2, while links are drawn between the superionic transition temperature and oxygen Frenkel disorder. PMID:27796314

Study of flow and loss processes at the ends of a linear theta pinch. Progress report for the period June 1, 1976--May 31, 1977

International Nuclear Information System (INIS)

York, T.M.; Klevans, E.H.

1977-02-01

Experimental and analytical studies initiating and supporting research on flow and energy losses at the ends of a linear theta pinch have been carried out. A 25 cm linear pinch coil has been driven by a 515,000 A discharge with 10 μsec half-cycle time supplied by a 100 μF, 18 kV energy storage system. With reliable preionization generated up to 400 mT He, current sheath behavior has been identified with magnetic loop probes and double loop probes. Spectroscopic determination of preionization has been made. A ruby laser Thomson scattering diagnostic has been designed and is being procured. A study of transient plasma behavior in a 10 cm theta pinch has been carried out with a Twyman-Green interferometer using a 7 mW He--Ne CW laser. Pressure, electric field, and velocity probe diagnostics have received preliminary testing. Design work has been completed for the doubling of pinch length and energy storage system. Studies of particle loss scaling and reactor scaling of linear theta pinch devices have been reported. Detailed calculations of plasma properties at the end of the pinch coil following expansion from the central coil have been carried out. A O--D, time dependent computer code that includes conduction, convection, and magnetic field diffusion has been developed. Predicted plasma behavior is in good agreement with experimental data

A H2O2 Biosensor Based on Immobilization of HorseradishPeroxidase in a Gelatine Network Matrix

Directory of Open Access Journals (Sweden)

Jun-Jie Zhu

2005-05-01

Full Text Available A simple and promising H2O2 biosensor has been developed by successfulentrapment of horseradish peroxidase (HRP in a gelatine matrix which was cross-linkedwith formaldehyde. The large microscopic surface area and porous morphology of thegelatine matrix lead to high enzyme loading and the enzyme entrapped in this matrix canretain its bioactivity. This biosensor exhibited a fast amperometric response to hydrogenperoxide (H2O2. The linear range for H2O2 determination was from 2.5×10-5 to2.5×10-3 M, with a detection limit of 2.0×10-6 M based on S / N = 3. This biosensorpossessed very good reproducibility.

Reactions of Ferrous Coproheme Decarboxylase (HemQ) with O2 and H2O2 Yield Ferric Heme b.

Science.gov (United States)

Streit, Bennett R; Celis, Arianna I; Shisler, Krista; Rodgers, Kenton R; Lukat-Rodgers, Gudrun S; DuBois, Jennifer L

2017-01-10

A recently discovered pathway for the biosynthesis of heme b ends in an unusual reaction catalyzed by coproheme decarboxylase (HemQ), where the Fe(II)-containing coproheme acts as both substrate and cofactor. Because both O 2 and H 2 O 2 are available as cellular oxidants, pathways for the reaction involving either can be proposed. Analysis of reaction kinetics and products showed that, under aerobic conditions, the ferrous coproheme-decarboxylase complex is rapidly and selectively oxidized by O 2 to the ferric state. The subsequent second-order reaction between the ferric complex and H 2 O 2 is slow, pH-dependent, and further decelerated by D 2 O 2 (average kinetic isotope effect of 2.2). The observation of rapid reactivity with peracetic acid suggested the possible involvement of Compound I (ferryl porphyrin cation radical), consistent with coproheme and harderoheme reduction potentials in the range of heme proteins that heterolytically cleave H 2 O 2 . Resonance Raman spectroscopy nonetheless indicated a remarkably weak Fe-His interaction; how the active site structure may support heterolytic H 2 O 2 cleavage is therefore unclear. From a cellular perspective, the use of H 2 O 2 as an oxidant in a catalase-positive organism is intriguing, as is the unusual generation of heme b in the Fe(III) rather than Fe(II) state as the end product of heme synthesis.

The role of magnetoelastic strain on orbital control and transport properties in an LaTiO(3)-CoFe(2)O(4) heterostructure.

Science.gov (United States)

Li, J; Chu, H F; Zhang, Y; Wang, J; Zheng, D N; Song, Q; Wang, P; Ma, Y G; Ong, C K; Wang, S J

2009-07-08

Epitaxial heterostructures of CoFe(2)O(4)/LaTiO(3)/LaAlO(3) have been successfully prepared by using the pulsed laser deposition technique. The magnetoresistance (MR) of the samples is negative and linear with field at H≥2 T, exhibiting no dependence on field directions. Nevertheless, when Hstrains on the bottom LaTiO(3) layer. Apparently the orbital status and the one-electron bandwidth in the LaTiO(3) layer are altered, which leads to a change in resistance.

Effect of temperature on the structural, linear, and nonlinear optical properties of MgO-doped graphene oxide nanocomposites

Directory of Open Access Journals (Sweden)

Kimiagar Salimeh

2018-01-01

Full Text Available Magnesium oxide (MgO-graphene oxide (GO nanocomposites were prepared by the hydrothermal method at different temperatures. The effect of growth temperature on the structural, linear, and nonlinear optical (NLO parameters was investigated. The decoration of MgO on GO sheets was confirmed by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and UV-visible (UV-vis spectroscopy analyses. The energy band-gaps of MgO-GO nanocomposites were calculated from UV-vis spectrum using Tauc plot. The NLO parameters of MgO-GO nanocomposites were calculated for the first time by the simple Z-scan technique with nanosecond Nd:YAG laser at 532 nm. The nonlinear absorption coefficient β and nonlinear refractive index n2 for MgO-GO nanocomposites at the laser intensity of 1.1×108 W/cm2 were measured to be in the order of 10−7 cm/W and 10−12 cm2/W, respectively. The third-order NLO susceptibility of MgO-GO nanocomposites was measured in the order of 10−9 esu. The results showed that MgO-GO structures have negative nonlinearity as well as good nonlinear two-photon absorption at 532 nm. Furthermore, the NLO parameters increased by the enhancement of the growth temperature. As the investigation of new materials plays an important role in the advancement of optoelectronics, MgO-GO nanocomposites possess potential applications in NLO devices.

The Partial Molar Volume and Compressibility of the FeO Component in Model Basalts (Mixed CaAl2Si2O8-CaMgSi2O6-CaFeSi2O6 Liquids) at 0 GPa: evidence of Fe2+ in 6-fold coordination

Science.gov (United States)

Guo, X.; Lange, R. A.; Ai, Y.

2010-12-01

FeO is an important component in magmatic liquids and yet its partial molar volume at one bar is not as well known as that for Fe2O3 because of the difficulty of performing double-bob density measurements under reducing conditions. Moreover, there is growing evidence from spectroscopic studies that Fe2+ occurs in 4, 5, and 6-fold coordination in silicate melts, and it is expected that the partial molar volume and compressibility of the FeO component will vary accordingly. We have conducted both density and relaxed sound speed measurements on four liquids in the An-Di-Hd (CaAl2Si2O8-CaMgSi2O6-CaFeSi2O6) system: (1) Di-Hd (50:50), (2) An-Hd (50:50), (3) An-Di-Hd (33:33:33) and (4) Hd (100). Densities were measured between 1573 and 1838 K at one bar with the double-bob Archimedean method using molybdenum bobs and crucibles in a reducing gas (1%CO-99%Ar) environment. The sound speeds were measured under similar conditions with a frequency-sweep acoustic interferometer, and used to calculate isothermal compressibility. All the density data for the three multi-component (model basalt) liquids were combined with density data on SiO2-Al2O3-CaO-MgO-K2O-Na2O liquids (Lange, 1997) in a fit to a linear volume equation; the results lead to a partial molar volume (±1σ) for FeO =11.7 ± 0.3(±1σ) cm3/mol at 1723 K. This value is similar to that for crystalline FeO at 298 K (halite structure; 12.06 cm3/mol), which suggests an average Fe2+ coordination of ~6 in these model basalt compositions. In contrast, the fitted partial molar volume of FeO in pure hedenbergite liquid is 14.6 ± 0.3 at 1723 K, which is consistent with an average Fe2+ coordination of 4.3 derived from EXAFS spectroscopy (Rossano, 2000). Similarly, all the compressibility data for the three multi-component liquids were combined with compressibility data on SiO2-Al2O3-CaO-MgO liquids (Ai and Lange, 2008) in a fit to an ideal mixing model for melt compressibility; the results lead to a partial molar

Rapid reagent-less on-line H2O2 quantification in alkaline semiconductor etching solution, Part 2: Nephelometry application.

Science.gov (United States)

Zlatev, Roumen; Stoytcheva, Margarita; Valdez, Benjamin

2018-03-01

A simple and rapid reagent less nephelometric method for on-line H 2 O 2 quantification in semiconductors etching solutions was developed, optimized, characterized and validated. The intensity of the light scattered by the oxygen gas suspension resulted from H 2 O 2 catalytic decomposition by immobilized MnO 2 was registered as analytical response. The influences of the light wave length, the agitation rate, the temperature and the catalyst surface area on the response amplitude were studied and optimization was done. The achieved linear concentration range from 10 to 150mmolL -1 at 0.9835 calibration curve correlation coefficient, precision from 3.65% to 0.95% and response time from 35 to 20s respectively, at sensitivity of 8.01µAmmol -1 L and LOD of 2.9mmolL -1 completely satisfy the semiconductor industry requirements. Copyright © 2017 Elsevier B.V. All rights reserved.

Low-temperature specific heat of single-crystal Bi2CaSr2Cu2O8 and Tl2Ca2Ba2Cu3O10

International Nuclear Information System (INIS)

Urbach, J.S.; Mitzi, D.B.; Kapitulnik, A.; Wei, J.Y.T.; Morris, D.E.; Physics Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720)

1989-01-01

We report specific-heat measurements from 2 to 15 K on single crystals of Bi 2 CaSr 2 Cu 2 O 8 and Tl 2 Ca 2 Ba 2 Cu 3 O 10 We find low-temperature deviations from the Debye law that can be attributed to spin-glass behavior of a small concentration of isolated impurity copper moments. At higher temperatures, we observe contributions to the specific heat that can be attributed to a soft-phonon mode, possibly associated with the superstructure in the Bi-O and Tl-O layers. From our single-crystal data, we conclude that the thallium- and bismuth-based copper oxide superconductors show no measurable linear term in the specific heat [γ(0) less than or equal to 1 mJ/mole K 2

A METHOD FOR SOLVING LINEAR PROGRAMMING PROBLEMS WITH FUZZY PARAMETERS BASED ON MULTIOBJECTIVE LINEAR PROGRAMMING TECHNIQUE

OpenAIRE

M. ZANGIABADI; H. R. MALEKI

2007-01-01

In the real-world optimization problems, coefficients of the objective function are not known precisely and can be interpreted as fuzzy numbers. In this paper we define the concepts of optimality for linear programming problems with fuzzy parameters based on those for multiobjective linear programming problems. Then by using the concept of comparison of fuzzy numbers, we transform a linear programming problem with fuzzy parameters to a multiobjective linear programming problem. To this end, w...

Effects of TiO2 and Co3O4 Nanoparticles on Circulating Angiogenic Cells

Science.gov (United States)

Spigoni, Valentina; Cito, Monia; Alinovi, Rossella; Pinelli, Silvana; Passeri, Giovanni; Zavaroni, Ivana; Goldoni, Matteo; Campanini, Marco; Aliatis, Irene; Mutti, Antonio

2015-01-01

Background and Aim Sparse evidence suggests a possible link between exposure to airborne nanoparticles (NPs) and cardiovascular (CV) risk, perhaps through mechanisms involving oxidative stress and inflammation. We assessed the effects of TiO2 and Co3O4 NPs in human circulating angiogenic cells (CACs), which take part in vascular endothelium repair/replacement. Methods CACs were isolated from healthy donors’ buffy coats after culturing lymphomonocytes on fibronectin-coated dishes in endothelial medium for 7 days. CACs were pre-incubated with increasing concentration of TiO2 and Co3O4 (from 1 to 100 μg/ml) to test the effects of NP – characterized by Transmission Electron Microscopy – on CAC viability, apoptosis (caspase 3/7 activation), function (fibronectin adhesion assay), oxidative stress and inflammatory cytokine gene expression. Results Neither oxidative stress nor cell death were associated with exposure to TiO2 NP (except at the highest concentration tested), which, however, induced a higher pro-inflammatory effect compared to Co3O4 NPs (p<0.01). Exposure to Co3O4 NPs significantly reduced cell viability (p<0.01) and increased caspase activity (p<0.01), lipid peroxidation end-products (p<0.05) and pro-inflammatory cytokine gene expression (p<0.05 or lower). Notably, CAC functional activity was impaired after exposure to both TiO2 (p<0.05 or lower) and Co3O4 (p<0.01) NPs. Conclusions In vitro exposure to TiO2 and Co3O4 NPs exerts detrimental effects on CAC viability and function, possibly mediated by accelerated apoptosis, increased oxidant stress (Co3O4 NPs only) and enhancement of inflammatory pathways (both TiO2 and Co3O4 NPs). Such adverse effects may be relevant for a potential role of exposure to TiO2 and Co3O4 NPs in enhancing CV risk in humans. PMID:25803285

The mercury chromates Hg6Cr2O9 and Hg6Cr2O10-Preparation and crystal structures, and thermal behaviour of Hg6Cr2O9

International Nuclear Information System (INIS)

Weil, Matthias; Stoeger, Berthold

2006-01-01

The basic mercury(I) chromate(VI), Hg 6 Cr 2 O 9 (=2Hg 2 CrO 4 .Hg 2 O), has been obtained under hydrothermal conditions (200deg. C, 5 days) in the form of orange needles as a by-product from reacting elemental mercury and K 2 Cr 2 O 7 . Hydrothermal treatment of microcrystalline Hg 6 Cr 2 O 9 in demineralised water at 200deg. C for 3 days led to crystal growth of red crystals of the basic mercury(I, II) chromate(VI), Hg 6 Cr 2 O 10 (=2Hg 2 CrO 4 .2HgO). The crystal structures were solved and refined from single crystal X-ray data sets. Hg 6 Cr 2 O 9 : space group P2 1 2 1 2 1 , Z=4, a=7.3573(12), b=8.0336(13), c=20.281(3)A, 3492 structure factors, 109 parameters, R[F 2 >2σ(F 2 )]=0.0371, wR(F 2 all)=0.0517; Hg 6 Cr 2 O 10 : space group Pca2 1 , Z=4, a=11.4745(15), b=9.4359(12), c=10.3517(14)A, 3249 structure factors, 114 parameters, R[F 2 >2σ(F 2 )]=0.0398, wR(F 2 all)=0.0625. Both crystal structures are made up of an intricate mercury-oxygen network, subdivided into single building blocks [O-Hg-Hg-O] for the mercurous compound, and [O-Hg-Hg-O] and [O-Hg-O] for the mixed-valent compound. Hg 6 Cr 2 O 9 contains three different Hg 2 2+ dumbbells, whereas Hg 6 Cr 2 O 10 contains two different Hg 2 2+ dumbbells and two Hg 2+ cations. The Hg I -Hg I distances are characteristic and range between 2.5031(15) and 2.5286(9)A. All Hg 2 2+ groups exhibit an unsymmetrical oxygen environment. The oxygen coordination of the Hg 2+ cations is nearly linear with two tightly bonded O atoms at distances around 2.07A. For both structures, the chromate(VI) anions reside in the vacancies of the Hg-O network and deviate only slightly from the ideal tetrahedral geometry with average Cr-O distances of ca. 1.66A. Upon heating at temperatures above 385deg. C, Hg 6 Cr 2 O 9 decomposes in a four-step mechanism with Cr 2 O 3 as the end-product at temperatures above 620 deg. C

Understanding Effect of Constraint Release Environment on End-to-End Vector Relaxation of Linear Polymer Chains

KAUST Repository

Shivokhin, Maksim E.; Read, Daniel J.; Kouloumasis, Dimitris; Kocen, Rok; Zhuge, Flanco; Bailly, Christian; Hadjichristidis, Nikolaos; Likhtman, Alexei E.

2017-01-01

of a linear probe chain. For this purpose we first validate the ability of the model to consistently predict both the viscoelastic and dielectric response of monodisperse and binary mixtures of type A polymers, based on published experimental data. We

Study of the optical properties of TeO2-PbO-TiO2 glass system

Directory of Open Access Journals (Sweden)

Raul F. Cuevas

1998-06-01

Full Text Available We describe the preparation and some optical properties of high refractive index TeO2-PbO-TiO2 glass system. Highly homogeneous glasses were obtained by agitating the mixture during the melting process in an alumina crucible. The characterization was done by X-ray diffraction, Raman scattering, light absorption and linear refractive index measurements. The results show a change in the glass structure as the PbO content increases: the TeO4 trigonal bipyramids characteristics of TeO2 glasses transform into TeO3 trigonal pyramids. However, the measured refractive indices are almost independent of the glass composition. We show that third-order nonlinear optical susceptibilities calculated from the measured refractive indices using Lines' theoretical model are also independent of the glass composition.

In Situ Synchrotron XRD on a Capillary Li-O2 Battery Cell

DEFF Research Database (Denmark)

Storm, Mie Møller; Johnsen, Rune; Norby, Poul

2014-01-01

of a electrolyte filled capillary with anode and cathode in each end suspended on stainless steel wires, the oxygen in-let is placed on the cathode side of the capillary with a flushing system for oxygen in-let. In this study we present a flexible design of a capillary based Li-O2 battery with discharge and charge...... a stainless steel wire where the cathode is attached. The in situ XRD measurements show how the Li2O2 growth depend on current discharge rate and how the FWHM changes dependent on reflection and charge/discharge.Several cells were tested both ex situ and in situ, and in situ XRD for 1st discharge/charge and 2...

Thermodynamics of CoAl2O4-CoGa2O4 solid solutions

International Nuclear Information System (INIS)

Lilova, Kristina I.; Navrotsky, Alexandra; Melot, Brent C.; Seshadri, Ram

2010-01-01

CoAl 2 O 4 , CoGa 2 O 4 , and their solid solution Co(Ga z Al 1-z ) 2 O 4 have been studied using high temperature oxide melt solution calorimetry in molten 2PbO.B 2 O 3 at 973 K. There is an approximately linear correlation between lattice parameters, enthalpy of formation from oxides, and the Ga content. The experimental enthalpy of mixing is zero within experimental error. The cation distribution parameters are calculated using the O'Neill and Navrotsky thermodynamic model. The enthalpies of mixing calculated from these parameters are small and consistent with the calorimetric data. The entropies of mixing are calculated from site occupancies and compared to those for a random mixture of Ga and Al ions on octahedral site with all Co tetrahedral and for a completely random mixture of all cations on both sites. Despite a zero heat of mixing, the solid solution is not ideal in that activities do not obey Raoult's Law because of the more complex entropy of mixing. - Graphical abstract: Measured enthalpies of mixing of CoAl 2 O 4 -CoGa 2 O 4 solid solutions are close to zero but entropies of mixing reflect the complex cation distribution, so the system is not an ideal solution.

Linear chain compounds of molybdenum (II) acetate linked by pyrazine, 4,4'-bipyridine, and 1,4-diazabicyclo[2.2.2]octane

International Nuclear Information System (INIS)

Handa, Makoto; Yamada, Kori; Nakao, Tadahiro; Matsumoto, Hiroki; Kasuga, Kuninobu; Mikuriya, Masahiro; Kotera, Takanori.

1995-01-01

A series of linear-chain complexes of molybdenum (II) acetate linked by bidentate bridging ligands, [Mo 2 (O 2 CCH 3 ) 4 L] n (L=pyrazine (pyz), 4,4'-bipyridine (4,4'-bpy), and 1,4-diazabicyclo[2.2.2]octane (dabco)), have been prepared, and their crystal structures determined by an X-ray diffraction method. It has been shown that the relatively weak coordinations of the bridging ligands at the axial positions of Mo 2 (O 2 CCH 3 ) 4 (Mo-N=2.619 (8)-2.658(6) A) can effectively control the arrangement of the dimer units to give chain structures with good linearities. No significant interactions between the dimer units have been observed. (author)

Rotational excitation of linear triatomic molecules: Ar, Kr + N2O, CO2

International Nuclear Information System (INIS)

Farrar, J.M.; Parson, J.M.; Lee, Y.T.

1974-01-01

Rotational excitation of N 2 O and CO 2 in collisions with Ar and Kr has been studied by crossing two supersonic molecular beams and detecting scattered products with a mass spectrometer. Measurement of the time of flight spectrum of the products as a function of laboratory scattering angle theta indicates that the inelasticity is concentrated in the forward direction in the center of mass system. Difference between CO 2 and N 2 O are discussed briefly

Properties of SrBi2Nb2O9 thin films on Pt-coated Si

International Nuclear Information System (INIS)

Avila, R.E.; Navarro, P.O.; Martin, V. del C.; Fernandez, L.M.; Sylvester, G.; Retuert, P.J.; Gramsch, E.

2002-01-01

SrBi 2 Nb 2 O 9 powders and thin films, on Pt-coated Si, were synthesised by the sol-gel method. Three-layer thin films appear homogeneous down to the 100 nm scale, polycrystalline in the tetragonal Aurivillius phase, at a average thickness of 40 nm per layer. The index of refraction at the center of the visible range increases with the sintering temperature from roughly 2.1 (at 400 Centigrade) to 2.5 (at 700 Centigrade). The expression n 2 -1 increases linearly with the relative density of the thin films, in similar fashion as previous studies in PbTiO 3 thin films. The dielectric constant in quasistatic and high frequency (1 MHz) modes, is between 160 and 230. (Author)

Absolute non-linear optical coefficients measurements of CsLiB 6O 10 single crystals by second harmonic generation

Science.gov (United States)

Sifi, A.; Klein, R. S.; Maillard, A.; Kugel, G. E.; Péter, A.; Polgár, K.

2003-10-01

We present absolute measurements of the effective non-linear optical coefficients deff of cesium lithium borate crystals (CsLiB 6O 10, CLBO) by second harmonic generation using a continuous Nd-YAG laser source. The experiments were carried out at room temperature, on crystals cut perpendicular to type I or type II phase matching directions, with two different crystal lengths along the propagation direction. The d36 and d14 non-linear coefficients involved in deff developments are deduced and are shown to be equal as it is predicted by the Kleinman symmetry. Two different compositions prepared by the Czochralski technique from melt with compositions of 1:1:6 and 1:1:5.5 molar ratios of Cs 2O, Li 2O and B 2O 3 are comparatively studied.

Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO-SiO2 coating on titanium alloy.

Science.gov (United States)

Li, H C; Wang, D G; Chen, C Z; Weng, F

2015-03-01

To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO2 and Y2O3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular-dendrite structure to compact cellular crystal. The addition of CeO2 or Y2O3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. Y2O3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris-HCl solution, the samples doped with CeO2 or Y2O3 present a lower weight loss, indicating the addition of CeO2 or Y2O3 improves the degradability of laser cladding sample. Copyright © 2015 Elsevier B.V. All rights reserved.

Thermal expansion studies on europium titanate (Eu2TiO5)

International Nuclear Information System (INIS)

Panneerselvam, G.; Subramanian, G.G.S.; Antony, M.P.

2008-01-01

The lattice thermal expansion characteristics of europium titanate (Eu 2 TiO 5 ) have been studied by measuring the lattice parameter by high temperature X-ray diffraction technique (HT-XRD) in the temperature range 298-1573K. Percentage linear thermal expansion and mean linear thermal expansion coefficients were computed from the lattice parameter data. The percentage linear thermal expansion in the temperature range 298-1573 K along a, b and c axes are 1.05, 1.15 and 0.95 respectively. (author)

Interplay between O2 and SnO2: oxygen ionosorption and spectroscopic evidence for adsorbed oxygen.

Science.gov (United States)

Gurlo, Alexander

2006-10-13

Tin dioxide is the most commonly used material in commercial gas sensors based on semiconducting metal oxides. Despite intensive efforts, the mechanism responsible for gas-sensing effects on SnO(2) is not fully understood. The key step is the understanding of the electronic response of SnO(2) in the presence of background oxygen. For a long time, oxygen interaction with SnO(2) has been treated within the framework of the "ionosorption theory". The adsorbed oxygen species have been regarded as free oxygen ions electrostatically stabilized on the surface (with no local chemical bond formation). A contradiction, however, arises when connecting this scenario to spectroscopic findings. Despite trying for a long time, there has not been any convincing spectroscopic evidence for "ionosorbed" oxygen species. Neither superoxide ions O(2)(-), nor charged atomic oxygen O,(-) nor peroxide ions O(2)(2-) have been observed on SnO(2) under the real working conditions of sensors. Moreover, several findings show that the superoxide ion does not undergo transformations into charged atomic oxygen at the surface, and represents a dead-end form of low-temperature oxygen adsorption on reduced metal oxide.

The hybridized front end electronics of the Central Drift Chamber in the Stanford Linear Collider Detector

International Nuclear Information System (INIS)

Lo, C.C.; Kirsten, F.A.; Nakamura, M.

1987-10-01

In order to accommodate the high packaging density requirements for the front end electronics of the Central Drift Chamber (CDC) in the SLAC Linear Collider Detector (SLD), the CDC front end electronics has been hybridized. The hybrid package contains eight channels of amplifiers together with all the associated circuits for calibration, event recognition and power economy switching functions. A total of 1280 such hybrids are used in the CDC

Porous HKUST-1 derived CuO/Cu2O shell wrapped Cu(OH)2 derived CuO/Cu2O core nanowire arrays for electrochemical nonenzymatic glucose sensors with ultrahigh sensitivity

Science.gov (United States)

Yu, Cuiping; Cui, Jiewu; Wang, Yan; Zheng, Hongmei; Zhang, Jianfang; Shu, Xia; Liu, Jiaqin; Zhang, Yong; Wu, Yucheng

2018-05-01

Self-supported CuO/Cu2O@CuO/Cu2O core-shell nanowire arrays (NWAs) are successfully fabricated by a simple and efficient method in this paper. Anodized Cu(OH)2 NWAs could in-situ convert to HKUST-1 at room temperature easily. Cu(OH)2 NWAs cores and HKUST-1 shells transform into CuO/Cu2O simultaneously after calcinations and form CuO/Cu2O@CuO/Cu2O core-shell NWAs. This smart configuration of the core-shell structure not only avoids the agglomeration of the traditional MOF-derived materials in particle-shape, but also facilitates the ion diffusion and increases the active sites. This novel structure is employed as substrate to construct nonenzymatic glucose sensors. The results indicate that glucose sensor based on CuO/Cu2O@CuO/Cu2O core-shell NWAs presents ultrahigh sensitivity (10,090 μA mM-1 cm-2), low detection limit (0.48 μM) and wide linear range (0.99-1,330 μM). In addition, it also shows excellent anti-interference ability toward uric acid, ascorbic acid and L-Cysteine co-existing with glucose, good reproducibility and superior ability of real sample analysis.

NO2-initiated multiphase oxidation of SO2 by O2 on CaCO3 particles

Science.gov (United States)

Yu, Ting; Zhao, Defeng; Song, Xiaojuan; Zhu, Tong

2018-05-01

The reaction of SO2 with NO2 on the surface of aerosol particles has been suggested to be important in sulfate formation during severe air pollution episodes in China. However, we found that the direct oxidation of SO2 by NO2 was slow and might not be the main reason for sulfate formation in ambient air. In this study, we investigated the multiphase reaction of SO2 with an O2 / NO2 mixture on single CaCO3 particles using Micro-Raman spectroscopy. The reaction converted the CaCO3 particle to a Ca(NO3)2 droplet, with CaSO4 ⚫ 2H2O solid particles embedded in it, which constituted a significant fraction of the droplet volume at the end of the reaction. The reactive uptake coefficient of SO2 for sulfate formation was on the order of 10-5, which was higher than that for the multiphase reaction of SO2 directly with NO2 by 2-3 orders of magnitude. According to our observations and the literature, we found that in the multiphase reaction of SO2 with the O2 / NO2 mixture, O2 was the main oxidant of SO2 and was necessary for radical chain propagation. NO2 acted as the initiator of radical formation, but not as the main oxidant. The synergy of NO2 and O2 resulted in much faster sulfate formation than the sum of the reaction rates with NO2 and with O2 alone. We estimated that the multiphase oxidation of SO2 by O2 initiated by NO2 could be an important source of sulfate and a sink of SO2, based on the calculated lifetime of SO2 regarding the loss through the multiphase reaction versus the loss through the gas-phase reaction with OH radicals. Parameterization of the reactive uptake coefficient of the reaction observed in our laboratory for further model simulation is needed, as well as an integrated assessment based on field observations, laboratory study results, and model simulations to evaluate the importance of the reaction in ambient air during severe air pollution episodes, especially in China.

Synthesis of Zr2WP2O12/ZrO2 Composites with Adjustable Thermal Expansion

Directory of Open Access Journals (Sweden)

Zhiping Zhang

2017-11-01

Full Text Available Zr2WP2O12/ZrO2 composites were fabricated by solid state reaction with the goal of tailoring the thermal expansion coefficient. XRD, SEM and TMA were used to investigate the composition, microstructure, and thermal expansion behavior of Zr2WP2O12/ZrO2 composites with different mass ratio. Relative densities of all the resulting Zr2WP2O12/ZrO2 samples were also tested by Archimedes' methods. The obtained Zr2WP2O12/ZrO2 composites were comprised of orthorhombic Zr2WP2O12 and monoclinic ZrO2. As the increase of the Zr2WP2O12, the relative densities of Zr2WP2O12/ZrO2 ceramic composites increased gradually. The coefficient of thermal expansion of the Zr2WP2O12/ZrO2 composites can be tailored from 4.1 × 10−6 K−1 to −3.3 × 10−6 K−1 by changing the content of Zr2WP2O12. The 2:1 Zr2WP2O12/ZrO2 specimen shows close to zero thermal expansion from 25 to 700°C with an average linear thermal expansion coefficient of −0.09 × 10−6 K−1. These adjustable and near zero expansion ceramic composites will have great potential application in many fields.

Synthesis of Zr2WP2O12/ZrO2 Composites with Adjustable Thermal Expansion.

Science.gov (United States)

Zhang, Zhiping; Sun, Weikang; Liu, Hongfei; Xie, Guanhua; Chen, Xiaobing; Zeng, Xianghua

2017-01-01

Zr 2 WP 2 O 12 /ZrO 2 composites were fabricated by solid state reaction with the goal of tailoring the thermal expansion coefficient. XRD, SEM and TMA were used to investigate the composition, microstructure, and thermal expansion behavior of Zr 2 WP 2 O 12 /ZrO 2 composites with different mass ratio. Relative densities of all the resulting Zr 2 WP 2 O 12 /ZrO 2 samples were also tested by Archimedes' methods. The obtained Zr 2 WP 2 O 12 /ZrO 2 composites were comprised of orthorhombic Zr 2 WP 2 O 12 and monoclinic ZrO 2 . As the increase of the Zr 2 WP 2 O 12 , the relative densities of Zr 2 WP 2 O 12 /ZrO 2 ceramic composites increased gradually. The coefficient of thermal expansion of the Zr 2 WP 2 O 12 /ZrO 2 composites can be tailored from 4.1 × 10 -6 K -1 to -3.3 × 10 -6 K -1 by changing the content of Zr 2 WP 2 O 12 . The 2:1 Zr 2 WP 2 O 12 /ZrO 2 specimen shows close to zero thermal expansion from 25 to 700°C with an average linear thermal expansion coefficient of -0.09 × 10 -6 K -1 . These adjustable and near zero expansion ceramic composites will have great potential application in many fields.

The role of Sr2+ on the structure and reactivity of SrO-CaO-ZnO-SiO2 ionomer glasses.

Science.gov (United States)

Boyd, Daniel; Towler, Mark R; Watts, Sally; Hill, Robert G; Wren, Anthony W; Clarkin, Owen M

2008-02-01

The suitability of Glass Polyalkenoate Cements (GPCs) for use in orthopaedics is retarded by the presence in the glass phase of aluminium, a neurotoxin. Unfortunately, the aluminium ion plays an integral role in the setting process of GPCs and its absence is likely to hinder cement formation. However, the authors have previously shown that aluminium free GPCs may be formulated based on calcium zinc silicate glasses and these novel materials exhibit significant potential as hard tissue biomaterials. To further improve their potential, and given that Strontium (Sr) based drugs have had success in the treatment of osteoporosis, the authors have substituted Calcium (Ca) with Sr in the glass phase of a series of aluminium free GPCs. However to date little data exists on the effect SrO has on the structure and reactivity of SrO-CaO-ZnO-SiO(2) glasses. The objective of this work was to characterise the effect of the Ca/Sr substitution on the structure of such glasses, and evaluate the subsequent reactivity of these glasses with an aqueous solution of Polyacrylic acid (PAA). To this end (29)Si MAS-NMR, differential scanning calorimetry (DSC), X-ray diffraction, and network connectivity calculations, were used to characterize the structure of four strontium calcium zinc silicate glasses. Following glass characterization, GPCs were produced from each glass using a 40 wt% solution of PAA (powder:liquid = 2:1.5). The working times and setting times of the GPCs were recorded as per International standard ISO9917. The results acquired as part of this research indicate that the substitution of Ca for Sr in the glasses examined did not appear to significantly affect the structure of the glasses investigated. However it was noted that increasing the amount of Ca substituted for Sr did result in a concomitant increase in setting times, a feature that may be attributable to the higher basicity of SrO over CaO.

Effective role of CaO/P2O5 ratio on SiO2-CaO-P2O5 glass system

Directory of Open Access Journals (Sweden)

P. Kiran

2017-05-01

Full Text Available In the present work, the effect of the CaO/P2O5 ratio on the composition of sol-gel synthesized 58SiO2-(19 − xP2O5–(23 + xCaO (x = 0, 5, 10 and 15 mol% glass samples was studied. Further, the effect of NBO/BO ratio on hydroxy carbonated apatite layer (HCA forming ability based on dissolution behavior in simulated body fluid (SBF solution was also investigated. CaO/P2O5 ratios of synthesized glass samples were 1.2, 2, 3.6, and 9.5, respectively. NBO/BO ratios were obtained using Raman spectroscopic analysis as 0.58, 1.20, 1.46, and 1.78, respectively. All samples were soaked in the SBF solution for 7 days. The calculated weight losses of these samples were 58%, 64%, 83%, and 89% for corresponding NBO/BO ratios. The increase in CaO/P2O5 ratio increases the NBO/BO ratios. However, the increase in NBO/BO ratio increases HCA forming ability of SBF treated samples. The HCA crystalline layer formation was confirmed through X-ray Diffraction (XRD, Transmission Electron Microscopy (TEM, Scanning Electron Microscopy (SEM, Raman and Infrared spectroscopic analysis. Higher CaO/P2O5 ratio favors the increase in HCA formation for SBF treated calcium phospho silicate glasses.

Theoretical studies on photoelectron and IR spectral properties of Br2.-(H2O)n clusters.

Science.gov (United States)

Pathak, A K; Mukherjee, T; Maity, D K

2007-07-28

We report vertical detachment energy (VDE) and IR spectra of Br2.-.(H2O)n clusters (n=1-8) based on first principles electronic structure calculations. Cluster structures and IR spectra are calculated at Becke's half-and-half hybrid exchange-correlation functional (BHHLYP) with a triple split valence basis function, 6-311++G(d,p). VDE for the hydrated clusters is calculated based on second order Moller-Plesset perturbation (MP2) theory with the same set of basis function. On full geometry optimization, it is observed that conformers having interwater hydrogen bonding among solvent water molecules are more stable than the structures having double or single hydrogen bonded structures between the anionic solute, Br2.-, and solvent water molecules. Moreover, a conformer having cyclic interwater hydrogen bonded network is predicted to be more stable for each size hydrated cluster. It is also noticed that up to four solvent H2O units can reside around the solute in a cyclic interwater hydrogen bonded network. The excess electron in these hydrated clusters is localized over the solute atoms. Weighted average VDE is calculated for each size (n) cluster based on statistical population of the conformers at 150 K. A linear relationship is obtained for VDE versus (n+3)(-1/3) and bulk VDE of Br2.- aqueous solution is calculated as 10.01 eV at MP2 level of theory. BHHLYP density functional is seen to make a systematic overestimation in VDE values by approximately 0.5 eV compared to MP2 data in all the hydrated clusters. It is observed that hydration increases VDE of bromine dimer anion system by approximately 6.4 eV. Calculated IR spectra show that the formation of Br2.--water clusters induces large shifts from the normal O-H stretching bands of isolated water keeping bending modes rather insensitive. Hydrated clusters, Br2.-.(H2O)n, show characteristic sharp features of O-H stretching bands of water in the small size clusters.

Theoretical studies on photoelectron and IR spectral properties of Br2.-(H2O)n clusters

Science.gov (United States)

Pathak, A. K.; Mukherjee, T.; Maity, D. K.

2007-07-01

We report vertical detachment energy (VDE) and IR spectra of Br2•-•(H2O)n clusters (n=1-8) based on first principles electronic structure calculations. Cluster structures and IR spectra are calculated at Becke's half-and-half hybrid exchange-correlation functional (BHHLYP) with a triple split valence basis function, 6-311++G(d,p). VDE for the hydrated clusters is calculated based on second order Moller-Plesset perturbation (MP2) theory with the same set of basis function. On full geometry optimization, it is observed that conformers having interwater hydrogen bonding among solvent water molecules are more stable than the structures having double or single hydrogen bonded structures between the anionic solute, Br2•-, and solvent water molecules. Moreover, a conformer having cyclic interwater hydrogen bonded network is predicted to be more stable for each size hydrated cluster. It is also noticed that up to four solvent H2O units can reside around the solute in a cyclic interwater hydrogen bonded network. The excess electron in these hydrated clusters is localized over the solute atoms. Weighted average VDE is calculated for each size (n) cluster based on statistical population of the conformers at 150K. A linear relationship is obtained for VDE versus (n+3)-1/3 and bulk VDE of Br2•- aqueous solution is calculated as 10.01eV at MP2 level of theory. BHHLYP density functional is seen to make a systematic overestimation in VDE values by ˜0.5eV compared to MP2 data in all the hydrated clusters. It is observed that hydration increases VDE of bromine dimer anion system by ˜6.4eV. Calculated IR spectra show that the formation of Br2•--water clusters induces large shifts from the normal O-H stretching bands of isolated water keeping bending modes rather insensitive. Hydrated clusters, Br2•-•(H2O)n, show characteristic sharp features of O-H stretching bands of water in the small size clusters.

Reply to Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO2 chains of Li2CuO2-δ ’

Science.gov (United States)

Shu, G. J.; Tian, J. C.; Lin, C. K.; Hayashi, M.; Liou, S. C.; Chen, W. T.; Wong, Deniz P.; Liou, H. L.; Chou, F. C.

2018-05-01

In this reply to the comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO2 chains of {{{Li}}}2{{{CuO}}}2-δ ’ (2017 New Journal of Physics 19 023206), we have clarified several key questions and conflicting results regarding the size of the intra-chain nearest neighbor coupling J 1 and the sign of the Weiss temperature Θ defined in the Curie–Weiss law of χ(T) = χ ◦ + C/(T ‑ Θ). Additional data analysis is conducted to verify the validity of the Curie–Weiss law fitting protocol, including the negative sign and size of Θ based on the high-temperature linear temperature dependence of 1/χ(T) for T > J 1 and \\tfrac{g{μ }B{SH}}{{k}BT}\\ll 1. The consistency between the magnetic antiferromagnetic (AF) ground state below T N and the negative sign of Θ in the high-temperature paramagnetic (PM) state is explained via the reduction of thermal fluctuation for a temperature-independent local field due to magnetic interaction of quantum nature. A magnetic dipole–dipole (MDD)-type interaction among FM chains is identified and proposed to be necessary for the 3D AF magnetic ground state formation, i.e., the Heisenberg model of an exchange-type interaction alone is not sufficient to fully describe the quasi-1D spin chain system of {{{Li}}}2{{{CuO}}}2. Several typical quasi-1D spin chain compounds, including {{{Li}}}2{{{CuO}}}2,{{{CuAs}}}2{{{O}}}4,{{{Sr}}}3{{{Fe}}}2{{{O}}}5, and CuGeO3, are compared to show why different magnetic ground states are achieved from the chemical bond perspective.

Crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses; Li2O-SiO2, Na2O-SiO2, Na2O-CaO-SiO2 kei glass no kessho sekishutsu kyodo

Energy Technology Data Exchange (ETDEWEB)

Tsutsumi, K.; Otake, J.; Nagasaka, T.; Hino, M. [Tohoku University, Sendai (Japan)

1998-06-01

It has been known that crystallization of mold powder is effective on the disturbance of heat transfer between mold and solidified shell in production of middle carbon steel slabs in continuous casting process. But it has not yet been made clear which composition of mold powder is the most suitable for crystallization. The crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses was observed by differential thermal analysis (DTA) and hot-thermocouple methods with DTA in the present work. As a result, addition of alkaline metal and alkaline earth metal oxides to SiO2 increased the critical cooling rate for glass formation in binary system of Li2O-SiO2 and Na2O-SiO2 and Li2O-SiO2 system crystallized easier than Na2O-SiO2 system. In ternary system of Na2O-CaO-SiO2, addition of Na2O hurried the critical cooling rate at CaO/SiO2=0.93 mass ratio, but the rate was almost constant in the composition range of more than 15 mass% Na2O. The slag of CaO/SiO2=0.93 made the rate faster than the slag of CaO/SiO2=0.47 at constant content of 10mass% Na2O. 17 refs., 10 figs., 3 tabs.

Characterization and Comparison of Photocatalytic Activity Silver Ion doped on TiO2(TiO2/Ag+) and Silver Ion doped on Black TiO2(Black TiO2/Ag+)

Science.gov (United States)

Kim, Jin Yi; Sim, Ho Hyung; Song, Sinae; Noh, Yeoung Ah; Lee, Hong Woon; Taik Kim, Hee

2018-03-01

Titanium dioxide (TiO2) is one of the representative ceramic materials containing photocatalyst, optic and antibacterial activity. The hydroxyl radical in TiO2 applies to the intensive oxidizing agent, hence TiO2 is suitable to use photocatalytic materials. Black TiO2was prepared through reduction of amorphous TiO2 conducting under H2 which leads to color changes. Its black color is proven that absorbs 100% light across the whole-visible light, drawing enhancement of photocatalytic property. In this study, we aimed to compare the photocatalytic activity of silver ion doped on TiO2(TiO2/Ag+) and silver ion doped on black TiO2(black TiO2/Ag+) under visible light range. TiO2/Ag+ was fabricated following steps. 1) TiO2 was synthesized by a sol-gel method from Titanium tetraisopropoxide (TTIP). 2) Then AgNO3 was added during an aging process step for silver ion doping on the surface of TiO2. Moreover, Black TiO2/Ag+ was obtained same as TiO2/Ag+ except for calcination under H2. The samples were characterized X-ray diffraction (XRD), UV-visible reflectance (UV-vis DRS), and Methylene Blue degradation test. XRD analysis confirmed morphology of TiO2. The band gap of black TiO2/Ag+ was confirmed (2.6 eV) through UV-vis DRS, which was lower than TiO2/Ag+ (2.9 eV). The photocatalytic effect was conducted by methylene blue degradation test. It demonstrated that black TiO2/Ag+ had a photocatalytic effect under UV light also visible light.

Relationship of O2 Photodesorption in Photooxidation of Acetone on TiO2

International Nuclear Information System (INIS)

Henderson, Michael A.

2008-01-01

Organic photooxidation on TiO2 invariably involves the coexistence of organic species with oxygen on the surface at the same time. In the case of acetone and oxygen, both species exhibit their own interesting photochemistry on TiO2, but interdependences between the two are not understood. In this study, a rutile TiO2(110) surface possessing 7% surface oxygen vacancy sites is used as a model surface to probe the relationship between O2 photodesorption and acetone photodecomposition. Temperature programmed desorption (TPD) and photon stimulated desorption (PSD) measurements indicate that coadsorbed oxygen is essential to acetone photodecomposition on this surface, however the form of oxygen (molecular and dissociative) is not known. The first steps in acetone photodecomposition on TiO2(110) involve thermal activation with oxygen to form an acetone diolate ((CH3)2COO) species followed by photochemical decomposition to adsorbed acetate (CH3COO) and an ejected CH3 radical that is detected in PSD. Depending on the surface conditions, O2 PSD is also observed during the latter process. However, the time scales for the two PSD events (CH3 and O2) are quite different, with the former occurring at ∼10 times faster than the latter. By varying the preheating conditions or performing pre-irradiation on an O2 exposed surface, it becomes clear that the two PSD events are uncorrelated. That is, the O2 species responsible for O2 PSD is not a significant participant in the photochemistry of acetone on TiO2(110) and likely originates from a minority form of O2 on the surface. The CH3 and O2 PSD events do not appear to be in competition with each other suggesting either that ample charge carriers exist under the experimental conditions employed or that different charge carriers or excitation mechanisms are involved

Effect of SnO2/SiO2 nano particle dispersant on the performance characteristic of complex multi-doped composite coating produced through electrodeposition on oil and gas storage tap

Directory of Open Access Journals (Sweden)

P.A.L. Anawe

2018-06-01

Full Text Available The effect of SnO2/SiO2 nano particle dispersant on the performance characteristic of complex zinc multi-doped composite coating produced through electrodeposition is studied. The degradation behaviour in term of wear and chemical corrosion activities were considered as a major factor in service. The wear mass loss was carried out with the help of reciprocating tester. The electrochemical corrosion characteristics were investigated using linear polarization technique in 3.5% simulated sodium chloride media. The outcome of the analysis shows that the developed coating was seen to provide a sound anti wear characteristics in its multidoped state. The corrosion resistance properties were observed to be massive compared to the binary based sample. It is expected that this characteristic will impact on the performance life span of storage tap in oil and gas. Keywords: Zn-SnO2-SiO2, Nanocomposite, Electrodeposition, Coatings and corrosion resistance

Thermophysical and anion diffusion properties of (U x ,Th1-x )O2.

Science.gov (United States)

Cooper, Michael W D; Murphy, Samuel T; Fossati, Paul C M; Rushton, Michael J D; Grimes, Robin W

2014-11-08

Using molecular dynamics, the thermophysical properties of the (U x ,Th 1- x )O 2 system have been investigated between 300 and 3600 K. The thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure is explained in terms of defect formation and diffusivity on the oxygen sublattice. Vegard's law is approximately observed for solid solution thermal expansion below 2000 K. Different deviations from Vegard's law above this temperature occur owing to the different temperatures at which the solid solutions undergo the superionic transition (2500-3300 K). Similarly, a spike in the specific heat, associated with the superionic transition, occurs at lower temperatures in solid solutions that have a high U content. Correspondingly, oxygen diffusivity is higher in pure UO 2 than in pure ThO 2 . Furthermore, at temperatures below the superionic transition, oxygen mobility is notably higher in solid solutions than in the end members. Enhanced diffusivity is promoted by lower oxygen-defect enthalpies in (U x ,Th 1- x )O 2 solid solutions. Unlike in UO 2 and ThO 2 , there is considerable variety of oxygen vacancy and oxygen interstitial sites in solid solutions generating a wide range of property values. Trends in the defect enthalpies are discussed in terms of composition and the lattice parameter of (U x ,Th 1- x )O 2 .

Thermophysical and anion diffusion properties of (Ux,Th1−x)O2

Science.gov (United States)

Cooper, Michael W. D.; Murphy, Samuel T.; Fossati, Paul C. M.; Rushton, Michael J. D.; Grimes, Robin W.

2014-01-01

Using molecular dynamics, the thermophysical properties of the (Ux,Th1−x)O2 system have been investigated between 300 and 3600 K. The thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure is explained in terms of defect formation and diffusivity on the oxygen sublattice. Vegard's law is approximately observed for solid solution thermal expansion below 2000 K. Different deviations from Vegard's law above this temperature occur owing to the different temperatures at which the solid solutions undergo the superionic transition (2500–3300 K). Similarly, a spike in the specific heat, associated with the superionic transition, occurs at lower temperatures in solid solutions that have a high U content. Correspondingly, oxygen diffusivity is higher in pure UO2 than in pure ThO2. Furthermore, at temperatures below the superionic transition, oxygen mobility is notably higher in solid solutions than in the end members. Enhanced diffusivity is promoted by lower oxygen-defect enthalpies in (Ux,Th1−x)O2 solid solutions. Unlike in UO2 and ThO2, there is considerable variety of oxygen vacancy and oxygen interstitial sites in solid solutions generating a wide range of property values. Trends in the defect enthalpies are discussed in terms of composition and the lattice parameter of (Ux,Th1−x)O2. PMID:25383028

Modelos linear e não linear em análises genéticas para sobrevivência de crias de ovinos da raça Santa Inês Linear and nonlinear models in genetic analyses of lamb survival in the Santa Inês hair sheep breed

Directory of Open Access Journals (Sweden)

W.H. Sousa

1999-06-01

Full Text Available Registros de sobrevivência do nascimento ao desmame de 3846 crias de ovinos da raça Santa Inês foram analisados por modelos de reprodutor linear e não linear (modelo de limiar, para estimar componentes de variância e herdabilidade. Os modelos usados para sobrevivência, analisada como característica da cria, incluíram os efeitos fixos de sexo, da combinação tipo de nascimento-criação da cria e da idade da ovelha ao parto, efeito da covariável peso da cria ao nascer e efeitos aleatórios de reprodutor, da classe rebanho-ano-estação e do resíduo. Componentes de variância para o modelo linear foram estimados pelo método da máxima verossimilhança restrita (REML e para o modelo não linear por uma aproximação da máxima verossimilhança marginal (MML, pelo programa CMMAT2. O coeficiente de herdabilidade (h² estimado pelo modelo de limiar foi de 0,29, e pelo modelo linear, 0,14. A correlação de ordem de Spearman entre as capacidades de transmissão dos reprodutores, com base nos dois modelos foi de 0,96. As estimativas de h² obtidas indicam a possibilidade de se obter, por seleção, ganho genético para sobrevivência.Records of 3,846 lambs survival from birth to weaning of Santa Inês hair sheep breed, were analyzed by linear and non linear sire models (threshold model to estimate variance components and heritability (h². The models that were used to analyze survival, considered in this study as a lamb trait, included the fixed effects of sex of the lamb, combination of type of birth-rearing of lamb, and age of ewe, birth weight of lamb as covariate, and random effects of sire, herd-year-season and residual. Variance components were obtained using restricted maximum likelihood (REML, in linear model and marginal maximum likelihood in threshold model through CMMAT2 program. Estimate of heritability (h² obtained by threshold model was 0.29 and by linear model was 0.14. Rank correlation of Spearman, between sire solutions

An end-to-end coupled model ROMS-N 2 P 2 Z 2 D 2 -OSMOSE of ...

African Journals Online (AJOL)

An end-to-end coupled model ROMS-N 2 P 2 Z 2 D 2 -OSMOSE of the southern Benguela foodweb: parameterisation, calibration and pattern-oriented validation. ... We also highlight the capacity of this model for tracking indicators at various hierarchical levels. Keywords: individual-based model, model validation, ...

Crystallization and electrical resistivity of Cu2O and CuO obtained by thermal oxidation of Cu thin films on SiO2/Si substrates

International Nuclear Information System (INIS)

De Los Santos Valladares, L.; Salinas, D. Hurtado; Dominguez, A. Bustamante; Najarro, D. Acosta; Khondaker, S.I.; Mitrelias, T.; Barnes, C.H.W.; Aguiar, J. Albino; Majima, Y.

2012-01-01

In this work, we study the crystallization and electrical resistivity of the formed oxides in a Cu/SiO 2 /Si thin film after thermal oxidation by ex-situ annealing at different temperatures up to 1000 °C. Upon increasing the annealing temperature, from the X ray diffractogram the phase evolution Cu → Cu + Cu 2 O → Cu 2 O → Cu 2 O + CuO → CuO was detected. Pure Cu 2 O films are obtained at 200 °C, whereas uniform CuO films without structural surface defects such as terraces, kinks, porosity or cracks are obtained in the temperature range 300–550 °C. In both oxides, crystallization improves with annealing temperature. A resistivity phase diagram, which is obtained from the current–voltage response, is presented here. The resistivity was expected to increase linearly as a function of the annealing temperature due to evolution of oxides. However, anomalous decreases are observed at different temperatures ranges, this may be related to the improvement of the crystallization and crystallite size when the temperature increases. - Highlights: ► The crystallization and electrical resistivity of oxides in a Cu films are studied. ► In annealing Cu films, the phase evolution Cu + Cu 2 O → Cu 2 O → Cu 2 O + CuO → CuO occurs. ► A resistivity phase diagram, obtained from the current–voltage response, is presented. ► Some decreases in the resistivity may be related to the crystallization.

Evidence of Coulomb correction and spinorbit coupling in rare-earth dioxides CeO 2, PrO 2 and TbO 2: An ab initio study

KAUST Repository

Kanoun, Mohammed; Reshak, A. H.; Kanoun-Bouayed, Nawel; Goumri-Said, Souraya

2012-01-01

The current study investigates the structural, elastic, electronic and optical properties of CeO 2, PrO 2 and TbO 2 using the full potential (linearized) augmented plane wave plus local orbital method within the WuCohen generalized gradient approximation (GGA) with Hubbard (U) correction and spinorbit coupling (SOC). The GGAU implementation lead us to describe correctly the relativistic effect on 4f electrons for CeO 2. We clarify that the inclusion of the Hubbard U parameter and the spinorbit coupling are responsible for the ferromagnetic insulating of PrO 2 and TbO 2. The magnetic description is achieved by the spin-density contours and magnetic moment calculations, where we show the polarization of oxygen atoms from the rare earth atoms. The mechanical stability is shown via the elastic constants calculations. The optical properties, namely the dielectric function and the reflectivity are calculated for radiation up to 12 eV, giving interesting optoelectronic properties to these dioxides. © 2011 Elsevier B.V. All rights reserved.

Evidence of Coulomb correction and spinorbit coupling in rare-earth dioxides CeO 2, PrO 2 and TbO 2: An ab initio study

KAUST Repository

Kanoun, Mohammed

2012-04-01

The current study investigates the structural, elastic, electronic and optical properties of CeO 2, PrO 2 and TbO 2 using the full potential (linearized) augmented plane wave plus local orbital method within the WuCohen generalized gradient approximation (GGA) with Hubbard (U) correction and spinorbit coupling (SOC). The GGAU implementation lead us to describe correctly the relativistic effect on 4f electrons for CeO 2. We clarify that the inclusion of the Hubbard U parameter and the spinorbit coupling are responsible for the ferromagnetic insulating of PrO 2 and TbO 2. The magnetic description is achieved by the spin-density contours and magnetic moment calculations, where we show the polarization of oxygen atoms from the rare earth atoms. The mechanical stability is shown via the elastic constants calculations. The optical properties, namely the dielectric function and the reflectivity are calculated for radiation up to 12 eV, giving interesting optoelectronic properties to these dioxides. © 2011 Elsevier B.V. All rights reserved.

Seleção e classificação multivariada de modelos de crescimento não lineares para bovinos Nelore

Directory of Open Access Journals (Sweden)

N.A.M. Silva

2011-04-01

Full Text Available Utilizou-se análise de agrupamento para classificar e selecionar modelos não lineares de crescimento de bovinos Nelore, tendo em vista os resultados de diferentes avaliadores de qualidade de ajuste. Ajustaram-se 12 modelos não lineares. A qualidade de ajuste dos modelos foi medida pelo coeficiente de determinação (R², quadrado médio do erro (QME, critério de informação de Akaike (AIC, critério de informação Bayesiano (BIC, erro quadrático médio de predição (MEP e coeficiente de determinação de predição (R²p. O modelo Brody foi o que apresentou o melhor ajuste para o conjunto de dados.

On Optimal Linear Filtering of Speech for Near-End Listening Enhancement

DEFF Research Database (Denmark)

Taal, Cees H.; Jensen, Jesper; Leijon, Arne

2013-01-01

In this letter the focus is on linear filtering of speech before degradation due to additive background noise. The goal is to design the filter such that the speech intelligibility index (SII) is maximized when the speech is played back in a known noisy environment. Moreover, a power constraint i...

Studies on the O-polysaccharide of Escherichia albertii O2 characterized by non-stoichiometric O-acetylation and non-stoichiometric side-chain l-fucosylation.

Science.gov (United States)

Naumenko, Olesya I; Zheng, Han; Xiong, Yanwen; Senchenkova, Sof'ya N; Wang, Hong; Shashkov, Alexander S; Li, Qun; Wang, Jianping; Knirel, Yuriy A

2018-05-22

An O-polysaccharide was isolated from the lipopolysaccharide of Escherichia albertii O2 and studied by chemical methods and 1D and 2D 1 H and 13 C NMR spectroscopy. The following structure of the O-polysaccharide was established: . The O-polysaccharide is characterized by masked regularity owing to a non-stoichiometric O-acetylation of an l-fucose residue in the main chain and a non-stoichiometric side-chain l-fucosylation of a β-GlcNAc residue. A regular linear polysaccharide was obtained by sequential Smith degradation and alkaline O-deacetylation of the O-polysaccharide. The content of the O-antigen gene cluster of E. albertii O2 was found to be essentially consistent with the O-polysaccharide structure established. Copyright © 2018 Elsevier Ltd. All rights reserved.

Synthetic, structural, spectroscopic and theoretical study of a Mn(III)-Cu(II) dimer containing a Jahn-Teller compressed Mn ion

DEFF Research Database (Denmark)

Berg, Nelly; Hooper, Thomas N.; Liu, Junjie

2013-01-01

The heterobimetallic complex [Cu(II)Mn(III)(L)(2)(py)(4)](ClO(4))·EtOH (1) built using the pro-ligand 2,2'-biphenol (LH(2)), contains a rare example of a Jahn-Teller compressed Mn(III) centre. Dc magnetic susceptibility measurements on 1 reveal a strong antiferromagnetic exchange between the Cu...

On index-2 linear implicit difference equations

NARCIS (Netherlands)

Nguyen Huu Du, [No Value; Le Cong Loi, [No Value; Trinh Khanh Duy, [No Value; Vu Tien Viet, [No Value

2011-01-01

This paper deals with an index-2 notion for linear implicit difference equations (LIDEs) and with the solvability of initial value problems (IVPs) for index-2 LIDEs. Besides, the cocycle property as well as the multiplicative ergodic theorem of Oseledets type are also proved. (C) 2010 Elsevier Inc.

Modelos não lineares para a liberação de potássio de estercos animais em latossolos Non linear models to potassium release from animals manure in Latosols

Directory of Open Access Journals (Sweden)

Walmes Marques Zeviani

2012-10-01

Full Text Available Modelos não lineares são adequados para a descrição da liberação de nutrientes, uma vez que estimam quantidades de interesse prático e apresentam boa qualidade de ajuste. Embora seu processo inferencial seja baseado em argumentos assintóticos, existem meios de se conhecer a intensidade da não linearidade. Neste trabalho, avaliou-se a não linearidade de dois modelos de regressão não linear por meio das curvaturas de Bates e Watts, vício de Box e do estudo das propriedades amostrais dos estimadores de mínimos quadrados, obtido por simulação. Os dados são provenientes do estudo, ao longo do tempo, da liberação de K de quatro estercos animais em combinação com dois solos. O modelo Exponencial foi mais adequado, em termos inferenciais e para aplicação prática, uma vez que por todas as medidas apresentou menor não linearidade.Nonlinear models are appropriate to describe nutrient release, since they estimate quantities of practical interest and they have goodness of fit. Although its inferential process is based on asymptotic arguments, there are ways to know the nonlinearity intensity. In this work, we evaluate the nonlinearity of two nonlinear regression models through the curvatures of Bates e Watts, bias of Box and the least squares estimator sampling properties by simulation study. The data are from the study, over time, of the K release from 4 animal manure in combination with 2 soils. The exponential model was more appropriate in terms of inferential and practical aspects, since by all measures showed lower nonlinearity.

A novel H(2)O(2) amperometric biosensor based on gold nanoparticles/self-doped polyaniline nanofibers.

Science.gov (United States)

Chen, Xiaojun; Chen, Zixuan; Zhu, Jinwei; Xu, Chenbin; Yan, Wei; Yao, Cheng

2011-10-01

A new kind of gold nanoparticles/self-doped polyaniline nanofibers (Au/SPAN) with grooves has been prepared for the immobilization of horseradish peroxidase (HRP) on the surface of glassy carbon electrode (GCE). The ratio of gold in the composite nanofibers was up to 64%, which could promote the conductivity and biocompatibility of SPAN and increase the immobilized amount of HRP molecules greatly. The electrode exhibits enhanced electrocatalytic activity in the reduction of H(2)O(2) in the presence of the mediator hydroquinone (HQ). The effects of concentration of HQ, solution pH and the working potential on the current response of the modified electrode toward H(2)O(2) were optimized to obtain the maximal sensitivity. The proposed biosensor exhibited a good linear response in the range from 10 to 2000 μM with a detection limit of 1.6 μM (S/N=3) under the optimum conditions. The response showed Michaelis-Menten behavior at larger H(2)O(2) concentrations, and the apparent Michaelis-Menten constant K(m) was estimated to be 2.21 mM. The detection of H(2)O(2) concentration in real sample showed acceptable accuracy with the traditional potassium permanganate titration. Copyright © 2011 Elsevier B.V. All rights reserved.

Manganese Driven Carbon Oxidation along Oxic-Anoxic Interfaces in Forest Soils

Science.gov (United States)

Jones, M. E.; Keiluweit, M.

2017-12-01

Soils are the largest and most dynamic terrestrial carbon pool, storing a total of 3000 Pg of C - more than the atmosphere and biosphere combined. Because microbial oxidation determines the proportion of carbon that is either stored in the soil or emitted as climate active CO2, its rate directly impacts the global carbon cycle. Recently, a strong correlation between oxidation rates and manganese (Mn) content has been observed in forest soils globally, leading researchers conclude that Mn "is the single main factor governing" the oxidation of plant-derived particulate organic carbon (POC). Many soils are characterized by steep oxygen gradients, forming oxic-anoxic transitions that enable rapid redox cycling of Mn. Oxic-anoxic interfaces have been shown to promote fungal Mn oxidation and the formation of ligand-stabilized Mn(III), which ranks second only to superoxide as the most powerful oxidizing agent in the environment. Here we examined fungal Mn(III) formation along redox gradients in forest soils and their impact on POC oxidation rates. In both field and laboratory settings, oxic-anoxic transition zones showed the greatest Mn(III) concentrations, along with enhanced fungal growth, oxidative potential, production of soluble oxidation products, and CO2 production. Additional electrochemical and X-ray (micro)spectroscopic analyses indicated that oxic-anoxic interfaces represent ideal niches for fungal Mn(III) formation, owing to the ready supply of Mn(II), ligands and O2. Combined, our results suggest that POC oxidation relies on fungal Mn cycling across oxic-anoxic interfaces to produce Mn(III) based oxidants. Because predicted changes in the frequency and timing of precipitation dramatically alter soil moisture regimes in forest soils, understanding the mechanistic link between Mn cycling and carbon oxidation along oxic-anoxic interfaces is becoming increasingly important.

Solid state compatibility in the ZnO-rich region of ZnO-Bi2O3-Sb2O3 and ZnO-Bi2O3-Sb2O5 systems

Directory of Open Access Journals (Sweden)

Jardiel, T.

2010-04-01

Full Text Available The obtaining of ZnO-Bi2O3-Sb2O3 (ZBS based varistor thick films with high non-linear properties is constrained by the bismuth loss by vaporization that takes place during the sintering step of these ceramics, a process which is yet more critical in the thick film geometry due to its inherent high are/volume ratio. This volatilization can be controlled to a certain extent by modifying the proportions of the Bi and/or Sb precursors. Obviously this requires a clear knowledge of the different solid state compatibilities in the mentioned ZBS system. In this sense a detailed study of the thermal evolution of the ZnO-Bi2O3-Sb2O3 and ZnO-Bi2O3-Sb2O5 systems in the ZnO-rich region of interest for varistors, is presented in this contribution. A different behaviour is observed when using Sb2O3 or Sb2O5 as starting precursor, which should be attributed to the oxidation process experimented by Sb2O3 compound during the heating. On the other hand the use of high amounts of Bi in the starting formulation leads to the formation of a liquid phase at lower temperatures, which would allow the use of lower sintering temperatures.La obtención de varistors en lámina gruesa basados en ZnO-Bi2O3-Sb2O3 (ZBS y con propiedades altamente no-lineales está limitada por la perdida de bismuto por volatilización durante la sinterización de estos cerámicos, un proceso que es todavía más crítico en la geometría de lámina gruesa debido a su elevada relación área/volumen inherente. Dicha volatilización puede ser no obstante controlada hasta cierta extensión modificando las proporciones de los precursores de Bi y/o Sb. Obviamente ello conlleva un amplio conocimiento de las diferentes compatibilidades en estado sólido en el mencionado sistema ZBS. En este sentido, en la presente contribución se presenta un estudio detallado de la evolución térmica de los sistemas ZnO-Bi2O3-Sb2O3 y ZnO-Bi2O3-Sb2O5 en la región rica en ZnO de interés para varistores. Como

Ni2Sr(PO42·2H2O

Directory of Open Access Journals (Sweden)

Lahcen El Ammari

2010-12-01

Full Text Available The title compound, dinickel(II strontium bis[orthophosphate(V] dihydrate, was obtained under hydrothermal conditions. The crystal structure consists of linear chains ∞1[NiO2/2(OH22/2O2/1] of edge-sharing NiO6 octahedra (overline{1} symmetry running parallel to [010]. Adjacent chains are linked to each other through PO4 tetrahedra (m symmetry and arranged in such a way to build layers parallel to (001. The three-dimensional framework is accomplished by stacking of adjacent layers that are held together by SrO8 polyhedra (2/m symmetry. Two types of O—H...O hydrogen bonds involving the water molecule are present, viz. one very strong hydrogen bond perpendicular to the layers and weak trifurcated hydrogen bonds parallel to the layers.

Study on rapid bio-drying technology of cow dung with CaO2

Science.gov (United States)

Chen, Xiaotian; Qu, Guangfei; Liu, Shugen; Xie, Ruosong; He, Yanhua

2017-05-01

Effect of CaO2 on cow dung rapid bio-drying technology was researched. A static aerobic composting system was applied to this experiment which combining natural ventilation with Turing in the process of composting. The physical characteristics of cow dung was observed and the compost temperature, moisture content, organic matter, total nitrogen, total phosphorus, potassium content was determined which in order to study the effect of CaO2 on rapid drying of cattle in the compost. In the initial stage of compost, adding CaO2 groups compared with the control group, the temperature rise faster, 4-6 days in advance to the thermophilic phase; at the end of composting, the CaO2 composition and moisture content decreased significantly to below 30%. The addition of CaO2 in fertilizer was shorten the composting time, extend the thermophilic phase, to provide sufficient oxygen meeting the growth needs of aerobic microorganisms. It convinced that the rapid bio-drying of dairy manure has a good effect and provided a new idea for the effective treatment of cow dung.

Non-linear absorption for concentrated solar energy transport

Energy Technology Data Exchange (ETDEWEB)

Jaramillo, O. A; Del Rio, J.A; Huelsz, G [Centro de Investigacion de Energia, UNAM, Temixco, Morelos (Mexico)

2000-07-01

In order to determine the maximum solar energy that can be transported using SiO{sub 2} optical fibers, analysis of non-linear absorption is required. In this work, we model the interaction between solar radiation and the SiO{sub 2} optical fiber core to determine the dependence of the absorption of the radioactive intensity. Using Maxwell's equations we obtain the relation between the refractive index and the electric susceptibility up to second order in terms of the electric field intensity. This is not enough to obtain an explicit expression for the non-linear absorption. Thus, to obtain the non-linear optical response, we develop a microscopic model of an harmonic driven oscillators with damp ing, based on the Drude-Lorentz theory. We solve this model using experimental information for the SiO{sub 2} optical fiber, and we determine the frequency-dependence of the non-linear absorption and the non-linear extinction of SiO{sub 2} optical fibers. Our results estimate that the average value over the solar spectrum for the non-linear extinction coefficient for SiO{sub 2} is k{sub 2}=10{sup -}29m{sup 2}V{sup -}2. With this result we conclude that the non-linear part of the absorption coefficient of SiO{sub 2} optical fibers during the transport of concentrated solar energy achieved by a circular concentrator is negligible, and therefore the use of optical fibers for solar applications is an actual option. [Spanish] Con el objeto de determinar la maxima energia solar que puede transportarse usando fibras opticas de SiO{sub 2} se requiere el analisis de absorcion no linear. En este trabajo modelamos la interaccion entre la radiacion solar y el nucleo de la fibra optica de SiO{sub 2} para determinar la dependencia de la absorcion de la intensidad radioactiva. Mediante el uso de las ecuaciones de Maxwell obtenemos la relacion entre el indice de refraccion y la susceptibilidad electrica hasta el segundo orden en terminos de intensidad del campo electrico. Esto no es

Genetic characterization and role in virulence of the ribonucleotide reductases of Streptococcus sanguinis.

Science.gov (United States)

Rhodes, DeLacy V; Crump, Katie E; Makhlynets, Olga; Snyder, Melanie; Ge, Xiuchun; Xu, Ping; Stubbe, JoAnne; Kitten, Todd

2014-02-28

Streptococcus sanguinis is a cause of infective endocarditis and has been shown to require a manganese transporter called SsaB for virulence and O2 tolerance. Like certain other pathogens, S. sanguinis possesses aerobic class Ib (NrdEF) and anaerobic class III (NrdDG) ribonucleotide reductases (RNRs) that perform the essential function of reducing ribonucleotides to deoxyribonucleotides. The accompanying paper (Makhlynets, O., Boal, A. K., Rhodes, D. V., Kitten, T., Rosenzweig, A. C., and Stubbe, J. (2014) J. Biol. Chem. 289, 6259-6272) indicates that in the presence of O2, the S. sanguinis class Ib RNR self-assembles an essential diferric-tyrosyl radical (Fe(III)2-Y(•)) in vitro, whereas assembly of a dimanganese-tyrosyl radical (Mn(III)2-Y(•)) cofactor requires NrdI, and Mn(III)2-Y(•) is more active than Fe(III)2-Y(•) with the endogenous reducing system of NrdH and thioredoxin reductase (TrxR1). In this study, we have shown that deletion of either nrdHEKF or nrdI completely abolishes virulence in an animal model of endocarditis, whereas nrdD mutation has no effect. The nrdHEKF, nrdI, and trxR1 mutants fail to grow aerobically, whereas anaerobic growth requires nrdD. The nrdJ gene encoding an O2-independent adenosylcobalamin-cofactored RNR was introduced into the nrdHEKF, nrdI, and trxR1 mutants. Growth of the nrdHEKF and nrdI mutants in the presence of O2 was partially restored. The combined results suggest that Mn(III)2-Y(•)-cofactored NrdF is required for growth under aerobic conditions and in animals. This could explain in part why manganese is necessary for virulence and O2 tolerance in many bacterial pathogens possessing a class Ib RNR and suggests NrdF and NrdI may serve as promising new antimicrobial targets.

Genetic Characterization and Role in Virulence of the Ribonucleotide Reductases of Streptococcus sanguinis * ♦

Science.gov (United States)

Rhodes, DeLacy V.; Crump, Katie E.; Makhlynets, Olga; Snyder, Melanie; Ge, Xiuchun; Xu, Ping; Stubbe, JoAnne; Kitten, Todd

2014-01-01

Streptococcus sanguinis is a cause of infective endocarditis and has been shown to require a manganese transporter called SsaB for virulence and O2 tolerance. Like certain other pathogens, S. sanguinis possesses aerobic class Ib (NrdEF) and anaerobic class III (NrdDG) ribonucleotide reductases (RNRs) that perform the essential function of reducing ribonucleotides to deoxyribonucleotides. The accompanying paper (Makhlynets, O., Boal, A. K., Rhodes, D. V., Kitten, T., Rosenzweig, A. C., and Stubbe, J. (2014) J. Biol. Chem. 289, 6259–6272) indicates that in the presence of O2, the S. sanguinis class Ib RNR self-assembles an essential diferric-tyrosyl radical (FeIII2-Y•) in vitro, whereas assembly of a dimanganese-tyrosyl radical (MnIII2-Y•) cofactor requires NrdI, and MnIII2-Y• is more active than FeIII2-Y• with the endogenous reducing system of NrdH and thioredoxin reductase (TrxR1). In this study, we have shown that deletion of either nrdHEKF or nrdI completely abolishes virulence in an animal model of endocarditis, whereas nrdD mutation has no effect. The nrdHEKF, nrdI, and trxR1 mutants fail to grow aerobically, whereas anaerobic growth requires nrdD. The nrdJ gene encoding an O2-independent adenosylcobalamin-cofactored RNR was introduced into the nrdHEKF, nrdI, and trxR1 mutants. Growth of the nrdHEKF and nrdI mutants in the presence of O2 was partially restored. The combined results suggest that MnIII2-Y•-cofactored NrdF is required for growth under aerobic conditions and in animals. This could explain in part why manganese is necessary for virulence and O2 tolerance in many bacterial pathogens possessing a class Ib RNR and suggests NrdF and NrdI may serve as promising new antimicrobial targets. PMID:24381171

Lattice contraction and lattice deformation of UO{sub 2} and ThO{sub 2} doped with Gd{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Baena, Angela [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Boeretang 200, B-2400 Mol (Belgium); KU Leuven, Department of Chemistry, Celestijnenlaan 200F, P.O. Box 2404, B-3001 Heverlee (Belgium); Cardinaels, Thomas; Govers, Kevin; Pakarinen, Janne [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Boeretang 200, B-2400 Mol (Belgium); Binnemans, Koen [KU Leuven, Department of Chemistry, Celestijnenlaan 200F, P.O. Box 2404, B-3001 Heverlee (Belgium); Verwerft, Marc, E-mail: marc.verwerft@sckcen.be [Belgian Nuclear Research Centre (SCK-CEN), Institute for Nuclear Materials Science, Boeretang 200, B-2400 Mol (Belgium)

2015-12-15

The lattice deformations in two doped fluorite systems, (U{sub 1−x}Gd{sub x})O{sub 2.00} and (Th{sub 1−x}Gd{sub x})O{sub 2−x/2}, have been reassessed by precise X-ray and electron diffraction investigations and the results were interpreted using the Bond Valence Sum (BVS) approach. For the (U{sub 1−x}Gd{sub x})O{sub 2.00} system, the experimental findings and theoretical assessment confirm earlier work: the lattice keeps its fluorite structure with a unit cell parameter that contracts linearly with dopant concentration. The lattice contraction in the (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} system has for the first time been analyzed up to the solubility limit. Similar as for (U{sub 1−x}Gd{sub x})O{sub 2.00}, the (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} solid solution contracts linearly as a function of dopant concentration but additionally, it develops a superstructure which is closely related to the parent fluorite structure. An excess anion bixbyite trial model is proposed to describe this superstructure. - Highlights: • Lattice deformations of (U{sub 1−x}Gd{sub x})O{sub 2.00} & (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} are not identical. • (U{sub 1−x}Gd{sub x})O{sub 2.00} retains its fluorite structure. • (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} forms an excess-anion bixbyite structure. • (U{sub 1−x}Gd{sub x})O{sub 2.00} and (Th{sub 1−x}Gd{sub x})O{sub 2−x/2} contractions were evaluated with high precision.

Al2O3 Passivation Effect in HfO2·Al2O3 Laminate Structures Grown on InP Substrates.

Science.gov (United States)

Kang, Hang-Kyu; Kang, Yu-Seon; Kim, Dae-Kyoung; Baik, Min; Song, Jin-Dong; An, Youngseo; Kim, Hyoungsub; Cho, Mann-Ho

2017-05-24

The passivation effect of an Al 2 O 3 layer on the electrical properties was investigated in HfO 2 -Al 2 O 3 laminate structures grown on indium phosphide (InP) substrate by atomic-layer deposition. The chemical state obtained using high-resolution X-ray photoelectron spectroscopy showed that interfacial reactions were dependent on the presence of the Al 2 O 3 passivation layer and its sequence in the HfO 2 -Al 2 O 3 laminate structures. Because of the interfacial reaction, the Al 2 O 3 /HfO 2 /Al 2 O 3 structure showed the best electrical characteristics. The top Al 2 O 3 layer suppressed the interdiffusion of oxidizing species into the HfO 2 films, whereas the bottom Al 2 O 3 layer blocked the outdiffusion of In and P atoms. As a result, the formation of In-O bonds was more effectively suppressed in the Al 2 O 3 /HfO 2 /Al 2 O 3 /InP structure than that in the HfO 2 -on-InP system. Moreover, conductance data revealed that the Al 2 O 3 layer on InP reduces the midgap traps to 2.6 × 10 12 eV -1 cm -2 (compared to that of HfO 2 /InP, that is, 5.4 × 10 12 eV -1 cm -2 ). The suppression of gap states caused by the outdiffusion of In atoms significantly controls the degradation of capacitors caused by leakage current through the stacked oxide layers.

H2O2 sensing using HRP modified catalyst-free ZnO nanorods synthesized by RF sputtering

Science.gov (United States)

Srivastava, Amit; Kumar, Naresh; Singh, Priti; Singh, Sunil Kumar

2017-06-01

Catalyst-free ( 00 l) oriented ZnO nanorods (NRs) -based biosensor for the H2O2 sensing has been reported. The (002) oriented ZnO NRs as confirmed by X-ray diffraction were successfully grown on indium tin oxide (ITO) coated glass substrate by radio frequency (RF) sputtering technique without using any catalyst. Horseradish peroxidase (HRP) enzyme was immobilized on ZnO NRs by physical adsorption technique to prepare the biosensor. In this HRP/ZnO NR/ITO bioelectrode, nafion solution was added to form a tight membrane on surface. The prepared bioelectrode has been used for biosensing measurements by electrochemical analyzer. The electrochemical studies reveal that the prepared HRP/ZnO NR/ITO biosensor is highly sensitive to the detection of H2O2 over a linear range of 0.250-10 μM. The ZnO NR-based biosensor showed lower value of detection limit (0.125 μM) and higher sensitivity (13.40 µA/µM cm2) towards H2O2. The observed value of higher sensitivity attributed to larger surface area of ZnO nanostructure for effective loading of HRP besides its high electron communication capability. In addition, the biosensor also shows lower value of enzyme's kinetic parameter (Michaelis-Menten constant, K m) of 0.262 μM which indicates enhanced enzyme affinity of HRP to H2O2. The reported biosensor may be useful for various applications in biosensing, clinical, food, and beverage industry.

Electronic structures and Eu3+ photoluminescence behaviors in Y2Si2O7 and La2Si2O7

International Nuclear Information System (INIS)

Zhang Zhiya; Wang Yuhua; Zhang Feng; Cao Haining

2011-01-01

Research highlights: → Host excitation near the band gap of Y 2 Si 2 O 7 and La 2 Si 2 O 7 is analyzed. → The calculated result well explains Eu 3+ PL behaviors in Y 2 Si 2 O 7 and La 2 Si 2 O 7 . → The electronic structure and Eu 3+ VUV PL in La 2 Si 2 O 7 are first estimated. - Abstract: The electronic structures and linear optical properties of Y 2 Si 2 O 7 (YSO) and La 2 Si 2 O 7 (LSO) are calculated by LDA method based on the theory of DFT. Both YSO and LSO are direct-gap materials with the direct band gap of 5.89 and 6.06 eV, respectively. The calculated total and partial density of states indicate that in both YSO and LSO the valence band (VB) is mainly constructed from O 2p and the conduction band (CB) is mostly formed from Y 4d or La 5d. Both the calculated VB and CB of YSO exhibit relatively wider dispersion than that of LSO. In addition, the CB of YSO presents more electronic states. Meanwhile, the VB of LSO shows narrower energy distribution with higher electronic states density. The theoretical absorption of YSO shows larger bandwidth and higher intensity than that of LSO. The results are compared with the experimental host excitations and impurity photoluminescence in Eu 3+ -doped YSO and LSO.

Nonlinear to Linear Elastic Code Coupling in 2-D Axisymmetric Media.

Energy Technology Data Exchange (ETDEWEB)

Preston, Leiph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-08-01

Explosions within the earth nonlinearly deform the local media, but at typical seismological observation distances, the seismic waves can be considered linear. Although nonlinear algorithms can simulate explosions in the very near field well, these codes are computationally expensive and inaccurate at propagating these signals to great distances. A linearized wave propagation code, coupled to a nonlinear code, provides an efficient mechanism to both accurately simulate the explosion itself and to propagate these signals to distant receivers. To this end we have coupled Sandia's nonlinear simulation algorithm CTH to a linearized elastic wave propagation code for 2-D axisymmetric media (axiElasti) by passing information from the nonlinear to the linear code via time-varying boundary conditions. In this report, we first develop the 2-D axisymmetric elastic wave equations in cylindrical coordinates. Next we show how we design the time-varying boundary conditions passing information from CTH to axiElasti, and finally we demonstrate the coupling code via a simple study of the elastic radius.

Nonlinear acoustic properties of the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) phosphate glasses

International Nuclear Information System (INIS)

Senin, H.B.; Sidek, H.A.A.; Saunders, G.A.

1994-01-01

From measurements of changes in transit time of 10 MHz of ultrasonic wave as a function of temperature and hydrostatic pressure, the linear and non-linear acoustic properties of the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses with compositions near to that corresponding to the metaphosphate have been determined. For each glass the second order elastic stiffness tensor components C sub ijs (SOEC) continue to increase down to 10K in a manner consistent with phonons interactions with two level systems. Measurements of the effects of hydrostatic pressure on the ultrasonic wave velocities have been used to determine the hydrostatic pressure derivatives (dC sub ij/dP) sub T,P=0 of the SOEC and (dB0 sup s)/dP) sub T,P=0 of the bulk modulus B0 sup s at room temperature (293K). For the ternary (La sub 2 O sub 3) sub x (Sm sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses, (dC sub 11/dP), (dC sub 44/dP), and (dBo/dP), are small but positives; these glasses stiffen under pressure. The elastic behaviour of these ternary glasses lies intermediate between those of (Sm sub 2 O sub 3)(P sub 2 O sub 5) sub (1-x) and (La sub 2 O sub 3) sub y (P sub 2 O sub 5) sub (1-x-y) glasses. Replacement of the Sm sup 3+ by La sup 3+ in the ternary phosphate glasses negates the acoustic mode softening. Possible sources of the different effects of La sub 3+ and Sm sub 3+ modifiers on the nonlinear acoustic properties of metaphosphate glasses are discussed

Linear-scaling density-functional simulations of charged point defects in Al2O3 using hierarchical sparse matrix algebra.

Science.gov (United States)

Hine, N D M; Haynes, P D; Mostofi, A A; Payne, M C

2010-09-21

We present calculations of formation energies of defects in an ionic solid (Al(2)O(3)) extrapolated to the dilute limit, corresponding to a simulation cell of infinite size. The large-scale calculations required for this extrapolation are enabled by developments in the approach to parallel sparse matrix algebra operations, which are central to linear-scaling density-functional theory calculations. The computational cost of manipulating sparse matrices, whose sizes are determined by the large number of basis functions present, is greatly improved with this new approach. We present details of the sparse algebra scheme implemented in the ONETEP code using hierarchical sparsity patterns, and demonstrate its use in calculations on a wide range of systems, involving thousands of atoms on hundreds to thousands of parallel processes.

[Influence of La2O3 and Li2O on glass powder for infiltrating ZTA all-ceramic dental material formed by gel-casting].

Science.gov (United States)

Jin, Qiong; Wang, Xiao-fei; Yang, Zheng-yu; Tong, Yi-ping; Zhu, Li; Ma, Jian-feng

2012-10-01

The influence of La2O3 and Li2O on glass powder was studied in this paper, which is to infiltrate ZTA all-ceramic dental material formed by gel-casting. The performance of different component was analyzed to optimize glass formula. Six groups of glass powder were designed and prepared by conventional melt-quenching method. ZTA ceramic blocks were covered with glass paste, which were formed by gel-casting and sintered in 1200 degrees centigrade, then infiltrated in 1150 degrees centigrade for twice to make glass/ZTA ceramic composites. By detecting differential thermal analysis and melting range of infiltration glass power, as well as flexural strength, linear shrinkage, SEM and EDS of glass/ZTA ceramic composites, the optimized glass group was determined out. Statistical analysis was performed using SPSS 13.0 software package by means of paired t test or one way ANOVA. The bending strength of group Li1 was (291.2±27.9) MPa, significantly higher than group Li2 and group La2(Pglass of group Li1 can lubricate ZTA ceramics well, their structure was compact and had a few small pores. Intergranular fracture existed on cross surface as well as transgranular fracture. The results showed that Li1(30%La2O3-15%Al2O3-15%SiO2-15%B2O3-5%Li2O) glass infiltrated ZTA ceramic composite had the best capability. Glass/ZTA composite material can be prepared by gel-casting and infiltrating way, and this process is simple and economically suitable for general dental laboratory.

Effect of titanium and calcium oxide additions on Zr2O2 polymorphism during Al2O3+Zr2O2 mixture fusion

International Nuclear Information System (INIS)

Gladkov, V.E.; Zhekhanova, N.B.; Fotiev, A.A.; Viktorov, V.V.; Ivashinnikov, V.T.; Zubov, A.S.

1985-01-01

The effect of titanium and calcium containing additions introduced into the Al 2 O 3 +ZrO 2 melt on the phase composition and temperature ranges of ZrO 2 polymorphous transformation in the material is investigated. It is shown that introducing sponge titanium into the 70Al 2 O 3 +30ZrO 2 prepared composition melt (mass. %) with its subsequent intensive cooling one can conserve upto room temperatures 50-70% of ZrO 2 metastable tetragonal modification and therefore reduce the volume changes causing metal cracking. Calcium oxide doping stabilizes the ZrO 2 cubic modification and reduces α-Al 2 O 3 content due to formation of aluminates

Ge interactions on HfO2 surfaces and kinetically driven patterning of Ge nanocrystals on HfO2

International Nuclear Information System (INIS)

Stanley, Scott K.; Joshi, Sachin V.; Banerjee, Sanjay K.; Ekerdt, John G.

2006-01-01

Germanium interactions are studied on HfO 2 surfaces, which are prepared through physical vapor deposition (PVD) and by atomic layer deposition. X-ray photoelectron spectroscopy and temperature-programed desorption are used to follow the reactions of germanium on HfO 2 . Germanium chemical vapor deposition at 870 K on HfO 2 produces a GeO x adhesion layer, followed by growth of semiconducting Ge 0 . PVD of 0.7 ML Ge (accomplished by thermally cracking GeH 4 over a hot filament) also produces an initial GeO x layer, which is stable up to 800 K. PVD above 2.0 ML deposits semiconducting Ge 0 . Temperature programed desorption experiments of ∼1.0 ML Ge from HfO 2 at 400-1100 K show GeH 4 desorption below 600 K and GeO desorption above 850 K. These results are compared to Ge on SiO 2 where GeO desorption is seen at 550 K. Exploiting the different reactivity of Ge on HfO 2 and SiO 2 allows a kinetically driven patterning scheme for high-density Ge nanoparticle growth on HfO 2 surfaces that is demonstrated

The ceramic SiO2 and SiO2-TiO2 coatings on biomedical Ti6Al4VELI titanium alloy

International Nuclear Information System (INIS)

Surowska, B.; Walczak, M.; Bienias, J.

2004-01-01

The paper presents the study of intermediate SiO 2 and SiO 2 -TiO 2 sol-gel coatings and dental porcelain coatings on Ti6Al4VELI titanium alloy. Surface microstructures and wear behaviour by pin-on-disc method of the ceramic coatings were investigated. The analysis revealed: (1) a compact, homogeneous SiO 2 and SiO 2 -TiO 2 coating and (2) that intermediate coatings may provide a durable joint between metal and porcelain, and (3) that dental porcelain on SiO 2 and TiO 2 coatings shows high wear resistance. (author)

Efficient 2-Nitrophenol Chemical Sensor Development Based on Ce2O3 Nanoparticles Decorated CNT Nanocomposites for Environmental Safety.

Directory of Open Access Journals (Sweden)

Mohammad M Hussain

Full Text Available Ce2O3 nanoparticle decorated CNT nanocomposites (Ce2O3.CNT NCs were prepared by a wet-chemical method in basic medium. The Ce2O3.CNT NCs were examined using FTIR, UV/Vis, Field-Emission Scanning Electron Microscopy (FESEM, X-ray electron dispersive spectroscopy (XEDS, X-ray photoelectron spectroscopy (XPS, and powder X-ray diffraction (XRD. A selective 2-nitrophenol (2-NP sensor was developed by fabricating a thin-layer of NCs onto a flat glassy carbon electrode (GCE, surface area = 0.0316 cm2. Higher sensitivity including linear dynamic range (LDR, long-term stability, and enhanced electrochemical performances towards 2-NP were achieved by a reliable current-voltage (I-V method. The calibration curve was found linear (R2 = 0.9030 over a wide range of 2-NP concentration (100 pM ~ 100.0 mM. Limit of detection (LOD and sensor sensitivity were calculated based on noise to signal ratio (~3N/S as 60 ± 0.02 pM and 1.6×10-3 μAμM-1cm-2 respectively. The Ce2O3.CNT NCs synthesized by a wet-chemical process is an excellent way of establishing nanomaterial decorated carbon materials for chemical sensor development in favor of detecting hazardous compounds in health-care and environmental fields at broad-scales. Finally, the efficiency of the proposed chemical sensors can be applied and utilized in effectively for the selective detection of toxic 2-NP component in environmental real samples with acceptable and reasonable results.

Effect of Cu2O morphology on photocatalytic hydrogen generation and chemical stability of TiO2/Cu2O composite.

Science.gov (United States)

Zhu, Lihong; Zhang, Junying; Chen, Ziyu; Liu, Kejia; Gao, Hong

2013-07-01

Improving photocatalytic activity and stability of TiO2/Cu2O composite is a challenge in generating hydrogen from water. In this paper, the TiO2 film/Cu2O microgrid composite was prepared via a microsphere lithography technique, which possesses a remarkable performance of producing H2 under UV-vis light irradiation, in comparison with pure TiO2 film, Cu2O film and TiO2 film/Cu2O film. More interesting is that in TiO2 film/Cu2O microgrid, photo-corrosion of Cu2O can be retarded. After deposition of Pt on its surface, the photocatalytic activity of TiO2/Cu2O microgrid in producing H2 is improved greatly.

The investigation of photo-induced chemiluminescence on Co2+-doped TiO2 nanoparticles and its analytical application.

Science.gov (United States)

Li, Guixin; Nan, Hongyan; Zheng, Xingwang

2009-07-01

A novel space- and time-resolved photo-induced chemiluminescence (PICL) analytical method was developed based on the photocatalysis of the Co2+-doped TiO2 nanoparticles. The PICL reaction procedure under the photocatalysis of Co2+-doped TiO2 nanoparticles was investigated using cyclic voltammetry and potentiometry. Meanwhile, the effect of the electrical double layer outside the Co2+-doped TiO2 nanoparticles on the PICL was investigated by contrasting with the Co2+-doped TiO2-SiO2 core-shell nanoparticles. Significantly, the CL intensity increased apparently and the time of the CL was prolonged in the presence of procaterol hydrochloride because the mechanism of the enhanced PICL reaction may be modified. The route of the PICL was changed due to the participation of the procaterol hydrochloride enriched at the surface of the Co2+-doped TiO2-SiO2 in the PICL reaction, which prolonged the time of the CL reaction and resulted in the long-term PICL. The analytical characteristics of the proposed in-situ PICL method were investigated using the procaterol hydrochloride as the model analyte. The investigation results showed that this new PICL analytical method offered higher sensitivity to the analysis of the procaterol hydrochloride and the PICL intensity was linear with the concentration of the procaterol hydrochloride in the range from ca. 2.0 x 10(-10) to 1.0 x 10(-8) g mL(-1).

Optical characteristics of a RF DBD plasma jet in various {Ar}/ {O}_{2}Ar/O2 mixtures

Science.gov (United States)

Falahat, A.; Ganjovi, A.; Taraz, M.; Ravari, M. N. Rostami; Shahedi, A.

2018-02-01

In this paper, using the optical emission spectroscopy (OES) technique, the optical characteristics of a radiofrequency (RF) plasma jet are examined. The Ar/O2 mixture is taken as the operational gas and, the Ar percentage in the Ar/O2 mixture is varied from 70% to 95%. Using the optical emission spectrum analysis of the RF plasma jet, the excitation temperature is determined based on the Boltzmann plot method. The electron density in the plasma medium of the RF plasma jet is obtained by the Stark broadening of the hydrogen Balmer H_{β }. It is mostly seen that, the radiation intensity of Ar 4p→ 4s transitions at higher argon contributions in Ar/O2 mixture is higher. It is found that, at higher Ar percentages, the emission intensities from atomic oxygen (O) are higher and, the line intensities from the argon atoms and ions including O atoms linearly increase. It is observed that the quenching of Ar^{*} with O2 results in higher O species with respect to O2 molecules. In addition, at higher percentages of Ar in the Ar/O2 mixture, while the excitation temperature is decreased, the electron density is increased.

The influence of interfacial barrier engineering on the resistance switching of In2O3:SnO2/TiO2/In2O3:SnO2 device

International Nuclear Information System (INIS)

Liu Zi-Yu; Zhang Pei-Jian; Meng Yang; Li Dong; Meng Qing-Yu; Li Jian-Qi; Zhao Hong-Wu

2012-01-01

The I—V characteristics of In 2 O 3 :SnO 2 /TiO 2 /In 2 O 3 :SnO 2 junctions with different interfacial barriers are investigated by comparing experiments. A two-step resistance switching process is found for samples with two interfacial barriers produced by specific thermal treatment on the interfaces. The nonsynchronous occurrence of conducting filament formation through the oxide bulk and the reduction in the interfacial barrier due to the migration of oxygen vacancies under the electric field is supposed to explain the two-step resistive switching process. The unique switching properties of the device, based on interfacial barrier engineering, could be exploited for novel applications in nonvolatile memory devices. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Cosmetic wastewater treatment by the ZVI/H2O2 process.

Science.gov (United States)

Bogacki, Jan; Marcinowski, Piotr; Zapałowska, Ewa; Maksymiec, Justyna; Naumczyk, Jeremi

2017-10-01

The ZVI/H 2 O 2 process was applied for cosmetic wastewater treatment. Two commercial zero-valent iron (ZVI) types with different granulations were chosen: Hepure Ferrox PRB and Hepure Ferrox Target. In addition, the pH and stirring method influence on ZVI/H 2 O 2 process efficiency was studied. During the ZVI and ZVI/H 2 O 2 processes, linear Fe ions concentration increase was observed. The addition of H 2 O 2 significantly accelerated the iron dissolution process. The highest COD removal was obtained using finer ZVI (Hepure Ferrox Target) for doses of reagents ZVI/H 2 O 2 1500/1600 mg/L, in a H 2 O 2 /COD weight ratio 2:1, at pH 3.0 with stirring on a magnetic stirrer. After 120 min of the process, 84.0% COD removal (from 796 to 127 mg/L) was achieved. It was found that the efficiency of the process depends, as in the case of the Fenton process, on the ratio of the reagents (ZVI/H 2 O 2 ) and their dose in relation to the COD (H 2 O 2 /COD) but does not depend on the dose of the iron itself. Statistical analysis confirms that COD removal efficiency depends primarily on H 2 O 2 /COD ratio and ZVI granulation, but ZVI dose influence is not statistically significant. The head space, solid-phase microextraction, gas chromatography, mass spectrometry results confirm high efficiency of the ZVI/H 2 O 2 process.

SeO2 adsorption on CaO surface: DFT study on the adsorption of a single SeO2 molecule

Science.gov (United States)

Fan, Yaming; Zhuo, Yuqun; Lou, Yu; Zhu, Zhenwu; Li, Liangliang

2017-08-01

Selenium is a hazardous element in coal. During coal combustion, most of the selenium will convert to SeO2 in the flue gas. Ca-based adsorbents, especially CaO, have been considered as a potential sorbent to adsorb SeO2 due to its low cost. In this paper, the adsorption mechanisms of single SeO2 on CaO surface were investigated by density functional theory (DFT) calculation. Both the physisorption and chemisorption structures were determined. It has been identified that the adsorption of SeO2 on CaO surface is primarily chemisorption, while physisorption takes effects at the initial stage of the process. Under O2 atmosphere, selenate is hard to form. Most of the adsorption products are selenite. Additionally, the electron density maps were obtained to reveal the surface active sites. The partial density of states (PDOS) was calculated for analyzing the electronic structural change of SeO2 and CaO surface during adsorption. The results provide fundamental information of the adsorption process, which could be meaningful for the development of new absorbents.

Impact of Ni promotion on the hydrogenation pathways of phenanthrene on MoS 2 /γ-Al 2 O 3

Energy Technology Data Exchange (ETDEWEB)

Schachtl, Eva; Yoo, Jong Suk; Gutiérrez, Oliver Y.; Studt, Felix; Lercher, Johannes A.

2017-08-01

The reaction network and elementary steps of the hydrogenation of phenanthrene are explored on parent and Ni-promoted MoS2/c-Al2O3. Two pathways were identified, i.e., Path 1: Phenanthrene _ 9,10-dihydrophenanthrene (DiHPhe)?1,2,3,4,4a,9,10,10a-octahydro-phenanthrene (asymOHPhe), and Path 2: Phenanthrene ?1,2,3,4-tetrahydrophenanthrene (TetHPhe)?1,2,3,4,5,6,7,8-octahydrophenan threne. The steps TetHPhe?asymOHPhe (hydrogenation), and DiHPhe?TetHPhe (hydrogenationisomerization) become notable at phenanthrene conversions above 20%. The reaction preferentially proceeds via Path 1 (90% selectivity) on MoS2/Al2O3. Ni promotion (Ni/(Ni + Mo) molar ratio of 0.3 at the edges on MoS2) increases the hydrogenation activity per active edge twofold and leads to 50% selectivity to both pathways. The reaction orders in H2 vary from _0.8 on MoS2/Al2O3 to _1.2 on Ni-MoS2/Al2O3, whereas the reaction orders in phenanthrene (_0.6) hardly depend on Ni promotion. The reaction orders in H2S are zero on MoS2/Al2O3 and slightly negative on Ni-MoS2/Al2O3. DFT calculations indicate that phenanthrene is preferentially adsorbed parallel to the basal planes, while H is located at the edges perpendicular to the basal planes. Theory also suggests that Ni atoms, incorporated preferentially on the S-edges, increase the stability of hydrogenated intermediates. Hydrogenation of phenanthrene proceeds through quasi-equilibrated adsorption of the reactants followed by consecutive addition of hydrogen pairs to the adsorbed hydrocarbon. The rate determining steps for the formation of DiHPhe and TetHPhe are the addition of the first and second hydrogen pair, respectively. The concentration of SH groups (activated H at the edges) increases with Ni promotion linearly correlating the rates of Path 1 and Path 2, albeit with different functions. The enhancing effect of Ni on Path 2 is attributed to accelerated hydrogen addition to adsorbed hydrocarbons without important changes in their coverages.

Review of Liquidus Surface and Phase Equilibria in the TiO2-SiO2-Al2O3-MgO-CaO Slag System at PO2 Applicable in Fluxed Titaniferous Magnetite Smelting

Science.gov (United States)

Goso, Xolisa; Nell, Johannes; Petersen, Jochen

The current liquidus surface and phase equilibria established in air for fluxed titaniferous magnetite (titanomagnetite) slags conforming to a composition of 37.19% TiO2, 19.69% SiO2, 13.12% Al2O3, and 30.00% of various ratios of CaO+MgO were reviewed at applicable PO2 using FactSage simulation and phase composition of a real plant titanomagnetite slag. The testwork included the incorporation into FactSage of a private MgTi2O5-Al2TiO5 pseudobrookite solution model. The results of the investigation showed that the liquidus surface and Ti3+/ Ti4+ mass fraction ratio increased with decreasing the PO2, At low PO2, perovskite crystallizes as a primary phase at high CaO content. The spinel solution, i.e. (Mg)(Al,Ti)O4, generally crystallizes as the primary phase at high MgO contents, though it is replaced by MgTi2O5-Al2TiO5 solution at PO2 of 10-10 atm to 10-15 atm. An intermediate equilibrium phase diagram established at PO2 of 10-16 atm is proposed. This phase diagram does not show the observed primary phase crystallization competition, however, the phase composition of a real titanomagnetite slag produced by Evraz Highveld Steel and Vanadium Corporation in South Africa does show primary phase crystallization competition between (Mg)(Al,Ti)2O4 and MgTi2O5-Al2TiO5. Smelting involving such slags is likely conducted around the transition PO2, i.e. PO2 of about 10-16 atm. Complex modelling with MgTi2O5, Al2TiO5 and Ti3O5 end members and experiments are underway to verify and update the intermediate phase diagram.

A review on the effects of TiO2 surface point defects on CO2 photoreduction with H2O

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Huilei Zhao

2017-03-01

Full Text Available Photocatalytic reduction of CO2 with water by photocatalysts such as TiO2 to produce solar fuels is an attractive approach to alleviate the environmental influences of greenhouse gases and in the meantime produce valuable carbon-neutral fuels. Among the materials properties that affect catalytic activity of CO2 photoreduction, the point defect on TiO2 is one of the most important but not frequently addressed and well understood in the literature. In this review, we have examined the major influences of TiO2 point defects on CO2 photoreduction with H2O, by changing the catalysts' gas adsorption capabilities, optical properties, and electronic structures. In addition, the performances of various defective TiO2 toward CO2 photoreduction are summarized and compared in terms of productivity, selectivity, and stability. We hope this review can contribute to understanding the mechanism of CO2 photoreduction on defective TiO2 and provide insights to the design of highly efficient defect-rich TiO2 to boost the CO2 utilization.

Enhancement effect of CdTe quantum dots-IgG bioconjugates on chemiluminescence of luminol-H2O2 system

International Nuclear Information System (INIS)

Kanwal, Shamsa; Traore, Zoumana; Zhao Chunfang; Su Xingguang

2010-01-01

In this paper we developed an entirely new and highly sensitive luminol-H 2 O 2 flow injection chemiluminescence system using the enhancement effect of CdTe quantum dots-IgG bioconjugates. Immunoglobulin G (IgG) as a kind of bio-molecule was conjugated to different sized CdTe semiconductor quantum dots (QDs). Using PL spectra and CL intensity profiles, it was found that chemiluminescence resonance energy transfer (CRET) was possibly occurring between CdTe-IgG bioconjugate and luminol. Under optimum conditions, increase of IgG concentration in CdTe-IgG bioconjugate resulted enhancing effect on CL intensity of luminol-H 2 O 2 system. Moreover quenching effects on CL intensity by addition of different proteases can construct turn off biosensor for these proteases with low detection limits and wide linear range. Furthermore, the effects of various organic and inorganic species on CdTe-IgG bioconjugates enhanced luminol-H 2 O 2 CL system were also studied in this paper.

Evaluation of H{sub 2}O{sub 2}-generation during oxygen reduction at electrodeposited Pt particles on mask scratched electrodes

Energy Technology Data Exchange (ETDEWEB)

Kishi, Akira; Inoue, Mitsuhiro; Umeda, Minoru, E-mail: mumeda@vos.nagaokaut.ac.jp

2013-08-15

In this study, the Pt particle deposition was systematically performed by our proposed mask scratch and subsequent Pt electrodeposition in order to investigate the H{sub 2}O{sub 2}-byproduct generation efficiency during O{sub 2} reduction. By peeling a part of polymer layer coated on a glassy carbon substrate using an atomic force microscope cantilever, scratched areas are regularly made. The Pt particles are deposited only on the above-mentioned scratched areas, indicating that the controlled Pt deposition has been achieved. The background cyclic voltammetry of the prepared electrodes showed that the deposited nanoparticles are certainly composed of Pt. Moreover, the electrochemical surface area of the deposited Pt (Pt-ESA) linearly increases with the increasing scratched area, revealing that the Pt-ESAs can be controlled by the mask scratch-based Pt electrodeposition method. It should be noted that an increase in the Pt-ESA not only increases the O{sub 2} reduction currents, but also enhances the H{sub 2}O{sub 2} generation efficiency.

Surface modelling on heavy atom crystalline compounds: HfO2 and UO2 fluorite structures

International Nuclear Information System (INIS)

Evarestov, Robert; Bandura, Andrei; Blokhin, Eugeny

2009-01-01

The study of the bulk and surface properties of cubic (fluorite structure) HfO 2 and UO 2 was performed using the hybrid Hartree-Fock density functional theory linear combination of atomic orbitals simulations via the CRYSTAL06 computer code. The Stuttgart small-core pseudopotentials and corresponding basis sets were used for the core-valence interactions. The influence of relativistic effects on the structure and properties of the systems was studied. It was found that surface properties of Mott-Hubbard dielectric UO 2 differ from those found for other metal oxides with the closed-shell configuration of d-electrons

Syntheses, crystal structures, and magnetic properties of four new cyano-bridged bimetallic complexes based on the mer-[Fe(III)(qcq)(CN)3]- building block.

Science.gov (United States)

Shen, Xiaoping; Zhou, Hongbo; Yan, Jiahao; Li, Yanfeng; Zhou, Hu

2014-01-06

Four new cyano-bridged bimetallic complexes, [{Mn(III)(salen)}2{Fe(III)(qcq)(CN)3}2]n·3nCH3CN·nH2O (1) [salen = N,N'-ethylenebis(salicylideneiminato) dianion; qcq(-) = 8-(2-quinoline-2-carboxamido)quinoline anion], [{Mn(III)(salpn)}2{Fe(III)(qcq)(CN)3}2]n·4nH2O (2) [salpn = N,N'-1,2-propylenebis(salicylideneiminato)dianion], [{Mn(II)(bipy)(CH3OH)}{Fe(III)(qcq)(CN)3}2]2·2H2O·2CH3OH (3) (bipy = 2,2'-bipyridine), and [{Mn(II)(phen)2}{Fe(III)(qcq)(CN)3}2]·CH3CN·2H2O (4) (phen = 1,10-phenanthroline) have been synthesized and characterized both structurally and magnetically. The structures of 1 and 2 are both unique 1-D linear branch chains with additional structural units of {Mn(III)(salen/salpn)}{Fe(III)(qcq)(CN)3} dangling on the sides. In contrast, 3 and 4 are cyano-bridged bimetallic hexanuclear and trinuclear clusters, respectively. The intermolecular short contacts such as π-π interactions and hydrogen bonds extend 1-4 into high dimensional supermolecular networks. Magnetic investigation reveals the dominant intramolecular antiferromagnetic interactions in 1, 3, and 4, while ferromagnetic and antiferromagnetic interactions coexist in 2. Alternating current measurement at low temperature indicates the existence of slow magnetic relaxation in 1 and 2, which should be due to the single ion anisotropy of Mn(III).

Effect of Al2O3 and TiO2 nanoparticles on aquatic organisms

International Nuclear Information System (INIS)

Gosteva, I; Morgalev, Yu; Morgaleva, T; Morgalev, S

2015-01-01

Environmental toxicity of aqueous disperse systems of nanoparticles of binary compounds of titanium dioxides (with particle size Δ 50 =5 nm, Δ 50 =50 nm, Δ 50 =90 nm), aluminum oxide alpha-forms (Δ 50 =7 nm and Δ 50 =70 nm) and macro forms (TiO 2 Δ 50 =350 nm, Al 2 O 3 A 50 =4000 nm) were studied using biological testing methods. The bioassay was performed using a set of test organisms representing the major trophic levels. We found the dependence of the toxic effect concentration degree of nTiO 2 and nAl 2 O 3 on the fluorescence of the bacterial biosensor 'Ekolyum', the chemotactic response of ciliates Paramecium caudatum, the growth of unicellular algae Chlorella vulgaris Beijer and mortality of entomostracans Daphnia magna Straus. We revealed the selective dependence of nTiO 2 and nAl 2 O 3 toxicity on the size, concentration and chemical nature of nanoparticles. The minimal concentration causing an organism's response on nTiO 2 and nAl 2 O 3 effect depends on the type of the test- organism and the test reaction under study. We specified L(E)C 50 and acute toxicity categories for all the studied nanoparticles. We determined that nTiO 2 (Δ 50 =5 nm) belong to the category «Acute toxicity 1», nTiO 2 (A 50 =90 nm) and nAl 2 O 3 (Δ 50 =70 nm) – to the category «Acute toxicity 2», nAl 2 O 3 (Δ 50 =7 nm) – to the category «Acute toxicity 3». No acute toxicity was registered for nTiO 2 (Δ 50 =50 nm) and macro form TiO 2 . (paper)

Effect of AL2O3 and TiO2 nanoparticles on aquatic organisms

Science.gov (United States)

Gosteva, I.; Morgalev, Yu; Morgaleva, T.; Morgalev, S.

2015-11-01

Environmental toxicity of aqueous disperse systems of nanoparticles of binary compounds of titanium dioxides (with particle size Δ50=5 nm, Δ50=50 nm, Δ50=90 nm), aluminum oxide alpha-forms (Δ50=7 nm and Δ50=70 nm) and macro forms (TiO2 Δ50=350 nm, Al2O3 A50=4000 nm) were studied using biological testing methods. The bioassay was performed using a set of test organisms representing the major trophic levels. We found the dependence of the toxic effect concentration degree of nTiO2 and nAl2O3 on the fluorescence of the bacterial biosensor "Ekolyum", the chemotactic response of ciliates Paramecium caudatum, the growth of unicellular algae Chlorella vulgaris Beijer and mortality of entomostracans Daphnia magna Straus. We revealed the selective dependence of nTiO2 and nAl2O3 toxicity on the size, concentration and chemical nature of nanoparticles. The minimal concentration causing an organism's response on nTiO2 and nAl2O3 effect depends on the type of the test- organism and the test reaction under study. We specified L(E)C50 and acute toxicity categories for all the studied nanoparticles. We determined that nTiO2 (Δ50=5 nm) belong to the category «Acute toxicity 1», nTiO2 (A50=90 nm) and nAl2O3 (Δ50=70 nm) - to the category «Acute toxicity 2», nAl2O3 (Δ50=7 nm) - to the category «Acute toxicity 3». No acute toxicity was registered for nTiO2 (Δ50=50 nm) and macro form TiO2.

Magnetic field induced changes in linear and nonlinear optical properties of Ti incorporated Cr2O3 nanostructured thin film

Science.gov (United States)

Baraskar, Priyanka; Chouhan, Romita; Agrawal, Arpana; Choudhary, R. J.; Sen, Pranay K.; Sen, Pratima

2018-03-01

We report the magnetic field effect on the linear and nonlinear optical properties of pulse laser ablated Ti-incorporated Cr2O3 nanostructured thin film. Optical properties have been experimentally analyzed under Voigt geometry by performing ultraviolet-visible spectroscopy and closed aperture Z-scan technique using a continuous wave He-Ne laser source. Nonlinear optical response reveals a single peak-valley feature in the far field diffraction pattern in absence of magnetic field (B = 0) confirming self-defocussing effect. This feature switches to a valley-peak configuration for B = 5000G, suggesting self-focusing effect. For B ≤ 750G, oscillations were observed revealing the occurrence of higher order nonlinearity. Origin of nonlinearity is attributed to the near resonant d-d transitions observed from the broad peak occurring around 2 eV. These transitions are of magnetic origin and get modified under the application of external magnetic field. Our results suggest that magnetic field can be used as an effective tool to monitor the sign of optical nonlinearity and hence the thermal expansion in Ti-incorporated Cr2O3 nanostructured thin film.

Effect of one-lung ventilation on end-tidal carbon dioxide during cardiopulmonary resuscitation in a pig model of cardiac arrest.

Science.gov (United States)

Ryu, Dong Hyun; Jung, Yong Hun; Jeung, Kyung Woon; Lee, Byung Kook; Jeong, Young Won; Yun, Jong Geun; Lee, Dong Hun; Lee, Sung Min; Heo, Tag; Min, Yong Il

2018-01-01

Unrecognized endobronchial intubation frequently occurs after emergency intubation. However, no study has evaluated the effect of one-lung ventilation on end-tidal carbon dioxide (ETCO2) during cardiopulmonary resuscitation (CPR). We compared the hemodynamic parameters, blood gases, and ETCO2 during one-lung ventilation with those during conventional two-lung ventilation in a pig model of CPR, to determine the effect of the former on ETCO2. A randomized crossover study was conducted in 12 pigs intubated with double-lumen endobronchial tube to achieve lung separation. During CPR, the animals underwent three 5-min ventilation trials based on a randomized crossover design: left-lung, right-lung, or two-lung ventilation. Arterial blood gases were measured at the end of each ventilation trial. Ventilation was provided using the same tidal volume throughout the ventilation trials. Comparison using generalized linear mixed model revealed no significant group effects with respect to aortic pressure, coronary perfusion pressure, and carotid blood flow; however, significant group effect in terms of ETCO2 was found (P < 0.001). In the post hoc analyses, ETCO2 was lower during the right-lung ventilation than during the two-lung (P = 0.006) or left-lung ventilation (P < 0.001). However, no difference in ETCO2 was detected between the left-lung and two-lung ventilations. The partial pressure of arterial carbon dioxide (PaCO2), partial pressure of arterial oxygen (PaO2), and oxygen saturation (SaO2) differed among the three types of ventilation (P = 0.003, P = 0.001, and P = 0.001, respectively). The post hoc analyses revealed a higher PaCO2, lower PaO2, and lower SaO2 during right-lung ventilation than during two-lung or left-lung ventilation. However, the levels of these blood gases did not differ between the left-lung and two-lung ventilations. In a pig model of CPR, ETCO2 was significantly lower during right-lung ventilation than during two-lung ventilation. However

TiO2-ITO and TiO2-ZnO nanocomposites: application on water treatment

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Bessais B.

2012-06-01

Full Text Available One of the most promising ideas to enhance the photocatalytic efficiency of the TiO2 is to couple this photocatalyst with other semiconductors. In this work, we report on the development of photo-catalytic properties of two types of composites based on TiO2 – ITO (Indium Tin Oxide and TiO2 – ZnO deposited on conventional ceramic substrates. The samples were characterized by X-ray diffraction (XRD and transmission Electron Microscopy (TEM. The photo-catalytic test was carried out under UV light in order to reduce/oxidize a typical textile dye (Cibacron Yellow. The experiment was carried out in a bench scale reactor using a solution having a known initial dye concentration. After optimization, we found that both nanocomposites exhibit better photocatalytic activity compared to the standard photocatalyst P25 TiO2.

Fabrication of hydrogen peroxide biosensor based on Ni doped SnO2 nanoparticles.

Science.gov (United States)

Lavanya, N; Radhakrishnan, S; Sekar, C

2012-01-01

Ni doped SnO(2) nanoparticles (0-5 wt%) have been prepared by a simple microwave irradiation (2.45 GHz) method. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies confirmed the formation of rutile structure with space group (P(42)/mnm) and nanocrystalline nature of the products with spherical morphology. Direct electrochemistry of horseradish peroxidase (HRP)/nano-SnO(2) composite has been studied. The immobilized enzyme retained its bioactivity, exhibited a surface confined, reversible one-proton and one-electron transfer reaction, and had good stability, activity and a fast heterogeneous electron transfer rate. A significant enzyme loading (3.374×10(-10) mol cm(-2)) has been obtained on nano-Ni doped SnO(2) as compared to the bare glassy carbon (GC) and nano-SnO(2) modified surfaces. This HRP/nano-Ni-SnO(2) film has been used for sensitive detection of H(2)O(2) by differential pulse voltammetry (DPV), which exhibited a wider linearity range from 1.0×10(-7) to 3.0×10(-4)M (R=0.9897) with a detection limit of 43 nM. The apparent Michaelis-Menten constant (K(M)(app)) of HRP on the nano-Ni-SnO(2) was estimated as 0.221 mM. This excellent performance of the fabricated biosensor is attributed to large surface-to-volume ratio and Ni doping into SnO(2) which facilitate the direct electron transfer between the redox enzyme and the surface of electrode. Copyright © 2012 Elsevier B.V. All rights reserved.

Water quality assessment by an integrated multi-sensor based on semiconductor RuO2 nanostructures

International Nuclear Information System (INIS)

Zhuiykov, Serge; O'Brien, David; Best, Michael

2009-01-01

A multi-sensor based on a nanostructured semiconductor ruthenium oxide (RuO 2 ) sensing electrode (RuO 2 -SE) deposited on an alumina substrate and capable of being coupled with a simple turbidity sensor has been evaluated for long-term pH stability during a 12-month non-stop trial. The multi-sensor is designed to detect the main parameters of water quality: pH, dissolved oxygen (DO), temperature, conductivity and turbidity over a temperature range of 9–30 °C. The morphology of the film SE used in the sensor structure was investigated by scanning electron microscopy and energy dispersive x-ray-analysis at the beginning of the trial and after 12 months of service. It was found that both morphology and surface compositions of nanostructured RuO 2 -SEs did not change significantly. They keep their high sensitivity to adsorption of superoxide ions (O 2 − ) despite heavy depositions of bio-fouling. The sensors with a RuO 2 -SE have demonstrated a stable Nernstian response to pH from 2.0 to 13.0 and were also capable of measuring DO in the range of 0.6–8.0 ppm. The measurement results show very good linearity, and excellent reproducibility was obtained during the trial. The Nernstian slope was approximately 58 mV pH −1 at a temperature of 23 °C. Although RuO 2 -SEs have been shown to exhibit very good response time for pH changes, within a few seconds at a temperature of 23 °C, as the water temperature cooled down, the sensor response time increased significantly and was about 8–10 min or longer at a temperature of 9 °C. The influence of hydrogen ion (H + ) diffusion in nanostructured RuO 2 films on the output emf drift during pH measurements was also investigated. Additional turbidity and conductivity measurements revealed that the multi-sensor is capable of measuring both high and low ranges at different temperatures, exhibiting a high linearity of characteristics

Structure and properties of PbO2-CeO2 anodes on stainless steel

International Nuclear Information System (INIS)

Song, Yuehai; Wei, Gang; Xiong, Rongchun

2007-01-01

The lack of ideal anodes with excellent activity and stability is one of the critical problems in electrochemical oxidation for organic wastewater treatment. It is reported in this paper that the PbO 2 -CeO 2 films electrodeposited on stainless steel were used as catalytic electrodes for treating antibiotic wastewater. The PbO 2 -CeO 2 films on stainless steel were proved to be high stability, good activity and relatively low cost. Because of these properties, the films are more attractive than any other electrocatalytic materials among conventional dimensionally stable anodes (DSA). Experimental results showed that the PbO 2 -CeO 2 electrode has a service life of 1100 h in 3 M H 2 SO 4 solution under a current density of 1 A cm -2 at 35 o C, compared with 300 h for PbO 2 under the same conditions. The X-ray diffraction (XRD) patterns and SEM images indicated that the PbO 2 -CeO 2 films on stainless steel have a dense structure and the preferred crystalline orientation on the substrate surface was changed. Color and chemical oxygen demand (COD) of antibiotics wastewater were studied by electrolysis by using these electrodes as anode and stainless steel as cathode. The results indicated that the anodes have excellent activity in antibiotic wastewater treatment. The PbO 2 -CeO 2 electrodes have high chemical stability which contributed by the superstable nature of the electrode, dense microstructure, good conductivity and the improvement of bonding with the stainless steel during electrodeposition

Photocatalytic degradation of Acephate, Omethoate, and Methyl parathion by Fe_3O_4@SiO_2@mTiO_2 nanomicrospheres

International Nuclear Information System (INIS)

Zheng, Lingling; Pi, Fuwei; Wang, Yifan; Xu, Hui; Zhang, Yinzhi; Sun, Xiulan

2016-01-01

Highlights: • An efficient photocatalyst Fe_3O_4@SiO_2@mTiO_2 with high magnetic response and large specific surface area was synthesized. • Photocatalytic efficiency of Fe_3O_4@SiO_2@mTiO_2 on Acephate, Omethoate, and Methyl Parathion was higher than TiO_2 P-25. • Possible photocatalytic degradation mechanisms for the Acephate, Omethoate, and Methyl Parathion were proposed. - Abstract: A novel magnetic mesoporous nanomicrospheres Fe_3O_4@SiO_2@mTiO_2 were synthetized and characterized by a series of techniques including FE-TEM, EDS, FE-SEM, PXRD, XPS, BET, TGA as well as VSM, and subsequently tested as a photocatalyst for the degradation of Acephate, Omethoate, and Methyl parathion under UV irradiation. The well-designed nanomicrospheres exhibit a pure and highly crystalline anatase TiO_2 layer, large specific surface area, and high-magnetic-response. Photocatalytic degradation of the three organophosphorus pesticides (OPPs) and the formation intermediates were identified using HPLC, TOC-V_c_p_n, IC, pH meter and GC–MS. Acephate, Omethoate, and Methyl parathion disappeared after 45 min, 45 min, and 80 min UV illumination, respectively. At the end of the treatment, the total organic carbon (TOC) of the OPPs was reduced 80–85%. The main mineralization products were SO_4"2"−, NO_3"− and PO_4"3"− and Omethoate additionally formed NO_2"−. Based on the results, we proposed the photocatalytic degradation pathways for Acephate, Omethoate, and Methyl parathion.