Zr-doped TiO2 supported on delaminated clay materials for solar photocatalytic treatment of emerging pollutants.

PubMed

Belver, C; Bedia, J; Rodriguez, J J

2017-01-15

Solar light-active Zr-doped TiO 2 nanoparticles were successfully immobilized on delaminated clay materials by a one-step sol-gel route. Fixing the amount of TiO 2 at 65wt.%, this work studies the influence of Zr loading (up to 2%) on the photocatalytic activity of the resulting Zr-doped TiO 2 /clay materials. The structural characterization demonstrates that all samples were formed by a delaminated clay with nanostructured anatase assembled on its surface. The Zr dopant was successfully incorporated into the anatase lattice, resulting in a slight deformation of the anatase crystal and the reduction of the band gap. These materials exhibit high surface area with a disordered mesoporous structure formed by TiO 2 particles (15-20nm) supported on a delaminated clay. They were tested in the solar photodegradation of antipyrine, usually used as an analgesic drug and selected as an example of emerging pollutant. High degradation rates have been obtained at low antipyrine concentrations and high solar irradiation intensities with the Zr-doped TiO 2 /clay catalyst, more effective than the undoped one. This work demonstrates the potential application of the synthesis method for preparing novel and efficient solar-light photocatalysts based on metal-doped anatase and a delaminated clay. Copyright © 2016 Elsevier B.V. All rights reserved.

Twin density of aragonite in molluscan shells characterized using X-ray diffraction and transmission electron microscopy

NASA Astrophysics Data System (ADS)

Kogure, Toshihiro; Suzuki, Michio; Kim, Hyejin; Mukai, Hiroki; Checa, Antonio G.; Sasaki, Takenori; Nagasawa, Hiromichi

2014-07-01

{110} twin density in aragonites constituting various microstructures of molluscan shells has been characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM), to find the factors that determine the density in the shells. Several aragonite crystals of geological origin were also investigated for comparison. The twin density is strongly dependent on the microstructures and species of the shells. The nacreous structure has a very low twin density regardless of the shell classes. On the other hand, the twin density in the crossed-lamellar (CL) structure has large variation among classes or subclasses, which is mainly related to the crystallographic direction of the constituting aragonite fibers. TEM observation suggests two types of twin structures in aragonite crystals with dense {110} twins: rather regulated polysynthetic twins with parallel twin planes, and unregulated polycyclic ones with two or three directions for the twin planes. The former is probably characteristic in the CL structures of specific subclasses of Gastropoda. The latter type is probably related to the crystal boundaries dominated by (hk0) interfaces in the microstructures with preferred orientation of the c-axis, and the twin density is mainly correlated to the crystal size in the microstructures.

Effect of local stress fields on twin characteristics in HCP metals

DOE PAGES

Arul Kumar, M.; Beyerlein, Irene Jane; Tomé, Carlos N.

2016-09-01

Here we study the effect of nearest neighboring grains on the propensity for {1012} twin growth in Mg and Zr. Twin lamellae lying within one grain flanked by two neighboring grains with several orientations are considered. The fields of resolved shear stress on the twin system are calculated in the multicrystal using a three-dimensional full-field crystal plasticity Fast Fourier Transform approach. The calculations were carried out for Mg and Zr using slip threshold stresses corresponding to 300K and 76K, respectively, where twin activity is important. We show that the neighboring grain constraint tends to oppose further growth and that themore » critical applied stress needed to overcome this resistance depends on neighboring grain orientation, more strongly in Zr than in Mg. We also present results for a pair of adjacent and parallel twins at various spacings. It is found that their paired interaction increases the resistive forces for twin growth above that for an isolated twin. The critical spacing above which this enhanced resistance is removed is smaller for Zr than Mg. Our analysis reveals that these two disparate responses of Zr and Mg are both a consequence of the fact that Zr is elastically and plastically more anisotropic than Mg. Additional calculations carried out on Ti support this conclusion. Finally, these findings can help explain why, for the same grain size, more twins per grain form in Zr than in Mg, twins in Zr tend to be thinner than those in Mg, and the relationship between the thickness of the twin and its Schmid factor in Zr is not as strong as in Mg.« less

Palladium-doped-ZrO2-multiwalled carbon nanotubes nanocomposite: an advanced photocatalyst for water treatment

NASA Astrophysics Data System (ADS)

Anku, William Wilson; Oppong, Samuel Osei-Bonsu; Shukla, Sudheesh Kumar; Agorku, Eric Selorm; Govender, Poomani Penny

2016-06-01

The photocatalytic degradation of organic pollutants from water using palladium-doped-zirconium oxide-multiwalled carbon nanotubes (Pd-ZrO2-MWCNTs) nanocomposites is presented. A series of Pd doped-ZrO2-MWCNTs nanocomposites with varying percentage compositions of Pd were prepared by the homogenous co-precipitation method. The photocatalytic applicability of the materials was investigated by the degradation of acid blue 40 dye in water under simulated solar light. The optical, morphological and structural properties of the nanocomposites were evaluated using X-ray powder diffraction, Fourier transformer infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, BET surface area analysis and (UV-Vis) spectroscopy. The Pd-ZrO2-MWCNTs nanocomposites showed enhanced photocatalytic activity toward the degradation of the acid blue 40 dye under visible light compared with bare ZrO2 and ZrO2-MWCNTs alone. The remarkable photocatalytic activity of Pd-ZrO2-MWCNTs nanocomposites in the visible light makes it an ideal photocatalyst for the removal of organic pollutants in water. The 0.5 % Pd-ZrO2-MWCNT was the most efficient photocatalyst with 98 % degradation after 3 h with corresponding K a and band gap values of 16.8 × 10-3 m-1 and 2.79 eV, respectively.

Effects of K and Ca doping on twin boundary energy of cupperate superconductors

NASA Astrophysics Data System (ADS)

Khoshnevisan, Bahram; Mohammadi, Mahnaz

2016-04-01

Ab-initio calculations under GGA approximation have been employed to find out the effect Ba substitution by K and Ca on the structural and electronic properties twined and untwined YBCO system. In this regard, the twin boundary energy, γ, and impact of the substitution on the boundary's charge distribution have been of special consideration. Our results show that despite the structural changes the presence of K (Ca) modifies substantially density of levels at the Fermi level, which could be responsible for empirical reports of decreasing the critical temperature (Tc) by increasing the K(Ca) content. Although, the K doping reduces the γ value in YBa2-xKxCu3O7 system, after calcium doping it remains more or less unchanged. In addition, reduction of the carrier density occurs at twin boundary in CuO2 layer for the substituted system with respect to the untwined YBCO system. Our results would be noticeable in conjunction with the experimentally reported twinned and alkali substituted superconductive properties of the YBCO samples.

Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO2-ZrO2 nanocomposite

NASA Astrophysics Data System (ADS)

Tomar, Laxmi J.; Bhatt, Piyush J.; Desai, Rahul K.; Chakrabarty, B. S.; Panchal, C. J.

2016-05-01

TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X -ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO2, TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphite coated conducting glass plate was used as counter electrode. The I - V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO2, TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites were found 0.71%, 1.97% and 4.58% respectively.

Synthesis and thermoelectric properties of tantalum-doped ZrNiSn half-Heusler alloys

NASA Astrophysics Data System (ADS)

Zhao, Degang; Zuo, Min; Wang, Zhenqing; Teng, Xinying; Geng, Haoran

2014-04-01

The Ta-doped ZrNiSn half-Heusler alloys, Zr1-xTaxNiSn, were synthesized by arc melting and hot-press sintering. Microstructure of Zr1-xTaxNiSn compounds were analyzed and the thermoelectric (TE) properties of Zr1-xTaxNiSn compounds were measured from room temperature to 823 K. The electrical conductivity increased with increasing Ta content. The Seebeck coefficient of Zr1-xTaxNiSn compounds was sharply decreased with increasing Ta content. The Hall mobility was proportional to T-1.5 above 673 K, indicating that the acoustic phonon scattering was predominant in the temperature range. The thermal conductivity was effectively depressed by introducing Ta substitution. The figure of merit of ZrNiSn compounds was improved due to the decreased thermal conductivity and increased electrical conductivity. The maximum ZT value of 0.60 was achieved for Zr0.97Ta0.03NiSn sample at 823 K.

Low-temperature CO oxidation over Cu/Pt co-doped ZrO2 nanoparticles synthesized by solution combustion.

PubMed

Singhania, Amit; Gupta, Shipra Mital

2017-01-01

Zirconia (ZrO 2 ) nanoparticles co-doped with Cu and Pt were applied as catalysts for carbon monoxide (CO) oxidation. These materials were prepared through solution combustion in order to obtain highly active and stable catalytic nanomaterials. This method allows Pt 2+ and Cu 2+ ions to dissolve into the ZrO 2 lattice and thus creates oxygen vacancies due to lattice distortion and charge imbalance. High-resolution transmission electron microscopy (HRTEM) results showed Cu/Pt co-doped ZrO 2 nanoparticles with a size of ca. 10 nm. X-ray diffraction (XRD) and Raman spectra confirmed cubic structure and larger oxygen vacancies. The nanoparticles showed excellent activity for CO oxidation. The temperature T 50 (the temperature at which 50% of CO are converted) was lowered by 175 °C in comparison to bare ZrO 2 . Further, they exhibited very high stability for CO reaction (time-on-stream ≈ 70 h). This is due to combined effect of smaller particle size, large oxygen vacancies, high specific surface area and better thermal stability of the Cu/Pt co-doped ZrO 2 nanoparticles. The apparent activation energy for CO oxidation is found to be 45.6 kJ·mol -1 . The CO conversion decreases with increase in gas hourly space velocity (GHSV) and initial CO concentration.

Highly efficient Zr doped-TiO2/glass fiber photocatalyst and its performance in formaldehyde removal under visible light.

PubMed

Huang, Chao; Ding, Yaping; Chen, Yingwen; Li, Peiwen; Zhu, Shemin; Shen, Shubao

2017-10-01

Zr-doped-TiO 2 loaded glass fiber (ZT/GF) composite photocatalysts with different Zr/Ti ratios were prepared with a sol-gel process. Zr 4+ can replace Ti 4+ in the TiO 2 lattice, which is conducive to forming the anatase phase and reducing the calcination temperature. The glass fiber carrier was responsible for better dispersion and loading of Zr-doped-TiO 2 particles, improving the applicability of the Zr-doped-TiO 2 . The ZT/GF photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-vis) and Barrett-Joyner-Halenda (BJH). The performance of photocatalysts with different loading was evaluated in formaldehyde degradation under visible light at room temperature. ZT/GF0.2 exhibited the highest activity, with a formaldehyde removal rate as high as 95.14% being observed, which is better than that of the photocatalyst particles alone. The stability of the catalyst was also tested, and ZT/GF exhibited excellent catalytic performance with 94.38% removal efficiency, even after seven uses. Copyright © 2017. Published by Elsevier B.V.

The mechanism of the UV band edge photorefractivity suppression in highly doped LiNbO3:Zr crystals

NASA Astrophysics Data System (ADS)

Xin, Fei-fei

2017-11-01

The ultraviolet (UV) band edge photorefractivity of LiNbO3:Zr at 325 nm has been investigated. The experimental results show that the resistance against photorefraction at 325 nm is quite obvious but not as strong as that at 351 nm, when the doping concentration of Zr reaches 2.0 mol%. It is reported that the photorefractivity in other tetravalently doped LiNbO3 crystals, such as LiNbO3:Hf and LiNbO3:Sn, is enhanced dramatically with doping concentration over threshold. Here we give an explicit explanation on such seemly conflicting behaviors of tetravalently doped LiNbO3, which is ascribed to the combined effect of increased photoconductivity and the absorption strength of the band edge photorefractive centers.

A Prototype of a Receptive Lexical Test for a Polysynthetic Heritage Language: The Case of Inuttitut in Labrador

ERIC Educational Resources Information Center

Sherkina-Lieber, Marina; Helms-Park, Rena

2015-01-01

This paper describes the process of designing, administering, and assessing a language-sensitive and culture-specific lexical test of Labrador Inuttitut (a dialect of Inuktitut, an Eskimo-Aleut language). This process presented numerous challenges, from choosing citation forms in a polysynthetic language to dealing with a lack of word frequency…

Influence of Zr doping on structure and morphology of TiO2 nanorods prepared using hydrothermal method

NASA Astrophysics Data System (ADS)

Muslimin, Masliana; Jumali, Mohammad Hafizuddin; Tee, Tan Sin; Beng, Lee Hock; Hui, Tan Chun; Chin, Yap Chi

2018-04-01

The aim of this work is to investigate the effect of Zr doping on TiO2 nanostructure. TiO2 nanorods thin films with different Zr-doping concentrations (6 × 10-3 M, 13 × 10-3 M and 25 × 10-3 M) were successfully prepared using a simple hydrothermal method. The structural and morphological properties of the samples were evaluated using XRD and FESEM respectively. The XRD results revealed that the TiO2 in all samples stabilized as rutile phase. The FESEM micrographs confirmed that TiO2 exist as square like nanorods with blunt tips. Although the crystallographic nature remains unchanged, the introduction of Zr has altered the surface density, structure and morphology of TiO2 which subsequently will have significant effect on its properties.

Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposite

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

Tomar, Laxmi J., E-mail: laxmi-tomar86@yahoo.com; Bhatt, Piyush J.; Desai, Rahul K.

TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X –ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO{sub 2}, TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphitemore » coated conducting glass plate was used as counter electrode. The I – V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO{sub 2}, TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites were found 0.71%, 1.97% and 4.58% respectively.« less

Raman spectroscopy and electron-phonon coupling in Eu3+ doped Gd2Zr2O7 nanopowders

NASA Astrophysics Data System (ADS)

Krizan, G.; Gilic, M.; Ristic-Djurovic, J. L.; Trajic, J.; Romcevic, M.; Krizan, J.; Hadzic, B.; Vasic, B.; Romcevic, N.

2017-11-01

The Raman spectra of Eu3+ doped Gd2Zr2O7 nanopowders were measured. We registered three phonons at 177 cm-1, 268 cm-1, and 592 cm-1, as well as their overtones at 354 cm-1, 445 cm-1, 708 cm-1, 1062 cm-1, 1184 cm-1, ∼1530 cm-1, and ∼1720 cm-1. The phonon at 592 cm-1 is known to be characteristic for Gd2Zr2O7 fluorite-type structure; however, the other two have not been registered so far. We found that the position of the newly detected phonons agrees well with the observed electron-phonon interaction. On the other hand, the registered multiphonon processes were a consequence of miniaturization that further induced changes in electronic structure of Eu3+ doped Gd2Zr2O7 nanopowders.

Understanding ferromagnetism and optical absorption in 3d transition metal-doped cubic ZrO{sub 2} with the modified Becke-Johnson exchange-correlation functional

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

Boujnah, M.; Zaari, H.; El Kenz, A., E-mail: elkenz@fsr.ac.ma

The electronic structure, magnetic, and optical properties in cubic crystalline phase of Zr{sub 1−x}TM{sub x}O{sub 2} (TM = V, Mn, Fe, and Co) at x = 6.25% are studied using density functional theory with the Generalized Gradient Approximation and the modified Becke-Johnson of the exchange-correlation energy and potential. In our calculations, the zirconia is a p-type semiconductor and has a large band gap. We evaluated the possibility of long-range magnetic order for transition metal ions substituting Zr. Our results show that ferromagnetism is the ground state in V, Mn, and Fe-doped ZrO{sub 2} and have a high value of energy in Mn-doped ZrO{sub 2}.more » However, in Co-doped ZrO{sub 2}, antiferromagnetic ordering is more stable than the ferromagnetic one. The exchange interaction mechanism has been discussed to explain the responsible of this stability. Moreover, it has been found that the V, Mn, and Fe transition metals provide half-metallic properties considered to be the leading cause, responsible for ferromagnetism. Furthermore, the optical absorption spectra in the TM -doped cubic ZrO{sub 2} are investigated.« less

Highly efficient sulfated Zr-doped titanoniobate nanoplates for the alcoholysis of styrene epoxide at room temperature

NASA Astrophysics Data System (ADS)

Zhang, Lihong; Hu, Chenhui; Mei, Weigang; Zhang, Junfeng; Cheng, Liyuan; Xue, Nianhua; Ding, Weiping; Chen, Jing; Hou, Wenhua

2015-12-01

Sulfated Zr-doped titanoniobate nanoplates were prepared and evaluated as a solid acid catalyst in the alcoholysis of styrene epoxide at room temperature. Compared with undoped and Zr-doped nanosheets, the resulting sulfated catalyst exhibited an excellent catalytic performance to afford corresponding β-alkoxyalcohols (99% yield with methanol as nucleophile in only 10 min) due to the high dispersion of zirconia species on nanosheets, appropriate Lewis acid strength and amount from the strong interaction between zirconia and sulfate species, and greatly increased surface area arisen from the exfoliation and house-of-cards restacking of nanosheets. The corresponding catalytic mechanism was proposed and discussed. The obtained material may act as a promising catalyst in many acid catalyzed reactions.

Doping Li and K into Na2ZrO3 Sorbent to Improve Its CO2 Capture Capability

NASA Astrophysics Data System (ADS)

Duan, Yuhua

Carbon dioxide is one of the major combustion products which once released into the air can contribute to global climate change. Solid sorbents have been reported in several previous studies to be promising candidates for CO2 sorbent applications due to their high CO2 absorption capacities at moderate working temperatures. However, at a given CO2 pressure, the turnover temperature (Tt) of an individual solid capture CO2 reaction is fixed and may be outside the operating temperature range (ΔTo) for a particularly capture technology. In order to shift such Tt for a solid into the range of ΔTo, its corresponding thermodynamic property must be changed by changing its structure by reacting (mixing) with other materials or doping with other elements. As an example, by combining thermodynamic database searching with ab initio thermodynamics calculations, in this work, we explored the Li- and K-doping effects on the Tt shifts of Na2ZrO3 at different doping levels. The obtained results showed that compared to pure Na2ZrO3, the Li- and K-doped mixtures Na2-αMαZrO3 (M =Li, K) have lower Tt and higher CO2 capture capacities.

Improved photocatalytic degradation rates of phenol achieved using novel porous ZrO2-doped TiO2 nanoparticulate powders.

PubMed

McManamon, Colm; Holmes, Justin D; Morris, Michael A

2011-10-15

This paper studies the photocatalytic degradation of phenol using zirconia-doped TiO(2) nanoparticles. ZrO(2) was chosen due to its promising results during preliminary studies. Particles smaller than 10nm were synthesised and doped with quantities of ZrO(2) ranging from 0.5 to 4% (molar metal content). Particles were calcined at different temperatures to alter the TiO(2) structure, from anatase to rutile, in order to provide an ideal ratio of the two phases. Powder X-ray diffraction (PXRD) analysis was used to examine the transformation between anatase and rutile. Degradation of phenol was carried out using a 40 W UV bulb at 365 nm and results were measured by UV-vis spectrometry. TEM images were obtained and show the particles exhibit a highly ordered structure. TiO(2) doped with 1% ZrO(2) (molar metal content) calcined at 700 °C proved to be the most efficient catalyst. This is due to an ideal anatase:rutlie ratio of 80:20, a large surface area and the existence of stable electron-hole pairs. ZrO(2) doping above the optimum loading acted as an electron-hole recombination centre for electron-hole pairs and reduced photocatalytic degradation. Synthesised photocatalysts compared favourably to the commercially available photocatalyst P25. The materials also demonstrated the ability to be recycled with similar results to those achieved on fresh material after 5 uses. Copyright © 2011 Elsevier B.V. All rights reserved.

Intense green and red upconversion emission of Er3+,Yb3+ co-doped CaZrO3 obtained by a solution combustion reaction

NASA Astrophysics Data System (ADS)

Singh, Vijay; Kumar Rai, Vineet; Haase, Markus

2012-09-01

CaZrO3 phosphors co-doped with Er3+ and Yb3+ ions have been prepared by the urea combustion route. The formation of the orthorhombic phase of CaZrO3 was confirmed by powder x-ray diffraction. The absorption in the 280-1800 nm region and excitation spectrum corresponding to the emission at 545 nm for CaZrO3:Er3+/CaZrO3:Er3+,Yb3+ phosphors have been recorded. Upon excitation at 978 nm, the material displays strong energy transfer upconversion emission in the green and red spectral regions. The upconversion emission of the CaZrO3:Er3+,Yb3+ co-doped material shows an increased red-to-green ratio, indicating cross relaxation between Er3+ ions.

One-pot synthesis and optical properties of Eu3+-doped nanocrystalline TiO2 and ZrO2

NASA Astrophysics Data System (ADS)

Julián, Beatriz; Corberán, Rosa; Cordoncillo, Eloisa; Escribano, Purificación; Viana, Bruno; Sanchez, Clément

2005-11-01

A simple and versatile one-pot sol-gel synthesis of Eu3+-doped nanocrystalline TiO2 and ZrO2 nanomaterials is reported in this paper. It consists of the controlled crystallization of Eu3+-doped TiO2 or ZrO2 nanoparticles from an initial solution containing the metal alkoxide, the lanthanide precursor, a complexing agent and a non-complexing acid. The main interest is that it could be extended to different lanthanide ions and inorganic metal oxides to prepare other multifunctional nanomaterials. The characterization by XRD, HRTEM and SAED techniques showed that the TiO2 and ZrO2 crystallization takes place at very low temperatures (60 °C) and that the crystallite size can be tailored by modifying the synthetic conditions. The optical properties of the resulting materials were studied by emission spectra and decay measurements. Both Eu3+:TiO2 and Eu3+:ZrO2 samples exhibited long lifetime values after removing organic components (τ = 0.7 and 1.3 ms, respectively), but the Eu3+:ZrO2 system is specially promising for photonic applications since its τ value is longer than some reported for other inorganic or hybrid matrices in which Eu3+ ions are complexed. This behaviour has been explained through an effective dispersion of the lanthanide ions within the ZrO2 nanocrystals.

Enhanced performance of P(VDF-HFP)-based composite polymer electrolytes doped with organic-inorganic hybrid particles PMMA-ZrO2 for lithium ion batteries

NASA Astrophysics Data System (ADS)

Xiao, Wei; Wang, Zhiyan; Zhang, Yan; Fang, Rui; Yuan, Zun; Miao, Chang; Yan, Xuemin; Jiang, Yu

2018-04-01

To improve the ionic conductivity as well as enhance the mechanical strength of the gel polymer electrolyte, poly(vinylidene fluoride-hexafluoroprolene) (P(VDF-HFP))-based composite polymer electrolyte (CPE) membranes doped with the organic-inorganic hybrid particles poly(methyl methacrylate) -ZrO2 (PMMA-ZrO2) are prepared by phase inversion method, in which PMMA is successfully grafted onto the surface of the homemade nano-ZrO2 particles via in situ polymerization confirmed by FT-IR. XRD and DSC patterns show adding PMMA-ZrO2 particles into P(VDF-HFP) can significantly decrease the crystallinity of the CPE membrane. The CPE membrane doped with 5 wt % PMMA-ZrO2 particles can not only present a homogeneous surface with abundant interconnected micro-pores, but maintain its initial shape after thermal exposure at 160 °C for 1 h, in which the ionic conductivity and lithium ion transference number at room temperature can reach to 3.59 × 10-3 S cm-1 and 0.41, respectively. The fitting results of the EIS plots indicate the doped PMMA-ZrO2 particles can significantly lower the interface resistance and promote lithium ions diffusion rate. The Li/CPE-sPZ/LiCoO2 and Li/CPE-sPZ/Graphite coin cells can deliver excellent rate and cycling performance. Those results suggest the P(VDF-HFP)-based CPE doped with 5 wt % PMMA-ZrO2 particles can become an exciting potential candidate as polymer electrolyte for the lithium ion battery.

The effect of TM doping on the superconducting properties of ZrNi2-xTMxGa (TM = Cu, Co) Heusler compounds

NASA Astrophysics Data System (ADS)

Basaula, Dharma Raj; Brock, Jeffrey; Khan, Mahmud

2018-05-01

We have explored the structural and superconducting properties of ZrNi2-xTMxGa (TM = Cu, Co) Heusler compounds via x-ray diffraction, scanning electron mi croscopy, electrical resistivity, dc magnetization and ac susceptibility measurements. All samples crystallized in the cubic L21 structure at room temperature. For x ≤ 0.25, all the ZrNi2-xCuxGa compounds showed superconducting properties and a decrease in TC with increasing Cu concentration. The dc magnetization data suggested type-II superconductivity for all the Cu-doped compounds. Contrary to the ZrNi2-xCuxGa compounds, no superconductivity was observed in the ZrNi2-xCoxGa compounds. Substitution of Ni by a small concentration of Co destroyed superconductivity in the Co-doped compounds. The experimental results are discussed and possible explanations are provided.

Electrical and dielectric properties of ZnO and CeO{sub 2} doped ZrTi{sub 2}O{sub 6} ceramic

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

George, Aneesh; Thomas, Jijimon K.; John, Annamma

2014-01-28

Zirconium oxide (ZrO{sub 2}) and titanium dioxide (TiO{sub 2}) are the important catalyst supports, since it has acidic and basic properties. The intermediate phase zirconium titanate ZrTi{sub 2}O{sub 6}, which is a solid solution with Zr:Ti ratio 1:2 has outstanding dielectric properties. The effects of doping of ZnO and CeO{sub 2} on the dielectric and electrical properties of ZrTi{sub 2}O{sub 6} ceramic are investigated. On adding 0.5 wt% ZnO, the dielectric constant is increased but, on adding CeO{sub 2}, the dielectric constant is decreased. The bulk density of pure sample sintered at 1530 °C is 91% of theoretical density whilemore » that of the doped samples sintered at 1450 °C is more than 94% of theoretical density. Scanning electron micrographs reveal that the samples are well sintered with minimum porosity. The semicircle behavior in the Cole-Cole plots at room temperature reveals that the samples are good ionic conductor. The induced impedance is reduced for doped samples and this can be used as a material for electrolyte in Solid Oxide Fuel Cell.« less

Synthesis and characterization of Eu{sup 3+}-doped CaZrO{sub 3}-based perovskite-type phosphors. Part I: Determination of the Eu{sup 3+} occupied site using the ALCHEMI technique

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

Sakaida, Satoshi; Shimokawa, Yohei; Asaka, Toru

2015-07-15

Highlights: • Eu{sup 3+}-doped CaZrO{sub 3}-based compounds were synthesized by the solid state reaction. • PL emission intensity at 614 nm was changed by the second dopant cations. • The site substituted by Eu{sup 3+} cations was investigated by using XRD and ALCHEMI technique. • The dominant Eu{sup 3+} substitution site was found as the B site (Zr{sup 4+}) in the CaZrO{sub {sup 3}}. • The dominant Eu{sup 3+} substitution site could be strongly influenced by the co-dopants. - Abstract: Eu{sup 3+}-doped CaZrO{sub 3}, SrZrO{sub 3}, and Mg{sup 2+}- or Sr{sup 2+}-co-doped CaZrO{sub 3} were synthesized by conventional solid statemore » reaction and their photoluminescence (PL) properties were characterized. The Eu{sup 3+}-doped CaZrO{sub 3}-based compounds exhibited characteristic emissions of Eu{sup 3+} (f–f transition). The intensity of the main PL emission peak at 614 nm increased with Mg{sup 2+} co-doping, while it decreased with the amount of co-doped Sr{sup 2+}. The site substituted by Eu{sup 3+} cations in the CaZrO{sub 3}-based compounds was investigated by X-ray diffraction analysis and energy-dispersive X-ray analysis based on the electron channeling effects in transmission electron microscopy. The Eu{sup 3+} cations were determined to occupy mainly the B site (Zr{sup 4+}) in CaZrO{sub 3}. The dominant Eu{sup 3+} substitution site was also strongly influenced by the co-dopant, and the ionic radius of the co-dopant was identified as an important factor that determines the dominant Eu{sup 3+} substitution site.« less

Y-doped Li 8ZrO 6: A Li-Ion Battery Cathode Material with High Capacity

DOE PAGES

Huang, Shuping; Wilson, Benjamin E.; Wang, Bo; ...

2015-08-11

We study—experimentally and theoretically—the energetics, structural changes, and charge flows during the charging and discharging processes for a new high-capacity cathode material, Li 8ZrO 6 (LZO), which we study both pure and yttrium-doped. We quantum mechanically calculated the stable delithiated configurations, the delithiation energy, the charge flow during delithiation, and the stability of the delithiated materials. We find that Li atoms are easier to extract from tetrahedral sites than octahedral ones. We calculate a large average voltage of 4.04 eV vs Li/Li + for delithiation of the first Li atom in a primitive cell, which is confirmed by galvanostatic charge/dischargemore » cycling data. Energy calculations indicate that topotactic delithiation is kinetically favored over decomposition into Li, ZrO 2, and O 2 during the charging process, although the thermodynamic energy of the topotactic reaction is less favorable. When one or two lithium atoms are extracted from a primitive cell of LZO, its volume and structure change little, whereas extraction of the third lithium greatly distorts the layered structure. The Li 6ZrO 6 and Li 5ZrO 6 delithiation products can be thermodynamically metastable to release of O 2. Experimentally, materials with sufficiently small particle size for efficient delithiation and relithiation were achieved within an yttrium-doped LZO/carbon composite cathode that exhibited an initial discharge capacity of at least 200 mAh/g over the first 10 cycles, with 142 mAh/g maintained after 60 cycles. Computations predict that during the charging process, the oxygen ion near the Li vacancy is oxidized for both pure LZO and yttrium-doped LZO, which leads to a small-polaron hole.« less

Y-doped Li 8ZrO 6: A Li-Ion Battery Cathode Material with High Capacity

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

Huang, Shuping; Wilson, Benjamin E.; Wang, Bo

We study—experimentally and theoretically—the energetics, structural changes, and charge flows during the charging and discharging processes for a new high-capacity cathode material, Li 8ZrO 6 (LZO), which we study both pure and yttrium-doped. We quantum mechanically calculated the stable delithiated configurations, the delithiation energy, the charge flow during delithiation, and the stability of the delithiated materials. We find that Li atoms are easier to extract from tetrahedral sites than octahedral ones. We calculate a large average voltage of 4.04 eV vs Li/Li + for delithiation of the first Li atom in a primitive cell, which is confirmed by galvanostatic charge/dischargemore » cycling data. Energy calculations indicate that topotactic delithiation is kinetically favored over decomposition into Li, ZrO 2, and O 2 during the charging process, although the thermodynamic energy of the topotactic reaction is less favorable. When one or two lithium atoms are extracted from a primitive cell of LZO, its volume and structure change little, whereas extraction of the third lithium greatly distorts the layered structure. The Li 6ZrO 6 and Li 5ZrO 6 delithiation products can be thermodynamically metastable to release of O 2. Experimentally, materials with sufficiently small particle size for efficient delithiation and relithiation were achieved within an yttrium-doped LZO/carbon composite cathode that exhibited an initial discharge capacity of at least 200 mAh/g over the first 10 cycles, with 142 mAh/g maintained after 60 cycles. Computations predict that during the charging process, the oxygen ion near the Li vacancy is oxidized for both pure LZO and yttrium-doped LZO, which leads to a small-polaron hole.« less

Microstructure modification and oxygen mobility of CeZrO2 nanocrystal doped with Y and Fe metals

NASA Astrophysics Data System (ADS)

Hadi, A.; Shah, M. N. A.; Ismail, K. N.; Roslan, A. B.

2017-09-01

CeZrO2-nanocrystals doped with Y3+ and Fe2+ have been successfully synthesized using the microemulsion method. In this study, the synergetic effect of the synthesis parameters on the formation of structure and catalytic property were reported. XRD analysis found that both doped samples reveal the symmetrical cubic phase and mix in a homogeneous solid solution. The crystallite size of both samples was in nanoscale, which were 11 and 15 nm for CZF and CZY, respectively. This finding was consistent with the physical size investigated by TEM, which was approximately 10 nm for both samples. Meanwhile, isotherm profiles for both samples appeared as the type IV group in the IUPAC classification which was the mesoporous materials. CZY crystal had higher BET surface area than CZF crystal, which was 141.30 and 135.5 m2/g, respectively. Oxygen mobility study found that CZF crystal promotes to active at lower temperature, which is 274.2˚C, than CZY at 302.7˚C. CZF crystal also revealed the higher oxygen removal, which was 286.35 mmol/g, than CZY was 250.49 mmol/g. The doping of transition metal, Fe into CeZrO2 tended to reduce the oxygen mobility's activation temperature, while the addition of rare earth metal, Y into CeZrO2 leaded to remarkable increase of surface area.

Dehydriding properties of Ti or/and Zr-doped sodium aluminum hydride prepared by ball-milling

NASA Astrophysics Data System (ADS)

Xiao, Xue-Zhang; Chen, Li-Xin; Wang, Xin-Hua; Li, Shou-Quan; Hang, Zhou-Ming; Chen, Chang-Pin; Wang, Qi-Dong

2007-12-01

The NaAlH4 complex is attracting great attention for its potential applications in hydrogen-powered fuel-cell vehicles due to its high hydrogen storage capacity and suitable thermodynamic properties. However, its practicable hydrogen storage capacity presently obtained is less than the theoretical capacity (5.6 wt.%). To improve the hydrogen capacity, we chose metallic Ti or/and Zr powder as catalyst dopants, and prepared the sodium aluminum hydride by hydrogenation of ball-milled NaH/Al mixture containing 10 mol% dopants with different proportions of Ti and Zr, and then investigated the effects on their hydrogen storage (dehydriding) properties. The results showed that different catalyst dopants affected the dehydriding properties greatly. The catalysis of metal Ti as a catalyst dopant alone on dehydriding kinetics for the entire dehydrogenation process of ball-milled (NaH/Al) composite was higher than that of adopting Zr alone. The synergistic catalytic effect of Ti and Zr together as co-dopants on the dehydrogenation process of (NaH/Al) composite was higher than that using only Ti or Zr as dopant individually. The composite doped with proper proportion of Ti and Zr together (8 mol% Ti+ 2 mol% Zr) as co-dopants exhibited the highest dehydriding kinetic property and desorption capacity.

Magnetic Compton scattering study of Laves phase ZrFe2 and Sc doped ZrFe2: Experiment and Green function based relativistic calculations

NASA Astrophysics Data System (ADS)

Bhatt, Samir; Mund, H. S.; Kumar, Kishor; Bapna, Komal; Dashora, Alpa; Itou, M.; Sakurai, Y.; Ahuja, B. L.

2018-05-01

Spin momentum densities of ferromagnetic ZrFe2 and Zr0.8Sc0.2Fe2 have been measured using magnetic Compton scattering with 182.65 keV circularly polarized synchrotron radiations. Site specific spin moments, which are responsible for the formation of total spin moment, have been deduced from Compton line shapes. At room temperature, the computed spin moment of ZrFe2 is found to be slightly higher than that of Sc doped ZrFe2 which is in consensus with the magnetization data. To compare the experimental data, we have also computed magnetic Compton profiles (MCPs), total and partial spin projected density of states (DOS) and the site specific spin moments using spin-polarized relativistic Korringa-Kohn-Rostoker method. It is observed that the spin moment at Fe site is aligned antiparallel to that of Zr site in both ZrFe2 and Zr0.8Sc0.2Fe2. The MCP results when compared with vibrating sample magnetometer based magnetization data, show a very small contribution of orbital moment in the formation of total magnetic moments in both the compounds. The DOS of ferromagnetic ground state of ZrFe2 and Zr0.8Sc0.2Fe2 are interpreted on the basis of a covalent magnetic model beyond the Stoner rigid band model. It appears that on alloying between a magnetic and a non-magnetic partner (with low valence), a polarization develops on the non-magnetic atom which is anti-parallel to that of the magnetic atom.

Nano-Scale Structure of Twin Boundaries in Shocked Zircon from the Vredefort Impact Structure.

NASA Astrophysics Data System (ADS)

Sharp, T. G.; Cavosie, A. J.

2017-12-01

Shock deformation of zircon produces distinct microstructures that can be used as evidence of shock in natural samples. These deformation features include {112} twins that have been observed in naturally shocked samples from Vredefort and elsewhere [1-3]. Electron backscatter diffraction (EBSD) has shown that these twins are polysynthetic, generally < 1µm wide and have a 65°/<110> crystallographic relation to the host zircon [2]. The structure and composition of these twin boundaries, and their effects on element mobility have not been explored previously. Here we use high-resolution TEM to investigate the nano-structure of a {112} twin in a shocked zircon crystal from the 2.0 Ga Vredefort impact structure [3]. Focused-ion-beam lift-out techniques were used to prepare a TEM foil with a 1 µm wide {112}-twin lamella. The foil was characterized by TEM imaging and electron diffraction using a FEI CM200-FEG transmission electron microscope. Selected area diffraction from the {112}-twin boundary, along a <111> zone, showed no apparent evidence of twining. However, the domain boundaries displayed weak diffraction contrast in this orientation. High-resolution images show a 50-nm wide zone of heterogeneous structural disorder and locally amorphous domains along the twin boundaries that is inferred to be a localized metamict zone. The detailed lattice structure of the interface was not discernable because of this structural disorder. Diffraction and imaging along <021> confirms that the {112}-twin composition plane is a mirror plane. The crystallographic relations observed along <110> and <021> are consistent with the 65°/<110> twin structure previously determined from EBSD [2]. Enhanced metamict disorder suggests a higher concentration of actinides along the twin boundaries and implies actinide mobility near twin boundaries. [1] Moser et al, 2011 Can J Earth Sci. [2] Erickson et al. 2013 Am Min. [3] Cavosie et al. 2015 Geol.

Hierarchical Na-doped cubic ZrO{sub 2} synthesis by a simple hydrothermal route and its application in biodiesel production

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

Lara-García, Hugo A.; Romero-Ibarra, Issis C.; Pfeiffer, Heriberto, E-mail: pfeiffer@iim.unam.mx

Hierarchical growth of cubic ZrO{sub 2} phase was successfully synthesized via a simple hydrothermal process in the presence of different surfactants (cationic, non-ionic and anionic) and sodium hydroxide. The structural and microstructural characterizations of different ZrO{sub 2} powders were performed using various techniques, such as X-ray diffraction, transmission electron microscopy, N{sub 2} adsorption–desorption, scanning electron microscopy and infrared. Results indicated that sodium addition stabilized the cubic ZrO{sub 2} phase by a Na-doping process, independently of the surfactant used. In contrast, microstructural characteristics varied as a function of the surfactant and sodium presence. In addition, water vapor (H{sub 2}O) and carbonmore » dioxide (CO{sub 2}) sorption properties were evaluated on ZrO{sub 2} samples. Results evidenced that sample surface reactivity changed as a function of the sodium content. Finally, this surface reactivity was evaluated on the biodiesel transesterification reaction using the different synthesized samples, obtaining yields of 93%. - Graphical abstract: Hierarchical growth of cubic Na-ZrO{sub 2} phase was synthesized by hydrothermal processes in the presence of surfactants and sodium. Sodium addition stabilized the cubic phase by a Na-doping process, while the microstructural characteristics varied with surfactants. Finally, this surface reactivity was evaluated on the biodiesel transesterification reaction. - Highlights: • Cubic-ZrO{sub 2} phase was synthesized via a simple hydrothermal process. • ZrO{sub 2} structure and microstructures changed as a function of the surfactant. • Cubic-ZrO{sub 2} phase was evaluated on the biodiesel transesterification reaction.« less

Preparation and characterization of mesoporous ZnO-ZrO2 doped by Cr, Nd and Dy as a catalyst for conversion of coumarin using ultrasensitive fluorometric method

NASA Astrophysics Data System (ADS)

Ibrahim, M. M.

2017-04-01

Doping of mesoporous ZnO-ZrO2 nanoparticles with transition metal and lanthanides (Cr, Nd, Dy) were used as a catalyst to develop an ultrasensitive fluorometric method for the conversion of non fluorescent coumarin to highly fluorescent 7-hydroxycoumarin using H2O2 or light. It was found that doped- ZnO-ZrO2 mixed oxide can catalyze the decomposition of H2O2 to produce •OH radicals, which in turn convert coumarin to 7-hydroxycoumarin. At contrast, the doping has deleterious effect on conversion of coumarin by light due to high band gap and high concentrations of doping increase the recombination rate of electron and holes. Doped mixed oxides prepared by impregnation method and characterized by studying their structural, surface and optical properties. Chromium doped ZnO-ZrO2 had the highest rate of formation of hydroxyl radical due to decomposition of H2O2 and therefore 7-hydroxycoumarin due to surface area, small crystal size and high redox potential.

Enhanced stability of Zr-doped Ba(CeTb)O(3-δ)-Ni cermet membrane for hydrogen separation.

PubMed

Wei, Yanying; Xue, Jian; Fang, Wei; Chen, Yan; Wang, Haihui; Caro, Jürgen

2015-07-25

A mixed protonic and electronic conductor material BaCe(0.85)Tb(0.05)Zr(0.1)O(3-δ) (BCTZ) is prepared and a Ni-BCTZ cermet membrane is synthesized for hydrogen separation. Stable hydrogen permeation fluxes can be obtained for over 100 h through the Ni-BCTZ membrane in both dry and humid conditions, which exhibits an excellent stability compared with Ni-BaCe(0.95)Tb(0.05)O(3-δ) membrane due to the Zr doping.

Transformations to granular zircon revealed: Twinning, reidite, and ZrO2 in shocked zircon from Meteor Crater (Arizona, USA)

USGS Publications Warehouse

Cavosie, Aaron; Timms, Nicholas E.; Erickson, Timmons M.; Hagerty, Justin J.; Hörz, Friedrich

2016-01-01

Granular zircon in impact environments has long been recognized but remains poorly understood due to lack of experimental data to identify mechanisms involved in its genesis. Meteor Crater in Arizona (United States) contains abundant evidence of shock metamorphism, including shocked quartz, the high pressure polymorphs coesite and stishovite, diaplectic SiO2 glass, and lechatelierite (fused SiO2). Here we report the presence of granular zircon, a new shocked mineral discovery at Meteor Crater, that preserve critical orientation evidence of specific transformations that occurred during its formation at extreme impact conditions. The zircon grains occur as aggregates of sub-µm neoblasts in highly shocked Coconino Formation Sandstone (CFS) comprised of lechatelierite. Electron backscatter diffraction shows that each grain consists of multiple domains, some with boundaries disoriented by 65°, a known {112} shock-twin orientation. Other domains have crystallographic c-axes in alignment with {110} of neighboring domains, consistent with the former presence of the high pressure ZrSiO4 polymorph reidite. Additionally, nearly all zircon preserve ZrO2 + SiO2, providing evidence of partial dissociation. The genesis of CFS granular zircon started with detrital zircon that experienced shock-twinning and reidite formation from 20 to 30 GPa, ultimately yielding a phase that retained crystallographic memory; this phase subsequently recrystallized to systematically oriented zircon neoblasts, and in some areas partially dissociated to ZrO2. The lechatelierite matrix, experimentally constrained to form at >2000 °C, provided an ultra high-temperature environment for zircon dissociation (~1670 °C) and neoblast formation. The capacity of granular zircon to preserve a cumulative P-T record has not been recognized previously, and provides a new method for retrieving histories of impact-related mineral transformations in the crust at conditions far beyond which most rocks melt.

Grain neighbour effects on twin transmission in hexagonal close-packed materials.

PubMed

Arul Kumar, M; Beyerlein, I J; McCabe, R J; Tomé, C N

2016-12-19

Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip. We show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.

Grain neighbour effects on twin transmission in hexagonal close-packed materials

NASA Astrophysics Data System (ADS)

Arul Kumar, M.; Beyerlein, I. J.; McCabe, R. J.; Tomé, C. N.

2016-12-01

Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip. We show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.

Potential of SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles in achieving integrated magneto-optical isolators

NASA Astrophysics Data System (ADS)

Zamani, Mehdi; Hocini, Abdesselam

2017-05-01

We have investigated the potential of the SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles in order to overcome the problem of integration of the magneto-optical isolators (MOIs). In this way, we have performed a theoretical study for the case of designing perfect and adjustable MOIs based on magnetophotonic crystals (MPCs) containing SiO2/ZrO2 matrix doped with CoFe2O4 magnetic nanoparticles as a magnetic medium. Despite the existence the attenuation coefficient for SiO2/ZrO2 matrix at wavelength 1550 nm that leads to a non-perfect transmittance, we could introduce an MPC structure having no reflectance; therefore, an ideal MOI for eliminating unwanted back-reflection could be achieved.

Nanostructured microtubes based on TiO2 doped by Zr and Hf oxides with the anatase structure

NASA Astrophysics Data System (ADS)

Zheleznov, VV; Voit, EI; Sushkov, YV; Sarin, SA; Kuryavyi, VG; Opra, DP; Gnedenkov, SV; Sinebryukhov, SL; Sokolov, AA

2016-01-01

The nanostructured microtubes based on TiO2 have been prepared on the carbon fiber template using the sol-gel method. The microtubes consist of nanoparticles of metal oxides: TiO2/ZrO2 and TiO2/HfO2. The dependence of microtubes morphology and nanoparticles structure on the synthesis conditions has been studied using the methods of SEM, SAXS, and Raman spectroscopy. It has been demonstrated that at the stoichiometric ratio of up to 0.04 for Zr/Ti and up to 0.06 for Hf/Ti microtubes consist of uniform nanoparticles with the anatase structure. Along with further increase of the dopants content in the microtubes composition, nanoparticles acquire the core-shell structure. It has been suggested that nanoparticles have a core composed of the solid solutions Ti1-xZrxO2 or Ti1-xHfxO2 and a shell consisting of zirconium or hafnium titanate. The fabricated Zr- and Hf-doped TiO2 materials were investigated in view of their possible use as anode materials for Li-ion batteries. Charge- discharge measurements showed that the doped samples manifested significantly higher reversibility in comparison with the undoped TiO2. The method opens new prospects in synthesis of nanostructured materials for Li-ion batteries application.

Grain neighbour effects on twin transmission in hexagonal close-packed materials

DOE PAGES

Arul Kumar, Mariyappan; Beyerlein, Irene Jane; McCabe, Rodney James; ...

2016-12-19

Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip.more » As a result, we show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.« less

Effect of Zr Doping on Structural and Ferroelectric Properties of Lead-Free Bi0.5(Na0.80K0.20)0.5TiO3 Films

NASA Astrophysics Data System (ADS)

Quan, Ngo Duc; Hung, Vu Ngoc; Dung, Dang Duc

2017-10-01

Environmentally friendly lead-free Bi0.5(Na0.80K0.20)0.5(Ti1- x Zr x )O3 (BNKT- xZr) ferroelectric films with Zr4+ doping concentration x in the range from 0 to 0.05 have been grown on Pt/Ti/SiO2/Si substrates via chemical solution deposition. The effects of Zr4+ substitution on the crystal structure and ferroelectric properties of the films were investigated. X-ray diffraction data revealed that the BNKT- xZr films possessed rhombohedral and tetragonal symmetries at a morphotropic phase boundary when a small amount of Zr4+ doping was added. P- E hysteresis loops typical of ferroelectric materials were observed for all compositions. Zr4+ substituted for Ti4+ in the BNKT- xZr films and remarkably enhanced the ferroelectric properties. The remanent ( P r) and maximum polarization ( P m) reached their highest values of 14.0 μC/cm2 and 35.7 μC/cm2, respectively, at x = 0.02. These values, which are equivalent to the highest P r and P m values in previous reports on lead-free films with different compositions, compare well with those of Pb(Zr,Ti)O3 (PZT) films. Therefore, BNKT- xZr films with optimal Zr4+ concentration could substitute for PZT films in lead-free piezo-microelectromechanical systems (MEMS) devices.

The Effects of Zr Doping on the Optical, Electrical and Microstructural Properties of Thin ZnO Films Deposited by Atomic Layer Deposition

PubMed Central

Herodotou, Stephania; Treharne, Robert E.; Durose, Ken; Tatlock, Gordon J.; Potter, Richard J.

2015-01-01

Transparent conducting oxides (TCOs), with high optical transparency (≥85%) and low electrical resistivity (10−4 Ω·cm) are used in a wide variety of commercial devices. There is growing interest in replacing conventional TCOs such as indium tin oxide with lower cost, earth abundant materials. In the current study, we dope Zr into thin ZnO films grown by atomic layer deposition (ALD) to target properties of an efficient TCO. The effects of doping (0–10 at.% Zr) were investigated for ~100 nm thick films and the effect of thickness on the properties was investigated for 50–250 nm thick films. The addition of Zr4+ ions acting as electron donors showed reduced resistivity (1.44 × 10−3 Ω·cm), increased carrier density (3.81 × 1020 cm−3), and increased optical gap (3.5 eV) with 4.8 at.% doping. The increase of film thickness to 250 nm reduced the electron carrier/photon scattering leading to a further reduction of resistivity to 7.5 × 10−4 Ω·cm and an average optical transparency in the visible/near infrared (IR) range up to 91%. The improved n-type properties of ZnO: Zr films are promising for TCO applications after reaching the targets for high carrier density (>1020 cm−3), low resistivity in the order of 10−4 Ω·cm and high optical transparency (≥85%). PMID:28793633

Investigation of magnetic and structural properties of Ni-Zr co-doped M-type Sr-La hexaferrites

NASA Astrophysics Data System (ADS)

Yang, Yujie; Wang, Fanhou; Shao, Juxiang; Huang, Duohui; Tang, Jin; Rehman, Khalid Mehmood Ur

2018-02-01

In this research, Ni2+ and Zr4+ co-doped Sr-La hexaferrites Sr0.7La0.3Fe12.0-2 x (NiZr) x O19 (0.0 ≤ x ≤ 0.5) were synthesized by the standard ceramic method. The phase identification of the hexaferrites was confirmed by X-ray diffraction analysis. X-ray diffraction analysis showed that all the samples were in single phase M-type hexagonal structure and no impurity phase was observed. Lattice parameters ( c and a) increased with increasing NiZr content ( x) from 0.0 to 0.5. The morphology of the hexaferrites was analyzed by a field emission scanning electron microscopy (FE-SEM). FE-SEM micrographs showed that the grains exhibited hexagonal shape in a plate-like structure with clear grain boundaries. Magnetization properties of the hexaferrites were carried out at room temperature using a physical property measurement system-vibrating sample magnetometer. The values of saturation magnetization ( M s), remanent magnetization ( M r) and coercivity ( H c) were calculated from magnetic hysteresis ( M- H) loops. M s and H c decreased with increasing NiZr content ( x) from 0.0 to 0.5. M r and M r/ M s ratio first increased with increasing NiZr content ( x) from 0.0 to 0.1, and then decreased when NiZr content ( x) ≥ 0.1.

Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling

PubMed Central

Bargmann, Swantje

2017-01-01

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall–Petch coefficient KC experimentally requires a sufficient number of specimens with different colony sizes λC but constant lamella thickness λL and domain size λD, difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient KC as a function of lamella thickness λL. The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%. PMID:28771218

Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling.

PubMed

Schnabel, Jan Eike; Bargmann, Swantje

2017-08-03

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall-Petch coefficient K C experimentally requires a sufficient number of specimens with different colony sizes λ C but constant lamella thickness λ L and domain size λ D , difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient K C as a function of lamella thickness λ L . The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%.

Promoting the ambient-condition stability of Zr-doped barium cerate: Toward robust solid oxide fuel cells and hydrogen separation in syngas

NASA Astrophysics Data System (ADS)

Yang, Ying; Zeng, Yimin; Amirkhiz, Babak S.; Luo, Jing-Li; Yan, Ning

2018-02-01

Increasing the stability of perovskite proton conductor against atmospheric CO2 and moisture attack at ambient conditions might be equally important as that at the elevated service temperatures. It can ease the transportation and storage of materials, potentially reducing the maintenance cost of the integral devices. In this work, we initially examined the surface degradation behaviors of various Zr-doped barium cerates (BaCe0.7Zr0.1Y0.1Me0.1O3) using XRD, SEM, STEM and electron energy loss spectroscopy. Though that the typical lanthanide (Y, Yb and Gd) and In incorporated Zr-doped cerates well resisted CO2-induced carbonation in air at elevated temperatures, they were unfortunately vulnerable at ambient conditions, suffering slow decompositions at the surface. Conversely, Sn doped samples (BCZYSn) were robust at both conditions yet showed high protonic conductivity. Thanks to that, the anode supported solid oxide fuel cells equipped with BCZYSn electrolyte delivered a maximum power density of 387 mW cm-2 at 600 °C in simulated coal-derived syngas. In the hydrogen permeation test using BCZYSn based membrane, the H2 flux reached 0.11 mL cm-2 min-1 at 850 °C when syngas was the feedstock. Both devices demonstrated excellent stability in the presence of CO2 in the syngas.

Antibacterial and Tribological Performance of Carbonitride Coatings Doped with W, Ti, Zr, or Cr Deposited on AISI 316L Stainless Steel

PubMed Central

Yao, Sun-Hui; Su, Yen-Liang; Lai, Yu-Cheng

2017-01-01

Carbonitride (CNx) coatings have existed for several decades but are not well understood. Related studies have indicated that CNx coatings exhibit behaviors comparable to diamond-like carbon (DLC) coatings. Metal-doped CNx coatings are expected to show superior performance to single CNx coatings. In this study, a CNx coating and a group of CNx coatings with 6 at. % metal doping (W, Ti, Zr, or Cr) were prepared on biograde AISI 316L stainless steel (SS316L) substrates, and they were then characterized and studied for antibacterial and wear performance. The microstructure, constituent phase, nanohardness, adhesion, surface roughness, and contact angle were evaluated. The antimicrobial test used Staphylococcus aureus and followed the Japanese Industrial Standard JIS Z 2801:2010. Finally, the wear behavior was assessed. The results showed that the CNx coating was a composite of amorphous CNx and amorphous C structures. The metal doping caused crystalline metal carbides/nitrides to form in the CNx coatings, which weakened their overall integrity. All the coatings showed antimicrobial ability for the SS316L samples. The CNx-Zr coating, the surface of which had the highest hydrophilicity, produced the best antibacterial performance. However, the CNx-Zr coating showed lower wear resistance than the CNx-W and CNx-Ti coatings. The CNx-Ti coating with a highly hydrophilic surface exhibited the lowest antibacterial ability. PMID:29039782

Ternary semiconductors NiZrSn and CoZrBi with half-Heusler structure: A first-principles study

NASA Astrophysics Data System (ADS)

Fiedler, Gregor; Kratzer, Peter

2016-08-01

The ternary semiconductors NiZrSn and CoZrBi with C 1b crystal structure are introduced by calculating their basic structural, electronic, and phononic properties using density functional theory. Both the gradient-corrected PBE functional and the hybrid functional HSE06 are employed. While NiZrSn is found to be a small-band-gap semiconductor (Eg=0.46 eV in PBE and 0.60 eV in HSE06), CoZrBi has a band gap of 1.01 eV in PBE (1.34 eV in HSE06). Moreover, effective masses and deformation potentials are reported. In both materials A B C , the intrinsic point defects introduced by species A (Ni or Co) are calculated. The Co-induced defects in CoZrBi are found to have a higher formation energy compared to Ni-induced defects in NiZrSn. The interstitial Ni atom (Nii) as well as the VNiNii complex introduce defect states in the band gap, whereas the Ni vacancy (VNi) only reduces the size of the band gap. While Nii is electrically active and may act as a donor, the other two types of defects may compensate extrinsic doping. In CoZrBi, only the VCoCoi complex introduces a defect state in the band gap. Motivated by the reported use of NiZrSn for thermoelectric applications, the Seebeck coefficient of both materials, both in the p -type and the n -type regimes, is calculated. We find that CoZrBi displays a rather large thermopower of up to 500 μ V /K when p doped, whereas NiZrSn possesses its maximum thermopower in the n -type regime. The reported difficulties in achieving p -type doping in NiZrSn could be rationalized by the unintended formation of Nii2 + in conjunction with extrinsic acceptors, resulting in their compensation. Moreover, it is found that all types of defects considered, when present in concentrations as large as 3%, tend to reduce the thermopower compared to ideal bulk crystals at T =600 K. For NiZrSn, the calculated thermodynamic data suggest that additional Ni impurities could be removed by annealing, leading to precipitation of a metallic Ni2ZrSn phase.

Photoluminescence and cathodoluminescence of Tb-doped Al 2O 3-ZrO 2 nanostructures obtained by sol-gel method

NASA Astrophysics Data System (ADS)

Zawadzki, M.; Hreniak, D.; Wrzyszcz, J.; Miśta, W.; Grabowska, H.; Malta, O. L.; Stręk, W.

2003-07-01

Terbium-doped Al 2O 3-ZrO 2 mixed oxides of 10 wt% zirconia content were prepared by the alkoxide sol-gel method. The obtained samples were characterized by XRD, SEM, thermal analysis, textural and TPR studies. The effect of thermal treatment of Tb-doped Al 2O 3-ZrO 2 samples on photo- and cathodoluminescence spectra was investigated. It was found that the photoluminescence spectrum induced by UV excitation was characterized by a green luminescence pattern arising from the 5D 4 → 7F J ( J=6-0) transitions of the Tb 3+ ion. This photoluminescence became almost completely damped for the samples sintered at 1200 °C. However, these samples have demonstrated an intense cathodoluminescence under high electron accelerating potential (60 kV). Moreover, it was observed that apart of the green luminescence, the blue emission lines arising from 5D 3 → 7F J transitions of Tb 3+ were observed. The nature of such behavior is discussed.

Effect of photocatalytic reduction of carbon dioxide by N-Zr co-doped nano TiO2.

PubMed

Zhang, Ru; Wang, Li; Kang, Zhuo; Li, Qiang; Pan, Huixian

2017-11-01

Modified sol-gel method was adopted to prepare TiO 2 , Zr-TiO 2 and N/Zr-TiO 2 composite catalyst. The as-synthesized photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Brunner- Emmet- Teller measurement and UV-Vis diffuse reflectance spectroscopy. And the photocatalytic performance toward CO 2 reduction was evaluated under ultraviolet light. The catalyst particles were demonstrated in the nanometer level size. When N and Zr are co-doped, on the one hand, Ti 4+ can be replaced by Zr 4  +, which leads to lattice distortion and inhibits electron-hole recombination. On the other hand, N enters into TiO 2 lattice gap to form O-Ti-N bond structure, and partial Ti 4+ are reduced to Ti 3+ . Compared with pristine TiO 2 , the specific surface area and the band gap of N/Zr-TiO 2 were improved and reduced, respectively. The N and Zr synergistically contribute to the obviously strengthened absorption intensity in visible region, as well as significantly improved photocatalytic activity. In the gas phase reactor, when the calcination temperature was 550°C, 0.125N/0.25Zr-TiO 2 composite performed the highest photocatalytic activity UV irradiation for 8 h, and the corresponding CH 4 yield was 11.837 µmol/g, which was 87.8% higher than that of pristine TiO 2 . For the visible light, the CH 4 yield was 9.003 µmol/g after 8 h irradiation, which was 83.9% higher than that of pristine TiO 2 .

Hierarchical Na-doped cubic ZrO2 synthesis by a simple hydrothermal route and its application in biodiesel production

NASA Astrophysics Data System (ADS)

Lara-García, Hugo A.; Romero-Ibarra, Issis C.; Pfeiffer, Heriberto

2014-10-01

Hierarchical growth of cubic ZrO2 phase was successfully synthesized via a simple hydrothermal process in the presence of different surfactants (cationic, non-ionic and anionic) and sodium hydroxide. The structural and microstructural characterizations of different ZrO2 powders were performed using various techniques, such as X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, scanning electron microscopy and infrared. Results indicated that sodium addition stabilized the cubic ZrO2 phase by a Na-doping process, independently of the surfactant used. In contrast, microstructural characteristics varied as a function of the surfactant and sodium presence. In addition, water vapor (H2O) and carbon dioxide (CO2) sorption properties were evaluated on ZrO2 samples. Results evidenced that sample surface reactivity changed as a function of the sodium content. Finally, this surface reactivity was evaluated on the biodiesel transesterification reaction using the different synthesized samples, obtaining yields of 93%.

ac conductivity in Gd doped Pb(Zr0.53Ti0.47)O3 ceramics

NASA Astrophysics Data System (ADS)

Portelles, J.; Almodovar, N. S.; Fuentes, J.; Raymond, O.; Heiras, J.; Siqueiros, J. M.

2008-10-01

This study is focused in the conduction processes taking place in 0.6 wt % Gd doped lead zirconate titanate samples PbZr0.53Ti0.47O3:Gd (PZT53/47:Gd) in the vicinity of the morphotropic phase boundary. Doped samples show very large dielectric permittivity with respect to that of undoped ones near the transition temperature. The frequency dependent ac conductivity of PZT53/47:Gd ceramics was studied in the 30-450 °C temperature range. X-ray diffraction analyses indicate the incorporation of Gd atoms to the structure. The changes in the dielectric properties as functions of temperature of the doped samples are taken as additional evidence of the incorporation of Gd into the crystal structure. Gd acts as donor center promoting extrinsic n-type conduction. The ac conductivity behavior obeys Jonscher universal relation in the 100 Hz-1 MHz frequency range for temperatures between 30 and 300 °C. The measured conductivity values for Gd doped PZT53/47 are higher than those of pure PZT53/47. According to the correlated barrier hopping model, the preponderant conduction mechanism in the frequency-temperature response was recognized as small polarons hopping mechanism.

Structural, magnetic and luminescent characteristics of Pr3+-doped ZrO2 powders synthesized by a sol-gel method

NASA Astrophysics Data System (ADS)

Isasi-Marín, J.; Pérez-Estébanez, M.; Díaz-Guerra, C.; Castillo, J. F.; Correcher, V.; Cuervo-Rodríguez, M. R.

2009-04-01

The structural, magnetic and luminescence properties of praseodymium-doped zirconia powders of compositions Pr0.03Zr0.97O2 and Pr0.05Zr0.95O2 synthesized by a sol-gel process have been investigated. X-ray diffraction patterns indicate that these materials crystallize in a tetragonal fluorite-type structure. Scanning electron microscopy shows that the powders exhibit an agglomerated microcrystalline structure and the grain size may be in the order of 5-20 µm. The study of the magnetic properties of these doped metal oxides indicates a Curie-Weiss behaviour in the temperature range (100-300) K that allow us to estimate an effective magnetic moment of 3.51 μB, which indicates the presence of Pr3+ in the grown samples. Cathodoluminescence spectra recorded at temperatures between 85 and 295 K show emission peaks that can be attributed to transitions between different states within the 4f2 configuration of Pr3+ ions incorporated in the zirconia crystal lattice. Thermoluminescence measured at temperatures ranging from 373 to 773 K and at 550 nm wavelength show an intense and broad peak around 653 K for the Pr-doped zirconia which is not observed in the undoped material.

Dopant concentration dependent optical and X-Ray induced photoluminescence in Eu3+ doped La2Zr2O7

NASA Astrophysics Data System (ADS)

Pokhrel, Madhab; Brik, Mikhail; Mao, Yuanbing

2015-03-01

Herein, we will be presenting the dopant (Eu) concentration dependent high density La2Zr2O7 nanoparticles for optical and X-ray scintillation applications by use of X - ray diffraction, Raman, FTIR, scanning electron microscope (SEM), transmission electron microscopy (TEM), optically and X-ray excited photoluminescence (PL). Several theoretical methods have been used in order to investigate the structural, electronic, optical, elastic, dynamic properties of Eu doped La2Zr2O7. It is observed that Eu: La2Zr2O7 shows an intense red luminescence under 258, 322, 394 and 465 nm excitation. The optical intensity of Eu: La2Zr2O7 depends on the dopant concentration of Eu3+. Following high energy excitation with X-rays, Eu: La2Zr2O7 shows an atypical Eu PL response (scintillation) with a red emission. The intense color emission of Eu obtained under 258 nm excitation, the X-ray induced luminescence property along with reportedly high density of La2Zr2O7, makes these nanomaterials attractive for optical and X-ray applications. The authors thank the support from the Defense Threat Reduction Agency (DTRA) of the U.S. Department of Defense (Award #HDTRA1-10-1-0114).

Characterization of oxygen vacancies and their migration in Ba-doped Pb(Zr0.52Ti0.48)O3 ferroelectrics

NASA Astrophysics Data System (ADS)

Zhang, M. F.; Wang, Y.; Wang, K. F.; Zhu, J. S.; Liu, J.-M.

2009-03-01

We investigate in detail the migration kinetics of oxygen vacancies (OVs) in Ba-doped Pb(Zr0.52Ti0.48)O3 (PZT) ferroelectrics by complex impedance spectroscopy. The temperature dependent dc-electrical conductivity σdc suggests that Ba doping into PZT can lower significantly the density of OVs, leading to the distinctly decreased σdc and slightly enhanced activation energy U for the migration of OVs, thus benefiting the polarization fatigue resistance. Furthermore, the polarization fluctuation induced by the relaxation of OVs is reduced by the Ba doping. The Cole-Cole fitting to the dielectric loss manifests strong correlation among OVs, and the migration of OVs appears to be a collective behavior.

Analysis of ? twinning via automated atomistic post-processing methods

NASA Astrophysics Data System (ADS)

Barrett, Christopher D.

2017-05-01

? twinning is the most prominent and most studied twin mode in hexagonal close-packed materials. Many works have been devoted to describing its nucleation, growth and interactions with other defects. Despite this, gaps and disagreements remain in the literature regarding some fundamental aspects of the twinning process. A rigorous understanding of the twinning process is imperative because without it higher scale models of plasticity cannot accurately capture deformation in important materials such as Mg, Ti, Zr and Zn. Motivated by this necessity, we have studied ? twinning using molecular dynamics, focusing on automated processing techniques which can extract mechanistic information generalisable to continuum scale deformation. This demonstrates for the first time the automatic identification of twinning dislocation lines and Burgers vectors, and the elasto-plastic decomposition of the deformation gradient inside and around a twin embryo. These results confirm predictions of most authors regarding the dislocation-based twin growth process, while contradicting others who have argued that ? twin growth stems from a shuffling process with no dislocation line.

Polarization induced self-doping in epitaxial Pb(Zr0.20Ti0.80)O3 thin films

PubMed Central

Pintilie, Lucian; Ghica, Corneliu; Teodorescu, Cristian Mihail; Pintilie, Ioana; Chirila, Cristina; Pasuk, Iuliana; Trupina, Lucian; Hrib, Luminita; Boni, Andra Georgia; Georgiana Apostol, Nicoleta; Abramiuc, Laura Elena; Negrea, Raluca; Stefan, Mariana; Ghica, Daniela

2015-01-01

The compensation of the depolarization field in ferroelectric layers requires the presence of a suitable amount of charges able to follow any variation of the ferroelectric polarization. These can be free carriers or charged defects located in the ferroelectric material or free carriers coming from the electrodes. Here we show that a self-doping phenomenon occurs in epitaxial, tetragonal ferroelectric films of Pb(Zr0.2Ti0.8)O3, consisting in generation of point defects (vacancies) acting as donors/acceptors. These are introducing free carriers that partly compensate the depolarization field occurring in the film. It is found that the concentration of the free carriers introduced by self-doping increases with decreasing the thickness of the ferroelectric layer, reaching values of the order of 1026 m−3 for 10 nm thick films. One the other hand, microscopic investigations show that, for thicknesses higher than 50 nm, the 2O/(Ti+Zr+Pb) atomic ratio increases with the thickness of the layers. These results suggest that the ratio between the oxygen and cation vacancies varies with the thickness of the layer in such a way that the net free carrier density is sufficient to efficiently compensate the depolarization field and to preserve the outward direction of the polarization. PMID:26446442

Zirconium doped TiO2 thin films deposited by chemical spray pyrolysis

NASA Astrophysics Data System (ADS)

Juma, A.; Oja Acik, I.; Oluwabi, A. T.; Mere, A.; Mikli, V.; Danilson, M.; Krunks, M.

2016-11-01

Chemical spray pyrolysis (CSP) is a flexible deposition technique that allows for mixing of the precursor solutions in different proportions suitable for doping thin films. The CSP method was used to dope TiO2 thin films with Zr by adding zirconium(IV) acetylacetonate into a solution of titanium(IV) isopropoxide in ethanol stabilized by acetylacetone at [Zr]/[Ti] of 0, 5, 10 and 20 at%. The Zr-doped TiO2 thin films were uniform and homogeneous showing much smaller grains than the undoped TiO2 films. Zr stabilized the anatase phase to temperatures above 800 °C depending on Zr concentration in the spray solution. The concentration of Zr determined by XPS was 6.4 at% for the thin film deposited from the 20 at% solution. According to AFM studies, Zr doping decreased the root mean square roughness of TiO2 film from 5.9 to 1.1 nm. An XRD study of samples with the highest Zr amount showed the ZrTiO4 phase started forming after annealing at 800 °C. The optical band gap for TiO2 decreased from 3.3 eV to 3.0 eV after annealing at 800 °C but for the TiO2:Zr(20) film it remained at 3.4 eV. The dielectric constant increased by more than four times with Zr-doping and this was associated with the change in the bond formations caused by substitution of Ti by Zr in the lattice.

Fabrication and characterization of polyvinyl alcohol/metal (Ca, Mg, Ti) doped zirconium phosphate nanocomposite films for scaffold-guided tissue engineering application.

PubMed

Kalita, Himani; Pal, Pallabi; Dhara, Santanu; Pathak, Amita

2017-02-01

Nanocomposite films of polyvinyl alcohol (PVA) and zirconium phosphate (ZrP)/doped ZrP (doped with Ca, Mg, Ti) nanoparticles have been developed by solvent casting method to assess their potential as matrix material in scaffold-guided tissue engineering application. The prepared ZrP and doped ZrP nanoparticles as well as the nanocomposite films were characterized by various spectroscopic and microscopic techniques. Nanoindentation studies revealed improved nanomechanical properties in the PVA/doped ZrP nanocomposite films (highest for PVA/Ti doped ZrP: hardness=262.4MPa; elastic modulus=5800MPa) as compared to the PVA/ZrP and neat PVA films. In-vitro cell culture experiments carried out to access the cellular viability, attachment, proliferation, and migration on the substrates, using mouse fibroblast (3T3) cell lines, inferred enhanced bioactivity in the PVA/doped ZrP nanocomposite films (highest for PVA/Ca doped ZrP) in contrast to PVA/ZrP and neat PVA films. Controlled biodegradability as well as swelling behavior, superior bioactivity and improved mechanical properties of the PVA/doped ZrP nanocomposite films make them promising matrix materials for scaffold-guided tissue engineering application. Copyright © 2016 Elsevier B.V. All rights reserved.

Ca(5)Zr(3)F(22).

PubMed

Oudahmane, Abdelghani; El-Ghozzi, Malika; Avignant, Daniel

2012-04-01

Single crystals of Ca(5)Zr(3)F(22), penta-calcium trizirconium docosafluoride, were obtained unexpectedly by solid-state reaction between CaF(2) and ZrF(4) in the presence of AgF. The structure of the title compound is isotypic with that of Sr(5)Zr(3)F(22) and can be described as being composed of layers with composition [Zr(3)F(20)](8-) made up from two different [ZrF(8)](4-) square anti-prisms (one with site symmetry 2) by corner-sharing. The layers extending parallel to the (001) plane are further linked by Ca(2+) cations, forming a three-dimensional network. Amongst the four crystallographically different Ca(2+) ions, three are located on twofold rotation axes. The Ca(2+) ions exhibit coordination numbers ranging from 8 to 12, depending on the cut off, with very distorted fluorine environments. Two of the Ca(2+) ions occupy inter-stices between the layers whereas the other two are located in void spaces of the [Zr(3)F(20)](8-) layer and alternate with the two Zr atoms along [010]. The crystal under investigation was an inversion twin.

Photoemission properties of Eu-doped Zr1- x Ce x O2 (x = 0-0.2) nanoparticles prepared by hydrothermal method

NASA Astrophysics Data System (ADS)

Ozawa, Masakuni; Matsumoto, Masashi; Hattori, Masatomo

2018-01-01

Photoluminescent Eu-doped ZrO2 and Zr1- x Ce x O2 (x = 0-0.2) nanoparticles were prepared by a hydrothermal method. X-ray diffraction and Raman spectra indicated the formation of tetragonal crystals of ZrO2 and its solid solutions with a grain size of less than 10 nm diameter after heat treatment at 400 °C. The photoemission spectra of Zr1- x Ce x O2:Eu3+ nanocrystalline samples showed the typical emission of Eu3+ ions assigned to 5D0 → 7F1 (590 nm) and 5D0 → 7F2 (610 nm) transitions and additional emissions of 5D0 → 7F J with higher J of 3-5. Increasing the CeO2 concentration reduced the emission intensity, and the emission peak shift was affected by a local lattice distortion, i.e., CeO2 concentration. The present study provided fundamental knowledge that is expected to enable the fabrication of ZrO2-based nanocrystal phosphor materials and a measure for controlling the emission peak shift and intensity in oxide fluorite-based phosphor.

Twin and habit plane microstructures due to the tetragonal to monoclinic transformation of zirconia

NASA Astrophysics Data System (ADS)

Simha, N. K.

1997-02-01

We first construct Bain strains for the tetragonal to monoclinic ( t → m) transformation of zirconia (ZrO 2), and then examine the resulting twin and habit plane microstructures. The ( t → m) transformation in zirconia occurs via two paths; transformation along path I has two Bain strains that involve shearing of a rectangular face of the tetragonal unit cell, and shearing of the square base corresponds to path II. The monoclinic variants resulting from each of the three Bain strains can form 12 twins, and four of the twins corresponding to path II are neither of type I nor of type II. Habit planes do not exist for the transformation along path I, whereas transformation along path II has: (± 0.8139, ± 0.3898, - 0.4309) t, (± 0.6489, ± 0.6271, - 0.4309) t, (± 0.7804, ± 0.4530, - 0.4309) t. We predict the exact twin planes observed by Bailey [(1964) Phase transformation at high temperatures in hafnia and zirconia. Proc. Roy. Soc.279A, 395-412], Bansal and Heuer [(1972) On a martensitic phase transformation in Zirconia ZrO 2—I. Metallographic evidence. Acta Metall.20, 1281-1289] and Buljan et al. [(1976) Optical and X-ray single crystal studies of the monoclinic ↔ tetragonal transition in ZrO 2. J. Am. Ceram. Soc.59, 351-354]; additional twins and habit planes that we predict have not yet been observed.

Needle twins and right-angled twins in minerals: comparison between experiment and theory

USGS Publications Warehouse

Salje, E.K.H.; Buckley, A.; Van Tendeloo, G.; Ishibashi, Y.; Nord, G.L.

1998-01-01

Transformation twinning in minerals forms isolated twin walls, intesecting walls with corner junctions, and wedge-shaped twins as elements of hierarchical patterns. When cut perpendicular to the twin walls, the twins have characteristic shapes, right-angled and needle-shaped wall traces, which can be observed by transmission electron microscopy or by optical microscopy. Theoretical geometries of wall shapes recently derived for strain-related systems should hold for most displacive and order-disorder type phase transitions: 1) right-angled twins show curved junctions; 2) needle-shaped twins contain flat wall segments near the needle tip if the elastic behaviour of the mineral is dominated by its anisotroyp; 3) additional bending forces and pinning effects lead to curved walls near the junction that make the needle tip appear more blunt. Bent right-angled twins were analyzed in Gd2(MoO4)3. Linear needle tips were found in WO3, [N(CH3)4]2.ZnBr4 CrAl, BiVO4, GdBa2Cu3O7, and PbZrO. Parabolic tips occur in K2Ba(NO2)4, and GeTe whereas exponential curvatures appear in BaTiO3, KSCN, Pb3(PO4)2, CaTiO3, alkali feldspars, YBa2Cu3O7, and MnAl. The size and shape of the twin microstructure relates to its formation during the phase transition and the subsequent annealing history. The mobility of the twin walls after formation depends not only on the thermal activation but also on the structure of the wall, which may be pinned to impurities on a favorable structural site. Depinnign energies are often large compared with thermal energies for diffusion. This leads to kinetic time scales for twin coarsening that are comparable to geological time scales. Therefore, transformation twins that exhibit needle domains not only indicate that the mineral underwent a structural phase transition but also contain information about its subsequent geological history.

Electronic Structure, Phonon Dynamical Properties, and CO 2 Capture Capability of Na 2 - x M x Zr O 3 ( M = Li ,K): Density-Functional Calculations and Experimental Validations

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

Duan, Yuhua; Lekse, Jonathan; Wang, Xianfeng

2015-04-22

The electronic structural and phonon properties of Na 2-αM αZrO 3 (M ¼ Li,K, α = ¼ 0.0,0.5,1.0,1.5,2.0) are investigated by first-principles density-functional theory and phonon dynamics. The thermodynamic properties of CO 2 absorption and desorption in these materials are also analyzed. With increasing doping level α, the binding energies of Na 2-αLi αZrO 3 are increased while the binding energies of Na 2-α K αZrO 3 are decreased to destabilize the structures. The calculated band structures and density of states also show that, at the same doping level, the doping sites play a significant role in the electronic properties.more » The phonon dispersion results show that few soft modes are found in several doped configurations, which indicates that these structures are less stable than other configurations with different doping levels. From the calculated relationships among the chemical-potential change, the CO 2 pressure, and the temperature of the CO 2 capture reactions by Na 2-αM αZrO 3, and from thermogravimetric-analysis experimental measurements, the Li- and K-doped mixtures Na 2-αM αZrO 3 have lower turnover temperatures (T t) and higher CO 2 capture capacities, compared to pure Na 2ZrO 3. The Li-doped systems have a larger T t decrease than the K-doped systems. When increasing the Li-doping level α, the T t of the corresponding mixture Na 2-αLi αZrO 3 decreases further to a low-temperature range. However, in the case of K-doped systems Na 2-αK αZrO 3, although doping K into Na 2ZrO 3 initially shifts its T t to lower temperatures, further increases of the K-doping level α causes T t to increase. Therefore, doping Li into Na 2ZrO 3 has a larger influence on its CO 2 capture performance than the K-doped Na 2ZrO 3. Compared with pure solidsM 2ZrO 3, after doping with other elements, these doped systems’ CO 2 capture performances are improved.« less

Enhancement of pairing interaction and magnetic fluctuations toward a band insulator in an electron-doped Li(x)ZrNCl Superconductor.

PubMed

Kasahara, Yuichi; Kishiume, Tsukasa; Takano, Takumi; Kobayashi, Katsuki; Matsuoka, Eiichi; Onodera, Hideya; Kuroki, Kazuhiko; Taguchi, Yasujiro; Iwasa, Yoshihiro

2009-08-14

The doping dependence of specific heat and magnetic susceptibility has been investigated for Li(x)ZrNCl superconductors derived from a band insulator. As the carrier concentration is decreased, the anisotropy of superconducting gap changes from highly anisotropic to almost isotropic. It was also found that, upon reducing carrier density, the superconducting coupling strength and the magnetic susceptibility are concomitantly enhanced in parallel with T(c), while the density of states at the Fermi level is kept almost constant. Theoretical calculations taking into account the on-site Coulomb interaction reproduced the experimental results, suggesting a possible pairing mediated by magnetic fluctuations, even in the doped band insulators.

Structural and electrical properties of atomic layer deposited Al-doped ZrO2 films and of the interface with TaN electrode

NASA Astrophysics Data System (ADS)

Spiga, S.; Rao, R.; Lamagna, L.; Wiemer, C.; Congedo, G.; Lamperti, A.; Molle, A.; Fanciulli, M.; Palma, F.; Irrera, F.

2012-07-01

Al-doped ZrO2 (Al-ZrO2) films deposited by atomic layer deposition onto silicon substrates and the interface with the TaN metal gate are investigated. In particular, structural properties of as-grown and annealed films in the 6-26 nm thickness range, as well as leakage and capacitive behavior of metal-oxide-semiconductor stacks are characterized. As-deposited Al-ZrO2 films in the mentioned thickness range are amorphous and crystallize in the ZrO2 cubic phase after thermal treatment at 900 °C. Correspondingly, the dielectric constant (k) value increases from 20 ± 1 to 27 ± 2. The Al-ZrO2 layers exhibit uniform composition through the film thickness and are thermally stable on Si, whereas chemical reactions take place at the TaN/Al-ZrO2 interface. A transient capacitance technique is adopted for monitoring charge trapping and flat band instability at short and long time scales. The role of traps nearby the TaN/Al-ZrO2 interface is discussed and compared with other metal/high-k oxide films. Further, analytical modeling of the flat band voltage shift with a power-law dependence on time allows extracting features of bulk traps close to the silicon/oxide interface, which exhibit energy levels in the 1.4-1.9 eV range above the valence band of the Al-ZrO2.

Simultaneous NOx and Particulate Matter Removal from Diesel Exhaust by Hierarchical Fe-Doped Ce–Zr Oxide

PubMed Central

2017-01-01

Particulate matter and NOx emissions from diesel exhaust remains one of the most pressing environmental problems. We explore the use of hierarchically ordered mixed Fe–Ce–Zr oxides for the simultaneous capture and oxidation of soot and reduction of NOx by ammonia in a single step. The optimized material can effectively trap the model soot particles in its open macroporous structure and oxidize the soot below 400 °C while completely removing NO in the 285–420 °C range. Surface characterization and DFT calculations emphasize the defective nature of Fe-doped ceria. The isolated Fe ions and associated oxygen vacancies catalyze facile NO reduction to N2. A mechanism for the reduction of NO with NH3 on Fe-doped ceria is proposed involving adsorbed O2. Such adsorbed O2 species will also contribute to the oxidation of soot. PMID:28603656

A-Site Cation Substitutions in Strained Y-Doped BaZrO 3 Multilayer Films Leading to Fast Proton Transport Pathways

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

Aruta, Carmela; Han, Chu; Zhou, Si

Proton-conducting perovskite oxides form a class of solid electrolytes for novel electrochemical devices operating at moderate temperatures. Here, we use hard X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and density functional theory calculations to investigate the structure and elucidate the origin of the fast proton transport properties of strained ultrathin films of Y-doped BaZrO 3 grown by pulsed lased deposition on NdGaO 3. Our study shows that our BaZr 0.8Y 0.2O 3 films incorporate a significant amount of Y dopants, and to a lesser extent also Zr ions, substituting for Ba 2+, and that these substitutional defects agglomerate forming columnarmore » regions crossing vertically from the surface to the interface the entire film. In conclusion, our calculations also show that, in regions rich in Y substitutions for both Zr and Ba, the proton transfer process involves nearly zero-energy barriers, indicating that A-site cation substitutions by Y lead to fast transport pathways and hence are responsible for the previously observed enhanced values of the proton conductivity of these perovskite oxide films.« less

Evolution of microstructural defects of TiO2 nanocrystals by Zr4+ or/and Ge4+ doping lead to high disinfection efficiency for CWAs

NASA Astrophysics Data System (ADS)

Shen, Zhong; Zhong, Jin-Yi; Chai, Na-Na; He, Xin; Zang, Jian-Zheng; Xu, Hui; Han, Xiao-Yuan; Zhang, Peng

2017-06-01

Zr4+, Ge4+ doped and co-doped TiO2 nanoparticles were prepared by a 'one-pot' homogeneous precipitation method. The photocatalytic reaction kinetics of DMMP and the disinfection efficiency of HD, GD and VX on the samples were investigated. By means of a variety of characterization methods, especially the positron annihilation lifetime spectroscopy, the changes in structure and property of TiO2 across doping were studied. The results show that the reasonable engineering design of novel photocatalysts in the field of CWAs decontamination can be realized by adjusting the bulk-to-surface defects ratio, except for crystal structure, specific surface area, pore size distribution and light utilization.

Dielectric and phonon spectroscopy of Nb-doped Pb(Zr1-yTiy)O3-CoFe2O4 composites

NASA Astrophysics Data System (ADS)

Sakanas, Aurimas; Nuzhnyy, Dmitry; Grigalaitis, Robertas; Banys, Juras; Borodavka, Fedir; Kamba, Stanislav; Ciomaga, Cristina Elena; Mitoseriu, Liliana

2017-06-01

Broad-band dielectric and phonon response of Nb-doped (1-x)Pb(Zr1-yTiy)O3-xCoFe2O4 composites with x = 10%-30% was investigated between 0.1 MHz and 100 THz. At room temperature, a broad distribution of relaxation times causes a constant dielectric loss below 1 GHz. Above room temperature, a strong Maxwell-Wagner relaxation process dominates below 1 GHz due to the conductivity of CoFe2O4 (CF). Two additional relaxation processes are seen between 1 GHz and 1 THz. The lower-frequency one, coming from domain wall motion, disappears above TC ≈ 650 K. The higher-frequency component slows down on heating towards TC, because it is the central mode, which drives the ferroelectric phase transition. Time-domain THz transmission and infrared reflectivity spectra reveal a mixture of polar phonons from both ferroelectric Nb-doped Pb(Zr,Ti)O3 (PZTN) and magnetic CoFe2O4 (CF) components, while the micro-Raman scattering spectra allow to study phonons from both components separately. Similar temperature behavior of phonons as in the pure PZTN and CF was observed. While in CoFe2O4 the Raman-active phonons gradually reduce their intensities on heating due to increasing conductivity and related reduced Raman-scattering volume, some phonons in PZTN disappear above TC due to change of selection rules in the paraelectric phase. Like in the pure Pb(Zr,Ti)O3, the soft phonon and central modes were also observed.

Vibrational micro-energy harvesters utilizing Nb-doped Pb(Zr,Ti)O3 films on stainless steel substrates

NASA Astrophysics Data System (ADS)

Van Minh, L.; Sano, T.; Fujii, T.; Kuwano, H.

2016-11-01

This work presents the micromachined energy harvesters using Nb-doped Pb(Zr,Ti)O3 (PNZT) films grown directly on the stainless steel substrates (SUS430). Piezoelectric materials on metallic substrates have been attracted to practical and robust energy harvesters. Nb-doped PZT films with (001)-preferred orientation grown on SUS substrates provided excellent properties for energy harvesting - high piezoelectric coefficient (e 31 = -10.6 C/m2) and low dielectric permittivity (ɛr = 373). The PNZT-based micro-energy harvester comprising a cantilever of 1.7 mm× 5 mm × 0.05 mm and a proof mass of 3 mm× 5 mm × 47 mm achieved the normalized power density (NPD) of 2.87 mW.g-2.cm-3. It is the highest performance among the published SUS-based energy harvesters, being closer to the best Si- based energy harvesters.

The behaviour of REE and Zr-Hf fractionation in the volcanic waters of Nevado del Ruiz system (Colombia)

NASA Astrophysics Data System (ADS)

Inguaggiato, Claudio; Censi, Paolo; Zuddas, Pierpaolo; Makario Londoño, John; Chacón, Zoraida; Alzate, Diego; Brusca, Lorenzo; D'Alessandro, Walter

2015-04-01

The geochemical behaviour of Rare Earth Element (REE), Zr and Hf have been investigated in the thermal waters of Nevado del Ruiz volcanic system. These fluids are characterised by a wide range of pH ranging between 1.0 and 8.8. The acidic waters are sulphate dominated with different Cl/SO4 ratios. The Nevado del Ruiz waters allowed to investigate the behaviour of investigated elements in a wide spectrum of pH and chemical composition of water. The important role of the pH and the ionic complexes have been evidenced in the distribution of REE, Zr and Hf in the aqueous phase. The pH rules the precipitation of authigenic oxyhydroxides of Fe, Al producing changes in REE, Zr, Hf amount and strong anomalies of Cerium and Europium. Y-Ho and Zr-Hf (twin pairs) have different behaviour in strong acidic waters with respect to the water with higher pH. Yttrium and Ho have the same behaviour of Zr and Hf in waters with pH near neutral-to-neutral, showing super-chondritic ratios. The twin pairs showed to be sensitive to the co-precipitation and/or adsorption onto the surface of authigenic particulate suggesting an enhanced scavenging of Ho and Hf respect to Y and Zr, leading to super-chondritic ratios. In acidic waters a different behaviour of twin pairs occurs with chondritic Y/Ho ratios (reflecting the Y/Ho ratio of average local rock) and sub-chondritic Zr/Hf ratios. For the first time, Zr and Hf have been investigated in natural acidic fluids to understand the behaviour of these elements in extreme acidic conditions and different major anions chemistry. Zr/Hf molar ratio changes from 4.75 to 49.29 in water with pH<3.6. In strong acidic waters, a different fractionation of Zr and Hf have been recognised as function of major anion contents (Cl and SO4), suggesting the formation of complexes leading to sub-chondritic Zr/Hf molar ratios.

100 MeV swift Si{sup 7+} ion induced thermoluminescence studies of nanocrystalline erbium doped ZrO{sub 2}

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

Lokesha, H. S.; Nagabhushana, K. R., E-mail: bhushankr@gmail.com; Singh, Fouran

2015-06-24

Pure and erbium (1mol%) doped nanocrystalline ZrO{sub 2} is synthesized by combustion technique. Thermoluminescence (TL) properties ZrO{sub 2}pellets annealed at 873 K and irradiated by 100 MeV swift Si{sup 7+} ion for various fluence are recorded. The evolution crystalline structure and crystallite size are done using by XRD data. Two TL glow curves, a well resolved one peak at ∼420 K and an unresolved with peak at ∼598 K are observed. TL intensity increases up to 3×10{sup 12} ions cm{sup −2} beyond which the TL intensity decreases. The glow peak shape method is used to calculate the TL trap parameter and discussed in thismore » paper.« less

Effects of Doping on Thermal Conductivity of Pyrochlore Oxides for Advanced Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Zhu, Dongming; Eslamloo-Grami, Maryam

2006-01-01

Pyrochlore oxides of general composition, A2B2O7, where A is a 3(+) cation (La to Lu) and B is a 4(+) cation (Zr, Hf, Ti, etc.) have high melting point, relatively high coefficient of thermal expansion, and low thermal conductivity which make them suitable for applications as high-temperature thermal barrier coatings. The effect of doping at the A site on the thermal conductivity of a pyrochlore oxide La2Zr2O7, has been investigated. Oxide powders of various compositions La2Zr2O7, La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 were synthesized by the citric acid sol-gel method. These powders were hot pressed into discs and used for thermal conductivity measurements using a steady-state laser heat flux test technique. The rare earth oxide doped pyrochlores La(1.7)Gd(0.3)Zr2O7, La(1.7)Yb(0.3)Zr2O7 and La(1.7)Gd(0.15)Yb(0.15)Zr2O7 had lower thermal conductivity than the un-doped La2Zr2O7. The Gd2O3 and Yb2O3 co-doped composition showed the lowest thermal conductivity.

Hydrogen absorption of Pd/ZrO2 composites prepared from Zr65Pd35 and Zr60Pd35Pt5 amorphous alloys

NASA Astrophysics Data System (ADS)

Ozawa, Masakuni; Katsuragawa, Naoya; Hattori, Masatomo; Yogo, Toshinobu; Yamamura, Shin-ichi

2018-01-01

Metal-dispersed composites were derived from amorphous Zr65Pd35 and Zr65Pd30Pt5 alloys and their hydrogen absorption behavior was studied. X-ray diffractograms and scanning electron micrographs indicated that mixtures containing ZrO2, the metallic phase of Pd, and PdO were formed for both amorphous alloys heat-treated in air. In the composites, micron-sized Pd-based metal precipitates were embedded in a ZrO2 matrix after heat treatment at 800 °C in air. The hydrogen temperature-programmed reduction was applied to study the reactivity of hydrogen gas with the oxidized Zr65Pd35 and Zr65Pd30Pt5 materials. Rapid hydrogen absorption and release were observed on the composite derived from the amorphous alloy below 100 °C. The hydrogen pressure-concentration isotherm showed that the absorbed amount of hydrogen in materials depended on the formation of the Pd or Pt-doped Pd phase and its large interface area to the matrix in the nanocomposites. The results indicate the importance of the composite structure for the fabrication of a new type of hydrogen storage material prepared from amorphous alloys.

Preparation and electrochemical properties of Zr-site substituted Li7La3(Zr2-xMx)O12 (M = Ta, Nb) solid electrolytes

NASA Astrophysics Data System (ADS)

Huang, Mian; Shoji, Mao; Shen, Yang; Nan, Ce-Wen; Munakata, Hirokazu; Kanamura, Kiyoshi

2014-09-01

Li7La3Zr2O12 (LLZ) solid electrolytes with Zr site partially substituted by Ta and Nb elements were prepared via the conventional solid-state reaction. All the compositions could lead to the cubic garnet-type structure after sintering at 1150 °C. The use of γ-Al2O3 as a sintering aid in the preparation of doped LLZ was studied. It was shown that Al could help to improve the micro-structure for Nb doping, but not necessary for Ta doping. The Ta and Nb doping enhanced the ionic conductivity at 25 °C to 4.09 × 10-4 S cm-1 and 4.50 × 10-4 S cm-1, respectively. A conductivity as high as 1.23 × 10-3 S cm-1 was obtained when measured at 50 °C in air for the Nb-doped LLZ. All-solid-state batteries with LLZTa and LLZNb solid electrolytes were assembled and tested. The cyclic voltammetry (CV) measurement indicated the successful working of the batteries.

Triple-twin domains in Mg doped GaN wurtzite nanowires: structural and electronic properties of this zinc-blende-like stacking

NASA Astrophysics Data System (ADS)

Arbiol, Jordi; Estradé, Sònia; Prades, Joan D.; Cirera, Albert; Furtmayr, Florian; Stark, Christoph; Laufer, Andreas; Stutzmann, Martin; Eickhoff, Martin; Gass, Mhairi H.; Bleloch, Andrew L.; Peiró, Francesca; Morante, Joan R.

2009-04-01

We report on the effect of Mg doping on the properties of GaN nanowires grown by plasma assisted molecular beam epitaxy. The most significant feature is the presence of triple-twin domains, the density of which increases with increasing Mg concentration. The resulting high concentration of misplaced atoms gives rise to local changes in the crystal structure equivalent to the insertion of three non-relaxed zinc-blende (ZB) atomic cells, which result in quantum wells along the wurtzite (WZ) nanowire growth axis. High resolution electron energy loss spectra were obtained exactly on the twinned (zinc-blende) and wurtzite planes. These atomically resolved measurements, which allow us to identify modifications in the local density of states, revealed changes in the band to band electronic transition energy from 3.4 eV for wurtzite to 3.2 eV in the twinned lattice regions. These results are in good agreement with specific ab initio atomistic simulations and demonstrate that the redshift observed in previous photoluminescence analyses is directly related to the presence of these zinc-blende domains, opening up new possibilities for band-structure engineering.

Density functional theory calculations of the water interactions with ZrO2 nanoparticles Y2O3 doped

NASA Astrophysics Data System (ADS)

Subhoni, Mekhrdod; Kholmurodov, Kholmirzo; Doroshkevich, Aleksandr; Asgerov, Elmar; Yamamoto, Tomoyuki; Lyubchyk, Andrei; Almasan, Valer; Madadzada, Afag

2018-03-01

Development of a new electricity generation techniques is one of the most relevant tasks, especially nowadays under conditions of extreme growth in energy consumption. The exothermic heterogeneous electrochemical energy conversion to the electric energy through interaction of the ZrO2 based nanopowder system with atmospheric moisture is one of the ways of electric energy obtaining. The questions of conversion into the electric form of the energy of water molecules adsorption in 3 mol% Y2O3 doped ZrO2 nanopowder systems were investigated using the density functional theory calculations. The density functional theory calculations has been realized as in the Kohn-Sham formulation, where the exchange-correlation potential is approximated by a functional of the electronic density. The electronic density, total energy and band structure calculations are carried out using the all-electron, full potential, linear augmented plane wave method of the electronic density and related approximations, i.e. the local density, the generalized gradient and their hybrid approximations.

Thermoluminescence glow curve analysis and CGCD method for erbium doped CaZrO{sub 3} phosphor

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

Tiwari, Ratnesh, E-mail: 31rati@gmail.com; Chopra, Seema

2016-05-06

The manuscript report the synthesis, thermoluminescence study at fixed concentration of Er{sup 3+} (1 mol%) doped CaZrO{sub 3} phosphor. The phosphors were prepared by modified solid state reaction method. The powder sample was characterized by thermoluminescence (TL) glow curve analysis. In TL glow curve the optimized concentration in 1mol% for UV irradiated sample. The kinetic parameters were calculated by computerized glow curve deconvolution (CGCD) techniaue. Trapping parameters gives the information of dosimetry loss in prepared phosphor and its usability in environmental monitoring and for personal monitoring. CGCD is the advance tool for analysis of complicated TL glow curves.

Thickness and Nb-doping effects on ferro- and piezoelectric properties of highly a-axis-oriented Nb-doped Pb(Zr0.3Ti0.7)O3 films

NASA Astrophysics Data System (ADS)

Zhu, Zhi-Xiang; Ruangchalermwong, C.; Li, Jing-Feng

2008-09-01

Tetragonal Nb-doped Pb(Zr0.3Ti0.7)O3 (PNZT) films with a lead oxide seeding layer were deposited on the Pt(111)/Ti/SiO2/Si(100) substrates by sol-gel processing. The as-grown PNZT films with thicknesses ranging from about 0.08 to 0.78 μm show highly a-axis preferential orientation, and their ferroelectric and piezoelectric properties improved with increasing film thickness. Due to the combined effects of Nb doping and a-axis texturing as well as reduced substrate constraint, a high d33 constant up to 196 pm/V was obtained for PNZT film at 0.78 μm in addition to a large remnant polarization of 69 μC/cm2. This well a-axis-oriented PNZT films on platinized Si with a high piezoresponse are suitable for the fabrication of microelectromechanical devices.

Modeling the effect of neighboring grains on twin growth in HCP polycrystals

DOE PAGES

Kumar, M. Arul; Beyerlein, I. J.; Lebensohn, R. A.; ...

2017-08-04

In this paper, we study the dependence of neighboring grain orientation on the local stress state around a deformation twin in a hexagonal close packed (HCP) crystal and its effects on the resistance against twin thickening. We use a recently developed, full-field elasto-visco-plastic formulation based on fast Fourier transforms that accounts for the twinning shear transformation imposed by the twin lamella. The study is applied to Mg, Zr and Ti, since these HCP metals tend to deform by activation of different types of slip modes. The analysis shows that the local stress along the twin boundary are strongly controlled bymore » the relative orientation of the easiest deformation modes in the neighboring grain with respect to the twin lamella in the parent grain. A geometric expression that captures this parent-neighbor relationship is proposed and incorporated into a larger scale, mean-field visco-plastic self-consistent model to simulate the role of neighboring grain orientation on twin thickening. We demonstrate that the approach improves the prediction of twin area fraction distribution when compared with experimental observations.« less

Modeling the effect of neighboring grains on twin growth in HCP polycrystals

NASA Astrophysics Data System (ADS)

Kumar, M. Arul; Beyerlein, I. J.; Lebensohn, R. A.; Tomé, C. N.

2017-09-01

In this paper, we study the dependence of neighboring grain orientation on the local stress state around a deformation twin in a hexagonal close packed (HCP) crystal and its effects on the resistance against twin thickening. We use a recently developed, full-field elasto-visco-plastic formulation based on fast Fourier transforms that account for the twinning shear transformation imposed by the twin lamella. The study is applied to Mg, Zr and Ti, since these HCP metals tend to deform by activation of different types of slip modes. The analysis shows that the local stress along the twin boundary are strongly controlled by the relative orientation of the easiest deformation modes in the neighboring grain with respect to the twin lamella in the parent grain. A geometric expression that captures this parent-neighbor relationship is proposed and incorporated into a larger scale, mean-field visco-plastic self-consistent model to simulate the role of neighboring grain orientation on twin thickening. We demonstrate that the approach improves the prediction of twin area fraction distribution when compared with experimental observations.

Investigation of holmium-doped zirconium oxide ceramic phosphor as an ultraviolet wavelength-discriminating laser beam viewer

NASA Astrophysics Data System (ADS)

Yamanoi, Kohei; Hori, Tatsuhiro; Minami, Yuki; Empizo, Melvin John F.; Luong, Mui Viet; Shiro, Atsushi; Watanabe, Jun; Iwano, Keisuke; Iwasa, Yuki; Cadatal-Raduban, Marilou; Gabayno, Jacque Lynn; Shimizu, Toshihiko; Sarukura, Nobuhiko; Norimatsu, Takayoshi

2018-01-01

We report the fluorescence spectra of ZrO2 and trivalent Ho-doped ZrO2 ceramics under ultraviolet (UV) excitation at 213, 266, and 355 nm wavelengths. The Ho3+-doped ZrO2 ceramics exhibited varying fluorescence color tones depending on the excitation wavelength used. The different color tones match the fluorescence spectrum characteristics at each excitation wavelength. Our results demonstrate that Ho3+-doped ZrO2 ceramics can discriminate between UV light, specifically the third, fourth, and fifth harmonics of a Nd:YAG laser. It can potentially be used for developing UV laser beam viewers to aid laser alignment.

X-Ray Absorption Spectroscopy Studies of the Atomic Structure of Zirconium-Doped Lithium Silicate Glasses and Glass-Ceramics, Zirconium-Doped Lithium Borate Glasses, and Vitreous Rare-Earth Phosphates

NASA Astrophysics Data System (ADS)

Yoo, Changhyeon

In the first part of this work, the atomic-scale structure around rare-earth (RE = Pr, Nd, Eu, Dy, and Er) cations (RE3+) in rare-earth sodium ultraphosphate (REUP) glasses were investigated using RE LIII -edge (RE = Nd, Er, Dy, and Eu) and K-edge (RE = Pr and Dy) Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. (RE2O 3)x(Na2O)y(P2O5) 1-x-y glasses in the compositional range 0 ≤ x ≤ 0.14 and 0.3 ≤ x + y ≤ 0.4 were studied. For the nearest oxygen shell, the RE-oxygen (RE-O) coordination number decreases from 10.8 to 6.5 with increasing RE content for Pr-, Nd-, Dy-, and Er-doped sodium ultraphosphate glasses. For Eu-doped samples, the Eu-O coordination number was between 7.5 and 8.8. Also, the RE-O mean distance ranges were between 2.43-2.45 A, 2.40-2.43 A, 2.36-2.38 A, 2.30-2.35 A, and 2.28-2.30 A for Pr-, Nd-, Eu-, Dy-, and Er-doped samples, respectively. In the second part, a series of Zr-doped (3-10 mol%) lithium silicate (ZRLS) glass-ceramics and their parent glasses and a series of Zr-doped (2-6 mol% ZrO2) lithium borate (ZRLB) glasses were investigated using Zr K-edge EXAFS and X-ray Absorption Near Edge Structure (XANES) spectroscopy. Immediate coordination environments of all ZRLS glasses are remarkably similar for different compositions. For the nearest oxygen shell, the Zr-O coordination number ranges were between 6.1 and 6.3 for nucleated and crystallized samples, respectively. Also, the Zr-O mean distance remains similar around 2.10 A. For these glasses, the composition dependence of structural parameters was small. Small changes in the coordination environment were observed for ZRLS glass-ceramics after thermal treatments. In contrast, Zr coordination environment in ZRLB glasses appear to depend appreciably on the Zr concentration. For the nearest oxygen shell, the Zr-O coordination number increased from 6.1 to 6.8 and the Zr-O distance decreased from 2.18 A to 2.14 A with decreasing ZrO2 content.

Study of twin-roll cast Aluminium alloys subjected to severe plastic deformation by equal channel angular pressing

NASA Astrophysics Data System (ADS)

Poková, M.; Cieslar, M.

2014-08-01

Aluminium alloys prepared by twin-roll casting method become widely used in industry applications. Their high solid solution supersaturation and finer grains ensure better mechanical properties when compared with the direct-chill cast ones. One of the possibilities how to enhance their thermal stability is the addition of zirconium. After heat treatment Al3Zr precipitates form and these pin moving grain boundaries when the material is exposed to higher temperatures. In the present work twin-roll cast aluminium alloys based on AA3003 with and without Zr addition were annealed for 8 hours at 450 °C to enable precipitation of Al3Zr phase. Afterwards they were subjected to severe plastic deformation by equal channel angular pressing, which led to the reduction of average grain size under 1 μm. During subsequent isochronal annealing recovery and recrystallization took place. These processes were monitored by microhardness measurements, light optical microscopy and in-situ transmission electron microscopy. The addition of Zr stabilizes the grain size and increases the recrystallization temperature by 100 °C.

ZrO2:Sm3+ nanophosphor: synthesis, Rietveld refinement, optical and thermoluminescent properties

NASA Astrophysics Data System (ADS)

Ponkumar, S.; Janaki, K.; Prakashbabu, D.; Ramalingam, H. B.; Munirathnam, K.; Sreekanth, T. V. M.; Dhoble, S. J.

2018-02-01

We have synthesized undoped and Sm3+ ions doped ZrO2 nanophosphors by solution combustion method. These nanophosphors crystallized in cubic structure. Rietveld refinement of the samples was performed to estimate lattice parameters. Spherical particles with the sizes of 10-25 nm were observed by transmission electron microscopy. Photoluminescence and thermoluminescence (TL) properties of samples were investigated. Under 400 nm excitation, the nanophosphors have intense red emission at 600 nm. The color coordinates (0.67, 0.33) were located in the red region of CIE diagram. TL properties of nanophosphors were studied by exposing the samples to γ-rays. 5 mol% Sm3+ doped ZrO2 nanophosphor has shown maximum TL intensity after γ-irradiation. To test suitability of the nanophosphors for practical application in dosimetry, the 5 mol% Sm3+ doped ZrO2 sample was irradiated by 14 MeV electron beam in various electron fluence ranging from 100 to 900 Gy and their TL response was recorded.

Structure and properties of ZrB2, ZrSiB and ZrAlSiB cathode materials and coatings obtained by their magnetron sputtering

NASA Astrophysics Data System (ADS)

Iatsyuk, I. V.; Lemesheva, M. V.; Kiryukhantsev-Korneev, Ph V.; Levashov, E. A.

2018-04-01

The ceramic ZrB2, ZrSiB, and ZrAlSiB cathodes were manufactured by means of self-propagating high-temperature synthesis (SHS). The parameters of SHS process including dependence of the combustion temperature and rate on the initial temperature of the reaction mixtures, as well as values of effective activation energy were estimated. Cathodes were subjected to the magnetron sputtering in the argon atmosphere. The structure and properties of cathodes and coatings were studied by means of X-ray diffraction, scanning electron microscopy, energy-dispersive and glow discharge optical emission spectroscopy. Bulk ceramic samples and coatings were characterised in terms of their hardness, elastic modulus, elastic recovery, density, and residual porosity. Results obtained shows that cathodes posses homogeneous structure with low porosity level in range 2-6% and hardness between 10 and 17 GPa. Coatings demonstrate dense defect-free structure and contain nanocrystallites of h-ZrB2 phase. The grain size and hardness decrease from 8 down to 2 nm and from 37 down to 16 GPa with the addition of the silicon and aluminum dopes.

Radiation damage in cubic ZrO 2 and yttria-stabilized zirconia from molecular dynamics simulations

DOE PAGES

Aidhy, Dilpuneet S.; Zhang, Yanwen; Weber, William J.

2014-11-20

Here, we perform molecular dynamics simulation on cubic ZrO 2 and yttria-stabilized zirconia (YSZ) to elucidate defect cluster formation resulting from radiation damage, and evaluate the impact of Y-dopants. Interstitial clusters composed of split-interstitial building blocks, i.e., Zr-Zr or Y-Zr are formed. Moreover, oxygen vacancies control cation defect migration; in their presence, Zr interstitials aggregate to form split-interstitials whereas in their absence Zr interstitials remain immobile, as isolated single-interstitials. Y-doping prevents interstitial cluster formation due to sequestration of oxygen vacancies.

Atomic site preferences and structural evolution in vanadium-doped ZrSiO4 from multinuclear solid-state NMR

NASA Astrophysics Data System (ADS)

Dajda, N.; Dixon, J. M.; Smith, M. E.; Carthey, N.; Bishop, P. T.

2003-01-01

Solid state NMR spectra of 29Si are reported from pure and vanadium-doped zircon (V-ZrSiO4) samples. The vanadium concentration is varied up to ˜1-mol % V4+ by using both conventional-firing and sol-gel routes, and 51V NMR data are also recorded. 17O NMR of 17O isotopically enriched samples shows that the initial gel is completely amorphous with the whole range of possible M-O-M' linkages detected, and that this structure evolves into a fully ordered ZrSiO4 structure with calcination. Static 91Zr NMR data is reported from a pure zircon sample. The NMR data are used to quantify the amount of vanadium entering the zircon structure, and to elucidate its site preference within the lattice. Two contact shifted peaks with very different T1 relaxation from the main zircon peak but attributable to the zircon lattice are observed in the 29Si NMR spectra for all samples. These spectra are consistent with vanadium substitution on both the tetrahedral and dodecahedral sites, with a slight preference for the silicon site. The data show that the relative occupation of these two sites is almost independent of the preparation method and vanadium concentration. At a higher vanadium concentration a third additional peak is observed which may indicate another substitution site. Variable temperature NMR and susceptibility measurements indicate the hyperfine nature of the interactions influencing silicon from V4+ ions in the different sites.

Electronic and magnetic properties of transition metal doped graphyne

NASA Astrophysics Data System (ADS)

Gangan, Abhijeet Sadashiv; Yadav, Asha S.; Chakraborty, Brahmananda; Ramaniah, Lavanya M.

2017-05-01

We have theoretically investigated the interaction of few 3d (V,Mn) and 4d (Y,Zr) transition metals with the γ-graphyne structure using the spin-polarized density functional theory for its potentials application in Hydrogen storage, spintronics and nano-electronics. By doping different TMs we have observed that the system can be either metallic(Y), semi-conducting or half metallic. The system for Y and Zr doped graphyne becomes non-magnetic while V and Mn doped graphyne have a magnetic moments of l μB and 3 μB respectively From bader charge analysis it is seen that there is a charge transfer from the TM atom to the graphyne. Zr and Y have a net charge transfer of 2.15e and 1.73e respectively. Charge density analysis also shows the polarization on the carbon skeleton which becomes larger as the charge transfer for the TM atom increases. Thus we see Y and Zr are better candidates for hydrogen storage devices since they are non-magnetic and have less d electrons which is ideal for kubas-type interactions between hydrogen molecule and TM.

Effect of sputtering atmosphere on the characteristics of ZrOx resistive switching memory

NASA Astrophysics Data System (ADS)

He, Pin; Ye, Cong; Wu, Jiaji; Wei, Wei; Wei, Xiaodi; Wang, Hao; Zhang, Rulin; Zhang, Li; Xia, Qing; Wang, Hanbin

2017-05-01

A ZrOx switching layer with different oxygen content for TiN/ZrOx/Pt resistive switching (RS) memory was prepared by magnetron sputtering in different atmospheres such as N2/Ar mixture, O2/Ar mixture as well as pure Ar. The morphology, structure and RS characteristics were systemically investigated and it was found that the RS performance is highly dependent on the sputtering atmosphere. For the memory device sputtered in N2/Ar mixture, with 8.06% nitrogen content in the ZrOx switching layer, the highest uniformity with smallest distribution of V set and high resistance states (HRS)/low resistance states (LRS) values were achieved. By analyzing the current conduction mechanisms combined with possible RS mechanisms for three devices, we deduce that for the device with a ZrOx layer sputtered in N2/Ar mixture, oxygen ions (O2-), which are decisive to the disruption/formation of the conductive filament, will gather around the tip of the filament due to the existence of doping nitrogen, and lead to the reduction of O2- migration randomness in the operation process, so that the uniformity of the N-doped ZrOx device can be improved.

Effects of Rapid Thermal Annealing on the Structural, Electrical, and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition.

PubMed

Wu, Jingjin; Zhao, Yinchao; Zhao, Ce Zhou; Yang, Li; Lu, Qifeng; Zhang, Qian; Smith, Jeremy; Zhao, Yongming

2016-08-13

The 4 at. % zirconium-doped zinc oxide (ZnO:Zr) films grown by atomic layer deposition (ALD) were annealed at various temperatures ranging from 350 to 950 °C. The structural, electrical, and optical properties of rapid thermal annealing (RTA) treated ZnO:Zr films have been evaluated to find out the stability limit. It was found that the grain size increased at 350 °C and decreased between 350 and 850 °C, while creeping up again at 850 °C. UV-vis characterization shows that the optical band gap shifts towards larger wavelengths. The Hall measurement shows that the resistivity almost keeps constant at low annealing temperatures, and increases rapidly after treatment at 750 °C due to the effect of both the carrier concentration and the Hall mobility. The best annealing temperature is found in the range of 350-550 °C. The ZnO:Zr film-coated glass substrates show good optical and electrical performance up to 550 °C during superstrate thin film solar cell deposition.

Effects of Rapid Thermal Annealing on the Structural, Electrical, and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition

PubMed Central

Wu, Jingjin; Zhao, Yinchao; Zhao, Ce Zhou; Yang, Li; Lu, Qifeng; Zhang, Qian; Smith, Jeremy; Zhao, Yongming

2016-01-01

The 4 at. % zirconium-doped zinc oxide (ZnO:Zr) films grown by atomic layer deposition (ALD) were annealed at various temperatures ranging from 350 to 950 °C. The structural, electrical, and optical properties of rapid thermal annealing (RTA) treated ZnO:Zr films have been evaluated to find out the stability limit. It was found that the grain size increased at 350 °C and decreased between 350 and 850 °C, while creeping up again at 850 °C. UV–vis characterization shows that the optical band gap shifts towards larger wavelengths. The Hall measurement shows that the resistivity almost keeps constant at low annealing temperatures, and increases rapidly after treatment at 750 °C due to the effect of both the carrier concentration and the Hall mobility. The best annealing temperature is found in the range of 350–550 °C. The ZnO:Zr film-coated glass substrates show good optical and electrical performance up to 550 °C during superstrate thin film solar cell deposition. PMID:28773816

Structure and Stoichiometry in Supervalent Doped Li 7La 3 Zr 2O 12

DOE PAGES

Mukhopadhyay, Saikat; Thompson, Travis; Sakamoto, Jeff; ...

2015-04-20

The oxide garnet material Li 7La 3 Zr 2O 12 shows remarkably high ionic conductivity when doped with supervalent ions that are charge compensated by Li vacancies and is currently one of the best candidates for development of a technologically relevant solid electrolyte. Determination of optimal dopant concentration, however, has remained a persistent problem due to the extreme difficulty of establishing the actual (as compared to nominal) stoichiometry of intentionally doped materials and by the fact that it is still not entirely clear what level of lattice expansion/contraction best promotes. ionic diffusion. By combining careful synthesis, neutron diffraction, high-resolution X-raymore » diffraction (XRD), Raman measurements, and density functional theory calculations, we show that structure and stoichiometry are intimately related such that the former can in many cases be used as a gauge of the latter. We show that different Li-vacancy creating supervalent ions (Al 3+ vs Ta 5+) affect the structure very differently, both in terms of the lattice constant, which is easily measurable, and hi terms of the local structure, which can be difficult or impossible to access experimentally but may have important ramifications for conduction. We carefully correlate the lattice constant to dopant type/concentration via Vegard's law and then further correlate these quantities to relevant local structural parameters. In conclusion, our work opens the possibility of developing a codopant scheme that optimizes the Li vacancy concentration and the lattice size simultaneously.« less

Musical Interests and Talent: Twin Jazz Musicians and Twin Studies/Twin Research: Loss of a Preterm Multiple; Conjoined Twin Conception; Depression in Fathers of Twins; Twin-to-Twin Transfusion Syndrome/Twin News: High-Achieving Twins; Twin Children of a Tennis Star; Conjoined Twin Separation; Twin Delivery to a Giant Panda.

PubMed

Segal, Nancy L

2017-12-01

Findings from twin studies of musical interests and talent are reviewed as a backdrop to the lives and careers of twin jazz musicians, Peter and Will Anderson. The Anderson twins exemplify many aspects of twin research, namely their matched musical abilities, shared musical interests, and common career. This overview is followed by reviews of studies and case reports of bereavement in families who have lost a preterm multiple birth infant, the conception of conjoined twins following in vitro fertilization (IVF), depression in fathers of twins, and twin-to-twin transfusion incidence in monochorionic-diamniotic IVF twin pairs. Twins highlighted in the media include high-achieving identical female twins with nearly identical academic standing, tennis star Roger Federer's two sets of identical twin children, surgical separation of craniopagus conjoined twins, and the rare delivery of twins to a 23-year-old giant panda.

Effects of Dopant on the Dielectric Properties of CaZrO3 Ceramic Sintered in a Reducing Atmosphere

NASA Astrophysics Data System (ADS)

Lee, W. S.; Su, C. Y.; Lee, Y. C.; Lin, S. P.; Yang, Tony

2006-07-01

In this study, the influence of CaZrO3 doped with three dopants, SiO2, MnO, and Nb2O5, and then sintered in a reducing atmosphere on microstructure, phase formation, and electrical properties is investigated. SiO2 plays the role of sintering aid to enhance the density of CaZrO3 leading to better performance of electrical properties as a function of SiO2 content. MnO, and Nb2O5 were incorporated into the Zr-site of CaZrO3 to make stoichometric CaZrO3 into non-stoichiometric CaZrO3 with Zr excess resulting in the formation of a second phase, CaZr4O9, which has a lower dielectric constant (13) in comparison with that of the main phase of CaZrO3 (32). Thus, the dielectric constant of CaZrO3 doped with Nb2O5, or MnO is decreased markedly. In addition, Mn+2 incorporated into Zr-sites of CaZrO3 plays the role of acceptor, which compensates for the number of conduction electrons and contributes to better performance of electrical properties such as insulation resistance and \\tanδ. Conversely, Nb+5 incorporated into Zr-sites of CaZrO3 plays the role of donor and provides more conduction electrons, leading to poor performance of electrical properties.

Microstructure and hydrogenation properties of a melt-spun non-stoichiometric Zr-based Laves phase alloy

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

Zhang, Tiebang, E-mail: tiebangzhang@nwpu.edu.cn; Zhang, Yunlong; Li, Jinshan

2016-01-15

Alloy with composition of Zr{sub 0.9}Ti{sub 0.1}V{sub 1.7} off normal stoichiometric proportion is selected to investigate the effect of defects introduced by non-stoichiometry on hydrogenation kinetics of Zr–Ti–V Laves phase alloys. Microstructure and phase constituent of melt-spun ribbons have been investigated in this work. The activation process, hydrogenation kinetics, thermodynamics characteristics and hydride phase constituent of as-cast alloy and melt-spun ribbons are also compared. Comparing with the as-cast alloy, the dominant Laves phase ZrV{sub 2} is preserved, V-BCC phase is reduced and α-Zr phase is replaced by a small amount of Zr{sub 3}V{sub 3}O phase in melt-spun ribbons. Melt-spun ribbonsmore » exhibit easy activation and fast initial hydrogen absorption on account of the increased specific surface area. However, the decrease in unit cell volume of the dominant phase leads to the decrease in hydrogen absorption capacity. Melt-spinning technique raises the equilibrium pressure and decreases the stability of hydride due to the decrease of unit cell volume and the elimination of α-Zr phase, respectively. Melt-spun ribbons with fine grains show improved hydrogen absorption kinetics comparing with that of the as-cast alloy. Meanwhile, the prevalent micro twins observed within melt-spun ribbons are believed to account for the improved hydrogen absorption kinetics. - Highlights: • Role of defects on hydrogenation kinetics of Zr-based alloys is proposed. • Microstructure and hydrogenation properties of as-cast/melt-spun alloy are compared. • Melt-spinning technique improves the hydrogenation kinetics of Zr{sub 0.9}Ti{sub 0.1}V{sub 1.7} alloy. • Refined grains and twin defects account for improved hydrogen absorption kinetics.« less

Creep Resistance of ZrO2 Ceramic Improved by the Addition of a Small Amount of Er2O3

NASA Technical Reports Server (NTRS)

Martinez-Fernandez, Julian; Sayir, Ali; Farmer, Serene C.

2003-01-01

Zirconia (ZrO2) has great technological importance in structural, electrical, and chemical applications. It is the crucial component for state-of-the art thermal barrier coatings and an enabling component as a solid electrolyte for solid-oxide fuel cell systems. Pure ZrO2 is of limited use for industrial applications because of the phase transformations that occur. Upon the addition of stabilizers, cubic (c-ZrO2) and tetragonal (t-ZrO2) forms can be preserved. It is the stabilized and partially stabilized forms of zirconia that function as thermal barrier coatings, solid electrolytes, and oxygen sensors and that have numerous applications in the electrochemical industry. The cubic form of ZrO2 is typically stabilized through Y2O3 additions. However, Y2O3-stabilized zirconia is susceptible to deformation at high temperatures (greater than 900 C) because of the large number of slip systems and the high oxygen diffusion rates, which result in high creep rates at high temperatures. Successful use of ZrO2 at high temperatures requires that new dopant additives be found that will retain or enhance the desirable properties of cubic ZrO2 and yet produce a material with lower creep rates. At the NASA Glenn Research Center, erbium oxide (Er2O3) was identified as a promising dopant for improving the creep resistance of. ZrO2. The selection of Er2O3 was based on the strong interactions of point defects and dislocations. Single crystals of 5 mol% Er2O3- doped ZrO2 rods (4 mm in diameter) and monofilaments (200 to 300 mm in diameter and 30 cm long) were grown using the laser-heated float zone technique, and their creep behavior was measured as a function of temperature. The addition of 5 mol% Er2O3 to single-crystal ZrO2 improved its creep resistance at high temperatures by 2 to 3 orders of magnitude over state-of-the-art Y2O3-doped crystals. Detailed microstructural characterization of ZrO2-Er2O3 single crystals has identified new mechanisms for improving the creep resistance

A combined experimental and theoretical study on ethanol conversion to propylene over Y/ZrO2 catalyst

NASA Astrophysics Data System (ADS)

Wang, Fangfang; Xia, Wei; Mu, Xichuan; Chen, Kun; Si, Huimin; Li, Zhihao

2018-05-01

ZrO2-based catalysts doped with Y were prepared by co-precipitation method. The effect of yttrium modification on the selective conversion of bio-ethanol to propylene over ZrO2 catalysts was investigated. The physical and chemical properties of the catalysts were characterized by N2 adsorption-desorption method, temperature programmed desorption and X-ray diffraction. The maximum yield of propylene reached 44.0% over 0.03Y/ZrO2 catalyst. A coordination of acid-base properties accounts for the remarkable improvement of reaction activities over Y-doped ZrO2 catalysts in this investigation. On the basis of calculation results, it can be concluded that significant charge transfer occurs as a result of introduction of Y or O-vacancy. The adsorption of ethanol and propylene on perfect t-ZrO2 (1 0 1), defect t-ZrO2 (1 0 1) and Y/ZrO2 (1 0 1) surfaces were investigated with density functional theory (DFT). The adsorption for ethanol on Y/ZrO2 (1 0 1) and defect t-ZrO2 (1 0 1) surfaces are more stable than that on perfect t-ZrO2 (1 0 1). On the defect t-ZrO2 (1 0 1) surface, ethanol dominantly absorbs at the O-vacancy site, indicating that O-vacancy becomes the favorable adsorption site. On the Y/ZrO2 (1 0 1) and defect t-ZrO2 (1 0 1) surfaces, the adsorption energy of propylene decreases, which makes propylene desorb quickly after formation.

Generating mixed morphology BaZrO3 artificial pinning centers for strong and isotropic pinning in BaZrO3-Y2O3 double-doped YBCO thin films

NASA Astrophysics Data System (ADS)

Chen, Shihong; Sebastian, Mary Ann; Gautam, Bibek; Wilt, Jamie; Chen, Yanbin; Sun, Lei; Xing, Zhongwen; Haugan, Timothy; Wu, Judy

2017-12-01

High concentration artificial pinning centers (APCs), such as BaZrO3 nanorods (BZO 1D APCs) aligned along the c-axis of the high temperature superconductor YBa2Cu3O7 (YBCO) can provide strong pinning of magnetic vortices and are desirable for applications in high magnetic fields. Unfortunately, in YBCO films with single-doping (SD) of BZO 1D APCs, a monotonic decreasing superconducting T c and critical current density J c(H) with BZO doping has been observed due to strain field overlap at high-concentration perfectly c-axis aligned BZO 1D APCs. In order to resolve this issue, double-doping (DD) of 2-6 vol% BZO 1D APCs and 3.0 vol% Y2O3 nanoparticles (Y2O3-NPs) in YBCO films has been explored to promote BZO-NR orientation misalignment from the c-axis. Remarkably, a monotonic increasing J c(H) with BZO 1D APCs concentration has been obtained in the BZO DD samples. Such a microstructure change is evidenced in the much smaller c-lattice parameter expansion of 0.103% in the DD samples as opposed to 0.511% in the SD counterparts and reduced c-axis alignment of the BZO 1D APCs as revealed in TEM. This yields a mixed 1D + 2D + 3D APC morphology and enhanced isotropic pinning with respect to the orientation of the H-field in the BZO DD samples.

Chemical reaction mechanisms between Y2O3 stabilized ZrO2 and Gd doped CeO2 with PH3 in coal syngas

NASA Astrophysics Data System (ADS)

Chen, Gang; Kishimoto, Haruo; Yamaji, Katsuhiko; Kuramoto, Koji; Gong, Mingyang; Liu, Xingbo; Hackett, Gregory; Gerdes, Kirk; Horita, Teruhisa

2014-12-01

To clarify the chemical stability of the key materials exposed to coal syngas (CSG) containing PH3 contaminant atmosphere, exposure tests of Y2O3 8 mol.% stabilized ZrO2 (YSZ) and Gd doped CeO2 (GDC) are carried out in simulated CSG with different concentrations of PH3. Significant reaction between YSZ and 10 ppm PH3 in CSG atmosphere is confirmed, and no obvious reaction is detected on the surface of YSZ after exposed in CSG with 1 ppm PH3. YPO4, Zr2.25(PO4)3 and monoclinic Y partial stabilized ZrO2 (m-PSZ) are identified on the YSZ pellet surface after exposed in CSG with 10 ppm PH3. GDC reacted with PH3 even at 1 ppm concentration. A (Ce0.9Gd0.1)PO4 layer is formed on the surface of GDC pellet after exposure in CSG with 10 ppm PH3. Possible reaction mechanisms between YSZ and GDC with PH3 in CSG are clarified. Compared with GDC, YSZ exhibits sufficient phosphorus resistance for devices directly exposed to a coal syngas atmosphere containing low concentration of PH3.

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

NASA Astrophysics Data System (ADS)

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

2016-12-01

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

Effects of Zirconium Ions Doping on the Structural and Thermochromic Properties of VO2 Thin Films

NASA Astrophysics Data System (ADS)

Li, Yuanbao; Liu, Juncheng; Wang, Danping; Dang, Yuanyuan

2017-11-01

As an inorganic functional material, VO2 thin films are expected to be used for smart windows. However, these films are not conducive to practical applications when the phase transition temperature ( Tc) of the VO2 is approximately 68°C, which is greater than room temperature. To decrease Tc, the effect of Zr4+ doping on the structure and properties of VO2 films were investigated. The films were prepared using a sol-gel process, spin-coating on quartz glasses, and annealing at 525°C in a tube furnace within a nitrogen atmosphere. The results demonstrate that these films have a highly preferential crystalline orientation on the substrate; however, the primary two x-ray diffraction pattern peaks shift slightly toward the small angle, and when 7 at.% Zr4+ was doped in the VO2 film, the deviation angle was 0.16°, and the crystallite size was approximately 98 nm. A large number of grains were found on the surface of the pure VO2 films, but all the Zr4+ doped films had a layered structure, and the thickness of the films was approximately 200 nm. The Tc of these films was characterized using differential scanning calorimetry, and the luminous and solar transmittance was characterized using a UV-Vis-NIR spectrophotometer, which demonstrated that the effect of Zr4+ doping decreased Tc by approximately 1°C per 1 at.% on average, and the Tc of the 7 at.% film was slightly greater than that of the 5 at.% film, the phase transition temperature of which was 61.4°C. The transmittance decreased as the doping concentration increased, and 1 at.% Zr4+ doping increased the luminous regulation efficiency (Δ T lum) and solar modulation efficiency (Δ T sol). The Δ T lum of the pure VO2 film and the 1 at.% Zr4+-doped VO2 films was 10.9% and 11.2%, and Δ T sol was 14.4 and 15.2%, respectively.

Enhanced Proton Conductivity in Y-Doped BaZrO3 via Strain Engineering.

PubMed

Fluri, Aline; Marcolongo, Aris; Roddatis, Vladimir; Wokaun, Alexander; Pergolesi, Daniele; Marzari, Nicola; Lippert, Thomas

2017-12-01

The effects of stress-induced lattice distortions (strain) on the conductivity of Y-doped BaZrO 3 , a high-temperature proton conductor with key technological applications for sustainable electrochemical energy conversion, are studied. Highly ordered epitaxial thin films are grown in different strain states while monitoring the stress generation and evolution in situ. Enhanced proton conductivity due to lower activation energies is discovered under controlled conditions of tensile strain. In particular, a twofold increased conductivity is measured at 200 °C along a 0.7% tensile strained lattice. This is at variance with conclusions coming from force-field simulations or the static calculations of diffusion barriers. Here, extensive first-principles molecular dynamic simulations of proton diffusivity in the proton-trapping regime are therefore performed and found to agree with the experiments. The simulations highlight that compressive strain confines protons in planes parallel to the substrate, while tensile strain boosts diffusivity in the perpendicular direction, with the net result that the overall conductivity is enhanced. It is indeed the presence of the dopant and the proton-trapping effect that makes tensile strain favorable for proton conduction.

Raman effect, structural and dielectric properties of sol-gel synthesized polycrystalline GaFe{sub 1-x}Zr{sub x}O{sub 3} (0≤x≤0.15)

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

Kumar, Rajeev, E-mail: rajeevgiitk@gmail.com; Mall, Ashish Kumar; Gupta, Rajeev

2016-05-23

Polycrystalline ceramic samples of Zirconium (Zr)-doped GaFeO{sub 3} (GaFe{sub 1-x}Zr{sub x}O{sub 3}) were studied using powder X-ray diffraction, complex impedance spectroscopy and Raman spectroscopic measurements to understand the effect of Zr doping on the structural and dielectric properties. The samples with varying Zr content were prepared by Sol-Gel method. X-ray data analysis confirmed the formation of single phase material without formation of any secondary phases and all are crystallized in Pc2{sub 1}n orthorhombic symmetry. Rietveld refinement of the X-ray data suggested an increase in the lattice constants due to size effect and decreases on x = 0.15 due to themore » effect of change in interplanner spacing. Impedance studies on the samples showed that the dielectric constant increases while loss tangent decrease as the Zr content increases. Raman scattering on GaFe{sub 1-x}Zr{sub x}O{sub 3} (x = 0, 0.05, 0.10, & 0.15) used to understand the composition dependence on phonon modes at room temperature. On Zr doping, Raman modes frequencies shifts to lower energies consistent with the X-ray data.« less

Hydroxyaptite nanorods patterned ZrO2 bilayer coating on zirconium for the application of percutaneous implants.

PubMed

Zhang, Lan; Han, Yong; Tan, Guoxin

2015-03-01

Percutaneous implant requires a tight bond between the underlying dermis of skin and implant surface to prevent epithelial down-growth and infection, while fibroblasts play a key role in the skin-implant integration. In this work, nanorod-shaped hydroxyaptite (HA) with a mean diameter of 70 nm and length of 400 nm was hydrothermally grown on micro-arc oxidized (MAOed) Ca- and P-doped ZrO2 to form a bilayer coating. The hydrothermal formation mechanism of HA nanorods was explored, and the adsorption of total protein on the coating from α-MEM medium containing 10% fetal bovine serum was examined. Employing L-929 cells, the behaviors of fibroblasts on the bilayer coating, including adhesion and proliferation were evaluated together the polished Zr and as-MAOed ZrO2. The obtained results show that the HA nanorods nucleated on ZrO2 and grew at the expense of the doped Ca and P ions during the hydrothermal treatment (HT). The HA nanorods patterned coating enhanced protein absorption, and significantly improved the adhesion and proliferation of fibroblasts compared to the as-MAOed ZrO2 and polished Zr. It suggests that the HA nanorods/ZrO2 coated zirconium has a potential application for percutaneous implants to enhance the attachment of skin. Copyright © 2015 Elsevier B.V. All rights reserved.

Local corrugation and persistent charge density wave in ZrTe 3 with Ni intercalation

NASA Astrophysics Data System (ADS)

Ganose, Alex M.; Gannon, Liam; Fabrizi, Federica; Nowell, Hariott; Barnett, Sarah A.; Lei, Hechang; Zhu, Xiangde; Petrovic, Cedomir; Scanlon, David O.; Hoesch, Moritz

2018-04-01

The mechanism of emergent bulk superconductivity in transition-metal intercalated ZrTe3 is investigated by studying the effect of Ni doping on the band structure and charge density wave (CDW). The study reports theoretical and experimental results in the range of Ni0.01ZrTe3 to Ni0.05ZrTe3 . In the highest doped samples, bulk superconductivity with TcZrTe3. Relativistic ab initio calculations reveal that Ni incorporation occurs preferentially through intercalation in the van der Waals gap. Analysis of the structural and electronic effects of intercalation indicate buckling of the Te sheets adjacent to the Ni site akin to a locally stabilized CDW-like lattice distortion. In contrast to the changes of TCDW observed in resistivity, experiments with low-temperature x-ray diffraction, angle-resolved-photoemission spectroscopy, as well as temperature-dependent resistivity reveal the nearly unchanged persistence of the CDW into the regime of bulk superconductivity. The CDW gap is found to be unchanged in its extent in momentum space, with the gap size also unchanged or possibly slightly reduced upon Ni intercalation. Both experimental observations suggest that superconductivity coexists with the CDW in NixZrTe3 .

Effect of Nd doping on structural, dielectric and thermodynamic properties of PZT (65/35) ceramic

NASA Astrophysics Data System (ADS)

Mohiddon, Md Ahamad; Kumar, Abhishek; Yadav, K. L.

2007-05-01

The influence of neodymium (Nd) addition on the phase formation and dielectric properties of Pb(Zr 0.65Ti 0.35)O 3 composition prepared from mixed oxide method was analyzed. Pellets were sintered in air and PbZrO 3 (PZ) atmosphere separately. Non-perovskite ZrO 2 phase was observed in samples which were sintered in air, also grain size was found to decrease with Nd doping in non-PZ environment samples. Decrease in transition temperature by 80 °C with increasing Nd concentration was observed in both set of samples. Maximum dielectric constant and dielectric losses are found to decrease with Nd doping. Complex impedance analysis revealed that grain boundary resistance increases with Nd doping. Thermodynamic parameters such as change in enthalpy, free energy and change in entropy were studied.

Oliver Sacks: Our Correspondence About Twins/Twin Research: Vanishing Twins Syndrome; Discordant Sex in MZ Twins; Pregnancy Outcomes in IVF and ICSI Conceived Twins/Print and Media: Superfetated Twins; Twins Discordant for Smoking; Twins in Fashion; Yale University Twin Hockey Players; Conjoined Twin-Visiting Professor.

PubMed

Segal, Nancy L

2017-08-01

The late neurologist and author, Oliver Sacks, published an insightful 1986 review of Marjorie Wallace's book, The Silent Twins, in the New York Times. Taking exception to his assertion about Sir Francis Galton, I wrote a letter to the Times' editor. The letter was unpublished, but it brought a wonderful response from Sacks himself that is reproduced and examined. Next, brief reviews of twin research concerning the vanishing twin syndrome (VTS), discordant sex in a monozygotic (MZ) twin pair, and multiple pregnancy outcomes from assisted reproductive technology (ART) are presented. This section is followed by popular coverage of superfetated twins, smoking-discordant co-twins, twins in fashion, Yale University twin hockey players, and a visiting professor who was a conjoined twin.

Reared-Apart Chinese Twins: Chance Discovery/Twin-Based Research: Twin Study of Media Use; Twin Relations Over the Life Span; Breast-Feeding Opposite-Sex Twins/Print and Online Media: Twins in Fashion; Second Twin Pair Born to Tennis Star; Twin Primes; Twin Pandas.

PubMed

Segal, Nancy L

2017-04-01

A January 2017 reunion of 10-year-old reared-apart Chinese twin girls was captured live on ABC's morning talk show Good Morning America, and rebroadcast on their evening news program Nightline. The twins' similarities and differences, and their participation in ongoing research will be described. This story is followed by reviews of twin research concerning genetic and environmental influences on media use, twin relations across the lifespan and the breast-feeding of opposite-sex twins. Popular interest items include twins in fashion, the second twin pair born to an internationally renowned tennis star, twin primes and twin pandas.

The affects of doping Eu 3+ on structures and morphology of ZrO 2 nanocrystals

NASA Astrophysics Data System (ADS)

Yu, Lixin; Liu, Hai; Nogami, Masayuki

2010-07-01

The ZrO 2 and ZrO 2:Eu 3+ nanocrystals (NCs) were prepared by a hydrothermal method. The samples were sintered at different temperatures (500, 800 and 1100 °C). The results indicate that the Eu 3+ ions affect not only the structures of hosts (ZrO 2), but also the morphology of hosts. The shape of ZrO 2:Eu 3+ NCs heated at 1100 °C is the one-dimensional nanorod, while is the zero-dimensional nanoparticle for pure ZrO 2 samples sintered at the same temperature. The excitation and emission spectra of ZrO 2:Eu 3+ NCs were studied. In excitation spectra, the charge transfer band of Eu 3+ in ZrO 2 NCs heated at 1100 °C evidently blue-shifts in comparison with the NCs calcined at 500 and 800 °C. The relative intensity of 5D-7F transitions of Eu 3+ ions and color chromaticity for nanorods are increased in comparison with the nanoparticles.

Twin-to-twin transfusion syndrome

MedlinePlus

... this page: //medlineplus.gov/ency/article/001595.htm Twin-to-twin transfusion syndrome To use the sharing features on this page, please enable JavaScript. Twin-to-twin transfusion syndrome is a rare condition ...

Local corrugation and persistent charge density wave in ZrTe 3 with Ni intercalation

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

Ganose, Alex M.; Gannon, Liam; Fabrizi, Federica

Here, the mechanism of emergent bulk superconductivity in transition-metal intercalated ZrTe 3 is investigated by studying the effect of Ni doping on the band structure and charge density wave (CDW). The study reports theoretical and experimental results in the range of Ni 0.01ZrTe 3 to Ni 0.05ZrTe 3. In the highest doped samples, bulk superconductivity with T c < T CDW is observed, with a reduced T CDW compared with pure ZrTe 3. Relativistic ab initio calculations reveal that Ni incorporation occurs preferentially through intercalation in the van der Waals gap. Analysis of the structural and electronic effects of intercalationmore » indicate buckling of the Te sheets adjacent to the Ni site akin to a locally stabilized CDW-like lattice distortion. In contrast to the changes of T CDW observed in resistivity, experiments with low-temperature x-ray diffraction, angle-resolved-photoemission spectroscopy, as well as temperature-dependent resistivity reveal the nearly unchanged persistence of the CDW into the regime of bulk superconductivity. The CDW gap is found to be unchanged in its extent in momentum space, with the gap size also unchanged or possibly slightly reduced upon Ni intercalation. Both experimental observations suggest that superconductivity coexists with the CDW in Ni xZrTe 3.« less

Local corrugation and persistent charge density wave in ZrTe 3 with Ni intercalation

DOE PAGES

Ganose, Alex M.; Gannon, Liam; Fabrizi, Federica; ...

2018-04-03

Here, the mechanism of emergent bulk superconductivity in transition-metal intercalated ZrTe 3 is investigated by studying the effect of Ni doping on the band structure and charge density wave (CDW). The study reports theoretical and experimental results in the range of Ni 0.01ZrTe 3 to Ni 0.05ZrTe 3. In the highest doped samples, bulk superconductivity with T c < T CDW is observed, with a reduced T CDW compared with pure ZrTe 3. Relativistic ab initio calculations reveal that Ni incorporation occurs preferentially through intercalation in the van der Waals gap. Analysis of the structural and electronic effects of intercalationmore » indicate buckling of the Te sheets adjacent to the Ni site akin to a locally stabilized CDW-like lattice distortion. In contrast to the changes of T CDW observed in resistivity, experiments with low-temperature x-ray diffraction, angle-resolved-photoemission spectroscopy, as well as temperature-dependent resistivity reveal the nearly unchanged persistence of the CDW into the regime of bulk superconductivity. The CDW gap is found to be unchanged in its extent in momentum space, with the gap size also unchanged or possibly slightly reduced upon Ni intercalation. Both experimental observations suggest that superconductivity coexists with the CDW in Ni xZrTe 3.« less

Room Temperature Magnetic Behavior In Nanocrystalline Ni-Doped Zro2 By Microwave-Assisted Polyol Synthesis

NASA Astrophysics Data System (ADS)

Parimita Rath, Pragyan; Parhi, Pankaj Kumar; Ranjan Panda, Sirish; Priyadarshini, Barsharani; Ranjan Sahoo, Tapas

2017-08-01

This article, deals with a microwave-assisted polyol method to demonstrate a low temperature route < 250°C, to prepare a high temperature cubic zirconia phase. Powder XRD pattern shows broad diffraction peaks suggesting nanometric size of the particles. Magnetic behavior of 1-5 at% Ni doped samples show a threshold for substitutional induced room temperature ferromagnetism up to 3 at% of Ni. TGA data reveals that Ni-doped ZrO2 polyol precursors decompose exothermically below 300°C. IR data confirms the reduction of Zr(OH)4 precipitates to ZrO2, in agreement with the conclusions drawn from the TGA analysis.

Brazilian Twin Registry: A Bright Future for Twin Studies/Twin Research: Twin Study of Alcohol Consumption and Mortality; Oxygen Uptake in Adolescent Twins/In the News: Superfecundated Twins In Vietnam; Adolescent Twin Relations; Twin and Triplet Co-Workers; A Special Twin Ultrasound; Monozygotic Twins With Different Skin Color; Identical Twin Returns from Space.

PubMed

Segal, Nancy L

2016-06-01

The establishment of the Brazilian Twin Registry for the study of genetic, social, and cultural influences on behavior is one of eleven newly funded projects in the Department of Psychology at the University of São Paulo. These 11 interrelated projects form the core of the university's Center for Applied Research on Well-Being and Human Behavior. An overview of the planned twin research and activities to date is presented. Next, two recent twin studies are reviewed, one on the relationship between alcohol consumption and mortality, and the other on factors affecting maximal oxygen uptake. Twins cited in the media include the first identified superfecundated twins in Vietnam, adolescent twin relations, twins and triplets who work together, monozygotic twins with different skin tones and a co-twin control study that addresses the effects of space travel.

Cancer risks in twins and singletons from twin and non-twin families.

PubMed

Chen, Lingjing; Cnattingius, Sven; Nyman Iliadou, Anastasia; Oberg, Anna Sara

2016-03-01

The unique intrauterine environment has been proposed to put twins at increased risk of certain cancers compared to singletons, still large population comparisons have generally indicated lower risks in twins. To improve the understanding of potential twin influence on cancer we compared twins to their singletons siblings, to target a unique twinning influence. Singletons from twin families were contrasted to singletons from non-twin families to further capture potential twin family influence on risk of cancer. Family relations were identified using the Swedish Multi-Generation Register. Among individuals born between 1932 and 1958, 49,156 twins and N = 35,227 singletons were identified from 18,098 unique twin families. All incident cases of specific cancer types were identified in the National Cancer Register up to the end of 2007. Standardized survival functions were estimated using weighted Cox proportional hazard regression and the corresponding cumulative risks plotted against age. Overall, primary cancers were identified in 9% and 18% of all male and female twins, compared to 11% and 19% of their male and female singleton siblings. When specific cancer sites were compared using standardized cumulative risk plots, no consistent statistically significant differences were noted either between twins and singletons of twin families or between singletons of twin and non-twin families. Despite a different intrauterine experience, twinning does not seem to have any greater negative influence on life-time risks of cancer. The findings also indicate that twin family membership has no substantial influence on cancer risks. © 2015 UICC.

Twin Legacies: Victor and Vincent McKusick/Twin Studies: Twinning Rates I; Twinning Rates II; MZ Twin Discordance for Russell-Silver Syndrome; Twins' Language Skills/Headlines: Babies Born to Identical Twin Couples; Identity Exchange; Death of Princess Ashraf (Twin); Yahoo CEO Delivers Identical Twins.

PubMed

Segal, Nancy L

2016-04-01

The lives of the illustrious monozygotic (MZ) twins, Victor A. and Vincent L. McKusick, are described. Victor earned the distinction as the 'Father of Medical Genetics', while Vincent was a legendary Chief Justice of the Maine Supreme Court. This dual biographical account is followed by two timely reports of twinning rates, a study of MZ twin discordance for Russell-Silver Syndrome (RSS) and a study of twins' language skills. Twin stories in the news include babies born to identical twin couples, a case of switched identity, the death of Princess Ashraf (Twin) and a new mother of twins who is also Yahoo's CEO.

Ag nanoparticle effects on the thermoluminescent properties of monoclinic ZrO2 exposed to ultraviolet and gamma radiation

NASA Astrophysics Data System (ADS)

Villa-Sanchéz, G.; Mendoza-Anaya, D.; Gutiérrez-Wing, C.; Pérez-Hernández, R.; González-Martínez, P. R.; Ángeles-Chavez, C.

2007-07-01

The goal of this work was to analyse ZrO2 in the pure state and when doped with Ag nanoparticles, by electron microscopy, x-ray diffraction and thermoluminescence methods. According to the results obtained, Ag nanoparticles did not modify the morphology or the crystalline structure of the ZrO2. The thermoluminescent (TL) response of pure ZrO2 showed two peaks, one at 334 K and the other at 417 K, when it was exposed to ultraviolet (UV) radiation, and at 342 and 397 K when gamma radiation was used. For ZrO2 impregnated with Ag nanoparticles a diminished TL intensity due to nanoparticle shielding was observed, but the glow curve shape was similar. However, when Ag nanoparticles were added during the ZrO2 synthesis, a shift of the TL peaks towards higher temperature values with reference to pure ZrO2 was observed. A linear dependence of the integrated TL signal as a function of the irradiation dose was observed in all analysed samples. It was possible to determine some kinetic parameters, such as activation energy, kinetic order and frequency factor, using the sequential quadratic programming glow curve deconvolution; it was found that these values are highly dependent on the type of radiation used. Ag nanoparticles present in ZrO2 also modified the kinetic parameters, mainly when they were added during the synthesis of ZrO2. Our results reinforce the possibilities of using pure and doped ZrO2 as an appropriate dosimetric material in radiation physics.

Zr-92(d,p)Zr-93 and Zr-92(d,t)Zr-91

NASA Technical Reports Server (NTRS)

Baron, N.; Fink, C. L.; Christensen, P. R.; Nickels, J.; Torsteinsen, T.

1972-01-01

The structures of Zr-93 and Zr-91 were studied by the stripping reaction Zr-92(d,p)Zr-93 and the pick-up reaction Zr-92(d,t)Zr-91 using 13 MeV incident deuterons. The reaction product particles were detected by counter telescope. Typical spectra from the reactions were analyzed by a nonlinear least squares peak fitting program which included a background search. Spin and parity assignments to observed excited levels were made by comparing experimental angular distributions with distorted wave Born approximation calculations.

Effect of doping ions on the structural defect and the electrical behavior of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

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

Xue, Renzhong; Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002; Zhao, Gaoyang, E-mail: zhaogy@xaut.edu.cn

Graphical abstract: The dielectric constant decreases with Ta doping, increases with Y doping and keeps almost constant with Zr doping compared with that of pure CCTO. - Highlights: • Y and Ta doping cause different defect types and concentration. • Defect influences the grain boundary mobility and results in different grain size. • Y doping increases the dielectric constant and decreases the nonlinear property. • Ta doping decreases the dielectric constant and enhances the nonlinear property. • Zr doped sample has nearly the defect type and dielectric properties as CaCu{sub 3}Ti{sub 4}O{sub 12}. - Abstract: The microstructure, dielectric and electricalmore » properties of CaCu{sub 3}Ti{sub 4−x}R{sub x}O{sub 12} (R = Y, Zr, Ta; x = 0 and 0.005) ceramics were investigated by XRD, Raman spectra, SEM and dielectric spectrum measurements. Positron annihilation measurements have been performed to investigate the influence of doping on the defects. The results show that all samples form a single crystalline phase. Y and Ta doping cause different defect types and increase the defect size and concentration, which influence the mobility of grain boundary and result in the different grain size. Y doping increases the dielectric constant and decreases the nonlinear property while Ta doping lead to an inverse result. Zr-doped sample has nearly the defect type, grain morphology and dielectric properties as pure CaCu{sub 3}Ti{sub 4}O{sub 12}. The effects of microstructure including the grain morphology and the vacancy defects on the mechanism of the dielectric and electric properties by doping are discussed.« less

Antiferroelectricity in lanthanum doped zirconia without metallic capping layers and post-deposition/-metallization anneals

NASA Astrophysics Data System (ADS)

Wang, Zheng; Gaskell, Anthony Arthur; Dopita, Milan; Kriegner, Dominik; Tasneem, Nujhat; Mack, Jerry; Mukherjee, Niloy; Karim, Zia; Khan, Asif Islam

2018-05-01

We report the effects of lanthanum doping/alloying on antiferroelectric (AFE) properties of ZrO2. Starting with pure ZrO2, an increase in La doping leads to the narrowing of the AFE double hysteresis loops and an increase in the critical voltage/electric field for AFE → ferroelectric transition. At higher La contents, the polarization-voltage characteristics of doped/alloyed ZrO2 resemble that of a non-linear dielectric without any discernible AFE-type hysteresis. X-ray diffraction based analysis indicates that the increased La content while preserving the non-polar, parent AFE, tetragonal P42/nmc phase leads to a decrease in tetragonality and the (nano-)crystallite size and an increase in the unit cell volume. Furthermore, antiferroelectric behavior is obtained in the as-deposited thin films without requiring any capping metallic layers and post-deposition/-metallization anneals due to which our specific atomic layer deposition system configuration crystallizes and stabilizes the AFE tetragonal phase during growth.

Local environments and transport properties of heavily doped strontium barium niobates Sr0.5Ba0.5Nb2O6

NASA Astrophysics Data System (ADS)

Ottini, Riccardo; Tealdi, Cristina; Tomasi, Corrado; Tredici, Ilenia G.; Soffientini, Alessandro; Burriel, Ramón; Palacios, Elías; Castro, Miguel; Anselmi-Tamburini, Umberto; Ghigna, Paolo; Spinolo, Giorgio

2018-02-01

Undoped as well as K-doped (40%), Y-doped (40%), Zr-doped (10%), and Mo-doped (12.5%) strontium barium niobate Sr0.5Ba0.5Nb2O6 (SBN50) materials have been investigated to explore the effect of heavy doping on the structural and functional properties (thermo-power, thermal and electrical conductivities) both in the as prepared (oxidized) and reduced states. For all materials, the EXAFS spectra at the Nb - K edge can be consistently analyzed with the same model of six shells around the Nb sites. Doping mostly gives a simple size effect on the structural parameters, but doping on the Nb sites weakens the Nb-O bond regardless of dopant size and charge. Shell sizes and Debye-Waller factors are almost unaffected by temperature and oxidation state, and the disorder is of static nature. The functional effects of heavy doping do not agree with a simple model of hole or electron injection by aliovalent substitutions on a large band gap semiconductor. With respect to the undoped samples, doping with Mo depresses the thermal conductivity by 30%, Y doping enhances the electrical conductivity by an order of magnitude, while Zr doping increases the Seebeck coefficient by a factor of 2-3. Globally, the ZT efficiency factor of the K-, Y-, and Zr-doped samples is enhanced at least by one order of magnitude with respect to the undoped or Mo-doped materials.

The USC Adult Twin Cohorts: International Twin Study and California Twin Program.

PubMed

Cozen, Wendy; Hwang, Amie E; Cockburn, Myles G; Hamilton, Ann S; Zadnick, John; Mack, Thomas M

2013-02-01

The study of twin subjects permits the documentation of crude heritability and may promote the identification of specific causal alleles. We believe that at the current time, the chief research advantage of twins as subjects, especially monozygotic twins, is that the commonality of their genetic and cultural identity simplifies the interpretation of biological associations. In order to study genetic and environmental determinants of cancer and chronic diseases, we developed two twin registries, maintained at the University of Southern California: The International Twin Study (ITS) and the California Twin Program (CTP). The ITS is a volunteer registry of twins with cancer and chronic disease consisting of 17,245 twin pairs affected by cancer and chronic disease, respectively, ascertained by advertising in periodicals from 1980-1991. The CTP is a population-based registry of California-born twin pairs ascertained by linking the California birth records to the State Department of Motor Vehicles. Over 51,000 individual California twins representing 36,965 pairs completed and returned 16-page questionnaires. Cancer diagnoses in the California twins are updated by regular linkage to the California Cancer Registry. Over 5,000 cancer patients are represented in the CTP. Twins from both registries have participated extensively in studies of breast cancer, melanoma, lymphoma, multiple sclerosis, systemic lupus erythematosus, diabetes mellitus type 1, mammographic density, smoking, and other traits and conditions.

Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations

DOE PAGES

Zhao, Xin; Ke, Liqin; Nguyen, Manh Cuong; ...

2015-06-23

The structures and magnetic properties of Co-Zr-B alloys near the composition of Co 5Zr with B at. % ≤6% were studied using adaptive genetic algorithm and first-principles calculations. The energy and magnetic moment contour maps as a function of chemical composition were constructed for the Co-Zr-B magnet alloys through extensive structure searches and calculations. We found that Co-Zr-B system exhibits the same structure motif as the “Co 11Zr 2” polymorphs, and such motif plays a key role in achieving strong magnetic anisotropy. Boron atoms were found to be able to substitute cobalt atoms or occupy the “interruption” sites. First-principles calculationsmore » showed that the magnetocrystalline anisotropy energies of the boron-doped alloys are close to that of the high-temperature rhombohedral Co 5Zr phase and larger than that of the low-temperature Co 5.25Zr phase. As a result, our calculations provide useful guidelines for further experimental optimization of the magnetic performances of these alloys.« less

A novel red phosphor of seven-coordinated Mn4+ ion-doped tridecafluorodizirconate Na5Zr2F13 for warm WLEDs.

PubMed

Xi, Luqing; Pan, Yuexiao; Huang, Shaoming; Lian, Hongzhou; Lin, Jun

2018-04-24

Herein, a novel red phosphor based on seven-coordinated Mn4+ ion-doped tridecafluorodizirconate, Na5Zr2F13 (NZF), has been synthesized by stirring a mixture of K2MnF6, NaF, and H2ZrF6 at room temperature. The crystal structure and morphology of the as-obtained phosphor NZF:Mn have been determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The composition and distribution of Mn4+ ions in NZF have been confirmed by energy-dispersive spectroscopy (EDS) and element mapping via transmission electron microscopy (TEM). The phosphor NZF:Mn exhibits a strong zero phonon line (ZPL) at 616 nm under excitation of blue light from a GaN light-emitting diode (LED) chip; this is attributed to the low symmetry of Mn4+ ions occupied in a seven-coordinated environment. The luminescence intensity of NZF:Mn has been optimized by controlling the synthesis procedure and synthetic parameters. The luminescence mechanism of the red phosphor NZF:Mn has been investigated according to the detailed experimental results. A warm white light has been produced by a WLED fabricated with the red phosphor NZF:Mn and the commercial yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce) on a GaN LED chip.

ZrO2 Layer Thickness Dependent Electrical and Dielectric Properties of BST/ZrO2/BST Multilayer Thin Films

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

Sahoo, S. K.; Misra, D.; Agrawal, D. C.

2011-01-01

Recently, high K materials play an important role in microelectronic devices such as capacitors, memory devices, and microwave devices. Now a days ferroelectric barium strontium titanate [Ba{sub x}Sr{sub 1-x}TiO{sub 3}, (BST)] thin film is being actively investigated for applications in dynamic random access memories (DRAM), field effect transistor (FET), and tunable devices because of its properties such as high dielectric constant, low leakage current, low dielectric loss, and high dielectric breakdown strength. Several approaches have been used to optimize the dielectric and electrical properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found thatmore » inserting a ZrO{sub 2} layer in between two BST layers results in a significant reduction in dielectric constant, loss tangent, and leakage current in the multilayer thin films. Also it is shown that the properties of multilayer structure are found to depend strongly on the sublayer thicknesses. In this work the effect of ZrO{sub 2} layer thickness on the dielectric, ferroelectric as well as electrical properties of BST/ZrO{sub 2}/BST multilayer structure is studied. The multilayer Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3}/ZrO{sub 2}/Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} film is deposited by a sol-gel process on the platinized Si substrate. The thickness of the middle ZrO{sub 2} layer is varied while keeping the top and bottom BST layer thickness as fixed. It is observed that the dielectric constant, dielectric loss tangent, and leakage current of the multilayer films reduce with the increase of ZrO{sub 2} layer thickness and hence suitable for memory device applications. The ferroelectric properties of the multilayer film also decrease with the ZrO{sub 2} layer thickness.« less

First-principles study of (Ba ,Ca ) TiO3 and Ba (Ti ,Zr ) O3 solid solutions

NASA Astrophysics Data System (ADS)

Amoroso, Danila; Cano, Andrés; Ghosez, Philippe

2018-05-01

(Ba ,Ca ) TiO3 and Ba (Ti ,Zr ) O3 solid solutions are the building blocks of lead-free piezoelectric materials that attract a renewed interest. We investigate the properties of these systems by means of first-principles calculations, with a focus on the lattice dynamics and the competition between different ferroelectric phases. We first analyze the four parent compounds in order to compare their properties and their different tendency towards ferroelectricity. The core of our study is systematic characterization of the binary systems (Ba ,Ca ) TiO3 and Ba (Ti ,Zr ) O3 within both the virtual crystal approximation and direct supercell calculations. In the case of Ca doping, we find a gradual transformation from B -site to A -site ferroelectricity due to steric effects that largely determines the behavior of the system. In the case of Zr doping, in contrast, the behavior is eventually dominated by cooperative Zr-Ti motions and the local electrostatics. In addition, our comparative study reveals that the specific microscopic physics of these solids sets severe limits to the applicability of the virtual crystal approximation for these systems.

Zirconium doped nano-dispersed oxides of Fe, Al and Zn for destruction of warfare agents

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

Stengl, Vaclav, E-mail: stengl@uach.cz; Houskova, Vendula; Bakardjieva, Snejana

2010-11-15

Zirconium doped nano dispersive oxides of Fe, Al and Zn were prepared by a homogeneous hydrolysis of the respective sulfate salts with urea in aqueous solutions. Synthesized metal oxide hydroxides were characterized using Brunauer-Emmett-Teller (BET) surface area and Barrett-Joiner-Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). These oxides were taken for an experimental evaluation of their reactivity with sulfur mustard (HD or bis(2-chloroethyl)sulfide), soman (GD or (3,3'-Dimethylbutan-2-yl)-methylphosphonofluoridate) and VX agent (S-[2-(diisopropylamino)ethyl]-O-ethyl-methylphosphonothionate). The presence of Zr{sup 4+} dopant can increase both the surface area and the surface hydroxylation of the resultingmore » doped oxides, decreases their crystallites' sizes thereby it may contribute in enabling the substrate adsorption at the oxide surface thus it can accelerate the rate of degradation of warfare agents. Addition of Zr{sup 4+} converts the product of the reaction of ferric sulphate with urea from ferrihydrite to goethite. We found out that doped oxo-hydroxides Zr-FeO(OH) - being prepared by a homogeneous hydrolysis of ferric and zirconium oxo-sulfates mixture in aqueous solutions - exhibit a comparatively higher degradation activity towards chemical warfare agents (CWAs). Degradation of soman or VX agent on Zr-doped FeO(OH) containing ca. 8.3 wt.% of zirconium proceeded to completion within 30 min.« less

Atomic layer deposition and properties of ZrO2/Fe2O3 thin films

PubMed Central

Seemen, Helina; Ritslaid, Peeter; Rähn, Mihkel; Tamm, Aile; Kukli, Kaupo; Kasikov, Aarne; Link, Joosep; Stern, Raivo; Dueñas, Salvador; Castán, Helena; García, Héctor

2018-01-01

Thin solid films consisting of ZrO2 and Fe2O3 were grown by atomic layer deposition (ALD) at 400 °C. Metastable phases of ZrO2 were stabilized by Fe2O3 doping. The number of alternating ZrO2 and Fe2O3 deposition cycles were varied in order to achieve films with different cation ratios. The influence of annealing on the composition and structure of the thin films was investigated. Additionally, the influence of composition and structure on electrical and magnetic properties was studied. Several samples exhibited a measurable saturation magnetization and most of the samples exhibited a charge polarization. Both phenomena were observed in the sample with a Zr/Fe atomic ratio of 2.0. PMID:29441257

Microstructural Improvement of Hydroxyapatite-ZrO2 Composite Ceramics via Thermal Precipitation Techniques.

NASA Astrophysics Data System (ADS)

Sangmala, A.; Limsuwan, P.; Kaewwiset, W.; Naemchanthara, K.

2017-09-01

Hydroxyapatite-ZrO2 composite ceramic were synthesized using a thermal precipitation techniques. The chemical precursors were prepared from di-ammonium hydrogen orthophosphate, calcium oxide (CaO) derived from chicken eggshell, zirconium dioxide (ZrO2) and distilled water. The mixture were heated at the various temperatures from 100 to 700 °C in the furnace with an incremental temperature of 100 °C. The ZrO2 contents in the composite ceramic were varied from 0 to 15 percent weight of CaO. The prepared composites were then annealed at 300, 600 and 700 °C for 4 h in air. The crystal structure, function group and morphology of all samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and universal testing machine (UTM), respectively. The results indicated that the undoped-ZrO2 samples hydroxyapatite phase with a hexagonal structure. However, the hydroxyapatite was transformed to the tri-calcium phosphate after thermal treatment at 700 °C. For the doped-ZrO2 samples, the hydroxyapatite and ZrO2 phases were found. Moreover, the result showed that the compressive strength of hydroxyapatite-ZrO2 composite ceramic increased with increasing the ZrO2 content.

Theoretical study of the promotional effect of ZrO2 on In2O3 catalyzed methanol synthesis from CO2 hydrogenation

NASA Astrophysics Data System (ADS)

Zhang, Minhua; Dou, Maobin; Yu, Yingzhe

2018-03-01

Methanol synthesis from CO2 hydrogenation on the ZrO2 doped In2O3(110) surface (Zr-In2O3(110)) with oxygen vacancy has been studied using the density functional theory calculations. The calculated results show that the doped ZrO2 species prohibits the excessive formation of oxygen vacancies and dissociation of H2 on In2O3 surface slightly, but enhances the adsorption of CO2 on both perfect and defective Zr-In2O3(110) surface. Methanol is formed via the HCOO route. The hydrogenation of CO2 to HCOO is both energetically and kinetically facile. The HCOO hydrogenates to polydentate H2CO (p-H2CO) species with an activation barrier of 0.75 eV. H3CO is produced from the hydrogenation of monodentate H2CO (mono-H2CO), transformation from p-H2CO with 0.82 eV reaction energy, with no barrier whether there is hydroxyl group between the mono-H2CO and the neighboring hydride or not. Methanol is the product of H3CO protonation with 0.75 eV barrier. The dissociation and protonation of CO2 are both energetically and kinetically prohibited on Zr-In2O3(110) surface. The doped ZrO2 species can further enhance the adsorption of all the intermediates involved in CO2 hydrogenation to methanol, activate the adsorbed CO2 and H2CO, and stabilize the HCOO, H2CO and H3CO, especially prohibit the dissociation of H2CO or the reaction of H2CO with neighboring hydride to form HCOO and gas phase H2. All these effects make the ZrO2 supported In2O3 catalyst exhibit higher activity and selectivity on methanol synthesis from CO2 hydrogenation.

Investigation of twin-twin interaction in deformed magnesium alloy

NASA Astrophysics Data System (ADS)

Sun, Qi; Ostapovets, Andriy; Zhang, Xiyan; Tan, Li; Liu, Qing

2018-03-01

Using transmission electron microscopy, we characterised the structures of the boundary caused by the interactions between different ? twin variants that share the same ? zone axis in a deformed magnesium alloy. We found that the twin-twin boundaries can adopt the habit planes that are parallel to the (0 0 0 2) basal plane or the ? prismatic plane or the ? twinning plane of the interacting twins. To investigate the formation mechanism of various twin-twin boundaries, we also performed atomic simulations. The results indicate that the formation of a twin-twin boundary may be related to the reaction of twinning disconnections that glide on the basal-prismatic planes of the interacting twins.

Color stable manganese-doped phosphors

DOEpatents

Lyons, Robert Joseph [Burnt Hills, NY; Setlur, Anant Achyut [Niskayuna, NY; Deshpande, Anirudha Rajendra [Twinsburg, OH; Grigorov, Ljudmil Slavchev [Sofia, BG

2012-08-28

A process for preparing color stable Mn.sup.+4 doped phosphors includes providing a phosphor of formula I; A.sub.x[MF.sub.y]:Mn.sup.+4 I and contacting the phosphor in particulate form with a saturated solution of a composition of formula II in aqueous hydrofluoric acid; A.sub.x[MF.sub.y]; II wherein A is Li, Na, K, Rb, Cs, NR.sub.4 or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, lower alkyl, or a combination thereof; x is the absolute value of the charge of the [MF.sub.y] ion; and y is 5, 6 or 7. In particular embodiments, M is Si, Ge, Sn, Ti, Zr, or a combination thereof. A lighting apparatus capable of emitting white light includes a semiconductor light source; and a phosphor composition radiationally coupled to the light source, and which includes a color stable Mn.sup.+4 doped phosphor.

Time-dependent stress concentration and microcrack nucleation in TiAl

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

Yoo, M.H.

1995-07-01

Localized stress evolution associated with the interaction of slip or twinning with an interface is treated by means of a superposition of the {open_quotes}internal loading{close_quotes} of a crystalline subsystem by dynamic dislocation pile-up and the stress relaxation by climb of interfacial dislocations. The peak value of a stress concentration factor depends on both the angular function that includes the effect of mode mixity and the ratio of characteristic times for stress relaxation and internal loading. The available experimental data on orientation and strain-rate dependences of interfacial fracture mode in polysynthetically twinned TiAl crystals are discussed in view of the theoreticalmore » concepts presented in this paper.« less

First-principles studies on 3d transition metal atom adsorbed twin graphene

NASA Astrophysics Data System (ADS)

Li, Lele; Zhang, Hong; Cheng, Xinlu; Miyamoto, Yoshiyuki

2018-05-01

Twin graphene is a new two-dimensional semiconducting carbon allotrope which is proposed recently. The structural, magnetic and electronic properties are investigated for 3d transition metal (TM) atom adsorbed twin graphene by means of GGA+U calculations. The results show most of single 3d transition metal atom except Zn can make twin graphene magnetization. The adsorption of single TM atom can also make the twin graphene systems turn to half metal (V adsorption), half-semiconductor (Fe adsorption) or metal (Sc, Cr, Mn, Co and Cu adsorption). The semiconducting nature still exists for Ti, Ni and Zn adsorption. All the 3d TM adatoms belong to n-type doping for transferring charge to the neighboring C atoms and have strong covalent bond with these C atoms. The influence of Hubbard U value on half-metallic V adsorbed system is also considered. As the U increases, the system can gradually transform from metal to half metal and metal. The effect of the coverage is investigated for two TM atoms (Sc-Fe) adsorption, too. We can know TM atoms adsorbed twin graphene have potentials to be spintronic device and nanomagnets from the results.

Tunable thermal expansion and magnetism in Zr-doped ScF 3

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

Wang, Tao; Xu, Jiale; Hu, Lei

The negative thermal expansion (NTE) behavior provides us an opportunity to design materials with controllable coefficient of thermal expansion (CTE). In this letter, we report a tunable isotropic thermal expansion in the cubic (Sc1-xZrx)F3+δ over a wide temperature and CTE range (αl = -4.0 to +16.8 x 10-6 K-1, 298–648 K). The thermal expansion can be well adjusted from strong negative to zero, and finally to large positive. Intriguingly, isotropic zero thermal expansion (αl = 2.6 x 10-7 K-1, 298–648 K) has been observed in the composition of (Sc0.8Zr0.2)F3+δ. The controllable thermal expansion in (Sc1-xZrx)F3+δ is correlated to the localmore » structural distortion. Interestingly, the ordered magnetic behavior has been found in the zero thermal expansion compound of (Sc0.8Zr0.2)F3+δ at room temperature, which presumably correlates with the unpaired electron of the lower chemical valence of Zr cation. The present study provides a useful reference to control the thermal expansion and explore the multi-functionalization for NTE materials.« less

Dielectric Properties of BST/(Y 2O 3) x(ZrO 2) 1-x/BST Trilayer Films

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

Sahoo, Santosh K.; Misra, D.

2011-01-31

Thin films of Ba1-xSrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and high dielectric breakdown strength. Various approaches have been used to improve the dielectric properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in dielectric constant as well as dielectric loss. In this work the effect of Y2O3 doped ZrO2 on the dielectric properties of BST/ZrO2/BST trilayer structure ismore » studied. The structure Ba0.8Sr0.2TiO3/(Y2O3)x(ZrO2)1-x/Ba0.8Sr0.2TiO3 is deposited by a sol-gel process on platinized Si substrate. The composition (x) of the middle layer is varied while keeping the total thickness of the trilayer film constant. The dielectric constant of the multilayer film decreases with the increase of Y2O3 amount in the film whereas there is a slight variation in dielectric loss. In Y2O3 doped multilayer thin films, the dielectric loss is lower in comparison to other films and also there is good frequency stability in the loss in the measured frequency range and hence very suitable for microwave device applications.« less

A study of suppressed formation of low-conductivity phases in doped Li 7La 3Zr 2O 12 garnets by in situ neutron diffraction

DOE PAGES

Chen, Yan; Rangasamy, Ezhiylmurugan; dela Cruz, Clarina R.; ...

2015-09-28

Doped Li 7La 3Zr 2O 12 garnets, oxide-based solids with good Li + conductivity and compatibility, show great potential as leading electrolyte material candidates for all-solid-state lithium ion batteries. Still yet, the conductive bulk usually suffers from the presence of secondary phases and the transition towards a low-conductivity tetragonal phase during synthesis. Dopants are designed to stabilize the high-conductive cubic phase and suppress the formation of the low-conductivity phases. In situ neutron diffraction enables a direct observation of the doping effects by monitoring the phase evolutions during garnet synthesis. It reveals the reaction mechanism involving the temporary presence of intermediatemore » phases. The off-stoichiometry due to the liquid Li 2CO 3 evaporation leads to the residual of the low-conductivity intermediate phase in the as-synthesized bulk. Appropriate doping of an active element may alter the component of the intermediate phases and promote the completion of the reaction. While the dopants aid to stabilize most of the cubic phase, a small amount of tetragonal phase tends to form under a diffusion process. Lastly, the in situ observations provide the guideline of process optimization to suppress the formation of unwanted low-conductivity phases.« less

Evaluation of mechanical and transport properties of Zr2CoSi Heusler alloy

NASA Astrophysics Data System (ADS)

Yousuf, Saleem; Khandy, S. A.; Bhat, T. M.; Gupta, D. C.

2017-05-01

Systematic investigation of mechanical and transport properties of Zr2CoSi within the density functional theory have been analysed. From the elastic constants, the shear modulus, Young's modulus, Poisson's ratio, we conclude the ductile nature of alloy. Thermoelectric properties show that Zr2CoSi as an n-type thermoelectric material with a higher increase in Seebeck coefficient with temperature. Further the power factor analysis confirms the heavily doping of the alloy fruitful for increase in thermoelectric performance and its use for the future thermoelectric spin generators.

The photoelectronic behaviors of MoO3-loaded ZrO2/carbon cluster nanocomposite materials

NASA Astrophysics Data System (ADS)

Matsui, H.; Ishiko, A.; Karuppuchamy, S.; Hassan, M. A.; Yoshihara, M.

2012-03-01

A novel nano-sized ZrO2/carbon cluster composite materials (Ic's) were successfully obtained by the calcination of ZrCl4/starch complexes I's under an argon atmosphere. Pt- and/or MoO3-loaded ZrO2/carbon clusters composite materials were also prepared by doping Pt and/or MoO3 particles on the surface of Ic's. The surface characterization of the composite materials was carried out using transmission electron microscopy (TEM). The TEM observation of the materials showed the presence of particles with the diameters of a few nanometers, possibly Pt particles, and of 50-100 nm, possibly MoO3 particles, in the matrix. Pt- and/or MoO3-loaded ZrO2/carbon cluster composite materials show the efficient photocatalytic activity under visible light irradiation.

First principles calculations of the electronic structure and magnetic properties of Y(Fe,M)9.2 and Y(Fe,M)9.2C (M= Si, Ga, Zr)

NASA Astrophysics Data System (ADS)

Tian, Guang; Zha, Liang; Yang, Wenyun; Qiao, Guanyi; Wang, Changsheng; Yang, Yingchang; Yang, Jinbo

2018-06-01

The preferential site substitution of the Fe by Si, Ga and Zr in the Y(Fe,M)9.2 and Y(Fe,M)9.2C compounds, and the doping effects on the magnetic properties have been studied by the first-principles calculations. It is found that the doping of the Si or Zr can improve the thermodynamic stability of the 1:9 phase, while the substitution of the Fe by Ga makes it unstable. Si atom tends to enter the 3g crystal site and Zr prefers to occupy the 2e site when Y(Fe,M)9.2 and their carbides are synthesized. Although the substitution of the Fe by Si and Zr will reduce the total magnetic moments of the YFe9.2 and their carbides, the volumetric and the d-band narrowing effects caused by the doping can still modify the electron density distributions of the Fe near the Fermi level, improving the magnetic ordering temperature of the non-carbonated compound YFe9.2. The calculated magnetic ordering temperatures of Y(Fe,M)9.2C decrease with the increasing content of the doping elements M due to the stronger hybridization of the d bands in the carbides. For the rare-earth(RE) iron based intermetallics REFe9.2 with the TbCu7-type structure, it is suggested that Zr is able to stabilize the phase and enhance the magnetic ordering temperature, indicating the possible further application in the field of permanent magnets, which has not been reported before.

Twins reunited: scientific and personal perspectives/twin research studies: multiple birth effects on IQ and body size; life style, muscles, and metabolism; monochorionic dizygotic twin with blood chimerism; amniocentesis for twins/twins in the media: identical doctors; freedom fighter for twins; twin scholarships; Auguste and Jean-Felix Piccard; twins born apart.

PubMed

Segal, Nancy L; Mulligan, Christy A

2014-04-01

A reunion of 38-year-old female monozygotic twins took place in Daegu, South Korea, on January 14, 2014. Scientific and personal perspectives on this extraordinary event are provided. A review of timely twin research follows, covering the effects of multiple births on IQ and body size, lifestyle and physical fitness associations, a rare case of a dizygotic twin with blood chimerism and definitional issues surrounding amniocentesis-related loss in multiple birth pregnancies. Interesting and informative mention of twins in the media includes twin doctors, a twin freedom fighter, the availability of college scholarships for twins, a new book about the Piccard family (two of whose members were twins), and co-twins born before and after the new year. A follow-up to a previous mention of identical twin biatheletes is also provided.

Complex superconductivity in the noncentrosymmetric compound Re 6Zr

DOE PAGES

Khan, Mojammel A.; Karki, A. B.; Samanta, T.; ...

2016-10-24

Here, we report the electronic structure, synthesis, and measurements of the magnetic, transport, and thermal properties of the polycrystalline noncentrosymmetric compound Re 6Zr . We observed a bulk superconducting transition at temperature T c ~ 6.7 K, and measured the resistivity, heat capacity, thermal conductivity, and the London penetration depth below the transition, as well as performed doping and pressure studies. From these measurements we extracted the critical field and the superconducting parameters of Re 6Zr. Lastly, our measurements indicate a relatively weak to moderate contribution from a triplet component to the order parameter, and favor a full superconducting gap,more » although we cannot exclude the existence of point nodes based on our data.« less

Tribute to dr louis keith: twin and physician extraordinaire/twin research reports: influences on asthma severity; chimerism revisited; DNA strand break repair/media reports: twins born apart; elevated twin frequencies; celebrity father of twins; conjoined twinning.

PubMed

Segal, Nancy L

2014-10-01

The International Society for Twin Studies has lost a valued friend and colleague. Dr Louis Keith, Emeritus Professor of Obstetrics and Gynecology at Northwestern University, in Chicago, passed away on Sunday, July 6, 2014. His life and work with twins will be acknowledged at the November 2014 International Twin Congress in Budapest, Hungary. Next, twin research reports on the severity of asthma symptoms, a case of chimerism, and factors affecting DNA breakage and repair mechanisms are reviewed. Media reports cover twins born apart, elevated twin frequencies, a celebrity father of twins, and a family's decision to keep conjoined twins together.

Luminescence properties of ZrW{sub 2}O{sub 8}:Eu{sup 3+} nanophosphors for white light emitting diodes

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

Liao, Jinsheng, E-mail: jsliao1209@126.com; Liu, Shaohua; Wen, He-Rui

2015-10-15

Highlights: • Eu{sup 3+} ions occupy C{sub 1} point group of the Zr{sup 4+} site in ZrW{sub 2}O{sub 8} crystals. • The optimum doping concentration of Eu{sup 3+} was determined for the red emission. • ZrW{sub 2}O{sub 8}:Eu possess high quantum efficiency and suitable chromaticity coordinates. - Abstract: ZrW{sub 2}O{sub 8}:Eu{sup 3+} nanophosphors (ca. 60 nm) with different Eu{sup 3+} doping concentrations were obtained using hydrothermal syntheses. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), photoluminescence excitation and emission spectra as well as decay curve measurements were used for the characterization. Under 466 nm excitation, strong redmore » emission at 616 nm corresponding to {sup 5}D{sub 0}–{sup 7}F{sub 2} transition of Eu{sup 3+} was observed for ZrW{sub 2}O{sub 8}:Eu{sup 3+} (9 mol%) phosphors. The values of intensity parameter Ω{sub 2} and Ω{sub 4} are 17.82 × 10{sup −20} cm{sup 2} and 1.092 × 10{sup −20} cm{sup 2}, respectively. The high quantum efficiency of 83.5% of the ZrW{sub 2}O{sub 8}:Eu{sup 3+} (9 mol%) suggests this material could be promising red phosphor for generating white light in phosphor-converted white light-emitting diodes (LED)« less

'Biracial'-Looking Twins: A New Twin Type?/Twin Research: Twins with Cystic Teratomas; Sleep Quality and Body Mass Index; Previable Membrane Rupture/Print and Online Reports: Twins Born to a Sister Surrogate; NASA Twin Study; African-Cosmopolitan Twin Fashion Inspirations; Triplet Hockey Stars.

PubMed

Segal, Nancy L

2017-06-01

Dizygotic (DZ) co-twins born to mothers and fathers from different racial or ethnic backgrounds often resemble one parent much more than the other. As such, these pairs comprise a unique subset of twins for investigating how others' responses to their different looks may affect their personalities and self-esteem. This article describes some of these twin pairs and some challenges of raising them, and suggests ways they may be used in research. Next, recent twin research on cystic teratomas, relations between sleep quality and body mass index, and previable membrane rupture is described. The final section concerns twins, twin studies, and related events in the media, namely: twins born to a sister surrogate, the NASA twin investigation, inspiring African-Cosmopolitan twins in fashion, and triplet Hockey Stars.

Investigations on Zr incorporation into Li3V2(PO4)3/C cathode materials for lithium ion batteries.

PubMed

Sun, Hua-Bin; Zhou, Ying-Xian; Zhang, Lu-Lu; Yang, Xue-Lin; Cao, Xing-Zhong; Arave, Hanu; Fang, Hui; Liang, Gan

2017-02-15

Li 3 V 2 (PO 4 ) 3 /C (LVP/C) composites have been modified by different ways of Zr-incorporation via ultrasonic-assisted solid-state reaction. The difference in the effect on the physicochemical properties and the electrochemical performance of LVP between Zr-doping and ZrO 2 -coating has also been investigated. Compared with pristine LVP/C, Zr-incorporated LVP/C composites exhibit better rate capability and cycling stability. In particular, the LVP/C-Zr electrode delivers the highest initial capacity of 150.4 mA h g -1 at 10C with a capacity retention ratio of 88.4% after 100 cycles. The enhanced electrochemical performance of Zr-incorporated LVP/C samples (LVZrP/C and LVP/C-Zr) is attributed to the increased ionic conductivity and electronic conductivity, the improved stability of the LVP structure, and the decreased charge-transfer resistance.

Remembering Irving I. Gottesman: Twin Research Colleague and Friend Extraordinaire/Research Studies: Face-Lift Technique Comparison in Identical Twins; Raising Preterm Twins; Fetal Behavior in Dichorionic Twin Pregnancies; Co-Bedding and Stress Reduction in Twins/Public Interest: Identical Co-Twins' Same Day Delivery; Teaching Twins in Bosnia; Twin Auctioneers; Sister, the Play.

PubMed

Segal, Nancy L

2016-12-01

Dr Irving I. Gottesman, a colleague, friend, and long-time member of the International Society of Twin Studies passed away on June 29, 2016. His contributions to twin research and some personal reflections are presented to honor both the man and the memory. This tribute is followed by short reviews of twin research concerning differences between cosmetic surgical techniques, the rearing of preterm twins, behavioral observations of dichorionic fetal twins, and the outcomes of co-bedding twins with reference to stress reduction. Interesting and informative articles in the media describe identical co-twins who delivered infants on the same day, educational policies regarding twins in Bosnia and the United Kingdom, unusual practices of twin auctioneers, and a theatrical production, Sister, featuring identical twins in the leading roles.

[Adult twins].

PubMed

Charlemaine, Christiane

2006-12-31

This paper explores the deep roots of closeness that twins share in their youngest age and their effect on their destiny at the adult age. Psychologists believe the bond between twins begins in utero and develops throughout the twins' lives. The four patterns of twinship described show that the twin bond is determined by the quality of parenting that twins receive in their infancy and early childhood. Common problems of adult twins bring about difficulties to adapt in a non-twin world. The nature versus nurture controversy has taken on new life focusing on inter-twin differences and the importance of parent-child interaction as fundamental to the growth and development of personality.

Energy band alignment of antiferroelectric (Pb,La)(Zr,Sn,Ti)O3

NASA Astrophysics Data System (ADS)

Klein, Andreas; Lohaus, Christian; Reiser, Patrick; Dimesso, Lucangelo; Wang, Xiucai; Yang, Tongqing

2017-06-01

The energy band alignment of antiferroelectric (Pb,La)(Zr,Sn,Ti)O3 is studied with photoelectron spectroscopy using interfaces with high work function RuO2 and low work function Sn-doped In2O3 (ITO). It is demonstrated how spectral deconvolution can be used to determine absolute Schottky barrier heights for insulating materials with a high accuracy. Using this approach it is found that the valence band maximum energy of (Pb,La)(Zr,Sn,Ti)O3 is found to be comparable to that of Pb- and Bi-containing ferroelectric materials, which is ∼1 eV higher than that of BaTiO3. The results provide additional evidence for the occupation of the 6s orbitals as origin of the higher valence band maximum, which is directly related to the electrical properties of such compounds. The results also verify that the energy band alignment determined by photoelectron spectroscopy of as-deposited electrodes is not influenced by polarisation. The electronic structure of (Pb,La)(Zr,Sn,Ti)O3 should enable doping of the material without strongly modifying its insulating properties, which is crucial for high energy density capacitors. Moreover, the position of the energy bands should result in a great freedom of selecting electrode materials in terms of avoiding charge injection.

Compositional changes at the interface between thorium-doped uranium dioxide and zirconium due to high-temperature annealing

NASA Astrophysics Data System (ADS)

Youn, Young-Sang; Lee, Jeongmook; Kim, Jandee; Kim, Jong-Yun

2018-06-01

Compositional changes at the interface between thorium-doped uranium dioxide (U0.97Th0.03O2) and Zr before and after annealing at 1700 °C for 18 h were studied by X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. At room temperature, the U0.97Th0.03O2 pellet consisted of hyperstoichiometric UO2+x with UO2 and ThO2, and the Zr sample contained Zr with ZrO2. After annealing, the former contained stoichiometric UO2 with ThO2 and the latter consisted of ZrO2 along with ZrO2·2H2O.

Synthesis, microstructure and dielectric properties of zirconium doped barium titanate

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

Kumar, Rohtash; School of Physical Sciences, Jawaharlal Nehru University, New Delhi; Asokan, K.

2016-05-23

We report on synthesis, microstructural and relaxor ferroelectric properties of Zirconium(Zr) doped Barium Titanate (BT) samples with general formula Ba(Ti{sub 1-x}Zr{sub x})O{sub 3} (x=0.20, 0.35). These lead-free ceramics were prepared by solid state reaction route. The phase transition behavior and temperature dependent dielectric properties and composition dependent ferroelectric properties were investigated. XRD analysis at room temperature confirms phase purity of the samples. SEM observations revealed retarded grain growth with increasing Zr mole fraction. Dielectric properties of BZT ceramics is influenced significantly by small addition of Zr mole fraction. With increasing Zr mole fraction, dielectric constant decreases while FWHM and frequencymore » dispersion increases. Polarization vs electric field hysteresis measurements reveal ferroelectric relaxor phase at room temperature. The advantages of such substitution maneuvering towards optimizing ferroelectric properties of BaTiO{sub 3} are discussed.« less

The effect of zirconium doping of cerium dioxide nanoparticles on pulmonary and cardiovascular toxicity and biodistribution in mice after inhalation.

PubMed

Dekkers, Susan; Miller, Mark R; Schins, Roel P F; Römer, Isabella; Russ, Mike; Vandebriel, Rob J; Lynch, Iseult; Belinga-Desaunay, Marie-France; Valsami-Jones, Eugenia; Connell, Shea P; Smith, Ian P; Duffin, Rodger; Boere, John A F; Heusinkveld, Harm J; Albrecht, Catrin; de Jong, Wim H; Cassee, Flemming R

2017-08-01

Development and manufacture of nanomaterials is growing at an exponential rate, despite an incomplete understanding of how their physicochemical characteristics affect their potential toxicity. Redox activity has been suggested to be an important physicochemical property of nanomaterials to predict their biological activity. This study assessed the influence of redox activity by modification of cerium dioxide nanoparticles (CeO 2 NPs) via zirconium (Zr) doping on the biodistribution, pulmonary and cardiovascular effects in mice following inhalation. Healthy mice (C57BL/6 J), mice prone to cardiovascular disease (ApoE -/- , western-diet fed) and a mouse model of neurological disease (5 × FAD) were exposed via nose-only inhalation to CeO 2 NPs with varying amounts of Zr-doping (0%, 27% or 78% Zr), or clean air, over a four-week period (4 mg/m 3 for 3 h/day, 5 days/week). Effects were assessed four weeks post-exposure. In all three mouse models CeO 2 NP exposure had no major toxicological effects apart from some modest inflammatory histopathology in the lung, which was not related to the amount of Zr-doping. In ApoE -/- mice CeO 2 did not change the size of atherosclerotic plaques, but there was a trend towards increased inflammatory cell content in relation to the Zr content of the CeO 2 NPs. These findings show that subacute inhalation of CeO 2 NPs causes minimal pulmonary and cardiovascular effect four weeks post-exposure and that Zr-doping of CeO 2 NPs has limited effect on these responses. Further studies with nanomaterials with a higher inherent toxicity or a broader range of redox activities are needed to fully assess the influence of redox activity on the toxicity of nanomaterials.

The Fourth International Network of Twin Registries: Overview from Osaka/Research Reviews: Familial Fraternal Twinning; Twin Study of Masculine Faces; Physical Aggression and Epigenetics; Prenatal Education for Parents of Twins/Current Events: 2016 Guinness Book of World Records; Oldest Living Male Twins; Twins Reunited at Sixty-Nine; Panda Twins; Twins.com.

PubMed

Segal, Nancy L

2015-12-01

The 4th International Network of Twin Registries (INTR) Consortium Meeting took place in Osaka, Japan, September 28-29, 2015. The venue was the Osaka Medical Center for Medical Innovation and Translational Research. An overview of presentations and other activities is provided. Next, 1930s research on familial fraternal twinning, preference for masculine faces, physical aggression and epigenetics, and a prenatal education program for parents of multiples are described. Current twin-related events include the 2016 Guinness Book of World Records (GWR), the oldest living male twins, newly reunited twins, the birth of panda twins and a controversial twin-based website.

Highly selective manganese-doped zinc sulfide quantum dots based label free phosphorescent sensor for phosphopeptides in presence of zirconium (IV).

PubMed

Gong, Yan; Fan, Zhefeng

2015-04-15

We report a room-temperature phosphorescence (RTP) sensor for phosphopeptides based on zirconium (IV)-modulated mercaptopropionic acid (MPA)-capped Mn-doped ZnS quantum dots (QDs). This sensor incorporates the advantages of the well-known Zr(4+)-phosphopeptide affinity pair and the RTP properties of doped QDs. The RTP of Mn-doped ZnS QDs capped with MPA can be effectively quenched by Zr(4+). The high affinity of phosphopeptides to Zr(4+) enables the dissociation of the ion from the surface of MPA-capped ZnS QDs, thereby forming a stable complex with phosphopeptides in the solution, and recovering the RTP of the QDs. The Zr(4+)-induced RTP quenching and subsequent phosphopeptide-induced RTP recovery for MPA-capped ZnS QDs provide a solid basis for the present RTP sensor based on QDs for the detection of phosphopeptides. The detection limit for phosphopeptides is 0.9ngmL(-1), the relative standard deviations is 2.5%, and the recovery of urine and serum samples with phosphopeptides addition rangs from 96% to 105% at optimal conditions. The proposed method was successfully applied to biological fluids and obtained satisfactory results. Copyright © 2014 Elsevier B.V. All rights reserved.

Diagnosis of twin-to-twin transfusion syndrome, selective fetal growth restriction, twin anaemia-polycythaemia sequence, and twin reversed arterial perfusion sequence.

PubMed

Sueters, Marieke; Oepkes, Dick

2014-02-01

Monochorionic twin pregnancies are well known to be at risk for a variety of severe complications, a true challenge for the maternal-fetal medicine specialist. With current standards of care, monochorionicity should be established in the first trimester. Subsequently, frequent monitoring using the appropriate diagnostic tools, and in-depth knowledge about the pathophysiology of all possible clinical presentations of monochorionic twin abnormalities, should lead to timely recognition, and appropriate management. Virtually all unique diseases found in monochorionic twins are directly related to placental angio-architecture. This, however, cannot be established reliably before birth. The clinician needs to be aware of the definitions and symptoms of twin-to twin transfusion syndrome, selective fetal growth restriction, twin anaemia-polycythaemia sequence, and twin reversed arterial perfusion sequence, to be able to recognise each disease and take the required action. In this chapter, we address current standards on correct and timely diagnoses of severe complications of monochorionic twin pregnancies. Copyright © 2014 Elsevier Ltd. All rights reserved.

The Placenta in Twin-to-Twin Transfusion Syndrome and Twin Anemia Polycythemia Sequence.

PubMed

Couck, Isabel; Lewi, Liesbeth

2016-06-01

Twin-to-twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS) are complications unique to monochorionic twin pregnancies and their shared circulation. Both are the result of the transfusion imbalance in the intertwin circulation. TTTS is characterized by an amniotic fluid discordance, whereas in TAPS, there is a severe discordance in hemoglobin levels. The article gives an overview of the typical features of TTTS and TAPS placentas.

Antenatal management of twin-twin transfusion syndrome and twin anemia-polycythemia sequence.

PubMed

Slaghekke, Femke; Zhao, Depeng P; Middeldorp, Johanna M; Klumper, Frans J; Haak, Monique C; Oepkes, Dick; Lopriore, Enrico

2016-08-01

Twin-twin transfusion syndrome (TTTS) and twin anemia polycythemia sequence (TAPS) are severe complications in monochorionic twin pregnancies associated with high mortality and morbidity risk if left untreated. Both diseases result from imbalanced inter-twin blood transfusion through placental vascular anastomoses. This review focuses on the differences in antenatal management between TTTS and TAPS. Expert commentary: The optimal management for TTTS is fetoscopic laser coagulation of the vascular anastomoses, preferably using the Solomon technique in which the whole vascular equator is coagulated. The Solomon technique is associated with a reduction of residual anastomosis and a reduction in post-operative complications. The optimal management for TAPS is not clear and includes expectant management, intra-uterine transfusion with or without partial exchange transfusion and fetoscopic laser surgery.

Electronic structure study of Ce1-xAxO2 (A = Zr & Hf) nanoparticles: NEXAFS and EXAFS investigations.

PubMed

Sharma, Aditya; Varshney, Mayora; Shin, Hyun-Joon; Park, Yong Jun; Kim, Min-Gyu; Ha, Tae-Kyun; Chae, Keun Hwa; Gautam, Sanjeev

2014-10-07

Single phase nanoparticles (NPs) of CeO2, Ce0.5Zr0.5O2, Ce0.5Hf0.5O2 and Ce0.5Hf0.25Zr0.25O2 were successfully synthesized by co-precipitation method at constant pH and temperature. The X-ray diffraction results revealed that the additive atoms did not segregate to form secondary phases but led to grain size variation in the NPs. The 10 Dq values in the near edge X-ray absorption fine structure (NEXAFS) spectra at the O K-edge did not vary in the same way as the average grain size was changed for the doped CeO2 NPs. The deconvolution of Ce M5-edge and detailed analysis of O K pre-edge peak have shown the higher Ce(+3)/(Ce(+3) + Ce(+4)) ratio in the Zr- and Hf-doped samples. The local atomic structure around the Ce, Zr and Hf atoms was investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy at Ce K-edge, Zr K-edge and Hf L3-edge, respectively, and the EXAFS data were fitted with the theoretical calculations. The 4f occupancy, Ce(+3)/(Ce(+3) + Ce(+4)) ratio of Ce ions, coordination number of Ce and Ce-Ce/Ce-O bond distances were sensitive to the additive atoms but not explicitly changed according to the grain size variation in the NPs.

A Possible Twin: The 1960s Twin Study Revisited/Twin Research: Twin-to-Twin Heart Transplantation; Distinguishing Monozygotic Twins; Twin Conceptions via Oocyte Donation; Factors Affecting Craniofacial Traits/In the Media: Triplet Delivery in the UK; Conjoined Twins and the Concept of Self; Colombian Twin Trainers; Skin Grafting to Save an Identical Co-Twin; Lack of Physical Flaws in Dolly the Cloned Sheep; Possible Conjoined Twins of Opposite-Sex; Passing of the Remaining Twin From the World's Longest Separated Pair.

PubMed

Segal, Nancy L

2018-04-01

This article begins with the story of a 51-year-old Los Angeles, California man, Justin Goldberg, whose daughter caught a glimpse of his striking look-alike at a popular market. Many people have so-called doppelgängers, but this occurrence is especially intriguing - the individual in question, born in New York City in the mid-1960s to an unwed mother, was an adoptee placed by the Louise Wise Adoption Agency. This agency, under the guidance of a prominent psychiatrist, decided to place twins in separate homes. Some of these twin children were part of a controversial child development study that was hidden from them and their parents. Next, recent and current twin research on heart transplantation, distinguishing monozygotic co-twins, twin conceptions via oocyte donation and factors affecting craniofacial traits are summarized. The article concludes with highlights on twins in the media, specifically, a triplet delivery in the United Kingdom, self-concept and consciousness in conjoined twins, Colombian twin trainers, skin grafting to save an identical co-twin, lack of physical flaws in Dolly the cloned sheep, possible opposite-sex conjoined twins, and the passing of the remaining twin from the world's longest separated pair.

College-age twins: university admission policies / twin research: birth weight and neuromotor performance; transfusion syndrome markers; vanishing twins and fetal sex determination; mz twin discordance for wilson's disease / media: big at birth; planned separation of conjoined twins; x factor twins; Cinema: the identical.

PubMed

Segal, Nancy L

2014-12-01

There is a lack of research findings addressing the unique college admissions issues faced by twins and other multiples. The advantages and disadvantage twins face, as reported by college administrators, twins and families are reviewed. Next, recent research addressing twins' birth weight and neuromotor performance, transfusion syndrome markers, the vanishing twin syndrome and monozygotic (MZ) twin discordance for Wilson's disease is described. News items concerning the birth of unusually large twins, the planned separation of conjoined twins, twin participants in the X Factor games and a film, The Identical, are also summarized.

148. TWIN FALLS MAIN CANAL DIVERSION, TWIN FALLS COUNTY, MILNER ...

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

148. TWIN FALLS MAIN CANAL DIVERSION, TWIN FALLS COUNTY, MILNER DAM; HEADGATES AT INLET, SOUTHWEST VIEW. - Milner Dam & Main Canal: Twin Falls Canal Company, On Snake River, 11 miles West of city of Burley, Idaho, Twin Falls, Twin Falls County, ID

98. SHOESTRING, TWIN FALLS MAIN CANAL, TWIN FALLS COUNTY NORTHWEST ...

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

98. SHOESTRING, TWIN FALLS MAIN CANAL, TWIN FALLS COUNTY NORTHWEST OF MURTAUGH, IDAHO; PROFILE VIEW, SOUTH. - Milner Dam & Main Canal: Twin Falls Canal Company, On Snake River, 11 miles West of city of Burley, Idaho, Twin Falls, Twin Falls County, ID

Comment on twinning in YNbO sub 4

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

Tsunekawa, S.

1992-04-01

The paper contains statements about an analogue of ZrO{sub 2} and the twins. The analogue is suggestive in connection with yttria-partially-stabilized zirconia, but an error is found in the description of the twins in YNbO{sub 4}. Because YNbO{sub 4} performs a pure, uncoupled ferroelastic transition (thermoelastic martensitic transformation), the composition plane is determined by the following formulas 4/mF2/m: x = pz and x = {minus}z/p, p = (b + (a{sup 2} + b{sup 2}){sup 1/2})/a a = (x{sub 33} {minus} x{sub 11})/2, b = {minus} tan ({beta} {minus} 90{degrees})/2) x{sub 11} = (a{sup I} {minus} a{sub 0})/a{sub 0}, x{sub 33}more » = (c{sup 1} {minus} a{sub 0})/a{sub 0} where a{sub 0} is the lattice parameter of a in the tetragonal phase, and a{sup I} and c{sup I} are the parameters of a and c, respectively, in the monoclinic phase represented by the I-lattice. The value of p at room temperature can be estimated by using the parameters included in this paper.« less

Investigation of ZrO x /ZrC-ZrN/Zr thin-film structural evolution and their degradation using X-ray diffraction and Raman spectrometry

NASA Astrophysics Data System (ADS)

Usmani, B.; Vijay, V.; Chhibber, R.; Dixit, A.

2016-11-01

The thin-film structures of DC/FR magnetron-sputtered ZrO x /ZrC-ZrN/Zr tandem solar-selective coatings are investigated using X-ray diffraction and room-temperature Raman spectroscopic measurements. These studies suggest that the major contribution is coming from h-ZrN0.28, c-ZrC, h-Zr3C2 crystallographic phases in ZrN-ZrC absorber layer, in conjunction with mixed ZrO x crystallographic phases. The change in structure for thermally annealed samples has been examined and observed that cubic and hexagonal ZrO x phase converted partially into tetragonal and monoclinic ZrO x phases, whereas hexagonal and cubic ZrN phases, from absorber layer, have not been observed for these thermally treated samples in air. These studies suggest that thermal treatment may lead to the loss of ZrN phase in absorber, degrading the thermal response for the desired wavelength range in open ambient conditions in contrast to vacuum conditions.

147. TWIN FALLS MAIN CANAL DIVERSION, TWIN FALLS COUNTY, MILNER, ...

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

147. TWIN FALLS MAIN CANAL DIVERSION, TWIN FALLS COUNTY, MILNER, IDAHO; VIEW OF MAIN HEADGATES, EAST VIEW. - Milner Dam & Main Canal: Twin Falls Canal Company, On Snake River, 11 miles West of city of Burley, Idaho, Twin Falls, Twin Falls County, ID

97. POINT SPILL, TWIN FALLS MAIN CANAL, TWIN FALLS COUNTY ...

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

97. POINT SPILL, TWIN FALLS MAIN CANAL, TWIN FALLS COUNTY NORTHWEST OF MURTAUGH, IDAHO; OVERALL WEST VIEW FROM CANAL SIDE. - Milner Dam & Main Canal: Twin Falls Canal Company, On Snake River, 11 miles West of city of Burley, Idaho, Twin Falls, Twin Falls County, ID

149. TWIN FALLS MAIN CANAL DIVERSION, TWIN FALLS COUNTY, MILNER ...

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

149. TWIN FALLS MAIN CANAL DIVERSION, TWIN FALLS COUNTY, MILNER DAM; CLOSE-UP OF MAIN CANAL GATES, SOUTH VIEW. - Milner Dam & Main Canal: Twin Falls Canal Company, On Snake River, 11 miles West of city of Burley, Idaho, Twin Falls, Twin Falls County, ID

141. TWIN FALLS MAIN CANAL DIVERSION, TWIN FALLS COUNTY, MILNER, ...

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

141. TWIN FALLS MAIN CANAL DIVERSION, TWIN FALLS COUNTY, MILNER, IDAHO; CLOSE-UP OF MAIN HEADGATES, RADIAL GATES INSIDE, SOUTHEAST VIEW. - Milner Dam & Main Canal: Twin Falls Canal Company, On Snake River, 11 miles West of city of Burley, Idaho, Twin Falls, Twin Falls County, ID

137. TWIN FALLS SOUTH SIDE MAIN CANAL DIVERSION HEADGATES, TWIN ...

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

137. TWIN FALLS SOUTH SIDE MAIN CANAL DIVERSION HEADGATES, TWIN FALLS COUNTY, MILNER, IDAHO; OVERALL VIEW OF MAIN HEADGATES, DAM IN BACKGROUND. - Milner Dam & Main Canal: Twin Falls Canal Company, On Snake River, 11 miles West of city of Burley, Idaho, Twin Falls, Twin Falls County, ID

Mechanical twinning and omega transition by ⟨111⟩ {112} shear in a metastable β titanium alloy

NASA Astrophysics Data System (ADS)

Xing, H.; Sun, J.

2008-07-01

{112} ⟨111⟩ mechanical twinning and stress-induced omega transition were observed by high-resolution transmission electron microscope in a metastable β titanium alloy with chemical composition of Ti-23Nb-0.7Ta-2Zr-1.2O at. % after deformation. The orientation relationships between the ω phase and β parent matrix are (accent="true">1¯010)ω‖(211)β, [1accent="true">2¯10]ω‖[0accent="true">1¯1]β and [0001]ω‖[accent="true">1¯11]β, and the habit plane of (accent="true">1¯010)ω‖(211)β for the stress-induced ω transition is different from that of (0001)ω‖(111)β often observed for the thermal ω transition. Both mechanical twinning and ω transition arise from the shear along ⟨111⟩ {112}. A dislocation mechanism for mechanical twinning and stress-induced ω transition was discussed additionally.

99. POINT SPILL, TWIN FALLS MAIN CANAL, TWIN FALLS COUNTY ...

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

99. POINT SPILL, TWIN FALLS MAIN CANAL, TWIN FALLS COUNTY NORTHWEST OF MURTAUGH, IDAHO; CLOSE-UP OF OUTLET SIDE OF GATES, SOUTH VIEW. - Milner Dam & Main Canal: Twin Falls Canal Company, On Snake River, 11 miles West of city of Burley, Idaho, Twin Falls, Twin Falls County, ID

Conversion of ethanol to 1,3-butadiene over Na doped ZnxZryOz mixed metal oxides

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

Baylon, Rebecca A.; Sun, Junming; Wang, Yong

2016-01-01

Despite numerous studies on different oxide catalysts for the ethanol to 1,3-butadiene reaction, few have identified active sites (i.e., type of acidity) correlated to the catalytic performances. In this work, the type of acidity needed for ethanol to 1,3-butadiene conversion has been studied over Zn/Zr mixed oxide catalysts. Specifically, synthesis method, Zn/Zr ratio, and Na doping have been used to control the surface acid-base properties, as confirmed by characterizations such as NH3-TPD and IR-Py techniques. The 2000 ppm Na doped Zn1Zr10Oz-H with balanced base and weak Bronsted acid sites was found to give not only high selectivity to 1,3-butadiene (47%)more » at near complete ethanol conversion (97%), but also exhibited a much higher 1,3-butadiene productivity than other mixed oxides studied.« less

Zr/ZrC modified layer formed on AISI 440B stainless steel by plasma Zr-alloying

NASA Astrophysics Data System (ADS)

Shen, H. H.; Liu, L.; Liu, X. Z.; Guo, Q.; Meng, T. X.; Wang, Z. X.; Yang, H. J.; Liu, X. P.

2016-12-01

The surface Zr/ZrC gradient alloying layer was prepared by double glow plasma surface alloying technique to increase the surface hardness and wear resistance of AISI 440B stainless steel. The microstructure of the Zr/ZrC alloying layer formed at different alloying temperatures and times as well as its formation mechanism were discussed by using scanning electron microscopy, glow discharge optical emission spectrum, X-ray diffraction and X-ray photoelectron spectroscopy. The adhesive strength, hardness and tribological property of the Zr/ZrC alloying layer were also evaluated in the paper. The alloying surface consists of the Zr-top layer and ZrC-subsurface layer which adheres strongly to the AISI 440B steel substrate. The thickness of the Zr/ZrC alloying layer increases gradually from 16 μm to 23 μm with alloying temperature elevated from 900 °C to 1000 °C. With alloying time from 0.5 h to 4 h, the alloyed depth increases from 3 μm to 30 μm, and the ZrC-rich alloyed thickness vs time is basically parabola at temperature of 1000 °C. Both the hardness and wear resistance of the Zr/ZrC alloying layer obviously increase compared with untreated AISI 440B steel.

Mixed conductivity, structural and microstructural characterization of titania-doped yttria tetragonal zirconia polycrystalline/titania-doped yttria stabilized zirconia composite anode matrices

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

Colomer, M.T., E-mail: tcolomer@icv.csic.e; Maczka, M.

2011-02-15

Taking advantage of the fact that TiO{sub 2} additions to 8YSZ cause not only the formation of a titania-doped YSZ solid solution but also a titania-doped YTZP solid solution, composite materials based on both solutions were prepared by solid state reaction. In particular, additions of 15 mol% of TiO{sub 2} give rise to composite materials constituted by 0.51 mol fraction titania-doped yttria tetragonal zirconia polycrystalline and 0.49 mol fraction titania-doped yttria stabilized zirconia (0.51TiYTZP/0.49TiYSZ). Furthermore, Y{sub 2}(Ti{sub 1-y}Zr{sub y}){sub 2}O{sub 7} pyrochlore is present as an impurity phase with y close to 1, according to FT-Raman results. Lower and highermore » additions of titania than that of 15 mol%, i.e., x=0, 5, 10, 20, 25 and 30 mol% were considered to study the evolution of 8YSZ phase as a function of the TiO{sub 2} content. Furthermore, zirconium titanate phase (ZrTiO{sub 4}) is detected when the titania content is equal or higher than 20 mol% and this phase admits Y{sub 2}O{sub 3} in solid solution according to FE-SEM-EDX. The 0.51TiYTZP/0.49TiYSZ duplex material was selected in this study to establish the mechanism of its electronic conduction under low oxygen partial pressures. In the pO{sub 2} range from 0.21 to 10{sup -7.5} atm. the conductivity is predominantly ionic and constant over the range and its value is 0.01 S/cm. The ionic plus electronic conductivity is 0.02 S/cm at 1000 {sup o}C and 10{sup -12.3} atm. Furthermore, the onset of electronic conductivity under reducing conditions exhibits a -1/4 pO{sub 2} dependence. Therefore, it is concluded that the n-type electronic conduction in the duplex material can be due to a small polaron-hopping between Ti{sup 3+} and Ti{sup 4+}. -- Graphical abstract: FE-SEM micrograph of a polished and thermal etched surface of a Ti-doped YTZP/Ti-doped YSZ composite material. Display Omitted Research highlights: {yields} Ti-doped YTZP/Ti-doped YSZ composite materials are mixed conductors

Art for twins: Yorùbá artists and their statues/twin research studies: twins' education and conceptions; diurnal preference; inherited eye diseases; ultrasound counseling when twins are conjoined/popular twin reports: twin sisters (the film); rare pregnancy; diet test; French twins reared apart and reunited.

PubMed

Segal, Nancy L

2014-06-01

The Yorùbá of Nigeria are well known for their high twinning rate and the statues they create to commemorate deceased twins. An impressive collection of this artwork was displayed at the University of California's Fowler Museum in Los Angeles between October 13, 2013 and March 2, 2014. An overview of this exhibit is provided. Next, twin research on maternal education and conception, diurnal preference, inherited eye diseases, and ultrasound counseling for couples with conjoined twins are briefly summarized. This article concludes with a discussion of media-based items related to twins. The topics include an award-winning twin film, a rare pregnancy, a diet test, and the separation and chance reunion of monozygotic female twins.

Electrical properties and x-ray photoelectron spectroscopy studies of Bi(Zn0.5Ti0.5)O3 doped Pb(Zr0.4Ti0.6)O3 thin films

NASA Astrophysics Data System (ADS)

Tang, M. H.; Zhang, J.; Xu, X. L.; Funakubo, H.; Sugiyama, Y.; Ishiwara, H.; Li, J.

2010-10-01

(1-x)Pb(Zr0.4,Ti0.6)O3-(x)Bi(Zn0.5,Ti0.5)O3 (PZT-BZT) (x =0, 0.03, 0.05, 0.08, and 0.1) films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by chemical solution deposition using spin-coating. All samples showed highly (111) oriented perovskite phase and no other phase was observed. The ferroelectric properties of PZT-BZT films were systematically investigated as a function of the content x of the BZT solution. It is found that BZT doping in PZT films could greatly enhance the remnant polarization (Pr), as well as improve the fatigue property. In a 3 wt % BZT-doped PZT film, the 2Pr and the coercive field (Ec) are 90 μC/cm2 and 95 kV/cm at 10 kHz, respectively, at an electric field of 500 kV/cm, and the leakage current density is less than 1×10-7 A/cm2. The impact of BZT doping on the structure of PZT has been investigated by x-ray photoelectron spectroscopy.

Ferroelectric and dielectric properties of BaTi0.9Zr0.1O3 doped with Li0.5Fe2.5O4 ceramics

NASA Astrophysics Data System (ADS)

Gajula, Ganapathi Rao; Buddiga, Lakshmi Rekha; Chidambara Kumar, K. N.; Ch, Arun Kumar; Samatha, K.; Kokkiragadda, Sreeramachandra Murthy; Dasari, Madhava Prasad

2018-06-01

We have prepared a composite BaTi0.9Zr0.1O3 (BTZr) doped with Li0.5Fe2.5O4 (LF) having chemical formulae (1- x) BTZr + (x) LF (x=0, 0.05, 0.1 and 0.15) conventional solid state reaction technique. We have sintered the grown composites at 1150 °C for 3 h. We have characterized the grown composites using XRD, FESEM, P-E loop tracer and LCR meter. The XRD measurements reveal the tetragonal nature of the composites. The morphological studies reveal that the composite exhibits dense microstructure with small pores. The P-E loops confirm that the composites exhibit remnant polarization and the coercive field increases with increasing concentration of Lithium Ferrite (LF). We have studied dielectric property of the composites by varying the temperature of the sample from 30 °C to 500 °C at 1 kHz, 10 kHz and also by varying the frequency from 1 Hz to 10 MHz at 30 °C. The dielectric property of BTZr has increased after doping LF in BTZr which reveals the enhancement of electrical properties of the grown composite.

Effect of solution treatment on the fatigue behavior of an as-forged Mg-Zn-Y-Zr alloy

NASA Astrophysics Data System (ADS)

Wang, S. D.; Xu, D. K.; Wang, B. J.; Han, E. H.; Dong, C.

2016-04-01

Through investigating and comparing the fatigue behavior of an as-forged Mg-6.7Zn-1.3Y-0.6Zr (wt.%) alloy before and after solid solution treatment (T4) in laboratory air, the effect of T4 treatment on fatigue crack initiation was disclosed. S-N curves illustrated that the fatigue strength of as-forged samples was 110 MPa, whereas the fatigue strength of T4 samples was only 80 MPa. Observations to fracture surfaces demonstrated that for as-forged samples, fatigue crack initiation sites were covered with a layer of oxide film. However, due to the coarse grain structure and the dissolution of MgZn2 precipitates, the activation and accumulation of {10-12} twins in T4 samples were much easier, resulting in the preferential fatigue crack initiation at cracked twin boundaries (TBs). Surface characterization demonstrated that TB cracking was mainly ascribed to the incompatible plastic deformation in the twinned area and nearby α-Mg matrix.

Piezoelectric properties and temperature stability of Mn-doped Pb(Mg1/3Nb2/3)-PbZrO3-PbTiO3 textured ceramics

NASA Astrophysics Data System (ADS)

Yan, Yongke; Cho, Kyung-Hoon; Priya, Shashank

2012-03-01

In this letter, we report the electromechanical properties of textured 0.4Pb(Mg1/3Nb2/3)O3-0.25PbZrO3-0.35PbTiO3 (PMN-PZT) composition which has relatively high rhombohedral to tetragonal (R-T) transition temperature (TR-T of 160 °C) and Curie temperature (TC of 234 °C) and explore the effect of Mn-doping on this composition. It was found that MnO2-doped textured PMN-PZT ceramics with 5 vol. % BaTiO3 template (T-5BT) exhibited inferior temperature stability. The coupling factor (k31) of T-5BT ceramic started to degrade from 75 °C while the random counterpart showed a very stable tendency up to 180 °C. This degradation was associated with the "interface region" formed in the vicinity of BT template. MnO2 doped PMN-PZT ceramics textured with 3 vol. % BT and subsequently poled at 140 °C (T-3BT140) exhibited very stable and high k31 (>0.53) in a wide temperature range from room temperature to 130 °C through reduction in the interface region volume. Further, the T-3BT140 ceramic exhibited excellent hard and soft combinatory piezoelectric properties of d33 = 720 pC/N, k31 = 0.53, Qm = 403, tan δ = 0.3% which are very promising for high power and magnetoelectric applications.

Pathology of twin placentas with special attention to monochorionic twin placentas.

PubMed

Nikkels, P G J; Hack, K E A; van Gemert, M J C

2008-12-01

The risk of perinatal morbidity and mortality in twins is 3-7 times higher than in singletons. In comparison to dichorionic twins, monochorionic twins are at increased risk for perinatal mortality and serious morbidity. In both type of twins growth discordance can occur. Discordant growth of dichorionic twins could be due to differences in placental mass or differences in placental parenchymal lesions, whereas birth weight discordancy in monochorionic twins is caused by placental vascular anastomoses. In this review the different types of complications (acardiac twins, acute and chronic twin-twin transfusion syndrome) due to different combinations of vascular anastomoses are discussed in relation to a computer model developed to gain more insight into the development of the twin-twin transfusion syndrome. The angioarchitecture of 395 monochorionic twin placentas was studied. Mortality was highest in the absence of an arterio-arterial anastomosis (42%) and lowest in the presence of an arterio-arterial anastomosis (15%). If mortality occurred, pregnancies with double mortality usually had an arterio-arterial anastomosis. If pregnancies were complicated by one death, a veno-venous anastomosis is more likely to be present. In conclusion, monochorionic twin pregnancies are a high risk pregnancy with a high chance of both mortality and morbidity; placental characteristics are a major contributor to adverse outcome in these pregnancies.

High-Temperature Stability and Grain Boundary Complexion Formation in a Nanocrystalline Cu-Zr Alloy

NASA Astrophysics Data System (ADS)

Khalajhedayati, Amirhossein; Rupert, Timothy J.

2015-12-01

Nanocrystalline Cu-3 at.% Zr powders with ~20 nm average grain size were created with mechanical alloying and their thermal stability was studied from 550-950°C. Annealing drove Zr segregation to the grain boundaries, which led to the formation of amorphous intergranular complexions at higher temperatures. Grain growth was retarded significantly, with 1 week of annealing at 950°C, or 98% of the solidus temperature, only leading to coarsening of the average grain size to 54 nm. The enhanced thermal stability can be connected to both a reduction in grain boundary energy with doping as well as the precipitation of ZrC particles. High mechanical strength is retained even after these aggressive heat treatments, showing that complexion engineering may be a viable path toward the fabrication of bulk nanostructured materials with excellent properties.

Twinning-induced plasticity (TWIP) and work hardening in Ti-based metallic glass matrix composites.

PubMed

Fan, J; Qiao, J W; Wang, Z H; Rao, W; Kang, G Z

2017-05-12

The present study demonstrates that Ti-based metallic glass matrix composites (MGMCs) with a normal composition of Ti 43 Zr 32 Ni 6 Ta 5 Be 14 containing ductile dendrites dispersed in the glass matrix has been developed, and deformation mechanisms about the tensile property have been investigated by focusing on twinning-induced plasticity (TWIP) effect. The Ti-based MGMC has excellent tensile properties and pronounced tensile work-hardening capacity, with a yield strength of 1100 MPa and homogeneous elongation of 4%. The distinguished strain hardening is ascribed to the formation of deformation twinning within the dendrites. Twinning generated in the dendrites works as an obstacle for the rapid propagation of shear bands, and then, the localized necking is avoided, which ensures the ductility of such kinds of composites. Besides, a finite-element model (FEM) has been established to explain the TWIP effect which brings out a work-hardening behavior in the present MGMC instead of a localized strain concentration. According to the plasticity theory of traditional crystal materials and some new alloys, TWIP effect is mainly controlled by stacking fault energy (SFE), which has been analyzed intensively in the present MGMC.

Origin of high thermoelectric performance of FeNb1−xZr/HfxSb1−ySny alloys: A first-principles study

PubMed Central

Zhang, Xiwen; Wang, Yuanxu; Yan, Yuli; Wang, Chao; Zhang, Guangbiao; Cheng, Zhenxiang; Ren, Fengzhu; Deng, Hao; Zhang, Jihua

2016-01-01

The previous experimental work showed that Hf- or Zr-doping has remarkably improved the thermoelectric performance of FeNbSb. Here, the first-principles method was used to explore the possible reason for such phenomenon. The substitution of X (Zr/Hf) atoms at Nb sites increases effective hole-pockets, total density of states near the Fermi level (EF), and hole mobility to largely enhance electrical conductivity. It is mainly due to the shifting the EF to lower energy and the nearest Fe atoms around X atoms supplying more d-states to hybrid with X d-states at the vicinity of the EF. Moreover, we find that the X atoms indirectly affect the charge distribution around Nb atoms via their nearest Fe atoms, resulting in the reduced energy difference in the valence band edge, contributing to enhanced Seebeck coefficients. In addition, the further Bader charge analysis shows that the reason of more holes by Hf-doping than Zr in the experiment is most likely derived from Hf atoms losing less electrons and the stronger hybridization between Hf atoms and their nearest Fe atoms. Furthermore, we predict that Hf/Sn co-doping may be an effective strategy to further optimize the thermoelectric performance of half-Heusler (HH) compounds. PMID:27604826

Twin Research and the Arts: Interconnections / Twin Research: Twin Studies of Sexual Orientation; A Historical Biological Twin Gem; GWAS Approach to Who Has Twins / Newsworthy: Twins on College Campuses; 'Brainprint': Personal Identification by Brain Waves.

PubMed

Segal, Nancy L

2016-08-01

The interrelatedness between twin research and the arts is explored via a new play about a famous case. In the 1960s, identical twin David Bruce Reimer was accidentally castrated as an infant during circumcision to correct a urinary problem. The decision to raise him as a girl, and the consequences of that decision, are explored in the new theatrical production of Boy. Other examples of the arts mirroring science, and vice versa, are described. Next, brief reviews and summaries of twin research on sexual orientation, 1860s' knowledge of placental arrangements and twinning mechanisms, and genes underlying multiple birth conception and fertility related measures are provided. This article concludes with a look at twins on college campuses and the identification of individuals by their brain waves. A correction and clarification regarding my article on the Brazilian Twin Registry in the last issue of THG (Segal, 2016) is also provided.

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

Arul Kumar, M.; Beyerlein, Irene Jane; Tomé, Carlos N.

Here we study the effect of nearest neighboring grains on the propensity for {1012} twin growth in Mg and Zr. Twin lamellae lying within one grain flanked by two neighboring grains with several orientations are considered. The fields of resolved shear stress on the twin system are calculated in the multicrystal using a three-dimensional full-field crystal plasticity Fast Fourier Transform approach. The calculations were carried out for Mg and Zr using slip threshold stresses corresponding to 300K and 76K, respectively, where twin activity is important. We show that the neighboring grain constraint tends to oppose further growth and that themore » critical applied stress needed to overcome this resistance depends on neighboring grain orientation, more strongly in Zr than in Mg. We also present results for a pair of adjacent and parallel twins at various spacings. It is found that their paired interaction increases the resistive forces for twin growth above that for an isolated twin. The critical spacing above which this enhanced resistance is removed is smaller for Zr than Mg. Our analysis reveals that these two disparate responses of Zr and Mg are both a consequence of the fact that Zr is elastically and plastically more anisotropic than Mg. Additional calculations carried out on Ti support this conclusion. Finally, these findings can help explain why, for the same grain size, more twins per grain form in Zr than in Mg, twins in Zr tend to be thinner than those in Mg, and the relationship between the thickness of the twin and its Schmid factor in Zr is not as strong as in Mg.« less

Stolen twin: fascination and curiosity/twin research reports: evolution of sleep length; dental treatment of craniopagus twins; cryopreserved double embryo transfer; gender options in multiple pregnancy/current events: appendectomy in one twin; autistic twin marathon runners; 3D facial recognition; twin biathletes.

PubMed

Segal, Nancy L

2014-02-01

The story of her allegedly stolen twin brother in Armenia is recounted by a 'singleton twin' living in the United States. The behavioral consequences and societal implications of this loss are considered. This case is followed by twin research reports on the evolution of sleep length, dental treatment of craniopagus conjoined twins, cryopreserved double embryo transfer (DET), and gender options in multiple pregnancy. Current events include the diagnosis of appendectomy in one identical twin, the accomplishments of autistic twin marathon runners, the power of three-dimensional (3D) facial recognition, and the goals of twin biathletes heading to the 2014 Sochi Olympics in Russia.

Anisotropy of the Irreversibility Field for Zr-doped (Y,Gd)Ba 2<\\sub>Cu3<\\sub>O<7-x<\\sub> Thin Films up to 45 T

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

Tarantini, C.; Jaroszynski, J.; Kametani, F.

2011-01-01

The anisotropic irreversibility fieldBIrr of twoYBa2Cu3O7 x thin films dopedwith additional rare earth (RE)= (Gd, Y) and Zr and containing strong correlated pins (splayed BaZrO3 nanorods and RE2O3 anoprecipitates) has been measured over a very broad range up to 45 T at temperatures 56 K < T < Tc. We found that the experimental angular dependence of BIrr ( ) does not follow the mass anisotropy scaling BIrr ( ) = BIrr (0)(cos2 + 2 sin2 ) 1/2, where = (mc/mab)1/2 = 5 6 for the RE-doped Ba2Cu3O7 x (REBCO) crystals, mab and mc are the effective masses along themore » ab plane and the c-axis, respectively, and is the angle between B and the c-axis. For B parallel to the ab planes and to the c-axis correlated pinning strongly enhances BIrr , while at intermediate angles, BIrr ( ) follows the scaling behavior BIrr ( ) (cos2 + 2 RP sin2 ) 1/2 with the effective anisotropy factor RP 3 significantly smaller than the ass anisotropy would suggest. In spite of the strong effects of c-axis BaZrO3 nanorods, we found even greater enhancements of BIrr for fields along the ab planes than for fields parallel to the c-axis, as well as different temperature dependences of the correlated pinning contributions to BIrr for B//ab and B//c. Our results show that the dense and strong pins, which can now be incorporated into REBCO thin films in a controlled way, exert major and diverse effects on the measured vortex pinning anisotropy and the irreversibility field over wide ranges of B and T . In particular, we show that the relative contribution of correlated pinning to BIrr for B//c increases as the temperature increases due to the suppression of thermal fluctuations of vortices by splayed distribution of BaZrO3 nanorods.« less

Fatigue in artificially layered Pb(Zr,Ti)O3 ferroelectric films

NASA Astrophysics Data System (ADS)

Jiang, A. Q.; Scott, J. F.; Dawber, M.; Wang, C.

2002-12-01

We have performed fatigue tests on lead zirconate titanate (PZT) multilayers having stacks of Pb(Zr0.8Ti0.2)O3/Pb(Zr0.2Ti0.8)O3 with repeated distances of 12 formula groups. The results are compared with single-layer n-type (0.5 at. % Ta-doped) PZT films. We conclude that fatigue is dominated by space-charge layers in each case, but that in the multilayer such space charge accumulates at the layer interfaces, rather than at the electrode-dielectric interface. The model, which includes both drift and diffusion, is quantitative and yields a rate-limiting mobility of 6.9±0.9×10-12 cm2/V s, in excellent agreement with the oxygen vacancy mobility for perovskite oxides obtained from Zafar et al.

The TWINS Science Data System after the launch of TWINS 1

NASA Astrophysics Data System (ADS)

Goldstein, J.; Valek, P.; Skoug, R.; Delapp, D.; Redfern, J.; Carruth, B.; McComas, D.

2007-05-01

The Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) 1 satellite is in orbit and science data are expected to commence in the near future. TWINS-1 comprises half of the TWINS stereoscopic neutral atom imaging system that will advance our knowledge of the Earth's ring current. To support the expected data return, we have developed a Science Data System (SDS) for the TWINS mission. The TWINS SDS is an IDL- and Java- driven data interface that operates primarily via a web browser, and has as its spine an SQL-queryable database. Through this interface, TWINS science data will be provided to the TWINS team, the space science community, and the public. In this paper we present the current and future capabilities of the TWINS SDS, as well as how the SDS fits into virtual observatory infrastructure.

Luminescent properties of ZrO2:Tb nanoparticles for applications in neuroscience

NASA Astrophysics Data System (ADS)

Słońska, A.; Kaszewski, J.; Wolska-Kornio, E.; Witkowski, B.; Wachnicki, Ł.; Mijowska, E.; Karakitsou, V.; Gajewski, Z.; Godlewski, M.; Godlewski, M. M.

2016-09-01

In this paper a new generation of non-toxic nanoparticles based on the zirconium oxide doped with 0.5%Tb and co-doped by the range of 0-70% with Y was evaluated for the use as a fluorescent biomarker of neuronal trafficking. The ZrO2:Tb nanoparticles were created by microwave driven hydrothermal method. Influence of the yttrium content and thermal processing on the Tb3+ related luminescence emission was discussed. The higher intensities were achieved, when host was cubic and for the nanoparticles with 33 nm. Presence of yttrium was associated with the energy coupling of the host and dopant, wide excitation band is present at 309 and 322 nm before and after calcination respectively.

Zirconium-doped magnetic microspheres for the selective enrichment of cis-diol-containing ribonucleosides.

PubMed

Fan, Hua; Chen, Peihong; Wang, Chaozhan; Wei, Yinmao

2016-05-27

Zirconium-doped magnetic microspheres (Zr-Fe3O4) for the selective enrichment of cis-diol-containing biomolecules were easily synthesized via a one-step hydrothermal method. Characterization of the microspheres revealed that zirconium was successfully doped into the lattice of Fe3O4 at a doping level of 4.0 at%. Zr-Fe3O4 possessed good magnetic properties and high specificity towards cis-diol molecules, as shown using 28 compounds. For ribonucleosides, the adsorbent not only has favorable anti-interferential abilities but also has a high adsorption capacity up to 159.4μmol/g. As an example of a real application, four ribonucleosides in urine were efficiently enriched and detected via magnetic solid-phase extraction coupled with high-performance liquid chromatography. Under the optimized extraction conditions, the detection limits were determined to be between 0.005 and 0.017μg/mL, and the linearities ranged from 0.02 to 5.00μg/mL (R≥0.996) for these analytes. The accuracy of the analytical method was examined by studying the relative recoveries of the analytes in real urine samples, with recoveries varying from 77.8% to 119.6% (RSDs<10.6%, n=6). The results indicate that Zr-Fe3O4 is a suitable adsorbent for the analysis of cis-diol-containing biomolecules in practical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Intragranular twinning, detwinning, and twinning-like lattice reorientation in magnesium alloys

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

Wu, Wei; Gao, Yanfei; Li, Nan

2016-12-01

Deformation twinning plays a critical role on improving metals or alloys ductility, especially for hexagonal close-packed materials with low symmetry crystal structure. A rolled Mg alloy was selected as a model system to investigate the extension twinning behaviors and characteristics of parent-twin interactions by nondestructive in situ 3D synchrotron X-ray microbeam diffraction. Besides twinning-detwinning process, the "twinning-like" lattice reorientation process was captured within an individual grain inside a bulk material during the strain reversal. The distributions of parent, twin, and reorientated grains and sub-micron level strain variation across the twin boundary are revealed. A theoretical calculation of the lattice strainmore » confirms that the internal strain distribution in parent and twinned grains correlates with the experimental setup, grain orientation of parent, twin, and surrounding grains, as well as the strain path changes. The study suggests a novel deformation mechanism within the hexagonal close-packed structure that cannot be determined from surface-based characterization methods. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Intragranular twinning, detwinning, and twinning-like lattice reorientation in magnesium alloys

DOE PAGES

Wu, Wei; Gao, Yanfei; Oak Ridge National Lab.; ...

2016-09-11

We present that deformation twinning plays a critical role on improving metals or alloys ductility, especially for hexagonal close-packed materials with low symmetry crystal structure. A rolled Mg alloy was selected as a model system to investigate the extension twinning behaviors and characteristics of parent-twin interactions by nondestructive in situ 3D synchrotron X-ray microbeam diffraction. Besides twinning- detwinning process, the twinning-like lattice reorientation process was captured within an individual grain inside a bulk material during the strain reversal. The distributions of parent, twin, and reorientated grains and sub-micron level strain variation across the twin boundary are revealed. A theoretical calculationmore » of the lattice strain confirms that the internal strain distribution in parent and twinned grains correlates with the experimental setup, grain orientation of parent, twin, and surrounding grains, as well as the strain path changes. In conclusion, the study suggests a novel deformation mechanism within the hexagonal close-packed structure that cannot be determined from surface-based characterization methods.« less

Twins and Kindergarten Separation: Divergent Beliefs of Principals, Teachers, Parents, and Twins

ERIC Educational Resources Information Center

Gordon, Lynn Melby

2015-01-01

Should principals enforce mandatory separation of twins in kindergarten? Do school separation beliefs of principals differ from those of teachers, parents of twins, and twins themselves? This survey questioned 131 elementary principals, 54 kindergarten teachers, 201 parents of twins, and 112 twins. A majority of principals (71%) believed that…

Backward optical gain originating from weak localization strengthened three-photon process in Er/Yb co-doped (Pb,La)(Zr,Ti)O₃ ceramics.

PubMed

Xu, Caixia; Zhang, Jingwen; Zou, Yingyin K; Zhao, Hua

2016-03-21

The enhancement of green upconverted emission from the Er³⁺/Yb³⁺ co-doped (Pb,La)(Zr,Ti)O₃ ceramic powder under a pumping light with a wavelength of 1480 nm was observed to be greater than 30 times that from the bulk of the same sample. Weak localization of light supported by the spatial profile of scattered light facilitated the three-photon process contributing to stronger green upconverted emission. Significant backward light amplification was also observed and studied in detail. Additionally, the distribution of the localization zones in the sample was investigated using a probing laser beam with a wavelength of 532 nm. The findings in this work could be used in improving the solar cell efficiency, modulating color, and designing smart devices.

Comparison and mechanism of photocatalytic activities of N-ZnO and N-ZrO2 for the degradation of rhodamine 6G.

PubMed

Sudrajat, Hanggara; Babel, Sandhya

2016-05-01

N-doped ZnO (N-ZnO) and N-doped ZrO2 (N-ZrO2) are synthesized by novel, simple thermal decomposition methods. The catalysts are evaluated for the degradation of rhodamine 6G (R6G) under visible and UV light. N-ZnO exhibits higher dye degradation under both visible and UV light compared to N-ZrO2 due to possessing higher specific surface area, lower crystalline size, and lower band gap. However, it is less reusable than N-ZrO2 and its photocatalytic activity is also deteriorated at low pH. At the same intensity of 3.5 W/m(2), UVC light is shown to be a better UV source for N-ZnO, while UVA light is more suitable for N-ZrO2. At pH 7 with initial dye concentration of 10 mg/L, catalyst concentration of 1 g/L, and UVC light, 94.3 % of R6G is degraded by N-ZnO within 2 h. Using UVA light under identical experimental conditions, 93.5 % degradation of R6G is obtained by N-ZrO2. Moreover, the type of light source is found to determine the reactive species produced in the R6G degradation by N-ZnO and N-ZrO2. Less oxidative reactive species such as superoxide radical and singlet oxygen play a major role in the degradation of R6G under visible light. On the contrary, highly oxidative hydroxyl radicals are predominant under UVC light. Based on the kinetic study, the adsorption of R6G on the catalyst surface is found to be the controlling step.

Twinning of dodecanedicarboxylic acid

NASA Technical Reports Server (NTRS)

Sen, R.; Wilcox, W. R.

1986-01-01

Twinning of 1,10-dodecanedicarboxyl acid (DDA) was observed in 0.1 mm thick films with a polarizing microscope. Twins originated from polycrystalline regions which tended to nucleate on twin faces, and terminated by intersection gone another. Twinning increased dramatically with addition of organic compounds with a similar molecular size and shape. Increasing the freezing rate, increasing the temperature gradient, and addition of silica particles increased twinning. It is proposed that twins nucleate with polycrystals and sometimes anneal out before they become observable. The impurities may enhance twinning either by lowering the twin energy or by adsorbing on growing faces.

Characteristics of high-k gate dielectric formed by the oxidation of sputtered Hf/Zr/Hf thin films on the Si substrate

NASA Astrophysics Data System (ADS)

Kim, H. D.; Roh, Y.; Lee, J. E.; Kang, H.-B.; Yang, C.-W.; Lee, N.-E.

2004-07-01

We have investigated the effects of high temperature annealing on the physical and electrical properties of multilayered high-k gate oxide [HfSixOy/HfO2/intermixed-layer(IL)/ZrO2/intermixed-layer(IL)/HfO2] in metal-oxide-semiconductor device. The multilayered high-k films were formed after oxidizing the Hf/Zr/Hf films deposited directly on the Si substrate. The subsequent N2 annealing at high temperature (>= 700 °C) not only results in the polycrystallization of the multilayered high-k films, but also causes the diffusion of Zr. The latter transforms the HfSixOy/HfO2/IL/ZrO2/IL/HfO2 film into the Zr-doped HfO2 film, and improves electrical properties in general. However, the thin SiOx interfacial layer starts to form if annealing temperature increases over 700 °C, deteriorating the equivalent oxide thickness. .

Absorption Characterization of Mn-Zr-Substituted La-Sr Hexaferrite Using Open-Circuit and Short-Circuit Approaches in 8.2-18 GHz Frequency Range

NASA Astrophysics Data System (ADS)

Narang, Sukhleen Bindra; Kaur, Pawandeep; Bahel, Shalini; Pubby, Kunal

2018-01-01

The present study reports on the microwave absorption characterization of Mn2+-Zr4+ substituted lanthanum strontium ferrites, Sr0.85La0.15(MnZr) x Fe12-2 x O19, where x = 0.0, 0.25, 0.50, 0.75 and 1.0 in the X- and Ku-band. The synthesized ferrites are characterized with regard to their electromagnetic properties such as complex permittivity ( {ɛ^' - jɛ^'' ) and complex permeability ( {μ^' - jμ^'' ) using vector network analysis in the 8.2-18 GHz frequency range. Real and imaginary parts of permittivity decrease with the increase in Mn-Zr concentration due to a reduction in electron hopping conduction and eddy current losses, respectively. Microwave permeability spectra are also affected by the doping. The amplitude of magnetic loss peak increases with the increase in doping except for the x = 1.0 composition. Two commonly used approaches, open-circuit and short-circuit, have been employed for the absorption analysis. The difference in the results of these two techniques is justified on the basis of the reflection mechanism. The presented experimental findings underline the potential of the synthesized compositions with Mn-Zr concentrations x = 0.25, 0.5 and 0.75 in the suppression of electromagnetic reflections and radar signatures.

Malaysian Twin Registry.

PubMed

Jahanfar, Shayesteh; Jaffar, Sharifah Halimah

2013-02-01

The National Malaysian Twin Registry was established in Royal College of Medicine, Perak, University Kuala Lumpur (UniKL) in June 2008 through a grant provided by UniKL. The general objective is to facilitate scientific research involving participation of twins and their family members in order to answer questions of health and wellbeing relevant to Malaysians. Recruitment is done via mass media, poster, and pamphlets. We now have 266 adult and 204 children twins registered. Several research projects including reproductive health study of twins and the role of co-bedding on growth and development of children are carried out. Registry holds annual activities for twins and seeks to provide health-related information for twins. We seek international collaboration.

Thermal shock behavior of W-ZrC/Sc2O3 composites under two different transient events by electron and laser irradiation

NASA Astrophysics Data System (ADS)

Chen, Hong-Yu; Luo, Lai-Ma; Zan, Xiang; Xu, Qiu; Tokunaga, Kazutoshi; Liu, Jia-Qin; Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng

2018-02-01

The transient thermal shock behaviors of W-ZrC/Sc2O3 composites with different ZrC contents were evaluated using transient thermal shock test by electron and laser beams. The effects of different ZrC doping contents on the surface morphology and thermal shock resistance of W-ZrC/Sc2O3 composites were then investigated. Similarity and difference between effects of electron and laser beam transient heat loading were also discussed in this study. Repeated heat loading resulted in thermal fatigue of the irradiated W-ZrC/Sc2O3 samples by thermal stress, leading to the rough surface morphologies with cracks. After different transient thermal tests, significant surface roughening, cracks, surface melting, and droplet ejection occurred. W-2vol.%Sc2O3 sample has superior thermal properties and greater resistance to surface modifications under transient thermal shock, and with the increasing ZrC content in W alloys, thermal shock resistance of W-Zr/Sc2O3 sample tends to be unsatisfied.

NOTE: Haemodynamic resistance model of monochorionic twin pregnancies complicated by acardiac twinning

NASA Astrophysics Data System (ADS)

Umur, Asli; van Gemert, Martin J. C.; van den Wijngaard, Jeroen P. H. M.; Ross, Michael G.; Nikkels, Peter G. J.

2004-07-01

An acardiac twin is a severely malformed monochorionic twin fetus that lacks most organs, particularly a heart. It grows during pregnancy, because it is perfused by its developmentally normal co-twin (called the pump twin) via a set of placental arterioarterial and venovenous anastomoses. The pump twin dies intrauterine or neonatally in about 50% of the cases due to congestive heart failure, polyhydramnios and prematurity. Because the pathophysiology of this pregnancy is currently incompletely understood, we modified our previous haemodynamic model of monochorionic twins connected by placental vascular anastomoses to include the analysis of acardiac twin pregnancies. We incorporated the fetoplacental circulation as a resistance circuit and used the fetal umbilical flow that perfuses the body to define fetal growth, rather than the placental flow as done previously. Using this modified model, we predicted that the pump twin has excess blood volume and increased mean arterial blood pressure compared to those in the acardiac twin. Placental perfusion of the acardiac twin is significantly reduced compared to normal, as a consequence of an increased venous pressure, possibly implying reduced acardiac placental growth. In conclusion, the haemodynamic analysis may contribute to an increased knowledge of the pathophysiologic consequences of an acardiac body mass for the pump twin.

Damage morphology study of high cycle fatigued as-cast Mg–3.0Nd–0.2Zn–Zr (wt.%) alloy

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

Yue, Haiyan; Fu, Penghuai, E-mail: fph112sjtu@sjtu.edu.cn; Peng, Liming

Laser scanning confocal microscopy (LSCM) and Electron back-scattered diffraction (EBSD) were applied to the study of surface morphology variation of as-cast Mg–3.0Nd–0.2Zn–Zr (NZ30K) (wt.%) alloy under tension-compression fatigue test at room temperature. Two kinds of typical damage morphologies were observed in fatigued NZ30K alloy: One was parallel lines on basal planes led by the cumulation of basal slips, called persistent slip markings (PSMs), and the other was lens shaped, thicker and in less density, led by the formation of twinning. The surface fatigue damage morphology evolution was analyzed in a statistical way. The influences of stress amplitude and grain orientationmore » on fatigue deformation mechanisms were discussed and the non-uniform deformation among grains and the PSMs, within twinning were described quantitatively. - Highlights: • Fatigue morphology evolution was studied by Laser Scanning Confocal Microscopy. • 3D morphology of persistent slip markings and twins was characterized. • Non-uniform deformation among grains, the PSMs and twins were quantified. • Initiations of fatigue crack were clearly investigated.« less

Zr-doped ceria additives for enhanced PEM fuel cell durability and radical scavenger stability

DOE PAGES

Baker, Andrew M.; Williams, Stefan Thurston DuBard; Mukundan, Rangachary; ...

2017-06-06

Doped ceria compounds demonstrate excellent radical scavenging abilities and are promising additives to improve the chemical durability of polymer electrolyte membrane (PEM) fuel cells. Here in this paper, Ce 0.85Zr 0.15O 2 (CZO) nanoparticles were incorporated into the cathode catalyst layers (CLs) of PEM fuel cells (based on Nafion XL membranes containing 6.0 μg cm -2 ion-exchanged Ce) at loadings of 10 and 55 μg cm -2. When compared to a CZO-free baseline, CZO-containing membrane electrode assemblies (MEAs) demonstrated extended lifetimes during PEM chemical stability accelerated stress tests (ASTs), exhibiting reduced electrochemical gas crossover, open circuit voltage decay, and fluoridemore » emission rates. The MEA with high CZO loading (55 μg cm -2) demonstrated performance losses, which are attributed to Ce poisoning of the PEM and CL ionomer regions, which is supported by X-ray fluorescence (XRF) analysis. In the MEA with the low CZO loading (10 μg cm -2), both the beginning of life (BOL) performance and the performance after 500 hours of ASTs were nearly identical to the BOL performance of the CZO-free baseline MEA. XRF analysis of the MEA with low CZO loading reveals that the BOL PEM Ce concentrations are preserved after 1408 hours of ASTs and that Ce contents in the cathode CL are not significant enough to reduce performance. Therefore, employing a highly effective radical scavenger such as CZO, at a loading of 10 μg cm -2 in the cathode CL, dramatically mitigates degradation effects, which improves MEA chemical durability and minimizes performance losses.« less

Zr-doped ceria additives for enhanced PEM fuel cell durability and radical scavenger stability

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

Baker, Andrew M.; Williams, Stefan Thurston DuBard; Mukundan, Rangachary

Doped ceria compounds demonstrate excellent radical scavenging abilities and are promising additives to improve the chemical durability of polymer electrolyte membrane (PEM) fuel cells. Here in this paper, Ce 0.85Zr 0.15O 2 (CZO) nanoparticles were incorporated into the cathode catalyst layers (CLs) of PEM fuel cells (based on Nafion XL membranes containing 6.0 μg cm -2 ion-exchanged Ce) at loadings of 10 and 55 μg cm -2. When compared to a CZO-free baseline, CZO-containing membrane electrode assemblies (MEAs) demonstrated extended lifetimes during PEM chemical stability accelerated stress tests (ASTs), exhibiting reduced electrochemical gas crossover, open circuit voltage decay, and fluoridemore » emission rates. The MEA with high CZO loading (55 μg cm -2) demonstrated performance losses, which are attributed to Ce poisoning of the PEM and CL ionomer regions, which is supported by X-ray fluorescence (XRF) analysis. In the MEA with the low CZO loading (10 μg cm -2), both the beginning of life (BOL) performance and the performance after 500 hours of ASTs were nearly identical to the BOL performance of the CZO-free baseline MEA. XRF analysis of the MEA with low CZO loading reveals that the BOL PEM Ce concentrations are preserved after 1408 hours of ASTs and that Ce contents in the cathode CL are not significant enough to reduce performance. Therefore, employing a highly effective radical scavenger such as CZO, at a loading of 10 μg cm -2 in the cathode CL, dramatically mitigates degradation effects, which improves MEA chemical durability and minimizes performance losses.« less

Exploiting magnetic properties of Fe doping in zirconia. From first-principles simulations to the experimental growth and characterization of thin films

NASA Astrophysics Data System (ADS)

Sangalli, Davide; Cianci, Elena; Lamperti, Alessio; Ciprian, Roberta; Albertini, Franca; Casoli, Francesca; Lupo, Pierpaolo; Nasi, Lucia; Campanini, Marco; Debernardi, Alberto

2013-05-01

In this study we explore, both from theoretical and experimental side, the effect of Fe doping in ZrO2 (ZrO2:Fe). By means of first principles simulation, we study the magnetization density and the magnetic interaction between Fe atoms. We also consider how this is affected by the presence of oxygen vacancies and compare our findings with models based on impurity band [J.M.D. Coey, M. Venkatesan, C.B. Fitzgerald, Nat. Mater. 4, 173 (2005)] and carrier mediated magnetic interaction [T. Dietl, H. Ohno, F. Matsukura, J. Cibert, D. Ferrand, Science 287, 1019 (2000)]. Experimentally, thin films (≈20 nm) of ZrO2:Fe at high doping concentration are grown by atomic layer deposition. We provide experimental evidence that Fe is uniformly distributed in the ZrO2 by transmission electron microscopy and energy dispersive X-ray mapping, while X-ray diffraction evidences the presence of the fluorite crystal structure. Alternating gradient force magnetometer measurements show magnetic signal at room temperature, however, with low magnetic moment per atom. Results from experimental measures and theoretical simulations are compared.

Twins and non-twin siblings: different estimates of shared environmental influence in early childhood.

PubMed

Koeppen-Schomerus, Gesina; Spinath, Frank M; Plomin, Robert

2003-04-01

Twin studies typically indicate shared environmental influence for cognitive abilities, especially in early childhood. However, across studies, DZ twin correlations tend to be greater than non-twin sibling correlations, suggesting that twin estimates of shared environment are to some extent specific to twins. We tested this hypothesis in a sample of more than 1800 MZ and 1800 same-sex DZ pairs from the Twins Early Development Study (TEDS), a study of twins born in England and Wales in 1994 and 1995. For this analysis, we obtained comparable data from more than 130 same-sex younger siblings of the twins. Twins and their younger siblings were assessed for language, cognitive abilities and behavior problems by their parents at 2 and 3 years of age. For language and cognitive measures at both 2 and 3 years, but not for behavior problems, estimates of shared environment were more than twice as large for twins as compared to non-twin siblings. We conclude that about half of twin study estimates of shared environment for cognitive abilities in early childhood are specific to twins. Although many possibilities exist for explaining the special shared environment effect for twins, we suggest that cognitive-relevant experiences that are not shared by siblings are shared by twins because they are exactly the same age.

Effect of co-twin gender on neurodevelopmental symptoms: a twin register study.

PubMed

Eriksson, Jonna Maria; Lundström, Sebastian; Lichtenstein, Paul; Bejerot, Susanne; Eriksson, Elias

2016-01-01

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are neurodevelopmental disorders thought to have both genetic and environmental causes. It has been hypothesized that exposure to elevated levels of prenatal testosterone is associated with elevated traits of ASD and ADHD. Assuming that testosterone levels from a dizygotic male twin fetus may lead to enhanced testosterone exposure of its co-twins, we aimed to test the prenatal testosterone hypothesis by comparing same-sex with opposite-sex dizygotic twins with respect to neurodevelopmental symptoms. Neuropsychiatric traits were assessed in a population-based twin cohort from the Child and Adolescent Twin Study in Sweden (CATSS). Parental interviews were conducted for 16,312 dizygotic twins, 9 and 12 years old, with the Autism-Tics, ADHD, and other Comorbidities inventory (A-TAC). Girls with a female co-twin had an increased risk of reaching the cut-off score for ADHD compared with girls with a male co-twin. Both boys and girls with a female co-twin displayed a larger number of traits related to attention deficit and repetitive and stereotyped behaviors than those with a male twin. In girls, this also extended to social interaction and the combined measures for ASD and ADHD, however, with small effect sizes. Our results are reverse to what would have been expected from the prenatal testosterone hypothesis but consistent with a previous study of ASD and ADHD traits in dizygotic twins. The seemingly protective effect for girls of having a twin brother may be an effect of parent report bias, but may also be an unexpected effect of sharing the intrauterine environment with a male co-twin.

Fabrication of solution-processed InSnZnO/ZrO2 thin film transistors.

PubMed

Hwang, Soo Min; Lee, Seung Muk; Choi, Jun Hyuk; Lim, Jun Hyung; Joo, Jinho

2013-11-01

We fabricated InSnZnO (ITZO) thin-film transistors (TFTs) with a high-permittivity (K) ZrO2 gate insulator using a solution process and explored the microstructure and electrical properties. ZrO2 and ITZO (In:Sn:Zn = 2:1:1) precursor solutions were deposited using consecutive spin-coating and drying steps on highly doped p-type Si substrate, followed by annealing at 700 degrees C in ambient air. The ITZO/ZrO2 TFT device showed n-channel depletion mode characteristics, and it possessed a high saturation mobility of approximately 9.8 cm2/V x s, a small subthreshold voltage swing of approximately 2.3 V/decade, and a negative V(TH) of approximately 1.5 V, but a relatively low on/off current ratio of approximately 10(-3). These results were thought to be due to the use of the high-kappa crystallized ZrO2 dielectric (kappa approximately 21.8) as the gate insulator, which could permit low-voltage operation of the solution-processed ITZO TFT devices for applications to high-throughput, low-cost, flexible and transparent electronics.

Influence of incoherent twin boundaries on the electrical properties of β-Ga2O3 layers homoepitaxially grown by metal-organic vapor phase epitaxy

NASA Astrophysics Data System (ADS)

Fiedler, A.; Schewski, R.; Baldini, M.; Galazka, Z.; Wagner, G.; Albrecht, M.; Irmscher, K.

2017-10-01

We present a quantitative model that addresses the influence of incoherent twin boundaries on the electrical properties in β-Ga2O3. This model can explain the mobility collapse below a threshold electron concentration of 1 × 1018 cm-3 as well as partly the low doping efficiency in β-Ga2O3 layers grown homoepitaxially by metal-organic vapor phase epitaxy on (100) substrates of only slight off-orientation. A structural analysis by transmission electron microscopy (TEM) reveals a high density of twin lamellae in these layers. In contrast to the coherent twin boundaries parallel to the (100) plane, the lateral incoherent twin boundaries exhibit one dangling bond per unit cell that acts as an acceptor-like electron trap. Since the twin lamellae are thin, we consider the incoherent twin boundaries to be line defects with a density of 1011-1012 cm-2 as determined by TEM. We estimate the influence of the incoherent twin boundaries on the electrical transport properties by adapting Read's model of charged dislocations. Our calculations quantitatively confirm that the mobility reduction and collapse as well as partly the compensation are due to the presence of twin lamellae.

Attractiveness Differences Between Twins Predicts Evaluations of Self and Co-Twin

PubMed Central

Principe, Connor P.; Rosen, Lisa H.; Taylor-Partridge, Teresa; Langlois, Judith H.

2012-01-01

One of the most consistent findings in psychology shows that people prefer and make positive attributions about attractive compared with unattractive people. The goal of the current study was to determine the power of attractiveness effects by testing whether these social judgments are made where attractiveness differences are smallest: between twins. Differences in facial attractiveness predicted twins’ evaluations of self and their co-twin (n = 158; 54 male). In twin pairs, the more attractive twin judged their less attractive sibling as less physically attractive, athletic, socially competent, and emotionally stable. The less attractive twin did the reverse. Given that even negligible differences in facial attractiveness predicted self and co-twin attitudes, these results provide the strongest test yet of appearance-based stereotypes. PMID:23467329

Synthesis, Luminescence Properties and Energy Transfer of CaZrO3:Sm3+, Bi3+ Phosphor

NASA Astrophysics Data System (ADS)

Cao, Renping; Han, Peng; Luo, Wenjie; Fu, Ting; Luo, Zhiyang; Liu, Pan; Chen, Zhiquan; Yu, Xiaoguang

2016-07-01

Novel CaZrO3:Sm3+, Bi3+ phosphor is synthesized by a solid-state reaction method in air and the crystal structures and luminescence properties are investigated. The emission spectrum with excitation 308 nm contains emission of Sm3+ and Bi3+ ions at the same time; however, it only has an emission of Sm3+ ion with excitation 408 nm. Emission intensity of CaZrO3:Sm3+ phosphor can be enhanced about four times owing to energy transfer from the Bi3+ ion to the Sm3+ ion and with the fluxing agent role of Bi3+ ion when Bi3+ ion is co-doped. The possible luminous mechanism is analyzed by energy level diagrams of Bi3+ and Sm3+ ions and the energy transfer process in CaZrO3:Sm3+, Bi3+ phosphor. The experimental results indicate that, hopefully, CaZrO3:Sm3+, Bi3+ phosphor can be used as a reddish orange phosphor candidate for white light-emitting diodes based on near an ultraviolet (~408 nm) chip.

Irreversible phase transitions due to laser-based T-jump heating of precursor Eu:ZrO{sub 2}/Tb:Y{sub 2}O{sub 3} core/shell nanoparticles

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

Gunawidjaja, Ray; Diez-y-Riega, Helena; Eilers, Hergen, E-mail: eilers@wsu.edu

2015-09-15

Amorphous precursors of Eu-doped-ZrO{sub 2}/Tb-doped-Y{sub 2}O{sub 3} (p-Eu:ZrO{sub 2}/p-Tb:Y{sub 2}O{sub 3}) core/shell nanoparticles are rapidly heated to temperatures between 200 °C and 950 °C for periods between 2 s and 60 s using a CO{sub 2} laser. During this heating process the nanoparticles undergo irreversible phase changes. The fluorescence spectra due to Eu{sup 3+} dopants in the core and Tb{sup 3+} dopants in the shell are used to identify distinct phases within the material and to generate time/temperature phase diagrams. Such phase diagrams can potentially help to determine unknown time/temperature histories in thermosensor applications. - Graphical abstract: A CO{sub 2}more » laser is used for rapid heating of p-Eu:ZrO{sub 2}/p-Tb:Y{sub 2}O{sub 3} core/shell nanoparticles. Optical spectra are used to identify distinct phases and to determine its thermal history. - Highlights: • Synthesized oxide precursors of lanthanide doped core/shell nanoparticles. • Heated core/shell nanoparticles via laser-based T-jump technique. • Observed time- and temperature-dependent irreversible phase transition.« less

DFT-based ab initio MD simulation of the ionic conduction in doped ZrO₂ systems under epitaxial strain.

PubMed

Oka, M; Kamisaka, H; Fukumura, T; Hasegawa, T

2015-11-21

The oxygen ionic conduction in ZrO2 systems under tensile epitaxial strain was investigated by performing ab initio molecular dynamics (MD) calculations based on density functional theory (DFT) to elucidate the essential factors in the colossal ionic conductivity observed in the yttria stabilized ZrO2 (YSZ)/SrTiO3 heterostructure. Three factors were evaluated: lattice strain, oxygen vacancies, and dopants. Phonon calculations based on density functional perturbation theory (DFPT) were used to obtain the most stable structure for nondoped ZrO2 under 7% tensile strain along the a- and b-axes. This structure has the space group Pbcn, which is entirely different from that of cubic ZrO2, suggesting that previous ab initio MD calculations assuming cubic ZrO2 may have overestimated the ionic conductivity due to relaxation from the initial structure to the stable structure (Pbcn). Our MD calculations revealed that the ionic conductivity is enhanced only when tensile strain and oxygen vacancies are incorporated, although the presently obtained diffusion constant is far below the range for the colossal ionic conduction experimentally observed. The enhanced ionic conductivity is due to the combined effects of oxygen sublattice formation induced by strain and deformation of this sublattice by oxygen vacancies.

Role of alloying elements on twin growth and twin transmission in magnesium alloys

DOE PAGES

Kumar, Mariyappan Arul; Beyerlein, Irene Jane; Lebensohn, Ricardo A.; ...

2017-08-24

A spatially-resolved crystal plasticity Fast Fourier Transform (FFT)-based model is employed to study the effect of alloying addition on twin thickening and twin transmission in hexagonal close packed (HCP) magnesium. In the simulations, the influence of alloying additions is represented through the differences in the critical resolved shear stress (CRSS) of different slip and twinning modes. The results show that for the same grain orientation, twin type and boundary conditions, anisotropy in the CRSS values have a significant effect on twin thickening and twin transmission. Those with large differences in CRSS favor both twin thickening and twin transmission, and vicemore » versa for those with small differences. Furthermore, less difference among the CRSS values enhances the dependence of thickening and transmission on the neighboring grain orientation.« less

Role of alloying elements on twin growth and twin transmission in magnesium alloys

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

Kumar, Mariyappan Arul; Beyerlein, Irene Jane; Lebensohn, Ricardo A.

A spatially-resolved crystal plasticity Fast Fourier Transform (FFT)-based model is employed to study the effect of alloying addition on twin thickening and twin transmission in hexagonal close packed (HCP) magnesium. In the simulations, the influence of alloying additions is represented through the differences in the critical resolved shear stress (CRSS) of different slip and twinning modes. The results show that for the same grain orientation, twin type and boundary conditions, anisotropy in the CRSS values have a significant effect on twin thickening and twin transmission. Those with large differences in CRSS favor both twin thickening and twin transmission, and vicemore » versa for those with small differences. Furthermore, less difference among the CRSS values enhances the dependence of thickening and transmission on the neighboring grain orientation.« less

Role of oxygen vacancies on the structure and density of states of iron-doped zirconia

NASA Astrophysics Data System (ADS)

Sangalli, Davide; Lamperti, Alessio; Cianci, Elena; Ciprian, Roberta; Perego, Michele; Debernardi, Alberto

2013-02-01

In this paper, we study the effect of iron doping in zirconia using both theoretical and experimental approaches. Combining density functional theory (DFT) simulations with the experimental characterization of thin films, we show that iron is in the Fe3+ oxidation state and, accordingly, the films are rich in oxygen vacancies (VO••). VO•• favor the formation of the tetragonal phase in doped zirconia (ZrO2:Fe) and affect the density of states at the Fermi level as well as the local magnetization of Fe atoms. We also show that the Fe(2p) and Fe(3p) energy levels can be used as a marker for the presence of vacancies in the doped system. In particular, the computed position of the Fe(3p) peak is strongly sensitive to the VO•• to Fe atoms ratio. A comparison of the theoretical and experimental Fe(3p) peak positions suggests that in our films this ratio is close to 0.5. Besides the interest in the material by itself, ZrO2:Fe constitutes a test case for the application of DFT on transition metals embedded in oxides. In ZrO2:Fe, the inclusion of the Hubbard U correction significantly changes the electronic properties of the system. However, the inclusion of this correction, at least for the value U=3.3 eV chosen in the present work, worsen the agreement with the measured photoemission valence band spectra.

Multiband nodeless superconductivity near the charge-density-wave quantum critical point in ZrTe 3–xSe x

DOE PAGES

Cui, Shan; He, Lan -Po; Hong, Xiao -Chen; ...

2016-06-09

It was found that selenium doping can suppress the charge-density-wave (CDW) order and induce bulk superconductivity in ZrTe 3. The observed superconducting dome suggests the existence of a CDW quantum critical point (QCP) in ZrTe 3–x Se x near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe 3–x Se x single crystals (x = 0.044 and 0.051) down to 80 mK. For both samples, the residual linear term κ 0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependencemore » of κ 0/T manifests a multigap behavior. Lastly, these results demonstrate multiple nodeless superconducting gaps in ZrTe 3–x Se x, which indicates conventional superconductivity despite of the existence of a CDW QCP.« less

Color stable manganese-doped phosphors

DOEpatents

Lyons, Robert Joseph; Setlur, Anant Achyut; Deshpande, Anirundha Rajendra; Grigorov, Ljudmil Slavchev

2014-04-29

A lighting apparatus capable of emitting white light includes a semiconductor light source; and a phosphor material radiationally coupled to the light source. The phosphor material includes a color-stable Mn.sup.+4 doped phosphor prepared by a process including providing a phosphor of formula I; A.sub.x[MF.sub.y]:Mn.sup.+4 I and contacting the phosphor in particulate form with a saturated solution of a composition of formula II in aqueous hydrofluoric acid; A.sub.x[MF.sub.y]; II wherein A is Li, Na, K, Rb, Cs, NR.sub.4 or a combination thereof; M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof; R is H, lower alkyl, or a combination thereof; x is the absolute value of the charge of the [MF.sub.y] ion; and y is 5, 6 or 7. In particular embodiments, M is Si, Ge, Sn, Ti, Zr, or a combination thereof.

Asymmetric twin Dark Matter

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

Farina, Marco

2015-11-09

We study a natural implementation of Asymmetric Dark Matter in Twin Higgs models. The mirroring of the Standard Model strong sector suggests that a twin baryon with mass around 5 GeV is a natural Dark Matter candidate once a twin baryon number asymmetry comparable to the SM asymmetry is generated. We explore twin baryon Dark Matter in two different scenarios, one with minimal content in the twin sector and one with a complete copy of the SM, including a light twin photon. The essential requirements for successful thermal history are presented, and in doing so we address some of themore » cosmological issues common to many Twin Higgs models. The required interactions we introduce predict signatures at direct detection experiments and at the LHC.« less

Asymmetric twin Dark Matter

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

Farina, Marco, E-mail: mf627@cornell.edu

2015-11-01

We study a natural implementation of Asymmetric Dark Matter in Twin Higgs models. The mirroring of the Standard Model strong sector suggests that a twin baryon with mass around 5 GeV is a natural Dark Matter candidate once a twin baryon number asymmetry comparable to the SM asymmetry is generated. We explore twin baryon Dark Matter in two different scenarios, one with minimal content in the twin sector and one with a complete copy of the SM, including a light twin photon. The essential requirements for successful thermal history are presented, and in doing so we address some of themore » cosmological issues common to many Twin Higgs models. The required interactions we introduce predict signatures at direct detection experiments and at the LHC.« less

Orange-red emitting Gd2Zr2O7:Sm3+: Structure-property correlation, optical properties and defect spectroscopy

NASA Astrophysics Data System (ADS)

Gupta, Santosh K.; Reghukumar, C.; Sudarshan, K.; Ghosh, P. S.; Pathak, Nimai; Kadam, R. M.

2018-05-01

Local structure analysis of dopant ion, understanding host to dopant energy transfer dynamics and defects characterization in a doped material which plays an important role in the designing a highly efficient opto-electronic material. In this connection a new Sm3+ doped Gd2Zr2O7 pyrochlore material was synthesized using gel-combustion technique and was characterized systematically using X-ray diffraction (XRD), time resolved photoluminescence spectroscopy (TRPLS), positron annihilation lifetime spectroscopy (PALS) and density functional theory (DFT) based ab-initio calculation. Based on DFT site selective energetics calculation and luminescence decay measurement, it was observed that the Sm3+ was distributed at both Gd3+ and Zr4+ site with higher Sm3+ fraction at the Gd3+ site. PALS was used to probe the presence of defects in the phosphor. In this work intense orange-red emission is realized through manipulating the energy transfer from host defect emission (oxygen vacancies) to Sm3+ which allows color emission from green in undoped to orange-red in doped samples. Effect of dopant concentration and annealing temperature was probed using TRPLS and PALS. These all information is highly important for researcher looking to achieve pyrochlore based phosphor materials with high quantum yield.

High critical currents in heavily doped (Gd,Y)Ba 2Cu 3O x superconductor tapes

DOE PAGES

Selvamanickam, V.; Gharahcheshmeh, M. Heydari; Xu, A.; ...

2015-01-20

REBa 2Cu 3O x superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J c) above 20 MA/cm 2 at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba 2Cu 3O x superconductor tapes,more » which is more than three times higher than the J c typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m 3 have also been attained at 20 K. A composition map of lift factor in J c (ratio of J c at 30 K, 3 T to the J c at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO 3 (BZO) nanocolumn defect density of nearly 7 × 10 11 cm –2 as well as 2–3nm sized particles rich in Cu and Zr have been found in the high J c films.« less

Extremely dense microstructure and enhanced ionic conductivity in hot-isostatic pressing treated cubic garnet-type solid electrolyte of Ga2O3-doped Li7La3Zr2O12

NASA Astrophysics Data System (ADS)

Qin, Shiying; Zhu, Xiaohong; Jiang, Yue; Ling, Ming’En; Hu, Zhiwei; Zhu, Jiliang

A large number of pores and a low relative density that are frequently observed in solid electrolytes reduce severely their ionic conductivity and thus limit their applicability. Here, we report on the use of hot isostatic pressing (HIP) for ameliorating the garnet-type lithium-ion conducting solid electrolyte of Ga2O3-doped Li7La3Zr2O12 (Ga-LLZO) with nominal composition of Li6.55Ga0.15La3Zr2O12. The Ga-LLZO pellets were conventionally sintered at 1075∘C for 12h, and then were followed by HIP treatment at 120MPa and 1160∘C under an Ar atmosphere. It is found that the HIP-treated Ga-LLZO shows an extremely dense microstructure and a significantly enhanced ionic conductivity. Coherent with the increase in relative density from 90.5% (untreated) to 97.5% (HIP-treated), the ionic conductivity of the HIP-treated Ga-LLZO reaches as high as 1.13×10‑3S/cm at room temperature (25∘C), being two times higher than that of 4.58×10‑4S/cm for the untreated one.

Modification of PdO/CeZrO2 doped with transition metals (Y and Fe) for reducibility properties

NASA Astrophysics Data System (ADS)

Shah, M. Nazri Abu; Jai, Junaidah; Faeqah, Nor; Ismail, Kamariah Noor; Hadi, Abdul

2017-12-01

This paper describes the synthesis of modified nanocatalysts of PdO/CeZrYO2(PdO/CZY), PdO/CeZrFeO2(PdO/CZF) and PdO/CeZrO2(PdO/CZ) via microemulsion followed by deposition - precipitation method. The structural, textural and redox properties of the synthesized nanocatalysts were investigated. The diffractogram of XRD showed that all the synthesized nanocatalysts indicate a symmetrical pattern of cubic phase crystallinity. The amount of PdO was detected using EDX analysis and PdO/CZF portrayed the highest Pd contents of about 4.63 %. Therefore it shows a good potential to have reducibility properties and can be manifested active at low temperature reduction.

The vector-like twin Higgs

DOE PAGES

Craig, Nathaniel; Knapen, Simon; Longhi, Pietro; ...

2016-07-01

Here, we present a version of the twin Higgs mechanism with vector-like top partners. In this setup all gauge anomalies automatically cancel, even without twin leptons. The matter content of the most minimal twin sector is therefore just two twin tops and one twin bottom. The LHC phenomenology, illustrated with two example models, is dominated by twin glueball decays, possibly in association with Higgs bosons. We further construct an explicit four-dimensional UV completion and discuss a variety of UV completions relevant for both vector-like and fraternal twin Higgs models.

Probing the Role of Zr Addition versus Textural Properties in Enhancement of CO₂ Adsorption Performance in Silica/PEI Composite Sorbents.

PubMed

Sakwa-Novak, Miles A; Holewinski, Adam; Hoyt, Caroline B; Yoo, Chun-Jae; Chai, Song-Hai; Dai, Sheng; Jones, Christopher W

2015-09-01

Polymeric amines such as poly(ethylenimine) (PEI) supported on mesoporous oxides are promising candidate adsorbents for CO2 capture processes. An important aspect to the design and optimization of these materials is a fundamental understanding of how the properties of the oxide support such as pore structure, particle morphology, and surface properties affect the efficiency of the guest polymer in its interactions with CO2. Previously, the efficiency of impregnated PEI to adsorb CO2 was shown to increase upon the addition of Zr as a surface modifier in SBA-15. However, the efficacy of this method to tune the adsorption performance has not been explored in materials of differing textural and morphological nature. Here, these issues are directly addressed via the preparation of an array of SBA-15 support materials with varying textural and morphological properties, as well as varying content of zirconium doped into the material. Zirconium is incorporated into the SBA-15 either during the synthesis of the SBA-15, or postsynthetically via deposition of Zr species onto pure-silica SBA-15. The method of Zr incorporation alters the textural and morphological properties of the parent SBA-15 in different ways. Importantly, the CO2 capacity of SBA-15 impregnated with PEI increases by a maximum of ∼60% with the quantity of doped Zr for a "standard" SBA-15 containing significant microporosity, while no increase in the CO2 capacity is observed upon Zr incorporation for an SBA-15 with reduced microporosity and a larger pore size, pore volume, and particle size. Finally, adsorbents supported on SBA-15 with controlled particle morphology show only modest increases in CO2 capacity upon inclusion of Zr to the silica framework. The data demonstrate that the textural and morphological properties of the support have a more significant impact on the ability of PEI to capture CO2 than the support surface composition.

Modulation-Doped SrTiO3/SrTi1-xZrxO3 Heterostructures

NASA Astrophysics Data System (ADS)

Kajdos, Adam Paul

surface reconstruction from (1x1) to (2x1) to c(4x4) is correlated with a change from mixed SrO/TiO2 to pure TiO2 surface termination. It is argued that optimal cation stoichiometry is achieved for growth conditions within the XRD-defined growth window that result in a c(4x4) surface lattice. The development of a doped perovskite oxide semiconductor with a suitable conduction band offset is then discussed as the next necessary step towards realizing modulation-doped heterostructures. The SrTixZr1-x O3 solid solution is investigated for this purpose, with a focus on optimizing cation stoichiometry to allow for controlled doping. In particular, the hybrid MBE growth of SrTixZr1-xO3 thin films is explored using a metal-organic precursor for Zr, zirconium tert-butoxide (ZTB). The successful generation of 2DEGs by modulation doping of SrTiO3 is then demonstrated in SrTiO3/La:SrTi0.95Zr0.05O 3 heterostructures, and the electronic structure is studied by Shubnikov-de Haas analysis using multiple-subband models.

Effect of variable cerium concentration on photoluminescence behaviour in ZrO2 phosphor synthesized by combustion synthesis method

NASA Astrophysics Data System (ADS)

Dubey, Vikas; Kaur, Jagjeet

2016-05-01

Present paper reports synthesis and characterization of trivalent cerium (Ce3+) doped zirconium dioxide (ZrO2) phosphors. Effect of variable concentration of cerium on photoluminescence (PL) is studied. Samples were prepared by combustion synthesis technique which is suitable for less time taking techniques also for large scale production for phosphors. Starting material used for sample preparation are Zr(NO3)3 and Ce(NO3)3 and urea used as a fuel. All prepared phosphor with variable concentration of Ce3+ (0.1 to 2mol%) was studied by photoluminescence analysis it is found that the excitation spectra of prepared phosphor shows broad excitation centred at 390nm. The excitation spectra with variable concentration of Ce3+ show strong peaks at 447nm. Spectrophotometric determinations of peaks are evaluated by Commission Internationale de I'Eclairage technique. Using this phosphor, the desired CIE values including emissions throughout the violet (390 nm) and blue (427 nm) of the spectra were achieved. Efficient blue light emitting diodes were fabricated using Ce3+ doped phosphor based on near ultraviolet (NUV) excited LED lights.

ZrO2-modified mesoporous nanocrystalline TiO2-xNx as efficient visible light photocatalysts.

PubMed

Wang, Xinchen; Yu, Jimmy C; Chen, Yilin; Wu, Ling; Fu, Xianzhi

2006-04-01

Mesoporous nanocrystalline TiO2-xNx and TiO2-xNx/ZrO2 visible-light photocatalysts have been prepared by a sol-gel method. The photocatalysts were characterized by XRD, N2 adsorption-desorption, TEM, XPS, UV/Vis, and IR spectroscopy. The photocatalytic activity of the samples was evaluated by the decomposition of ethylene in air under visible light (lambda > 450 nm) illumination. Results revealed that nitrogen was doped into the lattice of TiO2 by the thermal treatment of NH3-adsorbed TiO2 hydrous gels, converting the TiO2 into a visible-light responsive catalyst. The introduction of ZrO2 into TiO2-xNx considerably inhibits the undesirable crystal growth during calcination. Consequently, the ZrO2-modified TiO2-xNx displays higher porosity, higher specific surface area, and an improved thermal stability over the corresponding unmodified TiO2-xNx samples.

The mechanical, optoelectronic and thermoelectric properties of NiYSn (Y = Zr and Hf) alloys

NASA Astrophysics Data System (ADS)

Hamioud, Farida; Mubarak, A. A.

2017-09-01

First-principle calculations are performed using DFT as implemented in Wien2k code to compute the mechanical, electronic, optical and thermoelectric properties of NiYSn (Y = Zr and Hf) alloys. The computed lattice constants, bulk modulus and cohesive energy of these alloys at 0 K and 0 GPa are performed. NiZrSn and NiHfSn are found to be anisotropic and elastically stable. Furthermore, both alloys are confirmed to be thermodynamically stable by the calculated values of the standard enthalpy of formation. The Young’s and shear moduli values show that NiZrSn seems to be stiffer than NiHfSn. The optical properties are performed using the dielectric function. Some beneficial optoelectronic applications are found as exposed in the optical spectra. Moreover, the alloys are classified as good insulators for solar heating. The thermoelectric properties as a function of temperature are computed utilizing BoltzTrap code. The major charge carriers are found to be electrons and the alloys are classified as p-type doping alloys.

Ultrasound in twin pregnancies.

PubMed

Morin, Lucie; Lim, Kenneth

2011-06-01

To review the literature with respect to the use of diagnostic ultrasound in the management of twin pregnancies. To make recommendations for the best use of ultrasound in twin pregnancies. Reduction in perinatal mortality and morbidity and short- and long-term neonatal morbidity in twin pregnancies. Optimization of ultrasound use in twin pregnancies. Published literature was retrieved through searches of PubMed and the Cochrane Library in 2008 and 2009 using appropriate controlled vocabulary (e.g., twin, ultrasound, cervix, prematurity) and key words (e.g., acardiac, twin, reversed arterial perfusion, twin-to-twin transfusion syndrome, amniotic fluid). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. There were no date restrictions. Studies were restricted to those with available English or French abstracts or text. Searches were updated on a regular basis and incorporated into the guideline to September 2009. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. The evidence collected was reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada, with input from members of the Maternal Fetal Medicine Committee and the Genetics Committee of the SOGC. The recommendations were made according to the guidelines developed by The Canadian Task Force on Preventive Health Care (Table 1). The benefit expected from this guideline is facilitation and optimization of the use of ultrasound in twin pregnancy. SUMMARY STATEMENTS: 1. There are insufficient data to make recommendations on repeat anatomical assessments in twin pregnancies. Therefore, a complete anatomical survey at each scan may not be needed following a complete

Electronic and magnetic properties of SnS2 monolayer doped with 4d transition metals

NASA Astrophysics Data System (ADS)

Xiao, Wen-Zhi; Xiao, Gang; Rong, Qing-Yan; Chen, Qiao; Wang, Ling-Ling

2017-09-01

We investigate the electronic structures and magnetic properties of SnS2 monolayers substitutionally doped with 4-d transition-metal through systematic first principles calculations. The doped complexes exhibit interesting electronic and magnetic behaviors, depending on the interplay between crystal field splitting, Hund's rule, and 4d levels. The system doped with Y is nonmagnetic metal. Both the Zr- and Pd-doped systems remain nonmagnetic semiconductors. Doping results in half-metallic states for Nb-, Ru-, Rh-, Ag, and Cd doped cases, and magnetic semiconductors for systems with Mo and Tc dopants. In particular, the Nb- and Mo-doped systems display long-ranged ferromagnetic ordering with Curie temperature above room temperature, which are primarily attributable to the double-exchange mechanism, and the p-d/p-p hybridizations, respectively. Moreover, The Mo-doped system has excellent energetic stability and flexible mechanical stability, and also possesses remarkable dynamic and thermal (500 K) stability. Our studies demonstrate that Nb- and Mo-doped SnS2 monolayers are promising candidates for preparing 2D diluted magnetic semiconductors, and hence will be a helpful clue for experimentalists.

The Experimental Study of Nuclear Astrophysics Reaction Rate of 93Zr(n,γ)94Zr

NASA Astrophysics Data System (ADS)

Gan, L.; Li, Z. H.; Su, J.; Yan, S. Q.; Guo, B.; Du, X. C.; Wu, Z. D.; Zeng, S.; Jin, S. J.; Wang, Y. B.; Bai, X. X.; Zhang, W. J.; Sun, H. B.; Li, E. T.

The slow neutron capture (s-) process plays a very important role in the nucleosynthesis, which produces about half of the elements heavier than iron. 94Zr is mainly from 93Zr(n,γ)94Zr in the s-process, and the direct component of the 93Zr(n,γ)94Zr capture reaction can be derived from the neutron spectroscopic factor of 94Zr. As the existing neutron spectroscopic factors of 94Zr vary from each other up to 60%, a new work should be adopted to measure it exactly. In the present work, the angular distributions of 94Zr(13C,13C)94Zr, 94Zr(12C,12C)94Zr and 94Zr(12C,13C)93Zr were obtained using the highprecision Q3D magnetic spectrograph. In addition, distorted-wave Born approximation (DWBA) calculations of the transfer differential cross sections were performed. The calculated result displays a good agreement with the experiment data, and a value of 2.60±0.20 for the neutron spectroscopic factor of 94Zr was extracted, and the direct capture cross section versus neutron energy of 93Zr(n,γ)94Zr for the ground state of 94Zr was obtained too.

High Temperature Deformation of Twin-Roll Cast Al-Mn-Based Alloys after Equal Channel Angular Pressing.

PubMed

Málek, Přemysl; Šlapáková Poková, Michaela; Cieslar, Miroslav

2015-11-12

Twin roll cast Al-Mn- and Al-Mn-Zr-based alloys were subjected to four passes of equal channel angular pressing. The resulting grain size of 400 nm contributes to a significant strengthening at room temperature. This microstructure is not fully stable at elevated temperatures and recrystallization and vast grain growth occur at temperatures between 350 and 450 °C. The onset of these microstructure changes depends on chemical and phase composition. Better stability is observed in the Al-Mn-Zr-based alloy. High temperature tensile tests reveal that equal channel angular pressing results in a softening of all studied materials at high temperatures. This can be explained by an active role of grain boundaries in the deformation process. The maximum values of ductility and strain rate sensitivity parameter m found in the Al-Mn-Zr-based alloy are below the bottom limit of superplasticity (155%, m = 0.25). However, some features typical for superplastic behavior were observed-the strain rate dependence of the parameter m , the strengthening with increasing grain size, and the fracture by diffuse necking. Grain boundary sliding is believed to contribute partially to the overall strain in specimens where the grain size remained in the microcrystalline range.

High Temperature Deformation of Twin-Roll Cast Al-Mn-Based Alloys after Equal Channel Angular Pressing

PubMed Central

Málek, Přemysl; Šlapáková Poková, Michaela; Cieslar, Miroslav

2015-01-01

Twin roll cast Al-Mn- and Al-Mn-Zr-based alloys were subjected to four passes of equal channel angular pressing. The resulting grain size of 400 nm contributes to a significant strengthening at room temperature. This microstructure is not fully stable at elevated temperatures and recrystallization and vast grain growth occur at temperatures between 350 and 450 °C. The onset of these microstructure changes depends on chemical and phase composition. Better stability is observed in the Al-Mn-Zr-based alloy. High temperature tensile tests reveal that equal channel angular pressing results in a softening of all studied materials at high temperatures. This can be explained by an active role of grain boundaries in the deformation process. The maximum values of ductility and strain rate sensitivity parameter m found in the Al-Mn-Zr-based alloy are below the bottom limit of superplasticity (155%, m = 0.25). However, some features typical for superplastic behavior were observed—the strain rate dependence of the parameter m, the strengthening with increasing grain size, and the fracture by diffuse necking. Grain boundary sliding is believed to contribute partially to the overall strain in specimens where the grain size remained in the microcrystalline range. PMID:28793667

Sports pairs: insights on athletic talent; research reviews: twins with leukemia; parents and twins.

PubMed

Segal, Nancy L

2007-06-01

Twin research exploring genetic and environmental influences on athletic interests and talents is reviewed. Illustrative examples of twin athletes representing a variety of sports activities are presented. This is followed by an overview of twin studies offering critical insights into the onset and progress of leukemia. In the last section, timely events involving twins and parents of twins will be described--each case provides a new look at an old question.

Anisotropic magnetic susceptibility of erbium and ytterbium in zircon, ZrSiO4

USGS Publications Warehouse

Thorpe, A.N.; Briggs, Charles; Tsang, T.; Senftle, F.; Alexander, Corrine

1977-01-01

Magnetic susceptibility measurements have been made for both Er- and Yb-doped (1̃03ppm) zircon single crystals with the magnetic field perpendicular and parallel to the [001] axis. Large susceptibility anisotropies were found in both cases. Our observed anisotropies of ZrSiO4: Yb indicate small populations (1̃9%) of Yb ions at the axial (tetragonal) sites, as the susceptibility of ZrSiO4: Yb would be nearly isotropic if the Yb ions only occupied the orthorhombic sites. For Er3+ in orthorhombic sites of zircon, our data indicate that the first excited state is paramagnetic with gx = 9 and gy 5̃ at 20 cm-1 above the ground state (gx 0̃, gy 1̃5). The first excited state is quite similar to the ground states observed for Er3+ in many host lattices. ?? 1977.

The Brazilian Twin Registry.

PubMed

Ferreira, Paulo H; Oliveira, Vinicius C; Junqueira, Daniela R; Cisneros, Lígia C; Ferreira, Lucas C; Murphy, Kate; Ordoñana, Juan R; Hopper, John L; Teixeira-Salmela, Luci F

2016-12-01

The Brazilian Twin Registry (BTR) was established in 2013 and has impelled twin research in South America. The main aim of the initiative was to create a resource that would be accessible to the Brazilian scientific community as well as international researchers interested in the investigation of the contribution of genetic and environmental factors in the development of common diseases, phenotypes, and human behavior traits. The BTR is a joint effort between academic and governmental institutions from Brazil and Australia. The collaboration includes the Federal University of Minas Gerais (UFMG) in Brazil, the University of Sydney and University of Melbourne in Australia, the Australian Twin Registry, as well as the research foundations CNPq and CAPES in Brazil. The BTR is a member of the International Network of Twin Registries. Recruitment strategies used to register twins have been through participation in a longitudinal study investigating genetic and environmental factors for low back pain occurrence, and from a variety of sources including media campaigns and social networking. Currently, 291 twins are registered in the BTR, with data on demographics, zygosity, anthropometrics, and health history having been collected from 151 twins using a standardized self-reported questionnaire. Future BTR plans include the registration of thousands of Brazilian twins identified from different sources and collaborate nationally and internationally with other research groups interested on twin studies.

Effect of different Zr contents on properties and microstructure of Cu-Cr-Zr alloys

NASA Astrophysics Data System (ADS)

Jinshui, Chen; Bin, Yang; Junfeng, Wang; Xiangpeng, Xiao; Huiming, Chen; Hang, Wang

2018-02-01

The crystallography and morphology of precipitate particles of Cu-Cr-Zr alloys with varying Zr contents were studied by transmission electron microscopy (TEM) after solution treatments at 950 °C for 1 h and aging treatments at 500 °C for different times ranged from 0.5 h to 24 h. The microhardness and electrical conductivity of Cu-Cr-Zr alloys after various aging process were tested. The results show that the microhardness and electrical conductivity rapidly increased at first, then the microhardness decreased slowly after reaching the peak, while the conductivity continues to increase. Nano-scaled precipitates exhibit two kinds of morphology (coffee bean and ellipse shaped). With increasing Zr content, the Zr-containing precipitation sequence of Cu-Cr-Zr alloys at peak-ageing is Heusler CrCu2Zr → Cu5Zr → Cu4Zr. The Heusler CrCu2Zr phase decomposed into fine and homogeneous Cr and Cu4Zr, resulting in improved alloy properties.

Twin Loss: Implications for Counselors Working with Surviving Twins.(practice & Theory)

ERIC Educational Resources Information Center

Withrow, Rebecca; Schwiebert, Valerie L.

2005-01-01

Multiple births are becoming increasingly prevalent due to the use of fertility drugs and women choosing to wait until later life to conceive. With the growth in the twin population, little research has been done to investigate the effects on the grief process when 1 twin dies. Counselors must understand the unique experience of twins to formulate…

Is That Me or My Twin? Lack of Self-Face Recognition Advantage in Identical Twins

PubMed Central

Martini, Matteo; Bufalari, Ilaria; Stazi, Maria Antonietta; Aglioti, Salvatore Maria

2015-01-01

Despite the increasing interest in twin studies and the stunning amount of research on face recognition, the ability of adult identical twins to discriminate their own faces from those of their co-twins has been scarcely investigated. One’s own face is the most distinctive feature of the bodily self, and people typically show a clear advantage in recognizing their own face even more than other very familiar identities. Given the very high level of resemblance of their faces, monozygotic twins represent a unique model for exploring self-face processing. Herein we examined the ability of monozygotic twins to distinguish their own face from the face of their co-twin and of a highly familiar individual. Results show that twins equally recognize their own face and their twin’s face. This lack of self-face advantage was negatively predicted by how much they felt physically similar to their co-twin and by their anxious or avoidant attachment style. We speculate that in monozygotic twins, the visual representation of the self-face overlaps with that of the co-twin. Thus, to distinguish the self from the co-twin, monozygotic twins have to rely much more than control participants on the multisensory integration processes upon which the sense of bodily self is based. Moreover, in keeping with the notion that attachment style influences perception of self and significant others, we propose that the observed self/co-twin confusion may depend upon insecure attachment. PMID:25853249

Interface structures and twinning mechanisms of {1¯012} twins in hexagonal metals

DOE PAGES

Gong, Mingyu; Hirth, John P.; Liu, Yue; ...

2017-06-07

In this paper, a controversy concerning the description of {1¯012} {1¯012} twinning, whether it is shear-shuffle or pure glide-shuffle or pure shuffle, has developed. There is disagreement about the interpretation of transmission electron microscopic observations, atomistic simulations and theories for twin growth. In this article, we highlight the atomic-level, characteristic, equilibrium and non-equilibrium boundaries and corresponding boundary defects associated with the three-dimensional ‘normal’, ‘forward’ and ‘lateral’ propagation of {1¯011} growth/annealing and deformation twins. Although deformation twin boundaries (TBs) after recovery exhibit some similarity to growth/annealing TBs because of the plastic accommodation of stress fields, there are important distinctions among them.more » These distinctions distinguish among the mechanisms of twin growth and resolve the controversy. In addition, a new type of disconnection, a glide disclination, is described for twinning. Synchroshear, seldom considered, is shown to be a likely mechanism for {1¯012} twinning.« less

Fine Structure in Multi-Phase Zr8Ni21-Zr7Ni10-Zr2Ni7 Alloy Revealed by Transmission Electron Microscope

PubMed Central

Shen, Haoting; Bendersky, Leonid A.; Young, Kwo; Nei, Jean

2015-01-01

The microstructure of an annealed alloy with a Zr8Ni21 composition was studied by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The presence of three phases, Zr8Ni21, Zr2Ni7, and Zr7Ni10, was confirmed by SEM/X-ray energy dispersive spectroscopy compositional mapping and TEM electron diffraction. Distribution of the phases and their morphology can be linked to a multi-phase structure formed by a sequence of reactions: (1) L → Zr2Ni7 + L’; (2) peritectic Zr2Ni7 + L’ → Zr2Ni7 + Zr8Ni21 + L”; (3) eutectic L” → Zr8Ni21 + Zr7Ni10. The effect of annealing at 960 °C, which was intended to convert a cast structure into a single-phase Zr8Ni21 structure, was only moderate and the resulting alloy was still multi-phased. TEM and crystallographic analysis of the Zr2Ni7 phase show a high density of planar (001) defects that were explained as low-energy boundaries between rotational variants and stacking faults. The crystallographic features arise from the pseudo-hexagonal structure of Zr2Ni7. This highly defective Zr2Ni7 phase was identified as the source of the broad X-ray diffraction peaks at around 38.4° and 44.6° when a Cu-K was used as the radiation source. PMID:28793460

Twins Eye Study in Tasmania (TEST): Rationale and Methodology to Recruit and Examine Twins

PubMed Central

Mackey, David A; MacKinnon, Jane R; Brown, Shayne A; Kearns, Lisa S; Ruddle, Jonathan B; Sanfilippo, Paul G; Sun, Cong; Hammond, Christopher J; Young, Terri L; Martin, Nicholas G; Hewitt, Alex W

2013-01-01

Visual impairment is a leading cause for morbidity and poor quality of life in our community. Unravelling the mechanisms underpinning important blinding diseases could allow for preventative or curative steps to be implemented. Twin siblings provide a unique opportunity in biology to discover genes associated with numerous eye diseases and ocular biometry. Twins are particularly useful for quantitative trait analysis through genome-wide association and linkage studies. Although many studies involving twins rely on twin registries, we present our approach to the Twins Eye Study in Tasmania to provide insight into possible recruitment strategies, expected participation rates and potential examination strategies that can be considered by other researchers for similar studies. Five separate avenues for cohort recruitment were adopted: 1) piggy-backing existing studies where twins had been recruited; 2); utilising the national twin registry; 3) word of mouth and local media publicity; 4) directly approaching schools; and finally 5) collaborating with other research groups studying twins. PMID:19803772

The Italian Twin Project: from the personal identification number to a national twin registry.

PubMed

Stazi, Maria Antonietta; Cotichini, Rodolfo; Patriarca, Valeria; Brescianini, Sonia; Fagnani, Corrado; D'Ippolito, Cristina; Cannoni, Stefania; Ristori, Giovanni; Salvetti, Marco

2002-10-01

The unique opportunity given by the "fiscal code", an alphanumeric identification with demographic information on any single person residing in Italy, introduced in 1976 by the Ministry of Finance, allowed a database of all potential Italian twins to be created. This database contains up to now name, surname, date and place of birth and home address of about 1,300,000 "possible twins". Even though we estimated an excess of 40% of pseudo-twins, this still is the world's largest twin population ever collected. The database of possible twins is currently used in population-based studies on multiple sclerosis, Alzheimer's disease, celiac disease, and type 1 diabetes. A system is currently being developed for linking the database with data from mortality and cancer registries. In 2001, the Italian Government, through the Ministry of Health, financed a broad national research program on twin studies, including the establishment of a national twin registry. Among all the possible twins, a sample of 500,000 individuals are going to be contacted and we expect to enrol around 120,000 real twin pairs in a formal Twin Registry. According to available financial resources, a sub sample of the enrolled population will be asked to donate DNA. A biological bank from twins will be then implemented, guaranteeing information on future etiological questions regarding genetic and modifiable factors for physical impairment and disability, cancers, cardiovascular diseases and other age related chronic illnesses.

Probing the Role of Zr Addition versus Textural Properties in Enhancement of CO 2 Adsorption Performance in Silica/PEI Composite Sorbents

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

Sakwa-Novak, Miles A.; Holewinski, Adam; Hoyt, Caroline B.

2015-08-08

Polymeric amines such as poly(ethylenimine) (PEI) supported on mesoporous oxides are promising candidate adsorbents for CO 2 capture processes. One important aspect to the design and optimization of these materials is a fundamental understanding of how the properties of the oxide support such as pore structure, particle morphology, and surface properties affect the efficiency of the guest polymer in its interactions with CO 2. Previously, the efficiency of impregnated PEI to adsorb CO 2 was shown to increase upon the addition of Zr as a surface modifier in SBA-15. But, the efficacy of this method to tune the adsorption performancemore » has not been explored in materials of differing textural and morphological nature. These issues are directly addressed via the preparation of an array of SBA-15 support materials with varying textural and morphological properties, as well as varying content of zirconium doped into the material. Zirconium is incorporated into the SBA-15 either during the synthesis of the SBA-15, or postsynthetically via deposition of Zr species onto pure-silica SBA-15. The method of Zr incorporation alters the textural and morphological properties of the parent SBA-15 in different ways. Importantly, the CO 2 capacity of SBA-15 impregnated with PEI increases by a maximum of ~60% with the quantity of doped Zr for a “standard” SBA-15 containing significant microporosity, while no increase in the CO 2 capacity is observed upon Zr incorporation for an SBA-15 with reduced microporosity and a larger pore size, pore volume, and particle size. Finally, adsorbents supported on SBA-15 with controlled particle morphology show only modest increases in CO 2 capacity upon inclusion of Zr to the silica framework. The data demonstrate that the textural and morphological properties of the support have a more significant impact on the ability of PEI to capture CO 2 than the support surface composition.« less

Twin births in the Comoros.

PubMed

Abdul, M A

2000-11-01

To determine the prevalence and clinical significance of twin births in the Comoros Islands. Combined retrospective and non-randomised prospective study. Hospital El-Ma'aru Moroni Grand-Comoros and Center Medico-Chirurgical Domoni-Anjouan. One hundred and nine patients with twin deliveries. During the period of study, there were 4370 deliveries, out of which 109 were twin births, giving an incidence rate of 25/1,000 deliveries. Twin births rate increased with increasing parity. The perinatal mortality rate of twin delivery was seven times that of singleton. Low birthweight rate was 54% among twin births. Retention rate of second twin was 12%, with home delivery of the first co-twin in 62% of cases. Uterine atony and malpresentation were the principal factors in the aetiology of retained second twin. Multiple pregnancy is common in the Comoros and the epidemiology and clinical significance are consistent with established data. Clinicians and midwives in Comoros must be aware of these facts, and endeavour to make early diagnosis and institute appropriate management within the available scarce resources, in order to improve maternal and foetal outcome of twin births.

Superconductivity and charge density wave in ZrTe 3–xSe x

DOE PAGES

Zhu, Xiangde; Ning, Wei; Li, Lijun; ...

2016-06-02

Charge density wave (CDW), the periodic modulation of the electronic charge density, will open a gap on the Fermi surface that commonly leads to decreased or vanishing conductivity. On the other hand superconductivity, a commonly believed competing order, features a Fermi surface gap that results in infinite conductivity. Here we report that superconductivity emerges upon Se doping in CDW conductor ZrTe 3 when the long range CDW order is gradually suppressed. Superconducting critical temperature T c(x) in ZrTe 3–xSe x (0 ≤ x ≤ 0.1) increases up to 4 K plateau for 0.04 ≤ x ≤ 0.07. Further increase inmore » Se content results in diminishing T c and filametary superconductivity. The CDW modes from Raman spectra are observed in x = 0.04 and 0.1 crystals, where signature of ZrTe 3 CDW order in resistivity vanishes. As a result, the electronic-scattering for high T c crystals is dominated by local CDW fluctuations at high temperatures, the resistivity is linear up to highest measured T = 300 K and contributes to substantial in-plane anisotropy.« less

The formation mechanisms of surface nanocrystallites in β-type biomedical TiNbZrFe alloy by surface mechanical attrition treatment

NASA Astrophysics Data System (ADS)

Jin, Lei; Cui, Wenfang; Song, Xiu; Zhou, Lian

2015-08-01

A nanostructured surface layer was successfully performed on a biomedical β-type TiNbZrFe alloy by surface mechanical attrition treatment (SMAT). The results reveal that the surface layer along the depth from treated surface to strain-free matrix could be divided into an outer nanocrystalline layer (0-30 μm), a high-density dislocation region (30-200 μm) and an inner region with low-density dislocations and twins (200-700 μm) when the surface was treated for 60 min. The microhardness of the surface layer is enhanced and increases with increasing treatment time. Although the {1 1 2} <1 1 1> twin coordinates the deformations with dislocations, this coordination only occurs in the low strain area and cannot affect the nanocrystalline formation. The self-nanocrystallization of TiNbZrFe alloy is mainly attributed to dislocation movements. First, the dislocations start to move and easily form dislocation bands along certain crystal directions; then, multiple slips of dislocations gradually form dislocation tangles; after that, high-density dislocation tangles increases, which divides primary grains into many small domain areas. As high strain energies accumulate on the interfaces among these areas, the lattice rotation can be driven between the adjacent small domain areas, finally resulting in a large number of nanocrystalline regions with low or large angle grain boundaries.

Rational Design of Zirconium-doped Titania Photocatalysts with Synergistic Brønsted Acidity and Photoactivity.

PubMed

Ma, Runyuan; Wang, Liang; Zhang, Bingsen; Yi, Xianfeng; Zheng, Anmin; Deng, Feng; Yan, Xuhua; Pan, Shuxiang; Wei, Xiao; Wang, Kai-Xue; Su, Dang Sheng; Xiao, Feng-Shou

2016-10-06

The preparation of photocatalysts with high activities under visible-light illumination is challenging. We report the rational design and construction of a zirconium-doped anatase catalyst (S-Zr-TiO 2 ) with Brønsted acidity and photoactivity as an efficient catalyst for the degradation of phenol under visible light. Electron microscopy images demonstrate that the zirconium sites are uniformly distributed on the sub-10 nm anatase crystals. UV-visible spectrometry indicates that the S-Zr-TiO 2 is a visible-light-responsive catalyst with narrower band gap than conventional anatase. Pyridine-adsorption infrared and acetone-adsorption 13 C NMR spectra confirm the presence of Brønsted acidic sites on the S-Zr-TiO 2 sample. Interestingly, the S-Zr-TiO 2 catalyst exhibits high catalytic activity in the degradation of phenol under visible-light illumination, owing to a synergistic effect of the Brønsted acidity and photoactivity. Importantly, the S-Zr-TiO 2 shows good recyclability. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

CoSMoS and TwinPaW: initial report on two new German twin studies.

PubMed

Spinath, Frank M; Wolf, Heike

2006-12-01

After briefly recapitulating two earlier German twin studies (BiLSAT and GOSAT), we present two new German twin studies with a longitudinal perspective: CoSMoS and TwinPaW. The twin study on Cognitive ability, Self-reported Motivation and School performance (CoSMoS) aims to investigate predictors and influences of school performance in a genetically sensitive design, beginning with children in late elementary school. The Twin study on Personality And Wellbeing (TwinPaW) focuses on adult personality and its relation to physical health as well as health-related behavior in an adult sample of twins. Both studies are characterized by an effort to recruit new large twin samples through a novel recruitment procedure aimed at reducing self-selective sampling. In two German federal states, contact information on persons born on the same day and with the same name was retrieved from record sections. From the resulting pool of more than 36,000 addresses we contacted approximately 2000 parents of twins aged 9 and 10 for CoSMoS, as well as 2000 adult twin pairs for TwinPaW by telephone and mail. Personal contact by telephone proved to be more efficient with agreement rates of 63% in the children sample and 65% in the adult sample. In this article we briefly describe the rationale and the study aims of CoSMoS and TwinPaW as well as the characteristics of the sample we have recruited so far.

Twins, Triplets, and Other Multiples

MedlinePlus

... one baby naturally. Another reason is that more women are using fertility treatments to help them conceive. How twins are formed Twins form in one of two ways: Identical twins occur when a single fertilized egg splits into two. Identical twins look ...

Diffuse Phase Transitions and Giant Electrostrictive Coefficients in Lead-Free Fe3+-Doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 Ferroelectric Ceramics.

PubMed

Jin, Li; Huo, Renjie; Guo, Runping; Li, Fei; Wang, Dawei; Tian, Ye; Hu, Qingyuan; Wei, Xiaoyong; He, Zhanbing; Yan, Yan; Liu, Gang

2016-11-16

The electrostrictive effect has some advantages over the piezoelectric effect, including temperature stability and hysteresis-free character. In the present work, we report the diffuse phase transitions and electrostrictive properties in lead-free Fe 3+ -doped 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BZT-0.5BCT) ferroelectric ceramics. The doping concentration was set from 0.25 to 2 mol %. It is found that by introducing Fe 3+ ion into BZT-0.5BCT, the temperature corresponding to permittivity maximum T m was shifted toward lower temperature monotonically by 37 °C per mol % Fe 3+ ion. Simultaneously, the phase transitions gradually changed from classical ferroelectric-to-paraelectric phase transitions into diffuse phase transitions with a weak relaxor characteristic. Purely electrostrictive responses with giant electrostrictive coefficient Q 33 between 0.04 and 0.05 m 4 /C 2 are observed from 25 to 100 °C for the compositions doped with 1-2 mol % Fe 3+ ion. The Q 33 of Fe 3+ -doped BZT-0.5BCT ceramics is almost twice the Q 33 of other ferroelectric ceramics. These observations suggest that the present system can be considered as a potential lead-free material for the applications in electrostrictive area and that BT-based ferroelectric ceramics would have giant electrostrictive coefficient over other ferroelectric systems.

Surface Crystallization of a MgO/Y2O3/SiO2/Al2O3/ZrO2 Glass: Growth of an Oriented β-Y2Si2O7 Layer and Epitaxial ZrO2

PubMed Central

Wisniewski, Wolfgang; Seidel, Sabrina; Patzig, Christian; Rüssel, Christian

2017-01-01

The crystallization behavior of a glass with the composition 54.7 SiO2·10.9 Al2O3·15.0 MgO·3.4 ZrO2·16.0 Y2O3 is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD) and (scanning) transmission electron microscopy [(S)TEM] including energy-dispersive X-ray spectrometry (EDXS). This glass shows the sole surface crystallization of four different yttrium silicates of the composition Y2Si2O7 (YS). The almost simultaneous but independent nucleation of α-, β-, δ-, and ε-YS at the surface is followed by growth into the bulk, where ε-YS quickly dominates a first crystallized layer. An accumulation of Mg at the growth front probably triggers a secondary nucleation of β-YS, which forms a thin compact layer before fragmenting into a highly oriented layer of fine grained crystals occupying the remaining bulk. The residual glass between the YS growth structures allows the crystallization of indialite, yttrium stabilized ZrO2 (Y-ZrO2) and very probably μ-cordierite during cooling. Hence, this glass basically shows the inverted order of crystallization observed in other magnesium yttrium alumosilicate glasses containing less Y2O3. An epitaxial relationship between Y-ZrO2 and ε-YS is proven and multiple twinning relationships occur in the YS phases. PMID:28281661

Novel ZrO2 based ceramics stabilized by Fe2O3, SiO2 and Y2O3

NASA Astrophysics Data System (ADS)

Rada, S.; Culea, E.; Rada, M.

2018-03-01

Samples in the 5Fe2O3·10SiO2·xY2O3·(85-x)ZrO2 composition where x = 5, 10 and 15 mol% Y2O3 were synthesized and investigated by XRD, SEM, density measurements, FTIR, UV-Vis, EPR and PL spectroscopies. X-ray diffraction patterns confirm the presence of the tetragonal and cubic ZrO2 crystalline phases in all samples. The IR data show the overlaps of absorption bands assigned to Zrsbnd Osbnd Zr and Sisbnd Osbnd linkages in samples. UV-Vis and PL data indicate higher concentrations of intrinsic defects by doping with Y2O3 concentrations. The EPR spectra are characterized by two resonance lines situated at about g ∼ 4.3 and g ∼ 2 for lower Y2O3 contents.

Synthesis of Zr2WP2O12/ZrO2 Composites with Adjustable Thermal Expansion.

PubMed

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.

An Investigation of Exceptional Twins.

ERIC Educational Resources Information Center

Crismore, Avon

The author, herself a mother of twins, reviews research on exceptional twins. She considers reasons for fascination with twins and comments upon important advances in technology. Current research in Indianapolis to measure cognitive, perceptual, personality, and chromosome patterns of twins is described. Differences in the makeup of identical and…

Resistive switching mechanism of Ag/ZrO2:Cu/Pt memory cell

NASA Astrophysics Data System (ADS)

Long, Shibing; Liu, Qi; Lv, Hangbing; Li, Yingtao; Wang, Yan; Zhang, Sen; Lian, Wentai; Zhang, Kangwei; Wang, Ming; Xie, Hongwei; Liu, Ming

2011-03-01

Resistive switching mechanism of zirconium oxide-based resistive random access memory (RRAM) devices composed of Cu-doped ZrO2 film sandwiched between an oxidizable electrode and an inert electrode was investigated. The Ag/ZrO2:Cu/Pt RRAM devices with crosspoint structure fabricated by e-beam evaporation and e-beam lithography show reproducible bipolar resistive switching. The linear I- V relationship of low resistance state (LRS) and the dependence of LRS resistance ( R ON) and reset current ( I reset) on the set current compliance ( I comp) indicate that the observed resistive switching characteristics of the Ag/ZrO2:Cu/Pt device should be ascribed to the formation and annihilation of localized conductive filaments (CFs). The physical origin of CF was further analyzed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). CFs were directly observed by cross-sectional TEM. According to EDS and elemental mapping analysis, the main chemical composition of CF is determined by Ag atoms, coming from the Ag top electrode. On the basis of these experiments, we propose that the set and reset process of the device stem from the electrochemical reactions in the zirconium oxide under different external electrical stimuli.

Ventricular strain changes in monochorionic twins with and without twin-to-twin transfusion syndrome.

PubMed

Taylor-Clarke, Marisa C; Matsui, Hikoro; Roughton, Michael; Wimalasundera, Ruwan C; Gardiner, Helena M

2013-06-01

The objective of the study was to investigate whether vector velocity imaging (VVI), a non-Doppler speckle tracking ultrasound technology, is feasible in twin pregnancies and can aid management of twin-twin transfusion syndrome (TTTS). Twenty-seven women pregnant with monochorionic diamniotic twins affected by TTTS and 28 monochorionic pregnancies that did not develop TTTS were included in a prospective case-control study at a fetal medicine center. Fetal echocardiograms were recorded with dummy electrocardiography to retain original frame rates when exported for offline speckle tracking analysis using Syngo-VVI software (Siemens Corp, Munich, Germany). Right and left ventricular (LV) free wall Lagrangian strain was measured from the original coordinates. Within-twin pair ventricular strain differences including relationship to Quintero staging and response to laser therapy for TTTS were analyzed by Wilcoxon signed-rank test. The VVI strain measurements could be analyzed in 182 of 200 TTTS and 96 of 112 non-TTTS control ventricles. Within-pair strain was concordant in non-TTTS controls. Recipient LV strain was reduced at all Quintero stages compared with donors (P < .01). Recipient right ventricular strain was reduced only in stages 3 and 4 (P < .01). Strain improved at a median of 2 weeks following successful laser therapy. Intertwin differences in strain were independent of weight discordance. Recipient LV strain is reduced in stages 1 and 2 TTTS. Within-pair strain discordance may distinguish early TTTS from growth discordance and guide timing of and management following treatment. Copyright © 2013 Mosby, Inc. All rights reserved.

Effect of geometrical constraint condition on the formation of nanoscale twins in the Ni-based metallic glass composite

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

Lee, M H; Kim, B S; Kim, D H

2014-04-25

We investigated the effect of geometrically constrained stress-strain conditions on the formation of nanotwins in alpha-brass phase reinforced Ni59Zr20Ti16Si2Sn3 metallic glass (MG) matrix deformed under macroscopic uniaxial compression. The specific geometrically constrained conditions in the samples lead to a deviation from a simple uniaxial state to a multi-axial stress state, for which nanocrystallization in the MG matrix together with nanoscale twinning of the brass reinforcement is observed in localized regions during plastic flow. The nanocrystals in the MG matrix and the appearance of the twinned structure in the reinforcements indicate that the strain energy is highly confined and the localmore » stress reaches a very high level upon yielding. Both the effective distribution of reinforcements on the strain enhancement of composite and the effects of the complicated stress states on the development of nanotwins in the second-phase brass particles are discussed.« less

Myeloproliferative Neoplasms in Danish Twins.

PubMed

Andersen, Michael Asger; Bjerrum, Ole Weis; Ranjan, Ajenthen; Skov, Vibe; Kruse, Torben A; Thomassen, Mads; Skytthe, Axel; Hasselbalch, Hans Carl; Christensen, Kaare

2018-01-01

Myeloproliferative neoplasms (MPNs) are a heterogeneous group of diseases characterized by clonal hyperproliferation of immature and mature cells of the myeloid lineage. Genetic differences have been proposed to play a role in the development of MPNs. Monozygotic twin pairs with MPNs have been reported in a few case reports, but the MPN concordance pattern in twins remains unknown. All twin pairs born in the period 1900-2010 were identified in the nationwide Danish Twin Registry. Only pairs with both twins alive on January 1, 1977, and those born thereafter were included to allow identification in the Danish National Patient Registry. A total of 158 twin pairs were registered with an MPN diagnosis: 36 monozygotic, 104 dizygotic, and 18 pairs with unknown zygosity. MPNs were diagnosed in both twins in 4 pairs. The probandwise concordance rates for monozygotic twin pairs were higher than for dizygotic twin pairs (15 vs. 0%; p = 0.016). An estimated concordance rate of 15% (95% CI 0.059-0.31) is modest, but given the rarity of MPNs this finding is clinically relevant and provides further support for the role of genetic predisposition in the development of MPNs. © 2018 S. Karger AG, Basel.

I. 'Street of twins': multiple births in Cuba II. The Cuban twin registry: an update / twin research reports: cord entanglement; heritability of clubfoot; school separation / twins and twin researchers in the news: reunited at seventy-eight; basketball duo dissolved; delivered holding hands; the better brew; award winners.

PubMed

Segal, Nancy L; Marcheco-Teruel, Beatriz

2014-08-01

I was part of a people-to-people tour of Havana, Cuba during the first week in April 2014. Among the many highlights of that adventure were an informal meeting with Dr Beatriz Marcheco-Teruel, from Cuba's National Center for Medical Genetics, and a visit to the famous 'Street of Twins'. A fortuitous meeting with parents of twins in the fishing town of Jaimanitas was also an extraordinary event. The Cuban experience is followed by summaries of recent twin research, covering umbilical cord entanglement, the heritability of clubfoot and school separation policies for twins. Media reports include twins reunited at age 78, the future of UCLA's twin basketball players, MZ twins born holding hands, a twin conflict over beer and a pair of American Psychological Association honors for Drs Nancy L. Segal and Thomas J. Bouchard, Jr.

Effect of ambient oxygen on the photoluminescence of sol-gel-derived nanocrystalline ZrO2:Eu,Nb

NASA Astrophysics Data System (ADS)

Puust, Laurits; Kiisk, Valter; Eltermann, Marko; Mändar, Hugo; Saar, Rando; Lange, Sven; Sildos, Ilmo; Dolgov, Leonid; Matisen, Leonard; Jaaniso, Raivo

2017-06-01

The development of inorganic nanophosphors is an active research field due to many applications, including optical gas sensing materials. We found a systematic dependence of the photoluminescence (PL) of europium (Eu3+) impurity ions in zirconia (ZrO2) nanocrystals on the ambient oxygen concentration in a O2/N2 mixture at normal pressure. Europium-doped ZrO2 powders were synthesized via a sol-gel route. Heat-treatment at 1200 °C resulted in a well-developed monoclinic phase (XRD crystallite size of ~50 nm) and an intense PL of Eu3+ ions residing in the dominant phase (Eu3+ was excited directly at 395 or 464 nm). Co-doping with niobium resulted in a narrowing of the PL emission lines. Only Nb5+ was detected by XPS and is believed to charge-compensate Eu3+ activators throughout the material leading to a more regular crystal lattice. At room temperature, the exposure to oxygen suppressed the Eu3+ fluorescence, whereas, at elevated temperatures (300 °C), the effect was reversed. At 300 °C and under a focused continuous laser beam, a substantial PL response (>50%) was achieved when switching 100% of N2 for 100% of O2. PL decay kinetics clearly showed that at 300 °C fluorescence quenching centers were induced within the material by oxygen desorption. The relatively fast (<5 min) and sub-linear PL response to the changes of oxygen concentration shows that ZrO2:Eu,Nb is a promising PL-based oxygen sensing material over a wide-range of oxygen pressures.

Systematic investigation of structural and morphological studies on doped TiO2 nanoparticles for solar cell applications

NASA Astrophysics Data System (ADS)

Murugadoss, G.; Jayavel, R.; Rajesh Kumar, M.

2014-12-01

Optical, structural and thermal properties of the doped with different ions (transition metals, other metals or post transition metals, non-metals, alkali metals and lanthanides) in TiO2 nanocrystals were investigated. The doped nanoparticles were synthesized by modified chemical method. Ethanol-deionised water mixer (20:1) was used as solvent for synthesize of the undoped and doped TiO2 nanoparticles. Systematic studies on structural and morphological changes by thermal treatment on TiO2 were examined. It has been observed that with Eu and Al doping TiO2, the phase transition temperature for anatase to rutile phase increased. Blue and red shifting absorptions were observed for doped TiO2 in visible region. Among the dopant, significant blue shift was obtained for Cu, Cd, Ag, Y, Ce and In doped TiO2 and red shift was obtained for Zr, Sm, Al, Na, S, Fe, Ni, Eu and Gd doped TiO2 nanoparticles.

Structural and compositional evolution of Al{sub 3}(Zr,Y) precipitates in Al-Zr-Y alloy

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

Gao, Haiyan, E-mail: gaohaiyan@sjtu.edu.cn

Structural and compositional evolution of Al{sub 3}(Zr,Y) precipitates in aged Al-Zr-Y alloy was investigated through atom probe tomography (APT) and transmission electron microscope (TEM) analysis and first principles calculations. The results show that short-bar-shaped D0{sub 19}-Al{sub 3}Y with some Zr atoms dissolved in precipitated at the very beginning of decomposition and worked as heterogeneous nuclei for L1{sub 2}-Al{sub 3}Zr with spherical morphology after being aged at 400 °C for 2 h. Quasi-static coarsening happened as the aging treatment lasted from 2 h to 200 h. However, distribution of Zr and Y atoms in Al{sub 3}(Zr,Y) is nearly uniform and Al{submore » 3}(Zr,Y) do not have the typical “Al{sub 3}RE core-Al{sub 3}Zr shell” structure which observed in other RE containing Al-Zr-RE alloys with L1{sub 2}-Al{sub 3}RE as nuclei. First principles calculations revealed that binding energy between Y and Zr is strong during the growth of Al{sub 3}(Zr,Y), which led to the co-precipitation of Y and Zr atoms and attribute to the evolution of Al{sub 3}(Zr,Y). - Highlights: •Al{sub 3}Y precipitated firstly and then became nuclei for Al{sub 3}Zr during aging of Al-Zr-Y. •Al{sub 3}(Zr,Y) precipitates do not have the typical “Al{sub 3}Y core-Al{sub 3}Zr shell” structure. •Strong binding between Y and Zr led to the co-precipitation of Y and Zr atoms.« less

Fabrication and electrical properties of a (Pb,La)(Zr,Ti)O3 capacitor with pulsed laser deposited Sn-doped In2O3 bottom electrode on Al2O3(0001)

NASA Astrophysics Data System (ADS)

Takada, Yoko; Tamano, Rika; Okamoto, Naoki; Saito, Takeyasu; Yoshimura, Takeshi; Fujimura, Norifumi; Higuchi, Koji; Kitajima, Akira

2017-07-01

A Sn-doped In2O3 (ITO) electrode was deposited on Al2O3(0001) using pulsed laser deposition at different oxygen pressures to create the bottom electrode of a (Pb,La)(Zr,Ti)O3 (PLZT) capacitor. The crystallographic orientation of the ITO films was controlled via the oxygen pressure. At 600 °C the (111) peak became dominant when the O2 pressure was increased, and when the pressure reached 2.0 Pa the ITO films became preferentially (111) oriented. The remnant polarization was 58.8-90.7 and 46.0-47.5 µC/cm2 for the Pt/PLZT/ITO and ITO/PLZT/ITO capacitors, respectively; the ferroelectric properties of these capacitors were also determined.

Insight into mechanical properties and thermoelectric efficiency of Zr2CoZ (Z  =  Si, Ge) Heusler alloys

NASA Astrophysics Data System (ADS)

Yousuf, Saleem; Gupta, Dinesh C.

2017-11-01

We investigated the electronic, mechanical and thermoelectric properties of Zr2CoZ (Z  =  Si, Ge) Heusler alloys using the first-principles calculation. From the analysis of various elastic constants, the shear and Young’s moduli, Poisson’s ratio, the ductile nature of the alloys is predicted. Thermoelectric coefficients viz., Seebeck, electrical conductivity and figure of merit show Zr2CoZ alloys as n-type thermoelectric materials showing linearly increasing Seebeck coefficient with temperature. The value of total absolute Seebeck coefficients at 1200 K of Zr2CoSi and Zr2CoGe are 60 µV K-1 and 40 µV K-1 respectively mainly because of the existence of almost flat conduction bands along L to Г directions of high symmetry Brillouin zone. Further, the chemical potential variation of power factor confirms the n-type doping fruitful to increase their TE performance. The figure of merit achieves an upper-limit of 0.95 at 850 K and can favour their use for waste heat recovery at higher temperatures and thermoelectric spin generators.

Control of La-doped Pb(Zr,Ti)O3 crystalline orientation and its influence on the properties of ferroelectric random access memory

NASA Astrophysics Data System (ADS)

Wang, Wensheng; Nomura, Kenji; Yamaguchi, Hideshi; Nakamura, Ko; Eshita, Takashi; Ozawa, Soichiro; Takai, Kazuaki; Mihara, Satoru; Hikosaka, Yukinobu; Hamada, Makoto; Kataoka, Yuji

2017-10-01

We investigated the crystallization mechanisms of sputter-deposited La-doped Pb(Zr,Ti)O3 (PLZT) on a Pt/Ti metal stack in the postdeposition annealing (PDA) at 600 °C in O2-mixed Ar ambient. As-deposited amorphous PLZT generally transforms to a perovskite phase over 550 °C through a metastable pyrochlore phase during the PDA. We found that the O2 content of the PDA ambient crucially affects the pyrochlore-perovskite transformation (PPT) speed. While an O2 content much higher than 2% of the PDA ambient suppresses PPT, an O2 content much lower than 2% enhances PPT. An O2 content around of 2% of the PDA suppresses PPT near the surface of PLZT and simultaneously keeps PPT fast in the inner regions of PLZT in the pyrochlore phase because of the O2 diffusion limit from the PLZT surface, eventually resulting in almost only the growth of highly {111} oriented columnar PLZT on Pt, which reveals better electric properties than those obtained by the PDA with the ambient of O2 contents much higher or lower than 2%.

Ti-doped isotropic graphite: A promising armour material for plasma-facing components

NASA Astrophysics Data System (ADS)

García-Rosales, C.; López-Galilea, I.; Ordás, N.; Adelhelm, C.; Balden, M.; Pintsuk, G.; Grattarola, M.; Gualco, C.

2009-04-01

Finely dispersed Ti-doped isotropic graphites with 4 at.% Ti have been manufactured using synthetic mesophase pitch 'AR' as raw material. These new materials show a thermal conductivity at room temperature of ˜200 W/mK and flexural strength close to 100 MPa. Measurement of the total erosion yield by deuterium bombardment at ion energies and sample temperatures for which pure carbon shows maximum values, resulted in a reduction of at least a factor of 4, mainly due to dopant enrichment at the surface caused by preferential erosion of carbon. In addition, ITER relevant thermal shock loads were applied with an energetic electron beam at the JUDITH facility. The results demonstrated a significantly improved performance of Ti-doped graphite compared to pure graphite. Finally, Ti-doped graphite was successfully brazed to a CuCrZr block using a Mo interlayer. These results let assume that Ti-doped graphite can be a promising armour material for divertor plasma-facing components.

[Twins in myth (author's transl)].

PubMed

de Rachewiltz, B; Parisi, P; Castellani, V

1976-01-01

Twins have an important place in mythology and a sacred character appears to be attached to them since the most ancient times. In ancient Egypt, the royal placenta was worshipped, being considered as the Pharao's twin (a conception that is still alive among certain African populations), and actually everyone was considered to possess a spiritual twin, the Ka or astral body, through whom it was supposed to be possible to operate with magic rituals and hit enemies. Twin gods were worshipped by Babylonians and Assyrians (who even introduced them among astronomic constellations), and may be also found in the Persian and Veda religions. In the classic, Greco-Roman world, the examples of twin gods and heroes are innumerable: from the twin sons of Zeus, the Dioscuri, to the opposite-sexed twin gods Apollo and Diana, to Rome's founders, Romulus and Remus, etc. Since the most ancient times, a magic conception is connected to the twins, either in a positive or a negative sense, but often with some kind of a "fatidic" aspect. Such a two-faced approach to the phenomenon of twinning, that variously characterizes near-east, protomediterranean, classic, and other ancient civilizations, may still be found in contemporary primitive societies.

Variation in superconducting transition temperature due to tetragonal domains in two-dimensionally doped SrTiO 3

DOE PAGES

Noad, Hilary; Spanton, Eric M.; Nowack, Katja C.; ...

2016-11-28

Strontium titanate is a low-temperature, non–Bardeen-Cooper-Schrieffer superconductor that superconducts to carrier concentrations lower than in any other system and exhibits avoided ferroelectricity at low temperatures. Neither the mechanism of superconductivity in strontium titanate nor the importance of the structure and dielectric properties for the superconductivity are well understood. We studied the effects of twin structure on superconductivity in a 5.5-nm-thick layer of niobium-doped SrTiO 3 embedded in undoped SrTiO 3. We used a scanning superconducting quantum interference device susceptometer to image the local diamagnetic response of the sample as a function of temperature. We observed regions that exhibited a superconductingmore » transition temperature T c ≳ 10% higher than the temperature at which the sample was fully superconducting. The pattern of these regions varied spatially in a manner characteristic of structural twin domains. Some regions are too wide to originate on twin boundaries; therefore, we propose that the orientation of the tetragonal unit cell with respect to the doped plane affects T c. Finally, our results suggest that the anisotropic dielectric properties of SrTiO 3 are important for its superconductivity and need to be considered in any theory of the mechanism of the superconductivity.« less

Synthesis, characterization, and photocatalytic application of Pd/ZrO2 and Pt/ZrO2

NASA Astrophysics Data System (ADS)

Saeed, Khalid; Sadiq, Mohammad; Khan, Idrees; Ullah, Saleem; Ali, Nauman; Khan, Adnan

2018-05-01

Zirconia-supported palladium (Pd/ZrO2) and Zirconia-supported platinum (Pt/ZrO2) nanoparticles (NPs) are synthesized from their precursors via impregnation technique. The Pd/ZrO2 and Pt/ZrO2 NPs were analyzed via SEM and EDX, while the study of indigo disulfonate dye degradation was carried out by UV/VIS spectrophotometer. The SEM micrographs illustrated that the Pd and Pt NPs were well placed on ZrO2 surface. The Pd/ZrO2 and Pt/ZrO2 NPs were also employed as photocatalysts for the photodegradation of indigo disulfonate in an aqueous medium under UV-light irradiation. The photodegradation study presented that Pd/ZrO2 and Pt/ZrO2 NPs degraded 96 and 94% of indigo disulfonate in 14 h, respectively. The effect of pH of medium and catalyst dosage and efficiency of recovered Pd/ZrO2 and Pt/ZrO2 NPs on the photocatalytic degradation were also studied. It was also found that the maximum degradation of dye was found at pH 10 (95-97%) and at 0.02 g weight (40.28%).

Robustness of magnetic and electric domains against charge carrier doping in multiferroic hexagonal ErMnO 3

DOE PAGES

Hassanpour, E.; Wegmayr, V.; Schaab, J.; ...

2016-04-12

We investigate the effect of chemical doping on the electric and magnetic domain pattern in multiferroic hexagonal ErMnO 3 . Hole- and electron doping are achieved through the growth of Er 1-x Ca x MnO 3 and Er 1-x Zr x MnO 3 single crystals, which allows for a controlled introduction of divalent and tetravalent ions, respectively. Using conductance measurements, piezoresponse force microscopy and nonlinear optics we study doping-related variations in the electronic transport and image the corrsponding ferroelectric and antiferromagnetic domains. We find that moderate doping levels allow for adjusting the electronic conduction properties of ErMnO 3 without destroyingmore » its characteristic domain patterns. Our findings demonstrate the feasibility of chemical doping for nonperturbative property-engineering of intrinsic domain states in this important class of multiferroics.« less

Structure and Mechanical and Corrosion Properties of a Magnesium Mg-Y-Nd-Zr Alloy after High Pressure Torsion

NASA Astrophysics Data System (ADS)

Lukyanova, E. A.; Martynenko, N. S.; Serebryany, V. N.; Belyakov, A. N.; Rokhlin, L. L.; Dobatkin, S. V.; Estrin, Yu. Z.

2017-11-01

The structure and the properties of an Mg-Y-Nd-Zr alloy (WE43) are studied after high pressure torsion (HPT) in the temperature range 20-300°C. Structure refinement proceeds mainly by deformation twinning with the formation of a partial nanocrystalline structure with a grain size of 30-100 nm inside deformation twins. The WE43 alloy is shown to be aged during heating after HPT due to the decomposition of a magnesium solid solution. HPT at room temperature and subsequent aging causes maximum hardening. It is shown that HPT significantly accelerates the decomposition of a magnesium solid solution. HPT at all temperatures considerably increases the tensile strength and the yield strength upon tensile tests and significantly decreases plasticity. Subsequent aging additionally hardens the WE43 alloy. A potentiodynamic study shows that the corrosion resistance of this alloy after HPT increases. However, subsequent aging degrades the corrosion properties of the alloy.

The impact of thermal treatment conditions on the formation of crystalline structure of Ce-Zr-oxide composite obtained by a modified sol-gel technique

NASA Astrophysics Data System (ADS)

Trusova, E. A.; Khrushcheva, A. A.; Shvorneva, L. I.

2012-02-01

We present the results of the modified sol-gel synthesis of ultrafine ceria-doped zirconia powder for medical ceramics (implants) and catalytic purposes (environmental catalysis and petrochemistry). Special attention has been paid to study the influence of thermal treatment on crystallite size and crystal lattice parameters of zirconia doped by ceria. Zirconyl chloride and cerium nitrate were used as metal sources, and tetraethylammonium hydroxide (TEAH) was used as a sol stabilizer at molar ratio TEAH/Σ (Ce + Zr) equal to 0.5. It was proved that zirconium and cerium practically completely were included in the obtained solid solutions, since their phase compositions fully correspond to initial quantities of cerium and zirconium in reaction mixture. It was shown that average crystallite size of the obtained powders did not exceed 75Å, and the powders were resistant to thermal treatment. It was established that stabilization of the crystal lattice of ZrO2 occurs through formation of a cubic ceria sublattice.

Impact of the charge density wave state in the electrodynamic response of ZrTe3 -xSex : Optical evidence for a pseudogap phase

NASA Astrophysics Data System (ADS)

Chinotti, M.; Ethiraj, J.; Mirri, C.; Zhu, Xiangde; Li, Lijun; Petrovic, C.; Degiorgi, L.

2018-01-01

The emergence of superconductivity upon progressively suppressing the long-range, charge-density-wave (CDW) order characterizes the phase diagram of several materials of interest in the on-going solid-state physics research. Se-doped ZrTe3 compounds provide the most recent, suitable arena in order to investigate the interplay of otherwise competing orders in layeredlike two-dimensional systems. We present an optical study of the CDW state in ZrTe3 -xSex at selected Se dopings, based on the measurement of the reflectivity from the far-infrared up to the ultraviolet, as a function of temperature. We particularly focus our attention to the redistribution of the spectral weight, which images the impact of the CDW state within the optical conductivity across the phase diagram of the title compounds. The electrodynamic response is consistent with a scenario based on a long-range CDW condensate at low Se doping. Upon increasing the Se content, this then gives way to local, short-range order CDW segments. Our spectral weight analysis reveals the presence of a pseudogap phase, as fingerprint of the CDW precursor effects and thus shaping the charge dynamics of the title compounds in their normal state, preceding the onset of superconductivity.

Twin-enhanced magnetic torque

NASA Astrophysics Data System (ADS)

Hobza, Anthony; García-Cervera, Carlos J.; Müllner, Peter

2018-07-01

Magnetic shape memory alloys experience magnetic-field-induced torque due to magnetocrystalline anisotropy and shape anisotropy. In a homogeneous magnetic field, torque results in bending of long samples. This study investigates the torque on a single crystal of Ni-Mn-Ga magnetic shape memory alloy constrained with respect to bending in an external magnetic field. The dependence of the torque on external magnetic field magnitude, strain, and twin boundary structure was studied experimentally and with computer simulations. With increasing magnetic field, the torque increased until it reached a maximum near 700 mT. Above 200 mT, the torque was not symmetric about the equilibrium orientation for a sample with one twin boundary. The torque on two specimen with equal strain but different twin boundary structures varied systematically with the spatial arrangement of crystallographic twins. Numerical simulations show that twin boundaries suppress the formation of 180° domains if the direction of easy magnetization between two twin boundaries is parallel to a free surface and the magnetic field is perpendicular to that surface. For a particular twin microstructure, the torque decreases with increasing strain by a factor of six due to the mutual compensation of magnetocrystalline and shape anisotropy. When free rotation is suppressed such as in transducers of magneto-mechanical actuators, magnetic-field-induced torque creates strong bending forces, which may cause friction and failure under cyclic loading.

Atomistic study of the electronic contact resistivity between the half-Heusler alloys (HfCoSb, HfZrCoSb, HfZrNiSn) and the metal Ag

NASA Astrophysics Data System (ADS)

He, Yuping; Léonard, François; Spataru, Catalin D.

2018-06-01

Half-Heusler (HH) alloys have shown promising thermoelectric properties in the medium- and high-temperature range. To harness these material properties for thermoelectric applications, it is important to realize electrical contacts with low electrical contact resistivity. However, little is known about the detailed structural and electronic properties of such contacts and the expected values of contact resistivity. Here, we employ atomistic ab initio calculations to study electrical contacts in a subclass of HH alloys consisting of the compounds HfCoSb, HfZrCoSb, and HfZrNiSn. By using Ag as a prototypical metal, we show that the termination of the HH material critically determines the presence or absence of strong deformations at the interface. Our study includes contacts to doped materials, and the results indicate that the p -type materials generally form ohmic contacts while the n -type materials have a small Schottky barrier. We calculate the temperature dependence of the contact resistivity in the low- to medium-temperature range and provide quantitative values that set lower limits for these systems.

Twinning in magnesium under dynamic loading

NASA Astrophysics Data System (ADS)

Dixit, Neha; Hazeli, Kavan; Ramesh, Kaliat T.

2015-09-01

Twinning is an important mode of deformation in magnesium (Mg) and its alloys at high strain rates. Twinning in this material leads to important effects such as mechanical anisotropy, texture evolution, tension-compression asymmetry, and sometimes non-Schmid effects. Extension twins in Mg can accommodate significant plastic deformation as they grow, and thus twinning affects the overall rate of plastic deformation. We use an experimental approach to study the deformation twinning mechanism under dynamic loading. We perform normal plate impact recovery experiments (with microsecond pulse durations) on pure polycrystalline Mg specimens. Estimates of average TB velocity under the known impact stress are obtained by characterization of twin sizes and aspect ratios developed within the target during the loading pulse. The measured average TB velocities in our experiments are of the order of several m s-1. These velocities are several orders of magnitude higher than those so far measured in Mg under quasi-static loading conditions. Electron back-scattered diffraction (EBSD) is then used to characterize the nature of the twins and the microstructural evolution. Detailed crystallographic analysis of the twins enables us to understand twin nucleation and growth of twin variants under dynamic loading.

A Twin Protection Effect? Explaining Twin Survival Advantages with a Two-Process Mortality Model

PubMed Central

2016-01-01

Twin studies that focus on the correlation in age-at-death between twin pairs have yielded important insights into the heritability and role of genetic factors in determining lifespan, but less attention is paid to the biological and social role of zygosity itself in determining survival across the entire life course. Using data from the Danish Twin Registry and the Human Mortality Database, we show that monozygotic twins have greater cumulative survival proportions at nearly every age compared to dizygotic twins and the Danish general population. We examine this survival advantage by fitting these data with a two-process mortality model that partitions survivorship patterns into extrinsic and intrinsic mortality processes roughly corresponding to acute, environmental and chronic, biological origins. We find intrinsic processes confer a survival advantage at older ages for males, while at younger ages, all monozygotic twins show a health protection effect against extrinsic death akin to a marriage protection effect. While existing research suggests an increasingly important role for genetic factors at very advanced ages, we conclude that the social closeness of monozygotic twins is a plausible driver of the survival advantage at ages <65. PMID:27192433

A Computational Discriminability Analysis on Twin Fingerprints

NASA Astrophysics Data System (ADS)

Liu, Yu; Srihari, Sargur N.

Sharing similar genetic traits makes the investigation of twins an important study in forensics and biometrics. Fingerprints are one of the most commonly found types of forensic evidence. The similarity between twins’ prints is critical establish to the reliability of fingerprint identification. We present a quantitative analysis of the discriminability of twin fingerprints on a new data set (227 pairs of identical twins and fraternal twins) recently collected from a twin population using both level 1 and level 2 features. Although the patterns of minutiae among twins are more similar than in the general population, the similarity of fingerprints of twins is significantly different from that between genuine prints of the same finger. Twins fingerprints are discriminable with a 1.5%~1.7% higher EER than non-twins. And identical twins can be distinguished by examine fingerprint with a slightly higher error rate than fraternal twins.

Research on self-propagating high temperature synthesis prepared ZrC-ZrB2 composite ceramic

NASA Astrophysics Data System (ADS)

Yong, Cheng; Xunjia, Su; Genliang, Hou; YaKun, Xing

2013-03-01

ZrC-ZrB2 composite ceramic material is prepared by self-propagating high temperature synthesis, using Zr powders, CrO2 powders and Al powders as raw materials. Samples are studied by XRD and SEM, the results show that: ZrC-ZrB2 composite ceramic is attained after self-propagating high-temperature reaction, with Zr+ B4C as the main reactive system, and which is added respectively different content (CrO3 + Al) system. The study finds that the ceramic composite products are mainly composed of ZrC and ZrB2 phase, and other subphase. Compared to the main reactive system composite ceramic, composite ceramic grains grow up obviously, after introduction of the highly exothermic system (CrO3 + Al) in the main reactive system, and with the gradual increase of the content (CrO3 + Al).

The utility of twins in developmental cognitive neuroscience research: How twins strengthen the ABCD research design.

PubMed

Iacono, William G; Heath, Andrew C; Hewitt, John K; Neale, Michael C; Banich, Marie T; Luciana, Monica M; Madden, Pamela A; Barch, Deanna M; Bjork, James M

2018-08-01

The ABCD twin study will elucidate the genetic and environmental contributions to a wide range of mental and physical health outcomes in children, including substance use, brain and behavioral development, and their interrelationship. Comparisons within and between monozygotic and dizygotic twin pairs, further powered by multiple assessments, provide information about genetic and environmental contributions to developmental associations, and enable stronger tests of causal hypotheses, than do comparisons involving unrelated children. Thus a sub-study of 800 pairs of same-sex twins was embedded within the overall Adolescent Brain and Cognitive Development (ABCD) design. The ABCD Twin Hub comprises four leading centers for twin research in Minnesota, Colorado, Virginia, and Missouri. Each site is enrolling 200 twin pairs, as well as singletons. The twins are recruited from registries of all twin births in each State during 2006-2008. Singletons at each site are recruited following the same school-based procedures as the rest of the ABCD study. This paper describes the background and rationale for the ABCD twin study, the ascertainment of twin pairs and implementation strategy at each site, and the details of the proposed analytic strategies to quantify genetic and environmental influences and test hypotheses critical to the aims of the ABCD study. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Voice similarity in identical twins.

PubMed

Van Gysel, W D; Vercammen, J; Debruyne, F

2001-01-01

If people are asked to discriminate visually the two individuals of a monozygotic twin (MT), they mostly get into trouble. Does this problem also exist when listening to twin voices? Twenty female and 10 male MT voices were randomly assembled with one "strange" voice to get voice trios. The listeners (10 female students in Speech and Language Pathology) were asked to label the twins (voices 1-2, 1-3 or 2-3) in two conditions: two standard sentences read aloud and a 2.5-second midsection of a sustained /a/. The proportion correctly labelled twins was for female voices 82% and 63% and for male voices 74% and 52% for the sentences and the sustained /a/ respectively, both being significantly greater than chance (33%). The acoustic analysis revealed a high intra-twin correlation for the speaking fundamental frequency (SFF) of the sentences and the fundamental frequency (F0) of the sustained /a/. So the voice pitch could have been a useful characteristic in the perceptual identification of the twins. We conclude that there is a greater perceptual resemblance between the voices of identical twins than between voices without genetic relationship. The identification however is not perfect. The voice pitch possibly contributes to the correct twin identifications.

The Charles Perkins Centre's Twins Research Node.

PubMed

Ferreira, Lucas C; Craig, Jeffrey M; Hopper, John L; Carrick, Susan E

2016-08-01

Twins can help researchers disentangle the roles of genes from those of the environment on human traits, health, and diseases. To realize this potential, the Australian Twin Registry (ATR), University of Melbourne, and the Charles Perkins Centre (CPC), University of Sydney, established a collaboration to form the Twins Research Node, a highly interconnected research facility dedicated specifically to research involving twins. This collaboration aims to foster the adoption of twin designs as important tools for research in a range of health-related domains. The CPC hosted their Twins Research Node's launch seminar entitled 'Double the power of your research with twin studies', in which experienced twin researchers described how twin studies are supporting scientific discoveries and careers. The launch also featured twin pairs who have actively participated in research through the ATR. Researchers at the CPC were surveyed before the event to gauge their level of understanding and interest in utilizing twin research. This article describes the new Twins Research Node, discusses the survey's main results and reports on the launch seminar.

Structure of zirconium-93 and zirconium-91 as shown by the reactions Zr-92(d,p)Zr-93 and Zr-92(d,t)Zr-91

NASA Technical Reports Server (NTRS)

Baron, N.; Leonard, R. F.; Stewart, W. M.; Fink, C. L.; Christensen, P. R.; Nickles, J.; Thorsteinsen, T. F.

1972-01-01

Deuterons of 13-MeV incident energy were scattered from Zr-92(d,p)Zr-93. The Zr-92(d,p)Zr-93 data analysis resulted in the location of 47 levels up to an excitation energy of 4.84 MeV, and the spins of 43 of these levels were identified. Essentially all the strength of the 2d5/2, 3s1/2, 2d3/2, and 1g7/2 shells was observed; and the excitation energy of their centroids was computed to be 0.00, 1.21, 2.23, and 2.37 MeV, respectively. Also, 43 percent of the 1h11/2 strength, 21 percent of the 2f7/2 strength, and 3 percent of the 3p3/2 strength were observed. In addition, the Zr-92(d,t)Zr-91 data analysis resulted in the location of 26 levels up to an excitation energy of 4.01 MeV, and the spins of 21 of these levels were identified. Most of the expected strength of the 2d5/2 and 1g9/2 shells was obtained, and the excitation energy of their centroids was computed to be 0.31 and 3.19 MeV, respectively. In addition, six l=1 states are populated belonging to either the 2p1/2 or 2p3/2 shells.

Impact of the charge density wave state in the electrodynamic response of ZrTe 3 - x Se x : Optical evidence for a pseudogap phase

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

Chinotti, M.; Ethiraj, J.; Mirri, C.

The emergence of superconductivity upon progressively suppressing the long-range, charge-density-wave (CDW) order characterizes the phase diagram of several materials of interest in the on-going solid-state physics research. Se-doped ZrTe 3 compounds provide the most recent, suitable arena in order to investigate the interplay of otherwise competing orders in layeredlike two-dimensional systems. We present an optical study of the CDW state in ZrTe 3-xSe x at selected Se dopings, based on the measurement of the reflectivity from the far-infrared up to the ultraviolet, as a function of temperature. We particularly focus our attention to the redistribution of the spectral weight, whichmore » images the impact of the CDW state within the optical conductivity across the phase diagram of the title compounds. The electrodynamic response is consistent with a scenario based on a long-range CDW condensate at low Se doping. Upon increasing the Se content, this then gives way to local, short-range order CDW segments. Thus, our spectral weight analysis reveals the presence of a pseudogap phase, as fingerprint of the CDW precursor effects and thus shaping the charge dynamics of the title compounds in their normal state, preceding the onset of superconductivity.« less

Impact of the charge density wave state in the electrodynamic response of ZrTe 3 - x Se x : Optical evidence for a pseudogap phase

DOE PAGES

Chinotti, M.; Ethiraj, J.; Mirri, C.; ...

2018-01-12

The emergence of superconductivity upon progressively suppressing the long-range, charge-density-wave (CDW) order characterizes the phase diagram of several materials of interest in the on-going solid-state physics research. Se-doped ZrTe 3 compounds provide the most recent, suitable arena in order to investigate the interplay of otherwise competing orders in layeredlike two-dimensional systems. We present an optical study of the CDW state in ZrTe 3-xSe x at selected Se dopings, based on the measurement of the reflectivity from the far-infrared up to the ultraviolet, as a function of temperature. We particularly focus our attention to the redistribution of the spectral weight, whichmore » images the impact of the CDW state within the optical conductivity across the phase diagram of the title compounds. The electrodynamic response is consistent with a scenario based on a long-range CDW condensate at low Se doping. Upon increasing the Se content, this then gives way to local, short-range order CDW segments. Thus, our spectral weight analysis reveals the presence of a pseudogap phase, as fingerprint of the CDW precursor effects and thus shaping the charge dynamics of the title compounds in their normal state, preceding the onset of superconductivity.« less

Upconversion luminescence in Er3+ doped and Er3+/Yb3+ codoped zirconia and hafnia nanocrystals excited at 980 nm

NASA Astrophysics Data System (ADS)

Gómez, Luis A.; Menezes, Leonardo de S.; de Araújo, Cid B.; Gonçalves, Rogeria R.; Ribeiro, Sidney J. L.; Messaddeq, Younes

2010-06-01

Frequency upconversion (UC) luminescence in nanocrystalline zirconia (ZrO2) and hafnia (HfO2) doped with Er3+ and Yb3+ was studied under continuous-wave excitation at 980 nm. Samples of ZrO2:Er3+, ZrO2:Er3+/Yb3+, and HfO2:Er3+/Yb3+ were prepared by the sol-gel technique and characterized using x-ray diffraction and electron microscopy. A study of the infrared-to-green and infrared-to-red UC processes was performed including the analysis of the spectral and the temporal behavior. The mechanisms contributing to the UC luminescence were identified as excited state absorption and energy transfer among rare-earth ions.

Zirconium and silver co-doped TiO2 nanoparticles as visible light catalyst for reduction of 4-nitrophenol, degradation of methyl orange and methylene blue

NASA Astrophysics Data System (ADS)

Naraginti, Saraschandra; Stephen, Finian Bernard; Radhakrishnan, Adhithya; Sivakumar, A.

2015-01-01

Catalytic activity of Zr and Ag co-doped TiO2 nanoparticles on the reduction of 4-nitrophenol, degradation of methylene blue and methyl orange was studied using sodium borohydride as reducing agent. The nanoparticles were characterized using X-ray diffraction, energy dispersive X-ray, high resolution transmission electron microscopy, selected area electron diffraction and UV-Vis spectroscopy. The rate of the reduction/degradation was found to increase with increasing amount of the photocatalyst which could be attributed to higher dispersity and small size of the nanoparticles. The catalytic activity of Zr and Ag co-doped TiO2 nanoparticles showed no significant difference even after recycling the catalyst four times indicating a promising potential for industrial application of the prepared photocatalyst.

Growth curves for twins in Slovenia.

PubMed

Bricelj, Katja; Blickstein, Isaac; Bržan-Šimenc, Gabrijela; Janša, Vid; Lučovnik, Miha; Verdenik, Ivan; Trojner-Bregar, Andreja; Tul, Nataša

2017-02-01

Abnormalities of fetal growth are more common in twins. We introduce the growth curves for monitoring fetal growth in twin pregnancies in Slovenia. Slovenian National Perinatal Information System for the period between 2002 and 2010 was used to calculate birth weight percentiles for all live born twins for each week from 22nd to 40th week. The calculated percentiles of birth weight for all live-born twins in Slovenia served as the basis for drawing 'growth' curves. The calculated growth curves for twins will help accurately diagnose small or large twin fetuses for their gestational age in the native central European population.

Zr-ZrO2 cermet solar coatings designed by modelling calculations and deposited by dc magnetron sputtering

NASA Astrophysics Data System (ADS)

Zhang, Qi-Chu; Hadavi, M. S.; Lee, K.-D.; Shen, Y. G.

2003-03-01

High solar performance Zr-ZrO2 cermet solar coatings were designed using a numerical computer model and deposited experimentally. The layer thickness and Zr metal volume fraction for the Zr-ZrO2 cermet solar selective coatings on a Zr or Al reflector with a surface ZrO2 or Al2O3 anti-reflection layer were optimized to achieve maximum photo-thermal conversion efficiency at 80°C under concentration factors of 1-20 using the downhill simplex method in multi-dimensions in the numerical calculation. The dielectric function and the complex refractive index of Zr-ZrO2 cermet materials were calculated using Sheng's approximation. Optimization calculations show that Al2O3/Zr-ZrO2/Al solar coatings with two cermet layers and three cermet layers have nearly identical solar absorptance, emittance and photo-thermal conversion efficiency that are much better than those for films with one cermet layer. The optimized Al2O3/Zr-ZrO2/Al solar coating film with two cermet layers has a high solar absorptance value of 0.97 and low hemispherical emittance value of 0.05 at 80°C for a concentration factor of 2. The Al2O3/Zr-ZrO2/Al solar selective coatings with two cermet layers were deposited using dc magnetron sputtering technology. During the deposition of Zr-ZrO2 cermet layer, a Zr metallic target was run in a gas mixture of argon and oxygen. By control of oxygen flow rate the different metal volume fractions in the cermet layers were achieved using dc reactive sputtering. A solar absorptance of 0.96 and normal emittance of 0.05 at 80°C were achieved.

Deformation twinning: Influence of strain rate

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

Gray, G.T. III

Twins in most crystal structures, including advanced materials such as intermetallics, form more readily as the temperature of deformation is decreased or the rate of deformation is increased. Both parameters lead to the suppression of thermally-activated dislocation processes which can result in stresses high enough to nucleate and grow deformation twins. Under high-strain rate or shock-loading/impact conditions deformation twinning is observed to be promoted even in high stacking fault energy FCC metals and alloys, composites, and ordered intermetallics which normally do not readily deform via twinning. Under such conditions and in particular under the extreme loading rates typical of shockmore » wave deformation the competition between slip and deformation twinning can be examined in detail. In this paper, examples of deformation twinning in the intermetallics TiAl, Ti-48Al-lV and Ni{sub 3}A as well in the cermet Al-B{sub 4}C as a function of strain rate will be presented. Discussion includes: (1) the microstructural and experimental variables influencing twin formation in these systems and twinning topics related to high-strain-rate loading, (2) the high velocity of twin formation, and (3) the influence of deformation twinning on the constitutive response of advanced materials.« less

Corrosion evaluation of zirconium doped oxide coatings on aluminum formed by plasma electrolytic oxidation.

PubMed

Bajat, Jelena; Mišković-Stanković, Vesna; Vasilić, Rastko; Stojadinović, Stevan

2014-01-01

The plasma electrolytic oxidation (PEO) of aluminum in sodium tungstate (Na(2)WO(4) · (2)H(2)O) and Na(2)WO(4) · (2)H(2)O doped with Zr was analyzed in order to obtain oxide coatings with improved corrosion resistance. The influence of current density in PEO process and anodization time was investigated, as well as the influence of Zr, with the aim to find out how they affect the chemical content, morphology, surface roughness, and corrosion stability of oxide coatings. It was shown that the presence of Zr increases the corrosion stability of oxide coatings for all investigated PEO times. Evolution of EIS spectra during the exposure to 3% NaCl, as a strong corrosive agent, indicated the highest corrosion stability for PEO coating formed on aluminum at 70 mA/cm(2) for 2 min in a zirconium containing electrolyte.

Fingerprint Recognition with Identical Twin Fingerprints

PubMed Central

Yang, Xin; Tian, Jie

2012-01-01

Fingerprint recognition with identical twins is a challenging task due to the closest genetics-based relationship existing in the identical twins. Several pioneers have analyzed the similarity between twins' fingerprints. In this work we continue to investigate the topic of the similarity of identical twin fingerprints. Our study was tested based on a large identical twin fingerprint database that contains 83 twin pairs, 4 fingers per individual and six impressions per finger: 3984 (83*2*4*6) images. Compared to the previous work, our contributions are summarized as follows: (1) Two state-of-the-art fingerprint identification methods: P071 and VeriFinger 6.1 were used, rather than one fingerprint identification method in previous studies. (2) Six impressions per finger were captured, rather than just one impression, which makes the genuine distribution of matching scores more realistic. (3) A larger sample (83 pairs) was collected. (4) A novel statistical analysis, which aims at showing the probability distribution of the fingerprint types for the corresponding fingers of identical twins which have same fingerprint type, has been conducted. (5) A novel analysis, which aims at showing which finger from identical twins has higher probability of having same fingerprint type, has been conducted. Our results showed that: (a) A state-of-the-art automatic fingerprint verification system can distinguish identical twins without drastic degradation in performance. (b) The chance that the fingerprints have the same type from identical twins is 0.7440, comparing to 0.3215 from non-identical twins. (c) For the corresponding fingers of identical twins which have same fingerprint type, the probability distribution of five major fingerprint types is similar to the probability distribution for all the fingers' fingerprint type. (d) For each of four fingers of identical twins, the probability of having same fingerprint type is similar. PMID:22558204

Fingerprint recognition with identical twin fingerprints.

PubMed

Tao, Xunqiang; Chen, Xinjian; Yang, Xin; Tian, Jie

2012-01-01

Fingerprint recognition with identical twins is a challenging task due to the closest genetics-based relationship existing in the identical twins. Several pioneers have analyzed the similarity between twins' fingerprints. In this work we continue to investigate the topic of the similarity of identical twin fingerprints. Our study was tested based on a large identical twin fingerprint database that contains 83 twin pairs, 4 fingers per individual and six impressions per finger: 3984 (83*2*4*6) images. Compared to the previous work, our contributions are summarized as follows: (1) Two state-of-the-art fingerprint identification methods: P071 and VeriFinger 6.1 were used, rather than one fingerprint identification method in previous studies. (2) Six impressions per finger were captured, rather than just one impression, which makes the genuine distribution of matching scores more realistic. (3) A larger sample (83 pairs) was collected. (4) A novel statistical analysis, which aims at showing the probability distribution of the fingerprint types for the corresponding fingers of identical twins which have same fingerprint type, has been conducted. (5) A novel analysis, which aims at showing which finger from identical twins has higher probability of having same fingerprint type, has been conducted. Our results showed that: (a) A state-of-the-art automatic fingerprint verification system can distinguish identical twins without drastic degradation in performance. (b) The chance that the fingerprints have the same type from identical twins is 0.7440, comparing to 0.3215 from non-identical twins. (c) For the corresponding fingers of identical twins which have same fingerprint type, the probability distribution of five major fingerprint types is similar to the probability distribution for all the fingers' fingerprint type. (d) For each of four fingers of identical twins, the probability of having same fingerprint type is similar.

Vascular twin nevi.

PubMed

Agirgol, Senay; Ozturk, Hatice Nur; Ozkok Akbulut, Tugba; Gunduzoglu, Ceyda; Koc, Leyli Kadriye; Turkoglu, Zafer

2017-04-27

Vascular twin nevi (VTN) are characterized by the simultaneous dermatological manifestatiton of a telangiectatic naevus close to a nevus anemicus. Nevus anemicus (NA) is a vascular anomaly characterized by localized pale patches with normal melanine and melanocyte level. According to twin spotting phenomenon crossing-over in heterozygous somatic-cells during mitosis results in two different offspring homozygous cells. Consequent to this mechanism, two different vascular anomalies may occur at the same region. We present a patient with VTN and NA combination which we think serves as an example for a rare twin spotting phenomenon in the literature. © 2017 Wiley Periodicals, Inc.

Some Features of Dialogue between Twins

ERIC Educational Resources Information Center

Savic, Svenka; Jocic, Mirjana

1975-01-01

Dialogues of sets of socially similar twins are studied. The opinion that twins have slower syntactic development than non-twins is seriously questioned. Dialogues with twins saying the same utterance together, correcting each other, quarreling, playing verbal games, etc. are analyzed in their deep structure. (SCC)

Mössbauer study of oxide films of Fe-, Sn-, Cr- doped zirconium alloys during corrosion in autoclave

NASA Astrophysics Data System (ADS)

Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.

2016-12-01

Mössbauer investigations were used to compare iron atom states in oxide films of binary Zr-Fe, ternary Zr-Fe-Cu and quaternary Zr-Fe-Cr-Sn alloys. Oxide films are received in an autoclave at a temperature of 350-360 °C and at pressure of 16.8 MPa. The corrosion process decomposes the intermetallic precipitates in alloys and forms metallic iron with inclusions of chromium atoms α-Fe(Cr), α-Fe(Cu), α-Fe 2O3 and Fe 3O4 compounds. Some iron ions are formed in divalent and in trivalent paramagnetic states. The additional doping influences on corrosion kinetics and concentration of iron compounds and phases formed in oxide films. It was shown the correlation between concentration of iron in different chemical states and corrosion resistance of alloys.

Dy3+ doped cubic zirconia nanostructures prepared via ultrasound route for display applications

NASA Astrophysics Data System (ADS)

Yadav, H. J. Amith; Eraiah, B.; Nagabhushana, H.; Basavaraj, R. B.; Deepthi, N. H.

2017-05-01

White light emitting dysprosium (Dy) doped Zirconia (ZrO2) nanostructures were prepared first time via ultrasound assisted sonochemical synthesis route using cetyltrimethylammonium bromide (CTAB) surfactant. The obtained product was well characterized. The powder X-ray diffraction (PXRD) profiles confirmed that the product was highly crystalline in nature with cubic phase. Various reaction parameters such as, effect of sonication time, concentration of the surfactant was studied in detail. Diffuse reflectance spectroscopy (DRS) was studied to evaluate the band gap energy of the products and the values were found in the range of 4.13 - 4.53 eV. The particle size was estimated by transmission electron microscope (TEM) and it was found in the range of 10-20 nm. Photoluminescence (PL) properties were studied in detail by recording emission spectra of all the Dy doped Zirconia nanostructures at an excitation wavelength of 350 nm. The emission peaks were observed at 480, 574 and 666 nm which corresponds to Dy3+ ion transitions. The 3 mol% Dy3+ doped ZrO2 nanostructures showed maximum intensity. Further photometric measurements were done by evaluating, Commission International De I-Eclairage (CIE) and correlated color temperature (CCT). From CIE it was observed that the color coordinates lies in white region. The color purity and quantum efficiency were also estimated and the results indicate that the nanophosphor obtained in this route can be used in preparing solid state lighting application.

Twin vaginal delivery: innovate or abdicate.

PubMed

Easter, Sarah Rae; Taouk, Laura; Schulkin, Jay; Robinson, Julian N

2017-05-01

Neonatal safety data along with national guidelines have prompted renewed interest in vaginal delivery of twins, particularly in the case of the noncephalic second twin. Yet, the rising rate of twin cesarean deliveries, coupled with the national decline in operative obstetrics, raises concerns about the availability of providers who are skilled in twin vaginal birth. Providers are key stakeholders for increasing rates of twin vaginal delivery. We surveyed a group of practicing obstetricians to explore potential barriers to the vaginal birth of twins with a focus on delivery of the noncephalic second twin. Among 107 responding providers, only 57% would deliver a noncephalic second twin by breech extraction. Providers who preferred breech extraction had a higher rate of maternal-fetal medicine subspecialty training (26.2% vs 4.3%; P<.01) and were more likely to be in an academic practice environment (36.1% vs 10.9%; P<.01) and to practice in high-volume centers that deliver >30 sets of twins annually (57.4% vs 34.8%; P=.02). Most providers (54.2%) were familiar with the findings from the recent randomized trial that demonstrated the safety of twin vaginal birth. However, knowledge of the trial was not associated statistically with a preference for breech extraction (62.3% vs 43.5%; P=.05). Providers who preferred breech extraction were more likely to agree with recent society guidelines that encourage the vaginal birth of twins (86.9% vs 63.0%; P<.01). In an adjusted analysis, the 46% of providers with a perceived need for more training were far less likely to prefer breech extraction for delivery of a noncephalic second twin (adjusted odds ratio, 0.38; 95% confidence interval, 0.16-0.95). Furthermore, 57% of providers who would not offer their patient breech extraction would be willing to consult a colleague for support with a noncephalic twin delivery. These results suggest that scientific evidence and society opinion are likely insufficient to reverse the national

Fetoscopic laser ablation of placental anastomoses in twin-twin transfusion syndrome using 'Solomon technique'.

PubMed

Ruano, R; Rodo, C; Peiro, J L; Shamshirsaz, A A; Haeri, S; Nomura, M L; Salustiano, E M A; de Andrade, K K; Sangi-Haghpeykar, H; Carreras, E; Belfort, M A

2013-10-01

To document perinatal outcomes following use of the 'Solomon technique' in the selective photocoagulation of placental anastomoses for severe twin-twin transfusion syndrome (TTTS). Between January 2010 and July 2012, data were collected from 102 consecutive monochorionic twin pregnancies complicated by severe TTTS that underwent fetoscopic laser ablation at four different centers. We compared outcomes between subjects that underwent selective laser coagulation using the Solomon technique (cases) and those that underwent selective laser coagulation without this procedure (controls). Of the 102 pregnancies examined, 26 (25.5%) underwent the Solomon technique and 76 (74.5%) did not. Of the 204 fetuses, 139 (68.1%) survived up to 30 days of age. At least one twin survived in 82 (80.4%) pregnancies and both twins survived in 57 (55.9%) pregnancies. When compared with the control group, the Solomon-technique group had a significantly higher survival rate for both twins (84.6 vs 46.1%; P < 0.01) and a higher overall neonatal survival rate (45/52 (86.5%) vs 94/152 (61.8%); P < 0.01). Use of the Solomon technique remained independently associated with dual twin survival (adjusted odds ratio (aOR), 11.35 (95% CI, 3.11-53.14); P = 0.0007) and overall neonatal survival rate (aOR, 4.65 (95% CI, 1.59-13.62); P = 0.005) on multivariable analysis. There were no cases of recurrent TTTS or twin anemia-polycythemia sequence (TAPS) in the Solomon-technique group. Use of the Solomon technique following selective laser coagulation of placental anastomoses appears to improve twin survival and may reduce the risk of recurrent TTTS and TAPS. Our data support the idea of performing a randomized controlled trial to evaluate the effectiveness of the Solomon technique. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.

Twin Higgs Asymmetric Dark Matter.

PubMed

García García, Isabel; Lasenby, Robert; March-Russell, John

2015-09-18

We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

Origin of magnetic anisotropy in doped Ce 2 Co 17 alloys

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

Ke, Liqin; Kukusta, D. A.; Johnson, Duane D.

2016-10-21

Magnetocrystalline anisotropy (MCA) in doped Ce 2Co 17 and other competing structures was investigated using density functional theory. We confirmed that the MCA contribution from dumbbell Co sites is very negative. Replacing Co dumbbell atoms with a pair of Fe or Mn atoms greatly enhance the uniaxial anisotropy, which agrees quantitatively with experiment, and this enhancement arises from electronic-structure features near the Fermi level, mostly associated with dumbbell sites. With Co dumbbell atoms replaced by other elements, the variation of anisotropy is generally a collective effect and contributions from other sublattices may change significantly. Furthermore, we found that Zr dopingmore » promotes the formation of 1-5 structure that exhibits a large uniaxial anisotropy, such that Zr is the most effective element to enhance MCA in this system.« less

Capture of Hydrogen Using ZrNi

NASA Technical Reports Server (NTRS)

Patton, Lisa; Wales, Joshua; Lynch, David; Parrish, Clyde

2005-01-01

Water, as ice, is thought to reside in craters at the lunar poles along with CH4 and H2 . A proposed robotic mission for 2012 will utilize metal/metal hydrides for H2 recovery. Specifications are 99% capture of H2 initially at 5 bar and 100C (or greater), and degassing completely at 300C. Of 47-systems examined using the van't Hoff equation, 4 systems, Mg/MgH2, Mg2Ni/Mg2NiH4, ZrNi/ZrNiH2.8, and Pd/PdH0.77, were considered likely candidates for further examination. It is essential, when selecting a system, to also examine questions regarding activation, kinetics, cyclic stability, and gas impurity effects. After considering those issues, ZrN1 was selected as the most promising candidate, as it is easily activated and rapidly forms ZrNiH 2.8 . In addition, it resists oxide poisoning by CO2, and H2O, while some oxidation by O2 is recommended for improved activation . The presence of hydrogen in the as received Zr-Ni alloy from Alfa Aesar posed additional technical problems. X-ray diffraction of the Zr-Ni powder (-325 mesh), with a Zr:Ni wt% ratio of 70:30, was found to consist of ZrH2, ZrNiH2.8, and ZrNi. ZrH2 in the alloy presented the risk that after degassing that both Zr and ZrNi would be present, and thus lead to erroneous results regarding the reactivity of ZrNi with H2 . Fortunately, ZrH2 is a highly stable hydride that does not degas H2 to any significant extent at temperatures below 300C. Based on equilibrium calculations for the decomposition of ZrH2, only 1 millionth of the hydride decomposed at 300C under a N2 atmosphere flowing at 25 ccm for 64 hours, the longest time for pretreatment employed in the investigation. It was possible, from the X-ray results and knowledge of the Zr:Ni ratio, to compute the composition of a pretreated specimen as being 76 wt% ZrNi and the balance ZrH2.

Cohort Profile: The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry)

PubMed Central

Gatz, Margaret; Harris, Jennifer R; Kaprio, Jaakko; McGue, Matt; Smith, Nicholas L; Snieder, Harold; Spiro, Avron; Butler, David A

2015-01-01

The National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry) is a comprehensive registry of White male twin pairs born in the USA between 1917 and 1927, both of the twins having served in the military. The purpose was medical research and ultimately improved clinical care. The cohort was assembled in the early 1960s with identification of approximately 16 000 twin pairs, review of service records, a brief mailed questionnaire assessing zygosity, and a health survey largely comparable to questionnaires used at that time with Scandinavian twin registries. Subsequent large-scale data collection occurred in 1974, 1985 and 1998, repeating the health survey and including information on education, employment history and earnings. Self-reported data have been supplemented with mortality, disability and medical data through record linkage. Potential collaborators should access the study website [http://www.iom.edu/Activities/Veterans/TwinsStudy.aspx] or e-mail the Medical Follow-up Agency at [Twins@nas.edu]. Questionnaire data are being prepared for future archiving with the National Archive of Computerized Data on Aging (NACDA) at the Inter-University Consortium for Political and Social Research (ICPSR), University of Michigan, MI. PMID:25183748

Exotic quarks in Twin Higgs models

DOE PAGES

Cheng, Hsin -Chia; Jung, Sunghoon; Salvioni, Ennio; ...

2016-03-14

The Twin Higgs model provides a natural theory for the electroweak symmetry breaking without the need of new particles carrying the standard model gauge charges below a few TeV. In the low energy theory, the only probe comes from the mixing of the Higgs fields in the standard model and twin sectors. However, an ultraviolet completion is required below ~ 10 TeV to remove residual logarithmic divergences. In non-supersymmetric completions, new exotic fermions charged under both the standard model and twin gauge symmetries have to be present to accompany the top quark, thus providing a high energy probe of themore » model. Some of them carry standard model color, and may therefore be copiously produced at current or future hadron colliders. Once produced, these exotic quarks can decay into a top together with twin sector particles. If the twin sector particles escape the detection, we have the irreducible stop-like signals. On the other hand, some twin sector particles may decay back into the standard model particles with long lifetimes, giving spectacular displaced vertex signals in combination with the prompt top quarks. This happens in the Fraternal Twin Higgs scenario with typical parameters, and sometimes is even necessary for cosmological reasons. We study the potential displaced vertex signals from the decays of the twin bottomonia, twin glueballs, and twin leptons in the Fraternal Twin Higgs scenario. As a result, depending on the details of the twin sector, the exotic quarks may be probed up to ~ 2.5 TeV at the LHC and beyond 10 TeV at a future 100 TeV collider, providing a strong test of this class of ultraviolet completions.« less

Rehabilitation of Conjoined Twins Pre- and Postsurgical Separation.

PubMed

Tozzi, Maria; Van Zant, R Scott

2017-05-01

Describe the rehabilitation, including two episodes of inpatient rehabilitation, early intervention, and outpatient services, of conjoined twins. The patients were 14-month-old female ischiopagus tripus twins that received 3 months of rehabilitation (mobility, feeding, communication, developmental skill training, developing adaptive equipment, educating caregivers) preseparation surgery. Surgery occurred at 24 months. At 27 months, the twins were admitted to inpatient rehabilitation, receiving 4 months of rehabilitation promoting strength, endurance, gait training, feeding, communication, developmental skill training, orthotics, adaptive equipment, and caregiver education. Presurgical WeeFIM was 18/126 (twin A) and 19/126 (twin B), and 28/126 (both twins A&B) postsurgical. Prior to surgery, patients performed supine to sit transfers with supervision. Following surgery, each twin sat and performed bed mobility independently. Twin B performed wheelchair mobility and supported standing at anterior surface with assistance. Discharge WeeFIM was 42/126 (twin A) and 45/126 (twin B). Twins performed floor mobility by scooting, stood at an anterior surface with assistance (maximum for twin A, minimal for twin B), and propelled a manual wheelchair indoors (minimal assistance for both twins A & B). Rehabilitation of conjoined twins improved presurgical functional status and addressed the unique functional needs of each twin postseparation.

Effects of Grain Size and Twin Layer Thickness on Crack Initiation at Twin Boundaries.

PubMed

Zhou, Piao; Zhou, Jianqiu; Zhu, Yongwei; Jiang, E; Wang, Zikun

2018-04-01

A theoretical model to explore the effect on crack initiation of nanotwinned materials was proposed based on the accumulation of dislocations at twin boundaries. First, a critical cracking initiation condition was established considering the number of dislocations pill-up at TBs, grain size and twin layer thickness, and a semi-quantitative relationship between the crystallographic orientation and the stacking fault energy was built. In addition, the number of dislocations pill-up was described by introducing the theory of strain gradient. Based on this model, the effects of grain size and twin lamellae thickness on dislocation density and crack initiation at twin boundaries were also discussed. The simulation results demonstrated that the crack initiation resistance can be improved by decreasing the grain size and increasing the twin lamellae, which keeps in agreement with recent experimental findings reported in the literature.

Labor patterns in twin gestations

PubMed Central

Leftwich, Heidi K.; Zaki, Mary N.; Wilkins, Isabelle; Hibbard, Judith U.

2014-01-01

Objective To compare labor progression in twin vs singleton gestations. Study Design Retrospective review of electronic database created by Consortium on Safe Labor, reflecting labor and delivery information from 12 clinical centers 2002-2008. Women with twin gestations, cephalic presentation of presenting twin, gestational age ≥34 weeks, with ≥2 cervical examinations were included. Exclusion criteria were fetal anomalies or demise. Singleton controls were selected by the same criteria. Categorical variables were analyzed by χ2; continuous by Student t test. Interval censored regression was used to determine distribution for time of cervical dilation in centimeters, or “traverse times,” and controlled for confounding factors. Repeated-measures analysis constructed mean labor curves by parity and number of fetuses. Results A total of 891 twin gestations were compared with 100,513 singleton controls. Twin gestations were more often older, white or African American, earlier gestational age, increased prepregnancy body mass index, and with lower birthweight. There was no difference in number of prior cesarean deliveries, induction, or augmentation, or epidural use. Median traverse times increased at every centimeter interval in nulliparous twins, in both unadjusted and adjusted analysis (P < .01). A similar pattern was noted for multiparas in both analyses. Labor curves demonstrated a delayed inflection point in the labor pattern for nulliparous and multiparous twin gestations. Conclusion Both nulliparous and multiparous women have slower progression of active phase labor with twins even when controlling for confounding factors. PMID:23871795

Why the Healing Gods Are Twins

PubMed Central

Hankoff, Leon D.

1977-01-01

The association of twins with health-giving powers is widespread in mythology, folklore, and religion. The Ashvins of the Rig-Veda, the classical Dioscuri, and the early Christian saints Cosmos and Damian are among the many examples of twins divinely empowered in the area of health and fertility. A characteristic set of attributes of twins recurs in different mythologies of wide distribution. In addition to healing, divine twins are often empowered with the ability to revive the dead, increase the fertility of man, animals, and crops, influence the weather, predict the future, and insure victory in battle. In some traditional societies these special attributes are thought to extend to all of the twins and their parents in the tribe. Ancient and primitive societies supposed that the birth of twins was associated with divine influence, the mother having been visited or otherwise affected by supernatural powers. A frequent explanation was that twins were the result of superfetation, a divine impregnation occurring along with that by the lawful husband. The specific powers of divine twins appear to be a reflection of the particular form of origin of twins through divine interference with the fertilization process. The twins thus share some of the powers of the divine parent, particularly those pertaining to fertility. Their dual paternity and its inherent competition is related to their martial interests as well as their ability to resolve ambivalent or ambiguous situations and predict outcomes. PMID:560764

Why the healing gods are twins.

PubMed

Hankoff, L D

1977-01-01

The association of twins with health-giving powers is widespread in mythology, folklore, and religion. The Ashvins of the Rig-Veda, the classical Dioscuri, and the early Christian saints Cosmos and Damian are among the many examples of twins divinely empowered in the area of health and fertility. A characteristic set of attributes of twins recurs in different mythologies of wide distribution. In addition to healing, divine twins are often empowered with the ability to revive the dead, increase the fertility of man, animals, and crops, influence the weather, predict the future, and insure victory in battle. In some traditional societies these special attributes are thought to extend to all of the twins and their parents in the tribe.Ancient and primitive societies supposed that the birth of twins was associated with divine influence, the mother having been visited or otherwise affected by supernatural powers. A frequent explanation was that twins were the result of superfetation, a divine impregnation occurring along with that by the lawful husband. The specific powers of divine twins appear to be a reflection of the particular form of origin of twins through divine interference with the fertilization process. The twins thus share some of the powers of the divine parent, particularly those pertaining to fertility. Their dual paternity and its inherent competition is related to their martial interests as well as their ability to resolve ambivalent or ambiguous situations and predict outcomes.

First-principles study of lattice thermal conductivity in ZrTe5 and HfTe5

NASA Astrophysics Data System (ADS)

Wang, Cong; Wang, Haifeng; Chen, Y. B.; Yao, Shu-Hua; Zhou, Jian

2018-05-01

Recently, the layered transition-metal pentatellurides ZrTe5 and HfTe5 have attracted increasing attention because of their interesting topological electronic properties. Nevertheless, some of their other good physical properties seem to be ignored now. Actually, both ZrTe5 and HfTe5 have high electric conductivities (>105 Ω-1 m-1) and Seebeck coefficients (> 100 μV/K) at room temperature, thus making them promising thermoelectric materials. However, the disadvantage is that the thermal conductivities of the two materials are relatively high according to the few available experiments; meanwhile, the detailed mechanism of the intrinsic thermal conductivity has not been studied yet. Based on the density functional theory and the Boltzmann transport theory, we present here the theoretical study of the intrinsic lattice thermal conductivities of ZrTe5 and HfTe5, which are found to be in the range of 5-8 W/mṡK at room temperature and well consistent with the experimental results. We also find that the thermal conductivities of the two materials are anisotropic, which are mainly caused by their anisotropic crystal structures. Based on the detailed analysis, we proposed that the thermal conductivities of the two materials could possibly be reduced by different kinds of structural engineering at the atomic and mesoscopic scales, such as alloying, doping, nano-structuring, and polycrystalline structuring, which could make ZrTe5 and HfTe5 good thermoelectric materials for room temperature thermoelectric applications.

Ferroelectric switching in epitaxial PbZr0.2Ti0.8O3/ZnO/GaN heterostructures

NASA Astrophysics Data System (ADS)

Wang, Juan; Salev, Pavel; Grigoriev, Alexei

As a wide-bandgap semiconductor, ZnO has gained substantial interest due to its favorable properties including high electron mobility, strong room-temperature luminescence, etc. The main obstacle of its application is the lack of reproducible and low-resistivity p-type ZnO. P-type doping of ZnO through the interface charge injection, which can be achieved by the polarization switching of ferroelectric films, is a tempting solution. We explored ferroelectric switching behavior of PbZr0.2Ti0.8O3/ZnO/GaN heterostructures epitaxially grown on Sapphire substrates by RF sputtering. The electrical measurements of Pt/PbZr0.2Ti0.8O3/ZnO/GaN ferroelectric-semiconductor capacitors revealed unusual behavior that is a combination of polarization switching and a diode I-V characteristics.

Co nanoparticle effects on the thermoluminescent signal induced by UV and gamma radiation in ZrO2 powders

NASA Astrophysics Data System (ADS)

Villa-Sánchez, G.; Mendoza-Anaya, D.; Eufemia Fernández-García, M.; Escobar-Alarcón, L.; Olea-Mejía, O.; González-Martínez, P. R.

2014-05-01

Zirconia powders, both pure and doped with Co nanoparticles were prepared by the sol-gel method followed by thermal treatment at 1000 °C. The morphological and crystallographic characteristics were studied by scanning and transmission electron microscopy, X-ray diffraction and the Rietveld refinements method. Analysis of the thermoluminescent (TL) signal induced by UV and gamma radiation was also conducted. According to the results, Co nanoparticles have a strong influence on the growth of ZrO2 particles and favor the formation of monoclinic zirconia. Moreover, an important influence of the added Co nanoparticles was observed on the position of the TL peaks of ZrO2, inducing a shift in the luminescence towards higher temperatures as well as the presence of more TL peaks at higher temperatures.

Hirschsprung's disease in twin to twin transfusion syndrome: a case report.

PubMed

Park, Hye Won; Cho, Min Jeng; Kim, Wook Youn; Kwak, Byung Ok; Kim, Min Hee

2014-12-14

Twin to twin transfusion syndrome (TTTS) is caused by aberrant vascular connections between infant twins and results in high morbidity and mortality in the perinatal period. In donor infants with TTTS and symptoms of intestinal obstruction, small-bowel lesions have been reported in most cases. We report on a 33(+6) gestational wk donor infant with TTTS who had intermittent obstructive episodes, including delayed meconium passage and colonic dilatation on abdominal X-ray. The diagnosis of Hirschsprung's disease was based on a lateral pelvic film with a reversed rectosigmoid ratio. A subsequent barium colon study and rectal suction biopsy indicated a short segment aganglionosis of the colon.

Twin methodology in epigenetic studies.

PubMed

Tan, Qihua; Christiansen, Lene; von Bornemann Hjelmborg, Jacob; Christensen, Kaare

2015-01-01

Since the final decades of the last century, twin studies have made a remarkable contribution to the genetics of human complex traits and diseases. With the recent rapid development in modern biotechnology of high-throughput genetic and genomic analyses, twin modelling is expanding from analysis of diseases to molecular phenotypes in functional genomics especially in epigenetics, a thriving field of research that concerns the environmental regulation of gene expression through DNA methylation, histone modification, microRNA and long non-coding RNA expression, etc. The application of the twin method to molecular phenotypes offers new opportunities to study the genetic (nature) and environmental (nurture) contributions to epigenetic regulation of gene activity during developmental, ageing and disease processes. Besides the classical twin model, the case co-twin design using identical twins discordant for a trait or disease is becoming a popular and powerful design for epigenome-wide association study in linking environmental exposure to differential epigenetic regulation and to disease status while controlling for individual genetic make-up. It can be expected that novel uses of twin methods in epigenetic studies are going to help with efficiently unravelling the genetic and environmental basis of epigenomics in human complex diseases. © 2015. Published by The Company of Biologists Ltd.

Twins and politics: political careers and political attitudes / twin research reviews: pair-bonding; facial expressivity in reared apart twins; educating multiples / stories that move and amaze us: a military funeral; a twins' reunion; Egyptian septuplets; rare occupations.

PubMed

Segal, Nancy L

2008-12-01

Twins and twin research are providing fresh insights into the roots of political behavior. This topic is approached from dual perspectives: why some individuals choose to become politicians, and why individuals vary in their political attitudes and interests. Reviews of timely twin studies in the areas of pair-bonding, facial expressivity and education follow. Finally, some extraordinary events in the lives of twins and their families are revealed.

Zr diffusion in titanite

NASA Astrophysics Data System (ADS)

Cherniak, D. J.

2006-11-01

Chemical diffusion of Zr under anhydrous, pO2-buffered conditions has been measured in natural titanite. The source of diffusant was either zircon powder or a ZrO2-Al2O3-titanite mixture. Experiments were run in sealed silica glass capsules with solid buffers (to buffer at NNO or QFM). Rutherford Backscattering Spectrometry (RBS) was used to measure diffusion profiles. The following Arrhenius parameters were obtained for Zr diffusion parallel to c over the temperature range 753-1,100°C under NNO-buffered conditions: D Zr = 5.33 × 10-7 exp(-325 ± 30 kJ mol-1/RT) m2 s-1 Diffusivities are similar for experiments buffered at QFM. These data suggest that titanite should be moderately retentive of Zr chemical signatures, with diffusivities slower than those for O and Pb in titanite, but faster than those for Sr and the REE. When applied in evaluation of the relative robustness of the recently developed Zr-in-titanite geothermometer (Hayden and Watson, Abstract, 16th V.M. Goldschmidt Conference 2006), these findings suggest that Zr concentrations in titanite will be less likely to be affected by later thermal disturbance than the geothermometer based on Zr concentrations in rutile (Zack et al. in Contrib Mineral Petrol 148:471-488, 2004; Watson et al. in Contrib Mineral. Petrol, 2006), but much less resistant to diffusional alteration subsequent to crystallization than the Ti-in-Zircon geothermometer (Watson and Harrison in Science 308:841-844, 2005).

The preparation of Zr-deuteride and phase stability studies of the Zr-D system

NASA Astrophysics Data System (ADS)

Maimaitiyili, T.; Steuwer, A.; Bjerkén, C.; Blomqvist, J.; Hoelzel, M.; Ion, J. C.; Zanellato, O.

2017-03-01

Deuteride phases in the zirconium-deuterium system in the temperature range 25-286 °C have been studied in-situ by high resolution neutron diffraction. The study primarily focused on observations of δ→γ transformation at 180 °C, and the peritectoid reaction α + δ ↔ γ at 255 °C in commercial grade Zr powder that was deuterated to a deuterium/Zr ratio of one to one. A detailed description of the zirconium deuteride preparation route by high temperature gas loading is also described. The lattice parameters of α-Zr, δ-ZrDx and ε-ZrDx were determined by whole pattern crystal structure analysis, using Rietveld and Pawley refinements, and are in good agreement with values reported in the literature. The controversial γ-hydride phase was observed both in-situ and ex-situ in deuterated Zr powder after a heat treatment at 286 °C and slow cooling.

'Twin2twin' an innovative method of empowering midwives to strengthen their professional midwifery organisations.

PubMed

Cadée, Franka; Perdok, Hilde; Sam, Betty; de Geus, Myrte; Kweekel, Liselotte

2013-10-01

midwives need professional support from a national midwifery organisation to be able to provide the services that are by regulatory mechanisms and accreditation expected of them. Not all midwives in the world are united in a professional organisation. The aim of this project was to strengthen the midwifery organisations of Sierra Leone and the Netherlands. During the process of the project it was realised that the development of a platform of exchange at organisational level would be enhanced by introducing personal exchange between individual midwives. In response to this new insight the original project plan was adjusted by incorporating the twin2twin method. twin2twin is a feminist methodology of mutual exchange between twenty pairs of midwives from different organisations (in this case Sierra Leone and the Netherlands). The method can be distinguished by 10 specific steps. It was developed, used and (re)evaluated through focus group discussions, storytelling and written evaluations. twinning of organisations was strengthened by adding a human component to the process. With the use of the 'twin2twin' method, midwives were encouraged to invested in a professional and personal bond with their 'twin sister'. This bond was independent and went beyond the relatively short four year project period. Through personal engagement and mutual exchange of knowledge and skills, midwives empowered each other to build and strengthen their midwifery organisations both in Sierra Leone and the Netherlands. (Empowerment refers to the expansion in people's ability to make strategic life choices in a context where this ability was previously denied to them (Narayan, 2005); organisational empowerment includes processes and structures that enhance members' skills and provides them with the mutual support necessary to effect community level change (Zimmerman, 1995).). despite challenges we are convinced that twin2twin can be of additional benefit for the success of other projects

Significant Improvement of Thermal Stability for CeZrPrNd Oxides Simply by Supercritical CO2 Drying

PubMed Central

Fan, Yunzhao; Wang, Zizi; Xin, Ying; Li, Qian; Zhang, Zhaoliang; Wang, Yingxia

2014-01-01

Pr and Nd co-doped Ce-Zr oxide solid solutions (CZPN) were prepared using co-precipitation and microemulsion methods. It is found that only using supercritical CO2 drying can result in a significant improvement of specific surface area and oxygen storage capacity at lower temperatures for CZPN after aging at 1000°C for 12 h in comparison with those using conventional air drying and even supercritical ethanol drying. Furthermore, the cubic structure was obtained in spite of the fact that the atomic ratio of Ce/(Ce+Zr+Pr+Nd) is as low as 29%. The high thermal stability can be attributed to the loosely aggregated morphology and the resultant Ce enrichment on the nanoparticle surface, which are caused by supercritical CO2 drying due to the elimination of surface tension effects on the gas-liquid interface. PMID:24516618

Ferroelectricity-induced resistive switching in Pb(Zr0.52Ti0.48)O3/Pr0.7Ca0.3MnO3/Nb-doped SrTiO3 epitaxial heterostructure

NASA Astrophysics Data System (ADS)

Md. Sadaf, Sharif; Mostafa Bourim, El; Liu, Xinjun; Hasan Choudhury, Sakeb; Kim, Dong-Wook; Hwang, Hyunsang

2012-03-01

We investigated the effect of a ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin film on the generation of resistive switching in a stacked Pr0.7Ca0.3MnO3 (PCMO)/Nb-doped SrTiO3 (Nb:STO) heterostructure forming a p-n junction. To promote the ferroelectric effect, the thin PZT active layer was deposited on an epitaxially grown p-type PCMO film on a lattice-matched n-type Nb:STO single crystal. It was concluded that the observed resistive switching behavior in the all-perovskite Pt/PZT/PCMO/Nb:STO heterostructure was related to the modulation of PCMO/Nb:STO p-n junction's depletion width, which was caused either by the PZT ferroelectric polarization field effect, the electrochemical drift of oxygen ions under an electric field, or both simultaneously.

Zero added oxygen for high quality sputtered ITO. A data science investigation of reduced Sn-content and added Zr

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

Peshek, Timothy J.; Burst, James M.; Coutts, Timothy J.

Here, we demonstrate mobilities of >45 cm 2/V s for sputtered tin-doped indium oxide (ITO) films at zero added oxygen. All films were deposited with 5 wt. % SnO 2, instead of the more conventional 8–10 wt. %, and had varying ZrO 2 content from 0 to 3 wt. %, with a subsequent reduction in In 2O 3 content. Moreover, these films were deposited by radio-frequency magnetron sputtering from nominally stoichiometric targets with varying oxygen partial pressure in the sputter ambient. Anomalous behavior was discovered for films with no Zr-added, where a bimodality of high and low mobilities was discoveredmore » for nominally similar growth conditions. However, all films showed the lowest resistivity and highest mobilities when the oxygen partial pressure in the sputter ambient was zero. This result is contrasted with several other reports of ITO transport performance having a maximum for small but nonzero oxygen partial pressure. Our result is attributed to the reduced concentration of SnO 2. The addition of ZrO 2 yielded the highest mobilities at >55 cm 2/V s and the films showed a modest increase in optical transmission with increasing Zr-content.« less

Zero added oxygen for high quality sputtered ITO: A data science investigation of reduced Sn-content and added Zr

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

Peshek, Timothy J.; Burst, James M.; Coutts, Timothy J.

The authors demonstrate mobilities of >45 cm{sup 2}/V s for sputtered tin-doped indium oxide (ITO) films at zero added oxygen. All films were deposited with 5 wt. % SnO{sub 2}, instead of the more conventional 8–10 wt. %, and had varying ZrO{sub 2} content from 0 to 3 wt. %, with a subsequent reduction in In{sub 2}O{sub 3} content. These films were deposited by radio-frequency magnetron sputtering from nominally stoichiometric targets with varying oxygen partial pressure in the sputter ambient. Anomalous behavior was discovered for films with no Zr-added, where a bimodality of high and low mobilities was discovered for nominally similar growth conditions.more » However, all films showed the lowest resistivity and highest mobilities when the oxygen partial pressure in the sputter ambient was zero. This result is contrasted with several other reports of ITO transport performance having a maximum for small but nonzero oxygen partial pressure. This result is attributed to the reduced concentration of SnO{sub 2}. The addition of ZrO{sub 2} yielded the highest mobilities at >55 cm{sup 2}/V s and the films showed a modest increase in optical transmission with increasing Zr-content.« less

Zero added oxygen for high quality sputtered ITO. A data science investigation of reduced Sn-content and added Zr

DOE PAGES

Peshek, Timothy J.; Burst, James M.; Coutts, Timothy J.; ...

2016-01-19

Here, we demonstrate mobilities of >45 cm 2/V s for sputtered tin-doped indium oxide (ITO) films at zero added oxygen. All films were deposited with 5 wt. % SnO 2, instead of the more conventional 8–10 wt. %, and had varying ZrO 2 content from 0 to 3 wt. %, with a subsequent reduction in In 2O 3 content. Moreover, these films were deposited by radio-frequency magnetron sputtering from nominally stoichiometric targets with varying oxygen partial pressure in the sputter ambient. Anomalous behavior was discovered for films with no Zr-added, where a bimodality of high and low mobilities was discoveredmore » for nominally similar growth conditions. However, all films showed the lowest resistivity and highest mobilities when the oxygen partial pressure in the sputter ambient was zero. This result is contrasted with several other reports of ITO transport performance having a maximum for small but nonzero oxygen partial pressure. Our result is attributed to the reduced concentration of SnO 2. The addition of ZrO 2 yielded the highest mobilities at >55 cm 2/V s and the films showed a modest increase in optical transmission with increasing Zr-content.« less

Purification of nuclear grade Zr scrap as the high purity dense Zr deposits from Zirlo scrap by electrorefining in LiF-KF-ZrF4 molten fluorides

NASA Astrophysics Data System (ADS)

Park, Kyoung Tae; Lee, Tae Hyuk; Jo, Nam Chan; Nersisyan, Hayk H.; Chun, Byong Sun; Lee, Hyuk Hee; Lee, Jong Hyeon

2013-05-01

Zirconium (Zr) has commonly been used as a cladding material of nuclear fuel. Moreover, it is regarded as the only material that can be used for nuclear fuel cladding because it has the lowest neutron capture cross section of any metal element and because it has high corrosion resistance and size stability. In this study, Hf-free Zr tubes (Zr-1Nb-1Sn-0.1Fe) were used as anode materials and electrorefining was performed in a LiF-KF eutectic 6 wt.% ZrF4 molten fluoride salt system. As a result of electrolysis, Zr scrap metal was recycled into pure Zr with low levels of impurities, and the size and density of the Zr deposit was controlled using applied current density.

Education in Twins and Their Parents Across Birth Cohorts Over 100 years: An Individual-Level Pooled Analysis of 42-Twin Cohorts.

PubMed

Silventoinen, Karri; Jelenkovic, Aline; Latvala, Antti; Sund, Reijo; Yokoyama, Yoshie; Ullemar, Vilhelmina; Almqvist, Catarina; Derom, Catherine A; Vlietinck, Robert F; Loos, Ruth J F; Kandler, Christian; Honda, Chika; Inui, Fujio; Iwatani, Yoshinori; Watanabe, Mikio; Rebato, Esther; Stazi, Maria A; Fagnani, Corrado; Brescianini, Sonia; Hur, Yoon-Mi; Jeong, Hoe-Uk; Cutler, Tessa L; Hopper, John L; Busjahn, Andreas; Saudino, Kimberly J; Ji, Fuling; Ning, Feng; Pang, Zengchang; Rose, Richard J; Koskenvuo, Markku; Heikkilä, Kauko; Cozen, Wendy; Hwang, Amie E; Mack, Thomas M; Siribaddana, Sisira H; Hotopf, Matthew; Sumathipala, Athula; Rijsdijk, Fruhling; Sung, Joohon; Kim, Jina; Lee, Jooyeon; Lee, Sooji; Nelson, Tracy L; Whitfield, Keith E; Tan, Qihua; Zhang, Dongfeng; Llewellyn, Clare H; Fisher, Abigail; Burt, S Alexandra; Klump, Kelly L; Knafo-Noam, Ariel; Mankuta, David; Abramson, Lior; Medland, Sarah E; Martin, Nicholas G; Montgomery, Grant W; Magnusson, Patrik K E; Pedersen, Nancy L; Dahl Aslan, Anna K; Corley, Robin P; Huibregtse, Brooke M; Öncel, Sevgi Y; Aliev, Fazil; Krueger, Robert F; McGue, Matt; Pahlen, Shandell; Willemsen, Gonneke; Bartels, Meike; van Beijsterveldt, Catharina E M; Silberg, Judy L; Eaves, Lindon J; Maes, Hermine H; Harris, Jennifer R; Brandt, Ingunn; Nilsen, Thomas S; Rasmussen, Finn; Tynelius, Per; Baker, Laura A; Tuvblad, Catherine; Ordoñana, Juan R; Sánchez-Romera, Juan F; Colodro-Conde, Lucia; Gatz, Margaret; Butler, David A; Lichtenstein, Paul; Goldberg, Jack H; Harden, K Paige; Tucker-Drob, Elliot M; Duncan, Glen E; Buchwald, Dedra; Tarnoki, Adam D; Tarnoki, David L; Franz, Carol E; Kremen, William S; Lyons, Michael J; Maia, José A; Freitas, Duarte L; Turkheimer, Eric; Sørensen, Thorkild I A; Boomsma, Dorret I; Kaprio, Jaakko

2017-10-01

Whether monozygotic (MZ) and dizygotic (DZ) twins differ from each other in a variety of phenotypes is important for genetic twin modeling and for inferences made from twin studies in general. We analyzed whether there were differences in individual, maternal and paternal education between MZ and DZ twins in a large pooled dataset. Information was gathered on individual education for 218,362 adult twins from 27 twin cohorts (53% females; 39% MZ twins), and on maternal and paternal education for 147,315 and 143,056 twins respectively, from 28 twin cohorts (52% females; 38% MZ twins). Together, we had information on individual or parental education from 42 twin cohorts representing 19 countries. The original education classifications were transformed to education years and analyzed using linear regression models. Overall, MZ males had 0.26 (95% CI [0.21, 0.31]) years and MZ females 0.17 (95% CI [0.12, 0.21]) years longer education than DZ twins. The zygosity difference became smaller in more recent birth cohorts for both males and females. Parental education was somewhat longer for fathers of DZ twins in cohorts born in 1990-1999 (0.16 years, 95% CI [0.08, 0.25]) and 2000 or later (0.11 years, 95% CI [0.00, 0.22]), compared with fathers of MZ twins. The results show that the years of both individual and parental education are largely similar in MZ and DZ twins. We suggest that the socio-economic differences between MZ and DZ twins are so small that inferences based upon genetic modeling of twin data are not affected.

Mass transport and crystal growth of the mixed ZrS2-ZrSe2 system

NASA Technical Reports Server (NTRS)

Wiedemeier, Heribert; Goldman, Howard

1986-01-01

The solid solubility of the ZrS2-ZrSe2 system was reinvestigated by annealing techniques to establish the relationship between composition and lattice parameters. Mixed crystals of ZrS(2x)Se2(1-x) for selected compositions of the source material were grown by chemical vapor transport and characterized by X-ray diffraction and microscopic methods. The mass transport rates and crystal growth of ZrSSe were investigated and compared with those of other compositions. The mass fluxes of the mixed system showed an increase with increasing selenium content. The transport products were richer in ZrSe2 than the residual source materials when the ZrSe2 content of the starting materials was greater than 50 mol.-pct. The mass transport rates revealed an increasing mass flux with pressure.

Using Twins to Better Understand Sibling Relationships.

PubMed

Mark, Katharine M; Pike, Alison; Latham, Rachel M; Oliver, Bonamy R

2017-03-01

We compared the nature of the sibling relationship in dyads of varying genetic relatedness, employing a behavioural genetic design to estimate the contribution that genes and the environment have on this familial bond. Two samples were used-the Sisters and Brothers Study consisted of 173 families with two target non-twin children (mean ages = 7.42 and 5.22 years respectively); and the Twins, Family and Behaviour study included 234 families with two target twin children (mean age = 4.70 years). Mothers and fathers reported on their children's relationship with each other, via a postal questionnaire (the Sisters and Brothers Study) or a telephone interview (the Twins, Family and Behaviour study). Contrary to expectations, no mean level differences emerged when monozygotic twin pairs, dizygotic twin pairs, and non-twin pairs were compared on their sibling relationship quality. Behavioural genetic analyses also revealed that the sibling bond was modestly to moderately influenced by the genetic propensities of the children within the dyad, and moderately to substantially influenced by the shared environment common to both siblings. In addition, for sibling negativity, we found evidence of twin-specific environmental influence-dizygotic twins showed more reciprocity than did non-twins. Our findings have repercussions for the broader application of results from future twin-based investigations.

Twins: A cloning experience.

PubMed

Prainsack, Barbara; Spector, Tim D

2006-11-01

Drawing upon qualitative interviews with monozygotic (identical) twins sharing 100% of their genes, and with dizygotic (fraternal) twins and singletons as control groups, this paper explores what it means to be genetically identical. (The twins interviewed were from the TwinsUK register in London.) In the context of the ongoing debate on human reproductive cloning, it examines questions such as: To what extent do identical twins perceive their emotional and physical bond to be a result of their genetic makeup? What would they think if they had been deliberately created genetically identical? How would they feel about being genetically identical to a person who was born a few years earlier or later? First, our respondents ascribed no great significance to the role of genes in their understanding of what it means to be identical twins. Second, the opinion that human reproductive cloning would "interfere with nature", or "contradict God's will", was expressed by our respondents exclusively on the abstract level. The more our respondents were able to relate a particular invented cloning scenario to their own life-worlds, the lower the prevalence of the argument. Third, for all three groups of respondents, the scenario of having been born in one of the other groups was perceived as strange. Fourth, the aspect that our respondents disliked about cloning scenarios was the potential motives of the cloners. Without equating monozygotic twins directly with "clones", these results from "naturally" genetically identical individuals add a new dimension to what a future cloning situation could entail: The cloned person might possibly (a) perceive a close physical and emotional connection to the progenitor as a blessing; (b) suffer from preconceptions of people who regard physical likeness as a sign of incomplete individuality; and (c) perceive the idea of not having been born a clone of a particular person as unpleasant.

Characterization of twin boundaries in an Fe–17.5Mn–0.56C twinning induced plasticity steel

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

Patterson, Erin E., E-mail: erin.diedrich@yahoo.com; Field, David P., E-mail: dfield@wsu.edu; Zhang, Yudong, E-mail: yudong.zhang@univ-metz.fr

2013-11-15

A twinning-induced plasticity steel of composition Fe–17.5 wt.% Mn–0.56 wt.% C–1.39 wt.% Al–0.24 wt.% Si was analyzed for the purpose of characterizing the relationship between tensile strain and deformation twinning. Tensile samples achieved a maximum of 0.46 true strain at failure, and a maximum ultimate tensile strength of 1599 MPa. Electron backscatter diffraction (EBSD) analysis showed that the grain orientation rotated heavily to < 111 > parallel to the tensile axis above 0.3 true strain. Sigma 3 misorientations, as identified by EBSD orientation measurements, and using the image quality maps were used to quantify the number of twins present inmore » the scanned areas of the samples. The image quality method yielded a distinct positive correlation between the twin area density and deformation, but the orientation measurements were unreliable in quantifying twin density in these structures. Quantitative analysis of the twin fraction is limited from orientation information because of the poor spatial resolution of EBSD in relation to the twin thickness. The EBSD orientation maps created for a thin foil sample showed some improvement in the resolution of the twins, but not enough to be significant. Measurements of the twins in the transmission electron microscopy micrographs yielded an average thickness of 23 nm, which is near the resolution capabilities of EBSD on this material for the instrumentation used. Electron channeling contrast imaging performed on one bulk tensile specimen of 0.34 true strain, using a method of controlled diffraction, yielded several images of twinning, dislocation structures and strain fields. A twin thickness of 66 nm was measured by the same method used for the transmission electron microscopy measurement. It is apparent that the results obtain by electron channeling contrast imaging were better than those by EBSD but did not capture all information on the twin boundaries such as was observed by transmission electron

Incidence of spontaneous twin anemia-polycythemia sequence in monochorionic-diamniotic twin pregnancies: Single-center prospective study.

PubMed

Yokouchi, Tae; Murakoshi, Takeshi; Mishima, Takashi; Yano, Hiroko; Ohashi, Madoka; Suzuki, Takashi; Shinno, Takashi; Matsushita, Mitsuru; Nakayama, Satoru; Torii, Yuichi

2015-06-01

The purpose of this study was to prospectively estimate the incidence of spontaneous twin anemia-polycythemia sequence (TAPS) in monochorionic-diamniotic twin pregnancies. We prospectively examined umbilical cord hemoglobin (Hb) and reticulocyte count of consecutive monochorionic-diamniotic twin pregnancies delivered at Seirei Hamamatsu General Hospital from December 2006 to September 2013. We excluded cases of twin-twin transfusion syndrome, intrauterine fetal demise, and missing data (Hb and reticulocyte count missing from the medical record). TAPS was diagnosed using the postnatal criteria of intertwin Hb difference >8.0 g/dL and reticulocyte count ratio >1.7. Acute feto-fetal hemorrhage was defined as Hb difference >7 g/dL and reticulocyte count ratio <1.7. A total of 185 monochorionic-diamniotic twin pregnancies were included in this study. Three fulfilled the diagnostic criteria for postnatal TAPS, and one fulfilled the diagnostic criteria for acute feto-fetal hemorrhage. The incidence of spontaneous TAPS in monochorionic-diamniotic twin pregnancies was 1.6% (3/185) at Seirei Hamamatsu General Hospital. © 2014 The Authors. Journal of Obstetrics and Gynaecology Research © 2014 Japan Society of Obstetrics and Gynecology.

The Texas Twin Project

PubMed Central

Harden, K. Paige; Tucker-Drob, Elliot M.; Tackett, Jennifer L.

2013-01-01

Socioeconomic position, racial/ethnic minority status, and other characteristics of the macro-environment may be important moderators of genetic influence on a wide array of psychosocial outcomes. Designed to maximize representation of low socioeconomic status families and racial/ethnic minorities, the Texas Twin Project is an on-going study of school-age twins (preschool through 12th grade) enrolled in public schools in the Austin, Texas and Houston, Texas metropolitan areas. School rosters are used to identify twin families from a target population with sizable populations of African-American (18%), Hispanic / Latino (48%), and non-Hispanic White (27%) children and adolescents, over half of whom meet U.S. guidelines for classification as economically disadvantaged. Initial efforts have focused on a large-scale, family-based survey study involving both parent and child reports of personality, psychopathology, physical health, academic interests, parent-child relationships, and aspects of the home environment. In addition, the Texas Twin Project is the basis for an in-laboratory study of adolescent decision-making, delinquency, and substance use. Future directions include geographic expansion of the sample to the entire state of Texas (with a population of over 25 million people) and genotyping of participating twins. PMID:23111007

Physical and mental development of Turkish twins.

PubMed

Ozçakar, Z Birsin; Sahin, Figen; Beyazova, Ufuk; Soysal, Sebnem

2003-12-01

Multiple gestations are known to bring some risks in the prenatal and natal period, but whether it is a risk for development in childhood is a matter of debate. The aim of the present study was to evaluate physical and mental development of Turkish twins and then to assess whether being a twin poses risks for their development. Fifty-two twin pairs (104 children) aged between 1 and 5 years were enrolled in the study. The control group consisted of 91 singletons, who were matched according to age, sex, gestational week and maternal educational level. The Denver Developmental Screening Test (DDST) was administered to assess cognitive development. Student t-test and chi2 test were used to compare the two groups. The mean age of the mothers of twins did not differ from that of singleton mothers (P > 0.05). Twins were more frequently born in cases of assisted fertilization and were more often born via cesarean section. The birthweights of twins were lower and they were more frequently hospitalized after birth. The breast feeding period was shorter in twins and they had more chronic diseases than singletons (P < 0.05). Mothers of twins needed more help while caring for their infants. Physical development of twins and singletons did not differ statistically (P > 0.05). Twins had more suspect and delayed results in the DDST, especially in the language section of the test. Physical and mental development of twins does not differ significantly from singletons except that twins might have a tendency towards slow language acquisition.

Low-temperature, solution-processed ZrO2:B thin film: a bifunctional inorganic/organic interfacial glue for flexible thin-film transistors.

PubMed

Park, Jee Ho; Oh, Jin Young; Han, Sun Woong; Lee, Tae Il; Baik, Hong Koo

2015-03-04

A solution-processed boron-doped peroxo-zirconium oxide (ZrO2:B) thin film has been found to have multifunctional characteristics, providing both hydrophobic surface modification and a chemical glue layer. Specifically, a ZrO2:B thin film deposited on a hydrophobic layer becomes superhydrophilic following ultraviolet-ozone (UVO) treatment, whereas the same treatment has no effect on the hydrophobicity of the hydrophobic layer alone. Investigation of the ZrO2:B/hydrophobic interface layer using angle-resolved X-ray photoelectron spectroscopy (AR XPS) confirmed it to be chemically bonded like glue. Using the multifunctional nature of the ZrO2:B thin film, flexible amorphous indium oxide (In2O3) thin-film transistors (TFTs) were subsequently fabricated on a polyimide substrate along with a ZrO2:B/poly-4-vinylphenol (PVP) dielectric. An aqueous In2O3 solution was successfully coated onto the ZrO2:B/PVP dielectric, and the surface and chemical properties of the PVP and ZrO2:B thin films were analyzed by contact angle measurement, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The surface-engineered PVP dielectric was found to have a lower leakage current density (Jleak) of 4.38 × 10(-8) A/cm(2) at 1 MV/cm, with no breakdown behavior observed up to a bending radius of 5 mm. In contrast, the electrical characteristics of the flexible amorphous In2O3 TFT such as on/off current ratio (Ion/off) and electron mobility remained similar up to 10 mm of bending without degradation, with the device being nonactivated at a bending radius of 5 mm. These results suggest that ZrO2:B thin films could be used for low-temperature, solution-processed surface-modified flexible devices.

Investigation of thick PLD-GdBCO and ZrO2 doped GdBCO coated conductors with high critical current on PLD-CeO2 capped IBAD-GZO substrate tapes

NASA Astrophysics Data System (ADS)

Takahashi, K.; Kobayashi, H.; Yamada, Y.; Ibi, A.; Fukushima, H.; Konishi, M.; Miyata, S.; Shiohara, Y.; Kato, T.; Hirayama, T.

2006-09-01

In order to increase the critical current, Ic, we have fabricated thick GdBa2Cu3O7-δ (GdBCO) coated conductors (CCs) by the pulsed laser deposition (PLD) method on PLD-CeO2/ion-beam assisted deposition (IBAD)-Gd2Zr2O7 (GZO)/hastelloy metal substrate tapes. The highest critical current value was 522 A cm-1 for a thickness of 3.6 µm in self-field at 77 K. It was found that a low volume fraction of a-axis orientated grains was obtained in the thick GdBCO CCs, compared to YBa2Cu3O7-δ (YBCO) CCs. Consequently, the GdBCO CCs showed higher critical current density (Jc) than YBCO CCs in all thicknesses from 0.2 to 3.6 µm. Furthermore, we have succeeded in improving Ic in a magnetic field by the introduction of artificial pinning centres using a 5 mol% ZrO2 doped GdBCO target. In the measurement of the Ic dependence on the magnetic field angle, θ, Ic was much improved, especially at 0°, i.e., with the magnetic field parallel to the c-axis. The Ic value at 3 T was 59.5 A cm-1 at 0° and it showed a minimum of 42.3 A cm-1 at 82° for 2.28 µm thick CC. The minimum value in the angular dependence of Ic at 3 T was about five times higher than that of YBCO CC and two times higher than that of pure GdBCO CC.

Development of a thick GdBCO and ZrO 2-doped GdBCO film with a high critical current on a PLD-CeO 2/IBAD-GZO metal substrate

NASA Astrophysics Data System (ADS)

Kinoshita, A.; Takahashi, K.; Kobayashi, H.; Yamada, Y.; Ibi, A.; Fukushima, H.; Konishi, M.; Miyata, S.; Shiohara, Y.; Kato, T.; Hirayama, T.

2007-10-01

In order to obtain a high critical current, Ic, we have fabricated a thick GdBa2Cu3O7-x (GdBCO) film by the pulsed laser deposition (PLD) method on a PLD-CeO2/ion-beam assisted deposition (IBAD)-Gd2Zr2O7 (GZO)/hastelloy metal substrate. The film of a 3.6 μm thickness exhibited the highest critical current of 522 A/cm at self-field and at 77 K. It was found that a low volume fraction of a-axis oriented grains was obtained in the thick GdBCO films, compared to YBa2Cu3O7-x (YBCO) films. The GdBCO films showed a higher critical current density (Jc), than YBCO films in all thicknesses from 0.2 to 3.6 μm. Furthermore, we have improved Ic in a magnetic field by the introduction of artificial pinning centers using a 5 mol% ZrO2-doped GdBCO target. In the measurement of angular dependence of Ic, which was much improved at 0°, the magnetic field was parallel to the c-axis. The Ic value at 3 T was 59.5 A/cm at 0° and showed a minimum of 42.3 A/cm at 82° for the film of a 2.3 μm thickness. The minimum value at 3 T in angular dependence of Ic was about five times higher than that of the YBCO film and two times higher than that of pure the GdBCO film.

Teaching about twins: college courses and public lectures.

PubMed

Segal, Nancy L

2013-12-01

The present article describes teaching experiences and observations in college courses and public lectures on twins. It is concluded that much more information about twins, at both research and practical levels, requires general dissemination. This discussion is followed by reviews of recent twin research on the topics of obesity control, post-zygotic mutation, in vitro fertilization, and schisis-associated defects. Media reports of twins accused of rape, infant Chinese twins sold separately for profit, a twin CEO, and twins pursuing the same career are presented.

Enhanced Dielectric Nonlinearity in Epitaxial Pb(0.92)La(0.08)Zr(0.52)Ti(0.48)O(3)

DTIC Science & Technology

2014-04-23

storage capacitors, electro-mechanical, or photo- mechanical transducers, etc.1–3 Among them, Lead zirconate titanate system ( PZT ), which exhibits...and at the interfaces between PZT and electro- des. Recently, lanthanum doped PZT with different Zr/Ti ra- tio, such as 65/35, 53/47, or 20/80, has...been investigated, since it can effectively reduce oxygen vacancy, decrease leakage current, and lower the fatigue and domain pinning.8–10 In general

Factors influencing twins and zygosity.

PubMed

Hankins, Gary V D; Saade, George R

2005-01-01

Zygosity is influenced by many factors. Monozygotic twins occur spontaneously in approximately 1 in 250 births and are felt to increase twofold with ovulation induction techniques. Monozygotic twinning also increases in proportion to the number of blastocysts transferred during in vitro fertilisation. In contrast, dizygotic twinning appears to be influenced by race, genetic factors, maternal age, fertility enhancing drugs, folic acid supplementation, and maternal nutritional status.

Fetal presentation and successful twin vaginal delivery.

PubMed

Easter, Sarah Rae; Lieberman, Ellice; Carusi, Daniela

2016-01-01

Despite the demonstrated safety of a trial of labor for pregnancies with a vertex-presenting twin and clinical guidelines in support of this plan, the rate of planned cesarean delivery for twin pregnancies remains high. This high rate, as well as variation in cesarean rates for twin pregnancies across providers, may be influenced strongly by concern about delivery of the second twin, particularly when it is in a nonvertex presentation. There are limited data in the literature that has examined the impact of the position of the nonpresenting twin on successful vaginal delivery or maternal/neonatal morbidity. We hypothesized that nonvertex presentation of the second twin would be associated with lower rates of successful vaginal birth for those patients attempting labor. This institutional review board-approved, retrospective cohort study of women who labored with twin pregnancies in a single urban hospital from 2007-2011. We included women with vertex-presenting first twins at >32 weeks gestation without a contraindication to labor and excluded those with uterine scar or lethal fetal anomaly. Vaginal delivery rates were evaluated according to vertex or nonvertex presentation of the second twin at admission and again at delivery. Maternal and neonatal morbidities were evaluated separately. Logistic regression was used to control for multiple confounders. Seven hundred sixteen patients met the inclusion criteria; 349 patients (49%) underwent a trial of labor. This included 73% (296/406) of eligible vertex/vertex twins and 17% (53/310) eligible vertex/nonvertex twins (P < .01). When compared with laboring patients with vertex/vertex-presenting twins, those with vertex/nonvertex twins were younger (median age, 32 vs 33 years; P = .05), were more often multiparous (60% vs 43%; P = .02), and were less likely to have hypertension (13% vs 27%; P = .03). Eighty-five percent of patients with nonvertex second twins at admission delivered vaginally, compared with 70% of

A tale of twin Higgs: natural twin two Higgs doublet models

DOE PAGES

Yu, Jiang-Hao

2016-12-28

In original twin Higgs model, vacuum misalignment between electroweak and new physics scales is realized by adding explicit Z 2 breaking term. Introducing additional twin Higgs could accommodate spontaneous Z 2 breaking, which explains origin of this misalignment. We introduce a class of twin two Higgs doublet models with most general scalar potential, and discuss general conditions which trigger electroweak and Z 2 symmetry breaking. Various scenarios on realising the vacuum misalignment are systematically discussed in a natural composite two Higgs double model framework: explicit Z 2 breaking, radiative Z 2 breaking, tadpole-induced Z 2 breaking, and quartic-induced Z 2more » breaking. Finally, we investigate the Higgs mass spectra and Higgs phenomenology in these scenarios.« less

Higher Incidence of Hypospadias in Monochorionic Twins.

PubMed

Visser, Remco; Burger, Nienke C M; van Zwet, Erik W; Hilhorst-Hofstee, Yvonne; Haak, Monique C; van den Hoek, Joop; Oepkes, Dick; Lopriore, Enrico

2015-10-01

Hypospadias is associated with twinning. The incidence of hypospadias in monochorionic and dichorionic male twins is, however, yet to be determined. All medical records of monochorionic and dichorionic twins admitted to our neonatal nursery between January 2004 and August 2013 were reviewed for the presence of hypospadias. A total of 350 monochorionic and 303 dichorionic male twins were included in the study. The incidence of hypospadias in monochorionic and dichorionic groups was 4% (14/350) and 1% (3/303) (p = .016) respectively. In 11 of the 15 twin couples, hypospadias occurred in the twin with the lowest birth weight. The rate of hypospadias in twin infants small-for-gestational-age group was 10% (6/60) compared with 2% (11/593) in the appropriate-for-gestational-age group (p = .002). In a multivariate analysis, both monochorionicity and small-for-gestational-age were independently associated with hypospadias, odds ratio 4.1 (95% confidence interval (CI): 1.1-14.7) and 6.1 (95% CI: 2.2-17.2) respectively. The incidence of hypospadias is four-fold higher in monochorionic twins compared with dichorionic twins. Hypospadias is also independently associated with small-for-gestational-age.

Viable twin cosmology from neutrino mixing

NASA Astrophysics Data System (ADS)

Csáki, Csaba; Kuflik, Eric; Lombardo, Salvator

2017-09-01

Twin Higgs models solve the little hierarchy problem without introducing new colored particles; however, they are often in tension with measurements of the radiation density at late times. Here we explore viable cosmological histories for twin Higgs models. In particular, we show that mixing between the Standard Model (SM) and twin neutrinos can thermalize the two sectors below the twin QCD phase transition, significantly reducing the twin sector's contribution to the radiation density. The requisite twin neutrino masses of O (1 - 20 ) GeV and mixing angle with SM neutrinos of 10-3-10-5 can be probed in a variety of current and planned experiments. We further find that these parameters can be naturally accessed in a warped UV completion, where the neutrino sector can also generate the Z2-breaking Higgs mass term needed to produce the hierarchy between the symmetry breaking scales f and v .

Multiband nodeless superconductivity near the charge-density-wave quantum critical point in ZrTe3-x Se x

NASA Astrophysics Data System (ADS)

Shan, Cui; Lan-Po, He; Xiao-Chen, Hong; Xiang-De, Zhu; Cedomir, Petrovic; Shi-Yan, Li

2016-07-01

It was found that selenium doping can suppress the charge-density-wave (CDW) order and induce bulk superconductivity in ZrTe3. The observed superconducting dome suggests the existence of a CDW quantum critical point (QCP) in ZrTe3-x Se x near x ≈ 0.04. To elucidate the superconducting state near the CDW QCP, we measure the thermal conductivity of two ZrTe3-x Se x single crystals (x = 0.044 and 0.051) down to 80 mK. For both samples, the residual linear term κ 0/T at zero field is negligible, which is a clear evidence for nodeless superconducting gap. Furthermore, the field dependence of κ 0/T manifests a multigap behavior. These results demonstrate multiple nodeless superconducting gaps in ZrTe3-x Se x , which indicates conventional superconductivity despite of the existence of a CDW QCP. Project supported by the National Basic Research Program of China (Grant Nos. 2012CB821402 and 2015CB921401), the National Natural Science Foundation of China (Grant Nos. 91421101, 11422429, and 11204312), the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, China, and STCSM of China (Grant No. 15XD1500200). Work at Brookhaven National Laboratory was supported by the US DOE under Contract No. DESC00112704.

A twin study of congenital hemiplegia.

PubMed

Goodman, R; Alberman, E

1996-01-01

Twins were more than three times more common in a large sample of London children with congenital hemiplegia than in the general population. This over-representation of twins could largely be explained by their higher rate of preterm birth, though twin-specific risk factors, including the consequences of a co-twin's death in utero, may also have played a part. None of the 34 co-twins who survived infancy had hemiplegia or any other form of cerebral palsy. Among 155 siblings of singletons with congenital hemiplegia, no child had hemiplegia and only one had cerebral palsy. Perhaps it is chance rather then genetic liability or an adverse environment that primarily governs who does and does not become congenitally hemiplegic.

Anorexia and bulimia nervosa in same-sex and opposite-sex twins: lack of association with twin type in a nationwide study of Finnish twins.

PubMed

Raevuori, Anu; Kaprio, Jaakko; Hoek, Hans W; Sihvola, Elina; Rissanen, Aila; Keski-Rahkonen, Anna

2008-12-01

The authors tested the hypothesis that either prenatal feminization or masculinization hormone influences in utero or later socialization affects the risk for anorexia and bulimia nervosa and disordered eating in members of opposite-sex twin pairs. Finnish twins (N=2,426 women, N=1,962 men with known zygosity) from birth cohorts born 1974-1979 were assessed at age 22 to 28 years with a questionnaire for eating disorder symptoms. Based on the questionnaire screen, women (N=292), men (N=53), and their cotwins were interviewed to assess diagnoses of anorexia nervosa and bulimia nervosa (per DSM-IV and broad criteria). In women from opposite-sex twin pairs, the prevalence of DSM-IV or broad anorexia nervosa was not significantly different than that of women from monozygotic pairs or same-sex dizygotic pairs. Of the five male anorexia nervosa probands, only one was from an opposite-sex twin pair. Bulimia nervosa in men was too rare to be assessed by zygosity; the prevalence of DSM-IV or broad bulimia nervosa did not differ in women from opposite- versus same-sex twin pairs. In both sexes, the overall profile of indicators on eating disorders was rather similar between individuals from opposite- and same-sex pairs. The authors found little evidence that the risk for anorexia nervosa, bulimia nervosa, or disordered eating was associated with zygosity or sex composition of twin pairs, thus making it unlikely that in utero femininization or masculinization or socialization effects of growing up with an opposite-sex twin have a major influence on the later development of eating disorders.

Heteropagus twinning on back -- a case report.

PubMed

Debnath, Bidyut; Biswas, Sumitra Kumar

2011-07-01

Heteropagus twins, also called parasitic twins, are malformation of the foetus where the development of one twin is incomplete. They are attached most commonly to the lower chest and upper abdomen. We report a case of heteropagus twin, where the parasite possessed well-formed limb as well as blind ending intestine. It was attached to the back of the host by a broad pedicle. We take this opportunity to classify areas of confusion prevailing regarding twinning, foetus in foetu, teratoma and caudal duplication.

Neurodevelopmental outcome at 2 years in twin-twin transfusion syndrome survivors randomized for the Solomon trial.

PubMed

van Klink, Jeanine M M; Slaghekke, Femke; Balestriero, Marina A; Scelsa, Barbara; Introvini, Paola; Rustico, Mariangela; Faiola, Stefano; Rijken, Monique; Koopman, Hendrik M; Middeldorp, Johanna M; Oepkes, Dick; Lopriore, Enrico

2016-01-01

The preferred treatment for twin-twin transfusion syndrome is fetoscopic laser coagulation of inter-twin vascular anastomoses on the monochorionic placenta. Severe postoperative complications can occur when inter-twin vascular anastomoses remain patent including twin-anemia polycythemia sequence or recurrent twin-twin transfusion syndrome. To minimize the occurrence of residual anastomoses, a modified laser surgery technique, the Solomon technique, was developed in which the entire vascular equator is coagulated. In the Solomon randomized controlled trial (NTR1245), the Solomon technique was associated with a significant reduction in twin-anemia polycythemia sequence and recurrence of twin-twin transfusion syndrome when compared with the standard laser surgery technique. Although a significant improvement in perinatal outcome was shown after the Solomon technique, the clinical importance should also be ascertained with long-term follow-up evaluation of the surviving children. The purpose of this study was to compare the long-term neurodevelopmental outcome in surviving children with twin-twin transfusion syndrome who were included in the Solomon randomized trial and treated with either the Solomon technique or standard laser surgery technique. Routine standardized follow-up evaluation in survivors, at least 2 years after the estimated date of delivery, was performed at 2 of the 5 centers that participated in the Solomon trial: Buzzi Hospital Milan (Italy) and Leiden University Medical Center (The Netherlands). The primary outcome of this follow-up study was survival without long-term neurodevelopmental impairment at age 2 years. Neurodevelopmental impairment was defined as cerebral palsy, cognitive and/or motor development score of <85, bilateral blindness, or deafness. Cognitive and motor development was evaluated with the use of Bayley-III. All analyses per fetus, neonate, or child were conducted with the generalized estimated equation module to account for the

Twin Paradox: A Complete Treatment from the Point of View of Each Twin.

ERIC Educational Resources Information Center

Perrin, Robert

1979-01-01

Modifies and expands on the treatment of the twin paradox by solving the gravitational field equations and geodesic equations of motion in the traveling twin's reference frame, thus determining the time elapsed on the Earth during the periods of acceleration. (Author/GA)

Biocompatible Ni-free Zr-based bulk metallic glasses with high-Zr-content: compositional optimization for potential biomedical applications.

PubMed

Hua, Nengbin; Huang, Lu; Chen, Wenzhe; He, Wei; Zhang, Tao

2014-11-01

The present study designs and prepares Ni-free Zr60+xTi2.5Al10Fe12.5-xCu10Ag5 (at.%, x=0, 2.5, 5) bulk metallic glasses (BMGs) by copper mold casting for potential biomedical application. The effects of Zr content on the in vitro biocompatibility of the Zr-based BMGs are evaluated by investigating mechanical properties, bio-corrosion behavior, and cellular responses. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high notch toughness. Electrochemical measurements demonstrate that the Zr-based BMGs are corrosion resistant in a phosphate buffered saline solution. The bio-corrosion resistance of BMGs is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. Regular cell responses of mouse MC3T3-E1 cells, including cell adhesion and proliferation, are observed on the Zr-Ti-Al-Fe-Cu-Ag BMGs, which reveals their general biosafety. The high-Zr-based BMGs exhibit a higher cell proliferation activity in comparison with that of pure Zr and Ti-6Al-4V alloy. The effects of Zr content on the in vitro biocompatibility can be used to guide the future design of biocompatible Zr-based BMGs. Copyright © 2014 Elsevier B.V. All rights reserved.

Novel approach to Zr powder production by smooth ZrCl4 bubbling through molten salt

NASA Astrophysics Data System (ADS)

Bae, Hyun-Na; Choi, Mi-Seon; Lee, Go-Gi; Kim, Seon-Hyo

2016-01-01

A reduction process using ZrCl4 bubbles as a reactant was investigated to produce zirconium metals. ZrCl4 vapor was bubbled through the lance in the bath, in which Mg melt and MgCl2 salt were separated. Zr powder was formed by a reduction of ZrCl4 bubbles in magnesium layer. However, the lance was clogged by the aggregate of zirconium occurred during ZrCl4 vapor injecting leading to interruption of ZrCl4 supply into the bath. This phenomenon could be caused by the presence of magnesium at the lance tip, which passes through MgCl2 salt during bubbling, and then zirconium was formed in the forms of intermetallic compounds with aluminum. In this study, the effect of molten salt on the troubled phenomena was investigated and it was verified that CaCl2 with relatively low Weber number meaning relatively high surface tension as molten salt is effective in inhibiting the lance clogging phenomena. Then, a few micrometer-sized Zr powder with the high purity of 91.6 wt% was obtained smoothly without the formation of intermetallic compound.

Best Practices for Twin Placement in School

ERIC Educational Resources Information Center

Lacina, Jan

2012-01-01

The children's book "Two Is for Twins" celebrates twins and illustrates the many "twos" in a child's world. The uniqueness of twos does not have to mean separate classrooms for twins in child development programs, preschool, or elementary school settings. With recent dramatic increases in the US twin population, how should educators address the…

Twins discordant for myositis and systemic lupus erythematosus show markedly enriched autoantibodies in the affected twin supporting environmental influences in pathogenesis

PubMed Central

2014-01-01

Background Studies of twin pairs discordant for autoimmune conditions provide a unique opportunity to explore contributing factors triggered by complex gene-environment interactions. Methods In this cross-sectional study, thirty-one monozygotic or dizygotic twin pairs discordant for myositis or systemic lupus erythematosus (SLE), along with matched healthy controls were evaluated for antibodies against a panel of 21 autoantigens. Results Autoantibody profiling revealed that 42% of the affected twins showed significant seropositivity against autoantigens in the panel. In many of these affected twins, but none of healthy controls, there were high levels of autoantibodies detected against two or more autoantigens commonly seen in systemic autoimmune diseases including Ro52, Ro60, RNP-70 K and/or RNP-A. In contrast, only 10% (3/31) of the unaffected twins showed seropositivity and these immunoreactivities were against single autoantigens not seen in systemic autoimmune diseases. While no significant differences in autoantibodies were detected between the affected or unaffected twins against thyroid peroxidase, transglutaminase and several cytokines, 23% of the affected twins with myositis showed autoantibodies against the gastric ATPase. Analysis of the monozygotic twins separately also revealed a higher frequencies of autoantibodies in the affected twins compared to the unaffected twins (P = 0.046). Lastly, clinical analysis of both the affected monozygotic and dizygotic twins revealed that the autoantibody seropositive affected twins had a greater global disease activity score compared to seronegative affected twins (P = 0.019). Conclusion The findings of significantly more autoantibodies in the affected twins with myositis and SLE compared to the unaffected twins are consistent with potential non-genetic factors playing a role in autoantibody production and pathogenesis of these autoimmune disorders. PMID:24602337

Aqueous Isolation of 17-Nuclear Zr-/Hf- Oxide Clusters during the Hydrothermal Synthesis of ZrO2/HfO2.

PubMed

Sung, Qing; Liu, Caiyun; Zhang, Guanyun; Zhang, Jian; Tung, Chen-Ho; Wang, Yifeng

2018-06-21

Novel 17-nuclear Zr-/Hf- oxide clusters ({Zr17} and {Hf17}) are isolated from aqueous systems. In the clusters, Zr/Hf ions are connected via μ3-O, μ3-OH and μ2-OH linkages into a pinwheel core which is wrapped with SO42-, HCOO- and aqua ligands. Octahedral hexanuclear Zr-/Hf- oxide clusters ({Zr6}oct and {Hf6}oct) are also isolated from the same hydrothermal system by decreasing the synthesis temperature. Structural analysis, synthetic conditions, vibrational spectra and ionic conductivity of the clusters are studied. Structural studies and synthesis inspection suggest that formation of {Zr6}oct and {Zr17} involves assembly of the same transferable building blocks, but the condensation degree and thermodynamic stability of the products increase with hydrothermal temperature. The role of {Zr6}oct and {Zr17} in the formation of ZrO2 nanocrystals are then discussed in the scenario of nonclassical nucleation theory. Besides, the Zr-oxide clusters exhibit ionic conductivity due to the mobility of protons. This study not only adds new members to the Zr-/Hf- oxide cluster family, but also establishes a connection from Zr4+ ions to ZrO2 in the hydrothermal preparation of zirconium oxide nanomaterials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physical properties of molten core materials: Zr-Ni and Zr-Cr alloys measured by electrostatic levitation

NASA Astrophysics Data System (ADS)

Ohishi, Yuji; Kondo, Toshiki; Ishikawa, Takehiko; Okada, Junpei T.; Watanabe, Yuki; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke

2017-03-01

It is important to understand the behaviors of molten core materials to investigate the progression of a core meltdown accident. In the early stages of bundle degradation, low-melting-temperature liquid phases are expected to form via the eutectic reaction between Zircaloy and stainless steel. The main component of Zircaloy is Zr and those of stainless steel are Fe, Ni, and Cr. Our group has previously reported physical property data such as viscosity, density, and surface tension for Zr-Fe liquid alloys using an electrostatic levitation technique. In this study, we report the viscosity, density, and surface tension of Zr-Ni and Zr-Cr liquid alloys (Zr1-xNix (x = 0.12 and 0.24) and Zr0.77Cr0.23) using the electrostatic levitation technique.

[Pregnancy outcome after fetoscopic laser photocoagulation for twin-twin transfusion syndrome: experience of an emerging center from China].

PubMed

Sun, Luming; Zou, Gang; Yang, Yingjun; Zhou, Fenghe; Yeung, Leung Tak; Kin, Lau Tze; Ryan, Greg; Duan, Tao

2014-06-01

To evaluate pregnancy outcomes after selective fetoscopic laser photocoagulation (SFLP) for twin-to-twin transfusion syndrome (TTTS). A total of 33 cases of TTTS were treated by SFLP in Shanghai First Maternity and Infant Hospital from January 2012 to August 2013. Clinical data on perinatal outcomes, fetaland maternalcomplicationswere recorded and retrospectively analyzed. (1) The mean gestational age for SFLP was (22.0 ± 2.3) weeks, the mean time for SFLP was (86 ± 32) minutes, the mean gestational age for delivery was 33(+6) weeks, the gestational age between SFLP and delivery was (9 ± 5) weeks. (2) The perinatal survival rate 28 days after the delivery was 70% (46/66). The survival rate was 52% (17/33) for both twins, 36% (12/33) for one twin, 88% (29/33) for at least one twin. Of all the survival twins, there were 21 donor twins (64%, 21/33) with the mean birth weight at delivery was (1 805 ± 523) g and 25 recipient twins (76%, 25/33) with the mean birth weight (2 214 ± 600) g. (3) There were 4 cases at TTTS stage I, 9 at TTTS stage II, 11 at TTTS stage III, 9 at TTTS stage IV; the survival number for at least one twin was 4, 7, 10, 8 respectively; the total survival rate was 7/8, 12/18, 68% (15/22), 12/18 respectively. (4) Four cases had both twins demises. 3 fetuses had special fetal complications with 2 of them developing twin anemia-polycythemia sequence (TAPS). Two cases had preterm premature rupture of membrane (PPROM) within 3 weeks after SFLP. (5) Placental injections were performed in 7 cases with SFLP after delivery. Residual anastomosis was identified in one case. As an emerging center, our study demonstrated favorable fetal outcomes with less maternal complications after SFLP for TTTS.

Nature versus nurture: identical twins and bariatric surgery.

PubMed

Hagedorn, Judith C; Morton, John M

2007-06-01

Genetics and environment both play a role in weight maintenance. Twin studies may help clarify the influence of nature vs nurture in weight loss. We present the largest U.S. experience with monozygotic (MZ) twins undergoing bariatric surgery. We retrospectively reviewed the charts of four sets of MZ twins who underwent Roux-en-Y gastric bypass (RYGBP) surgery and laparoscopic adjustable gastric band (LAGB) placement at three different institutions. BMI and co-morbidities were examined pre- and postoperatively, and laboratory values were recorded. All four sets of twins are female, live together, and have similar professions. Twin cohort 1 had near identical weight loss patterns after open RYGBP surgery in 1996 (preop 146/142 kg; 2 years 82/82; and 10 years 108/107). Twin cohort 1 also both underwent cholecystectomies within the first year postoperatively. Twin cohort 2 underwent laparoscopic RYGBP surgery and also required cholecystectomies in the first postoperative year. Cohort 2 also experienced nearly identical weight loss at 1 year (36.7% vs 37.0% BMI loss). Twin cohort 3 underwent LAGB placement with two different surgeons with differing amounts of weight loss at 6 months (6.5% vs 15.7% BMI loss). Finally, twin cohort 4 underwent laparoscopic RYGBP with 2-year BMI loss of 39% vs 34%. In twin cohort 4, the twin who lost less weight lived apart from her twin and extended family, and her weight loss was less than the twin living with her family. Two sets of MZ twins had identical responses to bariatric surgery. The other two sets of identical twins had differential weight loss results, possibly due to differences in surgical approach and social support. While genetics do exert a strong influence on weight loss and maintenance, this case series demonstrates the potential effect of social support and postoperative management upon postoperative weight loss in the presence of identical genetics.

On Teaching About Twins and Time

ERIC Educational Resources Information Center

Hewitt, Paul G.

1973-01-01

Discusses a four-step instructional presentation in which the twin on the earth is demonstrated older than the twin aboard a spaceship on the basis of the relativistic Doppler effect. Concludes that both twins can meet again at the same place in space at the expense of time. (CC)

The spread of substance use and delinquency between adolescent twins.

PubMed

Laursen, Brett; Hartl, Amy C; Vitaro, Frank; Brendgen, Mara; Dionne, Ginette; Boivin, Michel

2017-02-01

This investigation examines the spread of problem behaviors (substance use and delinquency) between twin siblings. A sample of 628 twins (151 male twin pairs and 163 female twin pairs) drawn from the Quebec Newborn Twin Study completed inventories describing delinquency and substance use at ages 13, 14, and 15. A 3-wave longitudinal actor-partner interdependence model (APIM) identified avenues whereby problem behaviors spread from one twin to another. Problems did not spread directly between twins across domains. Instead, 2 indirect pathways were identified: (a) Problems first spread interindividually (between twins) within a behavioral domain, then spread intraindividually (within twins) across behavioral domains (e.g., Twin A delinquency → Twin B delinquency → Twin B substance use); and (b) problems first spread intraindividually (within twins) across behavioral domains, then spread interindividually (between twins) within a behavioral domain (e.g., Twin A delinquency → Twin A substance use → Twin B substance use). Controls for genetic effects, gene-environment correlations, friend substance use and delinquency, and parenting behaviors increase confidence in the conclusion that twin siblings uniquely contribute to the spread of problem behaviors during adolescence. Twin sibling influence is a risk factor for illicit substance use, both because substance use by one twin predicts substance use by the other twin, but also because delinquency in one twin predicts delinquency in the other twin, which then gives rise to greater substance use. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Arsenic and fluoride removal from contaminated drinking water with Haix-Fe-Zr and Haix-Zr resin beads.

PubMed

Phillips, Debra H; Sen Gupta, Bhaskar; Mukhopadhyay, Soumyadeep; Sen Gupta, Arup K

2018-06-01

The objective of the study was to carry-out batch tests to examine the effectiveness of Haix-Fe-Zr and Haix-Zr resin beads in the removal of As(III), As(V) and F - from groundwater with a similar geochemistry to a site where a community-based drinking water plant has been installed in West Bengal, India. The groundwater was spiked separately with ∼200 μg/L As(III) and As(V) and 5 mg/L F - . Haix-Zr resin beads were more effective than Haix-Fe-Zr resin beads in removing As(III) and As(V). Haix-Zr resin beads showed higher removal of As(V) compared to As(III). Haix-Zr resin beads removed As(V) below the WHO (10 μg/L) drinking water standards at 8.79 μg/L after 4 h of shaking, while As(III) was reduced to 7.72 μg/L after 8 h of shaking. Haix-Fe-Zr resin beads were more effective in removing F - from the spiked groundwater compared to Haix-Zr resin beads. Concentrations of F - decreased from 6.27 mg/L to 1.26 mg/L, which is below the WHO drinking water standards (1.5 mg/L) for F - , after 15 min of shaking with Haix-Fe-Zr resin beads. After 20 min of shaking in groundwater treated with Haix-Zr resin beads, F - concentrations decreased from 6.27 mg/L to 1.43 mg/L. In the removal of As(III), As(V), and F - from the groundwater, Haix-Fe-Zr and Haix-Zr resin beads fit the parabolic diffusion equation (PDE) suggesting that adsorption of these contaminants was consistent with inter-particle diffusion. Copyright © 2018 Elsevier Ltd. All rights reserved.

Twins in Ancient Greece: a synopsis.

PubMed

Malamitsi-Puchner, Ariadne

2016-01-01

This brief outline associates twins with several aspects of life in Ancient Greece. In Greek mythology twins caused ambivalent reactions and were believed to have ambivalent feelings for each other. Very often, they were viewed as the representatives of the dualistic nature of the universe. Heteropaternal superfecundation, which dominates in ancient myths, explains on one hand, the god-like qualities and, on the other hand, the mortal nature of many twins. An assumption is presented that legends referring to twins might reflect the territorial expansions of Ancient Greeks in Northern Mediterranean, around the Black Sea, in Asia Minor, as well as North East Africa. In conclusion, in Greek antiquity, twins have been used as transitional figures between myth and reality.

Mechanical properties and bio-tribological behaviors of novel beta-Zr-type Zr-Al-Fe-Nb alloys for biomedical applications.

PubMed

Hua, Nengbin; Chen, Wenzhe; Zhang, Lei; Li, Guanghui; Liao, Zhenlong; Lin, Yan

2017-07-01

The present study prepares novel Zr 70+x Al 5 Fe 15-x Nb 10 (x=0, 5) alloys by arc-melting for potential biomedical application. The mechanical properties and bio-tribological behaviors of the Zr-based alloys are evaluated and compared with biomedical pure Zr. The as-prepared alloys exhibit a microstructure containing a micrometer-sized dendritic beta-Zr phase dispersed in a Zr 2 Fe-typed matrix. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high compressive strength. The wear resistance of the Zr-Al-Fe-Nb alloys in air and phosphate buffer saline (PBS) solution is superior to that of pure Zr. The wear mechanism of Zr-based alloys sliding in air is controlled by oxidation and abrasive wear whereas that sliding in PBS is controlled by synergistic effects of the abrasive and corrosive wear. Electrochemical measurements demonstrate that the Zr-based alloys are corrosion resistant in PBS. Their bio-corrosion resistance is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. The Zr 75 Al 5 Fe 10 Nb 10 exhibits the best corrosion resistance in PBS, which contributes to its superior wear resistance in a simulated body environment. The combination of good mechanical properties, corrosion resistance, and biotribological behaviors of the Zr-Al-Fe-Nb alloys offers them potential advantages in biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Paramagnetic centers in two phases of manganese-doped lanthanum gallate

NASA Astrophysics Data System (ADS)

Vazhenin, V. A.; Potapov, A. P.; Guseva, V. B.; Artyomov, M. Yu.

2009-05-01

An EPR study of two phases of manganese-doped lanthanum gallate (with a first-order structural transition occurring at 430 K) has revealed Gd3+, Fe3+, and Mn4+ centers at room temperature and 438 K. The parameters of spin Hamiltonians are determined for the Gd3+, Fe3+, and Mn4+ rhombohedral centers in the high-temperature phase (with no other centers found here) and for the monoclinic center Gd3+ in the low-temperature phase. Both in the orthorhombic and in the rhombohedral phase, crystallographic twins (or ferroelastic domains) are observed.

Solomon Technique Versus Selective Coagulation for Twin-Twin Transfusion Syndrome.

PubMed

Slaghekke, Femke; Oepkes, Dick

2016-06-01

Monochorionic twin pregnancies can be complicated by twin-to-twin transfusion syndrome (TTTS). The best treatment option for TTTS is fetoscopic laser coagulation of the vascular anastomoses between donor and recipient. After laser therapy, up to 33% residual anastomoses were seen. These residual anastomoses can cause twin anemia polycythemia sequence (TAPS) and recurrent TTTS. In order to reduce the number of residual anastomoses and their complications, a new technique, the Solomon technique, where the whole vascular equator will be coagulated, was introduced. The Solomon technique showed a reduction of recurrent TTS compared to the selective technique. The incidence of recurrent TTTS after the Solomon technique ranged from 0% to 3.9% compared to 5.3-8.5% after the selective technique. The incidence of TAPS after the Solomon technique ranged from 0% to 2.9% compared to 4.2-15.6% after the selective technique. The Solomon technique may improve dual survival rates ranging from 64% to 85% compared to 46-76% for the selective technique. There was no difference reported in procedure-related complications such as intrauterine infection and preterm premature rupture of membranes. The Solomon technique significantly reduced the incidence of TAPS and recurrent TTTS and may improve survival and neonatal outcome, without identifiable adverse outcome or complications; therefore, the Solomon technique is recommended for the treatment of TTTS.

Reflectance spectrometry of placental vessels in cases of twin-twin transfusion syndrome: experiments and modeling

NASA Astrophysics Data System (ADS)

Lines, Collin; Kim, Oleg; McMurdy, John; Luks, Francois; Alber, Mark; Crawford, Greg

2013-03-01

A stochastic photon transport model in multilayer skin tissue combined with reflectance spectroscopy measurements is used to study placental vessels in cases of twin-twin transfusion syndrome (TTTS). TTTS occurs in about 12% of monozygotic (identical) twin pregnancies wherein flow within placental vessels linking the twins together becomes unbalanced, leading to dual mortality. Endoscopic laser ablation can halt the syndrome by occluding the anastomoses connecting the two fetuses. The objective of this study is to develop a technique to determine hemoglobin (Hb) content through spectral analysis of diffuse reflectance spectra of placental vessels to aid in identification of the anastomoses. Previous work by researchers at Brown University has shown that the reflectance spectra of the donor twin and recipient twin are considerably different in the wavelengths for Hb absorbance. This presentation will give preliminary results for a Monte Carlo model adapted to fit the physiology of the placenta that can be used to quantitative determine the Hb levels. The reflectance spectra of the vessels are simulated for different values of Hb as well oxygenation and water concentration with the vessel and placental mass. The preliminary results will be shown to be in good approximation with the prior experimental data. The combination of modeling with spectroscopic measurement will provide a new tool for detailed prenatal study.

Defect-Rich Dopant-Free ZrO2 Nanostructures with Superior Dilute Ferromagnetic Semiconductor Properties.

PubMed

Rahman, Md Anisur; Rout, S; Thomas, Joseph P; McGillivray, Donald; Leung, Kam Tong

2016-09-14

Control of the spin degree of freedom of an electron has brought about a new era in spin-based applications, particularly spin-based electronics, with the potential to outperform the traditional charge-based semiconductor technology for data storage and information processing. However, the realization of functional spin-based devices for information processing remains elusive due to several fundamental challenges such as the low Curie temperature of group III-V and II-VI semiconductors (<200 K), and the low spin-injection efficiencies of existing III-V, II-VI, and transparent conductive oxide semiconductors in a multilayer device structure, which are caused by precipitation and migration of dopants from the host layer to the adjacent layers. Here, we use catalyst-assisted pulsed laser deposition to grow, for the first time, oxygen vacancy defect-rich, dopant-free ZrO2 nanostructures with high TC (700 K) and high magnetization (5.9 emu/g). The observed magnetization is significantly greater than both doped and defect-rich transparent conductive oxide nanomaterials reported to date. We also provide the first experimental evidence that it is the amounts and types of oxygen vacancy defects in, and not the phase of ZrO2 that control the ferromagnetic order in undoped ZrO2 nanostructures. To explain the origin of ferromagnetism in these ZrO2 nanostructures, we hypothesize a new defect-induced bound polaron model, which is generally applicable to other defect-rich, dopant-free transparent conductive oxide nanostructures. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and contribute to the design of exotic magnetic and novel multifunctional materials.

Chorionicity and Heritability Estimates from Twin Studies: The Prenatal Environment of Twins and Their Resemblance Across a Large Number of Traits.

PubMed

van Beijsterveldt, C E M; Overbeek, L I H; Rozendaal, L; McMaster, M T B; Glasner, T J; Bartels, M; Vink, J M; Martin, N G; Dolan, C V; Boomsma, D I

2016-05-01

There are three types of monozygotic (MZ) twins. MZ twins can either share one chorion and one amnion, each twin can have its own amnion, or MZ twins can-like dizygotic twins-each have their own chorion and amnion. Sharing the same chorion may create a more similar/dissimilar prenatal environment and bias heritability estimates, but most twin studies do not distinguish between these three types of MZ twin pairs. The aim of this paper is to investigate the effect of chorion sharing on the similarity within MZ twin pairs for a large number of traits. Information on chorion status was obtained for the Netherlands twin register (NTR) by linkage to the records from the database of the dutch pathological anatomy national automated archive (PALGA). Record linkage was successful for over 9000 pairs. Effect of chorion type was tested by comparing the within-pair similarity between monochorionic (MC) and dichorionic (DC) MZ twins on 66 traits including weight, height, motor milestones, child problem behaviors, cognitive function, wellbeing and personality. For only 10 traits, within-pair similarity differed between MCMZ and DCMZ pairs. For traits influenced by birth weight (e.g. weight and height in young children) we expected that MC twins would be more discordant. This was found for 5 out of 13 measures. When looking at traits where blood supply is important, we saw MCMZ twins to be more concordant than DCMZ's for 3 traits. We conclude that the influence on the MZ twin correlation of the intra-uterine prenatal environment, as measured by sharing a chorion type, is small and limited to a few phenotypes. This implies that the assumption of equal prenatal environment of mono- and DC MZ twins, which characterizes the classical twin design, is largely tenable.

Modeling the Effect of Primary and Secondary Twinning on Texture Evolution during Severe Plastic Deformation of a Twinning-Induced Plasticity Steel

PubMed Central

Toth, Laszlo S.; Allen, Robert; Lapovok, Rimma; Molodov, Dmitri A.; Cherkaoui, Mohammed; Kadiri, Haitham El

2018-01-01

Modeling the effect of deformation twinning and the ensuing twin-twin- and slip-twin-induced hardening is a long-standing problem in computational mechanical metallurgy of materials that deform by both slip and twinning. In this work, we address this effect using the twin volume transfer method, which obviates the need of any cumbersome criterion for twin variant selection. Additionally, this method is capable of capturing, at the same time, secondary or double twinning, which is particularly important for modeling in large strain regimes. We validate our modeling methodology by simulating the behavior of an Fe-23Mn-1.5Al-0.3C twinning-induced plasticity (TWIP) steel under large strain conditions, experimentally achieved in this work through equal-channel angular pressing (ECAP) for up to two passes in a 90° die following route BC at 300 °C. Each possible twin variant, whether nucleating inside the parent grain or inside a potential primary twin variant was predefined in the initial list of orientations as possible grain of the polycrystal with zero initial volume fraction. A novelty of our approach is to take into account the loss of coherency of the twins with their parent matrix under large strains, obstructing progressively their further growth. This effect has been captured by attenuating growth rates of twins as a function of their rotation away from their perfect twin orientation, dubbed here as “disorientation” with respect to the mother grain’s lattice. The simulated textures and the hardening under tensile strain showed very good agreement with experimental characterization and mechanical testing results. Furthermore, upper-bound Taylor deformation was found to be operational for the TWIP steel deformation when all the above ingredients of twinning are captured, indicating that self-consistent schemes can be bypassed. PMID:29786663

Deformation Mechanisms and Biocompatibility of the Superelastic Ti-23Nb-0.7Ta-2Zr-0.5N Alloy

NASA Astrophysics Data System (ADS)

Castany, P.; Gordin, D. M.; Drob, S. I.; Vasilescu, C.; Mitran, V.; Cimpean, A.; Gloriant, T.

2016-03-01

In this study, we have synthesized a new Ti-23Nb-0.7Ta-2Zr-0.5N alloy composition with the aim to obtain useful mechanical properties to be used in medicine such as high strength, good superelastic property, low modulus, and large ductility. Thus, mechanical properties including superelasticity and plasticity were investigated in relation with the different deformation mechanisms observed (stress-induced martensitic transformation, twinning and dislocation slip). On the other hand, the corrosion resistance in simulated body fluid (Ringer solution) and the in vitro cell behavior (MG63 human osteoblasts) of such biomedical alloy were also evaluated in order to assess its biocompatibility.

Effect of Bi doping on morphotropic phase boundary and dielectric properties of PZT

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

Joshi, Shraddha; Acharya, Smita, E-mail: saha275@yahoo.com

2016-05-23

In our present attempt, Pb{sub (1-x)}Bi{sub x}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} [PBZT] {where x = 0, 0.05, 0.1} is synthesized by sol-gel route. Effect of Bi addition on structure, sinterability and dielectric properties are observed. The presence of morphotropic phase boundary (coexistence of tetragonal and rhombohedral symmetry) is confirmed by X-ray diffraction. Enhancement of sinterability after Bi doping is observed through a systematic sintering program. Frequency and temperature dependent dielectric constant are studied. Bi doping in PZT is found to enhance room temperature dielectric constant. However, at high temperature the dielectric constant of pure PZT is more than that of dopedmore » PZT.« less

PAC characterization of Gd and Y doped nanostructured zirconia solid solutions

NASA Astrophysics Data System (ADS)

Caracoche, María C.; Martínez, Jorge A.; Pasquevich, Alberto F.; Rivas, Patricia C.; Djurado, Elizabeth; Boulc'h, Florence

2007-02-01

A perturbed angular correlation (PAC) study as a function of temperature has been carried out on spray pyrolysis-derived powders and compacts of 2.5 mol% Y 2O 3-ZrO 2 and 2 mol% Gd 2O 3-ZrO 2 nanostructured tetragonal zirconias. The powders undergo the ordinary thermal transformation between the two known defective t‧- and regular t-tetragonal forms and also a partial and irreversible change to an ordered cubic configuration. The dynamical nature of the t‧-form leads to an activation energy of about 0.15 eV for the oxygen vacancies movement. The as-obtained compacts do not exhibit any known cubic nanostructure but some additional contributions. In both of them a hyperfine component assigned to the orthorhombic phase is determined. In the smaller cation Y doped ceramic a small amount of monoclinic phase reflects an incomplete stabilization.

Association between the birth of twins and parental divorce.

PubMed

Jena, Anupam B; Goldman, Dana P; Joyce, Geoffrey

2011-04-01

Mothers of multiple births face higher rates of postpartum depression, yet evidence on the marital consequences of multiple births is limited. We examined the association between twin births and parental divorce. We used the 1980 U.S. Census to identify a large sample of mothers with and without twin births. The goal was to estimate multivariate logistic models of the association between birth of twins and divorce adjusting for race, age at marriage and first birth, and college education. We examined whether the association was affected by maternal education, age and sex composition of twins, and family size. Twins at first birth were associated with greater parental divorce compared with singletons (odds ratio, 1.08; 95% confidence interval, 1.01-1.16; absolute risk 13.7% with twins compared with 12.7%; P=.02). The association was statistically greater among mothers not attending college (14.9% with twins compared with 13.3%; P=.01) compared with those with some college (10.4% with twins compared with 10.5%; P=.34); those with children older than 8 years (15.6% with twins compared with 13.5%; P<.01) compared with younger children (10.6% with twins compared with 10.8%; P=.42); and those with at least one twin girl (13.8% with twins compared with 12.6%; P=.03) compared with twin boys (12.1% with twins compared with 12.5%, P=.38). Mothers with four or more children had a larger association between birth of twins and divorce (15.4% for mothers with twins at fourth birth compared with 11.3% for all other mothers with four or more children; P<.01) compared with mothers with twins at first birth (13.7% for twins at first birth compared with 12.7%; P=.02). Health consequences of twin births for children and mothers are well known. Twin births may be associated with longer-term parental divorce. Specific groups, namely mothers not completing college and mothers who already have more children, may be at higher risk. II.

Twin and Triplet Drugs in Opioid Research

NASA Astrophysics Data System (ADS)

Fujii, Hideaki

Twin and triplet drugs are defined as compounds that contain respectively two and three pharmacophore components exerting pharmacological effects in a molecule. The twin drug bearing the same pharmacophores is a "symmetrical twin drug", whereas that possessing different pharmacophores is a "nonsymmetrical twin drug." In general, the symmetrical twin drug is expected to produce more potent and/or selective pharmacological effects, whereas the nonsymmetrical twin drug is anticipated to show both pharmacological activities stemming from the individual pharmacophores (dual action). On the other hand, nonsymmetrical triplet drugs, which have two of the same pharmacophores and one different moiety, are expected to elicit both increased pharmacological action and dual action. The two identical portions could bind the same receptor sites simultaneously while the third portion could bind a different receptor site or enzyme. This review will mainly focus on the twin and triplet drugs with an evaluation of their in vivo pharmacological effects, and will also include a description of their pharmacology and synthesis.

Early-life mortality risks in opposite-sex and same-sex twins: a Danish cohort study of the twin testosterone transfer hypothesis

PubMed Central

Ahrenfeldt, Linda Juel; Larsen, Lisbeth Aagaard; Lindahl-Jacobsen, Rune; Skytthe, Axel; Hjelmborg, Jacob v.B.; Möller, Sören; Christensen, Kaare

2017-01-01

Purpose To investigate the twin testosterone transfer (TTT) hypothesis by comparing early-life mortality risks of opposite-sex (OS) and same-sex (SS) twins during the first 15 years of life. Methods We performed a population-based cohort study to compare mortality in OS and SS twins. We included 68,629 live-born Danish twins from 1973 to 2009 identified through the Danish Twin Registry and performed piecewise stratified Cox regression and log-binomial regression. Results Among 1933 deaths, we found significantly higher mortality for twin boys than for twin girls. For both sexes, OS twins had lower mortality than SS twins; the difference persisted for the first year of life for boys and for the first week of life for girls. Conclusions Although the mortality risk for OS boys was in the expected direction according to the TTT hypothesis, the results for OS girls pointed in the opposite direction, providing no clear evidence for the TTT hypothesis. PMID:28024904

Early-life mortality risks in opposite-sex and same-sex twins: a Danish cohort study of the twin testosterone transfer hypothesis.

PubMed

Ahrenfeldt, Linda Juel; Larsen, Lisbeth Aagaard; Lindahl-Jacobsen, Rune; Skytthe, Axel; Hjelmborg, Jacob V B; Möller, Sören; Christensen, Kaare

2017-02-01

To investigate the twin testosterone transfer (TTT) hypothesis by comparing early-life mortality risks of opposite-sex (OS) and same-sex (SS) twins during the first 15 years of life. We performed a population-based cohort study to compare mortality in OS and SS twins. We included 68,629 live-born Danish twins from 1973 to 2009 identified through the Danish Twin Registry and performed piecewise stratified Cox regression and log-binomial regression. Among 1933 deaths, we found significantly higher mortality for twin boys than for twin girls. For both sexes, OS twins had lower mortality than SS twins; the difference persisted for the first year of life for boys and for the first week of life for girls. Although the mortality risk for OS boys was in the expected direction according to the TTT hypothesis, the results for OS girls pointed in the opposite direction, providing no clear evidence for the TTT hypothesis. Copyright © 2016 Elsevier Inc. All rights reserved.

Hematological disorders at birth in complicated monochorionic twins.

PubMed

Verbeek, Lianne; Slaghekke, Femke; Sueters, Marieke; Middeldorp, Johanna M; Klumper, Frans J; Haak, Monique C; Oepkes, Dick; Lopriore, Enrico

2017-06-01

Monochorionic twins are at risk of severe complications including twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS) and acute peripartum TTTS. The pathophysiology is based on inter-twin blood transfusion through placental vascular anastomoses. Areas covered: This review focuses on the incidence, management and outcome of neonatal hematological complications at birth in TTTS, TAPS and acute peripartum TTTS. Expert commentary: Hematological disorders are often present at birth in monochorionic twins and include acute or chronic anemia, polycythemia and thrombocytopenia. Routine measurement of complete blood counts in all complicated monochorionic twins is strongly recommended. Increased awareness on these disorders and correct diagnostic tests will lead to prompt and adequate management at birth.

Crystal Nucleation and Growth in Undercooled Melts of Pure Zr, Binary Zr-Based and Ternary Zr-Ni-Cu Glass-Forming Alloys